Journal of African Earth Sciences 61 (2011) 94–104

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Journal of African Earth Sciences

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Late Triassic–early Jurassic block tilting along E–W faults, in southern Tunisia: Newinterpretation of the Tebaga of Medenine

Camille Raulin a,⇑, Dominique Frizon de Lamotte a, Samir Bouaziz b, Sami Khomsi c, Nicolas Mouchot d,Geoffrey Ruiz e, François Guillocheau f

a Géosciences et Environnement Cergy, Université de Cergy-Pontoise, 5 mail Gay Lussac, 95031 Cergy-Pontoise Cedex, Franceb Laboratoire Eau-Energie-Environnement, Université de Sfax, Ecole Nationale d’Ingénieurs de Sfax, Ad-10-02, BP W, 3038 Sfax, Tunisiac Department of Petroleum Geology and Sedimentology, Faculty of Earth Sciences, King Abdulaziz University, Jedda, Saudi Arabiad Laboratoire de Géologie, Ecole Normale Supérieure, CNRS-URA 8538-1316, 24 rue Lhomond, 75231 Paris Cedex 05, Francee Institut de Géologie et Paléontologie, Université de Lausanne, CH-1015 Lausanne, Suisse, Switzerlandf Géosciences-Rennes, UMR 6118, Université de Rennes 1, 35042 Rennes Cedex, France

a r t i c l e i n f o a b s t r a c t

Article history:Received 2 December 2010Received in revised form 15 April 2011Accepted 23 May 2011Available online 27 May 2011

Keywords:Tebaga of MedenineSouthern TunisiaRiftingUpper TriassicLower-Middle JurassicEast Mediterranean

1464-343X/$ - see front matter � 2011 Elsevier Ltd.doi:10.1016/j.jafrearsci.2011.05.007

⇑ Corresponding author. Tel.: +33 134257364; fax:E-mail address: camille.raulin@u-cergy.fr (C. Rauli

The Tebaga of Medenine is a puzzling structure situated at the northern edge of the Jeffara plain in south-ern Tunisia. It presents the unique outcropping marine Permian sequence in Africa as well as spectacularangular unconformities related to Mesozoic tectono-sedimentary events. Many hypotheses have beenproposed to explain this structure but some questions still remain. We present the result of an integratedstudy of the Mesozoic tectonic evolution of the region, based on new field work and a reassessment ofsome subsurface data. We propose a new structural hypothesis in which the Tebaga of Medenine is inter-preted as resulting from large scale block tilting, mainly controlled by inherited E–W major faults, theAzizia fault system. These E–W faults running along the Jeffara plain may represent inherited structuralfeatures in relation with deep faulting in the Paleozoic substratum. This rifting occurring during late Tri-assic up to the end of early Jurassic, is finally integrated in the general frame of the East Mediterranean.

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1. Introduction

Southern Tunisia constitutes the northern edge of the Saharaplatform (Ghadames Basin), a tabular domain made up of Paleozoicand Mesozoic sedimentary rocks (Fig. 1A and B). It includes theJeffara plain in which is exposed a south dipping monocline,known in the literature as the ‘‘Tebaga of Medenine’’. This E–Wtrending structure is situated close to the town of Medenine, eastof the Dahar plateau (Fig. 2). It intrigues geologists since the begin-ning of geological and petroleum exploration for three mainreasons:

(1) It constitutes the unique outcrop of marine Permian rocks inAfrica (Berkaloff, 1933; Newell et al. 1976; Khessibi, 1985).

(2) It exhibits a quite important dip (mean value of about20�–30�), contrasting with the almost tabular environmentof the Sahara platform.

(3) It recorded multiple unconformities and syn-sedimentarydeformations.

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+33 134257350.n).

