Stratigraphy and sedimentology of the Pennsylvanian Grande Anse Formation, Cumberland Basin, eastern Canada: its relationship to salt tectonics and coeval strata of the Joggins World Heritage Site

The Cumberland Basin is one of several sedimentary basins composing the late Paleozoic Maritimes Basin complex of eastern Canada. Pennsylvanian salt tectonics in the Cumberland Basin caused two salt mini-basins to evolve on either side of the Minudie Anticline, a salt wall. South of the wall (Athol Syncline), along the Joggins World Heritage shoreline, an--3000 m succession of strata (Little River, Joggins, Springhill Mines, and Ragged Reef formations) accumulated conformably on the Boss Point Formation. North of the wall (Black Point sub-basin), the biostratigraphically equivalent, but mostly unstudied,--600 m thick succession of Grande Anse Formation lies in angular unconformity on folded and faulted Boss Point and basal Little River formations. Grande Anse Formation sedimentology indicates four lithofacies associations: floodplain (LA1), braided channel (LA2), sheet flood (LA3), and debris flow deposits (LA4). One possible model has the Black Point sub-basin with its own hydrological system, completely separated from the Athol Syncline. A low subsidence rate combined with the low sedimentation rate produced the--600 m thick sand- and mud-prone succession that was contemporaneous with the--3 km succession to the south. The second model proposes that north of the salt wall was exposed to erosion during accumulation of Joggins and Springhill Mines formation strata to the south. Subsequently, the sediment of the lithologically similar Ragged Reef and Grande Anse formations either (i) onlapped to the north, unconformably on the folded Boss Point; or (ii) unconformably-disconformably on the underlying strata after a period of time indistinguishable in the biostratigraphic record. Key words: Grande Anse Formation, Joggins, salt tectonics, stratigraphy, sedimentology. Le bassin de Cumberland estun des bassins sedimentaires qui composent le complexe tardi-paleozoique de bassins des Maritimes, dans l'est du Canada. Une tectonique salifere au Pennsylvanien dans le bassin de Cumberland a entraine la formation de deux mini-bassins de sel de part et d'autre de l'anticlinal de Minudie, un mur de sel. Au sud du mur (synclinal dAthol), le long du littoral du Patrimoine mondial de Joggins, une sequence de quelque 3000 m de strates (Formations de Little River, Joggins, Springhill Mines et Ragged Reef) s'est accumulee de maniere concordante sur la Formation de Boss Point. Au nord du mur (sous-bassin de Black Point), la sequence equivalente du point de vue biostratigraphique, mais generalement non etudiee, de --600 m de la Formation de Grande Anse repose en discordance angulaire sur des roches plissees et faillees de la Formation de Boss Point et de la base de la Formation de Little River. La sedimentologie de la Formation de Grande Anse indique quatre associations de lithofacies, a savoir, des depots de plaines inondables (LA1), de chenaux anastomoses (LA2), d'inondations en nappe (LA3) et de coulees de debris (LA4). Dans un modele possible, le sous-bassin de Black Point et son reseau hydrologique sont completement separes du synclinal dAthol. Une faible vitesse de subsidence combinee a un faible taux de sedimentation a produit la sequence de--600 m riche en sable et en boue contemporaine de la sequence de--3 km situee au sud. Le deuxieme modele propose que le nord du mur de sel ait ete expose a l'erosion durant l'accumulation de strates des Formations de Joggins et Springhill Mines au sud. Par la suite, les sediments des Formations de Ragged Reef et de Grande Anse, semblables sur le plan lithologique, ont soit (i) ete deposes en discordance sur les roches plissees de la Formation de Boss Point, qu'elles ont debordees vers le nord ou (ii) ont ete deposes en discordance sur les strates sous-jacentes apres un intervalle de temps indistinguable dans le profil biostratigraphie. [Traduit par la Redaction] Mots-cles: Formation de Grande Anse, Joggins, tectonique salifere, stratigraphie, sedimentologie.
Introduction This paper provides the first detailed study of the Grande Anse Formation through the logging of its three main coastal outcrop localities on both sides of the New Brunswick-Nova [...]