131-9 Progressive Stages of Cenozoic Displacement and Strike-Slip Basin Development along the Denali Fault System: Sedimentary, Provenance, and Geochronologic Records

Session: Going with the Shear - New Insights into Lithospheric Extensional and Strike-Slip Systems

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Abstract:

The Denali fault system is one of the largest strike-slip faults in North America, but the amount and timing of displacement has been debated for decades. Most previous studies have documented 300 – 500 km of post-Cretaceous dextral displacement but the specific timing of displacement and the partitioning between different sections of the fault system has not been determined. Analysis of three sedimentary packages (SP) representing strata of exhumed strike-slip basins along the fault system allow us to define progressive stages of Cenozoic displacement. The eastern SP consists of 366 m of conglomerate and has a maximum depositional age of 49 Ma. Distinctive plutonic clasts in conglomerate, along with detrital zircon populations in sandstone, best match with potential sources of sediment derived from the Ruby Range in southwestern Yukon; this correlation would require up to 400 km of post-Eocene displacement. The central SP consists of 572 m of conglomerate and contains a 21 Ma tephra. A distinctive detrital zircon population in the sandstone ranges from 26 – 21 Ma. Potential source areas of this age are found only north of the Totschunda fault section; this correlation requires up to 230 km of post early Miocene displacement. The western SP consists of 564 m of siltstone and tephra and conglomerate. This package has an age range from 6.1 to 3.8 Ma and is interpreted to have been transported 90 – 79 km. Collectively, results from our analysis of strata of exhumed strike-slip basins indicate up to 470 km of progressive Cenozoic dextral displacement distributed on different sections of the eastern Denali fault system. Results from our study join a small but growing body of studies that require large-scale Cenozoic displacement in this part of the northern Cordillera.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-10762

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