Retispora Lepidophyta Research Articles

First record of late Devonian-early Carboniferous palynoflora from the Lipak Formation, Spiti Basin, Tethyan Himalaya, India, and their biostratigraphic implications

The present work elucidates palynofloral records from the Lipak Formation (late Devonian– early Carboniferous) of the Spiti Basin. The study has been carried out from three different sections of Spiti and Pin valleys to look for the signatures of terrestrial plants in the Tethyan realm and assess the relative palynodating of the studied sediments. The recovered palynoassemblage from the exposures of Lipak Formation, near Takche Locality, Spiti Valley, mainly comprises spores and has the dominance of Verrucosisporites, Dictyotriletes, Lophozonotriletes, Convolutispora followed by subordinate occurrences of Rugospora, Cymbosporites and Knoxisporites along with reworked pollen grain Plicatipollenites. The recovered palynoassemblage of Lipak Formation exposure at Guling Village of Pin Valley comprises Spelaeotriletes, Tricidarisporites, Calamospora, Callumispora and reworked pollen grains. The reworked pollen grains are characterised by the dominance of Faunipollenites, Scheuringipollenites and Parasaccites and followed by subordinate occurrences of the Densipollenites, Striatopodocarpites, Platysaccus, Alisporites, Striomonosaccites, Chordasporites and Verticipollenites pollen grains. The exposure of this Formation near Muth Village of Pin Valley is found to be palynologically barren. The recovered palynoflora is correlated with palynofloral records of the Tethyan realm of India and palynofloral records from coeval sequences worldwide. The recovered palynocomposition shows a close resemblance to Retispora lepidophyta–Verrucosisporites nitidus (LN) and Vallatisporites verrucosus–Retusotriletes incohatus (VI) Assemblage zones of Western Europe and Cordylosporites–Verrucosisporites Biozone of Argentina which indicates that studied section of the Lipak Formation is upper Famennian to early Tournaisian age. The recovered reworked palynomorphs belong to the Permian age, which may be deposited in the Lipak Formation through stratigraphic leakage. Palynomorphs include spores of affinities of Zygopteridiales, Marattiales, Botryopteridales, Equisetales/Noeggerathiales/Sphenophyllales group of plants. In contrast, palaeobotanical affinities of pollen grains are linked with the Filicales, Cordaitales and Glossopteridales group of plants.

Reinvestigation of Devonian-Carboniferous palynostratigraphy in Yalai village, Nyalam County, southern Tibet, China

Reinvestigation of the Devonian-Carboniferous boundary sequence in Yalai village, Nyalam County, southern Tibet, enabled the recovery of well-preserved palynomorphs and conodonts in the Yali section. Based on quantitative analysis of the relative abundances of various palynomorphs, two palynological assemblages are recognized in the Famennian-Tournaisian boundary beds of the Yali section. In ascending order, they are the Retispora lepidophyta–Verrucosisporites irregularis (LI) assemblage and the Retispora lepidophyta–Vallatisporites vallatus (LV) assemblage. Both assemblages are tentatively correlated with the Famennian LN Biozone of Western Europe because of the appearance of Retispora lepidophyta and other index spores such as Vallatisporites verrucosus, Vallatisporites pusillites, Indotriradites explanatus, and Densosporites spitsbergensis in both palynological assemblages. The lower limestones of the Yali Formation yield biostratigraphic markers for the Devonian-Carboniferous boundary, including the conodont Siphonodella sulcata and Protognathodus kockeli, correlated with the VI Biozone from Western Europe and parts of Gondwana. The upper Lazhabu Member of the Yali Formation yielded Retispora lepidophyta, Vallatisporites vallatus, and Vallatisporites pusillites of the LV Biozone, indicating that some typical palynomorphs elements of the LN Biozone of Western Europe persisted into Tournaisian in southern Tibet.

