|Geological Magazine, vol 33, 1896. pp.
THE DISLOCATION AND DISINTEGRATION OF THE CHALK IN EASTERN ENGLAND AND IN DENMARK
by Sir HENRY H. HOWORTH, K.C.I.E., M.P., F.R.S., F.G.S.
|I PROPOSE in the following paper to continue and complete the story
which I have partially printed in the GEOL. MAG., Feb. 1896, p.58; but
first, a few words about the Yorkshire evidence, which I had overlooked.
Mr. J. F. Blake, speaking of the Yorkshire chalk, says it "has been subjected to the action of some force, which has been strong enough to take hold of huge masses and contort them and stand them on end. A remarkable folding in the rocks was noticed many years ago at Scale Nab, on the coast, by Professor Sedgwick - an equally noteworthy instance of similar action has come under my observation on the summit of the crest between Sherburn and Weaverthorpe. On ascending the hill from Sherburn is a large quarry with the chalk perfectly horizontal, and not more than 2O feet above the level of its upper surface are found beds belonging to the next higher portion of the series standing up nearly vertical, having a dip of 70o to the south. . . . The same beds are seen crossing the surface of the road to a length of nearly 70 feet, so that we must have as much as 60 feet thus set on end . . . If we continue upwards a little higher we find a still more marked disturbance about the 500 feet level. Not only are the beds tilted up, but they are actually inverted, so that instead of dipping south at a very low angle they are dipping north at about 45o, having been turned through an angle of 135o. The date of this disturbance is also indicated by these chalk beds actually lying upon stratified Quaternary sand, which forms the mound on which they were stopped. These phenomena indicate a powerful force coming from the direction of the north, during a season in which the lower levels were protected from its influence." (Proc. Geol. Assoc., vol. v, pp.267-8.)
Again, he speaks of a quarry at Weaverthorpe, in which a mass chalk stands nearly vertical, and dips actually northward into the hill. . . . The quarry has, in fact, been opened in a huge mass which has broken off the rest, and has fallen or been forced over on to its end.
In another passage, Mr. Blake remarks that "In some quarries every fragment has its surface covered with parallel lines at different levels, like a broken mass of basalt in miniature, or even like the appearance of a worn massive coral. . . . This peculiarity has been noticed before by Mr. Mortimer, who thought it was actually due to coral growth ; that it is not, is of course proved by the total absence of any real animal structure. . . . The slickensided chalk may be found all over Yorkshire, but it is nowhere so remarkable as near the change of direction of the line of outcrop - that is, a little north of its highest elevation." (Blake, Proc. Geol. Assoc., vol. v, pp. 265-8. The italics are ours.)
These effects seem to me to be all due to one cause, and that a very recent one, namely, the same cause which gave the Yorkshire wolds their present contour, and which could be no other than a powerful subterranean impulse. How is it possible for anyone who has studied the work of ice in its native home to attribute these effects jauntily, as Mr. Blake does, to the action of ice? "Geologists," he says, " will see in this [i.e. in the faulting and bending of these solid beds of chalk], doubtless, another form of those glacial forces which have strewed the bottoms of the valleys, and in some instances hollows at high elevations with boulders and clay." What fantastic writing is this? As an alternative in another case, Mr. Blake suggests that these contortions and upheavals of solid chalk beds have been due to the wasting effect of springs. Uniformitarian champions ought surely to fall back on Mrs. Partington's mop. That would be a real instrument of denudation.
The large boulders referred to in my former paper as occurring further south, are also found north of the Humber. Thus, Mr. Jukes-Browne says: - "Large masses of chalk occur in the gravel; one such mass, with flint-bands nearly vertical, and now half-quarried away, must have measured some eight yards in length; according to the workmen's account, the part left is ten feet wide by eight feet in height. Another mass, eight feet broad, was just being exposed at the time of my visit, June 1883; while near the entrance there wass a third, long tabular mass of chalk about 20 feet long, and passing into reassorted White marl ; but the greater part having its bedding so little disturbed that it might have been is in situ." Speaking of the latter, he continues: - "The seam of dark-grey marly clay at the base of the chalk was from two to six inches thick, and exactly like the bands which so frequently occur in the chalk - with flints. It would seem, therefore, that a mass of chalk, together with the clay-band, had been quarried out of the hill and embedded in the gravel without disturbance of its bedding or destruction of the clay." ("Geol. North Lincolnshire and South Yorkshire," p. 171.) It seems to me that facts like these are only consistent with the cause I urged in my previous paper.
