22 research outputs found
Fundamental reassessment of the taxonomy of five Normapolles pollen genera
National audienceDiagnoses of the Normapolles pollen genera Hungaropollis,Krutzschipollis, Longanulipollis, Oculopollis and Trudopollis and56 of their species are emended and many specimens illustrated inorder to provide a basis for more successful and consistent identificationthan has been possible hitherto. These taxa were recoveredfrom palynological preparations of selected samples from Late Cretaceousdeposits in Europe, southern Sweden and eastern USA.As indicated on an accompanying range chart the majority are encounteredin Santonian and/or Campanian deposits. Eleven of thespecies described have been transferred from other genera and aretherefore in new combinations, namely: Hungaropollis granulatus(Kedves et Herngreen), Longanulipollis coronatiformis (GĂłczĂĄnet Siegl-Farkas), L. orbicularis (GĂłczĂĄn), L. ornatus (Kedves etDiniz), L. parvoculus (GĂłczĂĄn), L. skarbyae (Kedves et Diniz),Oculopollis artifex (Weyland et Krieger), O. rector (Pflug), O.triceps (Skarby), Trudopollis cuneolis (GĂłczĂĄn et Siegl-Farkas),and T. spinulosus (Skarby). Six are new: Hungaropollis pinguis,Krutzschipollis cucullus, K. immanis, Longanulipollis amabilis, L.lobus and Oculopollis viriosus. Thirteen genera are regarded assynonyms of Hungaropollis (Aveiropollenites and Romeinipollenites),Longanulipollis (Coronatipollis, Intercalaripollis, Portaepollenitesand Verruoculopollis), Oculopollis (Druggipollenites, Pseudoculopollisand Semioculopollis) and Trudopollis (Cuneipollis,Felderipollenites, Hofkeripollenites and Kriegeripollenites) respectively.As a result of some of these nomenclatural changes 14 otherspecies are in new generic combinations but are not otherwise considered.Seven morphotypes are identified in open nomenclatureand four placed in comparison
Re-examination of the palynological content of the Lower Cretaceous deposits of Angeac, Charente, south-west France::Age, palaeoenvironment and taxonomic determinations
International audienceFurther to the work published by NĂ©raudeau et al. six years ago, palynological matter recovered from the lignitic bone bed of Angeac in Charente (south-west France) has been re-examined in order to provide more evidence of its age, the previous HauterivianâBarremian interpretation being regarded as controversial. The samples come from four sedimentological units, An2âAn5, which together yielded an assemblage of 34 species, taxonomically dominated by palaeoecologically significant lygodiaceous verrucate spores, including eight species attributable to the genus Concavissimisporites and three species of Trilobosporites. A few bisaccate pollen grains, including Vitreisporites pallidus, have been recovered, but the gymnospermous pollen spectrum is clearly dominated by the cheirolepidiaceous genus Classopollis, its abundance diminishing progressively upwards from units An4 to An2. The great abundance and diversity of verrucate forms, along with the presence of other spores typical of Lower Cretaceous deposits, such as Aequitriradites verrucosus, and the scarcity of specimens referable to Cicatricosisporites, render this assemblage most similar to those of the Hastings Group of southern England, and the BĂŒckeberg Formation in north-western Germany. The time of deposition is, therefore, more likely to have been BerriasianâValanginian rather than HauterivianâBarremian, as previously stated. The associated small assemblage of megaspores is consistent with this determination. Except for Trilobosporites and Concavissimisporites, the use of several other genera commonly applied to Mesozoic verrucate spores, such as Converrucosisporites and Impardecispora, is considered unnecessary. To support this assertion, a Principal Components Analysis has been carried out on 120 verrucate spores from sedimentological units An2â4, taking into account ten morphological variables. The results show that specimens attributable to Trilobosporites are well be separated from the main cluster, which corresponds to Concavissimisporites, underlining the futility of using more than two genera for the species concerned
