COLLECTING AT THE GATOROSA

SMOKY HILL JASPER

Rockhounds seeking interesting minerals for their cabinets, or looking for specimens to cut and polish, often blaze across Kansas to better “picking grounds”.  However, they may be overlooking numerous collecting possibilities.

In western Kansas the Miocene Ogallala Formation crops out at many localities.   This unit, consisting of stream gravels, along with a few volcanic ash beds and lake deposits, represents debris shed off the rising and eroding Rocky Mountains to the west, as well as fragments of local Cretaceous rocks.  As such, these outcrops contain a wide variety of minerals that originally formed in igneous rocks of the mountains.  The problem in collecting such minerals is that the Ogallala outcrops are commonly consolidated and tightly cemented and many times are covered by younger wind-blown sediments.

The answer to locating interesting minerals, and one that collectors commonly overlook, is to examine sand and gravel deposits situated along the major river systems, especially the Republican, Arkansas, Smoky Hill, and Saline, in the western part of the state.  These rivers have cut through and eroded the Ogallala and underlying Niobrara formations and then deposited their load (as current drops in velocity) in flood plains and channels.  Today these Pleistocene sediments are often well-exposed in numerous sand and gravels “pits” found on the older terraces.   If these excavations are not available for searching, simply walk the stream beds.

I have found a variety of minerals in the gravels with the finest specimens being various shades of jasper ranging from red to orange to green to brown.  Some of these jasper specimens from along the Republican, Smoky Hill, and Saline rivers in northern Kansas represent silicified chalk from the Cretaceous Smoky Hill Chalk Member of the Niobrara Formation.  These jasper outcrops are scattered across northwestern Kansas and seem to represent a post-depositional enrichment of the chalk, possibly with some dissolution of the chalk, by ground water rich in silica.  The source of the silica—probably volcanic ash or bentonite (altered ash).

Petrified wood is fairly common and chalcedony occurs in a variety of colors.  Of additional interest are the “Kansas Diamonds”, pieces of rounded and egg-shaped crystalline quartz.  Feldspar fragments are numerous but seem much smaller in size that the various quartz minerals (~1 cm or less) and are generally angular (broken along cleavage planes).  In addition, sort of nondescript dark colored rocks with an obvious igneous source are locally abundant.

The quartz minerals derived from the Rocky Mountains are generally less than 5-6 cm and highly rounded as the transport distance is great.  The locally derived jasper may be large (up to 13 cm in my collections) and specimens are angular.

I have seen beautiful faceted specimens of quartz derived from “Kansas Diamonds” and when combined with silver settings are quite spectacular.  In addition, the jasper makes wonderful cabochons or just plain tumbled stones.  Native Americans often used the silicified chalk for projectile points and one see the terms Niobrarite or Smoky Hill Jasper used in the literature.

So, although gemstones and semi-precious gemstones are essentially non-existent in Kansas, the jasper, chalcedony, quartz  and petrified wood offer some nice specimens for the lapidariest or flintnapper. 

BTW, the Gatorosa is my brother's ranch along the Smoky Hill River in Trego, County!

mike 

LOCALLY DERIVED SMOKY HILL JASPER.  MANY SPECIMENS SHOW STRONG BANDING.

NON-LOCAL CHALCEDONY.

NON-LOCAL? CHALCEDONY.

SAND AND GRAVEL DEPOSIT ON THE "HIGH TERRACE" AT THE GATOROSA.  YUCCA PLANTS FOR SCALE.

ARTIFACTS CONSTRUCTED FROM SMOKY HILL JASPER.  PHOTO COURTESY OF DON BLAKESLEE AND KANSAS STATE HISTORICAL SOCIETY.

NOTCH PEAK: GREAT GEOLOGY

SHARP CONTACT BETWEEN METAMORPHOSED CAMBRIAN CARBONATES AND THE NOTCH PEAK INTRUSION.  IT IS NOT OFTEN THAT ONE CAN :PUT THEIR FINGER" ON SUCH A CONTACT

The House Range is one of those geological wonders found in the west desert of Utah and the Great Basin—it is a classic uplifted block of rocks, a horst, bounded by Tule and Sevier valleys, the grabens.  The Range is north-south trending (~40 mi X 7 mi) and generally exposes lower Paleozoic (Cambrian and Ordovician) rocks.  However, there is a major quartz monzonite (an igneous rock similar to granite but without the quartz) intrusive body of Jurassic age (Notch Peak Intrusion) called Sawtooth Mountain.  This name comes from the weathering of the monzonite into sharp points and ridges as compared to the more rounded peaks in the limestones and shales. 

