<p>This
study presents new detrital zircon geochronologic data from Jurassic to
Cretaceous sedimentary basins and modern rivers in south-central Alaska in
order to examine the sedimentary record of magmatism and tectonics associated
with the Mesozoic to Cenozoic growth of the southern Alaska convergent margin.
Jurassic to Cretaceous strata of the Wrangell Mountains, Nutzotin, and Wellesly
basins formed coeval with the Mesozoic accretion of the Wrangellia composite
terrane (WCT) to the continental margin. New detrital zircon data from the
Wrangell Mountains and Nutzotin basins demonstrate that these basins were
derived primarily from sources associated with the WCT, with little to no
derivation from continental margin sources. Detrital zircon ages from the Wrangell
Mountains and Nutzotin basins are very similar, suggesting that these basins
may have initially formed in a connected retroarc basin system. New detrital
zircon data from the Wellesly basin show that the basin was source chiefly from
continental margin sources. These ages show that the Wellesly basin is not
related to the Nutzotin basin as previously suggested, and may be genetically
related to the Kahiltna basin; this suggests that ~330-390 km of
post-collisional strike-slip offset occurred along the Denali Fault. Comparing
our new data with a regional detrital zircon database from similar-aged
depocenters shows that there is a strong provenance and temporal link between
outboard and inboard depocenters, with these depocenters being sourced from the
same magmatic arcs from the late Jurassic to the late Cretaceous. Our findings
from these comparisons are most consistent with a scenario where the WCT was
accreted to the margin along an eastward-dipping subduction zone, in contrast
to recent suggestions that the accretion was the result of westward-dipping
subduction. New and previously published detrital zircon ages from the Tanana,
Matanuska-Susitna, and Copper River watersheds in south-central Alaska document
the major magmatic episodes that occurred along the southern Alaska convergent
margin. These magmatic episodes display a periodicity that is similar to
documented cyclic magmatic patterns in other regions along the Cordilleran
margin, suggesting similar processes may be occurring margin-wide. The magmatic
record of south-central Alaska can also be compared with the magmatic record of
other regions in the northern Cordillera such as the Coast Plutonic Complex in
British Columbia and the western Alaska Peninsula, which shows a spatial and
temporal relationship of magmatism along the entire northern Cordilleran
margin.</p>
| Identifer | oai:union.ndltd.org:purdue.edu/oai:figshare.com:article/11306885 |
| Date | 02 December 2019 |
| Creators | Cooper R Fasulo (8067611) |
| Source Sets | Purdue University |
| Detected Language | English |
| Type | Text, Thesis |
| Rights | CC BY 4.0 |
| Relation | https://figshare.com/articles/Sedimentary_record_of_tectonic_growth_along_a_convergent_margin_Insights_from_detrital_zircon_geochronology_of_Mesozoic_sedimentary_basins_and_modern_rivers_in_south-central_Alaska/11306885 |
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