R. G. West

The Quaternary Deposits at Hoxne, Suffolk

The geology and palaeobotany of Quaternary deposits at Hoxne, Suffolk, have been investigated. It is shown that immediately after the ice which laid down the Lowestoft Till had retreated a lake basin was formed in the till. In the basin a series of interglacial lacustrine sediments was deposited, first clay-mud and later detritus mud. Reworking of these sediments under a periglacial climate with a fluctuating lake water level resulted in the deposition of alternating layers of silt, drift mud and brecciated clay-mud. After this, clay, sand and gravel were deposited in the lake by solifluxion under periglacial conditions. The lake basin as a topographical feature was then entirely obliterated, and clay, sand and till were deposited unconformably on the lake sediments. This till was formed during the Gipping Glaciation. After the retreat of the ice of this glaciation, the present valleys were excavated, and later to a small extent filled by fluvial deposits. Finally, aeolian sand, which now forms the surface deposit in the area, was deposited under periglacial conditions and, probably at the same time, a cryoturbation phase occurred. Macroscopic plant remains and pollen diagrams from the lacustrine interglacial sediments are described. They give evidence of the vegetational and climatic history of the interglacial period between the Lowestoft and Gipping Glaciations. Four major vegetational stages are distinguished; they are named the Late-Glacial, Early-Temperate, Late-Temperate and Early-Glacial stages. The Late-Glacial stage was characterized by Hippophaë scrub, the Early-Temperate stage by the development and persistence of mixed-oak forest, the Late-Temperate stage by the beginning of the replacement of the mixed-oak forest species by Carpinus and conifers, including Picea and Abies, and the Early-Glacial stage by the presence of park-tundra with scattered forest. There was a rapid climatic amelioration at the very beginning of the interglacial period, which led to a climatic optimum in the middle of the Early-Temperate stage. After that time there was a progressive deterioration of the climate, which resulted in the periglacial conditions under which the uppermost sediments of the lake were laid down. A phase of deforestation in the Early-Temperate stage and its relation to the Lower Palaeolithic (Acheulian) artifacts found during the investigations are described; they may be associated. The stratigraphical positions of those artifacts found recently and of those found by previous investigators at Hoxne are also described. The molluscan and mammalian faunas of the deposits and the glacial erratics from the covering till are described in Appendices. The stratigraphy demonstrated here differs from that previously found at Hoxne in showing that there is one interglacial temperate horizon, undivided by a cold phase, whereas previously two temperate horizons separated by a cold phase had been described. The origin of this difference is explained. A comparison of these Quaternary deposits is made with those elsewhere in Britain, in Ireland and on the continent. It is concluded that the Hoxne Interglacial is of Great (Elster/Saale, Mindel/Riss) Interglacial age.

Coastal Interglacial Deposits of the English Channel

Fossiliferous Late-Pleistocene deposits on the foreshore of the English Channel at Selsey (Sussex), Stone (Hampshire), and near Arromanches (Calvados), have been investigated. At each site analyses of pollen, macroscopic plant remains and Mollusca have been made and from these vegetational, faunal, environmental and climatic conditions have been reconstructed. At Selsey, it is shown that the deposits, which lie in a channel cut in Eocene rocks, are of Ipswichian (Eemian or Last) Interglacial age. Pollen analysis of the sediments of the channel filling show they were formed during zones b, c, d, e and f of this interglacial from open parkland vegetation to birch-, to pine-, to oak-dominated forests. Analysis of the macroscopic plant remains and of the molluscs suggests a rapid climatic amelioration at the beginning of the interglacial, so that by the beginning of zone f there are indications of summer warmth exceeding that of the present day in the area. In the upper part of the channel filling, estuarine deposits overlie freshwater deposits. It is shown that the marine transgression causing the change was taking place in zone f and was probably responsible later for the raised beach deposits which overlie the channel deposits and which form the cliffs at Selsey Bill. At Stone pollen analysis shows that brackish water deposits, below present high tide level, were formed in zone f of the Ipswichian Interglacial. At that time Quercus, Pinus and Acer were the chief trees forming the forest in the region. The macroscopic plant remains and the Mollusca indicate that the deposit was formed under saltmarsh conditions. As at Selsey, the raised beach gravel found overlying the interglacial deposit is related to the same marine transgression that produced the brackish water conditions. Near Arromanches, at St Côme de Fresne and Asnelles-Belle-Plage, two deposits showing a change from marine to freshwater sediments were investigated. The analysis of pollen and the Mollusca showed the prevalence of pine forest and its replacement by open steppe-like conditions as the marine regression occurred. After the regression, limon covered the freshwater deposits. The fossiliferous deposits are tentatively correlated with zone i of the Eemian Interglacial. The relative land- and sea-level changes indicated by all the deposits are considered. It is concluded that in the English Channel, during the Ipswichian (Eemian) Interglacial, sea level rose above its present height in zone f and fell below it during zone i. The Selsey-Brighton raised beach and the Normannien II raised beach are correlated with the same marine transgression. It is pointed out that if the Selsey-Brighton raised beach is to be correlated with the Monastirian II level of 7—8 m, then this level should be correlated with the Ipswichian (Eemian) Interglacial.

