the permo triassic transition in spitsbergen δ13corg chemostratigraphy fe and s geochemistry facies fauna and trace fossils new 13 c org analyses of two boundary sections between the late permian kapp starostin formation and the early triassic vardebukta formation of western spitsbergen confirm field evidence that their contact is a conformable one thus contrary to previous reports some spitsbergen sections contain a complete record of the environmental and faunal changes during the crisis interval of the end permian mass extinction no environmental deterioration is recorded in the late permian until near the end of the terminal changxingian stage whereupon the abundant siliceous sponge fauna of the kapp starostin formation disappears along with the deep burrowing fauna responsible for the zoophycus trace fossil a low diversity dysaerobic trace fossil assemblage is briefly developed before a transition to finely laminated pyritic facies immediately beneath the permo triassic boundary analysis of the s c ratios from the laminated strata suggests that free h 2 s was present in the water column euxinic conditions even in relatively nearshore settings subject to storm sandstone deposition the mass extinction crisis in spitsbergen is therefore coincident with the extensive development of oxygen poor conditions in the water column and compares closely both in timing and nature with the crisis seen in lower latitude tethyan settings however the subsequent aftermath and recovery in the boreal sections of spitsbergen was more rapid than in tethys thus a shoreface sandstone body within the dienerian stage contains an appreciable diversity of fauna by the standards of the early triassic including bryozoans calcareous algae and deep infaunal bivalves that suggests the marine ecosystem recovery began earliest in higher palaeolatitudes

climate warming in the latest permian and the permian triassic mass extinction high resolution oxygen isotope records document the timing and magnitude of global warming across the permian triassic p tr boundary oxygen isotope ratios measured on phosphate bound oxygen in conodont apatite from the meishan and shangsi sections south china decrease by 2 in the latest permian translating into low latitude surface water warming of 8 c the oxygen isotope shift coincides with the negative shift in carbon isotope ratios of carbonates suggesting that the addition of isotopically light carbon to the ocean atmosphere system by siberian traps volcanism and related processes resulted in higher greenhouse gas levels and global warming the major temperature rise started immediately before the main extinction phase with maximum and harmful temperatures documented in the latest permian meishan bed 27 the coincidence of climate warming and the main pulse of extinction suggest that global warming was one of the causes of the collapse of the marine and terrestrial ecosystems in addition very warm climate conditions in the early triassic may have played a major role in the delayed recovery in the aftermath of the permian triassic crisis

geochemical facies analysis of fine grained siliciclastics using th u zr rb and zr rb sr ratios abstract abundance of the trace elements zr rb sr th and u may provide insight into the sedimentological origin of fine grained siliciclastic sediments provided that the units are derived from similar source areas as demonstrated here with suites of the fine grained jurassic and cretaceous rocks from the barents sea and svalbard zr rb ratios can be interpreted to indicate grain size variations while zr rb sr values reflect variations in the siliciclastic versus carbonate contents the th u ratio can be applied as an indicator of the redox conditions in 3d plots such as presented here the interplay between these geochemical factors can be interpreted in terms of the sedimentological evolution of the depositional basin the geochemical facies analyses show that similar depositional conditions existed on the jurassic shelf in the two studied localities the succeeding prodeltaic cretaceous beds were generally coarser grained and deposited in ventilated depositional conditions

carbon isotope stratigraphy across the permian triassic boundary a review abstract the palaeozoic mesozoic transition is marked by distinct perturbations in the global carbon cycle resulting in a prominent negative carbon isotope excursion at the permian triassic p t boundary well known from a plethora of marine and continental sediments potential causes for this negative 13 c trend and their links to the latest permian mass extinction have been intensively debated in the literature in order to draw conclusions regarding causation a general 13 c curve was defined after consideration of all available datasets and with due reference to the biostratigraphic background the most important features of the p t carbon isotope trend are the following the 4 7 13 c decline lasting 500 000 years is gradual and began in the changhsingian at the stratigraphic level of the c bachmanni zone the decreasing trend is interrupted by a short term positive event that starts at about the latest permian low latitude marine main extinction event horizon eh indicating that the extinction itself cannot have caused the negative carbon isotope excursion after this short term positive excursion the 13 c decline continues to a first minimum at about the p t boundary a subsequent slight increase is followed by a second occasionally two peaked minimum in the lower and middle i isarcica zone the negative carbon isotope excursion was most likely a consequence of a combination of different causes that may include 1 direct and indirect effects of the siberian trap and contemporaneous volcanism and 2 anoxic deep waters occasionally reaching very shallow sea levels a sudden release of isotopically light methane from oceanic sediment piles or permafrost soils as a source for the negative carbon isotope trend is questionable at least for the time span a little below the eh and somewhat above the p t boundary

δ13c evidence that high primary productivity delayed recovery from end permian mass extinction euxinia was widespread during and after the end permian mass extinction and is commonly cited as an explanation for delayed biotic recovery during early triassic time this anoxic sulfidic episode has been ascribed to both low and high productivity states in the marine water column leaving the causes of euxinia and the mechanisms underlying delayed recovery poorly understood here we use isotopic analysis to examine the changing chemical structure of the water column through the recovery interval and thereby better constrain paleoproductivity the 13c of limestones from 5 stratigraphic sections in south china displays a negative gradient of approximately 4 from shallow to deep water facies within the lower triassic this intense gradient declines within spathian and lowermost middle triassic strata coincident with accelerated biotic recovery and carbon cycle stabilization model simulations show that high nutrient levels and a vigorous biological pump are required to sustain such a large gradient in 13c indicating that early triassic ocean anoxia and delayed recovery of benthic animal ecosystems resulted from too much productivity rather than too little

