Sequence Stratigraphy and Computer Simulation of the Khuff Formation (Late Permian-Early Triassic), Saudi Arabia and Other Gulf Countries

Kurt W. Johnson, Christopher G. Kendall university of South Carolina and Ibrahim A. Al-Jallal Saudi Aramco

The Khuff Formation ranges in age from Late Artinskian through the Scythian and consists of carbonates, evaporites, and minor clastic lithologies. These were deposited on a broad, shallow shelf and lithologic facies include siliciclastics, mixed evaporitic carbonates and siliciclastics restricted evaporitic carbonate shelf, shallow carbonate shelf, organic reefal and argillaceous deep marine carbonates. Sequence stratigraphy and a computer simulation were applied to interpret the Khuff Formation.

In Arabia, the formation is divided from base up into the siliciclastic Khuff E, and the carbonate/anhydrite Khuff D, C, B, and A units. It contains eight third order sequences, six of which contain relatively thick accumulations of anhydrite. Basal sequence boundaries are placed at the base of the anhydrite, which is interpreted to collect in lowstand systems tracts on the shelf. Not all the sequences within systems tracts within the Khuff Formation have this basal lowstand anhydrite.

The Khuff sequences were simulated with Schutter’s chart (personal communication) to simulate the Permian portion, while the Triassic portion was simulated using the Haq et al. (1988) chart. Subsidence rates during simulation were kept constant, reflecting the uniformity of the sedimentary section for the 21 million years duration of deposition. Carbonate rates increased from zero centimeters/1,000 years at 300 meters, to 2 centimeters/1,000 years at 20 meters, to 12 centimeters/1,000 years at the surface. The Khuff Formation has limited biostratigraphic age control, but coupling these ages with a sea level curve provides a method for dating its sequences. These sequence dates were tested with the simulation and used to date the five informal members of the Khuff Formation. The simulation suggests that the Khuff E is contained within the Khuff D member.

1998 GeoArabia v.3#1:106