MSU LIBRARIES m. RETJRNING MATERIALS L) '1’0 PTace in EO‘k u p remove this checkou: from your recs 0 Fzggg will returned SCGIIWPE’J :4 V be charced a t" A GRAVITY INVESTIGATION OF EASTERN IRON COUNTY, MICdIGAN by David Ray Paddock A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Geology 1982 ABSTRACT A GRAVITY INVESTIGATION OF EASTERN IRON COUNTY, MICHIGAN by David Ray Paddock A gravity survey was conducted in the Iron River-Crystal Falls district (IR-CF) to determine whether the "Paint River Group" is correlative with other parts of the Marquette Range Supergroup (HRS), the structure of the boundary, and, whether IR-CF belongs to MRS, is a greenstone belt, or is trapped or obducted ocean crust. TWO hundred gravity measurements were taken, modified Bouguer corrected, including removal of till effects, and reduced to datum using a bedrock density of 2.91 gm/cc. These data supplemented previously existing data which were linearly transformed to agree with the above reductions. Subsurface structure was modelled using a Talwani 2D gravity routine assuming laterally uniform thickness of formations. The existing U.S.G.S. interpretation is most consistent with the observed gravity. Interpretation of the IRrCF as an "uplifted" or "downdropped" fault-block would require a minimum lateral thickening of 2.1 and 3.8 kilometers, respectively; a minimum of 3.8 kilometers is required to model the Kiernan Sills as ophiolites. DEDICATION This work is dedicated to the friends with whom I shared many 100 mile (and shorter) bicycle rides: David Michael Riggs, Robin Theresa Cole, Jay Brian Silber, and April Poelvoorde. ii ACKNOWLEDGEMENTS I thank Dr. Hugh F. Bennett for his guidance, advice, and suggestions concerning a thesis topic which was somewhat forced upon him. Hugh's stints as tennis opponent were also appreciated; although they were too infrequent for both of us. I thank Kazuya Fujita for his drafting of most of the figures in this work, for his friendship, for the use of his Decwriter IV and personal library, and for his suggestions during the two years this study took place. Thanks go to Dr. Jim Trow for his seemingly limitless knowledge of and familiarity with the Lake Superior region and for his invariably cheery disposition. Dr. F. w. Cambray is to be thanked for his patience in approving my continual requests for more computer money. I would like to thank Nike Gottler for his help and company in the 1981 field work for this study, and to thank Robin Cole for her help in the 1980 OCT field session. Special thanks go to Jay Brian Silber, April Poelvoorde, Kazuya Fujita, and Cynthia Lynn Cordes for their understanding friendship and for getting me through the hard times. I would like to thank David K- Larue for data prior to publication (actually, they were used without his knowledge). iii F‘h‘h‘h‘h‘h‘h‘ NNNNNNN bob) 0 p—o u>uauauouauau>uauaoaua O C O C O O O O O G>\JO‘U!£~UDNJF‘P*F'F‘ O O b~h>h3hl O mVO‘wJ-‘th— fi§b§b§§b§bbb U‘UUU o o o WNNNNNNNNNH o O CON.— TABLE OF CONTENTS INTRODUCTION The Problem Geologic Setting Previous Works Geologic Works GeOphysical works Study Area FIELD WORK Time Instruments The Surveys Line Location and Station Spacing Base Station and Loops Data Collection DATA REDUCTION Drift Corrections, Translation From Gravity Meter Units to Milligals, and Translation to Absolute Milligals Gravity Elevation Errors in Drift Correction Elevation Error Latitude Corrections Till Thickness Free Air Correction Bouguer Corrections Terrain Correctins Correlation of Bouguer Anomalies of This and Other Studies Error Summary MODELLING Procedures Geologic Interpretations The United States Geologic Survey Interpretation The Pettijohn Interpretation The Paddock Interpretation The Trow Interpretation The Greenstone Belt Interpretation The Trapped Ocean Crust Interpretation The Larue Interpretation The "Badwater Ophiolite" Interpretation Detailed Gravity Survey Across the Riverton Iron Fomation SUMMARY, CONCLUSIONS, AND RECOMMENDATIONS Summary Conclusions Recommendations REFERENCES APPENDICES iv Page \DQNNHHH 11 ll 11 ll 11 15 18 20 20 20 20 21 23 23 24 26 29 29 30 32 33 34 37 37 38 43 47 47 51 51 54 59 61 61 62 64 66 69 LIST OF TABLES Table 1. Gravity Loop Lengths 2. Gravity Drift Rates 3. Altimeter L00p Lengths 4. Altimeter Drift Rates 5. Density Data 6. Thicknesses of Formations Page 16 16 17 17 34 36 LIST OF FIGURES Figure 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. James' Pre-Keweenawan stratigraphy Trow's pre-Keweenawan stratigraphy Index maps Geologic map showing location of gravity lines Reference map showing modelled profiles Diagram of "floating" base-station method of looping Diagram showing method used to determine drift error Contour map of till thickness. Contour map of Free Air anomaly. Contour map of modified Bouguer anomaly. Block diagram of the U.S.G.S. interpretation North-south gravity profile of U.S.G.S.-Pettijohn interpretation East-west gravity profile of U.S.G.S. interpretation Block diagram of Pettijohn interpretation East-west gravity profile of Pettijohn interpretation Block diagram of Paddock interpretation East-west gravity profile of Paddock interpretation North-south gravity profile of Paddock interpretation Block diagram of Trow interpretation East-west gravity profile of Trow interpretation Block diagram of greenstone-belt interpretation Block diagram of trapped ocean crust interpretation Block diagram of Larue interpretation Block diagram of "Badwater ophiolite" interpretation North-south gravity profile of "Badwater ophiolite" interpretation East-west gravity profile of "Badwater ophiolite" interpretation Gravity profile of line A across Riverton Iron Formation vi Page 10 13 14 16 22 25 27 28 39 4O 41 42 44 45 46 48 49 50 52 53 55 56 57 58 6O LIST OF PLATES Plate 1. Plate showing location and value of till thickness data. Plate 2. Plate showing location and value of Free Air anomaly data. Plate 3. Plate showing location and value of modified Bouguer anomaly data. vii X8 Xmin gab um XP sed pr prs Xpr Xpd gs Xb bas Xbb Xbm Xba th Xcr Wd "8 Wgn STRATIGRAPHIC NOMENCLATURE Middle Proterozoic granite Early Proterozoic mafic in Pond Complex gabbro ultramatics Early Proterozoic, "Paint oceanic sediments Early Proterozoic, "Paint Early Proterozoic, "Paint south member Early Proterozoic, "Paint Formation Early Proterozoic, "Paint greenstone Early Proterozoic, Baraga Badwater Greenstone basalt Early Proterozoic, Baraga Early Proterozoic, Baraga Early Proterozoic, Baraga Early Proterozoic, Baraga S trusives, including the Peavy River Group" River Group", Fortune Lake Slate River Group", Fortune Lake Slate River Group", Riverton Iron River Group", Dunn Creek Slate Group, generally does not include Group, Badwater Greenstone Group, Michigamme Formation Group, Amasa Formation Group, Hemlock Formation Early Proterozoic, Menominee Group Early Proterozoic, Chocola Archean, Dickinson Group Archean, granitic rocks Archean, granite gneiss Archean, Bell Creek Gneiss viii y Group, Randville Dolomite I. INTRODUCTION 1.1 The Problem Beginning in the late 1950's, a number of papers were published concerning the structure, stratigraphy, and tectonics of the Iron River- Crystal Falls district and its environs (James, 1958; James and others, 1968; Pettijohn and others, 1969; Cambray, 1977). These papers do not reacn a consensus in their interpretation of the Iron River-Crystal Falls district (IR-CF). In an attempt to discern which geologic model(s) were most feasible, a gravity survey was conducted in eastern Iron County, Upper Peninsula of Micnigan. The survey samples the eastern boundary and the eastern half of the northern boundary of the IR-CF district. The resulting data were then modelled using a Talwani two-dimensional gravity program (Talwani and others, 1959). 1.2 Geologic Setting The Iron River-Crystal Falls district is a triangular-shaped syncline of early Proterozoic (Precambrian X) metavolcanics and metasediments which belong to the'v2.0 Ga old (Cannon, 1978) Marquette Range Supergroup. The apices of the triangle are roughly located at Iron River, Crystal Falls, and the Michigan-Wisconsin border at US-l41, with an arm extending southeast along the state line for some distance. Regionally, the Marquette Range Supergroup rests unconformably on Archean (Precambrian W) gneisses, meta- volcanics, and granites whose ages vary from in excess of 3.0 Ca to about 2.6 Ca (Cannon, 1978). Also, present in the study area are intrusive rocks emplaced during two separate (?) events. The first 1 2 are early Proterozoic intrusives of mafic composition which were emplaced during deposition of the Marquette Range Supergroup ( 2.0 Ca) (Cannon, 1978). The other intrusives are of varying composition and synchronous with the Penokean Orogeny ( 1.9 Ca) (Cannon, 1978). Scattered remnants of Paleozoic rocks cover only a tiny percentage of outcrop area, which is itself a small percentage of the total study area. The region has been interpreted as an ancient passive margin, with Marquette Range Supergroup sediments and volcanics deposited both in grabens and on platformal or interbasinal areas (Cambray, 1977; Larue and $1088, 1980). Outcrops of Archean rocks on anticlines and domes are common and are generally of large area. Although the trends of folds in both the Archean and Proterozoic rocks are NW-SE, the frequent crossfolding and overturning of beds observed in the Proterozoics suggest that they have been more severely deformed than their Archaean counterparts (James and others, 1968). Folds in the Proterozoic beds are nearly isoclinal and beds generally dip at more than sixty degrees (James and others, 1968). Faults are mostly high angle thrusts (James and others, 1968), but are of unknown age. The two major unconformities are above and below the early Proterozoic rocks (Cannon, 1978). 