Sam Cason collecting sediment samples for snail recovery at the Genevieve Lykes Duncan site, on the 02 Ranch in Brewster County. This 2.8 meter high column in the arroyo wall runs from the modern ground surface to a level estimated at about 10,200 radiocarbon years before present. Excavations in the Paleoindian deposits are ongoing just out of view to the right, at about the same level where Sam is working. One of the completed sample bags can be seen at lower right (average weight, 15. 5 kilograms, or 34 pounds).