Abstract
The Magellan trough is a WNW-trending linear depression with flanking ridges that extends more than 300 km in the Central Pacific Basin. Depth of the trough axis exceeds 6600 m. Compilations and analyses of bathymetric, seismic, and geologic data of the trough and its adjacent areas reveal three discriminate acoustic layers: a transparent layer (Unit I), a semi-opaque layer (Unit II), and an opaque layer (acoustic basement) in descending order. In the southern part of the study area (south of the trough), calcareous turbidites (Unit I) whose ages range probably from the Oligocene to the middle Eocene, were derived from the Magellan Rise. This turbidite layer tends to become thinner towards the trough. The southern flanking ridge of the trough, therefore, may have been a barrier to the deposition of the turbidites. The thickness of the transparent layer in Unit I varies from place to place, particularly in the area north of the trough, whereas the thickness of Unit II is rather constant. Some 3.5- kHz profiles show the truncation and abrupt thinning of the transparent layer (Unit I). A hiatus between the late Pliocene and the late Miocene exists in Unit I. These geological findings suggest that the deposition of Unit I has been affected by bottom water currents such as the recent Antarctic bottom water current, which plays a significant role in the deposition of sediment. Major features of the sea floor, namely the surface topography of the acoustic basement and the pattern of faults within the basement around the trough, show trends concordant with those of the trough. The concordant features trend WNW-ESE and converge to the northwest. A detailed bathymetric chart of the study area has been constructed showing left and right lateral offsets of the trough together with the flanking ridges. These bathymetric features of the trough area are concordant with the fan-shaped magnetic anomaly lineations. The bathymetric and magnetic lineations are evidence of sea-floor spreading at the axis of the trough in the Early Cretaceous (M9 to M11). These morphotectonic observations are good indicators of fundamental processes of sea-floor spreading that produced the Magellan system.
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© 1992 Circum-Pacific Council for Energy and Mineral Resources
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Furukawa, M., Tamaki, K., Mizuno, A., Kimura, M. (1992). Morphology and Geology of the Magellan trough Area in the Central Pacific. In: Keating, B.H., Bolton, B.R. (eds) Geology and Offshore Mineral Resources of the Central Pacific Basin. Circum-Pacific Council for Energy and Mineral Resources Earth Science Series, vol 14. Springer, New York, NY. https://doi.org/10.1007/978-1-4612-2896-7_5
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DOI: https://doi.org/10.1007/978-1-4612-2896-7_5
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