1.3. Previous Works 1.3.1. Geologic Works Several significant United States Geologic Survey publications have been written concerning the Iron River-Crystal Falls district and its environs (Clements and Smyth, 1899; Gair and Weir, 1956; 3 James, 1958; Bayley, 1959; James and others, 1961; Weir, 1967; James and others, 1968; Dutton, 1971). The modern study of the geology of Iron and Dickinson Counties began with the introduction of a new stratigraphic column (James, 1958; Figure l), which is still generally accepted today. The premier work on the area is James and others (1968), which includes a fine geologic map, litholigic descriptions and thicknesses, a simple Bouguer gravity map, chemical analyses (including a whole-formation density determination of the Riverton Iron Formation), some magnetic coverage, descriptions of structural style, and dissent by co-author Pettijohn in structural interpretation: It is the Opinion of one of the authors (FJP) that the folds in the Michigamme Slate are unrelated to those in the Badwater Greenstone and Dunn Creek Slate and that in fact they are separated by a northerly trending fault marked by the Little Tobin Lake granite dike and similar dike-like bodies to the north. This inferred fault would terminate to the north or be displaced along the Cayia fault and, for much of its length, would separate Michigamme Slate to the east from Dunn Creek Slate to the west. In this view, the Badwater Greenstone might not be a continuous mass; rather it might reacn bedrock surface on a series of anticlines comparable to that in Sec. 19, T.42N., R.32W., and the adjacent part of Sec. 24, T.42N., R.33W. Publication of James and others (1968) was quickly followed by the release of investigations by the Michigan Geologic Survey (e.g., Pettijohn and others, 1969; James and others, 1970; Weir, 1971; Pettijohn, 1972) which contain essential information not included by James and others (1968). Although additional interpretations of the structure, stratigraphy, and tectonics of the area began to be published during Middle Proterozoic Granitic rocks gr Early Mafic intrusives min Paint Fortune Lakes Slate sl Stambaugh Slate mag 81 River Hiawatha Graywacke gggw Riverton Iron Formation if Marquette Group, Dunn Creek Slate sl Badwater Greenstone JE:_ Baraga Michigamme Formatin 81 Group Amasa Formation sl-if Proterozoic Range Hemlock Formation ##gs Menominee Vulcan Iron Formation 4gf Group Felch Formation sl Supergroup Saunders Randville “Chocolay Formation Dolomite dm Sunday Sturgeon Quartzite Quartzitequt Group Fern Creek Formation Efil Dickinson Margeson Archean Creek var Group Gneiss gr - granite, min - mafic intrusives, sl - slate, mag - magnetic, gw - graywacke, if - iron formation, gs - greenstone, dm - colomite, qzt - quartzite, cgl - conglomerate, var - variable. 1980, personal communication) Figure 1 James' pre-Keweenawan stratigraphy (James, 1958; Larue, 5 the late 1970's, the stratigraphic interpretations most directly affecting the Iron River-Crystal Falls district were first proposed (although not published) in the late 1950's. The first proposal suggests that the Paint River Group consists of strike-fault repetitions of facies of parts of the Baraga and Menominee Groups (Trow, 1960, Figure 2). This hypothesis requires some ”uplift" of the rocks in lR-CF to obtain the desired repetition of lighologies. The second interpretation suggests the stratigraphic equivalence of the Paint River Group and the Menominee Group (Cambray, 1977). Structurally, this model requires uplift of the Iron River-Crystal Falls district so that the older Menominee (Paint River) Group shares its present erosional surface with that of the younger Baraga Group, which virtually surrounds the IR-CF district in map view. The final stratigraphic interpretation, based upon observations in Baraga County (north of the present study area) correlates the Baraga Group with the Menominee Group (Mancuso, 1975). The most recent tectonic interpretations envision the granitic terrain of N. Wisconsin as the basal part of a volcanic arc complex beneath which oceanic lithosphere subducted. 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Aamomolmookmm coo Aanmov AmAsma ook coaumauoe goods»: akeon Loo: oomd akeaac now: coca Saom gaseous use: Amawav suham a muemsoau Apoddsv Asmaoo kmqkmm oooA Aansoc sookme comm eooomEEAA xoooamz Amoaqv Lam: oo~ Auoaav mum: CON coaumauom mmma< AwSASV .Am so Amasa comm Awoon .Am so Amasa coma bosom ussmwSeuoz Awomav .Hm um mason Aummmv o mcoumcomuo “assoc .Am no means flammav oocS weoov Am so seams ookm nauseous Aunmav anofimuumm Aummov was oumam Aoksov .Hm ow moses Basso oSA Aokaoo aeofioooma com goose case ANNmHV csofiuuuom Aummov ooa :oauwauom AOAASV .Sm om moans AomuaomS Aokooo .Se so seams oo~ scum couuo>oe A~naav ccohwuumm Aummmv 0H oxumSMQMU Aokaov .Am so magma Aommzo AS AoAAH~,.Sm um Amasa oA madman“: Aummmv an :owumauom Awmmdv enchauuom «gooey o~ Awomav .Hm um mason om nwomoEMum Aummov o- oumam Aokaoo .Am so seams adamao coco Aokaoo .Sm no means oooA amend mesommm moocwumuuz Aavmmmcxownu moucmummmm Asymmocxoacu coaumauos 37 In order for any model to be considered succesful, the parameters were varied until the r.m.s. residual relative to the observed gravity was less than 3.2 mgal. This figure represents an estimate of the error in the residual and is derived by adding the average uncertainty of the observed simple Bouguer gravity anomaly (:0.8 milligals) to the uncertainty of the calculated gravity (:2.4 mgal, produced by round-off of depth to the nearest 100 meters and of density to the nearest 0.01 grams per cubic centimeter). 4.2 Geologic Interpretations All models are consistent with surface geologic observations of James and others (1968), Pettijohn and others (1969), James and others (1970), Pettijohn (1970), Wier (1971), Pettijohn (1972), Foose (1978), and Cannon (1978). The models are (numbers correspond to subsection): 1. The United States Geologic Survey interpretation 2. The Pettijohn interpretation 3. The Paddock interpretation 4. The Trow interpretation 5. The Greenstone Belt interpretation 6. The Trapped Ocean Crust Interpretation 7. The Larue interpretation 8. The "Badwater ophiolite" interpretation 4.2.1 The United States Geologic Survey interpretation The United States Geologic Survey suggests that the IR-CF district is not fault bounded (James and others, 1968), or, if the district is fault bounded, that those faults do not reach the present erosional surface. Stratigraphy for the USGS model is identical to 38 that given in Table 1. A rough block diagram across the north and east margins of the eastern half of the Iron River-Crystal Falls district (hereafter referred to as the Crystal Falls district) can be found in Figure 11. The two front vertical sides of the block diagrams represent sections along which the two-dimensional profiles were modeled; this will also be true for the block diagrams which illustrate models of other interpretations. The United States Geological Survey's interpretation (James and others, 1968; Bayley, 1959; Wier, 1967; Gair and Wier, 1956; Cannon, 1978; Phase, 1978) was found to match the observed gravity within the required RMS residual using the densities and structure illustrated in figures 12 and 13 for the north-south and east-west profiles, respectively. Densities required to fit the observed gravity within an RMS residual of 3.2 mgal averaged 1.34 standards of deviation from the means. 4.2.2 the Pettijohn interpretation Pettijohn (1969; and James and others, 1968) retains James' (1958) stratigraphy but interprets the Little Tobin Lake granites as evidence of a fault which "would separate Michigamme Slate to the east from Dunn Creek slate to the west. In this view, the Badwater Greenstone ...only reaches...bedrock surface on a series of anticlines” (Pettijohn, 1969). Pettijohn proposed no such fault boundaries for any of the other margins of the Iron River-Crystal Falls district. A block diagram illustrating this interpretation is given in figure 14. Pettijohn's interpretation fails to match the observed gravity on the east-west profile under the assumption that individual 39 O kilomeie rs Figure 11 Block diagram of U.S.G.S. interpretation IO 40 30.1414'91. 1,;94,,L§p.4 3 O I gI o O I observed GO '3' If. 9 calculated ”3 -6 o .. II 6 -9 ' —9 42* ° "; ~-I2 _ u '. l5 it: 4.1!. 45 -IB‘ 0611* . -|8 ° ° I! 1 .25; ° [ I -2" .24} I; ~24 '27 ~27 0 '2 .4 -6 .3 40 -I2 44 I6 Figure 12 North-south gravity profile of U.S.G.S.-Pettijohn interpretation 41 0 § [0 [5 2,0 2,5 3,0 35 { observed 1 ‘r g calculated ' I (i locngt“ . is? I!) ‘IIII In 3 > J I 1 q C .0 . I I 45‘ i “5 4 .‘r “:0... ....H!:1 hr . ‘ In“ I It. .30. It -30 1 O I. " 0 j . 01‘]? - s6 2:3. mg; m? s: v... 3.24:: 0:23 prn 2WD -J / 2.39 [O Xbm 2.6 h/ th 2'78 . ‘ X» as: “1213- ‘”9" 2L64 p ~IO ° 5 lb :5 2'0 2'5 3‘0 35 Figure 13 East-west gravity profile of U.S.G.S. interpretation 42 '30 >20 ~|O IO kilometers Figure 14 Block diagram of Pettijohn interpretation 43 formations do not thicken appreciably laterally (see figure 15). The root-mean-square residual for the final computer model of the east-west profile was 5.6 milligals. Attempting to fit the gravity through the thickening of formations would require the addition of at least 10 kilometers of 2.82 gram/cubic centimeter material to the western portion of the east-west profile (the left portion of figure 15). This thickening would have to be uniformly distributed along the north-south profile, and would probably ruin the previously adequate fit shown in figure 12. 