Central High Atlas Mountains Research Articles

New Middle to ?Late Jurassic dinosaur tracksites in the Central High Atlas Mountains, Morocco.

Besides bones, fossil tracks and trackways are important sources of knowledge about dinosaur palaeobiology. Here, we report three new tracksites from two different synclines in the Imilchil area, Central High Atlas, Morocco. The tracks and trackways are preserved in fluvial deposits in different levels of the Isli Formation (Early Bathonian-?Upper Jurassic), and contain impressions made by sauropods, theropods and ornithopods, as well as tracks that might represent bird-like non-avian theropod dinosaurs. In addition to traditional field measurements, three-dimensional digital models of the track sites were created using photogrammetry. These new tracksites add to the rich faunal ichnoassemblage already recorded from the High Atlas Mountains and North Africa, which is considerably richer than the contemporaneous body fossil record, and also provide new data on dinosaurs-substrate interactions.

First record of Brongersma's toad Barbarophryne brongersmai (Anura, Bufonidae) in the central High Atlas Mountains, Morocco

Brongersma’s toad Barbarophryne brongersmai is known in the southern Moroccan Atlantic coast, in the Anti–Atlas, in the arid plain of Marrakech, and in several localities in North–western Algeria. However, its distribution in Morocco is far from clear and its range is not well known. We report a new record of B. brongersmai in Morocco, in the region of the central High Atlas. The habitat type in this region is different from areas where the species has been observed previously. It consists of temporary ponds, located between rock outcrops and filled by stormy rains or snow during the winter. We recommend conducting surveys to collect additional information about this toad in other Moroccan regions, such as in the Middle Atlas where suitable conditions for this species may exist. Dataset published through Zenodo (Doi:

Human–carnivore conflict management in the central High Atlas mountains of Morocco

Human–carnivore conflict management in the central High Atlas mountains of Morocco

Geological and geophysical studies of the Agoudal impact structure (Central High Atlas, Morocco): New evidence for crater size and age

AbstractSince the discovery of shatter cones (SCs) near the village of Agoudal (Morocco, Central High Atlas Mountains) in 2013, the absence of one or several associated circular structures led to speculation about the age of the impact event, the number, and the size of the impact crater or craters. Additional constraints on the crater size, age, and erosion rates are obtained here from geological, structural, and geophysical mapping and from cosmogenic nuclide data. Our geological maps of the Agoudal impact site at the scales of 1:30,000 (6 km2) and 1:15,000 (2.25 km2) include all known occurrences of SCs in target rocks, breccias, and vertical to overturned strata. Considering that strata surrounding the impact site are subhorizontal, we argue that disturbed strata are related to the impact event. Three types of breccias have been observed. Two of them (br1‐2 and br2) could be produced by erosion–sedimentation–consolidation processes, with no evidence for impact breccias, while breccia (br1) might be impact related. The most probable center of the structure is estimated at 31°59′13.73ʺN, 5°30′55.14ʺW using the concentric deviation method applied to the orientation of strata over the disturbed area. Despite the absence of a morphological expression, the ground magnetic and electromagnetic surveys reveal anomalies spatially associated with disturbed strata and SC occurrences. The geophysical data, the structural observations, and the area of occurrence of SCs in target rocks are all consistent with an original size of 1.4–4.2 km in diameter. Cosmogenic nuclide data (36Cl) constrain the local erosion rates between 220 ± 22 m Ma−1 and 430 ± 43 m Ma−1. These erosion rates may remove the topographic expression of such a crater and its ejecta in a time period of about 0.3–1.9 Ma. This age is older than the Agoudal iron meteorite age (105 ± 40 kyr). This new age constraint excludes the possibility of a genetic relationship between the Agoudal iron meteorite fall and the formation of the Agoudal impact site. A chronolgy chart including the Atlas orogeny, the alternation of sedimentation and erosion periods, and the meteoritic impacts is presented based on all obtained and combined data.

