Matière organique sédimentaire et paléoenvironnements du Tithonien inférieur quercynois (France)

The Solen 98 well corresponds to the limestones of the Lower Tithonian Cazals Formation (Gigas Zone). The iterative succession of six sedimentary terms expresses a cyclic peritidal dynamic. Limited by two emersion surfaces, each sequence evolves from an upper subtidal lagoon to a tidal flat, upper intertidal or supratidal environment, and ends with open sea depositional bioclastic and oolitic shoals deposits. Hierarchical ascendant classification applied to palynological data define 6 palynofacies types associated with different depositional facies. Type 1, characterizing open marine deposits, shows a diversified and balanced assemblage. The blade-shape woody particles are abundant and the amorphous organic matter is absent. Types 2 and 3 are linked to lagoonal and skeletal shoals deposits. Then microfossil population is dominated by Corculodinium or long-spine Micrhystridium. The Shannon-Weaver and the equitability indices are moderate. Type 4 is associated with the upper tidal flat, lagoonal and skeletal shoal deposits. When microfossils are present, the algal assemblages are more balanced than in type 5. This type, observed in all the palaeo-environments except the open marine, is enriched in elements attributed to the Hyalinsphaeridia complex. The marine component assemblages are balanced. The amorphous organic matter is relatively abundant and the oxydized woody particles absent. Type 6, mainly composed of amorphous organic matter and phytoclasts, is principally associated with the stromatolitic facies of tidal flat deposits. The example of the Solen 98 well, shows that hierarchical ascendant classification method is well suited for identification of palynofacies     

Tortonian ostracodes of Southwestern Europe

This paper analyzes the lithostratigraphic features and the ostracode associations of the Tortonian deposits located in the western and central sectors of the Guadalquivir basin (S Spain). Eight facies associations are defined (FA-1 to FA-8), being deposited in fluvial to upper bathyal paleoenvironments. The ostracofaune confirms the Tortonian age of these deposits, where three ostracode associations are defined: (a) infralittoral (i.e. Urocythereis favosa, Cytheretta orthezensis, Callistocythere spp.); (b) circalittoral (i.e. Costa batei, Celtia quadridentata, Echinocythereis scabra, Pterygocythereis ceratoptera/jonesii); and (c) outer platform/talus (Henryhowella asperima; Cytherella spp.; Krithe spp.). A comparison with the Tortonian associations of southwestern France and Portugal permits to define a common ostracod zonation for southwestern Europe for this period.     

Gastropodes sinémuriens du Monte Cucco (Apennins d’Ombrie-Marche, Italie centrale)

Recent researches carried out in the uppert part of the “Calcare Massiccio” formation of Monte Cucco allowed to recover a rich Sinemurian fauna of gastropods, bivalves, brachiopods, ammonoids and some solitary corals. The gastropod fauna is greatly dominant and includes 18 species which belong to the superfamilies Pleurotomarioidea, Fissurelloidea, Amberleyoidea, Neritoidea, Loxonematoidea, Cerithioidea, Nerineoidea, Littorinoidea and Acteonoidea. Ten species of gastropods are here described for the first time. This fauna shows a marked affinity with that of the Sinemurian of Sicily. Under a paleoecological point of view, it is indicative of free marine conditions, in photic zone but under a weak hydrodynamism, and therefore may suggests the reference to a deep infralittoral or upper circalittoral environment.     