progressive environmental deterioration in northwestern pangea leading to the latest permian extinction stratigraphic records from northwestern pangea provide unique insight into global processes that occurred during the latest permian extinction lpe we examined a detailed geochemical record of the festningen section spitsbergen a stepwise extinction is noted as starting with 1 loss of carbonate shelly macrofauna followed by 2 loss of siliceous sponges in conjunction with an abrupt change in ichnofabrics as well as dramatic change in the terrestrial environment and 3 final loss of all trace fossils we interpret loss of carbonate producers as related to shoaling of the lysocline in higher latitudes in relationship to building atmospheric co 2 the loss of siliceous sponges is coincident with the global lpe event and is related to onset of high loading rates of toxic metals hg as co that we suggest are derived from siberian trap eruptions the final extinction stage is coincident with redox sensitive trace metal and other proxy data that suggest onset of anoxia after the other extinction events these results show a remarkable record of progressive environmental deterioration in northwestern pangea during the extinction crises

derivation of isotope ratios errors and error correlations for u pb geochronology using 205pb 235u 233u spiked isotope dilution thermal ionization mass spectrometric data a comprehensive treatment of the derivation of u pb isotope ratios and their corresponding uncertainties from isotope dilution thermal ionization mass spectrometric measurements is presented standard parametric statistical methods of error propagation are utilized to convolve uncertainties associated with instrumental mass fractionation tracer subtraction blank pb and u subtraction and initial common pb correction derivations include errors and error correlations for total sample u pb and pb isotope ratios including radiogenic and initial common pb for two and three dimensional isochron calculations radiogenic u pb and pb isotope ratios for concordia and radiogenic model age calculations and the propagation of model age errors from radiogenic isotope ratios

anomalously diverse early triassic ichnofossil assemblages in northwest pangea a case for a shallow marine habitable zone early triassic trace fossil assemblages from the northwest margin of pangea record a diverse suite of postextinction infauna these ichnofossil assemblages occurred within well oxygenated shallow marine refuges in a panthalassa ocean otherwise characterized by widespread anoxia we propose an environmentally controlled model for their distribution in which wave aeration enhanced by frequent storms gave rise to an optimal zone for benthic colonization within this habitable zone extinction pressures were ameliorated and postextinction recovery duration was minimized

isotope excursions and palaeotemperature estimates from the permian triassic boundary in the southern alps italy abstract the end permian mass extinction event coincides with a dramatic negative shift in both the 13c and the 18o isotope record at or near the extinction horizon from multiple marine and terrestrial sections round the globe this study has identified the isotope excursions in a shallow water carbonate dominated section at val brutta in the southern alps high resolution bulk rock sampling revealed that there is an average 13ccarb negative shift of 4 and a 18ocarb shift of 6 this is similar to the isotope record at other nearby localities this section like many others shows a degree of recrystallisation which hampers absolute palaeotemperature calculations however some brachiopod fossils including specimens of comelicania and janiceps found within the beds that contain the bulk rock anomaly appear to be remarkably well preserved and still retain their internal structure and the primary isotopic variation across the shell as such they have been successfully analysed and the data used to produce a palaeotemperature estimate at the time of the isotope anomaly of between 26 and 29 c for latest permian

rb sr isotopic ages from late palaeozoic metamorphic rocks of central chile two metamorphic complexes of different lithology and structure crop out in the coast ranges of central chile the tanume metamorphics to the e which belong to a low p t series derived from a continental platform clastic sedimentary sequence give a whole rock isochron age of 347 32 2 ma and the accreted pichilemu metamorphics to the w an age of 311 10 2 ma the latter consist of stilpnomelane bearing cherts crossite bearing metabasites and siliceous metapelites an errorchron of c 370 ma was obtained from sillimanite cordierite gneisses of the low p t series different provenance of the protoliths is indicated by the higher sr 87 sr 86 initial ratios of the tanume rocks 0 7124 0 0007 2 relative to the pichilemu rocks 0 7060 0 0005 2 which were more affected than the former by the main d 2 phase of deformation and metamorphism in the area

permian triassic sedimentology of jameson land east greenland incised submarine channels in an anoxic basin the presence of deeply erosive conglomeratic sandstone filled channels around the permian triassic p tr boundary in east greenland has been widely cited as evidence for a major late permian eustatic lowstand facies analysis of such channels and their associated strata in fact suggests that they record part of an intrinsic style of basinal deposition that persisted into early triassic time their origin can be explained without the need to invoke eustatic sea level fall active faulting and hinterland elevation is envisaged to have generated powerful sediment gravity flows that were capable of submarine erosion of fine grained unconsolidated strata stacked turbidite sandstone filled lenses also occur beneath fan delta sandbodies and probably record infill of channels or chutes cut into the subaqueous slopes of such deltas shale successions developed between the incised channel locations record complete p tr transitions in which a rapid onset of anoxic deposition is seen in latest permian time this is the local manifestation of a global anoxic event unusual aspects of the lower triassic sequence in greenland include the presence of well oxygenated intervals stromatolite bioherms and red algae

