SEISMIC STRATIGRAPHY OF THE QUATERNARY AND ITS SUBSTRATUM IN SOUTHEASTERN KATTEGAT, SCANDINAVIA

Based on c. 1500 km reflection seismic profiles, the Quaternary format ions and their pre-Quaternary substratum in the southeastern Kattegat are described and a geological interpretation is suggested. The major volume of Quaternary deposits is found in a broad north-northwest sout h-southeast trending topographic depression. The substratum consists o f Upper Cretaceous limestone in the region north of the Sorgenfrei-Tor nquist Zone, and inside this zone older Mesozoic sedimentary rocks and Precambrian crystalline rocks are found. The Quaternary is divided in to four seismic units. No direct stratigraphic control is available, b ut the units are assumed to represent a period ranging from Late Saali an to Holocene. The oldest unit (unit 3) is composed of deposits of su pposed Late Saalian to Middle Weichselian age. This unit was severely eroded probably by the Late Weichselian ice sheets in a zone extending 40-50 km from the Swedish coast. Unit 2 represents the Late Weichseli an till deposits. North and east of the island of Anholt unit 3 is cut by a system of channels eroded by glacial meltwater. By the erosion a relief up to c. 100 m was formed. After the recession of the Late Wei chselian ice, an up to 100 m thick sequence of water-lain sediments (u nit 1) was deposited in the erosional basin and channels. Holocene dep osits (unit 0) of considerable thickness have only been identified in the channels in the northern part of the area.