Title: Depositional environment and provenance analysis of the Lower Cretaceous sedimentary rocks at the Peskowesk A-99 well, Scotian Basin
Abstract: Seven conventional cores are available from the Peskowesk A-99 well: four from the Cree Member of the Logan Canyon Formation, one each from the Upper and Middle members of the Missisauga Formation, and one from the top of the Mic Mac formation. These cores were described and lithofacies interpreted. Sandstone samples were analysed in polished thin sections to identify detrital petrology, using petrographic microscope and electron microprobe analyses and backscattered electron images. The cores predominantly contain shore-face prodeltaic facies in the Mic Mac Formation and Middle Member of the Missisauga Formation, whereas in the Upper Member of the Missisauga Formation and the Cree Member of the Logan Canyon Formation, channel and tidal flat facies predominate. In the Logan Canyon Formation, transgressive deposits with low sedimentation rates tend to be cemented by siderite and in one case include coated grains of glauconite, mantling a core of chlorite pseudomorphing feldspar or biotite, and rimmed by siderite. The detrital petrology of sandstones show only minor variations from the Mic Mac Formation to the Logan Canyon Formation. Lithic clasts are abundant, with mildly alkaline rhyolite - microgranite - syenite predominating. Clasts of metamorphic rocks, arenites and mylonitized polycrystalline quartz become more abundant in the Cree Member. Detrital feldspars are predominantly perthites. Detrital ilmenite and its alteration deposits are the dominant heavy mineral, with almandine garnet, chromite, rutile, tourmaline and zircon present in minor amounts. This detrital petrology differs from that in the southwest Scotian basin in many ways: the character of lithic clasts, feldspar composition, abundance of mica, rarity of tourmaline. Chemical composition of garnet and chromite are also different. These data suggests that the Peskowesk area was persistently fed by a different river compared to the southwest Sable sub-basin. That river drained central Newfoundland, including widespread granitoid rocks of the alkaline Topsails complex.