Annually laminated Late Pleistocene sediments from Llangorse Lake, South Wales, UK: a chronology for the pattern of ice wastage

PALMER, A. P., ROSE, J., LOWE, J. J. & WALKER, M. J. C. 2008. Annually laminated I-ate Pleistocene sediments from Llangorse Lake, South Wales, UK: a chronology for the pattern of ice wastage. Proceedings of the Geologists' Association, 119, 245-258. This paper presents the results of microfacies analysis of proglacial lake sediments from the Llangorse basin in South Wales. It is the first detailed micromorphological investigation of mineral-laminated lake sediments in the UK. Four microfacies of the mineral-laminated sequence are identified and subsequently compared to modern and palaeo-datasets. The laminated sediments are interpreted as glaciolacustrine varves, thereby validating previous interpretations. The total number of varves in the core indicates that Glacial Lake Llangorse existed for a minimum Of 574 years. This sequence cannot be 'fixed' to a specific age other than the latter part of the Dimlington Stadial. The varve thickness decreases through the core, suggesting that the ice margin, which initially impounded the lake, became progressively more distal to the locus of sedimentation. These data, when related to Lewis' model of deglaciation in the area, imply that the ice margin retreated at an average rate of 5.2 m a(-1).