Pleistocene glaciation of Fenland, England and its implications for evolution of the region

The East Anglian Fenland is a striking region in the English landscape, its low-lying nature belying the apparent lack of striking geological features. Rivers from the surrounding uplands to the east, south and west enter the Fenland, discharging into the The Wash, where they enter the North Sea. Extensive areas now slightly above or below present sea level, enclosing island-like high ground, the geology is sensitive to sea-level changes. These have affected the nature of sediments deposited over the last half-million years, a period associated with Middle and Late Pleistocene glaciation.

Although the history and filling of the basin during the Holocene (from c.11 ky) has been thoroughly investigated, and despite the abundant geological information available, the basin’s earlier, post-Anglian, history has received no treatment. It is known that the Fenland was glaciated on three occasions, these advances linked to the formation of The Wash and the remodelling of the landscape. Intervening between these glaciations were periods of cold, periglacial climate, of low sea level and of marine transgression during interglacials.

Investigations of the Fenland geology over the last decade have demonstrated that the basin originated from glaciation during the Anglian, Wolstonian and Devensian Stages. Critical to understanding the evolution of the Fenland basin, is the recognition of glaciation during the late Wolstonian Stage (c.180-160 ka); these dates determined by Optically Stimulated Luminescence (OSL). This Tottenhill glaciation reached the E and S Fenland margin. This glaciation, previously unidentified in the basin, impounded rivers entering the Fenland and imposed new courses.

Both before and after the glaciation for much of the Wolstonian time (~350-180 ka) periglacial climates persisted, significant for understanding the evolution of the Fenland, during which time the area was occupied, intermittently by Palaeolithic humans. Initiation of the basin occurred during the preceding Anglian Stage (c. 478-424 ka), whilst glaciation during the subsequent Devensian Stage (MIS 2; c. 29-18 ka) resulted in blockage of The Wash, causing further river diversions.

The recognition of the late Wolstonian-age Tottenhill glaciation, controversial at present, holds significant implications for the Pleistocene stratigraphy and palaeogeographical evolution of the region, the subject of this application.

The work so far has concentrated solely on the eastern and southern Fenland basin margins, in effect only the eastern half of the area invaded by the Tottenhill ice lobe. What is still required is a systematic, review of the region as a whole, requiring a complimentary investigation of the western margin, from Cambridge to Peterborough areas and beyond, to complete the study. The work will also involve completion of a synthesis of the Fenland history from the pre-Anglian to pre-Holocene interval (i.e. 500 ka). Initial examination of the region, combining both a thorough literature review and preliminary field visits, has established the viability of the project. These investigations have indicated exciting prospects for linking the Fenland basin with the established sequences to the west and north of the proposed study area and to the North Sea.

This work requires the study of sites to determine their landform morphology, internal stratigraphy, lithology and where relevant their contained Palaeolithic archaeology. The sites identified from fieldwork and map interpretation will be described and studied using standard field and laboratory techniques, supported by ground penetrating radar investigation. A rigid geochronological basis is required to support the relative dating framework to provide as strong as possible a stratigraphical sequence for unravelling the evolution of the region.

The research comprises:

1. Detailed investigation of geological and topographic maps of the region, to determine the nature of the sequences to be studied.
2. Field investigation of the W and SW Fenland areas to link the sequences already identified from the previous research in the E and SE Fenland districts, and to collect samples for analysis, by boreholes and excavations, and numerical dating.
3. Laboratory analysis of samples for sediment analysis (e.g. grain-size, clast fabric, etc.) to establish the genesis and potential provenance of the materials.
4. Submission of samples to the Geochronology Laboratory (Department of Geography, University of Sheffield) for numerical OSL dating to provide a dependable independent chronology as appropriate.
5. Three-dimensional modelling using the publicly available British Geological Survey borehole database.
6. Digitisation of borehole data, plotting and interpretation of data using the Intrepid Geomodeller programme. This work to be carried out by Dr D. Bisht (Cambridge Geoconsultants Ltd.: CGC). Interpretation to compliment the field observations.
7. Synthesis to be produced from all the evidence assembled. To be submitted to the Royal Society Open Science online journal. Individual site studies (as appropriate) will be submitted to academic journals.

The work to date, over the last decade, has been jointly undertaken by Dr Gibbard with Professor R.G.West F.R.S. This highly productive co-operation has seen several important new interpretations emerge.

Publications

Publications arising so far:

• Gibbard, P.L., West R.G., Andrew, R. & Pettit, M. 1991 Tottenhill. In: Central East Anglia & the Fen Basin Field Guide. 131-143 Ed. S.G. Lewis, C.A. Whiteman & D.R. Bridgland. Cambridge: Quaternary Research Association.
• Gibbard, P.L., West R.G., Andrew, R. & Pettit, M. 1992. The margin of a Middle Pleistocene ice advance at Tottenhill, Norfolk, England. Geological Magazine129, 59-76.
• Clark, C.E. Gibbard, P.L. & Rose, J. 2004 Glacial limits in the British Isles. In: Ehlers, J., & Gibbard, P.L. (editors) Extent and Chronology of Glaciation. Volume 1 Europe. Elsevier Science: Amsterdam.
• Gibbard, P.L., Pasanen, A., West, R. G., Lunkka, J.P., Boreham, S., Cohen, K. M. & Rolfe, C. 2009. Late Middle Pleistocene glaciation in eastern England. Boreas 38, 504-528.
• Gibbard, P.L. & Clark, C.D. 2011. Chapter 7 – Pleistocene Glaciation Limits in Great Britain. p. 75-93 In: Ehlers, J., Gibbard, P.L. & Hughes, P.D. (eds) 2011 Quaternary Glaciations – Extent and Chronology – A Closer Look. Developments in Quaternary Science 15. ISBN: 978-0-444-53447-7.
• Gibbard, P.L., West, R.G., Boreham, S. & Rolfe, C.J. 2012. Late Middle Pleistocene ice-marginal sedimentation in East Anglia, England. Boreas 41, 319-336.
• Gibbard, P.L., West, R.G., Boreham, S., Rolfe, C.J. 2012. Late Middle Pleistocene glaciofluvial sedimentation in Norfolk, England. Netherlands Journal of Geosciences 91, 63-78.
• West, R.G., Gibbard, P.L., Boreham, S., & Rolfe, C. 2014. Geology and geomorphology of the Palaeolithic site at High Lodge, Mildenhall, Suffolk, England. Proceedings of the Yorkshire Geological Society 60, 99-121.
• West, R.G. & Gibbard, P.L. 2017. The Observatory Gravels and the Travellers’ Rest Pit, Cambridge. Proceedings of the Yorkshire Geological Society (in press).