Acritarch distribution along an inshore–offshore transect in the Gorstian (lower Ludlow) of Gotland, Sweden

To better understand palaeoecological signatures in Palaeozoic acritarch assemblages, the distribution of palynomorphs has been quantitatively studied in eight localities from the Gorstian, lower Ludlow (Late Silurian) of Gotland, Sweden. The localities are situated along an inshore–offshore transect comprising shallow marine lagoonal environments to distal shelf facies. Process-bearing acritarchs and sphaeromorphs constitute the main components within the palynomorph assemblages. The lateral distribution of palynomorphs exhibits characteristic features at three different levels as follows. (1) With regard to the overall composition of the palynomorph assemblages, the abundance of process-bearing acritarchs increases towards the distal shelf, while the abundance of sphaeromorphs decreases. (2) At the generic level, the acritarchs Micrhystridium and Dilatisphaera are more abundant in the proximal facies, while Evittia, Percultisphaera and Oppilatala are more common in distal environments. (3) At an infrageneric level, Micrhystridium morphotypes with shorter processes are mainly present in proximal environments, while those with longer and ramified processes occur in more distal shelf environments. The palynomorph distribution along the inshore–offshore transect highlights the potential of acritarchs and prasinophytes as palaeoenvironmental indicators.     

Upper Silurian microplankton of the Leintwardine Group, Ludlow Series, in the type Ludlow area and adjacent regions

The acritarchs and prasinophyte algae from the Upper Bringewood, Lower Leintwardine, Upper Leintwardine and Lower Whitcliffe formations of the Ludlow type area and surrounding regions are described. The following new taxa are proposed: Cymatiosphaera pumila sp. nov., Melikeriopalla pustula sp. nov., Cheleutochroa beechenbankensis sp. nov., Cymbosphaeridium molyneuxii sp. nov., Flammulasphaera bella gen. et sp. nov., Percultisphaera incompta sp. nov., Salopidium aldridgei sp. nov. and Umbellasphaeridium? wicanderi sp. nov. A holotype is defined for Lophosphaeridium galeatum Hill and a further 34 new taxa are described under open nomenclature. Two biozones, identified by the first appearance of the zone taxon, are defined in the Sunnyhill section, Ludlow [Global Stratotype Section and Point (GSSP) for the base of the Ludfordian Stage, Ludlow Series]. The base of the Leoniella vilis Biozone is identified at 4.52m below the top of the Upper Bringewood Formation at Beechenbank, Aymestrey. The base of the Triangulina sanpetrensis Biozone is identified at 15.49m above the base of the Lower Leintwardine Formation and Ludfordian Stage at the Sunnyhill section. These biozones allow correlation with sections in north–west Spain, Podolia and Gotland. The possibility of using Visbysphaera whitcliffense and U.? wicanderi as biozonal indicators is suggested.     

Cardiolinka bohemica (Barrande, 1881) – A first representative of the Late Silurian Bohemian type Bivalvia fauna from the northern Arabian Plate,Southeast Turkey

The Rheic Ocean was a major oceanic domain between Baltica, Laurentia, Perunica and Gondwana in Ordovician-Silurian times. The cosmopolitan nepiomorphian bivalves Praecardioidei Newell, 1965 and Antipleuroidei Kříž, 2007 are characteristic of the Silurian of Perunica, peri-Gondwana, and Baltica, and occur also in Laurentia and Siberia. The Bohemian-type bivalve Cardiolinka Kříž, 1981 (Nepiomorphia Kříž, 2007, Cardiolidae Hoernes, 1884), from the Late Silurian of the Bahar-1 well core, has been found for the first time in southeastern Turkey. The strata containing the species Cardiolinka bohemica (Barrande, 1881) occur in the middle part of the Dadaş Formation in the interior Petroleum District X-Siirt of the northern parts of the Arabian Plate. The cosmopolitan species C. bohemica was until now known from the Latest Ludlow to Pridoli of the Prague Basin, France, Carnic Alps, Sardinia, East European Platform (Poland), eastern Serbia, Moesian Platform, and Arctic Canada. The new surprising subsurface data on C. bohemica in Diyarbakır-Bismil area (southeastern Turkey) therefore represent another piece of evidence in favour of strong faunistic affinity between Perunica, peri-Gondwanan Europe and the northern Gondwana margin.     

