Late Carboniferous palaeobotany of the upper Bideford Formation, north Devon: a coastal setting for a Coal Measures flora

摘要

The Culm Seams are thin coals in the Upper Carboniferous upper Bideford Formation of north Devon. Clastic sedimentary rocks associated with the coals have yielded a fossil macroflora dominated by the remains of the Calamostachyales and Medullosales, together with subsidiary lycophytes, sphenophylls, ferns, lagenostomaleans, rare cordaites, and a possible early cycad. The flora is probably early Langsettian in age, which is in agreement with the evidence of the non-marine bivalves and marine bands. It is broadly similar in composition to contemporaneous macrofloras from South Wales. It is unlikely to represent an assemblage formed from plant remains subject to long-distance transportation. Rather, it was probably preserved in the lower reaches of a 'bird-foot' delta that had temporarily transgressed into the Culm Basin. The distal margin of this delta would represent a comparable habitat to the levees of the rivers further inland, and thus would have supported vegetation similar to that which generated the more usual Coal Measures macrofloras.