Anomalías magnéticas de gran amplitud en torno a la cuenca Powell (extremo NE de la Península Antártica)
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[1] Universitat de Barcelona
Universitat de Barcelona
Barcelona, España
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[2] Universidad de Granada
Universidad de Granada
Granada, España
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[3] Instituto Andaluz de Ciencias de la Tierra
Instituto Andaluz de Ciencias de la Tierra
Granada, España
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- Localización: Revista de la Sociedad Geológica de España, ISSN 0214-2708, Vol. 8, Nº. 3, 1995, págs. 285-295
- Idioma: español
- Enlaces
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Resumen
- español
Los perfiles de magnetometría de la campaña HESANT92/93 muestran anomalías que superan 1000 nT, a lo largo de una banda de 100 km de ancho en la Dorsal Sur de Scotia. Estas anomalías pueden constituir la continuación de la rama norte de anomalías magnéticas de la Península Antártica. La interpretación de estas anomalías en cuatro perfiles, mediante modelización interactiva bidimensional, permite determinar que los cuerpos anómalos tienen elongación N60ºE, base a 15 km y susceptibilidades magnéticas equivalentes entre 0,04 y 0,1 SI. Los cuerpos anómalos corresponden al zócalo acústico en los perfiles de sísmica de multicanal y con batimetría en zonas con escasos sedimentos. Los cuerpos anómalos de la Dorsal Sur de Scotia con probablemente rocas plutónicas básicas, similares a las de la Península Antártica. En la Cuenca Powell, un cuerpo tabular se atribuye a las capas 2 y 3 de la cortea oceánica. Las zonas con anomalías magnéticas de los márgenes oriental y occidental de la Cuenca Powell pueden representar la continuación de la rama sur de las bandas de anomalía de la Península Antártica. Todos los cuerpos anómalos en la corteza continental son probablemente previos a la apertura de la Cuenca Powell.
- English
Magnetic profiles obtained during the HESANT 92/93 cruise with the B/O HESPERIDES show significant amplitude anomalies along a broad band in the northern margin of the Powell Basin. These anomalies exhibit amplitudes of up to 1000 nT and are up to 100 km in width. The anomalies are attributed to the continuation of the two branches of magnetic anomalies described previously in the Antarctic Peninsula (PMA). The northern branch would continue along the fragments of continental crust of the South Scotia Ridge located at the northern limit of the Powell Basin, whereas the southern branch would be located only in the eastern and western passive margins of the Powell Basin. Interactive modelling of two-dimensional bodies in four profiles oriented NNW-SSE allows us to determine the main features of the magnetic source bodies of the northern branch. In the continental crust, the bodies are elongated in the direction N60ºE and their base is located at a depth of approximately 15 km. Equivalent magnetic susceptibilities between 0,04 and 0,1 (SI) are employed, and we assume that, as in the case of the Antarctic Peninsula batholith, remanent magnetization is sub-parallel to the present geomagnetic field. The general trends of the bathymetry are consistent with the superficial shape of these bodies. There is also agreement between the geometry of the magnetic bodies and the location of the acoustic basement in multichannel seismic profiles. The magnetic bodies are probably igneous in origin and may represent basic plutonic rocks similar to those described from the Antarctic Peninsula. In the oceanic crust of the Powell Basin it is also necessary to consider a second tabular shaped body with induced magnetization in almost all the profiles, which could represent layers 2 and 3 of the oceanic crust. Magnetic anomalies are also identified in the eastern and western margins of the Powell Basin. In the southern branch, the apparent splitting of the anomalous body into the two opposing margins of the Powell Basin seems to indicate that it was emplaced before Late Eocene-Oligocene times, when the opening of this basin took place, and that it was subsequently fragmented during the Cenozoic.
- español
