MSU

LlBRARlES
“—

 

 

 

RETURNING MATERIALS:
PTace in book drop to
remove this checkout from
your record. FINES will
be charged if book is
returned after the date
stamped beIow.

 

775518544260

 

 

A PALYNOLOGICAL STUDY OF THE SOUTH-EAST REGION
OF THE BOSCAN FIELD, VENEZUELA

By

Omar A. Colmenares

A THESIS

Submitted to
Michigan State University
in partial fulfillment of the requirements

for the degree of

MASTER OF SCIENCE

Department of Geological Sciences

1986

ABSTRACT
A PALYNOLOGICAL STUDY OF THE SOUTH-EAST REGION
OF THE BOSCAN FIELD, VENEZUELA
By
Omar A. Colmenares

The palynological study of 71 core samples from the
Boscén Field was performed. The main purposes of this study
were the dating and the biostratigraphic and paleoecological
characterization of the sedimentary sequences under study.

The palynological assemblage was determined to be Middle
Eocene in age, according to the recent zonation published by
Muller et a1. (1985). In general, sedimentological and palyno-
logical results indicate environmental changes within a
deltaic complex existing at the time of deposition. An ap-
proximate biozonation, based on the results of the cluster
analysis and the fluctuations of the relative abundances of
the different groups of palynomorphs, indicates a transition
from a low deltaic plain to an upper deltaic plain in the 3
subsurface sections under study. A mixed plant community,
with coastal and mixed-swamp vegetational components, is

inferred to have been present at the time of deposition.

A la Memoria de mi Padre
A mi Madre y a mi Hermano

Por todo lo grande que me han ensefiado
Por todo lo significativo que son para mi

ii

ACKNOWLEDGMENTS

The author of this study would like to express his recognition
and gratitude to:

- Dr. Aureal T. Cross, who always knew how to give his valua-
ble and continuous support and stimulus, not only during this
study, but also during the last 3 years of my life at Michigan
State University.

— Dr. Efe Sinanoglu, Dr. Iraida de Ramos, Dr. Armando Fasola
and Dr. Izaskun Azpiritxaga, of INTEVEP S.A., for their val-
uable time and help, that made possible the realization of
this study.

- Centro de Adiestramiento del Personal de la Industria Petro-
lera y Petroquimica (CEPET), for their significant contribu-
tion to my education.

- Dr. R.L. Anstey, Dr. R.E. Taggart and Dr. M.A. Velbel, for
their professional judgement of this study.

- Dr. A. Jameossanaie, for permission to use his software of
cluster analysis.

- Dr. B. van Geel, Dr. A. Graham and Dr. J. Wren, for their
prompt identification of some of the palynomorphs reported

in this study.

iii

TABLE OF CONTENTS

Page
LIST OF TABLES vii
LIST OF FIGURES viii
I. INTRODUCTION 1
I-l. Objectives I
I-2. Geological evolution of the Lake Maracaibo Basin 1
1-3. The Boscén Field: Stratigraphy and sedimentary
models 18
1-4. Palynological studies in northern South America 26
I-4-1. Stratigraphical applications 28
1-4-2. Paleoecological applications 29
II. MATERIALS AND METHODS 34
11-1. Samples 34
11-2. Maceration procedure 34
11-3. Preparation of microscope slides 38
II-4. Counting of palynomorphs 39
11-5. Photographic material 40
11-6. Palynomorph diagrams 40
11-7. Cluster analysis 42
III. RESULTS 45
III-1. Abundance of palynomorphs 45
III-2. Sedimentological and palynological results 49
Well B244 49
Well B248 59
Well B252 69
III-1. Cluster analysis results 79
IV. DISCUSSION 82
IV—l. Geological age range 82
IV—2. Abundance of palynomorphs 83
IV-3. Paleoenvironmental and paleocommunity inferences 86
IV-4. Comparison to other palynological assemblages 96
IV-S. Limitations of this study 97
V. CONCLUSIONS AND SUMMARY 98

iv

TABLE OF CONTENTS

(cont.)
Page
VI. BIBLIOGRAPHY 102
APPENDIX A 108
APPENDIX B 111

PLATES 115

vi

Table 1.
Table 2.
Table 3.

Table 4.

Table 5.

Table 6.

LIST OF TABLES

Absolute number of palynomorphs: Well B244
Absolute number of palynomorphs: Well B248
Absolute number of palynomorphs: Well B252

Percentages of the different palynomorph
groups: Well B244

Percentages of the different palynomorph
groups: Well B248

Percentages of the different palynomorph
groups: Well 8252

vii

Page
46
47

48

57

67

77

Figure
Figure
Figure
Figure

Figure

Figure
Figure

Figure
Figure
Figure
Figure
Figure

Figure
Figure

Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure

Figure

Figure

LIST OF FIGURES

1. Geomorphological provinces of Venezuela

Location of the Boscén Field

Sedimentary provinces in northwestern

Venezuela: Cenomanian-Coniacian

4. Sedimentary provinces in northwestern
Venezuela: Paleocene

5. Sedimentary provinces in northwestern
Venezuela: Early Eocene

6. Location of the Macoa Arch (Middle Eocene)

7. Location of sandstone accumulation in the
the Lake Maracaibo Basin during the Eocene

8. Tectonic deformation during the Early
Oligocene

9. Tectonic deformation during the Late
Miocene and Pliocene

10.Abbreviated stratigraphic column of the
Lake Maracaibo Basin

11.8ubdivisions of the Misoa Formation in
the Bolivar Coastal Fields

12.Deltaic model and different sedimentary
facies

13.8edimentary model of the Boscén Field

14.Mode1 of sea level fluctuation and shore
vegetation changes

15.Location of the three wells in the Boscén
Field

16.SP curve and environments of sedimentation
Well 3244

17.Lithology of the core of well B244

18.Well B244: Palynomorph diagram

19.SP curve and environments of sedimentation
Well B248

20.Lithology of the core of well B248

21.Well B248: Palynomorph diagram

22.SP curve and environments of sedimentation
Well B252

23.Lithology of the core of well B252

24.Well 5252: Palynomorph diagram

25.Cluster diagram of samples from the Boscén
Field

26.Proposed biozonation for the sections under
study in the Boscén Field

WM
0 0

viii

Page

11

14
14
17
19
21

23
27

33
35
51
53
58
62
63

72
73
78

8O

93

I. INTRODUCTION

I-l. Objectives.

The objectives of this research are:

a) Identify and describe the palynological assemblage from
sediments of the Boscén Field, Venezuela.

b) Correlate comparable biostratigraphic zones in three sub-
surface wells.

c) Date different stratigraphic sections on the basis of
biostratigraphic zonations.

d) Achieve the biostratigraphic integration of the subsurface
sections by the use of palynological correlation and prepa-
ration of charts showing these correlations.

e) Develop information on the paleoecology and community
structure of plants comprising these floras.

I-2. Geological evolution of the Lake Maracaibo Basin.

The Lake Maracaibo Basin is one of the twelve geomor-
phological provinces of Venezuela (Figure 1), as defined by
Feo-Codecido et a1. (1984). It is located in a tectonic de-
pression in northwestern Venezuela, and encompasses a
surface area of approximately 52,000 km’. The basin is limit-
ed to the west by the Sierra de Perijé, and to the east and
south by the Venezuelan Andes.

Since the beginning of this century, the basin has been

one of the main oil producing regions of the world. After
1

 

N
camaaem sea
/ I A”, I
‘ 1"“ n
’ "—- .—-""-\
III I V , ' N ,— __,
\ /"\’ \ ’ \\
I Iv \/ n..- VI ,-,»I \\
/ I / / 'V‘“—'-—-——-' \ ’\XI
/ I \ \‘
/Vll// l\ x / \\
/ VIII | \ /’_// “"'\~ /
/ 'x \//Orinoc River
I I °
/
I, XII
/
/
COLOMBIA /
BRAZIL
9...)?“

 

 

 

Figure 1. Geomorphological provinces of Venezuela:
I— Guajira-Paraguana; II- Venezuelan-Caribbean
Islands; III— Sierra de Perijé; IV- Lake Mara—
caibo Basin; V- Falcén and Lara Region;
VI- Caribbean Mountains; VII- Venezuelan Andes;
VIII-Barinas and Apure Basin; IX- El Baul
Swell; X— Eastern Venezuela Basin; XI- Orinoco
Delta Region; XIII- Guayana Shield.
(After Feo-Codecido et al., 1984).

limited discoveries in the southern area of the basin, the
Venezuelan government granted the first concessions for oil
exploration in 1909 (Coronel, 1983). By the middle 1910's,
exploratory wells had been drilled in the eastern part, Zuma-
que-1 being the first significant and productive discovery.
In 1917, well Los Barrosos-Z, also located in the eastern
shore of Lake Maracaibo, blew out producing nearly 100,000
barrels per day. This series of discoveries led to intense
activity of exploration and exploitation of oil, especially
in the eastern shore area of the Lake Maracaibo, in the
Bolivar Coastal Fields, considered to be one of the three
largest oil fields of the world (Coronel, 1983). Exploration
in the western area of the basin began in the early 1920's,
leading to the discoveries of the Concepcién, La Paz and the
Boscén Fields (Figure 2).

The intensive exploratory activity developed since then,
has generated important publications summarizing the geologi-
cal evolution of the basin. By the middle 1940's and 1950's,
papers by Sutton (1946), Schaub (1948) and Mencher et a1.
(1953) presented detailed descriptions of the geology and
stratigraphy of the area. More recently, and based on new
evidence and data, Zambrano et a1. (1971), Gonzalez de Juana
et al. (1980), Bockmeulen et al. (1983), Kellogg (1984) and
Talukdar et al. (1985), have presented new interpretations
on the evolution of the basin.

Case et al. (1984) pointed out that the basin contains

Jurassic red beds, Cretaceous marine carbonates and Cenozoic

 

 

-—'z

Maracaibo

LIFE: .‘
. \

Boscdn I oncapcidn

s'
9‘
a

VENEZUELA

0 100 KM

 

 

Figure 2. Location of the Boscén Field in western Vene-
zuela. (After Bockmeulen et al., 1983).

deltaic, fluviatile, marine and lacustrine deposits. Since
the main events related to the geological evolution of the
basin, as well as to oil generation in the basin, occurred
after the Jurassic, the following discussion will present a
synopsis of the evidence describing and interpreting the
history of the basin, from the Cretaceous to the Pliocene.
Mencher et al. (1953) and Zambrano et al. (1971) pointed
out that during the Early Cretaceous, a shallow epicontinental
sea covered not only the current Lake Maracaibo, but also
most of the northern part of Venezuela, leaving the Guayana
Shield as the only positive area. Talukdar et al. (1985)
presented a detailed analysis of the types of organic matter
contained in different formations of the Lake Maracaibo
Basin. They concluded that the Early Cretaceous Rio Negro
Formation was deposited in continental environments, being
followed by the Ap6n, Lisure and Maraca Formations, deposited
in a shallow marine platform. This transgression extended
into the Cenomanian-Coniacian, reaching its maximum with the
deposition of La Luna Formation. According to Talukdar et al.
(1985), this calcareous shale-limestone constitutes the main
source rock for hydrocarbons generated in the Lake Maracaibo
Basin. Zambrano et a1. (1971) described the existence of
three sedimentary provinces during the Cretaceous. These
were the coastal, neritic and pelagic provinces, which were
roughly parallel to the northwestern edge of the Guayana

Shield (Figure 3).

 

 

 

 

 

: .35
m PELAGEO
z .- -
o . O
A . :
O a '
o ; PROVINCE
NERITIC
f PROVINCE
COASTAL
PROVINCE
.....'...'.."'H......“;-__ 9 KM 1304'
Figure 3. Sedimentary provinces in northwestern

Venezuela during the Cenomanian-Coniacian.
Dotted line shows the current coastline
and international border for reference
(After Zambrano et al., 1971).

7

Gonzalez de Juana et al. (1980), in their important
review "Geologia de Venezuela y de sus cuencas petroliferas"
(Geology of Venezuela and its oil basins), pointed out that
a gradual period of regression followed the maximum trans-
gression of the Cenomanian-Coniacian. This fact is evidenced
by the gradual transition between La Luna Formation and the
overlying Colén Formation. The latter is characterized as a
thick shale sequence, deposited in an open marine environment.
Towards the t0p of the Colén Formation, it becomes sandier,
with intercalated coal layers, indicating the regressive
nature of the sequence. Gonzalez de Juana et al. (1980) also
noted the presence of faunal indicators of shallow water in
the upper section of this Formation.

Beginning in the Cenozoic, a significant change took
place to the southwest of the basin area. Zambrano et al.
(1971) and Gonzalez de Juana et al. (1980) distinguished
three sedimentary provinces, that unlike those described for
the Cretaceous, have their zones in a southwest—northeast
trend (Figure 4). This fact seems to suggest an incipient
uplift to the southwest, in Colombia. Shagan et a1. (1984)
postulated that the incipient orogeny of the Central Cordi-
llera in Colombia occurred at this time, caused by the rela-
tive motions of the Caribbean and the South American plates.

Bockmeulen et al. (1983) postulated that the sea re —
treated from the southwestern area of the basin. Gonzalez
de Juana et al. (1980) pointed out the existence of a fluvial

province in this area. The Catatumbo, Barco and Los Cuervos

 

 

   

PLATFORM“

COLOMBIA

   

PROVINCE

 
 
   
 

\..
‘..

K FLUVIAL

:‘PROVINCE ° "" ‘°°

 

Figure 4. Sedimentary provinces in northwestern
Venezuela during the Paleocene. Dotted

line shows the current coastline and

international border for reference
(After Zambrano et al., 1971).

 

9

Formations, comprising the Orocue Group (Figure 10), are
characterized as being deposited in continental (fluvial)
conditions. To the northeast of this area, marine and
brackish conditions were still present. The so-called platform
province (Gonzalez de Juana et al., 1980) was limited to the
southeast by the Mérida arch (a prolongation of the Guayana
Shield present since pre-Cretaceous times). The Guasare
Limestone was deposited in this province. A third province,
located to the northeast of the platform province, is the
geosynclinal province, characterized by deep water sediments,
such as those of the Trujillo Formation (Gonzalez de Juana et
al., 1980).

During the Eocene, the location of the sedimentary prov-
inces remained the same as in the Paleocene. However, the
first signs of the incipient orogenies of the Venezuelan An-
des and of the Sierra de Perijé are postulated to have oc-
curred during the Middle Eocene (Kellogg, 1984). Kellogg
(1984) proposed significant tectonic deformation of the basin,
with the formation of a series of anticlines with northeast-
southwest axes, and large unconformities, that are observed
in the oil fields of the Lake Maracaibo and in the Boscén
Field. Shagan et al. (1984) seem to support this hypothesis
in regard to the timing of this event, based on fission-
track age determinations, made in rocks of western Venezuela
and eastern Colombia. These events, as it will be pointed out
later in this discussion, will be important for defining the

evolution and configuration of the basin.

10

Bockmeulen et al. (1983) suggested that the coastline of
the Caribbean Sea was located on what is now the Lake Maracai—
bo during the Early Eocene (Figure 5). The fluvial-deltaic
province in the southwest was still developing. The Mirador
(fluvial) and the Misoa (deltaic) Formations were deposited
in this province. Shallow and deep marine sedimentation took
place in the northeast area of the basin. Zambrano et al.
(1971) noted that the thickness of the Misoa and the Trujillo
Formations increases towards the northeast, reaching a total
of 20,000 feet (approximately 6,096 m) of Eocene deposits.
0n the basis of the analysis of electric and radioactivity
logs, Zamora (1977) noted that the sedimentation of the Misoa
Formation had a cyclic nature, with minor deltaic regressions
and transgressions. Bockmeulen et al. (1983) proposed that
rapid and continuous subsidence of the area caused the sig-
nificant thickness of the sediments, without major seaward
progradation. This fact suggests the formation of many super—
imposed deltas, as it was proposed by Zambrano (1977).

By the Middle Eocene, tectonic deformation in the area
is proposed by Zambrano et al. (1971) and Kellogg (1984).
This deformation is evidenced by the formation of the
Macoa arch (Figure 6), unconformities in the Lake Maracaibo
oil fields and, according to Zambrano et a1. (1971), a hiatus
in the deposition of the Mirador Formation in the southwest
of the Basin. However, Gonzalez Guzman (1967), based on
palynological evidence, did not find evidence of this hiatus

in eastern Colombia. Continuous sedimentation has been

11

 

 

   
 
 

 

< GEOSYNCLINAL

H

m

2

O

._3 .

8|; , PROVINCE

;' FLUVIAL- a.
DELTAIC
: 0 KM {um
~PROVINCE 4* ,4

 

 

Figure 5. Sedimentary provinces in northwestern
Venezuela during the Early Eocene.
Arrow indicates direction of prograda-
tion of the Fluvial-Deltaic Province.
Dotted line shows the current coastline
for reference (After Gonzalez de Juana
et al., 1980).

 

12

 

COLOMBIA

 

0 KM 100

 

 

Figure 6. Location of the Macoa Arch (Middle Eocene).

The tectonic reconstruction includes

Eocene isopachs (Contour interval is

1,000 feet). Dotted line shows the

current coastline and international

border for reference (After Kellogg, 1984).

13

assumed for the rest of the basin. The Pauji Formation was
deposited in relatively deep water in the northeastern area
of the basin. These shaly deposits are considered to be the
marine equivalent to the Misoa Formation (Gonzalez de Juana,
et al., 1980). During the Late Eocene, the sea covered most
of the basin area, except the southwestern part. In this area,
the deposition of the Mirador and Carbonera Formations
(Figure 10) had minor marine influence overall. In the west,
La Sierra Formation (Figure 10) was deposited in brackish
water conditions.

The pronounced subsidence in the northeastern area of
the basin during the Middle and Late Eocene, has been proposed
by Bockmeulen et al. (1983) and Talukdar et al. (1985), to
have caused the generation of oil, in zones buried deeply
enough, and the primary migration of hydrocarbons towards
the thick Eocene sandstones, located up—dip in the central
area of the basin (Figure 7).

In the Early Oligocene, the tectonic deformation in
the basin area continued. In the central part of the basin,
in what is now the Lake Maracaibo, a series of anticlines
and closely spaced faults, with north—south trend, began to
develop (Figure 8). Zambrano et al. (1971) and Bockmeulen et
al.(1983) noted that the erosion undergone by Eocene sediments
was severe, with estimates of nearly 9,000 feet (2,743 m) of
Eocene sediments being removed in the central part of the
basin. Continuous sedimentation, as proposed by Zambrano et

al. (1971), Bockmeulen et al. (1983) and Kellogg (1984),

14

SOUTHWEST NORTHEAST

 

       
 

Pauji

Maraca
Lisure Trujillo

Ap6n

 

 

 

Figure 7. Location of sandstone accumulation in
the Lake Maracaibo Basin during the
Eocene (After Bockmeulen et al.,1983).

 

SOUTHWEST , NORTHEAST

 

 

Maraca
Lisure

Ap6n

 

 

 

 

Figure 8. Tectonic deformation during the Early
OligOcene (After Bockmeulen et al.,

1983).

15

took place in most of the western-southwestern area of the
basin. The Peroc Formation, part of El Fausto Group (Figure
10), was deposited in this area under non-marine conditions.
To the east of the basin, the effects of the incipient
orogeny of the Venezuelan Andes began to be noted, with the
erosion of Eocene sediments, but without the significance
previously noted for the central area of the basin. The only
Oligocene marine sediments are found to the north of the
basin. This fact seems to suggest a significant regressive
period, suggested by Bockmeulen et al. (1983) as part of

a worldwide event taking place at that time.

In zones where erosion and removal of sediments took
place, the central and eastern areas of the basin, are
characterized by a marked unconformity between the Misoa
Formation and the Oligocene IcoteaFormation. This unconformi-
ty has also been described in the Boscén Field, in the north-
western area of the basin, by Sutherland (1964) and Azpirit-
xaga (1985). The age and environment of deposition of the
Icotea Formation have not been precisely determined. The
sediments contain only reworked Eocene foraminifera (Lexico
Estratigrafico de Venezuela, 1970) and lack palynomorphs
(Kuyl et al., 1955). Interpretations concerning the environ-
ment of deposition are varied; Sutton (1946), based on grain
size distribution, prOposed an eolian origin for these sed-
iments. Talukdar et a1. (1985) reported a fluvial environment.
Azpiritxaga (1985) reported that these sediments were depos—

ited in a continental environment during a regressive cycle

16

in the Oligocene. The age of the Icotea Formation has been
prOposed to be Oligocene-Miocene (Léxico Estratigréfico de
Venezuela, 1970 and Kellogg, 1984).