Palynostratigraphy and palaeogeography of the Padeha, Khoshyeilagh, and Mobarak formations in the eastern Alborz Range (Kopet-Dagh region), northeastern Iran

A total of 113 surface samples collected from the Padeha, Khoshyeilagh, and Mobarak formations of Kuh-e-Ozum, northeast of Jajarm town were processed for palynomorphs, in order to determine age relationships. Well-preserved and abundant palynomorphs dominated by organic-walled-marine microphytoplankton (acritarchs and prasinophyte phycomata), miospores and subordinate chitinozoans, and scolecodonts were recovered. Seven species of prasinophyte phycomata (four genera), 19 acritarch species (14 genera), one species of chitinozoa, and 26 miospore species (19 genera) were recorded and assigned to eight local Assemblage Zones. Assemblage Zones I-IV occur in the Padeha Formation and suggest an Early Late Devonian (Frasnian) age whilst assemblages zones V-VII are present in the Khoshyeilagh Formation and indicate Late Devonian (Famennian) ages. Assemblage zone VIII, which occurs in the basal part of Mobarak Formation, suggests a Lower Mississippian (Tournaisian) age for this formation. Many of the palynomorph groups encountered are closely comparable with coeval assemblages recorded from Western Australia, southwest Ireland, England, Turkey, Saudi Arabia, North Africa, and South America, indicating the close relationship of the Iranian Platform to other parts of the northern Gondwana Domain during the time interval represented by these strata. The presence of marine palynomorphs (acritarchs/prasinophyte phycomata, chitinozoans, and scolecodonts), and shelly macrofauna (brachiopods, gastropods, and corals) in Member c of the Padeha Formation (as well as the Khoshyeilagh and Mobarak formations), together with associated miospores, indicate an open marine (moderately nearshore) depositional environment for the Upper Devonian and Lower Carboniferous deposits in northeastern Alborz Range (Kopet-Dagh region) of Iran.     

Late Silurian plant microfossil assemblage from Guangyuan,Sichuan, China

A dispersed plant microfossil assemblage is described from Late Silurian deposits from Guangyuan, Sichuan, China. These strata are interpreted as nearshore, shallow marine deposits, and brachiopods suggest a late Ludlow–early Pridoli age. The palynomorph assemblage is dominated by terrestrial forms, including cryptospores and trilete spores, tubular structures and cuticle-like sheets, although rare marine acritarchs are also present. This microfossil assemblage is comparable to coeval assemblages from around the world (South and Southwest Wales; Libya; Canada; Southeastern Turkey; Northwest Spain; and Jiangsu, China). The sporomorphs from this assemblage indicate the existence of early land plants during the late Ludlow–early Pridoli in Guangyuan, Sichuan, China; and suggests that floras of this age were cosmopolitan and exhibited little palaeogeographical differentiation.     

The Crassispora kosankei–Cystoptychus azcuyi palynozone of the Upper Carboniferous Tupambi Formation,Tarija Basin,northern Argentina

Well-preserved and diverse palynomorph assemblages were recovered from surface and core samples from the middle to upper section of the Tupambi Formation. The latter is the basal unit of the Macharetı́ Group (Upper Carboniferous) of the Tarija Basin, northern Argentina. Assemblages are composed of trilete miospores, one hilate species, monosaccate pollen grains (one species striated), one praecolpate species and green algae (Botryococcus). Two key species are Cystoptychus azcuyi sp. nov. and Crassispora kosankei (Potonié and Kremp) Bharadwaj emend. Smith and Butterworth enable definition of the first palynozone for this basin. The age, as well as the biostratigraphic and paleogeographic significance of the palynoflora is discussed.     

