calcareous nannofossil zonation of the jurassic cretaceous boundary interval and correlation with the geomagnetic polarity timescale abstract calcareous nannofossil stratigraphy has been investigated in six european land sections and at two deep sea drilling project sites 391c and 534a ranging from the upper kimmeridgian to the lower valanginian most of the sections contain a continuous record of the jurassic cretaceous boundary interval a time of rapid increase in nannofossil abundance and diversity and allow development of a revised nannofossil zonation scheme for this period numerous nannofossil lineages have been studied in detail and the results help to increase potential stratigraphic resolution in this interval the proposed scheme consists of six zones which are units recognizable in all sections regardless of nannofossil preservation and eleven subzones determinable in all but the most poorly preserved material thirty eight additional biohorizons are proposed based on the stratigraphy of the two dsdp sites these can be accurately established only in moderately well preserved material but spotty occurrences of these taxa in other sections may be stratigraphically useful most of the sections studied have been investigated magnetostratigraphically and the results of this study allow correlation between nannofossil zonation and the geomagnetic polarity time scale magnetostratigraphy indicates that many nannofossil events can be quite precisely determined and are not significantly time transgressive finally the magnetostratigraphic definitions of two stage boundaries are refined the kimmeridgian tithonian and berriasian valanginian boundaries are placed within chrons cm22n and cm15n respectively two new genera faviconus and umbria and seven new species are described umbria granulosa rhagodiscus nebulosus cretarhabdus octofenestratus faviconus multicolumnatus nannoconus infans nannoconus compressus and nannoconus wintereri eight subspecies and three taxonomic emendations are also described

the guadalupian permian kamura event in european tethys article i nfo in order to document paleoenvironmental conditions of the equatorial western paleo tethys during the late middle permian prior to the end guadalupian mass extinction chemostratigraphic analysis using stable carbon isotopes was conducted for the guadalupian rocks at brusane in the velebit mtn central croatia by analyzing 72 carbonate samples of the capitanian upper guadalupian velebit formation we found an interval with unusually high 13 ccarb values 4 to 6 in the ca 150 m thick yabeina fusuline zone the present find clarifies that the primary productivity and burial rate into the sediments were considerably high during the capitanian in westernmost paleo tethys this chemostratigraphic signal is properly correlated with the kamura event detected in a mid panthalassan paleo atoll limestone in japan the present results identify the capitanian kamura event for the first time in european paleo tethys on the opposite side of the globe from the mid panthalassan paleo seamount and prove the global context of the event as well as its utility in chemostratigraphic correlation in order to enhance bioproductivity on a global scale the increase in nutrient supply is inevitable in addition to riverine run off from pangea active oceanic circulation in particular upwelling of deep sea water enriched in nutrients was likely vital both in panthalassa and paleo tethys the extinction of some guadalupian fauna in particular photosymbiotic community large tested fusulines large bivalves rugose corals was likely related to a temporary cooling coupled with eutrophication in low latitude shallow marine environments of paleo tethys and panthalassa

organic geochemical proxies of paleoceanographic paleolimnologic and paleoclimatic processes abstract organic matter constitutes a minor fraction of marine and freshwater sediments yet its important contribution to the sedimentary record can be used to reconstruct marine and continental paleoenvironments the organic matter content of sediments is the residue of past biota the amounts and types of organic matter present in sediments consequently reflect environmental conditions that impacted ecosystems at different past times general sources of the organic matter are inferred from bulk properties such as elemental compositions carbon and nitrogen stable isotope ratios rock eval pyrolysis data and organic petrography details of organic matter origins are refined by analyses of biomarker molecular compositions source changes are proxies for fluctuations in sea level oceanic surface currents and continental climates algal paleoproductivity rates are indicated by organic carbon mass accumulation rates and carbon and nitrogen stable isotopic compositions these parameters record past availability of nutrients and therefore are proxies of surface mixing in the oceans and amount of land runoff to lakes sea surface paleotemperatures are recorded by the number of carbon carbon double bonds in lipid biomarkers produced by marine algae larger proportions of the double bonds are proxies for the cooler surface waters that accompanied periods of global glaciation and intervals of enhanced upwelling the 13c and d values of plant organic matter record past concentrations of carbon dioxide in the atmosphere and changes in delivery of atmospheric moisture respectively diagenesis which causes the concentration and composition of organic matter in sedimentary settings to differ from those of the original biologically synthesized materials can bias organic geochemical paleoenvironmental records the magnitude of this potential source of misinformation must always be considered and evaluated comparison of multiple organic geochemical proxies of past conditions helps to compensate for the effects of diagenetic alterations and thereby to improve interpretations of paleoenvironmental change

the stable isotopic composition of modern soil carbonate and its relationship to climate the oxygen isotopic composition of modern soil carbonate is well correlated with the isotopic composition of local meteoric water the carbon isotopic cycle for co 2 in soils can be described in terms of the proportion of biomass using the c 4 photosynthetic pathway and the co 2 respiration rate of the soil at low soil respiration rates significant atmospheric co 2 mixing can occur in general the carbon isotopic composition of soil carbonate is related to the proportion of c 4 biomass present in soil but soils that freeze to the depth of carbonate formation often have a significant atmospheric component this suggests that freezing of the soil solution should be considered as another important mechanism for soil carbonate formation because of these relationships the isotopic composition of soil carbonate may be a paleoclimatic and paleoecologic indicator in cases in which diagenetic alteration has not occurred

guadalupian lopingian conodont and carbon isotope stratigraphies of a deep chert sequence in japan abstract to improve international stratigraphic correlation of the lower guadalupian lower lopingian permian we examined the stratigraphies of conodonts and organic carbon isotopes from pelagic chert sequences in the gujo hachiman section gifu southwest japan age diagnostic conodonts such as jinogondolella nankingensis and jinogondolella shannoni were found in the study section the conodont stratigraphy in the gujo hachiman section was correlated with those in south china and west texas usa to date the study section from these correlations it was found that the study section was from the upper roadian lower guadalupian through wuchiapingian lower lopingian kerogen 13 c values were relatively high around 29 0 in the upper roadian wordian middle guadalupian decreasing over time to 29 4 a negative positive swing in 13 c values of around 1 magnitude was recognized in the middle capitanian upper guadalupian a similar negative positive swing was also found in the guadalupian lopingian g l transitional zone in the gujo hachiman section and is comparable to the isotopic change around the g l boundary in the penglaitan section south china subsequently 13 c values decreased to values below 30 0 above the g l transitional zone i e at the lower wuchiapingian overall 13 c values decreased from the lower capitanian to the lower wuchiapingian by over 1 4 a gradual increase in the 13 c values followed this long term negative trend these 13 c trends in the gujo hachiman section are comparable with time equivalent 13 c records in different sections suggesting that they record first order variations in atmospheric 13 c the high 13 c values during the upper roadian wordian interval could reflect high primary productivity in the surface water of the pelagic panthalassa ocean and imply global cooling in contrast the negative 13 c shift during the capitanian wuchiapingian interval implies global warming

active thrusting and folding along the northern tien shan and late cenozoic rotation of the tarim relative to dzungaria and kazakhstan we have studied geometries and rates of late cenozoic thrust faulting and folding along the northern piedmont of the tien shan mountain belt west of urumqi where the m 8 3 manas earthquake occurred on december 23 1906 the northern range of the tien shan rising above 5000 m overthrusts a flexural foredeep filled with up to 11 000 m of sediment of the dzungarian basement our fieldwork reveals that the active thrust reaches the surface 30 km north of the range front within a 200 km long zone of neogene quaternary anticlines fault scarps are clearest across inset terraces within narrow valleys incised through the anticlines by large rivers flowing down from the range in all the valleys the scarps offset vertically the highest terrace surface by the same amount 10 2 0 7 m inferring an early holocene age 10 2 kyr for this terrace which is continuous with the largest recent fans of the piedmont yields a rate of vertical throw of 1 0 0 3mm yr on the main active thrust at the surface a quantitative morphological analysis of the degradation of terrace edges that are offset by the thrust corroborates such a rate and yields a mass diffusivity of 5 5 2 5 m 2 kyr a rather fresh surface scarp 0 8 0 15 m high that is unlikely to result from shallow earthquakes with 6 m 7 in the last 230 years is visible at the extremities of the main fold zone we associate this scarp with the 1906 manas earthquake and infer that a structure comprising a deep basement ramp under the range gently dipping flats in the foreland and shallow ramps responsible for the formation of the active fault propagation anticlines could have been activated by that earthquake if so the return period of a 1906 type event would be 850 380 years the small size of the scarp for an earthquake of this magnitude suggests that a large fraction of the slip at depth 2 3 is taken up by incremental folding near the surface comparable earthquakes might activate flat detachments and ramp anticlines at a distance from the front of other rising quaternary ranges such as the san gabriel mountains in california or the mont blanc aar massifs in the alps we estimate the finite cenozoic shortening of the folded dzungarian sediments to be of the order of 30 km and the cenozoic shortening rate to have been 3 1 5 mm yr assuming comparable shortening along the tarim piedmont and minor additional active thrusting within the mountain belt we infer the rate of shortening across the tien shan to be at least 6 3 mm yr at the longitude of manas 85 5 e a total shortening of 125 30 km is estimated from crustal thickening assuming local airy isostatic equilibrium under the same assumption serial n s sections imply that cenozoic shortening across the belt increases westwards to 203 50 km at the longitude of kashgar 76 e as reflected by the westward increase of the width of the belt this strain gradient implies a clockwise rotation of tarim relative to dzungaria and kazakhstan of 7 2 5 around a pole located near the eastern extremity of the tien shan west of hami 96 e 43 5 n comparable to that revealed by paleomagnetism between tarim and dzungaria 8 6 8 7 a 6 mm yr rate of shortening at the longitude of manas would imply a rate of rotation of 0 45 m y and would be consistent with a shortening rate of 12 mm yr north of kashgar taking such values to be representative of late cenozoic rates would place the onset of reactivation of the tien shan by the india asia collision in the early to middle miocene 16 22 9 m y in accord with the existence of particularly thick late neogene and quaternary deposits such reactivation would thus have started much later than the collision roughly at the time of the great mid miocene changes in tectonic regimes denudation and sedimentation rates observed in southeast asia the himalayas and the bay of bengal and of the correlative rapid change in seawater sr isotopic ratio 20 to 15 ma like these other changes the rise of the tien shan might be a distant consequence of the end of indochina s escape

mercury evidence from the sino korean block for emeishan volcanism during the capitanian mass extinction a prominent large negative 13 c org excursion and a coeval notable spike in mercury hg total organic carbon ratio are observed in the middle upper permian gohan formation in central korea located in the eastern sino korean block skb which may represent the capitanian mass extinction event the skb was separated from the south china block by the eastern palaeo tethys ocean this finding from the skb supports the widespread hg loading to the environment emitted from the emeishan volcanic eruptions in sw china this study demonstrates that the hg cycle was globally perturbed in association with global carbon cycle perturbation that occurred during the capitanian extinction

