Contrasts in late Precambrian-early Paleozoic tectonothermal history between Avalon composite terrane sensu stricto and other possible peri-Gondwanan terranes in southern New Brunswick and Cape Breton Island, Canada

1996 ◽  
pp. 95-108 ◽  
Author(s):  
Sandra M. Barr ◽  
Chris E. White
Keyword(s):  
New Brunswick ◽  
Sensu Stricto ◽  
Early Paleozoic ◽  
Cape Breton Island ◽  
Late Precambrian ◽  
Cape Breton

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.

Nd isotopic compositions of felsic igneous rocks in Cape Breton Island, Nova Scotia

1992 ◽  
Vol 29 (4) ◽  
pp. 650-657 ◽  
Author(s):  
Sandra M. Barr ◽  
Ernst Hegner
Keyword(s):  
New Brunswick ◽  
Small Variation ◽  
Igneous Rocks ◽  
Northwestern Part ◽  
Isotopic Data ◽  
Cape Breton Island ◽  
Late Precambrian ◽  
Cape Breton ◽  
Depleted Mantle ◽  
Juvenile Crust

Nd isotopic data from 18 felsic plutonic and volcanic units in Cape Breton Island show variations consistent with other geological and geophysical evidence for at least three distinct terranes. A ca. 1.2 Ga syenite considered to be part of Grenvilleage basement exposed in the northwestern part of the island yields an initial εNd value of +0.4 and a depleted-mantle model age (TDM) of 1.66 Ga, suggesting substantial involvement of older (Archean or Early Proterozoic) crust in its petrogenesis. A TDM of 1.38 Ga indicated by Nd isotopic data for a Devonian granite spatially associated with the syenite is also consistent with the presence of older crust in that part of Cape Breton Island. In contrast, Silurian rhyolite and Devonian granites from the Aspy terrane have TDM ranging from 0.7 to 1.1 Ga and initial εNd between +2.8 and −1.2, and overlap in isotopic characteristics with late Precambrian and Early Ordovician plutons in the Bras d'Or terrane that yield TDM of 0.9–1.1 Ga and initial εNd of +1.4 to −1.8. The relatively small variation in εNd and TDM in these terranes suggests that old crust like that under the Blair River Complex may not be present. Granitic plutons and rhyolite in the Mira terrane of southeastern Cape Breton Island have a range in TDM (0.8–1.2 Ga) similar to that of the Aspy and Bras d'Or terranes, but initial εNd values ranging from +0.8 to +5.0 indicate more juvenile crust. This juvenile crust also appears to be present under southern New Brunswick and eastern Newfoundland and may be characteristic of the Avalon terrane.

Nd isotopic characteristics of terranes within the Avalon Zone, southern New Brunswick

2000 ◽  
Vol 37 (7) ◽  
pp. 1039-1052 ◽  
Author(s):  
Scott D Samson ◽  
Sandra M Barr ◽  
Chris E White
Keyword(s):  
New Brunswick ◽  
Sedimentary Rocks ◽  
Sensu Stricto ◽  
Head Group ◽  
Isotopic Data ◽  
Cape Breton Island ◽  
Cape Breton ◽  
Depleted Mantle ◽  
Clastic Sedimentary ◽  
Nd Isotopic Composition

Nd isotopic data are presented for rock units in four terranes within the traditional Avalon Zone of southern New Brunswick. Initial εNd values for igneous rocks within the Caledonia terrane range from -1.6 to +4.6, whereas values for sedimentary rocks range from -8.4 to +3.6. A granite within the Kingston terrane has εNd(438 Ma) = +4.0. Nd isotopic compositions for the Kingston and Caledonia terranes are similar to those of the Mira terrane in Cape Breton Island, the Antigonish Highlands of Nova Scotia, and plutonic rocks of eastern Newfoundland. Each of these regions may be a dismembered part of a single terrane, the Avalon terrane sensu stricto. Initial εNd values for rocks from the Brookville terrane range from -1.3 to +2.8. The Coverdale anorthosite within the Brookville terrane has a present day εNd value of -12.1 and a depleted mantle model age of 1.3 Ga, similar to Mesoproterozoic anorthosites in Laurentia. Clastic sedimentary rocks in the Green Head Group have εNd(750 Ma) values of -2.0 and -10.9. Viewed as a whole, the Brookville terrane is isotopically more evolved than the Caledonia terrane. Initial εNd values for rocks in the New River terrane range from -2.9 to 0.0. The Nd isotopic composition of the Brookville and New River terranes are thus similar to one another and have isotopic character similar to that of the Bras d'Or terrane of Cape Breton Island. It is suggested that all three regions belong to a single terrane (Bras d'Oria).