Palynology of the Dockum group (Upper Triassic), Texas,U.S.A.

A palynofloral assemblage is described from the Upper Triassic Dockum Group of Texas. Forty palynomorph species are recorded and these are correlated with European Upper Triassic assemblages. The Dockum Group assemblage is considered to be of late Karnian age.Two new genera, Tulesporites gen. nov., type species T. briscoensis sp. nov., and Daughertyspora gen. nov., type species D. chinleanus (Daugherty) comb. nov. have been erected; new species are Converrucosisporites matsenii sp. nov., Pyramidosporites traversei sp. nov., Callialasporites triassicus sp. nov., Plicatipollenites minutotriletus sp. nov., Triadispora dockumensis sp. nov., Bhardwajispora jansonii sp. nov., Protodiploxypinus americus sp. nov., P. ujhelyi sp. nov., Klausipollenites gouldii sp. nov., Pityosporites old-hamensis sp. nov., Abietineaepollenites bujakii sp. nov., Falcisporites oviformis sp. nov. and F. tecovasensis sp. nov.     

Siluro-Devonian miospore biostratigraphy of the Urubu River area, western Amazon Basin, northern Brazil

Well-preserved miospores have been observed in the Urubu River area from the western part of the Amazon Basin, northern Brazil, in rocks belonging to the uppermost Pitinga and Manacapuru Formations. A previous palynological work based on chitinozoans has dated these strata as Late Ludlow, Early Pridoli and Early Lochkovian. Although samples are relatively poor in miospores, the present study reveals the most diversified Silurian-Earliest Lochkovian palynoflora ever reported from South America, an interval where miospore information is still very rare. Sixty-four species have been identified, of which two are new (Artemopyra urubuense and Retusotriletes amazonensis). One single specimen attributed to the genus Grandispora, identical to unpublished forms identified by one of us (P.S.) in Lochkovian sections of Saudi Arabia, has been found in a Lochkovian sample from the Urubu River. These constitute the oldest geological record of Grandispora. Among the abundant acritarchs, specimens of the genus Schizocystia have been observed for the first time in pre-Devonian rocks.Although the Late Silurian-Early Lochkovian miospore biostratigraphy is still in its infancy in South America, it seems that Amazon Basin assemblages do not show significant differences in composition in comparison to coeval palynofloras from other areas of northwestern Gondwana. This is surprising since the miospore localities under consideration are widely distributed over high to low paleolatitudes, i.e. from cool temperate to dry subtropical belts. Conversely, Siluro-Devonian Gondwanan assemblages differ considerably from the contemporary palynofloras of the Old Red Sandstone Continent and adjacent areas, thus contradicting recent phytogeographic interpretations based on megafloras.     

Silurian-Devonian miospores from the western and central Algeria

The age of Rock Units B1 and B2 of the Middle Silurian-Lower Devonian of Sahara (Algeria) is assessed and confirmed as late Homerian to ?earliest Lochkovian on the basis of moderately well preserved miospore assemblages. The data upon which this age assessment is provided by recent palynological studies in the Cantabrian Mountains (NW Spain), the type Wenlock area, Shropshire (England), south and south-west Wales, the Midland Valley of Scotland and the Ghadames Basin, Libya. Quantitative study shows that cryptospores decrease in number and variety upwards, laevigate miospores are prevalent and the representatives of the rugulate, crassitate genus Scylaspora are dominant. The occurrence and range of these species as well as other miospore taxa recorded during this study provide the basis for recognizing three miospore assemblage and one interval biozones, namely Scylaspora vetusta-Scylaspora kozlica, Chelinospora sanpetrensis-Cymbosporites triangulatus, Chelinospora hemiesferica and Scylaspopra radiata-Apiculiretusispora synoria. Of these biozones, two assemblage biozones are proposed as new. Core samples of Rock Unit B1 from borehole NGS-1 of the Triassic Province contain the oldest two miospore assemblage biozones. Rock Unit B2 from the boreholes GMD-2, ISS-1 (Tidikelt Plateau) and NGS-1 (Triassic Province) comprise the youngest two miospore biozones. The assemblage and interval biozones allow inter-regional correlation with latest Middle Silurian to probably earliest Devonian strata. The inadequacy of coverage of core samples result in the absence of critical palynological evidence, to determine the exact position of the base of the Ludlow, Pridoli and Lochkovian. Comparison with the zonal and sub-zonal divisions of Mid-Palaeozoic sequences from other parts of the world shows crucial differences in the distribution of the spore flora within Gondwanan and Euramerican regions during Pridoli and early Lochkovian. Six new miospore species namely Retusotriletes delicatus nov. sp., Scylaspora cymba nov. sp., S. distincta nov. sp., S. radiata nov. sp., S. undulata nov. sp. and Cymbosporites triangulatus nov. sp. are described. Three more possibly new miospore forms are described and illustrated but not specifically named.     