Miospores from the Upper Devonian and lowermost Carboniferous strata of the Khoshyeilagh area, northeastern Alborz, Iran

Diverse and well-preserved terrestrial palynomorphs occur in the Padeha, Khoshyeilagh, and Mobarak formations in the Khoshyeilagh area, northeastern Alborz, northern Iran. The spore assemblages consist of 36 species belonging to 24 genera. The vertical distribution of index spores allows the erection within these strata of five local biozones (BT, FF, LE, LN, and VI). The data show that assemblages recorded from the Khoshyeilagh section can be correlated with the VCo, LE, LN, and VI Miospore biozones of Europe, Canada, and USA. Many of the palynomorph species, such as Archaeoperisaccus ovalis, Ancyrospora ampulla, Diducites mucronatus, D. versabilis, Grandispora cornuta, G. echinata, Indotriradites explanatus, Retispora lepidophyta, Retusotriletes incohatus, R. phillipsii, Rugospora flexuosa, Teichertospora torquata, Tumulispora malevkensis, Vallatisporites pusillites, Verrucosisporites bulliferus, and Verrucosisporites nitidus, are closely comparable with coeval assemblages recorded from Belgium, Portugal, Canada, North Africa, South America, and North America. This indicates the close relationship of the Iranian Platform to other parts of the northern Gondwana and southern Laurentian domain during this time interval. Moreover, parent plants of the Late Devonian miospores in the Khoshyeilagh area generally belong to herbaceous Class Rhyniopsida (orders: Rhyniales, Trimerophytales), Zosterophyllopsida, and various classes such as, Lycopsida (herbaceous order: Isoetales, Selaginellales, Protolepidodendrales), Progymnospermopsida (Order Archaeopteridales and Aneuropthytales), and Filicopsida. The presence of marine shelly macrofauna (brachiopods and corals) suggest a nearshore depositional environment comprising rivers, fluvial deltas, tidal flats, and lagoons for the Upper Devonian and lowermost Carboniferous deposits studied herein.

An investigation of a Devonian/Carboniferous Boundary section on the Bolivian Altiplano

AbstractThe Devonian/Carboniferous Boundary (DCB) interval is associated with mass extinction, isotope excursions and a short glacial episode. This study investigates how boundary extinction and environmental change is expressed in the glacial high-palaeolatitudinal record of the Bolivian Altiplano (western Gondwana). A latest Devonian and early Carboniferous section has been investigated using sedimentology, palynology, total organic carbon and bulk δ13Corganic. The Colpacucho Formation is a Late Devonian shelfal–marine siliciclastic sequence. It is overlain in the study area by a unit of coarse sandstones and sandy diamictites, interpreted as glaciomarine. This distinctive glaciomarine unit is at least 7 km wide and 60–120 m thick with a variably incisive basal contact (<100 m). It is of very latest Famennian age and is a stratigraphic equivalent of proven glacigenic deposits across central South America. The offshore marine Kasa Formation overlies the glacigenic unit above a basal flooding surface. The DCB is 12 m above this flooding surface on the last occurrence of Retispora lepidophyta and significant palynological assemblage changes. This includes the loss of the Umbellasphaeridium saharicum phytoplankton bioprovince, endemic to Gondwana. Marine and terrestrial palynological extinctions are synchronous with a 2 ‰ positive carbon isotope excursion interpreted to be reflective of changes in organic matter delivery and preservation during an interval of environmental stress. These results inform wider debates on global environmental change and mass extinction at the DCB.

