SEDIMENTARY STYLE & RELATED FACIES ARCHITECTURE IN FAULT-ASSOCIATED MIX CLASTIC-CARBONATE SYSTEMS OF ISOLATED BASINS: AN EXAMPLE FROM EDIACARAN DHAIQA BASIN IN SAUDI ARABIA

Ediacaran sedimentary successions of NW Arabian plate are distributed in several, isolated Najd fault-associated basins along the NW region of the kingdom. Although preliminary work focusing on the geochemistry and radiometric dating has been carried out, no detailed sedimentary facies description and depositional framework of any of these outcrops had been established. Due to lack of detailed sedimentological control, previously formulated results also fail to delineate the extant and environment of deposition of these sediments leading to confusion and debate. This confusion makes the regional and global correlation of these successions difficult and hinders research advancements. For this purpose, our study act as pioneer in understanding and describing the best exposed Ediacaran section “The Dhaiqa Basin” among all Ediacaran exposures in the Kingdom of Saudi Arabia. Detailed sedimentology of the Dhaiqa basin has been established to determine the much-debated depositional environment of these units scattered around in different small basins in central and NW region of Saudi Arabia. Contrary to popular belief, the studied section is found to be more of a mixed clastic-carbonate system rather than a continuous carbonate succession. These sedimentological findings are further used to interpret the depositional environment. Detailed mineralogical and geochemical studies using state of the art equipment’s are also performed to aid-in our understanding and to confirm and corelate with previous works done on the area. The Dhaiqa basin is found to be a potentially fault-controlled basin, originated at flank of a normal fault developed during some stage of left-lateral transcurrent Najd Fault system. Sediments deposited include basal fanglomerates covered by mix clastic-carbonates and microbialites facies of limestones. Laminated sandstones overlie these carbonates indicating a shallow water origin predominantly lacustrine with close proximity to the source. Based on previous as well as newly performed stable isotope results, the basin seems to be isolated with no contact relationship found with the open seas of Ediacaran times so far. Acquired results will further help in correlation of sediments across the Arabian plate as well as with other similar sediments across the globe.