West Thurrock model information

Dartford Bridge

Built in GSI3D as a demonstration model by the BGS (Royse et al. 2009) this model covers about 10 km2 along the eastern flank of the M25 motorway on the north bank of the Thames.

The model is calculated from a digital elevation model (DEM) with a 20 m grid spacing and is based on primary 1:10 000 survey and borehole evidence.

It depicts an extensively modified and developed landscape with several extensive areas of artificial ground including the building of the Lakeside shopping complex within an old chalk quarry.

Superficial geology

The southern part of the model occupies the Thames floodplain and intertidal flats. Here interbedded alluvial silts and clays and peats overlie basal gravel deposits, together these sediments are up to 15m in thickness. Older river terrace deposits comprising sands and gravels fringe the alluvium and are also preserved as erosional remnants farther north.

Bedrock geology

The bedrock geology is dominated by the Chalk which underlies the whole area with the model extending to a depth of -150m OD. In the northern portion of the model, younger northward dipping bedrock units are found comprising the Thanet Sand, Lambeth, Harwich and London Clay formations in ascending order.

By adjusting the colour scheme using a dropdown menu the model can be coloured up to reflect several useful geological, hydrogeological and engineering properties, thus generating a series of derived models making the model fit for many purposes.

If the model is viewed in the 3D window, at a vertical exaggeration of x10 with all the artificial ground and superficial deposits switched off, then the top surface of the chalk shows the effects of excavation over large areas and the presence of a buried cliffline up to 10 m high beneath the northern limit of the current Thames floodplain.

This model forms part of an extensive programme to model the Thames Gateway development zone and lies within the FutureThames project area.

Reference

Royse, K R, Rutter, H K and Entwisle, D C.  2009.  Property attribution of 3D geological models in the Thames Gateway: New ways of visualising geoscientific information. Bulletin of Engineering Geology and the Environment 68, 1–16