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John C. Hampson

Publications and source records attributed to John C. Hampson.

6 recordsLinked to original sources
USGS1986

Mapping nuclear craters on Enewetak Atoll, Marshall Islands

In 1984, the U.S. Geological Survey conducted a detailed geologic analysis of two nuclear test craters at Enewetak Atoll, Marshall Islands, on behalf of the Defense Nuclear Agency. A multidisciplinary task force mapped the morphology, surface character, and subsurface structure of two craters, OAK and KOA. The field mapping techniques include echo sounding, sidescan sonar imaging, single-channel and multichannel seismic reflection profiling, a seismic refraction survey, and scuba and submersible operations. All operations had to be navigated precisely and correlatable with subsequent drilling and sampling operations. Mapping with a high degree of precision at scales as large as 1:1500 required corrections that often are not considered in marine mapping. Corrections were applied to the bathymetric data for location of the echo- sounding transducer relative to the navigation transponder on the ship and for transducer depth, speed of sound, and tidal variations. Sidescan sonar, single-channel seismic reflection, and scuba and submersible data were correlated in depth and map position with the bathymetric data to provide a precise, internally consistent data set. The multichannel and refraction surveys were conducted independently but compared well with bathymetry. Examples drawn from processing the bathymetric, sidescan sonar, and single- channel reflection data help illustrate problems and procedures in precision mapping.

Enewetak Atoll↗
USGS1983

Furrowed outcrops of Eocene chalk on the lower continental slop offshore New Jersey

A sea bottom of middle Eocene calcareous claystone cut by downslope-trending furrows was observed during an Alvin dive to the mouth of Berkeley Canyon on the continental slope off New Jersey. The furrows are 10 to 50 m apart, 4 to 13 m deep, linear, and nearly parallel in water depths of 2,000 m. They have steep walls and flat floors 3 to 5 m wide, of fine-grained sediment. Mid-range sidescan-sonar images show that similarly furrowed surfaces are found on nearby areas of the lower continental slope, not associated with canyons. The furrows are overlain in places by Pleistocene sediments. Although they show evidence of erosional origin, they do not appear to be related to observed structures, and their straight, parallel pattern is not well understood. A general cover of flocky unconsolidated sediments implies that bottom-current erosion is not active now.

New Jersey↗
USGS1981

Bathymetric map of the continental slope and uppermost continental rise between Lindenkohl Canyon and South Toms Canyon, offshore Eastern United States

This map was prepared as part of a study of geologic hazards to resource exploration and development on the Continental Slope in the Baltimore Canyon Trough area, off southern New Jersey. Detailed bathymetric maps are required for enfineering studies of bottom stability and for geologic interpretation of the nature of the submarine topography. This map presents the morphology of the Continental Slope in greater detail than do other available bathymetic maps (Veatch and Smith, 1939; Uchupi, 1965, sheet 2; U.S. Coast and Geodetic Survey, 1967; Belding and Holland, 1970, sheet 1; National Ocean Survey, 1977).

Lindenkohl Canyon, South Toms Canyon↗
USGS1981

Geology and potential hazards of the continental slope between Lindenkohl and South Toms Canyons, offshore mid-Atlantic United States

Because sediment instability, or slumping, has been identified as a potential hazard to petroleum development of the east-coast Continental Slope, the U.S. Geological Survey, in cooperation with the U.S. Bureau of Land Management, began a detailed study of a segment of the Continental Slope between Lindenkohl and South Toms Canyons off New Jersey. This 40-km x 35-km area was chosen for study because it lies within the area of high interest for petroleum development (Lease sales 49 and 59), and because it includes several wells which provide stratigraphic control. This report discusses the results of geologic mapping, using seismic-reflection data acquired in 1978 and 1979. Some initial results from more recently acquired data are included. The Continental Slope in the study area has a complex surface with ridges, canyons, and valleys. Three slump or slide features were observed in the heads and on the walls of canyons and valleys, and two slides were identified on an intercanyon area. The identified slumps or slides are found in Quaternary sediments and total about 1.3 percent of the Continental Slope area mapped. The slope is generally mantled by less than 2 m of Holocene sediments. Pleistocene sediment (primarily silty clay) is about 450 m thick at the top of the slope and thins to nearly zero or is absent on much of the mid and lower slope, where sediments of Miocene to Eocene age are exposed. Ridges on the midslope (water depths of 800-1,500 m) and parts of the lowr slope (1,500-2,150 m) result primarily from Pleistocene and older deposition. The intervening valleys show evidence of erosion along the deepest parts of their courses. Mid-range sidescan-sonar data show evidence that processes of bottom-current erosion and downcanyon transport of material may be active in the present day. However, major features of the sea floor appear to be unchanged since late-Pleistocene time.

Lindenkohl and South Toms Canyons↗
USGS1978

Geotechnical properties of sediments from the Continental Shelf south of Icy Bay, northeastern Gulf of Alaska

Studies of geotechnical properties of marine sediments have recently intensified as the search for natural resources has expanded on the continental shelf. The U. S. Geological Survey has begun a detailed evaluation of geologic environmental conditions in continental shelf regions in order to facilitate safe development of continental shelf resources. Investigations of geohazards in the northeastern Gulf of Alaska (Fig. 1) began in 1974 when 6500 km of high and medium resolution seismic reflection data were collected from the eastern gulf between Yakutat and Montague Island (Carlson, Bruns and Molnia, 1975; Von Huene and others, 1975). The first extensive sediment sampling program was begun in 1975 when approximately 400 samples of continental shelf sediments were collected from the same area of the gulf (Carlson and others, 1977b). A limited number of geotechnical measurements were made from these samples and samples collected by subsequent programs, however, systematic measurement of geotechnical properties was not started until the 1977 cruise of the NOAA ship DISCOVERER. Once unstable environments or "geohazards", such as slumps and slides, are delineated, geotechnical testing is an important means of quantifying such geologic processes and consequently furthering our understanding of them. The purposes of this report are two-fold: (1) to report variations of physical properties in 1-2 meter gravity cores and (2) to recognize any variations in the areal distribution of these properties within and adjacent to an area of mass movement in the northeastern Gulf of Alaska.

Alaska↗