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At least 919 records · Page 51Linked to original sources
USGS1991

Large-scale coastal evolution of Louisiana's barrier islands

The prediction of large-scale coastal change is an extremely important, but distant goal. Here we describe some of our initial efforts in this direction, using historical bathymetric information along a 150 km reach of the rapidly evolving barrier island coast of Louisiana. Preliminary results suggest that the relative sea level rise rate, though extremely high in the area, has played a secondary role in coastal erosion over the last 100 years, with longshore transport of sand-sized sediment being the primary cause. Prediction of future conditions is hampered by a general lack of erosion processes understanding; however, an examination of the changing volumes of sand stored in a large ebb-tidal delta system suggests a continued high rate of shoreline retreat driven by the longshore re-distribution of sand.

Conference Paper↗
USGS1999

Potential effects of gas hydrate on human welfare

For almost 30 years, serious interest has been directed toward natural gas hydrate, a crystalline solid composed of water and methane, as a potential (i) energy resource, (ii) factor in global climate change, and (iii) sub-marine geohazard. Although each of these issues can affect human welfare, only (iii) is considered to be of immediate importance. Assessments of gas hydrate as an energy resource have often been overly optimistic, based in part on its very high methane content and on its worldwide occurrence in continental margins. Although these attributes are attractive, geologic settings, reservoir properties, and phase-equilibria considerations diminish the energy resource potential of natural gas hydrate. The possible role of gas hydrate in global climate change has been often overstated. Although methane is a 'greenhouse' gas in the atmosphere, much methane from dissociated gas hydrate may never reach the atmosphere, but rather may be converted to carbon dioxide and sequestered by the hydrosphere/biosphere before reaching the atmosphere. Thus, methane from gas hydrate may have little opportunity to affect global climate change. However, submarine geohazards (such as sediment instabilities and slope failures on local and regional scales, leading to debris flows, slumps, slides, and possible tsunamis) caused by gas-hydrate dissociation are of immediate and increasing importance as humankind moves to exploit seabed resources in ever-deepening waters of coastal oceans. The vulnerability of gas hydrate to temperature and sea level changes enhances the instability of deep-water oceanic sediments, and thus human activities and installations in this setting can be affected.

Conference Paper↗
USGS2023

Gulf Islands National Seashore regional sediment budget research and data needs—Workshop series summary

