Search USGS⌕ Search

SEARCH · Search USGS

Results for “Developments in Sedimentology”

Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 55 records · Page 3Linked to original sources
USGS2022

Tectonic subsidence modeling of diachronous transition from backarc to retroarc basin development and uplift during Cordilleran orogenesis, Patagonian-Fuegian Andes

Backstripped tectonic basin subsidence histories are critical for interpreting phases of lithospheric deformation and paleoenvironmental change from the stratigraphic record. This study presents new subsidence modeling of the Rocas Verdes Backarc Basin (RVB) and Magallanes-Austral retroarc foreland basin (MAB) of southernmost South America to evaluate along-strike changes in tectonic subsidence related to the Late Jurassic through Miocene history of the Southern Andes. We compiled composite stratigraphic sections for seven basin localities that span 47°–54°S from published sedimentological records of paleoenvironment, paleobathymetry, and geochronology. Modeling results resolve regional trends in basin tectonic subsidence, uplift, and sedimentation rate that influenced the depositional environment during five broad phases of RVB-MAB development: (a) Late Jurassic tectonic subsidence and basin deepening associated with rift-related backarc extension that postdated regional diachronous rift-related magmatism. (b) Southward younging of Early to Late Cretaceous pronounced acceleration in tectonic subsidence interpreted as the initiation of flexural loading and development of the MAB foreland basin system. (c) Late Cretaceous (ca. 85–70 Ma) tectonic uplift within the central foredeep ∼49° to 52°S, coeval with a shift from slope to shelf deposition at these latitudes. (d) A protracted period of low-magnitude basin uplift and relative tectonic quiescence during the Paleogene, with the exception of southernmost localities; and (e) Synchronous latest Oligocene-early Miocene tectonic subsidence linked to basin deepening and transgression across the northern and central basin sectors. Backstripped tectonic subsidence analysis corroborates existing interpretations for orogenic development in the RVB-MAB and sheds new light on complex polyphase basin histories where extension precedes convergence.

Andes Mountains, Magallanes-Austral retroarc forel↗
USGS2006

Holocene environmental and parasequence development of the St. Jones Estuary, Delaware (USA): Foraminiferal proxies of natural climatic and anthropogenic change

The benthic foraminiferal record of marshes located along western Delaware Bay (St. Jones Estuary, USA) reflects the response of estuaries to sea-level and paleoclimate change during the Holocene. System tracts are recognized and within them parasequences based on sedimentological and foraminiferal assemblages identification. The parasequences defined by foraminiferal assemblages appear correlative with rapid Holocene climate changes that are of worldwide significance: 6000-5000, 4200-3800, 3500-2500, 1200-1000, and 600??cal years BP. Following postglacial sea-level rise, modern subestuaries and marshes in the region began to develop between 6000 and 4000??years BP, depending on their proximity to the mouth of Delaware Bay and coastal geomorphology. Initial sediments were fluvial in origin, with freshwater marshes established around 4000??years BP. The subsequent sea-level transgression occurred sufficiently slowly that freshwater marshes alternated with salt marshes at the same sites to around 3000??years BP. Locally another two transgressions are identified at 1800 and 1000??years BP respectively. Marine influence increased in the estuaries until 600??years BP (Little Ice Age), when regression occurred. Sea-level began to rise again during the mid-19th Century at the end of the Little Ice Age, when marshes became established. The presence of a sand lens in the upper and middle estuary and the reduction in the number of tests in the top samples in cores from the same area also suggest an anthropogenic influence. The estuary infill resulted in a sharp transgressive sequence, represented by salt marsh foraminiferal assemblages in the upper part of the cores. The increase in marsh foraminifera in both areas suggests an increase in marine influence that might be due to the transgression beginning at the end of the Little Ice Age about 150-180??years ago coupled with anthropogenic straightening of the channel in 1913. ?? 2006 Elsevier B.V. All rights reserved.

