Earth and Planetary Sciences ETDs

Publication Date

5-1971

Abstract

The sedimentary history of the Gallup Sandstone is studied through the field investigation and laboratory analysis of samples taken from four measured sections in the vicinity of the San Juan River and one section near the Red Rock Highway. In addition to field data, textural parameters and dolomite and glauconite content of sandstone samples are the basis for interpretations of the sedimentary history and environment of deposition of the Gallup Sandstone.

A plot of the mean grain-size and sorting along with stratigraphic sections reveals that most of the Gallup Sandstone was deposited in a regressive sea, and that the regression occurred in a step-like manner. Deposition of the regressive sandstone was ended because of diminishing supply of the quartzose debris to the basin. Regression was followed by erosional activity which occurred mostly at the northern part of the basin. The sediment on top of this unconformity was deposited in a transgressive sea, and consisted of medium-to coarse-grained glauconitic sandstone of Niobrara age.

In the vicinity of the New Mexico State Highway 504, the transgressive unit is found directly on top of the regressive unit. Possibly this transgressive unit is also found south of the study area. In the vicinity of the San Juan River, this unit forms a thin sandstone blanket, sand bar, or channel-fill sandstone. There is no similarity in petrographic characteristics to the reservoir rocks in Bisti oil field.

In the vicinity of the Red Rock Highway the Gallup Sandstone was deposited under littoral conditions, whereas in the vicinity of the San Juan River it was deposited in a sublittoral to near-bathyal environment.

Because of the difference in lithology and age, the sandstone on top of the unconformity should be excluded from the Gallup Sandstone and be given a new name. The Gallup Sandstone which locally includes the transgressive unit probably terminates about three miles south of the San Juan River.

Degree Name

Earth and Planetary Sciences

Level of Degree

Masters

Department Name

Department of Earth and Planetary Sciences

First Committee Member (Chair)

Sherman Alexander Wengerd

Second Committee Member

Roger Yates Anderson

Third Committee Member

P. M. Terlecky

Language

English

Document Type

Thesis

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