Éditeur(s) : HAL CCSD Cambridge University Press (CUP)
Résumé : We present detailed biostratigraphy based on conodonts and palaeoenvironmental trends deduced from microfacies and conodont abundance through the Famennian (Late Devonian) at Col des Tribes (Montagne Noire, France). The succession is characterized by micritic limestones deposited in settings oscillating between mid to outer ramp. Facies contain poor fauna, widely dominated by nektonic organisms. This section is complete and one of the most conodont-rich for the Famennian of the north Gondwana-related area. The Upper Kellwasser event (Frasnian–Famennian boundary) and the Hangenberg (Devonian–Carboniferous boundary) have been lithologically identified. They are characterized by decimetre-thick black dysoxic to anoxic argillaceous sediments. The Condroz and annulata events, although not materialized by lithological changes, have been positioned due to the precise stratigraphy. The first event occurred during the deposition of condensed ferruginous facies (griotte limestones) and the second event during the deposition of micrites barren of benthic fauna. The combination of information from both facies and conodont biofacies changes allows a general sea-level curve through the entire Famennian for north Gondwana to be proposed for the first time. At Col des Tribes, the general trend is a slight deepening upwards from triangularis to trachytera zones, then a pronounced shallowing-upwards trend from upper trachytera to praesulcata zones. This curve correlates with the well-known reference curve from Euramerica concerning the late Famennian (trachytera to praesulcata Zones). There are some discrepancies in minor cycles which can be explained by tectonical phenomena at the onset of the edification of the Variscan belt in Europe.
ISSN: 0016-7568

hal-01115222
https://hal.archives-ouvertes.fr/hal-01115222
DOI : 10.1017/S0016756813000927

Éditeur(s) : HAL CCSD Elsevier Elsevier Masson
Résumé : Thalattosuchia was a diverse clade of marine crocodylomorphs known from the Early Jurassic to the Early Cretaceous. Recent studies have hypothesized that their extinction was two-phased: (1) habitat loss near/at the Jurassic-Cretaceous boundary heavily reduced their morphofunctional diversity, particularly in Europe, while (2) climate change and a shift in marine fauna during the Early Cretaceous (either at the Valanginian-Hauterivian boundary or during the early Hauterivian) finished off the already stressed clade. Unfortunately, the Cretaceous fossil record of thalattosuchians is poor, with only one putative “teleosaurid” specimen and approximately ten metriorhynchid specimens. Here we re-describe the youngest known teleosaurid from the Cretaceous (Valanginian of south-eastern France). Originally considered to be a teleosaurid (possibly Steneosaurus), we demonstrate that it belongs to Metriorhynchidae, and a newly discovered subclade, Plesiosuchina. It differs from Plesiosuchus in the pattern of tooth enamel ornamentation and the variation in dentary alveoli size. Referring this specimen to Metriorhynchidae means there are no definitive Cretaceous teleosaurid specimens. Furthermore, it suggests that both durophagous and piscivorous teleosaurids became extinct at the end of the Jurassic. Interestingly, this is the fourth metriorhynchid lineage known to cross the Jurassic-Cretaceous boundary. As such, it would appear that the two thalattosuchian families responded very differently to the lowering sea levels at the end of the Jurassic: teleosaurids possibly became extinct, while metriorhynchids were seemingly unaffected.
ISSN: 0753-3969

hal-01122803
https://hal.archives-ouvertes.fr/hal-01122803
DOI : 10.1016/j.annpal.2014.01.002

