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Tasa Graphic Arts, Inc. 1210B Salazar Road - Taos, NM USA 87571 Phone: (800) 293-2725 or (575) 758-5535 - Fax: (575) 758-5536 E-mail: info@tasagraphicarts.com |
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Tasa Graphic Arts, Inc. 1210B Salazar Road - Taos, NM USA 87571 Phone: (800) 293-2725 or (575) 758-5535 - Fax: (575) 758-5536 E-mail: info@tasagraphicarts.com |
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Tasa Photo CD-ROM:
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Angular unconformity1.jpg
Angular unconformity at Siccar Point, Scotland. Angular
unconformities are unconformities in which the rocks below the
unconformity lie at a different angle than those above the
unconformity. This particular unconformity, in which Devonian Old Red
Sandstone overlies Ordovician slate, has historical significance to
geology as it was discovered by James Hutton when he was formulating
his concept of geologic time. Angular unconformity2.jpg
Angular unconformity, Death Valley, California. Angular
unconformities are unconformities in which the rocks below the
unconformity lie at a different angle than those above the
unconformity. In this photograph, Holocene alluvial fan deposits
overlie tilted rocks of the Miocene-Pliocene Furnace Creek Formation. Angular unconformity3.jpg
Angular unconformity separates Proterozoic Uncompahgre Group
quartzites and slates from Devonian Elbert Formation sandstones.
Distant peaks are Oligocene San Juan Tuff. Box Canyon Falls near
Ouray, Colorado. Angular unconformity4.jpg
Angular unconformity separating steeply dipping Permian redbeds of
the State Bridge Formation from gently dipping Miocene basalts. The
Permian redbeds were tilted during the Late Cretaceous-Early Tertiary
Laramide Orogeny. Photographed along the Colorado River in the White
River National Forest, Colorado. Anticline-syncline.jpg
Anticline-syncline pair in Devonian Old Red Sandstone, SW Wales, UK.
These upright folds are characterized by steeply dipping axial
surfaces.
Basin and range.jpg
Basin and Range topography, southern Nevada. The extensional Basin
and Range Province is marked by alternating linear mountain ranges
and intervening basins. Most ranges are bounded by normal or listric
faults, formed during Tertiary extension.
Boudins1.jpg
Boudinage of felsic sill. Boudins form by elongation of relatively
stiff rock that is enclosed in a more ductile matrix. The stiffer
rock can then pinch-out or break apart while the more ductile
material flows in to fill the empty space.
Boudins2.jpg
Boudinage of granitic rock. Boudins form by elongation of relatively
stiff rock that is enclosed in a more ductile matrix. The stiffer
rock can then pinch-out or break apart while the more ductile
material flows in to fill the empty space.
Box folds.jpg
Box folds are composed of three planar limbs connected by two hinge
zones. These fold and thrust structures were developed during the
late Cretaceous and Early Tertiary Laramide orogeny. The fault in the
center of the photograph was probably reactivated during Tertiary
extension along the Rio Grande rift. Photograph of the Permian Yeso
Formation in the Fra Cristobal Range, New Mexico.
Calaveras fault1.jpg
The Calaveras fault in Hollister, California is creeping about 0.5
inches (13 mm) per year resulting in visible offset to historic
houses, sidewalks, and curbs. The offset structures make this a
particularly good location to view the surface trace of the active
fault. The Calaveras and San Andreas faults merge approximately five
miles to the south of Hollister.
Calaveras fault2.jpg
The Calaveras fault in Hollister, California is creeping about 0.5
inches (13 mm) per year resulting in visible offset to historic
houses, sidewalks, and curbs. The offset structures make this a
particularly good location to view the surface trace of the active
fault. The Calaveras and San Andreas faults merge approximately five
miles to the south of Hollister.
Calcite-filled extension.jpg
Calcite-filled extension fractures in limestone. Fluids circulating
through fractured rock typically carry quartz or calcite that may
precipitate as veins.
