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At least 955 records · Page 53Linked to original sources
USGS2004

Surficial Geologic Map of the Great Smoky Mountains National Park Region, Tennessee and North Carolina

The Surficial Geology of the Great Smoky Mountains National Park Region, Tennessee and North Carolina was mapped from 1993 to 2003 under a cooperative agreement between the U.S. Geological Survey (USGS) and the National Park Service (NPS). This 1:100,000-scale digital geologic map was compiled from 2002 to 2003 from unpublished field investigations maps at 1:24,000-scale. The preliminary surficial geologic data and map support cooperative investigations with NPS, the U.S. Natural Resource Conservation Service, and the All Taxa Biodiversity Inventory (http://www.dlia.org/) (Southworth, 2001). Although the focus of our work was within the Park, the geology of the surrounding area is provided for regional context. Surficial deposits document the most recent part of the geologic history of this part of the western Blue Ridge and eastern Tennessee Valley of the Valley and Ridge of the Southern Appalachians. Additionally, there is great variety of surficial materials, which directly affect the different types of soil and associated flora and fauna. The surficial deposits accumulated over tens of millions of years under varied climatic conditions during the Cenozoic era and resulted from a composite of geologic processes.

North Carolina, Tennessee↗
USGS2021

Warming sea surface temperatures fuel summer epidemics of eelgrass wasting disease

Seawater temperatures are increasing, with many unquantified impacts on marine diseases. While prolonged temperature stress can accelerate host-pathogen interactions, the outcomes in nature are poorly quantified. We monitored eelgrass wasting disease (EWD) from 2013-2017 and correlated mid-summer prevalence of EWD with remotely sensed seawater temperature metrics before, during, and after the 2015-2016 marine heatwave in the northeast Pacific, the longest marine heatwave in recent history. Eelgrass shoot density declined by 60% between 2013 and 2015 and did not recover. EWD prevalence ranged from 5-70% in 2013 and increased to 60-90% by 2017. EWD severity approximately doubled each year between 2015 and 2017. EWD prevalence was positively correlated with warmer temperature for the month prior to sampling while EWD severity was negatively correlated with warming prior to sampling. This complex result may be mediated by leaf growth; bigger leaves may be more likely to be diseased, but may also grow faster than lesions, resulting in lower severity. Regional stressors leading to population declines prior to or early in the heatwave may have exacerbated the effects of warming on eelgrass disease susceptibility and reduced the resilience of this critical species.

Marine Ecology Progress Series↗
USGS1997

New explorations along the northern shores of Lake Bonneville

This field trip begins in Salt Lake City and makes a clockwise circuit of Great Salt Lake, with primary objectives to observe stratigraphie and geomorphic records of Lake Bonneville. Stops include Stansbury Island, Puddle Valley, gravel pits at Lakeside and the south end of the Hogup Mountains, several stops in Curlew Valley and Hansel Valley, and a final stop at the north end of Great Salt Lake east of the Promontory Mountains. Stratigraphie observations at gravel-pit and natural exposures will be linked to interpretations of lake-level change, which were caused by climate change. Evidence of paleoseismic and volcanic activity will be discussed at several sites, and will be tied to the lacustrine stratigraphic record. The trip provides an overview of the history of Lake Bonneville and introduces participants to some new localities with excellent examples of Lake Bonneville landforms and stratigraphy.

Brigham Young University Geology Studies↗
USGS2018

Genetic integrity, population status, and long-term viability of isolated populations of shoal bass in the upper Chattahoochee River basin, Georgia

