The Upper Jurassic and Lower Cretaceous series of southern Tunisia and northwestern Libya revisited

The Upper Jurassic and Lower Cretaceous series of southern Tunisia and northwestern Libya revisited

Journal of African Earth Sciences 110 (2015) 100–115 Contents lists available at ScienceDirect Journal of African Earth Sciences journal homepage: w...

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Journal of African Earth Sciences 110 (2015) 100–115

Contents lists available at ScienceDirect

Journal of African Earth Sciences journal homepage: www.elsevier.com/locate/jafrearsci

The Upper Jurassic and Lower Cretaceous series of southern Tunisia and northwestern Libya revisited Saïd Tlig Unité de Recherche URGAMM, Université Tunis El Manar-Faculté des Sciences de Tunis, Campus Universitaire, Le Belvédère, 1060 Tunis, Tunisia

a r t i c l e

i n f o

Article history: Received 15 December 2014 Received in revised form 17 June 2015 Accepted 22 June 2015 Available online 23 June 2015 Keywords: Lithostratigraphy South Tunisia Northwestern Libya Upper Jurassic Lower Cretaceous

a b s t r a c t The Upper Jurassic–Lower Cretaceous series in southern Tunisia and northwestern Libya are revisited in the light of fieldwork, facies patterns, biostratigraphy and wellbore data. Five megacycles delineated by major unconformities are described. The megacycles I & II (Callovian–Tithonian) capped by the Neo-Cimmerian unconformity contain marine, neritic and lagoonal facies that extend from the northwestern Libya (Shakshuk and Ar Rajban Fms) to southern Tunisia (Calcaires et Marnes de Foum Tataouine Fm). These equate with the neritic, Callovian–Upper Tithonian, Upper Nara Formation in the central Tunisia. The megacycle III contains marine dolostones, sands and lagoonal clays at the base, overlain by marine Green Clays that alternate dolostones and sands, capped by the Early Barremian unconformity. The megacycle IV that terminates in the Austrian unconformity is Barremian–Early Aptian coarse-grained sands enriched in vertebrate remains and quartz pebbles, and conglomerates with quartzite cobbles deposited in a broad area from northwestern Libya to central Tunisia. The megacycle V starts in the Middle–Upper Aptian dolostones and continues by coarse-grained Albian sand sequences with quartz pebbles and dolostone and clay stringers that pass upwards into the Upper Albian and Cenomanian carbonate, marl and gypsum sequences. The megacycle III correlates the Kabaw Formation in the northwestern Libya with the Sidi Khalif and Meloussi Formations in the central Tunisia (Berriasian–Hauterivian), and the megacycle IV correlates the lower Member of Kiklah Formation of northwestern Libya with the Barremian Boudinar, Bouhema and Sidi Aich Formations in the central Tunisia. Well to well correlations indicate that the Middle–Upper Aptian dolostones that are coeval with the Orbata Formation in the Salt Marshes rift-basin and central Tunisia, pinch-out toward the Dahar cuestas in Tunisia and the Nalut and Nafusa cliffs in northwestern Libya where Albian sands disconformably overlie their Barremian–Early Aptian counterparts or even the Berriasian Hauterivian megacycle III with Green Clays in exposed areas (Tataouine, Nalut) through the Austrian unconformity. The Stage ages and lithostratigraphic subdivisions suggested by previous authors are discussed and the new biostratigraphical results explain the geology of the region and correlations help establish a new lithostratigraphical chart for the study area. Ó 2015 Elsevier Ltd. All rights reserved.

1. Introduction The Upper Jurassic and Lower Cretaceous series of southern Tunisia, northeastern Algeria and northwestern Libya (Figs. 1 and 2) fill the large Mesozoic basin described by Burollet and Dumestre (1952), Burollet (1963, 1977), Busson (1967, 1972), Hammuda (1969), Reyre (1970), Tlig (1978), El Zouki (1980) and Fatmi et al. (1980). Busson (1972) and Tlig (1978) rejected the concepts ‘‘Continental Intercalaire’’ (Kilian, 1931) and ‘‘Purbekian-W ealdian’’ (Rat, 1962) and the use of lithostratigraphic subdivision of the series, and referred to the ‘‘Upper Jurassic and Lower E-mail address: [email protected] http://dx.doi.org/10.1016/j.jafrearsci.2015.06.014 1464-343X/Ó 2015 Elsevier Ltd. All rights reserved.

Cretaceous’’ sedimentary packages that encompass the whole Kimmeridgian to the Albian time interval. Burollet and Dumestre (1952) described the most complete Merbah El Asfer section between Tataouine and Chenini village to the west (Boulouha Mountain; Fig. 1). These are Upper Jurassic sands, marls, clays and dolostones with nautiloids, echnoids and mollusks at the base, overlain by Lower Cretaceous clays, dolostones and sands with mollusk moulds (Busson and Albanesi, 1967; Tlig, 1978) and wood, fish, turtle and saurian remains, approximately 250 m in total thickness. Busson (1967, 1972), Reyre (1970) and Tlig (1978) subdivided this section into three main ‘megacycles’: (1) an up to 121 m thick cycle of fine-grained sands, lagoonal to marine clays and ocher-colored dolostones, (2)

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Fig. 1. Location of study area; open circles: oil-wells; full circles: towns and villages; stars: locations of field sections and stratotypes of the Upper Jurassic and Lower Cretaceous series in the central and southern Tunisia, and in Nalut–Nafusa ranges of Mountains.

up to 104 m marine Green Clays with dominant sandstones that alternate clays and dolostones at the base (Busson, 1967), and thin-bedded dolostones with mollusk and bioclast moulds, and rare sand stringers upwards, and (3) 1–100 m thick packages of coarse-grained sands with quartz pebbles, and conglomerates with quartzite cobbles and a few layered clays (Barremian–Early Aptian), enriched in vertebrate and saurian remains. Tlig (1978) identified a succession of gypsiferous marls, sands and lime and dolostones at the base of the Upper Jurassic–Lower Cretaceous series, that varies in thickness from 40 m at Oued Zaafrane to the north of the Haddada village, up to 50 m at Bir Miteur further north (Figs. 1 and 2). Limestones at Oued Zaafrane contain the foraminifered Pseudocyclammina sp., Pseudocyclammina jaccardi Schrodt, Kurnubia sp., Kurnubia wellingsi Henson, ostracods, algae (Arabicodium sp., Salpingoporella annulata Carozzi), echnoids (Moniodiadéma cotteaui de Loriol) and mollusks (Modiolus imbricatus Sowerby subpulligera Freneix, Pholadomya cf. lirata Sowerby, Catinula sandalina Goldfuss, Liostrea mairei de Loriol and Ceratomyopsis striata d’Orbigny). This series is capped by a reference bed of dolostone (2–3 m thick) enriched in polyps of hexacorals that extends broadly (Tlig, 1978) in the Ghomrassene-Haddada-Bir Miteur area (Fig. 1). The diagnostic foraminifered association Kurnubia wellingsi Henson and Pseudocyclammina jaccardi Schrodt was found to indicate the Lower Kimmeridgian (Tlig, 1978). Tlig (1978) collected bones and teeth of the saurian Theropod Carcharodontosaurus saharicus Depéret and Savornin (1925) Sromer 1931 which may date the Albian to Cenomanian period (see Lapparent, 1960; Depéret and Savornin, 1925; Brusatte and Sereno, 2007; Hendrickx and Mateus, 2014 for a discussion), in the uppermost coarse-grained sand sequences at Bir Miteur (Figs. 1 and 2). This species was identified earlier by Lapparent

