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.

海底地质10K（Seabed Geology 10k）：布里斯托尔海峡数据集是一幅数字地质图，以1:10000的比例尺呈现了海床基岩与未固结沉积层等不同地质基质单元的分布特征。除海床基质图层外，该数据集还包含两类附加图层：i) 地貌（Geomorphology）图层，用于展示海床地貌形态特征的存在状态与分布规律；ii) 构造地质（Structural Geology）图层，用以勾勒岩面处观测到的主要构造特征。

本数据集基于2011年民用水文测量计划（Civil Hydrographic Programme, CHP）所采集的三套高分辨率多波束测深声呐（multibeam echo-sounder, MBES）测深数据集的地质解译成果编制而成，该计划由海事与海岸警备局（Maritime and Coastguard Agency, MCA）为英国海道测量局（UK Hydrographic Office）实施。此次勘测范围覆盖布里斯托尔海峡中部位于斯旺西以南的区域，直至纽波特的厄斯克河注入海峡的水域。

解译过程中，研究团队结合了多波束测深声呐反向散射数据、实物采样样品（包括抓斗采样、岩心采样与钻孔采样）、学术文献资料，以及英国地质调查局（British Geological Survey, BGS）此前发布的大比例尺地质解译成果，以完善本次地质解译工作。

本数据集所呈现的多数海床区域要么已被沉积物完全冲刷殆尽，要么仅覆盖了一层极薄的沉积盖层，因此下伏地质构造往往清晰可见。

基岩被划分为七个地层单元：彭布罗克灰岩群（Pembroke Limestone Group）、默西亚泥岩群（Mercia Mudstone Group）、珀纳斯群（Penarth Group）、里阿斯群的圣玛丽井湾段（St Mary’s Well Bay）、拉弗诺克页岩段（Lavernock Shales）与波特克里成员（Porthkerry members），以及劣质灰岩群（Inferior Oolite Group）。

本次测绘的表层沉积仅包含海洋沉积物，研究人员根据沉积物粒度将其划分为六类：砾石、砂与砾石、砂、砂与泥、泥，以及砾石、砂与泥混合型沉积物。