Middle Telychian (upper Llandovery, Silurian) graptolites from boreholes of northwestern Libya: Their biostratigraphic significance and palaeogeographical implication

A low-diversity but stratigraphically and palaeobiogeographically important graptoloid association comprising Metaclimacograptus flamandi (Legrand), Parapetalolithus meridionalis (Legrand), and Torquigraptus australis Štorch was identified in the core samples of wells A1-66, F1-66 and A1-43 in the Ghadamis Basin of Libya. The former two species have been originally recovered from Algeria. All three taxa are common and widespread in the middle Telychian strata of Spain (Central Iberian Zone and western Iberian Cordillera) and France (Brittany). In European sections, the species are associated with other, moderately diverse graptoloid fauna, which enables a more precise and worldwide biostratigraphic correlation of Saharan boreholes and surface sections. The present faunal association indicates a middle Telychian age (upper crispus, griestoniensis and lowermost crenulata/tullbergi biozones) for the strata and suggests palaeobiogeographical links between North African pericratonic basins and Ibero-Armorican shelves. M. flamandi has not been found outside this NW-Gondwanan realm.     

Llandovery sporomorphs and graptolites from the Manbo Formation,the Mojiang County,Yunnan, China

Llandovery sporomorphs and graptolites have been recovered from the Manbo Formation, Mojiang area, western Yunnan, China, which belonged to the Indo-China Palaeoplate in the Palaeozoic. The graptolite fauna, including 8 genera and 12 species, is considered Mid Telychian, Llandovery in geological age, confirming the existence of Llandovery rocks in this region. The Silurian stratigraphical sequence of this area is reconsidered as in the ascending order: Manbo Formation (Llandovery–early Wenlock), Shuiqing Formation (late Wenlock–Ludlow) and unnamed formation (Pridoli?). The sporomorph assemblage from the Manbo Formation includes seven species in five genera. The dominant members of this assemblage are Tetrahedraletes medinensis and Laevolancis chibrikovae. Based on the low diversity and low abundance, the geological age of this assemblage is considered to be approximately the Telychian, Llandovery. The parent plants of sporomorphs probably inhabited the landmass near Mojiang area, these sporomorph-producing plants probably included bryophyte-like land plants and primitive vascular land plants. The sporomorph evidence shows that the South China and Indo-China palaeoplates may have been in close proximity (maybe with some continental bridges linking them) to each other at least in the Llandovery. They were also closely related with Gondwanaland in the Llandovery.     

Palynostratigraphic,palynofacies, organic geochemical and palaeoenvironmental analysis of the Silurian Tanezzuft Formation in the Ghadames Basin of north-west Libya

Two palynofacies associations are documented from the Silurian Tanezzuft Formation in the Ghadames Basin. These are characteristic of the basal ‘Hot Shale’ and the overlying deposits, referred to here as the Cold Shale. The former reflects deposition in distal suboxic anoxic conditions and is dominated by highly oil-prone amorphous organic matter (AOM) typical of deposition in generally anoxic, restricted marine basins. Only a few acritarchs, prasinophyte algae and chitinozoans occur in association: virtually no spores or cryptospores were recorded. Thick-walled prasinophytes are most numerous in this part of the Tanezzuft Formation in both the Ghadames and Murzuq basins, suggesting enhanced surface water productivity. Deposition took place after the melting of the Late Ordovician ice sheets, which led to a major marine transgression. The palynofacies recorded from the overlying ‘Cold Shale’ deposits indicate deposition in distal shelf and basin conditions that were also relatively anoxic. They contain more palynomorphs, especially acritarchs, and generally less AOM. The phytoplankton assemblages are dominated by simple and thin-walled prasinophyte algae (leiospheres), suggesting dysoxic–anoxic conditions. Overall the middle and the upper parts of the Tanezzuft Formation are regarded as being deposited in distal dysoxic–anoxic shelf, distal dysoxic–oxic shelf and distal suboxic–anoxic basin respectively. Because chitinozoans are very rare, age determinations of the samples investigated are based mainly on acritarchs. The Hot Shale is dated as early-mid Rhuddanian (early Llandovery) whereas the rest of the formation is considered to late Rhuddanian–Telychian in age. As documented previously from other samples of the Tanezzuft Formation in both the Ghadames and Murzuq basins, the Hot Shale has a very high TOC content and excellent source potential for liquid hydrocarbons, whereas rest of the formation is less rich in organic matter with larger terrestrial and oxidized components and hence reduced potential for sourcing hydrocarbons (both oil and gas).     