Upper Cretaceous amber from Vendée, north-western France:Age dating and geological, chemical, and palaeontological characteristics
International audienceThe 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
Les assemblages palynologiques continentaux du CrĂ©tacĂ© infĂ©rieur de France (TithonienâCĂ©nomanien) : palĂ©oenvironnements, palĂ©oclimats, stratigraphie, et taxonomie
In order to improve our knowledge regarding the evolution of Lower Cretaceous plant paleoecosystems, being a fundamental period of their evolutionary history, here is presented the first bibliographical, paleoclimatic, palaeoenvironmental, stratigraphic, and taxonomic synthesis of continental palynological assemblages from French Lower Cretaceous deposits. This study is based on the observation of palynofloras recovered from 20 French sites (mostly Charentes, north of the Paris Basin, and subalpins massifs), and four sites from England, the age of deposits, mostly continental, ranging from Tithonian to Cenomanien. 446 palynological species were identified following the observation of 120 samples, mainly corresponding to spores and pollen grains, but algae and dinocysts were also recovered. A Morpho-statistical analysis of Lower Cretaceous verrucate spores was carried out in order to determine precisely the diagnostic features of the morpho-species, and improve their stratigraphic and palaeoenvironmental resolution in the long run. The palaeoenvironmental and paleoclimatic evolution inferred from palynological observations suggests the existence of arid to semi-arid climatic conditions between late Tithonien and mid-Berriasian (sebkhas-type environments), followed by an abrupt change marked by a pronounced humid phase during late Berriasien and earliest Valanginian, and by a progressive decrease of the humidity from the mid Valanginian to early Aptian (floodplains and humid forests-types environments). Albian and Cenomanian ages are characterized by generally humid conditions, thus less so than the humid phase associated with the late Berriasian (mangrove-type environments). Several aridification phases are noted between late Berriasian and late Albian : at the end of early Valanginian, between late Barremian and early Aptian (thus not very pronounced in northern France), and to a lesser extent during the mid Albian in northern France. Lower Cretaceous continental palynomorphs are rarely considered as strong briostratigraphic markers. Thus, two complementary dating methods have been developed herein, in order to facilitate the dating process of continental deposits. Their validity was tested using Lower Cretaceous continental assemblages from Purbeck and Wealden strata of England, and they were used to determine precisely the age of deposition of Angeac (Charente), and Pays de Bray (Normandie) strata.Afin dâamĂ©liorer les connaissances, jusquâalors lacunaires en France, quant Ă lâĂ©volution des palĂ©oĂ©cosystĂšmes vĂ©gĂ©taux durant le CrĂ©tacĂ© InfĂ©rieur, pĂ©riode fondamentale de leur histoire Ă©volutive, il est ici proposĂ© de dresser la premiĂšre synthĂšse bibliographique, palĂ©oenvironnementale, palĂ©oclimatique, stratigraphique, et taxonomique des assemblages