Study of the geology and ore deposits of the Breckenridge District in Colorado.

Physiography and glacial geology of the Yakutat Bay Region in Alaska.

Stratigraphy, structure, and economic geology of parts of Monterey, San Luis Obispo, and San Benito Counties.

Introduction: This work is an alphabetical list of the geographic names that are now applied and have been applied to to places and features of the Alaska Landscape.

Abstract: Aerial photographs today are widely used to obtain both qualitative and quantitative geologic information; vertical aerial photographs are used almost to the exclusion of other types. Techniques and procedures described herein relate primarily to vertical photography.

This report describes, in 7 sections, physiographic and hydraulic studies of rivers.

From abstract: This report describes the comprising the western two-thirds of the Pearce quadrangle and the eastern two-thirds of the Benson quadrangle of the Geological Survey's Topographic Atlas of the United States and includes about 1,400 square miles in the west-central part of Cochise County, Arizona.

From introduction: This report describes the mapping of the surface geology of the San Francisco and adjacent districts in Utah.

From abstract: Reconnaissance examination of widely scattered outcrops of Upper Cretaceous rocks in the heavily glaciated areas of eastern North Dakota provides the basis for the first formal subdivision of the Pierre Shale in these areas.

Abstract: The Oquirrh Group of Pennsylvanian and Permian age in the southern East Tintic Mountains, Utah, is more than 15,000 feet (4,572 m) thick and consists of an incomplete section of the West Canyon Limestone (Morrowan) 960 feet (293 m) thick, a nearly complete section of the Butterfield Peaks Formation (Atokan(?) and Des Moinesian) about 5,800 feet (1,768 m) thick, a complete section of the Bingham Mine Formation (Missourian) 3,200-3,400 feet thick (975-1,036 m), and a complete section of the newly named Furner Valley Limestone (Missourian to Wolfcampian) 5,000-6,000 feet (1,524-1,829 m) thick. The formations below the Furner Valley Limestone are generally similar to their counterparts in their type areas in the central and southern Oquirrh Mountains but are somewhat thinner and less arenaceous. The Furner Valley Limestone, more than 90 percent carbonate, is apparently unique. Strata of the same age in the Wasatch, Stansbury, Cedar, Hogup, and Promontory Mountains in Utah are all considerably arenaceous; in the southern Oquirrh Mountains in the upper plate of the Midas thrust fault they have been largely removed by erosion. The Oquirrh Group in the East Tintic Mountains is overlain by the Diamond Creek Sandstone; the latter, in turn, is overlain by the …

From abstract: Jurassic ammonites of late Bathonian to middle Callovian Age have been found in 12,000-13,000 feet (3,660-3,960 m) of strata exposed in the area near and south of Izee and Seneca in east-central Oregon. Ammonites of early Callovian Age and possibly also late Bathonian Age occur in several hundred feet of black shale exposed along Dennett Creek near Mineral, Idaho. Early Callovian ammonites also occur in similar black shale exposed on the Oregon side of Snake River Canyon about 32 miles (52 km) south of the northeast corner of Oregon.

From Purpose and Scope of Report: This report presents a detailed description of the ore deposits of the Picher field and all phases of geology having a bearing on their localization, origin, and the search for them. It is based mainly on work done by the U.S. Geological Survey, but it also incorporates pertinent data from published literature, especially from the outstanding work of George M. Fowler and associates, and some unpublished data obtained from the geologic staffs of the mining companies.

From introduction: Since 1898 the United States Geological Survey has been carrying on a systematic investigation of the mineral resources of Alaska.As the northern mining districts of southeastern Alaska had already been the subject of an investigation by Dr. Becker in 1895,a and as the Ketchikan district was being rapidly developed, it was decided to spend the greater part of the short season in the Ketchikan district and in the fall to make a more hasty reconnaissance of the northern belt, in order to obtain a general familiarity with the region and, if possible, to establish some correlations. This plan was carried out, and the results of the work are embodied in the following report.

From abstract: Platinum placers were discovered in 1926 in a small area south of Goodnews Bay, in southwestern Alaska. Beginning in 1927, the placers were worked for 7 years by small-scale mining methods; in later years dragline excavators and a dredge were utilized. These deposits are important, not only because they are of high grade but because they are the only commercial source of platinum metals in the United States. This report details the deposits in this district.

