Ouled Abdoun Basin
Coordinates: 32 ° 54 ′ 0 ″ N , 6 ° 57 ′ 0 ″ W.
The Ouled Abdoun Basin is a region as well as an important raw material and fossil deposit in Morocco . It is located in the central part of the country in the northern foothills of the High Atlas , about 100 km southeast of Casablanca . In addition to its wealth of fossils, the basin achieved outstanding supraregional importance due to its immense phosphate reserves , which are among the largest in the world. The phosphates are stored in a compact sediment unit consisting of limestone and marl stones, some of which are only 15 to 30 m thick, and are formed in several layers. The sequence of layers is referred to as the "phosphate series". It continues to the southwest over individual further basins to the north of the Western Sahara and is also found on the southern edge of the High Atlas. It sometimes increases in thickness, but the phosphates sometimes lose their quality. The formation of the phosphate layers extended over a period from the Upper Cretaceous to the Middle Paleocene around 72 to 48 million years ago. They have their origins in what was then a shallow sea that formed the southern edge of the former Tethys Ocean . Today the phosphates are mined economically in the order of several million tons annually in both opencast and underground mining and are exported worldwide.
Fossils can be found in all sections of the phosphate series, but they are sometimes concentrated. Due to the long formation period of the deposits of more than 25 million years, they include the Cretaceous-Paleogene boundary around 66 million years ago and the Paleocene / Eocene temperature maximum around 56 million years ago. The vast majority of fossil finds include animals, plants only play a subordinate role. According to the educational environment of the phosphate series, marine life dominates. Among these, the shark and ray-like have a prominent position, as they form the most common find category on the one hand, and are used via biostratigraphy to classify the individual layers over time. Furthermore, a larger number of bony fish is also documented. In addition, there is a very diverse reptile community . This is composed of turtles , crocodiles , mosasaurs and plesiosaurs , but also includes snakes and monitor lizards . The occurrence of various pterosaurs and birds can be regarded as remarkable , as well as that of land-dwelling animals, which include both dinosaurs and mammals . Above all, these residues indicate that the phosphate series was formed relatively close to the coast. In contrast to the finds of marine reptiles, some of which are available as complete skeletons, the material of land-living forms is more fragmented.
The first mention of phosphate layers in the Ouled-Abdoun Basin was in 1917, and commercial extraction of the raw materials began only a few years later. The rich fossil sites already known at that time led to an intensive investigation by Camille Arambourg from the mid-1930s . Over the next twenty years he worked out a detailed stratigraphic structure and chronological classification of the phosphate series, which is still in existence today. After his departure in the 1950s, scientific investigation in the Ouled Abdoun Basin largely came to a standstill. It was not until the discovery of individual remains of land-dwelling mammals in the 1990s that the focus of scientific interest returned to the region, which has remained uninterrupted to this day.
Geographical location
The Ouled Abdoun Basin is located in central Morocco about 100 km southeast of Casablanca . It is located in the western section of the Moroccan meseta. Furthermore, it belongs to several important phosphate basins in the country, which in turn form part of the Mediterranean (Tethyan) phosphogenic province , which extends as a broad deposit belt from the Middle East to the east of Brazil . In Morocco, various basins are assigned to this province. In the northeast the Ouled Abdoun Basin forms the beginning, to the southwest the Ganntour , Meskala and Sous follow , while the Oued Eddahab Basin closes the series in the Western Sahara . The individual basins are separated from one another by the atlas unfolding processes .
Of the five phosphate basins in Morocco, the Ouled Abdoun basin is the largest. It stretches over 80 km in east-west and 60 km in north-south direction and covers an area of around 9,000 km². In the east the High Atlas borders the basin, in the west the Rhamna massif . and to the south the Beni Amir plateau . In addition, the Oum er-Rbia flows around it in the south and west . The larger cities are Khouribga in the north, Oued Zem in the northeast and El Borouj in the southwest of the Ouled Abdoun Basin. The altitudes range from 500 m in the southwest to 875 m in the north. The predominantly flat landscape is determined by the dry desert climate . The heaviest precipitation falls from November to May, but it barely exceeds 400 mm over the year. The vegetation is rather sparse. The local population lives off cattle breeding and seasonal agriculture. It is spread over several localities. Groundwater is generally rare and is sometimes drawn from wells over 100 m deep.
geology
Geological sequence in the Ouled Abdoun basin
The basis of the sediment sequence is formed by paleozoic deposits consisting of mica schist and quartzites . This is followed by the layers of the Upper Cretaceous and the Paleogene , so that a large temporal hiatus exists between these and the basal layers . The lower units of the Upper Cretaceous are largely composed of marls , limestone , clay and silt stones with a thickness of up to 200 m. They are classified in the period from the Cenomanium to the Campanium . A layer of partly intensely weathered plaster forms the upper end .
The actual "phosphate series" ( série phosphatée ) can only be found in the hanging wall of this series of layers . It has a relatively uniform structure throughout the area and is stored horizontally. Four types of rock can be distinguished within the sediment sequence, which are usually also found in other phosphate deposits . The most important is represented by the phosphate rocks. These occur either as a loose, sandy-marly pseudo- oolithic phosphorites (Phospharenit) or as solid phosphate-containing limestones (Phospharudit) on. The latter are in turn baked with primary dolomite or with secondary calcite cement . In addition to this main component, clay and marl stones as well as limestone and mainly as nodules or platy silicate rocks occur as other types of rock . The sequence is differentiated into four deposit units or megasequences, which belong to the Maastrichtian (outgoing Upper Cretaceous), the Danium / Thanetian ( Paleocene ), the Ypresian (Lower Eocene ) and the Lutetian (Middle Eocene). The three lower contain the main phosphate deposits. These most important layer units are each separated from one another by a major discontinuity. In general, the phosphate series in the Ouled Abdoun basin is composed as follows:
- Maastrichtian (Megasequence A): mainly composed of sandy phosphorites, which are often bedded on clays and marls and are sometimes interrupted by limestones; lenticular silicate rocks are typical; partly yellowish in color;
- Danium / Thanetium (megasequence B): consists of sandy and marly phosphorites and siliceous marls in between; the danium is characterized by the absence of clay and marly intermediate layers, its upper end is indicated by the accumulation of the von Cardita coquandi shells;
- Ypresium (megasequence C): forms an alternating layer of yellowish to grayish sandy phosphorites, greyish phosphatic limestones and whitish to greenish marl limestones and compact greenish to brownish clay marls with silicate tubers;
- Lutetium (megasequence D): is formed as an alternating layer of silicate and calcitic marls and marly limestones in which silicate nodules are embedded and occasionally thin phosphate horizons appear.
The phosphate series shows a fluctuating thickness. In the north and northeast of the Ouled Abdoun basin, it is only about 15 to 30 m thick. The individual deposit units reach a vertical extent of 3 to 5 m with the Maastrichtian, about 3 m with the Danium / Thanetium and a good 12 m with the Ypresium, while the Lutetium is still very thin. Towards the south with sloping terrain, the phosphate series increases significantly in thickness. At the southern edge of the Ouled Abdoun Basin, the layers are 8 to 10 m thick for the Maastrichtian, 8 m for the Danium / Thanetium and 12 m for the Ypresium. The lutetium, however, reaches a good 25 to 30 m. Included here is the so-called Thersite limestone , also called Dalle à Thersitées ("Thersitea plate"). The solid, banky limestone forms the upper end of the series and is characterized by the frequent appearance of the remains of the hemithersitea snail .
The individual phosphate layers are referred to as couche ("bed") or sillon ("furrow" or "horizon") and are numbered according to the stratigraphic sequence. The best breakdown is found in the northeast part of the Ouled Abdoun Basin, in the area with the most intensive mining at the moment. The Maastrichtian phosphate layer is called Couche III , but is sometimes divided into two parts: a lower and an upper section. The Danium / Thanetium corresponds to the phosphate layers couche IIb and couche IIa . The ypresium consists of at least four phosphate layers , which are named couches I , couches 0 , sillon A and sillon B from the lying to the hanging wall . A thin layer of phosphate marked with Couche 0 ' may also be deposited between Couche I and Couche 0 , as well as individual phosphate areas above sillon B with continuous letters ( sillon C and sillon D ). The layers between the different phosphate layers are referred to as intercalaire ("separating layer"). Accordingly, intercalaire II / I refers to the separating layer between couche II and couche I , intercalaire III / II to the one between couche III and couche II . The separating layers vary greatly in thickness and sometimes contain pockets or lenses of phosphates.
Supraregional context
The entire phosphate series is of marine origin and can be found in a similar structure in the other phosphate basins in Morocco. The strong variations in the thickness between the north and south edges of the Ouled-Abdoun Basin can be explained by the conditions in which the phosphate layers formed in what was once a bay-like sea inlet. The northern areas were located near the coast and are characterized by a high level of phosphate. However, the location at the edge of the sea led to a heavily condensed structure with several layer gaps and also sharp layer transitions. To the south, towards the formerly open sea, this condensation largely dissolves and changes to a complete sequence of layers. This is then occupied from the neighboring Ganntour basin to the south. The differences between the deposits near and away from the coast can be seen in the uppermost sections of the Upper Cretaceous, the Maastrichtian. In the north of the Ouled Abdoun Basin, this is only 3 to 5 m thick, whereas in the Ganntour Basin it is a good 45 m thick. As a result, seven phosphate layers can be distinguished here in the Maastrichtium alone, some of which are already apparent on the south-western edge of the Ouled-Abdoun basin. In the overlying Danium / Thanetium and in the Ypresium, four to six individual phosphate deposits in the Ganntour basin can be kept apart due to the increasing layer thickness and differentiation. Both the increase in layer thickness and the decrease in condensation are associated with a decrease in the phosphate content and an accumulation of organic material. The phosphate layers change from a predominantly yellowish-grayish color in the north of the Ouled-Abdoun basin to a dark tint and also take on a pungent odor.
The repetitive sediment sequences of the phosphate series are the result of a cyclical advance and subsequent retreat of the sea. The phases of transgression are indicated by the calcareous sections, the regression phases by the sandy-silty sections. The marine deposits of the Upper Cretaceous and the Paleogene continue beyond the phosphate basin to the south and can also be observed in the Ouarzazate basin on the southern edge of the High Atlas . However, the phosphate deposits there are comparatively marginal. However, they are still found abundantly under a mighty layer of outer layers in the Tadla Plain and are also found in relics in outcrops in the Ben Cherro basin near Beni Mellal , both located on the northern edge of the High Atlas. The marine deposits thus extend over the entire width of the Atlas, but were later masked by the folding of the mountains. According to the varying sediment thicknesses of the marine deposits in the Ouarzazate Basin, the rock sequence was formed on an area of land that once rose to the south. As a result, the southern end of the sea was probably to be found in the area of today's Anti-Atlas .
Origin of the phosphate deposits
Phosphorites usually form rounded rocks, the individual phosphate grains of which are more or less firmly bonded together by secondary cement. The phosphate grains mostly consist of organic waste, small concretions with a concentric structure, micro-oncoliths , coated grains (“pellets”), fecal pellets and various phosphated microorganisms such as algae , bacteria or fungi . In some cases, larger organic components such as bones and teeth also occur. In contrast, organic schill that does not contain phosphates is rather rare. Regardless of their origin, all phosphate grains consist of carbonate fluoroapatite , each of which appears as a structured crystal .
