Paper No. 12
Presentation Time: 9:00 AM-6:30 PM


RAMSEY, Meridith A.1, ZAMORA, Felix J.2, LEPPER, Kenneth3 and LEWIS, Adam R.1, (1)Department of Geosciences, North Dakota State University, P.O. Box 6050 Dept. 2745, Fargo, ND 58108-6050, (2)Geosciences, North Dakota State University, NDSU Dept 2745, PO Box 6050, Fargo, ND 58108-6050, (3)Department of Geosciences, North Dakota State University, P.O. Box 6050, Dept. 2745, Fargo, ND 58108-6050,

As part of an ongoing study of high-elevation alluvial fans in the McMurdo Dry Valleys region of the Transantarctic Mountains it was necessary to develop field sampling and laboratory processing procedures for optically stimulated luminescence (OSL) dating of frozen samples. Alluvial deposits at elevations above 1000 m are small and record occasional sedimentation events indicating brief periods of increased warmth, thereby serving as potential proxies for meltwater production along terrestrial margins of the East Antarctic Ice Sheet. Several stratigraphic layers within six alluvial fans are being dated using OSL to determine when the melting events occurred and to potentially correlate between the fans and climate records. Unfrozen, near-surface samples were collected using metal cylinders and pipes. However, frozen samples, occurring below 10 to 30 cm, resented a new challenge for sample collection and preparation. Our approach was to collect samples from small pits excavated using a jackhammer. Samples were taken from the pit walls using a rotary hammer drill equipped with a concrete coring bit. The entire frozen sample and core bit were shipped to the laboratory and stored in a chest freezer until they were to be processed for dating. The frozen cores were prepared for analysis within the light-controlled OSL lab environment by cutting off both ends of the core bit, including the light exposed sediments, using a masonry chop-saw with a diamond edged abrasive blade. There was insignificant melting adjacent to the cut and no heating of the interior of the samples. The frozen interiors of the samples were allowed to thaw and processed in standard fashion for OSL dating. Although initial analyses indicate low signal intensities, we are able to determine that several fans record multiple depositional events of differing ages. We will report preliminary age results and correlations, if found, in the presentation.