~ INFOCRMIARTICONULAR~ A GRAVITY SURVEY OF THE SOUTH- CENTRAL GEORGIA PIEDMONT by Robert H. Carpenter . and Preston Prather THE GEOLOGICAL SURVEY OF GEORGIA DEPARTMENT OF MINES, MINING AND GEOLOGY Jesse H. Auvil, Jr. State Geologist and Director ATLANTA 1971 For convenience in selecting our reports from your bookshelves, they will be color-keyed across the spine by subject as follows: Red Dk. Purple Maroon Lt. Green Lt. Blue Dk. Green Dk. Blue Olive Yellow Dk. Orange Brown Black Valley & Ridge mapping and structural geology Piedmont & Blue Ridge mapping and struc- tural geology Coastal Plain mapping and stratigraphy Paleontology Coastal Zone studies Geochemical and Geophysical studies Hydrology Economic geology Mining directory Environmental studies Engineering studies Bibliographies and lists of publications Petroleum and natural gas Field trip guidebooks. Colors have been selected at random, and will be augmented as new subjects are published . A GRAVITY SURVEY OF THE SOUTH -CENTRAL GEORGIA PIEDMONT by Robert H. Carpenter and Preston Prather THE GEOLOGICAL SURVEY OF GEORGIA DEPARTMENT OF MINES, MINING AND GEOLOGY Jesse H. Auvil, Jr. State Geologist and Director ATLANTA 1971 CONTENTS Abstract . . Introduction Acknowledgment. Method of Study . Results. Conclusions . References . Appendix A computer print-out. ILLUSTRATIONS Figure 1. Location Map of Area Studied . . . . . Figure 2. Bouguer Gravity Anomaly Map of Georgia Figure 3. Generalized Geologic Map of the Study Area Plate 1. Bouguer Anomaly Map of the South-Central Georgia Piedmont Page 1 1 1 1 3 3 6 following page 6 2 4 5 in pocket A GRAVITY SURVEY OF THE SOUTH-cENTRAL GEORGIA PIEDMONT by Robert H. Carpenter! and Preston Prather2 ABSTRACT A gravity survey of a 1000 square mile area (210 gravity stations ) in the south-central Georgia Piedmont defines in considerable detail a segm ent of a major gravity anomaly that extends along the Appalachians from Alabama to Vermont. The major feature is a northeast-trending gravity ridge with a steep negative northwest gradient which averages about 2 mgal/mile. Superimposed on the ridge is a pronounced positive anomaly with an amplitude of 20 mgals and a diameter of approximately 12 miles. The anomaly is interpreted to reflect the subsurf~ce distribution of diorite, gabbro, and norite intrusives. Small bodies of these rocks exposed at the surface are probably apophyses from much larger intrusive bodies at depth. INTRODUCTION This report describes a gravity survey of an area of approximately 1000 square miles in the southcen tral Georgia Piedmont. Bouguer anomaly values are reported for 210 stations in Butts, Jasper, Putnam, Jones, Bibb, and Monroe Counties (Figure 1). Previously, Carpenter and Hughes (1970) described a detailed gravity survey in southern Jasper County in the vicinity of the Gladesville Norite. Disclosure of a pronounced gravity gradient suggested that exposed mafic intrusives in the area were probably apophyses from a large mafic intrusive at depth. The present study was undertaken to obtain closure on the indicated positive anomaly and to determine t he subsurface distribution of dense 1 Dr. Carpenter is Associate Professor of Geology, University of Georgia. 2 Mr. Prather was a candidate for Masters degree, Department of Geology, University of Georgia. mafic rocks which appear to account for the anomalous positive Bouguer values in this area. ACKNOWLEDGMENTS The authors would like to express their appreciation to the Georgia Department of Mines, Mining and Geology for providing financial support for this investigation and to Mr. R. W. Johnson, Jr., of the Geologic Branch, Tennessee Valley Authority, for assistance in arranging for computer analysis of the gravity data on the TVA computer. METHOD OF STUDY A LaCoste and Romberg Model G geodetic gravity meter was utilized in measurement of gravitational