Stratigraphic significance of Upper Devonian and Lower Carboniferous miospores from the type area of the Horton Group, Nova Scotia

1993 ◽  
Vol 30 (5) ◽  
pp. 1091-1098 ◽  
Author(s):  
A. Thomas Martel ◽  
D. Colin McGregor ◽  
John Utting
Keyword(s):  
Nova Scotia ◽  
Upper Devonian ◽  
Late Devonian ◽  
The South ◽  
Lower Carboniferous ◽  
Northeastern Part ◽  
South Mountain Batholith ◽  
Type Area ◽  
Minimum Age ◽  
Maritimes Basin

Late Devonian (late Famennian) miospores have been found in the lowermost 7.3 m of the Horton Group on Harding Brook in the type area, Windsor Subbasin, Nova Scotia, below Tournaisian miospores of the Emphanisporites rotatus – Indotriradites explanatus Zone. Extending the age of the Horton Group in the type area down into the latest Devonian shows that the lowest beds of the ~ 1000 m thick group are coeval with latest Devonian rocks elsewhere in the Maritimes Basin that have been excluded from the Horton Group by some authors. Evidence presented here favours the argument that Late Devonian rocks lithologically similar to the Horton Group, deposited on the Acadian unconformity, should be included in that group. Miospore evidence indicates a minimum age of about 355 Ma for exhumation of the northeastern part of the South Mountain Batholith.

Sediment sources and dispersion as revealed by single-grain 40Ar/39Ar ages of detrital muscovite from Carboniferous and Cretaceous rocks in mainland Nova ScotiaGeological Survey of Canada contribution 20090289.

2010 ◽  
Vol 47 (7) ◽  
pp. 957-970 ◽  
Author(s):  
Peter H. Reynolds ◽  
Georgia Pe-Piper ◽  
David J.W. Piper
Keyword(s):  
Nova Scotia ◽  
Early Cretaceous ◽  
Early Carboniferous ◽  
Metamorphic Rocks ◽  
Sediment Sources ◽  
The South ◽  
Lower Carboniferous ◽  
South Mountain Batholith ◽  
Single Grain ◽  
Meguma Terrane

Single-grain ages of detrital muscovite from 15 sand(stone) samples from the Lower Carboniferous Horton Group and the Lower Cretaceous Chaswood Formation of central Nova Scotia were used to infer the nature of the Early Carboniferous unroofing of the Meguma terrane and the reworking of Carboniferous rocks in the Early Cretaceous. In the western Windsor Basin, a sample from the oldest Horton Group rocks yielded ages principally between ca. 400 and 380 Ma, suggesting that most of the muscovite present came from the metamorphic rocks of the Meguma terrane but was variably reset by the intrusion of the South Mountain Batholith at ca. 380 Ma. Other samples in this part of the basin show partial post-depositional resetting. Younger Horton Group metamorphic rocks in the eastern Windsor Basin contain many grains with ages of ca. 370–360 Ma, suggesting derivation from the central core of the South Mountain Batholith or the Musquodoboit Pluton. Horton Group sandstones from the western part of the St. Marys Basin contain muscovite derived from the Liscomb Complex along with metamorphic muscovite variably reset by the intrusion of this complex. In general, our data suggest predominant northward dispersion of muscovite from the Meguma terrane to the Horton Group and a lack of axial transport along the Horton grabens through central Nova Scotia, a pattern compatible with tectonic models in which the Meguma terrane is ramped over the Avalon terrane. Muscovite ages obtained for the Chaswood Formation compare well with those from the Horton Group rocks in the western St. Marys Basin. These rocks may have been exposed to rapid erosion by reactivation of the Cobequid–Chedabucto fault zone in the Early Cretaceous and the resulting sediments were perhaps transported to depositional sites along northeast-trending faults. Unlike the detrital monazites in these rocks, there is no evidence that any of the detrital muscovites came from distal sources outside the Meguma terrane.

Syn-Acadian emplacement model for the South Mountain batholith, Meguma Terrane, Nova Scotia: Magnetic fabric and structural analyses

1997 ◽  
Vol 109 (10) ◽  
pp. 1279-1293 ◽  
Author(s):  
Keith Benn ◽  
Richard J. Horne ◽  
Daniel J. Kontak ◽  
Geoffrey S. Pignotta ◽  
Neil G. Evans
Keyword(s):  
Nova Scotia ◽  
Magnetic Fabric ◽  
The South ◽  
South Mountain Batholith ◽  
Meguma Terrane

Oxygen isotope evidence for the genesis of Upper Paleozoic granitoids from southwestern Nova Scotia

1980 ◽  
Vol 17 (1) ◽  
pp. 132-141 ◽  
Author(s):  
F. J. Longstaffe ◽  
T. E. Smith ◽  
K. Muehlenbachs
Keyword(s):  
Nova Scotia ◽  
Oxygen Isotope ◽  
Large Scale ◽  
The South ◽  
Metasedimentary Rocks ◽  
South Mountain Batholith ◽  
Oxygen Isotope Ratios ◽  
Upper Paleozoic ◽  
Isotope Evidence ◽  
Alteration Processes