First documentation of Llandovery (Silurian) conodont genus Astropentagnathus in China (Langao,Shaanxi Province) and the age of Baiyaya Formation

Age of the Baiyaya Formation in the Ziyang-Langao region of Shaanxi Province remains debatable. Ten samples were taken for conodont biostratigraphical studies from the Tianwancun section. The first discovery of Astropentagnathus in China indicates that the genus has a wider geographical distribution than previously known. Conodont fauna from the Baiyaya Formation suggests that the lower part of the unit corresponds to the Pterospathodus eopennatus Superbiozone, and its upper part to the lower Wenlock (probably mainly to the Kockelella ranuliformis Superbiozone). Diachroneity of the Baiyaya Formation in the region is confirmed by conodont studies from the Tianwancun and Qiaoxi sections. Further studies are required to find out age-variation of the formation more precisely.     

Silurian to Mississippian series of the eastern Catalan Pyrenees (Spain), updated by conodonts, foraminifers and algae

Stratigraphic sections and microfossils samples from the upper part of the “Graptolitic Shales-Orthoceras Limestones” and from the Camprodon Formation lying in the area of Camprodon, eastern Pyrenees, Spain, have been studied. Some beds at the top of the “Graptolitic Shales-Orthoceras Limestones” correspond to the Torres Member of the Rueda Formation, and conodont faunas, indicating a Lochkovian age, are described. The Camprodon Fm. is interpreted to be turbidites deposited in deep sea fans, although slope deposits prevail in the eastern sections. One reworked carbonate clast from the Camprodon Fm. provided a valuable early Ludlow conodont fauna, from the Kockelella crassa Zone, reported for the first time in the Iberian Peninsula. Late Devonian conodonts and late Visean (Asbian-Brigantian) foraminifers and algae were also obtained from reworked limestone clasts, and latest Visean or Serpukhovian foraminifers from the sandstone matrix in the Camprodon Fm. The studied microfossils suggest a late Mississippian age for the Camprodon Fm. instead of the previously assigned late Silurian-Lochkovian age. This age must be considered when discussing the distribution of the Culm Facies in the Pyrenees and the significance of the contact between the Camprodon Fm. and the underlying “Graptolitic Shales”.     

An Unusually Diverse Llandovery (Silurian) Diplograptid Fauna from the Southern Urals of Russia and Its Evolutionary Significance

This vesiculosus Biozone assemblage of chemically-isolated graptolites from the Orenburg District of Russia was obtained from limestones associated with pillow lavas of the Sakmara Formation of Silurian–Early Devonian age. It comprises 30 species, of which 24 are described. Nine are new, one is a new subspecies, and eight are left under open nomenclature. The assemblage is unique in its diversity of minute biserial graptolites referable to the genera ' Glyptograptus ', Normalograptus , Sudburigraptus , and Metaclimacograptus ; and is unusual in that well-preserved graptolite faunas are rare at this stratigraphical level, which is fixed by the occurrence of Cystograptus vesiculosus (Nicholson) s.l. and Paraclimacograptus innotatus (Nicholson). The following new forms are described: ' Glyptograptus ' tamariscus praecursor subsp. nov., G. mazovoensis sp. nov., G. nikitini sp. nov., G. pavlinovi sp. nov., G. telarius sp. nov., G. zimai sp. nov., Normalograptus legrandi sp. nov., N. melchini sp. nov., N. sobolevskayae sp. nov., and Metaclimacograptus bjerreskovae sp. nov. Five evolutionary lineages are defined within the ' Glyptograptus ' tamariscus (Nicholson) plexus, modifying and extending the pioneer work of Packham (1962). The diverse ' Glyptograptus ' faunas are considered to be a replacement for the Normalograptus fauna which peaked in the late Ordovician and early Silurian. Metaclimacograptus , although reasonably diverse in its speciation, exhibits a conservative style of evolution with little fundamental change throughout the Llandovery. It is suggested that cortical bandages have species-specific dimensions and micro-features. Some problematical micro- and ultrastructural features are described, notably fibrillar textures, parallel to the fusellar margins, in several species.     

