A 12 000 year palynological record of temperature and precipitation trends in southwestern British Columbia

Abstract

Transfer functions for converting pollen frequencies to estimates of mean July temperature and mean annual precipitation were applied to fossil pollen data from a sediment core in Marion Lake. The paleotemperature curve shows low July temperatures near 14 °C at the base of the core at about 12 000 before present (B.P.), rising rapidly between 10 400 B.P. and 10 000 B.P. to maximum values slightly above 16 °C. Maximum temperatures cluster between 10 000 B.P. and approximately 7500 B.P., declining steadily thereafter until 6000 B.P. Little change is apparent from 6000 B.P. to the present. The reconstructed precipitation curve also shows a three-part zonation, with moderately high values between 12 000 and 10 400 B.P. dropping rapidly to minimum Holocene values between 10 000 and 7500 B.P. Precipitation rises to modern levels near the Mazama ash bed. The informal term "early Holocene xerothermic interval" is applied to the pre-Mazama interval of maximum temperatures and minimum precipitation.The late-glacial age at the base of the core is confirmed by a new radiocarbon date of 11 920 ± 245 years B.P. (I-6857) on lodgepole pine needles screened from the basal clays.