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At least 595 records · Page 33Linked to original sources
USGS2022

Active‐source interferometry in marine and terrestrial environments: Importance of directionality and stationary phase

We utilize active‐source seismic interferometry with dense seismic arrays both offshore and onland to explore the utility of this method to create virtual sources and reveal body‐wave reflections in these two different environments. We first utilize data from an ocean‐bottom cable (OBC) array in the Gulf of Mexico with equal numbers of sources (160 airgun shots) and receivers (160 ocean‐bottom four‐component sensors). We next use data from a geophone array across the Bighorn Mountains of Wyoming with many receivers (1300 vertical‐component geophones) but a small number of sources (14 borehole active‐source shots). We find that the OBC virtual source results, which produce strong reflections from sub‐seafloor structures, are far superior to the onland results which lack usable reflections, and we explore reasons for these differences through a set of selective stacking approaches. We present techniques to account for the direction the seismic waves travel (directionality) and stationary phase and show that improvements can be made when incorporating these corrections. Although interferometric methods are based on assumptions of large numbers of widely distributed actual sources, we find that selective exclusion of potentially problematic source–receiver pairs can yield improved results. These geometric adjustments to active‐source interferometry methods have utility for dense‐nodal‐array surveys that are now common in academic studies, but that often suffer from sparse source geometry.

Bulletin of the Seismological Society of America↗
USGS2011

Making United States Integrated Ocean Observing System (U.S. IOOS) inclusive of marine biological resources

An important Data Management and Communication (DMAC) goal is to enable a multi-disciplinary view of the ocean environment by facilitating discovery and integration of data from various sources, projects and scientific domains. United States Integrated Ocean Observing System (U.S. IOOS) DMAC functional requirements are based upon guidelines for standardized data access services, data formats, metadata, controlled vocabularies, and other conventions. So far, the data integration effort has focused on geophysical U.S. IOOS core variables such as temperature, salinity, ocean currents, etc. The IOOS Biological Observations Project is addressing the DMAC requirements that pertain to biological observations standards and interoperability applicable to U.S. IOOS and to various observing systems. Biological observations are highly heterogeneous and the variety of formats, logical structures, and sampling methods create significant challenges. Here we describe an informatics framework for biological observing data (e.g. species presence/absence and abundance data) that will expand information content and reconcile standards for the representation and integration of these biological observations for users to maximize the value of these observing data. We further propose that the approach described can be applied to other datasets generated in scientific observing surveys and will provide a vehicle for wider dissemination of biological observing data. We propose to employ data definition conventions that are well understood in U.S. IOOS and to combine these with ratified terminologies, policies and guidelines.

Conference Paper↗
USGS2016

Common carp disrupt ecosystem structure and function through middle-out effects

Middle-out effects or a combination of top-down and bottom-up processes create many theoretical and empirical challenges in the realm of trophic ecology. We propose using specific autecology or species trait (i.e. behavioural) information to help explain and understand trophic dynamics that may involve complicated and non-unidirectional trophic interactions. The common carp ( Cyprinus carpio ) served as our model species for whole-lake observational and experimental studies; four trophic levels were measured to assess common carp-mediated middle-out effects across multiple lakes. We hypothesised that common carp could influence aquatic ecosystems through multiple pathways (i.e. abiotic and biotic foraging, early life feeding, nutrient). Both studies revealed most trophic levels were affected by common carp, highlighting strong middle-out effects likely caused by common carp foraging activities and abiotic influence (i.e. sediment resuspension). The loss of water transparency, submersed vegetation and a shift in zooplankton dynamics were the strongest effects. Trophic levels furthest from direct pathway effects were also affected (fish life history traits). The present study demonstrates that common carp can exert substantial effects on ecosystem structure and function. Species capable of middle-out effects can greatly modify communities through a variety of available pathways and are not confined to traditional top-down or bottom-up processes.