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
New outcrops in the Sinis peninsula (Sardinia, Italy) allow a detailed description of the Messinian erosion surface. The correlation between outcrops, industrial seismic data and data collected offshore Oristano from a recent cruise permits reconstruction of the geometry of this surface from presently emerged interfluves to the deep canyons offshore, with: - onshore: an eroded karstic plateau presently cropping out over a 20 km × 5 km area. Well-preserved karst structures occur locally and can form several metres high reliefs. The southernmost edge of the plateau is limited by a cliff. The karstic plateau and the cliff are sealed by transgressive deposits of Pliocene age; - offshore, an interfluve zone with a mostly flat and low-angle dipping plateau, westward dissected by paleovalleys which were identified down to a depth of 2000 m. In the Oristano Gulf, Messinian paleovalleys were also identified. The Capo San Marco paleocliff was probably located on the edge of a canyon. Onshore, only one major erosion surface was identified, located at the top the Messinian sequence. Offshore, this surface extends down to the abyssal plain. The surface was emplaced above deposits related to the Terminal Carbonate Complex. This indicates that the marginal evaporites are older than the major drawdown of the Mediterranean sea-level. The major drawdown is related to the deposition of the deep evaporites.
ISSN: 0037-0738

hal-00407864
https://hal.archives-ouvertes.fr/hal-00407864
DOI : 10.1016/j.sedgeo.2008.06.005

Éditeur(s) : HAL CCSD Borntraeger Science Publishers
Résumé : This study characterizes the stratigraphical context as well as the palaeoenvironmental and sealevel trends during the Late Frasnian and Famennian in the Buschteich section (Thuringia, Germany). An integrated approach combines conodont biostratigraphy, chemostratigraphy based on carbon and oxygen isotopes, conodont biofacies analyses and investigations of the morphotypes of foraminifera that occur in the section was applied. Conodonts provided a fine-scale biostratigraphical framework. All the Famennian conodont biozones were identified, with the exception of the three lowest. The Frasnian – Famennian transition was further identified by a positive carbon isotope excursion. This continuous Famennian record is developed in a condensed limestone succession. The reddish Griotte facies, typical of strata of this period, were not documented. Black shales were not developed except for an interval of dark colored mud rocks corresponding to the Hangenberg event at the top of the section. The carbonate succession of Buschteich was deposited in an outer ramp environment, pelagic organisms are the dominant fauna. This is corroborated by the overall dominance of the deep-water conodont genus Palmatolepis. Microfacies, conodont biofacies and foramini fera indicated a deepening trend from the Lower crepida to the Lower rhomboidea Zone, followed by a shallowing trend from the Upper rhomboidea to the praesulcata Zone. This sequence overall matches the sea level reference curve for Euramerica. The timing of maximum water depth at Buschteich, as well as the general sea-level reference record, differs from the Col des Tribes (Montagne Noire, France). Differential uplift or overprinting of the long-term eustatic changes may be the cause of the discrepancy in the local sea-level records.
ISSN: 0078-0421

hal-01623111
https://hal.archives-ouvertes.fr/hal-01623111
DOI : 10.1127/nos/2016/0318

Éditeur(s) : HAL CCSD Blackwell Publishing
Résumé : International audience
Pliocene and Pleistocene deposits from Grande-Terre (Guadeloupe archipelago, French Lesser Antilles) provide a remarkable example of an isolated carbonate system built in an active margin setting, with sedimentation both controlled by rapid sea-level changes and tectonic movements. Based on new field, sedimentological and palaeontological analyses, these deposits have been organized into four sedimentary sequences (S1 to S4) separated by three subaerial erosion surfaces (SB0, SB1 and SB2). Sequences S1 and S2 ('Calcaires inférieurs à rhodolithes') deposited during the late Zanclean to early Gelasian (planktonic foraminiferal Zones PL2 to PL5) in low subsidence conditions, on a distally steepened ramp dipping eastward. Red algal-rich deposits, which dominate the western part of Grande-Terre, change to planktonic foraminifer-rich deposits eastward. Vertical movements of tens of metres were responsible for the formation of SB0 and SB1. Sequence S3 ('Formation volcano-sédimentaire', 'Calcaires supérieurs à rhodolithes' and 'Calcaires à Agaricia') was deposited during the late Piacenzian to early Calabrian (Zones PL5 to PT1a) on a distally steepened, red algal-dominated ramp that changes upward into a homoclinal, coral-dominated ramp. Deposition of Sequence S3 occurred during a eustatic cycle in quiet tectonic conditions. Its uppermost boundary, the major erosion surface SB2, is related to the Cala1 eustatic sea-level fall. Finally, Sequence S4 ('Calcaires à Acropora') probably formed during the Calabrian, developing as a coral-dominated platform during a eustatic cycle in quiet tectonic conditions. The final emergence of the island could then have occurred in late Calabrian times.
ISSN: 1469-3496

hal-00760906
https://hal.archives-ouvertes.fr/hal-00760906
DOI : 10.1111/j.1365-3091.2011.01311.x

