A Contribution to the Geological History of Suffolk (Part 3)

A CONTRIBUTION TO THE GEOLOGICAL HISTORY OF SUFFOLK Part 3 THE GLACIAL EPOCHS HAROLD E . P . SPENCER,

F.G.S.

I am writing the ground is thinly covered with snow, small icicles hang from the eaves and frost has whitened the ground for a week. Such conditions are very mild compared with other regions and particularly so with regard to the bygone periods popularly known as " T H E ICE AGE". The fact is however that there was a series of such cold ages of which a number of glaciations have left material evidence in the form of boulder clays, or tills, glacial outwash gravels, sands, and laminated brickearths.

WHILE

In 1909, Penck and Bruckner* published the results of their survey of the Alpine Valleys in which evidence of four major glaciations was discovered which they named GUNZ, M I N D E L , RISS, and WĂœRM. These glaciations each had phases of varying intensity with somewhat warmer intervals known as interstadials. The three earlier cold eras were double and the latter triple with two interstadials.

East Anglia, particularly Norfolk and Suffolk, is a very important region for students of glacial phenomena and the deposits left by the later glaciations. Here earlier landscapes have been destroyed by the succession of ice sheets a hundred or more feet thick which in their passing sometimes overturned earlier strata as by a giant plough. A fact which seems seldom to have been recognised is that each new glaciation largely destroyed earlier formations, in particular the deposits of the preceding temperate to warm interglacials with relics of the mammalia of the age and their prehistoric hunters. The indestructible artifacts of flint are however found, sometimes in large numbers, in river gravels of a later era having been redeposited by flood water and mixed with fossils, etc., of the later period. Sandy or silty beds within the tills possibly indicate a temporary recession and readvance of the ice. Examples of this type of phenomena have been recorded from Peyton Hall Pit, Hadleigh, and from the quarry of Needham Chalks Ltd., Needham Market.

Evidence of the tremendous power of moving ice sheets over land may be seen in Runton Cliff, near Cromer where a mass of chalk 600 yards long and about fifty feet thick has been pushed up over the Weybourne Crag. Near Ely a mass of Gault, Greensand, • P e n c k & B r u c k n e r , 1909, D i e Alpen Eiszeitalter.

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and Chalk 450 yards by sixty yards wide has been pushed into a depression in the Kimmeridge Clay and at Biggleswade, Beds., a sixty-seven feet thick mass of Ampthill Clay occurs in the boulder clay*.

Unfortunately earlier accounts of the glacial deposits of East Anglia have been rather confusing because workers have perhaps seen too few exposures and have formed conclusions other than those previously published resulting in a new series of names being introduced. This may possibly be due to the variable character of the Upper Chalky Boulder Clay or Gipping Till which varies from very stony to extremely chalky. The terms Lowestoft and Gipping Till now in general use were introduced

by D. F. W. Baden-Powell and are used herewith for the lower and upper Chalky Boulder Clays respectively. Observations over more than forty years, particularly in the networks of trenches for housing estates in the Gipping Valley, have shown how the Gipping Till varies from its normal character in its increased stony content, or in being excessively chalky. The latter feature was formerly exposed in a disused pit in the Finn Valley near Tuddenham St. Martin, also in temporary sections at Dales Road brickfield (now an industrial site), at Maidenhall, Ipswich, and now somewhat less chalky at Church Lane, Claydon.

The earliest tili surviving in East Anglia is the Cromer Till for many years so well exposed along the Norfolk Coast. Another early tili is the Norwich Brickearth which unlike other tills is lacking in chalk but is generally assumed to have been deposited by the same glaciation. T h e writer is unaware of any section where the transition between the Cromer and Norwich Tills has been exposed and is of the opinion that it may yet be proved they were deposited from two separate ice sheets. Weathering agencies tend to remove the chalk from tills and the absence of chalk in the Norwich Brickearth has long been a puzzle as the weathering action is generally confined to the upper part of a tili to varying depths, but never effecting the complete decalcification of a thick formation. It is reasonable to suppose that the Brickearth was chalk free in the first instance, the ice from which it originated having crossed a large area of Norwich Crag sand could only have picked up chalk-free sand which imparted its brown colour to the deposit. T h e Norwich Brickearth extends southward into Suffolk as far as the Blyth Valley where it has recently been exposed above the Westleton shingle beds; at Holton Pit, Haiesworth, it has also been identified (1966) at the top of Easton Bavents Cliff, Southwold. In the cliffs of north-east Suffolk, Norwich Brickearth occurs at the base of the cliffs southward to Covehithe where P. Chatwin, Brit. Regional Geology East Anglia, Geological Survey,

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it is much contorted and contains molluscan remains derived from Norwich Crag* and was formerly thought to be part of the Chillesford Beds.

Because of the difficulty of exact correlation between the Alpine region and more northerly areas other names are used for north European glaciations, see Table 1. In America local names are used for the western series of ice sheets. Greenland is still mainly buried beneath vast masses of ice but the marginal area of ice free land is increasing.

East Anglia H u n s t a n t o n glaciation (Ipswichian interglacial)

Alpine Würm

G i p p i n g glaciation (Hoxnian interglacial) Lowestoft glaciation Cromer glaciation (Cromer interglacial) U p p e r Norwich Crag Pre-Red Crag glacial (and possibly earlier cold phases) TABLE

1.

EUROPEAN

Riss Mindel Mindel ?Günz PDonau

GLACIAL

flll < II

}.;

i

ii ii

N. Germany Pomeranian Weichel Warthe Saale Elster Elster —

NOMENCLATURE

Evidence of six pre-Günz glaciations has been recorded in Italy, presumably similar evidence in East Anglia was destroyed by the incursion of the Crag Seas and this is indicated by the striated flints, the blue and white "Basket patinated" flints, erratic igneous rocks and Cretaceous and Jurassic fossils, etc., in the Basement Bed of the Red Crag.

