On the Red Chalk of England.

by Thomas Wiltshire.

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 t.i.tle 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 ma.s.s 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.

[Ill.u.s.tration: Lign. 1.--Map of Part of Yorkshire, Lincolnshire, and Norfolk, showing the Outcrop and Range of the Red Chalk.]

As I wish to conduct the members of the a.s.sociation to the Red Chalk _in sit_, 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-sh.o.r.e, 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 pa.s.ses 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.

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 ma.s.s of rocks of the coralline oolite, jutting out to sea at right angles from the sh.o.r.e, 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 pa.s.s 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 sh.o.r.e.

This gulley pa.s.ses 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 sit_, because sometimes vegetation, sometimes diluvium, sometimes fallen ma.s.ses, 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 a.s.sociation 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 serpulae), 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; terebratulae, serpulae, and belemnites will be all that will be obtained.

Having now procured specimens, we had better walk southward along the sh.o.r.e; 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 serpulae, 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 terebratulae. 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.

Let us now return to the village of Speeton, and endeavour to follow the winding course of the Red Chalk to its visible termination, some hundred miles to the south-east, in the county of Norfolk.

By a reference to the map (page 2), where the bed is laid down, it is seen that the Red Chalk adjoins the White Chalk during its entire length; that it first takes a westerly direction for about twenty miles, and then suddenly turning at a sharp angle proceeds south-east for the remainder of its course.

Some persons might suppose when they see the map, that if they were to travel to any of the towns or villages near the line, they would of necessity be able to see the Red Chalk _in sit_. No such thing; the upper soil, or vegetation, or man's work, may quite conceal all traces.

It is only at natural sections like the cliffs just spoken of, or by other means, such as wells, &c., that we can acquire a true idea of the ground beneath us. Who, for example, that lives in the City of London, could imagine, unless he had seen the fact for himself, when sewers were opened, or foundations cut, that he was dwelling over beds of gravel as bright and yellow as any that cover the paths of a flower-garden?

When, therefore, the nature of the surface of the ground is such that the eyes cannot detect traces of any particular formation we may be in search of, we must seek other testimony, we must ask what have other men seen, and what have they recorded, and in whose custody have they placed the keeping of those facts.

In the present case I can refer to two excellent works, to help us,--Professor Phillips' Geology of Yorkshire, and Young and Bird's Survey of the Yorkshire Coast.

Let us turn to the latter. The authors write that in the year 1819 a Mr. George Rivis, of Sherburn, bored for coal in a deep dale about a mile and a half south of Staxton; the boring was continued for some considerable depth. First they pa.s.sed through the White Chalk, next came upon the Red seam, and finally, at the depth of 288 feet from the mouth of the bore, reached the Speeton clay. Thus then near Staxton, a few miles west of Speeton, the Red Chalk exists; there it is, though it may not be visible.

If we proceed still farther west along the northern foot of the Yorkshire Wolds, it is possible that at Knapton we shall actually see the Red and White Chalk again _in sit_; for Young and Bird tell us that, at a clay-pit near that village, it was to be seen in their day.

At North Grimston, they add, the coloured chalk seems to be wanting, for at a copious spring issuing on the hill-side, about a mile above the village, the White Chalk is seen lying immediately over the blue clay.

This statement is not to be wondered at. Look at the map (page 2). Not far from North Grimston there must evidently be great unconformity of strata. Notice several of the formations, instead of running parallel to one another, actually are at right angles. For instance, we have the Speeton clay, the oolites, and the lias, almost perpendicular in direction to the White Chalk, a little to the west of Great Driffield.

Such a condition of affairs must have resulted from great disturbances, and there would be nothing strange in a part of the series being displaced or altogether wanting.

Some miles to the south, near the town of Pocklington, the strata are again parallel in direction to each other, and accordingly the Red Chalk is found, as before, at the base of the Wolds. Professor Phillips, in his work on the Geology of Yorkshire, figures some Red Chalk fossils from Goodmanham, near Market Weighton, and alludes to their also occurring at Brantingham, not far from the River Humber, the boundary of the county.

Thus, then, the Red Chalk has been traced through Yorkshire; speaking roughly one might say, that it for the most part takes an undulating course at the base of the Wolds; that it rises with a very gentle inclination from the sea near the village of Speeton; that it proceeds nearly due west until it approaches the neighbourhood of Malton, that it then suddenly changes its direction, and advances south-east until it sinks below the marsh-land six or seven miles to the west of Hull, having occupied a distance of about fifty miles.

