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Martin, Jean-Paul Saint, Merle, Didier, Martin, Simona Saint (2022): The Sarmatian (middle Miocene) "petrified forest" of Gramada (NW Bulgaria): role of the calcareous crusts. Geodiversitas 44 (29): 911-932, DOI: 10.5252/geodiversitas2022v44a29

International audience; The presence of “geological” amber (or “succin” in old French monographs) has been reported for several centuries in the Mesozoic deposits of Provence, southeastern France. Diverse amber-bearing sites were inventoried by the authors but their location and stratigraphical context remain unclear for most of them. In the past decades, various data concerning chemistry, palaeontological content and comparison with archaeological discoveries improved our knowledge of the ambers of Provence, but only those of Cretaceous age. The present paper aims at providing a comprehensive description of all the presently known amber-bearing deposits of Provence, including the description of new sites. We highlight the great potential of Provence ambers and allow to consider a wider time range, from the Early Cretaceous to the Miocene.; La présence d’ambre « géologique » ou « succin » a été signalée en Provence depuis plusieurs siècles. Un certain nombre de gisements ambrifères crétacés, plus ou moins bien localisés précisément, avaient été ainsi répertoriés. Plus récemment des données variées concernant la chimie, le contenu paléontologique, la comparaison avec des ambres archéologiques ont amené à mieux connaître les ambres, uniquement d’âge crétacé, de la région. La présente revue des gisements ambrifères de Provence, incluant la découverte de nouveaux sites ambrifères, permet de mettre en évidence le potentiel en ambre de la Provence et d’envisager un large éventail de temps jusqu’à présent inenvisagé allant du Crétacé inférieur au Miocène.

International audience; The Upper Cretaceous sedimentary succession cropping out in the Sainte-Baume Massif (Var, southeastern France) is of late Turonian to Campanian age. There, complex imbrication and rapid evolution in space and time of shallow-marine, fluvio-deltaic and lacustrine environments at the front of the North Provence Durancian uplift occur during the Santonian. Marly and/or sandy strata rich in lignite remains and amber grains are interspersed throughout the Santonian series. According to new in situ collections, the features of the amber grains, and their micro-inclusions, are similar to those found in well-known amber-bearing sites from the Bouches-du-Rhône department. This testifies of a widespread resin-producing tree forests in southeastern France at that time.; Les couches du Crétacé Supérieur du massif de la Sainte-Baume (Var, sud de la France) s’échelonnent entre le Turonien Supérieur et le Campanien. Dans cette région, les dépôts du Santonien montrent une imbrication complexe, et une évolution spatio-temporelle rapide, des environnements de mers peu profondes, fluvio-deltaïque et lacustres résultant du bombement Durancien Nord Provençal. Des niveaux marneux ou sableux à débris ligniteux et grains d’ambre sont présents sur toute l’épaisseur de la série santonienne. Nos récentes découvertes in situ montrent que les caractéristiques des grains d’ambre collectés, et leurs micro-inclusions, sont similaires à ceux trouvés dans les sites ambriféres connus des Bouches-du-Rhône. Ces résultats témoignent de la présence d’un environnement de forêts résinifères dans le Sud-Est de la France pendant le Santonien.

