Abstract
Research Article| June 01, 2014 Magmatic activity and plate motion during the latent stage of Midcontinent Rift development Nicholas L. Swanson-Hysell; Nicholas L. Swanson-Hysell 1Department of Earth and Planetary Science, University of California–Berkeley, Berkeley, California 94720, USA Search for other works by this author on: GSW Google Scholar Seth D. Burgess; Seth D. Burgess 2Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA Search for other works by this author on: GSW Google Scholar Adam C. Maloof; Adam C. Maloof 3Department of Geosciences, Princeton University, Princeton, New Jersey 08544, USA Search for other works by this author on: GSW Google Scholar Samuel A. Bowring Samuel A. Bowring 2Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA Search for other works by this author on: GSW Google Scholar Geology (2014) 42 (6): 475–478. https://doi.org/10.1130/G35271.1 Article history received: 06 Nov 2013 rev-recd: 10 Feb 2014 accepted: 12 Feb 2014 first online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share MailTo Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation Nicholas L. Swanson-Hysell, Seth D. Burgess, Adam C. Maloof, Samuel A. Bowring; Magmatic activity and plate motion during the latent stage of Midcontinent Rift development. Geology 2014;; 42 (6): 475–478. doi: https://doi.org/10.1130/G35271.1 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 The Keweenawan Midcontinent Rift of North America records significant continental rifting between ca. 1110 and 1085 Ma, and preserves the most detailed paleomagnetic record of plate motion of any continent in Precambrian time. U/Pb dates from extrusive and intrusive rocks of the western Lake Superior Basin suggest a latent stage of reduced magmatic activity from ca. 1106 to 1100 Ma that places constraints on the dynamics of rift development and the record of plate motion. However, it has remained unclear whether this stage is a feature of the entire >2500-km-long rift. The succession of picritic and basaltic lava flows at Mamainse Point in the eastern Lake Superior Basin may be the most continuous and best exposed record of rift-related volcanism and magnetic reversals, but its age and duration relative to the latent stage has been uncertain due to a lack of radioisotopic dates. We present a weighted mean 206Pb/238U date of 1100.36 ± 0.25 Ma on zircon crystals isolated from a newly discovered tuff within the upper reversed polarity portion of the stratigraphy below the Great Conglomerate. This date indicates that eruptive activity at Mamainse Point continued during the interval of diminished magmatic activity in the western Lake Superior Basin. This result strengthens the chronostratigraphic framework of rift development while explaining the preservation of additional geomagnetic reversals at Mamainse Point and the record of progressively decreasing paleomagnetic inclination that is indicative of rapid paleogeographic change. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.
Highlights
Over a period of ~25 m.y. in the late Mesoproterozoic, more than2.0 × 106 km3 of volcanic rocks formed from eruptions in the middle of the Laurentian craton associated with the development of the Keweenawan Midcontinent Rift (Cannon, 1992)
While the presence of additional reversals may suggest that eruptive activity continued at Mamainse Point during the latent stage magmatic hiatus elsewhere, Midcontinent Rift correlation schemes hypothesize that deposition of an ~300-m-thick conglomerate at Mamainse Point corresponds to the entirety of the latent magmatic stage (Miller and Vervoort, 1996; Nicholson et al, 1997; Miller, 2007)
Vervoort et al (2007) hypothesized that the silicic volcanism in the North Shore Volcanic Group, where rhyolites comprise as much as 25% of the stratigraphy (Fig. 1), could be related to longer term crustal heating during the latent stage that contributed to partial melting in higher levels of the crust
Summary
Over a period of ~25 m.y. in the late Mesoproterozoic, more than2.0 × 106 km3 of volcanic rocks formed from eruptions in the middle of the Laurentian craton associated with the development of the Keweenawan Midcontinent Rift (Cannon, 1992). In the Powder Mill Group and the North Shore Volcanic Group, U-Pb dates on extrusive felsic units (Davis and Green, 1997; Zartman et al, 1997) suggest significant hiatuses in volcanism during the time period of the latent stage, during which there was a change from reversed to normal magnetic polarity (Fig. 1).
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