The age of igneous and metamorphic events in the western Cape Breton Highlands, Nova Scotia

1986 ◽  
Vol 23 (12) ◽  
pp. 1891-1901 ◽  
Author(s):  
R. A. Jamieson ◽  
O. van Breemen ◽  
R. W. Sullivan ◽  
K. L. Currie
Keyword(s):  
Metamorphic Rocks ◽  
Western Cape ◽  
Cape Breton Island ◽  
Late Proterozoic ◽  
The North ◽  
Cape Breton ◽  
Gneiss Complex ◽  
Form Part ◽  
Plutonic Rocks ◽  
High Level

Plutonic rocks of four different ages have been recognized in the Cape Breton Highlands on the basis of U–Pb dating of zircons. Two plutons, the North Branch Baddeck River leucotonalite [Formula: see text] and the Chéticamp pluton (550 ± 8 Ma), give dates that fall within the range of Late Proterozoic to Cambrian ages considered characteristic of the Avalon tectonostratigraphic zone of the eastern Appalachians. Late Ordovician to Silurian tonalite (Belle Côte Road orthogneiss, 433 ± 20 Ma) was metamorphosed, deformed, and incorporated into the central Highlands gneiss complex by approximately 370–395 Ma. High-level subvolcanic plutons (Salmon Pool pluton, [Formula: see text]) postdate all metamorphic rocks in the area. The presence of the older plutons is consistent with interpretation that the Cape Breton Highlands form part of the Avalon zone, but the presence of Ordovician–Silurian plutonic rocks and Devonian amphibolite-facies metamorphism is anomalous in comparison with the Avalon zone of Newfoundland and southeastern Cape Breton Island. Terranes with similar Late Proterozoic to mid-Paleozoic plutonic and metamorphic histories form a discontinuous belt along the northwest side of the Avalon zone southwest of Cape Breton Island. These rocks probably reflect events during and after the accretion of the Avalon zone to North America.

Late Devonian – Early Carboniferous volcanism in western Cape Breton Island, Nova Scotia

1984 ◽  
Vol 21 (7) ◽  
pp. 762-774 ◽  
Author(s):  
Marie-Claude Blanchard ◽  
Rebecca A. Jamieson ◽  
Elizabeth B. More
Keyword(s):  
Tectonic Setting ◽  
Early Carboniferous ◽  
Alluvial Fan ◽  
Late Devonian ◽  
Fluvial Sediments ◽  
Western Cape ◽  
Cape Breton Island ◽  
The North ◽  
Cape Breton ◽  
Geochemical Studies

The Fisset Brook Formation of western Cape Breton Island and its equivalents at MacMillan Mountain and the north Baddeck River are examples of Late Devonian and Early Carboniferous volcanic sequences associated with the formation of post-Acadian successor basins in the northeastern Appalachians. They consist of bimodal basalt–rhyolite suites interbedded with alluvial fan, lacustrine, and rare fluvial sediments. The earliest volcanic products are rhyolites and somewhat evolved basalts associated with coarse sediments, followed by tholeiitic to transitional basalt flows interlayered with lacustrine-type deposits. Geochemical studies on the Fisset Brook Formation indicate extensive remobilization of alkalies, Ca, Rb, and Sr, making these elements inappropriate for determining tectonic setting or magmatic affinity. Use of less mobile elements (Ti, Nb, Y, and Zr) suggests that the basalts are tholeiitic and that the apparent alkalinity of the type section lavas is a result of alteration. We conclude that volcanism in western Cape Breton Island started at MacMillan Mountain and migrated westwards, probably towards the centre of the deepening Magdalen Basin.

