Abstract

Subbasins composing a larger basin can have similar appearing sediment fills that are diachronous. It is important to construct a chronostratigraphic section for each subbasin to correctly correlate between subbasins. A methodology is presented that incorporates the sequence-stratigraphic interpretation of each subbasin, which improves correlation of systems tracts between adjacent and widely separated subbasins. The growth-faulted subbasins in the Corpus Christi Bay area along the western margin of the Gulf of Mexico are used to demonstrate this methodology.

A composite wire-line log created by splicing unfaulted and relatively conformable log segments from the deepest wells in an area provides a stratigraphic record that captures a complete succession of depositional and cyclic history. Site-specific sequence-stratigraphic section (S5) benchmark charts are composite logs containing additional data that summarize available geologic information for a subbasin, site-specific area. Color-coded sequences and component systems tracts are basic information displayed on S5 benchmark charts. This physical framework can then be calibrated with ages (Ma) of sequences and bounding surfaces. Ages are based on geologic time charts representing latest consensus from isotopic, polarity, and microfossil integration. Sequence-bounding unconformities and internal maximum flooding surfaces delineated on S5 benchmark charts, when correlated with other wire-line logs and placed into the seismic time domain, produce a chronostratigraphic framework for an area. Comparison of S5 benchmark charts among adjacent, widely spaced, or isolated sites facilitates correlation of diachronous lithostratigraphic units.

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