Volume–biomass functions reveal the effect of browsing on three Moroccan dwarf shrubs

We studied the effects of browsing on the plant architecture and volume-biomass relationships of three dominant dwarf shrubs – Artemisia herba-alba, A. mesatlantica and Teucrium mideltense – in a sagebrush steppe in the Central High Atlas Mountains, southern Morocco. For this purpose, we developed power-law volume-biomass functions based on nonlinear regressions for each of these species, under both browsed and unbrowsed conditions. These functions were then applied to individual-based annual monitoring data from inside and outside a browsing exclosure to calculate standing biomass for each of the years from 2004 to 2009. The biomass of the three species was well predicted by the allometric functions, and different functions for the browsed and unbrowsed conditions reflected changes in plant architecture. Browsing had a significant negative impact on biomass for A. herba-alba but not for A. mesatlantica, whereas its effects on T. mideltense were inconsistent between years. The fact that the latter two species hardly benefited from browsing exclusion might be because of increased competition from the more dominant A. herba-alba. During the study period, the standing biomass increased whether or not there was browsing, which might be because of the recovery of the shrubs after a preceding severe drought. Further studies are needed in order to investigate the generality of the findings.

Comparative analysis of Late Jurassic sauropod trackways from the Jura Mountains (NW Switzerland) and the central High Atlas Mountains (Morocco): implications for sauropod ichnotaxonomy

Late Jurassic sauropod trackways from the Jura Mountains (NW Switzerland) and the central High Atlas Mountains (Morocco) are described and compared. Emphasis is put on track preservation and trackway configuration. The trackways are similar with respect to preservation and the pes and manus track outlines, but they show a large range of trackway configuration. Only one of the trackways reveals digit and claw impressions, and thus differences in trackway gauge and the position of pes and manus tracks are the most explicit characters for their distinction. The Late Jurassic to Early Cretaceous ichnotaxa Brontopodus, Parabrontopodus and Breviparopus are reviewed and a differential diagnosis is given for the trackways studied. The reference trackway of Breviparopus corresponds to one of the studied trackways of Morocco. Parabrontopodus and Breviparopus are considered to be both valid ichnotaxa, even though we recommend the latter to be formally erected based on better-preserved tracks than those currently exposed. The analysed trackways and ichnotaxa suggest that trackway configuration, notably trackway gauge (width), is not decisively influenced by extrinsic factors such as ontogenetic stage, locomotion speed and substrate properties. However, it cannot be excluded that it is related to other factors such as individual behaviour or even sexual dimorphism.

Didactyl, tridactyl and tetradactyl theropod trackways from the Lower Jurassic of Morocco: evidence of limping, labouring and other irregular gaits

Two theropod trackways with alternating long–short pace lengths and a didactyl theropod trackway were discovered from Ait Blal tracksite situated in central High Atlas Mountains, Morocco. They are described here together with other tridactyl and tetradactyl footprints. The track-bearing bed belongs to the Lower Jurassic (Pliensbachian) Aganane Formation. One of the theropod trackways with alternating pace lengths indicates locomotion by a limping dinosaur. In this trackway, the pathological irregularities in the morphology of right footprints suggest that the trackmaker had injured its right foot. Another trackway with alternating pace lengths suggests the accidental problem while walking of theropod trackmaker. The morphology of the didactyl theropod trackway may be attributable to a dromaeosaurid or dromaeosaurid-like trackmaker whose body fossil remains have not been reported from the Jurassic. If the trackmaker of the didactyl prints was a dromaeosaurid, the discovery supports the idea that dromaeosaurid dinosaurs had early origins and also are ancestral to birds.

A reconstruction of Tazoudasaurus naimi (Dinosauria, Sauropoda) from the late Early Jurassic of Morocco

The basal sauropod Tazoudasaurus naimi from the late Early Jurassic of Morocco is represented by at least ten juvenile to adult individuals. Over the past seven years, the Toundoute continental series of Ouarzazate Province, a lateral equivalent of the Azilal and Wazzant Formations of the central High Atlas mountains (Toarcian to Early Aalenian age), produced over 600 skeletal elements pertaining to Tazoudasaurus. About a fifth of the available material has been prepared and studied. Except for the skull, the osteology of Tazoudasaurus is completely known. Superb preservation and the abundance of osteological data from the presently known Tazoudasaurus individuals make it possible to provide a detailed skeletal reconstruction for the first time.

