Page:VCH Lancaster 1.djvu/51

GEOLOGY The Third Grit.—This consists of two, sometimes three, beds of grit, flagstones, and shales, the lowest bed being especially massive and at times passing into conglomerate. The grit occurs at Belmont between Turton and Rivington, where it forms the cliff known as 'the Ratchers,' and then runs northwards, being again seen in Roddlesworth Brook below Tockholes. Along the Pendle range two and sometimes three beds of grit divided by shales are met with, the basement bed being especially coarse or passing into conglomerate. A good section of this bed is exposed in a cutting of the Lancashire and Yorkshire Railway at Brown Hill, about two miles north of Blackburn. Here the beds are violently contorted, owing to the proximity of a fault passing from N.N.W. to S.S.E.

Contorted Beds in Clitheroe and Blackburn Railway.

The Third Grit is exposed at various places along the Sabden valley north-eastwards to Colne and Foulridge, and down the eastern side of the coalfield by Widdop and Stiperden Moor to the heights above Littleborough, where the top bed is pierced by the Summit tunnel on the Lancashire and Yorkshire Railway, and southwards to Stalybridge. At Ramsden Clough and Clough Foot in Dulesgate, a thin coal and shale parting occurs in the top bed of grit. A similar thin coal seam lies under the grit at Black Clough.

The Third Grit is well exposed at Gauxholme in Dulesgate, and along the Irwell valley between Rawtenstall and Waterfoot in Rossendale. In the latter district it contains two thin coal seams. Below Rawtenstall it forms the floor and sides of the Irwell valley from Holden Wood to Ramsbottom, where it can be seen at several places along the railway. Shuttleworth Moss and Harden Moor are capped by the upper beds of grit.

Shales below Second Grit.—These shales have not received much attention, except from the late E. W. Binney, who described them as the 'Holcombe Brook Series,' at which place they contain three thin seams of coal, one being 15 inches thick and formerly worked at Cheeseden Brook. Similar thin coals have been found in the shales in the Foulridge district, notably at Laneshaw Bridge, and on Pule Hill on the eastern side.

Second Grit, or Haslingden Flags.—This valuable series reaches its highest development in the Rossendale area and the Whitworth and Facit valleys. It consists of fine grained sandstones well bedded and exceedingly hard and durable. The utilisation of these beds has increased considerably during recent years, so that over large areas on the Brandwood Moors, Cowpe Moss, and at Back Cowm, the hill crests are being studded with great quarries. In the Rossendale area the Haslingden Flag Rock consists of three beds of grit, averaging 36 feet in thickness, and separated by 30 to 100 feet of shale.

Away from this particular area the beds deteriorate in character, and even pass into 'raggy' shale as at Newchurch-in-Rossendale. In the Pendle Range they approach the overlying Rough Rock, being only separated by 15 to 20 feet of shale. On the eastern side they are feebly represented. North of Rivington the series is well developed and can be seen in the valley below the Anglezark Lead Mines on the western and southern slopes of Rivington Pike, and at Tockholes, and in the river Roddlesworth.

First Grit, or Rough Rock.—The Rough Rock forms the highest member of the Millstone Grit, and may usually be recognized by its coarse character and the presence of a thin coal seam in its upper portion. It is not very useful as a building stone, being often soft and incoherent and readily breaking down into a coarse sand. For this reason it is sometimes called the 'Sandrock,' and the coal seam the 'Sandrock Mine.' More commonly the latter is styled the 'Feather-Edge' Mine. Quartz pebbles occur abundantly in the beds, and hand specimens of the latter may at times be mistaken for a conglomerate. The Rough Rock forms a capping to many of the hills in the Millstone Grit areas, and hence can be easily traced around the coalfield. From Hoghton Towers, where it forms a lofty hill and is estimated at 400 feet thick, to the south slopes of Pendle and eastwards to Colne, it is well in evidence, the latter town being built on a ridge of this rock. Good exposures can be seen in the river bottom on the eastern side of the town. In the Anglezark area it is found at Pike Low, Withnell, and Stanworth Edge, and crops in massive beds at the top of Blackburn Park. At Winewall, near Colne, large quarries are opened in it, and south from this point it forms a hilly crest by Entwistle Moor, Shedden Edge, and Stiperden Moor to the Portsmouth valley at Red Water Brook. On the opposite side of the valley it is continued along the side 11