palynologiques continentaux du CrĂ©tacĂ© InfĂ©rieur de France. Cette Ă©tude sâappuie sur lâanalyse des palynoflores provenant de 20 sites français (principalement Charentes, nord du Bassin de Paris, et massifs subalpins), et de quatre sites dâAngleterre, dont lâĂąge des dĂ©pĂŽts, pour la plupart continentaux, sâĂ©chelonne entre le Tithonien et le CĂ©nomanien. Lâobservation de 120 Ă©chantillons a permis lâidentification de 446 espĂšces correspondant principalement Ă des spores et Ă des grains de pollen, mais Ă©galement Ă quelques kystes dâalgues et de dinoflagellĂ©s. Lâanalyse morpho-statistique de spores verruquĂ©es rapprochĂ©es de la famille des Lygodiaceae, trĂšs abondantes au CrĂ©tacĂ© InfĂ©rieur, a permis de caractĂ©riser plus prĂ©cisĂ©ment les caractĂšres taxonomiques discriminants, dont lâapplication pourra, Ă terme, amĂ©liorer la rĂ©solution stratigraphique et palĂ©oenvironnementale de ces espĂšces. LâĂ©volution palĂ©oenvironnementale et palĂ©oclimatique infĂ©rĂ©e des observations palynologiques suggĂšre lâexistence de conditions arides Ă semi-arides durant la fin du Tithonien et le dĂ©but du Berriasien (environnements de type sebkhas), suivies par un changement abrupt marquĂ© par une phase humide prononcĂ©e au Berriasien supĂ©rieur et au Valanginien infĂ©rieur, puis par une diminution progressive de lâhumiditĂ© du Valanginien moyen Ă lâAptien (environnements de types plaines dâinondation, forĂȘts humides). LâAlbien et le CĂ©nomanien sont caractĂ©risĂ©s par un retour Ă des conditions gĂ©nĂ©ralement humides, cependant moins marquĂ©es quâĂ la fin du Berriasien (environnements de types mangroves). Plusieurs phases dâaridification ont Ă©tĂ© notĂ©es entre le Berriasien supĂ©rieur et lâAlbien supĂ©rieur : Ă la fin du Valanginien infĂ©rieur, au BarrĂ©mien supĂ©rieur/Aptien infĂ©rieur (gĂ©nĂ©ralisĂ©e Ă lâEurope de lâOuest, mais peu marquĂ©e dans le nord de la France), et Ă moindre Ă©chelle durant lâAlbien moyen au nord du Bassin de Paris. Les palynomorphes continentaux du CrĂ©tacĂ© InfĂ©rieur nâĂ©tant pour la plupart pas considĂ©rĂ©s comme des marqueurs stratigraphiques fiables, deux mĂ©thodes de datation complĂ©mentaires sâappuyant uniquement sur les assemblages continentaux ont Ă©tĂ© dĂ©veloppĂ©es, afin de faciliter la datation des dĂ©pĂŽts continentaux. Leur validitĂ© a Ă©tĂ© testĂ©e sur des assemblages de rĂ©fĂ©rence dâAngleterre, et elles ont ainsi permis de prĂ©ciser lâĂąge des dĂ©pĂŽts dâAngeac (Charente) et du Pays de Bray (Normandie)
Palynological continental assemblages from French Lower Cretaceous deposits (Tithonian-Cenomanian) : palaeoenvironments, paleoclimats, stratigraphy, and taxonomy
Afin dâamĂ©liorer les connaissances, jusquâalors lacunaires en France, quant Ă lâĂ©volution des palĂ©oĂ©cosystĂšmes vĂ©gĂ©taux durant le CrĂ©tacĂ© InfĂ©rieur, pĂ©riode fondamentale de leur histoire Ă©volutive, il est ici proposĂ© de dresser la premiĂšre synthĂšse bibliographique, palĂ©oenvironnementale, palĂ©oclimatique, stratigraphique, et taxonomique des assemblages palynologiques continentaux du CrĂ©tacĂ© InfĂ©rieur de France. Cette Ă©tude sâappuie sur lâanalyse des palynoflores provenant de 20 sites français (principalement Charentes, nord du Bassin de Paris, et massifs subalpins), et de quatre sites dâAngleterre, dont lâĂąge des dĂ©pĂŽts, pour la plupart continentaux, sâĂ©chelonne entre le Tithonien et le CĂ©nomanien. Lâobservation de 120 Ă©chantillons a permis lâidentification de 446 espĂšces correspondant principalement Ă des spores et Ă des grains de pollen, mais Ă©galement Ă quelques kystes dâalgues et de dinoflagellĂ©s. Lâanalyse morpho-statistique de spores verruquĂ©es rapprochĂ©es de la famille des