scholarly journals Stratigraphy, tectonic setting, and geological history of late Precambrian volcanic-sedimentary-plutonic belts in southeastern Cape Breton Island, Nova Scotia

1996 ◽  
Author(s):  
S M Barr ◽  
C E White ◽  
A S Macdonald
Keyword(s):  
Nova Scotia ◽  
Tectonic Setting ◽  
Geological History ◽  
Cape Breton Island ◽  
Late Precambrian ◽  
Cape Breton ◽  
History Of

Contrasting metamorphic terranes near Chéticamp, Cape Breton Highlands, Nova Scotia

1987 ◽  
Vol 24 (12) ◽  
pp. 2422-2435 ◽  
Author(s):  
K. L. Currie
Keyword(s):  
Nova Scotia ◽  
The Other ◽  
Biotite Gneiss ◽  
Cape Breton Island ◽  
Late Precambrian ◽  
Cape Breton ◽  
Facies Metamorphism ◽  
Cover Relation ◽  
Metamorphic Terranes

Two contrasting metamorphic terranes can be recognized in northwestern Cape Breton Island. One terrane (Pleasant Bay complex) consists of biotite gneiss and quartzite with minor calc-silicate lenses that were metamorphosed in Late Precambrian time (about 550 Ma) and were subsequently intruded by Silurian salic and mafic plutons that were, in turn, deformed and intruded by granite in Devonian time. The other terrane (Jumping Brook complex) consists of volcanogenic and sedimentary schists of probable Silurian age that were metamorphosed in Devonian time. P–T estimates indicate that the older parts of the Pleasant Bay complex were metamorphosed at about 790 °C and 7 kbar (1 kbar = 100 MPa) at low to moderate water fugacities during a major intrusive episode. The Jumping Brook complex exhibits a single progressive metamorphic sequence now disrupted by faulting. P–T conditions during this Devonian (370–390 Ma) metamorphism varied from greenschist (300 °C at <3 kbar) to amphibolite (650 °C at 4 kbar) facies. Metamorphism probably occurred in a thermal dome. The data suggest a moderately deformed basement–cover relation between the Pleasant Bay and Jumping Brook complexes.

Upper Placentian—Branchian series of mainland Nova Scotia (middle-upper Lower Cambrian): Faunas, paleoenvironments, and stratigraphic revision

1995 ◽  
Vol 69 (3) ◽  
pp. 475-495 ◽  
Author(s):  
Ed Landing
Keyword(s):  
Nova Scotia ◽  
Lower Cambrian ◽  
Preliminary Evidence ◽  
Middle Cambrian ◽  
Cape Breton Island ◽  
Cape Breton ◽  
History Of ◽  
Placentia Bay ◽  
Stratigraphic Nomenclature ◽  
Eastern Massachusetts

Lithostratigraphy and depositional and epeirogenic history of the upper Placentian Series (Cuslett-Fosters Point Formations of the Bonavista Group) and Branchian Series (Brigus Formation) are identical in the northern Antigonish Highlands; Cape Breton Island; and eastern Placentia Bay, southeastern Newfoundland. Preliminary evidence suggests that the lower Middle Cambrian is present in the field area. A unified, uppermost Precambrian–Lower Cambrian, formation- and member-level nomenclature is appropriate to Avalonian North America, and the stratigraphic nomenclature of southeastern Newfoundland is applied in northern mainland Nova Scotia.Latest Placentian shoaling and deposition of a peritidal carbonate lithosome and unconformable onlap of the trilobite-bearing Branchian Series occurred in shallow Avalonian shale basins from eastern Massachusetts to central England.Uppermost Placentian Series faunas are very diverse in the Fosters Point Formation. Limited similarities with the South Australian Lower Cambrian are indicated by the presence of Camenella sp. cf. C. reticulosa, Conotheca australiensis, and Hyptiotheca sp., but these forms do not contribute to highly resolved correlation.Twenty-eight taxa are illustrated from the upper Placentian and Branchian Series. Caveacus rectus n. gen. and sp., a phosphatic problematicum, is limited to the upper Placentian Series. The oldest, skeletalized, macrophagous predators are the Pseudoconodontida and the later appearing Protoconodontida (n. orders). The Pseudoconodontida includes the Protohertzinacea n. superfamily and Strictocorniculacea n. superfamily (with the Rhombocorniculidae and Strictocorniculidae n. families). Strictocorniculum vanallerum n. gen. and sp. is described. The tommotiid family Sunnaginiidae emend. includes Eccentrotheca, Sunnaginia, Kulparina, and Jayceia deltiformis n. gen. and sp.

