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RESEARCH POSTER PRESENTATION DESIGN © 2019
www.PosterPresentations.com
1. 12 sites from three transects along the north-south trending East
Kaibab Monocline (EKM), are presented as a pilot study for
understanding magnetic fabrics in the Navajo Sandstone.
Specifically, trying to quantify tectonic strain, fluid directions and
timing. 10 sites are from deformation bands (DBs) which are used
as a proxy for understanding layer parallel tectonic strain. While
the two other sites are from concretions, which are used as a proxy
for fluid movement in the crust. Minerals can be either
ferromagnetic, paramagnetic or diamagnetic in nature with the first
two attracting the magnetic field and the later repelling. DB
development occurred when tectonic strain caused cataclasis in the
well sorted porous sandstone (Fossen et al., 2007). Concretion
formation occurred early in burial diagenesis with carbonate-rich
waters first forming the concretions. A pH-buffering reaction later
turned the carbonate concretions into iron-oxide rich concretions
from the movement of reducing fluids through fault conduits
(Yoshida et al., 2018). Both deformation band and concretion
formation are believed to have initiated during the Laramide
Orogeny, ~80-40 my (Tindal & Davies, 1999; Garden et al., 2001).
This study looks at capturing the feasibility of using magnetic
fabrics in the Navajo Sandstone, to better understand its geologic
history from the time of deposition, some 190 mya to present day.
2. OBJECTIVES
7. MAGNETIC FABRIC
10. FUTURE WORK
•Acquire a larger data-set of DBs across the EKM, including the antithetic
left lateral faults seen in the north and center of the EKM.
•Compare the shape anisotropy of orientated thin sections from SEM work
to understand if the AMS is picking is picking up the realignment of
mineral grains.
•Interpret fold test data using thermal demagnetization to deduce if the
fluids are pre, syn or post folding. This part of the study could be
developed further into another thesis for comparison to the work of Garden
et al (2001), as only 7/12 preliminary samples produced good data.
•Combine isotope work from lab partner Peter Stevens to understand the
temperature of formation, depth and relative timing at which the carbonate
formed at site 12.
11. REFERENCES
Bird, P. 2002. Stress direction history of the western United States and Mexico
since 85 Ma. Tectonics,21(3), 5-1.
Fossen, H., Schultz, R. A., Shipton, Z. K., & Mair, K. 2007. Deformation
bands in sandstone: a review. Journal of the Geological Society,164(4), 755-
769.
Garden, I. R., Guscott, S. C., Burley, S. D., Foxford, K. A., Walsh, J. J., &
Marshall, J. 2001. An exhumed palaeo‐hydrocarbon migration fairway in a
faulted carrier system, Entrada Sandstone of SE Utah, USA. Geofluids,1(3),
195-213.
Tindall, S. E., Storm, L. P., Jenesky, T. A., & Simpson, E. L. 2010. Growth
faults in the Kaiparowits Basin, Utah, pinpoint initial Laramide deformation in
the western Colorado Plateau. Lithosphere,2(4), 221-231.
Tindall, S. E., & Davis, G. H. 1999. Monocline development by oblique-slip
fault-propagation folding: the East Kaibab monocline, Colorado Plateau,
Utah. Journal of Structural Geology,21(10), 1303-1320.
Yoshida, H., Hasegawa, H., Katsuta, N., Maruyama, I., Sirono, S., Minami,
M., & Metcalfe, R. 2018. Fe-oxide concretions formed by interacting
carbonate and acidic waters on Earth and Mars. Science advances,4(12),
eaau0872.
i. To understand why deformation bands might be recording different
fabrics at each site and how they correspond or differ.
ii. To understand if tectonic strain is related to the Laramide orogeny or the
Sevier fold and thrust shortening directions.
iii. To acquire a relative timing of events through tectonic relationships, fold
tests and paragenesis.
iv. To combine this studies data and the work of others to model the history
of the Navajo Sandstone in this area.
Contact: rp734@nau.edu
By Rhys Park
Understanding Tectonic Strain And Syn-Tectonic Fluid Flow
Processes Using Magnetic Fabrics In Diamagnetic Rocks: Example
From The East Kaibab Monocline, Southern Utah
4. MAGNETIC MINEROLOGY 9. CONCLUSIONS
3. METHODS
6. MAGNETIC SUSCEPTIBILITY ANGLES
5. BULK SUSCEPTIBILITY & ANISOTROPY
Anisotropy of Magnetic Susceptibility
(AMS) (
✓
)
•Looks at the preferred alignment and
shape of magnetic minerals.
Hysteresis Loops (
✓
)
•Determines magnetic signal strength
and magnetic behavior.
Thin Sections (
✓
)
•Determines paragenesis and mineral
types.
X-Ray Diffraction (XRD) (
✓
)
•Acquires mineralogical data and relative
abundance in a sample.
Deformation bands (DBs) and the relatively undeformed zones (RUZs)
•High amount of quartz >90 wt.%, some feldspars, clays and few iron
oxides. Quartz is diamagnetic, which makes up most of the rock.