Marine and Freshwater Research↗
USGS1954

Stratigraphy and history of the Moenkopi formation of Triassic age

The Moenkopi formation of Triassic age is composed of a series of deposits that form a wedge thinning eastward from a maximum of about 2000 feet in western Utah and southern Nevada to the vanishing point along an irregular margin in western Colorado, northeastern Arizona, and western New Mexico. Partly marine and partly continental in the thick western sections, it is entirely continental in the east. Invertebrate faunas indicate that deposition began either during or preceding the middle of the Early Triassic (Meekoceras zone) and continued into late Early Triassic (Tirolites zone) and probably into Medial Triassic time. Vertebrate faunas also indicate an Early Triassic and probably, in part, a Medial Triassic age . Studies of the deposits indicate three major transgressions and three regressions across southern Utah and northern Arizona. Analysis of sedimentary rock types and original structures in them suggests a complex mixture of environments involved in the development of the formation : stream beds, lagoons, playas, flood plains or tidal flats, shallow sea floors, and others. Some types are clear cut and readily demonstrated; others are open to question. Evidence from flora, fauna, and sediments indicates a semiarid to arid climate. Except for uplift in the Uncompahgre region of Colorado indicated by conglomeratic beds in the Moenkopi near by, the entire region probably remained very low and flat during Moenkopi deposition.

Colorado, Arizona, New Mexico↗
USGS2017

Influence of the Eastern California Shear Zone on deposition of the Mio-Pliocene Bouse Formation: Insights from the Cibola area, Arizona

The Eastern California Shear Zone (ECSZ) is a wide zone of late Cenozoic strike-slip faults and related diffuse deformation that currently accommodates ~20–25% of relative Pacific–North America plate motion in the lower Colorado River region (Fig. 1A; Dokka and Travis, 1990; Miller et al., 2001; Guest et al., 2007; Mahan et al., 2009). The ECSZ is kinematically linked southward to dextral faults in the northern Gulf of California (Bennett et al., 2016a), and it may have initiated ca. 8 Ma when major strike-slip faults developed in the northern Gulf and Salton Trough region (Bennett et al., 2016b; Darin et al., 2016; Woodburne, 2017). Thus deformation related to the ECSZ occurred in the lower Colorado River region during deposition of the Bouse Formation, which is commonly bracketed between 6.0 and 4.8 Ma (House et al., 2008; Sarna-Wojcicki et al., 2011; Spencer et al., 2013) and may be as old as 6–7 Ma in the south (McDougall and Miranda Martínez, 2014, 2016). Post-4.5 Ma broad sagging is recognized along the lower Colorado River (Howard et al., 2015), but the possibility that faults of the ECSZ influenced local to regional subsidence patterns during deposition of the Bouse Formation has received little attention to date (e.g., Homan, 2014; O’Connell et al., 2016). The Bouse Formation is a widespread sequence of late Miocene to early Pliocene deposits exposed discontinuously along the lower Colorado River corridor (Fig. 1A). In the southern Blythe basin it consists of three regionally correlative members: (1) Basal Carbonate, consisting of supratidal and intertidal mud-flat marls, intertidal and shallow subtidal bioclastic grainstone and conglomerate, and subtidal marl; (2) Siliciclastic member, consisting of Colorado River-derived green claystone, red mudstone and siltstone, and cross-bedded river channel sandstone; and (3) Upper Bioclastic member fossiliferous sandy calcarenite, coarse pebbly grainstone, and calcareous-matrix conglomerate (Homan, 2014; Dorsey et al., 2016; O’Connell et al., 2016, 2017). The southern Bouse Formation has been interpreted as recording deposition in either a lake (Spencer and Patchett, 1997; Spencer et al., 2008, 2013; Bright et al., 2016) or shallow marine setting (Buising, 1990; McDougall, 2008; McDougall and Miranda Martínez, 2014; O’Connell et al., 2017). In this paper we summarize key results from five field seasons of detailed stratigraphic analysis south of Cibola, Ariz. ( . 1). The data reveal systematic stratal thinning and thickening, pinch-outs, and wedging patterns in the Bouse Formation that we conclude were produced by syn-depositional tilting in response to growth of normal faults near the eastern margin of the basin. Similar stratal patterns in other nearby areas suggest widespread structural controls on deposition of the Bouse Formation. A palinspastic reconstruction of the lower Colorado River region at 5 Ma, modified from Bennett et al. (2016), provides insight to regional fault geometries in the ECSZ that may have controlled syn-depositional tilting and subsidence in Bouse depocenters shortly prior to and during initiation of the Colorado River.