early late permian coupled carbon and strontium isotope chemostratigraphy from south china extended emeishan volcanism abstract carbon isotope compositions of carbonates 13ccarb document a new 3 5 cie toward lower values concomitant with an emeishan large igneous province elip related drowning event mapojiao event southern guizhou during the early wuchiapingian organic carbon isotope data 13corg have a 2 shift toward higher values across the drowning event showing decoupling with the 13ccarb evolution rock eval and palynofacies analyses suggest an elevated flux of terrestrial organic matter om during the drowning episode therefore the decoupling between 13ccarb and 13corg is best explained by the mixing of different organic carbon pools in the 13corg curve strontium isotope data 87sr 86sr also show a transient shift from 0 70715 to 0 70694 associated with this early wuchiapingian carbon isotope excursion cie which is superimposed on the late permian prolonged global rising trend this short lived 87sr 86sr excursion is best interpreted as an enhanced hydrothermal flux related to a short pulse of elip related volcanism comparison of the mapojiao event with other c isotope records from south china and other parts of tethys reveals substantial discrepancies moreover older capitanian cies concomitant with elip related drownings are also not laterally reproducible in time the local distribution of cies across guadalupian lopingian g l interval indicates the influence of local factors such as bathymetry and increased burial rate of terrestrial om rather than perturbations in the global carbon cycle to due volcanism this prevents the c isotope record to be used as a global correlation tool during capitanian and wuchiapingian times comparison of palaeobiodiversity changes with perturbations in c isotope compositions across the g l interval shows that only the oldest cie was associated with a modest extinction event as documented in south china hence this study undermines any systematic coupling and causal relation between extinctions and iterative perturbations of the c isotope record during the g l interval

palaeoenvironmental change during the end guadalupian permian mass extinction in sichuan china abstract the end guadalupian mass extinction has been investigated in sichuan province sw china in the south of the province the platform carbonates of the maokou formation are overlain by the emeishan flood basalts a possible factor in the extinction event and in the north of the province the formation is succeeded by shallow marine carbonates of the wuchiaping formation late permian the extinction event is primarily recorded by the loss of fusulinaceans and possibly by species level turnover amongst calcareous algae the high diversity middle permian microfossil assemblages are last seen beneath a surface recording widespread emergence and karstification in northern sichuan emergence occurred early in the capitanian stage and the succeeding strata record restricted hypersaline deposition that preceded the deposition of a thick ash horizon the wangpo bed these mid capitanian arid conditions are replaced by humid conditions towards the end of the stage as indicated by the development of a widespread coal seam in southern sichuan only a thin development of this humid coaly facies is seen developed atop the maokou karstic surface and below the oldest flood basalt the guadalupian interval saw the development of large c isotope excursions in the carbonate record these include a positive then negative swing late in the capitanian and a newly discovered negative spike superimposed on an early capitanian heavy interval this spike may be a global phenomenon but the magnitude 8 may have been exaggerated by an increased contribution from light respired c derived from soils during relative sea level fall a plethora of environmental factors approximately coincide with the extinction event including regression acidic volcanism and flood basalt volcanism making it difficult to unravel the relative significance of each

cenozoic tectonics in the urumgi korla region of the chinese tien shan cenozoic deformation within the tien shan of central asia has accommodated part of the post collisional indentation of the indian plate into asia within the urumgi korla region of the chinese tien shan this occurred dominantly on thrusts with secondary strike slip faulting the gross pattern of deformation is of moderate to steeply dipping thrusts that have overthrust foreland basins to the north and south of the range the junggar and tarim basins respectively smaller foreland basins lie within the margins of the range itself turfan chai wo pu korla and qumishi basins these lie in the footwalls of local thrust systems both the turfan and the korla basins contain major thrusts within them they are complex foreland basins deformation has progressively affected regions further into the interior of the junggar basin and propagated into the interiors of the intermontane basins no unidirectional deformation front has passed across the tien shan in the neogene and quaternary an oligocene unconformity may indicate the time of the onset of the cenozoic deformation but most of the cenozoic molasse has been deposited after the palaeogene the rate of deposition in basins next to the uplifted ranges has increased since the onset of deformation there has been at least about 80 km of cenozoic shortening across this part of the tien shan cenozoic shortening is greater in sections of the range further west these are nearer to the northern margin of the indian indenter cenozoic compression has reactivated structures created by the two late palaeozoic collisions that created the ancestral tien shan these palaeozoic structures have exerted a strong control over the style and location of the cenozoic deformation

new timing and geochemical constraints on the capitanian middle permian extinction and environmental changes in deep water settings evidence from the lower yangtze region of south china the capitanian guadalupian witnessed one of the major crises of the phanerozoic and like many other extinctions it coincided with the eruption of a large igneous province in this case the emeishan traps of sw china however the timing and causal relationships of this event are in dispute this study concentrates on the deep water chert mudstone strata of the gufeng formation and its transition to the yinping formation at chaohu zircons from tuffs in the uppermost gufeng formation yield a u pb age of 261 6 1 6 ma and comparison with sections around emeishan suggests that the tuffs appeared in the jinogondolella altudaensis conodont zone and persisted to the jinogondolella xuanhanensis zone this coincides with the emeishan eruptions and suggests that the tuffs probably derived from this province mineralogical and geochemical characteristics also show the tuffs are of acid volcanogenic origin and have a geochemical fingerprint of the emeishan large igneous province our dating shows that a crisis amongst radiolarian and a subsequent productivity decline occurred during the middle capitanian prior to the guadalupian lopingian boundary the emeishan eruptions began immediately before this indicating a likely causal relationship between these events major regression and marine anoxia euxinia are two other important extinction relevant environmental changes that occurred during this critical interval

widespread shoaling of sulfidic waters linked to the end guadalupian permian mass extinction multiple sulfur isotopes 32s 33s 34s and 36s measured on pyrites from the penglaitan section the global stratotype section and point gssp for the guadalupian lopingian series boundary and from the auxiliary tieqiao section in south china show a sulfur isotope signal of negative and positive 34s with negative 33s we suggest that these data indicate mixing of 34s enriched and 34s depleted sulfur in the sediments which may have been driven by shoaling of sulfidic waters similar isotopic data of negative 34s with negative 33s were also observed from the ef section in the delaware basin of west texas usa the consistency of the minor sulfur isotopic anomalies from both south china and west texas suggests a causal link between widespread shoaling of sulfidic waters and the end guadalupian mass extinction

a high resolution stable isotopic record from the junggar basin nw china implications for the paleotopographic evolution of the tianshan mountains this study presents high resolution oxygen and carbon isotopic records of paleosol carbonates from fluvial sediments and lacustrine carbonates sampled from the jingou he and kuitun he stratigraphic sections located in the northern tianshan piedmont these sections expose remarkable outcrops of junggar foreland basin sediments that have been previously dated by high resolution magnetostratigraphy to between 23 6 and 1 ma and 10 5 and 3 1 ma a total of 216 samples of fluvio lacustrine sediments were collected from which isotopic analyses yield 18o smow values that range from 13 7 to 29 9 in the jingou he section and 16 3 to 21 0 in the kuitun he section 13c pdb values range from 12 9 to 3 0 in the jingou he section and from 7 8 to 4 0 in the kuitun he section 18o values decrease between 25 and 23 ma and then remain relatively steady with the exception of one period that contains samples with higher oxygen isotope values at 16 ma during the periods when there are samples that overlap in time from the kuitun he and jingou he sections we observe a difference of 1 7 between values from the two locales the 13c values also decrease between 25 and 23 ma and then remain relatively steady until 10 ma with again one short period of higher values at 16 ma then between 10 and 3 1 ma carbon isotope values progressively increase we interpret that 18o and 13c isotopic values during lacustrine periods 25 23 ma and 16 ma as largely controlled by evaporation and opening closing of the lake to external inputs we interpret the 18o values of paleosol carbonate in the junggar basin to be influenced by the hypsometry of the high tianshan range while the 13c values may record the uplift history of the depositional area in the foreland basin itself as well as the isotopic composition of plants consequently we conclude that the jingou he and kuitun he drainage basins in the central tianshan have remained at relatively unchanged elevations for the past 20 ma we also suggest that the elevation of the southern part of the foreland basin increased between 10 and 3 1 ma probably as a result of tectonic deformation in the piedmont and sedimentary filling of the sedimentary basin the carbon isotope record remains relatively stable through time and isotopic values suggest that there was little or no expansion of c4 plants in this region in the late miocene

intrabasin variability of the carbon isotope record across the permian triassic transition sverdrup basin arctic canada abstract a major late paleozoic depocentre the sverdrup basin canadian high arctic has been largely left out of the latest permian extinction debate as early workers presumed middle to late permian strata were absent basin scale sequence stratigraphic and chemostratigraphic correlations indicate late permian strata are only missing on the basin margins where they were removed by sub triassic erosion whereas continuous deposition is recorded in the basin centre the varying degree of sub triassic erosion has significant impact on the carbon isotope record across the latest permian extinction event where both the apparent rate and magnitude of carbon isotope shift vary as a function of basin position the intrabasin variability in apparent 13corg shift across the event is equivalent to that observed globally in contrast to the abrupt isotope shifts recorded on the basin margin similar to many records reported globally the basin centre section shows a systematic shift associated with the latest permian extinction the earth likely underwent a prolonged period of increasing environmental stress leading up to the event

constraining the cause of the end guadalupian extinction with coupled records of carbon and calcium isotopes abstract a negative c 13 excursion in carbonate sediments near the guadalupian lopingian middle late permian boundary has been interpreted to have resulted from a large carbon cycle disturbance during the end guadalupian extinction event ca 260 ma however the carbon isotope data alone are insufficient to uniquely determine the type and magnitude of perturbation to the global carbon cycle calcium isotopes can be used to further constrain the cause of a carbon isotope excursion because the carbon and calcium cycles are coupled via caco3 burial in this study we present coupled carbon and calcium isotope records from three guadalupian lopingian g l sections in china penglaitan and chaotian and turkey koserelik tepe the c 13 and ca 44 40 records differ among our studied sections and do not co vary in the same manner no section shows c 13 and ca 44 40 changes consistent with massive rapid volcanic co2 emissions or methane clathrate destabilization additionally many sections with large 3 changes in c 13 exhibit o 18 evidence for diagenetic alteration only one section exhibits a large excursion in the ca 44 40 of limestone but the absence of a similar excursion in the ca 44 40 of conodont apatite suggests that the limestone excursion reflects a mineralogical control rather than a perturbation to the global calcium cycle hence we interpret the large isotopic changes observed in some sections to have resulted from local burial conditions or diagenetic effects rather than from a large carbon and calcium cycle disturbance perturbations to the global carbon and calcium cycles across the g l transition were much less intense than the disturbances that occurred across the subsequent permian triassic boundary this finding is consistent with the much smaller magnitude of the end guadalupian extinction relative to the end permian

cenozoic tectonic and geodynamic evolution of the kyrgyz tien shan mountains a review of geological thermochronological and geophysical data abstract the complex crustal structure of the tien shan has a strong impact on the distribution of strain induced by the india eurasia collision with intracontinental deformation in eurasia s interior as a distant effect the northward propagation of the india eurasia deformation front is suggested by the rejuvenation of mountain ranges and intermittent intramontane basins the tien shan basement is formed by the rigid heterogeneous precambrian blocks microcontinents of tarim issyk kul or central tien shan and aktyuz boordin surrounded by a soft matrix of paleozoic accretion collision belts the kyrgyz tien shan mountains are situated between the active structures of the tarim plate and the pamir indenter south and the stable kazakhstan shield north underplating by the tarim plate and thrusting by the pamirs are responsible for the building of the cenozoic tien shan the reactivation of its inherited structural fabric and the tectonic layering of the upper lithosphere underlying the area large earthquakes m 6 delineate the northern and southern margins of the issyk kul microcontinent indicating that crustal heterogeneity influenced the location of active structures in the northern kyrgyz tien shan

