Extension of the geomagnetic polarity time scale to 6.5 m.y.: K-Ar dating, geological and paleomagnetic study of a 3,500-m lava succession in western Iceland

Research Article| January 01, 1977 Extension of the geomagnetic polarity time scale to 6.5 m.y.: K-Ar dating, geological and paleomagnetic study of a 3,500-m lava succession in western Iceland IAN McDOUGALL; IAN McDOUGALL 1Research School of Earth Sciences, Australian National University, Canberra, A.C.T., 2600 Search for other works by this author on: GSW Google Scholar KRISTJAN SAEMUNDSSON; KRISTJAN SAEMUNDSSON 2National Energy Authority, Reykjavik, Iceland Search for other works by this author on: GSW Google Scholar HAUKUR JOHANNESSON; HAUKUR JOHANNESSON 2National Energy Authority, Reykjavik, Iceland Search for other works by this author on: GSW Google Scholar NORMAN D. WATKINS; NORMAN D. WATKINS 3Graduate School of Oceanography, University of Rhode Island, Kingston, Rhode Island, 02881 Search for other works by this author on: GSW Google Scholar LEO KRISTJANSSON LEO KRISTJANSSON 4Science Institute, University of Iceland, Reykjavik, Iceland Search for other works by this author on: GSW Google Scholar Author and Article Information IAN McDOUGALL 1Research School of Earth Sciences, Australian National University, Canberra, A.C.T., 2600 KRISTJAN SAEMUNDSSON 2National Energy Authority, Reykjavik, Iceland HAUKUR JOHANNESSON 2National Energy Authority, Reykjavik, Iceland NORMAN D. WATKINS 3Graduate School of Oceanography, University of Rhode Island, Kingston, Rhode Island, 02881 LEO KRISTJANSSON 4Science Institute, University of Iceland, Reykjavik, Iceland Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1977) 88 (1): 1–15. https://doi.org/10.1130/0016-7606(1977)882.0.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation IAN McDOUGALL, KRISTJAN SAEMUNDSSON, HAUKUR JOHANNESSON, NORMAN D. WATKINS, LEO KRISTJANSSON; Extension of the geomagnetic polarity time scale to 6.5 m.y.: K-Ar dating, geological and paleomagnetic study of a 3,500-m lava succession in western Iceland. GSA Bulletin 1977;; 88 (1): 1–15. doi: https://doi.org/10.1130/0016-7606(1977)882.0.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 More than 400 successive lavas in Borgarfjördur, western Iceland, have been subjected to paleomagnetic and K-Ar age analysis. Volcanism in the region was virtually continuous between about 7.0 and 2 m.y. ago, during which time more than 3,500 m of volcanics and interbedded sediments accumulated. Regression analysis of the K-Ar age and aggregate thickness data demonstrates that the rate of growth of the lava pile was remarkably uniform at 730 m/m.y. throughout the whole period. The magnetostratigraphic and K-Ar data indicate a nearly complete record of the geomagnetic polarity history and extend the polarity time scale based upon data from subaerial volcanic rocks to about 6.5 m.y. ago. The boundaries of polarity epoch 5 are shown to be 5.34 and 5.83 m.y. Epoch 6 lies between about 6.54 and 5.83 m.y. ago, during which time three normal polarity events are recognized. The ages determined for the polarity-interval boundaries in this study confirm recent estimates derived from analyses of marine magnetic anomalies using sea-floor–spreading assumptions.The results show that it is possible to obtain reliable K-Ar ages on lavas that have undergone zeolite facies metamorphism at temperatures up to about 150°C by careful selection of samples that are well crystallized and have their original high-temperature mineralogy preserved.A revised estimate of 5.2 ± 0.1 m.y. is proposed for the age of the Miocene-Pliocene boundary. 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.