Red Sea having an almost classical oceanic evolution

For geoscientists, the Red Sea is a fascinating and still enigmatic area of study. Its age and whether it is a special case in the formation of ocean basins, or if it has evolved similarly to other, larger ocean basins, are contentious issues. A new tectonic model published by researchers suggests that the Red Sea is not only a typical ocean but also more mature than previously thought.

The Red Sea is 2,250 kilometers long but only 355 kilometers wide at its widest point—it hardly resembles an ocean on a world map. However, this is deceptive. Between Africa and the Arabian Peninsula, a new, albeit still narrow, ocean basin is forming. For decades, geosciences have debated how young it is and whether it can truly be compared to other young oceans in Earth’s history. The issue is that the newly formed oceanic crust along the narrow, north-south aligned rift is heavily buried beneath a thick blanket of silt and sediments. This makes direct investigations more difficult.

Researchers published a study that makes a good case for the Red Sea being quite mature and having an almost classical oceanic evolution.

The Red Sea is approximately 1000 miles long and only slightly more than 170 miles wide at its widest point. The Greeks referred to it as a sea, but they also referred to the Persian Gulf as a sea. It could instead be an ocean, as there is an ocean basin between Africa and the Arabian Peninsula. The Greeks were unaware of this, and the problem with discovering it now is that the oceanic crust along the narrow, north-south aligned rift is widely buried beneath a thick blanket of silt and sediments, making direct investigations difficult.

Scientists from GEOMAR Helmholtz Centre for Ocean Research Kiel, King Abdullah University for Science and Technology in Thuwal (Saudi Arabia), and the University of Iceland have published a study in the international journal Nature Communications that makes a strong case for the Red Sea being quite mature and exhibiting almost classical oceanic evolution. “We can show for the first time using a combination of different methods that the structures in the Red Sea are typical for a young but already fully developed ocean basin,” says Dr. Nico Augustin of GEOMAR, the study’s lead author.

The team primarily used gravity and earthquake data to develop a new tectonic model of the Red Sea basin, in addition to information from high-resolution seafloor maps and chemical analyses of rock samples. Gravity anomalies have already assisted in the detection of hidden seafloor structures such as rift axes, transform faults, and deep-sea mountains in other regions, such as the Gulf of Mexico, the Labrador Sea, and the Andaman Sea.

The Red Sea is no longer a baby ocean

The current study’s authors compared gravity patterns of the Red Sea axis with comparable mid-ocean ridges and discovered more similarities than differences. They discovered positive gravity anomalies perpendicular to the rift axis, which are caused by variations in crustal thickness along the axis. “These ‘off-axis segmentation trails’ are very common features of oceanic crust that originate from magmatically more active, thicker, and thus heavier areas along the axis. However, this is a first for the Red Sea “Dr. Nico Augustin says.

Bathymetric maps and earthquake data support the idea of a nearly continuous rift valley running through the Red Sea basin. Geochemical analyses of rock samples from the few areas where salt masses are not overlain confirm this. “All of the samples we have from the Red Sea rift have geochemical fingerprints of normal oceanic crust,” says co-author Dr. Froukje van der Zwan.

The team’s new analysis of gravity and earthquake data limits the onset of ocean expansion in the Red Sea to approximately 13 million years ago. “That’s more than twice the commonly accepted age,” says Dr. Augustin. That means the Red Sea is no longer a baby ocean, but rather a young adult with a structure similar to that of the young southern Atlantic 120 million years ago.

According to the lead author, “the model now presented is, of course, still being debated in the scientific community.” “However, it is the most straightforward explanation for what we see in the Red Sea. Many previously difficult-to-explain details in salt- and sediment-covered areas suddenly make sense with our model.” While the model has thus been able to answer some questions about the Red Sea, it has also raised many new ones, inspiring further research in the Red Sea from a completely new scientific perspective.