Abstract
Abstract. Reconstructing the growth and decay of palaeo-ice sheets is critical to understanding the relationships between global climate and sea-level change and to testing numerical ice sheet models. In this study, we integrate recently acquired high-resolution 2D seismic reflection and borehole datasets from two wind-farm sites offshore of the Netherlands to investigate the sedimentary, geomorphological, and glaciotectonic records left by the Saalian Drenthe substage glaciation, when Scandinavian land ice reached its southernmost extent in the southern North Sea (ca. 160 ka, Marine Isotope Stage 6). A complex assemblage of glaciogenic sediments and glaciotectonic structures is buried in the shallow subsurface. The northern wind-farm site revealed a set of NE–SW-oriented subglacial meltwater channels filled with till and glaciofluvial sediments and an E–W-trending composite ridge with local evidence of intense glaciotectonic deformation that denotes the maximum limit reached by the ice. Based on the identified glacial geomorphology, we refine the mapping of the maximum ice sheet extent offshore, revealing that the ice margin morphology is more complex than previously envisaged and displaying a lobate shape. Ice retreat left an unusual paraglacial landscape characterised by the progressive infilling of topographic depressions carved by ice-driven erosion and a diffuse drainage network of outwash channels. The net direction of outwash was to the west and southwest into a nearby glacial basin. We demonstrate the utility of offshore wind-farm data as records of process–form relationships preserved in buried landscapes, which can be utilised in refining palaeo-ice sheet margins and informing longer-term drivers of change in low-relief settings.
Highlights
The Greenland and Antarctic Ice Sheets have experienced net mass loss since the end of the Last Glacial (Alley et al, 2010; Anderson et al, 2002; Prothro et al, 2020), and are continuing to shrink at increasing rates due to anthropogenically-driven climatic change and oceanic warming (Hanna et al, 2020; Shepherd et al, 2020, 2019)
Using a dense grid of high-resolution seismic reflection data acquired to support the development of offshore windfarms, we 550 present sedimentological, seismic stratigraphic and geomorphic analyses of a preserved glacial landscape buried in late Quaternary sediments, offshore the Netherlands
Our mapping identifies a lobate shape to the ice margin, which is a consequence of contrasting subglacial bed conditions
Summary
The Greenland and Antarctic Ice Sheets have experienced net mass loss since the end of the Last Glacial (Alley et al, 2010; Anderson et al, 2002; Prothro et al, 2020), and are continuing to shrink at increasing rates due to anthropogenically-driven climatic change and oceanic warming (Hanna et al, 2020; Shepherd et al, 2020, 2019). To further understand ice sheet responses to differing climate states, we focus on ice-sheet advance and retreat during the penultimate glacial cycle (late Marine Isotope Stage [MIS] 6) in NW Europe. This period directly preceded the Last 40 Interglacial Together with climatic forcing and associated ice sheet responses over the MIS 6/5 glacial termination, the distribution of global ice sheets during MIS 6 is critical to understanding the nature of the LIG highstand regionally and globally.
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