The structure of the bottom of the Red Sea is typical for a young, but already fully developed ocean basin. The researchers came to this conclusion by combining the results of gravimetric, seismic, and bathymetric surveys. The new data halved the age of the Red Sea oceanic crust. The study is published in Nature Communications.
The Red Sea region is a kind of field laboratory for the study of tectonic processes, where the cracking of the continental crust is replaced by the formation of a new low-power oceanic crust. The Red Sea filled the crevice that originated during the African and Arabian plates 25 million years ago. Today, the pool grows wide at a rate of one centimeter per year, and its axial part is occupied by a rift, an area of stretching bark.
The question of whether the Red Sea can be compared with other young oceans in the Earth's geological past remains debatable. The thickness of sediments prevents direct observation of the structures of the bottom and complicates the interpretation of geophysical signals. A number of studies claim that the Red Sea is in the stage of continental fault with the point formation of the oceanic crust. Alternative models suggest that the sea has already passed this stage and smelts basalts along the entire length of the basin like a real ocean.
An international team of geologists led by Nico Augustin from the GEOMAR Ocean Research Centre in Kiel has developed a tectonic model for the development of the Red Sea basin over the past 13 million years. The gravimetric survey was combined with seismic data to determine the structure of the crust under a thick pack of sedimentary rocks. In addition, geologists studied the General Bathymetric Map of the Oceans (GEBCO) and performed a geochemical analysis of magmatic samples from the seabed.
Data from the vertical gradient of gravity indicated structures hidden under the cover of sediments. Bands of positive gravitational anomalies cross the rift. These segments are associated with changes in the thickness of the crust along the axis of stretching and are typical of the oceanic crust originating from magmatically active, thick, and heavy rift areas. The same structures are known in ultra-slow (stretching speed less than two centimeters per year) mid-ocean ridges, such as the South Atlantic and the Reykjanes Range.
Bathymetric maps confirmed the idea of an oceanically mature Rift of the Red Sea. On areas of the bottom without sedimentary cover in the relief is expressed the crest of the mid-ocean ridge. Analysis of rocks from the naked areas of the bark showed characteristics of the ocean floor basalt. Where bottom morphos are camouflaged with sediment, scientists have turned to seismic data. Earthquakes in the Red Sea are localized along the linearly elongated central part of the reservoir. The range of magnitude and spatial density of aftershocks are similar to those observed on other ultra-slow ridges.
The new data corrected the area of the bottom occupied by the oceanic crust: it continuously lines the axial part of the reservoir up to the Red Sea-Dead Sea fault. According to the tectonic model, the oceanic crust began to be smelted 13 million years ago throughout the basin. This doubles previous age calculations. The authors of the study suggested that the continental stage of life of the Red Sea is complete and today it develops as a mature ocean basin.