Curtis C. Bentley and James L. Knight 



taxa of turtles, including Gopherus sp. and Malaclemys terrapin which were not 

 recovered from the Ardis local fauna and possibly three species of Pseudemys, P. 

 floridana and/or P. concinna, and P nelsoni. 



The Ardis local fauna was discovered in a large open-pit mine, operat- 

 ed by the Giant Cement Company, located 5 km NNE of Harley ville, Dorchester 

 County, South Carolina (33° 14'N, 80° 26'W). Quarry operations exposed San- 

 tee Limestone (middle Eocene) and the clay-rich Harleyville Formation (late 

 Eocene) which underlie Plio-Pleistocene surficial deposits (Ward et al. 1979, 

 Harris and Zullo 1991). Locally, groundwater differentially dissolved the Santee 

 Limestone in its upper portions, so that many solution cavities contacted and 

 penetrated the overlying Harleyville Formation and thereby opened several of 

 the cavities to the Pleistocene surface (Bentley et al, 1994). The radiocarbon 

 dates of the Ardis material place the time of deposition at or near the height of 

 the Wisconsinan glaciation (Bowen 1988, Tushingham and Peltier 1993). Fur- 

 ther discussion on the geology, dating methods of the Ardis fossil material, pre- 

 vious fossil collections from the quarry, fossil collection procedures, and a local- 

 ity map are available in prior publications (Bentley and Knight 1993, Bentley et 

 al. 1994). 



TAPHONOMY 



At least part of the fossil assemblage collected from inside the solution 

 cavities at the Ardis site appears to represent an obrution deposit, the very rapid 

 burial of intact organisms (Brett 1990) in which many of the specimens exhibit 

 incipient decay. Surface openings leading to the cavities varied from a gentle 

 downward slope to a vertical shaft, generally allowing the Pleistocene fauna ease 

 of ingress and egress. This permitted animals to enter the cavities in three dif- 

 ferent ways: (1) "walk-in" taxa, which may have used the site for 

 estivation/hibernation or as denning sites and hunting grounds, for example 

 muskrats, mink, and woodrats (Bentley et al. 1994); (2) "wash-in" taxa from the 

 surface, either alive or dead, which applies most readily to large animals known 

 only from isolated remains e.g., Mammut sp., Bison sp., Equus sp. (Bentley et al. 

 1994), that would have been unable to enter the cavities during life; and (3) "fall- 

 in" taxa which fell into exposed verticle shafts, fossil accumulations resulting 

 from this type of natural trap are well documented (e.g., Webb 1974). 



Because of the interconnecting "tunnel-like" nature of the cavities, a 

 single episodic event could produce differing water velocities within the cavities 

 and different rates of deposition. Seasonal flooding, depending on the intensity, 

 may have simultaneously smothered living animals within the cavities and 

 buried or reworked those that had died just prior to, or in a preceding, deposi- 

 tional event. Consequently, specimens incompletely or shallowly buried during 

 an event with a low sedimentation rate (low energy) could be completely or par- 

 tially exhumed and reburied by a succeeding event. This resulted in the preser- 