The great earth-movements that raised the chalk wolds of Yorkshire, in doing so necessarily caused transverse fissures at right angles to the anticlinal lines, thus forming the steep-sided transverse dales which mark them. This was well seen and urged by the older geologists, who had studied mechanics and physics, and did not construct their camels out of their imaginations only. The most important of all these transverse valleys is probably that in which the Humber flows, and which, if not a fissure, presents to us the chalk bent down or sunk to a great depth below high-water mark, and the hollow filled up by the chalky clay, etc., showing that it was made at the same time as the great depressions of the chalk marked hy the well-borings at Boston, in Lincolnshire, and Yarmouth, in Norfolk.
The steep sides of these buried valleys are remarkable. Thus, Mr. Jukes-Browne says of a gravel-pit west of Wold Newton church: "From this depth of 40 feet the chalk rises steeply on either side in a series of rough slopes" (op. cit., p. 171). Again, Mr. C. Reid says: "Great Limber is partly on gravel and partly on chalk, the gravel having its limit generally well defined by a sharp rise of chalk . . . . The abrupt rise of the chalk at Limber brickyard is very curious; for one of the cottages belonging to the pit is on chalk, while not 80 yards away, on the same level, there is at least 37 feet of sand and warp" (id., p. 180).
Turning to the valley of the Humber, Mr. C. Reid, in his "Geology of Holderness," tells us that under it "there is evidently a considerable thickness of boulder-clay, though none of the borings yet made have shown the full depth of the old, probably pre-Glacial, Humber valley . . . . They prove that boulder-clay, interstratified with sand and gravel, reaches a depth of at least 83 feet below the present level of high-water; and, judging from the dip, there will be a still greater thickness in the old channel." He quotes other cases thus: one boring, 300 yards east of Hessle ferry, reached chalk at 42½ feet below high-water; a second, immediately within the Humber bank, reached it at 44 feet; another, in 26 feet of water, reached it at 24½ feet; another, in 33 feet of water, at 22 feet; anotlier, in 33 feet of water, at 23 feet. In one case, a boring in 25½ feet of water, chalk was not reached at 58½ feet. In another, where the bore-hole started at 3 feet below high-water, chalk was not reached at 72½ feet. (Op. Cit., pp. 39, 151.) In a bore-hole at Reed's Island, in the Humber, chalk was reached at l85 feet.
Mr. Reid speaks of the chalk south of Barton as glaciated (that is, in ordinary language, broken and dis1ocated) to a depth of several feet; and the irregular depths at which it occurs from the surface show that it must be much crumpled, bent, and warped; and inasmuch as the hollows created by the flexures, which go down considerably below low-water, are filled in boulder-clay only, it is virtually certain that they occurred either coincidentally or just before the clay was distributed.
That these flexures and dislocations were caused by a very different force than any that could be exercised either by glaciers or icebergs, seems evident when we test the problem in the true inductive way, namely, by placing side by side the phenomena in question from Eastern England with those from Dorsetshire, where we have effects largely of the same kind and degree, in an area where ice-sheets and icebergs cannot be postulated. The dislocation about Purbeck and in the Dorsetshire Chalk are good indices that the effects in question were due to subterranean forces, and not to the great ice monster continually invoked by the wilder glacialists.
Let us now turn our glance further east. It is a great pity that so little has been done during the last half-century to illustrate the constitution of the sea-bottom of the German Ocean. We know its contour well enough, but the distribution of the rocks that form its bed we can hardly be said to know, and yet materials are available. At Southwold and other places on the east coast, the so-called "crabs" to which the fishermen fasten their boats, are piled up with subangular masses of rock, including lumps of chalk, of Coralline Crag, as well as of crystalline rocks, which have been trawled, and about whose provenance the fishermen have collected considerable details; and it is a great pity that the Geological Surveyors, who have spent so much time on this coast, have not made more inquiries on the subject, and furnished us with more materials for settling some doubtful questions.
