Rygel, Michael C., Lally, Corinne, Gibling, Martin R., Ielpi, Alessandro, Calder, John H., and Bashforth, Arden R.
The 1125-m-thick type section of the Pennsylvanian Boss Point Formation is well exposed along the shore of the Bay of Fundy in Nova Scotia. We provide the first comprehensive account of the entirety of this formation, which comprises nearly one-third of the stratigraphic thickness of the Joggins Fossil Cliffs UNESCO World Heritage Site. The basal Chignecto Bay Member (0-91.5 m) is composed of redbeds, single-storey channel bodies with northerly paleoflow, and thin palustrine limestones. The middle Ward Point Member (91.5-951.7 m) contains up to 16 megacycles composed of alternations between thick packages of braided fluvial sandstone and fine-grained deposits. Although regional studies of the Boss Point Formation suggest that the fine-grained deposits are largely composed of lacustrine sediments, these intervals consist largely of poorly drained and well-drained floodplain deposits in the type section. The facies variations and southeast-directed paleoflow in the Ward Point Member record modest uplift associated with the growth of the salt-cored Minudie Anticline. The North Reef Member (951.7-1125 m) is composed of redbeds and two distinctive multistorey channel bodies. This uppermost member records a shift to more arid, oxidizing conditions, was the precursor to a major phase of salt withdrawal, and represents a transition to the overlying Little River Formation. The sedimentological framework, revised stratigraphy, and detailed measured section and map will provide a foundation for future study of this remarkable Pennsylvanian exposure. Le stratotype de 1 125 metres depaisseur de la formation de Boss Point du Pennsylvanien est bien expose sur la rive de la baie de Fundy, en Nouvelle-Ecosse. Nous presentons le premier compte rendu complet de cette formation dans son integralite, qui comprend pres du tiers de lepaisseur stratigraphique des falaises fossiliferes de Joggins, reconnues site du patrimoine mondial de l'UNESCO. Le membre basal de la baie Chignectou (de 0 m a 91,5 m) se compose de couches rouges, de corps de chenaux monostratifies au paleo-ecoulement vers le nord et de minces couches de calcaire palustre. Le membre moyen de Ward Point (de 91,5 m a 951,7 m) renferme jusqua 16 megacycles composes en alternance depaisses masses de gres fluvial anastomose et de depots a grains fins. Meme si des etudes sur la region de la formation de Boss Point donnent a penser que les depots a grains fins sont surtout composes de sediments lacustres, ces intervalles sont constitues en grande partie de depots alluviaux mal draines et bien draines dans le stratotype. Les variations dans le facies et le paleo-ecoulement en direction du sud-est dans le membre de Ward Point temoignent d'un soulevement modeste associe a la croissance de l'anticlinal de Minudie a noyau salifere. Le membre de North Reef (de 951,7 m a 1 125 m) se compose de couches rouges et de deux corps de chenaux multistratifies distinctifs. Ce membre superieur atteste d'une transition vers des conditions oxydantes, plus arides, il a ete le precurseur d'une importante phase de retrait du sel et il represente une transition vers la formation susjacente de Little River. Le cadre sedimentologique, la stratigraphie revisee ainsi que la coupe et la carte detaillees mesurees serviront de fondement a une prochaine etude sur ce remarquable affleurement de la periode pennsylvanienne. [Traduitpar la redaction], INTRODUCTION The 1125-m-thick type section of the Boss Point Formation comprises approximately one third of the stratigraphic thickness of the Joggins Fossil Cliffs UNESCO World Heritage Site. It is of [...]