acceleration. The instrument has a reading accuracy of 0.01 milligals and a drift rate normally less than 1 milligalfmonth. All measurements are relative to a base station established by the Coast and Geodetic Survey in the town square of Monticello, Georgia. The value reported for this station is 979563.00 milligals (written communication, J. A. Kozlosky). A secondary base station was established at station 5061 in eastern Monroe County. During field operation, base stations were reoccupied every 3 or 4 hours to determine the rate of instrumental and diurnal drift. Observed gravity values are corrected for drift and are estimated to be accurate to 0.03 milligals. For the computer programs, the value is rounded off to the nearest 0.1 milligal. Sites selected for measurement are separated by distances normally less than 2 miles. The sites are either at bench marks or at road intersections where elevations are presented on the topographic maps published by the U. S. Geological Survey. The maximum uncertainty in elevation is probably 4 feet at road intersections and the corresponding maximum error in Bouguer anomaly values is about .24 milligals. 1 Figure 1. Location Map of Area Studied 2 Bouguer values were calculated for each station on the Tennessee Valley Authority IBM 360/50 computer utilizing a program developed at the University of Wisconsin. The basic equation involved in the calculation is: Bouguer anomaly = Obs. Gravity - (theoretical gravity + free air correction - Bouguer correction) Observed gravity is the measured value corrected for drift and related to a station for which the absolute gravity has been determined. Theoretical gravity is the calculated gravity at sea level for any particular latitude according to the International Gravity Formula of 1930. This formula is: Theoretical gravity = 978.049 (1 + 0.0052884 sin2 w - 0.0000059 sin2 w) where w is the latitude in degrees. Both the free air correction and the Bouguer correction are elevation-dependent terms. The free air correction compensates for the vertical distance a gravity station stands above sea level. The correction is 0.09406 milligals/foot. The Bouguer correction compensates for the effect of the rock lying between the land surface and sea level. This correction requires an assumption of the density of the rock mass. The formula for the Bouguer correction is: Bouguer correction Where G 0 h 2rrG o h Gravitational Constant, density, and Elevation. From the above discussion, it is apparent that the principal facts necessary for computation of Bouguer anomaly values are: observed gravity, latitude, and elevation. This information is summarized on the computer print-out (Appendix A), as well as Bouguer anomaly values calculated for the following assumed densities: 2.20, 2.35, 2.50, 2.67, 2.75, and 2.85. Results A Bouguer anomaly map of the study area is shown in Plate 1 for an assumed density of 2.67 gm fcc. A striking feature of the map is the pronounced gravity gradient along the western edge of a northeast trending gravity high. In a distance of only 26 miles, values range from -32.0 milligals for station 5110 in the northwest to +38.2 milligals for station 5009 on the positive closure at the Jones-Jasper County boundary. This amounts to a total variation of 70.2 milligals or 2.7 milligals /mile ~ There are some relationships between features on the gravity map and major geological features shown on the Geologic Map of Georgia (1939) (Figure 2). The unit mapped as Hornblende Gneiss and described by the statement, "includes diorite gneiss, gabbro, and injection gneiss," underlies the gradient northwest of the central gravity ridge. The axis of the gravity ridge corresponds reasonably well with the eastern boundary of the hornblende gneiss unit in the eastern portion of the study area. However, the hornblende gneiss unit is shown