Palynostratigraphic reassessment of the Late Devonian of Bjørnøya, Svalbard

A comprehensive study of the Late Devonian palynostratigraphy of Bjørnøya, Svalbard Archipelago is presented. A total of 61 samples collected from 10 outcrops located along the eastern coast of the island were analyzed for palynology yielding a mid- to latest Famennian age. A reassessment of the existing palynostratigraphy of the Ursa Sandstone Unit of the Røedvika Formation was undertaken. As no independent age control exists for this succession, the palynological assemblages were correlated to well-calibrated palynological zonations from the Eastern and Western Europe. The middle to upper part of the Vesalstranda Member and the Kapp Levin Member were assigned a mid- to late Famennian age (CVa to VF biozones), and the middle to lower-upper part of the Tunheim Member was dated as latest Famennian in age (LL to LN biozones). For the first time, a palynological age was assigned to the upper part of the Kapp Levin Member. Correlation with other Arctic areas show close resemblance to Late Devonian assemblages from Europe and the Arctic region. However, differences in the stratigraphical ranges of several taxa were identified. In terms of Late Devonian paleophytogeographic provinces the miospore assemblages are assigned to the Northern Euroamerican Cornispora varicornata Realm for the mid-Famennian. A more cosmopolitan trend was recognized for the latest Famennian (Strunian), with assemblages including abundant Retispora lepidophyta. The paleobotanical affinities of the palynomorphs reveal a flora of lycopods and progymnosperms occupying this area during the Late Devonian, with Retispora lepidophyta becoming a common element in the latest Famennian.

A terrestrial Devonian-Carboniferous boundary section in East Greenland

Terrestrial Devonian-Carboniferous boundary sections are present in the East Greenland Devonian Basin. The boundary section on Stensiö Bjerg developed in deep, distal lake sediments with a pair of lakes representing the boundary. A diverse spore assemblage developed as the lake flooded the basin. Previously abundant spores, notably Retispora lepidophyta, Diducites spp., Rugospora radiata and all forms with bifurcate tips (Ancyrospora and Hystricosporites), then became extinct through just over a metre of section. The spore assemblage is then lost into AOM rich very high TOC% lake sediments. There is a negative δ13CTOC excursion in the Stensiö Bjerg section interpreted to represent the upper part of the positive excursion known from marine sections. The upper lake contains the simple VI spore assemblage of the earliest Carboniferous age. The correlative section on Rebild Bakker was developed in shallow proximal facies without AOM and shows that a Devonian-Carboniferous LN* to VI spore zone boundary can be picked in the lower lake based on the last occurrence of Retispora lepidophyta in an assemblage otherwise dominated by simple spores and Grandispora cornuta. Spores in this VI spore assemblage, particularly Grandispora cornuta, show sculpture malformation that is entirely characteristic of UV-B radiation damage to their DNA prior to deposition of its protective wall layer. This palynological record showing the rapid extinction of major elements within the Late Devonian microflora can be reconciled with accounts claiming there was no mass extinction of plants and spores across the boundary. The palaeobiology of the major spore groups that became extinct is reviewed.

Lower Sappington Formation palynofacies in Montana confirm upper famennian black shale paleoenvironments and sequences across western North America

For the first time, Late Devonian palynofacies analyses of the Lower Sappington shale units U1A─D was carried out at Peak 9559 (Sacajawea) and Ainger Lake in the Bridger Range of Montana. Diagnostic spore species Apiculiretusispora verrucosa, Diducites mucronatus and D. versabilis allowed the correlation of our U1A-D with the European Late Famennian A. verrucosa-V. hystricosus Palynozone. The first appearance of Gorgonisphaeridium winslowiae in U1 is the oldest record before the inception of Retispora lepidophyta. Four palynofacies correlative with U1A-D and new findings of invertebrates and microfossils allow the interpretation of paleoenvironmental changes. Amorphous organic matter, marine phytoplankton and pyrite in black shales of U1A-B indicate anoxic bottom conditions occurred in offshore marine environments. An erosional fossiliferous phosphatic lag above these units confirms a regional SB. U1C black shales composed by AOM, marine and terrestrial phytoplankton, land–derived remains and pyrite reveal shallower, dysoxic-anoxic, brackish water environments. A thin layer at the base of Unit 1D yielded AOM and marine phytoplankton and low terrestrial input indicating dysoxic-anoxic conditions were maintained. The lack of organic matter and the presence of invertebrates and microfossils in a thin green fossiliferous mudstone supports the establishment of normal, oxygenated marine conditions maintained in the basal Middle Sappington Member (U2). These two thin units are not part of the underlying anoxic black shale (U1A-B) sequence as commonly was over-simplified. Instead, they are part of a transgressive interval with the basal Middle Sappington. A correlation of the U1 shale interval is established with the global multiphase Dasberg Event.

