Introduction

Quaternary deposits exposed along the Coast of Tunisia have been studied since the beginning of the past century and their nomenclature has evolved over time with the advances in dating and analysis techniques. These deposits have been the subject of several studies (Issel 1914; Allemand-Martin, 1923, 1924; Solignac 1927; Gruet 1950; Castany 1952; Castany et al. 1954; Castany 1955; Bonifay and Mars 1959; Paskoff and Sanlaville 1976, 1977, 1978, 1980, 1983; Fournet 1982; Bonvallot and Miossec 1985; Mahmoudi 1986; Oueslati 1986) enabling researchers to assign the stratigraphic succession to the so-called “Tyrrhenian.” Recently, several researchers have been interested in these deposits, especially those along the eastern shorelines (the Sahel and the Cap Bon peninsula, Djerba Island) and the northern shorelines (Rafraf) (Jedoui 2000; Jedoui et al. 2001, 2002, 2003; Davaud, 2003; Chakroun et al. 2005; Chakroun 2006; Chakroun et al. 2009a, b, 2016; Chakroun and Zaghbib-Turki, 2017; Elmejdoub and Jedoui 2009; Gzam et al. 2009; Mauz et al. 2009; Elmejdoub et al. 2011, Mejri 2012; Mejri et al. 2012; Balescu et al. 2015). They have established a new frame on stratigraphy, sedimentology, paleoecology, and chronology of the Pleistocene based on correlation with glacio-eustatic changes and related them to the last interglacial period, especially to the Marine Isotopic Stage 5 (MIS 5).

Toward the north, the Bizerte Coast exhibits various Quaternary deposits with varied ages and lithologies providing spectacular landscapes. The Pleistocene deposits exposed along the northeastern Coast of Tunisia are given special attention to their various facies (littoral, continental, and eolian) and fauna content. By using classical sedimentology tools (field study and sample, a study of granulometry, morphoscopy, and petrography), this study shows new results about these deposits leading us to a better understanding of their sedimentary evolution and stacking in high-frequency cycles.

Geographic setting and stratigraphy

The Bizerte area (northeastern of Tunisia) lies on the scale area (Rouvier 1977; Paskoff and Sanlaville 1983) and is characterized by a marine Cretaceous-upper Eocene succession that is overlaid by the Numidian thrust sheet (Oligo-Miocene) (Fig. 1). The studied Pleistocene succession and cross-section crops out in the rocky cliffs are around 5–6 m thick.

Fig. 1
figure 1

Structural and tectonic map of the Bizerte area (from Rouvier 1977) and location of the studied cross-sections (Ras el Korane, East of Cap Blanc, Cap Bizerte, and Ras Blatt)

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The “Tyrrhenian” term was designated to the Persististrombus latus (a senior synonym of Strombus bubonious) Mediterranean Quaternary deposits (Issel, 1914). Paskoff and Sanlaville (1977) provide geomorphological arguments and present a summarized description and subdivision of Tunisian Pleistocene deposits into different formations being genetically linked to climate events (Table 1). The three first formations were associated to the Tyrrhenian transgression. The oldest one corresponds to Douira formation and corresponds to mollusk shell–bearing beach deposits. The second formation was called Rejiche formation and includes two members; the first one is formed up by coarse-grained calcareous sandstone containing shallow marine fauna especially P. latus; the second member corresponds to eolian sediments rich in ooliths and pellets. The third formation was called Chebba formation and is represented by conglomerates rich in reworked and broken mollusks shells. The recent formations were linked instead to MIS 4 (eolianite of Cap Blanc formation) separated by a red sand layer indicating a regression (respectively Ain Oktor and Sidi Daoud formations). Toward the south, the Cap Blanc II formation equivalent is represented by the Tlêt formation.

Table 1 Evolution of the Quaternary nomenclature of Tunisia. The brown squares indicate a sedimentary gap
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Paskoff and Sanlaville’s stratigraphy was subsequently confirmed by Oueslati (1986) based on the Aterian artifacts found in the dunes and terrestrial deposits outcropping in the northwestern coast of Tunisia.

