Thermochronology and provenance of the Yakutat terrane, southern Alaska based on fission-track and U/Pb analysis of detrital zircon
Northward transport of the Yakutat terrane along the Transition and Queen Charlotte-Fairweather transform faults led to Neogene collision of the Yakutat terrane with the southern continental Alaska margin. Northward translation resulted in a stratigraphy that records the erosion of thermotectonic te...
| Summary: | Northward transport of the Yakutat terrane along the Transition and Queen Charlotte-Fairweather transform faults led to Neogene collision of the Yakutat terrane with the southern continental Alaska margin. Northward translation resulted in a stratigraphy that records the erosion of thermotectonic terranes along its path. The strata of the Yakutat terrane includes the Lower Oligocene to Lower Eocene Kulthieth Formation, the Upper Eocene to Lower Miocene Poul Creek Formation and the Miocene-Pleistocene Yakataga Formation. Detrital zircon fission-track (DZFT) ages from stratigraphically coordinated samples collected in the Northern Robinson Mountains yield provenance information of the units that can shed light on their transport history. For all dated samples 50 grains were counted and morphology/color noted and grain ages were deconvolved into component populations. The Kulthieth Formation has three primary cooling age populations at ~70-97 Ma, 38-58 Ma and 28-31 Ma. The Poul Creek Formation has three primary cooling age populations at ~61-67 Ma, 39-42 Ma and 24-33 Ma. The Yakataga Formation has three primary cooling age populations at ~68-77 Ma, 30-35 Ma and 15-21 Ma. The DZFT grains were then analyzed by LA-ICPMS to determine U/Pb crystallization ages. For the Yakataga Formation three crystallization peak age populations resulted: ~52 Ma, ~71 Ma and ~155 Ma. For the Poul Creek Formation four crystallization peak ages resulted: ~59 Ma, ~71 Ma, ~94 Ma, and ~147 Ma. Three grains yielded U/Pb ages of ~318 Ma, ~365 Ma, ~1864.71 Ma. Analysis of the Kulthieth Formation resulted in three U/Pb crystallization age populations of ~59 Ma, ~94 Ma, and ~159 Ma.Paleocene to Eocene deposition of the Yakutat terrane stratigraphy records a long-lived, non-volcanic source terrain that crystallized from ~50-220 Ma and cooled from ~48-110 Ma. Miocene cooling episodes in the Kulthieth and the Poul Creek Formations likely records deposition associated with plutons located in the northern Coast Plutonic Complex and the Kuiu-Etoilin ... |
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