CONTORTED SANDSTONE EarthCache
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about 3 miles north of Licking, MO right on the highway right-of-way US Highway 63. light traffic.
This is a solution feature of Karst topography. Karst topography is a landscape shaped by the dissolution of a layer or layers of soluble bedrock usually carbonate rock (CaCO3) such as limestone or dolomite. The feature is not an uncommon phenomenon in karst areas. You will observe contortions, consisting of sharp folds and deep dips. The site access and unique exposure make this spot one of a kind and camera shots a must. Because highway 63 runs north/south between the exposure, the best time for photography is around noon or slightly before as the better exposures in general are on the west side. The coordinates are for the best photographic point.
Those unfamiliar with the area and regional geology might be tempted to blame the folding and dipping on a dramatic mountain-building force. The feature is actually the dissolving of soluble dolomites leaving a residuum of relatively insoluble chert, sandstone, and clay. In this exposure reddish-brown sandstone, cherts, and clays of the Roubidoux Formation have been distorted as they were let down through the dissolving action of percolating waters which removed the dolomite. So, the major active force in creating the observed structures in the contorted sandstone was gravity.
The geological interpretation for the folding and dipping is they are probably the result of squeezing as the material contracted, slumping with some possible lateral movement, and some draping of the insoluble material over pinnacles of dolomite remaining below. (Geologic Wonders and Curiosities of Missouri, 2ed Edition; Vineyard 1990)
The Roubidoux Formation is Ordovician in age and is part of the Canadian Series. The formation consists of sandstone, dolomite sandstone, and cherty dolomite. In the CONTOURED SANDSTONE outcrop like most of the exposures in central Missouri, it is predominantly a quartzose sandstone. The sandstone is composed of fine- to medium-grained quartz (SiO2) sand, which is sub rounded and frosted. The red color is an indication of fresh sandstone at the surface. The sandstone may exhibit cross-bedding or preserved ripple marks or mud cracks. Dolomites of the Roubidoux Formation that are not seen at the outcrop are finely crystalline, light gray to brown color. Individual beds of these dolomites contain brown to gray, banded, oolitic, sandy chert. (The Stratigraphic Succession in Missouri Vol. XL, 2ed Series; Koenig 1961)
To log this EarthCache you must perform the following task and answer the questions about the site.
1. On the web site log your find and with the log upload a picture of yourself with your GPS at the outcrop. Please include some general statements about the site that you learned by visiting this site.
For the following questions send me an email with the answers.
2. What was the actual major active force in creating this feature?
3. What does Karst topography mean?
4. Describe the physical appearance of the sandstone found in the Roubidoux Formation. Include grain size and shape as well mineral composition in your description.
5. Estimate the thickness of the formation at this site.
6. How old is the estimated age of the Roubidoux Formation?
Please send me an email that documents everything. Your email should include answers to all the questions above. Please do not include answers in your on-line log. Your log will be deleted if answers in your log.
Logs not accompanied by email within a reasonable amount of time will be deleted per EarthCache rules.
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