Algunos aspectos de la distribución de trincheras en la Sierra Madre Occidental de Mexico

The ancient cultural relationship between the SW United States and Mexico has never been fully established. The abundant data of Southern Mexico and the Southwestern States over the border has attracted closer attention from archeologists than the interlying areas. This article discusses some of the discoveries made by an expedition to the Sierra Madre Occidental in the summer of 1965 for the purpose of studying the extent of ancient cultural remains, particularly the distribution of a phenomenon known as "trincheras" (trenches), and estimating its connection with other cultural features in a medium where the Sierra Madre displays an extremely complicated physiographic pattern which, as an integral part of a geological and geomorphic system, crosses the frontier between Mexico and the United States in a general direction SE-NW. Structurally, the Sierra Madre Occidental forms a part of the province of the North American intramontane plateau, which extends from the center of Alaska down to the volcanic axis of South Central Mexico, where the streams have cut deep, steepsided ravines, e. g. the Barranca del Cobre. On this volcanic plateau, profoundly and ruggedly dissected, the trench-builders lived and worked; the area is one of the least accessible on the American continent, and this is why it has been largely ignored by archeologists and anthropologists. In every-day speech, the word "trinchera" means a deep cutting, ditch or pit. In Chihuahua and Sonora, however, it has taken on a more particular sense, and is used to describle forms that are structurally alike, but were no doubt intended for different purposes: (1) in the West Central part of Sonora, trenches are found on the summits of isolated mountains, resemble rough stone terraces, and are called "cerros de trincheras" (trench hilltops) by Sauer and Brand; they were probably built as means of defence or residential sites; (2) to the east, in the high valleys of the Sierra Madre Occidental, the trenches are different from those of the Sonora Desert and more like stone walls or dykes; they occur typically in canyons and gulches, arranged in tiers. It is the second type that is examined in this article. Basing his classification on the shape and size of the trench wall, its location on the earth mantle, physiographic situation and relation to the mantle, Herold has identified four main types of trench in the mountains. The most important is the socalled restriction dyke, while the other three — lineal