Algeria Depicted by Geosciences – GASS – Geo Africa Sciences Society

1. INTRODUCTION

This ongoing open book aims a global outline, continuously updated of the Geology of Algeria and beyond that, Algeria depicted by GeoSciences. Does that means it should never end, such as a nonstop research for a better knowledge?

In addition to the classical Geology of Algeria, underground resources should be included, and Geophysics, Geothermal, Seismotectonics, Geotechnics, environment and pollution, and other topics such as Geoheritage and Geotourism.

Any GASS member can contribute as editor/author/reviewer, by submitting article(s) to the editor.

Preferably, members should review their article proposal by colleagues from their working environment or from other places, and in the same time the reviewers will be mentioned in the article proposal. A basic ethic rule in Geosciences.

English and French are used because they are the major languages to communicate GeoSciences in Africa and globally.

In this first version, only the Alpine Algeria of the Overview is presented, the Gondwana part of Algeria (Sahara) is in progress and hopefully will be ready in the oncoming versions.

2. OVERVIEW

This chapter targets an overview of the geology of Algeria. Foregoing and summing up the others in depth oncoming chapters, hopefully and certainly with more and more contributions from colleagues (from Algeria and elsewhere).

2. 1. ALGERIA WITHIN AFRICA

Algeria partly encompasses two (2) African domains, Fig. 1:
-1) North Africa or Alpine zone and
-2) African Domain or Gondwana, preserved from major alpine events.

-1) North Africa or Maghrebian Belt is structured by alpine events (Cretaceous-Miocene); it extends to parts of Morocco, Algeria and Tunisia.

In Algeria, it encompasses the whole northern part bounded to the south by Saharan Atlas south mountain flank, major South Atlasic Fault (ASA) of Eocene age, Fig. 2.

-2) Saharan Domain belongs to Gondwana and is sutured to Atlasic Domain along a major Fault Zone (ASA) resulting from Middle-Upper Eocene (39-33 Ma).

Geoscientists divide into two (2) domains: -i) Panafrican one stable since 600 Ma (Million years) and -ii) Western Africa stable since 2000 Ma, not affected by the Panafrican orogeny (500-600 Ma).

These two (2) domains are flanked side by side along a suture zone mainly underlined by Ougarta Mountains, Fig. 3.

2. 2. NORTHERN (OR ALPINE) ALGERIA

The Alpine Algerian Crust is made of sound geologic domains known from South to North as: -1) the Atlasic Foreland, -2) the External Tellian Zone, -3) Internal Zone, i.e. Kabylian Zone, and -4) Magmatic and Sedimentary Formations, called Post Nappes (post Miocene tectonics), outcropping in the whole northern Algeria, Fig. 4.

22. 1. ATLASIC DOMAIN

The Atlasic Domain is mainly built up by Mesozoic formations overlying a genuine Palaeozoic basement. The Triassic evaporites (gypsiferous shale bearing salt) are often playing a major tectonic role as a “décollement” horizon.

Formations are mainly Carbonates (Jurassic) and sandy (Cretaceous), Fig. 5.

While presenting this structural scheme of Northern Algeria, based on several publications, mainly the geological map at 1:500 000 scale, it is interesting to look at the first structural and geological map of Northern Algeria publish by Renou in 1847, Fig. 6.

Transpressive dextral tectonics during Middle-Upper Eocene (39-33 Ma) period, sutured Sahara to Algerian Alpine zone, and in the same time deformed the Atlasic Domain into:

A deformed zone (Saharan Atlas) into false anticline structures associated with horizontal zones, the whole building up a frame of an “en-echelon” lenses trending NE-SW typically characterising shear zones.Four (4) major sets of mounts (Ksours, Amours, Ouled Nails and Aures) look to be separated by two (2) minor striking dextral faults (NW-SE), while the Aures are isolated from the rest of the Saharan Atlas by a major NW-SE striking zone (Algiers-Biskra), 120-150 Km wide with a lateral horizontal displacement of about 50-150 Km.

