Stratigraphic and Sedimentological Predictions, From Regional to Field Scale Approach: Examples from Aptian Intrashelf Strata, Saudi Arabia

Summary The carbonate ramp model has been commonly used to interpret the depositional settings of the Lower Cretaceous calcareous strata across the Arabian Plate. This model generally fits at the field scale; however, it fails when regional data is integrated across a broader area. As a consequence, this may mislead stratigraphic predictions. The integration of physical stratigraphy, core-based sedimentology, petrophysics, and seismic interpretation helped to build a robust stratigraphic framework and to construct gross depositional environment (GDE) indicators from each subject matter (e.g., 3D strata distribution, gross and net thickness maps, rock types trends, common vertical facies successions and lateral facies associations, and geomorphological seismic character from various attributes). The integrated analysis of GDE indicators helps not only to build comprehensive GDE maps but also to predict additional geomorphologic or paleoenvironmental details. The study herein shows an integrated GDE mapping depicting platform interior geomorphology within associated intrashelf settings for the Aptian strata. Extraction and display of a number of maps, time slices, and cross sections helped to capture observations regarding the 4D distribution of strata showing clastic wedges and shoal/bank complexes across the studied area. The Aptian strata across the AOI display lateral changes from clastic-dominated systems (sandy to muddy) passing into calcareous platform interior systems (muddy to grainy). The calcareous systems are associated with a highly heterogeneous rudist shoal/bank complex. This complex was vertically subdivided in two intermediate frequency base-level cycles. The basal cycle shows a landward stacking pattern, and the overlying cycle shows a seaward (basinward) stacking pattern. At intermediate or local mapping scale, the discrete rudistic shoals may laterally display clinoform-like morphologies at a scale of 10s of km. When shoals are observed isolated and out of regional context, their morphologies may be misinterpreted as a carbonate ramp. This study showcases 2D and 3D diagrams to illustrate the architecture and distribution of the intrashelf Aptian rudist shoal/bank complexes and their implication for stratigraphic and sedimentologic predictions. The findings of this study helped to recognize the widespread and overuse of ramp models throughout many stages, including the Aptian, across the Arabian Peninsula. In the past, this localized view and interpretation of the data have prevented geoscientists from making reasonable stratigraphic predictions. Herein, we appeal for an integrated GDE mapping approach to further enhance predictions and unveil stratigraphic exploration concepts across the Arabian Plate.