(1960) in the Sahara who described Elaphrosaurus iguidiensis Lapparent 1960 and the Sauropod Rebbachisaurus tamesnensis Lapparent 1960 and Iguanodon mantelli Meyer at Chenini, Guermassa and at Remada–Kamboute. Fish remains of Lepidotus and the non-marine shark (Hybotontid) Priohybodus arambourgi d’Erasmo (1960) were reported by Busson (1967) and Busson and Albanesi (1967) in the Upper Jurassic–Lower Cretaceous sands at the Jebel Haddada (Fig. 1). Other vertebrate remains including teeth of mesosuchian crocodilians, saurian coelusaurian theropods, and turtles were collected by Tlig (1978) at El Itime and Haddada Mountains and at Batene El Hameima and Bir Miteur localities. The author avoided the modification of the stratigraphical subdivisions proposed by Busson (1967, 1972) and by Reyre (1970) because of the poor diagnostic value of the saurian species recognized that remain poorly understood (see Soto et al., 2012; Hendrickx and Mateus, 2014). Many authors studied these series poor in diagnostic fauna and flora since the early 1990s and distinguished Groups, Formations, Members and Units in lithostratigraphic charts with continuously changing subdivisions, gaps and ambiguities concerning the assignments of both Epochs and Stage ages. These changes started by the works of Kamoun (1988) and Kamoun et al. (1988) and continued in a number of papers by Peybernes et al. (1996), Ouaja et al. (2002), Barale and Ouaja (2002), Kamoun et al. (2003), Bodin et al. (2010), Le Loeuff et al. (2010), Fanti et al. (2012) and Contessi (2013). Thus, the lithostratigraphic subdivisions and correlations of the Upper Jurassic and Lower Cretaceous series of northwestern Libya to those counterparts of southern Tunisian published by previous authors should be reexamined. The regional correlations and lithostratigraphic nomenclature from the northwestern Libya to southern Tunisia (Figs. 1 and 2) given by Bodin et al. (2010), Le Loeuff et al. (2010), Fanti et al.

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Fig. 2. Simplified map of the central and southern Tunisia and of the Salt Marshes basin (Geological Map: 1/500.000; Service Géologique National de Tunisie). The wellbores used for correlations and the main tectonic features of the series recognized on field and by seismotectonic studies are reported on this map. The location of Nalut–Nafusa cliffs and location of the main stratotype sections in Libya are also indicated. Full stars: towns and villages; full circles: Mountains; open circles: oil wells; dashed line indicates correlation. For additional information see Fig. 1.

(2012) and Contessi (2013) for the so-called ‘‘Continental Intercalaire’’ produced no evidence concerning the Epochs and Stage ages. This dating and correlations lack the appropriate fieldwork observations to ensure the basins framework, the lateral continuity of megacycles, and the description of changes and correlations of the lithofacies from Libya to southern or even central Tunisia.

The reconstruction of basin frameworks in the study area is of great importance for: (1) the understanding and evaluation of one of the most important fossil aquifers contained in the Continental Intercalaire in Tunisia, Libya and Algeria (UNDP-UNESCO, 1972a,b), and (2) oil exploration in the Jeffara area and Gulf of Gabes areas where the Jurassic–Upper Cretaceous series are oil prone (Ezzaouia and El Bibane oilfields;

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Fig. 3. Petrographic interpretation and microfacies of Megacycle I (Units 1 and 2; Callovian–Oxfordian) in outcrops at the Smida Mountain modified after Tlig (1978) and Enay et al. (2002). Samples from levels containing algae and benthic foraminifers are indicated. See Fig. 1 for section location.

Fig. 2), and in the Ghadames and Illizi Basins (Klett, 2000). The hydrocarbon and especially water resources were at the heart of the Tunisian industry since the 1970s, as well as those of the neighboring countries. The main goals of this paper are (1) to identify and date sedimentary megacycles in order to precise the

stratigraphy and lithostratigraphy of the series in southern Tunisia and northwestern Libya, (2) to produce evidence for the erroneous lithostratigraphic results of Bodin et al. (2010), Le Loeuff et al. (2010), Fanti et al. (2012) and Contessi (2013), and (3) to correlate the Upper Jurassic–Lower Cretaceous series of the

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Fig. 4. Petrographic interpretation and microfacies of Megacycle II (Unit 3; Lower Kimmeridgian) in outcrops at the Oued Zaafrane to the north of Haddada village, modified after Tlig (1978). Samples from levels containing algae and benthic foraminifers are indicated. See Fig. 1 for section location.

southern Tunisia with their counterparts in the central Tunisia and northwestern Libya. 2. Methodology Field work was completed during 1975–1978, 1998–2003 and 2011–2013 field seasons when thirty sections totaling approximately 9300 m of strata were measured at Dhehiba, Remada– Kamboute, Oum Ed Dhiab, Merbah El Asfer, Douiret, Batene Hameima, Oued Zaafrane, Bir Miteur, Foum El Hassene, and at the Smida, Boulouha, El Itime, Zemlet El Beidha, Jerouala, Orbata, Sidi Aïch, Bouhedma, Meloussi, Boudinar, Sidi Khalif and Nara-Bouzer Mountains (Fig. 1) and in other localities. The description of field sections of northwestern Libya are based on the works

of Burollet (1963, 1977), Hammuda (1969), El Zouki (1976), Novovic (1977), Fatmi et al. (1980), Shiref and Salaj (2007), Bodin et al. (2010) and Le Loeuff et al. (2010). Sandstones, and lime and dolostones of southern Tunisia were observed in thin sections, and the carbonate rocks were studied using the terminology established by Folk (1962) and Dunham (1962). Allochem proportions were estimated on a semiquantitative basis, with four subdivisions: absent, rare, common and abundant. Clay mineral identifications in grounded whole samples and separate aggregates were by X-ray diffraction methods (Co-ka, 2h). Determinations of Ages based on fossil vertebrate remains, echinoids and mollusks from different sites in the region, and foraminifers, ostracoda and algae in thin sections, were performed. Exoscopic observations of quartz grains were carried out by

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Scanning Electron Microprobe. Major elements in whole samples were measured by X-ray Fluorescence, Na was analyzed by Flame Photometry, and boron was determined by Spark Spectrometry, while trace elements (Mn, Sr, Li, Ni, Zn, Cu, Co, Cr) contents were measured by Atomic Absorption Spectrometry (Tlig, 1978). The rare earth elements in the samples that were irradiated and determined following the neutron activation analysis (INAA) method described in Jaffrezic et al. (1980). The main results on the major, trace and REE elements were published by Tlig (1978) and Tlig and Steinberg (1980). Wellbore data based on core and well cutting descriptions compared to wireline log details were also provided. The wells with total depths varying from 2900 to 3200 m are located in the north of the Ghadames basin and on the Dahar plateau of southern Tunisia. Seismic reflection profiles acquired onshore in the Ghadames basin, Salt Marshes basin and central Tunisia in the period 1978–2010, were used. The seismic facies calibrated to well sections and wireline logs help recognize seismic horizons, delineate seismic sequences and megacycle boundaries including local gaps, and correlate depositional cycles in the subsurface with the lithostratigraphical descriptions of cores, well-cuttings and outcrop data in the Dahar and Nalut–Nafusa cliffs, Salt Marshes basin and central Tunisia. 3. Biostratigraphy and lithostratigraphy Seismic sections, and wellbore and outcrop data indicate that the study area has undergone Panafrican (750–540 Ma), Mesozoic Cimmerian and Austrian, and Cenozoic Atlassic tectonics. The latter was currently described by Maghrebian Geologists, whereas the former three tectonics remains poorly understood (see Tlig, 2015a). The Cimmerian tectonics with Lower Triassic (Eo-Cimmerian), Bathonian and Late Jurassic (Neo-Cimmerian) phases and the Austrian tectonics (Aptian–Albian) that have governed rifting, subduction and deformations in the Tethyan realm were defined by Stille (1924). These were discussed by authors for the Carpathians (Sengör et al., 1985; Ziegler, 1990), the Eastern Mediterranean (Mountrakis, 1986), and the Maghrebian Sahara (Lefranc and Guiraud, 1990). The tectonic events during the Phanerozoic have generated regional unconformities identified on field and by drilling in the study area that delimit first to second order megacycles (sensu Miall, 1995) as described below. 3.1. Lithofacies, cycles and cycle boundaries Megacycle I (Callovian–Lower Kimmeridgian) is comprised of three Units. The Lower Unit alternates marls, a few sandstones, and limestones (Calcaires et Marnes de Foum Tataouine Fm; Busson, 1967) that contain pelecypods (Modiolus imbricatus Sowerby, Lopha solitaria Sowerby subpulligera Freneix, Protocardia lehmani Freneix; Liostrea hebridica Forbes; Ceratomyopsis striata d’Orbigny; Ceratomya wimmiensis Gillieron, Plagiostroma sp.), gastropods (Nerinea sp.), brachiopods (Terebratula sp., Rhynchonella pseudoazizi Dubar; Rhynchonella sp.), echinoids (Acrosalenia meslei Gauthier), algae (Thamatoporella sp.; Bathonian–Hauterivian Salpingoporella annulata Carozzi; see Carras et al., 2006) , corals, bryozoans, ostracods (Hustonia sp., Cytheropteron sp., Metacypris sp., Acrocythere sp., Bisulcocypris sp.), foraminifers (Kurnbia sp., Nautiloculina sp.), and the Latest Callovian ammonoids Erymnoceras (Busson, 1967, 1972) and Pachyerymnoceras cf. spathi Lewy (Enay et al., 2002) collected in the upper beds (Fig. 3). The identified species indicate the Callovian. The second Unit is comprised of limestones and dolomitic limestones (Ghomrassene Limestones), Oxfordian–Lower Kimmeridgian

