Earth and Planetary Sciences ETDs

Publication Date

1965

Abstract

The San Mateo Mountains of south-central New Mexico consist of an uplifted block of Tertiary volcanics 20 miles wide by 4 miles ling. The San Mateo uplift is one of the bounding uplifts along the western side of the Rio Grande depression.

The basement rock as exposed just east of the San Mateos is a Precambrian granite; it is overlain in order by the Cambrian Bliss formation, the Ordovician Sierrite Limestone, Cable canyon sandstone, and Upham Dolomite, the Pennsylvanian Magdalena Group, and the Permian Abo Formation. These sedimentary rocks are unconformably overlain by Tertiary volcanic rocks of the Lower volcanic Group, the Indian Creek Tuff-Vitrophyre, the Vicks Peak Phyolite, the Springtime Canyon Rhyolite, and the San Mateo Peak Rhyolite. The volcanic rocks comprise the main mass of the San Mateo Mountains and may have a total thickness of 8,000 feet.

The preciously unknown lower Paleozoic section exposed in the San Mateos had provided new information regarding Cambro-Ordovician sedimentation and tectonic activity. First, Cambrian and Ordovician sedimentation is now known to extend farther to the northwest than previously believed. Second, Middle Ordovician tectonism along the Texas-New Mexico arch is shown in the way the Cable Canyon Sandstone truncates progressively older sediments northward. Third, enough control is now available to show that the Cambro-ordovician wedge-edges make a drastic southward nosing in the vicinity of the Fra Cristobal Mountains. This southward nosing supports evidence of a north-south arch along the Caballo-Fra Cristobal axis that was active in late Mississippian to early pennsylvanian time.

The distinct sequences of Tertiary volcanism are exposed on the eastern side of the San mateos. The first sequence, of uncertain age, is composed of andesite tuffs and flows with intrusions of monzonite and felsite breccia. Following considerable erosion a second eruption, probably Miocene, resulted in thick masses of rhyolite which form most ridges and peaks of the San Mateos.

Near the end of late Miocene volcanism, Basin and Range type block-faulting began uplifting the area in conjunction with development of the Rio Grande depression. Early block-faulting was especially disruptive, with displacements of thousands of feet in some instances. Deformation decreased in late Pliocene, and smaller blocks were downfaulted along high-angle normal faults only a few hundred feet in most instances.

Degree Name

Earth and Planetary Sciences

Level of Degree

Masters

Department Name

Department of Earth and Planetary Sciences

First Committee Member (Chair)

Vincent Cooper Kelley

Second Committee Member

J. Paul Fitzsimmons

Third Committee Member

Stuart Alvord Northrop

Fourth Committee Member

Abraham Rosenzweig

Language

English

Document Type

Thesis

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