size variation of conodonts during the smithian spathian early triassic global warming event the early triassic smithian spathian boundary ssb crisis coincided with an episode of extreme warmth a high resolution stratigraphic framework comprising six conodont zones is provided in the jiarong section nanpanjiang basin in south china detailed size measurements of 441 conodont elements of the closely related genera neospathodus triassospathodus and novispathodus show for the first time that this clade suffered a temporary but significant size reduction during the ssb crisis the size reduction of conodonts was probably caused by an episode of global warming

the triassic isotope record a variety of stable isotope measurements have been found useful in studying processes of environmental change measurements of d 13 c d 18 o d 34 s and 87 sr 86 sr all can provide infor mation about the conditions of the water column in which sediment deposition occurred but the most widely applied of these is d 13 c the carbon isotope record for the triassic system is a complex one a pronounced negative excursion begins below the base of the triassic system and continues into the basal triassic the succeeding 4 to 6 ma lower triassic interval is marked by isotopic instability with positive and negative excursions continuing through the basal middle triassic in contrast to the lower triassic most of the middle and upper triassic display relative isotopic stability with rising values of d 13 c likely reflecting environmental recov ery and increasing storage of organic carbon in terrestrial environments the uppermost triassic is marked by a pronounced negative excursion near the system boundary that has been linked to significant biotic turnover the causes of the various excursions remain under investigation particularly those at the system boundaries with outgassing during volcanic activity changes in productivity ocean anoxia and seafloor methane releases all suggested as mechanisms both for perturbing the global carbon cycle and for forcing biotic extinction

transient global cooling at the onset of early aptian oceanic anoxic event oae 1a the onset of the early aptian oceanic anoxic event oae 1a ca 120 ma coincided with a major perturbation of the carbon cycle which is reflected in the sedimentary carbon isotope record triggering mechanisms duration and climatic repercussions of this episode of accelerated organic matter burial remain poorly constrained here we present millennial scale bulk rock carbon and oxygen isotope data from a marly subtropical intrashelf basin la bedoule southeast france with unusually high sedimentation rates which track the onset of oae1a in unprecedented resolution our record reveals that the negative low amplitude delta 13 c excursion preceding oae1a lasted 100 k y implying that enhanced volcanic co 2 emission and or pulsed methane dissociation over a prolonged time span were instrumental in triggering oae1a the main positive carbon isotope shift at the onset of oae1a previously regarded as continuous occurred stepwise over an extended period of 300 k y transient climate cooling during the initial delta 13 c increase probably reflects ephemeral high latitude glaciation triggered by changes in radiative forcing and drawdown of atmospheric co 2

evolution and facies architecture of paleogene surtseyan volcanoes on chatham islands new zealand southwest pacific ocean abstract this paper reports for the first time phreatomagmatic deposits and preserved surtseyan tuff cones in the chatham islands new zealand fieldwork has located the relicts of at least six closely spaced paleogene surtseyan cones and associated volcaniclastic sediments within the red bluff tuff formation the complete stratigraphic section of the cones consists of two parts 1 the lower part represents volcanic aggradational processes that constructed tuff cones in a short period of time and is composed of a bedded interval of explosively fragmented vesicular glassy basaltic pyroclasts ash and lapilli sizes as well as feeder dykes pillow lavas and pillow sills and 2 the upper part represents the rapid denudation of these cones by shallow marine currents or gravity flows reflecting the instability of the tephra pile forming the cones and a much later marine faunal colonization stage e g corals brachiopods molluscs etc erosion could have occurred almost immediately after or even during the emplacement of the volcanic pile similar to what occurred at surtla vent a satellite submerged cone of the basaltic island volcano surtsey iceland the waiareka deborah volcanics bridge point aorere point and lookout bluff surtseyan cones otago new zealand and marion and prince edward islands southwest indian ocean amongst others by contrast the complete faunal colonization and stabilization of a diverse marine community could have taken hundreds or perhaps even thousands of years to reach their acme following the volcanic pulses the structural textural and compositional characteristics of the red bluff tuff formation support a phreatomagmatic mode of fragmentation similar to that at surtsey volcano iceland the red bluff tuff sequence represents one of the most complete marine tuff cones described in the geologic record

end permian mass extinction in the oceans an ancient analog for the twenty first century the greatest loss of biodiversity in the history of animal life occurred at the end of the permian period 252 million years ago this biotic catastrophe coincided with an interval of widespread ocean anoxia and the eruption of one of earth s largest continental flood basalt provinces the siberian traps volatile release from basaltic magma and sedimentary strata during emplacement of the siberian traps can account for most end permian paleontological and geochemical observations climate change and perhaps destruction of the ozone layer can explain extinctions on land whereas changes in ocean oxygen levels co2 ph and temperature can account for extinction selectivity across marine animals these emerging insights from geology geochemistry and paleobiology suggest that the end permian extinction may serve as an important ancient analog for twenty first century oceans

