The Yorkshire Oolites.-Part 1

283 ORDINARY MEETING, DEOEMBER 5TH, 1873. HENRY WOODWARD, ESQ;, F.R.S., F.G.S., &c., President, in the Chair. The following Donations were announced:- " Winchester and Hampshire Scientific and Literary Society Journal and Proceedings," 1870-1, 1871-2; from that Society, " Journal of the London Institution i" from that Institution. "Fugitive Poems," by C. Daubeny, F.G.S.; from James Parker, Esq., F.G.S. The following were elected Members of the Association : Edwyn Godwin Clayton, Esq.; Frank Crisp, Esq., LL.B., B.A., F.L.S., F.Z.S., &c. j Dr. Walter Flight; Henry Fisher, Esq. i Rev. Cosmo Reid Gordon, D.D., M.A., F.G.S.; W. J. Gordon, Esq.; William Abbott Green, Esq., M.R.e.S., F.G.S.; Algernon S. Marshall Hall, Esq.; Edward Jaques, Esq., F.R.M.S.; C. T. Malins, Esq.; C. Gill Martin, Esq. i A. O. Robinson, Esq.; John Ellor Taylor, Esq., F.L.8., F.G.S. The following Paper was read :- THE YORKSHIRE OOLITES.-PART 1. By WU,FRID H. HUDLESTON, ESQ., M.A., F.G.S., &0. INTRODUOTION. In offering to your notice this evening a fewobservations on the Oolites of Yorkshire, I shall be going over ground which has already been well worked, and on which much has been written by eminent geologists. The standard works of Young and Bird, and of Professor Phillips, and the contributions of Williamson, Wright, Leckenby, Morris and Lycett, and manyothers, to the volumes of the Geological and Palreontographical Societies have already largely illustrated this district. It is not, therefore, claimed for the ensuing paper that it contains much matter which is new, or altogether unknown to many of you. PHYSICAL GEOGRAPHY OF THE DISTRICT. The region with which we propose to deal forms a lobe of elevated land occupying the north-eastern portion of- Yorkshire. To the west it presents 8 series of lofty escarpments, overlooking 8 broad Triassic plain; and to the east, a series of mural cliffs, overhanging the sea, which thus present magnificent sections of the strata composing them. This mass of land consists entirely 284 W. II. HUDLESTON ON of Mesozoic rocks, from th e Lias to the Coralline Oolite inclusive. With the Lias we have nothing to do; but your attention is in vited to the ext ensive and vari ed series of beds succeeding th e Lias, which are known as the Yorkshir e Oolites. The group, viewed as a whole, is essentially arenaceous, and this fact must be borne in mind, lest the term " oolites " should lead persons unacquainted with t he district to suppose th at we have to deal with a system principally calcareous. It is true, however, that where limestones are developed they frequently assume a type more or less oolitic. Anything like pure limestones, except in the upper most beds of the system, are rare. Thus, as one walks over th e north-eastern moorland s, their general similarity to Millstone Grit districts is most striking; indeed, it is difficult to avoid th e re flection that we see about our feet the transported mat erial of th e Palieozoic mountains of the North laid out once more in a kind of coal formation, but also, like the Millstone Grit, barren of really useful and workable coal. Another feature of th e system, and one especially applicable to the lower beds, is its extreme irregul arity of development, and th e very considerable difference which exists between the coast sections and those of the inland valleys and great south and west escarp ments, the arenaceous and argillaceous beds of the Lower Oolites being enormously expanded towards the north-east, whilst on th e south they seem to attain their minimum. On th e other hand, in th e south-western parts of our area the limestone beds of all th e formations are, as a rule, better developed, and this applies equally to the Lower and Middle Oolites. E xcluding those portions which lie north of the E sk valley, this Oolitic series may be viewed as forming a sort of elongate d crescent of hig-h g round, everywhere sloping inwards towards a tri angular fiat area known as the Vale of Pickering, the mouth of the crescent or horse-shoe being closed by that portion of the Cretaceous escarpment which faces th e north, and which stretches across it like the chord of an arc. Following up th e idea of the crescent, which, however, is only a rough illustration, as the out line is by no means symmetrical, we shall find that the left hom abu ts against the north-west corner of the Cretaceous escarpment, and, as we shall see subsequently, plunges beneath it, under very remark able circumstances. Commencing froth thi s position, near the village of North Grimston, at the foot of the W olds, th e Oolites may be said to run THE YORKSHIRE OOLITES. 