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R.R. Rendigs

Publications and source records attributed to R.R. Rendigs.

10 recordsLinked to original sources
USGS2002

The effect of the new Massachusetts Bay sewage outfall on the concentrations of metals and bacterial spores in nearby bottom and suspended sediments

Since the new outfall for Boston's treated sewage effluent began operation on September 6, 2000, no change has been observed in concentrations of silver or Clostridium perfringens spores (an ecologically benign tracer of sewage), in bottom sediments at a site 2.5 km west of the outfall. In suspended sediment samples collected with a time-series sediment trap located 1.3 km south of the outfall, silver and C. perfringens spores increased by 38% and 103%, respectively, in post-outfall samples while chromium, copper, and zinc showed no change. All metal concentrations in sediments are <50% of warning levels established by the Massachusetts Water Resources Authority. An 11-year data set of bottom sediment characteristics collected three times per year prior to outfall startup provides perspective for the interpretation of post-outfall data. A greater than twofold increase in concentrations of sewage tracers (silver and C. perfringens) was observed in muddy sediments following the exceptional storm of December 11-16, 1992 that presumably moved contaminated inshore sediment offshore. ?? 2002 Elsevier Science Ltd. All rights reserved.

Boston Harbor↗
USGS1999

Seafloor environments in the Long Island Sound estuarine system

Four categories of modern seafloor sedimentary environments have been identified and mapped across the large, glaciated, topographically complex Long Island Sound estuary by means of an extensive regional set of sidescan sonographs, bottom samples, and video-camera observations and supplemental marine-geologic and modeled physical-oceanographic data. (1) Environments of erosion or nondeposition contain sediments which range from boulder fields to gravelly coarse-to-medium sands and appear on the sonographs either as patterns with isolated reflections (caused by outcrops of glacial drift and bedrock) or as patterns of strong backscatter (caused by coarse lag deposits). Areas of erosion or nondeposition were found across the rugged seafloor at the eastern entrance of the Sound and atop bathymetric highs and within constricted depressions in other parts of the basin. (2) Environments of bedload transport contain mostly coarse-to-fine sand with only small amounts of mud and are depicted by sonograph patterns of sand ribbons and sand waves. Areas of bedload transport were found primarily in the eastern Sound where bottom currents have sculptured the surface of a Holocene marine delta and are moving these sediments toward the WSW into the estuary. (3) Environments of sediment sorting and reworking comprise variable amounts of fine sand and mud and are characterized either by patterns of moderate backscatter or by patterns with patches of moderate-to-weak backscatter that reflect a combination of erosion and deposition. Areas of sediment sorting and reworking were found around the periphery of the zone of bedload transport in the eastern Sound and along the southern nearshore margin. They also are located atop low knolls, on the flanks of shoal complexes, and within segments of the axial depression in the western Sound. (4) Environments of deposition are blanketed by muds and muddy fine sands that produce patterns of uniformly weak backscatter. Depositional areas occupy broad areas of the basin floor in the western part of the Sound. The regional distribution of seafloor environments reflects fundamental differences in marine-geologic conditions between the eastern and western parts of the Sound. In the funnel-shaped eastern part, a gradient of strong tidal currents coupled with the net nontidal (estuarine) bottom drift produce a westward progression of environments ranging from erosion or nondeposition at the narrow entrance to the Sound, through an extensive area of bedload transport, to a peripheral zone of sediment sorting. In the generally broader western part of the Sound, a weak tidal-current regime combined with the production of particle aggregates by biologic or chemical processes, cause large areas of deposition that are locally interrupted by a patchy distribution of various other environments where the bottom currents are enhanced by and interact with the seafloor topography.