carbon and sulfur isotopic fluctuations associated with the end guadalupian mass extinction in south china abstract concentrations of total organic matter toc carbon isotopic compositions of carbonate and organic matter 13 c carb 13 c org and sulfur isotopic compositions of carbonate associated sulfate 34 s sulfate across the guadalupian lopingian g l boundary were analyzed from identical samples of tieqiao section laibin guangxi province south china the 13 c carb values show a positive excursion from 0 45 to the peak of 3 80 in the laibin limestone member of the maokou formation followed by a drastic drop to 2 60 in the lowest heshan formation then returned to about 1 58 similar to the trends of the 13 c carb values 13 c carb org values also show a positive excursion followed by a sharp negative shift the onset of a major negative carbon isotope excursion postdates the end guadalupian extinction that indicates subsequent severe disturbance of the ocean atmosphere carbon cycle the first biostratigraphic 34 s sulfate values during the g l transition exhibit a remarkable fluctuation a dramatic negative shift followed by a rapid positive shift ranging from 36 88 to 37 41 these sulfate isotopic records suggest that the ocean during the g l transition was strongly stratified forming an unstable chemocline separating oxic shallow water from anoxic euxinic deep water chemocline excursions together with subsequent rapid transgression and oceanic anoxia were likely responsible for the massive diversity decline of the g l biotic crisis

widespread coastal upwelling along the eastern paleo tethys margin south china during the middle permian guadalupian implications for organic matter accumulation abstract guadalupian organic rich depositions within the eastern paleo tethys margin have been attributed to coastal upwelling but the idea has not been tested here a suite of geochemical proxies from the gufeng formation of the lower yangtze region south china are used to investigate the formation mechanisms of organic matter accumulation a high organic carbon content and similar enrichments of bio redox sensitive trace metals show strong similarities to the geochemical characteristics of modern upwelling sediments the use of high cd mo ratios and low co x mn values characteristic of modern upwelling settings sweere et al 2016 is replicated in the gufeng strata implying that lower yangtze area was dominated by persistent upwelling that become less intense seasonal later in the guadalupian application of these new geochemical proxies shows that the characteristics of modern upwelling systems such as the formation of an intense oxygen minimum zone omz can be confirmed in the ancient calculation estimates show that primary productivity was sustained at moderate to high levels and was at comparable levels to those of the modern peru upwelling system omz related anoxic conditions with transient euxinic episodes dominated permanently during the deposition of the gufeng formation and then became more intense conditions euxinia later in the guadalupian the radiolarian chert siliceous mudstone rhythms that coincide with fluctuations in major elements organic carbon total sulfur and trace metal concentrations may reflect dilution by biogenic silica chert zr al ratios are also higher than in mudstone suggesting the cherts may record more winnowed deposition at the margin of an ancient omz compared with a location within the omz for the mudstone the organic matter accumulation of the middle permian gufeng formation may be mainly controlled by the upwelling driven primary productivity and also influenced by the changes of anoxic euxinic conditions and the dilution of biogenic silica

a smooth negative shift of organic carbon isotope ratios at an end permian mass extinction horizon in central pelagic panthalassa abstract the end permian mass extinction is associated with a global perturbation in the carbon isotopic composition of carbonates and organic matter but such changes are not well documented from pelagic deep sea sediments one of the most continuous pelagic deep sea permian triassic boundary ptb sections the am 2 section is exposed in the accretionary complexes of japan new data for organic carbon isotope ratios 13corg were obtained from 36 samples from section am 2 the 13corg excursion curve exhibits a negative shift of 2 0 in the low latitude pelagic panthalassic ocean at the end of the permian which coincides with a radiolarian extinction the 13corg values of pelagic deep sea panthalassic sections and those of shallow water sections from panthalassic seamounts exhibit a smooth negative shift that lacks temporary increases like those reported from paleotethyan ptb sections absence of temporary 13corg increases at the ptb in panthalassa may reflect less algal and bacterial blooming in pelagic panthalassa compared to the shallow water paleotethys

the carbon isotope excursion on gssp candidate section of lopingian guadalupian boundary an isotopic stratigraphically well documented outcrop in penglaitan guangxi province south china has been proposed as a candidate gssp for the lopingian guadalupian boundary correlatable outcrops from the west wing tieqiao section and east wing penglaitan section of the laibin syncline exhibit synchronous excursions in carbon isotopes the isotopic excursions 13c show the best placement of the boundary may lie at the base of bed 6k which coincides with the clarkina postbitteri conodont zone and with eustatic change 13c increases during the uppermost guadalupian jinogondolella granti conodont zone from the top of 3c to the base of 6i a 13c peak value of 5 is located at the transition between these two conodont zones and is suggested as a proxy for the transition from transgression to regression a gradual depletion of carbon isotopes occurs in the c postbitteri zone from bed 6e to 7b and this gradual 13c excursion also suggests the sequences around the guadalupian lopingian boundary at the candidate section are conformable during the middle later c postbitteri zone a 3 5 dramatic 13c depletion is recorded at the tieqiao section but only a 2 depletion at the deeper facies penglaitan section synchronous with conodont zones that mark eustatic changes

magnetostratigraphy in pursuit of missing links since the last quadrennial report magneto stratigraphy has continued to flourish the primary issues have been 1 refinements to the geomagnetic reversal time scale grts including recalibrations correlation of biostratigraphic data to the crts and revision of the terminology 2 use of magnetostratigraphic data for estimating rates of such processes as sediment accumulation evolution and faunal migration and 3 magnetic mineralogy and the origin of remanence for convenience we have divided the publications into studies of continental and marine sediments and highlight the most exciting issues within each of these sub headings in the first section of this review we will concentrate on the development of the geomagnetic reversal time scale grts with particular emphasis on refinements from the last few years we then turn our attention to applications of magnetostratigraphy in marine and continental sequences

structural framework of a major intracontinental orogenic termination zone the easternmost tien shan china the barkol tagh and karlik tagh ranges of the easternmost tien shan are a natural laboratory for studying the fault architecture of an active termination zone of a major intracontinental mountain range barkol and karlik tagh and lesser ranges to the north are bounded by active thrust faults that locally deform quaternary sediments major thrusts in karlik tagh connect along strike to the east with the left lateral gobi tien shan fault system in sw mongolia from a mongolian perspective karlik tagh represents a large restraining bend for this regional strike slip fault system and the entire system of thrusts and strike slip faults in the karlik tagh region defines a horsetail splay fault geometry regionally there appears to be a kinematic transition from thrust dominated deformation in the central tien shan to left lateral transpressional deformation in the easternmost tien shan this transition correlates with a general eastward decrease in mountain belt width and average elevation and a change in the angular relationship between the nne directed maximum horizontal stress in the region and the pre existing basement structural grain which is northwesterly in the central tien shan orthogonal to sh max but more east west in the eastern tien shan acute angular relationship with sh max ar ar ages indicate that major range bounding thrusts in barkol and karlik tagh are latest permian triassic ductile thrust zones that underwent brittle reactivation in the late cenozoic it is estimated that the modern mountain ranges of the extreme easternmost tien shan could have been constructed by only 10 15 km of late cenozoic horizontal shortening

a temporal link between the emeishan large igneous province sw china and the end guadalupian mass extinction abstract previous studies have suggested that there were two mass extinction events in the late permian one that occurred at the permo triassic p t boundary 251 ma and a second smaller mass extinction that occurred 5 8 myr earlier at the end of the guadalupian many workers have argued that there is a causal relationship between large scale volcanic activity and mass extinctions the major mass extinction event at the p t boundary coincides with the outpouring of huge quantities of lava that formed the siberian flood basalt province in russia courtillot et al earth planet sci lett 166 1999 177 195 and wignall earth sci rev 53 2001 1 33 suggested that the earlier late permian mass extinction coincided with the eruption of the lavas that formed the emeishan flood basalt efb province in sw china however the age of eruption of the efb lavas is poorly constrained using the sensitive high resolution ion microprobe to analyze zircons we have established the age of the xinjie intrusion believed to be a feeder to the main phase of efb volcanism to be 259 3 ma hence the formation of the efb is coincident with a proposed extinction event at 256 259 ma this result supports a temporal link between the emeishan large igneous province and the end guadalupian mass extinction

permian palaeogeographic evolution of the jiangnan basin south china abstract the most striking geographic feature of the permian of south china is the jiangnan basin which intimately reflects the interplay between the yangtze and cathaysia blocks geographic and sedimentological evolution suggests that the jiangnan basin superposed on a precambrian collisonial megasuture and a folded early paleozoic deep basin was an extensional intracratonic basin it opened in the longlinian and became more passive and restricted in the latest maokouan the remarkably similar geographic patterns of the jiangnan basin in the early and late palaeozoic suggest that the yangtze and cathaysia blocks were coherent during the paleozoic

an isotopic study of biogeochemical relationships between carbonates and organic carbon in the greenhorn formation carbon isotopic compositions of total carbonate inoceramid carbonate micritic carbonate secondary cements total organic carbon and geoporphyrins have been measured in 76 different beds within a 17 m interval of a core through the greenhorn formation an interbedded limestone and calcareous shale unit of cretaceous age cenomanian turonian from the western interior seaway of north america results are considered in terms of variations in the processes of primary production which led to the biosynthesis of the molecular precursors of the geoporphyrins and in secondary processes those mediating the transformation of primary organic material into sedimentary total organic carbon it is shown that the porphyrin isotopic record reflects primary isotopic variations more closely than the toc isotopic record and that in these sediments toc is enriched in 13c relative to its primary precursor by 0 6 to 2 8 this enrichment is attributed to isotope effects within the consumer foodweb and is associated with respiratory heterotrophy variations in this secondary enrichment are correlated with variations in the isotopic composition of marine carbonate this correlation is attributed to effects of environmental changes on the marine foodweb these may have included increased atmospheric oxygen associated with the cenomanian turonian oceanic anoxic event the isotopic fractionation associated with fixation of carbon by primary producers is observed to have varied by 1 5 during the interval of deposition it is suggested that this change is due to a variation in the makeup of the community of primary producers and or to a decrease in the atmospheric abundance of co2 during the oceanic anoxic event

timing of formation of forebergs in the northeastern gobi altai mongolia implications for estimating mountain uplift rates and earthquake recurrence intervals bedrock and quaternary alluvial fans in the forelands of the northern gobi altai have been faulted and warped by foreland propagating thrust faults to form elongate hills known as forebergs forebergs near bogd town north of arsta bogd and at ih hetsuu north of baga bogd were mapped and their formation constrained using luminescence dating of lacustrine and fanglomerates sediments to give localized uplift rates of c 0 05 m ka 1 and between c 1 6 and 4 1 m ka 1 respectively comparisons between vertical surface rupture during the 1957 gobi altai earthquake with the age and amount of uplift of lacustrine sediments provide a tentative estimate of between 1288 382 to 497 120 years for the average recurrence interval of great earthquakes in the baga bogd region these localized uplifts rates support the view that the gobi altai mountains probably took between 50 and 25 million years to form and were therefore coeval with the uplift of the himalayas and the tibetan plateau