Palaeogeography, Palaeoclimatology, Palaeoecology↗
USGS1998

Pebble orientation on large, experimental debris-flow deposits

Replicable, pronounced orientation of discoid pebbles (≥8 mm) embedded on surfaces of large (∼10 m 3 ) experimental debris-flow deposits reveals that strongly aligned, imbricate fabric can develop rapidly over short distances in mass flows. Pebble long axes aligned subparallel to deposit margins as well as subparallel to margins of surge waves arrested within the deposits. Pebble alignment exhibited modes both parallel to ( a(p) ), the primary flow direction; intermediate axes dipped preferentially inward from surge-wave margins ( b(i) orientation). Repetitive development of margin-parallel, imbricate fabric distributed across deposit surfaces provides compelling evidence that deposits formed dominantly through progressive incremental accretion rather than through simple en masse emplacement. Pronounced fabric along deposit and arrested surge-wave margins reflects significant grain interaction along flow margins. This sedimentological evidence for significant marginal grain interaction complements theoretical analyses (Iverson, 1997) and other experimental data (Major, 1996; Iverson, 1997) that indicate that resistance along flow margins is an important factor affecting debris-flow deposition. The fabric on the experimental deposits demonstrates that debris flows can develop strongly imbricate particle orientation that mimics fabric developed during fluvial deposition. Particle shape and local stress fields appear to have more control over fabric development than does general depositional process. Other criteria in addition to particle orientation are needed to discriminate mass flow from fluvial gravel deposits and to unravel depositional history.

Sedimentary Geology↗
USGS2004

Regional paleohydrologic and paleoclimatic settings of wetland/lacustrine depositional systems in the Morrison Formation (Upper Jurassic), Western Interior, USA

During deposition of the Upper Jurassic Morrison Formation, water that originated as precipitation in uplands to the west of the Western Interior depositional basin infiltrated regional aquifers that underlay the basin. This regional groundwater system delivered water into the otherwise dry continental interior basin where it discharged to form two major wetland/lacustrine successions. A freshwater carbonate wetland/lacustrine succession formed in the distal reaches of the basin, where regional groundwater discharged into the Denver-Julesburg Basin, which was a smaller structural basin within the more extensive Western Interior depositional basin. An alkaline-saline wetland/lacustrine complex (Lake T'oo'dichi') formed farther upstream, where shallower aquifers discharged into the San Juan/Paradox Basin, which was another small structural basin in the Western Interior depositional basin. These were both wetlands in the sense that groundwater was the major source of water. Input from surface and meteoric water was limited. In both basins, lacustrine conditions developed during episodes of increased input of surface water. Inclusion of wetlands in our interpretation of what had previously been considered largely lacustrine systems has important implications for paleohydrology and paleoclimatology. The distal carbonate wetland/lacustrine deposits are well developed in the Morrison Formation of east-central Colorado, occupying a stratigraphic interval that is equivalent to the "lower" Morrison but extends into the "upper" Morrison Formation. Sedimentologic, paleontologic, and isotopic evidence indicate that regional groundwater discharge maintained shallow, hydrologically open, well oxygenated, perennial carbonate wetlands and lakes despite the semi-arid climate. Wetland deposits include charophyte-rich wackestone and green mudstone. Lacustrine episodes, in which surface water input was significant, were times of carbonate and siliciclastic deposition in scarce deltaic and shoreline deposits. Marginal lacustrine deposits include ooid and skeletal packstone-grainstone, siltstone, and sandstone. Distal lacustrine units are skeletal mudstone-wackestone, microbialites, and laminated (siliciclastic) mudstone. Differentiation between wetlands and distal lacustrine units is not always possible. Palustrine features, Magadi-type chert (MTC), and evaporites record episodes of increased aridity and exposure. Farther upstream, during deposition of the upper part of the Brushy Basin Member, the ancestral Uncompahgre Uplift imposed a barrier to shallow, eastward-flowing groundwater that discharged into the San Juan/Paradox Basin on the upstream side of the uplift. This created the closed hydrologic setting necessary for development of an alkaline-saline wetland/lacustrine complex ("Lake" T'oo'dichi'). Silicic volcanic ash, delivered by prevailing winds from calderas west and southwest of the basin, contributed to the pore-water evolution in the sediments. A distinctive lateral hydrogeochemical gradient, reflecting increasing salinity and alkalinity in the pore waters, altered the ash to a variety of authigenic minerals that define concentric zones within the basin. The basinward progression of diagenetic mineral zones is smectite???clinoptilolite???analcime ??potassium feldspar???albite. The groundwater-fed wetlands were shallow and frequently evaporated to dryness. Scarce laminated gray mudstone beds record distinct episodes of freshwater lacustrine deposition that resulted from intermittent streams that carried detritus well out into the basin. ?? 2004 Elsevier B.V. All rights reserved.

Sedimentary Geology↗
USGS2016

Holocene climate variability and anthropogenic impacts from Lago Paixban, a perennial wetland in Peten, Guatemala

Analyses of an ~ 6 m sediment core from Lago Paixban in Peten, Guatemala, document the complex evolution of a perennial wetland over the last 10,300 years. The basal sediment is comprised of alluvial/colluvial fill deposited in the early Holocene. The absence of pollen and gastropods in the basal sediments suggests intermittently dry conditions until ~ 9000 cal yr. BP (henceforth BP) when the basin began to hold water perennially. Lowland tropical forest taxa dominated the local vegetation at this time. A distinct band of carbonate dating to ~ 8200 BP suggests regionally dry conditions, possibly associated with the 8.2 ka event. Wetter conditions during the Holocene Thermal Maximum are indicated by evidence of a raised water level and an open water lake. The timing of this interval coincides with strengthening of the Central American Monsoon. An abrupt change at 5500 BP involved the development of a sawgrass marsh and onset of peat deposition. The lowest recorded water levels date to 5500–4500 BP. Pollen, isotope, geochemical, and sedimentological data indicate that the coring site was near the edge of the marsh during this period. A rise in the water table after 4500 BP persisted until around 3500 BP. Clay marl deposition from 3500 to 210 BP corresponds to the period of Maya settlement. An increase in δ 13 C, the presence of Zea pollen, and a reduction in the percentage of forest taxa pollen indicate agricultural activity at this time. In contrast to several nearby paleoenvironmental studies, proxy evidence from Lago Paixban indicates human presence through the Classic/Postclassic period transition (~ 1000 BP) and persisting until the arrival of Europeans. Cessation of human activity around 210 BP resulted in local afforestation and the re-establishment of the current sawgrass marsh at Lago Paixban.

Peten↗
USGS2022

Sedimentological and geochemical perspectives on a marginal lake environment recorded in the Hartmann’s Valley and Karasburg members of the Murray formation, Gale crater, Mars

This study utilizes instruments from the Curiosity rover payload to develop an integrated paleoenvironmental and compositional reconstruction for the 65-m thick interval of stratigraphy comprising the Hartmann's Valley and Karasburg members of the Murray formation, Gale crater, Mars. The stratigraphy consists of cross-stratified sandstone (Facies 1), planar-laminated sandstone (Facies 2), and planar-laminated mudstone (Facies 3). Facies 1 is composed of sandstone showing truncated sets of concave-curvilinear laminae stacked into cosets. Sets are estimated to be meter-to sub-meter-scale, consistent with low-height dunes. Thin stratigraphic intervals of Facies 1 and stacking patterns with Facies 2 and 3 support a wet aeolian dune interpretation. Meter-thick packages of planar-laminated sandstone (Facies 2) are interpreted to represent interfingering dune-interdune strata. Facies 3 consists of meter-thick packages of planar-laminated mudstone interpreted to represent lacustrine deposition with persistent standing water. Integration of geochemistry with each facies reveals some compositional control based on the depositional process. Models for source rock composition from Alpha Particle X-Ray Spectrometer measurements show that facies derived from a basaltic source. Alteration indices and geochemical trends provide evidence that moderate chemical weathering occurred before compositional changes due to diagenesis. Differences in wt% FeO (T) and TiO 2 between facies are minimal, though trends point to sediment sorting in transport. Comparisons to terrestrial basaltic sedimentary systems indicate that the Hartmann's Valley and Karasburg facies reflect deposition in an environment where diverse subaqueous and subaerial facies persisted adjacent to a long-lived body of water.

Journal of Geophysical Research Planets↗
USGS1991

Molluscan paleoecology and sedimentation patterns of the Cenomanian-Turonian extinction interval in the southern Colorado Plateau region

Lithology, carbonate and organic carbon geochemistry, and molluscan macrofauna were investigated in fine-grained clay-dominated strata spanning the Cenomanian-Turonian Stage boundary in the southern Colorado Plateau region. Analyses of these data show basinal and onshore to offshore changes in sedimentologic and molluscan assemblage trends through the upper Cenomanian Sciponoceras gracile and Neocardioceras juddii and lower Turonian Watinoceras coloradoense Biozones. Diverse infaunal/epifaunal bivalve assemblages are best developed in the Sciponoceras gracile Biozone and at the more clay-rich nearshore sections. Gastropod and infaunal bivalve abundance and diversity decrease in an offshore and up-section direction as carbonate and organic carbon percentages generally increase. The Neocardioceras juddii Biozone precedes the stage boundary and is characterized in Utah and Arizona by pulsed increases in organic carbon and detrital-feeding gastropods, and by a shift in infaunal bivalve dominance toward species adapted for soft-substrate conditions. These data suggest that pulses of increased organic detrital resources and decreased substrate firmness were associated with the stage boundary extinctions. The stage boundary is marked by a change to depauperate epifaunal assemblages at western sections. At all sections, the base of the Watinoceras coloradoense Biozone is reflected by an abrupt increase in carbonate and decrease in organic carbon percentages as well as by the immigration of Mytiloides bivalves. Periods of progressive recovery through this biozone were associated with carbonate-rich depositional periods.