Previous geological studies focused either on the significance ofthe Permian basin located at the junction between the Paleozoic‘‘Talemzane and Nefusa Arches’’ (major Paleozoic arches of theSahara domain) and the Pelagian Sea (Fig. 1A and B) or on thestructural interpretation of the Tebaga as a large monocline(Busson, 1972) or as an asymmetric faulted anticline (Mathieu,1949; Bouaziz, 1995). Concerning the first aspect, Stampfli et al.(1991, 2001) and Stampfli and Borel (2002) use the existence ofa Permian marine basin below the Jeffara plain to defend their ideaof a late Permian rifting/drifting responsible for the opening of theEast Mediterranean basin. The topic of the present paper is not todiscuss directly this hypothesis but to replace the Tebaga ofMedenine in its geodynamic and structural context. This approach,based on new field investigations, a reassessment of existinggeological maps (geological maps of Tunisia (Ben Haj Ali et al.,1985; Bouaziz et al., 1986; Zouari et al., 1987; Bouaziz and Mello,1990; Bouaziz, 1990a,b, 1991, 1998) and Libya (El Hinnawy andCheshitev, 1975; Mann, 1975; Smetana, 1975; Antonovic, 1977;Novovic, 1977; Zivanovic, 1977), a reassessment of previous works(Mathieu, 1949; Busson, 1972; Bouaziz, 1995) and well correla-tions, allow us to revisit the structural significance of the ‘‘Tebagaof Medenine’’.

Pantellaria graben

Sahel

SICILY

TUNISIA

LIBYA SIRT BASIN

Ionian abyssal basin

Malta escarpm

ent

Talemzane Arch

htr oN

Sout

hAx

is Gulf of Hammamet

Gulf of Gabes

Sabratah basin

IONIAN SEAPELAGIAN SEA

GHADAMES BASINALGERIA

Nefusa Arch

Fig. 2

Hun graben

Agedabia graben

Tumayam graben

Sarir graben

Maradah graben

Ashtart-Tripolitania graben

Mediterranean Ridge

Linosa graben

Malta graben

30°

10° 20°

10° 20°

30°

-

AFRICA

IBERIAANATOLIA

APULIA

Peri-Atlas basin (flexural basin)

Atlas system

Main Anticline

Jeffara plain

Sahara platform

Sirt-Pelagian system

Main grabens

Ionian oceanic basin

Paleozoic arch

Undifferentiated fault

Normal fault

Thrust fault

Main overthrust

Limit of the Messinian salt

AA

B

BA

M id-crustal detachm ent

Cenozoic

Mesozoic

Paleozoic

Permian

Proterozoic

CarboniferousDevonianSilurian

Cambro-Ordovician

Triassic

Jurassic

Cretaceous

(Continental crust)

PELAGIAN SEANEFUSA ARCHNS

0

(km)-40

-20

??

GHADAMES BASIN

50 km

A

B

Studied area

Fig. 1. A = Map of the Central Mediterranean, locating the Jeffara basin at the junction between the Sahara platform, the Pelagian Sea and the Atlas system. The map ismodified from Jongsma et al. (1985, 1987), Chamot-Rooke et al. (2005), Rusk (2001), Casero and Roure (1994), Finetti (1982), and Burollet (1991). B = General cross-sectionfrom the middle part of the Pelagian sea to the Sahara platform modified from Jongsma et al. (1985), Hallett (2002), Boote et al. (1998), Klett (2001), and Boccaletti andManetti (1978), in Frizon de Lamotte et al. (2011).

C. Raulin et al. / Journal of African Earth Sciences 61 (2011) 94–104 95

Fig. 2. Geological map of the Jeffara Basin (Tunisia Libya), adapted from the geological maps of Tunisia (Ben Haj Ali et al., 1985; Bouaziz et al., 1986; Zouari et al., 1987 Bouazizand Mello, 1990; Bouaziz, 1990b, 1991, 1998) and Libya (El Hinnawy and Cheshitev, 1975; Mann, 1975; Smetana, 1975; Antonovic, 1977; Novovic, 1977; Zivanovic, 1977). Aand B locates the figure 5’s cross-section.