δ18o and δ13c of permian brachiopods a record of seawater evolution and continental glaciation abstract two hundred sixty four 18 o and 13 c values of permian articulate brachiopod shells were analyzed and 81 of these values were characterized as well preserved and biostratigraphically well defined these were then utilized for construction of baseline oxygen and carbon isotope curves for the permian interval in addition 21 13 c whole rock values are reported for the wordian and capitanian the early permian asselian to artinskian times are characterized by 2 5 decrease in oxygen isotope values from 0 7 to 3 3 v pdb this is attributed to a 4 7 c increase in temperature in the southern urals concomitant with the retreat of the permo carboniferous ice sheets and return of the 18 o depleted melt water into the oceans the late permian samples from iran jolfa at kuh e ali bashi and china meishan yield 18 o values and presumably temperatures similar to those that followed the termination of the large scale glaciation in the lower permian in between the upper kungurian to capitanian samples from the delaware basin guadalupe mountains are enriched in 18 o at 1 5 to 3 we have no definitive explanation for these data but tentatively suggest that the anomaly can potentially be a result of evaporative enrichment of seawater in 18 o due to intracratonic arid setting of the basin the 18 o enriched nature of the zechstein samples 1 2 to 2 5 on the other hand is in all probability a reflection of the high evaporation rates in the zechstein sea the permian interval is characterized by a relatively constant 13 c at about 4 the exceptions are again the brachiopods from the delaware basin guadalupe mountains which show 1 6 increase in the guadalupian to values of up to 5 9 in the wordian a tentative explanation as in the case of oxygen is based on the proposition that the semi enclosed delaware basin was likely stratified with sequestration of the 13 c depleted carbon to the deeper water layers and a complementary 13 c enrichment in the upper oxygenated layer the coeval open ocean water dic may have been similar to that of the remainder of the permian interval at 4 as indicated by whole rock carbonate samples from oman sicily and iran in the latest permian the trend mimics the well known 13 c drop at the permian triassic boundary

the middle permian capitanian mass extinction on land and in the oceans abstract a middle permian mass extinction first discovered in 1994 has become known as the end guadalupian event in the literature however recent studies of foraminifera and brachiopod range truncations in conodont dated sections on the south china block have shown that the losses occur below this level in the middle of the capitanian stage extinctions were suffered by several other groups notably the corals whilst the mollusc record is more enigmatic a major bivalve crisis has been reported in some studies the giant alatoconchids being notable victims but not others gastropods were unaffected by the crisis whilst a roughly contemporaneous ammonoid mass extinction may have occurred in the early wuchiapingian a few million years after the main marine losses compilation of data from plant species in south china reveals a significant 24 loss suggesting that the capitanian crisis also occurred on land an intra capitanian extinction of 56 of plant species in north china block sequences may also have coincided with these losses correlation of these marine and terrestrial extinction events using the palaeomagnetic record provides two alternatives either turnover amongst plant species is contemporaneous with the marine extinction and the eruption of the emeishan flood basalt province in southwest china or plant losses post date the marine extinction and instead coincide with the waning phase of the igneous province current understanding of the major dinocephalian extinction suggests this event occurred during the preceding stage the wordian but future improvements in both sampling and dating this tetrapod crisis may reveal a synchronicity of plant animal and marine invertebrate extinctions the clear temporal link of the capitanian marine extinction with emeishan volcanism suggests that these flood basalt eruptions triggered the crisis a contemporaneous major negative c isotope excursion suggests that like many other mass extinction events methane release from hydrates may also be implicated however in the best dated chinese sections the main excursion is found to slightly post date the extinction which occurs at the end of an unusual and unexplained interval of exceptionally heavy 13c values other usual suspects for mass extinctions either lack geological and palaeontological evidence e g marine anoxia and global cooling or do not precisely correlate with the extinction e g major eustatic regression

significance of high c n ratios in organic carbon rich neogene sediments under the benguela current upwelling system corganic ntotal values change from 5 in middle miocene sediments deposited under the benguela current upwelling system to 15 in latest miocene and pliocene sediments although the change appears to record a larger proportion of land derived material in younger sediments bulk 13corg values indicate a predominance of marine origin for organic matter throughout the sequence marine paleoproductivity as represented by mass accumulation rates of caco3 and organic carbon increased over this time interval we postulate that the larger corganic ntotal values record a shift towards greater recycling rates of nitrogen rich relative to carbon rich organic matter components as the flux of total organic matter to the seafloor increased furthermore we propose that high corganic ntotal values may record enhanced paleoproductivity in other sedimentary sequences dominated by marine organic matter

carbon and conodont apatite oxygen isotope records of guadalupian lopingian boundary sections climatic or sea level signal abstract the guadalupian lopingian g l boundary 260 4 ma is one of the major extinction events in earth history that coincides with the emeishan large igneous province and palaeoclimatic changes carbon isotopes of whole rock samples were studied in order to document changes in the global carbon cycle in contrast to earlier studies we observe no major negative excursion in 13 c in the middle capitanian a positive 13 c excursion is observed in the latest capitanian with a 1 5 increase registered in the j xuanhanensis zone to c postbitteri hongshuiensis subzone followed by a decrease of 1 within the c postbitteri postbitteri subzone and a 2 decrease in the c dukouensis to c asymmetrica zone oxygen isotopes of conodonts from two g l boundary sections were measured in order to reconstruct conodont habitat and potential changes in water temperature oxygen isotope ratios of gondolellid conodonts are higher in comparison to oxygen isotope ratios measured on hindeodid conodonts suggesting that gondollelids lived in cooler and thus deeper waters compared with hindeodids the oxygen isotope record reconstructed from gondollelid conodonts suggests warming of water temperatures of about 4 c in the late capitanian j postserrata to j granti zone cooling of about 6 to 8 c across the g l boundary and in the earliest wuchiapingian and again significant warming in the wuchiapingian c dukouensis to c liangshanensis zone the temperature increase can be correlated with the main phase of emeishan volcanism suggesting that climatic warming may have resulted in an intensified hydrological cycle fertilisation of the oceans and enhanced primary productivity the latter documented in the positive late capitanian carbon isotope excursion however changes in sea level seem to parallel reconstructed water temperatures suggesting that changes in water depth in combination with superimposed climatic changes may be responsible for the observed temperature changes this study documents that oxygen isotope studies on permian conodonts should be performed on mono generic conodont samples and that oxygen isotopes not only provide valuable palaeoclimatic information but also may help to constrain the life habitat of conodonts

marine redox variations and nitrogen cycle of the early cambrian southern margin of the yangtze platform south china evidence from nitrogen and organic carbon isotopes the early cambrian is a crucial interval during which the marine environment encountered significant perturbations alongside key biological innovations the nitrogen isotopic composition of ancient sediments has the potential to record co variation between the marine ecosystem and environmental conditions here we report bulk nitrogen and organic carbon isotopic compositions accompanied by mo concentration data a proxy for redox conditions for a shelf marginal drill core section sancha and a deep basinal outcrop section yuanjia in hunan province south china for the cambrian fortunian stage variable delta n 15 bulk values 4 to 2 parts per thousand and low delta c 13 org values 35 parts per thousand to 33 from the yuanjia section indicate that anoxic waters shoaled into the photic zone with ammonia assimilation competing with anammox in the basinal area in the late cambrian stage 2 low delta n 15 bulk and delta c 13 org values together with high mo bulk concentrations delta n 15 bulk 5 to 0 parts per thousand delta c 13 org 33 5 to 31 0 parts per thousand 100 ppm mo bulk in sancha section and delta n 15 bulk 0 parts per thousand delta c 13 org similar to 33 parts per thousand 100 ppm mo bulk in yuanjia section reflect intense n 2 fixation accompanied by intermittent ammonia assimilation under expanded euxinic condition with shoaling chemocline possibly into the photic zone in the early cambrian stage 3 relatively high delta n 15 bulk values alongside positive delta c 13 org excursions at both sections indicate an increasing contribution from n 15 enriched nitrate assimilation and hence more oxic conditions shelf margin sediments from the middle and late parts of cambrian stage 3 are characterized bylaw delta n 15 bulk values similar to 0 parts per thousand being lowest in the basinal area 3 to 0 parts per thousand in combination with high mo bulk concentration 100 ppm and high mo tocbulk ratios averaging similar to 18 in deep basinal sediments these data suggest that the photic zone became anoxic again but that sulfidic conditions occurred in the basinal area only compared with stage 2 euxinia was less extensive during this interval with photosynthetic biomass dominating over chemoautotrophic biomass at both localities based on a combination of delta n 15 data from this study and published data from studies on contemporaneous sections in yunnan province and the three gorges area it is possible to reconstruct the spatial variability and temporal evolution of redox conditions in the various marine environments along the southern margin of the yangtze platform the basinal area appears to have been dominated by anoxia and intermittent euxinia in the photic zone during most of the early cambrian fortunian stage to stage 3 with the exception of more oxic conditions during early stage 3 on the platform oxygenated shallow water prevailed with the exception of the notable cambrian stage 2 anoxic event the outer shelf area experienced anoxia from stage 2 to stage 3 of the early cambrian although of possibly limited areal extent the high mo bulk concentrations and mo tocbulk ratios suggest that the south china basin was well connected with the considerably oxygenated open ocean and that the mean low delta n 15 bulk values similar to 1 6 parts per thousand from the basin may reflect generally lower delta n 15 composition for seawater nitrate in the early cambrian compared with modern value c 2015 elsevier b v all rights reserved

co2 forced climate and vegetation instability during late paleozoic deglaciation the late paleozoic deglaciation is the vegetated earth9s only recorded icehouse to greenhouse transition yet the climate dynamics remain enigmatic by using the stable isotopic compositions of soil formed minerals fossil plant matter and shallow water brachiopods we estimated atmospheric partial pressure of carbon dioxide pco2 and tropical marine surface temperatures during this climate transition comparison to southern gondwanan glacial records documents covariance between inferred shifts in pco2 temperature and ice volume consistent with greenhouse gas forcing of climate major restructuring of paleotropical flora in western euramerica occurred in step with climate and pco2 shifts illustrating the biotic impact associated with past co2 forced turnover to a permanent ice free world

sedimentary environments of the middle permian phosphorite chert complex from the northeastern yangtze platform china the gufeng formation a continental shelf radiolarian chert abstract radiolarian chert deposited on a continental shelf occurs in the middle permian gufeng formation on the northeastern yangtze platform china the sedimentary environments of radiolarian cherts from accretionary complexes have been well studied however there are few studies about radiolarian chert deposited on continental shelves therefore we have completed a sedimentological and geochemical study of the gufeng formation the gufeng formation is subdivided into the phosphate nodule bearing mudstone member pnmm and the siliceous rock member srm in ascending order the basal pnmm consists of glauconite bearing mudstone which indicates deposition under aerobic shallow marine conditions whereas the upper pnmm is composed of mudstone including abundant phosphate nodules suggesting deposition near the outer shelf in suboxic conditions the srm consists mainly of alternating beds of black chert mudstone and siliceous mudstone with minor tuffaceous mudstone and porous chert beds the black chert contains abundant radiolarians sponge spicules and organic matter framboidal pyrite occurs in the black chert porous chert in the srm includes abundant rhombohedral cavities which are dolomite moulds surrounded by quartz suggesting dolomitization before silicification during early diagenesis the gufeng chert is characterized by high si mo ni cu and zn contents and extremely low mn content the gufeng chert has high normal paraffin concentrations with petroleum like markers these geochemical features suggest that the gufeng chert was deposited under sulfate reducing conditions and is not hydrothermal but rather biogenic in origin the sedimentological and geochemical data suggest that the gufeng formation was deposited mainly on the outer shelf in suboxic anoxic conditions caused by organic matter produced during upwelling the upwelling probably led to high radiolarian productivity abundant silica and organic matter were deposited in the gufeng basin compared with chert from other sites the gufeng chert shows many similarities with chert from platformal basins but not with chert from accretionary complexes especially with respect to age rock type stratigraphy and geochemical features the chert of the gufeng formation is similar to that of the phosphoria formation in the western u s a which is a world class phosphorite giant these similarities suggest that upwelling occurred around the eastern margins of panthalassa and the paleotethys concurrently during the middle permian in general shelf type radiolarian chert represented by the gufeng chert usually shows some of the following features dark color lack of rhythmical bedding association with phosphorite platformal limestone felsic tuff abundant organic matter and sulfides shelf type radiolarian chert is deposited in a poorly aerated restricted basin or in an oxygen minimum zone