However, Mahmoudi (1986, 1988) used the concept of “stratigraphic regional unit” to describe the Tyrrhenian sedimentary units of the Sahel (Table 1). Later, toward the south (Djerba Island), Jedoui (2000) suggested a new chronologic data and subdivided the series into two units: a lower quartzous unit and an upper carbonate unit, separated by a discontinuity. Likewise, Chakroun (2006) and Chakroun et al. (2009) detailed the Tyrrhenian of the Cap Bon peninsula and identified two transgressive cycles displaying a quartzous unit and a carbonate unit. Those units were respectively attributed to the MIS 5e by correlation to the identified units in the south by Jedoui (2000).

Recently, several authors adopted an isotopic stratigraphy (Elmejdoub and Jedoui 2009; Mauz et al. 2009, 2012; Mejri 2012; Balescu et al. 2015). In fact, Elmejdoub and Jedoui (2009) divided the entire Pleistocene deposits into five Pleistocene units (Table 1) and attributed unit 4 (Khniss formation equivalent) and unit 5 (Rejiche formation equivalent) to the MIS 5. Mauz et al. (2009, 2012) assumed that the interglacial period in Tunisia is between 125 and 75 ka. The same team established a new chronology based on the OSL (optically stimulated luminescence) dating technique. Besides, Mejri (2012) followed by Balescu et al. (2015) attribute the Douira unit to the MIS 7–9 based on the IRSL (infra-red stimulated luminescence) dating technique.

Materials and methods

This study of the Pleistocene deposits exposed along the northeastern coast of Tunisia is based on classical sedimentological analysis, including granulometry, morphoscopy, petrography, and description of sedimentary structures and the fauna assemblage content.

The different outcrops detailed by Paskoff and Sanlaville (1983) were revisited and discussed. Four cross-sections were investigated with the most complete Pleistocene succession: Ras el Korane, East of Cap Blanc, Cap Bizerte, and Ras Blatt (Fig. 1). The stratigraphic sections were logged and coastal sediments were sampled. We have analyzed the sandy sediment (samples Gr5, Gr7, Gr8, Gr9, and Gr11 from East Cap Blanc section and RB3 from Ras Blatt section) by the granulometric method through an “AFNOR” column composite by 9 sieves for 20 mm. Weight percentage frequencies and cumulative weight percentage frequencies were computed. The grain size parameters like graphic mean size (Mz), sorting (So), skewness (SK), and kurtosis (K) were calculated according to Folk and Ward (1957) method, parameters widely used to reconstruct the depositional environment of sediments. Once decalcified with hydrochloric acid (0.1 N) and dried at 45 °C, a morphoscopic analysis was performed on the 0.25 mm and 0.5 mm refusals for all the samples, adequate size to provide quartz grains suitable for a record of both marine and eolian features. The petrographic studies of the Ras El Korane section (samples RK2, RK6, RK9, RK11, and RK13), East Cap Blanc section (samples Gr3, Gr6, Gr10, and Gr12), and Cap Bizerte section (CB2 and CB3) provide information on environmental deposits and diagenetic transformations. The sedimentary structures and the fossil content were also studied, providing valuable information about environments prevailing during the Pleistocene period. Taxonomic attributions of the fauna content were based on the World Register of Marine Species Database and the Paleobiology Database.

The correlation established in this paper is based on results from earlier-dating works (Table 2) on northern Bizerte (Paskoff and Sanlaville 1983; Richards 1986; Mathlouthi 1988; Mauz et al. 2009) and Cap Bon area (Miller et al. 1986; Elmejdoub et al. 2011), the Sahel and Southern Tunisia (Jedoui et al. 2003; Mejri 2012).

