Search

Néraudeau, Didier, Philippe, Marc, Albani, Abderrazak El, Moreau, Jean-David, Polette, France, Martin, Jean-Paul Saint (2022): Taphonomie et minéralisation de bois carbonatisés du Purbeckien de l'Usine, à Cherves-Richemont (Charente). Geodiversitas 44 (24): 665-682, DOI: 10.5252/geodiversitas2022v44a24

A palynological analysis of 45 samples from six mid-Cretaceous amber-bearing outcrops from Charentes has been carried out. A total of 227 taxa have been recorded in the studied palynofloras. Palynological data support earlier evidence and indicate an early Cenomanian age for the assemblages. The heterogeneous compositions of the palynofloral assemblages indicate the existence of different coastal depositional settings with a variable but usually weak marine influence. The local vegetation was subdivided in various types including herbaceous formations integrating ferns and eudicots which may have colonised frequently-disturbed, fluvial, open environments and xeric arboreal communities dominated by Cheirolepidiaceae and probably integrating drought- and/or salt-tolerant angiosperms and ferns (Anemiaceae and Gleicheniaceae) and other gymnosperms (Araucariaceae, Ginkgoales and scarce Cycadales and Gnetales). The existence of riparian and freshwater wetland communities integrating taxodioids, aquatic and/or hygrophilous angiosperms, ferns, lycopods, mosses and clubmosses is proposed. Coastal/?lagoonal counterparts including plants tolerant to periodical floods by saline or brackish waters is suggested by palynological evidence. Conifer forests mainly integrating Pinaceae and Podocarpaceae in raised hinterlands may also be interpreted on the basis of taphonomical considerations. The wide variety of depositional settings inferred by the palynological data support enhanced transport capabilities for amber and/or a widespread occurrence of producers in local vegetation during the early Cenomanian.

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; A 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 Berriasian–Albian 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 (Hauterivian–Barremian),and Isère (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 Berriasian–Valanginian 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. Hauterivian–Barremianassemblages 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 tri– and polyaperturatepollen grains associated with the virtual disappearance oflygodiaceous verrucate spores.

International audience; A first attempt at a biostratigraphic synthesis of the palynological content of French Lower Cretaceous continental deposits is the subject of this paper. Palynomorphs listed in previous studies on Berriasian–Albian non-marine palynology have been taken into account, gathering 360 species of pollen grains and spores altogether. In addition, 70 samples have been recovered from outcrops of argillaceous rocks, mostly corresponding to the Purbeck and Wealden facies of southern England. The samples concerned are from the departments of Charente-Maritime, Charente, Savoie (Berriasian, Valanginian, Albian), Oise, Seine-Maritime, Pas-de-Calais (Hauterivian–Barremian), and Isère (Aptian). Early Cretaceous miospores are commonly long-ranging; hence, it is necessary to consider fluctuations in their abundance within palynological assemblages if they are to have any biostratigraphic value. Lower Berriasian assemblages are often dominated by gymnosperm pollen grains, associated with anemiaceous spores such as Cicatricosisporites australiensis and C. hughesii. These taxa are also found in younger strata, but upper Berriasian–Valanginian assemblages are characterized by containing more abundant lygodiaceous verrucate spores associated with the appearance of gleicheniaceous Clavifera triplex from the Valanginian onwards. Many genera have been erected to accommodate Mesozoic verrucate spores. The considerable overlap between diagnoses diminishes the stratigraphic significance of the constituent species. Only the genera Concavissimisporites and Trilobosporites are considered useful here. Hauterivian–Barremian assemblages are similar to those of the Valanginian, but differ in the reduction in numbers of verrucate spores and a commensurate increase in abundance of Cicatricosisporites and Appendicisporites associated with the first occurrences of monoaperturate angiosperm pollen grains, such as Clavatipollenites hughesii, within Barremian deposits of northern France. Considered to be more typical of Albian assemblages, Clavatipollenites rotundus has been recovered from lower Aptian deposits in south-eastern France. Aptian palynofloras arealso characterized by the appearance of other monoaperturate pollen forms, such as Retimonocolpites. Very little information is available on French Albian assemblages. They are defined by the diversification of dicotyledonous tri– and polyaperturate pollen grains associated with the virtual disappearance of lygodiaceous verrucate spores

