滇西巍山地区上三叠统诺利阶三合洞组牙形石年代及沉积相分析*

滇西兰坪-思茅地块晚三叠世诺利期(Norian)发育一套海相碳酸盐岩沉积(三合洞组)。对巍山三合洞剖面进行了实测与采样, 分离了三合洞组碳酸盐岩中的牙形石, 经鉴定其种属为Epigondolella vialovi, Epigondolella uniformis和Epigondolella aff. triangularis, 时代为早诺利期(Lacian亚期)。通过野外剖面及室内显微薄片观察, 采用微相分析的方法对剖面三合洞组碳酸盐岩的微相类型和沉积环境进行研究, 将巍山三合洞剖面三合洞组沉积归纳为9种微相, 并根据微相特征结合野外宏观特征, 将三合洞剖面划分为3种沉积相类型, 即局限台地相、开阔台地相和台地边缘礁相。在剖面不同层位的碳酸盐岩中发现的热液矿物石榴子石及发黑的牙形石化石(CAI指数约为5), 表明该区曾遭受热液作用的影响, 可能与三合洞组沉积后大陆边缘裂谷下陷或板块拼合引起的热卤水上涌有关。     

Integrated radiolarian and conodont biostratigraphy of the Middle Permian Gufeng Formation (South China)

Radiolarians are usually abundant in chert sequences and they have thus been widely used for the biostratigraphy of deep-water sediments. However, there are many difficulties in the correlation of radiolarian biostratigraphic schemes with the standard conodont zones. In this study, 21 radiolarian species were extracted from the Gufeng Formation that crops out in the Luojiaba (LJB) section (western Hubei, China), together with 5 co-occurring conodont species. In this way, it is the first time that the Pseudoalbaillella globosa, Follicucullus monacanthus and F. scholasticus radiolarian zones can be directly correlated with the Jinogondolella nankingensis gracilis, J. aserrata and J. postserrata conodont zones. Accordingly, the 3 radiolarians zones are now firmly correlated with the Roadian to middle Capitanian interval (Middle Permian).     

A biogeographically mixed, Middle Permian brachiopod fauna from the Baoshan Block, western Yunnan, China

A small brachiopod fauna is described from the carbonate rocks of the basal Shazipo Formation of the Baoshan Block, western Yunnan, south-west China, including significant new ventral and dorsal internal morphological features of Cryptospirifer omeishanensis Huang. This fauna is regarded as Wordian (Middle Guadalupian, Middle Permian) because of the presence of Cryptospirifer omeishanensis Huang and associated fusulinids ( Neoschwagerina craticulifera Zone). Palaeobiogeographically, the brachiopod fauna is of considerable interest because of its admixed nature characterized by typical warm-water Cathaysian elements intermingled with temperate Peri-Gondwanan taxa. This in turn is interpreted to indicate that the Baoshan Block may have been situated in an intermediate palaeogeographical position between Gondwanaland to the south and Cathaysia to the north during the Mid Permian and, as such, it probably furnished an important 'stepping stone' for the dispersal of Mid Permian eastern Tethyan marine invertebrate taxa (e.g. Cryptospirifer ) to the western Tethys.     

Carnian-Norian biomagnetostratigraphy at Silická Brezová (Slovakia): correlation to other Tethyan sections and to the Newark Basin

Correlations of Upper Triassic magnetic stratigraphies from Tethyan sections have been hampered by difficulties with conodont biostratigraphy and taxonomy, and discontinuous sedimentation, particularly in the ‘Hallstatt Limestones’ of Turkey and Austria. The magnetic stratigraphy and conodont biostratigraphy from the Upper Carnian to Upper Norian limestones exposed at Silická Brezová (Slovakia) can be correlated to other Tethyan sections and to the continental succession in the Newark Basin. The resulting correlations help to resolve some of the apparent discrepancies in existing conodont zonations, and result in a revised correlation to North American terrestrial vertebrate and palynological zones. The correlations imply that the Norian-Rhaetian boundary lies within Newark polarity zone E17r at ∼207 Ma. The Carnian-Norian boundary lies close to the base of Newark polarity zone E7r at ∼226 Ma. This implies durations for the Norian and Rhaetian stages of 19 Myr and 7 Myr, respectively.     

