Crosscutting relations and relative ages of ridges and faults in the Tharsis region of Mars |
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| Authors: | Thomas R Watters Ted A Maxwell |
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| Institution: | Center for Earth and Planetary Studies, National Air and Space Museum, Smithsonian Institution, Washington, D.C. 20560, USA |
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| Abstract: | Observations of ridge-fault crosscutting relationships on the ridged plains units surrounding the Tharsis region of Mars have led to the development of a classification scheme involving three distinct types of intersections. Ridges crosscut by faults are designated Type C and account for 81% of the observed intersections. Ridges terminated at one end by a fault (Type T), as well as those superposed on grabens (Type S), are less numerous. Interpretation of the morphology of these intersections and the angles of intersection between ridges and faults with radial trends to major topographic features in the Tharsis region have led to the following conclusions: (1) the major ridge forming events in the Tharsis region were roughly coincident with, and in some cases possibly prior to, the extensional events that produced the faulting of the Tempe and Mareotis regions, the Coprates and Memnonia regions, and the rifting of Valles Marinrris; (2) the compressional events that formed most of the ridges are restricted in time both by the irrelationship to regional extensional events and by the age of the units on which they formed. The suggestion that compressional ridges are a result of a single long term viscoelastic response of the lithosphere to loading of the crust is not supported by this study. A model involving one or more isostatically compensated uplifts and subsequent relaxation of the crust after the emplacement of the ridged plains volcanic units is favored. |
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