Notes on the Fenland

Part 1

Transcriber's Note: Minor typographical errors have been corrected without note. Irregularities and inconsistencies in the text have been retained as printed. Words printed in italics are noted with underscores: italics.

Notes on the Fenland

by T. McKENNY HUGHES, M.A., F.R.S., F.G.S., F.S.A. Woodwardian Professor of Geology

with

A Description of the Shippea Man

by ALEXANDER MACALISTER, M.A., F.R.S., M.D., Sc.D. Professor of Anatomy

Cambridge: at the University Press 1916

CAMBRIDGE UNIVERSITY PRESS C. F. CLAY, MANAGER London: FETTER LANE, E.C. Edinburgh: 100 PRINCES STREET

New York: G. P. PUTNAM'S SONS Bombay, Calcutta and Madras: MACMILLAN AND Co., Ltd. Toronto: J. M. DENT AND SONS, Ltd. Tokyo: THE MARUZEN-KABUSHIKI-KAISHA

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CONTENTS

PAGE

GEOGRAPHY OF THE FENLAND 1

SUBSIDENCE OF THE VALLEY OF THE CAM 2

TURBIFEROUS AND ARENIFEROUS SERIES 3

ABSENCE OF ELEPHANT AND RHINOCEROS IN TURBIFEROUS SERIES 6

ABSENCE OF PEAT IN ARENIFEROUS SERIES 6

FEN BEDS NOT ALL PEAT 7

SECTIONS IN ALLUVIUM 7

PEAT; TREES ETC.: TARN AND HILL PEAT; SPONGY PEAT AND FLOATING ISLANDS; BOG-OAK AND BOG-IRON 13

MARL: SHELL MARL AND PRECIPITATED MARL 17

THE WASH: COCKLE BEDS (Heacham): BUTTERY CLAY (Littleport) 18

LITTLEPORT DISTRICT 18

BUTTERY CLAY 19

THE AGE OF THE FEN BEDS 20

PALAEONTOLOGY OF FENS 20

BIRDS 25

MAN 27

Part 2

DESCRIPTION OF THE SHIPPEA MAN BY PROF. A. MACALISTER 30

GEOGRAPHY OF THE FENLAND.

The Fenland is a buried basin behind a breached barrier. It is the "drowned" lower end of a valley system in which glacial, marine, estuarine, fluviatile, and subaerial deposits have gradually accumulated, while the area has been intermittently depressed until much of the Fenland is now many feet below high water in the adjoining seas.

The history of the denudation which produced the large geographical features upon which the character of the Fenland depends needs no long discussion, as there are numerous other districts where different stages of the same action can be observed.

In the Weald for instance where the Darent and the Medway once ran off higher ground over the chalk to the north, cutting down their channels through what became the North Downs, as the more rapidly denuded beds on the south of the barrier were being lowered. The character of the basin is less clear in this case because it is cut off by the sea on the east, but the cutting down of the gorges pari passu with the denudation of the hinterland can be well seen.

The Thames near Oxford began to run in its present course when the land was high enough to let the river flow eastward over the outcrops of Oolitic limestones which, by the denudation of the clay lands on the west, by and by stood out as ridges through which the river still holds its course to the sea--the lowering of the clay lands on the west having to wait for the deepening of the gorges through the limestone ridges. A submergence which would allow the sea to ebb and flow through these widening gaps would produce conditions there similar to those of our fenlands. So also the Witham and the Till kept on lowering their basin in the Lias and Trias, while their united waters cut down the gorge near Lincoln through a barrier now 250 feet high.

The basin of the Humber gives us an example of a more advanced stage in the process. The river once found its way to the sea at a much higher level over the outcrops of Jurassic and Cretaceous rocks west of Hull, cutting down and widening the opening, while the Yorkshire Ouse, with the Aire, the Calder and other tributaries, were levelling the New Red Sandstone plain and valleys west of the barrier and tapping more and more of the water from the uplands beyond. The equivalent of the Wash is not seen behind the barrier in the estuary of the Humber, but the tidal water runs far up the river and produces the fertile estuarine silt known as the Warp.

