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Geology topics

D. W. Folger

Publications and source records attributed to D. W. Folger.

At least 19 recordsLinked to original sources
USGS2017

The origin and distribution of subbottom sediments in southern Lake Champlain

Three units, correlatable with recent Lake Champlain, late-glacial marine Champlain Sea, and proglacial Lake Vermont sediments, have been identified from about 200 km of high-resolution seismic reflection profiles and eight piston cores collected in southern Lake Champlain. Lake Vermont deposits are nonfossiliferous and range from thin to absent nearshore and on bedrock highs to more than 126 m thick near Split Rock Point. Champlain Sea sediments contain marine foraminifers and ostracodes and are fairly uniform in thickness (20–30 m). Recent Lake Champlain sediments range in thickness from 0 to 25 m. Average sedimentation rates for Lake Vermont are considerably higher (4–8 cm/yr) than those for the Champlain Sea (0.8–1.2 cm/yr) and Lake Champlain (0.14–0.15 cm/yr). Bedrock, till, and deltaic and alluvial deposits were also identified on the acoustic records but were not sampled. An unconformity separating Champlain Sea deposits from Lake Champlain deposits is associated with numerous benches at water depths of 20–30 m. These benches, the alluvial deposits, and the onset of deltaic deposition are probably associated with a low water level stillstand at the close of the Champlain Sea episode.

New York, Vermont↗
USGS1997

Maps showing the surficial geology of the Culebra shelf, Puerto Rico

This study presents the surficial and shallow subbottom geology of the insular shelf around Culebra, Puerto Rico. In view of the need for sand and gravel for construction purposes in the area, we inferred the thickness of unlithified, surficial sediment deposits from high-resolution acoustic-reflection profiles and described seafloor sediment samples collected with a Shipek grab.

Open-File Report↗
USGS1994

The geologic framework of southern Lake Michigan

The bathymetry is controlled by the underlying bedrock. Bedrock comprises Silurian dolomite and Devonian limestone and shale. Quaternary sediment, 10 to 40 m thick, overlies bedrock. From Waukegan, Illinois, south to Indiana Harbor, the bottom is floored by till, sand, pebbles, and cobbvles. The lake floor is erosional or nondepositional where till or gravel-cobble pavement is exposed. In contrast, north of Waukegan and east of Indiana Harbor, fine sand covers much of the bottom and grades offshore to muddy sand. The complex surficial bottom sediment distribution between Waukegan and Michigan City, Indiana, could be mapped in detail only where sidescan sonar mosaics are available. Sand, important for protecting the substrate from erosion and for maintaining beaches, is not abundant throughout much of the area. -from Authors

Illinois, Indiana, Michigan, Wisconsin↗
USGS1993

Paper plant effluent revisited-southern Lake Champlain, Vermont and New York

We used geologic and geochemical techniques to document the change with time of the distribution and concentration of contaminated bottom sediments in southern Lake Champlain near an International Paper Company plant. Our work, initiated in 1972, was expanded on behalf of Vermont citizens in a class-action suit against the International Paper Company. To update our 1972-1973 results, we collected nine cores in 1988 upstream and downstream from the paper plant effluent diffuser. Water content, volatile solids, organic carbon, and three ratios, Al/Si, Cl/Si, and S/Si, in addition to megascopic and microscopic observations, were evaluated to identify and trace the distribution of effluent and to measure the thickness of sediment affected by or containing components of effluent. Analyses were carried out on samples from the cores as well as from effluent collected directly from the plant's waste treatment facility. In 1973, two years after the plant opened, we cored near the diffuser; sediment contaminated with effluent was 4.5 cm thick. In 1988, in the same area, sediment contaminated with effluent was 17 cm thick. In 15 years, water content increased from 72 to 85 percent, volatile solids from 7 to 20 percent, and organic carbon from 2 to 12 percent. Cl/Si and S/Si were high only near the diffuser and were zero elsewhere. In the area of the diffuser, contaminated sediment appears to be accumulating at a rate of about 1 cm/yr. At a control location 22 km upstream (south) from the plant, the top, poorly consoli-dated layer was only 1 cm or less thick both in 1973 and in 1988. The class-action suit was settled in favor of the plaintiffs for $5 million. ?? 1993 Springer-Verlag.

New York, Vermont↗
USGS1990

Map showing free-air gravity anomalies off the western coast of Africa Senegal (south of 15° north latitude) to Sierra Leone

This map is one of six in a series presenting marine gravity data off the western coast of Africa (fig. 1). The data, collected by the U.S. Geological Survey (USGS) in 1987 in response to a request from the Defense Mapping Agency, are intended to improve gravity coverage where it has been insufficient or inadequate. The information shown on this and the other three maps that cover the African coast represents a total of approximately 32,000 line kilometers of marine gravity data from Western Sahara south to Gabon. This map includes data collected off the coasts of Senegal, Gambia, Guinea-Bissau, Guinea, and Sierra Leone from July 22 to August 20, 1987.

Miscellaneous Field Studies Map↗