Geology of Belle Isle—northern extremity of the deformed Appalachian miogeosynclinal belt

1969 ◽  
Vol 6 (5) ◽  
pp. 1145-1157 ◽  
Author(s):  
Harold Williams ◽  
R. K. Stevens
Keyword(s):  
Long Range ◽  
Lower Cambrian ◽  
Volcanic Rocks ◽  
Precambrian Rocks ◽  
Southeast Coast ◽  
Anticlinal Structure ◽  
Basement Rocks ◽  
Inclined Surfaces ◽  
Uplifted Block ◽  
Southwest Part

Belle Isle, situated between northern Newfoundland and the southeast coast of Labrador, consists of an uplifted block of Precambrian plutonic rocks intruded by northeast-trending diabase dikes and uncomformably overlain by Lower Cambrian and earlier (?) sedimentary and volcanic rocks. The Precambrian rocks lie along strike and are similar to Grenville gneisses of the Long Range Complex of western Newfoundland. In the southwest part of Belle Isle, the cover rocks are gently dipping basaltic flows and agglomerates that are succeeded conformably by arkosic sandstones and fossiliferous upper Lower Cambrian shales. In the northeast, the basement rocks are overlain by steeply dipping boulder conglomerates and arkosic sandstones, followed conformably by white quartzites.Diabase dikes are inseparable from overlying flows, but do not penetrate higher sedimentary strata of the southwestern Lower Cambrian succession. Toward the northeast, plutonic boulder conglomerates and quartzites are cut by the dikes.The distribution of supracrustal rocks around the periphery of the island, combined with local steeply inclined surfaces of unconformity between basement and cover rocks, indicate a major anticlinal structure produced by Paleozoic deformation. The study also shows that at Belle Isle the established Lower Cambrian succession of southeast Labrador and western Newfoundland is locally underlain by basalts and conglomerates and quartzites that thicken southeastward and northeastward.

Age of the Grenville dyke swarm, Ontario–Quebec: implications for the timing of lapetan rifting

1995 ◽  
Vol 32 (3) ◽  
pp. 273-280 ◽  
Author(s):  
S. L. Kamo ◽  
T. E. Krogh ◽  
P. S. Kumarapeli
Keyword(s):  
Long Range ◽  
Volcanic Rocks ◽  
Canadian Shield ◽  
Dyke Swarm ◽  
Alkaline Complex ◽  
Southeastern Part ◽  
Time Marker ◽  
Continental Breakup ◽  
Iapetus Ocean

U–Pb baddeleyite and zircon ages for three diabase dykes from widely spaced localities within the Grenville dyke swarm indicate a single age of emplacement at [Formula: see text] Ma. The 700 km long Grenville dyke swarm, located in the southeastern part of the Canadian Shield, was emplaced syntectonically with the development of the Ottawa graben. This graben may represent a plume-generated lapetan failed arm that developed at the onset of the breakup of Laurentia. Other precisely dated lapetan rift-related units, such as the Callander Alkaline Complex and the Tibbit Hill Formation volcanic rocks, indicate a protracted 36 Ma period of rifting and magmatism prior to volcanism along this segment of the lapetan margin. The age of the Grenville dykes is the youngest in a progression of precisely dated mafic magmatic events from the 723 Ma Franklin dykes and sills to the 615 Ma Long Range dykes, along the northern and northeastern margins of Laurentia, respectively. Thus, the age for these dykes represents a key time marker for continental breakup that preceded the formation of the Iapetus ocean.

Lower Palaeozoic and Precambrian igneous rocks from eastern England, and their bearing on late Ordovician closure of the Tornquist Sea: constraints from U-Pb and Nd isotopes

1993 ◽  
Vol 130 (6) ◽  
pp. 835-846 ◽  
Author(s):  
S. R. Noble ◽  
R. D. Tucker ◽  
T. C. Pharaoh
Keyword(s):  
Volcanic Rocks ◽  
Igneous Rocks ◽  
Calc Alkaline ◽  
Nd Isotopes ◽  
Nd Isotope ◽  
Magmatic Arc ◽  
The North ◽  
Basement Rocks ◽  
Continental Arc ◽  
Lower Palaeozoic