An Alpine immigrant: Phragmoceras Broderip, 1839 from the Silurian of the Carnic Alps (Austria)

A rare occurrence of Phragmoceras imbricatum Barrande is recorded from moderately shallow marine Silurian sequences in the Carnic Alps (Austria). The specimen was collected from a condensed series of nautiloid-bearing wackestones/packstones which are documented as being one of the earliest levels of the Silurian Cephalopod Limestone Biofacies deposited along the North Gondwana margin. The presence of this genus and particular species in the Alpine area, whether as an in situ fauna or as a “stray immigrant”, during a period of global eustatic lowstand, adds new data with regard to the mechanisms of faunal exchange of nectobenthic nautiloid taxa between the Carnic Alps, the Prague Basin, SW Sardinia, Avalonia and Baltica which must have been made possible by currents connecting all five areas. It seems likely that some of the nautiloid taxa appearing in the Prague Basin during the Ludlow may have already been present in the Carnic Alps much earlier in the Silurian; these document early faunal affinities with Baltica. As well as confirming the existence of open migrational seaways between these terranes at a precise stratigraphic interval during the Silurian (lower Homerian: Wenlock), the presence of this species also indicates a prevailing more temperate paleoenvironment in these areas which this element of a usually tropical fauna could tolerate, and provides significant evidence that warm water currents reached the Carnic Alps at this time. In addition due to the bathymetric restrictions of the shells of these particular faunas, exchange by currents could not have taken place over great distances, even considering drifted individuals, and therefore indicates the relatively close positions/connections of various peri-Gondwana Terranes such as the Carnic Alps, SW Sardinia and the Prague Basin to Avalonia and Baltica during this time slice.     

黔东早—中寒武世凯里组疑源类组合及其界线意义

通过对台江八郎和丹寨两条剖面凯里组中疑源类化石的分析,研究,台江剖面产疑源类化石有17属35各（12未定种）,其中以Leiosphaeridia,Synsphareidium,Cymatiosphaera,Pterospermella最为丰富,可划分为3个组合,即Cymatiosphaera cf.cristata-Fimbriaglomerella memebrancea组合,Cristallinium-Micrhystridium-Pterospermella组合和Dictyotidium-Granomarginata组合,丹寨平寨剖面凯里组所产疑源类化石有：13属21种（5未定种）,同样划分为3个组合,即Leiosphaeridia-Tasmanites组合,Retisphaeridium-Micrhystridium tentatium组合和Baltisphaeridium-Bubomorpha hunjiangensis组合,本文对两条剖面中的凝源类化石的组成,相对含量做了详细的统计,发现在八郎剖面9－2层和平寨剖面3层疑源类的丰度,分异度开始发生明显的变化,表现由早寒武世向中寒武世疑源类组合面貌的转变,这一疑源类转变层位正好是与三叶虫划分的中,下寒武统界线的层位位置相一致,这充分表明疑源类化石可作为划分中,下寒武统的极有价值的微体生物化石证据。     