Marine Geology↗
USGS1996

Seafloor environments in Cape Cod Bay, a large coastal embayment

Cape Cod Bay is a glacial, semi-enclosed embayment that has a patchy distribution of modern seafloor sedimentary environments of erosion or nondeposition, deposition, and sediment reworking. Sidescan-sonar records and supplemental bathymetric, sedimentary, subbottom, and physical-oceanographic data indicate that the characteristics and distribution of these three categories of bottom environments are controlled by a combination of geologic and oceanographic processes that range from episodic to long-term and from regional to local. (1) Environments of erosion or nondeposition comprise exposures of bedrock, glacial drift, and coarse lag deposits that contain sediments (where present) ranging from boulder fields to gravelly coarse-to-medium sands. These environments are dominant on the shallow margins of the bay (water depths < 30 m) where they reflect sediment resuspension, winnowing, and transport during modern northerly storms. (2) Environments of deposition are blanketed by fine-grained sediments ranging from muds to muddy fine sands. These environments are dominant across the floor of the central basin (water depths = 30–60 m) where fine-grained sediments (derived from regional and local sources and emplaced primarily during episodic wind- and density-driven flow) settle through the water column and accumulate under weak bottom currents during nonstorm conditions. (3) Environments of sediment reworking contain patches with diverse textures ranging from gravelly sands to muds. These environments occupy much of the transitional slopes between the margins and the basin floor and reflect a combination of erosion and deposition. The patchy distribution of sedimentary environments within the bay reflects not only regional changes in processes between the margins and the basin but local changes within each part of the bay as well. Small-scale patchiness is caused by local changes in the strengths of wave- and wind-driven currents and (on the margins) by local variations in the supply of fine-grained sediments. This study indicates areas within Cape Cod Bay where fine-grained sediments and associated contaminants are likely to be either moved or deposited. It also provides a guide to the locations and variability of benthic habitats.

Cape Cod Bay↗
USGS1996

Geohydrology and potential water-supply development on Bumkin, Gallops, Georges, Grape, Lovell, and Peddocks Islands, eastern Massachusetts

An investigation of the geohydrology and of the potential for water-supply development on several of the Boston Harbor Islands, eastern Massachusetts, was conducted to evaluate the possibility of developing a permanent small-capacity water supply to support recreational activities, such as camping, hiking, and swimming. The Boston Harbor Islands, including Bumkin, Gallops, Georges, Grape, Lovell, and Peddocks Islands are part of a larger group of glacially deposited drumlins, which are composed of thick, dense, homogeneous till in their core that are overlain by a thin layer of stratified-beach deposits. The surficial materials over-lie a weathered zone of the metasedimentary Cambridge Argillite in the Boston Harbor area and were deposited by continental ice sheets that covered New England twice during the late Pleistocene Epoch, and by near-shore processes in the Holocene Epoch. The thickness of these materials range from less than 1 to about 300 feet where present. The till was deposited by glacial ice and is characterized as an unsorted matrix of sand, silt, and clay with variable amounts of stones and large boulders. The stratified deposits primarily consist of sorted and layered sand and gravel that accumulated and formed the beaches and tombolos of the harbor islands. These deposits overlie the till at altitudes generally less than 10 feet above sea level. A cross-sectional, ground-water-flow model was developed to estimate depth to the water table for a hypothetical drumlin-island flow system, which was assumed to be representative of the drumlin islands in Boston Harbor. Areas were identified in each island flow system with the greatest potential for small-capacity water-supply development based on the model-calculated depth to water and surficial geology of the islands. Model-calculated depth to water estimates were used because of the lack of available hydrologic data for the islands. Model results indicate that the simulated depth to water is less than 20 feet within 240 feet from the shore of the hypothetical drumlin-island flow system. This area on the topographic maps of the six Boston Harbor Islands roughly coincides with the high transmissivity zones of stratified-beach deposits and weathered till on the lower slopes of the drumlins where ground-water discharge and surface and subsurface runoff occurs.

Massachusetts↗
USGS1991

Modern sedimentary environments in Boston Harbor, Massachusetts

Analyses of sidescan-sonar records supplemented by available bathymetric, sedimentary, subbottom, and bottom-current data reveal the distributions of the following three categories of sedimentary environments within the glaciated, topographically complex Boston Harbor estuary in Massachusetts. 1) Environments of erosion appear on the sonographs either as patterns with isolated strong reflections or as uniform patterns of strong reflectivity. These patterns define outcrops of bedrock or till and coarse lag deposits that are being scoured and winnowed by tidal- and wave-induced currents. Erosional areas are located primarily along mainland and insular shores, within large channels that have strong tidal currents, atop submerged ridges and knolls, and across much of the harbor entrance. 2) Environments of deposition are depicted on the sidescan-sonar records as smooth, featureless surfaces that have low to moderate reflectivity. Depositional environments are found predominantly over shallow subtidal flats and in broad bathymetric lows where tidal currents are weak. Sediments within depositional areas are organic-rich sandy and clayey silts that are accumulating at rates ranging from 0.01 to 0.11 g/cm 2 /yr or 4000 to 46,100 metric tons/yr. The cumulative mass of modern mud in harbor depocenters is 24.3 million metric tons. 3) Environments of sediment reworking constitute areas affected by a combination of erosional and depositional processes. They are characterized on the sonographs by mosaics of light and dark patches produced by relatively subtle and gradational changes in reflectivity. Reworked sediments have diverse grain sizes that overlap and are transitional between those of the other two sedimentary environments, and they are indicative of highly variable bottom currents.

