Tabulation of the ostracode assemblages and associated organisms from selected bottom grab samples taken in the northeast Gulf of Alaska, F.R.S. Townsend Cromwell Cruise IGAL-75-KC, 1975

Abstract

The U.S. Geological Survey is conducting studies of the Alaskan continental shelf, identifying areas and processes of geological hazard that may affect resource development offshore. These hazards include areas of rapid accumulation of unconsolidated sediment, areas of intense erosional activity, and regions of submarine sliding and slumping; shallow faults are also being identified and classified. The region of concern in this report is the continental shelf of the Northeast Gulf of Alaska, between Montague Island (longitude 148° W.) and Icy Bay (longitude 141° W.), figs. 2 and 3. During 1975, nearly 350 bottom grab samples were collected from this region by the Fisheries Research Ship Townsend Cromwell. These samples formed the basis for the initial characterization of the surface deposits. Four major sedimentary units were defined on the basis of the bottom grab samples and seismic data (fig. 1) (Carlson and Molnia, 1977; Molnia and Carlson, 1978). These units are (1) Holocene glacial—marine sediments (normal marine deposition), (2) Holocene morainal deposits, (3) Quaternary glacial—marine sediments, and (4) Pleistocene and older lithified sediments. Each of these sedimentary units is in turn composed of various facies defined by lithological, structural, and biological parameters (Molnia and Carlson, 1980). As part of the Northeast Gulf of Alaska project, I am examining the ostracode assemblages occurring in the Cromwell bottom grab samples. This report provides a tabulation of the fauna and flora contained in 102 selected bottom grab samples (figs. 2 and 3). A baseline datum is being established of the environmental factors that significantly control or contribute to the distributional patterns of modern ostracode species occurring in the Gulf of Alaska. The ostracode biofacies defined by characteristic assemblages of species, together with information on the sedimentary facies, provides a model of the environments presently occurring in the Gulf of Alaska, (Brouwers, 1981). This model forms a vital basis for the interpretation of Neogene and Quaternary glaciomarine environments in the Gulf of Alaska Tertiary Province.