4.2.3 the Paddock interpretation The author retains James' (1958) stratigraphy and Pettijohn‘s (1969; James and others, 1968) fault-bounded eastern margin, but suggests the existence of faults bounding the entire Iron River- Crystal Falls district. Such a series of faults would separate Dunn Creek Slate from Michigamme Slates on the east margin of the district and would therefore, lie at either the Dunn Creek-Badwater Greenstone contact or the Badwater Greenstone-Michigamme Slate contact on the northern margin of the Iron River-Crystal Falls district. It was found that the second option was more successful at matching the gravity, and that the fault contact dips 10 and 15 degrees to the south. This interpretation is illustrated in figure 16. The author's interpretation fails to match the observed gravity on the east-west profile within the required r.m.s. residual of 3.2 mgals under the assumption that no formation appreciably thickens laterally. The final computer model of the east-west profile of this interpretation had a root-mean-square residual of 4.4 milligals (see figure 17). The interpretation might be further modelled on the 44 UV 5 IS) L5 2ND 25: 3!) §fi$ . i If { observed ’ q so L II E ’0 . ’1‘ I3 *1 . l“ ‘ o I: 0 calculated 3 . I ~15 3.1 so 0 01‘ ,8 I °° 0&4 pfil 0 o 0 -3o- 11:; .° :40 i 1‘ .r a?» 3'38 :3: Xmin\ gig x930 556 3:: "O »5 IO an 2.64 IS‘ _ . ‘ :5 w ‘ lb 7 2‘0 so E Figure 15 East-west gravity profile of Pettijohn interpretation 45 Figure 16 Block diagram of Paddock interpretation 46 I 1 I' . o°°b H .4 I observed o I To 9 I 0 calculated II I °% ' II I 3 , ' I 00 * E o L --20— o 2, *cn°93> o ‘5" 'I 1 11° . 0 III I I? <9 I I I; O .— -so- * o dT°° O o .I’ 00 9’ -4o . . m viii-fir: l m £24m”; II o » Xbm 2.so x» 2.75 Kllli. 210 :fl; GIRZF?‘ g Xmin=2.79- . z: ‘ Xc'rzsoxm z'n—xWZ'“ Won 2.64 . I: I: _ glo— ‘ o ‘ ‘35— ‘ 4k 117—“- DISTANCE (KM) Figure 17 East-west gravity profile of Paddock interpretation 47 east-west profile by thickening the West Kiernan Sill (density 2.82) by approximately 3.8 kilometers in the Iron River-Crystal Falls district. The area north of IR-CF would also receive this additional mass, but those areas to the east would not. While this additional mass would presumably improve the fit of the east-west profile, it would also probably ruin the previously acceptable fit of the north-south profile (figure 18). 4.2.4 the Trow interpretation Trow (1960) interprets the Paint River Group as repetitions of facies of parts of the Baraga and Menominee Groups (see Figure 2). In the context of the Iron River-Crystal Falls district (IR-CF), Trow's interpretation is identical to the author's (see subsection 4.2.3) except that Trow requires non-existence of the Michigamme Formation, the Amasa Formation, and the Hemlock Eormation from below the IR-CF (see figure 19). Trow's model fails because the Badwater Greenstone-Hemlock Formation is required to have a high density where it outcrops between x I 0 and x I 1.3 km on Figure 20, while needing a low density where it outcrops between x I 17.4 kilometers and x I 21.6 kilometers. The density used in figure 17 (2.70 grams per cubic centimeter) is a good compromise between the two requirements, but will not adequately fit the observed gravity. Solving this inadequacy by thickening the West Kiernan Sill requires replacement of at least 2.1 kilometers of Hemlock Formation with sills. 4.2.5 The Greenstone Belt interpretation Cambray (personal communication, 1980-81) has noted the similarity between the Iron River-Crystal Falls district and greenstone belts. Both contain sequences of basalt, slates and iron 48 I I ‘ ° I observed O-- I 0 a calculated 0 O 0 co . . o <>° ‘ .. o e 1* .§.40- ° 0’ T o 6 I ‘ I: I' 09 66611;?31Q 0" E w‘ mi... ° ‘D-ZOr-o ‘ l :11 1‘ I I . 304 1 l ‘ I ‘ I 082333 Vim °|""'J\xpm ass ‘ WE/ 355;]: x» 2.77 ‘ " /x‘/ w 2.54 . I h .- d. I. glo- 1 I L I l l O .0 20 30 DISTANCE (Km) Figure 18 North-south gravity profile of Paddock interpretation 49 Won ‘1“ / 0 Xmln \O Xb / A \/ o 2 /’ VMgn ,zfiyo Figure 19 Block diagram of Trow interpretation (mgal, 3 o o GRAVITY -40 (Km) DEPTH 50 { observed 0 calculated X". 2.70 .0 DISTANCE (Km) Figure 20 East-west gravity profile of the interpretation 51 formations. Interpreting the IR-CF district as a greenstone belt requires fault bounding all margins of the district at the Badwater Greenstone-Michigamme Slate "contact". The possibility of extensive thickening of the Badwater Greenstone also exists since greenstones regularly extend to a depth of 25 kilometers (Windley, 1977). The greenstone belt interpretation is illustrated in figure 21. The greenstone-belt model is inconsistent with the shallow dip gravitationally required on the contact separating the Badwater Greenstone from the Michigamme Slate on the northern margin of the Iron River-Crystal Falls district. 4.2.6 The Trapped Ocean Crust interpretation Cambray (personal communication, 1979) interpreted the Iron River-Crystal Falls district as trapped ocean crust which has escaped subduction (figure 22). The ocean crust was created either directly as a result of spreading between Michigan and Wisconsin in early Proterozoic time, or as the result of back-arc spreading as the proposed ocean floor between Michigan and Wisconsin was subducted to the north (VanSchmus, 1976). The ocean crust in the Iron River- Crystal Falls district would escape subduction due to the peculiar geometry of the area. Unfortunately, this interpretation is inconsistent with the shallow dip (10° to 15°) gravitationally required on the contact between the Badwater Greenstone and Michigamme Slate on the northern margin of the Iron River-Crystal Falls district. 4.2.7 the Larue interpretation Larue (personal communication, 1981) interprets eastern Iron County, Michigan, USA as a large number of overthrusting ophiolites 52 Figure 21 Block diagram of greenstone belt interpretation 53 Figure 22 Block diagram of trapped ocean crust interpretation 54 terminating at the edge of a stable cratonic margin. These ophiolites would lie upon thinned continental crust, but would terminate at the edge of thicker (and more stable) cratonic crust to the northeast (Larue, personal communication, 1°81; 1982). A block view of these ideas is found in figure 23. Larue's interpretation was found to be virtually identical to the Paddock model, except that thrust faults were inserted along appropriate contacts. For this reason, Larue's interpretation was not tested separately. The model fails for the same reasons as the Paddock inter- pretation, and can possibly be remodelled using the same additional thickness as the Paddock interpretation (see subsection 4.2.3). 4.2.8 the "Badwater ophiolite" interpretation. A second ophiolite interpretation views the Badwater Greenstone as an ophiolite whose remains are found in topographic lows of the underlying rock. This model requires the removal of the Badwater greenstone from the stratigraphic column and placing it instead at the top of the column above the Fortune Lakes Slate. Its stratigraphic position with respect to the Little Tobin Lake granite trend would be ambiguous. The ophiolite could be abducted over continental crust of any of the previously mentioned models. The "Badwater ophiolite" model fits best when the continental crust is as described by Trow (see subsection 4.2.4, see figure 24). The interpretation matches the north-south gravity profile very well (figure 25), but fails to fit the east-west profile within an RMS error of 3.2 milligals (figure 26). The Badwater "ophiolite" interpretation might be viable through the thickening of the Kiernan Sills by 17 kilometers. However, the Kiernan Sills have a maximum observed thickness of approximately four kilometers. 55 Won « Xb O 0 Figure 23 Block diagram of Larue interpretation Wgn 56 Xb , o X i m n / \0 0 / 2 Won a/‘so J fl‘ 50$ 20 \0 \0 0 0 Figure 24 Block diagram of "Badwater ophiolite" interpretation S7 j —l j ° { observed 0'- "' . ’ ’ 0 calculated _ 0° 0 °3é° . == 6 2 *5, U -.OF- 9 O o 0 T 1 I j > 00 06 o * l . : 0°00“:me { o E ‘4’“. 2 0 6.9-20— ‘ l 1 O 1 L! *" i P { ‘ -30 J l ‘ l I ! I prn 2.83 IJHWSX/bim 0% 277 . e ' ' 1‘. ”A E . x a; ‘ fl. 1 J 1 I 1 l 0 IO 20 3O DISTANCE (Km) Figure 25 North-soucth gravity profile of "Badwater ophiolite" interpretation 58 I I T {I I observed I 9 I 0 calculated A I I I 00 o, , 0 . o I I I q’I ..“°" 0 '- ‘3 °{ 2' o , I h- r- .0 I t l 5:20 (booo o - < 96> :5 I I o '- I I “o O " HI I° o I * 'I ° -30 - + o _ Mo . o Io ° . ° . I' 00 . o -40' . l 4 0 9m 8E3}, 13%; m ,_ ,7 Xb Wdu 27}‘ - ’ A; m ' é? g. 270 Xbb 5 2.40 ‘ __ ___ _Jflfln:222: . “anZGO ' E ASL-L250 ' ' 4—1 . 3. 0 IO *- _ * 4 J l l J 1 l J 0 IO 20 3O DISTANCE (Km) Figure 26 East-west gravity profile of "badwater ophiolite" interpretation 59 4.3 Detailed Gravity Survey Across the Riverton Iron Formation A detailed gravity survey (with stations spaced every 300 meters) was performed along CR9424 through Alpha, Michigan. That survey revealed that a negative residual anomaly of approximately 0.3 milligals occurs where the Riverton Iron Formation reaches bedrock surface. Figure 24 illustrates the results of that survey, with surface lithology and density from Table 5 indicated along the bottom margin. Computer modelling of this profile predicts a positive gravity anomaly of 1.5 milligals over the Riverton Iron Formation. The inability of this detailed survey to detect the iron formation is thought to result from unmapped variations in till thickness. This detailed survey had only four stations located over the iron formation. It is believed that over a larger set of gravity measurements, the iron formation would probably be visible as a positive residual anomaly. 