TRANSACTIONS OF THE HULL GEOLOGICAL SOCIETY

RECENT SECTIONS IN EAST YORKSHIRE GLACIAL BEDS.

T. SHPPARD, M.Sc., F.G.S.

 On one of my first geological excursions with a party of Yorkshire naturalists along the Holderness coast, I was fascinated by the number of erratic blocks and the wonderful stories of their origin which were told to us by the late S. A. Adamson, of Leeds, and Dr. Harker, who is still with us. I well remember carrying, for miles, a weight of specimens which today I should not like to carry for many yards. What impressed me also was the statement made by the then Vicar of 'Patrington, the late Canon Maddock, that unfortunately he was living on Boulder clay which could have no interest to anybody. Previously he had resided in Sussex, where the chalk and its fossils interested him.

The statement that glacial deposits were uninteresting, amazing as it was to me then, would be still more so today. Led by Professor Kendall, the late G. W. Lamplugh, local geologists, and a whole army of others from different parts of the country and abroad, we have examined the wonderful series of glacial beds which exist in the East of Yorkshire, and no doubt the key to our knowledge of what happened in England during the great Ice Age is to be gained by an examination of the drift deposits of this area. The buried cliff extending from Hessle to Sewerby, the fine moraine, transported masses of Speeton clay lifted on to the top of Flamborough Headland; the wonderful sections in the basement Boulder clay, the purple Boulder clay and the Hessle clay, seen to such excellent advantage on the coast, and the fine series of gravel deposits in Holderness, all assist in giving facts relating to the various changes which took place in the more recent of our geological epochs.

In addition to the sections exposed by the action of the North Sea, various railway cuttings and pits for the supply of gravel for building and other purposes, have enabled us to get a very clear idea of the strata resting upon the chalk. Particularly in the years since the war, new sections have been made and old ones have disappeared.

The gravels in different areas, as with the different beds of Boulder clay, contain shells, mammalian remains, and erratic blocks, which vary in different districts.

In our young days we used to sing about the 'ever- lasting hills,' but recent experience shows that –

In my 'Geological Rambles in East Yorkshire,' which I published more years ago than I care to remember, I gave an illustration of Brandesburton Barfe, a large rounded gravel mound in central Holderness, a favourite hunting ground for derived glacial shells, erratic blocks, and an occasional mammoth tooth. Today the hill has disappeared from the landscape, having been carted away piece-meal by the Beverley Corporation, which has mixed the gravel with Hull-made cement, and in this way has housed a large number of its inhabitants. In the same vicinity large and important sections have been made in other hills, and at Paull are large holes in the glacial mound which originally diverted the course of the stream from flowing due east, to south-east.

The well-known Burstwick Gravel Pits have been considerably extended in many directions, resulting in much of the hilly ground here being reduced to the level of the surrounding fens.

A study of these various beds gives interesting results. In The Naturalist for February, 1922, I gave details of some recent glacial sections in Holderness, and then described deposits at Skirlaugh, Coney Garth, Leven, Keyingham, Catwick and other places.

In Clement Reid's 'Geology of Holderness', published in 1885, are some of the first detailed descriptions of the Holderness gravels, which that author considered to be interglacial, as they certainly rested upon Purple Boulder Clay, and for the most part were covered by the less compact foxy-red Hessle Boulder Clay, the erratics in each deposit indicating a different source of origin.

More recent workers, however, following Lamplugh, consider that the gravels were deposited during an interval between the oscillations of the ice front of the great North Sea glacier. His experience of glacial phenomena in Alaska, and other places, showed that such oscillations had actually taken place; and, in Spitsbergen particularly, Sir Martin Conway and Professor Garwood have described glacial mounds containing erratics, Arctic shells, and bones of whales and other animals, which had been over-ridden precisely as our Holderness mounds seem to have been.

With regard to the mammalian remains in the gravels, recent excavations have produced quite a large number, some from localities where hitherto they have not been recorded, as, for example, at Paull and in one of the Brandesburton pits. It would seem that these bones of extinct animals occur fairly deep down in the gravel, and while reindeer, rhinoceros, walrus, seal, bison, mammoth, and animals of that type have been identified, by far the greater number of bones found in recent years have been of Bos primigenius, or great ox, the horn cores, leg bones and vertebrae of which seem particularly numerous, and indicate that this species was fairly common in the neighbourhood during the glacial period. It is possibly due to modern methods of quarrying, which enable the sections to be cut deeper, that more bones are nowadays being found.

