Hydrodynamic Controls on Sedimentology and Geomorphology: A Field and Modeling Analysis of Modern Marine Carbonate Ramp, Northern Yucatan Shelf, Mexico

Abstract

Many large and productive hydrocarbon reservoirs are from carbonate successions deposited on ramps. Despite numerous studies documenting the sequence stratigraphy of these carbonates ramps, the complex processes controlling the variability and patterns of sedimentation are less well understood. This project characterizes and numerically models the Holocene northern Yucatan (Mexico) ramp system near Holbox to enhance understanding of carbonate ramp sedimentary dynamics in general. These understandings are important for constructing realistic depositional models of variability within ancient analogous ramps. The project integrates remote sensing, field, petrographical and granulometrical observations of surficial modern sediments with climate data, oceanographic observations and 2D numerical hydrodynamic modeling of waves, tides and currents across the study area. Results indicate that the area includes a barrier island, lagoon, and shoreface complex passing northward to the gently dipping homoclinal Yucatan ramp. Data illustrate the role of periodic tropical and winter storms along with trade winds in generating waves and creating a persistent westerly longshore current. This current carries episodically upwelled (cooler) and nutrient-rich water along the coastline and to the west. The shoreface includes primarily coarse to fine carbonate sand; finer sediment is winnowed. Despite its tropical location and lack of detrital influx, a heterozoan grain association dominates the shoreface with photozoan association sediment (e.g. coral and ooids) likely suppressed by the upwelled water. Numerical models illustrate that large sand bodies (e.g. 12 × 1.5 km subaqueous dune field near lagoon mouth) accumulate in areas with accentuated wave and tidal forces. Continuing synthesis of sedimentologic analysis and modeling provide qualitative and quantitative results on variability of, and controls on, sediment transport and accumulation in the shoreface. As calibrated by the Holocene patterns, systematic modification of geologic and oceanographic parameters (e.g. bathymetry, waves, tides) create a series of conceptual scenarios representing different ramps, as could be present in the stratigraphic record. These conceptual analyses constrain the impact of a variety of processes and controls on carbonate ramp systems, including ancient reservoir analogs.

AAPG Datapages/Search and Discovery Article #90259 ©2016 AAPG Annual Convention and Exhibition, Calgary, Alberta, Canada, June 19-22, 2016