Buried Late Pleistocene and Holocene channel systems in the southern North Sea

The southern North Sea region has been profoundly impacted by dynamic climatic fluctuations during the Quaternary. Global sea levels varied significantly during the Last Glacial Cycle (115-11.7 ka BP), globally dropping by ∼130 m below present levels at the Last Glacial Maximum (ca. 26 to 19 ka BP). These environmental shifts resulted in diverse glacial and post-glacial depositional environments, the remnants of which are now sparsely and patchily preserved offshore. This study specifically examines the Late Pleistocene and Holocene depositional systems southeast of Dogger Bank and Oyster Ground to unravel their intricate sedimentary and geomorphological evolution.

To achieve this, we integrated high-resolution 2D acoustic reflection data, acquired through the WALDO project surveys between 2022 and 2023 with extant lower-resolution petroleum exploration 3D seismic data. This multi-scale dataset enabled the detailed mapping of the primary stratigraphic units and key geomorphological features preserved in the region. The regional stratigraphy is dominated by glacial-age sequences and numerous buried valley-like incisions that erode the older stratigraphic units. The incisions are highly complex, showing significant variations in dimensions and orientation, and multiple infill phases. Cutting from levels around 35-50 m below MSL down to 90 m below MSL, the incisions illustrate diverse morphologies, including straight, meandering and braided patterns. They reflect shifts in hydrodynamic conditions, sediment transport pathways, and the interaction between glacial, fluvial, and marine processes. Even though previous studies in adjacent areas identified similar features, our data reveal unrecognised complexity in channel morphologies and infill, offering new insights into the glacial and post-glacial processes.

Our findings illustrate that the region experienced a multi-stage geological evolution since the last glaciation. Although the erosional and depositional processes that shape such features are crucial for paleolandscape reconstruction, they are often challenging to identify. A preliminary interpretation suggests their genesis may have resulted from glacial processes (e.g. subglacial or proglacial meltwater channels), with later modification by fluvial activity after deglaciation. These findings underscore the interplay between ice sheet dynamics, sea-level oscillations, and climatic variability in shaping the region during the last glacial period and Holocene. Integrating 2D and 3D datasets has proven invaluable for accurately mapping these depositional systems, offering a more detailed paleolandscape reconstruction.