climate changes caused by degassing of sediments during the emplacement of large igneous provinces most mass extinctions during the last 500 m y coincide with eruptions of large igneous provinces lips the cretaceous tertiary extinction was synchronous with the deccan flood volcanism the permian triassic extinction with the eruption of the enormous siberian traps and the end guadalupian extinction with the emeishan volcanic province the causal link remains disputed however and many lips apparently had no significant impact on the biosphere here we show that a key control on the destructive consequences of lip emplacement is the type of sedimentary rock in basins beneath the flood basalts contact metamorphism around intrusions in dolomite evaporite coal or organic rich shale generates large quantities of greenhouse and toxic gases co 2 ch 4 so 2 which subsequently vent to the atmosphere and cause global warming and mass extinctions the release of sediment derived gases had a far greater impact on the environment than the emission of magmatic gases

major geological events in the late guadalupian and carbon strontium isotope responses in the yangtze platform south china two sections of marine carbonate strata podu and lengshuixi from the yangtze platform south china are investigated in terms of major geological events and carbon strontium isotope responses the results show a large scale regression and a large igneous province lip event occurred in succession in the short interval of the late guadalupian inducing a biodiversity crisis the regression event marked by an increase in the 87sr 86sr ratio is observed in the jinogondolella postserrata zone it contributed significantly to the reduction in species habitat leading to notable losses within the shallow water species assemblage a subsequent lip event occurred after the appearance of jinogondolella altudaensis releasing co2 and numerous other deleterious gases that further amplified the crisis in shallow water to deep sea environments the corresponding decline in sr and c isotopes could have been a response to the basaltic eruption relative increase from mantle derived sr and release of 12c enriched c

the mid capitanian middle permian mass extinction and carbon isotope record of south china abstract conodont c isotope and fossil and facies data are presented for the capitanian middle permian mass extinction record seen in platform carbonates maokou and wuchiaping formations of south china where limestones interdigitate with the volcanic succession of the emeishan large igneous province the maokou formation provides an extinction record marked by the loss of keriothecal walled fusulinaceans and a turnover in calcareous algae in sections within the emeishan province this crisis occurs at the base of the oldest record of volcanism from the jinogondolella altudaensis conodont zone of mid capitanian age around the periphery of the emeishan province this extinction level lies within the upper part of the maokou formation at a level where platform carbonate deposition was frequently interrupted by thick volcanic ash depositional events the assemblages of the uppermost maokou formation are characterised by typical late permian taxa although these levels still lie within the middle permian guadalupian series disaster taxa such as earlandia and diplosphaerina are locally prolifically abundant in the aftermath of the mass extinction the crisis is particularly noteworthy amongst photosynthetic taxa such as calcareous algae and fusulinaceans that probably harboured photosymbionts therefore a kill mechanism involving cooling from explosive volcanism and potentially acid rain from sulphate aerosols appears appropriate a composite 13ccarb curve calibrated against a high resolution conodont biostratigraphy reveals a major intra capitanian negative excursion of 5 superimposed on typically heavy 4 5 middle permian values this curve can also be recognised in panthalassan seamount carbonates of japan although this requires reassignment of apparently upper permian limestones to the middle permian in both china and japan the capitanian mass extinction occurs during the early stage of this major intra capitanian negative excursion assuming typical platform carbonate accumulation rates the records of the maokou formation suggest 13ccarb values fell at 0 01 kyr suggesting a catastrophic origin such as gas hydrate destabilisation is unlikely although a volcanic source is possible

a major anomaly in the carbon cycle during the late cisuralian permian timing underlying triggers and implications abstract the kungurian late cisuralian is associated with elevated atmospheric p co 2 levels and numerous substantial changes in the ocean and terrestrial systems but carbon cycle perturbations through this time interval are poorly understood here three well dated organic carbon isotope 13 c org curves from south china paired with their respective carbonate carbon isotope 13 c carb data published before are presented for the first time their comparison demonstrates that a prominent rapid and synchronous negative excursion in 13 c org and 13 c carb occurred in the early kungurian the herein proposed kcie event dated to ca 277 9 277 4 ma a comparable shift is observed in other deeper water marine sections in south china and two terrestrial sections in north china and eastern australia based on carbon mass balance calculations and a review of concurrent geological records we propose that the kcie event was driven by an intensive volcanism of a large igneous province in northern gondwana dissociation of voluminous methane hydrates induced by this volcanism and the ensuing worldwide conflagrations predicted elevated production of greenhouse gases involved would have warmed the earth and further resulted in ocean stagnation anoxia and acidification all of which are in conformity with the documented sedimentological geochemical and palaeontological data this major anomaly in the carbon cycle in the late cisuralian is considered here to play a key role to promote the transition of the earth to a greenhouse mode

magnetostratigraphy of the berriasian stratotype section berrias france the berriasian early cretaceous stratotype section berrias ardeche france 30 m thick consists of well bedded blue gray pelagic limestone the biostratigraphic subdivision of this section is based on ammonite and calpionellid zonations magnetostratigraphic study has yielded a reliable magnetic polarity sequence magnetite is the principal ferrimagnetic mineral and the characteristic remanent magnetization chrm directions are clearly defined after thermal or alternating field demagnetization ammonite and calpionellid zones allow biostratigraphic calibration of the magnetic polarity sequence with precision on the order of an ammonite sub zone this magnetic polarity sequence can be correlated with marine magnetic anomalies m15 to m17n m15 occurs within the upper part of theboissieri ammonite zone while m17n occurs within theoccitanica ammonite zone

permian carbon isotope and clay mineral records from the xikou section zhen an shaanxi province central china climatological implications for the easternmost paleo tethys abstract permian carbon isotopic and clay mineralogical records were recovered from the carbonates in the xikou section a complete and uninterrupted upper carboniferous to lower triassic carbonate dominated succession exposed in zhen an shaanxi province central china which were used to document carbon isotopic signatures and climatic changes affecting the easternmost paleo tethys region during the permian both carbon isotope and clay mineralogical data suggest fluctuating climatic conditions and trends that can be approximately correlated with eastern australian glaciations and north american craton during the artinskian to capitanian stages two global carbon isotopic anomalies across the permian triassic boundary and the guadalupian lopingian series boundary were detected for the first time in the stratigraphic record of the south qinling micro continental block the capitanian stage comprises an early phase of climatic warming followed by a later phase of climatic cooling the kungurian stage represents a climatic warming interval and the main phase of deglaciation during the late paleozoic ice age lpia a 13c positive shift across the boundary of the artinskian to kungurian stages together with the following negative excursion recorded in the early kungurian stage can be used as an indicator for the boundary between the artinskian and kungurian stage

triassic jurassic organic carbon isotope stratigraphy of key sections in the western tethys realm austria the late triassic period is recognized as one of the five major mass extinctions in the fossil record all these important intervals in earth history are associated with excursions in c isotope records thought to have been caused by perturbations in the global carbon cycle the nature and causes of c isotopic events across the triassic jurassic t j transition however are poorly understood we present several new high resolution organic c isotope records from the eiberg basin austria including the proposed global boundary stratotype section and point gssp for the base of the jurassic the triassic jurassic boundary interval in these records is characterized by the initial and main negative organic carbon isotope excursions cie of up to 8 the initial and main cies are biostratigraphically constrained by first and last occurrences of boundary defining macro and microfossils e g ammonites high resolution c isotope records appear to be an excellent correlation proxy for this period in the eiberg basin pyrolysis analysis demonstrates increased hydrogen index hi values for organic matter coinciding with the initial cie terrestrial organic matter influx and mass occurrences of green algae remains may have influenced the c isotope composition of the sedimentary organic matter this may have contributed to the extreme amplitude of the initial cie in the eiberg basin

high resolution δ13ccarb chemostratigraphy from latest guadalupian through earliest triassic in south china and iran large carbon cycle perturbations are associated with the end permian mass extinction and subsequent recovery but late permian lopingian carbon cycle dynamics prior to the mass extinction event remain poorly documented here we present a high resolution 13ccarb chemostratigraphic framework from latest guadalupian to earliest triassic time calibrated with high resolution conodont biostratigraphy and high precision geochronology we observe two large negative excursions in 13ccarb the first in uppermost guadalupian strata and the second at the end of the changhsingian stage and between these events distinctive excursions from the middle wuchiapingian to the early changhsingian the end changhsingian excursion represents a major reorganization of the global carbon cycle associated with the end permian mass extinction however the extent to which the end guadalupian and wuchiapingian changhsingian boundary excursions result from local versus global controls remains unresolved regardless of their underlying causes these three excursions provide chemostratigraphic markers for global correlation of lopingian strata

δ13c depth profiles from paleosols across the permian triassic boundary evidence for methane release stable carbon isotopic analyses of organic carbon 13 c in individual paleosol profiles from permian triassic sequences of antarctica reveal systematic isotopic variations with profile depth these variations are in many cases analogous to those in modern soils which are functions of redox conditions soil development and degree and type of microbial decay in modern soils these isotopic depth functions develop independently from vegetation changes c 3 versus c 4 vegetation and can be diagnostic of soil orders this study shows that soil intrinsic functions can be preserved in the 13 c values of paleosols as old as 260 ma and constitute valuable data for paleoecological interpretations a large carbon isotopic offset of as much as 10 in whole paleosol profiles across the permian triassic boundary indicates significant changes in the soil biogeochemistry and the soil atmosphere system early triassic paleosols are distinctive in their extremely low 13 c values to 42 and often show an anomalous 13 c depth distribution compared to both permian paleosols and modern soils highly depleted 13 c values as the ones in early triassic paleosols are suggested to be associated with microbial methane oxidation methanotrophy this hypothesis implies increased methane concentrations in the early triassic soil atmosphere system increased atmospheric methane was probably partly responsible for the global carbon isotopic shift documented in marine and terrestrial sediments across the permian triassic boundary

middle permian organic carbon isotope stratigraphy and the origin of the kamura event abstract large carbon cycle perturbations associated with the middle permian capitanian mass extinction have been widely reported but their causes and timing are still in dispute low resolution carbon isotope records prior to this event also limit the construction of a middle permian chemostratigraphic framework and global or local stratigraphic correlation and hence limit our understanding of carbon cycle and environmental changes to investigate these issues we analyzed the 13corg values from the middle permian chert mudstone sequence gufeng formation in the lower yangtze deep water basin south china and compared them with published records to build a chemostratigraphic scheme and discuss the underlying environmental events the records show increased 13corg values from late kungurian to early guadalupian followed by a decrease to the late wordian early capitanian the early mid capitanian was characterized by elevated 13corg values suggesting the presence of the kamura event an interval of heavy positive values seen in the 13ccarb record we propose that these heavy capitanian 13c values may be a response to a marked decline in chemical weathering rates on pangea and associated reduction in carbonate burial which we show using a biogeochemical model the subsequent negative 13c excursion seen in some carbonate records especially in shallower water sections and in a muted expression in organic carbon coincide with the capitanian mass extinction may be caused by the input of isotopically light carbon sourced from the terrestrial decomposition of organic matter