The Cheticamp pluton: a Cambrian granodioritic intrusion in the western Cape Breton Highlands, Nova Scotia

1986 ◽  
Vol 23 (11) ◽  
pp. 1686-1699 ◽  
Author(s):  
Sandra M. Barr ◽  
Alan S. Macdonald ◽  
John Blenkinsop
Keyword(s):  
Nova Scotia ◽  
Chemical Compositions ◽  
Western Cape ◽  
Fractionation Process ◽  
Cape Breton Island ◽  
Stratigraphic Unit ◽  
The North ◽  
Rock Types ◽  
Cape Breton ◽  
Appalachian Orogen

The Cheticamp pluton consists of biotite granodiorite (locally megacrystic) in the north and museovite–biotite granodiorite in the south, in probable faulted contact. These two rock types, especially the biotite granodiorite, show a broad range in modal and chemical compositions. They are interpreted to be cogenetic, with the museovite–biotite grandiorite derived from the biotite granodiorite by crystal fractionation involving mafic minerals, plagioclase, and sphene. The overall peraluminous composition of the suite resulted from the fractionation process, probably enhanced by alteration, rather than from derivation from peraluminous source rocks.A seven-point, whole-rock, Rb–Sr isochron indicates an age of 525 ± 40 Ma. The pluton intruded dioritic rocks and quartzo-feldspathic gneisses, thus indicating Precambrian ages for these units. It probably also postdates the Western Highlands volcanic–sedimentary complex, a major undated stratigraphic unit in the Cape Breton Highlands. Although the age overlaps the range of Rb–Sr ages from plutons of the Avalon Terrane of the Appalachian orogen, the geological setting of the Cheticamp pluton differs from that of true Avalonian plutons, such as those in southeastern Cape Breton Island.

Geophysical modeling of Devonian plutons in the southern Gulf of St. Lawrence: implications for Appalachian terrane boundaries in Maritime Canada

2007 ◽  
Vol 44 (11) ◽  
pp. 1551-1565 ◽  
Author(s):  
Lori A Cook ◽  
Sonya A Dehler ◽  
Sandra M Barr
Keyword(s):  
Magnetic Anomaly ◽  
Prince Edward Island ◽  
Sedimentary Cover ◽  
Complex Structure ◽  
Physical Property ◽  
Gravity Anomalies ◽  
The South ◽  
Cape Breton Island ◽  
The North ◽  
Cape Breton

A prominent positive magnetic anomaly spans the 100 km distance between Prince Edward Island and Cape Breton Island in the southern Gulf of St. Lawrence. The anomaly occurs in an area of complex structure where Appalachian terrane boundaries are poorly resolved because of thick late Paleozoic sedimentary cover. Analysis of the magnetic anomaly led to the interpretation that it is produced by four separate, approximately circular, source bodies aligned along the northwesterly trend of the anomaly. Seismic data, physical property measurements, and magnetic and gravity anomalies were used to further investigate the anomaly sources through forward modeling techniques. The four source bodies have densities and magnetic susceptibilities compatible with dioritic to granitic compositions. Modeling also suggests that basement to the north of the plutons has higher density and susceptibility than basement to the south, and hence the source bodies are interpreted as plutons emplaced along the boundary between Ganderian composite terranes to the north and the Ganderian Brookville – Bras d’Or terrane to the south. This interpretation suggests that the Ganderia–Avalonia boundary is located farther south, and shows the need for re-evaluation of the location and role of the Canso fault in offsetting terranes between Cape Breton Island and southern New Brunswick.

Ephelota sp., a Suctorian found on the euphausiid Meganyctiphanes norvegica

1984 ◽  
Vol 62 (4) ◽  
pp. 744-746 ◽  
Author(s):  
Stephen Nicol
Keyword(s):  
Bay Of Fundy ◽  
Cape Breton Island ◽  
Cape Breton ◽  
Meganyctiphanes Norvegica ◽  
High Level

Examination of specimens of the euphausiid Meganyctiphanes norvegica from surface swarms in the Bay of Fundy revealed the presence of a suctorian epibiont, subsequently identified as Ephelota sp. Between 8 and 82% of the euphausiids in samples from surface swarms in the Bay of Fundy and off Cape Breton Island were found to be infested by this epibiont. In contrast, in samples taken at depth offshore, less than 2% of the euphausiids were infested. Since the animals constituting the surface swarms were old, mature euphausiids, it is hypothesized that the high level of infestation may be due to either senility or to a delayed ecdysis in reproductive animals. This record is of interest since it is only the fifth type of epibiont reported on euphausiids.