Trace and soft body fossils from the Pedroche Formation (Ovetian, Lower Cambrian of the Sierra de Córdoba, S Spain) and their relation to the Pedroche event

The low Lower Cambrian rocks from the Sierra de Córdoba contain one of the best successions in Europe, which consists of well exposed mixed facies with abundant fossil assemblages showing long stratigraphical ranges throughout the Pedroche Formation. These assemblages include diverse Ovetian archaeocyaths, trilobites, small shelly fossils, calcimicrobes, trace fossils and stromatolites. Trace fossils are still poorly known, and thus they are the main objective of this work. Ichnological data are obtained from the Arroyo de Pedroche 1, Arroyo de Pedroche 2 and Puente de Hierro sections. Trace fossils include the ichnogenera Bergaueria, aff. Bilinichnus, Cochlichnus, aff. Cosmorhaphe?, Cylindrichnus, Dactyloidites, Dimorphichnus, Diplichnites, Monocraterion, Palaeophycus, aff. Phycodes, Planolites, Psammichnites, Rusophycus, Skolithos, Torrowangea and Treptichnus, as well as faecal pellets, meniscate trace fossils and others. They are abundant in shales and sandstones, and indicate important changes in the benthic conditions with respect to the underlying Torreárboles Formation. Changes in fossil assemblages within Member I of the Pedroche Formation indicate palaeoecological disruptions, which led to the disappearance of numerous archaeocyath species and the decrease of stromatolite biodiversity. This was followed by dominance of trilobite and brachiopod assemblages, accompanied by trace fossils of the Psammichnites ichnosp. A ichnoassociation. This biotic turnover (Pedroche event) occurred at the lower part of the archaeocyath Zone III, within the Bigotina bivallata biozone. The diagnoses of the ichnospecies Cochlichnus anguineus and Dactyloidites cabanasi are emended.     

High-resolution stratigraphy of the Cenomanian-Turonian boundary interval at Pueblo (USA) and wadi Bahloul (Tunisia): stable isotope and bio-events correlation