The formation of phosphate- containing sediment layers, the so-called phosphatogenesis , is complex and widely discussed. It includes tectonic , geomorphological , climatic , biochemical and biological factors. The phosphate deposits of the Mediterranean (Tethyan) phosphogenic province were formed in a long-lasting process that, geologically speaking, ranges from the Turonian in the Upper Cretaceous to the Lutetian in the Eocene. It began around 94 million years ago and came to a standstill more than 41 million years ago, i.e. it lasted for around 50 million years. The educational region corresponds to the outskirts of what was then Tethys . There, however, phosphatogenesis did not occur simultaneously everywhere. Rather, it began in the northeastern section, in today's Turkey, and gradually shifted to other regions. The Moroccan phosphate deposits occupied one of the longest periods of formation, stretching over a good 25 million years from the Maastrichtian to the Ypresian.
Phosphatogenesis is an organic sedimentation (bioproductite) that is linked to marine conditions. Here it can take place in a wide variety of locations, including continental slopes , islands , deep-sea mountains or guyots . In addition to a few other processes, it is mainly promoted by rising cold water currents. Such vertical water movements are documented in the northern Atlantic for the first time since the early Upper Cretaceous and intensified towards the end of the Upper Cretaceous. The rising currents bring, among other things, detritus material enriched with phosphates from the sea depths to the shelf areas . This then leads to a primary precipitation of apatite due to oversaturation . In a later processing controlled by hydrological and biological processes, the typical phosphorites made up of rounded grains emerge from this. Microorganisms , which are also fossilized from the Ouled-Abdoun basin in the form of gram-negative bacteria , have an important influence here . Favorable storage conditions in a basin are particularly important for the second phase of phosphatogenesis, as this requires stable environmental conditions, such as stratified water columns with only a small exchange between the individual water layers. This secondary stage of phosphatogenesis is typical of the shelf areas. This also includes the Moroccan phosphate basins, which formed on the edge of an epicontinental sea gorge.
Properties and importance of phosphate deposits
In the Ouled Abdoun Basin there are predominantly two types of phosphate grains: On the one hand, as a poorly sorted collection of grains with a diameter of more than 500 μm, in which numerous organic material is incorporated, and on the other hand as well-formed grains of spherical shape with a Diameter from 100 to 500 μm. The last variant dominates in the deposits, the first has a share of less than 10%. In general, the phosphate in the phosphate basins of Morocco is low in silicon , aluminum or iron and comparatively high with a phosphate content of 78 to 82%, which corresponds to 35.7% to 38% of phosphorus pentoxide . Exceptions are the phosphate deposits of the Maastrichtium, where the content of phosphorus pentoxide is 25 to 28%. The phosphate deposits with the best properties are found in the layers of the Ypresium in the Grand Daoui. They largely still contain 14 to 16% of water, but are slightly weathered.
With an estimated 51 billion tons of phosphorites, the phosphate deposits in Morocco are considered to be the world's richest sources of raw materials of this kind. According to some data, they represent around three quarters of the world's resources. Some of the figures are viewed critically, but both the Ouled Abdoun Basin and the other phosphate deposits in Morocco have not yet been fully explored. Every year around 19 million tons of phosphates are mined in the country, of which between 13 and 15 million tons are sold worldwide. A large proportion of this comes from the Ouled Abdoun Basin, the reserves of which were estimated to be around 28 billion tons of phosphorites in the mid-1990s. More than a dozen deposits have been explored in the Ouled Abdoun Basin, the most important of which are to be found with Mrzig , Khouribga and Grand Daoui in the north, with Meraâ El Arech and Ouled Farès in the central and with El Borouj , El Halassa and Sidi Chennane in the south Section. Most of the phosphorite mining takes place underground because of the hard surface layers . Only in the north of the Ouled-Abdoun-Basin, where the overlying limestones are partly more weathered, has an open-cast mine been widespread since the middle of the 20th century . He was also helped by the development of large excavation machines such as the dragline excavator "Marion 7900", which when he started work in 1960 in the Grand Daoui mining area with a weight of 1870 t, a crane boom 84 m in length, an action radius of 59 m and a The bucket volume of 39 m³ was the largest of its kind. The work is made more difficult by sterile sections of silicate limestone, which penetrate from the hanging wall into the phosphate store and are between 10 and 150 m in diameter. Possibly they go back to the evaporite layer at the upper end of the Campanium series , which formed cavities through karst weathering . These then collapsed, causing the overlying sediments to slide down.
Fossil sites
Vertebrate fossil remains occur throughout the sequence of the phosphate series, both in the phosphate layers and in the interlayers. But they differ in their wealth, their composition and their preservation. In the deposits of the Maastrichtian, sea creatures dominate, from fish to crocodiles , scaled reptiles and turtles . In addition, pterosaurs and the occasional remains of dinosaurs are documented. In addition to individual finds of bones and teeth, there are also some well-preserved skeletons. A large part of the fossils is concentrated in a bone bed , marked by its abundance of fish vertebrae and shark teeth, which is formed approximately in the middle of the couche III . In the strata of the Paleogene , crocodiles and turtles predominate in addition to fish. Birds and mammals, on the other hand, are rather rare and also consistently more fragmented. The occurrence of land-dwelling mammals in the marine sediments of the Paleogene, comparable to the dinosaur remains from the Upper Cretaceous, requires longer transport from the coastal areas and the continental hinterland. However, since there are some well-preserved skulls with occasionally complete rows of teeth, this rearrangement probably took place under rather low-energy conditions. Finds of mammals come mainly from several enriched bone layers , which are located on the one hand at the base and within the couch IIa (F1 or the so-called Eritherium bone bed and F2 or the big coprolite bone bed ), on the other hand at the base of the intercalaire II / I (F3 or the so-called Otodus obliquus bone bed or Phosphatherium bone bed ). The bone concentrations are characterized by a large abundance of disarticulated vertebrate remains embedded in a layer of silicate pebbles and greenish clays , possibly smectites . Due to the phosphate mining, most of the sites of vertebrate remains are in the northeastern Ouled-Abdoun Basin, mainly in the area of Grand Daoui . Eight different locations can be named for mammals alone. Furthermore, several sites with vertebrate remains are documented in the Sidi Chennane section in the southeast.
Finds
composition
The fossil wealth of the Ouled Abdoun Basin is enormous. There are remains of more than 330 species of vertebrate animals , which are divided into over 190 genera in over 85 families . A final overview of the fossil content of the region was made in 2017 by Nathalie Bardet and colleagues, but since then several new taxa have been introduced. The largest part of the composition of the paleontological finds is made up of the fish , among them again especially the shark and ray-like species , which alone represent more than 250 species and 120 genera. They occur in all found locations. Their great diversity and their frequent occurrence are of inestimable importance for biostratigraphy and thus for the chronological classification of the fossil-bearing layers. Other fish, especially the bony fish , on the other hand, are much rarer with around 20 species from almost as many genera and families. Some groups, such as the lizard- like species , have so far been restricted to the Upper Cretaceous , while others, such as the perch- like species , are restricted to the Palaeogene . A very heterogeneous group form the sauropsids , which include the transmitted reptiles including the dinosaurs and the birds . They can refer to over 55 species in more than 40 genera and nearly 20 families. The finds are distributed relatively uniformly over the different time levels of the deposits, but the birds have so far largely only been passed on from the Paleogene and the dinosaurs from the Upper Cretaceous. Mammals have so far been sparse . They only occur in the Paleocene and Eocene and represent around a dozen species in over nine genera from a handful of families. Compared to vertebrates, invertebrates and plants have only a small proportion in the fossil record .
flora
Macrofossils of plants are extremely rare in the Ouled Abdoun Basin. So far only the silicified wood residue of Pterocarpus from the group of legumes has been reported, which possibly dates to the Lower Eocene. The evergreen trees are common in tropical Africa and Asia today . On the other hand, phytoplankton in the form of dinoflagellates , microalgae with sizes from 50 to 500 μm , was extensively represented and intensively studied . Analyzes of a borehole from the southern part of the basin revealed 90 species from 50 genera alone. These can be broken down into four sequences that extend from the beginning to the end of the Maastrichtium. In the lowest, Trichodinium dominates and represents almost 50% of the finds, in addition to which Palaeohystrichophora and Chatangiella are relatively common. The old age of this episode is confirmed mainly by Odontochitina . The second sequence is again characterized by very high proportions of isabelidinium , followed by Svalbardella and Trithyrodinium . The third sequence is indicated by Deflandrea , Fibradinium and Muratodinium , with Trithyrodinium still largely preserved. The fourth episode is very poor in species. Isabelidinium , spiniferite and impagidinium occur in particular . That the entire dinoflagellate sequence here belongs to the Maastrichtium can be deduced from the constant occurrence of dinogymnium . In the higher altitudes of the Paleogene, among other things, Isabelidinium , Liesbergia , Spinidinium and Manumiella could be observed in further investigations . All four forms are present in the Paleocene, while Bitubericysta is registered from the Eocene .
fauna
Invertebrates
The invertebrates are mainly represented by the molluscs . Among these, the mussels are particularly common and are mainly distributed among the autolamellibranchiata . These include the Cucullaeidae , which with Cucullaea already occur in the early Upper Cretaceous in the Ouled Abdoun Basin. Cucullaea does not appear in the actual phosphate series, but is later detectable again in the lutetium. Pteriidae be in the Maastrichtian including through Heligmopsis displayed. Oysters , in turn, form dense layers in the Paleocene with Liostrea . The same applies to Venericardia from the group of trapeze shells . On the other hand, snails are rarely documented in the Maastrichtian and early Paleogene, but were very diverse and common in the early Cretaceous. The impoverishment of the snail fauna is possibly related to the peculiarities of phosphatogenesis and the high proportion of calcium phosphates, as some forms of this time developed an extremely thick shell . Among other things, the Ampullinidae with Ampullinopsis and the tower snails with Turritella were detected . In the later Lutetium, the Thersiteidae with Thersitea and Hemithersitea in particular have an important stratigraphic significance. Under the cephalopods , the pearl boats can be highlighted, which are present, for example, with Cimomia as a representative of the Hercoglossidae in the Lower Eocene.
Other invertebrates are present with the radiant animals , the foraminifera and the mussel crabs. These very often form the core of the phosphate grains. As a result, however, their tradition is largely poor and they thus largely evade precise determination.
