10 research outputs found
New insights on the latest Messinian-to-Piacenzian stratigraphic series from the Dahra Massif (Lower Chelif Basin, Algeria): Lago Mare, reflooding and bio-events
Geological investigations carried out on the Dahra Massif have revealed sedimentary changes and bioevents characterizing the post-gypsum detrital sediments (from Messinian to Piacenzian), which are followed by the Trubi equivalent Pliocene marls or white marly limestones.
Structured into two superimposed steps, the late Messinian deposits yielded two successive ostracod assemblages. They indicate a brackish environment for the lower and a fairly open shallow brackish environment for the second. Based on their ostracod content, assemblage 1 (Cyprideis, Loxoconcha muelleri) corresponds to the Lago Mare biofacies 1 of the Apennine foredeep, which is correlated with the Lago Mare 1 episode dated between 5.64 and 5.60 Ma. Assemblage 2 (Loxocorniculina djafarovi) is referred to the Lago Mare biofacies 2 described in the same region. It is correlated with the Lago Mare 3 episode, dated between 5.46 and 5.33 Ma.
Moreover, the stratigraphic succession is marked by a major discontinuity indicated by a hardground, separating step 1 from step 2 and corresponding to the ostracod assemblages 1 and 2, respectively. This discontinuity is considered here to be equivalent to the Messinian Erosional Surface, already evidenced in the region and widely known around the Mediterranean Basin.
These late Messinian deposits and their ostracod assemblage 2, notably the detrital sedimentation with Ceratolithus acutus, Globorotalia margaritae, Reticulofenestra cisnerosii document a marine incursion into the Lower Chelif Basin, corresponding to the latest Messinian marine reflooding of the Mediterranean Basin, that happened before the earliest Zanclean R. cisnerosii occurrence. Finally, the bioevents evidenced in the Dahra Massif, reinforce the evidence of the late Messinian Lago Mare 3 episode, and support the ante-Zanclean age of the marine reflooding of the Mediterranean.
The overlying deposits are marked by coral constructions (cf. Cladocora cf. caespitosa, Dendrophyllia sp) never described before and covering the entire early Zanclean, testifying the existence, at that time, of warm enough conditions, which may correspond to the marine isotopic stage TG5
Le Neogene de la bordure nord-occidentale du massif du Dahra (Algerie)
SIGLECNRS T Bordereau / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc
Signification paléoécologique des assemblages de diatomées du Messinien du Dahra sud-occidental (bassin du Chélif, Algérie nord-occidentale)
Constituant lâune des composantes sĂ©dimentaires majeures du Messinien du bassin du ChĂ©lif au mĂȘme titre que la formation gypseuse, les diatomites ont fait lâobjet dâune Ă©tude dĂ©taillĂ©e reposant sur quatre coupes rĂ©parties sur le versant sud-occidental du massif du Dahra. Les coupes Ă©tudiĂ©es montrent dâimportants changements verticaux et latĂ©raux de faciĂšs, permettant ainsi de distinguer deux unitĂ©s sĂ©dimentaires (membre infĂ©rieur et membre supĂ©rieur). Le membre infĂ©rieur est caractĂ©risĂ© par un assemblage diatomique nĂ©ritico-ocĂ©anique et ocĂ©anique (Coscinodiscus marginatus, C.âŻoculus-iridis, C.âŻradiatus, Nitzschia reinholdii, N.âŻfossilis, Thalassiossira eccentrica, T.âŻmiocenica, Thalassiothrix longissima, etc. ) tandis que les formes planctoniques littorales (Actinoptychus senarius, Thalassionema nitzschioides, Actinocyclus octonarius, A.âŻtenellus, Paralia sulcata, etc.) et accessoirement benthiques marquent surtout le membre supĂ©rieur, traduisant ainsi une Ă©volution bathydĂ©croissante du milieu de dĂ©pĂŽt. LesâŻvariations horizontales deâŻces assemblages dans les quatre secteurs accusent dâouest en est un approfondissement du milieu tout en Ă©voluant en un milieu de sĂ©dimentation en contexte de bassin. Lâabondance des diatomĂ©es «âfroidesâ», Coscinodiscus marginatus dans le membre infĂ©rieur et Actinocyclus curvatulus dans le membre supĂ©rieur, semble conforter la subdivision lithologique et permet de considĂ©rer ce dĂ©coupage comme source des repĂšres stratigraphiques Ă lâĂ©chelle locale (bassin du ChĂ©lif) voire rĂ©gionale (Bassin mĂ©diterranĂ©en). Cette sĂ©dimentation diatomitique est caractĂ©risĂ©e jusquâaux derniers niveaux qui prĂ©cĂšdent les dĂ©pĂŽts de gypses, par des espĂšces marines Ă affinitĂ©s nĂ©ritico-ocĂ©aniques et ocĂ©aniques tĂ©moignant ainsi, avec les silicoflagellĂ©s et les radiolaires, dâun milieu marin franc, en connexion avec le domaine ocĂ©anique. Par ailleurs lâabondance de Thalassionema nitzschioides, espĂšce constamment prĂ©sente et souvent dominante associĂ©e Ă Thalassiothrix longissima, suggĂšre un milieu Ă forte productivitĂ© caractĂ©ristique des zones Ă upwellings responsable du dĂ©veloppement de la flore diatomique.As one of the main sedimentary Messinian components of the Chelif basin with the gypsum deposits, the diatomites were studied in detail along four sections from the southwestern border of the Dahra.The studied sections show significant vertical and lateral lithological changes, allowing to distinguish two units (the lower member and the upper member). The lower member is dominated by the neritic-oceanic and oceanic planktonic assemblage (Coscinodiscus marginatus, C.