Title: Tectonic implications of paleomagnetic and geochronologic data from the Yukon-Koyukuk province, Alaska
Abstract: Research Article| September 01, 1987 Tectonic implications of paleomagnetic and geochronologic data from the Yukon-Koyukuk province, Alaska R. A. HARRIS; R. A. HARRIS 1Geophysical Institute, University of Alaska, Fairbanks, Alaska 99775 Search for other works by this author on: GSW Google Scholar D. B. STONE; D. B. STONE 1Geophysical Institute, University of Alaska, Fairbanks, Alaska 99775 Search for other works by this author on: GSW Google Scholar D. L. TURNER D. L. TURNER 1Geophysical Institute, University of Alaska, Fairbanks, Alaska 99775 Search for other works by this author on: GSW Google Scholar GSA Bulletin (1987) 99 (3): 362–375. https://doi.org/10.1130/0016-7606(1987)99<362:TIOPAG>2.0.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 R. A. HARRIS, D. B. STONE, D. L. TURNER; Tectonic implications of paleomagnetic and geochronologic data from the Yukon-Koyukuk province, Alaska. GSA Bulletin 1987;; 99 (3): 362–375. doi: https://doi.org/10.1130/0016-7606(1987)99<362:TIOPAG>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 paleomagnetic and geochronologic record of Alaska is complicated by overprints that make it difficult to relate the terranes of northern and southern Alaska to each other and to North America. To better understand these relationships and the overprinting, paleomagnetic and K-Ar dating samples were analyzed from the three major geologic units of the Yukon-Koyukuk province (YKP) of central Alaska. These units consist of a basal Jurassic-Early Cretaceous volcanic (island-arc) assemblage, Albian-Cenomanian clastic sedimentary rocks, and bimodal Eocene volcanic rocks.K-Ar age determinations of the early Tertiary volcanic rocks form two distinct groups. The older group (65–49 Ma) is mostly felsic and probably represents the maximum inboard penetration of low-angle subduction-related volcanism. These older rocks were deformed during the regional deformation of the YKP. The younger group (44−43 Ma) is post-deformational and composed dominantly of basalt. These results bracket a time (49−44 Ma) when deformation ceased in the province. This time interval is coincident with a major transition from convergence to strike-slip and extensional tectonic style throughout Alaska.The geologic units of the YKP display two characteristic paleomagnetic signatures. Primary directions (based on positive reversal, conglomerate, and/or bedding tilt stability tests) were obtained from the Albian-Cenomanian sedimentary rocks and Eocene volcanic rocks. The mid-Cretaceous sedimentary rocks show about 15° of poleward motion between 90−56 Ma (a time of high rates of convergence between Alaska and the Pacific and Eurasian plates). Age-equivalent rocks from neighboring regions (St. Matthew Island and the Alaskan North Slope) also indicate similar amounts of poleward (northward) motion, which suggests that the whole of western and northern Alaska may have moved northward about 10° relative to North America as a more or less coherent block. Paleomagnetic results from the Eocene volcanic rocks indicate that the YKP was in place by 56 Ma and formed part of the accretionary nucleus that served as a backstop for the accreted terranes of southern Alaska. Secondary (remagnetized) directions are recorded in the basal island-arc assemblage and in Albian-Cenomanian sediments near younger igneous occurrences. The clustering of secondary directions in the geographic reference frame indicates that they were acquired after deformation ceased (⩽49−44 Ma), which is consistent with the coincidence of the mean of these directions and the 54−44 Ma North American reference direction. 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.
Publication Year: 1987
Publication Date: 1987-01-01
Language: en
Type: article
Indexed In: ['crossref']
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Cited By Count: 49
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