Bioerosion traces on late cretaceous invertebrate skeletons from the Aruma Formation, central Saudi Arabia: Stratigraphic and paleoecological significance

The Upper Cretaceous Aruma Formation in central Saudi Arabia provides critical insights into the paleoenvironmental and paleoecological conditions of the Arabian Plate during the Late Cretaceous. This study documents and analyzes bioerosion traces on invertebrate skeletons (bivalves and echinoids) from the Aruma Formation to infer depositional environments and biotic interactions. A total of 383 bioeroded specimens were examined, revealing diverse ichnofossils, including Gastrochaenolites (bivalve borings), Entobia (sponge borings), Caulostrepsis, Maeandropolydora, Trypanites (polychaete borings), and Rogerella (barnacle borings). These traces indicate a shallow marine environment with fluctuating energy levels, firm substrates, and periods of low sedimentation. The high diversity of bioeroders suggests a complex ecosystem with intense competition for rigid substrates, while suspension-feeding borers point to nutrient-rich waters. The findings align with a carbonate platform setting influenced by regional tectonics and eustatic sea-level changes. This study enhances our understanding of Late Cretaceous marine ecosystems in the Arabian Plate and provides insights into the interplay between bioerosion, paleoecology, and depositional environments.