By the Late Oligocene, the definite orogeny of the
Venezuelan Andes began (Kohn et al., 1984). In terms of the
geology of Venezuela, this event is important because it
marks the total separation of the Lake Maracaibo Basin and
the Barinas Basin (provinces IV and VIII,respectively, Figure
l) (Zambrano et al., 1971). Contemporaneous with the uplift,
that extended into the Miocene, marked subsidence occurred to
the southeast and to the east of the basin, along the in-
cipient orogenic belt. Bockmeulen et al. (1983) noted impor—
tant structural changes as having taken place during the
Late Oligocene and Early Miocene, such as the tilting of the
basin to the west (Figure 9), and marked subsidence through—
out most of the basin. La Rosa Formation, composed of basal
sands followed by marine shales, was deposited during a
transgressive period. Zambrano et al. (1971) noted that
Miocene sediments commonly become thicker towards the south-
western area of the basin, evidence of the rapid uplift of
the Venezuelan Andes to the east.

The main uplift of the Sierra de Perijé occurred during
the late Miocene and extended into the Pliocene (Shagan et
al., 1984). Bockmeulen et al. (1983) pointed out that sub-
sidence continued throughout most of the basin during the
Pliocene. Bockmeulen et al. (1983) and Talukdar et al. (1985)

pointed out that the directions of maximum subsidence changed

17

 

MIOCENE

      

”53.Mirador

 

‘\\\\\-Maraca
Lisure

Ap6n

 

 

 

 

 

 

 

Figure 9. Tectonic deformation during the Late

Miocene and the Pliocene
(After Bockmeulen et al., 1983).

18

from the southwest (Late Oligocene—Early Miocene) to the
south (Late Miocene-Pliocene). This period is characterized
by a regression, observed in the transition between the
marine La Rosa Formation and the overlying Lagunillas
Formation, deposited in subaerial conditions (Zambrano et
al., 1971). In the southwest, continental deposits of El
Fausto Group and Los Ranchos Formation were laid down. A
synopsis of the stratigraphy of the basin is presented in
Figure 10.

I—3. The Boscén Field: Stratigraphy and sedimentary models.
The Boscén Field is located about 25 miles (40 km)
southwest of the city of Maracaibo, in a low-lying flat area

(Sutherland, 1964). By the late 1920's, exploratory wells
had been drilled in the area, without any comercial success.
By the middle 1940's, Richmond Exploration Company (former
Chevron Oil Company of Venezuela) performed seismic surveys
in areas located to the west of the Lake Maracaibo, including
the Boscén Field. The results led to the drilling of new wells
in the eastern area of the field. The results at this time
were productive and by the late 1940's, the importance and
size of the Boscén Field were known. Later, in 1951, former
Shell Oil Company of Venezuela, and in 1963, the former Cor-
poracién Venezolana del Petréleo (CVP), extended their oper-
ations in the area. Currently, the field is operated by
CORPOVEN s.A..

The field covers an area of approximately 102,502 acres

(414 km”), produces oil with an average of 10.4°. Since 1946,

19

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

WEST EAST
L Los
g RANCHOS LAGquLLAs
o
9
a E EL
I“ LA 905A
2 " FAUSTO
u:
o
o GROUP
9 ICOTEA
.l
o E g AAAAAA , A..--A
L J» ., gaff
% :3 °§
3 Q Q PAUJI
o MISOA
u, uInAoon
E
"24 L
In OROCUE TRUJILLO
8 GUASARE
In GROUP
2, .
a. E
m
3 '- COLON
Iu LA LUNA
2
5 MARACA
I LISURE
o E APON

 

Figure 10. Abbreviated stratigraphic column of
the Lake Maracaibo Basin.

 

20

a total of 651 million barrels have been produced, with
proven reserves of 26,363,758 barrels (Azpiritxaga, 1985).

As most of the oil fields of the Lake Maracaibo Basin,
the Boscén Field has the Eocene Misoa Formation and the
basal Oligocene Icotea Formation, as the main reservoirs
(Miller, 1958 and Azpiritxaga, 1985). Sutherland (1964) cited
the relative isolation of the Boscén Field from other fields
to the east of the Lake Maracaibo, as the reason for the de—
velopment of an informal stratigraphic nomenclature. This no-
menclature is poorly related to that of other areas of the
basin. Zambrano et al. (1971) summarized the subdivisions of
the Misoa Formation into the B and C sands in the Bolivar
Coastal Fields (Figure 11). Sutherland (1964) referred to
the producing horizons in the Boscén Field as the lower and
the upper Boscén sands, with Las Flores Shales in between.
Germeraad et al. (1968) reported that the Misoa Formation can
be correlated with the B sand of the Bolivar Coastal Fields
and to La Sierra Formation in the Sierra de Perijé. These
authors limited the deposition of this formation to their
Retibrevitricolpites triangulatus and Retitricolporites
guianensis palynological zones (Lower to Middle Eocene).

As it was previously summarized, the Misoa Formation is
characterized as a part of a vast deltaic complex existing
in the Eocene of western Venezuela. The Misoa Formation was
initially described by Garner in 1926. However, the lack of
precision of the original description led Bronijk (1967) to

redefine it. It is characterized by sands intercalated with

21

 

 

 

 

 

 

 

 

 

 

MAJOR SUB
DIVISIONS DIVISION THICKNESS LITHOLOGY

Upper 2,900' Predominantly

2 Unit (883.9 m) Shales

S

m Lower 1,200' Sand and
Unit (365.8 m) Shales
Upper 700' Predominantly
Unit (213.4 m) Shales

2 Middle 1,500' Shaées

< Unit an

m (457.2 m) sand
Lower 2,600' Massive sand

0 Unit (792.5 m) and shale

 

 

Figure 11. Characteristics of the subdivisions
of the Misoa Formation in the Boli-
var Coastal Fields (After Zambrano
et al., 1971).

22

Shales and limestone. van Veen (1977) studied the lithologic
characteristics of the Mirador and the Misoa Formations, and
recognized a fluvial environment for the deposition of the
Mirador Formation. For the Misoa Formation, van Veen (1977)
recognized transgressive-regressive sequences, with increas-
ing marine influence towards the central and northern areas
of the Lake Maracaibo. Based on lithologic features, van Veen
(1977) recognized different types of deposits:

a) Pointbar -

b) Filling of distributary channels

c) Coastal barrier.

In general van Veen (1977) described a decrease in
grain size towards the top of the section, as well as from
the south to the north of the Lake Maracaibo.

Zamora (1977) recognized several cycles of sedimenta-
tion, that have been attributed to a prograding delta in an
area undergoing extensive subsidence. Based on electric and
gamma ray logs, Zamora (1977) recognized at least five
different categories of sand deposits:

a) Delta front
b) Filling of distributary channels
c) Overbank
d) Meander
e) Transgressive sequences.
The deltaic model proposed by Zamora (1977) is shown in

Figure 12.

.AnmoH .muoemN umuw<v umfiuumn Mancufla

no Hmummou IH> cam mufimoamc m>wmmmummcmue I>

.amn ammusnfluumwvumucm I>H .umn zuaoz IHHH

.maoccmnu aumuanfiuumwm IHH .um>wu wcfiumucmmz IH
“wwwumu ammucmswvmm acmummm“u ucm Hmcoe uwmuamo .NH muswwm

 

23

 

Hzomm <quo
mucmswcwm

umuuoamcmuu
m>m3

      

3,,
'l

\\ /

I
I

\llhl/
[I /
Z SHE:

t-
\ I

OWWmmwmmcmuH

\ \
\ \

 

2H<Am UH<HAMQ

s e

4 RD

Bm<oo

 

 

 

24

Three sedimentological models for the Boscén Field are
discussed in the following paragraphs.

Sutherland (1964) reported that erosion of Eocene sedi-
ments was more pronounced towards the northern area of the
field. Sutherland (1964) also noted that the grain size
tends to decrease towards the north, whereas coarse-grained
sands with relatively high porosity are located in the south-
ern part of the field. Sutherland (1964) also reported that
the dipping direction of the strata in the field area is
towards the west-southwest (approximately 25 feet/mile or
7.6 m/Km).

Sutherland (1964) and Azpiritxaga (1985) noted that the
main structural features of the field are caused by normal
faulting. These authors reported that the fault trend is
north-northwest (N 18° W) and that the relative displacement
along the fault planes is more pronounced towards the south
of the field. Both authors agreed that tectonic events taking
place during the Oligocene caused these faults.

Reservoir Inc., in 1983, prepared a report on the geo—
logy and sedimentology of the Boscén Field. This report, as
well as the information reported by Azpiritxaga (1985), con-
cluded that the sediments of the Boscén Field were laid down
in a vast deltaic system, probably similar in extent to the
Missisippi Delta. Reservoir Inc. reported that the lower
Boscén sands appear to have been deposited in a low deltaic
plain, with minor marine influence. As the delta prograded,

a gradual transition to an upper deltaic plain occurred. For

25

the purposes of this study, low deltaic deposits are those
laid down in environments of a delta subjected to tidal
influence. Busch and Link (1985) defined the low deltaic
plain as that area of the delta extending from the highest
zone of marine influence or tidal influence, to the low tide
line. On the other hand, upper deltaic deposits are those
laid down in environments with none or minor tidal influence.
Busch and Link (1985) considered it as the continuation of
the fluvial valley into the delta.

Azpiritxaga (1985) proposed a sedimentary model, in
which she recognized seven informal stratigraphic intervals
for the Misoa Formation in the Boscén Field. The opinions
of Azpiritxaga coincides with the interpretations made by
Reservoir Inc. in regard to the main genetic units of sedi-
mentation; that is, the low and the upper deltaic plains.

Azpiritxaga (1985) observed that deposits of the low
deltaic plain are characterized as those of distributary
channels, overbank, delta front and interdistributary plain
sediments. 0n the other hand, the upper deltaic plain depos-
its are those of channels, meander pointbars, flood plains,
ox-bow lakes and natural levees.

In the deepest cores surveyed by Azpiritxaga (1985), she
observed the first two informal intervals (corresponding to
low deltaic deposits). These two intervals are overlaid by a
sequence characteristic of an upper deltaic plain. Finally,
towards the top of the surveyed cores, characteristic depos-

its of a low deltaic plain were observed. An illustrated

26

model of these observations is shown in Figure 13.
I-4. Palynological studies in northern South America.

Palynology has been widely used in northern South America
since the middle 1940's. Its principal application, in the
specific case of Venezuela, has been in petroleum geology, as
reviewed by Kuyl et al. (1955). In spite of the extensive
research carried out, the amount of information that is a-
vailable is scarce; most of it being in prOpietary files of
oil companies.

Among the few publications available, that of Germeraad
et al. (1968) reveals important aspects of the palynology of
tropical areas. These authors pointed out the high diversity
of the palynological assemblages, estimating at 800—1,000
different types of palynomorphs in an average collection.

Of this number, less than 20% is of importance for strati-
graphical purposes. Graham (1985) pointed out that the
Eocene vegetation of northern South America is still largely
unknown, a fact that constrains paleoecological recons-
tructions. Frederiksen (1985) pointed out that the palyno—
logical information for most of the environmental suites
observed in tropical areas is incomplete.

In order to organize the available information, the fol-
lowing discussion will be divided into two main categories.
The first part will be related to the stratigraphical uses
of palynology in northern South America. This part will re-
view the main publications containing zonations, based on

palynological determinations. The second part will deal with

27

.Amon .mwmxuwuflax< Cmuw<v cHOSm :wumom was How ummoQona Hmcoe ammucoeflvmm .m~ muzwflm

 

 

 

 

cmeQ zumuanwpumwquDCH I>H
umn zusoz IHHH

amaam mmmm>mnu IHH
floccmcu sumusnfiuumfln IH

"zH<Am UH<HJMQ 304

 

 

 

wm>mq IxH

mxma zoalxo IHHH>
:HmHa vocab IHH>
nan ucfiom IH>
Hmccmcu m>fluu< I>

“2H<qm 0H<qun mmmm:

 

 

Ah new oIm mg<>mmezH
uHmmamoHeamem gazmomsz

nmuuuummwwmwMHNquImu cflmfla IcmsssflcumfletmueH I>H
% E :3 £32 A:

ufl amaam mmmm>muo IHH
>~ Hmccmnu zumuznwuumwn IH
I "2H<Am UH<HAMQ 304

 

 

 

28

an overview of the methodology used for the characterization
of the paleoecology and paleoenvironments of Tertiary palyno-
logical assemblages in this area.

I—4-1. Stratigraphic applications.

Three main publications are considered to provide an
useful insight view of the stratigraphic applications of
palynology in northern South America.

The first publication is that of Germeraad et al. (1968),
that compiles almost 20 years of experience in the field,
not only in South America, but also in Asia and Africa. The
information reported in this paper is highly diverse and
points out the different aspects to be considered in a
palynological study. The main result of this publication
is related to the establishment of three major zone catego-
ries for Late Cretaceous—Tertiary-Quaternary tropical sedi-
ments. The first major zone is the Pantropical zone, defined
by those palynomorphs that have widespread distribution in
all the areas of the study. The second major zone, the Trans-
atlantic zone, is defined by those palynomorphs found in
South America and Africa. Unlike the palynomorphs used for
the definition of the third type of zone, these two cate-
gories are defined based on palynomorphs with significant
stratigraphical importance. Finally, the third type of zone,
the Intracontinental or local zones, are defined based on
the local occurrence of palynomorphs. In total, these authors
defined a total of 6 Pantropical zones, 5 Transatlantic

zones and numerous local zones.

29

Regali et al. (1974a) defined a zonation for Mesozoic
and Cenozoic sediments from Brazil. The zonation has been
used as reference in palynological work in other areas
of northern South America.

Muller et a1. (1985) reported a detailed zonation for
the Cretaceous-Tertiary-Quaternary sediments of northern
South America, including Brazil. These authors recognized
a total of 10 Superzones and 31 zones that, when compared to
the number of zones recognized by Germeraad et al. (1968),
represent a continual refinement due to the experience accu-
mulated since the middle 1940's. These authors also recognized
8 zones for the Eocene, 5 of which have been determined in
the Misoa Formation, beginning with the Rugotricolporites
fglix (Lower Eocene) up to the Retitricolporites guianensis
(Middle Eocene) zones. The scope of this publication, how-
ever, is still limited, pending more complete analyses yet
to be published.

I-4-2. Paleoecological applications.

As previously noted, the unknown nature of the floras
existing during the Early Tertiary in northern South America
limits paleoecological studies. Flenley (1979) noted that
tropical floras are highly diversified and consist mostly of
angiosperms. This author, as well as Graham (1985), noted the
lack of extensive studies in the area, or at least, of avail-
able information. Frederiksen (1985) and Flenley (1979)
described different types of vegetation and correlated these

with the environments where they occurred. Frederiksen (1985)

30

acknowledged that for Early Tertiary palynological studies,
only two types of paleocommunities have been characterized;
a brackish water assemblage and peat forming swamps. The
principal factor permitting such a detailed characterization
is the high proportion of autochthonous palynomorphs present
in the sediments deposited in these environments. An excel-
ent illustration of this fact was presented by Cohen and
Spackman (1972). For other types of environments, the in-
terpretation becomes more difficult, due to a higher propor-
tion of allochthonous palynomorphs. Graham (1985) pointed
out the transport of large numbers of allochthonous pollen
to different environments due to the significant runoff
present in tropical areas.

Paleoecological analyses involving paleoenvironmental
interpretations have been reported in various publications
by Thomas van der Hammen, Thomas Wijmstra, Enrique Gonzalez
Guzman and Alan Graham. The following discussion will consid-
er some important aspects of paleoecological interpretations
in tropical areas.

van der Hammen and Wijmstra (1964), on their study of
Cretaceous and Tertiary sediments from British Guiana, ob—
served that marked fluctuations in the percentage of the
Rhizophora pollen were good indicators for the identification
of transgressive and regressive cycles. A diminution of this
type of pollen indicates regressive sequences, in which in-
land vegetation (swamp forest dominated by palms) becomes

more conspicuous.

31

Gonzélez Guzman (1967), in a palynological study of the
Upper Los Cuervos and the Mirador Formations in eastern Colom—
bia, was able to distinguish the transgressive sequences,
characterized by high proportions of the Brevitricolpites
group. This observation led Gonzalez Guzman to con sider
this group as an ecological equivalent, in a broad sense, to
the mangrove community. On the other hand, regressive se—
quences were characterized by the dominance of the Psila-
monocolpites group, or palms in general, as well as other
angiosperm pollen types and fern spores.

Wijmstra (1969), in a detailed study of Cretaceous,
Tertiary and Quaternary sediments from Surinam, used a simi—
lar approach for the determination of environments. The re-
sulting pollen diagrams reflected changes through all the
section, such as:

3) Towards the top of the section (mainly Pliocene-
Pleistocene), Wijmstra recognized the dominance of grass

pollen types corresponding to Byrsonima and Curatella, indi-

 

cating an open savanna-type of environment.

b) Below the sediments containing high proportions of grass
pollen types, Wijmstra noted sequences with marked changes
in the proportions of Rhizophora and palm pollen types.
These sequences contain minor amounts of grass pollen, indi-
cating a mangrove forest and swamp forest. The relative
proportions of each one are dependent on the transgressive
or regressive nature of these sediments.

c) Towards the lower part of the surveyed section, the palyno-

32

logical assemblages were observed to be dominated by palm
pollen types, other types of angiosperm pollen and fern
spores.

Due to the absence of the typical mangrove representa-
tives, such as Rhizophora or Avicennia, in the lower part of
the section, the paleoenvironmetal interpretation was more
difficult. Wijmstra (1969) used the so-called PAF (Palmae-
Angiosperm-Fern spores) diagram to infer the transgressive
and regressive cycles based on the variations of the propor-
tions of the palm pollen types. Regressive sequences were
observed to follow periods with maxima of palm pollen types.
Similar observation was made by Gonzalez Guzman (1967). The
general model proposed by Gonzalez Guzman is shown in Figure
14.

Other studies that have been done in Recent sediments,
include those by Wijmstra and van der Hammen (1966) in the
tropical savannas of northern South America, and by Salgado-
Laboriau (1979 and 1980) in the Venezuelan Andes and in the
Lake Valencia (central Venezuela). Graham and Jarzen (1969)
and Graham (1985) have also reported the results of studies
of neotropical communities in the Caribbean area and in
Central America.

Numerical clustering techniques have not been used for
the study of palynological assemblages of northern South
America. Due to the high diversity of the flora, these types
of technique can be useful for the better understanding of

the paleoecology and community structure.

33

.Asoas .caguao umdwneoo Cmuw<v
mowcmcu :ofiumuomm> wuocm tam cofiumsuusaw Hm>ma new no Hone: .QH muswflm

  
  

I '1;’9.'¢~v.':: '

asouu :
mmumeOUfiuufi>mum .

 

mzmme »

nacho III )llllI HP.
mmcfiufluzmzk @

mozmsomm m>Hmmmmomz<me

. o.-
Q=°HU 7 .2!!! .‘2.’JJD7....I \ F ”a.”
mmuflewouoeosmflflmm e elem; q 9 4+

 

 

 

 

 

 

 

|Il
‘UNUNINHIUJ

 

 

 

 

 

A»;
mmemmOHUz< mozmsomm m>Hmmmm0mm Wm
«mayo _ w“
Eagles;
oz<m mm“ muzmsomm m>Hmmmmumm .4

><qo _mu

II. MATERIALS AND METHODS

II‘1. Samples.

A total of 71 core samples from 3 wells of the Boscén
Field were selected by the Section of Biostratigraphy of the
Venezuelan Institute for Petroleum Research (INTEVEP S.A.).
The samples were selected according to their lithology (very
fine—grained sand and siltstone). The 3 wells are located in
an approximately NW—SE traverse in the southeast area of the
Boscén Field (Figure 15).

INTEVEP S.A. also provided electric well logs and litho-
logic descriptions of the 3 cores. It should be noted that
there is no regularity on the sampled intervals.

The samples were tightly wrapped in plastic bags, packed
and sent to the author of this study in July, 1984. The sam—
ples were assigned a maceration number and were transferred
to plastic containers.

II—2. Maceration procedure.

All samples were treated with the same general method.
The time of reaction varied for various samples. Lignite and
carbonaceous siltstone required longer time of reaction with
the Schulze's reagent. The procedure is as follows:

1) A brief lithologic description was obtained, taking into

consideration the presence of relevant sedimentological fea-

34

35

 

flz

BOSCAN
FIELD

 

 

B244

 

3252
‘B248

 

0 KM 10
L______J

 

 

Figure 15. Location of the three wells
under study in the Boscén Field
(After Axpiritxaga, 1985). The
location of the field within
the area of the Lake Maracaibo
Basin is seen in figure 2.

 

36.

tures. These observations were later complemented with the
lithologic information provided by INTEVEP S.A..

2) The drilling mud was removed by scrubbing the surface of
the sample with a hard brush.