96 C. Raulin et al. / Journal of African Earth Sciences 61 (2011) 94–104

2. Geological setting, previous interpretation

In southern Tunisia, the Dahar plateau is made up of UpperAlbian to Santonian shallow marine carbonate rocks dipping gentlyto the south-west and overlain by the sand dunes of the OrientalGreat Erg (Fig. 2). This almost flat domain rests unconformablyon the Permian to Lower Cretaceous sediments, which are croppingout in the Jeffara plain. A complete Triassic to Lower Cretaceoussuccession is known in the Tataouine area delimited by the Azizianorth dipping fault system, which crops out mostly in Libya, andthe Zemlet el Ghar south dipping fault (Fig. 2). Another set of fault,known as the Jeffara fault system, is trending NW–SE (Fig. 2)(Gabtni et al., 2009). This direction played a major role duringthe Cretaceous–Paleocene development of the Sirt Basin (Fig. 1),which is characterized by a NE–SW direction of extension(Jongsma et al., 1985; Klett, 2001). However, the Jeffara fault sys-tem is inherited from a long history and acted likely as a transformdirection during the lower Mesozoic (Burollet, 1991; Piqué et al.,2002; Lazzez et al., 2008).

In the Jeffara plain, the approximately 2000 m thick sedimen-tary column is composed of (Fig. 3): a Lower and Middle Triassiccontinental sandstone overlain by marls interbedded withcarbonates and evaporites of Upper Triassic age. An evaporiticcomplex developed during the Liassic, followed by evaporitesincreasingly replaced by shallow carbonates during the MiddleJurassic up to the Oxfordian. Then, a major hiatus and/or

erosional gap separates the Jurassic succession from the siliciclas-tic deposits of the ‘‘Continental Intercalaire’’, which is mainlyBarremian to Albian in the region of interest (Ouaja et al., 2002;Bodin et al., 2010). Finally the Upper Cretaceous is dominatedby carbonate sedimentation.

From a structural point of view, the regional geological mapsuggests the progressive truncation and piching out of the Triassicto Early Cretaceous rocks toward the E–W trending Tebaga ofMedenine, where Permian rocks are dipping southward (Fig. 2).Busson (1972) interprets this particular geometry as the result ofvertical uplift during the Middle Triassic, prior to the progressivesubsidence and drowning of the Tebaga from late Triassic up tothe end of middle Jurassic. From this point of view, the interpreta-tion of Busson (1972) contrasts with the previous work by Mathieu(1949) who has suggested that the tilting observed in the Tebagawas the result of folding related to a compressive tectonic eventpredating the deposition of the Bathonian. More recently, Bouaziz(1995) and Bouaziz et al. (2002), based on geological mapping,clarified the structural configuration of the Tebaga by interpretingit as an asymmetric anticline with a steep northern limb, whichwas subsequently cut out by steep normal faults. These authors da-ted a late Triassic folding event based on an Upper Carnian uncon-formity and interpreted the Tebaga as the result of large scaleright-lateral transcurrent movement along E–W trends. Howeversuch a Triassic compressive event is difficult to integrate in geody-namic context of southern Tunisia.

Fig. 3. Synthetic lithostratigraphic column of the Tataouine sub-basin with themaximum thickness assumed.

C. Raulin et al. / Journal of African Earth Sciences 61 (2011) 94–104 97

3. Structural analysis of the Tebaga system

We will first examine the geometrical relationships betweenPermian, Triassic, and Jurassic rocks at the scale of the Jeffara plain,and then we will focus on the northern flank of the Tebaga.

3.1. The progressive unconformity of Upper Triassic to Upper Doggerrocks onto the southern limb of the Tebaga

The Jeffara plain, bordering the Dahar cliff (Fig. 2), exhibits analmost complete Middle Triassic to Jurassic sedimentary pile,which thins and finally truncates toward the Tebaga of Medenine,where Upper Albian rocks (the so-called Vraconian) rests uncon-formably onto Permian rocks (Mathieu, 1949) (Fig. 4A). In thisregion, a set of angular unconformities has been recognized inthe field, and attributed to local or regional tectonic events. Twoof them are of particular importance: (1) in the Jebel Rehach, theRehach formation (Upper Carnian) rests unconformably onto theLower and Middle Triassic sandstones (Robaux and Choubert,1941), and (2) just southeast of the Tebaga of Medenine, in JebelTajera, Mathieu (1949) identifies a spectacular unconformity be-tween the Bathonian pp to Callovian limestone and Lower to Mid-dle Triassic sediments (Fig. 4B). Within rocks older than UpperCarnian, Bouaziz (1995) evidences a Norian unconformity. By con-trast, Lower to Middle Triassic rocks rest conformably onto thePermian sedimentary succession. Within rocks younger than theOxfordian and up to the Late Albian, other unconformities havebeen recognized but they are related to younger geodynamicevents (Bodin et al., 2010), out of the scope of the present paper.

