The Day Creek Bed EarthCache
Hidden : 1/24/2024
Difficulty:
2 out of 5
Terrain:
3 out of 5

Size: Size: other (other)

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Geocache Description:


In this Earth Cache you will view two formations, called the Rush Springs Layer and the Day Creek Bed, and compare two types of white rock found at this site.


The Permian Period was 300 to 350 million years ago. During this time what is now Oklahoma was covered by shallow seas. The sedimentary rocks that are so frequently seen in Oklahoma were formed during this time. By the end of the Permian these seas had retreated and Oklahoma became a terrestrial environment characterized by swamps and river deltas. Oklahoma is known for the rich variety of fossils from both the animal and plant life that lived during this time.


Image: Sam Noble Museum

The Rush Springs layer is comprised of a layer of red sandstone and siltstone capped by the Day Creek Bed, a distinct layer of white dolomite that is several feet thick in places. Both of these were formed during the late Permian period. In this location you can clearly see the dolomite cap. This is a bit unusual, as in most locations the dolomite has been lost to erosion. Under the Rush Springs layer is a thin layer of gypsum.


Dolomite is an anhydrous carbonate mineral composed of calcium magnesium carbonate. The term is also used for a sedimentary carbonate rock composed mostly of the mineral dolomite, which is the case here. Dolomite is fairly soft, rating 3.5 to 4 on the Moh Hardness Scale. The specific gravity of Dolomite is about 2.5, meaning that Dolomite is about two and a half times as heavy as an equal volume of water. Dolomite is predominately white, sometimes with pink or reddish hues.

Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate that is not nearly as "hard" as Dolomite, usually registering about a 2 on the Moh Hardness Scale. Gypsum is a natural insulator and often feels warmer to the touch than other rocks. It is also slightly lighter than Dolomite, with a specific gravity of 2.3 or so. Gypsum is often found in its crystalline form. Gypsum is also predominately white, sometimes with pale hues of red, pink, or yellow.

VISIT INSTRUCTIONS

Make your way to the Dolomite cap and examine the white rock there. What are its physical characteristics? Does it feel smooth, rough, or grainy? Do you see any evidence of crystal formation?

Now look for the mounds of white rock that are at ground level. Examine this rock. What are its physical characteristics? Does it feel smooth, rough, or grainy? Do you see any evidence of crystallization?

Based on these observations and on your comparison of these rocks, do you believe that the white rock at ground level is Dolomite or is it Gypsum?

Email or message your answers to the CO to receive credit for this Earth Cache. Photos of you and your crew at the site are also welcome.

SOURCES:

Geologic Field Trips In Northwest Oklahoma by Kenneth S. Johnson (Oklahoma Geologic Survey, 1982)

Roadside Geology of Oklahoma by Neil Suneson (Mountain Press, 2020)

Additional Hints (No hints available.)



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