Sedimentation, sea-level change, and tectonics on an early Pleistocene continental shelf, northern California

Abstract

Research Article| October 01, 1989 Sedimentation, sea-level change, and tectonics on an early Pleistocene continental shelf, northern California ELANA L. LEITHOLD; ELANA L. LEITHOLD 1Department of Geological Sciences, University of Washington AJ-20, Seattle, Washington 98195 Search for other works by this author on: GSW Google Scholar JOANNE BOURGEOIS JOANNE BOURGEOIS 1Department of Geological Sciences, University of Washington AJ-20, Seattle, Washington 98195 Search for other works by this author on: GSW Google Scholar Author and Article Information ELANA L. LEITHOLD 1Department of Geological Sciences, University of Washington AJ-20, Seattle, Washington 98195 JOANNE BOURGEOIS 1Department of Geological Sciences, University of Washington AJ-20, Seattle, Washington 98195 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1989) 101 (10): 1209–1224. https://doi.org/10.1130/0016-7606(1989)101<1209:SSLCAT>2.3.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation ELANA L. LEITHOLD, JOANNE BOURGEOIS; Sedimentation, sea-level change, and tectonics on an early Pleistocene continental shelf, northern California. GSA Bulletin 1989;; 101 (10): 1209–1224. doi: https://doi.org/10.1130/0016-7606(1989)101<1209:SSLCAT>2.3.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 The Rio Dell Formation was deposited in a tectonically active area during a time of fluctuating eustatic sea-level. Detailed interpretation of Rio Dell shelf sediments, facilitated by comparison to the nearby, analogous, modern Eel River shelf, has proved a vital tool for decoding the record of these influences. Understanding of the nature and relative roles of processes on the modern and ancient shelf, including those associated with storms and with river floods, not only allows for detailed paleobathymetric reconstruction of the ancient sequence, but also for recognition of relatively subtle effects of syndepositional tectonism.Shelf sediments of the Rio Dell Formation comprise four depositional sequences bounded by thin, submarine condensed sections. The condensed sections formed during periods of rapid, probably largely eustatic, sea-level rise. The sequences each record progradation of the shelf, predominantly during sea-level highstands. Paleobathymetric reconstruction provides the basis for interpretation of the magnitude of local, relative sea-level changes within and between the sequences.Subsidence of the Rio Dell shelf apparently played a role in recorded local sea-level fluctuations, as did eustasy. Subsidence ("geohistory") analysis of the sequence indicates that the shelf was subsiding throughout its existence, due not only to sediment loading but also due to tectonism. The analysis points to a period of rapid shelf subsidence, accompanied by onland uplift, between about 1.3 and 1.2 Ma.An increase in subsidence rates after about 1.3 Ma apparently caused an increase in Rio Dell shelf gradient, which changed the balance between flood and storm processes on the middle shelf. Increased shelf inclination evidently resulted in restriction of storm-wave reworking to a narrower zone extending from the shoreline, whereas distance from shoreline to the shelf area most influenced by river-flood deposition remained unchanged. The resultant increased segregation of flood and storm effects caused a fining of background grain-size distributions at mid-shelf sites. 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.