Large-scale, crustal-block vertical extrusion between the Hines Creek and Denali faults coeval with slip localization on the Denali fault since ca. 45 Ma, Hayes Range, Alaska, USA

Author:

Benowitz Jeff A.1ORCID,Roeske Sarah M.2,Regan Sean P.3,Waldien Trevor S.4,Elliott Julie L.5,O’Sullivan Paul B.6

Affiliation:

1. Unaffiliated

2. Earth and Planetary Sciences, University of California, Davis, California 95616, USA

3. Geophysical Institute, University of Alaska Fairbanks, Fairbanks, Alaska 99775, USA

4. Department of Geology and Geological Engineering, South Dakota School of Mines and Technology, South Dakota 57701, USA

5. Department of Earth and Environmental Sciences, Michigan State University, Michigan 48824, USA

6. GeoSep Services, Moscow, Idaho 83843, USA

Abstract

Abstract Oblique convergence along strike-slip faults can lead to both distributed and localized deformation. How focused transpressive deformation is both localized and maintained along sub-vertical wrench structures to create high topography and deep exhumation warrants further investigation. The high peak region of the Hayes Range, central Alaska, USA, is bound by two lithospheric scale vertical faults: the Denali fault to the south and Hines Creek fault to the north. The high topography area has peaks over 4000 m and locally has experienced more than 14 km of Neogene exhumation, yet the mountain range is located on the convex side of the Denali fault Mount Hayes restraining bend, where slip partitioning alone cannot account for this zone of extreme exhumation. Through the application of U-Pb zircon, 40Ar/39Ar (hornblende, muscovite, biotite, and K-feldspar), apatite fission-track, and (U-Th)/He geo-thermochronology, we test whether these two parallel, reactivated suture zone structures are working in tandem to vertically extrude the Between the Hines Creek and Denali faults block on the convex side of the Mount Hayes restraining bend. We document that since at least 45 Ma, the Denali fault has been bent and localized in a narrow fault zone (<160 m) with a significant dip-slip component, the Mount Hayes restraining bend has been fixed to the north side of the Denali fault, and that the Between the Hines Creek and Denali faults block has been undergoing vertical extrusion as a relatively coherent block along the displacement “free faces” of two lithospheric scale suture zone faults. A bent Denali fault by ca. 45 Ma supports the long-standing Alaska orocline hypothesis that has Alaska bent by ca. 44 Ma. Southern Alaska is currently converging at ~4 mm/yr to the north against the Denali fault and driving vertical extrusion of the Between the Hines Creek and Denali faults block and deformation north of the Hines Creek fault. We apply insights ascertained from the Between the Hines Creek and Denali faults block to another region in southern Alaska, the Fairweather Range, where extreme topography and persistent exhumation is also located between two sub-parallel faults, and propose that this region has likely undergone vertical extrusion along the free faces of those faults.

Publisher

Geological Society of America

Subject

Stratigraphy,Geology

Reference144 articles.

1. Ten kilometer vertical Moho offset and shallow velocity contrast along the Denali Fault zone from double-difference tomography, receiver functions, and fault zone head waves;Allam;Tectonophysics,2017

2. Neogene sedimentary record of the evolution of translated strike-slip basin along the Denali fault system: Implications for timing of displacement, composite basin development;Allen;and regional tectonics of southern Alaska: Geosphere,2022

3. 40Ar/39Ar eruption ages and geochemical characteristics of Late Tertiary to Quaternary intraplate and arc-related lavas in interior Alaska;Andronikov;Lithos,2010

4. Bedrock geologic map of the Liberty Bell area, Fairbanks A-4 Quadrangle, Bonnifield mining district;Athey,2006

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