3) Before crushing and weighing the sample, it was dispersed
on paper and divided into numerous pieces. Some of these
pieces were randomly selected for the maceration.

4) The pieces were crushed in a clean metallic mortar, until
fragments of 2-3 mm were obtained.

5) Using a balance, 5 gms of each sample were obtained and
placed in a previously washed 25 m1 plastic tube, marked with
the maceration number of the sample. In the cases of samples
yielding very low amounts of palynomorphs, 15 gms were used.
6) Approximately 15 m1 of hydrochloric acid (HCl, 10%) was
added to each sample. The samples were frequently stirred.
The reaction time was 1 hour and 30 minutes at room temper-
ature.

7) After this period, the samples were centrifuged at 2,000
rpm for approximately 5 minutes. After the centrifugation,
the supernatant liquid was discarded and distilled water was
added to wash out the remaining HCl. This process was re-
peated 3 times for each sample.

8) After rinsing free of HCl, the samples were treated with
hydrofluoric acid (HF, 52—55%) for nearly 18 hours at room
temperature. I

9) A similar procedure to the one described in step 7 was

used to wash out the HF from the samples. However, the sample

37

was rinsed with HCl (10%) once, and with distilled water 3
times.

10) During the last rinse with distilled water, the samples
were transferred to glass tubes, taking care to transfer all
the residue.

11) The samples were then left to react with the Schulze's
reagent, 5 parts of nitric acid (HN03) and 1 part of potas—
sium chlorate (KC103). The amount of reagent that was used
was determined by using a fixed liquid/residue height ratio
of 2. This ratio was used in order to maintain uniformity

in the treatment of all the samples. The time of reaction
varied, as it was previously noted, from 1 hour 30 minutes

to 6 hours, at room temperature.

12) Step 7 was repeated in order to remove the excess reagent.
13) Using the same liquid/residue height ratio mentioned in
step 11, potassium hydroxide (KOH, 5%) was added to the sam-
ples and left to react for 5 minutes. The samples were then
rinsed with distilled water.

14) Before using the heavy liquid, zinc bromide (ZnBr, spe-
cific gravity 1.91), the residues were rinsed with HCl (10%).
After discarding the excess of HCl, ZnBr was added to the
samples using a liquid/residue height ratio of 3:5. The
sample and the liquid were thoroughly mixed and centrifuged
for 2 minutes at 2,000 rpm. The supernatant liquid containing

the organic fraction was collected and diluted in HCl (10%)

38

in order to concentrate the organic residue. The excess HCl,
was removed by rinsing with distilled water.

15) 1 or 2 drops of ammonium hydroxide (NHAOH) were added to
each residue, in order to make it basic for the staining pro-
cedure.

l6) 2 or 3 drops of Safranin O (1%) were added and left to
react for 5 minutes at room temperature. Excess stain was
removed by successive rinses with distilled water.

17) The stained residues were sieved through a 10,Am mesh, in
order to remove undesired particulate material from the final
residue. Microscopic observation were done on the material
that passed through the mesh, in order to verify that no
palynomorphs were present.

18) The residues were transferred to vials and stored until
the moment of preparing the microscope slide.

II-3. Preparation of microscope slides.

In order to prepare microscope slides, each residue was
diluted in distilled water to a concentration that was deter-
mined to be suitable for avoiding any excess of organic res-
idue in the final slide. The total number of drops of this
dilution was determined by using a Pasteur pipette. The di-
lution was evenly mixed in order to get an uniform suspension.
Using the same pipette, an aliquot of the suspension was ob-
tained, and a given number of drops was added to a previous-
ly cleaned cover slip, placed on a hot table. Using a tooth—
stick, the suspension was dispersed on the glass cover slip

as uniformily as possible. The excess solvent was evaporated,

39

leaving a thin film of organic residue adhering to the cover
slip. Microscope slides were prepared by turning the cover
slip over and placing it on the glass microscope slide, using
Kleermount resin as the sealing agent. 3 slides were prepared
for each sample.

By determining the total number of drops of the dilution
(Dt) and the number of drops placed on the cover slip, an
estimation of the absolute number of palynomorphs can be
made, using the following relation:
- Since the number of drops per slide is known, and depending
on how many slides per sample were counted, a total number of
drops that were used (DC) is obtained. Using the absolute
frequency of the different palynomorphs (AC), an extrapolation
to the absolute number of palynomorphs in each sample can be

calculated by:

where At is the absolute number of palynomorphs in the sam-
ple. By dividing At by the weight of sample used for the
maceration, the absolute frequency of palynomorphs per gram
of sample can be estimated.
II-4. Counting of palynomorphs.

The counting was done using a Leitz-Wetzlar Ortholux

microscope. The whole cover slip area was observed, in most

40

of the cases.

It was determined that by using the 12.5 X objective
lens, one division of the coordinate scale of the microscope
was equal to a field of view. The counting of each slide was
always started at the upper left corner of the cover slip,
using the 12.5 X objective lens for the scanning. Detailed
morphological observations and identification of palynomorphs
were done with the 54 X and the 95 X oil immersion objective
lenses.

Because the highly variable abundance of palynomorphs
in the different samples (see next chapter), it was decided
to count up to a number at which no new type was recognized
for the next 60 palynomorphs observed. Counting of fungal
spores, hyphae and fructifications was kept separated from
the total of other palynomorphs.

II-S. Photographic material.

Photographs of the different palynomorphs were obtained
by using a Leitz-Wetzlar Orthomat automatic microscope cam-
era. The developing and printing were done at facilities
existing at Michigan State University, using standard tech—
niques.

II-6. Palynomorph diagrams.

The result of the tabulation of palynomorphs are present-
ed in palynomorph diagrams. These diagrams show the main
trends of the relative frequencies of the different groups
of palynomorphs.

Grouping of palynomorphs into different categories per-

41

mitted a better evaluation for paleoenvironmental interpreta-
tions. The approach used in designing the diagrams was simi-
lar to those mentioned in the previous chapter. However,
based on the results obtained, a different type of diagram
was used. The palynomorphs were included in 6 main categories:
a) Mangrove group; consisting of those palynomorphs that have
been typically characterized as being produced in brackish
water swamps. Muller (1964) defined the mangrove communtity
as the vegetation growing under tidal influence, in water

of fluctuating salinity. Similar definition was used by
Blasco and Caratini (1973), in their study of the mangrove

of Pichavaran, India.

Using the important information provided by Frederiksen
(1985), it was decided to include the following palynomorphs
as components of this mangrove group:

Echitriporites trianguliformis, Psilatricolporites crassus,
(Pelliceria, Theaceae), the Spinizonocolpites (Nypa) group,
and the Brevitricolpites group.

The description of these palynomorphs, as well as illus-
trations of all the palynological assemblage, are presented
in Appendices A and B.

b) Peltandripites sp. group; formed by a triporate, echinate
pollen grain of unknown botanical affinity, that was found
to be very conspicuous in Some samples.

c) Palmae group; including those pollen grains that were

attributed to this family.

42

d) SpOre group; including fern and other types of plant
spores.

e) Dinoflagellate-Algae-Foraminifera group; formed by the
following palynomorphs:

The dinoflagellate cyst identified as belonging to the genus
Operculodinium (Dr. J. Wren, personal communication), the
fresh water algae cf. Micrasterias sp., the fresh water algae
cf. Pseudoschizaea sp., and unidentified chitinous inner
linings of foraminifera.

f) General group; including those palynomorphs that were not
grouped in the previously defined categories.

A phylogenetic list of the palynological assemblage is
presented in Appendix B.

II-7. Cluster analysis.

Using the relative frequencies of the previously defined
groups of palynomorphs, calculations of the Similarity Index
used by Jameossanaie (1983) were performed. The calculations
involve two-by-two comparisons of the different samples under

study, and the determination of chi—square values as follows:

 

 

 

SAMPLE No. GROUP A GROUP B ...... GROUP K ROW TOTAL
1 x81 ' xb2 ...... xk1 N1
2 X32 sz . .. sz N2
COLUMN TOTAL x; Xé ...... X'k N'
where Xal, Xb1,... and sz represent the relative frequencies

43

of the different groups of palynomorph in each sample.

 

 

 

 

 

 

a x’/N x’/N X'/N
X=(—-—‘}—+-—-—'3-—+...+ lf)-N'
Pa Pb Pk
where: X2 x’
a a
2 1 2
Xa/N = ( + )
N1 N2
2 2
. be sz
xb/N = < + >
N
1 N2
0 2 2
xk1 xk2
xi/N - ( + )
I
N1 '‘2

and

In this analysis, the chi-square values are considered
as coefficients of similarity, regardless their level of sig-
nificance. Then, the values of chi—square were converted

into Similarity Index (8.1.) values by:

xzmax

a . .
where x:is the calculated value of chi—square for each two—by-

44

two comparison, and afggx is the highest value of chi-square

among all possible comparisons. This index ranges from O to
1 (1 indicating maximun similarity).

The calculations were performed using a BASIC program,
implemented for personal computers by Dr. A. Jameossanaie.
The results are presented in a dendrogram showing the differ-

ent clusters.

III. RESULTS

III-1. Abundance of palynomorphs.

A general clasiffication was used to describe the ap—
proximate abundance of palynomorphs in the different samples:
- Very low abundance; 1-100 counted palynomorphs per sample
- Low abundance; 101-200 counted palynomorphs per sample
- High abundance; 201-300 counted palynomorphs per sample
- Very high abundance; 301 or more counted palynomorphs per
sample.

Out of the 71 samples studied, 6 (8%) were barren of
palynomorphs, 27 (38%) were found to have very low abundance,
17 (24%) had low abundance, 15 (22%) had high abundance and
only 6 (8%) had very high abundance.

The absolute abundance or number of palynomorphs per
gram of sample was calculated according to equation 2
(refer to page 39). The values for the different samples in
each well are presented in Tables 1, 2 and 3. The absolute
number of palynomorphs per gram of sample is quite variable,
as evidenced in the large values of standard deviation pres-
ented for each well in Tables 1-3. Larger number of palyno-
morphs seem to have been recovered in wells B244 and B248
(see calculated averages of the number of palynomorphs for

each well).

45

46

A~.Nmm no can m.sss um
.«qmm Ham: pom Au<v mHaemm mo Emuw no; mnauoeocaam

v
a mo Lassa: musaomn< .~ manmfi

 

 

 

 

 

 

 

 

Noe.~ m m mms omm =s.soeo
as AH om o~_ 0mm =m.sws¢
NH ms cm as mm =Hs.mkso
mm mm cm ms_ ~e_ .mmso
om ms om wk mks =ss.qwso
ls ms om am New =~.m~so
ms ml cm as ems =~.asso
o ms am mm o =o_.o_so
0 mm on mm o =s.cosa
0 ms cm mm o =a.soso
0 mm on mm o =k.momo
an ms om mms omm =N.oamo
n ma cm as am :os.okma
omN as «N mes osN =m.oc~o
Ems ms ms m~s mms =H.esma
a v ms cm on m =~.m-o
a ma cm as me =H.ooNa
ea As om oh all =~.mo~o
om ms om om cos =~.HoNo
ems ms ms ems mNN =os.wmsa
Na ms on so am =~.mmso
em as am ems osm =~.Hsso
mm ms cm ma ama =m.kcoo
AN mg on HA sea =k.wmoo
mm ms am wk so =s.mmoa
Au<v amm: Auav Apes Au<v Aemmmv
mmamozozssaa m4a2<m 9mm: onmzmamam mnemozozssaa zsamn
mo ammzaz mo maomn so a 3<HstH Lo amezsoo maaz<m
msaqomm< mzamu maomo we a mo ammzsz

 

 

47

Aw.~0¢ ”D van H.OON n
.wqmm Ham: you Au<v maqemm no swam Cog mnauosoczam

v
W «0 Conan: muaaomn< .N manmh

 

 

 

 

 

 

 

 

mm ms ms Hm mes =k.smso
mm ms ms me am =c.okso
mm ms ms HA mm =m.mkqo
sol ms ms so ohm :e.acso
mok.s m m as oms =m.moso
em ms «N mo cam =HH.~mso
mom ms oz Nos Now =m.wsqa
em ms on ma omz =k.msso
Noe m oz No «He =zs.moso
m ms am an as =m.smmo
Hem m om mo «ms =o.Hmmo
Ema m oz mo «mm =m.m~mo
0 ms cm mm o .smmo
a mm on em «a =Hs.mm~o
w ms cm mm mo zm.sm~a
No ms ms an mam =H~.~c~o
mm ms on mm «as .emmo
woo m oz me can =-.os~o
ks ms cm so mos =o.oa~a
mm mm on no mam =n.ommo
mm mm on om 8mm =m.~m~o
mm mm am we oss =m.m¢~o
ms ms cm an «m =a.Hk~o
as ms om so He =A.Hs~o
0 ms am mm o =s.mooo
NH ms om as we =s.mmoa
alas Aunv Aunv Au<v Aemmav
mzamozoz>4<a cam: gum: onmzmamsm mzmmozozsq<a menu:
.aummmzaz maaz<m mo mnemn no * S<HeHzH mo amezsoo maaz<m
meaqcmm< mz<mo mmoma mo * mo mmmzaz

 

 

48

A©.o~ no can ~.m~ uwv
.Nmmm Ham: you Au<v maaemm «o Emuw uma mzquoeocaama mo penezc musaomn< .m manme

 

 

 

0N ms om Na oss =w.wNaN

ON As on ma oss =w.mNow

oN ms om ow NHL =S.NNaw

am As om mN we =m.Neow

mm ms on all soN =os.wsow

H ms om em ml =c.sNoN

s v ms om mm N =s.Nomm

N ml om cs HN =N.soww

a ma on Na Nm zm.Nmmm

No ms om oos mNN =N.N¢Nm

w ms on so as =N.omom

N ml om me me =s.ooow

NH ms om mm Na =m.chm

N As on so as =N.ssow

N ms om om mN =N.ssom

mm ms om all . mNN =o.NNom

N ms om os as =o.mNmN

NH ms om EN Nos =oz.mNmm

H v mm on em w .mmmm
AI<V Auav Away Au<v AHNNLV
mmaNOZOZNaaa mam: amm: onmzmamsm mzamozozssaa zeama
so mmmzaz maaz<m so maoma so a 3<NHN2H No amszsoo msaz<m

r mesaomma mzamo maoma mo 4 mo Nmmzaz

 

 

 

 

 

 

 

49

III-2. Sedimentological and palynological results.

In this section, detailed descriptions of the sedi-
mentological and palynological characteristics of each well
are presented. The lithologic descriptions, as well as the
determinations of the different intervals corresponding to
each sedimentary environment, are based on the information
provided by INTEVEP S.A. and the characteristics of the SP

curves for each well.

Well 8244.
a) Sedimentology.

In this well, as in the others, two genetic sedimentary
units were recognized. In the lower part of the recovered
core, from 9492' to 9364'6", deposits are characteristic of
a low deltaic plain. Overlying them, deposits characterized
as being deposited in an upper deltaic plain occur (9364'6"
to 9026").

In each genetic sedimentary unit, it was possible to

identify different sedimentary facies:

- Low deltaic plain deposits;

Crevasse splay deppsits (9492' to 9486' and 9415' to 9396'),
characterized by fine-grained sandstone with laminations of
silt. Laminations are irregular (not parallel) for most of
these intervals. Sideritic nodules and zones occur. Sand—

stone is oil impregnated and relatively massive.

50

Interdistributary plain deppsits (9486' to 9475'), charac—
terized by dark siltstone, with laminations of fine-grained
sandstone.

Distributary channel deposits (9475' to 9456'4"; 9456'4" to
9424' and 9424' to 9414'), characterized by basal sandstone
showing erosional contact with underlying fine-grained sedi—
ments. The three intervals seem to represent sequences of
abandoned distributary channels, because of the continuous
and significant decrease in grain size towards the tOp of
each interval. High-angle cross bedding (20° to 30°), ripple
marks and some carbonaceous laminations also occur.
Distributary mouth bar deposits (9396' to 9364'6"), charace
terized by the transition from fine-grained sand and silt-
stone, to massive coarse-grained sandstone towards the top
of the interval. As Coleman (1982) noted, deposits of a
distributary mouth complex show a tendency of becoming
coarser towards the top, resulting in the typical "bell"
shape of the SP curve. This feature is shown in Figure 16,

that presents the SP curve of this well.

- Upper deltaic plain deposits;

Meander bar deposits (9364'6" to 9308'4"; 9308'4" to 9270';
9200' to 9134'7"; 9134'7" to 9110'; 9110' to 9051'6" and
9051'6" to 9026'), characterized by relatively massive sand—
stone, with decreasing grain size towards the top of the
sequences. Cross-bedding (10° to 30°), ripple marks and

silt clasts are the most evident sedimentological features.

51

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0 SP (4V) 100
MEANDER BAR
'9100

MEANDER BAR E
<
.J
On
MEANDER BAR U
H
<
53
F9200 m
G
ABANDONED CHANNEL N
E
O-
D

MEANDER BAR

’9300

MEANDER BAR

DISTRIBUTARY

MOUTH BAR
F9400 z
CREVASSE SPLAY :
DISTRIBUTARY CHANNEL, :
DISTRIBUTARY CHANNEL 3
DISTRIBUTARY CHANNEL :
INTERDISTRIBUTARY PLAIN i
Q
CREVASSE SPLAY g
.—1

 

 

 

 

Figure 16. SP curve and environments of sedimentation-
Well B244.

 

52

Sideritic nodules and zones, bioturbation (mostly burrowing)
also occur. This type of deposit constitutes the largest
proportion of the sediments inferred to have been deposited
in an upper deltaic plain. The SP curve clearly shows the
thick sequence of sandstone in this interval.

Abandoned channeI‘deposits (9270' to 9200'), characterized
by sandstone sequences, with progressively decreasing grain
size towards the top of the interval. At the bottom, the
sandstone is relatively massive, with high-angle cross-bed-
ding (25°to 30°). Laminated siltstone and layers of lignite
occur towards the top, indicating the progressive abandon-
ment of the channel. Sideritic zones and nodules also occur
in this interval.

Figure 17 presents the lithology of the surveyed core
and the locations of the samples that were processed for
the palynological study.

b) Palynology.

In general, the palynological assemblages observed in
samples of this well are relatively homogeneous. There is a
tendency for larger recovery of palynomorphs and more diverse
assemblages (roughly measured by the number of different
types identified) in samples of the lower part of the section
under study.

Table 4 shows the percentages of the different palyno-
morph groups, and Figure 18 presents the palynomorph diagram
for well 3244. Important trends to be noted are those of

the Mangrove group, the Spore group and the Palmae group.

53

Figure 17. Lithology of the core of well B244

 

 

 

 

 

 

 

 

§

SAND

SILT

LEGEND

I LIGNITE

CORE WAS NOT RECOVERED AT THIS
INTERVAL

 

 

CROSS-BEDDING .é)‘\ RIPPLE MARKS

- . CARBONACEOUS NODULES

90 2 6 ' .---.-:-' 3: 33:.-

2//

 

 

 

 

 

0

FEET

15

Figure 17-a. Lithology of the core of well B244

(continued)

9100'- II.'

//

20°

 

 

.:fl.i:.

54

PB14239 (9055'4"); fine-grained sand with
carbonaceous material and micaceous plates.

P813994 (9058'7"); fine-grained sand inter-
calated with silt.

PB1398OAI9076'3"); fine-grained sand inter-
calated with silt and carbonaceous materi-
al.

D P314238 (9111'2"); massive gray silt with
carbonaceous material.

 

PB14237 (9135'2"); fine-grained sand inter—
calated with silt.

 

 

 

 

 

PB14236 (9188'10"); fine-grained sand with
carbonaceous nodules (fusain and resinite
present).

 

PB14233 (9201'2"); massive gray silt.

Figure 17-b. Lithology of the core of well B244

(continued)

55

PB13995 g9205'1"2; massive gray silt.

 
   
 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

- — -.- P814232 (9209'1"); gray silt intercalated
with fine—grained sand.
PB14231 (9213'1"); fine-grained sand inter-
calated with gray silt.
'. B13996 (9217'1"); lignite.
30° 1 It 1..
I.’.:'
- - ~ .'
§ '.‘ .‘ ,I ‘- I
30° 1.27;;
-3".
m --_-;',°;.':. P813998 (9266'S"); massive fine-grained
4:??Sfix}. sand with carbonaceous nodules. . .
s I” _H. P814234 (9270 10 ); ma551ve gray Silt with
395-5:'- carbonaceous nodules.
¢f|§ ; .I‘l'
10° ‘ . -.
9300'-
% ..'._i_'.._,
450 ;-.7":"T:.‘.
‘t .:
20o :I':I-

Figure 17-c. Lithology of the core of well B244
(continued)

56

9364'6'3. ', 3‘31:

 

 

//

 

 

 

 
   
  
    
 
    
 

30° .-:.5.;; P814230 (9390'2"); fine-grained sand inter-
" calated with silt. Sideritic nodules occur.

