Quaternary Geologic Studies on the Playas of the Nevada Test and Training Range In Support of the Nellis AFB Training Mission

The US Air Force maintains responsibility to inventory, evaluate, and protect cultural resources, including archaeological sites, as they construct target facilities and other facilities associated with the training and testing missions on the Nevada Test and Training Range (NTTR) in southern Nevada. Playa surfaces provide excellent target locations, but playa margins show evidence of aboriginal use. This study was initiated (A) to determine possible locations of potential archaeological sites associated with Late Pleistocene/Early Holocene pluvial lake shorelines, seasonal lakes, and wetland environments, (B) to determine probable climatic changes from the Late Pleistocene for the modern dry lake playas, and (C) to differentiate various surficial features with a geologic origin from those with a probable human origin. Aerial photo-interpretation and surface mapping were completed for ten playas, selected sampling for isotopic analysis was conducted at three playas, and an RTK GPS survey was conducted at one playa. Criteria were established for consistently differentiating between manmade and natural features for all of the playas.

Of the ten playas mapped and sampled, three contained pluvial lakes during the Late Pleistocene (Mud Lake, Kawich Lake, and Gold Flat), four contained spring-fed wetlands (Stonewall Flat, Indian Springs playa, Three Lakes Valley playa, and Desert Lake), two contained wet grasslands (Dog Bone Lake playa, and Pahute Mesa playa) and two playas in Cactus Flat contained surface-fed wetlands and seasonal lakes. Results from this study suggest that development of pluvial lake instead of wetlands during the wetter and cooler climate cycles depended on basin latitude, basin altitude, and basin size. Basins below a critical size contained wetlands, seasonal lakes, and grassy meadows instead of perennial lakes. Favorable habitats for aboriginal use were delineated based on the paleoenvironment, and areas unfavorable for site preservation due to active geologic surface processes were defined and potentially released for military activity.