What: Nevada Petroleum & Geothermal Society Monthly Dinner Meeting
When: Thursday, January 8, 2015
Speaker: Dr. Wanda Taylor, Professor of Geoscience, Applied Geophysics Center and Department of Geoscience at UNLV
Title: Cenozoic structure and tectonics of southern Nevada
A significant change in tectonism occurred in the Northern Basin and Range (NBR) and Central Basin and Range (CBR) sub-provinces between the Miocene and Pliocene-Quaternary. These changes are demonstrated by structures, volcanic rocks, and young sedimentary rocks in southern Nevada.
In the Miocene (and earlier), the NBR-CBR boundary (~37.2oN) accommodated differences across it in the timing of initiation, rate and magnitude of extension. Differences in magnetic anomalies, gravity anomalies and structures also occur across the NBR-CBR boundary. This boundary is marked by two caldera complexes, the Caliente caldera complex and the southern Nevada volcanic field, and two NE-striking left-lateral fault systems: the Caliente-Enterprise zone and the Pahranagat Shear Zone. New work on the Pahranagat Shear Zone, s system with three major faults, shows restraining bends and transfer fault geometries. The faults also cut an older, but post-volcanic (~18 Ma) set of normal faults, suggesting at least two different episodes of extension.
In the late Miocene, a portion of the right-lateral slip along the San Andreas fault (ie., the plate boundary) stepped to the east of the Sierra Nevada and resulted in a change in tectonism in southern Nevada. The Pliocene-Quaternary faults have a wider spacing and geometries that differ from those in the Miocene. The Miocene and earlier NBR-CBR boundary is spatially coincident with the southern Nevada seismic belt (SNSB). Geodetic strain rates are higher north of the belt than south of it. The region south of the SNSB lies between the active Eastern California Shear Zone on the west and the northern Arizona seismic belt on the east, however, this region have been called both seismically inactive and active. New paleoseismic data on the Stewart Valley fault/Pahrump fault of the Stateline right-lateral fault system, a part of the Eastern California Shear Zone, indicate at least two recent earthquakes. The latest of these occurred within the last ~1000 years. New paleoseismic data on normal faults such as the California Wash fault also suggest that these faults have been active within the Holocene. Together these data suggest that the region is tectonically and seismically active.
Las Vegas basin is a clear example of these changes in tectonism. Well log and geologic map data show that the Miocene sedimentary depocenter was controlled by the right-lateral Las Vegas Valley Shear Zone and the normal oblique slip Frenchman Mountain fault. In contrast, well log and map data show that the deepest part of the Pliocene-Quaternary basin lays west of that in the Miocene. These relations are interpreted to indicate that the Las Vegas Valley fault system became active then and impacted the basin geometry at a time consistent with the changes in the plate boundary.
Where: Ramada Reno Hotel; 6:30 PM
1000 East 6th Street, Reno, NV 89512
Details: Open Bar 6:30 pm, Skyline Room 14th Floor
Dinner Served at 7:00 PM
Cost: NPGS Members $20, Non-Members $23, Students $10
Please RSVP by Tuesday, Jan 6 with the following link: