The Aoufous Formation is a geological

formation Formation may refer to: Linguistics * Back-formation, the process of creating a new lexeme by removing or affixes * Word formation, the creation of a new word by adding affixes Mathematics and science * Cave formation or speleothem, a secondary ...

that contains some of the

vertebrate Vertebrates () comprise all animal taxon, taxa within the subphylum Vertebrata () (chordates with vertebral column, backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the ...

assemblage of the Kem Kem Group, of

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''creta'', ...

date.Cavin et al., 2010, p.391Dal Sasso, C., Maganuco, S., Buffetaut, E., Mendez, M.A., 2005. New information on the skull of the enigmatic theropod ''Spinosaurus'', with remarks on its size and affinities. Journal of Vertebrate Paleontology 25 (4), 888–896. Two other formations comprise the Kem Kem beds: the underlying Ifezouane Formation and the overlying Akrabou Formation.

Description

The Aoufous Formation was first reported by Dubar (1948) as part of the “Sillon Preafricain”. Dubar described it from a

lithological The lithology of a rock unit is a description of its physical characteristics visible at outcrop, in hand or core samples, or with low magnification microscopy. Physical characteristics include colour, texture, grain size, and composition. Lith ...

point of view as consisting mainly of clay-sandstones and green marls with

gypsum Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula . It is widely mined and is used as a fertilizer and as the main constituent in many forms of plaster, blackboard or sidewalk chalk, and dr ...

. Dubar dated the sediments to the

Albian The Albian is both an age of the geologic timescale and a stage in the stratigraphic column. It is the youngest or uppermost subdivision of the Early/Lower Cretaceous Epoch/ Series. Its approximate time range is 113.0 ± 1.0 Ma to 100.5 ± ...

/ Cenomanian stages. Later, Sereno et al. (1996) reported an informal division of the Kem Kem Beds: a lower red sandstone unit ("''gres infrecenomanien''") and an upper marley unit ("''marne versicolores a gypse''"). Because of the absence of hiatuses between and within the three formations, the represented time scale is of around 8 million years, covering the time from the Early Cenomanian to the Middle

Turonian The Turonian is, in the ICS' geologic timescale, the second age in the Late Cretaceous Epoch, or a stage in the Upper Cretaceous Series. It spans the time between 93.9 ± 0.8 Ma and 89.8 ± 1 Ma (million years ago). The Turonian is preceded ...

. The Aoufous Formation is exposed from the

Anti-Atlas The Anti-Atlas ( ar, الأطلس الصغير, shi, Aṭlas Mẓẓiyn), also known as Lesser Atlas or Little Atlas is a mountain range in Morocco, a part of the Atlas Mountains in the northwest of Africa. The Anti-Atlas extends from the Atlanti ...

and

High Atlas High Atlas, also called the Grand Atlas ( ar, الأطلس الكبير, Al-Aṭlas al-Kabīr; french: Haut Atlas; shi, ⴰⴷⵔⴰⵔ ⵏ ⴷⵔⵏ ''Adrar n Dern''), is a mountain range in central Morocco, North Africa, the highest part of t ...

mountain ranges up to the Sahara craton, in the southeastern part of Morocco. The formation is thick.Cavin et al., 2010, p.394

Geological history

In the early

Mesozoic The Mesozoic Era ( ), also called the Age of Reptiles, the Age of Conifers, and colloquially as the Age of the Dinosaurs is the second-to-last era of Earth's geological history, lasting from about , comprising the Triassic, Jurassic and Creta ...

Era, the main displacement of the African continent was from south to north, in the direction of

Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a subcontinent of Eurasia and it is located enti ...

