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At least 181 records · Page 10Linked to original sources

Marine radiocarbon reservoir age variation in Donax obesulus shells from northern Peru: Late Holocene evidence for extended El Niño

For at least 6 m.y., El Niño events have posed the greatest environmental risk on the Peruvian coast. A better understanding of El Niño is essential for predicting future risk and growth in this tropical desert. To achieve this we analyzed archaeological and modern pre-bomb shells from the surf clam Donax for the radiocarbon reservoir effect (ΔR) to characterize late Holocene coastal upwelling conditions in northern Peru (8°14′S). Mean ΔR values from these shells suggest that modern upwelling conditions in this region were likely established between A.D. 539 and A.D. 1578. Our radiocarbon data suggest that upwelling conditions ca. A.D. 539 were less intense than those in modern times. The observed coastal water enrichment in 14 C may be consequence of frequent strong El Niño events or extended El Niño–like conditions. These ΔR-inferred marine conditions are in agreement with proposed extended El Niño activity in proxy and archaeological records of ca. A.D. 475–530. Extended El Niño conditions have been linked to political destabilization, societal transformation, and collapse of the Moche civilization in northern Peru. A return to such conditions would have significant impacts on the dense population of this region today and in the near future.

Geology

Great Lakes rivermouths: a primer for managers

Between the North American Great Lakes and their tributaries are the places where the confluence of river and lake waters creates a distinct ecosystem: the rivermouth ecosystem. Human development has often centered around these rivermouths, in part, because they provide a rich array of ecosystem services. Not surprisingly, centuries of intense human activity have led to substantial pressures on, and alterations to, these ecosystems, often diminishing or degrading their ecological functions and associated ecological services. Many Great Lakes rivermouths are the focus of intense restoration efforts. For example, 36 of the active Great Lakes Areas of Concern (AOCs) are rivermouths or areas that include one or more rivermouths. Historically, research of rivermouth ecosystems has been piecemeal, focused on the Great Lakes proper or on the upper reaches of tributaries, with little direct study of the rivermouth itself. Researchers have been divided among disciplines, agencies and institutions; and they often work independently and use disparate venues to communicate their work. Management has also been fragmented with a focus on smaller, localized, sub-habitat units and socio-political or economic elements, rather than system-level consideration. This Primer presents the case for a more holistic approach to rivermouth science and management that can enable restoration of ecosystem services with multiple benefits to humans and the Great Lakes ecosystem. A conceptual model is presented with supporting text that describes the structures and processes common to all rivermouths, substantiating the case for treating these ecosystems as an identifiable class. 1 Ecological services provided by rivermouths and changes in how humans value those services over time are illustrated through case studies of two Great Lakes rivermouths—the St. Louis River and the Maumee River. Specific ecosystem services are identified in italics throughout this Primer and follow definitions described by the Millennium Ecosystem Assessment (Table1). Collectively, this primer synthesizes existing information in a new way that aims to support management of rivermouths as distinct and important ecosystems. The development and management decisions made around rivermouths today will shape the future of these ecosystems, and the human communities within them, well into the future. 1 The information presented in this paper was derived from discussions and draft documents of the Great Lakes Rivermouth Collaboratory. The Great Lakes Rivermouth Collaboratory was established by the U.S. Geological Survey's Great Lakes Science Center (USGS-GLSC) in collaboration with the Great Lakes Commission to engage the Great Lakes scientific community in sharing and documenting knowledge about freshwater rivermouth ecosystems. For more information, see http://www.glc.org/habitat/Rivermouth-Collaboratory.html.

