The end of the Messinian salinity crisis: Evidences from the Chelif Basin (Algeria)

https://doi.org/10.1016/j.palaeo.2007.06.015Get rights and content

Abstract

How did the Messinian Salinity Crisis end is a matter of intense debate between two opposite concepts i.e., the generalised dilution event, the so-called Lago–Mare, followed by the sudden restoration of the marine conditions at the base of the Zanclean, or the early partial or complete marine refill that would have happened earlier during the upper Messinian. The Chelif Basin of Northwestern Algeria, one of the greatest Messinian marginal basins of the Mediterranean, provides an exceptional opportunity to study in detail how this major paleoenvironmental change occurred through continuous sedimentary records of the Miocene–Pliocene boundary. Five sections representative of both the central and marginal areas of the Chelif basin were analysed in detail for sedimentology, mineralogy, foraminifera and ostracod assemblages, and stable isotope composition of carbonates. The late Messinian deposits exhibit a great lithological variability with predominant clastic deposits (sandstones, siltstones, conglomerates, carbonates) with, in some marginal areas, large slided masses of lower Messinian (Tripoli Unit) that settled just before the base of the Zanclean. Most sediments are either azoic or contain microfossils typical of hyposaline conditions sometimes mixed with benthic foraminifera known to be adapted to stressed environments and even to lacustrine conditions. Fewer types of sediment contain assemblages of planktonic foraminifera, including typical Messinian species, which are thought to be reworked. In contrast, diversified communities of benthic and planktonic foraminifera returned suddenly at the base of the Zanclean; the Messinian–Pliocene transition was marked by an abrupt change of the δ18O values of carbonates from variable but predominantly negative values characteristic of low salinity conditions in the upper Messinian to higher and more stable values in the Zanclean typifying marine conditions. The southern margin continued, however, to be submitted to large inputs of continental waters. The beginning of the marine inundation was a transitional period with poorly diversified assemblages of planktonic foraminifera and benthic communities tolerant to oxygen deficient bottom conditions; more stable marine conditions with better bottom water ventilation were set up after a lag time which would roughly correspond to a precession cycle. Except for the more marginal areas where conglomerates and erosional features are observed, the restoration of marine conditions occurred, without any significant erosion in the more central areas where the contact is well marked by strong burrowing activity by benthic organisms. This indicates the rapid substitution in the basin of brackish waters by marine waters. Both mixing of these two kinds of waters and permanence of freshwater inputs in the initial stage of the Pliocene transgression may explain why the community of marine planktonic foraminifera, introduced by the inflowing Atlantic waters, hardly survived in such unfavourable ecological conditions in the Mediterranean and reached a normal development later when more stable marine conditions settled. This study and the comparison with other sections from both marginal and deep Mediterranean basins confirm that the Lago–Mare was a widespread dilution event that affected the whole Mediterranean at the end of the Messinian which was abruptly interrupted by the sudden marine inundation at the base of the Zanclean.

Introduction

An intense debate rose in the middle of the 1990's on how the Messinian salinity crisis ended and how marine conditions were restored at the onset of Pliocene in the Mediterranean basins. This debate examined whether the late Messinian conditions changed to lacustrine settings before the abrupt marine reflooding in the earliest Zanclean, or whether marine conditions were restored earlier, either episodically or definitely, during the upper Messinian.

During more than 30 years, a lot of studies carried out both in marginal and deep offshore Mediterranean basins provided a great amount of data indicating that the salinity crisis ended by generalised low salinity conditions, the so-called Lago–Mare, that was suddenly interrupted in the earliest Zanclean by an exceptionally fast marine transgression. This change of the regional water budget that started during deposition of the upper evaporites and climaxed after the end of the evaporite deposition, was reported everywhere in land basins from Spain to Cyprus (Decima and Wezel, 1973, Ruggieri and Sprovieri, 1974, Ruggieri and Sprovieri, 1976, Sturani, 1978, Casati et al., 1978, Ciaranfi et al., 1978, Colalongo et al., 1978, Vismara-Shilling et al., 1978, Cita and Colombo, 1979, Roep and van Harten, 1979, Orszag-Sperber and Rouchy, 1979, Rouchy et al., 1980, Geerlings et al., 1980, Cita et al., 1980, Giammarino et al., 1984, Orszag-Sperber et al., 1989, Fortuin et al., 1995, Cipollari et al., 1999, Bonaduce and Sgarrella, 1999, Gliozzi, 1999, Orszag-Sperber et al., 2000, Rouchy et al., 2001, Rouchy et al., 2003, Bassetti et al., 2006, Cosentino et al., 2006, Orszag-Sperber, 2006, Pierre et al., 2006, Rouchy and Caruso, 2006). Fresh water dilution was also reported in deep sea cores, from the Algero–Balearic, Tyrrhenian, Ionian, Cretan and Levantine basins (Lawrence, 1973, Cita et al., 1978, Schrader and Gersonde, 1978, Pierre and Rouchy, 1990, Blanc-Valleron et al., 1998, Pierre et al., 1998, Iaccarino and Bossio, 1999, Iaccarino et al., 1999a, Iaccarino et al., 1999b, Marsaglia and Tribble, 1999, Pierre et al., 2006). The most striking feature pointed out by many studies, beside the absence or scarcity of in-situ marine fossils and the common occurrence of hyposaline dwellers, was the presence of Paratethyan immigrants whose ecological significance is still under discussion.

