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