 Irwin-Williams divided the Oshara Tradition into six phases, and during the Armijo phase (1800 to 800) the Arroyo Cuervo area east of Chaco Canyon saw the introduction of maize and the use of rock shelters.She hypothesized that this period saw the beginning of seasonal gatherings of people from around the San Juan Basin, who eventually began to aggregate into larger social units.By 200 BCE, the Basketmaker culture had begun to develop from the Oshara Tradition.