\ --'.-*.-.-+'- P313999 (9393'7"); laminated gray silt.

20°. 57-"- ‘3."

9400"~ 33' P814222 (9401'9"); fine-grained sand inter-
" calated with silt.

PB14223 (9406'4"); fine-grained sand inter-

calated with gray silt.

PB14224 (9410'10"); laminated gray silt.

PB14225 (9419'2"); gray silt intercalated

with fine grained sand. Sideritic nodules

occur.

PB14226 (9423'2H); gray silt intercalated

with fine-grained sand.

PB14227 (9424'll"); fine-grained sand with
carbonaceous nodules.

//

ME _'._' .P313981 (9458'); laminated gray silt with
- carbonaceous material.

 

 

P314228 (9478'11"); massive dark-gray silt.

PB14229 (9484'8"); massive dark-gray silt.

 

 

9492' P313997 (9491'4"); relatively massive dark-

gray silt.

Figure 17-d. Lithology of the core of well B244.

57

mo moaasmm mpou ecu cw mnquoeocaama we masouw ucmumwmwc mcu mo mmwmucmuumm .q manmb

.Amcmswumqm m cmcwmucou sacs mHaEmm mfizu *v «cum Ham:

 

 

 

 

 

 

 

 

 

s e SH as N aN =S.Haea
H HH NH aN HH am ew.emea
H NH NN me 0 SN eHH.mNsa
0 EH NH me e mH .mmea
SH mH NH om oH NH eHH.eNSa
H NH eH NS SH 0 eN.mNsa
H oH SH Ns NN HH =N.aHsa
o o o o o o eoH.oHea
o o o o o o =3.eosa
o o o o o o sa.Hosa
o o o o o o =N.Nama
o eH SH Nm NN eH eN.oama
o oN o Nm SH SH eoH.oNNa
N Nm oN SN 0 m =m.eeNa
e aH Hm Hm NH H =H.NHNa
o o as as o o ssH.mHNa
e mm HN eN NH N eH.eoNa
e mm oH cm H o eH.moNa
eH mN NH mm m N =N.HoNa
e m m oN cm eH eoH.NwHa
O OH N as mN m =N.mmHa
N NH m eN oe NH eN.HHHa
N NH a Nm NN NH =N.Neoa
N NH NN eN mN e =N.mmoa
H NN N aH oN HN =3.mmoa

isomo anomu «amass
.zemoa anomo aaomu aaoau .am mmeHaHm aaomu zaams
N<OH<IozHa macaw m<2H<a Hemmzmo -azesHma m>omoz<z mHazem

 

 

DC?!”

SAMPII

(If!!!

(If)

I00
«Jun
-'D'I'

906‘ 3'

911‘ 2'

91359

918810"

92C12'
92551”
92091

92131'
92ITI"

93902

9419‘2'
9423'2',
942411

9455‘

94 7 5'11‘
9484'8’

9491' 4‘

1.5.

58

PIICINVAGE
IO 20”‘OSOOO 7O IO’OIOO

 

r72: nuauoavnns it c.

 

m1;

L\\III '1‘ Ill]

._

 

mu,” nu:

 

Film? r11 Irl

 

I244. Pg! ynomorph the. '0 m

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

r mxxxxlxix 11111—3
:1 M
I
W r‘\x\\xxxlxxm1111L:n
mn— unuuu
l
.
will”: :Esmw
.
m J‘-\\‘IILL-
m: m

 

 

I

11 mm

 

I!

(ft). GCNIIAI 0.

C1173 IIGAI" DINO. - IOIAM. GROUP

6.

unnriPOl'

6.

- MANGIOVI

R'T‘i‘ PAIM‘I G.

We”

'0'.qu I. .

59

In general, the percentages of the Mangrove group tend to
decrease towards the middle of the section, passing from
29-39% to only 1-2% at 9266'5", 9217'1", 9209'1" and 9210'2".
It can also be observed that the proportions of the Spore

and the Palmae groups, relatively constant towards the bottom
of the section, increase in the same interval at which the
percentages of the Mangrove group decrease. An opposite tend—
ency is observed at the top of the section. It should be
noted that the drastic decrease of the Mangrove group occurs
at the approximate level at which deposits corresponding to
an upper deltaic plain begin to be observed.

The percentages of the Dinoflagellate-Algae-Foraminifera
group varied throughout the section, but they are a very
small part of the total assemblage, both in absolute number
and in the number of different types. The main palynomorphs
included in this group and found in this section are the
fresh water algae Micrasterias sp. and Pseudoschizaea sp..
The dinoflagellate cyst Operculodinium sp. was observed in
only one sample (9111'2").

The number of different types and absolute number of
pollen grains related to grasses is very low in all the

samples.

Well B248.
a) Sedimentology.

As in the case of well B244, two genetic sedimentary

units were recognized:

6O

- Low deltaic plain deposits (9485' to 9355");

Crevasse splay deppsits (9485' to 9445'6"), characterized by
relatively fine-grained sandstone with laminations of silt-
stone and carbonaceous material.

Distributary channel deposits (9455'6" to 9407'), charac-
terized by relatively massive fine-grained sandstone, show-
ing an erosional contact with the underlying fineegrained
sediments. Cross-bedding (20°) occur. Unlike the sequence

of well B244, the diminution of grain size is not as great,
suggesting that this sequence represents deposits of an
active distributary channel.

Distributary mouth bar deposits (9407 to 9353'), charac-
terized by the transition from fine-grained sediments (silt-
stone) to laminated sandstone-siltstone towards the top.
Meander bar deposits (9348' to 9264'; 9215' to 9203' and
9181' to 9104'), characterized by relatively massive sand-
stone with high-angle cross-bedding (20°), intercalated with
siltstone laminations. A sequence characteristic of an ox-
bow lake occurs in the interval 9299'-9281'. This sequence
consists of massive basal sandstone, exhibiting decreasing
grain size towards the top. Well-laminated siltstone occurs
at the top of the interval, suggesting the progressive
abandonment of the meander channel and the progressive
isolation of the ox-bow lake.

Natural leveé deposits (9264' to 9259' and 9203' to 9195'),
characterized by fine-grained sandstone with intercalated

siltstone, clay clasts, Sideritic nodules and ripple marks.

61

Flood plain deposits (9259' to 9230'), characterized by gray
siltstone showing convolute bedding in the lower part of

the interval; becoming more massive towards the top.
Abandoned channel deposits (9100' to 9056'), characterized
by sandstone sequences, with decreasing grain size and bio-
turbation towards the top. Laminations of carbonaceous mate-
rial and cross-bedding (10°) occur in the basal part.

The SP curve is shown in Figure 19 and the lithology of
the recovered core is presented in Figure 20.

b) Palynology.

As in well B244, the assemblages throughout the section
are relatively homogeneous. The same tendency for more di-
verse assemblages towards the lower part of the sectiOn was
also observed.

Table 5 and Figure 21 present the fluctuations of the
percentages of the different groups of palynomorphs. As in
well B244, the percentages of the Mangrove group decrease
drastically towards the middle of the section. Again, this
dimunution of the abundance of this group roughly coincides
with the approximate level at which characteristic deposits
of an upper deltaic plain begin to be observed.

The percentages of the Palmae group and the Spore group
are more variable than in well 8244 and do not show similar
tendencies to those noted in well B244. However, the Palmae
group seems to increase in frequency in the interval at

which the Mangrove group abundance diminishes. The Spore

62

 

 

 

 

 

 

 

 

 

 

 

 

 

0 SP (MV) 100
ABANDONED CHANNEL
-9100

Z
0—4
4;
:

MEANDER BAR
U
H
<2
E-*
:3
~9200 NATURAL LEVEE Q
MEANDER BAR m
NOT RECOVERED E
On
FLOOD PLAIN 3

NATURAL LEVEE

~93OO
MEANDER BAR
DISTRIBUTARY
MOUTH BAR

2
H
"9400 j
0..
DISTRIBUTARY CHANNEL 8
E
a
CREVASSE SPLAY E
3
O
.._1

 

 

 

 

 

Figure 19. SP curve and environments of sedimentation-
Well 8248.

 

63

Figure 20. Lithology of the core of well B248.

LEGEND

 

 

 

 

SAND - LIGNITE

SILT Egg: CORE WAS NOT RECOVERED AT THIS
H _ , INTERVAL

 

 

 

 

 

Q CROSS-BEDDING [9,, RIPPLE MARKS

O O CARBONACEOUS NODULES
0

FEET

15

9055'«

PB14128 (9058'4"); gray silt intercalated

with fine-grained sand and carbonaceous
material.

 

 

 

 

 

Figure 20-a. Lithology of the core of well 8248

(continued)

§
10° —.--.-.
91002
\\ ‘ ' ".
10° a ' :. 1. a
\\ ‘H...’ .
+=.-‘.-'-
100 7......:

9200'-5.. a. :5.

10°

 

 

 

 

 

 

64

7.6.5-3".3. P813982 (9095'4"); fine-grained sand inter-

calated with carbonaceous nodules.

2. P814000 (914l'7"); fine-grained sand inter—

calated with gray silt.

p P814129 (9171'92); fine-grained sand with

carbonaceous material.

 

 

.‘T'P814127 (9198'3H); gray silt with Sideritic

nodules.

 

 

 

 

Lithology of the core of well 8248
(continued)

65

P814001 (232'3"); massive gray silt with
carbonaceous material and sideritc nodules.
P814186 (9236'7" ; massive dark-gray silt
with carbonaceous material.

814187 (9240'9"); massive dark-gray silt
with Sideritic nodules.

P814188 (9246'11"); massive dark-gray silt.

  
 
 
    
 

P814189 (9257'); dark'gray silt intercalated
with fine-grained sand.

P814002 (9262'11"); fine-grained sand with
carbonaceous material.

 

 

 

.. ,. . P814190 (9281'3" ; Sine-grained sand inter-
" “ ” calated with gray silt. Sideritic zones

—-_-‘-°'—' occur.
.777; PB14003 (9288'11"); massive dark-gray silt.

 

 

20° 1. :_'.° 3:...

9300‘ '
:- a....:‘
u a;

 

 

 

 

 

9355u,f?{2r;. P314191 (93541); massive gray silt.

200 . : °..'.. .

 

 

 

 

,i2_ii=H[»P31aooa (9375'531; dark-gray silt.

P814198 (9381'6"); massive dark-gray silt
with Sideritic nodules.

Figure 20-c. Lithology of the core of well 8248
(continued)

9400'“

‘3 //

9485'

66

P814197 (9384'4"); massive dark-gray silt

 

 

 

 

 

 

 

 

O
._.—'-.

 

with Sideritic nodules.

r P814192 (9405'111); dark-gray silt.

P814193 (9445'7"); massive gray silt.
P814194 (9448'8"l; massive gray silt.
P814005 (9452'11"); massive gray silt.

P8141954(9463'3"); massive gray silt
P814196 i9469'7")3

P813983 (9473'3"); fine-grained sand with
carbonaceous material.

P814199 (9479'6"); gray silt intercalated
with fine-grained sand.

P814200 (9484'7"); gray silt.

dark-gray silt.

Figure 20-d. Lithology of the core of well 8248.

67

.mQNm HHmz

 

 

 

Ho mmHaemm muou mag :H masouw mnauosoczama ucmeHHHu mnu Ho mmwmucouHmm .m anm%
n NH o «m H Nm :m.¢wqo
m 0H 0. Nm 0 mm :o.omqo
c 0N OH Nm H «N :m.mmqo
H 0 NH om HH mm :N.ooqo
m q 0N mm mH mN :m.moco
H NN mH Hq N HN :HH.quo
N HH 5 mm m NH =w.mqqo
O NH m oq N mm :n.mqeo
N 0N oH cm 0 NN .moqo
q mm o as o o =w.<wmo
H mN q mm o mN =©.meo
o HN m NN m mq :m.mmmo
o o o o o o .qmmo
o NN «H so 0 o :HH.wwNo
w mN w Hm m m :m.HwNo
q OH «H we NH 0 :HH.NcNo
H «m wN mm q o .NmNo
q mm NH mN m 0H =HH.cQNo
NN 0H NH ow o o :0.0QNO
m mm «H ow H N :m.omNa
m «m HN cm H m :NHNMNo
H mN mN om o H :m.moHo
o NH ON ON m ON :m.HnHo
c «H m cm 0H s :N.Hqu
o o o o o o :q.mooo
0H m o Nm 0 NH :q.wmoo
asomu asosu Hemmav

.z<mom maomo macaw macaw .mm meHme macaw =Hmma
m<UH<IozHo mmomm m<24<m H<mmzmo Imz<HHmm m>omoz<z mqmz<m

 

 

 

 

 

 

 

 

DIPIH

SAM'II

(I!!!)

90534

91417"

91983.

9232'3

92367
Q2409'
92461f

9257
926211'

92813'
92881f

93’55'
93816‘
938:6’

9405‘

9484'7‘

68

 

 

 

 

 

PENCENFAG‘

IO 2O 30 40 50 60 7O .0 9 '00
r_._,_._ _. . . . . . _..__
i
I
m m
I
I
I

m
—1111 L\1xlu

 

 

 

 

In

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

.: L\\‘uxxxnxx111111@
9 L\\V111xllxrr _—n
i L\\‘III uhllnmm
L—s ;:j:SSS:==::n:nI
I

I

I

I

I

I

A H

__ nxwvuumnnmxn

 

 

 

 

 

k\\‘lllllIIllEn

 

I

CINIIAI O.

I. J

C

m“. near- omo - IORAM

[77112 PIIIANDIIPHUS SP. 6.

[11.1.1]! S'OI I O.

— MANGIOV! O.

LEW“ 'AIMAI 6.

it I. can

DO'yflOMOIph

3' We" .24.;

"'00.

69

group is more erratic, but there is some increase in its
abundance towards the middle-top parts of the section.

The abundance of the Dinoflagellate-Algae-Foraminifera
group is quite variable for most of the section. The maximum
value of abundance of this group, was observed at 9240'9"
(23%). At that level, it is composed of only the fresh water
algae Micrasterias sp.. The only dinoflagellate cyst in this

well was that of Operculodinium sp., at 9463'3".

Well 8252.
a) Sedimentology.
As in the other two wells, two genetic sedimentary

units were distinguished:

—Low deltaic plain deposits (8979'5" to 8921');

Crevasse splay deposits (8979' to 8967'), characterized by
laminated fine-grained sandstone and siltstone, with irregu-
lar laminations and ripple marks.

Distributary channel deposits (8967' to 8948' and 8948' to
8921'), characterized by basal sandstone showing erosional
contact with the underlying fine-grained sediments. As in
well 8248, the decrease in grain size towards the top is
small, suggesting that these deposits represent sequences of

active distributary channels.

- Upper deltaic plain deposits (8921' to 8555');

7O

Meander bar deposits (8921' to 8869'/ 8852' to 8788' and
8788' to 8753'), characterized by sandstone with high—angle
cross-bedding (20° to 30°), ripple marks and some inter-
calations of gray siltstone. The sequences contain sideritic
zones and nodules, and bioturbation by rootlets and burrow-
ing.

Natural leveé deposits (8869' to 8856'), characterized by
gray siltstone, intercalated with laminations of fine-grained
sandstone. The sequence contains sideritic zones and nodules,
ripple marks and bioturbation.

Crevasse splay deposits (8735'6" to 8600'), characterized by
intercalated fine-grained sandstone and siltstone. Sandstone
is relatively massive and shows sideritic nodules. Bioturba—
tion by rootlets and burrowing occur. Sandstone sequences
are thicker in this sequence than in those described for the
low deltaic plain deposits.

Abandoned cahnnel deposits (8600' to 8551'), characterized
by basal sandstone with distinctive erosional contact with
the underlying sediments. Basal sandstone is mostly massive,
showing high-angle cross-bedding. Grain size decreases
markedly towards the top. A lignitic layer occurs near the
tOp of the section, indicating the progressive abandonment
of the channel. A clear indication of the low energy envi-
ronment is provided by a dicotyledon leaf compression,

that is undistorted at 8644'2". Siltstone towards the top

is well-laminated.

The SP curve and the lithology of the recovered core of

71

this well are presented in Figures 22 and 23.
b) Palynology.

Table 6 and Figure 24 show the fluctuations of the rela-
tive abundances of the different groups of palynomorphs. Sim—
ilar tendencies to those reported for well 8244 and 8248, in
regard to recovery and diversity of assemblages, were observed.
However, the recovery and preservation were the poorest of the
three wells under study.

Unlike tendencies observed for the other two wells, the
percentages of the Mangrove group shows a more erratic
distribution. In the lower part of the section, the abundance
remains relatively constant, and decreases drastically at
8867'4" and 8857'5". Towards the top, the abundances of this
group tend to increase, with maximun values at 8792'8" and
8622'9". Those were also the samples with the largest amount
of palynomorphs recovered in this well.

Another important tendency is shown by the so-called
Peltandripites sp. group, that is observed to be very a-
bundant towards the top of the section.

The Dinoflagellate-Algae-Foraminifera group also shows
significant variation, composed mainly by the fresh water

algae Micrasterias sp.. The only specimen of Operculodinium

 

 

sp. was observed at 8573'10".
Unlike those tendencies observed for the other two wells,
the abundances of the Spore group and the Palmae group were

observed to decrease towards the top of the section.

72

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

-160 SP(MV) 40
ABANDONED CHANNEL
r8600
CREVASSE SPLAY 2
H
<
.4
D.
”8700 3
<1:
E-4
._1
Cd
NOT RECOVERED Q
E
MEANDER BAR E
D
#8800
MEANDER BAR
NATURAL LEVEE
v8900 MEANDER BAR
DISTRIBUTARY CHANNEL E32
23::
DISTRIBUTARY CHANNEL .353:
CREVASSE SPLAY 9
Figure 22. SP curve and environments of sedimentation-

Well 8252.

 

73

Figure 23. Lithology of the core of well 8252.

 

 

 

 

 

 

 

SAND

SILT

LEGEND

I LIGNITE

CORE WAS NOT RECOVERED AT THIS
INTERVAL

 

 

 

 

§ CROSS-BEDDING If}, RIPPLE MARKS
. . CARBONACEOUS NODULES

8551'

FEET

15

 

uni-0'..-

p--
——-

 

 

H P814041 (8558'); gray silt with sideritic
zones,

 

P814042 (8573'10"); lignite,

Figure 23-a. Lithology of the core of well 8252

30°

8600'

8700'

74

P813984 (8575'6" ; dark colored fine-grained

 

sand,

 

 

§P3139784862rwn dark-gray silt-

' rvP814043 (8644'2"); fine-grained sand inter-

calated with silt. Carbonaceous material
and leaf compression occur.

-3 "P8140444(8652'5"); fine—grained sand inter—

calated with silt.

 

P813985 (8669'4"); fine-grained sand inter-
calated with silt. Organic nodules occur.

 

 

 

.-iBIP814045 (8686'2"); dark-gray silt with

carbonaceous material.

gfir P813986 (8698'2"); fine-grained sand with

carbonaceous material.

 

Figure 23-b. Lithology of the core of well 8252

(continued)

 

Bl//

8800"‘R---'

 

 

§ .J

20° .Jé 3::
it: , :

35° ;-'1.:?

 

 

 

 

 

 

Figure 23-c.

P813987 (8735'8");

nodules.

75

gray silt with sideritic

P813988 (8792'8"); dark-gray silt with
carbonaceous material.

P314108 (8857'5"l:
P814109 (8861'7");

P813989 (8867'4");

ZODBS.

dark-gray silt.
dark-gray silt.

gray silt with sideritic

Lithology of the core of well 8252

(continued)

76

 

§ 3...... L...
300 . .0. ..-.. :°
8900' " 2.2
8921'

 

§ ‘I:—:=-_‘_—"__-_b P314122 (8921'6"); dark—gray silt.

 

 

 

;¥—;¥%7 P814123 (8948'10H); gray silt intercalated
"' '--‘ with fine-grained sand.‘

 

 

P814124 (8967'3"); laminated gray silt with
sideritic nodules.

P814125 (8972'4"); fine-grained sand with
intercalated silt.

P813979 (8975'8"); dark-gray silt.

P814126 (8978'8"); gray silt intercalated
with fine-grained sand.

 

 

 

8979'

Figure 23—d. Lithology of the core of well 8252.