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in age (Bismuth et al., 1967; Bonnefous, 1972; Tlig, 1978), with a 2–3 m thick bed at the base (Fig. 3). This is a grainstone containing gravel, peloids, algal laminae, pelecypods (Pecten sp.), echinoids (Echinopygurus meslei Lambert), brachiopods (Terebratula sp.), algae (Arabicodium sp.), and foraminifers (Nautiloculina sp., Kurnubia sp.). The overlying massive (2 m thick) limestones alternate packstones and grainstones locally dolomitized, up to 40 m in total thickness. These facies that were deposited under high energy contain chalcedony, and mollusks, bryozoans, corals, algae (Arabicodium sp.), ostracods and foraminifers (Trocholina sp., Nautiloculina sp., Kurnubia sp.) dated Oxfordian to Lower Kimmeridgian by Bismuth et al. (1967). The series contains decameter scale microbialite, spongal and algal bioconstructions exposed near the Haddada village and at Oued El Khil (Tlig, 1978). The third Unit conformably rests over the Oxfordian Ghomrassene Limestones. These are up to 40 m thick packages of dolomicrite and dolosparite that alternate gypsiferous marls, fine-grained sandstones and limestones (Fig. 4). The latter are bioclastic wakestones to packstones containing pelecypods (Modiolus imbricatus Sowerby subpulligera Ferneix, Ceratomya wimmiensis Gillieron, Pholadomya cf. lirata Sowerby, Catinula sandalina Goldfuss, Liostrea mairei de Loriol, Ceratomyopsis striata d’Orbigny), echinoids (Monodiadema cotteaui de Loriol), nautiloids, brachiopods, bryozoans, corals, sponges, ostracods, algae Solenoporacae, and foraminifers (Kurnubia wellingsi Henson, Pseudocyclammina sp.; Pseudocyclammina jaccardi Schrodt) (Fig. 4). This association of diagnostic foraminifers that indicate the Early to Lower Kimmeridgian was identified in the middle Unit section (Tlig, 1978; Velic, 2007) capped by a reference bed of dolomicrite (2 m) with polyps of hexacorals and gastropods. The Jurassic sections described in the Jeffara wells to the east on Dahar and wells to the west on the Grand Erg Oriental, are similar to those in the Dahar outcrops, but are lagoonal, highly sandy and evaporitic beneath the Grand Erg Oriental. Coeval marls, sands, mudstones, and limestones that vary from packstones to grainstones alternate dolomicrite and dolomicrosparite in successions up to 2660 m thick in CF-1 and 2835 m thick in CF-2 wells drilled to the north in the Salt Marshes rift-basin (Figs. 1 and 2). The marls and limestones were characterized by either lituolids or globigerinids up-section in the wells DJM-1 and DE-1 in the Gulf of Gabes, that were dated Middle–Upper Jurassic (Mzoughi, 1991; Fig. 1). A Mid-Upper Jurassic section of the Tigi Group (Burollet, 1963, 1977; Fatmi et al., 1980) in the Nafusa Mountain that is comprised of the Bathonian Takbal and Khashm Az Zarzur Fms, the Callovian Shakshuk Fm and the Oxfordian to Upper Jurassic (?) Ar Rajban Fm was provided by Shiref and Salaj (2007). Limestones alternate marls at the base of section with occasional of conglomeratic beds that represent the Shakshuk Fm dated Callovian (Novovic, 1977; Banerjee, 1980) disconformably overlain by the Ar Rajban Fm (=Scecsciuch Fm; Burollet, 1977; see Fatmi et al., 1980 for a lithostratigraphical synthesis). Megacycle I is 40–50 m thick, with a lower boundary placed at the base of channelized sands disconformably overlying the megacycle I at Oued Zaafrane, even if the 3rd sequence-type boundary character of this limit cannot be precluded. The upper boundary of this cycle is clearly evidenced on field (Tlig, 1976–2014, unpublished) and is thought to represent the Neo-Cimmerian unconformity (Fig. 5). The latter is recorded by 2–5 m thick conglomerates with decimeter-scale clay and ocher dolostone cobbles in reworked quartzose sandstones with quartz pebbles, iron oxides, wood, vertebrate remains and fish teeth, bones and vertebra (e.g., East of El Itime, Boulouha and Haddada Mountains, and Batene Hameima) (Figs. 1, 2, 4 and 5). These sandstones and geodic quartz

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Fig. 5. Petrographic interpretation and microfacies of Megacycles I (Oxfordian–Lower Kimmeridgian; Units 2 & 3), II (Kimmeridgian–Tithonian), III (Berriasian–Hauterivian) and possibly V pro parte (Albian–Cenomanian) in outcrops at the Merbah El Asfer and Boulouha Mountains between Tataouine and Chenini–Douiret villages modified after Tlig (1978). Samples numbers are reported by groups of 5. See Fig. 1 for section location.

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Fig. 6. Megacycles (First to 2nd Order sequences) identified in sections, regional unconformities and correlations of the Upper Jurassic–Lower Cretaceous lithofacies in the Tataouine area.

in beds below this unconformity were identified in the Boulouha and Haddada Mountains, Batene Hameima and Bir Miteur sections (Tlig, 1978). This megacycle contains varicolored lagoon clays, sandy clays, fine-grained sandstones containing either petrified or floated wood trunks, and vertebrate teeth and bones. These facies show planar (wash-over?) and cross stratifications (coastal dunes), and flaser bedding in sequences capped by either dolomicrite or dolosparite with bioclast and mollusk moulds (Busson and Albanesi, 1967), and ostracods, while gypsum stringers are absent. Well crystallized kaolinite prevails over illite, with 70, up to 95% semiquantitative proportions determined on X-ray diagrams, while smectites are absent. Lithofacies are organized in stacked fourth to fifth order basinfill sequences. A typical sequence with an erosive base starts

in planar and cross stratified sands that pass upwards to sandy clay and clay interbeds, and is capped by dolomicrite or dolosparite. Shallow bathymetries (0–3 m?) should have dominated, with retreat and transgression of marine waters. Dolostones may show laminate, sabkha-dolomicrite patterns deposited in intertidal to supratidal environments, or display dolosparite facies that testify to recrystallization by the action of meteoric waters during short periods of exposure. The laterally equivalents of this cycle in the Salt Marshes rift-basin alternate sand, marl, and dolostones and limestones with lituolids and globigerinids described in the wells CF-1 and CF-2 (Mzoughi, 1991), and lime and dolostones with radiolarians and Saccocoma contained in the Upper Nara Fm of central Tunisia (Burollet, 1956; Soussi, 2002).

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Fig. 7. Correlations of the Upper Jurassic–Lower Cretaceous series cut in oil-wells on the Dahar and Grand Erg Oriental areas showing the Austrian unconformity overlain by the middle–upper Aptian dolostones pinching out toward the Dahar cuestas and the Nalut–Nafusa ranges of Mountains and cliffs. Note the highly reduced thickness (2–3 m) of the megacycles IV (Barremian–Lower (Early) Aptian) and V (Albian sands) at the Boulouha Mountain near Tataouine, thus indicating the transgressive megacycle V possibly resting above the megacycle III through a gullied surface and incision of the exposed areas by the Austrian tectonic phase.

The Ar Rajban Fm in northwestern Libya (Fig. 1) capped by the Neo-Cimmerian unconformity (El Hinnawy and Cheshitev, 1975; Burollet, 1977; Shiref and Salaj, 2007) represents this megacycle. It consists of two Units: (1) a lower conglomeratic and cross-bedded sandstone with clays draping sequences disconformably overlies the Shakshuk Fm (Callovian; Burollet, 1977; Fatmi et al., 1980), and (2) an upper red Unit of clay and sandstone sequences with minor carbonate stringers and gypsum beds (Novovic, 1977). Limestones in this upper Unit that contain abundant brachiopods and mollusks were dated Oxfordian to Upper Jurassic (?) (Burollet, 1963, 1977; Shiref and Salaj, 2007). Megacycle III contains the marine Green Clays’ interval (Fig. 5; Busson, 1967; parts of the Aptian Douiret Fm of Ouaja et al., 2002). This cycle that extends between the Neo-Cimmerian unconformity at the base and the Early Barremian unconformity at the top (Fig. 3), varies in facies and thicknesses (0–110 m) both vertically and laterally. It is enriched in sands and dolostones to the North, while these Green Clays’ lithofacies pinch out toward the Haddada Mountain (Fig. 1; Busson, 1967; Tlig, 1978). Sands contain wood and vertebrate fragments, while thin sections of dolomicrite and dolosparite packages that cap sequences show ostracods, and bioclast and mollusk moulds. The megacycle III is ubiquitous in wellbores of the Ghadames basin (Figs. 5–7) and was described in the Nafusa cliffs (Kabaw Fm; Burollet, 1963, 1977; Hammuda, 1969; El Zouki, 1976; Fatmi et al., 1980). This cycle in the Dahar cliffs alternates sands and clays enriched in microvertebrates, vertebrate and fish teeth and bones

(Priohybodus sp., Priohybodus arambourgi d’Erasmo 1960), and dolosparite and dolomicrite with mollusk and bioclast moulds at the base (Busson, 1967; Busson and Albanesi, 1967; Tlig, 1978). Illites prevail over kaolinite in the clay deposits. Fifth to fourth order sequences identified down-section, are similar to those described for the previous megacycle. These pass upwards to an interval of marine clays with fine-grained sand and dolomicrite alternations that contain abundant nanno-mollusks and bioclast moulds. Ghosts of orbitolinidae, verneuillinidae and ophtalmiidae in these clays were described in oil wells (Busson, 1972) and in outcrops at Boulouha Mountain (Tlig, 1978; Fig. 5). The compact Green Clays enriched in illites, that alternate thin beds of sand and dolostones are stacked in sequences capped by dolomicrite. The clay packages near Douiret thicken considerably (104 m) and admit hectometer – scale lens – shaped bodies of sand with cross-stratifications enriched in vertebrate remains that may be sampled in local quarries. Coeval deposits in the Salt Marshes basin and central Tunisia alternate pelagic marls, sands and limestones, in an at least 300 m thick succession. Limestones and marls are enriched in belemnites, ammonoids, pelecypods, brachiopods, coral colonies (Montlivoltia), foraminifers and calpionellids (Sidi Khalif Fm; Burollet, 1956; Busnardo et al., 1980; Marie et al., 1984; Masse, 1984; Damotte et al., 1987; M’Rabet, 1987; Soussi, 2002; Boughdiri et al., 2005). Thicknesses measured 1089 m in the well SO-1 and 789 m in the well KAR-1 (Figs. 1 and 2). A section at the base of this interval shows an up to 212 m thick sandy and

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Fig. 8. Correlations of the well-P2 section with the representative stratigraphic sections in the central and southern Tunisia and northwestern Libya organized into five second order megacycles as defined in text. For well P2 location see Figs. 1 and 2.

conglomeratic interval cut in the well ABK-2 that record the Neo-Cimmerian unconformity, overlain by clays with interbedded sand, limestone, dolostone and anhydrite. This is the Sidi Khalif Fm in the central Tunisia, overlain by an up to 400 m thick series of clays, sands and dolostones that constitute the Meloussi Fm (Burollet, 1956; M’Rabet, 1987; Figs. 3 and 8). Coeval sand, sandstone, dolostone and Green Clay sequences that were described in the Kabaw Fm are delimited by the Neo-Cimmerian unconformity at the base (Figs. 3 and 8) Burollet, 1963, 1977; El Zouki, 1976; Fatmi et al., 1980; Shiref and Salaj, 2007). These deposits are capped by the Early Barremian unconformity (see below; Burollet, 1963, 1977; Fatmi et al., 1980).

Megacycle IV is delimited at the base by the latter unconformity and capped by a ubiquitous Austrian counterpart (Lower– Middle Aptian). This Austrian unconformity was evidenced by wireline logging in many oil-wells on the Grand Erg oriental and Dahar (Figs. 1–4). The cycle is coarse-grained fluvial and coastal marine sands and conglomerates enriched in quartzite cobbles (Kamboute, Oum Ed Dhiab, Bir Amir, Bir Miteur, and El Itime and Boulouha Mountains), wood, saurian and vertebrate remains, with a few dolostone beds and clay stringers that were dated Barremian–Early Aptian by Busson (1967, 1972) and Tlig (1978). This was because the dolosparitic Middle–Upper Aptian sequences disconformably overlying the megacycle IV were

