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At least 613 records · Page 34Linked to original sources

Silicoflagellate and diatom biostratigraphy in successive Burdigalian transgressions, middle Atlantic coastal plain

The earliest Miocene strata on the Middle Atlantic Coastal Plain were deposited in two distinct marine transgressions separated by a hiatus in sedimentation of approximately one million years. The older unit (Bed 3A of the Calvert Formation and its correlatives) was deposited in a relatively restricted basin of middle Burdigalian (middle early Miocene) age. The younger unit (Bed 3B of the Calvert Formation and its correlatives) was deposited in a much more widespread basin of late Burdigalian (late early Miocene) age. The older deposit was completely overlapped by the younger deposit. These two beds of substantially differing geologic age are difficult, if not impossible, to distinguish solely by lithostratigraphy. They are, however, readily differentiated on the basis of their distinctive silicoflagellate and diatom assemblages.

Delaware, Maryland, New Jersey↗

Attributes for MRB_E2RF1 Catchments by Major River Basins in the Conterminous United States: Bedrock Geology

This tabular data set represents the area of bedrock geology types in square meters compiled for every catchment of MRB_E2RF1 catchments for Major River Basins (MRBs, Crawford and others, 2006). The source data set is the "Geology of the Conterminous United States at 1:2,500,000 Scale--A Digital Representation of the 1974 P.B. King and H.M. Beikman Map" (Schuben and others, 1994). The MRB_E2RF1 catchments are based on a modified version of the U.S. Environmental Protection Agency's (USEPA) ERF1_2 and include enhancements to support national and regional-scale surface-water quality modeling (Nolan and others, 2002; Brakebill and others, 2011). Data were compiled for every MRB_E2RF1 catchment for the conterminous United States covering New England and Mid-Atlantic (MRB1), South Atlantic-Gulf and Tennessee (MRB2), the Great Lakes, Ohio, Upper Mississippi, and Souris-Red-Rainy (MRB3), the Missouri (MRB4), the Lower Mississippi, Arkansas-White-Red, and Texas-Gulf (MRB5), the Rio Grande, Colorado, and the Great basin (MRB6), the Pacific Northwest (MRB7) river basins, and California (MRB8).

Data Series↗

National Assessment of Shoreline Change: Part 1, Historical Shoreline Changes and Associated Coastal Land Loss Along the U.S. Gulf of Mexico

EXECUTIVE SUMMARY Beach erosion is a chronic problem along most open-ocean shores of the United States. As coastal populations continue to grow and community infrastructures are threatened by erosion, there is increased demand for accurate information regarding past and present trends and rates of shoreline movement. There is also a need for a comprehensive analysis of shoreline movement that is consistent from one coastal region to another. To meet these national needs, the U.S. Geological Survey is conducting an analysis of historical shoreline changes along open-ocean sandy shores of the conterminous United States and parts of Hawaii and Alaska. One purpose of this work is to develop standard repeatable methods for mapping and analyzing shoreline movement so that periodic updates regarding coastal erosion and land loss can be made nationally that are systematic and internally consistent. This report on states bordering the Gulf of Mexico (Florida, Alabama, Mississippi, Louisiana, and Texas) represents the first in a series that will eventually include the Atlantic Coast, Pacific Coast, and parts of Hawaii and Alaska. The report summarizes the methods of analysis, interprets the results, provides explanations regarding the historical and present trends and rates of change, and describes how different coastal communities are responding to coastal erosion. Shoreline change evaluations are based on comparing three historical shorelines with a recent shoreline derived from lidar (Light Detection and Ranging) topographic surveys. The historical shorelines generally represent the following periods: 1800s, 1920s-1930s, and 1970s, whereas the lidar shoreline is 1998-2002. Long-term rates of change are calculated using all four shorelines (1800s to lidar shoreline), whereas short-term rates of change are calculated for the most recent period (1970s to lidar shoreline). The historical rates of change presented in this report represent past conditions and therefore are not intended for predicting future shoreline positions or rates of change. Rates of erosion for the Gulf of Mexico region are generally highest in Louisiana along barrier island and headland shores associated with the Mississippi delta. Erosion is also rapid along some barrier islands and headlands in Texas, and barrier islands in Mississippi are migrating laterally. Highest rates of erosion in Florida are generally localized around tidal inlets. The most stable Gulf beaches are along the west coast of Florida where low wave energy and frequent beach nourishment minimize erosion. Some beach segments in Texas have accreted as a result of net longshore drift convergence, and around tidal inlets that have been stabilized by long jetties. Seawalls and riprap revetments were constructed in all the Gulf Coast states as initial community responses to long-term beach erosion. Although some states, such as Florida, still permit shoreline stabilization structures, beach nourishment has become the preferred method of mitigating long-term erosion.

