Conodont biofacies of a monotonous middle Famennian pelagic carbonate succession (Upper Ballberg Quarry, northern Rhenish Massif)

Abstract

A succession of mostly thin-bedded, cyclic pelagic limestones is exposed in the abandoned, previously unstudied Upper Ballberg Quarry in the northern Sauerland (northern Rhenish Massif, Germany). Macro- and microfacies analyses show a rather uniform lithology of bioturbated, microsparitic mud-wackestones deposited below storm wave base on an outer shelf submarine rise formed by the drowned Honne Valley Reef Complex. Twelve conodont samples are assigned to the middle Famennian Pa. marginifera marginifera-marginifera utahensis zones (former Lower and Upper marginifera zones), which are difficult to separate in the Rhenish Massif. There are 30 taxa, including Icriodus ballbergensis n. sp., a representative of the I. cornutus Group. A refined conodont biofacies analysis, based on the separation of species groups within genera with potentially different palaeoecology, led to the distinction of five subfacies of the outer shelf Palmatolepid Biofacies. A detailed comparison with the available global quantitative conodont record proves their significance in pelagic settings. The distinctive fluctuations in conodont assemblages despite a monotonous lithology prove that refined conodont biofacies analyses have the potential to reconstruct palaeoenvironmental changes with a much higher precision than microfacies studies.