Now showing items 1-20 of 34

    • Accelerating Neoproterozoic research through scientific drilling 

      Condon, D. J.; Boggiani, P.; Fike, D.; Halverson, G. P.; Kasemann, S.; Knoll, Andrew Herbert; Macdonald, Francis Alexander; Prave, A. R.; Zhu, M. (Copernicus GmbH, 2015)
    • Agglutinated tests in post-Sturtian cap carbonates of Namibia and Mongolia 

      Bosak, T.; Lahr, D.J.G.; Pruss, S.B.; Macdonald, Francis Alexander; Dalton, L.; Matys, E. (Elsevier BV, 2011)
      Paleomagnetic data suggest that the early Cryogenian (Sturtian) glaciation extended to sea level at low latitude. The impact of this dramatic environmental change on biota, and the composition of ecosystems in the immediate ...
    • Authigenic Carbonate and the History of the Global Carbon Cycle 

      Schrag, Daniel P.; Higgins, John A.; Macdonald, Francis Alexander; Johnston, David T (American Association for the Advancement of Science (AAAS), 2013)
      We present a framework for interpreting the carbon isotopic composition of sedimentary rocks, which in turn requires a fundamental reinterpretation of the carbon cycle and redox budgets over Earth's history. We propose ...
    • A Basin Redox Transect at the Dawn of Animal Life 

      Sperling, Erik A.; Halverson, Galen P.; Knoll, Andrew Herbert; Macdonald, Francis Alexander; Johnston, David T (Elsevier BV, 2013)
      Multiple eukaryotic clades make their first appearance in the fossil record between ~810 and 715 Ma. Molecular clock studies suggest that the origin of animal multicellularity may have been part of this broader eukaryotic ...
    • Calibrating the Cryogenian 

      Macdonald, Francis Alexander; Schmitz, Mark D.; Crowley, James L.; Roots, Charles F.; Jones, David S.; Maloof, Adam C.; Strauss, Justin Vincent; Cohen, Phoebe; Johnston, David T; Schrag, Daniel P. (American Association for the Advancement of Science (AAAS), 2010)
      The Neoproterozoic was an era of great environmental and biological change, but a paucity of direct and precise age constraints on strata from this time has prevented the complete integration of these records. We present ...
    • Constraints on Global Carbon Cycling, Basin Formation, and Early Animal Evolution During the Neoproterozoic and Early Cambrian 

      Smith, Emily (2015-09-25)
      Within this dissertation, I document different time intervals during the Neoproterozoic through the early Cambrian (1000 – 525 Ma), one of the most dynamic and non-uniformitarian intervals in the history of the Earth. This ...
    • Dynamics of a Snowball Earth Ocean 

      Ashkenazy, Yosef; Gildor, Hezi; Losch, Martin; Macdonald, Francis Alexander; Schrag, Daniel P.; Tziperman, Eli (Nature Publishing Group, 2013)
      Geological evidence suggests that marine ice extended to the Equator at least twice during the Neoproterozoic era (about 750 to 635 million years ago), inspiring the Snowball Earth hypothesis that the Earth was globally ...
    • Early Neoproterozoic Basin Formation in Yukon, Canada: Implications for the Make-Up and Break-Up of Rodinia 

      Macdonald, Francis Alexander; Halverson, Galen P.; Strauss, Justin Vincent; Smith, Emily F.; Cox, Grant; Sperling, Erik A.; Roots, Charles F. (Geological Association of Canada, 2012)
      Geological mapping and stratigraphic anaylsis of the early Neoproterozoic Fifteenmile Group in the western Ogilvie Mountains of Yukon, Canada, has revealed large lateral facies changes in both carbonate and siliciclastic ...
    • Early Neoproterozoic scale microfossils in the Lower Tindir Group of Alaska and the Yukon Territory 

      Macdonald, Francis Alexander; Cohen, Phoebe; Dudas, Francis Ő.; Schrag, Daniel P. (Geological Society of America, 2010)
      The Tindir Group is a <4-km-thick Neoproterozoic succession exposed in the Tatonduk inlier of east-central Alaska and the western Yukon Territory. The Tindir Group is informally divided into the Lower Tindir Group, which ...
    • Fossils of Putative Marine Algae From the Cryogenian Glacial Interlude of Mongolia 

      Cohen, P. A.; Macdonald, Francis Alexander; Pruss, S.; Matys, E.; Bosak, T. (Society for Sedimentary Geology, 2015)
      Neoproterozoic carbonate successions provide a new taphonomic window into the diversification of eukaryotes. We report recently discovered macroscopic organic warty sheets (MOWS) in macerates of limestone from the ca. ...
    • Geology of Five Small Australian Impact Craters 

