Palynological response to the Late Jurassic palaeoclimate and sealevel variations in the western Tethys (Binalud Mountains, NE Iran)

The upper Oxfordian to middle Tithonian strata in the Binalud Mountains were analysed to assess the response of palynomorph assemblages to palaeoclimate and sealevel variations. Palynofacies analysis indicates that the lower part of the section (upper Oxfordian – Kimmeridgian) was deposited in a distal shelf environment. A subsequent sealevel fall during the late Kimmeridgian and Tithonian is recorded by deposition in a proximal shelf basin. The sealevel history for this succession is inconsistent with the global record, suggesting that local tectonics, rather than eustasy, controlled the sealevel changes in the Binalud Basin. The floral assemblages record significant shifts in both terrestrial and marine environments during this interval. The late Oxfordian vegetation was characterized by low abundance of cooler‐adapted Araucarian conifers, whereas the Kimmeridgian–Tithonian witnessed a pronounced increase in the abundance and diversity of warm‐adapted cheirolepid conifers. This transition suggests a regional warming trend, further supported by the disappearance of key intermediate‐palaeotemperature dinoflagellate cysts such as Gonyaulacysta spp., Rhynchodiniopsis cladophora and Scriniodinium crystallinum , by the end of the Oxfordian. The Kimmeridgian–Tithonian warming in the studied section correlates with the southward drift of Eurasia, which positioned the Binalud Basin within the tropical arid belt ( c . 20°N) during the Late Jurassic. However, the global warming event during the Kimmeridgian may have amplified the regional tectonic factors.