Abstract: Structural and petrologic studies in the Berry Creek quadrangle at the north end of the western metamorphic belt of the Sierra Nevada have yielded new information that helps in distinguishing between the chemically similar Paleozoic and Mesozoic rocks. The distinguishing features are structural and textural and result from different degrees of deformation. Most Paleozoic rocks are strongly deformed and thoroughly recrystallized. Phenocrysts in metavolcanic rocks are granulated and drawn out into lenses that have sutured outlines. In contrast, the phenocrysts in the Mesozoic metavolcanic rocks show well-preserved straight crystal faces, are only slightly or not at all granulated, and contain fewer mineral inclusions than do those in the Paleozoic rocks. The groundmass in the Paleozoic rocks is recrystallized to a fairly coarse grained albite-epidote-amphibole-chlorite rock, whereas in the Mesozoic rocks the groundmass is a very fine grained feltlike mesh with only spotty occurrence of well-recrystallized finegrained albite-epidote-chlorite-actinolite rock. Primary minerals, such as augite, are locally preserved in the Mesozoic rocks but are altered to a mixture of amphibole, chlorite, and epidote in the Paleozoic rocks. In the contact aureoles of the plutons, and within the Big Bend fault zone, which crosses the area parallel to the structural trends, all …

From introduction: This is a progress report on regional stratigraphic and paleontologic studies of the Upper Cretaceous Montana Group and equivalent rocks in the northern part of the western interior of the United States. It presents preliminary data on the positions of strandlines during a 14-m.y. (million year) span of the Late Cretaceous as well as our interpretations of the geologic history of this period.

From abstract: Geologic and aeromagnetic data show that a major tectonic unit underlies rocks of the Musconetcong nappe in the Great Valley of eastern Pennsylvania and New Jersey. This structure, the Lyon Station-Paulins Kill nappe, can be traced from Lyon Station, Pa., at least to Branchville, N.J., a distance of about 120 km. The nappe has a core of Precambrian crystalline rocks as shown by an aeromagnetic anomaly that has the same signature as the outcropping Precambrian rocks of the Musconetcong nappe. This core extends at least 70 km east from Lyon Station to Bangor, Pa., the eastern limit of the aeromagnetic survey. This report details the frontal structure of this system.

Abstract: Examination of previously described and some undescribed leaves of Ulmus and Zelkova from the later Oligocene, Miocene, and Pliocene of western North America indicates that at least eight species of Ulmus and two species of Zelkova are represented. Three new species are described: Ulmus chaneyi, U. knowltoni, and Zelkova browni.

From introduction: The two papers published here refer practically to the whole region included in the National Park. The one. Part I, treats primarily of the geology, the development of the great volcano, Mount Mazama, and its collapse, which gave birth to Crater Lake; the other, Part II, deals with the petrography, and gives a special description of the various rocks occurring in the park.

Abstract: Quantitative statistical sampling of plant debris entombed within deltaic sediments of a Holocene fluviolacustrine environment at Silwood Lake, Berkshire, demonstrates that patterns of deposition exist that can be used to reconstruct the relative spatial distributions of species within the source vegetation.

From abstract and introduction: Mineralogic and stratigraphic studies of the lower part of the Pierre Shale of Late Cretaceous age along the Missouri River indicate correlations different from those generally accepted. The purposes of this paper are to present evidence for the new correlations and to resolve problems of formal nomenclature that result from them.

From abstract: The Geysers-Clear Lake geothermal area lies within the central belt of the Franciscan assemblage in northern California. The structure of this terrane is characterized by northeast-dipping imbricate thrust slices that have been warped and cut by steeply dipping strike-slip and normal faults. Introduction of magma into the crust beneath the Geysers-Clear Lake area can be related to eastsoutheast extension accompanying northward propagation of the San Andreas transform system between the Clear Lake region and Cape Mendocino within the last 3 million years. The initiation of strike-slip faulting during this time terminated subduction of elements of the Farallon plate beneath North America as strike-slip motion was taken up along the Pacific-North American plate boundary. The mechanism for magma generation appears to require a heat source in the mantle that mixed mantle-derived melts with various crustal rocks. These crustal rocks may have included the Franciscan central and coastal belts, ophiolite, Great Valley sequence, and possibly middle and late Tertiary rocks subducted before initiation of strike-slip faulting.

From abstract: The seismic history of the southeastern United States is dominated by the 1886 earthquake near Charleston, S.C. An understanding of the specific source and the uniqueness of the neotectonic setting of this large earthquake is essential in order to properly assess seismic hazards in the southeastern United States. Such knowledge will also contribute to the fundamental understanding of intraplate earthquakes and will aid indirectly in deciphering the evolution of Atlantic-type continental margins. The 15 chapters in this volume report on the first stage of an ongoing multidisciplinary study of the Charleston earthquake of 1886.

From introduction: In response to an urgent demand by the public, the Geological Survey, in 1900, undertook a topographic and geologic reconnaissance of the southern half of the Seward Peninsula.( The area mapped embraced the more important gold fields of the peninsula. The topographic map made in 1900 included the drainage of Bering Sea from Cape Darby to Port Clarence, the southern drainage of Grantley Harbor and Imuruk Basin, and the northern drainage of Norton Sound. A geologic reconnaissance was also made of the York mining district and of part of the Kuzitrin drainage.