Late Eocene sea retreat from the Tarim Basin (west China) and concomitant Asian paleoenvironmental change

The Paleogene sediments of the southwest Tarim Basin along the West Kunlun Shan in western China include the remnants of the easternmost extent of a large epicontinental sea. This shallow sea once extended across the Eurasian continent before it retreated westward and eventually separated as the Paratethys Sea. Climate modeling results suggest that this sea retreat is an equally important forcing mechanism as the Tibetan plateau uplift in the aridification of the Asian continental interior and the intensification of the Asian monsoon system. The age and paleogeography of the retreat are poorly constrained, hindering the understanding of its cause and paleoenvironmental impacts. This study reports litho- and biostratigraphic results from two sections recording the last major regression out of the Tarim Basin that is expressed by a regional transition from marine clastics and limestones to continental red-beds. Rich micro- and macrofossil assemblages, including benthic foraminifera, ostracods, bivalves, calcareous nannofossils and organic walled dinoflagellate cysts (dinocysts), indicate a shallow, proximal and marine environment. Strong similarity to assemblages known from Central Asia and Europe confirms that surface–ocean connections extended across Eurasia from the Tarim Basin to the western Tethys during the latest Eocene. Moreover, the recovered fossil associations date the last marine sediments as earliest Priabonian in age (~ 37 Ma; overlap between dinoflagellate Mps Interval Zone and calcareous nannofossil Zone CP 14). The retreat of the sea from the Tarim Basin is time-equivalent with the sea level lowstand at the Bartonian–Priabonian boundary but pre-dates both the Oligocene–Miocene regional uplift of the Pamir mountains and Kunlun Shan and the major eustatic sea-level falls of the Eocene–Oligocene Transition (~ 34 Ma) and mid-Oligocene (~ 30 Ma), which are usually held responsible for the sea retreat. Furthermore, a concomitant and significant aridification step occurs at ~ 36.6 Ma (top of chron C17n.1n) as recorded by regional sedimentary records of the Xining Basin along the northeastern Tibetan Plateau, suggesting that the Tarim Sea served as a significant moisture contributor for the Asian interior.     

Phylogeography of a widespread terrestrial vertebrate in a barely-studied Palearctic region: green toads (<Emphasis Type="Italic">Bufo viridis</Emphasis> subgroup) indicate glacial refugia in Eastern Central Asia

The phylogeography of western Palearctic species is relatively well studied, but data on Eastern Central Asia are scarce. We present one of the first data sets from a widespread terrestrial vertebrate (Bufo pewzowi) inhabiting Eastern Central Asian mountains and deserts to gain knowledge on its phylogeography in this region. We applied combined phylogenetic and demographic analyses to understand the evolutionary history using mitochondrial DNA D-loop variation of toads from 37 locations. Genetic structure of Bufo pewzowi is strongly affected by landscape: we found three haplotype groups in eastern Kazakhstan, Dzungaria and Tarim Basin, divided by the Tian Shan and Dzungarian Alatau ranges. A vicariant hypothesis may explain divergence among groups. The divergence time of the three major clades was estimated about 0.9 million years ago (confidence interval 0.5–1.4), and is discussed with respect to Quaternary uplifting and glaciation in the Tian Shan. Demographic analyses provided evidence for both historical bottlenecks and population expansions and suggested Pleistocene signatures. Glacial refugia were inferred in the Tarim Basin (around the Turpan depression), in southern Dzungaria (Urumqui region), at the northern foot of the Tian Shan (Gongnaisi) and perhaps at the Altai range (Terekti). Regional Post-Last Glacial Maximum dispersal patterns are proposed. A taxonomic hypothesis is presented. This study provides a detailed history of how a widespread terrestrial vertebrate responded to geological change and Quaternary glacial events in Eastern Central Asia and may have significance for future phylogeographic research in this understudied region.     

