Search USGS⌕ Search

SEARCH · Search USGS

Results for “The Sedimentary Record”

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 757 records · Page 42Linked to original sources
USGS2024

Indications of preferential groundwater seepage feeding northern peatland pools

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

Maine↗
USGS1989

Observed parameters for turbidity-current flow in channels, Reserve Fan, Lake Superior

Fine-grained tailings discharged from a taconite-ore processing operation near the shore of Lake Superior produced turbidity currents that transported the sediment from a small delta into deep water at Silver Bay, Minnesota. Deposition over nearly 20 years produced a sublacustrine fan with two prominent channels. During 1972 and 1973, a current meter anchored 5 m above the lake floor adjacent to one of the channels recorded episodic turbidity-current flow events lasting as long as two weeks. To understand flow parameters for turbidity currents better, a short-term experiment within a channel on Reserve Fan in 1975 measured those variables not previously directly observed for channelized turbidity currents: flow thickness, flow density, and concurrent velocity. The observed flow thickness, approximately 16 m, is nearly four times the channel depth. Calculations using the average flow speeds (8 to 12 cm/sec) and the dilute concentration of the flow as measured during the experiment yield a value for the drag coefficient that is in remarkable agreement with estimated values commonly used for deriving speeds of turbidity currents using dimensions of submarine channels and properties of the sediments.

Journal of Sedimentary Petrology↗
USGS2012

Crustal structure of east central Oregon: Relation between Newberry Volcano and regional crustal structure

A 180-km-long seismic refraction transect from the eastern High Cascades, across Newberry Volcano, to the eastern High Lava Plains is used to investigate the subvolcanic crustal and upper mantle velocity structure there. Near-surface volcanic flows and sedimentary debris (1.6-4.7 km/s), ranging from 3 to 5 km in thickness, overlie subvolcanic Basin and Range structures. East and west of Newberry Volcano, the subvolcanic basement (5.6 km/s) has been downwarped, producing 5-km-deep basins. The midcrust (8- to 28-km depth) is characterized by velocities ranging from 6.1 to 6.5 km/s and varies laterally in thicknesses. The lower crust is characterized by an unusually high velocity (about 7.4 km/s), and its geometry mirrors the subvolcanic basement geometry. The Moho is located at a depth of 37 km and represents a transition to an upper mantle velocity of 8.1 km/s. The shallow subsurface (1.2 km) beneath Newberry Volcano is characterized by high-velocity 5.6 km/s, versus 4.1 km/s for the surrounding area) intrusions and appears to be located on a basement high. Beneath the seismic refraction array at Newberry Volcano, an absence of low-velocity anomalies suggests that large silicic magma chambers do not exist in the upper crust, but apparent high attenuation of the seismic wave field may be consistent with either partial melts in small volumes, elevated crustal temperatures, and/or poor geophone-recording site coupling.

Oregon↗
USGS2013

Tracking sedimentation from the historic A.D. 2011 Mississippi River flood in the deltaic wetlands of Louisiana, USA

Management and restoration of the Mississippi River deltaic plain (southern United States) and associated wetlands require a quantitative understanding of sediment delivery during large flood events, past and present. Here, we investigate the sedimentary fingerprint of the 2011 Mississippi River flood across the Louisiana coast (Atchafalaya Delta, Terrebonne, Barataria, and Mississippi River Delta basins) to assess spatial patterns of sedimentation and to identify key indicators of sediment provenance. The sediment deposited in wetlands during the 2011 flood was distinguished from earlier deposits based on biological characteristics, primarily absence of plant roots and increased presence of centric (planktonic) diatoms indicative of riverine origin. By comparison, the lithological (bulk density, organic matter content, and grain size) and chemical (stable carbon isotopes of bulk organic matter) properties of flood sediments were nearly identical to the underlying deposit. Flood sediment deposition was greatest in wetlands near the Atchafalaya and Mississippi Rivers and accounted for a substantial portion (37% to 85%) of the annual accretion measured at nearby monitoring stations. The amount of sediment delivered to those basins (1.1–1.6 g cm −2 ) was comparable to that reported previously for hurricane sedimentation along the Louisiana coast (0.8–2.1 g cm −2 ). Our findings not only provide insight into how large-scale river floods influence wetland sedimentation, they lay the groundwork for identifying previous flood events in the stratigraphic record.

