Past Climate of the Navajo Reservoir District

Abstract

The hypothesis is advanced that Yellow-bellied Marmots (Marmota flaviventris) are affected in their geographic distribution by seasonality of precipitation in such a manner that their presence in Southwestern archaeological sites indicates a minimum of about two inches of winter precipitation. Application of this hypothesis to past changes in marmot distribution in the Navajo Reservoir District (northwestern New Mexico and adjacent Colorado) indicates an early period of high effective moisture produced predominantly by summer rains. At about A.D. 700-800, there occurred a change to dominant winter precipitation which lasted until ca. A.D. 1000 or later. This model agrees with previous work based on faunal analysis but is exactly counter to that proposed on the basis of alluvial and pollen studies.