Investigation of a suspected meteorite impact at Upham, New Mexico
— Gerald Lindsey

A circular feature in the Jornada del Muerto Basin in southern New Mexico has been interpreted in this investigation as a probable meteor impact crater. The feature has a diameter of about 12.6 km, and is split by Sierra County Road A013 that follows the historic 1598 El Camino Real. The site is on the gentle eastern slope of the Caballo Mountains. A dense band of vegetation, over about 60 percent of the circumference, defines the shape. The best evidence for an impact site, besides satellite photographs, is a magnetometer survey “snapshot” across one well-defined edge that depicts a disturbed mega-breccia bedrock in abrupt lateral contact with a uniform deposit, possibly lacustrine crater fill. More subtle indications of a structure include an erosional scarp and possible evidence of karst sinkholes on the southwest perimeter and subsidence of a slump block on the northern perimeter. The impact may have occurred in the interval between the deposition of the marine Cretaceous Crevasse Canyon Formation and the closed basin deposits of the Paleocene/Eocene Love Ranch Formation that overlie the northern side of the feature. Three isolated volcanic outcrops dated about 29 to 35 Ma border the southern and eastern perimeters. It is estimated a few hundred meters of Tertiary deposits and Cretaceous bedrock have been removed by erosion since the uplift of the Caballo Mountains during the Rio Grande rift, effectively removing any direct surficial evidence of an impact. A discussion is presented of arguments for and against this being an impact crater.