GEOLOGY OF BLACK DOG MESA ARCHEOLOGICAL COMPLEX, SOUTHERN NEVADA

The Black Dog Mesa Archeological Complex lies within Moapa Valley in southern Nevada. The mesa is bounded to the north by the Muddy River and to the south by California Wash. The site sits about 20 meters above the valley floor and lies within the Muddy River Formation, which consists of alternating caliche-cemented alluvium and fine-grained lake deposits. The complex includes pit houses on the mesa edge and Black Dog Cave, which was first discovered in 1936 by the Civilian Conservation Corps. Among the many artifacts recovered, several are indicative of Basketmaker II occupations while others are known to date to the Basketmaker III period. Preliminary research at Black Dog Mesa indicates that the river valleys of southern Nevada became part of the Pueblo world at a much earlier date than previously thought. The underlying mesa is very susceptible to mass wasting and erosion. The fine material is poorly indurated, allowing undercutting and mass wasting of the protective caliche cap. Caliche blocks that once formed roofs of rock shelters on the mesa rim have fallen into Moapa Valley. The cap hosts numerous fractures, some of which can be seen within caves along the mesa edge. These fractures allow throughflow that erodes material from the underlying formation. Black Dog Mesa is a delicate system, and this delicacy has been tested by activities related to a neighboring coal-burning power plant. The northern and southern portions of the Black Dog Mesa cultural site are separated by a landfill. The top of Black Dog Mesa has been bladed, severely decreasing the protective capacity of the caliche cap. In addition, a test well has been dug through the cap, providing yet another passageway for water. It is difficult to assess what has already been lost, but it is imperative that Black Dog Mesa be studied as completely as possible before mass wasting and erosion destroy large portions of this intriguing site.