Philip Burke King

Correlation of the outcropping Cretaceous formations of the Atlantic and Gulf Coastal Plain and trans-Pecos Texas

INTRODUCTION This is Number 9 of a series of correlation charts prepared by the Committee on Stratigraphy of the National Research Council, which will cover the post-Proterozoic sedimentary formations of North America. For general information about the project the reader is referred to the general introduction preceding this paper. The senior author, Lloyd W. Stephenson, is responsible for that part of the chart treating of the Upper Cretaceous series in the Atlantic and Gulf Coastal Plain (exceptions noted below) and the Lower Cretaceous series of the North Atlantic Coastal Plain; with respect to the Upper Cretaceous his presentation is based largely on his personal knowledge of the paleontology and stratigraphy of the area, gained from field and laboratory studies ranging from reconnaissance to detailed; all published information has been considered, and much of it utilized, but it is not practicable to include a complete bibliography. References are given to papers . . .

CORRELATION OF THE PERMIAN FORMATIONS OF NORTH AMERICA

The chart (PI. 1) indicates the present stratigraphic classification of the Permian rocks in each important area of outcrop in North America and the time relations of the deposits in the several areas as now understood. Annotations in the text suggest the evidence for many of the correlations and point out unsolved and controversial problems.

The Ouachita and Appalachian Orogenic Belts

Orogenic belts of Paleozoic age border the southeastern and southern sides of the North American continent in Canada, the United States, and Mexico. The Appalachian orogenic belt extends 3700 km along the southeastern side, from Newfoundland to Alabama, plunging under the continental shelf on the northeast and under the deposits of the Gulf Coastal Plain on the southwest. The Ouachita orogenic belt begins near the southwestern terminus of the Appalachian belt and extends 1800 km across the southern United States and probably into Mexico (Fig. 1). Unlike the widely exposed Appalachian belt, the Ouachita belt is only exposed for 450 km of this distance—in the Ouachita Mountains of Arkansas and Oklahoma, and in the Marathon region and several smaller areas in western Texas. The remainder is covered by Mesozoic and Cenozoic deposits of the Gulf Coastal Plain, but much is known about the covered part from the records of drilling.

Tectonic framework of southeastern United States

This paper reviews the relations in space and time of the mountain system formed during Paleozoic time which dominates the tectonics of the southeastern states. The most conspicuous representatives of the system are the structures of the Appalachian Highlands, but other structures occur in the Ouachita Mountains and other ranges west of the Mississippi Embayment, and still others are concealed by the post-orogenic deposits of the Atlantic and Gulf Coastal plains. From northwest to southeast, the Appalachian Highlands are divisible into the following. 1. The gently deformed Cumberland and Allegheny plateaus, which constitute a foreland area on the northwest flank of the system. 2. The Valley and Ridge province, made up of more strongly folded and faulted Paleozoic rocks but whose structures are nevertheless marginal to the zones farther southeast. 3. The Blue Ridge province, composed of older Paleozoic and pre-Cambrian rocks, which are not only strongly folded, but are also more or less metamorphosed. 4. A metamorphic and plutonic zone, forming the greater part of the Piedmont province, made up of gneisses and other thoroughly metamorphosed rocks, invaded by granite plutons. This zone is believed to lie along the central axis of the Appalachian system. 5. A belt of less metamorphosed sedimentary and volcanic rocks forming the southeast part of the Piedmont province, and lying southeast of the central axis. In addition to these exposed rocks, unmetamorphosed and little folded sedimentary and volcanic rocks occur still farther southeast, beneath the Mesozoic rocks of Florida. The Appalachian system of the southeastern states has been assumed to have been deformed mostly during the Appalachian revolution, toward the end of Permian and Paleozoic time, but there is evidence of earlier movements during the Paleozoic era, beginning with an orogeny of probable Middle Ordovician age. Late Paleozoic movements may well have been merely the concluding phases of the orogeny. The relations between the Appalachian system and the Ouachita system farther west have long been a puzzle. Further evidence on the problem has been obtained as a result of deep drilling in Mississippi and Alabama, but evidence is as yet insufficient to establish the relation. It is tentatively suggested that the Ouachita system is a westward extension of an interior belt of the Appalachian system, which has been thrust northward to a moderate extent over the westward extension of the belt of the Valley and Ridge province. End_Page 635------------------------------ Fig. 1. Tectonic sketch map of southeastern United States to show mountain systems of Paleozoic time, and their relations to other structural features. End_Page 636------------------------------ Fig. 1. Continued. See caption on page 636. End_Page 637------------------------------

Permian stratigraphy of trans-Pecos Texas

INTRODUCTION GENERAL FEATURES OF THE PERMIAN SERIES The Permian series of North America attains its greatest development in trans-Pecos Texas. Strata of this age have an important influence on the geography of the region. Permian limestones, sandstones, and shales constitute many of the mountain ranges and plateaus, and the more resistant rocks crop out in bold cliffs and ledges on numerous escarpments. The highest peak in Texas, El Capitan (8750 feet), is the summit of a cliff of Permian limestone at the crest of the Guadalupe Mountains (Fig. 13 A). In New Mexico, not far northeast of this peak, is the great Carlsbad Cavern, which is carved from limestones of the same age. Permian strata beneath the plains east of the mountains have produced vast quantities of oil, and contain large deposits of valuable potash salts. Strata of the Permian series in trans-Pecos Texas reach a thickness of about 7000 . . .

