SEDIMENTOLOGY OF PLEISTOCENE WACCAMAW AND CANEPATCH FORMATIONS, TODD PIT, BRUNSWICK COUNTY, NORTH CAROLINA

Pleistocene stratigraphy of the Atlantic Coastal Plain in northeastern S.C. and southeastern N.C. has been the focus of debate among geologists and paleontologists for decades. Assignment of ages for these units has also been controversial.

Todd Pit is located off N.C. Hwy. 179 in Shallotte, Brunswick County. This site consists of several pits, all but one of which have been reclaimed. Two distinct biostratigraphic units were exposed during the course of this study. Both units were analyzed on the basis of their sedimentology and paleontology. Sedimentary characteristics such as color, structures, carbonate percentage and grain size were used in conjunction with paleontologic evidence (macrofaunal assemblages, taphonomy, and abundance of black shells) to determine depositional environments.

Based on results obtained during this study, as well as comparison with type sections in the Atlantic Coastal Plain, the lower unit at Todd Pit is assigned to the upper Waccamaw Formation, and the upper unit to the Canepatch Formation. The upper Waccamaw was most likely deposited in a subtropical, shallow shelf environment, whereas the Canepatch was probably deposited under higher energy conditions in a cooler climate much like that of today.

Faunal specimens from the Waccamaw and Canepatch Formations were submitted for dating by amino acid racemization. Results from the analyses yielded an average D/L ratio of 0.875 for the lower unit; the upper unit yielded an average D/L ratio of 0.863. These ratios correspond to a late Pleistocene age for both units. Additionally, a C-14 age for a specimen of cypress from the Canepatch Formation yielded an age of >45,890 ybp.