Publications
Filter Total Items: 1423
Suitability of nonwelded pyroclastic-flow deposits for studies of magnetic secular variation: A test based on deposits emplaced at Mount St. Helens, Washington, in 1980 Suitability of nonwelded pyroclastic-flow deposits for studies of magnetic secular variation: A test based on deposits emplaced at Mount St. Helens, Washington, in 1980
Paleomagnetic directions obtained from nonwelded pyroclastic-flow deposits that were emplaced at Mount St. Helens, Washington, in 1980 have a precision and accuracy similar to data obtainable from lava flows. It is concluded that nonwelded pyroclastic-flow deposits, like lava flows, are suitable for studies of magnetic secular variation. Although clast rotations apparently caused an...
Authors
Richard P. Hoblitt, Richard L. Reynolds, Edwin E. Larson
Classification of deep-sea, fine-grained sediments Classification of deep-sea, fine-grained sediments
Most deep-sea sediments contain one or more biogenic components and one dominant nonbiogenic component, usually clay or silty clay. The authors present a descriptive classification scheme in which deep-sea, fine-grained sediments are placed within a three-components system of calcareous-biogenic, siliceous-biogenic, and nonbiogenic components. In a three-procedure the user assesses...
Authors
Walter E. Dean, Margaret Leinen, D.A. Stow
Variations in the global carbon cycle during the Cretaceous related to climate, volcanism, and changes in atmospheric CO2 Variations in the global carbon cycle during the Cretaceous related to climate, volcanism, and changes in atmospheric CO2
The stratigraphic record from both deep-sea and shallow-water depositional environments indicates that during late Aptian through Cenomanian time (1) global climates were considerably warmer than at present; (2) latitudinal gradients of atmospheric and oceanic temperatures were considerably less than at present; (3) rates of accumulation of organic matter of both marine and terrestrial...
Authors
M.A. Arthur, Walter E. Dean, S.O. Schlanger
Cyclic variations in calcium carbonate and organic carbon in Miocene to Holocene sediments, Walvis Ridge, South Atlantic Ocean Cyclic variations in calcium carbonate and organic carbon in Miocene to Holocene sediments, Walvis Ridge, South Atlantic Ocean
The entire upper Miocene to Holocene sedimentary sequence recovered in a hydraulic piston core at DSDP Site 532 on Walvis Ridge shows distinct cycles in amount of CaCO sub(3) that correlate with dark and light cycles of sediment color. The average periodicities of the carbonate cycles for the Quaternary, upper Pliocene, and lower Pliocene are about 35, 46, and 28 ky, respectively, with...
Authors
Walter E. Dean, J. V. Gardner
Sedimentation in a blast-zone lake at Mount St. Helens, Washington—Implications for varve formation Sedimentation in a blast-zone lake at Mount St. Helens, Washington—Implications for varve formation
Sediment collected in traps in a newly formed lake in the blast-impact area at Mount St. Helens recorded a sediment yield that is about two orders of magnitude greater than for comparable basins with vegetation and similar precipitation. Most sediment was mobilized by storms and runoff at the onset of the wet season. The sedimentation response to strongly seasonal precipitation, in the...
Authors
R.Y. Anderson, E.B. Nuhfer, Walter E. Dean
Geologic evolution, sedimentation, and paleoenvironments of the Angola Basin and adjacent Walvis Ridge: Synthesis of results of Deep Sea Drilling Project Leg 75 Geologic evolution, sedimentation, and paleoenvironments of the Angola Basin and adjacent Walvis Ridge: Synthesis of results of Deep Sea Drilling Project Leg 75
The section recovered at Site 530 (Holes 53OA and 530B) consists of eight sedimentary units and one basalt unit. The composition of the basalt recovered in Hole 53OA is distinct from typical mid-ocean ridge basalts (MORBs) but is similar to that of Hawaiian tholeiites and basalt from the central part of Walvis Ridge. Throughout most of its history, the southern Angola Basin received...
