The eastern Sierra Nevada Mountains rise steeply along the entire west side of Owens Valley. The Sierra Nevada Frontal Fault System (SNFFS) crops out along numerous fault strands that collectively account for much of the Pliocene to Recent uplift of the Sierra. The rate, timing, magnitude, and mechanisms of Sierran uplift have been debated for greater than 100 years. The 100+ year paradigm for SNFFS faults has been that they dip ~60 degrees based on Andersonian mechanics of faulting. The assumed steep dip is used in calculations of uplift and extension rates and overall kinematic history of the Sierra-Owens Valley tectonic system. However, work by Phillips and Majkowski (Lithosphere, V.3, 2011) in northern Owens Valley north of Bishop show that normal faults there often dip <35 degrees. More recent work by several CSUF undergraduate students from Lone Pine to Big Pine in southern to central Owens valley shows that faults of the SNFFS system dip 23-35 degrees in every measured case for this area. These shallow dips, when decomposed on to a horizontal direction perpendicular to the SNFFS strike lead to Pleistocene and Holocene extension rates that are similar to geodetic rates for the Sierra Nevada-Owens Valley region. In this talk, I will highlight some of the terrific student work on these projects to show some of our evidence for the low-angle faults and discuss our interpretations and future directions.
Phil Armstrong is a Professor of Geological Sciences at Cal State Fullerton and for the last 2.55 years he has been chair of the department. He received his BA in Geology from UC Santa Barbara and his Masters and Ph.D at the University of Utah working on structure/tectonic problems using a variety of tools from geophysics to basic field work to geochronology working in Nevada, Utah, and New Zealand. Since 1999, he has continued this work at CSUF but focusing on rock uplift processes at many time scales; he and his CSUF students have worked in Utah, southern California, Alaska, and Owens Valley. Armstrong’s research along the eastern Sierran Front is a natural transition that links structure/tectonics with of a lifetime of hiking, running, exploring, and fly fishing throughout the eastern Sierras and Owens Valley.
Address: 7 Hutton Dr., Santa Ana, CA
Meal: Regular or Vegetarian
Cost: $30 (member),