Timing the Cambrian Sauk Transgression in the Southeastern Arabian Plate: Evidence from Radiogenic Strontium of Early Calcite Cement

The Cambrian Sauk transgression marks one of the most extensive episodes of marine inundation in Earth’s geological record. Despite its importance, accurately constraining its timing remains problematic in many regions because of limited biostratigraphic indicators and the scarcity of robust chronometric tools. In this study, we introduce an integrated petrographic, geochemical, and geochronological framework to constrain the age of the Sauk transgression on the southeastern Arabian Plate. This is achieved through analysis of trace-fossil burrows developed along the Cambrian maximum flooding surface (Cm20 MFS) within the middle Miqrat Formation of central Oman. Microscopic examination shows that calcite cement infilling the burrows is characterized by a drusy crystal fabric and occupies loosely arranged framework grains, indicating early cementation under near-surface conditions soon after sediment deposition. This interpretation is corroborated by clumped isotope (Δ47) data, which indicate calcite precipitation temperatures between 33.8°C and 36.4°C, with a mean value of approximately 34.8°C. These temperatures align well with independently estimated middle Cambrian sea-surface conditions. Measured Sr87/86 ratios of the burrow-filling calcite range from 0.7088456 to 0.7090134 (mean 0.7089270), yielding an inferred age of approximately 508.20–509.86 Ma, with an average age of 509.26 Ma. This age assignment falls within the middle Cambrian and is marginally younger than the maximum depositional age of ~511 Ma obtained from detrital zircon analyses. The ages reported here represent the first direct numerical constraints on the Sauk transgression from the southeastern Arabian Plate and demonstrate consistency with equivalent ages documented from the northern and northwestern parts of the plate. Overall, the results highlight the effectiveness of Sr87/86 isotope analysis of early diagenetic calcite as a chronostratigraphic tool. Because such calcite precipitates from marine-derived fluids shortly after deposition, it faithfully records the seawater isotopic composition at the time of cementation, allowing reliable dating of sedimentary successions.