Abstract: Stratigraphy, Sedimentation, and Paleoenvironments of Middle Cretaceous Rocks of Central Saudi Arabia

Mohamed A. Moshrif

Field and laboratory investigations of the middle Cretaceous Buwaib-Biyadh-Wasia Formations of central Saudi Arabia as to lithologic character and texture, facies variations, paleocurrent vectors, X-ray analysis of clays, heavy minerals, cementation, and diagenesis show the following sequence of events.

During Hauterivian time the Buwaib carbonate rocks were developed along a shoreline and formed successive belts of lagoonal intertidal, and supratidal character responsible for deposition of the calcilutites, dolomites, gypsum, and a restricted fauna. The open shelf lay east of the lagoon zone, accounting for the development of calcarenites (shallow shelf) and calcilutites (deeper shelf) together with a diversified biota.

During early Barremian time a regressive depositional phase led to the accumulation of the alluvial substratum (dominant) and top-stratum deposits of the Biyadh sandstone. This fluvial lithofacies of the Biyadh was formed in the west as the result of seasonal rainfall over the basement complex of the Arabian shield (igneous and metamorphic rocks, mantled by Paleozoic and early Mesozoic sedimentary rocks), and the development of temporary, relatively low-sinuosity streams, following generally toward the east.

Between the Biyadh and Wasia Formations, the intervening Shu'aiba carbonate and clastic units were formed during Aptian time in a very shallow-marine environment coeval with deposition of the upper Biyadh sandstone in central Arabia.

During Cenomanian-Turonian time, the sedimentation of the Wasia Formation involved alluvial flood-plain conditions. The Wasia sands and gravels were derived from the same sources as the Biyadh and were formed in comparable environments and by east-flowing low-sinuosity streams.

A major marine transgression occurred during Companian-Maestrichtian time when the Aruma carbonate beds were deposited.

AAPG Search and Discovery Article #90961©1978 AAPG Annual Convention and Exhibition, Oklahoma City, Oklahoma