The Geology of North-West Cumberland

231 THE GEOLOGY OJ! NORTH-WES'r C UMUERLAND. By T. V. HOLMES, F.G.S., President. ( Read Jul.,! so; 1889.) I .- THE CA RBONIFE ROUS, P E RMIAN-TR[ASSrc, AND L IASSIC R OCKS. It is obvious, on glancing at a geological map, th at t he Carboniferous rocks of this district encircle t he Siluria n strata of t he Lake Country, and are t hemselves encircled by the P ermian-Triassic beds. They consist of beds of limestone, sand stone, shale, and coal, thick limestones being found only among t he lowermost beds of the series, in the high ground ju st outside the mountain country. There th e fells rise to a heigh t of 1,000 t o 1,200 feet or more, while as we approach the Solway t he average height of the gl'ound gradually diminishes. On the day of our ascent of Chalk Beck we shall begin our walk on th e St. Bees Sandstone at a hei gh t of about 200 feet above t he sea, and ar rive before th e end of the day among th e Carbonifero us Limestones and other beds of Warnell F ell at a height of be t ween 900 and 1,000 feet. Chalk (Shalk, Shawk, or Choke) Beck affords an admirable and almost continuous seri es of sections in th e Carboniferous strata intermediate between the lowest beds, in which t hick lim estones predominate, and t he Coal-measures or upperm ost division. It will be found that, though there is lim estone of Carboniferous age near t he old lim e-kiln, ju st above the spot at whic h the Carbon iferous-Permian-Triassic junction is seen, no more band s of limestone are visible nearer than a spot ju st below the house called Ninegills, about t hree miles high er up t he stream, th e measures seen consisting of sandstones and shales. These beds vary in the direction of their dip fr om about 10° north of east to 10° east of north, th e amount being ofte n high. Th eir colour varies, hut is frequentl y reddi sh or purple-grey. At Ninegill s a fault ranges across the Beck in a north-west and sout h-east direction, having It downthrow to the south-west , so t hat while from the P ermi an- Triassic boundary V Ol•. XL , No. 5. 16 232 T. V. HOLMES ON THJ<: GE OLOGY OF to Ninegills we have been gradually traversing lower and lower beds, we are,' after crossing this fault, on beds geologica'!ly higher than those a few yar-ds down t he stream. These high er beds above Ni negi lls are cons iderably r edder in tint t han those ju st below the house, t houg h not more so th an the measures a mile or mor e nearer t he P ermian-Triassi c juncti on. On getting on to the high common, a li ttl e beyond the head of Chalk Beck , indications of many old coal-workings may be seen. Hutchinson (Vol. ii, p. 390) quotes some r emarks by a r esident at Caldbeck on the Warnell F ell coal, fr om which it appears that t his coal was worked in a pit th ere, where it was found at a depth of 5St fathoms and wa s 16 inches thick. The following is t he section given, reduced to feet :- Thickness. Depth. Clay 60ft. 60ft. Day fre estone metal 24ft. 84ft. Day fre estone ." 84ft. 168ft . Day freestone metal 84ft. 252ft. Day lim estone ., . 9ft. 261ft. :Main limestone metal ... 33ft. 294ft. .Main lim estone... 12ft. 306ft . Coal freestone ., . 18ft. 324ft . Grey-beds and metal 9ft. 333ft . Coal Ht.4in. T he term " metal" means shale. In thr ee boreholes on the ' tVat-nell E state made in 1888, one 29 feet 6 inches deep , anothe r 85 feet, and a third 105 feet, neither coal nor Jimestone see ms to hav e been met with . At Den ton H olme Colliery, Sebergham (E ngine P it) the sec tion was :- Ft. In. Soil, clay, and gravel 23 6 Sandstone and shale .. 88 0 Hard, grey limestone .. 13 4 Sandstone and shale ;.. 