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At least 595 records · Page 33Linked to original sources
USGS1999

Internal surface water flows

Introduction The South Florida Ecosystem Restoration Program is an intergovernmental effort to reestablish and maintain the ecosystem of south Florida. One element of the restoration effort is the development of a firm scientific basis for resource decision making.The U.S. Geological Survey (USGS) provides scientitic information as part of the South Florida Ecosystem Restoration Program. The USGS began its own project, called the South Florida Ecosystem Project in fiscal year 1995 for the purpose of gathering hydrologic, cartographic, and geologic data that relate to the mainland of south Florida, Florida Bay, and the Florida Keys and Reef ecosystems. Historical changes in water-management practices to accommodate a large and rapidly growing urban population along the Atlantic coast, as well as intensive agricultural activities, have resulted in a highly managed hydrologic system with canals, levees, and pumping stations. These structures have altered the hydology of the Everglades ecosystem on both coastal and interior lands. Surface-water flows in a direction south of Lake Okeechobee have been regulated by an extensive canal network, begun in the 1940's, to provide for drainage, flood control, saltwater intrusion control, agricultural requirements, and various environmental needs. Much of the development and subsequent monitoring of canal and river discharge south of Lake Okeechobee has traditionally emphasized the eastern coastal areas of Florida. Recently, more emphasis has been placed on providing a more accurate water budget for internal canal flows.

Florida↗
USGS1994

Precambrian zircons from the Florida basement: A Gondwanan connection

A Gondwanan origin for the pre-Cretaceous basement of Florida is suggested by U- Pb ages of 515 to 2860 Ma for single zircons separated from subsurface samples of lower Paleozoic sandstone of the Suwannee basin (Alachua County, Florida) and Neoproterozoic Osceola granite (Osceola County, Florida). Forty individual grains analyzed by SHRIMP ion microprobe yielded ages from 515 to 2860 Ma; ages >1000 Ma were predominantly concordant. Two principal populations are evident: (1) 515 to 637 Ma (avg. = 574 Ma; 206 Pb/ 238 U ages) and (2) 1967 to 2282 Ma (avg. = 2130 Ma; 207 Pb/ 206 Pb ages). Only six zircons were recovered from the granite; four are Pan-African and two are Archean. For the sandstone, the similarity between the Sm-Nd model age (1245 Ma) and the average of the single zircon ages (1326 Ma) suggests that these zircons are chronologically representative of the aggregate provenance of the sandstone. The two dominant zircon age groupings correspond chronologically to the Pan-African and Birimian or Eburnian (Africa) and to the Brasiliano and Trans-Amazonian (South America) orogenic cycles. The presence of detritus from rocks of these two orogenic cycles clearly places the basement of Florida in Gondwanaland proximal to the West African and/or Trans-Amazonian-San Luis cratons in the early Paleozoic, a location it probably shared with other circum-Atlantic exotic terranes (Avalonian, Cadomian, and/or Carolina).

Geology↗
USGS2013

Evidence for extensive methane venting on the southeastern U.S. Atlantic margin

We present the first evidence for widespread seabed methane venting along the southeastern United States Atlantic margin beyond the well-known Blake Ridge diapir seep. Recent ship- and autonomous underwater vehicle (AUV)–collected data resolve multiple water-column anomalies (>1000 m height) and extensive new chemosynthetic seep communities at the Blake Ridge and Cape Fear diapirs. These results indicate that multiple, highly localized fluid conduits punctuate the areally extensive Blake Ridge gas hydrate province, and enable the delivery of significant amounts of methane to the water column. Thus, there appears to be an abundance of seabed fluid flux not previously ascribed to the Atlantic margin of the United States.

Geology↗
USGS2013

Meeting the Science Needs of the Nation in the Wake of Hurricane Sandy-- A U.S. Geological Survey Science Plan for Support of Restoration and Recovery

