Anomalous seafloor mounds in the northern Natal Valley, southwest Indian Ocean: Implications for the East African Rift System


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Wilfried.Jokat [ at ] awi.de

Abstract

The Natal Valley (southwest Indian Ocean) has a complicated and protracted opening history, as has the surrounding southwest Indian Ocean. Recently collected multibeam swath bathymetry and 3.5 kHz seismic data from the Natal Valley reveal anomalous sea floor mounds in the northern Natal Valley. The significance, of these domes,as recorders of the geological history of the Natal Valley and SE African Margin has been overlooked with little attempt made to identify their origin, evolution or tectonic significance. This paper aims to describe these features from a morphological perspective and to use their occurrence as a means to better understand the geological and oceanographic evolution of this basin. The sea floor mounds are distinct in both shallow seismic and morphological character from the surrounding sea floor of the Natal Valley. Between 25 km and 31 km long, and 16 km and 18 km wide, these features rise some 400 m above the sedimentary deposits that have filled in the Natal Valley. Such macro-scale features have not previously been described from the Natal Valley or from other passive margins globally. They are not the result of bottom water circulation, salt tectonics; rather, igneous activity is favoured as the origin for these anomalous sea floor features. We propose a hypothesisthat the anomalous seafloor mounds observed in the Natal Valley are related to igneous activity associated with the EARS. The complicated opening history and antecedent geology, coupled with the southward propagation of the East African Rift System creates a unique setting where continental rift associated features have been developed in a marine setting.



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ISI/Scopus peer-reviewed
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Published
Eprint ID
36589
DOI 10.1016/j.tecto.2014.05.030

Cite as
Wiles, E. , Green, A. , Watkeys, M. K. , Jokat, W. and Krocker, R. (2014): Anomalous seafloor mounds in the northern Natal Valley, southwest Indian Ocean: Implications for the East African Rift System , Tectonophysics, 630 , pp. 300-312 . doi: 10.1016/j.tecto.2014.05.030


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