Great Lakes

The Chesapeake Bay bolide impact: a new view of coastal plain evolution

A spectacular geological event took place on the Atlantic margin of North America about 35 million years ago in the late part of the Eocene Epoch. Sea level was unusually high everywhere on Earth, and the ancient shoreline of the Virginia region was somewhere in the vicinity of where Richmond is today (fig. 1). Tropical rain forests covered the slopes of the Appalachians. To the east of a narrow coastal plain, a broad, lime (calcium carbonate)- covered continental shelf lay beneath the ocean. Suddenly, with an intense flash of light, that tranquil scene was transformed into a hellish cauldron of mass destruction. From the far reaches of space, a bolide (comet or asteroid), 3-5 kilometers in diameter, swooped through the Earth's atmosphere and blasted an enormous crater into the continental shelf. The crater is now approximately 200 km southeast of Washington, D.C., and is buried 300-500 meters beneath the southern part of Chesapeake Bay and the peninsulas of southeastern Virginia (fig. 1). The entire bolide event, from initial impact to the termination of breccia deposition, lasted only a few hours or days. The crater was then buried by additional sedimentary beds, which accumulated during the following 35 million years.

Fact Sheet

Narrow-headed garter snake (Thamnophis rufipunctatus)

The narrow-headed garter snake is a harmless, nonvenomous snake that is distinguished by its elongated, triangular-shaped head and the red or dark spots on its olive to tan body. Today, the narrow-headed garter snake is a species of special concern in the United States because of its decline over much of its historic range. Arizona's Oak Creek has historically contained the largest population of narrow-headed garter snakes in the United States. The U.S. Geological Survey (USGS) and the Arizona Game and Fish Department jointly funded research by USGS scientists in Oak Creek to shed light on the factors causing declining population numbers. The research resulted in better understanding of the snake's habitat needs, winter and summer range, and dietary habits. Based on the research findings, the U.S. Forest Service has developed recommendations that visitors and local residents can adopt to help slow the decline of the narrow-headed garter snake in Oak Creek.

Fact Sheet

Cooperative Fish and Wildlife Research Units program—2020 Year in review

Established in 1935, the Cooperative Fish and Wildlife Research Units program (CRU program) is a unique cooperative partnership among State fish and wildlife agencies, universities, the Wildlife Management Institute, the U.S. Geological Survey (USGS), and the U.S. Fish and Wildlife Service. Designed to meet the scientific needs of natural resource management agencies and the necessity for trained professionals in the growing field of wildlife management, the program has grown from the original 9 wildlife-only units to a program that today includes 40 Cooperative Fish and Wildlife Research Units located on university campuses in 38 States. The partnerships that form each unit are some of the USGS’s strongest links to Federal and State land and natural resource agencies as mandated by the Cooperative Research and Training Units Act of 1960 (P.L. 86–686). This report highlights the activities and accomplishments of the program and its cooperators for calendar year 2020.

Circular

The river and the rocks: The geologic story of Great Falls and the Potomac River Gorge

The Great Falls of the Potomac River has figured prominently in the purposes of men since prehistoric time. Long before John Smith reached the falls in 1609, groups of Indians from East and West met at this great river barrier to trade and perform ceremonies in honor of the spirit of the "Roaring Waters". As early as 1754, George Washington visualized the Potomac River as an important avenue of trade and communication with the interior. Records show that with the exception of Mount Vernon, Great Falls was perhaps as intimately associated with George Washington's everyday life as any other place in the country. As first President of the "Patowmack Canal Company," Washington frequently visited the working parties as they constructed the canal and lock system which skirted the treacherous falls on the Virginia side. Matildaville, a town of about 40 acres named after the wife of "Light Horse" Harry Lee and consisting of various dwellings, grist mill, market house, forge, sawmill, and tavern, sprang up along the banks of the canal. In 1802, the Patowmack Company canals were essentially completed, and hundreds of boats plied the river, bringing corn and wheat, coal and limestone, flaxseed and furs downstream from the mountainous region of Cumberland. Many of the boats were sold for lumber in Georgetown, thus sparing the boatmen an arduous upstream journey. After the establishment of the Nation's Capital, Great Falls became a popular scenic attraction for residents and visitors alike. But Great Falls was not always so easily accessible as it is today. In 1845, a newspaper columnist, after praising the beauty and historic interest of the region, added, "... the access to this interesting spot is, on both sides of the river, by the most infamous of roads and the accommodations for visitors anything but what they ought to be!" Visitors to Great Falls now number close to a half million annually and, because of this continuing and mounting interest, the U.S. Geological Survey has joined with the National Park Service in preparing this booklet for better understanding and enjoyment of the Great Falls of the Potomac River.

