Age of the Brookville Gneiss and associated rocks, southeastern New Brunswick

1982 ◽  
Vol 19 (11) ◽  
pp. 2158-2166 ◽  
Author(s):  
William J. Olszewski Jr. ◽  
Henri E. Gaudette
Keyword(s):  
New Brunswick ◽  
Source Area ◽  
Head Group ◽  
Low Grade ◽  
Tectonic Event ◽  
Cape Breton Island ◽  
Eastern Margin ◽  
Saint John ◽  
Loss Event ◽  
Single Zircon

The Brookville Gneiss is a medium- to high-grade quartz–feldspar–biotite and hornblende–quartz–feldspar–biotite gneiss found north and northeast of Saint John, New Brunswick. The Green Head Group, a sequence of low-grade metasediments, surrounds the Brookville Gneiss. Analyses of zircons with euhedral to subhedral overgrowths and rounded to subrounded cores from the Brookville Gneiss yield an upper intercept age on concordia of 1641 Ma, considered to be the age of the source area for the zircons. The zircon analyses also indicate two Pb-loss events at approximately 780 and 370 Ma. These ages are confirmed by zircon analyses of a quartz diorite gneiss from Green Head Island, which yields ages of 827 and 333 Ma. A small euhedral single zircon from the Brookville Gneiss, believed to be formed during metamorphism, gives a concordant age of 814 Ma corresponding to the first Pb-loss event. Rb–Sr whole-rock analyses of a granite from the east side of Musquash Harbour southwest of Saint John give an age of 392 Ma and an initial Sr ratio of 0.7187 substantiating the second Pb-loss event.The results indicate that the Brookville Gneiss and Green Head Group are older than 800 Ma and probably younger than 1200 Ma. The zircon source area age (1641 Ma) and first Pb-loss event (800 Ma) are similar to ages found in rocks of the eastern margin of the Appalachian orogen from Massachusetts and Cape Breton Island, respectively. They suggest a setting and tectonic event correlated in time for the Late Precambrian of the eastern margin distinct from the younger so-called "Avalonian."

The Stromatolite Archaeozoon acadiense from the Proterozoic Green Head Group of Saint John, New Brunswick

1974 ◽  
Vol 11 (8) ◽  
pp. 1098-1115 ◽  
Author(s):  
H. J. Hofmann
Keyword(s):  
New Brunswick ◽  
Tectonic Deformation ◽  
Head Group ◽  
Saint John

The columnar branching stromatolite Archaeozoon acadiense Matthew 1890 occurs in platy fault-slivers of a biohermal or biostromal limestone that accumulated on a shallow submerged platform, possibly during Neohelikian time. The columns show that the stromatolitic beds at Green Head face north, and can be used to provide a partial estimate of amount and type of local tectonic deformation. Archaeozoon Matthew has attributes similar to those for such Riphean groups as Tungussia, Baicalia and Jacutophyton, and it is likely that one or more of these are junior subjective synonyms of Archaeozoon, or represent at least morphologic variants.

On the inorganic character of Halichondrites graphitiferus Matthew, a supposed sponge from the Precambrian of Saint John, New Brunswick

1987 ◽  
Vol 24 (9) ◽  
pp. 1913-1915 ◽  
Author(s):  
Randall F. Miller
Keyword(s):  
New Brunswick ◽  
Head Group ◽  
Similar Nature ◽  
Saint John

Discovery of the holotype of Halichondrites graphitiferus Matthew in the collections of the New Brunswick Museum made it necessary to reexamine its affinity to the Porifera as first described by G. F. Matthew in 1890. Since its publication, the organic nature of H. graphitiferus has been questioned; however, the holotype has not been accessible until recent organization of the museum's collections. Examination of the holotype suggests the "spicules," described by Matthew from the Precambrian Green Head Group of Saint John, New Brunswick, are more likely a combination of scratches on the surface of the graphite and cleavage demonstrated by the mineral. Other "spicules" from Musquash Harbour, New Brunswick, are of a similar nature.

Discovery of the Holotype of Cyathospongia(?) eozoica Matthew, a supposed Precambrian sponge from Saint John, New Brunswick

1990 ◽  
Vol 27 (3) ◽  
pp. 473-475 ◽  
Author(s):  
Randall F. Miller
Keyword(s):  
New Brunswick ◽  
Head Group ◽  
Saint John

Discovery of the holotype of the supposed sponge Cyathospongia(?) eozoica Matthew in the collections of the New Brunswick Museum completes a search for two doubtful Precambrian "sponges" described by Matthew almost a century ago. The organic nature of C.(?) eozoica had been questioned almost since its publication in 1890, but the specimen had been inaccessible. Examination of the holotype of C.(?) eozoica suggests the "spicules" from the Green Head Group of Saint John are probably a boxwork-like weathering pattern and are not organic.