A high-resolution stratigraphy has been developed for the interval encompassing the Cenomanian-Turonian boundary (CTBI), by means of several lithological, biological and geochemical events. This work entails the study of two sections selected on the base of the completeness of their sedimentary record and their contrasting paleogeographical setting: (1) The Rock Canyon Anticline section west of Pueblo, Colorado, (US Western Interior Basin), which is the Global Boundary Stratotype Section and Point (GSSP) candidate for the base of the Turonian stage, as well as the reference section for the ammonite biostratigraphy of the CTBI; and (2) The wadi Bahloul section in Central Tunisia which is the best and complete section spanning this time interval in the southern Tethyan Margin. These sections record similar biogeochemical events that can be correlated over a great distance.Several important biological and geochemical events determined in these sections relative to the ammonite zonation of the CTBI are listed below in chronological order from old to young: 1. FO (first occurrence) of Sciponoceras gracile-Metoicoceras geslinianum ammonite Assemblage-Zone, 2. δ¹³C peak I, 3. LO (last occurrence) of Rotalipora cushmani, 4. “Heterohelix shift”, 5. FO of the ammonites Pseudaspidoceras pseudonodosoides and Neocardioceras juddii, 6. δ¹³C peak II, 7. δ¹³C peak III, 8. LO of Cenomanian ammonites (Ps. pseudonodosoides and N. juddii), 9. LO of Anaticinella, 10. FO of Turonian ammonites (Watinoceras devonense, base of the Turonian stage), 11. “filament event”, 12. FO of Pseudaspidoceras flexuosum, 13. FO of the Tethyan Helvetoglobotruncana helvetica, 14. FO of Mammites nodosoides, 15. FO of the Western Interior H. helvetica.In the two sections, the Cenomanian-Turonian (C/T) boundary, as defined by the ammonite biostratigraphy, is placed within an interval about 50 cm thick. This interval is termed here as the C/T boundary “precision interval”. The δ¹³C peak III slightly precedes the precision interval. The genus Anaticinella planktic foraminifer disappears in the middle part of this interval. The “filament event” occurs just above it and is coeval with the first occurrence of Turonian ammonites. These events are useful for placing the C/T boundary precision interval in absence of ammonite markers.Comparing ammonite and planktic foraminiferal biostratigraphy we have dated and correlated changes occurring in planktic foraminiferal assemblages. On this base, as an important result, we have demonstrated the diachroneity of the FO of Helvetoglobotruncana helvetica and the variable duration of the Whiteinella archaeocretacea PRZ.     

Benthic foraminiferal assemblages of the Cretaceous platform carbonate succession in the Yavca area (Bolkar Mountains, S Turkey): biostratigraphy and paleoenvironments

The microbiostratigraphic analysis of the three outcrop sections from the Cretaceous inner platform carbonate succession in the Yavca area (Bolkar Mountains) allows to recognize the four local benthic foraminiferal zones. These are: (1) Voloshinoides murgensis and Praechrysalidina infracretacea Cenozone in the Lower Aptian; (2) Pseudorhapydionina dubia and Biconcava bentori Cenozone in the Middle-Upper Cenomanian; (3) Ostracoda and Miliolidae Interval Zone in the probable Turonian, represented by dolomitized limestones without any significant markers; (4) Moncharmontia compressa and Dicyclina schlumbergeri Cenozone in the Coniacian-Santonian. The benthic foraminiferal assemblages correspond to those in other areas of the Mediterranean realm, with the exception of a lack of alveolinids and orbitolinids due to unfavorable environmental conditions (inner platform, restricted shelf). After the regionally well-known emergence during the late Aptian, Albian and early Cenomanian, very shallow subtidal to intertidal conditions were re-established during the middle-late Cenomanian time. The Coniacian-Santonian benthic foraminiferal assemblage shows an increase in diversity and abundance as a result of open marine influence, confirmed by the presence of larger foraminifera (Dicyclina), Rotaliidae and radiolitid fragments. Thaumatoporella and Aeolisaccus-bearing wackestone intercalations still indicate the existence of sporadic restricted environment conditions. The Cretaceous shallow-water platform carbonate succession of the Yavca area is conformably overlain by gray pelagic limestones with calcispheres and planktonic foraminifera. The Campanian flooding of the Bolkar Da? carbonate platform resulted in drowning of the pre-existing biota and facies.     

Proetid trilobites from the middle Telychian (Llandovery,Silurian) Ningqiang Formation,Shaanxi, China

Four proetid trilobite species, Chuanqianoproetus guizhouensis Yin in Yin and Li, 1978, C. shuangheensis Wu, 1977, C. sp., and Latiproetus guizhouensis Yin in Yin and Li, 1978, are described from the Ningqiang Formation in Ningqiang County, Shaanxi, China. They are middle Telychian (Llandovery, Silurian) in age. Chuanqianoproetus and Latiproetus are both regarded as members of the subfamily Warburgellinae; the former has been considered to be a junior subjective synonym of Astroproetus, but on the basis of its morphology we argue here that they represent two independent genera. The poorly sorted bioclastic grainstones containing trilobite sclerites may indicate their deposition in turbulent conditions on an open marine platform.     

