Slip Redistribution onto the Totschunda Fault of Southern Alaska: A Result of a Pacific Plate Motion Change at ca. 6 Ma

Jacob L. Rosenthal, Paul G. Fitzgerald, Jeffrey A. Benowitz, James R. Metcalf, Paul M. Betka

Research output: Chapter in Book/Entry/PoemChapter

Abstract

Uplift and cooling along the intersecting Totschunda and Denali strike-slip faults of southern Alaska can be used to investigate when these faults were active. Activity on these faults is tied to relative plate motion changes where the transfer of stress inland from the plate boundary changes the slip distribution between fault strands. We apply geochronology (zircon U-Pb) and thermochronology (apatite fission track, zircon, and apatite (U-Th)/He) along the southern Totschunda fault and integrate our new data with published regional thermochronology. New thermochronology data from along the Totschunda fault indicate an increase in rapid cooling, interpreted as exhumation, in the Late Miocene that continues until the present. We link this increase in vertical tectonics to Totschunda fault strike-slip motion increasing from 2 mm/year in the Oligocene to the modern rate of 14 mm/year at ca. 6 Ma. An 18° clockwise change in Pacific plate convergence vector occurs at ca. 6 Ma which we tie to the acceleration and rejuvenation of slip on the Totschunda fault and the diminution of strike-slip motion on the northern Eastern Denali Fault. We further suggest that in other locations around the Pacific margin the Pacific plate motion change in the Late Miocene also triggered fault system reorganization.

Original languageEnglish (US)
Title of host publicationTectonics and Seismic Structure of Alaska and Northwestern Canada
Subtitle of host publicationEarthScope and Beyond
PublisherWiley
Pages497-524
Number of pages28
ISBN (Electronic)9781394195947
ISBN (Print)9781394195916
DOIs
StatePublished - Jan 1 2024

Keywords

  • Geochronology
  • Pacific plate
  • Southern Alaska
  • Thermochronology
  • Totschunda fault
  • Totschunda-Denali fault system

ASJC Scopus subject areas

  • General Earth and Planetary Sciences

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