This tectonic event, transtensive and dextral is dated Upper Bartonian (34-33 Ma), finalising the transpressive dextral striking tectonic of the Middle-Upper Eocene (39-33 Ma).

Northerly to Saharan Atlas, an apparently horizontal non-deformed zone (High Plateaux), displaying some pop-ups compressive structures showing up basement formations within horst and flower structures such as Ghar Rouban (Tlemcen), Tifrit (Saida) and Nador (Tiaret) mounts.

22. 2. TELLIAN DOMAIN (EXTERNAL DOMAIN)

The North of the Atlasic domain is the external zone of the Maghrebian Belt, i.e. the Tellian area of Northern Algeria.

In the South, it is bounded by the South Front of the Tellian Nappes; in the North by the South Kabylian Fault, Fig. 7.

Geoscientists distinguish the following group of formations:

The autochthon, par-autochthon, schistose and intra Chelif massifs. These are Jurassic (dated or assumed) and Cretaceous and also with unknown ages.
Tellian Nappes, mainly Cretaceous and marly formations, outcrop in vast areas in the Tell region. They are building up piles of thin sheetlike nappes with often slices of Triassic evaporites sole
Flysch (Turbidites) Nappes, mainly Cretaceous, make up the upper part of the Tellian nappe piles. Geoscientists generally distinguish Massylian & Mauritanian Flyschs.
Flysch (or flyschlike) and molasses dated Oligo-Miocene formations containing mainly the Numidian and other sandy-mica bearing formations such as Boghari sandstones often are located at the top of the Tellian Nappes.

These four (4) geologic groups are structured by two (2) major events: -1) thrusting tectonic during the Lower Miocene, and -2) Mio-Pliocene extension synchronic of the Mediterranean opening.

The transcurrent tectonic events of the Eocene look to be missing or poorly (not) characterised by field studies up to date.

22. 3. INTERNAL ZONE

The Internal Domain of the Maghrebian Belt in Northern Algeria is also called Kabylian Domain, because most of it is outcropping in the two Kabylia regions: “Grande” and “Petite”, Fig. 7 .

Geoscientists distinguish three (3) ensembles, well defined, extending from North to South:

Crystalline Massifs
Paleozoic
Calcareous Range
Flyschs and Molasses.

223. 1. THE INTERNAL CRYSTALLINE MASSIFS

This ensemble outcrops within massifs mainly along the coast known from West to East as following: -i) Berinshel (rocky islet off the coast of Chenoua massif), ii) Algiers Massif, iii) Great Kabylia, iv) Petite Kabylie, and v) Edough, Fig. 8.

i) In the Berinshell cap, only phyllites outcrop separated from the Paleozoic ensemble (Permian-Triassic) along a subvertical cataclastic fault striking W-E.

Through structural studies, the interpretation of this fault shows that it has acted as a normal fault bringing down phyllites with probably a previous dextral striking displacement, Fig 9. (Belhai, 1987; Saadallah, 1992).

ii) Metamorphic rocks of Algiers massif are structured into a metamorphic/tectonic pile (Low Pressure/High Temperature). Most of the contact surfaces, bounding the units, are cataclastic and often with slices of orthogneiss, such as those of Sidi Ferruch and Agha (Saadallah, 1970).

It is worth noting phyllite unit is the top of the pile. Within a composite structure there are cataclastic and gouges bands cutting the previous architecture (Saadallah, 1981 & 1992), Fig. 10.

iii) In Great Kabylia Two Groups are defined: a) Sidi Ali Bou Nab (SABN) massif, and b) Grande Kabylie s.s. (sensu stricto)

Fig. 11 presents the main domains and units of Grande Kabylie within its geologic setting and to ease correlation for readers who wish to correlate within Google Earth, Fig. 12 (a low resolution picture, after Google Earth) is provided to help locate quickly and directly within Google Earth, where the resolution is much better.

The SABN massif is made up of granites and its autochthonous intruded schists, the whole is extruded as crocodile-like nappe within paragneiss previously structured and intruded by post tectonic granites and related rocks. This crocodile nappe is bounded at top and bottom by cataclastic contacts.

