Close-up view of Twelvemile Creek chert gravels. Cobbles range from 5-20 cm in length, but average around 10 cm (4 inches). Though the pieces are fairly small, flaking quality is good,. They are quite variable in color, indicating they probably derived ultimately (in the Pliocene) from multiple sources. The chert is very similar in size and color to that found in archaeological sites in the area. Photo by Michael R. Bever.