INTEGRATED CHRONOSTRATIGRAPHIC FRAMEWORK FOR CORRELATION OF UPPER CRETACEOUS STRATA, GULF OF MEXICO

Establishment of a chronostratigraphic framework based on an integrated biostratigraphic and sequence stratigraphic (transgressive-regressive (T-R) sequences) approach is fundamental to the correlation of strata of a basin. Planktonic foraminiferal biozones and T-R sequences are recognized in Upper Cretaceous strata of the northern Gulf of Mexico. Sequences include the T-R 4 (upper Albian to lower Cenomanian), T-R 5 (upper middle Cenomanian to upper Turonian), T-R 6 (middle Coniacian to middle Campanian), T-R 7 (middle to upper Campanian) and T-R 8 (lower to lower upper Maastrichtian). Sequence recognition is based on stratal geometries, nature of sequence boundaries, facies stacking patterns, and large-scale shifts in major facies belts. Sequences are controlled by the change in accommodation space resulting from stratigraphic base-level changes (eustatic and tectonic effects) and sediment supply and accumulation. T-R sequences are composed of aggrading and backstepping intervals of a transgressive phase (upward deepening section) and an infilling interval of a regressive phase (upward shallowing section), which are separated by a surface of maximum transgression. The aggrading interval marks the change from base-level fall and erosion to base-level rise and sediment accumulation. Transgressive events of the backstepping interval are widespread and provide regional correlation datums. Progradational events associated with the infilling interval represent major influxes of siliciclastic sediments and result in a loss of accommodation space. These Upper Cretaceous T-R sequences are correlated throughout the northern Gulf of Mexico.