新疆塔里木盆地中侏罗世塔尔尕组孢粉植物群及地层和古地理意义

新疆塔里木盆地侏罗系分布广泛,在库车凹陷和塔西南区发育最好。目前对库车凹陷的三叠纪和侏罗纪孢粉植物群研究较为深入,而对塔西南区侏罗纪孢粉化石专题研究不多,尚未建立孢粉组合。作者基于塔西南区乌恰中侏罗统塔尔尕组发现的孢子花粉33属48种的研究,建立了塔尔尕组孢粉组合。该组合以掌鳞杉科花粉Classopollis的优势和真蕨目桫椤科孢子Cyathidites的繁盛为特征,并含有丰富多样且颇具侏罗纪色彩的孢子花粉化石类型。该组合与西欧和俄罗斯巴柔期至巴通期孢粉组合以及北美和澳大利亚巴柔期至卡洛夫期孢粉组合可以进行对比;与我国新疆库车恰克马克组、陕西延安直罗组和湖北兴山沙溪庙组等孢粉组合也可对比。根据孢粉学证据,塔尔尕组的时代应属于中侏罗世晚期(巴通期至卡洛夫期)。当前孢粉植物群支持我国侏罗纪南北植物地理区系之西端分界之划分方案,即塔西南乌恰处于界线以南,而库车处于分界以北。     

Lithostratigraphy, petrography and facies analysis of the Late Cenozoic sediments in the foreland basin of the West Kunlun

The Yecheng profile, lying in the southwest Tarim Basin at the northern foot of the West Kunlun Mountains, comprises 4.5 km of conformable Miocene to Pliocene strata. The lower part of the section, the Wuqia Group, is composed of interbedded red mudstone and pale-coloured fine sandstone with a thickness of 1700 m. The Artux Formation is 800 m thick and composed of mudstone, sandstone with thin gravel and conglomerate beds. The upper part of the section, known as the Xiyu Formation, consists of 2000 m of cobble and boulder conglomerate intercalated with massive siltstone lenses.Compositional study of the sandstones in the Wuqia Group and Artux Formation indicates that they were sourced from low relief areas of the Kunlun region and probably further south from Tibet. The provenance of the conglomerate in the Xiyu Formation is the West Kunlun Mountains. Compositional trends within the conglomerate indicate that Upper Palaeozoic marine, and Mesozoic to Tertiary terrestrial silicic rocks were eroded first, along with the Proterozoic to Lower Palaeozoic Proto-Tethys metasedimentary rocks. Erosion into deeper levels of the Kunlun Mountains provided igneous and high-grade metamorphic sediment, which first appears 640 m above the base of the Xiyu Formation.Lithofacies change from fine-grained mudstone and sandstone to coarse clasts coincides with the onset of aeolian sedimentation, indicating major shift of regional palaeoclimatic regime. Although climatic changes may have played an important role in controlling the sedimentary regime worldwide, our study of the lithostratigraphy and petrography of the Yecheng section suggests that the lithofacies change recorded the progressive unroofing history of the source rocks in the West Kunlun Mountains.     

Oligo-Miocene fluvial-dominated deltas on the shelf of the South Caspian Sea (Paratethys)

The Oligo-Miocene Zivah Formation forms the principal reservoir unit in the Moghan area of northwest Iran. Characterization of the constituent facies of the formation and their spatial distribution represent a major aspect of this investigation. The combination of results from the field and laboratory studies lead to the determination of 18 lithofacies and 13 petrofacies (petrographic lithofacies). Three major types of sedimentary cycles (small-, medium-, and large-scale cycles) of variable thickness (few meters, few tens of meters, few hundreds of meters, respectively) are recognized on the basis of facies association properties. Depositional environments representing each facies and facies association are defined and interpreted on the basis of their sedimentological characteristics. The major depositional systems of the Zivah Formation are interpreted as fluvial-dominated deltas on the shelf of the South Caspian Sea (or Paratethys). The principal controls on sedimentation are discussed in terms of lithofacies/petrofacies characteristics and the nature of sedimentary cycles. Development of large-scale cycles is related to world-wide sea-level change (eustasy), medium-scale cycles to tectonism along the basin margin, and small-scale cycles to the rate of sediment supply and local environmental conditions. Active tectonism seems to be the main cause for high sediment supply to the Zivah Basin.     

