Arbuckle M🌎untains EarthCache
Beneath what is now Oklahoma, continents once came together then broke apart; land masses moved and collided; shallow seas came and went; rocks were folded, faulted, uplifted and eroded and great changes (sometimes rapidly in geologic time and seemingly forever in human years) came about. Join me in learning more about the Arbuckle Mountains by visiting this EarthCache and reading about the great geologic history this area has to offer.
It's perfect for the highway traveler and is an easy 3 minute drive from Exit 51!
To get credit for this EarthCache, be sure to complete the logging tasks at the bottom of this page.
How did the Arbuckle Mountains form?
Southern Oklahoma has long been recognized as the home to a series of very large geologic structures (Figure 1) that were part of a rift zone that in essence tried to separate Oklahoma from Texas about 600 million years ago. The result was that large volumes of dense volcanic rock intruded the crust along the rift.
These movements formed the Anadarko Basin, with some parts of the basin obtaining depths of almost 10 miles! Compare that to today's deepest ocean feature, the Marianas Trench, which tops out at almost 7 miles deep. Over time, the basin was filled in with many 1000’s of feet of sedimentary rocks (primarily sandstone, dolomite, shale, and limestone). These rocks were deposited in the shallow seas that covered most of Oklahoma.
Click to enlarge
Later, about 300 million years ago, a major tectonic plate collision occurred in southwestern Oklahoma that turned the basin inside out. This collision caused the uplift and intense faulting and folding of rocks in southern Oklahoma and produced the Wichita, Arbuckle, and Ouachita Mountains.
The highway I-35 road cuts through the mountains make it possible to see dramatic evidence of these geologic movements as you travel that stretch of road (best seen between exit 42 and exit 51). These now visible features are so unique that geologists from around the world have stopped to get a look.
Looking at a cross-section of the Arbuckle mountains, the general pattern is older rocks in the middle, younger in the north and south. This means that the structure of the mountains here is an anticline, in which tectonic forces have pushed from two sides and the lower formations have been squeezed up between the younger formations (a convex shape). One such result is that many of the rock layers that were once laid horizontally are now standing nearly vertical!
Back in their day, these mountains were similar to the Rocky Mountains of today standing several thousand feet above the surrounding plains and seaways. Due to eons of wind and water erosion, the mountains now mostly range from 100 to 600 feet in height and the highest elevation (about 1,415 feet) is in the West Timbered Hills about 9 miles west-southwest of Davis.
Although the relief in this mountain area is low, it is still impressive because it is six times greater than any other topographic feature between Oklahoma City and Dallas, Texas.
To Get Credit For This EarthCache
Copy the questions below and send your answers via geocaching messages.
- DO NOT post the answers in your log.
- Group answers are fine, just let me know who all was there.
- Note: The photo task is a requirement for each account claiming a find. See acceptable EarthCache logging tasks effective June 10th, 2019.
- Please send the answers in a timely manner or it may result in the deletion of your log (no offense intended).
Logging Tasks
  1| The name of this EarthCache: Arbuckle M🌎untains
  2| In your log, please provide a photo of yourself with the rocky outcropping behind you.
- If you prefer, the photo can be of a personal item here instead. Just make the photo unique to you and your visit. Feel free to have fun with this!
  3| Roughly how much deeper was the Anadarko Basin compared to the Marianas Trench?
  4a| In your own words, describe the difference between an anticline and a syncline. You can use the description and image above to help.
  4b| Which of these describe the Arbuckle mountains?
At the posted coordinates, examine the wall closely and answer the following questions:
  5a| Tell me the orientation of the rock layers. Are they pointing mostly horizontal or vertical? Are they perpendicular or parallel to the road?
  5b| Is the rocky wall eroding mostly from the top or the bottom? In a short sentence, please explain your answer.
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