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Cenozoic giant pectinids from California and the Tertiary Caribbean Province: Lyropecten, "Macrochlamis," Vertipecten, and Nodipecten species

Tertiary pectinids recognized for more than 125 years by field geologists can now be used to date and correlate 3-4 m.y. increments of the geologic record and to determine faunal distributions in relation to tectonic terranes. Fossil pectinids are commonly preserved in shallowmarine clastic deposits that mostly lack microfossils. The stratigraphic ranges of Lyropecten, "Macrochlamis," Vertipecten , and Nodipecten can be used to subdivide provincial megafaunal stages in California and to correlate chronostratigraphic units in the Pacific Northwest and Atlantic Coastal Plain. One New World taxon, "Macrochlamis" magnolia ojaiensis, n. subsp., supports a direct correlation between the middle "Vaqueros" Stage of California (interpolated as 27-23 m.y. B.P.) and an Upper Chattian-Lower Aquitanian Stage section in southwestern Switzerland. Two lithologic units widespread in California, the Vaqueros Formation (spanning 12 m.y., from the late Oligocene into the early Miocene) and Temblor Formation (deposited over a period of 26 m.y., from the late Eocene or early Oligocene to the middle Miocene), transgress much longer periods of time than have been generally recognized. Certain species pairs are identified as cognates, close relatives descended from a common ancestor. Close similarities are found between widely separated assemblages from the Salton Trough of California and the Caribbean, the Gulf Coastal Plain of eastern Mexico and the Sinu Valley of western Colombia, the Santa Rosalia area in Baja California Sur, Mexico, and the Paraguana Peninsula of Venezuela. Distribution patterns for relatively recently dispersed taxa have important implications for middle to late Cenozoic paleogeography and tectonic history, especially in west Mexico and the Caribbean. Speciation was concurrent with the closure of the Isthmus of Panama, the opening of the Gulf of California, and possibly with the northward translation of segments of the California Continental Borderland. Tertiary Caribbean and PacificPanamic Lyropectens and Nodipectens are plotted on a simplified tectonic map as an early step in considering Cenozoic molluscan distributions in relation to major plate boundaries. Taxa having unusual distributions are tabulated with the tectonic events that may have modified their observed geographic ranges. Southern California and the Baja California peninsula include tectonostratigraphic terranes and tectonic slivers that may have moved on the order of hundreds or thousands of kilometers in the Paleogene. Relations between recently dispersed faunas and tectonic terrane boundaries are further complicated by short-term variations in oceanographic phenomena such as currents, El Nino events, and shifts in areas of upwelling. Lyropecten evolved in the late Oligocene or early Miocene, Nodipecten by the late middle Miocene. According to the classification used here, Lyropecten still lives in the Galapagos. Holocene Nodipectens divide the Pacific-Panamic and Caribbean provinces into two subprovinces each. Habitat, life history, dispersal, and growth data are summarized for living Nodipectens, whose distinctive shell features include ledges and hollow nodes. Phylogenetic lineages are based on progressive trends in node formation and rib schemes, some of which have biostratigraphic significance.

Professional Paper↗

Science for avian conservation: Priorities for the new millennium

Over the past decade, bird conservation activities have become the preeminent natural resource conservation effort in North America. Maturation of the North American Waterfowl Management Plan (NAWMP), establishment of Partners in Flight (PIF), and creation of comprehensive colonial waterbird and shorebird conservation plans have stimulated unprecedented interest in, and funding for, bird conservation in the United States, Canada, Mexico, and other countries in the western hemisphere. Key to that success in the United States has been active collaboration among federal, state and local governments, conservation organizations, academia, and industry. The U.S. Department of the Interior (DOI), which has primary statutory responsibility for migratory bird conservation and management, has been a key partner. Despite the great strides that have been made in bird conservation science, historical approaches to research and monitoring have often failed to provide sufficient information and understanding to effectively manage bird populations at large spatial scales. That shortcoming, and the lack of an integrated strategy and comprehensive set of research priorities, is more evident in light of the goals established by the North American Bird Conservation Initiative (NABCI). The NABCI is a trinational, coalition-driven effort to provide an organizational umbrella for existing conservation initiatives. The expanded focus of NABCI and individual bird conservation initiatives is to work together in an integrated, holistic fashion to keep common birds common and to increase populations of declining, threatened, and endangered species. To assist bird conservation initiatives in defining goals and developing new approaches to effective research, the U.S. Geological Survey (USGS), the research agency of DOI, convened a workshop, “Science for Avian Conservation: Understanding, Modeling, and Applying Ecological Relationships,” on 31 October–2 November 2000, which brought together 51 scientists from USGS, as well as scientists and conservationists from other agencies and organizations actively participating in NABCI. As the lead federal agency involved in bird conservation research, USGS has a clear legislative mandate to provide scientific information upon which future management plans and actions will be built. This article summarizes key issues and recommendations that arose from that workshop. The principal goal of the workshop was to guide USGS in defining its role, assessing capabilities, and directing future agency planning in support of bird conservation. A major component was to identify key areas of research needed in this new era of bird conservation science. Although tailored to the mission of USGS, workshop recommendations visualize a bold direction for future avian conservation science in which research and monitoring work in tandem with management to increase our understanding of avian populations and the processes that affect them. The USGS is a science agency whose role is to provide objective scientific information to management agencies and therefore is not directly involved in high-level resource policy-making or on-the-ground management decision making. Nevertheless, it is important to note that effective policy decision making must integrate the best available science with political and economic realities to achieve successful avian conservation—an important subject acknowledged in the workshop, but largely beyond its scope of discussion. Williams (2003) questions regarding how scientific information can be effectively communicated to decision makers and incorporated into natural resource policy. Without an aggressive vision and the willingness of researchers, managers, and policy makers to implement it, conservation of North American birds is likely to proceed without the full benefit of scientific investigation. These recommendations represent the principal conclusions drawn by workshop participants and do not necessarily reflect official USGS policy.

