U – Pb zircon date from Avalonian Cape Breton Island and geochronologic calibration of the Early Ordovician

A U–Pb zircon date of 483 ± 1 Ma is recorded from an uppermost Tremadoc K-bentonite from the Chesley Drive Group on McLeod Brook, eastern Cape Breton Island. The associated fauna, with the trilobite Peltocare rotundifrons, is also known from the Reversing Falls section in Saint John, New Brunswick, and the traditional reference of the latter section to the Arenig is incorrect. A 483 ± 1 Ma age is significantly older than a U – Pb zircon age reported from the classical base of the Arenig Series in north Wales and about 10 Ma older than strata regarded herein as upper Arenig in central Newfoundland. If the global standard for the base of the Arenig is defined at the Tetragraptus approximatus Zone base, then the base of the type Arenig in Wales is younger than the latter horizon. The McLeod Brook occurrence is from an uppermost Tremadoc (Hunnebergian Stage) interval that has been removed below the unconformity in north Wales. The age of the Tremadoc –Arenig series boundary remains uncertain; however, a tentative estimate that it is significantly younger than 483 Ma is suggested by fossil evidence.

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

Geological Magazine ◽

10.1017/s0016756800003769 ◽

2000 ◽

Vol 137 (2) ◽

pp. 137-153 ◽

Cited By ~ 13

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.

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

Canadian Journal of Earth Sciences ◽

10.1139/e90-127 ◽

1990 ◽

Vol 27 (9) ◽

pp. 1200-1208 ◽

Cited By ~ 27

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.

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

The Canadian Field-Naturalist ◽

10.22621/cfn.v127i4.1514 ◽

2014 ◽

Vol 127 (4) ◽

pp. 332 ◽

Cited By ~ 2

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.

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

Canadian Journal of Earth Sciences ◽

10.1139/e09-013 ◽

2009 ◽

Vol 46 (3) ◽

pp. 169-180 ◽

Cited By ~ 7

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.

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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

Canadian Journal of Earth Sciences ◽

10.1139/e17-013 ◽

1997 ◽

Vol 34 (2) ◽

pp. 156-168 ◽

Cited By ~ 10

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.

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

Atlantic Geology ◽

10.4138/atlgeol.2018.002 ◽

2018 ◽

pp. 021-080 ◽

Cited By ~ 5

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.

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

Géographie physique et Quaternaire ◽

10.7202/033034ar ◽

2007 ◽

Vol 49 (1) ◽

pp. 141-162 ◽

Cited By ~ 7

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.

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