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USGS2025

Pediment formation and subsequent erosion in Gale crater: Clues to the climate history of Mars

Evidence of paleo-rivers, fans, deltas, lakes, and channel networks across Mars has prompted much debate about what climate conditions would permit the formation of these surface water derived features. Pediments, gently sloping erosional surfaces of low relief developed in bedrock, have also been identified on Mars. On Earth, these erosional landforms, often thought to be created by overland flow and shallow channelized runoff, are typically capped by fluvial sediments, and thus in exceptionally arid regions, pediments are interpreted to record past wet periods. Here we document the Greenheugh pediment in Gale crater, exploiting the observational capability of the Curiosity rover. The absence of a fluvial cap suggests that the pediment was likely cut by wind erosion, not fluvial processes. The pediment was then buried by an aeolian deposit (Stimson sandstone) that mantled the lower footslopes of Aeolis Mons (informally known as Mt. Sharp). This burial terminated active wind erosion, preserving the pediment surface (as an angular unconformity). Groundwater was present prior-to, during, and shortly after Stimson deposition, perhaps contributing to lithification and certainly to early diagenesis. Post lithification, wind erosion first cut canyons in the northern most footslopes (north of Vera Rubin ridge). Unlithified gravels were deposited in these canyons, likely due to runoff from Mt. Sharp. Boulder-rich fluvial and debris flow deposits built a > 70 m thick sequence (Gediz Vallis ridge) on the southern Greenheugh pediment. Continued wind erosion left elevated patches of gravel on the northern footslopes, and exposure age dating shows that erosion essentially ceased before 1 Ga (but possibly much earlier). Erosion to the south led to emergence of Vera Rubin ridge, retreat of the Greenheugh pediment, and the formation of Glen Torridon valley. Hence, this footslope environment of Mt. Sharp records climate-driven periods of wind erosion, aeolian deposition (and groundwater activity), surface runoff and sediment deposition, followed by further significant wind erosion that declined to present very slow rates. This likely occurred during the late Hesperian and possibly into the Amazonian.

Icarus↗

USGS2025

Borehole geophysical time-series logging to monitor passive ISCO treatment of residual chlorinated-ethenes in a confining bed, NAS Pensacola, Florida

In-situ chemical oxidation (ISCO) is a common method to remediate chlorinated ethene contaminants in groundwater. Monitoring the effectiveness of ISCO can be hindered because of insufficient observations to assess oxidant delivery. Advantageously, potassium permanganate, one type of oxidant, provides the opportunity to use its strong electrical signal as a surrogate to track oxidant delivery using time-series borehole geophysical methods, like electromagnetic (EM) induction logging. Here we report a passive ISCO (P-ISCO) experiment, using potassium permanganate cylinders emplaced in boreholes, at a chlorinated ethene contamination site, Naval Air Station Pensacola, Florida. The contaminants are found primarily at the base of a shallow sandy aquifer in contact with an underlying silty-clay confining bed. We used results of the time-series borehole logging collected between 2017 and 2022 in 4 monitoring wells to track oxidant delivery. The EM-induction logs from the monitoring wells showed an increase in EM response primarily along the contact, likely from pooling of the oxidant, during P-ISCO treatment in 2021. Interestingly, concurrent natural gamma-ray (NGR) logging showed a decrease in NGR response at 3 of the 4 wells possibly from the formation of manganese precipitates coating sediments. The coupling of time-series logging and well-chemistry data allowed for an improved assessment of passive ISCO treatment effectiveness.

Florida↗

USGS2024

Groundwater and surface-water interactions in the Lower Duwamish Waterway, Seattle, Washington

The U.S. Geological Survey (USGS), in cooperation with the Washington State Department of Ecology (Ecology), conducted a study to describe the current understanding of the regional groundwater system of the lower Duwamish River valley and groundwater and surface-water interactions in the lower Duwamish Waterway. The lower Duwamish Waterway is the final 5-mile (mi) reach of the Duwamish River before it empties into Elliott Bay in Puget Sound near Seattle, Washington. A nearshore site (hereinafter referred to as “Nearshore Site” to distinguish the particular site from general discussions of nearshore areas) along the western shoreline of the Duwamish River, about 1.5 mi upstream from the river mouth, was selected for focused groundwater data collection by USGS. Data loggers were deployed in seven groundwater wells and one stilling well in the Duwamish River to measure specific conductance, temperature, and depth at 15-minute intervals for a period of about 2 years. At the Nearshore Site during 2020–22, water levels in the shallow wells were 3–8 feet (ft) higher than water levels in the deep wells, providing evidence for a low-permeability layer between the shallow and deep aquifers in this area. The shallow wells had a pronounced seasonal variability, with high water levels in winter and low water levels in summer. Data from the deep wells showed far less seasonal variability, with slight increases in winter and a near-constant water level from spring to autumn. The deep wells had a strong hydraulic connection to the Duwamish River, as evidenced by the synchronous water-level variability during the tidal cycle, whereas the shallow wells had minimal to no tidal response. The potentiometric maps developed for the Nearshore Site and surrounding areas indicate large differences in groundwater-flow directions for the shallow and deep aquifers at low and high tides. For the shallow aquifer, flow is toward the lower Duwamish Waterway near the Nearshore Site, regardless of the tidal condition. For the deep aquifer, a potentiometric trough forms parallel to the shoreline during high tide, indicating that groundwater flow converges from the uplands to the west and the Duwamish River to the east. The geometry of the potentiometric surfaces between the nearshore-most well and the shoreline is complex and is further confounded by intermittent shoreline armoring and other buried infrastructure, which could serve as either a barrier or a conduit to flow. Groundwater and surface-water interactions in the lower Duwamish Waterway are inherently complex as a result of three overarching factors. First, water levels in the lower reaches of the Duwamish River vary daily by 11–16 ft because of tides from Puget Sound, which create large swings in the hydraulic gradient in the nearshore groundwater system. Second, the density and chemical composition of water in the Duwamish River change daily with the tides and seasonally, which constrains how river water entering the nearshore sediments interacts with discharging groundwater. Third, the nearshore subsurface and shoreline conditions are heterogenous because of extensive shoreline armoring over the past century, which governs the flow of groundwater and infiltrating river water. These unique features of groundwater and surface-water interactions in the lower Duwamish Waterway thus govern the transport of terrestrial contaminants to the lower Duwamish Waterway. Furthermore, the heterogenous aquifer properties in the lower Duwamish Waterway contribute to spatially and temporally dynamic contaminant-transport processes.