The Auk↗

Tracking the source of metals to the San Juan River

Introduction The San Juan River is a major water source for communities in the Four Corners Region of the United States (Colorado, Arizona, New Mexico, Utah) and is a vital source of water for the Navajo Nation. The Navajo Nation Environmental Protection Agency (NNEPA) periodically samples surface water on the Navajo Nation and has found that some elements exceed NNEPA surface water standards (the upper limits of an element for consumption or other use of water). Constituents of concern are substances that could be harmful if present in sufficient quantities, and it is important to keep track of the concentrations of these substances in the environment. In the San Juan River, constituents of concern include metals detected in river water, such as arsenic, lead, and aluminum. These metals can come from natural sources or can result from human activities (anthropogenic) and can affect the health of people, plants, and animals. The Animas River is one natural source of metals to the San Juan River because of the types of rock through which the Animas River flows and because of hard rock mining at the headwaters. Other potential sources of metals are oil and gas development, coal mining, coal-fired power plants, urban areas, illegal trash dumping, abandoned uranium mines and mills, overgrazed areas, natural geology, and leaching from subsurface agricultural return flows. Determining how much each of these sources contributes and the relative effect of each source on San Juan River water will help the Navajo Nation in their efforts to protect human health and the environment along the San Juan River. The U.S. Geological Survey (USGS) is working with the NNEPA to identify sources of metals and trace elements entering the San Juan River from tributaries in the reach flowing through the Navajo Nation and to quantify the contribution from each natural and human-caused source. The USGS and NNEPA worked with local community members to locate tributaries where sampling equipment was installed. The 3-year source-tracking project, starting in spring 2021, will identify where metals at concentrations above safe surface water standards might be entering the river by evaluating the chemical signatures of water in the major tributaries of the San Juan River. Results will provide valuable information to the Navajo Nation, public drinking-water managers, irrigation districts, other stakeholders, scientists, and the public.

Colorado, Arizona, New Mexico, Utah↗

Plan of study to define hydrogeologic characteristics of the Madera Limestone in the east mountain area of central New Mexico

The east mountain area of central New Mexico includes the eastern one-third of Bernalillo County and portions of Sandoval, Santa Fe, and Torrance Counties. The area covers about 320 square miles. The Madera Limestone, the principal aquifer in the east mountain area, is the sole source of water for domestic, municipal, industrial, and agricultural uses for many residents. Some water is imported from wells near Edgewood by the Entranosa Water Cooperative, which serves a population of approximately 3,300. The remaining population is served by small water systems that derive supplies locally or by individually owned domestic wells. The population of the east mountain area has increased dramatically over the past 20 years. In 1970, the population of the east mountain area was about 4,000. Demographic projections suggest that approximately 1,000 people per year are moving into the area, and with a growth rate of 3.0 percent the population will be 16,700 in 2000. Consequently, ground-water withdrawals have increased substantially over the past 20 years, and will continue to increase. Little is known about the flow characteristics and hydrogeologic properties of the Madera Limestone. This report describes existing information about the geologic and hydrologic framework and flow characteristics of the Madera Limestone, and presents a plan of study for data-collection activities and interpretive studies that could be conducted to better define the hydrogeologic characteristics of the Madera Limestone. Data-collection activities and interpretive studies related to the hydrogeologic components of the Madera Limestone are prioritized. Activities that are necessary to improve the quantification of a component are prioritized as essential. Activities that could add additional understanding of a component, but would not be necessary to improve the quantification of a component, are prioritized as useful.

