A LATE GLACIAL - EARLY HOLOCENE PALEOCLIMATE SIGNAL FROM THE OSTRACODE RECORD OF TWIN PONDS, VERMONT

Recent studies indicate that during key climate episodes of the Holocene, such as the 8.2 kyr event, New England experienced wetter conditions than did the Laurentian Great Lakes region, which experienced drought, although both regions experienced similar responses to the Younger Dryas (Shuman et al.,2006; Williams et al., 2010). Here, we use paleoecological and isotopic analysis of ostracodes from a New England lake record to examine paleoclimate conditions in the region from the Late Glacial through the Early Holocene. In 2012, a sediment core was collected from Twin Ponds Lake in Brookfield, Vermont. Twin Ponds Lake is located in central Vermont in bedrock composed of Silurian to Devonian age phyllite and limestone, and thus provides a carbonate – rich record, a rarity in New England paleolimnology. This study is part of a multi-proxy analysis: additional research focuses on pollen, loss on ignition, charcoal and bulk carbonate isotopic analysis of the core. Twin Ponds provides the first Holocene record of ostracodes for New England, outside of Lake Champlain.

The Twin Ponds core is about 260 cm in length and spans the Late Glacial through the Holocene but the most detailed records bracket the Younger Dryas. The Late Holocene is not well represented. Isotopic analysis of bulk carbonate indicates a regional correlation with the Younger Dryas record from sites in the northeastern U.S. The ostracode record of the Younger Dryas in this core includes Candona stagnalis, Candona candida, and Cyclocypris globosa, a cold tolerant species living today no further south than the Yukon and Northwest Territories of Canada (as recorded in the North American Combined Ostracode Database, (Curry et al., 2013)). At about 9,000 cal yrs, Candona candida declines, and Candona ohioensis appears in the record. This core contains 8 species of ostracodes, and provides the easternmost known distribution in North America for Candona ohioensis, Candona paraohioensis, and Candona candida, although C. candida is known worldwide. The other species include Cyclocypris ampla, Cypridopsis vidua, and Darwinula stevensoni. The species found in the Twin Ponds core are all common extant species with well-known biogeographies and environmental tolerances which can be used to draw inferences about the past paleoclimatic record of the region.