Louisiana↗
USGS2013

Sedimentary history of the Tethyan margins of eastern Gondwana during the Mesozoic

A composite Mesozoic geological history for the Gondwana margins to the Eastern Tethys Ocean can be assembled from stratigraphic successions on the Australian and Himalayan margins and from drill sites of Ocean Drilling Program Legs 122 and 123. During the Triassic, this region drifted northwards, entering tropical paleolatitudes during the Late Triassic-Early Jurassic, then returned to mid-latitudes for the Middle Jurassic through Early Cretaceous. Shallow-water carbonates are restricted to the tropical-latitude interval; at other times, the margins are dominated by clastic deposition. Episodes of deltaic sandstone progradation over the shelves are caused by eustatic sealevel fluctuations, by wet climatic conditions within the source regions and by local tectonic activity. A major hiatus between Callovian shallow-water shelf deposits and Oxfordian deep-water sediments is an ubiquitous feature, which may be related to a widespread plate tectonic reorganization and the cascading effects of associated sealevel rise and elevated carbon dioxide levels. Off Northwest Australia, this Callovian/Oxfordian event also coincides with an episode of block faulting. Marginal sediments deposited during the Late Jurassic are mainly marine claystone containing abundant terrigenous organic matter. Shallow depths of carbonate compensation (CCD) during the Late Jurassic through Early Cretaceous prevented the preservation of carbonate over most of the Argo basin off Northwest Australia, and these deep-sea sediments consist mainly of condensed, oxygenated radiolarian-rich claystone. During the late Kimmeridgian-early Tithonian, a downward excursion in the CCD enabled limited preservation of some larger nannofossils and mollusc fragments within the pelagic deposits, a feature also recorded in coeval deposits in the Atlantic. Explosive volcanism accompanied the final stages of rifting between India and Australia during the late Berriasian and Valanginian, producing volcaniclastic debris washing into the deltas and widespread ash deposits. The late Barremian and Aptian sediments indicate a rise in the CCD, accompanied by warming of the region and an increased delivery of organic-rich claystone into the basins.

Book chapter↗
USGS1984

Origin of epigenetic calcite in coal from Antarctica and Ohio based on isotope compositions of oxygen, carbon and strontium

Isotopic compositions of oxygen, carbon and strontium of calcite cleats in coal seams of southern Victoria Land, Antarctica, and Tuscarawas County, Ohio, contain a record of the conditions a the time of their formation. The Antarctic calcites (?? 18O(SMOW) = +9.14 to +11.82%0) were deposited from waters enriched in 16O whose isotopic composition was consistent with that of meteoric precipitation at low temperature and high latitude. The carbon of the calcite cleats (?? 13C(PDB) = -15.6 to -16.9%0) was derived in part from the coal (?? 13C(PDB) = -23.5 to -26.7%0) as carbon dioxide and by oxidation of methane or other hydrocarbon gases. The strontium ( 87Sr 86Sr = 0.71318-0.72392) originated primarily from altered feldspar grains in the sandstones of the Beacon Supergroup. Calcite cleats in the Kittaning No. 6 coal seam of Ohio (?? 18O(SMOW) = +26.04 to +27.79%0) were deposited from waters that had previously exchanged oxygen, possibly with marine carbonate at depth. The carbon (?? 13C(PDB) = 0.9 to +2.4%0) is enriched in 13C even though that cleats were deposited in coal that is highly enriched in 12C and apparently originated from marine carbonates. Strontium in the cleats ( Sr 87 0.71182-0.71260) is not of marine origin but contains varying amounts of radiogenic 87Sr presumably derived from detrital Rb-bearing minerals in the adjacent sedimentary rocks. The results of this study suggest that calcite cleats in coal of southern Victoria Land, Antarctica, were deposited after the start of glaciation in Cenozoic time and that those in Ohio precipitated from formation waters derived from the underlying marine carbonate rocks, probably in the recent geologic past. ?? 1984.

Chemical Geology↗
USGS2005

Implications of volcanism in coastal California for the Neogene deformation history of western North America

The geologic record of coastal California includes evidence of numerous volcanic centers younger than 30 Ma that do not appear to have erupted in an arc setting. By correlating these volcanic centers with specific slab windows predicted from analysis of magnetic anomalies on the Pacific plate, we add new constraints to tectonic reconstructions since 30 Ma. Our correlations, such as erupting the Morro Rock–Islay Hill complex south of the Pioneer fracture zone and the Iversen Basalt south of the Mendocino fracture zone, require larger displacements within western North America than advocated by most previous authors. Specifically, we infer at least 315 km of motion between the Sierra Nevada and rigid North America at an azimuth of about N60°W and at least 515 km between Baja California and rigid North America in a similar direction. A consequence of inferring a large displacement of Baja California is that the Pacific–North American plate boundary must have developed most of its current form prior to 10 Ma. We interpret a slab window developing between Cocos and Monterey plates after 19 Ma that reconstructs under nearly all of the southern California volcanic centers dated at 18–14 Ma. Most of the sedimentary basins associated with volcanic rocks show brief periods of rapid subsidence synchronous with volcanism, followed by slow subsidence of variable but often extended duration, consistent with rapid extension of cold lithosphere over recently introduced hot asthenosphere.

