ORIGIN AND SIGNIFICANCE OF CLASTIC SEDIMENTS WITHIN WEYBRIDGE CAVE, VERMONT

A varied deglacial history of the Champlain Valley has been interpreted following the retreat of the Laurentide ice sheet, including a series of proglacial lakes, a marine extension of the Atlantic Ocean and modern-day Lake Champlain. However, very few records of climatic conditions exist for northern New England prior to the retreat of ice ~14 kyr ago. To begin filling this gap, we present a detailed chronological, sedimentological and geochemical examination of clastic sediment within Weybridge Cave, Vermont. The majority of the clastic sediment studied consists of a thick sequence (>2 m) of silt and clay with <1 mm laminae. Rip-up clasts and a mélange containing intact blocks of finely laminated clays suggest that deposition of this fine-grained unit was punctuated by higher-energy discharge events. Optically Stimulated Luminescence (OSL) evidence from coarse sand underlying the fines provides an upper age limit for this unit near the end of isotope stage 5. Comparing paleomagnetic declination and inclination variations to existing, dated records help further narrow the exact age of the fine-grained sediment and correlate between outcrops. The sediments described here offer a paleoenvironmental record that could aid further interpretation of New England landscape evolution prior to and during the most recent glaciation.