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.     

Disentangling allometry and response to Kellwasser anoxic events in the Late Devonian conodont genus Ancyrodella

Is the ability to respond to minor perturbations a key to survival to major crisis? This idea was supported by previous studies on Late Devonian conodonts. Genera surviving the Frasnian/Famennian (F/F) crisis, at the end of the Upper Kellwasser anoxic event, had shown a response to a similar but minor event, the Lower Kellwasser (LKW). In contrast, the genus Ancyrodella went extinct at the F/F crisis. This study aims to assess whether this extinction was associated with the absence of response to the minor LKW event. For this purpose, the shape of the P1 platform elements of the conodont Ancyrodella curvata was quantified based on their 2‐D outlines. Conodonts were extracted from two outcrops documenting the Late Devonian Kellwasser events, Coumiac (France) and Mrirt (Morocco). Ancyrodella curvata is characterized by a marked allometric growth that may blur any other source of shape difference, like response to the LKW. Hence, a multivariate method was developed to disentangle size‐free from size‐related shape variations. No coherent temporal size variations emerged from the analysis, but allometry occurring along the growth of the element indeed appeared as the prevailing source of shape variation. By isolating size‐free variations, however, we were able to evidence a morphometric response of A. curvata to the LKW independent from the allometric pattern. Hence, the extinction of A. curvata at the F/F crisis cannot be attributed to an absence of response to minor events. The amount of shape change involved in the LKW shift is, however, of minor importance in comparison with the shape variation due to allometric growth. Alternate hypotheses have been further investigated. Ancyrodella curvata appears as a rare species in the assemblages, and its distribution worldwide suggests a rather specialist taxon. Considering survivorship curves (i.e. frequency distribution of the conodont as a function of its size) A. curvata was characterized by low and constant mortality rate. This may be a clue for a long growth and progressive investment in the reproduction. These arguments support the view that A. curvata was a rather specialist, rare and ‘K‐selected’ taxon. All these factors may not be exclusive and their unfavourable conjunction might have been the key to the extinction of A. curvata.     

Step-wise morphological trends in fluctuating environments: Evidence in the Late Devonian conodont genus Palmatolepis

Long-term morphological changes were investigated in the conodont genus Palmatolepis, using a Fourier analysis of the outline of platform elements. Three time-slices and four Late Frasnian - Early Famennian sections on North Gondwana were studied. No difference existed between locations, but shape variations were recorded associated with the successive Kellwasser events. The Middle Famennian period was analyzed in a section located at the Baltica margin across the annulata event. Some morphological changes may be related to the deposition of the corresponding black shales, but the main feature is a heterogeneity of the populations, which can be split into two morphological types. Latest Famennian conodonts from another North Gondwanan section show only minor shape changes during this time interval, which is environmentally stable prior to the global Hangenberg event. Based on synthetic shape variations across the whole period an morphological trend towards narrower elements is observed. This morphological change happens step-wise in response to global events. The amplitude of the shape shift is proportionally related to the extend of the successive Late Devonian global events.     

The fate of the homoctenids (Tentaculitoidea) during the Frasnian–Famennian mass extinction (Late Devonian)

The homoctenids (Tentaculitoidea) are small, conical‐shelled marine animals that are among the most abundant and widespread of all Late Devonian fossils. They were a principal casualty of the Frasnian–Famennian (F‐F, Late Devonian) mass extinction, and thus provide an insight into the extinction dynamics. Despite their abundance during the Late Devonian, they have been largely neglected by extinction studies. A number of Frasnian–Famennian boundary sections have been studied, in Poland, Germany, France, and the USA. These sections have yielded homoctenids, which allow precise recognition of the timing of the mass extinction. It is clear that the homoctenids almost disappear from the fossil record during the latest Frasnian ‘Upper Kellwasser Event’. The coincident extinction of this pelagic group, and the widespread development of intense marine anoxia within the water column, provides a causal link between anoxia and the F‐F extinction. Most notable is the sudden demise of a group, which had been present in rock‐forming densities, during this anoxic event. One new species, belonging to Homoctenus is described, but is not formally named here.     

