23 Sedimentology and Stratigraphy

Friday, 30 March 2007
8:00 AM - 12:00 PM

IMPLICATIONS OF LATE-PLEISTOCENE EOLIAN DEPOSITS IN THE CHESAPEAKE BAY REGION OF THE EASTERN U.S

Paper number: 23-1
Program: Technical Sessions
Time: 8:00 AM – 8:20 AM

Authors

Abstract

In the Chesapeake Bay region (CPR) sand sheets and dunes are present along major Coastal Plain rivers (such as the Potomac and Nottoway) and throughout the Delmarva Peninsula. This episodic eolian activity occurred during the late Wisconsinan, when the present Chesapeake Bay mostly was emergent. Data for these deposits are found in geologic, pedologic, and archaeologic studies (Denny et al., 1979; Mixon, 1985; Stolt and Rabenhorst, 1987; Wagner and McAvoy, 2004; and USDA-NSSL data). Dune orientation in the CBR indicates NW source winds. Recent pedologic and geologic mapping, combined with 2-m lidar data, indicate dune fields along the tidal portion of the Potomac River (PR). These dunes suggest a PR-valley sediment source that is below present-day sea level and NW source winds. Uncalibrated 14C ages for PR dunes and other CBR eolian deposits indicate multiple events during oxygen isotope stage 2 (OIS2; 26 to 11 ka) with two regionally significant intervals (~20 ka and ~16 ka). OIS2 pollen data from the Blue Ridge Mountains west of the tidal PR indicate coeval boreal forest and forest tundra, with estimated mean annual paleotemperatures ranging from from ~1.5°C to colder than from ~1.5°C (Litwin et al., 2004). Similarly, CBR pollen data (OIS2) document dominant birch, pine, and spruce with some shrub.

Chronostratigraphic, sedimentologic, mineralogic, and paleoclimatic data for these spatially-extensive eolian deposits provide a "snapshot" of a 15-20 kyr period, during which the CBR was a mostly emergent landmass with a cold, dry, and windy climate. Presently available and future data for the region can be used to better constrain global climate models, particularly regarding rates and degree of change in temperature, vegetation, precipitation, and wind patterns during OIS2. These data also comprise oldest age limits for late Pleistocene human activity in the CBR of the eastern U.S.