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Bruce F. Molnia

Publications and source records attributed to Bruce F. Molnia.

25 records · Page 2Linked to original sources
USGS1978

Minisparker profiles and sedimentologic data from R/V Acona Cruise (April 1976) in the Gulf of Alaska and Prince William Sound

In April 1976, the U.S. Geological Survey, Office of Marine Geology conducted a geophysical and sediment sampling cruise in the northern Gulf of Alaska between Seward and Kayak Island (Fig. 1) to obtain data on seafloor hazards pertinent to the OCS oil and gas lease sales. Stormy weather interrupted the planned data collection, during which time supplemental profiles and samples were collected in Prince William Sound including Montague Strait, Valdez Arm, Port Valdez, and Columbia Bay (Fig. 1). High resolution seismic profile records were made using a 600 Joule Del Norte Minisparker along 1151 km of track lines as shown on maps 1 and 2. Sediment samples collected with grab samplers (58) and gravity core (3) and bottom camera stations (14) are also shown on the track line maps and on figures 2 and 3. This report indicates the seismic reflection records and shipboard logs that are publicly available and includes track line maps and a text that; (1) shows examples of characteristic seismic profiles, (2) describes geologic hazards observed on specific profiles, and (3) includes summary descriptions of sediment samples and bottom photographs.

Alaska↗
USGS1978

Impact of coastal processes on resource development with an example from Icy Bay, Alaska

The coastline of Alaska is dynamic and continually readjusting to changes in the many processes that operate in the coastal zone. Because of this dynamic nature, special consideration must be made in planning for development, and. caution must be exercised in site selection for facilities to be emplaced in the coastal zone. All types of coastal processes from continuously active normal processes to the low frequency-high intensity rare event must be considered. Site-specific evaluation-s considering the broad range of possible processes must precede initiation of development. An example of the relation between coastal processes and a proposed resource treatment facility is presented for Icy Bay, Alaska. Icy Bay is the only sheltered bay near many of the offshore tracts leased for petroleum exploration in the 1976 northern Gulf of Alaska OCS (Outer Continental Shelf) lease sale. Consequently, it has been selected as a primary onshore staging site for the support of offshore exploration and development. The environment of Icy Bay has many potentially hazardous features, including a submarine moraine at the bay mouth and actively calving glaciers at the bay's head which produce many icebergs. But most significant from the point of view of locating onshore facilities and pipeline corridors are the high rates of shoreline erosion and sediment deposition. If pipelines or any onshore staging facilities are to be placed in the coastal areas of Icy Bay, then the dynamic changes in shoreline position must be considered so that man-made structures will not be eroded away or be silted in before the completion of development.

Open-File Report↗
USGS1977

Submarine faults and slides on the continental shelf, northern Gulf of Alaska

Submarine faults and slides or slumps of Quaternary age are potential environmental hazards on the outer continental shelf (OCS) of the northern Gulf of Alaska. Most faults that approach or reach the seafloor cut strata that may be equivalent in age to the upper Yakataga Formation (Pliocene‐Pleistocene). Along several faults, the seafloor is vertically offset from 5 to 20 m. A few faults appear to cut Holocene sediments, but none of these shows displacement at the seafloor. Submarine slides or slumps have been found in two places in the OCS region: (1) seaward of the Malaspina Glacier and Icy Bay, an area of 1200 km 2 with a slope of less than 0.5°, and (2) across the entire span of the Copper river prodelta, an area of 1730 km 2 , having a slope of about 0.5°. Seismic profiles across these areas show disrupted reflectors and irregular topography commonly associated with submarine slides or slumps. Potential slide or slump areas have been delineated in areas of thick sediment accumulation and relatively steep slopes. These areas include (1) Kayak Trough, (2) parts of Hinchinbrook Entrance and Sea Valley, (3) parts of the outer shelf and upper slope between Kayak Island and Yakutat Bay, and (4) Bering Trough.

Alaska↗
USGS1977

Surface sedimentary units of the Gulf of Alaska continental shelf: Montague Island to Yakutat Bay

Four major sedimentary units occur on the sea floor of the continental shelf in the northern Gulf of Alaska. These units, defined on the basis of seismic and sedimentologic data, are: (1) Holocene sediments, (2) Holocene mind moraines, C3) Quaternary glacial marine sediments, and (4) Tertiary and Pleistocene lithified deposits. A wedge of Holocene fine sand to clayey silt covers most of the inner shelf, reaching maximum thicknesses of about 350 m seaward of the Copper River and about 200 m seaward of Icy Bay. Holocene end moraines are found at the mouth of Icy Bay, south of Bering Glacier, and at the mouth of Yakutat Bay. Quaternary glacial marine sediments are found in a narrow arc that borders, on the north and west side of Tart Bank and in a large arc 20 km or more offshore that parallels the shoreline between Kayak Island and Yakutat Bay. Tertiary or Pleistocene stratified sedimentary rocks, which in profile commonly are folded, faulted, and truncated, crop out on Tarr Bank, offshore of Montague Island, and in several localities southeast and southwest of Cape Yakataga. The lack of Holocene cover on Tarr Bank and Middleton, Kayak and Montague Island platforms may be due to the scouring action of swift bottom currents and large storm waves. West of Kayak Island the Copper River is the primary source of Holocene sediment. East of Kayak Island the major sediment sources are streams draining the larger ice fields, notably, the Malaspina and Bering Glaciers. Transport of bottom and suspended sediment is predominantly to the west. If deglaciation of the shelf was completed by 10,000 years B.P., maximum rates of accumulation of Holocene sediment on the inner shelf may be as high as 10-35 m per 1,000 years.

Open-File Report↗
USGS1976

Report on the environmental geology OCS area, eastern Gulf of Alaska

In anticipation of oil and gas leasing of the outer continental shelf (OCS lease area 39) in the northeastern Gulf of Alaska, the U. S. Geological Survey began a regional reconnaissance in 1974. The study area, which extends from Prince William Sound on the west to Yakutat Bay on the east, is in a region fraught with natural hazards. The tectonic history of the area suggests that future major earthquakes could pose serious hazards to installations on the continental shelf or along the coast of the Gulf of Alaska. The hazard may be either direct, by ground shaking or fault displacement, or indirect, through ground failure or generation of tsunami waves. Storm waves sometimes are responsible for ground failures, especially in areas of rapid accumulation of sediment.

Alaska↗