Scientific Drilling of Lake Sediments at Darwin Crater, Tasmania

A 70 meters long continental sediment record was recovered at Darwin Crater in western Tasmania, Australia. The new sedimentary archive includes a pre-lake deposit and the complete lake sediment succession accumulated over several glacial/interglacial climate cycles in the ~816 ka meteorite impact crater. A total of 160 meters of overlapping sediment cores were drilled from three closely-spaced holes. Here we report on the drilling operations at Darwin Crater and present the first results from multi-sensor whole core logging, sediment description and multi proxy pilot analysis of core end samples. The multi-proxy dataset includes spectrophotometry, particle size, natural gamma ray, paleo- and rock-magnetism, loss-on-ignition and pollen analyses. The results provide clear signatures for alternating glacial and interglacial sediment facies. The succession returns a minimum of seven inferred glacial cycles. Initial paleomagnetic analysis indicate reversed magnetic polarity in the deepest sediments drilled at Hole B. If geomagnetic in origin, this result constrains the sediment 2.5 m below commencement of lacustrine deposition to an age between ~816 ka and the Matuyama-Brunhes geomagnetic reversal ~773 ka, which is consistent with the interpretation of seven glacial cycles. High-resolution analysis and detailed multi-disciplinary studies are underway with a primary focus on dating, paleomagnetism, and paleoclimate.

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