Paper No. 23-5
Presentation Time: 9:05 AM
NOVEL ADAPTATIONS OF OSL DATING PROCEDURES REVEAL EPISODIC DEPOSITION ON HIGH ELEVATION ANTARCTIC FANS
Our team has been using optically stimulated luminescence (OSL) dating as part of an effort to recover high temporal resolution climate data archived in high elevation fan deposits in the McMurdo Dry Valleys of Antarctica. Although OSL has been used to investigate fan deposits for decades and used previously in Antarctic studies, we present this work as new because of the novel OSL procedural adaptations we developed for field sampling, laboratory pre-processing, and data analysis for this application. Fan deposits in general can be a challenge for OSL dating as sediments delivered to the fan by a combination of water-, gravity-, and wind-driven processes can yield a wide range of signal resetting among grains leading to complex OSL equivalent dose distributions. In addition, previous OSL studies of Antarctic sediments have noted very weak signal response or very low optical output. Despite the challenges, we were able to determine ages for 25 of 28 field samples. The OSL dating results are also novel in that they indicate distinct episodes of fan activity/deposition in the Holocene (1 to 3 ka; 8 to 10 ka) and latest Pleistocene (14 to 16 ka) within a landscape that had been considered essentially devoid of meltwater for 12-13 million years. Activation of the fans on these time scales suggests the fans are sensitive to fine-scale climatic drivers that produce melting in catchments along the margin of the East Antarctic Ice Sheet.