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recognized and dated in many wellbores on the Illizi and Ghadames basins (Fig. 7). These cycle sands in the Remada–Kamboute and Dhehiba area underwent rubefaction that generated paleosoils. Lapparent (1960) described the saurian theropods Carcharodontosaurus saharicus (Depéret and Savornin, 1925) Stromer 1931 and Elaphrosaurus iguidensis Lapparent (1960) in the Sahara, and Busson (1967) and Busson and Albanesi (1967) recognized fish remains of Lepidotus and the Hybotontid shark Priohybodus arambourgi d’Erasmo (1960) in sands and sandstones of this and underlying megacycle III. The temporal and geographical distribution of the latter species is restricted to the Kimmeridgian–Haute rivian/Barremian time period (Soto et al., 2012). These Barremian–Early Aptian sandstones that total 1–60 m thickness, fit laterally into extremely thick deposits in the Salt Marshes rift-basin that opened during the Kasimovian (Tlig, 2015a), and in central Tunisia (Figs. 1 and 8). The succession consists of (1) an up to 320 m thick (well BK-1), cross-bedded and channel-fill, coarse-gained sandstones with gravel layers and fossil wood in central Tunisia (Boudinar Fm; Burollet, 1956), (2) an up to 600 m thick sandstone, clay, dolostone and gypsum series that represents the Bouhedma Fm dated the Late Hauterivian–Barremian (Burollet, 1956; Damotte et al., 1987), and (3) an up to 200 m thick interval of fine-grained sands with clay and dolostone stringers, floated wood, and quartz lags and pebbles at the base of sequences contained in the Sidi Aïch Fm (Burollet, 1956; Marie et al., 1984; M’Rabet, 1987). These were dated Upper Barremian in the Salt Marshes area (Ben Youssef, 1999). The cycle deposits in the northwestern Libya correspond to the lower Member of Kiklah Fm (=Chicla Fm; Figs. 1 and 8; Burollet, 1963, 1977; Hammuda, 1969; El Zouki, 1976; Fatmi et al., 1980; Shiref and Salaj, 2007; Bodin et al., 2010). These are dominant cross-bedded and coarse-grained sandstones with quartz pebbles, and yellowish red clays and paleosoils described as the Cabao Fm by Le Loeuff et al. (2010) and by Smith et al. (2010). Megacycle V starts above the Austrian unconformity in the study area and shows complete sections identified in oilwells on the Grand Erg Oriental. This has deposited the massive, Middle– Upper Aptian, dolosparites (‘Dolomie Noisette’ of Petroleum Geologists) containing orbitolinids and choffatellids, that total 10–50 m thickness or even more in well sections. These carbonates pass upwards into coarse-grained Albian sands (10–70 m thick) with a few dolostone and clay stringers that extend broadly in the Ghadames Basin from the northwestern Libya to the northeastern Algeria and the central Tunisia. These Albian sands are transgressed over by Upper Albian (old Vraconian) to Cenomanian dolostone and gypsum sequences with sand and pebble components in the lower beds (Figs. 6–8). Note that the Mid-Upper Aptian dolostones pinch-out toward the Dahar and the Nalut– Nafusa cliffs. Thus it makes it difficult to distinguish the Barremian sands (megacycle IV) from the disconformably overlying Albian sandy sequences (megacycle V), both cropping out broadly in the Dahar cliffs, notably at Remada and Dhehiba (Busson and Albanesi, 1967), Kamboute, Oum Ed Dhiab and Bir Amir, and Boulouha and Haddada Mountains, and in the western Nafusa cliffs (Figs. 1, 2, 7 and 8).

3.2. New biostratigraphical and lithostratigraphical results The Haddada Member (Service Géologique de Tunisie, 1984) referring to the Lower Kimmeridgian lithofacies identified in megacycle I by Tlig (1978), has no lithostratigraphic value and should be abandoned. Kamoun et al. (1988), Kamoun (1988) and Kamoun et al. (2003) took the biostratigraphic results of Tlig (1978) at Oued Zaafrane with no citation nor cautionary discussion

and used the synonymy between Pseudocyclammina jaccardi (Schrodt) and Alveosepta jaccardi (Schrodt) to describe this microfauna and associated algae in the laterally overlying but totally dolomitic facies at Bir Miteur and defined the Upper Oxfordian– Lower Kimmeridgian Bir Miteur Member. Cyclammina jaccardi Schrodt 1894 synonym of Alveosepta jaccardi Schrodt 1894, which is known in the peri-Mediterranean area was proposed by Schrodt (1894) from the Kimmeridgian of Col des Roches, Neuchâtel Jura, in Switzerland. This species was later redescribed by Maync (1958) as Pseudocyclammina jaccardi Schrodt (equals Pseudocyclammina sequana Tobler) (Tobler, 1926), and by Hottinger (1967), as A. jaccardi Schrodt. Bismuth et al. (1967) studied the Callovian–Oxfordian marls and limestones (megacycle I) in the Tataouine and Ghomrassene area (Fig. 1) and wrote ‘‘. . . the limestone formation of Ghorrassene [upper part of the ‘Calcaires et Marnes de Foum Tataouine’; Busson, 1967] can be considered as a good reference section of upper Oxfordian and basal Kimmeridgian’’. This was confirmed by Pseudocyclammina jaccardi Schrodt dating the Kimmeridgian, and Kurnubia wellingsi (Henson) dating the Oxfordian to Late Kimmeridgian, associated in the uppermost beds of the ‘Calcaires et Marnes de Foum Tataouine’, in the presence of Algae Arabicodium sp. and Salpingoporella annulata Carozzi. as it became clear that the megacycle I continues upwards in Lower Kimmeridgian sequences untill the dolostone reference bed with hexacorals and gastropoda (Tlig, 1978; Figs. 1–4 and 6). The abundant but poorly diagnostic mollusks, wood and vertebrate remains prevented the dating of overlying sand, dolostone and clay sequences in the Upper Jurassic–Lower Cretaceous (?) megacycle II that might be Lower Kimmeridgian–Tithonian in age, but certainly not Upper Oxfordian–Lower Kimmeridgian as ascertained by Kamoun (1988), and Kamoun et al. (1988), notably for the Bir Miteur section (Fig. 3). This Member (ranked as the Bir Miteur Formation by Ouaja, 2003) that is totally dolomitized and coeval with the Oued Zaafrane section (Haddada Member), was described in the less representative section of the Upper Jurassic and the disconformably overlying Lower Cretaceous sands, dolostones and clays. It is clear that the Bir Member totally lacks stratigraphic and lithostratigraphic values. The megacycle III with Berriasian to Hauterivian Green Clays (Figs. 5 and 6; Busson, 1967; Tlig, 1978) is marine as indicated by the high (300–400 ppm) boron contents inherited from seawater in the <0.4 nm illitic clays (Harder, 1963; Tlig, 1978), This dating is confirmed by the specimen discovery (Mohamed Ouaja) of the Terebratulid Loriolithyris russilensis (de Loriol) (see Middlemiss, 1968, 1980, for synonymy and age) in the dolomitic beds located below facies at Bir Miteur, coeval with the Green Clays. This discovery was reported by Peybernes et al. (1996). The Terebratulid was claimed by Pictet and de Loriol (1872) in the Valanginian of Sainte-Croix (Vaud), by Ager (1974) and by Ager and Evany (1964) in the Berriasian of southern Jura, by Benest et al. (1996) in Berriasian strata in Algeria, and by Middlemiss (1980) in Hauterivian to Aptian (?) series of southwest Morocco. This indicates that the distribution of this poorly diagnostic Terebratulid is from the Berriasian to at least Barremian. These results and the presence of Priohybodus arambourgi d’Erasmo 1960 (Kimmeridgian–Hauterivian/Barremian; Soto et al., 2012) confirm the Berriasian to Hauterivian age assigned to the Megacycle III with Green Clays by Busson (1967, 1972), Reyre (1970) and Tlig (1978). These findings and results above indicate that the Continental Intercalaire after Kilian (1931) and Pubecko–Wealdian series (Rat, 1962) in the study area are marine and thus these concepts should totally be abandoned. The exoscopic study distinguished: (1) clean quartz grains in megacycle 1 having undergone an early winnowing stage and rare

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silica precipitation onto grain surfaces that show polished crystal edges, smoothed ‘v’ notches, and clear dissolutions in intertidal to infratidal marine environments of sedimentation; (2) quartz grains in megacycles II to IV suffered diagenesis, but traces of polished ‘v’ notches, rare silica precipitates onto grain surfaces, and smoothed crystal edges testify to sands settled in coastal marine environments. The fluvial to marine-coastal Barremian and Albian coarse-grained sands, sandstones and conglomerates with clays draping sequences that crop out in the Dahar and Nafusa cliffs were regrouped in the Ain Guettar Fm (Ouaja et al., 2002; Bodin et al., 2010 and references cited) and the coeval Kiklah Fm (sensu Burollet, 1977; Fatmi et al., 1980) in northwestern Libya. These sediments may show paleosoils generated during exposure. Bouaziz et al. (1988), Ouaja (2003), Bodin et al. (2010); Fanti et al. (2012) and Contessi (2013) subdivided the Ain El Guettar Fm into the lower Chenini and upper Oum Ed Dhiab Members, while Smith et al. (2010) and Le Loeuff et al. (2010) described the Chenini Member as the Cabao Fm, incoherently with the lithostratigraphical assignments of Burollet (1963, 1977), Hammuda (1969); El Zouki (1976); Fatmi et al. (1980), Shiref and Salaj (2007) and Bodin et al. (2010).