This report characterizes the status of multiple isolated Shoal Bass ( Micropterus cataractae ) populations in the upper Chattahoochee River basin (UCRB), Georgia. The Shoal Bass, a sport fish endemic to the Apalachicola-Chattahoochee-Flint River (ACF) basin, is a fluvial-specialist species considered vulnerable to local extirpations and extinction due to habitat fragmentation and introgression with non-native congeners. Perhaps one of the most isolated populations of Shoal Bass exists in a 2-km reach of Big Creek, a tributary of the Chattahoochee River located near Roswell, Georgia. Big Creek is partially contained within the Chattahoochee River National Recreation Area, although the Big Creek watershed is riddled with urban land cover. Roswell Mill Dam limits the upstream extent of the Shoal Bass population at Big Creek, and the downstream extent is presumably limited to the confluence of Big Creek and the Chattahoochee River. This reach of the Chattahoochee River is thermally depressed because of coldwater releases from Lake Lanier, and is considered unsuitable for Shoal Bass. Herein, we examine the genetic integrity, population status, and long-term viability of the Shoal Bass population in Big Creek. We also examine two additional Shoal Bass populations that occur in the UCRB, specifically the Chestatee River and the upper Chattahoochee River, both of which are impounded at Lake Lanier. Together, the Shoal Bass inhabiting these three stream systems comprise a distinct genetic stock of Shoal Bass (Taylor 2017), underscoring the importance of conserving these populations towards maintaining the overall diversity and adaptive potential of the species. We assessed genetic diversity and estimated effective population sizes within these three rivers by genotyping fish with 16 microsatellite DNA markers. Results demonstrated that the Shoal Bass population in Big Creek has experienced high rates of introgression with non-native Smallmouth Bass (M. dolomieu), purportedly introduced into the Chattahoochee River in the past 10-15 years. Alarmingly, only 24% (15 of 62) of putative Shoal Bass collected from Big Creek were genetically pure Shoal Bass, whereas the majority of fish were first-filial (F1) generation hybrids and unidirectional backcrosses towards Shoal Bass. Fleeting opportunity may remain to conserve the native genome of the Shoal Bass population in Big Creek. High hybridization rates prevented genetic diversity analysis for the Big Creek population. Shoal Bass populations in the Chestatee and Chattahoochee rivers displayed levels of genetic diversity similar to populations that persist in other rivers in the ACF basin, namely the Flint and Chipola rivers. Effective population sizes of 93.8– 197.4 for the Chestatee and Chattahoochee rivers (combined) suggest that the conservation status of these populations is stable for the short-term, but may be at risk of losing genetic diversity and adaptive potential in the long-term. To estimate age and mortality of the three populations, we used fish scales and capture-markrecapture (CMR) as complementary, non-lethal methods for age estimation. Estimated ages of phenotypic Shoal Bass ranged from 1-12 years in all three populations, demonstrating increased longevity compared to populations elsewhere within the native range. Catch-curve estimates of annual mortality ranged from 18.4-23.7%, which are markedly lower than those observed in other Shoal Bass populations in the ACF basin. These differences in life-history characteristics underscore the need for the development of population-specific management and conservation strategies for Shoal Bass in the UCRB. The lowest recruitment variability (i.e., the variation in year-class strength) was observed in the Chestatee River, a forested watershed, whereas the highest variability was observed in Big Creek, an urbanized watershed. Recruitment strength in Big Creek was negatively influenced by discharge variability in the summer months, suggesting that flashy, sediment-laden flows hinder survival of recently hatched young. Other statistically significant models from Big Creek and the Chattahoochee River indicated that over-winter survival could be an important pinch-point for recruitment in UCRB populations. A multi-agency sampling effort was conducted from May 2013-May 2016 to estimate the population size of Shoal Bass occupying the 1-km of wadeable shoal habitats in Big Creek. Using CMR models, we estimated that approximately 219-348 Shoal Bass (≥ 70 mm total length) occupied the area throughout the duration of our study. These estimates largely reflect abundance of individuals aged 0-2 years, as only 9% (36 of 408) tagged fish were aged ≥ 7 years. Local abundance appeared similar to that reported for a population that inhabited Little Uchee Creek, a similar-sized tributary of the Chattahoochee River, prior to its recent functional extirpation. The low abundance of large, adult Shoal Bass further suggests the long-term viability of the Big Creek population may be in jeopardy. Perhaps most importantly, CMR estimates reflect abundance of phenotypic Shoal Bass – genetic analyses suggest the abundance of pure Shoal Bass could be an order of magnitude smaller. To evaluate the potential for adult Shoal Bass to emigrate from Big Creek into the mainstem Chattahoochee River, we tagged eight adults with acoustic telemetry tags and assessed their seasonal residency at two stationary receiver locations located in increasing proximity to the confluence with the Chattahoochee River. Fish took up residency near the confluence during the fall and winter months, during which time water temperatures in Big Creek were periodically colder than the Chattahoochee River. Although we were unable to document emigration, we conclude that the potential for emigration is highest during the winter months when the Chattahoochee River may be warmer than Big Creek. Two of the tagged fish were caught by anglers near the confluence, suggesting that angling pressure at Big Creek may be higher than previously suspected. Overall, this study observed unique life-history characteristics and characterized the population status of multiple Shoal Bass populations in the UCRB. Populations in the Chestatee and Chattahoochee rivers appear stable at present and likely represent the last remaining strongholds for pure Shoal Bass in the UCRB. Efforts to preserve forested watershed conditions, natural hydrology, and shoal habitats would contribute to the long-term persistence of Shoal Bass populations in these two rivers. Additionally, the detection of non-native Alabama Bass and their associated hybrids in both rivers is cause for concern. Diligent monitoring of hybridization dynamics between Alabama Bass and Shoal Bass is warranted, along with an assessment of Alabama Bass invasion extent upstream of Lake Lanier. The Shoal Bass population in Big Creek is threatened by elevated levels of introgression with nonnative Smallmouth Bass, recruitment variability, low abundance of adults, and isolation from other populations. Conservation intervention is urgently needed to restore and preserve this genetically distinct population, which would contribute to preservation of range wide genetic diversity and adaptability of the species. Additionally, an urban sport fishery for Shoal Bass at Big Creek has the potential to serve as a tool for increasing public awareness, engagement, and support of Shoal Bass conservation efforts in the UCRB. We suggest strategies for conservation of the remnant shoal habitats and Shoal Bass population in Big Creek, including potential development of a supplemental stocking program, selective removal of non-native congeners, and delivery of environmental education programs that could bolster awareness and appreciation.