. The

Atlantic Ocean The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth#Surface, Earth's surface and about 29% of its water surface area. It is known to separate the "Old World" of Afr ...

was opening with high rates of expansion. This caused the uplift of the western part of Morocco, causing exposure of

Precambrian The Precambrian (or Pre-Cambrian, sometimes abbreviated pꞒ, or Cryptozoic) is the earliest part of Earth's history, set before the current Phanerozoic Eon. The Precambrian is so named because it preceded the Cambrian, the first period of th ...

and

Paleozoic The Paleozoic (or Palaeozoic) Era is the earliest of three geologic eras of the Phanerozoic Eon. The name ''Paleozoic'' ( ;) was coined by the British geologist Adam Sedgwick in 1838 by combining the Greek words ''palaiós'' (, "old") and ' ...

rocks, and prevented a continuous deposition of Mesozoic sediments in western Morocco. In the

Jurassic The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately Mya. The J ...

, most of modern Morocco had already emerged. The first

marine transgression A marine transgression is a geologic event during which sea level rises relative to the land and the shoreline moves toward higher ground, which results in flooding. Transgressions can be caused by the land sinking or by the ocean basins filling ...

is dated to the Early

Barremian The Barremian is an age in the geologic timescale (or a chronostratigraphic stage) between 129.4 ± 1.5 Ma ( million years ago) and 121.4 ± 1.0 Ma). It is a subdivision of the Early Cretaceous Epoch (or Lower Cretaceous Series). It is pre ...

. During the Barremian-Aptian, two elongated marine

gulf A gulf is a large inlet from the ocean into the landmass, typically with a narrower opening than a bay, but that is not observable in all geographic areas so named. The term gulf was traditionally used for large highly-indented navigable bodies ...

s extended northwards along the Middle-Atlas and from the western

Essaouira Basin Essaouira ( ; ar, الصويرة, aṣ-Ṣawīra; shi, ⵜⴰⵚⵚⵓⵔⵜ, Taṣṣort, formerly ''Amegdul''), known until the 1960s as Mogador, is a port city in the western Moroccan region of Marakesh-Safi, on the Atlantic coast. It ha ...

. In the

Early Cretaceous The Early Cretaceous (geochronological name) or the Lower Cretaceous ( chronostratigraphic name), is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 145 Ma to 100.5 Ma. Geology Pr ...

, Northern Africa was covered with deltaic and

brackish Brackish water, sometimes termed brack water, is water occurring in a natural environment that has more salinity than freshwater, but not as much as seawater. It may result from mixing seawater (salt water) and fresh water together, as in estuari ...

environments. These deposits comprise the Kem Kem Beds and thus the Aoufous Formation too.

Age

The Aoufous Formation shows a similar fauna to that one found in the

Bahariya Formation The Bahariya Formation (also transcribed as Baharija Formation) is a fossiliferous geologic formation dating back to the early Cenomanian, which outcrops within the Bahariya depression in Egypt, and is known from oil exploration drilling across ...

Egypt Egypt ( ar, مصر , ), officially the Arab Republic of Egypt, is a transcontinental country spanning the northeast corner of Africa and southwest corner of Asia via a land bridge formed by the Sinai Peninsula. It is bordered by the Med ...

. In both these formations, '' Carcharodontosaurus saharicus'' and ''

Spinosaurus aegyptiacus ''Spinosaurus'' (; ) is a genus of spinosaurid dinosaur that lived in what now is North Africa during the Cenomanian to upper Turonian stages of the Late Cretaceous period, about 99 to 93.5 million years ago. The genus was known first ...

'' are found. In addition, several species of

crocodilian Crocodilia (or Crocodylia, both ) is an order of mostly large, predatory, semiaquatic reptiles, known as crocodilians. They first appeared 95 million years ago in the Late Cretaceous period ( Cenomanian stage) and are the closest living ...

s and fishes are shared. The Bahariya Formation is well dated to the Early Cenomanian. The rare

microfossil A microfossil is a fossil that is generally between 0.001 mm and 1 mm in size, the visual study of which requires the use of light or electron microscopy. A fossil which can be studied with the naked eye or low-powered magnification, ...

s found in the Aoufous Formation were not helpful in dating these sediments. For these reasons, the age of the Aoufous Formation is considered early Cenomanian.

