Short-wavelength Contractional Structures in Venusian Fold Belts: Additional Constraints From New Models

Details Short-wavelength Contractional Structures in Venusian Fold Belts: Additional Constraints From New Models Short-wavelength Contractional Structures in Venusian Fold Belts: Additional Constraints From New Models

Dec 2002

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2002agufm.p71b0469g&link_type=abstract

American Geophysical Union, Fall Meeting 2002, abstract #P71B-0469

Mathematics

Logic

3210 Modeling, 5475 Tectonics (8149), 8005 Folds And Folding, 8020 Mechanics, 8164 Stresses: Crust And Lithosphere

Scientific paper

We have previously reported on the development of very short-wavelength (<1 km) contractional topography (VST) in Venusian crustal plateau fold belts, which show structures with wavelengths from ~100 m to >30 km [1, 2]. We simulated the initiation and growth of VST using finite-element models with uniform composition and elasto-visco-plastic rheology undergoing simultaneous cooling and shortening. The models were constrained by Magellan SAR imagery and motivated by the current plume hypothesis for crustal plateau origin [3, 4]. We determined that VST developed only in models with surface temperatures near 1000 K and elevated thermal gradients derived from a halfspace cooling model with initial uniform temperatures of 1200-1400 K. Model rheological profiles indicated a truly viscoplastic character, in which both creep and plastic mechanisms were significant at shallow depths. The resulting topography showed both very short-wavelength components and slightly longer-wavelength, low amplitude folds, as is common in Venusian crustal plateau fold belts. New simulations with greater spatial extent and higher mesh resolution allow further exploration of the interplay between viscous and plastic processes during VST development. Wider models allow more detailed investigation of viscous folding on the 1-4 km scale. We also employ temperature-dependent thermal conductivity [5] to better represent the thermal behavior of the model crust. The additional insight and expanded parameter space provided by these new models allow us to place improved constraints on the early thermal and mechanical evolution of crustal plateaus. [1] Ghent, R.R., R.J. Phillips, V.L. Hansen, and D.C. Nunes, Eos Trans. AGU, 83(19), Spring Meet. Suppl., Abstract P21A-05, 2002. [2] Ghent, R.R., R.J. Phillips, and V.L. Hansen, 2001, Eos Trans. AGU, 82(47), Spring Meet. Suppl., Abstract T41B-0865, 2001. [3] Hansen, V.L. and J.J. Willis, Icarus, 132, 321-343, 1998. [4] Phillips, R.J. and V.L. Hansen, Science, 279, p1492, 1998. [5] Hofmeister, A, Science, 283, p1699, 1999.

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