AbstractThe U-Pb isotope ages and Nd isotope characteristics of asuite of igneous rocks from the basement of eastern England show that Ordovician calc-alkaline igneous rocks are tectonically interleaved with late Precambrian volcanic rocks distinct from Precambrian rocks exposed in southern Britain. New U-Pb ages for the North Creake tuff (zircon, 449±13 Ma), Moorby Microgranite (zircon, 457 ± 20 Ma), and the Nuneaton lamprophyre (zircon and baddeleyite, 442 ± 3 Ma) confirm the presence ofan Ordovician magmatic arc. Tectonically interleaved Precambrian volcanic rocks within this arc are verified by new U-Pb zircon ages for tuffs at Glinton (612 ± 21 Ma) and Orton (616 ± 6 Ma). Initial εNd values for these basement rocks range from +4 to - 6, consistent with generation of both c. 615 Ma and c. 450 Ma groups of rocksin continental arc settings. The U-Pb and Sm-Nd isotope data support arguments for an Ordovician fold/thrust belt extending from England to Belgium, and that the Ordovician calc-alkaline rocks formed in response to subductionof Tornquist Sea oceanic crust beneath Avalonia.

Upper Precambrian through Lower Cambrian of Cape Breton Island: faunas, paleoenvironments, and stratigraphic revision

1991 ◽  
Vol 65 (4) ◽  
pp. 570-595 ◽  
Author(s):  
Ed Landing
Keyword(s):  
Lower Cambrian ◽  
Volcanic Rocks ◽  
Depositional Sequence ◽  
Cape Breton Island ◽  
Tectonic History ◽  
Small Shelly Fossils ◽  
Cape Breton ◽  
Local Erosion ◽  
Lake Formation ◽  
Random Block

Latest Precambrian through Early Cambrian tectonic history and stratigraphy are comparable in southeastern Cape Breton Island and the western Placentia–Bonavista axis, southeastern Newfoundland. The lithostratigraphic nomenclature of southeastern Newfoundland is used for this interval in Cape Breton Island. Upper Precambrian volcanic rocks of the Forchu Group (=“Giant Lake Complex,’ designation abandoned) are unconformably overlain by uppermost Precambrian through lowest Cambrian strata termed the “Morrison River Formation’ (designation abandoned). This depositional sequence consists of three formations: 1) red beds through tidalites of the Rencontre Formation (to 279+ m; =“Kelvin Lake Formation,’ designation abandoned); 2) prodeltaic clastics of the Chapel Island Formation (to 260 m); and 3) macrotidal quartzites of the Random Formation (to 71 + m). Post-Random block faulting and 300 m of local erosion took place prior to onlap of the “MacCodrum Formation’ (abandoned). Siliciclastic mudstones of the lower “MacCodrum’ are re-assigned to the middle Lower Cambrian Bonavista Group. Sub-trilobitic faunas from the Bonavista Group include “Ladatheca’ cylindrica from the West Centre Cove Formation(?) and higher diversity faunas (23 species) in the Camenella baltica Zone of the Cuslett and Fosters Point Formations. Trilobite-bearing, upper Lower Cambrian (Branchian Series) strata (Brigus Formation, =upper “MacCodrum’ and overlying “Canoe Brook’ Formations) unconformably overlie the Placentian Series in Cape Breton Island, southeastern Newfoundland, Shropshire, and, probably, eastern Massachusetts. Correlations based on small shelly fossils indicate an earlier appearance of trilobites in Avalon than on the South China Platform. Twenty-six species are illustrated. Halkieria fordi n. sp., the conodont(?) “Rushtonites’ asiatica n. sp., and the zhijinitid(?) Samsanoffoclavus matthewi n. gen. and sp. are described. Ischyrinia? sp. may be the oldest ischyrinoid rostroconch.

Early Cenozoic resetting of potassium–argon dates and geothermal history of north Okanagan area, British Columbia

1981 ◽  
Vol 18 (8) ◽  
pp. 1310-1319 ◽  
Author(s):  
Wm. H. Mathews
Keyword(s):  
Vitrinite Reflectance ◽  
Volcanic Rocks ◽  
Blocking Temperature ◽  
Low Grade ◽  
High Grade ◽  
Basement Rocks ◽  
Thermal Changes ◽  
History Of ◽  
The Trinity ◽  
Early Cenozoic

