Results 131 to 140 of about 4,233 (188)
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1982
Abstract Phanerozoic tectonics have not affected the basic integrity of the North American continent. From time to time, sialic crustal elements have been rifted off, accreted onto, and slipped along the continent’s margins, but the vast continental interior has remained intact.
P. F. Hoffman, K. D. Card, A. Davidson
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Abstract Phanerozoic tectonics have not affected the basic integrity of the North American continent. From time to time, sialic crustal elements have been rifted off, accreted onto, and slipped along the continent’s margins, but the vast continental interior has remained intact.
P. F. Hoffman, K. D. Card, A. Davidson
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Life on Land in the Precambrian
Science, 1994Microfossils have been discovered in cavity-fill and replacement silica that occurs between chert-breccia clasts in 1200-million-year-old paleokarst at the top of the Mescal Limestone, central Arizona, and in ∼800-million-year-old paleokarst at the top of the Beck Spring Dolomite, southeastern California.
R J, Horodyski, L P, Knauth
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Precambrian Research, 1986
Abstract The Subcommission on Precambrian Stratigraphy, consisting at the time of its last formal meeting in 1982 of 12 titular Members and 30 Correspondents, has been actively working toward an acceptable subdivision of Precambrian time for more than a decade.
Kenneth A. Plumb, Harold L. James
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Abstract The Subcommission on Precambrian Stratigraphy, consisting at the time of its last formal meeting in 1982 of 12 titular Members and 30 Correspondents, has been actively working toward an acceptable subdivision of Precambrian time for more than a decade.
Kenneth A. Plumb, Harold L. James
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Nature, 1963
IN his recent book on The Geological Aspects of the Origin of Life on Earth, Prof. M. G. Rutten has adopted as his central thesis the postulate that the Earth retained its primaeval reducing atmosphere up to 1,500–2,000 million years ago. This conclusion is based on the premise that the gold–uranium ores of the Witwatersrand (South Africa), Blind River
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IN his recent book on The Geological Aspects of the Origin of Life on Earth, Prof. M. G. Rutten has adopted as his central thesis the postulate that the Earth retained its primaeval reducing atmosphere up to 1,500–2,000 million years ago. This conclusion is based on the premise that the gold–uranium ores of the Witwatersrand (South Africa), Blind River
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Subdivision of the Precambrian
Geological Society, London, Memoirs, 1985Abstract The Precambrian record is so fragmentary and from such widely contrasting terrains that attempts to erect any formal subdivisions would appear to be premature. The methods that have been used in the Phanerozoic rocks cannot be used for subdividing the Precambrian as they are peculiarly suitable for fossiliferous largely undeformed ...
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The Development and Diversification of Precambrian Life
Origins of Life, 1974During the past decade, important strides have been made toward deciphering the paleobiology of the Precambrian Eon, the earliest seven-eighths of Earth history. This progress has accrued chiefly from micropaleontological and organic geochemical studies of fine-grained, ancient cherts.
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A Discussion on the evolution of the Precambrian crust - Crustal development in the Precambrian
Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences, 1973Abstract The oldest Archaean rocks in most shield regions are largely granulites and gneisses, and in west Greenland there is evidence of 1000 Ma of crustal history before the final high-grade metamorphism. Archaean greenstone belts are mostly younger than the high-grade terrains although in some areas, such as southern Africa, this ...
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