Maryland, Virginia

Does Europa have a subsurface ocean? Evaluation of the geological evidence

It has been proposed that Jupiter's satellite Europa currently possesses a global subsurface ocean of liquid water. Galileo gravity data verify that the satellite is differentiated into an outer H 2 O layer about 100 km thick but cannot determine the current physical state of this layer (liquid or solid). Here we summarize the geological evidence regarding an extant subsurface ocean, concentrating on Galileo imaging data. We describe and assess nine pertinent lines of geological evidence: impact morphologies, lenticulae, cryovolcanic features, pull‐apart bands, chaos, ridges, surface frosts, topography, and global tectonics. An internal ocean would be a simple and comprehensive explanation for a broad range of observations; however, we cannot rule out the possibility that all of the surface morphologies could be due to processes in warm, soft ice with only localized or partial melting. Two different models of impact flux imply very different surface ages for Europa; the model favored here indicates an average age of ∼50 Myr. Searches for evidence of current geological activity on Europa, such as plumes or surface changes, have yielded negative results to date. The current existence of a global subsurface ocean, while attractive in explaining the observations, remains inconclusive. Future geophysical measurements are essential to determine conclusively whether or not there is a liquid water ocean within Europa today.

Journal of Geophysical Research: Planets

Geology of the petroleum and coal deposits in the North China basin, eastern China

The North China basin evolved initially from a rifted intracratonic graben system on the east-central Sino-Korean platform during the Jurassic and Cretaceous Yanshanian orogeny. The basin reached its maximum stage of development in the Neogene owing to rift reactivation by the Himalayan orogeny. As indicated by geophysical data, extensional rifting within the basin is still active today.

North China basin

New quantitative evidence of extreme warmth in the Pliocene Arctic

The most recent geologic interval characterized by warm temperatures similar to those projected for the end of this century occurred about 3.3 to 3.0 Ma, during the mid-Piacenzian Age of the Pliocene Epoch. Climate reconstructions of this warm period are integral to both understanding past warm climate equilibria and to predicting responses to today's transient climate. The Arctic Ocean is of particular interest because in this region climate proxies are rare, and climate models struggle to predict climate sensitivity and the response of sea ice. In order to provide the first quantitative climate data from this region during this interval, sea surface temperatures (SST) were estimated from Ocean Drilling Program Sites 907 and 909 in the Nordic Seas and from Site 911 in the Arctic Ocean based on Mg/Ca of Neogloboquadrina pachyderma (sin) and alkenone unsaturation indices. Evidence of much warmer than modern conditions in the Arctic Ocean during the mid-Piacenzian with temperatures as high as 18C is presented. In addition, SST anomalies (mid-Piacenzian minus modern) increase with latitude across the North Atlantic and into the Arctic, extending and confirming a reduced mid-Piacenzian pole-to-equator temperature gradient. The agreement between proxies and with previously documented qualitative assessments of intense warming in this region corroborate a poleward transport of heat and an at least seasonally ice-free Arctic, conditions that may serve as a possible analog to future climate if the current rate of Arctic sea-ice reduction continues.

Stratigraphy

Critical minerals in Climax-type magmatic-hydrothermal systems

Today’s global economy is challenged to meet the growing demand for commodities used in existing and emerging advanced technologies. Critical minerals are commodities found in a wide variety of ore deposits that are vital to the economic or national security of individual nations that are vulnerable to supply disruption. The U.S. Geological Survey is striving to advance understanding of critical mineral resources by employing a Mineral Systems approach. Climax-type systems are one of 17 mineral systems currently under investigation. The aim of this work is to inventory and assess knowledge gaps on the abundance of 50 critical minerals in Climax-type systems. Here we synthesize geochemical data from ore concentrates, ore, waste, and minerals together with information on production from, and resources in, ore deposits. The goal of this work is to estimate the amount of critical minerals present in processed mine waste and unmined resources, discuss those that could potentially be recovered in the future, and identify important future areas of research.

