Tight recumbent folds in a fresh exposure of Bigfork Chert, Ouachita Mountains Arkansas. Thin chert beds divided by siliceous shale beds are the basic lithology of this Ordovician age (540 to 490 Ma) formation. Complicated structures like those pictured below are characteristic of the rocks that form the Ouachita Mountains. The complex folds and faults resulted from plate tectonic forces that compressed the rock and caused many of the structures to rotate and overturn.
For more views of this and similar folds click here
This week was a hot one, so we did some creek work, but also did some road work. Went up a section of lower Lost Creek on Monday. Narrowed down the Cane Hill/Imo to a fairly small area.
Saw more nice trace fossils in the Imo.
Got a few points on the Middle Fork where it leaves the Shirley quad and enters Greers Ferry Lake.
Also, took points on a 4 different shale pits or quarries.
The persimmons aren’t quite ripe yet!
Found these deformation bands right by Highway 16 near Fairfield Bay. These bands are associated with structural features like faults and folds. They form in more coarsely grained sandstone when the stress crushes the individual sand grains along a plane, then recrystallizes to form a slightly more resistant lithology, that when weatherd, stand in slight relief. We will keep looking in this area for more clues and hopefully figure out what the rocks are trying to tell us!