Structural and kinematic evolution of the Yukon-Tanana upland tectonites, east-central Alaska: A record of late Paleozoic to Mesozoic crustal assembly

Research Article| February 01, 1998 Structural and kinematic evolution of the Yukon-Tanana upland tectonites, east-central Alaska: A record of late Paleozoic to Mesozoic crustal assembly V. L. Hansen; V. L. Hansen 1Department of Geological Sciences, Southern Methodist University, Dallas, Texas 75275 Search for other works by this author on: GSW Google Scholar C. Dusel-Bacon C. Dusel-Bacon 2U.S. Geological Survey, M.S. 901, 345 Middlefield Road, Menlo Park, California 94025 Search for other works by this author on: GSW Google Scholar Author and Article Information V. L. Hansen 1Department of Geological Sciences, Southern Methodist University, Dallas, Texas 75275 C. Dusel-Bacon 2U.S. Geological Survey, M.S. 901, 345 Middlefield Road, Menlo Park, California 94025 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1998) 110 (2): 211–230. https://doi.org/10.1130/0016-7606(1998)110<0211:SAKEOT>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 V. L. Hansen, C. Dusel-Bacon; Structural and kinematic evolution of the Yukon-Tanana upland tectonites, east-central Alaska: A record of late Paleozoic to Mesozoic crustal assembly. GSA Bulletin 1998;; 110 (2): 211–230. doi: https://doi.org/10.1130/0016-7606(1998)110<0211:SAKEOT>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 Yukon-Tanana terrane, the largest tectonostratigraphic terrane in the northern North American Cordillera, is polygenetic and not a single terrane. Lineated and foliated (L-S) tectonites, which characterize the Yukon- Tanana terrane, record multiple deformations and formed at different times. We document the polyphase history recorded by L-S tectonites within the Yukon-Tanana upland, east-central Alaska. These upland tectonites compose a heterogeneous assemblage of deformed igneous and metamorphic rocks that form the Alaskan part of what has been called the Yukon-Tanana composite terrane. We build on previous kinematic data and establish the three-dimensional architecture of the upland tectonites through kinematic and structural analysis of more than 250 oriented samples, including quartz c-axis fabric analysis of 39 samples.Through this study we distinguish allochthonous tectonites from parautochthonous tectonites within the Yukon-Tanana upland. The upland tectonites define a regionally coherent stacking order: from bottom to top, they are lower plate North American parautochthonous attenuated continental margin; continentally derived marginal-basin strata; and upper plate ocean-basin and island-arc rocks, including some continental basement rocks. We delineate three major deformation events in time, space, and structural level across the upland from the United States–Canada border to Fairbanks, Alaska: (1) pre-Early Jurassic (>212 Ma) northeast-directed, apparent margin-normal contraction that affected oceanic rocks; (2) late Early to early Middle Jurassic (>188–185 Ma) northwest-directed, apparent margin-parallel contraction and imbrication that resulted in juxtaposition of the allochthonous tectonites with parautochthonous continental rocks; and (3) Early Cretaceous (135–110 Ma) southeast-directed crustal extension that resulted in exposure of the structurally deepest, parautochthonous continental rocks. The oldest event represents deformation within a west-dipping (present coordinates) Permian-Triassic subduction zone. The second event records Early to Middle Jurassic collision of the arc and subduction complex with North American crust, and the third event reflects mid-Cretaceous southeast-directed crustal extension. Events one and two can be recognized and correlated through southern Yukon, even though this region was affected by mid-Cretaceous dextral shear along steep northwest-striking faults. Our data support a model of crustal assembly originally proposed by D. Tempelman-Kluit in which previously deformed allochthonous rocks were thrust over parautochthonous rocks of the attenuated North American margin in Middle Jurassic time. Approximately 50 m.y. after tectonic accretion, east-central Alaska was dissected by crustal extension, exposing overthrust parautochthonous strata. 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.