Executive Summary The National Park Service (NPS), in collaboration with the U.S. Geological Survey (USGS), recognizes the need to quantify the sediment budget of the barrier islands within the Gulf Islands National Seashore (GINS) to understand the coastal processes affecting island resiliency. To achieve this goal, identifying and quantifying the physical parameters that drive long-term change is necessary to model the processes that are both generative and terminal in island evolution and capture island response to long-term human alteration and climatic patterns. For example, measuring change across periods of storminess is more effective at assessing island resiliency than measuring change resulting from a single storm impact. Understanding changes to the physical environment over time is key to successfully predicting island responses to future storm impacts, human alteration, and sea-level rise and is necessary for effective decision making and management response. Yet, the diversity of factors affecting natural and cultural resources necessitates a strategic approach to data collection priorities that can inform sediment budget quantification and integrated resource management. This study sought to advance sediment budget modeling efforts by conducting a “Needs Assessment Workshop” at the GINS. The purpose of the workshop was to identify and prioritize the specific research and data needs regarding the sediment budget at the GINS that can enhance the NPS efforts to conserve the islands’ natural resources, cultural resources, and the facilities and infrastructure that support both conservation and visitor use of those resources. This effort explored two research questions: (1) “what research and data needs exist for the sediment budget at Gulf Islands National Seashore” (research question 1) and (2) “how can research to address these needs capitalize on regional partnerships to advance natural and cultural resource conservation at Gulf Islands National Seashore” (research question 2)? The workshop was conducted virtually in a two-part, two-day series. The workshop series was organized by researchers from North Carolina State University in collaboration with NPS and USGS staff and was facilitated by National Oceanographic and Atmospheric Administration staff. The workshop series (two paired, sequential, partial-day workshops) addressed two target audiences: (1) NPS and USGS staff (April workshop) and (2) regional Federal, State, county, and nongovernmental organization staff, including NPS and USGS staff (May workshop). A total of four workshop sessions were held, comprising two sessions with each target audience. The workshop series intended to identify sediment management research and data needs that could enhance natural and cultural resource stewardship at the GINS. One objective was to share information about regional sediment transport and management, available sediment management plans, and predictive modeling capabilities, including geomorphologic and hydrodynamic predictive models. This information was shared through a series of presentations by park managers and NPS and USGS researchers that identified park issues and available capabilities and data. The second objective was to elicit research and data needs, with a primary goal of assessing the importance and urgency of the identified needs. This assessment was partly determined by requesting that the workshop participants identify and prioritize research themes through polls, comments, and discussion. The polls explicitly asked participants to qualitatively evaluate the importance (not at all, slightly, somewhat, very, or extremely) and urgency (not at all, slightly, somewhat, very, or extremely) of the thematically grouped research and data needs. These evaluations were plotted and shared during the workshop to visualize how the relative importance ( x -axis) and relative urgency ( y -axis) of each “need,” relative to other needs, to identify the most necessary (importance) and time-sensitive (urgent) items, thereby allowing an enhanced, holistic understanding of the sediment budget at GINS. Results of the poll are published as a USGS data release. The assessment results revealed that the most important and urgent research and data needs included mapping (for example, elevation, habitat, and cultural resources), a regional sediment budget and management plan, and the dynamic modeling of sediment processes. During the workshop, these issues were visualized using scatter plots to demonstrate the relative importance and urgency of each theme, provide descriptive statistics, and elicit discussion. This format of iterative presentation, discussion, and prioritization allowed the project team to effectively accomplish their objective of identifying important and urgent research needs for natural and cultural resource stewardship at the GINS. Through the workshop, it was determined that expanded communication with the broader research community was needed to coordinate research activities and streamline potential funding opportunities and that research and policy should be integrated through a structured decision-making process. At the conclusion of the workshop, an administered poll showed that the presentations effectively identified data and research needs and that the goals of the workshop were achieved. The results suggest that this type of needs-assessment workshop can effectively identify existing research capabilities and data, determine and prioritize research and data needs, and address how these efforts can use regional partnerships to aid natural and cultural resource conservation and management at National Parks.

Florida, Mississippi↗
USGS2020

Spatially referenced models of streamflow and nitrogen, phosphorus, and suspended-sediment loads in streams of the northeastern United States

SPAtially Referenced Regression On Watershed attributes (SPARROW) models were developed to quantify and improve the understanding of the sources, fate, and transport of nitrogen, phosphorus, and suspended sediment in the northeastern United States. Excessive nutrients and suspended sediment from upland watersheds and tributary streams have contributed to ecological and economic degradation of northeastern surface waters. Recent efforts to reduce the flux of nutrients and suspended sediment in northeastern streams and to downstream estuaries have met with mixed results, and expected ecological improvements have been observed in some areas but not in others. Effective watershed management and restoration to improve surface-water quality are complicated by the multitude of nutrient sources in the Northeast and the multitude of natural and human landscape processes affecting the delivery of nutrients and suspended sediment from upland areas to and within surface waters. Individual models were constructed representing streamflow and the loads of total nitrogen, total phosphorus, and suspended sediment from watersheds draining to the Atlantic Ocean from southern Virginia through Maine. Northeastern streams contribute 303,000 metric tons (t) of nitrogen, 25,300 t of phosphorus, and 14,700,000 t of suspended sediment, annually (on average), to waters along the Atlantic Coast of North America. Although atmospheric deposition and natural mineral erosion contribute to nitrogen and phosphorus loads, respectively, in northeastern streams, most of the contributions are attributable to urban or agricultural sources. Within the Northeast, average yields of nutrients are therefore generally greater from densely populated or intensively cultivated areas of the mid-Atlantic region, the Hudson, Mohawk, and Connecticut River valleys, and the coastal areas of southern New England than in predominantly forested areas such as northern New England. Average upland sediment yields are similarly greater from agricultural areas than from urban or forested areas and are therefore generally greatest in areas yielding the greatest nutrients. Landscape conditions that are significant to nitrogen delivery from uplands to streams likely reflect the importance of groundwater transport in carbonate settings and of denitrification for removing nitrogen from uplands. Nitrogen losses to streams in agricultural areas are apparently mitigated by the use of cover crops but are exacerbated by the use of conservation tillage or no-till practices. The transport of phosphorus and suspended sediment from uplands to streams is greater in areas of more erodible soils but mitigated in agricultural areas with greater use of conservation tillage or no-till practices. Loads of nutrients and suspended sediment are significantly reduced within the stream network in impounded reaches, and nitrogen load is also significantly reduced in small flowing reaches.