Maastrichtian calcareous nannofossil biostratigraphy and paleoecology in the Equatorial Atlantic (Demerara Rise, ODP Leg 207 Hole 1258A)

Species richness, absolute and relative abundances of Maastrichtian calcareous nannofossils were analyzed in Hole 1258A. Absolute abundances of taxa were used for the biozonation of this hole and the record of successive bio-events. Distribution patterns of cool water taxa such as Ahmuellerella octoradiata, Gartnerago segmentatum and Kamptnerius magnificus underscore two major cooling events. These events occurred during Chron C31r and during undifferentiated Chrons C31n to C30n. The latter event appears to be accompanied by lowered productivity, as expressed by the lower abundances of fertility index taxa Biscutum constans and Zeugrhabdotus spp. An end-Maastrichtian warming event is recorded in Chron C29r by the sudden drop in abundance of cool water taxa and acme of tropical taxon Micula murus. The disappearance of B. constans just before this event and the significant increase of Micula decussata, respectively, suggest lowered productivity and high-stress environmental conditions prior to the K/P boundary (Cretaceous-Paleogene). These results correlate very well with the climatic scenario proposed by Li and Keller (1998a) in South Atlantic Hole 525A as suggested by stable isotopes and distribution patterns of planktic foraminifera.     

Decapod Crustacea from the Agrio Formation (Lower Cretaceous) of the Neuquén Basin,Argentina

Abstract: Two species of decapod crustacean are recorded from the Agua de la Mula Member of the Agrio Formation (Upper Hauterivian – Lower Barremian) of the Neuquén Basin of west‐central Argentina, namely Astacodes falcifer Bell and a new species of Palaeohomarus, P. pacificus. The preservation of the specimens is exceptional, some showing delicate compound eyes and a stridulatory apparatus, features rarely found in fossil forms. Many specimens are preserved articulated inside calcareous nodules, within dark‐grey shales. The lobster‐bearing sediments accumulated in a low‐energy marine environment and diagenetic mineralization occurred very rapidly, prior to significant decay, thus allowing exceptional preservation of specimens. Palaeohomarus was a rare genus in the Cretaceous with a palaeogeographic distribution restricted to the Mediterranean Tethys, the eastern USA and Madagascar, while Astacodes falcifer has been recorded only from Speeton (eastern England) and Neuquén.     

Sheinwoodian (Silurian) conodonts and graptolites from NE Anti‐Atlas,Morocco

Männik, P., Loydell, D.K. & Lubeseder, S. 2010: Sheinwoodian (Silurian) conodonts and graptolites from NE Anti‐Atlas, Morocco. Lethaia, Vol. 44, pp. 410–416. Conodonts and graptolites from a limestone at the base of the Tamaghrout Formation indicate that this is of early Wenlock age. This is the first unequivocal dating of a Sheinwoodian limestone from Morocco. All of the conodonts are known also from several other regions and suggest that there was no major difference in conodont faunas in northern Gondwana, Baltica and Laurentia at this time. Biostratigraphy, conodonts, graptolites, Morocco, Silurian, Sheinwoodian.     

Late Viséan foraminifers and algae from the Cataloturan Nappe, Aladag Mountains, eastern Taurides, southern Turkey

The Aladag Mountains at the western end of the eastern Taurides, southern Turkey, are composed of nappe structures imbricated in the Late Cretaceous by ophiolite emplacement. The Cataloturan Nappe contains Mississippian (i.e., Early Carboniferous) deep-water (basinal-lower slope) facies in the lower part and shallow-water (shelf edge) facies in the upper part. These Mississippian strata belong to the Nohutluk Formation. The main outcrop occurs at Nohutluktepe where it is 460 m thick. Eighty taxa of algae, foraminifers, and calcareous microproblematica permit dividing the upper part of the formation into three informal assemblage biozones: (1) Howchinia bradyana longa - Lituotubella magna - Koktjubina (?) sp. biozone (late Viséan Cf6γ1), (2) Bradyina rotula - Euxinita tauridiana biozone (Cf6γ2), (3) Janischewskina typica - Biseriella aff. parva biozone (upper Cf6δ). The genus Euxinita is discussed and a new species E. tauridiana nov. sp. is described. A paleobiogeography, based on Euxinita, Koktjubina (?), Vissarionovella, Janischewskina and Hortonella, is reconstructed, where the Taurides are juxtaposed to the northwestern border of the Paleotethys, with possible direct connections with Russia, Kazakhstan, western Europe, and Morocco.     

