My initial "Oklahoma Blog" centered on the eastern
one-third of Oklahoma, home of deciduous trees, Mississippian and Pennsylvanian
rocks, coal mines, a coastal plain, large lakes, the Ouachita and Ozark
Mountains, and the lead-zinc mines. In this Blog I move further west where the middle third of the state is dominated by
exposures of late Pennsylvanian and Permian rocks, many of which are red in
color. The Panhandle region has
exposures of dinosaur-containing Mesozoic rocks along with a Tertiary cover and
a few basalt flows. Interrupting this
logical sequence of rocks are two interesting “mountain” regions—the Arbuckle Mountains
south of Oklahoma City and the Wichita Mountains in the southwest near Lawton---subjects
for my next Blog.
Geologic
map of Oklahoma (from Oklahoma Geological Survey). Note the light blue streak (Permian) trending
north-south through the state.
Physiographic regions of Oklahoma (courtesy Oklahoma Geological Survey). A the Arbuckle Mountains, W the Wichita Mountains, RB, the Permian redbeds, HP, the High Plains. Compare with map above.
A more detailed province map of central
Oklahoma (courtesy of Oklahoma Geological Survey).
To better understand the geology
and related landforms of Oklahoma, readers should keep in mind above maps.
The sandstone cuestas (Spanish for
cliffs) region has gently dipping, to the west, sandstone layers protecting
underlying, slope-forming shale layers.
The sandstone of the province is late Pennsylvanian in age and was
formed as flowing rivers carried sand and other sediments into deltas and estuaries
of an ocean. These sandstone hills are quite scenic with a
somewhat distinct flora and fauna and extend into Kansas as the Chautauqua
Hills. The dipping beds of the
cuestas are associated with the large Ozark dome to the east. I have collected some nice tree-fern fossils
in the northern reaches of the province but mostly I just visited the area for
the scenic beauty and camping, noting the old-growth forests of post oak and
blackjack oak with blooming redbuds in the spring.
In Kansas, the Flint Hills are one
of the major physiographic provinces in the state (trending north-south) and
provide a unique landscape of native tallgrass prairie in a rocky and hilly terrain with major relief (at least for the plains states). In Oklahoma this province is known as the
Limestone Hills (also The Osage or the Limestone Cuestas) and only extend
about one-third of the way south. The
Flint Hills/The Osage have marine early Permian rocks exposed and are quite
fossiliferous. I have not collected in the Osage but have pulled hundreds/thousands of fossils from the Flint Hills in
Kansas. For 20 plus years I took my
undergraduate invertebrate paleontology class to the Flint Hills and students
routinely collected over 100 different species from Permian rocks.
Cartoon showing configuration of continents
at the end of the Paleozoic Era. Note
how Africa and South America collided with North America and produced the
Appalachian and Ouachita Mountains.
Public Domain map.
The later Permian represents the
end of the great Paleozoic seaway in the U.S. where marine waters that had
covered parts/most of the continent since the late Precambrian were receding
and drying. Plate activity had moved
continents world-wide so that a single large continent, Pangaea, was formed
and, except for continental margins, marine waters receded from the (current)
North American continent. The
later Permian represented the culmination of the Appalachian-Ouachita Orogen
where Gondwana was attached/sutured to (current) North America. As the Permian seas were drying and receding
the continent experienced restricted circulation waters and widespread deposition
of halite and other “salts” and gypsum.
In addition, wind and fluvial (stream) deposits containing grains of
iron-rich minerals later “rusted” and created the color in the widespread
redbeds trending north-south through the center of the state. As these beds extend north into Kansas they
are known as the Red or Gyp Hills. I
have examined the gypsum, anhydrite, and dolomite but found them rather
uninteresting as mineral specimens and “left them in place.”
Now, I have to admit that my
experience with the central Oklahoma redbeds essentially has been driving I-35
south to the Arbuckles or Texas Cretaceous!
About the only prospecting accomplished has been to look for the barite
roses. Of course, I suppose these concretions are the
best-known mineral in this part of the state.
Barite rose collected near Norman from
Permian Garber Formation. Width of left
single rose ~3.5 cm.