Scientific Investigations Report↗
USGS2023

Designation of a composite-stratotype section for the lower Paleocene (Danian) Brightseat Formation in Prince George’s County, Maryland, U.S.A.

The lower Paleocene (Danian) Brightseat Formation consists of fine-grained, dark-gray, micaceous sand and silty clay, with glauconite and abundant, but generally poorly preserved, fossils. The Brightseat Formation represents deposition of lower, but not lowermost, Paleocene sediments that were deposited on the middle to outer shelf of what is now the Atlantic Coastal Plain. A basal disconformity separates the Brightseat from the underlying Upper Cretaceous Severn Formation, and it is disconformably overlain by the middle to upper Paleocene Aquia Formation. The type locality of the Brightseat Formation, previously exposed approximately 1 mile (1.6 km) west-southwest of the former village of Brightseat in Prince George’s County, Maryland, just outside ofWashington, D.C., has been destroyed by urban development, prompting the establishment of a composite-stratotype section from nearby outcrops approximately a half mile to the south-southwest of the original location. The outcrop at Cabin Branch is hereby designated as the principal reference section for the Brightseat Formation and the “Cabin Creek” outcrop (an informally designated tributary of Cabin Branch) is designated as a supplementary reference section that illustrates the boundary of the Brightseat with the overlying Aquia Formation. Paleontological analyses, grain-size analyses, and petrographic techniques are used to document this new stratotype section and to correlate and contrast it with underlying and overlying sediments. This composite-stratotype section is designated using the guidelines outlined in Article 8, remarks (d) and (e) of the North American Code of Stratigraphic Nomenclature.

Maryland↗
USGS2003

Sedimentation History of Lago Guayabal, Puerto Rico, 1913-2001

The Lago Guayabal dam, located in the municipality of Villalba in southern Puerto Rico, was constructed in 1913 for irrigation of croplands in the southern coastal plains and is owned and operated by the Puerto Rico Electric Power Authority. The reservoir had an original storage capacity of 11.82 million cubic meters and a drainage area upstream of the dam of 112 square kilometers. Sedimentation has reduced the storage capacity to 6.12 million cubic meters in 2001, which represents a storage loss of about 48 percent. However, the actual sediment accumulation in the reservoir during the 88 years is greater, because some sediment removal was conducted between 1940 and 1948 by dredging and sluicing. This report summarizes the historical data from a 1913 land survey and eight bathymetric surveys conducted between 1914 and 2001, and the relation of high sedimentation to agricultural land practices within the Lago Guayabal basin and six major hurricanes which made landfall on the island. The reservoir had an area-normalized sedimentation rate of about 1,863 cubic meters per square kilometer per year between 1913 and 1936 from a 112 square kilometer basin. In 1972, a new dam upstream along the Rio Toa Vaca impounded runoff from 57.5 square kilometers, and sediment transport to Lago Guayabal was reduced. A comparison of bathymetric survey results between 1972 and 2001 indicates an area-normalized sedimentation rate of 1,120 cubic meters per square kilometer per year or about 60 percent of the rate between 1913 and 1936. The significant reduction (almost half) of the sedimentation rate after the Toa Vaca dam was built may indicate that erosion susceptibility of the Rio Toa Vaca watershed is about twice that of the Rio Jacaguas watershed impounded by Lago Guayabal.