Evolution of Permian conodont provincialism and its significance in global correlation and paleoclimate implication

The main components of Asselian through Artinskian conodont faunas found around the world are basically the same, and the provincialism is indicated only by less common endemic elements such as Gondolelloides and New Genus A Henderson in North Pangea, Sweetognathus bucaramangus around the equator and Vjalovognathus in eastern Gondwana. Provincialism is marked by differences at the species level of Mesogondolella, Neostreptognathodus and Sweetognathus during the Kungurian, and becomes very distinct with differences at the genus level during the Guadalupian and Lopingian. Three provinces of Permian conodonts, referred to as the North Cool Water Province (NCWP), the Equatorial Warm Water Province (EWWP) and the peri-Gondwana Cool Water Province (GCWP), are recognized. The NCWP is marked by Gondolelloides in the early Cisuralian, dominance of Neostreptognathodus and no or rare Sweetognathus in the late Cisuralian, dominance of Merrillina and Mesogondolella and absence of Sweetognathus in the Guadalupian, and dominance of Merrillina and Mesogondolella and absence of Iranognathus in the Lopingian. The EWWP is characterized by the absence of Gondolelloides and Vjalovognathus in the Cisuralian, abundance of Sweetognathus and Pseudosweetognathus in the Kungurian (late Cisuralian), Jinogondolella and Sweetognathus in the Guadalupian, and Clarkina and Iranognathus in the Lopingian. The GCWP is marked by Vjalovognathus, Merrillina in the Cisuralian, Vjalovognathus, Merrillina and Mesogondolella in the Guadalupian, and Vjalovognathus and Merrillina in the Lopingian. Mixed faunas are recognized in regions bordering between the EWWP and GCWP including Western Timor during the Artinskian, Pamirs during the Kungurian and the Salt Range during the Guadalupian and Lopingian.

Three different conodont zonations are proposed, one for each of the three conodont provinces. Four potential horizons for inter-provincial correlation of Permian conodonts are recognized. They are in ascending order: (1) the first appearance of Sweetognathus whitei, which is closely related to the last occurrence of Carboniferous-type conodonts such as Streptognathodus and Adetognathus; (2) the first appearance of Neostreptognathodus pequopensis; (3) the base of the Jinogondolella nankingensis Zone; and (4) the base of the Clarkina postbitteri–Iranognathus erwini Zone.

The spatial and temporal distribution pattern of Permian conodonts suggests that temperature is the primary controlling factor. Evolution of Permian conodont provincialism reveals a glaciation during the Asselian and Sakmarian, a global warming during the Artinskian, a climate cooling in North Pangea during the Kungurian, a continuation of Kungurian climate trends in the Guadalupian, a relatively minor warming during the Wuchiapingian, a returned cooling in the Changhsingian and Lower and Middle Griesbachian, and a global warming in the Late Griesbachian, which ended the Permian conodont lineage.     

Short-term climate changes in the southern Aegean Sea over the last 48,000 years

High-resolution palaeoenvironmental changes, corresponding to a mean time interval of 450 years covering the last 48,000 years, were examined in a core from the Cretan Basin in the southern Aegean Sea. The intensity and duration of the climatic and oceanographic events were determined by examining the compositional changes in the planktonic foraminifera and pollen assemblages, along with the δ¹⁸O signal of Globigerinoides ruber. A reconstruction of sea-surface temperatures was attempted using the Modern Analogue Technique (MAT). In total, 10 stadials and 6 interstadials occurred over the last 48,000 years. These fluctuations in climatic conditions coincide with fluctuations documented in the western and central Mediterranean and seem to be associated with Dansgaard–Oeschger events. Some of these climatic fluctuations are correlated with changes in the vegetation in the surrounding land.

Between 48 and 10 cal kyr BP the most pronounced stadials occurred at 41 cal kyr BP (C69-ST10) and at 13 cal kyr BP (C69-ST4). These events are characterized by: (i) high positive δ¹⁸O values of Globigerinoides ruber, (ii) drops in SST and (iii) increases in aridity. These events may be correlated with the Heinrich H4 event and the Younger Dryas event, respectively. Two other stadials at 23 cal kyr BP (C69-ST6) and at 16 cal kyr BP (C69-ST5) which are characterized by increases in the abundance of the cold plaktonic foraminifera species and increases in aridity may be correlated with the H2 and H1 events, respectively. The dominant planktonic foraminiferal species during the stadials witch are correlated with the Heinrich events were Turborotalita quinqueloba and Globorotalia scitula. The most pronounced interstadials occurred between 39.5 and 38.5 cal kyr BP (C69-IST6) and between 25 and 24 cal kyr BP (C69-IST3) and are characterized by depletion in δ¹⁸O values, increases in SST and increases in humidity. The former event coincides with the formation of the sapropelitic layer S2.