Crustal structure under the central High Atlas Mountains (Morocco) from geological and gravity data

Seismic wide angle and receiver function results together with geological data have been used as constraints to build a gravity-based crustal model of the central High Atlas of Morocco. Integration of a newly acquired set of gravity values with public data allowed us to undertake 2–2.5D gravity modelling along two profiles that cross the entire mountain chain. Modelling suggests moderate crustal thickening, and a general state of Airy isostatic undercompensation. Localized thickening appears restricted to the vicinity of a north-dipping crustal-scale thrust fault, that offsets the Moho discontinuity and defines a small crustal root which accounts for the minimum Bouguer gravity anomaly values. Gravity modelling indicates that this root has a northeasterly strike, slightly oblique to the ENE general orientation of the High Atlas belt. A consequence of the obliquity between the High Atlas borders and its internal and deep structure is the lack of correlation between Bouguer gravity anomaly values and topography. Active buckling affecting the crust, a highly elevated asthenosphere, or a combination of both are addressed as side mechanisms that help to maintain the high elevations of the Atlas mountains.

Climatic and tectonic control of Ordovician sedimentation in the western and central High Atlas (Morocco)

The sedimentology of Ordovician deposits in the western and central High Atlas mountains defines several depositional environments: tidal-dominated littoral; wave- and storm-dominated delta, tidal-dominated delta; wave- and storm-dominated shelf. The sediments are mainly siliciclastic and mixed limestone-sili ciclastic, with sparse deposits of ooidal ironstone, basal transgressive sand, and glauconite. The sediments were derived from different levels of the Pan-African chain in the Lower and Middle Ordovician, and from the Sahara in the Upper Ordovician. The sedimentary and sequential evolution indicate that deposition occurred in two independents epeiric seas, influenced mainly by the interplay of tectonics and climate.

A survey of multi-stage diagenesis and dolomitization of Jurassic limestones along a regional shelf-to-basin transect in the Ziz Valley, Central High Atlas Mountains, Morocco

Abstract Petrographic and geochemical data from five localities in the Ziz Valley of Morocco indicate that Jurassic limestones have undergone early diagenesis that varied with location from shelf to basinal settings, burial diagenesis that was most pronounced in basinal settings, and late diagenesis caused by compression and uplift of the High Atlas Mountains. Marine cements occur at all five localities from shelf-to-basin center, although cement types vary from peloidal microcrystalline cements updip on the shelf-to-equant calcite in basinal settings. Presence of moldic grains and/or Mg-poor, Fe-poor blocky cements suggest that meteoric waters influenced early diagenesis at all shelf localities and on an upturned fault block in the basinal region, leaving only one locality unaffected by early meteoric processes. 87 Sr/ 86 Sr ratios of 0.70810–0.70895 (greater than 87 Sr/ 86 Sr of coeval limestones), Mg contents that decrease upward from 47.5 to 43.0 mol% MgCO 3 , presence of dolomitized marine cements, and dolomite cements that postdate marine cements but predate meteoric-to-burial cements suggest that dolomitization and dolomite cementation at two shelf localities took place in mixed meteoric and marine waters early in diagenesis. However, poorer preservation of depositional fabrics, lower δ 18 O values, and larger and more anhedral crystals suggest that dolostones downdip underwent later modification during burial, whereas those updip did not. Compaction during diagenesis generated numerous concavo–convex and sutured intergranular contacts at updip shelf, downdip shelf, and basinal localities where earlier meteoric cementation was not extensive. Compaction was insignificant in more extensively cemented mid-shelf settings. High Sr (1200–3800 ppm) and Fe (1000–2300 ppm) contents in brachiopod grains suggest that LMC components underwent some modification during burial in basinal settings in Sr-rich reducing waters. Fe contents of late intergranular cements increase from 2000 ppm at the basin's edge to as much as 6000 ppm in the basin's center. Bedding-parallel stylolites occur at all localities. The most negative δ 18 O values of sparry dolomites near the Tizi n'Firest fault (−6.2‰ vs. PDB) imply diagenetic temperatures of 65–85°C assuming water δ 18 O values of 0.0–2.0‰ vs. SMOW. Those temperatures are much less than previous estimates of burial temperatures in the High Atlas basin. An isotopic gradient extrapolating to roughly 5‰/km in diagenetically modified dolostones likewise suggests a geothermal gradient less than gradients previously proposed for at least parts of the area. Comparison of morphologies of transverse stylolites, which are found at all localities, with morphologies of bedding parallel stylolites suggests that transverse stylolites formed due to compression during late diagenesis. Uplift accompanying that compression allowed influx of low-Mg waters that, along with other factors, caused calcitization of dolomites. The Fe concentration of calcite that fills late fractures increases from less than 2000 ppm at the basin center to values in excess of 3000 ppm at the basin edge, opposite trends in earlier cements and reflecting uplift of the High Atlas Mountains and resultant changes in patterns of groundwater flow.