中国新疆塔里木盆地上奥陶统良里塔格组的钙藻化石

钙藻是可以发生生物钙化作用形成钙质"骨骼"的分属多个门类的藻类的俗称。钙藻最早出现于寒武纪,奥陶纪发生第一次辐射演化。本文系统讨论了绿藻门绒枝藻目(Dasycladales)、羽藻目钙扇藻科(Udoteaceae)的科和属级分类标准和红藻门珊瑚藻科、管孔藻科(Solenoporaceae)属级分类标准及其中各属分类中存在的问题。塔里木盆地晚奥陶世在塔中—巴楚台地和塔北台地发育了一套礁滩相良里塔格组碳酸盐岩,其中含有丰富的钙藻化石。本文系统描述了来自塔里木盆地塔中、巴楚、塔北地区取心井上奥陶统良里塔格组岩层中的钙藻化石11个属15个种。包括绿藻门绒枝藻目西莱特藻科(Seletonellaceae)的Dasyporella,Kazakhstanelia,Vermiporella,Aphroporella,Arthroporella,绿藻门的羽藻目Bryopsidales(siphonales)的钙扇藻科的Dimor phosiphon,Palaeo porella,红藻门珊瑚藻目(Corallinales)的管孔藻科的Solenopora,Parachaetetes及Corallinales incertus familiae的Petro-phyton,以及分类位置不明的Monili porella。其中绒枝藻Ajakmalajsoria被视作Kazakhstanelia的同义名。     

Palaeogene marine stratigraphy in China

Palaeogene deposits are widespread in China and are potential sequences for locating stage boundaries. Most strata are non‐marine origin, but marine sediments are well exposed in Tibet, the Tarim Basin of Xinjiang, and the continental margin of East China Sea. Among them, the Tibetan Tethys can be recognized as a dominant marine area, including the Indian‐margin strata of the northern Tethys Himalaya and Asian‐margin strata of the Gangdese forearc basin. Continuous sequences are preserved in the Gamba–Tingri Basin of the north margin of the Indian Plate, where the Palaeogene sequence is divided into the Jidula, Zongpu, Zhepure and Zongpubei formations. Here, the marine sequence ranges from Danian to middle Priabonian (66–35 ma), and the stage boundaries are identified mostly by larger foraminiferal assemblages. The Paleocene/Eocene boundary is found between the Zongpu and Zhepure formations. The uppermost marine beds are from the top of the Zongpubei Formation (~35 ma), marking the end of Indian and Asian collision. In addition, the marine beds crop out along both sides of the Yarlong Zangbo Suture, where they show a deeper marine facies, yielding rich radiolarian fossils of Paleocene and Eocene. The Tarim Basin of Xinjiang is another important area of marine deposition. Here, marine Palaeogene strata are well exposed in the Southwest Tarim Depression and Kuqa Depression. They comprise mostly neritic and coastal lagoon facies of the Tethyan realm. Palaeontological evidence suggests that the Paleocene/Eocene boundary here is in middle of the Qimugen Formation. The Tarim Basin was largely drained by Late Oligocene. To the east, the marine offshore Palaeogene strata are widespread in the North Taiwan and East Zhejiang depressions of the continental shelf basin of East China Sea. Abundant fossils including foraminifera, calcareous nannofossils, ostracods, pollen and bivalves occur in the marine environment. Biostratigraphically, the sequence is well correlated with the international planktonic foraminiferal and nannofossil zonations.     

Sarmatian (Late Middle Miocene) gastropod assemblages of the Central Paratethys

Summary A rather diverse gastropod fauna from Sarmatian deposits of the Austrian/Hungarian Eisenstadt-Sopron Basin was studied. The fauna derives from two layers of clay and silt within a siliciclastic section at St. Margarethen in Burgenland (Austria). These layers are interpreted as littoral mudflats which formed during the Sarmatian (Late Middle Miocene) along the western coast of the Central Paratethys. Strong shifts in the composition of the gastropod fauna, dominated by Potamididae (Cenogastropoda: Cerithioidea), within each layer indicate successions of limnic-fluvial to oligohaline, brackish-littoral, and marine-littoral environments. These shifts in facies are reflected by an alternational of thePotamides hartbergensis assemblage,Granulolabium bicinctum assemblage, and thePotamides disjunctus assemblage. The speciesJujubinus turriculus (Eichwald, 1850),Gibbula buchi (Dubois, 1831), andCylichnina elongata (Eichwald, 1830) are reported for the first time from the Sarmatian of the Paratethys.Mitrella agenta nov. sp. (Neogastropoda: Columbellidae) is introduced as a new species. These species might represent relics of the diverse Badenian fauna but could also prove a minor ingression of marine species from an adjacent bioprovince in the Late SarmatianMactra “Zone”.     