By contrast, several authors proposed, from regional studies, that the Lago–Mare corresponded to very local freshwater settings along the shores of the Mediterranean sea and that marine conditions would have been definitely restored during the upper Messinian (Butler et al., 1995, Riding et al., 1998, Braga et al., 2006). These authors considered the presence of assemblages of planktonic foraminifera as being in-situ living organisms whereas most of the preceding authors interpreted them as reworked. Recently, Carnevale et al. (2005) reported the occurrence of otoliths of marine fishes within the Lago–Mare deposits of Tuscany, which would strengthen the marine hypothesis. Due to the presence, at some levels within the Lago–Mare deposits, of a dinocyst (Galeacysta etrusca) associated to calcareous nannoplancton belonging to the NN11 biozone from the Dacic Basin, Clauzon et al. (2005) assumed that episodes of sea level highstands occurred coevally in the Mediterranean and Paratethys allowing for free exchanges between the two realms during the upper Messinian.

The Chelif Basin in northern Algeria displays a complete sedimentary record of the Messinian salinity crisis and of the Miocene–Pliocene transition (Anderson, 1936, Perrodon, 1957, Rouchy, 1982). The evaporites (only calcium-sulfate deposits) grade upward into typical Lago–Mare reaching locally thickness of several hundreds of meters. The Miocene–Pliocene transition is exposed in many spectacular sections among which we have selected five sites in marginal (Djebel Touaka, Saouria, El Ghomri) and central (Djebel Meni, Oued el Aicha) areas of the basin (Fig. 1). These sections were measured and sampled during field investigations realised in 1979 and 1986.

Section snippets

Geological background

The Chelif Basin is a gutter-shaped basin elongated ENE–WSW over about 260 km long and 35 km wide between the sabkha of Oran to the west and El Asnam city to the east (Fig. 1), so that it represented, with the Central Sicilian Basin, one of the largest Messinian peripheral sub-basins. The basin is an intramountainous post-nappes basin located in the Tellian Atlas, which is a complex chain constituted by alpine folded and thrusted units, composed of Mesozoic to lowermost Miocene deposits, which

Methodology

In order to correlate the paleoenvironmental changes at the Miocene/Pliocene boundary (MPB) through the Mediterranean we have previously defined a methodology (Pierre et al., 2006) that was also used for the investigations in the Chelif Basin. The analytical approach combines sedimentology, biostratigraphy, and stable isotopes of carbonates allowing thus a reconstruction of the paleoenvironmental changes and an estimation of the rate of fresh waters inputs relative to marine water influxes.

Geological setting

The section is exposed on the Djebel Touaka, a hill located on the southeastern margin of the basin and on the edge of the Tessala mountain (Geological map at the 1/50 000, no. 182 of Saint-Denis-du-Sig) (Fig. 1), 1.5 km south to the Sig city and 2 km NE of the Sig River along which a continuous sedimentary succession of lower Messinian deposits is cropping out. In the Djebel Touaka as well as in the Sig River, the Messinian sedimentary succession starts with blueyish marls interbedded with

The late Messinian paleoenvironments

The uppermost Messinian deposits of the Chelif basin in Algeria exhibit a wide range of lithologies dominated by clastic deposits i.e., siltstones, sandstones, conglomerates, with locally, as in the Saouria section, sandy carbonates and finely laminated stromatolitic limestones. In the deeper areas of the basin (Djebel Meni–Abreuvoir and Oued-el-Aicha), sedimentary successions, exclusively composed of siltstones with interbeds of sandstones, are more homogeneous and reach a greater thickness up

Conclusions

The Chelif Basin with well exposed and continuous sections through the Miocene–Pliocene transition, is one of the key areas to improve our understanding of how the Messinian salinity crisis ended and how the marine conditions were restored into the Mediterranean in the Early Pliocene times. Five sections representative of marginal and central parts of the basin have been selected and investigated in detail for mineralogy, microfaunal assemblages, and stable isotope composition of the carbonate

Acknowledgements

We acknowledge Anne-Marie Brunet for sample processing, Vincent Rommevaux for thin sections, Marie-José Urrutiaguer for stable isotope analyses, Christiane Chancogne for the SEM observations, Maria-Elena Gargano for the help in the foraminifera picking, Agate Cambreleng for the illustration of the paper, Pierre Clément for X-ray diffraction assistance. Elsa Gliozzi and Silvia Iaccarino are gratefully acknowledged for their thorough revision, critical comments and suggestions. This study is a

References (103)

  • F.J. Hilgen

    Extension of the astronomically calibrated (polarity) time scale to the Miocene/Pliocene boundary

    Earth Planet. Sci. Lett.