Interglacial deposits at Bobbitshole, Ipswich

The stratigraphy and palaeobotany of fresh-water interglacial deposits at Bobbitshole, Ipswich, Suffolk, have been investigated. The interglacial deposits are shown to occupy a lake basin in a valley cut in the local plateau, which is partly formed by a chalky boulder clay assigned to the Gipping ice advance. In this basin was deposited a series of lacustrine sediments, first silt (probably of aeolian origin), then clay-mud and finally clay. These interglacial sediments are sealed unconformably by sandy gravel, probably deposited under cold conditions. Pollen diagrams and macroscopic plant remains from the interglacial deposits are described. They give evidence of the vegetational and climatic history during the first half of an interglacial period. The succession of pollen zones found is similar to that described from the Eemian (Last) Interglacial in north-west Europe, with which the interglacial is correlated. The Eemian pollen zones b, c, d, e and f which show the succession from birch- to pine- to oak-dominated forest, are all present. An analysis of the very abundant macroscopic plant remains, together with the pollen results, suggests a rapid amelioration of the climate at the beginning of the interglacial period, and in zone f, the final zone represented, there are indications of a summer warmth exceeding that of the present day in the area. The interglacial flora is particularly rich in aquatic plants, and an analysis of the abundance of each species indicates a vegetational succession, as the lake filled with sediment, from open-water to reed-swamp to marsh vegetation. The palaeobotany of the deposits is briefly compared with that of other interglacial deposits in Britain and on the continent. The correlation of the interglacial deposits with the continental Eemian (Last) Interglacial provides confirmation of the correlation of the Gipping ice advance with the Saale Glaciation of northern Germany, and indicates that the covering gravels are of Last Glaciation age. The interglacial deposits are partly below sea-level, and close to the tidal Orwell estuary. The significance of this for local relative land- and sea-level changes in and after the interglacial is discussed.

Radiocarbon dating of Flandrian pollen zones at Red Moss, Lancashire

A pollen diagram from Flandrian (post-glacial) organic deposits at Red Moss, Lancashire, has been constructed and six pollen assemblage zones defined. Radio carbon dating, using equipment described in outline, has been applied to sixteen horizons with in this sequence, so that boundaries of the pollen assemblage zones, and significant changes with in them, have been dated. The sixteen dates fall between 9798+200 b. p. and 4370+ 80 B.P., and form a consistent series, apart from the basal date, which lies near the Late Weich selian-Flandrian boundary. The sequence of assemblage zones has been assigned to three major chronozones of the Flandrian: FI, corresponding to the first four assemblage zones, covering the period of time before the clear establishment of mixed oak forest; FII, corresponding to the mixed oak forest zone (Quercus-Ulmus-Alnus) starting at 7107 + 120 B.P., and FIll, corresponding to the Quercus-Alnus zone, starting at 5010 + 80 B.P. The dating of the pollen assemblage zones at Red Moss is briefly compared with dates from other dated long Flandrian sequences in north-west Europe. It is shown that certain pollenanalytically defined horizons associated with the Alnus and Corylus rises have diachroneity while the horizon of the Ulmus decline is broadly synchronous. The significance of these differences is briefly discussed. Many more dated profiles are required before interpretation of these differences can be made interms of migration, succession or climatic change.

Interglacial Deposits at Ilford, Essex

At Ilford, Essex, organic sediments have been found beneath the brickearth, long famous for its rich mammalian fauna. Pollen analysis shows that these organic sediments and the lower part of the overlying brickearth were deposited during the Ipswichian (Last) Interglacial. The pollen diagrams show the vegetational succession typical of the first half of the interglacial, with pollen zones b, c, d, e and f, which cover the early treeless part of the interglacial and the change to forested conditions with Pinus and Quercus. The rich flora of macroscopic plant remains indicates that a climate with summers warmer than now obtain in the area prevailed probably in zone c and more certainly in the later zones. Analyses of the macroscopic plant remains and the non-marine Mollusca demonstrate that the organic deposits were formed in a large pond or a small stream, tributary to the Thames at that time. A rising base level, probably resulting from the rise in sea-level known to occur in zone f of the interglacial, caused the Thames floodplain to extend over the organic deposits, and brickearth was deposited up to a height of 42 ft. O.D. at least. The surface of the brickearth was contorted by cryoturbation during the Weichselian (Last) Glaciation. The Ilford temperate deposits are correlated with temperate fossiliferous deposits at Little Thurrock (Grays), and more tentatively, with temperate fossiliferous deposits at Erith, Crayford and Ebbsfleet. The consequences of the dating of the Ilford brickearth to the Ipswichian Interglacial for the terrace succession of the lower Thames valley are considered.

