The Hettangian–Sinemurian (Lower Jurassic) strata of Redcar, Cleveland Basin, NE England: facies and palaeoecology

Abstract

The foreshore at Redcar hosts the oldest Jurassic succession exposed on the Yorkshire-Cleveland Coast but has received little attention since the late nineteenth century. Temporary removal of beach sands by winter storms early in 2018 allowed for a sedimentological and palaeontological study of a nearly 60 m-thick foreshore section. The rocks are latest Hettangian to Early Sinemurian in age (Early Jurassic) and comprise five coarsening-upward cycles (parasequences) that grade from mudstones through siltstones into Gryphaea -rich shell beds. Ammonites are reasonably common along with a diverse benthos that includes abundant bivalves (e.g. Gryphaea, Cardinia, Luciniola, Plagiostoma and Oxytoma ) and rarer serpulids, gastropods, foraminifera and solitary corals. In the upper part of the section thicker-shelled taxa are commonly bored by cirripedes and bryozoans. Despite relatively high benthic diversity and intense bioturbation, pyrite framboids are common with size distributions suggesting deposition under a moderately oxygen-restricted water column. The Redcar succession post-dates the end-Triassic mass extinction by as much as 4 Ma and the diverse marine assemblages indicate that recovery was substantially complete by this time.