Palaeoenvironmental interpretation of the Pliocene fan-delta system of the Vera Basin (SE Spain): Fossil assemblages,ichnology and taphonomy

The marine fossil assemblages of the Pliocene of south Spain constitute the record of the marine fauna that colonised the western part of the Mediterranean after the Messinian Salinity Crisis. This work focuses on the analysis of lithofacies and fossil assemblages including trace fossils, invertebrates, and vertebrates with special attention to taphonomic features, for interpreting palaeoenvironmental conditions in the Vera Basin (SE Spain). The sedimentary sequences of the northern region of the Vera Basin display diverse stratigraphical, sedimentological, and palaeontological features that correspond to the evolution of a fan-delta in a narrow basin. The Vera Basin was characterised by shallow-marine shelf conditions during the early-mid Pliocene (Cuevas Formation). The basin emergence with the development of Gilbert-type fan deltas (Vera Member), and a protected, partially-enclosed marine embayment (Almanzora Member) occurred during the mid-late Pliocene due to regional uplift and movements of the Palomares strike-slip Fault along the eastern basin margin. The progradation of the central fan-delta lobes and the interaction with marginal fan-delta resulted in the partitioning of the basin that formed a small sub-basin with restricted stagnant conditions that favoured a Konservat Fossil-Lagerstätte. The high input of siliciclasts due to the uplift context of the margins of the basin favoured a high sedimentation rate and the fast burial of vertebrate remains. Fossil marine mammals occurs from shallow shelf deposits (Cuevas Formation) to bottomset (Cuevas Formation-Vera Member transition) and lower part of the clinoforms in the foreset (Vera Member). Cetacean remains are usually recorded not only in the relatively deep-water silty marls and sandy marls of the outer shelf and distal facies of the fan-delta (Espiritu Santo Formation), but also in the shallower coarse sands and conglomerates (Cuevas Formation and Espiritu Santo Formation). Sirenian remains, in contrast, are only recorded in coarse sand facies (Cuevas Formation and Espiritu Santo Formation) associated to charcoal wood fragments deposited in shallow waters near the shoreline. This narrow and relatively protected basin is interpreted as an area of reproduction and nursery of juveniles on the basis of the presence of cetaceans.     

A new skull of early cetacean Remingtonocetus harudiensis from the Eocene of Kutch Basin,India

A nearly complete skull of Remingtonocetus harudiensis was discovered from the Harudi Formation of the Kutch Basin, western India. Though several specimens have been collected over the last two decades by earlier workers, this skull shows variations in morphology within the species that were not known earlier. Hence, this finding is significant because it helps in expanding our knowledge of the skull morphology with the addition of characters such as the larger size of the skull, the difference in dental morphology, and the two-ridged external nasal feature and our understanding of how the molar morphology can vary within the same species. The newly excavated skull is the largest Remingtonocetus skull so far discovered and is similar to the size of Dalanistes ahmedi from Kutch, India and from Baluchistan, Pakistan. Thus, the range of the overall body size of the species will change considerably towards the higher side nullifying a major distinction between Dalanistes and Remingtonocetus. The new skull was excavated from the chocolate brown shales of the clastic facies of the Harudi Formation, in the inner ramp of a lagoonal phase. It is approximately 4 m above the nodular limestones from which the other Remingtonocetus materials were previously described. The limestone represents the carbonate facies of the Formation formed in a middle to outer ramp setting. An emended diagnosis of R. harudiensis is provided in this study. The Bartonian Harudi Formation of the Kutch Basin, thus, becomes unique in having Remingtonocetus specimens discovered from two different lithological facies from both the inner and outer ramp settings.     

Facies characteristic and paleoenvironmental reconstruction of the Fahliyan Formation,Lower Cretaceous,in the Kuh-e Siah area,Zagros Basin,southern Iran

The Lower Cretaceous Fahliyan Formation, part of the Khami Group, unconformably overlies the Hith Formation and is conformably overlain by the Gadvan Formation in the study area in southern Iran. The Fahliyan Formation is a reservoir rock in Zagros Basin. This formation was investigated by a detailed petrographic analysis in order to clarify the depositional facies and sedimentary environment in the Kuh-e Siah Anticline in Boushehr Province. Petrographic studies led to the recognition of 25 microfacies that were deposited in four facies belts: tidal flat, lagoon, and shoal in inner ramp and shallow open-marine in mid-ramp environment. An absence of turbidite deposits, reefal facies, and gradual facies changes indicate that the Fahliyan Formation was deposited on a carbonate ramp. Calcareous algae and benthic foraminifera are abundant in the shallow marine carbonates of the Fahliyan Formation. These skeletal grains have been studied in order to increase the understanding of their distributions in time and space. A total of ten genera belonging to different groups of calcareous algae and 16 genera of benthic foraminifera are recognized from the Fahliyan Formation at Kuh-e Siah section.     

