In the Teran Wash geology tour (see Link to get fuller context), shortly above the point where we encounter the Mineta Lakebeds, at Mile 3.0, we encounter a very striking exposure of two thick orange lakebed strata, with multiple beds of darker color above and below: (Click on the image to enlarge it.)       In one of these beds, geologists have found the petrified tracks of large mammals, probably made along the shore of a lake formed by the extensional deformation and basin sinking which considerably predated the main episodes of Galiuro Volcanics (which are not exposed directly along our route, but which run from 27-19 MYA in our area). The image at right was also taken in August 2001. (Click on the image to enlarge it.)     At right is another image of the tracks, taken in late December 2004. The track patterns appear a bit more distinctly from this angle and in this light. (Click on the image to enlarge it.) (Note also in the enlargement how the geology students have been gradually exposing more tracks as they dig back into the side of the hill.)   This silty limestone dates from Oligocene times (ca 28 Million YA), but is now tilted at about 18 degrees. These quite large footprints (25-45 cm in diameter) may be those of the large animal herbivore Brontotherium;       Brontotherium stood about 2.5 M high at the shoulder, larger than any living rhinoceros and almost elephantine in its build. Its teeth were suited to chewing only soft vegetation. (This time preceded the proliferation of grasslands in the world, which led to the evolution of much faster herbivores.)

(Click on image below to enlarge it.)