A statistical method for relative-age dating of moraines in the Sawatch Range, Colorado
1979; Geological Society of America; Volume: 90; Issue: 12 Linguagem: Inglês
10.1130/0016-7606(1979)90 2.0.co;2
ISSN1943-2674
Autores Tópico(s)Climate change and permafrost
ResumoResearch Article| December 01, 1979 A statistical method for relative-age dating of moraines in the Sawatch Range, Colorado C. DAN MILLER C. DAN MILLER 1U.S. Geological Survey, Box 25046, Mail Stop 903, Federal Center, Denver, Colorado 80225 Search for other works by this author on: GSW Google Scholar GSA Bulletin (1979) 90 (12): 1153–1164. https://doi.org/10.1130/0016-7606(1979)90 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 C. DAN MILLER; A statistical method for relative-age dating of moraines in the Sawatch Range, Colorado. GSA Bulletin 1979;; 90 (12): 1153–1164. doi: https://doi.org/10.1130/0016-7606(1979)90 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 A relative-age classification of Pleistocene moraines in the northern Sawatch Range, Colorado, has been developed using information- and graph-theoretic methods applied to moraine morphology and weathering characteristics.At 89 stations on moraines in the study area, measurements were made of the six best age-dependent criteria; listed in order of importance, they are percentage of pitted granite, percentage of fresh granite, depth of pitting, width of moraine crest, surface-boulder frequency, and distal-moraine slope angle. Data were evaluated using computer programs CHARANAL (character analysis) and GRAPH (similarity clustering analysis) to produce an age classification of stations according to similarity with respect to the six criteria. Groups of moraines were then tentatively assigned Rocky Mountain geologic-climate names on the basis of weathering parameters and qualitative consideration of deposit morphology, downvalley position, and soil-profile development.Two pre–Bull Lake(?) glaciations are recognized in the area and tentatively correlated with the Cedar Ridge and Sacagawea Ridge Glaciations described by Richmond (1960, 1962, 1965) in the Rocky Mountains. Early(?) and late Bull Lake(?) glaciers occupied Lake Creek Valley; however, evidence of Bull Lake Glaciation was not found in the valleys of East Brush Creek or Nolan Creek. Early Pinedale glaciers occupied all major valleys in the study area, and most were more extensive than late Bull Lake glaciers, possibly explaining the lack of evidence in some valleys for Bull Lake Glaciation. Most valleys in the northern Sawatch Range were again glaciated during middle and late Pinedale time.The information- and graph-theoretic methods used in this study are useful tools for relative-age dating of Pleistocene deposits. Use of the methods (1) allows more objective age classification of glacial deposits to be made on the basis of qualitative data and measurements of several or many weathering characteristics, (2) may help to determine whether deposits represent different glaciations or phases of the same glaciation, and (3) may aid in correlation of glacial deposits between regions of similar climate and bedrock over great distances. 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.
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