Abstract
Abstract. The Zackenberg River delta is located in northeast Greenland (74°30′ N, 20°30′ E) at the outlet of the Zackenberg fjord valley. The fjord-valley fill consists of a series of terraced deltaic deposits (ca. 2 km2) formed during relative sea-level (RSL) fall. We investigated the deposits using sedimentological and cryostratigraphic techniques together with optically stimulated luminescence (OSL) dating. We identify four facies associations in sections (4 to 22 m in height) exposed along the modern Zackenberg River and coast. Facies associations relate to (I) overriding glaciers, (II) retreating glaciers and quiescent glaciomarine conditions, (III) delta progradation in a fjord valley, and (IV) fluvial activity and niveo-aeolian processes. Pore, layered, and suspended cryofacies are identified in two 20 m deep ice-bonded sediment cores. The cryofacies distribution, together with low overall ground-ice content, indicates that permafrost is predominately epigenetic in these deposits. Fourteen OSL ages constrain the deposition of the cored deposits to between approximately 13 and 11 ka, immediately following deglaciation. The timing of permafrost aggradation was closely related to delta progradation and began following the subaerial exposure of the delta plain (ca. 11 ka). Our results reveal information concerning the interplay between deglaciation, RSL change, sedimentation, permafrost aggradation, and the timing of these events. These findings have implications for the timing and mode of permafrost aggradation in other fjord valleys in northeast Greenland.
Highlights
Glaciated valleys and fjords are sedimentary depocentres in which large volumes of sediment have accumulated during the late Weichselian and early Holocene (Aarseth, 1997; Hansen, 2001; Eilertsen et al, 2011)
Our results reveal information concerning the interplay between deglaciation, relative sea-level (RSL) change, sedimentation, permafrost aggradation, and the timing of these events
The valley-fill deposits in the Zackenberg lowlands formed during highstand and RSL fall following deglaciation, ca. 13 to 11 ka
Summary
Glaciated valleys and fjords are sedimentary depocentres in which large volumes of sediment have accumulated during the late Weichselian and early Holocene (Aarseth, 1997; Hansen, 2001; Eilertsen et al, 2011). The formerly ice-covered areas of coastal Greenland experienced isostatic rebound following deglaciation (Fleming and Lambeck, 2004). This has resulted in uplifting, incision, and erosion of valley-fill deposits by Holocene fluvial and coastal activity. Recent studies have examined the deltaic infill of fjords in high-relief landscapes (Hansen, 2004; Corner, 2006; Eilertsen et al, 2011; Marchand et al, 2013). Few of these studies were in landscapes with permafrost. The relationship between ground ice and the depositional setting in high-relief
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