International audience; In memory to Gérard BretonWe wish to dedicate this special issue devoted to amber to the memory of our recently deceased colleague Gérard Breton. Associate professor in Natural Sciences, doctor of state “ès-science”, Gérard Breton first taught in secondary schools and then served for 32 years as director of the Museum of Natural History of Le Havre (1973–2005). As a true naturalist animated by a constant scientific curiosity, Gérard Breton, tackled many study themes in the field of paleontology. More particularly, its contribution to the knowledge of micro-inclusions of amber for over the past twenty years has been constant and rich in information and concepts. Following a few authors who have described and figured microorganisms contained in amber (e.g. Poinar, 1977, 1992; 1994; Waggoner, 1993, 1994; Poinar et al., 1993a, 1993b; Dörfelt and Schäfer, 1998; Schönborn et al., 1999), he was the first to tackle the difficult exercise of identifying these micro-inclusions in French ambers. In a first work, he thus mentioned the microflora contained in amber of Sparnacian age in the South of France (Breton et al., 1999). Aware of the difficulty of directly assimilating micro-inclusions to current microorganisms determined today on genomic bases, he developed a comparative taxonomy essentially based on morphology (Breton, 2010). He is the author of numerous new taxa of actinomycetes, bacteria, cyanobacteria and filamentous fungi (Breton and Tostain, 2005; Breton, 2010, 2012; Breton et al., 2013, 2014). From a taphonomic point of view, he first favored the trapping process, especially on the surface of resin flows, to explain the presence of real microbial mats (Breton and Tostain, 2005; Breton, 2007), then he integrated subsequently the colonization process by networks of centripetal growth microorganisms in the resin (Breton, 2010, 2011, 2012, Breton et al., 2013, 2014, 2018). Consequently, he considered the resin as a real culture medium (Breton, 2011). Thanks to his knowledge of amber microorganisms, he has also been able to provide his expertise and collaborate in numerous works (Girard et al., 2008, 2009a, 2009b; 2011; 2013; Adl et al., 2011; Néraudeau et al., 2020).; À la mémoire de Gérard BretonNous avons souhaité dédier ce numéro spécial consacré à l’ambre à la mémoire de notre collègue Gérard Breton récemment décédé. Titulaire de l’agrégation en Sciences Naturelles, docteur d’État es-sciences Gérard Breton a d’abord enseigné dans des établissements d’enseignement secondaire puis a exercé pendant 32 ans les fonctions de directeur du Muséum d’histoire naturelle du Havre (1973–2005). En véritable naturaliste animé d’une constante curiosité scientifique, Gérard Breton, a abordé de nombreux thèmes d’études dans le domaine de la paléontologie. Plus particulièrement, son apport pour la connaissance des micro-inclusions de l’ambre depuis un peu plus d’une vingtaine d’années a été constant et riche en informations et concepts. À la suite des auteurs qui ont décrit et figuré des microorganismes contenus dans des ambres d’âge et provenances variées (e.g. Poinar, 1977, 1992; 1994 ; Waggoner, 1993, 1994 ; Poinar et al., 1993a, 1993b ; Dörfelt and Schäfer, 1998 ; Schönborn et al., 1999), il a été le premier à aborder le difficile exercice d’identification de ces micro-inclusions dans les ambres de France. Il a ainsi évoqué dans un premier travail la microflore contenue dans l’ambre d’âge sparnacien du Sud de la France (Breton et al., 1999). Conscient de la difficulté d’assimiler directement les micro-inclusions à des microorganismes actuels déterminés aujourd’hui sur des bases génomiques, il a développé une taxonomie comparative essentiellement basée sur la morphologie (Breton, 2010). Il est ainsi l’auteur de nombreux nouveaux taxons d’actinomycètes, de bactéries, de cyanobactéries et de champignons filamenteux (Breton and Tostain, 2005 ; Breton, 2010, 2012 ; Breton et al., 2013, 2014). Du point de vue taphonomique, il a d’abord plutôt privilégié le processus de piégeage, surtout en surface des coulées de résine, pour expliquer la présence de véritables feutrages microbiens (Breton and Tostain, 2005 ; Breton, 2007), puis il a intégré par la suite le processus de colonisation par des réseaux de microorganismes à croissance centripète dans la résine (Breton, 2010, 2011, 2012 ; Breton et al., 2013, 2014, 2018). En conséquence il a considéré la résine comme un véritable milieu de culture (Breton, 2011). De par sa connaissance des microorganismes de l’ambre il a pu également apporter son expertise et collaborer à de nombreux travaux (Girard et al., 2008, 2009a, 2009b, 2011, 2013 ; Adl et al., 2011 ; Néraudeau et al., 2020).

International audience; The origin of the diatoms still remains enigmatic. Their fossil record is scarce until the Late Cretaceous and great divergences exist between molecular data and the earliest fossil evidence. While molecular data indicate an origin during the Triassic or Early Jurassic, early fossil evidence is only from the Late Jurassic-Early Cretaceous. The discovery of diatoms in French mid-Cretaceous amber by the end of the 2000s already suggested a potential bias in the diatom fossil record as it made older many diatom lineages, the record of which hitherto began at the end of the Cretaceous. The Jurassic/Early Cretaceous fossil record of diatoms is extremely sparse and any new occurrence is important for retracing the evolutionary, palaeogeographical and palaeoenvironmental history of diatoms. Thai amber has yielded a new diatom specimen that has been attributed to the genus Hemiaulus . Fossil assemblages and sedimentological data indicate that Thai amber and its Hemiaulus specimen are Late Jurassic in age. This discovery represents the oldest hitherto known specimen of Hemiaulus and so extends the fossil record of the bipolar diatoms and of the genus Hemiaulus by several dozens of millions of years and brings closer the fossil evidence and molecular data (that estimated an origin of the bipolar diatoms about 150 Ma ago). It reinforces the hypothesis of a pre-Cretaceous fossil diatom records and also supports an origin of the diatoms in shallow coastal environments.; L’origine des diatomées reste toujours énigmatique. Leur registre fossile est rare jusqu’au Crétacé supérieur et il existe de grandes différences entre les données moléculaires et les premières évidences fossiles du groupe. Tandis que les données moléculaires indiquent une origine durant le Trias ou le Jurassique inférieur, les plus anciennes traces fossiles sont seulement de la fin du Jurassique, début du Crétacé. La découverte de diatomées dans l’ambre médio-crétacé français à la fin des années 2000 avait déjà suggéré un potentiel biais dans le registre fossile des diatomées car cela vieillissait plusieurs lignées précédemment connues uniquement à partir du Crétacé supérieur. Le registre fossile des diatomées du Jurassique et du Crétacé inférieur est extrêmement limité et toute nouvelle occurrence est importante pour retracer l’histoire évolutive, paléogéographique et paléoenvironnementale des diatomées. L’ambre de Thaïlande a permis la découverte d’un nouveau spécimen de diatomée attribué au genre Hemiaulus . Les données paléontologiques et sédimentologiques attestent que l’ambre thaïlandais et la diatomée qu’il contient sont d’âge Jurassique supérieur. Cette découverte représente le plus ancien spécimen du genre Hemiaulus connu à présent et étend donc le registre fossile des diatomées bipolaires et du genre Hemiaulus de plusieurs dizaines de millions d’années et rapproche ainsi le registre fossile des données moléculaires (qui estimaient l’origine des diatomées bipolaires à environ 150 millions d’années). Cela renforce l’hypothèse d’un registre fossile pré-crétacé et soutient une origine des diatomées au sein d’environnements marins néritiques.

International audience; A large number of fossil-rich beds have been located from over 30 km along the Tours-Poitiers High Speed Line (LGV) during earthworks prior to its construction, and in particular amber was collected from Scorbé-Clairvaux (locality of La Bergeonneau) to the north of Poitiers. The paper describes also amber pieces from Châtellerault (locality of La Désirée) discovered during the development of sewage treatment plant along the Vienne river. Lower Cenomanian shelly sandstones and siltstones of Scorbé-Clairvaux contain rare amber pieces associated with seed plants ( Frenelopsis sp., Nehvizdya sp., and angiosperm seeds) and a diversified fauna, composed of micro-remains of 27 taxa, comprising elasmobranchs ( Haimirichia amonensis Cappetta and Case, 1975, Protolama sp. and Squalicorax sp.), actinopterygians ( Enchodus sp. and Pycnodontidae), reptiles including vertebrae the marine snake Simoliophis rochebrunei Sauvage, 1880, some rare helochelydrid plates ( cf. Plastremys ), teeth of three crocodilian families (Atoposauridae, Goniopholididae and Bernissartiidae) and an undetermined dinosaurian long bone fragment.; Un grand nombre de niveaux riches en fossiles a été trouvé sur plus de 30 km le long de la Ligne à Grande Vitesse (LGV) Tours-Poitiers pendant les terrassements préalables à sa construction, et en particulier de l’ambre sur le site de la Bergeonneau à Scorbé-Clairvaux au nord de Poitiers. De l’ambre a également été collecté sur les bords de la Vienne au lieu-dit de La Désirée à Châtellerault lors de travaux d’aménagement d’une station d’épuration. Les grès coquillers et les roches argileuses du Cénomanien inférieur de Scorbé-Clairvaux contiennent de rares morceaux d’ambre associés à des méso-fossiles de plantes à graines ( Frenelopsis sp., Nehvizdya sp. et des graines) et 27 taxons micro-fossiles de vertébrés, dont des élasmobranches (en particulier Haimirichia amonensis Cappetta et Case, 1975, Protolama sp. et Squalicorax sp), des actinoptérygiens ( Enchodus sp. et Pycnodontidae), des reptiles incluant des vertèbres du serpent marin Simoliophis rochebrunei Sauvage, 1880, quelques rares plaques d’une tortue helochelydridée ( cf. Plastremys) , des dents de trois familles de crocodiliens (Atoposauridae, Goniopholididae et Bernissartiidae) ainsi qu’un fragment d’os long de dinosaurien indéterminé.