Éditeur(s) : HAL CCSD Elsevier Masson
Résumé : In southern Corsica, three successive Upper Burdigalian coral reef episodes (R1, R2 subdivided into R2A and R2B subunits, and R3) developed within the Cala di Labra Formation. Tabular corals dominated under high water energy and siliciclastic input conditions. The R1 reefs show the highest coral diversity with 16 species described for the first time. A coral impoverishment was recorded in the R2 and R3 reefal episodes. The reefs did not reach a climax growth stage, except the R1 ones. Analogous to North Sardinian reefs, they reflect local vanishing conditions in the Corsican-Sardinian block through Upper Burdigalian because of constant siliciclastic inputs and deepening of the Bonifacio straight.
ISSN: 1631-0713

hal-01054332
https://hal.archives-ouvertes.fr/hal-01054332
DOI : 10.1016/j.crte.2014.02.003

Éditeur(s) : HAL CCSD
Résumé : Présentation orale
Q7
besancon, France

hal-00481847
https://hal.archives-ouvertes.fr/hal-00481847

Éditeur(s) : HAL CCSD Elsevier Masson
Résumé : International audience
Une surface d'émersion majeure (S1) au sein de l'unité récifale Pliocène supérieur à Pléistocène inférieur des « calcaires supérieurs » de Grande-Terre (avant-arc des Petites Antilles) révèle une baisse du niveau marin relatif d'au moins 60 m et permet de définir un nouveau découpage stratigraphique. S1 est surmontée par un cortège transgressif sablo-calcaire, puis par une formation récifale à Acropora. L'ensemble représente l'enregistrement d'un cycle eustatique complet par cette plateforme carbonatée de marge active. La comparaison avec la plate-forme carbonatée de marge stable du banc des Bahamas permet d'estimer que S1 correspond à l'émersion majeure de 1,66 Ma et qu'elle est d'origine glacio-eustatique.
ISSN: 1631-0713

hal-00180663
https://hal.archives-ouvertes.fr/hal-00180663
DOI : 10.1016/j.crte.2005.01.012

Éditeur(s) : HAL CCSD Société géologique de France
Résumé : In the western Mediterranean Sea, the Liguro-Provençal Basin (LPB) is a key area for studying passive margins because of its recent formation and abundance of onshore and offshore data. The Nerthe area located in the northern margin of LPB provides the unique continuous Oligo-Miocene deposits contemporaneous of the transition rifting to drifting. However, the age of the deposits remains debated and the link between outcrops and offshore seismic data is poorly constrained. The purpose of this paper is double. First, we intend to propose a new chronostratigraphic frame based on bio- (planktonic foraminifera, calcareous nannofossils) and magneto-stratigraphy. Second, we aim to make, through the integration of new highly time-resolved seismic data and field works, a coherent onshore-offshore link concretized by a 3D geological model. The new temporal and spatial data presented in this paper allow correlating the Oligo-Miocene sequences, defining their geometry and specifying precisely the timing of syn- and post-rift stages. The first marine transgression is now precisely dated latest Chattian within the syn-rift deposits and appears to be synchronous with the first marine deposits in the offshore wells and other marginal basins. The transition from syn-rift to post-rift appears to last 3.3 Ma at maximum, between 21.8 and 18.5 Ma (late Aquitanian to early Burdigalian). It is underlined by two major erosional unconformities bearing a hiatus of around 1 Ma. The post-rift started with a major marine transgression that is now dated from middle Burdigalian, at around 18.5 Ma, as elsewhere in the LPB. Contrarily to recent proposals, the post-rift deposits are widely represented on the northeastern margin of the "Golfe du Lion". There, the subsidence of the margin was low during the syn-rift and the transitional periods and high during the post-rift. The onset of this high post-rift subsidence appears to be synchronous with the slowdown of the Corsica-Sardinia block (CSb) motion.
EISSN: 1777-5817