T h e Cromer and Lowestoft Tills are regarded as the product of the sea ice and land ice respectively with a marine sand intervening between them at Corton representing an interstadial (temporary retreat of the ice). T h e Corton Sand has been thought to be of marine origin from the molluscan remains it contains in patches. Alternatively it has been suggested the shells may be derived from the destruction of a marine sand and redepositedf. Part of a cervid metapodial reputed to have been found in sand of Corton age has proved to belong to one of the * T h e Norwich Crag consists mainly of sand with beds of clay, gravel and shells included. f T h i s has b e e n objected to on the grounds of the fragile nature of the shells b u t the n u m b e r of shells f r o m the Crag beds included unbroken in the C r o m e r Till proves that this is possible. Observations by the late J. E. Sainty and the author.

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larger deer from Norwich Crag Sand; its fossil condition is typical of Crag bones. The Corton cliff section has Lowestoft Till at the top succeeded by glacial outwash sand fĂźll of small rounded chalk grains, Corton Sand, Norwich Brickearth or Cromer Till, Cromerian Forest Bed Seriesâ&#x20AC;&#x201D;Rootlet Bed (mammaliferous). The chalky sand has been recorded from sites where the tili has been eroded as far inland as Rendlesham.

Lowestoft Till In north-east Suffolk the Lowestoft Till blankets most of the countryside extending up the Waveney Valley where at Homersfield and Weybread it occurs on the slopes and underlies the valley gravels. It was temporarily exposed in the Valley bottom north of Fressingfield Church in 1953 and occurs below the lake beds at Hoxne, also in the Wattisfield area where it is associated with a micaceous laminated brickearth. This brickearth was used for pottery by the Romans and is still excavated at Calke Wood for the Wattisfield Pottery. Lowestoft Till was used for brick making at Frostenden and at other sites, it is still so used at Gisleham. At Roydon, near Diss, the Lowestoft and Gipping Tills together have a total thickness of about 100 feet.

The included erratics show the Lowestoft Ice originated in the Lake District and proceeded down the west side of the Pennines, it appears to have been diverted eastward by the pressure of Welsh ice and crossed the Midland Piain. It presumably ploughed out part of the Fens judging from the quantity of Kimmeridgian material from the Isle of Ely area contained therein, to which its slate blue colour is largely due. This ice extended as far south as the Thames Valley. Jurassic rocks and fossils are frequent, particularly large Septarian nodules up to five or even eight feet across from the marine Kimmeridge Clay; these often have good Calcite crystals in the interior.

Reptilian remains, chiefly from the Kimmeridge Clay, occur in the Lowestoft Till and were more frequently found when the cement works quarry at Great Blakenham was worked by hand.

A Pliosaur* tooth has been discovered near Rickinghall and part of a limb bone at Kessingland, also part of a mandible at Westhall.

A block of limestone with a number of vertebrae was found at Great Blakenham and a solitary Ichthyosaur tooth in the same pit.

One lone vertebra of a Pliosaur is recorded from Creeting St. Mary. With modern mechanical excavators these interesting fossils are seldom seen. *Pliosaurs attained a length of forty feet.

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In south-east Suffolk the Lowestoft Till is represented by isolated remnants the most easterly of which is near Bentwaters.

Over thirty feet of this Till was proved in a bore at minus seventy feet below the bed of the River Orwell at London Road, Ipswich; the base of the deposit was not penetrated: therefore the total thickness is unknown. This is irrefutable evidence that the Ipswich buried Channel was formed by the agency of a glacier of Lowestoft Ice most probably in advance of the main ice sheet.

There are a number of buried Channels in Norfolk and Suffolk and where evidence is available they appear to have been ploughed out by Lowestoft ice. Suffolk has the distinction of having the deepest buried Channel in the country, at Glemsford where there are no less than 470 feet of glacial deposits presumably and mainly of Lowestoft age. Details of the Glemsford section are as follows:â&#x20AC;&#x201D; Soil and stones Rough bailast Sandy bailast R o u g h bailast Ballast Blue sandy clay Brown gravel and clay Boulder clay (iGipping) Sand Ballast Boulder clay, flints, stones, etc. (Lowestoft Sandy boulder clay Boulder clay and stones Clayey sand and stones Clayey sand Hard sand Sand, hard and soft layers Brown clayey sand Hard sand with gravelly base Live sand coarser at base Sand and flints Gravel Blowing sand and flints Gravel and sand Blowing sand Blowing sand and flints Chalk and flints Chalk to

Till)

3' 3' 2' 1' 5' 1' 4' 14' 2' 16' 169' 7' 10' 32' 11' 5' 7' 13' 18' 67' 47' 2' 5' 1' 8' 27' 1' 39'

(, 8 9 14 15 19 33 35 51 220 227 237 269 280 285 292 305 323 380 427 429 434 435 443 470 471 510

From about 270 feet downward the beds of sand, etc., were undoubtedly deposited by the subglacial meltwater stream flowing beneath the ice which would obviously have deepened the Channel by its erosive action on the chalk.

Great Blakenham After Mason's Cement works were taken over by the Associated Portland Cement Company about 1945 the older pits at the edge of the plateau were abandoned and new ones opened on land

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belonging to College Farm. Very interesting glacial phenomena were exposed in the cutting from the old to the new quarries consisting of Channels eroded in the chalk by meltwater from the Lowestoft lce and filled with coloured sands (see PART 2 F I G 7) There were also pot holes, presumably formed where there were pre-existing Solution pipes, below the glacial Channel where deposits laid down by a subglacial stream varied from very fine grey and ochreous sand to coarse gravel with well rounded flints The pot holes contained fine sand in thin layers with the bedding vertical and parallel with the walls; the bedding in the sand hlled Channels is similar. This appears to be due to the Solution ot the chalk which permitted seepage between the chalk and the frozen material, the space being filled with very fine sand The process was repeated seasonally and the layers probably represent the period of summer melting.

Another feature associated with the subglacial stream is the Induration of the chalk which absorbed additional calcium carbonate from the meltwater becoming almost as hard as marble. Some of the gravel, which occasionally contains angular pieces of chalk became indurated, also forming a hard conglomerate; similarly hardened sand patches have also been noticed.