Water-Resources Investigations Report↗
USGS1993

Allostratigraphy of the U.S. middle Atlantic continental margin; characteristics, distribution, and depositional history of principal unconformity-bounded upper Cretaceous and Cenozoic sedimentary units

Publication of Volumes 93 and 95 ('The New Jersey Transect') of the Deep Sea Drilling Project's Initial Reports completed a major phase of geological and geophysical research along the middle segment of the U. S. Atlantic continental margin. Relying heavily on data from these and related published records, we have integrated outcrop, borehole, and seismic-reflection data from this large area (500,000 km^2 ) to define the regional allostratigraphic framework for Upper Cretaceous and Cenozoic sedimentary rocks. The framework consists of 12 alloformations, which record the Late Cretaceous and Cenozoic depositional history of the contiguous Baltimore Canyon trough (including its onshore margin) and Hatteras basin (northern part). We propose stratotype sections for each alloformation and present a regional allostratigraphic reference section, which crosses these basins from the inner edge of the coastal plain to the inner edge of the abyssal plain. Selected supplementary reference sections on the coastal plain allow observation of the alloformations and their bounding unconformities in outcrop. Our analyses show that sediment supply and its initial dispersal on the middle segment of the U. S. Atlantic margin have been governed, in large part, by hinterland tectonism and subsequently have been modified by paleoclimate, sea-level changes, and oceanic current systems. Notable events in the Late Cretaceous to Holocene sedimentary evolution of this margin include (1) development of continental-rise depocenters in the northern part of the Hatteras basin during the Late Cretaceous; (2) the appear ance of a dual shelf-edge system, a marked decline in siliciclastic sediment accumulation rates, and widespread acceleration of carbonate production during high sea levels of the Paleogene; (3) rapid deposition and progradation of thick terrigenous delta complexes and development of abyssal depocenters during the middle Miocene to Quaternary interval; and (4) deep incision of the shelf edge by submarine canyons, especially during the Pleistocene. Massive downslope gravity flows have dominated both the depositional and erosional history of the middle segment of the U. S. Atlantic Continental Slope and Rise during most of the last 84 million years. The importance of periodic widespread erosion is recorded by well-documented unconformities, many of which can be traced from coastal-plain outcrops to coreholes on the continental slope and lower continental rise. These unconformities form the boundaries of the 12 allostratigraphic units we formally propose herein. Seven of the unconformities correlate with supercycle boundaries (sequence boundaries) that characterize the Exxon sequence-stratigraphy model.

Professional Paper↗
USGS2025

Interacting sea-level rise, sea-ice loss, storm flooding, erosion, and permafrost thaw threaten ecosystems, wildlife, and communities on the Yukon-Kuskokwim Delta

The Yukon-Kuskokwim Delta has the largest intertidal wetland in North America, is a globally critical breeding area for waterbirds, and is home to the largest regional indigenous population in the Arctic. Here, coastal tundra ecosystems, wildlife, and indigenous communities are highly vulnerable to sea-ice loss in the Bering Sea, sea-level rise, storm flooding, erosion, and collapsing ground from permafrost thaw caused by climate warming. These drivers interact in non-linear ways to increase flooding, salinization, and sedimentation, and thus, alter ecosystem trajectories and broader landscape evolution. Rapid changes in these factors over decadal time scales are highly likely to cause transformative shifts in coastal ecosystems across roughly 70% of the outer delta this century. We project saline and brackish ecotypes on the active delta floodplain with frequent sedimentation will maintain dynamic equilibrium with sea-level rise and flooding, slightly brackish ecotypes on the inactive floodplain with infrequent flooding and low sedimentation rates will be vulnerable to increased flooding and likely transition to more saline and brackish ecotypes, and fresh lacustrine and lowland ecotypes on the abandoned floodplain with permafrost plateaus will be vulnerable to thermokarst, salinization and flooding that will shift them toward brackish ecosystems. This will greatly affect bird nesting and foraging habitats, with both winners and losers. Already, some Yup'ik communities are facing relocation of their low-lying villages. The societal challenges and consequences of adapting to these changing landscapes are enormous and will require a huge societal effort.

