A long time ago both in date and setting, Flat Rock Ranch was awash in a shallow sea. Fish and sharks casually swam over beds of shelled animals now known only by their remains. Where land poked thought the salty water, swamps of ferns and cycads flourished. It was nearly 300 million years ago, during what we today call the Pennsylvanian Period.

Today one can recreate the ancient setting of Flat Rock Ranch by examining the rocks that seas and streams left behind, exhumed most recently by West Creek. The flood plain of the creek is the lowest topography, covered by alluvium, which are the sands and gravels transported by the creek at times of flood, and which underlie the bean fields where prairie chickens feed. As the creek flows southward, it cuts deeper into the rocks.

Above the Spring Branch Limestone, which is not well exposed except across the road and south from the cabin, are marine shales. Above the shales is the Beil Limestone, which forms the first bench to the west. The low topography on top of the Beil is mostly eroded in the Tecumseh Shale, which has few thin limestones in it, and then above the shale unit is the main plateau-forming unit, about a mile west of the ranch house, the Ervine Creek Limestone. These limestones are all very fossiliferous.

Corals are common the Beil, along with brachiopods shells and the shells of an extinct foraminifera, called fusulinids. These look a lot like wheat grains.

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West of the low water crossing between section 21 and 28, the Beil is exposed at the base of the slope break, and the Ervine Creek forms the top of the ridge about three fourths of a mile west of the crossing. The youngest major rock unit in the immediate area is the Topeka Limestone, which forms the flats about a mile and a quarter west of the low water crossing. This cannot be seen west of the headquarters, as soil covers everything above the Beil.

The Indians and early pioneers found the valley along West Creek to be excellent hunting. Cattle were first brought into this valley about 1850 and remains the main industry in Greenwood county, Kansas today.

Oil has been produced from the Virgil field, northeast of the ranch headquarters, since 1917. Oil is mostly from Mississippian age limestones, the next period older than the Pennsylvanian. During its heyday in 1929, there were 193 oil wells and 10 gas wells in the field.

Lee C. Gerhard
State Geologist
January 8, 1997