      Macdonald, Francis Alexander; Shoemaker, Carolyn S.; Shoemaker, Eugene M. (Wiley Blackwell, 2005)
      Here we present detailed geological maps and cross-sections of Liverpool, Wolfe Creek, Boxhole, Veevers and Dalgaranga craters. Liverpool crater and Wolfe Creek Meteorite Crater are classic bowlshaped, Barringer-type ...
    • Initiation of Snowball Earth with volcanic sulfur aerosol emissions 

      Macdonald, Francis Alexander; Wordsworth, Robin (Wiley-Blackwell, 2017)
      We propose that the first Neoproterozoic Snowball Earth event, the Sturtian glaciation, was initiated by the injection of sulfate aerosols into the stratosphere. Geochronological data indicate that the Natkusiak magmatic ...
    • A Low Temperature Transfer of ALH84001 from Mars to Earth 

      Weiss, B. P.; Kirschvink, Joseph L.; Baudenbacher, Franz J.; Vali, Hojatollah; Peters, Nick T.; Macdonald, Francis Alexander; Wikswo, John P. (American Association for the Advancement of Science (AAAS), 2000)
      The ejection of material from Mars is thought to be caused by large impacts that would heat much of the ejecta to high temperatures. Images of the magnetic field of martian meteorite ALH84001 reveal a spatially heterogeneous ...
    • Microbial facies in a Sturtian cap carbonate, the Rasthof Formation, Otavi Group, northern Namibia 

      Pruss, Sara B.; Bosak, Tanja; Macdonald, Francis Alexander; McLane, Marie; Hoffman, Paul (Elsevier BV, 2010)
      Microbial structures in Neoproterozoic cap carbonates record the environmental processes present in the aftermath of global glaciation. The Rasthof Formation of northern Namibia is a unique carbonate depositional sequence ...
    • Neoproterozoic and early Paleozoic correlations in the western Ogilvie Mountains, Yukon 

      Macdonald, Francis Alexander; Smith, Emmy; Strauss, J. V.; Cox, G. M.; Halverson, G. P.; Roots, C. F. (2010)
      Continued investigations of sedimentary units in the Tatonduk and Coal Creek inliers of the western Ogilvie Mountains have resulted in a refinement of the regional Neoproterozoic and early Paleozoic stratigraphy. The ...
    • The Neoproterozoic and Early Paleozoic Tectonic and Environmental Evolution of Alaska and Northwest Canada 

      Strauss, Justin Vincent (2015-05-04)
      Neoproterozoic and early Paleozoic sedimentary deposits of the North American Cordillera record large fluctuations in global biogeochemical cycles, the establishment and diversification of multiple eukaryotic clades, the ...
    • Neoproterozoic glaciation on a carbonate platform margin in Arctic Alaska and the origin of the North Slope subterrane 

      Macdonald, Francis Alexander; McClelland, William C.; Schrag, Daniel P.; Macdonald, Winston P. (Geological Society of America, 2009)
      The rotation model for the opening of the Canada Basin of the Arctic Ocean predicts stratigraphic links between the Alaskan North Slope and the Canadian Arctic islands. The Katakturuk Dolomite is a 2080-m-thick Neo protero ...
    • Neoproterozoic iron formation: An evaluation of its temporal, environmental and tectonic significance 

      Cox, Grant M.; Halverson, Galen P.; Minarik, William G.; Le Heron, Daniel P.; Macdonald, Francis Alexander; Bellefroid, Eric J.; Strauss, Justin Vincent (Elsevier BV, 2013)
      Neoproterozoic iron formation (NIF) provides evidence for the widespread return of anoxic and ferruginous basins during a time period associated with major changes in climate, tectonics and biogeochemistry of the oceans. ...
    • Neoproterozoic to Paleozoic Geology of Southwestern Mongolia 

      Bold, Uyanga (2016-05-10)
      The Neoproterozoic and Paleozoic evolution of global climate, tectonics, ocean geochemistry, and biological diversification are recorded in stratigraphic successions globally. The rock record of southwestern Mongolia has ...
    • Oxygen, facies, and secular controls on the appearance of Cryogenian and Ediacaran body and trace fossils in the Mackenzie Mountains of northwestern Canada 

      Sperling, Erik; Carbone, Calla; Strauss, Justin; Johnston, David T; Narbonne, Guy M.; Macdonald, Francis Alexander (Geological Society of America, 2015)
      The causes behind the appearance of abundant macroscopic body and trace fossils at the end of the Neoproterozoic Era remain debated. Iron geochemical data from fossiliferous Ediacaran successions in Newfoundland suggested ...