The northwest European “sea-level laboratory” and regional holocene eustasy

Abstract

The northwest European coasts and shelf, including rising, subsiding and semi-stable areas, can be regarded as an immense “sea-level laboratory” where the interaction between eustasy, crustal movements and local paleoenvironmental effects can be analyzed, separated and checked. Central Fennoscandia has risen by 830 m and the North Sea basin has subsided by 170 m in response to the Late Weichselian glaciation. This implies rapid horizontal motions of a low-viscosity asthenosphere. Sea-level oscillations are recorded both in uplifted and subsided areas. The Fennoscandian shorelines are uplifted and tilted, and hence separated so that they can be clearly identified and dated. Each little Postglacial transgression maximum (PTM) is represented by a morphologically identified shoreline that has been followed for some 250 km in the direction of tilting in the Kattegat region. The amplitudes of the interjacent regressions are well expressed in the stratigraphy and can be determined with great accuracy. The Kattegat sea-level spectrum offers a “eustatic test area”. The eustatic curve calculated from the Kattegat data agrees in such detail with the records from other parts of northwestern Europe (e.g., northwest England, The Netherlands, northern Norway) that it must be concluded that it reflects the regional eustatic changes. It is a low-amplitude oscillating curve. Local paleoenvironmental effects are sometimes recorded, e.g., in relation to the climatic deterioration at the Subboreal/Subatlantic transition. Paleotidal changes seem to be recorded from the Atlantic coast of France. The eustatic fluctuations correlate with fluctuations in paleomagnetism and paleotemperature. This suggests a mutual origin. With the theory of paleogeoid changes, we must solve each region within itself and establish regional eustatic curves. The northwest European region provides such a solution. When similar solutions are established from other parts of the globe, the directions, amplitudes and rates of the paleogeoid changes can be measured.