Cartilaginous fish
The cartilaginous fish with the shark and ray-like have by far the largest share of all fossil finds . Their finds are naturally limited to teeth and a few vertebrae. At least eight larger lines can be detected among the sharks . These include original groups such as the gray shark- like , the nail-shark , the sawshark-like , the dogfish-like and the angel-shark-like , all of which are grouped together to form the Squalomorphii . With the exception of the nail sharks, which have so far only been found in the Paleogene in the Ouled Abdoun Basin, all other forms also occur in the Maastrichtian. One of the nail sharks is Heptranchias . The genus still includes the pointed head seven-gill shark , which lives on the seabed. It is fossilized by about 1.2 cm long teeth, which typically have a main point and several smaller secondary points arranged in a row. The bullhead shark-like , the nurse-shark-like , the mackerel-shark-like and the ground-shark-like summarize the more modern sharks of the Galeomorphii . Of these, however, only the last three are very often found in fossil form in the Ouled Abdoun Basin. The nurse shark species make up 14 genera alone. Palaeorhincodon came to light from the Paleogene layers. It is regarded as a predecessor of the whale shark , the largest fish of our time and today the only member of the Rhincodontidae. Finds are rather rare, however, so far a little more than 40 teeth have been discovered. These are up to 4 mm high at the main tip. The main point, in turn, is strongly curved back or to the side, flanking a smaller point on each side. The nurse sharks themselves appear much more frequently, including with ginglymostoma . Other forms refer to the bamboo sharks , the blind sharks or the carpet sharks . In the latter, Squatiscyllium was around 1.5 m long and was thus about half the size of today's forms. Its remains date to the Paleocene. The sand sharks , which developed a high level of diversity in the Paleocene , reached almost twice as large , among others with the genus Odontaspis . Carcharias was originally also placed in the group, but is now one of the sand tiger sharks . The genus is only documented in the Maastrichtium. Both the sand sharks and the sand tiger sharks are part of the mackerel shark species, which with a total of almost two dozen genera represent the largest group of sharks in the Ouled Abdoun Basin. They include the largest predatory fish, the goblin sharks and the extinct Otodontidae . The goblin shark Scapanorhynchus, which occurs in Maastrichtium, reached a length of around 5 m due to its 7 cm high front teeth. Comparable body dimensions are assumed for the Otodontidae representative Otodus from the Paleogene. Also traditional vertebrae sometimes have a diameter of over 10 cm. They consist of ring-shaped layers which, according to isotope studies, indicate annual growth rates, whereby an individual could be determined to be around 19 years at the time of his death. The genus also includes the much younger and giant megalodon . The thresher sharks are also present, whose teeth, which are less than 1 cm long, were equipped with additional small, low tips next to the main tip. The extinct Anacoracidae proved to be very common . Here Squalicorax highlight, a 3 to 4 m long animal whose laterally pressed and finely serrated teeth on the edge of the bit which is not more closely related tiger shark are similar and suggest an effective robber blank. He presumably ate turtles . The genus, which includes several species, is restricted to the Maastrichtium. The same applies to the also no longer existing Cretoxyrhinidae with Cretolamna . Similar in size to Squalicorax , its teeth are often found in the remains of marine reptiles, so that this form was probably scavenging . Another extinct group are the Serratolamnidae , whose type form Serratolamna is again from the Maastrichtian. Finally, the basic sharks should be mentioned, which mainly occur very frequently in the Paleogene. Almost as many genera of them have been documented as there are in the mackerel shark species. Abdounia and Physogaleus from the group of requiem sharks form two character forms . The cat sharks appear extremely diverse, although they were mostly less than 2 m long. Are occupied, among other Pteroscyllium , Scyliorhinus and Premontreia . Other shapes such as Palaeogaleus and Triakis refer to the occurrence of smooth dogfish .
The rays as the second largest group of fossils in the Ouled Abdoun basin can be identified with the Rajiformes , the Rhinopristiformes , the electric ray -like and the stingray-like . Among these four large groups, the latter occupy a dominant position with over 30 described genera and more than twice as many species and make up a good half of the finds. The stingrays already appear in the Maastrichtium, but are particularly well represented in the Lower Palaeogene. Many forms from the Ouled Abdoun Basin no longer exist today and probably belong in another relational environment. This includes Coupatezia , whose small teeth were equipped with low and flat tooth crowns. Around the same time, the butterfly rays developed a high diversity. Found forms are represented by the still existing genus Gymnura and the extinct form Ouledia . The pointed teeth were sometimes only 1 to 2 mm high, which is a striking contrast to their body span of 1.5 m and more. Gymnura is mostly documented from the earliest Paleocene, Ouledia appeared a little later. The Myliobatidae include forms such as Lophobatis , Leidybatis or Pseudaetobatus . They were equipped with high, flat teeth and probably ate mainly hard-shell prey such as molluscs or crabs . Rhombodus and Dasyrhombodus form the group of the Rhombodontidae , which disappeared at the end of the Cretaceous Period. As a result, they are only widespread in the Maastrichtium and occur there in high numbers. In terms of their tooth structure, they are somewhat similar to the Myliobatidae, but usually have diamond-shaped tooth surfaces. The diet should also have been comparable. Up to now, devil rays have been found very rarely, only Rhinoptera comes from the Paleogene . The cow-nosed rays appear more frequently , mainly with Burnhamia , which undergoes a significant reduction in size in the course of the paleogene. From the group of Rhinopristiformes the saw rays are to be mentioned, which appear in the Ouled-Abdoun-Basin only in the developed Paleogene, but are only documented by their foremost teeth. The extinct Sclerorhynchidae , documented in the Ouled Abdoun Basin by bits of Schizorhiza , for example , have an outward correspondence with the sawfish, but no relationship . Other extinct groups such as the Hypsobatidae and the Parapalaeobatidae are only documented by individual teeth. With the Rhinobatidae and the Rhynchobatidae , the former with finds from the Maastrichtian, the latter present in the Palaeogene, there are still systematic difficulties that currently do not allow an exact assignment. Electric rays also rarely appear. Described previously Narcine from the group of narcinidae and Eotorpedo from the group of electric ray . The small number of teeth of both representatives dates to the Paleogene.
Odontorhytis , a small form that was originally described from South West Africa, but has also been from the Ouled Abdoun Basin since the early 1980s, cannot be assigned to any special group of shark and ray-like species . The uniform teeth were severely flattened. A third group within the cartilaginous deer is the sea cats . However, their proof is extremely rare. In addition to individual teeth of Edaphodon , there is a remnant of the spiky dorsal fin, which is covered with fine spikes on the edge. Both finds belong to the palaeogues.
Bony fish
The bony fish are much less extensive than the cartilaginous fish. There are eight large groups, of which the bone-winged , puffer-like and ichthyodectiformes can largely show only one genus. The plaster toothfish turned out to be more extensive . Mention should be made here of the Serrasalmimidae , among which two piranha-like forms were described with Eoserrasalmimus and Serrasalmimus , both of which have bits of teeth. They are not closely related to the actual piranhas. Their teeth had sharp cutting edges and were possibly used to prey on soft prey, such as small fish and cephalopods. Both Eoserrasalmimus and Serrasalmimus belong to the early Paleocene. A third form of the cobblestone fish is already given with Phacodus from the Maastrichtian. The lizardfish-like , however, are occupied with Enchodus and Stratodus , which only occur in the Maastrichtian. Remnants of teeth and skulls were found from Enchodus . The bony fish include albula and phosphonatator . The former still exists today, the latter has only been proven in fossil form. A crushed skull a good 36 cm long was recovered from the Maastrichtian layers of the Ouled Abdoun Basin. The most diverse group is found in the perch-like and their immediate relatives. Among them saw bass , sea bream , barracudas , mackerel and tuna , hairtails and swordfish . The evidence of most forms is made up of individual teeth. In rare cases, as in the case of Phosphichthys from the group of sawfish, remains of the skull are preserved or, as in Xiphiorhynchus and Cylindracanthus as representatives of the swordfish, parts of the elongated upper jaw occur. The last group are the tarpon-like . The tarpon themselves are represented by Protarpon , whose finds consist of two incomplete skulls, each of which has been preserved with the brain segment. The larger of the two is around 19 cm long. Further group members belong to the Phyllodontidae . With a few exceptions, both the perch-like and the tarpon-like have come down to us from the Palaeogene.
Scale reptiles and plesiosaurs
The scale reptiles are relatively numerous, but only the snakes and monitor lizards are known of the lines that still exist today . Palaeophis belongs to the former , of which several partial skeletons have been found, some of them with more than 40 connected vertebrae. Complete specimens are not known, but it is believed that the skeleton is composed of several hundred vertebrae. The dimensions of the individual vertebrae, which almost double that of today's reticulated pythons , indicate an extremely large animal of 6 m in length and more. The barely squeezed vertebrae and the lack of pachyostosis suggest an animal adapted to shallow water conditions and coastal habitats. Finds came to light in both the Maastrichtian and the Palaeogene. On the other hand, Pachyvaranus, from the closer relationship of the monitor lizards, remains limited to the oldest deposits. Individual partial skeletons with vertebrae and ribs have also been recovered from this. Reconstructed, the animal was possibly around 1.5 m long. Noticeable bone compression in Pachyvaranus can be interpreted as a clear sign of life in the open sea.
The largest and most diverse group of scale reptiles , however, are the mosasaurs , sometimes huge animals with an eel-like elongated monitor body and a large skull. All mosasaurs found in the Ouled Abdoun Basin belong to the most recent lineage and were fully adapted to aquatic life. Their hallmarks are trained fins with redundant limbs and a pelvis that was not connected to the spine. With a total length of 3 to 4 m, Halisaurus represents one of the smallest and most primitive representatives . As in the tribal history of the younger mosasaurs, the spine in the tail area assumed a downward curve. A crescent-shaped tail fin formed there served as a drive in the water, which means that the animals are already pure sea creatures. From halisaurus several partial skeletons and skulls are documented. The set of teeth is made up of slender, needle-like teeth that are curved backwards. Skulls and skeletal parts as well as numerous individual teeth are assigned to another family group within the mosasaurs. Originally assigned to Platecarpus , the approximately 6 m long animal probably belongs to a different genus. The 90 cm long skull had an extremely extended snout that made up a good two thirds of the total length. All other forms from the Ouled-Abdoun-Basin belong to the Mosasaurinae , whose snout was mostly shorter and about half the length of the skull. Its best-known relative is Mosasaurus , which is rarely seen here and has been passed down as single teeth and two fragmented skulls. Its dimensions of 100 cm indicate a total length of the animals of almost 10 m. Eremiasaurus was only half the size , a comparatively common form. Their description is based on an almost complete skeleton, albeit broken up into eight sub-blocks. Like Mosasaurus , Eremiasaurus has high, pointed and sharp teeth, but the shape of the latter varies. The largest representative of the mosasaurs was Prognathodon , who is identified with several species in the Ouled-Abdoun-Basin. They can be distinguished by the shape of the teeth, which range from slightly pointed to clearly rounded. The skull alone measures up to 150 cm in length. In addition, there are two more closely related genera, on the one hand Globidens and on the other hand Carinodens . Both are very small members of the mosasaurs, which are largely known from isolated teeth and individual skull fragments. They stand out from the other mosasaurs of the Ouled Abdoun basin by their characteristic blunt-ended teeth, which are spherical in the former shape, but flattened laterally in the latter. The design of the teeth thus advocates a specialized diet based on molluscs . While Carinodens is largely rare, Globidens is much more common.
Compared to the mosasaurs, the plesiosaurs are very rare in the Ouled-Abdoun basin. Both groups are not closely related, as indicated by the deviating body plan with the large paddle-like limbs and the short torso. However, they share the marine way of life, although the plesiosaurs moved more like today's sea turtles in the water, sliding with their fins as the main drive and less undulating over the spine like other aquatic reptiles. A complete skeleton and individual skull parts go back to Zarafasaura from the group of Elasmosauridae . Like all late plesiosaurs, this one also had an extremely long neck that took up over half of the entire body length. The generic name alludes to this. This is of Arabic origin and is derived from the name for the giraffes . The spine comprises more than 120 vertebrae, 56 of which are made up of the neck alone. The skull, on the other hand, was extremely short. Other postcranial skeletal elements belong to an as yet undescribed form, the neck of which consists of 64 vertebrae. The material includes young and adult animals and comes from the same source. The fact leads to the assumption that the different age stages of the plesiosaurs apparently used the same food resources.
