Living and teaching
in western Kansas did not allow much interaction with either igneous or
metamorphic rocks, nor with Paleozoic rocks older than the Mississippian (and
these age rocks are restricted to the southeastern most 50 sq. miles of the
state). So, what to do? How could a geology student become better
acquainted with rocks that are not Tertiary, Cretaceous, Permian or
Pennsylvanian in age? Well, it seemed
like an easy answer—road trip! So
off we went either south or west, depending upon the time of year. In early fall the Colorado mountains were
beautiful with color and outcrops vacant of people. During the spring semester
Colorado was often cool-cold and snow lingered in the high country. Therefore, Oklahoma to the south seemed like
a good choice. And, the most interesting
places to visit were the Wichita Mountains in the southwest, and the Arbuckle
Mountains in the south central part of the state.
Geologic map of Oklahoma (from Oklahoma
Geological Survey). The Arbuckle
Mountains are located to the south of Oklahoma City (and a little east) while
the Wichita Mountains are to the southwest.
Both appear on the map as isolated “blobs.”
These two ranges
present some very interesting stratigraphy and geologists still seem to be
debating about the origin of the “basement rocks” cropping out in the
mountains. If readers would travel to
Colorado or Wyoming or New Mexico (and other western states) they would note
that the oldest rocks, especially in the Laramide front ranges, are Precambrian
in age—older than ~542 Ma. However, the
igneous rocks, lots of rhyolite, granite and diorite, in the Wichita Mountains are
perhaps latest Precambrian (Neoproterozoic: 1000Ma to 542 Ma) but are mostly
Cambrian in age, something younger than ~542 Ma. And, that is the really
interesting part .
Location of the Southern Oklahoma Rift System
penetrating the continent at about 90 degrees to the edge of the
continent. Map taken from Hansen and
others, 2011.
The Wichita
Mountains are situated in the southwestern part of Oklahoma and
actually have some relief, maybe 500 to 1100 feet, and dominate the topography. I remember climbing Mt. Scott at
~2462 feet and essentially the highest peak in the range; Mt. Pinchot at 2479
feet is on a special area of the wildlife refuge and off limits to visitors,
while Haley Peak on private property is 2481 (maybe). The oldest rocks in the
Wichitas are known as the Tillman “metasedimentry group” and represent latest
Precambrian-early Cambrian marine sandstones that are now turned to quartzite. However, beginning at about the same time as
their deposition, massive volcanism and plutonic placement of granite was
beginning in a structural basin termed the Southern Oklahoma Rift System (SORS). Some geologists argue that the
SORS sequence represents a sea floor spreading event, a rift-rift-rift triple
junction, with one arm extending into the old proto-North American continent
(known to geologists as Laurentia) while the other two arms are now obscured by
ocean basins (Hansen and others, 2011). The
Oklahoma arm has been given the name
Southern Oklahoma Aulacogen or Wichita Aulacogen since the arm ultimately
failed (an aulacogen). However, Thomas (2011) believed the plutonic events are
part of a large fault zone extending inward into the proto continent. These magmatic rocks in Oklahoma also seem
related to other igneous events stretching from New Mexico to Utah and
Colorado. Whatever the cause, the igneous
rocks in southwestern Oklahoma (latest Precambrian? to Cambrian in age) represent
a major tectonic event along the southern margin of proto North America; the
older Raggedy Mountain gabbro group and the Navajoe Mountain basalt group are
unconformably overlain by the widespread Carleton Rhyolite Group and the
intrusive Wichita Mountain Granite Group. The latter two units are the igneous rocks
that form the rugged mountains and are well exposed and easy to observe. All in all, the Wichitas are a great
place to visit, to observe the buffalo (bison) at the wildlife preserve, and
see some igneous “basement” rocks that are not Precambrian in age.
Mt Scott in the Wichita Mountains is the most
easily accessible peak in the Range. Public Domain photo.
Map showing location of the Wichita Mountains in
southwestern Oklahoma. Igneous rocks
dominate the mountains in the south, near Fort Sill, and are the most visited
section. North of the Meers Fault there
are large exposures of the Ordovician (488-443 Ma) Arbuckle Group limestones. Map taken from Hansen and others, 2011.
