Late Quaternary pollen record from the Sanpoil River Valley, Washington

Abstract

An 8.5-m core from Simpsons Flats, Ferry Co., Washington, includes at least four pollen zones spanning the last 10 000 years. With retreat of the Sanpoil lobe of Pinedale continental ice in the river valley, vegetation with low pollen influx (zone I) and dominated by Artemisia, Gramineae, and Pinus became prominent. Owing to the narrowness of the valley near Simpsons Flats, it is not clear whether pines were in the valley or on the adjacent upland sites.Mazama ash (ca. 6700 years before present (B.P.)) probably lies disconformably atop zone I and is included within a long-term warmer drier period (zone II) characterized by diploxylon pine pollen. Evidence for an effect of the Mazama ashfall on the vegetation is inconclusive. Zone III (4050–2700 years B.P.) marks a comparatively short period in which climatic conditions were slightly moister (although not necessarily cooler) than today, and the vegetation was dominated by diploxylon pine but with increased influx and frequency of Picea, Abies, and some haploxylon pine. The modern vegetation in the vicinity of the mire is dominated by Pinus ponderosa and Gramineae (including Festuca idahoensis) and seems to have emerged within the last 2700 years (zone IV).