Alaska↗
USGS2020

How plants influence resilience of salt marsh and mangrove wetlands to sea-level rise

This review evaluates the importance of plants and associated biological processes in determining the vulnerability of coastal wetlands to sea-level rise. Coastal wetlands occur across a broad sedimentary continuum from minerogenic to biogenic, providing an opportunity to examine the relative importance of biological processes in wetland resilience to sea-level rise. We explore how plants influence sediment accretion, elevation capital (vertical position in the tidal frame), and compaction or erosion of deposited material. We focus on salt marsh and mangrove wetlands, which occupy a similar physiographic niche and display similar physical and biological controls on resilience to sea-level rise. In both habitats, plants stabilize emergent mudflats and help sustain the wetland position in the tidal frame relative to ocean height through both surface and subsurface process controls on soil elevation. Plants influence soil elevations by modifying (1) mineral sediment deposition and retention, (2) organic matter contributions to soil volume, and (3) resistance to compaction and erosion. Recognition of the importance of plants in coastal wetland resilience to sea-level rise is key to accurate predictions about the future fate of salt marshes and mangrove forests and for development of effective management and restoration plans.

Estuaries and Coasts↗
USGS2011

Fire in Chile

The mediterranean-type climate (MTC) in Chile (Fig. 6.1) is distributed from La Serena (30° S; Región IV, see Appendix 6.1) in the north to Concepción (37° S; Región X) in the south. It is constrained to the west side of the Andean mountain range, although as the height of this range decreases in the south, a MTC is observed at least as far eastward as Bariloche, Argentina. Although a pattern of winter rains and summer droughts extends northward into the Atacama Desert, this area falls outside our definition of MTC because winter evaporation exceeds rainfall in these areas of extremely low precipitation. The northern border of the MTC region is the transition from desert communities to shrubby matorral, while the southern border corresponds to the point of transition from sclerophyll woodlands to Valdivian evergreen forests (Gajardo 1994; Amigo & Ramirez 1998; Rundel et al . 2007). The landforms of central Chile can be divided into three north–south trending geomorphic zones (Fig. 6.1): the Coastal Cordillera, the Central Valley, and the high Andean Cordillera (Armesto et al . 2007). The Coastal Cordillera rises relatively sharply from the coast, with little extent of coastal terraces, and reaches elevations as high as 2222 m at Cerro Roble and 1880 m at Cerro Campana, which lie between Valparaíso (Región V) on the coast and Santiago (Región Metropolitana) at the base of the Andes. The Central Valley is a structural basin filled to great depth by sediments from the surrounding mountains. North of Santiago, spurs from the Andes extend west across the valley and connect with the Coastal Cordillera, separating individual river basins such as that of the Río Aconcagua (Región V). From Santiago to the south, however, the valley extends uninterrupted for a distance of 900 km to Puerto Montt (Región X), with typical elevations of 400–700 m. The Andean Cordillera marks the eastern boundary of the MTC zone of central Chile. It is the product of complex tectonic activity beginning in the Cretaceous (see Fig. 9.1), but with major uplift in the late Tertiary. Paleobotanical evidence suggests that the central Andes had not attained more than half their current elevation by 10 Ma (Gregory-Wodzicki 2000), but was close to the present height by the end of the Miocene (Reynolds et al . 1990). Elevations reach from 4000 m to nearly 7000 m. To the north of Santiago the Andes are largely composed of metamorphosed sedimentary rock, but a major volcanic zone extends from south of Santiago through the Lake District (Los Lagos Región X).

Book chapter↗
USGS2007

Morphology and textures of modern sediments on the inner shelf of South Carolina's Long Bay from Little River Inlet to Winyah Bay

