Reinterpreting Rotherslade, Gower Peninsula: implications for Last Glacial ice limits and Quaternary stratigraphy of the British Isles

Abstract

Rotherslade on the Gower Peninsula in south Wales has been viewed as a key site for the reconstruction of Quaternary depositional environments in the British Isles. Since the early 20th century, and certainly since the 1980s, the accepted view has been that Rotherslade is the most westerly location on the south Gower coast where there is in situ basal till exposed and that, logically, this location marks the position of the LGM ice limit. However, reinvestigation of the sediments and their architecture, and analysis of clast fabrics and thin sections of critical sedimentary units, show that none of the exposed sediments has properties diagnostic of subglacial deposition or deformation. We postulate here that LGM ice terminated at the western side of Swansea Bay, a few kilometres to the north-east of Rotherslade, and propose that the sedimentary sequence comprises Early to Middle Devensian periglacial sediments, overlain by a complex of Late Devensian, ice-proximal outwash fan deposits, an assemblage of paraglacial debris and, finally, periglacial mass movement deposits. The proposed repositioning of the Late Devensian ice limit and the associated new subaerial interpretation of the sediments suggest that a reassessment of sedimentary sequences (Hunts Bay, Western Slade) and landforms (Paviland Moraine) farther west on Gower, which have attained similar stratigraphical status, is now warranted.

Re‐assessment of the age and depositional origin of the Paviland Moraine, Gower, south Wales, UK

“…Instead, we envisage the W–E moraine section building up by laminar sediment gravity flows emerging from points along a static ice front, the same proglacial process thought to have carried sediment to dry valley fans in southeast Gower at Rotherslade (Hiemstra et al . ) and Hunts Bay (Shakesby & Hiemstra ). Such flows would have formed a relatively even moraine crestline and smooth distal slope where closely spaced, but an undulating crestline and irregular slope where wider apart (e.g.…”

“…Despite different views about ice limits across Gower, it was widely agreed prior to research by Rijsdijk () and Hiemstra et al . () that, from inspection of glacigenic sediments in extensive Quaternary exposures along the south coast, Rotherslade in southeast Gower (Fig. B) was the most westerly point reached by LGM ice.…”

“…Rijsdijk () and Hiemstra et al . () raised the possibility of an LGM date but this was emphatically rejected by Bowen ().…”

Stratigraphic architecture and sedimentology of a Late Pleistocene subaqueous moraine complex, southwest Ireland

“…Rotherslade in south Wales; Hiemstra et al, 2009), where crudely stratified diamictons and gravelly clinoforms have been traditionally classified as 'till', but in fact document deposition as ice-proximal subaqueous and subaerial fans. Collectively, this suggests considerable variation in the internal structural and facies architecture of such moraines and underscores the importance of ice-marginal subaquatic processes in their formation.…”

Trimline Trauma: The Wider Implications of a Paradigm Shift in Recognising and Interpreting Glacial Limits

“…Generations of university students have visited the area to examine the Ipswichian raised beaches, spectacular cave deposits and of course the ice limits. The established wisdom is that there are two ice limits on Gower: one at Rotherslade in the east, representing the Devensian ice limit (disputed by Hiemstra et al 2009) and one further west, marked by the 'Paviland Moraine', that represents some earlier glaciation (Bowen et al 2002). It has always seemed unlikely to me that a narrow peninsula like Gower would, just by chance, retain clear evidence of the limits of two glaciations.…”