Open-File Report↗

Atlantic Margin Coring Project 1976: Preliminary Report on Shipboard and Some Laboratory Geotechnical data

This report presents reduced shipboard geotechnical data collected during the 1976 Atlantic Margin Coring Project; results of laboratory tests of specific gravity, water content, bulk density, and Atterberg limits; and sedimentation-compression e log p curves showing consolidation. A description of the procedures used at sea and in the laboratory and a short preliminary summary of the shipboard results also is included. The involvement of Marine Geotechnical Laboratory (MGL), Lehigh University, personnel in the 1976 Atlantic Margin Coring Project can be divided into two phases. In Phase One, the Lehigh nuclear-transmission densitometer was rebuilt to process cores at sea more rapidly than previously had been done in the laboratory, the equipment was assembled and tested aboard the Glomar Conception, and at-sea geotechnical measurements were made during the duration of the cruise. Data sheets were prepared for both unopened core sections (Appendix III) and split-core samples (Appendix IV). Completed data forms are on file at the MGL and at the Geological Survey in Woods Hole. Phase Two included reduction of the shipboard data, testing of all geotechnical samples taken from cores split aboard the ship, and certain other analytical work ashore utilizing the geotechnical measurements. Water content and weight/volume bulk density tests were performed at the MGL. Specific gravity and Atterberg limit tests and certain calculations were performed by Geological Survey personnel at the Corpus Christi, Texas, laboratory. During Phase One, 37 unopened, 1.5-m-long core sections were selected by Lehigh personnel for subsequent static and dynamic triaxial and consol­idation testing ashore. The disposition of these cores is controlled by Geological Survey Project personnel; they are not further discussed in this report. A depth convention has been adopted in this report for the convenience of labeling core sections and analyzing the data. Each 9.2-m-long (30 ft) core liner had a maximum penetration depth referenced to the water-sediment interface; these data are given in Hathaway, et al. (1976). Each 9.2-m-long core liner was cut into six or fewer sections, each 1.5 m (5 ft) in length, aboard the ship. To the maximum penetration depth, 0.2 m was subtracted to obtain the depth at the bottom of the first 1.5 m section above the core catcher. To obtain values at the bottom of the remaining 1.5 m sections, an additional 1.5 m was added for each section. The depth of the bottom of each core section was used for all values obtained using the nuclear densitometer. Tests within core sections and samples collected from core sections were assigned depths based on the location of the test or sample within the core section. It should be clearly recognized that all depths within a 9.2-m-long core are estimates of the true depth, which cannot be uniquely calculated because of the uncertainty of the relationship of sediment contained within the core liner to true in situ depths. This report is considered to be preliminary because the author has not had access to the final lithologic logs or paleontological results, upon which a more accurate description of geotechnical results could be based. It would be inappropriate to comment on geological hazards until this information is made available.

Atlantic Ocean↗

Geology of the Petersburg batholith, eastern Piedmont, Virginia

The 295-300 Ma Petersburg batholith in east-central Virginia forms one of the largest and northernmost of the Alleghanian plutonic complexes in the southern Appalachian Piedmont. The batholith is primarily composed of granite including massive and foliated (both magmatic and solid-state fabrics) varieties. The plutonic complex intruded medium-grade metamorphosed volcanic/plutonic rocks of the Roanoke Rapids terrane. The western edge of the batholith experienced right lateral transpressional deformation associated with movement on the Hylas fault zone during the Alleghanian orogeny; this was followed by normal faulting and exhumation during the development of the Triassic Richmond basin. Much of the batholith was buried by a thin veneer of primarily Cenozoic siliciclastic sediments at the western edge of the Atlantic Coastal Plain. Granite rocks of the Petersburg batholith have long been quarried for both dimension and crushed stone. The purpose of this trip is to discuss the age, origin, and tectonic significance of the Petersburg batholith.

