Collaborative Research: Tectonic and climatic forcing of hydrological systems in the southern Great Basin: Implications for ancient and future aquatic system resilience

University Of The Pacific, Stockton CA

Investigators

Abstract

The southern Great Basin is among the most arid regions in North America. It has almost no perennial streams, but does have >1,000 springs. These springs are islands of aquatic habitat in an ocean of desert. Remarkably, many of these isolated springs contain diverse aquatic ecosystems and even endemic species of fish, spring snails, and other aquatic organisms. The presence of many aquatic species that can only survive in water is evidence that the springs are remnants of a perennial drainage system, and the presence of endemic species requiring intervals in the million-year range for genetic divergence are evidence that at least some of these springs have never desiccated over the geological time scale. Aquatic biogeographical patterns thus inform the geological and hydrological history of the region. This is a project to expand the already-large regional biogeographical database and to use the combined new and preexisting data to test models of tectonic and paleohydrological evolution of the southern Great Basin. The PIs will focus on two timescales: that of the extensional breakup of the region from the late Miocene to the present and that of glacial/interglacial climate cycles. Extensive work has been done to understand the extensional history of the region, which started in the eastern portion of the study area at ~14 Ma and migrated westward to the Sierra Nevada front, driven by plate-boundary dynamics. They will simulate this evolution using a regional quasi-3D kinematic/tectonic-geomorphic-hydrologic coupled model that fully couples movement along faults, mass distribution, magmatism, isostatic compensation and flexural deformation with hydrology and surface geomorphic processes, including erosion and deposition. The extensional fragmentation of the hydrological system will be studied and groundwater flow, necessary to simulate the resulting development of springs, will be an integral part of the regional tectonic-geomorphic-hydrologic model. . Modeled paleohydrologic histories will be tested against biotic data (aquatic biota inventories, microbial and macrofaunal DNA, and genetic divergence times) with island biogeography theory. The PIs will test for relations of hydrologic fragmentation chronology with endemic species and for ecosystem diversity with spring resilience, as inferred from groundwater ages and climatically driven modeling. They will use these results to assess and improve their tectonic/paleohydrologic models.