Above: This is a photo of the sun setting on Lake Ouachita. Lake Ouachita is the largest manmade lake in the state at 47,000 acres. Photo from Arkansas State Parks website.

The structures of the Ouachita Mountains were created during an episode of continent-continent collision. In the Pre-Cambrian North and South America were seprated by an ocean, which was later closed due to a collision during the Mississippian-Late Devonian. The lithosphere from the North American plate subducted under the South American plate creating an accretionary prism. Accretionary prisms are wedges of sediment formed by the subducting slab, which contain thrust faults.These processes of intense subduction and high water levels created a great place to study deep water sedimentary units and intensely folded beds.

Above: Dr. Juan Lorezno gives a brief introduction to the students of the regional geology of the area.

At this stop the students observed the sedimentary units, which consisted of thin, interbedded shales, with some coarser sands. At this stop you are located on a limb of a fold, and the students used strike and dip measurements and younging indicators to figure out which way is "up."

Above: This is a photo of a load cast structure seen at stop 1, which is to the left of the hammer. This feature can be used as a younging indicator because it forms by competency differences between the layers above and beneath, and gravity causes the heavier layer to sink.

At this stop the students observed a large fold structure that exhibited both first and second generation folding. The hinge was immersed in water somewhere under the tree in the picture below. 

Above: The black lines are traces along some of the prominent bedding seen in this fold. The assymetry of this fold indicates a high temperature environment creating intense deformation.