to terminate east of Forsyth even though the gravity ridge extends southwest of the terminus. The de- crease in gradient between the 0 and + 20 milligal contours in northeastern Monroe County possibly reflects the southern termination of the hornblende gneiss as shown on the Geologic Map of Georgia. Along the crest of the gravity ridge in central Jones County, the gravity surface is relatively flat. Two weak gravity lows are present on the ridge southwest of Gray. These features appear to be related to the outcrop of a granitic intrusive shown on the Geologic Map of Georgia (1939 ). Known norite occurrences lie in a rather restricted zone which parallels the isogal contours. The relationship is probably not fortuitous as the isogal contours bend away from the northeast regional strike. The Gladesville Norite, mapped by Matthews (1967) in southwestern Jasper County, occurs between the +8 and +16 milligal contours. Three other norites have been mapped by Prather (M. S. Thesis, Univ. of Georgia, in preparation) in northeastern Monroe County. These lie between the +4 and +16 milligal contours. CONCLUSIONS The gravity ridge with the steep western gradient is probably a part of a long, more or less continuous, gravity anomaly that extends from Vermont to Alabama (Figure 3). The gravity pattern determined in the present study is virtually identical to 3 BOUGUER GRAVITY ANOMALY MAP OF GEORGIA Figure 2. Contour interval 10 milligals Reduction density 2.67 g/cm3 0 20 40 miles D After: Bouguer Gravity Anomaly Map of the United States, Amer. Geophy. Union and USGS, 1964. 4 Figure 3 . GENERALIZED GEOLOGIC MAP OF THE STUDY AR EA agn CJ \1 Area of Study .,'\ ' cgn LEGEND I.1 cgn biotite gneiss and schist, includes in jection gneiss ~ ems muscovite schist bd ggn granite gneiss [ ! ] hgn hornblende gneiss, includes diorite gneiss gabbro, and injection gneiss D. Cgr biotite and muscovite granite OJ agn augen gneiss IS1 diabase dike E;J CPs Coastal Plain sediments. 121 fault Modified after: Geologic Map of Georgia. Georgia Department of Mines, Mining and Geology, 1939 5 that determined by Mann (1962) and Best and others (1970) in portions of the Piedmont of North Carolina. Based on a model analysis of the gradient near Lexington, North Carolina, Best and others (1970) determined that the best model was represented by a mass 50,000 feet thick, with a density contrast of 0.28 ,gm {cc. The top of the mass is estimated to be within 2000 feet of the surface. Preliminary model analysis of the gravity data in the south-central Piedmont of Georgia suggests a similar subsurface distribution of anomalously dense rocks. Basic intrusives of the diorite-gabbro-norite association commonly occur along the Piedmont gravity high in the eastern United States. However, even the largest of these intrusives is too small to account for the magnitude of the observed gravity anomaly. The most probable explanation is that the anomaly reflects a more or less continuous mafic intrusive originating in the mantle or lower crust and extending upward to within a few thousand feet of the present erosional surface. Small mafic intrusives occurring along the _gravity high probably represent apophyses from the parent intrusive at depth. REFERENCES American Geophysical Union and the U. S. Geological Survey, Bouguer gravity anomaly map of the United States, 1964. Best, David M., Wilburt H . Geddes, Tse-Chuang Hu, Joel S. Watkins, and David H . Walz, 1970, Gravity investigation of the contact between the Carolina Slate Belt and Charlotte Belt in central North Carolina: Paper presented at Southeastern Section Meeting of the Geological Society of America at Lexington, Kentucky. Carpenter, Robert H., and Thomas C. Hughes, 1970, A geochemical and geophysical survey of the Gladesville Norite, Jasper County, Georgia: Ga. Dept. of Mines, Mining and Geology, Inf. Circ. 37, 7 p. Georgia Geological Survey, 1939, Geologic Map of Georgia: Ga. Dept. of Mines, Mining and Geology Mann, Virgil 1., 1962, Bouguer gravity map of North Carolina: Southeastern Geology, v. 3, no. 4, p. 207-220. Matthews, Vincent, III, 1967, Geology and petrology of the pegmatite district in southwestern Jasper County, Georgia: Unpublished M. S. thesis, Univ. of Georgia, 68 p. 6 APPENDIX A -- ~AVITY PROGRA)j. __jjQ_,_ l . A I _ _.Ul:H.G E!..f.'L..Q~_D_ _THE_OB__ __ _ L_O~.._ _ _ _ LA.I___ _ FA_ __ ___92 .2 0 B2 . 