There are several instances where
minerals, mostly calcite, barite, and selenite gypsum, have formed clusters of
crystal “roses” or sand crystals. In
some case the roses are formed from “pure” minerals, with maybe an encrustation
of sand grains, such as the selenite roses (Desert Roses) from St. David,
Arizona (see Blog Feb. 4, 2013).
However, in parts of northwestern Nebraska the selenite roses have been
replaced by chalcedony.
In other cases the mineral solution
carries along sand-size grains from the host rock as inclusions. London (2008), in an article in The Mineralogical Record, noted that “roses are mineral specimens, not
rocks, because the shapes of rocks are indeterminate, whereas the shapes of
minerals are determined by a combination of forms and habits derived from the
interplay of crystal structure and environment of growth.” Each of the petals of the rose are individual
barite crystals. The Oklahoma roses are due
to the “intergrowth of crystals of barite…into a cluster of divergent blades…
The rose-like concretions incorporated the iron-stained quartz sand grains and
thus acquired the red color of the host Garber Sandstone” (Tulsa Geoscience
Center, 2012). The Oklahoma Geological
Survey (London, 2009) noted that “the best explanation for the roses is that
deep basinal groundwater containing barium and reduced sulfur species (sulfide)
migrated upward along fractures and porous layers into the Garbar
Sandstone. Upon reaching an aerated
region, the sulfur in the groundwater was then oxidized from sulfide to
sulfate, leading to the precipitation of barite.”
Barite roses were designated as the
official “State Rock” in 1968. It seems
unfortunate that no mineralogist (or so it seems) told Governor Bartlett and
the legislature that barite roses are minerals, as opposed to rocks. But, life goes on!
In Kansas, the red to orange barite
roses are similar except they have been collected from the Cretaceous
Kiowa Formation (see Blog July 23, 2013) derived from
barium-rich solutions in the underlying Permian rocks.
Barite Rose collected many years ago near the hamlet of Bavaria, Kansas,
in Cretaceous rocks. Width ~6 cm.
Calcite sand crystals are similar
to the barite roses except the form takes on the shape of calcite crystals. I suppose the most famous locality for
collecting these latter crystals has been Rattlesnake Butte in South Dakota
(now off-limits see Blog Jan. 9, 2014) although some crystals have started
to come from Wyoming (see Blog Dec. 17, 2011).
The further west one goes in
Oklahoma, the less time I have spent in the region other than traveling south
to the Wichita Mountains or to southwestern Texas where my son attended a
university. A long time ago (my favorite
phrase) I did take my students to: 1) Alabaster Caverns State Park; and 2) the
Great Salt Plains. The cave is formed in
Permian age massive gypsum and is a solution cavity. In my home state of Kansas a few miles to the
north, there are large sinkholes such as Big Basin that are related to
subsurface dissolution of similar age gypsum and halite. At one time, before collapse, a large natural
bridge near Sun City was 35 feet wide, 55 feet long, and 12 feet above stream
level. In addition, there are at least
117 gypsum caves in Barber County (Kansas Geological Survey, 2013).
The second place that we visited
was the well-known Great Salt Plains near the Arkansas River to dig and collect
selenite gypsum crystals--there is both a state park and a federal wildlife
refuge and collecting is on the refuge and hours/days etc. are posted. Check ahead before you drive to collect!
 |
| Big Basin is a sinkhole south of Dodge City, Kansas. Permian halite and gypsum beds in the subsurface have dissolved allowing the surficial Ogallala Formation to collapse. |
As it appears to me, the salt plains
are essentially a playa with incoming fresh water, at times, but without an
outlet. The original source of the salt
and gypsum are beds in the underlying Permian rocks---as noted above, the great
Paleozoic seaway was receding and drying and evaporation of brine waters left
behind a number or different minerals.
In the playa, the saline- and gypsum-infused groundwater is usually a
few inches to to few feet below the surface.
If the groundwater reaches the surface for a short duration but then
evaporates a crust of halite forms while the gypsum crystals form below the
surface. These selenite crystals at the salt plains are sort of a
chocolate brown to orange color due to minor amounts of iron oxide used as a
coloring agent. What makes the crystals
unique is that they have included tiny sand grains and these grains are in the
shape of a hourglass! Some crystals are
covered by a thin layer of sand while others are quite transparent and the
included sand grains are clearly observed.
