Capen Crinoids EarthCache

Do not park on the highway! Instead, start at the indicated parking coordinates in the waypoint list. The trail there leads to some fantastic views and incredibly steep drops. Watch your step as there aren't any guardrails to prevent accidental falls! Recreational rock climbing is available with the right gear but not necessary to complete this cache.

Planetary Transitions

Planet Earth is constantly changing. Key to such change is the motion of large sections of the surface rock layer, or crust. These sections, known as tectonic plates, move against one another reforming the surface constantly. It is difficult to see in our lifetimes, but, over millions of years, the alterations are quite evident. One way to witness this constant flux is careful study of the planet's current geology.

Missouri's geology shows a varied past that is easier to observe. Much of the present day rock in the state is sedimentary in nature. Sedimentary rocks are formed from debris left behind in a depositional environment, or a location where particulate matter can collect. Over millions of years, the deposits of soil, grains of sand and past living creatures add up and are compacted in a process called lithification. Water is expelled as pressure increases from upper layers and density increases. Each layer's characteristics can be identified visually by casually looking at an eroded bluff.

Tropical Paradise

This leads us to the bluffs at Capen Park in Columbia, Missouri. They are exemplary, and, to find out why, we'll have to step back millions of years into the past.

Approximately 410 million years ago, Missouri was tropically located just south of Earth's equator. This was long before the supercontinent of Pangea existed, and the tectonic plates constantly moved landforms around the planet's surface as they do today. A Sloss sequence, or period of sea level fluctuation, began around this time. There were four such sequences during the Paleozoic era (542 to 251 million years ago) that influenced Missouri's sedimentary rocks; we will be focusing on the Kaskaskia sequence that occurred during the Mississippian period (359 to 325 million years ago).

The Kaskaskia sequence saw radical changes in sea levels during the Mississippian period. Missouri, at the beginning of this time, found itself shallowly underwater catching the nutrient-rich sediment deposited by ancient streams and rivers. Simple aquatic lifeforms consequently colonized the area and flourished. Among them were crinoids, brachiopods, horn corals, blastoids, bryozoan, radiolaria and gastropods. Toward the end of the Mississippian period and Kaskaskia sequence, sea levels dropped sharply dooming this ecosystem to extinction. Tectonic plate collision would reorient the area now known as Missouri further introducing new life and geology.

Logically, it would seem that future sedimentation and changes in geology would bury the past under layers and layers of rock. Not completely so! Sloss sequences over millions of years ensured uneven exposure and inundation. As some portions were exposed, the easily soluble sedimentary rock eroded and erased eras of depositation. Such action leaves gaps in observable geological history. Others remained buried and untouched for future revelation.

Layers of History

Capen Park exemplifies an outcrop, or a natural surface exposure, of limestone that was created during the Mississippian period and revealed through erosion by Hinkson Creek. When standing at the bottom of the bluff, one will note three distinct features. Starting from the bottom, a layer of lower Burlington limestone was produced between the early and middle Mississippian period. Upper Burlington limestone follows and comprises a majority of the bluff right to the top; it was produced during the middle to later Mississippian period. Small bands of crumbly, white stone known as chert may be found throughout.

Lower Burlington limestone is fairly easy to identify. It is somewhat fossiliferous, fine to medium grained and brown in color. Impure phases of development as well as ferriginous material lends to the pigmentation. This layer is typically between 10 and 20 feet tall.

Much more famous and recognizable is the upper Burlington limestone. Highly fossiliferous, the upper member is coarsely crystalline and light to dark grey or brown in coloration. Fossils found are commonly identified as crinoid stems (appearing as segmented straws) that are in actuality calcite crystals. These remains comprise up to 90% of the limestone. This layer is much more imposing standing between 100 and 160 feet tall.

Chert intermingles freely with both forms of Burlington limestone. The organisms responsible for its creation, radiolaria, excreted silica from the water and thus their remains were filled with the compound. Globules of the stuff collected on the sea floor and were consequently flattened by other sediments layering above. Mostly white or grey, the stone can be discovered in round sections or lensing layers, also known as bands, of irregular length. They are mostly between two inches to two feet tall.

Traversing the Trails

Now let's put the above information to practice! Visit each of the coordinates below (listed later in the Additional Waypoints section) and answer the questions posed. Send your responses to the cache owner via the link on the caching handle at the top of this cache page. Photos, while not required, will not only document your visit but show off some of the nice vistas along the way.

N 38° 56.000 W 92° 19.130

The area behind the Capen Park bluffs once served as a quarry. A remnant of that time can be found at the posted coordinates in the form of a limestone boulder.

1a) On the southern side approximately one and a half feet off the ground, a well-worn and sizable crinoid stem is easily discovered. What is its length?

1b) Is the boulder upper or lower Burlington limestone?

N 38° 55.852 W 92° 19.244

Differences in erosion can be seen at the second waypoint in the upper Burlington limestone. A small ledge on the walking path hides a short section that is mostly shielded from erosional elements.

2a) Name two differences between the exposed and lesser exposed limestone. Are there identifiable fossils?

2b) What is the elevation at this location?

N 38° 55.829 W 92° 19.233

Carefully following a path around the bluff, one will find themselves near Hinkson Creek and close to the base of the bluff. A path stands near the separation between the upper and lower Burlington segments.

3a) The separation is approximately 8 feet up from the path. Using your GPS, measure the elevation at these coordinates and add 8. Then, subtract your answer from the reading taken at the second waypoint. Approximately how tall is the upper Burlington limestone segment?

3b) How many bands of chert can be identified in both the upper and lower Burlington limestone?

3c) Define Sloss sequence. How do Sloss sequences preserve formations like the Capen Park bluffs?

Sources

Spencer, Charles G. Roadside Geology of Missouri. Missoula : Mountain Press Publishing Company. 2011. pp. 2 - 25.

Wilson, Woodrow P. Geology of the South Half of the Columbia Quadrangle Boone County Missouri. Columbia : University of Missouri. 1938. pp. 5 - 26, plates I, IV.

Permission to place this EarthCache was provided by the City of Columbia Parks and Recreation Department.