n late October 2012, Hurricane Sandy came ashore during a spring high tide on the New Jersey coastline, delivering hurricane-force winds, storm tides exceeding 19 feet, driving rain, and plummeting temperatures. Hurricane Sandy resulted in 72 direct fatalities in the mid-Atlantic and northeastern United States, and widespread and substantial physical, environmental, ecological, social, and economic impacts estimated at near $50 billion. Before the landfall of Hurricane Sandy, the USGS provided forecasts of potential coastal change; collected oblique aerial photography of pre-storm coastal morphology; deployed storm-surge sensors, rapid-deployment streamgages, wave sensors, and barometric pressure sensors; conducted Light Detection And Ranging (lidar) aerial topographic surveys of coastal areas; and issued a landslide alert for landslide prone areas. During the storm, Tidal Telemetry Networks provided real-time water-level information along the coast. Long-term network and rapid-deployment real-time streamgages and water-quality monitors reported on river levels and changes in water quality. Immediately after the storm, the USGS serviced real-time instrumentation, retrieved data from over 140 storm-surge sensors, and collected other essential environmental data, including more than 830 high-water marks mapping the extent and elevation of the storm surge. Post-storm lidar surveys documented storm impacts to coastal barriers informing response and recovery and providing a new baseline to assess vulnerability of the reconfigured coast. The USGS Hazard Data Distribution System served storm related information from many agencies on the Internet on a daily basis. This science plan was developed immediately following Hurricane Sandy to coordinate continuing USGS activities with other agencies and to guide continued data collection and analysis to ensure support for recovery and restoration efforts. The data, information, and tools that are produced by implementing this plan will: (1) further characterize impacts and changes, (2) guide mitigation and restoration of impacted communities and ecosystems, (3) inform a redevelopment strategy aimed at developing resilient coastal communities and ecosystems, (4) improve preparedness and responsiveness to the next hurricane or similar coastal disaster, and (5) enable improved hazard assessment, response, and recovery for future storms along the hurricane prone shoreline of the United States. The activities outlined in this plan are organized in five themes based on impact types and information needs. These USGS science themes are: Theme 1: Coastal topography and bathymetry. Theme 2: Impacts to coastal beaches and barriers. Theme 3: Impacts of storm surge and estuarine and bay hydrology. Theme 4: Impacts on environmental quality and persisting contaminant exposures. Theme 5: Impacts to coastal ecosystems, habitats, and fish and wildlife. A major emphasis in the implementation of this plan will be on interacting with stakeholders to better understand their specific data and information needs, to define the best way to make information available, and to support applications of USGS science and expertise to decisionmaking.

Connecticut;Delaware;Maine;Maryl;Massachusetts;New↗
USGS2010

Update on geographic spread of invasive lionfishes ( Pterois volitans [Linnaeus, 1758] and P. miles [Bennett, 1828]) in the Western North Atlantic Ocean, Caribbean Sea and Gulf of Mexico

The Indo-Pacific lionfishes ( Pterois volitans [Linnaeus, 1758] and P. miles [Bennett, 1828]: Family Scorpaenidae) are the first nonnative marine fishes to establish in the Western North Atlantic/Caribbean region. The chronology of the invasion was reported last year (Schofield 2009) using records from the US Geological Survey's Nonindigenous Aquatic Species database. This article provides an update of lionfish geographic spread (as of October 2010) and predictions of future range.

Aquatic Invasions↗
USGS2012

Carbon export by rivers draining the conterminous United States

Material exports by rivers, particularly carbon exports, provide insight to basin geology, weathering, and ecological processes within the basin. Accurate accounting of those exports is valuable to understanding present, past, and projected basin-wide changes in those processes. We calculated lateral export of inorganic and organic carbon (IC and OC) from rivers draining the conterminous United States using stream gaging and water quality data from more than 100 rivers. Approximately 90% of land area and 80% of water export were included, which enabled a continental-scale estimate using minor extrapolation. Total carbon export was 41–49 Tg C yr −1 . IC was >75% of export and exceeded OC export in every region except the southeastern Atlantic seaboard. The 10 largest rivers, by discharge, accounted for 66% of water export and carried 74 and 62% of IC and OC export, respectively. Watershed carbon yield for the conterminous United States was 4.2 and 1.3 g C m −2 yr −1 for IC and OC, respectively. The dominance of IC export was unexpected but is consistent with geologic models suggesting high weathering rates in the continental United States due to the prevalence of easily weathered sedimentary rock.

