OXYGEN ISOTOPES IN FRESH-WATER BIOGENIC OPAL - NORTHEASTERN US ALLEROD-YOUNGER DRYAS TEMPERATURE SHIFT

The first oxygen isotope analysis of biogenic opal from lake sediments , from the Allerod/Younger Dryas transition in a core from Linsley Pon d, Connecticut, gives an average estimate of a 6 degrees C drop in tem perature during the Younger Dryas. This shift represents temperatures during the bloom season, and may be less than the winter temperature d rop. The sharp transition itself, with a duration of about 200 years, suggests that the temperature decrease may have been as large as 12 de grees C. Previous estimates of the Allerod/Younger Dryas temperature s hifts are controversial, and range from 3-20 degrees C, suggesting tha t further interdisciplinary research on the same samples is warranted.