microbial deposits in the aftermath of the end permian mass extinction a diverging case from the mineral mountains utah usa the lower triassic mineral mountains area utah usa preserves diversified smithian and spathian reefs and bioaccumulations that contain fenestral microbialites and various benthic and pelagic organisms ecological and environmental changes during the early triassic are commonly assumed to be associated with numerous perturbations productivity changes acidifica tion redox changes hypercapnia eustatism and temperature changes post dating the permian triassic mass extinction new data acquired in the mineral mountains sediments provide evidence to decipher the relationships between depositional environments and the growth and distribution of microbial structures these data also help to understand better the controlling factors acting upon sedimentation and community turnovers through the smithian early spathian the studied section records a large scale depositional sequence during the dienerian spathian interval during the transgression depositional environments evolved from a coastal bay with continental deposits to intertidal fenestral microbial limestones shallow subtidal marine sponge microbial reefs to deep subtidal mud dominated limestones storm induced deposits microbialite sponge reefs and shallow subtidal deposits indicate the regression three microbialite associations occur in ascending order i a red beds microbialite association deposited in low energy hypersaline supratidal conditions where microbialites consist of microbial mats and poorly preserved microbially induced sedimentary structure ii a smithian microbialite association formed in moderate to high energy tidal conditions where microbialites include stromatolites and associated carbonate grains oncoids ooids and peloids and iii a spathian microbialite association developed in low energy offshore conditions that is preserved as multiple decimetre thick isolated domes and coalescent domes data indicate that the morphologies of the three microbialite associations are controlled primarily by accommodation hydrodynamics bathymetry and grain supply this study suggests that microbial constructions are controlled by changes between trapping and binding versus precipitation processes in variable hydrodynamic conditions due to the presence of numerous metazoans associated with microbialites throughout the smithian increase in accommodation and spathian decrease in accommodation the commonly assumed anachronistic character of the early triassic microbialites and the traditional view of prolonged deleterious conditions during the early triassic time interval is questioned

the nature extent and subsequent dispersal of the permian tethys on the basis of the sedimentary and biotic facies characteristics of permian strata deposited in different climatic zones scepticism is expressed about some recent palaeogeographical reconstructions that demand a vast wedge shaped tethys in asia or movement over considerable latitudes of allochthonous terranes

late palaeozoic palaeomagnetic data for wrangellia resolution of the polarity ambiguity wrangellia and the alaska peninsula terrane are two of the many allocthonous terranes making up southern alaska today palaeomagnetic data from these areas clearly indicate low palaeolatitudes in the early mesozoic because of local and regional rotations the mean declination of the palaeomagnetic vectors is uncertain this in addition to incomplete temporal coverage has led to an ambiguity in the polarity of the vector and hence an ambiguity in whether the palaeolatitudes determined are in the northern or southern hemisphere the data considered here have resolved the ambiguity for wrangellia and by implication for the alaska pennisula terrane and also allow the construction of a highly speculative apparent polar wander curve

early history of scleractinian corals and its geological consequences conventional views have implied that scleractinian corals were hermatypic and thus were potentially reef building from the onset of their appearance in early mesozoic time in shallow shelf carbonate environments however for almost 25 m y they held rather subordinate positions and generally did not participate in extensive ecologic reef framework evidence from both north america and europe demonstrates that triassic corals had ecologic preferences quite different from those in the cenozoic a key step in the evolutionary success of these corals may have been the advent of a symbiotic association with algae this association believed to have developed at the end of the triassic could have been responsible for thrusting scleractinians into prominent positions as reef builders and may account for their dramatic radiation in mesozoic time

geographic differentiation of triassic brachiopods abstract the main palaeobiogeographic patterns and trends of triassic brachiopods are analysed during the triassic taxonomic diversity of brachiopods increased and this was accompanied by intensification of their geographic differentiation thus the maximum differention was attained during the late triassic for which at least five biochores of first rank boreal northern tethyan peri gondwanian notal or maorian and eastern pacific may be distinguished

