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.

Recent crustal movements on the Labrador Shelf

1970 ◽  
Vol 7 (2) ◽  
pp. 571-575 ◽  
Author(s):  
A. C. Grant
Keyword(s):  
Sedimentary Rocks ◽  
Outer Shelf ◽  
Inner Shelf ◽  
Glacial Erosion ◽  
Precambrian Rocks ◽  
Crustal Movements ◽  
Channel One ◽  
Seaward Side ◽  
Isostatic Adjustment ◽  
Structural Disturbance

Seismic profiler investigations have confirmed that the marginal channel that occurs on the Labrador Shelf separates crystalline Precambrian rocks underlying the inner shelf from sedimentary rocks on the outer shelf. The relief of the channel is thought to be mainly the result of glacial erosion, but there is also evidence of structural disturbance associated with this feature. Most seismic profiler transects show pronounced upwarping of the sedimentary strata underlying the seaward side of the marginal channel. One explanation offered for this upwarping is that it may possibly be due to isostatic adjustment following removal of material by glacial erosion.

Petrochemistry of volcanic rocks of the Harbour Main Group, Avalon Peninsula, Newfoundland

1970 ◽  
Vol 7 (6) ◽  
pp. 1485-1498 ◽  
Author(s):  
V. S. Papezik
Keyword(s):  
Volcanic Rocks ◽  
Main Group ◽  
Range Type ◽  
Volcanic Suite ◽  
High Alkali ◽  
Tectonic Belt ◽  
Basic Rocks ◽  
Avalon Peninsula ◽  
Block Faulting ◽  
Different Parts

The predominantly volcanic Harbour Main Group of Proterozoic (Hadrynian) age forms a northerly-trending belt in the central part of the Avalon Peninsula, Newfoundland. The rocks include flows, pyroclastics, and several belts of well-preserved ignimbrites.Twenty-two recent chemical analyses of volcanic rocks, sixteen of them not previously published, show that the Harbour Main volcanic suite is distinctly sodic and weakly alkalic, ranging from basic rocks of the hawaiite–mugearite type to sodic rhyolites with relatively high alkali content; the alkali-lime index of the suite is 52.The Harbour Main rocks are shown to be chemically similar to the Late Precambrian Uriconian volcanic suite in Central Britain, with which it has been previously tentatively correlated on other grounds. It is suggested that the volcanic rocks of the Avalon Peninsula and the British Midlands were formed in different parts of a possibly continuous tectonic belt in a period of post-orogenic block-faulting of the Basin and Range type, prior to the opening of the present Atlantic Ocean.

A geophysical interpretation of the onshore and offshore geology of the southern Avalon Terrane, Newfoundland

1987 ◽  
Vol 24 (1) ◽  
pp. 60-69 ◽  
Author(s):  
H. G. Miller
Keyword(s):  
Sedimentary Basin ◽  
Gravity Data ◽  
Volcanic Rocks ◽  
Geophysical Data ◽  
Magnetic Data ◽  
Ultramafic Rocks ◽  
Volcanic Island ◽  
Thrust Faulting ◽  
Geophysical Interpretation ◽  
Avalon Peninsula

This paper presents new land and underwater gravity data for the southern portion of the Avalon Terrane of Newfoundland. These gravity data are combined with existing airborne and marine magnetic data to produce a detailed geophysical interpretation of the geology of the southern Avalon Peninsula and the adjacent portions of Placentia and St. Mary's bays.Qualitative interpretation of the geophysical data in conjunction with the known geology reveals that the major faults previously mapped only on land and inferred beneath St. Mary's Bay can be traced offshore geophysically. In addition, the previously unknown offshore limits of a small sedimentary basin in the southeast part of the area can be delineated.Quantitative modelling demonstrates that (1) Precambrian mafic to ultramafic rocks underlie the whole area, (2) thrust faulting in the St. Mary's Peninsula and elsewhere has led to the juxtaposition of Bull Arm volcanic rocks over Harbour Main volcanic rocks, and (3) the evolution of the area may be explained by a combination of earlier volcanic island and extensional models.The mapping has also revealed the presence of previously unknown northwest–southeast lineations in the geophysical patterns, which may be related to the late wrench faulting.

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 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.

scholarly journals Nisyros Volcanic Island: A Geosite through a Tailored GIS Story

Geosciences ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 132
Author(s):  
Varvara Antoniou ◽  
Paraskevi Nomikou ◽  
Dimitrios Panousis ◽  
Effrosyni Zafeirakopoulou
Keyword(s):  
Spatial Data ◽  
Hot Springs ◽  
Volcanic Rocks ◽  
Data Communication ◽  
Aegean Sea ◽  
Volcanic Island ◽  
Eastern Aegean ◽  
Strongly Connected ◽  
Historical Heritage ◽  
Available Information

The volcanic island of Nisyros (Greece) is here presented as it presents unique characteristics being a Quaternary volcano in the eastern Aegean Sea, composed of volcanic rocks, and featuring a central caldera that is surrounded by volcanic domes and thick lavas. Its history is strongly connected to the volcano impressing the visitors with steaming hydrothermal craters, intensive smell of sulfur and fumarolic gases, and hot springs. Due to its morphology and geographical position, its cultural and historical heritage has been unchanged in time, bequeath to the island plenty of churches, monasteries with hagiographic frescoes, castles, caves, and spas. To present the geodiversity, the cultural environment, and the biodiversity of this geosite, a relatively new geographic approach was used, ESRI Story Maps. Being web-based applications, they are widespread as an interactive responsive tool used for spatial data communication and dissemination, by combining thematic 2D and 3D webmaps, narrative text, and multimedia content. Such applications can be an ideal way for presenting the available information of places characterized as geosites or protected areas worldwide, providing quick access to the available information to a broader, non-technical audience, developing the interest, and possibly motivating the public to learn more or visit them.

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