塔里木盆地晚奥陶世良里塔格型生烃母质生物

本文描述塔里木盆地晚奥陶世塔中北斜坡带良里塔格组的生烃生物组合特征。指出缓斜坡背景下与灰泥丘有关的良里塔格组的生烃母质生物先质以混合型母质为特征。其组成主要有底栖宏观藻类、线叶植物、隐孢子、疑源类和几丁虫等。这是一类区别于世界上其它奥陶纪烃源岩Guttenburgen型的一类与灰泥丘有关的烃源岩的生烃母质生物类型。     

Depositional facies and cyclic patterns in a subtidal-dominated ramp during the Early-Middle Ordovician in the western Tarim Basin (NW China)

Due to a long-term transgression since the Early Cambrian, an extensive shallow-water carbonate platform was developed in the entire Tarim Basin (NW China). During the deposition of the Yingshan Formation (Early-Middle Ordovician), a carbonate ramp system was formed in the intrashelf basin in the Bachu-Keping area of the western basin. Four well-exposed outcrop sections were selected to investigate their depositional facies, cycles, and sequences, as well as the depositional evolution. Detailed facies analyses permit the recognition of three depositional facies associations, including peritidal, semi-restricted subtidal, and open-marine subtidal facies, and eleven types of lithofacies. These are vertically arranged into meter-scale, shallowing-upward peritidal, semi-restricted subtidal, and open-marine subtidal cycles, in the span of Milankovitch frequency bands, suggesting a dominant control of Earth’s orbital forcing on the cyclic sedimentation on the platform. On the basis of vertical facies (or lithofacies) and cycle stacking patterns, as well as accommodation changes illustrated graphically by Fischer plots at all studied sections, six third-order depositional sequences are recognized and consist of lower transgressive and upper regressive parts. In shallow depositional settings, the transgressive packages are dominated by thicker-than-average, shallow subtidal cycles, whereas the regressive parts are mainly represented by thinner-than-average, relatively shallow subtidal to peritidal cycles. In relatively deep environments, however, the transgressive and regressive successions display the opposite trends of cycle stacking patterns, i.e., thinner-than-average subtidal cycles of transgressive packages. Sequence boundaries are mainly characterized by laterally traceable, transitional zones without apparent subaerial exposure features. Good correlation of the long-term changes in accommodation space inferred from vertical facies and cycle stacking patterns with sea-level fluctuations elsewhere around the world suggests an overriding eustatic control on cycle origination, platform building-up and evolution during the Early-Middle Ordovician, although with localized influences of syndepositional faulting and depositional settings.     

Horse‐mounted invaders from the Russo‐Kazakh steppe or agricultural colonists from western Central Asia? A craniometric investigation of the Bronze Age settlement of Xinjiang

Numerous Bronze Age cemeteries in the oases surrounding the T?klamakan Desert of the Tarim Basin in the Xinjiang Uyghur Autonomous Region, western China, have yielded both mummified and skeletal human remains. A dearth of local antecedents, coupled with woolen textiles and the apparent Western physical appearance of the population, raised questions as to where these people came from. Two hypotheses have been offered by archaeologists to account for the origins of Bronze Age populations of the Tarim Basin. These are the "steppe hypothesis" and the "Bactrian oasis hypothesis." Eight craniometric variables from 25 Aeneolithic and Bronze Age samples, comprising 1,353 adults from the Tarim Basin, the Russo-Kazakh steppe, southern China, Central Asia, Iran, and the Indus Valley, are compared to test which, if either, of these hypotheses are supported by the pattern of phenetic affinities possessed by Bronze Age inhabitants of the Tarim Basin. Craniometric differences between samples are compared with Mahalanobis generalized distance (d2), and patterns of phenetic affinity are assessed with two types of cluster analysis (the weighted pair average linkage method and the neighbor-joining method), multidimensional scaling, and principal coordinates analysis. Results obtained by this analysis provide little support for either the steppe hypothesis or the Bactrian oasis hypothesis. Rather, the pattern of phenetic affinities manifested by Bronze Age inhabitants of the Tarim Basin suggests the presence of a population of unknown origin within the Tarim Basin during the early Bronze Age. After 1200 B.C., this population experienced significant gene flow from highland populations of the Pamirs and Ferghana Valley. These highland populations may include those who later became known as the Saka and who may have served as "middlemen" facilitating contacts between East (Tarim Basin, China) and West (Bactria, Uzbekistan) along what later became known as the Great Silk Road.     

