First published description; first noted on map legend only (Kottlowski, 1960). Report area is south-central Dona Ana Co, NM, central part of Potrillo Volcanic field, Orogrande basin. "Aden-Afton Basalts" lie in a graben bounded on east and west by faults; downthrown fault on east side can be traced north of Aden Cone as an eroded fault scarp and a series of elongate depressions--south of Aden the scarp is still visible. Fault cannot be traced directly into Aden Basalt field, although existence is inferred by presence of elongate depressions and collapse craters. Two periods of basalt extrusion--Aden Basalt--associated with this fault: A1 (oldest Aden flow) and A2 (youngest Aden flow). Afton Basalt extrusions, which are thought to be older than Aden, are associated with fault downthrown on west side. Both Aden and Afton overlie rocks of Santa Fe Group. In area of Aden crater, Aden Basalt extends [about 6 mi] east of crater; a tongue of Aden extends [about 5 mi] southeast. Aden crater is composed of the younger, A2 flow. Flows were of low viscosity, indicated by narrowness and length of lava tubes and tongues. Gives volcanic history of Aden crater. The final activity was confined to a fumarole on east side; a ground sloth recovered from the fumarole by Lull is dated as 11,000 yrs old (Simons and Alexander, 1964). Is Quaternary in age.

Source: GNU records (USGS DDS-6; Denver GNULEX).

The Aden-Afton basalt [author lumps these two flows together] crops out over approximately 50 sq mi in central Potrillo field, east flank of West Potrillo Mountains, Dona Ana Co, NM, Orogrande basin. The two Aden flows are those that crop out in Aden crater and adjacent areas north, east, and southeast of the crater; the three Afton flows are those that crop out south of Afton, east of the Aden flows. Afton flows are thought to be older than Aden because of greater degree of weathering, heavier cover of blow sand, and apparent onlap of the middle Afton flow by the Aden lavas. Oldest Afton flow, exposed in walls of Kilbourne Hole and Hunts Hole (maar volcanoes) gave K-Ar whole-rock dates of 141,000 +/-75,000 yrs and 103,000 +/-84,000 yrs (R. E. Denison, 1970, written communication). Hence, Aden flows are younger than these dates.

Source: GNU records (USGS DDS-6; Denver GNULEX).