Two things, however, seem perfectly plain: one is, that the folds and bends which mark the chalk in East Anglia, Lincolnshire, and Yorkshire, also mark the beds underlying the German Ocean; and inasmuch as we meet with the chalk again in folds when we reach Denmark, it seems probable that the Cretaceous beds were once continuous right across the North Sea. I am informed by a distinguished hydrographer, that when the Trinity House proposed to erect a lighthouse on the Goodwins a boring was put into the ground, and that chalk was rapidly reached. 1'his shows that the Goodwin Sands form an anticlinal saddle or down. The Admiralty charts show a chalk bottom off the eastern coast of England, both off Kent and Essex, indicating that this depression is a synclinal hollow in the chalk.
It is equally probable, although of this we have not the same direct evidence, that the Dogger Bank is another chalk down covered with sand, and it is not unlikely that some of the chalk lumps brought in by the Southwold fishermen have been dredged on the Dogger. Between that bank and Denmark there has been some denudation, for when we reach the Danish coast, some of the beds below the chalk are exposed: perhaps this has been an area stripped of its covering of chalk, like the Fen depression and the Weald.
Proceeding still eastward, we come to the chalk of Jutland, and then to the broken and dislocated chalk beds of Moen and the other Danish islands, which present such a remarkable parallel to the dislocated chalk beds of England, and the discussion of which by the foremost German geologists has apparently largely escaped our own writers - the only person known to me who in recent years has referred to them, and he only casually, being professor James Geikie.
I will give a short conspectus of the most recent views. First, as to Lyell's observations and conclusions. He says: - "The chalk in the cliffs at Moen, which are from 300 to 500 feet high, is in beds partially vertical, partly curved, and has undergone extreme disturbance. As we find a range of the English chalk in Purbeck and the Isle of Wight, where the strata are much dislocated and thrown on their edges, while in the immediate neighbourhood of the line of convulsion strata of similar chalk are traced over a wide area in horizontal or slightly tilted position, so in Denmark we remark the like contrast between the state of the white chalk-with-flints which occurs in the neighbouring islands of Seeland and Moen. . . . The Moen cliffs are subdivided by deep ravines into separate and distinct masses . . . . they are, in fact, narrow clefts, coinciding with lines of fracture and dislocation. . . .The first opening or narrow valley is near a rock called Taleren: a deep ravine here comes down at right angles to the line of coast . . . Another great line of fracture further south, at Sommerspiret, where another ravine, filled with clay and sand, comes down to the sea. Here, as afterwards, in a third break in the cliffs further south, I observed the strata of chalk dipping on the opposite sides of the ravine towards the hollow. . . . The cliff called Dronningestolen is between 300 and 400 feet high, nearly three-fourths of which are perpendicular, but the lower part is a sloping mass of solid chalk-with-flints, the beds of flint being highly inclined towards the sea. . . Two rents descend perpendicularly, and terminate, the one at a depth of 100 feet and the other of more than 150 feet, from the top of the cliff. They are filled with sand, and near the termination are two caves, one of which is 14 feet and the other 16 feet high. They may be sections of subterranean passages, and are distinctly connected with dislocations in the chalk." . . . . Lyell suggests, that the upper portions of some of the chasms may have c1osed again . . . . "Their movements," he said, "have produced sharp curves in places, and in others great faults in the strata of the chalk, which are beautifully marked by the lines of black flints. Occasionally a mass of chalk, divided by regular layers of enclosed flints, abuts abruptly against another in which no flints, or scarcely any, are visible. Almost every other imaginable form of dislocation may sometimes be observed. I did not see any flints shattered in situ, but I am told they have rarely been observed." Lyell compares the phenomena at Moen with the large masses of chalk in the Norfolk cliffs, and says the appearances are strictly analogous, but in Norfolk are on a much smaller scale. ''In both cases, they compel us to assign a comparatively modern date for an era of partial but violent convulsion, by which the chalk has been deranged." (Trans. Geol. Soc., 2nd ser., v., pp. 252-7.)
