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Proterozoic Atmospheric Oxygen
, 2014 This article is concerned with the evolution of atmospheric oxygen concentrations through the Proterozoic Eon. In particular, this article will seek to place the history of atmospheric oxygenation through the Proterozoic Eon in the context of the evolving physical environment including the history of continental growth and volcanic outgassing, as well ...
Canfield, Donald Eugene; id_orcid +1 more
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Scientific American, 1991
Living organisms have inhabited the surface of our planet for nearly four billion years. Yet the plants and animals that define our everyday existence have far more recent origins. The ancestors of modern trees and terrestrial animals first colonized land only about 450 million years ago.
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Living organisms have inhabited the surface of our planet for nearly four billion years. Yet the plants and animals that define our everyday existence have far more recent origins. The ancestors of modern trees and terrestrial animals first colonized land only about 450 million years ago.
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1982
The Dominion Group, Witwatersrand Supergroup, and Ventersdorp Supergroup constitute a volcanosedimentary sequence that is famous for its fossil gold placers. It has been estimated that since gold-bearing conglomerates were discovered near Johannesburg (Fig. 4-1) in 1886, mines in the Transvaal and Orange Free State have produced more than 55 percent of
A. J. Tankard +5 more
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The Dominion Group, Witwatersrand Supergroup, and Ventersdorp Supergroup constitute a volcanosedimentary sequence that is famous for its fossil gold placers. It has been estimated that since gold-bearing conglomerates were discovered near Johannesburg (Fig. 4-1) in 1886, mines in the Transvaal and Orange Free State have produced more than 55 percent of
A. J. Tankard +5 more
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A small marine biosphere in the Proterozoic
Geobiology, 2018AbstractThe riverine supply of the globally limiting nutrient, phosphorus, to the ocean accounts for only a few percent of nutrient supply to photosynthetic organisms in surface waters. Recycling of marine organic matter by heterotrophic organisms provides almost all of the phosphorus that drives net primary production in the modern ocean.
Thomas A. Laakso, Daniel P. Schrag
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Tectonophysics, 1987
Abstract Proterozoic rifts at various stages of extension have been involved in different types of endogenous activity. As a result, the following evolutionary gradation of riftogenous structures is recorded: Aulacogens—continental paleorifts that are not affected by metamorphism and granite formation; intracontinental ensialic folded systems which ...
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Abstract Proterozoic rifts at various stages of extension have been involved in different types of endogenous activity. As a result, the following evolutionary gradation of riftogenous structures is recorded: Aulacogens—continental paleorifts that are not affected by metamorphism and granite formation; intracontinental ensialic folded systems which ...
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Proterozoic Granitoids of Rajasthan
Journal of the Geological Society of India, 2005Abstract Two granitoid bodies each from Palaeo-, Meso- and Neo-proterozoic periods have been studied for their chemical, petrological and source characteristics The Proterozoic granitoids are megacrystic as well non-megacrystic with variable effect by tectonometamorphic events The Palaeo-proterozoic granitoids are peraluminous ...
S.K Bhushan, V.K. Chittora
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Paleobiology, 2005
Abstract A large, morphologically heterogeneous population of acanthomorphic acritarchs from the early Neoproterozoic Wynniatt Formation, Victoria Island, northwestern Canada, is ascribed to two form-genera, Tappania and Germinosphaera, but just a single natural taxon, Tappania. Analysis of Tappania morphology shows it to have been an actively growing,
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Abstract A large, morphologically heterogeneous population of acanthomorphic acritarchs from the early Neoproterozoic Wynniatt Formation, Victoria Island, northwestern Canada, is ascribed to two form-genera, Tappania and Germinosphaera, but just a single natural taxon, Tappania. Analysis of Tappania morphology shows it to have been an actively growing,
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