Late-glacial and Holocene palaeoceanography of the North Icelandic shelf

Abstract

High-resolution gravity cores and box cores from the North Icelandic shelf have been studied for palaeoceanographic history based on lithological and biostratigraphical foramin- iferal data. Results from two outer shelf cores covering the last 13.6 k 14 C yr BP are presented in this paper. The sediments accumulated in north-south trending basins on each side of the Kolbeinsey Ridge at water depths of ca. 400 m. Sedimentation rates up to 1.5 m kyr -1 are observed during the Late-glacial and Holocene. The Vedde and Saksunarvatn tephras are present in the cores as well as the Hekla 1104. A new tephra, KOL-GS-2, has been identified and dated to 13.4 k 14 C yr BP, and another tephra, geochemically identical to the Borrobol Tephra, has been found at the same level. At present, the oceanographic Polar Front is located on the North Icelandic shelf, which experiences sharp oceanographic surface boundaries between the cold East Icelandic Current and the warmer Irminger Current. Past changes in sedimentological and biological processes in the study area are assumed to be related to fluctuations of the Polar Front. The area was deglaciated before ca. 14 kyr BP, but there is evidence of ice rafting up to the end of the GS-1 (Greenland Stadial 1, Younger Dryas) period, increasing again towards the end of the Holocene. Foraminiferal studies show a relatively strong GS-2 (pre-13 kyr BP) palaeo-Irminger Current, followed by severe cooling and then by unstable conditions during the remainder of the GI-1 (Greenland Interstadial 1, Bolling-Allerod) and GS-1 (Younger Dryas). Another cooling event occurred during the Preboreal before the Holocene current system was established at about 9 kyr BP. After a climatic optimum between 9 and 6 kyr BP the climate began to deteriorate and fluctuate. Copyright © 2000 John Wiley & Sons, Ltd.