The Oligocene Haynes Creek Flora of Eastern Idaho (UC Publications in Geological Sciences)

This flora of 70 species is dominated by deciduous trees, many with descendants in China. Precipitation was 890 mm, mean annual temperature 12.5°C, the annual range 10°C, and freezing rare. Elevation was about 1000 meters. Comparison with the Horse Prairie flora, 30 miles east and across the present continental divide, indicates that the divide was then low and discontinuous, with warmer climate to the east.