Cudahy Camp formation of Loomis and Burbank [1988]
Cudahy Camp formation of Loomis and Burbank [1988]
early Miocene
Predominantly mafic to intermediate lava flows, pyroclastic deposits, and volcanic breccias interbedded with (though mostly overlying) coarse conglomerates and sandstones occurring in the El Paso Mountains (in southeastern map area) and northwest-adjacent basin (Loomis and Burbank, 1988). Volcanic deposits include basaltic to andesitic lava flows, flow breccias, tuff breccias, and pyroclastic flow and fall deposits (some waterlain; Cox and Diggles, 1986; Loomis and Burbank, 1988). Basal sedimentary unit consists of polylithologic boulder to cobble conglomerate and arkosic sandstone (Loomis and Burbank, 1988). The stratigraphically highest and capping unit is the Black Mountain Basalt, a succession of at least 15 subalkaline olivine-augite basalt flows dated by K-Ar at 15.1 ± 0.5 Ma, 17.1 ± 0.5 Ma, and 17.9 ± 1.6 Ma (Cox, 1982; Cox and Diggles, 1986; Loomis and Burbank, 1988). Intruded by a series of predominantly east-west-trending dikes that are petrographically similar to and may be the source of the Black Mountain Basalt (Loomis and Burbank, 1988). Defined as the lower unit of the Ricardo Group by Loomis and Burbank (1988); unconformably overlain by the upper Dove Spring Formation unit of the group (map unit dos). Cox and Diggles (1986) obtained K-Ar ages of 18.1 ± 1.2 and 17.2 ± 0.8 Ma on andesite flows and breccia underlying the Black Mountain Basalt.