Recent Mapping and Sampling on the Chukchi Borderland and Alpha/Medeleev Ridge

• Main Authors: Mayer, Larry A., Brumley, K, Andronikov, A, Chayes, D, Armstrong, Andy, Calder, Brian R., Hall, John K., Clyde, W C, Bothner, W A, Gardner, James
• Format: Text
• Language: unknown
• Published: University of New Hampshire Scholars' Repository 2008
• Subjects: Computer Sciences; Oceanography and Atmospheric Sciences and Meteorology; Arctic; Arctic Ocean; Amerasia Basin; Chukchi Borderland; Northwind Escarpment; Chukchi; Iceberg*; Law of the Sea; ice covered waters
• Online Access: https://scholars.unh.edu/ccom/660; http://abstractsearch.agu.org/meetings/2008/FM/C11C-0516.html

Since 2003, four cruises on the icebreaker USCG HEALY have collected high-resolution multibeam sonar mapping data in the Amerasia Basin in support of a potential submission by the U.S. for an extended continental shelf as defined under the United Nations Convention on Law of the Sea Article 76. The latest of these cruises (HEALY0805), completed in early Sept.of 2008, extended this mapping to the southern portions of the Alpha/Mendeleev Ridge complex, and supplemented the mapping with seven dredge stations, providing rare, direct sampling of both regions. While sparse in comparison to complete-coverage multibeam sonar surveys (due to the difficulties associated with operating in ice-covered waters), the new multibeam sonar data still provide an unprecedented new view of the tectonic, sedimentary, glacial and fluid- flow related processes in the Arctic Ocean. The Chukchi Borderland is characterized by shallow plateaus that often show evidence of interaction with icebergs and glaciers (scours and grooves) at depths as great as 900 m, as well as the presence of numerous gas/fluid expulsion features (pockmarks and acoustic wipe-out zones). The topographic highs associated with the Borderland are often bounded by very steep scarps including the eastern edge of Northwind Ridge (the Northwind Escarpment) which is a 600 km long NNE trending feature with an average slope of 10-15 degrees. Similar steep-sided ridges, separated by deep linear valleys also appear in mapped areas of the Alpha/Mendeleev Ridge complex. Some of these features have slopes as great at 60 degrees and thus are excellent targets for dredging. Our dredging of these slopes has returned a wide array of volcanic and sedimentary rock types, many of which appear to be representative of outcrops (rather than ice rafted material). A preliminary shipboard examination of these samples (they were just collected this morning � 3 September 2008 � a few days before the abstract is due) shows them to include mudstone, sandstone, shale, breccia, along with volcanic ...