Conference Paper↗
USGS1995

Breeding seabirds in California, Oregon and Washington

More than two million seabirds of 29 species nest along the west coasts of California, Oregon, and Washington, including three species listed on the federal list of threatened and endangered species: the brown pelican ( Pelecanus occidentalis ), least tern ( Sterna antillarum ), and marbled murrelet ( Brachyramphus marmoratus ). The size and diversity of the breeding seabird community in this region reflect excellent nearshore prey conditions; subtropical waters within the southern California Bight area; complex tidal waters of Strait of Juan de Fuca and Puget Sound in Washington; large estuaries at San Francisco Bay, Columbia River, and Grays Harbor-Willapa bays; and the variety of nesting habitats used by seabirds throughout the region, including islands, mainland cliffs, old-growth forests, and artificial structures. Breeding seabird populations along the west coast have declined since European settlement began in the late 1700's because of human occupation of, commercial use of, and introduction of mammalian predators to seabird nesting islands. In the 1900's, further declines occurred in association with rapid human population growth and intensive commercial use of natural resources in the Pacific region. In particular, severe adverse impacts have occurred from partial or complete nesting habitat destruction on islands or the mainland, human disturbance of nesting islands or areas, marine pollution, fisheries, and logging of old-growth forests (Ainley and Lewis 1974; Bartonek and Nettleship 1979; Hunt et al. 1979; Sowls et al. 1980; Nettleship et al. 1984; Speich and Wahl 1989; Ainley and Boekelheide 1990; Sealy 1990; Ainley and Hunt 1991; Carter and Morrison 1992; Carter et al. 1992; Vermeer et al. 1993).

California, Oregon, Washington↗
USGS1978

Reconnaissance engineering geology of the Petersburg area, southeastern Alaska, with emphasis on geologic hazards

A program to study the engineering geology of most larger Alaska coastal communities and to evaluate their earthquake and other geologic hazards was started following the 1964 Alaska earthquake; this report about the Petersburg area is a product of that program. Field-study methods were of a reconnaissance nature, and thus, interpretations in the report are tentative. Landscape of the northern end of Mitkof Island on which Petersburg is situated is characterized by a gently sloping, muskeg-covered terrain, with altitudes mostly less than 30 m. In contrast, much of the rest of the island is composed of mountainous terrain with many steep valleys. During the Pleistocene Epoch, the Petersburg area presumably was covered by ice several times; glaciers deeply eroded many valleys on Mitkof Island and adjacent areas. The last major deglaciation probably was largely completed by 12,000 years ago. Delayed rebound of the earth's crust, after the melting of large amounts of ice, permitted extensive inundation of land in the Petersburg area. Subsequently, emergence has elevated marine deposits to a present-day altitude of at least 65 m and probably to 75 m. Bedrock in the Petersburg map area is composed of relatively hard metamorphic rocks, chiefly phyllite and probably some graywacke. Rocks are of Middle(?) Jurassic to Early Cretaceous age. Five types of surficial geologic material of Quaternary age were recognized: (1) mixed deposits consisting of diamicton, silt-clay, and sand or sandy pebble gravel, (2) alluvial deposits, (3) shore and delta deposits, (4) organic deposits, and (5) artificial fill. Geologic structure in southeastern Alaska is complex because several cycles of tectonic deformation since at least early Paelozoic time have affected different parts of the region. The latest of the major tectonic events in southeastern Alaska occurred in Tertiary time, with some minor activity continuing into the Quaternary Period. Along the outer coast of southeastern Alaska, active strike-slip movement is occurring along the Chichagof-Baranof and Queen Charlotte faults. A segment of the prominent Coast-Range lineament, part of which may be a fault, lies 18 km northeast of Petersburg. Many earthquakes occur along the outer coast of southeastern Alaska. Most of these shocks are associated with movements along the Chichagof-Baranof, Queen Charlotte, and Transition faults. A few small earthquakes occur in the region between the outer coast and the southern part of the Coast Mountains. 0nly a few earthquakes have been recorded as felt at Petersburg; these shocks and others possibly felt in the Petersburg region are tabulated. Among the recorded earthquakes the highest intensity (about V-VI) as the magnitude 7.1 earthquake of October 24, 1927, that occurred probably along the Chichagof-Baranof fault, and about 225 km northwest of Petersburg; damage was reported as minor. Other large earthquakes along the Chichagof-Baranof fault that affected or probably affected the Petersburg area in a minor way occurred on August 22, 1949 (magnitude 8.1) and on July 30, 1972 (magnitude 7.25). From a consideration of the tectonics and earthquake history of the region, earthquakes similar to the 1927, 1949, and 1972 shocks are expected to recur on segments of the Chichagof-Baranof or Queen Charlotte faults. The closest of these fault segments is about 170 km southwest from Petersburg. The likelihood of destructive earthquakes being generated along faults closer to Petersburg is unknown. A very generalized discussion of possible geologic effects that could occur in the area during a postulated, theoretically reasonable worst case earthquake of magnitude 8 occurring along the outer coast about 170 km southwest from Petersburg notes that ground shaking probably would be strongest on organic deposits and least on bedrock and on firm, compact diamicton. Among other effects that could happen are: (1) liquefaction of some of the few delta and alluvial

