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Modern and ancient submarine fans: Reply
No abstract available.
Sandstone-body and shale-body dimensions in a braided fluvial system: Salt wash sandstone member (Morrison formation), Garfield County, Utah
Excellent three-dimensional exposures of the Upper Jurassic Salt Wash Sandstone Member of the Morrison Formation in the Henry Mountains area of southern Utah allow measurement of the thickness and width of fluvial sandstone and shale bodies from extensive photomosaics. The Salt Wash Sandstone Member is composed of fluvial channel fill, abandoned channel fill, and overbank/flood-plain strata that were deposited on a broad alluvial plain of low-sinuosity, sandy, braided streams flowing northeast. A hierarchy of sandstone and shale bodies in the Salt Wash Sandstone Member includes, in ascending order, trough cross-bedding, fining-upward units/mudstone intraclast conglomerates, singlestory sandstone bodies/basal conglomerate, abandoned channel fill, multistory sandstone bodies, and overbank/flood-plain heterolithic strata. Trough cross-beds have an average width:thickness ratio (W:T) of 8.5:1 in the lower interval of the Salt Wash Sandstone Member and 10.4:1 in the upper interval. Fining-upward units are 0.5-3.0 m thick and 3-11 m wide. Single-story sandstone bodies in the upper interval are wider and thicker than their counterparts in the lower interval, based on average W:T, linear regression analysis, and cumulative relative frequency graphs. Multistory sandstone bodies are composed of two to eight stories, range up to 30 m thick and over 1500 m wide (W:T > 50:1), and are also larger in the upper interval. Heterolithic units between sandstone bodies include abandoned channel fill (W:T = 33:1) and overbank/flood-plain deposits (W:T = 70:1). Understanding W:T ratios from the component parts of an ancient, sandy, braided stream deposit can be applied in several ways to similar strata in other basins; for example, to (1) determine the width of a unit when only the thickness is known, (2) create correlation guidelines and maximum correlation lengths, (3) aid in interpreting the controls on fluvial architecture, and (4) place additional constraints on input variables to stratigraphie and fluid-flow modeling. The usefulness of these types of data demonstrates the need to develop more data sets from other depositional environments.
Geohistory and thermal maturation in the Cherokee Basin (Mid-Continent, U.S.A.): results from modeling
The Cherokee basin in southeastern Kansas contains a stratigraphic section consisting mostly of Permian-Pennsylvanian alternating clastics and thin carbonates overlying carbonates of Mississippian and Cambrian-Ordovician age on a Precambrian crytalline basement. Based on a conceptual model of events of deposition, nondeposition, and erosion, a burial history model for (1) noncompaction, and a series of models for (2) compaction are computed for a borehole location in the south-central part of the basin. The models are copled with the calculation of nonsteady-state geothermal conditions. Maximum temperatures during basin evolution of about 70??C at the base of the organic-rich Pennsylvanian are predicted by our models, assuming pure heat conduction and a heat flow from the basement of 60 m W/m2. The maturation of organic matter as indicated by three different vitrinite reflectance (Ro) models is on the order og 0.3-0.5% Ro for Pennsylvanian rocks and 0.6% Ro for the Devonian-Mississippian Cattanooga Shale. Vitrinite reflectance was measured on subsurface smaples from three wells. The measured values correlate in the upper part of the sequence with modeled data, but diverge slightly in the Lower Pennsylvanian and Cattanooga Shale. The differences in maturation may be a result of differing local geological conditions within the basin. The relatively high Ro-depth gradients observed in one borehole may be explained by conditions in the Teeter oil field, which is a typical plains-type anticline that has been affected by fluid flow through vertical faults. Higher Ro values correlate positively with the grade of sulfidfe mineralization in the sediment, which may be a hint of fluid impact. The high Ro values relative to the shallow depth of the Mississippian and the Chattanooga Shale in the Brown well are on the order of Ro values modeled for the same stratigraphic units at present-day greater depths and may reflect uplift of the Ozark dome, located further east, affecting the eastern side of the Cherokee Basin.Based on a concept model of deposition, nondeposition and erosion, a burial history model for noncompaction, and a series of models for compaction are developed for a borehole location in a south-central part of the Cherokee basin in southeastern Kansas. Coupled with the calculation of nonsteady state-state geothermal conditions, the models predict maximum temperatures during evolution of about 70 ??C at the base of the organic-rich Pennsylvanian. A difference in organic matter maturation in the Pennsylvanian and the Chattanooga shale exhibited by vitrinite reflectance models indicate probably differing local geological conditions within the basin.