90/00) NOIL'NUO! HOV3 JO ALISNBO NVBN ONV 'NOILVNUOJ '(Ux) SONVLSIO 60 HOOFEO OOUGUER MONALY (mgal) 5 o I 1 V ' m "'2 adi‘ {It M m “I P X STE ZGZLL'Z ‘"4flx . P X [.152 Figure 27 Gravity profile of line A across Riverton Iron Formation 61 5 SUMMARY, CONCLUSIONS AND RECOMMENDATIONS 5.1 Summary Carefully collected and reduced gravity measurements in eastern Iron County provided gravity values, Free Air anomalies and modified Bouguer anomalies accurate to about 0.1, 0.35 and 0.6 milligals, respectively, relative to the Iron River datum. Modified Bouguer anomalies were supplemented by simple Bouguer anomalies from Bacon and Wyble (1952) and Klasner and Jones (1979). Since the three sets of data had been corrected in different ways, a correlation function was created to bring the simple Bouguer anomalies of a Bacon and Wyble (1952) and Klasner and Jones (1979) into agreement with the anomalies of this study. Accuracy of correlation-function values is :L1'3 milligals and :_l.0 milligals for input from Bacon and Wyble (1952) and Klasner and Jones (1979), respectively. Final accuracy of this enlarged set of simple Bouguer anomalies averages i 0.8 mgal. This includes approximately 200 points from the present study, and another 100 each from Bacon and Wyble (1952) and Klasner and Jones (1979). Modified Bouguer anomalies were interpreted to determine which of several different geologic models by the United States Geologic Survey, Pettijohn, the author, Trow, Cambray, and Larue best fit the observed gravity (see Chapter 4). Modelling was two-dimensional using the method of Talwani and others (1959) on a CDC Cyber 750 computer. All models were consistent with known surface geology, including outcrop data, mine geology, diamond drill hole data, water well data, and seismic surveys. In particular, lateral variation from the thickness observed or inferred from the outcrop of each 62 formation was minimized. In order to fit the theoretical model to the observed gravity, additional structure was introduced and densities varied within a range of :;2.49 standard deviations for the north-south profile and 1:2.56 standard deviations on the east-west profile according to the number of stations on the profile. 5.2 Conclusions Modelling revealed that the existing USGS interpretation (Gair and Wier, I956; Bayley, 1959; Heir, 1967, James and others, 1968; Cannon, 1978; Foose, 1978) will fit the observed gravity under the assumption that no formation appreciably thickens laterally. That interpretion holds that lR-CF is not fault bounded (at least at the surface), and that none of the geologic features in eastern Iron County, Michigan, is an ophiolite. None of the remaining seven interpretations (see Chapter 4) were able to match the observed gravity within a root-mean-square residual of 3.2 milligals under the assumption that the thickness of each formation is fairly uniform laterally. Of these seven interpretations, three are potentially salvageable through lateral thickening of the proper formations. Trow's (1960) interpretation would require a replacement of at least 2.1 kilometers of Hemlock Formation with west Kiernan Sill under IRrCF and to the north of IRrCF with no replacement to the east of IR-CF. The other potentially salvageable models are the author's and Larue's (1982, personal communication) interpretations. These two models are virtually identical, except for the insertion of thrust faults along the proper lithologic contacts to accommodate Larue's (1981, personal communication) ophiolites. These interpretations would both require 63 replacement of at least 3.8 kilometers of Hemlock FOrmation with Kiernan Sill. This replacement would be restricted to the Iron River-Crystal Falls district and to the area north of the district with no thickening of the Kiernan Sills east of the IRPCF district. In the case of the author's and Larue's interpretation, thickening of the sills may help to fit the east-west profile, but might also harm the acceptably small residual currently existing on the north-south profile. Pettijohn's interpretation and the "Badwater ophiolite" interpretation (see chapter 4) are both salvageable through lateral thickening of high-density formations, but both require an unrealistic additional thickness (10 kilometers and 17 kilometers, respectively). The remaining two models, the "Greenstone Belt" and "Trapped Ocean Crust" interpretations were found to be inconsistent with the ten to fifteen degree southern (apparent) dip of the Badwater Greenstone-Michigamme Formation (fault?) contact obtained by gravity modeling the northern margin of IR-CF. A feature not specifically modelled, but which was required in the U.S.G.S. model (and some other models as well) was the crustal thinning of the south half of Iron Cbnty, Michigan suggested by Larue (1980, personal communication). That thinning can be seen on figure 12 at x-28 kilometers and on figure 13 at x-26 km. Another required feature was the subdivision of Cannon's (1978) Fortune Lakes Slate into two separate lithologies, labelled prn (Fortune Lakes Slate (north)) and prs (Fortune Lakes Slate (south)) on figures 12, 18, and 25. Although densities for the ”north" and ”south” members are labelled 2.90 and 2.37, 64 respectively, on figure 1, a density of 2.56 for the "southern" member would give a better fit. The "southern" member of the Fortune Lakes Slate produces an intense magnetic low in addition to the gravity low illustrated on figure 12. This magnetic low can be traced from Chicagon Lake southeast into Wisconsin (q.v. U.S.G.S. Geophysical Investigations Map GP607). The approximate extent of the ”southern" member can be seen on older geologic maps, where it is labelled "Paint River Group Undivided" (q.v. Dutton and Linebaugh, 1967, or James and others, 1968). The "southern" member is probably at the base of the Fortune Lakes Slate, but is only evident on the east half of the southern margin of the basin. Its thickness there is approximately a kilometer; presumably, the "southern" member is missing elsewhere in the district. 5.3 Recommendations The best ways to test the eight interpretations presented in Chapter 4 is through drill holes. The required depth of these holes (tens of kilometers) lead one to suggest that the endeavor might be best assigned to the Midcontinent Drilling Project. Cores through the center of the Iron River or Crystal Falls districts, through the Dunn Creek Slate, and through the Hemlock Formation/Kiernan Sill complex would be the most desirable. They would test for stratigraphy, fault boundaries, and ophiolites, respectively. The drawback of such an undertaking is the occasional inability of cores to reveal faults (q.v. Weir, 1971). A less expensive investigation would be the detailed field study of the Little Tobin Lake Granites to determine whether or not Pettijohn's fault actually exists. The 65 emphasis of such a study should be on evidence for shearing (Trow, personal communication, 1981). To further investigate the ophiolite theories for eastern Iron County, a chemical analysis might be done on each of what should be identical "thrust sheets" along M-69 between Crystal Falls and Sagola. Observations and chemical analyses by Bayley (1959) suggest that these sheets are significantly different. In addition, the E: similarity in stratigraphy between the Hemlock Formation in Lake Mary and Ned Lake quadrangles (Bayley, 1959; Foose, 1978) strongly suggests that the Hemlock Formation actually is a distinct formation rather than a series of thrust sheets. 0r Investigation should be made of the "southern" member of the Fortune Lakes Slate mentioned in the previous section. The gravity and magnetic lows above this member could be the result of rocks with low magnetic susceptibility and density or perhaps a thick body of glacial deposits. The final recomendation is that more density determinations be made for the southern Lake Superior region. No density determinations for the Fortune Lakes Slate (and its "southern member"), the Kiernan Sills or the Dickinson Group currently exist. REFERENCES REFERENCES CITED Bacon, L. 0., and Wyble, D. 0., 1952, Gravity investigations in the Iron River-Crytal Falls mining district of Michigan: Am. Inst. Mining Metall. Engineers Trans., v. 193, Tech. Paper 3383L, p. 943-979. Bayley, R. W., 1959, Geology of the Lake Mary Quadrangle, Iron County, Michigan: U.S. Geol. Survey Bull. 1077, 112 p. Cambray, F. W., 1977, The geology of the Marquette district, a field guide: Michigan Basin Geological Society, 62 p. Cannon, W. F., 1978, Geologic map of the Iron River l°x2° Quadrangle, Michigan and Wisconsin: U.S. Geol. Survey Open File Map 78-342, Scale 1:250,000. Cannon, W. F., and Klasner, J. S., 1976, Geologic map and geophysical interpretation of the Witch Lake Quadrangle, Marquette, Iron, and Baraga Counties Michigan: U.S. Geol. Survey Map 1-987, scale l:62,500. Carlson, B. A., 1974, A gravity study of the geology of northeastern Wisconsin (Ph.D. thesis): Michigan State University, 120 p. Clark, 8. P., Jr., ed., 1966, Handbook of physical constants (rev. ed.): Geol. Soc. America Mem. 97, 587p. Clemens, J. M., and Smyth, H. L., Jr., 1899, The Crystal Falls iron-bearing district of Michigan: U.S. Geol.Survey Mon. 36, 512 p. Duerksen, J. A., 1949, Pendulum gravity data in the United States: U.S. Coast and Geodetic Survey Spec. Pub. 244, 218 p. Dutton, C. E., 1971, Geology of the Florence area, Wisconsin and Michigan: U.S. Geol.Survey Professional Paper 633, 54 p. Foose, M. P., 1978, Preliminary geologic map for the Ned Lake Quadrangle, Michigan: U.S. Geol. Survey Open File Report 78-386, scale l:62,500. Frye, K., 1974, Modern Mineralogy: Englewood Cliffs, New Jersey. Prentice-Hall, Inc. 325 p. Gair, J. F., and Weir, K. L., 1956, Geology of the Kiernan Quadrangle, Iron County, Michigan: U.S. Geol Survey Bull 