Page:VCH Staffordshire 1.djvu/48

 A HISTORY FO STAFFORDSHIRE and south, from off which they dip to all points of the compass, and are broadest in the great central syncline occupied by the Keuper Marls. BUNTER PERIOD Lower Red and Mottled Sandstone. If the sub-aerial origin of the Bunter, as is now generally accepted, be correct, we might expect to find a varied distribution of the sediments ; especially would this be the case with the wind-borne deposits, to which some geologists consider a large portion of the Lower Mottled Sandstone may be directly or in- directly attributed. To the west of Wolverhampton, where this sub- division appears at its best, it reaches a thickness of 300 feet ; it is only met with locally in North Staffordshire, and is altogether absent on the east side of the South Staffordshire Coalfield. In the Wolverhampton area the strata consist of sandstones of the most varied hues, ranging from yellow through brown to bright ver- milion. Here also the remarkable false-bedding or ' oblique lamination,' characteristic of the sub-division, is admirably exhibited in a road cutting near the entrance to the lower town. Whether this be due to currents of water or wind the general roundness of the sand particles must be attributed to wind action, for no other agency is considered to be capable of rounding small sand grains, while it is one of the characteristic features of the desert sands of to-day. 1 Owing to their soft nature the rocks are generally denuded into broad valleys, but in the interesting escarpment of Kinver Edge the top beds have been hardened by a calcareous cement, and overhang a deep valley excavated in the underlying softer portion. The ease with which the stone can be quarried has been taken advantage of by the inhabitants of Enville and Kinver, the neighbourhood of these villages showing numerous rock houses, of which those cut out of the sandstone of Holy Austin Rock are the best known. Bunter Pebble Beds. The strata of this sub-division are well developed in the north and south, where they hem in the Carboniferous formations against which they abut, sometimes with a faulted junction, but more frequently unconformably superimposed. They consist essen- tially of coarse false-bedded sandstones, through which pebbles of vein quartz and other rocks are widely scattered or are massed together with little or no intervening matrix, forming beds of shingle sometimes over 50 feet thick. At their outcrop the sandstones and conglomerates are usually incoherent, but in wells and borings the matrix is often highly calcareous, when the rock is intensely hard and much dreaded by well-sinkers. In the shingle beds the pebbles are of all sizes up to or slightly exceeding that of a man's head. The majority are quartzites white, brown, yellow or liver-coloured ; others consist of well rounded fragments of Mountain Limestone, chert, grits of various Palaeozoic 1 For our knowledge of desert conditions the student is referred to Das gesetz der Wtistenbildung, by Professor Walther (Berlin, 1900). 20