Open-File Report↗
USGS2014

Advances in a distributed approach for ocean model data interoperability

An infrastructure for earth science data is emerging across the globe based on common data models and web services. As we evolve from custom file formats and web sites to standards-based web services and tools, data is becoming easier to distribute, find and retrieve, leaving more time for science. We describe recent advances that make it easier for ocean model providers to share their data, and for users to search, access, analyze and visualize ocean data using MATLAB® and Python®. These include a technique for modelers to create aggregated, Climate and Forecast (CF) metadata convention datasets from collections of non-standard Network Common Data Form (NetCDF) output files, the capability to remotely access data from CF-1.6-compliant NetCDF files using the Open Geospatial Consortium (OGC) Sensor Observation Service (SOS), a metadata standard for unstructured grid model output (UGRID), and tools that utilize both CF and UGRID standards to allow interoperable data search, browse and access. We use examples from the U.S. Integrated Ocean Observing System (IOOS®) Coastal and Ocean Modeling Testbed, a project in which modelers using both structured and unstructured grid model output needed to share their results, to compare their results with other models, and to compare models with observed data. The same techniques used here for ocean modeling output can be applied to atmospheric and climate model output, remote sensing data, digital terrain and bathymetric data.

Journal of Marine Science and Engineering↗
USGS1984

Reconnaissance geology of the Zarghat Quadrangle, sheet 26/40 B, Kingdom of Saudi Arabia

The Zarghat quadrangle is located in the northern Precambrian shield of Saudi Arabia between lat 26°30' and 27°00' N. and long 41°00' and 41°30 ' E. The area is underlain by three Precambrian volcanosedimentary units and a range of Precambrian dioritoid and granitoid plutonic intrusive rocks. Paleozoic(?) sandstone crops out in small areas in the northwestern part of the quadrangle, and a lobe of QuaternaryC?) basalt from Harrat Ithnain penetrates the southwest corner of the quadrangle. The Banana greenstone, the oldest unit in the quadrangle, is composed of basic to intermediate volcanic and subvolcanic rocks and minor interbedded marble that have been metamorphosed to greenschist-facies assemblages. The volcanic rocks range from basalt to andesite and dacite, and the subvolcanic rocks are diabase and diorite. Two less-metamorphosed Precambrian units, the Hadn formation and the Zarghat formation, unconformably overlie the Banana greenstone. The Hadn formation is composed of predominantly rhyolitic to dacitic volcanic rock and minor amounts of continental sedimentary rock; it is exposed only in the east half of the quadrangle. The Zarghat formation is also rhyolitic to dacitic volcanic rock but contains much more sedimentary rock that appears to have been deposited in a shallow-marine environment. The relation between these two formations is not clear at this time. Two groups of intrusive rocks are recognized on the basis of their ages relative to the Hadn and Zarghat formations. An older group is composed of hornblende quartz diorite, granodiorite, tonalite, and lesser amounts of granite. Tnese rocks intrude the Banana greenstone but predate the Hadn and Zarghat formations. Post-Hadn/Zarghat intrusive rocks are voluminous undivided granite, several varieties of alkali-feldspar granite, monzogranite, granophyre, hypabyssal rhyolite, aplite, diabase, and gabbro. The structural grain within the quadrangle appears to trend north-south. The Precambrian volcanosedimentary rocks and older plutonic rocks define three major north-trending lithologic belts. The Zarghat formation makes up the westernmost belt, and the Hadn formation comprises the easternmost belt. The central belt consists of Banana greenstone and older plutonic rocks. The north-south structural grain is crosscut by large plutons that postdate the Hadn and Zarghat formations. The dominant faults in the area belong to a northeast-trending system of shears; less common fault orientations are northwesterly, northerly, and east-westerly. Outcrops of magnesite in the southwest corner of the quadrangle constitute the only known economic potential in the area.