Turtles and crocodiles
The extensive material of the turtles of the Ouled Abdoun Basin stratigraphically stretches from the Maastrichtian to the Paleogene. It is divided into around a dozen genera from four families. Both come Halswender- and cryptodira ago. The former are only represented by the extinct group of Bothremydidae . This is a cosmopolitan and very diverse group that occurred from the Lower Cretaceous to the Miocene and occupied numerous ecological niches . They include small to large species from 30 to 150 cm in length. In the Ouled Abdoun Basin, a good half of the genera described fall into the hands of the Bothremydidae, which are almost exclusively based on skull finds. All of these forms are palaeogenic, but there are also remains from the Upper Cretaceous, but have not yet been investigated in more detail. Within the Bothremydidae, Ummulisani , Phosphatochelys and Taphrosphys form a closer relationship group. The former genus can refer to three, the latter two to two documented skulls. As a specialty, Ummulisani has a pair of horns on the prefrontal , which was originally covered with horn scales. The characteristic is unique among turtles and does not occur in the directly related forms either. Other genera from the relationship environment can be found with Rhothonemys and Labrostochelys , the latter was very narrow-nosed compared to the others. The skull lengths of all genera vary between 6.8 and 20 cm with the smallest in Phosphatochelys and the largest in Ummulisani . Bothremys and Araiochelys belong to a different kinship . Their skull sizes are in the range of the dimensions of Phosphatochelys . Only from Araiochelys , as the only form of Bothremydidae from the Ouled-Abdoun basin, several parts of the back armor have been recovered, and from Ummulisani a belly armor is also documented.
Almost as diverse are the Halsberger tortoises, which probably only immigrated from the northern mainland areas of today's Eurasia via the Tethys in Africa during the Upper Cretaceous. In the Ouled Abdoun Basin, they have been handed down both from the Maastrichtian and from the Paleogene and, similar to the turn-neck turtles, are only known from their skulls. The Dermochelyoidae are still represented today by the leatherback turtle . During the course of their tribal history, they produced some unusual shapes. This includes ocepechelon from Maastrichtian, which was possibly one of the largest turtles in the history of the earth. Their approximately 70 cm long skull has a tube-like, elongated snout, with which the animals probably sucked their food from the sea water , comparable to today's humpback whales . The Alienochelys, about the same old, are different . A massive, semicircular curved and flat lower jaw is formed on its broad and 55 cm long skull. This probably fulfilled a special vomiting function during food intake. Another form of leatherback turtles is only documented through individual fragments of the belly shell and has not yet been named. Various other fossil remains can be assigned to the sea turtles . It is mainly a matter of basal representatives that have a second palate as a special characteristic. In addition, they were all relatively small with skull lengths between 9 and 23 cm. According to their often triangular lower jaw with a broadened scraping surface, they largely fed on molluscs. Some forms had comparatively short limbs, which meant that they were only partially adapted to marine life and probably lived closer to the coast. These include Euclastes , a medium-sized sea turtle that is present in both the Maastrichtian and Palaeogene regions and includes several species (including one with an original position in the genus Osteopygis , which later turned out to be a chimera ). It is characterized by a broad, triangular and flat skull. Furthermore, it was Argillochelys described, the largest known sea turtle from the Ouled Abdoun-basin. Their blunt snout easily separates from the skull. In contrast, in Tasbacka and Puppigerus , two very small members of the group, the skull is clearly elongated and the snout is thus more pointed. The former may already have been more adapted to life in the open sea. As another group, Brachyopsemys, a genus of the Sandownidae, has been documented. The Sandownidae are extinct, but are relatively related to the sea turtles. The skull, which is only 11 cm long and very wide, is also flat, but clearly rounded at the front and equipped with a secondary palate.
The crocodiles are also represented with around a dozen genera, which are distributed over several lines. The most extensive are the now extinct Dyrosauridae , a basic group of forms. They are among the first to be scientifically known in the Ouled Abdoun Basin. These are exclusively marine forms that were already present in the Maastrichtian but reached their greatest diversity in the Paleogene. This is also the case in Morocco, where all dyrosaurid crocodiles in the Ouled Abdoun basin belong to the paleogene. As a special feature of the group, the sometimes extremely long snout can be emphasized, which is to be seen as an adaptation to food containing fish. In its largely uniform dentition, which comprised a good two dozen teeth on each side, the seventh tooth of the lower jaw was extremely reduced and positioned close to the eighth. The fourth, on the other hand, was clearly enlarged and fitted into a correspondingly large tooth gap in the upper jaw. The noticeably long snout can be seen among other things in the type form Dyrosaurus as well as in Atlantosuchus , in which it claims a good 75 or 79% of the skull length. From dyrosaurus more complete individuals have been found, including but only a few pups. From the relatively long-legged shape, parts of the scale armor of the back have also been preserved. Their laterally smooth osteoderms had numerous typical depressions on the surface. Atlantosuchus, in turn, is represented by a found skull with adhering parts of the cervical spine. Compared to these two, Chenanisuchus , documented over two skulls, appeared rather short-snouted with around 63% muzzle proportion based on the skull length. In terms of body size, Chenanisuchus was also significantly smaller than Dyrosaurus and Atlantosuchus . While in these the skull is 90 to 100 cm long, in Chenanisuchus it measures only a good 58 cm. His body length was therefore estimated to be around 4.5 m. In terms of the design of the snout, Arambourgisuchus is more intermediate between these extreme forms. Skull material of the genus is also largely available. Other dyrosaurid crocodiles from the Ouled Abdoun Basin are Hyposaurus and Rhabdognathus . The Pholidosauridae , in which the Dyrosauridae were originally included, are closely related . An individual who is only known from the body skeleton and has not yet been scientifically named is assigned to these. This small animal, probably only around 2 m long, is, to the exclusion of the Dyrosauridae from the Pholidosauridae, their youngest representatives, since most of the other forms disappeared at the beginning of the Upper Cretaceous. The shape was probably adapted to life in rivers.
In addition to these extinct lines, remains of members of groups that still exist today have been discovered. These are largely related to the Gaviale family . These crocodiles, which are also long-snouted, have, in addition to some other features, differences in the structure of the palate. Their largely homodontic set of teeth of the same size should also be emphasized in comparison with other modern crocodiles. The earliest gavials are already present in the Ouled-Abdoun-Basin with Ocepesuchus in the Maastrichtian, the evidence of which consists of a severely crushed skull. It is one of the oldest fossil records of modern crocodiles in Africa. It is believed that the animals may have been partially or completely confined to rivers, as other reptiles dominated the seas at that time. Further gavials only appeared in the paleogene. Forms found are classified as Agrochampsa and Thoracosaurus . The first of both has been handed down with at least four skulls, the holotype specimen measures around 43 cm, the snout alone 31 cm. As a noticeable characteristic of the animals, the front part of the snout bends significantly downwards. The tomistominae , the dentition of which is more variable, can be deposited within the gaviale . Maroccosuchus is one of the oldest representatives of this line, which still makes the Sunda Gavial today . The designation of the shape is based on numerous skull material from the Ouled Abdoun Basin. Compared to the Sunda Gavial, its skull is built much more robustly, which makes the snout appear broader overall.
Pterosaurs, dinosaurs and birds
Pterosaurs produced the largest flight animals in the history of the earth. They are extremely rare in the Ouled Abdoun Basin and were not even used until the early 2000s. Since then, more than 200 finds have come to light. The first finds, individual vertebrae, were made at Phosphatodraco , a comparatively large animal with a reconstructed wingspan of around 5 m. Later further vertebrae could be assigned to the genus. The tubular and strongly elongated vertebral bodies represent the shape of the Azhdarchidae . A so far unnamed representative belongs to the same family, whose fragment of the cubit refers to a significantly larger animal with a wingspan of 9 m. Furthermore, with Alcione , Simurghia and Barbaridactylus , three representatives of the Nyctosauridae are documented. The group is characterized by four-fingered hands and an extremely strong, ax-like muscle crest on the humerus . Of the three forms, the former has the most extensive material. It consists of a partial skeleton and additional wing elements. Based on the 9.3 cm long upper arm, it is a small member of the family. The shortened wing bones are striking. They could be an adaptation to a strong, rapid flapping of the wings or speak for longer dives. Of the other two representatives, only individual limb bones are known to a large extent. Due to their significantly larger humerus bones, they sometimes exceeded Alcione by more than five times in size. Tethydraco in turn represents the Pteranodontidae , which are characterized by a long occipital ridge. Also handed down only through individual arm and leg bones, the animal had a wingspan of around 5 m.
Comparable to pterosaurs, land-dwelling dinosaurs are rarely found in the fossil record of the Ouled-Abdoun Basin, here too the first finds date from the early 2000s. One of the few indications is a hind leg of a small sauropod , which, however, has not yet been assigned to a specific shape. Possibly it can be defined as a basal representative of the Titanosauria within these sometimes huge, four-footed and long-necked herbivores . In addition, a high, anterior mandibular fragment and several individual teeth indicate the appearance of theropoda , two-legged carnivores. The teeth, ten of which are still in the lower jaw, are triangular-pointed and have sharp, finely jagged side edges. The remains were described as belonging to Chenanisaurus , a 7 to 8 m long member of the Abelisauridae .
All of the birds presented so far from the Ouled Abdoun Basin date to the paleogene and are located within the new pine birds ; these are currently the oldest specimens from Africa. These include, among other things, Dasornis from the extinct group of Pelagornithidae . These large seabirds with serrated beak edges, which are reminiscent of teeth and also earned them the designation as "pseudo-toothed birds", were originally considered to be close to the pelicans , but now belong to an independent group. Dasornis has been handed down in the Ouled Abdoun Basin with at least three species, the wingspan of which varied between 1.5 and 4.5 m. The material found is quite extensive, but overall very strongly fragmented, which corresponds to the nature of the fragile skeleton structure. In contrast to other members of the group, Dasornis may not have been such a highly specialized glider and, due to the longer hind legs, also more agile on land. Two other bird representatives join the closer environment of the tropical birds . One is Lithoptila , a shape that was originally set up based on a brain skull. Subsequently, numerous limb bones came to light, which distinguish the animal as a skilful flyer with slender wings, the tips of which were spread apart about 1 m apart. The second form is represented by Phaetusavis , of which only one humerus was revealed. In terms of body dimensions , it largely corresponded to Lithoptila , but in Phaetusavis the upper joint end was designed more massive.
Mammals
The paleogenic deposits also contain a significant number of mammalian remains , all of which are terrestrial forms. There are representatives of two of the four major lines of the higher mammals with less than a dozen genera. The most varied and extensive material belongs to the Afrotheria . Here Ocepeia and Abdounodus represent two representatives from the older Palaeogene, who are closely related to the Paenungulata without being directly incorporated into them. The former has extensive skull material. It shows a small animal with a body weight of 8 to 20 kg and a short snout that ate a soft vegetable diet. The latter is occupied by some upper and lower jaws and can be classified as a little more modern according to the tooth features. The hyrax , a group of Paenungulata that was extremely variable in its past but has now shrunk to a few marmot-like shapes, are documented with a single molar, which may correspond to the primitive genus Seggeurius . With an age dating in the beginning of the middle section of the Paleogens, it represents the first record of hyraxes. The same is true for the proboscis . They come in several forms. Eritherium from the older Paleogene is considered to be the most original , from which a partial skull and individual mandibular fragments came to light . In contrast to all later proboscis, the lower jaw still showed the complete dentition of the higher mammals. The somewhat younger and, due to the beginning reduction of the front teeth, also more modern, Phosphatherium was the first mammalian form to be detected in the Ouled-Abdoun-Basin. Several more specimens have been added since a skull was first found. The youngest representative of the trunk animals in the Ouled Abdoun Basin is assigned to Daouitherium and can be classified in the middle Paleogene. There are various remains of the lower jaw. All of the elephants in the Ouled Abdoun Basin were very small compared to today's elephants . A body weight of 3 to 8 kg can be reconstructed for Eritherium , whereas Phosphatherium was almost doubly heavy. The strong increase in body size of the proboscis can already be seen in Daouitherium , which weighed 80 to 170 kg. They mostly have teeth with low crowns and therefore probably ate a soft vegetable diet. As far as the find material suggests, no proboscis or tusks were formed in any of the shapes. The extinct Embrithopoda , whose character form Arsinoitherium from the Lower Oligocene of the Fayyum in Egypt developed huge body dimensions and is characterized by bony horns on the skull , are closely related to the proboscis . In the Ouled Abdoun Basin, Stylolophus , documented by several crushed skulls, is an early ancestor who weighed between 30 and 80 kg and was therefore significantly smaller. It is also more original with regard to the teeth, as these are not yet as extremely high-crowned.
