Morphometric and sedimentological characteristics of Late Holocene earth hummocks in the Zackenberg Valley (NE Greenland)

Abstract

A multi-approach characterization of three earth hummock fields has been conducted to understand the morphometrical characteristics and distribution pattern of these periglacial features in the Zackenberg Valley, NE Greenland. Earth hummocks develop in poorly-drained areas affected by intense cryogenic conditions. An accurate analysis of the morphometrical properties of hundreds of earth hummocks distributed between different Early Holocene moraine systems of the eastern slope of the Zackenberg Valley reveals an important control of microtopography on their distribution. Sedimentological analysis of selected earth hummocks shows evidence of alternating organic-rich layers and mineral units. Radiocarbon dates of the basal organic layers in contact with the permafrost table yielded ages 615 ± 25 and 1755 ± 60 cal yr BP, with lower sedimentation rates over the last centuries when soil formation prevailed. Geochemical analysis of the soils (Glacic Reductaquic Cryosols) showed also significant differences in the properties and composition among the soils of the different fields of hummocks.