High-resolution sea-floor mapping techniques, including sidecan-sonar, seismic-reflection, swath bathymetric systems, and bottom sampling, were used to map the geologic framework offshore of the northern South Carolina coast in order to provide a better understanding of the physical processes controlling coastal erosion and shoreline change. Four general sea floor environments were identified through analysis of sidescan-sonar, swath bathymetry, and surface sediment texture: inlet shoal complexes, shore-detached shoals, hardground, and mixed zones. Inlet shoal complexes generally lie offshore of modern inlet systems, with the exception of a shore-detached shoal lying offshore of Myrtle Beach. The shoals show 1 - 3 m in relief and comprise the largest accumulations of modern sediment within the inner shelf survey area. Surficial sediments within the shoal complexes are characterized by a low-backscatter, moderately sorted fine sand. Hardground areas are characterized by exposures of Cretaceous and Tertiary strata and Pleistocene channel-fill deposits. These areas display little to no bathymetric relief and are characterized by high-backscatter, coarser grained sand. Mixed zones show small-scale spatial variations in bathymetry, surface texture and backscatter. These areas are characterized by a thin layer of modern sediment (< 1 m) and exposures of Cretaceous strata and Pleistocene channel-fill deposits. Textural and geomorphic variations suggest a long-term net southerly flow within the study area. The general acoustic and textural character of the inner shelf within Long Bay suggests long-term erosion, reworking and continued modification of inner-shelf deposits by modern nearshore processes.

South Carolina↗
USGS2003

Patterns and controls of surface sediment distribution: West-central Florida inner shelf

The west-central Florida inner shelf represents a transition between the quartz-dominated barrier-island system and the carbonate-dominated mid-outer shelf. Surface sediments exhibit a complex distribution pattern that can be attributed to multiple sediment sources and the ineffectiveness of physical processes for large-scale sediment redistribution. The west Florida shelf is the submerged extension of the Florida carbonate platform, consisting of a limestone karst surface veneered with a thin unconsolidated sediment cover. A total of 498 surface sediment samples were collected on the inner shelf and analyzed for texture and composition. Results show that sediment consists of a combination of fine quartz sand and coarse, biogenic carbonate sand and gravel, with variable but subordinate amounts of black, phosphorite-rich sand. The carbonate component consists primarily of molluskan fragments. The distribution is patchy and discontinuous with no discernible pattern, and the transition between sediment types is generally abrupt. Quartz-rich sediment dominates the inner 15 km north of the entrance into Tampa Bay, but south of the Bay is common only along the inner 3 km. Elsewhere, carbonate-rich sediment is the predominate sediment type, except where there is little sediment cover, in which cases black, phosphorite-rich sand dominates. Sediment sources are likely within, or around the periphery of the basin. Fine quartz sand is likely reworked from coastal units deposited during Pleistocene sea-level high stands. Carbonate sand and gravel is produced by marine organisms within the depositional basin. The black, phosphorite-rich sand likely originates from the bioerosion and reworking of the underlying strata that irregularly crop out within the study area. The distribution pattern contains elements of both storm- and tide-dominated siliciclastic shelves, but it is dictated primarily by the sediment source, similar to some carbonate systems. Other systems with similar sediment attributes include cool-water carbonate, sediment-starved, and mixed carbonate/siliciclastic systems. This study suggests a possible genetic link among the three systems. ?? 2003 Elsevier B.V. All rights reserved.

Marine Geology↗
USGS2018

High-resolution climate of the past ∼7300 years of coastal northernmost California: Results from diatoms, silicoflagellates, and pollen

Piston core TN062-O550, collected about 33 km offshore of Eureka, California, contains a high-resolution record of the climate and oceanography of coastal northernmost California during the past ∼7.34 kyr. Chronology established by nine AMS ages on a combination of planktic foraminifers, bivalve shell fragments, and wood yields a mean sedimentation rate of 103 cm kyr −1 . Marine proxies (diatoms and silicoflagellates) and pollen transported by the nearby Eel River reveal a stepwise development of both modern offshore surface water oceanography and coastal arboreal ecosystems. Beginning at ∼5.4 cal ka the relative abundance of coastal redwood pollen, a proxy for coastal fog, displays a two fold increase suggesting enhanced coastal upwelling. A decline in the relative contribution of subtropical diatoms at ∼5.0 cal ka implies cooling of sea surface temperatures (SSTs). At ∼3.6 cal ka an increase in the relative abundance of alder and oak at the expense of coastal redwood likely signals intensified riverine transport of pollen from inland environments. Cooler offshore SSTs and increased precipitation characterize the interval between ∼3.6 and 2.8 cal ka. A rapid, stepwise change in coastal climatology and oceanography occurs between ∼2.8 and 2.6 cal ka that suggests an enhanced expression of modern Pacific Decadal Oscillation-like (PDO) cycles. A three-fold increase in the relative abundance of the subtropical diatom Fragilariopsis doliolus at 2.8 cal ka appears to mark an abrupt warming of winter SSTs. Soon afterwards at 2.6 cal ka, a two fold increase in the relative abundance of coastal redwood pollen is suggestive of an abrupt intensification of spring upwelling. After ∼2.8 cal ka a sequence of cool-warm, PDO-like cycles occurs wherein cool cycles are characterized by relative abundance increases in coastal redwood pollen and decreased contributions of subtropical diatoms, whereas opposite proxy trends distinguish warm cycles.