According to all references I could locate, this is the only locality in
the world where this hourglass inclusion occurs. I don’t have the slightest idea “why” and it
appears that other geologists are also “stumped” at the shape of the inclusions. At times the crystals are solitary, sometimes
they are twinned (penetration twins common), and many times are in clusters. A
gazillion of these crystals have been collected since they are “for sale” in
virtually every rock/mineral shop, and in the rock and mineral shows. But they are also fun to collect if you don’t
mind getting a little muddy during the process.
Penetrating twin hourglass
selenite with sand inclusions. Length
~4.0 cm. In 2005 Oklahoma designated
hourglass selenite as the official State Crystal.
Along the Cimarron and Canadian
Rivers a hummocky terrain of both grass covered (stabilized) and active sand
dunes is found. Most of the dune fields
are on the north side of the rivers as a southern wind blows sand- and
silt-size grains from the current alluvium and the older terrace deposits. These dune fields are similar to the large
fields on the north side of the "big bend" of the Arkansas River.
I have always had an interest in
history, and especially of western U.S history between ~1800 (Lewis and Clark)
to ~ 1890 (Wounded Knee). This was a
time of great conflict between representatives of the federal government and
the Native Americans. Since I grew up in
Ottawa County Kansas I have been particularly interested in the summer of 1868
when Southern Cheyennes and some of their allies raided settlements along the Saline
and Solomon rivers (I grew up fishing in these rivers) killing several Caucasian settlers. Partially as a
result of these raids General Phillip Sheridan, Commander of the U.S. Army’s
Department of Missouri, an area of over a million square miles between the
Rocky Mountains and the Mississippi, decided to conduct a winter campaign
against the “insurgents.” In this manner
he hoped to destroy food stores and horses along with people and housing at a
time when the Native Americans were usually semi-permanently camped for the
winter. In late 1868 Sheridan sent Lt. Colonel George A. Custer on a winter mission
to subdue the Southern Cheyenne in western Oklahoma. At the ensuing battle or massacre (I will not
get into that argument) on November 27, 1868, Custer destroyed the village of,
and killed, the Cheyenne Peace Chief Black Kettle at an encampment along the
Washita River in the redbed plains of far western Oklahoma. If readers ever get a chance, take a side
trip and visit the national monument.
About where the Panhandle “hooks on
to” the main segment of Oklahoma the Plains Border section of the Great Plains
Physiographic Province ends and the large High Plains section begins. At one time in the late Tertiary the Ogallala
Formation (Group) extended from the Rocky Mountains (the source for its
sediments) eastward to the Missouri River and beyond. However, uplift to the west, and erosion by
rivers on all sides, has essentially left the High Plains as an island, one that
is capped by the Ogallala Formation. Today
the High Plains extend from the Pine Ridge Escarpment along the South
Dakota-Nebraska border south to the breaks at the Edwards Plateau in
Texas. The western boundary is situated
at the eroded breaks along the mountain front (such as the Colorado Piedmont). In the east the formation feathers and thins
and the High Plains end. Most people
know about the High Plains as being the source of the rapidly depleting
Ogallala Aquifer. Exposures of the
Ogallala Formation are common in the Panhandle.
A very unique geological area is
located in the far western Panhandle of Oklahoma and much geology is preserved
in Black Mesa State Park and the surrounding area along the Cimarron River
where rocks from the Triassic to Recent are well-exposed. Triassic and Jurassic rocks in the Great
Plains are relatively rare east of New Mexico and Colorado as are Cenozoic
volcanics. However, a nice section of of
the Triassic Dockum Group and the overlying Entrada and Morrison Formations of
Jurassic age crop out in the area. Of
additional interest are the remains of dinosaurs, both body fossils and
ichnofossils (dinosaur tracks), from the Morrison. Most people with even a slight interest in
natural history usually associate dinosaur fossils with places like Dinosaur
National Monument and the Cleveland-Lloyd Quarry in Utah, and Canon City and
Dinosaur Ridge in Colorado. However, an
Oklahoma geologist by the name of Willis Stovall collected thousands of
dinosaur bones from the Morrison around Black Mesa in the late 1930’s and early
1940’s. Today most of these fossils
reside in the Sam Noble Oklahoma Museum of Natural History.