Inland Waters↗
USGS2013

Surface electric fields for North America during historical geomagnetic storms

To better understand the impact of geomagnetic disturbances on the electric grid, we recreate surface electric fields from two historical geomagnetic storms—the 1989 “Quebec” storm and the 2003 “Halloween” storms. Using the Spherical Elementary Current Systems method, we interpolate sparsely distributed magnetometer data across North America. We find good agreement between the measured and interpolated data, with larger RMS deviations at higher latitudes corresponding to larger magnetic field variations. The interpolated magnetic field data are combined with surface impedances for 25 unique physiographic regions from the United States Geological Survey and literature to estimate the horizontal, orthogonal surface electric fields in 1 min time steps. The induced horizontal electric field strongly depends on the local surface impedance, resulting in surprisingly strong electric field amplitudes along the Atlantic and Gulf Coast. The relative peak electric field amplitude of each physiographic region, normalized to the value in the Interior Plains region, varies by a factor of 2 for different input magnetic field time series. The order of peak electric field amplitudes (largest to smallest), however, does not depend much on the input. These results suggest that regions at lower magnetic latitudes with high ground resistivities are also at risk from the effect of geomagnetically induced currents. The historical electric field time series are useful for estimating the flow of the induced currents through long transmission lines to study power flow and grid stability during geomagnetic disturbances.

Space Weather↗
USGS2016

Measuring, interpreting, and responding to changes in coral reefs: A challenge for biologists, geologist, and managers

What, exactly, is a coral reef? And how have the world’s reefs changed in the last several decades? What are the stressors undermining reef structure and function? Given the predicted effects of climate change, do reefs have a future? Is it possible to “manage” coral reefs for resilience? What can coral reef scientists contribute to improve protection and management of coral reefs? What insights can biologists and geologists provide regarding the persistence of coral reefs on a human timescale? What is reef change to a biologist… to a geologist? Clearly, there are many challenging questions. In this chapter, we present some of our thoughts on monitoring and management of coral reefs in US national parks in the Caribbean and western Atlantic based on our experience as members of monitoring teams. We reflect on the need to characterize and evaluate reefs, on how to conduct high-quality monitoring programs, and on what we can learn from biological and geological experiments and investigations. We explore the possibility that specific steps can be taken to “manage” coral reefs for greater resilience.

Book chapter↗
USGS2008

Data to support statistical modeling of instream nutrient load based on watershed attributes, southeastern United States, 2002

This report presents and describes the digital datasets that characterize nutrient source inputs, environmental characteristics, and instream nutrient loads for the purpose of calibrating and applying a nutrient water-quality model for the southeastern United States for 2002. The model area includes all of the river basins draining to the south Atlantic and the eastern Gulf of Mexico, as well as the Tennessee River basin (referred to collectively as the SAGT area). The water-quality model SPARROW (SPAtially-Referenced Regression On Watershed attributes), developed by the U.S. Geological Survey, uses a regression equation to describe the relation between watershed attributes (predictors) and measured instream loads (response). Watershed attributes that are considered to describe nutrient input conditions and are tested in the SPARROW model for the SAGT area as source variables include atmospheric deposition, fertilizer application to farmland, manure from livestock production, permitted wastewater discharge, and land cover. Watershed and channel attributes that are considered to affect rates of nutrient transport from land to water and are tested in the SAGT SPARROW model as nutrient-transport variables include characteristics of soil, landform, climate, reach time of travel, and reservoir hydraulic loading. Datasets with estimates of each of these attributes for each individual reach or catchment in the reach-catchment network are presented in this report, along with descriptions of methods used to produce them. Measurements of nutrient water quality at stream monitoring sites from a combination of monitoring programs were used to develop observations of the response variable - mean annual nitrogen or phosphorus load - in the SPARROW regression equation. Instream load of nitrogen and phosphorus was estimated using bias-corrected log-linear regression models using the program Fluxmaster, which provides temporally detrended estimates of long-term mean load well-suited for spatial comparisons. The detrended, or normalized, estimates of load are useful for regional-scale assessments but should be used with caution for local-scale interpretations, for which use of loads estimated for actual time periods and employing more detailed regression analysis is suggested. The mean value of the nitrogen yield estimates, normalized to 2002, for 637 stations in the SAGT area is 4.7 kilograms per hectare; the mean value of nitrogen flow-weighted mean concentration is 1.2 milligrams per liter. The mean value of the phosphorus yield estimates, normalized to 2002, for the 747 stations in the SAGT area is 0.66 kilogram per hectare; the mean value of phosphorus flow-weighted mean concentration is 0.17 milligram per liter. Nutrient conditions measured in streams affected by substantial influx or outflux of water and nutrient mass across surface-water basin divides do not reflect nutrient source and transport conditions in the topographic watershed; therefore, inclusion of such streams in the SPARROW modeling approach is considered inappropriate. River basins identified with this concern include south Florida (where surface-water flow paths have been extensively altered) and the Oklawaha, Crystal, Lower Sante Fe, Lower Suwanee, St. Marks, and Chipola River basins in central and northern Florida (where flow exchange with the underlying regional aquifer may represent substantial nitrogen influx to and outflux from the surface-water basins).

