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Geochronologic and isotopic evidence for Triassic-Jurassic emplacement of the eugeoclinal allochthon in the Mojave Desert region, California

1995; Geological Society of America; Volume: 107; Issue: 12 Linguagem: Inglês

10.1130/0016-7606(1995)107 2.3.co;2

1943-2674

Jonathan S. Miller, Allen F. Glazner, J. Douglas Walker, Mark W. Martin,

Geological formations and processes

Research Article| December 01, 1995 Geochronologic and isotopic evidence for Triassic-Jurassic emplacement of the eugeoclinal allochthon in the Mojave Desert region, California Jonathan S. Miller; Jonathan S. Miller 1Department of Geology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3315 Search for other works by this author on: GSW Google Scholar Allen F. Glazner; Allen F. Glazner 1Department of Geology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3315 Search for other works by this author on: GSW Google Scholar J. Douglas Walker; J. Douglas Walker 2Isotope Geochemistry Laboratory, Department of Geology, University of Kansas, Lawrence, Kansas 66045 Search for other works by this author on: GSW Google Scholar Mark W. Martin Mark W. Martin 2Isotope Geochemistry Laboratory, Department of Geology, University of Kansas, Lawrence, Kansas 66045 Search for other works by this author on: GSW Google Scholar Author and Article Information Jonathan S. Miller 1Department of Geology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3315 Allen F. Glazner 1Department of Geology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3315 J. Douglas Walker 2Isotope Geochemistry Laboratory, Department of Geology, University of Kansas, Lawrence, Kansas 66045 Mark W. Martin 2Isotope Geochemistry Laboratory, Department of Geology, University of Kansas, Lawrence, Kansas 66045 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1995) 107 (12): 1441–1457. https://doi.org/10.1130/0016-7606(1995)107 2.3.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 Jonathan S. Miller, Allen F. Glazner, J. Douglas Walker, Mark W. Martin; Geochronologic and isotopic evidence for Triassic-Jurassic emplacement of the eugeoclinal allochthon in the Mojave Desert region, California. GSA Bulletin 1995;; 107 (12): 1441–1457. doi: https://doi.org/10.1130/0016-7606(1995)107 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 The geologic history of the outer continental margin (eugeoclinal) rocks in the El Paso Mountains and northern Mojave Desert has long been important in models for the development of the active continental margin in the western Cordillera. Current interpretations call for either strike-slip or thrust juxtaposition of eugeoclinal rocks against miogeoclinal/cratonal (platformal) rocks, or some combination of both strike-slip faulting and thrusting. Two broad and interrelated aspects of the history of the eugeoclinal rocks are at issue: (1) How much primary displacement is necessary to account for the present position of the eugeoclinal rocks? and (2) When were the eugeoclinal rocks thrust against platformal rocks? This study primarily addresses the second issue.Lithologic correlation indicates that the outcrop belt of eugeoclinal rocks is bounded by platformal rocks to the east and south. Platformal rocks are also present to the west, but many of these exposures restore to a position structurally beneath the eugeoclinal rocks when Tertiary extension is restored, implying stacking by a thrust. New U-Pb zircon geochronology and whole rock geochemistry and Sr, Nd, and Pb isotopic data for plutons in the El Paso Mountains and northern Mojave Desert lend insight into the timing of this thrusting. The outcrop belt of eugeoclinal rocks coincides with the only known Permian and Triassic plutons in the El Paso Mountains and northern Mojave Desert, which are dated at 260 to 240 Ma by U-Pb zircon in this report. Initial Sr and ϵNd(t) isotopic values from these plutons are distinct ≤0.704 and ≥+2, respectively) from continental lithosphere isotopic signatures ≥0.705 and ≤−2) of both Middle Jurassic plutons in the same area and Triassic plutons in the southern and eastern Mojave Desert. Feldspar common lead data for the Permian and Triassic plutons within the eugeoclinal outcrop belt also indicate limited crustal involvement and do not overlap previously reported values for common lead data from Mesozoic plutons in the eastern Mojave Desert region where Proterozoic basement is widespread.The observations and data reported here indicate that Late Permian–Early Triassic plutons in the northern Mojave Desert and El Paso Mountains were generated within or passed primarily through oceanic lithosphere, but later Jurassic plutons were derived from and/or interacted extensively with continental lithosphere. We hypothesize that the eugeoclinal rocks were deposited on oceanic crust that was thrust eastward over Precambrian cratonal basement and overlying strata between approximately 240 Ma and 175 Ma, a time of little documented tectonic activity in the Mojave Desert region. Postulated Permian or late Middle Jurassic east-directed thrusting is incompatible with our data and observations. The data also fill an important gap in palinspastic reconstructions of the early Mesozoic arc and indicate that this arc was northwest-trending and oblique to Paleozoic facies trends in the Mojave Desert. 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.