Scales of Sequence Stratigraphic Investigation: Integrating Differing Perspectives in Basin Analysis

Louis M. Liro

Sequence stratigraphy allows the integration of methodologies which ordinarily are used at dissimilar perspectives. By identifying and describing genetically linked stratal packages, sequence stratigraphy allows the integration of perspectives from the regional scale of seismic data to the microscopic scale of thin sections and micropaleontology. However, the identification of specific sequence stratigraphic elements is often strongly biased by the stratigraphic resolution (or lack thereof) of the primary data set or expertise of the investigator, often giving rise to inaccurate or incomplete description of the sequences involved.

Sequence boundaries, where lowered relative sea level has resulted in significant subaerial erosion, are most reliably interpreted on seismic data sets or volumes. The erosion associated with these regional processes can be identified and mapped laterally to demonstrate the regional extent of the erosion surface. The same erosion surface on well logs, core data or in limited outcrop may be due to other, smaller scale processes resulting in similar but localized stratigraphic expression. This effect is particularly likely in fluviatile and other nonmarine conditions.

Differing investigative perspectives raises considerable differences in evaluation of maximum flooding surfaces and 'condensed sections'. Multiple and varied criteria for identifying these depositional concepts can result in several 'correct' interpretations within the same data set. Extrapolation of these interpretations can have profound effect on the economic evaluation of a study area.

One aspect often overlooked in sequence stratigraphy is the likelihood of autocyclic processes mimicking allocyclic processes. Particularly in deltaic and other sediment supply-dominated environments, this aspect of stratigraphic interpretation is often overlooked in favor of a eustatic interpretation.

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