Palynostratigraphy of the Devonian–Carboniferous transition in the Tulong section in South Tibet: A Hangenberg Event sequence analogue in the Himalaya-Tethys zone

Palynological assemblages from the Tulong succession in South Tibet enabled the recognition of three miospore biozones within the Zhangdong and ‘Yali’ formations. In ascending order, they are the Retispora lepidophyta–Verrucosisporites nitidus (LN) Biozone, the Vallatisporites vallatus–Foveosporites pellucidus (VP) Biozone and the Rugospora polyptycha–Tricidarisporites arcuatus (PA) Biozone. The LN Biozone in the Tulong section can be correlated to the LN Biozone of Western Europe, based on the first and last appearances of many index miospore species. However, Tournaisian palynological assemblages of Western Europe and South Tibet show compositional differences. The VP and PA biozones of South Tibet are correlated tentatively to the VI–HD and BP–TC biozones of Western Europe based on the occurrences of rare miospore index species in both regions. The Zhangdong and ‘Yali’ formations are now dated as Famennian to possibly earliest Visean. This age assessment is supported by rare conodonts and ammonoids recovered from intercalated limestones in the basal part of ‘Yali’ Formation. In the Everest region, the Devonian–Carboniferous boundary is now placed c. 10 m above the lower boundary of the ‘Yali’ Formation, which was originally suggested by Lin and Qiu (1985) to be position of the D–C boundary. Unlike western Gondwana, i.e. Bolivia and Brazil, the Himalaya-Tethys zone at the northeastern margin of Gondwana does not show obvious lithological evidence for glaciations. The new palynostratigraphic data, including information on sea-level changes reflected by variations in palynological composition and lithology around the Devonian–Carboniferous boundary allow, an interregional, approximate correlation with the classical Hangenberg Event sequence in the Rhenish Massif. The analogous Hangenberg Event sequence in South Tibet further supports the hypothesis that the rapid Hangenberg Event regression/transgression was a global eustatic event of significant magnitude. The co-occurrence of probably reworked Frasnian Geminospora lemurata and Archaeoperisaccus spores in the Himalaya-Tethys zone indicates the palaeogeographical proximity of the northern margin of Gondwana to the South China Block in the palaeoequatorial belt.

The palynostratigraphy of the Lower Carboniferous (middle Tournaisian–upper Viséan) Shishtu Formation from the Howz-e-Dorah section, southeast Tabas, central Iranian Basin: discussion

ABSTRACTThis assessment of the article by Aria-Nasab et al. (2016), on the palynostratigraphy of the upper part of the Shishtu Formation (Shishtu 2) in central Iran, reveals many shortcomings. The majority of the defects are judged to reflect unwarranted or erroneous taxonomic identifications of the adversely preserved miospores. This, in turn, casts considerable doubt on the compositional integrity of Aria-Nasab et al.'s three proposed stratigraphically successive miospore assemblages, which they dated as encompassing the mid Tournaisian through late Viséan; i.e. within the generalised Mississippian age for Shishtu 2 that had previously been established from marine faunal evidence. We confirm, through examination of their illustrations, the presence of recycled Late Devonian palynomorphs, including Retispora lepidophyta. A late Tournaisian through late Viséan or early Serpukhovian age for the sampled Shishtu 2 section is suggested here.

