Quaternary stratigraphy of the Draugen area, Mid-Norwegian Shelf

Abstract

Lithostratigraphic, biostratigraphic and chronostratigraphic studies on a 130 m long core from Haltenbanken, Mid-Norwegian Shelf (DR 88 30 ) shows sequences of short episodic glacigenic sedimentation and periods of more continuous marine sedimentation. The sediment sequence is dated, by palaeomagnetism as well as the amino-acid and the strontium isotope methods, back to ca. 1.1 Ma. Previous seismostratigraphic interpretations placed the regional Pliocene/Pleistocene boundary at ca. 90 m depth at the core site; this level was dated to be of Brunhes/Matuyama age. The study area has been covered by grounded glaciers at least five times during the last 1.1 Ma. The first expansion of the Scandinavian ice sheet was at ca. 1.1 Ma, depositing a diamicton. These sediments are overlain by a long sequence of normal marine sediments deposited during both glacial and interglacial conditions. Two interglacial periods from this sequence have been given an informal interglacial notation. Except for the glaciation at ca. 1.1 Ma the glacials during the Early Pleistocene, which are identified in the core, were relatively limited. A transition to more extensive glaciations occurs in the early Middle Pleistocene. During these more extensive glacial phases, major erosion took place along the inner continental shelf. This erosional phase resulted in overdeepening of the inner shelf, which during the Middle and Late Pleistocene influenced the depositional dynamics in the central and the outer part of the shelf. In the study area the Middle and Late Pleistocene periods are dominated by glacigenic sediments, with only very thin interglacial sediments occasionally preserved. One interglacial period from the Middle Pleistocene has been given an informal interglacial notation. The core has been correlated to cores from the North Sea Basin on the basis of amino-acid stratigraphy and palaeomagnetism. The lithological and the foraminiferal stratigraphy indicates a synchronous appearance of the major lithological units and of the fauna assemblages in these areas.