The arc of the Snowball: U-Pb dates constrain the Islay anomaly and the initiation of the Sturtian glaciation

Abstract

Research Article| April 26, 2018 The arc of the Snowball: U-Pb dates constrain the Islay anomaly and the initiation of the Sturtian glaciation Scott MacLennan; Scott MacLennan 1Department of Geosciences, Princeton University, Princeton, New Jersey 08544, USA Search for other works by this author on: GSW Google Scholar Yuem Park; Yuem Park 2Earth and Planetary Sciences Department, University of California, Berkeley, California 94720, USA Search for other works by this author on: GSW Google Scholar Nicholas Swanson-Hysell; Nicholas Swanson-Hysell 2Earth and Planetary Sciences Department, University of California, Berkeley, California 94720, USA Search for other works by this author on: GSW Google Scholar Adam Maloof; Adam Maloof 1Department of Geosciences, Princeton University, Princeton, New Jersey 08544, USA Search for other works by this author on: GSW Google Scholar Blair Schoene; Blair Schoene 1Department of Geosciences, Princeton University, Princeton, New Jersey 08544, USA Search for other works by this author on: GSW Google Scholar Mulubrhan Gebreslassie; Mulubrhan Gebreslassie 3School of Earth Sciences, Addis Ababa University, P.O. Box 1176, Addis Ababa, Ethiopia Search for other works by this author on: GSW Google Scholar Eliel Antilla; Eliel Antilla 2Earth and Planetary Sciences Department, University of California, Berkeley, California 94720, USA Search for other works by this author on: GSW Google Scholar Tadele Tesema; Tadele Tesema 3School of Earth Sciences, Addis Ababa University, P.O. Box 1176, Addis Ababa, Ethiopia Search for other works by this author on: GSW Google Scholar Mulugeta Alene; Mulugeta Alene 3School of Earth Sciences, Addis Ababa University, P.O. Box 1176, Addis Ababa, Ethiopia Search for other works by this author on: GSW Google Scholar Bereket Haileab Bereket Haileab 4Department of Geology, Carleton College, Northfield, Minnesota 55057, USA Search for other works by this author on: GSW Google Scholar Geology (2018) 46 (6): 539–542. https://doi.org/10.1130/G40171.1 Article history received: 03 Oct 2017 rev-recd: 02 Apr 2018 accepted: 04 Apr 2018 first online: 26 Apr 2018 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Tools Icon Tools Get Permissions Search Site Citation Scott MacLennan, Yuem Park, Nicholas Swanson-Hysell, Adam Maloof, Blair Schoene, Mulubrhan Gebreslassie, Eliel Antilla, Tadele Tesema, Mulugeta Alene, Bereket Haileab; The arc of the Snowball: U-Pb dates constrain the Islay anomaly and the initiation of the Sturtian glaciation. Geology 2018;; 46 (6): 539–542. doi: https://doi.org/10.1130/G40171.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search nav search search input Search input auto suggest search filter All ContentBy SocietyGeology Search Advanced Search Abstract In order to understand the onset of Snowball Earth events, precise geochronology and chemostratigraphy are needed on complete sections leading into the glaciations. While deposits associated with the Neoproterozoic Sturtian glaciation have been found on nearly every continent, time-calibrated stratigraphic sections that record paleoenvironmental conditions leading into the glaciation are exceedingly rare. Instead, the transition to glaciation is normally expressed as erosive contacts with overlying diamictites, and the best existing geochronological constraints come from volcanic successions with little paleoenvironmental information. We report new stratigraphic and geochronological data from the upper Tambien Group in northern Ethiopia, which indicates that the glacigenic diamictite at the top of the succession is Sturtian in age. U-Pb zircon dates obtained from two tuffaceous siltstones that are 74 and 84 m below the diamictite are 719.68 ± 0.46 Ma and 719.68 ± 0.56 Ma (2σ), respectively. We also report a U-Pb date of 735.25 ± 0.25 Ma from a crystal-rich tuff located 2 m above the nadir of a high-amplitude, basin-wide, negative δ13C excursion previously correlated with the Islay anomaly. This age for the anomaly agrees with Re-Os age constraints from Laurentia, suggesting that the δ13C signal is globally synchronous and preceded the Sturtian glaciation by ∼18 m.y. The interval between the Islay anomaly and Sturtian glaciation is recorded in the Tambien Group as an ∼600 m succession of predominantly shallow-water carbonates and siliciclastics with δ13C values recording a prolonged period at +5‰, followed by an interval of lower, but still positive, values leading up to the glaciation. Our data are consistent with synchronous global onset of the Sturtian glaciation at ca. 717 Ma. Shallow-water carbonates in strata directly below the first diamictite suggest that glacial onset was rapid in terranes of the Arabian-Nubian Shield. You do not currently have access to this article.