Acritarchs from the MacLean Brook Formation, southeastern Cape Breton Island, Nova Scotia, Canada: New data on Middle Cambrian-Lower Furongian acritarch zonation

摘要

We present here the results of a pilot study on Cambrian acritarchs from Cape Breton Island, Nova Scotia, based on a material from the MacLean Brook Formation in the Mira River Valley. An assemblage from the base of the formation contains 8 species including Eliasum llaniscum, Cristallinium dubium and Symplassosphaeridium cambriense, and correlates with a position close to the Paradoxides davidis-P. forchhammeri Zone boundary. An assemblage from the upper part of the formation contains 16 species, of which 3 are new, including Cristallinium aciculatum, Petaloferidium lacrimiferum n. sp., Pirea orbicularis, Stelliferidium pingiculum, S. magnum n. sp., S. albanii n.sp, and Timofeevia microretis, correlated to the Olenus Zone. The upper assemblage is particularly noteworthy as it provides the first direct evidence for the Olenus Zone in the MacLean Brook Formation. Furthermore, it contains stratigraphically significant taxa known from sections on Baltica, and northern Gondwana but which have not been reported previously on Avalonia. The distinction between Stelliferidium and Timofeevia is discussed in part based on new data on Timofeevia lancarae from its type area in northern Spain. It is suggested that many reports of Furongian Timofeevia phosphoritica and T lancarae are better referred to Stelliferidium.