Conference Paper

Isotopic evidence for shifts in atmospheric circulation patterns during the late Quaternary in mid-North America

Wyoming is now at the eastern margin of westerlies originating in the Pacific, but in the Pleistocene appears to have received moisture from elsewhere, possibly the Gulf of Mexico. Oxygen isotope ratios of pedogenic carbonate in postglacial terraces correspond to ratios in equilibrium with present meteoric waters, which show a strong relation to precipitation seasonality and storm sources. In contrast, the oxygen isotope ratios of all pre-Holocene soils are significantly more positive, even though the carbon isotope composition of coexisting organic matter suggests that the carbonate formed in temperatures cooler than today. The oxygen isotope ratios of paleowaters in mid–North America appear to be more useful for identifying past storm sources than for estimating paleotemperatures.

Geology

U.S. Geological Survey response to white-nose syndrome in bats

Overview Since its discovery in 2007, the fungal disease known as white-nose syndrome (WNS) has killed more than six million bats. Ten of 47 bat species have been affected by WNS across 32 States and 5 Canadian Provinces. The cold-growing fungus ( Pseudogymnoascus destructans ) that causes WNS infects skin covering the muzzle, ears, and wings of hibernating bats. The fungus erodes deep into the vitally important skin of bat wings and fatally disrupts hibernation of bats through physical damage and energy depletion as they try to cope with infection. U.S. Geological Survey (USGS) science has been critical in identifying the causal fungus, characterizing the effects of WNS, and tracking the fungus as it rapidly spreads through many populations of bats in North America. Early USGS research enhanced our understanding of how WNS affects individual bats and how the fungus persists in the environment. Today, USGS scientists are engaged in a nationwide response to WNS, in close coordination with our partners at the U.S. Fish and Wildlife Service (USFWS), National Park Service (NPS), and U.S. Forest Service (USFS).

Fact Sheet

Geology of the Monte Blanco borate deposits, Furnace Creek Wash, Death Valley, California

The Monte Blanco borate deposits are located along the southern margin of Death Valley’s Furnace Creek Wash, south of Twenty Mule Team Canyon road in California. Topographic and geologic mapping by S. Muessig and F.M. Byers, Jr., in 1954 documented these deposits’ geologic settings, geometries, mineralogies, and chemical characteristics. They estimated borate resources at the time to be in excess of 550,000 tons B 2 O 3 . The borate bodies are composed of predominantly ulexite and colemanite. They lie beneath Monte Blanco itself and along a northwest-trending series of conspicuous, white hills and mounds formed by northeasterly dipping, fine-grained sedimentary beds and basaltic volcanic rocks of the Miocene and Pliocene Furnace Creek Formation. Geologic data suggest that in Miocene and Pliocene time, fine-grained sediments, volcanic debris and flows, and volcanically associated, boron-rich fluids gradually filled a fairly flat playa-like environment. At times, thick beds of felty crystals of ulexite developed and were interlayered as lenses in a thick series of mudstones as is seen today at the Eagle Borax works. After burial, the exterior of the ulexite deposit was altered to massive colemanite by ground water, which produced the “shell” of colemanite that typically surrounds the presently outcropping ulexite bodies.

California

Our changing continent

Where were the land areas and oceans of the North American Continent one million years ago, compared to our present geography? Was North America always about the same size and shape as it is today? To answer these questions, we must construct maps of the lands and sea that existed during the past ages. This process of reconstructing ancient geography is called paleogeography (from the Greek word "palaios," meaning ancient).

