Depth anomalies in the Arabian Basin, NW Indian Ocean |
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Authors: | K K Ajay A K Chaubey |
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Institution: | (1) National Institute of Oceanography, Dona Paula, Goa, 403004, India |
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Abstract: | We present previously unreported depth anomalies in the Arabian Basin, northwest Indian Ocean, to provide constraints on the
evolution of the oceanic lithosphere of that basin. The depth anomaly reported in this study was calculated as the difference
between the observed depth to oceanic basement (corrected for sediment load) and the calculated depth to oceanic basement
of the same age. The results indicate an anomalous depth to basement of oceanic crust in the Arabian Basin in the age bracket
of 63–42 Ma, suggesting that subsidence in this basin does not follow the age–depth relationship of normal oceanic crust.
The depth anomalies in the basin vary from +501 to −905 m. A negative depth anomaly zone, mapped in the eastern part of the
basin near the Laccadive Ridge, indicates that here the basement depth is shallower than predicted. By contrast, a positive
depth anomaly zone, mapped in the western part of the basin, indicates a deeper basement depth than expected. We propose that
the excess subsidence of basement of the western part of the basin is probably caused by a relatively cold mantle, compared
to the nearby eastern part of the basin which is affected by the intense thermal field of the former Reunion hotspot. Here,
the rise in oceanic basement is caused by the vertical upwelling of oceanic crust due to convection, followed by a lateral
across-axis flow facilitated by the Reunion hotspot at the time of spreading in early Tertiary times. This interpretation
is in good agreement with spreading-ridge propagation and ridge-hotspot interaction reported earlier for the basin. |
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