syntectonic growth strata and implications for late cenozoic tectonic uplift in the northern tian shan china abstract propagation of faults and folds in the foreland basins of tian shan is an important process accommodating cenozoic crustal shortening and mountain building but little is known about the accurate time of the cenozoic tectonic deformation based on growth strata and age determination we show that syntectonic growth strata began to develop in the middle part of tian shan since 6 ma ago geometry analysis indicates that formation of the growth strata is associated with progressive fold limb rotation formation of the growth strata is contemporaneous with the tectonic deformation in the thrusting and folding zones together with the remarkable increase of sedimentation rate as well as the accumulation of coarse molasse deposits we conclude that the late cenozoic crustal shortening and mountain building in the region initiated since about 6 ma and lasted to the early pleistocene as a consequence of intracontinental deformation within the india eurasia convergent system

dome and basin refolding and transpressive inversion along the karatau fault system southern kazakstan the karatau fault system of southern kazakstan forms a crustal scale zone of strike slip dominated transpressional tectonics which has undergone multiple phases and styles of deformation during a protracted history of reactivation from the neoproterozoic to the cenozoic ductile fabrics associated with dextral kinematic indicators are present in amphibolites along the main karatau fault the ages of the possibly ophiolitic protoliths and the ductile fabrics are not well constrained but they are plausibly pre late riphean late ordovician granites stitch thrusts and folds which deform late riphean to llanvirn clastics preserved beneath a regional late devonian angular unconformity this deformation may be related to a contemporary continental collision ne of the karatau two phases of late palaeozoic deformation affected the upper devonian and carboniferous carbonate succession the first phase is related to sinistral transpression along the karatau fault system the second to dextral transpressional reactivation the combination of these events produced a regional scale dome and basin fold interference pattern similar polyphase deformation appears to have affected large areas of central asia and was possibly caused by the late palaeozoic orogenies at asia s margins such as the accretion of tarim and the east european craton to asia and the closure of the kazakstan orocline normal faults in the karatau are related to the formation of the leontiev graben south turgay basin and the yarkand fergana basin in the early to mid jurassic during renewed dextral slip along the karatau talas fergana fault late cenozoic deformation is minor and resulted in the uplift and incision of a cretaceous palaeogene peneplain without a major tectonic overprint reversals in the sense of strike slip dominated transpressive deformation across major fault systems results in transpressive inversion this represents an ideal process with which to generate overprinting orthogonal fold systems resulting in classic dome and basin interference patterns on a regional scale

methane release from igneous intrusion of coal during late permian extinction events abstract unusually large and locally variable carbon isotope excursions coincident with mass extinctions at the end of the permian period 253 ma and guadalupian epoch 260 ma can be attributed to methane outbursts to the atmosphere methane has isotopic values 13c low enough to reduce to feasible amounts the carbon required for isotopic mass balance the duration of the carbon isotopic excursions and inferred methane releases are here constrained to 10 000 yr by counting annual varves in lake deposits and by estimating peat accumulation rates on paleogeographic maps the most marked carbon isotope excursions form linear arrays back to plausible methane sources end permian siberian traps and longwood bluff intrusions of new zealand and end guadalupian emeishan traps of china intrusion of coal seams by feeder dikes to flood basalts could create successive thermogenic methane outbursts of the observed timing and magnitude but these are unreasonably short times for replenishment of marine or permaf

primary carboniferous and permian paleomagnetic results from the yili block nw china and their implications on the geodynamic evolution of chinese tianshan belt in order to better understand the tectonic role of the yili block on the paleozoic evolution of the chinese tianshan belt we performed a primary paleomagnetic study on carboniferous and permian rocks from different areas in the yili block nw of china more than 320 sedimentary and volcanic samples were collected from 39 sites except for the ordovician samples showing a weak and unstable magnetic remanence the majority of this collection presents characteristic remanent magnetization carried by magnetite and hematite in the study area though positive fold test has been observed on the early carboniferous rocks a general remagnetization of these rocks has been identified and attributed to the late carboniferous magmatism moreover all early and late carboniferous samples from the interior of the yili block yield stable and coherent magnetic directions with exhaustively reverse magnetic polarity the late carboniferous c2 is considered as the magnetic remanence age since these rocks are covered or intruded by synchronous magmatic rocks of the yili arc which lasted until to 310 ma the c2 paleomagnetic pole is therefore calculated at 68 6 n 290 6 e with 95 6 4 and n 15 the late carboniferous rocks located close to a deformation zone present a consistentmagnetic inclination but significant different declination with respect to other areas and are suspected to have probably experienced a local rotation although no fold test can be performed due to the monoclinal bedding stable magnetic components are isolated from late permian p2 red beds in the interior of the yili block with also a solo reverse magnetic polarity the p2 paleomagnetic pole of the yili block has been therefore calculated from the characteristic remanent magnetization 79 7 n 172 0 e with 95 11 3 and n 5 keeping important uncertainties in mind comparisons of the c2 and p2 paleomagnetic poles of the yili block with available coeval poles of junggar tarim and siberia indicate 1 no significant relative motion between the yili and junggar blocks since the late carboniferous 2 no significant or weak latitudinal relative motion occurred since the late carboniferous among these blocks but 3 the 46 2 15 1 and the 31 6 15 1 counterclockwise rotations of the yili junggar blocks with respect to tarim and siberia took place during c2 to p2 these rotations are accommodated by the permian dextral strike slip faults along the northern and southern sides of tianshan belt and sinistral strike slip faulting along the erqishi fault of altay belt resulting in about 1000 km and 600 km lateral displacements in the tianshan and altay belts respectively

mercury anomalies associated with three extinction events capitanian crisis latest permian extinction and the smithian spathian extinction in nw pangea strata of permian early triassic age that include a record of three major extinction events capitanian crisis latest permian extinction and the smithian spathian extinction were examined at the festningen section spitsbergen over the c 12 ma record examined mercury in the sediments shows relatively constant background values of 0 005 0 010 g g 1 however there are notable spikes in hg concentration over an order of magnitude above background associated with the three extinctions the hg total organic carbon toc ratio shows similar large spikes indicating that they represent a true increase in hg loading to the environment we argue that these represent hg loading events associated with enhanced hg emissions from large igneous province lip events that are synchronous with the extinctions the hg anomalies are consistent across the nw margin of pangea indicating that widespread mercury loading occurred while this provides utility as a chemostratigraphic marker the hg spikes may also indicate loading of toxic metals to the environment a contributing cause to the mass extinction events

vertical δ13corg gradients record changes in planktonic microbial community composition during the end permian mass extinction abstract the global carbon cycle experienced a major perturbation during the permian triassic transition reflected inter alia in a large increase in the vertical shallow to deep gradient of carbonate 13c 13ccarb in early triassic seas however the effect of this perturbation on the vertical gradient of organic matter 13c in seawater 13corg is less known to date here we examine geographic and secular variations in 13corg in late permian early triassic seas of the south china craton and their implications for contemporaneous changes in microbial community composition and paleoredox conditions vertical 13corg gradients document the existence of a narrow and relatively shallow oxygen minimum zone omz within the open ocean northern deepwater basin ndw and a deeper and thicker omz within the semi restricted nanpanjiang basin npjb for the pre extinction interval 13corg gradients between the shallow and intermediate watermasses of the ndb and between the shallow and deep watermasses of the npjb record contributions to the sediment of organic matter from bacteria living below the ocean surface layer these bacteria were mainly anaerobic chemoautotrophs that inhabited suboxic to anoxic waters of an omz and that produced more strongly 13c depleted organic matter than surface water eukaryotic algae thus increasing 13corg for the post extinction interval a reversed 13corg in the ndb is attributed to blooms of green sulfur bacteria or other anaerobic photoautotrophic bacteria that were resident in a deep chlorophyll maximum layer and that had smaller carbon isotopic fractionation than surface water algae although quantitatively important in intermediate to deep water areas during the early triassic such bacteria were absent in coeval shallow water sections reflecting water depth controls on microbial community composition a concurrent flatting of the 13corg gradient in the npjb was caused by a return of oxic conditions and or a decline of primary productivity in the surface ocean

middle upper permian carbon isotope stratigraphy at chaotian south china pre extinction multiple upwelling of oxygen depleted water onto continental shelf abstract in order to examine the causal relationships between the carbon cycle in a shallow euphotic zone and the environmental changes in a relatively deep disphotic zone at the end guadalupian middle permian isotopic compositions of carbonate carbon 13ccarb of the guadalupian lopingian upper permian rocks were analyzed in the chaotian section in northern sichuan south china by analyzing exceptionally fresh drill core samples a continuous chemostratigraphic record was newly obtained the ca 65 m thick analyzed carbonate rocks at chaotian comprise three stratigraphic units i e the limestone unit of the guadalupian maokou formation the mudstone unit of the maokou formation and the lower part of the wuchiapingian lower lopingian wujiaping formation in ascending order the limestone unit of the maokou formation is characterized by almost constant 13ccarb values of ca 4 followed by an abrupt drop for 7 to 3 in the topmost part of the unit in the mudstone unit of the maokou formation the 13ccarb values are rather constant around 2 although distinct three isotopic negative excursions for 3 from ca 2 to 1 occurred in the upper part of the unit in the lower part of the wujiaping formation the 13ccarb values monotonously increase for 5 from ca 0 to 5 the present data newly demonstrated four isotopic negative excursions in the topmost part of the maokou formation in the capitanian late guadalupian at chaotian it is noteworthy that these negative excursions are in accordance with the emergence of an oxygen depleted condition on the relatively deep disphotic slope basin on the basis of litho and bio facies characteristics they suggest multiple upwelling of oxygen depleted waters with dissolved inorganic carbon of relatively low carbon isotope values along the continental margin from the deeper disphotic slope basin to the shallower euphotic shelf slightly before the end guadalupian extinction although the negative excursions at chaotian are apparently correlated with the previously proposed large negative excursion in the middle capitanian in south china the age difference according to the biostratigraphic constraints clearly exclude this interpretation the isotopic negative excursions at chaotian are unique and no similar isotopic signal in the same period has been reported elsewhere the multiple upwelling of oxygen depleted waters onto the euphotic shelf may have represented local phenomena that occurred solely around northwestern south china

basaltic volcanism and mass extinction at the permo triassic boundary environmental impact and modeling of the global carbon cycle the siberian traps represent one of the most voluminous continental flood basalt provinces on earth the mass extinction at the end of the permian was the most severe in the history of life in the present paper these two major concurrent events that occurred are analysed and a geochemical model coupled with an energy balance model is used to calculate their environmental impact on atmospheric co2 oceanic 13c and marine anoxia the latitudinal temperature gradient is reduced relative to today resulting in warmer temperatures at high latitudes the warmer climate and the presence of fresh basaltic provinces increase the weatherability of the continental surfaces resulting in an enhanced consumption of atmospheric co2 through weathering first the eruption of the siberian traps is accompanied by a massive volume of 13c depleted co2 degassed from the mantle and added to the ocean through silicate weathering thus lowering marine 13c second the rapid collapse in productivity induces a strong decrease in the global organic carbon burial this too tends to increase the proportion of light carbon in the ocean these two effects can explain the low 13c values across the pt boundary and methane release need not be invoked to explain the 13c fluctuations it is proposed that the phosphorus cycle which drives primary production in the model plays an important role on the recovery of productivity and the 13c variations

