An Overview of Postglacial Sediment Records from Colluvial Accumulations in Northwestern and North Iceland

Abstract

Active denudation processes occurring on slopes in north and northwestern Iceland have contributed to the buildup of large colluvial cones. These processes have been active since around 10,000 ¹⁴C yr BP when the ice sheet retreated during the last deglaciation. Stratigraphic records provide information of the kind of sedimentary transfer processes that have been active on slopes through time. Vertical sections in colluvial cones in north and northwestern Iceland exhibit a characteristic stratigraphy with successions of material from mass-movements interbedded with soil horizons occurring throughout the Holocene, under periglacial conditions of varying intensity. The alternating organic and minerogenic units are indicators of phases of slope activity and stability.

The dating of the deposits is possible with tephrochronology and ¹⁴C dating. The quantitative analysis of sediment on colluvial cones shows the relative importance of aggradation due to slope processes vs. soil formation during the Holocene. Increasing accumulation rates have been observed over historical time since at least a.d. 1104. The clastic deposits observed in north and northwestern Iceland are thought to provide information on extreme events during the Holocene, as the occurrence of mass-wasting release cannot be clearly related to Holocene climatic trends.

Acknowledgments

This study was supported by the Natural Research Center of Northwestern Iceland, Sauðárkrókur, Iceland, the French Arctic Research Group CNRS-GDR3062, Besançon, France, and the Laboratory of Physical and Environmental Geography Geolab CNRS-UMR6042, Clermont-Ferrand, France. The authors thank Susan Conway for reviewing the English language of the paper. The authors also thank the referees for their useful comments on the manuscript.