Cyclic environmental changes during the Early Toarcian at the Mochras Farm Borehole (Wales): a variable response of the foraminiferal community

Abstract

Cyclostratigraphical analysis of the foraminiferal assemblages from the Early Toarcian at the Mochras Farm Borehole (Wales) was conducted in order to evaluate the incidence of cyclic palaeoenvironmental changes on the foraminiferal community. Different variables such as type of morphogroup, evolutionary strategy, habitat, particular taxa, diversity and abundance were studied using the Lomb-Scargle periodogram implemented in the computer program SLOMBS. A well-developed cyclostratigraphical pattern is recognized, with the presence of several cycles (in metres) at 3.

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).…”