Précisions sur le patron d’empilement de dépôts du Cénomanien-Turonien de Somolinos (Chaîne Ibérique, Espagne) d’après l’étude palynologique

The Somolinos outcrop was widely studied in detailed correlations, stratigraphical architecture and high frequency sequence analysis of Central System and Iberian range successions. A rich assemblage of echinoids, ammonites, bivalves and bryozoans was described; conversely, the palynological study of the Late Cretaceous levels from Somolinos has never been performed up to now. A palynological study of two intervals within a monotonous alternation of grey marls and nodular limestone succession in the Somolinos section was carried out. The two intervals sampled are located in two correlative sequences of Late Cenomanian-Early Turonian and mid Turonian ages, respectively. Both sequences are separated by a sequence boundary, but its location and age in the stratigraphic record differs depending on the authors and the Basin considered. A rich palynofacies with abundant dinoflagellate cysts, pteridophyte spores, conifer pollens and breviary angiosperm grains of the normapolles group is described; besides, inner linings of acid resistant microforaminiferal tests were also found. The analysis of the palynological diagrams clearly indicates that the upper interval corresponds to open sea neritic sediments, deposited in more distal sedimentary environments than those of the lower interval, which were deposited in more proximal environments. This evolution of sedimentary environments represents a major sedimentary change in the general shallowing upwards trend of the late Albian-mid Turonian 2nd order succession, revealing a major facies belt retrogradation of the sequence containing the upper interval. This retrogradational event allows to accurately place the sequence boundary and to improve the arrangement of the low frequency (3rd order) depositional stacking pattern of the Early-mid Turonian in the Iberian Basin and other European and Tethyan basins.     

Heterosteginapapyracea Seguenza du Miocène du Corridor Sud-Rifain (Maroc) : biométrie et particularités paléoécologiques

Biometric study of the inner features of Heterostegina specimens preserved in tortonian sediments of the oued Yhoudi member allows to confirm the presence of species Heterostegina papyracea Seguenza, 1880. Analysis of both large and small components of the foraminiferal assemblage in all examined samples establishes the dominant character of species Heterostegina papyracea Seguenza (more than 60% of total benthic foraminifera). The assemblage of small benthic foraminifera associated with the Heterostegina is different from that described from Recent sediments, as well as from Miocene sediments of Calabria and Spain. In order to explain this result, two hypotheses can be put forward: (1) the Tortonian Heterostegina from Morocco proliferated abundantly in very shallow environments in association with small foraminifera (i.e. abundant Ammonia beccarii). (2) Because of powerful tidal currents in the South Rifian Corridor, Heterostegina tests were probably transferred after death. This transfer could possibly be due to the narrowness of the South Rifian Corridor in the Early Late Tortonian and its position between the Atlantic and the Mediterranean. Similar cases foraminiferal displacements are also known from modern basins. This study illustrates the difficulties in reconstructing the paleogeography of the studied area and the importance of considering all available components of the assemblage.     

Les ostracodes plio-pléistocènes de la côte orientale de la Péninsule du Cap Bon (Tunisie)

This article concerns the study of the ostracods of the Upper Pliocene-Lower Pleistocene sedimentary deposits cropping out along the south-eastern coast of the Cape Bon Peninsula (Tunisia, Hammamet region, Sidi Khelas section). Fourteen samples were taken along a thirty-two-meters thick sedimentary silico-clastic series. Seventy species of ostracods belonging to twenty-four genera were found. The autochthonous association, which originally lived in an environment located in the infralittoral and upper circalittoral stages of the benthic marine domain, is cyclically affected by inputs from the more superficial environments due to the presence of relatively well-developed lagoon and/or estuary environments in the surrounding coastal areas. Within the ostracod association, the presence of Bythocythere turgida – a true “northern guest” – is particularly significant. This species indicates that these sediments were deposited during the cold phases of the Early Pleistocene. Among the ostracods found, those belonging to the families Trachyleberididae, Hemicytheridae and Bythocytheridae, which are dominant and include particularly significant species from the environmental and paleoclimatic point of view, are systematically recorded and commented on. Some species that are probably new have been described and photographed, but are currently left in open nomenclature because of how few specimens have been found.     