Calcite-filled tension.jpg
Calcite-filled tension gashes in siltstone. Fluids circulating
through fractured rock typically carry quartz or calcite that may
precipitate as veins. The en echelon arrangement of these fractures
suggests that they formed from left-lateral shear, parallel to the
zone.
Chevron folds.jpg
Chevron folds in ribbon chert, western Sierra Nevada, California.
Chevron folds are those with straight limbs and sharp hinges.
Cross-cutting relations.jpg
Cross-cutting relations such as these are critical in determining
timing of a deformation event. For example, this photograph shows a
small pegmatite dike that cuts across earlier folded gneiss. An age
on the pegmatite would give us a minimum age for folding of the
gneiss.
Detachment fault.jpg
Low-angle normal (detachment) fault, Death Valley, California. This
fault, the Boundary Canyon fault, separates rocks deformed in the
middle crust (green, footwall) from rocks deformed in the upper crust
(tan, hanging wall).
Disconformity.jpg
A disconformity is an unconformity separating strata that are
parallel to each other. In this photograph, a disconformity separates
Pliocene marine sedimentary rocks of the Purisima Formation from
Pleistocene fluvial conglomerates. Liquefaction and soft sediment
deformation in the central layer of the photograph was caused either
by large storm events or by earthquakes. San Gregorio State Park, San
Mateo County, California.
Disharmonic folds1.jpg
Disharmonic folds are those in which the shapes of different layers
of the fold do not conform to each other. They also commonly show
significant changes in layer thickness, which reflects their mobility
during deformation. Such folds usually result from "space problems"
in fold hinges.
Disharmonic folds2.jpg
Disharmonic folds are those in which the shapes of different layers
of the fold do not conform to each other. They also commonly show
significant changes in layer thickness, which reflects their mobility
during deformation. Such folds usually result from "space problems"
in fold hinges.
Ductile shear zone.jpg
Ductile shear zone and cross-cutting pegmatite. Similar to fault
zones, ductile shear zones displace rock on either side of the zone
relative to each other, but they do not involve breakage of the rock.
Instead, offset markers are continuous across the zone. Pegmatite
intruded across this ductile shear zone after it formed.
Fault breccia1.jpg
Fault breccia. Breccias typically form along fault zones because of
the breaking and crushing of rock that accompanies fault slip. This
breccia is cemented with calcite.
Fault breccia2.jpg
Fault breccia. Breccias typically form along fault zones because of
the breaking and crushing of rock that accompanies fault slip. The
fragments in this breccia consist of pegmatite.
Fault scarp.jpg
Fault scarp in alluvial fan, Death Valley, California. Fault scarps,
or sudden steps in the topography, indicate recent faulting because
erosion has not had the time to smooth it over. This fault scarp
formed over a recently active normal fault.
Fault surface.jpg
Slickensides and epidote-coated fault surface. The striations reflect
fault movement parallel to the pen and from the lower left to the
upper right-hand corner of the photograph.
Folded calcite vein.jpg
Folded calcite vein and cleavage in micritic limestone. In this
photograph, cleavage formation affected the finer grained limestone
but did not affect the coarser grained calcite vein. Consequently,
the vein shortened perpendicular to the cleavage.
Folded gneiss1.jpg
Folded mylonitic gneiss. At high temperatures, the gneiss was
deformed by ductile flow, i.e., it can fold or otherwise change shape
without visible fracturing. These rocks were deformed at temperatures
in excess of 300 degrees C.
Folded gneiss2.jpg
Folded gneiss. At high temperatures, rock can flow ductilely-that is,
it can fold or otherwise change shape without visible fracturing.
Folded gneiss3.jpg
Folded Precambrian (1750 Ma) gneiss near James Peak in the Front
Range of Colorado. Gneiss is a middle-to high-grade metamorphic rock
that is defined by compositional bands of different mineralogy,
color, and/or texture. The compositional banding arises through a
combination of recrystallization, mechanical shearing, and
dissolution.
