Local and Worldwide Composite Standards: Toward a More Effective Integration of Biostratigraphic Data in Developing Sequence Stratigraphic Architecture

J. A. Stein, R. W. Aurisano, H. R. Lane

Quantitative biostratigraphic methods offer a versatile range of approaches to managing large, heterogeneous datasets. Among the more traditional of these methods is graphic correlation, which relies on Cartesian crossplotting to integrate data from selected local sections (y-axis) into a standard reference section (x-axis) or composite standard. A mature composite standard comprises a scaled optimum sequence of fossil datums, interrelating all reported fossil types, marker and lessor known accessory forms. The optimum sequence obviates the use of separate, discipline-specific zonal schemes and thus simplifies the development and communication of results. Moreover, a higher level of potential resolution is achieved in a composite standard due to the precise sequencing of oth recognized markers and all accessory taxa.

The computerization of graphic correlation permits the rapid development of composite standards and the practical application of these databases. As a general practice, a worldwide composite standard may be developed to catalog the maximum chronostratigraphic ranges of taxa. The applicability of such universal composite standards to a given study area depends on the paleoenvironmental constraints and associated endemism of the fossil assemblage. In particular, areas encompassing non-marine to near shore deltaic sediments may be difficult to calibrate initially to a database of maximum ranges. Instead, a local composite standard may be generated, using the most thoroughly documented reference sections. In the process of building a local standard, the occurrences of rare marine marker f ssils may accumulate within the optimum sequence. Later, the net sum of accumulated marker taxa may be compared to the worldwide composite standard in a calibration crossplot. The resulting database provides optimum refinement for regional correlations, while resolving important basinwide time-stratigraphic breaks undetected by purely local zonations.

AAPG Search and Discovery Article #91020©1995 AAPG Annual Convention, Houston, Texas, May 5-8, 1995