The Fenland is only an example of a still further stage in this process. The Great Ouse and its tributaries kept on levelling the Gault and Kimmeridge and Oxford Clays at the back of the chalk barrier which once crossed the Wash between Hunstanton and Skegness.

The lowlands thus formed lie in the basin of the Great Ouse which includes the Fenland, while the Fenland includes more than the Fens properly defined, so that things recorded as found in the Fenland may be much older than the Fen deposits.

SUBSIDENCE OF THE VALLEY OF THE CAM.

During the slow denudation which resulted in the formation of this basin many things happened. There were intermittent and probably irregular movements of elevation and depression. Glacial conditions supervened and passed away.

The proof of this may be seen in the Sections, Figs. 1, 2 and 3, pp. 8, 9 and 10.

At Sutton Bridge the alluvium has been proved to a depth of 73 feet resting on Boulder Clay. At Impington the Boulder Clay runs down to a depth of 86 feet below the surface level of the alluvium. That means that this part of the valley was scooped out before the glacial deposits were dropped in it, and that the bottom of the ancient valley is now far below sea level.

In front of Jesus College, gravel with Elephas primigenius was excavated down to a depth of 30 feet below the street, while in the Paddocks behind Trinity College the still more recent alluvium was proved to a depth of 45 feet, i.e. 16 feet below O.D. These facts indicate a comparatively recent subsidence along the valley, as no river could scoop out its bed below sea level.

We need not for our present purpose stop to enquire whether this depression was confined to the line of the valley or was part of more widespread East Anglian movements which are not so easy to detect on the higher ground. From the above-mentioned sections it is clear that the denudation, which resulted in the formation of the basin in the lowest hollow of which the Fen Beds lie, was a slow process begun and carried on long before glacial conditions prevailed and before the gravel terraces were formed.

As soon as the sea began to ebb and flow through the opening in the barrier, the conditions were greatly altered and we see the results of the conflict between the mud-carrying upland waters and the beach-forming sea.

TURBIFEROUS AND ARENIFEROUS SERIES.

The Fen Beds belong to the last stage and, notwithstanding their great local differences, seem all to belong to one continuous series. Seeing then that their chief characteristic is that they commonly contain beds of peat it may be convenient to form a word from the late Latin turba, turf or peat, and call them Turbiferous to distinguish them from the Areniferous series which consists almost entirely of sands and gravels.

When the land had sunk so far that the velocity of the streams was checked over the widening estuary and on the other hand the tide and wind waves had more free access, some outfalls got choked and others opened; turbid water sometimes spread over the flats and left mud or was elsewhere filtered through rank plant growth so that it stood clear in meres and swamps, allowing the formation of peat unmixed with earthy sediment.

Banks are naturally formed along the margin of rivers by the settling down of sand and mud when the waters overflow, as seen on a large scale along the Mississippi, the Po, as well as along the Humber and its tributaries.

The effect of a break down of the banks is very different. A great hole is scooped out by the outrush, and the mud, sand and gravel deposited in a fanshape according to its degree of coarseness and specific gravity.

A good example of this was seen in the disastrous Mid-Level flood at Lynn in 1862 and the more recent outburst near Denver in the winter of 1914-15, of which accounts were published in contemporary newspapers. The varied accompanying phenomena can be well studied in the process of warping in Yorkshire or the colmata in Italy.

Times, Cambridge Chronicle, May 31, 1862.

Times, Jan. 16, 1915.

This was a much commoner catastrophe in old times, before the banks were artificially raised, and, as the streams could never get back into their old raised channel, this accounts for the network of ancient river beds which intersect the Fens.

The bottom of the Turbiferous alluvium is always, as far as my experience goes, sharply defined. This of course cannot be seen in a borehole or very small section.

The surface of the older deposits seems to have been often washed clean either by the encroaching sea or by the upland flood waters.

In saying that there is an absence of sand and gravel in the Fen Beds we must be careful not to force this description too far. For when the first encroaching water was washing away any pre-existing superficial deposits the first material left as the base of the Fen Beds must have depended upon the character of the underlying strata, the velocity of the water and other circumstances.

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