Lygodiaceae, trĂšs abondantes au CrĂ©tacĂ© InfĂ©rieur, a permis de caractĂ©riser plus prĂ©cisĂ©ment les caractĂšres taxonomiques discriminants, dont lâapplication pourra, Ă terme, amĂ©liorer la rĂ©solution stratigraphique et palĂ©oenvironnementale de ces espĂšces. LâĂ©volution palĂ©oenvironnementale et palĂ©oclimatique infĂ©rĂ©e des observations palynologiques suggĂšre lâexistence de conditions arides Ă semi-arides durant la fin du Tithonien et le dĂ©but du Berriasien (environnements de type sebkhas), suivies par un changement abrupt marquĂ© par une phase humide prononcĂ©e au Berriasien supĂ©rieur et au Valanginien infĂ©rieur, puis par une diminution progressive de lâhumiditĂ© du Valanginien moyen Ă lâAptien (environnements de types plaines dâinondation, forĂȘts humides). LâAlbien et le CĂ©nomanien sont caractĂ©risĂ©s par un retour Ă des conditions gĂ©nĂ©ralement humides, cependant moins marquĂ©es quâĂ la fin du Berriasien (environnements de types mangroves). Plusieurs phases dâaridification ont Ă©tĂ© notĂ©es entre le Berriasien supĂ©rieur et lâAlbien supĂ©rieur : Ă la fin du Valanginien infĂ©rieur, au BarrĂ©mien supĂ©rieur/Aptien infĂ©rieur (gĂ©nĂ©ralisĂ©e Ă lâEurope de lâOuest, mais peu marquĂ©e dans le nord de la France), et Ă moindre Ă©chelle durant lâAlbien moyen au nord du Bassin de Paris. Les palynomorphes continentaux du CrĂ©tacĂ© InfĂ©rieur nâĂ©tant pour la plupart pas considĂ©rĂ©s comme des marqueurs stratigraphiques fiables, deux mĂ©thodes de datation complĂ©mentaires sâappuyant uniquement sur les assemblages continentaux ont Ă©tĂ© dĂ©veloppĂ©es, afin de faciliter la datation des dĂ©pĂŽts continentaux. Leur validitĂ© a Ă©tĂ© testĂ©e sur des assemblages de rĂ©fĂ©rence dâAngleterre, et elles ont ainsi permis de prĂ©ciser lâĂąge des dĂ©pĂŽts dâAngeac (Charente) et du Pays de Bray (Normandie).In order to improve our knowledge regarding the evolution of Lower Cretaceous plant paleoecosystems, being a fundamental period of their evolutionary history, here is presented the first bibliographical, paleoclimatic, palaeoenvironmental, stratigraphic, and taxonomic synthesis of continental palynological assemblages from French Lower Cretaceous deposits. This study is based on the observation of palynofloras recovered from 20 French sites (mostly Charentes, north of the Paris Basin, and subalpins massifs), and four sites from England, the age of deposits, mostly continental, ranging from Tithonian to Cenomanien. 446 palynological species were identified following the observation of 120 samples, mainly corresponding to spores and pollen grains, but algae and dinocysts were also recovered. A Morpho-statistical analysis of Lower Cretaceous verrucate spores was carried out in order to determine precisely the diagnostic features of the morpho-species, and improve their stratigraphic and palaeoenvironmental resolution in the long run. The palaeoenvironmental and paleoclimatic evolution inferred from palynological observations suggests the existence of arid to semi-arid climatic conditions between late Tithonien and mid-Berriasian (sebkhas-type environments), followed by an abrupt change marked by a pronounced humid phase during late Berriasien and earliest Valanginian, and by a progressive decrease of the humidity from the mid Valanginian to early Aptian (floodplains and humid forests-types environments). Albian and Cenomanian ages are characterized by generally humid conditions, thus less so than the humid phase associated with the late Berriasian (mangrove-type environments). Several aridification phases are noted between late Berriasian and late Albian : at the end of early Valanginian, between late Barremian and early Aptian (thus