scholarly journals New and noteworthy records of Orthoptera and allies in the Maritimes and the Îles-de-la-Madeleine, Quebec

2014 ◽  
Vol 127 (4) ◽  
pp. 332 ◽  
Author(s):  
Paul M. Catling ◽  
Donald F. McAlpine ◽  
Christopher I. G. Adam ◽  
Gilles Belliveau ◽  
Denis Doucet ◽  
...  
Keyword(s):  
Nova Scotia ◽  
New Brunswick ◽  
Prince Edward Island ◽  
Forficula Auricularia ◽  
Cape Breton Island ◽  
Cape Breton ◽  
La Madeleine

Chortophaga viridifasciata, Forficula auricularia, Melanoplus stonei, Scudderia furcata furcata, Scudderia pistillata, and Trimerotropis verruculata from Prince Edward Island and Doru taeniatum, Melanoplus punctulatus, Orchelimum gladiator, and Spharagemon bolli from New Brunswick are new provincial records. Other records of interest include the endemic Melanoplus madeleineae from Île d’Entrée in the Îles-de-la-Madeleine, Quebec; Trimerotropis verruculata from the Îles-de-la-Madeleine, Quebec; and Chortophaga viridifasciata, Stethophyma lineatum, and Tetrix subulata, new for Cape Breton Island, Nova Scotia. The ranges of Conocephalus brevipennis, Tetrix arenosa angusta, Tetrix ornata, and Tetrix subulata are significantly extended in New Brunswick. A previously unpublished record from 2003 of Roeseliana roeselii (Metrioptera roeselii) is the earliest report of this European introduction to the Maritimes.

Provenance of detrital muscovite in Cambrian Avalonia of Maritime Canada: 40Ar/39Ar ages and chemical compositions

2009 ◽  
Vol 46 (3) ◽  
pp. 169-180 ◽  
Author(s):  
Peter H. Reynolds ◽  
Sandra M. Barr ◽  
Chris E. White
Keyword(s):  
New Brunswick ◽  
Age Distribution ◽  
Chemical Compositions ◽  
Rock Unit ◽  
Original Source ◽  
Cape Breton Island ◽  
Cape Breton ◽  
Single Grain ◽  
Maritime Canada ◽  
Age Range

We report single-grain ages for detrital muscovite separated from sandstone samples from five localities in southern New Brunswick and southeastern Cape Breton Island, Nova Scotia, and from two quartzite clasts from a quartzite-pebble conglomerate that underlies the sampled sandstone units in New Brunswick. The oldest detrital grains were found in one of the quartzite clasts; their age range, ca. 650−630 Ma, is defined not only by the single-grain analyses but also by spot dating (using a UV laser) within a single large grain, suggesting that these grains came from a single source. The second quartzite clast has a blastomylonitic fabric with muscovite “fish,” and most of the muscovite ages have been partially reset (at ca. 550 Ma) from the original ca. 650–630 Ma ages. The age distribution plots obtained for the sandstone samples suggest the presence of muscovite that still retains the original source age, but most of the grains have been partially reset by the same ca. 550 Ma event that reset muscovite ages in the second quartzite clast. We suggest that the quartzite source that produced the two clasts was also the source of muscovite in the Avalonian Cambrian rocks of Maritime Canada. The original source rock was likely a metamorphic or perhaps granitic rock unit situated relatively proximal to the site of deposition of the quartzite protolith, but the actual source is not known, and locally, no potential candidates are exposed. The resetting event at ca. 550 Ma may be linked to initial stages of regional transtension associated with rifting of Avalonia from Gondwana.

