Lower Triassic conodont succession and carbon isotope profile from Zaluch, Salt Range, Pakistan

Abstract

The Salt Range in northern Pakistan is a key reference area for studying Lower Triassic biostratigraphy and chemostratigraphy, particularly with respect to conodonts and carbon isotopes. However, our current understanding of the conodonts from this region relies mainly on studies conducted in the previous century, the results of which require revision in light of recent taxonomic advancements. This paper presents an updated conodont taxonomy and biostratigraphy for the Zaluch section of the Salt Range. Twelve conodont zones are recognized, in ascending order: the Hindeodus parvus, Isarcicella lobata, Is. isarcica, Neoclarkina krystyni, Sweetospathodus kummeli, Neospathodus dieneri-Ns. cristagalli, Novispathodus waageni eowaageni, Ns. posterolongatus, Nv. shani, Nv. pingdingshanensis, Triassospathodus homeri, and Tr. sosioensis zones. These conodont zones, integrated with a high-resolution organic carbon isotope record, enable robust correlations between the Zaluch section and other well-studied Lower Triassic sections worldwide. The Permian-Triassic boundary is tentatively placed at the base of the Mianwali Formation, marked by the lowest occurrence (LO) of Hindeodus parvus. The Induan-Olenekian boundary, identified based on the LO of Novispathodus waageni eowaageni, is positioned in the middle part of the Ceratite Marls, 11.45 m above the base of the Mianwali Formation and 5 m below the P2 peak of carbon isotopic excursion of the Early Triassic. The Smithian-Spathian boundary, marked by the LO of Nv. pingdingshanensis, is placed at the base of the Bivalve Beds, 34.75 m above the base of the Mianwali Formation, and is associated with a sharp positive carbon isotope excursion. Additionally, two new conodont species, Neospathodus prolixus and Ns. diminutus, are described.