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Note:
This
report is proprietary and confidential and may only be released to the
project sponsor. The material below is presented to illustrate ESRI-USCs'
research capabilities and activities.
Objective: Examine the
current concepts of the regional framework for the MSB. Identify
those tectonic events, particularly in the Precambrian, that may have
controlled orientation and growth of structures and determine how this
knowledge can be translated into an exploration strategy for the area.
Plan: Utilize
primarily public domain data to examine the regional framework and
integrate that data with Pennzoil information. Focus on
documented, basement faults or zones of weakness that may affect
structural grain, orientation of structures and recurrent movements
(rejuvenation) of faults in the overall area that affect the MSB during
geologic time but specifically from Jurassic to present.
The tectonics of the
southeastern US and adjacent regional areas was examined with emphasis
placed on the basement features. Seismic, magnetics, gravity
and satellite imagery was examined. Conclusions show that major features
in the basement, some of which have been active from Precambrian to the
Holocene have had a major effect on the sedimentation in areas such as
the Mississippi Salt Basin an that displacement on major faults
have changed from vertical to lateral motion during the history of
the area.
Displays:
-
Chart of geologic ages and
events
-
N America Regional -
18 panel montage
-
SE US regional - 18
sheets (county legend)
-
Wrench Tectonics - examples
w/ triple junction concept
-
Gravity Interpretations -
Reelfoot - Triple Junction
-
Fracture Zones
-
Florida / BFZ / Cottage
Grove fault analog
-
Zones of Weakness
-
Bibliography (copy
for Pennzoil)
-
Models of stress
forces/strain patterns
Data / Bibliographic
Resources:
-
Gravity
-
Magnetics
-
Seismic
(COCORP
regional lines and Pennzoil lines)
-
MT
-
Publications
with interpretations, age dating, etc.
-
GCS maps,
provided by Pennzoil
-
Pennzoil
internal reports
Note: Copies of
published information have been cataloged and is included in a
categorized bibliography.
Methodology:
Itemized the tectonic
events by geologic age (Chart) This was done for the
Precambrian to Holocene. All events have not been charted but most
of the events that affect the area surrounding the MSB and in the basin
are included. This was done by literature work then reinterpreting
and integrating the data as required.
NOTE: Colors/Ages of
significant events
Basic Questions:
1) What are the
Precambrian features that are present in the area that controlled
structural development in the MSB? What are the dominant tectonic
controls? What has been the movement history of the faults?
2) Are these structural
features correctly identified using stress/strain relationships?
Have we traditionally mapped these correctly? How relevant are the
commercial maps that we have used in the area?
3) Can we determine the
stress/strain relationship to determine if other structural orientations
are possible and segregate them for different periods of geologic time?
4) Can we identify periods
of time that are most important (tectonically) and their effect on
structural growth, orientation of structures, complexity of structures,
trap formation (and destruction) that help us to focus on significant
events in the MSB?
5) Can we put these events
into a framework that can further define the correct orientation and
subsequent movement throughout geologic time?
6)Can we documents new
concepts with the data base that currently exists for the MSB?
7) From the above
(assuming that we can answer the questions) can we develop a
successful exploration strategy for the MSB.
8) Can this methodology be
used in other basins for determination of additional trapping mechanisms
and evolution of structure.
Comments:
As with most literature in geology there are many articles that are very
important and contain relevant interpretations and/or raw data and there
are many others that are of little or no use. Probably 10% of the
publications reviewed were useful and contained data and interpretations
that are significant.
Maps and Charts:
To support the chart of
events that was constructed, Supraregional and subregional maps were
constructed which gives us both a time and geographic domain to
examine. Subregional maps are at county level in order to get a a more
specific definition of location.
Supraregional Map
Montage - 18 panels Precambrian to Holocene
Subregional Maps - 18 sheets -
Use only 7-8 for detailed presentation
Precambrian,
Mississippian, Pennsylvanian, Triassic, Jurassic, early and late
Cretaceous
Assumptions:
From this work on the maps and
literature a premise has emerged under which assumptions have been made.
-That major zones of
weakness were most likely set up in the Precambrian and early Paleozoic.
A major rifting episode was apparently ongoing at about 1200 mya
(Precambrian)
-That these zones of
weakness have been rejuvenated - perhaps several times throughout
geologic history - some have reversed direction on movements, left
lateral to right lateral to dip slip - from normal to reverse - from
normal to thrust - etc.
-In several cases fault
zones have become avenues for igneous intrusions and volcanic events in
the area all of which has changed the complexity of the basin and
has stimulated salt movement since the Jurassic. A main period of
complex activity was the late Cretaceous.
MAJOR ZONES OF WEAKNESS
INCLUDE:
Those closest to the study
area
1) Pickens-Gilberton
system
2) Phillips system
3) Reelfoot
4) Wiggins Arch
5) Bahamas Fracture Zone (BFZ)
6) Cottage Grove/Rough
Creek fault system
7) Eastern seaboard
fault(?) systems
8) Igneous activity -
volcanics and intrusions
9) Appalachian
Thrust/Fold Belt
Those furthest from study
area
10) Western Margin
Transform (WMT)
11) Nemaha and
Mid-continent gravity anomaly (MCGA) (left lat. @ OKC field)
12) Mexico fracture zones
(left lateral)
13) Cuba Subduction Zone
14) Texas Lineament
15) Rio Grande Rift -
Colo. and NM
16) Ouachita Thrust
17) Marathon Thrust
PRELIMINARY CONCLUSIONS
1) Structural features
seem to fit a wrench system (divergent wrench system) more closely than
applying other structural assumptions - using a strain
ellipsoid.
2) Some areas in the SE
US there are competitive stresses and resultant strain configurations at
nearly the same time (Reelfoot and Cottage Grove; Phillips
and Pickens-Gilberton). These resultant configurations are
conceptual but models have been built that can account for today's
structural features.
3) The primary
tectonic/structural features are probably:
- Precambrian rifting and early
establishment of first zones of weakness
- Permian reactivation
during continental collusion
- Triassic and early Jurassic
reactivation as a result of rifting and plate reversal movements
- Cretaceous igneous activity
(late Cretaceous) along previous established zones of weakness but which
probably caused very little displacement and may have even “healed”
some portions of these zones. However, because of this healing
effect, it probably resulted in a higher variation of weakness (or
strength) than existed previously. This quite probably had an
effect on the type of subsequent movement.
- Subsequent interference
structures have resulted, and change of direction of faulting which in a
wrench system produces antithetic and synthetic faulting episodes.
(This can be inferred at Tinsley if we assume wrench faulting occurred).
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