THESIS - GMRY n ic (“all “I“ University This is to certify that the thesis entitled Gravity Modelling of the western Marquette area, Michigan presented by Soo-Meen Wee has been accepted towards fulfillment of the requirements for Master of Science degreein Geological Sciences Major rofessor Date 5/17/85 Kazuya Fujita 0.7639 MSU is an Alfirmative Action/Equal Opportunity Institution IV1ESI_J RETURNING MATERIALS: Place in book drop to LJBRARJES remove this checkout from 4—::—~- your record. FINES will be charged if book is returned after the date stamped below. #fiMT - _ GRAVITY MODELLING OF THE WESTERN MARQUETTE AREAI’IICHIGAN DY SOO-MEEN WEE A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Geology 1985 ABSTRACT Gravity Modelling of The Western Marquette Area, Michigan. by SOO-MEEN WEE A gravity survey was conducted in the western Marquette district, Michigan, to delineate the relationship of the Proterozoic Marquette Supergroup rocks ( Precambrian X) and Archean basement (Precambrian W) where the Republic and Marquette troughs join. Three hundred and forty gravity stations were established in the area of 380 m2. Positive anomalies are associated with the Precambrian X, meta- sedimentary sequence which has a higher density with respect to the Precambrian w, basement rocks. The dominant positive gravity anomalies follow the axes of the three troughs which are filled with Precambrian X l‘OCKS. Subsurface structure was modelled by using the method of Talwani et al. Gravity model studies indicate that the Marquette trough is asymetrically shaped and steeply dipping at the north edge except in the eastern part of study area. The interpretive results obtained from two dimensional model studies suggest that the basement structure of the study area is relatively flat, and that the troughs were formed contemporaneously. ACKNOWLEDGEMENTS l sincerely thank Dr. Kazuya Fujita for his advices, guidance, and suggestions during the study and preparation of this manuscript and for his invaluable assistance in the l984 field session and for assistance in locating station locations . l sincerely thank Dr. J. T. Wilband for his sincere interest, guidance, and helpful criticism during preparation of this manuscript. Dr. F. w. Cambray is to be thanked for his helpful suggestions. i would like to thank Dr. J. Trow for providing me with many good references, Mike Lipsey for photo reduction assistance, the Mead Paper Company for providing logging maps, and the Michigan Department of Natural Resources for providing airphotos. ii TABLE OF CONTENTS Chapter page 1. lNTRODUCTioN ................................................................................ 1 1.1 Purpose of the study .............................................................. 1 1.2 Study Area .................................................................................. 2 1.2.1 Location and Topography ....................................................... 2 1.2.2 General Geology ....................................................................... 2 1.3 Previous work .......................................................................... 8 2. FlELD WORK .................................................................................... 12 2.1 Gravity survey and Instrumentation ............................... 12 2.2 Accuracy of Horizontal Coordinates .............................. 15 2.3 Elevation Control ..................................................................... 16 3. DATA REDUCTION ............................................................................ 17 3.1 Gravity ........................................................................................... 17 3.2 Elevation Correction ................................................................ 17 3.3 Mass Correction ......................................................................... 17 3.4 Latitude Correction .................................................................. 21 3.5 Error Analysis ............................................................................. 2S 4. GRAVITY DATA INTERPRETATION ............................................. 28 4. 1 Procedure ..................................................................................... 28 4.2 Interpretation of the Bouguer Gravity Map ................... 29 4.3 Modelling ..................................................................................... 32 4.4 Summary of the Results ......................................................... 68 5. Conclusion and Recommendations ............................................. 72 REFERENCES ......................................................................................... 7S APPENDlCES ......................................................................................... 78 iii LIST OF TABLES Table 1. Stratigraphic column for western Marquette Range ...... 2. Stratigraphic sections of Precambrian rocks in parts of northern Michigan .............................................. 3. Drift Rates ......................................................................................... 4. Error Analysis ................................................................................... 5. Rock Density Data ............................................................................. 6. Thickness of Formation of the Menominee and Baraga group ......................................................................... iv Page 27 35 38 LIST OF FIGURES Figure Page 1. Index Map ........................................................................................... 3 2. Geologic Map of the study area ................................................ 4 3. Geologic Map showing location of gravity lines ............. 13 4. A1timeter(W) drift curve for J and K loops ........................ 18 S. A1timeter(W) drift curve for V and W loops ...................... 19 6(a) Bouguer Gravity Map ....................................... 23 (b) Station locations of the study area ............................... 24 7. Gravity Profile A-A' (I) ............................................................... 34 8. Alternate Gravity Profile A-A‘ .............................................. 43 9. Gravity Profile A-A' (II) ............................................................ 44 IO. Gravity Profile 8-8“ (1) ............................................................... 47 11. Gravity Profile 8-8‘ (H) ............................................................. 48 12. Gravity Profile C-C' ...................................................................... SO 13. Gravity Profile D-D' ...................................................................... 53 14. Gravity Profile E-E‘ ...................................................................... S7 15. Alternate Gravity Prof i1e E-E‘ ................................................. 6O 16. Gravity Profile F-F‘ (I) ................................................................ 61 17. Gravity Profile F-F' (II) .............................................................. 62 18. Alternate Gravity Profile F-F' ................................................ 64 19. Gravity Profile H-H‘ (I) ............................................................... 66 20. Gravity Profile H-H‘ (II) ............................................................. 67 21. Thickness of the sedimentary rocks and distribution of faults ..................................................... 