California↗
USGS2016

Ground-penetrating radar and differential global positioning system data collected from Long Beach Island, New Jersey, April 2015

Scientists from the United States Geological Survey, St. Petersburg Coastal and Marine Science Center, U.S. Geological Survey Pacific Coastal and Marine Science Center, and students from the University of Hawaii at Manoa collected sediment cores, sediment surface grab samples, ground-penetrating radar (GPR) and Differential Global Positioning System (DGPS) data from within the Edwin B. Forsythe National Wildlife Refuge–Holgate Unit located on the southern end of Long Beach Island, New Jersey, in April 2015 ( FAN 2015-611-FA ). The study’s objective was to identify washover deposits in the stratigraphic record to aid in understanding barrier island evolution. This report is an archive of GPR and DGPS data collected from Long Beach Island in 2015. Data products, including raw GPR and processed DGPS data, elevation corrected GPR profiles, and accompanying Federal Geographic Data Committee metadata can be downloaded from the Data Downloads page.

New Jersey↗
USGS2007

Beach morphology monitoring in the Elwha River Littoral Cell, 2004-2009

This report describes the methods used, data collected, and results of the Beach Morphology Monitoring Program in the Elwha River Littoral Cell, starting in 2004. The U.S. Geological Survey and the Washington State Department of Ecology collaborated in the data collection with the support of the local Lower Elwha Klallam Tribe. Beach monitoring efforts consisted of collecting topographic and bathymetric horizontal and vertical position data by using a Real Time Kinematic Differential Global Positioning System (RTK-DGPS). The monitoring program was designed to characterize the littoral system of the Elwha River before the scheduled removal of two large dams in 2012. A primary objective of this work is to quantitatively describe the topography and bathymetry of the Elwha River littoral system so that the effects of dam removal may be quantified. Sediment inputs following dam removal are hypothesized to result in (A) larger amounts of fine sediment grain-sizes entering the littoral system and, (B) a reduction or reversal of coastal erosion.

Washington↗
USGS1975

Palynological and stratigraphic investigations of four deep wells in the Salisbury Embayment of the Atlantic Coastal Plain

Use of palynological zones defined by Brenner and Doyle from the Cretaceous outcrop belt in Maryland, Delaware, and New Jersey permit correlation of the Cretaceous section in four wells drilled to basement in the Salisbury Embayment in the Eastern Shore of Maryland and in Accomack Co., Virginia. These correlations, supplemented by electric log correlations between wells, clarify the Mesozoic depositional history of the outer margin of the Atlantic Coastal Plain. The bulk of the Cretaceous section consists of continental to marginal is marine sediments correlative with and probably older than the outcrop Potomac Group (Aptian-lower Cenomanian?). Lower Cretaceous palynlogical assemblages also occur in at least the top of basal "red beds" considered Triassic or Jurassic by earlier authors. Dinoflagellates and lithological criteria indicate several transgressive-regressive cycles within the generally transgressive Potomac sequence, with maximum marine incursions in the Late Albian and the Early Cenomanian. Equivalents of the lower Raritan Formation of New Jersey (middle-upper Cenomanian?), absent at the Maryland outcrop, are recognized for the first time in the Taylor and Bethards wells. Potomac and lower Raritan equivalents are separated from overlying Magothy equivalents (upper Santonian-lower Campanian) by a major regional unconformity. Well data suggest that further downdip, under the continental shelf, most of the formations should be marine and contain abundant organic matter. Given sufficient heat and trapping structures, oil and gas may have accumulated.

