Luis Galán

Chronostratigraphy of the sedimentary record of Limnopolar Lake, Byers Peninsula, Livingston Island, Antarctica

Abstract The chronostratigraphy of the sedimentary record of Limnopolar Lake, located on Byers Peninsula (Livingston Island, South Shetland Islands, Maritime Antarctica), is described based on radionuclides and radiocarbon age dating. The oldest moss macrofossil age was 6700±50 yr bp (7510±80 cal yr bp) from which the age/depth model estimates a basal age for the sedimentary record of c. 8300 cal yr bp, suggesting an earlier deglaciation of Byers Peninsula than reported in previous studies. Lithological units and other stratigraphic zones are described throughout the sediment core, showing different mineralogical composition and a fine alternation of clays and silty clays and moss layers of Drepanocladus longifolius. Based on magnetic susceptibility analyses, a number of probable primary and reworked tephra layers were identified, seven of them confirmed by SEM observations, and most of them in agreement with the regional tephrachronology stratigraphy for the north-west Antarctic Peninsula. Sedimentation rates showed no significant changes during the last 5000 years with the exception of an abrupt event that took place around 5400 cal yr bp, which implied the sedimentation of c. 30 cm of clays in a very short time, probably related to a period of glacial re-advance that caused abrupt changes in geomorphological processes in the catchment.