Open-File Report↗
USGS2018

Efficacy of otoliths and first dorsal spines for preliminary age and growth determination in Atlantic Tripletails

The Atlantic Tripletail Lobotes surinamensis is a popular sport fish for which age and growth data are scarce in general and nonexistent for Georgia (GA), USA, waters. These data are necessary to ensure that management regulations are adequate to protect this species, especially given its popularity as a sport fish. We evaluated whether otoliths and spines were suitable for determining the estimated age (hereafter, “age”) and growth rates of Atlantic Tripletails, and we ascertained whether one method was more accurate than the other. Atlantic Tripletails were sampled by angling and trawling during March 30–August 10, 2009, and March 14–August 6, 2010, in nearshore GA waters of the Atlantic Ocean. During the study, 243 Atlantic Tripletails were captured and sampled for aging structures. Sagittal otoliths and the first dorsal spine were removed from each fish and used to estimate the age and growth rate. Mean differences in TL at age for spine and otolith data were evaluated with ANOVA. Estimated ages for males and females ranged from 1 to 5 years based on otoliths and spines. Both otolith and spine mean TLs at ages 1 and 2 were significantly different from each other as well as all other age‐classes, whereas mean TLs for ages 3–5 were not significantly different. Differences in Atlantic Tripletail TL among the otolith‐ and spine‐derived age‐classes were not significant. Each method used to age Atlantic Tripletails had advantages and disadvantages. Otoliths had higher initial reader agreement than spines, although agreement between the structures was 84.1%. However, otoliths require sacrifice of the fish, whereas a spine can be taken without sacrificing the fish. The lack of concrete life history data and population estimates suggests that when feasible, nonlethal aging methods would be preferred over lethal methods to ensure the survival of Atlantic Tripletail populations.

Georgia↗
USGS2017

Inner-shelf ocean dynamics and seafloor morphologic changes during Hurricane Sandy

Hurricane Sandy was one of the most destructive hurricanes in US history, making landfall on the New Jersey coast on Oct 30, 2012. Storm impacts included several barrier island breaches, massive coastal erosion, and flooding. While changes to the subaerial landscape are relatively easily observed, storm-induced changes to the adjacent shoreface and inner continental shelf are more difficult to evaluate. These regions provide a framework for the coastal zone, are important for navigation, aggregate resources, marine ecosystems, and coastal evolution. Here we provide unprecedented perspective regarding regional inner continental shelf sediment dynamics based on both observations and numerical modeling over time scales associated with these types of large storm events. Oceanographic conditions and seafloor morphologic changes are evaluated using both a coupled atmospheric-ocean-wave-sediment numerical modeling system and observation analysis from a series of geologic surveys and oceanographic instrument deployments focused on a region offshore of Fire Island, NY. The geologic investigations conducted in 2011 and 2014 revealed lateral movement of sedimentary structures of distances up to 450 m and in water depths up to 30 m, and vertical changes in sediment thickness greater than 1 m in some locations. The modeling investigations utilize a system with grid refinement designed to simulate oceanographic conditions with progressively increasing resolutions for the entire US East Coast (5-km grid), the New York Bight (700-m grid), and offshore of Fire Island, NY (100-m grid), allowing larger scale dynamics to drive smaller scale coastal changes. Model results in the New York Bight identify maximum storm surge of up to 3 m, surface currents on the order of 2 ms-1 along the New Jersey coast, waves up to 8 m in height, and bottom stresses exceeding 10 Pa. Flow down the Hudson Shelf Valley is shown to result in convergent sediment transport and deposition along its axis. Modeled sediment redistribution along Fire Island showed erosion across the crests of inner shelf sand ridges and sedimentation in adjacent troughs, consistent with the geologic observations.

