Sedimentary Response to Tectonic and Eustatic Changes: an Example From the Mid-Cretaceous Wasia Formation, Saudi Arabia

ABSTRACT Deposition of the dominantly siliciclastic Cretaceous Wasia Formation (Albian through Turonian) in Saudi Arabia was initiated when tectonic movement uplifted a portion of the Arabian Shield. The magnitude of this uplift was greatest to the north as evidenced by the Pre-Wasla Unconformity, The Wasia, which is normally conformable to the Aptlan Shu'alba Formation, overlaps increasingly older formations from the Cretaceous Biyadh in the south to the Lower Devonian carbonates in the north. The primary sources of the Wasia sediments are the older formations eroded when the Pre-Wasla Unconformity was active. Feldspar, heavy mineral and quartz type distributions within the Wasia members suggest that the Arabian Shield was not a major contributor of sediments for the Wasia until the Wara member was deposited in late Albian Time. The depositional sequence of the Wasia is reconstructed from evidence derived from outcrop, cores, and various subsurface maps. Eustatic cycles documented worldwide are correlated with the Wasia members, with limestone units representing Mid-Cretaceous transgressions.