Open-File Report↗

Testing hypotheses on signatures of precipitation variability in the river and floodplain deposits of the Paleogene San Juan Basin, New Mexico, USA

Much progress has been made in recent years towards a set of recognition criteria for river discharge variability in river channel deposits, and thus sedimentary proxies for precipitation variability. Despite this progress, there is currently no consensus on how different styles of discharge variability are reflected in river sedimentary records, and whether variable-discharge river records from different climate types can be distinguished. Herein, river discharge and precipitation variability in the Paleogene is investigated using associations between river channel and floodplain deposits across the Paleocene-Eocene boundary from the Paleocene upper Nacimiento Formation and the early Eocene San Jose Formation in the San Juan Basin, New Mexico, USA. The succession is identified as deposits of variable-discharge river systems based on shared channel-deposit characteristics with modern and ancient variable-discharge river systems and the proposed facies models, in addition to alternations of poorly drained and well-drained floodplain deposits and/or slickensides indicating alternating wet-dry cycles. A long-term stratigraphic trend toward increasingly well-drained floodplain deposits is also observed and hypothesized to indicate successively more arid conditions from the Paleocene into the early Eocene. Comparisons with modern rivers from various climate zones suggest a long-term shift from a monsoonal climate in the Paleocene, to a fluctuating subhumid climate, ultimately leading to semiarid to arid conditions in the early Eocene. These observations suggest that floodplain deposits may be a better indicator of ambient climate, whereas channel deposits are records for frequency and magnitude of high-intensity precipitation events. Therefore, the existing facies models for variable-discharge rivers that consider only channel facies may not capture critical information needed to make accurate interpretations of paleoclimatic conditions. This study also adds to a growing body of evidence from geologic records of mid-latitude Paleogene river systems suggesting increases in the magnitude or variability of river discharge coinciding with established climate perturbations.

New Mexico↗

Gulf of Mexico summary report 2, August 1981: A revision of Outer Continental Shelf oil and gas activities in the Gulf of Mexico and their onshore impacts: A summary report, September 1980

The Gulf of Mexico Outer Continental Shelf (OCS) continues to be the most intensively developed offshore oil- and gas-producing region in the world. With the development of technology, exploration, development, and production are being extended to include areas off the coast of southwest Florida and deep-water areas near the Mississippi River Delta. Development in both areas requires careful analyses of local considerations. The hydrocarbon potential of the region, while not well established in the frontier portions, generally remains favorable. A total of 482 fields have been discovered to date in the federally regulated part of the Gulf of Mexico. Reserve estimates have been made for the 435 producing fields in the region. Through December 31, 1980, those fields have produced 5.0 billion barrels of oil and condensate, and 48.7 trillion cubic feet of gas. Remaining recoverable reserves are 3.1 billion barrels of oil and 40.2 trillion cubic feet of gas. Estimates of undiscovered recoverable resources for the Gulf of Mexico are 6.6 billion barrels of oil and 71.9 trillion cubic feet of gas. Since enactment of the Outer Continental Shelf Lands Act in 1953, there have been 42 oil and gas lease sales in the Gulf of Mexico. An average of three lease sales per year are scheduled through 1986. Since 1953, the Bureau of Land Management (BLM) has leased 3,119 tracts in the Gulf of Mexico; 1,825 leases are currently active. The distribution of leased tracts exhibits a regionwide pattern as shown by Lease Sales A62, 62, A66, and 66. Proposed Lease Sales 67, 69, 72, and 74 will probably continue that pattern. Tracts off the coast of southwest Florida in the Charlotte Harbor, Howell Hook, and Pulley Ridge Areas will be offered in upcoming sales. Operations on tracts in deepwater areas slated for future sales may require additional technology. Exploration, development, and production in the Gulf of Mexico Region are continuing at a rapid pace throughout the Gulf of Mexico. Between January 1, 1980, and April 15, 1981, 197 initial plans of exploration and 165 supplemental plans of exploration were submitted to the U.S. Geological Survey (USGS). During the same period, 107 initial and 131 supplemental plans of development/production were submitted to the USGS. As of May 1981, there were 121 offshore mobile drilling units operating in the Gulf of Mexico. Pipelines continue to be the preferred mode of transport for Gulf of Mexico OCS oil and gas production. Pipeline additions to the existing network average 69 miles (111 km) per month. At any given time, numerous pipeline projects are under way in the Gulf of Mexico. To supplement OCS oil and gas production several deepwater port projects, designed to handle imported crude oil, are being planned or constructed in the region. The process of transportation planning in the Gulf of Mexico is done by industry and government through BLM's Intergovernmental Planning Program and its Regional Technical Working Group (RTWG). The RTWG has completed the First Edition Gulf of Mexico Regional Transportation Management Plan. The nearshore and onshore facilities in the Gulf of Mexico service both the domestic onshore and offshore oil and gas industry as well as the global market. Most of the major centers along the Gulf Coast, including Houston, Corpus Christi, Galveston, Beaumont, Port Arthur, and Freeport, Texas; New Orleans, Lake Charles, Lafayette, Baton Rouge, Morgan City, and Houma, Louisiana; Pascagoula, Mississippi; Mobile, Alabama; and Port Manatee, Florida, have ties to the offshore industry. A wide array of services and support industries, ranging from small independent vendors to major international manufacturing contractors, can be found within the region. Profiles of selected centers reveal typical industries and patterns of activity that are characteristic throughout the Gulf Coast region.

Alabama, Florida, Louisiana, Mississippi, Texas↗

Geologic assessment of undiscovered oil and gas resources in Aptian carbonates, onshore northern Gulf of Mexico Basin, United States

Carbonate lithofacies of the Lower Cretaceous Sligo Formation and James Limestone were regionally evaluated using established U.S. Geological Survey (USGS) assessment methodology for undiscovered conventional hydrocarbon resources. The assessed area is within the Upper Jurassic–Cretaceous–Tertiary Composite total petroleum system, which was defined for the assessment. Hydrocarbons reservoired in carbonate platform Sligo-James oil and gas accumulations are interpreted to originate primarily from the Jurassic Smackover Formation. Emplacement of hydrocarbons occurred via vertical migration along fault systems; long-range lateral migration also may have occurred in some locations. Primary reservoir facies include porous patch reefs developed over paleostructural salt highs, carbonate shoals, and stacked linear reefs at the carbonate shelf margin. Hydrocarbon traps dominantly are combination structural-stratigraphic. Sealing lithologies include micrite, calcareous shale, and argillaceous lime mudstone. A geologic model, supported by discovery history analysis of petroleum geology data, was used to define a single regional assessment unit (AU) for conventional reservoirs in carbonate facies of the Sligo Formation and James Limestone. The AU is formally entitled Sligo-James Carbonate Platform Oil and Gas (50490121). A fully risked mean undiscovered technically recoverable resource in the AU of 50 million barrels of oil (MMBO), 791 billion cubic feet of natural gas (BCFG), and 26 million barrels of natural gas liquids was estimated. Substantial new development through horizontal drilling has occurred since the time of this assessment (2010), resulting in cumulative production of >200 BCFG and >1 MMBO.

Cretaceous Research↗

Glacial chronology of the Southern Rocky Mountains

In order to extend the chronology and validate the five substages of the Wisconsin glaciation recognized in the Cache la Poudre Valley in the Colorado Front Range, a reconnaissance was made of the Southern Rocky Mountains, from southern Wyoming to Santa Fe, New Mexico. The chronology determined in the Cache la Poudre Valley was used to date the culture layer of the Lindenmeier (Folsom) Site in northern Colorado. The earliest or Twin Lakes substage is named for the "early moraine" mapped by Capps at Twin Lakes in the Upper Arkansas Valley. This substage is believed to have been contemporaneous with the Durango glaciation of the San Juan Mountains. Throughout the Southern Rocky Mountains the second, third, and fourth, or Home, Corral Creek, and Long Draw substages, can be readily correlated from valley to valley. The fifth or youngest substage, represented in some cirques by protalus ramparts, is named the Sprague substage. The validity of five distinct substages of Wisconsin ice advance, separated from one another by interstadial ice retreat or complete disappearance, is based on: (1) the character and topographic position of the moraines; (2) the relationship between successive terraces (valley trains) and the terminal moraines, as determined in the Cache la Poudre Valley; (3) the differences in weathering of the tills composing the moraines; and (4) the reported finding of an old soil zone between tills assigned to the Twin Lakes and Home substages. © 1940 Geological Society of America.

Geological Society of America Bulletin↗

Water-quality trends in the Rio Grande/Rio Bravo Basin using sediment cores from reservoirs

Water-quality trends reflect the relation between water quality and human activities, chronicling changes in concentrations of environmental contaminants, introduction of new contaminants, and successful efforts in environmental pollution remediation. Historical data available for analyzing trends often have severe limitations, from questionable accuracy to unknown sampling and analytic methodologies. Where data are unavailable or have such limitations, water-quality trends sometimes can be reconstructed using sediment cores from lakes and reservoirs. The purpose of this fact sheet is to summarize the findings of a study to assess historical changes in surface-water quality in the Rio Grande Basin (known as the Río Bravo Basin in Mexico) by analyzing changes in sediment chemistry in cores from three reservoirs: Elephant Butte Reservoir, Amistad International Reservoir, and Falcon International Reservoir (fig. 1). Sediments that erode from the land surface are transported by tributaries into the Rio Grande/Río Bravo. Metals and some persistent pesticides and industrial organic compounds sorb to these sediments, which eventually accumulate at the bottom of the reservoirs or are transported to the Gulf of Mexico. Although use of reservoir cores has limitations—for example, the cores do not record trends in non-persistent compounds—in many cases the data provide a partial historical record of water quality. In 1991, the U.S. Geological Survey (USGS) began full implementation of the National Water-Quality Assessment (NAWQA) Program (Leahy and others, 1990). Also in 1991, the State of Texas established the Clean Rivers Program (CRP) administered by the Texas Natural Resource Conservation Commission (TNRCC). The coring study reported here was a collaborative effort between the NAWQA Program and the CRP Rio Grande Border Environmental Assessment Team, with additional funding support from the El Paso County Water Improvement District No. 1.

Colorado, New Mexico, Texas↗

Status Assessment of Laysan and Black-Footed Albatrosses, North Pacific Ocean, 1923-2005

Over the past century, Laysan (Phoebastria immutabilis) and black-footed (Phoebastria nigripes) albatrosses have been subjected to high rates of mortality and disturbance at the breeding colonies and at sea. Populations were greatly reduced and many colonies were extirpated around the turn of the 20th century as a result of feather hunting. Populations were recovering when military occupation of several breeding islands during World War II led to new population declines at these islands and additional colony extirpations. At sea, thousands of Laysan and black-footed albatrosses were killed each year in high-seas driftnet fisheries, especially from 1978 until the fisheries were banned in 1992. Through the 1990s, there was a growing awareness of the large numbers of albatrosses that were being killed in longline fisheries. During the 1990s, other anthropogenic factors, such as predation by non-native mammals and exposure to contaminants, also were documented to reduce productivity or increase mortality. In response to the growing concerns over the impacts of these threats on albatross populations, the U.S. Fish and Wildlife Service contracted with the U.S. Geological Survey to conduct an assessment of Laysan and black-footed albatross populations. This assessment includes a review of the taxonomy, legal status, geographic distribution, natural history, habitat requirements, threats, and monitoring and management activities for these two species. The second part of the assessment is an analysis of population status and trends from 1923 to 2005. Laysan and black-footed albatrosses forage throughout the North Pacific Ocean and nest on tropical and sub-tropical oceanic islands from Mexico to Japan. As of 2005, 21 islands support breeding colonies of one or both species. The core breeding range is the Hawaiian Islands, where greater than 99 percent of the World's Laysan albatrosses and greater than 95 percent of the black-footed albatrosses nest on the small islands and atolls of the Northwestern Hawaiian Islands. These islands are all protected as part of the Papahanaumokuakea Marine National Monument. Albatrosses are long-lived seabirds with deferred maturity, low fecundity, and high rates of adult survival. Their life history characteristics make populations especially vulnerable, to small increases in adult mortality. The primary threats to Laysan and black-footed albatrosses include interactions with commercial fisheries, predation by introduced mammals, reduced reproductive output due to contaminants, nesting habitat loss and degradation due to human development and invasive plant species, and potential loss and degradation of habitat due to climate change and sea-level rise. Incidental mortality (bycatch) in commercial fisheries is the greatest anthropogenic source of mortality (post-fledging) for both species. We found that longline fishing effort prior to the 1980s was greater than previously estimated and a very significant source of mortality. Regulations to minimize and monitor albatross mortality have been enacted in most U.S. and Canadian longline fisheries, but monitoring of bycatch rates and regulations to minimize seabird mortality are extremely limited in the much larger multinational longline fleets. Management to address threats at the breeding colonies is ongoing and includes eradication or control of non-native species, habitat management, and abatement programs to reduce impacts of contaminants. Effective long-term conservation and management of the Laysan and black-footed albatrosses require management and monitoring at the breeding colonies and at sea and continued assessment of population status and trends. We evaluated the status and trends of Laysan and black-footed albatross populations using linear regression, population viability analysis (PVA), and age-structured matrix models. Analyses were predominantly based on nest-count data gathered at French Frigate Shoals, Laysan Island, and Midw

