JOURNAL OF QUATERNARY SCIENCE (2006) 21(2) 155–179 ß British Geological Survey/Natural Environment Research Council copyright 2005. Reproduced with the permission of BGS/NERC. Published by John Wiley & Sons, Ltd.
Published online 23 December 2005 in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/jqs.957
Sea-level changes, river activity, soil development and glaciation around the western margins of the southern North Sea Basin during the Early and early Middle Pleistocene: evidence from Pakefield, Suffolk, UK JONATHAN R. LEE,1,2* JAMES ROSE,2 IAN CANDY2,3 and RENE W. BARENDREGT4 1 British Geological Survey, Keyworth, Nottingham, UK 2 Department of Geography, Royal Holloway, University of London, Egham, Surrey, UK 3 Department of Geography, Loughborough University, Loughborough, Leicestershire, UK 4 University of Lethbridge, Lethbridge, Alberta, Canada Lee, J. R., Rose, J., Candy, I. and Barendregt, R. W. 2005. Sea-level changes, river activity, soil development and glaciation around the western margins of the southern North Sea Basin during the Early and early Middle Pleistocene: evidence from Pakefield, Suffolk, UK. J. Quaternary Sci., Vol. 21 pp. 155–179. ISSN 0267-8179. Received 23 June 2004; Revised 15 June 2005; Accepted 16 June 2005
ABSTRACT: This paper outlines evidence from Pakefield (northern Suffolk), eastern England, for sea-level changes, river activity, soil development and glaciation during the late Early and early Middle Pleistocene (MIS 20–12) within the western margins of the southern North Sea Basin. During this time period, the area consisted of a low-lying coastal plain and a shallow offshore shelf. The area was drained by major river systems including the Thames and Bytham. Changes in sea-level caused several major transgressive–regressive cycles across this low-relief region, and these changes are identified by the stratigraphic relationship between shallow marine (Wroxham Crag Formation), fluvial (Cromer Forest-bed and Bytham formations) and glacial (Happisburgh and Lowestoft formations) sediments. Two separate glaciations are recognised—the Happisburgh (MIS 16) and Anglian (MIS 12) glaciations, and these are separated by a high sea level represented by a new member of the Wroxham Crag Formation, and several phases of river aggradation and incision. The principal driving mechanism behind sea-level changes and river terrace development within the region during this time period is solar insolation operating over 100-kyr eccentricity cycles. This effect is achieved by the impact of cold climate processes upon coastal, river and glacial systems and these climatically forced processes obscure the neotectonic drivers that operated over this period of time. ß British Geological Survey/Natural Environment Research Council copyright 2005. Reproduced with the permission of BGS/NERC. Published by John Wiley & Sons, Ltd. KEYWORDS: sea-level changes; glaciation; pre-glacial river systems; Early and Middle Pleistocene; palaeomagnetism; lithological analysis; North Sea.
Introduction The late Early and early Middle Pleistocene is a period of intense climatic and palaeoenvironmental complexity that is driven by the increased influence of the 100-kyr (eccentricity) orbital forcing cycle (Ruddiman and Raymo, 1988; Rose et al., 2001). In the British Isles and adjacent North Sea Basin, climate change during this period has been traditionally identified through a series of climostratigraphic assemblages defined by pollen assemblage biozones recorded within organic-bearing fluviatile and shallow marine sediments (Mitchell et al., 1973; West, 1980; Gibbard et al., 1991). However, this * Correspondence to: Jonathan R. Lee, British Geological Survey, Keyworth, Nottingham, NG12 5GG, UK. E-mail:
[email protected]
approach and the fragmentary nature of the evidence means that it has not yet been possible to reconstruct a sound stratigraphy and hence cannot document the history of climate change displayed within the marine isotope record with any degree of confidence (see, for example, Funnell and West (1977) and West et al. (1980) for contradictory views of the same evidence). Furthermore, the value of pollen assemblage biostratigraphy as a correlative stratigraphic tool has been undermined by inherent taphonomic problems (Bennett, 1988; Seppa¨ and Bennett, 2003), the replication of pollen assemblages during different climostratigraphic stages (Cox and Nickless, 1972; Davies et al., 2000; Rose et al., 2001), and the development of biostratigraphic controls such as the first and last appearance of molluscs (Preece, 2001), microtine rodent faunas (Preece and Parfitt, 2000) and large mammals (Schreve, 2001a; Stuart and Lister, 2001).