oldest scleractinian coral reefs on the north american craton upper triassic carnian northeastern british columbia canada abstract bioclastic accumulations composed of crinoids brachiopods molluscs spongiomorphs and scleractinian corals occur within upper triassic strata of the lower baldonnel formation at pardonet hill in northeastern british columbia canada these small buildups 100 to 500 m3 have planar bases and broadly convex tops these mounds are interpreted as small patch reefs composed of packstone bioclastic floatstone rudstone and carbonate breccia intercalated with mixed siliciclastic carbonate sediments deposited in a shallow subtidal setting i e above fairweather wave base amalgamated hummocky cross stratified to current ripple laminated quartz dominated sandstone beds and numerous sharp based normally graded bioclastic commonly encrinitic packstone grainstone quartz sandstone couplets characterize inter reef lithologies conodont biostratigraphy indicates that the pardonet hill patch reefs occur within strata dated as earliest upper carnian lower nodosus zone the pardonet hill patch reefs originated and developed during an interval of regional sea level lowstand strata within which these patch reefs occur represent the westernmost migration of the triassic shoreline in western canada disappearance of coral reefs in the study area may have been affected by rapid marine transgression and failure of reef faunas to recolonize the new shore zone further to the east the pardonet hill locality occurred on the western margin of the north american craton during the triassic prior to their discovery reef like structures dominated by corals in the western panthalassa were limited to allochthonous terranes now part of the cordillera the pardonet hill patch reefs occur at approximately 30 triassic paleolatitude in modern settings this is at the extreme latitudinal margin of subtropical zooxanthellate reef development the presence of benthic faunas characteristic of low paleolatitude settings on the northwestern coast of pangea has significant implications in paleotectonic and paleoenvironmental reconstructions

early mesozoic southward migration of cordilleran transpressional terranes oblique plate convergence can cause forearc arc and back arc regions of active margin orogenic belts to behave as semi independent terranes relative to bordering continental and oceanic lithospheric plates these terranes called here transpressional terranes are bound by the subduction zone on one side by arc parallel strike slip faults in the forearc in the volcanic arc or in the back arc region on the other and are underlain by throughgoing basal decollements these terranes undergo shortening in a direction perpendicular to the subduction zone and migrate as coherent structural bodies parallel to the subduction zone along bounding strike slip faults many terranes of the north american cordillera may have behaved in this manner and perhaps did not travel across the pacific basin but rather were always peripheral to north america we propose that during the triassic to mid cretaceous portions of the cordillera borderland generally were displaced southward with respect to the north american craton due to left oblique convergence since the mid cretaceous they moved northward due to right oblique subduction the proposed displacements are consistent with structural paleomagnetic and paleontologic data and with the relative and absolute motions of north america and the pacific basin plates based on hotspot reference frame models

metallogenetic evolution of the east alpine paleozoic basement paleo metallogenetic sketch maps of the east alpine area are presented for the ordovician silurian the devonian lower carboniferous and the upper carboniferous permian mineralization and tectonic evolution are then discussed in the frame of a plate tectonic model compatible with recent results in western europe

a low oxygen tolerant east pacific flat clam posidonotis semiplicata from the lower jurassic of the canadian cordillera flat clams represent a loosely defined group of thin shelled flat valved bivalves their distribution and high concentration in some especially mesozoic rocks have attracted interest and several contrasting paleoecologic interpretations have been proposed to explain their occurrence we present a comprehensive study of posidonotis semiplicata hyatt an early jurassic flat clam common in western north and south america posidonotis symmetrica hyatt posidonotis balteata crickmay and posidonotis cancellata leanza are interpreted as subjective junior synonyms in north america p semiplicata occurs in the upper sinemurian to lower toarcian of several cordilleran allochthonous terranes the south american record is restricted to upper pliensbachian to lower toarcian occurrences suggesting that the species originated in the northeast pacific in late sinemurian time and spread to the southeast pacific by the late pliensbachian the closely related posidonotis dainellii losacco sporadically kno