Georgia↗
USGS2023

Characterizing historic streamflow to support drought planning in the upper Missouri River basin

This project combined tree-ring based paleo and modern climate and hydrologic research aimed at understanding the primary influences on drought risk and water reliability in basins critical for western U.S. water resources. New paleohydrologic datasets and analyses were developed and applied to contextualize future streamflow projections and address specific water management questions. These questions centered around optimizing future water management protocols for numerous objectives ranging from improving agricultural water allocation during drought while maintaining instream flows for aquatic ecosystem health, to the testing of operations across large river systems with complex infrastructure critical for downstream flood control, navigation, and hydropower generation. USGS scientists worked closely with the Bureau of Reclamation to estimate both past and future drought risk at key management locations throughout the Missouri basin, the Milk and St. Mary River system, and across the major managed river systems in the western United States. These efforts provided a roadmap for future water management strategies under changing climate and water supply conditions, which are detailed in Reclamation’s newly completed Missouri Headwaters Basin Study, the 2021 SECURE Water Act Report, and the forthcoming update of the St. Mary and Milk Rivers Basin Study. Among the major scientific findings to emerge was a new understanding of the long-term (1200-year) history of drought variability for the Missouri River, which highlighted the unusual severity of the early 2000s drought across the Rocky Mountain headwaters and adjacent high plains. By combining the extended drought record with extensive modern and paleoclimate records, we document how warming exacerbates severities of naturally occurring droughts, with recent decades defined by “hot” droughts and the 2000s (2001-2010) drought ranking as the most severe event in 1200 years. Increasingly severe drought events such as this strain already over-allocated water resources that multiple sectors of society depend heavily upon.

upper Missouri River basin↗
USGS2024

Secondary contact erodes Pleistocene diversification in a wide-ranging freshwater mussel (Quadrula)

The isolated river drainages of eastern North America serve as a natural laboratory to investigate the roles of allopatry and secondary contact in the evolutionary trajectories of recently diverged lineages. Drainage divides facilitate allopatric speciation, but due to their sensitivity to climatic and geomorphological changes, neighboring rivers frequently coalesce, creating recurrent opportunities of isolation and contact throughout the history of aquatic lineages. The freshwater mussel Quadrula quadrula is widely distributed across isolated rivers of eastern North America and possesses high phenotypic and molecular variation across its range. We integrate sequence data from three genomes, including female- and male-inherited mitochondrial markers and thousands of nuclear encoded SNPs with morphology and geography to illuminate the group's divergence history. Across contemporary isolated rivers, we found continuums of molecular and morphological variation, following a pattern of isolation by distance. In contact zones, hybridization was frequent with no apparent fitness consequences, as advanced hybrids were common. Accordingly, we recognize Q. quadrula as a single cohesive species with subspecific variation ( Q. quadrula rumphiana ). Demographic modeling and divergence dating supported a divergence history characterized by allopatric vicariance followed by secondary contact, likely driven by river rearrangements and Pleistocene glacial cycles. Despite clinal range-wide variation and hybridization in contact zones, the process-based species delimitation tool delimitR, which considers demographic scenarios like secondary contact, supported the delimitation of the maximum number of species tested. As such, when interpreting species delimitation results, we suggest careful consideration of spatial sampling and subsequent geographic patterns of biological variation, particularly for wide-ranging taxa.

eastern North America↗
USGS2003

Holocene evolution of the western Orinoco Delta, Venezuela

The pristine nature of the Orinoco Delta of eastern Venezuela provides unique opportunities to study the geologic processes and environments of a major tropical delta. Remote-sensing images, shallow cores, and radiocarbon-dating of organic remains form the basis for describing deltaic environments and interpreting the Holocene history of the delta. The Orinoco Delta can be subdivided into two major sectors. The southeast sector is dominated by the Rio Grande-the principal distributary-and complex networks of anastomosing fluvial and tidal channels. The abundance of siliciclastic deposits suggests that fluvial processes such as over-bank flooding strongly influence this part of the delta. In contrast, the northwest sector is represented by few major distributaries, and overbank sedimentation is less widespread relative to the southeast sector. Peat is abundant and occurs in herbaceous and forested swamps that are individually up to 200 km2 in area. Northwest-directed littoral currents transport large volumes of suspended sediment and produce prominent mudcapes along the northwest coast. Mapping of surface sediments, vegetation, and major landforms identified four principal geomorphic systems within the western delta plain: (1) distributary channels, (2) interdistributary flood basins, (3) fluvial-marine transitional environments, and (4) marine-influenced coastal environments. Coring and radiocarbon dating of deltaic deposits show that the northern delta shoreline has prograded 20-30 km during the late Holocene sea-level highstand. Progradation has been accomplished by a combination of distributary avulsion and mudcape progradation. This style of deltaic progradation differs markedly from other deltas such as the Mississippi where distributary avulsion leads to coastal land loss, rather than shoreline progradation. The key difference is that the Orinoco Delta coastal zone receives prodigious amounts of sediment from northwest-moving littoral currents that transport sediment from as far away as the Amazon system (???1600 km). Late Holocene progradation of the delta has decreased delta-plain gradients, increased water levels, and minimized over-bank flooding and siliciclastic sedimentation in the northwest sector. These conditions, coupled with large amounts of direct precipitation, have led to widespread peat accumulation in interdistributary basins. Because peat-forming environments cover up to 5000 km2 of the delta plain, the Orinoco may be an excellent analogue for interpreting ancient deltaic peat deposits.

Geological Society of America Bulletin↗
USGS2022

New Jersey and Landsat

New Jersey ranks among the smallest of States but packs a lot within its borders. Of course, that includes the more than 9 million people who make it the most densely populated State, but it also includes diverse landscapes. Ranging from Atlantic Ocean barrier islands and beaches to the Appalachian Mountains, and Pine Barrens forests to swampland, the “Garden State” retains remnants of an agricultural past with produce, horse, and dairy farms and plant nurseries. The third State to join the Union has had a strong geographic presence in U.S. history. More than 200 American Revolution battles and skirmishes were fought in New Jersey—more than in any other State. Manufacturing, tourism, and fishing have each had a significant effect on New Jersey’s industrial history. Today, many residents commute from this strategic location to work in New York City, just across the Hudson River to the northeast, or in Philadelphia, just across the Delaware River to the west. A dense population and environmental changes can increase risks for residents and the natural resources around them. Landsat helps officials monitor and plan for resilient cities and landscapes.

New Jersey↗
USGS1992

Crystalline Silica Primer

Crystalline silica is the scientific name for a group of minerals composed of silicon and oxygen. The term crystalline refers to the fact that the oxygen and silicon atoms are arranged in a threedimensional repeating pattern. This group of minerals has shaped human history since the beginning of civilization. From the sand used for making glass to the piezoelectric quartz crystals used in advanced communication systems, crystalline silica has been a part of our technological development. Crystalline silica's pervasiveness in our technology is matched only by its abundance in nature. It's found in samples from every geologic era and from every location around the globe. Scientists have known for decades that prolonged and excessive exposure to crystalline silica dust in mining environments can cause silicosis, a noncancerous lung disease. During the 1980's, studies were conducted that suggested that crystalline silica also was a carcinogen. As a result of these findings, crystalline silica has been regulated under the Occupational Safety and Health Administration's (OSHA) Hazard Communication Standard (HCS). Under HCS, OSHAregulated businesses that use materials containing 0.1% or more crystalline silica must follow Federal guidelines concerning hazard communication and worker training. Although the HCS does not require that samples be analyzed for crystalline silica, mineral suppliers or OSHAregulated businesses may choose to do so if they wish to show that they are exempt from the requirements of HCS. Because crystalline silica is an extremely common mineral and the HCS will affect many mineral commodities, it is important then, that there be as clear an understanding as possible of what is and what is not crystalline silica, and where it is found and used, and how it is qualitatively and quantitatively identified. This primer is an attempt to accomplish this in as nontechnical a manner as possible. This primer will examine crystalline silica. Part I will describe, in nonscientific terms, what crystalline silica is and how we come in contact with it. Part II will discuss the regulatory decisions that have created new interest in this ancient and widespread substance and will present a nontechnical overview of the techniques used to measure crystalline silica. Because this primer is meant to be a starting point for anyone interested in learning more about crystalline silica, a list of selected readings and other resources is included. The detailed glossary, which defines many terms that are beyond the scope of this publication, is designed to help the reader move from this presentation to a more technical one, the inevitable next step.

