HR: 0800h
AN: T31A-1267    [Abstracts]
TI: Who Needs Isostasy? Non-Isostatic Support for Major Mountain Belts, an Example From the Northern Iran-South Caspian System
AU: * Guest, B
EM: bguest@ess.ucla.edu
AF: University of California Los Angeles, 595 Charles Young Dr. East, Los Angeles, Ca 90095
AU: Guest, A S
EM: aliceguest@jpl.nasa.gov
AF: California Institute of Technology, Jet Propulsion Laboratory, 4800 Oak Grove Drive , Pasadena, Ca 91109
AU: Axen, G J
EM: gaxen@ess.ucla.edu
AF: University of California Los Angeles, 595 Charles Young Dr. East, Los Angeles, Ca 90095
AB: What supports mountains and creates deep basins on earth? We present a new mechanism for the coeval development of an isostatically unsupported 2 to 4 km high mountain belt and flanking sedimentary basins. Within the Arabia-Eurasia continent-continent collision zone, contrasts in strength and geometry between northern Iranian continental lithosphere and south Caspian oceanic lithosphere focuses collision-related deformation at the Caspian northern-Iran interface. This process is responsible for Late Miocene to Recent rapid south Caspian subsidence, rapid uplift of northern Iran (Alborz Mountains) and subsidence within the Turkish Iranian Plateau (central Iran). A north-south oriented, 600 km long by 130 km deep, cross-sectional finite element model for the south Caspian and northern Iran system is centered on the continent-oceanic lithospheric interface at 10 million years before present when there was ~10km of sediment overlying the south Caspian oceanic lithosphere and low topography along the south Caspian margin. The model is displaced 90 km from the south with its northern margin fixed, causing the oceanic lithosphere to warp down and the continental lithosphere to warp up adjacent to the interface. Deformation decreases to the north and south with a lower amplitude depression forming south of the up-warped continental lithosphere and a lower amplitude up-warp forming north of the depressed oceanic lithosphere. This model fits geological and geophysical observations from northern Iran and indicates that high mountains can be supported flexurally by horizontal compression without calling on other mechanisms like Pratt isostasy and Airy isostasy. Similarly, the Caspian basin to the north and the central Iranian basin to the south are flexurally depressed explaining the great thickness of the south Caspian basin ($>$20 km) and the development of a broad basin within the Turkish-Iranian Plateau.
DE: 8099 General or miscellaneous
DE: 8149 Planetary tectonics (5475)
DE: 8159 Rheology--crust and lithosphere
DE: 8164 Stresses--crust and lithosphere
DE: 3040 Plate tectonics (8150, 8155, 8157, 8158)
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting