摘要 :
This document constitutes the final report of efforts taken under grant numberN00014-89-J-3172. Under this program, students from the MAST Academy, and other Dade County Public High Schools, were placed in laboratory positions at ...
展开
This document constitutes the final report of efforts taken under grant numberN00014-89-J-3172. Under this program, students from the MAST Academy, and other Dade County Public High Schools, were placed in laboratory positions at three oceanographic institutions on Virginia Key, Miami, Florida during the summer of 1991. These students received direct supervision from faculty members at the Rosenstiel School of Marine and Atmospheric Science (RSMAS) and from staff scientists at the Atlantic Oceanographic and Meteorological Laboratories (AOML) and at the Southeast Fisheries Center (SEFC). This program provided the students an opportunity to work in a scientific environment and to appraise career opportunities in oceanographic science.
收起
摘要 :
The Canton Trough is an extremely deep linear feature flanked by large en echelon ridges. This system, located in the equatorial Central Pacific Basin, can be traced ENE from the Phoenix Islands for a distance of more than 500 km....
展开
The Canton Trough is an extremely deep linear feature flanked by large en echelon ridges. This system, located in the equatorial Central Pacific Basin, can be traced ENE from the Phoenix Islands for a distance of more than 500 km. The surrounding topography is lineated parallel to the ridge-trough-ridge system and probably originated by block faulting. A similar mode of formation is inferred for the main trough itself, the implication being that the vertical displacement may exceed 3000 m in some localities. This interpretation is reinforced by the occurrence near the base of the trough of an unusually diverse assemblage of igneous rocks, including normal oceanic tholeiitic basalts, coarse-grained diabases, anorthositic gabbros, pegmatic gabbros, and cumulate gabbros. Simple vertical displacements of crustal blocks also could produce the major components of the observed gravity anomaly signatures as well as explain the necessity in the gravity models for a crustal root beneath the Canton Trough. Sediments within the Canton Trough region are predominately radiolarian oozes and calcareous turbidites, which correlate with transparent layers and highly stratified units observed on reflection profiler records. Residual magnetic anomalies are at least partly produced by the great topographic relief of the ridge-trough-ridge zone. Although there is some evidence that the Canton Trough and its surrounding structures represent an extension of the Clipperton Fracture Zone into the Central Pacific Basin, the absence of structural continuity, the lack of regional depth changes, and limitations imposed by the regional tectonic patterns argue against this hypothesis.
收起