40Ar/39Ar ages of detrital muscovite within Lower Cambrian and Carboniferous clastic sequences in northern Nova Scotia and southern New Brunswick: implications for provenance regions

1997 ◽  
Vol 34 (2) ◽  
pp. 156-168 ◽  
Author(s):  
R. D. Dallmeyer ◽  
J. D. Keppie ◽  
R. D. Nance
Keyword(s):  
Nova Scotia ◽  
New Brunswick ◽  
Lower Cambrian ◽  
Source Region ◽  
Regional Distribution ◽  
Coarse Grained ◽  
Cape Breton Island ◽  
Late Proterozoic ◽  
Cape Breton ◽  
Meguma Terrane

Detrital muscovite from lowermost Cambrian sequences exposed in the Avalon Composite Terrane in Nova Scotia and New Brunswick record 40Ar/39Ar plateau ages of ca. 625–600 Ma. These are interpreted to date times of cooling in source areas. The regional distribution of coarse-grained detrital muscovite in Lower Cambrian rocks of Avalonian overstep sequences suggests a source region of dimensions considerably larger than any presently exposed in Appalachian segments of the Avalon Composite Terrane. Late Proterozoic tectonic reconstructions locate the Avalon Composite Terrane adjacent to northwestern South America, thereby suggesting a possible source within Late Proterozoic PanAfrican – Brasiliano orogens. Detrital muscovite from clastic sequences of the proximally derived, Lower Carboniferous (Tournaisian) Horton Group and the more distal Upper Carboniferous (Westphalian D – Stephanian) Pictou Group in Nova Scotia records 40Ar/39Ar spectra that define plateau ages of ca. 390–380 Ma (Horton Group) and and ca. 370 Ma (Pictou Group). Finer grained fractions from samples of the Horton Group display more internally discordant age spectra defining total-gas ages of ca. 397–395 Ma. A provenance for the finer muscovite may be found in southern Nova Scotia where Cambrian–Ordovician turbidites of the Meguma Group display a regionally developed micaceous cleavage of this age. The ca. 390–380 Ma detrital muscovites probably were derived from granite stocks presently exposed in proximal areas of northernmost Cape Breton Island. A more distal source for the ca. 370 Ma detrital muscovites in the Pictou Group is suggested by its original extensive distribution, although a local, possibly recycled, source may also have been present. The presence of only 400–370 Ma detrital muscovite suggests a rapidly exhumed orogenic source with characteristics similar to those of crystalline rocks presently exposed in the Cape Breton Highlands and (or) the Meguma Terrane.

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.

scholarly journals Vegetation and Climate of Maritime Canada 6000 Years BP: A Synthesis

2007 ◽  
Vol 49 (1) ◽  
pp. 141-162 ◽  
Author(s):  
Hélène Jetté ◽  
Robert J. Mott
Keyword(s):  
New Brunswick ◽  
Prince Edward Island ◽  
Deciduous Forest ◽  
White Pine ◽  
Cape Breton Island ◽  
Cape Breton ◽  
Complete Sequences ◽  
Maritime Canada ◽  
High Elevations ◽  
Vegetation And Climate

ABSTRACT Environmental conditions (vegetation and climate) of Maritime Canada are reconstructed as a regional contribution to a national synthesis on the paleoenvironment of Canada 6000 yr BP. Ten new sites, including three complete sequences and seven short sequences bracketing the 6 ka period, are added to the existing pollen dataset for this region. The vegetation prevalent 6000 yr BP in New Brunswick was a mixed coniferous-deciduous forest with pine, mostly white pine (Pinus strobus) in the northwest, and a mixed coniferous-deciduous forest with hemlock (Tsuga canadensis) in the south and southeast. In the northwest, fir (Abies) replaced pine at high elevations and a boreal forest grew on the New Brunswick Highlands. The dominant vegetation at 6000 yr BP in Prince Edward Island and Nova Scotia was a mixed coniferous-deciduous forest with hemlock dominating. Cape Breton Island was covered by a mixed coniferous-deciduous forest with pine and/or fir, except for the southern part of the Island where hemlock was probably present. Analysis of the fossil sites indicate that a warm-dry period influenced the composition of the vegetation 6000 yr BP.

Superposed Neoproterozoic and Silurian magmatic arcs in central Cape Breton Island, Canada: geochemical and geochronological constraints

2000 ◽  
Vol 137 (2) ◽  
pp. 137-153 ◽  
Author(s):  
J. D. KEPPIE ◽  
J. DOSTAL ◽  
R. D. DALLMEYER ◽  
R. DOIG
Keyword(s):  
New Brunswick ◽  
New England ◽  
Volcanic Rocks ◽  
Geochemical Data ◽  
Zircon Age ◽  
Cape Breton Island ◽  
Northern Margin ◽  
Element Abundances ◽  
Southern New England ◽  
Cape Breton

