Abstract
Terranes, spreading ridges, and oceanic plateaus; a tale of the south-central Alaskan Forearc
Abstracts with programs - Geological Society of America, Vol.53(5)
Geological Society of America, 2021 annual meeting; GSA connects 2021
10/2021
DOI: 10.1130/abs/2021AM-365367
Abstract
Upper Jurassic to Pliocene forearc basin strata in south-central Alaska record variations in sedimentary basin development associated with Late Mesozoic terrane accretion and translation of the Insular terranes along western North America, Paleocene-Eocene spreading ridge subduction, and Oligocene-Recent oceanic plateau subduction. Detrital zircon U-Pb populations in Upper Jurassic to Upper Cretaceous strata display trends of more evolved Hf isotopic data that record nearly equal 40 Myr orogenic cycles of magmatic flare-up and crustal thickening during the Late Triassic-Early Jurassic and Late Jurassic. Detrital zircon U-Pb and fission track double-dating and Hf isotopes from Upper Cretaceous to Pliocene strata and modern rivers reveal the effects of two different modes of flat-slab subduction. Slab flattening driven by a subducting spreading ridge results in uplift of the forearc region and more regional retro-arc sources of sediment. This process also results in thermal resetting of rocks in the upper plate that is revealed by young zircon fission track populations found in subsequent, thin sedimentary strata in the forearc basin. Slab flattening driven by subduction of an oceanic plateau results in diminished basin catchments with local sediment sources more predominant. Crustal thickening drives widespread topographic inversion and significant vertical uplift in rheologically weak zones that, combined, create topography and increase rock exhumation rates. Consequently, the thermochronologic signature of plateau subduction has generally young age peaks that generate short lag times indicating rapid exhumation. One of the difficulties with provenance studies in this region is that with Alaska's prolonged magmatic history, individual igneous belts are geographically extensive and plutonic belts of different ages often overlap. An integrated approach of modern river sampling and basin strata characterization in conjunction with an inverse Monte Carlo approach of mixture modeling allows for partitioning of widespread and pervasive ages in sediment source terranes. Our data suggest that the character and obliquity of down-going slabs provides a fundamental control on the nature of depositional systems, location of dominant sediment source regions, and areas of maximum subsidence in forearc basins.
Details
- Title: Subtitle
- Terranes, spreading ridges, and oceanic plateaus; a tale of the south-central Alaskan Forearc
- Creators
- Emily Finzel - University of Iowa, Department of Earth and Environmental Sciences Iowa City, IA USA United StatesEva EnkelmannKenneth D. RidgwayJeffrey M. TropWilliam C. McClelland
- Resource Type
- Abstract
- Publication Details
- Abstracts with programs - Geological Society of America, Vol.53(5)
- Conference
- Geological Society of America, 2021 annual meeting; GSA connects 2021
- Publisher
- Geological Society of America (GSA)
- DOI
- 10.1130/abs/2021AM-365367
- ISSN
- 0016-7592
- Alternative title
- Geological Society of America, 2021 annual meeting; GSA connects 2021
- Language
- English
- Date published
- 10/2021
- Academic Unit
- Earth and Environmental Sciences
- Record Identifier
- 9984268959702771
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