On the Red Chalk of England

Part 1

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Every effort has been made to replicate this text as faithfully as possible.

Italic text has been marked with underscores. Superscript letters are preceded by ^. OE ligatures have been expanded.

The Geologists' Association.

THE RED CHALK OF ENGLAND.

THE REV. THOS. WILTSHIRE, M.A. F.G.S. PRESIDENT OF THE GEOLOGISTS' ASSOCIATION.

A PAPER READ AT

THE GENERAL MEETING,

4TH APRIL, 1859.

LONDON: PRINTED FOR THE ASSOCIATION, AND PUBLISHED AT THE OFFICE OF "THE GEOLOGIST," 154, STRAND. 1859.

LIST OF PLATES.

PLATE I.

Fig. 1. Inoceramus Coquandianus, from Speeton. 2. Fragment of Inoceramus, striated by glacial action, Muswell Hill. 3. Nautilus simplex, Hunstanton. 4. Inoceramus Crispii, Hunstanton. 5. I. tenuis, Hunstanton.

PLATE II.

1. Spongia paradoxica, Hunstanton. 2. Siphonia pyriformis, Hunstanton. 3. Cardiaster suborbicularis, Hunstanton. 4. Ostrea frons, Muswell Hill. 5. O. vesicularis, Hunstanton. 6. Exogyra haliotoidea, Hunstanton. 7. Cytherella ovata, Speeton. 8. Cristellaria rotulata, Speeton. 9. Trochocyathus (?) ----, Hunstanton.

PLATE III.

1, 1a. Vermicularia elongata. Upper and under surface of two different specimens, Speeton. 2. Vermicularia umbonata, Hunstanton. 3. Serpula irregularis, Hunstanton. 4. S. antiquata, Hunstanton. 5. Bourgueticrinus rugosus, Hunstanton. 6. Diadema tumidum, Hunstanton. 7. Cidaris Gaultina (?), Hunstanton.

PLATE IV.

1. Terebratula biplicata, 1a. mag. surface, Hunstanton. 2. T. semiglobosa, 2a. mag. surface, Speeton. 3. Kingena lima, 3a. mag. surface, Hunstanton. 4. Terebratula capillata, 4a. mag. surface, Hunstanton. 5. Belemnites attenuatus, Hunstanton. 6. B. Listeri, Speeton. 7. B. ultimus, Speeton. 8. B. minimus, Speeton.

ON THE RED CHALK OF ENGLAND

A Paper read 4th April, by Rev. THOMAS WILTSHIRE, M.A., F.G.S., Etc., President.

Persons in general take as the type or representative of chalk the material which mechanics employ for tracing out rough lines and figures. It is a substance of a bright white colour, somewhat yielding to the touch, and capable of being very easily abraded or rubbed down.

But the geologist gives a much wider interpretation to the term, not limiting it by these few characteristics; and, accordingly, he includes under the same title many strata which would hardly be so grouped together by the uninitiated.

For instance, there is at the base of the upper portion of the cretaceous system a certain hard, often pebbly, and highly coloured band, which, notwithstanding its great departure from the popular type, is nevertheless styled in geological language the "Red Chalk." This stratum, the subject of the present paper, nowhere forms a mass of any great thickness or extent; perhaps if thirty feet be taken as its maximum of thickness, four feet as its minimum, and one hundred miles as its utmost extent in length, the truth will be arrived at. It may be said, also, to be peculiar to England, for the Scaglia, or Red Chalk of the Italians, has little in common with that of our country. The two differ widely in appearance, in situation, and in fossils.

The first view of the seam in the north is to be obtained about six miles north-west of Flamborough Head, in Yorkshire, near the village of Speeton, where its structure, dip, and general appearance can be remarkably well studied.

Speeton is a small village, a place of no great note in the business-world, yet of much fame amongst the lovers of geology, inasmuch as in its neighbourhood there are several interesting formations, to one of which--the Speeton clay--it gives a name.

In these days of rapid travelling, the village has the great convenience of a railway-station, from whence the cliffs below can be reached without the slightest difficulty.

As I wish to conduct the members of the Association to the Red Chalk in sitû, let us suppose that, starting from some locality near the Hull and Scarborough Railway, we have taken tickets for Speeton station, and have in due time arrived at that latter place. On alighting from the train we must direct our steps to the houses in front, and then inquire the way to the sea-shore, above which we shall be standing at some considerable height--say four hundred feet. We shall be told to walk by the church, to turn to the right along a little lane, and then to look for an obscure path which passes across the fields. We shall soon afterwards, being on high ground, be able, by the light of nature, to find a way down to the sands below.

