SEDIMENTOLOGICAL AND PALEOCLIMATE STUDY OF A LAKE CORE FROM NORTHERN CONNECTICUT
The bottom ~1.0 m of the core consists of poorly-sorted reddish medium to coarse-grained sand with magnetic susceptibility values of 90 to 110 10-6 SI units. The sediment is dominantly quartz with abundant pyroxene, amphibole, feldspars and opaques. Organic carbon (based on LOI) is 1-2% and water content increases upward from 6 to 30%. This lower layer is overlain by ~1.2 m of fine-grained reddish-brown quartz sand with susceptibility values decreasing upward from 30 10-6 SI units to near zero. Organic carbon and water content increase upward from 2 to 45% and 30 to 88% respectively. The dominance of clastic material in this lower section implies no surrounding wetland filters and poorly vegetated slopes. The abundance of quartz suggests that the sediment is glacially derived since the surrounding rock is primarily basalt. Both layers are characterized by high coercivity magnetic minerals (hematite?)
The next ~1.0 m layer of medium gray, clastic-poor, organic-rich, diatomaceous sediment suggests the development of a wetlands filter approximately 14,500 yr BP. The organic carbon content decreases upward from 68% to 33% and water content is 88%. Sedimentation rate was 0.037 cm yr-1. The remaining 8 m of core is organic mud with trace amounts of very-fine grained clastic material. Organic carbon and water decreases upward from 45% to 76% and 88 to 94% respectively. Sedimentation rate was 0.08 cm yr-1. The magnetic susceptibility of both layers is near zero.
Preliminary pollen data indicate low pollen deposition rates (<12,000 grains cm2 y-1) to about 12,000 yr BP with pine, spruce, grasses, sedges and willow dominating in a tundra environment. High deposition rates (up to 60,000 grains cm2 y-1) follow the establishment of a forest dominated by oak, pine, grasses and hemlock. At ~5,000 yr BP pollen deposition rates fall off (<10,000 grains cm2 y-1) as the forest progresses to one with primarily oak, pine, birch, beech, and hemlock.