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| Marinoan | |
|---|---|
| Name | Marinoan |
| Caption | Cryogenian glacial deposits, example locality |
| Time start myr | 650.0 |
| Time end myr | 635.0 |
| Chronostrat unit | Series |
| Chronostrat lower boundary def | Global stratotype section and point proposals |
| Chronostrat upper boundary def | Cap carbonate sequences |
| Named for | Mount Marino |
Marinoan is a late Cryogenian glacial episode traditionally dated to the interval around 650–635 million years ago. It is recognized for extensive glacial deposits, hypothesized global ice coverage, and distinctive postglacial cap carbonates preserved in numerous Antarctica, Australia, China, Greenland, and Namibia localities. The event appears in correlations among work by geologists studying Stratigraphy, Paleoclimatology, and Precambrian research and features prominently in debates involving Snowball Earth hypothesis, Neoproterozoic glaciation, and the rise of late Proterozoic life.
The interval is associated with extensive diamictites, striated pavements, and glacial erratics documented in classic sections near Mount Marino and global localities such as the Varanger Peninsula, Ghaub Formation, and the Nantuo Formation. Field campaigns by researchers from institutions including the United States Geological Survey, CSIRO, Chinese Academy of Sciences, and various universities mapped sedimentary successions and cap carbonate units interpreted as deglacial deposits. The episode has been invoked in syntheses by authors associated with Deep Time studies, Cryogenian stratigraphy compendia, and reviews published in journals like Nature, Science, and Geology.
Glacial strata attributed to this interval occur across multiple cratons such as the Yangtze Craton, South China Craton, Kalahari Craton, Laurentia, and Baltica. The sequence stratigraphy commonly shows diamictite overlain by metre-scale cap carbonates with characteristic isotope excursions recorded in carbonate and organic matter. Radiometric constraints derive from interbedded volcanic ash beds dated using techniques developed at facilities like Argonne National Laboratory and analytical groups at ETH Zurich and Massachusetts Institute of Technology. Correlation frameworks employ chemostratigraphy tied to excursions in carbonate carbon isotopes and palaeomagnetic data from studies originating at the University of Cambridge and University of California, Berkeley.
Hypotheses for causation range from global-scale runaway albedo feedbacks emphasized by proponents of the Snowball Earth hypothesis to regional glaciation models supported by some researchers at Lamont-Doherty Earth Observatory and Scripps Institution of Oceanography. Climate modelers from National Center for Atmospheric Research and University of Oxford have simulated scenarios invoking reduced greenhouse forcing, drawing on volcanism records from the Siberian Traps analogues and methane cycle dynamics examined by groups collaborating with Woods Hole Oceanographic Institution. Mechanistic proposals also include ice dynamics studies involving sea-ice physics addressed by teams at Bjerknes Centre for Climate Research and ocean circulation changes tested in models by Princeton University.
Field evidence includes glacial diamictites, dropstones, striated pavements, and facies transitions documented in the Ediacara Hills, Guanling Formation, and Rawnsley Quartzite. Cap carbonates with metre-scale isotopic shifts occur in sections studied by researchers from University of Toronto and Peking University. Paleomagnetic records supporting low-latitude glaciation have been reported by groups at ETH Zurich and Australian National University, whereas sedimentological interpretations from University of Leeds and University of Glasgow emphasize local depositional contexts. Geochemical proxies such as iron speciation and sulfur isotopes analyzed at laboratories including Caltech and University of Minnesota provide redox reconstructions that feed into regional syntheses.
Post-glacial cap carbonate intervals coincide stratigraphically with the appearance and diversification of late Proterozoic macrofossils in assemblages like the Ediacaran biota preserved in Mistaken Point, South Australia, and Charnwood Forest. Teams led by paleontologists at University of Oxford, Harvard University, and University of Cambridge have explored links between nutrient surges, redox shifts, and biological innovation. Geochemical work from Scripps Institution of Oceanography and University of Kiel implicates changes in carbon cycling and oxygenation potentially relevant to metazoan evolution examined by investigators at Max Planck Institute for Marine Microbiology and Monash University.
Chronology relies on integrated approaches: U–Pb zircon geochronology performed at facilities such as University of Lausanne and Los Alamos National Laboratory, stable isotope chemostratigraphy developed by researchers at University of Southampton and Imperial College London, and paleomagnetic pole determinations generated by teams at ETH Zurich and University of Alberta. Sequence stratigraphic markers and regional lithostratigraphic frameworks assembled by groups from Geological Survey of Canada and British Geological Survey aid correlation among far-flung basins. Bayesian and statistical correlation methods from groups at Columbia University and University of Edinburgh have been applied to reconcile disparate datasets.
Debates persist between advocates of a near-global glaciation scenario championed by scholars publishing in Nature and critics emphasizing diachronous, regional glaciation articulated in papers in Journal of the Geological Society and Precambrian Research. Alternative models from researchers at University of Copenhagen and University of Bergen propose slushball or marine-terminating ice schemes. Interpretational disputes focus on paleomagnetic reliability, cap carbonate genesis, and isotope stratigraphy, with differing analyses advanced by teams at Stanford University, University of California, Los Angeles, and University of Western Australia. Ongoing fieldwork and multi-proxy studies by consortia including International Geoscience Programme aim to resolve these tensions.