Early glaciation ice rafting in the North Sea

Wroxham Crag deposits resting on chalk.  Bottom left is the modern beach.  

Location - Weybourne, Norfolk

This is a very interesting article that I missed in 2011 and came across in 2024:

https://brian-mountainman.blogspot.com/2024/11/ice-rafted-erratics-norfolk.html 

Suddenly it seems to have considerable relevance.  Sadly, the full paper still seems to be behind a paywall.   

Possible ice-rafted erratics in late Early to early Middle Pleistocene shallow marine and coastal deposits in northeast Norfolk, UK.
Nigel R. Larkin, Jonathan R. Lee & E. Rodger Connell

Proc Geol Assoc 2011

https://nora.nerc.ac.uk/id/eprint/14695/1/Larkin_et_al.pdf

Abstract

Erratic clasts with a mass of up to 15 kg are described from preglacial shallow marine deposits (Wroxham Crag Formation) in northeast Norfolk. Detailed examination of their petrology has enabled them to be provenanced to northern Britain and southern Norway. Their clustered occurrence in coastal sediments in Norfolk is believed to be the product of ice-rafting from glacier incursions into the North Sea from eastern Scotland and southern Norway, and their subsequent grounding and melting within coastal areas of what is now north Norfolk. The precise timing of these restricted glaciations is difficult to determine. However, the relationship of the erratics to the biostratigraphic record and the first major expansion of ice into the North Sea suggest these events occurred during at least one glaciation between the late Early Pleistocene and early Middle Pleistocene (c. 1.1−0.6 Ma). In contrast to the late Middle (Anglian) and Late Pleistocene (Last Glacial Maximum) glaciations, where the North Sea was largely devoid of extensive marine conditions, the presence of far-travelled ice-rafted materials implies that earlier cold stage sea-levels were considerably higher.

The evidence for a high sea level is quite convincing, as is the evidence of shallow marine conditions, sea floor deposits and contained dropstones weighing up to 15 kg.  The erratics are from Northern England and Norway.  The stratigraphic relationships indicate that the deposits (in th Wroxham Crag Formation) date from an early glaciation maybe a million years ago.  Samples came from West Runton and Sidestrand.

Preferred explanation of the occurrence of these erratics in beach and estuarine conditions:  "the far-travelled clasts were deposited by melt-out from (possibly grounded) icebergs in estuarine (Sidestrand) and beach (West Runton) environments with minimal local reworking. It is predicated on parts of the BIIS and SIS in northern Britain and southern Norway having floating ice margins within the northern and eastern North Sea Basin, upstream of which ice was actively eroding and entraining bedrock lithologies. This hypothesis is supported by both the clustered spatial and stratigraphic concentration of the erratics, and their frequently comparatively ‘fresh’ form. An ice-wedge cast penetrating the host deposit at West Runton indicates that the subsequent climate was sufficiently cold to support the development of permafrost after deposition of the erratic-bearing sediments."

Conclusions

Concentrations of erratics within WCF coastal deposits at Sidestrand and West Runton in northern East Anglia are considered the product of melt-out from (possibly grounded) icebergs.

The provenance of the erratics implies that these icebergs were derived from glaciers that were eroding bedrock in the Southern Uplands, Midland Valley and southern Grampian Highlands of Scotland, and Oslofjord in southern Norway.

The age of these erratic-bearing beds can be broadly constrained to a period from the late Early Pleistocene to early Middle Pleistocene interval (c. 1.1–0.6 Ma, a time period that spans the ‘Menapian’ (MIS 34)) to late ‘Cromerian Complex’ (MIS 16) stages.

These erratics demonstrate both the existence of restricted glaciations in Scotland and Norway, and their periodic expansion into the North Sea Basin prior to the maximum extent of the ice sheets during the Anglian Glaciation (MIS 12) of the Middle Pleistocene.

This research supports the work of Sejrup et al. (1987) and Ekman (1999) that argues that both the BIIS and SIS were active in the North Sea Basin on at least one occasion well before the Anglian stage of the Middle Pleistocene.

The deposition of the erratic-bearing beds during these early glaciations appears to coincide with higher glacial sea-levels than occurred during the late Middle and Late Pleistocene.

Like the authors of the paper, I am intrigued by the glacio-isostatic and eustatic interactions here on the west side of the North Sea, where one would not expect ice rafting and the dumping of dropstones during one or more glacial episodes -- at times when relative sea levels would have been far below present msl.  But here the features are, suggesting GLACIAL sea levels not far removed from those of today..................  and the authors are clear in their own minds that the features relate to marine conditions, not glacio-lacustrine conditions.

For many years there has been a widsespread belief that the North Sea Basin as a whole has been sinking tectonically while the western part of the British Isles has been slowly rising.  This means that deposits currently at sea-level were deposited at an even HIGHER level around a million years ago.  All very confusing.

I am checking out the current views on this paper, which was published 15 years ago.........