New Discoveries of Diplocraterion and Tidal Rhythmites in the Upper Devonian Rocks of Grab-all Bay, Cork Harbour: Palaeoenvironmental Implications

Geological mapping of the Upper Devonian succession on the northern side of Grab-all Bay in Cork Harbour has led to a new interpretation of the local lithostratigraphy. Rocks previously mapped as the Ballyknock Member of the Gyleen Formation are now reassigned to the Toe Head Sandstone Formation which is here divided into two new members, the Rams Head and Grab-all Bay Members and to the Old Head Sandstone Formation. The axis of the Grab-all Bay Syncline is re-positioned 160m further to the north in Grab-all Bay, revealing a younger and previously undescribed interval of strata here assigned to the Old Head Sandstone Formation. Miospore assemblages recorded from the Toe Head Sandstone and the lower part of the Old Head Sandstone Formation are assigned to the Retispora lepidophyta—Knoxisporites literatus (LL) Miospore Biozone, indicating a late Devonian (Uppermost Famennian) age for the succession. New discoveries of U-shaped burrows, assignable to the trace fossil Diplocraterion, are recorded from several intervals in the Toe Head Sandstone Formation and the lower part of the Old Head Sandstone Formation. These monospecific ichnofaunas are believed to have colonised finely laminated sediments of the intertidal flat environment. In addition, rhythmically laminated sandstone and siltstone beds interpreted as tidal rhythmites are recorded for the first time in the Toe Head Sandstone Formation. The paleoenvironmental significance of the tidal rhythmites and Diplocraterion beds in the Toe Head Sandstone is important in understanding the nature of the fluvial–tidal transition zone in the Cork Harbour region in late Devonian times. It is proposed that in late Devonian (LL Biozone) times the upper Toe Head Sandstone Formation sediments in the Cork Harbour area were deposited in the upper reaches of an estuarine embayment within a low gradient fluvial coastal plain.

Maranhites isaacsonii sp. nov., from the Upper Devonian Cabanillas Group, Peru

Maranhites isaacsonii sp. nov. was recovered from an outcrop sample of the Upper Devonian Cabanillas Group, Oxapampa Province, Peru. This acritarch displays the discrete equatorial thickenings that characterize the genus, but differs from all described species by having a lobate vesicle margin with processes or process groups. The processes taper distally and terminate in capitate, rounded, or clavate tips. The palynomorph assemblage is dominated by marine elements, including acritarchs, prasinophytes, scolecodonts, and chitinozoans. The occurrence of Retispora lepidophyta indicates a Late Famennian–Early Tournaisian (Fa2c-Tn1a) age for the sample yielding Maranhites isaacsonii sp. nov. Palynomorphs exhibit a thermal alteration index equivalent to gas-window maturation.

Geochemical and palynological study of the Upper Famennian Dasberg event horizon from the Holy Cross Mountains (central Poland)

AbstractIntegrated palynological, organic and inorganic geochemical and petrographical methods have been used for deciphering the depositional redox conditions and character of organic matter of the Famennian Dasberg event horizon from the deep-shelf Kowala succession of the Holy Cross Mountains. The ages of the investigated samples have been established, using miospore data, as VF (Diducites versabilis–Grandispora famenensis) and LV (Retispora lepidophyta–Apiculiretusispora verrucosa) miospore Zones of the Middle/Upper Famennian. In the standard conodont zonation, this corresponds to the uppermost postera to lowermost praesulcata Zones. The presence of green sulphur bacteria biomarkers and dominance of small-sized framboids together with the presence of large framboids and low values of the U/Th ratio may indicate that during sedimentation of the lower Dasberg shale, intermittent anoxia occurred in the water column, or the anoxic conditions prevailed in the upper part of the water column, while the bottom waters were oxygenated, at least briefly. Deposition of the upper Dasberg shale was characterized by both bottom water and water column anoxia. The lack of acritarcha taxa from these intervals could have been due to anoxia in the photic zone. Moreover, organic content is high in those samples. There is no geochemical evidence for anoxia during sedimentation of the deposits sandwiched between the lower and upper Dasberg shales, or in the deposits which underlie and overlie both Dasberg shale horizons. The two discrete anoxic events are interpreted to be the result of major transgressions and the blooming of primary producers. Above the Dasberg shales, small fragments of charcoal and raised concentrations of polycyclic aromatic hydrocarbons are detected. This supports the presence of wildfires during deposition of shales just above the boundary of VF/LV palynological zones. Temperatures calculated from the fusinite reflectance values suggest that the charcoal was formed in low-temperature ground and/or surface fires. The typical marine character of sedimentation combined with the high proportion of charcoals suggests that wildfires were large-scale, and that there was intensive transport of terrestrial material. The main causes of intensive wildfires were a significant rise of O2 in the atmosphere and important progress in the land plant diversity during Late Devonian times. Palynofacies studies suggest that the transgression corresponds to the part IIf of the Late Devonian sea-level curve.