Monograph

An introduction to standardized sampling

It was probably one of the oddest riots in the history of the United States. In Erie, Pennsylvania during 1853. federal marshals were called to restore order during bloody uprisings. A mob of women, equipped with sledgehammers, was tearing up railroad rack to protest standardization of track width (Nesmith 1985). All across the United States, standardization of rail gauges was talking place to improve transportation across the country,but many people did not want consistency. Jobs moving freight from, a train running on one gauge of track to a train running on another gauge were plentiful at this time, and standardization would mean these jobs would disappear. Fortunately, for us today, the riots were quelled and standardization of railroad tack gauges went ahead. The magnificent transportation system of North America was aided by the standardization of rails, contributing to robust economies. Standardization of industrial processes, languages, measurements, and data collection methods has been essential for world progress (Figure 1.1). Today , we are often unaware of the degree of standardization of the most basic elements of our society--from bolts and nuts where thread sizes are standard to computer components that can be used interchangeably to the standard sizes of photos we carry in our wallets or purses. Data collection and presentation are standardized in many disciplines, including medicine, meteorology, geology, and water chemistry. For example, our cholesterol, body temperature, and blood pressure are measured by standard medical tests and compared to averages calculated from the results of the same standard tests for many other people to determine if individuals are higher, lower, or average compared to the population in general. If these diagnostic tests were not standardized, it is unlikely that we would be able to evaluate eve the most basic data about our health. In fact, if standardization was not used in countless other facets of our society our lives would be much more difficult. For data collection purposes, standardization means to collect data in one way so comparisons can be easily made. Although routine data collection has been standardized in many other disciplines, data from freshwater fish sampling across North America have not. Previously, most data collection has been standardized only at local, state, and provincial levels (Bonar and Hubert 2002). Several years ago, when one of the authors (Bonar) was a biologist for a state agency, he was asked to compile as much data as he could about the state's warmwater fish communities to provide information to managers developing fishing regulations. These data had been collected by many biologists over time using different methods, including rotenone, electrofishing, gill netting, and hook-and-line sampling. Data were written carefully on detailed data sheets or in scribbled notes in a biologists's notebook. As you can imagine, these data were a nightmare to compile. However, they were even worse to interpret. How could length-frequency distributions be compared among lakes if the methods used to catch the fish were dissimilar with differing efficiencies in sampling fish of various species and lengths? How could catch per unit effort (CPUE), a common index of population density, be compared when samples were collected one year using fyke nets and the next year by electrofishing? Ultimately, how could one compare if fish population were high, low, or average in growth, body condition, or abundance if there was no compilation of distributions of standard data to facilitate comparison? Months were spent trying to interpret these data, and finally a body of comparable data gathered by similar methods was assimilated. However, much of the nonstandard data had to be discarded--data that had taken thousands of hours to collect but were essentially useless. If all data jhad been collected and recorded in a standard manner, whoch would have required very little extra work, all of these hours of survey effort would not have gone to naught and isights regardimng the fisheries would have been imporived by a larger number of samples.

Book chapter

Contaminants from Cretaceous black shale: I. Natural weathering processes controlling contaminant cycling in Mancos Shale, southwestern United States, with emphasis on salinity and selenium

