THE 2009 ICDP DRILLING PRJECT INTO THE EL'GYGYGTGYN IMPACT CRATER, SIBERIA

The 3.6 Ma, 18-km-diameter El’gygytgyn impact crater is located in central Chukotka, northeastern Russia. The flat floor of the crater is in part occupied by Lake El’gygytgyn, 12 km in diameter, and surrounding terraces. The El’gygytgyn crater was formed in the volcanic strata of Late Cretaceous age. Thus, the El’gygytgyn is the only known terrestrial impact structure where it is possible to investigate shock metamorphism in siliceous volcanic rocks. An ICDP-led drilling project was conducted in early 2009 with two main scientific goals. First and foremost, the crater represets the largest and oldest, unglaciated lake basin in the Arctic, from which sediments were collected that represent the longest, most time-continuous record of late Cenozoic Arctic climate evolution. The second goal is to study meteorite impact rocks from a metavolcanic bedrock sequence that will allow to study the shock response of volcanic rocks, as well as to provide a comparison with impact process on other planets. Drilling took place from the frozen crater lake. Recovery of the first lake sediment cores commenced on March 18, 2009. Lake sediments, representing 3.6 million years of climate record, were recovered until a depth of 315 m below lake floor, when the transition to the impact breccia was drilled on April 14, 2009. Recovery of impact brecia continued into monomictly brecciated bedrock of the central uplift. Recovered rocks include a 60 m thick sequence of suevitic breccia and underlying shocked volcanics.