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An ocean 13 million years in the making

Spreading of the seafloor in the Red Sea basin is found to have begun along its entire length around 13 million years ago, making its underlying oceanic crust twice as old as previously believed.

An ocean 13 million years in the making
3D Render of a Topographic Map of the Red Sea, North Africa, Middle East
[Credit: iStock Photo]

The formation history and age of the Red Sea basin has long been contested, largely because the crust under the sea is widely overlain by thick layers of salt and sediment, making it difficult to observe directly.

"Existing geological models of the Red Sea often contradict each other, largely due to limited high-resolution data and the influence of overlaying salt layers," says Froukje van der Zwan from KAUST, who worked on the project. "For example, magnetic methods do not work well because of the salt layers, where lava erupting under the salt blankets develops significantly different magnetic signatures than those from other oceans."

"We decided to start afresh without preconceptions and make use of gravity and earthquake data, which allowed us to 'see through' the salt layers to the crust beneath," explains van der Zwan.

An ocean 13 million years in the making
Bathymetric chart of a part of the Red Sea [Credit: GEOMAR]

Areas of thick crust, such as mountains and volcanoes, and denser rock types have a high gravity index, and oceanic crust displays different gravity properties compared with continental crust. These differences are mapped by satellites monitoring the gravitational field of the Earth, and the resulting "vertical gravity gradient" (VGG) data are readily available.

The international team combined VGG data with high-resolution seafloor maps, rock chemistry and earthquake data to gain a comprehensive overview of the basin. Their results indicate that the Red Sea has the fairly simple geological structure of a young ocean, with large volcanoes running the length of the slow-spreading rift. These features are typical of mid-ocean ridges around the world and suggest that the entire Red Sea is not a young sea, but rather a maturing "teenage" ocean basin of around 13 million years old.

"Most of the basin is underlain by oceanic crust, and the continental crusts on either side are further apart than previously indicated," says van der Zwan.

The new model explains features found in the northern Red Sea that are unaccounted for in earlier models. Furthermore, dating the spreading of the seafloor changes the understanding of the region's geological history and could help researchers better understand the formation of other oceans, such as the South Atlantic.

"With a stronger sense of where the earth plate boundaries are, we may improve our understanding of regional seismic activity," says van der Zwan. "Our model will enable us to conduct detailed studies of the ocean crust, active fault systems and the volcanic explosion craters that we found."

The study is published in Nature Communications.

Source: King Abdullah University of Science and Technology [April 29, 2021]

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1 comment :

  1. Very interesting, thanks a lot. Perhaps this was also important for hominoid evolution. In a few papers (e.g. in TREE), we hypothesized that Miocene hominoids (apes & humans) originated in coastal forests, where they evolved an aquarboreal locomotion (aqua=water, arbor=tree): they became already upright (with centrally-placed spine) for wading bipedally in forest swamps as well as for climbing arms overhead in de branches above the swamp ("Aquarboreal Ancestors?" Trends Ecol.Evol. 17:212-217, 2002), as apes still do sometimes, google e.g. "bonobo wading", "gorilla bai" or "orangutan wading" illustrations. Possibly the incipient Red Sea was where early apes became aquarboreal? Google "ape human evolution made easy PPT".


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