Table 2 Summary of dating results of Pleistocene littoral deposits from the Tunisian Coast
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Description and sedimentology of the studied cross-sections

Ras el Korane section (GPS coordinates N37°20′0880″, E9°41′0583″)

The Ras el Korane section was detailed by Paskoff and Sanlaville (1983) where they distinguished 9 levels; however, in the present work, three main units have been differentiated (Fig. 2). This section brings up new data about the significant variation of facies, thickness, and coastal depositional prism. The described series disappears toward the west and exhibits only its lower part. However, its uppermost part appears toward the east. Those deposits outcrop in small cliffs notched by the sea and do not exceed 5 m in thickness.

Fig. 2
figure 2

Ras el Korane section with samples’ location and field picture. Formations and levels from Paskoff and Sanlaville (1983) and detailed units recognized in the present work are also indicated

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Unit 1 has been attributed to Rejiche formation (Paskoff and Sanlaville 1983) and includes four levels ((a) to (d) in Fig. 2). The unit starts up with a shoreface bioclastic limestone (30 cm) rich in boulders and cobbles reworked from the Oligo-Miocene turbidites (level (a), Figs. 2 and 3). Size of these boulders (decimeter) and presence of lithophageal perforations indicate a river mouth where sediments are strongly removed by waves. Boulders and cobbles are embedded in a bioclastic packstone matrix rich in red algae, echinoids, miliolids, and bivalve shells (Table 4). This level is topped by hard-ground surface and is overlaid by a thin bed (20 cm) of brown clays and sandstone with mud balls (2–3 cm), which indicate a point bar estuarine deposit.

Fig. 3
figure 3

Detail of the contact between Quaternary and Oligo-Miocene deposits

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The following level (b) corresponds to foreshore deposits represented by bioclastic calcarenites with low-angle cross-stratification (Fig. 4). The series evolves to continental facies as yellow to brown silty marls (level (c), Fig. 4), to sandstone-limestone level (level (d)) with Helix shells and root structures on top. The level (d) matrix hosts several microfauna such as red algae and polypier (Fig. 5).

Fig. 4
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Contact between level (b) and level (c); (b) foreshore deposit and (c) sandstone deposit with cross-stratification

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Fig. 5
figure 5

Microfacies photographs of samples RK8, RK9, and RK13 from Ras el Korane section and sample Gr4 from East Cap Blanc section. (A) RK8 sample from Ras el Korane section, consolidated silty marl sediment and attributed to the eolien member of Rejiche formation, quartz grains showing angular forms. Diversified marine fauna fragments (red algae, bryoroans). (B) RK9 sample from Ras el Korane section formed by sandstone-limestone sediment, level (d) from unit 1 and attributed to Rejiche formation, quartz grains moderately classified showing sub-angular to sub-rounded forms rich in microfauna such as polypier and red algae. (C) RK13 sample from Ras el Korane section composed by consolidated sand (unit 3) with quartz grains (moderately classified and usually sub-rounded), echinoderm debris and bivalve fragments. (D) Gr4 sample from East Cap Blanc section attributed to the continental member of Rejiche formation, packstone to grainstone, misclassified quartz grains showing sub-angular to sub-rounded forms. In the middle is a large recrystallized gastropods

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The lower boundary of unit 2 is an erosional surface which corresponds to a wave-ravinement transgressive surface (WRS) (Catuneanu et al. 2011), related to a second sea level rise. This unit includes three levels (a, b, and c in Fig. 2). Level (a) has been assigned to Chebba formation (Paskoff and Sanlaville 1983) based on its direct contact and clear reworking of the underlying formation (Rejiche formation). It consists of a lag deposit with reworked clasts (centimeter in size) from the underlying unit 1and Eocene limestones, and rich in entire shells of marine mollusks such as Bolma rugosa, Cerithium vulgatum, Conus ventricosus, Columbella rustica, Glycymeris glycymeris, and Venus verrucosa. The matrix hosts several marine fossils (gastropods, bivalves, red algae, echinoderms, calcareous sponges, bryozoans, and corals) (Fig. 5). Pebbles have features indicative of waves reworking (rounded to worn and flatted surfaces) and often include lithophageal perforations. Glossifungites ichnofacies appears on the upper part of this level and indicates starvation.

Level (b) is represented by continental sandstone rich in Helix shell and vertical root structures, attributed to the Ain Oktor paleosoil formation (Paskoff and Sanlaville 1983). The unit ends with level (c), an eolianite with root traces, attributed to the Cap Blanc formation (Paskoff and Sanlaville 1983).

Unit 3 is 20–30 cm thick corresponding to a lag deposit (Fig. 2) rich in centimeter-size pebbles and marine macrofauna (Cerithium, Pecten, oysters, sponges, corals) and a fine limestone crust with algal laminations on top. The observed matrix (Fig. 5) holds diversified microfauna (echinoids, red algae, green algae, benthic foraminifera, miliolids, and oysters). The series is topped by a sub-aerial unconformity marked by a ferruginous surface.

Unit 3 is thicker towards the west and clearly displays a shallowing-upward sequence beginning with marine deposits, lagoon deposits, and ending with eolian facies (Beseme 1981; Paskoff and Sanlaville 1983) allowing their interpretation as a distinct sedimentary sequence. In this work, we related this unit to a lenticular lagoonal deposit coeval backward of the Cap Blanc formation (level (c)).

East Cap Blanc section (GPS coordinates N37°19′5843″, E9°50′3398″)

The Cap Blanc area and its surroundings have attracted the attention since pioneer works of Aubert (1892) and Paskoff and Sanlaville (1983). The present section is logged in a cliff known locally as “les Grottes.” Here, the Pleistocene deposits show a significant lateral continuity and are overlaying on the Paleocene strata with an angular unconformity.

Two units have been recognized in East Cap Blanc section (Fig. 6). Unit 1 belongs to Rejiche formation (Paskoff and Sanlaville 1983; Paskoff and Oueslati 1988) and includes four levels ((a) to (d)). Level (a) is a shoreface bioclastic marl (bivalves, gastropods) and sandy limestone. As in Ras el Korane outcrop, this first level contains pebbles from the underlying unit (Paleocene-Eocene). Pebble sizes range from centimeters to decimeters, and its blunted surfaces indicate wave reworking. The level hosts several marine shells such as Cerithium vulgatum, Conus ventricosus, Conus ermineus (synonym of Conus testudinarius), Columbella rustica, Gibbula ardens, Patella caerulea, Phorcus richardi, Trochus sp., and Vermetus triquetrus. However, it does not contain P. latus fossil. This fauna assemblage characterizes the so-called Senegalese fauna (especially Conus ermineus and Vermetus triquetrus) which refers to warm shallow sea water (Chakroun 2006; Chakroun et al. 2016; Chakroun and Zaghbib-Turki 2017). Level (a) is followed by a shoreface limestone layer (level (b)) with grainstone to packstone texture hosting several marine fossils (red algae, miliolids, bivalves, planktonic foraminifera and spicules of echinoderms) and reflecting an intertidal environment (Table 4), a foreshore sandy marl level (level (c), Fig. 5, sample Gr4), and a continental well-sorted fine sandstone (level (d), Table 3, sample Gr5) with Helix shells, calcareous concretions, and a ferruginous surface on top.

Fig. 6
figure 6

East of Cap Blanc section with samples’ location and field picture. Formations and levels from Paskoff and Sanlaville (1983); detailed units recognized in the present work are also indicated

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Table 3 Granulometric indices of the sandy fraction of East Cap Blanc section with mean size (Mz), sorting (SO), skewness (SK), and kurtosis (K)
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Unit 2 includes 5 levels. The shoreface limestone of level (a) (Table 4) and the continental-sandstone of level (b) are attributed to the Chebba formation (Paskoff and Sanlaville 1983). This first level (level (a)) has a brecciated facies with a packstone texture, largely reworked intraclasts of clay and feldspar, and micritic cement. Its matrix hosts several marine shells (red algae, reworked miliolids, and bivalves). While, level (b) has a micro-brecciated facies with a mudstone texture and few marine shells (red algae, echinoderm spicules, and bivalves). Following levels (c) and (e) are characterized by clay and sandstone (Table 3) with angular to sub-angular pebble lenses (Fig. 7), deposited by fluvial process. These levels are attributed to Ain Oktor and Sidi Daoud formations, respectively. The intercalated eolianite level (d) belongs to the Cap Blanc formation.