scholarly journals Granitoid plutons in peri-Gondwanaan terranes of Cape Breton Island, Nova Scotia, Canada: new U-Pb (zircon) age constraints

2018 ◽  
pp. 021-080 ◽  
Author(s):  
Sandra M. Barr ◽  
Deanne Van Rooyen ◽  
Chris E. White
Keyword(s):  
Tectonic Setting ◽  
Magmatic Activity ◽  
Zircon Age ◽  
Cape Breton Island ◽  
The Past ◽  
Late Cambrian ◽  
Cape Breton ◽  
History Of ◽  
Tectonic Settings ◽  
Age Constraints

Granitoid plutons are a major component of pre-Carboniferous rocks in Cape Breton Island and knowledge of the time and tectonic setting of their emplacement is crucial for understanding the geological history of the island, guiding exploration for granite-related economic mineralization, and making along-orogen correlations. The distribution of these plutons and their petrological characteristics have been used in the past for recognizing both Laurentian and peri-Gondwanan components in Cape Breton Island, and for subdividing the peri-Gondwanan components into Ganderian and Avalonian terranes. However, ages of many plutons were assumed on the basis of field relations and petrological features compared to those of the relatively few reliably dated plutons. Seventeen new U–Pb (zircon) ages from igneous units reported here provide enhanced understanding of the distribution of pluton ages. Arc-related plutons in the Aspy terrane with ages of ca. 490 to 475 Ma likely record the Penobscottian tectonomagmatic event recognized in the Exploits subzone of central Newfoundland and New Brunswick but not previously recognized in Cape Breton Island. Arc-related Devonian plutonic activity in the same terrane is more widespread, continuous, and protracted (445 Ma to 395 Ma) than previously known. Late Devonian magmatism in the Ganderian Aspy terrane is similar in age to that in the Avalonian Mira terrane (380 to 360 Ma) but the tectonic settings are different. In contrast, magmatic activity in the Bras d’Or terrane is almost exclusively arc-related in the Late Ediacaran (580 to 540 Ma) and rift-related in the Late Cambrian (520 to 490 Ma). The new data support the terrane distinctions previously documented.

Paleomagnetism of the Late Precambrian Fourchu Group, Cape Breton Island, Nova Scotia

1986 ◽  
Vol 23 (11) ◽  
pp. 1673-1685 ◽  
Author(s):  
Rex J. E. Johnson ◽  
Rob Van der Voo
Keyword(s):  
Nova Scotia ◽  
Eastern Cape ◽  
Early Paleozoic ◽  
Cape Breton Island ◽  
Late Precambrian ◽  
Cape Breton ◽  
Younger Age ◽  
Recent Origin ◽  
Gabbroic Intrusion ◽  
Dual Polarity