Continental Shelf Research↗
USGS2024

Indications of preferential groundwater seepage feeding northern peatland pools

Groundwater seepage from underlying permeable glacial sedimentary structures, such as eskers, has been hypothesized to directly feed pools in northern peat bogs. These hypotheses directly contradict classical peat bog models for ombrogenous systems, wherein meteoric water is the sole water input to these systems. Variations in the underlying mineral sediment in contact with the peat imply that unrecognized hydrogeologic connectivity may exist with pools in northern peat bogs, particularly where high permeability materials are in contact with the peat. Seepage dynamics originating from these structural variations were investigated using a suite of thermal and hydrogeophysical methods deployed around pools in a peat bog of northeastern Maine, USA. Thermal characterization methods mapped anomalies that were confirmed as matrix seepage or preferential flow pathways (PFPs). Geochemical methods were employed at identified thermal anomalies to confirm upwelling of solute-rich groundwater. Conduits around pools were associated with surficial terminations of suspected peat pipes, based on the inference of pathways extending down into the peat, that focus flow through PFPs in the peat matrix. Discharge also occurred through the peat matrix adjacent to suspected pipe structures and matrix seepage rates were quantified using analysis of diurnal temperature signals recorded at multiple depths. Seepage rates, with a maximum of nearly 0.4 m/d, were measured at localized points around pools. Periods of synchronized temperatures paired with highly muted diurnal temperature signals, recorded in diurnal temperature with depth data, were interpreted qualitatively as activation of strong upward discharge rates through suspected peat pipes. These time periods correlated strongly with local precipitation events around the peatland. Ground-penetrating radar surveys revealed discontinuities in the low permeability glacio-marine clay at the mineral sediment-peat interface, interpreted to be regional glacial esker deposits, which were located beneath and around pools. Heat tracing, specific conductance contrasts, seepage rates, and trace metal concentrations all imply groundwater seepage originating from underlying permeable glacial esker deposits and directly sourcing pools. Preferential groundwater inputs into northern peat bogs may play a key role in developing and maintaining pool systems, with enhanced solute transport impacting peatland ecology, water resources, and carbon cycling.

Maine↗
USGS2015

Exploration of the canyon-incised continental margin of the northeastern United States reveals dynamic habitats and diverse communities

The continental margin off the northeastern United States (NEUS) contains numerous, topographically complex features that increase habitat heterogeneity across the region. However, the majority of these rugged features have never been surveyed, particularly using direct observations. During summer 2013, 31 Remotely-Operated Vehicle (ROV) dives were conducted from 494 to 3271 m depth across a variety of seafloor features to document communities and to infer geological processes that produced such features. The ROV surveyed six broad-scale habitat features, consisting of shelf-breaching canyons, slope-sourced canyons, inter-canyon areas, open-slope/landslide-scar areas, hydrocarbon seeps, and Mytilus Seamount. Four previously unknown chemosynthetic communities dominated by Bathymodiolus mussels were documented. Seafloor methane hydrate was observed at two seep sites. Multivariate analyses indicated that depth and broad-scale habitat significantly influenced megafaunal coral (58 taxa), demersal fish (69 taxa), and decapod crustacean (34 taxa) assemblages. Species richness of fishes and crustaceans significantly declined with depth, while there was no relationship between coral richness and depth. Turnover in assemblage structure occurred on the middle to lower slope at the approximate boundaries of water masses found previously in the region. Coral species richness was also an important variable explaining variation in fish and crustacean assemblages. Coral diversity may serve as an indicator of habitat suitability and variation in available niche diversity for these taxonomic groups. Our surveys added 24 putative coral species and three fishes to the known regional fauna, including the black coral Telopathes magna , the octocoral Metallogorgia melanotrichos and the fishes Gaidropsarus argentatus , Guttigadus latifrons , and Lepidion guentheri . Marine litter was observed on 81% of the dives, with at least 12 coral colonies entangled in debris. While initial exploration revealed the NEUS region to be both geologically dynamic and biologically diverse, further research into the abiotic conditions and the biotic interactions that influence species abundance and distribution is needed.

