This earth cache does not require you to climb this formation. You can safely pull over to the side of the road and make the observations required to get credit. Although this is a quiet road, always be observant of your surroundings as there can always be a car coming down the road. Please pull over far enough where you are not in the way of traffic. There is plenty of room.
Burkesville Concretion
What is a concretion?
“Concretions” take on a variety of forms and appearances. The precise details of the processes which create them are as varied as the resulting forms and appearances. However we may generalize the process. Very generally the process involves dissolving minerals from one place, transporting them in solution, and then depositing them in another. The transport is typically water. The process may involve change in the pressure, temperature, or chemistry of the water which either enhance or reduce the water’s ability to hold minerals in solution at different stages of the process. In places where minerals are deposited they tend to fill voids and weld particles together more firmly. This makes the resulting concretion denser and more resistant to erosion than the surrounding rock. Many concretions grow from a central “nucleus” which may be a seashell or other fossil. Rocks from which minerals have been leached are more vulnerable to erosion. Evidence of this is visible here in the form of depressions in the sandstone faces near the Earthcache coordinates. Some of the depressions still retain the central rock which is the actual concretion. In other examples wave action during storms may have washed the concretion away – leaving only the depression where softer rock has eroded away.
The Fort Payne Formation of southern Kentucky & Tennessee is a shale and limestone succession of Early Mississippian age. Fossils are common to abundant in many intervals. The unit is dominated by crinoids, which are stalked, sessile, benthic, filter-feeding echinoderms. Among the shale dominated portion found here, some non-shale horizons are present as are some ellipsoidal to lenticular concretions of various sizes.
What are crinoids?
Crinoids are marine animals that make up the class Crinoidea, one of the classes of the phylum Echinodermata, which also includes the starfish, brittle stars, sea urchins and sea cucumbers.[3] Those crinoids which, in their adult form, are attached to the sea bottom by a stalk are commonly called sea lilies, while the unstalked forms are called feather stars or comatulids, being members of the largest crinoid order, Comatulida.
Well-preserved specimens are found in the limestone cliffs along the Mississippi River between Burlington and Alton. The oldest crinoids come from Ordovician rocks. Some crinoids live today, mainly in deep parts of the ocean, but they are not nearly as common as in the past.
QUESTIONS/TASKS:
1. Examine the concretions along this formation. What is the average size of the concretions at eye level? How wide do you estimate each horizontal layer to be?
2. Is this formation smooth to the touch or rough and grainy? Pick up a piece from where you are standing. Is it delicate and easily broken or is it a very tough rock?
3. To prove that you were here, please post a picture of yourself or your GPS with the the formation in the background. Any other photos of the area are also greatly appreciated.