California↗
USGS2011

Sedimentary response to orogenic exhumation in the northern Rocky Mountain Basin and Range province, Flint Creek basin, west-central Montana

Middle Eocene through Upper Miocene sedimentary and volcanic rocks of the Flint Creek basin in western Montana accumulated during a period of significant paleoclimatic change and extension across the northern Rocky Mountain Basin and Range province. Gravity modelling, borehole data, and geologic mapping from the Flint Creek basin indicate that subsidence was focused along an extensionally reactivated Sevier thrust fault, which accommodated up to 800 m of basin fill while relaying stress between the dextral transtensional Lewis and Clark lineament to the north and the Anaconda core complex to the south. Northwesterly paleocurrent indicators, foliated metamorphic lithics, 64 Ma (40Ar/39Ar) muscovite grains, and 76 Ma (U-Pb) zircons in a ca. 27 Ma arkosic sandstone are consistent with Oligocene exhumation and erosion of the Anaconda core complex. The core complex and volcanic and magmatic rocks in its hangingwall created an important drainage divide during the Paleogene shedding detritus to the NNW and ESE. Following a major period of Early Miocene tectonism and erosion, regional drainage networks were reorganized such that paleoflow in the Flint Creek basin flowed east into an internally drained saline lake system. Renewed tectonism during Middle to Late Miocene time reestablished a west-directed drainage that is recorded by fluvial strata within a Late Miocene paleovalley. These tectonic reorganizations and associated drainage divide explain observed discrepancies in provenance studies across the province. Regional correlation of unconformities and lithofacies mapping in the Flint Creek basin suggest that localized tectonism and relative base level fluctuations controlled lithostratigraphic architecture.

Canadian Journal of Earth Sciences↗
USGS1992

Beach-ridge development and lake-level variation in southern Lake Michigan

The most accurate source of information on lake-level fluctuations in the Great Lakes is the historical record from lake-level gauges. Although it can be semiquantitatively extended back into the late 1700's, the historical record is too short to recognize long-term patterns of lake-level behavior. To extend the historical record, information must be obtained from the Great Lakes geologic record. Such information includes the elevation and age of geomorphic features and stratigraphic sequences. One of the longest geologic records of late Holocene lake-level variation is preserved in a beach-ridge complex along the southern shore of Lake Michigan called the Toleston Beach. This strandplain contains over 150 beach ridges that arc across northwestern Indiana and fan out into northeastern Illinois. Each ridge was formed during the fall from a high lake level, and the elevation of the foreshore deposits in each ridge provides information on the upper physical limit of lake level over the past 4000 years. Three scales of quasi-periodic lake-level variation were determined by radiocarbon-dating basal peats of wetlands between the ridges and by measuring the elevation of foreshore (swash) deposits within ridges. These three scales are: (1) a short-term and small-scale fluctuation of 25 to 35 years with a range of about 0.5 to 0.6 m; (2) an intermediate-term and meso-scale fluctuation of 140 to 160 years and a range of about 0.8 to 0.9 m; and (3) a long-term and large-scale fluctuation of 500 to 600 years and a range of 1.8 to 3.7 m. The short-term and intermediate-term fluctuations are reflected in the historical record. An increase in the rate of shoreline progradation from east to west across Indiana's shoreline causes differential preservation of the lake-level fluctuations. That is, groups of four to six ridges in the western part of the strandplain that formed in response to the small-scale fluctuations combine eastward into single ridges and groups of ridges representing the meso-scale fluctuations. The large-scale fluctuations produced the most dramatic response in the western part of the Toleston Beach. Here, following each high stand, individual spits prograded southward off of a bedrock headland. The successive spit extensions created several small lakes landward of the spits and started the 20 km eastward stream-mouth deflection of the Grand Calumet River across Indiana's western lakeshore.

Illinois, Indiana↗
USGS1984

Shoreface translation and the Holocene stratigraphic record: Examples from Nova Scotia, the Mississippi Delta and eastern Australia