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

faunal turnover and changing oceanography late palaeozoic warm to cool water carbonates sverdrup basin canadian arctic archipelago abstract carbonate sedimentary rocks in the fosheim hamilton sub basin at the eastern end of the sverdrup basin contain a particularly sensitive record of changing palaeoceanography and faunal turnover during the northward movement of pangaea through the late palaeozoic carboniferous and earliest permian inner ramp carbonates are a photozoan association of colonial corals fusulinids algae and ooids with sparse heterozoan elements crinoids brachiopods and bryozoans based on modern analogues these biotic components reflect warm water oligotrophic marine environments contemporaneous mid ramp and basin biotas are dominated by a heterozoan fauna solitary corals crinoids bryozoans and brachiopods that grew in cooler deeper waters that may have been beneath a thermocline initial cooling began in the latest sakmarian with an influx of cool deep water and climatic deterioration allowing cool and warm waters to mix disrupting the thermocline and producing a sub tropical marine biota whose remains were reworked by storms and re deposited as tempestites faunas are heterozoan crinoids bryozoans brachiopods and sponges with photozoan elements colonial corals and symbiont bearing fusulinids prominent only in inner ramp facies by late artinskian these photozoan components are only present in shallowest basin margin environments artinskian subtropical waters contained somewhat elevated trophic resources that together with mixing of photozoan and heterozoan elements in the subtropical inner ramp produced the greatest faunal diversity seen in the sverdrup basin the biota was completely boreal in nature and warm shallow waters with a warm refuge biota were now supplemented by cool waters derived from the panthalassa ocean profound change took place in the kungurian coincident with localised uplift during the melville disturbance and increased siliciclastic input neritic storm dominated sediments are wholly heterozoan brachiopods bryozoans crinoids and sponges with no remaining photozoan elements nutrient levels are elevated but not eutrophic as indicated by phosphate and glauconite extensive bioerosion numerous infaunal foraminifers and an impressive and diverse shelly biota that during times of high siliciclastic input was replaced by a profuse zoophycos infauna brachiopod and bryozoan faunas are distinctly boreal continued cooling relatively high nutrients as indicated by abundant glauconite and phosphate and decreased siliciclastic input eventually resulted in an abundant heterozoan biota brachiopods bryozoans crinoids and sponges with local gigantism but reduced brachiopod and bryozoan diversity these middle permian rocks may be the coolest water deposits in the sverdrup basin the faunas are still part of a boreal arctic province with strong ties to cool water faunas of uralian basin the succession ends with late permian biosiliceous spiculitic cherts containing accessory heterozoan components brachiopods bryozoans and few crinoids these sediments in part coeval with evaporites and terrestrial red beds on the eastern european platform are interpreted to reflect a combination of cool waters elevated nutrients and mid latitude storminess

zircon and whole rock nd pb isotopic provenance of middle and upper ordovician siliciclastic rocks argentine precordillera graptolite bearing middle and upper ordovician siliciclastic facies of the argentine precordillera fold thrust belt record the disintegration of a longlived cambro mid ordovician carbonate platform into a series of tectonically partitioned basins a combination of stratigraphic petrographic u pb detrital zircon and nd pb whole rock isotopic data provide evidence for a variety of clastic sediment sources four upper ordovician quartzo lithic sandstones collected in the eastern and central precordillera yield complex u pb zircon age spectra dominated by 1ae05 1ae10 ga zircons secondary populations of 1ae22 1ae30 and 1ae46 ga rare 2ae2 and 1ae8 ga zircons and a minor population 2 of concordant zircons in the 600 700 ma range archaean age grains comprise 1 of all zircons analysed from these rocks in contrast a feldspathic arenite from the middle ordovician estancia san isidro formation of the central precordillera has two well defined peaks at 1ae41 and 1ae43 ga with no grains in the 600 1200 ma range and none older than 1ae70 ga the zircon age spectrum in this unit is similar to that of a middle cambrian quartz arenite from the la laja formation suggesting that local basement rocks were a regional source of ca 1ae4 ga detrital zircons in the precordillera terrane from the cambrian onwards the lack of grains younger than 600 ma in upper ordovician units reinforces petrographic data indicating that ordovician volcanic arc sources did not supply significant material directly to these sedimentary basins nd isotopic data n 32 for middle and upper ordovician graptolitic shales from six localities define a poorly mixed signal end 450 ma 9ae 6t o 4ae5 that becomes more regionally homogenized in upper ordovician rocks 6ae 2 1 ae0 tdm 1ae51 0ae15 ga n 17 a trend reinforced by the u pb detrital zircon data it is concluded that proximal recycled orogenic sources dominated the siliciclastic sediment supply for these basins consistent with rapid unroofing of the precordillera terrane platform succession and basement starting in mid ordovician time common pb data for middle and upper ordovician shales from the western and eastern precordillera n 15 provide evidence for a minor 30 component that was likely derived from a high l u pb terrane

parasequence types in shelfal mudstone strata quantitative observations of lithofacies and stacking patterns and conceptual link to modern depositional regimes mudstone strata have a vast variety of physical biogenic and chemical attributes at the lamina to bed scale approximately millimeters to decimeters thick our observations of more than 7 km of paleozoic to cenozoic mudstones revealed ordered patterns in this variety i e recurrent associations of lithofacies bedding style sedimentary structures and stratal architecture at bedset to parasequence scales approximately decimeters to meters thick we quantified characteristics of each association and their stacking patterns in vertical succession and linked them to sets of depositional processes most shelf mudstone strata appear to have accumulated in one of three facies association successions fass that can be related to depositional regimes through characteristic modes of sediment transport and accumulation as well as variations in benthic energy and oxygen levels we interpret these three fass as records of mud accumulation on different portions of continental shelves that were dominated by storm waves river floods or tidal currents each fas records a distinct parasequence type this approach can help fully integrate insights from oceanographic studies into more robust interpretations of the rock record and rock property maps

abiological origin of described stromatolites older than 3 2 ga the three well documented occurrences of three dimensional stromatolites older than 3 2 ga meet most criteria for biogenicity except the presence of fossil bacteria however they also show features more consistent with nonbiological origins small conical structures in the strelley pool chert in the upper part of the warrawoona group 3 5 3 2 ga western australia lack the structure typical of stromatolites and probably formed mainly through evaporitc precipitation a domal structure from the north pole chert warrawoona group formed by soft sediment deformation or originally flat layers laminated chert containing domal and pseudocolumnar structures in the onverwacht group 3 5 3 3 ga barberton greenstone belt south africa extends downward into veins and cavities where it formed through inorganic precipitation although bacterial communities were widespread on earth prior to 3 2 ga these particular three dimensional structures are probably abiotic in origin and do not provide information on the paleobiology or paleoecology of early organisms the paucity of archean stromatolites older than 3 2 ga probably reflects the paucity of known and possibly extant carbonate deposits of this age

