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Erk Reimnitz

Publications and source records attributed to Erk Reimnitz.

At least 55 records · Page 3Linked to original sources
USGS1981

Ice-gouge data, Beaufort Sea, Alaska, 1972-1980

The interaction of sea ice with the sea floor is an important factor affecting geologic processes on high latitude shelves. One of the most obvious forms of this interaction is the formation of furrow-like gouges or the sea floor. These gouges are caused by wind- and current-driven ice masses that rake the seabed with their keels. Since the advent of side-scanning sonar about 1970, the morphology and character of these seabed features have been under study. Ice gouges have been reported from the Bering Sea (Thor and Nelson, 1980); from the Chukchi Sea (Rex, 1955; Toimil, 1978); from the Beaufort Sea off Alaska (Brooks, 1974; Carsola, 1954; Reimnitz et al., 1972); from the Beaufort Sea off Canada (Kindle, 1924; Lewis, 1978; Pelletier and Shearer, 1972; Wahlgren, 1979); from the east coast of Canada (Harris, 1974); from the northeast Atlantic (Belderson et al., 1973); and from the Great Lakes (Berkson and Clay, 1973).

Alaska↗
USGS1980

Dinkum Sands

The State/Federal Beaufort Sea lease sale in December 1979 attracted over one billion dollars in bids. Tracts with the highest bids, and apparently with the highest oil potential, lie in the area south of Dinkum Sands, and within a three-mile radius of the shoal (Fig. 1). Jurisdiction over the tracts within the three-mile radius depends on whether Dinkum Sands is an island, as shown by published charts and claimed by the State, or a mainly submerged shoal or bar as claimed by the U.S.G.S. If Dinkum Sands were an island, even the tracts halfway between the mainland and the island chain might be disputed as they then would be considered to form an enclave totally surrounded by State lands. Thus Dinkum Sands holds a strategic position within the lease sale area and, for the production life of the oil field, will be monitored at 5-minute intervals to provide a basis for division of the income from future oil production in that lease sale area.

Alaska↗
USGS1980

Seismic evidence for an extensive gas-bearing layer at shallow depth, offshore from Prudhoe Bay, Alaska

High resolution seismic reflection data recorded offshore from Prudhoe Bay, Alaska, were processed digitally to determine the reflectivity structure of the uppermost layers of the seafloor. A prominent reflector found at 27 m below the mudline (water depths 7-9 m) has a negative reflection coefficient greater than 0.5. The large acoustic impedance contrast, coupled with a report of gas encountered at a corresponding depth in a nearby drillhole, shows that the reflector is the upper boundary of a zone containing gas. The gas exists in sandy gravel capped by stiff, silty clay. Analysis of unprocessed conventional high-resolution records from the region indicates that the gas-bearing layer may extend over an area of at least 50 km at depths of 19-35 m below the mudline. Similar-appearing reflectors, previously unexplained, occur in patches over wide regions of the shelf where offshore oil development is beginning at a rapid pace. This suggests the exercise of caution with respect to possible hazards from shallow gas pockets.

Alaska↗
USGS1979

A herringbone bedform pattern of possible Taylor-Görtler type flow origin seen in sonographs

Side-scan sonar records collected in a shallow arctic lagoon (2&ndash;2.5 m depth) reveal a herringbone pattern of current-aligned linear reflectors with branching diagonals. The major longitudinal reflectors have no detectable relief (<20 cm), are spaced 5&ndash;10 m apart, and may represent current-aligned helical cell boundaries preserved in the silty fine sand of the lagoon floor. The pattern suggests a three-dimensional flow regime of the Taylor-G&ouml;rtler type.

Sedimentary Geology↗
USGS1979

Fast-ice thickness and snow depth in relation to oil entrapment potential, Prudhoe Bay, Alaska

In winter, the undersurface of the sea ice on shallow arctic shelves acts upon the sea bed directly by contact and indirectly by influencing currents and turbulence. The under-ice surface would serve as a trap for pollutants such as oil and gas released from the sea bed. A knowledge of the morphology of the undersurface of the ice is a first step in understanding the sea-bed interactions and in evaluating the quantities, configuration, and dispersal patterns of sub-ice pollutants. Investigations show thicker sea-ice correlates with a thin snow cover and thin sea-ice underlies elongate snow ridges. In early May, 1978, the relationships between under-ice morphology, sea bed morphology, tidal currents, and variations in snow thickness were studied. At three sites representing three different environments--protected bay, deep, open lagoon, and narrow tidal channel--trenches were cut through the ice. The trenches were parallel and perpendicular to the sastrugi-sculptured northeast-southwest trending snow ridge pattern. Snow depth, ice thickness, and ice drafts were measured and an upward-directed side-scanning sonar was towed to examine the morphology of the under-ice surface in an area 100 m square. Snow depth and ice thickness vary about 30-40 cm and exhibit a negative correlation--thin ice coinciding with a thicker insulating snow cover. The areal snow and ice morphology patterns reinforced the correlation. Elongate ridge and trough patterns on the under-ice surface parallel the surface snow ridge patterns on wavelengths typically 10 m wide, yielding sub-ice voids of 25 to 47 x 10 3 m 3 /km 2 (600-1200 barrels per acre). Diving observations indicate a smaller set of depressions 5 cm or less in depth, oriented parallel to the ice crystal fabric, and an escape of sub-ice released air to the snow-ice interface. The results imply that there is a seasonal stability to the snow ridge pattern and that oil concentrations under the ice would be indicated by surficial snow morphology in the fast ice zone. Spreading directions would be enhanced in the elongate dimensions of the under-ice ridges and troughs, that is, upwind and downwind. In spring, gases will leak to the surface.

Alaska↗
USGS1979

Ice gouge obliteration and sediment redistribution event: 1977-1978, Beaufort Sea, Alaska

In 1978 major changes in shelf morphology were observed during a routine re-survey of part of the inner shelf region of the central Beaufort Sea. Regional observations are coupled with a detailed diving and side-scan study of a single ice gouge of known age to develop a detailed description of the altered seabed conditions. Hydrodynamic activity has caused extensive sediment reworking, obliterating ice gouges to water depths of at least 13 m and has caused ponding of sediment in ice gouge terrain in deeper waters. Ponded sediment is characterized as a soft, sometimes very poorly consolidated, mud unit underlain by a stiffer, more consolidated, silty clay. In places, stiff silty clay is exposed in windows in the sediment pond and displays a fine-textured ice gouge morphology. Rates of sediment reworking and redisposition from apparently episodic events are an order of magnitude greater than the average sediment accumulation rates on the Beaufort Sea shelf. Reported maximum ice gouge incision depths are not representative of maximum ice keel penetrations into the seabed because these sedimentation events preferentially infill gouges. Furthermore, because these sedimentation events concentrate sediments in gouge troughs, a series of overlapping and interfingering 'shoestring' deposits is developed which should characterize the ice gouge stratigraphy. The specific hydraulic mechanisms for sediment redistribution and sediment compaction observed in this study are only poorly understood.

Open-File Report↗