Downloaded from http://pygs.lyellcollection.org/ at University of St Andrews on May 2, 2015 VOL. XL] [PART III. PROCEEDINGS OF THE YORKSHIRE GEOLOGICAL AND POLYTECHNIC SOCIETY. EDITED BY JAMES W. DAVIS, P.S.A., F.G.S., &c. 1890- ON THE CHANGES OF THE LOWER CARBONIFEROUS ROCKS IN YORKSHIRE FROM SOUTH TO NORTH. BY J. R. DAKYNS, OF H.M. GEOLOGICAL SURVEY. In order to understand the geology of the country north of the Aire, I will first give a short sketch of the chief features presented by the Millstone Grit and Lower Carboniferous measures, as we follow the beds from Derbyshire to Wensleydale. In Derbyshire the Millstone Grit, as hitherto defined, consists in descending order of four or five well-marked grits, separated by shales, viz.. the so-called first or topmost grit, named also Rough rock from its coarse character ; the second grit, generally a flagstone ; the bold, well-jointed rock of Hathersage Edge and Stanedge, or the third grit; and lastly, the fourth or Kinderscout grit, which some• times consists of two beds. Below the Kinderscout grit comes a thick and variable series of sandstones and sandy shales, the " shale grit" of Farey, which has been generally called the Yoredale or Upper Yoredale grit; and then come shales in which sometimes occur siliceous sandstones, known as Yoredale Sandstones, or Lower Yoredale Grit ; then come calcareous shales; and finally the Carboniferous Limestone of unknown thickness, the upper part of which is thin-bedded and cherty, the lower massive and free from chert. Downloaded from http://pygs.lyellcollection.org/ at University of St Andrews on May 2, 2015 354 DAKYNS : LOWER CARBONIFEROUS ROCKS IN YORKSHIRE. Going northwards this type undergoes great changes ; the second grit is merely a basement bed to the Rough Rock, from which it cannot always be separated ; the third grit loses its massive character in many places ; and other beds of sandstone show themselves amid the shales overlying the Kinderscout grit. In the valley of the Coine there are four sandstones between the Rough or Sand Rock and the recognised Kinderscout grit ; the same is the case in the valley of the Yorkshire Calder ; but in the basin of the Aire the series consists in descending order of the following beds : First, the Rough Rock, which maintains throughout its usual character till it is lost to sight beneath the Permians ; seccondly, a very variable basement bed to the last, consisting generally of flag• stones. Below this comes a series of variable sandstones and shales, sometimes containing as many as fifteen or sixteen distinct beds of sandstone between the Rough Rock and the regular Kinderscout grit. This set of beds may, however, be conveniently divided into two by means of the massive grit of Hallan Hill and Earl Crag, which is continuous with the third grit of Lancashire. It is this rock which, according to the mapping of Mr. Lucas, forms the well-known Brimhain Rocks, near Pateley Brig. Owing to the number of sandstones that have now come in, it is somewhat uncertain what ought to be taken as the top of the Kinder• scout grit; but there is no doubt whatever about the main mass of the bed, for it retains throughout the country its character of a very coarse and massive grit, forming crags and stacks of rock. It is underlaid by a thick but variable series of sandstones with shale partings. As there is ofttimes no definite line of separation between these beds and the Kinderscout grit, we now classify them with the millstone grit, and call them Pendle grits, because they form the chief features of that conspicuous hill. Below them lie the Black Bolland shales, at the base of which comes sometimes what Mr. Tiddeman has called the "Lower Yoredale Grit." In litho- logical character the beds of this grit answer very well to certain hard silicious sandstones of the Yoredale series, known to miners as Dirt. Pot grits. In the neighbourhood of Skipton the Kinderscout and Pendle grits are underlaid by a great thickness of shales con- Downloaded from http://pygs.lyellcollection.org/ at University of St Andrews on May 2, 2015 DAKYNS : LOWER CARBONIFEROUS ROCKS IN YORKSHIRE. 