We couldn’t have asked for a more beautiful day for a field trip, the temperature was perfect and the sky was crystal clear. Chris Munson was the CCGMS Field Trip Team member who was in charge of the trip. When members arrived at the Patty Construction site they were greeted by Chris and asked to sign in. At the sign in area Chris had a display which showed examples of what the rocks to collect at the Patty Construction site looked like in the rough: crazy lace agate, oolitic chert, colored cherts and drusy quartz of different colors. He also had a great display of what the rough material could look like when cut and cabbed. His display could make any specimen-only rockhound turn into a cabber, the transformation from rock to cab were truly amazing.
The geology at the Patty Quarry and Chatooga County is very interesting. We were lucky that the bed rock was exposed near the back of the quarry in a road cut. Here you could see that a thin slice of chert (likely the Fort Payne Formation of Mississippian age) was thrust up and over older rocks. The normal sequence of rocks in the area was greatly disturbed when North America collided with Africa some 300 million years ago.
Many of the narrow ridges in Chattooga County are held up by large faulted pieces of the Fort Payne Chert, a rock that is very resistant to erosion. The road cut showed where the faulting had crushed rocks forming breccias made of sharp fragments of old rock mixed with pulverized chert.
In some areas ground water flowed through the cracks made during the collision of the continents and turned some of the older limestone rocks into chert. The oolites found in the chert were originally little “bb-sized” ball bearings of calcite that were rolling around on some tropical beach that was part of the original limestone before the hot solutions transformed the limestone into an oolitic chert. Large openings in the chert had grown layers of quartz and chalcedony to form the banded and lacey agates the area is known for. Iron staining by hematite extended into some of the cavities and added color to some of the layers within the banded agate.
Chris and fellow Field Trip Team Member, Wes Manley, answered questions and advised people about which rocks were best for cabbing or taking home to the rock garden. Most of our rockhounds came away from the trip with buckets of great materials and a few new insights.
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