Preliminary Pollen Studies at Lake Zeribar, Zagros Mountains, Southwestern Iran.

A late Pleistocene Artemisia steppe, implying a cool, dry climate, changed about 13,000 years ago to an oak-pistachio savanna, as the climate became warmer. About 5500 years ago the savanna thickened to an oak forest, presumably reflecting an increase in precipitation or decrease in temperature to modern levels.