85 resultados para Clipperton-A


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On the basis of a long term research of the authors a database model of grain size composition of unlithified marine and ocean bottom sediments has been created. An improved method of water-mechanical analysis has been offered. Grain size parameters of main types of bottom sediments have been measured and calculated. The genetic interpretation of results and regularities of sandy, aleuritic and pelitic material in basins of sedimentation are under discussion.

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Fe, Mn, Cu, Ni, and Co contents in bottom sediment samples from the Clarion Clipperton fracture zone and Guatemala Basin were studied; maps of their distribution in the upper layer of sediments were prepared. At some stations contents of these elements were also measured in Pleistocene and Oligocene sediments. Elevated contents of five ore elements (except for Zn) were found at the East Pacific Rise and in the Clarion-Clipperton province; and of Mn, Ni, and Cu in the Guatemala basin. Increased zinc contents occur only in sediments of the East Pacific Rise and Guatemala Basin. Enrichment of sediments in these elements results from under¬water hydrothermal activity and high biological productivity.

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DSDP 161 is located on the lower west flank of the East Pacific Rise about midway between the Clipperton and Clarion fracture zones which define the boundaries of a large structural block in the eastern Pacific. The site is about 4,000 km west of the present crest of the Rise. It is located near the northern edge of a zone of thick Cenozoic sediments which marks the general location of the equatorial zone of high biological productivity.

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DSDP 162 is located due north of DSDP 161 on the lower west flank of the East Pacific Rise about 3900 km west of the crest. It is in the Clarion-Clipperton block, about 80 km south of the Clarion Fracture Zone. The site lies at the extreme northern edge of the zone of thick sediments that parallels the equator in the Pacific and marks the region of high biological productivity.

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Site 42 is one of the series of sites selected by the Pacific Advisory Panel along the 140th meridian to sample the longitudinal variation in sediment composition in the eastern Pacific. The site is located in an area of abyssal hills between the Clarion and Clipperton Fracture Zones, and is at the northern margin of the thick development of acoustically transparent sediment extending along the equator.

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Polymetallic nodule mining at abyssal depths in the Clarion Clipperton Fracture Zone (Eastern Central Pacific) will impact one of the most remote and least known environments on Earth. Since vast areas are being targeted by concession holders for future mining, large-scale effects of these activities are expected. Hence, insight into the fauna associated with nodules is crucial to support effective environmental management. In this study video surveys were used to compare the epifauna from sites with contrasting nodule coverage in four license areas. Results showed that epifaunal densities are more than two times higher at dense nodule coverage (>25 versus ≤10 individuals per 100 m2), and that taxa such as alcyonacean and antipatharian corals are virtually absent from nodule-free areas. Furthermore, surveys conducted along tracks from trawling or experimental mining simulations up to 37 years old, suggest that the removal of epifauna is almost complete and that its full recovery is slow. By highlighting the importance of nodules for the epifaunal biodiversity of this abyssal area, we urge for cautious consideration of the criteria for determining future preservation zones.