An Update on Glacial Ice Extent and Erratics

At last the latest findings about the extent of the Last Glacial Maximum and the Glacial Erratics has been published.

The map below is self explanatory and so is the conclusion: High relative sea level during MIS4 and 3 (Marine Isotope Stages) coincident with adjacent calving ice sheet margins provides an explanation for the rafted giant erratics found around the shores of southern Britain and Ireland.

The article is free and open source:

Scourse, J.D. (2024), The timing and magnitude of the British–Irish Ice Sheet between Marine Isotope Stages 5d and 2: implications for glacio-isostatic adjustment, high relative sea levels and ‘giant erratic’ emplacement. J. Quaternary Sci. https://doi.org/10.1002/jqs.3611 

 ABSTRACT:  The extent, chronology and dynamics of the pre-Marine Isotope Stage (MIS) 2 last British–Irish Ice Sheet (BIIS) are not well known. Although the BRITICE-CHRONO Project has detailed the maximum extent and retreat phases of the last BIIS for the period after 30 ka and into the Last Glacial Maximum (LGM), the Project identified several pre-existing datasets and generated new data that implied glaciation pre-dating the LGM but which post-dated the Last Interglacial (Eemian; MIS5e); these data are reviewed here. There are no dated till units but are other indicators clearly indicative of glaciation: deep-sea ice-rafted detritus flux into the adjacent NE Atlantic, cosmogenic rock-exposure age dating from glaciated surfaces in Wales and the island of Lundy (Bristol Channel), and optically stimulated luminescence (OSL) ages of proximal glacifluvial sequences on the Isle of Lewis (Outer Hebrides) and in the Cheshire Basin. Taken together these indicate BIIS inception during MIS5d, growth into MIS4 and evidence for dynamic retreat–advance phases during MIS3. OSL evidence for high relative sea level indicated by raised beaches in southern Ireland during MIS4 and 3 at a time of lowered glacio-eustatic sea level indicates substantial glacial isostatic loading, explained by the early growth of the BIIS during the last cold stage. High relative sea level during MIS4 and 3 coincident with adjacent calving ice sheet margins provides an explanation for the rafted giant erratics found around the shores of southern Britain and Ireland.

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FIGURE 1 Location map. Cores MD01‐2461 (Porcupine Seabight), MD95‐2006 (Barra Fan), MD04‐2822 (Rockall Trough), MD04‐2829 (Rosemary Bank), CE18011_VC2 IRD (Porcupine Bank) and DSDP 548 (Goban Spur); Isles of Scilly, BRITICE‐CHRONO MIS2 maximum ice limit, Lundy, Snowdon/Glyderau, Suianebost (Lewis), Glacial Lake Pickering, Glacial Lake Fenland, Courtmacsherry, Howe's Strand, Broad Strand, Fethard, Arclid and Porthleven. [Color figure can be viewed at wileyonlinelibrary.com]