57th Annual Report on Research 2012 Under Sponsorship of the ACS Petroleum Research Fund

ACS-PRF support to work at the Arizona Laserchron Center has fostered one of the most satisfying and productive periods of intellectual growth that I’ve enjoyed in my 21 years at CSU Fullerton. In learning the details of detrital zircon (dz) methodology, the breadth of my scientific perspective has expanded significantly, adding an understanding of sediment transport and depositional environments to my former training in magmatism-tectonics. As a result, my perspective of the Mesozoic evolution of California is now more holistic, benefitting the range of research projects in which my students and I are involved. 

This project has already had a significant impact on my research career. Two years ago I was invited to present our preliminary results at a GSA Penrose conference regarding the evolution of the Sierra Nevada arc. Subsequently, colleagues from USC, Caltech and UA invited me to join a collaboration focused on the pre-Mesozoic tectonics of this segment of the North American margin. The stellar performance of the CSUF lab group prompted an open invitation to conduct future research at the over-booked Arizona Laserchron Center. Operating a million-dollar instrument (the LA-ICP-MS) and interacting with the staff at this R1 institution lead to increased confidence amongst the CSUF students and generated more expansive visions of their scientific futures. The ability to pay students for their lab time and for travel to professional meetings has opened doors for all of us to more fully engage with the research and professional communities.

Originally budgeted to support one M.S. and three undergraduate students, I was able expand the grant’s impact to two M.S. and five B.S. theses. Kevin Tomita reported that an interviewer asked to inspect his undergraduate thesis overnight. Kevin received his first environmental geology job offer the next day and is convinced the ACS-PRF-funded thesis played a major role. I anticipate that Natalie Hollis will feel similar gratitude regarding her 3 years on this project: after presenting preliminary results at ACS and AAPG meetings, she will present her completed study at the national GSA meeting this fall. With thesis in hand, Natalie will search for graduate opportunities studying structural geology. Lastly, I was able to support non-thesis research experiences for four students. Undergraduate Michelle Gevedon was inspired to return to CSUF for her graduate studies, using the same instrumentation (LA-ICP-MS) to study hafnium isotopes in the mantle. Currently funded by a prestigious CSU Pre-Doctoral Fellowship, the inspiration for Michelle’s ambitious geochemical research was her experience working on this ACS-PRF-funded project.

SCIENTIFIC RESULTS

This field- and laboratory-based project focused on a recently discovered sedimentary-volcanic formation in the western Sierra Nevada. Specific goals were to assess whether the Goldstein Peak Formation’s apparent, and unusual, Early Cretaceous depositional age was correct, as well as determining the sediment provenance. The overarching goal was to assess whether the Goldstein Peak rivers could have contributed sediment to California’s oil-rich Great Valley Group.

Substantial outcomes include >2000 zircon dates, which support the following findings:

• Mike Martin’s graduate thesis confirms that the depositional age of the Goldstein Peak (GP) formation is indeed Early Cretaceous (141+3 Ma). As such, the GP formation is the oldest recognized nonmarine deposit in the Sierra arc-Great Valley forearc system.
• Approximately half of the GP zircons have ages consistent with local derivation from the Jurassic-Early Cretaceous arcs.
  • There is significant, unanticipated variation within the GP dz populations. Such intra-formation variation does not appear to have been documented elsewhere.
  • The remaining GP zircons have crystallization ages that date as far back as 3.5 Ga. Research by Chris Buchen demonstrates that the stratigraphically underlying Jurassic Kings Sequence and the Triassic Calaveras Complex(?) are likely sources for the older dz populations in the Goldstein Peak Formation.
  • Undergraduate studies of the arc’s metamorphic framework resulted in some tectonic surprises:
    • the Slate Mountain pendant correlates with the Snow Lake tectonic block, interpreted as representing displaced Paleozoic passive margin sediments;
    • a previously unknown pendant contains
      • correlatives of the Golconda thrust sheet, which may have been displaced 300-500 km SE prior to Mesozoic arc construction; and
      • a 98 Ma sandstone, which now represents the youngest metasediment documented in the arc framework.
      • Undergraduate studies of the Gravelly Flat Formation, the oldest forearc unit in the southern Great Valley
        • demonstrate that initial deposition of the marine Gravelly Flat Formation was synchronous with the nonmarine Goldstein Peak Formation;
        • suggest that the lowermost Gravelly Flat formation could be a distal correlative of the Goldstein Peak Formation;
          • dz populations of the upper Gravelly Flat formation, however, are more similar to coeval rocks of the Sacramento Valley, confirming earlier suggestions that the Great Valley forearc evolved to a well mixed basin by the Late Cretaceous.
• With additional funding from an NSF-LSAMP grant to CSUF, Natalie Hollis embarked on a parallel study exploring the provenance of Late Cretaceous forearc sediments associated with the Peninsular Ranges arc, a southern continuation of the Sierra Nevada arc.
  • As with the Sierra Nevada forearc basin, the Peninsular Ranges forearc appears to have been entirely filled by arc-derived detritus;
  • a population of extraregional zircons appears in the Late Cretaceous section.

DISSEMINATION PLAN

To date, 8 published student-faculty abstracts report various results of this study

• 3 presentations at the regional 2011 ACS meeting in a session that I co-convened entitled Frontiers in Geochemistry: The Growing Legacy of PRF-funded Research.
• 3 presentations at the 2012 national meeting of the American Association of Petroleum Geologists.
• 2 abstracts at the 2012 national GSA meeting in Charlotte, NC.

I anticipate 3-4 manuscripts will be generated by this project. Currently, Mike Martin and I are finalizing a manuscript on the Goldstein Peak Formation; I anticipate co-writing another with current student Chris Buchen on the provenance of Jurassic-Triassic metasediments. Another will synthesize the results of the entire Sierra arc-interarc basin-Great Valley forearc basin depositional system, and the tectonic implications of this data will be incorporated in a collaborative paper with colleagues. Lastly, Natalie Hollis will submit her thesis to the CSUF Student Journal, Dimensions.