stable carbon and oxygen isotope shifts in permian seas of west spitsbergen global change or diagenetic artifact we performed petrographic cathodoluminescence electron microprobe and isotopic analyses of brachiopod shells from the permian kapp starostin formation in west spitsbergen to reevaluate the 9 negative shift in 13c and 18o values reported in 1989 by m gruszczynski s halas a hoffman and k malkowski the 13c and 18o values within shells typically decrease with increasing luminescence indicating diagenesis nonluminescent nl shell 13c and 18o values are 4 3 and 6 2 higher respectively than those of associated cements and matrix for the same stratigraphic interval 13c and 18o values of the nl shells are equal to or substantially greater than those reported by gruszczynski et al for the interval where those authors saw a 10 13c shift our mostly nl spiriferella polaris shells only yield a 1 5 shift gruszczynski et al reported a 9 18o shift whereas we observe almost none our results strongly suggest that the 9 isotopic shifts reported in gruszczynski et al are diagenetic artifacts on the other hand their kazanian tatarian 13c maximum of 7 5 is substantiated by our data this late permian 13c maximum represents the highest spiriferid brachiopod 13c values in the phanerozoic and within stratigraphic uncertainty correlates with the whole rock 13c maximum in east greenland and northwestern europe the 13c shift may reflect changes in global storage of organic carbon indicated by coal volume changes in the late permian

phase relationships of north atlantic ice rafted debris and surface deep climate proxies during the last glacial period we report stable isotope core scanning xrf and ice rafted detritus ird data in glacial aged sediments from piston core kn166 14 jpc 13 hereafter referred to as jpc 13 retrieved at 53 1 n 33 5 w on the southern gardar drift north atlantic a chronology was established by correlating millennial scale features in the benthic delta 18o record to portuguese margin core md95 2042 once the alignment of benthic delta 18o of jpc 13 to md95 2042 is fixed the relative timing of proxy variables is used to determine the phasing of changes in ird and surface deep hydrography each peak in north atlantic ird coincided with a decrease in benthic delta 18o that in turn has been linked to warming in antarctica events a1 a7 the ird pulses are followed shortly thereafter by abrupt decreases in planktonic delta 18o indicating warming and increased heat transport to the subpolar north atlantic associated with greenland interstadials gis 8 12 14 and 16 17 grain size and elemental k ti variations indicate that iceland scotland overflow water isow was stronger during these long warm interstadial periods of marine isotope stage mis 3 the results are consistent with interhemispheric phase relationships inferred from iberian margin sediment cores and with methane synchronization of greenland and antarctic ice cores

a brachiopod calcite record of the oceanic carbon and oxygen isotope shifts at the permian triassic transition the permian triassic p t mass extinction was the most dramatic of all such events but its cause has thus far remained elusive1 3 carbon and oxygen isotope analyses may offer clues to this puzzle because their results identify major changes in the earth s exosystem4 5 several studies have already dealt with carbon and oxygen isotope records at the p t transition2 6 11 but we present here empirical data derived from the brachiopod shell calcite whose isotope composition generally corresponds to that of the sea water in which the animals lived originally12 15 these data allow us to assess quantitatively the magnitude of changes in the earth s exosystem during that critical time interval

sedimentary fractionations between al ti and zr and the genesis of strongly peraluminous granites sedimentary sorting produces alternating shales and sandstones with complementary chemistries the preferential partitioning of quartz and zircon in the coarse grained fraction of the sediments results in a strong fractionation between sio 2 zr and other components al 2 o 3 tio 2 as a consequence shales may be defined chemically as having higher al 2 o 3 sio 2 and tio 2 zr ratios than their source rocks sandstones have the opposite characteristics and vary in composition according to the maturity of their source and the intensity of sorting processes most sedimentary suites display a good correlation between al 2 o 3 sio 2 and tio 2 zr this result is used to evaluate an average bulk composition for recent clastic materials and to model their composition on a ternary al ti zr diagram because the al 2 o 3 tio 2 ratio of igneous rocks is highly sensitive to magmatic differentiation igneous and sedimentary trends crosscut in the al ti zr di

north atlantic marine rifting in the early triassic new evidence from east greenland two early triassic marine rifting events have been recognized in new outcrop data from east greenland increasing our understanding of this important tectonic episode in the development of the ne atlantic norwegian greenland sea a detailed ammonoid stratigraphy together with stratigraphic and radiometric evidence show that the first rifting event took place in the early griesbachian this event was largely confined to major basin margin faults the second rifting event which involved splay faulting and intra basinal fault block tilt is dated as late griesbachian deposition in east greenland took place in half grabens dominated by deep water gravity flow sandstones and mudstones as well as shallow marine conglomerates and sandstones similarly recent core data from offshore mid norway show that deposition on the eastern margin of the norwegian greenland sea took place in deep marine settings dominated by gravity flows this suggests that the early triassic marine realm extended from east greenland to the present day norwegian coastline and that the marine rift basin was significantly wider than previously thought

palaeotethys seawater temperature rise and an intensified hydrological cycle following the end permian mass extinction abstract the end permian mass extinction has been associated with severe global warming main stage volcanism of the siberian traps occurred at or near the extinction interval and has been proposed as a likely greenhouse catalyst in this study a high resolution 18o record is established using diagenetically resistant apatite of conodonts and low mg calcite of brachiopods from stratigraphically well constrained permian triassic p tr boundary successions in northwestern iran a new evaluation is made for previously published conodont 18o values from south china and revised palaeotemperatures are presented together with new data from wuchiapingian to griesbachian sections in iran 18o data from p tr sections in iran document tropical sea surface temperatures sst of 27 33 c during the changhsingian with a negative shift in 18o starting at the extinction horizon translating into a warming of ssts to over 35 c the results are consistent with re calculated ssts of the south chinese sections warming was associated with an enhanced hydrological cycle involving increased tropical precipitation and monsoonal activity in the tethys sea global warming intensification of the hydrological cycle and associated processes vertical water column stratification eutrophication and subsequent local anoxia may all have facilitated an extinction event