35 B2 . 50 82.67 82 .75 82.85 T500l 33 14.10 83 37.40 621 979.5839 979.5978 - 8~.6233333 33.235 0~00 44.5 2 7.~ 25. 8 24 .7 L3 . 3 22.7 l1.Y .I59_0?~3 _1~~. 1!9_1!~ 36. IQ_____23b ~1'~.!.58?.?.._2I~-?__98_8__-83!~_1_!_6~67 - 2.3~ 24~_6_o_~ _ ~3_. 5 L5 .1 l4. 4 23.2 21 . 9 2!_~ ~-~~ T 5 003 3 ,~--- 3- -1 4w-.7-0 -8--3 3--5 . 9-0- -b-30- -97-9. 5-83 8- -9 7-9. 5-9-8 7 -83.5983333 ------ - ~~ - ____ 33.2450000 -_.. _.__, _ 44.4 T'iQ0_4__ 3~.1~--~_83 34.40 556 9J''!~_5916 ~19~9b~__:J! ~?733333 33. 22Q..000_9_ __ '!7 3 26 .7 :n . 7 25 .. 5 30 .o 24. 3 29.6 2 -2.9 -- -2--2-.3-- 28 . 4 27.8 .ll. !l 27 .1 __'[5QQ_5_ 33 !~'!. -~__9. -~3 33.80 634 979._ ?85~ 979~98!_-8~._?.633333 33.23p3~ 33 47.3 L9.5 28. 3 27.1 25 .7 2~hl 24.3 __ - - - - - - - --- ----- - - -- -- -. --- T5006 - 3 3........1 4 .6 ., 0 83 33.30 ---~ --~ - -6- ...15 979.5854 919.5985 - 83.5550000 -- ~ 33.2433-33-3- ...4. 4-.-7- - - 27-.5 1~.001 33 14. 70 83 30.50 585 979.5865 -9 79.5987 -83.5083333 33.2450000 42.9 26.4 ___L5008 33 13.40 83 30.10 621 979.5861 9H.5969 -83.5016667 33.223.H33 47.6 J .J . 2 26.3- --2-5.-1--.. 25 . 3 24 . 2 29 . 0 27. e 23.8 22 . 9 -- - - - - 2~.1 22.3 22.3 21.b ~~-- 25.8 l5. 0 T50Q.~..l3 J0.~7_Q _~3 35.70 !_5010_ 33 !1-2.0_ 8~_37.40 5J.LJ.79 : 5._9_7..!___9_7_~-~s9E.z ~.?~ 5?.?..200.9. ~3. 17 ~~3~L_5.!.! 1 . 62.~ .~7~5.ill __?_1_~.59~_--:-.3_._6~3~~~3- 33.1866667 52 .8 41.7 35. 3 4 0 .6 34.1 39.5 32.9 3 8 .3 31.5 .H . 7 3 . C 35 .1 34 . 0 33. 5 3l .6 _T5.0~ _3_J__ _ _7~!>0_ _jl3 39 ~ ~9. _ 6l4_~79._~.3~ _ '?J9~-~d89 -;:83 . 6 L3 3333 3J .1 2666o 7 ::il . 8 J5 . 5 3 " 3 3-'>. L .:>1. 1?. 31.l 30 .4 - - GIUWU.Y PROGUa ----- - -- - ------------- ~ LAJ LONG ELEV OBSERVED THEOR_ LQ~ LAT ~A rl2 .2 0 l:l 2.3S B2 .50 'd 2.o7 B2.75 62.1!!> JSQjQ 33 7.40 83 35.60 JSOJ1 33 6. 10 83 37.00 626 979.5800 979.5886 -83_.5933333 33.1233333 50.3 630 979.5725 979.5868 -83.6166667 33.1016667 44.9 J2.7 27.2 1l. -'-- 30.3 2d.9 2o. 0 ____3 4. 8____ 23 . 5 28.3 22.8 27.; 22.0 TS~~ 33 5.10 83 35.60 T5013 33 3.70 83 36.90 601 979.5740 979~58~5 -83.5933333 33 .0850000 45.1 621 979.5702 979.5835 -83.6150000 .H.0616667 45.1 23 . 2 27.6 27.0 26 .4 25.9 24.6 25!3_ _ _23.9 24.0 23.2 _ E.~_.i __ a.._; _ T50i4 33 1.50 83 34.40 545 979.5694 979.5805 -83.5733333 33.0250000 40.1 24.8 23.8 22 .8 21. 6 21.0 L0.3 T50~5 33 1.00 83 36.20 477 979.5703 979.5798 -83.6033333 33.0166667 35.3 21.9 21.0 20 .1 19 .1 18. b 1o.o T50i6 33 2.50 83 35.50 603 979.5676 979.5819 -83 .5916667 33.0416667 42.4 25.5 24.3 23.2 21. 9 21.3 20.5 T5.0i7 33 18.80 83 45.60 T5M8 33 18.70 83 48.40 TSOJ9 33 18.50 83 50.60 T5-MO 33 ;zo. so 83 52.20 693 979.5534 979.6043 -83.760000.0 33.3133333 14.3 656 979.5507 979~o604.2 -83.6066667 33.3116667 8.2 533 979.5525 979.6039 -83.8433333 33.3083333 -1.3 571 979.~460 979.6067 -83.8700VOO 33.3416667 -7. 0 -5.2 -10.2 -16.2 - 23. 0 -6.; -11.!> -17.3 -24.1 -7. 8 -12.7 -9. 3 ----10-.1 -14.1 -14. ti -1-8.-3------- 1 Y- .4 -2.5.2 -26.4 -2o.o -27.U -J.0. 9 -1:5.o -20.7 -27.7 T5~~1 33 17.60 83 52.40 647 979.5421 979.60.27 -83.8733333 33.2933333 0.5 -17.7 -18.9 -20.1 -21.5 -22.2 -23. 0 __I5G~2~. 80 83 51.80 565 979. 54_~~_2 79. ~002___:-83._ 8633333 ~3 _~!_~o. 7_g__~_~5.3_o_ _~l_!_ 979. 55QL~?.~6Q.~9-=_~} ?55()_goo 33-.-2-6-3--3-33- 3 ---4.0 33.3450000 11.7 T~ 33 22.10 63 45.30 716 979.5494 979.6089 -83.7550000 33.3683333 7. 9 -1.2.4 -d.7 -12.2 -13.5 -14. <> -15. 