Synchronous deposition of massive sulphide deposits in the Iberian Pyrite Belt: New data from Las Herrerías and La Torerera ore-bodies

Two small to medium sized massive sulphide deposits, Las Herrerías and La Torerera, located in the Iberian Pyrite Belt (IPB) are examined from a geological and palynostratigraphic perspective. The palynological assemblages are assignable to the Retispora lepidophyta–Verrucosisporites nitidus (LN) miospore Biozone (Latest Devonian: Latest Famennian/Strunian) of Western Europe. This age permits correlation with some of the main massive sulphide deposits dated so far in the region (viz., Tharsis, Aznalcóllar, Sotiel-Coronada or Neves-Corvo), and validates once again the hypothesis that a single mineralizing event was responsible for the genesis of most of the IPB’s massive sulphide deposits. The present study confirms that palynostratigraphy is an invaluable high-resolution biostratigraphic tool in the IPB, applicable to dating, correlation and ore-exploration.

Late Devonian–earliest Mississippian glaciation in Gondwanaland and its biogeographic consequences

Late Devonian glaciation is well-documented in three Brazilian basins, and newer work has shown a wider extent for this event, reaching Bolivia, Peru, Central African Republic, Niger, and the USA. Physical evidence for this event includes glacial pavements and polymict striated, and faceted clasts as dropstones and within marine resedimented deposits. Late Devonian (Frasnian? and Famennian) onset of Gondwanaland's glaciations resulted in fundamental changes in coeval and later (Mississippian) depositional systems worldwide. Palynomorphs date the more widespread event within the Retispora lepidophyta (miospore) palynozone, which often occurs with the marine acritarch Umbellasphaeridium saharicum. This initial glaciation continued into earliest Carboniferous (Tournaisian) time. There were several consequences from the short-term glacioeustasy. In North America, central Europe and southern China there is a coeval sea-level fall that exhumed and eroded carbonate platforms, deposited siliciclastics, and generated lacunae in the Famennian record. The lowstand resulted in extensive carbonate breccias, shallow-water deposits and evaporites in western U.S.A. Lowstand clastic wedges were deposited in a regression (eastern U.S.A.) with widespread black shales. In Moravia, Famennian siliciclastic influx increased as a result of subaerial weathering in newly-emergent highs that resulted from sea-level drop. Partial sea-level drops were also manifested by ferruginous oolites, which developed in nearshore environments and were subsequently dispersed down adjacent slopes by storm resedimentation. In southern China, aggradation, siliciclastic influx, reflux-dolomitization from evaporation, and shallow-water carbonate resulted from Famennian sea-level fall. The coupling of glacial and lowstand events explains the sudden appearance of shallow-marine, as well as subaerially-affected features after the Frasnian transgression that breached the North American craton.