mafic and ultramafic crustal fragments of the southwestern precordillera terrane and their bearing on tectonic models of the early paleozoic in western argentina new u pb zircon ages and initial nd isotope data from mafic and ultramafic rocks that have been tectonically imbricated on the southwest margin of the precordillera terrane western argentina indicate that these rocks do not constitute a single ophiolite pseudostratigraphy as previously thought rock units include late proterozoic 576 17 ma microgabbro and silurian 418 10 ma sills both of which have initial nd isotope values of 6 0 to 7 3 and identical trace element geochemistry indicating formation in extensional settings late ordovician 450 20 ma layered gabbro has a distinct initial nd isotope value of 0 6 it intrudes quartzofeldspathic gneiss and tectonized ultramafic rocks this assemblage represents the deep part of a continental margin volcanic arc that formed on the eastern margin of chilenia as the ocean basin west of the precordillera terrane began to close in the middle ordovician the new tectonic interpretations generally support existing hypotheses that the precordillera terrane rifted and drifted from southeastern laurentia in the cambrian to early ordovician and that the western margin of the precordillera terrane represents a suture between two fragments of continental crust

an integrated biomarker isotopic and palaeoenvironmental study through the late permian event at lusitaniadalen spitsbergen abstract the largest extinction of the phanerozoic occurred near the permian triassic p tr boundary some 252 ma ago several scenarios and drivers have been proposed for this event here we report for the first time an integrated study comprising sedimentological data biomarker distributions abundances and selected stable carbon and hydrogen isotopes along with bulk isotopes 34spyrite 13ccarb 13corg for a late permian section from lusitaniadalen spitsbergen norway sedimentological and geochemical data support a marine transgression and collapse of the marine ecosystem in the late permian strong evidence for waxing and waning of photic zone euxinia throughout the late permian is provided by chlorobiaceae derived biomarkers including 13c data and 34spyrite implying multiple phases of h2s outgassing and potentially several pulses of extinction a rapid decrease in abundance of various land plant biomarkers prior to the marine collapse event indicates a dramatic decline of land plants during the late permian and or increasing distance from palaeoshoreline as a consequence of sea level rise changes in d of selected biomarkers also suggest a change in source of organic matter om or sea level rise we also found biomarker and isotopic evidence for a phytoplanktonic bloom triggered by eutrophication as a consequence of the marine collapse compound specific isotope analyses csia of algal and land plant derived biomarkers as well as 13c of carbonate and bulk om provide strong evidence for synchronous changes in 13c of marine and atmospheric co2 attributed to a 13c depleted source the source could be associated with isotopically depleted methane released from the melting of gas clathrates and or from respired om due to collapse of the marine ecosystem

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

new early triassic bryozoa trepostomata from spitsbergen with some remarks on the stratigraphy of the investigated horizons new trepostomatous bryozoan species paralioclema winsnesi sp nov paralioclema mariaholmensis sp nov and paralioclema sp cf mariaholmensis are described from the lower triassic succession of spitsbergen the investigated bryozoan faunas are associated with coarse sandstones calcareous siltstones and shelly limestones the bryozoan colonies are mostly well preserved in situ and show limited evidence of transportation some zoarial fragments show bioerosion the conodont species neogondolella elongata ellisonia triassica neospathodus dieneri and neospathodus svalbardensis extracted from the investigated horizons are dienerian smithian in age

beyond whole rock geochemistry of shales the importance of assessing mineralogic controls for revealing tectonic discriminants of multiple sediment sources for the ouachita mountain flysch deposits the origin of the ouachita mountains has been the focus of significant debate for decades considerable confusion also exists concerning the provenance of the carboniferous flysch of the ouachitas trace element geochemistry of shales from the stanley group delineates the provenance of the sediments and provides clues to the plate tectonic evolution of the southern continental margin during mississippian time th sc and cr th ratios indicate a cratonic source for the majority of the stanley group sedimentary rocks however in several samples low th sc ratios and high cr th ratios suggest a contribution from a mafic source using element ratio diagrams all of the samples plot along a curve consistent with a two component mixing model consisting of a dominant felsic and a subordinate mafic source the heavy mineral fraction of these shales sequester many of the trace elements used in whole rock studies monazite is ubiquitous in trace amounts and is the probable site for much of the rare earth elements in the whole rock the occurrence of monazite almost exclusively in sialic igneous rocks implies that sm nd isotopic signatures are not sensitive to sediment input from more mafic sources in some stanley shale samples chromite and mn oxides were identified and positively identify an oceanic crustal component as a source of stanley group sediment the results of this study emphasize the importance of determining the mineralogic sites of trace elements and realization of specific mineralogic contributions from mafic or sialic tectonic provenances

basement composition and basin geometry controls on upper crustal deformation in the southern central andes 30 36 s deformation and uplift in the andes are a result of the subduction of the nazca plate below south america the deformation shows variations in structural style and shortening along and across the strike of the orogen as a result of the dynamics of the subduction system and the features of the upper plate in this work we analyse the development of thin skinned and thick skinned fold and thrust belts in the southern central andes 30 36 s the pre andean history of the area determined the formation of different basement domains with distinct lithological compositions as a result of terrane accretions during palaeozoic time the development of a widespread permo triassic magmatic province and long lasting arc activity basin development during palaeozoic and mesozoic times produced thick sedimentary successions in different parts of the study area based on estimations of strength for the different basement and sedimentary rocks calculated using geophysical estimates of rock physical properties we propose that the contrast in strength between basement and cover is the main control on structural style thin v thick skinned and across strike localization of shortening in the study area