71 vi STRATIGRAPHI C NOMENCLATURE Yd - Diabase of Keweenawan age Xmus - Early Proterozoic, Baraga Group, Upper Slate member me - Early Proterozoic, Baraga Group, Bi jiki Iron formation member Xms = Early Proterozoic, Baraga Group, Lower Slate member de - Metadiabase chv- Early Proterozoic, Baraga Group, Clarksburg Volcanics member me - Early Proterozoic, Baraga Group, Strata near Fence Lake Xf r . Early Proterozoic, Baraga Group, Fence River formation th - Early Proterozoic, Baraga Group, Hemlock formation X9 = Early Proterozoic, Baraga Group, Goodrich Ouartzite Xn - Early Proterozoic, Menominee Group, Negaunee Iron formation Xs - Early Proterozoic, Menominee Group, Siamo Slate Xa = Early Proterozoic, Menominee Group, A jibik Ouartzite Wg - Archean, Granitic rocks vii 1. Introduction ‘1 o 1 n , x The western Marquette area is underlain by an elongate trough of Pro- terozoic (Precambrian X) metasediments of the Marquette supergroup which has a small offshoot known as the Republic trough. These troughs unconformably overlie Archean (Precambrian W) basement schists and gneisses. At the junction of the Marquette trough, the Republic trough, and the Michigan River trough, the complex structural and stratigraphicai patterns of Precambrian X rocks may be related to previous deformations of the basement structure which occured prior to 2.5 Ga. Subsequent faulting of the basement developed during the Penokean orogeny. The surface geology 01 the study area is well known as a result of many investigations which delimited the extensive iron ore deposits in the susergroup section. However, geophysical inves igations have oniv been conducted in a limited area and started only in the 19705 (Cannon and Klasrer, 1974). These studies have provided vaiuaole information about rock densities, particularly the significant density contrast existing between the Precambrian X sedimentrv seouence and the basement rocks. however. tnere are Insufficient data to allow for estimates of the deb-tn, structure, and cross-sectional configuration of the western Marquette area. In the present investigation, the subsurface geology of the western Marquette area was modelled based on gravity measurements. Wm 1.2.1. Location and Topography The area under investigation (Fig.1) lies within western Marquette and southeastern Baraga counties, Michigan. The survey area is bounded by 46°25” and 46°35 north latitude and by 87°55 and 88°10' west longitude. and includes parts of Townships 46, 47, 48, and 49 north, Ranges 29, 30, and 31 west. The surface elevation rises 1800 feet above sea level in the north- western part of the study area and is 1500 feet at the southern end of Lake Michigamme. The elevation is never more than 300 feet above Lake Michigamme. A swamp covers a large area in the southern half of the study area. 1.2.2. General Geology The area under investigation is composed of Precambrian rocks of three ages. The majority of the rocks are Precambrian W and Precambrian X ( Fig. 2 l. The Precambrian W (lower Precambrian .thm an vmxnma ma AGOfipdum coaasmnov :owaopm omdm .ozfiH cognac ha copuowncfl ma mono hczam was .Qda noccH .P ohzmwh ht» i gt: , :58 hi? . bKB _ an film-ll . 3... .n m m lie $0 )4 Vmwr . 340m ))4w . N \wdv v a I 90 I ea 236% if: I coo mi. b u iiiii!.un h. 94%? a .4. PM: £253 22: . v6 . .Iflmymwiidaflm ss . . m u s n - t m. u A . <22 :55 n m — N u so: . - m m . u . . c g u ’5 n . 4 $49 . aw _ . u _ u u . 1 n . I m 49,6 . u _. ................ 1.1. ..... i .. .. - .u . n b N n - n hu .9. .ww> omen co :o>flm mew mcoflpww>onpn< .mxoon x :wwnnewoohm csw z :wfihnamoopm mo Ahmczson ohm moCHH xowze .mpazmm myocawzw mocwa cmzmwa .wohw aczum onp mo an: OHwOHoow .N ohzmwm ““050 8000 basement rocks, mostly granitic gneiss, are 2.5 billion years old or older by Rb-Sr dating (Cannon and Simmons, 1973), while the Marquette Range supergroup, a Precambrian X (middle Precambrian) sedimentary sequence is about 2.0 billion years old (Cannon and Klasner, I974). Keweenawan rocks (Precambrian Y) exist only in outcrops on an island in Lake Michigamme and forms a circular stock and very small dikes which trend approximatly east-west (Klasner and Cannon, I978). The basement rocks are unconformably overlain by Precambrian X rocks which wer deposited during an extensive period of sedimentation with minor volcanic activity. The contact between Precambrian W and Precambrian X rocks was originally an unconformity, but it became a zone of major slippage as the sedimentary rocks were down folded into the develooing graben (Klasner and Cannon, 1978). The general stratigraphic column of this area is shown in Table I. The Menominee and Baraga groups of the Marquette Range supergroup are present in this study area. Previous geological investigators have shown that the Menominee and the Baraga groups had different depositional environments. The former was deposited in shallow water, while the latter was deposited in a deep water eugeosynclinal environment resulting from rapid subsidence of the depositional basin (Van Schmus, Table 1 Stratigraphic column for western Marquette Range. (After Cannon and Klasner, 1972 and 1975) ' SIJI'I‘LITQZIIUIII’ , HRUHP FHNHATIH“. MID/0R llEIIBI-‘Jl HEflHHTPTION Ug-pvr .I‘rvcnnl-rIM}. I-IIIIJI" I'I'm'nqu-Iun Iii-imminimn Intrunlvn dlwhunu Nnnnvtnnnrphnnnd dlnhnnu dike" and otnckn. Pennnlitn Cnnrnnournlnnd-nlvrnclInn-quartzouuncovitn rocks. Relatively rnrc. Motor“ '1 Imn'.‘ Amphihullilc rock, much with rellct dlnbnnn texturn. Huntly an nllln In ulddlo Precambrian ruu'hn riml nIlIu-n In Inut-r I'rnnmphrlnn rat-kn. Hui-Ii I:: 'n'nliulily nummlntod with rockn of UM) Ulnrkubnru Volunulun Houber of tho Htvhlgnnno Furnntlnn. Hvinpnllto and outnurnyuockn with calc-alliuntn c-nm'rvam. AIzm pyt'lhlc hlnck nlnlm. Upyrr ninth mmlmr Dljlkl Iruu- formation member ”0... .. unuLIy rhrrLy nlllcnbo Iron-forlntion. grimr‘rl I In m-h I fit. 80-0 Lower ulnhn Hctupvlltln and nutngrayuncko with cone pyrttic 0 nonhur rnrhunnunnuu nlnLc. v. 8 Q ' yqurl nxpnflnd nucuunco or onihlhollllc "Chint- n 'IrnLn nrnr y I I ”- L. l) ' Vl'nymu-Itr. lruu l'cll'llltlnn. cnngln-nrntr. Mill :3 o FU'IIun Inika' ' . .h', g g . . "ck-1 8 '“ 'Iyl no .1 t It . o '1 u . n 3 Fence Rlvnr Handed lrnn ollllruLn-nugnotlto tron-forlntton. 3' ’0 Format Icm v-wmiiily v-mLIIInIng pelluc Iicdu. u H c: if Lurrvly hnnultl» rnrkn and lens ro-unn fvluln ‘ ”"M|')"k ‘ o - :3 kW _ g. In iuill l niuI rvnilniwiiury hrulu. bruituliia lliiu ' "NH" ' H . "nil I‘VI'UI'I I|;II.II' rur‘ktl. Houdrlrh Hounlv" Ln hundud prutoquurtxtto with conglo- I.)um-i7.l i." sum-nin- iii-hr I-mm. Lot-"l unconfnrml'y “re (II 'f«"vtll'r»|'unl if; d! IIPIUIIIIHH‘ Ir'mi- ”113' I)‘ i‘IIt‘i'Ly nlllrntn iron-fornntion UIUI fllIdi ' : rurmnllnn Irv-rurmntlnn nrur top. n‘ 3 ‘f :‘IIim-i ' I'l'." Immiimi i--| "ml nimI I LG I! f) :1 f; M 1m .._ '}Illll".'.’.' I -' I.-~v"iI Luau-r I'I'm-nmlu' I nu 'Illt"IIII"‘I’Ill I I '1' dlnvunfvrmlly 'i‘lH“ I :‘1? I!" no r I Iwr°i riml :H'Ill IHH'H r'umll I t‘X":l kudnd Lu nnnuivv, light colored quartzltn. Cur-wiry. nt’ y'rvalrIc rind mnl'ic Km‘lnn. "ml "run-lift Minn. pnguntita I976). The Menominee group is a fining upward sequence with a basal quartzite overlain by laminated argillites, and chemical precipitates with local conglomerates (Klasner and Cannon, 1978). It was deposited unconformably on the Precambrian W basement rocks with mild tectonic disturbances during sedimentation (Van Schmus, 1976). The Baraga group is composed of a greatly varied sequence of meta- sedimentary and metavolcanic rocks (Klasner and Klasner, 1975). It is the most extensive of four groups composing the Marquette Range superguoup (Cannon and Gair, 1970). In the study area, it is composed of the Goodrich quartzite, Hemlock formation, Fence River formation, "strata near Fence Lake, " and the Michigamme formation. The last covers the large area in this study area. The "strata near Fence Lake " is considered to be part of the Michigamme formation (Cannon and Klasner, 1975). Regional metamorphism, ranging from sillimanite to staurolite grade, recrystallized the rocks at approximatly the same time as deformation (Cannon and Klasner, 1.977). Deformation in the trough is attributed to the Penokean Orogeny (Cannon, 1973), which occured about 1.9 Ga ago, and 15 related to the development of a subduction zone resulting in compression of the basement and the overlying sediments (Cambray, 1977). An early tensional phase caused rupturing of the continental shelf which produced grabens and was followed by a compression phase which produced folds (Cambray, 1977). l m i I ‘ Numerous studies have been conducted concerning the extensive iron ore deposits in the vicinity of study area. In 1881, Rominger investigated iron bearing districts in Marquette area and analyzed the basic structure of the Marquette synclinorium (Boyum, 1975). An analysis of the distribution of the rock types and contacts was performed by Van Hise and Bayley (1897). Introduction of a new stratigraphic column by James (1958) initiated modern geological surveys of the area. Although this stratigraphic column is generally accepted, the name Marquette Range supergroup as been proposed to supplant the term Animikie Series by Cannon and Gair (1970) as shown in Table 2. This proposal is due to the failure to prove a correlation between the middle Precambrian rocks in the Marquette (ii ‘J‘ U": trlct of Michigan and the type area of the Huronian. The geology of the southern parts of the Marquette district were also investigated (Cannon and Simmons, 1973). The tectonic events and depositional history of Early Table 2 Stratigraphic sections of Precambrian rocks in parts of northern Michigan. Imflivw- . . We” cmrmm mm mm m m mm mm mm a I not M WW“ Wham-ha M mam a" I Minn-Fm 1 menu!