Special Publication↗
USGS2019

Evaluation of potential sources of sauger Sander canadensis for reintroduction into Lake Erie

Sauger ( Sander canadensis ) supported recreational and commercial fisheries in Lake Erie until the fishery collapsed in the early-1950s, with extirpation of sauger occurring soon after. Previous attempts to rebuild populations via stocking programs were unsuccessful, and the reasons for lack of success are unclear. The Ohio Department of Natural Resources-Division of Wildlife is re-examining the feasibility of reintroducing sauger because the current fish community and habitat conditions appear more suitable for sauger survival and proliferation. Selecting potential sources for reintroduction programs requires consideration of several factors. Donor and recipient ecosystems and life histories should be similar, the source population should have sufficient genetic diversity to withstand losses in diversity associated with hatchery practices, and the source and donor populations should have similar genetic diversity metrics and should be accessible while broodstock is developed. A review of the literature and a genetic analysis of historical sauger collections from Lake Erie and contemporary samples from possible donor populations in five different watersheds was performed to evaluate potential candidate sources for a re-introduction program. We compared genetic diversity, life history parameters, and ecosystem conditions of historical Lake Erie sauger to contemporary sauger populations from the Ohio River (Bellville, Meldahl, and New Cumberland pools), Missouri River, Ottawa River, Lake of the Woods, and Lake Winnebago. While life history and ecological conditions were similar across populations, there was genetic differentiation among potential donor sources and historical collections of sauger from Lake Erie, with contemporary populations from the Ohio River being most like historic Lake Erie sauger.

Lake Erie↗
USGS2023

Impacts of spontaneous waterfall development on bedrock river longitudinal profile morphology

River profiles are shaped by climatic and tectonic history, lithology, and internal feedbacks between flow hydraulics, sediment transport and erosion. In steep channels, waterfalls may self-form without changes in external forcing (i.e., autogenic formation) and erode at rates faster or slower than an equivalent channel without waterfalls. We use a 1-D numerical model to investigate how self-formed waterfalls alter the morphology of bedrock river longitudinal profiles. We modify the standard stream power model to include a slope threshold above which waterfalls spontaneously form and a rate constant allowing waterfalls to erode faster or slower than other fluvial processes. Using this model, we explore how waterfall formation alters both steady state and transient longitudinal profile forms. Our model predicts that fast waterfalls create km-scale reaches in a dynamic equilibrium with channel slope held approximately constant at the threshold slope for waterfall formation, while slow waterfalls can create local channel slope maxima at the location of slow waterfall development. Furthermore, slow waterfall profiles integrate past base level histories, leading to multiple possible profile forms, even at steady-state. Consistency between our model predictions and field observations of waterfall-rich rivers in the Kings and Kaweah drainages in the southern Sierra Nevada, California, supports the hypothesis that waterfall formation can modulate river profiles in nature. Our findings may help identify how bedrock channels are influenced by waterfall erosion and aid in distinguishing between signatures of external and internal perturbations, thereby strengthening our ability to interpret past climate and tectonic changes from river longitudinal profiles.

Journal of Geophysical Research - Earth Surface↗
USGS2010

The 7Q10 in South Carolina water-quality regulation: Nearly fifty years later

The annual minimum 7-day average streamflow with a 10-year recurrence interval, often referred to as the 7Q10, has a long history of being an important low-flow statistic used in water-quality management in South Carolina as evidenced by its adoption into South Carolina law in 1967. State agencies, such as the South Carolina Department of Health and Environmental Control and the South Carolina Department of Natural Resources, use such lowflow statistics to determine Wasteload Allocations for National Pollutant Discharge Elimination System discharges, develop Total Maximum Daily Loads for streams, prepare the State Water Plan, and restrict the quantity of water that can be transferred out of basin. The U.S. Geological Survey, working cooperatively with the South Carolina Department of Health and Environmental Control, is updating low-flow statistics at continuous-record streamflow gages in South Carolina on a basin-by-basin approach. Such statistics are influenced by length of record and hydrologic conditions under which the record was collected. Statewide low-flow statistics in South Carolina were last updated in 1987. Since that time several droughts have occurred with the most severe occurring from 1998-2002 and the most recent occurring from 2006-2009. The low-flow statistics for the Pee Dee River basin were the first to be completed in this ongoing investigation.