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In order to provide a robust stratigraphic framework to support the biostratigraphic record and gain a greater understanding of the palaeoenvironmental evolution of the British Isles and adjacent southern North Sea Basin during the Early and early Middle Pleistocene, a major research programme is being undertaken by the Department of Geography, Royal Holloway University of London, and the British Geological Survey (Rose et al., 1996a,b, 2000, 2002; Riding et al., 1997, 2000; Briant et al., 1999; Moorlock et al., 2002; Lee, 2003; Lee et al., 2003a, 2004a,b). This programme aims to develop an integrated stratigraphic model for the Early and early Middle Pleistocene of the region based upon the interrelationship between the lithostratigraphic record, neotectonic subsidence and climate change that drive palaeoenvironmental change at a regional and global scale. Ultimately, it is these forcing mechanisms that drive regional scale changes in sea level, and river catchment processes and glaciation, with temporal and spatial changes in these mechanisms recorded within the terrace sequences of the lower reaches of river catchments and adjacent shallow marine coastal deposits (Rose et al., 2001). This study contributes to this stratigraphic and process model by reporting detailed sedimentological, lithological and stratigraphic investigations of sediments from the north Suffolk coast of eastern England. These sediments provide a contextual basis for synchronising elements of the marine, fluvial and glacial stratigraphic sequences and enable an insight to be gained into the dynamic response of terrestrial land-systems to changes in sea level, catchment processes and climatic and environmental change.
Location of study site and its geological context Pakefield (National Grid Reference: TM 537 888) is situated on the north Suffolk coast in eastern England, to the south of
Figure 1 Eastern East Anglia showing the location of Pakefield ß British Geological Survey/Natural Environment Research Council copyright 2005. Reproduced with the permission of BGS/NERC. Published by John Wiley & Sons, Ltd.
Lowestoft (Fig. 1). The geology of the coastal cliff sections was first investigated by Blake (1890) who identified a twotiered sequence of pre-glacial fluviatile and marine sediments overlain by glacial deposits. Subsequent reinvestigations focused largely upon the floral and faunal content of the fluvial deposits (Cromer Forest-bed Formation) and their palaeoenvironmental and biostratigraphic significance (West, 1980; Stuart and Lister, 2000, 2001). The Early and early Middle Pleistocene stratigraphic succession of the area consists of fluvial, shallow marine and glacial sediments that were deposited close to and within the margins of the southern North Sea Basin (Zalasiewicz and Gibbard, 1988; Arthurton et al., 1994; Funnell, 1996; Allen and Keen, 2000; Rose et al., 2001, 2002) (Table 1). The earliest shallow marine and coastal deposits of this age correspond to the silts, sands and gravels of the Norwich Crag and Wroxham Crag formations (Rose et al., 2001). These sediments exhibit a complex geometric arrangement that reflects repeated regressive–transgressive sea-level fluctuations across a relatively flat low-lying coastal plain caused by both neotectonic and eustatic processes (Funnell, 1995, 1996; Briant et al., 1999; Allen and Keen, 2000; Rose et al., 1996b, 2001, 2002; Lee, 2003) (Fig 2). Three pre-glacial members of the Wroxham Crag Formation (Table 1) have been identified to date—the Dobbs Plantation, How Hill, and Mundesley members, and these have been related to one another on the basis of their stratigraphic position and their lithological composition (clast lithologies, derived palynomorphs, heavy minerals) which reflects temporal variability in the dynamics and processes operating within the Thames, Bytham and Ancaster river catchments that drained central and eastern England (Rose et al., 1996b, 2001, 2002; Riding et al., 1997, 2000; Briant et al., 1999; Moorlock et al., 2002; Lee, 2003). Extensive terrace sequences exist for the Thames and Bytham river systems and are classified on the basis of elevation, sedimentology and clast lithologies (Whiteman and Rose, 1992; Lewis, 1993; Rose et al., 1999b; Lee, 2003). No terrace aggradations of the Ancaster River have yet been recognised but the presence of the river system has been inferred from the form of the bedrock surface (Clayton, 2000), and the presence of clast lithologies within shallow marine coastal sediments that are derived from the Ancaster catchment (Green and McGregor, 1990; Hamblin et al., 1996; Rose et al., 1996a). Floodplain and estuarine deposits of these river systems that crop out in coastal areas form the Cromer Forest-bed Formation, and have high palaeoecological and biostratigraphic significance (West, 1980; Preece and Parfitt, 2000; Preece, 2001; Stuart and Lister, 2000, 2001). Evidence for the earliest glaciation of East Anglia and the adjoining North Sea Basin has traditionally been called the First Cromer Till of the North Sea Drift which was believed to have been deposited by Scandinavian ice (Perrin et al., 1979; Bowen et al., 1986; Ehlers and Gibbard, 1991) during the MIS 12 (Marine Oxygen Isotope Stage 12) Anglian