Foraminiferal assemblages, extinctions and appearances associated with the Early Toarcian Oceanic Anoxic Event in the Llanbedr (Mochras Farm) Borehole, Cardigan Bay Basin, United Kingdom

Microfossil assemblages and geochemistry for interpreting the incidence of the Jenkyns Event (early Toarcian) in the south-eastern Iberian Palaeomargin (External Subbetic, SE Spain)

“…The dominance of shallow infauna and the record of potential deep infauna such as Eoguttulina (MG-J3) and Lenticulina (MG-K) indicate good tiering as well as unrestricted trophic resources and oxygen availability. The same good tiering for foraminiferal assemblages is reported for the top of the Pliensbachian in the Lusitanian Basin (Rita et al, 2016;Reolid et al, 2019a), the Basque-Cantabrian Basin (Herrero, 1998), Cardigan Bay Basin (Reolid et al, 2019b), Atlasic Basin (Reolid et al, 2012b(Reolid et al, , 2013, and Umbria-Marche Basin (Bartolini et al, 1992), among others. The ostracods in the upper part of the Pliensbachian are also diverse in the Cueva del Agua section, and the record of bioclasts of other benthic organisms -echinoid, ophiuroid, and holothurian plates -confirms the favourable conditions at the seafloor.…”

“…Studies based on modern and ancient foraminiferal shells demonstrate that the mode of coiling, chamber arrangement, position of perforations, and features of aperture, among other aspects, are directly related to different lifestyles and trophic strategies (Corliss, 1985(Corliss, , 1991Jones and Charnock, 1985;Nagy, 1992;Tyszka, 1994). This work follows the morphogroup nomenclature proposed for Jurassic foraminifera by Reolid et al (2008bReolid et al ( , 2012b and modified by Rita et al (2016) and Reolid et al (2019b). A total of nine morphogroups were individualized (C, D, E, F, G, H, I, J, and K) in view of morphological features (test form, chamber arrangement, and mode of coiling), corresponding primarily to distinct lifestyles and secondly trophic strategies (Fig.…”

“…The abundance and α diversity of foraminifera in the Polymorphum Zone of the Cueva del Agua section decrease with respect to the top of the Pliensbachian, as observed at the Yorkshire coast (Hylton, 2000), Mochras borehole (Wales; Reolid et al, 2019b), the Peniche and Maria Pares sections (Portugal; Rita et al, 2016;Reolid et al, 2019a), and the Ratnek El Kahla section (Algeria; Reolid et al, 2012b). Epifaunal forms such as Reinholdella, Trochammina, and Spirillina increase near the top of the Polymorphum.…”

“…In other sections of the Tethys with less incidence of oxygenrestricted conditions (T-OAE), the biotic crisis is only represented by decreased abundance, α diversity, and size of foraminifera and ostracods, with a dominance of opportunist forms, but there is no barren benthic interval. Such is the case of the Aït Albegal and Issouka sections from the Middle Atlas (Morocco;Bejjaji et al, 2010;Reolid et al, 2013), Beni Snassen from Rif (northern Morocco; Boudchiche et al, 1987), the Mellala section of Tlemcen domain (Algeria; Reolid et al, 2014b;Soulimane et al, 2017a, b), the Maria Pares section from the north Lusitanian Basin (Portugal; Reolid et al, 2019a), the Muro de Aguas, Moneva, and Ricla sections from the Iberian Range (Spain; Herrero, 1994), the Pont de Suert section of the Pyrenees (Spain; Nicollin et al, 1995), the Quercy section of the Aquitaine Basin (France; Rey et al, 1994), Truc de Balduc (France; Hylton, 2000), the Valdorbia section from Umbria-Marche (Italy; Bartolini et al, 1992;Nocchi and Bartolini, 1994), and the Mochras borehole, Cardigan Bay Basin (western Wales; Reolid et al, 2019b). Therefore, the biotic crisis could be linked not only to oxygen-depleted conditions in the bottom, but also global warming, as the Jenkyns Event is identified as a hyperthermal event (e.g.…”

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

“…2. Stratigraphical distribution of the main foraminiferal morphogroups and subgroups and microhabitat depth (epifaunal, shallow infaunal and potential deep infaunal) according to Reolid et al ( , 2013Reolid et al ( , 2019a. value of 3.30 m and a median of 2.87 m. Figure 3 shows the histogram and basic statistics of the distance between two consecutive experimental data (sampling interval).…”