Facies architecture of Lower Fars Formation at Jal Az-Zor escarpment, Kuwait

The Lower Fars Formation exposed at Jal Az-Zor escarpment north Kuwait is the largest outcrop site in the country. Despite its size and accessibility, little work is done to understand its depositional environment. This could be attributed to the complex architecture of the exposed facies, where dramatic changes in vertical and lateral facies distribution can be challenging to decipher. The complex facies architecture of the Lower Fars Formation exposed at Jal Az-Zor is analyzed in detail over a 3-year period. Multiple traverses and stations have been performed over the largest valley at Jal Az-Zor escarpment. The detailed analysis included outcrop facies description utilizing basic geological concepts and advanced analytics such as XRD/XRF lab analysis was performed. The main objective was to characterize the various facies and facies associations to identify the associated depositional environments. The field work resulted in the identification of sixteen facies that are grouped into six facies associations revealing a predominant regressive stacking pattern. These facies are: Bioturbated cross-bedded facies (F1) Cross-bedded conglomeratic facies (F2) Red claystone facies (F3a) Reddish-green claystone facies (F3b) Calcareous sandstone facies (F4) Cross-bedded sandstone facies (F5a) Lateral accretion red sandstone facies (F5b) Bedded red muddy sandstone facies (F5c) Fine-grained-bedded sandstone facies (F6b) Microbialites facies (F6c) Trough cross-bedded sandstone facies (F7) Yellowish-green siltstone facies (F8) Coarsening-upward calcareous sandstone facies (F9) Fossiliferous sandstone facies (F6a) Unconsolidated silty-sand facies (F6d) Calcareous sandstone lenses (F10) These facies are grouped into six facies associations that suggest: Estuarine depositional environments (FA-1) Tidal channel depositional environments (FA-2) Shoreface depositional environments (FA-3) Terrestrial depositional environments (FA-4) Barrier island depositional environments (FA-5) Back-barrier depositional environments (FA-6) It has been concluded that these exposures were deposited in a riverine to tidally influenced estuary depositional environment that was associated with a barrier island complex. The system extended for at least 40 km flowing to the NE direction perpendicular to a paleoshoreline that trends in the NW-SE direction.