Organic-walled microfossils from Cambrian Stage IV in the Jiaobang section,eastern Guizhou,China

The lower Cambrian succession in the Jiaobang section, Jianhe County, eastern Guizhou, China, includes, in ascending order, the Bianmachong, Balang, and Tsinghsutung formations, with a total thickness of about 645 m. Twenty-six morphological genera (including one new genus) are identified from the Balang and the underlying Bianmachong formations, many of which are common and widely distributed. Six acritarch assemblages are discerned in the Balang Formation. They are, in ascending order, the Adara alea‒Skiagia ornata, the Acrum radiale‒Pterospermella velata, the Comasphaeridium molliculum‒Solisphaeridium baltoscandium, the Corrugasphaera perfecta n. sp.‒Pterospermella vinctusa n. sp., the Acrum novum‒Heliosphaeridium oligum, and the Acrum membranosum‒Adarve diafanum acritarch assemblages. An obvious change of organic-walled microfossil assemblages occurred in the interval between 84 m and 98 m from the bottom of the Balang Formation which roughly corresponds to the boundary between the Oryctacarella duyunensis trilobite Zone and the overlying Arthricocephalus chauveaui trilobite Zone. In addition, organic-walled microfossils are scarce in about 24 m thick from the bottom of the Balang Formation. One new genus and five new species including Plagasphaera balangensis n. gen. n. sp., Asteridium tubulus n. sp., Cymatiosphaera spina n. sp., Corrugasphaera perfecta n. sp., and Pterospermella vinctusa n. sp. are described.     

Silurian acritarchs from the type Wenlock and Ludlow of Shropshire,England

Acritarch taxa are recorded and listed from the Wenlock and Ludlow from the type areas in Shropshire, England, and other localities in the Welsh Basin of South Wales and the Welsh Borderland of England. The ranges of 141 taxa of stratigraphic value are plotted. Five new genera are described: Hogklintia, Lepto brachion, Rhaco brachion, Salopidium and Wrensnestia. 36 new species are described, and 32 new combinations proposed. Seven acritarch zones are recognised in the Wenlock and Ludlow.     

Environmental changes reflected by palynomorphs in the early Middle Ordovician Hanadir Member of the Qasim Formation, Saudi Arabia

Core samples from the QASIM-801 (QSIM-801) water well in the Qasim Region of central Saudi Arabia were investigated palynologically. The interval studied contains the transgressive succession from the Sajir Member of the Saq Formation to the Hanadir Member of the Qasim Formation, and yields well-preserved and abundant cryptospores, microphytoplankton (acritarchs and chlorophycean algae), and chitinozoans, indicative of a Darriwilian (Llanvirn) age. The lowermost portion of the cored interval from the upper Sajir Member consists of fine-grained sandstones deposited in tidal flat, and shallow-marine settings. It is characterized by abundant and diverse cryptospores (permanent tetrads, dyads, monads), cuticle-like phytoclasts, and a low diversity assemblage of marine palynomorphs. The upper part of the cored interval from the Hanadir Member is composed of hemipelagic to pelagic, organic-rich, graptolitic shales, and micaceous shales, of middle- to outer-shelf depositional settings, which yield abundant marine palynomorphs (acritarchs and chitinozoans). Cryptospore-bearing horizons are interspersed in the succession. Changes in the composition of palynomorph assemblages reflect higher frequency environmental changes within an overall transgressive succession. Four new acritarch species are described in open nomenclature, Tyrannus sp. A, Clypeolus sp. A,?Pulvinosphaeridium sp. A, and?Tinacula sp. A.     

