Hondo Group
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The Hondo Group is a group of geologic formations that crops out in most of the Precambrian-cored uplifts of northern New Mexico. Detrital zircon geochronology gives a maximum age for the lower Hondo
Hondo Group (Ortega Formation) in the Tusas Mountains, New Mexico
Pilar Formation
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The Pilar Formation is a geologic formation that crops out in the Picuris Mountains of northern New Mexico. It has a radiometric age of 1488 ± 6 million years, corresponding to the Calymmian period.
Hondo Group
…where the Hondo Group fills an overturned syncline. Detrital zircon geochronology establishes an age for the lower Hondo Group of 1765 to 1704 Mya. The Pilar and Piedra Lumbre Formations were originally included in the Hondo Group. However, a metamorphosed tuff bed in the Pilar Formation yields an age of…
Pilar Formation carbonaceous phyllite beds near Pilar, New Mexico.
Pilar Formation exposures on Arroyo del Plomo
Outcrop of Pilar Formation showing metatuff beds (white layers)
Sample of carbonaceous phyllite from the Pilar Formation