Geophysical down-hole recognition of the Lower Devonian ‘Psammosteus’ Limestone and Townsend Tuff Bed,South Wales

Geophysical down-hole logs from the Maesteg and Senghenydd boreholes permit the recognition of the Townsend Tuff Bed and ‘Psammosteus’ Limestone markers on the basis of distinctive log motifs. The thickness of the interval between these markers is greater than at basin-margin localities and may be an indication of rapid deposition in the centre of the Anglo-Welsh basin in Lower Devonian times.