Paleotemperatures through the Younger Dryas Interval at Glovers Pond, Northern N J, Derived from Fossil Chironomidae

Glovers Pond, a dimictic lake lying north of the Wisconsinan last glacial maximum in New Jersey, has been the site of long-term examination of limnologically based paleoclimate proxies that have included lithologic, geochemical, palynological, isotopic, and acarological data. Here we discuss a new data set through the Younger Dryas Interval that describes paleo-surface-water temperatures for July. Analysis follows the methods developed by Walker (1988; 2007)) and employed in the northeastern US and Canada by several workers (Walker, et al., 1991; Cwynar and Spear, 2001; Whitney, et al., 2005). We have applied both the classical and inverse deshrinking models for temperature calculation and have used thermal values for various chironomid genera as developed for northeastern Canada. No data set or transfer function for the region of New Jersey and Pennsylvania yet exists, a situation that may influence the accuracy of model solutions shown here. Presently the average July surface temperature of Glovers Pond is 27 ºC and the depth is 9.5 meters. Bottom temperatures range between 4 and 7 ºC over the year.

Approximately 2.5 m of Core C-I-4 which includes the Younger Dryas Interval yielded 50 genera of fossil midges (Chironomidae and Ceratopogonidae). Based on the classical deshrinking model YD July surface temperatures of 10.5 ºC characterize the low values whereas temperature fluctuations as high as 17.2 ºC mark warm episodes within the YD. Preboreal temperatures rise to 23.0 ºC and values ranging between 29 ºC and 33.1 ºC characterize the early Boreal. Preliminary analyses suggest that depositional settings affect the quality of the chironomid record to some degree and may, in turn influence temperature estimates when specific taxa become excluded from particular strata. A number of significant fluctuations within the Boreal are being further examined.