Folded marble.jpg
Folded marble. At high temperatures, rock can flow ductilely-that is,
it can fold or otherwise change shape without visible fracturing.
This sheath fold resembles a cone in three dimensions. In this
cross-sectional view, this sheath fold appears as closed circles.
These rocks were deformed at temperatures in excess of 300 degrees C.
Folded sandstone.jpg
Folded Devonian Old Red Sandstone, SW Wales. This syncline-anticline
pair shows well-developed, nearly vertical, axial planar cleavage.
Fractured marine rock.jpg
Fractured Middle Miocene marine rocks exposed at low tide. Note the
gentle seaward dip of the layers above the tide pool. Crystal Cove
State Park, Orange County, California.
Grabens.jpg
"The grabens", Canyonlands National Park, Utah. Grabens are the down
dropped blocks between inwardly dipping normal faults. In
Canyonlands, multiple grabens formed as the upper several hundred
meters of crust experienced extensional stresses due to dissolution
of underlying salt beds.
Hazard assessment.jpg
This trench was excavated in Quaternary alluvial deposits to study
the stratigraphy and offset marker beds along the Concord Fault in
the San Francisco Bay area, California. Earthquake hazards assessment
relies upon such studies to provide important constraints on the
recurrence intervals and slip rates along faults in urban areas. The
Bay Area Rapid Transit (BART) tracks are shown in the background.
Intruded quartz.jpg
The dark-colored Precambrian Pinto Gneiss is intruded by the
light-colored Cretaceous White Tank quartz monzonite in Joshua Tree
National Park, California. The Pinto Gneiss formed from the
metamorphism of pre-existing sedimentary and igneous rocks
approximately 1,650 to 1,400 Ma.
Isoclinal folds.jpg
Isoclinal folds in Archean Banded Iron Formation, SW Montana.
Isoclinal folds are those in which both limbs are parallel, or nearly
parallel to each other.
Joint surfaces1.jpg
Vertical joints in Jurassic sandstone, Arches National Park, SE Utah.
Vertical joints, such as these, typically form by horizontal
extension of the crust, perpendicular to the length of the joint.
Weathering and erosion along the joints isolates the rock into slabs
or "fins".
Joint surfaces2.jpg
Joint surfaces in Permian sandstone, Canyonlands National Park, Utah.
Vertical joints, such as these, typically form by horizontal
extension of the crust, perpendicular to the length of the joint.
Weathering and erosion along the joints isolates the rock between the
joints as single "fins".
Joints1.jpg
Students entering joint within the Jurassic Entrada Sandstone at
Fiery Furnace in Arches National Park, Utah. The vertical joints were
formed in the sandstone due to upward movement of underlying salt
deposits and development of an anticline. The joints were enlarged
due to weathering of the fractured sandstone.
Joints2.jpg
Joints in Jurassic Navajo Sandstone, Paria Canyon Wilderness, Arizona.
Klippe of Lewis Thrust.jpg
Klippe of Lewis Thrust at Chief Mountain, Glacier National Park,
Montana. Where portions of the hanging walls of low-angle thrust
faults become erosionally isolated from the rest of the thrust sheet,
they are called klippen. In this photograph, the prominent blocky
mountain (Chief Mountain) on the right is a klippe because it
consists of rock of the Proterozoic Belt Supergroup that was carried
by the Lewis Thrust over Cretaceous and Tertiary rock below. The
trace of the fault lies along the base of the cliffs.
Left-lateral fault.jpg
Left-lateral faults in siltstone. Strike-slip faults are those in
which motion occurs parallel to the strike of the fault. If the block
opposite the viewer moves to the left, such as in this photograph,
the faults are called "left-lateral"; if the block opposite the
viewer moves to the right, the fault is called "right-lateral".
Listric fault1.jpg
Listric fault cutting Tertiary volcanic rocks in southeastern Nevada.
The footwall consists of dark-colored andesite flows and the hanging
wall consists of light-colored airfall tuffs. Listric faults exhibit
a curved concave-upward surface and strata in the hanging wall rotate
downward relative to the footwall.