The SABN group (granite & intruded rocks) is strongly deformed by a synmetamorphic shear with blastomylonites, resulting from a sinistral transpressive tectonics, Fig. 13.

The remaining of Grande Kabylie is made up by a metamorphic & tectonic pile of metapelites and slices of orthogneisses. The paragneisses (intruded by SABN crocodile nappe) stretch out at the lower part with marbles and orthogneisses at the very bottom of the outcropping pile. Micaschists are the following upper unit, overlying paragneisses along orthogneisses, and finally at top of the pile phyllites including mylonites as a sole.

Undeformed granites intrude all the units of the ductile pile, except the crocodile SABN nappe and the upper phyllite unit, Fig. 14.

Cataclastic contacts (normal and striking faults) juxtapose phyllites of the top pile to all other units.

Several facts allow inferring the hypotheses of ductile structuration followed by cataclastic one are of alpine age and contemporaneous of the extension related to the opening of the Mediterranean Sea (Gani, 1988; Benkerrou, 1989; Loumi, 1989; Bettahar, 1990; Saadallah, 1992; Saadallah & Caby, 1996).

iv) The Petite Kabylie Crystalline formations of Petite Kabylie extend across a vast region along the cost from Jijel to Skikda, Fig. 15.

In the western part (Texenna), according to Djellit (1987) it is possible to suggest a schematic figure as following: a) formation of khondalite & kinzigite gneisses at the lower part and b) phyllites (Beni Affeur Unit) at the top; units are separated by a cataclastic contact, Fig. 16.

The central and eastern parts of Petite Kabylie, from Mahdjoub’s thesis (1991), one might suggest: -a) paragneisses partly melted into migmatites with micaschists and marbles; orthogneisses are inserted at different levels of the pile, and –b) phyllites at the top of the pile.

v) The Edough Massif (Annaba) is made up by high grade metamorphic formations (HP & HT: High Pressure & High Temperature) and overlying epizonal formations along a cataclastic contact, Fig. 16.

223. 2. PALEOZOÏC

Paleozoic formations, non-metamorphic, of the Internal Domain are known in the massifs of: -i) Chenoua, -ii) Grande Kabylie (Great Kabylia) , and –iii) of Petite Kabylie (Lesser Kabylia).

-i) In Chenoua Massif, Belhai in his thesis (1987 and 1996) describes a Devonian –Carboniferous with a turbidite facies (schists and sandstones with intercalations of lyddites known of Tournaisian age), analogue of the formations in Great Kabylia, Fig. 17.

-ii) In Grande Kabylie, Paleozoic formations outcrop in Aissa Mimoun, Kouriet, Djurdjura and Chellata mounts, Fig. 11.

In Aissa Mimoun, non metamorphic schists known as Upper Cambrian are in contact (cataclastic) with paragneiss of the Crystalline ensemble of Great Kabylia,

In Djurdjura, non metamorphic schists (assumed Cambrian-Ordovician in age) are known and Devonian (schists, calcareous, marly limestone, volcaniclastic terms and dolomite) as well, according to Gélard (1979).

Carboniferous formations outcrop as flysch facies with a sequence of micaceous pelitic layers, sandstones and conglomerates with lyddites.

Permian is part of the Permo-Triassic (Verrucano facies) made of sandstone, conglomerates and red pelitic sequence with intercalations of carbonates (dolomites & limestones).

The Paleozoic ensemble is the autochthonous basement of the Mesozoic and Cenozoic formations of the Calcareous Range.

-iii) In Petite Kabylie, western part (Texenna), Silurian and Devonian rocks are made up by black schists at the bottom, covered by psammites (Lower-Middle Devonian) and limestones at the top; according to Djellit (1987).

These formations are overlaid by phyllites along a cataclastic contact.

