Terraces along the Potomac River south of Washington, D.C. provide dates of sea level highstands over the past 150ka. Hybla Valley contains a long pollen record of climate variations over much of that time interval.
This project focuses on age dating, palynology and geomorphology of late Quaternary sedimentary terraces along the lower Potomac River, along the Chesapeake Bay shoreline, and on the Delmarva Peninsula. Chronostratigraphy of estuarine and marine units deposited over the past 150ka is based on new 14C, 10Be and Optically Stimulated Luminesce (OSL) dating of organic material, soils and sands. Palynology shows millennial-scale cycles back to OIS6 (~150ka) are recorded in thick stratigraphic sections flanking the Potomac River. OSL dating of dunes identified using LiDAR shows the periglacial impact of the Laurentide Ice Sheet just prior to and during the last glacial maximum. The integration of dated transgressive units into stratigraphic and process models shows the importance of glacioisostatic adjustments (GIA) in the mid-Atlantic region. Quantifying past GIA rates interglacial-period subsidence and glacial-period uplift improves our understanding of present post-glacial subsidence its contribution to rates of relative sea level rise in the mid-Atlantic region. Freshwater marsh response to sea level rise is being investigated in Dyke Marsh near Washington, D.C.
Why is this research important?
Sea level rise is one of the most important issues on the densely populated east coast of the U.S. The rate of relative sea level rise in Chesapeake Bay is abnormally high due to a variety of processes, one of which is the ongoing collapse of the glacial forebulge produced by the Laurentide Ice Sheet during the last glaciation. A long pollen record is being used to reconstruct paleotemperature variations between the last glacial maximum and the last interglacial, for comparison with other Northern Hemisphere climate proxies.
The dating of periglacial intervals that include dunes and other geomorphic records of cold climate provides evidence for abrupt climate changes and the thresholds of landscape response to climate variations.
Principal Investigator: Milan J. Pavich
Project Team: Helaine Markewich, Ron Litwin, Joe Smoot, Nancy Durika, Inga Clark