coupled carbon isotopic and sedimentological records from the permian system of eastern australia reveal the response of atmospheric carbon dioxide to glacial growth and decay during the late palaeozoic ice age abstract proxy geochemical records from high latitude ice proximal deposits have the potential to provide key insights into past icehouse climates but such records are rare the permian system of eastern australia contains a rich record of environmental and climatic changes that occurred in areas proximal to glaciation during the acme and waning stages of the late palaeozoic ice age within this succession a wealth of fine grained organic matter rich facies provides an opportunity to construct a bulk 13corg record that records changes in atmospheric co2 through the permian fluctuations in 13corg track changes in climate determined independently on the basis of sedimentological criteria in the same strata these patterns are also broadly consistent with multiple proxy records derived from palaeoequatorial sites the results of this geochemical investigation 1 support recent studies using the high latitude ice proximal sedimentologic and stratigraphic record and palaeoequatorial geochemical proxies that document highly variable climatic conditions within the overall permian icehouse to greenhouse transition and 2 confirms that the sedimentary record of glaciation from eastern australia reflects global changes in atmospheric co2 on several m y order timescales

a magnetic polarity time scale for the early cretaceous and late jurassic abstract the ages of polarity chrons in previous m sequence magnetic polarity time scales were interpolated using basal sediment ages in suitably drilled dsdp holes this method is subject to several sources of error including often large paleontological age ranges magnetostratigraphic results have now tied the early cretaceous and late jurassic paleontological stage boundaries to the m sequence of magnetic polarity the numeric ages of most of these boundaries are inadequately known and some have been determined largely by intuition an examination of relevant data suggests that 114 ma 136 ma and 146 ma are optimum estimates for the ages of the aptian barremian cretaceous jurassic and kimmeridgian oxfordian stage boundaries respectively each of these boundaries has a good correlation to the m sequence of magnetic reversals the magnetostratigraphic tie level ages are linearly related to the spreading distance and have been used to calculate a new magnetic polarity time scale for the early cretaceous and late jurassic all stage boundaries in this time interval were correlated by magnetic stratigraphy to the proposed new time scale which was then used to estimate their numeric ages these are with the approximate relative errors of placement within the m sequence aptian barremian 114 ma 0 5ma barremian hauterivian 121 ma 2 0 1 5ma hauterivian valanginian 126 ma 0 5 3 0ma valanginian berriasian 131 ma 0 5 2 5ma berriasian tithonian 136 ma 1 0ma tithonian kimmeridgian 143 ma 0 5ma kimmeridgian oxfordian 146 ma 0 2ma the absolute errors of these interpolated stage boundary ages depend on the accuracy of the tie level ages

geodynamics of the western part of the mongolia okhotsk collisional belt trans baikal region russia and mongolia abstract after the western edge of the mongolian microcontinent joined the siberian continent in the region of central mongolia in the earliest permian these two continental blocks remained turned at an angle of about 120 with respect to each other and separated on greater extent of their present day boundary by an enormous gulf of the paleopacific called the mongolia okhotsk ocean closure of this ocean at the early middle jurassic boundary led to the complete collision of siberia and mongolia which by then had already become part of the mongolia north china continent this main collisional episode which lasted through the middle and late jurassic involved thrusting folding and magmatism and produced the mongolia okhotsk belt the onon island arc which was located in the mongolia okhotsk ocean was squeezed between the two major continents inasmuch as the third element the island arc was involved in the collision it is reasonable to distinguish two branches of the mongolia okhotsk suture these branches control the spatial distribution of gold mineralization in the trans baikal region on the southeastern periphery of siberia the crust thickened considerably after the collision and a plateau like uplift formed in the early cretaceous when compression ceased the collisional uplift collapsed and the thrusts were transformed into low angle normal faults the motions on which were responsible for the formation of rift basins and exhumation of metamorphic core complexes

an abrupt extinction in the middle permian capitanian of the boreal realm spitsbergen and its link to anoxia and acidification the controversial capitanian middle permian 262 ma extinction event is only known from equatorial latitudes and consequently its global extent is poorly resolved we demonstrate that there were two severe extinctions amongst brachiopods in northern boreal latitudes spitsbergen in the middle to late permian separated by a recovery phase new age dating of the spitsbergen strata belonging to the kapp starostin formation using strontium isotopes and d 13 c trends and comparison with better dated sections in greenland suggests that the first crisis occurred in the capitanian this age assignment indicates that this middle permian extinction is manifested at higher latitudes redox proxies pyrite framboids and trace metals show that the boreal crisis coincided with an intensification of oxygen depletion implicating anoxia in the extinction scenario the widespread and near total loss of carbonates across the boreal realm also suggests a role for acidification in the crisis the recovery interval saw the appearance of new brachiopod and bivalve taxa alongside survivors and an increased mollusk dominance resulting in an assemblage reminiscent of younger mesozoic assemblages the subsequent end permian mass extinction terminated this late permian radiation

a positive c isotope excursion induced by sea level fall in the middle capitanian of south china abstract a new carbon isotope excursion was recovered from the capitanian marine carbonates at the rencunping rcp section of south china significantly a pronounced excursion with elevated 13ccarb values over 5 was coeval with the conodont jinogondolella prexuanhanensis zone and resembles the kamura event recorded in tethys the excursions in 13ccarb constrained by conodont biostratigraphy however present inconsistent carbon cycle behaviors especially between the separated basins in south china and evidently reflect regional litho facies controls in addition a transitional environment in association with a fall in sea level was recovered from deposits of anoxic cherty carbonates subsequent to shallow water carbonates around the positive excursion in 13ccarb accordingly instead of this being a signal of global scale climatic cooling we suggest that the positive excursion in 13ccarb can be attributed to eutrophication effects regionally along a continental shelf in this scenario the increasing dissolved o2 level in the mixing zone that induced by the initial sea level fall will efficiently impede denitrification and increase the bio available n in n p ratio to satisfy the demands of primary producers in surface waters subsequently deposits of shallow water carbonates comprising calcareous algae and massively bedded lime muds accumulated widely around south china these deposits appear to represent an unusual environment and ecosystem fertilized perhaps by the weathering products from the earliest stages of volcanism prior to the main emeishan flood basalt eruptions at the guadalupian lopingian boundary glb

carboniferous permian carbon isotope stratigraphy of successions from china yangtze platform usa kansas and russia moscow basin and urals abstract the pennsylvanian and early permian were times of extreme sea level changes of 100 to perhaps up to 200 m for example glacio eustatic sea level changes are well documented from the us midcontinent moscow basin and yangtze platform where more than 100 stacked subtidal to supratidal sequences have been described in contrast carbonates developed in the ural mountains and south guizhou of the yangtze platform were deposited in ramp and slope settings 13c values of whole rock samples from the us midcontinent and moscow basin were intensively affected by diagenesis only well preserved brachiopod shells maintained their original carbon isotope ratios in contrast limestones deposited in the deeper water slope environments were not affected by meteoric diagenesis and are interpreted to have mainly retained their carbon isotope ratios mean 13c values of slope carbonates of the yangtze platform increase from about 3 during the visean and serpukhovian to 5 at the carboniferous permian boundary and decrease to values around 2 in the early kungurian this positive 13c excursion coincides with low 13c values in the yangtze platform successions which were reset by meteoric diagenesis the highest 13c values recorded in the slope succession coincide with the inferred maximum glaciation that caused pronounced sea level lowstands short lived but significant negative 13c excursions in the chinese slope succession are interpreted to reflect changes in ocean circulation due to sea level rises which caused enhanced production and or preservation of organic matter which influenced the subsequent early diagenetic cementation

magnetostratigraphic record of the early evolution of the southwestern tian shan foreland basin ulugqat area interactions with pamir indentation and india asia collision the tian shan range is an inherited intracontinental structure reactivated by the far field effects of the india asia collision a growing body of thermochronology and magnetostratigraphy datasets shows that the range grew through several tectonic pulses since 25 ma however the early cenozoic history remains poorly constrained the time lag between the eocene india asia collision and the miocene onset of tian shan exhumation is particularly enigmatic this peculiar period is potentially recorded along the southwestern tian shan piedmont there late eocene marine deposits of the proto paratethys epicontinental sea transition to continental foreland basin sediments of unknown age were recently dated we provide magnetostratigraphic dating of these continental sediments from the 1700 m thick mine section integrated with previously published detrital apatite fission track and u pb zircon ages the most likely correlation to the geomagnetic polarity time scale indicates an age span from 20 8 to 13 3 ma with a marked increase in accumulation rates at 19 18 ma this implies that the entire oligocene period is missing between the last marine and first continental sediments as suggested by previous southwestern tian shan results this differs from the southwestern tarim basin where eocene marine deposits are continuously overlain by late eocene oligocene continental sediments this supports a simple evolution model of the western tarim basin with eocene oligocene foreland basin activation to the south related to northward thrusting of the kunlun shan followed by early miocene activation of northern foreland basin related to overthrusting of the south tian shan our data also support southward propagation of the tian shan piedmont from 20 to 18 ma that may relate to motion on the talas fergana fault the coeval activation of a major right lateral strike slip system allowing indentation of the pamir salient into the tarim basin suggests far field deformation from the india asia collision zone affected the tian shan and the talas fergana fault by early miocene

astronomical forcing of a middle permian chert sequence in chaohu south china abstract astronomical forcing has been shown to be a fundamental driver of climate change through geological time pelagic bedded cherts deposited in mesozoic ocean basins with chert mudstone cycles have been shown to contain the imprint of milankovitch astronomical climate forcing in the chaohu region south china we studied a middle permian radiolarian chert sequence gufeng formation with chert mudstone couplets reminiscent of the mesozoic cherts but deposited on a continental shelf spectral analysis of lithologic bed thickness data from two sections of this chert sequence reveals that 13 cm to 20 cm chert mudstone cycles in the stratigraphic domain match theoretical 32 kyr middle permian obliquity cycling together with a hierarchy of other cycles with 12 cm 9 cm 7 cm 6 6 cm and 5 4 cm wavelengths tuning the 13 cm to 20 cm stratigraphic cycles to earth s obliquity cycle periodicity indicates that the cm scale cycles are precession scale variations with a strong 400 kyr amplitude modulation tuning to theoretical precession terms provides further support for the astronomical forcing of the chert sequence we propose that monsoon controlled upwelling contributed to the development of the chert mudstone cycles a seasonal monsoon controlled by astronomical forcing i e insolation influenced the intensity of upwelling stronger upwelling increased radiolarian productivity in the surface ocean increasing silica deposition glacio eustatic oscillations from ice sheet dynamics in southern gondwana modulated terrigenous mud flux to the basin the two processes jointly contributed to the astronomical rhythms of these tropical chert mudstone sequences which are characterized by comparably strong obliquity and precession responses subsequent diagenesis distorted the chert and mudstone layering but not enough to destroy the original stratigraphic patterns the resulting astronomical time scale ats assumes a roadian wordian boundary age of 268 8 ma for the onset of the first chert layer at the base of the sequence and ends at 264 1 ma for a total duration of 4 7 myr

volcanism mass extinction and carbon isotope fluctuations in the middle permian of china the 260 million year old emeishan volcanic province of southwest china overlies and is interbedded with middle permian carbonates that contain a record of the guadalupian mass extinction sections in the region thus provide an opportunity to directly monitor the relative timing of extinction and volcanism within the same locations these show that the onset of volcanism was marked by both large phreatomagmatic eruptions and extinctions amongst fusulinacean foraminifers and calcareous algae the temporal coincidence of these two phenomena supports the idea of a cause and effect relationship the crisis predates the onset of a major negative carbon isotope excursion that points to subsequent severe disturbance of the ocean atmosphere carbon cycle