Table 4 Petrographic description of indurated levels of Ras el Korane and East of Cap Blanc sections
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Fig. 7
figure 7

Upper part of the eastern side of Cap Blanc section; detail of fluvial facies of level (e), unit 2

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Sandstones of level (c) are medium-grained and well to moderately sorted and display a positive asymmetry relating to a better classification of the finest sediments (Gr7 and Gr8, Table 3). Indeed, according to Chamley (2000), positive asymmetries are mainly found in fluvial sediments enriched with fine particles decanted at the end of the flood. As a result, level (c) is a typical fluvial facies with high particle size heterogeneity (platykurtic distribution). Level (c) ends with red silty marl composed of moderately sorted, medium to coarse-grained sand grains (sample Gr9, Table 3), interpreted as a paleosoil. The eolianite of level (d) pinches out laterally as is overlaid by the fluvial sediments of level (e), representing fine sand channel with pebble lenses (sample Gr11, Table 3).

The eolianite and fluvial sediments of levels (d) and (e) are capped by an erosional surface with iron oxide and limestone crust, which separated them from the current sandy dunes.

Cap Bizerte section (GPS coordinates N37°20′0063″, E9°51′4303″)

The Cap Bizerte section was previously examined by Paskoff and Sanlaville (1983) then by Oueslati (1994) where they distinguish several levels (from (1) to (6)) (Fig. 8). Logged in a cliff near the current shoreline, the described Pleistocene series lies on Eocene limestones and laterally decreases in thickness before disappearing.

Fig. 8
figure 8

Cap Bizerte section with sample location and field picture. Formations and levels from Paskoff and Sanlaville (1983); detailed units recognized in the present work are also indicated

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The Cap Bizerte section includes unit 2 of the present work (Fig. 8). It starts with a basal conglomerate (level (a)) attributed to the Chebba formation (Paskoff and Sanlaville 1983; Oueslati 1994). This attribution is based essentially on its facies, its geometry, and its stratigraphic position below the continental and eolian deposits of following levels. It is outcropping at 0 m unlike its higher altimetry observed at Ras el Korane section (3 m) and East Cap Bizerte section (3.5 m), due to recent tectonic action in the Bizerte area causing a collapse of about 100 m (Solignac 1927; Castany, 1954; Paskoff and Sanlaville 1983). This level is rich in marine fossils (red algae, bivalves, and gastropods) and animal bioturbations and includes Eocene pebbles that are centimeter to decimeter in size, dull-shaped, with frequent lithophageal perforations. This basal conglomerate ends with an unconformity marked by emersion surface and local iron concentrations.

Level (b) is a marl-sandy-red paleosoil corresponding to the Ain Oktor formation (Paskoff and Sanlaville 1983). Level (c) is a 3-m-thick eolianite (Cap Blanc I) and rich in Helix shells overcomes this paleosoil. Level (d) is the second darkest color (red to brown) paleosoil (Sidi Daoud formation; Paskoff and Sanlaville 1983). Its matrix is packstone, characterized by a high porosity percentage and the occurrence of iron oxide and phosphate grains. The meniscus cement indicates intertidal vadose environment. The series ends with a second eolianite (level (e), Cap Blanc II), less developed than the first one (2 m) and darker, showing large-scale cross-stratification and root structures (Fig. 8). The Cap Bizerte section is the only outcrop offering a superposition of the two members of the Cap Blanc formation separated by a continental level (Sidi Daoud formation). The weathered sand and silt of level (d) reflect a marine regression and a coastline too far away to supply sand-sized grains to the dune.

