The channels in Storebælt, Denmark: Implications of new radiocarbon ages

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Abstrakt

The brackish water Baltic Sea and the more saline Kattegat in the north are connected by three straits, Lillebælt, Storebælt and Øresund (Fig. 1). Storebælt (the Great Belt) is the deepest and widest of the straits. The strait is characterised by deeply incised channels that are partly filled by sediments. The water depth in major parts of Storebælt is about 20 m, though in some areas the channels are more than 50 m deep. The formation of the channels has been subject to discussion. Andersen (1927) suggested that the channels formed due to strong currents that are still active today or by fluvial erosion during the so-called continental period (Fastlandstiden) in the Early Holocene. At this time, the relative sea level in the region was lower than at present and a huge lake, the Ancylus Lake, which occupied the Baltic Basin, may have drained via Storebælt. Andersen dismissed the idea that the channels were formed by subglacial erosion by meltwater during the last deglaciation. More Recently, Mathiassen (1997) interpreted some of the deposits in the channels as late glacial, a viewpoint followed by Bennike et al. (2004). However, the age of the late glacial deposits in the channels are poorly constrained. The first studies of sediment cores from Storebælt were carried out by Krog (1973), Winn (1974) and Mathiassen (1997), but these studies concentrated on the Holocene development from mires to lakes to brackish and marine environments. Wiberg-Larsen et al. (2001) documented the presence of Early Holocene river deposits. Here we report on some new ages of macrofossils from late glacial deposits in the Storebælt channels. In the late 1970s, the Danish state began to map deposits of sand and gravel in Storebælt and several potential aggregate resources were identified east of Romsø. In this part of Storebælt there are two parallel south–north-orientated incised channels. In 2017, new vibrocores were collected by the Geological Survey of Denmark and Greenland (GEUS) as part of a mapping programme of submarine aggregates for The Danish Environmental Protection Agency. Coring positions were selected from interpretations of shallow seismic data acquired during the initial mapping projects. Two of the new cores from Storebælt contained remains of plants that are typical of late glacial deposits from Denmark. Three samples were submitted for radiocarbon dating, and here we report on the results.

OriginalsprogEngelsk
Artikelnummere2019430106
Antal sider4
TidsskriftGeological Survey of Denmark and Greenland Bulletin
Vol/bind43
DOI
StatusUdgivet - 24 jun. 2019

Programområde

  • Programområde 5: Natur og klima

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