223. 3. CALCAREOUS RANGE

The Calcareous Range outcrops, from West to East, in: i) Tenes, ii) Chenoua, iii) Grande Kabylie and iv) Petite Kabylie.

i) The Calcareous Range in Tenes is made up mainly by Lias, displaying an identical facies to those of Djurdjura (Great Kabylia). There is a marly-limestone formation dated Cenomanian-Turonian, “Scaglia” facies of Senonian and limestone bearing Lutetian Nummulites (Lepvrier and Sigal, 1967 and Belhai, 1996), Fig.

Post-tectonic molassic cover (Top Lutetian), dated Eo-Oligo-Miocene is represented by conglomerates, (Belhai, 1996)

ii) The Calcareous Range in the Chenoua is represented by formations analogue to Grande Kabylie, dated Lias-Eocene.

Post-tectonic molassic cover (Top Lutetian), dated Eo-Oligo-Miocene is present too (Belhai, 1996), Fig.

iii) Grande Kabylie

The formations are complete in Djurdjura (Great Kabylia), made up by: a) Middle-Upper Jurassic of marly limestones, marls and limestones, red pelites, marly carbonates, nodular carbonates, carbonates with “filaments”, carbonates with thin layers bearing cherts and Radiolarites; c) Cretaceous-Lutetian, also called “Senono-Eocene” a marly limestone (green and pink Scaglia facies), black marls inferred to Albien; d) Lower Eocene with a facies of massif limestone, Fig.

The molassic cover (Priabono-Oligocene), a deposit posterior to the transcurrent dextral tectonic event dated Top of Lutetian, is not considered as a continuously stratigraphic member of the other formations of the Calcareous Range, even if it is particular to it.

iv) Petite Kabylie

The Calcareous Range formations are present in Petite Kabylie, as tectonic slices, without building up important reliefs as it is well displayed in landscape in other massifs, because of its particular tectonic setting, Fig.

223. 4. CRETACEOUS FLYSCHS

All type of flyschs, outcropping in the internal zone, are gathered on the basis of the age, in one ensemble: Cretaceous Flyschs. They have different structural positions vs. the other ensembles and formations of the internal domain: they are side by side, under/over laid.

The olistostromes and others such as the Numidian formations are gathered into the ensemble called Oligo-Miocene Formations, based on their ages.

223. 5. OLIGO-MIOCENE FORMATIONS

Oligo-Miocene Formations outcropping in the Internal Domain, are often very particular to their immediate structural environment. They are molassic and/or flyschs-like formations, posterior to the dextral transcurrent tectonic, striking W-E.

They are as following: -i) Kabylian Oligo-Miocene (OMK) very related to Internal Crystalline Domain; -ii) Molassic Oligo-Miocene of the Calcareous Range; -iii) Numidien Flyschs; -iv) Sandy-Micaceous Flyschs of Kabylia and –v) the Olistostromes.

-i) Kabylian Oligo-Miocene (OMK) is mainly asandy and conglomeratic formation containing detrital elements from crystalline, schists, Paleozoic and Calcareous Range units. OMK is overlaying unconformably schists of the Crystalline Internal Domain, already structured, thus sealing the earlier tectonic events. OMK is known in Great and Petite Kabylie.

-ii) The Molassic Oligo-Miocene of the Calcareous Range in Grande Kabylie is a detrital formation containing eroded products from the Calcareous Range, Paleozoic and Crystalline units. It is unconformable on different units of the Calcareous Range, already structured by the transcurrent tectonics of the Top-Lutetian.

This formation is known in the Chenoua (Belhai, 1987) and Petite Kabylie (Raoult, 1974), too.

-iii) The Numidian, called by some geoscientists “Flyschs”, is known in almost all areas of the Internal and External Zones. It is mainly a sandy formation, with a particular structural position: sheet-nappe located at the top of the gliding nappe-pile (Cretaceous Flyschs and/or Tellian).

-iv) The Sandy-Micaceous Flyschs outcrop surrounded by Cretaceous Flyschs in the internal zones. Micas are obviously from eroded crystalline materials; in the same time there are sheets and clasts from crystalline, Calcareous Range and Cretaceous Flyschs units.