hal-00558497
https://hal.archives-ouvertes.fr/hal-00558497
DOI : 10.2113/gssgfbull.181.6.591

Éditeur(s) : HAL CCSD Société géologique de France
Résumé : New radiolarian assemblages of Late Jurassic age were extracted from seven chert localities of the basement comp ex of La Desirade Island (Guadeloupe), the oldest geological unit of the Lesser Antilles arc and the eastern Caribbean region. These fauna range in age from Kimmeridgian or early Tithonian to early or early late Tithonian, showing that La Desirade cherts are not all coeval, contrary to what was established by previous studies. Furthermore, the close spatial association of cherts and volcanic elements composed of basaltic flows and volcaniclastics suggests a mixed setting of hydrothermal siliceous deposits and biogenous sedimentation consistent with an arc-related oceanic setting rather than an ophiolite-type oceanic crust. As the Youngest age is obtained to the northwest of the basement complex where as older data are found to the southeast, it also Suggests that La Desirade basement complex may have undergone some structural stacking consistent with an accretion-type geodynamic getting. Our biochronological data provide a preliminury try tectonic model of an eastward subduction zone for Lesser Antilles arc basement emplacement during the Mesozois.
EISSN: 1777-5817

hal-00445252
https://hal.archives-ouvertes.fr/hal-00445252
DOI : 10.2113/gssgfbull.180.5.399

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Plio-Pleistocene diatomitic sequences in the Shamb paleo-lake (South Armenia, Lesser Caucasus) offer a rare opportunity to give new insights on the paleo-climate of Western Asia. We present an integrated palynological, 40Ar/39Ar geochronologic and magnetostratigraphic study for the most complete section in the sedimentary deposits of the Shamb paleo-lake. 40Ar/39Ar dating of two volcaniclastic layers provided ages of 1.24 ± 0.03 and 1.16 ± 0.02 Ma (2. Magnetostratigraphic data show that the entire Shamb section is of reversed polarity which, combined with 40Ar/39Ar dating, suggests that the entire section correlates with part of the Matuyama period (1.785-1.070 Ma). Pollen assemblages and macroremains diversity clearly show an alternation of glacial and interglacial phases. Age calibrations and accumulation rate extrapolation allow a direct correlation of climate changes with the global isotopic curve, and show that the Shamb section probably ranges from approximately 1.300 to 1.080 Ma (marine isotopic stages 40 to 31). The vegetation of the Lesser Caucasus developed in a mosaic pattern in a Pleistocene continental, mostly arid climate, comparable to the present-day climate. The observed vegetation changes record a dominant climate response to the obliquity orbital parameter, but the influence of precession could not be established from the Shamb data. Pollen and macroflora both indicate that glacial periods were cold and dry and that interglacials were warm with local humidity. The early Pleistocene climatic model for Western Asia is thus similar to the climatic model for the Mediterranean area.
ISSN: 0012-821X

hal-00470353
https://hal.archives-ouvertes.fr/hal-00470353
DOI : 10.1016/j.epsl.2010.01.007