In the Holocene the most pronounced stadial occurred between 8 and 6.5 cal kyr BP (C69-ST2), during the interruption of S1 and is characterized by a reduction in SST and an increase in aridity. The most pronounced interstadials of Holocene occurred during the formation of S1a and S1b between 9 and 8 cal kyr BP (C69-IST1) and between 6.5 and 5.5 cal kyr BP (C69-IST2), respectively. These events are characterized by depletion in δ¹⁸O values, increased SST and an increase in humidity as is indicated by the expansion of temperate evergreen and Mediterranean taxa in the pollen record.     

Depositional conditions during the Lower Kellwasser Event (Late Frasnian) in the deep‐shelf Łysogóry Basin of the Holy Cross Mountains Poland

Integrated biostratigraphical, microfacial and geochemical studies of the Lower Kellwasser Event in the P?ucki succession (southern Poland) provide details about redox conditions during the deposition of this horizon in the deep‐shelf ?ysogóry basin of the Holy Cross Mountains. The environment is characterized by calm sedimentation and soft, muddy carbonate substrate. However, microfacies changing from wackestones to grainstones, the presence of crushed or current‐oriented nautiloid shells and the occurrence of redeposited material from shallow‐water Dyminy Reef environments (such as calcispheroids, algae and girvanellid cyanobacteria) suggest episodes of a higher‐energy regime. Uranium/thorium ratios indicate that bottom‐water redox conditions changed periodically from being mainly anoxic in the middle part of the Lower Kellwasser Horizon to dysoxic in the lower and upper parts. During a short‐term episode of bottom‐water ventilation, the seafloor was rapidly colonized by a dense assemblage of opportunistic buchiolid bivalves, which suffered mass mortality upon the return to anoxic conditions. A very rich concentration of cephalopods and homoctenids may be regarded as reflecting a bloom of high‐density populations during high‐productivity events. Similarly, they suffered mass mortality when episodically increasing anoxia/euxinia reached the upper part of the water column. The Late Frasnian inorganic carbon isotope records in the P?ucki section show a positive shift with a maximum amplitude of 3‰. This enrichment in δ¹³C can be correlated with the deposition of the Lower Kellwasser Horizon and reflects the expansion of anoxic and probably high‐productivity regimes.     

Ostracod and conodont faunal changes across the Frasnian-Famennian (Devonian) boundary at Els Castells,Spanish central Pyrenees

Diverse conodont and silicified ostracod assemblages were found in the Spanish Pyrenees (Els Castells section), in the Frasnian/Famennian boundary beds (late rhenana and/or linguiformis to late triangularis zones), in strata below and above the well-known Kellwasser Extinction Event. Many of the ostracods studied here are conspicuous elements of the “Thuringian Mega-Assemblage”, and show maximum affinities with faunas from the southeastern Cantabrian Mountains (Spain), eastern Thuringia and the Harz (Germany). The composition of the faunas, however, is not uniform through the Els Castells section. A rather sharp break exists, roughly coinciding with the Frasnian/Famennian boundary. The break is characterized by the disappearance of many ostracods typical of the “Thuringian Mega-Assemblage”. This correlates with an important change in the conodont faunas related to the Kellwasser Event. The Frasnian (late rhenana and/or linguiformis zones) palmatolepid-polygnathid biofacies is followed in Famennian strata (middle and late triangularis zones) by a palmatolepid-icriodid biofacies. The icriodid maximum in the earliest Famennian rocks of the Pyrenees correlates with the “Icriodid Peak” described elsewhere. These changes depend on the age and palaeoenvironmental conditions.     

