Assessing Milankovitch forcing during and in the aftermath of the Early Eocene Climate Optimum: Dammam Formation, Saudi Arabia

The Eocene Epoch was a time of great climatic significance owing to its records of the Paleocene-Eocene Thermal Maximum (PETM), the Early Eocene Climate Optimum (EECO), and the Middle Eocene Climate Optimum (MECO). In the Arabian Plate, the EECO and its aftermath coincided with the development of the Lower to Middle Eocene Dammam Formation, a cyclic shallow-water carbonate ramp with meter-scale parasequences. Previous studies have shown the significance of Milankovitch forcing in pacing the Eocene events and deposition of sedimentary strata. However, the controlling process behind the high-resolution parasequences of the Dammam Formation remains enigmatic, particularly on the relative dominance between random and quasi-periodic Milankovitch forcing. To investigate this issue, we coupled continuous records of Spectral Gamma Ray (SGR), Magnetic Susceptibility (MS), and δ¹³C - δ¹⁸O data to assess the influence of astronomical forcing and the signature of how the Eocene climatic events are recorded in this formation. Results show that the overall low sedimentation rate recorded in the Dammam Formation is comparable with globally reported sedimentation rates of some shallow marine Eocene carbonates and compatible with low accommodation space on the Arabian carbonate ramp. Deposition was interpreted to be astronomically influenced based on the presence of eccentricity-paced parasequences, rejection of the null hypothesis (p < 1 %), and the detection of Milankovitch cycles. The EECO event is detected within the shales and Alveolina-Nummulitic intervals of the Midra and Alveolina Limestone members of the formation. This study provides the first assessment of Milankovitch forcing during and after the EECO marine records of the Arabian Plate, which could be compared elsewhere.