Open-File Report↗
USGS2015

A method for determining average beach slope and beach slope variability for U.S. sandy coastlines

The U.S. Geological Survey (USGS) National Assessment of Hurricane-Induced Coastal Erosion Hazards compares measurements of beach morphology with storm-induced total water levels to produce forecasts of coastal change for storms impacting the Gulf of Mexico and Atlantic coastlines of the United States. The wave-induced water level component (wave setup and swash) is estimated by using modeled offshore wave height and period and measured beach slope (from dune toe to shoreline) through the empirical parameterization of Stockdon and others (2006). Spatial and temporal variability in beach slope leads to corresponding variability in predicted wave setup and swash. For instance, seasonal and storm-induced changes in beach slope can lead to differences on the order of 1 meter (m) in wave-induced water level elevation, making accurate specification of this parameter and its associated uncertainty essential to skillful forecasts of coastal change. A method for calculating spatially and temporally averaged beach slopes is presented here along with a method for determining total uncertainty for each 200-m alongshore section of coastline.

North Carolina↗
USGS1985

Comparison of marine gas hydrates in sediments of an active and passive continental margin

Two sites of the Deep Sea Drilling Project in contrasting geologic settings provide a basis for comparison of the geochemical conditions associated with marine gas hydrates in continental margin sediments. Site 533 is located at 3191 m water depth on a spit-like extension of the continental rise on a passive margin in the Atlantic Ocean. Site 568, at 2031 m water depth, is in upper slope sediment of an active accretionary margin in the Pacific Ocean. Both sites are characterized by high rates of sedimentation, and the organic carbon contents of these sediments generally exceed 0.5%. Anomalous seismic reflections that transgress sedimentary structures and parallel the seafloor, suggested the presence of gas hydrates at both sites, and, during coring, small samples of gas hydrate were recovered at subbottom depths of 238m (Site 533) and 404 m (Site 568). The principal gaseous components of the gas hydrates wer methane, ethane, and CO2. Residual methane in sediments at both sites usually exceeded 10 mll-1 of wet sediment. Carbon isotopic compositions of methane, CO2, and ??CO2 followed parallel trends with depth, suggesting that methane formed mainly as a result of biological reduction of oxidized carbon. Salinity of pore waters decreased with depth, a likely result of gas hydrate formation. These geochemical characteristics define some of the conditions associated with the occurrence of gas hydrates formed by in situ processes in continental margin sediments. ?? 1984.

Marine and Petroleum Geology↗
USGS2000

Last interglacial reef growth beneath Belize barrier and isolated platform reefs

We report the first radiometric dates (thermal-ionization mass spectrometry) from late Pleistocene reef deposits from offshore Belize, the location of the largest modern reef complex in the Atlantic Ocean. The results presented here can be used to explain significant differences in bathymetry, sedimentary facies, and reef development of this major reef area, and the results are significant because they contribute to the knowledge of the regional geology of the eastern Yucatán. The previously held concept of a neotectonically stable eastern Yucatán is challenged. The dates indicate that Pleistocene reefs and shallow-water limestones, which form the basement of modern reefs in the area, accumulated ca. 125–130 ka. Significant differences in elevation of the samples relative to present sea level (>10 m) have several possible causes. Differential subsidence along a series of continental margin fault blocks in combination with variation in karstification are probably the prime causes. Differential subsidence is presumably related to initial extension and later left-lateral movements along the adjacent active boundary between the North American and Caribbean plates. Increasing dissolution toward the south during Pleistocene sea-level lowstands is probably a consequence of higher precipitation rates in mountainous southern Belize.

