Dr. Cassel presents "Ancient Lakes & Mountains of the Great Basin: Records of Paleogene Tectonics.."
- Thursday, February 2, 2017 from 4:30pm to 5:30pm
- Gaines Hall, Room 243 - view map
On February 2nd, 2017, at 4:30PM- 5:30PM in Gaines Hall 243, Dr. Elizabeth Cassel from the University of Idaho will give a presentation titled, "Ancient Lakes & Mountains of the Great Basin: Records of Paleogene Tectonics in the US Cordilleran Hinterland.”
Below is a summary from Dr. Cassel about the presentation:
"The North American Cordillera provides a record of continental plate deformation that is a global model for subduction and mantle dynamics, and the construction of Cretaceous high topography in the hinterland of the Sevier fold-thrust belt has been proposed by many authors. The timing and mechanisms driving the transition from orogen construction to extension and collapse remain poorly understood due to tectonic overprinting and the inherent complexity of terrestrial facies assemblages. Through a multi-proxy approach, we reconstruct the high-resolution archive of orogenic processes and continental climate that accumulated in the hinterland Elko Basin. Paleogene Elko Basin terrestrial and volcanic strata record continental drainage ponding, increasingly proximal magmatism, the dynamics of Farallon slab rollback, and the timing of the onset of surface-lowering extension. Carbonate-rich lacustrine strata present across northeastern Nevada record prolonged Eocene continental drainage ponding and the transition from overfilled to balanced-fill lake conditions over time. Detrital zircon U-Pb-He double dating indicates that this basin received sediment from both local basement sources and from the Challis volcanic field, demonstrating that hinterland lakes were fed, in part, by a south-flowing drainage from a higher elevation terrain in central Idaho. Elko basin expansion and lake facies transition in the middle Eocene is contemporaneous with a provenance shift from extra-regional to local basement and proximal volcanic sources, likely triggered by the thermal effects of Farallon slab rollback. Volcanic glass hydration waters at multiple latitudes show decreasing hydrogen isotope values eastward from the paleo-coast, showing that a broad orogen stretched across Nevada with elevations up to 3.5 km and a distinct crest that divided a continuous westward-draining slope extending to central California from an internally drained orogenic plateau in the east. Lacustrine glass hydration waters also record increasingly evaporative waters, consistent with the late Eocene transition from overfilled to balanced-fill lake conditions as indicated by stratigraphy. Despite the long-term high gravitational potential energy of the crust supporting high hinterland topography, surface-lowering extension did not occur until the transition to a transform margin changed the external kinematic framework of the Cordillera in the late Oligocene."
We hope to see you at the presentation!
- Department of Earth Sciences