A SIMPLIFIED GUIDE FOR SEQUENCE STRATIGRAPHY: NOMENCLATURE, DEFINITIONS AND METHOD

Attempts to codify Sequence Stratigraphy had failed since first attempts in the 80’s, fore reasons including: cumbersome nomenclature; conflicting causing mechanisms; disagreement on definitions; or simply that Sequence Stratigraphy is a young science that might need more time to mature. Interestingly, Biostratigraphy has clear rules and terminology (code) followed by all biostratigraphers. Biostratigraphy also has similar challenges: it has a cumbersome nomenclature classification of fossils; driving mechanisms for rate of evolution of different taxa is debatetable; classification of different species and genera is debatable; and it is also a young science.

Success in the paleontological community is linked to their approach for defining a code. Biostratigraphy is codified as a method, not a science, based on simple criteria that can be directly observed from available data. Implications for interpretation, in terms of causal mechanisms, follow after initial interpretation, and are not part of the code.

Then, why we don't agree on basic rules for identifying surfaces and systems tracts based on direct observational criteria? We suggest that the source of this problem lies on the terminology proposed originally for surfaces and systems tracts. Highstand, Transgressive, and Lowstand are ambiguous terms. Two of them (Highstand and Lowstand) imply sea-level positions and one of them (Transgressive) relates to a lateral movement of shoreline. We pose that this mixing of terminology is at the heart of the problem, implying to be necessary to integrate interpretation of causal mechanisms with direct observations from data to classify a surface or a systems tract.

A Sequence Stratigraphic code should be based on criteria directly observable from outcrop, core, well-log, and seismic data, independent of mechanisms, duration, or magnitude of events. This proposed approach leaves the interpretation of mechanisms as a step after the definition of surfaces and systems tracts. In this presentation, we offer guidelines for interpretation and updated definitions of classical terms, slightly modified from the original definitions. Our modifications are intended to emphasize observations, as well as to clarify communication of terminology through the use of translation terms taken from literature.