Facies associations and stratigraphic sequence of the Dhruma Formation (Middle Jurassic) at its type locality, Khashm adh Dhibi, Saudi Arabia

Abstract

The lithofacies, microfacies, and depositional environments of the Dhruma Formation were studied at the type locality at Khashm adh Dhibi to better understand the sedimentology and depositional history on the Arabian Platform. Twelve lithofacies were identified that can be grouped into four lithofacies associations corresponding to depositional paleoenvironments ranging from peritidal to open marine. The vertical distribution of the lithofacies and their corresponding depositional settings allow for the division of the Dhruma Formation into six 3rd-order sequences (DS1–DS6), each bounded by sharp vertical facies changes, and/or hiatuses. Abrupt negative shifts in both δ¹³C_carb and δ¹⁸O_carb values coincide closely with the placement of sequence boundaries on the Arabian Platform. This suggests that the carbonates in these zones underwent meteoric diagenesis during episodes of subaerial exposure. Comparison of the sequence stratigraphy interpreted from the vertical distribution of facies with published eustatic sea-level curves improves our understanding of the eustatic sea-level variation and/or local tectonics in forming both local hiatuses and regional unconformities.