Classic descriptive models of barrier sedimentation have been developed with data from the Atlantic and Gulf coasts of the United States. These models are dominated by low to moderate rates of relative sea level (RSL) rise and wave energy. Barriers respond by landward recycling of sediment through the mechanism of shoreface retreat. Sedimentation processes on the central coast of New South Wales (N.S.W.), Australia, consist of rapid RSL rise in early Holocene times followed by a stillstand since 6500 B.P. Wave energy is relatively high year-round and sand sources for barrier formation are only found on the inner shelf. Barrier sedimentation on the central coast of N.S.W. exhibits a thick, composite sequence composed of a basal marine transgressive sand overlain by regressive beach and dune facies. The Louisiana coast surrounding the Mississippi delta is underlain by compacting deltaic muds which generate very rapid rates of RSL rise. The Louisiana coast experiences low wave energy punctuated by high-energy tropical and extra-tropical storm events. Barrier sediments accumulate from the erosion of deltaic headlands and undergo a transformation from subaerial barrier island systems to subaqueous shoals located on the inner shelf. Drumlins experience coastal erosion on the Eastern Shore of Nova Scotia and provide a sediment source for compartmented estuary mouth barriers. An ongoing, moderate rise of RSL results from the passage of a glacial forebulge. Wave energy is intermediate between Louisiana and N.S.W. and displays a seasonal pattern dominated by frequent winter storms. Coastal barrier sedimentation is episodic, consisting of a period of beach ridge progradation followed by barrier destruction and re-establishment further landward. The three contrasting sedimentary sequences found in examples from Louisiana, N.S.W. and Nova Scotia indicate that presently available sedimentation models from locations such as the middle Atlantic or Texas coasts of the United States may only represent well-documented regional case studies. A true generalised coastal sedimentation model is required which can identify the parameters controlling vertical and horizontal translation of the depositional surface and provide relationships between these parameters which quantitatively predict the genesis, distribution and geometry of coastal sedimentary facies.

Marine Geology↗
USGS2004

Pocomoke Sound Sedimentary and Ecosystem History

Summary of Results: Pocomoke Sound Sediment and Sediment Processes Transport of sediment from coastal marshes. Analyses of pollen and foraminifera from surface sediments in Pocomoke Sound suggest that neither the upstream forested wetlands nor coastal marshes bordering the sound have contributed appreciably to particulate matter in the 10- to 1000-micron size range that is currently being deposited in the sound. Sediment processes derived from short-lived isotope. Analyses of beryllium-7, cesium-137 and lead-210 and redox sensitive elements from Pocomoke sediments showed that there has been a significant increase in anthropogenic elements since the late 1940's when the Delmarva Peninsula became more accessible from the Baltimore-Washington region. Cesium-137 was found to be a useful tool to determine changes in sedimentation within the system. Three major stages of sedimentation occurred. Before 1950, the system was equilibrium with the agriculture activity in the watershed, whereas urbanization and agricultural activity changes during and immediately preceding World War II resulted in increased sediment flux. Around 1970, the sediment flux diminished and there was an apparent increase in bank erosion sediment to the deeper parts of the system. Rates of sediment deposition. Radiocarbon, lead-210, and pollen dating of sediment cores from Pocomoke Sound indicate relatively continuous deposition of fine-grained sediments in the main Pocomoke channel at > ~7 m water depths. Mean sediment accumulation rates during the past few centuries were relatively high (>1 cm yr -1 ). The ages of coarser-grained sediments (sands) blanketing the shallow (< ~ 7 m water depth) flanks of Pocomoke Sound are not well constrained but were probably deposited discontinuously. Impacts of land-use on benthic biota. The Pocomoke Sound paleoecological record shows that in the 1940-50s and again in the 1970-80s, the sound experienced unprecedented changes in the benthic assemblages of both ostracodes and foraminifera that can be attributed to degradation in water quality. These changes represent perturbations to the natural variability in faunal assemblages, which are normally driven by climatically influenced changes in salinity regimes. Changes in 20th century benthic communities were characterized by the rise to dominance of facultative anaerobic taxa tolerant of hypoxia and detrital-feeding species, reflecting increased influx of organic matter, and perhaps greater turbidity. Results support the hypothesis of Orth et al. (2002) and Orth and Moore (1983) that unprecedented changes to the bay ecosystem affected submerged aquatic vegetation in the Tangiers-Pocomoke region prior to large-scale monitoring began in the 1970s and 80s. Comparison of Pocomoke paleoecological record with those from the mainstem bay indicate that environmental degradation during the 20th century was nearly synchronous bay-wide within the limits of sediment core chronology (10-20 years). Stable isotopic evidence for decadal water quality changes. Stable isotopic records from benthic foraminifera in Pocomoke Sound sediment cores, especially oxygen isotopes, document regional decadal and centennial climate processes which influence salinity and water quality over the past few centuries. These results provide indirect evidence for discharge-driven changes in freshwater and presumably river-borne sediment from the watershed to the sound. They are consistent with studies in the mainstem indicating the important influence of climatic and hydrological processes on water quality. Pollen evidence for high sedimentation and vegetation change during colonial land clearance. Pollen assemblages from sediment cores in Pocomoke Sound document high sedimentation rates (0.7->4.0 cm yr -1 ) at most sites throughout the Sound in post-Colonial time. These results confirm those from other regions of the bay that land-clearance increased the flux of river-borne sediment to certain r

Open-File Report↗
USGS2002

Sequence stratigraphic and sedimentologic significance of biogenic structures from a late Paleozoic marginal- to open-marine reservoir, Morrow Sandstone, subsurface of southwest Kansas, USA

