<p>Despite decades of research on the Aptian-Albian Kazhdumi source rock of SW Iran, uncertainties exist about its petroleum generation and expulsion behavior at both local and regional scales. The present study presents both macroscopic and microscopic evidence supporting the petroleum generation and expulsion from the Kazhdumi source rock at Kuh-e-Bangestan reference section. The studied outcrop section is composed of ~ 270 m of organic-rich marls with interbedded carbonates and provides an ideal setting to study the complete Kazhdumi succession from base to top. Organic petrographic observations reveal that the organic-rich marls are characterized by abundant fluorescing algal organic matter with bituminite and widespread solid bitumen. The equivalent vitrinite reflectance (VReq%) of 8 samples from the Kazhdumi Formation, estimated based on solid bitumen reflectance, shows an average value of 0.61% consistent with maturity corresponding to the early stages of oil window. Burial history reconstruction further suggests that the Kazhdumi source rock experienced enough burial required for oil generation before being uplifted in the study area. Carbonates of the overlying Sarvak Formation provide unambiguous evidence at both macroscopic and microscopic scales supporting petroleum expulsion from the Kazhdumi source rock. Field-scale evidence include: i) abundant petroleum-filled fractures, and ii) weathered surfaces mottled with purple stains. On the other hand, microscopic evidence include petroleum occurrences inside intra-crystalline pores and in the fracture porosity of the Sarvak carbonates. These observations suggest that unknown amounts of petroleum were expelled from the Kazhdumi source rock at Kuh-e-Bangestan section, which led to the charging of the overlying Sarvak carbonates. Nevertheless, the paleo-oil accumulation was lost at the surface due to the erosion of the Sarvak Formation during intense structural deformation and breaching of the Kuh-e-Bangestan Anticline.</p>