In addition to the Afrotheria, the Laurasiatheria are the second registered line of mammals in the Ouled Abdoun Basin. So far only members of the hyaenodonta have been found, a group of extinct carnivorous forms that are close to the predators , but differ from them by a pair of crushing claws that are shifted further back in the teeth. From the older Paleogene comes Lahimia , however, is younger Boualitomus , from both multiple mandible were uncovered. In contrast to other very early hyaenodonts, the teeth in Lahimia and Boualitomus are more specialized and, in addition to the reduction of the anterior molars, show a tendency towards a predominantly cutting function. Both genera probably belong to an originally African radiation group of hyaenodonts. In addition, a lower jaw fragment with a single preserved tooth with two transverse ridges can be mentioned here. Its exact assignment is unclear; it may be the remains of an original ungulate .
Age position
The deposits of the phosphate series do not yet allow any absolute age dating . The chronological assignment of the individual layers and their finds is largely based on biostratigraphy , for which the species-rich shark and ray fauna are mainly used. The basis for this was worked out in the first half of the 20th century and later refined, for example by taking microfauna into account. In general, the Plattenkiemer date the phosphate series to the period from Maastrichtian as the last section of the Upper Cretaceous to the exit of the Ypresian , i.e. the transition from the Lower to the Middle Eocene within the Paleogene . The absolute age data are between 72 and almost 48 million years, which spans around 24 million years. Two significant geological events are embedded within this period: on the one hand the Cretaceous-Paleogene boundary around 66 million years ago associated with the disappearance of the dinosaurs and numerous related groups and the rise of mammals , on the other hand the Paleocene / Eocene temperature maximum a good 56 million years ago , which led to a short-term sharp rise in global temperature. Some shark forms such as Squalicorax , Plicatoscyllium or Serratolamna achieve a very large stratigraphic range, others such as Ginglymostoma , Anomotodon or Ganntouria only appear briefly. The same applies to rays like Rhombodus or Ganopristis compared to Youssoubatis or Duwibatis . With their sometimes alternating individual species, they enable a very precise relative age classification of the layers, which applies to almost all areas of the phosphate deposits. The strong compression and condensation of the sequence of layers in the Ouled-Abdoun Basin have a disadvantage for biostratigraphy. As a result, the Maastrichtium, for example, can be broken down less well and more finely subdivided than is offered by the Ganntour Basin with its much more powerful and more complete series of deposits. The Paleocene sequence is also problematic , as here, among other things, the Seelandium as its middle section cannot be separated from the Danium and Thanetium and remains hidden within these two levels.
In addition to this stratigraphic resolution by means of the marine fauna community, geochemical analysis methods have also been used since the 2010s . Isotope studies based on oxygen and carbon should be emphasized here , with which only the sequences of the paleogene could be differentiated for the time being. Fossil remains formed the basis, especially from the bone beds . The investigations were able to confirm the biostratigraphic approaches to a large extent and are particularly instructive with regard to the carbon analyzes. Accordingly, the lower bone bed (F1) within the Couche IIa , from where the remains of Eritherium and Ocepeia originate, encompasses the incipient Thanetium due to some positive δ 13 C fluctuations and partially includes the Seelandium. This is where the boundary between the Seelandium and the Thanetium is located, which is dated around 59 million years ago. The upper bone bed (F2) from the couch IIa belongs in the further course of the Thanetium. In contrast, the third bone bed (F3) at the base of the intercalaire II / I with the fossil finds of Phosphatherium marks the beginning of the Ypresian period around 56 million years ago. However, the Paleocene / Eocene temperature maximum that also sets in here, which is characterized worldwide by a very low δ 13 C ratio, is difficult to detect. The higher altitudes then also belong to the Ypresium. Here, in the section from couche 0 to sillon A, the carbon isotope values are very low, which most likely correlates with two further thermal fluctuations, which are designated as ETM-2 and ETM-3 and cover the period 54 and 53 million years ago. Due to difficulties in resolving the isotope analyzes, it is unclear whether the uppermost layers of the phosphate series also include the outgoing Ypresium, but some of the higher sillon layers can be equated with the early Heocene climatic optimum around 52 to 50 million years ago, which in turn is represented by positive δ 13 C-values drop. The lutetium does not seem to be included. In comparison with magnetostratigraphy , which documents the change in polarity of the earth's magnetic field , the entire analyzed section extends from Chron 26 to, most likely, Chron 22 , which dates between 61 and 49 million years ago.
Landscape reconstruction
The phosphate deposits in Morocco and the general marine deposits are evidence of a former sea that existed from the Upper Cretaceous to the Eocene . This is also indicated by the numerous fossil remains such as the foraminifera and the shark and ray-like species . The latter also refer to varying sea depths, in some cases from shelf areas with a depth of 100 to 150 m to deep sea regions . There are various reconstructions of the landscape of today's phosphate deposits. In a classic view, largely developed by Georges Choubert and Henri Gauthier in the 1950s, three narrow gulfs stretched inland from the western Atlantic coast . The "northern gulf" began with a wide estuary between Safi and El Jadida and ran between the mainland blocks of the Jbilets in the north and the Meseta in the south eastwards over the Ganntour basin to the Ouled Abdoun basin and surrounded the Rhamna massif , which thereby emerged as an island. To the south, the "Gulf of Essaouira" joined, which flowed into the city of the same name and occupied the Meskala Basin and the Ouarzazate Basin . It was framed by the Jbilet in the north and the western High Atlas in the south. The southern end was the “Gulf of Sous” near Agadir with the Sous basin as the center. In this model, the estuary areas in particular remained unclear, as later uplifts in the coastal area overprinted the deposits there. However, it has been modified several times, including by Armand Boujo in the 1970s. Among other things, he considered the Rhamna massif to be peninsula-like, which means that the "northern gulf" at Youssoufia met the Atlantic Ocean very narrowly. Alternatively, individual authors saw a second Atlantic connection of the "northern Gulf" via Settat .
Another model was developed by H. Salvan in the 1980s. In its reconstruction, the two northern narrow gulfs united to form a broad epicontinental sea, the "Phosphate Sea", whose access to the Atlantic stretched between Casablanca and Essaouira. The Rhemna massif existed as an island analogous to the view from Boujo, while a land connection to the south was formed from Jbilet. Salvan largely rejected the existence of a southern oleus near Sous, rather the Sous Basin connected to the north with the Meskala Basin. Around the same time, Hans-Georg Herbig designed a similar picture, but assumed that the entire area would be flooded over a large area. To the east, the sea also covered the Ouarzazate basin and thus also occupied the area of today's High Atlas. Herbig did not rule out the existence of individual islands. The reconstruction by Jörg Trappe from the early 1990s can be seen as a variation of this . Here the sea connection of the Epicontinental Sea extended from Casablanca far south to Agadir.
The design of the sea at that time has not yet been clearly clarified. Because of the composition of the fish fauna, some scientists are more critical of complete marine cover, while others are in favor of a uniform sea, referring to the charophytes and hermit crabs . The former coastline will only be modified locally, for example on the edge of the High Atlas. From a sedimentological point of view, there is also the assumption of a partially narrowing sea access from the Upper Cretaceous to the Lutetium. However, this contradicts analyzes of the rare earth metals from the fossils across all layers. No shortage of these elements could be determined, so that a continuous and constant supply of fresh sea water can be assumed. In addition, the then "phosphate sea" seems to have benefited from the increasing water exchange between the northern and southern Atlantic at that time in the course of the further opening of the ocean. In general, both the “phosphate sea” and the narrow Gulf areas are considered to be relatively warm, the temperatures of which in the Upper Cretaceous may have been around 27 ° C, which was shown by analyzes of oxygen isotopes from fish fossils. In the Paleocene there was a rapid cooling of the "phosphate sea" to around 19 ° C, which was then followed by warming in the Eocene . The causes are not clear and can be related to both increasing ocean depth and changes in the earth's atmosphere , with the noticeable drop in temperature at the Cretaceous-Paleogene boundary advocating the latter.
The rich marine fauna of the Upper Cretaceous is characterized by a dominance of top predators , which included great sharks, mosasaurs, and plesiosaurs. Typically, such influential predators use different food sources in modern ecosystems. This is also assumed for the various mosasaurs and explained with the varying tooth design, which speaks for a diverse niche use . According to this, there were fish-eating animals with sharp and pointed teeth as well as shapes specialized in hard-shelled mussels with rounded, blunt teeth. Investigations on calcium isotopes showed that the majority of the predators of the "phosphate sea" fed on fish, whereby the range of prey was greatly narrowed and a "wasp waist" ecosystem existed in which the predators' existence depends on a few prey animals. Under today's conditions, such communities are very unstable, as the disappearance of the prey also leads to a decimation of the predators, for which only individual changes in the ecological environment can be decisive. It is possible that the drastic upheavals during the Cretaceous-Paleogene transition also led to the local disappearance of large predatory reptiles, but also of fish. In the early Paleogene some dyrosaurid crocodile relatives and sharks continued to take over the role of the great marine predators. However, they then largely disappeared later on. Here the beginning of the Ypresium indicates a more pronounced disappearance of the sharks.
The presence of land-dwelling dinosaurs and mammals in the Ouled Abdoun Basin suggests that the coastal area is only a short distance away. Their often greater decomposition points to longer transport routes into the marine environment. This hinterland was probably overgrown with a tropical rainforest or a mangrove forest, which was crossed by slowly flowing waters. As an indicator for this in addition to the Pterocarpus -Funden from the Ouled-Abdoun Basin directly among other fruits of and stem remains nipa palm are used that originate from the South Rim of the High Atlas in Ouarzazate basin, dating to the Eocene in the period of transition from the Paleocene . With a position at the end of the Lower Eocene, pollen accumulations from the same region are a little younger , which go back to plants with adaptations to brackish water . Occasional macro residues from leaves also indicate this, for example from water lettuce . In general, the pollen flora from the southern Atlas region is similar to that from the Ganntour basin of the same period, but there are no clear mangrove and salt marsh indicators here. Various vertebrate remains such as crocodiles and turtles also point to a tropical to subtropical climate . Occasionally developed layers of smectites and gypsum in the Ouarzazate basin suggest a possibly more seasonal climate with alternating dry and rainy seasons. Geographically, the landscape was then in the area of the 20th to 23rd northern latitude.
Comparison with regionally and supra-regionally important sites
The closest comparisons formally form similar phosphate- containing basin structures in North Africa as the neighboring Ganntour Basin or the Meskala Basin and the Sous Basin . All of these basins show a very extensive sedimentary sequence of the Maastrichtian , which can be broken down in part with higher resolution than in comparison to the Ouled-Abdoun basin. On the other hand, the deposits of the paleogene are rather sparsely developed, except for the Ganntour basin. Coinciding with the Ouled Abdoun Basin, there is a rich cartilage and bony fish fauna, which serves as the basis of the biostratigraphic classification. Finds of reptiles from the Meskala- and Sous-Basin have only rarely been reported and are largely limited to crocodiles and turtles . Significant occurrences, however, are from the Ganntour Basin with around 60 species of shark and ray-like species, over half a dozen species of bony fish and more than a dozen species of reptiles. The fauna mirrors that of the Ouled Abdoun Basin, but local peculiarities occasionally occur. Among the reptiles, the mosasaurs dominate over the plesiosaurs . In addition to crocodiles, mainly the Dyrosauridae , turtles and monitor lizards are also recorded . With the exception of the Ouled Abdoun Basin, none of the other phosphate basins in Morocco has so far produced remains of birds and mammals .
