Azilal Formation
The Azilal Formation, also known as Toundute Continental Series & Wazzant Formation is a geological unit in the Azilal & Ouarzazate provinces of the High Atlas of Morocco, that cover the Middle Toarcian to Lower Aalenian stages of the Jurassic Period. It is a terrestrial deposit which overlies marine dolomites of equivalent age to the Budoš Limestone of Montenegro or the Marne di Monte Serrone of Italy. Dinosaur remains, such the Sauropod Tazoudasaurus and the Basal Ceratosaur Berberosaurus are known from the unit, along with several undescribed genera. The Units inside the group have been considered individual on the past, being a division of the so-called "Couches rouges", and subdivided by a supposed geological scale. The strata of the group extends towards the Central High Atlas, covering different anticlines, and topographic accidents along the range of the Mountains. Although new studies have suggested that the strata is coeval in age, and should be referred to as a unique unit. The Group is believed to have been a mostly deltaic, and river channels filled a succession of seashore and inland environments, covering the late Liassic coast of modern northern Africa. Based on observed halokinetic strata, the Tazoult Ridge evolved as a Salt Wall forming a 20 km long NE-SW trending structural and sedimentary high for at least 20 million years, between Pliensbachian-Bajocian periods. This emerged small landmass generated a great local Diapir, with continuous Diapirism until the end of the Aalenian.
Main Azilal Strata
The Azilal Formation is the main sedimentary unit inside the Group. It was the first named unit, and one of the most studied since the 1980s. It consists mostly on a succession of detritic rocks with Red Marls, deposited on an alluvial environment occasionally interrupted by shallow marine incursions, a Mudflat setting. The lithology of the unit recovers also a Claystone-dominated interval, incised by metric dolomitized beds of Mudstones, Peloid-rich Packstones, Ooid-rich Grainstones, and Polymictic Conglomerates, all rich in Terrestrial plant debris, with faunal content very poor and mostly dominated by microbial facies. The Jbel El Abbadine zone provides the biggest afloration of the parts of a Calcareous massif, with strata of the Late Lias. Mostly of this strata is recovered inside the Azilal Formation, with a succession of seashore and inland deposits. Several seismic events located on the Tethian realm where the main genesis of the Tectonic activity locally, with emerged strata from the Paleozoic, that was eroded due to the local conditions. Along with the Wazzant Formation, the Two units and Azilal characterize the outer borders of the Atlas Gulf during the Toarcian-Aalenian. The Formations are a connected continuation, with the presence of abundant marine y Brackish common material, along with th fluvial facies of the Wazzant formation. On the disposition of the facies from north to south and from west to east, a lateral passage shows from coastal to fluvial sedimentary deposition, with foreshore facies and beach facies. The Azilal Formation was deposited on an environment more influenced by marine sedimentation than the Wazzant Formation. Along the main Toarcian strata, there is a predominantly presence of basinal facies, dominant and quite uniform, leading to know a possible deposition controlled by thermal subsidence, generating a deposit of more than 5000 m of marls and calci-Turbidites accumulated until the end of Bajocian. Part of the marine deposits of the Azilal Formation are a continuation of the common Lithiotid-Coral reef deposits from the Toarcian Central High Atlas. Those reef-related facies start mostly on upper Pliensbachian-lower Toarcian boundary, and are commonly filled with Lithioperna, Cochlearites, and specially Phaceloidea corals that built reefal Framestones extended on lateral Biostromes. The Azilal Formation coralline strata is nearly unexistent, compared with other formations of the High Atlas, showing a decreasing on these kinds of habitats as the Aalenian period started. The aftermath of the Toarcian Oceanic Anoxic Event is also highly present on the marine strata of the formation, with the so-called Toksine Section, a succession of near shore marine strata disposed along