77

.Am:OEwumam N NHco Omcwmucou mHaEmm mHnu *** HmcmeHumqm mN HHco c0

lawmucou mHaEmm mwzu ** “mameumqm w Omcwmucou NHco maqemm mfise*v NmNm HH03

mo mmHaEmm muou mnu cw mnauoeocaHma mo mason acmumwmww ozu Ho mmwmucmuumm .O mHan

 

 

 

 

 

 

 

 

 

H ON MN Hm OH mH :w.mNOm
O Om mH Hm NH «H :m.mmow
H OH mH mm OH NH :MHNNOO
O NH mH mq O NH :m.noow
N mH HH mN Oq HH =OH.quw
O OO mH 5N N mH :O.HNOO
O ON O mm «H O ***:q.noww
q me OH me O O :N.Homm
N mm OH «O O O :mHwaw
m HN O mH ON ON :w.NONw
O OH O NN Nm OH :w.mmnm
m mN OH ms N O :N.moom
HH OH O Nq NH N :N.Om©m
HH O H mN mm NH :c.OOOw
m ON q me NN w :m.Nmom
q NH 8 ON 00 O **=N.qqcm
H mH N mH sq NH :O.NNOm
HH OH N mN mm O :O.mmmm
q N < mH O8 HN :OH.mmmw
O HO mH NH O mH #:m.wmmw
macaw maomu Ahmmmv
.2<mom macaw macaw maomo .mm mMHHmHm macaw 28mm:
m<OH<IOZHO mmomm m<24<m H<mmzmu IOz<HHmm m>omoz<z m4m2<m

 

 

DIP!”

”I!!!

SAMPlI

78

PEICINYOGE
IO 20 x 40 $0 60 70 .0 ”I10

 

   

 

 

 

E: 5 5 E 3 _“\uaaaaaaaaaaaaaaaaaa-aaaaaaaoaaaauu
E 5 I 3 ‘C '

_, In A 14 w unu- n- m
=3 =' f 1: PM 1.2.-- [in at.— 31.11 w;

 

‘T _.-

 

fl A
be ‘ c 9 mlilil [wuy11 \aaoaaaaa

as“ 2

 

 

IIIIL'IIIIIIII 11 IIIIIIA Ill m
86 52 5 ill—111711 K‘llllnlm

566“ 'me‘u‘a—m

 

 

 

8686?

 

 

 

 

F11-
8696 2 'm -“‘.‘...........-..
p

 

873 s a min”; m

 

 

8:926

I

 

88's.~ 5 W
8861 7

 

    

 

.....-..u....l......n~

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

8867 ‘ I'Uljlllllxm

I

I

I

I

,‘
852‘ 6 -71 1 N\ , fiulxrrxxxlxulxr 111:
8 9‘ e 1: 1411111 [111/L11 m
896 ‘ 3 .111 TOOL .\l|1m1[m
59724 m r \\\111111111111
8 9’5 8 .21 . LX\‘HJHLIAIA IIALD
8975 8 m k\ H\\ HIIXIrrrTrIIfl

I

O.
m PIIIADIIPHIS S' G.
G.

(:2) CINE!!!
-MANGIOVI

'clyn. Dolph duogaom

I252.

IOIAM. 6.
'v’ulO 2‘. w."

L::::J Atcll- DINO.

11mm SPOI! 6.
MRS PAIMAO G.

79
III-3. Clusterggpalysis resultg.

The dendrogram of the clustering of the different sam-
ples under study is shown in Figure 25.

As seen, four principal clusters resulted. It should
be noted that for the purposes of this study, the chi-square
values obtained from two-by-two comparison of samples are
considered as coefficients of similarity, regardless of their
significance.

The characteristics of these four cluster elements are
as follows:

1) Cluster I; characterized by very low relative abundances
(O-2%) of the Mangrove group and high abundances of the
General group and the Spore group. It is important to note
that all the samples of this cluster, except one (9384'8" of
well 8248), correspond to sediments of an upper deltaic
plain, and are located at the approximate level at which the
transition from a low deltaic plain to an upper deltaic
plain was inferred in the three wells.

2) Cluster II; characterized by high frequencies of the
General group and by relatively moderate abundances of the
Mangrove group (3-22%), of the Spore and the Palmae groups
(8-40%). The location of the samples included hithiscluster
element was observed to be distributed in both the low and
the upper deltaic plain deposits, with certain tendency
towards the middle part of the sections.

3) Cluster III; characterized by the highest abundances of

the Mangrove group. Samples of this cluster were observed

80

.0133. .0 issue;

 

.1Ha: c1»... 0.: E0;

.0330

29$ Q

.2 3.3.;

 

w

 

n

   

 

0.0

0.0

Nd

find

 

AIIIV'HWIS

XJONI

81

in wells 8244 and 8248 only, at the lowest parts of the
surveyed cores.

4) Cluster IV; characterized by samples with relatively high
proportions of the so—called Peltandripites sp. group (14-
60%) and variable relative abundances of other groups. Sam-
ples of this cluster were observed in wells 8244 and 8252.
Their distribution corresponds mostly towards the top of the

surveyed sections of these wells but also in the middle part.

IV. DISCUSSION

IV-1. Geological age range.

As mentioned in the introduction, the thickness of
Eocene sediments is calculated at about 20,000 feet (6,096 m)
in some areas of the Lake Maracaibo Basin. The recovered
cores used in this study have lengths of about 440-470 feet
(134-143 m), a fact that clearly indicates the limited time
interval under consideration.

For the determination of geological time range, the
recent zonation of Muller et al. (1985) was used. Fortunate-
ly, some of the palynomorphs with significant stratigraphic
importance were easily identified in the palynological assem-
blages of the Boscén Field sediments. The presence of
Retibrevitricolpites triangulatus and Echitriporites
trianguliformis throughout all the sections under study
clearly indicates that these sections are not younger than
Late Eocene. The range distribution of R. triangulatus is
restricted to the Eocene in northern South America (Muller
et al., 1985), whereas that of E. trianguliformis extends
from the Cretaceous to the late Eocene.

In addition, the presence of Retitricolpites magnus,
Psilatricolporites operculatus and Retitricolporites

irregularis, seems to delimit the age range of these assem-

82

83

blages to the Middle Eocene. As noted, the presence of these
palynomorphs were recognized in the Misoa Formation by Muller
et al. (1985).

A final point should be made in regard to the existence
of an Eocene-Oligocene unconformity in the sections under
study. Studies made by CORPOVEN S.A. and Swanson (Azpiritxa-
ga, personal communication) reported the existence of this

unconformity at the following depths:

WELL CORPOVEN S.A. SWANSON
8244 9213' 9050'
8248 9036' 9036'
8252 8861' 8600'

However, according to the results obtained in this
study, there is not an abrupt change of the flora that could
indicate the existence of this unconformity at the levels
predicted by CORPOVEN S.A. in the three sections under
study or in well 8252, at the level predicted by Swanson.

The palynological assemblages of the Oligocene are considered
to be very different to those of the Eocene, due to climatic

changes (Germeraad et al., 1968). Therefore, it can be stated
that the absence of characteristic flora of the Oligocene in

the samples under study seems to negate the existence of the

Eocene-Oligocene boundary in the sections under study.

IV-2. Abundance of palynomorphs.

As previously mentioned, the absolute abundances of
palynomorphs per gram of sample showed marked variations

throughout the sections under study. Unfortunately, palyno-

84
logical studies reporting absolute abundances, were not found
for comparison. Frederiksen (1985, p. 27) pointed out the
fact that few palynologistswnrkinglon Early Tertiary palyno-
logical assemblages, used this type of data for their paleo-
ecological interpretations.

The marked fluctuations in the abundance of palyno-
morphs per unit of sediment may be attributed to several
different factors. The principal ones considered to be im-
portant in the samples studied are briefly reviewed below.

The first is the preservation of organic matter in the
sediments after deposition. This fact is related to the oxi-
dation of the organic matter, due to the interaction with
fungi—bacteria and the atmosphere. Since sideritic zones and
nodules occur in all the sections under study, this inter-
action could have played a significant role in causing the
observed fluctuations. These sideritic zones and nodules can
be formed in the sediments in periods between flooding, when
the sediments are left exposed to the atmosphere because
variations in the water table level. The interaction of
oxygen with minerals containing iron, leads to the oxidation
of these minerals, forming Fe+3 (very insoluble) as the dom-
inant form of iron in the sediments.

It should be noted that the largest recoveries of
palynomorphs were obtained in dark-gray sediments, with a-
bundant carbonaceous material. Because of the characteristic
color and the absence of sideritic nodules and zones, these

sediments seem to have undergone no oxidation. Therefore,

85

it can stated that the oxidation of organic matter after dep-
osition is one of the main factors causing the observed
fluctuations in the samples under study.

A second important factor is the supply of palynomorphs
into a particular type of environment. Muller (1959) noted
that the abundances of palynomorphs varied due to local
shifting of sedimentary environments in the Orinoco River
Delta. Muller (1959) observed that the local transport of
palynomorphs can be reduced in some areas of the delta. For
example in the back-swamp area, water movement, is restricted
to the periods of flood stage, affecting the supply, and
therefore, the amount of palynomorphs in a given sedimentary
environment.

It should be recalled that the more diverse assemblages
in the samples studied were found in the interval character-
ized as a low deltaic plain. This fact can be related to
the role of sorting and mixing of the palynological assem—
blage, not only in the distributary channels, but also in
distributary mouth bar complex, where the palynomorphs under-
go hydraulic sorting along with the clastic sedimentary par-
ticles. Moreover, tidal influence also causes mixing of the
assemblage in different environments,especially in the low
deltaic plain.

Other factors, such as distance of the source plants
from the sites of deposition and long-shore currents, also
have noticeable effects not only in the composition of the

palynological assemblages, but also in the abundance of the

86

different types of palynomorphs in different environments of
deposition.
IV—3. Paleoenvironmental and paleocommunity inferences.

The absence of significant amounts or of high frequen-
cies of marine elements clearly indicates that the sediments
under study were deposited under minor marine or tidal in-
fluence. Except for the dinoflagellate cyst of Operculodinium
sp. (found in very low frequencies), the rest of the palyno-
logical assemblage has a clear terrestrial origin.

The frequencies of the Mangrove group, especially in
the lower part of the surveyed cores, also seem to indicate
minor marine or tidal influence. It should be recalled that
the general definition of the mangrove community (Muller,
1964) includes the estuarine vegetation growing under tidal
influence and in environments with variable salinity.

Using the results presented for the fluctuations of
the different groups of palynomorphs, and the results of the
cluster analysis, two extreme situations are observed. One,
in which the relative abundance of the Mangrove group is
relatively high, and in the other, in which the relative a-
bundance of this group is very low. In between, the other two
cluster elements seem to represent a kind of transitional
situation.

Before going into the discussion of the results of
this study, a brief review of the factors affecting the rela-
tive abundances of the different types of palynomorphs, in

deltaic and swampy environments, is presented.

87

Muller (1959), in a detailed study of the dispersal
patterns of palynomorphs, noted that the relative frequen-
cies of different types of pollen were significantly affected
by the type of vegetation located in the proximity of the
environment of deposition. This fact becomes quite important
in a deltaic environment, in which several vegetational
belts or zones have been described by different authors. For
example, Allen (1965) distinguished two main vegetational
belts in the Niger Delta; that of mangrove dominated vege-
tation and the other dominated by more inland vegetation.
Muller (1959) clearly distinguished at least 7 different
types of vegetational zones in the Orinoco Delta, going from
the mangrove forest, mixed-swamp forest and Erythrina swamp
forest (located mainly in the low deltaic plain), to the
palm and herbaceous swamps and rain forest, located towards
the higher plains and leveés of the upper delta. Blasco and
Caratini (1973) distinguished three different types of plant
communities, the distribution of which were affected by
tidal influence in a mangrove swamp. The first, near to the
coast, is the mangrove~type community, subdivided into two
zones; one that was continuously immersed by salt-water
and that was dominated mainly by Rhizophora, and the other
that was variably immersed, dominated by Avicennia. The
second belt of vegetation that Blasco and Caratini distin-
guished was found in terrains with occasional tidal or marine
immersion. This vegetational belt was characterized by the

presence of plants of the family Chenopodiaceae and Palmae.

88
Finaly a third type of vegetational belt was observed to be
found in areas that lacked tidal or marine influence, and it
was mainly dominated by palms. These authors determined that
the frequencies of the different palynomorphs had high varia-
bility, depending on the location of the collecting spot
within the swamp.The palynological spectra clearly reflected
the influence of the nearby vegetation. The percentages of
autochthonous pollen were significantly higher in flood plain
and swamp environments than those of allochthonous pollen.
These authors, on the other hand, observed that allochthonous
pollen became more significant in samples collected in river
channels. These observations clearly agree with the main
tendencies observed by Muller (1959) in regard to the effects
of the dispersal patterns of the palynomorphs on the palyno-
logical spectra found in different environments. Other
factors affecting the distribution of palynomorphs, such as
the grain size of the palynomorphs, are discussed by Muller
(1959) and will not be repeated here. The effect of the
vegetation located in proximity to the environments of depo-
sition, on the abundances of palynomorphs, was also discussed
by Cohen and Spackman (1972) and Cohen (1975) in their studies
of the Okefenoke Swamp and Everglades of Florida.

Returning to the results obtained in this study, it is
clear that an established dominance by a given type of palyno-
morph or group of palynomorphs, such as those reported by
van der Hammen and Wijmstra (1964), Gonzalez Guzman (1967)

and Wijmstra (1969), was not observed. Muller (1959) and

89

Blasco and Caratini (1973) noted that mixing of the palyno-
logical assemblage was more efficient in channel samples. It
should be noted that most of the sequence under study com-
prises distributary channels (in the low deltaic plain) and
meander bar deposits (in the upper deltaic plain). Therefore,
it seems reasonable to suggest that the type of sedimentary
environment is one of the factors controlling the relative
abundances of the different groups of palynomorphs. The lack
of dominance by any group of palynomorph in this study can

be caused in part by the mixing of the assemblage in channels
of the deltaic system, where the proportions of the allo-
chthonous pollen should be found in higher proportions than
autochthonous pollen.

As mentioned in the results, the tendencies shown by
the relative abundances of the different groups of palyno-
morphs seem to suggest a transition from a low deltaic plain
to an upper deltaic plain. Based on the results obtained in
the cluster analysis, it can be inferred that such changes
occurred accordingly.

In the lower part of the surveyed cores, specifically
in wells 8244 and 8248, samples clustered under III (charac-
terized by relatively high frequencies of the Mangrove group)
were observed to be common. Then, a gradual decline in the
frequencies of this group was noted. This decline was noted
in samples clustered under II and IV, characterized by sam-
ples containing moderate frequencies of the Mangrove group.

In well 8252, the lower part of the surveyed core was also

90

characterized by samples containing moderate frequencies

of the Mangrove group (clusters II and IV). Towards the
middle part of the three sections under study, a significant
decrease in the frequency of the Mangrove group was observed.
In wells 8244 and 8252, these samples were observed to be
restricted to the middle part of the sections, whereas in
well 8248, they were observed to occur in the middle and in
the upper parts of the sections. Finally, towards the top

of the three sections under study, samples clustered under

II and IV were observed to be common.

This type of distribution seems to suggest environ-
mental changes, that are reflected in the changes of the
distribution and relative frequencies of the different groups
of palynomorphs.In the three wells, it was observed that the
range of Juglansppllenites sp. (Chenopodiaceae) goes from
the middle of the section to the upper parts, and tends to
disappear in the uppermost samples. Blasco and Caratini
(1973) noted that several species of this family were observed
in swampy terrains subjected to occasional immersion. This
occurrence was observed to happen at the same intervals at
which the relative abundances of the Mangrove group show a
gradual decline. These two facts; therefore, seems to suggest
the prograding nature of the deltaic system under study, and
the gradual transition towards an upper deltaic plain.

A further vegetational change is observed at the level
at which the sedimentological model proposed by INTEVEP S.A.

predicted the transition from sediments of a low deltaic

91
plain to those of an upper deltaic plain. This change is
characterized by the drastic decrease in the frequencies of
the Mangrove group, and in some cases, of the Peltandripites
sp. group. As noted in the previous chapter, the relative
frequencies of the Palmae group, General group and the
Spore group, tend to increase at this level, also indicating
the transition from a low deltaic plain to an upper deltaic
plain. For example, in sample 9217'10" of well 8244, a lig-
nite, the frequencies of the Palmae group and the Spore group
totalled almost 50% of the total palynological assemblage,
with the frequencies of the Mangrove group characterized by
a very low value.

Towards the top of the sections under study, samples
clustered under II and IV were observed to be common. As
previously mentioned, these types of cluster elements seem
to represent transitional palynological assemblages. In these
samples, the frequencies of the Mangrove group were observed
to be moderate. This fact could indicate that towards the
tOp of the sections, there was minor tidal influence and that
a kind of transition to a low deltaic plain could have been
taking place. This inference would agree with the sediment—
ological model proposed by Azpiritxaga (1985) for other areas
of the Boscén Field (refer to pages 25 and 27 of the intro-
duction). This transition could also be related to the sig-
nificant subsidence proposed by Zamora (1977) and Bockmeulen
et al. (1983) for some areas of the Lake Maracaibo Basin.

It should be recalled that according to these authors, the

92
significant subsidence caused the piling up of deltaic
sequences without major transgressive and regressive cycles.

A final point should be made in regard to the tran-
sitional clusters II and IV. The latter, as mentioned before,
is characterized by relatively high frequencies of the so-
called Peltandripites sp. group. This fact seem to suggest
that the environments of deposition under study in wells
8244 and 8252 were closer to places where plants producing
this palynomorph were growing. Besides this difference,
other elements of the assemblage observed in these two cluster
elements were quite similar to each other.

Figure 26 presents the proposed biozonation for the
three wells under study. The type of biozone used for this
purpose is the Assemblage-zone (International Stratigraphic
Guide, 1976, p.50-52). The different Assemblages-zones
were recognized based on the components of the palynological
assemblages of the Boscan Field sediments, as well as on the
results of the cluster analysis. Assemblages-zones are par-
ticularly significant as indicators of environments at the
local level.

In regard to the type of community present at the time
of deposition, one limitation should be emphasized. As in
other publications dealing with the palynology of Tertiary
tropical sediments, the interpretations of this study were
made based on few taxa. Graham (1985) pointed out that most
of the elements of the palynological assemblages of trOpical

areas lack defined botanical affinities. He also noted that

.uxou onu :H vommsumwu HaumsHo Ho mmazu

acoumwwww mcu ou Ocoamouuou mHmuossc :meom .czozm mH >v=um Hove:

meowuoom mcu New coaumcouofln meoaoua och .3.wNz wcwxfluum omH0>mHu
m wcon .OHOHH :womom mcu Ho Hmcuou ammocusom 05H Ho :owuuom mmOHO .ON 0szfim

 

‘lfihicfl

93
[I "Ch .'.

||.J

 

 

x?
N
no

.OOmO

II

 

4.5. SN _ 3.5 NS?

:1
H: \\

=

OOqO

A

.OOMO

(5 a
>
h
0
'3' 3:". flit '3 i u

uh l GONG

.. nu

.884.“
l

E ..H..
= «QNm .OOOOlz

IN
>_ so :

 

 

 

a
.834.“
2 .e : (
U. .oomm

H .OONw

 

 

. .oosm
KL

NmNm 1. .Ex H . OOmm

 

 

94

the definition of these affinities in Eocene palynomorphs
is made more difficult by the fact that at that time transi-
tion to modern floras was taking place, and that the morpho—
logies of numerous taxa do not match those of current ones.

Based on the results obtained in this study, it can be
stated that the type of plant paleocommunity existing at the
time of deposition seems to be characterized by the following
attributes:
1) The lack of dominance by any group of palynomorphs, that
is caused by the influence of the sedimentary environment
or by a mixed and diverse community.
2) The very low frequencies of the Brevitricolpites group,
proposed by Gonzalez Guzman (1967) as an ecological equiva-
lent to the mangrove community in Eocene sediments of Colom-
bia, seems to indicate that the environments of deposition
under study could have been located behind the vegetational
belt located closer to the coast.
3) The presence of various species of the genus Bombacacidites
(Bombacaceae) and Juglanspollenites (Chenopodiaceae), seems
to suggest the presence of a mixed-swamp vegetation, such as
those described by Muller (1959, p. 4) and Blasco and Caratini
(1973). Frederiksen (1985) also documented the main components
of this type of mixed or marsh-swamps, noting the presence of
specimens of the genus Bombacacidites.
4) The nearby presence of mangrove-type community can be
inferred from the presence of the following palynomorphs:

a) Brevitricolpites group (discussed before)

95

b) Psilatricolporites crassus (Pelliceria, Thaceae), reported
by Wijmstra (1968) as presently associated to mangrove com—
munities occurring in the Pacific coasts of Central America
and Colombia. According to Wijmstra (1968), the distribution
of this palynomorph showed a wider range, including the
Caribbean area during the Tertiary.

c) Nypa pollen types, reported by Muller (1964 and 1968) as
being related to mangrove palms.

d) Echitriporites trianguliformis, that was associated with
coastal vegetation by Germeraad et al. (1968).

