scholarly journals The provenance of Jurassic and Lower Cretaceous clastic sediments offshore southwestern Nova Scotia

2017 ◽  
Vol 54 (1) ◽  
pp. 33-51 ◽  
Author(s):  
Dan-Cezar Dutuc ◽  
Georgia Pe-Piper ◽  
David J.W. Piper
Keyword(s):  
Nova Scotia ◽  
Deep Water ◽  
Lower Cretaceous ◽  
Middle Jurassic ◽  
Sedimentary Rocks ◽  
Petroleum Exploration ◽  
Ultramafic Rocks ◽  
Meguma Terrane ◽  
Clastic Sedimentary ◽  
Fundy Basin

Jurassic and Cretaceous sandstones in the Shelburne subbasin and Fundy Basin offshore Nova Scotia, are poorly known but are of current interest for petroleum exploration. The goal of this study is to determine the provenance of sandstones and shales, which will contribute to a better understanding of regional tectonics and paleogeography in the study area. Mineral and lithic clast chemistry was determined from samples from conventional cores and cuttings from exploration wells, using scanning electron microscopy and an electron microprobe. Whole-rock geochemical composition of shales was used to test the hypotheses regarding provenance of Mesozoic clastic sedimentary rocks in the SW Scotian Basin. Lower Jurassic clastic sedimentary rocks in the Fundy Basin contain magnetite, biotite, and chlorite, suggesting local supply from the North Mountain Basalt and Meguma Terrane, whereas pyrope and anthophyllite suggest small supply from distant sources. In the SW Scotian Basin, detrital minerals, lithic clasts, and shale geochemistry from Middle Jurassic to Early Cretaceous indicate a predominant Meguma Terrane source and transport by local rivers. Rare spinel and garnet grains of meta-ultramafic rocks, only in the Middle Jurassic at the Mohawk B-93 well, suggest minor supply from the rising Labrador rift, via the same river that transported distant sediments to the Fundy Basin. Lower Cretaceous sandstones from the Mohican I-100 well contain minor garnet, spinel, and tourmaline from meta-ultramafic rocks, characteristic of sediment supplied to the central Scotian Basin at that time. The dominant Meguma Terrane provenance precludes thick deep-water sandstones in the eastern part of the Shelburne subbasin, but the evidence of Middle Jurassic distant river supply through the Fundy Basin is encouraging for deep-water reservoir quality in the western part.

Ophiolitic mélange and its significance in the Fleur de Lys Supergroup, northern Appalachians

1977 ◽  
Vol 14 (5) ◽  
pp. 987-1003 ◽  
Author(s):  
Harold Williams
Keyword(s):  
Continental Margin ◽  
Full Range ◽  
Sedimentary Rocks ◽  
Ultramafic Rocks ◽  
Eastern North America ◽  
Plate Boundaries ◽  
Polyphase Deformation ◽  
Ophiolitic Mélange ◽  
Ophiolite Suite ◽  
Clastic Sedimentary

Ophiolitic mélange consists of a chaotic mixture of sedimentary rocks and igneous rocks derived from the ophiolite suite of rock units. Its formation involves surficial mass wastage, gravity sliding, and tectonism at consuming plate boundaries. Most worldwide examples relate to ophiolite obduction and the destruction of stable continental margins.The Fleur de Lys Supergroup of the northern Appalachians consists of polydeformed and metamorphosed, mainly clastic sedimentary rocks that accumulated at the Hadrynian to early Paleozoic stable continental margin of eastern North America. Greenschists at or near the top of the succession in the east (Birchy Complex) contain zones of typical ophiolitic mélange. These contain large blocks of serpentinized ultramafic rocks, actinolite–fuchsite alterations of smaller ultramafic blocks, altered gabbro, a variety of clastic sedimentary blocks, and marble. All of the rocks are multideformed and metamorphosed so that the mélange was subjected to the full range of Fleur de Lys deformations.The presence of polydeformed and metamorphosed ophiolitic mélange in the Fleur de Lys Supergroup implies an early disruption or imbrication of its rock units. This disruption and mélange formation are interpreted to be related to transport of ophiolite complexes such as the Bay of Islands Complex across an initially undisturbed continental rise prism, the Fleur de Lys Supergroup. Later polyphase deformation and metamorphism of the Fleur de Lys Supergroup are possible results of continued structural submergence and telescoping of the continental margin beneath a thick cover of transported ophiolite rock units.

Detrital muscovite geochronology and the Cretaceous tectonics of the inner Scotian Shelf, southeastern Canada 1This article is one of a series of papers published in this CJES Special Issue on the theme of Mesozoic–Cenozoic geology of the Scotian Basin. 2Geological Survey of Canada Contribution 20120142.

