Keywords and Phrases
He-dating; Nacimiento block; thermochronology
"Through the analysis of both U-Pb and (U-Th)/He ages from detrital zircon grains we can constrain thermal histories by establishing ages which correspond to crystallization and exhumation events, respectively. This combined geo-/thermochronologic approach is used here to constrain the history of the polyphase Nacimiento fault. This fault traverses central and southern California and has accumulated at least 150 km of slip since Late Cretaceous time. Major displacements along the structure occurred between 75 and 56 Ma, with Neogene to Holocene strike-slip remobilization linked to the San Andreas fault system. Detrital zircon U-Pb geochronology from Franciscan subduction assemblages west of the Nacimiento fault suggest that deposition of these rocks occurred between ca. 95 and 80 Ma. (U-Th)/He ages from the same samples indicate that these zircon grains have been partially reset during Franciscan subduction, with resetting taking place between ca. 75 and 55 Ma. These results suggest that zircon grains experienced burial and exhumation during fault activity. However, some zircon grains record a more complex history with (U-Th)/He ages well after fault activity, as young as 9 Ma. These young ages may be related to passage of the Mendocino triple junction beneath central California. Most ages suggest that the Franciscan complex west of the Nacimiento fault was deposited, subducted, and exhumed within a ~ 10 to 20 Myr window"--Abstract, page iii.
Hogan, John Patrick
Chapman, Alan D.
Geosciences and Geological and Petroleum Engineering
M.S. in Geology and Geophysics
Missouri University of Science and Technology
ix, 138 pages
© 2016 Lisa Marie Arnold Lori, All rights reserved.
Thesis - Open Access
Continental margins -- California
Electronic OCLC #
Lori, Lisa Marie Arnold, "Exhumation of the Nacimiento block: A thermochronologic analysis" (2016). Masters Theses. 7560.