Congrats to CDDULANEY for FTF!!!!!
HISTORY/GEOLOGY
The Paleozoic Era spans from 541 to 252 millions years ago. It is the longest of the Phanerozoic Eras, and is subdivided into several geologic periods. The Cambrian being the oldest; 541 million years to 485 million years ago, to the Permian being the youngest; 299 million to 252 million years ago. When most of the sediments that compose the rocks in Arkansas were being deposited, during the Carboniferous Period, between 359 million to 299 million years ago, north Arkansas was a shallow sea floor (continental shelf), the Arkansas River Valley was near the edge of the shelf, and the Ouachita area was the deep sea floor. Late in the Paleozoic Era, the northern part of Arkansas, (north of the Arkansas River), referred to as the Boston Mountain Plateau, a/k/a Ozarks, was forced up in an "intact mass" in the collision with the South American Continent that also formed the Ouachitas Mountains, (south of the Arkansas River).
This multimillion-year-long process of folding, faulting and erosion between the Boston Mountain Plateau, a/k/a Ozarks, and the Ouachitas Mountains created the Arkansas River Valley. This formation is mostly made up of tan to gray sandstones and gray/black shale and dominates the exposures in the Arkansas River Valley. The individual layers of sandstone, siltstone and/or shale can be less than an inch thick to several feet thick. This Earthcache is a excellent example of sedimentary rock layers in the Atoka Formation.
SEDIMENTARY ROCK
Due to it's marine history, Arkansas has a lot of sedimentary rock formations. A sedimentary rock is made up of two parts: the particles and the binder that holds them together. Sedimentary rocks are geologically classified as clastic (rocks made up of grains of sand, silt, and clay) or chemical (rocks made up of shell fragments, saline water deposits, and other materials). The clastic sedimentary rocks are made up of shales, siltstones and sandstones. The chemical sedimentary rocks are limestone and dolostone.
To log this EarthCache, you must do the following and email us your answers. You can go ahead and log your find, (i.e. you don't need to wait for permission) but if we don’t think you have honestly completed the required tasks we will delete your log (after emailing you first of course). Do not post answers or a photo of this formation in your log or your log will be deleted. There is no informational sign. You will not need any special equipment other than your GPS to arrive at the coordinates. Please don't climb on the rocks.
Questions:
1. At the coordinates, how many layers to you see?
2. What color are the layers? How are the colors/layers separated?
3. What direction do the sedimentary layers lay?
4. Do the layers run straight? Explain your answer.