Evidence of warm climate during late Sakmarian–early Artinskian in Posht‐e Badam Block, Central Iran and its paleogeographic implication

Abstract

Examination of the geochemical data, faunal associations, and bauxite/laterite horizons in the Khan Formation, in Kalmard area, Posht‐e Badam Block, Central Iran are presented. The data provide insights on the paleogeographic position of Central Iran as part of the Cimmerian during the late Sakmarian–early Artinskian time. Bauxite/laterite as valuable warm and humid paleoclimate proxies are observed in all studied sections of the mixed siliciclastic‐carbonate Khan Formation and are meters to tens of meters thick. The warm and humid climate is also verified by the previous studies of Khan Formation sandstones yielding high chemical weathering and highly mature quartz grains. Plant fossils recovered from these sandstones are further evidence of the warm and wet climate. The results of the geochemical studies of the Khan Formation carbonates are in robust agreement with the inferred paleoclimate condition from bauxite/laterite horizons and sandstone studies of the Khan Formation. The bivariate plot of major and minor elements shows that aragonite as an indicator of warm water conditions was the major carbonate mineralogy of the Khan Formation limestones. Temperature calculation based on the heaviest oxygen isotope value of the least‐altered sample indicates that the temperature was around 36 and 29 °C for dolomites and limestones of the Khan Formation, respectively. The skeletal grains of the Khan Formation limestones are representative of a photozoan association with fusulinids, smaller foraminifers, calcareous algae, and common crinoids, brachiopods and bryozoans and also ooids and peloids as non‐skeletal grains. Therefore, the results of this study are not in agreement with previous fusulinid‐based paleogeographic interpretations, which suggested a high‐latitude paleoposition for the Posht‐e Badam Block and its separation from other Central Iran terrains during the late Sakmarian–early Artinskian. These data indicate that Posht‐e Badam Block was part of Central Iran during the late Sakmarian–early Artinskian, and its paleoposition was at a low paleolatitude.