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. AMS 14C‐dating of aquatic mosses (Drepanocladus exannulatus and Scorpidiurn 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 of Salix arctica which immigrated to N Greenland c. 7 ka BP. Armeria scabra, now extinct in the area, larval cases and apotomes of Apatcmiu 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 of Salix pollen and leaves, indicates a large hiatus. This is confirmed by the dating to c. 7 ka BP of mosses just below the sand, and of Salix leaves just above it to c. 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 old 14C‐ages for the moss is discussed.

Isolation basin stratigraphy and Holocene relative sea-level change on Arveprinsen Ejland, Disko Bugt, West Greenland

“…This, together with the coarse sand (506.5 cm to 505.5 cm), suggests that a hiatus in sedimentation occurred during the isolation process. A similar thin sand layer is reported by Fredskild (1995) J. Quaternary Sci., Vol. 14(4) 323-345 (1999) hiatus caused by sediment slumping.…”

Late Quaternary history around Nioghalvfjerdsfjorden and Jøkelbugten, North-East Greenland

“…Remains of three southern extra-limital plants, the dwarf shrub Empetrum nigrum and the macro-limnophytes Potamogeton liformis and Nitella sp. BOREAS 30 (2001 were also reported from early Holocene deposits on Amdrup Land (Fredskild 1995), from a region where this plant is not found at present. Similarly, calyces of Armeria scabra, found in two samples from delta foresets on Hovgaard Ø, and dated to 8500 and 8800 years BP, indicate summer temperatures higher than at present, because this species does not appear to grow on Hovgaard Ø at the present.…”

Holocene environmental history in high‐Arctic North Greenland revealed by a combined biomarker and macrofossil approach

“…-The combined radiocarbon-based age-depth succession was systematically younger than expected and shows an age reversal ( Table 1). Aquatic mosses have been shown to provide erroneous ages in the record from nearby Lille Sneha Sø (Wagner & Bennike 2015) and a lake on Amdrup Land (Fredskild 1995), most likely resulting from the contribution of reworked material. In addition, both terrestrial macrofossil samples were small (352 and 665 lg) and the sample from 68 to 70 cm composite core depth yielded a much more depleted d 13 C value (À36.7&) indicative of machine-induced fractionation.…”

“…Previous palynological and macrofossil data from Klaresø, Sommersø and Lille Sneha Sø show that the HTM was characterized by immigration of relative warmth-indicating species such as Salix arctica as well as occurrences of aquatic invertebrates indicating prolonged ice-free summers, e.g. While the age models for Klaresø and Sommersø are uncertain (Fredskild 1973(Fredskild , 1995Funder & Abrahamsen 1988), the macrofossil assemblages of Lille Sneha Sø suggest the HTM peaked around 7 cal. While the age models for Klaresø and Sommersø are uncertain (Fredskild 1973(Fredskild , 1995Funder & Abrahamsen 1988), the macrofossil assemblages of Lille Sneha Sø suggest the HTM peaked around 7 cal.…”