“ mm mm Wm” WM Mil-i. whim Ann-arm o 3|". Farm” mm W (In. mm WM m Function“ m I mm m ecu mm Il . mm mm mm Sun-Ooh mm mm W Mum in: MM Chump m m m rm M Me In M m W 8mm WW 6'” Wu“ 'mW'm rm WWW" —— WM -—-—- W" W" — m M (W 0mm Gain m Gunman. mm; 0'th Compiled from Leith and others, 1935, Table facing p. 10; James, 1958, p. 30; and Gair and Thaden, 1968, Table l; and Cannon and Gair, 1970, Figure 2. TO Proterozoic strata in Michigan were studied by Van Schmus (1976). Klasner (1978) investigated deformation and associated metamorphism in the western Marquette range related to the Penokean orogeny. Geophysical studies were conducted by Cannon and Klasner (1974) and are the only detailed gravity work concerning the study area. They contributed to the interpretation of subsurface geology by determining the depth of some parts of the elongated troughs, and providing rock densities. Their general method is used for the present study. A magnetic and gravity survey, with additional density determinations, of the Witch Lake area was performed by Cannon and Klasner (1976), and a bedrock geologic map of southern part of the Diorite and Champion 7 1/2 minute quadrangles, with cross-sectional interpretations of the Marduette trough based on gravity data, was published (Cannon and Klasner, 1977). Subsequently. the bedrock geologic map of the southern part of the Michigamme and Three Lake quadrangles, Marquette and Baraga counties, based on a gravity and magnetic survey, was published (Klasner and Cannon, 1978). Aeromagnetic maps of some parts of Marquette area have been published by Case and Gair(1965) and of parts of the Witch Lake quadrangle oy Cannon and Klasner (1976). 11 Gibb ( l 967) contributed to the determination of the density of the Pre- cambrian rocks exposed in northern Manitoba. 12 2. Field Work W The survey was carried out during the periods of July S-July i4, l 984. The gravity observations of this survey were taken with a LaCoste- Romberg geodetic-quality gravity meter number, 6-180, which has a range of 7000 milligals with an accuracy of z 0.01 milligal. Elevation was controlled using a Wallace and Tiernan altimeter (Model No. FA l l2) and read directely from topographic maps. This altimeter is marked in units of ten feet. A second Wallace and Tiernan altimeter was used in con juction with the first one to reduce possible errors and to enhance accuracy. Four base stations were used in order to determine instrumental drift by reoccupation. The magnitude of the drift was checked at least once every four hours and yielded a mean drift curve, without respect to sign, of 0.018 milligal per hour with a standard deviation of x 0.021 milligal per hour. Three hundred and forty stations were measured in this study along several loops with their lengths varying from 8 to 20 kilometers (Fig.3). The station spacing varied according to the amount of 13 .N musmwm :H mm mHonamm .mmHHmopQ >pH>wpm cmaamuoa mo :owumooa mnazonm an: afimoaomo .m mmsmwm nnokb 000nm 8600 0:8 - d . u . s o u I... D : . .x .3. . .. .E: . 9.... x a. . .. 3:: b2 9’28. 8.? ~ g. s s . .< "0.. . a! N \cv . o 4 s s \~).Q '3 . s . Q \ s. ~_ 8K \\ 9 s. v; 5X f \ \\ \s\ a -- y 3 a! . W “ V o . W. uv\ on u ML . a . .s _ a: 3 3 ”xx 3. l or? ’3! O I.— .l 3. ’ 2.x 6 u _ u 0. 35x usagexea . /v i <4 9 \ O” - ~V ox.» OX . . .. . 1%. a a .. a . ax .il 0’ v M.“ o o m N_ o / IL— 0. A I’ no . _ ¢ . L . _ a . 14 resolution desired and varied from i00 m to l km. The existing road network did not provide as good a coverage of the area as desired. However, the survey covered a large area in which logging roads provided access. Most of these road do not appear on U.S.G.S. topographic maps and have been built in the last decade. in order to minimize the location error, station locations were determined by using the following sources of data. l. U.S.G.S. 7 1/2 minute (Witch Lake NE, Michigamme, and Three Lakes) quadrangles, and U.S.G.S. l5 minute (Witch Lake) quadrangles. The 15 minute quadrangle was blown-up to 1: 24,000 photographically. 2. Michigan Department of Natural Resources airphotoes of the Witch Lake quadrangle taken on August i4, l978, provided by the Michigan D.N.R field office in lshpeming, which were traced and expanded to 1: 24,000. 3. Mead Paper Co. timber classification maps provided by Mead Paper, Co, Champion Office. These maps are at an approximate scale of l0cm = l mile. These were photo reduced to 1: 24,000. 4. Mead Paper Co. Field Maps at 8"= 1 mile drawn for road construction. These maps were also photo-reduced to l:24,000, but accuracy proved often to be in error by up to l/8 mile (660‘). 15 S. Mead Paper Co. logging maps at l"- l 320'. These were at best schematic diagrams. in addition to the above maps, a pace and compass survey was run in section 5 and odometer-topography-bearing survey were performed in section l4 and for line P. All locations were plotted onto U.S.G.S. topographic maps. Whales Latitude and longitude coordinates were determined for each station from 08.6.5. topographic maps (scale, l:24,000). Stations were located at road intersections or at recognizable locations whenever possible. The location error for most stations at such intersections does not exceed r. i 50 m with very few exceptions. All stations north of Lake Michigamme and south of US-4l are probably very accurate. The largest potential errors seemed to be on line V, particularly stations V26 through V32. The possible mislocations in line V are :75 m to 150 m with some exceptions. i 6 WM Elevations of all the stations were established by using two Wallace and Tiernan altimeters, one metal, and one wood cased. The metal cased altimeter drifted considerably more than wooden one (Paddock, 1982), especially in direct sunlight because of ground temperature. Only two bench marks were actually found during the survey, lS96 feet (station N l 0) along the Soo trackage south of the Mud Lake, and 1679 feet (station T l 0) northeast of St. Johns Lake. When culturally identifiable locations were unavailable, gravity stations were located at topographically identifiable features, such as in the center of depressions or on the crests of gentle hills. The accuracy of these elevations, therefore, is estimated to be 2 5 feet and no case exceed 2 i 0 feet, resulting in error of .+. 0.21 milligal. 17 3. Data Reduction mm Observed gravimeter readings were drift-corrected based on drift curves ( Fig.4 and Fig.5 ) for lines J, K, V, and W which had high frequency instrumental drift due to climatic conditions. Other lines were corrected assummlng linear drift within each loop. The readings were then converted to milligals using the calibration constant of the gravimeter. This process produced the observed gravity values listed in Appendix B. Drift rates are listed in Table 3. Table 3 Drift Rate Drift Rate No min/hour max/hour mean st dev Gravimeter 18 0.00 0.03 0.01 & £0021 Altimeter *M 14 0.0] 0-17 0.08 1 0.05 *w 14 0.01 0.17 0-08 x 0.05 (* M: Metal cased altimeter W: Wooden altimeter) 32 E] I’ : l‘ The elevation, or free-air, correction takes into account the 18 .ammm can no mafia: :H vmxmwa soapw>mam .maooa a 6:8 h pom vow: m>nzo pmwpc mpflmomaoo mnp mpcmmmuamn mafia nwaom .coauwpm comm map mo m>nzo pmauc weapapaw pzmmmnamn mmcwa cmnmwn .mmooa M cam w you pmanc sznmpmmfipa¢ .v mpsmflm d 4 . d d u q . USN—a.” .099 005. 00K. comm. Donn. DO”! 00%. CONN. On? .5de 19 o>nso pmwau anamoasoo map mpcmmmnmmh mafia UHHom pmwno ovzpfipaw pcmmmhmou mmcfia cognac .pmom :ma mo mafia: :H omxpwa coapw>mam .mQQOH 3 can > now now: .moapmpm comm man no m>nzo .mQOOH 3 6:8 > new amauc szhmpmswpa< .m mgzmfim 8.5.: 00K. 09m. 00%. 09¢. 08. CON. 00.: 006. 5a d u d u d d u (Hi -i----------_..- 25 ..... L ...... .. I.|l| i r |||||| : iiiiiiiiiiailiii Y 1 I. .l I. A!!! .I A me. I I I I .I I. I (L. A _ . Qfiml . ._ QmNI mm > . ¢>u4mv 20 vertical decrease of gravity with an increase in elevation with following formula (Telford et al., l976 ). cigfa /dRe = - 2GMe/Re3 z -2g/Req z -0.09406 mgal/f t =-0.3080 mgal/m Me: mass of Earth R,3 :Radius of the Earth at latitude a G : Gravitational constant Req : equatorial radius Gravity data were reduced to base station level (the elevation of the platform at Champion railroad station, i598 feet ) using a correction factor of 0.09406 mgal per foot ( 0.3080 mgal per meter ). Won The Bouguer correction takes into account of the vertical increase of the gravity with an increase in elevation due to the attraction of the material between the datum and each station. This correction is calculated from the following formula (Telford et al., 1976) dgb/dRe z dgb/dReq = 2116p mgal/ft =0.0 l 277 p mgal/ft = 0.04i 88 p mgal/meter 2i p: material density (g/cm3) Re: Radius of the Earth at latitude a Rea: equatorial radius Elevation values for each stations are listed in Appendix B. No correction was made for the terrain effect, since the topographic relief in the survey area was small enough to make the terrain correction negligible. 