1044, 88 p. James, H. L., 1958, Stratigraphy of pre-Keweenawan rocks in parts of northern Michigan: U.S. Geol. Survey Prof. Paper 314-C, p. 27-44. James, H. L., Dutton, C. E., Pettijohn, F. J., and Weir, K. L., 1968, Geology and are depostis of the Iron River-Crystal Fall district, Iron County,Michigan: U.S. Geol Survey Prof. Paper 570, 134 p. 66 67 James, H. L., Pettijohn, F. J., and Clark, L. C., 1970, Geology and magnetic data between Iron River and Crystal Falls, Michigan: Michigan Geol. Survey, Report of Investigation 7, 17p. Klasner, J. S., and Jones, W. J. 1979, Simple Bouguer gravity map and geologic interpretation: Iron River l°x2° quadrangle, Northern Michigan and Wisconsin: U.S. Geol. Survey Open File Report 79-1564. Larue, D. K., 1981, (unpublished preliminary version of Larue, 1982), Evolution of a purported early Proterozoic passive margin, Lake Superior region. Larue, D. K., 1982 (in press), Three early Proterozoic terranes in the southern Lake Superior region bearing on passive margin sedimentation and plate collision. Larue, D. K., and Sloss, L. L., 1980, Early Proterozoic sedimentary basins of the Lake Superior region, Geol Soc. America Bull. 91, p. 450-452, 1936-1874. Leney, G. W., 1966, Field studies in iron ore geophysics in Mining Geophysics, vol. 1, Soc. Expl. GeOphysicists, p. 319-417. Mancuso, J. J., Lougheed, M., and Shaw, R., 1975, Carbonate-apatite in Precambrian cherty iron-formation, Baraga County, Michigan: Econ. GeOlo, V. 70, p. 583-586. Pettijohn, F. J., 1972, Geology and magnetic data for southern Crystal Falls area, Michigan: Michigan Geol. Survey, Report of Investigation 9, 31 p. Pettijohn, F. J., Gair, J. F., Weir, K. L., and Prinz, W. C., 1969 Geology and magnetic data for Alpha-Brule River and Panola Plains area, Michigan: Michigan Geol. Report of Investigation 10, 12 p. Talwani, M., WOrzel, J. L., and Landisman, M., 1959, Rapid gravity computations for two-dimensional bodies with application to the Mendocino Submarine Fracture Zone: J. Geophys. Res., vol. 64, pp. 49-59. Telford, W. M., Geldart, L. P., Sheriff, R. F., and Keys, D. A., 1980, Applied geophysics: New YOrk, Cambridge University Press, 860 p. Trow, J.W., 1960, Final report on Outside Exploration 1247 (unpublished): Cleveland Cliffs Iron Company. Weir, K. L., 1967, Geology of the Kelso Junction quadrangle, Michigan: U.S. Geol. Survey Bull. 1226, 47 p. , 1971, Geology and magnetic data for northeastern Crystal Falls area, Michigan: Michigan Geol. Survey, Report of Investigation 11’ 14 p. 68 Windley, B. F., 1977, The Evolving Continents: N.Y., Wiley, 385 p. Woollard, G. P., and Rose, J. C., 1963, International gravity measurements: Tulsa, Soc. Expl. GeOphys. Spec. Pub. APPENDICES 69 APPENDIX I STATION STATION LOCATION IR 1A 18 IC 1D 1E 1F 16 1H 11 1N 10 1? 1Q 1R On the playgrounds of Central School (no longer used) on Cayuga Street between Second and Third Streets. The station is 37.5 meters N60°W of the "Iron River 1940" standard gravity reference mark. The mark is set flush in the concrete sidewalk along the east side of the school, 2 meters due magnetic south of the north end of the walk. The station is also 33.8 meters due magnetic west of the west curbing of Second Street, 38.4 meters due magnetic east of the center of the brick stack at the boiler room, 15 meters due magnetic north of the north side of the school, and 37.8 meters NSSW of the northeast corner of the school (Duerksen, 1949). North side of CR424 at center of Wood Lot Rd. JCT Wbodlot Road and circa 1940's two track, center of both. Center of two track at drive to building south of southern more point of southwest lobe of Third Lake, at end of pea gravel. From U.S. 2, go 1220 m "south“ on CR639. Take two-track south from CR639 for 1300 meters. Center of intersection. Map elevation labeled 1526 feet. At entrance to driveway on CR639, 1020 meters "south" of U.S. 2. East side of CR639, center of driveway. On BM just north of JCT U.S. 2 and CR639. Witness post. At curve 1440 meters north of U.S. 2 on Gas Road. Ctr of both roads. Corner of sections 17, 18, 19 and 20, ctr of Gas Rd, 2640 m N Of U.S. 2. At top of sub-hill with 1518 BM "X", NE, NE, NE, Sec 18, T43N, R33W. At apex of curve on Gibson Lk Rd, 1180 m from new U.S. 141. BM N'of JCT CR643 and Raunio Rd. Elev. 1428 ft. On west side of Snuff Country Road, 580 meters north of CR643, at junction with chained off 2-track. Ctr of JCT Maki Rd and Snuff Country Rd, elev. 1484 feet. BM 1440, SE.of JCT Park Cty Rd and Maple Ave., between telephone pole & stop sign. 70 APPENDIX I (cont) STATION STATION LOCATION 18 IT 2A 2B 2C 2D 2E 2F 26 2H 2I 2J 2K 2L-9H 2M-8C Apex of curve, ctr of rd, Kahma Ave., 200 m E of new U.S. 141, elev. 1451 ft. 200 m N of Corral Rd on old U.S. 141. Ctr of old 141. Close as possible to old house. 1600 meters north of Corral Rd on new 0.8. 141, then west until reaching a topographic high. Ctr of JCT of Carney Dam Rd and Rainbow Tr. Elev. 1420 ft. JCT of Carney Dam Rd and Bara Rd. Ctr of both rds. Elev. 1459 feet. JCT Carney Dam Rd at Buck Lk. Pk. Rd. Ctr of both rds. JCT CR424 at N bd. dirt rd, .7 km west of Buck Lk Rd. Elev. 1486. Just off pavement on W side of Tobin-Alpha Rd at Alpha Cr. JCT’of McClaren and Bible Camp Rds. Ctr of both roads. Center of junction, Bible Camp Road at Idelwild Road. Elevation 1482 ft. JCT‘of Fortune Lake Camp Road at Bible Camp Road. West side of Bible Camp Road. Ctr of Fortune Lake Camp Road. JCT New Bristol Rd at U.S. 2. Ctr New Bristol Rd, N side of U.S. 2. 1451 ft. Ctr of Knivila Rd at N side of Lind Rd. Elev. 1397 ft. Ctr of Ron's Rd at W side of Knivila Rd. Elev. 1398 ft. Ctr of driveway to 283 Knivila Rd at W side of Knivila Rd. Elev. 1430 ft. Ctr of N bd 2-track at N side of Sheltrow Rd, 400 m E of Paint River Public Access. Elevation 1372 ft. N1/2, sec 11, T43N, R33W. Center of driveway to 547 Sheltrow Road at southwest side of Shertrow Road. At benchmark ”X" on a concrete culvert, west side of old U.S. 141, 40 meters south of Swan Lake Road. 71 APPENDIX 1 (cont) STATION STATION LOCATION 2N-8E 20 2? 2Q 2R 28 2T 2U 3A 3B 3C 3D 3E 3G1 At entrance to 159 S Casagranda Rd driveway, SE side of S. Casagranda Rd. Elev. 1457. PLEASE NOTE ELEV IS 1457, NOT 1557. Ctr of N Casagranda Rd at section line, 500 m N of U.S. 141. Elev. 1453. Ctr of Premo Cr. Rd at E. side of old U.S. 141. Not at BM. BM 1512 ft at Balsam Sta. SE of JCT of 2-track and CMS+P&P RR. Where Carlson Rd enters section 12. 1600 m road distance from Premo Cr. Rd. Take left fork at end of Carlson Rd. Follow trail to end of clearing. Ctr of C&NW RR at S side of Buck Lk Truck Tr. Elev. 1526 ft. From Buck Lk Truck Tr at Buck Lk-Premo Lk Cr, go "west” along Buck Lk Truck Tr through a right-hand turn to a sharp left-hand turn around a topographic high. Center of trail at the apex. Traffic extremely dangerous. SEl/4, SWl/4, sec. 35. On 2-track, 273 m "NE" of station 3B, at JCT w/new trail not on topo map. Ctr new 2-track, SE track of mapped two track. 3600 m from M-69 along Hope Mine Rd at JCT of Hope Mine Rd and mapped two track. 400 m "SE” of station 3C. NE side of Hope Mine Rd., ctr. of mapped 2-track. At bend in Hope Mine Rd, 2400 m S of M-69 (3200 m along Hope Mine Rd from M-69). 400 m S of ctr of sec 34 and 35 bdry. E side of Hope Mine Rd across from last fence post on E side of rd. TRAFFIC EXTREMELY DANGEROUS. Ctr of E1/2, sec 34, T43N., R.32W., 2000 meters south of M-69 (2400 meters along Hope Mine Rd from M-69) 1/8th mile (200m) east of the center of section 34, T.43N., R.32W. S bd on Old Lk. Mary Rd, cross Blaney Cr, then follow Old Lk Mary Rd 940 meters further "south”. At exit to right-hand curve, left tire track. 72 APPENDIX 1 (cont) STATION STATION LOCATION 362 3H 31 3J 3K 3L 3M 3N 30 3? 3Q 3R 3S 3T 3U 4A 4B 4C S bd. on Old Lk. Mary Rd., cross Blaney Cr., then follow 01d Lk Mary Rd 720 meters further sourth. At south bound left-hand curve. Center of road. Ctr of SW1/4, SEl/4, sec 33, T.43N., R.32W. On floor of waste control lagoon. NE side of Kimball Rd at ctr Dunn Cr. bridge. Center of Kimball Rd at center of Iron County Recreation Trail. Elev. 1304 ft. Center of Iron County Recreation Trail at center of Dunn Creek bridge. Center of trail. Between two ponds. El/2, sec. 32, T.43N., R.32W. North tiretrack of Wiggins Road at west side of U.S. 2 - U.S. 141. ELEV 1314.4 feet. North tiretrack of Wiggins Road at center of driveway to 128 Wiggins Road. Center of boundary, sections 31 and 32, T.43N., R.32W. At end of Valley View Road, south tiretrack, one meter past pine tree. Southwest side of Valley View Road at powerline. West side of Carpenter Road at old light-duty road. Old road blocked by stop sign. 450 meters “west" of Carpenter Road, measured along light duty road. Center of gravel at intersection of Tobin-Alpha Road and Idlewild Road. Elev. 1413 ft. N side of Idlewild Rd. at ctr of abandoned RR, just E of Dunn Cr. N edge of pavement at ctr of driveway to 135 S. Shore Rd. East side of Lake Mary Road at center of South Shore Road. Elev. 1357 ft. W track of Old Lk. Mary Rd. at ctr of ski pathway. SWl/4, SE1/4, SE1/4, sec 12. 73 APPENDIX 1 (cont) STATION STATION LOCATION 4D 4E 4F 46 4M 4I u 4K 4L 4L1 4M 4N 4O 4P 4Q 4R 48 Also station 10K. Old Lk Mary Rd at fork to Paint River. Elev. 1348 ft. SE, NW, SE. At end of fork to Paint River from 4D. Center of turn-around clearing. From corner of Little Bull Road and Lake Mary Road, proceed west 1300 meter (approx). From there take two-track "west“ instead of following Little Bull road south. After 160 meters, take left fork. Follow main road. Makes two T's to the right. Stop at second T. Pace 690 meters 318°. 