Ediacaran fossils are now largely known in different parts of the world. However, some countries are poorly documented on these remains. Thus, rare fossils from the Neoproterozoic Histria Formation of central Dobrogea (Romania) have been reported. Two specimens with discoid imprints are described here in detail and assigned to the typical Ediacaran species Beltanelliformis brunsae Menner in Keller, Menner, Stepanov & Chumakov, 1974. This palaeontological development confirms both the large geographical distribution of this species and the Ediacaran age of the Histria Formation.

International audience; A new Cenomanian amber- and plant-bearing deposit has been discovered at Neau, in the Mayenne department (France). The Cenomanian fossiliferous lignites are located in karst filling in a substratum of Cambrian limestones. The amber corresponds mainly to tiny millimetric grains, devoid of arthropod inclusions, but rich in microorganisms, especially the sheated bacteria Leptotrichites resinatus , and containing pollen grains ( Classopollis ) and wood fibers (Araucariacae or Cheirolepidiaceae). The lignites provide abundant conifer and ginkgoale cuticle fragments ( Frenelopsis , Eretmophyllum ) and a lot of palynomorphs ( e.g. Gleicheniidites senonicu s, Cyathidites , Deltoidospora , Appendicisporites and Cicatricosisporites ). The chemical signature of the amber suggests it was produced by conifers of the extinct family Cheirolepidiaceae. According to the palynological assemblage, the age of the lignites is upper lower Cenomanian or lower mid Cenomanian. The deposit environment corresponded to the upstream portion of a mangrove or the most inner part of a lagoon.; Un nouveau site à ambre et plantes du Cénomanien a été découvert à Neau, en Mayenne (France). Les lignites fossilifères cénomaniens sont localisés dans des remplissages de karsts développés dans des calcaires du Cambrien. L’ambre se présente essentiellement sous forme de grains millimétriques, dépouvus d’inclusions d’arthropode, mais riches en microorganismes, notamment en bactéries gainées de type Leptotrichites resinatus , et contenant des grains de pollen ( Classopollis ) et des fibres de bois (Araucariacae ou Cheirolepidiaceae). Les lignites fournissent d’abondants fragments de cuticules de conifères et de ginkgoales ( Frenelopsis , Eretmophyllum ) et une grande quantité de palynomorphes ( e.g. Gleicheniidites senonicu s, Cyathidites , Deltoidospora , Appendicisporites et Cicatricosisporites ). La signature chimique de l’ambre suggère qu’il a été produit par des conifères de la famille éteinte des Cheirolépidiacées. D’après l’assemblage palynologique, l’âge des lignites est Cénomanien inférieur tardif ou Cénomanien moyen basal. L’environnement de dépôt correspondait à la partie amont d’une mangrove ou la partie la plus interne d’un lagon.

International audience; Body fossils are described for the first time from the Upper Brioverian (Ediacaran-Fortunian) deposits of Central Brittany (NW France). The material consists of a dozen of specimens preserved on two slates, recently collected in a quarry in Saint-Gonlay. The fossils, centimetric in size, have an elliptical and acuminated outline, with a peripheral bulge but without conspicuous concentric or radial lines. These body fossils are preserved in slates that are locally rich in grazing traces, sometimes associated with microbial mats. The sedimentological characteristics of these deposits correspond to a shallow marine shelf environment, with a low to moderate hydrodynamism. Such findings, in concomitance with previous ichnological discoveries, unravel the potential of the Brioverian strata from Brittany as a new locality to provide answers on Ediacaran and early Cambrian biocenoses.

