Subtidal flat-pebble conglomerate from the Upper Devonian of Poland: a multiprovenant high-energy product

Abstract

SummaryCalcirudites in the Upper Devonian (Frasnian) of Central Poland are often couplets with a laminated intrapelsparite upper part and a lower section of intraformational calcarenitic and micritic flat pebbles. The pebbles are associated with bioclasts derived from 3 offshore environments: I, a fully marine area (echinoderms, rugose and tabulate corals, brachiopods, trilobites and conodonts); II, phytogenic banks (globose stromatoporoid stromatolites and Renalcis); III, restricted lagoons (ramose stromatoporoids, calcispheres, ostracodes and peloids). Many of the flat pebbles are only slightly displaced and had been partially cemented before being reworked. The depositional environment was subtidal. The considerable size of the flat pebbles and the complex nature of the surrounding matrix suggest that storm surges or tsunami may have disrupted beds and led to channelling and pebble formation.