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Kathryn M. Scanlon

Publications and source records attributed to Kathryn M. Scanlon.

42 records · Page 3Linked to original sources
USGS1985

Sedimentary framework of Penobscot Bay, Maine

Analyses of seismic-reflection profiles, along with previously collected sediment samples and geologic information from surrounding coastal areas, outline the characteristics, distribution, and history of the strata that accumulated within Penobscot Bay, Maine, during the complex period of glaciation, crustal movement, and sea-level change since late Wisconsinan time. Sediments that overlie the rugged, glacially eroded surface of Paleozoic bedrock range in thickness from near zero to more than 50 m and consist of four distinct units. Massive to partly stratified, coarse-grained drift forms thin (< 15 m) isolated patches along the walls and floors of bedrock troughs and constitutes a thick (up to 30 m), hummocky end moraine in the central part of the bay. The drift was deposited by the last ice sheet between 12,700 and 13,500 years ago during deglaciation and coastal submergence (due to crustal depression). Well-stratified, fine-grained glaciomarine deposits are concentrated in bedrock depressions beneath the main passages of the bay. During the period of ice retreat and marine submergence, these sediments settled to the sea floor, draped the irregular underlying surface of bedrock or drift, and accumulated without disturbance by physical or biologic processes. Heterogeneous fluvial deposits fill ancestral channels of the Penobscot River beneath the head of the bay. The channels were incised during a −40 m postglacial low stand of sea level (due to crustal rebound) and later were filled as base level was increased during Holocene time. Muddy marine sediments, which are homogeneous to weakly stratified and rich in organic matter, blanket older deposits within bathymetric depressions in the middle and lower reaches of the bay and cover a pronounced, gently dipping, erosional unconformity in the upper reach. These sediments were deposited during the Holocene transgression as sea level approached its present position and the bay became deeper. Late Wisconsinan and Holocene sedimentation in Penobscot Bay has smoothed the sea floor, but it has not completely obscured the ice-sculptured bedrock topography.

Marine Geology↗
USGS1985

Maps showing sea-floor topography, depth to bedrock, and sediment thickness, Penobscot Bay, Maine

This report presents results of a high-resolution seismic-reflection survey conducted by the U.S. Geological Survey to determine the subbottom characteristics of Penobscot Bay, Maine. Penobscot Bay is one of the major embayments along the U.S. Atlantic coast (fig. 1), extending more than 50 km from the Gulf of Maine to the mouth of the Penobscot River. The bay constitutes an area of about 1,100 km" and is divided into three main passages by numerous islands. The bay and surrounding coastal area have had a complex history of glaciation and sea-level change since late Wisconsinan time. The last ice sheet advanced across the area about 20,000 years ago, eroding the bedrock surface, removing most older sediments, and isostatically depressing the crust (Schafer and Hartshorn, 1965; Stuiver and Borns, 1975; Thompson, 1979). Deglaciation followed between about 12,700&ndash;13,500 years ago and was accompanied by a marine transgression (because of crustal depression), with ice and sea in contact (Stuiver and Borns, 1975; Thompson, 1979, 1982; Smith, 1982). Isostatic recovery of the crust then caused the coast to emerge during the immediate postglacial period, and emergence was completed by about 11,500 years ago (Stuiver and Borns, 1975; Thompson, 1979, 1982; Thompson and Smith, 1983). Finally, resubmergence of the Maine coast has accompanied the Holocene rise of sea level that began about 9,000 to 11,000 years ago (Bloom, 1963; Kaye and Barghoorn, 1964; Schmitker, 1974; Oldale and others, 1983). In the maps presented here, we illustrate and briefly describe the sea-floor topography, bedrock morphology, and variable sediment thickness within Penobscot Bay that were either produced or modified during the period of geologic change since late Wisconsinan time.

Maine↗
USGS1984

The continental slope off New England: A long-range sidescan-sonar perspective

The first continuous overview of a large segment of the continental slope and rise off the northeastern United States has been obtained using the GLORIA II long-range sidescan-sonar system. Extensive dissection by canyon and gully systems and evidence of possible large-scale sediment sliding are seen on the slope. The style and degree of incision, as well as the numbers and locations of canyons, have been found to differ significantly from previously published maps. It is suggested that the slope is a significant source of the sediment that has been deposited on the rise, and that some abrupt changes in the courses of canyons may be the result of local structural control.

Georges Bank↗
USGS1982

GLORIA sidescan and seismic data collected by the DESV STARELLA along the continental slope and upper continental rise of the Eastern United States in 1979

A cruise on the- DESV STARELLA was conducted between October 23. 1979, and November 8, 1979, by the U.S. Geologic.al Survey (USGS) in cooperation with the United Kingdom's Institute of Oceanographic Sciences (IOS). The purpose of the study was to gain an overview of the morphology of large areas of the Continental Slope and upper Continental Rise off the eastern ·united States. Sidescan-sonar and single-channel seismic-reflection data were collected along the tracklines. The ship's position. was monitored using LORAN_C and satellite navigation techniques. The sidescan data were collected using the !OS-developed Geologic Long­-Range Inclined Asdic, Mark II (GLORIA II) system. GLORIA was operated at either a 20-second or 40-second sweep, giving maximum slant-range distances of 15 or 30 kilometers, respectively, to each side of the towed fish. The sidescan data were collected on graphic recorders and analog tapes. The tapes were played onto photographic paper in a facsimile machine; then these prints were photographically stretched to produce approximately isometric images .. The images were not corrected for slant-range distortion. Mosaics at a scale of 1:250,000 (Mercator projection) were made from the photographic images. The seismic· data consist of 40-in 3 airgun and 10-kHz echo-sounder profiles. The airgun data were recorded on EPC recorders at both 8- and 4- second sweep rates. The 10-kHz echo-sounder data were recorded on a wet-paper recorder at a 2-second sweep rate. Approximately 4,820 km of seismic and sonar-data wera collected from four areas of interest and along the lines connecting those areas. Area 1 includes the Continental Slope and upper Rise seaward of Georges Bank, between Northeast Channel and Alvin Canyon. Numerous lines were run here, resulting in approximately 2,500 km of seismic data and complete and overlapping GLORIA coverage of the area. A similar survey, consisting of approximately 1 2 200 km of trackline, was run in area 2, which includes the Continental Slope and upper Rise seaward of the middle Atlantic states between Hudson Canyon and Baltimore Canyon. A single line, 250 km long, was run through area 3 along the base of the Continental Slope from Cape Hatteras to latitude 33°N. off North and South Carolina. Two parallel lines, totaling 870 km, were run through area 4 along the Blake Escarpment, from the Blake Spur south to latitude 27°40'N. One line was run along the top of the escarpment and the other was run along the base of the escarpment. All the data can be studied at the U.S. Geological Survey offices in Woods Hole, MA 02543. Microfilm copies of the sidescan-monitor record as well as the airgun and 10-kHz profiles can be purchased only from the National Geophysical Data Center, NOAA, Code E64, 325 Broadway, Boulder, CO 80303 (303/497-6338). Photographic copies of the GLORIA mosaics can also be obtained only from this address.

Open-File Report↗