Carbonate mounds formed by mud volcanism at the Cretaceous-Paleogene boundary, Saudi Arabia

Abstract

More than 1,000 mound structures have been mapped in shallow marine sediments at the Cretaceous – Paleogene boundary in the Rub’ Al-Khali of Saudi Arabia. Mapping utilized 3D reflection seismic data in a 37,000 square kilometer study area. No wells penetrate the mounds themselves. The mounds are at a present-day subsurface depth of approximately 1 km and are convex-up with diameters of 200 – 400 m and elevation of 10 – 15 m. The mounds display spatial self-organization with a mean separation of approximately 3.75 km. Comparison with mound populations in other study areas with known spatial distribution statistics and modes of origin indicates that the mound population in this study has the characteristics of fluid escape structures, and they are interpreted here as mud volcanoes. The observation that the mounds occur at the Cretaceous – Paleogene boundary demands a singular trigger at that moment in time. We develop a model of seismic energy – related mud volcanism mechanism including the Chicxulub asteroid impact as the energy source that accounts for the timing of the mound structures, and a drainage cell model based on producing water wells that provides a mechanism for spatial self-organization into a regular pattern.