The origins of the Egyptian phosphate deposits in the oasis of Dachla in the western part of the country are in some cases significantly older than those of Moroccan . Above all, the sediment sequences of the Quseir , Duwi and Dakhla Formations are exposed here . Their origins range from the Cenomanium to the Maastrichtian and the Paleocene. The phosphate-containing formations are limited to the Duwi Formation and are enclosed here in a sequence of clay , sand and silt stones as well as conglomerates . The lying Quseir Formation is largely made up of stratified slates , while the hanging Dakhla Formation is characterized by slate, sand and siltstones, and marl . Fossil finds were found in all three rock units, although it must be said that paleontological work here has only been carried out sporadically so far. Various sharks and lungfish , dyrosaurid and possibly gavialoid crocodiles, turtles and dinosaurs, possibly Spinosaurus , have been reported from the Quseir formation , without a more detailed description of most of the forms being available so far. For the Duwi formation, fish as well as plesiosaurs and mosasaurs, here Globidens , are documented. The Dakhla Formation provided vertebrate remains and plant material plus a previously unspecified limb of a medium-sized sauropod. The phosphate basin of Gafsa in Tunisia also has a long formation period, but the main deposits date to the Lower and Middle Eocene and contain numerous shark and ray teeth, occasionally remains of turtles and crocodiles. Among other things, the first known skull of a dyrosaurid was presented from here in 1893.
Outside of this special educational environment, sites of the Upper Cretaceous in North Africa are quite well documented, only the Bahariya Formation in Egypt or the Kem Kem Beds in Morocco, which both belong to a significantly earlier section of the geological series with a dating to the Cenomanium . Locations that are closer in time are, however, much rarer. The Wadi Milk Formation in Sudan , which was originally considered to be as old as the Bahariya Formation, but according to more recent absolute dates, was formed in the Campanian at about 79.2 million years . A big difference to the phosphate basins is the predominance of terrestrial fauna elements, even if the formation of the rock unit took place relatively close to the coast. This is indicated by various sneak amphibians , turtles and dinosaurs , which include both large sauropods such as the Titanosauridae or the Carcharodontosauridae and theropods such as the Dromaeosauridae or ornithopods such as the Iguanodontidae or the Hypsilophodontidae .
The Ouarzazate Basin on the southern edge of the High Atlas in Morocco is to be understood as a temporal equivalent to the paleogenic deposits of the Ouled Abdoun Basin . The deposits here partly also contain phosphates and are equipped with a very rich fossil fauna, which is distributed over several sites. With Adrar Mgorn, Ilimzi or Talazit from the end of the Paleocene , N'Tagourt from the Lower and Aznag from the Middle Eocene, these cover a period of more than 10 million years. The dating of the individual sites is carried out both magneto- and biostratigraphically, the latter as in the phosphate basins north of the High Atlas via the extensive shark and ray community. What is striking about the find material in the Ouarzazate Basin is the high degree of fragmentation of the finds and the large proportion of land-dwelling forms, which includes not only mammals but also herpetofauna , the latter represented, for example, by frogs , geckos , skink-like and double creeps . Numerous small mammals are present among the mammals, shown among other things in insectivore-like forms such as Afrodon , Todralestes or Garatherium . This is probably an endemic faunal community that is less related to the genera occurring at the same time in the northern Tethys border area , today's Eurasia, than to the later Afroinsectiphilia . In addition, early are already in the oldest layers Fund primates before, so Altiatlasius , initially as a the tarsiers interpreted related party animal, but maybe in today's opinion as Basalform the evolution of monkeys heralds. Analogous to the Ouled Abdoun Basin, Tinerhodon represents the carnivorous Hyaenodonta . In the younger Fund layers then finds can also be the first time by Fledertieren and Soricomorpha of the lineage of, shrews , moles and similar forms, and possibly also the elephant shrews show.
In the Lower and Middle Eocene, sites such as El-Kohol and Gour Lazib in northern and western Algeria and Chambi in Tunisia, respectively , fall . Regarding the development of the mammalian fauna, some similarities with the Ouled-Abdoun-Basin and Ouarzazate can be determined, for example in El-Kohol where early insectivore-like forms such as Garatherium or the original hyrax Seggeurius appeared . However, there is evidence of more developed forms, some of which are genetically more developed. This can be seen, among other things, in the proboscis Numidotherium , which not only increased significantly in size compared to the early forms of the Ouled-Abdoun basin, but also has a much more reduced dentition and already shows signs of a proboscis. The increasing formation of phylogenetically more developed forms can be seen in Gour Lazib, where in turn there are remains of Titanohyrax , Megalohyrax and Microhyrax and thus hyrax that no longer belong to the old Seggeurius group, but represent more modern and ecologically clearly diverse forms. In addition, early primates with Azibius and Algeripithecus have been identified here, as well as rodents . Chambi comes up with early elephants like Chambius as well as slivers and primates. The sites lead to the extremely fossil-rich deposit of Fayyum in northern Egypt. The Fayyum is one of the most important fossil regions of the Paleogene Africa and dates to the Upper Eocene and Lower Oligocene . The extremely rich fauna is characterized by fish, reptiles, birds and mammals. Among the latter are proboscis, which are at the basis of the development of elephant-like forms, various monkeys in the ancestral line to the Old World monkeys and members of an early fragmentation of whales and manatees . There are also tenreks , hyrax , ungulates , bats and rodents, as well as some lines that are now extinct. Similar to the Fayyum, the Upper Oocene section of the Samlat Formation near Ad-Dakhla in Western Sahara yielded fish, turtles, crocodiles and individual birds as well as marine and land mammals.
Research history
Beginnings
The discovery of phosphate- containing deposits in northern Africa goes back to the end of the 19th century. In 1885 Philippe Thomas reported on Eocene occurrences near Gafsa in Tunisia . The first fossils were described only a short time later, while commercial mining began around 1899. In comparison, information about the Moroccan phosphate deposits reached the public much later. The first mention of sedimentary rocks of the Eocene in Morocco between Essaouira and Marrakech was formulated by Abel Brives in 1905. He had discovered them the year before on his trip through North Africa. Only three years later, after another trip to the area, he announced the occurrence of phosphates in these layers, which also contained remains of mussel shells . The outcrops initially met with little interest, which did not change until 1917 when Brives reported significant phosphate deposits between the villages of Oued Zem and El Borouj . In a publication published two years later, Brives first described the geological situation in more detail and divided the sequence into three sections. The bottom, made of clays and plaster of paris, was dark in color, followed by an alternating layer of marl and limestone with embedded silica layers and a non- silicate , phosphate- containing sandstone bank , closed off by a solid limestone layer . Here he also submitted a first fossil list, which mainly took into account various sharks . According to his observations, the lower layer contained only poorly preserved fossils, while the middle one was characterized as very rich in finds and the upper one was characterized by numerous mollusc remains. According to Brives, all three sections belonged to the Eocene . The strategic and economic importance of the Ouled-Abdoun Basin, which had increased by leaps and bounds due to the phosphate layers, led to the establishment of the Office Chérifien des Phosphates (OCP) in 1920 , a large company that destroyed the mining of phosphates in Morocco in the Ouled one year later -Abdoun Basin, later coordinated in neighboring areas such as the Ganntour Basin .
In 1922, Léonce Joleaud presented a number of vertebrate fossils, including the crocodile Dyrosaurus and various fossil shark shapes. In his estimation, the deposits of the Ouled-Abdoun-Basin belonged to a geological framework that extended in time, from the late Cretaceous to the Eocene. This contradicted Brives, but agreed with Louis Gentil's opinion . In the same year, he gave a comparable age estimate and referred to biostratigraphically significant fossils and their distribution in the deposits. Other early finds go back to Charles Depéret and P. Russo from the mid-1920s. They reported remains of sharks, crocodiles and mosasaurs from the region around Melgou in the north-eastern part of the Ouled-Abdoun basin.
The time of Arambourg
At the request of the then General Director of the OCP to clarify the existing stratigraphic problems in the Ouled-Abdoun Basin, Camille Arambourg began his research in 1934 . They should be decisive for the next two decades. Arambourg, who works at the Muséum national d'histoire naturelle in Paris, chose the vertebrates that most frequently appear in the phosphate layers, namely sharks, rays and reptiles. He carried out an examination of the individual geological layers and sorted or sifted the relevant finds. After an investigation period of almost ten years, Arambourg had sighted around 100,000 tooth and bone fragments. He presented a first rough layer structure as early as 1935. His main publication appeared in 1952 under the title Les Vertébrés fossiles des gisements de phosphates (Maroc-Algérie-Tunisie) . In this, Arambourg subdivided the sequence of layers of the Ouled-Abdoun basin into three main phosphate-containing members, called couches ( French for "layer" or "bed"), with the youngest ( Couche I ) from the Eocene and the oldest ( Couche III ) from the Maastrichtium . He also recognized an increasing layer thickness from northeast to southwest, which continues into the Ganntour basin to the southwest. He also succeeded in correlating the strata of the Ouled Abdoun Basin with that of the Ganntour Basin. The sequence of layers established by Arambourg for the Ouled-Abdoun Basin has largely been in place to this day. Corrections were only made in the fine stratigraphy, since, among other things, the oldest Paleocene could not be separated from Arambourg. The study of the fossil material also led to the introduction of numerous new taxa . What is striking here, however, is that, despite the richness of the fossil record , Arambourg did not consider any bird or turtle remains. Turtles were first mentioned in 1951, but the finds do not belong to the Ouled Abdoun Basin, but to the Sous Basin far to the south and date to the Upper Cretaceous. Henri Salvan worked with Arambourg in the phosphate basin. In 1955, in an extensive monograph entitled Les invertébrés fossiles des phosphates marocains, he presented the region's molluscs in detail .
Modern research
Following Arambourg's pioneering work, exploration of the Ouled Abdoun Basin largely came to a standstill over the next few decades. Only the various remains of sharks and rays received attention, to which Henri Cappetta and Abdelmajid Noubhani , among others , devoted themselves in the 1980s and 1990s. Individual reptiles were also taken into account selectively, for example by Eric Buffetaut . The situation only changed again in the mid-1990s. It was then that the Ouled Abdoun Basin gained new attention with the relatively unexpected discovery of Phosphatherium , the oldest member of the proboscis to date . This led to the signing of an official contract between the OCP, the Paris Muséum national d'histoire naturelle and the Moroccan Ministry of Energy, Mining, Water and Environment in 1997 to promote the investigation of fossil finds from the phosphate deposits. Various universities such as those in Marrakech , El Jadida , Montpellier and Bilbao were also involved . As a result of this collaboration, a large number of new fossils were recovered and examined in the period that followed. In addition to the known forms, these also included groups of animals that were still completely unknown in the Ouled-Abdoun Basin at the time of Arambourg, such as pterosaurs and land-dwelling mammals . Important scientists involved in the research include Nathalie Bardet (turtles and mosasaurs), Haiyan Tong (turtles), Stéphane Jouve (crocodiles), Nicholas R. Longrich (dinosaurs and pterosaurs), Xabier Pereda Suberbiola (dinosaurs and pterosaurs), Peggy Vincent (plesiosaurs), Alexandra Houssaye (scaled reptiles), Estelle Bourdon (birds) and Emmanuel Gheerbrant (early mammals). Most of the finds are kept at the OCP or in the Muséum national d'histoire naturelle. In addition, there were also large private collections and sales of fossil finds, which ended up in various institutions in Europe, North America or Asia.