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The Ain El Guettar equivalent to the Kiklah Fms should be revised. The Aptian beds sandwiched between the upper and lower Members of these Formations, have been eroded and reworked due to Austrian tectonics in the broadly uplifted and exposed area covering the Tebaga Mountain, Tataouine, Hamada El Hamra and Nafusa–Nalut areas. The lower Members of Kiklah and Aïn El Guettar (Chenini) Fms are Barremian to at least Lower Aptian as assigned by Busson (1967, 1972) who described the fish species Lepidotus and the Hybodontid Priohybodus arambourgi d’Erasmo (1960) in the previous megacycles III and IV at the Haddada Mountain. These species date the Kimmeridgian to Hauterivian/Barremian period (see Soto et al., 2012 for a discussion). Thus, there appears no discrepancy in Age distributions of this Hybodontid between the South-American (Peru) and African continents as suggested by Le Loeuff et al. (2010). Our results conform to the rifting from South to North of the Southern Atlantic Ocean and started drifting of the South American plate away from Africa during the Aptian as demonstrated by Piccirillo et al. (1990). These events coincide with the Austrian tectonic phase (Stille, 1924) in the study area. Tlig (1978) identified Carcharodontosaurus saharicus Depéret and Savornin (1925) Stromer 1931 in Albian sands at Bir Miteur

Fig. 9. Stratigraphical subdivisions of the Upper Jurassic–Lower Cretaceous series of southern Tunisia based on field and oil well sections and on facies correlations taking into account their sequence stratigraphy and their sedimentological and tectonic features.

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resting above the megacycle III. These sands may correspond to the upper Members of Aïn El Guettar and coeval Kiklah Fms. However, it is still difficult to delineate the discontinuity between the lower Barremian–Aptian megacycle IV and the Mid-Upper Aptian–Albian megacycle V in outcrops, because of the highly similar facies of the superposed coarse and conglomeratic sandy sequences and syndepositional tectonics. 4. Correlations with Upper Jurassic and Lower Cretaceous series of central Tunisia The five megacycles in the southern Tunisia may be correlated with those stratotypes described in the central Tunisia (Fig. 6). The lower megacycles I (Callovian–Lower Kimmeridgian) and II (Lower Kimmeridgian–Tithonian) in the southern Tunisia pass upwards from pelagic Callovian facies with diagnostic ammonoids (Busson, 1967, 1972; Enay et al., 2002) to Oxfordian transgressive limestones with microbial, biohermal and biostromal constructions, to neritic Kimmeridgian and inner lagoon deposits affected by water runoff from exposed areas (megacycle II; Tlig, 1978; Tlig and Steinberg, 1980). These cycles correlate with the Mid-Upper Jurassic marls and pelagic to neritic lime and dolostones in the Callovian to Upper Tithonian Upper Nara Formation described in the Nara–Boudzer Mountains in central Tunisia (Figs. 1 and 6; Burollet, 1956; Soussi, 2002). The megacycle III that includes Green Clays correlates with the both Late Tithonian–Valanginian Sidi Khalif Formation (Burollet, 1956; Busnardo et al., 1980) made up of green marls and limestones dated by ammonoids, and the conformably overlying Meloussi Formation considered Valanginian–Hauterivian in age, described at the Meloussi Mountain in central Tunisia (Burollet, 1956; Marie et al., 1984; Damotte et al., 1987). Thus, it may be argued that the Neo-Cimmerian unconformity should be placed between the neritic Nara and the pelagic Sidi Khalif sequences in the central Tunisia. The Barremian–Lower (or Early) Aptian megacycle IV recorded by coarse-grained sands with quartz pebbles, and conglomerates with quartzite cobbles capped by the Austrian unconformity and extending broadly in southern Tunisia, is coeval with the Barremian Boudinar, Bouhedma and Sidi Aich Formations (Figs. 1 and 6) in central Tunisia (Burollet, 1956) and Salt Marshes basin (Ben Youssef, 1999). These formations are transgressed over by the Late Barremian–Aptian lime and dolostones of the Orbata and Bidha (Ben Youssef, 1999) Fms both capped by Austrian unconformity. The cycle V in the southern Tunisia and northwestern Libya forms the Lower–Middle Aptian Transgressive System’s Tract that has drowned the Austrian paleoreliefs (Figs. 1, 2, 7 and 8). The Albian sands, often coarse-grained, conglomeratic and with a few dolostone beds and clay stringers have extended broadly in the entire Tunisia. These conformably overlie the Upper Aptian dolostones in the Sahara and occur in continuity with the overlying Cenomanian sequences. These sands may overlie the Austrian unconformity to the north of study area that caps the Late Barremian–Lower Aptian dolostones of the Orbata Fm (Burollet, 1956) in the central Tunisia and the lower beds of Bidha Fm (Ben Youssef, 1999) in the Salt Marshes area. 5. Correlations with the Lower Cretaceous and Upper Jurassic series of northwestern Libya The Callovian Shakshuk Fm (Novovic, 1977; Fatmi et al., 1980; Shiref and Salaj, 2007) in northwestern Libya contains the uppermost marine and fossiliferous Jurassic beds in the area between the Gharian and the Nafusa–Nalut cliffs located to the East of the

Tunisian Dhehiba village (Figs. 1 and 2). These facies are disconformably overlain by the Ar Rajban Fm with mollusks and brachiopods that may span the whole Oxfordian to Tithonian (Burollet, 1963, 1977; Fatmi et al., 1980; Shiref and Salaj, 2007). It is formed by sands, clays and conglomerates capped by the Neo-Cimmerian unconformity, Thus, it may be argued that the Shakshuk and Ar Rajban Fms are coeval with the Mid-Upper Jurassic megacycles I and II (Callovian–Tithonian) described in this study (Figs. 1 and 6). The Ages, facies and limits of the Kabaw Fm (Cabao Fm; Burollet, 1963, 1977; Hammuda, 1969; El Zouki, 1980; Fatmi et al., 1980; Mateer et al., 1992) are imprecise since the Ar Rajban beds may have been integrated in the former (see Burollet, 1963, 1977; Fatmi et al., 1980; Bodin et al., 2010). These beds have often been considered as disconformably overlying the older deposits in the Shakshuk Fm (see Fatmi et al., 1980; Le Loeuff et al., 2010). Other authors consider that the Cabao Fm (Burollet, 1963) encompasses the whole Oxfordian to Lower Aptian (lower Member in the Kiklah or Chicla Fm; see Fatmi et al., 1980). For these reasons the comparison between the findings of Tunisian Geologists and those of their Libyan partners (Hallett, 2002; Shiref and Salaj, 2007; Smith et al., 2010; Bodin et al., 2010; Le Loeuff et al., 2010; Fanti et al., 2012; Contessi, 2013) is difficult to resolve. Based on the sequential subdivisions in this work (Figs. 3–9) constrained by facies patterns, seismic profiles, well data, biostratigraphy and major tectonic unconformities, I propose the following: (1) the Shashuk and Ar Rajban beds should equate with the uppermost Jurassic sequences in the southern Tunisia including the Callovian–Oxfordian limestones and marls plus the overlying limestones, sands, dolostones and clays considered Kimmeridgian to Tithonian capped by the Neo-Cimmerian unconformity (megacycles I & II) (Figs. 3, 6 and 9); (2) the Cabao (Kabaw) Fm (sensu stricto) described by Burollet (1963, 1977) is Berriasian to Hauterivian in age and is coeval with the megacycle III with the Green Clays (read Smith et al., 2010). Its lower boundary corresponds to the Neo-Cimmerian unconformity, whereas its uppermost boundary is recorded by the Early Barremian unconformity located at the base of Barremian–Lower (Early) Aptian coarse-grained sands and sandstones (Busson, 1967, 1972; Tlig, 1978; Lower Member of the Kiklah Fm in Bodin et al., 2010) (Figs. 1, 5 and 8); (3) the Kiklah Fm fits laterally into the coarse-grained sands and conglomerates in the megacycle IV in southern Tunisia. Thus, the Kiklah Formation contains a Barremian–Lower Aptian (?) megacycle (lower Member), and the basal sandy and conglomeratic beds (upper Member) of the Albian–Cenomanian megacycle V (Sidi As Sid Fm of northwestern Libya). The Austrian unconformity and reworked Aptian and other beds herewith are sandwiched between these two Members, due to the pinching out of the Middle–Upper Aptian dolostones identified in oil-wells to the west, from Dhehiba to the Nalut and Nafusa Mountains. Therefore, the Kiklah (Chicla) as well as the Aïn El Guettar Formations cannot be accepted and need total revision.

