16 research outputs found
PALĂORIVAGES, DUNES CĂTIĂRES ET OCCUPATIONS HUMAINES Ă LâEMBOUCHURE DE LâOUED TAMRI, MAROC ATLANTIQUE, AU PLĂISTOCĂNE SUPĂRIEUR (SIM 5)
A lâembouchure de lâoued Tamri, rive gauche, un palĂ©orivage de faciĂšs marin et fluvio-marin (unitĂ© U1) culmine aux environs de + 6m a.s.l. Une coquille marine de Patella sp. prĂ©levĂ©e dans cette unitĂ© U1 (faciĂšs marin) a Ă©tĂ© datĂ©e 100,02 ± 1,662 ka et 101,188 ± 1,339 ka par la mĂ©thode U/Th (SIM 5.3). La dune surincombante (sĂ©rie Sx) a Ă©tĂ© datĂ©e par OSL 84 ± 4 ka (SIM 5.1). A Tighrine Imksawne, Ă 200 m au Sud de lâembouchure, ce palĂ©orivage est surmontĂ© dâune sĂ©quence de dĂ©pĂŽts dunaires et colluviaux de plus de 20 m dâĂ©paisseur. Ces derniers renferment plusieurs palĂ©osols rubĂ©fiĂ©s interstratifiĂ©s et des encroĂ»tements, tĂ©moins de pĂ©riodes humides et de ruissellements, qui permettent de distinguer trois unitĂ©s principales (unitĂ©s U2, U3, U4) :(U2), unitĂ© dâaccumulation interdunaire infĂ©rieure, oĂč dominent les faciĂšs dĂ©tritiques continentaux de colluvionnement/ruissellement, avec de nombreux HĂ©licidĂ©s et de rares tĂ©moins dâoutillage lithique. (U3), unitĂ© dâaccumulation Ă©olienne moyenne, Ă sĂ©ries dunaires encroĂ»tĂ©es, oĂč la sĂ©rie (S5) a Ă©tĂ© datĂ©e par OSL 92 ± 6 ka (SIM 5.3 ou SIM 5.2), et oĂč le palĂ©osol rubĂ©fiĂ© (S6) a fourni une industrie Ă proto-hachereaux. (U4), unitĂ© dâaccumulation Ă©olienne supĂ©rieure Ă sĂ©ries friables, sĂ©parĂ©e de la prĂ©cĂ©dente par une palĂ©o-surface encroĂ»tĂ©e (S6/S7) Ă industrie probablement Ă©pipalĂ©olithique, et oĂč des coquilles dâĆufs dâAutruche de la sĂ©rie (S8) sont datĂ©es par radiocarbone Ă plus de 30 ka. BPLes analyses gĂ©omorphologiques, sĂ©dimentologiques et pĂ©trographiques aboutissent Ă un modĂšle sĂ©dimentaire dâaccumulation de pied de falaise morte qui permet de rĂ©pondre aux contradictions apparentes entre la position de lâindustrie lithique et des datations.A lâembouchure de lâoued Tamri, rive gauche, un palĂ©orivage de faciĂšs marin et fluvio-marin (unitĂ© U1) culmine aux environs de + 6m a.s.l. Une coquille marine de Patella sp. prĂ©levĂ©e dans cette unitĂ© U1 (faciĂšs marin) a Ă©tĂ© datĂ©e 100,02 ± 1,662 ka et 101,188 ± 1,339 ka par la mĂ©thode U/Th (SIM 5.3). La dune surincombante (sĂ©rie Sx) a Ă©tĂ© datĂ©e par OSL 84 ± 4 ka (SIM 5.1). A Tighrine Imksawne, Ă 200 m au Sud de lâembouchure, ce palĂ©orivage est surmontĂ© dâune sĂ©quence de dĂ©pĂŽts dunaires et colluviaux de plus de 20 m dâĂ©paisseur. Ces derniers renferment plusieurs palĂ©osols rubĂ©fiĂ©s interstratifiĂ©s et des encroĂ»tements, tĂ©moins de pĂ©riodes humides et de ruissellements, qui permettent de distinguer trois unitĂ©s principales (unitĂ©s U2, U3, U4) :(U2), unitĂ© dâaccumulation interdunaire infĂ©rieure, oĂč dominent les faciĂšs dĂ©tritiques continentaux de colluvionnement/ruissellement, avec de nombreux HĂ©licidĂ©s et de rares tĂ©moins dâoutillage lithique. (U3), unitĂ© dâaccumulation Ă©olienne moyenne, Ă sĂ©ries dunaires encroĂ»tĂ©es, oĂč la sĂ©rie (S5) a Ă©tĂ© datĂ©e par OSL 92 ± 6 ka (SIM 5.3 ou SIM 5.2), et oĂč le palĂ©osol rubĂ©fiĂ© (S6) a fourni une industrie Ă proto-hachereaux. (U4), unitĂ© dâaccumulation Ă©olienne supĂ©rieure Ă sĂ©ries friables, sĂ©parĂ©e de la prĂ©cĂ©dente par une palĂ©o-surface encroĂ»tĂ©e (S6/S7) Ă industrie probablement Ă©pipalĂ©olithique, et oĂč des coquilles dâĆufs dâAutruche de la sĂ©rie (S8) sont datĂ©es par radiocarbone Ă plus de 30 ka. BPLes analyses gĂ©omorphologiques, sĂ©dimentologiques et pĂ©trographiques aboutissent Ă un modĂšle sĂ©dimentaire dâaccumulation de pied de falaise morte qui permet de rĂ©pondre aux contradictions apparentes entre la position de lâindustrie lithique et des datations