Apparatus architecture of the conodont Nicoraella kockeli (Gondolelloidea,Prioniodinina) constrains functional interpretations

We reconstruct the apparatus architecture of the gondollelid conodont Nicoraella kockeli based on fused clusters from the early Middle Triassic (middle Anisian, Pelsonian) of Luoping County, east Yunnan Province, south‐west China. This material was characterized non‐invasively using synchrotron x‐ray tomographic microscopy and the ensuing data analysed using computed tomography, allowing us to infer the composition, homologies and architectural arrangement of elements within the apparatus. Much of the original three‐dimensional architecture of the apparatus is preserved and our apparatus reconstruction is the best characterized of any taxon within the superfamily Gondolelloidea. This allows us to test architectural models for gondolelloids and prioniodinins, more generally, as well as the functional interpretations based upon them. In particular, we reject a recent functional interpretation of the conodont feeding apparatus which was based on a biomechanically‐optimized inference of apparatus architecture in a close gondolelloid relative of Nicoraella. Nevertheless, our architectural model provides a foundation for future functional interpretations of gondolleloids and prioniodinins, more generally.     

Eustatic trends in conodont diversity across the Frasnian–Famennian boundary in the stratotype area, Montagne Noire, Southern France

Trends in generic diversity of successive conodont communities are analysed in sections of different environmental settings across the Frasnian–Famennian (F–F) boundary in the stratotype area, Montagne Noire, France. The evolution of conodont biofacies and abundances matches the overall pattern already observed in many sections elsewhere in the world and supports the interpretation of an important eustatic sea-level fall during the Upper Kellwasser event. The change from late Frasnian deep-water palmatolepid–polygnathid biofacies to shallower-water polygnathid-icriodid biofacies during the Upper Kellwasser event occurred in all sections studied. The shallowing trend culminated at the end of the Kellwasser Event as indicated by the substantial increase of formerly poorly represented icriodids, whereas palmatolepids concomi-tantly diminished. This event occurred earlier on oxygenated outer platform submarine rises than in oxygen-depleted depressions. The sudden sea-level fall prior to the Frasnian–Famennian boundary was followed, at the beginning of the Famennian, by a deepening trend when palmatolepids dominated again. These changes in conodont generic associations and abundances occurred rapidly and synchronously. As a result, the stratigraphic resolution obtained with the evolution of biofacies is higher: it permits not only a more accurate location of the base of the Upper Kellwasser event in environments where it cannot be distinguished lithologically, but it also allows the recognition of intrazonal gaps.     

Early Triassic conodont clusters from South China: revision of the architecture of the 15 element apparatuses of the superfamily Gondolelloidea

Abstract: Several fused clusters of conodont elements of the genera Neospathodus and Novispathodus were recovered from limestone beds at the Dienerian–Smithian and Smithian–Spathian boundaries, respectively, from several localities in Guangxi province, South China. Conodont clusters are otherwise extremely rare in the Triassic, and these are first described for the Early Triassic. The exceptional specimens partially preserve the relative three‐dimensional position and orientation of ramiform elements and are therefore extremely important for testing hypotheses on the architecture of apparatuses. These specimens partly confirm the previous reconstruction of the Novispathodus apparatus by Orchard. Within apparatuses of members of superfamily Gondolelloidea, elements previously identified as occupying the S₁ and S₂ positions instead occupy the S₂ and S₁ positions. Similarly, within apparatuses of members of the subfamily Novispathodinae, elements previously referred to S₃ and S₄ positions are reinterpreted to have occupied S₄ and S₃ positions, respectively.     