Various features which exist in these quarries have been descnbed and illustrated in PART 2 of these contributions which t u l t ^ P P ^ g V a l l e y ( s e e F i g s - 7-10). On a visit in mid March, 1967, the cavernous hollows shown at (4) in FIG. 8 were seen to have been hidden by fallen material loosened by the winter frost.

T h e boulder clay quarry on the plateau between Clay Pit Grove and the site of College Farm over a quarter of a square mile m extent is one of the finest exposures of glacial clay or Till m eastern England, the main mass is Lowestoft Till with some (jippmg Till above. M u c h of the latter has been eroded and washed away and as a consequence the Valley slopes have been moulded into softly rounded hills to the east of the workings ijormerly some eight to ten feet of calcareous sandy hillwash in the bottom of the hanging Valleys contained sparsely distributed upper palaeolithic flint artifacts but this was removed in order to extract the chalk, which mixed with the sludge washed from the boulder clay, is used in the manufacture of Portland cement 1 he recent construction of a 400 feet high chimney and a gigantic kiln undoubtedly heralds the more rapid removal of chalk and clay and possibly the destruction of interesting phenomena before thev can be recorded.

Excavations for the electricity pylons between Bramford and Uttle Blakenham at G R 118474 were made in the upper part of

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a thick mass of Lowestoft Till between the stream from Offton and the road junction where there is an outcrop of chalk, the southernmost and smallest of a chain of three hills. It is noteworthy that the bed of the stream is in the chalk for the latter part of its course therefore the mass of tili may be associated with the buried Channel which has been proved to exist at Bramford (see PART 2 p.298).

At Great Blakenham interesting examples have been seen of ice-transported masses of soft rocks in Lowestoft Till (see PLATES 3 and 4). T h e mass shown in PLATE 3 was found by Dr. I. W. Cornwall to be loessic in character but Dr. R. G. West found no fossil pollens therein. It appeared blackish when first exposed but faded to dark grey after weathering.

Large boulders of gravel about three feet across were formerly exposed in Gipping gravel at the Dales Road Brickfield, Ipswich which were presumably derived from deposits laid down after the the Lowestoft Glaciation; sand boulders have frequently been observed also in Gipping Till.

Ipswich Lowestoft Till has been exposed in temporary excavations at Ipswich in Vernon and Gower Streets (GR 166439), also in Grove Lane opposite the Park Gate (GR 175444), just below the 100 feet contour, with Gipping Till above. It occurs also below the brickearth and gravels of the former Valley Brickworks in Foxhall Road, a site now occupied by E. R. & F. Turner's Works, from which numerous Acheulean artifacts were extracted early in the Century. This appears to be the furthest point in south-east Suffolk at which Lowestoft Till has been recorded.

It was in Lady Lane excavations for the underground car park however that the most significant phenomena of the Lowestoft glaciation were exposed in a section forty feet deep. The beds revealed were:â&#x20AC;&#x201D; M a d e soil M a d d e r b r o w n loessic bed of the ?Hunstanton glaciation .1..

Interbedded outwash sand and gravel G i p p i n g silty beds interbedded with fine sand with m i n u t e chalk grains Gipping Till Displaced raft of L o n d o n Clay Lowestoft Till Undermelt gravel and sand Reading Sand with Sarsens T h a n e t Bed Chalk

1 ' to 4 ' 5 ' to 6 ' circa 1 2 ' 4' 3 ' to 8 ' 6 ' to 12' 6' 5' 5' 10'

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The Lowestoft Till is of an exceptional blue colour and unlike other exposures, the base is not level but tilted at a 60° angle on the west side and 80° on the north. To the south the base is level except on the east side where it is deflected downward below London Clay; it was here where the Gipping Till resting directly on the Lowestoft was found to be thickest and capped with gravel of which the upper part had been disturbed by solifluction. In the north face of the section the upper edge of the Lowestoft Till is turned upward in a twenty-five feet curve to the east of which is first a tilted bed of waterlaid gravel and three waves of Lowestoft undermelt sand below London clay, with finally a contorted mass of coarse morainic gravel. The London Clay was found to have been subjected to pressure by Gipping ice from the north which had forced gravel against the Clay causing slickensides within it and a southward bulge of the gravel into the Clay. (See F I G S . 12, 13, 14, 15, 16.)

The north-westerly section has only two or three feet of Gipping Till on the Lowestoft, the upper part having been scoured away by meltwater which deposited an assortment of beds of sand, fine sand with minute chalk grains, and chalky gravels. In the upper part of this tili two beds of fine silt which terminate abruptly at the middle of the section where the side of a deep Channel was exposed filled with fine current bedded sands. Similar sands were revealed in excavations for the basement of the new Police headquarters on the east side of Lady Lane. They were seen to be associated with contorted beds of gravel.

N o r w i c h — B r a m f o r d Road, Ipswich West of the railway between Bramford and Norwich Roads trenches for a storm water sewer exposed Lowestoft Till with Gipping Till above but the base of the older tili was not exposed and no sand or gravel was observed between them. In 1938, however, about three feet of mammaliferous gravel was found between these tills at Riverside Road from which a horn core of Bison was obtained. Patches of white stoneless clay were observed in Bramford Lane near Westbourne Schools which appeared to be similar to white clays seen in glacial gravel at Speedwell Avenue, Chantry and (with mammoth and red deer remains) interbedded with the Stoke Hill loams at Maidenhall in 1948. So far as is known white clays are associated with Gipping deposits and the Ipswichian (last) interglacial.

South-West Suffolk In south-west Suffolk tili of Lowestoft age differs in having erratic rocks and fossils derived from the Oxford Clay instead of the Upper Jurassic Kimmeridge Clay, but because there have been

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fewer exposures it seems to have received less attention than the tills of the eastern part of the county. It is referred to by Boswell as the Oxfordian Chalky Boulder Clay* and to comply with modern practice in the use of local names for deposits it is suggested the term SUDBURY T I L L might be adopted for it. The Sudbury Till was well exposed above a thick deposit of varved clay at Alexander Brickworks, Sudbury ( G R - T L 885416), the site is now a timber yard. At Jordan's chalk pit in East Street this tili was referred to by Boswell as the best inland glacial section in East Anglia, but it has sadly deteriorated since his day. Here the tili rests on the most westerly exposure of Red Crag which lies on the chalk. (Part of this Crag sand has been converted into a ferruginous sandstone like that at Hall's Pit, Playford Heath, Kesgrave.) Outliers of Sudbury Till occur at Jordan's Gravel Pit, Edwardstone, at the top of the hill above the Police Station at Boxford ( G R - T L 968402), and at Aldham near Red Hall Farm ( G R - T L 031444), lying above the 150 feet contour line but it has been noted in the bank of the stream from Whatfield near Peyton Hall Watermill.