Massachusetts↗
USGS1984

The Georges Bank monitoring program, 1984: Analysis of trace metals in bottom sediments during the second year of monitoring

Of the 12 elements analyzed in bulk (undifferentiated) sediments collected adjacent to drilling rigs on Georges Bank, only barium was found to increase in concentration during the drilling period (July 1981 until September 1982). The maximum postdrilling concentration of barium (a major element in drilling mud) reached 172 ppm in bulk sediments near the drill site in block 410. This concentration is a factor of 5.9 times higher than the predrilling concentration at that location. This maximum postdrilling barium concentration is within the range of predrilling concentrations {28-300 ppm} measured in various sediment types from the regional stations of this program. No drilling-related changes in the concentrations of chromium or other metals have been observed in bulk sediments at any of the locations sampled in this program to date. We estimate that between 21 percent and 31 percent of the barite (principal barium-bearing mineral} discharged at block 312 was present in the sediments within 6 km of the rig, 4 weeks after drilling was completed. The barite deposited near this well was found to decrease in concentration with a half-life of 0.4year. At this rate, the average barium concentration in sediments within 6 km of the drilling rig in block 312 is expected to be only 10 percent higher than the predrilling concentration within approximately 1.5 years. Although the inventory of the barite discharged on Georges Bank is based on only a few data points, most (approximately 69 percent) of the barite discharged by the eight exploratory wells apparently can be found in sediments west of the drilling locations. The increase in barium concentration above background can be measured in the fine fraction of sediment at a distance of 65 km to the west of block 312. Analysis of sediment-trap samples collected 25 m above the bottom in block 312 indicates that the dispersion of barmm-rich fine sediment is enhanced by resuspension from the sea floor and transport to the west with the mean current flow. Evidence exists of small accumulations of barium near the heads of Lydonia and Oceanographer Canyons. However, the increased concentrations can be defined only by analyzing the fine fraction of sediment.

Georges Bank↗
USGS1981

Geochemical evidence for modern sediment accumulation on the continental shelf off southern New England

An area of fine-grained sediment approximately 170 km x 74 km in size, located in water depths between 60 m and 150 m, south of Martha's Vineyard, Mass., is a site of modern sediment deposition. The 14 C ages systematically increase with sediment depth from about 1,300 years B.P. at the surface to 8,000-10,000 years B.P. at the depth of maximum core penetration. The old age for the surface sediments probably results from a combination of deposition of old carbon and faunal mixing. In the finest sediments, the sedimentation rates were approximately 130 cm/1,000 yrs when deposition began and have decreased to about 25 cm/1,000 yrs. The decreasing sedimentation rate reflects a diminishing source of fine sediments, which presumably came from the Georges Bank and Nantucket Shoals area. Inventories of excess 210 Pb in undisturbed cores average 70 dpm/cm 2 (disintegrations per minute per square centimeter), more than two times higher than the flux of 210 Pb from the atmosphere and from 226 Ra decay in the overlying water. This additional influx of 210 Pb either must be with new fine-grained sediment material or from solutions that are stripped of their 210 Pb by particulates in the bottom nepheloid layer. Stable Pb concentrations in surface sediments are about 28 ppm, as much as two times higher than concentrations at depth. The high accumulation rates, 210 Pb inventories, and trace-metal profiles imply that this area is a modern sink for fine-grained sediments and for pollutants associated with particulate matter in the water column. To our knowledge, this is the only site of present-day natural deposition on the Continental Shelf off the eastern United States, exclusive of the Gulf of Maine. Because the net currents on the outer half of this Continental Shelf flow from northeast to southwest, this fine-grained deposit may receive its sediments and possible contaminants from the Nantucket Shoals and Georges Bank regions.

Massachusetts↗