This image is a sign showing the geologic formation in cross section, to allow visitors to better understand the reason for the unusual rock formations they see along Highway 77 in Oklahoma.
Photo by K.N. Howell
The description states:
Geological sign on summit of Arbuckle Mountains on U.S. 77.
–The mountains are situated in south-central Oklahoma. Because the formation sits atop an aquifer, and drains readily into it through the tilted limestone strata, it is home to over 1000 caves and springs.
This card likely dates from the 1950s.