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Full-Text Articles in Physical Sciences and Mathematics
The Geology Of The Oceanographer Transform Fault, Richard H. Moody Jr.
The Geology Of The Oceanographer Transform Fault, Richard H. Moody Jr.
Geology Theses and Dissertations
A detailed survey of the Oceanographer transform fault and environs at 35º N, 35ºW has yielded detailed information with respect to the generation and evolution of seafloor at a slowly accreting plate margin. From this data detailed bathymetric maps and maps of depth to basement have been constructed for a swath of seafloor 1800 km long and 100-200 km wide centered about the offset region. This data was used to subdivide major phases of seafloor spreading during the Tertiary. The ridge crest and all major topographic features near the transform appear to be affected by their proximity to the transform. …
Geology Of The Mafic/Ultramafic Transition, Table Mountain, Western Newfoundland, Suzanne O'Connell
Geology Of The Mafic/Ultramafic Transition, Table Mountain, Western Newfoundland, Suzanne O'Connell
Geology Theses and Dissertations
A thin (<200 m.) mafic suite and well developed mafic/ultramafic transition zone are exposed above a flat lying peridotite contact on northwestern Table Mountain. The igneous layering and sedimentary features indicate mineral deposition under conditions which promoted adcumulate growth, were capable of minor transport, and were subjected to at least minor tectonic activity during consolidation. Feldspathic,. mafic, and ultramafic dikes and veins cross-cut the layering. Microscopic futures indicate deformation at elevated temperature and/or low strain rates. Deformation is best developed within the transition zone, but cataclastic zones are most common in the hornblende gabbros. Orientations of layering, foliation, and lineation indicate a variable mafic/ultramafic transition and macroscopic folding. Geometric analysis indicates three distinct fold axis orientations: an east-west horizontal fold axis, a northeast trending modestly plunging axis, and a vertical though poorly defined axis. Such features demonstrate that an apparently simple contact relationship may be extremely complex. This has important implications for ocean floor accretion. The relatively simple ocean floor seismic stratigraphy masks very complex petrological and structural processes. Such processes may involve deposition in an actively convecting magma chamber with a differentially subsiding wedge (Dewey and Kidd, 1977), in which folding occurs in response to the steepening angle between the cumulate banding and the base of the magma chamber. The instability is enhanced by the different accumulation rates and densities of the minerals involved. The lineation may originally be a sedimentary feature indicative of transport direction from the convection cell, and perpendicular to the compressive stress which produced. the folding. The different orientations of lineations and fold axes could be produced by rotation of the ocean crustal blocks during lateral transport along the ocean floor and/or obduction. Further detailed study of ophiolite complexes will continue to shed light upon the nature and development of oceanic crust.
Petrology Of The Oceanographer Fracture Zone (35ºn35ºw), Tsugio Shibata
Petrology Of The Oceanographer Fracture Zone (35ºn35ºw), Tsugio Shibata
Geology Theses and Dissertations
During a geological and geophysical survey of the Oceanographer Fracture Zone (35°N, 35°W), seventeen dredge hauls containing a variety of rocks were obtained. Petrographic study shows that these rock samples can be classified into six main rock types: fresh basalt, weathered basalt, metabasalt, gabbro, metagabbro, and serpentinite. Most of the dredge hauls were positioned on the steep, southern wall of the fracture zone, and an inference from the dredging results suggests that basalt is the most abundant rock type which outcrops at the junction between the rift valley and the fracture zone; however, as we move away from the junction, …