Integrated ichnologic, sedimentologic, and stratigraphic studies of cores and well logs from Lower Pennsylvanian oil and gas reservoirs (lower Morrow Sandstone, southwest Kansas) allow distinction between fluvio-estuarine and open marine deposits in the Gentzler and Arroyo fields. The fluvio-estuarine facies assemblage is composed of both interfluve and valley-fill deposits, encompassing a variety of depositional environments such as fluvial channel, interfluve paleosol, bay head delta, estuary bay, restricted tidal flat, intertidal channel, and estuary mouth. Deposition in a brackish-water estuarine valley is supported by the presence of a low diversity, opportunistic, impoverished marine ichnofaunal assemblage dominated by infaunal structures, representing an example of a mixed, depauperate Cruziana and Skolithos ichnofacies. Overall distribution of ichnofossils along the estuarine valley was mainly controlled by the salinity gradient, with other parameters, such as oxygenation, substrate and energy, acting at a more local scale. The lower Morrow estuarine system displays the classical tripartite division of wave-dominated estuaries (i.e. seaward-marine sand plug, fine-grained central bay, and sandy landward zone), but tidal action is also recorded. The estuarine valley displays a northwest-southeast trend, draining to the open sea in the southeast. Recognition of valley-fill sandstones in the lower Morrow has implications for reservoir characterization. While the open marine model predicts a "layer-cake" style of facies distribution as a consequence of strandline shoreline progradation, identification of valley-fill sequences points to more compartmentalized reservoirs, due to the heterogeneity created by valley incision and subsequent infill. The open-marine facies assemblage comprises upper, middle, and lower shoreface; offshore transition; offshore; and shelf deposits. In contrast to the estuarine assemblage, open marine ichnofaunas are characterized by a high diversity of biogenic structures representing the activity of a benthic fauna developed under normal salinity conditions. Trace fossil and facies analyses allow environmental subdivision of the shoreface-offshore successions and suggest deposition in a weakly storm-affected nearshore area. An onshore-offshore replacement of the Skolithos ichnofacies by the Cruziana ichnofacies is clearly displayed. The lower Morrow fluvio-estuarine valley was incised during a drop of sea level coincident with the Mississippian-Pennsylvanian transition, but was mostly filled during a subsequent transgression. The transgressive nature of the estuarine infill is further indicated by the upward replacement of depauperate brackish-water trace fossil assemblages by the open-marine Cruziana ichnofacies. Additional stratal surfaces of allostratigraphic significance identified within the estuary include the bayline surface, the tidal ravinement surface, the wave ravinement surface, and a basinwide flooding surface recording inundation of the valley interfluves. A younger sequence boundary within the lower Morrow is also recorded in the Gentzler field at the base of a forced regression shoreface, demarcated by the firmground Glossifungites ichnofacies, indicating a rapid basinward facies migration during a sea-level drop. Trace fossil models derived from the analysis of Mesozoic and Cenozoic reservoirs are generally applicable to the study of these late Paleozoic reservoirs. Pennsylvanian brackish-water facies differ ichnologically from their post-Paleozoic counterparts, however, in that they have: (1) lower trace fossil diversity, (2) lower degree of bioturbation, (3) scarcity of crustacean burrows, (4) absence of firmground suites, and (5) absence of ichnotaxa displaying specific architectures designed to protect the tracemaker from salinity fluctuations. Morrow open-marine ichnofaunas closely resemble their post-Paleozoic equivalents. ?? 2002 Elsevier Science B.V. All rights reserved.

Sedimentary Geology↗
USGS2018

A regime shift in sediment export from a coastal watershed during a record wet winter, California: Implications for landscape response to hydroclimatic extremes

Small, steep watersheds are prolific sediment sources from which sediment flux is highly sensitive to climatic changes. Storm intensity and frequency are widely expected to increase during the 21st century, and so assessing the response of small, steep watersheds to extreme rainfall is essential to understanding landscape response to climate change. During record winter rainfall in 2016–2017, the San Lorenzo River, coastal California, had nine flow peaks representing 2–10‐year flood magnitudes. By the third flood, fluvial suspended sediment showed a regime shift to greater and coarser sediment supply, coincident with numerous landslides in the watershed. Even with no singular catastrophic flood, these flows exported more than half as much sediment as had a 100‐year flood 35 years earlier, substantially enlarging the nearshore delta. Annual sediment load in 2017 was an order of magnitude greater than during an average‐rainfall year, and 500‐fold greater than in a recent drought. These anomalous sediment inputs are critical to the coastal littoral system, delivering enough sediment, sometimes over only a few days, to maintain beaches for several years. Future projections of megadroughts punctuated by major atmospheric‐river storm activity suggest that interannual sediment‐yield variations will become more extreme than today in the western USA, with potential consequences for coastal management, ecosystems, and water‐storage capacity. The occurrence of two years with major sediment export over the past 35 years that were not associated with extremes of the El Niño Southern Oscillation or Pacific Decadal Oscillation suggests caution in interpreting climatic signals from marine sedimentary deposits derived from small, steep, coastal watersheds, to avoid misinterpreting the frequencies of those cycles.

