Description

The Tucson 1o x 2o quadrangle exhibits a wide variety of basin landforms and late Cenozoic surficial geologic deposits. Several factors contribute to this diversity. The Tucson quadrangle spans the transition between the relatively low ranges and typically undissected basins of south-central Arizona and the higher ranges and typically dissected basins of southeastern Arizona. Dissected basins have been dominated by base-level lowering of axial streams and their tributaries, while undissected basins have had relatively stable base-levels. The higher ranges of the eastern half of the quadrangle receive more precipitation due to orographic lifting of moist air. This Is superimposed on a distinct regional climatic gradient, with increasing annual precipitation and cooler annual temperatures from west to cast across the quadrangle. Lithologies vary dramatically both within mountain ranges and between ranges; in some cases, rock type appears to profoundly affect piedmont evolution. Scale 1:250,000