not very pronounced in northern France), and to a lesser extent during the mid Albian in northern France. Lower Cretaceous continental palynomorphs are rarely considered as strong briostratigraphic markers. Thus, two complementary dating methods have been developed herein, in order to facilitate the dating process of continental deposits. Their validity was tested using Lower Cretaceous continental assemblages from Purbeck and Wealden strata of England, and they were used to determine precisely the age of deposition of Angeac (Charente), and Pays de Bray (Normandie) strata
Réexamen du contenu palynologique des sédiments du Crétacé Inférieur d'Angeac (Charente, SO France)
International audienceSuite aux Ă©tudes prĂ©liminaires rĂ©alisĂ©es par NĂ©raudeau et al. (2012), le contenu palynologique des niveaux ligniteux du bone bed dâAngeac (Charente, SO France) a Ă©tĂ© de nouveau Ă©tudiĂ©, quatre Ă©chantillons supplĂ©mentaires Ă lâappui, dans le but de prĂ©ciser lâĂąge de leur dĂ©pĂŽt, toujours controversĂ©. Lâassemblage rĂ©sultant de cette Ă©tude est composĂ© de 29 espĂšces, dominĂ©es par des spores verruquĂ©es telles que Converrucosisporites sp., Concavissimisporites verrucosus, Trilobosporites apiverrucatus, Verrucosisporites sp., leurs critĂšres de distinction Ă©tant cependant considĂ©rĂ©s comme problĂ©matiques. Quelques grains de pollen biailĂ©s, comprenant Vitreisporites pallidus, ont Ă©tĂ© rencontrĂ©s mais le spectre pollinique gymnospermien est largement dominĂ© par des spĂ©cimens appartenant au genre Classopollis, rattachĂ© aux Cheirolepidiaceae, reprĂ©sentant 60% de lâassemblage total. Cette dominance des Classopollis est commune Ă la palynoflore dâAngeac et Ă celle du purbeckien de lâĂźle dâOlĂ©ron, mais est Ă©galement connue dans lâAlbo-CĂ©nomanien charentais. Par contre, lâassemblage dâAngeac est plus proche de ceux des dĂ©pĂŽts berriasiens-valanginiens de la Formation anglaise dâAshdown et des lignites « wealdiens » de lâAvesnois par lâabondance et la diversitĂ© des formes verruquĂ©es et la prĂ©sence dâespĂšces typiques du dĂ©but du CrĂ©tacĂ© (ex : Aequitriradites spinulosus). En consĂ©quence, il est probable que les sĂ©diments dâAngeac se soient dĂ©posĂ©s au Berriasien-Valanginien, et non Ă lâHauterivien-BarrĂ©mien, comme le suggĂšrent les travaux antĂ©rieurs (Allain et al., 2014; NĂ©raudeau et al., 2012)
Re-examination of the palynological content of the Lower Cretaceous deposits of Angeac (Charente, south-west France)
International audienceFurther to the work published by NĂ©raudeau et al. (2012), palynological matter recovered from the lignitic bone bed of Angeac (Charente, SW France) has been re-examined, an additional sample having been processed in order to provide more evidence of its age, the previous determination being regarded as controversial (Benoit et al., in press). The samples come from four sedimentological units (An2âAn5), which together yielded an assemblage of 31 species, taxonomically dominated by verrucate spores, including Concavissimisporites montuosus, Concavissimisporites verrucosus, Trilobosporites apiverrucatus, Trilobosporites canadensis, Verrucosisporites major, and other taxa. The criteria for their identification commonly being regarded as problematic, a PCA has been carried out on 60 well-enough preserved specimens from the most productive unit An2, taking into account eight morphological variables. The results show one group consisting of specimens referred to Trilobosporites, and a second larger group comprising Concavissimisporites, Verrucosisporites, and various morphologically intermediate forms, thus underscoring the subjectivity of their generic and specific attributions. A