Harnessing stratigraphic bias at the section scale: conodont diversity in the Homerian (Silurian) of the Midland Platform,England

Fossil abundance and diversity in geological successions are subject to bias arising from shifting depositional and diagenetic environments, resulting in variable rates of fossil accumulation and preservation. In simulations, this bias can be constrained based on sequence‐stratigraphic architecture. Nonetheless, a practical quantitative method of incorporating the contribution of sequence‐stratigraphic architecture in community palaeoecology and diversity analyses derived from individual successions is missing. As a model of faunal turnover affected by the stratigraphic bias, we use the ‘Mulde event’, a postulated mid‐Silurian interval of elevated conodont turnover, which coincides with global eustatic sea‐level changes and which has been based on regionally constrained observations. We test whether conodont turnover is highest at the boundary corresponding to the ‘event’ and post‐‘event’ interval against the alternative that conodont turnover reflects habitat tracking and peaks at facies shifts. Based on the previously documented, parasequence‐level stratigraphic framework of sections in the northern and central part of the Midland Platform, the relative controls of sequence‐stratigraphic architecture, time and depositional environment over conodont distribution are evaluated using permutational multivariate analysis of variance. The depositional environment controls the largest part of variability in conodont assemblage composition, whereas the postulated ‘Mulde event’, or genuine temporal change in conodont diversity, cannot be detected. Depending on the binning of the stratigraphic succession, contrasting diversity and turnover patterns can be produced. The simple approach proposed here, emulating partitioning of β diversity into spatial and temporal components, may help to constrain the stratigraphic bias, even at the scale of an individual 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.     

Middle Ordovician cephalopod biofacies and palaeoenvironments of Baltoscandia

During the Middle Ordovician cephalopods became an important part of the macrofauna of the Baltoscandian carbonate platform. The earliest cephalopod abundance peak was reached during the early Darriwilian, within the Kunda Stage Yangtzeplacognathus crassus and Lenodus pseudoplanus conodont zones. In sediments of this time interval large orthoconic cephalopods often occur in masses with more than one specimen per square‐meter on bedding surfaces. The assemblages are characterized by the strong dominance of often large endocerids. In proximal depositional settings coiled tarphycerids and other cephalopod groups are an important additional component. In the most distal settings orthocerids are the most important secondary component. Correspondence Analysis of assemblages throughout Baltoscandia revealed three distinct biofacies, which here are termed Orthocerid, Proterovaginoceras and Anthoceras Biofacies, respectively. The biofacies reflect differences in depth and proximity to the shoreline and are consistent with the Baltoscandian Confacies Belts. Spatial changes in absolute abundance and taxonomic composition indicate increased original cephalopod population densities and habitat expansion within the Y. crassus and L. pseudoplanus conodont zones. A nearly coeval abundance peak in a similar facies in South China indicates supraregional causes of the mass occurrence, probably reflecting a globally increased nutrient availability in the water column during the Darriwilian.     

降解水稻秸秆的复合菌系及其微生物群落结构演替北大核心CSCD

【目的】比较和分析从堆肥中富集的水稻秸秆降解菌系F1和F2的纤维素分解能力、微生物群落结构及其在秸秆降解过程中的演替,从而探究微生物群落结构与秸秆降解效率的相关性。【方法】采用DNS(3,5-二硝基水杨酸,3,5-dinitrosalicylic acid)定糖法测定发酵液中的外切纤维素酶活;采用范氏(Van Soest)洗涤纤维分析法测定发酵前与发酵后的秸秆纤维素、半纤维素、木质素的含量,并计算降解率;采用16S r RNA基因序列分析和实时荧光定量PCR(Quantitative real-time PCR,Q-PCR)对秸秆降解过程中的微生物物种组成及特定的功能微生物进行定性和定量分析。【结果】复合菌系F1的水稻秸秆总降解率、纤维素降解率、半纤维素降解率显著高于复合菌系F2;2种复合菌系的外切纤维素酶活性与cel48基因的拷贝数变化趋势一致;复合菌系F1的物种较丰富,优势物种是好氧细菌,复合菌系F2的物种组成较单一,培养后期具有较高比例的厌氧纤维素分解菌;培养前4天,复合菌系F1和F2的优势物种均为Unclassified Bacillales和Bacillus;第4天之后,不同复合菌系的优势物种及丰度出现差异,F1的优势物种主要属于Bacteroidetes,F2的优势物种主要属于Firmicutes;虽然Petrimonas和Pusillimonas是培养后期的共有优势物种,但是Petrimonas在复合菌系F2中的相对丰度(38.30%)显著高于F1(9.47%),且培养第8天的F2中的Clostridiales OPB54增加至14.85%。【结论】cel48基因拷贝数变化与秸秆纤维素的降解效率、外切纤维素酶活性变化具有一定的相关性,cel48基因可作为潜在的生物分子标记监测秸秆纤维素的降解过程;微生物群落结构对秸秆纤维素的降解效率具有显著影响,Unclassified Bacillales,Bacillus,Petrimonas,Pusillimonas是复合菌系F1和F2降解秸秆纤维素过程中的重要物种。     