Scientific Investigations Report↗

USGS assessment of undiscovered oil and gas resources in Paleogene strata of the U.S. Gulf of Mexico coastal plain and state waters

This report presents a review of the U.S. Geological Survey ( USGS ) 2007 assessment of the undiscovered oil and gas resources in Paleogene strata underlying the U.S. Gulf of Mexico Coastal Plain and state waters. Geochemical, geologic, geophysical, thermal maturation, burial history, and paleontologic studies have been combined with regional cross sections and data from previous USGS petroleum assessments have helped to define the major petroleum systems and assessment units. Accumulations of both conventional oil and gas and continuous coal-bed gas within these petroleum systems have been digitally mapped and evaluated, and undiscovered resources have been assessed following USGS methodology. The primary source intervals for oil and gas in Paleogene (and Cenozoic) reservoirs are coal and shale rich in organic matter within the Wilcox Group (Paleocene-Eocene) and Sparta Formation of the Claiborne Group (Eocene); in addition, Cretaceous and Jurassic source rocks probably have contributed substantial petroleum to Paleogene (and Cenozoic) reservoirs. For the purposes of the assessment, Paleogene strata have divided into the following four stratigraphic study intervals: (1) Wilcox Group (including the Midway Group and the basal Carrizo Sand of the Claiborne Group; Paleocene-Eocene); (2) Claiborne Group (Eocene); (3) Jackson and Vicksburg Groups (Eocene-Oligocene); and (4) the Frio-Anahuac Formations (Oligocene). Recent discoveries of coal-bed gas in Paleocene strata confirm a new petroleum system that was not recognized in previous USGS assessments. In total, 26 conventional Paleogene assessment units are defined. In addition, four Cretaceous-Paleogene continuous (coal-bed gas) assessment units are included in this report. Initial results of the assessment will be released as USGS Fact Sheets (not available at the time of this writing). Comprehensive reports for each assessment unit are planned to be released via the internet and distributed on CD-ROMs within the next year.

U.S. Gulf Coast↗

National assessment of carbon dioxide enhanced oil recovery and associated carbon dioxide retention resources — Results

In 2020, the U.S. Geological Survey (USGS) completed a probabilistic assessment of the volume of technically recoverable oil resources available if current carbon dioxide enhanced oil recovery (CO 2 -EOR) technologies were applied to amenable oil reservoirs underlying the onshore and State waters areas of the conterminous United States. The assessment also includes estimates of the mass of CO 2 that could be stored (retained) as a result of CO 2 -EOR activities. The USGS assessment team evaluated more than 3,500 oil reservoirs that were miscible to injected CO 2 . The assessed reservoirs are in 185 previously defined USGS plays in 33 petroleum provinces of 7 national regions. The assessment team estimated that the technically recoverable oil associated with CO 2 -EOR ranges from approximately 25,000 million barrels (MMbbl) at the P 5 percentile to as much as 32,000 MMbbl at the P 95 percentile, with a mean of 29,000 MMbbl. The associated CO 2 retention ranges from approximately 7,400 million metric tons (Mt) at the P 5 percentile to as much as 9,500 Mt at the P 95 percentile, with a mean of 8,400 Mt. The West Texas and Eastern New Mexico region and the Gulf Coast region together contain 60 percent of the mean assessed CO 2 -EOR oil potential and 61 percent of the mean assessed CO 2 retention. Other regions with significant resource potential include the Midcontinent region and Rocky Mountains and Northern Great Plains region.

Continental United States↗

Interim guidance for calibration checks on a submersible acoustic backscatter sediment sensor

Over the past two decades, the U.S. Geological Survey (USGS) and other agencies have pioneered the use of active acoustic sensors to monitor suspended-sediment concentrations and particle sizes in rivers and streams at the subdaily time scale. The LISST-ABS submersible acoustic backscatter sediment sensor (or “ABS sensor”) was developed by Sequoia Scientific, Inc., as an alternative to turbidity sensors for monitoring suspended-sediment concentrations in surface waters. The ABS sensor is different than traditional active acoustic instruments because it is small, lower in cost, lightweight, and requires less power; and the sampling volume is within the first 15 centimeters of the transducer face. Initial testing by the USGS indicated the ABS sensor had utility as a novel, cost-effective, off-the-shelf tool for monitoring suspended-sediment concentration in surface waters, and its use within the agency has increased in since its introduction around 2016. However, initial testing did not account for the potential of transducer calibration drift over longer deployments. As part of its mission to unify and standardize research and development activities of Federal agencies involved in fluvial sediment studies, the Federal Interagency Sedimentation Project partnered with the USGS Wyoming-Montana and New Mexico Water Science Centers to examine the potential for use of standard, low-tech laboratory equipment to perform calibration checks on ABS sensors on long-term deployments. The experiments were intended to provide USGS scientists and the public with interim guidance to assist in operating and maintaining the ABS sensor.

