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| Sturtian | |
|---|---|
| Name | Sturtian |
| Start | 717 Ma |
| End | 660 Ma |
| Color | #99CCFF |
| Chronology | Cryogenian |
| Preceded by | Tonian |
| Followed by | Marinoan |
Sturtian
The Sturtian is a major Cryogenian glacial episode recognized in Neoproterozoic stratigraphy and paleoclimate studies. It marks one of the most extensive glaciations in Earth history and has been correlated with glacial deposits, isotopic excursions, and tectonic events preserved across multiple cratons and basins. Researchers from institutions such as University of Cambridge, University of Oxford, Harvard University, Massachusetts Institute of Technology, and Stanford University have contributed to mapping its global extent and implications for biospheric evolution.
The interval commonly attributed to this glacial event spans much of the Cryogenian and is associated with diamictites, tillites, dropstones, cap carbonates, and striated pavements found on continents including Laurentia, Rodinia, Gondwana, Siberia and Kalahari. Field studies by teams from Geological Survey of Canada, United States Geological Survey, British Geological Survey, and universities have documented sedimentary successions in basins like Windermere Supergroup, Marino Basin, Eleonora Basin and Harts Range. Key stratigraphic correlations use chemostratigraphy and radiometric dates produced at facilities such as CAMECA, Lamont–Doherty Earth Observatory, and Australian National University.
The Sturtian is placed within the Cryogenian, bounded by radiometric dates from U–Pb zircon geochronology and correlated with negative carbon isotope excursions preserved in marine carbonate successions. Important dated units include ash beds analyzed at Geoscience Australia labs and detrital zircons from cores collected by expeditions including teams from Antarctic Research Centre and Geological Survey of India. Chronostratigraphic frameworks reference global timescales endorsed by organizations like the International Commission on Stratigraphy and integrate magnetostratigraphy, sequence stratigraphy, and biostratigraphic ties to microfossil assemblages curated at the Smithsonian Institution.
Glacial deposits attributed to the Sturtian crop out across multiple shields and orogenic belts, including the Australian Shield, Kaapvaal Craton, Yilgarn Craton, Fennoscandian Shield, Canadian Shield, and the East European Craton. Successions commonly show a basal diamictite overlain by rhythmically bedded glaciolacustrine and glaciomarine sediments and capped by large-scale carbonate units similar to cap carbonates described in the Dwyka Group and Nantuo Formation. Stratigraphic frameworks integrate core logs from companies like Rio Tinto, BHP, and national surveys, and are refined using data from drillholes logged by Schlumberger and geochemical laboratories at ETH Zurich.
Multiple lines of evidence support low-latitude and high-latitude glaciation during this interval: glacial striations, faceted clasts, diamictite facies documented in field campaigns led by researchers from University of Melbourne, Monash University, Yale University, Princeton University, and petrographic and isotopic analyses from California Institute of Technology. Geochemical signatures include profound shifts in δ13C and δ18O preserved in cap carbonates and dolostones archived at museums such as the Natural History Museum, London and the American Museum of Natural History. Paleomagnetic studies conducted at institutes like Potsdam Institute for Climate Impact Research and Institute of Earth Sciences, Academia Sinica have been used to infer paleolatitudes of glacial deposits.
Hypotheses for initiation, maintenance, and termination include changes in plate tectonics such as supercontinent assembly and breakup, variations in greenhouse gases including carbon dioxide and methane, and feedbacks involving marine albedo and ice–albedo runaway processes. Proposed mechanisms reference tectonic settings like continental rifting in regions studied by Geological Survey of Western Australia and volcanic degassing records linked to large igneous provinces documented by researchers at Scripps Institution of Oceanography and Woods Hole Oceanographic Institution. Modeling efforts by groups at NASA Goddard Institute for Space Studies, National Center for Atmospheric Research, and Max Planck Institute for Meteorology explore climate thresholds and geochemical cycles.
The Sturtian interval coincides with critical stages in eukaryotic evolution, affecting microbial mats, stromatolite communities, and early multicellular lineages recorded in fossil collections at Royal Ontario Museum and Field Museum. Biomarker studies led by teams at University of California, Berkeley and University of British Columbia reveal shifts in lipid signatures, while molecular clock analyses published by researchers at University College London and University of California, San Diego address timing of divergences among metazoans, algae, and protists. Environmental stressors likely drove selection and refugia dynamics explored in paleoecological syntheses from Scripps Institution of Oceanography and Monterey Bay Aquarium Research Institute.
Initial recognition of extensive Neoproterozoic glaciations emerged from fieldwork by geologists associated with University of Adelaide and University of Sydney and was advanced by stratigraphers from University of Wollongong and University of Otago. The Sturtian plays a central role in debates about Snowball Earth, paleogeography, and the drivers of evolutionary innovation; publications in journals edited by Nature Publishing Group, Elsevier, and American Geophysical Union have shaped contemporary paradigms. Ongoing drilling projects coordinated by consortia including Integrated Ocean Drilling Program partners and national geological surveys continue to refine our understanding, making the interval pivotal for studies at centers like Paleontological Research Institution and Geological Society of America.