Part 2

Whilst descending, let us survey the scene that lies before us. It is a grand one, rendered picturesque by the broken ground, the solitude, and the sounding of the waves. Right ahead, there is the open Bay of Filey; on the left hand, the town of Filey and its Brig; not a ship, as one might imagine, but a huge mass of rocks of the coralline oolite, jutting out to sea at right angles from the shore, like a pier formed by human hands, and crowned on the land-side by strangely cut pinnacles of pink and rugged drift. On the right hand there are the high and perpendicular white chalk cliffs of the Flamborough range. As we pass down we shall meet with a gulley or bed of a small stream, in all probability quite dry, by following the winding course of which we shall reach the shore. This gulley passes over an escarpment of diluvial matter (the whole place being in confusion through the effects of small landslips), and traverses the Red Chalk itself, the first trace of which will be rendered visible by means of rolled fragments, which the force of the stream has at different times detached.

It will be only here and there that we shall find the Red Chalk in sitû, because sometimes vegetation, sometimes diluvium, sometimes fallen masses, entirely conceal its real position. However, there will be plenty of rounded pieces at the feet. Some of these had better be examined on the spot, in order that we may gain a clear perception of the appearance of the bed, should we meet with it again. These pieces are found to be hard and rough to the touch, and of a bright red tinge, though occasionally marked with streaks of white. Most likely on some of their sides a fossil or two will be seen peeping out; a blow from a hammer will divulge still more. So plentiful are the rolled fragments, that a few hours' work will satisfy the conscience, and fill the pockets of the traveller.

If I might be permitted to give advice to any member of our Association who should hereafter visit the place, it would be this--that it would be well for him to carry away moderate sized boulders entire, rather than to break them on the spot. The fossils will best be developed at leisure. The material is so hard, and the fossils so brittle (especially the belemnites and serpulæ), that imperfect specimens only will result from the quick and rough treatment of the hammer. The "find" will not produce any very great variety, only numbers; terebratulæ, serpulæ, and belemnites will be all that will be obtained.

Having now procured specimens, we had better walk southward along the shore; after a short time will be seen a fine perpendicular section of this particular stratum; we shall notice it is bounded on the one side by the White Chalk, to which it is parallel; on the other by the Speeton clay, which is not conformable to it, that is, not parallel.

The thickness of the bed of the Red Chalk is at this place, as I said just now, about thirty feet. First of all, taking it in descending order, that is to say, having reached its limit at the White Chalk, and retracing our steps in the direction of Filey, we notice about twelve feet of red matter containing serpulæ, and we note that the upper portion of this division is much filled with greyish nodules, showing that the change from the White Chalk to the Red is gradual. Next comes a bed of about seven feet thick, of darkish White Chalk; and finally, another bed of about twelve feet thick, of bright Red Chalk, containing belemnites and terebratulæ. The whole is followed by the Speeton clay, of which a short and accurate account will be found in No. 13 of THE GEOLOGIST magazine. The line of division between these two being well marked by runs of water, which are caused by the percolation through the chalk being stopped by the impervious clay.

The Speeton clay is singular in some of its characteristics. At its upper portion, in contact with the Red Chalk, it contains fossils belonging to the Neocomian or Greensand era, whilst at the lower part there are the representatives of the Kimmeridge clay. And thus it would appear to be one of those peculiar formations which have resulted from a number of beds thinning out, and becoming absorbed into each other. Three of the well-marked fossils of the Speeton clay may be adduced: Belemnites jaculum; a small crustacean, Astacus ornatus; and a large hamite, called Hamites Beanii.

To the south of the Red Chalk at Speeton, and adjoining it, occurs, as I lately mentioned, the White Chalk. The fossils in this part are not numerous; an inoceramus, a terebratula, and rarely an ammonite, are found. But the White Chalk higher up, that is, farther south, below Flamborough Head, near Bridlington Quay, is very fossiliferous, containing corals, echini, a bed of marsupites, as well as that very remarkable and extensive collection of marine forms, the silicified sponges, thousands of which can be seen at low water scattered up and down, and imbedded in the scars, or rocks. This chalk, however, has its drawbacks, for being very hard--indeed, so much so as to ring under the strokes of a hammer--specimens cannot be obtained without much trouble. I must make an exception with regard to the sponges. They are composed of silex; hence, long soaking in very dilute hydrochloric acid will do more and better work after the fossils have been brought home, than fifty chisels. The calcareous matter is slowly dissolved away, and then forms come into view as delicate and lovely as any that can be noted in the modern sponge tribe. Most of the common kinds of the Flamborough sponges will be found figured and named in Professor Phillips' Geology of Yorkshire; the rarer in the Magazine of Natural History for 1839.

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