Facies

The Aoufous Formation is characterized by three

facies In geology, a facies ( , ; same pronunciation and spelling in the plural) is a body of rock with specified characteristics, which can be any observable attribute of rocks (such as their overall appearance, composition, or condition of formatio ...

: variegated

claystone Mudrocks are a class of fine-grained siliciclastic sedimentary rocks. The varying types of mudrocks include siltstone, claystone, mudstone, slate, and shale. Most of the particles of which the stone is composed are less than and are too sm ...

s, gypsum layers and

dolomitic Dolomite () is an anhydrous carbonate mineral composed of calcium magnesium carbonate, ideally The term is also used for a sedimentary carbonate rock composed mostly of the mineral dolomite. An alternative name sometimes used for the dol ...

limestones. Claystones contain organic matter. Vertebrate remains (mostly fishes) are found in these claystones. No calcitic shells are found there, but apatitic microfossils are present.

Quartz Quartz is a hard, crystalline mineral composed of silica ( silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon-oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical ...

and

marcasite The mineral marcasite, sometimes called “white iron pyrite”, is iron sulfide (FeS2) with orthorhombic crystal structure. It is physically and crystallographically distinct from pyrite, which is iron sulfide with cubic crystal structure. Bot ...

(typical of a reducing environment) are quite frequent. In carbonaceous facies, vertebrate fossils are present. The dolomitisation of these sediments destroyed any organic presence in them.

Gastropods The gastropods (), commonly known as snails and slugs, belong to a large taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, from freshwater, and from land. ...

, thin-shelled and thick-shelled

ostracod Ostracods, or ostracodes, are a class of the Crustacea (class Ostracoda), sometimes known as seed shrimp. Some 70,000 species (only 13,000 of which are extant) have been identified, grouped into several orders. They are small crustaceans, typic ...

s and some rare agglutinated

foraminifer Foraminifera (; Latin for "hole bearers"; informally called "forams") are single-celled organisms, members of a phylum or class of amoeboid protists characterized by streaming granular ectoplasm for catching food and other uses; and commonly ...

s are present in this facies. Quartz is present with different morphologies, suggesting eolian (wind-based) and

fluvial In geography and geology, fluvial processes are associated with rivers and streams and the deposits and landforms created by them. When the stream or rivers are associated with glaciers, ice sheets, or ice caps, the term glaciofluvial or fluv ...

(river-based) transport. In the gypsum layers, fossils are absent. These layers testify to long periods of dryness connected to evaporation of salty waters. The facies and the fossil remains suggest a paleoenvironment as a coastal

lagoon A lagoon is a shallow body of water separated from a larger body of water by a narrow landform, such as reefs, barrier islands, barrier peninsulas, or isthmuses. Lagoons are commonly divided into '' coastal lagoons'' (or ''barrier lagoons' ...

or a paralic sebkha.

OT1

OT1 is a locality ( away from Tafraout) characterized by lenses of claystone. Several fossil articulated fishes, gastropods and crustaceans specimens were recovered from this locality. The stratigraphic position of these lenses of claystone lies within the Aoufous Formation. Several features differentiate this facies from the others that are commonly encountered in the Aoufous Formation, and, for this reason, they are usually described apart. The fauna of these lenses is characterized from three cladistians (''

Serenoichthys kemkemensis ''Serenoichthys'' is an extinct genus of small bichir from the Late Cretaceous ( Cenomanian) of southeastern Morocco. The genus is monotypic, the type and only species being ''Serenoichthys kemkemensis''. Only known at first from postcranial ske ...

'' and two other unnamed genera), an indeterminate actinopterygian, and the oldest known freshwater acanthomorph ('' Spinocaudichthys oumtkoutensis''). The paleoenvironment of OT1 has been interpreted as a quiet lake, where the process of fossilization was quite rapid (soft tissues are generally preserved).

