Welsh Glacial Palaeoenvironments

Reconstructing Quaternary Glacial Palaeoenvironments in Wales

James Etienne, Glasser, Neil, Michael Hambrey and Krister Jansson

The evolution of the glacial landscape of Wales has proved a hot topic in recent British Quaternary studies, particularly regarding the reconstruction of glacial environments and establishment of the impact of Irish Sea glacier and Welsh ice cap on the dynamics of the last British and Irish Ice Sheet. Sedimentological and geomorphological investigations by the Aberystwyth group have concentrated on the southwest Wales region in order to test competing hypotheses regarding the style of Irish Sea glaciation (glacioterrestrial versus glaciomarine), the results of which contribute to a wider debate regarding relative sea level change during the past 25,000 years.

Palaeogeographical reconstruction of the last British-Irish Ice sheet and Irish Sea glacier.
Palaeogeographical reconstruction of the last British-Irish Ice sheet and Irish Sea glacier.

This project builds on recent work undertaken in the lower Afon Teifi region by the British Geological Survey, including mapping, geophysical and borehole surveys used to identify potential geohazards (principally landslides) and provide some means for their mitigation. Combined analyses of sedimentology, stratigraphy, structural geology and geomorphology reveal a number of important findings concerning glacial events, especially those associated with the last glaciation named the Devensian. These findings include: (i) the recognition of a pre-late Devensian period of Irish Sea glaciation, responsible for significant landscape modification in the north Pembrokeshire and Afon Teifi regions of southwest Wales, (ii) widespread establishment of periglacial environments both prior to and following the late Devensian glaciation, (iii) complex evolution of the lower Teifi drainage system in much earlier times (the Tertiary Period, before 2 million years ago), including the development and abandonment of two preglacial courses and associated tributary drainage, (iv) the formation of a large (>25 km length) ice-contact glacial lake succession which developed during advance of the late Devensian Irish Sea glacier inland, and (v) the dominance of terrestrial rather than marine processes of glacial sedimentation in southwest Wales during the last glaciation.

Reconstruction to show the location and possible extent of glacial Llyn Teifi and peripheral lake bodies dammed in coastal river valleys by the late Devensian Irish Sea glacier. The three-dimensional reconstruction shows the profile of the Cippyn channel, and its potential as a control on the level of glacial Lake Teifi during early stages of advance.

Although the influence of Welsh glacial masses is recognised within these areas, little specific research has been undertaken to allow a more detailed evaluation of the interaction between these and the late Devensian Irish Sea glacier, as is desirable for establishing the dynamics of the last British Ice Sheet.

These projects have been funded by grants from the British Geological Survey (NERC), a NERC funded [CASE] studentship in association with the British Geological Survey, the Royal Physiographic Society in Lund, Countryside Council for Wales (CCW) and a research grant from the Quaternary Research Association and University of Wales, Aberystwyth Gooding fund.