Stratigraphic Statistical Curvature Analysis Techniques
C. A. Bengtson, John P. Ziagos
SCAT applies statistical techniques to dipmeter data to identify patterns of
bulk curvature, determine transverse and longitudinal structural
directions, and
reconstruct
cross
sections
and contour
maps
. STRAT-SCAT applies the same
concepts to geometric interpretation of multistoried unimodal, bimodal, or
trough-type
cross
-bedding and also to seismic stratigraphy-scale stratigraphic
structures. "
Structural
dip," which comprises the bulk of dipmeter data, is
related to beds that (statistically) were deposited with horizontal attitudes;
"stratigraphic dip" is related to beds that were deposited with preferentially
oriented nonhorizontal attitudes or to beds that assumed such attitudes because
of differential compaction. Stratigraphic dip generates local zones of departure
fr m
structural
dip on special SCAT plots. The RMS (root-mean-square) of
apparent
structural
dip is greatest in the (
structural
) T-direction and least in
the perpendicular L-direction; the RMS of stratigraphic dip (measured with
respect to
structural
dip) is greatest in the stratigraphic T*-direction
and least in the stratigraphic L*-direction. Multistoried
cross
-bedding appears on T*-plots as local zones of either greater
scatter or statistically significant departure of stratigraphic median dip from
structural
dip. In contrast, the L*-plot (except for trough-type
cross
-bedding) is sensitive to
cross
-bedding.
Seismic stratigraphy-scale depositional sequences are identified on Mercator
dip versus azimuth plots and polar tangent plots as secondary cylindrical-fold
patterns imposed on global structural
patterns. Progradational sequences
generate local cycloid-type patterns on T*-plots, and compactional
sequences generate local half-cusp patterns. Both features, however, show only
structural
dip on L*-plots.
AAPG Search and Discovery Article #91038©1987 AAPG Annual Convention, Los Angeles, California, June 7-10, 1987.