塔里木盆地奥陶系苔虫多样性演变

本文研究了塔里木盆地奥陶系苔虫的分布延限和演化规律。苔虫的演化分为四个阶段:第一阶段为鹰山组—一间房组中下部沉积期,苔虫多样性和丰度均很低;第二阶段为一间房组上部—吐木休克组沉积期,苔虫的多样性处在一种波动上升的状态;第三阶段包括良里塔格组良五段—良四段沉积期,苔虫多样性和丰度均有一定程度的增加,而且绝大部分属种在接下来的第四阶段都有出现;第四阶段在良里塔格组良三段—良一段沉积期,是苔虫总体多样性明显增长的时期,也是本区奥陶纪苔虫的重要辐射期。随后,展开苔虫的多样性分析的研究。研究发现塔里木盆地奥陶系苔虫的演化趋势与世界范围的演化趋势基本一致,说明是受苔虫宏演化规律控制的。     

Cherty carbonate facies of the Montoya Group, southern New Mexico and western Texas and its regional correlatives: a record of Late Ordovician paleoceanography on southern Laurentia

The Upper Ordovician Montoya Group in southern New Mexico and westernmost Texas records predominantly subtidal deposition on a gently dipping carbonate ramp that was subsequently nearly entirely dolomitized. The medial unit of the Montoya Group, the Aleman Formation is unique because it contains abundant chert (10–70% by volume). The chert occurs as: (1) thin continuous beds of sponge spicules within mudstone or calcisiltite; (2) discontinuous, lenses or nodules within skeletal wackestones and packstones; or (3) as a replacement of skeletal grains and burrows. Coeval skeletal grainstones and muddy peritidal facies contain little chert. Phosphate (up to 5 wt.%) occurs within the underlying Upham Formation and the Aleman Formation as replacement of fossils and peloids. The abundance of chert and phosphate in these subtidal facies indicates they formed within a region of strong upwelling. Regional correlation with Upper Ordovician cherty units along the periphery of southern Laurentia and other low latitude continents suggests that upwelling was widespread and long-lived during the Late Ordovician. The upwelling is interpreted to record vigorous oceanic circulation produced by the onset of glaciation on Gondwana during this period. Late Ordovician relative sea-level curves around the periphery of Laurentia indicate correlative third-order (1–3 my duration) fluctuations that may provide a means for high-resolution global correlations. However, the mechanism(s) that produced these long-term fluctuations are unclear.     

Charophyten und Otolithen aus den Cyrenen-Schichten des nördlichen Alpenvorlandes

Charophytes and otoliths from theCyrena Beds of the northern Alpine foreland (Hausham and Miesbach synclines, Upper Bavaria) have been studied. A very abundant charophyte flora comprising 12 species, includingStephanochara martinii n. sp., is described and figured. The moderately diverse otolith fauna is documented by tables and SEM-pictures. The studiedCyrena Beds can be dated biostratigraphically as early Chattian and correlated with theChara microcera Zone. The charophytes show strong paleobiogeographic relations to floras in the Mainz Basin/Upper Rhine Graben as well as to western Switzerland and southern France. The otolith fauna is strikingly different from late Chattian faunas of the western Paratethys. The paleoecology indicated by charophytes, otoliths and the accompanying fauna suggests short term variation including freshwater, brackish water and marine influenced environments.     

