Parts of the Atlas Mountains in Morocco are flat due to specific tectonic uplift histories
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Geological literature reports that parts of the Atlas mountain system feature elevated, low-relief provinces such as the Tabular Middle Atlas, which are shaped by regional tectonic and uplift histories.
The Atlas Mountains are a mountain range in the Maghreb in North Africa. They separate the Sahara from the Mediterranean Sea and the Atlantic Ocean; the mountain range stretches around 2,500 km (1,600 mi) through Morocco, Algeria and Tunisia. The mountains are associated with the Titan Atlas. The range's highest peak is Toubkal, in central Morocco, with an elevation of 4,167 metres (13,671 ft). T
The Anti-Atlas Mountains are believed to have originally been formed as part of the Alleghenian orogeny. These mountains were formed when Africa and America collided and were once a chain rivaling today's Himalayas. Today, the remains of this chain can be seen in the Fall Line region in the Eastern United States. Some remnants can also be found in the later formed Appalachians in North America.
A second phase took place during the Mesozoic Era (before ~66 My). It consisted of a widespread extension of the Earth's crust that rifted and separated the continents mentioned above. This extension was responsible for the formation of many thick intracontinental sedimentary basins including the present Atlas. Most of the rocks forming the surface of the present High Atlas were deposited under the ocean at that time.
In the Paleogene and Neogene Periods (~66 million to ~1.8 million years ago), the mountain chains that today constitute the Atlas were uplifted, as the land masses of Europe and Africa collided at the southern end of the Iberian Peninsula. Such convergent tectonic boundaries occur where two plates slide towards each other forming a subduction zone (if one plate moves underneath the other), and/or a continental collision (when the two plates contain continental crust). In the case of the Africa-Europe collision, it is clear that tectonic convergence is partially responsible for the formation of the High Atlas, as well as for the closure of the Strait of Gibraltar and the formation of the Alps and the Pyrenees.
However, there is a lack of evidence for the nature of the subduction in the Atlas region, or for the thickening of the Earth's crust generally associated with continental collisions. One of the most striking features of the Atlas to geologists is the relatively small amount of crustal thickening and tectonic shortening despite the important altitude of the mountain range. Recent studies suggest that deep processes rooted in the Earth's mantle may have contributed to the uplift of the High and Middle Atlas.
The Tell Atlas is a mountain chain over 1,500 kilometres (900 mi) in length, belonging to the Atlas mountain ranges and stretching from Eastern…
<p>The Middle Atlas mountain range represents the northeastern branch of the Atlas system, which spans approximately 2000 km from the Atlantic coast of Morocco to Tunisia. The Atlas system is a prominent example of active intracontinental mountain belts that developed in the African plate of the Cenozoic Alpine belt.</p><p>The Middle Atlas is an inverted Mesozoic rift that began to rise during the late Cretaceous with limited crustal thickening. It can be divided into two geomorphological provinces: 1) an elevated, low-relief area called Tabular Middle Atlas (TMA), which is located in the north-western orogenic sectors and consists of weakly deformed Mesozoic sediments in stratigraphic contact with the Paleozoic basement of the western Meseta, and 2) a deeply dissected, high-relief area known as Folded Middle Atlas to the southeast, where crustal deformation is dominated by transpressive tectonics induced by a NNW-SSE maximum shortening direction. Seismicity and geomorphic landforms suggest that tectonic deformation is still active, at least in some sectors of the orogen.</p><p>In order to investigate the tectonic evolution of the Middle Atlas, we combined structural and geomorphic analysis. Although the age control of the continental syn-orogenic deposits is limited, the eastern boundary of the orogen shows evidence of recent tectonic deformation and flexural subsidence with the development of a foreland basin. Conversely, the western boundary of the orogen does not include syn-orogenic foreland basins suggesting the lack of flexural subsidence. This boundary is also characterized by alkaline late Miocene-Quaternary lava flows over a wide surface of ca. 960 km<sup>2</sup>. These lava flows cover part of the TMA where they fill valleys crossing the Meseta and draining towards the Atlantic Ocean. The degree of subsequent fluvial incision of the lavas is lower in the TMA than in the Meseta. While incision does not go beyond the stratigraphic contact lava-substratum in the TMA, it goes further down in the Meseta indicating a higher magnitude of uplift. The lack of contractional deformation, however, suggests that such an uplift is not controlled by tectonics.</p><p>Overall, our preliminary observations suggest the occurrence of an asymmetry between the two orogenic flanks. Uplift along the eastern orogenic boundary has been triggered by late Cenozoic contractional deformation, whereas deep-seated, most likely mantle-driven processes essentially control uplift of the western boundary.</p>
Le rôle du manteau asténosphérique dans le développement de la topographie des systèmes Atlas-Meseta (Maroc)
L'interaction entre le soulèvement, principalement contrôlé par la tectonique ou les mécanismes profonds liés à la dynamique du manteau, et l'efficacité des processus de surface, principalement déterminée par le climat, module la croissance et la décroissance de la topographie à diverses échelles temporelles et spatiales. Dans les contextes tectoniquement calmes, quelques études de terrain ont montré que le contrôle principal de la topographie est exercé par l'érodabilité du substratum rocheux et, dans une moindre mesure, par le climat. Les régions qui ont connu une augmentation des taux de soulèvement (c'est-à-dire un rajeunissement topographique) sont en déséquilibre et sont caractérisées par la coexistence d'un paysage transitoire qui conserve encore les conditions aux limites précédentes et d'une topographie abrupte qui s'est déjà adaptée aux nouveaux taux de soulèvement
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