Offshore continuation of Meguma Terrane, southwestern Nova Scotia

Abstract

Eight short drill cores have been examined from the continental shelf southwest of Nova Scotia. Four cores recovered granitoid rocks of two types. Ilmenite-bearing granitoid rocks petrographically and geochemically resemble granodiorites of the South Mountain Batholith and granites of the Seal Island Pluton. Magnetite-bearing granitoid rocks are also peraluminous but have no exact analogues onshore in Nova Scotia. Two cores recovered metamorphic rocks in a small area 50 km south of Seal Island. One consits of chlorite-muscovite-quartz schist, geochemically similar to rocks of the Halifax Formation. The second sampled epidote-chlorite-quartz schist similar to metavolcanic rocks of the White Rock Formation. One further core sampled quartzite, and another sampled a metavolcanic rock (possibly erratic).The regional extent of these lithotypes can be inferred from gravity and aeromagnetic data. Regional gravity data suggest the presence of a large granite body off southwestern Nova Scotia. In this area, magnetic anomalies are irregular, apparently reflecting the presence of magnetite-bearing granites. The layer-stripping method of analyzing the magnetic field shows that the area is underlain at depth by high magnetic anomalies. Large near-surface linear magnetic anomalies are used to map the extent of the volcanic rocks of the White Rock Formation. The area is cut by several northwest-trending faults that postdate Acadian folding but predate the earliest Jurassic magmatism of the Shelburne Dyke and North Mountain basalt. The unusual magnetic signature of the area off southwestern Nova Scotia may reflect a different basement; it is possible that Meguma rocks are thrust over the Avalon Terrane. Alternatively, it may be solely the result of magnetite-bearing granites. These granites may be related to a Permian thermal event in southwest Nova Scotia, and they have some petrographic similarity to young granites of the Piedmont Zone of South Carolina.On a examink huit carottes de forage de longueur restreinte pr6levCes sur la plate-forme au sud-ouest de la ~ouvelle-~cosse. Parmi elles, quatre sont constitutkes de roches granitoides de deux types diffkrents. Un premier type contient de I'ilmCnite, et sa composition petrographique et geochimique est analogue a celle des granodiorites du batholite de South Mountain et des granites du pluton de Seal Island. Ledeuxikme type, Cgalement peralumineux, renferme de la magnCtite, cependant il n'existe pas sur le temtoire de la Nouvelle-Ecosse des roches exactement analogues. Les roches mCtamorphiques sont repksentCes dans deux carottes pklevkes dans une petite kgion situCe a 50 km au sud du Seal Island. Une est formCe d'un schiste chlorite -muscovite-quartz, gCochimiquement semblable a celui de la Formation d'Halifax, l'autre est constituke d'un schiste 2 1 Cpidote -chlorite -quartz ressemblant aux roches volcaniques de la Formation de White Rock. Les deux autres carottes sont formCes respectivement d'un quartzite et d'une mCtavolcanite (possiblement erratique).Les ltvts gravimCtriques...

Effects of fluid flow, cooling and deformation as recorded by40Ar/39Ar, Rb–Sr and zircon fission track ages in very low- to low-grade metamorphic rocks in Avalonian SE Cape Breton Island (Nova Scotia, Canada)

“…However, Meguma is a large terrane that extends SW offshore to southern New England (e.g. Pe-Piper & Loncarevic, 1989; Keen, MacLean & Kay, 1991; Pe-Piper & Jansa, 1999); the piece of Meguma that initially collided with composite Laurentia may therefore now be situated offshore somewhere between Nova Scotia and southern New England. The Neoacadian sinistral motion in the Mira terrane that is coeval with dextral translation along the east–west-oriented Cobequid–Chedabucto Fault Zone appears to form part of a conjugate fault set, which accommodated escape of the Mira terrane towards the NE following convergence with Meguma (Fig.…”

Glacial landforms on German Bank, Scotian Shelf: evidence for Late Wisconsinan ice-sheet dynamics and implications for the formation of De Geer moraines

“…2) is dominated by outcropping CambroOrdovician metasedimentary rocks (Meguma Group) intruded by Late Devonian ÁCarboniferous granitoid plutons Pe-Piper & Loncarevic 1989;Pe-Piper & Jansa 1999). Bedrock was modified by glaciogenic erosion and is separated from the discontinuous and thin overlying unconsolidated Quaternary sediments by a rugged erosional surface.…”

Global geoscience transect 8, Quebec-Maine-Gulf of Maine transect, southeastern Canada, northeastern United States of America

“…The Cape Cod (Nauset) fault system is taken to be the boundary between the Esmond-Dedham block of the Atlantica composite terrane and the Meguma terrane, which underlies the bulk of Nova Scotia. Magnetic and gravity anomaly maps allow the identification of the Meguma terrane to at least as far west as 67° W. longitude (Pe-Piper and Loncarevic, 1989). But farther from land and especially where younger sediments are present, the location of the terrane boundary and even the presence of the Meguma terrane beneath the sea are not well established.…”