BELEMNITES FROM THE CLAYS EXPOSED ON THE FORESHORE AT SOUTH FERRIBY, LINCOLNSHIRE.
By T. SHEPPARD, M.Sc., F.G.S.
For some time local geologists have known of a deposit of dark grey clay on the foreshore at South Ferriby, Lincolnshire, exposed about mid-tide- mark between the jetty of the Ferriby Chalk Quarry, and the old Hall, rather towards the latter.
About twenty years ago a series of septarian nodules, thoroughly embedded in this clay, was exposed, many of them showing glacial striation from east to west, on the top, so that they had evidently been near the surface during the Great Ice Age.
In the vicinity of these nodules belemnites have always been plentiful on the beach, and from their fresh condition it seemed evident that they had been washed out of the adjoining clays.
In addition to the belemnites, quite large numbers of small ribbed Ammonites, remarkedly like those from the Speeton Clays, have been found, and examples of Ostrea dilatata (a typical Kimmeridge form; in the possession of Dr. Walton and Mr. Sheppard), and Exogyra sinuata (a typical Neocomian oyster, in the possession of Mr. Sheppard) indicate that at least two different horizons in the Cretaceous and Oolitic Series may be represented in these small outcrops of clay at South Ferriby.
A little to the east of this exposure, and nearer to the chalk pit, on the beach, are sections of Lower Chalk and Red Chalk, with their typical fossils, and in some cases the beds here are almost perpendicular and in others at an angle of about 45 degrees, doubtless due to the squeezing-out action of the weight of the Lincolnshire Wolds at this point. Bearing this in mind, it is quite possible that the clay beds referred to may not strictly be in their proper stratigraphical sequence, but are mixed.
When it is remembered that the Speeton Clay at Speeton and Knapton is a typical dark-coloured clayey deposit, which so far as we know has no exposures between the northern end of the Yorkshire Wolds and the Humber, and in Lincolnshire a few miles south of the Humber the deposit is in part a ferruginous sand- stone in part clay, in part limestone, it seems clear that considerable differences in the mode of deposition must have occurred between Speeton and Lincolnshire, and if it is proved that some of the clays on the Lincolnshire Shore of the Humber are similar in character, lithologically, to the clays at Speeton, and of the same horizon, then it is evident that the great difference which .occurs in the nature of the deposit must have taken place within a few miles, namely, between South Ferriby and Caistor.
It seemed desirable therefore to prove definitely the nature of the clays exposed at South Ferriby, and in order to help in this Mr. J. W. Stather invited interested members to his house. There were present besides Mr. Stather, Messrs: C. Thompson, F. F. Walton, W. S. Bisat, W. C. Ennis, W. H. Crofts, R. Davy, Simpson, and T. Sheppard, most of whom brought with them the Belemnites they had collected from this site.
Mr. Stather had prepared a diagram which was placed upon the table showing the various Belemnite zones as worked out by Mr. C. G. Danford in his paper on " The Belemnites of the Speeton Clays," printed in The Transactions of the Hull Geological Society (vol. vi, pt. i, pages 1-14), and upon each zone he had placed the actual Belemnites identified and named by Mr. Danford (which were in Mr. Stather's collection), the blanks being filled by the actual figured specimens in the Danford Collection which were lent for the purpose by the Hull Museum authorities.
Many of the geologists present had spent a considerable time in investigating the Belemnite fauna of these clays, and the collections were carefully examined, specimen by specimen, with, as far as it was possible to judge, the following results; the actual specimens mentioned being in the possession of Messrs. Ennis, Davy, Walton and Stather, who numbered them in case question arose in the future as to identification: .....
Bel. abbreviatus (i.e., Pavlow's breviaxis).
8. Bel. subquadratus Roem.
9. Bel explanatoides, Pavl.
11. Bel lateralis Phill. .
12. Bel iaculum Phill.
18. Bel brunsvicensis Stromb.
19. Bel jasikowi Lahus.
20. Bel speetonensis Pavl. .
21. Bel, absolutijformis Sinz.
In examining the different collections, some of which were obtained many years ago, others a few years since, others quite recently, it seemed obvious that there was a facies characteristic of each particular period, that is to say in any collections made twenty-five years ago, it was apparent that one particular species was predominant, in another made ten years ago a different species, whereas at the present time still another species is predominant. This is what might be expected as a result of gradual erosion taking place from one bed to another.
The result of the examination seemed to suggest that various beds in the Kimmeridge and Speeton Clays at Speeton were also represented in situ at South Ferriby, under similar lithological conditions in each place. However, the investigation is still being carried on, by the aid of a grant from the Geological Society of London, and
we hope to give further particulars later.
Copyright Hull Geological Society 2016