-v) The olistostromes, are generally soles of flyschs nappes, within zones and basins along contacts and mainly within the Internal Domain.

22. 4. POST TECTONIC ENSEMBLES

Post Tectonic Ensembles, posterior to Lower Miocene tectonics, are located all over Alpine Algeria including internal, external and the Atlasic foreland. They are –i) Post Nappe Basins and -) Magmatic Complexes.

-i) The Post-Nappe Basins (Sebkha d’Oran, Chlef, Mitidja, Sebaou, Sommam, Annaba and Hodna) are filled up with detrital and marly formations Mio-Plio-Quaternary in age, with intercalations of volcanic et volcano-detrital layers.

-ii) The Magmatic Complexes gather volcanic lavas (mainly basalts) and intruding cores (mainly granites). Both are characterised by a calc-alkaline nature with a twofold origin: mantellic and crustal.

There is a tendency of increasing mantellic contamination and supply toward the East, to final peridotite rocks of Collo in Petite Kabylie.

2. 3. ALGERIAN SAHARA

This chapter is in progress and hopefully will be ready for the next version of this e-book.

2. 4. REFERENCES & MORE…

This chapter aims to indicate References (mentioned authors), inspiring Sources, i.e., compiled to write down the chapter of interest; and recommended authors that might help colleagues to go deeper in the very topics.

24. 1. REFERENCES

Belhai, D., 1987. Massif du Chenoua (Algérie): mise en place des flyschs en relation avec un cisaillement dextre transcurrent EW responsable de la structure en éventail Thèse de Magister pp. 135. Carte H.T. au 1/50 000.Univ. USTHB Alger

Belhai, D., 1996. Evolution Tectonique de la Zone Ouest-Algeroise (Tenes-Chenoua) : Approche Stratigraphique et Structurale, Thèse ès Sciences, H.T. au 1/200 000.Univ. USTHB Alger

BenKerrou, N., 1989. Etude pétro métamorphique et structurale du massif cristallin d’Oued Ksari (Grande Kabylie, Algérie). Thèse de Magister pp. 143. Carte H.T. au 1/25 000. Univ. USTHB. Alger.

Bettahar, A., 1990. Massif de Sidi Ali Bou Nab (Grande Kabylie). Mise en place d’un granite au cours d’un cisaillement tangentiel à vergence NW à W. Thèse de Magister. pp. 144. carte H.T. au 1/25 000. Univ. USTHB Alger.

Cornet A. et al., 1952. Carte Géologique de l’Algérie au 1 :500 000 éditée par le Service de la Carte Géologique d’Algérie.

Coutelle, A., 1980. Etude Géologique du Sud-Est de la Grande Kabylie et des Babors d’Akbou. Thèse Sciences, Univ. Bretagne Occidentale, 567pp. Carte HT.

Djellit, H., 1987. Evolution Tectono-Metamorphique du Socle Kabyle et Polarité de Mise en Place des Nappes de Flysch en Petite Kabylie Occidentale (Algerie). Thèse Doctorat, 206 Universite Paris Sud, 206 p.

Gani, R., 1988. Etude petro structurale des massifs cristallins de Larbaa Naith Irathen et de Djemaa Saharidj (Grande kabylie, Algérie). Thèse de Magister 147 pp. Carte H.T. au 1/25 000. Univ. USTHB. Alger.

Gélard, J.P., 1979. Géologie du Nord-Est de la Grande Kabylie. Thèse de Doctorat d’Etat, Mém. Géol. Univ. Dijon, 5 : 335 pp.

Lepvrier C., Sigal J., 1967. Observations sur la Stratigraphie de la Chaîne Calcaire au Cap Ténès (Algérie). C. R. Acad. Sci. Paris, T.264, Sér. D, no 8, p. 1001-1002.

Loumi, K., 1989. Etude structurale de la région de Beni Douala (socle cristallophyllien de Grande Kabylie-Algérie) : mise en évidence de mouvements vers le N-W. Thèse de Magister pp. 156 Carte H.T. au 1/25 000. Univ. USTHB Alger.