So, somewhere between Jebel Rehach and Jebel Tebaga ofMedenine, which are separated by a distance less than 80 km,the whole Upper Triassic–Jurassic sedimentary succession (about1600 m thick) disappears due to its progressive thinning and/ordisruption by syn-sedimentary faults. From the reconstruction pro-posed by Bouaziz (1995), completed by boreholes data, it appearsthat the Lower Jurassic evaporitic complex is mainly confined inthe asymmetric graben bounded by the Azizia and Zemlet el Gharfault defining the Tataouine sub-basin (Fig. 5). By contrast, theMiddle Jurassic formation overflows the limit of the Tataouinesub-basin and onlaps the Tebaga of Medenine to the north as wellas the Garian High of Jebel Nefusa to the south-east (Fig. 5). So, atlarge scale, the observed geometry is a half-graben bounded on thesouth by the E–W Azizia fault system. The wedge-like geometry ofthe Jurassic units is related to progressive sedimentary infill duringthe tilting of the Tebaga panel as a consequence of the normalfaulting along the Azizia fault system. In this context, the Zemletel Ghar fault is interpreted as a secondary feature cutting theTebaga panel. We propose to call this important feature the Tatao-uine tilted block (Fig. 5). The E–W faults are truncated by NW–SEfaults pertaining to the Jeffara system (Fig. 2) (Gabtni et al.,2009). During the late Triassic-early Jurassic rifting, they couldhave acted as transform faults delineating sub-basins exhibitingsome differences in sedimentary infilling.

3.2. Geometry and tectonic-sedimentation relationships along thenorthern side of the Tebaga

As indicated above, the structural interpretation of the Tebaga iscontroversial. The contentious question concerns the significance(or even the existence) of a northern limb allowing to interpret itas a fold. At first glance, the Tebaga appears as a large monoclineand this is confirmed at larger scale by the borehole TEB01 situatedjust north of the Tebaga (Fig. 6), which encountered about 4000 mof south dipping Upper Permian rocks (Mejri et al., 2006). How-ever, the northern side of the Tebaga exhibits some interestingstructures showing that its geometry cannot result only from theerosion of a south dipping monocline. Mathieu (1949) has beenthe first to propose the existence of more or less steeply north dip-ping Permian rocks north of the Tebaga crest, which led to hisinterpretation of the Tebaga as a faulted anticline. This interpreta-tion was rejected by Busson (1972), on the basis of general geomet-rical consideration, taking into account the progressive pinch out

E W

PERMIAN

VRACONIAN

NW SE

LOWER TRIASSIC

BATHONIAN-OXFORDIAN

A

B

Fig. 4. Regional unconformities: (A) Unconformity between the Vraconian and the Permian at the western termination of the Tebaga of Medenine (N33� 250 03.800

E10� 100 04.800). (B) Unconformity between the Bathonian and the Triassic (N33� 240 28.600 E10� 250 24.600).

98 C. Raulin et al. / Journal of African Earth Sciences 61 (2011) 94–104

of the Mesozoic series, but without new precise tectonic study.Within the Tebaga of Medenine, the key area is Merbah Crouz al-ready discussed by Mathieu (1949) and Bouaziz (1995) (Fig. 6).In order to present the geometry of this area, we present a 3D viewillustrating the structural relationships between Permian andMesozoic rocks (Fig. 7). More precisely, a photographic panoramaexhibits the following elements from southwest to northeast(Fig. 8): (1) the main south dipping Tebaga panel (Permian rocks),(2) a fault zone, (3) a north dipping panel made up of brecciatedPermian dolomite, (4) a Middle Jurassic cover made up of marl/limestone alternation with a beautiful ‘‘onlap’’ geometry onto thebreccias, and (5) a top cover of ‘‘Vraconian’’ and younger rocksequivalent to the ones observed along the Dahar cliff. Mathieu(1949) did not recognize the sedimentary contact between the