Cenozoic sedimentary dynamics of the Ouarzazate foreland basin (Central High Atlas Mountains, Morocco)

Cenozoic continental sedimentary deposits of the Southern Atlas named "Imerhane Group" crop out (a) in the Ouarzazate foreland basin between the Precambrian basement of the Anti Atlas and the uplifted limestone dominated High Atlas, and (b) in the Ait Kandoula and Ait Seddrat nappes where Jurassic strata detached from the basement have been thrust southwards over the Ouarzazate Basin. New biostratigraphic and geochronological data constraining the final Eocene marine regression, the characterization of the new "Ait Ouglif Detrital Formation" presumed to be of Oligocene age, and the new stratigraphic division proposed for the Continental Imerhane Group clarify the major tectonogenetic alpidic movements of the Central High Atlas Range. Four continental formations are identified at regional scale. Their emplacement was governed principally by tectonic but also by eustatic controls. The Hadida and Ait Arbi formations (Upper Eocene) record the major Paleogene regression. They are composed of margino-littoral facies (coastal sabkhas and fluviatile systems) and reflect incipient erosion of the underlying strata and renewed fluvial drainage. The Ait Ouglif Formation (presumed Oligocene) had not been characterized before. It frequently overlies all earlier formations with an angular unconformity. It includes siliciclastic alluvial deposits and is composed predominantly of numerous thin fining-upward cycles. The Ait Kandoula Formation (Miocene–Pliocene) is discordant, extensive, and represents a thick coarsening-upward megasequence. It is composed of palustro-lacustrine deposits in a context of alluvial plain with localized sabkhas, giving way to alluvial fans and fluviatile environments. The Upper Conglomeratic Formation (Quaternary) is the trace of a vast conglomeratic pediment, forming an alluvial plain and terraces. The second and third formations correspond to two megasequences engendered by the uplift of the Central High Atlas in two major compressive phases during late Oligocene and Miocene–Pliocene times. These two geodynamic events were separated by a tectonically calm phase, materialized by palustro-lacustrine sedimentation (Gorler et al. 1988). Tectono-sedimentary analysis of the two megasequences shows that the basin structure and depositional processes were controlled by the compressive tectonic context generated by the collision of North Africa and Iberia in Tertiary times (Jacobshagen et al. 1988). The Quaternary Formation was apparently controlled by a tectonic continuum and by climatic variations.

Les ammonites du Sinémuriensupérieur du Jebel-Bou-Hamid (Haut-Atlas central, Rich, Maroc). Approches paléontologique et biostratigraphique

The examination of more than 25 ammonite taxa and their biostratigraphic succession in an exceptionally complete and fossiliferous section near Rich in the Central High Atlas Mountains (Morocco) indicates there are 10 basic biochronological units (=assemblages) for a period extending from the end of the Early Sinemurian to the Late Sinemurian. These are the most precise biostratigraphical data so far collected in North Africa for the Oxynotum and Racicostatum zones. The many newly acquired data for the Early Sinemurian and Obtusum zone complete and/or confirm an initial horizon scale recently proposed for the Béni-Mellal area of the High Atlas Mountains. Some 25 per cent of the forms identified in this paper are new and one species, Asteroceras langi nov. sp., is described. The regional distinctiveness of the fauna, which is very marked throughout the period under consideration, makes correlation with other Mediterranean regions difficult and more difficult still with North Western Europe. Consequently the widely accepted subzone scale cannot be used. Quantified analysis of morphologies shows a correlation between shell coiling patterns and variations in argillaceous supply.