Virginia↗

Attributes for MRB_E2RF1 Catchments by Major River Basins in the Conterminous United States: Artificial Drainage (1992) and Irrigation (1997)

This tabular data set represents the estimated area of artifical drainage for the year 1992 and irrigation types for the year 1997 compiled for every MRB_E2RF1 catchment of Major River Basins (MRBs, Crawford and others, 2006). The source data sets were derived from tabular National Resource Inventory (NRI) data sets created by the National Resources Conservation Service (NRCS, U.S. Department of Agriculture, 1995, 2000). Artificial drainage is defined as subsurface drains and ditches. Irrigation types are defined as gravity and pressure. Subsurface drains are described as conduits, such as corrugated plastic tubing, tile, or pipe, installed beneath the ground surface to collect and/or convey drainage. Surface drainage field ditches are described as graded ditches for collecting excess water. Gravity irrigation source is described as irrigation delivered to the farm and/or field by canals or pipelines open to the atmosphere; and water is distributed by the force of gravity down the field by: (1) A surface irrigation system (border, basin, furrow, corrugation, wild flooding, etc.) or (2) Sub-surface irrigation pipelines or ditches. Pressure irrigation source is described as irrigation delivered to the farm and/or field in pump or elevation-induced pressure pipelines, and water is distributed across the field by: (1) Sprinkle irrigation (center pivot, linear move, traveling gun, side roll, hand move, big gun, or fixed set sprinklers), or (2) Micro irrigation (drip emitters, continuous tube bubblers, micro spray or micro sprinklers). NRI data do not include Federal lands and are thus excluded from this dataset. The tabular data for drainage were spatially apportioned to the National Land Cover Dataset (NLCD, Kerie Hitt, U.S. Geological Survey, written commun., 2005) and the tabular data for irrigation were spatially apportioned to an enhanced version of the National Land Cover Dataset (NLCDe, Nakagaki and others, 2007). The MRB_E2RF1 catchments are based on a modified version of the U.S. Environmental Protection Agency's (USEPA) ERF1_2 and include enhancements to support national and regional-scale surface-water quality modeling (Nolan and others, 2002; Brakebill and others, 2011). Data were compiled for every MRB_E2RF1 catchment for the conterminous United States covering New England and Mid-Atlantic (MRB1), South Atlantic-Gulf and Tennessee (MRB2), the Great Lakes, Ohio, Upper Mississippi, and Souris-Red-Rainy (MRB3), the Missouri (MRB4), the Lower Mississippi, Arkansas-White-Red, and Texas-Gulf (MRB5), the Rio Grande, Colorado, and the Great basin (MRB6), the Pacific Northwest (MRB7) river basins, and California (MRB8).

Data Series↗

Errors in using modern stream-load data to estimate natural rates of denudation

The practice of calculating natural rates of denudation from routinely collected data on the loads of suspended and dissolved matter in modern rivers is subject to several significant errors. The sources of these errors are demonstrated by examples from the Atlantic drainage of the United States, where their total effect has apparently doubled the natural rate of erosion. The largest error is caused by assuming that modern sediment loads in populated areas represent natural erosion, whereas in fact they mainly reflect the influence of man. Conversion of forests to croplands in the middle Atlantic states causes about a tenfold increase in sediment yield. Coal mining, urbanization, and highway construction have added extra loads of sediment to the streams. Modern sediment loads in the Atlantic-draining rivers are probably 4 to 5 times greater than they would be if the area had remained undisturbed by man. Errors in calculating the chemical denudation are caused by atmospheric contributions to the dissolved loads of streams and by pollutants that are added directly to stream waters. About one-quarter of the salts in Atlantic-draining streams were contributed from the atmosphere, either as recycled sea salts or as pollutants and soil dust that originally became airborne as a result of the activities of man. Perhaps another one-tenth of the dissolved load consists of industrial and agricultural wastes or acid mine waters that have been added directly to the streams.