Middle Jurassic and the brecciated Permian rocks (he draw a faultin between), whereas Bouaziz (1995) has recognized the sedimen-tary nature of the contact but has interpreted the breccias as a sed-imentary formation interbedded within the Middle Jurassic rocks.The facts established in the field can be integrated in a new inter-pretation (Fig. 9) in which the brecciated Permian rocks exposedalong the northern limb of the Tebaga results from fracturationand faulting in a damaged zone along the normal faults corridors.The Middle Jurassic sedimentary rocks are filling a drag synclinedeveloped north of the Tebaga fault zone. In the brecciated Perm-ian dolomite, Bouaziz (1995) analyzed micro-faults within threesites. All of them show NW–SE to E–W faults corresponding toNE–SW and N–S extensional deformation. The same tectonic re-gime has been found in the Jurassic and Cretaceous formations

?

?

?

?

AZIZIA FAULT SYSTEM

ZEMLET EL GHAR FAULT

TEBAGA FAULT

?

SA B

TALEMZANE ARCH

TATAOUINE TILTED BLOCK

TATAOUINE SUB-BASIN

N

-3

1

0

-1

-2

0 180170160150140130120110100908070605040302010 (km)

(km)

Upper CretaceousLower CretaceousMalmDoggerLiassicUpper TriassicMiddle TriassicPermian and Lower Triassic Paleozoic Projected wells

Fig. 5. General section across the Tataouine sub-basin (see location on Fig.2), built from the geological map of Zouari et al. (1987), and from boreholes and subsurface data.

C. Raulin et al. / Journal of African Earth Sciences 61 (2011) 94–104 99

overlying the Tebaga of Medenine in the Merbah Grouz area (seebelow).

The absence of the Lower and Middle Triassic rocks in theTebaga area is indicative of erosion on the top of the Tataouinetilted block, whereas the lack of the Lower Jurassic is likely signif-icant of no-deposition at that time. In our model, the fault flankingthe northern crest of the Tebaga has been developed at a late stage

Fig. 6. Geological map of the Tebaga of Medenine, modified from Zouari et al. (1987). TheGEBCO; �2011 Cnes/Spot Image; Image �2011 DigitalGlobe).

of the larger Tataouine tilted block building and is probably due tothe accommodation of deformation close to the head of the block.In such a context, it is known that the bending in the hanging wallof a normal fault can generate minor compressive structures as re-verse faults or folds (e.g. Roure et al., 1992). We propose such anexplanation to explain the minor folding observed within thePermian at Bateun Beni Zid (Mathieu, 1949; Bouaziz, 1995).

background is a composite view from Google Earth (Data SIO, NOAA, US, Navy, NGA,

Fig. 7. 3D geological view of the Merbah Grouz key area. This 3D view is a zoom of the Fig. 6.

100 C. Raulin et al. / Journal of African Earth Sciences 61 (2011) 94–104

4. Discussion

Our results allow us to propose a new kinematic and structuralconceptual model for the evolution of the Tataouine tilted blockand to discuss its geodynamic significance in the frame of the tran-sition between the Sahara platform and the East Mediterraneandomain as well as with the Atlas system.

4.1. Kinematic model for the Tataouine tilted block

In our model (Fig. 10), the Azizia E–W fault system plays a ma-jor role controlling the south tilting of the Tataouine block as wellas its sedimentary infilling. Block tilting has been mainly activeduring the late Triassic and Liassic. By contrast, the geometry ofthe Middle Jurassic deposits is rather the one of a sag basin dueto thermal subsidence post-dating the main extensional episode(Patriat et al., 2003). However, the geometry of the Middle Jurassicalong the northern side of the Tebaga shows that extensionaldeformation continued at that time at least along secondary faultsas the one fringing the Tebaga to the north. Different studies in theforeland of the Atlas system, as in the Chotts basins reconstruction,outline the role of E–W normal faults in the control of basin infill-ing during the late Triassic–Jurassic times (e.g. Ben Ferjani et al.,1990; Soussi, 2002). Otherwise paleo-stress field reconstructionsat the scale of the Mesozoic platforms in southern Tunisia are inagreement with N–S stretching controlled by E–W striking syn-sedimentary faults controlling grabens and hemigrabens (Bouazizet al., 2002).

