Pollen accumulation rates at Rogers Lake, Connecticut, during late-and postglacial time

Pollen accumulation rates have been estimated by dividing the pollen number per unit volume in 1 ml samples from a core from Rogers Lake, Connecticut, by the number of years represented by each sample. The latter variable was estimated from 24 radiocarbon-dated levels within the core. The result shows that total pollen deposition rose steeply from 1,000/cm 2 /year, 14,000 years ago to 10,000 / cm 2 / year in later Late Glacial time, reaching a maximum of 40,000/cm 2 /year, 9,000 years ago when the Pine Pollen Zone (B) was deposited. Subsequently the deposition rate fell to 20,(KI0-25,000/cm 2 /year, remaining stable at this level for the last 8,000 years. The pollen-percentage stratigraphy at Rogers Lake is similar to that at other sites in the vicinity. The changes in pollen percentages in sediments less than 8,000 years old directly reflect changes in deposition rates for these types, since the pollen total was almost constant. A rise in the numbers of Carya pollen grains took place about 5,000 years ago, and minimum rates for Tsugapollen deposition occurred between 1,500 and 4,000 years ago. These changes have been considered evidence for a xerothermic interval, but this event may be represented instead by the maximum in percentages and increase in deposition rates for Ambrosia pollen that occurred between 5,000 and 8,000 years ago. In sediments older than 8,000 years, the changes in pollen percentages are quite different from the changes in rates of pollen deposition of individual types. The pollen-accumulation-rate diagram shows that few pollen grains from trees were being deposited 12,000 years ago. Spruce pollen increased at that time, reaching a maximum 10,000 years ago, when an open spruce woodland may have grown in the region. Pine pollen began to increase 12,000 years ago, reaching maximum rates 9,000 years ago 18 times higher than the later Postglacial rate. Oak pollen increased in numbers 12,000 years ago and held steady throughout the remainder of Late Glacial time, increasing rapidly by a factor of 30 during Early Postglacial time.