Seafloor geology and natural environment of the Monterey Bay National Marine Sanctuary
No abstract available.
California↗
Geology topics
Stephen L. Eittreim
Publications and source records attributed to Stephen L. Eittreim.
Continental shelf GIS for the Monterey Bay National Marine Sanctuary
A marine sanctuary is an environment where the interests of science and society meet. Sanctuary managers need access to the best scientific data available that describe the environment and environmental processes in sanctuaries. Seafloor mapping and sampling in the Monterey Bay National Marine Sanctuary have revealed new details about the geology, morphology, and active geologic processes of this region. Data from sidescan sonar, multibeam sonar bathymetry, physical samples, and instrument moorings, are consolidated with new and existing maps in a geographic information system (GIS). The GIS provides researchers and policymakers a view of the relationship among data sets to assist science studies and to help with economic and social policy-making decisions regarding this protected environment.
California↗
Seafloor Rocks and Sediments of the Continental Shelf From Monterey Bay to Point Sur, California
Introduction Acoustic swath mapping of the greater Monterey Bay area continental shelf from Point Ano Nuevo to Point Sur reveals complex patterns of rock outcrops on the shelf, and coarse sand bodies that occur in distinct depressions on the inner and mid-shelves. This publication portrays the seafloor components in a 36- by 48-inch map sheet at 1:100,000 scale.
Miscellaneous Field Studies Map↗
Observations in Monterey Canyon and Fan Valley using the submersible Alvin and a photographic sled
Explore the source record for details and available documents.
Open-File Report↗
Observations on Cretaceous abyssal hills in the northeast Pacific
An abyssal hills area of 50 × 60 km in the northeast Pacific was studied using bottom transponder navigation, closely spaced survey lines, and long-traverse oblique photography. The block-faulted north—south hills are bounded by scarps, commonly with 40° slopes. On these steep scarps sedimentation is inhibited and pillow basalts often crop out. An ash layer of high acoustic reflectivity at about 7 m subbottom depth blankets the area. This ash occurs in multiple beds altered to phillipsite and is highly consolidated. A 24 m.y. age for the ash is based on ichthyolith dates from samples in the overlying sediments. Acoustically transparent Neogene sediments above the ash are thickest in trough bottoms and are absent or thin on steep slopes. These Neogene sediments are composed of pale-brown pelagic clays of illite, quartz, smectite, chlorite and kaolinite. Dark-brown pelagic clays, rich in smectite and amorphous iron oxides, underlie the Neogene surficial sediments. Manganese nodules cover the bottom in varying percentages. The nodules are most abundant near basement outcrops and where the subbottom ash layer is absent.
Marine Geology↗
Geology and physiography of the continental margin north of Alaska and implications for the origin of the Canada Basin
The continental margin north of Alaska is of Atlantic type. It began to form probably in Early Jurassic time but possibly in middle Early Cretaceous time, when the oceanic Canada Basin of the Arctic Ocean is thought to have opened by rifting about a pole of rotation near the Mackenzie Delta. Offsets of the rift along two fracture zones are thought to have divided the Alaskan margin into three sectors of contrasting structure and stratigraphy. In the Barter Island sector on the east and the Chukchi sector on the west the rift was closer to the present northern Alaska mainland than in the Barrow sector, which lies between them. In the Barter Island and Chukchi sectors the continental shelf is underlain by prisms of clastic sedimentary rocks that are inferred to include thick sections of Jurassic and Neocomian (lower Lower Cretaceous) strata of southern provenance. In the intervening Barrow sector the shelf is underlain by relatively thin sections of Jurassic and Neocomian strata derived from northern sources that now lie beneath the outer continental shelf. The rifted continental margin is overlain by a prograded prism of Albian (upper Lower Cretaceous) to Tertiary clastic sedimentary rocks that comprises the continental terrace of the western Beaufort and northern Chukchi Seas. On the south the prism is bounded by Barrow arch, which is a hingeline between the northward-tilted basement surface beneath the continental shelf of the western Beaufort Sea and the southward-tilted Arctic Platform of northern Alaska. The Arctic platform is overlain by shelf clastic and carbonate strata of Mississippian to Cretaceous age, and by Jurassic and Cretaceous clastic strata of the Colville foredeep. Both the Arctic platform and Colville foredeep sequences extend from northern Alaska beneath the northern Chukchi Sea. At Herald fault zone in the central Chukchi Sea they are overthrust by more strongly deformed Cretaceous to Paleozoic sedimentary rocks of Herald arch, which trends northwest from Cape Lisburne. Hope basin, an extensional intracontinental sedimentary basin of Tertiary age, underlies the Chukchi Sea south of Herald arch.
Open-File Report↗