the Toarcian boundary, where its last 40 m belong to the lower part of the Azilal Formation and are composed of dolomitized Mudstones and ooidal Grainstones, that show a slowly recovering a low-depth nearshore marine environment after in the Pliensbachian-Toarcian boundary a dramatic Tethys-wide collapse of the Neritic Carbonate System happened. There is also a local record of a Cold Snap, where the Akenzoud section, that has 182 section meters on the Azilal Formation, and shows that after cold event that affect the local waters, related to the Karoo & the Atlantic Rift vulcanism the present Brachiopods, based on their preserved oxygen isotope data show that warm seawater temperatures re-established during the early Late Toarcian. The study of this section also revealed that the beach to nearshore deposits of the formation were part of a storm-dominated platform. On the related strata there is a wide presence of storm events, as after the Toarcian AE and the rising of the temperatures on the late Toarcian the presence of ubiquitous storm deposits appear correlated to the warming of sea-surface temperatures, pointing to an intensification of tropical cyclones during the T-OAE and other warmer periods on the Toarcian.| Unit | Lithology | Thickness | Sandstone with a wine tone, composed by grains that range from 1/4 to 1 mm | 0.2 m | Non present |
| 2) | Red Pelites: these levels form the horizontal table of the Summit | 4–5 m | Non present | ||
| 3) | Red Sandstone composed by grains of 1/2 mm in benches of 10 to 20 cm | 1 m | Non present | ||
| 4) | Lithified red Pelite | 2 m | Non present | ||
| 5) | Coarse red sandstone | Sandy red pelites | 2 m | Non present | |
| 7) | Red pelites passing through Leafy sandstone | 2 m | Non present | ||
| 8) | Sandy red pelites | 8–10 m | Non present | ||
| 9) | Yellowish marno-conglomeratic Sandstone, with bones and remains of plants, which, when not transformed into Lignite, show traces of preserved structure; this lenticular layer, which does not seem to exceed 80 cm, locally contains regions of sandstone and Calcite Geodes | 0.8 m |
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| 10) | Bluish sandstones of fairly variable composition: fine particles, with grains of 0.5 mm, thar contain various minerals such as Angular Quartz, Plagioclases, abundant Chlorite, clastic Andalusite and Iron Oxide; The coarse parts, the grain reaches 2 mm, consisting of often hexagonal Quartz and Moscovite, over Cemented Calcite; on the whole, there is an arched afloration of not only of a solid mass of Granite, locally of Granulite, but decorated with its metamorphic mass; Overall, this level has surface impregnations of Malachite | 2 m | |||
| 11) | Yellowish marno-conglomeratic Sandstone, like the level 9, also containing abundant bone material. | 0.7 m | |||
| 12) | Pelite and Bluish sandstones | 0.7 m | |||
| 13) | Very finely lit bistrated limestone, with green and purple grains | 0.2-0.3 m | |||
| 13) | Red, Bluish and Green Pelites, disposed on lenticular bands over yellow Breccia marls, parallel deposited with bodies od Calcite | 10–15 m |
Geology
The Central High Atlas of Morocco is part of a double‐vergent mountain belt that originated due to Cenozoic shortening and inversion of a rift that developed between the Triassic‐Jurassic periods. The structure of the High Atlas can be defined by two main groups of faults, thrust and oblique‐slip faults, that occur from W‐E to NE‐SW. The presence of different fault systems also suggests partitioning of deformation under a transpressive regime. The presence of Tectonic inversion in the Atlas Mountains has shown that are a intracontinental mountain belts that appeared from the uplift of pre-existing rift systems, where here is represented by a major rift system originated on the Mesozoic, that was later uplifted and inverted in the Cenozoic. The impact and convergence movements of the African-Iberian plates after the Mesozoic end with an inversion of the previous deposited strata, transporting the sediments of that and forming new low angle thrusts. The High Atlas develops in a parallel way to the Paleozoic Anti‐Atlas belt, disposed across the south and rises up to 2.5 km. The High Atlas and the Anti-Atlas are linked at the same time with the latter