Geology topics
Publications and source records attributed to Monty A. Hampton.
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Because lower Cook Inlet and Kodiak shelf are being explored and developed for their petroleum resources, it is essential for environmental reasons to understand the sediment dispersal routes and current patterns. The Susitna River flows into upper Cook Inlet and is the source of clay minerals in Holocene deposits found in western lower Cook Inlet. The Copper River, in the northern Gulf of Alaska, provides clay minerals to the Kodiak shelf and southeastern lower Cook Inlet. In addition, crosion of local bedrock outcrops on the shelf produces some clays that are deposited on the Kodiak shelf. Current patterns can be inferred from the clay-mineral distribution pattern. This is true even if the clay-size fraction is a minor sediment component, and in areas where coarse-grained relict deposits occur. Some potential dangers from offshore petroleum development include: (1) rapid and complete mixing of Cook Inlet waters, (2) adsorption of pollutants by clay deposited in quiet bays, and (3) ion-exchange and adsorption of chemical pollutants on clays that are part of the suspended sediment load in lower Cook Inlet.
The third U.S. Geological Survey geo-environmental cruise in lower Cook Inlet and on the Kodiak shelf and adjacent continental slope, Gulf of Alaska, was conducted aboard the R/V SEA SOUNDER from 2 August to 22 August, 1978 (Fig. 1, 2, and 3). The objectives of the cruise were to study in detail specific potentially hazardous environmental conditions identified as a result of the first reconnaissance cruise conducted in June and July of 1976 and from work by other investigators, and to initiate reconnaissance characterization studies on the continental slope. High-resolution seismic reflection profiling (sparker, Uniboam: 3.5 kHz, 12 kHz) and side-scanning sonar surveys formed the basis for selecting stations for observation with bottom television and 70 mm bottom camera as well as for sampling of surficial sediments (gravity corer, grab sampler), Generalized trackline charts are given in Figures 2 and 3. Detailed shot-point charts could not be constructed clearly, because of the overlap and coincidence of many of the lines. Station locations are shown in Figure 4 and 5, and sampling information is given in Table 4. Table 5 contains the navigation records from the cruise. The results of our investigations to date can be found in the references listed at the end of this text, Background information in lower Cook Inlet with several references is given in Open-File Report 75-429 (Magoon and others, 1975), and on the Kodiak shelf in Open-File Report 76-325 (von Huene and others, 1976). In addition, this report accompanies the basic seismic-reflection and side-scanning sonar records acquired on the cruise. The seismic-reflection records are publicly available from the National Geophysical and Solar Terrestrial Data Center EDS/NOAA, Boulder, Colorado 80302. These records can be inspected at U.S. Geological Survey offices at Rm B-164, Deer Creek Facility, 3475 Deer Creek Road, Palo Alto, California 94303.
During the period from September 14 through October 10, 1977 the second U.S. Geological Survey geo-environmental cruise was conducted in lower Cook Inlet and on the Kodiak shelf and adjacent upper continental slope, Gulf of Alaska, aboard the R/V SEA SOUNDER (Figure 1, Tables 1, 2 and 3). The objective of this cruise was to study in detail specific potentially hazardous environmental conditions identified as a result of the first reconnaissance geo-environmental cruise conducted from June 18 through July 30, 1976 (Bouma and Hampton, 1976; Hampton and Bouma, 1976). In particular, the distribution and movement of seafloor bedforms were studied in lower Cook Inlet, and sediment dispersal patterns and submarine sediment slides were investigated on the Kodiak shelf and slope. High resolution seismic profiling (sparker, uniboom, minisparker, 3.5 khz, 12 khz) and side-scanning sonar surveys formed the basis for selecting stations for observations with bottom television and 70 mm bottom camera as well as for different types of sampling of surficial sediments (piston corer, gravity corer, hydroplastic corer, Soutar grab sampler). The success of the 1977 cruise was limited by adverse weather conditions.
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This summary of the regional geology, petroleum potential, geologic hazards and time frame for exploration of the western Gulf of Alaska has been written to aid the Bureau of Land Management in preparing the Draft Environmental Impact Statement. A preliminary version was written in Sept., 1975.(von Huene and others, 1975) in support of the Call for Nominations, Proposed OCS Oil and Gas Lease Sale #46. Since that time, there has been a substantial increase in information as the result of a two-month examination of recent studies of the adjacent Gulf of Alaska Tertiary Province and a preliminary interpretation of some publicly available common depth point (CDP) seismic reflection data recently acquired by the U.S. Geological Survey. The main source of geologic and geophysical data used in the preparation of this summary is published and unpublished information of the U.S. Geological Survey (Plafker and others, 1975,Bruns and Plafker, 1975; Carlson, Bruns and Molnia, 1975; Carlson and Molnia, 1975; Core, Mattick, and Bayer, 1975; Molnia and Carlson, 1975 a & b; von Huene and others, 1975). Prior to 1975, data were gathered mainly for purposes other than for assessment of oil and gas resources and of the environmental consequences of exploration and development. A systematic survey for such an assessment is planned for the summer of 1976 and, therefore, this summary is tentative. Although the major problems and regional setting are discussed in this paper, a great deal more specific data and interpretations will begin to become available in about one year. In this summary we consider the geology of a broad region on the continental shelf off the Kodiak group of islands and the Kenai Peninsula. We will concentrate on the area proposed for leasing in Sale #46. The area lies between about 56°N latitude and 60°N latitude (Fig. 1), and it measures approximately 660 km x 100 km. Water depths are generally less than 200 m.
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