Outline of Structural Development of Trans-Pecos Texas

The mountain area of trans-Pecos Texas is divisible into a northern part, which has been more or less stable, and a southern part, which has shown considerable mobility from Paleozoic down to Cenozoic time. Strong folds and overthrusts of late Pennsylvanian age, raised from a geosyncline, are found in the Marathon and Solitario uplifts in the southern part of the province. Northwest of them, in the stable area, Permian rocks later than the deformation lie unconformably on broadly folded older Paleozoic foreland rocks, and were deposited in broad basins. In some mountain ranges of western trans-Pecos Texas, and extending southward into Mexico, are close folds and overthrusts raised from a Mesozoic geosynclinal area. East of them are broad folds, domes, and basins of marginal type. These structural features were produced during two movements, one older and the other younger than the extensive Tertiary lavas of central trans-Pecos Texas. These may be classed as the northern ends of the Sierra Madre Oriental of Mexico. After the last folding, trans-Pecos Texas was extensively broken by normal faults, some of the movements being of late Tertiary age, and some of relatively recent date. In the northern stable part of the province, features of Basin and Range type were produced. Here, thick intermontane deposits were laid down in the areas epressed by faulting. The present surface features of trans-Pecos Texas result in part directly from the various later tectonic movements, and to a greater degree from the modification of the structural features by stream erosion.

TERRAIN DIAGRAMS OF THE PHILIPPINE ISLANDS

This paper presents four terrain diagrams, on a scale of 1:1,000,000, which cover all the Philippine Islands. The diagrams were prepared during World War II by the Military Geology Unit of the U. S. Geological Survey for the Chief of Engineers, U. S. Army. Terrain features shown on the diagrams owe their individuality to the nature of the rock formations and the tectonics. Mountain areas are made up of pre-Tertiary basement rocks, and of Tertiary and Quaternary volcanics; Tertiary and Quaternary sediments from the lowland areas. The mountain areas of basement rocks are geanticlines or horsts, and the lowland areas of Tertiary sedimentary rocks are downwarps. A striking tectonic feature, which has strongly influenced the terrain, is the Philippine fault zone, a belt of dislocation which extends southeast from Luzon to Mindanao.

Stratigraphy of Outcropping Carboniferous and Permian Rocks of Trans-Pecos Texas

The later Paleozoic systems are exposed in several disconnected areas in trans-Pecos Texas, including the Marathon region, the Delaware-Guadalupe Mountains, and the Diablo Plateau. The Carboniferous of the Marathon Basin is nearly 8,000 feet in thickness and consists mostly of clastic sediments. On the northwest these give place to limestones, which are best exposed in the Hueco Mountains, where they are about 2,000 feet thick. These beds are separated from the overlying Permian in all of trans-Pecos Texas by a notable structural unconformity. In the Glass Mountains and Delaware-Guadalupe Mountains the Permian is represented by normal marine deposits whose rich and varied faunas refute the common notion of a general impoverishment of Permian life. These pass laterally int rocks of different facies, including limestones bearing poor faunas, and deposits of red beds, salt, and anhydrite.

Older Rocks of Van Horn Region, Texas

Some new facts are given, based on recent detailed surveys, regarding the pre-Cambrian, possible Cambrian, and early Ordovician rocks of the Van Horn region. A geosyncline existed here in later pre-Cambrian time, and in this a thick mass of sediments accumulated, constituting the Allamoore and Hazel formations. These were afterwards deformed, and were overridden from the south by a thrust block of an older formation, the Carrizo Mountain schist. After the deformed rocks were deeply eroded, the clastic, unfossiliferous Van Horn sandstone was laid down over them. Its age is unknown, but may be late pre-Cambrian or early Cambrian. It was tilted, faulted, and eroded before the first marine Paleozoic deposits were spread over it. These are of early Ordovician age, and correlat with the Bliss sandstone farther west. The type Bliss has hitherto been classed as Cambrian, but paleontological evidence for this is questionable. If the suggested correlation is correct, wide areas in western Texas and southern New Mexico, where the Bliss is the basal Paleozoic formation, may never have been covered by the Cambrian seas.

Tectonics of the North American Cordillera near the Fortieth Parallel

Abstract The North American Cordillera near the Fortieth Parallel consists of the following tectonic units: 1. (A) To the east is a reactivated cratonic area, in the Southern Rocky Mountains and Colorado Plateau, in which the supracrustal rocks (Cambrian to Cretaceous) were broadly deformed during the late Cretaceous-Paleocene Laramide orogeny, and the Precambrian basement was raised in folds of wide amplitude. 2. (B) West of it is a miogeosynclinal belt, in the eastern Great Basin, in which a thick sequence of Paleozoic carbonates and related deposits was thrust eastward along low-angle faults during the middle to late Cretaceous Sevier orogeny. The miogeosyncline is the downwarped western margin of the original North American continent, and its rocks accumulated on Precambrian basement. 3