Open-File Report↗

Updated estimates of long-term average dissolved-solids loading in streams and rivers of the Upper Colorado River Basin

The Colorado River and its tributaries supply water to more than 35 million people in the United States and 3 million people in Mexico, irrigating over 4.5 million acres of farmland, and annually generating about 12 billion kilowatt hours of hydroelectric power. The Upper Colorado River Basin, part of the Colorado River Basin, encompasses more than 110,000 mi 2 and is the source of much of more than 9 million tons of dissolved solids that annually flows past the Hoover Dam. High dissolved-solids concentrations in the river are the cause of substantial economic damages to users, primarily in reduced agricultural crop yields and corrosion, with damages estimated to be greater than 300 million dollars annually. In 1974, the Colorado River Basin Salinity Control Act created the Colorado River Basin Salinity Control Program to investigate and implement a broad range of salinity control measures. A 2009 study by the U.S. Geological Survey, supported by the Salinity Control Program, used the Spatially Referenced Regressions on Watershed Attributes surface-water quality model to examine dissolved-solids supply and transport within the Upper Colorado River Basin. Dissolved-solids loads developed for 218 monitoring sites were used to calibrate the 2009 Upper Colorado River Basin Spatially Referenced Regressions on Watershed Attributes dissolved-solids model. This study updates and develops new dissolved-solids loading estimates for 323 Upper Colorado River Basin monitoring sites using streamflow and dissolved-solids concentration data through 2012, to support a planned Spatially Referenced Regressions on Watershed Attributes modeling effort that will investigate the contributions to dissolved-solids loads from irrigation and rangeland practices.

Arizona, Colorado, New Mexico, Utah, Wyoming↗

Evolution of the Mazatzal province and the timing of the Mazatzal orogeny: Insights from U-Pb geochronology and geochemistry of igneous and metasedimentary rocks in southern New Mexico

New U-Pb zircon ages, geochemistry, and Nd isotopic data are presented from three localities in the Paleoproterozoic Mazatzal province of southern New Mexico, United States. These data help in understanding the source regions and tectonic setting of magmatism from 1680 to 1620 Ma, the timing of the Mazatzal orogeny, the nature of postorogenic maginatism, Proterozoic plate tectonics, and provide a link between Mazatzal subblocks in Arizona and northern New Mexico. The data indicate a period from 1680 to 1650 Ma in which juvenile felsic granitoids were formed, and a later event between 1646 and 1633 Ma, when these rocks were deformed together with sedimentary rocks. No evidence of pre-1680 Ma rocks or inherited zircons was observed. The igneous rocks have ENd(t) from -1.2 to +4.3 with most between +2 and +4, suggesting a mantle source or derivation from similar-aged crust. Nd isotope and trace element concentrations are consistent with models for typical are magmatism. Detrital zircon ages from metasedimentary rocks indicate that sedimentation occurred until at least 1646 Ma. Both local and Yavapai province sources contributed to the detritus. All of the samples older than ca. 1650 Ma are deformed, whereas undeformed porphyroblasts were found in the contact aureole of a previously dated 1633 Ma gabbro. Regionally, the Mlazatzal orogeny occurred mainly between 1654 and 1643 Ma, during final accretion of a series of island arcs and intervening basins that may have amalgamated offshore. Rhyolite magmatism in the southern Mazatzal province was coeval with gabbro intrusions at 1633 Ma and this bimodal magmatism may have been related to extensional processes following arc accretion. ?? 2007 Geological Society of America.

