Detrital Garnet and Muscovite in Late Precambrian Sandstone near St. John's, Newfoundland, and their Significance

1973 ◽  
Vol 10 (3) ◽  
pp. 430-432 ◽  
Author(s):  
V. S. Papezik
Keyword(s):  
Main Group ◽  
Precambrian Basement ◽  
Granitic Pluton ◽  
Late Precambrian ◽  
Lower Member ◽  
Western Flank ◽  
Basement Rocks ◽  
Avalon Peninsula

The lower member of the Signal Hill Formation of Late Precambrian age, a lithofeldspathic sandstone exposed near St. John's, Newfoundland, contains small but persistent amounts of garnet and muscovite. These minerals are not known to occur in rocks of the Harbour Main Group and the Holyrood granitic pluton of the Avalon Peninsula, previously considered to be the source of the Signal Hill sediments. As paleocurrent studies indicate a northeasterly provenance of the sediment it is suggested that the rock may have been derived from Precambrian gneissic and granitic basement, now covered by the ocean, similar to the Precambrian(?) basement rocks along the western flank of the Avalon Platform.

Late Precambrian Rocks of Eastern Avalon Peninsula, Newfoundland — A Volcanic Island Complex

1971 ◽  
Vol 8 (8) ◽  
pp. 899-915 ◽  
Author(s):  
C. J. Hughes ◽  
W. D. Brückner
Keyword(s):  
Volcanic Rocks ◽  
Main Group ◽  
Volcanic Island ◽  
Precambrian Rocks ◽  
Crustal Movements ◽  
Late Precambrian ◽  
Isostatic Adjustment ◽  
Avalon Peninsula ◽  
Vertical Crustal Movements

A model of island volcanism is presented in which rocks are referred to (1) a "syn-volcanic" constructional phase represented by rocks of four penecontemporaneous facies—vent, alluvial, marine, and plutonic—whose interrelationships are discussed and (2) a "post-volcanic" destructional phase of erosion and sedimentation accompanied by isostatic adjustment resulting in the spreading of an apron of volcanic sediments around a slowly rising and eroding island core.The late Precambrian rocks of the eastern part of the Avalon Peninsula, southeasternmost Newfoundland, are shown to fit this model rather closely, both petrographically and in their distribution and field relationships. The Harbour Main Group of volcanic rocks, the Conception Group of marine volcanic sediments and tuffs, and the Holyrood Plutonic Series, dated at 574 ± 11 m.y., were all formed during the syn-volcanic constructional phase. Their apparently conflicting age relationships can be reconciled to the view that they are penecontemporaneous facies. The Cabot and Hodgewater Groups of marine and alluvial volcanic sediments were formed during the post-volcanic destructional phase. Apart from vertical crustal movements, only minor diastrophic deformation appears to have occurred during these two phases.This model of volcanic island environment may help in interpreting the geology of several other belts in eastern and central Newfoundland comprising late Precambrian and Paleozoic volcanic rocks and sediments.

Late Precambrian ignimbrites on the Avalon Peninsula, Newfoundland

1969 ◽  
Vol 6 (6) ◽  
pp. 1405-1414 ◽  
Author(s):  
V. S. Papezik
Keyword(s):  
Volcanic Belt ◽  
Main Group ◽  
Granitic Magma ◽  
Late Precambrian ◽  
Volcanic Pile ◽  
Avalon Peninsula

The predominantly volcanic Harbour Main Group of Late Precambrian age, forming a broad northerly trending belt in the central part of the Avalon Peninsula of Newfoundland, includes some well-developed ignimbrites. The ignimbrite sequence, best exposed in the western part of the volcanic belt, consists of ash-flow tuffs intercalated with tuff–breccias of various origins and minor volcanigenic sediments. Some of the ignimbrite sheets are densely welded, with distinct eutaxitic structures. Although the original glass is recrystallized, shard outlines are perfectly preserved and fragments of obsidian and perlite can be recognized; albite crystals are abundant, and quartz, augite, and biotite are present locally. The ignimbrites have been folded, faulted, and are now almost vertical. In composition, they range from rhyolites to dacites and are distinctly sodic.It is suggested that the ignimbrites may be derived from the gas-charged upper part of a granitic magma intruded into a pre-existing part of the Harbour Main volcanic pile; the lower, gas-poor part of the magma may have formed the present discordant "Holyrood batholith" of the Avalon Peninsula.

Structure de la region d'Ijibiten (feuille El Gleitat, E d'Akjoujt, Mauritanie occidentale)

1969 ◽  
Vol S7-XI (2) ◽  
pp. 222-232 ◽  
Author(s):  
Jean Paul Lecorche
Keyword(s):  
Sedimentary Cover ◽  
Precambrian Basement ◽  
Basement Rocks

Abstract Folds, overthrusts, four units, Precambrian basement rocks, sedimentary cover of Paleozoic age, Reg unit overthrust, and the epimetamorphic formations

On the position of the Variscan front in southern New Brunswick and its relation to Precambrian basement

1976 ◽  
Vol 13 (1) ◽  
pp. 194-196 ◽  
Author(s):  
N. Rast ◽  
K. L. Currie
Keyword(s):  
New Brunswick ◽  
Precambrian Basement ◽  
Precambrian Rocks ◽  
Late Precambrian ◽  
Mylonite Zone

The Variscan front is marked by a zone of cataclasis that generally follows an older and larger mylonite zone, but locally cuts across relatively undeformed Precambrian rocks. The older mylonite zone probably developed in Late Precambrian (Avalonian) time. Correlative Precambrian rocks extend across both the Variscan front, and the Bellisle fault to the northwest.

scholarly journals From source to sink in central Gondwana: Exhumation of the Precambrian basement rocks of Tanzania and sediment accumulation in the adjacent Congo basin

Tectonics ◽  
2016 ◽  
Vol 35 (9) ◽  
pp. 2034-2051 ◽  
Author(s):  
Charles Happe Kasanzu ◽  
Bastien Linol ◽  
Maarten J. de Wit ◽  
Roderick Brown ◽  
Cristina Persano ◽  
...  
Keyword(s):  
Sediment Accumulation ◽  
Congo Basin ◽  
Precambrian Basement ◽  
Basement Rocks ◽  
Source To Sink

Volcanogenic cherts in the late Precambrian Conception Group, Avalon Peninsula, Newfoundland

1976 ◽  
Vol 13 (4) ◽  
pp. 512-519 ◽  
Author(s):  
Charles J. Hughes
Keyword(s):  
Sea Water ◽  
Chemical Data ◽  
Pyroclastic Material ◽  
Late Precambrian ◽  
Avalon Peninsula ◽  
Bedded Rocks

Bedded rocks of cherty appearance are locally abundant and conspicuous in the late Precambrian Conception Group of the Avalon Peninsula, southeast Newfoundland. Structural, petrographical, and chemical data from a well exposed locality near St. John's indicate that these beds are tuffaceous, predominantly of acid vitric composition, formed by pyroclastic material derived from contemporaneously active subaerial volcanic sources accumulating in sea water, and subjected to submarine transport. Appreciable quantities of acid material were thus erupted in 'Conception time.'

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