Chitinozoan biostratigraphy of the Upper Ordovician Fågelsång GSSP, Scania, southern Sweden

In the Fågelsång section, the new Global Stratotype Section and Point (GSSP) for the base of the Upper Ordovician Series, 22 samples from the E14 (a, b and c) and E15 outcrops have been studied for chitinozoans. They yield rich and rather diverse species assemblages of this microfossil group. The approximately 16-m-thick sampled part of the section can be subdivided, from bottom to top, into two biozones and a subbiozone: the Laufeldochitina stentor zone, the Eisenackitina rhenana subzone and the Lagenochitina dalbyensis zone. The boundary between the lowest biozone and the subzone is situated 1.7 m below the marker “Fågelsång Phosphorite” bed, thus only slightly lower (0.3 m) than the base of the Nemagraptus gracilis graptolite biozone, which defines the base of the Upper Ordovician Series. The base of the L. dalbyensis zone is located just above the Fågelsång Phosphorite, remarkably low compared to the graptolite biostratigraphy. It is evident that the chitinozoan biozonation provides an additional tool to recognise the base of the Upper Ordovician in this section. Furthermore, a distinct faunal change is shown across the phosphorite bed, possibly indicating a hiatus.     

The Permian fusulinoidean faunas of the Sibumasu and Baoshan blocks: their implications for the paleogeographic and paleoclimatologic reconstruction of the Cimmerian Continent

Permian fusulinoidean faunas occur in mainly four stratigraphic levels in the Baoshan Block of West Yunnan and the Sibumasu Block of Southeast Asia, which constituted part of the eastern Cimmerian Continent. The oldest fauna, from the upper part of the Dingjiazhai Formation in the Baoshan Block, consists of Pseudofusulina, Eoparafusulina, and a new boultoniid genus, and is assignable to the Yakhtashian (=Artinskian). The second one, which occurs in the basal part of the Ratburi Limestone and its equivalent strata in the Sibumasu Block, is represented by Monodiexodina, and is probably referable to the Bolorian (=Kungurian). The third fauna, composed of Eopolydiexodina, Rugososchwagerina, Yangchienia, Chusenella, Jinzhangia, and several other genera, is dated to the Murgabian (=Wordian), and occurs in the lower part of the Shazipo and Daaozi formations in the Baoshan Block and the main part of the Ratburi Limestone in the Sibumasu Block. The youngest fauna of probably Dzhulfian (=Wuchiapingian) age is found in the upper part of the Ratburi Limestone, and contains Nanlingella, Reichelina, Codonofusiella?, and a few staffellid genera. A smaller foraminiferal genus, Shanita, found from the upper part of the Ratburi Limestone and the upper part of the Shazipo Formation is also an important element of the foraminiferal assemblage near the Midian-Dzhulfian (=Capitanian-Wuchiapingian) boundary in the Baoshan and Sibumasu blocks.In the eastern Cimmerian Continent, low generic diversity throughout the Permian and the paucity of Tethys-characterizing neoschwagerinid and verbeekinid genera during Middle Permian time are two remarkable features of the Permian fusulinoidean faunas. In the Cimmerian Continent, the generic diversity of Permian fusulinoidean faunas in space and time gradually increases from the Early Permian to late Middle Permian as well as from the eastern Cimmerian areas to western ones. The temporal increase of the generic diversity can be explained by the northward drift of the Cimmerian Continent during Permian time. In contrast, the lower generic diversity of the eastern Cimmerian Permian fusulinoidean faunas against western ones is possibly due to an oblique arrangement of the continent to paleolatitude. Thus, the western Cimmerian Continent was more proximal to the tropical Tethyan domain than its eastern part. In addition, the Middle Permian Cimmerian paleobiogeographic region is likely to be subdivided into two subregions, the western Tethyan Cimmerian and the eastern Gondwanan Cimmerian, based on the distribution pattern of verbeekinid and neoschwagerinid fusulinoideans and overall generic diversity. The scarce occurrence or total absence of these essentially Tethys-indicating fusulinoideans in the Baoshan and Sibumasu blocks suggests that the eastern Cimmerian Continent was still far from the equatoro-tropical Cathaysian domain and was probably in a warm temperate or subtropical zone until the end of the Permian. The eastern Cimmerian areas finally migrated into a tropical zone by the Late Triassic judging from well-developed Carnian sponge-coral buildups in the Chaiburi Formation in the Sibumasu Block.     