Biotic structure and morphology of patch reefs from South China (Ningqiang Formation, Telychian, Llandovery, Silurian)

Summary Ningqiang Formation (late Telychian, Llandovery, Silurian), characterized by nearly 3000 m of shales in tercalated with carbonates, is situated between Ningqiang (S. Shaanxi Province) to Guangyuan (N. Sichuan Province) adjacent to the northwest margin of the Yangtze Platform. The high diversity “Xiushan Fauna”, and abundant reef development, illustrate a relatively warm and persistent shallo marine environment in these early Silurian sediments. The sequence shows reef radiation after recovery from the end Ordovician mass extinction envents. Multiple horizons of reef-building occurred within a relatively short geological interval and resulted in more than 30patch reefs up to 200 m in diameter and 1–50 m vertically, composed of abundant fossils. Reef biota include frame-building corals, stromatoporoids, bryozoans, and microbialites, and reef-associated oranisms such as crinoids, brachiopods, trilobites, gastropods, nautiloids and ostracods. Three reefrelated biotic associations are recognised: a) reefs dominated by framework with crinoids and microbia; b) reefs dominated by only crinoids and microbia; and c) crinoiddomainated facies. Seven representative reef examples illustrate different morphologies and growth styles. A high terrigenous debris input and shallow epicontinental ramp, which lacked obvious topographic variation, were major controls which resulted in rather simple reefs; sedimentation was apparently the main constraint on lateral and vertical extension of reefs, and prevented large-scale reef complexes developing.     

Melanosclerites from the Wilhelmi Formation (Lower Silurian,north-eastern Illinois,USA)

Melanosclerites, a little-known group of organic microfossils, are recorded for the first time from the Lower Silurian Wilhelmi Formation, Illinois, USA. The taxa described herein include Melanorhachis regularis Eisenack, 1942, Melanoarbustum balticum Górka 1971, Melanocyathus dentatus Eisenack, 1942, Eichbaumia incus? Schallreuter, 1981, Menola os Schallreuter, 1981 and Melanoporella clava Schallreuter, 1981.     

Biostratigraphic control of the latest-Ordovician glaciogenic unconformity in Alnif (Eastern Anti-Atlas, Morocco), based on brachiopods

In the Alnif region of the Eastern Atlas (Morocco), seven fossiliferous horizons within the Lower-Ktaoua and Upper-Tiouririne formations (Ktaoua Group), as well as in the glaciomarine microconglomeratic shales of the Upper Formation of the Second-Bani Group have yielded biostratigraphically significant brachiopods and other taxa, such as trilobites and echinoderms. Several brachiopod species with short stratigraphic ranges, well-known in south-western Europe, allow a precise chronostratigraphic control of a succession that displays important lateral lithological and facies changes, when compared with the type sections in the Central Anti-Atlas. They have also permitted a better consensus between the macrofauna-determined age and that based on micropaleontological analyses. For the first time, the occurrence of a Hirnantia Fauna within the microconglomeratic shales of the Upper Formation of the Second Bani Group is reported. The biostratigraphic conclusions restrict the age of the Latest Ordovician glaciation to the early Hirnantian.     