Glaciation of the early Middle Pleistocene (Mitchell et al., 1973; Bowen et al., 1986; Bowen, 1999). A recent reappraisal of the glacial stratigraphy of northern East Anglia, has shown that the First Cromer Till can be subdivided into two distinctive till units, the Happisburgh and Corton Till members of the newly defined Happisburgh Formation (Lee et al., 2004b), and that these were deposited by British rather than Scandinavian ice (Lee et al., 2002). Furthermore, the stratigraphic relationship of the Corton Till Member, and associated outwash lithofacies to the terrace sequence of the Bytham River, suggests that the deposits of the Happisburgh Formation were deposited during a pre-Anglian ‘Happisburgh Glaciation’ considered to be equivalent to MIS 16 (Hamblin et al., 2000; Lee et al., 2004a). The attribution of this glaciation to MIS 16 age is based upon the modelling J. Quaternary Sci., Vol. 21(2) 155–179 (2006)
EARLY AND MIDDLE PLEISTOCENE AT PAKEFIELD, SUFFOLK, UK
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Table 1 Early and early Middle Pleistocene lithostratigraphy in eastern East Anglia based upon palaeoenvironmental grouping (modified from Lee et al., 2004). Units that crop-out at Pakefield are highlighted in bold. 1The Pakefield Member refers to shallow marine coastal deposits that were deposited between the Happisburgh and Lowestoft formations, thus the Wroxham Crag Formation spans the early Middle Pleistocene upto the Anglian Glaciation (MIS 12); 2Bytham river deposits that post-date the deposition of the Happisburgh Formation, but pre-date the Lowestoft Formation; 3terrace deposits of the Bytham that grade upwards into glaciolacustrine sediments and Lowestoft Formation till Lithostratigraphy (Group/Formation) (Member) Lowestoft Formation Lowestoft Till Member Walcott Till Member Happisburgh Formation Corton Sand Member Leet Hill Sand and Gravel Member Corton Till Member Happisburgh Sand Member Ostend Clay Member Happisburgh Till Member Bytham Group Castle Bytham Terrace Member3 Warren Hill Terrace Member2 High Lodge Member (T)2 Timworth Terrace Member Knettishall Terrace Member Ingham Terrace Member Seven Hills Terrace Member Cromer Forest-bed Formation Wroxham Crag Formation Pakefield Member1 Mundesley Member How Hill Member Dobbs’ Plantation Member Norwich Crag Formation
Sediment
Environment and process
Chronostratigraphy
Chalky, clayey diamicton Chalky, silty diamicton
Scottish Ice Source Glaciation—subglacial till Glaciation—subglacial till
Anglian (MIS 12)
Chalky, fine sand Sands and gravels Sandy, brown diamicton Bedded sands Stratified silt and clay Sandy, grey diamicton
Northern Ice Source Distal proglacial outwash Proximal proglacial outwash Glaciation—subaqueous till Distal proglacial outwash Glaciolacustrine Glaciation—subglacial till
Coloured quartzose-rich terrace gravels
Bytham river terrace aggradation followed by incision
Organic muds
Alluvial/estuarine
Quartzose sands and gravels
Coastal North Sea
Shelly sand, silt and clay
Coastal North Sea
Early
Middle
Pleistocene
Early Pleistocene
Figure 2 Palaeogeography of central and eastern England during the late Early and early Middle Pleistocene showing the distribution of the major river systems and the position of the coastline (modified from Rose et al., 2001; Lee, 2003)
of patterns of river terrace development with the Bytham River and the global record of ice volume. It challenges the traditional interpretation based upon biostratigraphy (Banham et al., 2001; Preece, 2001) and permafrost development (Whiteman, 2002). These arguments have been discussed and rejected in Lee et al. (2003a,b, 2004a). The MIS 12 Anglian ß British Geological Survey/Natural Environment Research Council copyright 2005. Reproduced with the permission of BGS/NERC. Published by John Wiley & Sons, Ltd.
Glaciation is represented in East Anglia by glacial sediments of the Lowestoft Formation and includes two tills, the Lowestoft Till Member and the Walcott Till Member (formerly Second Cromer Till/ Walcott Diamicton of the North Sea Drift), of the Lowestoft Formation (Lee et al., 2004b). During this glaciation, the Bytham River was overridden and destroyed J. Quaternary Sci., Vol. 21(2) 155–179 (2006)
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by British ice (Rose, 1987, 1994; Lewis, 1993), and the course of the ancestral Thames was diverted southwards (Gibbard, 1977; Bridgland, 1994).
ried out using a Schonstedt GSD-5 with tumbler in peak fields up to 80 mT. Samples were demagnetised using 5–6 step increments, and directions were determined by principal component analysis (Kirschvink, 1980).
Methodology Lithofacies description and interpretation Sections were chosen to reflect the full stratigraphic sequence in the area. Particular attention was given to the geometry, colour (Munsell Color value), texture, type of bedding and sedimentary structures, and the nature of the lower and upper contacts of the facies units. Clast fabric measurements in diamictons were performed on the a-axis, where the a:b ratios exceeded 1.5:1 and plotted as direction/angle of dip on equal area, lower hemisphere stereographic projections. Particle-size distributions were determined by a combination of wet and dry sieving for >63 mm size ranges (Gale and Hoare, 1991), and the Sedigraph method for