literature
- Nathalie Bardet, Emmanuel Gheerbrant, Abdelmajid Noubhani, Henri Cappetta, Stéphane Jouve, Estelle Bourdon, Xabier Pereda Suberbiola, Nour-Eddine Jalil, Peggy Vincent, Alexandra Houssaye, Floréal Solé, Khadija El Houssaini,. Sylvain Adnet, France, Jean-Claude Rage Lapparent de Broin, Jean Sudre, Baâdi Bouya, Mbarek Amaghzaz and Saïd Meslouh: Les Vertébrés des Phosphates cretacés-paléogènes (70.6 - 46.6 Ma) du Maroc. In: Samir Zouhri (ed.): La Paléontologie des Vertébrés du Maroc. Paris, Mémoires de la Société Géologique de France, nouvelle série, 180, 2017, pp. 351–452
- E. Jourani, F. Khaldoune and N.-E. Aoudjehane (Ed.): Promoting Geological Heritage: Challenges and Issues. La Conférence Internationale RALI 2015, Marrakech 05–11 octobre 2015. Notes et Mémoires du Service Géologique du Maroc, Numéro Spécial dédié au Patrimoine Géologique du Maroc, 2018, pp. 103–136 ( [12] )
Individual evidence
- ↑ a b c d e f g h i Camille Arambourg: Les Vertébrés fossiles des gisements de phosphates (Maroc-Algérie-Tunisie). Paris, 1952, pp. 1–396
- ↑ a b c d e f g Nathalie Bardet, Xabier Pereda Suberbiola, Stéphane Jouve, Estelle Bourdon, Peggy Vincent, Alexandra Houssaye, Jean-Claude Rage, Nour-Eddine Jalil, Baâdi Bouya and Mbarek Amaghzaz: Reptilian assemblages from the latest Cretaceous - Palaeogene phosphates of Morocco: from Arambourg to present time. Historical Biology 22 (1), 2010, pp. 186-199, doi: 10.1080 / 08912961003754945
- ↑ Aaron RH Leblanc, Michael W. Caldwell and Nathalie Bardet: A new mosasaurine from the Maastrichtian (Upper Cretaceous) phosphates of Morocco and its implications for mosasaurine systematics. Journal of Vertebrate Paleontology 32 (1), 2012, pp. 82-104
- ↑ a b c d e f g h i Office Chérifien des Phosphates: The phosphates basins of Morocco. In: AJG Northolt, RP Sheldon and DF Davidson (eds.): Phosphate deposits of the world, Vol. 2 - Phosphate rock resources. Cambridge University Press, 1989, pp. 301-311
- ↑ a b c d Saad Bakkali: A resistivity survey of phosphate deposits containing hardpan pockets in Oulad Abdoun, Morocco. Geofísica Internacional 45 (1), 2006, pp. 73-82
- ↑ Hamid El Haddia, Abdelmajid Benbouziane, Mustapha Mouflih, Es-said Jourani and M'barek Amaghzaz: Siliceous forms of phosphate deposits of Cretaceous age in Oulad Abdoun basin (Central Morocco). Mineralogy, geochemistry and diagenetic phenomena. Procedia Engineering 83, 2014, pp. 60-69
- ↑ a b c d e f g h i j k Emmanuel Gheerbrant, Jean Sudre, Henri Cappetta, Cécile Mourer-Chauviré, Estelle Bourdon, Mohamed Iarochène, Mbarek Amaghzaz and Baâdi Bouya: Les localités à mammifères des carrières de Grand Daoui, bassin des Ouled Abdoun, Maroc, Yprésien: premier état des lieux. Bulletin de la Societe Geologique de France 174 (3), 2003, pp. 279-293
- ^ A b N. El Assel, A. Kchikach, C. Durlet, N. AlFedy, K. El Hariri, M. Charroud, M. Jaffal, E. Jourani and M. Amaghzaz: Mise en évidence d'un Sénonien gypseux sous la série phosphatée du bassin des Ouled Abdoun: Un nouveau point de départ pour l'origine des zones dérangées dans les mines à ciel ouvert de Khouribga, Maroc. Estudios Geológicos 69 (1), 2013, pp. 47-70, doi: 10.3989 / egeol.40781.168
- ↑ a b c H. El Haddi, A. Benbouziane and M. Mouflih: Geochemical Siliceous and Silicified Facies of Phosphate Series of Ouled Abdoun Basin (Morocco). Open Journal of Geology 4, 2014, pp. 295-302, doi: 10.4236 / ojg.2014.47022
- ↑ a b c d J. Lucas and L. Prévôt-Lucas: Tethyan phosphates and bioproductites. In: AEM Nairn, L.-E. Ricou, B. Vrielynck, and J. Dercourt (Eds.): The Ocean Basins and Margins, the Tethys Ocean. Plenum Press, New York, 1995, pp. 367-391
- ↑ a b c N. Bardet, X. Pereda Suberbiola, M. Iarochène, M. Amalik and B. Bouya: Durophagous Mosasauridae (Squamata) from the Upper Cretaceous phosphates of Morocco, with description of a new species of Globidens. Netherlands Journal of Geosciences - Geologie en Mijnbouw 84 (3), 2005, pp. 167-175
- ↑ a b c Hans-Georg Herbig: The paleogene on the southern edge of the central High Atlas and in the Middle Atlas of Morocco. Stratigraphy, facies, paleogeography and paleotectonics. Berliner Geoscientific Abhandlungen Series A 135, 1991, pp. 1–289
- ↑ a b c Hans-Georg Herbig and Jörg Trappe: Stratigraphy of the Subatlas Group (Maestrichtian - Middle Eocene, Morocco). Newsletter on Stratigraphy 30 (3), 1994, pp. 125-165
- ↑ Nadia El Kiram, Mohammed Jaffal, Azzouz Kchikach, Driss El Azzab, Mustapha El Ghorfi, Oussama Khadiri, Es-Said Jourani, Ahmed Manar and Mohamed Nahim: Phosphatic series under Plio-Quaternary cover of Tadla Plain, Morocco: Gravity and seismic data . Comptes Rendus - Geoscience 351, 2019, pp. 420-429, doi: 10.1016 / j.crte.2019.05.002
- ↑ Radouan El Bamiki, Michel Séranne, El Hassane Chellaï, Gilles Merzeraud, Mohamed Marzoqi and Mihaela Carmen Melinte-Dobrinescu: The Moroccan High Atlas phosphate-rich sediments: Unraveling the accumulation and differentiation processes. Sedimentary Geology, 2020, doi: 10.1016 / j.sedgeo.2020.105655
- ^ Gerhard Einsele and Jost Wiedmann: Turonian black shales in the Moroccan Coastal basins: first upwelling in the Atlantic Ocean. In: U. von Rad, K. Hinz, M. Sarnthein and E. Seibold (eds.): Geology of the Nordwest African Continental Margin. Springer, 1982, pp. 396-414
- ↑ Krzysztof P. Krajewski, Philippe Van Cappellen, Jean Trichet, Oliver Kuhn, Jacques Lucas, Agustín Martín-Algarra, Liliane Prévôt, Vinod C. Tewari, Luis Gaspar, Robin I. Knight and Michel Lamboy: Biological processes and apatite formation in sedimentary environments. Eclogae geologicae Helveticae 87 (3), 1994, pp. 701-745
- ^ Heide N. Schulz and Horst D. Schulz: Large Sulfur Bacteria and the Formation of Phosphorite. Science 307, 2005, pp. 416-418
- ↑ J. Cosmidis, K. Benzerara, E. Gheerbrant, I. Estève, B. Bouya and M. Amaghzaz: Nanometer ‐ scale characterization of exceptionally preserved bacterial fossils in Paleocene phosphorites from Ouled Abdoun (Morocco). Geobiology 11 (2), 2013, pp. 139–153, doi: 10.1111 / gbi.12022
- ↑ Craig R. Glenn, Karl B. Föllmi, Stanley R. Riggs, Gleb N. Baturin, Kurt A. Grimm, Jörg Trappe, Abdulkader M. Abed, Carlos Galli-Olivier, Robert E. Garrison, Andrei V. Ilyin, Caroline Jehl, Vera Rohrlich, Rushdi MY Sadaoah, Manfred Schidlowski, Richard E. Sheldon and Hendrik Siegmund: Phosphorus and phosphorites: Sedimentology and environments of formation. Eclogae geologicae Helveticae 87 (3), 1994, pp. 747-788
- ↑ Gabriel M. Filippelli: Phosphate rock formation and marine phosphorus geochemistry: The deep time perspective. Chemosphere 84, 2011, pp. 759-766, doi: 10.1016 / j.chemosphere.2011.02.019
- ↑ a b Oskar Bär: The phosphates of Morocco. Geographica Helvetica 23 (2), 1968, pp. 89-94 ( [1] )
- ↑ Jacques Lucas, Liliane Prévôt and Mohamed El Mountassir: Les phosphorites rubéfiées de Sidi Daoui, transformation météorique locale du gisement de phosphate des Ouled Abdoun (Maroc). Sciences Géologiques. Bulletin 32 (1-2), 1979, pp. 21-37
- ↑ Steven J. Van Kauwenbergh: World Phosphate Rock Reserves and Resources. International Fertilizer Development Center, Muscle Shoals, Alabama, 2010, pp. 1–48 ( [2] )
- ↑ JD Edixhoven, J. Gupta and HHG Savenije: Recent revisions of phosphate rock reserves and resources: a critique. Earth System Dynamics 5, 2014, pp. 491-507
- ↑ a b Azzouz Kchikach, Pierre Andrieux, Mohammed Jaffal, Mostafa Amrhar, Mohammed Mchichid, Baadi Boya, Mbarek Amaghzaz, Thierry Veyrieras and Khadija Iqizou: Les sondages électromagnétiques temporels comme outil de reconnaissance du gisement: phosphaté de Maridiport de Socidiport du gisement: la résolution d'un problem d'exploitation. Comptes Rendus - Geoscience 338, 2006, pp. 289-296
- ↑ Bruce A. Kennerdy: Surface Mining, Second Edition. Littleton, Colorado, 1990, pp. 1-1206 (p. 622)
- ↑ Azzouz Kchikach, Mohammed Jaffal, Tahar Aïfa and Lahcen Bahi: Cartographie de corps stériles sous couverture quaternaire par méthode de résistivités électriques dans le gisement phosphaté de Sidi Chennane (Maroc). Comptes Rendus - Geoscience 334, 2002, pp. 379-386
- ↑ Armand Boujo: About shape and development of sterile bodies in phosphatic deposits. Comptes Rendus - Geoscience 334, 2002, pp. 1113-1114
- ^ A b c Nicholas R. Longrich, Xabier Pereda Suberbiola, Nour-Eddine Jalil, Fatima Khaldoune and Essaid Jourani: An abelisaurid from the latest Cretaceous (late Maastrichtian) of Morocco, North Africa. Cretaceous Research 76, 2017, pp. 40-52, doi: 10.1016 / j.cretres.2017.03.021
- ↑ a b c Nicholas R. Longrich, David M. Martill and Brian Andres: Late Maastrichtian pterosaurs from North Africa and mass extinction of Pterosauria at the Cretaceous-Paleogene boundary. PLoS Biology 16 (3), 2018, p. E2001663, doi: 10.1371 / journal.pbio.2001663
- ↑ a b Lászlό Kocsis, Emmanuel Gheerbrant, Mustapha Mouflih, Henri Cappetta, Johan Yans and Mbarek Amaghzaz: Comprehensive stable isotope investigation of marine biogenic apatite from the late Cretaceous – early Eocene phosphate series of Morocco. Palaeogeography, Palaeoclimatology, Palaeoecology 394, 2014, pp. 74-88