These additional sections have also assisted our investigating an interesting problem first raised by Prestwich in his paper dealing with the Holderness Gravels, so long ago as 1861. This relates to the occurrence in tremendous profusion of a freshwater bivalve, Corbicula (or Cyrena) fluminalis. This species occurs to-day in the Nile and some Asiatic rivers, but has long been extinct in this area. In the old Kelsey Hill Pit,

excavated for the Hull and Barnsley Railway, the species occurred literally in thousands. It is also numerous in the adjoining quarry at Burstwick. The shell itself is fairly thick, is almost invariably found whole, and has clearly not been transported any great distance. This led to the assumption that it probably occupied the old estuary of the Humber, which before the Ice Age ran out to sea across Holderness where Withernsea now is. The difficulty here, however, is that the shelly gravels rest upon purple Boulder clay, left by the ice which filled the Humber and should, therefore, have buried the Humber fauna beneath the clay! On the advance of the ice, marine shells dragged from the bed of the North Sea were commingled with the fresh-water Corbicula, and the two occur together in the gravels, with pholas-bored stones and other evidences of marine life. An odd shell of Corbicula has been recorded in the North Lincolnshire gravels, and at Paull, but for many years East Yorkshire geologists have been endeavouring to confirm these records, without result.

In the new sections at Paull, which are particularly shelly in patches, the molluscan remains vary from mature oysters to Bullae and other of our smallest and most fragile shells. Here, however, after hours of search on the part of several local geologists, not a single fragment of Corbicula has been seen. This is all the more remarkable when it is borne in mind that the gravel at Paull is practically on the same line, east and west, as the old course of the Humber, and is only a distance of three or four miles from the other beds where the shells occur so abundantly.

Recent engineering operations at Filey, towards the north end of our fine glacial sections, and at Salt End, the southern extremity, have provided an interesting problem with regard to the former levels of this country before, during, and since the Great Ice Age. The fact that the pre-glacial chalk-strewn beach at Hessle, and near Sewerby, the southern and northern extremities of the pre-glacial cliff line respectively, are practically on the same horizon as the present beach, has always led one to assume that there had been no great changes in the levels of this country since pre-glacial times. (note - A record of a so-called raised beach at Cat Nab, near Saltburn, was proved by Lamplugh to be of the kitchen-midden type, and of no geological significance.)

During the past few months a boring has been put down near the Gasworks at Filey, which seems to have been placed precisely in the centre of a very deep ravine, which, in pre-glacial times, flowed east into the North Sea at Filey; probably this was the old course of the Derwent. The advancing glaciers entirely filled this ravine with drift, and in the recent search for water, this drift-filled hollow was penetrated to a depth of no fewer than 189½ feet from the surface, and as this is 138 feet above sea-level, it means that if the borings can be relied upon, 71½ feet of this ravine occur below sea-level. This is a much greater depth than would ordinarily be the case by ordinary river erosion, consequently the evidence of this boring and of an adjoining boring recorded by the late C. Fox Strangways, indicates that formerly the land at Filey was at a higher level than it now is.

With regard to Salt End, the London and North Eastern Railway Company at present is dredging the Humber near the shore there. The dredgers are removing the different deposits foot by foot, so that by examination of the material brought up, it has been possible to prepare a geological section of the deposits. I have recently had sent to me a large number of hazel nuts taken from the peat at Salt End at a depth of 35 feet below O.D. I understand that the dredger is also bringing up Boulder Clay in patches, so that it would seem at this depth the peat has occupied hollows in the glacial beds, as indeed it does on a higher level in other parts of Holderness. In view of the importance of this depth, I have made particular enquiry from the Engineering staff of the Railway Company, and I am assured that the measurements can be relied upon. This being so, it is to be inferred that the land level when this peat grew must have been considerably higher than it now is. In view of this, the post-glacial changes that have taken place in this district in comparatively recent times must have been on a much more gigantic scale than had previously been supposed. This is, of course, assuming that the peat is in situ, but as the site is near the out-fall of an old fleet drain, one must be a little cautious before forming very definite conclusions.

I am informed that the section, as dredged, consisted first of 2 feet of dirty gravel, then 3 feet of greasy black clay, followed by 5 feet of Boulder clay, and 14 feet of clean sand; this section beginning at 5 feet below low water spring tides. When dredging in the Alexandra Dock, which is not far away, peat is occasionally brought up in the buckets from a depth of 22 feet below O.D., a difference of 13 feet in depth between Salt End, which is only a distance of about 2½ miles away.

 Mr. J. W. Stather and others have shown that by examining the moorlog and associated deposits dredged from the bed of the North Sea by trawlers, a quite modern fauna and flora existed in marshy deposits over a great part of the North Sea area in comparatively recent times, and probably that sheet of marine water is not so old, by any means, as has usually been supposed.

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