3 l l l 'l | C !' The latitude correction takes into account those gravity changes that are attributable to latitudinal differences, such as the increase in gravity from the equator to the poles. For stationary gravimeters, the value of the Earth's gravitational attraction varies with latitude due to the effect of the centrifugal accleration by the f oliowing formula (Telford et al., i976). g = 90 - WZRa cos22 a g : observed gravity measured with stationary gravimeter go; Earth gravitational field at pole 22 B: latitude W: angular velocity Ra: Equatorial Radius of Earth The gravity data were normalized to the latitude of the 46°30'00“, which is close to Champion station, and was selected as the base latitude. The latitude corrections were made by using following formula. The i967 international F omula for gravity variation with latitude is (Nettleton, i976 ) : g (cm/secz) = 978.0490 ( i + A sinzz + 8 sin 2 21a ) A = 5.2884 *10‘3 B = -s.9 * 10‘5 B : latitude Observed gravity values were then adjusted for the above corrections to obtain the Bouguer gravity anomalies according to the following: Bouguer gravity anomaly = observed gravity + free-air correction + Bouguer correction 23 SCALE I 82800 FLSOW lusw Figure 6(a). Bouguer Gravity map of the study area. In unsurveyed areas, the contour lines are marked with a dashed line. Base station (Champion station) is marked by star. 74." um 24 ! .... I a. i OOH i u. 'I. O“ i C. 0.. on "' '1 | flu 41" *. YIL .01.; r: o." .0" O. . an '5' £7 O".II'.- “O O”... . o- , W; U, ." a: .- ...“..' on ’ o . ° 0 0.. ' a. a” lb“; '3'. (lg, “5L." 9 ..~ 0. 0.: ' III-o '" LA“ memo“. . .u '" 0“ Q 3+0 . O:- 000 o“ o. .00 “fig 0” .9 .quI 9??&n*' (u .‘l. :0... a. “.003 8a , III ' o ... I. I. .- tn. .0. Tm d . on m .u "a DC 0.. 0.. '.‘ .CS " m nouoo o l O l M m. 2 I O I I g. Figure 6(b). RSOW RZQW Station locations of the study area. Base station (Champion station) is marke d by star. 25 + latitude correction - base station gravity The Bouguer gravity anomaly map and the locations of the gravity stations are shown in Figures 6a and 6b. W In making the gravity reductions, the potential sources of error may stem from the survey procedure itself. These errors can be divided into following four possibilities. A. Errors in reading the gravimeter. 8. Errors in elevation determination. C. Errors in latitude determination. D. Errors caused by incorrect assumed values of density of subsurface material The magnitude of the above errors can be estimated in the following manner. An estimate of the accuracy of the gravimeter readings can be obtained by multiple readings at some stations. The standard deviation for these repeated gravity observation is z 0.02 mgai. Elevation errors within the study area can be determined by comparing topographic map values with those measured by the 26 altimeter. Twenty six stations of known elevation (e.g., road intersections,bridges) were selected for this comparison. The standard deviation for these errors is z 3.25 feet which produces the error :. O.2l mgal according to the following combined fomula (Nettleton, 1976 )1 9&5 = ( 0.09406 - 0.01278 0 ) h 9F 8 : combined correction for Bouguer and free-air anomaly p: rock density (g/cm‘) h : relief (ft) Errors in the latitude correction depend on the accuracy of the latitude determinations. The latitude errors of the most stations do not exceed + 30 m which result in an error of x 0.02 mgal except in line V. in line V, there is maximum misiocation of stations of: l50 in, probably considerably less than that, which results in an error of : 0i i mgal. An incorrect value of the subsurface material density causes an error in the mass correction. An error in the density of 0.1 g/cm3 causes an error of 0.00i mgal per foot (Nettleton, i976 ): 39 = 0.0l27 ap h mgal/ft ag : gravity error 27 ab : density error (g/cmé) h :eievation (ft) in this study, an error in the density of O. l g/cm3 will cause an error of 0.0l3 mgal per 10 feet. The largest density contrast in the geologic column is between glacial deposits and the bedrock. Therefore, the distribution of till significantly influences the gravitational field. However, no data were available about the till thickness in this area. Deviations in the till thickness of i0 m, with a tiii density of 2.0 g/cm3 (Paddock, i982), will cause an error of i 0.28 mgal. Assumming that above factors are independent, possible errors in this survey are listed in Table 4. Table 4 Error Sources Error Sources No Min Max Mean St. Dev Mgai Errors inReading 8 0.00 0-05 0.0i9 fix 0.02 5002 ErrorsinElevation 24 0.00ft lift l-l2ft:3.52ft :92] ErrorsinLatitude - 0.00 m 150m - - £0.11 Probable Error 1 0.24 28 4. interpretation of Gravity Data interpretation of gravity data has been carried out using all available data, including published geological information, measured Bouguer gravity, and rock density data determined by previous workers. in the present study, seven gravity profiles were considered from the area (Fig.3): i) two north-south oriented; 2) one east-west oriented; 3) three northwest-southeast oriented; 4) the one oriented from northwest to southeast. The gravity data were interpreted in a step by step manner. First, the overall structural trends were determined from the Bouguer gravity map. Several geological models were made for each profile based on all the available information. Then the best one was chosen after computation. Gravity models were calculated for the two dimensional subsurface geological models using the method of Talwani et al. (1959) using a program by Paddock (1982). Computation was performed using a CDC Cyber 750 computer. The assumption of two dimensionality is justified because most anomalies are horizontally linear having greater lengths then widths (Oray, l97i ) except of 29 profile C-C'. Some minor errors may also be encountered in profile F-F' and southern parts of prof lie B-B'. Models were also required to match every point where separate profiles crossed. One of the most important causes of error in the model studies is the density determination for each rock unit. The density of the rock units were fixed as shown in Table 5 except the Negaunee and Goodrich formation. Densities of the Negaunee and Goodrich formations were varied depending on the percentage of iron content which was determined by previous workers. WOW The major purpose of the interpretation of the Bouguer gravity map is to determine the general structural trends throughout the area by using a qualitative approach concerning the gradient, the shape of the anomaly and anomaly values. The Bouguer gravity map shown in Figure 6a shows the results of reducing the observed gravity. Figure 6a shows three major directions of the anomalies. The major trend is oriented east-west and two branches with north-south and northwest to southeast directions occure in the southern part of the present area. These anomalies 30 coincided with the existence of three troughs which are filled with Precambrian X sediments with higher densities than that of the basement rocks. in the east-central part of the area, the anomaly is assymetric with steeper gradients on the south side compared to the north side. in the southern part of figure 6a, there are two branches of positive anomalies, one stretching north-south and the other northwest-southeast; Both have a very narrow width and a relatively steep gradient. The gradient may be attributed to either the steep dip of the troughs' limbs or by the existence of iron formation on both limbs of the troughs. The Michigan River trough, however, is most likely to be a fault monocline, with iron formation present only on one limb on the basis of detailed geologic mapping and magnetic surveys by Cannon and Klasner ( i 974, l 976). in the southern part of this map, gravity lows are associated with the Smith Creek uplift, Grant Lake uplift and the Twin Lake uplift which are composed of Precambrian W granitic gneiss (2.64 g/cm3). The eliipticaliy shaped high positive anomaly present in the northeastern part of T.47N, R.3OW appears to be due to a large exposure of the Negaunee iron formation. The circular shaped positive anomaly in the center of this map, may suggest the possibility 31 of the existance of the Keweenawan diabase dike. in the unsurveyed areas, gravity contour lines are dashed and based on geologic maps and other available information. 