Site-Specific Sequence Stratigraphic Sections (S⁵ Benchmark Charts); Practical Tool for Correlating Chronostratigraphic Units in the Texas Gulf Coast Tertiary Section

Robert G. Loucks, Ramón H. Treviño, L. Frank Brown, Jr., and Ursula Hammes
Bureau of Economic Geology
John A. and Katherine G. Jackson School of Geosciences
The University of Texas at Austin
University Station Box X
Austin, Texas 78713-8924

Subregional stratigraphic correlations within the complex depositional architecture of Texas Tertiary sandstones are difficult because of extensive growth faulting and similar- appearing diachronous systems tract sediment packages. Time correlation, rather than lithologic correlation, is necessary to ensure stratigraphic equivalency. Site-specific sequence stratigraphic sections (S⁵ benchmark charts) are a simple stratigraphic tool to help ensure correct chronostratigraphic correlations. S⁵ benchmark charts are based on composite wireline logs in a specific area so that the most complete stratigraphic section can be assembled. All relevant lithostratigraphic, chronostratigraphic, sequence stratigraphic, paleontological and tectonic data are integrated within the composite chart. A series of S⁵ benchmark charts can be correlated such that chronostratigraphic boundaries are not violated, leading to an accurate stratigraphic architecture of an area.

Correlation of a series of S⁵ benchmark charts for the Frio interval from the Corpus Christi region of Texas allowed construction of the sequence stratigraphic architecture of this area. Off-shelf, third-order, lowstand systems tract sediment packages are isolated within growth-fault controlled subbasins. Subbasins become younger seaward. Overlying these third-order lowstand systems tracts are on-shelf transgressive and highstand systems tracts that can be correlated across several subbasins, although younger, on-shelf, highstand systems tracts pinch out progressively seaward relative to older ones.

A sequence stratigraphic architectural framework is a basic data element necessary for production or exploration projects. Such a framework can be derived from S⁵ benchmark charts, whose assembly should be considered a fundamental task similar to preparing isopach or structure maps.

AAPG Search and Discover Article #90069©2007 GCAGS 57th Annual Convention, Corpus Christi, Texas