: The Geological Story of the Isle of Wight by Hughes J Cecil John Cecil - Geology England Isle of Wight; Paleontology England Isle of Wight; Geology Stratigraphic Tertiary

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es near Chale, and flows through a strip of alluvium, overgrown with marsh vegetation, known as "The Wilderness." This upper course of the Medina, from the absence of gravels or brick earth, has the appearance of a comparatively modern river. But the Medina has a further history. If you look at the map you will see branches of the Yar running south to north as transverse streams, but the main course is that of a lateral river. Look at the two chief sources of the Yar--the stream from near Whitwell and Niton, and that from the Wroxall valley. When they get down to the marshes near Rookley and Merston, they are not flowing at all in the direction of Sandown or Brading. They rather look as if they would flow along the marshy flat by Blackwater into the Medina. But the Yar cuts right across their course, and carries them off eastward to Sandown. When we look, we find a line of river valley with a strip of alluvium running up from the Medina at Blackwater in the direction of these two streams--a valley which the railway up the Yar valley from Sandown makes use of to get to Newport. There can be little doubt that these streams from Niton and Wroxall originally ran along this line into the Medina; but the Yar, cutting its course backward, has captured them, and diverted their course. They probably represent the main branches of the Medina in earlier times, the direction of flow from south-east to north-west instead of south to north being possibly due to the overlapping in the neighbourhood of Newport of the ends of the Brook and Sandown anticlines. The sheet of gravel on Blake Down belongs to this period of the river's history. The river must have diverted between the deposition of the Plateau Gravels and that of the Valley Gravels of the Yar. For the former follow the original valley, the latter the new course of the river.

We must now take a wider outlook, and see what became of our rivers after they had flowed across what is now the Isle of Wight from south to north. We have been speaking of times when the Island was of much greater extent than at present. Standing on the down above the Needles, and looking westward, we see on a clear day the Isle of Purbeck lying opposite, and we can see that the headland there is formed by white chalk cliffs like those beneath us. In front of them stand the Old Harry Rocks, answering to the Needles, both relics of a former extension of the land. In fact Purbeck is just like a continuation of the Isle of Wight. South of the Chalk lie Greensand and Wealden strata in Swanage Bay, and north towards Poole are Tertiaries. Clearly these strata were once continuous with those of the Isle of Wight. We must imagine the chalk downs of the Island continued as a long range across what is now sea, and on through Purbeck. A great Valley must have stretched from west to east, north of this line, along the course of the Frome, which runs through Dorset, and now enters the sea at Poole Harbour, on by Bournemouth, and along the present Solent Channel--a valley still much above sea level, not yet cut down by rivers and the sea--and down the centre of this valley a river must have flowed, which may be called the River Solent. It received as tributaries from the south the rivers of the Isle of Wight, and others from land since destroyed by the sea. There flowed into it from the north the waters of the Stour and Avon, and an old river which flowed down the line of what is now Southampton Water. Southampton Water looks like the valley of a large river, much larger than the present Test and Itchen. Its direction points to a river from the north west; and it has been shown by Mr. Clement Reid that the Salisbury rivers--Avon, Nadder, and Wily--at a former time, when they flowed far above their present level--continued their course into the valley of Southampton Water. For fragments of Purbeck rocks from the Vale of Wardour, west of Salisbury, have been found by him in gravels on high land near Bramshaw, carried right over the deep vale of the Avon in the direction of the Water. The lower Avon would originally be a tributary of the Solent River; and it enters the sea about mid-way between the Needles and the chalk cliffs of Purbeck, just opposite the point where we might suppose the sea would have first broken through the line of chalk downs. No doubt it broke through a gap made by the course of an old river from the south, as it is now breaking through the gap made by the old Yar at Freshwater. When the river Solent had been tapped at this point, the Avon just opposite would have acquired a much steeper flow, causing it to cut back at a faster rate, till it cut the course of the old river which ran by Salisbury to Southampton, and, having a steeper fall, diverted the upper waters of this river into its own channel.