In the abstract of this paper, which was read before the Geological Society, on May l3th, 1835, Lyell says: - "In consequence of the disturbances the chalk has been made to alternate on a great scale with interposed and unconformable strata of clay and sand. These alternations cannot be explained by supposing the detritus of superincumbent strata to have been washed by running water into clefts; but masses of the Tertiary beds seem rather to have been eugulfed." (Proc. Geol. Soc., ii, 192.) He further adds, that Dr. Forchhammer had discovered similarly disturbed chalk in the Danish island of Seeland.
In his address to the Geological Society in 1836, Lyell again refers to these dislocations, and says: - "The movements have been on so great a scale that masses of the overlying clay and sand have subsided bodily into large fissures and chasms, intersecting the chalk to the depth of several hundred feet. Some of the intercalations of clay and sand, in the midst of great masses of unconformable chalk, can only, I think, be explained by supposing engulfments of superincumbent matter, such as are described to occur in earthquakes." (Id., p. 366.)
Dr. Beck, in a paper communicated to the Geological Society in 1835, speaks of the masses of gravel and sand which in Moen have, in consequence of great disturbances, become entangled with portions of disrupted chalk. In the neighbourhood of Thisted, at Thye, to the north of Mors, and in the island of Fr, Dr. Beck observed in 1831, dislocations which affect equally the Tertiary strata and the Chalk. He further says that since the sandy beds of Denmark sometimes contain shells identical with those now living in the German Ocean, it is evident that the chalk in Denmark has been submerged since the existence of the living species of testacea. (Proc. Geol. Soc., ii, p. 217, etc.)
The next reference I can find to these dislocated chalk beds is in a memoir by C. Puggaard, entitled "Uebersicht der Geologie du Insel Moen," published at Berne in 1851. Lyell speaks of him as a most able and reliable authority. To be clear, he says: - "The escarpment of Moens Klint is about 18,000 metres in length; along this length of cliff it is only at each end that the chalk and the superincumbent beds lie in a horizontal position. In the intermediate space the strata of chalk are twisted, curved, and bent in all ways, in the form of an S or a Z, in a semicircle or stirrup-shae, or, again, cut by chasms, forming enormous faults, and interlaced in the most extraordinary fashion. About the middle of the scarp, at a place called Dronningestol, the confusion attains its maximum, and there the cliff rises to its highest point, 420 metres. The dip of the strata also varies greatly and changes continually, in some places passing abruptly from a horizontal position to a vertical one; and, what is most remarkable, the inclination of the strata seems less marked at the summit of the scarp, and the inclination of the beds increases rapidly as we go down, and sometimes the beds are more than vertical, the chalk resting on the diluvian beds, but always in order" (toujours en stratification concordante). He gives several sections showing how in several ravines in the island the layers of clay and sand follow the exact lines of the chalk. In other ravines it is only on one side that we have this continuous superposition; on the other the drift beds are sharply cut off, and often plunge below the chalk, so that the chalk lies on the drift in discordant fashion. The faults are often difficult to find, especially those occurring where the strata are much inclined. By means of these breaks aud faults, beds of clay and sand often look as if intercalated in the chalk; but on examining the place closer, it is found that where the chalk looks as if it rested on the clay it is separated from it by a breccia filled with angular pieces of flint and mixed with clay containing rolled pieces of granite.
It is often found that the edges of the inclined strata in the ravines are bent over in a direction opposite to the run of the ravine, showing whence the force has come which made them. The hills in the centre of the island have very steep sides, with pronounced outlines, and are separated by deep ravines, showing that notwithstanding the soft surface mantle, the contour of the country is really due to subterranean forces. The lines of fracture extend to Denmark, and are marked there by fjords, etc. "I am convinced," says Puggaard, "that the surface of Denmark owes its contour much more to the bending and plication of its strata, and to subterranean movements, than could at first sight be supposed from a mere examination of its surface beds." He further argues that the dislocations in the Isle of Moen referred to, all date from about the same geological epoch; but from the different directions of the rents, he attributes them to different shocks. In addition to the principal dislocations, there are secondary ones almost at right angles to the former.