âŻoculus-irridis, C.âŻradiatus, Nitzschia reinholdii, N.âŻfossilis, Thalassiosira eccentrica, T.âŻmiocenica, Thalassiothrix longissima, etc.). Whereas, the littoral planktonic species (Actinoptychus senarius, Thalassionema nitzschioides, Actinocyclus octonarius, A.âŻtenellus, Paralia sulcata, etc.) and benthic forms characterized the upper member, indicating a general decrease in bathymetry over the Messinian diatoms. This assemblage is also dominated by cold water diatoms characteristic of boreal area (Coscinodiscus marginatus) in the lower member and Actinocyclus curvatulus in the upper member), which correspond to the defined lithological units. The paleoecological data from diatoms, silicoflagellates and radiolarians indicate that the diatomites were deposited in open marine environment submitted to the inputs of Atlantic cold water, until last levels before gypsum deposits. Moreover, the abundance of Thalassionema nitzschioides, constantly present from the base to the top of the section and often associated with Thalassiothrix longissima, is indicative of a high productivity, which can be characteristic of an upwelling regime, responsible of the development of the diatom microflora.</p
Signification paléoécologique des assemblages de diatomées du Messinien du Dahra sud-occidental (bassin du Chélif, Algérie nord-occidentale)
Mansour, Bouhameur, Bessedik, Mostefa, Martin, Jean-Paul Saint, Belkebir, Lahcene (2008): Signification paléoécologique des assemblages de diatomées du Messinien du Dahra sud-occidental (bassin du Chélif, Algérie nord-occidentale). Geodiversitas 30 (1): 117-139, DOI: 10.5281/zenodo.537326
Evolution de la diversité des bivalves messiniens de la bordure méridionale du bassin du Bas Chélif (Algérie nord occidentale)
International audienc
Biostratigraphie et lithologie des séries serravallo-tortoniennes du massif du Dahra et du bassin du Chélif (Algérie). Implications sur la position de la limite serravallo-tortonienne
Belkebir, Lahcene, Labdi, Amel, Mansour, Bouhameur, Bessedik, Mostefa, Martin, Jean-Paul Saint (2008): Biostratigraphie et lithologie des séries serravallo-tortoniennes du massif du Dahra et du bassin du Chélif (Algérie). Implications sur la position de la limite serravallo-tortonienne. Geodiversitas 30 (1): 9-19, DOI: http://doi.org/10.5281/zenodo.537316
Apports des foraminifÚres planctoniques à la biostratigraphie du MiocÚne supérieur et du PliocÚne de Djebel Diss (bassin du Chélif, Algérie)
Belhadji, Ahmed, Belkebir, Lahcene, Martin, Jean-Paul Saint, Mansour, Bouhameur, Bessedik, Mostefa, Conesa, Gilles (2008): Apports des foraminifÚres planctoniques à la biostratigraphie du MiocÚne supérieur et du PliocÚne de Djebel Diss (bassin du Chélif, Algérie). Geodiversitas 30 (1): 79-96, DOI: http://doi.org/10.5281/zenodo.537418
Contributions biostratigraphiques et paléoenvironnementales de l'étude des nannofossiles calcaires des dépÎts tortonomessiniens du bassin du Chélif (Algérie)
Mansouri, Mohamed El Habib, Bessedik, Mostefa, Aubry, Marie-Pierre, Belkebir, Lahcene, Mansour, Bouhameur, Beaufort, Luc (2008): Contributions biostratigraphiques et paléoenvironnementales de l'étude des nannofossiles calcaires des dépÎts tortonomessiniens du bassin du Chélif (Algérie). Geodiversitas 30 (1): 59-77, DOI: http://doi.org/10.5281/zenodo.537694
Biostratigraphic and paleoenvironmental contributions of calcareous nannofossil study from Tortonian-Messinian deposits of Chelif basin (NW Algeria)
Special Meeting of the APF on Biodiversity and Biodiversity Crisis in North Africa during Neogene, Paris, FRANCE, NOV 28-29, 2006International audienceFifty calcareous nannofossil species were listed in the upper Miocene deposits of the Northern Chelif Basin (Dahra, Ben Dourda section). The frequence of some of them (Discoaster loeblichii, D. quinqueramus, Amaurolithus primus and A. amplificus) suggests the presence of four subzones (NN 10a, NN 10b, NN 11b, NN 11 c) which are assigned to the Tortonian and Messinian stages. The NN 11 a subzone is absent (hiatus), testified by the (first) simultaneous occurrence (FO) of D. quinqueramus and A. primus. In the same samples, planktonic foraminifera analysis revealed a comparable succession of biozones (Neogloboquadrina acostaensis, N. humerosa-N. dutertrei and Globorotalia mediterranea) which make possible a good calibration between biostratigraphic scales (calcareous nannofossils, foraminifera). The Tortonian-Messinian boundary is pointed out at the sample 28 of the section and characterized by the first occurrence (FO) of A. delicatus and Reticulo/enestra rotaria on the one hand and G. mediterranea on the other hand. The assemblage analysis and relative abundance fluctuations of Coccolithus pelagicus and R. pseudo-umbilicus show evidence of seven successive phases which are characterized, alternately, by cold and hot water marine masses, light intensity variations and nutrient availability