Landscape response to glacial-interglacial cycles: insights from a southern North Sea offshore wind farm dataset

Landscape evolution during periods of Quaternary climate change can be reconstructed using integrated subsurface datasets acquired by the offshore wind industry. Reconstruction of landscapes that evolved during changes in past climates aid understanding the responses to future changes in climate. The bathymetry of the southern North Sea region makes it an attractive location for wind farm developments. The integration of a dense 2D grid of seismic reflection data, with sedimentological and geotechnical data, allow detailed documentation of depositional environments and landscape evolution from the Middle Pleistocene to present day over a 1040 km2 area.

The stratigraphic architecture records multiple phases of transgression and regression linked to multiple glacial-interglacial cycles and relative sea-level change. Middle Pleistocene stratigraphy (MIS 19-13) reveals a predominantly fluviatile depositional environment, with northward draining river valleys that are filled with a seismic architecture that support changing depositional environments from terrestrial to marginal marine. North-south orientated tunnel valleys provide evidence for subglacial conditions and southwards drainage, most likely during the Anglian stage (MIS 12). During the late Pleistocene (MIS 5d-2), a regressive stratigraphy is preserved, with geomorphology and stratigraphy recording multiple fluctuations in relative sea level in an overall low energy setting. Late Devensian postglacial stratigraphy reveals a terrestrial landscape with southward draining fluvial networks contemporaneous with peats that formed in freshwater wetlands. Early Holocene geomorphological features record marine transgression across a low relief coastal plain. Carbon stocks of postglacial peats are estimated and upscaled for the southern North Sea (726 Mt). The peats crop out on the seabed, and their susceptibility to reworking is considered.

The landscape evolution of the study area has revealed abrupt and opposing drainage directions, subglacial conditions, and postglacial marine transgression. Subtle topographic relief is a primary control on sedimentary process, and stratigraphic preservation. Improved 3D understanding of the subsurface has direct commercial application to the offshore wind industry, and for informing understanding of landscape response to changing climate.