Mahdjoub, Y. 1991. Cinématique des Déformations et Evolution P. T. Ante-Alpines et Alpines en Petite Kabylie (Algérie Nord-Orientale). Un Modèle d’Evolution du Domain Tellien Interne. Thèse ès Sciences pp. 193. Univ. USTHB Alger.

Raoult, J.F., 1974. Geologie du Centre de la Chaine Numide (Nord Constantinois, Algerie). These es Sciences Mem. Soc. Geol. Fr. N.S :-T. LIII.-1. Mem. No 121.-1 pp.162.

Renou, E. 1847. Carte Géologique du Tell Algérien, publication de la Commission Scientifique d’Algérie.

Saadallah, A., 1970. Les gneiss de Sidi Ferruch. Rap. de DEA 46 p. carte H.T. Univ. Alger.

Saadallah, A., 1981. Le massif cristallophyllien d’El-Djazaïr (Algérie) : Evolution d’un charriage à vergence nord dans les internides des Maghrébides. Thèse 3ème cycle 160 pp Univ. Carte au 1/25,000 H.T. USTHB (Alger).

Saadallah, A. 1992. Le Cristallin de la Grande Kabylie (Algérie) : sa place dans la chaîne des Maghrébides. Thèse ès Sciences pp. 260, Cartes HT au 1 / 100 000 de la Grande. Kabylie, carte HT de Sidi Ali Bou Nab au 1/50 000 et coupes HT. USTHB (Alger).

Saadallah, A. 2013. Structural geological model about Algeria : “Le légendaire « schéma de DD » a besoin d’être mis à jour. J’en propose un en hommage à son auteur” in Hommage à Michel Durand-Delga. Géologue des chaînes alpines méditerranéennes, 47-51, Bull. Soc. Hist. Nat. Toulouse, 149, 2013, 3-5

Saadallah, A. 2017. La Grande Kabylie dans le Contexte Algérien vue par les Géosciences. Livre, pp 237, et carte HT ISBN : 978-9931-9211-5-8. Dépôt légal 2017 ; Editions INGESE, Alger (Algérie).

Saadallah, A. 2018. Presentation “New Tectonic Frame of the Algerian Alpine and Subsequently New Strategy for Hydrocarbon Exploration” at the JST11 (11th Journées Scientifiques et Techniques) organized by Sonatrach in Oran (Algeria) 16-19 April 2018.

Saadallah, A. Belhai, D., Djellit, H., Seddik, N.1996. Coulissage dextre entre zones interne et externe des Maghrébides, et structuration en fleur de la Dorsale calcaire du Djurdjura (Algérie). Geodinamica Acta 9, 4, 177-188.

Saadallah, A., Caby, R. 1996. Alpine extensional detachment tectonics in the Grande Kabylie metamorphic core complex of the Maghrebides (northern Algeria). Tectonophysics 267 : 257-273.

Vila, J.M., 1980. La Chaine Alpine d’Algérie Orientale et des Confins Algéro-Tunisiens. Thèse Sci. 3 vols. 663 pp. Univ. Paris VI

24. 2. INSPIRING SOURCES

Zeck, H.P. 1999. Alpine Plate Kinematics in the Western Mediterranean: a Westward-directed Subduction Regime Followed by Slab Roll-back and Slab Detachment. In: Durand et al., (eds) The Mediterranean Basins: Tertiary Extension within the Alpine Orogen. Geological Society, London. Special Publications, 156, 109-120.

24. 3. RECOMMENDATIONS

Cornet A. et al,. 1952. Carte Géologique de l’Algérie au 1 :500 000 éditée par le Service de la Carte Géologique d’Algérie.

Wildi, W. 1983. La Chaine Tello-Rifaine (Algérie, Maroc, Tunisie): Structure, Stratigraphie et Evolution du Trias au Miocène. Rev. Géol. Dyn. Géogr. Phys. 24: 201-297

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