Pennsylvanian carbonate buildups, Paradox basin: Increasing reserves in heterogeneous, shallow-shelf reservoirs
Productive carbonate buildups of Pennsylvanian age in the southern Paradox basin, Utah, contain up to 200 million bbl remaining oil potentially recoverable by enhanced recovery methods. These buildups comprise over 100 satellite fields to the giant Greater Aneth field, where secondary recovery operations thus far have been concentrated. Several types of satellite buildups exist and produce oil from the Desert Creek zone of the Paradox Formation. Many of the relevant fields have undergone early abandonment; wells in Desert Creek carbonate mounds commonly produce at very high initial rates (>1000 bbl/day) and then suffer precipitous declines. An important new study focused on the detailed characterization of five separate reservoirs has resulted in significant information relevant to their future redevelopment. Completed assessment of Anasazi field suggests that phylloid algal mounds, the major productive buildup type in this area, consist of ten separate lithotypes and can be described in terms of a two-level reservoir system with an underlying high-permeability mound-core interval overlain by a lower permeability but volumetrically larger supramound (mound capping) interval. Reservoir simulations and related performance predictions indicate that CO 2 flooding of these reservoirs should have considerable success in recovering remaining oil reserves.
Origin of minerals in joint and cleat systems of the Pottsville Formation, Black Warrior basin, Alabama: Implications for coalbed methane generation and production
Coalbed methane is produced from naturally fractured strata in the lower Pennsylvanian Pottsville Formation in the eastern part of the Black Warrior basin , Alabama . Major fracture systems include orthogonal fractures, which consist of systematic joints in siliciclastic strata and face cleats in coal that strike northeast throughout the basin . Calcite and minor amounts of pyrite commonly fill joints in sandstone and shale and, less commonly, cleats in coal. Joint -fill calcite postdates most pyrite and is a weakly ferroan, coarse-crystalline variety that formed during a period of uplift and erosion late in the burial history. Pyrite forms fine to coarse euhedral crystals that line joint walls or are complexly intergrown with calcite. Stable-isotope data reveal large variations in the carbon isotope composition of joint - and cleat -fill calcite (-10.3 to +24.3 per mil Peedee belemnite [PDB]) but only a relatively narrow range in the oxygen-isotope composition of this calcite (-16.2 to -4.1 per mil PDB). Negative carbon values can be attributed to (super 13) C-depleted CO (sub 2) derived from the oxidation of organic matter, and moderately to highly positive carbon values can be attributed to bacterial methanogenesis. Assuming crystallization temperatures of 20-50 degrees C, most joint- and cleat-fill calcite precipitated from fluids with delta (super 18) O ratios ranging from about -11 to +2 per mil standard mean ocean water (SMOW). Uplift and unroofing since the Mesozoic led to meteoric recharge of Pottsville strata and development of freshwater plumes that were fed by meteoric recharge along the structurally upturned, southeastern margin of the basin. Influxes of fresh water into the basin via faults and coalbeds facilitated late-stage bacterial methanogenesis, which accounts for the high gas content in coal and the carbonate cementation of joints and cleats. Diagenetic and epigenetic minerals can affect the transmissivity and storage capacity of joints and cleats, and they appear to contribute significantly to interwell heterogeneity in the Pottsville Formation. In highly productive coalbed methane fields, joint- and cleat-fill calcite have strongly positive delta (super 13) C values, whereas calcite fill has lower delta (super 13) C values in fields that are shut in or abandoned. Petrographic analysis and stable-isotope geochemistry of joint- and cleat-fill cements provide insight into coalbed methane reservoir quality and the nature and extent of reservoir compartmentalization, which are important factors governing methane production.