Connecticut, Delaware, Georgia, Maryland, Massachu↗

Strengthening ties between the U.S. Geological Survey and Interstate Fisheries Commissions

Fish inhabiting marine coastal and Great Lakes waters of the United States forage, migrate, and reproduce without regard to human-made boundaries. In the mid-20th century, the 32 states along the U.S. coasts and Great Lakes recognized the growing need for coordinated, interjurisdictional fisheries management and formed four interstate or international fisheries commissions through federal legislation. While distinct in their authorities, each commission shares functions to support their regional partners, including coordinating fisheries science and supporting information sharing. The U.S. Geological Survey (USGS) is a federal bureau focused exclusively on science with substantial fisheries research capacity. This empowers USGS to serve as an independent broker of scientific information, which is greatly appreciated by decision-making agencies. The USGS does not maintain broad infrastructure for engaging partners across regions. Therefore, collaboration between the USGS and fisheries commissions ensures that USGS fisheries science helps address the most pressing interjurisdictional management priorities. The USGS has worked with fisheries commissions for decades to a greater or lesser extent in each of the four coastal regions: Atlantic, Pacific, Gulf, and Great Lakes. In 2020, the USGS began efforts to cohesively strengthen these partnerships across the regions. In 2024, leadership from four USGS fisheries science centers and headquarters met with the four fisheries commissions in person for the first time during the American Fisheries Society Annual Meeting. During the gathering, the new Interstate Fisheries Commissions–USGS Partnership developed coordination mechanisms and identified shared science priorities where the USGS capacity best aligns with the science needs of the commissions. Here we describe the history of collaboration between the USGS and fisheries commissions and the emerging interregional partnership.

Fisheries↗

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↗

Geologic framework of the offshore region adjacent to Delaware

Several multichannel, common depth point (CDP) seismic reflection profiles concentrated in the area of the entrance to Delaware Bay provide a tie between the known onshore geology of the Coastal Plain of Delaware and the offshore geology of the Baltimore Canyon Trough. The data provide a basis for understanding the geologic framework and petroleum resource potential of the area immediately offshore Delaware. Our research has focused on buried early Mesozoic rift basins and their geologic history. Assuming that the buried basins are analogous to the exposed Newark Supergroup basins of Late Triassic-Early Jurassic age, the most likely possibility for occurrence of hydrocarbon source beds in the area of the landward margin of the Baltimore Canyon Trough is presumed to be lacustrine, organic-rich shales probably present in the basins. Although buried basins mapped offshore Delaware are within reach of drilling, no holes have been drilled to date; therefore, direct knowledge of source, reservoir, and sealing beds is absent. Buried rift basins offshore Delaware show axial trends ranging from NW-SE to NNE-SSW. Seismic reflection profiles are too widely spaced to delineate basin boundaries accurately. Isopleths of two-way travel time representing basin fill suggest that, structurally, the basins are grabens and half-grabens. As shown on seismic reflection profiles, bounding faults of the basins intersect or merge with low-angle fault surfaces that cut the pre-Mesozoic basement. The rift basins appear to have formed by Mesozoic extension that resulted in reverse motion on reactivated basement thrust faults that originated from compressional tectonics during the Paleozoic. Computer-plotted structure contour maps derived from analysis of seismic reflection profiles provide information on the burial history of the rift basins. The postrift unconformity bevels the rift basins and, in the offshore area mapped, ranges from 2000 to 12,000 m below present sea level. The oldest postrift sediments that cover the more deeply buried rift basins are estimated to be of Middle Jurassic age (Bajocian-Bathonian), the probable time of opening of the Atlantic Ocean basin and onset of continental drift about 175–180 m.y. ago. By late Oxfordian-early Kimmeridgian time, the less deeply buried basins nearshore Delaware had been covered. A time-temperature index of maturity plot of one of the basins indicates that only dry gas would be present in reservoirs in synrift rocks buried by more than 6000 m of postrift sediments and in the oldest (Bathonian?-Callovian?) postrift rocks. Less deeply buried synrift rocks landward of the basin modeled might still be within the oil generation window.