Late Devonian Acritarchs from the Gneudna formation in the Western Carnarvon basin,Western Australia

The Gneudna Formation is a Late Devonian(Frasnian) sequence of marine calcareous sediments that occurs in the Carnarvon Basin, Western Australia. The present palynological study is based upon subsurface silty strata from a borehole (Pelican Hill or Bibbawarra Bore) that was drilled early this century near the western coastal limit of the Carnarvon Basin.The subject strata have previously been attributed to the Gneudna Formation on lithostratigraphic grounds. They contain a rich and varied assemblage of marine microphytoplankton (acritarchs), associated with trilete miospores of which Geminospora lemurataBalme, 1962 is the dominant form. Forty-seven species of acritarchs are recognizable in the palynoflora, which corresponds very closely with that described recently (Playford & Dring, 1981) from the Gneudna Formation in the vicinity of its type section on the opposite (eastern) side of the Carnarvon Basin. The apparently parochial complexion of the Gneudna acritarch suite is probably illusory, insofar as early Late Devonian acritarchs have not been studied extensively or intensively from either the northern or southern hemispheres.The following new species of acritarchs areformally instituted herein: Elektoriskos villosa, Lophosphaeridium pelicanensis, and Pterospermella tenellula.     

Upper Cretaceous paleogeography of the Central Southern Pyrenean Basins (Catalonia, Spain) from microfacies analysis and charophyte biostratigraphy

The most extensive latest Cretaceous deposits of the Pyrenees are non-marine facies traditionally called “Garumnian”, which represent the first continentalization of the Pyrenean Foreland Basins. The age and paleogeography of the basal Garumnian facies in the different parts of the Pyrenean Basin has been a matter of debate. Charophyte biostratigraphy and microfacies analysis suggest that the continentalization was diachronous in the Central Southern Pyrenean basins, i.e., between the Àger and Tremp basins, and the emersion progressed from south to north. In the Àger Basin, to the south, the first Upper Cretaceous non-marine rocks are represented by the La Maçana Formation. This unit is mainly formed by freshwater lacustrine limestones organized into hundreds of shallowing-upwards sequences ranging from deeper lacustrine facies, through marginal, well-illuminated environments dominated by characean meadows, and finishing with lakeshores dominated by clavatoracean meadows. The charophyte assemblage from the La Maçana Fm is mainly formed by Peckichara cancellata, P. sertulata, Microchara cristata, M. parazensis, Platychara caudata, and Clavator brachycerus, which belong to the Peckichara cancellata charophyte biozone (Late Campanian). In contrast, in the Tremp Basin, located to the north, the beginning of the non-marine sedimentation is organized into a few cycles of the well-known La Posa Fm. These cycles begin with brackish deposits formed by thick marls with euryhaline molluscs at the base, followed by lignite and brackish to freshwater limestones. The brackish facies are dominated by porocharaceans. The charophyte assemblage of the La Posa Formation is formed by Feistiella malladae, Peckichara sertulata, Microchara cristata, and Clavator brachycerus, which belong to the Septorella ultima charophyte biozone (Early Maastrichtian).     

新疆裂腹鱼类的系统发生关系及物种分化时间

文章采用线粒体COI、ND4、16S rRNA基因联合数据分析了新疆分布的裂腹鱼类4属10个种或亚种的分子系统发育,并通过鲤亚科的分化时间、黄河上游和青海湖隔离的地质时间来校正分子钟,进而探讨了裂腹鱼类分化时间与塔里木盆地周边地区主要地质事件和气候变化的关系。结果发现,扁吻鱼属未能形成独立的分支,与塔里木裂腹鱼、厚唇裂腹鱼聚在一起。进一步基于COI基因序列,利用Kimura双参数模型计算遗传距离,发现扁吻鱼属和裂腹鱼属间的遗传距离未达到属间区别,扁吻鱼可能是裂腹鱼属内特化的物种;聚类分析结果不同于裂腹鱼属的形态学分类方法,不支持裂腹鱼属鱼类的亚属划分;原始等级裂腹鱼类(包括裂腹鱼属和扁吻鱼属)两个族群的分化时间(8.18 Ma)与新疆裸重唇鱼和斑重唇鱼的分化时间(7.67 Ma)均发生于晚中新世,这可能与8Ma左右青藏高原北缘和北天山抬升、塔里木盆地气候干旱化等重大地质事件和气候转型导致青藏高原北缘(昆仑山)和北天山水系间出现分离相关。而塔里木盆地裂腹鱼属鱼类现今的分布格局可能与第四纪喜马拉雅运动使盆地形成西高东低的地势、罗布泊成为塔里木盆地周边高山发源河流的汇水中心相关。