On the occurrence of rare nannoliths (calcareous nannofossils) in the Early Jurassic and their implications for the end‐Triassic mass extinction

Abstract

A peculiar record of previously undescribed and/ or rarely described nannoliths from the Hettangian to lower Pliensbachian of the Llanbdr (Mochras Farm) core, Wales (UK) is documented here. Some of the observed morphotypes are assigned to didemnid ascidians, commonly observed in the upper Rhaetian, as evidence of the resilience of ascidian tunicates during the end-Triassic mass extinction. One newly described nannolith present throughout the Hettangian and Sinemurian, Quadrifolium hesselboi, is similar to forms previously observed in the upper Rhaetian, and is therefore considered to be a new nannofossil survivor from the end-Triassic mass extinction. High-amplitude changes observed in the absolute and relative abundances of nannoliths, schizosphaerellids and coccoliths across the Hettangian suggest a recovery interval from the end-Triassic crisis spanning the planorbis-liasicus ammonite zones in four distinct steps with high volatility in environmental conditions, followed by the establishment of more stable environmental conditions in the angulata ammonite zone.

Initial results of coring at Prees, Cheshire Basin, UK (ICDP JET project): towards an integrated stratigraphy, timescale, and Earth system understanding for the Early Jurassic

“…∼ 1.5 m) stratigraphic intervals (Storm et al, 2020). Although much work has been carried out on the legacy Mochras core as part of the JET project (Percival et al, 2016;Ruhl et al, 2016;Baker et al, 2017;Xu et al, 2018a, b;Deconinck et al, 2019;Storm et al, 2020;Hollaar et al, 2021Hollaar et al, , 2023Menini et al, 2021;Munier et al, 2021;Pieńkowski et al, 2021;Damaschke et al, 2022;Ruhl et al, 2022;Ullmann et al, 2022;Paulsen and Thibault, 2023), the poor physical state of the lower half of the core (Hettangian and Sinemurian) means any signal of orbital cy-4 S. P. Hesselbo et al: Initial results of coring at Prees, Cheshire Basin, UK (ICDP JET project)…”

Early Jurassic extrinsic solar system dynamics versus intrinsic Earth processes: Toarcian sedimentation and benthic life in deep-sea contourite drift facies, Cardigan Bay Basin, UK

“…1). The Toarcian part of the core has been studied in many respects, including biostratigraphy (Woodland 1971; Page in Copestake and Johnson 2014;McArthur et al 2016), lithology (Woodland 1971;Dobson and Whittington 1987;Hesselbo et al 2013;Copestake and Johnson 2014;McArthur et al 2016), carbon cycle and climatedriven local sedimentary processes (Jenkyns et al 2002;Xu et al 2018a), ostracod and foraminiferal assemblages (Boomer 1991;Copestake and Johnson 2014;Reolid et al 2019;Rodríguez-Tovar et al 2020), magnetostratigraphy (Xu et al 2018b), and calcareous nannofossils and primary productivity (Bown 1987;Menini et al 2021;Paulsen and Thibault 2023). A chemostratigraphic reference record shows a major ∼ 7‰ negative excursion in δ 13 C TOC , associated with the Toarcian Oceanic Anoxic Event (T-OAE) preceded and followed by early Toarcian positive excursions (Jenkyns et al 2002;Xu et al 2018b).…”