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.

Allerød–Younger Dryas Coleoptera from western Cape Breton Island, Nova Scotia, Canada

1996 ◽  
Vol 33 (1) ◽  
pp. 33-41 ◽  
Author(s):  
Randall F. Miller
Keyword(s):  
Nova Scotia ◽  
Younger Dryas ◽  
Late Glacial ◽  
Cold Climate ◽  
Western Cape ◽  
Cape Breton Island ◽  
Cape Breton ◽  
Beetle Assemblages ◽  
Climate Indicator ◽  
Younger Dryas Event

Studies of Coleoptera remains from two late-glacial sites on Cape Breton Island, Nova Scotia, Canada, present a picture of the paleoenvironment and paleoclimate during the Allerød–Younger Dryas transition in the Maritimes region. They provide evidence for the Younger Dryas event in northeastern North America. Between 11 300 and 10 800 BP, the beetle assemblages at the Campbell site are typical of faunas of the modern middle to northern boreal forest. The West Mabou site contains beetle fossils younger than 10 900 BP, possibly as young as 10 500 BP, extending into the time period of the Younger Dryas, dated from 10 800 to 10 000 BP in the Maritimes. A "cold climate" indicator recognizable in the beetle fauna, Olophrum boreale, occurs in relative abundance and provides an interesting comparison with sites in Europe where the same northern boreo-montane species is evident at the beginning of the Younger Dryas.

Tremadocian (Lower Ordovician) sea-level changes and biotas on the Avalon microcontinent

2011 ◽  
Vol 85 (4) ◽  
pp. 678-694 ◽  
Author(s):  
ED Landing ◽  
Richard A. Fortey
Keyword(s):  
Sea Level ◽  
Sea Level Changes ◽  
Low Oxygen ◽  
Cape Breton Island ◽  
Lower Upper ◽  
The North ◽  
Cape Breton ◽  
Lower Ordovician ◽  
Bottom Waters ◽  
History Of

The Chesley Drive Group, an Upper Cambrian-Lower Ordovician mudstone-dominated unit, is part of the Ediacaran–Ordovician cover sequence on the North American part of the Avalon microcontinent. The upper Chesley Drive Group on McLeod Brook, Cape Breton Island (previously “McLeod Brook Formation”), has two lithofacies-specific Tremadocian biotas. An older low-diversity benthic assemblage (shallow burrowers, Bathysiphon, phosphatic brachiopods, asaphid trilobites) is in lower upper Tremadocian green-gray mudstone. This wave-influenced, slightly dysoxic facies has Bathysiphon–brachiopod shell lags in ripple troughs. The upper fauna (ca. 483 +/- 1 Ma) is in dysoxic-anoxic (d-a), unburrowed, dark gray-black, upper upper (but not uppermost) Tremadocian mudstone with a “mass kill” of the olenid Peltocare rotundifrons (Matthew)—a provincial trilobite in Avalonian North America that likely tolerated low oxygen bottom waters. Scandodus avalonensis Landing n. sp. and Lagenochitina aff. conifundus (Poumot), probable nektic elements and the first upper Tremadocian conodont and chitinozoan reported from Avalon, occur in diagenetic calcareous nodules in the dark gray-black mudstone. An upper Tremadocian transition from lower greenish to upper black mudstone is not exposed on McLeod Brook, but is comparable to a coeval green-black mudstone transition in Avalonian England. The successions suggest that late late Tremadocian (probable Baltic Hunnebergian Age) sea level was higher in Avalon than is suggested from successions on other paleocontinents. The Tremadocian sea-level history of Avalon was a shoaling-deepening-shoaling sequence from d-a black mudstone (lower Tremadocian), to dysoxic green mudstone (lower upper Tremadocian), and back to black mudstone (upper upper Tremadocian).Scandodus Lindström is emended, with the early species S. avalonensis Landing n. sp. assigned to the emended Family Protopanderodontidae. Triangulodus Van Wamel is considered a junior synonym of Scandodus. Peltocare rotundifrons is emended on the basis of complete specimens.

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