The structure and stratigraphy of Nidderdale between Lofthouse and Dacre.

Abstract

The geology of the south-east corner of the Askrigg Block and part of the Craven Basin surrounding Nidderdale, Yorkshire is described. The succession, more than 1,200 feet thick in the north and twice this thickness south of the North Craven Fault, ranges from the base of the Millstone grit to the base of the Permian, and is of Namurian and Westphalian age. The stratigraphy of each horizon is described in detail, attention being drawn to the following new finds: (i) The continuation of the Cockhill Marine Band, containing Cravenoceras cowlingense, (ii) Tylonautilus nodiferus in the Colsterdale Marine Series, (iii) shelly fossiliferous phases in the Upper Follifoot Grit, the Libishaw Sandstone, the Beverley Shales and the First Brimham Grit, (iv) Reticuloceras circumplicatile group in the Cayton Gill Shell Bed and Reticuloceras aff. pulchellum in the overlying shales, (v) an unconformity at the base of the First Brimham Grit, south of North Craven Fault, (vi) two Lingula bands and a band with Gastrioceras cumbriense in the Winksley Shales, the position of the latter suggesting the local absence of the R2 stage (vii) the presence of the basal Coal Measures, including a lingula band near the base. The succession is correlated with neighbouring areas. Structurally the district includes a northern area with gentle eastward dips and a southern area of shallow E.N.E. folds crossed by folds of N-S trend. The North Craven Fault, which approximately coincides with the junction of the two areas, is shown to have been active during R1 times in this district, but not subsequently. Its relation to the edge of the Askrigg Block is examined. The petrography of the sediments is described, a general absence of microline and garnet from the sandstones of the E stage being noted. Aspects of the water supply and mineral products of the area are mentioned and an appendix of borehole records incorporated.