Arizona, Colorado, New Mexico, Utah↗
USGS2023

Observations of coastal circulation, waves, and sediment transport along West Maui, Hawaiʻi (November 2017– March 2018), and modeling effects of potential watershed restoration on decreasing sediment loads to adjacent coral reefs

Terrestrial sediment discharging from watersheds off West Maui, Hawaiʻi, has been documented as a primary stressor to local coral reefs, causing coral reef health to decline. The U.S. Geological Survey acquired and analyzed physical oceanographic and sedimentologic field data off the coast of West Maui to calibrate and validate physics-based, numerical hydrodynamic and sediment transport models of the study area developed by Deltares. These models simulated terrestrial sediment transport and dispersal from West Maui watersheds into coastal waters and how terrestrial sediment affects nearby coral reefs under different oceanographic forcing and watershed restoration scenarios. Wave energy and near-bed turbidity are positively correlated in the field observations, illustrating a process not captured by the model simulations in which sediment already deposited on the seabed is resuspended by wave action and subsequently transported by prevailing currents. In the model simulations, large waves during flood events led to a decrease in suspended-sediment concentrations. Notably, however, the model results only consider sediment entering coastal waters from five stream sources and do not simulate sediment already present on the seabed. The model simulations project that the Honokeana and Māhinahina coral reefs would experience the greatest reduction in sediment impacts from theoretical watershed restoration. Additionally, when large waves coincide with flood events, post-storm sedimentation generally decreases in the nearshore region, but increases in the region offshore of the reefs. The measured and modeled sediment dynamics demonstrate a demarcation between the coral reefs sheltered within embayments (Honolua reef) or behind points (Wahikuli reef) and those along the relatively open coastline between Kapalua and Kāʻanapali (Kapalua, Honokeana, Māhinahina, and Honokōwai reefs). The sheltered sites are affected by terrestrial sediment from single stream mouths, where most sediment is delivered within hours of a flood (rain) event. Once this sediment enters the nearshore, it settles out and remains within the reef area for a prolonged period owing to a lack of wave or current-driven bed shear stress. Thus, the primary effect of sediment on the reefs within these sheltered areas is sedimentation. In contrast, coral reefs along the unsheltered (or “open”) section of coastline (between Kapalua and Kāʻanapali) are more exposed to waves and terrestrial sediment from multiple stream sources. At these reefs, fine-grained terrestrial sediment can rarely settle but instead remains in suspension. Thus, even long after a flood event has occurred, these sites chronically experience light attenuation from suspended sediment. These analyses underscore the importance of understanding how coastal ocean waves and circulation can lead to different sediment dynamics and stressors for coral reefs along the same region of the West Maui coastline. These differing factors indicate that the most effective watershed restoration and mitigation strategies may vary among the different coral reefs and streams. An important next step is to determine how the science of this study can support management goals for these coral reefs: what are target reductions of sedimentation, suspended-sediment concentrations, or the resulting light attenuation? Then, using the coupled hydrodynamic-sediment model, we can examine which watershed restoration scenarios in each stream will best achieve those targets.

Hawaii↗
USGS2005

Origin and development of plains-type folds in the mid-continent (United States) during the late Paleozoic