Water column euxinia and wildfire evidence during deposition of the Upper Famennian Hangenberg event horizon from the Holy Cross Mountains (central Poland)

A palynological study of the uppermost Famennian section from Kowala Quarry (Holy Cross Mountains, central Poland) allowed recognition of two miospore zones: LV (Retispora lepidophyta–Apiculiretusispora verrucosa) and LN (Retispora lepidophyta–Verrucosisporites nitidus). Based on palynology and sedimentology, the black shale within the upper part of the section is identified as equivalent to the Hangenberg Black Shale, which is known globally. This black shale contains compounds characteristic of photic zone euxinia, including isorenieratane and its derivatives. Such compounds are absent in the organic-poor marls and shales occurring below the LN Zone, and are present only as traces in the layers just above the black shale, indicating fluctuations in the oxygen minimum zone during uppermost Famennian sedimentation. Palynofacies show high amounts of amorphous organic matter and prasinophyte concentrations in the black shale, and a subsequent significant decrease of amorphous organic matter concomitant with a rapid increase of terrestrial input (mainly miospores with common tetrads) in the layers above the black shale. This supports the relatively rapid change in the taxonomic composition of phytoplankton caused by fluctuations of the chemocline. The whole succession corresponds to one sea-level rise and fall. The presence of high concentrations of peri-condensed polycyclic aromatic hydrocarbons and large amounts of small charcoal particles at the Hangenberg event horizon indicate the occurrence of wildfires. Such observations suggest that atmospheric O22 levels had exceeded the critical threshold of 13 %, above which wildfires may occur, by latest Famennian time.

The massive sulphide event in the Iberian Pyrite Belt: confirmatory evidence from the Sotiel-Coronada Mine

Well-preserved miospore and organic-walled microphytoplankton assemblages have been recovered from the black shaly series hosting the massive sulphide deposits of Sotiel-Coronada Mine (Iberian Pyrite Belt). The productive samples yielded miospore assemblages representing the uppermost Famennian Retispora lepidophyta–Verrucosisporites nitidus (LN) miospore Biozone of Western Europe. This palynological evidence has important implications for the local geology, constraining the commencement of the volcanic activity and corroborating the previously-defined local tectonic style. Moreover, at regional scale, the new data permit correlation of the black shaly series (which hosts the mineralization in all the sulphide deposits hitherto dated in the region), reinforcing the hypothesis of an anoxic event occurring in the Iberian Pyrite Belt in the latest Devonian times.

Biometry and paleoenvironment of Retispora lepidophyta (Kedo) Playford 1976 and associated miospores in the latest Famennian nearshore marine facies, eastern Ardenne (Belgium)

The size diameter of Retispora lepidophyta, a stratigraphically important miospore, is reexamined in greater detail than in previous studies using three sections of the latest Famennian nearshore marine facies of the eastern Ardenne. The evolutionary character of the size reduction with time is confirmed and is used for accurate correlations between the three sections. Cluster analyses (dendrograms) are performed on the percentages of a selection of miospore species from the two most complete sections and show a clear analogy in the lateral distribution of R. lepidophyta and Vallatisporites hystricosus, a species known elsewhere (West Virginia, USA) to belong to coastal ‘downstream’ near-swamp plant communities [Streel and Scheckler, Rev. Palaeobot. Palynol. 64 (1990) 315–324]. By comparison also with the West Virginia data, three Diducites species are believed to represent the ‘coal’ swamp vegetation. A decrease in the proportion of the Diducites species from the lower to the upper portion of the studied sections is observed. Using biometric analysis, high resolution correlation between these sections reveals a lateral shift of facies with time during the latest Famennian in the eastern Ardenne. Local synsedimentary block-faulting processes were probably responsible.

Stratigraphy and depositional evolution of the uppermost Devonian‐carboniferous (Tournaisian‐ Westphalian) non‐marine deposits in north‐east Greenland

