13 million years of seafloor spreading throughout the Red Sea Basin

Nico Augustin,Colin W Devey,Bryndís Brandsdóttir,Froukje M Van Der Zwan

doi:10.1038/s41467-021-22586-2

Abstract

The crustal and tectonic structure of the Red Sea and especially the maximum northward extent of the (ultra)slow Red Sea spreading centre has been debated—mainly due to a lack of detailed data. Here, we use a compilation of earthquake and vertical gravity gradient data together with high-resolution bathymetry to show that ocean spreading is occurring throughout the entire basin and is similar in style to that at other (ultra)slow spreading mid-ocean ridges globally, with only one first-order offset along the axis. Off-axis traces of axial volcanic highs, typical features of (ultra)slow-spreading ridges, are clearly visible in gravity data although buried under thick salt and sediments. This allows us to define a minimum off-axis extent of oceanic crust of <55 km off the coast along the complete basin. Hence, the Red Sea is a mature ocean basin in which spreading began along its entire length 13 Ma ago.

Highlights

The crustal and tectonic structure of the Red Sea and especially the maximum northward extent of theslow Red Sea spreading centre has been debated—mainly due to a lack of detailed data
Despite its geological importance, tectonic models developed for the Red Sea are highly diverse and debated (Fig. 2), making it difficult to determine what role this type-locality can play in our understanding of continental breakup
Common structural features of all previously proposed models are the presence of the Zabargad fracture zone (ZFZ) and fault and lineament patterns of varying complexity both to explain anomalies in geophysical data and to accommodate the variably complicated tectonic processes thought necessary to create the observed bathymetry[4,5,6,7,8] (Fig. 2)

Summary

Results and discussion

Long-lived axial segmentation and discontinuities produce along-axis variations in crustal structure whose trails, on other ridges, can be traced up to 1000 km and over 30 Ma (million years ago) off-axis[17]. These segmentation trails are an integral part of (slow-spreading) oceanic crust and can be observed where, e.g. the ultra-slowspreading Southwest Indian Ridge opens between the Central. South of 20 °N, where the axis is continuously exposed, we do not see along-axis variations in water depth or volcanic activity and the off-axis rift-perpendicular trails are absent This transition corresponds to a significant shallowing of the axis.

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