late cretaceous palaeogene topography of the chinese tian shan new insights from geomorphology and sedimentology abstract the cenozoic growth of the intra continental tian shan range initiated during the late eocene oligocene and led to a tectonic reactivation of the complex palaeozoic and mesozoic lithospheric structure due to the very low erosion rates linked to the semi arid climate that characterised the tian shan region during most of the cenozoic the topography of the range is not at equilibrium with deformation fragments of pre orogenic low relief surfaces are preserved among the late cenozoic alpine type topography using field observations and satellite image mapping of those fragments as well as sedimentology and biostratigraphic analysis we show that the pre oligocene topography of the tian shan region was indeed complex combining hundreds of metres to one and a half kilometre high reliefs with a multi phased mesozoic planation surface incised by late mesozoic paleo valleys the occurrence of several metres thick late cretaceous palaeogene calcareous paleosols in the basins surrounding the range further implies a semi arid climate very low subsidence rates and no uplift at that time late cretaceous and early miocene fossil records in the northern tian shan suggest a possible connection even if episodic between the drainage system of the south junggar foreland basin and the proto paratethys sea to the west a renewed late eocene early oligocene sedimentation probably marks the onset of the tian shan uplift we argue that in addition to the growth of the pamir and western kunlun ranges this incipient uplift was one of the driving mechanisms for the final retreat of the proto paratethys sea from the tarim basin this regression apparently did not change the climate in the studied area because semi arid conditions seem to prevail at least since the late cretaceous finally the tian shan uplift remained very limited up to the miocene as revealed by the occurrence of burdigalian lake deposits preserved in the paleo valleys inside the present day range in contrast post early miocene deformation of the northern tian shan has produced 4000 to 5000 m of differential vertical movement between the uplifted range and the subsiding proximal foreland basin

the source and fate of massive carbon input during the latest paleocene thermal maximum lithologic faunal seismic and isotopic evidence from the blake nose subtropical western north atlantic links a massive release of biogenic methane 55 5 million years ago to a warming of deep ocean and high latitude surface waters a large perturbation in the combined ocean atmosphere carbon cycle the largest of the past 90 million years a mass extinction event in benthic faunas and a radiation of mammalian orders the deposition of a mud clast interval and seismic evidence for slope disturbance are associated with intermediate water warming massive carbon input to the global exogenic carbon cycle pelagic carbonate dissolution a decrease in dissolved oxygen and a benthic foraminiferal extinction event these events provide evidence to confirm the gas hydrate dissociation hypothesis and identify the blake nose as a site of methane release

neogene uplift of the tian shan mountains observed in the magnetic record of the jingou river section northwest china the tian shan mountains constitute central asia s longest and highest mountain range understanding their cenozoic uplift history thus bears on mountain building processes in general and on how deformation has occurred under the influence of the india asia collision in particular in order to help decipher the uplift history of the tian shan we collected 970 samples for magnetostratigraphic analysis along a 4571 m thick section at the jingou river xinjiang province china stepwise alternating field and thermal demagnetization isolate a linear magnetization component that is interpreted as primary from this component a magnetostratigraphic column composed of 67 polarity chrons are correlated with the reference geomagnetic polarity timescale between 1 ma and 23 6 ma with some uncertainty below 21 ma this correlation places precise temporal control on the neogene stratigraphy of the southern junggar basin and provides evidence for two significant stepwise increases in sediment accumulation rate at 16 15 ma and 11 10 ma rock magnetic parameters also undergo important changes at 16 15 ma and 11 10 ma that correlate with changes in sedimentary depositional environments together with previous work we conclude that growth history of the modern tian shan mountains includes two pulses of uplift and erosion at 16 15 ma and 11 10 ma middle to upper tertiary rocks around the tian shan record very young 5 ma counterclockwise paleomagnetic rotations on the order of 15 to 20 which are interpreted as because of strain partitioning with a component of sinistral shear that localized rotations in the piedmont

progress problems and prospects an overview of the guadalupian series of south china and north america abstract the guadalupian epoch is marked by the formation of the pangean supercontinent global sea level change rifting and drifting of the cimmerian continents formation of large igneous provinces and dramatic biotic changes a high resolution biostratigraphic chemostratigraphic and high precision geochronologic framework of this critical transition is fundamental to understanding these events extensive studies of the latest cisuralian and guadalupian series in both south china and north america reveal the same conodont lineages but the conodont interval zones based on jinogondolella within the guadalupian series are slightly diachronous high precision u pb geochronological studies ca id tims method calibrate the base of the guadalupian series base roadian at 273 01 0 14 ma a previously reported age from an ash bed overlying the emeishan flood basalts 259 51 0 21 ma is adopted for the guadalupian lopingian boundary glb based on recently published geochronology and bayesian age modeling from the guadalupian series the base of the capitanian is constrained at 264 28 0 16 ma and the base of the wordian is interpolated to be 266 9 0 4 ma the illawarra reversal is of early middle wordian age both north america and south china possess a distinct negative 13ccarb excursion of 3 5 at the latest kungurian and early roadian lk er cie which coincides with the early stages of a significant 3rd order sea level rise the large end guadalupian 13ccarb negative excursion may have been affected by post depositional diagenesis or a warming event associated with the emeishan volcanism the 87sr 86sr ratios in both regions declined from the latest kungurian to the late capitanian but have different ratios and reveal several fluctuations in the middle guadalupian measured 18oapatite values suggest that the delaware basin was 3 4 c cooler than the eastern yangtze block analysis of a new high resolution database of marine taxa indicates only a minor pre lopingian diversity drop from 261 04 ma to 259 98 ma which coincides with the peak emeishan volcanism the widely perceived end guadalupian mass extinction in north america is evidently masked by and possibly an artefact of a stratigraphic truncation effect due to rapid lithofacies changes from limestone to laminated evaporites with the closure of the west texas basins

the paleozoic to mesozoic carbon cycle revisited the carbon isotopic composition of terrestrial organic matter 1 two thousand one hundred forty eight carbon isotope values for terrestrial organic matter plant fossils coal bulk terrestrial organic matter provide a proxy record for temporal changes in the global carbon cycle 13ctom 13ccarb and 13cco2 allow a full evaluation of carbon transfer in the atmosphere ocean system as well as between the marine and the terrestrial realm the temporal evolution of 13ctom parallels respective data sets from marine carbonate carbon thus reflecting the linkage between both reservoirs via atmospheric carbon dioxide on the basis of a comparison between measured and predicted isotope records for 13ctom changes in the carbon isotopic fractionation associated with plant metabolism are discernible this contradicts the notion of an invariable carbon isotopic fractionation associated with c3 plant metabolism in light of results from current plant growth experiments these changes are viewed as dependent on the atmospheric o2 co2 hence 13ctom might serve as a proxy signal for atmospheric composition

interpreting carbon isotope excursions carbonates and organic matter abstract variations in the carbon isotopic compositions of marine carbonate and organic carbon provide a record of changes in the fraction of organic carbon buried through time and may provide clues to changes in rates of weathering and sources of organic carbon paired carbonate and organic carbon isotope determinations provide a possibility of interpreting not only changes in the global carbon cycle through time but changes in atmospheric pco2 as well interpretations of these types of data are typically rather qualitative a quantitative basis is required to develop a better understanding of changes in the carbon cycle for this purpose we employ a simple model of the global carbon cycle which is subjected to a number of different perturbations each lasting 500 ky i e much longer than the residence times of carbon and phosphorus in the ocean atmosphere system in addition to standard considerations of carbon mass and isotopic fluxes to the ocean atmosphere system from weathering and volcanism and fluxes of organic carbon and carbonate carbon to sediments the model incorporates sensitivity of the photosynthetic carbon isotope effect to changes in pco2 the inclusion of this parameter leads to unexpected carbon isotope responses to forcing that causes increased rates of organic carbon burial a series of simple to more complex simulations illustrates the significant effects of varying differences between the carbon isotopic composition of sedimented carbonate and organic carbon b with constant b a 50 increase in organic carbon burial produces a parallel increase in carbonate and organic carbon isotopic compositions however the same simulation with b responsive to pco2 changes produces an initial parallel 13 c increase but this is followed by an even greater 13 c enrichment in organic carbon because pco2 falls in response to increased organic carbon burial the counterintuitive overall result of the enhanced organic carbon burial event is that the carbonate carbon isotopic composition actually decreases because of the more substantial increase in 13 c org in addition we illustrate the effects on carbon isotopic compositions of the oceanic inorganic carbon reservoir and buried organic matter of a 50 increase in volcanic co2 outgassing a 50 increase in weathering rate with coupled phosphate and riverine carbon flux responses a 50 decrease in shale associated organic carbon weathering a 50 decrease in silicate weathering rate and the possible effects of the rise in abundance of c4 plants in the late miocene to recent we compare the model simulated carbon isotopic responses for some of these experiments to paired carbonate and organic carbon records to illustrate how these records might be interpreted in light of the model response

use of a regional relict landscape to measure vertical deformation of the eastern tibetan plateau 1 field work and topography analysis show that remnant local areas of a low relief landscape or erosion surfaces are geographically continuous across the southeastern tibetan plateau margin we correlate these remnant surfaces as a paleolandscape that formed at low elevation remnants of this paleolandscape are preserved because incision of the fluvial system has been largely limited to major rivers and principal tributaries and has not yet progressed throughout the entire fluvial network the incomplete adjustment of the fluvial system signals initiation of rapid bedrock incision into a developing plateau margin and erosional denudation is concentrated in the major river channels this interpretation contradicts earlier notions that low gradient regional topography is the product of regional elevation reduction by intense landscape dissection due to the presence of several large southeast flowing rivers the modern altitude of the reconstructed paleolandscape or relict landscape constrains the vertical displacement of the plateau surface in response to crustal thickening and subsequent erosion during the lateral growth of the tibetan plateau regional preservation of the relict landscape is consistent with minor surface disruption by late cenozoic thrust faults and folds and supports a model of distributed lower crustal thickening because significant erosion is limited to narrow river gorges an increase in the plateau elevation due to isostatic rebound is minor therefore we propose that the modern elevation of the relict landscape reflects isostatically compensated thickening of the lower crust

calibrating the guadalupian series middle permian of south china abstract the guadalupian epoch represents one of the most critical intervals during the earth history which is characterized by a series of global geological and biological events however it is poorly constrained by radioisotopic ages in comparison with the high precision dates from the lopingian and lowest triassic in south china and the cisuralian in southern urals russia in this study we report combined ca id tims and sims u pb zircon geochronology for three ash beds from the base and lower part of the kuhfeng formation in the chaohu area southeastern china zircons from ash beds a c and d were initially analyzed by sims and yielded weighted mean 206pb 238u dates of 269 0 1 4 ma mswd 1 03 n 31 266 3 2 2 ma mswd 2 2 n 29 and 262 2 1 7 ma mswd 1 0 n 20 in ascending order however high precion u pb geochronology of the same ash beds by the ca id tims method point to important inaccuracies in the sims results due to pb loss in zircons ash beds a and c yielded two tims weighted mean 206pb 238u dates of 272 95 0 11 ma mswd 1 9 n 7 and 271 038 0 097 ma mswd 2 2 n 8 respectively the depositional age of 272 95 0 11 ma for ash bed a is postulated as the traditional cisuralian guadalupian boundary cgb age in south china our new geochronology suggests that the guadalupian series in south china had a total duration of 13 85 0 52 myr given a guadalupian lopingian boundary glb age of 259 1 0 5 ma the new age calibration of the base of the guadalupian series is ca 0 65 0 51 myr older than and improves upon the previous estimates for the cgb age and the duration of the guadalupian epoch based on the 2016 international chronostratigraphic chart icc and the 2012 geologic time scale gts