Washington↗

USGS2025

Chemostratigraphy of the Cretaceous Hue Shale in Arctic Alaska: Exploring paleoceanographic controls on trace element enrichment, organic matter accumulation, and source-rock evolution

We document chemostratigraphy in an outcrop of late Albian to early Campanian (∼103–82 Ma) marine source rocks to better understand paleoenvironmental controls on trace element (TE) enrichment and organic matter accumulation in the distal Colville foreland basin of Arctic Alaska and how those drivers are linked to arc volcanism and successions of Cretaceous oceanographic and climatic biogeochemical events. This unique, 113-m-thick section of Cretaceous Hue Shale deposited during a series of previously undocumented Arctic Cretaceous oceanic anoxic events (Lease et al., 2024) is the only known exposure of thermally immature (0.48–0.52% R o , random vitrinite reflectance) Hue Shale in Arctic Alaska. Strata comprise mainly clay-rich mudstone with elevated total organic carbon (TOC) and hydrogen index values reaching 26.3 wt% (mean = 7.5 wt%) and 689 mg hydrocarbon (HC)/g TOC (mean = 385 mg HC/g TOC), respectively. Maceral composition consists predominantly of fluorescent amorphous organic matter, with abundant brightly fluorescent alginite, including Tasmanites , acritarchs, and Leiosphaeridia . Discrete layers of volcanic ash (preserved as bentonite) are present throughout the section and provide quantitative age control based on U–Pb dates. Chemostratigraphic trends are investigated to advance our understanding of local oceanographic conditions and controls on stratigraphic and temporal heterogeneity of Brookian source rocks. Concurrent sedimentary enrichment in Mo, U, V, Pb, and Cu across the Albian–Cenomanian boundary of the exposed basal gamma-ray zone, may reflect anoxic to euxinic benthic redox conditions favoring organic matter accumulation and preservation. Fluctuating degrees of anoxia-euxinia are inferred throughout the overlying Hue Shale succession, reflected by varying patterns of TE enrichment and TE–TOC covariation. Elevated C org /P molar ratios (>250) across most of the section, with several values exceeding 690, signify that enhanced biological productivity is sustained throughout deposition. Enhanced productivity, recorded by both C org /P and excess Ba, also parallels increases in source rock richness (elevated TOC and S 2 values) during the late Albian–early Cenomanian and late Cenomanian – Turonian. Enhanced productivity and variations in oceanic circulation/stratification likely both drove changes in benthic redox conditions that favored organic carbon accumulation and preservation. Increased continental arc volcanism (e.g., Okhotsk–Chukotka volcanic belt) and High Arctic Large Igneous Province magmatic eruptions throughout the Cretaceous, inferred to have influenced nutrient cycling and local aqueous nutrient availability, also have been invoked as potential drivers of organic carbon burial and source-rock development across the sedimentary sequence. Results presented here document the organic-rich and oil-prone source-rock quality of the Hue Shale in the distal part of the Colville foreland basin and bolster the potential for a Cretaceous petroleum system beneath the eastern North Slope.

Alaska↗

USGS2024

Groundwater, surface-water, and water-chemistry data, Black Mesa area, northeastern Arizona—2019–2021

The Navajo (N) aquifer is an extensive aquifer and the primary source of groundwater in the 5,400-square-mile Black Mesa area in northeastern Arizona. Water availability is an important issue in the Black Mesa area because of the arid climate, past industrial water use, and continued water requirements for municipal use by a growing population. Precipitation in the area typically ranges from less than 6 to more than 16 inches per year, depending on location. The U.S. Geological Survey water-monitoring program in the Black Mesa area began in 1971 and provides information about the long-term effects of groundwater withdrawals from the N aquifer for industrial and municipal uses. This report presents the results of data collected as part of the monitoring program in the Black Mesa area from calendar years 2020–2021 and, additionally, uses streamflow statistics from November and December 2019. The monitoring program includes measurements of (1) groundwater withdrawals (pumping), (2) groundwater levels, (3) spring discharge, (4) surface-water discharge, and (5) groundwater chemistry. In calendar year 2020, total groundwater withdrawals were estimated to be 2,680 acre-feet (acre-ft), and, in 2021, total withdrawals were estimated to be 2,570 acre-ft. Total withdrawals during 2021 were about 65 percent less than total withdrawals in 2005 because the Peabody Western Coal Company discontinued its use of water to transport coal in a coal slurry pipeline after 2005 and ceased mining operations in 2019. Owing to Navajo Nation and Hopi Reservation access restrictions during the Coronavirus pandemic, water levels were not collected from municipal wells in 2020 or 2021. Water levels measured in 2021 from wells completed in the unconfined areas of the N aquifer within the Black Mesa area showed a decline in 7 of 13 wells when compared with water levels from the prestress period (prior to 1965). The changes in water levels across all 13 wells ranged from +8.4 feet (ft) to −42.4 ft, and the median change was −0.4 ft. Water levels also showed decline in 11 of 12 wells measured in the confined area of the aquifer when compared to the prestress period. The median change for the confined area of the aquifer was −25.9 ft, with changes across all 12 wells ranging from +17.3 ft to −133.7 ft. Spring flow was measured at four springs between 2020 and 2021. Flow fluctuated during the period of record for Burro Spring and Pasture Canyon Spring, but a decreasing trend was statistically significant (p<0.05) at Moenkopi School Spring and Unnamed Spring near Dennehotso, Arizona. Discharge at Burro Spring has remained relatively constant since it was first measured in the 1980s, and discharge at Pasture Canyon Spring has fluctuated for the period of record. Continuous records of surface-water discharge in the Black Mesa area were collected from streamflow-gaging stations at the following sites: Moenkopi Wash at Moenkopi 09401260 (1976–2021), Dinnebito Wash near Sand Springs 09401110 (1993–2020), Polacca Wash near Second Mesa 09400568 (1994–2020), and Pasture Canyon Springs 09401265 (2004–2021). Median winter flows (November through February) of each winter were used as an estimate of the amount of groundwater discharge at the above-named sites. For the period of record, the median winter flows have generally remained constant at Polacca Wash and Pasture Canyon Springs, whereas a decreasing trend was observed at Moenkopi Wash and Dinnebito Wash. In 2020 and 2021, water samples were collected from a total of four springs in the Black Mesa area and analyzed for selected chemical constituents. Results from the four springs were compared with previous analyses from the same springs. Dissolved solids, chloride, and sulfate concentrations increased at Moenkopi School Spring during the more than 30 years of record at that site. Concentrations of dissolved solids and sulfate at Pasture Canyon Spring have not varied significantly (p>0.05) since the early 1980s, and there is no increasing or decreasing trend in those data. However, concentrations of chloride from Pasture Canyon Spring show a diminishing trend. Concentrations of dissolved solids, chloride, and sulfate at Unnamed Spring near Dennehotso have varied for the period of record, but there is no statistical trend in the data. Concentrations of dissolved solids at Burro Spring have varied for the period of record, but there is no statistical trend in the data. However, concentrations of chloride and sulfate from Burro Spring show a trend towards lower concentrations.