record of the end permian extinction and triassic biotic recovery in the chongzuo pingguo platform southern nanpanjiang basin guangxi south china abstract the chongzuo pingguo platform is a vast isolated platform 180 km across in the southern part of the nanpanjiang basin the end permian extinction is recorded in conformable sections in the northern part of the platform pingguo area upper permian skeletal packstone contains diverse open marine fossils including nankinella and sphaerulina it is overlain by a 4 6 m thick horizon of calcimicrobial framestone constructed by globular calcified microbial framework similar to renalcis the ptb event horizon is interpreted to occur at the top of the packstone coincident with the abrupt change to calcimicrobial framestone lacking permian macrofossils the transition from hindeodus latidentatus to h parvus occurs 1 m above the base of the calcimicrobial framestone marking the conformable biostratigraphic boundary during the early triassic the platform developed as a low relief bank rimmed with oolite shoals but was bordered by a high relief fault controlled escarpment along its southern margin platform interior facies of the majiaoling and beisi formations are 900 m thick and consist of thin bedded lime mudstone oolite and dolostone with restricted marine biota in four shallowing upward packages that define depositional sequences in the chongzuo area the platform was terminated at the end of the early triassic by burial with up to 1600 m of felsic pyroclastic volcanics and lava flows transgression and shallow marine carbonate sedimentation resumed early in the middle triassic followed by drowning in the bithynian as indicated by a shift to deep marine carbonate and clastic deposition in the pingguo area volcanic deposits are much thinner and only briefly interrupted carbonate accumulation here the platform interior drowned during a major back step early in the middle triassic anisian bithynian smaller pinnacle platforms of the guohua fm up to 1700 m thick continued to accumulate above the early triassic platform margin and were eventually drowned by the late pelsonian in the anisian the pinnacle platforms shifted to sharply defined reef rimmed margins with tubiphytes reefs the shift coincides with accelerated metazoan biotic recovery in the anisian however the reefs lack metazoan frameworks and are composed almost entirely of tubiphytes reinforced by large volumes of marine cement these observations indicate that controls beyond the recovery of framework building metazoans governed the re establishment platform margin reefs in the middle triassic

evidence for recurrent changes in lower triassic oceanic circulation of the tethys the δ13c record from marine sections in iran abstract stable carbon isotope curves derived from lower triassic carbonate rocks from three iranian sections are established to investigate changes in the carbon cycle during the early triassic in this area the sections are located in the south center abadeh north amol and northwest zal of iran all three curves show a similar pattern starting out with high 13 c values in the uppermost permian decreasing across the permian triassic boundary an increase toward more positive values during the griesbachian that slowly increase further up during the dienerian followed by a positive excursion to values as high as 8 near the dienerian smithian boundary during the smithian values return to below 0 whereas second positive excursion to values higher than 3 is recorded at the smithian spathian boundary again followed by a drop in 13 c into the spathian and a final excursion to positive values at the spathian anisian boundary the results from these iranian sections are consistent with previous studies from italy and china thus strongly suggesting that the recorded 13 c variability represents at least tethys wide geochemical signals moreover the new curves reveal evidence of high amplitude frequent oscillations pointing toward rapid and profound changes in the global carbon cycle during the lower triassic stratification of the ocean interrupted by episodic overturning transporting deep water to the ocean surface is a viable mechanism to account for the recorded isotope variations provided that the 13 c curve is representative of the global lower triassic ocean it has high potential for accurately dating sedimentary successions via chemostratigraphy