Vertebrate assemblage

Because fossils from the formation are usually retrieved by local people who are untrained as geologists, it is difficult to know the exact provenance of many of them. For this reason, the provenance of a fossil from the Ifezouane and the Aoufous Formations is not generally specified; in any case the two formations seem to present the same fauna. The most common vertebrate remains belong to the

elasmobranch Elasmobranchii () is a subclass of Chondrichthyes or cartilaginous fish, including sharks (superorder Selachii), rays, skates, and sawfish (superorder Batoidea). Members of this subclass are characterised by having five to seven pairs of g ...

fish '' Onchopristis numidus''. Another seven elasmobranchs are reported: '' Asteracanthus aegyptiacus'', '' Distobatus nutiae'', ''

Tribodus ''Tribodus'' is an extinct genus of hybodont shark from the Romualdo Formation of northeastern Brazil. It lived during the Early Cretaceous period (Aptian to Albian The Albian is both an age of the geologic timescale and a stage in the str ...

'' sp., ''

Lissodus ''Lissodus'' is an extinct genus of freshwater shark. It lived from the Early Carboniferous stage Early may refer to: History * The beginning or oldest part of a defined historical period, as opposed to middle or late periods, e.g.: ** Early ...

'' sp., '' Haimirichia amonensis'', Cretoxyrhinidae indet., and '' Marckgrafia lybica''. Lungfish fossils are referred to '' Ceratodus humei'' and '' Neoceratodus africanus''.

Coelacanth The coelacanths ( ) are fish belonging to the order Actinistia that includes two extant species in the genus '' Latimeria'': the West Indian Ocean coelacanth (''Latimeria chalumnae''), primarily found near the Comoro Islands off the east c ...

remains are referred to '' Mawsonia lavocati'' and to the genus ''

Axelrodichthys ''Axelrodichthys'' is an extinct genus of mawsoniid coelacanth from the Cretaceous of Africa, North and South America, and Europe. Several species are known, the remains of which were discovered in the Lower Cretaceous (Aptian-Albian) of Brazi ...

''. Several taxa of

Cladistia Cladistia is a clade of bony fishes whose only living members are the bichirs. Their major synapomorphies are a heterocercal tail in which the dorsal fin has independent rays, and a posteriorly elongated parasphenoid. Cladistia are the earlies ...

and two genera of seminiomorphs (an unnamed ''

Lepidotes ''Lepidotes'' (from el, λεπιδωτός , 'covered with scales') (previously known as ''Lepidotus'') is an extinct genus of Mesozoic ray-finned fish. It has been considered a wastebasket taxon, characterised by "general features, such as thic ...

''-like species and '' Oniichthys falipoui'') are recovered in the Kem Kem beds. Teleosteans are represented by ''

Cladocyclus pankowskii ''Cladocyclus'' (derived from the Greek κλάδος/kládos ("branch") and κύκλος/kýklos ("circle")) is an extinct genus of Ichthyodectidae. It was a predatory fish of about in length, found in the Albian Romualdo and Crato Formatio ...

'', '' Palaeonotopterus greenwoodi'', '' Erfoudichthys rosae'' and '' Concavotectum moroccensis''.

Amphibians Amphibians are four-limbed and ectothermic vertebrates of the class Amphibia. All living amphibians belong to the group Lissamphibia. They inhabit a wide variety of habitats, with most species living within terrestrial, fossorial, arb ...

are also present: '' Kababisha'' sp., the pipid frog '' Oumtkoutia anae'' and non-pipids frogs.

Turtle Turtles are an order of reptiles known as Testudines, characterized by a special shell developed mainly from their ribs. Modern turtles are divided into two major groups, the Pleurodira (side necked turtles) and Cryptodira (hidden necked ...

s are represented by several species: '' Dirqadim schaefferi'', the podocnemidids '' Hamadachelys escuilliei'', the bothremydids '' Galianemys whitei'' and ''G. emringeri'', and the araripemydids '' Araripemys'' sp.