Pattern of conodont reworking in the Upper Devonian of the Alps: palaeoenvironmental and palaeotectonic implications

Transfer of sediments from shallow shelf to basin usually implies vertical (stratigraphic) reworking of fossils, but in a few instances produces only lateral reworking (actually within the time span of a subzone). An Upper Devonian (Frasnian) pelagic carbonate sequence with allodapic intercalations and thick intraclast parabreccias triggered by seismic shocks and related tsunami and turbidity currents has been studied. Here, the standard biozone sequence is undisturbed at the zonal as well as the subzonal level. However, distribution of conodonts is discontinuous, and ranges of some important species are altered; mature specimens are commonly broken, whereas complete specimens are mostly juvenile forms. Maxima and minima of element frequency and anomalous thickening or thinning of subzones are recognized. Such distribution patterns of conodonts are compared with the four main facies distinguished and related to the environmental interpretation (a platform-basin system, the original gentle slope of which was fragmenting in fault-controlled blocks). The mean frequency of shallow-water, proximal conodonts is 10% whereas transitional to distal deeper-water genera dominate throughout the entire section. In the dominant biofacies, conodonts settled vertically, in the subordinate one they were transported laterally. The 'intraclast parabreccia' is interpreted as a peculiar type of seismitc. The anomalous thickness variation of biozones is related to the step topography of the slope in a fault-controlled carbonate basin.     

A high-precision global biostratigraphy of myodocope ostracods for the Silurian upper Wenlock Series and Ludlow Series

The wide, trans-oceanic geographical distribution of myodocope ostracods during the Silurian (especially during the Ludlow and Pridoli epochs), and their widespread preservation in rocks of that age, permits the establishment of a transcontinental biostratigraphy of comparable resolution to coeval graptolite/chitinozoan/conodont biozones. Seven myodocope biozones, extending from the Homerian Stage, upper Wenlock Series Cyrtograptus lundgreni graptolite biozone to the middle part of the Ludfordian Stage of the Ludlow Series, enable a time-resolution for each biozone of circa 1 million years. These biozones can provide high-resolution correlation across Europe into Arctic Russia and Central Asia. There is also the potential for a myodocope biostratigraphy applicable from the uppermost Silurian (Pridoli) to the Carboniferous.     

High‐resolution conodont biostratigraphy from the Darriwilian Stage (Middle Ordovician) of the Argentine Precordillera and biodiversity analyses: a CONOP9 approach

Ordovician conodonts have been extensively documented in the Argentine Precordillera, providing a robust database for a diverse set of palaeontological studies. Despite the numerous studies, the published taxonomy and stratigraphical ranges, data remain contradictory for particular time intervals. Data from a new conodont collection from the Gualcamayo Formation exposed at the Cerro La Chilca section, and new information on the occurrence and ranges of species from the Las Chacritas and Las Aguaditas sections are presented herein. We used a computer‐assisted numerical sequencing program (CONOP9) to construct a composite stratigraphical range chart from data of 57 conodont species in four sections from the Argentine Precordillera. The identified zones of Lenodus variabilis, Yangtzeplacognathus crassus, Eoplacognathus pseudoplanus and Eoplacognathus suecicus allowed us to verify and adjust the biostratigraphical scheme for the Darriwilian of the Central Precordillera. Additionally, species of the genera Histiodella, namely Histiodella sinuosa, Histiodella holodentata, Histiodella kristinae and Histiodella bellburnenisis, enable a reasonable correlation between the Histiodella‐based zonation and the Baltoscandian zonation. Conodont diversity is evaluated using conventional measures (total diversity and normalized diversity) and an interval‐free approach with CONOP9 software. Our data show a positive pattern in conodont diversification, increasing rapidly through the L. variabilis to the Y. crassus zones and reaching a peak in the E. pseudoplanus Zone. When analysing diversity fluctuations with respect to the environmental changes within the depositional basin, migrations in and out of the basin related to local sea level fluctuations appear to be an important process driving the conodont diversity pattern in the Precordillera.     

