The Geology of the Districts Around Settle and Harrogate
Total Page：16
File Type：pdf, Size：1020Kb
27 THE GEOLOGY OF THE DISTRICTS AROUND SETTLE AND HARROGATE. By P ER C Y FRY I-:EI\DALL, M.Sc ., F. G.S. f R ead J llly tst, 19/0. ) Some adva nce cop ies of this Pape r were printed and Iss ued to Memb ers, in connection wit h the Long E xc ursion, in July- August lase. T he Paper is now rcp rtnted with a, few slight alterations. COXTE:\TS. PA GE !.-[NTROU l ICT IOK • • 27 [I.-PRE-C A MUlH A N R OCKS • 30 III.-LOWER P ALA':0 7.0IC R OCKS 3 1 I V.-CARBO:-;IF E ROl :S R OCKS- Basement Beds . 35 Carboniferous Limeston e . 36 Yoredale (Pendleside) Series . 37 Millstone G rit 4° Coal Measu res 42 V .-PER~1IA;\I R OCKS 44 VI.-ICNEOlTS ROCKS . 49 VI I.-GLACIAL PH n :OMENA 5° V III .-TECTO NICS 53 I X .- R EFERENCE S 5R I.-I NT R OD{; CTIO~. H E principal districts to be visited," na mely, the western T dales ab out Sett le and th e mid dle region of Nidderdale, constitute two repr esentative portions of a west to east traverse of the Pennine Chain, which, both by its resembl an ces and contrasts, form s an interesting and useful com ple ment to the st udies made by th e members of th e Associat ion of the northern sections near Appleby, visited under Dr. Man 's guidance in 190 7, and of the southe rn terminati on visited in 19°3, when Dr. Wheelton H ind led an excursion to North Staffordshire, an d in 190 4, when Dr. Arno ld Be mros e conducted an excursion to North Derbyshire. The Pennine Chain consists essentially of a great fold of wide amplitude and generally 'low gradie nts extendi ng from th e T yne-Irthing depression, where it is abruptly tru ncated by faulting, to the Trent valley, where its greatly denuded arch falls away below an unconformable cover. Its western edge is cut off for long distan ces by a great system of dislocations, but on th e cast it dips gentl y beneath the unconformable cover of Magnesian Limestone. In the section entitled " Tectonics " som e more det ailed dis cussion of the structure ofthe Chain wi11 be attempted, bu t for th e present purpose it will suffice to point out that th e western fractured bo undary is interrup ted for a distan ce of over 30 miles, namely, from the neigh bourhood of Settle to the Saddleworth '" Th is refers to the Lon g: E xcursion of I 9 1C'. 28 PERCY FRY KENDALL ON THE GEOLOGY OF Valley, near Oldham, by a folded region consisting of a pair of great S.W. and N.E. folds-the Clitheroe and Rossendale anti clines-with the intervening syncline of the Burnley coalfield. The western area to be studied lies on the northern boundary of this folded region, and several days will be devoted to the examination of the faults by which it is limited. The Dales and Craven Highlands, near Settle, consist of a dissected plateau of nearly horizontal Carboniferous rocks that has been deeply trenched by streams such as the Twiss or Greta, Clapham, and Austwick Becks, the Ribble, Aire, and Wharfe. These streams have in several places cut through the Carboniferous strata and exposed in a series of small inliers the underlying Archreau and older Paleeozoic Rocks. The massive Great Scar Limestone forms an elevated plateau upon which are seated the great elongated piles of the Yoredales with, in each case, a capping of Millstone Grit. These hills are the most mountain-like of the Pennine system, and the stately forms of Penyghent, Whernside, and Ingleborough form an imposing triad, whose geological structure is displayed in bold scars and slopes with the clearness of a diagram. To the southward the scenery abruptly changes at the line of the Craven Faults, and the knobbed and undulating country of the folded strata stretches away to the middle course of the Ribble, with the Yoredale and Millstone Grit escarpment of Pendle for a background. The day spent in Wharfedale will disclose another type of scenery characterised by a remarkable range of gigantic knolls of limestones lying at the foot of another escarpment of Millstone Grit. The Harrogate country stands on the edge of the eastern slope of the Pennines just where the Carboniferous rocks descend below the Magnesian Limestone. The great line of folded country comes through here from the west. Harrogate itself is on the edge of a steep-pitched anticline, faulted along its north-western flank, bringing up the Yoredale rocks from beneath the Millstone Grit. Between this place and the Magnesian Limestone outcrop the surface has been etched out of the eroded plain upon which the Permian rocks were de posited. The Nidd Valley, in the region to be visited, presents two strongly contrasted aspects, the dividing line being defined by the Nidd Viaduct of the North Eastern Railway. The western portion is a broad valley with fairly steep sides, the normal aspect of a stream flowing through a Millstone Grit country, while on the east the valley has a gorge-like aspect whether the country con sists of Millstone Grit or of Magnesian Limestone, and this feature, as will be shown in a later chapter, is related to the glacial history of the district. THE DISTRICTS ABOUT SETTLE AND HARROGATE. 