Abstract

Very similar high‐resolution δ 13 C carb and δ 13 C org curves are reported for the early Aptian “Livello Selli” (LS, oceanic anoxic subevent 1a) at two pelagic successions of the Alpine Tethys: “Roter Sattel” (Swiss Préalpes), deposited along the northwest margin, and “Cismon” (southern Alps of northern Italy), deposited along the southeast margin. The δ 13 C carb and δ 13 C org curves are both divided into eight segments, six of which occur within the early Aptian Globigerinelloides blowi foraminiferal zone, indicating significant subzonal resolution. Most of the LS coincides with a chemostratigraphically defined “Selli event”: a period of constant isotopic values (mean values of δ 13 C carb and δ 13 C org ≈ +2.6‰ and −25‰ respectively) lasting 500 kyr to 1 Myr, rather than of positive excursion as previously supposed. This uniformity may reflect an equilibrium between C org burial and increased recycling rates of 12 C and nutrient‐rich intermediate water resulting from the intensification of oceanic thermohaline circulation.