DECIPHERING DIAGENETIC INFLUENCES AND LOCAL CONDITIONS IN LATE EDIACARAN STRATA, CENTRAL OMAN (Invited Presentation)

This study investigates diagenetic alteration and local controls on geochemical variability in the geologically rich Ediacaran-aged strata of Central Oman. Here, marked carbon and oxygen isotopic variability is present (δ¹³C ranging from +9 to -12.8‰, VPDB and δ¹⁸O ranging from +6 to -11.6‰, VPDB) in rocks that closely resemble those found in modern and ancient sabkhas. We present results from our field work included mapping, stratigraphic sections, and outcrop-scale characterization. Lab based characterization includes the examination of ~100 thin sections of rocks and cements. We also present carbon, oxygen, and clumped isotope analyses, supplemented by EPMA elemental mapping, XRD, SEM analysis, and U/Pb geochronology for dating key diagenetic events.

Our findings reveal a complex paragenetic history for the Huqf outcrop area with at least four distinct diagenetic events including authigenic carbonate and clay precipitation, meteoric alteration, karst brecciation, and deep burial fluid-driven alteration. Each event preserves unique petrographic and geochemical signatures linked to specific cement phases. For instance, meteoric cements have clumped isotope temperatures of ~35°C and show precipitation from waters with δ¹⁸O values of ~-7‰, VSMOW while deep burial cements record clumped isotope temperatures of ~80°C. We examine the petrographic and geochemical characteristics of the host rocks within the Khufai, Shuram, and Buah formations (including both dolomitic and calcitic intervals) within the context of these geochemically distinct cement end-members. Not all isotopic variability can be explained by these post-depositional diagenetic events, highlighting the importance of facies and stratigraphic controls on geochemical trends such as the Shuram carbon isotope excursion. Lastly, we explore the influence of depositional environment on key geochemical trends, leveraging the nearly complete depth gradient from shallow, marginal marine to basinal environments preserved in Oman's outcrops and subsurface. Our comprehensive approach aims to unravel the complex interplay between local and global processes and post-depositional modification, shedding new light on the drivers behind geochemical variability in Oman's Ediacaran strata.