According to Frederiksen (1985), the first three palyno-
morphs constitute valuable indicators of salt-water coastal
environments. Frederiksen also mentioned the genus
Proxapertites as another possible indicator of coastal en-
vironments. However, Thanikaimoni et al. (1985) reported that
this palynomorph is associated with some climbers in ever-
green forests of tropical regions. Therefore, for this study,
this palynomorph was not used for this type of interpretation.

This Set of observations seems to suggest that the
plant paleocommunities existing at the time of deposition
were relatively diverse. The palynological assemblages seem
to include elements of characteristic coastal vegetation and
elements of mixed-swamp vegetation. This interpretation seems
to agree with the inferences of the sedimentological model
and the vegetational changes inferred from the fluctuations

of the proportions of the different groups of palynomorphs.

96

IV—4. Comparison to other palynological assemblages.

Due to the lack of complete and detailed published in-
formation from palynological studies in northern South Ameri-
ca, limited comparison can be done at this moment. Only two
palynological assemblages of similar age and geographical
proximity were found in the literature. The first is the one
described by Gonzalez Guzman (1967), from the Paleocene-
Eocene Upper Los Cuervos and Mirador Formations in eastern
Colombia. Some of the palynomorphs described by Gonzalez Guz-
mén were also observed in the palynological assemblages from
the Boscén Field; however, the similarity is less than ex-
pected in sediments believed to be of the same age. Two
possible explanations can be postulated for explaining the
observed differences:

1) Geographical distance between zones under study.

2) Differences in the sedimentary environments. The Mirador
Formation was deposited in a fluvial environment, whereas
the Misoa Formation was deposited in a deltaic complex.

The second palynological assemblage is the one described
by Graham (1985) from the Late Eocene of Panama. Again, some
similarity was observed.

As seen in Appendices A and 8, some of the palynomorphs
identified in this study have been described in other publi-
cations dealing with tropical palynological assemblages
(Graham, 1985) or subtropical palynological assemblages
(Frederiksen, 1980). This fact clearly indicates that trOpi-

cal or subtropical conditions existed existed at that time.

97

IV-5. Limitations of this study.

There are two principal factors limiting the interpre-
tations previously presented. The first is the limited knowl-
edge on Tertiary floras of northern South America. As Graham
(1985) noted, more extensive studies are necessary for the
understanding and characterization of Tertiary tropical
floras and their paleocology.

The second factor is related to the types of lithology
considered for this study and the type of sampling used. Fisk
(1986) pointed out that palynomorphs undergo hydraulic sort-
ing, as clastic sedimentary particles do. Therefore, a more
detailed sampling, comprising different types of lithology,
would have provided a more complete paleoecological view,
avoiding the possible bias caused by considering only a re-

stricted range of lithologies.

V. CONCLUSIONS AND SUMMARY

The palynological analysis of 71 core samples from
three wells of the Boscén Field, Venezuela, was performed.

As described, the palynological assemblage, as a whole,
was mainly composed of angiosperm pollen, fern spores, fresh
water algae, a species Of a dinoflagellate cyst, and abundant
fungal spores and fructifications. The low abundance of
gymnosperm pollen has also been noted by other authors, and
according to Penny (1969, p. 349), it is due to the signifi-
cant replacement of gymnosperms by angiosperms during the
Paleocene in South America. Comparison to other palynological
assemblages is still superficial and inconclusive. In gen-
eral, it reveals a subtropical or tropical paleoclimate at
the time of deposition.

The palynological assemblage is characterized to be

of Middle Eocene age. The presence of Echitriporites

 

trianguliformis, Retibrevitricolpites triangulatus, Psilatri-
colporites operculatus, Retitricolporites irregularis and
Retitricolpites magnus, delimit the assemblage to zones 19
and 20 of the recent palynological zonation published by
Muller et al. (1985). Future characterization will be done as
soon as the complete information of this zonation is pub—

lished. The results of this study also show that an Eocene-

98

99

Oligocene unconformity, previously proposed by other workers,
does not occur in the sections studied.

The absence of abundant marine elements in the palyno-
logical assemblages clearly indicates that the sediments
under study were deposited in environments with minor marine
influence. Based on the lithologic characteristics, it was
concluded that the general environment was a deltaic complex.

Throughout the sections under study, environmental
changes were noted. Lithologic information clearly indicates
the existence of two genetic sedimentary units; a low deltaic
plain and an upper deltaic plain. The SP logs clearly indi-
cates the different nature of the curves for these two main
sedimentary units.

Palynological results agree with the interpretation
mentioned in the previous paragraph. By using the fluctu-
ation of the relative frequencies of the different groups
of palynomorphs, a gradual transition from a low deltaic
plain to an upper deltaic plain is apparent. This transition
is characterized by the gradual decrease of the relative
frequencies of the so—called Mangrove group, and the increase
of the frequencies of the Palmae group and the Spore group.

A similar tendency was reported by other authors as indi-
cation of regressive periods. In the case of this study, how-
ever, the author would like to relate this tendency to the
prograding nature of the delta complex (there is not enough
evidence in the sections under study for complete regressive—

transgressive cycles).

100

A difference of the results of this study and those
reported by van der Hammen and Wijmstra (1964), Gonzalez Guz-
mén (1967) and Wijmstra (1969) is the lack of dominance
(very high abundances) by any group or type of palynomorph.
In the case of this study, this fact is attributed to the
types of environment of deposition. They were mostly deposits
associated to channels (either distributary or meander).
According to Muller (1959) and Blasco and Caratini (1973),
allochthonous pollen were observed to be in larger propor-
tions in channel samples than in samples taken directly in
the swamp, that reflected more the nearby vegetation.

The gradual transition from a low deltaic plain to an
upper deltaic plain is also verified by the different cluster
groups obtained using the Similarity Index of Jameossanaie
(1983). As extensively described in the previous chapter,
those samples showing relatively high frequencies of the
Mangrove group (cluster type III) were observed to be located
in the lower parts of the sections corresponding to wells
8244 and 8248. Then, samples with moderate frequencies of
this group were observed to begin in the middle part of the
sections of the three wells (cluster types II and IV). A more
drastic decrease was then observed in the middle part of the
sections (cluster type 1), whereas transitional situations
(clusters II and IV) were also observed towards the top of the
three sections. This transitional situation seems to suggest
incipient tidal or marine influence in the area at that time,

and a probable transition towards a low deltaic environment,

101

as it was postulated by Azpiritxaga (1985). Future evalu-
ations of samples above and below the depths included in
this study would provide evidence for a more complete view
of environmental changes in the area and the subsequent
changes of vegetation. Based on.theseresu1ts, the biozonation
of the three subsurface sections was accomplished, using the
results of the cluster analysis and the fluctuations of the
relative abundances of the different groups of palynomorphs
(Figure 26).

Finally, in regard to the paleocommunities of plants
present at the time of deposition, 3 mixed community, with
a coastal vegetational component (the so-called Mangrove
group) and a mixed-swamp vegetational component, growing
under minor or no tidal influence, existed. This inference
agrees with the sedimentological model proposed by INTEVEP
S.A.. Future research in areas near the zone under study,
would provide a better paleogeographical View of the distri—
bution of the vegetation in the area. Future characterization
of the botanical and paleoecological affinities of the taxa
found in sediments of the Boscén Field, will help to improve
the knowledge in regard to the types of plant paleocommuni-

ties existing in the Middle Eocene of northwestern Venezuela.

VI. BIBLIOGRAPHY

Allen, J.R.L.. 1965. Late Quaternary Niger Delta and adjacent
areas: Sedimentary environments and lithofacies. American
Association of Petroleum Geologists, 49: 547-600.

Azpiritxaga, I.. 1985. Modelo geolégico del area piloto del
Campo Boscén. Reporte Interno INTEVEP S.A.. Los Teques, Vene—
zuela. 74 p.

Blasco, F. and C. Caratini. 1973. Mangrove de Pichavaram
(Tamil Nadu, Inde du Sud); phytogeographie and palynologie.
Travaux d' etudes de geographie tropicale. Centre Nationale
de la Recherche Scientifique.80rdeaux,FTance. p. 163-179.

Bockmeulen, H., C. Barker and P.A. Dickey. 1983. Geology and
geochemistry of crude oils, Bolivar Coastal Fields, Venezue-

la. American Association of Petroleum Geologists Bulletin,

Brondjik, J.F.. 1967. Eocene formations in the southwestern
part of the Maracaibo Basin. Asociacién Venezolana de Geolo-
gia, Mineria y Petréleo, Boletin Informativo, 10: 35-50.

Busch, D.A. and D.A. Link. 1985. Exploration methods for sand-
stone reservoirs. Oil and Gas Consultants International Inc.
Publications. Tulsa, Oklahoma. 327 p.

Case, J.E., T.L. Holocombe and R.G. Martin. 1984. Map of geo-
logic provinces in the Caribbean region. 13: W. Bonini, R.
Hargrave and R. Shagan (eds.). The Caribbean-South American
plate boundary and regional tectonics. Geological Society of
America Memoir 162, p. 1-30.

Christopher, R.A.. 1976. Morphology and taxonomic status of
Pseudoschizaea Thiegart and Frantz ex. R. Potonie emend..
Micropaleontology, 22: 143-150.

Cohen, A.D.. 1975. Peat from the Okefenokee swamp-marsh
complex. Geoscience and Man, 11: 123-131.

and W. Spackman. 1972. Methods in peat petrology
and their application to reconstruction of paleoenvironments.
Geological Society of America Bulletin, 83: 129-142.

 

102

103

Coleman, J.M.. 1982. Deltas; processes of deposition and
models for exploration. Second edition. International Human
Resources Development Corporation Publications. Boston,
Massachusetts. 124 p.

Coronel, G.. 1983. The nationalization of the Venezuelan oil
industry. Lexington Books. Lexington, Massachusetts. 282 p.

Couper, R.A.. 1960. New Zealand Mesozoic and Cainozoic plant

microfossils. New Zealand Geological Survey, Palaeontological
Bulletin, 22. 77 p.

Elsik, W.C.. 1978. Classification and geologic history of the
mycrothyriaceous fungi. IV International Palynological Con-
ference, Lucknow, 1: 331-342.

Erdtman, G.. 1957. Pollen and spore morphology (II)/ Plant
taxonomy: Gymnospermae, Pteridophyta and Bryophyta. The
Ronald Press, New York. 151 p.

Feo-Codecido, G., F.D. Smith, W. Aboud and E. de Di Giacomo.
1984. Basement and Paleozoic rocks of the Venezuelan Llanos
basins. lg: W. Bonini, R. Hargrave and R. Shagan (eds.). The
Caribbean-South American plate boundary and regional tecto-
nics. Geological Society of America Memoir 162, p. 175-187.

Fisk, L.H.. 1986. Taphonomic bias in pollen and spore record:
A review (Abstract). American Association of Petroleum Geo-
logists, 70: 590.

Flenley, L.H.. 1979. The equatorial rain forest: A geological
history. Butterworths. London. 162 p.

Frederiksen, N.O.. 1980. Sporomorphs from the Jackson Group
(Upper Eocene) and adjacent strata of Mississippi and west—

ern Alabama. United States Geological Survey Professional
Paper 1084. 162 p.

. 1985. Review of Early Tertiary sporomorph
paleoecology. American Association of Stratigraphic Palyno-
logists. Contribution Series Number 15. 92 p.

 

Graham, A.. 1985. Studies in neotropical paleobotany. IV.
The Eocene communities of Panama. Annals of the Missouri
Botanical Gardens, 72: 504-534.

and D.M. Jarzen. 1969. Studies in neotropical
paleobotany. I. The Oligocene communities of Puerto Rico.
Annals of the Missouri Botanical Gardens, 56: 308-357.

 

Germeraad, J.H., C.A. Hopping and J. Muller. 1968. Palyno-
logy of Tertiary sediments from tropical areas. Review of
Palaeobotany and Palynology, 6: 189-348.

104

Gonzalez de Juana, C., J.M. Iturralde-Arozenema and X. Pi-
card. 1980. Geologia de Venezuela y de sus cuencas petrole-
ras. Ediciones FONINVES. Caracas, Venezuela. 2 tomos. 1031 p.

Gonzalez Guzman, A.E.. 1967. A palynological study of the
Upper Los Cuervos and Mirador Formations. E.J. Brill, Leiden.
68 p.

Hammen, T. van der. l956-a. A palynologic systematic nomen-
clature. Boletin de Geologia, Bogota, Colombia. 4: 63-301.

. 1956-b. Description of some genera and

species of fossil pollen and spores. Boletin de Geologia. Bo-
gota, Colombia. 4: 111-117.

 

and T.A. Wijmstra. 1964. A palynological
study of the Tertiary and Upper Cretaceous of British Guiana.
Leidse Geologische Mededelingen, 30: 183-241.

 

and C. Garcia de Mutis. 1965. The Paleocene

flora of Colombia. Leidse Geologische Mededelingen, 35:
105-116.

 

Hoeken-Klinkenberg, P.M.J. van. 1964. A palynological investi-
gation of some Upper Cretaceous sediments in Nigeria. Pollen
et Spores, 6: 27-48.

. 1966. Maastrichtian, Paleocene
and Eocene pollen and spores from Nigeria. Leidse Geologische
Mededelingen, 38: 27-48.

 

International Stratigraphic Guide. 1976. H.D. Hedberg (ed.).
John Wiley & Sons, New York. 200 p.

Jameossanaie, A.. 1983. Palynology and environments of depo-
sition of the lower Menefee Formation (Lower Campanian),
South Hospah area, Mckinley County, New Mexico. Ph.D.
Dissertation in Geology. Michigan State University, East
Lansing, Michigan. 285 p.

Kellogg, J.N.. 1984. Cenozoic tectonic history of the Sierra
de Perijé, Venezuela-Colombia and adjacent basins. lg:

W. Bonini, R. Hargrave and R. Shagan (eds.), The Caribbean-
South American plate boundary and regional tectonics. Geo-
logical Society of America Memoir 162, p.239-261.

Kohn, B.P., R. Shagan, P.O. Banks and L.A. Burkley. 1984.
Mesozoic-Pleistocene fission-track ages of rocks of the Ve-
nezuelan Andes and their tectonic implications. 13:

W. Bonini, R. Hargrave and R. Shagan (eds.), The Caribbean-
South American plate boundary and regional tectonic. Geo—
logical Society of America Memoir 162, p. 365-384.

105

Kuyl, 0.8., J. Muller and H.T. Waterbolk. 1955. Application
of palynology to oil geology, with special reference to west-
ern Venezuela. Geologie en Mijnbouw, New Series, 17: 49-75.

Léxico Estratigréfico Venezolano. 1971. Editorial Sucre.
Caracas, Venezuela. 755 p.

Mencher, E., H.J. Fichter, H.H. Renz, W.E. Wallis, H.H. Renz,
J.M. Paterson and R.H. Robie. 1953. Geology of Venezuela and

its oil fields. American Association of Petroleum Geologists
Bulletin, 37: 690-777.

Miller, J.B., K.L. Edwards, P.P. Wolcot, H.W. Amisgard and
H. Anderegg. 1958. Habitat of oil in the Maracaibo Basin,
Venezuela. 1p: L.G. Weeks (ed.). Habitat of oil. American

Association of Petroleum Geologists Special Publication.
p. 601-640.

Muller, J..1959. Palynology of Recent Orinoco Delta and shelf
sediments. Micropaleontology, 5: 1-32.

. 1964. A palynological contribution to the history

of the mangrove vegetation in Borneo. 1p; L.M. Cranwell (ed.).
Ancient Pacific floras. University of Hawaii Press. Honolulu,

Hawaii, p. 32-42.

 

. 1968. Palynology of the Pedawan and Plateau Sand-
stone Formations (Cretaceous-Eocene) in Sarawak, Malaysia.
Micropaleontology, 14: 1-37.

 

, E. de Di Giacomo and A. van Erven. 1985. A palyno-
logical zonation for Cretaceous, Tertiary and Quaternary of
northern South America. Memoria del VI Congreso Geolégico
Venezolano. Caracas, Venezuela. p. 1041-1079.

 

Penny, J.S.. 1969. Late Cretaceous and Early Tertiary palyno-
logy. Ip: R.H. Tschudy and R.A. Scott (eds.). Aspects of
palynology. Wiley-Interscience Publications, New York.

p. 331-376.

Regali, M.S.P., N. Uesugui and A. da Silva Santos. 1974a.
Palinologia dos sedimentos Meso-Cenozoicos do Brasil. 1.
Boletim Tecnico Petrobrés. Rio de Janeiro, Brasil. 17:
177-191.

, and . 1974b.
Palinologia dos sedimentos Meso-Cenozoicos do Brasil. II.

Boletim Tecnico Petrobrés. Rio de Janeiro, Brasil. 17:
263-301.

 

 

Salgado-Laboriau, M.L.. 1979. Modern pollen deposition in
the Venezuelan Andes. Grana Palynologica, 18: 53-68.

106

Salgado-Laboriau, M.L.. 1980. A pollen diagram of the Pleisto-
cene-Holocene boundary of Lake Valencia, Venezuela. Review of
PalaeobotanyzuuiPalynology, 30: 297-312.

Schaub, H.P.. 1948. Outline of sedimentation in the Maracaibo

Basin, Venezuela. American Association of Petroleum Geologists
Bulletin, 32: 215-227.

Shagan, R., B.P. Kohn, P.O. Banks, L.E. Dasch, R. Vargas,

G.I. Rodriguez and N. Pimentel. 1984. Tectonic implications

of Cretaceous-Pliocene fission-track ages from rocks of the
circum-Maracaibo Basin region of western Venezuela and east-
ern Colombia. 13: W. Bonini, R. Hargrave and R. Shagan (eds.).
The Caribbean-South American plate boundary and regional

tectonics. Geological Society of America Memoir 162, p. 385-
412.

Sutherland, J.A.F.. 1964. The Boscén Field, western Venezuela.
13: R.E. King (ed.). Stratigraphic oil and gas fields- Classi-
fication, exploration methods and case histories. American
Association of Petroleum Geologists Memoir 16, p. 559-567.

Sutton, F.A.. 1946. Geology of the Maracaibo Basin, Venezuela.

American Association of Petroleum Geologists Bulletin, 30:
1621-1741.

Talukdar, S., O. Gallango and M. Chin-t-Lien. 1985. Generation
and migration of hydrocarbons on the Maracaibo Basin, Venezue-
la. Publicaciones del 11 Simposio Bolivariano de Exploracién
Petrolera de las Cuencas Sub-Andinas. Bogota, Colombia. 42 p.

Thanikaimoni, G., C. Caratini, 8.8. Venkatachala, C.G.K. Rama-
nujam and R.K. Kar (eds.). 1985. Selected Tertiary angiosperm
pollens from India and their relationship with African Tertia-
ry pollens. Institute Francais de Pondichéry. Travaux de la
Section Scientifique et Technique. Volumen XIX. 92 p.

Veen, F.R. van. 1977. Ambientes sedimentarios de las Forma-
ciones Mirador y Misoa del Eoceno Inferior y Medio en la
Cuenca del Lago de Maracaibo. Memorias del V Congreso Ge016-

gico Venezolano. Caracas, Venezuela. Publicacién Especial
No. 5, p. 1073-1104.

Wall, D.. 1967. Fossil microplankton in deep-sea cores from
the Caribbean Sea.Palaeontology, 10: 92-123.

Wijmstra, T.A.. 1968. The identity of Psilatricolporites
crassus and Pelliceria. Acta Botanica Netherland, 17: 114-116.

. 1969. Palynology of the Alliance well. Geo-
logie en Mijnbouw, 48: 125-133.

 

107

Wijmstra, T.A. and T. van der Hammen. 1966. Palynological data
on the history of tropical savannas in northern South America.
Leidse Geologische Mededelingen, 38: 71-90.

Zambrano, E., E. Vasquez, B. Duval, M. Latreille and B.
Coffinieres. 1971. Sintesis paleogeogréfica y petrolera del
occidente de Venezuela. Memorias del IV Congreso Geolégico
Venezolano. Caracas, Venezuela, p. 483-552.

Zamora, L.G. 1977. Uso de perfiles en la identificacién de
ambientes sedimentarios del Eoceno del Lago de Maracaibo.
Memorias del V Congreso Geolégico Venezolano. Caracas, Vene—
zuela. Publicacién Especial No. 5, p. 1359-1376.

