Observations of Iceberg Rafting in Glacier Bay, Alaska, and the Identification of Ancient Ice-Rafted Deposits

Research Article| March 01, 1970 Observations of Iceberg Rafting in Glacier Bay, Alaska, and the Identification of Ancient Ice-Rafted Deposits A. THOMAS OVENSHINE A. THOMAS OVENSHINE U.S. Geological Survey, Menlo Park, California 94025 Search for other works by this author on: GSW Google Scholar GSA Bulletin (1970) 81 (3): 891–894. https://doi.org/10.1130/0016-7606(1970)81[891:OOIRIG]2.0.CO;2 Article history received: 09 Oct 1969 first online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation A. THOMAS OVENSHINE; Observations of Iceberg Rafting in Glacier Bay, Alaska, and the Identification of Ancient Ice-Rafted Deposits. GSA Bulletin 1970;; 81 (3): 891–894. doi: https://doi.org/10.1130/0016-7606(1970)81[891:OOIRIG]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 Observations of icebergs in a modern glacial marine environment indicate that ancient rocks that received iceberg-rafted material should contain: (1) local concentrations of stones that originated when icebergs overturned, and (2) small pellets of till that were originally sediment filling the spaces between clear ice crystals.The till pellets are especially significant in identifying an ancient glacial setting because they originate through a process unique to glaciers—the flow-and recrystallization-induced segregation of originally disseminated fine sediment. Thus when freed by melting and deposited by iceberg rafting, the pellets would reliably indicate the presence of glacial ice in an ancient environment. In the Gowganda Formation, a Precambrian glacial deposit, strata that contain outsized, presumably iceberg-rafted stones also contain abundant small flattened clasts of unsorted graywacke interpreted as the lithified counterparts of the till pellets observed on modern icebergs. 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.