The grey laminated brickearth below the Sudbury Till occurs also at Little Cornard Brickyard where the bedding has been disturbed by later ice pressure. A closely adjoining section of gravel had the bedding crumpled in a concertina-like manner— W W W W W W . Another very remarkable feature of this site is the large boulder-like mass of redeposited chalk which was described by Boswell as "remaine Chalk"f, had he examined the mass closely he would have found it füll of entire freshwater shells which is an indication that the deposit accumulated in a pool fed by a stream flowing over an area of chalk. It now is an isolated mass from the sides of which brickearth has been dug away. T h e brickearth, etc., rests on Eocene Reading Clay, above which there are indications of glacial disturbance.

At Boxford the Sudbury Till lies on glacial gravel which in turn rests on the crushed surface of another thinly laminated brickearth, or varved clay. This, unlike that at Cornard and Sudbury, is buff in colour like the post Lowestoft varved clay of the Gipping Valley and has been proved to be much thicker, presumably because it has been protected from erosion by the overlying deposits. It outcrops nearly half way up the hill and a boring to a depth of twenty feet made at the foot of the hill failed to penetrate the bed beneath, therefore it may be presumed the deposit is forty to fifty feet thick. A test has shown the clay is eminently suitable for making pottery (FIG. 17).

•Boswell, P. G . H., T h e Geology of the country around Sudbury, M e m .

Geol. Survey, 1929. tBoswell, P. G. H., T h e Geology of the country around Sudbury, M e m Geol. Survey, 1929, Plate 2.

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S E

Representation of the Ieft Valley slope of the R. Box at Boxford. scale).

S

V

(Not to

Varved or laminated clays are important products resulting from the melting of an ice sheet, the varves or laminae vary in thickness and are believed to record each season's melting. A retreating glacier in summer produces volumes of water which transport boulders, coarse gravel, medium and fine gravel, sand, silt, etc., the heavier material is deposited near the ice front and the other grades proportionately as the rate of flow of water is reduced. The finest material, rock flour, is conveyed furthest by water in a turbid condition and is deposited when the flow is retarded by the stream entering a Iake; thus over a period of years a series of layers accumulate which record the warmer and cooler years. In northern Europe it has been possible to identify groups of varves from the upper part of southern lake deposits with those from the lower part of more northerly lakes and arrive at the approximate number of years since the earlier lake sites were uncovered by the retreating ice of the last glaciation. Here no one has so far attempted to apply such methods and only at a few sites has pollen analysis been applied.

Suffolk varved deposits fall into three groups, first the grey Sudbury Brickearth*, the buff Boxford Brickearth, the buff Gipping Brickearth, and the micaceous Brickearth of Wattisfield; the latter is associated with Lowestoft Till but its relationship has not been established. The first and last are the oldest â&#x20AC;˘Brickearth is a general term for argillaceous material from which bricks may be made.

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known m situ but erratic rafts of varved grey and blackish clays (PLATES 3 and 4) have been observed within the Lowestoft Till at Great Blakenham of which the parent deposits are so far undiscovered. The Gipping buff varved beds are obviously post Lowestoft and precede the Gipping Till which in some places, such as the parish of Pettistree, is distinctly yellowish and this implies varved clay derived from this tili would be yellowish, or r 5'. T h l s 1S m f a c t P r o v e d by the product of each day's washing of Gipping Gravel at gravel pits forming similar varve like deposits of a buff colour. Had there not been Oxfordian Sudbury Till above the Boxford formation it might have been regarded as the same age as that in the Gipping Valley whereas from the present evidence is appears as an odd man out. Another area of laminated deposits exists in the Woolpit district some of which are more arenaceous, the sand content gradually increasing downward.

The fact is that it appears the lower varves in borings tend to alternate with layers of fine sand which become coarser downward This suggests that the velocity of the water was greater in the early stages of deposition and as the ice retreated the sand was deposited earlier, nearer the source. The Woolpit brickpits from which the noted Suffolk White bricks originated have long been abandoned making investigation difficult, if not impossible. It is considered that a programme of boring in this district would reveal deposits mdicating a large lake resting on a tili.

The varved micaceous clay of Wattisfield was used for the manufacture of pottery in Roman times at Foxledge Common to the west of Calke Wood and is also used today at Watson's Wattisfield Pottery.

The Wattisfield clay is unique in its micaceous character and is the most westerly laminated brickearth so far recorded in buffolk. At Calke Wood it rests on chalk and the Lowestoft Till occurs on the plateau above and in the absence of a section showing their true relationship it is possible that it is older than the tili ur 11 e v e n t u a l l y b e Proved to be older than the Lowestoft Till a problem arises as to which earlier glaciation it is associated with t a c h varve varies in thickness and contains minute flakes of mica.

In parts of the deposit however it has been observed that the amount of mica increases upward and a layer of slightly larger flakes intervenes below the varve above. The laminated deposit, passes up into a stony brickearth, essentially a gravelly deposit with a high oercentaee of non-flint siliceous erratics. Similar gravels occur in the Gipping Valley above the Red Crag at Bramfeld and above the Creeting white sands (which are part of the Lrag series) and it is desirable that there should be a comparative investigation of the metamorphic rocks in these gravels. As the Creeting Sands also contain mica it may be useful to compare the micas from both deposits to ascertain if they have a common

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origin, the source of such a phenomenal amount of mica in the Wattisfield clay is one of the more interesting problems to be solved.

DĂźring the excavation of clay for the manufacture of pottery odd features were discovered which at first were thought to be shafts dug by Neolithic people because fragments of pottery of that period were found therein. The truth is however that the pits are the result of collapse of the strata into cavities in the underlying chalk.