81/8, W1/4, sec 11, T.42N., R.32W. South track of Panola Plains Road at south-bound two-track. Elev. 1312 ft. North track of Panola Plains Road at center of Mud Lake Road. Elev. 1318. South track of Panola Plains Road at southwest track of two-track to Tim Bowers Fond. South track of Panola Plains Road at section line (9 and 10). Vegetation change. North track of Panola Plains Road at north-bound two track. E1/2, section 9. Center of Panola Plains Road at center of section 9, T.42N., R.32W. From 4N, go "east" 360 meters through right-left "8" curve. At entrance to the next right-hand bend, on south tire track of Panola Plains Road. Panola Plains Road at barely visible old two-track which crosses at very low angle. Elevation is 1361. South side of Panola Plains Road at center of old two-track. Center of Iron County Recreation Trail at center of Panola Plains Road. South side of CR424, directly in front of house, 151 CR424. Center of Hill Farm road at east side of Stager Lake Road. South side of CR424 where center of old Stager Lake Rd would have been. 1428. N side of CR424 at ctr of Book Rd. Elev. 1407 ft. 74 APPENDIX 1 (cont) STATION STATION LOCATION 4T 40 5A SB SC SD 5E SE SG 5H 51 SJ SK SL SM 5N East side of Mastadon Road at center or Iron County Recreation Trail. Elevation 1398. Ctr of Mastadon Rd at ctr of Alpha Cr. At ctr of intersection near BM "X" 1337, El/2, sec 26, TOAZNO ’ R.32W. Center of both runways, Iron County Airport, elevation 1340 ft. Northwest end of main runway, Iron County Airport. ctr of runway. North side of County Airport Road at south side of two-track where County Airport Road bends from WNW-ESE to NW-SE. SW, NE, NE, sec 27. NEl/4, sec 27, at apex of road, 340 meters northwest of unfindable BMl337. South side of County Airport Road at center of two track, 120 meters west of creek to Mallard Lake. N side of Co. Airport Rd. at ctr of old light duty rd. 180 m W of SF. 170 m E of 7 Springs Pond 2-track along main 2-track. N track, in ctr of straight between two E bd right-handers. SEl/4, NEl/4, sec 28. S side of main 2-track at ctr of 7 Springs Pond 2-track. SE, NE, sec. 28. 70 m N'of point INCORRECTLY labeled 1317 feet elevation on Crystal Falls 7 1/2 Quad. 630 m S of Airport Rd. On U.S. 2-U. S. 141. ELEVATION 13 1323.6 FEET AT STATION SJ. 420 m "SW" along 2-track from point INCORRECTLY labeled 1317 feet on Crystal Falls 7 1/2 Quad on top of rise. Well cleared. 370 m, 340° from Rusek Dr. at bdry sect. 28 and 29. At south point of the northernmost of two kettle lakes separated by two-track. 390 m "NW“ of SL along two track, at right-hander in valley. Where sec. 29 2-track changes dir from 280° to 300°. Ctr of 2-track. 75 APPENDIX 1 (cont) STATION STATION LOCATION 50 5? 5Q SR 58 ST 5U 6D 6F 6H 61 6J 6K 6L 6M 7A 7B 7C E side of CR424 at ctr of sec. 29 2-track. Not accessible from east. Sec. corner (19, 20, 29, 30). On old RR not shown on any maps. Iron County Recreation Trail at Stager Creek. Center of both. Center of Nl/2, sec 30, T.42N., R.32W. Where road curves southeast. 1498. Top of hill, NW1/4, sec 30, T.42N., R.32W. 270 meter due west of SR. At end of rd. to burnt-out homestead, Wl/2, NW1/4, sec.30. Fenceline at center of Blockaniec Rd, 1200 m E,of Buck Lk. Rd. 1549. Ctr of 2-track, 400 m E of section line (secs. 20 and 21). E side of Deer Lk Rd at ctr. of two track. Wl/2, NWl/4, sec 29. N track of sec 24 two-track at acute SE bd right-hand curve. sw1/4. Center of sec. 23 two-track, where 2-track dir changes from 135° to 090°. E side of The Grade at ctr of Hemlock R. SE, SE, NE, sec 22. Northernmost of 3 crossings of RRCr on The Grade. Ctr cr, W side of rd. Old U.S. 141 at the section 28-29 bdry. At concrete marker. Old U.S. 141 at Chicago, Milwaukee, St. Paul, and Pacific Railroad tracks. Center of both. 2T. S side of Buck Lk Truck Trail at ctr of C&NW RR. Elev. 1526. North side of Buck Lake Truck Trail at northeast-bound two-track. Sec. 3. Ctr. of Virostek Rd at ctr of DNR Rd. Elev. 1540. 76 APPENDIX 1 (cont) STATION STATION LOCATION 7D 7E 8A 88 8D 8E 8F 8H 9A 9B 9C 9D 9E 9F 9G 1R. BM1440, Amasa. NE side of intersection of Pk Cty Rd and Maple Ave. Between telephone pole and stop sign. BM"X" 1457, SW of intersection Pks. Farm Rd. and Snuff Country Rd. On culvert. O. S. side of WPA Rd. at ctr. of St. Paul Cr. Not at BM"X" 139 S side of WPA Rd at ctr of C. M. St. P. & P. RR. Traffic may damage meter. 2M. BM"X" 1535 on culvert, W side of old 141, 40m S of Swan Lk Rd. "E" side of U. S. 141 at ctr of Old U.S. 141, El/Z, NWl/4, SEl/4, sec 26. 2N. Ctr of drive to 159 S Casagranda Rd, SE side of S. Casagranda Rd. Elev. 1457 NOT 1557. (Map shows 1557 incorrectly). Ctr of drive to 264 Clark Rd at W side of Clark Rd. Elev. 1462 ft. Ctr of drive to 210 Gibson Lk Rd at N side of rd. Elev. 1496 ft. 1N. Apex of curve on Gibson Lk Rd. Wl/2, NEl/4, SEl/4, sec 21. Rock Crusher Rd. at fork. Ctr of sec. 4, T.42N., R.32W. 1489. E side of Rock Crusher Rd at ctr of Finn Lady Swamp Camp driveway. 1420. E side of Paint R. Rd at 2-track running along sec 17-18 bdry. Nl/4. W side of Paint R Rd at 2-track to gravel pit near sec 7-18 bdry. Ctr Soderena Rd at W side CR141. NOT at BM1389. Ctr of drive to 310 Sheltrow Rd at N side of Sheltrow Rd. Elev. 1365. 21. Ctr of Ron's Rd at W side of Knivila Rd. Elev. 1398 ft. “ 77 APPENDIX 1 (cont) STATION 9H 91 9J 10A 10B IOC lOD 10E 10F lOG 10H 101 lOJ 10K 10L 10M lON 100 10? STATION LOCATION 2L. Ctr of driveway to 547 Sheltrow Rd. at 8 side of Sheltrow Rd. SWl/4, NW1/4, sec 10, T.43N., R.33W. Main 2-track at 2-track N to river. Northernmost point on Long Lk Rd, NWl/4, sec 16, T.43N., R.33W. SB. Ctr of both runways, Iron Co. Airport. Elev. 1340 ft. SE. S side of old light duty road at apex, NEl/4 sec 27, T.42N, R.32W. E side of Diversion Canal Rd at northernmore crossing of powerline. W side of Diversion Canal Rd at Section line, 480 m N of 10C. Little Bull Rd at curve, 350 m. S of JCT Little Bull Rd and diversion Canal Rd. Outside of curve. NW side of Little Bull Rd at ctr of 2-track, near BM"X" 1355. 2-track at trail (let "T"). 8 side of thru rd at ctr terminating rd. Elev. 1349. Very severe mosquitoes. W side 01d Lk Mary Rd at NW-SE 2-track, SE, SE, NE, Sec 13. W side of Old Lk Mary Rd at ENE-WSW 2-track, NE3, sec 13. 4C. W side of Old Lk Mary Rd at ctr of ski pathway, sec 12. 4D. W side of Old Lk Mary Rd at 2-track to Paint R. 1348. W side of Old Lk Mary Rd at SW bd 2-track. Elev. 1358. W side of Old Lk Mary Rd at Little Mud Lk 2-track, Elev. 1362. Ctr of Old Lk Mary Rd. 600m SE.of 3C-10Q. Nl/2, Nl/Z, SE, sec 2. E side of Old Lk Mary Rd at ctr of Hope Mine Rd. Nl/2, Nl/2 sec 2. Ctr Hope Mine Rd at ctr of Hope Mine Rd-Old Lk Mary Rd cutoff. 1347. 78 APPENDIX 1 (cont) STATION STATION LOCATION lOQ 10R 10V 11A 118 116 11D 12A 12B 12C 120 12F 126 12H 121 12J 3C. 400 m N of corner, secs. 34, 35, 2,3. T.42-43N. R.32W. E side Lk Mary Rd at cr., 400 m S of M-69. 120. N side M-69 at ctr of Mansfield Cutoff. Elev. 1375. 12Q. Near BM 1383, sec 25. 12R. South side of M-69 at creek. Approx. 2 km W of Lk. Mary Rd. BM 1386. S side of M-69 near Lohrey Ln. NW1/4, sec 27. W side of Peavy Fond Rd at kettle 1k. Nl/2, sec 18, T.42N., R.31W. W side of Peavy Pond Rd at Z-track to Old Lk Mary Rd. Elev. 1341. 48. E side of Lk Mary Rd at ctr S. Shore Rd. Elev. 1357. E side of Lk Mary Rd at ctr of driveway to 423 Lk Mary Rd. BM "X" 1423, SE of JCT M-69 and Camp 5 Rd. On culvert. 8 side of M-69 at ctr line of driveway to 2939 M-69. S side of M-69 at ctr of Kania Rd. Elev. 1404 ft. Benchmark 1377, just south of M-69, 600 meters east of station 12E. South side of M-69, across from center of Old 69 Rd. Elev. 1363. S side of M-69 at ctr of Dawson Lk Rd. Elev. 1356 ft. S slide of M-69 at ctr of Parks Cr. NWl/4, NWl/4, NWl/4, sec 34. Southside of M-69 at gas pipeline, 525 meters "east" of benchmark 1366, as measured along M-69. NEl/4, sec 33. T.42N., R.31W. BM1366, S side of M-69, NWl/4, sec 33, T.43N., R.31W. S side of M-69 at topo low near cr. El/2, E1/2, El/2, sec 33. ‘ 79 APPENDIX 1 (cont) STATION STATION LOCATION 12K 12L 12M 12N 120 12P 12Q 12R A1 A2 A3 A4 A5 A6 A7 A8 A9 A10 All North side of M-69 at two-track, near center of sec 32. S side of M-69 at ctr of driveway to 2250 M-69, NWl/4, sec 32. BM 1294 on M-69 bridge over Michigamme River, west end of bridge. S side of M-69, in front of house, 2125 M-69. Nl/2, sec. 31. 108. North side of M-69 at center of Mansfield Cutoff. 8 side of M-69 at ctr of Lk Mary Rd, W1/2, NEl/4, NEl/4, sec. 36. lOT. Benchmark 1383, SWl/4, SWl/4, SWl/4, sec. 25, T.43N., R.32W. 100. S side of M-69 at cr., approx. 2 km W of Lk Mary Rd. SEl/4. 2B. N side of CR424 at ctr of N bd 2-track. Elev. 1486. 300 m E of Al, N side of CR 424. E of Manito Rd. NWl/4. 600 m E of Al, N side of CR424, NEl/4, NWl/4, sec 14. 775 m "W" of Buck Lake Road, measured along CR424. South side of CR424. 175 meters "E" of A3, as measured along CR424. 450 m W of Buck Lk Rd. S side of CR424. S side of CR424 at ctr Buck Lk Rd. Elev. 1427 ft. W of Alpha. S side of lst St. at intermittent stream, between CR424 and 5th Ave. N side of lst St. at ctr of 6th Ave., Alpha. CR424 goes thru traffic circle. S side of let St. at ctr 8th Ave. (Mastadon Rd.), Alpha. N side of lst St. at ctr. S. Main St. (CR424), Alpha. Floods during heavy rain. North side of CR424, across from center of Stager Snowmobile Trail. 80 APPENDIX 2 STA ELEV (m) GRAVITY* LAT(deg) LAT Free Air (mgal)(j-_.06) Correct. Anomaly(mgal) 1R 460.95 1 0.02 980,633.10 46.0936 08.44 47.23 i .07 1A 453.6 :1: 0.2 27.08 46.0440 03.86 43.43 i .12 13 460.9 1 1.5 29.14 46.0509 04.60 47.12 i .52 1C 426.1 1 1.5 42.66 46.0633 05.71 48.80 i .52 11) 465.1 : 0.2 39.14 46.0725 06.54 56.48 i .12 1E 489.8 1 1.5 32.00 46.0854 07.71 55.80 i .52 1F 470.6 1 0.2 33.24 46.0941 08.48 50.30 1- .12 16 438.6 _-1_-_ 0.2 37.28 46.1087 09.80 43.18 i .12 1H 437.4 j; 2.4 34.17 46.1160 10.46 39.03 -_+_ .80 11 462.7 : 0.2 30.47 46.1282 11.56 42.04 i .12 IN 448.7 : 1.5 31.18 46.1931 17.42 32.93 i .52 10 435.3 1 0.2 34.02 46.2050 18.49 30.19 i .12 IP 448.4 1: 0.2 32.32 46.2119 19.11 31.92 i .12 1Q 452.3 I 0.2 33.86 46.2247 20.26 32.53 i .12 1R 438.9 1 0.2 41.51 46.2314 20.87 36.44 i .12 18 442.3 1 0.2 42.16 46.2389 21.56 37.45 1 .12 IT 468.5 1 1.5 41.09 46.2501 22.55 43.46 i .52 1U 503.2 : 2.4 35.39 46.2527 22.79 48.25 -_I-_ .80 *Datum: Iron River . 