355 taining two well-marked limestones, viz., those of Eastby and of Embsay. Below the shales conies the thick limestone (800 feet seen) of Haw Bank. It is a dark thin-bedded limestone, precisely similar in character to the Thornton limestone, to which it is probably equivalent. It is extensively quarried for road metal in the Haw Bank near Skipton. The strike of the beds south of the Aire is generally N.E. and S.W., the dip increasing westward ; but about the latitude of Skipton the beds bend round so as to strike nearly east and west, with a dip of 20° to the south on Skipton Moor. An anticlinal ranges along Skibeden from Skipton to Bolton Abbey, with a steady dip to the north, and many a fold on the south. Thus the mountain limestone of Haw Bank has been brought up between two ranges of millstone grit hills, viz., Skipton Moor on the south and Embsay Moor on the north. The beds are much faulted and contorted, particularly along the south side of Skibeden. Good instances of contortion are to be seen at Draughton and Wheelam Rock Quarries, and at the Hambleton Rock Quarry : and a fine section of contorted beds is to be seen in Haltongill. The Kinderscout grit of Skipton and Draughton Moors striking east descends to the River Wharf, north of Addingham. Its high southerly dip carries it up the slope of Langbar Moor, its base running just below Beamsley Beacon. It then, under the influence of a branch of the Skipton anticlinal, plunges down northward to the Kex Beck, where the beds bend up again and rise northward to Hazlewood Moor and Bolton Park. Here, on the strike of the Skipton anticlinal, the beds bend over northward, and recross the Wharfe below Laund House. South of this, as far as Bolton Abbey, limestones and shales are seen along the river. The Pendle grits run along the slope of Skipton Moor to Fair• field Hall; and east of the Wharfe are found about Beamsley and Storriths. They have not been everywhere identified on the north side of Skibeden. The general run of the beds on this side is, how• ever, tolerably plain. A set of bold crags marks the escarpment of this Kinderscout grit along Halton and Embsay Moors, Rylstone, Burnsall, and Thorpe Fells. Beneath the western escarpment of the Kinderscout grit, the Pendle grit forms at intervals promontories on Downloaded from http://pygs.lyellcollection.org/ at University of St Andrews on May 2, 2015 35G DAKYNS : LOWER CARBONIFEROUS ROCKS IN YORKSHIRE. the Fell side. It has not been traced further than the northern extremity" of Burnsall Fell. The Kinderscout grit lies in the shape of a synclinal trough dipping eastward ; and it thus occupies with its various members the whole extent of Burnsall Fell, Barden, and Embsay Moors. The rock is well seen along the Wharfe, particularly at the celebrated Strid in Bolton Woods. On the east of the Wharfe these grits rise up in a sort of broken dome, with a quaquaversal dip to form the summit of Barden Fell, marked by the bold crags of Simon Seat. Near these crags, at the very summit of the Fell, more than 1,450 feet above the sea, some pot holes, one of which from its size is called " the great shak," mark the presence of limestone beneath the surface. The grits may be seen in Howgill and in Fell Plantation, dipping steeply to the N.W. into the valley ; but along Skyreholme Beck they turn up and dip steeply to the S.E. From Appletreewick the grits strike north-eastward, underlaid by a mass of shale, from beneath which massive beds of white scar-forming lime• stone rise regularly with a similar strike, as far as High Crag. Here the beds abut against the Craven Fault. The details of the lime• stone country immediately south of the fault are complicated, but the general structure is simple enough. A broad band of limestone stretches across the Wharfe from High Crag to Cracoe in the form of an anticlinal ridge, which between Cracoe and the river runs from S.W. to N.E. Along its N.W. flank we find the limestone dipping N.W., at angles of 40° beneath beds of shale having a similar dip. On the S.E. side the dip is to the S.E. ; but on this side the boun• dary seems to be partly a faulted one, as the lower grits on the flanks of Thorpe Fell are striking nearly at the limestone ; but I shall not insist upon this, as Mr. Tiddeman has recently made some dis• coveries which will throw great light on the structure of the country, and it may turn out that the above-mentioned appearance of a fault is deceptive. I shall therefore merely give a brief statement of observed facts, without drawing any inference from them. The limestone is everywhere precisely similar in external appearance to the massive thick-bedded white scar-forming limestone, which forms the main portion of the carboniferous limestone of the Yorkshire Dales, and is very fossiliferous. It forms five striking hills, more or Downloaded from http://pygs.lyellcollection.org/ at University of St Andrews on May 2, 2015 DAKYNS : LOWER CARBONIFEROUS ROCKS IN YORKSHIRE. 357 less conical, that stand out abruptly from the general level of the ground lying at the foot of the Gritstone Fell.