litho bio and chemostratigraphy across the cenomanian turonian boundary oae 2 in the vocontian basin of southeastern france the oceanic anoxic event 2 oae 2 was one of at least two large oceanic anoxic events during the cretaceous period and it is characterized in the stratigraphic record by double positive peaks in the 13c curves of carbonate and organic carbon since the positive 13c shift is believed to have resulted from massive burial of isotopically depleted organic carbon generated globally in anoxic oceanic environments the positive 13c shift tend to coincide with widespread deposition of organic rich sediments in the case of oae 2 however the organic rich horizons do not accord exactly with the two intervals with positive 13c shifts at many sites such as pueblo tarfaya eastbourne and gubbio e g tsikos h jenkyns h c walsworth bell b petrizzo m r forster a kolonic s erba e premoli silva i baas m wagner t sinninghe dameste j s 2004 carbon isotope stratigraphy recorded by the cenomanian turonian oceanic anoxic event correlation and implications based on three key localities journal of the geological society london 161 711 719 the thomel level of the cenomanian turonian c t boundary in the vocontian basin southeastern france accumulated during the oae 2 and it is marked by frequent intercalations of black shale and organic rich marl detailed litho bio and chemostratigraphy analyses across the c t boundary in the vocontian basin indicate that the 13ccarbonate profile fluctuation across the thomel level corresponds well with changes in lithofacies total organic carbon toc and calcium carbonate caco3 abundance positive 13c excursions within the oae 2 correlate with basal and middle parts of the thomel level that are characterized by high toc low caco3 and predominantly contain organic rich sediments such as black shale and dark gray marl on the other hand negative 13c intervals within the oae 2 correspond with lower and upper parts of the thomel level that consist of marly limestone and limy marl with low toc and high caco3 values since the fluctuation of redox conditions during thomel level deposition in the vocontian basin coincides well with the global carbon burial rate indicated by its 13c profile the thomel level could be an ideal candidate for the reference section of the oae 2

carbon isotopic excursions and detailed ammonoid and conodont biostratigraphies around smithian spathian boundary in the bac thuy formation vietnam abstract the smithian spathian boundary is indicated by the first occurrence of the ammonoid tirolites cf cassianus in the olenekian bac thuy formation northeastern vietnam the boundary is intercalated within organic rich dark gray mudstone that accumulated under anoxic to dysoxic conditions in the an chau and nanpanjiang basins on the south china block in lang son area three conodont zones novispathodus ex gr waageni novispathodus ex gr pingdingshanensis and icriospathodus collinsoni are recognized in the formation the smithian spathian boundary is intercalated within n ex gr pingdingshanensis conodont zone the positive excursion in 13c with values increasing from around 2 3 to 5 7 was recorded in the uppermost smithian xenoceltites variocostatus ammonoid beds and n ex gr pingdingshanensis conodont zone the 13c values decrease across the smithian spathian boundary these 13c isotopic patterns are correlated with well known positive excursions around the smithian spathian boundary globally

conodont diversity and evolution through the latest permian and early triassic upheavals abstract a study of latest permian and early triassic multielement conodonts identifies eight steps in their evolutionary history during an interval when earth s biosphere was highly stressed these steps are 1 gradual decline of families and genera through the changhsingian up to the late griesbachian 2 conodont biofacies change and extinction of tethyan endemic species close to the permian triassic boundary ptb 3 faunal turnover with extinction and origination in the late griesbachian 4 initial radiation in gondolellids and diversification in apparatuses during the dienerian 5 explosive radiation in the early middle smithian 6 major extinction in the late smithian 7 major radiation early in the spathian 8 gradual turnover and decline in the late spathian through early anisian conodontophorids were reduced from five families at the beginning of the changhsingian to three by the ptb and to two late in the griesbachian from the changhsingian to the late griesbachian there was a single multielement apparatus represented in the gondolellidae whereas by the olenekian there were at least twelve given absolute age constraints the conodont recovery in the aftermath of the ptb was extraordinary conodont evolution during the dienerian remains obscure but was very significant in terms of changes in multielement apparatuses in spite of induan extinctions generic diversity generally increased from the ptb up to the late smithian in terms of species genera and multielement apparatuses the acme of triassic conodonts was in the middle smithian and the biggest extinction was in the late smithian after this extinction generic and apparatus diversity quickly returned to high levels marking a significant spathian recovery gradual decline characterized the late spathian and persisted into the early anisian a synthetic summary of the temporal distribution and proposed relationships amongst all known lower triassic conodonts provide an improved foundation for biostratigraphic and biochronologic studies extinction and radiation trends correlate well with sea level changes and sequence boundaries faunal turnovers correspond to lowstands in the late griesbachian late smithian and late spathian and radiations correspond to transgressions in the early griesbachian early smithian and early spathian the trends also correlate with perturbations in the carbon cycle with lower triassic 13c minima corresponding to extinction and faunal turnover and positive values generally occurring during radiations however middle triassic recovery of marine benthos follows a positive maxima and an overall decline in conodont diversity new taxa borinella chowadensis b megacuspa neogondolella griesbachensis and n mongeri are described

large perturbations of the carbon cycle during recovery from the end permian extinction high resolution carbon isotope measurements of multiple stratigraphic sections in south china demonstrate that the pronounced carbon isotopic excursion at the permian triassic boundary was not an isolated event but the first in a series of large fluctuations that continued throughout the early triassic before ending abruptly early in the middle triassic the unusual behavior of the carbon cycle coincides with the delayed recovery from end permian extinction recorded by fossils suggesting a direct relationship between earth system function and biological rediversification in the aftermath of earth s most devastating mass extinction

