- German scientists have discovered a giant canyon in the relatively shallow waters off north-western Africa. The morphology of the offshore valley indicates that a mighty river once must have passed through this flooded landscape.
An expedition of the research vessel 'Meteor', which recently returned to its home harbour of North-German Bremen, today announced what it termed "a sensational discovery". The marine researchers of the Research Centre Ocean Margins in Bremen had come across the canyon by accident.
Off the coast of Mauritania they came across an enormous underwater canyon "in a marvellous shape." It meanders a distance of more than 200 kilometres from the shallow coast until way out towards the Atlantic deep-sea.
The German scientists could still follow the deep gorge in the sea floor in water depths of more than 3000 meters. The leader of the expedition, Prof. Horst Schulz, concludes that "the canyon certainly plays a central roll in the transport of sediment from the continental slope into the deep-sea".
The "Cape Timiris Canyon", recently named after a nearby coastal projection, was discovered right at the beginning of the expedition at about 19 degrees latitude north. It was a big surprise: "Even on new maps, only large areas of level seafloor were recorded where we came across the canyon," Prof. Schulz reported.
The geoscientist from Bremen therefore changed the research program in order to cartographically record the gorge system on the seafloor. A good week later, the picture was almost complete.
- In many respects the 'Cape Timiris Canyon' is reminiscent of the [German-Dutch] Rhine river says Horst Schulz. At the foot of the continental slope, where the African continent descends at a water depth of 3000 meters into the deep-sea, it is two to three kilometres wide and cuts about 300 meters deep into its environment.
Similar to the River Rhine, the newly discovered flooded canyon features many meanders, or sharp river curves. These 'loops in the river' are part of the history of the origin of such canyons, which up to now has not really been understood in many fundamental details.
Seismic investigations of the deep subsurface show that the canyon has been stationary for at least the last ten million years. From the images of the seafloor the scientists from the Bremer Research Centre could recognise amazing details: in addition to the meanders there were also old cut off arms, diverse branching points, the change from steeper to flatter areas of the canyon, and also levees on the border of the canyon.
The investigations which were carried out on board the 'Meteor' vessel suggest that deposits on the seafloor in the region of the continental slope were mobilised and transported in large quantities into the deep-sea. The 'Cape Timiris Canyon' apparently played a key role in these transport processes.
Sediment cores of about ten meters in length, which were cut out of the seafloor using a large hollow cylinder with a diameter of 12 cm, supported this assumption. They showed that time and again so-called turbidity currents - a mixture of water and sediment - flowed in the direction of the deep-sea. In time cycles each of only a few years, the currents rolled through the canyon down the continental slope.
- Actually it is hard to believe, that such large up to now unknown objects can still be found on our planet resumes Prof. Horst Schulz. "We are already excited to see the results of the further analysis of the material brought back from the expedition."
In nearby areas, the Mauritanian sea floor is seismically mapped for the supposed occurrence of petroleum. However, the oil surveys have not reached the area off the famous Banque d'Arguin offshore national park, where the 'Cape Timiris Canyon' is located.
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