CÎnes plio-quaternaires du piémont nord de l'Anti-Atlas occidental (Maroc) et leur évolution récente
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Modélisation du transport éolien dans le systÚme plage-dune de la baie d'El Haouzia (cÎte atlantique marocaine)
International audienc
Evolution géomorphologique quaternaire de la bordure anti-atlasique de la partie centrale de la plaine du Souss (Maroc)
La partie centrale de la plaine du Souss sâĂ©tend entre le Haut Atlas au nord et lâAnti-Atlas au sud sur 40 km de large. Sa morphologie montre une prĂ©dominance des formes hĂ©ritĂ©es, tant dans les rĂ©gions proximales des piĂ©monts que dans leurs parties distales. Dans les rĂ©gions proximales subsistent les restes dâau moins trois gĂ©nĂ©rations principales de cĂŽnes de dĂ©jections, plus Ă©tendus et plus aplatis sur le piĂ©mont anti-atlasique que sur le piĂ©mont atlasique, les deux premiĂšres Ă©tant conservĂ©es grĂące aux cimentations et encroĂ»tements calcaires. La troisiĂšme gĂ©nĂ©ration de cĂŽnes, cĂŽnes adventices, essentiellement limono-sableuse en surface, occupe les parties moyennes et distales. Le systĂšme morphogĂ©nique majeur est hĂ©ritĂ© de la transition plio-plĂ©istocĂšne « plio-villafranchien ». De cette Ă©poque la plaine conserve les parties apicales encroĂ»tĂ©es des cĂŽnes et le soubassement carbonatĂ© de sa rĂ©gion centrale, entre El Freija et Ouled TeĂŻma, tĂ©moins de lâexistence de palĂ©olacs. Ce systĂšme dĂ©jĂ consolidĂ© est aussi tectonisĂ©. Dans les rĂ©gions distales, la vallĂ©e actuelle du Souss entaille Ă peine dâĂ©paisses accumulations carbonatĂ©es, restes dâau moins deux gĂ©nĂ©rations de palĂ©olacs contemporaines des cĂŽnes anciens. Depuis la transition PlĂ©istocĂšne-HolocĂšne, les cĂŽnes adventices et le lit majeur de lâoued Souss donnent naissance, en surface, Ă un modelĂ© fluvio-Ă©olien particuliĂšrement actif depuis la transition PlĂ©istocĂšne-HolocĂšne.The middle part of the Souss plain extends over 40 km between the High Atlas in the north and Anti-Atlas in the south. Its morphology between Taroudannt and the Admine Forest shows a dominance of inherited forms, both in proximal regions of piedmont and in their distal parts. Relics of at least three main generations of alluvial fans remain in proximal regions, which are vaster and more flattened on the anti-atlasic piedmont than on the atlasic one; the first two ones being preserved owing to the incrusted limestones and cementations. The third generation of alluvial fans - adventitious cones - essentially composed of sandy loam in surface, occupies both the median and distal parts. The major morphogenic system is inherited from the Plio-Pleistocene (or Plio-Villafranchian) transition. From that period, the plain has kept incrusted cone apical parts as well as a carbonated bedrock in its central part, between El Freija and Ouled TeĂŻma, witnesses of the existence of palaeolakes. This system, already consolidated, is also tectonised. In distal parts, the current Souss Valley hardly cuts thick carbonated accumulations representing remains of at least two generations of contemporaneous palaeoplayas of the former alluvial fans. Since the Pleistocene-Holocene transition, adventitious cones and the major bed of the Souss wadi have given birth to a particularly active fluvio-eolian relief, on surface