17 6-142'4 Coal 1 8 These sections are given both to illustrate the ave rage thick nesses of the coals which have been worked on this ge ological NORTH-WEST CUMBERJ,AND. 233 horizon hereabouts and the nature of the beds associated with them. But one thin limestone band occurs in each of the two coliieries. The lowest Carboniferous beds in the neighbourhood of Caldbeck, those in which thicklimestonespredominate, are so much dislocated by faults and obscured by drift that any given bed of lime stone is with difficulty traced for more than a mile, if so far. For example, if on arriving at the common a little be yond the head of Chalk Beck we proceedin a south-easterly direction, in order to inspect the thick limestones about Park head before descending to the village of Caldbeck, we find below the Parkhead Limestone two other massive beds of that rock, which make bold escarpments on the fine hillside between Parkhead and the stream called the Caldbeck. But to get to the village of Caldbeck we must go from Parkhead, not III a southerly, but a south-westerly direction, for a distance of about a mile. However, instead of cross ing, as might be expected,the thick limestones below that of Parkhead, we find no signs whatever of their existence, such beds as are visible being sandstone and shale, while here and there old coal-work- 234 T. V. HOLMB S ON THE GEOI.OGY OF ings, such as we sa w on the top of "Varnell F ell, appear. In short, a fault, ranging about N.N.W. and S.S.E. , with a down th row to the west , crosses t he hillside, and th rowing down the limestones some distance, g ives us at th e sur face in the ir stead, measures such as those whi ch overlie the lim eston es on t he top of W al'llell Fell. The sudden di sappeara nce of the limestone terraces on the hillside is well shown fr om the r oad between Caldbeck and H esk et Newm arket, which commands a fine view of t he bold hillside nor th of the stream. Th e most common fossils in the limestones are encrinites; but in some a spec ies of Producius is very abundant. The experience gained in Chalk Beck, to the effect that lim e stone beds are few and thi n.as we ascend in the series, is one that would be confirm ed should any other route be taken from the low ground near the Solway to the Limestone F ell s. I have already stated t hat though we started from the Perm ian-Triassic juncti on at Chalk Be ck, the upper-most Carboniferous rocks there visibl e are on a lower geological horizon than the measures of the Coalfield of the coas t between Whitehaven and Maryport, whi ch forms a narrow belt of country south of t he Permian-Triassic area about D earham, Bl enn crhasset , and Mealsgato. The north -easterly prolongation of t his coalfield, fr om Dearham to Meal sgat e and Bolt on-Low H ouses, is du e to the existence of a line of fault, ran ging in a uort.h-east er-ly and sout h- westerly directi on, a little nor thward of Plumbland , 'I'or-penho w, and Boltongate, wh ich has a clown th row to the nor th-west , The effect of this faul t may be t hus pointed out. W e have seen t hat in Chalk Beck there is a vast t hickness of beds of sandstone and shale, with scarce ly any limeston e, bet ween th e t hick lim eston es of the fells and the P ermian-Triassic boun dary. Now if we t ravel five or six miles westward of the up per part of Chalk Beck we come to Catlands Hill, where thick Iimestones predominate. But in stead of a series of rocks such as we found in Chalk Beck , directly north ward of Catlands Hill we have collieries in whi ch are, or were, worked the thick coal-seams of the Coal-measures proper, the intermediate seri es exis ti ng in th c Caldew an d in Cha lk Beck ceasing to appeal' at t he su rface at all. Cons ider ing th e shortness of th e distance betw een Chalk Beck an d Ca tlands, and the great thickness of this inter mediate series, it is obvious that NORTH-WEST CUMBERLAND. 235 the existence of a line of fault of great magnitude is the only agency which will account for the state of things observed. (See Fig. 3.) .l3olLon-.£oH' .lhFe.f· t N. I I I I c f a..C t.t:nu.fwH4 b.BecIo in.- C/ud.U3ed:.., c adnua..sure.J, d.J:~ee.s Sand.rOJne,fllud.U· }'IG. 3.-Diagrammatio Section from Catlands Hill to Bolton-Low-Houses. I need say nothing about the Coal-measures of the White haven and Maryport Coalfield as regards the thicknesses of the coals worked there, or the average distances between those of most repute; but there is a certain bed which we shall see between Whitehaven and St.

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