Geology of Hood Spring Quadrangle, Brewster County, Texas

RI0021. Geology of Hood Spring Quadrangle, Brewster County, Texas, by R. W. Graves, Jr. 51 p., 4 figs., 1 map, 7 plates, 1954.  Print.


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ABSTRACT
The Hood Spring quadrangle, in the central part of Brewster County, Texas, contains a segment of the southeast rim of the Marathon basin. It includes a part of the complexly folded and faulted Paleozoic rocks that occur in the center of the Marathon basin and also includes Cretaceous rocks exposed in the Maravillas scarp. This scarp has three stratigraphically separate cuestas that are formed by southeastward gently dipping beds. The southwestern corner of the quadrangle contains a faulted and folded segment of the Santiago Mountain range.

Rocks of Cambrian (Dagger Flat formation), Ordovician (Marathon, Alsate, Fort Peña, Woods Hollow, and Maravillas formations), Devonian (Caballos novaculite), and Pennsylvanian (Tesnus formation)ages occur in the area of Paleozoic outcrops. A conodont fauna from the upper part of the Caballos novaculite indicates a Middle to Upper Devonian age for those beds. Most of the Cretaceous rocks exposed in the quadrangle belong to the Comanche series (Glen Rose, Maxon, Walnut—ComanchePeak, Edwards, Kiamichi, Georgetown, Grayson, and Buda formations) and are similar to equivalent age strata in central Texas. Gulf series rocks (Boquillas and Terlingua formations) have a restricted occurrence in the southwestern corner of the quadrangle contains a faulted and folded segment of the Santiago Mountain range.

Tertiary intrusions include plugs, dikes, and sills of rhyolite, trachyte, and basalt which cut Cretaceous and Paleozoic rocks. These intrusives belong to the southern Trans-Pecos Texas suite of alkalic igneous rocks.


Keywords: Hood Spring Quadrangle, Brewster County, Texas, Marathon Basin, Maravillas scarp

CONTENTS
Abstract

Introduction

Location

    Purpose and scope of the work

    Field work

    Acknowledgments

Physiography

    Physical features

    Erosional agencies

    Climate and vegetation

General geology

    Distribution of rocks

    Cambrian system

         Dagger Flat sandstone

    Ordovician system

        Marathon limestone

        Alsate shale

        Fort Pena formation

        Woods Hollow shale

        Maravillas formation

    Devonian system

            Caballos novaculite

    Pennsylvanian system

          Tesnus formation

    Cretaceous system

         Glen Rose formation

         Maxon sandstone

         Walnut and Comanche Peak formations

         Edwards limestone

         Kiamichi ·marl

          Georgetown limestone

         Grayson (Del Rio) marl

         Buda limestone

         Boquillas formation

         Terlingua· formation

Alluvial deposits

    General features

    Stream alluvium

    Gravel mantle on pediments and rock floors

    Bolson deposits

Igneous rocks

    General features

    Rhyolites and trachytes

    Basalts

Contact metamorphism

Structural geology

 

Figures

1. Index map showing Hood Spring quadrangle and adjacent quadrangles covered by published geologic reports

2. Cross section of Paleozoic rocks in the northwest corner of Hood Spring quadrangle in a ridge 1.5 miles east-northeast of Buttrill ranch

3. Sketch map and cross section of Caballos novaculite on north side of State highway No. 227, one-fourth mile southeast of Three-Mile Hill (Santiago Peak quadrangle), 17 miles south of Marathon, Texas

4. Representation of the fold and thrust fault which produced the ridge parallel to Maravillas Creek in the southwest part of Hood Spring quadrangle

 

PLATES

I. Geologic map and structure sections of the Hood Spring quadrangle

II. Angular unconformity in Maravillas scarp

III. Caballos formation

IV. Cretaceous formations and Quaternary alluvium

V. Edwards limestone

VI. Igneous intrusives

VII. Geologic map and structure sections of the Maravillas Creek area

VIII. Geologic map and structure sections of the Tinaja Range area



Citation
Graves, R. W., 1954, Geology of Hood Spring Quadrangle, Brewster County, Texas: The University of Texas at Austin, Bureau of Economic Geology, Report of Investigations No. 21, 51 p.