Igneous and Tectonic Events in Northeastern Cape Breton Island, Nova Scotia

1972 ◽  
Vol 9 (10) ◽  
pp. 1262-1277 ◽  
Author(s):  
Robert A. Wiebe
Keyword(s):  
Subduction Zones ◽  
Coarse Grained ◽  
Island Arcs ◽  
Cape Breton Island ◽  
Cape Breton ◽  
Igneous Activity ◽  
Northern Cape ◽  
History Of ◽  
George River ◽  
Metamorphic Unit

The geology of northern Cape Breton Island is characterized by two structurally and compositionally distinct metamorphic units and an extended history of igneous activity ranging in age from Precambrian to Devonian. The older metamorphic unit (George River Group(?)) is composed of metamorphosed psammitic and semipelitic rocks with some distinctive quartzite and coarse-grained marble layers. It was deformed and probably metamorphosed, prior to emplacement of Precambrian diorites. A younger metamorphic unit (Fourchu Group(?)) consists mostly of metamorphosed intermediate to acidic volcanic and volcaniclastic rocks and rests with angular unconformity on the George River Group (?) and the diorites. Shallow-level plutonic activity was contemporaneous with the Fourchu Group(?). Younger leucocratic granodiorites (410 m.y.) were emplaced at a depth of about 15 km and require deposition of a thick surficial sequence during the early Paleozoic (between 560 and 410 m.y.). Mississippian sedimentary rocks rest unconformably on all of the older rocks.Igneous rocks of the Precambrian are dominantly andesitic and are similar to present-day suites in island arcs associated with subduction zones. Their composition requires that they be generated in the mantle. The average compositions of igneous rocks emplaced from late Precambrian to Devonian time become more granitic and probably reflect increasing generation of magma from crustal sources.

New U–Pb age constraints on the geological history of the Ganderian Bras d’Or terrane, Cape Breton Island, Nova Scotia

2019 ◽  
Vol 56 (8) ◽  
pp. 829-847 ◽  
Author(s):  
D. van Rooyen ◽  
S.M. Barr ◽  
C.E. White ◽  
M.A. Hamilton
Keyword(s):  
Detrital Zircon ◽  
Subduction Zones ◽  
Detrital Zircons ◽  
Passive Margin ◽  
Mountain Areas ◽  
Mountain Area ◽  
Cape Breton Island ◽  
Cape Breton ◽  
Amazonian Craton ◽  
History Of

The northern Appalachian orogen preserves evidence of a complex history of amalgamation of terranes with both Laurentian and Gondwanan affinities. The Ganderian Bras d’Or terrane of central Cape Breton Island is not well represented elsewhere in the orogen and its relationship to other Ganderian terranes is enigmatic, particularly with respect to its pre-Neoproterozoic history. The Boisdale Hills and Kellys Mountain areas contain the oldest metamorphic rocks in the Bras d’Or terrane. Quartzite units in the Boisdale Hills have detrital zircon populations with ages ranging from 3.2 to ca. 1 Ga. Paragneiss units from the Kellys Mountain area contain Meso- to Neoproterozoic detrital zircons, in which the youngest grains indicate that the maximum depositional age is <600 Ma. The detrital zircon populations of rocks from both areas are consistent with Gondwanan provenance for the protoliths, most likely the Amazonian craton. New U–Pb dates for subduction-related dioritic to granodioritic plutons in the Boisdale Hills yielded ages of 560 to ca. 540 Ma. Sedimentary, bimodal volcanic and plutonic rocks from the Bourinot belt in the Boisdale Hills and related plutons in the Kellys Mountain area have ages of ca. 510–490 Ma and are interpreted to have formed during extension related to separation of Ganderia from Gondwana. The southeastern Bras d’Or terrane preserves rocks formed in Pan-African subduction zones on a former passive margin of Gondwana as well as rocks formed during the initial stages of rifting of Ganderia from Gondwana and the subsequent opening of the Rheic Ocean.

Petrology, age, and tectonic setting of the rapakivi-bearing Margaree pluton, Cape Breton Island, Canada: evidence for a Late Devonian posttectonic cryptic silicic-mafic magma chamber

2020 ◽  
Vol 57 (9) ◽  
pp. 1011-1029
Author(s):  
Gabriel Sombini dos Santos ◽  
Sandra M. Barr ◽  
Chris E. White ◽  
Deanne van Rooyen
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
Magma Chamber ◽  
Magma Mixing ◽  
Tectonic Setting ◽  
Mafic Magma ◽  
Coarse Grained ◽  
Late Devonian ◽  
Cape Breton Island ◽  
Cape Breton