geochemical evidence from bio apatite for multiple oceanic anoxic events during permian triassic transition and the link with end permian extinction and recovery abstract a detailed 20 myr redox history of permian to triassic oceans changhsingian to carnian stages has been constructed using ce anomaly ce and th u ratios from conodont albid crown apatite material the results show that the well established phenomenon of intense ocean anoxia coincident with the end permian mass extinction is faithfully recorded in conodont ce and th u data extending this conodont redox record shows that end permian anoxia persisted possibly into the earliest dienerian stage and that two intense oceanic anoxic events also occurred later in the early triassic earliest smithian earliest spathian and middle spathian followed by a weaker manifestation of anoxia in the anisian stage seen in ce data marine benthic radiation following the end permian mass extinction began after the smithian earliest spathian anoxic event suggesting a suppression of evolution prior to this due to these inimical conditions the failure of the middle spathian anoxic event to retard the evolutionary rebound implies shallow shelf seas remained well ventilated at this time even if the oceans did not other attributes of the early triassic record also closely coincide with redox fluctuations phases of anoxia intensification saw the proliferation of microbial carbonates and major negative carbon isotope swings that can be attributed to chemocline shallowing causing alkalinity pulses and enrichment in light remineralised carbon and or indicate a trigger meachnaims related to increased fluxes of light c from siberian volcanic sources

lower triassic conodont sequence in chaohu anhui province china and its global correlation abstract the early triassic paleogeographical setting of the chaohu section in china was in a deep part of the yangtze platform and this has resulted in a rather complete lower triassic sequence with rich ammonoid and conodont successions three lower triassic sections west pingdingshan north pingdingshan and south majiashan have been sampled in detail for a systematic conodont study eight conodont zones are recognized in ascending order these are the zones of hindeodus typicalis neogondolella krystyni neospathodus kummeli neospathodus dieneri neospathodus waageni neospathodus pingdingshanensis neospathodus homeri and neospathodus anhuinensis these are correlated with the sequences in north america and other areas of the world the succession provides a good basis for the definition of the global stratotype of the induan olenekian boundary gssp which has been proposed at the base of the neospathodus waageni zone in west pingdingshan seven new species are introduced neospathodus chaohuensis n chii n concavus n eotriangularis n pingdingshanensis n posterolongatus n tongi a new subspecies n waageni eowaageni and three morphotypes of n dieneri

reconstruction of early triassic ocean redox conditions based on framboidal pyrite from the nanpanjiang basin south china abstract widespread oceanic anoxia has been implicated as an important factor in the ptb permian triassic boundary mass extinction and the delayed recovery of early triassic marine ecosystems an investigation of framboidal pyrite in the bianyang section nanpanjiang basin south china suggests that euxinia dysoxia peaked during the induan late smithian to earliest spathian and late spathian these anoxic episodes show a relationship albeit imperfect to major episodes of climatic warming during the early triassic that were associated with intensified oceanic stratification reduced marine productivity and organic carbon sinking fluxes as well as diminished burial fluxes of organic carbon and reduced sulfur in contrast intervals of better oxygenated marine conditions were associated with episodes of relative climatic cooling during the early to middle smithian and mid spathian the degree of ventilation of the thermocline region in particular had a profound effect on marine biotas with intervals of improved ventilation resulting in increased global diversity among ammonoids and conodonts and increased local abundance of foraminifera in the nanpanjiang basin these observations suggest that oceanic redox fluctuations played an important role in the delayed recovery of early triassic marine ecosystems and specifically that episodic expansion of oceanic oxygen minimum zones omzs resulted in repeated setbacks to the recovery process a pattern that persisted until the late spathian

smithian spathian boundary event evidence for global climatic change in the wake of the end permian biotic crisis one of the most important carbon cycle perturbations following the end permian mass extinction event straddles the smithian spathian boundary ssb olenekian early triassic this anomaly is characterized by a prominent positive carbon isotope excursion known from tethyan marine rocks its global signifi cance is established here by a new high paleolatitude record spitsbergen paleontological evidence such as boreal palynological data barents sea norway and global patterns of ammonoid distribution indicates a synchronous major change in terrestrial and marine ecosystems near the ssb the reestablishment of highly diverse plant ecosystems including the rise of woody gymnosperms and decline of the formerly dominating lycopods is interpreted as an effect of a major climate change this hypothesis is supported by modeling of ammonoid paleobiogeography the distribution patterns of which are interpreted as a proxy for sea surface temperatures sst the latest smithian thus appears to have been a time of a warm and equable climate as expressed by an almost fl at pole to equator sst gradient in contrast the steep spathian sst gradient suggests latitudinally differentiated climatic conditions we propose that this drastic climate change and the global carbon cycle perturbation were triggered by a massive end smithian co2 injection the ssb event could therefore represent one of the causes for stepwise and delayed recovery of marine and terrestrial biotas in the wake of the end permian biotic crisis