    (1991)
  • F.J. Hilgen et al.

    The age of the Miocene/Pliocene boundary in the Capo Rossello area (Sicily)

    Earth Planet. Sci. Lett.

    (1988)
  • F.J. Hilgen et al.

    Extending the astronomical (polarity) time scale into the Miocene

    Earth Planet. Sci. Lett.

    (1995)
  • T.J. Kouwenhoven et al.

    A reconstruction of late Miocene Mediterranean circulation patterns using benthic foraminifera

    Palaeogeogr. Palaeoclimatol. Palaeoecol.

    (2006)
  • W. Krijgsman et al.

    Late Miocene magnetostratigraphy, biostratigraphy and cyclostratigraphy in the Mediterranean

    Earth Planet. Sci. Lett.

    (1995)
  • B. Mansour et al.

    L'enregistrement par les associations de diatomées des environnements messiniens: l'exemple de la coupe de Sig (Bassin du Chélif-Algérie)

    Géobios

    (1995)
  • M. Meghraoui et al.

    Late Holocene earthquake sequences on the EL Asnam (Algeria) thrust fault

    Earth Planet. Sci. Lett.

    (1988)
  • F. Orszag-Sperber

    Changing perspectives in the concept of the “Lago Mare” in Late Miocene Mediterranean evolution

    Sediment. Geol.

    (2006)
  • F. Orszag-Sperber et al.

    La transition Messinien–Pliocène en Méditerranée orientale (Chypre): la période du Lago–Mare et sa signification

    C.-R. Acad. Sci. Paris, II

    (2000)
  • C. Pierre et al.

    Reconstruction of the paleoenvironmental changes around the Messinian–Pliocene boundary along a West–East transect across the Mediterranean

    Sediment. Geol.

    (2006)
  • J.C. Plaziat

    Paleogeographic significance of the Cardium, Potamids and Foraminifera living in intra-continental salt lakes of North Africa (Sahara Quaternary Egypt Present lakes)

    J. Afr. Earth Sci.

    (1991)
  • R. Riding et al.

    Mediterranean Messinian Salinity Crisis: constraints from a coeval marginal basin, Sorbas, southeastern Spain

    Mar. Geol.

    (1998)
  • J.M. Rouchy et al.

    The Messinian salinity crisis in the Mediterranean Basin: a reassessment of the data and an integrated scenario

    Sediment. Geol.

    (2006)
  • J.M. Rouchy et al.

    Sedimentary and diagenetic markers of the restriction in a marine basin: the Lorca Basin (SE Spain) during the Messinian

    Sediment. Geol.

    (1998)
  • J.M. Rouchy et al.

    Paleoenvironmental changes at the Messinian–Pliocene boundary in the eastern Mediterranean: southern Cyprus basins

    Sediment. Geol.

    (2001)
  • J.M. Rouchy et al.

    Late Messinian to early Pliocene changes in the Melilla Basin (NE Morocco) and their relations to Mediterranean evolution

    Sediment. Geol.

    (2003)
  • G. Ruggieri et al.

    Messinian salinity crisis and its paleogeographical implications

    Palaeogeogr. Palaeoclimatol. Palaeoecol.

    (1976)
  • F.J. Sierro et al.

    The Abad composite (SE Spain): a Messinian reference section for the Mediterranean and the APTS

    Palaeogeogr. Palaeoclimatol. Palaeoecol.

    (2001)
  • R.V.V. Anderson

    Geology in the coastal Atlas of Western Algeria

    Geol. Soc. Am., Mem.

    (1936)
  • R.E. Arnal

    Limnology, sedimentology and micro-organisms of the Salton Sea California

    Geol. Soc. Amer. Bull.

    (1961)
  • M.A. Bassetti et al.

    Evolution of depositional environments after the end of Messinian Salinity Crisis in Nijar Basin (SE Betic Cordillera)

    Sediment. Geol.

    (2006)
  • A. Bellanca et al.

    Sedimentary record of the transition from marine to hypersaline conditions in the Messinian Tripoli Formation in the marginal areas of the Sicilian Basin

    Sediment. Geol.

    (2001)
  • M. Bessedik et al.

    Révision du Miocène inférieur (au sens des anciens auteurs) des dépôts du bassin du bas Chelif (Oran, Algérie): conséquences biostratigraphiques et géodynamiques

    Mem. Serv. Geol. Alger.

