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Dodging snowballs; geochronology of the Gaskiers glaciation and the first appearance of the Ediacaran biota

Judy P. Pu, Samuel A. Bowring, Jahandar Ramezani, Paul Myrow, Timothy D. Raub, Ed Landing, Andrea Mills, Eben Hodgin and Francis A. Macdonald
Dodging snowballs; geochronology of the Gaskiers glaciation and the first appearance of the Ediacaran biota
Geology (Boulder) (September 2016) 44 (11): 955-958


The snowball Earth hypothesis predicts that low-latitude glaciation lasted millions of years while CO (sub 2) built up to critical levels to culminate in catastrophic deglaciation in a supergreenhouse climate. The Gaskiers Formation of eastern Newfoundland (Canada) has been attributed to a snowball glaciation event, but the lack of robust paleomagnetic data and precise geochronological constraints has precluded tests of the hypothesis. Here we present high-precision U-Pb zircon geochronology (chemical abrasion-isotope dilution-thermal ionization mass spectrometry) from eight tuffs from multiple distant stratigraphic sections that bracket glacial diamictites and the first appearance of large Ediacaran fossils. Including internal error, deposition of the Gaskiers diamictite on the Avalon Peninsula is constrained to have been between 580.90 + or - 0.40 and 579.88 + or - 0.44 Ma, and the Trinity diamictite on Bonavista Peninsula was deposited between 579.63 + or - 0.15 and 579.24 + or - 0.17 Ma. Assuming approximately synchronous deglaciation, these results imply a maximum duration for deposition of the Trinity diamictite of < or =340 k.y.; this is inconsistent with the multimillion year duration predicted by the snowball Earth hypothesis. Our geochronologic data also constrain the first appearance datum of Ediacaran fossils to <9.5 m.y. after the Gaskiers glaciation. Thus, despite existing paleomagnetic constraints that indicate that marine ice sheets extended to low to middle latitudes, it appears that Earth narrowly escaped a third Neoproterozoic snowball glaciation just prior to the late Ediacaran expansion of metazoan ecosystems.

ISSN: 0091-7613
EISSN: 1943-2682
Serial Title: Geology (Boulder)
Serial Volume: 44
Serial Issue: 11
Title: Dodging snowballs; geochronology of the Gaskiers glaciation and the first appearance of the Ediacaran biota
Affiliation: Massachusetts Institute of Technology, Department of Earth, Atmospheric and Planetary Sciences, Cambridge, MA, United States
Pages: 955-958
Published: 20160928
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 32
Accession Number: 2016-094410
Categories: StratigraphyGeochronology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: GSA Data Repository item 2016326
Illustration Description: illus. incl. 1 table
N46°30'00" - N48°10'00", W54°15'00" - W52°30'00"
Secondary Affiliation: Colorado College, USA, United StatesUniversity of St. Andrews, GBR, United KingdomNew York State Museum, USA, United StatesGeological Survey of Newfoundland and Labrador, CAN, CanadaHarvard University, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201646
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