6. Discussion and conclusions 6.1. Remarks on the lithostratigraphic subdivisions and corresponding Stage ages The studies of vertebrate remains (Smith and Dalla Vecchia, 2006; Smith et al., 2010; Le Loeuff et al., 2010; Fanti et al., 2012; Contessi, 2013) were based on the lithostratigraphic subdivisions of the series summarized by Peybernes et al. (1996), Ouaja et al. (2002), Barale and Ouaja (2002) and Bodin et al. (2010). These subdivisions cannot be accepted due to the great discrepancies

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between the Stage ages of the megacycles assigned by microfauna, Terebratulids, and fish and vertebrate fauna as explained above, and calibrated to wellbore data (see also Bismuth et al., 1967; Busson, 1967, 1972; Reyre, 1970; Bonnefous, 1972; Tlig, 1978). The Members (Haddada, Bir Miteur) and formations (Boulouha, Aïn El Guettar, Kiklah) that include gaps and unconformities, lack biostratigraphic and field evidence and should totally be revised. The map sheets of 1:100.000 scale of the area should be redrawn and explanatory booklets (Service Geologique National, 1984) should be revised since these were based on all these invoked lithostratigraphic errors. For example, the Lower Kimmeridgian–Tithonian megacycle II is considered either Upper Oxfordian–Lower Kimmeridgian (Bir Miteur Member: Kamoun, 1988; Kamoun et al., 1988; =Bir Miteur Fm of Ouaja, 2003) or Late Hauterivian–Barremian (Boulouha Fm; Ouaja et al., 2002; Bodin et al., 2010; Fanti et al., 2012; Contessi, 2013; see Tlig, 2015b) in age. The Berriasian– Hauterivian megacycle III is assigned an Aptian age (Douiret Fm; Ouaja et al., 2002; Barale and Ouaja, 2002; Srarfi et al., 2004; Bodin et al., 2010; Le Loeuff et al., 2010; Fanti et al., 2012; Contessi, 2013); however, it is clear that the Mid-Upper Aptian dolostones exist upwards but were not considered by these authors and pinch out in outcrops of the Dahar and Nafusa cliffs. The Barremian–Early Aptian megacycle IV (Busson, 1967; Tlig, 1978) is assigned either an Albian or Upper Aptian–Albian ages (Ain El Guettar Fm: Bouaziz et al., 1988; Ouaja et al., 2002; Srarfi et al., 2004; Bodin et al., 2010; Fanti et al., 2012; Contessi, 2013). Hence it may be argued that the diagnoses and Age distributions given by these authors of fish and saurian remains with known spatial and temporal distributions (see Lapparent, 1951, 1960; Busson, 1967, 1972; Soto et al., 2012 and references cited), were influenced by the erroneous Stage ages assigned to the formations in study area (see Smith and Dalla Vecchia, 2006; Le Loeuff et al., 2010 for a discussion) defined by many authors since the 1990s, with the lack of appropriate literature (Lapparent, 1951, 1960; Busson, 1967; Busson and Albanesi, 1967) and should thus be revised, in particular the publications by Bodin et al. (2010), Le Loeuff et al. (2010), Fanti et al. (2012) and Contessi (2013). The species Priohybodus arambourgi d’Erasmo (1960) described as the new discovery by Srarfi et al. (2004) and Le Loeuff et al. (2010) ignores the findings of Busson (1967) and Busson and Albanesi (1967) The discovery of the species Carcharodontosaurus saharicus Depéret and Savornin (1925) Stromer 1931 by Bouaziz et al. (1988), discards the works of de Lapparent (1960), Busson (1967, 1972), Busson and Albanesi (1967) and Tlig (1978). The Haddada (=Oued Zaafrane = Bir Miteur Member/Fm; Kamoun et al., 1988) Member, the Kimmeridgian reference beds with hexacorals, and the association of Pseudocyclammina (=Alveosepta) jaccardi Schrodt with Kurnubia wellingsi Henson, Arabicodium sp., and algae Solenoporacae invoked in the latter Member by Kamoun (1988), Kamoun et al. (1988) and Kamoun et al. (2003) reproduces the work and ignores citation of its first author (Tlig, 1978). 6.2. Paleogeographic implications The lower megacycles I & II (Callovian–Tithonian) are marine in the southern Tunisia. The latter cycle (Lower Kimmeridgian– Tithonian) contains lagoon to marine facies approximately 83 m in total thickness (Boulouha Fm; Lower Barremian–Aptian Boulouha Fm in Bodin et al., 2010) and is capped by the Neo-Cimmerian unconformity (Fig. 9). These megacycles correlate with the Callovian–Tithonian pelagic to neritic lime and dolostones of the Upper Nara Formation in the central Tunisia and fit laterally into the Sahkshuk and Ar Rajban Fms (Nafusa Mountain) in the northwestern Libya (Fig. 8). The latter formation is capped and