South Carolina↗
USGS2011

40Ar∗ loss in experimentally deformed muscovite and biotite with implications for 40Ar/39Ar geochronology of naturally deformed rocks

The effects of deformation on radiogenic argon ( 40 Ar ∗ ) retentivity in mica are described from high pressure experiments performed on rock samples of peraluminous granite containing euhedral muscovite and biotite. Cylindrical cores, ∼15 mm in length and 6.25 mm in diameter, were drilled from granite collected from the South Armorican Massif in northwestern France, loaded into gold capsules, and weld-sealed in the presence of excess water. The samples were deformed at a pressure of 10 kb and a temperature of 600 °C over a period 29 of hours within a solid medium assembly in a Griggs-type triaxial hydraulic deformation apparatus. Overall shortening in the experiments was approximately 10%. Transmitted light and secondary and backscattered electron imaging of the deformed granite samples reveals evidence of induced defects and for significant physical grain size reduction by kinking, cracking, and grain segmentation of the micas. Infrared (IR) laser (CO 2 ) heating of individual 1.5–2.5 mm diameter grains of muscovite and biotite separated from the undeformed granite yield well-defined 40 Ar/ 39 Ar plateau ages of 311 ± 2 Ma (2σ). Identical experiments on single grains separated from the experimentally deformed granite yield results indicating 40 Ar ∗ loss of 0–35% in muscovite and 2–3% 40 Ar ∗ loss in biotite. Intragrain in situ ultraviolet (UV) laser ablation 40 Ar/ 39 Ar ages (±4–10%, 1σ) of deformed muscovites range from 309 ± 13 to 264 ± 7 Ma, consistent with 0–16% 40 Ar ∗ loss relative to the undeformed muscovite. The in situ UV laser ablation 40 Ar/ 39 Ar ages of deformed biotite vary from 301 to 217 Ma, consistent with up to 32% 40 Ar ∗ loss. No spatial correlation is observed between in situ 40 Ar/ 39 Ar age and position within individual grains. Using available argon diffusion data for muscovite the observed 40 Ar ∗ loss in the experimentally treated muscovite can be utilized to predict average 40 Ar ∗ diffusion dimensions. Maximum 40 Ar/ 39 Ar ages obtained by UV laser ablation overlap those of the undeformed muscovite, indicating argon loss of <1% and an average effective grain radius for 40 Ar ∗ diffusion ⩾700 μm. The UV laser ablation and IR laser incremental 40 Ar/ 39 Ar ages indicating 40 Ar ∗ loss of 16% and 35%, respectively, are consistent with an average diffusion radius ≪100 μm. These results support a hypothesis of grain-scale 40 Ar ∗ diffusion distances in undeformed mica and a heterogeneous mechanical reduction in the intragrain effective diffusion length scale for 40 Ar ∗ in deformed mica. Reduction in the effective diffusion length scale in naturally deformed samples occurs most probably through production of mesoscopic and submicroscopic defects such as, e.g., stacking faults. A network of interconnected defects, continuously forming and annealing during dynamic deformation likely plays an important role in controlling both 40 Ar ∗ retention and intragrain distribution in deformed mica. Intragrain 40 Ar/ 39 Ar ages, when combined with estimates of diffusion kinetics and distances, may provide a means of establishing thermochronological histories from individual micas.

Brittany↗
USGS2022

The cycles driving Io’s tectonics

Io is famous for its active volcanoes, but its vigorous tectonics, which are unlike Earth’s plate tectonics, are no less remarkable. The nature of Io’s thick, cold, brittle lithosphere has been revealed through decades of investigations. The dynamics of this system is most easily explained by considering three cycles: magmatic, tectonic, and sulfurous. The magmatic cycle transports heat by a “heat pipe” process that may have operated during the earliest histories of many of the rocky bodies in the Solar System. The subsidence of the erupted lavas drives mountain uplift in the tectonic cycle. Sulfurous fluids could have a significant impact on the movement of both heat and rock.

Elements↗
USGS2010

Why Study Paleoclimate?

U.S. Geological Survey (USGS) researchers are at the forefront of paleoclimate research, the study of past climates. With their unique skills and perspective, only geologists have the tools necessary to delve into the distant past (long before instrumental records were collected) in order to better understand global environmental conditions that were very different from today's conditions. Paleoclimatologists are geologists who study past climates to answer questions about what the Earth was like in the past and to enable projections, plans, and preparations for the future. The Intergovernmental Panel on Climate Change (IPCC) has projected a future warmer climate that has the potential to affect every person on Earth. Extreme weather events, rising sea level, and migrating ecosystems and resources could result in worldwide socio-economic stresses if not met with prudent and proactive action plans based on quality scientific research. Still, the most dangerous aspect of our changing climate is the uncertainty in the exact nature and rate of projected climate change. To reduce the uncertainties, USGS paleoclimatologists are studying a possible analog to a future warmer climate. The middle part of the Piacenzian Stage of the Pliocene Epoch, about 3.3 to 3.0 million years ago, is the most recent period in Earth's history in which global warmth reached and remained at temperatures similar to those projected for the end of this century, about 2 degrees C to 3 degrees C warmer on average than today over the entire globe. This past warmer time interval preceded the ice ages but was recent enough, geologically, to be very similar to today in terms of ocean circulation and the position of the continents. Also, the populations of plants and animals were much like those of today, and so geologists can use their fossils to estimate past environmental conditions such as temperature and sea level.

Fact Sheet↗
USGS2006

Geologic map of the national parks in the National Capital region, Washington, D.C., Virginia, Maryland, and West Virginia

More than 51,000 acres within the National Capital Region (NCR) are administered by the National Park Service (NPS). These parks consist of parkways, trails, statues, monuments, memorials, historic sites, scenic areas, theatres, parks for performing arts, and Civil War battlefields. Although largely established for historical and cultural resources, each park is situated on a landscape that is influenced by bedrock and surficial geology of the central Appalachian mid-Atlantic region. Geologic mapping and field studies conducted for over 130 years are summarized here to provide the earliest history of the parklands. The age, type, names, and the interpreted origin of the rocks, as well as the processes active in the formation of surficial deposits and the landscape are discussed. These data are intended for educational and interpretative programs for visitors as well as the management of natural resources.

District of Columbia, Maryland, Virginia↗
USGS2014

The hydrogeology of the Tully Valley, Onondaga County, New York: an overview of research, 1992-2012

Onondaga Creek begins approximately 15 miles south of Syracuse, New York, and flows north through the Onondaga Indian Nation, then through Syracuse, and finally into Onondaga Lake in central New York. Tully Valley is in the upper part of the Onondaga Creek watershed between U.S. Route 20 and the Valley Heads end moraine near Tully, N.Y. Tully Valley has a history of several unusual hydrogeologic phenomena that affected past land use and the water quality of Onondaga Creek; the phenomena are still present and continue to affect the area today (2014). These phenomena include mud volcanoes or mudboils, landslides, and land-surface subsidence; all are considered to be naturally occurring but may also have been influenced by human activity. The U.S. Geological Survey (USGS), in cooperation with the U.S. Environmental Protection Agency and the Onondaga Lake Partnership, began a study of the Tully Valley mudboils beginning in October 1991 in hopes of understanding (1) what drives mudboil activity in order to remediate mudboil influence on the water quality of Onondaga Creek, and (2) land-surface subsidence issues that have caused a road bridge to collapse, a major pipeline to be rerouted, and threatened nearby homes. Two years into this study, the 1993 Tully Valley landslide occurred just over 1 mile northwest of the mudboils. This earth slump-mud flow was the largest landslide in New York in more than 70 years (Fickies, 1993); this event provided additional insight into the geology and hydrology of the valley. As the study of the Tully Valley mudboils progressed, other unusual hydrogeologic phenomena were found within the Tully Valley and provided the opportunity to perform short-term, small-scale studies, some of which became graduate student theses—Burgmeier (1998), Curran (1999), Morales-Muniz (2000), Baldauf (2003), Epp (2005), Hackett, (2007), Tamulonis (2010), and Sinclair (2013). The unusual geology and hydrology of the Tully Valley, having been investigated for more than two decades, provides the basis for this report.

New York↗
USGS2018

Characterization and occurrence of confined and unconfined aquifers in Quaternary sediments in the glaciated conterminous United States