Puggaard gives many details about the changes in the dip of the strata in various parts of the island, and many sections to show the actual facts; and he concludes that the dislocations were the result of some very violent lateral pressure, which lie attributes to the shrinkage of the earth's crust, aud which gave way in certain weak places. From the fact of the lower strata being more affected than the upper, be judges that it was rather the result of collapse than of elevation, and that the effects so remarkable in Moen were the result of the sinking in of the bed of the surrounding sea to the depth of 500 to 600 feet; this affected the whole island, together with Denmark, which afterwards rose again covered with its mantle of sand aud clay aud boulders. Then it was that the scarped cliffs of Moen were formed, and became the subject-matter of attack by the waves of the Baltic, reinforced by the waters of the Arctic Ocean, coming by way of the Bothnian Channel. He considers that this sinking probably affected the whole of the the North and East European districts where the drift phenomena occur, and also extended to the mainland of Denmark and of Scandinavia, and he considers the Swedish Åsar and the Danish sand rücken as due to the same cause. The depth to which he carries this sinking is apparently based on the height above the sea-level at which marine shells have occurred in Scandinavia and England. He attributes the dislocations in the strata of Moen to about the time of the so-called Glacial age, and adds the notable words - "Ich glaube dieses Ereigniss als eine bequeme Grenze der Tertiäaren und Quaternären Periode für Nord Europa ansehen zu können obschon eine scharfe Scheidung der beiderseitigen Bildungen nur ausnahmsweise moglich ist." (Op. cit. See also Puggaard, "Sur la geologie de l'île de Moen": Bull. Soc. Geol. France, 2nd ser., viii, p.532, etc.)
Lyell, the great champion of Uniformity and a very keen critic of the work of others, adopts aud incorporates the arguments and results of Puggaard in his "Antiqiuty of Man."
We must now pass on a few years. In his memoir published in 1874 on the dislocations in Moen and Rugen, F. Johnstrup endeavoured to account for them by appealing to ice.
Against this view more than one famous German geologist protested. Von Koenen, in examining the broken and dislocated chalk of the Danish islands, contests the possibility of ice having anything to do with it; he traverses Johnstrup's case in detail, and compares the phenomena discussed by him with the very similar phenomena he has himself described in Hessen and on the Weser, aud notably in the districts of Kreiensen, Göttingen, Marburg, Hersfeld, Geisa, and Vacua, where no traces of northern erratics or ice-work occur, and where they cannot, therefore, be attributed to ice. He especially quotes the underpinning of the great chalk masses hy boulder-clay and sand, which lie compares with the reversed strata at Hüggel, near Osnabruck, where the middle and Upper Lias are thrust in below the beds of Zechstein. He compares the hollows and basins of various shapes occurring in Rugen with the similar hollows in Central Germany, which he had already shown to be due to the sinking of the ground; he points out that the faults which occur in this district are of Pleistocene age, and argues that the general dislocations were coincident with a sinking of the bed of the Baltic. (See A. von Koenen, "Ueber post-glaciale Dislokationen": Jahrbuch der Königl. Preuss. Geologischen Landesanstalt und Bergakademie, 1886, pp. 1-19.)