middle triassic biostromes from the liard formation british columbia canada oldest examples from the mesozoic of nw pangea abstract mesozoic carbonate accumulations are rare in northwestern pangea this is due initially to the demise of many carbonate secreting organisms during the terminal permian biotic crisis and subsequently to increased siliciclastic sedimentation resulting from the tectonic development of western north america ecological voids resulting from the extinction however resulted in new opportunities for surviving taxa terebratulid brachiopod echinoderm dominated biostromes within the primarily siliciclastic liard formation middle triassic ladinian of northeastern british columbia provide a unique example the liard biostromes are composed primarily of whole and unabraded terebratulid brachiopods aulacothyroides liardensis articulate crinoid elements isocrinus sp and cidaroid echinoid spines and interambulacral plates miocidaris sp many of the terebratulid brachiopods are characterized by the pedicle attachment trace fossil podichnus other organisms which occupied the biostromes include discinid cf orbiculoidea sp and spiriferid spiriferina abichi brachiopods bivalves including oysters and gastropods as well as rare bryozoans and possibly scleractinian corals sedimentary units deposited on the margins of the biostromes are characterized by an abundance of body fossils decapod crustaceans bivalves and ophiuroids and trace fossils asterosoma cylindrichnus palaeophycus rosselia teichichnus and thalassinoides this trace fossil assemblage contains a mix of dwelling traces horizontal deposit feeding traces and vertical suspension feeding traces consistent with deposition in a lower shoreface setting hiatal surfaces and laterally restricted bioclastic sandstone layers and lenses within these features suggest that frequent turnover of infaunal and epifaunal communities occurred at the edges of the liard brachiopod echinoderm biostromes development of the liard brachiopod echinoderm biostromes depended on initial storm induced concentration of shell material to create patches or zones of stable substrate promoting colonization by terebratulid brachiopods discinid brachiopods crinoids and cidaroid echinoids

a new genus and species of polychelid lobster crustacea decapoda eryonidae from the early jurassic hettangian of british columbia a single specimen of decapod crustacean preserved in ventral view and compressed represents a new genus and species of eryonid lobster wrangelleryon perates the discovery in lower jurassic hettangian sediments of the sandilands formation in british columbia represents the first occurrence of eryonidae in north america and reinforces a global distribution of the family in the jurassic the occurrence in british columbia on the wrangellia terrane supports the lower latitude setting in which the species lived resume un specimen unique de crustace decapode preserve en vue ventrale et comprime represente un nouveau genre et une nouvelle espece de homard eryonide wrangelleryon perates la decouverte dans des sediments du jurassique inferieur hettangien de la formation de sandilands en colombie britannique represente la premiere occurrence d un eryonide en amerique du nord et consolide la these d une repartition planetaire de cette famille au jurassique la presence du specimen en colombie britannique dans le terrane de wrangellie appuie la these voulant que l espece ait vecu abasse latitude traduit par la redaction

evidence from neodymium isotopes for mantle contributions to phanerozoic crustal genesis in the canadian cordillera sm nd and rb sr isotopic studies of several phanerozoic orogenic belts have shown that much of the crust in these belts is composed of reworked pre existing continental crust in contrast isotopic data collected from two of the largest terranes in the canadian cordilleran orogenic belt the alexander and stikine terranes show that these tectonic fragments are composed of mantle derived continental crust in many respects the style and rate of crustal accretion of these and related terranes appear similar to those of some proterozoic crustal regions

allochthonous terranes in alaska implications for the structure and evolution of the bering sea shelf abundant evidence has been gathered in support of the concept that much of the pacific margin of north america consists of allochthonous terranes that were accreted during mesozoic and early tertiary time in particular southern alaska is almost completely composed of separate terranes whose stratigraphy and paleomagnetism indicate distant origins the bering sea continental shelf is among the largest shelves in the world almost half as large as alaska itself some of the allochthonous terranes in alaska probably continue beneath the continental shelf but their distribution beyond the shoreline has not been determined we believe that much of the continental shelf is probably composed of allochthonous terranes in much the same way as southern alaska geophysical data from the bering continental shelf have been used to test this hypothesis although inconclusive without extensive drilling multichannel seismic profiles and magnetic data indicate the composite character of the shelf basement the magnetic anomalies can be separated into specific domains of limited extent these magnetic variations suggest a corresponding variation of rock terranes beneath the shelf in addition multichannel seismic profiles show possible thrust faults within the shelf basement that could be sutures between separate terranes

the early triassic ammonoid recovery paleoclimatic significance of diversity gradients ammonoids recovered much faster than other marine shelly invertebrates after the end permian mass extinction based on a refined global data set at the basin level we investigate the paleobiogeographical global latitudinal and longitudinal diversity patterns in terms of climatic changes during the early triassic such analysis differs from already published qualitative or quantitative studies in that it estimates faunal patterns and endemicity at an ecologically meaningful level of spatial resolution i e at the basin level during the early triassic the global first order trend in increasing ammonoid diversity was accompanied by a progressive change from cosmopolitan to latitudinally restricted distributions this led to the emergence of a clear latitudinal diversity gradient during most of the smithian and spathian stages which entails increased steepness of the sea surface temperature gradient during the late early triassic however two brief episodes of ammonoid cosmopolitanism combined with low global diversity interrupted the first order increasing trend at the very beginning of the smithian and at its very end the longitudinal analysis of smithian distributions indicates a westward decrease of diversity within the tethys which faded away during the spathian analysis of endemicity indicates a rapid biogeographical maturing and structuring of faunas concomitant with the edification of the latitudinal diversity gradient

