Deposition of upper Mesozoic resedimented conglomerates and associated turbidites in southwestern Oregon

Abstract

Research Article| February 01, 1977 Deposition of upper Mesozoic resedimented conglomerates and associated turbidites in southwestern Oregon ROGER G. WALKER ROGER G. WALKER 1Department of Geology, McMaster University, Hamilton, Ontario, Canada L8S 4M1 Search for other works by this author on: GSW Google Scholar Author and Article Information ROGER G. WALKER 1Department of Geology, McMaster University, Hamilton, Ontario, Canada L8S 4M1 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1977) 88 (2): 273–285. https://doi.org/10.1130/0016-7606(1977)88<273:DOUMRC>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 MailTo Tools Icon Tools Get Permissions Search Site Citation ROGER G. WALKER; Deposition of upper Mesozoic resedimented conglomerates and associated turbidites in southwestern Oregon. GSA Bulletin 1977;; 88 (2): 273–285. doi: https://doi.org/10.1130/0016-7606(1977)88<273:DOUMRC>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 The upper Mesozoic sedimentary rocks of southwestern Oregon include turbidites, dark shales, and great thicknesses of resedimented conglomerates. At two localities, these lithologies are arranged in thinning- and fining-upward sequences that begin abruptly with graded conglomerates (individual beds as much as 50 m thick) and pass upward into massive sandstones, classical turbidites, and dark mudstones. Detailed study of the fabric of the conglomerates indicates paleoflow roughly toward the southeast; this direction is confirmed by sole marks on the associated turbidites. The highest angles of imbrication occur at the bases of beds; upward, the imbrication angle flattens, and the preferred alignment of clasts is better developed.The angle of imbrication is not related to clast size (as expressed by D/10, the mean of the ten largest clasts), but D/10 is strongly related to conglomerate bed thickness, which indicates that the conglomerates (thickness, 1.85 to 50.0 m; mean, 17.5 m) are probably single flows.Some of the thinner conglomerates belong to the graded-stratified model described by Walker. The thicker conglomerates are characterized only by normal grading (inverse grading is rare or poorly developed; no stratification), and a new model, the graded bed, is suggested as an intermediate form between the inverse-to-normally graded and graded-stratified models.The thinning- and fining-upward sequences range from 3.40 to 85.0 m (mean, 31.5 m) and are tentatively interpreted to be the result of progressive channel abandonment on a submarine fan. In this interpretation, the conglomerates, although prominent in the section, are unusual events, transported by flows that were far too big for the scale of the channel. Thus, conglomerates plugged the channel bases, subsequently causing diversion of the normal flows into other channels. 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.