Authors
Walter E. Dean, W.W. Hay, Jean-Claude Sibuet
Origin and geochemistry of Cretaceous deep-sea black shales and multicolored claystones, with emphasis on Deep Sea Drilling Project Site 530, southern Angola Basin Origin and geochemistry of Cretaceous deep-sea black shales and multicolored claystones, with emphasis on Deep Sea Drilling Project Site 530, southern Angola Basin
Deep-water sedimentary sequences of mid-Cretaceous age, rich in organic carbon, have been recovered at many DSDP sites in the Atlantic Ocean. Most of these sequences have a marked cyclicity in amount of organic carbon resulting in interbedded multicolored shale, marlstone, and (or) limestone that have cycle periods of 20,000 to 100,000 years and average 40,000 to 50,000 years. These...
Authors
Walter E. Dean, M.A. Arthur, D.A.V. Stow
Carbonate and organic-carbon cycles and the history of upwelling at Deep Sea Drilling Project Site 532, Walvis Ridge, South Atlantic Ocean Carbonate and organic-carbon cycles and the history of upwelling at Deep Sea Drilling Project Site 532, Walvis Ridge, South Atlantic Ocean
Detailed carbonate and organic-carbon stratigraphies were constructed from samples collected every 20 cm in a 250-m hydraulic piston core recovered at DSDP Site 532 on Walvis Ridge. This sampling interval represents about one sample every 5000 yr., based on sediment accumulation rates calculated from nannofossil biostratigraphic zones. All samples were analyzed for percent CaCO3...
Authors
J. Gardner, Walter E. Dean, C.R. Wilson
Middle Cretaceous black shales at Site 530 in the southeastern Angola Basin Middle Cretaceous black shales at Site 530 in the southeastern Angola Basin
The middle Cretaceous black shale interval at Site 530 is 170 m thick and late Albian to Coniacian in age. The organic-carbon-rich sediments occur as 260 separate beds (average 4 cm, maximum 60 cm thick) and make up less than 10% of the recovered section. Associated lithologies are greenish, grayish, and reddish mudstones, marlstones, and rare limestones. Organic-carbon contents of the...
Authors
D.A. Stow, Walter E. Dean
Shimada Seamount: An example of recent mid-plate volcanism Shimada Seamount: An example of recent mid-plate volcanism
Shimada Seamount is an isolated volcanic feature located between the Clipperton and Clarion Fracture Zones ∼1,150 km west of the East Pacific Rise and ∼600 km west of the inactive spreading center represented by the Mathematician Seamounts. It rises ∼3,900 m above the surrounding sea floor to within 50 m of present-day sea level. The area of Shimada Seamount should be volcanically...
Authors
J. V. Gardner, Walter E. Dean, Richard J. Blakely
Models for the deposition of Mesozoic-Cenozoic fine-grained organic-carbon-rich sediment in the deep sea Models for the deposition of Mesozoic-Cenozoic fine-grained organic-carbon-rich sediment in the deep sea
The widespread occurrence of organic-carbon-rich strata (‘black shales’) in certain portions of Jurassic, Cretaceous and Cenozoic sequences has been well-documented from Deep Sea Drilling Project sites in the Atlantic and Pacific Oceans and from sequences, now exposed on land, originally deposited in the Tethyan ocean. These ancient black shales usually have been explained by analogy...
Authors
M.A. Arthur, Walter E. Dean, D.A.V. Stow
Rhythmic bedding in Mesozoic- Cenozoic pelagic carbonate sequences: The primary and diagenetic origin of Milankovitch-like cycles Rhythmic bedding in Mesozoic- Cenozoic pelagic carbonate sequences: The primary and diagenetic origin of Milankovitch-like cycles
No abstract available.
Authors
M.A. Arthur, Walter E. Dean, D.J. Bottjer, Peter A. Scholle