Possible Late Ordovician Glaciation of Nova Scotia

Abstract

A thin, poorly stratified, polymictic diamictite at the the base of the White Rock Formation (perhaps Caradocian or younger) contains unsorted, clustered, faceted, and grooved clasts apparently dropped into a shaly or sandy lithotope. Ice probably transported these stones from a distant source. Other lithosomes of the formation are of almost every sedimentary/volcanic lithology, shape, and extent. Supermature orthoquartzite may be eolian or beach dune, or intertidal; immature quartzites are channel-fills, probably fluvioglacial; bouldery diamictite may be morainic or glaciomarine. Underlying and overlying conformable formations are thick, graptolitic black slate. White Rock contacts may mark glacio-eustatic lowering and rising of sea-level. Locally at the top of the Halifax Formation, small-scaled folding resulting in detailed and superficial angular discordance with the overlying White Rock. Formation may be ice-thrust phenomena.Both the gross stratigraphic succession and detail of lithosomes of the White Rock Formation are remarkably similar to those of the latest Ordovician (Ashgillian) of northwest Africa. There, this stage records extensive continental glaciation well-established by sedimentology, stratigraphy, paleomagnetism, and paleontology. Ordovician–Silurian glaciation of North America is unknown. If the White Rock Formation is glacio-genetic, then it is Ashgillian and correlative with the Dunn Point Volcanics of northeastern Nova Scotia. Moreover the underlying Halifax Formation could encompass almost all of the Ordovician, and the overlying Kentville perhaps most of the Silurian. Furthermore the hypothesis would be supported that Nova Scotia and the rest of southeastern Canada is a remnant of northwestern Africa.