Crocodilian Crocodilia (or Crocodylia, both ) is an order of mostly large, predatory, semiaquatic reptiles, known as crocodilians. They first appeared 95 million years ago in the Late Cretaceous period ( Cenomanian stage) and are the closest living ...

s are commonly found; four species are present: '' Elosuchus cherifiensis'', a genus belonged to the

Trematochampsidae Trematochampsidae is an extinct family of mesoeucrocodylian crocodylomorphs. Fossils are present from Madagascar, Morocco, Niger, Argentina, and Brazil (in the case of ''Caririsuchus'', where some specimens have been found in the Romualdo Membe ...

, '' Araripesuchus rattoides'' and ''

Laganosuchus maghrebensis ''Laganosuchus'' is an extinct genus of stomatosuchid crocodyliform. Fossils have been found from Niger and Morocco and date back to the Upper Cretaceous. Discovery The name means "pancake crocodile" from the Greek , ("pancake") and , ("croc ...

''. In regards to

dinosaurs Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...

, a

rebbachisaurid Rebbachisauridae is a family of sauropod dinosaurs known from fragmentary fossil remains from the Cretaceous of South America, Africa, North America, Europe and possibly Central Asia. Taxonomy In 1990 sauropod specialist Jack McIntosh included t ...

(''

Rebbachisaurus garasbae ''Rebbachisaurus'' (meaning " Aït Rebbach lizard") is a genus of sauropod dinosaur of the superfamily Diplodocoidea, that lived during the Late Cretaceous period in Africa and possibly also South America about 99-97 million years ago. Remains at ...

'') and some

ornithischia Ornithischia () is an extinct order of mainly herbivorous dinosaurs characterized by a pelvic structure superficially similar to that of birds. The name ''Ornithischia'', or "bird-hipped", reflects this similarity and is derived from the Greek ...

n footprints were recovered in the Kem Kem Beds; the most important presence belongs to

theropod Theropoda (; ), whose members are known as theropods, is a dinosaur clade that is characterized by hollow bones and three toes and claws on each limb. Theropods are generally classed as a group of saurischian dinosaurs. They were ancestrally ...

s. Among theropods, two carcharodontosaurids ('' Carcharodontosaurus saharicus'' and '' Sauroniops pachytholus''), one spinosaurid (''

''), one coelurosaur (''

Deltadromeus agilis ''Deltadromeus'' (meaning "delta runner") is a genus of theropod dinosaur from Northern Africa. It had long, unusually slender hind limbs for its size, suggesting that it was a swift runner. The skull is not known. One fossil specimen of a ...

''), an unnamed abelisaur and an unnamed

dromaeosaur Dromaeosauridae () is a family of feathered theropod dinosaurs. They were generally small to medium-sized feathered carnivores that flourished in the Cretaceous Period. The name Dromaeosauridae means 'running lizards', from Greek ('), meaning ...

characterize the assemblage.

Pterosaur Pterosaurs (; from Greek ''pteron'' and ''sauros'', meaning "wing lizard") is an extinct clade of flying reptiles in the Order (biology), order, Pterosauria. They existed during most of the Mesozoic: from the Late Triassic to the end of the Cre ...

s are also present, although their fossils are extremely rare and enigmatic: an azhdarchid, an

ornithocheirid Ornithocheiridae (or ornithocheirids, meaning "bird hands") is a group of pterosaurs within the suborder Pterodactyloidea. These pterosaurs were among the last to possess teeth. Members that belong to this group lived from the Early to Late ...

, a tapejarid and a

pteranodontid The Pteranodontidae are a family of large pterosaurs of the Cretaceous Period of North America and Africa. The family was named in 1876 by Othniel Charles Marsh. Pteranodontids had a distinctive, elongated crest jutting from the rear of the h ...

are recognized.

References

{{reflist

Bibliography

Cavin L., et al. 2010. Vertebrate assemblages from the early Late Cretaceous of southeastern Morocco: An overview. Journal of African Earth Sciences 57, 391-412