UNSOLVED PROBLEMS 



The interpretations as given in the text, on the maps, and in the geologic sections must be considered 

 preliminary rather than final. The authors realize that much interpretation is based on meager data and 

 that more detail will be added as additional data are obtained. As yet it is only conjectural as to whether 

 anomalies found in the study of the data for the Coastal Plain are indicative of local variations in thick- 

 ness of sedimentation or possible presence of two or more sets of faults. Also, some of the anomalies 

 could be due to errors in determining land surface elevations of wells or errors in collecting and labelling 

 well samples. The indications are enough to make tantalizing the desire for answers but inadequate to 

 permit much more than guesses. However, it is possible that finding the answers may have considerable 

 economic significance to Georgia. 



The surficial deposits of Oligocene age in Georgia have been mapped as the Flint River Formation 

 by Cooke (1943) and as the Suwanee Limestone by MacNeil (1947). Additional work is needed to establish 

 whether two different formations of Oligocene age occur in Georgia or whether these two are the same 

 formation with the Flint River Formation representing the weathered and eroded remnants of the Suwanee 

 Limestone. This problem needs to be solved before a really valid correlation can be established between 

 surface outcrops and the subsurface. 



The age of the phosphate-bearing, sandy limestone at the base of the Miocene in southeastern Georgia 

 and adjacent parts of South Carolina is uncertain. Owing to a lack of fossils the age of this limestone is 

 regarded in this report as basal Miocene though it could be late Oligocene. If the Cooper Marl in Georgia 

 is found to be Oligocene in age (now considered to be late Eocene(?)) then this phosphatic limestone lying 

 at the base of the Miocene could be equivalent to the uppermost Cooper Marl in this part of Georgia and 

 South Carolina. 



The age and areal extent of the Cooper Marl in Georgia also needs further study. As noted previously, 

 the fauna of the Cooper Marl in Georgia suggests that the formation is the updip equivalent of the upper 

 unit of the Ocala Limestone. From this correlation, both would seem to be late Eocene in age. However, 

 the Cooper Marl of South Carolina is now considered to be Oligocene in age (Malde, 1959, p. 19). Until 

 positive correlation can be established between the Cooper Marl of both Georgia and South Carolina, 

 the reader is urged to consider that all mention of the Cooper Marl in this report applies only to the de- 

 posits of that name as found in Georgia. 



In a report on a tropical Oligocene sea in central Georgia, Esther R. Applin (1960) published a log 

 of a well in Coffee County showing 640 feet of Oligocene sediments. This thickness is so unusual in 

 Georgia that the senior author examined another cut of the samples and found himself in substantial 

 agreement with Mrs. Applin. In none of the other wells does the Oligocene exceed much over 200 feet. 

 The reason for this local thickening is as yet an enigma. The fossils found indicate an orderly sequence 

 throughout rather than a repetition of strata such as could result from faulting. Further study is needed 

 to explain this anomaly and to determine its areal extent and structural significance. Because the data 

 were so anomalous they were not entered on the maps in this report. 



The upper Eocene and Oligocene Foraminifera found in the Dougherty Plain of southwest Georgia 

 suffice to indicate that rocks of those ages once covered part or all of the Plain. More work is needed 

 to know why this large area should have been so uniformly leached of its limestone cover and when 

 it occurred. 



In Georgia the upper division of the Ocala Limestone contains Asterocyclina nassauensis , Operculinoides 

 floridensis , and Pseudophragmina flintensis. The presence of these three larger Foraminifera indicates 

 definite upper Eocene age of this unit. However, the remainder of the fauna appears to be closely re- 

 lated to that of the Cooper Marl suggesting that the Cooper Marl in Georgia is late Eocene in age rather 

 than Oligocene as in South Carolina. The upper division of the Ocala in Chatham County appears to be 

 the downdip limestone equivalent of the Cooper Marl as exposed in Jenkins and Houston Counties. 



As yet, the age of the Sandersville Limestone Member of the Barnwell Formation is subject to question. 

 It may be a limestone of Oligocene rather than late Eocene age. Further study of its occurrence in the 

 subsurface of east-central Georgia is needed to solve this problem. 



A sand is found between the Ocala Limestone of late Eocene age and the Lisbon Formation of middle 

 Eocene age. In the logs of the well-log report (Herrick, 1961) this sand was either called Gosport Sand or 

 included in the Lisbon Formation. Further study is needed to ascertain whether this is actually Gosport 

 or whether it may be entirely or in part equivalent to the Moodys Marl Member of the Jackson For- 

 mation of late Eocene age. 



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