paleoecology biogeography and evolution of reef ecosystems in the panthalassa ocean during the late triassic insights from reef limestone of the sambosan accretionary complex shikoku japan upper triassic reefs from the panthalassa ocean have been understudied in comparison to their tethyan counterparts and are therefore pivotal to understanding the global reef evolution during the late triassic to fill this gap upper triassic reef limestone from ten localities of the sambosan accretionary complex at shikoku island japan has been investigated biotic assemblages quantitative microfacies analysis and integrated biostratigraphy allow us to characterize two types of reefs those attributed to the ladinian early carnian and those attributed to the late carnian rhaetian at the regional scale our data refine the biostratigraphic framework of the upper triassic sambosan limestone at the global scale multivariate analyses support a strong paleobiogeographic affinity of the western panthalassa reef biota with those of the south tethys ocean during the ladinian carnian and norian rhaetian additionally they indicate connections with east panthalassa reefs during the norian rhaetian

the smithian spathian boundary late early triassic a review of ammonoid conodont and carbon isotopic criteria abstract the transition from the smithian substage to the spathian substage of the olenekian stage of the late early triassic was a critical time marked by a series of biological and environmental changes during the multimillion year recovery interval following the end permian mass extinction however the smithian spathian boundary ssb does not yet have an agreed definition a shortcoming that complicates high resolution analysis of events during the smithian spathian transition here we review key biostratigraphic i e ammonoid and conodont studies of the smithian and spathian substages in historically important regions e g the canadian arctic for the boreal realm western north america for the eastern panthalassic ocean and more recently re studied locations e g pakistan and india in the southern tethys south china in the eastern tethys as well as the carbon isotope chemostratigraphy of 29 major smithian spathian sections globally key ammonoid genera e g wasatchites anasibirites glyptophiceras and xenoceltites of the late smithian and bajarunia tirolites and columbites of the early spathian conodont species e g scythogondolella milleri novispathodus waageni and borinella buurensis of the late smithian and triassospathodus hungaricus neogondolella aff sweeti and icriospathodus spp of the early spathian and carbonate carbon isotope excursions provide appropriate markers for constraining the ssb use of the first occurrence of the conodont novispathodus pingdingshanensis as a potential marker of the ssb is also discussed based on correlations of biostratigraphic and carbon isotope data globally we propose to revise previous placements of the ssb transition in some sections finally we show that the smithian thermal maximum stm herein named was middle smithian in age and not correlative with the ssb as inferred in some earlier studies and that the ssb coincided with a subsequent major global cooling event

smithian and spathian early triassic ammonoid assemblages from terranes paleoceanographic and paleogeographic implications early triassic paleobiogeography is characterised by the stable supercontinental assembly of pangea however at that time several terranes such as the south kitakami massif sk south primorye sp and chulitna respectively and presently located in japan eastern russia and alaska straddled the vast oceans surrounding pangea by means of quantitative biogeographical methods including cluster analysis non metric multidimensional scaling and bootstrapped spanning network applied to smithian and spathian early triassic ammonoid assemblages we analyze similarity relationships between faunas and suggest paleopositions for the above cited terranes taxonomic similarities between faunas indicate that primary drivers of the ammonoid distribution were sea surface temperature and currents possible connections due to current controlled faunal exchanges between both sides of the panthalassa are shown and terranes such as sk sp and chulitna played an important role as stepping stones in the dispersal of ammonoids sk and sp terranes show strong sub equatorial affinities during the smithian thus suggesting a location close to south china at the same time the chulitna terrane shows strong affinities with equatorial faunas of the eastern panthalassa this paleoceanographic pattern was markedly altered during the spathian possibly indicating significant modifications of oceanic circulation at that time as illustrated by the development of a marked intertropical faunal belt across tethys and panthalassa