Frost and rain and rivers cut down the valleys of the river system for hundreds of feet; the sea which had broken through the chalk range gradually cut away the south side of the main river valley from Purbeck to the Needles; and eventually the valley itself was submerged by a subsidence of the land, and the sea flowed between the Isle of Wight and the mainland.

A gravel of somewhat different character to the rest is the sheet of flint shingle at Bembridge Foreland. It forms a cliff of gravel about 25 feet high resting on Bembridge marls, and consists of large flints, with lines of smaller flints and sand showing current bedding, and also contains Greensand chert and sandstone, which must have been brought from some district beyond the Chalk. The shingle slopes to north-east. To the south-west it ends abruptly, the dividing line between shingle and marls running up steeply into the cliff. This evidently marks an old sea cliff in the marls, against which the gravel has been laid down.

One or two comparatively recent deposits may be mentioned here. At the top of the cliff in Totland Bay, about 60 ft. above the sea, for a distance of 350 yards, is a lacustrine deposit, consisting in the main of a calcareous tufa deposited by springs flowing from the limestone of Headon Hill. The tufa contains black lines from vegetable matter, and numerous land and freshwater shells of present-day species--many species of Helix, especially H. nemoralis and H. rotundata, Cyclostoma elegans, Limnaea palustris, Pupa, Clausilia, Cyclas, and others.

Between Atherfield and Chale at the top of the cliff is a large area of Blown Sand. The sand is blown up from the face of the cliff below. It reaches a thickness of 20 feet, and possibly more in places, and forms a line of sand dunes along the edge of the cliff. The upper part of Ladder Chine shows an interesting example of wind-erosion. The sand driven round it by the wind has worn it into a semi-circular hollow like a Roman theatre.

Small spits, consisting partly of blown sand, extend opposite the mouths of the Western Yar, the Newtown river, and the most extensive--at the mouth of the old Brading Harbour, separating the present reduced Bembridge Harbour from the sea. This is called St. Helen's Spit, or "Dover,"--the local name for these sand spits.

THE COMING OF MAN.

We have watched the long succession of varied life on the earth recorded in the rocks, and now we come to the most momentous event of all in the history--the coming of Man. The first certain evidence of the presence of man on the earth is found with the coming of the Glacial Period,--unless indeed the supposed flint implements found by Mr. Reid Moir, under the Crag in Suffolk, should prove him earlier still. It is a rare chance that the skeleton of a land animal is preserved; especially rare in the case of a skeleton so frail as that of man. The best chance for the preservation of bones is in deposits in caves, which were frequently the dens of wild beasts and the shelters of man. But the implements used by early man were happily of a very imperishable nature. His favourite material, if he could get it, was flint. Flint could by dexterous blows have flake after flake taken off, till it formed a tool or weapon with sharp point and cutting edge. The implements, though only chipped, or flaked, were often admirably made. They have very characteristic shapes. Moreover, the kind of blow--struck obliquely--by which these early men made their tools left marks which stamp them as of human workmanship. The flake struck off shows what is called a "bulb of percussion"--a swelling which marks the spot where the blow was struck--and from this extends a series of ripples, producing a surface like that of a shell, from which this mode of breaking is called conchoidal fracture. Often, by further chipping the flake itself is worked into an implement. Implements have also been made of chert, but it is far more difficult to work, as it naturally breaks in an irregular way into sharp angular fragments. Flint, on the other hand, lent itself admirably to the use of early man, who in time acquired a perfect mastery of the material. The working of flints is so characteristic that, once accustomed to them, you cannot mistake a good specimen. Sea waves dashing pebbles about will sometimes produce a conchoidal fracture, but never a series of fractures in the methodical way in which a flint was worked by man. And, of course, specimens may be found so worn that it is difficult to be sure about their nature. Again early man may, especially in very early times, have been content to use a sharp stone almost as he found it, with only the slightest amount of knocking it into shape. So that in such a case it will be very difficult to decide whether the stones have formed the implements of man or not. In later times men learnt to polish their implements, and made polished stone axes like those the New Zealanders and South Sea Islanders used to make in modern times. The old age of chipped or flaked implements is called the Palaeolithic; the later age when they were ground or polished the Neolithic. The history of early man is a long story in itself, and of intense interest. But we must not leave our geological story unfinished by leaving out the culmination of it all in man. In the higher gravels--the Plateau Gravels--no remains of man are found; but in the lower--the Valley Gravels,--of the South of England is found abundant evidence of the presence of man. Large numbers of flint implements have been collected from the Thames valley and over the whole area of the rivers which have gravel terraces along their course. Over a large sheet of gravel at Southampton, whenever a large gravel pit is dug, implements are found at the base of the gravel. The occurrence of the mammoth and other arctic creatures in the gravels shows that in the Glacial Period man was contemporary with these animals. Remains in caves tell the same story. In limestone caverns in Devon, Derbyshire, and Yorkshire, implements made by man are found in company with remains of the cave bear, cave hyaena, lion, hippopotamus, rhinoceros, and other animals either extinct or no longer inhabitants of this country--remains which have been preserved under floors of stalagmite deposited in the caves. In caves of central France men have left carvings on bone and ivory, representing the wild animals of that day--carvings which show a remarkable artistic sense, and a keen observation of animal life. Among them is a drawing of the mammoth on a piece of mammoth ivory, showing admirably the appearance of the animal, with his long hair, as he has been found preserved in ice to the present day near the mouths of Siberian rivers. Drawings of the reindeer, true to life, are frequent.

