Fold
A geological fold occurs when one or a stack of originally flat and planar surfaces, such as sedimentary strata, are bent or curved as a result of permanent deformation. Synsedimentary folds are those due to slumping of sedimentary material before it is lithified. Folds in rocks vary in size from microscopic crinkles to mountain-sized folds. They occur singly as isolated folds and in extensive fold trains of different sizes, on a variety of scales.
There's a natural formation known as an anticline. An anticline exists at the falls. It's a part of a larger anticline known as the Cincinnati Arch. It's a vast area that extends over the three-way intersection of Ohio, Kentucky and Indiana, and extending well into central Kentucky. The oval's Eastern side runs along Cincinnati, hence the name.
Strata in the northwestern part of the Falls of the Ohio (downstream from the mouth of Cane Run Creek) dip to the northwest, however, while strata in the east-ern part of the Falls (adjacent to the Pennsylvania Railroad Bridge) dip to the southeast. There are several folds along the way. For this reason, Kepferle (1974) mapped an anticline in the Ohio River at the Falls (see map). Because of this structure, the Louisville Limestone (the lowest strata exposed at the Falls at low water) can be seen only in the central area of the fossil beds at the Falls of the Ohio.
According to the book Elements of Geology by William Harmon Norton, the anticline is of great interest to those studying the fossil record. The anticline is almost entirely composed of Ordovician strata, and the Silurian and Devonian decrease as they approach it. Norton takes this to mean that the anticline is "an island upwarped from the sea at the close of the Ordovician or shortly thereafter."
Supposedly it's this anticline that makes much of Kentucky so rich in fossils from the ancient ocean, including the Falls of the Ohio along Louisville's riverside - and yet the Falls of the Ohio is said to be of Devonian origin, not Ordovician. I leave the matter for professional geologists to sort out.
According to the Kentucky Encyclopedia, the anticline is also indirectly responsible for Kentucky being the thoroughbred horse capitol of the world. Early settlers noticed the geological qualities of the anticline contributed to making Kentucky a land with densely fertile soil, rich in calcium and phosphorus, and this in turn led to it being prized by horse ranchers:
"This legacy of phosphatic limestone, inherited from millions of shells and skeletons, deposited millions of years earlier when central Kentucky was an ocean bed, was now to be used to build the skeletons of horses... the phosphatic limestone which forms the basis of central Kentucky's soil has proved its efficacy."
The posted coordinates will bring you to the Wave Rock shelf, a layer of limestone situated some 15 feet below the Wave Rock Dike. This layer will be under water at 16 feet on the lower McAlpine gage but will be available on a paddle hike. Call 502 775-5056 and listen to the one-minute recording on river conditions.
To earn credit for this earthcache and to demonstrate the educational value of your visit, please send answers to the below questions:
1. Which of the images in the six-block above represents the subject?
2. How wide x tall is this fold?
3. In your observation, which direction does the axis of the fold trend?
4. Could you discern the anticline as described above?
5. Did you see an Ordovician presence at this location? In what form?
Do not post answers in your log. And no pics here, please. As always, logs not followed by answers within 48 hours will be deleted.
DO NOT POST IMAGES OF THIS LOCATION PLEASE