The upper Triassic Chedabucto Formation, Guysborough County, Nova Scotia: depositional and tectonic context

The Chedabucto Formation of presumed Late Triassic age crops out at the wes tern end of the Orpheus basin. The formation consists of interbedded conglo merate, sandstone, and mudstone interpreted as the deposits of sand-dominat ed braided streams, and clast-supported conglomerate interpreted as debris- flow deposits derived from nearby fault talus. The facies and presumed age of the Chedabucto Formation are similar to that of the Wolfville Formation in the Minas subbasin of the Fundy rift basin. These facies may also be pre sent in the lower portion of the Eurydice Formation at the base of the sedi mentary section in the offshore Orpheus basin. The location of the outcrops of the Chedabucto Formation suggests that a continuous belt of sedimentati on connected the Orpheus and Fundy rift basins in the Late Triassic, formin g a "broad terrane" extending from eastern New Brunswick to the Scotian She lf. The Chedabucto Formation was deposited primarily by an axial river syst em flowing eastward from the Fundy rift basin to the Orpheus basin. The Min as subbasin of the Fundy rift basin and the Orpheus basin are interpreted a s segments of a larger transtensional basin formed by synchronous obliques- sinistral motion on the bounding Cobequid-Chedabucto Fault. Basin inversion in the Middle Jurassic probably initiated uplift, resulting in the erosion al isolation of the Fundy and Orpheus basins.