Nature, origin, and production characteristics of the Lower Silurian regional oil and gas accumulation, central Appalachian basin, United States
Low-permeability sandstones of the Lower Silurian regional oil and gas accumulation cover about 45,000 mi2 (117,000 km 2 ) of the Appalachian basin and may contain as much as 30 tcf of recoverable gas resources. Major reservoirs consist of the "Clinton" sandstone and Medina Group sandstones. The stratigraphically equivalent Tuscarora Sandstone increases the area of the Lower Silurian regional accumulation (LSRA) by another 30,000 mi2 (78,000 km 2 ). Approximately 8.7 tcf of gas and 400 million bbl of oil have been produced from the Clinton/Medina reservoirs since 1880. The eastern predominantly gas-bearing part of the LSRA is a basin-center gas accumulation, whereas the western part is a conventional oil and gas accumulation with hybrid features of a basin-center accumulation. The basin-center accumulations have pervasive gas saturation, water near irreducible saturation, and generally low fluid pressures. In contrast, the hybrid-conventional accumulations have less-pervasive oil and gas saturation, higher mobile-water saturation, and both normal and abnormally low fluid pressures. High mobile-water saturation in the hybrid-conventional reservoirs form the updip trap for the basin-center gas creating a broad transition zone, tens of miles wide, that has characteristics of both end-member accumulation types. Although the Tuscarora Sandstone part of the basin-center gas accumulation is pervasively saturated with gas, most of its constituent sandstone beds have low porosity and permeability. Commercial gas fields in the Tuscarora Sandstone are trapped in naturally fractured, faulted anticlines. The origin of the LSRA includes (1) generation of oil and gas from Ordovician black shales, (2) vertical migration through an overlying 1000-ft (305-m)-thick Ordovician shale; (3) abnormally high fluid pressure created by oil-to-gas transformation; (4) updip displacement of mobile pore water by overpressured gas; (5) entrapment of pervasive gas in the basin center; (6) postorogenic uplift and erosion, causing gas leakage and a marked reduction in fluid pressure. Most future natural-gas production in the Clinton/Medina sandstones is anticipated to come from the basin-center accumulation. The Tuscarora Sandstone has additional gas resources but typically low reservoir porosity and permeability, and the likelihood of low-energy (in British thermal units) gas reduce the incentive to explore for it.
Sequence stratigraphy of the Kingak Shale (Jurassic-Lower Cretaceous), National Petroleum Reserve in Alaska
Beaufortian strata (Jurassic-Lower Cretaceous) in the National Petroleum Reserve in Alaska (NPRA) are a focus of exploration since the 1994 discovery of the nearby Alpine oil field (>400 MMBO). These strata include the Kingak Shale, a succession of depositional sequences influenced by rift opening of the Arctic Ocean Basin. Interpretation of sequence stratigraphy and depositional facies from a regional two-dimensional seismic grid and well data allows the definition of four sequence sets that each displays unique stratal geometries and thickness trends across NPRA. A Lower to Middle Jurassic sequence set includes numerous transgressive-regressive sequences that collectively built a clastic shelf in north-central NPRA. Along the south-facing, lobate shelf margin, condensed shales in transgressive systems tracts downlap and coalesce into a basinal condensed section that is likely an important hydrocarbon source rock. An Oxfordian-Kimmeridgian sequence set, deposited during pulses of uplift on the Barrow arch, includes multiple transgressive-regressive sequences that locally contain well-winnowed, shoreface sandstones at the base of transgressive systems tracts. These shoreface sandstones and overlying shales, deposited during maximum flooding, form stratigraphic traps that are the main objective of exploration in the Alpine play in NPRA. A Valanginian sequence set includes at least two transgressive-regressive sequences that display relatively distal characteristics, suggesting high relative sea level. An important exception is the presence of a basal transgressive systems tract that locally contains shoreface sandstones of reservoir quality. A Hauterivian sequence set includes two transgressive-regressive sequences that constitute a shelf-margin wedge developed as the result of tectonic uplift along the Barrow arch during rift opening of the Arctic Ocean Basin. This sequence set displays stratal geometries suggesting incision and synsedimentary collapse of the shelf margin.
Sediments from lakes Pontchartrain and Maurepas: Database development and preliminary synthesis of historical chemical and other environmental data
No abstract available.
In search of the Abrams post office, Trinity County
An understanding of earth history depends in part on stratigraphy, a division of geology in which the distinctive features of natural units or formations of layered rocks are studied and described and names are assigned to them. The procedures for describing and naming rock units in a uniform way are incorporated in documents known as stratigraphic codes. The North American Stratigraphic Code (1983) is currently used by most geologists in the United States when formation names are selected. Rock unit names consist of a geographic name, generally taken from a natural feature near the locality where the unit was first described, followed by a descriptive feature, usually the dominant rock type in the unit. Although the procedure for naming a rock unit seems straightforward, stratigraphic nomenclature can lead to confusion when the principles outlined in the stratigraphic code are ignored or incorrectly applied. This paper traces the naming of the Abrams Mica Schist, one of the major units of the northern California Klamath Mountains. It describes how uncertainty about the location of the geographic feature after which the unit was named has led to conflicting terminology. The search revealed some interesting history of the early days of mining in the Coffee Creek region of the Trinity Alps in Trinity County.