The oxygen isotope ratios for 127 rocks and coexisting minerals from Paleozoic granitoids and clastic metasedimentary rocks of southwestern Nova Scotia have been measured. The whole-rock δ18O values for samples of the South Mountain batholith range from 10.1–12.0‰.But discrete granitoid plutons, located to the south of the South Mountain batholith, have lower δ18O values (7.8–10.4‰). Coexisting minerals from the Nova Scotia granitoids are near isotopic equilibrium, indicating that the whole-rock δ18O values primarily reflect the δ18O of the magma, rather than secondary alteration processes. The Meguma Group clastic metasedimentary rocks that host the Nova Scotia granitoids range in δ18O from 10.1–12.9‰. These clastic metasedimentary rocks show no systematic geographic variation in δ18O. The greenschist facies Meguma Group rocks that host the South Mountain batholith have similar δ18O values to the amphibolite facies equivalents located about the southern discrete plutons. Large scale isotopic exchange between the Meguma Group and the South Mountain batholith, or the southern plutons, is not evident.The relatively high δ18O values of the peraluminous South Mountain batholith (10.1–12.0‰) indicate that it formed by anatexis of 18O-rich clastic metasedimentary rocks. The southern plutons were also derived by partial melting of clastic metasedimentary rocks, but their lower δ18O values reflect exchange of the source material with a low 18O reservoir (mafic magmas?) prior to, or during anatexis.The sheared Brenton pluton is much lower in δ18O (5.0‰) than any of the other rocks, probably because of exchange with low 18O fluids during shearing.

Kennetcook thrust system: late Paleozoic transpression near the southern margin of the Maritimes Basin, Nova Scotia

2010 ◽  
Vol 47 (2) ◽  
pp. 137-159 ◽  
Author(s):  
John W.F. Waldron ◽  
Carlos G. Roselli ◽  
John Utting ◽  
Stanley K. Johnston
Keyword(s):  
Nova Scotia ◽  
Early Carboniferous ◽  
Late Paleozoic ◽  
The South ◽  
Seismic Profiles ◽  
Southern Margin ◽  
Fault Structures ◽  
Thrust System ◽  
Maritimes Basin

A major zone of deformation affects Early Carboniferous rocks in the southern part of the Maritimes Basin of Nova Scotia, close to the boundary between the Avalon and Meguma terranes of the Appalachians. Field relationships at Cheverie indicate thrusting of Tournaisian Horton Group clastics over Viséan Windsor Group carbonates, evaporites, and clastics, a relationship confirmed by the Cheverie #01 well. Mapped relationships to the south indicate that a system of thrusts, here termed the Kennetcook thrust system, climbs upsection to the southeast, becoming a décollement within Windsor Group evaporites. Industry seismic profiles clearly show deformed Windsor Group, and include fold and fault structures indicative of evaporite flow and solution collapse. Below the Windsor Group, half-grabens filled with Horton Group are clearly imaged; offsets at graben-related faults show that these structures were inverted during later shortening. Above the Windsor Group, less deformed rocks of the Pennsylvanian Scotch Village Formation (Cumberland Group) fill minibasins created by the withdrawal or solution of deformed Windsor evaporites. The timing of thrusting is constrained by these relationships and by crosscutting intrusions to a narrow interval around the Mississippian–Pennsylvanian boundary prior to ∼315 Ma. Deformation was probably related to dextral transpression along the former Avalon–Meguma boundary. Depending on how shortening was transmitted to the southeast, up to 1500 km2 of southern mainland Nova Scotia may be underlain by tectonically transported rocks.

An evaluation of crustal assimilation within the Late Devonian South Mountain Batholith, SW Nova Scotia

2012 ◽  
Vol 149 (3) ◽  
pp. 353-365 ◽  
Author(s):  
J. GREGORY SHELLNUTT ◽  
JAROSLAV DOSTAL
Keyword(s):  
Nova Scotia ◽  
Chemical Evolution ◽  
Hydrothermal Fluids ◽  
Eastern North America ◽  
Late Devonian ◽  
Metal Enrichment ◽  
Crustal Assimilation ◽  
South Mountain Batholith ◽  
Appalachian Orogen ◽  
Zircon Saturation

AbstractThe Late Devonian South Mountain Batholith (SMB) of southwestern Nova Scotia is the largest batholith in the Appalachian Orogen of Eastern North America and contains economic deposits of U and Sn. The SMB comprises at least 11 individual plutons, which range in composition from granodiorite to biotite monzogranite, leucomonzogranite and leucogranite. Previous studies have suggested that a combination of fractional crystallization, assimilation of Meguma Supergroup country rocks and an influx of magmatic fluids contributed to the chemical evolution of the SMB. The amount of crustal assimilation is estimated to be as high as 33%. MELTS modelling assuming a starting composition of granodiorite with H2O = 4 wt%, pressure = 4 kbar (~12 km) and fO2 = FMQ can reproduce the chemical evolution observed in the SMB. However, some leucogranites likely require an additional component (e.g. hydrothermal fluids) to explain their alkali metal enrichment (e.g. Na, K, Rb). Zircon saturation thermometry estimates indicate the Salmontail Lake and Scrag Lake granodiorite plutons had high minimum initial temperatures of 823 ± 6°C and 832 ± 2°C, respectively, which are similar to low zircon-inheritance granitoids. The TiO2/Al2O3 and alkali-lime ratios of the surrounding country rocks and the leucogranites indicate the amount of crustal assimilation is likely to be between 10% and 20%. Our findings suggest the granodiorites of the SMB were likely produced by partial melting of the sub-Meguma Supergroup (e.g. Avalon terrane) lower crust caused by the contemporaneous injection of high temperature mafic to ultramafic magmas.

Magmatic andalusite from the South Mountain batholith, Nova Scotia

1976 ◽  
Vol 56 (3) ◽  
pp. 279-287 ◽  
Author(s):  
D. B. Clarke ◽  
C. B. McKenzie ◽  
G. K. Muecke ◽  
S. W. Richardson
Keyword(s):  
Nova Scotia ◽  
The South ◽  
South Mountain Batholith
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