Volcanogenic sediments of the Fourchu Group and a gabbroic intrusion, which are found in the Avalonian terrane of south-eastern Cape Breton Island, have been sampled for paleomagnetic analysis. Upon detailed thermal and alternating-field demagnetization, three often-superimposed components of magnetization are obtained. One of these is aligned with the present-day geomagnetic field direction in Nova Scotia and is assumed to be of recent origin. The second group of directions is south-southeasterly and shallow, is postfolding in age, and is inferred to represent a Carboniferous overprint. The third direction, carried almost always by hematite, is also postfolding and yields a dual-polarity mean direction to the northwest or south-east, with a fairly steep inclination (D = 132°, I = −63°). This last direction is not seen in Avalonian or other North American rocks of Devonian or younger age; it is, therefore, bracketed in age between the earliest folding of the rocks and the latest Silurian. Given that Taconic folding has not been reported for this area, we assume that this magnetization was introduced in the rocks during uplift and oxidation after an Avalonian folding phase. For the Avalon terrane of Nova Scotia, the available paleomagnetic data reveal a set of moderately high paleolatitudes for the Late Precambrian and early Paleozoic, in contrast to the near-equatorial values predicted for the area under the assumption that it remained fixed with respect to the craton. On the other hand, strong similarities exist between Avalonian paleolatitudes and those for Armorica and Gondwana; a tentative reconstruction is proposed in which Avalon is adjacent to Armorica and Gondwana in the Late Precambrian and early Paleozoic.

scholarly journals Remnants of Early Mesozoic basalt of the Central Atlantic Magmatic Province in Cape Breton Island, Nova Scotia, Canada

2017 ◽  
Vol 54 (4) ◽  
pp. 345-358 ◽  
Author(s):  
Chris E. White ◽  
Daniel J. Kontak ◽  
Garth J. DeMont ◽  
Douglas Archibald
Keyword(s):  
Nova Scotia ◽  
Tectonic Setting ◽  
Geochemical Data ◽  
Cape Breton Island ◽  
Cape Breton ◽  
Early Mesozoic ◽  
Central Atlantic Magmatic Province ◽  
Zeolite Formation ◽  
Newark Supergroup ◽  
Central Atlantic

Amygdaloidal basaltic flows of the Ashfield Formation were encountered in two drill holes in areas of positive aeromagnetic anomalies in the Carboniferous River Denys Basin in southwestern Cape Breton Island, Nova Scotia. One sample of medium-grained basalt yielded a plateau age of 201.8 ± 2.0 Ma, similar to the U–Pb and 40Ar/39Ar crystallization ages from basaltic flows and dykes in the Newark Supergroup. A second sample of zeolite-bearing basalt yielded a discordant age spectrum and a younger age of ca. 190 Ma, which is interpreted to date a widespread hydrothermal event related to zeolite formation. Whole-rock chemical data show that the Ashfield Formation basalt is low-Ti continental tholeiite, consistent with its within-plate tectonic setting. Chemically, it resembles basaltic flows in the Mesozoic Fundy and Grand Manan basins exposed in southern Nova Scotia and eastern New Brunswick and elsewhere in Central Atlantic Magmatic Province (CAMP). The age and geochemical data from the Ashfield Formation provide the first evidence for early Mesozoic CAMP volcanism in Cape Breton Island and demonstrate that the event was more widespread in Nova Scotia than previously thought, which has implications for its continuity and extent elsewhere within CAMP.

Geochemistry and tectonic setting of late Precambrian volcanic and plutonic rocks in southeastern Cape Breton Island, Nova Scotia

1993 ◽  
Vol 30 (6) ◽  
pp. 1147-1154 ◽  
Author(s):  
Sandra M. Barr
Keyword(s):  
Subduction Zone ◽  
Continental Margin ◽  
Tectonic Setting ◽  
Volcanic Arc ◽  
Cape Breton Island ◽  
Late Precambrian ◽  
Cape Breton ◽  
Coastal Belt ◽  
Plutonic Rocks ◽  
Mountain Belts

