42 Paleontology (Posters)

Friday, 11 April 2014
1:00 PM - 5:00 PM
Latham A/B/C

SPATIAL COMPARISON OF THE PALEOECOLOGY OF MOLLUSCAN ASSEMBLAGES FROM THE LOWER WACCAMAW FORMATION (PLEISTOCENE) ACROSS MULTIPLE LOCALITIES IN SOUTHEASTERN NORTH CAROLINA

Paper number: 42-6
Program: Technical Sessions
Time: 1:00 PM – 5:00 PM

Authors

Abstract

The paleontology class at Georgia State University (GSU) processed ~5800 shells contributing to research on Plio-Pleistocene molluscan extinctions in the western Atlantic. Specimens were collected from Snake Island Pit in Columbus County near Old Dock, NC. Five bulk samples were sieved (¼” mesh); bivalves (=B) with umbos (75% of individuals) and gastropods (=G) with apices (25% of individuals) were picked and sorted. Genera were counted, diversity was analyzed, and predatory drillholes were documented. Life modes were assigned using the NMITA database. Data from Snake Island Pit are compared here with previous results from nearby localities Register Quarry (~9000 specimens) and Holloman Pit (~2100 specimens) for examining spatial variation in the paleoecology of the lower Waccamaw Formation.

Over 100 genera were found at Register Quarry with individuals dominated by Plicatula (25%), Glycymeris (16%), Lirophora (8%), and Crepidula (7%). The most abundant genera of the 54 recorded at Holloman Pit are Laevicardium (13%), Crepidula (8%), Diplodonta (7%), Conus (7%), Olivella (6%), and Abra (5%). Identification of rare genera is ongoing for Snake Island Pit; so far 85 are reported. Abundances >5% are recorded in Lirophora (12%), Plicatula (12%), Glycymeris (11%), Crepidula (11%), and Laevicardium (10%).

Drilling frequency (=DF) is the # of complete drillholes divided by overall # of whole (>85% of shell intact) individuals. DFs at Register Quarry are 9% (G) and 15% (B); Holloman Pit DFs are 11% (G) and 12% (B). Snake Island Pit yielded DFs of 2% (G) and 19% (B).

Life modes (B) at Register Quarry were distributed evenly for unattached and cemented (52% vs. 47%) and immobile and actively mobile (47% vs. 44%) individuals. Over 71% were epifaunal; 95% were suspension feeders. Gastropods included 49% suspension feeders and 41% predatory carnivores. Holloman Pit individuals (B) were represented mostly by unattached (85%), actively mobile (79%), infaunal (82%), suspension feeders (79%). Gastropods consisted of 60% predatory carnivores and 32% suspension feeders. Snake Island Pit individuals (B) were dominated by infaunal (84%), unattached (80%), actively mobile (83%), suspension feeders (80%); most gastropods were predatory carnivores (75%). Taxa yet to be identified in GSU samples (~3% of specimens) will add to this work.