4.2. The question of the Permian basin predating the Tataouine tiltedblock

The Tataouine tilted block developed in a basin filled by morethan 4000 m of Upper Permian sediments (see a synthesis in Mejri

et al. (2006)), and a more or less complete Paleozoic pile. Toexplain such a thick Permian sequence, Stampfli et al. (2001) pro-posed the existence of a Late Permian rifting phase preceding theonset of sea-floor spreading in the East Mediterranean. In the mod-el defended by these authors, the Triassic series are interpreted aspost-rift sequences overstepping the Talemzane Arch (Fig. 1),which they consider as a Permian rift shoulder. In contrast, ourwork documents an active block tilting during the late Triassic–early Jurassic in the Jeffara basin and bordering sectors. In fact,Permian rifting cannot be really recognized in the Jeffara despitethe existence of syn-sedimentary little normal faults in the Tebaga(Bouaziz et al., 2002). Together with the Lower and Middle Triassic,the Permian sequence could represent a post-rift infill relative toan older rifting phase. However, in any case we show the existenceof a renewed rifting activity during the late Triassic to late Jurassic.Further work is required to constrain this model.

4.3. Integration in the geodynamic context of the Mediterranean

The Jeffara basin occupies a key position at the transition be-tween the Sahara platform, the Central Mediterranean and thesouthern front of the Atlas system (Fig. 1). It is located, close tothe Ionian Basin, which is interpreted as an oceanic remnant ofthe southernmost branch of the Neo-Tethys (Chamot-Rookeet al., 2005) This oceanic or sub-oceanic crust has never been da-ted, which makes very controversial the age of the oceanic spread-ing (Stampfli et al., 1991; Dercourt et al. 1993; Ricou, 1994;Robertson et al., 1996; Dercourt et al. 2000; Barrier and Vrielynck,2008). By reference to the Ionian Basin, the Jeffara represents avery proximal margin. However, the two basins are separated bythe so-called Pelagian Sea, which recorded a complex evolutionincluding a huge Cenomanian to Paleocene extensional deforma-tion along NW–SE faults (Jongsma et al., 1985; Khomsi et al.,2009), connected southeastward to the Cretaceous Sirt System

NESW

PERMIAN

UPPER BATHONIAN-CALLOVIAN

LATE HAUTERIVIAN-BARREMIAN

APTIAN

0 5 m

Brecciated Permian rocksOnlap of the Upper Bathonian-Callovian level onto brecciated Permian rocks Carbonates and sandstones alternation

11

NESW

PERMIAN

UPPER BATHONIAN-CALLOVIAN

0 20 m

1 2 34

5

3

4

5

LATE HAUTERIVIAN-BARREMIAN

APTIAN

Fig. 8. The Merbah Grouz key area. Panoramas showing the onlap of the Upper Bathonian–Callovian level onto brecciated Permian rocks from the Tebaga of Medenine.

Fig. 9. Interpretation of the Merbah Grouz key area (see explanation in the text).

C. Raulin et al. / Journal of African Earth Sciences 61 (2011) 94–104 101

(Fig. 1). The volume of sediments accumulated during this periodin the offshore domain (more than 10 km thick?) superimposedto the previous rifting tectonic history (Fig. 1) makes quite difficultto discuss possible relationships between the late Triassic–earlyJurassic extensional deformation observed in the Jeffara and thesubsequent drifting in the Ionian Basin.