Plains-type folds are local, subtle anticlines formed in the thin sedimentary package overlying a shallow, crystalline basement on the craton. They are small in areal extent (usually less than 1-3 km 2 [0.4-1.2 mi2]), and their amplitude increases with depth (usually tens of meters), which is mainly the result of differential compaction of sediments (usually clastic units) over tilted, rigid, basement fault blocks. The development of these structural features by continuous but intermittent movement of the basement fault blocks in the late Paleozoic in the United States mid-continent is substantiated by a record of stratigraphic and sedimentological evidence. The recurrent structural movement, which reflects adjustment to external stresses, is expressed by the change in thickness of stratigraphic units over the crest of the fold compared to the flanks. By plotting the change in thickness for different stratigraphic units of anticlines on different fault blocks, it is possible to determine the timing of movement of the blocks that reflect structural adjustment. These readjustments are confirmed by sedimentological evidence, such as convolute, soft-sediment deformation features and small intraformational faults. The stratigraphic interval change in thickness for numerous structures in the Cherokee, Forest City, and Salina basins and on the Nemaha anticline of the mid-continent United States was determined and compared for location and timing of the adjustments. Most of the adjustment occurred during and after time of deposition of the Permian-Pennsylvanian clastic units, which, in turn, reflect tectonic disturbance in adjacent areas, and the largest amount of movement on the plains-type structures occurred on those nearest and semiparallel to major positive features, such as the Nemaha anticline. Depending on the time of origin and development of plains-type folds, they may control the entrapment and occurrence of oil and gas. Copyright ??2005. The American Association of Petroleum Geologists. All rights reserved.

American Association of Petroleum Geologists Bulle↗
USGS1990

Perturbation and melting of snow and ice by the 13 November 1985 eruption of Nevado del Ruiz, Colombia, and consequent mobilization, flow and deposition of lahars

A complex sequence of pyroclastic flows and surges erupted by Nevado del Ruiz volcano on 13 November 1985 interacted with snow and ice on the summit ice cap to trigger catastrophic lahars (volcanic debris flows), which killed more than 23,000 people living at or beyond the base of the volcano. The rapid transfer of heat from the hot eruptive products to about 10 km2 of the snowpack, combined with seismic shaking, produced large volumes of meltwater that flowed downslope, liquefied some of the new volcanic deposits, and generated avalanches of saturated snow, ice and rock debris within minutes of the 21:08 (local time) eruption. About 2 ?? 107 m3 of water was discharged into the upper reaches of the Molinos, Nereidas, Guali, Azufrado and Lagunillas valleys, where rapid entrainment of valley-fill sediment transformed the dilute flows and avalanches to debris flows. Computed mean velocities of the lahars at peak flow ranged up to 17 m s-1. Flows were rapid in the steep, narrow upper canyons and slowed with distance away from the volcano as flow depth and channel slope diminished. Computed peak discharges ranged up to 48,000 m3 s-1 and were greatest in reaches 10 to 20 km downstream from the summit. A total of about 9 ?? 107 m3 of lahar slurry was transported to depositional areas up to 104 km from the source area. Initial volumes of individual lahars increased up to 4 times with distance away from the summit. The sedimentology and stratigraphy of the lahar deposits provide compelling evidence that: (1) multiple initial meltwater pulses tended to coalesce into single flood waves; (2) lahars remained fully developed debris flows until they reached confluences with major rivers; and (3) debris-flow slurry composition and rheology varied to produce gradationally density-stratified flows. Key lessons and reminders from the 1985 Nevado del Ruiz volcanic eruption are: (1) catastrophic lahars can be generated on ice- and snow-capped volcanoes by relatively small eruptions; (2) the surface area of snow on an ice cap can be more critical than total ice volume when considering lahar potential; (3) placement of hot rock debris on snow is insufficient to generate lahars; the two materials must be mechanically mixed together for sufficiently rapid head transfer; (4) lahars can increase their volumes significantly by entrainment of water and eroded sediment; and (5) valley-confined lahars can maintain relatively high velocities and can have catastrophic impacts as far as 100 km downstream. ?? 1990.

Journal of Volcanology and Geothermal Research↗
USGS1990

Modern configuration of the southwest Florida carbonate slope: Development by shelf margin progradation

Depositional patterns and sedimentary processes influencing modern southwest Florida carbonate slope development have been identified based upon slope morphology, seismic facies and surface sediment characteristics. Three slope-parallel zones have been identified: (1) an upper slope progradational zone (100–500 m) characterized by seaward-trending progradational clinoforms and sediments rich in shelf-derived carbonate material, (2) a lower gullied slope zone (500–800 m) characterized by numerous gullies formed by the downslope transport of gravity flows, and (3) a base-of-slope zone (> 800 m) characterized by thin, lens-shaped gravity flow deposits and irregular topography interpreted to be the result of bottom currents and slope failure along the basal extensions of gullies. Modern slope development is interpreted to have been controlled by the offshelf transport of shallow-water material from the adjacent west Florida shelf, deposition of this material along a seaward advancing sediment front, and intermittent bypassing of the lower slope by sediments transported in the form of gravity flows via gullies. Sediments are transported offshelf by a combination of tides and the Loop Current, augmented by the passage of storm frontal systems. Winter storm fronts produce cold, dense, sediment-laden water that cascades offshelf beneath the strong, eastward flowing Florida Current. Sediments are eventually deposited in a relatively low energy transition zone between the Florida Current on the surface and a deep westward flowing counter current. The influence of the Florida Current is evident in the easternmost part of the study area as eastward prograding sediments form a sediment drift that is progressively burying the Pourtales Terrace. The modern southwest Florida slope has seismic reflection and sedimentological characteristics in common with slopes bordering both the non-rimmed west Florida margin and the rimmed platform of the northern Bahamas, and shows many similarities to the progradational Miocene section along the west Florida slope. As with rimmed platform slopes, development of non-rimmed platform slopes can be complex and controlled by a combination of processes that result in a variety of configurations. Consequently, the distinction between the two slope types based solely upon seismic and sedimentological characteristics may not be readily discernible.

