KANSAS FIELD TRIPS: HALITE AND CONE-IN-CONE

One of the joys of growing up in a small Kansas town in the 1950s was the lack of strict rules governing learning in the schools.  Our schools were very small (47 students in the 1961 high school); however, I always believed that the teachers were very good and the total education received was certainly more than adequate, and was fully supported by both parents and the community.  I always enjoyed “learning” but especially was fascinated by “experiments” (chemistry class: putting raw sodium in water [explosion]; physics class: constructing an AM radio transmitter; English class: presenting information via a “speech”; civics class: visiting the state capitol building in Topeka and climbing up to the outside catwalk; history/science classes: field trips).  In grade school (no kindergarten, and two classes per room in grades 1-8) I learned much about the world beginning in grade 3 (and continuing through grade 8) when each Wednesday students brought a newspaper clipping to class and then gave a verbal report. But several events really sick out in my mind in grades 5-6 when our teacher was excited about taking her students on field trips!

One of my fifth grade school trips was to the salt mines at Hutchinson where we wandered around underground without hardhats picking up pieces of halite. We had gone subsurface in some sort of a steel cage that transported workers to the main mining area.  In today’s world a fifth grader would not even get close to a working mine let along be taken down to wander and pick up minerals!  One small piece of halite remains in my collection from this little excursion by my class of 15 or so students. 

The salt that we collected was the mineral halite (NaCl) and is very common in several Permian beds stretching across Kansas.  The best known salt bed is the Hutchinson Salt Member (reaches perhaps 700 feet in thickness and covers perhaps 37,000 sq. miles; ~275 Ma) of the Wellington Formation. Mining of the halite in Hutchinson started in the late 1800s and I believe that at least one mine is still operating.  In addition, a couple of companies produce salt by evaporating halite brine.  North and west of Hutchinson is the small community of Kanopolis in Ellsworth County and a small company that mines halite from the same bed at about 650 feet below the surface. 

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).  The Flint Hills expose marine early Permian rocks and are quite fossiliferous.  I have pulled hundreds/thousands of fossils from rocks of the Flint Hills since for 20 plus years I took my undergraduate invertebrate paleontology class to the Hills.

Physiographic Map of Kansas from Kansas Geological Survey.  The Flint Hills expose early Permian fossiliferous limestone and mudrocks and represent the easternmost Permian rocks in Kansas.  However, the central and western parts of the state have thick sequences of Permian rocks in the subsurface.  The Red Hills expose late Permian mudrock redbeds and evaporitic beds of gypsum, anhydrite and dolomite.

Conditions gradually changed as 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 (southern continent) 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 evaporitic minerals, including gypsum.  In addition, wind and fluvial (stream) deposits containing grains of iron-rich minerals later “rusted” and created the color in the widespread redbeds known as the Red or Gyp Hills.  However, halite is easily dissolved in water and therefore the mineral does not appear on the earth’s surface.  The Hutchinson Salt Member is widespread in the subsurface of the state but not present on the surface.

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.

Today travelers to Hutchinson may visit a commercial, large underground salt museum known as Stratica and be whisked down in an elevator several hundred feet to the caverns.  Tours on trams are given and visitors may bring up a small piece of souvenir halite. 

Another field trip in the fifth grade was to Kanopolis Reservoir, a Corp of Engineers impoundment, southwest of Tescott in Ellsworth County.  This field trip, believe it or not, was to go fishing---the entire class packed up their (or borrowed) rods and reels and bait and lunch and off we went. If a little boredom ensued, we could wander around and collect rocks or minerals or whatever. “Whose parent would like to drive” asked the teacher (no school buses in this small district)? 

I now know that stratigraphic units exposed at the reservoir include both the Kiowa and Dakota formations that are mixed marine and/or streams/beaches/deltas/floodplains and represent the initial incursion (Early Cretaceous) of the Western Interior Seaway (WIS) into central Kansas.  It is very difficult for the average person (like me) to differentiate between these two formations. However, along the dam and the spillway are mapped exposures of gray-black shales of the Kiowa Formation.  Unique specimens of high-spired Turritella gastropods, often replaced by pyrite/marcasite, are scattered along the shoreline of the reservoir as are nuggets of marcasite.  In addition to the gastropods, strange nests of fibrous calcite, named cone-in-cone, occur in beds and lenses. These are somewhat resistant to erosion and therefore are scattered around on the surface and I remember taking home a pocketful that sort of melted into the ground, well really just disappeared, as I grew older. 

