Physics
Scientific paper
Dec 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009agufm.p51a1121b&link_type=abstract
American Geophysical Union, Fall Meeting 2009, abstract #P51A-1121
Physics
[5400] Planetary Sciences: Solid Surface Planets, [5422] Planetary Sciences: Solid Surface Planets / Ices, [5475] Planetary Sciences: Solid Surface Planets / Tectonics, [6280] Planetary Sciences: Solar System Objects / Saturnian Satellites
Scientific paper
Kinematic analysis of extensional fractures (“tiger stripes”) in the South Polar Terrane (SPT) of Enceladus and comparisons with terrestrial diapir systems supports the hypothesis of active and paleo-diapirism on Enceladus. The crust overlying terrestrial diapirs is characterized by a circular to elliptical shaped region of uplift. Within the structural aureole surrounding the diapir, contractional deformation occurs along the distal margin of the aureole and extension may occur over the crest. Three or more radial-trending extensional fault zones initiate over the crest and extend outward, tapering away from the structure. As diapirism continues these extensional fault zones progressively widen with the amount of throw being largest near the crest and progressively decreasing towards the margins of the dome. The widening of these zones creates a gradient in deformation within the aureole. The outer regions of the aureole undergo lower magnitudes of contraction relative to the inner regions. This may result in local bending about sub vertical axes of preexisting structures. On Enceladus, the ‘tiger stripes’ are situated within uncratered terrain and are surrounded by three annular, discontinuous contractional belts, termed the inner, intermediate, and outer belts. The inner belt contains two prominent extensional fault zones that cut across the older intermediate belt. Differing orientations of grooves within the outlying terrain surrounding the intermediate belt may have formed due to the differing magnitude of contraction between the inner and outer regions of the aureole during the formation of five radial-trending extensional fault zones. These fault zones extend from the intermediate belt and cut across the outlying terrain and the outer belt. The throw along these extensional fault zones is greatest in the vicinity of the tiger stripes and progressively decreases northward, creating large graben systems adjacent to the tiger stripes. Ice from the uplifted contractional belt has flowed down slope into the grabens producing concave-outward bands analogous to ogives found in terrestrial valley glaciers, thus giving the contractional belts a sinuous geometry in map view. A similar but older configuration of structures is located in the equatorial region at Sarandib and Diyar Planitiae (SDP). Ridges with amplitudes of ~1000 m have fractured crests and are analogous to pressure ridges found in sea ice on earth, implying the presence of a liquid water substrate as the overlying icy crust cracked and resealed. These now healed fractures may have once emanated water vapor during active diapirism similar to the currently active SPT. The pressure ridges occur within a terrain containing ridges and grooves that are sub-parallel to a sinuous contractional belt encircling the SDP. This contractional belt has been partially overprinted by younger structures emanating from the SPT. This older contractional belt may be analogous to the contractional belts encircling the active SPT. The structures in the SPT and SDP may have formed due to two separate events of diapirism or due to the relative movement of a single diapir with respect to the overlying ice.
Beddingfield C. B.
Yoshinobu A. S.
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