One particular dinosaur collected
by Stovall from near Black Mesa was designated in 2000 as the State Fossil of
Oklahoma. Saurophaganax maximus is a large theropod (meat-eating) maybe 50
feet in length and 17+ feet tall. It is
most likely related to the allosaurs, the dominant theropods of the
Morrison. A cast of a front claw is
shown below.
Terminal phalanx or claw of Saurophaganax
maximus (cast replica).
I once participated in a field trip
to the area, mainly to examine the exposures of Cretaceous rocks. This section is very similar to the
Cretaceous rocks in Kansas, the big difference being the aerially widespread
exposures in Kansas compared to quite limited outcrops in Oklahoma. The oldest Cretaceous units are the Cheyenne
Sandstone, a fluvial sandstone (mostly), overlain by the marine Kiowa
Shale. The latter formation is quite
interesting is that it contains a “southern” assemblage of invertebrate
fossils. That is, marine waters invaded
the continent from the south and the resulting rocks contain fossils normally
associated with Gulf Coast Cretaceous rocks in Texas.
Marine waters then retreated south
and the mostly non-marine (wind, stream, delta, estuary) Dakota Formation was
deposited. Some units in the formation
contain dinosaur tracks (similar to Dinosaur Ridge in Colorado).
The widespread Western Interior
Seaway (WIS) is represented in Oklahoma by the Graneros and Greenhorn
Formations (calcareous shales and limestones) overlying the Dakota. Invertebrate fossils such as coiled ammonites
and straight-shelled baculites, along with inoceramid bivalves, are
abundant. The WIS had marine waters
transgressing from both the north and the south and the resulting northern fauna is
completely different from fossils found in the Kiowa Shale.
Image of Mesa de Maya and Black Mesa,
Colorado, New Mexico and Oklahoma. Image
© Google Earth.
One of the best known structures in
south-central/southwestern Colorado is the Raton Mesas starting near Trinidad
and continuing eastward along the Colorado-New Mexico state line where thick
(~800 feet) late Tertiary basalt flows (~3.5--9.0 Ma) cap the Poison Canyon
Formation (Tertiary: Paleocene) and hold up the topography. The area, including Barella Mesa and Johnson
Mesa, is often referred to as the Raton-Clayton Volcanic Field since the basalt
extends as far east as Clayton, New Mexico.
Near Trinidad, Fishers Peak (9626 feet) is the highest point in the
United States east of I-25. Further east
on the plains, “near” Tobe, and Walt’s Corner, Colorado, is an isolated, but related, mesa termed Mesa
de Maya where 400-500 feet of basalt cover the Ogallala Formation at an
elevation of around 6500 feet. The Mesa
continues south and eastward as Black Mesa and actually extends into the
Oklahoma Panhandle where at 4973 feet it is the highest point in Oklahoma. Suneson and Luza (1999) believe the age of the capping basalt flow at Black Mesa is ~5 Ma.
For additional reading see:
Neil Suneson, 2010, Petrified Wood
in Oklahoma: The Shale Shaker, v 60, no.6.
Oklahoma Crystal Collecting: www.brightok.net/~rockman/
REFERENCES CITED
Anonomous, 2013, Red Hills: Rocks
and Minerals: Geofacts, Kansas Geological Survey.
London, D., 2008, The Barite Roses
of Oklahoma: the Mineralogical Record.
London, D., 2009, The Barite Rose;
State Rock of Oklahoma: Oklahoma Geological Survey.
Tulsa Geoscience Center, 2012,
Barite Rose: Our State Rock: www.tulsageosciencecenter.org
Suneson, N. H. and K. V. Luza,
1999, A Field Trip Guide to the Geology of the Black Mesa State Park Area,
Cimarron County, Oklahoma: Oklahoma Geological Survey Open-file Report OF4-99.