APPENDIX A

108
Appendix A

Alphabetical list of the Boscén palynomorphs

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

TAXA PLATE FIGURE
Aglaoreidia sp. 1 X 8
Anacolosidites sp. 1 XI 6
Bombacacidites sp. 1 -IX 8
Bombacacidites sp. 2 IX 9
Bombacacidites sp. 3 IX 10
Bombacacidites sp. 4 IX 11
Cingutriletes sp. 1 III 2
Cingutriletes sp. 2 III 3
Cingutriletes sp. 3 III 4
Classites sp. 1 XIII 1
Clavatricolpites sp. 1 VII 1
Clavastephanocolporites? sp. 1 X1 8
Cricotriporites sp. 1 XI 5
Curvimonocolpites sp. 1 IV 11
Echimonocolpites sp. 1 V 7
Echimonocolpites sp. 2 V 8
Echimonocolpites sp. 3 V 9
Echiminocolpites sp. 4 V 10
Echitricolpites sp. 1 VII 2
Echitriletes sp. 1 II 10
Echistephanoporites sp. 1 XI 9
Echitriporites trianguliformis X 11
Echitriporites sp. 1 X 12
Equisetosporites sp. 1 IV 1
Fungal fruit-body (Acrostoma) I 5
Fungal Spore Type A I 1
Fungal Spore Type B I 2
Fungal Spore Type C I 3
Fungal Spore Type D I 4
Graminidites sp. 1 X 7
Gemmamonocolpites sp. 1 V 2
Gemmatriletes sp. 1 II 7
Gemmatriletes sp.2 II 8
Gemmatriletes sp. 3 II 9
Juglanspollenites sp. 1 XI 7
Laevigatosporites sp. 1 II 3
Longapertites sp. 1 IV 7
Longapertites sp. 2 IV 8
Longapertites sp. 3 IV 9
Longapertites sp. 4 IV 10
Micrasterias sp. I 6
Margocolporites sp. 1 X 1
Margocolporites sp. 2 X 2
Operculodinium sp. X111 6
Peltandripites sp. 1 XIII 2
Perfotricolpites digitatus VI 1
Proteacidites sp. 1 X 13
Proxapertites sp. 1 V 3

 

109

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

TAXA PLATE FIGURE
Pseudoschizaea sp. I 7
Psilabrevitricolpites? sp. 1 X 3
Psilamonocolpites sp. 1 V 1
Psilastephanocolpites sp. 1 VII 4
Psilastephanocolporites sp. 1 X 5
Psilastephanocolporites sp. 2 X 6
Psilatricolpites sp. 1 VII 1
Psilatricolporites crassus VII 6-7
Psilatricolporites obscurus VIII 1
Psilatricolporites operculatus VII 8
Psilatricolporites sp. 1 VIII 2
Psilatricolporites sp. 2 VIII 3
Psilatricolporites sp. 3 VIII 4
Psilatricolporites sp. 4 VIII 5
Psilatricolporites sp. 5 VIII 6
Psilatricolporites sp. 6 VIII 7
Psilatriletes sp. 1 II 11
Psilatriletes sp. 2 II 12
Psilatriletes sp. 3 III 1
Retibrevitricolpites triangulatus VI 3
Retidiporites sp. 1 X 9
Retidiporites sp. 2 X 10
Retimonocolpites sp. 1 IV 2
Retimonocolpites sp. 2 IV 3
Retimonocolpites sp. 3 IV 4
Retimonocolpites Sp. 4 IV 5
Retimonocolpites sp. 5 IV 6
Retitricolpites antonii VI 6
Retitricolpites clarensis VI 5
Retitricolpites magnus VI 4
Retitricolpites simplex VI 7
Retitricolpites sp. 1 VI 8
Retitricolpites sp. 2 VI 9
Retitricolporites irregularis VIII 8
Retitricolporites quadrosi VIII 9
Retitricolporites sp. 1 VIII 10
Retitricolporites sp. 2 IX 1
Retitricolporites sp. 3 IX 2
Retitricolporites sp. 4 IX 3
Retitricolporites sp. 5 IX 4
Retitricolporites sp. 6 IX 5
Retitricolporites sp. 7 IX 6
Retitricolporites sp. 8 IX 7
Retitriletes sp. 1 III 6
Retitriporites sp. 1 XI 1
Retitriporites sp. 2 X1 2
Retitriporites sp. 3 X1 3
Retitriporites sp. 4 X1 4
Spinizonocolpites baculatus V 4
Spinizonocolpites echinatus V 5-6
Spyrosyncolpites spiralis VII 5
Striatricolpites catatumbus VI 2
Syncolporites sp. 1 X 4

 

110

TAXA PLATE FIGURE

 

 

 

 

Tetrad Type A XII 1
Tetrad Type B XII 2
Tetrad Type C XII 3
Tilia sp. 1 IX 12
Undulatisporites sp. 1 III 3
Unidentified chitinous foram. XIII 7
Unknown Type 1 XIII 3
Unknown Type 2 XIII 4
Unknown Type 3 XIII 5
Verrucatosporites usmensis II 1-2
Verrucatriletes sp. 1 II 4
Verrucatriletes sp. 2 II 5
Verrucatriletes sp. 3 II 6

 

APPENDIX B

111
Appendix B

Phylogenetic list of the Boscén palynomorphs
This list also includes information regarding the groups of
palynomorphs that were used in the palynomorph diagrams. Each
palynomorph was included in a given group and this list pro-
vides information into which group they were included, accord-
ing to the following legend:
-Mangrove Group: MG
-Peltandripites sp. Group: PSP
-General Group: GG
-Palmae Group: PC
-Spore Group: SG

-Dinoflagellate-Algae-Foraminifera Group: DAF.

 

 

 

 

 

 

 

 

 

 

 

PALYNOMORPH
TAXA PLATE FIGURE GROUP
DIVISION EUCOMYCOPHYTA
Fungal Spore Type A I 1 -
Fungal Spore Type B I 2 -
Fungal Spore Type C I 3 -
Fungal Spore Type D I 4 -
Fungal fruit-body (Acostroma) I 5 -
SUBKINGDOM ALGAE
Micrasterias sp. I 5 DAF
Psedoschizaea sp. I 6 DAF
SPORES
Verrucatosporites usmensis II 1-2 SG
Laevigatosporites sp.1 II 3 SG
Verrucatriletes sp. 1 II 4 SG
Verrucatriletes sp. 2 II 5 SG
Verrucatriletes sp. 3 II 6 SG
Gemmatriletes sp. 1 II 7 SG
Gemmatriletes sp. 2 II 8 SG
Gemmatriletes sp. 3 II 9 SG
Echitriletes sp. 1 II 10 SG

 

112

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

PALYNOMORPH
TAXA PLATE FIGURE GROUP
Psilatriletes sp. 1 II 11 SG
Psilatriletes sp. 2 II 12 SG
Psilatriletes sp. 3 III 1 SG
Cingutriletes sp. 1 III 2 SG
Cingutriletes sp. 2 III 3 SG
Cingutriletes sp. 3 III 4 SG
Undulatisporites sp. 1 III 5 SG
Retitriletes sp. 1 III 6 SG
POLYPLICATE GYMNOSPERM POLLEN
Equisetosporites sp. 1 IV 1 GG
ANGIOSPERM POLLEN
MONOCOLPATES
Retimonocolpites sp. 1 IV 2 PG
Retimonocolpites sp. 2 IV 3 PG
Retimonocolpites sp. 3 IV 4 CG
Retimonocolpites sp. 4 IV 5 CG
Retimonocolpites sp. 5 IV 6 GG
Longapertites sp. 1 IV 7 PG
Longapertites sp. 2 IV 8 PG
Longapertites sp. 3 IV 9 PG
Longapertites sp. 4 IV 10 PG
Curvimonocolpites sp. 1 IV 11 PG
Psilamonocolpites sp. 1 V 1 CG
Gemmamonocolpites sp. 1 V 2 PG
Proxapertites sp. 1 V 3 CG
Spinizonocolpites baculatus V 4 MG
Spinizonocolpites echinatus V 5-6 MG
Echimonocolpites sp. 1 V 7 PG
Echimonocolpites sp. 2 V 8 PG
Echimonocolpites sp. 3 V 9 PG
Echimonocolpites sp. 4 V 10 PG
TRICOLPATES
Perfotricolpites digitatus VI 1 CG
Striatricolpites catatumbus VI 2 CG
Retibrevitricolpites triangulatus VI 3 MG
Retitricolpites magnus VI 4 CG
Retitricolpites clarensis VI 5 CG
Retitricolpites antonii VI 6 CG
Retitricolpites simplex VI 7 CG
Retitricolpites sp. 1 VI 8 CG
Retitricolpites sp. 2 VI 9 CG
Psilatricolpites sp. 1 VII 1 CG
Clavatricolpites sp. 1 VII 2 GO
Echitricolpites sp. 1 VII 3 CG
STEPHANOCOLPATES

Psilastephanocolpites sp. 1 VII 4 CG

113

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

PALYNOMORPH-
TAXA PLATE FIGURE GROUP
SYNCOLPATES
Spyrosyncolpites spiralis VII 5 CG
TRICOLPORATES
Psilatricolporites crassus VII 6-7 MG
Psilatricolporites Operculatus VII 8 CG
Psilatricolporites obscurus VIII 1 GO
Psilatricolporites sp. 1 VIII 2 CG
Psilatricolporites sp. 2 VIII 3 CG
Psilatricolporites sp. 3 VIII 4 CG
Psilatricolporites sp. 4 VIII 5 CG
Psilatricolporites sp. 5 VIII 6 CG
Psilatricolporites sp. 6 VIII 7 CG
Retitricolporites irregularis VIII 8 CG
Retitricolporites quadrosi VIII 9 CG
Retitricolporites sp. 1 1 VIII 10 CG
Retitricolporites sp. 2 IX 1 CG
Retitricolporites sp. 3 IX 2 CG
Retitricolporites sp. 4 IX 3 CG
Retitricolporites sp. 5 IX 4 CG
Retitricolporites sp. 6 IX 5 GO
Retitricolporites sp. 7 IX 6 CG
Retitricolporites sp. 8 IX 7 CG
Bombacacidites sp. 1 IX 8 CG
Bombacacidites sp. 2 IX 9 CG
Bombacacidites sp. 3 IX 10 CG
Bombacacidites sp. 4 IX 11 CG
Tilia sp. 1 IX 12 CG
Margocolporites sp. 1 X 1 CG
Margocolporites sp. 2 X 2 GG
Psilabrevitricolpites? sp. 1 X 3 CG
SYNCOLPORATES
Syncolporites sp. 1 X 4 CG
STEPHANOCOLPORATES
Psilastephanocolporites sp. 1 X 5 CG
Psilastephanocolporites sp. 2 X 6 GO
MONOPORATES
Graminidites sp. 1 X 7 G0
Aglaoreidia sp. 1 X 8 GO
DIPORATES
Retidiporites sp. 1 X 9 CG
Retidiporites sp. 2 X 10 CG
TRIPORATES
Echitriporites trianguliformis X 11 MG
Echitriporites sp. 1 X 12 CG
Proteacidites sp. 1 X 13 CG

 

114

 

 

 

 

 

 

 

 

 

 

 

 

 

PALYNOMORPH
TAXA PLATE FIGURE GROUP
Retitripprites sp. 1 XI 1 GO
Retitriporites sp. 2 XI 2 GG
Retitriporites sp. 3 XI 3 CG
Retitriporites sp. 4 XI 4 CG
Cricotriporites sp.-1 XI 5 GG
STEPHANOPORATES
Anacolosidites sp. 1 X1 6 CG
Juglanspollenites sp. 1 X1 7 CG
Clavastephanocolporites? sp. 1 X1 8 GG
Echistephanoporites sp. 1 X1 9 CG
TETRADS
Tetrad Type A XII 1 CG
Tetrad Type B XII 2 GG
Tetrad Type C XII 3 GO
INCERTAE SEDIS
Classites sp. 1 XIII 1 GG
Peltandripites sp. 1 XIII 2 PSP
Unknown Type 1 XIII 3 CG
Unknown Type 2 XIII 4 GG
Unknown Type 3 XIII 5 GO
DIVISION PYRROPHYTA
Operculodinium sp. XIII 6 DAF
PHYLUM PROTOZOA
Unidentified foram. inner
chitinous linnings X111 6 DAF

PLATES

FIGURE
1

115
PLATE I

(All illustrations lOOOX)

Fungal Spore Type A

Figured specimen: P814186 (126.0 x 31.0);

50 um x 20.um.

Nggg: Multicellate, septate, psilate spores. Two
apical pori.

Fungal Spore Type B

Figured specimen: P814195 (123.1 x 44.6);

43 an x 14 um.

Nggg: Multicellate, septate, psilate spores.
Fungal Spore Type C

Figured specimen: P814004 (126.8 x 29.0);

65 um x 14.um.

Nggg: Multicellate, septate, psilate spores. At
least one apical pore.

Fungal Spore Type D

Figured specimen: P813995 (128.0 x 41.6);

62 um x 16.um.

Nggg: Tetracellate, septate, psilate spores. Size
of the cell decreasing towards the endings. Each
septum with a septal pore with annulus. Distinct
median septum. Two apical pori.

Fungal Fruit-body (Acrostoma)

Figured specimen: P814001 (116.7 x 22.4);

431Lm x 431Mm.

NgEg: According to Elsik (1978), this specimen could
be included within the genus Microthallites, because
of the absence of a central ostiole or of a dense
knob.

Micrasterias sp.

Figured specimen: P814195 (119.0 x 45.1);

19-25 Mm.

Note: Deeply lobed circular flattened cells.

116
PLATE I (Cont.)

 

 

FIGURE
7 Pseudoschizaea sp.
Figured specimen: P814195 (125.5 x 30.9);
27-29 Mm.

Note: Ovoidal-circular test with complex muri in
concentric ribs. Similar to some specimens described
by Christopher (1976).

PLATE

 

FIGURE
1-2

117

PLATE II
(All illustrations 1000X)

Verrucatosporites usmensis (van der Hammen, 1956-b)
Germeraad, Hopping and Muller, 1968.

Figured specimens: P814195 (124.1 x 29.3) (Fig. 1)
P814189 (112.9 x 42.7) (Fig. 2); 30-40.um and 48-55
Mm.

Nggg: Two size ranges were observed.
Laevigatosporites sp. 1

Elgpred specimen: P814195 (119.0 x 13.4);

37-41.Mm.

Nggg: Botanic affinities to Polypodiaceae.
Verrucatriletes sp. 1

Figpred specimen: P814001 (112.7 x 39.6);

32-37ALm.

Nggg: Rounded-triangular amb. Verrucae, 3-6le. wide.
Verrucatriletes sp. 2

Figured specimen: P814195 (128.2 x 17.4);

27-30 Mm. '

Eggs: Radially symmetrical amb. Verrucae, 2-3 um.
wide.

Verrucatriletes sp. 3

Figured specimen: P814001 (126.9 x 36.8);

26-29 m.

Nggg:Rounded triangular amb with slightly undulating
laesurae. Verrucae, 1-21Lm wide, in cases with spiny
ends.

Gemmatriletes sp. 1

Figured specimen: P814127 (126.4 x 14.5);

26-29 Mm.

Nggg: Radially symmetrical amb. Gemmae, 2-3me wide.
Gemmatriletes sp. 2

Figured specimen: P814194 (120.0 x 41.0);

30-341Hm.

Note: Trilete mark not very conspicuous.

FIGURE
9

10

11

12

118
PLATE II (Cont.)

Verrucatriletes sp. 3

Figured specimen: P814001 (120.4 x 22.0);

36 Am x 29 km.

Nggg: Only one specimen was observed.

Echitriletes sp. 1

Figured specimen: P814232 (113.8 x 22.9);

22-31 Mm.

N253: Circular amb. Echinae, 1-21Lm long. Similar to
some spores of Selaginella, identified by Graham
(1985) from the Late Eocene of Panama.
Psilatriletes sp. 1

Figured specimen: P813998 (113.0 x 27.4);

30-38 Am.

Eggs: The rounded-triangular amb, with characteristic
concave sides, seems to suggest some similarity to
the spores of Microlepia (Pteridaceae) described by
Erdtman (1957).

Psilatriletes sp. 2

Figpred specimen: P814195 (124.8 x 41.4);

37-451Lm.

Nggg: Circular amb, with laesurae extending to the

margins.

PLATE H

 

1. Ii‘l '1’... II. II:

FIGURE
1

119

PLATE 111
(All illustrations 1000X)

Psilatriletes sp. 3
Figured specimen: PB14189 (125.3 x 37.7);
41-60 Am.

Note: Circular amb. Laesurae do not extend to the

 

spore margins.

Cingutriletes sp. 1

Figured specimen: PB14227 (120.3 x 24.0);

35-42 Mm.

flggg: Graham (1985) identified specimens similar to
those observed in this study, as belonging to the
genus Pteris (Polypodiaceae).

Cingutriletes sp. 2

Figured specimen: PB14009 (118.2 x 38.7);
40—47Akm.

Cingutriletes sp. 3

Figured specimen: PB14189 (125.3 x 37.8);

SOle. x 451cm.

Note: Only one specimen was observed.

 

 

Undulatisporites sp. 1

Figured specimen: PB14001 (122.9 x 15.4);
20.um x 184Mm.

333$: Only one specimen was observed.
Retitriletes sp. 1

Figured specimen: PB14001 (113.1 x 14.9);
26-28ALm.

Note: Rounded triangular amb, finely reticulate.

 

PLATE m

 

FIGURE
1

120

PLATE IV
(All illustrations 1000X)

Equisetosporites sp. 1

Figured specimen: P313998 (127.9 x 37.0);

40-42;un.

flggg: Polyplicate gymnosperm pollen. Affinities to
Ephedra (Gnetopsida).

Retimonocolpites sp. 1

Figured specimen: PB14195 (127.3 x 37.0);

30-35 Am.

3353: Prolate,reticulate,monocolpate pollen grains.
Size of the lumina, uniform (1.0ALm). Intectate,
exine 1.0 Hm. Probably related to Palmae.
Retimonocolpites sp. 2

Figured specimen: PB14195 (125.5 x 16.9);

28-31 Mm.

flggg: Globular-ovoidal reticulate pollen grains.
Size of the lumina, 2-3,um. Intectate; exine 1—24Mm.
Retimonocolpites sp. 3

Figured specimen: P814198 (123.0 x 32.0);

30-34 Am.

flggg: Prolate, reticulate monocolpate pollen grains.
Size of the lumina, 2.5-3.0ALm. Intectate, exine 1.2
Aim.

Retimonocolpites sp. 4

Figured specimen: PB14188 (113.0 x 23.7);

46-49ALm.

flggg: Prolate, reticulate, monocolpate pollen grains.
Size of the lumina, 3—4/um, decreasing towards the
colpus.

Retimonocolpites sp. 5

Figpred specimen: PB14195 (127.3 x 23.7);

25-29 um.

FIGURE
7

10

11

121

PLATE IV (Cont.)

Longapertites sp.1

Figured specimen: P814195 (126.8 x 16.9);

25—28 Mm .

.flggg: Prolate, psilate monocolpate pollen grains.
Colpus dividing the grains in two halves. Related to
Palmae.

Longapertites sp. 2

Figured specimen: PB14195 (125.9 x 23.9);

17—23fiLm.

Note: Similar to Longapertites sp. 1, but differs in

 

range of size and the reticulate sculpture. Related
to Palmae.

Longapertites sp. 3

Figured specimen: PB14187 (114.0 x 30.5);

47-524Lm.

£232: Globular shape, reticulate. Colpus dividing the
grain in two unequal halves. Related to Palmae.
Longapertites sp. 4

Figured specimen: PB14188 (117.3 x 30.4);

23-27 km.

Note: Reticulate, monocolpate pollen grains. Colpus

 

dividing the grain in two halves. Related to Palmae.
Curvimonocolpites sp.

Figured specimen: PB14189 (124.0 x 39.9);

36-411Lm.

Note: Kidney—bean shaped pollen grain, with colpus

 

in the convex side of the grain. Psilate.

PLATE IV

 

FIGURE
1

5—6

122

PLATE V
(All illustrations 1000X)

Psilamonocolpites sp. 1

Figured specimen: P813998 (128.8 x 37.2);
26-33ALm.

flggg: Psilate, monocolpate pollen grains.
Gemmamonocolpites sp. 1

Figured specimen: P814005 (116.1 x 25.8);

42/Lm x 221Lm.

£332: Prolate, Only one specimen was observed.
Prolate, gemmate, monocolpate pollen grain. Wall,
finely perforate.

Proxapertites sp. 1

Figpred specimen: P814188 (115.1 x 31.3);

20-23 Mun.

flggg: Circular monocolpate pollen grains. The wide
colpus divides the grain in two halves. Germeraad
et al. (1968) suggested some similarities to the
pollen of Astrocaryum. Thanikaimoni et al. (1985)
related it to unnamed climbers in evergrenn forests.
Spinizonocolpites baculatus Muller, 1968

Figured specimen: P814196 (117.9 x 38.4);

301Lm x ISALm.

figgg: Only one specimen was observed. Related to
the mangrove palm fllp_.