International audience; S’appuyant sur les quelques travaux précurseurs publiés par Delcourt et Sprumont, Herngreen, et Koeniguer entre 1959 et 1980, deux campagnes de terrain ont été organisées en mars et juillet 2017 afin d’affiner les connaissances sur la palynoflore des dépôts continentaux du Crétacé Inférieur de l’Avesnois (Nord), du Boulonnais (Pas de Calais) et du Pays de Bray (Oise, Seine-Maritime). 29 échantillons argileux ont été récoltés dans les niveaux néocomiens du Pays de Bray et du Boulonnais, les anciennes carrières de l’Avesnois étant désormais toutes inaccessibles.Des 27 sites et anciennes carrières visitées au Pays de Bray, les échantillons provenant de la sablière de Cuy-Saint-Fiacre (Seine-Maritime) ont livré le contenu palynologique le plus diversifié, 48 espèces ayant pu être identifiées au niveau de la lentille argilo-ligniteuse à la base de la série. L’assemblage est taxonomiquement dominé par des spores de bryophytes, lycophytes et filicophytes fréquemment rencontrées au Crétacé Inférieur, appartenant aux genres Aequitriradites, Coronatispora, Trilobosporites, Ischyosporites, et Concavissimisporites, ainsi que d’autres spores dont la distribution temporelle est plus étendue, telles que Cyathidites australis Couper, Densoisporites microrugulatus Brenner, et Cicatricosisporites spp. Les grains de pollen de gymnospermes sont peu diversifiés mais abondants, en particulier Classopollis torosus (Reissinger) Couper, forme associée aux Cheirolepidiaceae, ainsi que de nombreux grains de pollen disaccates et inaperturés. La présence de Callialasporites dampieri (Balme) Dev, et Taxodiaceaepollenites hiatus (Potonié) Kremp est également notée. Un grain de pollen tricolpé a été rencontré, mais son état de préservation ne permet pas d’être catégorique quant à sa signification au sein de l’assemblage. Deux autres échantillons ont été prélevés dans des lentilles d’argile grise. Ils sont très riches en matière organique amorphe, mais ne contiennent que quelques spores. Les proportions respectives des spores verruquées et cicatricosées au sein de l’assemblage, ainsi que la potentielle présence d’Angiosperme, indiqueraient que l’âge de dépôt, jusqu’alors considéré comme Néocomien, semblerait plus jeune que Berriasien-Valanginien, possiblement Hauterivien.Trois sites ont été échantillonnés au Boulonnais, mais seuls les échantillons prélevés dans une lentille argileuse de l’ancienne carrière de Longueville ont été traités à ce jour. Le contenu palynologique est très similaire à celui de Cuy-Saint-Fiacre, différant cependant par l’augmentation de l’abondance et de la diversité des spores d’Anemiaceae Cicatricosisporites, et par la présence du grain de pollen monoaperturé Clavatipollenites. Ces différences suggèreraient que les sédiments de la carrière de Longueville se sont déposés postérieurement à ceux de Cuy-Saint-Fiacre, possiblement au Barrémien comme suggéré auparavant par Herngreen.

International audience; The Ediacaran–Fortunian ichnofauna from Central Brittany (NW France) is revised for the first timesince the pioneering work by Lebesconte at the end of the 19th century. The study is based onfossils from the type-localities of the historical Brioverian taxa Montfortia (traces from Montfortsur-Meu) and Neantia (wrinkle surfaces from Neant-sur-Yvel), and on two new outcrops fromSaint-Gonlay. The ichnofossil assemblage includes Helminthoidichnites tenuis, Helminthopsis tenuis,Gordia marina, Palaeophycus tubularis, ?Neonereites uniserialis, and ?Spirodesmos archimedeus.Locally, the grazing traces are associated with wrinkle surfaces considered as microbially inducedsedimentary structures (MISS). The sedimentological characteristics of these deposits correspond toa shelf marine environment. Both U-Pb datings on detrital zircon and ichnostratigraphic criteriatend toward an Ediacaran age of the fossiliferous deposits, but we cannot exclude the possibility ofa Fortunian age at the present state of knowledge.

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.

International audience; Diagnoses of the Normapolles pollen genera Hungaropollis, Krutzschipollis, Longanulipollis, Oculopollis and Trudopollis and 55 of their species are emended and many specimens illustrated in order to provide a basis for more successful and consistent identification than has been possible hitherto. These taxa were recovered from palynological preparations of selected samples from Upper Cretaceous deposits in Europe and the eastern USA. As indicated on an accompanying range chart the majority are encountered in Santonian and/or Campanian deposits. Eleven of the species described have been transferred from other genera and are therefore in new combinations, namely: Hungaropollis granulatus (Kedves et Herngreen), Longanulipollis coronatiformis (Góczán et Siegl-Farkas), L. orbicularis (Góczán), L. ornatus (Kedves et Diniz), L. parvoculus (Góczán), L. skarbyae (Kedves et Diniz), Oculopollis artifex (Weyland et Krieger), O. rector (Pflug), O. triceps (Skarby), Trudopollis cuneolis (Góczán 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 as synonyms of Hungaropollis (Aveiropollenites and Romeinipollenites), Longanulipollis (Coronatipollis, Intercalaripollis, Portaepollenites and Verruoculopollis), Oculopollis (Druggipollenites, Pseudoculopollis and Semioculopollis) and Trudopollis (Cuneipollis, Felderipollenites, Hofkeripollenites and Kriegeripollenites) respectively. As a result of some of these nomenclatural changes 14 other species are in new generic combinations but are not otherwise considered. Seven morphotypes are identified in open nomenclature and two placed in comparison. This taxonomic synthesis, which updates work published since the 1950s, is aimed primarily at rendering biostratigraphic analyses easier, but it is also a necessary first step towards the resolution of Normapolles taxonomy and the relationships between these pollen grains and biological species.