9 -16 .!> -17. 2 -10.1 - -----1-1--.5- - ---13-.1- - --1-3.-8 -- -1-4-.--7. -13.o -15. 0 -16.5 -17. 2 -1 d.~ __!_504'?-..~~~2.30 83 48.70 630 979.5484 979.6091 -~2._-~_!~~~7_33~...:!_.!__6667_--= !~-- _ _:.~ -- . :-l~_-4 ___ _:-~-- -~?__2_~9 _ _!~~~. ltll _~j..Q_9___!B 50._]_Q__ 582~:J.9.5~62 ~7~.60__!~=8].8 450000 33.3500000 -6. 1 -22. !> -2 3 .7 -24. ~ - 26 . ;_ -23.o -26.7 -24.4 -2"1.4 T5046 33 20.70 83 48.70 480 979.558B 979.6069 -8~~8116667 33 .3450000 - 3.0 -16. 5 -17.4 -18.j -U.3 -19.1! -2G.4 ____U0~7 33 1_~. 70 83 -~9.40_ __?.~3 979_~ 5~~ - ~7_.C> T5061 ~3 1.40 83 44.7G 363 97~.5891 979 .5804 -83.74~0000 33.0233333 33.9 . - J5\.Z,__33 ___g.J! ~0 -~;l~h!Q___ 53_! .2J9. ~b8~- --~n_9 . 5 7..21> -S_h 79~666 I 33 .Ql3~H? ___ 2'?..d. _J5063 _3~ _.9. 3Q 8~- ~I-9Q ;3~ - 9~9. 5?48 _9?_9.5789 -83.6316667 33. oos_oooo__3_1.1 3 .1 - -- -2-3.~ --2-2--.3 24.4 23 ~_! _ ___f_Z..!.L__ 24 . 8 2~ . .-&3~-~.3~666 1 33. osooo oo _42 .L .. -l:.!?..!.-_5_ __25. 4 0.~~ - 33_ __}~ 10 83 40.5Q_ _T5 2Q~ __33 2. 90 83 41.50 5Q6 ~79.5 724 . 979.583.!) - 83.6750000 33.0o1oC>67 41.9 451 ?l92J84 979.282~ -d3.6916667 33.048333~ 3~.4 26.0--*- 2--4-. ~-25.7 24.9 22 . 7 24.3 Z3 . b 24.J Ll.4 23 .l a .o a .c 2o.a 20.1 .1~ ~ s_ ___L 1__ ~ __ a. J--- -- 2--1--.-3- - 22.b 2L.O - -~1-l PROGR.UI ~ ....LAT._ LQNG _EllV....Q~Ii!.l-V.~D __ It!.E.QR J,..ONJ> LAr f-A - - .8.?. ~ ~jg-~3.2_,_ _ti.2.~5.:) o_f_:_6J . _B<: . 7':> az.s':> T5i05_ 33_ _~.._90 83 .42.{1Q I.~ 20_1>_ ~3 - 5._30 83 - 44.._ 50 437 _ 979.~J7.!L'U'!.5624 -83.713,t333 ~.3!04iJ33~ 36 . ()___ 528 _ 97~~?6B _ 9?9.5857 -d3.J~lo667 3}.08o333j ~o.7 2}!.7 ).~ 2.! . 9 --- ~? - 0 -- ~~ . -~!.!..?. _ 2} - J_ . - - 22.7 - -- 20 . o <:0 .1 ---~ - --- 22.L 21 . 5 n2Q7 33 3. c;o 83 43.70 479 979.5776 ~79.5838 -83.7 .283333 B.!..oo5 QY.9.SL. . a~!ll 25. 4 4. 5 23 . 6 - _p ? -. -- 2 ~ 0 .21 4 ~-T22Q..8 33 T52Q9 33 T5210 33 5. U> 6.90 6.70 83 40.l.Q____?85 9.1_~.5739_ 97_~..212 33 7. 20 83 lt4.70 T5067 32 58.80 83 36.50 427 979.5831 979.5d64 -83. 74500QQ_ _~~ !_200Q_q_9 34 .9 498 979.5687 979.5768 -83.6083 333 32~98900 0___~~ .7 22.9 - - -2- -.1- - - -2 1-. -3 24 .1 23 . 8 22.8 20 .4 21 .8 19.'1 2 1.3 19.4 20 . o T5069 32 56.60 83 36.40 490 979.5646 979.5738 -83.6066667 &9433333_ 36 . 9 23 .J. ___I2!11.Q_32 . ~4. so 83 36.50 - ~.Y.L 979.5643 ~ 79.!.? .?.1_3 _-8~_.60833_3L 32 .?13~~~ P!.~..1 td.l3 TS07l 32 53.it0 83 36.10 496 979.5546 9 79.~~94 -=.!!_~ .6012_~~--g-._!!~000 00 3 1: 8 17.9 T50.7L~2 52.60 83 34.70 T5073 _3_U4._00 83 31.50 TS014 32 55.80 83 30.10 408 .~J9.5~7J ~79_~5~8_3 -_~3-~_ 78~-n~ 658 979._?_~3~~ ? ~?}Q~ - -8~.5250000 530 9?9.5584 979.57?1-=~3 - ?0 16667 -32.87. .6666. 7 - 2 7-. .8- - - 16.3 32- . 900000 --~---- 0 - --3-~.-3----- - l ~ . B 32.9300000 35.5 L0 .7 T5075 32 51t.20 83 33~90 509 979.5570 9 79.S705 -8~5650000 _ 32 . 9033333 3 4.4 20. 1 ____IS0~6.3. L55 .9.0 __ 83_ _l3._IQ__ -~ l.Q__'l79!..~65~ 97_9. '2.7 28 _- ~~~l?l_6_66.L .2.? . 93166_6 L ..l 1_. _L 1 :J . o J59]7 32 57.20 83 32.60 555 979.5__584 979.5746 -,!t-h~_3_3333 32.9533333 36 . o 20. 4 --~078 3_l~~-~ 8D __ ~J ._3_1~80 ____b_~n9!. 56 05 . 279.57~8..~~~ ~466~-~.L-?f..~!!OOO_QQ_ _40.7 23~7. ___I~l..9~9...,J!!l._!!_3_37.~Q. 443 979 ~57_2_1 _ 97!t_~_578 ~ -83.~~33333 _..l]. .9966o6L 36 .2 ~3 .1 2.2 . 2 18. 0 Ll.3 17.3 17.0 lo. O 15..-5 - - -14-. 7 15. 5 14.3 1'1.1 18. 6 19. 1 1 l:l. 1 18 . 8 1'1. 3 22 . S 18 . o J. o .3 2 1.4 22 . 9 22. 0 20.2 1o.4 14.9 13.9 12. d 17.5 17.0 17.2 11.1 20 . 0 21 .1 19.7 16. 0 14.4 13 ... 12 .2 17. 0 16 .5 16.7 16.5 19. 4 20.6 19.1 1:) . 5 D.8 12. 9 11.3 16.3 1j.9 16.2 1~. 8 l d.6 20.1 _. ..T~.QSQ.JL.~-~-~-~9.-..L~~~ - .?J.? __9]~.!..59..r?.. 97'!.51.ll_;-.~~5.?QPOOO _3_2!99.]1.3..-L....l.2!9_ - .f.'! 7 2j . 7 22. 1 -~ 5 - - 21 0 - 20 . 3 .T5.081 32_ !>9.-5.0 __63_~0. 2.0. 5.11 'H9-~656 9 79~5778_-~_2 .503.} ~? 32 .991 6667 ~5. 9. 'U08.Z .,32 58.10 83 34.99_ 492 979.5675 979~5759 - !H .581666 7 32.9683333 J7 . 