Marine Geology↗

Morphologic evolution of the wilderness area breach at Fire Island, New York—2012–15

Introduction Hurricane Sandy, which made landfall on October 29, 2012, near Atlantic City, New Jersey, had a significant impact on the coastal system along the south shore of Long Island, New York. A record significant wave height of 9.6 meters (m) was measured at wave buoy 44025 , approximately 48 kilometers offshore of Fire Island, New York. Surge and runup during the storm resulted in extensive beach and dune erosion and breaching of the Fire Island barrier island system at two locations, including a breach that formed within the Otis Pike Fire Island High Dune Wilderness area on the eastern side of Fire Island. The U.S. Geological Survey (USGS) has a long history of conducting morphologic change and processes research at Fire Island. One of the primary objectives of the current research effort is to understand the morphologic evolution of the barrier system on a variety of time scales (from storm scale to decade(s) to century). A number of studies that support the project objectives have been published. Prior to Hurricane Sandy, however, little information was available on specific storm-driven change in this region. The USGS received Hurricane Sandy supplemental funding (project GS2–2B: Linking Coastal Processes and Vulnerability, Fire Island, New York, Regional Study) to enhance existing research efforts at Fire Island. The existing research was greatly expanded to include inner continental shelf mapping and investigations of processes of inner shelf sediment transport; beach and dune response and recovery; and observation, analysis, and modeling of the newly formed breach in the Otis Pike High Dune Wilderness area, herein referred to as the wilderness breach. The breach formed at the site of Old Inlet, which was open from 1763 to 1825. The location of the initial island breaching does not directly correspond with topographic lows of the dunes, but instead the breach formed in the location of a cross-island boardwalk that was destroyed during Hurricane Sandy. From 2013 to November 2015, bathymetric data were collected by the USGS St. Petersburg Coastal and Marine Science Center during three surveys of the breach channel and tidal shoals, and shoreline positions on each side of the breach (also collected by the National Park Service). Additionally, pre-storm topography/bathymetry EAARL–B light detection and ranging (lidar) data were collected by the USGS the day prior to Hurricane Sandy’s landfall. These data serve as a baseline for change analyses during four subsequent periods: June 2013, June 2014, October 2014, and May 2015. The June 2013 single-beam bathymetry data were collected in collaboration with the U.S. Army Corps of Engineers (USACE), using the Lighter Amphibious Resupply Cargo (LARC) vessel, and included the ebb shoal and breach channel. The USGS collected and processed the three additional bathymetric datasets using personal watercraft equipped with single-beam echo sounders and backpack Global Positioning System (GPS) over shallow flood shoals. Eastern and western breach shorelines were surveyed weekly to monthly beginning on November 6, 2012 (by the National Park Service [NPS], and USGS St. Petersburg Coastal and Marine Science Center), with measurements made every few weeks for the first year and every few months after October 2013. The NPS and researchers from Stony Brook University monitored the breach by collecting field data of the breach channel bathymetry, conducting aerial photographic overflights, and performing water-quality analyses (see http://po.msrc.sunysb.edu/GSB/ ). The aerial photography collected and rectified by Stony Brook University is used extensively in our morphologic change description to examine changes to breach shorelines (supplementing shoreline data collected in the field), channel width, and orientation. Due to the uncertainties and the variation in survey methods, a rigorous quantitative analysis was not performed. However, average calculations of various breach metrics allow a qualitative analysis of breach development and evolution. This report presents an overview of the data collected and a summary discussion of the observed changes to the breach system and the seasonal wave climatology associated with the breach morphodynamic response.

New York↗

Geophysical observations on northern part of Georges Bank and adjacent basins of Gulf of Maine