anatomy of a mass extinction sedimentological and taphonomic evidence for drought induced die offs at the permo triassic boundary in the main karoo basin south africa abstract the southern part of the karoo basin of south africa contains a near complete stratigraphic record of the permo triassic boundary ptb isotope and magneto stratigraphy confirm that these predominantly fluvial strata are approximately the same age as zircon dated marine ptb sections 252 mya by august 2013 our team had found 579 in situ vertebrate fossils mostly of the clade therapsida in ptb exposures at three widely separated locations in the southern karoo basin biostratigraphic ranges of the various taxa found in each of the sections reveal three separate phases of die off within the same roughly 75 metre thick stratigraphic interval displaying the same sequence of sedimentary facies interpreted as indicative of climatic drying increased seasonality and the onset of an unpredictable monsoon type rainfall regime the three phases of an inferred ecologically stepped mass extinction are phase 1 45 m 30 m below ptb datum brought on by lowered watertables which led to loss of shallow rooting groundcover in the more elevated proximal floodplain areas and the disappearance of the smaller groundcover grazing herbivorous dicynodonts and their attendant small carnivores phase 2 20 0 m below ptb datum is the main extinction that occurs in massive maroon grey mudrock culminating in an event bed of laminated reddish brown siltstone mudstone couplets this facies reflects progressively unreliable rainfall leading to vegetation loss in proximal and distal floodplain areas the larger tree browsing herbivores and their attendant carnivores are confined to watercourses before finally disappearing phase 3 25 30 m above ptb datum occurs in massive maroon siltstone facies with evidence of climatic aridity including the accumulation of mummified carcasses buried by windblown dust all of the surviving permian taxa disappear within 30 m of the ptb temporal resolution based on accretion rates and pedogenic maturity of each stratigraphic section reveals that phase 1 and phase 2 die offs lasted 21 000 and 33 000 years separated by a short period of 7000 years where no disappearances are recorded and this was followed by 50 000 years of stasis for the final extinction phase lasting only 8000 years that removed all the permian survivor taxa we propose that the recorded disappearances are real rather than preferential preservation failure and that they represent drought induced die offs moving progressively up the food chain as the terrestrial ecosystem collapsed the latter mostly likely caused by volcanogenic greenhouse gas emissions and rapid global warming

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

a new high resolution stratigraphic and palaeoenvironmental record spanning the end permian mass extinction and its aftermath in central spitsbergen svalbard abstract research on the permian triassic boundary ptb along the northern margins of pangaea exposed today in the arctic region has been heavily reliant on field observations where data resolution was consequently determined by outcrop condition and accessibility core drilling in central spitsbergen allowed for a near complete recovery of two 90 m cores through the ptb analyses of the core and nearby outcrops include stratigraphic logging and sampling xrf scanning petrography biostratigraphy isotope geochemistry and geochronology the first appearance datum fad of h parvus in svalbard places the base of the triassic ca 4 m above the base of the vikinghogda formation and ca 2 50 m above the end permian mass extinction epme and its associated sharp negative 13c the ptb therefore falls within the reduviasporonites chalastus assemblage zone in svalbard precise u pb tims dating of two zircon crystals in a tephra layer just above the first documented hindeodus parvus in svalbard gives an age of 252 13 0 62 ma high resolution palaeoenvironmental proxies including si kcps kilo counts per second zr rb k ti fe k and v cr indicate a transition towards a more arid climate in the earliest triassic contemporaneous with prolonged bottom water dysoxic anoxic conditions following an increase in volcanic activity in the late permian statistical analysis of zr rb k ti and v cr elemental ratios suggests that the system was impacted by long eccentricity 400 kyr cyclicity the 13c excursion in organic carbon 13corg record signals a large negative carbon isotope excursion cie associated with the mass extinction event but also records a second smaller negative cie ca 22 m above this interval this younger 13corg excursion correlates to similar cies in the dienerian late induan records of other sections notably in the tethys ocean which have been interpreted as recording a small biotic crisis during the post extinction recovery evidence of this negative cie in spitsbergen suggests that the dienerian crisis may have been global in extent the negative 13corg values are associated with evidence for dysoxia or anoxia in the core and the occurrence of tephra layers in the same interval suggests a possible connection between the dienerian crisis and a discrete episode of volcanic activity

the early paleozoic evolution of the argentine precordillera as a laurentian rifted drifted and collided terrane a geodynamic model paleontologic and stratigraphic evidence points to the early paleozoic precordilleran terrane of western argentina as being the conjugate rift pair of the appalachians stratigraphic similarities of the cambrian and early arenig carbonate series and very strong affinities among trilobite conodont and brachiopod faunas show their close relationship the most probable provenance areas are the appalachian ouachita rifted margin and the newfoundland appalachians although the former fits better with geometric and drifting paths suggested by faunal affinities increasing celtic and baltic brachiopod genera and divergent stratigraphy since the arenig indicate the drifting of the precordilleran terrane collisional foredeeps developed on collapsed former platform carbonates as flexural subsidence progressed the collision of the precordillera with western gondwana occurred during the mid llanvirn to llandeilo a magmatic arc related to eastward subduction present coordinates was active in the famatina range east of the precordillera this region of celtic affinity shows faunal exchange with the precordilleran terrane since the late arenig and may represent accreted intra iapetus volcanic island arc complexes the rifting and drifting stages are consistent with paleoclimatic and paleomagnetic data that show the migration of the precordilleran terrane from periequatorial to peripolar latitudes between the cambrian and latest ordovician the deep ocean to the west of the precordillera started to close by the late ordovician with the eastward drift of the chilenian terrane absence of volcanic or pyroclastic arc derived rocks in the precordillera indicate west dipping subduction as chilenia approached the continental margin a new forebulge was established on the former collided precordilleran terrane developing an erosional unconformity in central precordillera talacasto tambolar arch a gondwanic signature was fully developed by the middle silurian when the malvinokaffric clarkeia fauna flourished before then the late ordovician glacial record and associated hirnantia fauna were the first clear tie to gondwana during the silurian the marginal basin behaved as a foreland with lithosphere rheology and eustasy governing the sequence stratigraphy wrench faulting along its eastern boundary displaced the precordillera toward the south continued shortening during closure with the chilenian terrane in the mid devonian produced thrust loading of the basin and generated a thick graywacke succession final accretion of chilenia late devonian generated a regional angular unconformity between the lower and upper paleozoic new eastward subduction was initiated west of the accreted chilenian terrane during the late permian triassic as indicated by the choiyoi volcanic complex which presently outcrops in the frontal cordillera