The margin of a middle Pleistocene ice advance at Tottenhill, Norfolk, England

Exposures at Tottenhill quarry, west Norfolk, are described. Detailed sediment logs, lateral sediment distribution and facies relationships are presented, together with palaeocurrent measurements and pebble counts. It is concluded that the sequence represents a delta-like subaquatic fan accumulation that was deposited by glacier meltwater at the eastern margin of the present Fenland. The ice must have entered the area from the west to northwest. An arctic leaf flora is associated with still water pool sediments within the fan sequence. Pollen assemblages appear to be largely derived by reworking from underlying in situ temperate stage sediments which are correlated with the Hoxnian Stage. The age of the deposits is discussed and it is concluded that the glaciation concerned must date from the early part of the Wolstonian Stage on the basis of the previously established stratigraphical sequence in the area.

Late and Middle Pleistocene deposits at Somersham, Cambridgeshire, U.K.: a model for reconstructing fluvial/estuarine depositional environments

Gravel quarries at Somersham, Cambridgeshire, have yielded evidence for a Pleistocene channel of the R. Great Ouse, containing temperate stage sediments between cold stage sediments. In the earlier cold stage, fluviatile gravels and floodplain loessic sediment accumulated. In the later cold stage a further series of gravel units and floodplain sediments were deposited, together with lake sediments. The lake sediments are associated with Lake Sparks, dammed by Late Devensian ice in the Wash at ca. 18.5 ka BP. The lake sediments overlie gravels with a radiocarbon date from an organic horizon indicating a Middle Devensian age. Clast lithological analyses from the earlier and later gravels suggest that reworking of gravels has occurred within a relatively stable catchment. The petrography of the earlier cold stage loessic sediment and temperate stage fine sediment indicates an Anglian affinity, which conflicts with the biostratigraphic interpretation. Pollen and macroscopic plant remains from sediments of both cold stages and from the temperate stage indicate, respectively, assemblages with a typical full-glacial aspect with a rich flora of shrubs and open ground herbs(including an assemblage at ca. 18 ka), and temperate freshwater and marine-influenced organic sediments. On the basis of pollen analysis these are ascribed to substages Ip II and III of the Ipswichian Stage(O.I.S. 5e), with a Pinus-Quercus-Corylus biozone in the former and a biozone with Carpinus in the latter. Marine-influenced sediments, at −3.7 to −0.3 m OD, indicate transgression in Ip II and regression in Ip III. Molluscan assemblages from the temperate stage and the later cold stage are described; two are from the Late Devensian, at a time near the maximum extension of ice into the Wash. Foraminifer and ostracod faunas are described from post-Ipswichian sediments and may be reworked. Radiocarbon dates confirm the age of the later gravel suite as Devensian and a calibration of the measurements is given. Amino acid ratios from Corbicula fluminalis valves from temperate stage sediments are reported, with measurements from different parts of the valve; the results tend to support an Ipswichian age. TL measurements of the earlier cold stage loessic sediment and associated sand indicate a pre-Ipswichian age for the sediments. The earlier cold stage is correlated with the pre-Ipswichian cold stage, the Wolstonian of Mitchell et al.(1973); problems with this correlation are discussed. Various periglacial phenomena, including thermal contraction networks and cracks, diapirs, involutions and coversand are associated with the Devensian sequence. The complex environmental history, based on stratigraphy and palaeontology, is described, and related to other nearby sites in southern Fenland.

The interglacial deposits at Stutton, Suffolk

As complete a series as possible of samples from the brickearth exposed on the northern bank of the Stour estuary at Stutton, Suffolk, has been taken and the contained non-marine Mollusca analysed. These show persisting and almost uniform river conditions but a steady climatic deterioration. Although the deposits are mostly oxidised and devoid of pollen, one sample from near the base of the fossiliferous section was shown to belong to Zone g of the Ipswichian (Last) Interglacial. As the bulk of the brickearth is contained between this and gravels disturbed by cryoturbation above the brickearth, the deposit must represent aggradation in a river valley in the second half of the Ipswichian Interglacial.

On the origin of Grunty Fen and other landforms in southern Fenland, Cambridgeshire

Depressions and embayments of the southern Fenland margin and islands are ascribed to periglacial processes in the Devensian Stage (last cold stage) of the Pleistocene. The processes, which may be included in the general term thermokarst, include thermal erosion as an important element. The age of the active landscape evolution appears to be Late Devensian. The Crowland Bed of the Fenland Pleistocene succession is a product of these processes.

Plant remains from the Corton Beds at Lowestoft, Suffolk

A flora found in a clay lens in the Corton beds at Lowestoft indicates a late- or full-glacial type of environment during an interval in the deposition of the Corton beds. The interval may be related to drainage changes associated with the retreat of the North Sea Drift ice and the advance of the Lowestoft Till ice.