Abrupt early Eocene global climatic change as a control of carbonate facies and diagenesis: A new record of the Palaeocene-Eocene Thermal Maximum in the Umm er Radhuma Formation, Saudi Arabia and Kuwait

摘要

Records of the Palaeocene-Eocene Thermal Maximum (PETM) and associated Carbon Isotope Excursion (CIE) are relatively rare in shallow- marine carbonates when compared with those from other regimes, and it remains unclear exactly what effect this global climatic event had upon the widespread epeiric carbonate platforms of the Palaeogene. In this study, we demonstrate that the Umm er Radhuma Formation in the Wafra field, Kuwait and Saudi Arabia, shows a carbon isotope profile consistent with the CIE that can be correlated globally and further, that global climate change during and subsequent to the PETM exerted a fundamental control on primary depositional facies and subsequent diagenesis. The Palaeocene-Eocene Thermal Maximum was a brief hyper-thermal event marking the onset of sustained high global temperatures during the Early Eocene. This warm period increased aridity in epeiric carbonate platform interiors of what is now the Middle East, affecting composition of depositional facies and the precipitation of early dolomite. This is demonstrated through the use of new data from the Umm er Radhuma Formation, Wafra field, Partitioned Zone, Saudi Arabia and Kuwait. Biostratigraphy and carbon isotope profiles have been used to constrain the position of the PETM and Carbon Isotope Excursion; a distinct ～2-3‰ negative spike. The observed excursion is demonstrated to correlate globally and provides age dating of this regionally important succession. Core and thin-section data show marked restriction of facies across the PETM, evidence of increasing aridity reflected in proportion of evaporite precipitates and a stratigraphically restricted non-mimetic dolomite coeval to the CIE that is interpreted to relate to a change in the rate of dolomite precipitation. This work provides an example of how a global environmental event is manifest in depositional and early diagenetic changes in marine carbonates.