Sedimentological and stratigraphic associations of Earlandia (Foraminifera) from the Lower Triassic Khuff carbonates in central Saudi Arabia

Foraminifera belonging to the genus Earlandia are reported from the Lower Triassic Upper Khartam Member of the Khuff Formation in central Saudi Arabia, where four outcrop localities were studied in detail for sedimentology and micropaleontology. Out of more than 300 samples collected for sedimentological and micropaleontological analysis, only six samples recovered a foraminiferal assemblage, consisting entirely of Earlandia. These foraminifera are predominantly observed in an interlaminated quartz-bearing recrystallized limestone lithofacies. Earlandia occur in associations with quartz grains, peloids, ooids, ostracods, bivalves, bryozoans, cephalopods, and stromatolites. Sedimentological analysis indicates a widespread shallow epeiric sea that was sporadically connected to the open marine system. The sedimentological and architectural elements indicated agitated depositional conditions. The occurrences of Earlandia are restricted to the lower fourth-order sequence of the Upper Khartam Member, where non-skeletal grains (mostly oolitic grainstones) prevail. The skeletal grains co-occurring with Earlandia are found as a thin (20 cm) transgressive lag. Furthermore, the regional occurrences of Earlandia are consistent with a previously established high-frequency fifth-order sequence stratigraphic scheme, therefore, the occurrence of Earlandia in an otherwise unfossiliferous succession could be used as a biomarker for regional biostratigraphic correlation, and enhance the sequence stratigraphic correlations of theUpperKhartam Member of theKhuff Formation.