Marine Geology↗
USGS2022

Chandeleur Islands to Breton Island bathymetric and topographic datasets and operational sediment budget development: Methodology and analysis report

This study is part of the Coastal Protection and Restoration Authority (CPRA) Louisiana Barrier Island Comprehensive Monitoring (BICM) program. The goal of the BICM program is to provide long-term data on the barrier islands of Louisiana for monitoring change and assisting in coastal management. The BICM program uses historical data and acquires new data to map and monitor shoreline position, sediment properties, topography, bathymetry, and habitat. Since 2006, the U.S. Geological Survey (USGS) has collected geophysical and sedimentologic data across the Breton National Wildlife Refuge (BNWR) through the BICM program and collaborative USGS projects such as the Barrier Island Evolution Research project (under CPRA contract number 2000339324, BICM2–Chandeleurs TopoBathy DEM), which builds upon the previous BICM physical assessment of the BNWR outlined in a separate report. This project uses topographic and bathymetric data from three periods (1917–1922, 2006–2007, and 2013–2015) to develop digital elevation models (DEMs), measure elevation change, and calculate sediment budgets for the barrier island system. The sediment budget analysis, derived from the volumetric change between the three periods, is necessary for understanding sediment transport dynamics along barrier islands and providing information for effective coastal management. This report describes the methods used to acquire, process, and produce these products.

Louisiana↗
USGS1999

Techniques for restoration of disturbed coastal wetlands of the Great Lakes

A long history of human-induced degradation of Great Lakes wetlands has made restoration a necessity, but the practice of wetland restoration is relatively new, especially in large lake systems. Therefore, we compiled tested methods and developed additional potential methods based on scientific understanding of Great Lakes wetland ecosytems to providc an overview of approaches for restoration. We addressed this challenge by focusing on four general fields of science: hydrology, sedimentology, chemistry, and biology. Hydrologic remediation methods include restoring hydrologic connections between diked and hydrologically altered wetlands and the lakes, restoring water tables lowered by ditching, and restoring natural variation in lake levels of regulated lakes Superior and Ontario. Sedimentological remediation methods include management of sediment input from uplands, removal or proper management of dams on tributary rivers, and restoration of protective barrier beaches and sand spits. Chemical remediation methods include reducing or eliminating inputs of contaminants from point and non-pont sources, natural sediment remediation by biodegradation and chemical degradation, and active sediment remediation by removal or by in situ treatment Biological remediation methods include control of non-target organisms, enhancing populations of target organisms, and enhancing habitat for target organisms. Some of these method were used in three major restoration projects (Metzger Marsh on Lake Erie and Cootes Paradise and Oshawa Second Marsh on Lake Ontario), which are described as case studies to show practical applications of wetland restoration in the Great Lakes. Successful restoration techniques that do not require continued manipulation must be founded in the basic tenets of ecology and should mimic natural processes. Success is demonstrated by the sustainability, productivity, nutrient-retention ability, invasibility, and biotic interactions within a restored wetland.