the proto andean margin of gondwana an introduction a basic background is presented for the discussion of the early palaeozoic geology of western argentina covered by this book this includes the definition and terminology of orogenic cycles on this part of the gondwana margin represented by the eastern sierras pampeanas the pampean orogeny early cambrian relates to an intense but short lived period of terrane collision predating the rifting of the precordillera terrane from laurentia the famatinian cycle is predominantly represented by intense subductionrelated magmatism of early middle ordovician age developed on the continental margin of gondwana during the rifting and drifting of the precordillera terrane the grenvillian basement of the latter is further exemplified by a new rb sr whole rock isochron age of 1021 12 ma for orthogneisses from the western sierras pampeanas a mid ordovician granite in this area dated at 481 6 ma by u pb ion microprobe data may be related to rifting while the precordillera terrane was still attached to laurentia a divergence of opinion is pointed out between some authors in this book who favour mid ordovician collision of the precordillera with gondwana and others who place it much latter in silurian or devonian times

rapid and synchronous collapse of marine and terrestrial ecosystems during the end permian biotic crisis a newly studied permian triassic p tr boundary section in jameson land east greenland contains an abundant and well preserved marine fauna as well as terrestrial palynomorphs for the first time it is possible to compare the biotic crises of the marine and terrestrial realms using the same samples from the same section the sediments record a negative excursion in 13 c carb values of 8 9 and in 13 c org values of 10 11 the presence of the conodont hindeodus parvus combined with the 13 c carb record enables correlation with the proposed global stratotype section at meishan this shows that the greenland section is the most expanded p tr section known collapse of the marine and terrestrial ecosystems took between 10 and 60 k y it took a further few hundred thousand years for the final disappearance of permian floral elements collapse of the terrestrial and marine ecosystems began at the same stratigraphic level and preceded the sharp negative excursion in the 13 c record

the crustal evolution of south america from a zircon hf isotope perspective hf isotope data of 1100 detrital zircon grains from the palaeozoic south central andean gondwana margin record the complete crustal evolution of south america which was the predominant source the oldest grains with crustal residence ages of 3 8 4 0ga are consistent with complete recycling of existing continental crust around 4ga we confirm three major archaean palaeoproterozoic transamazonian and late mesoproterozoic to early neoproterozoic crust addition phases as well as six igneous phases during proterozoic to palaeozoic time involving mixing of juvenile and crustally reworked material a late mesoproterozoic to early neoproterozoic grenville age igneous belt can be postulated along the palaeo margin of south america this belt was the basement for later magmatic arcs and accreted allochthonous microcontinents as recorded by similar crustal residence ages crustal reworking likely dominated over juvenile addition during the palaeozoic era and proterozoic and archaean zircon was mainly crustally reworked from the eroding thickened ordovician famatinian arc

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

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

latest permian to early triassic basin to shelf anoxia in the sverdrup basin arctic canada a combined sequence stratigraphic and geochemical study of the latest permian extinction event in nw pangea provides new insight into the onset and extension of basin anoxia onto the adjacent shallow shelf the latest permian transgression in the sverdrup basin of arctic canada initiated prior to onset of deep water anoxia and continued past the latest permian extinction event deep water anoxia initiated after the shelf was flooded in mid to late changhsingian time requiring a much more rapid and much greater vertical rise in the chemocline than that associated with relative sea level supporting the chemocline upward excursion model our work also extends evidence of global euxinc conditions to nw pangea euxinic conditions developed just prior to the main extinction event and we suggest that this was associated with a significant pyrite rain out event which stripped bio essential nutrients from anoxic seawater prior to the main disruption of the global carbon cycle as recorded by shifts in the carbon isotope record

growth and demise of permian biogenic chert along northwest pangea evidence for end permian collapse of thermohaline circulation abstract the permian chert event pce was a 30 ma long episode of unusual chert accumulation along the northwest margin of pangea and possibly worldwide the onset of the pce occurred at about the sakmarian artinskian boundary in the sverdrup basin canadian arctic where it coincides with a maximum flooding event the ending of high frequency high amplitude shelf cyclicity the onset of massive biogenic chert deposition in deep water distal areas and a long term shift from warm to cool water carbonate sedimentation in shallow water proximal areas a similar and coeval shift is observed from the barents sea to the northwestern usa a landward and southward expansion of silica factories occurred during the middle and late permian at which time warm water carbonate producers disappeared completely from the northwest margin of pangea biotically impoverished and increasingly narrow cold water carbonate factories characterised by non cemented bioclasts of sponges bryozoans echinoderms and brachiopods were then progressively replaced by silica factories by late permian time little carbonate sediments accumulated in the barents sea and in the sverdrup basin where the deep to shallow water sedimentary spectrum was occupied by siliceous sponge spicules by that time biogenic silica sedimentation was common throughout the world silica factories collapsed in the late permian abruptly bringing the pce to an end in northwest pangea the end permian collapse of the pce was associated with a major transgression and with a return to much warmer oceanic and continental climatic conditions chert deposition resumed in the distal oceanic areas during the early middle triassic anisian after a 8 10 ma interruption early triassic chert gap the conditions necessary for the onset expansion and zenith of the pce were provided by the thermohaline circulation of nutrient rich cold waters along the northwestern and western margin of pangea and possibly throughout the world oceans these conditions provided an efficient transportation mechanism that constantly replenished the supply of silica in the area created a nutrient and oxygen rich environment favouring siliceous biogenic productivity established cold sea floor conditions hindering silica dissolution while increasing calcium carbonate solubility and provided conditions adverse to organic and inorganic carbonate production the northwest margin of pangea was for nearly 30 ma bathed by cold waters presumably derived from the seasonal melting of northern sea ice the assumed engine for thermohaline circulation this process started near the sakmarian artinskian boundary intensified throughout middle and late permian time and ceased suddenly in latest permian time it led to oceanic conditions much colder than normally expected from the palaeolatitudes and the influence of cold northerly derived water was felt as far south southern nevada the demise of silica factories was caused by the rapid breakdown of these conditions and the establishment of a much warmer marine environment accompanied by sluggish circulation and perhaps a reduced input of dissolved silica to the ocean complete thawing of northern sea ice would have ended thermohaline circulation and led to warm and sluggish oceanic conditions inimical to the production accumulation and preservation of biogenic silica