Geology of the Sanokole Quadrangle, Liberia
As part of a program undertaken cooperatively by the Liberian Geological Survey (LGS) and the U. S. Geological Survey (USGS), under the sponsorship of the Government of Liberia and the Agency for Inter-national Development, U. S. Department of State, Liberia was mapped by geologic and geophysical methods during the period 1965 to 1972. The resulting geologic and geophysical maps are published in ten folios, each covering one quadrangle (see index map). Systematic map synthesis by Force began in 1971 and included field data as shown on figure 1. Observations but not interpretations made by Offerberg and Tremaine (1961) were incorporated in the mapping. The area compiled by Berge (fig. 1) is the LAMCO (Liberian American-Swedish Minerals Co.) Nimba Concession Area. Mapping has been done by company geologists since 1955 and summarized by Berge (1966, 1968, 1973, 1974). Detailed mapping has been done in many areas underlain by iron deposits, but the concession area as a whole has been mapped only by reconnaissance methods. For both compilers, photogeologic mapping and the interpretation of air-borne magnetic and radiometric surveys (Behrendt and Wotorson, 1974, a and b) are integral to the interpretation as shown.
American Tertiary mollusks of the genus Clementia
Aside from its value as an aid in determining the age of Tertiary beds, the chief interest of the genus Clementia lies in the anomalous features of its present and former distribution. An attempt is made in this paper to trace its geologic history, to point out its paleobiologic significance, and to describe all the known American Tertiary species. The fossils from Colombia used in preparing this report were collected during explorations made under the direction of Dr. 0. B. Hopkins, chief geologist of the Imperial Oil Co. (Ltd.), who kindly donated them to the United States National Museum. Dr. T. Wayland Vaughan, of the Scripps Institution of Oceanography, furnished information relating to specimens collected by him in Mexico. Dr. Bruce L. Clark, of the University of California; Dr. G. Dallas Hanna, of the California Academy of Sciences; Dr. H. A. Pilsbry, of the Philadelphia Academy of Natural Sciences; and Dr. W. D. Matthew, of the American Museum of Natural History, generously loaned type specimens and other material. Doctor Clark and Doctor Hanna also gave information concerning the Tertiary species from California. Mr. Ralph B. Stewart, of the University of California, read the manuscript, and I have taken advantage of his suggestions. I am also indebted to Mr. L. R. Cox, of the British Museum, for information relating to the fossil species from Persia, Zanzibar, and Burma, and to Dr. Axel A. Olsson, of the International Petroleum Co., for data concerning undescribed Tertiary species from Peru.
Appendix F—Ground‐water studies in Central America
In June, 1943, the United States Geological Survey assigned two ground‐water geologists, A. N. SAYRE and G. C. TAYLOR, Jr., to study water‐supply problems in Central America for the Coordinator of Inter‐American Affairs and to make recommendations for remedial measures to provide water for cities and towns, especially along the Inter‐American Highway. El Salvador, where a large number of towns along the highway have serious water‐shortages during the six‐month dry season from December to June, was selected as the country in which most of the work was to be done. The Direccion de Sanidad de Salvador, through its Director, Dr. V. A. SUTTER, provided a list of some 35 cities which suffered the most serious water‐shortages and each of these cities was visited. The geological and ground‐water conditions in the vicinity were studied by reconnaissance‐methods and remedial measures were recommended. In nearly every case the water‐shortage was due in large part to improper or incomplete development of the available supplies. Most municipalities obtained their water‐supplies from springs which either had inadequate flow or were improperly developed. In a few cases the spring‐flow was adequate but a large quantity of water was wasted either through poor distribution‐systems or through breaks in the line that conducted water from the spring to the city. Nearly all of the water works were unsanitary. In most places it appeared likely that adequate supplies can be obtained from wells at relatively shallow depth. In some places adequate supplies can be obtained by proper improvements of springs that are now in use. In a very few cases no remedy for the shortage of water could be suggested.
