GC7FQE5 Oklahoma Mudballs (Earthcache) in Oklahoma, United States created by The Snowdog

GC7FQE5 ▼

A cache by The Snowdog Message this owner

Hidden : 12/5/2017

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Terrain:

Size: Size: other (other)

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Geocache Description:

A geode is a geological secondary structure that occurs in some types of sedimentary and volcanic rocks. Geodes are hollow, vaguely spherical masses of mineral matter with an inner hollow cavity that is lined with minerals such as quartz or calcite. When opened the crystal interior of the geode is revealed.

A volcanic geode containing quartz and amethyst

This area of Lake Arcadia is home to geode-like structures called Oklahoma Mudballs. These mudballs resemble geodes but have a different origin: they form when sediment suspended in the water aggregates into clot-like masses, and then form interior shrinkage cracks as they dry. After the mudballs are buried and lithified, calcite and other minerals precipitate out of the ground water that seeps through the mudball and partially fills these cracks to form a geode-like structure.

This mudball containing a geode-like structure was found at this location on May 14, 2016

Oklahoma Mudballs are common in the shale and siltstone layers in the Wellington Formation that underlies the later layers of Garber sandstone. Both the Wellington and the Garber layers date back to the Permian period, when the world was dominated by two supercontinents known as Pangaea and Siberia that were surrounded by a global ocean called Panthalassa, long before the evolution of the mighty dinosaurs that ruled the much later Cretaceous period. This area of the Arcadia Lake shoreline consists of a slab of sandstone that overlays a layer of softer siltstone. The siltstone has eroded, leaving an overhanging ledge of sandstone. There are numerous spherical cobbles under the ledge, and some of these are Oklahoma Mudballs. Oklahoma Mudballs are often found in the shale and siltstone layers of the Wellington Formation, but the mudballs in this particular area originate in the newer Garber sandstone that is exposed here along the shoreline northwest of the dam.

To log this Earth Cache:

Send an email or message to the CO in which you explain the difference in how geodes and Oklahoma Mudballs are formed.

Photos of yourself at or near the posted coordinates, or of any mudballs you might happen to find, are welcome but are not required.

Access:

While most of Arcadia Lake requires a fee for access, you can park at the designated parking coordinates at no cost and walk down by the dam to access the EarthCache.

Reference:

Some information for this Earth Cache was taken from Oklahoma Geology, Volume 60, Number 1 (Spring 2000).

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Oklahoma Mudballs EarthCache

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