Page:VCH Staffordshire 1.djvu/50

 A HISTORY OF STAFFORDSHIRE formations known to exist in the Midlands beneath the Trias. Diver- gent as these views appear, they probably all contain an element of truth, for not from one but from many areas should the pebbles be derived if they were laid down under continental conditions. 1 The strata are almost wholly unfossiliferous. In other parts of England the presence of Labyrinthodonts has been detected, but then only rarely, and consisting chiefly of footprints. The spongy nature of the sandstone and shingle beds renders the sub-division an almost unlimited reservoir of underground water, admirably suited for drinking pur- poses. The pebble beds are thus the source from which the chief towns of Staffordshire obtain their water supply. The strong springs, issuing from the rocks along lines of faults and major joints, or at their junction with the less pervious Carboniferous strata, help in no small degree to keep the streams and rivers from running dry during the summer months. The springs at Wall Grange pouring out over 2,000,000 gallons daily, supplied to the Potteries, are a case in point ; the Tern river also issues from the spring-fed lake at Maer Hall as a stream of no inconsiderable size. In other respects the Pebble Beds, beyond yielding road-metal for second class roads, possess little commercial importance. Upper Mottled Sandstone. This sub-division of vermilion-coloured non-pebbly sandstone, closely resembling the lower sub-division, follows conformably and runs parallel with the outcrop of the Pebble Beds to the west of the southern coalfield, but is hardly separable from them and not always present in North Staffordshire. One of the best sections in the Midlands is opened out in the road cutting at Tettenhall to the west of Wolverhampton. Flanked by the Pebble Beds and overlain by the hard Keuper basement beds the Upper Mottled Sandstone usually occupies low lying tracts overlooked by the inferior and superior sub-divisions of the Trias. Some of the most beautiful country lanes have been cut deep into these soft red sandstones, whose bright red colours so strikingly contrast with the delicate greens of lichen, moss and fern which cling to their damp crumbling surfaces. The soft incoherent nature of the stone renders it a favourite source of building sand, while the more loamy varieties yield good foundry and moulding sand, and are extensively quarried at Baldwins Gate near Maer for the Crewe Engineering Works. KEUPER PERIOD Keuper Basement Beds and Waterstones. During the whole of the Bunter period the elevatory forces were going on or were only temporarily stationary : in the succeeding Keuper period the successive overlaps of the individual members point to a cessation of any upward movements, while towards its close the Triassic continent began to slowly sink until it became finally submerged beneath the seas which were to hold sway during the whole of Mesozoic times. 1 T. G. Bonney, Geol. Mag. Dec. n, vii. 404 (1880), ibid. Dec. 4, ii. 75 (1895); W. J. Harrison, Proc. Birm. Phil. Soc. vol. iii. (1881-3). 22