Isotopic and geochemical data indicate that intrusions in the eastern Creignish Hills of central Cape Breton Island, Canada represent the roots of arcs active at ∼ 540–585 Ma and ∼ 440 Ma. Times of intrusion are closely dated by (1) a nearly concordant U–Pb zircon age of 553±2 Ma in diorites of the Creignish Hills pluton; (2) a lower intercept U–Pb zircon age of 540±3 Ma that is within analytical error of 40Ar/39 Ar hornblende plateau isotope-correlation ages of 545 and 550±7 Ma in the River Denys diorite; and (3) an upper intercept U–Pb zircon age of 586±2 Ma in the Melford granitic stock. On the other hand, ∼ 441–455 Ma 40Ar/39 Ar muscovite plateau ages in the host rock adjacent to the Skye Mountain granite provide the best estimate of the time of intrusion, and are consistent with the presence of granitic dykes cutting the Skye Mountain gabbro–diorite previously dated at 438±2 Ma. All the intrusions are calc-alkaline; the Skye Mountain granite is peraluminous. Trace element abundances and Nb and Ti depletions of the intrusive rocks are characteristic of subduction-related rocks. The ∼ 540–585 Ma intrusions form part of an extensive belt running across central Cape Breton Island, and represent the youngest Neoproterozoic arc magmas in this part of Avalonia. Nearby, they are overlain by Middle Cambrian units containing rift-related volcanic rocks, which bracket the transition from convergence to extension between ∼ 540 and 505/520 Ma. This transition varies along the Avalon arc: 590 Ma in southern New England, 560–538 Ma in southern New Brunswick, and 570 Ma in eastern Newfoundland. The bi-directional diachronism in this transition is attributed to northwestward subduction of two mid-ocean ridges bordering an oceanic plate, and the migration of two ridge–trench–transform triple points. Following complete subduction of the ridges, remnant mantle upwelling along the subducted ridges produced uplift, gravitational collapse and the high-temperature/low-pressure metamorphism in the arc in both southern New Brunswick and central Cape Breton Island. The ∼ 440 Ma arc magmatism in the Creignish Hills extends through the Cape Breton Highlands and into southern Newfoundland, and has recently been attributed to northwesterly subduction along the northern margin of the Rheic Ocean.

Geological correlations between Cape Breton Island and Newfoundland, northern Appalachian orogen

1998 ◽  
Vol 35 (11) ◽  
pp. 1252-1270 ◽  
Author(s):  
S M Barr ◽  
R P Raeside ◽  
C E White
Keyword(s):  
Sensu Stricto ◽  
Mobile Belt ◽  
Cape Breton Island ◽  
Small Areas ◽  
Isotopic Signatures ◽  
The North ◽  
Rock Types ◽  
Cape Breton ◽  
Appalachian Orogen ◽  
Back Arc

Geological correlations between Cape Breton Island and Newfoundland are apparent both in surface geology and at deeper crustal levels, based on similarities in Sm-Nd isotopic signatures. The Mira terrane of southeastern Cape Breton Island is part of the Avalon terrane sensu stricto and is composed of Neoproterozoic volcanic-sedimentary-plutonic belts and overlying Cambrian rocks directly comparable to those in the western part of the Newfoundland Avalon terrane. The Bras d'Or terrane is also mainly of Neoproterozoic age, but shows lithological and isotopic contrasts with the Mira terrane. Small areas of similar Neoproterozoic rocks occur in southern Newfoundland and to the north as inliers in the Exploits terrane. The Bras d'Or terrane and similar rocks in Newfoundland are interpreted to represent a peri-Gondwanan terrane where rocks of the Gander terrane were later formed. Hence this area is part of the Central Mobile Belt and distinct from Avalon terrane sensu stricto. The Aspy terrane is a complex area that may include fragments of Bras d'Or crust and components of the Gander, Exploits, and possibly Notre Dame terranes of Newfoundland. It formed by subduction and back-arc basin opening and closure during the Silurian to Early Devonian. The Blair River Inlier is a fragment of Grenvillian rocks, similar to those in the Grenvillian inliers in the Humber zone of western Newfoundland in terms of age, rock types, and isotopic composition. Silurian and Devonian promontory-promontory collision resulted in juxtaposition and stacking of these elements in Cape Breton Island, as in the Hermitage Flexure - Port aux Basques area of Newfoundland. Because the lower crust under Bras d'Or - Gander - Aspy terranes seems distinct from that under Avalon terrane sensu stricto, it is preferable to use the term peri-Gondwanan rather than Avalonian to refer to these areas.

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