Conference proceeding
Upper plate response to varying subduction styles in the forearc Cook Inlet basin in South central Alaska
American Geophysical Union Fall Meeting, Vol.2016
American Geophysical Union 2016 fall meeting
12/2016
Abstract
The Cook Inlet forearc basin strata record the upper plate response to changes in subduction since 170 Ma. Subduction of normal oceanic crust during the Jurassic and Cretaceous was followed by spreading ridge subduction in the Paleocene, which initiated near trench magmatism and a shallow subduction angle. This was followed by a period of normal subduction until the Oligocene when subduction of an oceanic plateau commenced causing flat-slab subduction. We study the sedimentary record of the Cook Inlet Basin and analyze the sediment provenance, magmatic sources, paleotopography, and rock exhumation of southern Alaska, and their changes through time. We use a double dating technique on single detrital zircon grains from 25 samples combining fission track and U-Pb dating. We collected Jurassic to Pliocene sandstone, and modern fluvial deposits. Eight Mesozoic samples were taken from the eastern inverted section of the Cook Inlet Basin. Seven Cenozoic samples were taken from outcrops on the northern and southern margin of the basin, and four from northern offshore cores. Six modern river sands were sampled from four rivers to analyze what is currently draining into the basin from the north, east, and south. Zircon fission track data reveal that the Jurassic samples have been fully reset, while Cretaceous and Eocene samples have been partially reset. Subduction of the spreading ridge probably increased the geothermal gradient in the upper plate and caused thermal resetting of the underlying strata. Oligocene to Pliocene sediments contain the youngest age populations with lag times ranging 13-25 Myr. Samples from the northern margin (arc side) yield generally shorter lag times than samples from the south side (prism side). This pattern is consistent with modern sediments that show the youngest ages are sourced from the Alaska Range, revealed by a 14 Ma age peak in the Susitna River. In contrast, the youngest age populations found in the sediments of rivers draining the accretionary prism peak at 44-22 Ma.
Details
- Title: Subtitle
- Upper plate response to varying subduction styles in the forearc Cook Inlet basin in South central Alaska
- Creators
- Sonia Katherine Sanchez-Lohff - University of CincinnatiEva EnkelmannEmily FinzelMattie Morgan Reid
- Resource Type
- Conference proceeding
- Publication Details
- American Geophysical Union Fall Meeting, Vol.2016
- Conference
- American Geophysical Union 2016 fall meeting
- Publisher
- American Geophysical Union
- Alternative title
- AGU 2016 fall meeting
- Language
- English
- Date published
- 12/2016
- Academic Unit
- Earth and Environmental Sciences
- Record Identifier
- 9984240781002771
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