NOTCH PEAK IN THE HOUSE RANGE.  THE PEAK IS CAPPED BY THE NOTCH PEAK DOLOMITE.  NOTE THE ORANGE-COLORED AND INTRUSIVE QUARTZ MONZANITE OF THE NOTCH PEAK INTRUSION.  PHOTO COURTESY OF WIKIPEDIA.

The dominant topographic feature of the Range is Notch Peak at 9654 feet, but with a vertical rise (cliff) of about 2200 feet at the summit.  The peak itself is floored by the Notch Peak Intrusion with overlying Cambrian and Ordovician carbonates and topped by the Notch Peak Dolomite. The igneous rocks have produced minor amounts of placer gold and some claims are still active.  It seems as though the source of the gold dust has never been located, perhaps representing an opportunity for prospectors to “strike it rich”!  One of the really “neat things” about the fascinating geology at Sawtooth Mountain is that one is able to “put your finger” on the contact between a major intrusive feature and a sedimentary rock and follow the metamorphic aureole outward.  This intrusive event is related to tectonic activity associated with the Nevadan Orogeny and is approximately 150 Ma in age. 

mike  

HOT BATH ANYONE? THERMOPOLIS, WY

Thermopolis, Wyoming, is an interesting city (pop. ~3200) located at the southern end of the Big Horn Basin on U. S. 20.  The city was named after the Pass of Thermopylae, famed in Greek history as the Spartan battle ground. The word is combined from the Greek derivative which is literally translated “City of Hot Mineral Baths” (www.wiki.wyoming placenames.org).   The Big Horn River runs through town and carves the beautiful Wind River Canyon as it cuts across the Owl Creek Mountains to the south.  As an interesting sidelight, the Wind River changes names (to Big Horn) as it leaves the canyon flowing north!  Thermopolis is a common rest stop on the way to/from Yellowstone National Park and has a long history of thermal spring use by Native Americans and later settlers.  Most of the springs were, at one time, located on the Shoshone Reservation (ceded to the tribes in the 1868 Fort Bridger Treaty) but were acquired, through purchase, by the U. S. Government in 1896.  The city now bills itself as home to “The World’s Largest Mineral Hot Springs” and also is home to Hot Springs State Park.  In addition, there are at several other hot springs or wells in or near the city. 

Location and relief map of Wyoming.  Thermopolis (denoted by O) is located on the Big Horn River north of the Owl Creek Mountains (denoted by X’s).  Map adapted from U. S. Geological Survey.

As the great conservationist Aldo Leopold once said, everything is connected to everything else. So it is at Thermopolis where all of the springs and vents are connected to the same thermal system with total discharge perhaps over three million gallons per day (Breckenridge and Hinckley, 1978).  However, to a geologist, or even causal traveler, the most interesting aspect of these wells/springs may well be the related travertine deposits.

Wind River Canyon south of Thermopolis (looking south as river flows north) as the river cuts through the Owl Creek Mountains and exposes  formations that range in age from Precambrian through Triassic .  Relief in the canyon reaches 2500 feet.

The springs at Hot Springs State Park are those most visited by travelers, especially visitors wanting to “take a soak”!  Most of these related waters have high concentraions of Calcium, Magnesium, Sodium and Potassium ions and make human consumption somewhat problomatic.  I can personally attest to gastric discomfort (especially in 105^O F summer weather) after consuming similar water while working in South Dakota!  The thermal springs also have fairly high concentraions of HCO₃ (bicarbonate ion), SO₄ (sulfate), and Cl (clorine).  The pH usually is calculated as between 7-8 (basic), about the same as sea water. 

 

White Sulphur Springs is one of the largest springs in the park with a temperature of ~127^O F and flowing at a rate of about 200 gallons per minute (gpm) (Breckenridge and Hinckley, 1978).  The name most likely comes from its content of Hydrogen sulfide (H₂S), a compound notorious for the foul smell of rotten eggs.  At one time sulphur was mined from deposits near the spring.

Black Sulfur Spring in the park is now inactive but does form a pool in bottom of a 20 foot cavern with bubbling mud high in sulphur.  Dye tests indicate the spring now has Terrace Spring as its outlet (Breckenridge and Hinckley, 1978).

