Southeastern Section - 65th Annual Meeting - 2016

Paper No. 14-3
Presentation Time: 8:00 AM-5:30 PM


BERNHARDT, Christopher, U.S. Geological Survey, 12201 Sunrise Valley Drive, MS 926A, Reston, VA 20192,

This study interprets the lithologic and palynologic results from a 19.60 m core collected within a karst region known as Burnsville Cove in the Valley and Ridge Province of the eastern United States. Coring started at a ground elevation of xx m above sea level, and reached a total depth of 19.60 m. The specific site is known as the Pancake Field, located on the east side of State Highway 609 in Highland County, Virginia. This area is part of the surface and subsurface drainages of Sinking Creek that flow north over and through Silurian-Devonian strata to a large sinkhole named “Water Sinks” on the north side of the Pancake Field.

The core consists mainly of 20 to 50 cm thick beds of pale yellowish brown to grayish orange clay and silt, although there are several 10 to 20 cm thick beds of light gray to moderate yellowish brown sandy gravel composed of rounded clasts of limestone and fine-grained sandstone and angular clasts of black shale. Reflectance photospectrometry recorded downcore color variability in the following three spectra: L*, a*, b*. The silt and clay are interpreted as Quaternary lacustrine strata that accumulated when the Water Sinks sinkhole was blocked by rocks, dirt, and organic debris.

Palynomorphs are preserved in a laminated clay at 12 to 17 m depth, whereas the remainder of the core is barren of palynomorphs. The dominant taxa throughout this 5 m section include Picea spp., Abies, Pinus banksiana, and Lycopodium. Herbaceous taxa like Cyperaceae, Poaceae, and Polygonaceae are present in lower abundances. One bulk radiocarbon date from organic matter in clay at 1322 to 1324 cm depth yielded an age of 21,710 +/-90 14C years BP [USGS radiocarbon sample WW9119]. The pollen data and radiocarbon age indicate that a boreal-like forest occupied this site during the Last Glacial Maximum (LGM), suggesting colder mean annual temperatures. This LGM scenario contrasts with modern climate conditions and modern Appalachian Oak Forest vegetation (Ecoregion 67c. Northern Sandstone Ridges).