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NIO Scientists Report Anomalous Basement Depth in the NE Arabian Sea
In order to discriminate "normal" versus "anomalous" depths of portions of the oceans, NIO scientists reported anomalous basement depth in the NE Arabian Sea. The depth anomaly reported in the Arabian Sea is the difference between observed depth to oceanic basement corrected for sediment load and calculated depth to oceanic basement of same age. The results indicate anomalous depth to basement of 63-42 Ma aged oceanic crust in the Arabian Basin (NE Arabian Sea), suggesting that subsidence in this basin does not follow age-depth relationship of normal oceanic crust. The depth anomalies vary from +501 m to -905 m in the basin. Negative depth anomaly zone, mapped in the eastern part of the basin near the Laccadive Ridge, indicates that basement depth is shallower than predicted. Whereas positive depth anomaly zone, mapped in western part of the basin, indicates deeper basement depth than expected. It is proposed that the excess subsidence of basement of the western part of the basin, is probably caused due to relatively cold mantle as compared to nearby eastern part of the basin affected by the intense thermal field of the then Reunion hotspot. Whereas, the rise in oceanic basement of the eastern part of the basin is caused by the vertical upwelling due to convective current followed by a lateral across-axis flow facilitated by the Reunion hotspot at the time of spreading during the Early Tertiary period. This interpretation is in good agreement with spreading ridge propagation and ridge-hotspot interaction reported earlier for the basin.
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