2012 ◽  
Vol 49 (12) ◽  
pp. 1558-1566 ◽  
Author(s):  
Peter H. Reynolds ◽  
Georgia Pe-Piper ◽  
David J.W. Piper
Keyword(s):  
Nova Scotia ◽  
Lower Cretaceous ◽  
Special Issue ◽  
Scotian Shelf ◽  
Single Grain ◽  
Meguma Terrane ◽  
Maritimes Basin ◽  
Uplift And Erosion

Geochronology of detrital muscovite from the Lower Cretaceous of the central Scotian Basin has shown predominant supply of Meguma terrane detritus, including muscovite with Alleghanian (mid-Carboniferous to Permian) ages from the inner Scotian Shelf. In this study, 87 detrital muscovite grains from five wells in the eastern Scotian Basin, representing depositional ages from Tithonian to Early Albian, were dated by single-grain 40Ar/39Ar techniques. Previous work shows that the provenance of this sediment was different from wells in the central Scotian Basin. Compared with the central Scotian Basin, the muscovite age populations from the eastern Scotian Basin have more (20% versus 7%) pre-Devonian ages, derived from inboard terranes of the Appalachians. In both the central and eastern Scotian Basin, most old grains are found in the Tithonian and the Aptian–Albian, with fewer in the Valanginian and almost none in the Kimmeridgian and the Hauterivian–Barremian. These data suggest rapid unroofing of the Meguma terrane in the Kimmeridgian and Hauterivian–Barremian and greater supply of sediment from Newfoundland to the eastern Scotian Basin in the Tithonian and Aptian–Albian. Compared with the central Scotian Basin, which has most ages in the range 340–300 Ma, the muscovite age populations from the eastern Scotian Basin have a higher proportion of 420–340 Ma and in particular 300–260 Ma ages. Such late Alleghanian overprinting of argon ages is very rare on land in Nova Scotia, but in the Maritimes Basin, this was the time of uplift and erosion of strata.

Geochemistry and tectonic discrimination of Late Proterozoic arc-related volcaniclastic turbidite sequences, Antigonish Highlands, Nova Scotia

1993 ◽  
Vol 30 (12) ◽  
pp. 2273-2282 ◽  
Author(s):  
J. Brendan Murphy ◽  
Deborah L. MacDonald
Keyword(s):  
Nova Scotia ◽  
Tectonic Setting ◽  
Volcanic Rocks ◽  
Sedimentary Rocks ◽  
Widespread Application ◽  
Isotopic Signatures ◽  
Late Proterozoic ◽  
Felsic Volcanic ◽  
Clastic Sedimentary ◽  
End Members

The Late Proterozoic (ca. 618–610 Ma) Georgeville Group of northern mainland Nova Scotia lies within the Avalon Composite Terrane and consists of subgreenschist- to greenschist-facies mafic and felsic volcanic rocks overlain by volcaniclastic turbidites that were deposited in an ensialic basin within a rifted volcanic arc. Geochronological data indicate that the volcanic and sedimentary rocks are coeval. The geochemical and isotopic signatures of the sedimentary rocks are attributed to erosion of the coeval Avalonian volcanic rocks that flank the basin and are consistent with synorogenic deposition. There is no evidence of significant chemical contribution from Avalonian basement.Knowledge of the tectonic setting facilitates the testing of published geochemical discriminant diagrams for clastic sedimentary rocks. Discrimination diagrams using ratios such as K2O/Na2O and Al2O3/(CaO + Na2O) give inconclusive results, probably due to elemental mobility during secondary processes. Plots involving MgO, TiO2, and Fe2O3 detect the chemical contribution of mafic detritus, give much tighter clusters of data, and plot between Aleutian- and Cascade-type arc-derived sediments, suggesting a moderate thickness of continental crust beneath the arc.The arc-related signature of the Georgeville sedimentary rocks is clearly recognizable on ternary plots involving inter-element ratios of high field strength elements (e.g., Ti–Y–Zr, Nb–Y–Zr, and Hf–Ta–Th) in which the samples plot as mixing trends between mafic and felsic end members. Diagrams of this type may have widespread application to tectonic discrimination of sedimentary rocks because in most suites these ratios are relatively insensitive to sedimentary and metamorphic processes.

scholarly journals Paleomagnetism of Devonian sedimentary rocks and mafic sills from the Meguma Terrane, Nova Scotia.

1990 ◽  
Vol 42 (7) ◽  
pp. 833-855 ◽  
Author(s):  
Maurice K. SEGUIN ◽  
Jacques LANGLOIS ◽  
K. V. RAO ◽  
Ernst R. DEUTSCH
Keyword(s):  
Nova Scotia ◽  
Sedimentary Rocks ◽  
Meguma Terrane

Reply to the discussion by J.W.F. Waldron and C.E. White on “Geochemical signature of Ordovician Mn-rich sedimentary rocks on the Avalonian shelf”1Appears in Canadian Journal of Earth Sciences, 2012, 49(6): 772–774 [doi: 10.1139/e2012-004].