Le gisement de Lapugiu de Sus (Sud-Ouest de la Roumanie) est renomme pour la richesse et la diversite de la faune preservee dans les couches argilo-sableuses du Langhien (Miocene moyen). La faune corallienne y est egalement bien representee. Sur la base des travaux realises depuis le 19eme siecle et de recentes recoltes de materiel, une revision en est proposee. Elle permet d'etablir une liste d'environ 65 especes dont 22 sont nouvellement signalees. Le cadre environnemental est discute. L'exceptionnelle biodiversite corallienne du gisement, unique pour la Paratethys, est replacee dans son cadre paleoclimatique et paleogeographique.

Cretaceous ambers from different localities often contain abundant filamentous microorganisms that extend from the surface of the lumps of amber towards their center. These microfossils have been interpreted in the past as sheathed bacteria, cyanobacteria, and fungal hyphae, respectively. Here, we applied various techniques such as optical microscopy, confocal microscopy, and SEM to constrain the actual nature of these microorganisms. We evaluate published views and new evidence and conclude that the observed morphological and ultrastructural features correspond to sheathed bacteria. We propose a scenario explaining the observed differential preservations as various stages of the sheath construction around the bacterial filaments growing in the resin and the consequences of the transformation of the resin to amber. We suggest an abundant occurrence of at least one extinct resinicolous Leptothrix -like taxon in the Cretaceous Period.

International audience; Marine microorganisms trapped in amber are extremely rare in the fossil record, but are a very unexpectedoccurrence. Several different scenarios have been proposed to explain how these marine inclusions can becometrapped in a resin of terrestrial origin. The marine inclusions reported to date originate from very few pieces ofCretaceous amber from France, and a coastal setting for the amber source forests is generally proposed.However, there are conflicting suggestions about the conditions required for the marine inclusions to becomeentrapped in amber. These include: through high tides, directly blown in by the wind or from sea spray, orstorms and flooding of the littoral/estuarine forest floor or mangroves where the resin dropped into the seatrapping marine organisms. We tested the wind-blown and sea spray suggestions using a modern highly resinouscoastal forest domnated by Araucaria columnaris in New Caledonia as a model for the Cretaceous amberdeposits from France. We exposed fresh resin surfaces on the seaward side of the trees and collected older in situresins, and then examined them both. Marine microorganisms did become trapped on the freshly exposed resin,along with remnants from terrestrial organisms, and salt crystals. We suggest that for cases where only one ortwo marine inclusions are discovered in a deposit, an aeolian origin is most likely; however, a more energetic butpossibly still aeolian event is likely to be needed to be able to embed the high numbers of marine organismsrecorded from only two pieces of amber.

International audience; The Upper Cretaceous lignite deposits of La Garnache, Vendée (western France), consist of two lignitic clay series, Garnache 1 and Garnache 2, separated by a fault. The first series cropped out to the south of the fault during road works until 2002 but is now covered by an embankment. It has provided numerous pieces of amber containing arthropod and microorganism inclusions. The second lignitic series, exposed to the north of the fault, is rich in fossil wood but devoid of amber. Palynological analysis of Garnache 1 revealed several Normapolles species belonging to the genera Atlantopollis, Complexiopollis, Osculapollis, Plicapollis and Trudopollis, but larger forms typical of Senonian deposits are absent. By contrast, Garnache 2 proved to be dominated taxonomically and numerically by spores (Appendicisporites, Camarozonosporites, Gleicheniidites, Patellasporites, Stereisporites), associated with a few gymnosperm (Cerebropollenites, Phyllocladidites, Classopollis) and angiosperm (Liliacidites, Retitricolpites and a single specimen of the Normapolles Complexiopollis) taxa. Garnache 1 is, therefore, younger than Garnache 2, the latter being clearly Cenomanian in age whereas Garnache 1 is more likely to be Turonian. Lignitic clay of Garnache 1 contains numerous translucent, orange to red, pieces of amber. Vendean amber is rich in aquatic arthropods, such as tanaids and epicarideans (Crustacea), as well as marine or brackish siliceous microorganisms such as diatoms and sponge spicules. These aquatic inclusions indicate that resin-producing trees grew along and close to the seashore. The amber-bearing clay was deposited in a calm, estuarine or lagoonal, muddy environment.

