Spatial variations in focused exhumation along a continental-scale strike-slip fault: The Denali fault of the eastern Alaska Range
Author(s) -
Jeffrey A. Benowitz,
Paul W. Layer,
Phil Armstrong,
Stephanie Perry,
Peter J. Haeussler,
Paul G. Fitzgerald,
Sam VanLaningham
Publication year - 2011
Publication title -
geosphere
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.879
H-Index - 58
ISSN - 1553-040X
DOI - 10.1130/ges00589.1
Subject(s) - geology , thermochronology , neogene , fission track dating , seismology , fault (geology) , pleistocene , basin and range province , strike slip tectonics , fault scarp , paleontology , continental crust , crust , tectonics , structural basin
40 Ar/ 39 Ar, apatite fission-track, and apatite (U-Th)/He thermochronological techniques were used to determine the Neogene exhumation history of the topographically asymmetric eastern Alaska Range. Exhumation cooling ages range from ∼33 Ma to ∼18 Ma for 40 Ar/ 39 Ar biotite, ∼18 Ma to ∼6 Ma for K-feldspar minimum closure ages, and ∼15 Ma to ∼1 Ma for apatite fission-track ages, and apatite (U-Th)/He cooling ages range from ∼4 Ma to ∼1 Ma. There has been at least ∼11 km of exhumation adjacent to the north side of Denali fault during the Neogene inferred from biotite 40 Ar/ 39 Ar thermochronology. Variations in exhumation history along and across the strike of the fault are influenced by both far-field effects and local structural irregularities. We infer deformation and rapid exhumation have been occurring in the eastern Alaska Range since at least ∼22 Ma most likely related to the continued collision of the Yakutat microplate with the North American plate. The Nenana Mountain region is the late Pleistocene to Holocene (∼past 1 Ma) primary locus of tectonically driven exhumation in the eastern Alaska Range, possibly related to variations in fault geometry. During the Pliocene, a marked increase in climatic instability and related global cooling is temporally correlated with an increase in exhumation rates in the eastern Alaska Range north of the Denali fault system.
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