HR: 0800h
AN: C21A-0050    [Abstracts]
TI: Cryogenic Structure of Perennially Frozen Lacustrine Sediments
AU: * Kanevskiy, M
EM: ffmzk@uaf.edu
AF: Institute of Northern Engineering University of Alaska Fairbanks, 237 Duckering Bldg., P.O. Box 755910, Fairbanks, AK 99775-5910, United States
AU: Shur, Y
EM: ffys@uaf.edu
AF: Institute of Northern Engineering University of Alaska Fairbanks, 237 Duckering Bldg., P.O. Box 755910, Fairbanks, AK 99775-5910, United States
AU: Jorgenson, T
EM: tjorgenson@abrinc.com
AF: ABR,Inc., P.O. Box 80410, Fairbanks, AK 99708, United States
AB: The existing data on cryogenic structure of lacustrine sediments in various permafrost regions of Eurasia and North America show that these sediments can vary from ice-poor to extremely ice-rich. Complicated cryogenic structure of lacustrine sediments can indicate the conditions of freezing; its study helps to reconstruct the history of permafrost development. There are four mechanisms of lacustrine sediments freezing and formation of their cryogenic structure: 1) epigenetic; 2) syngenetic; 3) para-syngenetic; 4) quasi-syngenetic. Para-syngenetic type of freezing is the most widespread for the lacustrine sediments accumulating in the taliks surrounded by permafrost. The freezing of such sediments goes in various directions (from the surface, from the bottom, from the sides). The ice layers and lenses in para-syngenetic sediments are usually inclined, and the ice content is relatively small in the central parts of the lens-like geological bodies of lacustrine origin. Ice content increases towards top, bottom, and marginal parts of these geological bodies. Such distribution of the ice content is connected with water migration to the multidirectional fronts of freezing. Our study includes the data from several field sites located in Russia and Alaska. One of the most interesting sections was studied in the Kular mining region, Northern Yakutia, where the big lens of lacustrine silts, whose thickness reaches 18-20 m, was observed. This lens was enclosed in the ice-rich syngenetic Late Pleistocene "Yedoma" sediments containing huge ice wedges. The cryogenic structure of the most part of the observed geological body is typical for para-syngenetic sediments. Gravimetric moisture content of lacustrine silts varies in wide range: from 35% up to 130%. At the upper part of the section the ice lenses up to 10-15 cm thick were observed. Ice wedge pseudomorphs were found at the boundary between lacustrine sediments and underlying alluvial gravels. Para-syngenetic part of this section includes lens of syngenetically frozen lacustrine sediments with small ice wedges, which was presumably formed during the period of lowering of the water level in the lake.
DE: 0702 Permafrost (0475)
DE: 0706 Active layer
DE: 0738 Ice (1863)
DE: 0746 Lakes (9345)
DE: 0770 Properties
SC: Cryosphere [C]
MN: 2007 Fall Meeting