Arizona↗

USGS2025

Ungulate migrations of the Western United States, volume 5

Many ungulates migrate between distinct summer and winter ranges to take advantage of spatially and temporally variable food sources and avoid threats such as predators and deep snow. In 2018, the U.S. Department of the Interior established Secretarial Order 3362, which provided Federal support to expand existing research efforts to study ungulate populations and conserve their migrations by enhancing habitat quality for ungulates across the Western United States. In response to the order, the U.S. Geological Survey (USGS) created the Corridor Mapping Team, which is a collaboration among 11 State agencies, regional and Federal partners, and an expanding number of Tribal wildlife agencies. Together, the Corridor Mapping Team maps ungulate migrations throughout the Western United States and publishes them in the USGS “Ungulate Migrations of the Western United States” report series. This report details migrations and seasonal ranges from 36 additional herds and includes 2 herd updates detailed in previous reports. The Corridor Mapping Team has mapped the migrations and seasonal ranges of 218 unique herds for the report series, including this report. The report series serves as a map-based inventory of the ungulate migrations across the Western United States for biologists, managers, policymakers, and conservation practitioners. Building on the previous report volumes in the series, volume 5 additionally describes some of the local and national initiatives that are incorporating the products, tools, and information from this growing USGS report series.

Navajo Nation↗

USGS2024

Influence of inherited structure on flexural extension in foreland basin systems: Evidence from the northern Arkoma basin and southern Ozark dome, USA

Extensional faults are key components of foreland basin systems. They form within the upper crust in response to flexure of the lithosphere and accommodate subsidence within the foredeep and forebulge depozones. Such faults are excellent proxies for orogenic system evolution and control the distribution of natural resources and hazards. However, the spatiotemporal evolution of flexural extension has not been documented previously at a regional scale, thereby limiting our understanding of underlying geodynamic controls. Here, we resolve late Paleozoic flexural extension in the northern Arkoma basin and southern Ozark dome, USA. We synthesize a large database of previous mapping, existing research, subsurface data, and geophysical data into 3D geologic and 2D kinematic models. Mesh surfaces representing several key horizons from the Carboniferous Period (ca. 335-306 Ma) were constructed. These surfaces were built from oil and gas well tops (n = ∼10,000) and surface geologic map contacts using an advanced kriging method. The mesh surfaces are offset by a complex 3D fault network, allowing detailed analysis of along-strike and down-dip variations in fault displacement. Analysis of the 3D model reveals a regular and repeated fault segmentation pattern wherein E -W striking, left- and foreland-stepping en échelon normal faults are segmented by inherited NE striking basement faults. Maximum vertical separation along the E -W normal faults is generally focused between the inherited NE-trending faults. This suggests that the inherited basement faults delocalized extensional strain during late Paleozoic normal faulting. Maximum vertical separation and fault localization may correlate to areas with high-amplitude positive magnetic anomalies interpreted as Mesoproterozoic granitic rocks. Speculative covariance of magnetic anomalies and fault displacements implies that the relatively strong basement granite concentrated stress, leading to localized faulting within the relatively thin sedimentary cover. Lastly, we show that flexural extension migrated southeast to northwest from the Chesterian-Morrowan (ca. 335-319 Ma) to the Desmoinesian (ca. 306 Ma). The migratory flexural extension may be explained by diachronous loading during Pangean assembly, or by synchronous loading but variable load compensation due to inherent factors.

Arkansas, Oklahoma↗

USGS2024

Reservoir evolution, downstream sediment transport, downstream channel change, and synthesis of geomorphic responses of Fall Creek and Middle Fork Willamette River to water years 2012–18 streambed drawdowns at Fall Creek Lake, Oregon

