Research Article| February 01, 1983 The ophiolitic North Fork terrane in the Salmon River region, central Klamath Mountains, California CLIFFORD J. ANDO; CLIFFORD J. ANDO 1Department of Geological Sciences, Cornell University, Ithaca, New York 14853 Search for other works by this author on: GSW Google Scholar WILLIAM P. IRWIN; WILLIAM P. IRWIN 2U.S. Geological Survey, 345 Middle field Road, Menlo Park, California 94025 Search for other works by this author on: GSW Google Scholar DAVID L. JONES; DAVID L. JONES 2U.S. Geological Survey, 345 Middle field Road, Menlo Park, California 94025 Search for other works by this author on: GSW Google Scholar JASON B. SALEEBY JASON B. SALEEBY 3Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California 91125 Search for other works by this author on: GSW Google Scholar Author and Article Information CLIFFORD J. ANDO 1Department of Geological Sciences, Cornell University, Ithaca, New York 14853 WILLIAM P. IRWIN 2U.S. Geological Survey, 345 Middle field Road, Menlo Park, California 94025 DAVID L. JONES 2U.S. Geological Survey, 345 Middle field Road, Menlo Park, California 94025 JASON B. SALEEBY 3Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California 91125 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1983) 94 (2): 236–252. https://doi.org/10.1130/0016-7606(1983)94<236:TONFTI>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 CLIFFORD J. ANDO, WILLIAM P. IRWIN, DAVID L. JONES, JASON B. SALEEBY; The ophiolitic North Fork terrane in the Salmon River region, central Klamath Mountains, California. GSA Bulletin 1983;; 94 (2): 236–252. doi: https://doi.org/10.1130/0016-7606(1983)94<236:TONFTI>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 North Fork terrane is an assemblage of ophiolitic and other oceanic volcanic and sedimentary rocks that has been internally imbricated and folded. The ophiolitic rocks form a north-trending belt through the central part of the region and consist of a disrupted sequence of homogeneous gabbro, diabase, massive to pillowed basalt, and interleaved tectonitic harzburgite. U-Pb zircon age data on a plagiogranite pod from the gabbroic unit indicate that at least this part of the igneous sequence is late Paleozoic in age.The ophiolitic belt is flanked on either side by mafic volcanic and volcaniclastic rocks, limestone, bedded chert, and argillite. Most of the chert is Triassic, including much of Late Triassic age, but chert with uncertain stratigraphic relations at one locality is Permian. The strata flanking the east side of the ophiolitic belt face eastward, and depositional contacts between units are for the most part preserved. The strata on the west side of the ophiolitic belt are more highly disrupted than those on the east side, contain chert-argillite melange, and have unproven stratigraphic relation to either the ophiolitic rocks or the eastern strata.Rocks of the North Fork terrane do not show widespread evidence of penetrative deformation at elevated temperatures, except an early tectonitic fabric in the harzburgite. Slip-fiber foliation in serpentinite, phacoidal foliation in chert and mafic rocks, scaly foliation in argillite, and mesoscopic folds in bedded chert are consistent with an interpretation of large-scale anti-formal folding of the terrane about a north-south hinge found along the ophiolitic belt, but other structural interpretations are tenable. The age of folding of North Fork rocks is constrained by the involvement of Triassic and younger cherts and crosscutting Late Jurassic plutons. Deformation in the North Fork terrane must have spanned a short period of time because the terrane is bounded structurally above and below by Middle or Late Jurassic thrust faults.The North Fork terrane appears to contain no arc volcanic rocks or arc-derived detritus, suggesting that it neither constituted the base for an arc nor was in a basinal setting adjacent to an arc sediment source. Details of the progressive accretion and evolutionary relationship of the North Fork to other terranes of the Klamath Mountains are not yet clear. 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.
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Ando et al. (1983) studied this question.