Baltoscandian conodont biofacies fluctuations and their link to Middle Ordovician (Darriwilian) global cooling

The Middle Ordovician conodont genera that are suitable for palaeoenvironmental interpretations from the epicontinental Baltoscandian platform have been identified and evaluated to establish and describe conodont biofacies and their relationship to global cooling. The construction of biofacies was based on multivariate statistical analyses of more than 375 700 conodont specimens from 520 samples and 21 localities across Baltica. Three distinct, recurrent and laterally extensive conodont biofacies existed across the Baltoscandian platform of the Baltica continent during the Dapingian and early to middle Darriwilian stages (Middle Ordovician). A relatively shallow water conodont assemblage named the Baltoniodus–Microzarkodina Biofacies characterized the inner shelf localities in central Sweden, Estonia, Russia and Ukraine. In the distal shelf areas, patterns are more complex. Here, genera of the Periodon Biofacies characterized the shelf margin areas of the Scandinavian Caledonides facing the relatively warm Iapetus Ocean towards the north, whereas the Protopanderodus Biofacies dominated the distal shelf areas facing the cooler Tornquist Sea towards the south‐west. Although these three main biofacies continued to dominate during the succeeding Darriwilian stage, distinct changes in the distribution of biofacies took place during the transition from the Dapingian Stage to the Darriwilian. We argue that the biofacies change was triggered by a regressive event related to early Darriwilian cooling, and that the palaeoclimatological changes influenced the Baltic conodont faunas near the Tornquist Sea margin before those of the Iapetus margin (early vs middle Darriwilian).     

Patterns of evolution and extinction in proetid trilobites during the late Devonian mass extinction event,Canning Basin,Western Australia

Abstract: In the early Late Devonian, terminal Frasnian proetid trilobites have previously only been known from Europe and North Africa. For the first time, a rich fauna of late Frasnian proetids is described from the Virgin Hills Formation, Canning Basin, Western Australia. Seventeen species in six genera are described, of which three are new: Rudybole gen. nov., Palpebralina gen. nov. and Canningbole gen. nov. A new subgenus, Chlupaciparia (Australoparia) subgen. nov. is also described. Fourteen of the species are new: Palpebralia initialis sp. nov., P. pustulata sp. nov., ?P. sp. nov. A, Rudybole depressa sp. nov., Palpebralina pseudopalpebralis sp. nov. (comprising the subspecies P. pseudopalpebralis pseudopalpebralis subsp. nov. and P. pseudopalpebralis ultima subsp. nov.), P. minor sp. nov., P. ocellifer sp. nov., Canningbole latimargo sp. nov., C. henwoodorum sp. nov., C. macromma sp. nov., Pteroparia extrema sp. nov., Chlupaciparia (Chlupaciparia) planiops sp. nov., Chlupaciparia (Australoparia) australis sp. nov. and C. (Australoparia) lata sp. nov. The subspecies Rudybole adorfensis angusta subsp. nov. is also described. The proetids range through conodont Zones 11–13b and terminate at the Upper Kellwasser Event, which marks the terminal Frasnian mass extinction event. Three of the six proetid lineages, Palpebralia, Canningbole and Pteroparia, show evolutionary trends of eye reduction. Two of the remaining lineages, Rudybole and Palpebralina, consist exclusively of blind taxa. The last, Chlupaciparia, also comprises forms with reduced eyes. The proetids show a stepped pattern of extinction during the late Frasnian, which correlate with two Kellwasser biocrises documented in European/North African Frasnian sections. The highest diversity preceded the Lower Kellwasser event that occurred at the end of conodont Zone 12 and saw the extinction of all species present in that zone. However, only one genus, Pteroparia, locally became extinct. A major higher‐level taxonomic mass extinction at the top of Zone 13b initiated the Upper Kellwasser extinction event. This included extinction at the generic level, with all five remaining genera becoming extinct, and at the family level, with the loss of the Tropidocoryphidae.     

