C. C. Bentley, J. L. Knight, and M. A. Knoll 



span. This tends to be confirmed by the limited range of carbon dates. 

 The Harleyville Formation was capped by a well sorted, cross-stratified 

 quartz sand having a maximum thickness of about 4 m. Fossils collected 

 from this layer were similar to those in the cavities, but fewer in number. 



Locally, several cavities which had no connections to the surface 

 were exposed by mining operations in the Santee Limestone. Conse- 

 quently, these cavities were not infilled from above. 



A systematic excavation was not possible because the area at 

 the time of discovery was actively being mined. The operators of the 

 mine graciously relocated their mining operation to another section of 

 the pit, allowing us the maximum possible study time and nearly unlimit- 

 ed access to the fossil deposit. Bert Ardis, an employee of the Giant 

 Cement Plant Company, played a crucial role in the discovery and 

 excavation of fossils from the quarry. In recognition of his efforts 

 the fauna was named in his honor. 

 Dating of the Deposit 



Kruger Enterprises, Inc., Cambridge, Massachusetts, used C 14 

 dated (C 13 corrected) mammal and reptile bone apatite to date fossil 

 materials from the lower levels of the solution cavities and from the 

 well-sorted sand layer above the Harleyville Formation. Dating was 

 done on apatite due to the paucity of collagen. The fossil material 

 from the solution cavities (300 g of mixed mammal and reptile bone) 

 were dated at 18,940 ± 760 y.b.p. and the fossil material (300 g of 

 mammoth bone), from the overlying unnamed, quartz sand layer (about 

 1 km from the primary deposit), dated at 18,530 ± 725 y.b.p. The 

 overlap of the two dates suggests that the material in the solution 

 tunnels and the homogeneous sand layer above the Harleyville Forma- 

 tion are contemporaneous. These dates place the time of deposition at, 

 or near, the height of the Wisconsin glaciation (Bowen 1988). 



Serious questions have recently been raised concerning the 

 reliability of C 14 dating based on bone apatite and collagen (Stafford 

 et al. 1991). They state that C 14 dates on noncollagenous bone may 

 yield dates potentially thousands of years too young. Efforts are under- 

 way to acquire an amino acid date, even though the apatite sample was 

 apparently very clean (Kruger Enterprises, Inc., personal communica- 

 tion). In light of recent work (Stafford et al. 1991), the C 14 dates we 

 used will be considered a minimal age for this deposit. The maximum 

 age of the deposit is not expected to exceed 22,000 y.b.p. (Kruger 

 Enterprises, Inc., personal communication). Whatever the date, how- 

 ever, there is little doubt that the fauna represents a late Rancholabrean 

 age, and minor revisions in the absolute dates would have little effect 

 on the ecological or climatic interpretations suggested in our paper. 