Ras Blatt section (GPS coordinates N37°19′4848″, E9°51′5448″)

The Ras Blatt section is located 500 m far from the Cap Bizerte section and exhibits an interesting litho-stratigraphic succession compared with that of Cap Bizerte. This series starts on the border of the sea water with a marine erosional surface (wave cut platform) (Fig. 9). Formed by the present work unit 2, the first outcropping level is level (a) formed by a thin (1 m) layer of consolidated sandstone with glauconite, phosphates, strong bioturbations (vertical perforations), and desiccation cracks on top. This level holds centimeter- to decimeter-sized pebbles showing various forms depending on their nature. Sandstone pebbles are sub-angular pebbles and often are the largest ones; however, calcareous pebbles are blunt and smaller. This level is assigned to the Chebba formation (Paskoff and Sanlaville 1983; Oueslati 1994).

Fig. 9
figure 9

Ras Blatt section with sample location and field picture. Formation and levels from Paskoff and Sanlaville (1983); detailed units recognized in the present work are also indicated

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Level (b) is a fine layer (about 10 cm) of reddish sand (Fig. 9, Ain Oktor formation; Paskoff and Sanlaville 1983). The following level (c) consists of medium to coarse sub-angular sands, attributed to the Cap Blanc formation eolianite (Paskoff and Sanlaville 1983). The uppermost part of this eolianite exhibits preserved cross-stratification commonly destroyed by intense root traces.

Discussion

High-frequency sequences

Based on the recognition of sedimentary trends, thickness (less than 5 m), and time span, two high-frequency 4th–5th-order sequences (sensu Vail et al. 1977; Catuneanu et al. 2011) can be differentiated (Fig. 10). Each sequence includes marine to intertidal deposits, supratidal deposits, and eolian or/and continental deposits on top. The same approach was used by Le Févre and Raynal (2002) to describe the Plio-Pleistocene formations of Casablanca and Mejri (2012) in the Pleistocene deposits of the Tunisian East Coast.

Fig. 10
figure 10

Litho-stratigraphic charter and high-frequency sequences of Pleistocene of the Tunisia Northeastern Coast (Bizerte area)

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The two sequences are separated by an unconformity (an erosional surface) identified along the Tunisian Coast (Fig. 10) (Chakroun et al. 2005; Chakroun 2006; Chakroun et al. 2009; Temani et al. 2008).

  1. 1.

    The 1st sequence (Rejiche sequence) is represented by the Rejiche formation and is a shallowing- upward sequence, from shoreface deposits with a channelized bottom surface, with pebbles, foreshore deposits, and continental facies with fossilized root structures and Helix shells.

  2. 2.

    The 2nd (Chebba sequence) includes the rest of the litho-stratigraphic units and begins with a conglomerate facies (lag deposit) that includes pebbles and marine macrofauna, attesting a relative sea level rise. The upper part is represented by an eolianite with fossilized root structures and Helix shells.

The basal discontinuity corresponds to an angular unconformity (depositional sequence boundary of a 3rd sequence order; Vail et al. 1977). Each high-frequency sequence corresponds to a regressive cycle and is separated by a transgressive surface. The origin of these sequences corresponds to the sea-level variations in relation to Quaternary climate changes (orbital cycles of Milankovitch 1930) with a 41,000-year period for each sequence.

A minor tectonic movement is noticed through these sequences which are in close relation with the general tectonic context. In fact, the northeastern part of Tunisia is one of the most tectonically active regions of North Africa (Melki et al. 2011; Bahrouni et al. 2014; Bejaoui et al. 2017). Those tectonic motions are well known along the Tunisian Coast (Kacem et al. 2001; Bouaziz et al. 2003; Mauz et al. 2009; Melki et al. 2010, 2011; Mejri 2012). Part of the northern coast is subsiding, so that the transgressive surface at the boundary of the two high-frequency cycles is below the current sea level (especially at R’Mel area; Ben Ayed et al. 1979); however, other parts are uplifted and the transgressive surface is 6 m above the modern sea level (at Ras Zebib area; Mauz et al. 2009). Moreover, Ras el Korane-Ras Angela region belongs to an anticline structure where Pleistocene marine deposits have been folded and faulted (Paskoff and Sanlaville 1983; Ben Ayed and Oueslati 1988). Thereby, significant differences in the present position of the two sequences are evident especially between Ras el Korane section and the other studied sections (East Cap Blanc, Cap Bizerte, and Ras Blatt).