Continuous-seismic-reflection and magnetic-intensity profiles provide data for inferences about the geology of the northern part of Georges Bank and the basins of the Gulf of Maine adjacent to the bank. Basement is inferred to be mostly sedimentary and volcanic rocks of Paleozoic age that were metamorphosed and intruded locally by felsic and mafic plutons near the end of the Paleozoic Era. During Late Triassic time, large fault basins formed within the Gulf of Maine and probably beneath Georges Bank. The fault basins and a possible major northeast-trending fault zone beneath the northern part of the bank probably formed as a result of the opening Atlantic during the Mesozoic. Nonmarine sediments, associated with mafic flows and intrusive rocks, were deposited in the fault basins as they formed. The upper surface of the Triassic and pre-Triassic rocks that comprise basement is an unconformity that makes up much of the bottom of the Gulf of Maine. Depth to the basement surface beneath the gulf differ greatly because of fluvial erosion in Tertiary time and glacial erosion in Pleistocene time. Beneath the northern part of Georges Bank the basement surface is smoother and slopes southward. Prominent valleys, cut before Late Cretaceous time, are present beneath this part of the bank. Cretaceous, Tertiary, and possibly Jurassic times were characterized by episodes of coastal-plain deposition and fluvial erosion. During this time a very thick wedge of sediment, mostly of Jurassic(?) and Cretaceous ages, was deposited on the shelf. Major periods of erosion took place at the close of the Cretaceous and during the Pliocene. Fluvial erosion during the Pliocene removed much of the coastal-plain sedimentary wedge and formed the Gulf of Maine. Pleistocene glaciers eroded all but a few remnants of the coastal-plain sediments within the gulf and deposited a thick section of drift against the north slope of Georges Bank and a thin veneer of outwash on the bank. Marine sediments were deposited in the basins of the Gulf of Maine during the retreat of the last ice and the postglacial rise in sea level.

Georges Bank, Gulf Of Maine↗

Petroleum exploration plays and resource estimates, 1989, onshore United States; Region 1, Alaska; Region 2, Pacific Coast

This study provides brief discussions of the petroleum geology, play descriptions, and resource estimates of 220 individually assessed exploration plays in all 80 onshore geologic provinces within nine assessment regions of the continental United States in 1989; these 80 onshore provinces were assessed in connection with the determination of the Nation's estimated undiscovered resources of oil and gas. The present report covers the 25 provinces that make up Region 1, Alaska, and Region 2, Pacific Coast. It is our intention to issue Region 3, Colorado Plateau and Basin and Range, and Region 4, Rocky Mountains and Northern Great Plains, in book form as well. Regions 5 through 9 (West Texas and Eastern New Mexico, Gulf Coast, Midcontinent, Eastern Interior and Atlantic Coast) will be released individually, as Open-File Reports.

Bulletin↗

History of the topographic branch (division)

From a very early period of the world's existence, man has endeavored to represent the earth's surface in a graphic form for the information of his fellow men, realizing that no oral or written description is capable of setting forth topographic facts so vividly and so clearly as a map. Mapping of the areas of the United States began with the charting of portions of its coast line by early explorers; the need for topographic maps was first recognized during the war of the Colonies for independence from Great Britain. On July 22, 1777, Congress authorized General Washington to appoint: 'Mr. Robert Erskine, or any other person that he may think proper, geographer and surveyor of the roads, to take sketches of the country and the seat of war.' By several acts during the Revolutionary War, Congress provided 'geographers' for the armies of the United States, some of them with the pay of a colonel, amounting to $60 a month and allowances. At the end of the War, a resolution of May 27, 1785, continued in service the 'geographer of the United States' for a period of 3 years. The War Department recognized the necessity of 'geographical engineers' and requested Congress to authorize their appointment, but it was not until the next war that Congress authorized on March 3, 1813, the appointment of eight topographic engineers and eight assistant topographic engineers under the direction of the General Staff of the Army. These officers formed the nucleus of the first Corps of Topographic Engineers in the Army, and that Corps continued to function as an independent unit until it was absorbed by the Corps of Engineers in 1863, during the Civil War between the States. Between the Louisiana Purchase in 1803, and the outbreak of the Civil War, more than a hundred exploring and mapping expeditions were sent into the vast territory lying west of the Mississippi River to investigate the natural resources of this newly acquired country and to find possible locations for wagon roads to the Pacific Coast. These expeditions were sent out by the War Department and were in charge of Army officers. It is interesting to note that such generals as George G. Meade, J.C. Fremont, Joseph E. Johnston, W.F. Smith, John Pope, A.W. Whipple, J.G. Parke, G.K. Warren, and H.L. Abbott, all officers of the Corps of Topographic Engineers, had charge of expeditions and were among our earliest map makers. Unfortunately, the data obtained by these editions were not of sufficient accuracy to serve as a basis for topographic maps of value other than in illustrating their voluminous reports. During this early period, numerous surveys were undertaken within the original Thirteen States, by the Federal government and by the States. The most important were those carried on by the U.S. Coast and Geodetic Survey, which made an accurate survey of the Atlantic Coastline and established a triangulation system that was of so high a standard as to constitute the first and only accurate data for topographic mapping obtained before the Civil War. The Coast and Geodetic Survey, while charting the coast and rivers, also mapped a strip of country extending a few miles inland, the relief being shown by means of hachures, together with contour lines, until 1846 when the first government topographic map on which the relief was shown by contours alone was made, covering an area in the vicinity of Boston Harbor. In 1835, however, the Geological and Topographical Survey of Maryland had issued a map on which the relief was shown by contours, and this is believed to be the first contoured map issued in this country. The outbreak of the Civil War stopped all mapping activities other than those needed by the U.S. Army. During the war, topographic surveys were carried on throughout the war zone under the supervision of the Corps of Engineers, the topographers being civilian employees. After the war, the country west of the Mississippi again became the center of the mapping activities