Miocene‐Pliocene Siroua Volcanic Field and the Saghro Massif volcanic field. Related with the Cenozoic Volcanic fields, the Souss Basin appears at the west, oriented towards the Atlantic Ocean, and the Ouarzazate Basin. While across the southern basins the Precambrian and Paleozoic are directly overlain by Cretaceous strata, here Triassic Sandstones and Evaporites extends being covered by Lower to Middle Jurassic strata composed mostly by Claystone. Triassic, Jurassic and Cretaceous strata are confined within basins controlled by the extensional structures of the Mesozoic rift. The Jurassic basins can be grouped into two main provinces located on either side of an emerged Massif Ancien: west, where the basin was open to the Early Atlantic, being related to its passive margin, and east with several epicontinental troughs connected to the Tethys Ocean. Across the Toarcian-Bajocian strata, there was a great deposition of marine shales as Marls, Calciturbidites and Reefal Limestones, that where accumulated in the Central High Atlas, while on the west margin around the Massif Ancien terrestrial, specially fluvial sedimentation dominated. The present Red Beds of Azilal indicate various marine transgressions across the Toarcian-Aalenian boundary, after end it´s sedimentation on the Bathonian. As that, Jurassic sediments are present of the central-southern basins, where they are up to 10 km thick carbonates, overlaid with minor Cretaceous and Paleogene deposits. Jurassic strata is usually absent beyond the southern and northern parts of the Atlas ranges. Along the Cretaceous strata this sediments had been exposed as part of an expansive body that we probably covered the entire Atlas domain, overlapping its margins, such as the Saharan Platform, the Anti‐Atlas and the Atlas Meseta, being part of a post-rift setting. That would implicate a similar succession of the Jurassic basins in the American Atlantic margin, with a marked postrift unconformity close to the Jurassic-Cretaceous boundary. Triassic and Jurassic synrift-related deposits are present especially on the external region of the Orogenic belt of the High Altas and nearly absent in the axial region, appearing in minor amounts within confined grabens.Rift Vulcanism
Along the High Atlas Triassic-Jurassic boundary, and until the Bathonian stage of the Middle jurassis, there is a record on vulcanism locally on the succession of different local formations, such as the own Azilal Formation and other, as the underlying Argane Formation. Mostly of the north-african Rhaetian-Bathonian volcanic events are related to the open of the Atlantic Ocean, with parallel records found on the North American coast and other zones such as Mexico. On some locations, such as Haute Moulouya, it is even possible to delimitate the transitions between the several Volcanic events that happened locally along the post Triassic-Jurassic boundary. Mostly of the effects of the volcanism occur on the main emerged terrestrial deposits, where some of the nearshore strata was turned down du to tectonics, and hit after by volcanic eruptions of different grades, leading different kinds of volcanic strata.The origin of the Vulcanism is related with the Geography of the zone. On the Hettangian-Sinemurian there was a post-rift carbonate platform developed in the Atlas area that emerged older marine strata. On the Middle Toarcian, subsiding basins appeared which isolated the Mesetas and Precambrian and Paleozoic massifs. Alkaline magmas overflowed the created Central High Atlas basin. This basins were fault-bounded basins, with variations of the sedimentary thicknesses and intra-formational breccias related to major blocks. The Magmatic Province of the Atlas influenced the deposition of the main strata, where the Terrestrial settings of some Formations was disposed over a series of cut extensional faults depicting a mosaic of horsts and grabens oriented to the East, North-East and East-West, with the Middle Atlas among the main areas of subsidence. The Central Atlantic Magmatic Province continue to erupt around the Pliensbachian–Toarcian event ∼ 183 Ma ago, overlapping the eruption of the Karoo–Ferrar igneous province. Middle-Late Toarcian Vulcanism was present but on smaller extension, as prove the Toundoute Continental Series Member.
