YOUNGER DRYAS TO LITTLE ICE AGE GLACIER FLUCTUATIONS IN THE FRASER LOWLAND AND ON MT. BAKER, WASHINGTON

During the Sumas Stade of the Fraser Glaciation, two periods of pre–Younger Dryas moraine building in the Fraser Lowland by the Cordilleran Ice Sheet were followed by two Younger Dryas episodes of moraine building. In the North Cascades, long alpine glaciers formed when the Cordilleran Ice Sheet melted down below the level of ridges about 12,300 yrs. B.P. Younger Dryas alpine glaciers built moraines in the Nooksack Middle Fork 10,600 14C yrs. B.P. Recently dated moraines in the North Cascades and Sawtooth Mts. of Idaho indicate that the Younger Dryas cooling affected all of western North America.

Glaciers on Mt. Baker and in nearby cirques constructed moraines in the early Holocene. Middle and late Holocene glaciers on Mt. Baker fluctuated. Logs dated at 2400 to 2900 14C yrs. B.P. were buried by moraines below the Deming glacier and logs in the left lateral moraine of the Coleman glacier have been dated at 690 ± 80 and 740 + 80 14C yrs B.P.

Multiple Little Ice Age (LIA) moraines are common on Mt. Baker and show a consistent pattern with other areas in Washington. Massive LIA moraines occur east of the Easton glacier on Mt. Baker and multiple LIA moraines occur below the Boulder, Deming, Coleman, Easton, and other glaciers. Tree rings indicate that the ages of these moraines correspond well with periods of cooler temperatures recorded in the GISP2 ice core.