few bisaccate pollen grains, including Vitreisporites pallidus, have been recovered, but the gymnospermous pollen spectrum is clearly dominated by the cheirolepidiaceous genus Classopollis, representing 60% of the total assemblage. This dominance, coupled with the great abundance of Trilobosporites and Concavissimisporites, along with the presence of other spores typical of Lower Cretaceous deposits, such as Aequitriradites spinulosus, renders this assemblage most similar to those of the Hastings Group of southern England, and the BĂŒckeberg Formation in north-western Germany. The time of deposition is therefore more likely to be BerriasianâValanginian than HauterivianâBarremian, as previously stated (NĂ©raudeau et al., 2012; Allain et al., 2014).Benoit, R-A., NĂ©raudeau, D., MartĂn-Closas, C.,. A review of the Upper Jurassic-Lower Cretaceous charophytes from the northern Aquitain Basin. Cretaceous Research, in press.Allain, R., Vullo, R., Le Loeuff, J., Tournepiche, J.F., 2014. European ornithomimosaurs (Dinosauria, Theropoda): an undetected record. Geologica Acta 12(2), 127-135.NĂ©raudeau, D., Allain, R., BallĂšvre, M., Batten, D.J., Buffetaut, E., Colin, J.P., Dabard, M.P., Daviero-Gomez, V., El Albani, A., Gomez, B., Grosheny, D., Le Loeuff, J., Leprince, A., MartĂn-Closas, C., Masure, E., Mazin, J.-M., Philippe, M., Pouech, J., Tong, H., Tournepiche, J.F., Vullo, R., 2012. The HauterivianâBarremian lignitic bone bed of Angeac (Charente, south-west France): stratigraphical, palaeobiological and palaeogeographical implications. Cretaceous Research 37, 1â14
La palynoflore continentale du Crétacé Inférieur du nord de la France: synthÚse des connaissances et nouveaux résultats
International audienceSâappuyant sur les quelques travaux prĂ©curseurs publiĂ©s par Delcourt et Sprumont, Herngreen, et Koeniguer entre 1959 et 1980, deux campagnes de terrain ont Ă©tĂ© organisĂ©es en mars et juillet 2017 afin dâaffiner les connaissances sur la palynoflore des dĂ©pĂŽts continentaux du CrĂ©tacĂ© InfĂ©rieur de lâAvesnois (Nord), du Boulonnais (Pas de Calais) et du Pays de Bray (Oise, Seine-Maritime). 29 Ă©chantillons argileux ont Ă©tĂ© rĂ©coltĂ©s dans les niveaux nĂ©ocomiens du Pays de Bray et du Boulonnais, les anciennes carriĂšres de lâAvesnois Ă©tant dĂ©sormais toutes inaccessibles.Des 27 sites et anciennes carriĂšres visitĂ©es au Pays de Bray, les Ă©chantillons provenant de la sabliĂšre de Cuy-Saint-Fiacre (Seine-Maritime) ont livrĂ© le contenu palynologique le plus diversifiĂ©, 48 espĂšces ayant pu ĂȘtre identifiĂ©es au niveau de la lentille argilo-ligniteuse Ă la base de la sĂ©rie. Lâassemblage est taxonomiquement dominĂ© par des spores de bryophytes, lycophytes et filicophytes frĂ©quemment rencontrĂ©es au CrĂ©tacĂ© InfĂ©rieur, appartenant aux genres Aequitriradites, Coronatispora, Trilobosporites, Ischyosporites, et Concavissimisporites, ainsi que dâautres spores dont la distribution temporelle est plus Ă©tendue, telles que Cyathidites australis Couper, Densoisporites microrugulatus Brenner, et Cicatricosisporites spp. Les grains de pollen de gymnospermes sont peu diversifiĂ©s mais abondants, en particulier Classopollis torosus (Reissinger) Couper, forme associĂ©e aux Cheirolepidiaceae, ainsi que de nombreux grains de pollen disaccates et inaperturĂ©s. La prĂ©sence de Callialasporites dampieri (Balme) Dev, et Taxodiaceaepollenites hiatus (PotoniĂ©) Kremp est Ă©galement notĂ©e. Un grain de pollen tricolpĂ© a Ă©tĂ© rencontrĂ©, mais son Ă©tat de prĂ©servation ne permet pas dâĂȘtre catĂ©gorique quant Ă sa signification au sein de lâassemblage. Deux autres Ă©chantillons ont Ă©tĂ© prĂ©levĂ©s dans des lentilles dâargile grise. Ils