Biostratigraphie d’après les foraminifères et paléoenvironnements des séries post-Éocène du sondage ASHTART 28, golfe de Gabès (Tunisie)

The Cenozoic sequence of Ashtart 28 well drilled in the Gulf of Gabes (Tunisia) is the subject of a biostratigraphical study. The samples recovered in cuttings from 390 m and downwards allowed to recognize, above the Late Eocene sediments, a sedimentary series, lithologically diversified, nearly 1600 m thick. Marine Pliocene deposits, generally attesting a low bathymetry, lie unconformably above the Messinian (Oued Bel Khedim formation), which shows the usual features of the Mediterranean confinement. The underlying Messinian pre-evaporitic platform series (Melqart formation), that is over 250 m thick, is typical of a perireefal environment. The sediments assigned to the Tortonian (Somâa Sands formation) are continental and occur unconformably above the approximately 500-metres-thick Middle Miocene strata (Saouaf, Mahmoud, Aïn Grab and Salammbô pars formations). The marine Lower Miocene and Oligocene sediments (Salammbô pars and Ketatna formations), that are more than 300 m thick, lie in continuity under the Middle Miocene. The infralittoral Chattian sequence has especially supplied a diversified assemblage of larger foraminifera recovered in other west-mediterranean basins. Datings were obtained based on planktonic and larger benthic foraminifera (Miogypsinidae, Nummulitidae, Lepidocyclinidae) and by correlations obtained by means of well loggings and lithostratigraphy. Benthic foraminifera, mainly listed for the Miocene and Oligocene, are studied from a systematic, stratigraphic and paleogeographic point of view. The paleoenvironments of deposits are defined for each considered stratigraphic interval. Comparisons are sketched with other drillings of the Gulf of Gabes. Thanks to the numerous data obtained by this detailed study, the Ashtart drilling can serve as a reference for the Tertiary sequence of this part of the Mediterranean domain.     

The Miocene vertebrate-bearing deposits of Scontrone (Abruzzo,Central Italy): Stratigraphic and paleoenvironmental analysis

The Miocene carbonate deposits of Scontrone (Abruzzo, Central Italy) are well known among palaeontologists because of their fossil vertebrate content that exhibits striking similarities to those of the remarkable “Terre Rosse” faunal complex of the Gargano region, defining the existence of the Miocene Central Mediterranean Apulia paleobioprovince. The main goal of this paper is to establish the age and environment of the Scontrone vertebrate bonebeds. The vertebrate remains are embedded in the basal portion of the Lithothamnion Limestone, a widespread carbonate-ramp lithosome representative of the Tortonian-early Messinian transgression over the entire Apulia Platform. The bonebeds belong to marginal-marine deposits (here called “Scontrone calcarenites”) preserved in a small area below transgressive ravinement surfaces. The rapid vertical and lateral facies variations displayed by the “Scontrone calcarenites”, together with paleoenvironmental considerations deriving from the vertebrate association, document a complex wave-dominated river-mouth depositional setting developed over a large, flat and semi-arid carbonate ramp. The “Scontrone calcarenites” have been split herein into five facies associations representing the stratigraphic response to a discontinuous or punctuated transgression within an overall rise of the relative sea level. Because of the absence of age-diagnostic fossils, the age of the “Scontrone calcarenites” cannot be directly defined through their paleontological content. However, a regional stratigraphic correlation between the Lithothamnion Limestone of Scontrone and the Lithothamnion Limestone of northern Majella, which is biostratigraphically well constrained, allows the attribution of the “Scontrone calcarenites” to the Tortonian.     

Euxinocythere (Ostracoda, Cytheridae, Leptocytherinae) du Miocène supérieur du Bassin de Turiec (Slovaquie) : taxonomie et paléoécologie

Eight new species of the family Cytheridae have been identified in the Upper Miocene deposits of the Turiec Basin (Slovakia), a small isolated intermountain depression. Six species are new - Euxinocythere aphroditae, E. delicata, E. lactea, E. minuscula, E. quadricostata, E. satyrica - and two are kept in open nomenclature. Their attribution to the genus Euxinocythere is based on arrangement of the hinge elements and of anterior marginal zone. This genus is known from brackish ostracod assemblages of the Paratethys and the Eastern Mediterranean while the species from the Turiec Basin are associated to fresh-water assemblages. The Euxinocythere have been found in littoral as well in deep limnic environment.     

