Deciphering the controls on silica and phosphate accumulation along the southern Tethys margin during the Coniacian–Maastrichtian (Jordan)

Over the past five years, the SEASTAR team at KAUST has developed a high-resolution sedimentological, sequence-stratigraphic, and chronostratigraphic framework for the Coniacian–Maastrichtian succession exposed along a ~300 km transect in Jordan. Exceptional outcrops document the transition from continental to shallow-marine environments, with a remarkable diversity of lithologies, including chalk, chert, carbonates, phosphorites, oyster bioherms, and organic-rich mudstones with TOC values reaching 22%. This succession records complex interactions between marine productivity, nutrient supply, sedimentation, and diagenesis in a shallow-marine carbonate ramp setting. The abundance of chert raises questions about the sources of silica, and the roles of biological productivity and diagenetic redistribution. Similarly, phosphorite accumulation may reflect variations in nutrient supply, upwelling, continental inputs, redox conditions, and sedimentary phosphorus recycling. The Coniacian–Maastrichtian of Jordan, which encompasses Oceanic Anoxic Event 3 (OAE 3, Coniacian) and subsequent environmental and climatic changes, provides an ideal framework to investigate these processes. Building on the newly defined stratigraphic framework and high-resolution sampling, this six-month Master’s project aims to characterize the mineralogy and geochemistry of two to three selected sections to better characterize the mineralogy and identify the main controls on silica and phosphate accumulation. Key questions include: (1) What is the origin of the chert, and to what extent does its abundance reflect enhanced silica production versus diagenetic redistribution? (2) What controlled phosphorite formation, and what were the respective roles of climate, nutrient supply, upwelling, continental inputs, productivity, redox conditions, and phosphorus recycling? The analytical programme will include XRF, micro-XRF, and XRD to characterize elemental composition and mineralogy; Rock Eval pyrolysis to characterize the type and preservation of organic matter, stable isotopes on carbonate (δ¹³C, δ18O) and organic matter (δ¹³Corg) to investigate carbon cycle dynamics; and, if feasible, total phosphorus measurements. Targeted petrographic or microscopic analyses will help constrain the origin of chert and phosphorites and distinguish primary biological signals from diagenetic processes. Results will be integrated with the existing stratigraphic framework to evaluate the influence of depositional environment, nutrient availability, sedimentation, and diagenesis. The internship will be conducted at KAUST under the supervision of Prof. Frans van Buchem, Dr. Amir Kalifi, and Dr. Alicia Fantasia (Université Bourgogne Europe, France). Laboratory work at the Université Bourgogne Europe may be considered depending on analytical requirements and logistical constraints.

Generate a genetic model of the controlling factors on silica and phosphate accumulation along the southern Tethys margin during the Coniacian–Maastrichtian (Jordan)