nd and sr isotopic characterization of the wrangellia terrane and implications for crustal growth of the canadian cordillera nd and sr isotopic data are reported from samples of most of the major lithologic units of the wrangellia terrane exposed on vancouver island and the queen charlotte islands initial epsilon nd values range from 1 0 to 7 3 and initial 87 sr 86 sr ratios range from 0 70323 to 0 70481 these ratios are similar to those of modern island arcs and demonstrate the unevolved juvenile nature of this terrane these data indicate that wrangellia probably resided in an intra oceanic environment until its accretion to north america nd crustal residence ages for clastic sedimentary rocks of wrangellia mean t cr 0 77 pm 0 33 ga t dm 0 57 pm 0 35 ga are much closer to their stratigraphic ages than is the case for the ages of many other phanerozoic sedimentary rocks thus providing strong evidence for phanerozoic crustal addition to north america early proterozoic crustal components cannot comprise more than about 6 of wrangellia therefore the terrane consists of 94 new mantle d

jurassic foraminifera from the queen charlotte islands british columbia canada biostratigraphy paleoenvironments and paleogeographic implications abstract lower and middle jurassic sinemurian to callovian foraminifera were examined from 66 localities of the queen charlotte islands british columbia canada over 200 species of well preserved benthic calcareous and agglutinated taxa belonging to 50 genera were identified foraminifera from the lower jurassic are represented by an abundant and diverse tethyan derived calcareous assemblage with boreally derived agglutinated taxa becoming gradually more dominant in the upper lower jurassic to lower middle jurassic sedimentary strata and their faunal components and position of hiatuses correlate approximately with the jurassic eustatic sea level curve sea level changes have resulted in a variety of depositional environments ranging from deep water euxinic shales with abundant tuff beds characterized by small pyritized foraminifera to a well oxygenated outer shelf setting characterized by a major faunal increase to shoreface sandstones and conglomerates with absent to rare benthic foraminifera a gradual shallowing from a slope to a shelf dominated deposition with a magmatic arc provenance is suggested for the lower jurassic changing in the middle jurassic to an inner shelf to upper shoreface setting dominated by sedimentary strata of volcaniclastic origin a marked faunal turnover is observed in the lower jurassic whiteaves formation middle toarcian with the extinction of several earlier species and the appearance of a new diverse assemblage of 225 taxa this turnover is also observed in the ammonite and radiolarian assemblages of the queen charlotte islands in comparison to the dominantly tethyan derived taxa of pre middle toarcian age many of the species from the middle toarcian are found in northern latitudes such as on the northern slope of alaska arctic islands and the northwest territories hence foraminifera in conjunction with existing radiolarian and ammonite data suggest a northward displacement of the queen charlotte islands from low to mid paleolatitudes by late early jurassic toarcian to early middle jurassic bajocian time

significance of tethyan fossils in the american cordillera equatorial faunas of the ancient tethyan seaway which extended from western europe to southeastern asia comprise some of the most diverse marine taxa in the fossil record comparable or identical tethyan species that occur far from the tethyan seaway in paleozoic and mesozoic rocks of the north and south american cordillera have long been considered as a major biogeographic anomaly two leading theories to account for the occurrence of these anomalous tethyan faunas in the cordillera are that they were transported long distances to the east on tectonic blocks suspect terranes that originated near the tethys or that they migrated westward via undiscovered marine corridors through continental areas of pangea an alternative model is that these tethyan fauna were pantropic species that extended with attenuated diversities into the eastern proto pacific ocean this pantropic model can better account for the distribution patterns of many paleozoic and early mesozoic tethyan species in the american cordillera and provides a steady state hypothesis against which the other models can be tested the distribution of pre cretaceous tethyan faunas is similar to the known pantropic distribution of many cretaceous and cenozoic tropical biotas during the cenozoic taxa were most diverse in the tethys and indo west pacific regions but extended with attenuated diversity to many parts of the equatorial pacific ocean including the west coasts of north and south america the eastern pacific occurrence of many indo west pacific species provides a modern analog for the occurrence of many anomalous tethyan fossils in the american cordillera

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

cordilleria a newly defined canadian microcontinent palaeomagnetic data and geological field evidence indicate that most of the western canadian cordillera lay 1 500 km south of its present position in the early cretaceous we suggest that this region comprised a microcontinent termed cordilleria which moved on the kula plate and collided with the craton 100 myr ago to form first the mackenzie mountains and then the rockies

offset of an upper pliensbachian geographic zonation in the north american cordillera by transcurrent movement the north to south climatic zonation of upper pliensbachian ammonites known in europe has been recognized in the north american cordillera this simple geographic arrangement has been disrupted by northwest trending dextral transcurrent faults with further documentation the amount of offset of these zones should provide a measure of the amount of movement on these faults since pliensbachian time and further document the allochthoneity of the western part of the cordillera

