In 2009 and 2010, I visited a couple of exposures of the Lower Pleistocene (Calabrian) Waccamaw Formation in North Carolina. The Waccamaw is 1.5-2.0 million years in age and is contemporaneous with the Caloosahatchee Formation in south Florida, the Nashua Formation of central/northern Florida and the James City Formation in northern North Carolina and Virginia. Its geographical range is even more restricted than the Duplin and found mostly in Bladen, Columbus and Brunswick Counties in North Carolina and Horry County, South Carolina. This area is known for the natural near circular lakes that some locals attribute to meteorite strikes, but were probably formed by the deposition and melting of flow ice that was carried down large rivers into sounds that existed during or shortly after the last ice age.

The Waccamaw is younger than the Duplin and as a result of a major extinction event at the end of the Piacenzian stage, it has a fauna as different from the Duplin as that of the Caloosahatchee is to the Pinecrest in Florida. The Waccamaw is extremely abundant in large fossil shells (fig. 1) and echinoids (fig. 2), however its fauna is less diverse than the Caloosahatchee as its waters were cooler.

Figure 1. Gastropods from the Waccamaw Formation. From left to right: Busyscon adversarium Conrad, 1862, Loc. 774, Brunswick County, North Carolina; Busycon carica (Gmelin, 1791), Loc. 774, Brunswick County, North Carolina; Oliva sayana Ravenel, 1834, Loc. 914, Columbus County, North Carolina; Conus oniscus Woodring, 1928 (oniscus=wacamawensis), Loc. 914, Columbus County, North Carolina; Ficus communis (Roding, 1798), Loc. 774, Brunswick County, North Carolina; Polinices duplicatus (Say, 1822), Loc. 914, Columbus County, North Carolina.

Figure 2. Echinoids from the Waccamaw Formation, Loc. 514, Horry County, South Carolina. From left to right: Mellita quinuesperforata (Leske, 1778); Arbacia rivuli Cooke, 1941; Arbacia waccamaw Cooke, 1941.

In late 2009, I visited a site on the Cape Fear River which Julia Gardner in her classic work described many of the Waccamaw species. Unfortunately our group took this trip during near record high water levels which excluded us from collecting fallen material from the high bluffs. Instead we made a somewhat trecherous climb to the top of the bluff to collect in situ. Most Waccamaw collecting is from pits so this was more difficult and as a result, only a small sample was collected. That said, one shell that I found was more similar to Marvacrassatella kauffmani Ward & Blackwelder, 1987 found in the more northernly James City Formation than Eucrassatella speciosa (A. Adams, 1852); the only Crassatella listed by Campbell to occur in the Waccamaw. I designated this as my site number 1008.

In 2010, I had the opportunity to collect from one of the temporary burrow pits that open from time to time in the Old Dock area of Columbus County, North Carolina (fig. 3). As usual with these pits, fossils were abundant and collecting good (site number 1009). I have collected at several Waccamaw sites throughout the region, however I still found some species new to my Waccamaw collection (fig 4). Of note from this site were many sand dollars which were unfortunately so fragile that they were nearly impossible to collect complete.

Figure 3. Shell pit, Locality 1009, Columbus County, North Carolina.

Figure 4. Gastropods from the Lower Pleistocene Waccamaw Formation, Loc. 1009, Columbus County, North Carolina. From left to right: Cancellaria venusta Tuomey & Holmes, 1856; Trigonostoma elizabethae (Olsson & Petit, 1964); Epitonium aciculum (H. Lea, 1843); Coralliophila cf. leonensis Mansfield, 1937).

My list of mollusks from the two reported sites are attached below.

Waccamaw Formation Mollusks Locality 1008.pdf

Waccamaw Formation Mollusks Locality 1009.pdf

REFERENCES

Campbell, Lyle. 1993. Pliocene Molluscs from the Yorktown and Chowan River Formations in Virginia. Virginia Division of Mineral Resources Publication 127.

Gardner, Julia. 1948. Mollusca from the Miocene and Lower Pliocene of Virginia and North Carolina. USGS Professional Paper 199.

Hendricks, Jonathan. 2008. The genus Conus (Mollusca: Neogastropoda) in the Plio-Pleistocene of the southeastern United States, Bulletins of American Paleontology 375.

Petuch, Edward J. 2004. Cenozoic Seas. CRC Press.