285 in a W.N.W. direction, in elevations from 300 to 580 feet, as far as Newburgh Park, near Coxwold, a distance of 20 miles, the newest beds being always on the N. N.E. or Vale of Pickering side, and the oldest beds always on the S. S. W. or Vale of York side. This portion or limb of the crescent is known as the Howardian Hills It terminates suddenly in the promontory of Beacon Banks, near Husthwaite, and we have a gap in the rim at Coxwold, 230 feet above sea level, where there must be an enormous derangement of the beds, as there certainly is a complete change in the direction of the escarpment.s The escarpment north of Coxwold faces the west, and greatly exceeds in altitude and abruptness the last-mentioned one j bnt here, again, the lowest beds are outside, or towards the Vale of Thirsk, which is the northerly continuation of the great Triassic plain of Yorkshire, whilst the more recent beds dip towards the Vale of Pickering. The Coralline Oolite, for instance, falls from 1,000 feet on Hambleton Moor to 120 feet near N unnington, in the Valley of the Rye (the distance being about eight miles), and then plunges under superior beds. On the Hambleton escarpment, as we proceed northwards, older beds are continually met with, being exactly the reverse of what obtains in the Howardian system, until the Great Kildale Gap is reached, which connects the valley of the Esk with the Triassic plain. North of this great valley some of the Lower Oolites are still to be met with, capping the Lias hills, but these are beyond the dis trict which it is proposed to treat of, and we may accept the Valley of the Esk as the northern boundary of the area under considera tion. Between this valley and the Vale of Pickering, the great mass of the Yorkshire Oolites occur; the watershed of the Humber drainage runs along it, varying in elevation from 1,4.80 feet at Burtonhead to 800 feet at Stow brow, near Peak, on the coast. The length of this mass, measured along the height of land from Ingleby on the west to Peak on the east, is 33 miles. As with the Howardian hills, so also with the Moorland chain, the inner portion consists almost invariably of Coralline Oolite, which is usually viewed as the topmost bed of the system. The excep tions to this will be shown subsequently. These beds have a southerly dip till they disappear under the " so-called Kimmeridge Clay" of the V ale of Pickering. • The passage, through which the Derwent escapes at Malton, is only 50ft. above sea level. 286 W. H. HUDLESTON ON Young and Bird state that about Helmsley and Kirby Moorside the Coralline Oolite dips with a steady slope a little east of south. Eastward of this the dip is southerly for many miles, whilst at Ayton andSeamer the dip is distinctly S.S. W., till the beds are lost sight of in the vale. We have seen that the south-eastern extremity of the Howardian system abuts against the Cretaceous escarpment, beneath which it is lost sight of ; in like manner the right, or eastern extremity of the Moorland chain, abuts against, or rather is cut off by the sea itself, and thus presents a section, as it were, of a mountain chain, which has been eaten back by marine denudation to its present limits. As this section is mainly in the direction of the dip of the beds, the entire Oolitic series, as developed in Yorkshire, is brought under observation. It may be considered as extending from the cliffs of the Peak 600 feet in height, to where the Middle Oolites finally sink into the sea at Filey Brigg, a distance of 17 miles. In this exposure, commencing from the north-west, we find the Oolitic group resting on the beds which succeed the Alum-shale, and may trace it continuously, with now and then an interruption from fault or intruded drift, as far as the base of the Coralline Oolite; and even a portion of the Coralline Oolite itself is displayed on Scar borough Castle Hill, having been let down by a fault, and apparently thus preserved from destruction. The general dip along the coast from Peak to Filey Brigg is south-east; but in Gristhorpe Bay it is S.S.W., the beds there pointing towards the Vale of Pickering, as seems to be invariably the case wherever they approach within a certain distance of that region. The Chalk escarpment, whose eastward prolongation terminates in Flamborough Head, completes the circuit of the Vale of Pickering.

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