Lower Devonian spore assemblages from the Arbuthnott Group at Canterland Den in the Midland Valley of Scotland

The Canterland Den locality in the Midland Valley of Scotland exposes sediments belonging to the Arbuthnott Group. They consist of typical Lower Old Red Sandstone terrestrial fluviatile deposits, which probably accumulated in an inland intermontane basin. Palynological investigation of these sediments has yielded diverse and well preserved palynomorph assemblages dominated by land-derived forms: spores, phytodebris (dispersed cuticles and tubular structures) and rare fragments of arthropod cuticle. Interestingly, rare acritarchs interpreted as deriving from non-marine algae are also present. The spore assemblages all belong to the lower subzone of the micrornatus–newportensis Spore Assemblage Biozone, indicating an early Lochkovian (Early Devonian) age. They are similar in general characteristics to previously described spore assemblages from the Arbuthnott Group, but exhibit minor differences in terms of taxon composition. They differ more significantly from coeval spore assemblages from the lowland floodplain deposits of the Anglo-Welsh basin, in terms of both relative abundance of morphotypes and taxon composition. An intriguing feature of the assemblage is the high abundance of undissociated spore tetrads. It is suggested that such tetrads are a genuine feature of Lochkovian spore assemblages, perhaps reflecting more flexible and unconventional reproductive strategies exhibited by early land plants.     

The stratigraphic distribution of organic-walled dinoflagellate cysts in the Cretaceous and Tertiary

All information concerning the stratigraphic distribution of organic-walled dinoflagellate cysts in the Cretaceous and Tertiary sediments of the world, published prior to 1974, has been critically assessed. Stratigraphically reliable records are presented in tabular form; stratigraphical subdivision to stage or formation is incorporated wherever possible. Records of doubtful authenticity are commented on and questions of stratigraphic and taxonomic interest are discussed in the text.A new family, Family Florentiniaceae nov. fam., is erected, and the following new taxonomic combinations are proposed: Astrocysta ampla (Harland, 1973) nov. comb.; Cooksoniella larjakense (Vozzhennikova, 1967) nov. comb.; ?Florentinia truncigera (Deflandre, 1937b) nov. comb.; Phthanoperidinium pannonium (Lentin and Williams, 1973) nov. comb.; Spiniferites scabrosus (Clarke and Verdier, 1967) nov. comb. and Veryhachium hermesinoides (O. Wetzel, 1940) nov. comb., the latter being now considered to be an acritarch.The rejection is proposed of the following species, which were nomenclaturally superfluous when published: Astrocysta koslowskii (Górka 1963) Davey, 1970; Gonyaulacysta fragosa Brideaux, 1971; Hystrichosphaeridium brideauxi Lentin and Williams, 1973; Oligosphaeridium diastema Singh, 1971 and Pseudoceratium regium Singh, 1971. Reasons are given for the rejection of the following generic reallocations: Hystrichodinium voigti (Alberti, 1961) Corradini, 1973 and Tenua anaphrissa (Sarjeant, 1966c) Benedek, 1972. Rhombodinium Gocht, 1955 is considered to be best treated as a subgenus of Wetzeliella Eisenack, 1938 emend. Williams and Downie, 1966b as originally proposed by Alberti, 1961.     

The Late Cambrian acritarch Cristallinium randomense: morphology,taxonomy and stratigraphical extension

The holotype of Cristallinium randomense Martin and other figured specimens are re-examined. The processes are often grouped as those of typical Vulcanisphaera species. Probable connections between Cristallinium and Vulcanisphaera are indicated. These genera form a plexus in which Retisphaeridium is also possibly involved. A complete bibliographical list of C. randomense is provided. Few published specimens are demonstrated to belong to this species. As a consequence, some stratigraphical dates, based on the restricted Late Cambrian range of the species, are questioned. The new combination Retisphaeridium ovillense (Cramer and Diez de Cramer) Vanguestaine nov. comb. is proposed.     