An 18 million year record of vegetation and climate change in northwestern Canada and Alaska: tectonic and global climatic correlates

We reconstruct long-term vegetation/paleoclimatic trends, spanning the last 18 million years, in Alaska, Yukon and far western Northwest Territories. Twenty-one average percentage spectra for pollen and spores are assembled from eight surface/subsurface sections. The sections are dated independently or by correlation. Pollen and spore ratios indicate the direction of change in vegetation and climatic parameters — growing season temperature (T_est), tree canopy density (C_est) and paludification at study sites (P_est). A global warm peak ca. 15 Ma is shown by the abundance of thermophilous taxa, including Fagus and Quercus. A temperature decline immediately following 15 Ma parallels climatic reconstructions based on marine oxygen isotopes. Subsequent declines correlate to the Messinian event and the onset of late Pliocene-Pleistocene glaciation. After 7 Ma herbs and shrubs become more important elements of the palynological assemblages, suggesting a more continental, colder/drier climate. However, a late Pliocene warm interval is evident. Vegetation/climatic changes during the early to late Miocene show synchrony with, and are most economically attributable to, global events. After 7 Ma, vegetation/climate change is attributed primarily to latest Miocene-to-Pleistocene uplift of the Alaska Range and St. Elias Mts. The continuing influence of global climatic patterns is shown in the late Pliocene warm interval, despite uplift to the south. The opening of the Bering Strait ca. 3 Ma may have moderated the climate in the study area.     

A palaeontological and phylogenetical analysis of squaliform sharks (Chondrichthyes: Squaliformes) based on dental characters

Squaliformes comprise the major proportion of modern deep-water sharks, yet their fossil history and phylogenetic relationships are still poorly understood. New analyses have been undertaken, however, and new living and fossil species have been discovered during the past 10 years. A cladistic analysis involving 29 dental characters has been made and most living and fossil genera are included. On the basis of their dental morphology, the monophyly of the Squaliformes can be supported if the fossil genus Protospinax is excluded. The traditional phylogenetic positions of most living genera, Protosqualus, Cretascymnus and Eoetmopterus, are confirmed despite the fact that the Oxynotidae, Etmopterinae, Palaeomicroides, Proetmopterus and Microetmopterus have some atypical phylogenetic relationships within the Squaliformes. The addition of the palaeontological data in a phylogenetic tree including fossil and living Squaliformes demonstrates some gaps in the fossil record. Nevertheless, and as a consequence of that stratigraphy-phylogeny inference, two particular events can be pinpointed in the history of the Squaliformes: the first one occurs after the major Cenomanian-Turonian anoxic event and the second one after the Cretaceous/Tertiary crisis. The first radiation involves the majority of the living Squaliformes (Somniosinae, Centrophorinae, most of the Etmopterinae, Oxynotinae) in deep-sea waters, the second, the more epipelagic sharks (most of the Dalatiidae), suggesting a secondary adaptation to more shallow environments.     

气候变暖背景下青藏高原草本植物物候变化空间换时间预测

气候变暖背景下的植物物候变化广受关注, 然而常用的植物物候变化预测模型未充分考虑植物对环境的适应性, 给预测结果带来了较大的不确定性。该文基于2002-2011年青藏高原10个站点的地面物候观测资料以及年平均气温数据, 对空间换时间模型预测车前(Plantago asiatica)和蒲公英(Taraxacum mongolicum)各主要物候事件(展叶始期、开花始期和黄枯普遍期)变化的可行性及其在升温背景下的变化规律进行了分析。首先利用不同海拔高度的气温和物候事件分别与地理因子(经度、纬度和海拔)建立多元线性回归模型, 然后在此基础上剔除经度和纬度的影响, 单独考察海拔变化所引起的气温与植物物候变化, 最后以海拔高度作为桥梁来考察物候变化与温度变化的关系。结果表明, 采用各站点对应的海拔高度来模拟年平均气温空间差异的R²均大于0.89, 表明海拔梯度可以用来反映时间尺度下的年际温度变化; 车前和蒲公英各物候事件发生日期拟合值均与海拔高度变化关系显著, R²均大于0.70, 表明海拔变化是影响它们各物候事件变化的主要地理因子; 在物候事件发生日期拟合值和年平均气温拟合值的回归方程中, R²均大于0.93, 说明基于不同海拔高度模拟得到的年平均气温变化可以对时间尺度上车前和蒲公英的物候事件变化进行预测。空间换时间预测表明, 温度每升高1 ℃, 车前展叶始期和开花始期分别提前5.1和5.4 d, 而黄枯普遍期推迟4.8 d; 蒲公英展叶始期和开花始期分别提前6.5和7.8 d, 而黄枯普遍期推迟6.7 d。     