high amplitude redox changes in the late early triassic of south china and the smithian spathian extinction abstract the early triassic was a time of remarkably high temperatures large carbon cycle perturbations and episodes of widespread ocean anoxia the sediments in the nanpanjiang basin of south china provide superb opportunities to examine the sedimentary response to these extreme conditions especially during the crisis interval at the smithian spathian s s boundary we have investigated a deep water section at jiarong and a shallower water section at mingtang these contain a range of facies including black shales micritic limestone units and rudaceous carbonate event beds that include flat pebble conglomerates and breccia debrites that bear similarities to the hybrid event beds seen in clastic turbidite successions redox proxies pyrite framboids and trace metals reveal that widespread anoxia in the late smithian persisted into the novispathodus pingdingshanensis zone of the early spathian before a sharp transition to highly oxygenated griotte facies red marine strata in the icriospathodus collinsoni zone that records an oxic rebound benthic faunas are locally common but of low diversity and dominated by thin shelled bivalves and ostracodes with small foraminifers and exceptionally rare fish remains bioturbation was intense only in the early middle spathian i collinsoni conodont zone griotte facies anoxia and extremely high temperatures probably played a role in severely restricting the abundance of fish and the small sizes of marine invertebrates at this time the presence of ooids and seafloor fan cements in our study sections indicates highly saturated conditions rather than acidification at the end of the smithian

terrestrial marine teleconnections in the collapse and rebuilding of early triassic marine ecosystems abstract the latest permian mass extinction lpe just prior to the permian triassic boundary at 252 ma resulted in the disappearance of 90 of skeletonized marine taxa and the replacement of the paleozoic fauna by the modern fauna in the immediate aftermath of the extinction shallow marine ecosystems were dominated by microbial communities and diminutive disaster taxa lilliput faunas and the post crisis period in general was characterized by high abundance low diversity marine communities occupying a reduced ecological space the recovery of marine ecosystems was a protracted process lasting throughout the 5 myr long early triassic some clades failed to recover and subsequently went extinct dead clades walking while others recovered only to suffer secondary crises during the early triassic profound environmental changes accompanied these biotic developments deep oceans experienced sustained hypoxia or anoxia for at least several million years following the boundary event anoxia was also widespread in shallow marine areas especially at the time of the lpe but it was more episodic and abated more rapidly than in the deep ocean making it an unlikely factor in the delayed recovery of early triassic marine ecosystems the development of anoxia was due at least in part to a sharp temperature rise following the lpe but may have been stimulated by changes in marine nutrient inventories and productivity rates as well these conditions may have been the result of a concurrent increase in subaerial weathering rates that was sustained into the early triassic in addition to increasing nutrient fluxes to marine areas rapid weathering caused a massive influx of sediment to shallow marine systems subjecting marine biotas to siltation stress this scenario implies close teleconnections between terrestrial and marine environments during the permian triassic boundary crisis with perturbations of the terrestrial realm contributing to the marine crisis

the origin and isotopic composition of dissolved sulfide in groundwater from carbonate aquifers in florida and texas the 34s values of dissolved sulfide and the sulfur isotope fractionations between dissolved sulfide and sulfate species in floridan ground water generally correlate with dissolved sulfate concentrations which are related to flow patterns and residence time within the aquifer the dissolved sulfide derives from the slow in situ biogenic reduction of sulfate dissolved from sedimentary gypsum in the aquifer in areas where the water is oldest the dissolved sulfide has apparently attained isotopic equilibrium with the dissolved sulfate 34s 65 per mil at the temperature 28 c of the system this approach to equilibrium reflects an extremely slow reduction rate of the dissolved sulfate by bacteria this slow rate probably results from very low concentrations of organic matter in the aquifer in the reducing part of the edwards aquifer texas there is a general down gradient increase in both dissolved sulfide and sulfate concentrations but neither the 34s values of sulfide nor the sulfide sulfate isotope fractionation correlates with the ground water flow pattern the dissolved sulfide species appear to be derived primarily from biogenic reduction of sulfate ions whose source is gypsum dissolution although upgradient diffusion of h2s gas from deeper oil field brines may be important in places the sulfur isotope fractionation for sulfide sulfate about 38 per mil is similar to that observed for modern oceanic sediments and probably reflects moderate sulfate reduction in the reducing part of the aquifer owing to the higher temperature and significant amount of organic matter present contributions of isotopically heavy h2s from oil field brines are also possible

