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Primary versus carbonate production in the Toarcian, a case study from the Llanbedr borehole (Mochras Farm, Wales)

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journal contribution
posted on 03.08.2021, 16:37 by Alessandro Menini, Emmanuela Mattioli, Stephen P. Hesselbo, Micha Ruhl, Guillaume Suan
Supplementary Figure S1. This figure summarizes most of the geochemical, sedimentary and biotic data available for the Mochras core. Comparisons are made with data from the Peniche section (grey curves). On the right side, ammonite biostratigraphy (Copestake and Johnson 2014). Calcareous nannofossil biostratigraphy based on Bown (1987), Mattioli and Erba (1999), and Ferreira et al. (2019). δ13Corg for the lower Toarcian (black dots) after Xu et al. (2018a) and for the upper Pliensbachian (grey dots) after Storm et al. (2020). (a) Envelope curve of δ180 (‰VPDB) values measured on brachiopod calcite from the Peniche section and interpreted as indicative of temperature changes (Suan et al. 2008a; Müller et al. 2020). (b) Peaks in low pH as deduced from δ11B (‰NIST951) measured on brachiopod calcite from the Peniche section (Müller et al. 2020). (c) Hg concentrations likely translating magmatic pulses of LIP (Large Igneous Province) volcanism in the Karro-Ferrar-Chon Aike provinces (Percival et al. 2015). (d) Osmium isotope trend (187Os/188Os) showing period of enhanced weathering rates (Percival et al. 2016). (e) Kaolinite/illite ratio percentage, whose peaks indicate the development of a more humid climate (Xu et al. 2018a). (f) High pyrite concentrations in the interval of the T-OAE negative CIE suggest transient photic-zone euxinia and episodic anoxia at the seafloor (Xu et al. 2018a). (g) Trends in calcium carbonate content for the lower Toarcian are after Xu et al. (2018b), and for the upper Pliensbachian are after Storm et al. (2020). (h) Trends in calcareous nannofossil flux as recorded in this paper. (j) Size variations of Schizosphaerella spp. valves as recorded in this paper. (k) Thickness of Schizosphaerella spp. valves as recorded in this paper. (l) Trends of meso-eutrophic taxa, mainly belonging to the Biscutaceae. (m) A prominent peak in Calyculaceae is recorded in the core of the T-OAE negative CIE, concomitant with the peak in pyrite. (n) The deep-dweller abundance trend (mainly Crepidolithus crassus) attest for the recovery of the deep-photic zone environments. (o) A peak in prasinophytes (green algae), and (p) a marked decrease of dinoflagellates in also documented at Mochras during the T-OAE by van de Schootbrugge et al. (2005). (q) Approximate ages of emplacement of Karoo and Ferrar LIPs (after Müller et al. 2020).

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