Conodont biostratigraphy and carbon isotope chemostratigraphy of the Middle to Upper Ordovician on the western Yangtze Platform,South China

Middle and Late Ordovician strata in the nearshore area of the western Yangtze Platform are investigated. In total, 241 δ¹³C_carb samples and 108 conodont samples from the Songliang and Tuanjie sections in the northeastern Yunnan Province were collected for chemostratigraphic and biostratigraphic studies. Altogether, 21 species belonging to 16 conodont genera were recovered from the two sections, among which Ansella jemtlandica, Drepanoistodus basiovalis, Hamarodus brevirameus, and Microzarkodina hagetiana are important age indicators within the Dapingian to early Katian interval. Four carbon isotope shifts are recognized in the studied sections: a negative shift in the early Darriwilian, the middle Darriwilian carbon isotope excursion (MDICE), the early Katian Guttenberg carbon isotope excursion (GICE), and a further positive carbon isotope shift later in the early Katian which is a new record of this event in South China. Integrated carbon chemostratigraphy and conodont biostratigraphy indicate early Darriwilian and early Katian ages for the base and top, respectively, of the Huadan Formation at the Songliang section, and a Darriwilian to early Katian age for the Shihtzupu Formation at the Tuanjie section.     

Late Paleozoic faunal, climatic, and geographic changes in the Baoshan block as a Gondwana-derived continental fragment in southwest China

The Carboniferous and Permian of the Baoshan block consist of three major depositional sequences: a Lower Carboniferous carbonate sequence, a Lower Permian siliciclastic sequence, and a Middle Permian carbonate sequence. These three sequences were interrupted by two major regressive events: first, the Namurian Uplift ranging in age from Serpukovian to Gzhelian, and second, the Post-Sakmarian Regression occurring probably at Artinskian time in the Baoshan block, although the precise time interval of the latter event is still unclear. The Baoshan block is characterized by warm-water, highly diverse and abundant faunas during the Early Carboniferous, by cold-water and low diversity faunas during the Early Permian, and by possibly warm-water but low diversity faunas during the Middle Permian. The Sweetognathus bucaramangus conodont fauna constrains the upper boundary of the diamictite-bearing siliciclastic deposits (Dingjiazhai Formation) to the Sakmarian to early Artinskian, as well as the eruption of the rifting basalts (Woniusi Formation) to, at least, the post-early Artinskian. Paleozoogeographically, affiliation of the faunas in the Baoshan block changed from Eurasian in the Early Carboniferous, to Peri-Gondwanan in the Early Permian, and to Marginal Cathaysian/Cimmerian in the Middle Permian. Cimmerian blocks have more or less comparable geohistory to one another in the Carboniferous and Permian. During the Middle Permian, the eastern Cimmerian blocks such as Sibumasu (s.s), Baoshan, and Tengchong are not far from the palaeoequator, but apparently more distant than the western Cimmerian blocks based on the presence or absence of some index taxa such as the fusulinaceans Eopolydiexodina and Neoschwagerina, and the corals Thomasiphyllum and Wentzellophyllum persicum.     

New dasycladalean algae from the Middle Norian (Upper Triassic) of northern Italy (Mt. Pramaggiore, Carnic Prealps)

In the Eastern Southern Alps of northern Italy (Carnic Prealps, Friuli region), the shallow-water carbonate platform deposits of the Dolomia Principale Fm. (Norian–Rhaetian, Upper Triassic) show best-preserved platform to basin facies transition. The palaeontological study of an algal-rich level recovered from the platform margin facies (Mt. Pramaggiore) has displayed a very interesting association of Dasycladales. Two new genera (Bystrickyella and Elliottporella) and four new species (Bystrickyella ottii, Elliottporella morelloae, Palaeodasycladus lorigae and Holosporella conradii) have been described. These new data suggest that the Norian represents a period of turnover in the evolutionary history of the green algae community. This stage, placed between two extinctions, end-Ladinian and end-Norian, is here interpreted as a re-organization period of the evolutionary schemes of Dasycladales. The new lineages originated in the Norian developed further and characterized the Early Jurassic scenery. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Integrated biostratigraphy and carbon isotopes from the Cambrian Tangwangzhai section,North China