Unmetamorphosed Early Eocene sediments and volcanic rocks of the Trinity Hills and Enderby Cliffs yield K–Ar dates of 42–49 Ma. These overlie high-grade gneisses yielding K–Ar ages on biotites, muscovites, and hornblende ranging from 47 to 60 Ma. The Eocene sediments and volcanics rest nearby on low-grade phyllites, greenstones, and schists yielding dates from 83 to 155 Ma. The gneiss dates are regarded as reset by some Late Cretaceous to earliest Cenozoic thermal event that did not affect, at least to the same degree, the nearby less metamorphosed basement rocks. A thermal history has been constructed to account for the decreasing apparent ages of biotite (assumed blocking temperature of 250 °C) with increasing depth below the sub-Eocene unconformity, for the greater ages of hornblende and muscovite in the same rocks (blocking temperatures of 500 and 350 °C), as well as for thermal changes associated with high vitrinite reflectance from coal at one site in the covering sediments. Very rapid stripping (something like 5 km in 12 Ma) is inferred for the areas of reset gneisses, but not for the schist areas, in early Cenozoic time.

Spectral correlation of magnetic and gravity anomalies of Ohio

Geophysics ◽  
1997 ◽  
Vol 62 (1) ◽  
pp. 365-380 ◽  
Author(s):  
Ralph R. B. von Frese ◽  
Michael B. Jones ◽  
Jeong Woo Kim ◽  
Wen Sheng Li
Keyword(s):  
Volcanic Rocks ◽  
Gravity Anomalies ◽  
Field Analysis ◽  
Positive Density ◽  
Upper Crust ◽  
Spectral Correlation ◽  
South Central ◽  
Basement Rocks ◽  
Positive Correlations ◽  
First Vertical Derivative

Geologic interpretation of Ohio's magnetic or gravity anomalies is hindered by the effects of anomaly superposition and source ambiguity inherent to potential field analysis. A common approach to minimizing interpretational ambiguities is to consider analyses of anomaly correlations. A spectral procedure is adapted which correlates anomaly fields in the frequency domain to produce filters separating positively and negatively correlated, as well as null correlated features. The correlation filter passes or rejects wavenumbers between coregistered fields based on the correlation coefficient between common wavenumbers as given by the cosine of their phase difference. This procedure is applied to reduced‐to‐pole magnetic and first vertical derivative gravity anomalies of Ohio for mapping correlative magnetization and density contrasts within the basement rocks. The analysis reveals predominantly positive correlations between anomaly maxima and minima. Correlative anomaly maxima may be generally modeled as mafic bodies of the upper crust. They map out a possible dike complex in northwestern Ohio, a batholith as a possible source of volcanic rocks in southwestern Ohio, and numerous mafic bodies related presumably to Keweenawan rifting and Grenville tectonics. Correlative anomaly minima include several isolated features that may define felsic terranes of the upper crust, and ringed features around some of the larger mafic bodies which also may contain significant edge‐effect components. A large circular feature in south‐central Ohio involves correlative minima of a possible anorthosite body that is ringed by an inversely correlative zone of positive density and negative magnetization contrasts. Another prominent negative correlation involves an extensive area of possible extrusive rocks with positive magnetization and negative density contrasts just north of the batholith in southwestern Ohio.

Rb–Sr geochronology and metamorphic history of Proterozoic to early Archean rocks north of the Cape Smith Fold Belt, Quebec

1987 ◽  
Vol 24 (4) ◽  
pp. 813-825 ◽  
Author(s):  
Ronald Doig
Keyword(s):  
Volcanic Rocks ◽  
Granitic Rocks ◽  
Iron Formation ◽  
Fold Belt ◽  
Metasedimentary Rocks ◽  
Metamorphic History ◽  
The North ◽  
Basement Rocks ◽  
History Of ◽  
Wide Zone

