GEISER, PETER, R. RATLIFF, and R. KLIGFIELD, CogniSeis Development, Boulder, CO

ABSTRACT: Balanced Cross Sections: Criticisms of Current Usage and Presentation of the "Validated" Interpretation Concept

Quantitative methods for generating cross sections in deformed areas are based on the "balanced" section concept which has origins extending back over 80 years (Chamberlain 1910). Recent studies illustrating "balanced" interpretations highlight a lax and uncritical usage of the term. In classical usage, a "balanced" interpretation refers to physically plausible interpretations in which bed lengths and/or areas are equal in the deformed and restored states along sections parallel to material transport. However, the development of new rule-based section construction techniques for extrapolating and projecting data to depth as well as kinematic methods for structural forward modeling provide additional tests for interpretation viability. We suggest that the label "validated" be applied t a section which: (1) is compatible with all available data constraints, including out-of-plane 3D map or section restrictions; (2) displays structural styles which can be observed in the field or are consistent with analogues from areas of similar deformation; (3) can be demonstrably restored to a reasonable undeformed state configuration via a set of stated rules; and (4) is kinematically admissible, either by forward modeling from the undeformed state or by virtue of its construction using analytical models (e.g., fault prediction algorithms, fault bend/propagation fold equations, block rotation models, etc.). Examples are discussed which demonstrate how improved and constrained structural imaging can be achieved through the use of the "validated" section construction techniques.

AAPG Search and Discovery Article #90987©1993 AAPG Annual Convention, New Orleans, Louisiana, April 25-28, 1993.