Geology and petrology of Tetilla Peak, Santa Fe County, New Mexico
— Charles J. Zimmerman and A. M. Kudo

TetiIla Peak is the southernmost andesite volcano in the Cerros del Rio volcanic field (fig. 1). The field predominantly consists of alkali olivine basalt flows and cinder cones erupted approximately 2.6 m.y. ago to form the Caja del Rio plateau, upon which andesite lavas were extruded (Aubele, 1978, this guidebook). The plateau is located on the La Bajada-Jemez constriction separating the Espanola and Santo Domingo basins of the central-northern Rio Grande rift (Kelley, 1952). This structural setting of the Cerros del Rio, within a shear zone transversely oriented to the north trend of the rift, may be an important factor in magma genesis and the chemistry of lavas found on the plateau (Baldridge, 1978). This paper describes the geology, petrography and geochemistry of the TetiIla Peak andesites and discusses their origin in light of a general model for andesite magmatism in this portion of the Rio Grande rift (Zimmerman and Kudo, 1979).