    (2002)
  • M.-M. Blanc-Valleron et al.

    Evidence of Messinian non-marine deposition at Site 968 (Cyprus Lower Slope)

  • L. Blanc-Vernet

    Foraminifères

  • E. Boltovskoy et al.

    The Foraminifera (except Allogromiidae) which dwell in freshwater

    J. Foraminiferal Res.

    (1971)
  • G. Bonaduce et al.

    Paleoecological interpretation of the latest Messinian sediments from southern Sicily (Italy)

  • J.C. Braga et al.

    Testing models for the Messinian Salinity Crisis: the Messinian record in Almería, SE Spain

    Sediment. Geol.

    (2006)
  • Brives, A., 1897. Les terrains miocènes du bassin du Chélif et du Dahra. Thesis University of...
  • A. Brives

    Sur l'âge des gypses du Dahra

  • A.A. Brodsky

    Foraminifera (Polythalamia) in the wells of the Kara–Kum desert

  • R.W.H. Butler et al.

    Tectonics and sequence stratigraphy in Messinian basins, Sicily: constraints on the initiation and termination of the Mediterranean salinity crisis

    Geol. Soc. Amer. Bull.

    (1995)
  • J.H. Cann et al.

    Fossil Quaternary and living Foraminifera from athalassic (non marine) saline lakes, Southern Australia

    J. Paleontol.

    (1981)
  • G. Carnevale et al.

    Mare versus Lago: marine fishes and the Mediterranean environment at the end of the Messinian Salinity Crisis

    J. Geol. Soc.

    (2005)
  • A. Caruso et al.

    Clastic vs. primary precipitated evaporites in the Messinian Sicilian basins

  • P. Casati et al.

    Stratigraphy and paleoenvironment of the Messinian “Colombacci” formation in the Periadriatic trough. A pilot study

  • N. Ciaranfi et al.

    Preliminary description of some Messinian evaporitic facies along the Abruzzi–Molise boundary

  • M.B. Cita et al.

    Sedimentation in the latest Messinian at Capo Rossello (Sicily)

    Sedimentology

    (1979)
  • M.B. Cita et al.

    Studi sul Pliocene e gli strati di passaggio dal Miocene al Pliocene. IV. The stratotype Zanclean foraminiferal and nannofossil biostratigraphy

    Riv. Ital. Paleontol. Stratigr.

    (1973)
  • M.B. Cita et al.

    Messinian paleoenvironments

  • Cited by (57)

    • Karstic geomorphology of carbonate Ouarsenis Piedmont (Boukadir region, Chelif) in Algeria: The role of the Messinian Salinity Crisis

      2022, Journal of African Earth Sciences
      Citation Excerpt :

      The Chelif Basin was reconnected to the Mediterranean Sea allowing the deposition of more than 1000 m of Zanclean marls with Mediterranean fauna (Belhadji et al., 2008; Atif et al. 2008; Arab et al., 2015). These transgressive marine clays are paired with thick deposits of Pliocene sandstones and conglomerates (gilbert delta) around the basin margins, and thus must have been associated with large river aggradation on the basin margins (Rouchy et al., 2007; Belhadji et al., 2008; Atif et al. 2008; Zhang and Jiang, 2011; Arab et al., 2015) (Fig. 17). This Pliocene river infilling is evidenced in the Taflout River whose valley was first filled by 35 m of clayey sediments, then by 30 m of Plio-Quaternary alluvium (Fig. 8-B).

    • Environmental conditions during the deposition of the diatomite –organic-rich marl alternation of the lower Messinian of the Lower Chelif Basin (Algeria) interpreted from microfossil assemblages and geochemistry

      2022, Journal of African Earth Sciences
      Citation Excerpt :

      Consequently, the extremely reduced or closed seaways between the Mediterranean and Atlantic created an environment where evaporation was dominant, with the deposition of gypsum and halite (e.g. Braga et al., 2006; Krijgsman et al., 2010; Manzi et al., 2013; Flecker et al., 2015; Capella et al., 2018). The MSC affected the Mediterranean Sea between 5.97 and 5.33 Ma and led to the deposition of huge evaporite accumulations, both in its marginal and deep basins (e.g. Krijgsman et al., 1995, 1999; Riding et al., 1998; Rouchy et al., 2007; Haq et al., 2020; Manzi et al., 2020, 2021; Sabino et al., 2021). The cyclical alternations of diatomites and sapropels of the lower Messinian have been interpreted as reflecting orbitally-controlled climatic changes (Hilgen and Krijgsman, 1999; Pérez-Folgado et al., 2003) including stratification of the water column in these basins, resulting in bottom-water anoxia or hypoxia (Pellegrino et al., 2018).

    View all citing articles on Scopus
    View full text