Luminescence Measurements of Sediment Cores from Lake Esmeralda and Monolith Lake, James Ross Island Archipelago

• Main Authors: Sanderson, David, Cresswell, Alan, Roman, Matěj, Píšková, Anna, Kopalová, Kateřina, Nývlt, Daniel, Lirio, Juan Manuel
• Format: Text
• Language: English
• Published: University of Glasgow 2017
• Subjects: GB Physical geography; GE Environmental Sciences; QC Physics; Antarctic; The Antarctic; Antarctic Peninsula; Ross Island; Monolith; Vega Island; Esmeralda; Monolith Lake; Antarc*; James Ross Island
• Online Access: http://eprints.gla.ac.uk/240319/; http://eprints.gla.ac.uk/240319/1/240319.pdf

The James Ross Island archipelago is located at the northern end of the Antarctic Peninsula, one of the most sensitive regions to global climate changes. The islands are characterised by large deglaciated areas containing remarkable sedimentary archives, including lacustrine sediments, which record past climatic conditions. Sedimentary sequences from two lakes in the area have been retrieved for multi-proxy analyses of sediment properties to reconstruct the past climatic and environmental evolution. This data needs to be set into a reliable chronological framework to correlate the environmental records with other regional palaeoreconstructions from ice cores, marine sediments and glacial chronologies. There are large uncertainties in radiocarbon chronologies ensuing from large reservoir effects and the scarcity of terrestrial macroremains. Luminescence dating techniques, which measure ages of commonly occurring minerals, could therefore provide a robust chronology and offer new insights into the age and mode of sediment deposition. Previous studies of Antarctic lacustrine sediments have shown large residual thermoluminescence (TL) signals, and smaller residual infra-red stimulated luminescence (IRSL) signals. Optically stimulated luminescence (OSL) has been applied to samples from raised Antarctic lake deltas and shorelines, and sediments from subglacial lakes. Sedimentary cores were collected from Lake Esmeralda (Vega Island) and Monolith Lake (James Ross Island), with one core from each lake examined in this work. Luminescence profiling has been conducted on the two cores, with measurements on bulk sediments using the SUERC Portable OSL instrument under blue and IR stimulation, and laboratory profiling using IRSL and TL on separated 90-250 µm polymineral grains and OSL on 90-250 µm quartz grains. The profile measurements show significant differences in estimated stored dose between methods, with the OSL giving the lowest doses, followed by IRSL and TL, consistent with previous studies showing large residual signals in TL and smaller residuals in some IRSL measurements. Quantitative OSL analyses were conducted on 150-250 µm quartz grains extracted from selected samples from these cores to calculate sedimentary ages. For Lake Esmeralda, the ages show a general increase with depth, from 0.4 to 0.8 ka, with some small age inversions between 40 and 50 cm and between 140 and 150 cm. For Monolith Lake, the top 5 cm cover an age range similar to the entire length of the Lake Esmeralda core and show significantly lower luminescence sensitivity. Below 5 cm there is a significant increase in apparent age, to 2.5-3.0 ka, which is approximately constant within ~0.5 ka for most of the core, and increased sensitivity. The lower samples below 26 cm are significantly younger and form a progression of older aged material at greater depth. This suggests that within the last 1000 years there has been a significant change in the sediment supply to Monolith Lake. The age profile for Monolith Lake, in particular the younger ages for material below 26 cm, suggests that the sediments below 5 cm carried a residual dose when they were deposited in the lake, with the deepest sediments in the core carrying a smaller residual, or even having being reset and thus giving a true age for these layers. The larger doses measured by IRSL and TL in the profiling indicate that it is likely that the luminescence centres associated with these signals carried a residual dose for all samples. Further exploration of these signals may reveal additional information on the sediment histories.