9 T5011.....JL~9.70_,.. . 83 .ol9.-~9 __554 2.!.9.~5653 979-!fl:fol. -8~6566_6 6 ~ - 32.995 0000 39 .4 2 ~.!..L -~Q ~--1 '!! 6 - -1-&. ::> - - -1 8-. 0 17.3 24 .1 2.> .2- 2- -2-. 2 21.2 20 .7 20 . 0 2 ~- b - _?_f.~ .?... _ _,__2_1 . 7 _ -~~--. 19~ _ ..!.~~-L--~- r5o&4 32_~8.90 83 39.ao 480 979.5637 979.5770 -83.6633333 32.981666 7 3 1. 9 1~.4 17 . ::> 16 .0 15 . 5 15.1 1 ~ .4 T5085 32 58.10 83 38.5Q 544 979.5648 979.5759 -83.6416667 32 .9o83333 40. 1 24. , 23 . o n.o 21 . 6 2l.:J 20 . 3 T5086 32 52.90 8~ . 37.70 489 9!9.5533 . 979.5687 -8~.62&3333 32.&8166o7 3C . u l?oO 1~.9 15. 0 l3 . 9 13 .~ lL . b T5087 32 54.30 83 39.60 T5088 32 54.00 83 38.10 311 9~9.56d3 919.5706 -83.6600000 32 .90 50000 26.9 503 979.5555 979.~702 -83.6350000 j2..90JGOOL JZ.6 13 . 2 1~.:> 17.6 11. s 17. I) 16. 5 16.3 l S.4 16.0 16.20 616 979.5400 979.6082 -83.8983333 33.360000C -1 0 . 2 688 979.5377 979.6076 -83.9366o67 }3.3533333 -5 . 2 - L T.~ - 2.4.5 -1.6 .--7------2-9.-9- - - --31-. 2---3-1. ~- ---32--. . 6- -- -25.8 - 2.7.2 - LB .o - 29 .4 - 30.2 T5 113 33 22.20 83 54.90 T5114 33 Z1.8Cl 83 53,00 541 979.5480 97'!.609_9 _..::_!13.9 15 0900 33.370000C -_l_Q . ~ 5b6 979.5449 979.6082 -83.iHB3333 33!3600()_00_ - d_:-2 -l 5 . 3 - 2/~.o :2o. 3 - 2.5 . 7 - 2 7_:-4_ _ _:Ld_. _5___ _:-_2_2!!_ _ - L~..!.~-- -- __ - 26_~ - 28_.!.!:.___ _ ::-~~-.. - ::-~~~!> 15115 33 15.&0 83 56.10 613 979.5399 979.6002 -83.9350000 33 .263Jj33 - 2.o -l 9.1j - 21 . 0 -22 .2. - 23.5 - 24 . 1 - 2-.. 9 ~_ll_li~ 83.JA~115 _ 979.5333 91_9.~02L.=_8_3~3;i_OO QQ__:n... 2_8_t.(,6~ --- 1-6 TS117 -~~ -~~.! ~Q__ ~ 54~30 631 979.540S 979~6038 -83.905~00 0 _33 . 3066667 -2.1 .6 - 2. l. o -23 . 0 -2 . 8 --- 24.4- - - 25 . 9 - 26 . 6 --2-7.-6 - --24-.-0----- - -l5-.-4- ------2-.6.- 1-- - 26 . 9 '"RA1lV PKOGU.. _ ___4t10__W lONG ~i,..~'(. O~!;~V~.!>-... .-T!:lsQ!L . __ _ !:._O~G . - . L_~J_ - . _FA .. ;g_._~- ti2~ ~- _az . 5Q. -- - -.~~7 - B2. 75 .?_? ~~ _. _. .UU8 33 l8,t_c;Ml_ ~ _.56.5.0 _ 608__9_?9.2_;.1.0._ 97_9.!>_04_5__~83 .~41.66 6L _n_._~~5_00_0() ..::_- 6. ~- __ :-2 3..!. ~_ -24..!.? _ ---~ ~~----=n-!...0. ____::_2]_. 6 -2d . 4 a . -.---- -------- - -- - - . _T5.ll.~Lll..20 .90 -~3 _H..._~.Q__ _7 ~3_979."-~J't5_<)_19. 6.0o Q_:-:-8J. 9~~-QOQQ. J.~...! ~-l~_33_3~- __:_e..! 5_ _ -23 !._~2 ~ ._2 -l6 .3 - - . ---2- d. 1 - 2 B. ~ d-- -- 2.~ . 8 .. ..... r.~uo 33 19. .10_8~- 52.90 638 979.5412__97~~~02~ ...::83. 8 .8_1_666_7_ __33.~-~2~~ 3 32._ .. :-..:+...!l.. - - --- - --- - - 22...3 - 23.5 - -- ~2... 4 . 7 .-..2..6 ..1. - 26 .7 -- - 27 . o T5_l31 33 1_4. :JQ_ ~~- 43 ~3Q_ . _63J_'!.l9.~_ 5.J.li.. 9?9.598 7__-:_83. 7 216667 .. 3 3. 24500 Q.Q 32 - '! --~~ - ___!}. '!__ - -~2. 2 10 .!:1 10 . 2 9.3 ._ I~..Ji2 ..3J_ 1_4.10_____~_! 40.~Q__ -~_5_2_~?~ .?..15 ___ .. -~ .! --- ~ 6. 0 4 . tl 4 .J ~.b T5ll 33 T512 33 7.10 9.10 83 49._3_Q__. lt4_D 97'1~ 5791__9_]~5? =.~ 3. 82166 ~7 33!1!_3_333_3 .. _23 . 3 __ ___ _!?_~ _ _ .!.!!~ 1 _ 9. 2 8 .3 83 50.10 ~16 979.5645 979.5910 ~}.:835_0090 ..2~~ 15! ~_6_~_7. ..!?..:.I..... ___ l. u ____2_:_._ _ - o . o -- -=~ .:5 ,.... 7. 6 -1. 9 7. 3 - l.~ ~143 33 _lli44 33 8.30 8 .51: 83 52.50 ?~. 'U~_J__?l_8__9]_9....!_')899_.= 83 . 8 7 50.QOO 83 53_~~-0_ _~99_ 979. 54 6 ~ _979~5?9 1 __-.!!_3 .~9!!3333 ~~. l3_8;B;3L. .!~- 3 ._ - _:- )-~ !l_ _ __::_! . 8_... __- 2 . ~--- _---- -4_. _(]_ -- 33.1 41 &&6 7 L3 .J - ~ - !3~ - - 5 . 1.) - 6 .1 -7.4 -4. ~ - <> . 'J - :> . <: - cl . d GIU.ltl JY PROGR.Ut MD LAT LONG cLtV OBSERVED THE OR LON G LAT FA d L. 20 tl2.3 5 BZ .50 82.6 7 _j)_2 .72.__E . 8 ~ 15145 33 10. 8.Q_ 83 50.70 1.2_!__~- 33 _ 11~.J.Q.J.L21! 1o 15147 33 13.40 83 50.50 4~4 979.5585 979.5933 - 83 . _845000_0 _ .H .I,_dJOuOO_ 1 0 .7 590 979.5478 979.5937 ::~3_._8B5oooo 3J .1 85GOOu 9 .o 536 979.5561 97945'j69 -83~84t~_66..l..__3~!2233333 9 . -'> ---2-.-9-- - -- 3.-3- ---- -4.7 - 5.a -o.3 - o.9 - .. ---1- -.