In 1889, Berendt published a paper in which he reverted to Johnstrup's explanation, and argued at considerable length in his favour. This, again, was answered, with great force and in great detail, in a memorable and, as it seems to me, conclusive memoir by R. Credner, in which he made the position so long ago sustained by Lyell unassailable. The fact is the more remarkable since R. Credner is himself a champion of extreme glacial views. He tells us, that the view held by von Koened was strongly supported by the geologists who went on an excursion after the Geological Congress at Grisswald in 1889. They noted also that the dislocations in the cliffs north and south of the Kiel Brook, formed a row of parallel ruptures extending from SSE. to NNW., and were accompanied by a series of step-like sinkings of the intervening strata. R. Credner addds, that during his own numerous excursions, and especially in 1890 and 1892, when he spent several weeks on the island of Moen, he was satisfied of the justice of von Koenen's conclusions, that the disruptions were due to the forces which gave the island its contour, and not to ice-action at all. The paper is too long to condense here, and those who still need convincing had better turn to its elaborate descriptions, arguments, and especially to the sections, to see how utterly inadequate ice, in any form we know it, would be to bend these great masses of chalk into reversed folds, into arches and synclinal hollows, and to do so frequently when the chalk was coated, and had its surface therefore padded, with layers of soft materials - sand, clay, etc. Credner's paper has not been answered, or criticized even ; and it seems to me not only conclusive in itself, but to be a very eloquent complement to the evidence of the disturbed chalk of Britain presenting the same features and preaching the same lesson.
Let us now revert somewhat. As we have seen, the Geological Surveyors in East Anglia and the German geologists in Denmark attribute the flexures and dislocations of the chalk to the same period, namely, that in which the boulder-clay was distributed. This is confirmed when we turn to the submerged downs of the North Sea, over all of which, over the Dogger Bank, the Goodwin Sands, the Haslow Oyster Bank, the Knole Sand, etc., numerous remains of mammoths and their contemporaries have occurred. This, it seems to me, can only be explained by the submergence of the North Sea being subsequent to the formation of the land-surface on which the mammoths lived. If, as some have held, these remains found under the North Sea were carried down by the Rhine (another of the postulates of Uniformity which outrage common-sense), it is extra-ordinary that they should occur so unweathered and unrubbed, not in the hollows where the river may have flowed - if it then existed, which is very doubtful - but along the ridges. The widely-spread area of the North Sea where the unrolled remains occur, and the fact that they are so often found on the submerged ridges and downs, make it plain that we have to do here with a wide area which has been recently submerged.
The fact of these bones and teeth being so fresh and unweathered, shows us further that the submergence was not gradual, the result of continuous cutting back of a sea-coast by diurnal causes, but a widespread and cataclysmic one, or these bones would not be found in some cases articulated, and in all cases with their finest muscular attachments intact, but would be rubbed and converted into a kind of bony shingle.
In this behalf I should like to quote an opinion of Murchison, now perhaps forgotten. Referring to the existence of mammoth bones in a submarine forest off the Norfolk coast, he said that this commixture had been pointed to as indicating long and slow action. He viewed it as evidence of sudden movement. "When examining a similar submarine forest," he says, "with the trunks of trees still erect, the late eminent Dr. Forchhammer, of Copenhagen, came to the conclusion, as he informed me, that the movement by which they were submerged must have been sudden. He argued that the rapid immersion of the trunks, and their having been quickly surrounded by marine mud, could alone have preserved them; for if the trees had been gradually sinking at the rate of an inch or two in a year, they would have been entirely decomposed under the atmosphere long before their submergence. ("Siluria," ed. 5, p. 491.)
These conclusions are further confirmed by another, for which I have fought very hard in these pages, namely, that the chalky clay of Eastern England is shown, by every case where the evidence is clear, to overlie the Land-surface on which the mammoth lived. Mr. Horace Woodward has quoted some cases bringing into close chronological sequence the destruction of the mammoth and the disintegration of the Chalk of Eastern England. Thus he quotes the discovery, about the middle of the last century, of "part of the horn and palm of a deer, found in a chalk-pit at a village called Baber, four miles east [west] of Norwich, at the depth of 16 feet, and almost converted into a chalky substance." S. Woodward confirmed the discovery by Arderon of deer's horns in the disturbed chalk at Whitlingham and Sprowston. Arderon describes a man's skeleton as having occurred in the same bed. Since this time, says Mr. Horace Woodward, Mr. J. W. Ewing, Mr. Fitch, and Mr. Bayfield have brought many specimens, including shed antlers, under the notice of the Norwich Geological Society. These include the mammoth, the red deer, and another species, like the roe deer; while the localities of Thorpe, near Norwich, Hartford Bridge, Markshall, and Eaton, have been added to the list.
