Triassic Basin Stratigraphy at Grand Manan, New Brunswick, Canada

Abstract

The island of Grand Manan (Canada) in the southwestern Bay of Fundy has the only exposed strata and basalt of the Grand Manan Basin, a mainly submerged Early Mesozoic riſt basin about 30 km wide by 70 km long. The basin is bounded on the southeast by the west-dipping Red Point Fault, which bisects the island, and on the northwest by a submarine border fault marked by the Murr Escarpment, a bathymetric feature that parallels the coast of Maine (USA). A fault-bounded horst of Ediacaran to Cambrian rocks separates the Grand Manan Basin from the much larger Fundy Basin to the east. The Ashburton Head, Seven Days Work, and Southwest Head members of the end-Triassic Dark Harbour Basalt cover most of western Grand Manan with a total thickness around 240 m. Up to 12 m of sub-horizontal grey mudstone and fine-grained red sandstone of the Dwellys Cove Formation are exposed along the western shoreline beneath the basalt. Coarse red arkosic sandstone a few metres thick at Miller Pond Road rests on a basement of Late Ediacaran rocks east of the basin. Exposures of the Dwellys Cove and Miller Pond Road formations are at the top and bottom, respectively, of several km (?) of sub-horizontal Late Triassic clastic basin strata, juxtaposed by the eastern border fault. Extending from beneath the Miller Pond Road sandstone, a level surface of low relief forms much of the eastern island and its archipelago, which may be interpreted as a relict Late Triassic peneplain that was beneath the Mesozoic strata.
 
 RÉSUMÉ
 
 L’île Grand Manan (Canada) au sud‑ouest de la baie de Fundy possède la seule strate et basalte qui affleure du bassin de Grand Manan, un bassin d’effondrement en bonne partie submergé du début du Mésozoïque qui fait environ 30 km de large sur 70 km de long. Ce bassin est bordé au sud-est par la faille de Red Point qui présente en pend-age vers l’ouest et qui traverse l’île de part en part, et au nord‑ouest, par une faille de bordure sous‑marine marquée par l’escarpement Murr, une structure bathymétrique qui longe la côte du Maine (É.‑U.). Un horst bordé par une faille et composé de roches de la période comprise entre Ediacara et le Cambrien sépare le bassin de Grand Manan du bassin de Fundy, beaucoup plus vaste, à l’est. Les membres de Ashburton Head, de Seven Days Work et de Southwest Head de la formation de basalte de Dark Harbour, de la fin du Trias, recouvrent la plus grande partie de l’ouest de l’île Grand Manan, et leur épaisseur totale serait d’environ 240 m. Des roches de mudstone gris subhorizontal et de grès rouge à grains fins de la Formation de Dwellys Cove dont l’épaisseur peut atteindre 12 m affleurent le long du rivage occidental, sous le basalte. Une couche de grès arkosique rouge grossier de quelques mètres d’épaisseur sur Miller Pond Road repose sur un socle de roches de la fin d’Ediacara, à l’est du bassin. Des affleurements des Formations de Dwellys Cove et de Miller Pond Road sont observés respectivement au sommet et à la base de la strate subhorizontale de plusieurs kilomètres (?) d’un bassin de roches clastiques de la fin du Trias, en juxtaposition avec la faille de bordure orientale. Sous le grès de Miller Pond Road, une surface de niveau en terrain peu accidenté se prolonge et compose la plus grande portion de la partie est de l’île et de son archipel, ce qui pourrait suggérer la présence d’une ancienne pénéplaine du Trias tardif qui se trouvait sous la strate du Mésozoïque.
 
 [Traduit par la redaction]

Stratigraphic and temporal context and faunal diversity of Permian-Jurassic continental tetrapod assemblages from the Fundy rift basin, eastern Canada

“…2). All these systems are reactivated Palaeozoic fault zones (Withjack et al 1995;McHone 2011). The southern and southeastern margins of overall geological context .…”

“…However, extensive outcrops of the basin deposits occur along the shores of west-central Nova Scotia and, to a much lesser extent, on the southeastern shores of New Brunswick. A thickness of at least 4 km of sedimentary and volcanic rocks is preserved in the deepest parts of the basin along the Fundy and Grand Manan fault zones based on industry seismic lines (Wade et al 1996;McHone 2011). However, the entire section thins dramatically to the east and south towards the outcrops in Nova Scotia by convergence, onlap, non-deposition and erosion.…”

“…McHone (2011) considered it a separate basin, and thus it will not be discussed further in the present paper. Powers (1915Powers ( , 1916 established an outline of the stratigraphy of the Fundy basin ( Fig.…”

The Grand Manan Terrane of New Brunswick: Tectonostratigraphy and Relationship to the Gondwanan Margin of the Iapetus Ocean

“…Volume 41tively, from whence they become buried beneath the Triassic rocks underlying the Bay of Fundy (McLeod and Rast 1988;McLeod et al 1994;McHone 2011). Correlation of rocks from Grand Manan with those on the mainland is further complicated by Grand Manan's location to the southwest of the Oak Bay Fault (Fig.…”

A Review of Proterozoic to Early Paleozoic Lithotectonic Terranes in New Brunswick, Canada and their Tectonic Evolution during Penobscot, Taconic, Salinic and Acadian Orogenesis

“…The upper part of the succession comprises columnar-jointed tholeiitic basalt encountered in an offshore borehole and underlying the western half of Grand Manan Island (inset in Fig. 3) (Pringle et al 1974;Greenough and Papezik 1987;Wade and Jansa 1994;McHone 2011). Correlative basalt on the south shore of the Bay of Fundy in Nova Scotia yielded 40Ar/39Ar dates of 199 ± 1 Ma and 201 ± 1 Ma, and a U-Pb zircon date of 201.3 ± 0.3 Ma indicative of a Late Triassic (Rhaetian) age (Kontak and Archibald 2003;Schoene et al 2006;Cirilli et al 2009;Jourdan et al 2009).…”