High-resolution stratigraphy of the deep-water lower Cloridorme Formation (Ordovician), Gaspé Peninsula, based on K-bentonite and megaturbidite correlations

The Ordovician Cloridorme Formation is a thick foreland-basin turbidite succession that for several decades has served as a natural laboratory for the long-distance physical tracing and study of single turbidites. A robust temporal correlation of these deposits is a prerequisite for the evaluation of sedimentary processes. Published stratigraphic subdivisions of the lower part of the Cloridorme Formation have impeded rather than facilitated such studies because of errors in the physical correlation of contemporaneous deposits. Tracing of the deposits of exceptionally large gravity flows, known as "megaturbidites," was previously recognized as a useful stratigraphic tool. Here, we strengthen and revise the stratigraphic framework based on megaturbidites by considering nine widely traceable and geochemically fingerprinted tuffs (K-bentonites). Two discriminant functions incorporating the abundances of six trace elements (V, Sm, Nd, Th, Er, Zr) permit the unambiguous distinction of the lower four tuffs. The ...