The Tangwangzhai section, western Shandong Province, North China, the type section for the Cambrian Kushan and Chaomitian formations, yielded a diverse and relatively well-preserved conodont fauna, in which we recognize the Westergaardodina orygma, Westergaardodina matsushitai, Muellerodus? erectus, and Westergaardodina aff. fossa–Prooneotodus rotundatus zones of the North China conodont zonation. The Tangwangzhai conodont succession can be correlated not only with the polymerid trilobites occurring in the section but also with the conodont zones established for South China. The first occurrence of Furnishina longibasis and Furnishina quadrata in the upper part of the Westergaardodina matsushitai Zone allows the recognition of the base of the Paibian Stage and Furongian Series in the upper part of the Kushan Formation. The base of the Jiangshanian Stage, in the uppermost Muellerodus? erectus Zone, can be recognized by the presence of Westergaardodina cf. calix close to the base of the Chaomitian Formation. Chemostratigraphic analyses of the Tangwangzhai section show the onset of a positive carbon isotope excursion, referred to the SPICE event, in the upper part of the Kushan Formation at a level corresponding to the first occurrence of F. longibasis and F. quadrata. The base of the Jiangshanian Stage in the section is close to the demise of the SPICE positive excursion.     

New insights into the ultrastructure, permeability, and integrity of conodont apatite determined by transmission electron microscopy

New crystalline structures have been observed in argon ion‐milled conodont elements from a diverse suite of Ordovician taxa (‘Cordylodus robustus’, Drepanoistodus suberectus, Panderodus gracilis, Plectodina? sp., Aphelognathus sp., Periodon aculeatus), using transmission electron microscopy (TEM). Electron diffraction patterns of albid tissue reveal that the component crystals are extraordinarily large, in the order of hundred(s) of microns. These large albid crystals show typical cancellate porosity, although a distinctly lamellar structure has also been observed within a large albid crystal positioned between hyaline lamellar and cancellate albid tissues. There is a distinct absence of ‘interlamellar space’ within all hyaline tissues examined, which are characterized by a polycrystalline matrix of micron‐scale elongate crystals that are both strongly aligned and tightly bound within a broader lamellar structure. Optical opacity, caused by light scattering within large (≥ 0.5 µm) pores, is also a feature of both albid and polycrystalline lamellar crown tissues. Accordingly, conodont hard tissues are differentiated by crystal size and shape, as well as inter‐ and intracrystalline porosity. These new observations highlight the structural complexities of conodont histologies and the need for more comprehensive investigations particularly of transitional crown tissues, which are not well defined by terms typically used in the literature. Their histological structures are interpreted to be a product of in vivo crystallization and thus provide new insights into the relative porosity, permeability, and inherent integrity of the tissues as well as their growth relationships. Accordingly, these data not only have implications for earlier histological and palaeobiological interpretations of conodont hard tissues but are also fundamental in determining their chemical integrity, which is crucial for characterizing palaeoseawater composition and palaeoenvironmental change. The potential for conodont apatite to retain primary chemical information depends on crystal size and permeability, so the large albid crystal domains are consistent with parallel geochemical studies that suggest that cancellate albid crown is more resistant to diagenetic modification.     

Mammalian lineages and the biostratigraphy and biochronology of Cenozoic faunas from the Riversleigh World Heritage Area,Australia

Lineage zones within nine contemporaneous mammalian lineages represented in the Cenozoic fossil vertebrate record from the Riversleigh World Heritage Area in northern Australia are used to resolve a series of faunal intervals from the Late Oligocene to Late Miocene. The results agree with previous interpretations of Cenozoic biostratigraphy, provide evidence for the presence of time horizons subdividing some of the four previously recognized Riversleigh biochrons A–D and also provide evidence supporting the allocation of a greater number of Riversleigh faunas to intervals within the Riversleigh biochronology than other methods in previous work. This approach demonstrates the biostratigraphical potential of evolutionary lineages.