2012 ◽  
Vol 49 (6) ◽  
pp. 775-780 ◽  
Author(s):  
Rolf L. Romer ◽  
Uwe Kroner
Keyword(s):  
Earth Sciences ◽  
Nova Scotia ◽  
Canadian Journal ◽  
Deep Water ◽  
Sedimentary Rocks ◽  
Geochronological Data ◽  
Early Ordovician ◽  
Geochemical Signature

In their comment, Waldron and White state that manganese-rich sedimentary rocks of Nova Scotia and Wales are Cambrian and were deposited in a deep-water turbidite basin called “Megumia” rather than on the Avalonian shelf. Available geochronological data are not in conflict with an Early Ordovician deposition age for manganese-rich sedimentary rocks north of the Rheic suture, including those of Nova Scotia and northern Wales. “Megumia” is part of the Avalonian plate, and the manganese-rich sediments were deposited on its shelf.

Discussion of “Geochemical signature of Ordovician Mn-rich sedimentary rocks on the Avalonian shelf”1Appears in Canadian Journal of Earth Sciences, 2011, 48(4): 703–718 [doi: 10.1139/e10-092].

2012 ◽  
Vol 49 (6) ◽  
pp. 772-774 ◽  
Author(s):  
John W.F. Waldron ◽  
Chris E. White
Keyword(s):  
Nova Scotia ◽  
Canadian Journal ◽  
Water Depth ◽  
Deep Water ◽  
Sedimentary Environment ◽  
Sedimentary Rocks ◽  
Geochemical Data ◽  
Geochemical Signature ◽  
North Wales ◽  
Mn Concentration

The paper “Geochemical signature of Ordovician Mn-rich sedimentary rocks on the Avalonian shelf” (Romer et al., published in 2011) describes six samples of which four are from the Meguma Supergroup of Nova Scotia. Previous work indicates that these samples are Cambrian and that they were deposited in a deep-water turbidite basin (“Megumia”), not on the Avalonian shelf. The geochemical data support models for Mn concentration, involving oxidation and reduction in a sedimentary environment but do not constrain water depth. Likely correlatives are in the Cambrian of North Wales and not in the European localities sampled by the authors.

Geochemical and isotopic characteristics of Early Silurian clastic sequences in Antigonish Highlands, Nova Scotia, Canada: constraints on the accretion of Avalonia in the Appalachian – Caledonlde Orogen

1996 ◽  
Vol 33 (3) ◽  
pp. 379-388 ◽  
Author(s):  
J. Brendan Murphy ◽  
J. Duncan Keppie ◽  
Mary Pat Cude ◽  
Jarda Dostal ◽  
John W. F. Waldron
Keyword(s):  
Nova Scotia ◽  
Volcanic Rocks ◽  
Sedimentary Rocks ◽  
Structural Data ◽  
Strike Slip ◽  
Late Ordovician ◽  
Igneous Rocks ◽  
Oblique Collision ◽  
Isotopic Signatures ◽  
Clastic Sedimentary

Avalonia is a terrane that accreted to Laurentia–Baltica during the development of the Appalachian–Caledonide Orogen. Interpretations of the timing of accretion have been constrained by comparing faunal affinities, overstep sequences, age and kinematics of inferred accretionary deformational events, and controversial paleomagnetic data. We show that the time of accretion of Avalonia may also be constrained by contrasts in the geochemical and isotopic signatures of its igneous rocks (which reflect the characteristics of the underlying continental basement and mantle) and sedimentary rocks (which reflect provenance). Early Silurian clastic sedimentary rocks of the Beechill Cove Formation, Antigonish Highlands, Nova Scotia, were deposited on Avalonian crust. The formation predominantly consists of approximately 80 m of siltstones and shales deposited in a nearshore environment and derived from the northeast. Their age is constrained by paleontological data and by directly underlying Late Ordovician – Early Silurian bimodal volcanic rocks that have typically Avalonian geochemical signatures. In comparison with typical Avalonian rocks, the Beechill Cove sediments are characterized by high SiO2, Ce/Yb, and initial 87Sr/86Sr, low Fe2O3, MgO, and TiO2, and strongly negative εNd(ur). These characteristics cannot be attributed to erosion of underlying Avalonian basement or coeval volcanic rocks and are consistent with derivation via significant transport from radiogenically enriched continental crust. εNd data are typical of Grenvillian basement compositions and suggest that the Beechill Cove sedimentary rocks were derived from an adjacent landmass with Grenvillian crust. The data, in conjunction with paleocontinental reconstructions and recent geochronological and structural data from the northern Appalachians, suggest that the Caledonide orogenic belt is the most likely source. Deposition of the Beechill Cove Formation is inferred to have occurred in an intracontinental basin associated with strike-slip tectonics during the oblique collision of the Avalon with Laurentia–Baltica.

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