-0- - ---H--.-1---- -~. ..2 --~- - ---1 C . 5- - - - - -. 1 1 . 1 -ll. 9 - 5 . 1t -o.4 -7.~- - - - -~- - 9 .~ - ~.~- -- -~I5J~8__ 3l__!~!ito 83 51.40 __ ~J '!~ 3_~__h_~o 83 46.00 ~5150 33 1.80 83 47.50 15151 33 1.70 83 49.90 528 979.5549 979.5983 -83.85661>67 33.2400000 6 .3 - ~.5 471 979.5718 S79. 580 4 ---H-3 .7--o--6- 666 7 -33 . 0 23 33>-3 35 .7 ,z . ., __ ---- -- 4 9o 979.~684 9 79.!>80~ _ :_~~ _._791_?6?:~- -3_J.! OJOOOO<.. 34 .1 ' ,_ 20 . 2 531 979.5610 979.5ti08 - 83 . &3 1 666 7 33 . 028333~ 30 . 2 15 . 2 - 'i .5 21 . 6 1 9 .~ 14. 2 -1 0.5 20.7 1ti.3 13.2 - 1--1- . 7 ~ -- -1 2- .2 --- --12-. 9- -- 1 1. 0 15153,. H 3. 30 83 53.60 T_5 153j, 33 .. __4. p.Q_ ~-51. 90 625 979.54 88 9 79.5830-- -o-3.-89-3-3-3-3.3 33 . 05~000l 24 .6 7. 1 5. 9 4.7 3.3 L.l s., 529 979. 5566 979.5840 -83.8650000 33 . 0 66 oo67 22 .4- - --7.-6 - - -6-. 5-- - - - - - - --4-.4- - -- -3-.-8 - J.5154 33__ s. c;o 83 52-.~-0- -4-3 9--9 7-9-.-5--609 979.5866 - 83 . 8 76666 7 33. 09d3333 1~ . 6 3. 3 . . 5 1.6 0 .7 0 .2 ____!2!.?2___33___2_. 30 15156 33 6. ac.. 83 55.80 ----- - - - -- -- 615 979.54 59 979.5857 - 83 ..9300000 __ J3 . 08d333J ___ ._ ~---- - -- Ul. O - --~ '} . 7 83 56.60- --- 5-34 -9-7"9 .--5 492 979.5878 -b3.943 3333 33 .1l3333j u . o - 3.4 - (' .4 -4.4 -1. 6 - 5.4 - 2 .~ - 6.6 -3.o -7.1 T5167 33 8 . 2() 83 58.80 578 979.5423 979 .58 97 -d3.980COOO 33 . 136b66 7 6.9 -~.3 -1 0 .4 -11.5 -12.7 -13.3 u.j !.9 3.2 - 0 .3 - 4.4 -7.d -14 .1 .____!2_!~8-.33 8. 10 83 56.60 15168 ~33 _ 9. 6.9. .. _!!~- -~7_. 40 - ------ - -- - - - - - - - 582 979.-54-5-5- -9 7-9 -.5-o9.6.- 8 -3 .943 -. 33j . 3 -33 .13-50-0G-C 10.7 - 5 .1 -6. 8 -7.9 642 ~7~~~~~ _ 979.5917 -83.9566667 33 .160 000C o.9 -11.1 -12. 3 -13. 5 -9.2 -14.9 -9.J -15.6 -10. 5 -1u.4 T5159 33 12.10 83 55.30 T:51_~.Q...l.L!.~-~O 83 54.70 T5161 33 l2.6C 83 52.80 517 979.5454 9 79.5951 -83.9216667 ~-~?_979.!..~431 .1.7._9 .?_9 L6 - 83 . 9 11666 7 4H5 979.5 54 5 979.5958 -83.o800000 33.2016667 4.6 -11. [) -1 2 .7 33 . 17l-o--oo 7- -10-. 2--- -------7-.-6 --- u-.-a 33.21000 Gl 4.3 -~. 3 -1 0 . 2 T5162 33 14.80 83 5h60 5 ?6 ~]9. 546~ '1 79.5988 -83.8933333 .B .~46 oo6 7 1. 8 -14.4 - - - - ___ - T5163 33 ~.3~ -~9....J:!~__5.2_~}0 _.. S_o;S _ _o ~ 7___~+ . 2 T5~67 3~ 5.60 83 58.70 65a 979.541 2 97 9 .5 8oL -83.97833 33 3 3.0933333 16.9 T5168 33 4.30 83 57.30 679 979.5417 9 79.5844 -83.9550000 33 . 0 71o6o7 2 l.L -n .o -U. 5 -1. 5 2. 1 ----------- - --- - - -L2... H -~- -.2-3 -.9 . - 2 5.~ - --~----~ -25.9 -26.1 -14.7 _,. 8 c. . 8 -15.9 -4. ::> - (;.:) -17.3 -5.5 -1.9 -17.9 -1o.7 -6.1 -- - ---7.-0--z.o - 3.:) ___.J~I4.2...J3 ...7- .?.Q__!l_3 45~Q.Q.._ 572~79.~-7 ~_2 . '?79_.sa..a 4 -:.~~-..760 ogoo 33.1 ZO.t!OQ.I,J .}.!h.1 2_2:6 21.! 5 ... ZQ:!!__ _ ..._ !~l___ . . 1.~.!2... .,_!!_!o... _ _J!U10 33 1._~ _83 sa.aQ... _ 6_7]_ ..'H9.5~08 _9 79_.58:34 -83.9b OCOOO 33 . 060Q_QO (,i _2J.!.l _____ 4.!1 --- T~li.l 33 0~90 83 5 !!.40 6 26 97~.._5_4 5 7 ~1~!5 79_? _.=~3 .97 33 3 33 33 . 0 1 500GO L4.9 7. 3 (' . b ----0-.-5- - 6 .1 4.'1 - 2 .o 3 .6 - 2.7 L.t; __::--3. ? - - 2 .1 - ~~T-P~a~a~~~R~A~M~--------------------- .0 LAT LONG ELEV OBSERVED THEOR LONG - - - - -- - -- ------- --- - ------- LAT FA az . 2o 8 2.3~ B2.50 ~67 15112 33 1.5Q 83 57.10 645 979.5454 979.~8Q2_=~3.951o667 3?.0250900 25 . 5 7.4 6.2 5. 0 3.6- 15113 33 o.9o e3 54.80 658 979.5485 979.5797 -83.9133333 33.o1soooc Jo. r 12. 2 u.o 9.7 !l.3 TS174 33 1.10 83 52.80 613 979.5522 979.S808 -83.8800000 33.0283333 29.1 11 .J 10 .7 9.5 8.2 TS175 33 ' 0.7~ 83 49.40 477 979.5656 979.5794 -83.8233333 33.0116667 31. 0 17.7 1o.7 15.d 14.8 82. 7S -~~.:..13_?.... .. 2.9-----~.-1 -- 7. 6 6 . 8 7.6 o . ti 14.3 13.7 T5116 32 59.40 83 46.50 15177 32 59. 7.() 83 48.80 151'18 32 59.40 83 50.70 T5U9 32 58.30 83 49.60 ~5180 32 56.60 83 48.80 T518~2 58.40 83 52.40 _I.iJjL;!~ 59.77 35 . d 570 979.5619 979.5738 -83.8133333 32.9433333 41.7 589 979.557& 979.5763 -83.8733333 32.973333j 36 . 