- ↑ a b c Johan Yans, M'Barek Amaghzaz, Baâdi Bouya, Henri Cappetta, Paola Iacumin, László Kocsis, Mustapha Mouflih, Omar Selloum, Sevket Sen, Jean-Yves Storme and Emmanuel Gheerbrant: First carbon isotope chemostratigraphy of the Ouled Abdoun phosphate Basin, Morocco; implications for dating and evolution of earliest African placental mammals. Gondwana Research 25, 2014, pp. 257-269
- ↑ a b c d e f g h i j k l m n o p q r Nathalie Bardet, Emmanuel Gheerbrant, Abdelmajid Noubhani, Henri Cappetta, Stéphane Jouve, Estelle Bourdon, Xabier Pereda Suberbiola, Nour-Eddine Jalil, Peggy Vincent, Alexandra Houssaye, Floréal Solé, Khadija El Houssaini, Sylvain Adnet, Jean-Claude Rage, France de Lapparent de Broin, Jean Sudre, Baâdi Bouya, Mbarek Amaghzaz and Saïd Meslouh: Les Vertébrés des Phosphates cretacés-paléogènes (70.6 - 46.6 Ma) you Maroc. In: Samir Zouhri (ed.): La Paléontologie des Vertébrés du Maroc. Paris, Mémoires de la Société Géologique de France, nouvelle série, 180, 2017, pp. 351–452
- ↑ a b Emmanuel Gheerbrant, Arnaud Schmitt and László Kocsis: Early African Fossils Elucidate the Origin of Embrithopod Mammals. Current Biology 28 (13), 2018, pp. 2167–2173, doi: 10.1016 / j.cub.2018.05.032
- ↑ a b c d E. Jourani, F. Khaldoune and N.-E. Jalil: Les fossiles des phosphates du Maroc, une mémoire de 24 millions d'années, valorisation et préservation par l'OCP. In: K. El Hariri and H. Chennaoui Aoudjehane (eds.): Promoting Geological Heritage: Challenges and Issues. La Conférence Internationale RALI 2015, Marrakech 05-11 octobre 2015. Notes et Mémoires du Service Géologique du Maroc, Numéro Spécial dédié au Patrimoine Géologique du Maroc, 2018, pp. 103-136
- ^ A b Edouard Boureau: Contribution à l'étude paléoxylologique de l'Afrique du Nord (III): Pterocarpoxylon arambourgii n. Gen., N. Sp., Bois silicifié de Leguminoseae – Papilioneae découvert dans les phosphates yprésiens de Khouribga (Maroc) . Bulletin du Muséum National d'Histoire Naturelle 2 (23), 1951, pp. 552–557 ( [3] )
- ↑ Raymond Rauscher and Jeanne Doubinger: Les dinokystes you Maestrichtien Phosphates du Maroc. Sciences Géologiques. Bulletin 35 (3), 1982, pp. 97-116
- ^ Marie-Jo Soncini and Raymond Rauscher: Morphologies particuliéres chez les dinokystes des genres lsabelidinium, Manumiella et Dinogymnium dans les phosphates maastrichtiens et paléocénes du Maroc. Bulletin des Centers de Recherches Exploration-Production Elf-Aquitaine 14 (2), 1990, pp. 583-596
- ^ Marie-Jo Soncini: Three new dinoflagellate cysts from the Moroccan Paleocene-Eocene phosphates. Review of Palaeobotany and Palynology 70, 1992, pp 325-338
- ↑ a b c Jean-Michel Pacaud and Patrice Lebrun: Les phosphates du Maroc (2): des faunes d'invertébrés dominées par les bivalves et les gastéropodes. Fossiles 40, 2019, pp. 17-37
- ↑ a b c Henri Cappetta: Additions à la faune de sélaciens fossil du Maroc. 1: Sur la présence des genres Heptranchias, Alopiaset Odontorhytisdans l'Yprésien des Ouled Abdoun. Geobios 14 (5), 1981, pp. 563-575
- ↑ a b c d e Abdelmajid Noubhani and Henri Cappetta: Les Orectolobiformes, Carcharhiniformes et Myliobatiformes (Elasmobranchii, Neoselachii) des bassins à phosphate du Maroc (Maastrichtien-Lutétien basal). Systématique, biostratigraphie, évolution et dynamique des faunes. Palaeo Ichthyologica 8, 1997, pp. 1-327
- ^ A b Jaques Herman: Contribution à la connaissance de la faune ichthyologique des phosphates du Maroc. Annales de la Société Géologique de Belgiqiie 95, 1972, pp. 271-284
- ↑ Bruce J. MacFadden, Joann Labs-Hochstein, Irvy Quitmyer and Douglas S. Jones: Incremental growth and diagenesis of skeletal parts of the lamnoid shark Otodus obliquus from the early Eocene (Ypresian) of Morocco. Palaeogeography, Palaeoclimatology, Palaeoecology 206, 2004, pp. 179-192
- ↑ a b Henri Cappetta, Sylvain Adnet, Driss Akkrim and Mohamed Amalik: New Squalicorax species (Neoselachii: Lamniformes) from the Lower Maastrichtian of Ganntour phosphate deposit, Morocco. Palaeovertebrata 38 (2), 2014, p. E3, doi: 10.18563 / pv.38.2.e3
- ↑ Henri Cappetta: Révision de Cestracion duponti Winkler, 1874 (Selachii, Batomorphii) you Bruxellien de Woluwe-Saint-Lambert (Eocene moyen de Belgique). Mededelingen van de Werkgroep voor Tertiaire en Kwartaire Geologie 19 (4), 1982, pp. 113-125
- ↑ Henri Cappetta: Découverte du genre Gymnura (Batomorphii, Myliobatiformes) dans le Thanétien of Ouled Abdoun, Maroc. Observations on the denture de quelques espèces actuelles. Geobios 17 (5), 1984, pp. 631-635
- ↑ Henri Cappetta: Un nouveau genre de sélacien (Batomorphii, Myliobatiformes) de l'Yprésien of Ouled Abdoun, Maroc. Geobios 19 (5), 1986, pp. 635-640
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- ^ Emmanuel Gheerbrant: Premières données sur les mammifères "insectivores" de l'Yprésien du bassin d'Ouarzazate. New Yearbook for Geology and Paleontology, Abhandlungen 187, 1993, pp. 225–242
- ↑ Emmanuel Gheerbrant, Jean Sudre, Sevket Sen, Claude Abrial, Bernard Marandat, Bernard Sigé and Moniue Vianey-Liaud: Nouvelles données sur les mammifères du Thanétien et de l'Yprésien du Bassin d'Ouarzazate (Maroc) et leur contexte stratigraphique. Palaeovertebrata 27, 1998, pp. 155-202
- ↑ Rodolphe Tabuce, Sylvain Adnet, Henri Cappetta, Abdelmajid Noubhani and Frédéric Quillevere: Aznag (bassin d'Ouarzazate, Maroc), nouvelle localité à sélaciens et mammifères de l'Eocène moyen (Lutétien) d'Afrique. Bulletin de la Societe geologique de France 176 (4), 2005, pp. 381-400
- ↑ Mohammed Mahboubi, R. Ameur, Jean-Yves Crochet and Jean-Jacques Jaeger: El kohol (Saharan Atlas, Algeria): A new Eocene mammal locality in northwestern Africa. Palaeontographica, Division A 192, 1986, pp. 15-49
- ^ J. Sudre: Nouveaux mammifères éocènes du Sahara occidental. Palaeovertebrata 9, 1979, pp. 83-115
- ↑ Mohammed Adaci, Rodolphe Tabuce, Fateh Mebrouk, Mustapha Bensalah, Pierre-Henri Fabre, Lionel Hautier, Jean-Jacques Jaeger, Vincent Lazzari, M'hammed Mahboubi, Laurent Marivaux, Olga Otero, Stéphane Peigné and Haiyan Tong: Nouveaux sites à vertébrés paleogènes dans la region des Gour Lazib (Sahara north-occidental, Algérie). Comptes Rendus Palevol 6, 2007, pp. 535-544
- ^ Jean-Louis Hartenberger, Claude Martinez and Ahmed Ben Said: Découverte de mammifères d'âge Éocène inférieur en Tunisie centrale. Comptes rendus de l'Académie des sciences. Série 2 301, 1985, pp. 649-652 ( [5] )
- ↑ Rodolphe Tabuce, Laurent Marivaux, Mohammed Adaci, Mustapha Bensalah, Jean-Louis Hartenberger, Mohammed Mahboubi, Fateh Mebrouk, Paul Tafforeau and Jean-Jacques Jaeger: Early Tertiary mammals from North Africa reinforce the molecular Afrotheria clade. Proceedings of the Royal Society B 274, 2007, pp. 1159-1166
- ↑ Elwyn L. Simons: Eocene and Oligocene mammals of the Fayum, Egypt. In: First International Conference on the Geology of the Tethys, Cairo University, November, 2005, Volume II. Cairo 2005, pp. 439-450
- ↑ Sylvain Adnet, Henri Cappetta and Rodolphe Tabuce: A Middle-Late Eocene vertebrate fauna (marine fish and mammals) from southwestern Morocco; preliminary report: age and palaeobiogeographical implications. Geological Magazine 147 (6), 2010, pp. 860-870, doi: 10.1017 / S0016756810000348
- ↑ Samir Zouhri, Philip D. Gingerich, Najia Elboudali, Samira Sebti, Abdelmajid Noubhani, Meriem Rahali and Saïd Meslouh: New marine mammal faunas (Cetacea and Sirenia) and sea level change in the Samlat Formation, Upper Eocene, near Ad-Dakhla in southwestern Morocco. Comptes Rendus Palevol 13, 2014, pp. 599-610, doi: 10.1016 / j.crpv.2014.04.002
- ↑ Samir Zouhri, Bouziane Khalloufi, Estelle Bourdoni, France de Lapparent de Broin, Jean-Claude Rage, Leila M'Haïdrat, Philip D. Gingerich and Najia Elboudali: Marine vertebrate fauna from the late Eocene Samlat Formation of Ad-Dakhla, southwestern Morocco . Geological Magazine 15 (7), 2018, pp. 1596-1620, doi: 10.1017 / S0016756817000759
- ^ Philippe Thomas: Description de quelques fossiles nouveaux ou critiques des terrains tertiaires et secondaires de la Tunisie recueillis en 1885 et 1886. Exploration Scientifique de la Tunisie. Paris: Imprimerie Nationale, 1893, pp. 1–46 ( [6] )
- ^ Abel Brives: Sur les terrains éocènes dans le Maroc occidental. Comptes rendus de l'Académie des Sciences 140, 1905, pp. 395–397 ( [7] )
- ↑ Abel Brives: Sur le Sénonien et l'Eocène de la bordure nord de l'Atlas marocain. Comptes rendus de l'Académie des Sciences 146. 1908, pp. 873–875 ( [8] )
- ↑ Abel Brives: Le Suessonien dans le Maroc central. Comptes Rendus de l'Académie des Sciences de Paris 168, 1917, pp. 776–777 ( [9] )
- ↑ Léonce Joleaud: Sur l'âge des dépôts de phosphate de chaux du Sud marocain, Algerien et Tunisien. Comptes Rendus de l'Académie des Sciences de Paris 174, 1922, pp. 178-181 ( [10] )
- ↑ Louis Gentil: Sur l'âge des phosphates marocains. Comptes rendus de l'Académie des Sciences de Paris 174, 1922, pp. 42–44 ( [11] )
Web links
- Center de recherche en paleontologie Paris: Current work and results from the phosphate Basins of Morocco ; last accessed on June 1, 2010