Geology↗
USGS2000

Data for Quaternary faults, liquefaction features, and possible tectonic features in the Central and Eastern United States, east of the Rocky Mountain Front

The USGS is currently leading an effort to compile published geological information on Quaternary faults, folds, and earthquake-induced liquefaction in order to develop an internally consistent database on the locations, ages, and activity rates of major earthquake-related features throughout the United States. This report is the compilation for such features in the Central and Eastern United States (CEUS), which for the purposes of the compilation, is defined as the region extending from the Rocky Mountain Front eastward to the Atlantic seaboard. A key objective of this national compilation is to provide a comprehensive database of Quaternary features that might generate strong ground motion and therefore, should be considered in assessing the seismic hazard throughout the country. In addition to printed versions of regional and individual state compilations, the database will be available on the World-Wide Web, where it will be readily available to everyone. The primary purpose of these compilations and the derivative database is to provide a comprehensive, uniform source of geological information that can by used to complement the other types of data that are used in seismic-hazard assessments. Within our CEUS study area, which encompasses more than 60 percent of the continuous U.S., we summarize the geological information on 69 features that are categorized into four classes (Class A, B, C, and D) based on what is known about the feature's Quaternary activity. The CEUS contains only 13 features of tectonic origin for which there is convincing evidence of Quaternary activity (Class A features). Of the remaining 56 features, 11 require further study in order to confidently define their potential as possible sources of earthquake-induced ground motion (Class B), whereas the remaining features either lack convincing geologic evidence of Quaternary tectonic faulting or have been studied carefully enough to determine that they do not pose a significant seismic hazard (Classes C and D). The correlation between historical seismicity and Quaternary faults and liquefaction features in the CEUS is generally poor, which probably reflects the long return times between successive movements on individual structures. Some Quaternary faults and liquefaction features are located in aseismic areas or where historical seismicity is sparse. These relations indicate that the record of historical seismicity does not identify all potential seismic sources in the CEUS. Furthermore, geological studies of some currently aseismic faults have shown that the faults have generated strong earthquakes in the geologically recent past. Thus, the combination of geological information and seismological data can provide better insight into potential earthquake sources and thereby, contribute to better, more comprehensive seismic-hazard assessments.

Open-File Report↗
USGS1984

Drainage areas in New Jersey; Atlantic coastal basins, South Amboy to Cape May

Drainage areas of New Jersey streams in the coastal basin from South Amboy to Cape May are listed for more than 700 sites. Tables list the descriptive location of each site, the latitude and longitude, county, and National Topographic map name. For gaged sites established through 1982, the U.S. Geological Survey station name and site number are also shown. The data are presented alphabetically by stream name and in downstream order. Drainage areas were tabulated for named streams and unnamed streams with a drainage area greater than 5 square miles. The methods used to delineate the drainage divides, measure areas, and determine mouths of streams follow the guidelines developed by the U.S. Water Resources Council. (USGS)

Open-File Report↗
USGS1974

Structure of the continental margin of Liberia, West Africa

Geophysical surveys made by R/V Unitedgeo I (USGS–IDOE Cruise Leg 5), combined with earlier surveys and available geologic information, provide the basis for interpreting the structure of the continental margin of Liberia. This area lies at the junction of the Americas and Africa in published reconstructions of Gondwanaland prior to the opening of the North and South Atlantic in Jurassic and Cretaceous time, respectively. Three fracture zones (St. Paul, Cape Palmas, and Grand Cess) are inferred in the area southeast of 9°30′ W. on the basis of magnetic and gravity data, which is supported by bathymetric and seismic reflection data. The three fracture zones appear to exist as separate lineaments near the African coast. Farther seaward, they may be part of the same transform fault crossing the Atlantic (St. Paul fracture zone). The magnetic anomalies associated with these fracture zones, which may have originated in Cretaceous time at the opening of the South Atlantic, are continuous with magnetic anomalies over crust of Eburnean age (∼2,000 m.y.) in southeast Liberia and its continental shelf. This suggests that Eburnean age structures may have been zones of weakness that were reactivated in Cretaceous time. A positive gravity anomaly (∼50 mgal) along the coast and continental shelf of Liberia is attributed to deep crustal rocks that were uplifted and exposed in Pan-African time (∼550 m.y.). The land boundary of this anomaly coincides with a shear zone that marks the boundary between the Pan-African and the Liberian age province (∼2,700 m.y.); the shearing (in a thrust-fault sense) may be the result of compressive stress associated with the closing of a proto-Atlantic ocean. Liberian age magnetic anomalies in the area northwest of 9°30′ W. cross the Pan-African province (and the positive coastal gravity anomaly) and continue over the continental shelf and slope to about the 3,000-m bathymetric contour; the seaward limit of the anomalies is interpreted as representing the seaward limit of the old continental crust. This westward extension of the continental crust does not completely fill the gap in fit in various published reconstructions of Gondwanaland, and we suggest that the northern Florida block may have been located near the Liberian margin at one time. Magnetic data indicate a thick section of sedimentary rock, possibly as great as 8 km, on the continental slope. Comparison of gravity data over magnetically inferred basins in the shelf, slope, and rise suggests that low-density sedimentary rocks constitute a greater proportion of the section in basins beneath the shelf and beneath the slope and rise northwest of 9°30' W. than beneath the slope and rise in the area of the fracture zones. The gravitational attraction that corresponds to a crust-mantle boundary dipping 45° to 60° can be computed to fit observed data – as might be expected at a rifted continental margin. A shallow high-density block beneath the coast and continental shelf is required to fit the coastal positive anomaly; this block is represented by exposures on land of granulite-grade metamorphic rock of the Pan-African province.