Biochronostratigraphy of the Reingraben Turnover (Hallstatt Facies Belt): Local black shale events controlled by regional tectonics, climatic change and plate tectonics

For the first time, two outcrops near Bad Dürrnberg (2 km SSW Hallein, Austria) allowed for a continuous multistratigraphical investigation of the Reingraben Turnover in the Hallstatt facies belt. After a phase of reefal sedimentation during the Julian 1 (Early Carnian), a sudden increase in terrigenous input (Reingraben Turnover) caused the breakdown of the carbonate factory at the beginning of the Julian 2 (late Early Carnian). In starved basins produced by syndepositional tectonism, black shales locally accumulated. Stable isotopes of oxygen and carbon do not suggest a change in seawater chemistry during the turnover. Shallow-water carbonate production resumed slowly during the Tuvalian (Late Carnian), and complete recovery was finished near the Carnian-Norian transition. Because similar events are recorded globally, climatic changes (monsoonal circulation) controlled by plate tectonics are favoured as triggers of the event.Based on lithology and microfacies, detailed sampling, and analysis of conodont faunas and the resulting detailed conodont zonation enabled us to establish the duration of the Reingraben Turnover (Julian 1/IIc to Julian 2/II).     

Predicting phenology shifts of herbaceous plants on the Qinghai-Xizang Plateau under climate warming with the space-for-time method

气候变暖背景下的植物物候变化广受关注, 然而常用的植物物候变化预测模型未充分考虑植物对环境的适应性, 给预测结果带来了较大的不确定性。该文基于2002-2011年青藏高原10个站点的地面物候观测资料以及年平均气温数据, 对空间换时间模型预测车前(Plantago asiatica)和蒲公英(Taraxacum mongolicum)各主要物候事件(展叶始期、开花始期和黄枯普遍期)变化的可行性及其在升温背景下的变化规律进行了分析。首先利用不同海拔高度的气温和物候事件分别与地理因子(经度、纬度和海拔)建立多元线性回归模型, 然后在此基础上剔除经度和纬度的影响, 单独考察海拔变化所引起的气温与植物物候变化, 最后以海拔高度作为桥梁来考察物候变化与温度变化的关系。结果表明, 采用各站点对应的海拔高度来模拟年平均气温空间差异的R²均大于0.89, 表明海拔梯度可以用来反映时间尺度下的年际温度变化; 车前和蒲公英各物候事件发生日期拟合值均与海拔高度变化关系显著, R²均大于0.70, 表明海拔变化是影响它们各物候事件变化的主要地理因子; 在物候事件发生日期拟合值和年平均气温拟合值的回归方程中, R²均大于0.93, 说明基于不同海拔高度模拟得到的年平均气温变化可以对时间尺度上车前和蒲公英的物候事件变化进行预测。空间换时间预测表明, 温度每升高1 ℃, 车前展叶始期和开花始期分别提前5.1和5.4 d, 而黄枯普遍期推迟4.8 d; 蒲公英展叶始期和开花始期分别提前6.5和7.8 d, 而黄枯普遍期推迟6.7 d。     

Microplankton changes through the early Silurian Ireviken extinction event on Gotland, Sweden

This paper documents and analyses the extinction and origination patterns of acritarchs and prasinophyte algae at the Llandovery/Wenlock boundary transition in the Lower Silurian on the island of Gotland, Sweden. Closely spaced samples were collected from two parallel sections: Lusklint 1 and Lickershamn 2, spanning the upper part of the Lower Visby Beds and almost all of the Upper Visby Beds (i.e. the uppermost Llandovery and lowermost Wenlock).

At least eight extinctions affecting the conodont record have been reported at these levels. This turnover (named the Ireviken Event) has been interpreted as an example of the change from a P to an S climate state, reflecting large changes in the ocean/atmosphere system.

The palynomorph data show a significant turnover in the phytoplankton, with most of the extinctions at the end of the event (85.3% in the top 4 m of the Lusklint 1 section). The originations are more numerous than the extinctions and they are distributed through the whole of the Ireviken Event. There is an uneven distribution across the event with more originations in the Lower Visby Beds forming a convex pattern.

Comparison of these data to other palynological studies suggests that there was a slightly higher number of migrations out of Gotland than in. The P and S model does not successfully explain all the changes recorded, but is the model most inclusive of all the climatic variables available at this time.