triassic ammonoid biostratigraphy an overview abstract the triassic chronostratigraphic scale was built on two centuries of research on ammonoid biostratigraphy and biochronology two triassic stage bases and all of the triassic substages are currently defined by ammonoid bioevents the study of triassic ammonoids began during the late 1700s and in 1895 edmund von mojsisovics wilhelm waagen and carl diener published an essentially complete triassic chronostratigraphic scale based on ammonoid biostratigraphy this scale introduced many of the triassic stage and substage names still used today and all terminology of stages and substages subsequently introduced has been based on ammonoid biostratigraphy early triassic ammonoids show a trend from cosmopolitanism induan to latitudinal differentiation olenekian and the four lower triassic substage griesbachian dinerian smithian and spathian boundaries are globally correlated by widespread ammonoid biotic events middle triassic ammonoids have provinciality similar to that of the olenekian and provide a basis for recognizing six middle triassic substages late triassic ammonoids provide a basis for recognizing three stages divided into five substages the main uncertainty for the future of triassic ammonoid biostratigraphy is not the decline of the ammonoids as a tool for dating and correlation of triassic strata but rather the dramatic decrease in the number of specialists due to the lack of replacement of experienced palaeontologists who started their activity in the 1950s and 1960s

early triassic conodonts of jiarong nanpanjiang basin southern guizhou province south china abstract jiarong huishui county guizhou province south china is a key locality for the study of the early triassic recovery after the end permian mass extinction the size reduction of conodonts at the smithian spathian transition was first documented in jiarong and it is also a locality that contributes to the documentation of the early triassic paleo seawater temperatures in the jiarong sections thirteen conodont zones were identified for the early triassic in ascending order they are hindeodus parvus zone hindeodus sosioensis zone clarkina krystyni zone neoclarkina discreta zone neospathodus cristagalli eurygnathodus costatus assemblage zone novispathodus waageni eowaageni zone novispathodus waageni waageni zone discretella discreta zone pachycladina parachirognathus assemblage zone novispathodus pingdingshanensis zone icriospathodus collinsoni zone triassospathodus homeri zone triassospathodus triangularis zone these conodont zones in the jiarong sections improve the global correlation of early triassic sections and also provide better regional age constraints in an area that is important for studies of recovery from the extinction based on the first appearance of nv waageni eowaageni the induan olenekian boundary is recognized at 3 6 m above the base of the jiarong iii section the dominance of blade shaped segminate conodonts was replaced by gondola shaped segminiplanate conodonts twice the first time was in the late griesbachian and the second time was in the early spathian the dominance of segminiplanate conodonts probably indicates that the deeper seawater environment became more oxygenated during the late griesbachian and early spathian for short time intervals as it is believed that the griesbachian segminiplanate conodonts favored deeper oxygenated water habitats a new genus spathogondolella gen nov and a new species spathogondolella jiarongensis sp nov have been recognized

a new high resolution δ13c record for the early triassic insights from the arabian platform a new carbon isotope record with conodont biostratigraphy is presented for the entire early triassic from the musandam peninsula united arab emirates uae this is a near continuous and exclusively shallow marine carbonate succession that allows analysis of a high resolution primary carbon cycling signature in the absence of significant depth dependent or lithologic controls the musandam carbon isotope record can be broadly correlated with global isotopic events but also resolves additional features including the presence of significant negative events during the previously identified positive excursions at both the dienerian smithian and smithian spathian boundaries a further positive event is revealed during the development of the mid spathian negative excursion a feature not previously reported in any other section these new short lived events are probably related to the occurrence of the more widely recognized early triassic excursions and may represent fluctuations in the driving mechanisms superimposed on the continued instability of the global carbon cycle in the aftermath of the end permian extinction together these features highlight additional complexities to the early triassic carbon cycle perturbations than previously documented