The new Traill Ø Group comprises the uppermost Devonian to Carboniferous sedimentary rocks in East Greenland. Palynologically productive intervals contain material described as five palynological zones and four assemblages, and suggest that the rocks are of Tournaisian to mid‐Viséan and early Westphalian age. The Retispora lepidophyta Abundance Zone (1) correlates to the Tournaisian (Tnla‐b) lepidophyta‐explanatus Miospore Zone, and the Spelaeotriletes spp.‐Lophozontriletes malevkensis Concurrent Range Assemblage (2) correlates to the Tournaisian (Tnlb) lepidophytanitidus Miospore Zone, both of Devonian age. The Bascaudaspora spp. Assemblage (3) has features shared with the hibernicus‐distinctus to pretiosus‐clavata Miospore zones, and the Grandispora uncata Assemblage (4) correlates to the pretiosusclavata Miospore Zone, both are of Tournaisian (Tn2–3) age. The Verrucosisporites spp.‐Lycospora spp. Assemblage (5) and the Lycospora Abundance Zone (6) both correlate to the Viséan Lycospora pusilla Miospore Zone. The Waltzispora sagittata‐Reticulatisporites variolates Abundance Zone (7) and the Densosporites spp., Schulzospora rara‐Murospora spp. Abundance Zone (8) both correlate to the Viséan nigra‐marginatus Miospore Zone. The Potonieisporites spp., Radiizonates aligerens‐Schulzospora rara, Savitrisporites nux Concurrent Range Zone (9) correlates to the Radiizonates aligerens Miospore Zone which is of Westphalian A age. This youngest assemblage relates more closely to the Arctic upper Bashkirian‐Moscovian deposits than to those of the lower Westphalian of Western Europe.

Revision of the late Famennian miospore zonation scheme in eastern Belgium

Abstract. New palynological data have been obtained from the Late Famennian Evieux and Comblain au Pont Formations of the Chanxhe section located in the Ourthe Valley in the eastern part of the Dinant Basin. In the light of this new data the stratigraphic ranges of several zonally important miospore taxa are now significantly different to those previously recorded. This has necessitated a re-evaluation and revision of the late Famennian miospore zonation scheme for this region. Apiculiretusispora verrucosa and Vallatisporites hystricosus are now found to occur below the inception of Retispora lepidophyta. Consequently, a new biozone, the Apiculiretusispora verrucosa–Vallatisporites hystricosus VH Biozone is described for the late Fa2c interval. The problematical relationship between the Retispora lepidophyta– Apiculiretusispora verrucosa LV Biozone and the Retispora lepidophyta–Knoxisporites literatus LL Biozone is resolved, and part of the LL Biozone is now considered equivalent to the LV Biozone, which it consequently replaces. The Retispora lepidophyta–Indotriradites explanatus LE Biozone is recorded from the upper part of the Comblain au Pont Formation. A continuous succession of miospore zones is now established for the late Famennian Fa2c/Fa2d interval which permits more accurate correlations with other regions in Europe and North America. Correlation with the standard conodont biostratigraphy shows that the base of LL Miospore Biozone is correlated with the middle or late expansa Conodont Biozone and the base of LE Miospore Biozone with the early to middle praesulcata Conodont Biozone.

Aspects of late devonian and early carboniferous palynology of Southern Ireland. V. The change in composition of palynological assemblages at the devonian-carboniferous boundary

The application of the appearance of the conodont Siphonodella sulcata as a new faunal criterion for correlation of the Devonian-Carboniferous boundary has recently been recommended. This paper aims at a better palynological characterization of the systemic boundary interval. It provides a description of the compositional change of palynological assemblages in southern Ireland, examplified by data from the Ballycrovane Harbour and Bantry Bay sections (Co. Cork). This palynological succession is taken as a standard for the palynological picture of the interregional floral development. Palynologically the most distinct floral change is taking place during the Retispora lepidophyta—Cyrtospora critifer (LCr) Phase. This phase is characterized by the drastic diminishment and subsequent disappearance of typical Late Devonian elements, such as the biostratigraphically important Retispora lepidophyta. The sudden quantitative change can be interregionally recognised. It is probably the result of climatic changes and nearly concurs with the entry of the conodont Protognathodus kuehni. On the other hand, a palynological characterization of the entry of Siphonodella sulcata is uncertain and it presumably takes place during the LCr Phase. From a palynological point of view, alternative criteria for correlation of the Devonian-Carboniferous boundary ought still to be considered.