HOWARD, J.H. , Structural Geology Services Group, Inc., Barker, TX
A cross-section through the Clemente-Tomas/Corsair/Wanda fault systems provides an opportunity to examine a new procedure for cross-section restoration and to comment on the value of restorations.
The ideas underlying popular procedures (e.g., line-length balancing), although well known, have recognized shortcomings. The most serious is the occurrence of gaps and overlaps between parts of restored sections. These features result from strains that have affected development of a section but could not be removed using popular procedures.
This paper explains a new method: "rules-based-restoration." Here, a set of points defining present-day structural geometry are removed or moved to approximate the two key features of cross-section development: (1) the accumulation of sediments and (2) the paths of movement that points within the accumulated sediments experience in forming a present-day section. The rules are simple but not unique. For instance, all stratal surfaces are eventually returned to horizontal, but they may be variably stretched or shortened.
The value of restorations has focused on their use to validate a proposed interpretation of a section. Restorability implies validity. However, a series of restorations through time, if arguably defensible, can provide still greater value, namely a basis for evaluating temperature/pressure regimes that sediments and their included fluids experience since deposition to present time. Because the Corsair profile is both public and extraordinarily well imaged, it provides a real-world case study for assessing methodology and practical value.
AAPG Search and Discovery Article #90908©2000 GCAGS, Houston, Texas