29 While all parts of the area to be covered by the excursion have received a full share of attention, the Western Dales and Highlands have, by their more varied structure and magnificent scenery, proved the most inspiring to geologists. A catalogue of the workers in this field would enumerate nearly all the great names of the first half-century of English geology, among which would be found those of William Smith, Adam Sedgwick (a Dalesman himself, with a type of physiognomy very characteristic of this region), Murchison, John Phillips, and many others. It is almost invidious to select from the names of contemporaries, but the brilliant researches of Prof. Hughes, Mr. Tiddeman, and Dr. Man have given to them, and to the place of their labours, a claim to grateful remembrance among geologists. Nor need the rising generation of geologists fear to find an exhausted field-problems grow out of problems, and the studies of the older Paleeozoic rocks, placed upon a sound basis by Prof. Hughes and Dr . Marr, are being continued in our own time by their disciples. John Phillips did not say the last word on the Marine Carboniferous, and Dr. Wheelton Hind, Mr. Cosmo Johns, and Dr. Wilmore have found more to do than the mere crossing of t's and dotting of i's. Mr. Tiddeman made this region the subject of a paper on Glacial phenomena that has served as a model and a basis for Glacial work all over the country; yet, even in the field that he worked, with results of inestimable value to all later students, much may still be done. STRATIGRAPHICAL SEQUENCE IN THE SETTLE DISTRICT. Recent . Alluvium, Peat, Shell Marl, etc. QUATERNARY. Plei f Boulder Clay, Sands, Gravels. { eistocene .) Cave Deposits. Penni i Upper Breccias and Sandstone. errman .. 'I Lower Breccia. Coal Measures. Millstone Grit. UPPER PRn1ARY.J Yoredale and Pendleside Series. 'l Carboniferous. Carboniferous Limestone. Basement Beds Homogenetic. Polygenetic. iGrits of the Rough Lands. Studfold Sandstone. Horton Flags. Austwick Grit. ~~ls:\~ira~e~'l~gnsd Silurian. 'lI Red Shale). LOWER PRIMARY, Graptolithic Mudstone (with Spen- gill Limestone and zone of Phacops elegalls). Conglomerate or Calcareous Grit. o d .. I Bala Shales (Ashgill Shales). r ovician . 1Coniston Limestone. 1Pre-Cambrian. Ingletonian Series. 30 PERCY FRY KENDALL ON THE GEOLOGY OF SEQUENCE IN THE HARROGATE DISTRICT. \ Recent • Alluvium, Peat, Shell Marl, etc. \ Tufa. QUATERNARY. PIeIS . t ocene 1 .I Boulder Clay, Sands and Gravels. ' upper :\larl. \ C pper Maguesian Limestone. '1' :\11ddle :\Iarl, Lower Magnesian Limestone. [p"mb" Lower Marl and Sandstone. r f (Plumpton Grit. "1 I) Shales. G~\ 1Cayton Gill Shell Bed. Millstone .I, Shales. UPPER -, Grit. 1 Follifoot Grit. PRDIARY. Shales. Carboniferous. +th (Kinderscout Grit 111 Grit. ] three beds. ( Shales. J Roadstone. Yoredale Rocks. < Shales. J Grit. ~ Shales. II.-PRE-CAMBRIAN ROCKS. The oldest rocks of the Settle District are, by common consent, admitted to be the series of hard, gritty, conglomeratic and slaty rocks exposed in Kingsdale, Chapel-le-Dale, and Ribblesdale, forming a belt at least two miles wide in Chapel-le-Dale, and apparently dipping uniformly to the south-west at a very high angle. These were referred by Sedgwick to the Green Slates, and correlated by him and later writers with the Borrowdale Series. The dip of the beds in Chapel-le-Dale has an appearance of regularity, and in the absence of clear signs of repetition by fault ing or folding in any of the exposures seen crossing their outcrop they were estimated to be 10,000 feet thick. It has long been felt that the ascription of this series to the Borrowdale division could be only a temporary expedient, and geologists working in the district were fully prepared for the revision suggested by Mr. R. H. Rastall, who proposed in a recent paper (9)* to refer them to the Archaean system under the name of the Ingletonian Series. Petrologically these rocks are different from any rocks exposed elsewhere in the North of England. The predominant materials are grits, for the most part of a green colour. They consist of angular grains of quartz and felspar, with some mica and occasional grains of quartzite.