Research Article| August 01, 1997 Recognition of units in coarse, unconsolidated braided-stream deposits from geophysical log data with principal components analysis Warren Barrash; Warren Barrash 1Center for Geophysical Investigation of the Shallow Subsurface, Boise State University, Boise, Idaho 83725 Search for other works by this author on: GSW Google Scholar Roger H. Morin Roger H. Morin 2U.S. Geological Survey, Denver Federal Center, Denver, Colorado 80225 Search for other works by this author on: GSW Google Scholar Geology (1997) 25 (8): 687–690. https://doi.org/10.1130/0091-7613(1997)025<0687:ROUICU>2.3.CO;2 Article history first online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share MailTo Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation Warren Barrash, Roger H. Morin; Recognition of units in coarse, unconsolidated braided-stream deposits from geophysical log data with principal components analysis. Geology 1997;; 25 (8): 687–690. doi: https://doi.org/10.1130/0091-7613(1997)025<0687:ROUICU>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 SocietyGeology Search Advanced Search Abstract Returns from drilling in unconsolidated cobble and sand aquifers commonly do not identify lithologic changes that may be meaningful for hydrogeologic investigations. Vertical resolution of saturated, Quaternary, coarse braided-stream deposits is significantly improved by interpreting natural gamma (G), epithermal neutron (N), and electromagnetically induced resistivity (IR) logs obtained from wells at the Capital Station site in Boise, Idaho. Interpretation of these geophysical logs is simplified because these sediments are derived largely from high-gamma–producing source rocks (granitics of the Boise River drainage), contain few clays, and have undergone little diagenesis. Analysis of G, N, and IR data from these deposits with principal components analysis provides an objective means to determine if units can be recognized within the braided-stream deposits. In particular, performing principal components analysis on G, N, and IR data from eight wells at Capital Station (1) allows the variable system dimensionality to be reduced from three to two by selecting the two eigenvectors with the greatest variance as axes for principal component scatterplots, (2) generates principal components with interpretable physical meanings, (3) distinguishes sand from cobble-dominated units, and (4) provides a means to distinguish between cobble-dominated units. 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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Barrash et al. (1997) studied this question.