The spring in the park that most visitors are familiar with, and the largest, is Big Spring with a temperature of ~133^O F and a flow of over ~2900 gpm (Breckenridge and Hinckley, 1978).  The spring water enters a 25-foot pool and then feeds the State Bathouse pools and pools/tubs of five commercial establishments.  The commercial entities vent their water vapors via a standpipe and this action has created a really interesting phenomenon known as Teepee Fountain (see at top of article).  This feature is a 20-foot high cone of travertine streaked with algal growth, a very impressive piece of artwork.  

North of town is another interesting thermal feature—Sacajawea Well, first drilled for oil in 1918.  Evidently at the 900 foot level the well hit artesian pressurized hot water that blew the drilling rig off the casing!  Travertine began forming around the pipe and continues today.  The well flows at 1.37 million gallons per day at ~130^O F. 

Sacajawea Well located north of town at Payne’s Fountain of Youth RV Park and is, according to the park, the “third largest hot mineral pool in the World”.  Photo courtesy of www.city-data.com

Travertine is a sedimentary rock, a type of chemical limestone, that usually precipitates from carbonate-rich waters associated with springs (especially thermal springs), streams (especially waterfalls), and caves. Both calcite (CaCO₃, forms in trigonal crystal system; most stable of calcium carbonate polymorphs) and aragonite (CaCO₃, a polymorph of calcium carbonate forming in orthorhombic crystal system; is metastable and alters to calcite) are found in travertine with the former usually found in cooler waters and the latter in hot water (Pentecost, 2005).   Travertine commonly forms when dissolved carbon dioxide (CO₂) in peculating groundwater, in this case the springs, creates a weak carbonic acid (H₂CO₃) that then reacts with limestone (CaCO₃) to form soluble calcium acid carbonate [CaH₂(CO₃)] which then precipitates when the water evaporates at an exposed surface (Rogers, 2011).  Pure travertine is generally white but impurities commonly impart a brown/tan color to the rock.  However, the bright colors at Thermopolis are due to thermophilic (heat loving) organisms: Bacteria (Schizophyta), Blue-green Algae (Cyanophyta), and Green Algae (Chlorophyta).  The algae are phtosynthetic in nature and contain green chlorophyll and impart a green color to the travertine.  In addition, the Blue-green Algae have a blue pigment, phycocyanin.  Some, such as those at Thermopolis also contain red, yellow, brown and orange pigments (Terrell, 1978).  The Bacteria lack a cell nucleus and are non-photosynthitic but may use sulphur in the water as part of their food production.  They may impart colors from white to pink/purple to yellow (Terrell, 1978).

Travertine “terraces” at Hot Springs State Park.

 Breckenridge and Hinckley (1978) described the geohydrology of the artesian Thermopolis thermal system as follows: water enters the Paleozoic rocks (all are aquifers but especially the Madison Limestone) exposed in the nearby Owl Creek Mountains.  These rocks are capped by the Jurassic Chugwater Formation, a rather impervious caprock, and dip away from the mountains toward the Big Horn River.  At Thermopolis a large fold, with a crest fault, appears and bring the Paleozoic rocks to the surface and the water is released under pressure.  The solution conduits of the Madison Limestone are thought to be the major source of the water.  The next major question involves the source of the heat.  Most thermal springs are related to either water heated at great depths in the earth’s surface, or heat generated from nearby igneous activity.  At Thermopolis “the water has become heated because it has circulated to great depths” (Whitehead, 1996). 

Geologic cross-section through Hot Springs State Park.  Sketch from Breckenridge and Hinckley (1978).

 Thermopolis is a great little town to visit and I plan on going back and “taking to the waters”.  The price is right---free at Hot Springs State Park!  In addition, the Wyoming Dinosaur Center in town is an interesting museum, and the nearby Wind River Canyon has some spectacular geologic outcrops.

REFERENCES CITED

Breckenridge, R. M. and B. S. Hinckley, 1978, Thermal Springs of Wyoming: Wyoming Geological Survey Bulletin 60.

Pentecost, A., 2005, Travertine: Kluwer Academic Publishers Group, Dordrecht, Netherlands.

Rogers, J. D., 2011, Grand Canyon Research Travertine and Pleistocene Lakes: http://web.mst.edu/~rogersda/grand_canyon_research/

Terrell, T. T., 1978, Vegetation of Wyoming Thermal Springs Outside of Wyoming in Breckenridge, R. M. and B. S. Hinckley, Thermal Springs of Wyoming: Wyoming Geological Survey Bulletin 60.

Whitehead, R. L., 1996, Ground Water Atlas of the United States; Montana, North Dakota, South Dakota, Wyoming: U. S. Geological Survey Report HA 730-I.