California↗
USGS2010

The construction of Chasma Boreale on Mars

The polar layered deposits of Mars contain the planet’s largest known reservoir of water ice 1,2 and the prospect of revealing a detailed Martian palaeoclimate record 3,4 , but the mechanisms responsible for the formation of the dominant features of the north polar layered deposits (NPLD) are unclear, despite decades of debate. Stratigraphic analyses of the exposed portions of Chasma Boreale—a large canyon 500 km long, up to 100 km wide, and nearly 2 km deep—have led most researchers to favour an erosional process for its formation following initial NPLD accumulation. Candidate mechanisms include the catastrophic outburst of water 5 , protracted basal melting 6 , erosional undercutting 7 , aeolian downcutting 7,8,9 and a combination of these processes 10 . Here we use new data from the Mars Reconnaissance Orbiter to show that Chasma Boreale is instead a long-lived, complex feature resulting primarily from non-uniform accumulation of the NPLD. The initial valley that later became Chasma Boreale was matched by a second, equally large valley that was completely filled in by subsequent deposition, leaving no evidence on the surface to indicate its former presence. We further demonstrate that topography existing before the NPLD began accumulating influenced successive episodes of deposition and erosion, resulting in most of the present-day topography. Long-term and large-scale patterns of mass balance achieved through sedimentary processes, rather than catastrophic events, ice flow or highly focused erosion, have produced the largest geomorphic anomaly in the north polar ice of Mars.

Nature↗
USGS1996

Earthquake site response in Santa Cruz, California

Aftershocks of the 1989 Loma Prieta, California, earthquake are used to estimate site response in a 12-km 2 area centered on downtown Santa Cruz. A total of 258 S -wave records from 36 aftershocks recorded at 33 sites are used in a linear inversion for site-response spectra. The inversion scheme takes advantage of the redundancy of the large data set for which several aftershocks are recorded at each site. The scheme decomposes the observed spectra into source, path, and site terms. The path term is specified before the inversion. The undetermined degree of freedom in the decomposition into source and site spectra is removed by specifying the site-response factor to be approximately 1.0 at two sites on crystalline bedrock. The S -wave site responses correlate well with the surficial geology and observed damage pattern of the mainshock. The site-response spectra of the floodplain sites, which include the heavily damaged downtown area, exhibit significant peaks. The largest peaks are between 1 and 4 Hz. Five floodplain sites have amplification factors of 10 or greater. Most of the floodplain site-response spectra also have a smaller secondary peak between 6 and 8 Hz. Residential areas built on marine terraces above the floodplain experienced much less severe damage. Site-response spectra for these areas also have their largest peaks between 1 and 4 Hz, but the amplification is generally below 6. Several of these sites also have a secondary peak between 6 and 8 Hz. The response peaks seen at nearly all sites between 1 and 4 Hz are probably caused by the natural resonance of the sedimentary rock column. The higher amplifications at floodplain sites may be caused by surface waves generated at the basin margins. The secondary peak between 6 and 8 Hz at many sites may be a harmonic of the 1- to 4-Hz peaks.

California↗
USGS2014

Description of landscape features, summary of existing hydrologic data, and identification of data gaps for the Osage Nation, northeastern Oklahoma, 1890-2012

