HR: 0800h
AN: T31A-1263    [Abstracts]
TI: Thrust Stacking and the Creation and Preservation of Cratonic Lithosphere
AU: * Cooper, C M
EM: cmcooper@rice.edu
AF: Rice University, Department of Earth Science 6100 Main St MS-126, Houston, TX 77005 United States
AU: Lenardic, A
EM: adrian@rice.edu
AF: Rice University, Department of Earth Science 6100 Main St MS-126, Houston, TX 77005 United States
AU: Moresi, L
EM: louis.moresi@sci.monash.edu
AF: Monash University, School of Mathematical Sciences Building 28, Melbourne, 3800 Australia
AB: Cratons are areas of continental crust, and often the corresponding thick lithosphere, that exhibit long term stability from deformation. One suggested mechanism for the formation of cratonic lithosphere invokes the thrust stacking of proto-cratonic lithospheric material. This leads to the possible conundrum of how cratons can originate from deformative processes and then once formed, resist further deformation over long geologic time scales. To test the physical viability of formation of cratons via thrust stacking, as well as providing a mechanism for stabilization, we conducted numerical simulations and scaling analysis of simple analogues that incorporate a chemical layer of variable rheology within the upper thermal boundary layer of a convecting layer. We found that formation of cratonic lithosphere via thrust stacking is most viable for proto-cratonic lithosphere possessing low effective friction coefficient values. Once formed, preservation depends on the total thickness of the newly formed cratonic lithosphere, as well as the friction coefficient. Higher friction coefficient values and/or greater cratonic lithosphere thicknesses are more conducive to long-term stability as they provide higher integrated yield stresses within cratons. The high yield stress can offset convective stresses and thus, stabilize cratons. Thin cratonic lithosphere or cratonic lithosphere with low friction coefficient values may not provide adequate stability against the increasing convecting stresses, thus providing a potential explanation as to why some cratons are not long lived.
DE: 8100 TECTONOPHYSICS
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting