Research Article| July 01, 1974 Geology of the Spring Mountains, Nevada B. C. BURCHFIEL; B. C. BURCHFIEL 1Department of Geology, Rice University, Houston, Texas 77001 Search for other works by this author on: GSW Google Scholar R. J. FLECK; R. J. FLECK 2U.S. Geological Survey, 345 Middlefield Road, Menlo Park, California 94025 Search for other works by this author on: GSW Google Scholar D. T. SECOR; D. T. SECOR 3Department of Geology, University of South Carolina, Columbia, South Carolina 29210 Search for other works by this author on: GSW Google Scholar R. R. VINCELETTE; R. R. VINCELETTE 4Trend Exploration Limited, 600 Capitol Life Center, Denver, Colorado 80203 Search for other works by this author on: GSW Google Scholar G. A. DAVIS G. A. DAVIS 5Department of Geology, University of Southern California, Los Angeles, California 90007 Search for other works by this author on: GSW Google Scholar Author and Article Information B. C. BURCHFIEL 1Department of Geology, Rice University, Houston, Texas 77001 R. J. FLECK 2U.S. Geological Survey, 345 Middlefield Road, Menlo Park, California 94025 D. T. SECOR 3Department of Geology, University of South Carolina, Columbia, South Carolina 29210 R. R. VINCELETTE 4Trend Exploration Limited, 600 Capitol Life Center, Denver, Colorado 80203 G. A. DAVIS 5Department of Geology, University of Southern California, Los Angeles, California 90007 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1974) 85 (7): 1013–1022. https://doi.org/10.1130/0016-7606(1974)85<1013:GOTSMN>2.0.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation B. C. BURCHFIEL, R. J. FLECK, D. T. SECOR, R. R. VINCELETTE, G. A. DAVIS; Geology of the Spring Mountains, Nevada. GSA Bulletin 1974;; 85 (7): 1013–1022. doi: https://doi.org/10.1130/0016-7606(1974)85<1013:GOTSMN>2.0.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 SocietyGSA Bulletin Search Advanced Search Abstract The northwest-trending Spring Mountains, Nevada, contain a 45-mi-wide (75-km) cross section of the eastern part of the North American Cordilleran orogenic belt and geosyncline. This cross section is probably the most southerly exposed section which exhibits structure and stratigraphy "typical" of the eastern part of the Cordillera.Stradgraphically, the transition from Paleozoic craton to miogeosyncline is present from east to west across the Spring Mountains. The sedimentary succession through the middle Permian thickens from 8,800 ft (2,660 m) east of the Spring Mountains to approximately 30,000 ft (9,000 m) in the west. Thickening of individual formations accounts for 6,800 ft (2,070 m) of added section, addition of formations at unconformities accounts for 4,600 ft (1,400 m) of added section, and addition of a thick terrigenous late Precambrian sequence accounts for 9,800 ft (3,000 m) of added section.Three major thrust plates are exposed in the Spring Mountains, each structurally higher plate containing a thicker sequence of Paleozoic rocks. The easternmost thrust is the Keystone thrust, except where the earlier Red Spring thrust plate is present below the Keystone as isolated remnants. The Keystone thrust appears to be a décollement thrust, but complications at depth suggest that additional thrust slices may be present below the thrust or several thousand feet of late Precambrian terrigenous rocks may be present above the thrust. The structurally higher Lee Canyon thrust plate probably contains at least 4,000 ft (1,200 m) of these terrigenous rocks at its base, and the Wheeler Pass thrust plate contains at least 11,000 ft (3,300 m) of these rocks. Pregeosynclinal basement could be involved in some of the higher thrust plates, particularly the Wheeler Pass plate, but depths of exposure are inadequate to determine its role.Thrust faulting has produced a shortening of from 22 to 45 mi (36.6 to 75 km) in the geosynclinal rocks based on geometric constructions of cross sections at depth. This range probably represents a minimum figure. Some folding and thrusting occurred during the early Late Cretaceous, but data within the Spring Mountains only establish a much wider time bracket, post–Early Jurassic to pre–late Cenozoic for the easternmost thrust faults and post–Early Permian to pre–late Cenozoic for the westernmost thrusts. 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.
The 40Ar/39Ar investigations of a large suite of fine-grained basaltic rocks of the Boring volcanic field (BVF), Oregon and Washington (USA), yielded two primary results. (1) Using age control from paleomagnetic polarity, stratigraphy, and available plateau ages, 40Ar/39Ar recoil model ages are defined that provide reliable age results in the absence of an age plateau, even in cases of significant Ar redistribution. (2) Grouping of eruptive ages either by period of activity or by composition defines a broadly northward progression of BVF volcanism during latest Pliocene and Pleistocene time that reflects rates consistent with regional plate movements. Based on the frequency distribution of measured ages, periods of greatest volcanic activity within the BVF occurred 2.7–2.2 Ma, 1.7–0.5 Ma, and 350–50 ka. Grouped by eruptive episode, geographic distributions of samples define a series of northeast-southwest–trending strips whose centers migrate from south-southeast to north-northwest at an average rate of 9.3 ± 1.6 mm/yr. Volcanic activity in the western part of the BVF migrated more rapidly than that to the east, causing trends of eruptive episodes to progress in an irregular, clockwise sense. The K2O and CaO values of dated samples exhibit well-defined temporal trends, decreasing and increasing, respectively, with age of eruption. Divided into two groups by K2O, the centers of these two distributions define a northward migration rate similar to that determined from eruptive age groups. This age and compositional migration rate of Boring volcanism is similar to the clockwise rotation rate of the Oregon Coast Range with respect to North America, and might reflect localized extension on the trailing edge of that rotating crustal block.
Research Article| September 01, 1978 Age of structural differentiation between the Colorado Plateaus and Basin and Range provinces in southwestern Utah: Comment and reply: REPLY Peter D. Rowley; Peter D. Rowley 1U.S. Geological Survey, Denver, Colorado 80225 Search for other works by this author on: GSW Google Scholar John J. Anderson; John J. Anderson 2Department of Geology, Kent State University, Kent, Ohio 44242 Search for other works by this author on: GSW Google Scholar Paul L. Williams; Paul L. Williams 3U.S. Geological Survey, Denver, Colorado 80225 Search for other works by this author on: GSW Google Scholar Robert J. Fleck Robert J. Fleck 4U.S. Geological Survey, Menlo Park, California 94025 Search for other works by this author on: GSW Google Scholar Geology (1978) 6 (9): 572–575. https://doi.org/10.1130/0091-7613(1978)6<572b:AOSDBT>2.0.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 Peter D. Rowley, John J. Anderson, Paul L. Williams, Robert J. Fleck; Age of structural differentiation between the Colorado Plateaus and Basin and Range provinces in southwestern Utah: Comment and reply: REPLY. Geology 1978;; 6 (9): 572–575. doi: https://doi.org/10.1130/0091-7613(1978)6<572b:AOSDBT>2.0.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 No Abstract Available. 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.
Research Article| October 01, 1994 Isotopic complexities and the age of the Delfonte volcanic rocks, eastern Mescal Range, southeastern California: Stratigraphic and tectonic implications ROBERT J. FLECK; ROBERT J. FLECK 1U.S. Geological Survey, M.S. 937, 345 Middlefield Road, Menlo Park, California 94025 Search for other works by this author on: GSW Google Scholar JAMES M. MATTINSON; JAMES M. MATTINSON 2Department of Geological Sciences, University of California, Santa Barbara, California 93106 Search for other works by this author on: GSW Google Scholar CATHY J. BUSBY; CATHY J. BUSBY 2Department of Geological Sciences, University of California, Santa Barbara, California 93106 Search for other works by this author on: GSW Google Scholar MICHAEL D. CARR; MICHAEL D. CARR 3U.S. Geological Survey, M.S. 104, National Center, Reston, Virginia 22092 Search for other works by this author on: GSW Google Scholar GREGORY A. DAVIS; GREGORY A. DAVIS 4Department of Geological Sciences, University of Southern California, Los Angeles, California 90089 Search for other works by this author on: GSW Google Scholar B. C. BURCHFIEL B. C. BURCHFIEL 5Department of Earth, Atmospheric, & Planetary Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 Search for other works by this author on: GSW Google Scholar GSA Bulletin (1994) 106 (10): 1242–1253. https://doi.org/10.1130/0016-7606(1994)106<1242:ICATAO>2.3.CO;2 Article history first online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share MailTo Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation ROBERT J. FLECK, JAMES M. MATTINSON, CATHY J. BUSBY, MICHAEL D. CARR, GREGORY A. DAVIS, B. C. BURCHFIEL; Isotopic complexities and the age of the Delfonte volcanic rocks, eastern Mescal Range, southeastern California: Stratigraphic and tectonic implications. GSA Bulletin 1994;; 106 (10): 1242–1253. doi: https://doi.org/10.1130/0016-7606(1994)106<1242:ICATAO>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 SocietyGSA Bulletin Search Advanced Search Abstract Combined U-Pb zircon, Rb-Sr, 40Ar/39Ar laser-fusion, and conventional K-Ar geochronology establish a late Early Cretaceous age for the Delfonte volcanic rocks. U-Pb zircon analyses define a lower intercept age of 100.5 ± 2 Ma that is interpreted as the crystallization age of the Delfonte sequence. Argon studies document both xenocrystic contamination and postemplacement Ar loss. Rb-Sr results from mafic lavas at the base of the sequence demonstrate compositionally correlated variations in initial 87Sr/86Sr ratios (Sri) from 0.706 for basalts to 0.716 for andesitic compositions. This covariation indicates substantial mixing of subcontinental lithosphere with Proterozoic upper crust. Correlations between Rb/Sr and Sri may result not only in pseudoisochrons approaching the age of the crustal component, but also in reasonable but incorrect apparent ages approaching the true age.Ages obtained in this study require that at least some of the thrust faulting in the Mescal Range-Clark Mountain portion of the foreland fold-and-thrust belt occurred later than ca. 100 Ma and was broadly contemporaneous with emplacement of the Keystone thrust plate in the Spring Mountains to the northeast. Comparison of the age and Rb-Sr systematics of ash-flow tuff boulders in the synorogenic Lavinia Wash sequence near Goodsprings, Nevada, with those of the Delfonte volcanic rocks supports a Delfonte source for the boulders. The 99 Ma age of the Lavinia Wash sequence is nearly identical to the Delfonte age, requiring rapid erosion, transport, and deposition following Delfonte volcanism. 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.
