THE BIG BEND REGION AS LABORATORY FOR
MAPPING THE RELATION OF STRUCTURES TO
PALEOSTRESS FIELD TRAJECTORY
Richard J. Erdlac, Jr.
University of Texas of the Permian Basin
Center for Energy & Economic Diversification
Richard J. Erdlac*
University of Pittsburgh
*Deceased
Local Stratigraphy
The strata that are colored, from
Santa Elena and younger, are
all exposed on and around the
Terlingua uplift and monocline.
Older strata are exposed within
the Solitario as well but were
not part of this study or
presentation.
Terlingua Uplift
Tascotal Mesa Fault Zone
Solitario
Terlingua Monocline
Colorized digital
elevation model
(DEM) of the
Terlingua uplift
(inside the white
square) and the
immediately
surrounding region.
Terlingua Monocline
Black Mesa
Terlingua Monocline
Colorized
digital
elevation
model
(DEM) of
the
Terlingua
monocline.
Structure Contour Map
Display
documents
areas less
than
or equal to
3000
feet
elevation
and
those
greater or
equal to 4000
feet.
Structure Contour Map
Display
documents
areas that
preserve
grabens
across the
uplift (in blue).
Terlingua Uplift
Tectonic Stylolite
Teeth
Santa Elena Limestone
Buda Limestone
Boquillas Limestone
Terlingua Uplift
Tectonic Stylolite
Teeth
Terlingua Uplift
Tectonic Stylolite
Teeth
Cumulative distribution of
only the NE-trending teeth
(above) can be broken into at
least 3 and possibly 4
separate distributions (right).
Means and 1st standard
deviations are shown.
Tectonic Stylolite Teeth Trend Plot
Circles display mean tooth trend at each site.
Stylolite Teeth Trend Versus Distance North Of Terlingua Monocline
Far Field Stress Trajectory
Based Upon Tooth Trends
Between N 60-90o E.
Far Field
Intermediate Field Stress
Trajectory Based Upon Tooth
Trends Between N 40-60o E.
Intermediate Field
Near Field Stress Trajectory
Based Upon Tooth Trends
Between N 0-40o E.
Near Field
Total
Laramide
Stress Field
Possible theoretical
total stress field
from inspection of
far, intermediate,
and near field
separation.
Actual total
stress field from
measurement of
tooth trends and
averaging trend
at each site.
Curved Mode I Fractures At Terlingua, Texas
Mode I Fractures
Curved Mode I Fractures At Terlingua, Texas
Calcite-Filled Shear Zone
Mode I Fractures
Curved Mode I Fractures In Hazel Sandstone Near Van Horn
Mode I Fractures
Curved Mode I Fractures In Tesnus Formation, Solitario
Mode I Fractures
Saint Venant’s Principle
Differences in
stress distribution
are strictly
confined to a very
small region close
to the loads. B
represents
loading at a point,
whereas C is a
distributed load.
Far field loads are
identical as
shown in this
birefringent
material.
Flamant-Boussinesq Solution Applied To An Edge Loaded Semi-Infinite Plate
Equations For Principal Stress Orientation & Magnitude
Equation 1
Equation 2
Normal, Shear, And Far-Field Stress Applied To A Shear Zone
Close Up Of Stress Trajectory Near Shear Zone
Tramway Graben, Boquillas Canyon area.
Dead Horse Graben, Boquillas Canyon area.
Dead Horse Graben
Laramide paleostress
trajectory map from
tectonic stylolites.
Adapted from Maler, 1990.
Terlingua Uplift
The Terlingua uplift provides important surface exposures for understanding how
structures respond to stress, as well as preserving features that can help determine
the geometry of the Laramide paleostress field.
Terlingua Monocline
Faults that control Terlingua monocline development demonstrate that a local, high
magnitude stress field can develop as part of a feed back system to the regional
stress affecting an area, and thus alter the local structural geometry.