Starting before the
conclusion of the Wichita magmatic event, and continuing after, sediments begin
to erode from the surrounding highlands into the rift or fault basin
(SORS). In addition, marine sedimentary
rocks, limestone, sandstone, shale, were deposited, on and off, in Oklahoma from
late Cambrian through the early Mississippian (~359-345 Ma). By the late Mississippian (~328-318 Ma), SORS
was rapidly subsiding and filling with clastic particles later forming a shale.
By the
Pennsylvanian (beginning ~311 Ma ) “things” begin to change in Oklahoma as a
result of what is termed the Ouachita Orogeny—plates of South America and
Africa bumping in to the southern margin of North America. In Arkansas and parts of eastern Oklahoma (see
previous Blog) the collision resulted in formation of thrusted and folded
mountains called the Ouachita Mountains.
In the Mountain West states, the collisional event produced large block fault
mountains—the Ancestral Rocky Mountains.
And in southern Oklahoma, the old SORS was no longer accepting sediments
but was activated by vertical uplift and faulting into a highland area and shedding
off large clasts that later cemented into sandstones and conglomerates. The erosion continued into the early part of
the Permian (~251 Ma) but by but the late Permian (~290 Ma) the mountains
(uplifted SORS) were covered and buried by sediments. Jurassic and Triassic (~228-145 Ma) rocks are
virtually unknown from western Oklahoma and Cretaceous (~145-65 Ma) rocks were
probably deposited but are mostly eroded away.
The current Wichita Mountains are the result of landforms that were established
in the Pennsylvanian/Permian and brought to light with Cenozoic erosion.
The Arbuckle
Mountains are almost straight south of Oklahoma City along I-25 north of the
Texas-Oklahoma border. These hills are
not really very high, ~1400 feet, there is not much relief—perhaps 600 feet,
but they represent a different sort of environment and are popular with
visitors. They do have some old rocks and one time on a field trip I was able
to visit a large granite quarry in the Tishomingo Granite, ~1.4 Ga. These rocks are, in turn, overlain by the
Cambrian Carleton Rhyolite (seen in the Wichitas), and maybe 15,000 feet of
Paleozoic rocks (mostly marine). The
Arbuckles have a similar geological history as the Wichitas and they were both
part of the SORS. The big difference is
that in the Wichitas, igneous rocks predominate while in the Arbuckles
sedimentary rocks are common, and many are quite fossiliferous. In addition, the USGS noted “the
Arbuckles contain the most diverse suite of mineral resources in Oklahoma:
limestone, dolomite, glass sand, granite, sand and gravel, shale, cement, iron
ore, lead, zinc, tar sands, and oil and gas; all these minerals are, or have
been, produced commercially” (http://vulcan.wr.usgs.gov).
Honey Creek, originally producing from a
spring(s), drops 77 feet at Turner Falls (near Davis) and is probably the most
photographed feature in Oklahoma. Public
Domain photo.
The geologic stories
of the Wichita and Arbuckle mountains are much too complex for a short article
like this. Unfortunately, I had to use
much geological jargon in the paragraphs above, and for this apologize. I did
try to insert approximate dates for the geological terms indicated by
Ma=millions of years ago. I guess an easy way to look at their history: 1)
rifting and/or faulting with accumulation of Cambrian igneous rocks; 2) stable
continent and accumulation of mostly marine rocks from Cambrian-early Pennsylvanian;
3) uplift of the SORS in late Pennsylvanian from tensional forces of the nearby
Ouachita Orogeny; 4) erosion in the Cenozoic producing current landforms that
were first established in the late Paleozoic.
I have to admit
that my visits to the Arbuckle and Wichita Mountains were many decades ago when
collecting by rockhounds and students were in much different circumstances. We simply contacted quarry owners by mail,
received permission (especially for non-working weekends), and collected
invertebrate fossils to our heart’s content.
In addition, everyone took home a few pieces of granite since the only igneous
outcrops in western Kansas were at local cemeteries. As a result, I really don’t have fossil
specimens (in museum collections) or minerals from either the Arbuckle or
Wichita Mountains and could not inform readers about any collecting
localities.
