Mark J. Brooks

New constraints on the evolution of Carolina Bays from ground-penetrating radar

Ground-penetrating radar (GPR) data for the Savannah River Site (SRS) in the Upper Coastal Plain of South Carolina, combined with geological, archaeological, and ecological data place new constraints on the evolution of Carolina Bays. Extant SRS bay morphology formed mainly during the Holocene and did not involve migration of bays across the landscape. Multiple periods of bay-rim accretion with intervening intervals of erosion may characterize the longer-term evolution of the bays. Bay evolution, however, did not involve significant modification of the Upland Unit underlying the region. During fluctuating, but generally open water conditions, breaking waves along bay shorelines eroded and transported sediment which was subsequently exposed for deflation during periods of low water. Deflation and transport of sand into standing vegetation along the margin of the bay depression created a rim in the form of a parabolic dune lacking obvious internal stratification. Simultaneously, infilling occurred by shoreline erosion and transport from adjacent elevated surfaces. This, coupled with growth of emergent vegetation, resulted in decreased hydroperiod, wave energy, shoreline modification, and rim accretion. Transport of some rim sediments back into the bays via alluvial and colluvial activity created wedges of infilling sediment during waning stages of evolution. The apparent contradiction of bay orientation with respect to prevailing winds might reflect seasonal changes in water level and wind direction: southwesterly winds during spring high water causes NW-SE elongation of the bays, whereas northwesterly winds during lower water in the fall and winter account for nearshore deflation and rim accretion along the east-southeastern bay margins.

Interpreting the hydrological history of a temporary pond from chemical and microscopic characterization of siliceous microfossils

The hydrological history of a temporary pond in South Carolina was inferred from a 5500-year record of siliceous microfossils, including diatoms, freshwater sponge spicules, chrysophyte cysts, plates of testate amoebae and plant phytoliths. Microfossil abundance was estimated by microscopic quantification of siliceous particles and by chemical extractions of silica. Diatom, sponge and mineral particle volumes were correlated with silica concentrations attributable to these fractions. Both techniques suggested a sequence of four distinct community types. Basal sediments (4630–5520 14C YBP) containing phytoliths and sponge spicules indicative of a wetland community were covered by sediments dominated by the remains of planktonic protists (3750–4630 14C YBP) suggesting a transition from a vegetated marsh to an open-water, permanently flooded pond. Microfossil assemblages above this zone indicate the return of a wetland community ca. 3750 YBP that persisted until recently, when pond water levels stabilized as a result of seepage from a reservoir constructed nearby in 1985. This study suggests that the suite of siliceous microfossils commonly found in pond sediments can be used to infer historical alternations between macrophyte and plankton-dominated states in shallow basins. Regional climate inferences from this record include a mid-Holocene hydrological maximum and the onset of the modern climate ca. 3500 YBP.

Carolina Bay geoarchaeology and Holocene landscape evolution on the Upper Coastal Plain of South Carolina

Surface water on the mainly dry, upland interfluves of the Upper Coastal Plain of South Carolina occurs currently as a sporadic distribution of shallow ponds held within Carolina bays and other small, isolated basins. At seven bays on the U.S. Department of Energys Savannah River Site on the Upper Coastal Plain of South Carolina, we investigated Holocene changes in bay morphology, ecology, and prehistoric human activity. At Flamingo Bay, we employed archaeological survey and testing, shovel and auger testing, sediment analysis, and ground-penetrating radar to document stratigraphy and chronology of the sand rim on the eastern side of the bay. Artifact assemblage indicate changes in intensity of human use of the bay. Radiocarbon dates from a sediment core establish time scales for depositional processes at the center of the basin. Ground-penetrating radar data from the other bays indicate that the stratigraphy of all seven bays is broadly similar. We conclude that: (1) Significant modification of the bays, including rim development and basin infilling, occurred during the Holocene; (2) ponds on the early Holocene landscape were larger and more permanent than at present; (3) early Holocene climate, as indicated by both depositional processes and human activity, was not characterized by prolonged periods of extremely dry conditions; and (4) fluvial-centric models of terminal Pleistocene—early Holocene human adaptations require revision to include intensive use of isolated upland ponds.

Carolina Bays: Time Capsules of Culture and Climate Change

Abstract We synthesize results of extensive archaeological surveys and geoarchaeological investigations of Carolina bays and other depressional wetlands on the U.S. Department of Energy’s Savannah River Site (SRS). The SRS is located along the Savannah River in the upper Coastal Plain of South Carolina. These data are augmented with data from Carolina bays elsewhere within their middle to south Atlantic Coastal Plain range. Carolina bays are shallow, oriented upland ponds that formed during the late Pleistocene under climatic conditions very different from present. Their use by prehistoric populations was most intensive during the Paleoindian and Archaic periods. Subsequent use by Woodland and Mississippian populations tended to be ephemeral. Change through time in the prehistoric use of Carolina bays and other depressional wetlands is linked to regional-scale changes in climate, particularly to the hydrologic regime.

Early Hunter-Gatherer Tool Use and Animal Exploitation: Protein and Microwear Evidence from the Central Savannah River Valley

Abstract Results of protein residue and lithic microwear analyses are reported for Paleoindian and Early Archaic stone tools from a Carolina bay sand rim on the Aiken Plateau of South Carolina, USA. Protein residue analysis is performed using crossover Immunoelectrophoresis (CIEP), and indicates positive results for Bovidae, Cervidae, Galliformes, and Meleagris gallopavo. These results are complemented by a larger immunological study of 135 diagnostic hafted bifaces from South Carolina and Georgia. Among other species identified, bovid residue was found on multiple Paleoindian hafted bifaces, an Early Archaic hafted biface, and a Middle Archaic hafted biface. Results suggest continuity of species selection and availability across the Pleistocene/Holocene boundary and provide no support for the exploitation of extinct fauna. The data do provide compelling evidence for a demographic shift and/or regional extirpation of Bovidae possibly as late as the early mid-Holocene in the Southeast. In addition, microwear analysis of artifacts from Flamingo Bay indicate intensive hide scraping, antler boring, bone graving/planing/pointing, wood whittling, and hafting traces. Microwear data suggest intentional snap-fracture or bipolarization of exhausted or broken Clovis points for reuse as hide scrapers, and use of large bifacial knives and unifacial scrapers in intensive defleshing activities consistent with large animal butchery.

Widespread platinum anomaly documented at the Younger Dryas onset in North American sedimentary sequences

Previously, a large platinum (Pt) anomaly was reported in the Greenland ice sheet at the Younger Dryas boundary (YDB) (12,800 Cal B.P.). In order to evaluate its geographic extent, fire-assay and inductively coupled plasma mass spectrometry (FA and ICP-MS) elemental analyses were performed on 11 widely separated archaeological bulk sedimentary sequences. We document discovery of a distinct Pt anomaly spread widely across North America and dating to the Younger Dryas (YD) onset. The apparent synchroneity of this widespread YDB Pt anomaly is consistent with Greenland Ice Sheet Project 2 (GISP2) data that indicated atmospheric input of platinum-rich dust. We expect the Pt anomaly to serve as a widely-distributed time marker horizon (datum) for identification and correlation of the onset of the YD climatic episode at 12,800 Cal B.P. This Pt datum will facilitate the dating and correlating of archaeological, paleontological, and paleoenvironmental data between sequences, especially those with limited age control.