Listric fault2.jpg
Listric normal fault, Republic of Kyrgyzstan, central Asia. Faults
that flatten with depth are called "listric" faults. Slip along
listric normal faults causes rotation of bedding in the hanging wall.
Marine terrace1.jpg
Uplifted marine terrace, Cape Blanco, Oregon. Marine terraces
generally form from wave-cut benches that can become stranded by
tectonic uplift of the land or a lowering of sea level.
Marine terrace2.jpg
Aerial photograph of Jurassic turbidites, uplifted marine terraces,
and gravel beach exposed at low tide. The waterfall in the center is
approximately 100 feet high. Paule Bay, Alaska Peninsula.
Melange1.jpg
Melange, SW Oregon. Melange is characterized by resistant blocks of
different rock types within a sheared, foliated "shaly" matrix.
Melanges form within accretionary prisms at subduction zones and they
contain high-pressure metamorphic minerals. Melanges are common in
coastal mountains along the western margin of North America.
Melange2.jpg
Cretaceous turbidites were deformed into isolated sandstone blocks in
a sheared shale-matrix melange about 100 million years ago during
subduction of the Farallon plate beneath North America. This outcrop
is located southwest of the Golden Gate Bridge in San Francisco,
California.
Monocline1.jpg
Monocline, SE Utah. Monoclines are folds in which nearly horizontal
rocks suddenly become very steep, and then abruptly flatten out
again. Most of the monoclines in southeast Utah formed above reverse
faults in the basement rock.
Monocline2.jpg
Monocline, NE Utah. Monoclines are folds in which nearly horizontal
rocks suddenly become very steep, and then abruptly flatten out
again. Most of the monoclines in southeast Utah formed above reverse
faults in the basement rock.
Nonconformity1.jpg
Angular unconformity and nonconformity, Grand Canyon, Arizona.
Angular unconformities are unconformities in which the rocks below
the unconformity lie at a different angle than those above the
unconformity. Nonconformities separate overlying and younger
sedimentary rocks from underlying and older igneous or metamorphic
rocks. This photograph in the Grand Canyon shows both. Where the
prominent brown sandstone (Cambrian Tapeats Sandstone) overlies
red-colored rock (Hakatai Shale), it is an angular unconformity; in
most other places it overlies metamorphic rock (Vishnu Schist) and so
is a nonconformity.
Nonconformity2.jpg
Nonconformity separates Mesozoic granitic rocks from Pliocene
volcanic rocks and mudflows of the Mehrten Formation. Highway 108 in
the central Sierra Nevada, California.
Normal fault1.jpg
Normal faults in marble, Death Valley, California. Normal faults form
by extension. They can be recognized because the footwall side goes
up relative to the hanging wall side. This photograph shows a pair of
normal faults that dip towards each other; the inner, down-faulted
block is called a graben.
Normal fault2.jpg
Aerial view of range-bounding normal fault, Death Valley, California.
Recently active faults, such as this one, are typically marked by
linear, abrupt transitions from valley floors to highlands. This
fault lies along the western edge of the Black Mountains in Death
Valley.
Normal fault3.jpg
Aerial view of range-bounding normal fault, Death Valley, California.
Recently active faults, such as this one, are typically marked by
linear, abrupt transitions from valley floors to highlands. This
fault lies behind "Artist Drive" along the western edge of the Black
Mountains in Death Valley.
Normal fault4.jpg
Normal fault, Death Valley, California. Normal faults are those in
which the footwall went up relative to the hanging wall. They form by
crustal extension. Tilting typically accompanies slip along normal
faults.
Normal fault5.jpg
Normal fault. View northward along the Sevier fault, SW Utah. This
fault places Quaternary basalt in its hanging wall against Eocene
sedimentary rock (Claron Fm.) in its footwall. That
younger-over-older relation indicates it is a normal fault.
