During the last decades, considerable work and discussion has focused on the causing mechanisms, amplitude and frequency of eustatic sea-level oscillations in the Cretaceous greenhouse world. Carbonate shelves and platforms are considered accurate gauges of changes in relative sea-level but only a very restricted number of geologic settings can be used pinpointing absolute water depths.

We have studied - within the framework of our Mid-Cretaceous Sea-Level Project - the Albian interval of the Arabian Platform in Northern Oman for its paleoceanographic and sea-level record. Five sections were measured and sampled on an approximately 100 km long transsect from paleo-marginal to paleo-basinal domains of an intracratonic basin. In all sections ferruginous hardground surfaces were recognised. Despite the lack of any diagnostic features such as karstification or spar-filled burrows, these hardgrounds were interpreted as subaerial exposure surfaces. This interpretation was mainly based on evidence from densely sampled carbon and oxygen isotope curves across these hardgrounds. Pronounced drops in carbon isotope ratios in the magnitude of 2.5 to 40 to values between +0.9 to -1.2 PDB were found in sediments underneath these hardgrounds. In sediments overlying the hardground surfaces values between +3 to 4 were obtained.

Based on these exposure surfaces an interpretation of the paleobathymetry and sequence stratigraphy has been undertaken suggesting that the Albian of Oman recorded seven transgressive-regressive cycles of third-order magnitude. Close correlation of these events with depositional cycles recorded in Albian sediments e.g. along the Texas Gulf Coast may suggest an eustatic nature of these signals.

AAPG Search and Discovery Article #90937©1998 AAPG Annual Convention and Exhibition, Salt Lake City, Utah