Late Precambrian volcanic–sedimentary belts in the Mira (Avalon) terrane of southeastern Cape Breton Island display differences in rock types, petrochemistry, and age, showing that they did not form contemporaneously above a single northwest-dipping subduction zone, as proposed in earlier models. The oldest rocks are 680 Ma mafic and felsic flows and tuffs, and abundant, mainly tuffaceous, sedimentary rocks in the Stirling belt. They are interpreted to have formed in a trough within or peripheral to a volcanic-arc complex. Northwest of the Stirling belt, the East Bay Hills, Coxheath Hills, and Sporting Mountain belts consist of ca. 620 Ma mafic to felsic subaerial pyroclastic rocks and flows and contemporaneous dioritic to granitic plutons. Both volcanic and plutonic rocks are calc-alkalic to high-K calc-alkalic suites, formed in a continental margin volcanic arc. A correlative 620 Ma plutonic suite intruded the western margin of the Stirling belt, suggesting that subduction may have been toward the present southeast. The ca. 575 Ma Coastal belt, located southeast of the Stirling belt, is significantly younger than the other belts and appears to represent a less evolved calc-alkalic to low-K continental margin volcanic-arc and intra-arc basin formed above a northwest-dipping subduction zone. These various volcanic–sedimentary belts were juxtaposed by lateral movements along major faults in the late Precambrian to form this part of the Avalon composite terrane. Subduction-related, calc-alkalic magmatism at ca. 620 Ma was apparently widespread throughout the Avalon terrane of the northern Appalachian Orogen. However, ca. 680 Ma magmatism like that in the Stirling belt has been documented elsewhere only in the Connaigre Bay Group of Newfoundland. Circa 575 Ma and younger subduction-generated igneous activity like that in the Coastal belt has been recognized in southern New Brunswick, but alkaline magmas were forming in extensional regimes in other areas of the Avalon terrane at that time.

Contrasting U–Pb ages from plutons in the Bras d'Or and Mira terranes of Cape Breton Island, Nova Scotia

1990 ◽  
Vol 27 (9) ◽  
pp. 1200-1208 ◽  
Author(s):  
S. M. Barr ◽  
G. R. Dunning ◽  
R. P. Raeside ◽  
R. A. Jamieson
Keyword(s):  
Nova Scotia ◽  
Close Similarity ◽  
Zircon Age ◽  
Middle Cambrian ◽  
Cape Breton Island ◽  
Early Ordovician ◽  
Late Precambrian ◽  
Cape Breton ◽  
Devonian Age

U–Pb dates from zircon, titanite, and monazite in plutons of the Bras d'Or and Mira terranes of southern Cape Breton Island, combined with 40Ar/39Ar and other radiometric age data, indicate that the Bras d'Or and Mira terranes had separate magmatic and metamorphic histories until at least the Middle Cambrian and possibly until the Devonian. The Bras d'Or Terrane is characterized by abundant late Precambrian (ca. 565–555 Ma) dioritic to granitic plutons, as exemplified by the Shunacadie granodiorite ([Formula: see text], U–Pb zircon). Early Ordovician granitic plutons, such as the Kellys Mountain leucogranite with a U–Pb (zircon) age of 498 ± 2 Ma, occur locally. Titanite and 40Ar/39Ar (hornblende) ages from plutons and metamorphic units suggest that widespread metamorphism may have occurred between these plutonic events and (or) during the Early Ordovician plutonism.Plutons in the Mira Terrane appear to have been emplaced at about 620 Ma or before, as exemplified by the Chisholm Brook granodiorite ([Formula: see text]), and to have been unaffected by younger thermal events, as indicated by close similarity of U–Pb (zircon and titanite) and 40Ar/39Ar (hornblende) ages. Plutons of Devonian age are localized in an easterly trending belt in the central part of the terrane. In contrast to the Bras d'Or Terrane, widespread latest Precambrian (ca. 565–555 Ma) to Early Ordovician plutonism and metamorphism appear to have been absent. It is unlikely that the Mira and Bras d'Or terranes were juxtaposed before the Early Ordovician.

Sign in / Sign up

Export Citation Format

Share Document