The Margaree pluton extends for >40 km along the axis of the Ganderian Aspy terrane of northern Cape Breton Island, Nova Scotia. The pluton consists mainly of coarse-grained megacrystic syenogranite, intruded by small bodies of medium-grained equigranular syenogranite and microgranite porphyry, all locally displaying rapakivi texture. The three rock types have similar U–Pb (zircon) ages of 363 ± 1.6, 364.8 ± 1.6, and 365.5 ± 3.3 Ma, respectively, consistent with field and petrological evidence that they are coeval and comagmatic. The rare earth elements display parallel trends characterized by enrichment in the light rare earth elements, flat heavy rare earth elements, moderate negative Eu anomalies, and, in some cases, positive Ce anomalies. The megacrystic and rapakivi textures are attributed to thermal perturbation in the magma chamber caused by the mixing of mafic and felsic magma, even though direct evidence of the mafic magma is mainly lacking at the current level of exposure. Magma evolution was controlled by fractionation of quartz, K-feldspar, and Na-rich plagioclase in molar proportions of 0.75:0.12:0.13. The chemical and isotopic (Sm–Nd) signature of the Margaree pluton is consistent with the melting of preexisting continental crust that was enriched in heat-producing elements, likely assisted by intrusion of mantle-derived mafic magma during Late Devonian regional extension. The proposed model involving magma mixing at shallow crustal levels in a cryptic silicic-mafic magma chamber during post-Acadian extension is consistent with models for other, better exposed occurrences of rapakivi granite in the northern Appalachian orogen.

The distribution, zoogeography, and composition of Prince Edward Island Carabidae (Coleoptera)

2008 ◽  
Vol 140 (1) ◽  
pp. 128-141 ◽  
Author(s):  
Christopher G. Majka ◽  
Yves Bousquet ◽  
Christine Noronha ◽  
Mary E. Smith
Keyword(s):  
Introduced Species ◽  
Prince Edward Island ◽  
Large Scale ◽  
Management Practices ◽  
Maritime Provinces ◽  
Cape Breton Island ◽  
History Of Collecting ◽  
Cape Breton ◽  
History Of ◽  
Faunal List

AbstractFourteen species of Carabidae are added to Prince Edward Island’s (P.E.I.) faunal list, bringing the known fauna to 167 species. Bembidion nitidum (Kirby) and Bembidion obtusum Audinet-Serville are newly recorded for the Maritime Provinces. Six species are removed from P.E.I.’s faunal list. The history of collecting of Carabidae on P.E.I. is briefly recounted. Despite differences in land area and distance from the mainland between P.E.I., Cape Breton Island, and insular Newfoundland, their carabid faunas exhibit many similarities in size and composition. The native carabid fauna of P.E.I. comprises 49% of the species in the combined Maritime Provinces fauna, perhaps reflecting an island-related diminution of species diversity. The proportion of flightless species on P.E.I. (4.9%) is less than that in the Maritime Provinces as a whole (7.1%), an apparent indication that the Northumberland Strait has been a barrier to colonization. Twenty-seven introduced species are found on P.E.I., 26 of which can be classified as synanthropic and may have originated in dry-ballast quarries in southwestern England. Although the earliest dates of detection of many introduced species on P.E.I. are substantially later than elsewhere in the Maritimes, this reflects the paucity of early collecting. Land-management practices on P.E.I. (large-scale and early forest clearances, intensive agriculture, and the extensive use of biocides) may have had an impact on P.E.I.’s carabid fauna.

scholarly journals Travelling in Time to Cape Breton Island in the 1920s: Protest Songs, Murals and Island Identity

2015 ◽  
Author(s):  
MacKinnon Richard ◽  
MacKinnon Lachlan
Keyword(s):  
Local History ◽  
Community Identity ◽  
Cultural Expression ◽  
Cape Breton Island ◽  
Cape Breton ◽  
Protest Songs ◽  
History Of ◽  
Steel Industries ◽  
Rich History

Islands are places that foster a unique sense of place-attachment and community identity among their populations. Scholarship focusing on the distinctive values, attitudes and perspectives of ‘island people’ from around the world reveals the layers of meaning that are attached to island life. Lowenthal writes: ‘Islands are fantasized as antitheses of the all-engrossing gargantuan mainstream-small, quiet, untroubled, remote from the busy, crowded, turbulent everyday scene. In reality, most of them are nothing like that. …’ 1 1 D. Lowenthal, ‘Islands, Lovers and Others’, The Geographical Review 97 (2007): 203. Islands, for many people, are ‘imagined places’ in our increasingly globalised world; the perceptions of island culture and reality often differ. Cape Breton Island, Nova Scotia, in eastern North America, a locale with a rich history of class struggle surrounding its former coal and steel industries, provides an excellent case study for the ways that local history, collective memory and cultural expression might combine to combat the ‘untroubled fantasy’ that Lowenthal describes.

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.

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.

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.

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.

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