Early Cretaceous volcanism in the Scotian Basin 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.

Abstract

Early Cretaceous volcanism is widespread in the eastern Scotian Basin. The stratigraphic position of volcanic rocks within wells was re-evaluated and the volcanological character of the rocks was refined by study of cuttings and well logs. Hauterivian–Barremian volcanic rocks on the SW Grand Banks and Aptian–Albian volcanic rocks in the Orpheus Graben and SE Scotian Shelf resulted from Strombolian type eruptions. More extensive Hawaiian type flows were mapped from seismic profiles near the Mallard and Brant wells on the SW Grand Banks and they appear to have been derived from local basement highs with a positive magnetic anomaly interpreted as volcanic centres. Igneous rocks in the Hesper well on the SE Scotian Shelf are the erosional remnant of basaltic flows that terminated at the paleoshoreline. They correlate with basalt flows both in extensive outcrop on Scatarie Ridge and in several Orpheus Graben wells. The interpretation of the Hesper basalts as an erosional remnant of more extensive basalt flows is consistent with detrital petrographic evidence for substantial uplift of the inboard part of the Scotian Basin in the Hauterivian–Aptian. Widespread volcanic activity indicates a regional and long-lived magma source, which resulted in elevated regional heat flow. Effects of this heat flow are seen in sedimentary rocks of the Sable Subbasin and it had a discernable impact on hydrocarbon maturation.

First-cycle sand supply and the evolution of the eastern Canadian continental margin: Insights from Pb isotopes in the Mesozoic Scotian Basin

“…Between 10% and 35% of detrital zircons are of Cretaceous age, and are interpreted to represent reworking of felsic trachytic tuffs in the Orpheus graben (Bowman et al, 2012). No corresponding detrital K-feldspar Pb group is observed (Fig.…”

“…Sedimentation at the base of the Aptian was accompanied by fault reactivation and uplift along the Scotian margin, associated with a prominent Barremian-Aptian unconformity on the inner Scotian Shelf (Bowman et al, 2012) and regional deformation of Chaswood Formation basins (Pe- Piper and Piper, 2012). Regionally, the base Aptian corresponds to the diminution of enhanced magmatism in the J-anomaly ridge, which had been active since the late Hauterivian (Tucholke et al, 2007), and which may have resulted in westward-directed motion on the crustal block south of the Cobequid-Chedabucto fault (Fig.…”

“…The Aptian-Albian boundary marks a major change in the evolution of the North Atlantic Ocean. It represents the time when normal oceanic spreading began between Iberia and the Grand Banks (Tucholke et al, 2007), and it is marked by a magmatic pulse in the eastern Scotian Basin (Bowman et al, 2012). With the onset of seafloor spreading, differential extension could no longer produce strike-slip motion on the Cobequid-Chedabucto fault.…”