The potential of carbonate ramps to record C‐isotope shifts: insights from the upper Miocene of the Central Mediterranean area

The late Miocene is a crucial interval for global climate evolution as well as for the regional geodynamic evolution of the Central Mediterranean area. It spans the transition from the warm Mid Miocene Climatic Optimum, associated with the major Monterey Carbon Isotope Excursion, to the cooler Pliocene, characterized by a bipolar glaciation. Within this climatic transition, during the early Tortonian, a positive carbon isotope excursion related to a global carbon cycle perturbation is recorded, named Carbon Maximum 7 (CM7). In this study, two upper Serravallian–lower Tortonian carbonate ramps of the Central Mediterranean have been analysed: the Latium‐Abruzzi and the Apula ramps (Central Apennines, Central Italy). Carbon isotope ratios have been coupled with facies and microfacies analyses with the aims: (1) to identify the CM7 in the Central Mediterranean carbonate ramp successions; (2) to evaluate potential carbonate factory changes or demises related to the CM7; and (3) to discriminate the role of global vs regional factors in affecting the Mediterranean carbonate ramps. The two studied ramps show different evolutions due to regional geodynamics causes. The Latium‐Abruzzi ramp drowns in the Tortonian, while the Apula shows a regressive trend, with upper Tortonian middle ramp facies overlying the lower Tortonian outer ramp. Despite the complex geodynamic setting, a positive carbon isotope shift has been identified in both ramps and correlated with the CM7. This positive carbon isotope shift may be linked to the strengthening of the global ocean circulation during the late Miocene cooling. This strengthening of the circulation enhanced the coastal upwelling, bringing nutrient‐rich waters to the surface and triggering an enhanced primary productivity consistent with the CM7.     

Les formations du jurassique supérieur du Bou Rheddou au Nord de Tiaret (Bordure sud-Tellienne,Algérie): âge et milieux de dépôt

In the Bou Rheddou mountain (Southern Tellian border), new biostratigraphic data based on Ammonites, allow precise and modify the age of the Arkell & Busson formations. The Oxfordian «Ammonitico rosso facies begin in the Transversarium zone and go into the Planula zone. This zone is characterized for the first time in this region. Lower Tithonian (Hybonotum zone) and Upper Tithonian (Microcanthum zone) are also recognized. Precisions on depositional environment and paleogeography are given. Facies and low sedimentation show a pelagic shoal (abundant planctonic organisms) slightly subsiding and lately recovered by the Jurassic transgression. During Oxfordian, episodic interruption of the «Ammonitico rosso deposits shows an unstable period with terrigenous deposits (intra-oxfordian tectonic movements). The facies of the Northern-Gondwanian carbonated platform begin earlier in the Bou Rheddou zone (Oxfordian-Kimmeridgian boundary) than in the Southern regions, where the same facies appears only in Upper Kimmeridgian.     

Ostracodes limniques de la Formation d'Irbzer, Crétacé terminal du Moyen-Atlas, Maroc : taxonomie, biostratigraphie, paléoécologie, paléobiogéographie

An association of limnic ostracodes has been discovered in the upper part of the Irbzer Formation, of Maastrichtian age, in the Moroccan Middle-Atlas. A new species is described, Gomphocythere achloujensis nov. sp. Paracandona occitanica, which is very common in terminal Cretaceous non-marine deposits of southern Europe (France, Spain), is found for the first time on the south Tethyan margin.     