Descriptive catalogue of photographs of North American Indians
Miscellaneous Publications of the United States Geological and Geographical Survey of the Territories is comprised of No. 1-12, some with multiple editions. Ferdinand Vandeveer Hayden is the United States geologist in charge of this series. Other contributors: United States Army. List of publications, with contents of each, and author and subject index may be found in "Catalogue and index of the publications of the Hayden, King, Powell, and Wheeler surveys" by L.F. Schmeckebier. 1904. (U.S. Geological Survey. Bulletin no. 222).
Report of committee on glaciers, 1940–41
The personnel of the Committee is now as follows: Harry Fielding Reid, Professor Emeritus of Geology, Johns Hopkins University, 608 Cathedral Street, Baltimore, Maryland; William H. Hobbs, Professor Emeritus of Geology, University of Michigan, Ann Arbor, Michigan; Lawrence Martin, Chief of the Division of Maps, Library of Congress, Washington, D.C.; J. E. Church, Professor of Meteorology, Agricultural Experiment Station, University of Nevada, Reno, Nevada; Wm. Osgood Field, Jr., Explorer, 18 West Twelfth Street, New York, New York; Oliver Kehrlein, Chairman, Committee on Glacier Studies of Sierra Club, 1050 Mills Tower, 220 Bush Street, San Francisco, California; Kenneth N. Phillips, Associate Hydraulic Engineer, Water Resources Branch, United States Geological Survey, Chairman, Research Committee of the Mazamas, 606 Post‐Office Building, Portland, Oregon; William S. Cooper, Professor of Botany, University of Minnesota, Minneapolis, Minnesota; Gerald Fitzgerald, Senior Topographic Engineer, Alaska Branch, United States Geological Survey, Washington, D.C.; Laurence M. Gould, Professor of Geology, Carleton College, Northfield, Minnesota; Dr. Max Demorest, Department of Geology, Yale University, New Haven, Connecticut; François E. Matthes (Chairman), Senior Geologist, Section of Glacial Geology, United States Geological Survey, Washington, D.C.
Minerals and mineral relationship of the clay minerals
The invitation to be the Edward Orton, Jr., Fellow Lecturer of the American Ceramic Society for 1945 is a very great honor and a privilege which one interested in the mineralogy of clays must heartily appreciate. Dr. Orton was a geologist as well as a founder of this Society, and no doubt in issuing this invitation you had in mind the maintenance of this historic relationship. Those of us who follow him cannot add to that relationship, but I hope that I can help to foster it. Perhaps not all geologists know of this common ground between ceramics and geology as you do, and no doubt you would have me remind my geologic colleagues of this and of the mutual contributions which its maintenance entails. Another common bond of interest is that ceramists have made use of mineralogic and petrographic techniques to an extent not matched in any other applied science. In particular, they have utilized the petrographic microscope, and ceramists and mineralogists alike have found in X rays a wonderful new method of research. Clays, the subject of this lecture, should provide a common meeting ground and one which no doubt would win the hearty approval of Dr. Orton.
Reflections on a trio of North American earthquakes in 1925
In 1925, three moderately large damaging earthquakes occurred in North America over four months: the 28 February (local time; LT) M 6.2 Charlevoix, 27 June (LT) M 6.6 Montana, and 29 June M 6.5 Santa Barbara earthquakes. The centennial anniversaries of these events motivated this retrospective consideration focused on the ground motions generated by the three events, including a reconsideration of early intensity assignments for the Montana earthquake. At the time, these three earthquakes appeared to support the arguments of some geologists who downplayed the severity of seismic hazard in southern California relative to other parts of the country. Some of the arguments advanced at that time, for example that Los Angeles “has the least to fear from ‘Acts of God’ of any city under the American flag,” ( Hill, 1928 ) sound naïve if not laughable now, but a comparison of well‐constrained shaking distributions for the three earthquakes reveals the dramatic difference in wave propagation efficiency in western versus eastern North America (ENAM), which leads to moderate ENAM events being felt to much larger distances. At M 6.2, the 1925 Charlevoix earthquake was a notably large event in ENAM. This earthquake was the largest event in eastern Canada since 1870 and caused damage in the epicentral region in addition to towns as far away as 200 km, with felt shaking extending over 1000 km. In contrast, felt shaking from the Santa Barbara earthquake barely extended beyond ∼200 km. Compiling published intensity distributions for larger ENAM earthquakes, we show that perceptible earthquake shaking is not uncommon in ENAM over century time scales, but experience with weakly felt shaking may incline people to downplay potential earthquake risk.