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

reconstruction of eastern gondwanaland substantial additions of large continental blocks to the smith et al 1 model of eastern gondwanaland are proposed here largely on the basis of the distribution of key land floras tropical and subtropical marine faunas lithofacies patterns and the identification of a triassic magmatic arc that characterized all the eastern margin of gondwanaland the continental fragments that must have been rifted from northern australia new guinea in the jurassic are identified as south tibet burma thailand malaya and sumatra the original site of deposition of the subtropical permian limestones and tropical late triassic limestones overthrust onto the northern margin of australia by the late cenozoic collision2 is located in this greater gondwanaland palaeomagnetic data except those from malaya3 support this reconstruction

evidence of displaced terranes from permian to jurassic faunas around the pacific margins for the permian to jurassic time interval tethyan marine invertebrate faunas which are generally accepted as having lived at low latitude can be distinguished from less diverse higher latitude faunas displacement of these low latitude faunas to positions of high latitude around the pacific margins therefore provides key evidence for the movement of so called suspect or displaced terranes the fullest story so far has been worked out for the western margin of n america as far north as southern alaska but there is also convincing evidence for the substantial northward movement of continental segments along the ne asian margin as regards the southern hemisphere the torlesse terrane of new zealand appears to have moved a considerable distance southwards but there is no fauna1 evidence of comparable far travelled suspect terranes along the andean margin of south america not only tethyan and boreal but e and w pacific elements are detectable in the faunas and the distribution of these argues for a panthalassia studded with islands of various sizes fringing the adjacent continents rather than for the disintegration of a single continent pacifica

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

biochronology of triassic bivalves substantial advances by numerous researchers over the past 20 years have made it possible to develop a composite biochronological scheme for the triassic based on the bivalves claraia peribositria enteropleura daonella halobia eomonotis and monotis these bivalves exhibit temporal durations nearly equal to ammonoids and conodonts widely distributed across the tethys panthalassa and boreal regions these bivalves occur in a wide variety of marine facies and water depths but are most notable for their thick shell accumulation in deeper water oxygen deficient environments they were most likely resting or reclining benthos may have housed chemosymbionts and were part of episodic opportunistic palaeocommunities in or near oxygen deficient settings a new biochronological zonation for bivalves is presented that encompasses the entire triassic and is integrated with standard ammonoid schemes the lower triassic is characterized by 2 3 zones of claraia most notably from the eastern tethys representing the entire induan and lower portion of the olenekian later in the olenekian and most notably from the boreal realm species of peribositria included by some workers within bositra provide useful zonal indexes the middle triassic is well represented by enteropleura middle anisian and daonella upper anisian through ladinian in the tethys and north america with significant occurrences through out the circum pacific and boreal realms the upper triassic can be subdivided into 8 13 bivalve zones based on the succession of halobia eomonotis and monotis sensu lato species with best representation in the tethys boreal and eastern panthalassa regions

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

early triassic gulliver gastropods spatio temporal distribution and significance for biotic recovery after the end permian mass extinction a reduction in body size lilliput effect has been repeatedly proposed for many marine organisms in the aftermath of the permian triassic pt mass extinction specifically reduced maximum sizes of benthic marine invertebrates have been proposed for the entire early triassic this concept was originally based on observations on early triassic gastropods from the western usa basin and the dolomites n italy and it stimulated subsequent studies on other taxonomic groups however only a few studies have tested the validity of the lilliput effect in gastropods to determine whether the paucity of large sized gastropods is a genuine signal or the result of a poor fossil record and insufficient sampling in combination with a review of the literature we document numerous new abundant large sized gastropods from the griesbachian outcrops of greenland and from the smithian early spathian interval in the southwestern usa we show that large sized gulliver gastropods i were present soon after the pt mass extinction ii occurred in various basins sedimentary facies and environmental contexts from shallow to deeper settings and iii belong to diverse higher rank taxa focusing on the western usa basin we investigate areas from which microgastropod shell beds were previously presented as being typical however we show that gulliver gastropods do occur in the very same areas insufficient sampling effort is probably the main reason for the rarity of reports of large early triassic gastropods which is supported by preliminary rarefaction based simulations finally it appears that the recently documented middle to late smithian climate shifts and the severe end smithian extinction of nekto pelagic faunas did not reduce maximum shell sizes of gastropods