The Osage Nation of northeastern Oklahoma, conterminous with Osage County, is characterized by gently rolling uplands and incised stream valleys that have downcut into underlying sedimentary rock units of Pennsylvanian through Permian age. Cattle ranching and petroleum and natural-gas extraction are the principal land uses in this rural area. Freshwater resources in the Osage Nation include water flowing in the Arkansas River and several smaller streams, water stored in several lakes, and groundwater contained in unconsolidated alluvial aquifers and bedrock aquifers. The Vamoosa-Ada aquifer is the primary source of fresh groundwater in this area. Fresh groundwater is underlain by saline groundwater in aquifers underlying the Osage Nation. Because of the potential for future population increases, demands for water from neighboring areas such as the Tulsa metropolitan area, and expansion of petroleum and natural-gas extraction on water resources of this area, the U.S. Geological Survey, in cooperation with the Osage Nation, summarized existing hydrologic data and identified data gaps to provide information for planning of future development of water resources in the Osage Nation. Streamflows in the Osage Nation are substantially affected by precipitation. During the relatively wet periods from the 1970s to 2000, the annual streamflows in the Osage Nation increased by as much as a factor of 2 relative to preceding decades, with subsequent decreases in streamflow of as much as 50 percent being recorded during intermittent drier years of the early 2000s. This report summarizes hydrologic data from 3 surface-water sites and 91 wells distributed across the Osage Nation. Data collected at those sites indicate that surface water in the Osage Nation generally has sufficient dissolved oxygen for survival of both coldwater and warmwater aquatic biota. Total dissolved solids concentration exceeded the secondary drinking-water standard of 500 milligrams per liter (mg/L) in up to 75 percent of the surface-water samples, indicating limited availability of potable water at some sites. Some surface-water samples collected in the Osage Nation contained dissolved chloride concentrations exceeding the secondary drinking-water standard of 250 mg/L, with greater chloride concentrations in selected basins appearing to be associated with greater densities of petroleum well locations. Several lakes sampled in the Osage Nation from 2011–12 contained sufficient chlorophyll-a concentrations to be ranked as mesotrophic to eutrophic, indicating impairment by nutrients. Relatively large dissolved phosphorus concentrations in many surface-water samples, compared to water-quality standards, indicate that eutrophication can occur in local streams and lakes. The amount of fresh groundwater stored in alluvial aquifers and the Vamoosa-Ada bedrock aquifer is adequate for domestic and other purposes in the Osage Nation at the current rate of usage. In areas where these aquifers are absent, groundwater must be pumped from minor bedrock aquifers that produce smaller volumes of water. About 30 and 60 percent of 32 and 54 water samples collected from the alluvial and Vamoosa-Ada aquifers, respectively, contained total dissolved solids concentrations larger than the secondary drinking-water standard of 500 mg/L. Local factors, such as natural seepage of brines or leakage from petroleum and natural-gas extraction activities, may cause substantial variations in dissolved chloride concentration in groundwater in the Osage Nation. Total phosphorus concentrations measured in groundwater samples were similar to dissolved phosphorus concentrations measured in the base flow of several streams. Total fresh surface-water withdrawals (use) and fresh groundwater withdrawals in the Osage Nation were estimated to have increased from 0.75 to 16.19 million gallons per day and from 0.13 to 2.39 million gallons per day, respectively, over the period from 1890 through 2010. Estimated saline-groundwater reinjection volumes at the heavily developed Burbank Oil Field in the Osage Nation from 1950 through 2012 were many times larger than the total amounts of freshwater withdrawn in this area, with estimated increases in saline-groundwater reinjection in the 2000s probably being related to increased petroleum extraction. Estimates of freshwater resources in local streams, lakes, and freshwater aquifers and of net annual precipitation indicate that less than 1 percent of freshwater resources and net annual precipitation currently is being withdrawn annually in the Osage Nation. In addition to freshwater resources, the Osage Nation may be underlain by 45,000,000 million gallons of brines, a small portion of which are withdrawn and reinjected during petroleum and natural-gas extraction. Ongoing development of desalinization technology may lead to the ability to expand use of these saline waters in the future. Several additional studies could improve understanding of the hydrologic resources of the Osage Nation. Development of computer models (simulations) of groundwater and surface-water flow for this area could enable testing of scenarios of localized and widespread effects of future climate variations and water-use changes on streamflows, lake-water levels, and groundwater levels in the Osage Nation. Installation of additional long-term streamflow and water-quality sampling stations, some with continuous water-quality monitors, could expand and improve understanding of surface-water quality. Periodic measurement of groundwater levels and sampling of water from a network of wells could provide better information about trends of groundwater quantity and quality with time. Measurement of water withdrawals at selected sites could enable more accurate estimates of water use. Lastly, better understanding of aquifer properties and spatial distribution of saline groundwater provided by geophysical surveys could improve understanding of fresh and saline groundwater resources underlying the Osage Nation.

Oklahoma↗
USGS2009

Petrographic observations on the Exmore breccia, ICDP-USGS drilling at Eyreville, Chesapeake Bay impact structure, USA