Concretions
•High amount of quartz in both. Site 7 has a significant amount of
ferromagnetic minerals such as hematite, goethite and limonite. Site 12 has
< 4 wt.% paramagnetic and ferromagnetic minerals but lots of calcite which
again is diamagnetic in nature.
1mm
0
Limonite
Hematite
Goethite
Site 7 Concretion
PPL Thin Section
4 mm
0
Site 2 DB
XPL Thin Section
DB
RUZ
RUZ
1
1.02
1.04
1.06
1.08
1.1
050 100 150 200 250
Corrected Degree of
Anisotropy (Pj)
Bulk Susceptibility (µKm)
Bulk susceptibility (BSu) is the measure of how well a material becomes
magnetized when applied with a magnetic field. Generally the more
ferromagnetic material in a sample the greater the BSu.
Site 7 has the highest BSu due to > ferromagnetic material in each sample
compared to site 12 and the deformation bands. Interestingly, site 12 has a
slightly higher degree of anisotropy (Pj) than site 7, probably from the
presence of anisotropic calcite. Deformation bands have a lower BSu due to
being diamagnetic in nature but have higher Pj relative to concretions from
tectonic induced grain reorientation and grain crushing. Quartz typically has a
-15 µKm BSu but a diamagnetic correction has been done to enhance the
paramagnetic and ferromagnetic components of deformation band samples.
Pj = 1 = isotropic fabric
Pj > 1 = anisotropic fabric
Pj of 1.1 = 10% anisotropy
Magnetic fabrics have been deduced by finding the angle between the Kmin
and pole to bedding. Angles < 35° are sedimentary, angles > 35° but < 65° are
intermediate and angles > 65° are tectonic. Interestingly, tectonic fabrics plot
in the prolate regime which is predictable for fabrics that have undergone
some induced strain. Initially, sedimentary fabrics start out as oblate ellipsoids
and then under a directional strain become more prolate in nature. Under
extreme strains the ellipsoids prograde back into the oblate domain with very
high degrees of anisotropy’s (Pj) i.e. metamorphic rocks.
AMS susceptibility
angles are tensors (Kmax,
Kint and Kmin). They
determine the magnetic
lineation direction and
magnetic foliation plane
of a sample. This study
correlates these angles
to a local and regional
tectonic strain direction
or potential fluid flow
direction.
-0.15
-0.10
-0.05
0.00
0.05
0.10
0.15
0.20
0.25
0.30
020 40 60 80 100
Shape Parameter (T)
Angle Between Kmin and Pole to Bedding
Tectonic Fabric
Intermediate
Fabric
Sedimentary
Fabric
Prolate domain
0 > T > -1
Oblate domain
0 < T < 1
AMS patterns in the deformation bands, locally or regionally caused?
1. The regional strain effects are discounted from this study as being strain
records in the magnetic fabrics: the Sevier orogeny occurred as a far-field
strain and was not a substantial cause for deformation in this area (Bird,
2002). Study bias from sampling 8/10 NE striking synthetic faults also
added to the appearance of a NW-SE shortening direction. 2/10 sites
appear to be sub-parallel to the mean shortening direction of the Laramide.
But are discounted as being regional from the identification of the
magnetic fabrics following local strain patterns associated with individual
DB development.
2. So, magnetic fabrics are classified as being caused by local strain effects,
mostly at the individual deformation band level. However, the sedimentary
DB magnetic fabrics may be recording bulk strain at the monocline level.
This is because all DB sedimentary magnetic fabrics appear to be
perpendicular to the strike of the EKM, parallel to the inferred local EKM
shortening direction and made up of mostly homogenous RUZs, separate
from localized DB formation.
Fluid directions and the relative timing of concretion formation:
1. Site 7 and site 12 both record fluid movement along bedding. Site 7 has
magnetic lineation's spread throughout the bedding plane while Site 12 has
a strong clustering of lineation directions towards the south. Possibly
indicative of fluid flow directions.
2. The carbonate in site 12 most likely precipitated from carbonate rich
meteoric waters early in Navajo Ss. deposition. The migration of reducing
fluids may have only slightly altered the carbonate rich concretions into
the iron-oxide rich concretions in this area. Potentially, an episode of
migrating fluids towards the south can be deduced from the AMS patterns.
DB compression direction: 8/10 DB sites trend NW-SE and are a mix of fabric
types. 2/10 DB sites trend NE-SW and are composed of just tectonic fabrics.
Concretion lineation directions: AMS data points towards a potential fluid
flow direction spread equally along the bedding plane for site 7 and due south
for site 12.
8. TECTONIC AND FLUID DIRECTIONS
M. Chadima (AGICO Inc)
AF/Thermal Demagnetizations (-)
•Acquires an estimate for when remanence was locked into the rock.
Scanning Electron Microscope (SEM) (-)
•Mineral identification and shape anisotropy of minerals, compare to AMS.
Geochemistry (From Lab Partner Peter Stevens) (-)
•Oxygen, carbon and clumped isotope data along the EKM.
(
✓
)Method complete
(-) Method in progress
Field Assistant:
Spencer Shellberg
8. INFERED SHORTENING DIRECTIONS
Sevier
Compression
Direction
Laramide
Compression
Direction Strike & Dip
50°
A’
A
Sedimentary
Fluid Flow