impact of differential tectonic subsidence on isolated carbonate platform evolution triassic of the nanpanjiang basin south china the nanpanjiang basin of south china contains four exceptionally well exposed isolated triassic carbonate platforms detailed mapping of two dimensional transects and description of stratigraphic sections allow the reconstruction of facies architecture sequence stratigraphy and evolution of the platforms biostratigraphy magnetic susceptibility profiles and volcanic ash horizons allow chronostratigraphic correlation and thus a basinwide evaluation of mechanisms controlling platform evolution a comparison of platform architecture demonstrates that southerly platforms have substantially greater thickness backstepping geometry pinnacle development and earlier drowning that resulted from greater tectonic subsidence proximal to a probable convergent margin along the southern perimeter of the basin felsic volcanics thicken southward and contributed to the termination of the southernmost platform indicating the development of a volcanic arc along the southern margin of the south china tectonic block the northernmost isolated platform had greater longevity and lesser accumulation and lacks backstepping and pinnacle phases of development basin margin intertonguing relationships or lack thereof demonstrate that earlier siliciclastic influx into the basin to the south and concurrent starved basin conditions to the north impacted the evolution of platform margin geometries comparative analysis of platform evolution shows that the timing and rates of tectonic subsidence controlled the timing of platform termination by drowning backstep geometries pinnacle development and overall platform thickness the timing of siliciclastic basin fill dictated differences in platform margin geometries such as slope angle relief above basin floor and the presence or absence of basinward platform progradation despite the dramatic differences in platform architecture eustatic sea level fluctuations imparted a basinwide sequence stratigraphic signal

devonian carboniferous transition containing a hangenberg black shale equivalent in the pho han formation on cat ba island northeastern vietnam abstract on cat ba island in northeastern vietnam the devonian to carboniferous d c transition consists mainly of ramp carbonates intercalated with black shale beds beds 1 to 176 in the pho han formation and is one of the few records of the d c transition of the eastern paleotethys the three main facies of the sequence are facies 1 alternations of whitish gray to gray limestone and marl facies 2 calcirudite bed 115b and facies 3 alternations of dark gray limestone and organic carbon rich black shale beds 115c 120 and 126 129 the latest famennian siphonodella praesulcata subzone conodont assemblage of s praesulcata palmatolepis gracilis palmatolepis sigmoidalis and rhodalepis polylophodontiformis was recognized in beds 113 115c beds 105 112 commonly contain palmatolepis expansa p gracilis and p sigmoidalis bed 119 yielded a basal carboniferous index conodont siphonodella sulcata in beds 116 118 solenoporids such as pseudochaetetes elliotti and parachaetetes sp were characteristic species in organic carbon rich dark gray limestone facies 1 is characterized by bioclastic peloidal and intraclastic grainstone and packstone containing massive normal grading and cross laminations and is interpreted to represent deep ramp carbonates above storm wave base facies 2 is represented by typical lag deposits overlying a transgressive surface facies 3 comprises organic carbon rich black shale and minor scour filling bioclastic peloidal and intraclastic packstone and may represent a marginal basin plain environment surrounding a carbonate ramp the alternations of organic carbon rich black shale and dark gray packstone facies 3 show no evidence of bioturbation and have high toc contents 0 18 5 73 wt a minor succession within the transgressive lag deposits from bed 115b of facies 2 to beds 115c 120 in the lower part of facies 3 is equivalent to the hangenberg black shale s l in the middle part of the siphonodella praesulcata to siphonodella sulcata zones because beds 115b 120 characterized by no evidence of bioturbation and high toc contents are interpreted to be accumulated in anoxic to dysoxic conditions

marine triassic faunas of north america their significance for assessing plate and terrane movements the distribution of marine triassic invertebrate faunas in north america is reviewed to recognize forms that may have paleolatitudinal significance

evolution of early triassic outer platform paleoenvironments in the nanpanjiang basin south china and their significance for the biotic recovery detailed microfacies and paleoenvironmental analyses were conducted through the early triassic interval of the outer platform ammonoid rich series of the nanpanjiang basin luolou formation guangxi province south china extensive investigations on outcrops and on thin sections reveal that the widely reported well diversified latest permian fauna dominated by abundant corals calcareous algae calcareous sponges crinoids brachiopods gastropods ostracods and foraminifera is abruptly replaced by decimated early triassic communities essentially composed of low diversity bivalves microgastropods ostracods and rare foraminifera along with this drastic change in faunal assemblages the recolonization of devastated habitats by calcimicrobial frameworks is observed in the aftermath of the end permian mass extinction calcimicrobialites of griesbachian age are followed by mixed ammonoid and conodont rich carbonate siliciclastic series consisting of dark suboxic laminated mudstones intercalated with organic rich shales of dienerian to late smithian age the carbonate siliciclastic series are interrupted by a brief carbonate episode during the early middle smithian massive carbonate production resumes only from the early spathian onward and persists throughout the spathian the initial deposition of both carbonate episodes is coeval with i re establishment of well oxygenated conditions ii a marked early smithian to extreme early spathian ammonoid conodont diversification iii a significant increase in the skeletal grain diversity and abundance and iv peak carbon isotope values a short interval of black organic rich shales precedes the onset of these two distinct carbonate events which are both marked by a positive carbonate carbon isotope excursion known from other tethyan marine localities the comparison between the early triassic stratigraphic evolution of tethyan outer platform paleoenvironments and platform basin margin settings of the nanpanjiang basin suggests a causal connection between large fluctuations of the global carbon cycle climate shifts sea level changes oxygen availability in the oceans and the biological rediversification in the wake of the end permian biotic crisis

