The Paleozoic succession on the northern Arabian Plate was deposited during several regressive and transgressive events. The Early Devonian Subbat Member of the Jauf Formation comprises several smaller-scale intervals of the Paleozoic succession that were interpreted based on large-scale observations from outcrop and subsurface data. This study utilizes process-based sedimentology and investigates facies stacking, lateral continuity of sand bodies, and ichnofacies to interpret an open marine wave-dominated forced regressive system, that is followed by transgressive shorelines.
This study integrates a total of 417 meters of the Devonian stratigraphy from four outcrops and two shallow cores. This dataset records a third-order sequence which developed through an extensive intra-plate siliciclastic influx in between two carbonate units during the deposition of the Subbat Member. This study illustrates the evolution of a falling-stage systems tract that is characterized by shoreface sand bodies and an erosional-based delta front in the lower Subbat Member. These sediments overlie a regressive surface of marine erosion (RSME), extending for hundreds of kilometers and transitioning to an overall transgression in the upper parts of the Subbat Member.
This study interprets a total of seven facies associations (FAs): i) offshore, ii) wave-dominated delta, iii) shoreface to offshore transition, iv) fluvial channels, v) crevasse splays, vi) paleosol, and vii) estuarine facies associations. In the lower part of the Subbat Member, the wave-dominated delta and shoreface to offshore transitional FAs overlie the marine shelf strata of the offshore FA and develop a RSME. Fluvial channels and crevasse splays FAs are interpreted.
Unique assemblages of trace fossils, in terms of intensity and diversity, ranging from the Nereites Ichnofacies to Skolithos Ichnofacies, play a major role in the understanding of the overall water depth and depositional setting. Distinctive terrestrial Prototaxites fossils are present in sheet-like bodies and are interpreted as part of extensive crevasse splays that formed during major river flooding events. This study provides a unique integrated approach using ichnology, sedimentology, and sequence stratigraphy to better understand the spatial and temporal facies distribution of a forced regressive sequence and refine the paleogeography of northern Arabia during Early Devonian time.