In the East Mediterranean, the late Triassic–early Jurassic evolu-tion of the margin seems similar to the one observed in Jeffara andthe relationships with the Herodotus deep basin are not masked bysubsequent complex evolution as in the Central Mediterranean.Garfunkel (1998) and Keeley (1994) have realized a synthesis deal-ing with the rifting phases responsible of the Platform reorganisa-tion at that time in the Levant and in the Western Desert

respectively. According to Garfunkel (1998) and Gardosh et al.(2010), the main rifting occurred in late Triassic–early Jurassictimes at right angle to the Levant margin (i.e. NE–SW), while inthe Western Desert much of the faulting should be Liassic in ageand E–W trending (Keeley, 1994) (Fig. 11). In fact, no deep waterbasin has been recorded in these regions before the early Jurassic(Garfunkel and Derin, 1984). So the late Triassic–early Jurassiccan be considered as a major step in the development of theCentral and East Mediterranean.

On the other hand, extensional deformation is recorded at thattime, in the ‘‘Chaîne des Chotts’’ (Hlaiem, 1999; Soussi, 2002;Frizon de Lamotte et al., 2009), immediately north of the Jeffarabasin (Fig. 2), as well as in the whole Atlas system of northern

Fig. 10. Conceptual kinematic model of the Tataouine tilted block showing the late development of the Tebaga of Medenine as a secondary tilted block.

102 C. Raulin et al. / Journal of African Earth Sciences 61 (2011) 94–104

Fig. 11. Paleotectonic map of the South-Tethys margin for Callovian times. The map is modified after Guiraud et al. (2005), Barrier and Vrielynck (2008), Ricou (1994), Keeley(1994), Gardosh et al. (2010), Frizon de Lamotte et al. (2011).

C. Raulin et al. / Journal of African Earth Sciences 61 (2011) 94–104 103

Africa (e.g. Frizon de Lamotte et al., 2000, 2009; Soussi, 2002;Bracène and Frizon de Lamotte, 2002; Khomsi et al., 2009), whichis inherited from a rim basin bounding the margin of the AlpineTethys (Fig. 11). So the Jeffara basin can be considered as the com-mon proximal margin of both Neo-Tethys and Alpine Tethys(Fig. 11).

5. Conclusion

This work allows us to propose a new tectonic model for theTebaga of Medenine. In this model, the Tebaga is interpreted asthe emerging part of a large tilted block, the Tataouine tilted blockcontrolled by the E–W Azizia fault system. The extensional defor-mation responsible for the formation of the Tataouine tilted blockis recorded by syn-rift infilling of late Triassic to early Jurassic agein the Tataouine sub-basin, the Tebaga itself being probablyemerged at that time (Fig. 10). During the middle Jurassic, whichis likely dominated by thermal subsidence, the extensional defor-mation continued as shown by the development of the north-Tebaga fault, which is sealed by Bathonian–Callovian sedimentsconserved in a top-fault drag syncline (Fig. 7). In such a context,the NW–SE Jeffara fault system (Fig. 2) may have acted as nor-mal-transcurrent faults intersecting obliquely and shifting the for-mer syn-rift basins. This may explain the rapid change in theTriassic thickness from each side of the fault system as presentedin many previous works (Bouaziz, 1995; Gabtni et al., 2009). Sucha tectonic scenario appears finally quite close to the one proposedin the East Mediterranean as well as in the Atlas system.

Acknowledgments

This paper benefited from discussions with many colleagues: C.Blanpied (TOTAL, Paris), J.L. Rubino (TOTAL, Pau), R. Bibonne(TOTAL, Pau), S. Hadouth (TOTAL, Pau), A. Virgone (TOTAL, Pau),P. Duringer (University of Strasbourg), J. Pelletier (TOTAL, Pau)and M. Schuster (University of Strasbourg). We thank F. Roureand an anonymous reviewer for their helpful review. C. Raulinacknowledges UCP for PhD Scholarship. N. Mouchot acknowledgesTOTAL for a PostDoc position. This paper is a contribution of theANR ‘‘TOPOAFRICA’’. It is also a contribution of ‘‘Groupe Recherche

Industrie’’ ‘‘ Marge Sud-Tethys’’, a research agreement betweenTOTAL on the one hand and l’Ecole Normale Supérieure (ENS),l’Université Pierre-et-Marie-Curie (UPMC) and l’Université de Cer-gy-Pontoise (UCP) on the other hand.

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