Tourisme et développement local dans le Haut-Atlas marocain : questionnement et réponses / Tourism and local development in the Moroccan High Atlas Mountains : some questions and answers

ENG : Morocco! central High Atlas Mountains! integrated development! tourism! local development of mountain areas

Crise, action et mutations : le Haut-Atlas marocain et les effets d'une programmation du tourisme / Crisis, action and change : the Moroccan High Atlas Mountains and the effects of tourism programming

Abstract : The author examines the changes brought about by the implementation of a tourism development project, begun in a pilot area of the central High Atlas Mountains in 1984 as part of a Franco-Moroccan cooperative programme aimed at the developing the mountain areas of Morocco. The decision to base development on a « soft tourism » model is discussed and an assessment made of the effects of tourist activity. The assessment draws attention to the complexity of relationships between tourists and host populations and to the development of a new social group made up of tour guides and gîte owners. The emergence and the practices of this new group have revived or generated rivalry and jealousy within regional communities which were formerly considered to be united.

Basin Development and Compressional Deformation in the Central High Atlas Mountains Northwest of Errachidia (Morocco)--Rejuvenated Tectonics: ABSTRACT

The development of the central High Atlas Mountains from the Triassic until today was controlled by a set of pre-existent basement faults which were reactivated in various manners. During the Triassic a graben began to subside at the northwestern border of the African craton. The graben's development was at least temporarily linked to the opening of the Atlantic Ocean. The growing basin was filled by red detrital material from the adjacent elevated regions. Evaporites were only locally formed. Mostly the red beds show an intercalation of basic volcanics. During the early and middle Liassic, a shallow shelf with reefs existed at the southern rim of the Atlas-Gulf, from which much carbonate material was delivered into the basin. This deposition is proved by turbiditic limestones of considerable thickness in the Pliensbachian. After a further deepening of the Atlas-Gulf in the late Liassic and the early Dogger, a trend toward shallowing began in the Bajocian, enabling reefs to grow from the south into the basin. Toward the end of the middle Dogger, the trough began to fill with red detrital material. This period of red-bed sedimentation lasted until the early part of the late Cretaceous and had abundant intercalation of gypsum nearmore » the top of the sequence. Due to a transgression a short marine period followed, documented by the Cenomanian-Turonian limestones. This marine period was succeeded again by the deposition of red beds in the middle of late Cretaceous. The Jurassic sediments are sometimes penetrated by small doleritic dikes. The development of the basin was controlled by east-northeast-striking faults. During compression in the Tertiary, the /sigma//sub 3/ direction (north-northwest) of the Mesozoic basin development changed into the /sigma//sub 1/ direction of compressional deformation and the synsedimentary normal faults were reactivated as upthrusts.« less

Shelf-to-Basin Resedimented Carbonates of the Southern Margin of the Jurassic Central High Atlas Trough, Morocco: ABSTRACT

The Central High Atlas Mountains occupy the site of an Early to Middle Jurassic east-west-trending seaway known as the Central High Atlas trough. Late Triassic-Early Jurassic continental rifting, combined with a transtensional structural regime, formed a system of pull-apart basins comprising the trough. A thick sequence of carbonate shelf-to-basin-plain deposits filled the trough and were later uplifted and exposed during the Oligocene Alpine orogeny. Stratigraphic analysis of 50 km/sup 2/ located along the trough's southern shelf margin reveals a 1,200 m-thick wedge of slope and basin-plain deposits. These deposits are divided into four lithostratigraphic units: (1) pelagic mudstones, (2) channel deposits composed of grainstones and packstones interbedded with marls and mudstones, (3) turbidite deposits composed of grainstones, packstones, and wackestones cyclically interbedded with marls and mudstones, and (4) cyclically interbedded marls and mudstones. This laterally continuous thick wedge of resedimented deposits suggests that a line source of platform-margin sediments fed coalescing base-of-slope aprons. These aprons probably accumulated in an actively subsiding half-graben parallel to the shelf margin. While tectonics played the major role in basin evolution, sea level fluctuations and climate influenced the influx of carbonate and terrigenous sediments. Rapid cessation of mid-Sinemurian shallow-water platform deposition and regionally transgressive Domerian-Toarcianmore » marls indicate eustatic sea level rises affected basin sedimentation. Periodic climate changes, perhaps related to the Milankovitch effect, may have led to systematic variations in carbonate sediment supply, resulting in cyclic sedimentation.« less

