STRUCTURE, CLIMATE, AND BASIN LAND FORMS IN ARIZONA AND NEW MEXICO.

The Purpose of this article is to point to some of the relations between structure, climate, and basin land forms in the San Pedro Valley, Arizona and to raise the question of the adequacy of the erosional-cycle concept as a tool in interpreting its geomorphic history. The San Pedro Valley in southeastern Arizona is about 120 miles long. The lower basins of the valley are relatively narrow, the surrounding mountain ranges being higher and closer together north of a constriction known as the Narrows than to the south. Deformation in the basins of the lower San Pedro Valley is indicated by the stratigraphic record and by topography.