In addition, the
Oklahoma Geological Survey will allow you to download: copies of Guidebook 26, Geology of the Arbuckle Mountains along
I-35, Carter and Murray Counties Oklahoma (Robert O. Fay). The publication describes the geology at the
numerous road cuts along I-35 north of the city of Ardmore; Guidebook 21, Geology of the Eastern Wichita Mountains, Southwestern
Oklahoma (Gilbert and Donavan); Guidebook 23, Petrology of the Cambrian Wichita Mountains Igneous Suite
(Gilbert); and Guidebook 24, The Slick
Hills of Southwestern Oklahoma—Fragments of an Aulacogen (Donovan). The Slick Hills are the limestone part of the
Wichita Mountains located north of the Meers fault. Go to http://www.ogs.ou.edu/pubsDLGBs.php. Finally, the
last time that I traversed through the Arbuckle Mountains the Ardmore
Geological Society had installed informative information on a number of road
signs. I presume they are still along
the highway.
SOME TRIVIA: Much land in the igneous rock part of the
Wichita Mountains is tied up in the Wichita Mountains National Wildlife Refuge
(~60,000 acres). President William
McKinley, in 1901, established the mountains as a “”Forest Reserve.” It took President Theodore Roosevelt, in
1905, to designate it as a "Game Preserve,” the forerunner of the federal refuge
system. In fact, the refuge is the
oldest in the nation. One of the
critical reasons for the establishment of the refuge was to protect endangered
species. Bison, six bulls and nine cows,
were introduced in 1907 with stock coming from the New York Zoological Park. Texas Longhorn Cattle were also introduced to
help preserve the “purity” of the strain.
Unfortunately, the original Oklahoma elk subspecies, Merriam’s I think, is
extinct so the Refuge imported Rocky Mountain Elk in 1911. There were also a number of other smaller
mammals and birds introduced to this protective island.
REAL TRIVIA: Shortly after McKinley’s designation of the
Forest Reserve he was assassinated by an anarchist in in 1901. He was succeeded by his Vice President,
Roosevelt. McKinley was the last
President to serve in the Civil War.
AND MORE: An
assassin also tried to take down Roosevelt in 1912 as he was campaigning for a
third term as President running in the Progressive Party (vernacular—Bull Moose
Party). The bullet (32 caliber) went through his steel eyeglass case and 50
pages of a speech (Roosevelt was a realer talker) and three inches of his
chest, but did not penetrate his pleura.
Roosevelt gave his speech (Ladies
and gentlemen, I don't know whether you fully understand that I have just been
shot; but it takes more than that to kill a Bull Moose) with blood staining his shirt and carried the bullet
around forever (too dangerous to remove).
Roosevelt entered
the presidency via an assassin’s bullet while another would-be assassin’s
bullet ended his campaigning right before the 1912 election and therefore his
chance to re-enter the office. Now, that
is real trivia.
According to the
Oklahoma Historical Society (2014) Spanish mining activity existed in the
Wichitas as early as the mid-1700’s.
Evidently they were not very successful.
However, in the 1890’s prospectors wandering around in the granite found
evidence of these old Spanish mines (and I use the term mine quite
loosely). By 1895 a “gold rush” was on
to the Wichitas but, in a similar situation as the Black Hills of South Dakota,
the land was part of the Kiowa-Comanche-Apache Indian Reservation. As usual, miners and settlers put pressure on
the U.S. Congress and by 1901 the Reservation was open to settlement and mining
(a question—was this why McKinley designated the Forest Preserve?). In the next 10 years over 2000 gold claims
were filed with no one, as
far as I can tell, “getting rich,” except some promoters. A few surface veins were located and
holes/mines penetrated into the granite but nothing really paid.
Comancheria, the
ancestral home of the various Comanche tribes and bands, occupied much of
Texas, Oklahoma, and New Mexico. Perhaps their most famous warrior was Quanah
Parker of the Noconis Band.
Parker was the son of Cynthia Ann Parker, a captured Caucasian from
Texas, and Peta Nocona. Most historians,
but not all, believe Quanah was born (ca.1850) in or near the Wichita
Mountains.
.
REFERENCES CITED
Hanson, R.E., R.E.
Puckett, Jr., D.A. McCleery, M.E. Brueseke, C.L. Bulen, and S.A. Mertzman,
2011, The Cambrian Wichita Bimodal large Igneous Province
in the Southern Oklahoma Rift Zone: Large Igneous Provinces Commission http://www.largeigneousprovinces.org
Oklahoma Historical Society, 2014, Gold: Encyclopedia of Oklahoma History and Culture,
www.digital.library.okstate.ed
Thomas, W.A., 2011, The Iapetan Rifted Margin of Southern
Laurentia: Geosphere, v. 7.
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