Soils derived from black shale can accumulate high concentrations of elements of environmental concern, especially in regions with semiarid to arid climates. One such region is the Colorado River basin in the southwestern United States where contaminants pose a threat to agriculture, municipal water supplies, endangered aquatic species, and water-quality commitments to Mexico. Exposures of Cretaceous Mancos Shale (MS) in the upper basin are a major contributor of salinity and selenium in the Colorado River. Here, we examine the roles of geology, climate, and alluviation on contaminant cycling (emphasis on salinity and Se) during weathering of MS in a Colorado River tributary watershed. Stage I (incipient weathering) began perhaps as long ago as 20 ka when lowering of groundwater resulted in oxidation of pyrite and organic matter. This process formed gypsum and soluble organic matter that persist in the unsaturated, weathered shale today. Enrichment of Se observed in laterally persistent ferric oxide layers likely is due to selenite adsorption onto the oxides that formed during fluctuating redox conditions at the water table. Stage II weathering (pedogenesis) is marked by a significant decrease in bulk density and increase in porosity as shale disaggregates to soil. Rainfall dissolves calcite and thenardite (Na 2 SO 4 ) at the surface, infiltrates to about 1 m, and precipitates gypsum during evaporation. Gypsum formation (estimated 390 kg m −2 ) enriches soil moisture in Na and residual SO 4 . Transpiration of this moisture to the surface or exposure of subsurface soil (slumping) produces more thenardite. Most Se remains in the soil as selenite adsorbed to ferric oxides, however, some oxidizes to selenate and, during wetter conditions is transported with soil moisture to depths below 3 m. Coupled with little rainfall, relatively insoluble gypsum, and the translocation of soluble Se downward, MS landscapes will be a significant nonpoint source of salinity and Se to the Colorado River well into the future. Other trace elements weathering from MS that are often of environmental concern include U and Mo, which mimic Se in their behavior; As, Co, Cr, Cu, Ni, and Pb, which show little redistribution; and Cd, Sb, V, and Zn, which accumulate in Stage I shale, but are lost to varying degrees from upper soil intervals. None of these trace elements have been reported previously as contaminants in the study area.

Colorado

Integrated geophysical analysis provides an alternate interpretation of the northern margin of the North American Midcontinent Rift System, Central Lake Superior

The Midcontinent Rift System (MRS) is a 1.1 Ga sequence of voluminous basaltic eruptions and multiple intrusions followed by widespread sedimentation that extends across the Midcontinent and northern Great Lakes region of North America. Previous workers have commonly used seismic-reflection data (Great Lakes International Multidisciplinary Program on Crustal Evolution [GLIMPCE] line A) to demonstrate that the northern rift margin in central Lake Superior developed as a normal growth fault that was structurally inverted to a reverse fault during a compressional event after rifting had ended. A prominent, curvilinear aeromagnetic anomaly that extends from Isle Royale, Michigan, to Superior Shoal in central Lake Superior, Ontario (the IR-SS anomaly), is commonly presented as a manifestation of this reverse fault. We have integrated multidisciplinary geophysical analyses (seismic-reflection, seismic-refraction, aeromagnetic, and gravity), physical-property information (density, magnetic susceptibility and remanence, and compressional-wave velocity), and geologic concepts to develop an alternate interpretation of the rift margin along GLIMPCE line A, where it intersects the IR-SS anomaly. Our new model indicates that a normal fault is the dominant structure at the northern rift margin along line A, contrary to the original rift-margin paradigm, which asserts that compressional structures are the dominant features preserved today. Integral to this alternate model is a newly interpreted, prerift sedimentary basin intruded by sills in northern Lake Superior. Our alternate model of the northern rift margin has implications for interpreting the style, scale, and timing of extension, rift-related intrusion, and compression during development of the MRS.

Lake Superior

Hydrologic implications of solid-water disposal

The disposal of more than 1,400 million pounds of solid wastes in the United States each day is a major problem. This disposal in turn often leads to serious health, esthetic, and environmental problems. Among these is the pollution of vital ground-water resources. Of the six principal methods of solid-waste disposal in general use today, four methods-open dumps, sanitary landfill, incineration, and onsite disposal-carry an inherent potential for pollution of water resources. Seepage of rainwater through the wastes leaches undesirable constituents which reach the ground water in the area. This leachate is generally both biologically and chemically contaminated. The extent of the pollution from this leachate is largely dependent upon the geologic environment in which the solid wastes are deposited. Pollution potential is highest in permeable areas with a shallow water table where the wastes are in direct contact with the ground water. In a relatively impermeable area, the pollution is generally confined locally to the vicinity of the waste-disposal site. Site selection for disposal of solid wastes must be based on adequate water-resources information if pollutional potential is to be minimized. This will require regional as well as localized data on the water resources of the area. Only through such an approach can adequate protection be afforded to the environment in general and the water resources in particular.

Circular