Although many ancient carbonate successions represent deposition on ramps, modern carbonate ramps are poorly understood. To characterize carbonate ramp systems in general, and to better understand the sedimentary dynamics and accumulations of Yucatan shelf Holocene ramp system in particular, this project tests two hypotheses: 1) sediment size, sorting and type and organic content varies with geomorphic position on the ramp. 2) hydrodynamics and bathymetry directly influence sediment characteristics and accumulations. For this project, surficial sediment and shallow (< 1.5 meter) core samples from the Isla de Holbox region of northeastern Yucatan will be collected and analyzed capturing the range of offshore, shore, beach ridge and lagoon geomorphic environments and reveal the sediment size, sorting, type, organic content and distribution and variety within these environments. In situ tide, wave and current measurements and regional physical oceanographic data will provide input into two-dimensional hydrodynamic computer models analyzing sediment transport pathways. Marked variation in sediment type, sorting, and content is expected among environments. Skeletal (or oolitic?) sand and gravel are expected to form beach ridges and offshore bars while lime mud (with abundant organic matter) is expected within the lagoon. Waves are expected to be the dominant hydrodynamic factor on sediment transport pathways. Understanding hydrodynamic controls on sedimentologic variability of carbonate ramps successions is important for constructing actualistic depositional models of ancient ramp systems, many of which provide important hydrocarbon resources.