Tectonic implications of 40Ar/39Ar mineral ages from late Precambrian – Cambrian plutons, Avalon composite terrane, southern New Brunswick, Canada

1992 ◽  
Vol 29 (11) ◽  
pp. 2445-2462 ◽  
Author(s):  
R. David Dallmeyer ◽  
R. Damian Nance
Keyword(s):  
New Brunswick ◽  
Quartz Diorite ◽  
Head Group ◽  
Low Grade ◽  
Marine Strata ◽  
Metasedimentary Rocks ◽  
Late Precambrian ◽  
Sedimentary Sequences ◽  
Stratigraphic Record ◽  
Isotope Correlation

Within the Avalon composite terrane exposed in southern New Brunswick, late Precambrian, low-grade volcanic–sedimentary sequences are juxtaposed against late Precambrian gneisses (Brookville Gneiss) and older platformal metasedimentary rocks (Green Head Group) along the Caledonia Fault. Both assemblages host petrographically similar suites of calc-alkalic dioritic and granodioritic plutons. Those intruding volcanic–sedimentary sequences (Caledonia terrane) record ca. 615–625 Ma crystallization ages typical of arc-related magmatism throughout the Avalon composite terrane. However, 40Ar/39Ar age data from stocks intruding gneisses and platformal metasedimentary rocks (Brookville terrane) suggest significantly younger crystallization ages.36Ar/40Ar versus 39Ar/40Ar isotope correlation ages recorded by hornblende are interpreted to closely date postmagmatic cooling within six plutons: Fairville Granite (547 ± 1 Ma); French Village Quartz Diorite (539 ± 2 and 537 ± 1 Ma); Rockwood Park Granodiorite (529 ± 2 and 523 ± 3.5 Ma); Musquash Granite (526 ± 2 Ma); Milkish Head Granite (Red Bridge pluton, 520 ± 1.5 Ma); Lepreau Diorite (Talbot Road pluton, 519 ± 2 Ma and Hansen Stream pluton, 518 ± 1.5 Ma. A hornblende isotope correlation age of 530 ± 2 Ma from penetratively foliated amphibolite within the French Village Quartz Diorite suggests that the magmatic activity was locally accompanied by ductile shear. Muscovite within granitic pegmatite in the Brookville Gneiss records a 40Ar/39Ar plateau age of 510 ± 1 Ma interpreted to date final phases of associated magmatic activity.Arc-related magmatism extending into the Cambrian contrasts with the characteristic tectono-stratigraphic record in the Avalon composite terrane where late Precambrian igneous rocks are overstepped by Cambrian–Ordovician shallow-marine strata with only a local and minor record of rift-related volcanic activity. Although the Brookville terrane shows affinities with the Avalon composite terrane during the late Precambrian, the 40Ar/39Ar age data suggest that it was isolated as a distinct tectono-stratigraphic element by the Early Cambrian.

Trace-element mobility during low-grade metamorphism and silicification of basaltic rocks from Saint John, New Brunswick

1983 ◽  
Vol 20 (3) ◽  
pp. 431-435 ◽  
Author(s):  
J. Dostal ◽  
D. F. Strong
Keyword(s):  
New Brunswick ◽  
Rare Earths ◽  
Low Grade ◽  
Element Mobility ◽  
Upper Carboniferous ◽  
Basaltic Rocks ◽  
Trace Element Mobility ◽  
Saint John ◽  
Ree Patterns ◽  
Basaltic Lavas

Upper Carboniferous basaltic lavas from Saint John, New Brunswick were metamorphosed under prehnite–pumpellyite conditions and some were also affected by extensive silicification. Silicification led to simple dilution of relatively immobile elements such as rare earths, Y, Zr, Hf, Th, and Sc. The chondrite-normalized REE patterns of the silicified rocks are parallel to those of basalts.

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

1997 ◽  
Vol 34 (5) ◽  
pp. 724-730 ◽  
Author(s):  
Ed Landing ◽  
Samuel A. Bowring ◽  
Kathleen L. Davidek ◽  
Richard A. Fortey
Keyword(s):  
New Brunswick ◽  
Eastern Cape ◽  
Associated Fauna ◽  
Zircon Age ◽  
Cape Breton Island ◽  
Early Ordovician ◽  
Cape Breton ◽  
Fossil Evidence ◽  
North Wales ◽  
Saint John

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.

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).

Petrography and provenance of the Marambio Group, Vega Island, Antarctica

1994 ◽  
Vol 6 (4) ◽  
pp. 517-527 ◽  
Author(s):  
Duncan Pirrie
Keyword(s):  
Late Cretaceous ◽  
Sedimentary Rocks ◽  
Clay Mineralogy ◽  
Minor Component ◽  
Source Area ◽  
Low Grade ◽  
Western Margin ◽  
Sediment Input ◽  
A Minor ◽  
Sandstone Petrography

Late Cretaceous sedimentary rocks assigned to the Santa Marta (Herbert Sound Member) and López de Bertodano (Cape Lamb and Sandwich Bluff members) formations of the Marambio Group, crop out on Cape Lamb, Vega Island. Although previous studies have recognized that these sedimentary rocks were derived from the northern Antarctic Peninsula region, the work presented here allows the provenance and palaeogeographical evolution of the region to be described in detail. On the basis of both sandstone petrography and clay mineralogy, the Herbert Sound and Cape Lamb members reflect sediment input from a low relief source area, with sand grade sediment sourced from low grade metasediments, and clay grade sediment ultimately derived from the weathering of an andesitic source area. In contrast, the Sandwich Bluff Member reflects a switch to a predominantly andesitic volcaniclastic source. However, this sediment was largely derived from older volcanic suites due to renewed source area uplift, with only a minor component from coeval volcanism. Regional uplift of both the arc terrane and the western margin of the James Ross Basin was likely during the Maastrichtian.

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