User update: BGS SDTM V8 release

The Superficial Deposit Thickness Model (SDTM) dataset presents the modelled regional variation in thickness of superficial and unconsolidated deposits across Great Britain. These include sediments of fluvial, glacial, marine or anthropogenic origin that were generally formed during the Quaternary geological period (the past 2.6 million years). The thickness of these deposits represents the depth down to the top of bedrock, known as geological rockhead.