Geological Society of America Bulletin↗

Structural and geochemical characteristics of faulted sediments and inferences on the role of water in deformatiion, Rio Grande Rift, New Mexico

The San Ysidro fault is a spectacularly exposed normal fault located in the northwestern Albuquerque Basin of the Rio Grande Rift. This intrabasin fault is representative of many faults that formed in poorly lithified sediments throughout the rift. The fault is exposed over nearly 10 km and accommodates nearly 700 m of dip slip in subhorizontal, siliciclastic sediments. The extent of the exposure facilitates study of along-strike variations in deformation mechanisms, archi tecture, geochemistry, and permeability. The fault is composed of structural and hydrogeologic components that include a clay-rich fault core, a calcite-cemented mixed zone, and a poorly developed damage zone primarily consisting of deformation bands. Structural textures suggest that initial deformation in the fault occurred at low temperature and pressure, was within the paleosaturated zone of the evolving Rio Grande Rift, and was dominated by particulate flow. Little geochemical change is apparent across the fault zone other than due to secondary processes. The lack of fault-related geochemical change is interpreted to reflect the fundamental nature of water-saturated, particulate fl ow. Early mechanical entrainment of low-permeability clays into the fault core likely caused damming of groundwater flow on the up-gradient, footwall side of the fault. This may have caused a pressure gradient and flow of calcite-saturated waters in higher-permeability, fault-entrained siliciclastic sediments, ultimately promoting their cementation by sparry calcite. Once developed, the cemented and clay-rich fault has likely been, and continues to be, a partial barrier to cross-fault groundwater flow, as suggested by petrophysical measurements. Aeromagnetic data indicate that there may be many more unmapped faults with similar lengths to the San Ysidro fault buried within Rio Grande basins. If these buried faults formed by the same processes that formed the San Ysidro fault and have persistent low-permeability cores and cemented mixed zones, they could compartmentalize the basin-fill aquifers more than is currently realized, particularly if pumping stresses continue to increase in response to population growth. ?? 2009 Geological Society of America.

Geological Society of America Bulletin↗

High-resolution seismic characterization of the gas and gas hydrate system at Green Canyon 955, Gulf of Mexico, USA

The Pliocene and Pleistocene sediments at lease block Green Canyon 955 (GC955) in the Gulf of Mexico include sand-rich strata with high saturations of gas hydrate; these gas hydrate accumulations and the associated geology have been characterized over the past decade using conventional industry three-dimensional (3D) seismic data and dedicated logging-while-drilling (LWD) borehole data. To improve structural and stratigraphic characterization and to address questions of gas flow and reservoir properties, in 2013 the U.S. Geological Survey acquired high-resolution two-dimensional (2D) seismic data at GC955. Combined analysis of all available data improves our understanding of the geological evolution of the study area, which includes basin-scale migration of the Mississippi River sediment influx as well as local-scale shifting of sedimentary channels at GC955 in response to salt-driven uplift, structural deformation associated with the salt uplift, and upward gas migration from deeper sediments that charges the main gas hydrate reservoir and shallower strata. The 2D data confirm that the sand-rich reservoir is composed principally of sediments deposited in a proximal levee setting and that episodes of channel scour, interspersed with levee deposition, have resulted in an assemblage of many individual proximal levee deposit “pods” each with horizontal extent up to several hundred meters. Joint analysis of the 2D and 3D data reveals new detail of a complex fault network that controls the fluid-flow system; large east-west trending normal faults allow fluid flow through the reservoir-sealing fine-grained unit, and smaller north-south oriented faults provide focused fluid-flow pathways (chimneys) through the shallower sediments. This system has enabled the flow of gas from the main reservoir to the seafloor throughout the recent history at GC955, and its intricacies help explain the distributed occurrences of gas hydrate in the intervening strata.

Gulf of Mexico↗

Contributions to the stratigraphy of southwestern Colorado

In the course of field work of the United States Geological Survey in the San Juan region of Colorado observations have been made in the last three seasons that considerably extend our knowledge of the great stratigraphic break below the La Plata sandstone, which is currently assumed to be of Jurassic age. The new data pertain partly to the relations existing in the Gunnison Valley, north of the San Juan Mountains, where the unconformity marking this break was already known at certain places, and partly to the conditions in the Piedra Valley, on the south side of the mountains, where the unconformity had not before been noted. The Piedra Valley is of special interest, and it seems well to call attention to the relations observed even though they were examined only in a reconnaissance. The first part of this paper is devoted to the evidence of the overlap of the La Plata sandstone; the second to the stratigraphic relations in the Piedra Valley. The section of sedimentary formations in Piedra Canyon is of much interest because none of the pre-La Plata formations are known east of this locality on the south side of the San Juan Mountains. Most of these formations exhibit a notably different facies where they reappear from beneath the overlying beds at their nearest exposures in New Mexico, southeast of the Piedra Valley. It is believed that the character of the formations in the Piedra section should be recorded for the benefit of geologists who may be studying the Paleozoic and Mesozoic rocks of New Mexico, and accordingly the second part of the paper presents details of the structure and the stratigraphic section of Piedra Valley.

Colorado↗