Warm-water carbonates in proximity to Gondwanan ice–sheets: A record from the Upper Paleozoic of Iran

Abstract

Sedimentologic and paleontologic proxies recovered from the Alborz Basin, the Sanandaj – Sirjan Zone, and additional Iranian peri–Gondwanan continental blocks near the Arabian margin of northeastern Gondwana record the formation of warm-water, shallow-marine carbonates throughout the Late Pennsylvanian – earliest Permian. This reflects a prevailing favorable climatic and environmental regime that contrasts with the cold conditions of slightly more southerly Gondwanan regions that experienced profound glaciations. The sedimentologic and paleobiologic properties of these Iranian carbonates also differ greatly from coeval cool-water carbonates of Bolivia that developed at equivalent paleolatitudes along the northwestern margin of Gondwana. The complex climatic patterns reflected in the dispersal of marine taxa and their colonization of ecosystems relatively remote to their customary habitats and climate zones are interpreted to record the influence of ocean circulation. Based on these sedimentologic and paleobiologic data, we utilized a climate model (Community Climate System Model Version 3 (CCSM3)) to help resolve the mechanisms responsible for enabling transport of warm water to higher latitudes in northeastern Gondwana. These simulations reveal that spatial variations in sea surface temperatures exerted a strong forcing on Paleo-Tethyan oceanic circulation and thereby governed the distribution, diversity, and abundance of taxa in late Paleozoic marine ecosystems. Based on this outcome, we conclude that the climatic contrasts registered across Upper Pennsylvanian – Lower Permian carbonate platforms of the Paleo-Tethys and Panthalassic Ocean originated through oceanic circulation driven by geographic differences in sea surface temperature.