980,633.10 81 APPENDIX 2 STA ELEV (m) GRAVITY LAT(deg) LAT Free Air (mgal)* Correct. Anomaly(mgal) 2-B 432.8 :_0.2 980,622.90 : 0.16 46.0148 01.33 37.29 i 0.26 2-A 444.7 -_+_ 0.2 24.71 i 0.16 .0219 01.97 38.51 i 0.26 2A 433.1 1:0.2 33.89 i 0.06 .0289 02.61 45.29 i 0.12 28 452.9 :1; 0.2 34.72 i 0.06 .0399 03.60 51.25 i 0.12 20 429.2 1 1.5 42.49 i 0.06 .0576 05.20 50.08 ~_n-_ 0.52 2D 458.4 1 0.2 40.42 i 0.06 .0653 05.89 56.34 i 0.12 21: 451.7 1 0.2 38.95 t. 0.06 .0796 07.18 51.53 1 0.12 2F 431.6 1 0.2 41.75 i 0.06 .0080 07.94 47.35 i 0.12 20 442.3 2‘. 0.2 40.40 _+_ 0.06 .0940 08.48 48.76 i 0.12 211 425.8 2‘. 0.2 38.84 i 0.06 .1122 10.12 40.48 i 0.12 21 426.1 1 .02 37.57 i 0.06 .1226 11.06 38.36 t. 0.12 2.] 435.9 :1; 0.2 34.49 i 0.06 .1282 11.56 37.78 i 0.12 2K 418.2 _+_ 0.2 38.50 1'. 0.06 .1420 12.81 35.10 i 0.12 2L 460.9 1: 0.2 27.12 i 0.06 .1517 13.68 36.00 1' 0.12 2M 467.9 :_0.2 26.84 :_0.06 .1661 14.98 36.59 t 0.12 2N 444.1 1: 0.2 32.24 i 0.06 .1776 16.02 33.62 i 0.12 20 442.9 f: 0.2 35.58 t. 0.06 .1886 17.01 35.59 i 0.12 2? 445.6 1 1.5 38.88 i 0.06 .1918 17.30 39.45 i 0.52 20 460.9 1 0.2 31.97 i 0.06 .2072 18.69 35.85 i 0.12 2R 460.9 :0: 1.5 32.34 i 0.06 ' .2174 19.61 35.30 i 0.52 25 460.9 1 1.5 32.64 i 0.06 .2234 20.15 35.06 i 0.52 21 465.1 1 0.2 36.70 i 0.06 .2324 20.96 39.62 i 0.12 20 469.7 1 1.5 32.53 i 0.06 .2435 21.96 35.87 i 0.52 * Datum: Iron River - 980,633.10 82 APPENDIX 2 STA ELEV (m) GRAVITY LAT(deg) LAT Free Air (mga1)(+0.06) Correct. Anoma1y(mgal) 3A 422.1 1 1.5 980,621.51 46.0750 6.76 25.37 i 0.52 38 419.4 1 1.5 20.02 46.0741 1.68 23.12 i 0.52 3C 410.9 1 1.5 21.01 46.0759 6.85 21.30 i 0.52 3D 417.0 1 1.5 21.15 46.0793 7.15 23.02 _-i_-_ 0.52 313 415.7 1 1.5 21.19 46.0793 7.15 22.68 i 0.52 361 401.4 1 2.4 23.24 46.0809 7.30 20.16 1 0.80 302 201.17 1 2.4 25.03 46.0827 7.46 21.89 i 0.80 3H 403.9 1 1.5 24.77 46.0742 6.69 23.06 i 0.52 31 394.7 : 2.4 28.00 46.0788 7.11 23.05 i 0.80 3.1 397.5 : 0.2 28.49 46.0797 7.19 24.31 i 0.12 3K 396.8 1; 2.4 29.19 46.0767 6.92 25.09 i 0.80 3L 410.0 :0; 1.5 28.51 46.0790 7.13 28.25 i 0.52 314 400.63 1 0.02 32.34 46.0760 6.85 29.47 i 0.07 3N 416.4 1 2.4 30.45 46.0763 6.88 32.42 i 0.80 30 430.1 1- 1.5 32.94 46.0797 7.19 38.82 i 0.52 3? 456.9 1 1.5 32.68 46.0820 7.40 46.43 i 0.52 30 455.4 1 1.5 34.63 46.0833 7.52 47.99 i 0.52 3R 448.1 I 1.5 36.84 46.0801 7.23 48.23 i 0.52 38 429.8 1 1.5 43.10 46.0812 7.33 48.75 -_|-_ 0.52 31‘ 430.7 1 0.2 42.03 46.0798 7.19 48.10 i 0.12 30 424.9 1 1.5 45.71 46.0799 7.21 49.97 i 0.52 83 APPENDIX 2 STA ELEV (m) GRAVITY LAT(deg) LAT Free Air (mgal) (+0.06) Correct . Anomaly(mga1)** 4A 405.1 1 1.5 980,613.87 46.0518 4.67 14.56 i 0.52 43 413.6 : 0.2 11.22 46.0527 4.75 14.46 i 0.12 4C 413.6 1 1.5 09.74 46.0474 4.28 13.45 i 0.52 4D 410.9 1- 0.2 10.85 46.0505 4.55 13.44 i 0.12 413 396.5 1 1.5 14.13 46.0460 4.15 12.71 1- 0.52 4}? 410.0 _-+_- 1.5 08.84 46.0412 3.72 11.98 i 0.52 4C 397.2 :1; 1.5 14.56 46.0456 4.11 13.36 i 0.52 4H 399.9 1 0.2 14.66 46.0504 4.55 13.88 i 0.12 41 401.7 f; 0.2 15.34 46.0520 4.69 14.96 i 0.12 4.] 413.9 : 1.5 13.25 46.0498 4.50 16.84 1- 0.52 4K 412.7 1 2.4 15.39 46.9514 4.64 18.46 i 0.80 4L 409.0 1 0.2 17.37 46.0516 4.65 19.30 i 0.12 4L1 413.3 -_+_ 2.4 19.79 46.0517 4.66 23.02 i 0.80 424 413.3 1: 1.5 21.00 46.0508 4.59 26.31 1 0.52 4N 414.8 -_i-_ 0.2 23.29 46.0500 4.51 27.15 i 0.12 40 409.7 1 1.5 28.09 46.0523 4.72 30.17 1 0.52 4? 428.5 1 1.5 32.00 46.0430 3.88 40.71 1- 0.52 4Q 439.8 1: 0.2 25.22 46.0401 3.62 37.68 i 0.12 4R 435.3 1 0.2 32.37 46.0485 4.38 42.66 i 0.12 48 428.9 1 0.2 34.14 46.0455 4.11 42.73 i 0.12 4T 426.1 i 0.2 37.07 46.0399 3.60 45.31 i 0.12 4U 425.8 1 1.5 38.89 46.0418 3.77 46.88 i 0.52 84 APPENDIX 2 STA ELEV (m) GRAVITY LAT(deg) LAT Free Air (mgal) (+0 . O6) Correct . Anomalyhgal) 5A 406.9 '1; 1.5 980,601.39 46.0086 0.78 06.53 i 0.52 58 408.4 1 0.2 03.03 46.0085 0.77 08.65 i 0.12 5C 408.1 1' 1.5 03.80 46.0114 1.03 09.07 i 0.52 SD 407.5 1 1.5 05.16 46.0109 0.98 10.28 i 0.52 513 407.8 1 1.5 06.72 46.0142 1.28 11.64 1 0.52 51* 399.0 1 1.5 07.51 46.0130 1.18 09.81 1 0.52 56 403.3 1 2.4 07.38 46.0138 1.24 10.93 i 0.80 5H 404.8 1 1.5 06.80 46.0095 0.86 11.20 i- 0.52 51 403.6 : 1.5 08.38 46.0097 0.88 12.39 1 0.52 5.] 403.43 1' 0.02 10.50 46.0088 0.80 14.55 i 0.07 5K 409.0 1 1.5 09.97 46.0061 0.55 16.00 1 0.52 5L 412.4 1 1.5 12.72 46.0061 0.55 19.78 i 0.52 511 413.0 1 2.4 15.59 46.0079 0.71 22.68 i- 0.80 5N 423.7 :1; 1.5 16.72 46.0131 1.18 26.63 i 0.52 50 424.6 : 1.5 18.02 46.0124 1.12 28.28 i 0.52 5? 423.4 1 1.5 20.18 46.0147 1.32 29.86 i 0.52 5Q 420.3 1 1.5 22.11 46.0122 1.10 31.07 i 0.52 53 456.6 1 0.2 17.38 46.0116 1.04 37.59 1 0.12 53 477.6 1 2.4 14.34 46.0117 1.06 41.02 1 0.80 51' 458.7 1 1.5 19.28 46.0108 0.98 40.21 i 0.52 50 472.1 1 0.2 22.01 46.0147 1.32 46.73 1 0.12 85 APPENDIX 2 STA ELEV (1n) GRAVITY LAT(deg) LAT Free Air (mgal) Correct . Anomaly (3&81) 6D 495.6 : 1.5 980,608.40 46.2784 25.11 16.06 i 0.62 6F 474.9 1 1.5 17.76 1 0.16 730 24.62 20.04 1 0.62 611 479.5 1 1.5 31.87 1 0.16 788 25.15 35.03 1 0.62 61 479.8 : 1.5 32.35 i 0.16 770 24.98 35.76 i 0.62 6.] 459.9 1 2.4 37.96 i 0.16 824 25.47 34.78 i 0.90 6K 448.4 1 2.4 41.88 1 0.16 590 23.36 37.23 1 0.90 6L 491.3 1 1.5 37.20 1 0.16 653 23.93 45.25 1 0.62 614 464.2 1' 1.5 39.75 i 0.16 824 25.47 37.89 i 0.62 7A 465.1 1 0.2 36.69 1 0.02 328 21.00 39.58 1 0.12 713 467.9 1 1.5 37.91 1 0.16 333 21.04 41.60 1 0.62 7c 469.4 1 0.2 39.29 1 0.16 322 20.94 43.55 1 0.22 70 438.9 1 0.2 41.51 1 0.02 318 20.91 36.40 1 0.12 71: 444.1 1 0.2 36.88 1 0.16 322 20.94 33.34 1 0.22 86 APPENDIX 2 STA ELEV (m) GRAVITY LAT(deg) LAT Free Air (mgal) Correct. Anoma1y(m§a1) 8A 424.0 1 1.5 980,634.76 1 0.16 46.1838 16.58 29.37 1 0.62 83 429.2 1 1.5 34.51 1 0.16 825 16.46 30.84 1 0.62 8C 467.9 1 0.2 26.84 1 0.02 663 15.00 36.57 1 0.12 8D 462.1 1 1.5 32.30 1 0.16 800 16.24 39.41 1 0.62 SE 444.1 1 0.2 32.24 1 0.02 778 16.04 33.59 1 0.12 8F 445.6 1 0.2 31.43 1 0.16 832 16.52 32.78 1 0.22 80 456.0 1 0.2 30.90 1 0.16 948 17.57 34.39 1 0.22 8H 448.7 1 1.5 31.54 1 0.02 937 17.47 32.88 1 0.48 9A 453.8 1 0.2 29.18 1 0.16 513 13.646 35.94 1 0.22 98 432.8 1 0.2 31.10 401 12.639 32.37 1 0.22 9C 417.9 1 1.5 35.17 276 11.507 32.97 1 0.62 9D 417.3 1 0.2 36.23 302 11.743 33.60 1 0.22 98 425.8 1 1.5 34.48 302 11.743 34.49 1 0.62 9F 416.1 1 0.2 38.07 407 12.687 34.13 1 0.22 9C 426.1 1 0.2 37.57 1 0.02 230 11.099 38.32 1 0.12 9H 460.9 1 0.2 27.12 520 13.709 35.98 1 0.12 91 411.8 1 2.4 39.93 + 0.16 408 12.702 32.66 1 0.90 9.] 436.5 1 1.5 38.06 255 11.319 41.78 1 0.62 87 APPENDIX 2 STA ELEV (m) GRAVITY LAT(deg) LAT Free Air (1531) Correct. Anomaljhngal) 10A 408.4 1 0.02 980,603.031 0.02 46.0083 0.75 08.67 1 0.08 108 407.8 1 1.5 06.72 142 1.28 11.64 1 0.48 10C 399.3 1 1.5 04.691 0.16 207 1.86 06.40 1 0.62 10D 408.4 1 1.5 05.731 247 2.22 09.90 1 0.62 108 410.3 1 1.5 06.001 271 2.44 10.51 1 0.62 10F 413.0 1 1.5 06.601 325 2.93 11.47 1 0.62 100 411.2 1 0.2 08.361 354 3.20 12.50 1 0.22 10H 412.7 1 1.5 08.611 389 3.51 12.81 1 0.62 101 412.7 1 1.5 09.251 438 3.95 13.57 1 0.62 lOJ 413.6 1 1.5 09.741 0.02 476 4.29 13.44 1 0.48 10K 410.9 1 0.2 10.851 505 4.56 13.44 1 0.08 10L 413.9 1 0.2 11.751 0.16 554 5.00 13.48 1 0.22 10M 415.1 1 0.2 13.671 601 5.42 16.71 1 0.22 10)! 414.8 1 1.5 15.881 655 5.90 18.35 1 0.62 100 416.7 1 2.4 18.221 698 6.30 20.86 1 0.90 10? 410.6 1 0.2 20.811 717 6.47 21.39 1 0.22 10Q 410.9 1 1.5 21.011 0.02 764 6.89 21.26 1 0.48 10R 411.5 1 1.5 23.011 0.16 813 7.33 23.02 1 0.62 105 419.1 1 0.2 22.541 847 7.64 24.58 1 0.22 10T 421.8 1 1.5 23.921 873 7.88 26.58 1 0.62 IOU 420.6 1 1.5 25.891 911 8.22 27.82 1 0.62 10V 422.5 1 0.2 23.281 976 8.80 25.20 1 0.22 88 APPENDIX 2 STA ELEV (m) GRAVITY LAT(deg) LAT Free Air (mgal) Correct. Mom1y(q&al) 11A 407.2 1 1.5 980,611.261 0.16 46.0418 3.77 13.50 1 0.62 118 408.7 1 0.2 11.03 467 4.21 13.30 1 0.22 11C 413.6 1 0.2 11.22 1 0.02 528 4.76 14.45 1 0.08 110 404.8 1 1.5 16.64 1 0.16 594 5.36 16.55 1 0.62 12A 433.7 1 0.2 09.29 1 0.16 873 7.88 15.61 1 0.22 128 432.5 1 1.5 09.16 873 .88 15.11 1 0.62 120 427.9 1 0.2 09.59 873 .88 14.12 1 0.22 12D 419.7 1 0.2 10.27 873 .88 12.26 1 0.22 1215 415.4 1 0.2 11.02 873 .88 11.70 1 0.22 12F 413.3 1 0.2 14.72 873 .88 14.73 1 0.22 126 405.4 16.69 872 .88 14.28 1 0.90 1211 424.6 1 1.5 14.41 847 .64 18.15 1 0.62 121 416.4 1 0.2 13.68 825 .44 15.08 1 0.22 12J 415.1 1 1.5 16.97 811 .31 18.12 1 0.62 12K 414.8 1 2.4 19.75 819 .39 20.72 1 0.90 12L 401.4 1 1.5 23.20 828 .47 19.95 1 0.62 1214 394.4 1 0.2 25.74 839 .56 20.24 1 0.22 12N 404.5 1 1.5 24.56 847 .64 22.09 1 0.62 120 419.1 1 0.2 22.54 847 .64 24.58 1 0.22 121’ 420.0 1 1.5 22.36 847 .64 24.68 1 0.62 12Q 421.8 1 1.5 23.92 873 .88 26.58 1 0.62 12R 420.6 1 1.5 25.89 911 8.22 27.82 1 0.62 89 APPENDIX 2 STA ELEV (m) GRAVITY LAT(deg) LAT Free Air (mgal) Correct. Anoma11(u531) Al 452.9 1 0.2 980,634.731 0.02 46.0399 3.60 51.25 1 0.08 A2 448.7 1 1.5 35.791 0.16 399 0 51.00 1 0.62 A3 454.2 1 1.5 34.73 408 8 51.55 1 0.62 A4 458.7 1 1.5 34.02 424 .82 52.11 1 0.62 A5 444.4 1 1.5 36.18 425 8 49.84 1 0.62 A6 434.9 1 0.2 38.19 425 4 48.93 1 0.62 A7 431.6 1 1.5 38.26 436 .93 47.86 1 0.62 A8 432.8 1 1.5 37.97 436 3 47.96 1 0.62 A9 431.3 1 1.5 38.54 436 3 48.05 1 0.62 A10 426.7 1 1.5 38.68 438 5 46.76 1 0.62 All 426.7 + 1.5 37.71 438 5 45.80 1 0.62 A12 426.4 1 2.4 35.29 439 6 43.27 1 0.90 A13 428.9 1 0.2 34.14 1 0.02 457 4.12 42.72 1 0.08 A14 430.1 1 1.5 33.80 1 0.16 472 .26 42.61 1 0.62 A15 435.3 1 0.2 32.37 1 0.02 486 .38 42.65 1 0.08 A16 444.4 1 1.5 29.37 1 0.16 505 .56 42.30 1 0.62 A17 436.2 1 1.5 31.53 510 .60 41.88 1 0.62 90 APPENDIX 3 STATION TILL THICKNESS Simple Bouguer Grav.Anom.