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Persistence of a freshwater surface ocean after a snowball Earth

2017; Geological Society of America; Volume: 45; Issue: 7 Linguagem: Inglês

10.1130/g38920.1

1943-2682

Jun Yang, Malte Jansen, Francis A. Macdonald, Dorian S. Abbot,

Paleontology and Stratigraphy of Fossils

Research Article| July 01, 2017 Persistence of a freshwater surface ocean after a snowball Earth Jun Yang; Jun Yang 1Department of Atmospheric and Oceanic Sciences, School of Physics, Peking University, Beijing 100871, China Search for other works by this author on: GSW Google Scholar Malte F. Jansen; Malte F. Jansen 2Department of the Geophysical Sciences, University of Chicago, Chicago, Illinois 60637, USA Search for other works by this author on: GSW Google Scholar Francis A. Macdonald; Francis A. Macdonald 3Department of Earth and Planetary Science, Harvard University, Cambridge, Massachusetts 02138, USA Search for other works by this author on: GSW Google Scholar Dorian S. Abbot Dorian S. Abbot 2Department of the Geophysical Sciences, University of Chicago, Chicago, Illinois 60637, USA Search for other works by this author on: GSW Google Scholar Author and Article Information Jun Yang 1Department of Atmospheric and Oceanic Sciences, School of Physics, Peking University, Beijing 100871, China Malte F. Jansen 2Department of the Geophysical Sciences, University of Chicago, Chicago, Illinois 60637, USA Francis A. Macdonald 3Department of Earth and Planetary Science, Harvard University, Cambridge, Massachusetts 02138, USA Dorian S. Abbot 2Department of the Geophysical Sciences, University of Chicago, Chicago, Illinois 60637, USA Publisher: Geological Society of America Received: 27 Dec 2016 Revision Received: 02 Mar 2017 Accepted: 17 Mar 2017 First Online: 28 Jun 2017 Online Issn: 1943-2682 Print Issn: 0091-7613 © 2017 Geological Society of America Geology (2017) 45 (7): 615–618. https://doi.org/10.1130/G38920.1 Article history Received: 27 Dec 2016 Revision Received: 02 Mar 2017 Accepted: 17 Mar 2017 First Online: 28 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 Jun Yang, Malte F. Jansen, Francis A. Macdonald, Dorian S. Abbot; Persistence of a freshwater surface ocean after a snowball Earth. Geology 2017;; 45 (7): 615–618. doi: https://doi.org/10.1130/G38920.1 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 Geochemical data from cap carbonates deposited above Cryogenian glacial deposits have been widely used to infer the conditions that prevailed in the aftermath of snowball Earth. However, the time scale over which these carbonates were deposited and the degree to which they record the chemistry of a globally well-mixed ocean have remained poorly constrained. During deglaciation, a large volume of meltwater entered the ocean, creating two distinct layers: the fresh, hot, and light upper layer, and the salty, cold, and dense lower layer. Here we estimate the ocean mixing time scale based on energetic constraints. We find that the mixing time scale is 104–105 yr, with a best estimate of ∼5 × 104 yr, or up to 100 times longer than that of the modern ocean. Mixing of the surface temperature anomaly implies a delayed sea-level rise of 40–50 m associated with pure thermal expansion. This result reconciles geological, geochemical, and paleomagnetic data from basal Ediacaran cap carbonates with physical oceanographic theory. In particular, our model suggests that (1) the cap dolostones formed predominantly in a freshwater environment; (2) the waters in which the dolostones formed were not well mixed with saline deep water, allowing for large geochemical differences between the cap dolostones and the deep ocean; and (3) the cap carbonate sequences formed in a two-phase transgression that lasted >104 yr, which is consistent with both local sea-level records and the preservation of magnetic excursions and reversals. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.