Executive Summary Chapter A. Introduction Fall Creek Dam impounds Fall Creek Lake, a 10-kilometer-long reservoir in western Oregon and is operated by the U.S. Army Corps of Engineers (USACE) primarily for flood-risk management (or flood control) in late autumn through early spring months, as well as for water quality, irrigation, recreation, and habitat in late spring through early autumn. Since 2011 (water year [WY] 2012), Fall Creek Lake has been temporarily drawn down each year to facilitate downstream passage of juvenile spring Chinook salmon ( Oncorhynchus tshawytscha ) through the 55-meter (m) high dam. This annual dam operation is temporary, typically lasting about 1–2 weeks from WY 2012 through 2020 (drawdown operations in WY 2022–24 have increased to more than 6 weeks). Drawdown of the reservoir results in lake levels being lowered to the elevation near the historical, pre-dam streambed. The annual streambed drawdowns of WY 2012–18 have improved fish passage and led the USACE to formally adopt streambed drawdowns as part of annual operations at Fall Creek Dam. However, temporarily lowering the lake to streambed creates free-flowing conditions in the reservoir that result in the erosion and episodic export of predominantly sand and finer-grained sediments (less than 2 millimeters [mm]) to the lower gravel-bed reaches of Fall Creek and the Middle Fork Willamette River. The introduction of large volumes of sand and finer-grain sediment into the dam-regulated reaches downstream from Fall Creek Dam prompted questions about the geomorphic responses to annual streambed drawdowns within Fall Creek Lake and downstream reaches along Fall Creek and the Middle Fork Willamette River. The U.S. Geological Survey (USGS) in partnership with USACE initiated a comprehensive geomorphic and sediment transport investigation to assess the coupled processes of reservoir erosion, sediment evacuation from Fall Creek Lake, and patterns of sediment transport and deposition in reaches downstream from the Fall Creek Dam that have resulted from annual streambed drawdowns. The purpose of this report is to systematically describe the processes of sediment erosion, transport, and deposition at Fall Creek Lake and geomorphic interactions between reaches upstream and downstream from Fall Creek Dam that relate to dam operations. Specifically, this report focuses on evaluating geomorphic responses to streambed drawdowns from WY 2012 through 2018 and placing drawdown-induced geomorphic responses within the broader context of physiographic and historical conditions and dam operations of Fall Creek and Middle Fork Willamette Rivers. Key objectives for this study were to characterize changes in reservoir morphology and substrate at Fall Creek Lake, describe the character and temporal pattern of sediment transport downstream from Fall Creek Dam, characterize geomorphic changes in channel reaches downstream from the Fall Creek Dam, and relate these data to the annual streambed drawdowns of WY 2012–18. This study uses multiple independent monitoring and measurement approaches to assess site, reach, and river-scale geomorphic responses to drawdowns to inform dam and reservoir management. Patterns and processes of reservoir evolution were assessed with geomorphic mapping and volumetric analyses of topography through comparison of multiple digital surface models (DSMs). Just downstream from Fall Creek Dam, analyses of sediment export from the reservoir focused on suspended sediment but also incorporated bedload analyses to assess sediment sizes. Geomorphic assessments downstream from the dam used reach-scale and site-scale approaches to document changes in channel morphology and substrate, including site measurements of sand and finer-grained sediment deposition and in-channel bed-material, volumetric change analyses from comparison of digital elevation models (DEMs), and repeat geomorphic mapping. Findings from this study inform river management and dam operations by providing an understanding of (1) coupled upstream-downstream geomorphic responses to the Fall Creek Lake streambed drawdowns, (2) geomorphic responses of Fall Creek Lake streambed drawdowns in comparison to drawdowns at other large dams, (3) controls on reservoir erosion and downstream geomorphic responses, and (4) implications for future hydrogeomorphic changes that may result from continued drawdowns and monitoring activities to assess those changes. Chapter B. Reservoir Morphology and Evolution Related to Dam Operations at Fall Creek Lake To understand the volume and distribution of sediment accumulation in Fall Creek Lake since dam closure in 1965, decadal-scale sedimentation patterns (spanning approximately 1965–2016) are evaluated using a combination of storage curve analyses and geomorphic mapping. Short-term (drawdown event-scale) patterns of erosion, sedimentation, and sediment export downstream are evaluated using a combination of geomorphic mapping and change detection analyses that quantify the distribution and total volume of sediment erosion and deposition within Fall Creek Lake. Geomorphic mapping of reservoir topography and analyses of historical datasets reveals four categories of landforms and sediment processes within Fall Creek Lake related to lake level operations: lacustrine sedimentation expressed in the reservoir floor, fluvial erosion and deposition within historical stream channels during streambed drawdowns, channel-like features created by erosion within the reservoir floor during streambed drawdowns, and erosion on reservoir hillslopes. Where the reservoir floor is mapped for this study as pelagic (deep water), deposition up to 3 meters (m) thick by lacustrine processes and burial of pre-dam topography with deposits thinning toward the edges of the valley floor and upstream areas of reservoir are observed. Despite over 50 years of sediment accumulation since dam construction, the main stream channels of Fall and Winberry Creeks (or reservoir thalwegs) through the reservoir are well defined, though their distinct morphology is likely influenced by a long history of recurring historical drawdowns to or near streambed since dam construction. Unregulated streamflow and sediment transport through the reservoir primarily are confined to these channels during the streambed drawdown periods. Erosional channel-like features created by drawdowns are carved through underlying, unconsolidated reservoir floor sediments and are most prominent in the lower reservoir below minimum conservation pool (the low pool elevation during winter flood season); sediment generated from the formation of these drawdown channels is more likely to be transported through and out of the reservoir than sediment deposits along the reservoir hillslopes at the valley margins that are separated from main channels by areas of low-gradient reservoir floor. Morphologic changes in the lower reservoir topography between January 2012 and November 2016 indicate overall net erosion of about 129,500 cubic meters (m 3 ). The most prominent geomorphic changes occurred along the main channels of Fall and Winberry Creeks near the Fall Creek Dam where incision, lateral migration, and slumping banks resulted in vertical and lateral adjustments to channel position, whereas most changes fell below the detectable limit on higher-elevation reservoir floor surfaces except where erosion occurred along features mapped as drawdown channels. Chapter C. Sediment Delivery from Fall Creek Lake and Transport through Downstream Reaches USGS implemented a sediment monitoring program in WY 2013–18 to evaluate the quantity and character of reservoir sediment exported from Fall Creek Lake during streambed drawdowns. Turbidity and suspended sediments were monitored annually autumn through spring to span the WY 2013–18 streambed drawdowns; however, unequal monitoring timeframes each year reduced the ability to compare results and factors affecting sediment export from the reservoir difficult between years. These data were originally measured to develop regressions and compute suspended-sediment loads (SSL). Bedload sediment monitoring from a cableway at the Fall Creek streamgage was completed in the autumn-winter of WY 2013 and 2017. The limited number of samples and presumed variability in sediment supply from the reservoir precluded construction of streamflow and bedload discharge relations to compute more than instantaneous bedload. Sand and finer-grained silts and clays were transported from the reservoir in suspension, though some coarser grains (up to 32 mm) were also mobilized and transported downstream from the dam as bedload. Observations of increased sediment transport downstream from Fall Creek Dam coincided with lake levels approaching about 3 m (10 feet [ft] or elevation 690 ft) above the streambed regulating outlets. Suspended-sediment loads computed for the full monitoring periods WY 2013–18 at the Fall Creek streamgage, located 1.4 kilometers (km) downstream from Fall Creek Dam, range from 54,700 metric tons (t) in WY 2013 to 13,900 t in WY 2018. Although the total annual SSL varied from year to year, the overall seasonal patterns of suspended sediment transport throughout each year were similar during monitoring in WY 2013-18. Suspended-sediment loads were low prior to the drawdown, then increased rapidly as lake levels lowered and approached the streambed. In the weeks following the drawdown period, as pool levels were increased, SSL remained slightly elevated above pre-drawdown levels but generally declined through the following winter and spring except during streamflow-driven pulses of suspended-sediment transport. WY 2013 had the greatest total computed SSL for each streambed drawdown and partial-year monitoring period. SSL computed for the partial-year period have generally decreased since WY 2013 and have varied by about 6,800 t with the exception of WY 2014. WY 2014 SSL reflects anomalously low sediment export due to low streamflows and freezing conditions that stabilized reservoir floor deposits. Bedload measurements in the short 1.4-km reach between Fall Creek Dam and the Fall Creek streamgage showed an inverse correlation between bedload transport rates and discharge, which probably reflects diminishing supply of coarse-sized sediment. Sand was more abundant (60–100 percent) than gravel in bedload samples confirming sand and finer-grained sediment dominated sediment evacuated from the reservoir during streambed drawdowns at Fall Creek Lake. Chapter D. Geomorphic Responses to Fall Creek Lake Streambed Drawdowns Downstream from Fall Creek Dam In the days, weeks, and months following streambed drawdown operations at Fall Creek Dam through WY 2018, sites downstream from the dam displayed a variety of geomorphic responses to reservoir sediment delivery within the main channel and overbank areas. Evaluation of streambed elevations at two streamgages located 1.4 km downstream from the dam on Fall Creek and 16.3 km downstream from the dam on the Middle Fork Willamette River indicated the effects of drawdown sediment on bed elevations were modest and transient. Repeat particle size measurements (October 2015 and September 2016) at five sites along Fall Creek and the Middle Fork Willamette River showed similar grain-sized distributions that do not reveal substantial deposition of fine-grained sediment related to the WY 2016 streambed drawdown. Altogether, these findings indicate that transport capacity in the main, low-flow channels of Fall Creek and Middle Fork Willamette River during WY 2012–18 was sufficient to mobilize and evacuate reservoir sediments from streambed drawdowns or other bank material and tributary