A Late Proterozoic–Early Paleozoic Magmatic Cycle in Sierra de la Ventana, Argentina

2004 ◽  
Vol 16 (7) ◽  
pp. 579-593
Author(s):  
D Gregori
Keyword(s):  
Early Paleozoic ◽  
Late Proterozoic

CAMBRIAN AND PRECAMBRIAN PETROLEUM AN APPRAISAL

1965 ◽  
Vol 5 (1) ◽  
pp. 7
Author(s):  
Grover E. Murray
Keyword(s):  
United States ◽  
North Africa ◽  
Sedimentary Rocks ◽  
The United States ◽  
Northern Territory ◽  
Early Paleozoic ◽  
Precambrian Rocks ◽  
Late Proterozoic ◽  
Organic Evolution ◽  
Early Phases

Accumulated evidence indicates that (1) the major portion of chemical and organic evolution occurred during the 3-5 x 109 years of the earth's history preceding the Paleozoic; (2) the basic elements constituting petroleum existed in the early phases of the earth's history; (3) unmetamorphosed Precambrian and Cambrian lithic types are similar to younger ones; and (4) the population of the later Precambrian and early Paleozoic seas was relatively rich and varied, though hard skeletal parts are notably absent in the Precambrian rocks and, in all probability, were not widely developed.As petroleum is now generally considered of organic origin and is a widely disseminated and integral part of most sedimentary rocks, unmetamorphosed Precambrian and Cambrian strata should be prospective for petroleum. Discoveries of large reserves of oil in the Cambrian in parts of North Africa, Russia and the United States support this asserted prospectivity. Shows of indigenous gas in the late Proterozoic of the Amadeus Basin, Northern Territory, Australia, indicate that unmetamorphosed Precambrian strata may also yield commercial amounts of hydrocarbons.

Structural relations at the eastern margin of the Shuswap Complex, near Revelstoke, southeastern British Columbia

1968 ◽  
Vol 5 (4) ◽  
pp. 831-849 ◽  
Author(s):  
John V. Ross
Keyword(s):  
British Columbia ◽  
Granite Gneiss ◽  
Early Paleozoic ◽  
Final Phase ◽  
Late Proterozoic ◽  
Eastern Margin ◽  
Deformational History ◽  
Facies Metamorphism ◽  
Absolute Age ◽  
Paleozoic Rocks

Three major phases of folding affected rocks of Late Proterozoic and Early Paleozoic age and members long assigned to the Shuswap Complex of southeastern British Columbia. The main and first phase of folding produced a large recumbent anticline, having a northerly trend, overturned to the east, that contains an exotic wedge of granite-gneiss within its core. This gneiss was mechanically emplaced into the Late Proterozoic and Early Paleozoic sediments, and already had a metamorphic and deformational history prior to its emplacement. Its age is possible Hudsonian equivalent. Metamorphism during this recumbent phase of folding was greenschist facies.Phase 2 folding was accompanied by amphibolite facies metamorphism, and caused refolding of the earlier composite recumbent anticline into open folds along southeasterly axes.A third and final phase of folding, associated with waning metamorphism, gave rise to folds along southeasterly striking axial-planes that dip steeply to the northeast. Thus, phase three folds caused tightening-up of the previously formed folds.The absolute age of these deformations is not yet known, but the Shuswap Complex, at its eastern margin, is shown to include Paleozoic rocks and some older gneisses, possibly of Hudsonian age.

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