Northeastern United States, Gulf of Maine, Georges↗
USGS2018

New data yield new geologic insights at the Fallon FORGE site, Carson Sink Region, Nevada

The geologic structure beneath the Fallon Frontier Observatory for Research in Geothermal Energy (FORGE) site represents a record of the Mesozoic through Cenozoic tectonism, volcanism, and sedimentation that has affected the Carson Sink local to Fallon, NV. A robust dataset confirms that the lithologic sequence consists of Quaternary through Miocene sedimentary and volcanic rocks resting non-conformably on Mesozoic crystalline basement. The basement consists of four lithologic units; 1) Triassic-Jurassic low-to-medium grade meta-rhyolites, 2) Jurassic low-to-medium grade quartzites and other metamorphosed marine sedimentary rocks, and 3) Jurassic low-to-medium grade meta-basalt and -basaltic-andesite lavas, all intruded by 4) Jurassic-Cretaceous quartz monzonite. The geologic section dips ~20-25° west, tilting that was accommodated by a predominant system of north-to-north-northeast striking, east and west moderately-to-steeply dipping normal faults. The above, relatively broad-scale characteristics of the geologic framework of the Fallon site have been developed throughout the ~3 year duration of the project. With the collection of new data and re-analysis of existing data in Phase 2B of the Fallon FORGE project, our detailed understanding of the relatively finer-scale aspects of the geologic framework, including aspects of the stratigraphic sequence and the locations and attitudes of individual faults have evolved and an updated 3D geologic map has been developed. Here, we compare the Phase 1 3D geologic map to the Phase 2B 3D geologic map and demonstrate the evolution of our understanding of the geologic framework of the Fallon site and the value of the new data that was collected in Phase 2B in developing this updated framework.

Geothermal Resources Council Transactions↗
USGS2015

An Arctic and Subarctic ostracode database: Biogeographic and paleoceanographic applications

A new Arctic Ostracode Database-2015 (AOD-2015) provides census data for 96 species of benthic marine Ostracoda from 1340 modern surface sediments from the Arctic Ocean and subarctic seas. Ostracoda is a meiofaunal, Crustacea group that secretes a bivalved calcareous (CaCO 3 ) shell commonly preserved in sediments. Arctic and subarctic ostracode species have ecological limits controlled by temperature, salinity, oxygen, sea ice, food, and other habitat-related factors. Unique species ecology, shell chemistry (Mg/Ca ratios, stable isotopes), and limited stratigraphic ranges make them a useful tool for paleoceanographic reconstructions and biostratigraphy. The database, described here, will facilitate the investigation of modern ostracode biogeography, regional community structure, and ecology. These data, when compared to downcore faunal data from sediment cores, will provide a better understanding of how the Arctic has been affected by climatic and oceanographic change during the Quaternary. Images of all species and biogeographic distribution maps for selected species are presented, with brief discussion of representative species’ biogeographic and ecological significance. Publication of AOD-2015 is open-sourced and will be available online at several public websites with latitude, longitude, water depth, and bottom water temperature for most samples. It includes material from Arctic abyssal plains and submarine ridges, continental slopes, and shelves of the Kara, Laptev, East Siberian, Chukchi, Beaufort Seas, and several subarctic regions.

Hydrobiologia↗
USGS2011

Nekton community response to a large-scale Mississippi River discharge: Examining spatial and temporal response to river management

Freshwater flow is generally held to be one of the most influential factors affecting community structure and production in estuaries. In coastal Louisiana, the Caernarvon Freshwater Diversion (CFD) is managed to control freshwater discharge from the Mississippi River into Breton Sound basin. Operational since 1991, CFD has undergone several changes in management strategy including pulsed spring flooding, which was introduced in 2001. We used a 20-yr time series of fisheries-independent data to investigate how variation in freshwater inflow (i.e., pre- and post-CFD, and pre and post spring pulsing management) influences the downstream nekton community (abundance, diversity, and assemblage). Analyses of long-term data demonstrated that while there were effects from the CFD, they largely involved subtle changes in community structure. Spatially, effects were largely limited to the sites immediately downstream of the diversion and extended only occasionally to more down-estuary sites. Temporally, effects were 1) immediate (detected during spring diversion events) or 2) delayed (detected several months post-diversion). Analysis of river management found that pulsed spring-time inflow resulted in more significant changes in nekton assemblages, likely due to higher discharge rates that 1) increased marsh flooding, thus increasing marsh habitat accessibility for small resident marsh species, and 2) reduced salinity, possibly causing displacement of marine pelagic species down estuary.

