The Carboniferous Section at Cattybrook, near Bristol

Abstract

I. I ntroduction . About 3½ miles east of the Severn Tunnel the South Wales branch of the Great Western Railway, in passing through the Patchway Tunnel, crosses the western margin of the Bristol Coalfield, and in the railway-cutting immediately to the west, Lower Carboniferous rocks are exposed. Here only the highest beds of the series are present, the Dibunophyllum Zone (D 2 and probably D 1 ), the main part of the sequence being cut out by the Cattybrook Fault, which brings in the Coal Measures. These are seen in the western end of the cutting, and are well exposed in the adjacent Cattybrook Brickworks. The Carboniferous Limestone has a general eastward dip—that is, towards the middle of the coal-basin; but, near the Cattybrook Fault, the beds are thrown into folds, and are much overthrust and broken by minor dislocations. The Coal Measures which are nearly vertical are ill-exposed near the line of fracture, and are seen in the adjacent brickworks to be intensely disturbed. The disturbance, in fact, on both sides of the fault is unequalled elsewhere in the Bristol district. The only published accounts of these exposures are (1) a brief reference by C. Richardson in the Report of the British Association (Manchester), 1861; (2) a somewhat fuller account in the Report of the Royal Coal Commission, 1871; (3) a short summary of the latter by H. B. Woodward in the Geology of East Somerset & the Bristol Coalfield and (4) an allusion by C. Lloyd Morgan to