E. primigenius has been found in the cutting below the viaduct, near Hartford Bridge, and in chalk rubble, Norwich; while antlers of deer have been found at Norwich, Trowse or Lakenham, Mark-shall, Eaton, and Whitlingham. On March 4, 1868, Mr. J. W. Ewing exhibited before the Norwich Geological Society several portions of antlers found in the rubble or disturbed chalk in the grounds at Eaton. Mr. Gunn says he was struck with the marks of cutting and abrasion, by some blunt instrument, of the pedicle of one specimen of the red deer, and of sawing on another. A stone implement was said to have been found with the bones of deer. (H. B. Woodward, "Geology of the Country round Norwich," pp. 137 and 138.)
I will now endeavour to sum up in a few phrases the main conclusions which seem established by the evidence.
1. Before the distribution of the Drift, the Chalk extending from Norfolk, Lincolnshire, and Yorkshire, to Scania, in Sweden, was, so far as we can judge, a perfectly continuous deposit, neither bent into folds nor marked by conspicuous alternations of valley and down.
2. This great stretch of more or less level chalk was overlain, either completely or partially, by beds of Eocene age, consisting of variegated clays and of smoothed and rounded flint pebbles, of which considerable remains still exist under the Drift in East Anglia; while the debris of those which have been denuded and broken up now form the shingle beds and various gravels of Eastern England, there not being in that area, so far as we know, any pebble gravels whose constituent pebbles do not date back to Tertiary times.
3. Over these Eocene beds were placed the Crags. How far the Crag beds extended over tile bed of the North Sea, we do not know; but among the lumps dredged by the Southwold fishermen are several of the White, or so-called Coralline Crag; while, as is well known, in more than one place in the North Sea area, dead shells of later Crag age have been dredged.
4. Over these Crag beds, again, was a land-surface, on which the mammoth and its companions roamed, and which extended from Denmark to Yorkshire. We have no evidence to show that the Rhine flowed through this now submerged land. It may be, on the contrary, that its drainage was entirely reversed and that it then flowed southwards.
5. The beds above named, from the Chalk or perhaps the Oolites upwards, were presently affected by a great movement, of which other examples occur in geological history, by which they were bent and moulded into a succession of welds and intervening valleys. This movement led to their very considerable dislocation aud disintegration, and to the denudation of large areas, such as that occupied by the Fenlands; and it was by this movement that the present contour of Eastern England, of the bed of the North Sea, and of Denmark, were shaped.
6. The products of this disintegration, in the shape of chalk-rubble,
were subsequently moulded and mixed into what we know as the Chalky Clay,
which was afterwards distributed in its present form. How this came about,
I may be able to show on another occasion. This view, which I reached independently,
is very largely the same conclusion arrived at by the father of the Woodwards,
who in his "Geology of Norfolk," published in 1833, says that "the elevations
in the neighbourhood of Cromer originated in the disruption of tile Chalk
strata, and are most probably of the same age as the valleys. The natural
section of the cliffs shows, in the disrupted chalk, the origin of the
Beacon hill at Trimingham; and to the westward of Cromer is seen a large
mass of chalk at the upper part of the cliff in a perpendicular position.
These are beyond doubt effects of the same cause. On the lighthouse hill
at Cromer also, the chalk is forced up to the surface, 200 feet above its
natural level, and a limekiln is worked on the spot. The valleys of Norfolk
are such as are denominated 'valleys of elevation'; that is, they
were formed by the upheaving of the chalk and its consequent fracture.
This is demonstrated by the agreement of the 'salient' with the 're-entering
angles' of their borders, and from the fact of the layers of flint in the
chalk, on each side of the valley, being found to decline from its line
of fracture." In describing the general results of his inquiries, S. Woodward,
inter alia, argues that the chalk was disrupted subsequently to
the period when the great mammals lived in Norfolk, when, he argues, this
country was separated from the continent, at the same time forming the
valleys of Eastern Norfolk and the drainage of the county. (Op. cit.,