Another interesting phenomenon was a thrust plane discovered along one of the varves bisecting a series of V shaped features which appear to be frost cracks. The upper part of the V's were displaced about three feet to the east presumably by pressure of ice and if these features are indeed frost cracks they represent a temporary halt in the deposition of the varves (FIG. 18).

This may be evidence in favour of a glacial lake of an earlier cold epoch than the Lowestoft glaciation.

N H

S W

FIG. 18

Showing bisection and lateral displacement of presumed frost crack in Wattisfield varved clay at Calke Wood. Lateral movement about three feet.

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Marks Tey So far as is known at present the thickest deposit of laminated clay in East Anglia is at Marks Tey, Essex which yields the clay from which Marks Tey bricks are made. The series of deposits are over 100 feet thick extending down from 110 feet O.D. to minus twenty feet below present sea level occupying a hollow in the Lowestoft Till. Deeper boring was prevented by the hydrostatic pressure which forced water up the borehole: possibly the pressure is partly due to the quantity of marsh gas trapped in the clay.

The lowest bed reached is gravel, the base of which was not penetrated. Above this is about eight feet of lake (laminated) clay succeeded by over forty feet of lacustrine clay mud and another seventy feet of lake clay below about ten feet of gravel.

DĂźring a personal visit to the site about 1955 the writer was shown a deposit of peat part way up the south-east side of the pit.

Some thirty years ago a fossil fish was discovered which is now in the British Museum (Natural History). These factors were indications that these lake beds were formed during an interglacial and not during a dry cold period following the recession of an ice sheet. Recent pollen analysis by Dr. Charles Turner of the Sub-Department of Quaternary Research, Cambridge, has proved the lower lake clay mud to be about the same age as Hoxne Brickearth which dates from about 250,000 years ago and is therefore associated with the Clacton Elephant Bed and the Swanscombe gravels of the Thames Valley, which yielded many bones of mammals of the period together with portions of a human cranium.

At Marks Tey (personal communication) the upper part of the Hoxnian interglacial deposits was found to represent a transition to wetter and colder conditions of the latter part of the interglacial. The varves, or laminae, are not so sharply defined as those deposited during the retreat stage of a glaciation and contain organic material. It is therefore considered that the main deposit at Marks Tey was laid down during the period of climatic deterioration preceding the Gipping glaciation when a vast amount of territory suffered reduction of height. This is proved by the present S i t u a t i o n of the Hoxne Lake Beds which were presumably originally in a V a l l e y and are now at plateau level with new V a l l e y s on each side.

Unpublished information on the constituents of the Marks Tey varved clay is from Dr. I. W. Cornwall who considers the material to be loessic in character and to have been originally wind sorted and subsequently transported by water, the average grain size is:â&#x20AC;&#x201D; Sand ( > 0-06 mm) 5% Silt ( 0-06-0-002 mm) 80% Clay ( < 0-002 mm) 15%

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Gipping Till T h e Gipping Till is normally greyish buff but varies from brown where it is excessively stony to white where it includes a great amount of chalk. The erratics indicate a source in Lowland Scotland with erratics of garnetiferous schist, Pennine Andesites, Derbyshire? Basalt with spheroidal weathering, Oolite, ferruginous limestone from northern Lincolnshire, Spilsby Sandstone and Red Chalk. The preferred orientation of the longer axes of stones also indicates its passage from the north. In south-east Suffolk it forms most of the heavy soil on farmland. It has been eroded from most of the coastal belt, but outliers occur on the outwash gravels as far north as Oulton near Lowestoft. This important site, Taylor's Gravel Pit at Campsheath (PLATE 5), disproves D. F. W. Baden-Powell's theory that there was no Gipping Till along the eastern coastal belt down to Ipswich and establishes the importance of frequently inspecting temporary sections.

T h e Oulton section near the edge of the plateau follows:â&#x20AC;&#x201D; G i p p i n g T i l l to 8 ' with a 1 2 ' long chalk b o u l d e r . gravel, beautifully c u r r e n t b e d d e d circa 15'.

G i p p i n g outwash L o w e s t o f t Till.

Most of the best sections of the Gipping Till have been exposed in the Gipping Valley, notably in the Paper Mill Lane Pit, Bramford and there are some excellent phenomena above the chalk in Church Lane Quarry, Claydon including unique solifluction structures.

From Claydon Church, T h e Slade(partof an ancient track which possibly dates from pre-Roman times, Early Iron Age and Roman relics having been found along its course from Akenham to Shrubland) continues north along former Chapel Lane to Sandy Hill. Near the northern end of the lane a small gravel pit was re-opened during 1966 exposing the edge of a glacial channel filled with Gipping Till. Such Channels are thought to be due to tongues of ice advancing ahead of the main ice sheet possibly following old shallow Valleys and a number have been revealed in the Ipswich area where Gipping Ice has spilled over the edge of the plateau; two, possibly three, were noted in the network of trenches for the Maidenhall Estate and the Locomotive depot, at Stoke in 1948-9, these were narrow and probably over thirty feet deep.

T o the east of Ipswich trenches for the Rushmere Hall area exposed six to thirteen feet of Gipping Till which became increasingly stony eastward and thinning towards the Heath. The underlying Gipping Gravel was formerly worked at the edge of Rushmere Heath near the end of Playford Road at the site of a Late Bronze Age urnfield. Creeting White Sand was exposed below the gravel at this site. An outlier of Gipping Till was revealed when the new school was built in Bell Lane, Kesgrave.

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Gioping Till occurs generally at plateau level to the north and west )f the A.12 and at Pettistree it is decidedly yellowish whereas at the H a u g h L a n e gravel pit, Woodbridge, it is the normal greybuff colour. At the latter site the base of the tili is typically streaky with chalky layers. T h e chalky streaks are considered to be due to layers of cleaner and dirtier ice moving at different speeds due to the braking action of the ground over which the ice was moving. Possibly in winter the movement was retarded or even arrested, with the result that the layer in contact with the earth allowed freezing to cement the ice sheet to the ground and when the summer warmth caused fresh movement. T h e included chalk acted as a lubricant until the whole mass attained its maximum velocity, perhaps a few yards a year. Below the base of the tili one usually finds thin deposits of silt and fine sands resulting from sub-glacial meltwater frequently containing rounded grains of chalk. T h e s e features occur at Creeting St. Mary (Broom Hill) and were exposed in trenches on the Chantry Estate near London Road where the tili covered area was found to be larger than is shown on the geological map.