Upper Ordovician microphytoplankton of the Bill's Creek Shale and Stonington Formation,Upper Peninsula of Michigan,U.S.A.: Biostratigraphy and paleogeographic significance

An abundant, diverse, and well-preserved organic-walled microphytoplankton assemblage is described from the Upper Ordovician Bill's Creek Shale and the lower Stonington Formation (Bay de Noc Member) in the Upper Peninsula of Michigan, U.S.A. Based on graptolite and conodont evidence, the Bill's Creek Shale and Stonington Formation are Richmondian (=Ashgill) in age. The assemblage is dominated by acritarchs, which comprise 29 species (including the enigmatic palynomorph Gloeocapsomorpha prisca) assigned to 20 genera. The prasinophyte phycomata are represented by undifferentiated species of Leiosphaeridia and Tasmanites. In addition, chitinozoans are abundant, and scolecodonts and graptolite fragments are common. Paleontologic-palynologic and sedimentologic evidence indicates that the Bill's Creek Shale was deposited in a low-energy, shallow, nearshore marine environment. The overlying Bay de Noc Member of the Stonington Formation also accumulated in a low-energy, normal marine environment, but in a more offshore, somewhat deeper water setting. Both formations experienced minor transgressive and regressive episodes as indicated by fluctuations in the composition of the palynoflora. The combined Bill's Creek/Stonington acritarch assemblage closely resembles those described from the Richmondian-aged Maquoketa Shale (Missouri and Kansas), Sylvan Shale (Oklahoma), and Vauréal Formation (Anticosti Island, Québec, Canada). The overall composition of the acritarch assemblage from these four formations reflects a distinctive, recognizably Laurentian character. Nonetheless, many of the Bill's Creek/Stonington acritarchs have been reported from Upper Ordovician localities elsewhere, providing additional evidence for Late Ordovician cosmopolitanism of the marine microphytoplankton community. Additionally, the restricted stratigraphic range of many of the taxa further enhances their biostratigraphic application, both regionally and globally, and reaffirms the Richmondian (=Ashgill) age of the Bill's Creek Shale and Stonington Formation.     

Miospore assemblages from the Silurian–Devonian boundary,in borehole A1-61, Ghadamis Basin,Libya

Well preserved and diversified miospore assemblages have been recorded from a relatively continuous sequence in borehole A1-61 which spans the Silurian–Devonian boundary in the northwestern part of the Ghadamis Basin, Libya. The sequence is represented by early Devonian Lochkovian beds of the Tadrart Formation that transgress onto the Silurian Ludlow-Pridoli beds of the upper part of the ‘Alternances Argilo-gréseuses’ Formation. The present work demonstrates a succession of miospore assemblages from closely sampled layers that have been stratigraphically dated as Ludlow–middle Pridoli and early Lochkovian by chitinozoans and acritarchs. Over 80 species of cryptospores and trilete spores have been identified. Modified detailed morphological interpretations are given. The miospore assemblages are correlated with miospore zonation schemes established for the type sequences of the Welsh Borderland, and those previously described from Libya. Early occurrences of some species as Streelispora newportensis on the western Gondwana plate, are put forward by comparison with the Old Red Sandstone continent. Phytogeographic and palaeobotanic implications based on these observations are discussed.     

Le Silurien et le Dévonien basal dans le Nord de la province de Seville (Espagne)

In the studied area, on the southern slope(«Ossa-Morena Zone) of the Sierra Morena (Spain) the Silurian and earliest Devonian (Lochkovian = approximately Gedinnian) consist of about 130 m of black, argillaceous, largely euxinic graptolitic slates, which, by the intermezzo of the dark «Limestones with Orthoceras and Scyphocrinus (late Ludlow and Pridolian), are divided into two inequal units, namely the Lower and Upper Graptolitic Slates. The occurence of 21 Graptolite zones and horizons was established, starting off with the basal Llandovery (A. acuminatus zone) and ending up with the Upper Lochkovian (M. hercynicas zone). This condensed tripartite graptolitic sequence, both lithologically and faunally, compares closely with the typical development of the Palaeotethys, as known from Thuringia, Carnic Alps, Sardinia and Northwest Africa. Certain graptolite species and details of the graptolitic succession (for instance across the Wenlock-Ludlow junction) that were hitherto known only or essentially from Thuringia, are recognized also in southern Spain.