sources. However, other monitoring for this study indicate low-velocity zones in off-channel areas are prime locations for sand and finer-grain sediment deposition. Patterns of overbank sediment accumulation indicate that the magnitude and timing of overbank deposition on bars and low-elevation floodplain varies with proximity to the dam, geomorphic setting, streamflows, and other factors. Sand and finer-grained reservoir sediments carried as suspended-sediment load in the reaches downstream from Fall Creek Dam were deposited in overbank areas as observed with clay-horizon markers during WY 2016–17. Overbank deposition quantified with Geomorphic Change Detection (GCD) software evaluated landform-scale patterns of erosion and deposition using repeat light detection and ranging (lidar) surveys at two sites in the Upper Fall Creek reach and one site in the Jasper reach for 3 years (2012–15) and one site in the Clearwater reach for 6 years (2009–15). Deposition thickness and spatial patterns from the GCD analysis were variable; some sites had dispersed but measurable deposition while at others, deposition was highly localized and exceeded 1 m in depth. Patterns of overbank deposition illustrate interactions among bar morphology, local hydraulics, and suspended-sediment transport dynamics that can create patches of highly localized deposition. The measured deposition at the two Fall Creek GCD sites likely resulted from reservoir sediments released from Fall Creek Lake during streambed drawdowns in WY 2016 and 2017 because the limited sediment inputs from bank material (geomorphically laterally stable reach) or tributaries (no significant tributaries) provided few other sediment sources. On the Middle Fork Willamette River, observed patterns of overbank deposition could reflect sediment sourced from upstream tributaries, bank erosion, or Fall Creek Lake streambed drawdown operations. Despite the introduction of several thousand tons of reservoir sediment delivered from the Fall Creek Lake streambed drawdowns to below-dam river corridors, reach-scale mapping of channel features downstream from Fall Creek Dam shows minimal evidence of changes in channel planform or landforms that can be attributed to a drawdowns in WY 2012–16. On Upper Fall Creek reach, widespread increases in gravel bars or other in-channel sediment did not result from the five streambed drawdowns. The main changes attributable to sediment releases from Fall Creek Lake were localized increases in vegetated bar area, particularly on channel margin areas where sand and finer-grain sediment was deposited and rapidly colonized by vegetation. The area of mapped secondary water features decreased between 2005 and 2016, but that may be due to lower discharges depicted in the 2016 aerial photographs and less mapped area of inundation. Primary changes along the Lower Fall Creek reach include a 6.4 percent decrease in area of secondary water features between 2011 and 2016, and a nearly twofold increase in the area of unvegetated bars. Immediately downstream from the Fall Creek confluence, there were negligible changes in the location and areas of vegetated bars and the main wetted channel between 2005 and 2016, and local increases in bar area cannot be attributed solely to deposition of reservoir sediments from Fall Creek Lake because (1) areas along the Middle Fork Willamette River just upstream from the Fall Creek confluence display similar type and magnitude of changes and (2) some of the increases at the confluence area pre-date the drawdowns. The cumulative effect of sediment releases from Fall Creek Lake streambed drawdowns from WY 2012 to 2016 on downstream channel planform and landforms are modest compared to the river-scale transformations and planform changes that occurred in the decades following dam construction. Chapter E. Discussion of Geomorphic Responses of Fall Creek and Middle Fork Willamette River to Streambed Drawdowns at Fall Creek Lake Multiple aspects of Fall Creek Dam infrastructure and operations exert first-order controls on the magnitudes of reservoir erosion that occur during the streambed drawdowns and ultimately determine the sediment delivery to downstream reaches. Key aspects of the dam and its operations that are most relevant to assessing geomorphic responses to streambed drawdowns include the (1) dam infrastructure, including configuration and size of regulating outlets and their proximity to the streambed which dictates the capacity and competence of the river to deliver sediment to downstream reaches and mode of sediment transport as suspended-sediment load or bedload; (2) frequency of historical drawdowns and long-term, year-round dam operations and lake level management, which partly dictate reservoir morphology and locations and magnitudes of readily erodible materials; (3) dam operations and hydroclimatic conditions during the streambed drawdown (including length of the drawdown and streamflows entering the reservoir), which directly control the timing, duration and magnitude of reservoir erosion and sediment evacuation; and (4) dam operations following the streambed drawdown operation that regulate streamflows (and thereby sediment transport conditions) downstream of Fall Creek Dam which primarily reflect interactions between hydroclimatic conditions and flood control operations. Patterns of sediment erosion and evacuation observed in this study at Fall Creek Lake from WY 2012–18 suggest that reservoir erosion during annual streambed drawdowns may remain similar or decrease in future years assuming (1) annual streambed drawdown operations are implemented in similar manner as the WY 2012–18 drawdowns (in terms of duration, late autumn or early winter implementation, rate of pool-level lowering to reach streambed, and other factors), (2) streambed drawdowns coincide with similar conditions as were observed WY 2012–18 (similar sediment yield into reservoir, low reservoir inflows, limited precipitation, moderate air temperature), and (3) no major geomorphic changes in the main reservoir channels of Fall and Winberry Creeks occur (for example, channel avulsion). Under such conditions, it is hypothesized that the stream channel within the reservoir would achieve a quasi-equilibrium state with respect to annual influx and export of sediment and aided by the substantial amount of in-channel bedrock, will remain laterally stable without erosion across reservoir deposits. Patterns of sediment transport measured at the Fall Creek streamgage downstream from Fall Creek Dam provide insight into the potential effects of future streambed drawdowns at Fall Creek Lake. Analyses of suspended sediment measured in WY 2013–18 show a major reduction in suspended-sediment loads between WY 2013 and later years, indicating streamflows transporting sediment through the reservoir to downstream reaches during streambed drawdowns have become supply limited. The 6-year suspended-sediment monitoring and sampling program is insufficient to make predictions about future sediment transport conditions because of uneven monitoring periods and varying controls on reservoir sediment erosion. It is likely that future suspended-sediment loads will be variable but similar to those observed in WY 2015–18 if operational, climatic, and geomorphological factors remain similar to those monitored WY 2015–18. Suspended-sediment loads downstream from Fall Creek Lake will likely remain highest when regulating outlets are fully open and Fall Creek is free flowing with the reservoir fully drained with little to no residual pool. Over time, it is possible that the suspended-sediment loads would reflect mobilization of reservoir sediment deposited in the previous year rather than erosion of sediment deposited years or decades earlier. Bedload is likely to remain a small fraction of the total sediment load evacuated from the reservoir and is relatively modest compared with pre-dam bedload transport rates because most coarse sediment remains trapped by the dam. If sediment releases from Fall Creek Lake and ensuing streamflow conditions follow a similar pattern in the future as was assessed in this study spanning WY 2012–18, near-term geomorphic adjustments downstream of the dam are expected to be modest. Barring major operational, climatic, and geomorphological changes, local site-scale deposition on bars, overbank areas, or off-channel features that persists several months after the streambed drawdown will likely continue to be highly variable, ranging from negligible to several centimeters of deposition. At the landform-scale, low velocity areas nearest to Fall Creek Dam will likely continue to undergo rapid deposition immediately during and after a streambed drawdown event, similar to patterns observed for WY 2012–18. Some of the sediment entering these off-channel features and margin areas may be temporarily stored, then later remobilized and dispersed farther downstream. But if newly deposited sediment persists through the following spring, there is a greater likelihood that local vegetation will establish, reinforce deposited material, and trap sediment during later drawdowns. The reach-scale geomorphic changes may become more apparent if (1) streambed drawdowns continued for several decades, and geomorphic changes were measured at decadal scales or (2) the amount of sediment introduced to downstream reaches substantially increased and (or) sediment transport capacity decreased. The continued streamflow regulation of Fall Creek Dam after sediment releases provides an opportunity to strategically manage streamflows during and after the streambed drawdowns to minimize downstream sediment impacts and ensure other operational thresholds are satisfied. This study provides a comprehensive foundation of datasets and geomorphic analyses to inform dam operations at Fall Creek Lake, monitor sediment transport downstream, and consider operational schemes for future drawdowns. The datasets from this study also provide baselines of sediment transport and geomorphic conditions to assess future changes in reservoir and downstream environments. Future monitoring could be tailored to address specific questions regarding the long-term geomorphic effects of streambed drawdowns on fluvial habitats, flood hazards, cultural resources, or downstream water quality. Future monitoring activities could focus on the relevant geomorphic processes and spatial domains within the three categories used for this study: (1) reservoir erosion and net sediment evacuation, (2) sediment delivery to downstream reaches, including magnitude and temporal pattern of sediment transport, and (3) geomorphic responses of downstream reaches to sediment delivery. Specifically, high priority future monitoring activities could include: Repeat topographic or photographic surveys in the reservoir to characterize changes occurring within individual drawdowns, to quantify sediment export, to determine temporal changes in reservoir storage, and to identify locations of erosion and deposition. Continuous, year-round turbidity monitoring supplemented with suspended-sediment measurements at a streamflow-gaging station immediately downstream from the dam to quantify sediment export. Repeat geomorphic monitoring, mapping, or modeling in downstream reaches to track changes in channel and over bank features using a combination of site- and reach-scale monitoring approaches. This could support assessments of sediment deposition and ensuing vegetation encroachment on flood hazards and habitats and examine how sediment transport and depositional processes may be affected by different sediment supply, streamflow, or dam management scenarios.

