The late Quaternary evolution of the Rio Grande system, offshore south Texas

A seismic and sequence stratigraphic investigation of the Rio Grande system provides information conceming: (1) the distribution of depositional units relative to the last glacio-eustatic cycle (120,000 ybp to present); (2) the spatial and temporal distribution of sand-prone units; and (3) whether the control of eustasy and sediment supply (climate) on deposition can be differentiated. The combination of biostratigraphic data (foraminiferal abundances and extinctions), oxygen isotope stratigraphy, and radiocarbon ages in the Rio Grande area provides the chronologic control for the study. The depositional unit dataset consists of 1850 kilometers of high-resolution seismic reflection profiles, 14 platform boring descriptions, and sediment samples from one platform boring. The study of the Rio Grande system indicates the following: (1) transgressive system tract units are primarily prograding deltas rather than back stepping fine grained units, as predicted by basic sequence stratigraphic theory; (2) fluvial- and wave-dominated delta systems exist simultaneously (geologically-speaking) creating difficulties in the prediction of reservoir distribution and quality; and (3) eustatic and climatic control on unit deposition can be differentiated, and the quantity of sediment supply coincides with the amount of moisture in the drainage area