Late Albian amber from Charente-Maritime (southwestern France) contains the first known marine diatoms preserved in a fossil resin. Approximately 70 inclusions were assignable to the genera Basilicostephanus, Coscinodiscus, Hemiaulus, Melosira, Paralia, Skeletonema, Stephanopyxis, Trochosira, ?Aulacoseira, and to the order Rhizosoleniales. Some of them are represented by several species. This diatom assemblage is mainly composed of colonial planktonic genera, which are typical for coastal shallow waters. The newly found amber inclusions extend the fossil record of four genera and one order from the Late Cretaceous and support certain molecular phylogenetic assumptions regarding the diversifi cation of marine diatoms in the Early Cretaceous. The unusual introduction of diatom shells from the beach or sea by wind, spray, or high tide onto the resin fl ows was possible because the amber forest grew close to the seashore.

Resume Le Messinien represente une des periodes de forte accumulation de silice biogenique dans le monde et plus particulierement en Mediterranee, ou il est marque par une importante sedimentation diatomitique. Dans le bassin de Boudinar (Maroc nord-oriental, Mediterranee occidentale), la coupe de Sidi Haj Youssef, localisee au pied du volcan de Ras Tarf, presente sur environ 100 m d’epaisseur une serie argilo-marneuse dans laquelle s’intercalent douze niveaux diatomitiques de puissance variable. Effectuee pour la premiere fois en detail, l’etude microfloristique de diatomees, portant sur 86 echantillons, a permis de reconnaitre 50 genres de diatomees (24 des centriques et 26 des pennees) representes par 185 especes (75 especes des centriques et 110 especes des pennees). Pour chaque echantillon un comptage de 400 individus a ete effectue permettant de determiner la frequence relative de chaque taxon au sein de l’assemblage de diatomees. Ainsi, plusieurs assemblages ont ete definis par la dominance des especes suivantes : Coscinodiscus marginatus, Actinoptychus senarius, Thalassionema nitzschioides, Actinocyclus curvatulus, Thalassiothrix longissima, Rhizosolenia styliformis et Actinocyclus ehrenbergii. Ces assemblages temoignent d’un milieu marin littoral en communication avec la mer ouverte. L’abondance des especes d’eaux froides vers la base et le sommet de la coupe traduit de larges echanges du bassin avec l’ocean atlantique au Messinien. La dominance des taxons comme Thalassionema nitzschioides et/ou Thalassiothrix longissima indique des periodes de forte productivite pouvant etre reliee au fonctionnement d’upwellings.

Middle Eocene siliceous bioaccumulation on Demerara Rise is explored using taphonomic and palaeoecological studies of radiolaria and diatoms, respectively. Enrichment and improved preservation of silica began just above the Lower to Middle Eocene transition (ca. 49 Ma) and was mainly due to radiolarian productivity. It reflects a profound change in the zooplankton communities of the western Equatorial Atlantic, dominated previously by planktic foraminifera. Diatoms are a minor siliceous component of the Middle Eocene chalk. This microflora is dominated by robust planktic species, typical of neritic environments, and includes some upwelling indicators. Benthic species are absent. No continental taxa were recorded. Onset of biogenic silica accumulation was probably due to the establishment of a vigorous bottom current circulation and higher levels of productivity. It coincides with a major palaeoceanographic shift from a Lower Eocene stagnant to a more vigorous Middle Eocene ocean, following some as yet poorly understood global climatic change.

The first prograding bioclastic bodies of the Messinian carbonate platform from Melilla-Nador (Morocco) contain numerous feeding tubes of Vermetidae (Petaloconchus) shells. This accumulation results from dense littoral settlements of vermetids, sometimes preserved in place in the higher part of the system, having produced during their life several tubes in a short duration, probably under repeated stressing environmental conditions. The progradation of the system allows, under constant sea level, the continuity of the process. This original construction–cutting–accumulation phenomenon could be related to the fluctuations of the palaeoproductivity characterizing this period

The occurrence of fossil fishes in the Messinian diatomites of Gavdos Island (Greece) was recently observed. This fish fauna is dominated by the Myctophids, which constitute more than two thirds of the collected material. Among them, Myctophum (s. l.) licatae (Sauvage) is by far the most abundant, with more than 50% of the specimens. Although the mesopelagic components are overwhelmingly dominant, epipelagic fishes, like Syngnathus cf. albyi Sauvage, are also present. The composition of this fish fauna is indicative of a sedimentation influenced by the action of upwelling currents, an interpretation that is also suggested by the composition of the diatom flora. Pour citer cet article : J. Gaudant et al., C. R. Palevol 5 (2006) .

