Superficial Deposits Thickness Model

• Introduction
• Details

Introduction

Superficial deposits are the youngest of the geological formations (less than two million years old). They are largely unconsolidated and cover much of the bedrock of Britain. They generally include sediments deposited during the Pleistocene (Quaternary) glacial episodes, subsequent Holocene rivers and coastal systems; superficial deposits also include modern man made deposits such as mining spoil and road embankments.

The Superficial Deposits Thickness Models show the depth of the bedrock surface and this information is critical in a number of areas of work. For example, in civil engineering, the evaluation of groundwater resources and possible water pollution, and in the prediction of surface hazards such as landslides and the collapse of underlying rocks.

The model has been created using digital mathematical interpolation techniques. It is produced by analysing information from approximately 600 000 borehole logs held in the BGS archives and also uses the extent of superficial deposits from the 1:50 000 scale digital geological map of Britain: DiGMapGB-50.

Details

The Superficial Deposits Thickness Model (SDTM) is a raster-based dataset designed to demonstrate the variation in thickness of Quaternary-age superficial deposits across Great Britain.

The SDTM comprises three individual datasets of information, two sets, Basic and Advanced, describe thickness variation as modelled via two standard geo-mathematical techniques, and a third set, a Distance Buffer, details 'proximity' or 'fit' of the data to the original source information (useful for determining confidence or uncertainty in the models).

• The Advanced Superficial Thickness Model (ASTM)  is a model of thickness variation indirectly derived from archive borehole records and map data.
• The Basic Superficial Thickness Model (BSTM) is a model of thickness variation directly derived from archive borehole records.
• The Distance Buffer (DBUFF) dataset is a calculation of spatial distance to the location of any data point used in the model. This provides the user with an indication as to how far the computer has had to interpolate and extrapolate the data from a measured observation point.

NOTE: the Advanced model uses a DTM to give the data a more natural appearance, however this can result in some artefacts in the data in areas where there are few direct measurements from boreholes to go on.