Sr isotope variations in the Upper Triassic succession at Pizzo Mondello, Sicily: Constraints on the timing of the Cimmerian Orogeny

Abstract

The Late Triassic Cimmerian Orogeny was a result of the final closure of the Palaeotethys Ocean and the accretion of Gondwana-derived (Cimmerian) continents to southern Eurasia. Determining the timing of the Cimmerian Orogeny is crucial to our understanding of the large-scale climate changes driven by the uplift of the Cimmerian Mountains. Here we present stratigraphic variations in 87Sr/86Sr values of Upper Triassic pelagic limestone from the Pizzo Mondello section, Sicily, Italy, that constrain the timing of uplift of the Cimmerian Mountains. The 87Sr/86Sr values remain relatively constant in the lower part of the section, decreasing slightly in the Tuvalian (upper Carnian) and Lacian (lower Norian). However, 87Sr/86Sr ratios rise sharply at the Lacian–Alaunian (lower–middle Norian) boundary and continue to rise through to the Sevatian (upper Norian). This observation indicates an increased input of radiogenic strontium derived from continental weathering, which resulted from the rapid uplift and erosion of the Cimmerian Mountains at this time. The climatic and environmental changes following the uplift of the Cimmerian Mountains provide an explanation for (1) an intense sea-surface-temperature warming event in the western Tethys Ocean, and (2) a rapid increase in precipitation on the northern coast of the Tethys during the Alaunian–Sevatian.