Sexual and individual morphometric variation in Libycosaurus (Mammalia, Anthracotheriidae) from the Maghreb and Libya

Anthracotheres of late Middle Miocene and Late Miocene age have been described from several localities in northern Africa, all of them currently assigned to the genus Libycosaurus Bonarelli, although in several previous works they were assigned to Merycopotamus Falconer and Cautley, a considerably younger and specialised form from the Indian subcontinent which has quite different dental and cranial morphology. Three species of Libycosaurus have been named, but there has been some doubt about the morphometric variation within the various species, with some authors such as Gaziry (1987) placing the fossils from Sahabi (Latest Miocene, Libya) and Beglia (end Middle Miocene to basal Late Miocene, Tunisia) into the same species despite marked size differences, and others (Ducrocq et al., 2001) creating a species for a restricted sample of small specimens from Nementcha (Late Middle Miocene, Algeria), but which overlaps with the range of size variation of Beglia fossils. The aim of this paper is to examine the available samples in greater depth in order to understand the morphometric variation in these anthracotheres. It is confirmed that the Beglia sample is quite variable (Black, 1972), both morphologically and metrically, but it is concluded that it nevertheless belongs to a single species, because specimens from some of the localities within the Beglia Formation (e.g. Loc. 17 in the lower levels at Beglia) span the entire range of variation (Pickford, 1994). The sample from Nementcha cannot be distinguished from the Beglia sample on any consistent metric or morphological basis, but in general the specimens fall at the low end of the range of variation of the Beglia sample. It is thus likely that L. algeriensis is a synonym of L. anisae. The Sahabi and Chad samples (L. petrocchii), in contrast, fall above the known range of variation of the Beglia material in almost all metric features, but are close to it morphologically, and they are considered to represent a species distinct from the Beglia sample.     

A late Rhuddanian (early Llandovery,Silurian) trilobite association from South China and its implications

A recovery trilobite association after the end-Ordovician mass extinction, the ‘Encrinuroides’ Association, is documented from the lower Niuchang Formation (upper Rhuddanian, lower Llandovery, Silurian) of Gaojiang, Meitan, northern Guizhou, South China paleoplate, including 10 genera of eight families. Three subassociations of this association could be differentiated, i.e., ascendingly the ‘Encrinuroides’-Eoleonaspis Subassociation, the ‘Encrinuroides’-Aulacopleura (Paraaulacopleura) Subassociation, and the ‘Encrinuroides’-Meitanillaenus Subassociation. The succession of these subassociations in the section indicates a shallowing upward trend of the environment as a result of regional tectonic activities (i.e., the Qianzhong Uplift) against the background of the Rhuddanian global transgression. A relatively complete trilobite succession in South China across the Ordovician–Silurian transition has been summarized and its implications for the trilobite macroevolution of this particular time interval are discussed in detail.     

Mississippian (Lower Carboniferous) microfossils from the Chios Mélange (Chios Island, Greece)

The Chios Mélange is a thick Paleozoic wildflysch sequence that crops out on the Greek island Chios. It is composed of chert, limestone and volcanic blocks floating in a siliciclastic turbiditic matrix. New data suggest that the youngest blocks within the Chios Mélange are clasts of a breccia from the Kouramia-Nenitouria area that contain conodonts of late Visean or early Serpukovian age. The conodont fauna from the breccias is characterized by the genera Gnathodus and Lochriea, which favored deeper-water, open-marine facies. Elsewhere on the island, in the Papalia-Nagos area, calcareous microfossils of middle to late Visean age have been recovered from lime grainstone beds within the Chios Mélange. Allochems making up the grainstones are interpreted to have been transported into deeper-water turbiditic facies, but there is no evidence of stratigraphic reworking. Age-diagnostic calcareous microfossils include the alga Koninckopora inflata and foraminifers in the genus Paraarchaediscus. In situ Mississippian microfossils indicate that the Chios Mélange is older than Pennsylvanian (Upper Carboniferous) - Permian, as previously thought. The revised age suggests that the origin of the Chios Mélange may be related to the development of an accretionary prism during the Hercynian Orogeny.© 2003 Éditions scientifiques et médicales Elsevier SAS. All rights reserved.