Zia Formation


The Zia Formation is a geologic formation in the southwestern Jemez Mountains and northwestern Santo Domingo Basin. It contains vertebrate fossils that date it to early to middle Miocene in age.

Description

Lithologically, the Zia Formation is a very soft quartz sandstone. The type section rests on about 10m of laminated greenish clay beds that in turn rest on the Galisteo Formation. The upper contact is with the Arroyo Ojito Formation, with the Cochiti Formation, or with Miocene volcanic rocks of the Jemez volcanic field.
The formation is divided into the Piedra Parada Member, the Chamisa Mesa Member. the Canada Pilares Member., and the Cerro Conejo Member. The basalt of Chamisa Mesa, with a radiometric age of 10.4 Ma, is interbedded with the Cerro Conejo Member.
The formation is interpreted as eolian deposits derived from volcaniclastics of the Jemez volcanic field. These were first transported south by the Jemez River, then transported by wind from the west.

Fossils

The Cerro Conejo Member includes the Rincon quarry and Zia prospect, which yield fossils of Barstovian age, about 11 to 14 Ma.

History of investigation

The formation was first described by Regan in 1903, who named it the Zia Marl. T. Galusha renamed it the Zia Sand Formation and divided it into the lower Piedra Parada Member and the upper Chamisa Mesa Member. He also recognized a subtle disconformity about 120 m above its base.

Footnotes