Spinizonocolpites echinatus Muller, 1968

Figured specimens: P814004 (115.5 x 41.4) (Fig. 5)
and P814188 (123.8 x 23.4) (Fig. 6);

40-50%.

flggg: Related to mangrove palm fllpg.
Echimonocolpites sp. 1

Figured specimen: P814186 (122.4 x 40.9);

32-36 Mm.

‘flggg: Probably related to Palmae.

FIGURE
8

10

123
PLATE V (Cont.)

Echimonocolpites sp. 2

Figured specimen: P813998 (113.1 x 22.7);
29-34Alm.

flggg: Probably related to Palmae.
Echimonocolpites sp. 3

Figured specimen: P814124 (121.1 x 46.7);
17-20 Mm.

Echimonocolpites sp. 3

Figured specimen: P814230 (122.1 x 34.3);
52 m x 33.4m.

flg£g: Only one specimen was observed. Characteristic

thick exine (4.0 Mm).

PLATE V

 

FIGURE
1

124

PLATE VI
(All illustrations 1000X)

Perfotricolpites digitatus Gonzalez Guzman, 1967
Figured specimen: P814195 (118.6 x 16.5);

39-55 Am.

2222: Germeraad et a1. (1968) related it to pollen of
Merremia (Convolvulaceae). Gonzalez Guzman (1967)
observed this species in the Eocene of Colombia.

In this study, it was mainly observed in samples
clustered under III.

Striatricolpites catatumbus Gonzalez Guzman, 1967
Figured specimen: P814195 (126.4 x 21.5);

33-35 Am.

2222: Related to Crudia (Fabaceae). Gonzalez Guzman
(1967) observed this species in the Eocene of Colom-
bia.

Retibrevitricolpites triangulatus van Hoeken—Klinken—
berg, 1966

Figured specimen: P814195 (122.6 x 41.4);

15-22 Am.

2222: Gonzalez Guzman (1967) observed this species in
the Eocene of Colombia. In this study, it was mainly
observed in samples clustered under III.
Retitricolpites magnus Gonzalez Guzman, 1967

Figured specimen: P814195 (125.6 x 21.4);

45-50Mm.

E222: Gonzalez Guzman observed this species in the
Eocene of Colombia. In this study, it was mainly
observed in samples clustered under III.
Retitricolpites clarensis Gonzalez Guzman, 1967.
Figured specimen: P814195 (124.0 x 31.0);

27-35 Am.

2222: Gonzalez Guzman (1967) observed this species in

the Eocene of Colombia.

FIGURE
6

125
PLATE VI (Cont.)

Retitricolpites antonii Gonzalez Guzman, 1967

Figured specimen: P814195 (125.7 x 21.1);

30-34 Am.

2222: Gonzalez Guzman (1967) observed this species in
the Eocene of Colombia.

Retitricolpites simplex Gonzalez Guzman, 1967

Figured specimen: P814188 (115.0 x 34.0);

40-50 #41:.

E222: Gonzalez Guzman (1967) observed this species in
the Eocene of Colombia.

Retitricolpites sp. 1

Figured specimen: P814188 (117.3 x 45.2);

43-49 11m.

E222: Prolate, reticulate, tricolpate pollen grains.
Size of the lumina, 1-1.5 Mm.

Retitricolpites sp. 2

Figured specimen: P814195 (123.2 x 24.2);

40-47 Rm.

2222: Prolate, reticulate, tricolpate pollen grains.
Reticulum arranged in such a way that it looks like

forming striae on the grain surface.

PLATE VI

 

FIGURE
1

126

PLATE VII
(All illustrations 1000X)

Psilatricolpites sp. 1

Figuredspecimen:PBl4195 (127.0 x 16.2);

22-27 Am.

2222: Prolate, psilate, tricolpate pollen grains.
Costae colpi.

Clavatricolpites sp. 1

Figured specimen: P814195 (121.9 x 18.3);

13-17 Jim.

2222: Prolate, clavate, tricolpate pollen grains.
Clavae, 1.01Lm long.

Echitricolpites sp. 1

Figured specimen: P814238 (123.2 x 40.3);

19-26 m.

Note: Prolate, echinate, tricolpate pollen grains.

 

Echinae, 1.0A&m, evenly dispersed on the grain
surface.

Psilastephanocolpites sp. 1

Figured specimen: P813988 (121.0 x 15.3);

32—42 LLm.

E222: Prolate—ovoidal, stephanocolpate (8-10 colpi),
psilate pollen grains.

Spyrosyncolpites spiralis Gonzélez Guzman, 1967
Figured specimen: P814189 (25.6 x 112.9);

30-501Lm.

E222: Gonzalez Guzman (1967) observed this species
in the Eocene of Colombia.

Psilatricolporites crassus van der Hammen and Wijmstra,
1964

Figured specimens: P814188 (117.0 x 44.1) (Fig. 6)
and P814195 (127.0 x 23.4) (Fig.7);

30-35.Mm and 42-501Lm.

2222: Two size ranges were observed. In this study,

it was mainly observed in samples clustered under III.

FIGURE

127

PLATE VII (Cont.)

Wijmstra (1968) related it to Pelliceria (Thaceae).
Psilatricolporites operculatus van der Hammen and
Wijmstra, 1964

Figured specimen: P814194 (115.7 x 37.0);

l7—251Lm.

2222: Germeraad et al. (1968) related it to pollen
of Alchornea (Euphorbiaceae). Gonzalez Guzman (1967)

observed this species in the Eocene of Colombia.

PLATE V"

 

FIGURE
1

128

PLATE VIII
(All illustrations 1000X)

Psilatricolporites obscurus Gonzalez Guzman, 1967
Figured specimen: P814195 (125.7 x 41.3);

35-45 Am.

2222: Gonzélez Guzmén (1967) observed this species in
the Eocene of Colombia. In this study. it was mainly
observed in samples clustered under III.
Psilatricolporites sp. 1

Figured specimen: P814195 (126.3 x 33.5);

29-35 Mm.

E222; Approximately circular limb. Large polar area.
Exine, 3-41Lm. In this study, it was mainly observed
in samples clustered under III.

Psilatricolporites sp. 2

Figured specimen: P814195 (127.2 x 33.4);

27-3114m.

.2222: Globular, psilate, tricolporate pollen grains.
Exine, 2.0.um.

Psilatricolporites sp. 3

Figured specimen: P814195 (125.9 x 32.2);

27-31AUn.

E222: Prolate, psilate, tricolporate pollen grains.
Exine, 1.0.Mm.

Psilatricolporites sp. 4

Figured specimen: P814195 (124.7 x 23.6);

17-19 Am.

2222: Sub-prolate, psilate, tricolporate pollen
grains. Equatorial lalongate pori. Costae colpi.
Psilatricolporites sp. 5

Figured specimen: P814195 (119.4 x 16.7);

261Lm x 16.4m.
Note: Only one specimen was observed. Prolate, psilate

tricolporate pollen grains. Costae colpi. Equatorial

pori.

FIGURE
7

10

129
PLATE VIII (Cont.)

Psilatricolporites sp. 6

Figured specimen: P814234 (116.0 x 39.2);

25—29 Rm.

2222: Prolate, psilate, tricolporate pollen grains.
Slightly aspidate equatorial pori.
Retitricolporites irregularis van der Hammen and
Wijmstra, 1964

Figured specimen: P814194 (115.7 x 37.0);

19-211Lm.

E222: Germeraad et al. (1968) related it to pollen

 

of Amanoa (Euphorbiaceae).

Retitricolporites quadrosi Ragali, Uesugui and
da Silva Santos, 1974-b

Figured specimen: P814189 (114.8 x 41.0);
52-59 Mm.

2222: Observed mainly in samples clustered under
III in this study.

Retitricolporites sp. 1

Figured specimen: P814195 (127.0 x 16.9);
40-431Lm. '

2222: Prolate, finely reticulate, tricolporate

pollen grains. Exine, 2.04um.

PLATE VI"

 

FIGURE
1

130

PLATE IX
(All illustrations 1000X)

Retitricolporites sp. 2

Figured specimen: P814195 (127.0 x 16.9);

15-20 Am.

2222: Prolate, finely reticulate, tricolporate pollen
grains. Lalongate equatorial pori. Costae colpi. Thin
exine.

Retitricolporites sp. 3

Figured specimen: P814195 (126.3 x 37.1);

30-37 Am.

2222: Prolate, reticulate, tricolporate pollen grains.
Equatorial pori. Costae colpi. Exine, 2.014m.
Retitricolporites sp. 4

Figured specimen: P814186 (118.2 x 40.2);

47.um x 35 um.

2222: Only one specimen was observed. Prolate,
reticulate, tricolporate pollen grains. Equatorial
pori. exine, 2.0.Mm.

Retitricolporites sp. 5

Figured specimen: P814002 (124.8 x 30.7);

18.Mm x 17 um.

2222: Only one specimen was observed. Circular
equatorial limb, reticulate (size of the lumina
increasing towards the equatorial area), tricolporate
pollen grain. Distinctive foot layer. Exine, 3.01Lm.
Retitricolporites sp. 6

Figured specimen: P814230 (125.9 x 22.4);

261Lm x 154km.

E222: Only one specimen was observed. Prolate, fine-

ly reticulate, tricolporate pollen grain. Exine,

1.0/an.

FIGURE
6

10

131

PLATE IX (Cont.)

Retitricolporites sp. 7

Figured specimen: P814195 (120.1 x 26.4);
19-24lbn.

E222: Roughly circular outline, reticulate, tri—
colporate pollen grains. Exine, 2.01am.
Retitricolporites sp. 8

Figured specimen: P814123 (111.2 x 29.1);

40 Am x 40‘um.

2222: Only one specimen was observed. Circular
equatorial outline. Reticulate, tricolporate pollen
grain. Exine, 1.0 Mm.

Bombacacidites sp. 1

Figured specimen: P814004 (127.0 x 23.9);

46-50 An. '

E222: Rounded-triangular polar view. Reticulate,
size of the lumina decreasing from the polar area
(2—4 Mm) to the equatorial area (less than 1.01Lm).
Planaperturate, tricolporate. Exine, 2.0;Lm.
Related to Bombacaceae.

Bombacacidites sp. 2

Figured specimen:P814002 (119.0 x 38.7);

28-331Lm.

2222: Similar to Bombacacidites sp. 1, but differs
in size range. Related to Bombacaceae.
Bombacacidites sp. 3

Figured specimen: P814001 (112.9 x 38.0);

23—28 Mm.

Note: Rounded-triangular polar view. Reticulate,

 

.size of the lumina decrasing from the polar area

(1.01am) towards the equatorial area (less than

1.0.um). Planaperturate, tricolporate. Exine, 1.0.Mm.

Related to Bombacaceae.

FIGURE
11

12

132

PLATE IX (Cont.)

Bombacacidites sp. 4

Figured specimen: P814188 (127.0 x 38.0);

24le x 22.dm.

2222: Only one specimen was observed. The preserva-
tion was not good. Planaperturate, tricolporate.
Exine, 1.0ALm. Probably reticulate with decreasing
size of the lumina towards the equatorial area.
Related to Bombacaceae.

Tilia sp. 1

Figured specimen: P813994 (127.1 x 22.7);

34 Am x 341Lm.

E222: Only one specimen was observed. Rounded-trian-
gular polar view. Reticulate-foveolate, size of the
lumina decreasing towards the equatorial limb.

Exine, 2-2.5le. Planaperturate, tricolporate.

IX

 

FIGURE
1

133

PLATE X
(All illustrations 1000X)

Margocolporites sp. 1
Figured specimen: P814195 (126.9 x 35.4);
291Lm x 19 um.

Note: Only one Specimen was observed. Circular polar

 

view. Reticulate, size of the lumina tends to de-
crease towards the polar area. Psilate margo.
Margocolporites sp. 2

Figured specimen: P814190 (114.3 x 22.5);

3414m x 3lle.

2222: Only one specimen was observed. Circular polar
view. Reticulate, size of the lumina relatively
uniform, except at margo, where smaller. Exine,
2.0Mm.

Psilabrevitricolpites? sp. 1

Figured specimen: P814195 (125.3 x 44.2);

331um x 27llm.

2222; Only one specimen was observed. Globular—oblate.
Psilate, finely perforate. Brevitricolporate, with
lolongate pori. van Hoeken-Klinkenberg (1966)
described the genus Psilabrevitricolpites. Even'
though the specimen found in the samples in this
study is clearly brevicolporate, it is still uncertain
that if it can be included in this genus.
Syncolporites sp. 1

Figured specimen: P814195 (120.9 x 13.5);

15-19 km.

2222: Rounded—triangular outline. Reticulate. Syn?
colporate, pori located at the equator. Exine, 1.0
ILm.

Psilastephanocolporites sp. 1

Figured specimen: P814188 (119.7 x 52.2);

211.011 x17;(,m.

FIGURE

134

PLATE X (Cont.)

2222: Only one specimen was observed. Prolate,
stephanocolporate (6-8 apertures), with equatorial
pori. Exine, l.0£¢m.

Psilastephanocolporites sp. 2

Figured specimen: P814239 (114.7 x 34.6);

34 Am x 261Lm.

2222: Only one specimen was observed. Circular polar
view. tetracolporate, with thickened margins. Exine,
2.0}Lm. Psilate. Some similarity is observed with
the specimens of stoxylum malabaricum (Meliaceae)
described by Thanikaimoni et a1. (1985).
Graminidites sp. 1

Figured speci222: P814188 (124.7 x 22.1);

55an x 30lkm.

Note: Only one specimen was observed. Prolate, mono-

 

porate. Probably psilate (the only specimen that_was
observed was not well-preserved). Related to pollen
of Gramineae.

Aglaoreidia sp. 1

Figured specimen: P814195 (126.4 x 22.1);

20 um x 16ALm.

2222: Only one specimen was observed. Ovoidal to
circular equatorial outline. Reticulate, size of the
lumina relatively uniform. Exine, 1.5,Mm. Related

to Ruppiaceae (Frederiksen, 1980).

Retidiporites sp. 1

Figured specimen: P814195 (120.5 x 33.6);

18-25 14m.

2222: Elongated ellipsoid. Diporate. Finely reticulate.
Exine, 1.0 um. In this study, it was mainly observed

in samples clustered under III.

FIGURE
10

11

12

13

135

PLATE X (Cont.)

Retidiporites sp. 2

Figured specimen: P814195 (121.0 x 14.1);

15-222Mn.

£222: Similar to Retidiporites sp. 1, but more fine-
ly reticulate. Very thin exine. In this study, it
was mainly observed in samples clustered under III.
Echitriporites trianguliformis van Hoeken-Klinken—
berg, 1964

Figured specimen: P814195 (126.5 x 26.3);

19—23 Mm.

2222: In this study, it was mainly observed in sam—
ples clustered under III.

Echitriporites sp. 1

Figured specimen: P813988 (118.6 x 20.7);

42 Mm x 321Mm.

E222: Only one specimen was observed. Almost circular
polar view. Echinae, 2-3.um. long. Exine, 1.0.Mm.
Wall, finely perforate or reticulate.

Proteacidites sp. 1

Figured specimen: P814189 (119.1 x 35.3);

30.um x 29 um.

E222: Triangular outline, triporate. Roughly concave
sides. Reticulate-foveolate. Costae pori. Exine,

1.5.Um. Related to Proteaceae.

PLATE X

 

FIGURE
1

136

PLATE XI
(All illustrations 1000X)

Retitriporites sp. 1

Figured specimen: P814195 (125.5 x 38.0);

57/.Lm x 52 am.

2222: Only one specimen was observed. Circular polar
view. Coarsely reticulate. Triporate, thickened pori.
Exine, 3-3.5 Um. Similar to Foveotriporites hammenii
described by Gonzalez Guzman (1967) in the Eocene of
Colombia.

Retitriporites sp. 2

Figured specimen: P813997 (127.0 x 34.6);

35-39 km.

.2222: Circular polar view. Triporate, probably 1a-
longate pori. Finely reticulate. Exine, 1.0l&m.
Retitriporites sp. 3

Figured specimen: P813997 (115.1 x 22.9);

'20-25AUn.

2222: Roughly circular polar View. Triporate. Pori
are not located at the equator. Reticulate. Exine,
1.0.Mm.

Retitriporites sp. 4

Figured specimen: P814126 (125.3 x 33.2);

381Lm x 31.Um.
Note: Almost circular outline. Triporate, pori with

distinctive annulus. Reticulate. Exine, 2.01Lm.
Cricotriporites sp. 1

Figured specimen: P814195 (126.6 x 21.3);

15-20 Am.

2222: Circular outline. Triporate, psilate. Exine,
1.24Mm.

Anacolosidites sp. 1

Figured specimen: P813981 (123.4 x 41.0);
18-251Lm.

Note: Rounded—triangular outline. Hexaporate, with

FIGURE

137
PLATE XI (Cont.)

3 pori in each face. Exine, 1- 1.5,Mm. Wall, finely
perforate. In this study, it was mainly observed in
samples clustered under II and IV. Related to Olacaceae.
Juglanspollenites sp. 1

Figured specimen: P814194 (127.7 x 25.7);

29-35 Mm.

E222: Circular outline, polyforaminate. Exine, 1.5
.Mm. In this study, it was mainly observed in samples
clustered under II and IV.

Clavastephanocolporites ? sp. 1

Figured specimen: P814230 (113.2 x 25.9);

24num x 23aum.

2222: Only one specimen was observed. Circular out-
line. Clavae, 1.51Lm. long. The author of this study
considers that the type of apertures are similar to
those described by Leidelmeyer (1966) for the genus
Clavatricolporites. However, the author of this

study thinks that the apertures of the specimen

found in this study are porate rather than colporate.
Echistephanoporites sp. 1

Figured specimen: P813988 (118.6 x 20.7);

30/Lm x 304um.

2222: Only one specimen was observed. Circular
equatorial outline, tetraporate. Pori, with annulus.
Exine, 1.01Lm. Echinae, 1.0,Mm long.

PLATE XI

 

138

PLATE XII
(All illustrations 1000X)
FIGURE
1 Tetrad Type A
Figured specimen: P814186 (125.7 x 17.0);
68-71 Am.
2222: Tetrad of echinate pollen grains. Wall, finely
perforate. Apertures were not observed. Exine, 2.0
Mmu Echinae, 6-71Lm long. It was only observed
in this sample.
2 Tetrad Type B
Figured specimen: P814001 (122.0 x 26.4);
32-37 LLm.
E222: Prolate individual grains. Tricolporate. Wall,
psilate or finely perforate. Exine, 2.04um. It was
mainly observed in samples clustered under II and IV.
3 Tetrad Type C
Figured specimen: P814108 (116.0 x 34.8);
551Lm x 451Lm.
2222: Only one specimen was observed. Tetrad of
coarsely reticulate pollen grains. Exine, 2-3.lm.

Apertures were not observed.

PLATE XH

 

FIGURE
1

139

PLATE XIII
(All illustrations 1000X)

Classites sp.
Figured specimen: P814195 (12.8 x 17.5);
30-32 Am.

Note: Inaperturate grains, with circular outline.

 

Exine is clearly divided in two layers. Psilate.
Similar specimens were described by Gonzalez Guzman
(1967) in the Eocene of Colombia.

Peltandripites sp. 1

Figured specimen: P814126 (126.9 x 38.9);

17-25 m. '

Note: Circular outline. Triporate, pori are not very

 

distinct in some views. Echinae, approximately 1.0
ALm long. Very thin and structureless exine. In this
study, it was mainly observed in samples clustered
under IV.

Unknown Type 1

Figured specimen: P814195 (118.5 x 35.1);

20—27 Mm.

E222: Rhomboidal-circular outline. Tetraporate, pori
with some thickening. Echinate, echinae 1.01am long.
Very thin and structureless exine. In this study, it
was mainly observed in samples clustered under III.
Unknown Type 2

Figured specimen: P814124 (109.9 x 26.1);

621km x 62}&m.

2222: Only one specimen was observed. Circular polar
view. Probably tetracolporate. Exine, 3.0.Um. Semi-
tectate,

Unknown Type 3

Figured specimen: P814225 (126.9 x 33.9);

40.Am.

2222: Only one specimen was observed. Fragmented

palynomorph, with large gemmae linked to a reticulate

FIGURE

140
PLATE XIII (Cont.)

wall. Gemmae, 10.um wide.

Operculodinium sp.

Figured specimen: P814195 (115.0 x 41.7);

41-46 Mm.

2222: Rarely found in the samples under study.
Circular cysts, without any evident ornamentation

or observable plates or sutures. Non—fibrous processes
with bifurcate ends.

Unidentified chitinous inner linings of Foraminifera
Figured spgcimen: P814195 (122.4 x 44.6);

23-34 Mm.

‘2222: Generally, kidney-bean shaped, with chambers

separated by septa.

PL ATE xm

 

 

MICHIGAN STATE UNIV. LIBIRQIIUES
1HWIWm1WWWWWWWIWNW
31293009941893