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

摘要: Abstract. By studying the facies, geochemistry, and microfossil assemblages of the uppermost Pliensbachian lower Toarcian Cueva del Agua section, I was able to appraise impact Jenkyns Event in eastern part of the South Iberian Palaeomargin (Western Tethys). Depleted oxygen conditions are envisaged for Polymorphum–Serpentinum Zone boundary (lower Toarcian), represented by dark marls, precisely a laminated interval. The decrease α diversity foraminifera ostracods, along with greater proportions opportunists such as Lenticulina, Eoguttulina, Cytherella just before the negative carbon isotopic excursion (CIE), would indicate disturbance the environmental conditions during initial phase biotic crisis. The peak crisis is characterized an absence trace fossils, increased organic matter content, increased Mo∕Al ratio, negative CIE and δ18 O, well fewer specialist forms more opportunists. This peak related oxygen-depleted the bottom waters sediment pore water, while warming negatively affected microfauna – point leaving barren benthic horizon in the record. Recovery evidenced occurrence carbonate layers with hummocky cross-stratification decrease the fossil In terms microfauna, the first recovery shows highly abundant foraminifera, and microgastropods, mainly opportunist forms. After proliferation of opportunist forms, second marked progressive increase diversity.