Abstract
Research Article| October 01, 1991 Sequence stratigraphy of Cenozoic continental rocks, southwestern Montana DEBRA L. HANNEMAN; DEBRA L. HANNEMAN 1Whitehall Geogroup, Inc., Whitehall, Montana 59759 Search for other works by this author on: GSW Google Scholar CHARLES J. WIDEMAN CHARLES J. WIDEMAN 2Department of Geophysical Engineering, Montana College of Mineral Science and Technology, Butte, Montana 59701 Search for other works by this author on: GSW Google Scholar Author and Article Information DEBRA L. HANNEMAN 1Whitehall Geogroup, Inc., Whitehall, Montana 59759 CHARLES J. WIDEMAN 2Department of Geophysical Engineering, Montana College of Mineral Science and Technology, Butte, Montana 59701 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1991) 103 (10): 1335–1345. https://doi.org/10.1130/0016-7606(1991)103<1335:SSOCCR>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 MailTo Tools Icon Tools Get Permissions Search Site Citation DEBRA L. HANNEMAN, CHARLES J. WIDEMAN; Sequence stratigraphy of Cenozoic continental rocks, southwestern Montana. GSA Bulletin 1991;; 103 (10): 1335–1345. doi: https://doi.org/10.1130/0016-7606(1991)103<1335:SSOCCR>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 Because the presently used Bozeman Group lithostratigraphy is difficult to apply to Cenozoic basin-fill rocks in the Jefferson, Beaverhead, Melrose, and Divide Valleys, southwestern Montana, we advocate the use of sequence stratigraphy. Surface sequence boundaries are in many cases marked by calcic paleosol zones; these zones can be projected into the subsurface and tied to seismic reflection data. Density/velocity contrasts between calcic paleosol zones and overlying nonpedogenic rocks generate bright reflectors that define sequence boundaries. Sequence boundary delineation is further enhanced by reflection termination patterns, similar to those found in marine strata. Sequence age calibration is based upon vertebrate fossil and radiometric age data.Five sequences, separated by basin-wide unconformities, are recognized. Most sequence-bounding unconformities are marked by paleosols, an occurrence not previously reported for Cenozoic strata of southwestern Montana. The sequences and their age ranges are (1) Bridgerian-Uintan (approximately 50 to 44 Ma) calc-alkaline volcanic flows and interstratified sedimentary rocks, (2) Duchesnian to Whitneyan (approximately 42 to 30 Ma) terrestrial sedimentary and volcanic rocks, (3) Arikareean (approximately 27 to 21 Ma) terrestrial sedimentary and volcanic rocks, (4) Barstovian to Blancan (approximately 16 to 4 Ma) terrestrial sedimentary and volcanic rocks, and (5) early Quaternary (approximately 1.8 Ma) to Holocene terrestrial sedimentary and volcanic rocks. 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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