Carbon (δ13C) isotope variations indicate climate shifts and reflect plant habitats in the Middle Triassic (Anisian, Pelsonian) succession at Kühwiesenkopf/Monte Prà della Vacca (Dolomites, Northeast Italy)

Abstract

We report carbon (δ13C) isotope records from the Middle Triassic (Anisian, Pelsonian) Kühwiesenkopf/Monte Prà della Vacca succession in the Dolomites of northeast Italy, to infer palaeoclimate and palaeoenvironmental changes. This interval comprises hemipelagic carbonate-terrigenous facies deposited in a marginal marine setting and includes a well-known allochthonous plant fossil assemblage at one horizon. We obtained two datasets: (1) carbon isotope records of bulk samples (dispersed organic carbon), which comprise a mixture of terrestrial and marine sources, for the whole 200 m thick succession, and (2) taxon-specific records for the plant bed at a single horizon. Analyses of the dispersed organic matter reveal several significant positive excursions through the Kühwiesenkopf/Monte Prà della Vacca section, some of which may be related to local conditions, whereas others match climate shifts recorded elsewhere in the Tethys Realm. For taxon-specific studies of the plant bed, isotopic values show a correspondence with the spectrum of habitats inferred to have been occupied by the plants. Species inferred to have grown in habitats along environmental gradients are characterized by wide isotopic ranges, whereas those restricted to narrow environmental conditions show a low isotopic variability. Our study highlights how organic carbon isotopic analyses on well-preserved plant remains are excellent tools to define the palaeoecology of plants and to improve our palaeoenvironmental reconstructions of the past.