secular variation in late cretaceous carbon isotopes a new δ13c carbonate reference curve for the cenomanian campanian 99 6 70 6 ma carbon stable isotope variation through the cenomanian santonian stages is characterized using data for 1769 bulk pelagic carbonate samples collected from seven chalk successions in england the sections show consistent stratigraphic trends and 13c values that provide a basis for highresolution correlation positive and negative 13cexcursions and inflection points on the isotope profiles are used to define 72 isotope events key markers are provided by positive 13c excursions of up to 2 the albian cenomanianboundary event mid cenomanian event i thecenomanian turonian boundary event the bridgewick hitch wood and navigation events of late turonian age and the santonian campanian boundary event isotope events are isochronous within a framework provided by macrofossil datum levels and bentonite horizons an age calibrated composite 13c reference curve and an isotope event stratigraphy are constructed using data from the english chalk the isotope stratigraphy is applied to successions in germany france spain and italy correlation with pelagic sections at gubbio central italy demonstrates general agreement between biostratigraphic and chemostratigraphic criteria in the cenomanian turonian stages confirming established relationships between tethyan planktonic foraminiferal and boreal macrofossil biozonations correlation of the coniacian santonian stages is less clear cut magnetostratigraphic evidence for placing the base of chron 33r near the base of the upper santonian is in good agreement with the carbon isotope correlation but generates significant anomalies regarding the placement of the santonian and campanian stage boundaries with respect to tethyan planktonic foraminiferal and nannofossil zones isotope stratigraphy offers a more reliable criterion for detailed correlation of cenomanian santonian strata than biostratigraphy with the addition of campanian 13c data from one of the english sections a composite cenomanian campanian age calibrated reference curve is presented that can be utilized in future chemostratigraphic studies the cenomanian campanian carbon isotope curve is remarkably similar in shape to supposedly eustatic sea level curves increasing 13c values accompanying sea level rise associated with transgression and falling 13c values characterizing sea level fall and regression the correlation between carbon isotopes and sea level is explained by variations in epicontinental sea area affecting organic matter burial fluxes increasing shallow sea floor area and increased accommodation space accompanying sea level rise allowedmore efficient burial ofmarine organic matter with the preferential removal of 12c from the marine carbon reservoir during sea level fall reduced seafloor area marine erosion of previously deposited sediments and exposure of basin margins led to reduced organiccarbon burial fluxes and oxidation of previously deposited organic matter causing falling 13c values additionally drowning of carbonate platforms during periods of rapid sea level rise may have reduced the global inorganic relative to the organic carbon flux further enhancing 13c values while renewed platform growth during late transgressions and highstands prompted increased carbonate deposition variations in nutrient supply changing rates of oceanic turnover and the sequestration or liberation of methane from gas hydrates may also have played a role in controlling carbon isotope ratios

lower middle triassic conodont biostratigraphy of the qingyan section guizhou province southwest china abstract the middle triassic qingyan formation at its type section the qingyan section of guizhou southwest china yields more than 300 species belonging to 17 fossil groups which mark the radiation of benthic organisms following the end permian mass extinction this study intends to establish a primary conodont biostratigraphical succession through the lower and middle triassic sequence at qingyan to provide a time framework for the understanding of the recovery and radiation process from the mass extinction a total of 30 species in 8 conodont genera are stratigraphically significant and assigned to the neospathodus dieneri neospathodus cristagalli neospathodus waageni neospathodus homeri chiosella timorensis and neogondolella cf bulgarica zones in ascending order most conodont zones correlate well with their counterparts recognized from elsewhere in china and even worldwide the first appearance of ns waageni marks the induan olenekian boundary which is placed at the lower middle part of the luolou formation 121 47 m above the permian triassic boundary the olenekian anisian early middle triassic boundary is here defined by the first occurrence of chiosella timorensis at the base of the qingyan formation although no conodonts retrieved from the upper qingyan formation containing the extraordinarily diverse biota i e the qingyan biota stratigraphical correlation with the neighbouring conodont bearing sections in guizhou and the ammonoid zones suggest that the qingyan biota has an age of early late anisian early middle triassic