The Churchill Province north of the Proterozoic Cape Smith volcanic fold belt of Quebec may be divided into two parts. The first is a broad antiform of migmatitic gneisses (Deception gneisses) extending north from the fold belt ~50 km to Sugluk Inlet. The second is a 20 km wide zone of high-grade metasedimentary rocks northwest of Sugluk Inlet. The Deception gneisses yield Rb–Sr isochron ages of 2600–2900 Ma and initial ratios of 0.701–0.703, showing that they are Archean basement to the Cape Smith Belt. The evidence that the basement rocks have been isoclinally refolded in the Proterozoic is clear at the contact with the fold belt. However, the gneisses also contain ubiquitous synclinal keels of metasiltstone with minor metapelite and marble that give isochron ages less than 2150 Ma. These ages, combined with low initial ratios of 0.7036, show that they are not part of the basement, as the average 87Sr/86Sr ratio for the basement rocks was about 0.718 at that time.The rocks west of Sugluk Inlet consist mainly of quartzo-feldspathic sediments, quartzites, para-amphibolites, marbles, and some pelite and iron formation. In contrast to the Proterozoic sediments in the Deception gneisses, these rocks yield dates of 3000–3200 Ma, with high initial ratios of 0.707–0.714. These initial ratios point to an age (or a provenance) much greater than that of the Archean Deception gneisses. The rocks of the Sugluk terrain are intruded by highly deformed sills of granitic rocks with ages of about 1830 Ma, demonstrating again the extent and severity of the Proterozoic overprint. The eastern margin of this possibly early Archean Sugluk block is a discontinuity in age, lithology, and geophysical character that could be a suture between two Archean cratons. It is not known if such a suturing event is of Archean age, or if it is related to the deformation of the Cape Smith Fold Belt.Models of evolution incorporating both the Cape Smith Belt and the Archean rocks to the north need to account for the internal structure of the fold belt, the continental affinity of many of the volcanic rocks, the continuity of basement around the eastern end of the belt, and the increase in metamorphism through the northern part of the belt into a broad area to the north. The Cape Smith volcanic rocks may have been extruded along a continental rift, parallel to a continental margin at Sugluk. Continental collison at Sugluk would have thrust the older and higher grade Sugluk rocks over the Deception gneisses, produced the broad Deception antiform, and displaced the Cape Smith rocks to the south in a series of north-dipping thrust slices.

Contributions to the Petrology of British East Africa

1903 ◽  
Vol 13 (61) ◽  
pp. 228-263 ◽  
Author(s):  
G. T. Prior
Keyword(s):  
East Africa ◽  
Rift Valley ◽  
Volcanic Rocks ◽  
Central Africa ◽  
British Museum ◽  
Basaltic Rocks ◽  
Basement Rocks ◽  
Great Rift Valley ◽  
Rock Specimens

The following notes on the petrology of British East Africa are the result of an examination of rock-specimens collected by Professor J. W. Gregory on his well-known expedition from Mombasa to Mt. Kenya and Lake Baringo in 1892-3, and of rock-collections from the Uganda Protectorate which have been recently presented to the British Museum by Sir Harry Johnston.The collections include examples of the Archaean gneisses, schists, and granites which constitute the prevailing basement rocks of Central Africa; of ferruginotls schists, coarse sandstones, and quartzites belonging to the Palaeozoic Karagwe series ; and of an interesting series of Tertiary volcanic rocks comprising phonolites, phonolltic traehytes, riebeckite-rhyolites, kenytes, and basalts from the volcanoes of the Great Rift Valley, as well as of nephelinites and basaltic rocks containing melilite and perofskite from Mr. Elgon.

The Dover Fault: Western Boundary of the Avalon Zone in Northeastern Newfoundland

1975 ◽  
Vol 12 (2) ◽  
pp. 320-325 ◽  
Author(s):  
R. F. Blackwood ◽  
M. J. Kennedy
Keyword(s):  
Structural Feature ◽  
Volcanic Rocks ◽  
Western Boundary ◽  
Gneiss Complex ◽  
Basement Rocks ◽  
Structural Relationships ◽  
Intrusive Rocks ◽  
Group Relationships ◽  
Western Side ◽  
Clastic Sedimentary

Basement rocks of the Hare Bay Gneiss Complex and associated granitic intrusive rocks on the western side of Bonavista Bay, northeastern Newfoundland, are separated from clastic sedimentary and volcanic rocks of the Avalon Zone (Love Cove and Musgravetown Groups) by a 300–500 m wide mylonite zone called the Dover Fault. The Dover Fault juxtaposes rocks of contrasting lithology and metamorphic, intrusive, and structural histories and represents the boundary between the Gander Zone and the Avalon Zone of the Newfoundland Appalachian System. Structural relationships across the fault zone indicate that early movement on the Dover Fault was contemporaneous with deformation of the Love Cove Group. Relationships elsewhere in the Avalon Zone indicate that the Love Cove Group was deformed in Hadrynian time and hence the Dover Fault was probably initiated as an Hadrynian structural feature, probably related to Hadrynian orogeny on the eastern side of the Appalachian system.