Resume Dans le bassin de Melilla-Nador, les diatomites representent, avec la plateforme carbonatee tres developpee, une des composantes sedimentaires importantes du Messinien. Deux coupes ont ete effectuees dans les series diatomitiques en position distale par rapport a la plateforme afin d’analyser et interpreter, pour la premiere fois dans ce bassin, une microflore de diatomees. Ainsi, 123 especes de diatomees ont ete determinees : 73 de centriques et 51 de pennees. Des assemblages caracteristiques ont ete definis a partir de l’analyse statistique traduisant des variations des conditions ecologiques selon les niveaux ou des parties de niveaux diatomitiques. L’ensemble des donnees est pris en compte pour proposer des modeles paleoenvironnementaux traduisant la complexite des interactions. Ainsi sont mis en evidence la permanence d’un milieu marin ouvert, l’influx d’eaux froides d’origine atlantique, une bathydecroissance generale de la serie marnodiatomitique messinienne, l’influence de la progradation de la plateforme carbonatee et l’impact de fonctionnement probable de systemes d’upwellings.

International audience; Late Cretaceous amber from La Garnache (France, Vendée) contains filamentous networksthat have all the characteristics of spider webs. Using methods of classic and confocalmicroscopy, the web architecture and the thread structure are described. The geometryof the webs preserved in amber is presented in 3D imaging. Unlike most of the spiderwebs identified in amber, there are no regular radiating webs growing in two dimensionscharacteristic of the well-known orb web. A number of the characters would correspondto the apparently irregular organization of cob-type web or sheet web. By using confocalmicroscopy, we can highlight the preserved autofluorescence of spider silk proteins andnew characters are proposed to identify the spider webs or fragments of webs in amber.

International audience; Les mines de lignite du Cénomanien du Sarladais (Dordogne, France) étaient connues depuis longtemps sur le plan géologique. La présence d'ambre y avait été ponctuellement signalée, mais aucun échantillon n'était disponible. Les récentes investigations qui ont porté sur les anciennes exploitations ont permis de récolter des grains d'ambre de petite taille, surtout extraits des déblais de mines. Les grains présentent le plus souvent une forme de goutte plus ou moins allongée et apparaissent globalement translucides, les parties opaques des grains correspondant à des colonisations de micro-organismes filamenteux qui restent à étudier.

The Middle Eocene diatom and silicoflagellate record of ODP Site 1260A (Demerara Rise) is studied quantitatively in order to throw light on the changes that siliceous phytoplankton communities experienced during a Middle Eocene warming event that occurred between 44.0 and 42.0 Ma. Both Pianka's overlap index, calculated per couple of successive samples, and cluster analysis, point to a number of significant turnover events highlighted by changes in the structure of floristic communities. The pre-warming flora, dominated by cosmopolitan species of the diatom genus Triceratium, is replaced during the warming interval by a new and more diverse assemblage, dominated by Paralia sulcata (an indicator of high productivity) and two endemic tropical species of the genus Hemiaulus. The critical warming interval is characterized by a steady increase in biogenic silica and a comparable increase in excess Ba, both reflecting an increase in productivity. In general, it appears that high productivity not only increased the flux of biogenic silica, but also sustained a higher diversity in the siliceous phytoplankton communities. The microflora preserved above the critical interval is once again of low diversity and dominated by various species of the diatom genus Hemiaulus. All assemblages in the studied material are characterized by the total absence of continental and benthic diatoms and the relative abundance of neritic forms, suggesting a transitional depositional environment between the neritic and the oceanic realms.

International audience; Amber usually contains inclusions of terrestrial and rarely limnetic organisms that were embedded in the places were they lived in the amber forests. Therefore, it has been supposed that amber could not have preserved marine organisms. Here we report the first known amber-preserved marine microfossils. Diverse marine diatoms as well as radiolarians, sponge spicules, a foraminifer, and a larval spine of a sea urchin were found in Late Albian and Early Cenomanian amber samples of southwestern France. The highly fossiliferous resin samples solidified ca. 100 million years ago on the floor of coastal mixed forests dominated by conifers. The amber forests of southwestern France grew directly along the coast of the Atlantic Ocean and were influenced by the nearby sea: shells and remnants of marine organisms were probably introduced by wind, spray or high tide from the beach or the sea onto the resin flows.