Atlantic Ocean↗
USGS2006

Drainage Areas of Selected Streams in Virginia

Drainage areas were determined for more than 1,600 basins in the three major river basins of Virginia -- the North Atlantic Slope, South Atlantic Slope, and Ohio River Basins. Drainage areas range from 0.004 square mile to 7,866 square miles. A geographic information system was used to digitize and store data associated with the drainage basins. Drainage divides were digitized from digital U.S. Geological Survey 7.5-minute, 1:24,000-scale, topographic quadrangles using procedures recommended by the Subcommittee on Hydrology, Federal Interagency River Basin Committee. Digital drainage basins were quality assured, polygons of the closed drainage basins were generated, and drainage areas were computed.

Open-File Report↗
USGS1969

Atlantic continental shelf and slope of the United States - Color of marine sediments

A systematic examination of the regional color distribution of the upper sediment layer on the Atlantic continental margin between Nova Scotia and southern Florida reveals that brown, dark green, and yellow predominate on the shelf north of Cape Hatteras, whereas olive, gray, and yellow predominate to the south. Color is affected by composition. texture, physiography, and geological events in the recent past. Many of the color patterns on the shelf are more closely related to Pleistocene and Holocene sedimentary events than to modern dispersal processes. Relict color patterns occur in areas such as Georges and Browns Banks, which were exposed during lower stands of sea level. Linear but discontinuous belts of yellow sediment on the outer shelf and along the shelf break south of Cape Hatteras are probably also related to strandline features formed during the Pleistocene low stands of sea level and during the transgressive advance of the Holocene sea. Color patterns on the continental slope and rise and on the Blake Plateau, unlike those on the shelf, are arranged in linear belts that trend parallel or subparallel to the shelf break. Major trends vary di redly with depth, ranging from olive and green at the top of the slope, through light gray and pale yellowish brown, to brown and yellow at. the top of the continental rise. These trends are probably related to the oxidation-reduction Potential of the environment, which results from a balance between the rate of deposition and the rate of bacterial decomposition of organic matter deposited with the sediment. Isolated areas of color on the slope and rise seem to be due to the slumping of sediment masses downslope and to the exposure of pre-Holocene outcrops. Red Pleistocene till masses, which were once exposed on the Scotian Shelf during the glacial epoch, may have been reworked during the Holocene rise in sea level. This may explain why 'brown and reddish-brown sediments are found at progressively shallower depths northeastward on the rise and slope off the Gulf of Maine and Nova Scotia.

Atlantic continental shelf↗
USGS1984

Bathymetric map of Lydonia Canyon, U.S. Atlantic Outer Continental Shelf

Lydonia Canyon is one of several large submarine canyons that indent the eastern U.S. Continental Shelf along the southern flank of Georges Bank (Index map). This bathymetric map of the upper part of Lydonia Canyon (water depths shallower than about 2,00 m) was prepared as part of a study of the physical oceanography and geology of Lydonia Canyon (Butman and others, 1983; Twichell, 1983). An accurate map of the canyon at a scale of at least 1:50,000 was needed for placement of current-meter morrings, for location of hydrographic and sediment sampling stations, and for interpretation of current-meter and geologic data. The map covers the area from 40°10'N. to 40°40'N. and from 67°28'W. to 67°50'W.

Atlantic Outer Continental Shelf, Lydonia Canyon↗