Éditeur(s) : HAL CCSD Museum National d'Histoire Naturelle Paris
Résumé : Au Burdigalien supérieur, des récifs coralliens se sont développés dans la Formation de Cala di Labra, aux alentours de Bonifacio (Corse-du-Sud, France). Ils sont organisés en trois épisodes successifs R1, R2 et R3. La faune corallienne comprenant 16 espèces récifales, est décrite pour la première fois. Deux associations coralliennes sont distinguées. Les principaux genres constructeurs sont Porites Link, 1807, Tarbellastraea Alloiteau, 1950 et Thegioastraea Sismonda, 1871. La diversité corallienne est maximale avec 15 espèces (8 genres) dans l'épisode R1, puis réduite (4 espèces appartenant à 3 genres) pour l'épisode R2, l'épisode R3 renfermant des coraux mal préservés pour être identifiés. Les formes de croissance sont en grande majorité massives étalées et superposées, associées à des conditions paléoenvironnementales de haute à moyenne énergie (rides de courant, bioclastes usés, peu de formes branchues), sous apports terrigènes réguliers. Les récifs, pour la plupart frangeants et à zonation récifale discrète, se sont développés en domaine de plate-forme peu profonde. Cette étude reprend également toutes les citations d'espèces dans la littérature pour cette région et replace ces épisodes coralliens remarquables dans l'évolution plus générale du Bassin Liguro-Provençal.
ISSN: 1280-9659

hal-01236095
https://hal.archives-ouvertes.fr/hal-01236095
DOI : 10.5252/g2015n3a5

Éditeur(s) : HAL CCSD Elsevier Masson
Résumé : International audience
Late Jurassic coral reefs are present in the Western High Atlas of Morocco along the eastern paleomargin of the young Atlantic Ocean. The Izwarn section shows two reef units made of scleractinian corals and microbialites, included in a progradational shallowing-upward succession. Changes in reefal composition and structure observed in a ca. 50 cm-thick interval at the base of the reef unit 1 are interpreted to represent the first well-documented ecological succession in Late Jurassic reefs. Bioclastic deposits, sparse and poorly diversified corals (five genera) preserved in life position, and finally a more diversified coral assemblage (11 genera) building a reef framework with stromatolitic crusts reflect pioneer, colonization and diversification stages, respectively. A specific depth window, where light was reduced but sufficient for a catch-up growth mode and below the erosive action of waves, probably at the lower slope of a fore-reef area, has made possible the development and the record of this ecological succession. With a more diversified coral assemblage (16 genera), the reef unit 2 reflects shallower and well-agitated waters of a fore-reef area. Overlaying this second reef unit, the upper part of the section reveals back-reef deposits made of reworked reef elements, whereas a putative reef crest area is not recorded.
ISSN: 0016-6995

hal-00795549
https://hal.archives-ouvertes.fr/hal-00795549
DOI : 10.1016/j.geobios.2012.05.002

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The marine Messinian deposits of Tunisia cover a narrow littoral strip some 300 km long between the northern Bizerte and Cap Bon areas and the central-eastern Sahel region. Litho- and biofacies analysis of six stratigraphic sections reveals the distinctive features of these deposits.;The lower Messinian deposits are characterized by ubiquitous siliciclastics and abundant oolitic/bioclastic limestones organized in an eastward facing ramp. Westward (landward), this ramp changes into coastal lagoons, sometimes containing evaporites. Eastward, the ramp passes to the reefal Pelagian Platform extending as far as Lampedusa.;Two main sedimentary cycles are distinguished: 1) an early Messinian siliciclastic retrogradational then oolitic/bioclastic progradational cycle (Beni Khiar Formation and lower Oued bel Khedim Formation): 2) a late Messinian brackish to continental cycle that probably accumulated in rapidly subsiding lagoons (Cued el Bir Formation and upper Oued bel Khedim Formation). The Tunisian early Messinian cycle is partly eustatically controlled, but the late Messinian cycle cannot be confidently correlated to other well-known Messinian series because of tectonic movements.;The lower Messinian deposits of Tunisia are also characterized by abundant suspension-feeding organisms (molluscs and bryozoans) and rare corals, calcareous algae, echinoids, and larger benthic foraminifers. The proposed palaeoenvironmental model shows that the lower Messinian ramp of Tunisia was located on a current-protected margin and subjected to continent-derived sediment and nutrient supply. Eastward, nutrient influx diminished and a shallow-water isolated carbonate platform with coralgal facies developed between the western and the eastern Mediterranean basins. The main hydrological connection between these two basins occurred through a narrow seaway situated to the northeast of the Pelagian Platform, south of Sicily and Malta.
ISSN: 0031-0182

hal-00475583
https://hal.archives-ouvertes.fr/hal-00475583
DOI : 10.1016/j.palaeo.2009.10.028