T h e best section of Gipping Till and the basal phenomena formerly seen at the Paper Mill L a n e pit of A. J . Brush L t d . at Bramford has latterly been obscured by rainwash, but excavations for gravel will undoubtedly expose fresh sections from time to time.

In the absence of sections it is not possible to distinguish which tili may be represented by the heavy soil of most parishes because the upper part of these chalky clays has inevitably been altered by weathering, the chalk having been dissolved by the mildly acid rain water. In open sections the zone of weathered tili can be seen varying in depth and brownish in colour. Usually the decalcified Lowestoft Till is darker than the Gipping and with experience the difference may be distinguished, but opportunities for comparison are rare.

Borings for wells afford valuable opportunities for ascertaining the nature and thickness of the boulder clays and often they may be identified from the borer's log in which his own terms are used but are sometimes difficult to relate with geological nomenclature: fortunately glacial mixtures of clay and chalk are usually unmistakable. In the following list the thickness of tili in sundry parishes is given:— UNSPECIFIED

70' on sand ^ Bricett 100' y°P t o n 60' Ulmwich Cliff 4' frostenden ?36' ?,essf;tt 30' •»lendlesham (site unrecorded) 40'

TILL

Mendlesham North of Church „ The Lodge „ The Green Uggeshall Wantisden Wrentham

80 90 91 36 ?20 10

382 Transactions

of the Suffolk

Naturalists',

DETERMINATE

G—Gipping Ashbocking G 8' L 80' Bacton SR' T, Barham C h u r c h Lane Cr 17' Battisford G 9' 95' L „ Council Houses G 10' 100' T, Beccles 9 0 ' O D T, 1V Belchamp L 56' Benacre Hall T, 71' Bradfield (Essex) L 100' Brome 9?.'

T,?

Burstall, Canes F a r m G 20' L 33' W h i t e House G 38' L 10*' T h e Cott's G 8' T, 36' Copdock G 20' Creeting St. Mary, Malting Farm Cr 7' L 20' Creeting St. M a r y , Bucks H e a d G 15' 25' I, Elmswell G 6' L 62' G t . Finborough G 10' L 26' Framsden, Bluebell F a r m G 124' L 464' ,, Basting's F a r m G 10' 75' L G i p p i n g Hill House F a r m I, 58' Gisleham, G r a n g e F a r m L 21' G t . Waldingfield G? 25' 115' L Haughley, Wassick's F a r m G 7' 76' L H e l m i n g h a m Hall G 12' L 40' School Cr 18' L 70' Hintlesham Old House G 16' I, 46' Homersfield (below Valley gravel) L tci 2 8 ' H o x n e R . D . C . Houses G 6' I. 15' Kessingland Field 270 L 264' Laxfield R . D . C . Houses G 10' L 80' Mendlesham G 12' I, 52' Mendham G 6' L 44' M o n k Soham, G r a n t ' s F a t m G 10' L 73'

Vol. 13, Part 6

TILLS

L—Lowestoft Nettlestead, H i g h House ,,

Rookery F a r m

Pakenham Hall F a r m Assington, Dillack's F a r m T h e Street „ Vicarage Badley, Hall „ Bridge F a r m Barrow, Wolfe F a r m „ P u m p i n g Station Baylham, Stone F a r m

G L G L G L G G G G G L j

13' 34' 6' 126' 2 r 10' 18'

30' 50' 7' 6' 124' 117' 724' 8' 32'

G L 54-' Glebe Close G 35' L 54' Bedfield G 75' L 38' Billingford, Public Well L 20' Bramford Hall G? 88' Brundish L 10' Buxhall, Rectory G 43' L 126' Cockfield L 24 Coddenham, Ivy F a r m G 534' Birch Farm L 10' Combs, Moats T y e .... G 80' L 15' D e b e n h a m , Hill F a r m ... G 57' L 12' Earl Stonham, Housing Site G 69' L 20' Edwardstone, Quick's F a r m G L(S) 40' Flowton, C h u r c h Acre 10' G 35' L ,, Valley F a r m 10' G 58' L 10' Fressingfield, Ufford Hall G 55' L 22' Gislingham, H o m e F a r m G? 52' L 12' Gosbeck G 104' L Hasketon, Rectory G12 f ? 8 ' 35' L 8' Harleston G r e e n G 60' L 18' G Henley, M a n o r F a r m 29' L 40' L R . D . C . Houses 13' G —?— Cottage 51' L 60' Holton, Dairy F a r m L 10' Horham, Thickthorn Farm G 60' L

383

GEOLOGICAI, HISTORY Kenton, Rectory

G

Lavenham, G r e v h o u n d I n n

G

,, Vicarage Mellis, R . D . C . Site

L G L L?

Metfield

10'

72' 14' 14' 45' 15' 19' 55'

Needham Houses

Market,

Occold O l d N e w t o n Hall Onehouse

R.D.C. G L L L G? L

Palgrave

The Last Glaciation The tills attributed to the ultimate ice sheet to affect East Anglia are the Hessle and Hunstanton Brown Boulder Clays. The latter is represented by a coastal strip along the western part of the north Norfolk coast from Hunstanton for about twenty miles and about one mile wide. Across The Wash the Hessle Till Covers much of Lincolnshire east of the Wolds and south-east Yorkshire between the Yorkshire Wolds and the sea, with a narrower coastal strip from Flamborough Head to beyond Scarborough.