We now cross the river Humber, and find the Red Chalk again near the banks at a place called Ferraby, to the west of Barton in Lincolnshire.

The Museum of the Geological Society of London possesses specimens taken from that part, and in a note attached to them there is this remark, that first came White Chalk, then Red Chalk, then a blue clay; thus it is evident there is the same state of things prevailing as we had at Speeton; and the same observation will apply to the appearance of the specimens themselves.

But as we travel along the western base of the Lincolnshire Wolds, or Chalk Downs (for Londoners would so term them), although we find the Red Chalk underneath the White, yet the blue clay beneath the Red Chalk is wanting; its place is supplied by a thick series of brown coloured sands, with included beds of sandy limestone, full of fossils like the Kentish Rag, only not possessing echini and belemnites. These beds have been referred to the lower greensand.

Only a few remarks can be offered in reference to Lincolnshire. My intention was to have visited the base of the chalk-hills, and have gathered together new facts; I have not been able to do so; neither have I been successful in discovering any authors who have written much about that county. There is a great geological darkness over that land, and much remains to be done in working out its fossiliferous deposits. I can, however, speak confidently regarding Louth.

One might fancy, as the town is placed to the right of the dark line on the map, which marks the position of the Red Chalk, that Louth could have nothing to do with the latter. But a friend who made some inquiries for me on the spot has forwarded two specimens, and says he saw them taken out of a chalk-pit at that town. They ran in veins, he writes, the lighter coloured over the darker, and were dug at no great distance below the surface. The bright red piece was just above where the springs arise--facts which correspond with evidence in other places.

As the inclination of the plane of the strata is small, and rising towards the south-west (the direction of the strata being north-west), it is easily comprehended that the Red Chalk may exist under Louth, and yet not appear at the surface of the ground until at some distance to the west of the town.

At Brickhill, near Harrington, the seam also has been met with; a specimen of it can be seen in the Museum of the Geological Society of London. This last and those from Louth differ little in appearance or character from what may be obtained at the Speeton beds.

I have no more to say about Lincolnshire, except that, according to the authority of geological maps, the Red Chalk of that county sinks and disappears below the marsh-lands, a few miles before reaching the sea.

And now it is time to cross the Wash, that great sea-bay, and land at Hunstanton, a little village on the north-western coast of Norfolk. As I am addressing a company of working geologists, I ought perhaps to say how in practice the locality can be arrived at, for it is not quite so easy to reach a place in reality as it is to see it on a map.

To go to Hunstanton, in the most ready way, a person must first reach Lynn; whence an omnibus, starting in the afternoon, at three or four o'clock, from the Lynn station, will convey pa.s.sengers to the village.

At Hunstanton there are two hotels, and several lodging-houses. I should recommend the Le Strange Arms, as being an old-fashioned comfortable inn, and nearer than the other to the section we are in quest of.

Perhaps it may be thought, Why dwell so much upon Hunstanton--its hotel--and its omnibus? I do so because at that village there is a most excellent natural section of the Red Chalk, better almost than at Speeton, and different certainly in many respects.

We will suppose that we have arrived at Hunstanton, and are walking towards the sh.o.r.e in front of the Le Strange Arms. A very few minutes will convey us to the wonderful cliff. I say wonderful, not from its height or length; for at its greatest height, under the lighthouse, it is not more than sixty feet; and it extends little more than a mile in length; but wonderful from its curious colour and general effect.

[Ill.u.s.tration: Lign. 2.--Hunstanton Cliff (looking to the North)]

The woodcut, copied from a water-colour drawing, made last autumn by a friend, will afford an idea of its appearance; but in it the absence of colour, of course, takes away from the beauty of the scene.

The cliff itself may be divided into five portions: first, White Chalk, forty feet thick; secondly, bright Red Chalk, four feet; thirdly, a yellow sandy ma.s.s, ten feet; fourthly, a dark brown pebbly stratum, forty feet; and, lastly, twenty feet of a bed almost black.

These divisions do not run one into the other, as is the case in most geological strata, but keep quite distinct. Thus the Red Chalk is as clearly separated from the White, as though the one had been covered by a broad band of paint. The same observation will hold good with respect to the others.

It will readily be understood that when the sun shines upon the cliff, and lights up the bright white, the bright red, the pale yellow, and the dark brown and black, and casts a shadow over the ma.s.s of gaily tinted materials at the base, a picture is produced not easy to be surpa.s.sed in beauty, and certainly not to be fully appreciated unless it be actually seen.