The distribution, variation and origins of pre-Devensian tills in eastern England

Abstract

In order to define quantitatively the lithological properties of the pre-Devensian tills in eastern England, calcium carbonate contents and mechanical compositions of 501 samples from 289 sites have been measured and heavy minerals counted in 102 of them. The results show that the tills may be divided into two groups: ( a ) a North Sea Drift group consisting of the Norwich Brickearth, the Cromer Tills, the Marly Drift of Cromer type and till members of the Contorted Drift, which is characterized by high sand and low opaque heavy mineral contents; and ( b ) a Lowestoft Till group including the Lowestoft Till of East Anglia, the Chalky Boulder Clay of the east Midlands, the Calcethorpe and Wragby Tills and the Lowestoft-type Marly Drift, which is characterized by low sand and high opaque values. The qualitative similarity of the mineral suites in the two groups, however, suggests a common origin in the North Sea basin. Automated contouring (SYMAP) has been used to represent the spatial distribution of till properties. These confirm that the Lowestoft Till group can be spatially separated from the North Sea Drift group, and divided into a Calcethorpe-Marly facies high in carbonates and lying astride the Wash, and a Lowestoft-Wragby facies with moderate but variable contents of calcium carbonate and occupying the rest of the region. Trend surface analysis has been applied to the Lowestoft Till group. At the first order level there are decreasing trends across the region, from northeast to southwest, in calcium carbonate, amphibole and epidote values and increasing trends in silt and clay. These are interpreted as showing a general movement from the North Sea of sandy and chalky material which became progressively modified by assimilation of Mesozoic clays. Higher order surfaces, particularly those of sand, garnet and amphibole values, point to the Wash as the focus of this glacial activity. It is proposed that the most vigorous stream of ice entered eastern England at this point, levelling the Cretaceous scarps and excavating the Jurassic clays of the Wash-Fens basin, and then fanned out into most of the region to deposit the clay-rich Lowestoft-Wragby facies. The Calcethorpe-Marly facies is considered to represent chalky North Sea material carried by marginal, and weaker, ice streams directly onto the Chalk of Lincolnshire and north Norfolk. The North Sea Drift group is believed to be the product of another ice body, penecontemporaneous with that depositing the Lowestoft group, which entered Norfolk from a more easterly part of the North Sea, incorporating sediments from this basin, but without crossing substantial outcrops of Jurassic or Lower Cretaceous formations or Tertiary clays. The Marly Drift includes a variant showing lithological affinities with both Lowestoft and Cromer Tills and which may be the product of complex interaction between the two ice sheets. All the tills studied seem most likely to be of Anglian age.

A polyphase glacitectonic model for ice-marginal retreat and terminal moraine development: the Middle Pleistocene British Ice Sheet, northern Norfolk, UK

“…The region is situated beyond the maximum limit of the Late Devensian (Weichselian) glaciation , but was repeatedly inundated by ice from the west (Central England) and north (North Sea) during the Middle Pleistocene (Perrin et al, 1979;Bowen et al, 1986;Hart and Boulton, 1991a;Lunkka, 1994; Clark et al., 2004;Scheib et al, 2011). Whether successive ice advances occurred during a single Anglian Glaciation (c.480-430ka) or multiple Middle Pleistocene glaciations centered on the Anglian is the Lee, J.R., Phillips, E., Booth, S.J., Rose, J., Jordan, H.M., Pawley, S.M., Warren, M., Lawley, R.S.…”

“…The Bacton Green Till was deposited by an earlier oscillation (A4) of the North Sea lobe of the British Ice Sheet into north Norfolk and consists of a complex sequence of subglacial and subaqueous diamictons (Lunkka, 1994;Lee and Phillips, 2008). As the margins of the North Sea lobe of ice retreated northwards, north Norfolk was crossed by a lobe of British ice that crossed the region broadly from west to east (Perrin et al, 1979;Ehlers et al, 1987;Scheib et al, 2011). This A5 advance led to the development of a variably pervasive glacitectonite which partly remobilised the underlying Bacton Green Till, and in places deposited a highly chalky till of western provenance, called the Weybourne Town Till (Dhonau and Dhonau, 1963;Banham and Ranson, 1965;Banham, 1966;Ehlers et al, 1987;Hart, 2007;Lee and Phillips, 2008;Phillips et al, 2008).…”

“…In recent years there has been much debate about the glacial history of East Anglia with a traditional concept advocating a single glaciation prior to the last (MIS 2) (Perrin et al, 1979;Bowen et al, 1986) and a multiphase glacial history with glacial deposits or landforms attributed to most of the Marine Isotope cold stage (MIS 16, MIS 12, MIS 10, MIS 6 and MIS 2) Rose, 2009). Most of the issues of this debate are considered elsewhere (see Preece et al, 2009 andRose, 2009 for overviews), but one of the critical Lee, J.R., Phillips, E., Booth, S.J., Rose, J., Jordan, H.M., Pawley, S.M., Warren, M., Lawley, R.S.…”

“…Each till is separated by variable thicknesses of glacilacustrine silts, clays and sands including the Mundesley Sand Member which crop-out between the Walcott and Bacton Green Till members. The sediment pile was then overridden and disrupted by ice advancing from the west/southwest (A5) leading to the formation of a glacitectonic mélange (Banham, 1965;Banham and Ranson, 1965;Lee and Phillips, 2008;Phillips et al, 2008; Fleming et al, this volume; Phillips and Lee, this volume), and the local deposition of a chalk-rich diamicton (Perrin et al, 1979; Ehlers et al, 1987; Ehlers et al, 1991;Pawley, 2006;Scheib et al, 2011). Recent work by Waller et al (2009) andWaller et al (2011) has suggested that an extensive permafrost developed prior to/during A5, with overriding of this 'warm permafrost' having influenced conditions within the bed of the ice sheet and the style of subglacial deformation.…”

Age limits on Middle Pleistocene glacial sediments from OSL dating, north Norfolk, UK

“…1a), and were correlated with the Elsterian and Saalian glaciations of northwest Europe respectively (Mitchell et al, 1973). The view of two Middle Pleistocene lowland glaciations persisted in Britain until deposits relating to the Wolstonian Glaciation in the English Midlands (Shotton, 1986) and northern East Anglia (Baden-Powell, 1948;West and Donner, 1956;Bristow and Cox, 1973;West, 1977, Straw, 1983 were subsequently re-interpreted as Anglian in age (Perrin et al, 1979;Rose, 1987Rose, , 1989Rose, , 1991. As a result, the concept of the Wolstonian Glaciation in Britain was abandoned leaving the Anglian glaciation as the only extensive Middle Pleistocene glaciation.…”