The glacial aquifer system, which is a collection of aquifers within Quaternary sediments in the glaciated conterminous United States, is a principal aquifer that supplies groundwater that serves about 42 million people and accounts for about 5 percent of the Nation’s drinking water. This aquifer system (the area of maximum glacial advance) underlies parts of 25 States and covers 1.87×10 6 square kilometers. A hydrogeologic framework is presented that divides the glaciated United States into 17 distinct hydrogeologic terranes using a geologic approach based on previous mapping. Each hydrogeologic terrane contains Quaternary sediment that is derived from a common depositional history and can be characterized by similar texture and thickness. Characteristics of Quaternary sediments are described using attributes computed from a lithologic database of well logs compiled from 24 States (excluding Kentucky). The hydrogeologic framework presents a nationwide picture of the glacial aquifer system and provides generalizations concerning the nature of aquifers within it (for example, whether the aquifers are shallow or deep, and unconfined or confined). In this way insights can be gained from understanding the similarities and differences in distinct parts of the glacial aquifer system and how they relate to water use and quality and to aquifer vulnerability. Delineation of hydrogeologic terranes was based on an interpretation of existing geologic mapping of Quaternary sediments and the thickness of unconsolidated material. Overall thickness of Quaternary sediment was used to qualitatively rank the generalized complexity of the hydrogeologic framework in each terrane: “lower” complexity (assigned a terrane code 1), “moderate” complexity (terrane code 2), and “higher” complexity (terrane code 3). Letter designations appended to the terrane codes (for example, 1A, 1B, or 1C) differentiate terranes of similar complexity. Two unique areas, where thick, stratified, coarse-grained sediment dominates, were assigned terrane code 4. Elements of this hydrogeologic framework include a glacial environments and surficial sediments geodatabase, which includes lithologic, geomorphic, and stratigraphic characterization of Quaternary sediments based on previous mapping; a gridded database of sediment and aquifer characteristics computed from lithologic logs obtained from water-well driller records; a water-use database with information on public-water supply systems and sources of groundwater; and estimated recharge computed from a geologically based soil-water balance model. A generalized map of the bedrock geology based on previous State-level mapping is included as well. Quaternary sediment in the glaciated United States includes glacial, postglacial (Holocene) and nonglacial sediments. At land surface, 60 percent of the glacial sediment is till. Large areas of outwash and ice contact sediments are extensive throughout the Midwest but generally are confined to valleys in the Northeast and the Northwest. Lacustrine sediments were deposited in proglacial lakes adjacent to the present Great Lakes and in glacial Lake Agassiz in the eastern Dakotas and northwestern Minnesota. The median thickness of Quaternary sediment ranges from 6 to 45 meters across the 17 hydrogeologic terranes, but the maximum thickness is more than 500 meters in some areas. Quaternary sediments generally contain less than 10 percent coarse material; the median range is near zero percent under till to about 50 percent under ice contact and outwash sediments. About 80 percent of the coarse material lies within 25 to 40 meters of land surface. In most of the glaciated United States, there is a small likelihood of penetrating an aquifer-material interval containing coarse material at least 3 meters thick. A single aquifer-material interval was recorded in about 44 percent of lithologic logs, whereas about 11 percent of the logs penetrated multiple intervals. About 44 percent of water wells in the lithologic database are completed in Quaternary sediment, and many of these Quaternary water wells (42 percent) are confined by at least 7.5 meters of fine materials. About 33 percent of these Quaternary water wells are unconfined—the remainder are where only thin layers (less than 3 meters) of coarse material are present. The median depths of Quaternary water wells range from 13 to 40 meters among the 17 hydrogeologic terranes. Recharge ranges from more than 400 millimeters per year in the Northeast to 11 millimeters or less per year in the Dakotas and Montana (median value of 136 millimeters per year). Annual groundwater withdrawals compiled by county range on an areal basis from less than 1 to 370 millimeters per year, and the mean is 7.4 millimeters per year. About 36 percent of the withdrawals are for public-water supply, of which 70 percent are derived from Quaternary sediments. Groundwater withdrawals are less than 10 percent of recharge throughout most of the glaciated conterminous United States but are a larger proportion of recharge near urban areas in the Northeast and the Midwest, and in counties throughout drier parts of the Midwest. The salient characteristics of the 17 hydrogeologic terranes are presented through maps and a set of descriptive plots to facilitate visual comparisons between selected sediment and aquifer characteristics. The thickness of Quaternary sediment generally increases from the lower complexity terranes through the higher complexity terranes, consistent with their delineation. Median proportions of coarse material in Quaternary sediment and depths to aquifer-material intervals are highly variable (less than 10 to 50 percent, and 0 to 30 meters, respectively). Median thicknesses of aquifer-material intervals generally fall within a narrow range (10 to 20 meters), except in two terranes that contain thick coarse-grained sediment (30 to 35 meters). The source of water in wells varies from mostly bedrock wells in the lower complexity terranes to mostly Quaternary wells in the higher complexity terranes where the sediment is thickest. A tree diagram compiled from a hierarchical cluster analysis of a matrix composed of metrics based on sediment and aquifer characteristics, and the distribution of water wells in each terrane, indicates some groups of terranes that can be treated as comparable when analyzing groundwater flow and quality. Aquifer-material intervals indicated on maps prepared from the lithologic logs, including unconfined and confined conditions, correlate well with aquifer systems delineated on state maps for Illinois, Indiana, and North Dakota. The large scale of the study limits the resolution at which the maps can be interpreted, however, and alluvial units are not mapped correctly for some valleys in the Northeast and the Northwest. Lithologic logs used in the study are biased toward shallow depths because not all logs penetrate the entire thickness of Quaternary sediment, but this bias should not limit the utility of the sediment and aquifer descriptions because shallow depths are commonly exploited for water supply. The hydrogeologic framework will support ongoing studies of groundwater flow and quality in the U.S. Geological Survey National Water Quality Assessment program for the glaciated United States.

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