carbonate platform depositional sequences upper cretaceous south central pyrenees spain abstract the upper cretaceous cenomanian maastrichtian of the south central pyrenees shows five carbonate platform sequences where the major parameters are tectonism relative sea level fluctuations and inherited depositional profile depositional geometries and basin analysis permit an understanding of the depositional history five depositional sequences have been recognized 1 the santa fe sequence middle upper cenomanian a ramp to a skeletal rimmed shelf with an escarpment bypass margin the lower boundary is an angular unconformity and the upper one records a sea level drop the platform location of the margin was determined by a listric normal fault 2 an abrupt sea level rise drowned the former platform the congost sequence turonian lower coniacian a distally steepened ramp with erosional distal deep slope the depositional model was largely controlled by pre existing basin morphology cessation of platform development was due to a relative sea level drop 3 the sant corneli sequence upper coniacian lower santonian a mixed terrigenous skeletal homoclinal ramp with upright margin deep slope and dysaerobic basin the slope results from the backstepping by 24 km of the previous margin and gentle basin tilting the platform margin remained more or less at the same position and relief between platform and slope increased indicating continuous relative sea level rise the upper boundary is an angular unconformity at the platform margin produced by an abrupt sea level rise and platform drowning and by listric normal faulting 4 the vallcarga sequence upper santonian campanian a distal steepened skeletal homoclinal ramp erosional escarpment and turbidite basin which corresponds to the mesozoic maximum marine expansion a listric normal fault created two depositional areas a more or less flat footwall block with a north northwest prograding carbonate ramp

late early triassic climate change insights from carbonate carbon isotopes sedimentary evolution and ammonoid paleobiogeography the late early triassic sedimentary facies evolution and carbonate carbon isotopemarine record 13ccarb of ammonoid rich outer platform settings show striking similarities between the south china block scb and the widely distantnorthern indianmargin nim the studied sections are located within the triassic tethyshimalayan belt losar section himachal pradesh india and the nanpanjiang basin in the south china block jinya section guangxi province respectively carbon isotopes from the studied sections confirm the previously observed carbon cycle perturbations at a time of major paleoceanographic changes in the wake of the end permian biotic crisis this study documents the coincidence between a sharp increase in the carbon isotope composition and the worldwide ammonoid evolutionary turnover extinction followed by a radiation occurring around the smithian spathian boundary based on recent modeling studies on ammonoid paleobiogeography and taxonomic diversity we demonstrate that the late early triassic smithian and spathian was a time of a major climate change more precisely the end smithian climate can be characterized by a warm and equable climate underlined by a flat pole to equator sea surface temperature sst gradient while the steep spathian sst gradient suggests latitudinally differentiated climatic conditions moreover sedimentary evidence suggests a transition froma humid and hot climate during the smithian to a dryer climate fromthe spathian onwards by analogywith comparable carbon isotope perturbations in the latedevonian jurassic andcretaceouswe propose that high atmosphericco2 levels could have been responsible for the observed carbon cycle disturbance at the smithian spathian boundary we suggest that the end smithian ammonoid extinction has been essentially caused by a warm and equable climate related to an increased co2 flux possibly originating froma short eruptive event of the siberian igneous province this increase in atmospheric co2 concentrations could have additionally reduced the marine calcium carbonate oversaturation and weakened the calcification potential of marine organisms including ammonoids in late smithian oceans

jurassic and cretaceous plutonic and structural styles of the eagle plutonic complex southwestern british columbia and their regional significance the eagle plutonic complex is an elongate north northwest trending body of deformed middle to late jurassic and middle cretaceous rocks which underlies the southwestern margin of the intermontane terrane new mapping of the complex and its country rocks in concert with geochronometry has defined episodes of contractional ductile deformation in the middle to late jurassic and middle cretaceous as well as brittle deformation in tertiary time synkinematic middle to late jurassic eagle tonalite at the eastern margin of the eagle complex intrudes mylonitic nicola group rocks and structurally overlies them along a southwest dipping belt of high strain eagle shear zone with a structural thickness of 1 km and a strike length of 100 km in the central and western eagle complex eagle tonalite grades into tonalite orthogneiss eagle gneiss and both are crosscut by mid cretaceous muscovite bearing plutons of the fallslake plutonic suite fallslake suite rocks are themselves ductilely deformed along the