ils are characterized by soil nodules, most of which formed below the water table that existed across the landscape. But, some soil nodules developed where carbonate cements formed in equilibrium with atmospheric gas concentrations. Calculations based on geochemical analyses of stable carbon isotopes, preserved in carbonate cements in these latest Permian soil nodules, and original organic matter, indicate that latest Permian carbon dioxide ranged from an estimated low concentrations of 500 to 900 ppm to high concentrations of 1300 to 1900 ppm, nearly five times that of current values, prior to the mass extinction event.
Volcanosedimentary paleoenvironments of Ediacaran fossils in Newfoundland
Gregory J. Retallack, Department of Geological Sciences, University of Oregon, Eugene, 97302 USA. Posted online ahead of print on 13 Feb. 2014; http://dx.doi.org/10.1130/B30892.1.
Ediacaran fossils from Mistaken Point, Newfoundland, did not live in the darkness of the deep ocean, as has been widely assumed, but in intertidal and coastal soils. New evidence for a terrestrial habitat comes from ungraded crystal and lapilli tuffs, volcanic bombs and block-and-ash flows. The Mistaken Point Formation is geochemically comparable with convergent continental margin sequences, rather than deep sea oceanic sediments. Beds formerly interpreted as turbidites, were instead paleosols, tsunamites, and seismites. Such coastal habitats support interpretation of the Ediacaran fossils of Newfoundland as fungi, lichens, and microbial colonies, rather than animals.
Provenance variability along the Early Ordovician north Gondwana margin: Paleogeographic and tectonic implications of U-Pb detrital zircon ages from the Armorican Quartzite of the Iberian Variscan belt
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