The International Continental Scientific Drilling Program (ICDP)-U.S. Geological Survey (USGS) Eyreville A and B drill cores sampled crater fill in the region of the crater moat, ??9 km to the NE of the center of the Chesapeake Bay impact structure, Virginia, USA. They provide a 953 m section (444-1397 m depth) of sedimentary clast breccia and intercalated sedimentary and crystalline megablocks knownas Exmore beds, deposited on top of the impactite sequence between 1397 and 1551 m depth. We petrographically investigated the sandy-clayey groundmass-dominated breccia, which resembles a diamictite ("Exmore breccia"), and which, in its lower parts, carries sedimentary and crystalline blocks. The entire breccia interval is characterizedby the presence of glauconite and bioclastic carbonate, which distinguishes the Exmore breccia from other sandy facies above and below in the stratigraphy. The sediment-clast breccia exhibits strong heterogeneity from sample to sample with respect to groundmass nature, e.g., clay versus sand content, as well as clast content, in general, and shocked clast content, in particular. There is a consistently signifi cantly larger macroscopic sedimentary to crystalline clast content. On the microscopic scale, the intersample sediment to crystalline clast ratios are quite variable. A very small component of shocked material, in the form of shock-deformed quartz, and to an even lesser degree feldspar, and somewhat more abundant but still relatively scarce shardshaped,altered melt particles, is present throughout the section. However, between ??458 and 469 m, and between 514 and 527 m depths, the abundance of such melt particlesis notably enhanced. These sections are also chemically distinct and relatively more mafic than the other parts of the Exmore breccia. It appears that from the time of deposition of the 527 m material, calming of the ocean occurred over the crater area as a result of abatement of resurge activity, so that ejecta from the plume abovethe crater could accumulate within the crater area to a larger degree. Deposition ofejecta fallout from the collapsing ejecta plume was terminated by the time of deposition of the 458 m material. This raises questions about the positioning of the exact upper contact of Exmore breccia to post-Exmore sediment (Chickahominy Formation), which is currently placed at 444 m depth and which possibly should be revisedto 458 m depth. Based on a signifi cant record of granite-derived material with shocked minerals, the shocked debris component seems to be largely derived from crystalline target rocks. This provides further evidence that the basement-derived material of the basal section of the Eyreville drill cores, which is essentially unshocked, is likely of an allochthonous nature and that the drilling did not intersect the actual crater floor. 76??W. ?? 2009 Geological Society of America.

Special Paper of the Geological Society of America↗
USGS2007

Geology and Mineral Resources of the East Mojave National Scenic Area, San Bernardino County, California

The rocks of the East Mojave National Scenic Area (EMNSA) record a history of dynamic geologic events that span more than 1,800 million years (m.y.). These geologic events contributed significantly to development of the spectacular vistas and panoramas present in the area today. The oldest rocks underlie much of the northern part of the EMNSA. These rocks were subjected to extreme pressures and temperatures deep in the Earth's crust about 1,700 million years ago (Ma). They were subsequently intruded by granitic magmas from about 1,695 to 1,650 Ma, by additional granitic magmas at about 1,400 Ma and, later, at about 1,100 Ma, by iron-rich magmas that crystallized to form dark igneous rocks termed diabase. Unusual potassium- and magnesium-rich rocks, emplaced at about 1,400 Ma, crop out in a few places within and near the EMNSA. Their distinctive composition results from very small degrees of partial melting of mantle peridotite that was highly enriched in incompatible trace elements. At Mountain Pass, just outside the northeast boundary of the EMNSA, the potassium- and magnesium-rich rocks are accompanied by a rare type of carbonatite, an igneous rock composed of carbonate minerals, that contains high-grade rare earth element mineralization. Subsequent to these igneous-dominated events, sedimentary strata began to be deposited at about 1,000 Ma; mostly sandstone and shale were deposited initially in marine and, less commonly, in continental environments along the west edge of the core of the North American continent. Sedimentation eventually culminated in the widespread deposition of thick marine limestones from about 400 to about 245 Ma. These limestones represent a continental-shelf environment where shallow-water limestone formed to the east and deeper water limestone formed to the west. The end of the formation of these sedimentary deposits probably was caused by uplift of the shelf, which marked the beginning of a long period of tectonic upheaval. At about 170 Ma, widespread emplacement of coarse-grained granitic magmas began again in the region; some of these magmas also erupted as volcanic rocks. Additional episodes of magmatism took place at about 100 Ma and at 75 Ma. Most of the metallic-mineral occurrences in the EMNSA are associated with the igneous rocks that range in age from 170 to 75 Ma. During each of these magmatic events, the previously deposited sedimentary strata were buckled and broken as the entire region, part of a continental-scale fold and thrust belt, underwent crustal shortening and compression. A period of tectonic quiescence characterized the region from about 65 Ma to about 20 Ma. The quiet period ended abruptly with widespread volcanism along the southern and eastern parts of the EMNSA. The major gold deposits in the Castle Mountains are associated with this episode of volcanism. During this volcanic outburst, the crust extended laterally in several areas that border the EMNSA: along the lower Colorado River 65 km to the east, in the Kingston Range 20 km to the north, and in the central Mojave Desert 75 km to the southwest. This extensional deformation is characterized by the superposition of upper-crustal rocks over midcrustal rocks along large flat-lying faults, several of which project beneath rocks now exposed at the surface in the EMNSA. The near-surface rocks of the EMNSA, however, apparently escaped much of this intense extensional deformation. High-angle faults, which cut several of the mountain ranges, possibly have undergone several periods of movement, which date back to approximately 70 to 100 Ma. Some faults are of local importance to the physiographic development of the mountain ranges and intervening basins, and, in places, the faults seem to have localized various kinds of ore bodies and mineral occurrences. Volcanism and extensional deformation waned from 14 to 11 Ma. By approximately 10 Ma, widespread erosion had produced broad erosional dome-shaped mountains in the n

Bulletin↗