Wetlands↗
USGS2018

Aeolian stratigraphy describes ice-age paleoenvironments in unglaciated Arctic Alaska

Terrestrial paleoenvironmental records with high dating resolution extending into the last ice age are rare from the western Arctic. Such records can test the synchronicity and extent of ice-age climatic events and define how Arctic landscapes respond to rapid climate changes. Here we describe the stratigraphy and sedimentology of a yedoma deposit in Arctic Alaska (the Carter Section) dating to between 37,000 and 9000 calibrated radiocarbon years BP (37–9 ka) and containing detailed records of loess and sand-sheet sedimentation, soil development, carbon storage, and permafrost dynamics. Alternation between sand-sheet and loess deposition provides a proxy for the extent and activity of the Ikpikpuk Sand Sea (ISS), a large dune field located immediately upwind. Warm, moist interstadial times (ca. 37, 36.3–32.5, and 15–13 ka) triggered floodplain aggradation, permafrost thaw, reduced loess deposition, increased vegetation cover, and rapid soil development accompanied by enhanced carbon storage. During the Last Glacial Maximum (LGM, ca. 28–18 ka), rapid loess deposition took place on a landscape where vegetation was sparse and non-woody. The most intense aeolian activity occurred after the LGM between ca. 18 and 15 ka when sand sheets fringing the ISS expanded over the site, possibly in response to increasingly droughty conditions as summers warmed and active layers deepened. With the exception of this lagged LGM response, the record of aeolian activity at the Carter Section correlates with other paleoenvironmental records from unglaciated Siberia and Alaska. Overall, rapid shifts in geomorphology, soils, vegetation, and permafrost portray an ice-age landscape where, in contrast to the Holocene, environmental change was chronic and dominated by aeolian processes.

Alaska↗
USGS2008

A Visual Basic program to plot sediment grain-size data on ternary diagrams

Sedimentologic datasets are typically large and compiled into tables or databases, but pure numerical information can be difficult to understand and interpret. Thus, scientists commonly use graphical representations to reduce complexities, recognize trends and patterns in the data, and develop hypotheses. Of the graphical techniques, one of the most common methods used by sedimentologists is to plot the basic gravel, sand, silt, and clay percentages on equilateral triangular diagrams. This means of presenting data is simple and facilitates rapid classification of sediments and comparison of samples. The original classification scheme developed by Shepard (1954) used a single ternary diagram with sand, silt, and clay in the corners and 10 categories to graphically show the relative proportions among these three grades within a sample. This scheme, however, did not allow for sediments with significant amounts of gravel. Therefore, Shepard's classification scheme was later modified by the addition of a second ternary diagram with two categories to account for gravel and gravelly sediment (Schlee, 1973). The system devised by Folk (1954, 1974)\ is also based on two triangular diagrams, but it has 21 categories and uses the term mud (defined as silt plus clay). Patterns within the triangles of both systems differ, as does the emphasis placed on gravel. For example, in the system described by Shepard, gravelly sediments have more than 10% gravel; in Folk's system, slightly gravelly sediments have as little as 0.01% gravel. Folk's classification scheme stresses gravel because its concentration is a function of the highest current velocity at the time of deposition as is the maximum grain size of the detritus that is available; Shepard's classification scheme emphasizes the ratios of sand, silt, and clay because they reflect sorting and reworking (Poppe et al., 2005). The program described herein (SEDPLOT) generates verbal equivalents and ternary diagrams to characterize sediment grain-size distributions. It is written in Microsoft Visual Basic 6.0 and provides a window to facilitate program execution. The inputs for the sediment fractions are percentages of gravel, sand, silt, and clay in the Wentworth (1922) grade scale, and the program permits the user to select output in either the Shepard (1954) classification scheme, modified as described above, or the Folk (1954, 1974) scheme. Users select options primarily with mouse-click events and through interactive dialogue boxes. This program is intended as a companion to other Visual Basic software we have developed to process sediment data (Poppe et al., 2003, 2004).

Computers & Geosciences↗
USGS2019

Estimating sand concentrations using ADCP‐based acoustic inversion in a large fluvial system characterized by bi‐modal suspended‐sediment distributions

Quantifying sediment flux within rivers is a challenge for many disciplines due, mainly, to difficulties inherent to traditional sediment sampling methods. These methods are operationally complex, high cost, and high risk. Additionally, the resulting data provide a low spatial and temporal resolution estimate of the total sediment flux, which has impeded advances in the understanding of the hydro‐geomorphic characteristics of rivers. Acoustic technologies have been recognized as a leading tool for increasing the resolution of sediment data by relating their echo intensity level measurements to suspended sediment. Further effort is required to robustly test and develop these techniques across a wide range of conditions found in natural river systems. This article aims to evaluate the application of acoustic inversion techniques using commercially available, down‐looking acoustic Doppler current profilers (ADCPs) in quantifying suspended sediment in a large sand bed river with varying bi‐modal particle size distributions, wash load and suspended‐sand ratios, and water stages. To achieve this objective, suspended sediment was physically sampled along the Paraná River, Argentina, under various hydro‐sedimentological regimes. Two ADCPs emitting different sound frequencies were used to simultaneously profile echo intensity level within the water column. Using the sonar equation, calibrations were determined between suspended‐sand concentrations and acoustic backscatter to solve the inverse problem. The study also analyzed the roles played by each term of the sonar equation, such as ADCP frequency, power supply, instrument constants, and particle size distributions typically found in sand bed rivers, on sediment attenuation and backscatter. Calibrations were successfully developed between corrected backscatter and suspended‐sand concentrations for all sites and ADCP frequencies, resulting in mean suspended‐sand concentration estimates within about 40% of the mean sampled concentrations. Noise values, calculated using the sonar equation and sediment sample characteristics, were fairly constant across evaluations, suggesting that they could be applied to other sand bed rivers.