(mgal)* IR 42.8 - 6.08 1 0.06 1A 42.8 -09.05 1 0.27 '3‘ 13 45.8 -06.13 i 0.82 1C 42.8 -00.81 i 0.79 1D 42.8 -02.62 i 0.30 1E 42.8 -Ol.00 i 0.83 E 11“ 58.0 ~03.64 : 0.32 1G 36.5 -07.74 i 0.26 111 55.0 -11.52 i 1.08 11 58.0 -10.20 :_0.24 101 30.5 -l9.41 : 0.80 10 24.5 -20.76 i 0.26 lP 24.5 -20.59 :_0.26 1Q 24.5 ~19.45 : 0.26 lR 15.2 -15.26 i 0.24 13 12.2 -14.77 i 0.24 1T 09.0 -ll.98 i 0.76 10 18.2 -ll.00 : 1.11 *Datum 395.3 meters above mean sea level 91 APPENDIX 3 (Co ntinued) STATION TILL THICKNESS Simple Bouguer Grav.Anom.(mgal)* 2—B 18.2 -13.58 i 0.39 2-A 21.2 -13.68 i 0.40 2A 27.5 -05.30 i 0.27 a“ 23 30.5 -01.59 i 0.30 2C 00.0 -00.79 i 0.63 2D 36.5 +03.07 : 0.23 2E 48.8 -00.52 i 0.26 ,- 2F 70.0 -02.72 i 0.26 2C 27.5 -02.92 i 0.25 2H 42.8 -09.10 i 0.18 21 51.8 -11.25 i 0.18 2.1 55.0 -12.64 i 0.20 2K 45.8 -13.84 i 0.10 2L 55.0 -16.92 i 0.32 214 48.8 -17.38 i 0.31 2N 30.5 -18.17 i 0.27 20 27.5 -l6.l6 : 0.33 2? 21.5 ~12.84 i 0.76 2Q 24.5 ~18.15 :- 0.27 2R 24.5 -18.70 i 0.79 ZS 24.5 -18.94 i 0.79 2T 15.2 -15.21 i 0.25 20 21.2 -19.29 1 0.76 92 APPENDIX 3 (Co ntinued) STATION TILL THICKNESS Simple Bouguer Grav.Anom.(mgal)* 3A 30.5 -23.90 1 0.78 38 42.8 -25.93 i 0.78 30 42.8 -27.02 1 0.76 ‘ 3D 42.8 -25.82 i 0.77 35 42.8 -26.05 i 0.77 361 39.5 -27.37 i 1.12 302 39.5 -25.76 i 1.12 311 39.5 -24.68 i 0.74 31 39.5 -23.93 i 1.11 3.1 36.5 -22.89 i 0.12 3K 36.5 -22.07 i 1.11 3L 36.5 -20.01 1- 0.76 311 36.5 -18.00 i 0.06 3N 36.5 -16.38 i 1.66 30 42.8 -11.12 -_+_ 0.79 3? 39.5 -O6.36 i 0.78 3Q 36.5 ~04.93 : 0.78 3R 51.8 -03.28 i 0.77 38 48.8 -01.16 i 0.76 3T 15.2 ~02.63 i 0.22 30 09.0 -00.28 I 0.76 93 APPENDIX 3 (Co ntinued) STATION TILL THICKNESS Simple Bouguer Grav.Anom.(mgal)* 4A 27.5 -33.29 i 0.75 4B 27.5 -34.10 i 0.19 4C 30.5 -35.11 i 0.77 4D 30.5 -34.89 i 0.14 4E 33.5 -34.42 i 0.73 4F 36.5 -36.27 i 0.76 40 39.5 -33.82 i 0.73 4H 39.5 -33.53 1 0.12 41 39.5 -32.60 i 0.12 4.1 39.5 -32.11 _+_- 0.77 4K 39.5 -30.02 i 1.15 4L 39.5 -28.88 i 0.14 4L1 36.5 -22.51 i 1.15 411 36.5 -22.22 i 0.76 4N 36.5 -21.51 -_1-_ 0.15 40 36.5 -l8.09 : 0.76 4? 33.5 -09.12 1: 0.79 4Q 27.5 -13.70 i- 0.27 4R 33.5 -O7.97 : 0.27 48 30.5 -07.25 i 0.26 4T 30.5 -04.34 i 0.25 40 21.2 -03.06 1 0.77 94 APPENDIX 3 ((2) ntinued) STATION TILL THICKNESS Simple Bouguer Grav.Anom.(mgal)* 5A 30.5 -4l.47 : 0.75 58 33.5 -39.47 i 0.14 5C 33.5 -39.03 i 0.75 r SD 30.5 -37.76 i 0.75 515 30.5 -36.43 I 0.75 5? 27.5 -37.53 i 0.74 SC 27.5 36.76 i 1.20 ;_ 5H 24.5 ~36.61 1 0.75 51 24.5 -35.32 i 0.74 5J 21.2 -33.15 -_+_ 0.07 5K 18.2 -32.17 -_+_ 0.76 5L 15.2 -28.77 i 0.76 5M 15.2 -25.94 i 1.08 5N 18.2 -23.16 i 0.77 50 15.2 -21.72 i 0.76 5P 12.2 -20.11 i 0.76 5Q 12.2 -18.54 i 0.75 5R 15.2 -l6.22 i 0.22 SS 15.2 -15.29 i- 1.07 ST 15.2 -l3.86 i 0.68 95 APPENDIX 3 (Ch ntinued) STATION TILL THICKNESS Simple Bouguer Grav.Anom.(mgal)* 6D 36.5 -41.64 1 0.96 6F 36.5 -35.20 1 0.95 6H 30.5 -20.96 1 0.94 61 27.5 -20.37 1 0.94 6J 25.5 -19.11 1 0.94 6K 12.2 -15.71 1 1.24 6L 12.2 -12.80 1 0.91 6H 18.2 -16.72 1 0.92 7A 15.2 -15.25 1 0.25 78 12.2 -13.66 1 0.90 7C 09.0 -12.00 1 0.38 70 15.2 -15.31 1 0.24 7E 12.2 -19.10 1 0.38 8A 12.2 -20.67 1 0.90 813 12.2 -l9.82 1 0.90 8C 48.8 -17.40 1 0.31 SD 30.5 -14.92 1 0.94 SE 30.5 -18.20 1 0.27 81" 30.5 -l9.l9 1 0.41 80 30.5 -18.82 1 0.42 8H 30.5 -19.46‘1 0.80 96 APPENDIX 3 (Continued) STATION TILL THICKNESS Simple Bouguer Grav.Anom.(mga1)* 9A 15.2 -17.55 1 0.39 98 09.0 ~18.82 1 0.37 9C 30.5 -15.94 1 0.92 90 30.5 ~15.26 1 0.30 9E 33.5 -15.09 1 0.93 9F 42.8 -14.63 1 0.29 90 39.5 -11.29 1 0.18 9H 55.0 -16.95 1 0.32 91 36.5 -14.65 1 2.12 97 APPENDIX 3 (Co ntinued) STATION TILL THICKNESS Simple Bouguer Grav.Anom.(mgal)* 10A 33.5 -39.45 1 0.14 108 30.5 -36.43 1 0.75 IOC 27.5 ~40.96 1 0.88 IOD 27.5 -38.23 1 0.90 10E 27.5 -37.76 1 0.90 10F 27.5 -37.04 1 0.90 100 30.5 -35.86 1 0.28 1011 27.5 -35.68 1 0.90 101 30.5 -35.06 1 0.91 10.] 30.5 -35.12 1 0.77 10K 30.5 -34.89 1 0.14 10L 30.5 -34.10 1 0.29 1011 30.5 -31.97 1 0.29 lON 36.5 -30.31 1 0.91 100 36.5 -27.96 1 1.30 10? 39.5 -26.91 1 0.28 10Q 42.8 -27.07 1 0.76 10R 30.5 -25.37 1 0.90 108 24.5 -24.44 1 0.30 10T 21.2 -22.89 1 0.92 10U 24.5 -21.39 1 0.92 10V 24.5 -24.23 1 0.31 98 APPENDIX 3 (Go ntinued) STATION TILL THICKNESS Simple Bouguer Grav.Anom.(mga1)* 11A 27.5 -34.52 1 0.89 118 27.5 -34.85 1 0.28 11C 27.5 -34.11 1 0.15 110 27.5 -31.27 1 0.89 12A 33.5 -34.84 1 0.42 128 33.5 -35.20 1 0.94 12C 27.5 -35.85 1 0.40 120 24.5 -36.84 1 0.38 12E 24.5 -37.01 1 0.29 12F 21.2 -33.80 1 0.29 126 18.2 -33.59 1 1.27 12H 15.2 -31.86 1 0.90 121 15.2 -33.94 1 0.40 12J 12.2 -30.87 1 0.89 12K 12.2 -28.23 1 1.22 12L 12.2 -27.58 1 0.88 12M 30.5 -26.71 1 0.25 12N 30.5 -25.70 1 0.89 120 24.5 -24.45 1 0.30 121’ 24.5 -24.46 1 0.92 120 21.2 -22.89 1 0.92 12R 24.5 -21.39 1 0.92 99 APPENDIX 3 (Co ntinued) STATION TILL THICKNESS Simple Bouguer Grav.Anom.(mgal)* A1 30.5 -Ol.59 1 0.30 A2 27.5 -01.44 1 0.96 A3 24.5 -01.65 1 0.95 A4 18.2 -Ol.85 1 0.94 A5 18.2 -02.42 1 0.93 A6 18.2 -02.20 1 0.40 A7 18.2 -02.87 1 0.91 A8 18.2 -02.92 1 0.90 A9 09.0 -02.96 1 0.91 A10 18.2 -03.38 1 0.91 All 18.2 -04.36 1 0.92 A12 21.2 -06.74 1 1.25 A13 30.5 -07.26 1 0.26 A14 30.5 -07.52 1 0.93 A15 33.5 -07.98 1 0.27 A16 36.5 -O9.31 1 0.93 A17 36.5 -08.76 1 0.93 100 O! ‘u I“ I he ‘1) I iALY AT A GRAVIT! STATIGN uUE E DISTRIBUTIJN OF ANGNALUUS CNS HAJE G ' ANGNALDUS MASS I UEN DENSI T”I. RULYSUN A ' Gm M m m mmu-cchU)v-cm<::u Ul H on m '1I C)!“ 3' P12 rIIJDZo—c (I ' “IDZ O-al'lCl N q IUNS:NEAN UE UESERVEU 5F PCL”IGGNSA RE READ FRCM T My OUTPUT VERSION OF TAPEEO. L SnON AN”I ERRORS IN VARIABLES K: L: OR I: I) $3 "I *1 "I 3! U) 'HID r) t: (I) "II CI 1| N GIT) cunt] [1th 2.10—- 2) f.) L1 3‘ :4: I Fl ’ STATIONS: 1.LE. L. LT. 100: READ FROM ' TE 0F GRAVITY STATICN NUMBER K: HAD FRGN TAPE 10 IN SUBRGUTINE LINE: F3.I: LAN BE NEGATI9E. HUNTER FUR LUOPS INUGLUII‘G SIHIIUNSlioLEok kIL:IL| {EEER uF RELYECNS IN MODEL: 1. LE.H.LT.100: READ FRUII P- a YIJ) = ANUNALUUS uENSITY uF RUL”IGGN J: rJ.L: READ FRGN TAFEZO. = HNuHHLuua GRAVE TY FER PULYGGN NUNS ER J. N I}: I :33'4333 hi I: 2' (I x. o—c - -I n of C] § 9 I he 27 r) ~| C 5L VINE FULHIGGNSI IILEIJILEIHI NUGLUIIWG IDES 0F FGLYGGN: . \ ‘ X CGLRDINATE BF APEX Nu NSER I uN PULYGEN NUNBER J: RELAT FIE TB THE EARTH. SET TO NEGATI"E INFINITY IF USER SETS IT TO 0. USER IS NOT NUTIF ED. F5.1. READ FROM TAFEZO. ZIJ:I) = Z-CGGRDINAT GE APEX NUMBER I UF PGLYGUN NUNSER J: T .4 : READ FRSN TAREL STAGRU = ANGNALGUSG RAUITY AT STTTATIGN K 3 SUN 5F ALL TTHE GIJ) FUR STATION K. 3 I + 1 IF I.LT.N(J) 3 1 IF I.EG.N{J). ‘ X(I) RELATIVE TO GRAVITTY STTATIDN NUMBER K. - {I * I) RELATIVE TO GRAVITY STTATTIUN NU:18ER K. 'ETAI = ANGLE FRGH HGRIZ NTAL TD APEX(I}: MEASURED CLOCKNISE: HITH ORIGIN AT STA(K). hETAZ = ANGLE FRJN HORIZONTAL TC APEXII + 1}: MEASURES CLUCKNISE: HITH GRIGIN ATT STAIK). PHI 3 SLOPE 0F TTHE SIDE OF THE PGLYGUN SETNEEN ARICES I AND I + 1: MEASURED LLGCKNISE FRDN nuRIZuNTAL. A 8 uISTANCE FROM STA(K) TO ORIGIN OF PHI: CAN BE EATIVE. SUNGRU 8 SUM OF STAGRU'S. GRVIK) 3 CALCULATED GRAVITY AT STATISN NUMBER K. v 1 E r52 rlrlr] Unfit)nnrlrlnrlrlnl‘ln (”It'll'lrlrirlrlrl r) Clrlrlrirlr’rlr‘lrlrjnnrlrlrlrlrlrlrlr'lrlr'lnnr) .(l READY 10.01.18 g— IDES ON FDLIGGN NUMBER J: 12: READ FRGW : T0 CnEL\ INPUT NHEN K: L: DR N nAS BEEN CHANGED. TAFEZO. 101 ' T:15260-20500:NS. AMNGRV * NEAN OF ALL CALCULATED GRAVITIES. SMBGGR 8 SIMPLE BOUGUER GRAVITY .- 4 U1 OBHNGR 3 THE MEAN OF THE OBSERVED GRAVITY ANOMALIES ON TAP SBGR(K) CALCULATED ANONALOUS GRAVITY - OBSERVED ANOHALOU SBGGR - OBOA(K). DECK STRUCTURE TAPEIO STA(1): FS.1. 5TA(Z): F5.1. STAIK). FS.1. STA(LI. F5.i. TAPEZO aanwaa. $5.2 L. :2. n. 12. DENSITYTI): F3.2. N(i): I2. X{1: 1)(F3.1}: 2(1: iII X(I: 2)(F5.1): 2(1: 2)( . XTI: I)(F3.1): 2(1: I)(F5.1). XII: N(1})(F5.13: 2(1: N(1))(F5.1). DENSITY(2): F5.2. N(2): 12. X(2: 1)(F5.1): 2(2: 1)(F5.1). X(Z: 2)(F5.1): 2‘2: 2}(F5.1). X(Z: I)(F5.1): 2(2: I)(F3.1I. XiZ: NIZIIIF5.1I:_ZCZ: N(2))(F5.i}. rznnnnnnnnnn nnnnnn nnnnnnnnnnnnnnnnrxnnnnnnnnrinnnnnnnnnnnr E40. HH— DD“ = GRV(K) - AfiNGRV - MEAN OF ALL L OBSERVED GRAVITIES. OBGAIKI = THE OBSERVED BOUOUER GRAVITY ANOHALY AT STATION NUMBER K. THE SIMPLE BOUGUER GRAVITY ERROR AT STATION NUMBER K. AVITY. LIST:ZOBvO-255voyks. C C C . C C DENSITY§J): F5.Z. C NiJ): 12. C X€Jy £)(FS.1): Z(J. 11(F5.1). C X(J: Z)(F3.l): ZCJ: 2)(F5.1). C . C . C . C X(J: I)(F3.i): ZiJ:I)(F5.1). C . C . C . C X(4, N{J))(FS.1}: 2(J: N(J))(F5.1}. C C . C C C . C C C . C C DENSITY(M): F5.2. C Nifi): 12. C Xéfl: 1)(F5.i}: 2(M: 1)(F5.1). C X€My Z)(FS.1): 2(M. Z){F5.1). C . C . C . C X€fip I){F5.1): 2(M: I)(F5.1). C . C . C . C X(fi: NIM3)(F5.1}: ZCM: N(fl))(F5.1). C C ?§PE4O C CBG§(1) C CBCA€2§ C . C . C . C GBGH(K) C . C . C . C BSGA(L) C C SUBPRUGRAMS C SUBRJUTINES C SUBRBUTINE LINE C READY 10.03.53 102 EC; I'II'JFIC’IK‘) I’ll" ls.) IT] 01 h n U) 70 ”C v-o U) 103 GOOD-SISOoyNS. RGGRAMHER DAVE PACDDCK DIMENSION STA(IGO)'DENSITY(100):N(100}:SBGRIIOO)p +XRELERT(IOO:100):Z{IOO.100):GRUIIOOI:GBCA(160) INTEGER ANS PI=3.I41352854 SUMGRV=0. RMS=0. INTERACTIVE INPUT 0? DESIRED OUTPUT AND DEBUG OPTION. FDRMRT(* UERSIGN?*) READ 4:ID FORMATIII) CONTINUE KRITE 6 FCRHATIi DEBUG ALCG? Y GR N. *) READ 8.15:3ua FCRHQTIAII IFIIDEBUG.NE.1HT.AND.IDEBCG.NE.1HNJGCTD 3 READi20:S)CB%NGR FORHAT(F6.Z) REAC(ZO:IO)L FORfiATIIZ) BRITE 20 FGRMAT(* L OK!) kRIT €50.10)L CALL LINE.x2-XII G=G-A&SIN(PHI3*C05(PHI)*(THETA2-PI/2+TAN{PHI)N +ALOG(COS(THETA2)*(TAN(THETAZ)-TAN(PHIJ))) OOTO 240 C END IF THEN. I 2 CONTINUE C ENO IF THEN. C IF THEN. IEIHzIzoo.Iss as CONTINUE IE THEN. IEIH2.EO.2