Earth and Planetary Sciences ETDs

Publication Date

7-1973

Abstract

The mapped area is in Sandoval County, New Mexico, and includes the San Ysidro 7-minute quadrangle. Precambrian rocks in the area consist mainly of quartz monzonite gneiss. Quartz diorite xenoliths and leucocratic dike rocks are less abundant.

Strata totaling 1300 meters, ranging from Morrow-age strata of Pennsylvanian age through the Zia Sand Formation of Miocene age, are exposed in area (fig. 3). Overlying the marine Pennsylvanian Morrow-age strata and Madera Formation is 900 meters of continental, marginal marine, and evaporite deposits consisting, in ascending order, of the Permian Abo Yeso, Glorieta, San Andres and Bernal Formations, the Chinle Formation of Triassic age, and the Entrada, Todilto, Summerville, and Morrision Formations of Jurassic age. Cretaceous rocks are represented by the marginal-marine Dakota Formation and part of the marine Mancos Formation, totaling 200 meters. The Zia Sand Formation of Miocene age is approximately 100 m thick in the area and consists of continental deposits.

Five major elements each contribute over 300 m of structural relief: 1) the Pajarito fault, 2) the San Ysidro fault, 3) north- and northwest-trending folds, 4) the Jemez Pueblo fault zone, and 5) the Jack Rabbit Flats fault zone. The Pajarito fault is a steeply dipping reverse fault and has no strike-slip component in the area.

There were two main periods of deformation. The first occurred during Paleocene and Eocene time and resulted in the development of northwest-trending folds, northeast-trending tension fractures and possibly north-trending fractures along which later vertical uplift occurred. Earliest deformation resulted from the right-shift of the Colorado Plateau. The second period of uplift occurred in post-middle Miocene time and is related to the formation of the Rio Grande depression. This is the main period of vertical uplift in the area and resulted in the formation of north- and northeast-trending faults including the Pajarito fault. This uplift resulted from the arching of the rim of the Rio Grande depression.

Extensive gypsum deposits occur in the area and gypsum is currently being quarried on White Mesa, 1 mile south of San Ysidro. Minor copper mineralization occurs in carbonaceous channel-sandstones in the Abo Formation.

Degree Name

Earth and Planetary Sciences

Level of Degree

Masters

Department Name

Department of Earth and Planetary Sciences

First Committee Member (Chair)

Lee A. Woodward

Second Committee Member

Douglas Gridley Brookins

Third Committee Member

Albert Masakiyo Kudo

Language

English

Document Type

Thesis

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