Open-File Report↗
USGS2026

Background and geologic model for the 2024 U.S. Geological Survey assessment of undiscovered conventional petroleum resources in the Norphlet Formation, U.S. Gulf Coast

The Upper Jurassic Norphlet Formation is a stratigraphic unit located in the subsurface of the United States Gulf coastal plain and offshore Gulf of America (Gulf of Mexico). The Norphlet consists of clastic sediments derived from the southern Appalachian highlands, and was deposited in a continental dryland setting on the margins of the early Gulf of America rift basin. The formation contains a variety of sedimentary facies, including facies representing updip alluvial fans, wadis, red beds, and a widespread erg, or eolian sand sea. The erg facies form the primary reservoirs from which hydrocarbons sourced from the overlying Smackover Formation are produced. Development of the Norphlet began in earnest in the late 1960s, with new discoveries, including large fields at Flomaton, Hatters Pond, and Mobile Bay, continuing through the 2000s–2010s with the discovery of major oil fields in the offshore Desoto Canyon area. Onshore, Norphlet hydrocarbon traps typically are faulted salt anticlines, although many fields also have a stratigraphic trapping component because of the preservation of dune-scale bedforms. Thermal maturity across the Norphlet play varies significantly with depth, resulting in oil production transitioning downdip to natural gas liquids production, then dry gas production; production depths reach to greater than 21,000 feet. A 2024 U.S. Geological Survey assessment divided the Norphlet into four conventional assessment units defined by the type and frequency of trapping mechanisms, sedimentology, and thermal maturity of each area, with little potential for hydrocarbon development observed west of the Mississippi River. Although petroleum resources in the Norphlet were revised downward, it is probable that significant resources remain to be discovered.

Alabama, Florida, Mississippi↗
USGS1993

Properties and chemical constituents in ground water from the middle Wilcox aquifer, Gulf Coast regional aquifer systems, south-central United States

The Gulf Coast Regional Aquifer-System Analysis is a study of regional aquifers composed of sediments of mostly Cenozoic age that underlie about 230,000 sq mi of the Gulf Coastal Plain. These regional aquifers are part of three aquifer systems: (1) the Mississippi Embayment Aquifer System, (2) the Texas Coastal Uplands Aquifer System, and (3) the Coastal Lowlands Aquifer System. The water chemistry of the Middle Wilcox Aquifer, which is part of the Mississippi Embayment Aquifer System and the Texas Coastal Uplands Aquifer System is presented by a series of maps. These maps show the area1 distribution of (1) the concentration of dissolved solids and temperature, (2) the primary water types and pH, (3) the concentration of major ions and silica, and (4) the milliequivalent ratios of selected ions. Dissolved constituents, pH, temperature, and ratios are based on the median values of all samples in each 100-sq-mi area. The concentration of dissolved solids in water from the Middle Wilcox Aquifer ranges from 26 mg/L in the northern part of the Mississippi Embayment Aquifer System to 125,500 mg/L in a down-dip area in southeastern Texas. The primary water types, which are based on the most frequently observed type in each 100-sq-mi area, are calcium bicarbonate in the outcrop in Missouri, Kentucky, Mississippi, and southern Texas; sodium bicarbonate in the remaining outcrop areas and all areas from outcrop to mid-dip; and sodium chloride in all down-dip areas. The concentrations of major ions in water from the Middle Wilcox Aquifer generally increase from the outcrop area to the down-dip limit of the data. The milliequivalent ratio of magnesium plus calcium to bicarbonate ranges from less than 0.01 to 158 and generally decreases from outcrop to mid-dip and increases from mid-dip to the down-dip limit of the data. From the Sabine Uplift eastward to southwestern Alabama the ratio of bicarbonate to chloride generally decreases from outcrop to down-dip in the area west of the Mississippi River and shows localized trends east of the Mississippi River.

Alabama, Arkansas, Kentucky, Louisiana, Mississipp↗