Portal de Periódicos da CAPES

The Trollheim alluvial fan and facies model revisited

1992; Geological Society of America; Volume: 104; Issue: 6 Linguagem: Inglês

10.1130/0016-7606(1992)104 2.3.co;2

1943-2674

Terence C. Blair, John G. McPherson,

Geological Modeling and Analysis

Research Article| June 01, 1992 The Trollheim alluvial fan and facies model revisited TERENCE C. BLAIR; TERENCE C. BLAIR 1Geological Consultant, Blair & Associates, 1949 Hardscrabble Place, Boulder, Colorado 80303 Search for other works by this author on: GSW Google Scholar JOHN G. MCPHERSON JOHN G. MCPHERSON 2Mobil Research and Development Corporation, Dallas Research Laboratory, P.O. Box 819047, Dallas, Texas 75381 Search for other works by this author on: GSW Google Scholar Author and Article Information TERENCE C. BLAIR 1Geological Consultant, Blair & Associates, 1949 Hardscrabble Place, Boulder, Colorado 80303 JOHN G. MCPHERSON 2Mobil Research and Development Corporation, Dallas Research Laboratory, P.O. Box 819047, Dallas, Texas 75381 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1992) 104 (6): 762–769. https://doi.org/10.1130/0016-7606(1992)104 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 Email Permissions Search Site Citation TERENCE C. BLAIR, JOHN G. MCPHERSON; The Trollheim alluvial fan and facies model revisited. GSA Bulletin 1992;; 104 (6): 762–769. doi: https://doi.org/10.1130/0016-7606(1992)104 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 Widely held, fundamental alluvial-fan facies concepts generated in past literature based on the Trollheim fan, Deep Springs Valley, California, are inconsistent with the actual characteristics of this fan. Previous publications have established, mostly without field study, that the Trollheim fan consists of debris-flow, sieve lobe, sheetflood, and channel facies; debris-flow and sieve deposits comprise the proximal area, giving way to channel or sheetflood deposits distally. Contrary to these views, clayey and gravelly, matrix-supported, debris-flow deposits dominate all parts of the Trollheim exposures, suggesting that this fan has been built almost exclusively by mass-wasting events. Channel-fill deposits constitute only a small component of the fan, and most are restricted to the proximal area where they have an inset relationship with debris-flow sequences. The channel facies consists of laterally restricted, clast-supported gravel lenses formed primarily through the winnowing of debris-flow fines by streamflow. The most widespread facies on the surface of the fan is a mantle of varnished, matrix-free pebbles, cobbles, and boulders that commonly are distributed in radially oriented lobes or levees characteristic of debris-flow deposits. This mantle was produced by the surficial winnowing of the fine-fraction from debris-flow deposits primarily by overland water flow. In contrast to previous conclusions, sheetflood and sieve deposits were not identified anywhere on the fan. Additionally, many of the facies depicted in the widely cited "Trollheim vertical profile," including ripple-bedded sand, cross-bedded sand, and overbank mud, are not present on, or in stratigraphic cuts of, the fan after which the profile was named. 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.