Seismic refraction studies of geological structure in the inner part of the Bristol Channel

Nine E-W seismic refraction lines about [ 2 km long provide information on the thickness and structure of the Mesozoic succession i the inner Bristol Channel area. About 2ooo m of mainly Jurassic strata occupy the Bristol Channel syn-eline north of Foreland Point but this structure attenuates eastwards and is replaced by the Glastonbury syncline which contains nearly 800 m of Mesozoic strata under Bridgwater Bay. The Central Bristol Channel fault zone has been traced eastwards towards Bridgwater Bay, and has a southerly downthrow of several hun-dred metres in mid-Channel north of Porlock. There is some evidence for an early phase of movement along the fault zone, bringing Lower Palaeozoic against Upper Palaeozoic rocks. i. In t roduct ion DURINO I973-74, nine E-W seismic refraction fines were established in the inner part of the Bristol Channel east of longitude 3°55'W (Fig. I). The study was designed to establish the thickness and structure of the local Mesozoic sequence and to investigate he possibility of subdividing the Palaeozoic floor on the basis o