Circular↗

Bathymetry at the head of the Cape Fear Slide, offshore North Carolina

The Cape Fear Slide is the largest mass-movement that has been observed on the U.S. Atlantic Margin. It is located off the Carolinas on the continental rise in approximately 1,200-5,500 m water depth and extends downslope for over 300 km (Popenoe, 1982). These maps show the bathymetry at the head of the Cape Fear Slide as interpreted from single-channel 3.5 kHz seismic-reflection profiles and mid-range Sea Marc I sidescan sonar imagery (Popenoe, 1985; Popenoe and others, 1991; Schmuck, 1991). The 3.5 kHz data consist of over 1000 km of profiles that were collected in 1988 for the University of North Carolina, Department of Geology. The UNC 3.5 kHz data were used as the main data set in interpreting the bathymetry. The sidescan sonar data were collected in 1980 by the U.S. Geological Survey in cooperation with the Lamont-Doherty Geological Observatory for the U.S. Bureau of Land Management Environmental Studies Program. Only 28 km (5 km swath width) of the sidescan data were used in the interpretation to identify the morphology of the main slump scarp and visible secondary scarps.

North Carolina↗

Well network installation and hydrogeologic data collection, Assateague Island National Seashore, Worcester County, Maryland, 2010

The U.S. Geological Survey, as part of its Climate and Land Use Change Research and Development Program, is conducting a multi-year investigation to assess potential impacts on the natural resources of Assateague Island National Seashore, Maryland that may result from changes in the hydrologic system in response to projected sea-level rise. As part of this effort, 26 monitoring wells were installed in pairs along five east-west trending transects. Each of the five transects has between two and four pairs of wells, consisting of a shallow well and a deeper well. The shallow well typically was installed several feet below the water table—usually in freshwater about 10 feet below land surface (ft bls)—to measure water-level changes in the shallow groundwater system. The deeper well was installed below the anticipated depth to the freshwater-saltwater interface—usually in saltwater about 45 to 55 ft bls—for the purpose of borehole geophysical logging to characterize local differences in lithology and salinity and to monitor tidal influences on groundwater. Four of the 13 shallow wells and 5 of the 13 deeper wells were instrumented with water-level recorders that collected water-level data at 15-minute intervals from August 12 through September 28, 2010. Data collected from these instrumented wells were compared with tide data collected north of Assateague Island at the Ocean City Inlet tide gage, and precipitation data collected by National Park Service staff on Assateague Island. These data indicate that precipitation events coupled with changes in ambient sea level had the largest effect on groundwater levels in all monitoring wells near the Atlantic Ocean and Chincoteague and Sinepuxent Bays, whereas precipitation events alone had the greatest impact on shallow groundwater levels near the center of the island. Daily and bi-monthly tidal cycles appeared to have minimal influence on groundwater levels throughout the island and the water-level changes that were observed appeared to vary among well sites, indicating that changes in lithology and salinity also may affect the response of water levels in the shallow and deeper groundwater systems throughout the island. Borehole geophysical logs were collected at each of the 13 deeper wells along the 5 transects. Electromagnetic induction logs were collected to identify changes in lithology; determine the approximate location of the freshwater-saltwater interface; and characterize the distribution of fresh and brackish water in the shallow aquifer, and the geometry of the fresh groundwater lens beneath the island. Natural gamma logs were collected to provide information on the geologic framework of the island including the presence and thickness of finer-grained deposits found in the subsurface throughout the island during previous investigations. Results of this investigation show the need for collection of continuous water-level data in both the shallow and deeper parts of the flow system and electromagnetic induction and natural gamma geophysical logging data to better understand the response of this groundwater system to changes in precipitation and tidal forcing. Hydrologic data collected as part of this investigation will serve as the foundation for the development of numerical flow models to assess the potential effects of climate change on the coastal groundwater system of Assateague Island.