Third-order sequence

Sequential analysis of the Late Pleistocene deposits exposed along the northeastern coast of Tunisia (Ras el Korane, East Cap Bizerte, Cap Bizerte, and Ras Blatt sections) and their correlation with the glacial-eustatic cycles are the basis of the definition of the sedimentary sequence (Le Févre and Raynal, 2002; Merzeraud 2009). In fact, after the rapid fall of the sea level during the Riss Glacial period (MIS 6, Emiliani 1955; Martinson et al. 1987), the platform was carved and an incised valley was formed (Fig. 11(A)). At the Riss-Würm interglacial transition (MIS 5), sea level rose and the platform was gradually flooded. During this elevation, gully bedrock is marked by the occurrence of multiple-sized pebbles at the base of the first high-frequency sequence (Rejiche sequence) originating from the underlying levels; it is indeed the initiation of the transgressive system tract (TST) of the 3rd-order sequence. The maximum flooding surface (MFS) of the 3rd-order sequence is characterized by the appearance of numerous fossils (Cerithium vulgatum, Conus ventricosus, Conus ermineus, Columbella rustica, Gibbula ardens, Patella caerulea, Phorcus richardi, Trochus sp., and Vermetus triquetrus) and minor channelized surfaces with flattened pebbles at the base of shoreface deposits of the high-frequency Chebba sequence (Fig. 11(C)). This facies evolves to non-marine sediment (eolianite) alternating with paleosoils, representing the last sedimentary tract (highstand system tract, HST) (Fig. 11(C)).

Fig. 11
figure 11

Field picture of Ras el Korane section with indication of sequences limits. TST, transgressive system tract; HST, highstand system tract; MSF, maximum surface flooding

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These sedimentary successions are well-matched in the Pleistocene deposits exposed along the Tunisian Coast (Mauz et al. 2009) taking into account lithology and facies changes. Thereby, the transgressive succession is represented in the Central and Southern Tunisia by siliciclastic and carbonate shoreface deposits separated by a discontinuity. However, the highstand system tract (HST) deposits contain only coastal dunes. This significant variation in facies is the result of, on the one hand, the local tectonics and, on the other hand, the inherited paleomorphology and also the coastal dynamics prevailing during the Late Pleistocene.

Based on the works of several authors (Ben Ayed et al. 1979; Mahmoudi 1986; Jedoui 2000; Elmejdoub and Jedoui 2009; Paskoff and Sanlaville 1983; Chakroun and Zaghbib-Turki, 2017), a correlation has been established between the northeastern Pleistocene deposits and other areas (Cap Bon, Sahel, and Southern Tunisia) (Fig. 12). This correlation shows, in spite of a constant homogeneity, variation in the thickness and the facies.

Fig. 12
figure 12

Correlation of the Late Pleistocene deposits exposed along the Tunisian Coast (in the North, Cap Bon, Sahel, and the South)

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Conclusion

A fine sedimentological analysis of the Pleistocene deposits exposed along the northeastern Coast of Tunisia (Bizerte Coast) provides valuable information regarding the depositional environments and sea level changes. The results obtained allowed us to recognize an alternate succession of lower marine facies and upper continental facies. These deposits are organized into 2 high-frequency sequences (Rejiche and Chebba sequences). These sequences are related to the sea-level variations in relation to orbital climate changes (glacio-eustatic) of the Milankovitch frequency band.

The originality of those Pleistocene deposits outcropping along the Bizerte Coast appears through their spatial distribution which is far from homogeneous and leads us to distinguish, over very short distances, significant differences in facies as well as in their stratigraphic position.

The chronology adopted for formations attribution and establishing correlation is based in several recent-dating works. Detailed geochronology is therefore needed to ascribe the sequences to the corresponding MIS and opens the way for further precision.