Éditeur(s) : HAL CCSD Blackwell Publishing
Résumé : International audience
The study of eight stratigraphic sections at the margin of the semi-enclosed Zsambek Basin (Hungary) allows the sedimentary anatomy of oolitic-bioclastic systems in the Sarmatian of the Central Paratethys to be reconstructed. The mollusc, foraminiferal and ostracod associations indicate that the carbonate systems are Latest Badenian to Late Sarmatian in age. The Lower-Upper Sarmatian deposits are organized in superimposed subaqueous dunes prograding towards the basin on a low-angle ramp. During the Late Sarmatian, the ramp underwent subaerial erosion linked to a moderate relative fall in sea-level. Lagoonal deposits were later formed and microbial-nubeculariid-bryozoan-serpulid buildups were emplaced. The 'abnormal' marine conditions of the Sarmatian, conducive to the development of a poorly diversified flora and fauna and dominant non-skeletal grains, are linked to fluctuating salinities, mesotrophic to eutrophic conditions and perhaps high alkalinity.
ISSN: 1469-3496

hal-00429337
https://hal.archives-ouvertes.fr/hal-00429337
DOI : 10.1111/j.1365-3091.2009.01055.x

Éditeur(s) : HAL CCSD Cambridge University Press (CUP)
Résumé : International audience
The Ben Zireg anticline NW of Bechar yields the currently most-important Frasnian succession on the northern margin of the Algerian Sahara. It represents 26.5 m of calcilutites which are attributed to the middle–late Frasnian. As the early Frasnian is not represented, the succession rests conformably on undifferentiated, probably late Givetian, substrate. Fine-scaled conodont biostratigraphy reveals a continuous sequence of Montagne Noire Zones 5–13, superseded by the earliest Famennian Lower triangularis Zone. The deposits are organized into 15 sedimentary cycles that are initially condensed and become dilated upwards. Conodont biofacies indicate an overall deepening towards the top of the section with an episode of slight shallowing at the MN11/12 transition marked by an increase of ancyrodellids, which is also seen in the Marhouma section of the Ougarta region (SW Algeria). Homogeneous calcareous microfacies with only a few shaly intercalations determine a predominantly oxygenated depositional environment on an outer platform, submarine rise or ramp setting. This is also indicated by relatively low sedimentation rates which are similar in selected sections from the Tafilalt platform, and contrast with those from the Marhouma trough and the Maider basin. Unlike other Frasnian successions south of the Atlas Fault, but similar to the Moroccan Meseta, the Upper Kellwasser horizon is clearly discriminated at Ben Zireg by an outstanding occurrence of black shales on top of the oxygenated latest Frasnian deposits.
ISSN: 0016-7568

hal-01217151
https://hal.archives-ouvertes.fr/hal-01217151
DOI : 10.1017/S0016756814000715