Normal fault6.jpg
Normal fault with minor faults in hanging wall. As normal faults
slip, minor faults in the hanging wall may also slip. These minor
faults typically end downward at the master "detachment".
Normal fault7.jpg
The Teton Mountain front is the youngest and steepest in the Rocky
Mountains and rises up to 7,000 feet above Jackson Hole. The break-in
slope is the approximate trace of the Teton normal fault, which has a
combined displacement of about 30,000 feet. The Snake River has
eroded through glacial deposits in the foreground. Grand Teton
National Park, Wyoming.
Overturned anticline1.jpg
Overturned anticline, southern Alberta, Canada. Folds are
"overturned" if one of their limbs consist of rocks that have been
tilted past 90 degrees. This overturned anticline lies along the Lewis
Thrust in southern Alberta.
Overturned anticline2.jpg
Overturned anticline. Folds are "overturned" if one of their limbs
consist of rocks that have been tilted past 90 degrees. This overturned
anticline shows disharmonic folding in its core.
Overturned folds1.jpg
Overturned folds in Mesozoic ribbon chert, Marin Headlands,
California. Overturned folds are those in which one limb has been
rotated past 90 degrees.
Overturned folds2.jpg
Overturned folds, southern Alberta, Canada. Folds are "overturned" if
one of their limbs consist of rocks that have been tilted past 90 degrees.
These overturned folds lie at the termination of the Lewis Thrust in
southern Alberta.
Parasitic folds.jpg
Parasitic folds in gneiss. Minor "parasitic folds" such as in this
photograph, may form on the limbs of larger folds. When looking at
the larger fold in a direction down its plunge, most parasitic folds
on the left limb will be shaped like the letter "z", those on the
right limb will be shaped like the letter "s", and those along the
crest will be shaped like the letter "m".
Pegmatite dikes.jpg
Pegmatite dikes cutting Mesozoic quartz diorite along the Big Sur
coast of California. Dikes with exceptionally large crystals are
called pegmatites. They consist primarily of quartz, feldspar, and
mica and crystallize at relatively low temperatures from magma with a
high proportion of water.
Pillow basalt.jpg
Early Cretaceous pillow basalts in Marin County, California. Pillow
basalts form when lava is erupted underwater, commonly at spreading
centers or hotspot seamounts such as the Hawaiian Islands. Their
unique cross-sectional geometry is characterized by rounded tops and
downward projecting lobes that are valuable facing indicators in
structurally complex terranes.
Plunging anticline1.jpg
Plunging anticline, SW Montana. Folds, such as this anticline, form
by compression of the earth's crust. This anticline has a very steep
eastern limb, as can be seen by the near-vertical beds in the stream
cuts on the right-hand side of the photograph. The Jurassic and
Cretaceous sedimentary rocks were folded during the Late Cretaceous
"Laramide" Orogeny.
Plunging anticline2.jpg
Plunging anticline, Dinosaur National Monument, Utah-Colorado. Folds,
such as this anticline, form by compression of the earth's crust. The
fold plunges beneath the ground to the right (west). The Green River
cuts a deep canyon across the structure from north to south.
Ptygmatic folds.jpg
Ptygmatic folds in gneiss. Ptygmatic folds are irregular folds whose
amplitude is greater than their wavelength. As they require high
temperatures to form, they are invariably found in metamorphic rock.
Quartz-filled fractures.jpg
Quartz-filled fractures in sandstone.
Recumbent fold,CA.jpg
Recumbent fold, Corkscrew Peak, Death Valley, California. Recumbent
folds are those in which the axial surface is nearly horizontal. This
recumbent fold is a syncline because the youngest rocks are in the
core.
Recumbent fold,UT.jpg
Recumbent fold, Raft River Range, Utah. Recumbent folds are those in
which the axial surface is nearly horizontal.