Oregon↗

USGS2025

Critical minerals in orogenic (gold) and Coeur d’Alene-type mineral systems of the United States

Orogenic and Coeur d’Alene-type mineral systems are produced by metamorphic devolatilization of thick volcanic or siliciclastic sedimentary rock sequences and the focused flow of hydrothermal fluids upwards along crustal-scale faults. Most orogenic systems are found along the Cordilleran orogen, stretching from California northwards into Alaska, whereas most Coeur d’Alene-type systems occur in the Proterozoic Belt Basin in Idaho and Montana. Although the deposit types in these systems are exploited for precious and base metals, potential exists for the production of critical minerals necessary for current (2025) societal needs in the United States. Publicly available geochemical data compiled for these mineral systems, coupled with mineralogical characteristics, indicate that several critical minerals could potentially be recovered from unmined resources and processed mine waste: arsenic, antimony, tellurium, cobalt, and tungsten from orogenic gold deposits and zinc, antimony, arsenic, and manganese from Coeur d’Alene-type systems. These critical minerals reside primarily in arsenopyrite (arsenic), scheelite (tungsten), siderite (manganese), sphalerite (zinc), tetrahedrite (antimony and arsenic), stibnite (antimony), and telluride (tellurium) minerals.

continental United States↗

USGS1997

Application of acoustical methods for estimating water flow and constituent loads in Perdido Bay, Florida

Water flow and quality data were collected from December 1994 to September 1995 to evaluate variations in discharge, water quality, and chemical fluxes (loads) through Perdido Bay, Florida. Data were collected at a cross section parallel to the U.S. Highway 98 bridge. Discharges measured with an acoustic Doppler current profiler (ADCP) and computed from stage-area and velocity ratings varied roughly between + or - 10,000 cubic feet per second during a typical tidal cycle. Large reversals in flow direction occurred rapidly (less than 1 hour), and complete reversals (resulting in near peak net-upstream or downstream discharges) occurred within a few hours of slack water. Observations of simultaneous upstream and downstream flow (bidirectional flow) were quite common in the ADCP measurements, with opposing directions of flow occurring predominantly in vertical layers. Continuous (every 15 minutes) discharge data were computed for the period from August 18, 1995, to September 28, 1995, and filtered daily mean discharge values were computed for the period from August 19 to September 26, 1995. Data were not computed prior to August 18, 1995, either because of missing data or because the velocity rating was poorly defined (because of insufficient data) for the period prior to landfall of hurricane Erin (August 3, 1995). The results of the study indicate that acoustical techniques can yield useful estimates of continuous (instantaneous) discharge in Perdido Bay. Useful estimates of average daily net flow rates can also be obtained, but the accuracy of these estimates will be limited by small rating shifts that introduce bias into the instantaneous values that are used to compute the net flows. Instantaneous loads of total nitrogen ranged from -180 to 220 grams per second for the samples collected during the study, and instantaneous loads of total phosphorous ranged from -10 to 11 grams per second (negative loads indicate net upstream transport). The chloride concentrations from the water samples collected from Perdido Bay indicated a significant amount of mixing of saltwater and freshwater. Mixing effects could greatly reduce the accuracy of estimates of net loads of nutrients or other substances. The study results indicate that acoustical techniques can yield acceptable estimates of instantaneous loads in Perdido Bay. However, estimates of net loads should be interpreted with great caution and may have unacceptably large errors, especially when saltwater and freshwater concentrations differ greatly.

Florida↗

USGS2026

Decadal trends in the quality of groundwater used for public drinking-water supply in California, 2004–23, California Groundwater Ambient Monitoring and Assessment Program, Priority Basin Project

This study provides a comprehensive assessment of decadal changes in the quality of groundwater used for public drinking-water supply at 444 monitoring sites across California during 2004–23. We assessed decadal step trends in groundwater quality for 145 water-quality constituents and geochemical indicators statewide and across geographic and land-use based network groups. We evaluated the statistical significance of directional changes (predominant increase or decrease of constituent concentrations) and the magnitude of those changes across all network groups. Uranium showed the most widespread directional and high-magnitude increases of all constituents with regulatory benchmarks statewide, particularly in the agriculture-dominated Central Valley as well as urban-and desert-dominated regions of Southern California. Fluoride and perchlorate showed the most widespread directional and high-magnitude decreases of all constituents with regulatory benchmarks statewide, which were also most pronounced in Southern California. Although arsenic and nitrate did not often register significant directional changes across network groups, they showed widespread, high-magnitude changes in both directions (increase and decrease) at levels often exceeding 10 percent of respective regulatory benchmarks statewide. Triazine herbicides (atrazine and simazine) and the gasoline oxygenate methyl tert -butyl ether showed significant directional decreases statewide, but not at levels considered to be of high magnitude compared to respective regulatory benchmarks. We observed significant directional and high-magnitude increases of total dissolved solids statewide, which were most pronounced in agricultural areas. Analysis of explanatory geochemical indicators indicated that prevalent statewide increases of alkalinity and calcium were the predominant components of the observed statewide increases in total dissolved solids by mass. Widespread increases in groundwater alkalinity and calcium across agricultural and urban areas may be related, in part, to warm-season irrigation and other anthropogenic factors that have shifted soil weathering dynamics over the long term. Increasing alkalinity concentrations were related to increasing uranium concentrations, particularly in areas with aquifer materials derived from granitic rocks. Conversely, increasing calcium concentrations were related to decreasing fluoride concentrations, particularly in areas where fluoride occurred naturally at elevated concentrations. Decrease of perchlorate, triazine herbicides, and methyl tert -butyl ether are likely related to decreased anthropogenic source inputs over time and natural attenuation in aquifers.

