BGS Seabed Geology 10k: Bristol Channel version 1.0

The Seabed Geology 10k: Bristol Channel dataset is a digital geological map portraying the distribution of the different geological substrate units (either of bedrock or unlithified deposits) present on the seabed at a 1:10 000 scale. Additionally to the seabed substrate layer, this dataset also includes i) a Geomorphology layer, revealing the presence and distribution of seabed morphological and geomorphological features and ii) a Structural Geology layer, delineating the principal structural features observed at rockhead.
This dataset is the result of the interpretation of three, high-resolution, multibeam echo-sounder (MBES) bathymetry datasets collected in 2011, during the Civil Hydrography Programme (CHP) surveys managed by the Maritime and Coastguard Agency (MCA) for the UK Hydrographic Office. These surveys covered the central part of the Bristol Channel south of Swansea to where the river Usk discharges into the channel at Newport. MBES backscatter, physical samples (e.g. grabs, cores, and boreholes), academic papers and previous BGS geological interpretations at broader scales were used to further inform this geological interpretation.
Much of the seabed portrayed in this dataset is swept clear of sediments, or covered only with a fine veneer of sediment, such that the underlying geological structure is often clearly visible. The bedrock is divided into seven stratigraphical units: Pembroke Limestone Group; Mercia Mudstone Group; Penarth Group; the Lias Groups' St Mary’s Well Bay, Lavernock Shales and the Porthkerry members; and the Inferior Oolite Group. The superficial deposits mapped are comprised of only marine sediments that were classified, based on their grain size, into: Gravel; Sand and Gravel; Sand; Sand and Mud; Mud; and Gravel, Sand and Mud.