by Julie Brigham-Grette, Martin Melles, Christian Koeberl

Lake El’gygytgyn, located in central Chukotka, NE Russia, is a 3.6 million year old impact crater lake with a diameter of 12 km and a water depth of 170 m. During the last 6 years the sedimentary record of the lake has become a major focus of multi-disciplinary multi-national paleoclimatic research and is now a world-class target for deep drilling. A full-length sediment core would yield a complete record of Arctic climate evolution; back one million years prior to the first major glaciation of the Northern Hemisphere. Geomorphological evidence from the catchment suggests that the crater was never glaciated during the entire Late Cenozoic. A 12.9 m long sediment core retrieved from the deepest part of the lake in 1998 revealed a basal age of approx. 250 ka, confirmed the lack of glacial erosion, and underlined the sensitivity of this lacustrine environment to reflect high-resolution climatic change. A 16.7 m long sediment core taken in 2003 confirms the reproducibility of the record and dates to nearly 300 ka. The first single channel seismic survey in 2000 and multi-channel seismic surveys in 2003 have now been processed suggesting a depth-velocity model of brecciated bedrock overlain by a suevite layer, in turn overlain by two undisturbed, lacustrine sedimentary units up to 400 m in thickness. This final pre-site survey expedition in 2003 included modern process studies, geomorphic and permafrost studies of lake and river terrace stratigraphies, additional lake sediment coring and some of the first permafrost coring. Two workshops in 2001 and 2004 provided the scientific framework for the synthesis of all available data. This proposal requests funds for a major drilling campaign in El´gygytgyn Lake in spring 2007. Our goal is to collect the longest most unprecedented record of climate change in the terrestrial arctic for comparison with lower latitude marine and terrestrial archives of hemispheric and global climate evolution. Coring objectives include replicate cores of 630 m length to retrieve a continuous paleoclimate record from the deepest part of the lake and into the underlying impact breccias and bedrock. Studies of the impact rocks offers the planetary community with the opportunity to study a well preserved crater uniquely found in igneous rocks like those on Mars. One additional core to ca. 200 m into permafrost from the adjacent catchment will allow us to test ideas about arctic permafrost history and sediment supply to the lake since the time of impact.

• Lake El'gygytgyn represents a world class drilling target for obtaining a paleoclimate record unique to the Northern Hemisphere. Having conducted three successful expeditions to the lake in the past five years and having created strong collaborative bonds between American, Russian and German researchers with similar goals, we as a group are in a ideal position to advance our knowledge of the Arctic and global systematics and promote international scientific cooperation. Our two primary objectives include:
• 1. Assessing the environmental dynamics recorded at El'gygytgyn against other arctic and lower latitude paleoenvironmental records and placing them in the contact of exiting knowledge concerning the impacts and responses of different regions to past and future change. The influence of the Eurasian ice sheet dynamics on the flow of the westerlies and moisture diversions is one of many perturbations that may or may not have confounded circumarctic teleconnections over time. We will also be able to compare the record from El'gygytgyn to records from other Asian lakes, like Lake Baikal, to compare paleoenvironmental changes possibly linked to global reorganizations of the ocean /atmospheric system over the North Atlantic /Greenland sector of the Northern Hemisphere or sourced from the tropics. This work will place El'gygytgyn into an interhemispheric context.
• 2. Evaluate El’gygytgyn has the only currently known impact structure formed in siliceous volcanics, including tuffs. The impact melt rocks and target rocks provide a unique opportunity on Earth to study shock metamorphism of volcanic rocks. As no impactites and shocked rocks occur at the crater in situ, a drill core is the only possibility to obtain exact information on impactites of known location and to study the depth progression of shock metamorphism of volcanic rocks.

Arctic, Climate Change, ELGYGYTGYN, El'gygytgyn, Global Environment, ICDP-2005/01, Impact Crater, Lake Drilling, Paleoclimatology, Russia, Siberia

Latitude: 67.4997, Longitude: 172.10394