Sandstone petrofacies of the Yager complex and the Franciscan Coastal belt, Paleogene of northern California

Abstract

Research Article| July 01, 1986 Sandstone petrofacies of the Yager complex and the Franciscan Coastal belt, Paleogene of northern California MICHAEL B. UNDERWOOD; MICHAEL B. UNDERWOOD 1Department of Geology, University of Missouri, Columbia, Missouri 65211 Search for other works by this author on: GSW Google Scholar STEVEN B. BACHMAN STEVEN B. BACHMAN 2Crouch, Bachman & Assoc. Inc., 910 Alphonse Street, Santa Barbara, California 93103 Search for other works by this author on: GSW Google Scholar Author and Article Information MICHAEL B. UNDERWOOD 1Department of Geology, University of Missouri, Columbia, Missouri 65211 STEVEN B. BACHMAN 2Crouch, Bachman & Assoc. Inc., 910 Alphonse Street, Santa Barbara, California 93103 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1986) 97 (7): 809–817. https://doi.org/10.1130/0016-7606(1986)97<809:SPOTYC>2.0.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation MICHAEL B. UNDERWOOD, STEVEN B. BACHMAN; Sandstone petrofacies of the Yager complex and the Franciscan Coastal belt, Paleogene of northern California. GSA Bulletin 1986;; 97 (7): 809–817. doi: https://doi.org/10.1130/0016-7606(1986)97<809:SPOTYC>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Paleogene strata of the Franciscan Coastal belt and the Yager complex (northern California) provide a vivid illustration of the problems encountered during studies of detrital provenance along accretionary continental margins. The northern portion of the Yager complex contains lower percentages of total quartz and higher percentages of feldspar than do correlative stratigraphic units to the south; mean Q-F-L modes are Q-30, F-54, L-16 (N-Yager) and Q-49, F-31, L-20 (S-Yager). A similar spatial trend is evident within the Coastal belt, where mean Q-F-L modes are Q-33, F-47, L-20 (N-CB) and Q-48, F-33, L-19 (S-CB). A third Coastal belt petrofacies (L-CB) is dominated by volcanic-lithic grains.Interpretations of generic provenance for each petrofacies are straightforward. The arkosic sands probably were eroded from deeply dissected granitic plutons, and the more-quartzose sands are attributed to recycling from both orogenic backarc terranes and an adjacent magmatic arc. The influx of volcanic detritus proves that magmatism was active within the drainage basin during Paleogene time. Identification of specific source areas is more problematic, however. Perhaps the north-to-south changes in detrital mineralogy were caused by influx from an Idaho batholith source (arkosic) versus a Sierra Nevada source (quartzose). The depositional paleolatitude of Franciscan sands is unknown, and, in the absence of latitudinal control, potential sources as far south as Mexico remain plausible. Regardless of these uncertainties, the variations common to both Coastal and Yager terranes demonstrate that amalgamation must have preceded any translational events, such that differential slip has not occurred between the two terranes. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.