Évolution des environnements littoraux du bassin de Melilla-Nador (Nord-Est Maroc) au Messinien supérieur entre 6,0 et 5,77 Ma

This study of late Messinian deposits (E2 = TCC) from Melilla-Nador carbonate complex (Morocco) allowed us to characterize the environmental evolution between 6.0 and 5.77 Ma, which is a period considered as contemporaneous of the onset and development of the “messinian salinity crisis”. A statistical approach coupled together with classical petrographic study allows us to constrain the sedimentary dynamic of platforms and to propose deposition environment models. The Melilla-Nador platforms E2 deposits show a progressive continuous evolution of littoral environments in two major stages of available space creation and infill. The first stage corresponds to the build up of a reef complex between 6.0 and 5.85 Ma then the second stage, between 5.85 and 5.77 Ma, corresponds to the development of a mixed oolitic shallow ramp during the progressive infill of Melilla-Nador basin. The comparison with the Sorbas basin (Spain) TCC deposits exhibits a very close evolution of late Messinian littoral environments, which could be used as a correlation tool.     

Ostracodes et stratigraphie du néogène et du quaternaire méditerranéens

A stratigraphical chart of marine ostracoda from Lower Miocene to Recent is established. Selected species (approximatively 220) are those morphologicaly well characterized and known from different parts of the Mediterranean area. It appears that: • lower Miocene ostracodes are still poorly known; • specific diversity is high during the Tortonian and the Lower Messinian before the complete disappearance of marine Mediterranean species during the Upper Messinian évaporitic episodes; • during the early Pliocene, about half of the Upper Miocene marine species are reintroduced with the Atlantic waters; other species migrate for the first time in the Mediterranean Sea by the same way; • at the end of the Pliocene or at the beginning of the Pleistocene several species known in Mediterranean since the Middle Miocene or before, such as Cytherella sp. gr. transversa and Ruggieria tetraptera, as well some “nordic guests” such as Hemicythere villosa and Cythere lutea, appear. This work is an opportunity to confirme a Late Miocene age for the Neogene of Skyros (Aegean Sea), to assign the “Upper Pliocene” of Terquem to the Lower Pleistocene and to refute the existence of a pliocene psychrosphere.     

Candoninae trapézoïdales (Crustacea, Ostracoda) du Bassin de Turiec (Slovaquie) du Miocène supérieur : systématique, écologie et évolution

The trapezoidal Candoninae from the Turiec Basin in Slovakia referred to the Candona sitari- and to C. aculeata-groups have characters that contrast with the valves of the Recent central European Candonines. The particularities concern the degree of calcification, the zone of concrescence, the overlap, and the presence of protuberances, the dorsum and the tubercles. Within the sitari-group, these characters evolve simultaneously with rapid evolution of the valve outline from subtrapezoidal to trapezoidal in shape. The species of this group acquire valve contours similar to those of the trapezoidal Candoninae of the Lake Pannon and the recent fauna of the long-lived lakes. The trapezoidal Candoninae of the Turiec Basin are associated with candonines that have triangular and rectangular carapaces with a pointed posteroventral margin. These three morphotypes indicate relatively stable habitats with weak environmental fluctuations. The trapezoidal species are rare in the littoral facies in both the north and the marginal areas of the Turiec Basin, but very abundant in the centre and south of the Basin. They probably lived in a profundal environment and their evolution probably occurred in relation to both sexual reproduction and a benthonic mode of life. The two groups comprise 18 species, of which 15 are described as new.     

Échinodermes de l'Ordovicien supérieur (Ashgill) de Sardaigne et d'Algérie

Research on the influence of sea level variations on the benthic faunas have been carried out in the Upper Ordovician of Sardinia. Study of the depositional facies and sequence analysis of the upper part (Lower Ashgill) of the Portixeddu Formation led to the identification of the sedimentary environments. Cystoids and crinoids are associated to bryozoans and brachiopods in most levels. The numerical analysis of associations and megaguilds shows that crinoids and cystoids have a higher frequency in the proximal and median facies of the upper offshore. The columnal association characterized by Conspectocrinus celticus and the coronoid Mespilocystites tregarvanicus has been discovered in the upper part of the formation. This material and complementary samples from Upper Ordovician of Sardinia and Kabylia (Algeria) bring additional data on the systematic and show the wide distribution of this fauna outside of the Ibero-armorican domain. The distribution of this echinoderm association supports a palaeogeographical position of the Ibero-armorican domain and Sardinia within the north gondwanan margin during the Lower Palaeozoic.     

