À partir de Cᵉ siècle av. J.-C.
Sahara and north-west Africa
Traduction non disponible · Original (anglais) · français indisponible
The Sahara Palaeoclimatic Sequence comprises alternating humid and arid phases documented through drainage systems, lacustrine deposits, fossil soils, animal distributions, and archaeological sediments. The extract emphasizes that the desert was substantially wetter during parts of the Pleistocene, allowing rivers, lakes, vegetation corridors, and central African fauna to extend into areas now arid. It presents the Villafrancian, Mazzerian, Ougartian, Saourian, and Guirian episodes as a proposed north-west African sequence.
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Le récit
The Sahara was not uniformly arid throughout its geological history. During several Pleistocene episodes, wetter climates supported streams, lakes, spring activity, and vegetation corridors across landscapes that are now dominated by wind erosion. The surviving evidence includes drainage channels, lacustrine sediments, fossil soils, and the presence of animals whose movement into the desert required access to water or vegetated routes.
Modern desert processes have nevertheless left a powerful imprint. Wind erosion produced broad pediplains, accumulated coarse sands into ergs or regs, and exposed bare rock surfaces known as hammadas. Internal depressions, including the Qattara Depression, became sites of alluviation, spring activity, and lake sedimentation when wetter conditions raised groundwater levels or increased runoff.
The drainage record points to former river systems of considerable extent. Wadi Saoura was traced for more than 500 kilometres and once carried enough water to remove aeolian sands from reaches now choked by them. In the eastern Sahara, wadis descending from the Red Sea hills drained large areas; Wadi Kharit carried sediments into the Kom Ombo plain, where fine-grained alluvial deposits exceed 100 metres in thickness.
The north-west Saharan sequence is organized around alternating humid and arid intervals. The Villafrancian pluvial was followed by an arid post-Villafrancian phase, then by the Mazzerian, Ougartian I, Ougartian II, Saourian, and Guirian humid episodes, with intervening arid phases marked by erosion, aeolian sands, scree, or palaeosols. Archaeological traces range from crudely worked pebble tools to possible middle Acheulian and Neolithic materials.
Villafrancian pluvial
Mazzerian pluvial
Ougartian I and II pluvials
Saourian pluvial
Guirian wet episode
The extract proposes correlations between the four principal north-west Saharan pluvials and East African climatic phases: the Mazzerian with the Kageran, Ougartian I with the Kamasian, Ougartian II with the Kanjeran, and Saourian with the Gamblian. It also suggests that the Guirian may correspond to post-Gamblian humid stages. These comparisons remain provisional, as the text stresses the need for further palaeomagnetic and radiometric work.
À partir de Cᵉ siècle av. J.-C.
Sahara and north-west Africa
Traduction non disponible · Original (anglais) · français indisponible
The Sahara Palaeoclimatic Sequence comprises alternating humid and arid phases documented through drainage systems, lacustrine deposits, fossil soils, animal distributions, and archaeological sediments. The extract emphasizes that the desert was substantially wetter during parts of the Pleistocene, allowing rivers, lakes, vegetation corridors, and central African fauna to extend into areas now arid. It presents the Villafrancian, Mazzerian, Ougartian, Saourian, and Guirian episodes as a proposed north-west African sequence.
Poursuivre l’exploration
Le récit
The Sahara was not uniformly arid throughout its geological history. During several Pleistocene episodes, wetter climates supported streams, lakes, spring activity, and vegetation corridors across landscapes that are now dominated by wind erosion. The surviving evidence includes drainage channels, lacustrine sediments, fossil soils, and the presence of animals whose movement into the desert required access to water or vegetated routes.
Modern desert processes have nevertheless left a powerful imprint. Wind erosion produced broad pediplains, accumulated coarse sands into ergs or regs, and exposed bare rock surfaces known as hammadas. Internal depressions, including the Qattara Depression, became sites of alluviation, spring activity, and lake sedimentation when wetter conditions raised groundwater levels or increased runoff.
The drainage record points to former river systems of considerable extent. Wadi Saoura was traced for more than 500 kilometres and once carried enough water to remove aeolian sands from reaches now choked by them. In the eastern Sahara, wadis descending from the Red Sea hills drained large areas; Wadi Kharit carried sediments into the Kom Ombo plain, where fine-grained alluvial deposits exceed 100 metres in thickness.
The north-west Saharan sequence is organized around alternating humid and arid intervals. The Villafrancian pluvial was followed by an arid post-Villafrancian phase, then by the Mazzerian, Ougartian I, Ougartian II, Saourian, and Guirian humid episodes, with intervening arid phases marked by erosion, aeolian sands, scree, or palaeosols. Archaeological traces range from crudely worked pebble tools to possible middle Acheulian and Neolithic materials.
Villafrancian pluvial
Mazzerian pluvial
Ougartian I and II pluvials
Saourian pluvial
Guirian wet episode
The extract proposes correlations between the four principal north-west Saharan pluvials and East African climatic phases: the Mazzerian with the Kageran, Ougartian I with the Kamasian, Ougartian II with the Kanjeran, and Saourian with the Gamblian. It also suggests that the Guirian may correspond to post-Gamblian humid stages. These comparisons remain provisional, as the text stresses the need for further palaeomagnetic and radiometric work.