California↗

USGS2026

Velocity-independent dry friction on mica: A realization of ideal Amontons-Coulomb friction

The Amontons-Coulomb friction law assumes that the frictional force between materials is independent of sliding velocity. However, as Coulomb noted, this is a rough approximation, and a second-order dependence of friction on the logarithm of sliding velocity is incorporated in a commonly used ‘rate- and state-dependent’ friction representation. Here we conduct shear experiments on mica, a layer-structured mineral, at temperatures ranging from 25 to 200ºC and under normal stress of 100 MPa. The friction coefficient clearly depends on the logarithmic sliding velocity at 25ºC, but rate sensitivity decreases with increasing temperature until at 200ºC, the friction coefficient is independent of sliding velocity. Our findings could initiate the development of velocity-independent frictional materials, realizing the ideal Amontons-Coulomb friction.

Physical Review Letters↗

USGS2024

Assessment and characterization of ephemeral stream channel stability and mechanisms affecting erosion in Grand Valley, western Colorado, 2018–21

The Grand Valley in western Colorado is in the semiarid Southwest United States. The north side of the Grand Valley has many ungaged ephemeral streams, which are of particular interest because (1) the underlying bedrock geology, Late Cretaceous Mancos Shale, is a sedimentary rock deposit identified as a major salinity contributor to the Colorado River and (2) despite infrequent streamflows of short duration, monsoon-derived floods in these ephemeral streams can carry substantial amounts of sediment downstream, affecting upstream and downstream banks and channel cross sections. The study area is of interest, because salinity, or the total dissolved solids concentration, in the Colorado River causes an estimated $300 million to $400 million per year in economic damages in the United States, and it is estimated 62 percent of the Upper Colorado River Basin’s total dissolved solid loads originate from geologic sources. In an effort to minimize salt contributions to the Colorado River from public lands administered by the Bureau of Land Management, a comprehensive salinity control approach is typically used to reduce nonpoint sources of salinity through land management techniques and practices. In 2018, the U.S. Geological Survey, in cooperation with the Bureau of Land Management, began an assessment of ephemeral streams located on the north side of the Grand Valley, western Colorado, to characterize stream channel stability and identify mechanisms affecting erosion. The U.S. Geological Survey developed a method for automatically extracting channel cross-section geometry from existing remotely sensed terrain models. Based on estimated flood stage and surrogate streamflows, hydraulic characteristics were calculated. Furthermore, the channel geometries and hydraulic characteristics were used to estimate channel stability using a statistical model. Cross-section stabilities were determined from a stream channel stability assessment for a subset of 1,406 visited (field observed) locations out of 13,415 cross sections, which were delineated from remotely sensed terrain models. The application of Manning’s resistance equation in combination with multiple logistic regression models demonstrated channel stability can be estimated with a 0.845 goodness of fit for a validation dataset when using a combination of drainage area, width-to-depth ratio, sinuosity, and shear stress as the explanatory variables. Stream channel stability was extrapolated for 13,415 unvisited (not field observed) cross sections using the multiple logistic regression model and defined explanatory variables. Mapping of the ephemeral streams and their associated stabilities may be used by the Bureau of Land Management to prioritize areas for remediation or changes in management strategies to reduce sediment and salinity loading to the Colorado River. The study found channel stability within the ephemeral streams to be spatially variable, longitudinally discontinuous, and dictated by changes in channel bed slope. The stable ephemeral streams were relatively wide and shallow and often had smaller drainage areas with less potential for producing shear stresses capable of overcoming channel adhesion. A change in channel bed slope can provide the means necessary to generate shear stresses appropriate to initiate erosion and a subsequent stability transition to incising channels. Channel widening happens when either or both banks of an incising channel reach a critical height for mass wasting, or when channel curvature causes higher sidewall stress. Regardless, widening channels can promote increases in sinuosity and subsequently reduce steep channel bed slopes. Consequently, stable and widening channels can have comparable bed slopes, making channel bed slope a poor explanatory variable to predict channel stability overall, despite its function to initiate channel instability. The results were based on a surrogate 0.10 annual exceedance probability (AEP; return period equal to the 10-year flood) interval streamflow, although it was recognized fluctuations in streamflow would also affect channel stability. Past and current changes within the study area affect streamflow; therefore, mechanisms affecting erosion include land use disturbances, soil compaction, loss of vegetation cover, drought, less frequent and more extreme precipitation, and fires—which all intensify the potential runoff and erosion within the study area.

Colorado↗

USGS2024

Conceptualization and simulation of groundwater flow and groundwater availability in the Boone and Roubidoux aquifers in northeastern Oklahoma, 1980–2017

Oklahoma Groundwater Law (Oklahoma Statute § 82-1020.5) requires that the Oklahoma Water Resources Board conduct hydrologic investigations to determine the maximum annual yield for the State’s groundwater basins. The Boone and Roubidoux aquifers (also known as the Springfield Plateau aquifer and Ozark aquifer, respectively) are bedrock aquifers that extend from northeastern Oklahoma into Kansas, Arkansas, and Missouri. At present (2024), the Oklahoma Water Resources Board has yet to legally issue orders for the final determination of maximum annual yields for the Boone and Roubidoux aquifers. To support determination of a maximum annual yield, the U.S. Geological Survey, in cooperation with the Oklahoma Water Resources Board, developed a hydrogeologic framework, a conceptual groundwater-flow model, and a calibrated numerical groundwater-flow model for the Boone and Roubidoux aquifers. Three types of groundwater-availability scenarios were simulated by using the calibrated numerical model. These scenarios were used to (1) estimate equal-proportionate-share groundwater withdrawal rates (groundwater withdrawal applied equally over the aquifer), (2) quantify the potential effects of projected groundwater withdrawals on groundwater storage over a 50-year period, and (3) simulate the potential effects of a hypothetical 10-year drought. For the Boone aquifer, equal-proportionate-share groundwater withdrawal rates were 1.10, 0.98, and 0.96 acre-feet per acre per year for the 20-, 40-, and 50-year scenarios, respectively. For the Roubidoux aquifer, equal-proportionate-share groundwater withdrawal rates were 1.76, 1.34, and 1.25 acre-feet per acre per year for the 20-, 40-, and 50-year simulations, respectively. For the 50-year scenarios, stream seepage was minimally affected. Over the 10-year drought scenario, groundwater storage in the Boone and Roubidoux aquifers decreased by 660,451 acre-feet (6.7 percent) and 508,472 acre-feet (1.0 percent), respectively.

