9526455 Phinney The first phase of the Southern Sierra Continental Dynamics Project (SSCD) yielded the surprising result that a mountain range standing up to 2800 m higher than surrounding lowlands has a sialic crust of thickness nearly equal to that of the lowlands (30-40km), based on both passive and active seismic imaging. Three-dimensional tectonic reconstruction of the adjacent Basin and Range province suggests Neogene thinning of both eastern Sierran and Basin and Range crust by a factor of two. These results confirm an upper mantle origin for buoyancy beneath the range, and present perhaps the starkest illustration of a major unsolved problem in the dynamics of the cordilleran lithosphere: How can the profound loss of buoyancy from Neogene crustal thinning be reconciled with long-standing paleobotanical, geomorphological, and stratigraphic arguments indicating 1-2 km or more of Cordillera-wide late Cenozoic uplift? Obvious end member solutions inalude: (1) little or no thinning of eastern sierran crust (2) an unusually large decrease in density in the upper mantle (3) regional subsidence of a high, Andean-type plateau, rather than uplift. This award is one component of the second phase of the SSCD that has as it's goal the evaluation of the above hypotheses with a focused, multidisciplinary approach involving balanced cross-sections, seismic tomography, thermochronometry and isotope tracer studies, long-period MT, and low-temperature thermochronometry of Sierran granitoids. ***

Agency
National Science Foundation (NSF)
Institute
Division of Earth Sciences (EAR)
Application #
9526455
Program Officer
Leonard E. Johnson
Project Start
Project End
Budget Start
1996-08-15
Budget End
2000-07-31
Support Year
Fiscal Year
1995
Total Cost
$166,209
Indirect Cost
Name
Princeton University
Department
Type
DUNS #
City
Princeton
State
NJ
Country
United States
Zip Code
08540