Découverte des sables à Mactres de la base du Burdigalien à Martillac (Nord Aquitaine ; SW France) ; données paléontologiques

The Early Burdigalian in the type area of the stage (Gironde, South of Bordeaux) comprises marine deposits with rather various facies, often rich in molluscs. Locally, the very basal Formation of “Sables à Mactres” is present, formerly known in Léognan, but very little studied in litteris. We have discovered first at Martillac deposits allocated to this Formation, and we study their paleontological contents. The macrofauna is more diversified than it was expected from the aspect of sediment; for instance, 210 mollusc species have been inventoried in these grey fine sands, bedded and very carbonatic, where Bivalvia shells are well preserved and dominant among the whole fauna. These shells are either scattered in the layers or accumulated in small beds. Echinoids, Asteroids, Crustacea, Annelida, Scleractinia, Brachiopoda, fishes, Alga Rhodophycea, are present, as well as an abundant microbenthos. Taphonomic observations are made on the sandy sequence, and taxonomic and biostratigraphic remarks concern some mollusc species. From a paleoecologic point of view, the endobiont forms are dominant within the malacofauna, they are accompanied by several epibiont and semi-endobiont taxa, and few pelagic and endolith ones. Concerning the trophics, the suspension-feeders molluscs are dominant in specimens number, notably amongst Bivalvia, and carnivores, detritivores/deposit-feeders, herbivores and commensal/parasites are more or less well represented. On the whole, the soft-substrate species are obviously in a majority. This paleobiofacies with Mactrids – Donax – Capsa – Pitar – Loripes – Ringicula corresponds to a deposit in a coastal tidal area, rather calm, of a shallow embayment type, with very few detritics, and submitted to a moderate hydrodynamism and to a subtropical to tropical climate. The reworking is insignificant in the sequence where shells are dispersed (parautochthonous species), and the transport has been limited to the falun beds (e.g. little channels, tides action). The conditions of settlement of the earliest phases of Burdigalian transgression are thus specified in this type area.     

Pliocene ostracods of Southwestern Europe

This paper analyzes the lithostratigraphic features and ostracod associations of the Pliocene deposits located in the western sector of the Guadalquivir basin (SW Spain). A regressive cycle is defined by the vertical distribution of five main facies (FA-1 to FA-5), which were deposited in upper bathyal to fluvial palaeoenvironments. The broad palaeontological record is utilized to draw a general outline of the food chain in each palaeoenvironment. A comparison with the Pliocene ostracod distribution of southeastern Spain, southwestern France and Portugal permits to define a common ostracod biozonation for southwestern Europe during this period. Four main marine biozones are distinguished: (a): Pontocythere elongata biozone (infralittoral); (b): Costa edwardsii biozone (shallow circalittoral); (c): Bosquetina carinella biozone (deep circalittoral); and (d): Henryhowella asperrima biozone (upper bathyal). Freshwater, brackish and lower bathyal/abyssal species are very scarce in this area during this period.     

L’ambre albo-cénomanien de la montagne de Lure (Alpes-de-Haute-Provence), outil stratigraphique et paléogéographique

Nodules of fossil resin or amber, first drifted and then deposited in the marine series with cephalopods, were discovered in several areas of High-Provence, in geological series of the Cretaceous system. These areas are located around the Mountain of Lure; amber nodules have been found in the upper Albian (Ongles, Revest-des-Brousses) and in the lower Cenomanian (Saint-Étienne-les-Orgues, Aubignosc and Salignac). These ambers have very homogeneous and characteristic FTIR spectra, making it possible to distinguish them not only from more recent ambers of the upper Cretaceous of Provence (Santonian), but also from tertiary ambers of the Baltic sea. These organic matters in marine environment, brought by the currents and deposited in shallow waters of the Ventoux-Lure area, are in agreement with close emerged grounds, which were set up by the Albo-Cenomanian tectonic movements.