Earth Surface Processes and Landforms↗
USGS2009

Recognizing former flood-tide deltas in the Holocene stratigraphic record from the Outer Banks, North Carolina, USA

Foraminiferal and sedimentologic data were collected by vibracoring a small, relict, short-lived, migrating inlet (New Inlet) and its flood-tide delta on the Outer Banks, North Carolina. These data, placed in the context of geospatial data derived from ground penetrating radar, were developed into a stratigraphic model for this sedimentary environment. The model was applied to vibracores collected from two additional barrier island segments within which historic inlets had not been recorded to investigate whether inlets had existed in these segments in the past. Five foraminiferal biofacies were recognized within the three barrier island segments. Biofacies 1 through 5 are all associated with interior and back-barrier depositional environments but Biofacies 4 and 5 contained foram-inifera indicating a sediment source on the shoreface or shallow inner shelf. Biofacies 4 and 5 thus represent overwash or flood-tide delta depositional settings. Utilizing the model as an interpretive tool, we recognized a previously undocumented inlet and flood-tide delta that existed prior to 962-662 cal. yrs BP, a few kilometers north of Rodanthe, NC. However, at a barrier island segment between Avon and Buxton, NC., the lack of information on stratal geometry and foraminiferal assemblages meant that it could not be determined whether this sedimentary succession was influenced more by overwash or inlet dynamics. Given the similarity of foraminiferal assemblages in overwash and flood-tide delta sediments, it is clear that additional lines of evidence (lithologic and geospatial) are required to recognize small-scale flood-tide delta deposits in the subsurface.

Stratigraphy↗
USGS2006

Controls on the accumulation of coal and on the development of anastomosed fluvial systems in the Cretaceous Dakota Formation of southern Utah

Alluvial strata of the Cretaceous Dakota Formation of southern Utah are part of a transgressive systems tract associated with a foreland basin developed adjacent to the Sevier orogenic belt. These strata contain valley fill deposits, anastomosed channel systems and widespread coals. The coals constitute a relatively minor part of the Dakota Formation in terms of sediment volume, but may represent a substantial amount of the time represented by the formation. The coals are separated by clastic units up to 20 m thick. The stratigraphically lowest clastic unit of the Dakota Formation lies above an unconformity cut into Jurassic rocks. Incised valleys associated with the unconformity are up to 12 m deep. Two discrete episodes of valley fill sedimentation are recognized, including a lower sandstone unit with conglomerate layers, and an upper, discontinuous, coal-bearing unit. After the valleys filled, the area became one of low relief where extensive mires formed. Peat accumulation was interrupted at least three times by deposition of clastic sediment derived from the west. The clastic units consist of sandstone, mudstone or heterolithic ribbon bodies, stacked tabular sandstones, and laminated mudstones, and contain minor coal beds less than 0·35 m thick. Ribbon bodies are 1–9 m thick and 15–160 m wide, have pronounced basal scours, and are filled with both lateral and vertical accretion deposits. An anastomosed channel complex is suggested by the large number of coeval channels of varying dimensions, the variation in the structure and grain size of channel fills, and the presence of abundant tabular sandstones interpreted as crevasse splays. Although some sandstone bodies have well developed lateral accretion surfaces, the overall ribbon geometry indicates that mature meandering streams were not well developed. This is in contrast to modern anastomosed systems, which are commonly thought to be a transitional morphology caused by avulsion of a meander belt to a new position on its floodplain. Rather than being a transitional channel pattern related to river avulsion, the anastomosed channels of the Dakota Formation may have formed part of a large inland delta that episodically invaded widespread mires. The mires developed during periods when clastic influx was reduced either by high rates of subsidence close to the thrust belt or by deflection of rivers by emergent thrusts.

Utah↗