Palynology and sediment slumping in a high arctic Greenland lake

Abstract

A 103‐cm core from a high arctic lake (80°49′N, 15°00′W) on Amdrup Land, NE Greenland has been analysed for pollen and other microfossils, as well as bulk samples from 10 cores for macrofossils. AMS14C‐dating of aquatic mosses (Drepanocladus exannulatusandScorpidiurn scorpioides) revealed that the lowermost 90 cm of the core was deposited during a 1.5‐2 ka interval in the early Holocene, before the appearance ofSalix arcticawhich immigrated to N Greenlandc. 7 ka BP.Armeria scabra, now extinct in the area, larval cases and apotomes ofApatcmiu zonella, today not known north of c. 77°N, and other indices point to a climate warmer than that of today. A thin, sandy layer 13 cm below the lake bottom, accompanied by marked changes in the content of pollen and macrofossils, such as the sudden occurrence of large amounts ofSalixpollen and leaves, indicates a large hiatus. This is confirmed by the dating toc. 7 ka BP of mosses just below the sand, and ofSalixleaves just above it toc. 1 ka BP. The hiatus must be caused by sediment slumping which transported all the sediment from the intervening period to the deeper part of the lake. A similar, sandy layer in the uppermost 2–6 cm may be caused by younger, (sub‐)recent slumping, or both may be the result of the same disturbance. The possibility of a reservoir effect causing too old14C‐ages for the moss is discussed.