sont trĂšs riches en matiĂšre organique amorphe, mais ne contiennent que quelques spores. Les proportions respectives des spores verruquĂ©es et cicatricosĂ©es au sein de lâassemblage, ainsi que la potentielle prĂ©sence dâAngiosperme, indiqueraient que lâĂąge de dĂ©pĂŽt, jusquâalors considĂ©rĂ© comme NĂ©ocomien, semblerait plus jeune que Berriasien-Valanginien, possiblement Hauterivien.Trois sites ont Ă©tĂ© Ă©chantillonnĂ©s au Boulonnais, mais seuls les Ă©chantillons prĂ©levĂ©s dans une lentille argileuse de lâancienne carriĂšre de Longueville ont Ă©tĂ© traitĂ©s Ă ce jour. Le contenu palynologique est trĂšs similaire Ă celui de Cuy-Saint-Fiacre, diffĂ©rant cependant par lâaugmentation de lâabondance et de la diversitĂ© des spores dâAnemiaceae Cicatricosisporites, et par la prĂ©sence du grain de pollen monoaperturĂ© Clavatipollenites. Ces diffĂ©rences suggĂšreraient que les sĂ©diments de la carriĂšre de Longueville se sont dĂ©posĂ©s postĂ©rieurement Ă ceux de Cuy-Saint-Fiacre, possiblement au BarrĂ©mien comme suggĂ©rĂ© auparavant par Herngreen
SYNTHESIS OF THE PALYNOLOGICAL CONTENT OF THE LOWER CRETACEOUS CONTINENTAL DEPOSITS IN FRANCE: STRATIGRAPHIC IMPLICATIONS
International audienceA first attempt at a biostratigraphic and palaeoenvironmental synthesisof the palynological content of French Lower Cretaceouscontinental deposits is the subject of this paper. Palynomorphslisted in previous studies on BerriasianâAlbian non-marine palynologyhave been taken into account, gathering 360 speciesof pollen grains and spores altogether. In addition, 70 sampleshave been recovered from outcrops of argillaceous rocks, mostlycorresponding to the Purbeck and Wealden facies of southernEngland. The samples concerned are from the departments ofCharente-Maritime, Charente, Savoie (Berriasian, Valanginian,Albian), Oise, Seine-Maritime, Pas-de-Calais (HauterivianâBarremian),and IsĂšre (Aptian). Early Cretaceous miospores are commonlylong-ranging; hence, it is necessary to consider fluctuationsin their abundance within palynological assemblages if they areto have any biostratigraphic value. Lower Berriasian assemblagesare often dominated by gymnosperm pollen grains, associatedwith anemiaceous spores such as Cicatricosisporites australiensisand C. hughesii. These taxa are also found in younger strata, butupper BerriasianâValanginian assemblages are characterized bycontaining more abundant lygodiaceous verrucate spores associatedwith the appearance of gleicheniaceous Clavifera triplex fromthe Valanginian onwards. Many genera have been erected to accommodateMesozoic verrucate spores. The considerable overlapbetween diagnoses diminishes the stratigraphic significance ofthe constituent species. Only the genera Concavissimisporites andTrilobosporites are considered useful here. HauterivianâBarremianassemblages are similar to those of the Valanginian, but differ inthe reduction in numbers of verrucate spores and a commensurateincrease in abundance of Cicatricosisporites and Appendicisporitesassociated with the first occurrences of monoaperturate angiospermpollen grains, such as Clavatipollenites hughesii, withinBarremian deposits of northern France. Considered to be moretypical of Albian assemblages, Clavatipollenites rotundus has beenrecovered from lower Aptian deposits in south-eastern France. Aptianpalynofloras are also characterized by the appearance of othermonoaperturate pollen forms, such as Retimonocolpites. Very littleinformation is available on French Albian assemblages. They aredefined by the diversification of dicotyledonous triâ and polyaperturatepollen grains associated with the virtual disappearance oflygodiaceous verrucate spores