Sedimentation and tectonic controls in the Early Jurassic Central High Atlas trough, Morocco

Stratigraphical and sedimentological studies of Lower Jurassic deposits at the western end of the Central High Atlas Mountains, Morocco, has led to a reappraisal of the tectonic significance of this linear feature during the critical period of the opening of the Atlantic Ocean. Lower Jurassic deposits south and east of Marrakech represent an extremely shallow water and supratidal marine carbonate accumulation that formed in fault-controlled basins at the western end of the trough. The basins were aligned east-northeast and the character and distribution of the deposits strongly suggests that no connection with the basins of the Western High Atlas existed. To the east, sediments indicate more open conditions, but no evidence of bathyal or abyssal conditions was seen. Sedimentation was probably structurally controlled by vertical tensional and compressional movements as the result of reorientation of stress between major strike-slip faults. Volcanic flows and shallow intrusions, which occur at the base of the Jurassic sequence, and associated carbonate and clastic sediments show no evidence of being part of ophiolite sequences; they more closely resemble extrusive basalt sequences associated with rifting as seen in the Triassic of the Eastern United States and the Tertiary of Northwest Europe. Evidence from this area suggests that the High Atlas seaway represented only an arm of the Tethyan Ocean, which extended along a long-standing zone of crustal weakness.

Genesis of Liassic Shallow and Deep Water Rhythms Central High Atlas Mountains, Morocco

ABSTRACT During Liassic time, carbonate sediments were deposited in a northeast-southwest oriented marine trough that now forms part of the High Atlas mountains, Morocco. Shelf and deep basin deposits of this trough consist of marls, micrites and marly micrites deposited during Late Pliensbachian and Early Toarcian time. Rocks of both shelf and deep basin origin are rhythmically arranged in vertical sequence. Carbonate rich micrite units alternate with carbonate poor marls and marly micrite units. Carbonate poor units deposited on the shelf contain a terrigenous fraction (illite, chlorite and silt-sized quartz) that can account for as much as 79% of the rock. Carbonate poor units of the deep basin also contain clays, illite and chlorite, but in smaller total amounts than occur on the shelf, ac ounting for only 30% of the rock. Detrital quartz is absent. The rhythmicity can be explained by variations in supply of siliciclastics, with the shelf environments receiving larger volumes and coarser grained materials than the offshore, basinal environment. On the shelf, rhythmicity is most probably related to climatic patterns that were responsible for controlling the supply of siliciclastics from a mature hinterland into a dominantly low energy environment of deposition on the shelf. Deep water rhythmicity can be explained in terms of 1) storms that caused entrainment of shelf clays and their subsequent redeposition in deeper, offshore areas; and 2) turbidity currents that originated at the shelf/trough margin and carried clays out into the axial part of the trough as part of the suspension load of the current, the bed load being deposited earer the shelf/trough margin.

Jurassic Proximal and Distal Carbonate Turbidites of Central High Atlas Mountains, Morocco: ABSTRACT

The Lower Jurassic sediments of the High Atlas Mountains of Morocco were deposited in a northeast-southwest-oriented trough approximately 100 km wide and 800 km long. The trough margins are characterized by carbonate and marl shelf deposits, whereas the central, axial part is characterized by offshore, deeper water carbonates and marls. The depositional history of some of the deeper water sediments can be determined from a thick, carbonate, turbidite sequence flanking the southern High Atlas shelf. Within this section (800 m thick), it is possible to trace a sequence from proximal turbidites near the base through progressively more distal turbidites in the upper part of the section. Distinctive turbidite units are observed and, when lithology and unit geometry are traced p through the section, distinct changes can be recognized. There is a reduction in bed thickness and grain size, a change in intraclast types, and an increase in bedding regularity; well-developed laminae are more common and beds become well graded. This turbidite sequence represents deposition from successive turbidity currents. The vertical changes from proximal to distal turbidites record either a deepening of the trough, a change in location of the sediment-source area, or a combination of both these factors. End_of_Article - Last_Page 778------------