Genesis of active sand-filled polygons in lower and central Beacon Valley, Antarctica
Bockheim, James G.
Kurz, Mark D.
Soule, Samuel A.
MetadataShow full item record
KeywordSand-wedge polygons; Patterned ground; Non-sorted polygons; Thermal contraction fissures; McMurdo Dry Valleys; Permafrost
Nonsorted polygons with sand-filled wedges were investigated in lower and central Beacon Valley, Antarctica (77.82ºS, 160.67ºE) using field observations coupled with a 2-m resolution Digital Elevation Model and a high-resolution aerial photograph. A gasoline-powered concrete breaker was employed to expose the sediments of four representative polygon centers and six wedges from geomorphic surfaces containing tills of two different ages. The excavated polygons ranged from 9 to 16 m in diameter (average = 12 m); the sand-filled wedges ranged from 0.2 m to 2.5 m in width (average = 0.9 m). The top of ice-bonded permafrost ranged from 12 to 62 cm in depth (average = 33 cm) in the polygon centers and from 64 to >90 cm (average = >75 cm) in wedges. One active thermal contraction fissure generally was apparent at the surface, but excavations revealed numerous inactive fissures. The wedges contain sand laminations averaging 3 mm in width when viewed in cross section. Although most of the polygons were of the sandwedge type, some contained ice veins up to 1 cm in width and could be classed as composite wedges. Three stages of polygon development were observed, including strongly developed polygons on Taylor II surfaces (ca. 117 ka), moderately developed polygons on Taylor III surfaces (ca. 200 ka), and poorly developed polygons on Taylor IVa and older (ca. >1.1 Ma) surfaces. This retrogressive development may be due to sublimation of ice-bonded bonded permafrost following thermal cracking. With the drop in ice content, the thermal coefficient of expansion is lowered, which causes a reduction in tensile stresses.
Author Posting. © The Author(s), 2009. This is the author's version of the work. It is posted here by permission of John Wiley & Sons for personal use, not for redistribution. The definitive version was published in Permafrost and Periglacial Processes 20 (2009): 295-308, doi:10.1002/ppp.661.
Showing items related by title, author, creator and subject.
Ciliate diversity, community structure, and novel taxa in lakes of the McMurdo Dry Valleys, Antarctica Xu, Yuan; Vick-Majors, Trista; Morgan-Kiss, Rachael; Priscu, John C.; Amaral-Zettler, Linda A. (Marine Biological Laboratory, 2014-10-01)We report an in-depth survey of next-generation DNA sequencing of ciliate diversity and community structure in two permanently ice-covered McMurdo Dry Valley lakes during the austral summer and autumn (November 2007 and ...
Berggren, William A.; Alegret, Laia; Aubry, Marie-Pierre; Cramer, Ben S.; Dupuis, Christian; Goolaerts, Sijn; Kent, Dennis V.; King, Christopher; Knox, Robert W. O'B.; Obaidalla, Nageh; Ortiz, Silvia; Ouda, Khaled A. K.; Abdel-Sabour, Ayman; Salem, Rehab; Senosy, Mahmoud M.; Soliman, Mamdouh F.; Soliman, Ali (Austrian Geological Society, 2012)The Dababiya corehole was drilled in the Dababiya Quarry (Upper Nile Valley, Egypt), adjacent to the GSSP for the Paleocene/ Eocene boundary, to a total depth of 140 m and bottomed in the lower Maastrichtian Globotruncana ...
Quantitative estimate of heat flow from a mid-ocean ridge axial valley, Raven field, Juan de Fuca Ridge : observations and inferences Salmi, Marie S.; Johnson, H. Paul; Tivey, Maurice A.; Hutnak, Michael (John Wiley & Sons, 2014-09-15)A systematic heat flow survey using thermal blankets within the Endeavour segment of the Juan de Fuca Ridge axial valley provides quantitative estimates of the magnitude and distribution of conductive heat flow at a mid-ocean ...