Biostratigraphic and aminostratigraphic constraints on the age of the Middle Pleistocene glacial succession in north Norfolk, UK

Abstract

Considerable debate surrounds the age of the Middle Pleistocene glacial succession in East Anglia following some recent stratigraphical reinterpretations. Resolution of the stratigraphy here is important since it not only concerns the glacial history of the region but also has a bearing on our understanding of the earliest human occupation of north-western Europe. The orthodox consensus that all the tills were emplaced during the Anglian (Marine Isotope Stage (MIS) 12) has recently been challenged by a view assigning each major till to a different glacial stage, before, during and after MIS 12. Between Trimingham and Sidestrand on the north Norfolk coast, datable organic sediments occur immediately below and above the glacial succession. The oldest glacial deposit (Happisburgh Till) directly overlies the 'Sidestrand Unio-bed', here defined as the Sidestrand Hall Member of the Cromer Forest-bed Formation. Dating of these sediments therefore has a bearing on the maximum age of the glacial sequence. This paper reviews the palaeobotany and describes the faunal assemblages recovered from the Sidestrand Unio-bed, which accumulated in a fluvial environment in a fully temperate climate with regional deciduous woodland. There are indications from the ostracods for weakly brackish conditions. Significant differences are apparent between the Sidestrand assemblages and those from West Runton, the type site of the Cromerian Stage. These differences do not result from contrasting facies or taphonomy but reflect warmer palaeotemperatures at Sidestrand and a much younger age. This conclusion is suggested by the higher proportion of thermophiles at Sidestrand and the occurrence of a water vole with unrooted molars (Arvicola) rather than its ancestor Mimomys savini with rooted molars. Amino acid racemisation data also indicate that Sidestrand is significantly younger than West Runton. These data further highlight the stratigraphical complexity of the 'Cromerian Complex' and support the conventional view that the Happisburgh Till was emplaced during the Anglian rather than the recently advanced view that it dates from MIS 16. Moreover, new evidence from the Trimingham lake bed (Sidestrand Cliff Formation) above the youngest glacial outwash sediments (Briton's Lane Formation) indicates that they also accumulated during a Middle Pleistocene interglacial -probably MIS 11. All of this evidence is consistent with a short chronology placing the glacial deposits within MIS 12, rather than invoking multiple episodes of glaciation envisaged in the 'new glacial stratigraphy' during MIS 16, 12, 10 and 6.

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

“…The age of the sediments and landforms within Domain 3 is more subjective. The simplest explanation, and that largely favoured here, is that Domain 3 records a further stage of ice-marginal wastage and retreat from Domain 2 -thus an Anglian MIS 12 age (Banham et al, 2001;Hoare et al, 2009;Preece et al, 2009). However, to-date no absolute dates have been produced that directly date glacigenic materials in this domain so this assertion is at best equivocal, and it remains a possibility that elements of Domain 3 could be younger.…”

“…3 subject of ongoing debate (Boulton et al, 1984;Hamblin et al, 2000;Banham et al, 2001;Hamblin et al, 2005;Preece et al, 2009;Rose, 2009;Lee et al, 2011cLee et al, , 2012.…”

“…The absolute chronology of the A6 event in north Norfolk is a controversial issue with several different models indicating glaciation during the Anglian glaciation (Lunkka, 1994;Banham et al, 2001;Pawley et al, 2008;Preece et al, 2009) or during a later Middle Pleistocene glaciation possibly equivalent to MIS 6 (Saalian) (Straw, 1973;Hamblin et al, 2000Hamblin et al, , 2005Rose, 2009). A detailed critique of the evidence and arguments behind this debate is beyond the scope of this paper (see Rose, 2009 for an overview of this debate) although 'dated' stratigraphic levels within the glacitectonised succession enable a chronostratigraphy to be applied to parts of the succession.…”

“…apparent kettle-hollow within deformed Briton's Lane Formation deposits at Sidestrand (Hart and Peglar, 1990;Preece et al, 2009). The age of the sediments and landforms within Domain 3 is more subjective.…”

“…Proceedings of the Geologists' Association, 124, 753-777. PRE-PROOF ACCEPTEF MANUSCRIPT.3 subject of ongoing debate (Boulton et al, 1984;Hamblin et al, 2000;Banham et al, 2001;Hamblin et al, 2005;Preece et al, 2009;Rose, 2009;Lee et al, 2011cLee et al, , 2012.The geology of the region consists of a thick layer of superficial deposits unconformably overlying bedrock; the latter comprising marl and fossiliferous limestone of the Cretaceous age Chalk Group (Mortimore et al, 2001(Mortimore et al, , 2011Moorlock et al, 2002). Bedding within the bedrock strikes northsouth and dips gently (<1°) to the east (Mortimore et al, 2001), with the regional rockhead surface, lying at a depth of between 15-20 m OD in the west of the study area, declining eastwards to beneath sea-level in the east ( Figure.…”