HR: 1330h
AN: PP32B-0287    [PDF]
TI: Successful Completion of Pre-Site Survey for Deep Drilling at El'gygytgyn Crater Lake
AU: Melles, M
EM: melles@rz.uni-leipzig.de
AF: University Leipzig, Institute for Geophysics and Geology, Talstrasse 35, Leipzig, D-04103 Germany
AU: Minyuk, P
EM: minyuk@neisri.magadan.ru
AF: North-East Interdisciplinary Scientific Research Institute, Russian Academy of Science, Portovaya 16, Magadan, 685010 Russian Federation
AU: Brigham-Grette, J
EM: juliebg@geo.umass.edu
AF: University of Massachusetts, Amherst, Morrill Science Center, Box 35820, Amherst, MA 01003-5820 United States
AU: * Niessen, F
EM: fniessen@awi-bremerhaven.de
AF: Alfred Wegener Institute for Polar and Marine Research, Columbusstrasse, Bremerhaven, D-27515 Germany
AB: 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. The sedimentary record of the lake has become a major focus of multi-disciplinary multi-national paleoclimatic research and is now a potential 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 13.0 m long sediment core retrieved from the deepest part of the lake in 1998 revealed a basal age of approx. 300 ka, confirmed the lack of glacial erosion, and underlined the sensitivity of this lacustrine environment to reflect high resolution climatic change. The first single channel seismic survey carried out in 2000 discovered undisturbed and well-stratified sediments to a depth of 160 m below the lake floor. Refraction data from sonobuoys indicated the top of the impact breccia at about 360 m subbottom. An ICDP workshop held in 2001 recognised the unique potential of the lake for both paleoclimate and impact-related research and suggested more site survey work. This final pre-site survey expedition took place from April to September 2003. Modern process studies of the lake hydrology, limnology, meteorology, and sedimentology took place over this entire period to better understand the various proxies we are using to decipher the paleoclimate record of the sediment fill. Geomorphic and permafrost studies of lake and river terrace stratigraphies contribute to our understanding of climate dependent landscape evolution. A 16 m long sediment core from the central part of the lake presumably extents the existing record towards more than 400 ka BP. The matching of proxies from this core and the core recovered in 1998 illustrates the lateral continuity of the record for recording regional and global events. Additional cores from the shelf and slope reflect lake-level changes, and the impact of debris flows on sediment redeposition in parts of the lake during Late Quaternary times. In total 8 multi-channel seismic profiles were shot using a 26 cubic inch GI-gun and a 280 m long streamer with 15 channels and 130 m offset. These data will form the major basis for site selection for deep drilling. Single-channel field results indicate bedrock surface at a depth of approximately 350 m subbottom and confirmed the existence of a central uplift structure in the northwestern portion of the lake. 160 km of new 3.5 kHz profiles completed the high-resolution sediment echosounding survey. In addition, a magnetic survey was carried out on the lake and in the catchment to localise impact-related magnetic anomalies. A dense net of new echosounding data will be used to finalise a high-resolution 3-d topographic model of the lake floor and the catchment.
DE: 5420 Impact phenomena (includes cratering)
DE: 5462 Polar regions
DE: 9315 Arctic region
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2003 Fall Meeting