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Provenance, Structural Geology, and Sedimentation of the Miocene and Pliocene Californias


Sabbeth, Leah (2021) Provenance, Structural Geology, and Sedimentation of the Miocene and Pliocene Californias. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/gbcs-9289.


The first chapter of this thesis documents a provenance study, in which orthoquartzite clasts deposited in the Miocene Sespe Formation are linked to the Mesoproterozoic Shinumo Quartzite. The Sespe Formation outcrops in the Santa Monica Mountains and the Santa Ana Mountains, both in California. The Shinumo Quartzite outcrops only in Grand Canyon. We determine that the Shinumo Quartzite can be distinguished from other sources that may feed the Sespe Formation through its unique combination of a moderate paleomagnetic inclination and 1.2, 1.4, and 1.7 Ga detrital zircon spectrum peaks. This provenance link places an important constraint on the drainage of a paleo-Colorado River from Grand Canyon during Miocene time.

The second and third chapters of this thesis are hinged upon a geologic mapping project on Isla Ángel de la Guarda, a microcontinental block, in Baja California, Mexico. A plate reorganization at the end of the late Miocene andesitic arc marks the transfer of Baja California and the not-yet-rifted Isla Ángel de la Guarda to the Pacific plate from the North American plate. Between 3 and 2 Ma, the plate boundary jumped again, northward along the Ballenas Transform fault. In this Pliocene time, units mapped in this study were deposited.

The oldest units mapped are Miocene-Pliocene volcanic flows, for which we have no lower age constraint. The oldest volcanic flow dated is a Pliocene andesite lava (3.916 ± 0.088 Ma from 40Ar/39Ar). We map Miocene to Pliocene volcanic flows and Pliocene to Quaternary sedimentary units in two field areas. The sedimentary units are probably results of Pliocene rifting-related basin subsidence. Geochemical data from X-ray fluorescence indicate that lavas are compositionally similar to ~12 Ma arc-related rocks mapped in the Puertecitos Volcanic Province. In the southern field area, the sedimentary units are overlain by a Pliocene basaltic andesite with an 40Ar/39Ar age of 2.754 ± 0.021 Ma. We map several NNE-striking faults throughout both field areas, which cut NNW-striking bedding in Pliocene units. The Pliocene volcanic flows and sedimentary units were probably tilted before faulting, and the faults are likely linked to the Northern Salsipuedes Basin, offshore of the island in the Ballenas Channel. Both of these events may be results of 3-2 Ma rifting.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Provenance, paleomagnetism, detrital zircon ages, geochronology, geologic mapping, structural geology, Ar-Ar dating, XRF geochemistry
Degree Grantor:California Institute of Technology
Division:Geological and Planetary Sciences
Major Option:Geology
Awards:Women Mentoring Women Candace Rypisi Outstanding Mentor Award, 2018.
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Stock, Joann M. (advisor)
  • Wernicke, Brian P. (co-advisor)
Thesis Committee:
  • Avouac, Jean-Philippe (chair)
  • Bucholz, Claire E.
  • Rossman, George Robert
  • Stock, Joann M.
  • Wernicke, Brian P.
Defense Date:30 July 2020
Non-Caltech Author Email:sabbeth.leah (AT)
Funding AgencyGrant Number
NSFEAR 17-28690
NSFEAR 10-19896
NSFEAR 14-51055
NSFEAR 16-49254
NSFOPP 13-41729
Record Number:CaltechTHESIS:09212020-084147468
Persistent URL:
Related URLs:
URLURL TypeDescription for Chapter 1.
Sabbeth, Leah0000-0001-6615-7949
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:13961
Deposited By: Leah Sabbeth
Deposited On:29 Sep 2020 23:22
Last Modified:17 Dec 2021 01:31

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