Stable carbon and oxygen isotopes of benthic and planktonic foraminifera as palaeoenvironmental and palaeoclimatic proxies for the Bartonian–Priabonian in northwestern Saudi Arabia

The Eocene epoch is known for its fluctuations in climate patterns and the dominance of global greenhouse climate. The Rashrashiyah Formation represents the middle to upper Eocene (biozones E13–E14) marine deposits of claystone to limestone in Saudi Arabia and contains well- to poorly-preserved planktonic and benthic foraminifera. Four different genera were selected for isotopic analysis (Acarinina spp., Subbotina spp., Cibicidoides spp., and Uvigerina spp.). Foraminiferal calcite was used to define the depth of habitat for each genus and mode of life. Four equations were used to infer palaeotemperatures from foraminiferal calcite; three equations are applicable for estimation of sea-surface temperatures (SST) from planktonic foraminifera data, while the fourth equation is applicable estimation of bottom-water temperatures using benthic foraminifera data. The mean SST derived from Acarinina spp. is ~38°C, while the mean bottom water temperature based on Uvigerina spp. is 26°C. Palaeotemperatures derived from this study are notably higher than those reported from this area in the existing literature. This discrepancy may be due to the unique palaeoclimatic and palaeogeographic conditions prevalent in the study area. The stable isotope curve is used to infer the transition between the Bartonian and Priabonian and the general cooling trend during this period.