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ABSTRACT: Cyclic Stratigraphy and the Significance of Resolution

John A. Lopez

The use of seismic data to interpret the stratal architecture of sediments has given new momentum to interpreting stratigraphy as cycles and/or sequences. Swept along with the new sequence stratigraphy is a genetic model indicates that these sequences are driven by sea level fluctuations. However, consideration of resolution of cycles (potential sequences) as observed in depth and over geologic time by different tools, points out several important constraints and limitations to sequence interpretations.

(1) Geologic processes that create the sedimentary record occur over a wide frequency range, e.g., the geologic spectrum is broad. (2) All of the common tools used to interpret stratigraphy have limits of resolution of the geologic spectrum, e.g., tools are bandwidth limited. (3) The bandwidth limitations of these tools are not just a function of the tools but of the geology, e.g., accumulation rates. (4) To properly associate particular cyclic events to a geologic process (and therefore create depositional models), the cyclicity of the geologic process should correspond to the cyclicity in the stratigraphy, e.g., absolute scale is important. (5) To match cyclicity in stratigraphy to geologic processes, it is best to observe much of the geologic spectrum by using a combination of inte pretational tools.

AAPG Search and Discovery Article #91003©1990 AAPG Annual Convention, San Francisco, California, June 3-6, 1990