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The chronostratigraphy of the lower Miocene deposits of northwestern Sardinia is refined in the Castelsardo Basin. The combination of new 40Ar/39Ar isotopic datings, 19 micropalaeontological datings (calcareous nannofossils, planktonic and large benthic foraminifers) and 16 palaeomagnetic polarity measurements led to a new chronostratigraphic framework. The continental deposits of the first megasequence (Valledoria and Casteldoria members) are possibly Aquitanian. The overlying marine sediments are early Burdigalian (Vaginella depressa Molasse). The marine transgression can be dated to around 19.7 Ma. Marine conditions ceased 18.83 ± 0.13 Ma, the age of the index aerial τ2 ignimbrite. The continental part of the second megasequence (“Lacustre” unit) is early–middle Burdigalian, between 18.8 and 18 Ma. The overlying marine part (Campulandu and Sedini members) is middle–late Burdigalian. The second marine transgression began in the earliest–late Burdigalian, during the Chron C5Dr reversal, at the time of the eustatic Bur 4 event. The Castelsardo basin went through two main extensional tectonic episodes. The first one occurred as the Valledoria Member was deposited and possibly dates back to the Aquitanian. The second one occurred as the uppermost part of the Vaginella depressa Molasse was deposited during the early Burdigalian. The second extensional episode is related to a rapid rotation of Sardinia. Palaeomagnetic results confirm that Corsica and Sardinia acted as a single block which suffered a 28 ± 17° ccw rotation after 19.2 Ma. The Castelsardo basin is held to be an Aquitanian–early Burdigalian intra-arc rift basin that later evolved in a thermally controlled subsident margin of the Ligurian-Provençal Basin during the middle–late Burdigalian.
ISSN: 0031-0182

hal-00498288
https://hal.archives-ouvertes.fr/hal-00498288
DOI : 10.1016/j.palaeo.2010.06.007

Éditeur(s) : HAL CCSD
Résumé : Présentation orale
Recherches sur les Paléoenvironnements arméniens Maison de l'Orient et de la Méditerranée (MOM)
Lyon, France

hal-00481907
https://hal.archives-ouvertes.fr/hal-00481907

Éditeur(s) : HAL CCSD Cambridge University Press (CUP)
Résumé : International audience
Diverse, abundant and usually well-preserved communities of skeletal organisms occur in the lower Pleistocene (Gelasian) siliciclastic deposits of the Greek island of Rhodes. Benthic foraminifers, molluscs and bryozoans have been studied in four measured and sampled sections located in the northern part of the island. Among these bottom-dwelling organisms, numerous extant taxa are good environmental indicators and, combined with field observations and sedimentological data, they provide information on the probable conditions in which they developed. The siliciclastic deposits of the Kritika Formation have been divided into 14 different bio- and lithofacies, which have been further grouped into four facies associations corresponding to four different environmental settings: (1) continental to fluviatile; (2) brackish-water (lagoonal/deltaic); (3) infralittoral (0–20 m); and (4) upper circalittoral (depths of 20–40 m, but also down to c. 50–60 m). Among the marine facies associations, several characteristic biocoenoses have been recognized: soft-bottoms (fine to coarse sands and gravels); seagrass meadows; biogenic calcareous crusts on drowned beachrock slabs; red algal rhodoliths; and bivalve shell beds. In the studied sections, 13 superimposed genetic sequences have been documented. The repetition of similar facies associations within each sequence suggests: (1) a possibly eustasy-controlled, cyclic sedimentation; (2) a general subsidence of Rhodes during the deposition of the studied facies associations; and (3) a mostly constant range of environmental conditions (i.e. sedimentation rates and temperature) throughout the Gelasian.
ISSN: 0016-7568

hal-01277829
https://hal.archives-ouvertes.fr/hal-01277829
DOI : 10.1017/S0016756815000230

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The coastal sediments of Rhodes in the eastern Mediterranean have recorded transgression-regression cycles that took place during the early Pleistocene. The sedimentary deposits from the Kritika Member of the Rhodes Formation consist in conglomerates, sandstones, siltstones and clays deposited in brackish to shallow marine environments. Faunal associations are dominated by molluscs and reveal rapid ecological changes. Carbon and oxygen isotope ratios of aquatic skeletal carbonates show that these ecological changes were most likely driven by large salinity changes while water temperature remained rather constant at about 22.0 ± 1.5 °C. The tectonic activity of the island rather than glacio-eustatic variations of climatic origin is advocated to be responsible for the ecological and salinity changes and sea-level variations recorded in the sedimentary sequence.
ISSN: 0031-0182

hal-00767568
https://hal.archives-ouvertes.fr/hal-00767568
DOI : 10.1016/j.palaeo.2012.06.009