Origins of deep crustal reflections: Implications of coincident seismic refraction and reflection data in Nevada

Abstract

Research Article| February 01, 1991 Origins of deep crustal reflections: Implications of coincident seismic refraction and reflection data in Nevada W. Steven Holbrook; W. Steven Holbrook 1Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543 Search for other works by this author on: GSW Google Scholar R. D. Catchings; R. D. Catchings 2U.S. Geological Survey, MS 977, 345 Middlefield Road, Menlo Park, California 94025 Search for other works by this author on: GSW Google Scholar Craig M. Jarchow Craig M. Jarchow 3Department of Geophysics, Stanford University, Stanford, California 94305 Search for other works by this author on: GSW Google Scholar Author and Article Information W. Steven Holbrook 1Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543 R. D. Catchings 2U.S. Geological Survey, MS 977, 345 Middlefield Road, Menlo Park, California 94025 Craig M. Jarchow 3Department of Geophysics, Stanford University, Stanford, California 94305 Publisher: Geological Society of America First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (1991) 19 (2): 175–179. https://doi.org/10.1130/0091-7613(1991)019<0175:OODCRI>2.3.CO;2 Article history First Online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation W. Steven Holbrook, R. D. Catchings, Craig M. Jarchow; Origins of deep crustal reflections: Implications of coincident seismic refraction and reflection data in Nevada. Geology 1991;; 19 (2): 175–179. doi: https://doi.org/10.1130/0091-7613(1991)019<0175:OODCRI>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract We compare seismic refraction and reflection results along the PASSCAL/COCORP 40°N transect in the northern Basin and Range of Nevada in order to determine the origin of the prominent reflections from the deep crystalline crust. Reflection data along the transect show a thick zone of discontinuous, subhorizontal reflections, beginning at 4-6 s two-way traveltime (10-20 km depth) and ending at 9-11 s (27-35 km). Two independently derived velocity models, based on refraction data, are largely similar and agree on many important aspects of the reflectivity-velocity relation. Both models show that the top of the reflective zone lies 3-8 km above a prominent mid-crustal velocity discontinuity, which is interpreted to separate bulk silicic from bulk dioritic-gabbroic crust; in most places, the silicic mid-crust is more strongly reflective than the mafic lower crust. This pattern is expected in areas where ductile shearing is the mechanism responsible for the reflectivity. One of the velocity models, however, suggests that, in places, the strongest reflectivity spans both the middle (6.1-6.3 km/s) and lower (6.6 km/s) crust; this pattern suggests that the combined influence of ductile strain fabrics and mafic intrusions gives rise to crustal reflections. Both models show that the lowermost crust and crust/mantle transition are highly reflective, also suggesting the presence of mafic and/or ultramafic intrusions. Thus the observed reflection patterns suggest that ductile shearing and the intrusion of mantle-derived magma—both of which are likely to have accompanied the extreme Cenozoic extension—are important factors in generating deep crustal reflections. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.