32 Wild The purpose of modelling is to delineate the complexity of Precambrian rocks based on measured gravity values and all the aforementioned information. The magnetic survey data of Cannon and Klasner ( l 976) were used for reference in some parts of profiles A-A', E-E', F-F' The results of the present study, however, may not be unique for several reasons. i ) The physical properties of the rock units (especially density) are not uniform and change in horizontally and vertically. For example, the Goodrich quartzite has an average density of 2.73 g/cm3. However, it changes up to 2.85 g/cm3 in the north edge of the Marquette trough because it contains a high percentage of iron formation (Cannon and Klasner, 1974). The density of the Negaunee iron formation is also variable, and may vary with depth. 2) The subsurface complexitybetween the rock units is unknown. 3) The gravity stations were not measured on the cross-section but projected ,to them. Observed and calculated gravity can be equally well matched in more than one way by varying the thicknesses of subsurface rock units and densities as shown in Figures 9,1 1,17,20. They give good correlations between the observed and calculated gravity values. I-u 33 However,they were not adopted in this study because they provide an unreasonable model considering that the Marquette trough was formed in two phases: tension, with sedimentation, followed by a compressional phase. However, these models indicate that the basement uplift caused during the early depositional period. Thus, to reduce the above mentioned ambiguities and to enhance the accuracy of the model, densities and thickness of the formations were varied within a limited range as shown in Tables 5 and 6. ELQIJJLAzA' Figure 7 illustrates a geological model of profile A-A', which is oriented north to south and extends from 0.5 mile west of Nelligan Lake to 1 mile southwest of St. Johns Lake in the western Marquette district, Michigan. The ends of the profile were modeled from the geophysical investigations of Cannon and Klasner (1974, 1976). Their model matches the observed and calculated gravity in the northern end relatively well, but fails to show a good correlation _ between the observed and calculated gravity in the southern part. Therefore, 1 analyzed the cause of failure and then remodelled this .mowpmnmmmmxm nwowphm> oz .www mmmm :o mm>fim mum mnoflp imfl>mhnn< .Ampcwoav zuw>mum umamasoamo can Amzwa wHHomv hafi>mnm mnpmmno mmfizonm .mpw .5 mpsmwm 34 4 OJ- 2: 3! m O‘- m .x A; 5. . . ._ 2x a» 2.... i o3 '< ( k\ >._._>mmmmo ll 91 »._._>HUCD mohzom AnEo\EMV Anewmfiww oz coapmspom a Heaps ee.m mo.m-4o.w NF Ammo? .pmcmmax w noccmo Aoborv Nb.N «noapmahom mass Hzofiz hocmmam w coccmo Nb.m ab.mivo.m b noose: mpmam nmzoq Aqua? .aaeaanx a eoeaao Aeaarv om.m "cofipmSHOM mean fiscaz Hocmmax w coccmo ww.m mo.mum>.m m popeoa mpmam pong: Apps? cone .zmcmqvmm.m “mpmHm mesmMH£OHz inshom mssmmHQOHz Apocmmax w nonsmovcowmeAOM :ona mo aom cam seasonazo apnne mo coapamomeoo mw.m «N.m mm.mum0.m m :oaumsnom copH Asbmwv Ampflmppmso Hmpocoovmo.m u m nocmmax w coccmo Nb.m Nb.m r N90 zmpm hppfic op xomam mpflu spamso coapcooo .Avbor .pmcmmam a nonsmov b.m op N.m eopm mwcmp cozosm zpfimcmw 0p mm ammonmm >Hm>fipmamy Aoomwvmucfim scam o>pso wcfima .a —m op om ma cowpmshom GOAH mm: ismmmz mo pampcoo coma ommhm>m mmmhm>m Hmpoe om. mm.Mibo.N PM was peep empapa Aspoevasmom pagamam a cognac b4.m mm.m-em.m Fm .mm unmopma aopm coccfieuopoc on Aubmrv :mo soapmahom :onfl mo zpwmcmm nmcmmam w cognac cm.m mm.mibm.m or :oamehom copH mmczmmmz oe.m u m mo.m-mo.m “emcee Awhmr .nomahmov om.m “Ammhm mzflnammvpammmn cmaficwucomhmm bb.m "maficwoaos oamamm ommoccfisd mo.m ”A.cw30 mHHH>£mmzvhhznmnom mpflaomnm m§.N “Amman maamm smasvsmm cmeinmpms momzwz mb.m “A.pz nocczne wmvopHHOhHm homer mm.m u mmhm ocfinammv moacmoao> Hmpcms mam oapammoc< mmmho>m Hmpoa ww.m FP.Mimm.N or me.m “flames peaneaav ep.m se.m-mm.m e onmflpm mnflxcmh mo zxoop msomOHHHm= Aoborv .mswmcoomwz chmnphoz mo nmcmmax w coccmo oo.m FF.Mimm.N o afimmz awHQH0H> map :fi maficmoao> hmsao soapmenom xooaem: mu Apemrvseemafia a eoeeao mm.m mmmhm>m Hmpoe Pw.N o soapmenoh :opH Abooevmnnflu Fo.m opfiaonfizms< pmfinom mafiz Aeoonannno me.m .epeeaapsnom .COHpmsyom maemmanowz Aquarv mo pnma conocwmcoo mfi =oxmq pmcmmam w coccmo «b.m amazom mpfiaopzmpm mocmm nmo: mpnwpm= .Ambmrv Nmor..am pm MMfihozm mo.m mxomzzmhu am pm coccmo .m.3 op wcflcpooom Nwor..am am mafipmzm vo.m pmHSOm mmsmoon Hxfinflm mm msmm :mxmp oxmq mm: :owpmemom :OAH mo hpwmcmo mocmm nmm: magnum Apemev soap pmcmmam w zoscmo wr.m Fm.mieo.m q imapom no>flh momma 8 3 mboF .azhom manmflhm> ormio m>flmspch cammz zpcsoo QOHH :nmpmmm moor ..Hm pm mmemw come gamma mmmpmm pmmm obow .3one moo gamma Ao>fim mama ova? .3ope com pofinpmfic oppmzdnmz :pmpmmz mbmr .coccmo w mmcmwax oomriooo msemmwsoflz emzopp ppppzenaz was? .eoeeao a apemafix ooeiom ommiom mcfiemmzmH mo pmms mum? .ezmom cow xms soancooo nmzonp ppmzv mbmF .coccmo a pmcmmax inmz onp mo when quopmmz bum? .memme w coccmo manmwpm> curiae mops mzwemaanioocsmmmz mums .szhom oomr xms mmcsmmmz peeamnpenz papa do paam heme .epemaax a coeeao ommiom_ opm-0me mam? .esaom ommiowr peanm :m:oyp mppmswnmz mo mmcm :pno: who? .cozcmo w pmcmmax .msemmH20Hz oxmq mo pmmm brow .pmsmmax w coccmo owmuom omriom . meme .ssaom omm-ome xnpnna coapmooq monsom mwcmm Aevmmmchflze :Oflpmapom muncho mmmpmm mam mocflsocmz esp mo 0 mHQmB m:0flpmsnom mo mmmmmchfise 39 mbop .esmom mQMiome copH coozcomnu 00mm AHQQQSV zpczoo conH sumpmmm oou Aoaccwsv omae .zmfizam oom AafinapvxoOHEp: [.0 profile. One reason for poor correlation of their model is the variable density of the “ strata near Fence Lake, " which are composed of materials of various densities and occurs in a very limited area; this suggestion is supported by very irregular magnetic and gravity anomalies (Cannon and Klasner, 1976). The positive anomalies seen in the prof lie are due to Precambrian X sedimentary rocks which have an average density of 0.22 g/cm3 (Cannon and Klasner, 1974 ) more than that of Precambrian W basement rocks. The small, sharp positive anomaly superimposed on the long wavelength positive anomaly across the Marquette trough suggests the possibility of the existence of Keweenawan diabase dike with a roughly east-west trend. The Menominee group, which occurs on the northern edge of the Marquette trough, pinches out a few kilometers from the north edge of the Marquette trough (Klasner and Cannon, 1978). The Goodrich quartzite thins out to the south and lies directly on the . basement block. The density of the Goodrich quartzite at the north edge of the Marquette trough is relatively high (2.85 g/cm3) because of the high percentage of iron formation in it (Cannon and Klasner, 1974 ). The Hemlock formation apparantly lies directly on ore-Baraga group rocks. The Fence River formation, which is an iron rich chemical precipitate, 41 blankets the Hemlock volcanic rocks and appear to be approximately coextensive (Cannon and Klasner, 1975). in this model, the block which is marked by the dotted line in the southern part (A on figures 7,8,9) has low magnetic and high gravity values. Presence of the low magnetic and high gravity values may have two possible causes. One possibility is the effect of the amphibolitic schist inthe "strata near Fence Lake Secondly, a continuation of the metadlabase sill which occurs near the area but is. not shown on the geologic map within the " strata near Fence Lake " could also cause this deviation. High magnetic and gravity values over unit 8 (Figure 7) suggests it is an iron formation, which is one of the materials composing the “strata near Fence Lake". Cannon and Klasner (1976 ) suggest that the observed and calculated gravity in the southern part of the district correlate poorly because the nature and density of the rocks are not well known and lack a two dimensional configuration of their structure. in constructing their density model, the density contrast for the "strata near Fence Lake " and the Hemlock formation were