Investigating the controls on the development of distally steepened carbonate ramps: A stratigraphic forward modelling of the Upper Miocene distally steepened Menorca ramp, Spain.

Despite the numerous studies dedicated to understanding distally steepened carbonate ramps, the origin of these carbonate systems and controls over their development remain an ongoing discussion. Previous studies have shown the possible impact of climate, tectonics, inherited slope, and differential sedimentation on distally steepened ramp development. However, how these processes create steep slopes in carbonate ramps has yet to be fully understood. To test the role of different processes such as sea-level fluctuation, paleosurface inclination, differential sedimentation, and wave propagation on the geometry of carbonate ramps, we developed a highly constrained stratigraphic forward model referenced to the well-studied Upper Miocene Menorca ramp (Spain). Based on this forward model, several sensitivity analyses were performed and revealed that a complex interaction of changes in accommodation, carbonate production and sediment transport controls steep slope development in carbonate ramps. The results also show that protracted sea level low stand followed by high-frequency sea-level fluctuations with amplitude between 30 m and 40 m favour the initiation of steepened slopes in carbonate ramps. In contrast, models developed with low-frequency and higher amplitude sea-level fluctuations of about 115 m showed no significant slope development. Testing with different inclinations of paleosurfaces shows that flat-to-subhorizontal paleosurfaces result in ramps that mirror the antecedent slope. In contrast, steeper paleosurfaces tend to result in ramps with well-defined slopes. Steeper paleosurfaces also enhance facies differentiation and steep slope development than flat paleosurfaces. Our models, thus, show that the ramp profile becomes more influenced by the depth constraints on the carbonate sediment producers than by the geometry of the underlying topography as the inclination of the paleosurface increases. The models also show that shallow carbonate production tends towards steep slopes due to the low-transport characteristic due to seagrass trapping. This steepness could, however, be altered by the introduction of high-transport sediment grains from deeper carbonate producers, which fill the slopes and more distal sections of the ramp profile.