Breton Sound↗
USGS2006

Groundwater dolocretes from the Upper Triassic of the Paris Basin, France: A case study of an arid, continental diagenetic facies

Thick dolomite-cemented horizons (dolocretes) occur within a fluvial sandstone-mudstone sequence of Late Triassic age in the western part of the Paris Basin, France. Two types of dolomites can be distinguished: (a) nodular dolomitic beds less than a few metres thick, which formed within mottled overbank siltstones and mudstones; and (b) massive dolomite up to 16 m thick, which occurs in coarse grained channel sandstones and conglomerates. The majority of the dolomite consists of a finely crystalline groundmass of dolomicrospar and, less commonly, dolomicrite. Glaebules, irregular spar-filled cracks, spheroidal dolomite, silicification and vuggy porosity are locally abundant in the massive dolomite. In contrast, biologically induced micromorphological features such as rhizocretions and alveolar-septal fabrics were observed in the thin, nodular dolomite beds. The dolomite is near stoichiometric, well ordered and non-ferroan. 18O values range from −7·7 to −0·4%o PDB and 18O values range from −5·1 to + 1·8%0 PDB and no obvious difference in the stable isotopic composition between both types of dolomites was observed. Sr isotope ratios range from 0·7101 to 0·7126 and are invariably higher than the contemporary Triassic sea water. A vadose—pedogenic origin for the thin dolocrete layers is indicated by the occurrence of rhizocretions and other biological structures. Several features, however, argue against a pedogenic origin for the massive carbonates, most notably the absence of biologically induced structures, the occurrence in coarse grained channel (and not overbank) deposits, and the great thickness. These units are thus interpreted as groundwater in origin. Phreatic calcretes of Quaternary age, widespread in inland Australia, are regarded as a modern analogue for the Triassic Paris Basin dolocretes. Petrographic observations argue in favour of primary (proto)dolomite precipitation, although early diagenetic replacement of calcite by (proto)dolomite cannot be ruled out. Strontium and carbon isotope data of early diagenetic dolocrete cements and oxygen isotope data of early diagenetic silica indicate an entirely non-marine, continental origin for the groundwaters. The poorly ordered and non-stoichiometric protodolomite probably underwent stabilization upon further burial resulting in a near-stoichiometric, well ordered dolomite that clearly lacks evidence for pervasive recrystallization.

Paris↗
USGS2015

Marshes to mudflats—Effects of sea-level rise on tidal marshes along a latitudinal gradient in the Pacific Northwest

Summary In the Pacific Northwest, coastal wetlands support a wealth of ecosystem services including habitat provision for wildlife and fisheries and flood protection. The tidal marshes, mudflats, and shallow bays of coastal estuaries link marine, freshwater, and terrestrial habitats, and provide economic and recreational benefits to local communities. Climate change effects such as sea-level rise are altering these habitats, but we know little about how these areas will change over the next 50–100 years. Our study examined the effects of sea-level rise on nine tidal marshes in Washington and Oregon between 2012 and 2015, with the goal of providing scientific data to support future coastal planning and conservation. We compiled physical and biological data, including coastal topography, tidal inundation, vegetation structure, as well as recent and historical sediment accretion rates, to assess and model how sea-level rise may alter these ecosystems in the future. Multiple factors, including initial elevation, marsh productivity, sediment availability, and rates of sea-level rise, affected marsh persistence. Under a low sea-level rise scenario, all marshes remained vegetated with little change in the present configuration of communities of marsh plants or gradually increased proportions of middle-, high-, or transition-elevation zones of marsh vegetation. However, at most sites, mid sea-level rise projections led to loss of habitat of middle and high marshes and a gain of low marshes. Under a high sea-level rise scenario, marshes at most sites eventually converted to intertidal mudflats. Two sites (Grays Harbor and Willapa) seemed to have the most resilience to a high rate of rise in sea-level, persisting as low marsh until at least 2110. Our main model finding is that most tidal marsh study sites are resilient to sea-level rise over the next 50–70 years, but that sea-level rise will eventually outpace marsh accretion and drown most habitats of high and middle marshes by 2110.

California, Oregon, Washington↗