Roof pendant.jpg
Steeply dipping Paleozoic metasedimentary rocks represent roof
pendants of the eastern Sierra Nevada, California. The Mount Morrison
roof pendant consists of Middle Cambrian through Ordovician rocks
that were originally deposited in a deepwater, continental-margin
setting. This roof pendant is preserved as a large mass of
metamorphosed country rock that projects into adjacent Mesozoic
granitic rocks.
Salt dome.jpg
Flowage and dissolution of Pennsylvanian salt deposits resulted in
localized folding and faulting of overlying Late Paleozoic
sedimentary rocks in the Grabens section of Canyonlands National
Park, Utah. Note the contrast between the folded lower strata and
undeformed upper beds.
San Andreas fault1.jpg
View northward along San Andreas fault, Pt. Reyes, California. Here,
the San Andreas fault underlies the linear, Tomales Bay that
separates the Pt. Reyes Peninsula (on the Pacific Plate) from the
mainland (North American Plate).
San Andreas fault2.jpg
During the Great San Francisco Earthquake of 1906, the San Andreas
fault ruptured the ground for a distance of about 270 miles. The
National Park Service reconstructed this fence along the Earthquake
Trail to show 16 feet of offset that was recorded in this area. Point
Reyes National Seashore, California.
Sandstone dike.jpg
Sandstone dike, eastern California. Unconsolidated deposits of sand
can intrude into open fissures if it is saturated and under pressure,
or if it accumulates from above. The sand, therefore, consolidates
into a sandstone dike, with many similar features as igneous
intrusions.
Sheeting joints1.jpg
Exfoliation or sheeting joints in granodiorite, Yosemite National
Park, California. Sheeting joints are also called "unloading joints"
because they form by outward expansion of bedrock as overlying
material is removed through erosion. Significantly, these joints
follow the topography. The joints in this photograph slope towards
the creek from either side.
Sheeting joints2.jpg
Sheeting joints in granodiorite, Yosemite National Park, California.
Sheeting joints3.jpg
Sheeting joints in granodiorite, southern British Columbia. Sheeting
joints are also called "unloading joints" because they form by
outward expansion of bedrock as overlying material is removed through
erosion. Significantly, these joints follow the topography. The
joints in this photograph wrap around the top of the dome.
Sierra Nevada.jpg
Owens Valley and the Sierra Nevada, California. The Owens Valley and
Sierra Nevada owe their existence to slip on a normal fault system
that runs along the base of the range on the right side of the
photograph. A recently active cinder cone erupted along one of the
faults.
Slaty cleavage1.jpg
Slaty cleavage and bedding. In this photograph, cleavage is nearly
vertical while sedimentary layering dips gently to the right.
Cleavage forms by dissolution creep of fine-grained material at low
to moderate temperatures and pressures. It typically accompanies
folding and forms approximately parallel to axial surfaces.
Slaty cleavage2.jpg
Slaty cleavage and bedding. In this photograph, cleavage is nearly
horizontal while sedimentary layering dips to the right. Cleavage
forms by dissolution creep of fine-grained material at low to
moderate temperatures and pressures. It typically accompanies folding
and forms approximately parallel to axial surfaces.
Slickensided fault surface.jpg
Slickensided fault surface and striations, northern Colorado.
Slickensides are polished fault surfaces; striations are grooves that
form parallel to the direction of slip on a fault surface. The
striations on this surface are nearly vertical.
Stretched cobble1.jpg
Stretched cobble conglomerate. Most pebbles or cobbles in undeformed
conglomerates are approximately spherical. In deformed conglomerates
such as this one, however, they are ellipsoidal. Analysis of the
ellipsoidal shapes of the deformed cobbles can give an estimate for
the amount of strain in the rock.
Stretched cobble2.jpg
Stretched cobble conglomerate. Most pebbles or cobbles in undeformed
conglomerates are approximately spherical. In deformed conglomerates
such as this one, however, they are ellipsoidal. Analysis of the
ellipsoidal shapes of the deformed cobbles can give an estimate for
the amount of strain in the rock.