major unknowns. The density constrast of the Hemlock formation varies from near zero for feisic volcanic rocks to about 0.30 g/cm3 for mafic volcanic rocks (Cannon and Klasner, 1976). in this 42 profile, the low gravity values suggest that the Hemlock formation here has a large f elsic component (Cannon and Klasner, l976). AW Figure 8 illustrates an alternate model for profile A-A‘. This model assumes that' a f auit exists between the north edge of the Marquette trough and the Smith Creek uplift. Figure 9 also shows good correlation between the observed and calculated gravity. This model was made with the assumption that the Menominee group rocks were terminated at the uplifted block. This model indicates that the uplift occured during the early depositional period. However, the compressional phase occured after sedimentation. Thus, with respect to the time of compression, the existance of the uplifted basement block makes this model geologically unlikely. E [.1 B-B' Figure 10 illustrates a geological model of profile 8-8, which is oriented northeast to southwest and extends of 14 km through the Marquette trough into the Republic trough. A large positive anomaly A3 .mowumnmmmmxm HmOflwpm> oz .HH> mmma :o 2o>wm ohm mnowpmw>mhnn< .Ampcflomv hpw>m9m nonmazoamo cam Amzwa cHHomv zwfl>mhm cm>nomno mzflzo:m _mhm wopmznmpfi< .w my:MHm wiziu. _ >._._>mwmmo .l >._._> oz [HH> mmmm :o :m>wm mum mcowp inasmnnn¢ .Ampswoav hpw>mnm vmpmazoamo can Aocwa vfiaomv hpw>mhm no>mmmpo mzwzonm .mpu .m emanam m 5.35 .omimmmoii >255 32.533. 1.5 exists at the north edge of the Marquette trough and a very f lat positive anomaly extends across the area to the south. Of several geological models attempted, a graben structure gives the best correlation between the observed and calculated gravity in the northern part of the Marquette trough on this profile. Between the northern edge of the Marquette trough (B on profile) and the Republic trough (B' on profile), a deep broad sedimentary basin exists which has a depth to basement of 2 km. The sedimentary sequence overlying the basement block was downfoided during the development of the graben during the Penokean orogeny (Klasner and Cannon, 1 978). The thickness of the sedimentary strata is very uniform while the southernmost metadlabase sill probably thins to the north. The anomaly has a difference of 10 milligal between the center and the ends of the profile. The average density contrast between the sedimentary rocks and basement rocks is 0. i 3 g/cm3. These are used to give a depth to basement of approximately 1850 meters under the flat-lying sediments according to the following formula (Bacon and Wyble, 1952): an=ag/ 2116p 1.6 pg 1 anomaly contrast G : gravitational constant p: density contrast The small, 1 mgal, irregularities in the gravity values could be caused by minor differences in surface material over very limited areas or folding in the Michigamme formation, particularly in the Bijiki iron formation. The folding was caused by compression of the developing graben during the Penokean orogeny. The irregularites also may be due to errors in elevation, misiocation of the stations and/or till distribution. The Menominee group rocks pinch out to the south from the north edge of the marquette trough. The upper slate member (Xmus) has a maximum thickness of approximately of 1500 meters in the center of the sedimentary basin and the lower slate member (Xms) becomes thinner to the south. The Goodrich quartzite covers the entire area of this profile. Figure l 1 shows a good example of the ambiguity of gravity modelling in that the observed and calculated gravity can be equally well matched in more than one way by varying the thickness of the subsurface rock units and densities. This model indicates that the uplift occured during the early deposionai period. However, the 1ft..- fir .ii mom :0 cm>wm who m:0Hp 4 nmmxm Hmowppm> oz wm> o z H>mpm i. h .rwflwmmmmav zpfi>mhm @opmHSQHmo cum Am:HH vMHmmw zwfl>mho .or mhsmflm iWwwwmwmw mcmzozm .mim moapoom macaw cmhnmmma flvaH.m . 47 MAE-M .lil-Jll. 3v. dx 2.5x 43 .— .C._>mummo 1| >._._> oz .Ha> mmmm no cm>am ohm mcowp ima>onnn< .Ampzfionv zpw>mhw umpmasoamo was Amcfia cHHomv zpw>mnm co>nmmno mcfizozm .mim :oapomm macaw omhsmmos AHHvoHHmonm zpfi>mpo .99 spawns rt>mwmmo .Iu 5.34:6 auh<504 oz .HH> mmmm no qo>Hm mum macapmfl>mhnn< ..oio :oaaoom macaw vaSmmme mammopm zpfi>mpo .NP mpsmwm I . m . we: w . 3w m . .. s a; 25? ii. ax image 3. «Ex «Ex 38x «3.2x .U E35 3588 I. 3403 $558 3.2.533 . 51 based on his remanent magnetization study. However, the observed gravity anomalies do not correlate well over the stock in my model. This is due to the projection of gravity stations,which were not measured over the Michigamme stock. in the eastern part, there is a reverse fault with a vertical displacement of approximately 200 meters. The A jibik quartzite and Siamo slate covers all of the area in northern edge of the Marquette trough, however, the Siamo disappears in cross-section in C-C'. The stratigraphic section changes abruptly across the'fault in the eastern part of the profile. West of the fault, the Negaunee iron formation is thick, the Goodrich quartzite is very thin, the Clarksburg volcanic members are relatively thin, and the Greenwood iron formation is absent. On the contrary, to the east, the Negaunee iron formation is absent, and the Goodrich quartzite and Greenwood iron formation are relatively thick. The Clarksburg volcanics gradually thicken to the east and reaches a maximum thickness (500 m) in the Humbolt area. The Goodrich quartzite has a variable thickness and a maximum thickness of 460 meters in the Humbolt area (Cannon and Klasner, 1974). The Clarksburg volcanics and Greenwood iron formation, now considered members of the Michigamme formation (James, 1958), lie 52 between the Goodrich quartzite and the lower slate member of the Michigamme formation. They have a stratigraphic position and lithology analagous to the Fence River formation and the "strata near Fence Lake" (Cannon and Klasner, i975), however, are not continuous with these latter units at the surface. Clearly, lateral f acies changes occur within distances-of a few kilometers to a few tens of kilometers, resulting in many units of only local extent (Cannon and E Klasner, 1975). The faulting may have occurred during the sedimentation of the younger Michigamme formation. This may be inferred from the geologic map in which the fault does not appear to have cut the youngest units of the Michigamme formation. E [.1 D-D' Figure l 3 illustrates a geological model of profile D-D', which is oriented northwest to southeast and extends west of the Michigamme Lake through sec. 1 7, T.47N,, R.3OW., where the Michigan River trough, the Republic trough and south edge of the Marquette trough intersect. The gravity anomalies over this area are relatively f lat contrary LO 53 0H“ m QOHQQH>QHDD< .mowvmnmmmmxm Hmowwmm> oz .HH> mmmq :o zo>Hm ..nim :owpomm mcomm nonsmmoa oaamopg zpw>mnm .mp assmne mac/TN . t._ a m 55. w . _ . Jo a x 35 1.. idxi / 1.5x ii «7 s: : 85x n. m; I O 0 O O O i I. i >._._>mmmmo 11. W— m m .Crgém om... oz .HH> omma :o co>wm ohm macapmfi>mhnn< ..mim :owvoom mnoam consmmoa oawmopg zpw>mpo .qr ohsmwm '11 3.: T N o. ut¢li E>§e 85881 mm E35 3.2.533. 