There is little reason to suppose these deposits were laid down by any but the last advance of ice from the north but various authorities have published conflicting conclusions, in particular with regard to the most southerly limit reached by the ice. A northerly limit was given by Farrington and Mitchell in 1951 at Flamborough Head; Valentin (1955) drew his line down to the mouth of the Humber but left a large area of tili outside his limit; Clayton (1957) put the western limit just west of the Fens and Suggate and West included the area given above but omitted to include the Cromer Ridge which most glaciologists regard as a fresh glacial topographical feature and our only surviving terminal moraine. A terminal moraine being a ridge of ice-transported materials deposited at the limit of an ice sheet where the rate of melting kept pace with the movement of the ice. The centuries of erosion along the Cromer coast have shortened the moraine and it now terminates at Lighthouse Hill, Cromer where there are some 200 feet of glacial deposits accumulated during the past half million years.

While no claim can be made that Hunstanton ice ever extended much to the south of the present limit there are many sites where glacial phenomena of this period exist and have been exposed in a number of temporary sections. Naturally all frost crack phenomena and solifluction structures in our present subsoils are indubitably attributable to the periglacial conditions beyond the limit of the Hunstanton ice. These features often occur above fluvio-glacial sands and gravels of post Gipping age.

The intensive study of the great networks of trenches for new housing estates around Ipswich and to a lesser extent at Felixstowe, Stowmarket, etc., has led to the discovery of a series of

12i' 19'

20' 57' 29' 50' 30'

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small ice cut Channels, some only about ten feet across, passing down the slopes from the plateau to feed small Valley glaciers.

These are invariably filled with a curious mixture of sand, gravel, and clays, the latter is sometimes clearly recognisable Gipping Till in small masses up to about two feet across, but one six feet long was exposed at Westerfeld, others are obviously the same tili in a decalcified condition. Inclusions of loamy material usually have a curious porous character attributable to the fact that when included particles of ice melted minute cavities remained open in the absence of any subsequent compacting agency, (in older deposits the weight of superincumbent ice compacted formerly frozen soils).

The first of these minor Channels was noted during the early 1920s it having been exposed by a fall of cliff at Bridge Wood near Alnesbourne Priory at a place where no other evidence of ice action has since been observed. This feature was flat bottomed and cut into London Clay; its shallow nature implied that erosion had reduced its depth. Most temporary trenches are too shallow to permit positive determination of such Channels but some of those in the Chantry and Maidenhall areas on sloping ground were from ten to over twenty feet deep. At the latter site, adjoining the Ipswich railway tunnel, the mammoth and red deer interglacial loams were buried below a curious deposit, up to five feet thick composed of masses of displaced local clay and loam (including London Clay), mixed with sand, in appearance like large argillaceous boulders in an arenaceous matrix, extending from the railway westward to the foot of the rising ground. This formation could not possibly have been deposited by water and its Position above beds laid down during the warmer part of the Ipswichian interglacial points to an origin toward, or during the last glacial epoch. To the south is an area of gravel the uneven surface of which has the hollows filled with very fine sand.

The Chantry Estate and Belstead Brook Valley The trenches for this estate extended from near Ipswich Station to Sprites Hall Lane, near Washbrook ranging over the uneven valley slopes from the railway up on to the plateau. The slopes to the north exhibited no features of the nature now being described but a number of small ice cut Channels were exposed by a trench from Bobbitshole to Stone Lodge cut along the south facing slope of Belstead Brook Valley. Most of the plateau is blanketed with a thickish mass of Gipping Till thinning toward the south. These Channels did not originate during the Gipping glaciation and could not be due to ice from the north and be part of the HessleHunstanton Till as there is every reason to believe that ice no more than just over-lapped what is now the Norfolk Coast. As these Channels passed down toward the valley bottom they cut through

GEOLOGICAL HISTORY

385

the Red Crag and the sandy part of the mixture was enriched and added to the stones from the plateau gravel below the tili. It was later discovered that the Bobbitshole lake beds, of the first half of the Ipswichian interglacial, had been cut through by a Valley glacier which deposited a stony tili. Only the right (south) side of this ice cut Channel was exposed by the excavation and this was vertical (FIGS. 19 and 20). Both the lake deposits and the gravelly tili were sealed in by glacio-fluvial sands and gravel in which were overfolds and other structures due to solifluction (slipping downhill during a phase of alternate freezing and thawing). The absence of Channels on the Ipswich side of the watershed is explicable owing to the fact that the frozen soil was not thawed on the north facing slope, whereas the south facing slope on the Belstead side would get the fĂźll effect of the sun throughout the greater part of the day.

FIG. 19

FIG. 20

FIG. 19, showing the late glacial Channel cutting t h r o u g h the Bobbitshole lake beds a n d fluvio-glacial gravel sealing in the interglacial deposits.

FIG. 20, s h o w i n g Eocene R e a d i n g Clay wedged aside below L o n d o n Clay, with O l d h a v e n Sand above. L I Fluvio-glacial gravel and sand, 2 Calcareous lake clay with a b u n d a n t n o n - m a r i n e mollusca, 3 Detrital lake m u d , 4 Loess, 5 ice c u t Channel. R1 as above, 2 O l d h a v e n Sand, 3 R e a d i n g Clay with slickensides d u e to pressure f r o m the left, 4 L o n d o n Clay. (Not to scale).

The origin of the small ice cut Channels is thought to be due to thick accumulations of snow on the plateau which became compacted into ice. During milder periods of the glaciation partial thaw caused runnels which found their way down the slopes, the water of which froze again at night. Eventually fingers of ice would fill the upper part of the Channels and gravity would then have played a part and the ice moved down gradually enlarging the channel. The mixture of material Alling the Channels would

386 Transactions of the Suffolk Naturalist?, Vol. 13

have merged in a Valley glacier eventually formi8ng theS gravel y lv tili of Bobbitshole.

Current excavations at Bobbitshole have revealed only one new fact of importance. The presence of elephant and other bones in the lower part of the gravels above the loess and lake beds implies this part of the deposit is possibly a river terrace gravel laid down during a later phase of the Ipswichian interglacial.

Barham At Broomfield Pit, Barham large areas of shallow gravels have been worked in a haphazard manner owing to the quantity of chalk in much of the gravel. The Chalky gravel appears to rest on, or is perhaps channelled into mammaliferous gravels of the latter part of the Ipswichian interglacial, or possibly an interstadial, (a mild phase not of the duration of an interglacial). The fauna of the gravels include mammoth, reindeer replacing the red dee woolly rhinoceros and a small horse and generally represent ä climatic condition similar to present day Lapland.