Till recently very few Palaeolithic implements had been recorded as found in the Isle of Wight. In the Memoir of the Geological Survey only one such is recorded, found in a patch of brick earth near Howgate Farm, Bembridge. A few more implements, which almost certainly came from this brick-earth, have been found on the shore since. In recent years a large number of Palaeolithic implements have been found at Priory Bay near St. Helen's. They were first observed on the beach by Prof. E. B. Poulton, F.R.S., in 1886, and were traced to their source in the gravel in the cliff by Miss Moseley in 1902. From that time, and especially from 1904 onwards, many have been found by Prof. Poulton, by R. W. Poulton . Up to 1909 about 150 implements had been found, and there have been more finds since.

The most important finds, besides those at Priory Bay, have been those of Mr. S. Hazzledine Warren at Freshwater, especially in trial borings in loam and clay below the surface soil in a depression of the High Downs, south of Headon Hill, at a level of about 360 ft. O.D., in which a number of Palaeolithic tools, flakes, and cores were found. Isolated implements have been found in recent years in various localities in the Island. There are references to finds of implements at different times in the past, but the descriptions are generally too vague to conclude certainly to what date they belong. Much of the gravel used in the Island comes from the angular gravel on St. Boniface Down, or the high Plateau Gravel of St. George's Down; but in the lower gravels and associated brick earth, it is highly probable that more remains of Palaeolithic man will yet be found in the Island, and quite possible that such have been found in the past, but for want of accurate descriptions of the circumstances of the finds are lost to us.

When Neolithic man appeared the land stood higher than at present, though not so high as during great part of the Pleistocene. Britain was divided from the Continent, but the shores were a good way out into what is now sea round the coasts, and forests clothed these further shores. Remains of these, known as submerged forest, are found below the tide mark round many parts of our coast. Peat as at Southampton Docks, is found under the estuarine mud off Netley. The wells at the Spithead Forts show an old land surface with peat more than 50 feet below the tide level. The old bed of the Solent river lies much lower still--124 feet below high tide at Noman's Land Fort; this channel was probably an estuary after the subsidence of the land till it silted up with marine deposits to the level on which the submerged forest grew.

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