Detrital zircon geochronology along a structural transect across the Kahiltna assemblage in the western Alaska Range: Implications for emplacement of the Alexander-Wrangellia-Peninsular terrane against North America
Geosphere
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Abstract
The Kahiltna assemblage in the western Alaska Range consists of deformed Upper Jurassic and Cretaceous clastic strata that lie between the Alexander-Wrangellia-Peninsular (AWP) terrane to the south, and the Farewell and other peri-cratonic terranes to the north. Differences in detrital zircon populations and sandstone petrography allow geographic separation of the strata into two different successions, each consisting of multiple units, or petrofacies, with distinct provenance and lithologic characteristics. The northwestern succession was largely derived from older, inboard peri-cratonic terranes and correlates along strike to the southwest with the Kuskokwim Group. The southeastern succession is characterized by volcanic and plutonic rock detritus derived from Late Jurassic igneous rocks of the AWP terrane and mid to Late Cretaceous arc related igneous rocks and is part of a longer belt to the southwest and northeast, here named the Koksetna-Clearwater belt. The two successions remained separate depositional systems until the Late Cretaceous, when the northwestern succession overlapped the southeastern succession at about 81 Ma and they were deformed together by about 80 Ma by southeast-verging fold-and-thrust style deformation interpreted to represent final accretion of the AWP terrane along the southern Alaska margin. We interpret the tectonic evolution of the Kahiltna successions as a progression from forearc sedimentation and accretion in a south-facing continental magmatic arc to arrival and partial underthrusting of the backarc flank of an active, south-facing island arc system (AWP terrane). A modern analogue is the ongoing collision and partial underthrusting of the Izu-Bonin-Marianas island arc beneath the Japan Trench-Nankai Trough on the east side of central Japan.
Suggested Citation
Box, S.E., Karl, S.M., Jones, J.V., Bradley, D., Haeussler, P., and O’Sullivan, P.B., 2019, Detrital zircon geochronology along a structural transect across the Kahiltna assemblage in the western Alaska Range: Implications for emplacement of the Alexander-Wrangellia-Peninsular terrane against North America: Geosphere, v. 15, no. 6, p. 1774-1808, https://doi.org/10.1130/GES02060.1.
Study Area
| Publication type | Article |
|---|---|
| Publication Subtype | Journal Article |
| Title | Detrital zircon geochronology along a structural transect across the Kahiltna assemblage in the western Alaska Range: Implications for emplacement of the Alexander-Wrangellia-Peninsular terrane against North America |
| Series title | Geosphere |
| DOI | 10.1130/GES02060.1 |
| Volume | 15 |
| Issue | 6 |
| Publication Date | October 16, 2019 |
| Year Published | 2019 |
| Language | English |
| Publisher | Geological Society of America |
| Contributing office(s) | Alaska Science Center, Central Mineral and Environmental Resources Science Center, Geology, Minerals, Energy, and Geophysics Science Center |
| Description | 35 p. |
| First page | 1774 |
| Last page | 1808 |
| Country | United States |
| State | Alaska |
| Other Geospatial | western Alaska Range |