9 o42 979.5522 979.5781-83.8950000 32.9950000 34.5 580 979.5564 979.5754 -83.9283333 32.~?33333 35:5 24.6 ;u. z 21.7 22..9 25.7 2J .4 1 :>.5 19.2 2 3 .5 20 .3 2C.6 22 . 0 24.6 1 ':1 .3 15.3 i !l .1 22.4 19. 't 19.5 2 1. 2 23.5 18.1 14. i 17.0 21. 2 18 . 3 18.3 20 . 2 22.3 16.9 12 .7 15.8 20. 6 l7 .a 17.7 19.7 21.7 16.3 12. 0 15.2 19.8 17.2 16.9 1-1.1 L-l-. O- 15.5 ll.L 14-.4 __ __TU.8. ~32_ -~~ ~Q____ll_-~~_,_g_Q_ 554 979.5556 ~-79. 5775_:-!)j. 9}33 333 _g_._2d833_~3 __ 30.2 14.7 ---- 1 3._6 12.5 11.3 10 . 8 J. U o1 _n_l~lt..33___9~~0 83 56.40 607 979.~_Q~_J79 .. S5Q_S _=._83.94000QO g.00333D__ ._ll_lft5 32 55.20 83 48.. 80 587 9]9.j575 979.5719 ~~3~]11~}43 32. 92000.Q.Y 40. B 24 .4 2J . 2 -- - - - - -- __..]5186 32 54_._!.9~ 49.!!.1L_ 537_ ~J9.557~_9_l~.5704_-:_8_3.~2-~3~?3_ 32 ~90l_o~o1__ 3"1.6 22 . 6 --~- 21. 5 .. J~ 187 _32. 54 .~0 83 51~~.9 ____5_07_ 9?9.569_7 'i_1.!!_.!2_1__0'? -83.8_~QOOOO 32.9050000 37.7 -- _?__~ ~,_?__ 2<:.~ 22. 1 20.5 21.6 B! - 20 . 8 19.3 LO . ~ 2 0 . 2 - - 1-9-.5 - 18.8 1tl .1 19.'-J l'-1.3 _ .J~J-!!1!....}2_55. 'iO .. 83 5_?_.Q_Q__ _2JP-....2..~~.!..?2~7'k2_I_28 __-8_3d!~~6~~_7 32. 93lof>_4_0.~-- 23 . 8 22.7 21.6 20 .3 19 . I i'J. O . _ T_Sl_89 ~-L~5~~- -~~- 5.:.90 _15l90 32 _54. 60 83_ 53.80 521 _~?9. 5616_ 9.l'l. '!..'n?t. -83.a~_tb{>{>I __3 ~~f.!!..666.J. . 3!!~~ -----fl ? __ ~~-_o_ -- 21. o -- 20.4 19.'-J 5)._2 _'!_79~_261_3_9?_9 5711 _ .=~3._ 896~~!>J~2. 910000C 38.4 24. 0 -~ : 0_____~2.1 _ ___1_!._!...0 ____10 .4 19.<: 19 . b T5!91 _32 ~~ ~~---8,:3_5_~-~ 10_... .?.1!4. _ 97'h..5.272 97..2.:..?..:!.?1..-_s~ .2.283_3_31__~_._93ooooc 39 .4_ ___ l> . o 21.9 1519~_ J2 __55. _~Q___ _ 83 _?6_,.40 . _ 540_~..J'!~5591__~J~.5.H9 _-:.f!~_.'l_40QOOQ__ ~-~_._92_0_QQ_O_y__~d_dL.. -~- 22._2____ .... ~.1~ L - 29. s_ _ _.~-9.?____ _ .!..~ - ~ . l--o-. <: - ~_0..!.8 19.-6-- ---1-9.-1----- 1-b.4 T5193 32 _56.20_ 83 58.50 628 9}_'l_~_ ?.?~-9~9.573_3_ -8_?!.9750000 }?_.936o667_ 30 .4 <:.J.a 1 9 . 6 -- -1-&- .4- .. _ ____ _ T5194 . 32 57.30 83 5_7._49 _. 635 ~J9.!l_?2~ 979.5?~~ _-oh9566~o7 _ _3~?...!.._9;55000_0__ 37__. _ __1 ~ 2 ~~? 1_2. 5 T5195 32 57.40 83 45.20 - 506 979!.~6~..! . '_H9.5_?_49 -83._7_?33~33 3 2 . 9 5 66 ~- 6 6-7- 38. d 24.o 23. 6 22.7 17. 0 H . l Llo6 16 .4 lS.':> 21 . 0 15 . 6 1-4-.7- 20 .4 T5196 32 55.20 83 42.60 326 979.5732 979.5719 -83.710o ooo 32.92oooo0 J~. o 2.2.d 22.2 Zl.t> 20.9 --- 2-0-.5----2-0--.1- 15197 32 54.40 83 ~5.50 528 9~~-55~1 9?9-~7.08 ::-:_8~.7583_333_ ~~- -99bt>~gl. 38. 0_., _ _23~L___ ~2~__1 _ ___2.!_~1 . 2.0...~ 0___ ___ _!_9~~ - - -. _1d.b__ T5198 32 53.70 83 45.70 531 979.557! 979.569o -H3.7616667 32.895000C 37.2 2~.3 21.3 20 .1 19 .1 1&.o 17 .>- T5199 32 52.20 83 46.90 456 979.5548 979.5678 -83.7816667 32 . 8 70JOOC 29 . -'J l 7. l l c .~ 15.4 14 .4 l3.-} 13. 3 --~n .J!RUGUfll-____ - ---- - - --- - - - ...._NQ. . --'~'-- ____ l,.Q!iG. - -- --~~..f.Y. .J}~-~~VED .. _J.ttJOR ___ _LONG T5200 32 ~2. 40 63 . 49.90_ 480 979.~573 919.5o8Q -83.8316667 LAT - . F~- - - _BZ! .?..Q._. ~~ .3.~ . !3 ~-~ .2_0 32.8733333 34 .4 20.9 20. 0 t '"'~ l T5.2Ql 32 51.80 83__ 52.60 536 979.5530 979.S672 -83.~766661 J2. 86.B33:, 36 . 2 .21.1 2C .1 19. l --- - ___!~~02 32 52. 8() 83 5?~jQ___2_13 ~:!~5524 97?_.5_6_f!_6 _-tlh._~316667 3..2- -.8-8 000-0-0-- 41. 5 __!'-._2(!3 ~~- ~~ OD_ 83 57.80 517__9~9.55~.~ 979.5689 -83.9633333 32.6833D3 40. ~ 24.3 24.7 2J.l 23.6 21.9 n.5 i:l 2 . 6 7 l tJ. l B2.75 d.85 ___ _ 17.6 ___..1, o.9 17.9 -- 17.4 16.7 ~ - ~ --- - - 20 . o 2.0. .0 19.2 21.3 20.7 19.9 /' ,/' """, / BOUGUER ANOMALY MAP OF THE SOUTH-CENTRAL GEORGIA PIEDMONT by R. H. CARPENTER and J. P PRATHER (PLATE I.) 5102 3 Gravt'ty statt.on and num ber - - lsogal contour (contour interval 2 milligals) Assumed density 2 .67 SCALE 0 I 2 miles ' !;;;;;;;;;;;;;; co. \NP..M QS0l4 -~--+-::::r:t~~- ;,.,---- 8ut ~ t otft9iiH frQnll Gt(uqio C.OUfll1 ~l'loy tl'oGJ'