Name proposed for sequence of basaltic, andesitic, dacitic, and rhyolitic rocks that form part of the central and most of northern Jemez Mountains. Name derived from Poldavera Peak, T21N, R5E, Rio Arriba Co, NM in San Juan basin, the second-highest peak in northern Jemez Mountains and one of major volcanic centers of the group. Includes (ascending): Lobato Basalt (new), andesites, dacites, rhyodacites, and quartz latites of Tschicoma Formation (Griggs, 1964), and El Rechuelos Rhyolite (new). Aggregate thickness of 5,000 ft, but because most formations are lenticular and only in part coextensive, maximum thickness in any one place doesn't exceed 3,500 ft. Is younger than Keres Group (new), which it overlaps to the south. Conformably overlies Keres Group in central Jemez Mountains; unconformably overlain locally by rocks of Tewa Group. Rocks of the group range in age from middle Pliocene to early Pleistocene. Lobato basalt dated radiometrically as 7.4 m.y., and one of the youngest domes of El Rechuelos Rhyolite has been dated as 2.0 m.y. (written communication to author, Dalrymple, 1967).

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

Age of Lobato Basalt, basal formation of Polvadera Group changed from middle Pliocene to Pliocene and late Miocene based on radiometric dates of 7.8, 7.6, 3.1, and 2.8 m.y. Report area is Canones quad, Rio Arriba Co, NM in the San Juan basin.

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