Tafraout Formation
The Tafraout Formation recovers a marginal marine to deltaic setting, with the presence of calcareous nodules, alternated along Marnes with bioclasts, and abundant ferruguinaceous material. The formation shows tides to the early Mesozoic Central Atlas rift, composed of Paleozoic rocks which provided the majority of the clasts present on the layers. A mostly marine margin recovers transgressions present on the Middle Toarcian on the basin, with accumulation of limestone with Lamellibranchians, that extends to the limit with the lowersmost Aalenian, along diverse sectors inside the Atlas Domain. The formation has an upper part with Lithiotid-dominated limestones, filled with the presence of Corals, brachiopods and ooids. Tafraout Formation sleeps over mostly Paleozoic strata, with granite and granodiorites, as well tectonic traces of Devonian Volcanic activity. On the Late Early Jurassic, the zone was part of a coastal Setting, with influence of fluvial facies at the north. Sinemurian deposition from older units was tectonically affected due to seismic activity on the Middle Toarcian, leading to a vertical stratification on some locations. The so-called Aït Bou Guemmez Platform emerged on the Atlas Gulf around the Lower Toarcian, creating a small island ecosystem, that begin to deposit marine facies on the lower part of the formation, being one of the major tectonic accidents locally. A series of sea transgressions recorded from the older Sinemurian to Aalenian strata show that various Island ecosystems appeared along the coast of the Goluf, implying changes on the sedimentation. The warm climate of the Toarcian led to atmospheric changes, manifested on the Formation with depositions caused by tropical cyclone action, that decreased towards the late Toarcian Deposits. The Trafraout Formation also recovers data from the post Toarcian Anoxic events on the Marocco Basin, with changes on the carbonate reserves on the lower layers, where hemipelagic marls suggest deposition after a change of the carbon cycle.Toundoute Continental Series
The Toundute Continental Series lithology of the unit is divided into 5 units from D to H,. The Toundoute sector recovers only the Middle to Late Toarcian, with an atypical paleogeographic element, located on the route of the South Atlas Accident, with several changes on the structure leading to show the instability of the deposit area. The formation shows the transition from carbonates to a series of continental detrital sediments, with palynomorphs and fossils. Aalenian deposits recover the uppermost part near the Dadès valley, without any upper sediment present on the Main Toundoute Strata. The presence of volcanic sedimentation is one of the most important aspects on the Toundoute strata. The fragments can come from a reworking of Triassic basalt flows, with most of the products homogeneous, probably of trachyandesitic nature. The deposits are young, probably related to the magmatism of the Middle Jurassic, with inflows probably contemporary with and related to eruptions, as in the case of many current volcanoes, in the form of dense flows. The tectonic processes on the high Atlas probably lead to most of the Volcanic manifestations locally.Stratigraphy
The formation is subdivided on several stratigraphic levels, starting with the so-called facies of term A, composed by Gypsum and Salt, from Triassic age, supported by the presence of Volcanic Intercalations of basalt. Above that, there are carbonates of term B alternated at the first with Dolomites, Pelites and Limestones along with Marly-Silt crimes with plant debris, which had regular influence of a marine environment. That is proved by the presence of Ooids, Oncoliths, debris of Molluscs and benthic Foraminifers, being dissolved and recrystallized as Sparite. The third level shows a transition between marine and continental deposits, through carbonate palustrine levels and Caliche horizons, being continental layers superimposed in stratigraphic continuity over the marine carbonates of the lower Lias. Those continental layers are rich in Coarse Volcano-detrital episodes as result of a sedimentary process of high sedimentation rates, where the strata, including the deposit with Dinosaur fossils, where deposited on a short time interval, where Middle Jurassic Bajocian-Bathonian carbonate levels, frequent within the Atlas domain, do not exist not in Toundoute. The sedimentation on the Toundoute member have some characteristics, such as lenticular channels with Sieve-Conglomerate of ~5 m thick for visible decametric, composed of several materials, like Volcanic products, as blocks of volcanic rocks such as sands made of Feldspars, black ferruginous grains from the surface of volcanic rocks on dry periods, siliceous green fragments from post-eruption processes, Limestone debris with traces of roots and cracks, where in some parts traces dark fine bushy algae filaments are still visible, similar to te genus Girvanella blue-green algae. Other materials include schist and Vein Quartz, without bone and wood debris with a good cellular structure. The Floodplain-like deposits are divided in two parts, with hard Limestone nodules, pink or brick and very irregular, typical of profiles of Calcimorph Soils formed on climates with pronounced dry phases. Those nodules had a visible reorganization in the channels, as a result of erosion of the alluvial plain by the fluvial network. Finally there are present interlays of fine sandstone often laminated that mark the Flood facies from channels in period of flood, being composed only by plagioclase Feldspars and in a lesser proportion of orthoclases, along with small ferruginous grains or fine silts of quartz.There is documentation of warm climatic conditions locally, that alternating wet and dry periods, as is seen on the other formations gave rise to soils with differentiated limestone profiles, such as Pedogenetic Nodules or Caliche. The accumulation in the channels from calcimorphic soil profiles shows the presence of an active erosion on soils with probably sparse vegetation.