Strike-slip fault1.jpg
Right-lateral strike-slip fault, SW Nevada. Strike-slip faults are
those in which motion occurs parallel to the strike of the fault. If
the block opposite the viewer moves to the right, such as in this
photograph, the fault is called "right-lateral"; if the block
opposite the viewer moves to the left, the fault is called
"left-lateral".
Strike-slip fault2.jpg
Right-lateral faults on wave-cut bench, western Oregon. Strike-slip
faults are those in which motion occurs parallel to the strike of the
fault. If the block opposite the viewer moves to the right, such as
in this photograph, the fault is called "right-lateral"; if the block
opposite the viewer moves to the left, the fault is called
"left-lateral".
Strike-slip fault3.jpg
Right-lateral faults on wave-cut bench, western Oregon. Strike-slip
faults are those in which motion occurs parallel to the strike of the
fault. If the block opposite the viewer moves to the right, such as
in this photograph, the fault is called "right-lateral"; if the block
opposite the viewer moves to the left, the fault is called
"left-lateral".
Stylolite.jpg
Photomicrograph of stylolite in limestone. Stylolites consist of the
insoluble residues that accumulate as the surrounding material is
dissolved during dissolution creep.
Syncline.jpg
Barstow syncline developed in Miocene sedimentary rocks. Skyline is
capped by flat-lining alluvial-fan deposits that lie unconformably on
the tilted strata. Rainbow Basin National Natural Landmark, Mojave
Desert, California.
Syncline-anticline.jpg
Syncline (left) and anticline (right) in Pliocene sandstone and
siltstone, San Andreas fault zone, Palmdale, California. Although
still contractional in nature, these folds formed in association with
slip on the San Andreas fault.
Thrust fault1.jpg
Red Spring thrust fault, SW Nevada. Thrust faults place older over
younger rocks. In this photograph, the overlying gray rock is
Cambrian limestone; the underlying red rock is Jurassic sandstone.
Thrust fault2.jpg
View to the south along Keystone thrust fault, SW Nevada. The
Keystone thrust forms the leading edge of the fold-thrust belt in SW
Nevada. It places gray limestone of the Cambrian Bonanza King
Formation over the red and tan Jurassic Aztec Sandstone. This view
shows that the fault dips gently westward.
Thrust fault and fold1.jpg
Thrust fault and fold in limestone and shale, SW Wales, UK. The
prominent limestone bed forms an anticline-syncline pair that is
offset along a thrust fault. Note the minor thrust faults along the
base of the limestone near the center of the photograph.
Thrust fault and fold2.jpg
Thrust fault and fold. Both thrust faults and folds form by
compression. Consequently, they are often found together.
Thrust fault and fold3.jpg
Thrust fault and fault-bend fold. Folds such as this one may form
along thrust faults as the hanging wall moves up and over a bend in
the fault (from a ramp to a flat).
Tilted strata.jpg
The Pennsylvanian-Permian Fountain Formation forms the scenic
backdrop for the Boulder Flatirons. The conglomeratic sandstones were
derived from erosion of the Ancestral Front Range Uplift. The strata
were later tilted during the Late Cretaceous-Early Tertiary Laramide
Orogeny. Southeast view towards Denver Basin. Note rockclimber for
scale on peak in center of photograph. Boulder Mountain Park,
Colorado.
Upheaval Dome.jpg
Upheaval Dome, Canyonlands National Park, SE Utah. Structural domes
are folds in which all sides dip away from the center. This
particular dome likely originated from upwards migration of salt. The
prominent sandstone around the rim is the Jurassic Navajo Sandstone.
Upright isoclinal fold.jpg
Upright isoclinal anticline, central Arkansas. Isoclinal folds are
those in which both limbs are parallel, or nearly parallel to each
other. The geologist in this photograph is in the core of the fold.
Xenoliths.jpg
Mesozoic granitic rocks and mafic xenoliths, near Donner Pass in the
Sierra Nevada of California. Xenoliths are fragments of older country
rock that are detached from the wall or roof of contact during
intrusion and are incorporated into the cooling magma.