Geospatial modelling for sinkholes hazard in the coastal area of Abda-Doukkala, Morocco
16ÂȘ ConferĂȘncia Internacional, realizada na Costa da Caparica, de 12-16 setembro de 2022.info:eu-repo/semantics/publishedVersio
Modélisation du transport éolien dans le systÚme plage-dune de la baie d'El Haouzia (cÎte atlantique marocaine)
Coastal dunes raise a special problem to scientists because of the high dynamic nature of most beach-dune systems. Coastal dunes can change shape quickly and frequently due to the violence of winds and waves during storms. This study analyses and interprets spatial and temporal patterns in sediment volume changes in a beach-dune system using different aeolian transport formulas.During the measurements (24 campaigns), traps allowed to collect particles transported by the wind in order to determine the grains size and the critical shear velocity. For the grains size, the mode varies between 160 and 250 ”m. The critical shear velocity is 0.23 m.s-1. Measured wind velocities range from 7.45 to 13.13 m.s-1. The transport flow varies between 0.19 and 1.14 kg.m-1.min-1. The measured transport rates were compared with the predictions of different models. The BAGNOLD-equation, using roughness length (zo) of 0.1 mm (S.M. ARENS, 1997) and adjustment length (K = 1.2), proved to have the best predictive ability: for every trap, the predictions are in the 95 percent confidence interval of the measurements (Root Mean Square = 30 %).The amount and direction of annual net transport have been computed with the BAGNOLD-equation. On the El Haouzia beach there is a positive transport flux in the direction of the dune field. This causes an annual increase of the average dune height of several centimetres. The used sand traps were compared
Flash Floods in the Guelmim Area/Southwest MoroccoâUse of Remote Sensing and GIS-Tools for the Detection of Flooding-Prone Areas
The violent storms of 22â30 November 2014, resulted in flash floods and wadi floods (rivers) in large parts of Southern Morocco, at the foot of the Atlas Mountains. The Guelmim area was the most affected part with at least 32 fatalities and damages due to inundations. The flooding hazard in the Guelmim region initiated this study in order to investigate the use of remote sensing and geographic information system (GIS) for the detection and identification of areas most likely to be flooded in the future again due to their morphologic properties during similar weather conditions. By combining morphometric analysis and visual interpretation based on Landsat 8 satellite data and derived images such as water index (NDWI) images, areas with relatively higher soil moisture and recently deposited sediments were identified. The resulting maps of weighted overlay procedures, aggregating causal, morphometric factors influencing the susceptibility to flooding (lowest height levels, flattest areas), allowed for the distinguishing of areas with higher, medium and lower susceptibility to flooding. Thus, GIS and remote sensing tools contribut to the recognition and mapping of areas and infrastructure prone to flooding in the Guelmim area
The typology of slope slides of the cliff coast of Safi-Morocco, and the role of the clay layer in triggering failure
International audienc