Detrital muscovite geochronology and the Cretaceous tectonics of the inner Scotian Shelf, southeastern Canada

Geochronology of detrital muscovite from the Lower Cretaceous of the central Scotian Basin has shown predominant supply of Meguma terrane detritus, including muscovite with Alleghanian (mid-Carboniferous to Permian) ages from the inner Scotian Shelf. In this study, 87 detrital muscovite grains from five wells in the eastern Scotian Basin, representing depositional ages from Tithonian to Early Albian, were dated by single-grain [sup.40]Ar/[sup.39]Ar techniques. Previous work shows that the provenance of this sediment was different from wells in the central Scotian Basin. Compared with the central Scotian Basin, the muscovite age populations from the eastern Scotian Basin have more (20% versus 7%) pre-Devonian ages, derived from inboard terranes of the Appalachians. In both the central and eastern Scotian Basin, most old grains are found in the Tithonian and the Aptian-Albian, with fewer in the Valanginian and almost none in the Kimmeridgian and the Hauterivian-Barremian. These data suggest rapid unroofing of the Meguma terrane in the Kimmeridgian and Hauterivian-Barremian and greater supply of sediment from Newfoundland to the eastern Scotian Basin in the Tithonian and Aptian-Albian. Compared with the central Scotian Basin, which has most ages in the range 340-300 Ma, the muscovite age populations from the eastern Scotian Basin have a higher proportion of 420-340 Ma and in particular 300-260 Ma ages. Such late Alleghanian overprinting of argon ages is very rare on land in Nova Scotia, but in the Maritimes Basin, this was the time of uplift and erosion of strata. La geochronologie de la muscovite detritique du centre du bassin Scotian (Cretace inferieur) montre un approvisionnement predominant de debris du terrane de Meguma, incluant de la muscovite presentant des ages alleghaniens (Cretace moyen a Permien) provenant de l'interieur de la plate-forme Scotian. Dans la presente etude, 87 grains de muscovite detritique de cinq puits dans l'est du bassin Scotian, representant des ages de deposition du Tithonien a l'Albien precoce, ont ete dates selon les technique [sup.40]Ar/[sup.39]Ar sur des grains uniques. Des travaux anterieurs montrent que la provenance de ces sediments differait de celle de puits dans le centre du bassin Scotian. Compare avec le centre du bassin Scotian, les populations d'age de la muscovite de l'est du bassin Scotian etaient plus pre-devoniennes (20 % p/r 7%), provenant de terranes internes des Appalaches. Dans le centre et l'est du bassin Scotian, la plupart des plus anciens grains provenaient du Tithonien et de l'Aptien-Albien, peu du Valanginien et presque aucun du Kimmeridgien et du Hauterivien-Barremien. Ces donnees suggerent que le degagement rapide du terrane de Meguma au Kimmeridgien et a l'Hauterivien-Barremien et un plus grand approvisionnement de sediments de Terre-Neuve vers l'est du bassin Scotian au Tithonien et a l'Aptien-Albien. Compare au centre du bassin Scotian, dont la plupart des ages se situent dans la plage 340-300 Ma, les populations de muscovite de l'est du bassin Scotian ont une plus grande proportion d'ages dans la plage 420-340 Ma et particulierement 300-260 Ma. Une telle surimpression d'ages argon de l'Alleghanien est tres rare sur la masse terrestre de la Nouvelle-Ecosse; cependant, dans le bassin des Maritimes, c'etait le moment du soulevement et de l'erosion des strates.
Introduction The geochronology of single grains of detrital muscovite is a powerful tool for identifying sediment provenance (Adams and Kelley 1998). Muscovite is abraded and comminuted during transport and is [...]