Later in life I started to explore the Kiowa Formation in a bit more detail as I hauled my students to Ellsworth County on field trips (see Blog posting 9-23-12).  One of the items we discovered along the face of the dam in the marine black shales, besides the cone-in-cone, pyritized gastropods, and a few clams  were impressions of a small crustacean (sort of small lobster-like) of an animal named Huhatanka kiowana (first named Squilla kiowana).  It was a treat for the students to collect fossils that did not have a calcareous shell; most of these specimens went into the University collections.

 

Mold of dorsal surface of Huhatanka kiowana. Photo from Feldman and West, 1978.

The cone-in-cone structure resembles a series of small elongate funnels stacked within one another.  Cone-in cone may sometimes be observed in concretions where the cones are small, less than one inch, and in other times as large cones, up to 8-10 inches, forming solid beds within another rock, usual black marine shale.  A top view of a cone-in-cone structure might resemble a series of circles.

 

Part of cone-in-cone structure that has broken away from the main mass.  Note circular pattern on top surface.  From the Cretaceous Kiowa Formation at Kanopolis Reservoir.

Bed of cone-in-cone, Kiowa Formation.  Note hammer for scale.

Cone-in-cone structures are composed essentially of calcite (calcium carbonate) fibers although some have a mixture of included clay particles----that much is known!  Occasionally they form in gypsum. What we do not know from the rock record is how the structure forms, nor the environment of deposition, as the formation of modern/recent cone-in-cone is unknown.  And, although cone-in-cone is almost always associated with marine black shale, certainly not all black shales display these structures.  In fact, cone-in- cone is somewhat rare in the rock record.

A geological debate periodically takes place as to the exact origin of the structure revolving around which came first---the cone-in-cone structure or the enclosing host rock.  Some geologists believe that the calcite fibers grow at the same time the host rock is forming.  Others believe the cones form after the deposition and lithification of the host rock---the fibers are intrusive.  This is sort of like a chicken or the egg first question.

The Kansas Geological Survey (2003) believes the cones form (precipitation of calcite) almost immediately after the deposition of the sediment (the host rock).  The pH in the sediment was perhaps lowered by the decomposition of organic matter so that the calcite was able to precipitate.  They also believe that stresses caused by gravity may have allowed for some of the near vertical beds of cones.  At any rate, the Survey has shown that the cones developed before the enclosing sediments were hardened into rock.

Phillips and others (2005) have studied cones and believe that the structures formed just below the sediment-water interface and are the result of submarine springs discharging carbonate-rich groundwater.

McBride and others, in studying sandstone with large concretions, note that formation of the cones is probably shallow (in terms of tens of meters) and most likely due to biogenic (coming from a living organism) processes.

 

Life as a university professor.  Photographer unknown.

On our University field trips we also visited what is now called Mushroom Rock State Park, the smallest of the Kansas state parks coming in at a whopping five acres.  Although tiny in size, the Park protects a number of large sandstone concretions within the upper part of the Kiowa Formation (maybe Dakota Formation but…?).  Although many Kansans call the concretions “quartzite” they are more accurately calcite-cemented sandstone; however, the rock is quite hard and more resistant to erosion than surrounding shale/mudstone.  For reasons unknown to me, the secondary calcium carbonate cement was deposited in a concentric pattern around a nucleus and therefore produced a rounded concretion.

Pulpit Rock at Mushroom Rock State Park.  Photo from Darton 1916.

So what did I learn on these 5^th grade excursions?  Well, I confirmed my love of the outdoors and nature and decided that some sort of a career in science was on the horizon (preferably a “forest ranger”).  Later in my teaching life I realized that field trips and out-of-classroom learning was an essential element of a total education.

See Blog Posting 10-27-2015

REFERENCES CITED

Kansas Geological Survey, 2003, Geology of the Kanopolis Lake Area: A Public Field Trip: Open-file Report 2003-52.

Feldman, R.M., and R.R. West, 1978, Huhatanka, a new genus of lobster (Decapoda: Mecochiridae) from the Kiowa Formation (Cretaceous: Albian) of Kansas: Journal of Paleontology, v. 5, no. 6. 

Darton, Nelson Horatio. 1916. Guidebook of the Western United States: Part C - The Santa Fe Route, With a Side Trip to Grand Canyon of the Colorado. U.S. Geological Survey. Bulletin 613.

McBride, E. F., M. D. Picard, and K. L. Milliken, 2003, Calcite-cemented concretions in Cretaceous sandstone, Wyoming and Utah, U.S.A. Journal of Sedimentary Research, v. 73, no. 3. 

Phillips, P.L., T. S. White, B. J. Witzke, G. A. Ludvigson, R. L. Brenner, L. A. marine mudstones. Geological Society of America Abstracts with Programs, Vol. 37, No. 2.