PALEOLIMNOLOGICAL INVESTIGATION OF AN EARLY HOLOCENE WETLAND IN A SHALLOW BAY OF LAKE CHAMPLAIN, VT

Sediment accumulated in lakes stores valuable information about past environments and paleoclimatological conditions. Cores obtained from St. Albans Bay, located in the Northeast Arm of Lake Champlain, VT record the transition from Champlain Sea to Lake Champlain. In this area of the lake, this transition is thought to be represented by a peat layer deposited within the bay.

This peat layer suggests the presence of a wetland, a lake level 7-8 m lower than at present, and the possible isolation of St. Albans Bay from the main lake during the early Holocene. Based on radiocarbon dating, this paleo-wetland existed in at least part of St. Albans Bay from ~ 9,600-8,600 cal yr BP. Palynological evidence from the peat reveals a changing climate, with pollen assemblages transitioning from Pine-dominated (cooler climate), to Pine and Hemlock/hardwood-dominated (warmer climate), followed by a return to a Pine-dominated community. These transitions may represent warming climate related to the onset of the Hypsithermal, briefly interrupted by a short-lived period of cooling, possibly related to the “8.2ka” cooling event.

The cores we collected will allow us to better constrain the spatial extent, thickness and age variability of the peat layer within the bay. This should enable us to determine if the bay was indeed isolated from the rest of the basin when water levels were at their lowest. If so, there is a possibility that the peat layer does not represent the Champlain Sea-Lake Champlain transition as previously thought. Also, completion of a paleoecological investigation of lacustrine sediment in St. Albans Bay will assist in understanding the type of environment that existed here, more specifically whether it was a marine/brackish or freshwater wetland.