Page:VCH Warwickshire 1.djvu/53

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GEOLOGY Rollwright or Rollerich Stones, are masses of one of the higher Inferior Oolite limestones distinguished as the Chipping Norton Limestone. 1 The county boundary just includes areas of the Northampton Sands south and east of Long Compton, near Whichford and near Epwell ; and there are several small outliers in the same neighbourhood. According to Professor Judd, the beds forming these tracts consist of limestone, sands and ironstones. In the outlier west of Whichford, beds of white freestone are underlain by sands. 2 The higher clayey and calcareous beds of the Great Oolite just enter the county in a long faulted strip east of Whichford, and again as an outlier, partly let down by faults, to the east of Compton Winyate. At Traitor's Ford east of Whichford the beds consist of marly limestone and oolite ; while east of Compton Winyate they are very similar. 3 The lowest beds usually consist of clay with Osfrea and Gervillia, and may represent the Upper Estuarine Series of the midland counties. PLEISTOCENE AND RECENT The deposits in our district which next succeed to those last described are certain irregular patches of sand, gravel, and stony clay which lie sporadically over the edges and fill up hollows in the surface of the older rocks. They belong to a time so long subsequent to the formation of the Oolitic beds that during the interval the Upper Jurassic rocks and some of the Cretaceous were not only deposited to the thick- ness of several thousand feet over a slowly sinking sea bottom, but were subsequently by gradual upheavals of the earth crust raised above the sea-level and worn down by rain and rivers to a surface configuration much the same as obtains at the present time. Over the irregular land surface so produced were strewn the glacial deposits or Drift, the pro- ducts of glaciers and ice-sheets which at this time spread over much of the northern hemisphere. By the combined influence of astronomical causes and geographical changes the temperature had become reduced ; the moisture falling on the earth's surface accumulated as snow ; the separate tracts of permanent snow invaded the intermediate ground till at the maximum much of the northern hemisphere was buried under a thick pall of ice, which over Britain extended as far south as the valley of the Thames. As has been shown by the researches of local glaciologists notably Dr. Crosskey, D. Mackintosh, and Mr. W. J. Harrison the Midlands were the meeting-place of three great glaciers; 4 one descended from the Arenig mountains in north Wales and entered our district by way of the Vale of Llangollen and the plain of Shropshire, scattering blocks of Arenig rocks about the country between Birmingham and Bromsgrove. The second or Irish Sea Glacier was made up of confluent ice-flows from the 1 H. B. Woodward, op. cit. pp. 151-2.

  • H. B. Woodward, op. cit. p. 156. 3 H. B. Woodward, op. cit. pp. 333, 335.

4 For an excellent summary on the Glacial Geology of the Birmingham District see W. J. Harrison, Proc. Geol. Assoc. xv. (1898), 400. 23