HR: 1330h
AN: P12B-1060    [PDF]
TI: Incipient Formation of Tharsis: a Lithospheric Flexure Model Using Venusian Coronae as an Analog
AU: * Williams, J
EM: jpierre@mars.ucla.edu
AF: University of California, Dept. Earth and Space Sciences 595 Charles E. Young Dr. East, Los Angeles, CA 90095 United States
AU: Moore, W B
EM: bmoore@ess.ucla.edu
AF: University of California, Dept. Earth and Space Sciences 595 Charles E. Young Dr. East, Los Angeles, CA 90095 United States
AB: The Tharsis region of Mars is an extensive volcanotectonic province that dominates the western hemisphere of the planet. The southeast portion of Tharsis is comprised of the tectonic plateau of Thaumasia, a $>$ 2500 km diameter quasi-circular plateau standing $\sim$4 km above the surrounding cratered highlands. The interior high plains are circumscribed by the mountain belts of Coprates Rise, Thaumasia Highlands, Warrego Rise, and Claritas Rise in the south and east, by Syria Planum in the west, and Valles Marineris to the north. The gravity data provided by the Mars Global Surveyor reveals a several hundred km wide negative free-air gravity anomaly in the adjacent cratered highlands peripheral to the Thaumasia Plateau in the south and east. This is likely the result of burial by less dense sediments and volcanics of a flexural trench produced by the load placed on the lithosphere from the high-standing plateau and mountains. The flexural wavelength of the buried trench indicates that the elastic lithosphere was $\sim$30 km in thickness at the time of load emplacement. Coronae on Venus commonly display a similar topographic configuration: a central plateau higher than the surrounding terrain, a raised rim, and a peripheral flexural moat. Similarities with $\sim$2600 km diameter Artemis Corona are evident. Having undergone very little alteration since its formation, Artemis Corona provides a relatively pristine analog as a basis for comparison and offers clues to the incipient formation of the Thaumasia region of Tharsis. We present a lithospheric flexure model that fits the gravity and topography across the buried trench. This provides constraints on parameters such as crustal, mantle, and trench infill densities, crustal and lithospheric thicknesses, and the amount of initial uplift and/or volcanic construction required prior to relaxation.
DE: 1227 Planetary geodesy and gravity (5420, 5714, 6019)
DE: 5400 PLANETOLOGY: SOLID SURFACE PLANETS
DE: 5417 Gravitational fields (1227)
DE: 6225 Mars
DE: 6295 Venus
SC: Planetary Sciences [P]
MN: 2003 Fall Meeting