Oklahoma↗

USGS2026

Bathymetric and velocimetric surveys at highway bridges crossing the Missouri River near Kansas City, Missouri, August 8–9, 2023

Bathymetric and velocimetric data were collected by the U.S. Geological Survey, in cooperation with the Missouri Department of Transportation, near 8 bridge crossings of the Missouri River near Kansas City, Missouri, on August 8–9, 2023. A multibeam echosounder mapping system was used to obtain channel-bed elevations for river reaches that extended about 1,550 to 1,640 feet longitudinally and generally extended laterally across the active channel from bank to bank during low floodflow to nonflood conditions. These surveys provided the channel geometry and hydraulic conditions of the river at the time of the surveys and provided characteristics of scour holes, which may be useful in developing or verifying predictive guidelines or equations for computing potential scour depth. The data collected from the surveys may also be useful to the Missouri Department of Transportation as a record of low floodflow conditions in regards to the stability and integrity of the bridges with respect to bridge scour. Bathymetric data were collected around every in-channel pier. Scour holes were at most piers where bathymetry could be obtained, except for those piers on banks or surrounded by riprap. All the bridge sites in this study were surveyed and documented in previous studies. The average difference between the bathymetric surfaces ranged from 0.07 to 4.16 feet higher in 2023 than 2019, which indicates overall deposition between the survey dates, as might be expected based purely on streamflow at the time of the survey. However, the average difference between the bathymetric surfaces ranged from 1.44 feet higher to 1.88 feet lower in 2023 than 2015, which indicates a dynamic equilibrium of scour and deposition overall between those surveys, despite the lower flow conditions in 2023. Similarly, the average difference between the bathymetric surfaces ranged from 3.18 feet higher to 5.19 feet lower in 2023 than 2011, which indicates a relative equilibrium between scour and deposition overall, albeit the trend was toward scour as might be expected because of the substantial flood event in 2011. Riprap blankets and alignment to flow had a substantial effect on the size of the scour hole for a given pier. Piers that were partially or fully surrounded by riprap blankets had scour holes that were substantially smaller (to nonexistent) compared to piers with no rock or riprap and effectively mitigated the scour holes historically observed at these piers. Several of the structures had piers that were skewed to primary approach flow. At most of the structures, the scour hole was deeper and longer on the side of the pier with impinging flow than the leeward side, with some amount of deposition on the leeward side, as typically observed at piers skewed to approach flow.

Kansas, Missouri↗

USGS2025

Arctic fold-and-thrust belts

The modern Arctic has been formed through a series of continent–continent collisions, accretion of terranes and phases of crustal extension. The Neoproterozoic Timanian, Paleozoic Caledonian and Uralian, and late Mesozoic Verkhoyansk–Kolyma, Chukotkan and Brookian orogenies formed several large fold-and-thrust belts (FTBs). The FTBs are exposed across vast areas of continents and continue offshore to form a complex tectonic basement for thick sedimentary basins, playing an important role in the history of accumulation and deformation of younger unmetamorphosed sedimentary successions that are the subject of this volume. Recognition of the importance of FTBs in the Arctic geological history and their role as a controlling factor of development of Arctic sedimentary basins resulted in this chapter, in which we review the current state of knowledge about Arctic FTBs and highlight questions that remain to be addressed. Enclosure D , a map showing boundaries of the FTB and their internal first-order structural fabric, is a part of the overview.

Book chapter↗

USGS2026

Prioritizing resource protection and understanding potential susceptibility of springs to surficial changes in a low-temperature geothermal system

Geothermal systems are vulnerable to changes in water budget and composition, requiring science-based management. This study uses a dataset of spring water temperatures, time series of groundwater residence time tracers (tritium and carbon-14), and stable isotopes of water to understand geothermal flow in a low-temperature geothermal system in north west Colorado, United States (Steamboat Springs). The geothermal system is bisected by the Yampa River, necessitating a stream mass balance approach to quantify total discharge. Time series analysis of water temperature data provides a ranked list of features more susceptible to surficial changes, which is corroborated using time series of tritium which indicate spatially distinct patterns of mixing between modern and pre-modern groundwater. All springs contain a portion of pre-modern groundwater that is thousands to tens of thousands of years old, a period coinciding with melting of extensive Pleistocene glaciers that was likely one of the recharge sources to the geothermal system. Stream mass balance indicates that greater than 80% of the total geothermal discharge is derived from diffuse or small springs, highlighting the extensive nature of the geothermal outflow zone and the association with local geologic structures. This study provides baseline data to support management of the Steamboat Springs geothermal system and indicates the utility of these approaches in developing science-based geothermal management.

Colorado↗

USGS2025

A spatial analysis of the groundwater emergence flood hazard in Long Island, New York and near coastal areas surrounding Long Island Sound in New York, Connecticut, and Rhode Island

Long Island, New York and near coastal areas surrounding Long Island Sound are densely populated and, like other coastal areas, are susceptible to flooding from several potential sources, including stormwater from precipitation events, tidal flooding and storm surge, and groundwater inundation or groundwater emergence flooding. The latter refers to the intersection of a rising water table with land surface or critical infrastructure. Many studies of flood drivers either neglect or only briefly discuss how shallow groundwater conditions may contribute to or exacerbate flood conditions. As part of a comprehensive study of compound flood hazards in the near coastal areas surrounding Long Island and Long Island Sound, a spatial analysis was completed, in cooperation with the Environmental Protection Agency’s Long Island Sound Study, using available regional datasets to characterize the potential hazard for groundwater emergence flooding. The approximately 3,100 square mile study area was subdivided into 11,407 900-meter by 900-meter (approximately 3,000-feet by 3,000-feet) grid cells, for the purposes of integrating the spatial datasets to calculate and map the groundwater emergence flood hazard. The depth to the water table, hydrologic soil groups, and National Land Cover Database were harmonized to the common grid. A groundwater emergence flood hazard rank was calculated for each grid cell for current average conditions following a set of rules accounting for the depth to the water table and the percent of area within each cell with slow infiltrating soils. A higher sea level position scenario was also calculated for the Long Island part of the study area. The calculated groundwater emergence flood hazard rank was reviewed in concert with the National Land Cover Data Base to identify developed areas and associated infrastructure that may be at risk to groundwater emergence flooding. Study results indicate that the groundwater emergence flood hazard is highest in coastal areas and near surface water where the water table is close to ground surface. Inland areas away from surface water bodies are not likely to be exposed to groundwater emergence flooding. For Long Island, under a scenario with higher sea level position, a greater groundwater emergence flood hazard is calculated in some locations closer to the coast and where land is submerged. Away from the coast and surface-water drainage, the groundwater emergence flood hazard is similar between the current average sea level condition and a higher sea level position scenario.

EarthArXiv↗