To the south of our region S. H. Warren recorded in 1912 the discovery in the Lea Valley of south-east Essex of low level beds representing a truly arctic climate, an indication of a true glaciation to the north*. From evidence such as this in the London area phenomena of periglacial conditions are to be expected in East Anglia and it is surprising that little or nothing has hitherto been recorded.

Geologists are dependent on commercial and temporary excavations made in critical areas and far too many such sections have not been seen and recorded. Most excavations occur in the vicinity of towns and usually few in the large areas of farmland between where there is less demand for sand, gravel or clay for building, etc., but it is in these regions where it is important to record the little information that may become available. It is only by chance that such interesting data as the frost cracks at Boyton in highly compacted comminuted Red Crag was recorded.

This was owing to the fact that lucerne growing where the greater depth of decalcification along the cracks allowed deeper penetration of the roots resulting in more vigorous growth to more than twice the height of plants growing on shallower subsoil which led to investigationf (FIG. 21).

In these contributions it is the intention to record date which have become available since the publication of the Geological Survey Memoirs in 1927, 1928, and 1929 on Ipswich, Felixstowe and Woodbridge, and Sudbury by the late Professor P. G. H. Boswell,

*S. H. Warren, 1912, Quart. Journ. Geological Soc., vol. 68, p. 213 â&#x20AC;˘ vol. 7 (1916) p. 164; and vol. 79 (1923) p. 603. fP. J. O. Trist, 1952, Trans. Suff. Nats., vol. 8, pp. 26-29.

GEOLOGICAL

387

HISTORY

Ph

o

o o

<

« o

388 Transactions of the Suffolk Naturalists',

Vol. 13, Part 6

and the 1885 Memoir by Wm. Whitaker who recorded many sections which have been obliterated for more than sixty years (FIG. 22). It has not been possible to inspect all temporary sections in south-east Suffolk and only a few in the more remote parts of the county so many interesting records must have been missed.

In the ahsence of a team of observers spread throughout the region it is inevitable that much valuable information is lost to science.

East pit 3

Central 2

pit

1

Wept

pit 4

FIG. 22

Section of a synclinal deposit of laminated brickearth at the former Kirton brickpit, after William Whitaker, 1874. 1 dark brickearth, 2 light grey brickearth, 3 chalky boulder clay (PLowestoft Till), 4 sand. T h e downfolding of the beds is indicative of action of subsequent major ice pressure and later large scale erosion.

Boswell in the Sudbury Memoir refers to high level glacial gravels in isolated patches around Cockfield and Waldingfield which are very ferruginous and are composed mainly of flint.

It is considered these remnants represent the only surviving evidence of an early and hitherto unrecognised glaciation but there is no evidence to show to which they are to be referred.

These gravels are important evidence of the great amount of erosion that has reduced the level of the landscape which is patently shown by the present Situation of the Hoxne lake beds.

The gravels at Acton below boulder clay and about forty feet thick are described by Boswell as irregularly arranged and probably deposited under torrential conditions with interbedded sands, some of which are composed mainly of chalk grains, they closely resemble the structures seen in the Cromer Ridge and in the Blakeney Esker. It is therefore suggested that the Acton site may well be a moraine possibly representing a halt in the advance of an ice sheet which subsequently overrode it. There is very little Jurassic erratic material and thus is unlikely to belong to the Lowestoft glaciation. At Jordan's pit Brundon, near Sudbury, Gipping Till was found underlying the mammaliferous sands and gravels of the Ipswichian interglacial and beds of chalky sand were observed here also. This site has been obliterated.

PLATE

2

L a r g e s e p t a r i a n n o d u l e ( c o n c r e t i o n a r v l i m e s t o n e ) 4 feet 6 ins. i n d i a m e t e r unearthed f r o m Lowestoft T i l l in the Clavpit G r o v e Q u a r r v of T h e Associated P o r t l a n d C e m e n t Co. L t d .

T h e s e boulders originated i n the K i m m e r i d g e Clav and often include ammonites.

W h e n e x p o s e d t h e y are split by frost exposing crystaline Calcite in the inferior.

[Photo

by F.

W.

Simpson

PLATE

3

Raft of dark grey loess included i n the Lowestoft T i l l at Clavpit Grove, Great Blakenham. T h i s was exposed in 1954, other similar masses were seen in 1955 and 1957. T h e deposit f r o m w h i c h they were derived has not been traced.

PLATE

4

Raft o f grey rather coarsely laminated b r i c k e a r t h f r o m an u n k n o w n source to the west, i n c l u d e d i n the L o w e s t o f t T i l l at C l a y p i t G r o v e , Great Blakenham. T h i s feature o n the s o u t h side o f the q u a r r y has been h i d d e n b e h i n d talus for some years.

[Photo

by F.

W.

Simpson

PLATE

5

Large chalk erratic, 12 feet long, in G i p p i n g T i l l at Taylor's Pit, Camps Heath, Lowestoft. A large flint is seen near the shovel. T h e T i l l is nosing into the underlving G i p p i n g Gravel which rests on Lowestoft T i l l .

PLATE

6

Current bedded Gipping Gravel rieh in derived shell fragments from the Red Crag. Similar deposits occur at Creeting St. Mary and at Sproughton which indicates the destruetion of a large amount of Crag to the north by the Gipping ice sheet.

[Photograph

of Haugh Latte Pit, Woodbridge, Dr. W. A. Macfadyen,

/g5J.

GEOLOGICAL

HISTORY

389

Near Hadleigh, at Red Hill (GR 031445), a deep pit in the steep valley slope exposed below Oxfordian Sudbury Till a thick series of sands and gravels with a series of loessic silts in the middle of the section. Unfortunately this pit was not discovered until Operations had ceased and the lower beds were hidden below talus. The site is on the 100 feet contour and the beds exceed fifty feet in depth. One remarkable feature was a bed about eight inches thick composed of varves sloping at an angle of about 40° in the middle of the series of loessic silts with normal horizontal bedding.