The Osage Cuestas have shown geomorphic changes since the Pennsyvannian and Permian. Cyclotherms, or alternating stratigraphic sequences of marine and non-marine sediments, are well-perserved in the region showing the movement of the sea, but exogenic and endogenic influences have also shaped the landscape.
Endogenic factors that changed the landscape and created the cuestas include plate movement and mountain building in the west and south. This caused the general shift of the stratigraphy to slope towards the east, which is why no cueastas in the area face the west.
Exogenic factors are more readily seen, affect the landscape today. Weather and climate change flucations affect the steepness of the cuestas, which are much more shallow today than in the past. Wind and water erosion deteriorate the shale and sandstone beds more readily leaving the limestone outcrops as the main rock type.
In certain areas the limestone, shale, and sandstone repeating layers can still be seen; they are a direct represenative of the cyclotherms in the area.
Limestone and shale are the most prominent rock types found in the region. The limestones contain fossils which include horn coral and brachiopods.
The sandstones of this region are interpreted as channel deposits that were established after the formation of the Ouachita Mountains, located on the southeastern border of modern day Oklahoma/western border of Arkansas. During the Pennsylvanian period, this was the geologic high point of the time; rain would erode the rocks on the slopes of these mountains, and the sediments would be washed down the stream channels into Kansas.
IF you wish to know more about this area's weather and how it affects the region, visit The Climate and Geomorphology Page