Correlation among lower to upper crustal components in an island arc: the Jurassic Bonanza arc, Vancouver Island, Canada

1999 ◽  
Vol 36 (8) ◽  
pp. 1371-1413 ◽  
Author(s):  
Susan M DeBari ◽  
Robert G Anderson ◽  
James K Mortensen
Keyword(s):  
Middle Jurassic ◽  
Volcanic Rocks ◽  
Vancouver Island ◽  
Island Arc ◽  
Calc Alkaline ◽  
Queen Charlotte Islands ◽  
Basement Rocks ◽  
Plutonic Rocks ◽  
Differential Uplift ◽  
Age Range

The Westcoast Crystalline Complex (WCC), Island Intrusions, and Bonanza Group of Vancouver Island, Canada, form three different crustal levels of the Early to Middle Jurassic Bonanza island arc. Differential uplift has exposed the plutonic roots and the volcanic carapace of the arc for a strike length of ~500 km, and for another 250 km on the Queen Charlotte Islands. At deeper crustal levels within the arc, influx of mantle-derived magmas was accompanied by metamorphism and melting of Wrangellian basement rocks, yielding the heterogeneous WCC. Upward mobilization and hybridization of magmas to shallower levels in the crust resulted in the batholiths of the Island Intrusions and the lavas and pyroclastic rocks of the Bonanza Group. New U-Pb crystallization ages for plutonic rocks of the arc span an age range of 190.3 ± 1.0 to 168.6 ± 5.3 Ma. Ages of the WCC and western Island Intrusions are indistinguishable and overlap with published fossil and isotopic ages for the Bonanza Group. Younger Middle Jurassic ages for the eastern Island Intrusions overlap with those for plutonic rocks in the southern Coast Belt and Queen Charlotte Islands. All plutonic and volcanic rocks within the arc have overlapping geochemical signatures, supporting their comagmatic origin. All are light rare earth element-enriched with abundances 10-50× chondrites. The most mafic noncumulate gabbroic rocks have compositions typical of island arc basalts, with intermediate values of Al2O3 (16-17 wt.%) and high MgO (7-9 wt.%). More differentiated rocks follow a calc-alkaline trend with concomitant increase in Al2O3 (18-20 wt.%). Their geochemistry indicates varying degrees of mixing with melts of mafic Wrangellian basement.

scholarly journals Testing of Permian – Lower Triassic stratigraphic data in a half-graben/tilt-block system: evidence for the initial rifting phase in Antalya Nappes

2019 ◽  
Vol 56 (11) ◽  
pp. 1262-1283 ◽  
Author(s):  
Nazif Şahin ◽  
Demir Altiner
Keyword(s):  
Hanging Wall ◽  
Volcanic Rocks ◽  
Lower Triassic ◽  
Normal Faulting ◽  
Triassic Boundary ◽  
Block System ◽  
Basement Rocks ◽  
Half Graben ◽  
Facies Change ◽  
Permian Triassic Boundary

Testing of Middle Permian – Lower Triassic stratigraphic data from the Antalya Nappes in a half-graben/tilt-block system has revealed the presence of episodic rifting events separated by periods of tectonic quiescence. Following a period of uplift during the Permian (Late Artinskian to Roadian), the basement rocks have been activated by displacement faults and several depocenters in half-graben-like asymmetrical basins began to be filled with Roadian to Wordian continental clastic deposits intercalated with coal and marine rocks. The Early Capitanian time was a period of tectonic quiescence. The second event occurred in Middle to Late Capitanian times and produced basaltic volcanic rocks intercalated in the shallow marine fossiliferous carbonate successions. Following the Lopingian (Wuchiapingian and Changhsingian) and Permian–Triassic boundary interval representing a long tectonic quiescence, the last rifting episode started with an abrupt facies change in the late Griesbachian. Variegated shales, limestones, volcanics, talus breccia, and debris flow deposits were laid down in a half-graben/tilt-block system. As normal faulting has become active, the deposition continued on the subsiding hanging wall side. The stratigraphic gap increased in magnitude as the erosional truncation has incised deeply the footwall side. This initial rifting phase in the Antalya Nappes is prior to the onset of a stronger and more continuous rifting event that occurred in the Anisian–Carnian interval including a variety of deepwater clastic and carbonate deposits, radiolarites containing sometimes blocks and clasts derived from the basin margins, and volcanic rocks carrying intraoceanic setting character.

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