Intrusive, Uplift and Erosional History of the Northern Sierra Nevada batholith

NSF Tectonics 0809226

The Mesozoic Sierra Nevada Batholith preserves an extensive record of continental-margin arc magmatism which serves as a classic, worldwide model for such tectonic environments. However, about one-third of the batholith actually extends northward from the Sierra Nevada proper into the Basin and Range Province of northwest Nevada, where it has received little study. Extensive recent research on late Cenozoic Basin and Range extension in that region has yielded considerable preliminary information on that portion of the batholith, highlighting three key, related issues that form the focus of this project.

Rock formation — Bloody Run Peak in northwestern Nevada is ~98 Ma granodiorite of the northernmost Sierra Nevada batholith

Magmatic arc history
Erosion and exhumation
Sedimentation and basin formation

Magmatic Arc History

Large plutonic complexes have been discovered in northwest Nevada that are apparently members of the voluminous ca. 95-83 Ma Cathedral Range intrusive suites previously defined in the eastern Sierra Nevada. This is preliminary evidence that the magmatic histories of these two parts of the batholith were similar. In contrast however, geophysical studies in northwest Nevada have shown that the crust beneath the Basin and Range part of the batholith is neither as thick nor as felsic as the crust beneath the southern part of the batholith. This project will document the distribution, age, petrology, and geochemistry of batholithic rocks in northwest Nevada, in order to more rigorously integrate their intrusive history and petrogenesis with other parts of the magmatic arc. Work will include reconnaissance investigations over the entire region and detailed work on key plutonic complexes.

Topical map of batholithic rocks shown in orange western US — Above: Batholithic rocks are shown in orange on this map of the western United States. The bounds of the Sierra Nevada batholith are shown by thin red dotted lines; the batholith can be seen to bend NNE to the north of the 87/86Sri = 0.706 line marking the edge of the cratonal crust. We are doing reconnaissance work throughout this area as well as detailed work in the box labeled 'Study Area'.

Topical map showing ages of plutonic rocks in Sierra Nevada Batholith — Above: Map showing the ages of plutonic rocks in the northernmost Sierra Nevada Batholith, highlighting some of our recent SHRIMP U-Pb ages (Van Buer and Wooden, 2007; Van Buer 2008).

Erosion and exhumation

Erosion has stripped an estimated 3 to 7 km of rock section from the top of batholithic rocks in northwest Nevada during the time interval between Late Cretaceous extinction of the arc and Tertiary (mostly Eocene) formation of the regionally extensive basal Tertiary unconformity. The history of this exhumation is poorly understood and has important implications for paleogeography, paleotopography, crustal thickness and structure, uplift mechanisms, tectonics, and sediment dispersal over a large region. This project will document the post-intrusive cooling and erosional history of this part of the batholith by applying a suite of thermochronometers to sample transects collected across 3-6 km thick tilted sections of batholithic rocks exposed beneath the Tertiary unconformity by Basin and Range normal faulting.

landscape view of mountains and valley — The dark, stratified rocks in the midground are Tertiary basalts, which nonconformably overlie the 105 Ma Santa Rosa pluton and its wall rocks in this panoramic view taken from the crest of the Santa Rosa Range in NW Nevada.

Paleogeologic map of Honey Lake, Pyramid Lake and Lake Tahoe — Above: The extensive basal Tertiary unconformity and underlying rocks can be used to construct an early Tertiary paleogeologic map. Line squiggles represent exposed traces of the unconformity today; color coding represents main rock types immediately beneath the unconformity. The colored fields represent a postextensional view of preunconformity surface geology. H-Honey Lake; P-Pyramid Lake; T-Lake Tahoe.

Hypothetical cooling curve diagrams — Hypothetical cooling curves showing how a suite of thermochonometers may be able to constrain the exhumational cooling history of the batholith.

Sedimentation and Basin Formation

Sedimentation and basin formation: Erosion has stripped huge volumes of rock off of the top of the batholith in northwest Nevada; where did all this material go? Preliminary data suggest that the detritus from this region may have been transported into basins to the north and west, rather than into the Great Valley, suggesting the ancient topographic expression of the batholith in northwest Nevada may have been radically different than the western edge of an Altiplano-like plateau envisaged for the Sierra Nevada proper. This project will characterize the basin sinks for these huge volumes of detritus by using single-grain U-Pb dating of detrital zircon populations from uppermost Cretaceous and lower Tertiary strata in the Great Valley, Sierra Nevada, Warner Range (northeastern California), and Oregon.

Publications

Colgan, Joseph P., Trevor A. Dumitru, Peter W. Reiners, Joseph L. Wooden, and Elizabeth L. Miller. 2006. “Cenozoic Tectonic Evolution of the Basin and Range Province in Northwestern Nevada.” AMERICAN JOURNAL OF SCIENCE 306 (8). AMER JOURNAL SCIENCE: 616–54. DOI: 10.2475/08.2006.023

Lerch, D. W., J. MG Glen, D. A. Ponce, E. L. Miller, and J. P. Colgan. 2007. “Crustal Structure of the Northwestern Basin and Range Province and Its Transition to Unextended Volcanic Plateaus.” GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS 8. AMER GEOPHYSICAL UNION. DOI: 10.1029/2006GC001429

Colgan, J. P., T. A. Dumitru, and E. L. Miller. 2004. “Diachroneity of Basin and Range Extension and Yellowstone Hotspot Volcanism in Northwestern Nevada.” GEOLOGY 32 (2). GEOLOGICAL SOC AMER, INC: 121–24. DOI: 10.1130/G20037.1

Gashawbeza, Ewenet M., Simon L. Klemperer, Charles K. Wilson, and Elizabeth L. Miller. 2008. “Nature of the Crust beneath Northwest Basin and Range Province from Teleseismic Receiver Function Data.” JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH 113 (B10). AMER GEOPHYSICAL UNION. DOI: 10.1029/2007JB005306

Dumitru, T. A., P. B. Gans, D. A. Foster, and E. L. Miller. 1991. “REFRIGERATION OF THE WESTERN CORDILLERAN LITHOSPHERE DURING LARAMIDE SHALLOW-ANGLE SUBDUCTION.” GEOLOGY 19 (11). GEOLOGICAL SOC AMERICA: 1145–48.

Lerch, Derek William, Elizabeth Miller, Michael McWilliams, and Joseph Colgan. 2008. “Tectonic and Magmatic Evolution of the Northwestern Basin and Range and Its Transition to Unextended Volcanic Plateaus: Black Rock Range, Nevada.” GEOLOGICAL SOCIETY OF AMERICA BULLETIN 120 (3-4). GEOLOGICAL SOC AMER, INC: 300–311. DOI: 10.1130/B26151.1