58 and sediment pinches out in a different direction. in this model, fault A developed in the basement, upthrowing the right side block. Either faulting occured concomitant with sedimentation or after sedimentation but before lithification of the sediments. The sediment would then overlie the basement with an angular unconformity, and slope off the upthrown block onto the downthrown block. This model predicts the pinching out of the Ajibik, Negaunee, and Goodrich formation to the west, while the Hemlock and Fence River formation, and the "strata near Fence Lake" were deposited from the west. Then the second period of faulting (B on Fig. 1 4) cut the sediment in the downthrown block, and eroded down to the present surface. However, the geometry suggests that faulting occured in one episode. The Hemlock and Fence River formations occur with uniform thickness. in the western part of this section, the unit west of the dotted line (C on figure) is considered to be an iron formation. This is one of the formation composing the "strata near Fence Lake", and is based on high magnetic anomalies seen in the magnetic survey performed by Cannon and Klasner( 1976). Eli"! lilEt'iE-E' Figure 15 illustrates an alternate geological model to profile 59 E-E'. This model was made based on the hypothesis that the metadlabase sill, which is exposed at sec.24, T.47N, R.3OW, continues to the west. Profile F-F‘ Figure 16 illustrates a geologic model of Profile F-F', which is oriented southwest to northeast. Long wavelength positive anomalies exist at both ends of the section, while it is fairly flat in the middle. The graben structure at the northern end yields the best correlation between the observed and the calculated gravity values among several geological models. The lower slate member is very thick in the northeastern part of this section, while it is very thin on the opposite side. The Goodrich quartzite overlies Precambrian W basement rocks and becomes thinner to the southeast and pinches out near the southern edge of Lake Michigamme. The Hemlock and Fence River formations pinch out to the north and are coextensive (Cannon and Klasner,1975). Figure 17 shows the good correlation between the observed and calculated gravity. However, it is a geologically unlikely model for this area. This model showes that the uplift caused during the early depositional period. However, the compressional phase occured after 60 .coapmpmmmmxm Hmowpum> oz .Hw> omen imfi>wupn¢ ..mim :owaomm macaw vmhsmmoa oaamoua :o mm>fim mum mzowp zpw>mhm cmpmznmaa< .m. .pamne Essa om>mmmmoii mm >235 3.2.50.2? 61 .coflamnmmmmXo Hmofiphm> oz .aw> mmmm no sm>wm ohm macaw imw>ounn< .Ampmfiomv zpw>mnm nonmasoamo cam Aocwa vHHomv zpfi>mhm ©m>hompo mnwzonm .mih :Oflpomm macaw cohzmmma AHVmHHmoma zpw>mno .cr onzmwh >235 _ ou>5mmo1 >538 3.2.533. m2 62 .qowpmammmmxo Hmowpho> oz .HH> ommm :o :m>ww ohm mcowp imw>ounn< .Ampcfiomv zpfi>mum nonmasoamo mam Amzwa cwaomv zpfi>mnm ©m>nomno msfizonm .zih :owpoom macaw wouzmmos AHHVmHflHOAQ zpfi>mnu .br onzmflm 5.2 .i p . N _ . A. 5.1 i. . u N . o - s .3 — a; 2.x r. :x 11 o 4.51 :51in LT \ sax j Pex/ Ex u D! 111 o o 00—... 349? “2 5.553 om>¢mmmo .11 3” rt>mAnn< om>homno mcfizonm .20Hpmhomwmxo Hmofiphm> oz .fifi> ommm so co>Hm M. .Ampnwomv z¢w>mhm woundsoamo cam .mim compomm macaw cohswmoa oaamog mafia cwaomv z¢w>mpm zpfl>mhm oopmmhmpa< .wr musmwm 1:1 rt><¢o ow>mummo iii >._._> oz mam mcowpmw>ohnn< .A zpw>mmm co>nmmno msflzozm 5.: n i N 2 x 61-1- 0 m .ww> omma :o cm>wm pcwomv zpw>mhm copmazoflmo and Amswfl cwaomv mi: :Ofiuomm macaw cmpzmmos mHflMOAa zafi>mnc <3-— °-- .- . n . . . . .. o o . N e 1\ ,‘ECIL- .I _ax .mr pasmnm 2.5430 Om>mummo .11 m m >C>¢¢o owbdifioizo o 67 .mowpmummmmxm Mmow¢um> oz .wfi> omma no 20>Hm ohm macaw imflpmnnp< .Ampcwoav zpw>mnm cmpmazoflmo cam Aozwa cwaomv zpw>mhm uosmmmno mmfizogm .miz coapoom macaw nonsmwos aHHVonmoym zuw>mno .ow onsmflm we: .1 . w . u N _ o 3. u . u . u N _ o ‘5 .\M ax . . ox :XT «x .. “u .62 . \m“ 2.2x w» J 2... z I 3x OI] b1b/hl‘ilh\\dil%iio 11m 0 _n1 (I 0.1 t._>mwmmo 1| m m 5.335 awhdiSanu 0 9|. 3 2 fi 440;. 68 W The gravity mOdels considered in this study were constructed using all the available information including published geologic maps (Cannon and Klasner, l 976, 1977; Klasner and Cannon, 1 978) and the Bouguer gravity map (shown in Fig. 6). A synthesis of the results f ron the modelling study interpretes the following two major distribution patterns of the overall rock units. The Menominee group rocks are restricted to within a few kilometers north edge of the Marquette trough, the Republic trough, and east flank of the Michigan River trough. The Ajibik quartzite, Siamo slate and probably the Negaunee iron formation pinch out to the south within a few kilometers of the north edge of Marquette trough (Klasner and Cannon, 1 978). The reason of the pinch out is unknown. it may be due either to the original sediment distribution or to the weathering and erosion which has partly or totally removed the Menominee group(Cannon and Klasner, 1974) prior to the deposition of the Baraga group. The Baraga group is composed of a varied sequence of metasedimentary and metavolcanic rocks. Detailed mapping by previous workers reveal many changes within the stratigraphic column 69 from area to area (Cannon and Klasner, 1975). The oldest unit of the Baraga group is the Goodrich quartzite which overlies the Precambrian w basement rocks over a large area with a various changes of thickness. it is not clear whether the thickness variations are due to the original sediment distribution or to erosion before the deposition of the Michigamme formation. The distribution of the "strata near Fence Lake" appears to be confined to the north flank of Smith Creek uplift and the Wilson Creek uplift. A few kilometers north of the Smith Creek uplift, the Goodrich quartzite and Hemlock formation occur together and pinch out in opposite directions. According to previous worker, the Goodrich underlies the Hemlock and it could be at least in part contemporaneous with the Goodrich or the lower slate member of the Michigamme (Cannon and K1asner,l975). The Hemlock, which is present a few kilometers southwest of the study area, apprently forms a broad apron, as much as a kilometer thick along the periphery of a centeral volcaic area, centered west or south of the Amasa uplift (Cannon and Klasner, 1975). Figure 21 shows the thickness of the sedimentary rocks (depth to basement) and the distribution of the faults in the study area. 70 ‘31 d L-fii'i 0-] I '- -1 : .3 i". i to. 3‘ + .0. '6‘ '71 .aoom n Hm>pmpcw hsopcoo .mxoop 3 cmwpnemomnm was x :meDEwo imum mo zmmvczon mpmoavcfi mocaa.vfiaom Mowne .mpasmm mpmowccfl mmcfla Umnmmo .mpazmm mo soapsnfinpmfio was mxoon zpmpcmEHcom on» no mmmchflze .FN onzmflz 53% . x24 +z-.;, _‘~.1V‘o -‘o' -4 I 1_ 6 ~f'l." f ‘ o‘l P, . .‘l 0 V .. ... 5'05 1’ .._,._ H.” Q .-. . R ‘t ‘- ‘ . p" ._‘. j- T .- 3:: 1 1 _ . “ u‘o.' ‘ - ‘ . n s . ‘jzg-zé ... hi '1 n .4 ..., 9' I . ‘. J‘- .'I V '-'. Q act . '1 80 I- ..1. .v1 a? I .0- I on, _ d- ‘ r1 . . .1. . G... .1 . 1 1 . .u . - ... 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' 'au' ‘- c i . 1": 1.! I a A . l.II ' \ II I .1 t 95 APPENDIXB STA ELEV.(ft) OBSER. GRAV. LAT. FREE.A1R. BOUG. GRAVITY AM) (mgal) (mgal) 80 1598 35.88 -1.24 0.00 0.00 34.64 81 1553 39.81 0.25 -4.23 1.54 37.37 82 1565.5 37.62 - 0.32 -3.06 1.11 35.99 83 1612.5 33.53 0.30 1.36 -O.50 34.69 84 1638.5 33.62 -0.35 3.81 -1.39 35.69 85 1600 35.90 -1.24 0.19 -0.07 34.78 86 1594 34.88 -1.64 0.38 0.14 33.00 87 1578 34.92 -2.07 -1.88 0.69 31.66 88 1559.5 35.1 1 2.61 -3.62 1.32 30.20 89 1579.5 32.46 3.20 -1.74 0.63 28.15 810 w 1594 33.1 1 3.37 -0.38 0.14 29.50 81 1 1590.5 33.28 -3.73 -0.71 0.26 29.10 812 1581 34.94 -3.83 -1.60 0.58 30.09 813 1576.5 33.02 -3.97 -2.03 0.74 27.77 814 1567.5 38.70 -3.45 -2.87 1.04 33.42 B 15 1570 37.93 4.01 -2.63 0.96 32.25 815A 1569 37.86 -4.01 -2.73 0.99 32.1 1 B16 H1 H2 H3 H4 H5 H6 H7 H8 H9 R1 R2 R3 R4 R5 R6 R7 R8 R9 1505 1594 16285 16085 15645 1568 15695 15705 15775 1526 1504 1496 1493 1496 1498 1515 1533 1544 1549 2482 3152 2180 1964 1962 1902 1655 1554 1486 2042 2201 2124 2092 2136 2312 2445 2484 2541 2605 223 223 435 494 602 675 727 780 778 727 667 637 573 528 490 450 399 -315 '282 -268 -259 -193 '677 ‘884 -959 -988 -959 ‘941 ‘781 '611 '508 -461 103 098 094 070 247 322 349 360 349 323 284 223 185 168 2732 3251 2586 2250 2197 2217 2087 2064 2090 2392 2417 2241 2131 2163 2287 2476 2585 2668 2711 WWW R10 M1 M2 M3 M4 M5 M6 M8 M9 M10 M12 M12 M13 M14 F1 F2 F3 F4 F5 1 555 1641 1554 1 655 1646.5 1 656 1593 1603 1565.5 1558.5 1 604 1675 1602 1587 1 565 1611 1568.5 1663.5 1637.5 26.77 33.29 35.93 29.41 27.69 28.81 32.57 30.58 33.21 32.75 30.1 3 26.83 32.43 32.83 38.29 35.56 38.53 31.99 32.23 3.67 -334 “2.43 *201 -1.91 -1.86 -1.91 -0.89 -0.50 ‘028 -0.55 -134 -2.31 -209 -325 -325 -2.89 -308 -2.64 -4.51 4.04 -4.14 5.36 4.56 5.46 -0.47 0.47 -306 -3.72 0.56 7.24 0.38 -1.03 -310 1.22 ‘277 6.16 3.72 1.64 -1.47 1.51 -1.95 “1.66 -1.99 0.17 “O. 17 1.1 1 1.35 -O.21 ‘264 -0.14 0.38 113 -0.45 1.01 “224 -1.35 27.57 32.52 30.87 30.81 28.68 30.42 30.42 29.99 30.76 30.10 29.93 30.09 30.36 30.09 3307 33.08 3388 32.83 F6 F7 F8 F9 F10 FH F12 F13 F14 F15 F16 16035 1600 1618 1688 16925 16885 17095 1688 1660 1644 16795 1609 1608 16315 1640 1642 1645 1694 1680 3627 3601 3404 2790 2758 2740 2555 2606 2639 2705 2811 3593 3595 3133 3032 3033 2838 2492 2513 -353 '330 '294 -251 -159 -160 -154 -103 -025 031 -199 -352 -365 -401 -420 -422 -456 ~488 -529 052 091 188 847 889 851 1049 847 583 433 767 103 094 310 395 414 442 903 771 -019 '007 -069 -308 '324 -310 -382 -308 ‘212 -158 -279 -038 '034 -115 -154 -151 -161 -329 -2.81‘ 3307 3283 3229 3078 3167 3121 3068 3042 2985 3011 3100 3306 3290 2927 2853 2874 2663 2578 2474 Slag—WM H0 H1 H2 C1 C2 C3 C4 C5 C6 C7 C8 C9 C10 C11 C12 C13 C14 C15 1688 1688 1599 1650 1675 1713 1776 1708 1799 1760 17775 1716 1732 17465 1716 1609 15895 1580 1585 2500 2507 3576 3124 3197 2961 2541 2905 2405 2623 2459 2829 2726 _ . 