Resume La sedimentation a caractere deltaique de la formation d’Aleria comprend a Casabianda des depots diatomitiques dont l’etude de detail a ete entreprise pour la premiere fois. La formation d’Aleria comble une depression de la surface d’erosion messinienne et est surmontee par le Pliocene inferieur en divers points, ce qui lui confere un âge Messinien superieur-Pliocene basal. La microflore de diatomees recensee se compose de 59 especes et se caracterise par une tres grande diversite des pennees, avec 54 especes, tandis que les centriques ne sont representees que par cinq especes. Les assemblages de diatomees montrent une composition relativement constante le long de la coupe, l’espece Aulacoseira granulata dominant largement la microflore avec pres de 90 % en moyenne des assemblages. La co-existence des taxons appartenant aux differentes classes de salinite et avec differents modes de vie laisse envisager des interactions multiples. Le modele environnemental suggere est celui d’un etang, situe dans une plaine cotiere, qui est de temps en temps soumis a de faibles influences marines et alimente par des apports permanents d’eau douce, en provenance d’un cours d’eau et de la nappe alluviale. L’etude de la microflore de diatomees, caracteristique du passage mio-pliocene en Corse, apporte des elements nouveaux a la discussion sur les paleoenvironnements et la chronologie des depots de type Lago-Mare eu egard a la proximite du milieu marin.

The Badenian (Middle Miocene) Gˆırbova de Sus Formation rests upon the basement in a transgressive trend (West of the Transylvanian depression). For the first time, an algalrich carbonate platform with coral build-ups is described in this area. These build-ups underline clearly a retrograding sequence. The coral assemblage is dominated by Faviidae and Porites colonies. Five types of coral build-ups without any zonation are distinguished. Their unusual width and their palaeogeographical situation testify to the generalization of subtropical conditions and the complexity of the marine connections in the Paratethian area.; La formation de Gîrbova de Sus (Ouest de la dépression de Transylvanie), d’âge Badénien (Miocène moyen), transgressive sur le substratum, correspond à une plate-forme carbonatée, riche en algues. Pour la première fois y sont décrites des constructions coralliennes, regroupées en cinq types principaux, marquant des étapes du développement de la plate-forme selon un dispositif rétrogradant. Les assemblages coralliens, dominés par des Faviidae et par Porites, forment des édifices immatures sans zonation marquée. Leur ampleur assez inhabituelle et leur situation paléogéographique témoignent de la généralisation des conditions à caractère subtropical et de la complexité des connexions caractérisant la Paratéthys.

Resume Une etude detaillee des assemblages de diatomees d’âge Sarmatien (Miocene moyen) a ete realisee dans un bassin a forte productivite biologique du domaine paratethysien en Roumanie, le bassin Zarand. Au total, 240 especes de diatomees ont ete determinees, ce qui a permis de mettre en evidence des variations successives de paleosalinite et paleobathymetrie. Des influx marins d’influence extra-paratethysienne sont correlatifs de l’elevation du niveau de la colonne d’eau, de l’instauration de conditions marines pour de courts intervalles et de l’apport des taxons d’affinite nord-boreale et/ou subtropicale. Apres chaque episode marin, le bassin evolue vers un systeme d’isolement ou se manifestent des influences continentales, attestees par la presence des taxons d’eau douce.

Distance correlations of Late Tortonian–Messinian littoral carbonate complexes are proposed from the study of eight platforms in the western and central Mediterranean. Correlations are based on the identification of two major biological sedimentary cycles and of two index surfaces. Surface A is a maximum flooding surface during cycle 1 at around 6.7 Ma. Surface B is a regional marine planation surface at around 5.95 Ma, at the base of cycle 2 (Terminal Carbonate Complex). A general sedimentary model is proposed for the 7–5.6-Ma time-span. The boundary between cycles 1 and 2 is coincident with the onset of the Messinian Salinity Crisis, and appears to be related to major environmental–paleo-oceanographic changes in the Mediterranean, rather than to a major sea-level drop or to climatic change.

International audience