User Guide for BGS Seabed Geology : Offshore East Anglia

British Geological Survey. 2024 User Guide for BGS Seabed Geology : Offshore East Anglia. Edinburgh, UK, British Geological Survey, 45pp. (OR/24/003) (Unpublished)

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Abstract/Summary

The BGS Seabed Geology: Offshore East Anglia digital map comprises three complementary components: 1) Substrate Geology, showing the distribution of Bedrock and Superficial geological units interpreted to be dominant within the top 1 m below seabed; 2) Structural Geology, delineating the principle structural features such as faults observed at rockhead; and 3) Seabed Geomorphology, classifying the physical morphology and interpreted geomorphic character of the seabed. This geospatial product is the result of analysing, interpreting, and classifying a number of high-resolution, multibeam echo-sounder (MBES) bathymetry datasets, supported by further data and information, e.g., MBES backscatter, shallow seismic data, physical samples (e.g., grab samples, cores, and boreholes), seismic data, academic and publicly accessible industry literature, and previous BGS mapping (e.g., 1:250,000 maps). The bedrock geology of the mapping area comprises Cretaceous age Chalk Group sedimentary rocks. These rocks crop-out extensively at seabed across the southern and central parts of the mapping area forming an extensive bedrock platform and Europe’s largest known offshore chalk reef. This reef has been designated the Cromer Shoal Chalk Beds Marine Conservation Zone (MCZ) owing to the range of unique floral and faunal habitats that it supports. The Chalk Group is covered across the central (partly) and southern parts of the mapping area by natural superficial deposits that accreted during the Quaternary. These include preglacial delta bottom-set (Westkapelle Ground Formation) and delta top-set (Yarmouth Roads Formation); and glacial sediments and landforms that were deposited and formed during at least two separate phases of glaciation that inundated parts of the southern North Sea and adjacent East Anglia during the Middle Pleistocene (Anglian / Elsterian) and Late Pleistocene (Late Devensian / Late Weichselian). Collective geological evidence includes extensive areas of out-cropping subglacial till; the presence of largely concealed and infilled over-deepened (>100 m deep) subglacial tunnel valleys, ice-marginal moraines, and a glacially disrupted chalk surface that includes the development of incised meltwater channels, detached and transported glacitectonic bedrock rafts and megablocks. Post-glacial environments from the Late-Pleistocene – Holocene (prior to marine inundation) included fluvial and estuarine deposition, that together with variable infill of Late Glacial valleys are included within the Botney Cut Formation. Holocene marine transgression flooded the region, with shallow marine sedimentation active through to modern times resulting in the variable cover of unconsolidated marine sediments, as well as the distribution of extensive current-induced bedforms, e.g., sediment banks, sediment waves and fields of mega ripples which are recorded within the Seabed Geomorphology layer. The map citation, metadata and overview is: British Geological Survey (2024): BGS Seabed Geology: Offshore East Anglia version 1.0. (Dataset). The information provided in this user guide is intended to provide a quick-start guide to using and understanding this BGS digital product.

Item Type:	Publication - Report
Funders/Sponsors:	British Geological Survey
Additional Information. Not used in RCUK Gateway to Research.:	This item has been internally reviewed, but not externally peer-reviewed.
Date made live:	11 Jun 2024 12:37 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/537561

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