| Unit | Lithology | Thickness | Dinosaur fossils |
| Alluvium | Holocene conglomerate | ||
| H | Clay-sandstone series | ≥ 100 | |
| G | Clay-sandstone series, with gypsum layer present at the top, just below this a second dinosaur bearing horizon is present with very similar lithology to unit F. | 50 | Tazoudasaurus, Berberosaurus |
| F | Greenish grey clay-marl, detrital gravel to pebble-sized clasts with lignite and bones. | ≤ 5 | Present, indeterminate |
| E | Alternation of red-brown clay, fine sandstone and sandstone coarse conglomerates | 100 | |
| D | Clay, fine sandstone and conglomerate, large volcanic rocks present. | 80 |
Wazzant Formation
The Wazzant Formation recovers a variation on the sedimentary process observed on the older Azmerai Formation. It is characterised by the presence of abundant Quartz sediments, along with the presence of red clays. Along the meridional border of the Guettioua Formation, on the same stratigraphic tendence is developed a red Sandstone-Pelitic deposition, that changes from Quartzo-Conglomerates to grains and fragments of Quartz, disposed with liassic calcareous strata. is equivalent to the main Azilal "Marnes Chocolat". The Main sector occurs near Acfarcid, with an exposure of ~800 m, recovering the most detritic sector. Along this expossure, the Wazzant member appears at the right lateral, along massive calcareous dolomites, over the Latest Pliensbachian strata, where the lower Toarcian strata is missing. The Wazzant facies never exceed 50 m, getting its maximum exposure at the north of the Guettioua Formation. The facies of the formation follow a deposition typical of Alluvial Plains. It also recovers a succession of reddish brown tones predominantly terrigenous: Conglomerates, Sandstone, clays related to Paleosoils, along with dolomitized Limestone. The Wazzant formation has a notorious proximal character compared to the Azilal formation. These deposits fill in many small tear pools in the Atlas Central. Only its The stratigraphic framing allows to locate the formation in the Toarcian interval. The predominantly terrigenous deposits of this formation suggest they were deposited in continental setting, influenced by at least 6 different river channels, that trace its path to the Atlas Gulf. On the Toarcian-Aalenian transgression, the High Atlas domain experienced a long process of extension and rifting, recorded by the presence of marine carbonates and shales, found on the Wazzant Formation Beds. It is related to the formation of the Atlantic Rifting to the west and of the formation of the Tethys Ocean to the north. The fluvial system of the Wazzant formation was led by a bigger River, and several minor freshwater currents, that where probably temporal and linked to rain seasons. The presence of many dwarf lamellibranchs in the South of Azilal, the fine oblique stratifications, the floating plants and imprints of raindrops demonstrate that these two formations are of Aquatic origin, may be lagoonal, with temporary emersions. Several Fish fossils have also been found.Plantae
Paleobotany of the zone has shown that the layers at the Toundute Continental Series there is not any major wood or plant macrofossil, although there is abundant infra-centimeter plant debris dispersed in the sediments. This debris is composed mostly probably Leaflets ofFerns, and also on lesser quantities, Cycadophytas, most of them with preserved epidermis. Palynological analysis did not deliver any palynomorph, but the Plant debris left some Tracheids. On the debris, however, it was possible to isolate many wood debris, that was revealed to had characters such as Homoxylated structure apparently devoid of Parenchymas, with uniform rays, tracheids with uniseriate punctuation of the genus Abies and finally apex pikeoid type Oculipores vertically oriented, aspects typical from Coniferales, like Abietoideae, Pinaceae or Taxaceae.