25.99 26.67 . ‘ 3303 3400 3532 3428 ‘549 -584 '310 '272 -162 -156 -166 -191 -193 -194 -262 -217 -105 -096 -089 -143 -168 '174 -186 847 847 009 489 724 1082 1674 1035 1891 1524 1688 1140 1260 1397 1110 103 -080 ~169 -122 -308 -308 -003 -178 '264 -394 '610 *377 '688 -555 ‘615 -404 -459 -509 -404 -038 029 065 045 2490 2462 3272 3164 3495 3493 3439 3372 3415 3398 3270 3308 3422 3391 3284 3225 3181 3254 3165 100 STA ELEV. OBSERGRAV. LAT FREEAIR BOUG- GRAV. C16 1681.5 29.02 -0.35 7.85 -2.86 33.66 C17 1707 28.10 -0.58 10.25 -373 34.04 C18 1715.5 28.54 -0.96 1 1.05 -402 34.61 R1 1532 29.67 3.55 -6.21 2.26 29.27 J1 1550 28.27 3.34 -4.51 1.64 28.74 J2 1570 26.84 3.18 -264 0.96 28.35 J3 1577.5 2748 2.89 -193 0.70 29.14 J4 1574 28.01 2.79 '226 0.82 29.36 J5 1581 27.85 2.57 -160 0.58 29.40 J6 1591.5 27.68 2.39 -0.61 0.22 29.68 J7 1604 27.48 2.09 0.56 -O.21 29.92 J8 1615 27.00 2.01 1.60 -0.56 29.36 J9 1634.5 25.26 1.99 3.43 - 1.25 29.43 J10 1642 25.16 1.76 4.14 -151 29.55 J1 1 1635 25.67 1.62 3.48 - 1.27 29.50 J12 1622.5 26.79 1.38 2.30 -O.84 29.63 J13 1618 27.10 1.15 1.88 -0.69 29.44 J14 1640 26.24 0.93 3.95 -1.44 29.68 J15 25.67 0.71 4.89 -178 29.49 1 650 EDA—W J16 J17 J18 J19 J20 J21 J22 J23 J24 J25 K1 K2 K3 K4 K5 K6 K7 K8 K9 1654 1647 1649 16545 1653.5 1641 1623 1625 1605.5 1590 1558 1584 1616.5 1653.5 1661 1635 1674 1706 1662 25.60 26.24 25.81 25.36 25.88 26.58 26.50 26.22 27.56 28.34 28.69 27.24 25.46 25.47 24.85 26.68 24.14 21.76 24.90 0.58 0.28 0.12 0.16 -0.04 0.51 1.71 1.89 1.87 2.16 2.79 2.59 2.37 1.72 1.88 1.70 0.61 0.55 0.51 5.27 4.61 4.80 5.31 5.22 4.04 2.35 2.54 0.71 '075 ~376 -1.32 1.74 5.22 5.93 3.48 7.15 10.16 6.02 -1.92 -1.68 -1.75 -1.94 -1.90 ~1.47 -0.86 -0.92 '026 0.27 1.37 0.48 -0.63 -190 -2.16 -1.27 ‘260 -370 -219 29.53 29.45 28.98 28.89 29.16 29.66 29.70 29.73 29.88 30.02 29.09 28.99 28.94 30.51 30.50 30.59 29.30 28.77 29.24 BIA—W K10 K11 K12 K13 K14 K15 K16 K17 K18 K19 ' K20 E1 122 E3 E4 135 E6 E7 E8 1653.5 1632 1 607 1 605.5 1 598 1 599 1597.5 1571.5 1571 1 603 1576 1561 1554 1 554 1559 1553 1 560 1 596 1716 25.51 27.28 28.90 29.24 30.29 30.61 31.35 33.73 33.59 29.98 31.28 35.18 36.63 36.20 35.46 36.32 35.22 32.48 25.88 0.40 0.30 0.10 '002 -0.18 -0.25 *041 '051 -0.28 -0.20 ‘074 '304 -2.33 '231 '184 -1.88 -184 -1.78 -0.93 5.22 3.20 0.85 0.71 0.00 0.09 -0.05 -2.49 ‘254 0.47 -2.07 -362 -419 -4.19 _ -3.95 -4.42 -357 -0.19 11.10 -190 ‘116 ‘031 '026 0.00 -0.03 0.02 0.91 0.92 -0.17 0.75 1.32 1.52 1.52 1.44 1.61 1.30 0.07 -404 29.23 29.62 29.54 29.59 30.1 1 30.42 30.91 31.64 31.69 30.08 30.70 29.84 31.63 31.22 31.1 1 31.63 31.1 1 30.58 32.01 Ella—W E9 E10 E11 E12 E13 E14 E15 E16 E17 E18 E19 D1 D2 D3 D4 D5 D6 D7 D8 17115 1708 1690 16895 1635 16335 1623 16165 16255 1647 16095 1577 1578 1576 1572 1567 1570 1578 1583 2879 2690 2698 2557 2885 2831 2805 2908 2584 2382 3030 3351 3314 3233 3261 3230 3216 3207 3172 -0.89 -0.75 067 -0.41 -0.28 -0.08 0.20 0.43 0.75 0.93 0.65 -2.80 —2.99 -3.34 -3.70 -4. 13 -4.62 -474 -521 1068 1035 865 861 348 334 235 174 259 461 108 -198 -188 -207 -245 ‘292 '263 -188 -141 -389 ‘377 '315 ‘313 '127 -122 -086 -063 “094 -168 -039 072 069 075 089 106 096 069 051 3469 3273 3181 3064 3078 3035 2974 3062 2824 2768 3164 2945 2896 2767 2735 2735 2587 2614 M 0n Ch ElA___JlE1fllLDflSEUflMflLJJfl;_£Bfllm1_flflwi_._QENL D9 D10 D11 D12 D13 D14 D15 D16 D17 D18 D19 N1 N2 N3 N4 N5 N6 N7 N8 1601 1589 1593 1604 1597 1607 1614 1617 15655 15625 1567 1598 1571 1570 1569 15775 1573 1591 16265 3064 3023 3028 3001 3086 2902 2849 2832 3070 3431 3388 3624 3300 3624 3437 3353 3540 3326 3274 “561 ‘586 -602 “601 7634 -679 '719 -745 -335 -328 -325 -353 -395 -355 -370 ‘387 -371 -385 -365 028 -085 '047 056 -009 085 150 179 “306 “334 -295 000 -254 ‘263 -273 -193 '235 '066 268 -010 031 047 '021 003 -031 '055 -065 141 122 106 000 092 096 099 070 086 024 -098 2521 2383 2396 2435 2446 2277 2225 2201 2540 2891 2877 3271 2743 3102 2893 2843 2990 2899 3079 m—W N9 N10 N11 N12 N13 N14 N15 N16 N17 N18 N19 N20 N21 N22 N23 N24 N25 N26 N27 15865 1580 1582 15685 1598 16425 1583 1554 1573 15485 1558 1564 16025 15685 15685 15665 15865 1607 15915 3385 3457 3588 3719 3496 3487 3541 3701 3530 3695 3575 3599 3439 3345 3363 3491 3495 3369 3429 “383 “370 “334 “310 “297 “320 “318 “340 “322 “290 “322 “287 “271 “320 “362 “334 “297 “280 “267 “108 “169 “150 “277 000 419 “141 “414 “235 “466 “376 “320 042 -2.77 -2.77 “296 “108 085 “061 039 062 055 101 000 “152 051 151 086 170 137 116 “015 101 101 108 039 “031 022 2933 2980 3159 3233 3199 3434 3133 3128 3039 3109 3014 3108 3195 2849 2825 2969 3129 3143 3123 106 SDi___iLELfllLflE5fliEMNLJJQ;__EBHQMBJEAE____68AM. N28 N29 131 P2 P3 P4 P5 P6 P7 P8 P9 P10 P11 P12 01 02 03 04 05 1597 1563 15785 15965 16345 1676 16675 1670 1643 16825 1707 1631 1622 15975 16475 1660 1655 1602 1609 3420 3334 3276 3128 2889 2559 2555 2555 2863 2599 2488 3244 3283 3631 . 29.34 2826 2831 3159 3111 “271 “395 “395 “401 “420 '-4.45 “474 “491 “417 “426 -4.40 “373 “371 “306 “187 “185 “185 “191 “187 “009 “329 “183 “014 343 734 654 677 423 795 1025 310 226 “005 466 583 536 038 103 003 120 067 005 “125 “267 “238 “247 “154 “289 “373 “113 “082 002 “170 “212 “195 “014 “038 3143 2734 2765 2718 2687 2581 2497 2494 2715 2679 2700 3068 3056 3302 3040 3012 2987 2992 2989 05 06 07 08 09 010 011 012 013 014 015 016 017 S1 S2 S3 54 55 56 15565 15565 15835 1630 15835 16365 16565 16635 1608 1604 16545 1660 1673 1517 1528 1560 1566 1567 1611 3034 3034 3287 3020 3309 2889 2778 2720 2966 2999 2499 2418 2363 2675 2924 2557 2529 2634 2555 “173 “173 “198 “220 “215 “166 “141 “117 “076 “062 023 008 008 460 335 361 370 364 337 “390 “390 “136 301 “136 362 550 616 094 056 531 583' 705 “762 “658 “357 “301 “292 122 142 142 050 “110 050 “132 “200 “224 “034 “021 “194 “212 “257 277 240 130 110 106 “045 2613 2643 3003 2991 3008 2953 2987 2995 2950 2972 2859 2795 2819 2650 2841 2691 2708 2812 2969 ffllL...fliNAfl1JXEEBEBAM_LEL_J$ELNB_JX&E____QREL 57 S8 S9 510 T1 T2 T3 T4 T5 T6 T7 T8 T9 T10 T11 U1 U2 U3 U4 1632 1649 1607 1560 1564 1642 1606 1596 1605 1610 1585 1624 1664 1657 1540 1560 1548 1551 1547 2383 2422 2579 2667 2445 2024 2304 2099 2340 2224 2327 2013 1741 1598 2839 2583 2646 2559 2543 344 335 376 380 391 405 438' 4.54 475 509 537 551 574 621 378 393 423 4.42 320 480 085 “357 “320 414 075 “019 066 143 “122 245 621 555 “546 “357 “470 “442 “480 “116 “175 “031 130 146 “151 “027 007 “024 “041 045 “089 “226 “202 199 130 171 161 175 2931 3062 3009 2820 2632 2692 2790 2541 2857 2805 2787 2720 2710 2572 2734 2740 2701 2680 109 m—Wfiflxfl. U5 U6 U7 U8 U9 U10 U11 V1 V2 V3 V4 V5 V6 V7 V8 V9 V40 V11 V12 1603 1636 1677 1649 1671 1702 1721 1701 1659 1674 1692 1692 1680 1681 1651 1640 1670 1702 1762 2211 1868 1350 1371 1196 946 841 2465 2663 2728 2592 2572 2626 2583 2677 2735 2466 2283 1952 4.44 452 458 509 528 541 524 “123 “123 “156 “129 “126 “092 “057 “025 027 057 077 148 047 357 743 480 687 978 1157 969 574 715 884 884 771 781 499 395 677 978 1543 “017 “130 “271 “175 “250 “356 “421 “353 “209 “260 “322 “322 “281 “284 “182 “144 “247 “356 “562 2685 2547 2280 2185 2161 2109 2101 2958 2905 3027 3025 3008 3024 3023 2969 3013 2953 2982 BIA—WM V13 V14 V15 V16 V17 V18 V19 V20 V21 V22 V23 V24 V25 V26 V27 V28 V30 V31 V32 1754 1752 1739 1749 1758 1769 1763 1756 1754 1765 1764 1754 1744 1745 1750 1707 1744 1733 1750 2009 1981 2163 2059 1890 1777 1808 1806 1798 1719 1547 1546 1599 1429 0745 815 871 1060 1134 171 188 214 245 261- 290 296 287 308 309 337 349 364 400 5.90 663 522 476 4.45 1467 1449 1326 1420 1505 1608 1552 1486 1467 1571 1561 1467 1373 1383 1430 1025 1373 1270 1430 “534 “527 “483 “517 “548 “586 “565 “541 “534 “572 “569 “534 “500 “503 “521 “373 “500 “462 “521 3113 3091 3220 3207 3108 3089 3091 3038 3039 3027 2876 2830 2836 2709 2244 2130 2266 2344 2488 flex—WM W1 W2 W3 W4 W5 W6 W7 W8 W9 W40 W11 W12 W13 W14 W15 W16 16705 16725 16405 16415 1644 1658 1659 16475 16495 16495 1664 1657 1663 1646 17295 16875 2449 2413 2690 2671 2683 2581 2573 2642 2572 2542 2423 2448 2468 2598 2133 2784 057 059 019 009 “021 “039 “043 “014 057 083 143 144 . 047 029 146 “187 682 701 400 409 433 564 574 466 4.84 4.84 621 555 611 451 1237 842 “248 “255 “146 “149 “158 “206 “209 “170 “176 “176 “226 “202 “223 “164 “450 “307 2940 2918 2963 2940 2937 2900 2895 2924 2937 2933 2931 2915 2903 2914 3036 3132 ER ”'111'1‘1’1111111’1111111111111111111111111111’111‘111‘“