Maryl↗

Application of the Graphic Correlation method to Pliocene marine sequences

Biostratigraphy — the use of paleontological evidence to establish relative chronologies, forms the cornerstone of many sedimentary geological investigations. Several different approaches to biochronology are available. Traditional interval zones, defined on lowest and/or highest occurrences of selected taxa, are used to place bodies of rock in a relative chronological framework. Fossil datum levels, which are more numerous than zones, are often used as chronohorizons for correlation purposs. The Graphic Correlation method, like interval zonations, synthesizes information from a number of different taxa but does not assume synchrony of any one taxon. A magnetobiostratigraphic model for deep-sea Pliocene sequences has been constructed by graphic correlation of Deep Sea Drilling project cores from the North Atlantic (606), Caribbean Sea (502), South Atlantic (516), Tasman Sea (590), Equatorial Pacific (573) and North Pacific (577). All cores are hydraulic piston cores which contain abundant planktonic foraminifers, calcareous nannofossils and which record many of the magnetic reversals expected in the Pliocene. The model is based on internally consistent paleontologic data gathered by the author. This study demonstrates the advantages of graphic correlation over conventional biostratigraphic procedures. Accurate inter-regional correlations can be made between core sites without resorting to multiple microfossil zonations and without invoking synchrony of fossil events. Important results of this study are: (1) many Pliocene planktonic foraminifer and calcareous nannofossil events are diachronous by more than 0.20 m.y., (2) Globorotalia truncatulinoides first occurs in the Southwest Pacific Ocean, approximately 0.50 m.y. earlier than previously reported, (3) a previously undetected hiatus of short duration (0.38 m.y.) exists just above the Cochiti subchron at DSDP 577A.

Marine Micropaleontology↗

Spatial distribution of the largest rainfall‐runoff floods from basins between 2.6 and 26,000 km2 in the United States and Puerto Rico

We assess the spatial distribution of the largest rainfall‐generated streamflows from a database of 35,663 flow records composed of the largest 10% of annual peak flows from each of 14,815 U.S. Geological Survey stream gaging stations in the United States and Puerto Rico. High unit discharges (peak discharge per unit contributing area) from basins with areas of 2.6 to 26,000 km 2 (1–10,000 mi 2 ) are widespread, but streams in Hawaii, Puerto Rico, and Texas together account for more than 50% of the highest unit discharges. The Appalachians and western flanks of Pacific coastal mountain systems are also regions of high unit discharges, as are several areas in the southern Midwest. By contrast, few exceptional discharges have been recorded in the interior West, northern Midwest, and Atlantic Coastal Plain. Most areas of high unit discharges result from the combination of (1) regional atmospheric conditions that produce large precipitation volumes and (2) steep topography, which enhances precipitation by convective and orographic processes and allows flow to be quickly concentrated into stream channels. Within the conterminous United States, the greatest concentration of exceptional unit discharges is at the Balcones Escarpment of central Texas, where maximum U.S. rainfall amounts apparently coincide with appropriate basin physiography to produce many of the largest measured U.S. floods. Flood‐related fatalities broadly correspond to the spatial distribution of high unit discharges, with Texas having nearly twice the average annual flood‐related fatalities of any other state.

Water Resources Research↗