Publication | Closed Access
Subdivision of Ordovician and Silurian time scale using accumulation rates of graptolitic shale
56
Citations
0
References
1977
Year
Facies AnalysisEngineeringGeomorphologySedimentary GeologyGeological SurveyEarth ScienceRegional GeologyBasin AnalysisGeological DataGeochronologyMarine GeologyGeological EngineeringBasin EvolutionGeographyGeologySilurian Time ScaleSedimentary PetrologyAccumulation RatesEngineering GeologySedimentologyRock PropertiesTectonicsStructural GeologyEconomic GeologyEarth SciencesGraptolitic Shale
Research Article| August 01, 1977 Subdivision of Ordovician and Silurian time scale using accumulation rates of graptolitic shale Michael Churkin, Jr.; Michael Churkin, Jr. 1U.S. Geological Survey, Menlo Park, California 94025 Search for other works by this author on: GSW Google Scholar Claire Carter; Claire Carter 1U.S. Geological Survey, Menlo Park, California 94025 Search for other works by this author on: GSW Google Scholar Bruce R. Johnson Bruce R. Johnson 1U.S. Geological Survey, Menlo Park, California 94025 Search for other works by this author on: GSW Google Scholar Author and Article Information Michael Churkin, Jr. 1U.S. Geological Survey, Menlo Park, California 94025 Claire Carter 1U.S. Geological Survey, Menlo Park, California 94025 Bruce R. Johnson 1U.S. Geological Survey, Menlo Park, California 94025 Publisher: Geological Society of America First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (1977) 5 (8): 452–456. https://doi.org/10.1130/0091-7613(1977)5<452:SOOAST>2.0.CO;2 Article history First Online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation Michael Churkin, Claire Carter, Bruce R. Johnson; Subdivision of Ordovician and Silurian time scale using accumulation rates of graptolitic shale. Geology 1977;; 5 (8): 452–456. doi: https://doi.org/10.1130/0091-7613(1977)5<452:SOOAST>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 SocietyGeology Search Advanced Search Abstract Sections of graptolitic shale within the Cordilleran foldbelt are very condensed. An average accumulation rate of 4 ∓ 1 m/m.y. calculated for these shales falls within the range of 2 to 5 m/m.y. for modern deep-sea clay and siliceous ooze. The Deep Sea Drilling Project has shown that once an age is determined for a stratigraphic horizon within a pelagic section, it is possible to estimate the ages of other horizons by assuming constant rates of sediment accumulation. This method, used on graptolitic shale, suggests that the time span represented by a graptolite zone is proportional to its thickness. The thickest zone analyzed is that of Nemagraptus gracilis, which is calculated to have spanned about 8 m.y., whereas the thinnest zone, Glyptograptus persculptus, took less than 1 m.y. to accumulate. The readily recognized zones of Nemagraptus gracilis and Climacograptus bicomis, which together consistently form thick biostratigraphic intervals, are the zones most commonly found, whereas the G. persculptus zone is very rare. A new subdivision of the Ordovician and Early Silurian time scale has been made on the basis of the calculated time duration of graptolite zones. 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.