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its deposits reworked by the Cimmerian unconformity. These facts indicate that the area between Tataouine, Dhehiba, Hamada El Hamra and Nalut–Nafusa Mountains has undergone exposure constrained by syndepositional tectonics during the Upper Jurassic and Early Cretaceous. The megacycle III (Berriasian–Hauterivian) contains sands, dolostones and clays that pass upwards into marine Green Clay sequences capped by the Early Barremian unconformity (Douiret and Kabaw Fms; Aptian in Bodin et al., 2010). This cycle correlates with pelagic deposits (Late Tithonian–Valanginian to possibly Early Hauterivian) of the Sidi Khalif and neritic to shoreface deposits of the Meloussi Fms (Hauterivian) in central Tunisia, and with the Cabao Fm sensu stricto (Burollet, 1963, 1977) in northwestern Libya (Figs. 1 and 8). The latter disconformably overlies the Ar Rajban Fm through the Neo-Cimmerian unconformity, and is capped by the Early Barremian unconformity that constitutes the lower boundary of the Kiklah Fm (sensu El Zouki, 1980; Fatmi et al., 1980). These results indicate that the Early Cretaceous transgression (Late Tithonian–Berriasian) has invaded exposed Neo-Cimmerian paleohighs in the study area during the Berriasian; however with some diachronism, since the lower beds of the Sidi Khalif Formation were dated Late Tithonian in the central Tunisia (Busnardo et al., 1980). The megacycle IV (Barremian–Lower (early) Aptian) extends broadly from central Tunisia to northwestern Libya and has carried coarse-grained sands and conglomerates enriched in vertebrate remains that vary in thickness both vertically and laterally. This cycle corresponds to the lower Member of Kiklah Fm delineated at the base by the Early Barremian unconformity and terminates in the Austrian unconformity (Lower Aptian; Figs. 1 and 8). Facies in this cycle record a diastrophic event interrelated with the Early Barremian and Austrian tectonics that have fed the northern Sahara, and the Salt Marshes, other Neo-Tethyan rift-basins and central Tunisia by siliciclastics shed from the Paleozoic bedrock having formed paloreliefs surrounding the Ghadames Basin. The megacycle V bounded at the base by the Austrian unconformity contains Mid-Upper Aptian dolostones conformably overlain by coarse-grained Albian sands with quartz pebbles, and conglomerates similar to those in megacycle IV. These facies pass upwards to the Upper Albian and Cenomanian carbonate, marl and evaporitic gypsum packages that overlie the Late Barremian–Early Aptian dolostones through the Austrian unconformity in the central Tunisia and Salt Marshes area (Ben Youssef, 1999). The Mid-Upper Aptian dolostones that pinch out toward the Dahar, Nalut and Nafusa cliffs in the northwestern Libya cause the Albian sands disconformably rest on their Barremian–Early Aptian counterparts in the area, through the Austrian unconformity (Fig. 8; Ain El Guettar and Kiklah Fms). The Late Barremian–Lower Aptian transgression in the Neo-Tethyan basin of central Tunisia may have preceded the Austrian phase. The flooding of paleoreliefs capped by broadly extending gullied surfaces (Austrian unconformity) having populated the Grand Erg Oriental, Dahar and Nalut–Nafusa areas occurred later during the Middle to Late Aptian, precluding those exposed paleoreliefs (Fig. 8). The ubiquitous Albian siliciclastic invasion may be explained by the uplift and erosion of Barremian siliciclastics and the Mid-Upper Aptian dolostones constrained by syndepositional Austrian tectonics. The eustatic lowering during the Albian times (Haq et al., 1988) might have enhanced the water runoff and basin fill by siliciclastics shed from paleoreliefs. Thus, it cannot be precluded that the Albian sands (megacycle V) containing the remains of Carcharodontosaurus saharicus Depéret and Savornin (1925) Stromer 1931 may disconformably overlie the Berriasian–Hauterivian Green Clays in megacycle III as it seems to be the case in the sections emplaced on blocks that were uplifted during these times (El Itime, Boulouha and Haddada

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Mountains, and Batene Hameima and Bir Miteur; Figs. 6, 8 and 9). Paleohighs having formed in the Nalut–Nafusa Mountains, might exhibit the Cabao Formation overlain by the Upper Member (Albian) of the Kiklah Formation. Acknowledgments The author is indebted to the Reviewers P. Erickson and W. Bosworth whose constructive comments resulted in the final balanced version of this manuscript. I particularly thank Professors F. Depeche, S. Gargouri-Razgallah, D. Turki and Ph. Taquet for the biostratigraphical study, and Dr. L. Le Ribault for the exoscopic evaluation of quartz grains. Many of the mineralogical, petrographical and geochemical analyses were carried out at the University Paris XI (Center of Orsay), Laboratory 504 of Geochemistry of Sedimentary Rocks, and at the Laboratory Pierre Süe (37) of the Center for Nuclear Studies of Saclay (Gi-sur-Yvette; France) with the recommendations of my Prs C.J. Allègre, M. Treuil, M. Steinberg, and G. Busson. I also thank the contributions to this work of the Technical Advisors H. Jaffrezic, N. Moureau and G. Meyer. References Ager, D.V., 1974. The western high atlas of Morocco and their significance in the history of the North Atlantic. In: Proceedings of the Geological Association, London, vol. 85, pp. 23–41. Ager, D.V., Evany, B.D., 1964. The geology of the southern French Jura. In: Proceedings of the Geological Association, London, vol. 74, pp. 325–355. Banerjee, S., 1980. Stratigraphic Lexicon of Libya. Industrial Research Center, Tripoli, Bull, 300 p. Barale, G., Ouaja, M., 2002. La biodiversité végétale des gisements d’âge Jurassique supérieur-Crétacé inférieur de Merbah el Asfer (Sud-Tunisien). Cretac. Res. 23, 707–737. Ben Youssef, M., 1999. Stratigraphie génétique du Crétacé de Tunisie. Micropaléontologie, stratigraphie séquentielle et géodynamique des bassins de la marge Sud et péri-téthysienne, 402 p. Benest, M., Gaspard, D., Ghali, M., 1996. Les brachiopodes de l’avant-pays ouestalgérien lors de la phase transgressive maximale du Berriasien supérieur; systématique, environnement et paléogéographie. Géobios 29, 13–34. Bismuth, H., Bonnefous, J., Dufaure, Ph., 1967. Mesozoic microfacies of Tunisia. Petr. Explo. Soc. Libya, in Guide Book to the Geology and History of Tunisia, Tripoli, pp. 159–214. Bodin, S., Petitpierre, L., Wood, J., Elkanouni, I., Redfern, J., 2010. Timing of early to mid-cretaceous tectonic phases along North Africa: new insights from the Jeffara escarpment (Libya–Tunisia). J. Afr. Earth Sci. 58, 489–506. Bonnefous, J., 1972. Contribution à l’étude stratigraphique et micropaléontologique du Jurassique de Tunisie. Thèse Sciences. Université Paris VI, 397p. Bouaziz, S., Buffertaut, E., Ghanmi, M., Jaeger, J.-J., Martin, M., Mazin, J.-M., Tong, H., 1988. Nouvelles découvertes de vertébrés fossiles dans l’Albien du Sud Tunisien. Bull. Soc. géol. France 4, 335–339. Boughdiri, M., Oloriz, F., Lopez Marques, B., Layeb, M., De Matos, E., Sallouhi, H., 2005. Upper Kimmeridgian and Tithonian ammonites from the Tunisian ‘Dorsale’ (NE Tunisia): updated biostratigraphy from J. Oust. Riv. Ital. Stratigr. Paleontol. 111 (2), 305–316. Brusatte, S., Sereno, P.C., 2007. A new species of Carcharodontosaurus (Dinosauria: Theropoda) from the Cenomanian of Niger and a revision of the genus. J. Vertebr. Paleontol. 27 (4), 902–916. Burollet, P.F., 1956. Contribution à l’étude stratigraphique de la Tunisie centrale. Ann. Mines Géol., Tunis 18, 345p. Burollet, P.F., 1963. Discussion sur la Stratigraphie Libyenne. Rev. l’Inst. Français Pétrole, Paris 18, 1323–1328. Burollet, P.F., 1977. Morphologie et pédologie d’une plaine couverte de sable: la Jeffara Libyenne. Notes Mémoir. Compagnie Française Pétrole 13, 11–30. Burollet, P.F., Dumestre, A., 1952. Report on Six Stratigraphic Sections in the Medenine–Tataouine Area. SNAP Géol. Progress Report, N 12, Sfax, 10 p., 13 pls. Busnardo, B., Donze, P., Le Hegarat, G., Memmi, L., MRabet, A., 1980. Précisions stratigraphiques nouvelles sur le Berriasien des Jebels Nara et Sidi Khalif (Tunisie Centrale). Géobios, Lyon 9 (3), 230–250. Busson, G., 1967. Le Mésozoïque saharien. 1ère partie: l’Extrême-Sud tunisien. Centre de Recherches sur les zones arides, Série Géologie, No. 8, CNRS, 194 p. Busson, G., 1972. Principes, méthodes et résultats d’une étude stratigraphique du Mésozoique Saharien. Mémoires du Muséum National d’Histoire Naturelle, Série C, tome XXVI, Paris, 443p. Busson, Albanesi, 1967. Le Crétacé inférieur et le Jurassique terminal de l’Extrêmesud Tunisien. Riv. Ital. Paleontol. 73 (2), 591–634, Milano. Carras, N., Conrad, M.A., Radoicic, R., 2006. Salpingoporella, a common genus of Mesozoic Dasycladales (calcareous green algae). Rev. Paléobiol., Genève 25 (2), 457–517.

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