provenance and evolution of the guarguariiz complex cordillera frontal argentina abstract the guarguardz complex basement of the cordillera frontal included in the proposed chilenia terrane consists of metasedimentary rocks deposited in clastic and carbonatic platforms turbiditic sequences point out to slope or external platform environments according to geochemical data the sedimentary protoliths derived through erosion of a mature cratonic continental basement volcanic and subvolcanic rocks with n and e morb signature were interbeded in the metasedimentary rocks during basin development a compressional stage starting with progressive deformation and metamorphism followed this extensional stage continuing deformation led to the emplacement of slices of oceanic crust conforming an accretionary prism during late devonian the guarguardz complex and equivalent units in western precordillera and also in the chilean coastal cordillera share common evolutional stages widely represented along the western gondwana margin these evidences imply that chilenia is not an allochthonous terrane to gondwana but a portion of its early paleozoic margin regional configuration indicates that the guarguardz complex and equivalent units represent the accretionary prism of the famatinian arc middle ordovician late devonian

new techniques in sediment core analysis an introduction marine sediment cores are the fundamental data source for information on seabed character depositional history and environmental change they provide raw data for a wide range of research including studies of global climate change palaeoceanography slope stability oil exploration pollution assessment and control and sea floor surveys for laying cables pipelines and siting of sea floor structures during the last three decades a varied suite of new technologies have been developed to analyse cores often non destructively to produce high quality closely spaced co located downcore measurements characterizing sediment physical properties geochemistry and composition in unprecedented detail distributions of a variety of palaeoenvironmentally significant proxies can now be logged at decadal and in some cases even annual or subannual scales allowing detailed insights into the history of climate and associated environmental change these advances have had a profound effect on many aspects of the earth sciences particularly palaeoceanography in this paper we review recent advances in analytical and logging technology and their application to the analysis of sediment cores developments in providing access to core data and associated datasets and data mining technology in order to integrate and interpret new and legacy datasets within the wider context of sea floor studies are also discussed despite the great advances in this field however challenges remain particularly in the development of standard measurement and calibration methodologies and in the development of data analysis methods new data visualization tools and techniques need to be developed to optimize the interpretation process and maximize scientific value amplified collaboration environments and tools are needed in order to capitalize on our analysis and interpretation capability of large multi parameter datasets sophisticated yet simple to use searchable internet databases with universal access and secure long term funding and data products resulting in user defined data mining query and display so far pioneered in the usa and australia provide robust models for efficient and effective core data stewardship

history of crustal growth and recycling at the pacific convergent margin of south america at latitudes 29 36 s revealed by a u pb and lu hf isotope study of detrital zircon from late paleozoic accretionary systems detrital zircon provides a powerful archive of continental growth and recycling processes we have tested this by a combined laser ablation icp ms u pb and lu hf analysis of homogeneous growth domains in detrital zircon from late paleozoic coastal accretionary systems in central chile and the collisional guarguaraz complex in w argentina because detritus from a large part of w gondwana is present here the data delineate the crustal evolution of southern south america at its paleopacific margin consistent with known data in the source regions zircon in the guarguaraz complex mainly displays an u pb age cluster at 0 93 1 46 ga similar to zircon in sediments of the adjacent allochthonous cuyania terrane by contrast zircon from the coastal accretionary systems shows a mixed provenance age clusters at 363 722 ma are typical for zircon grown during the braziliano pampean famatinian and post famatinian orogenic episodes east of cuyania an age spectrum at 1 00 1 39 ga is interpreted as a mixture of zircon from cuyania and several sources further east minor age clusters between 1 46 and 3 20 ga suggest recycling of material from cratons within w gondwana the youngest age cluster 294 346 ma in the coastal accretionary prisms reflects a so far unknown local magmatic event also represented by rhyolite and leucogranite pebbles it sets time marks for the accretion history maximum depositional ages of most accreted metasediments are middle to upper carboniferous a change of the accretion mode occurred before 308 ma when also a concomitant retrowedge basin formed initial hf isotope compositions reveal at least three juvenile crust forming periods in southern south america characterised by three major periods of juvenile magma production at 2 7 3 4 ga 1 9 2 3 ga and 0 8 1 5 ga the 176hf 177hf of mesoproterozoic zircon from the coastal accretionary systems is consistent with extensive crustal recycling and addition of some juvenile mantle derived magma while that of zircon from the guarguaraz complex has a largely juvenile crustal signature zircon with pampean famatinian and braziliano ages 660 ma originated from recycled crust of variable age which is however mainly mesoproterozoic by contrast the carboniferous magmatic event shows less variable and more radiogenic 176hf 177hf pointing to a mean early neoproterozoic crustal residence this zircon is unlikely to have crystallized from melts of metasediments of the accretionary systems but probably derived from a more juvenile crust in their backstop system

early carboniferous sub to mid alkaline magmatism in the eastern sierras pampeanas nw argentina a record of crustal growth by the incorporation of mantle derived material in an extensional setting a recently discovered granitic intrusion at cerro la gloria in western sierra de famatina nw argentina is representative of sub to mid alkaline carboniferous magmatism in the region the main rock type consists of microcline quartz and plagioclase with amphibole magnetite ilmenite biotite epidote zircon allanite and sphene as accessory minerals we report a u pb zircon shrimp age for the pluton of 349 3 ma mswd 1 1 i e tournaisian whole rock chemical composition and nd isotope analyses are compatible with an origin by melting of older mafic material in the lower crust endt between 0 58 and 0 46 and tdm values of about 1 1 ga the pluton is intruded by penecontemporaneous to late alkaline mafic dykes that are classified as back arc basalts coeval early carboniferous a type granites occur farther east in the sierras pampeanas probably generated during lithospheric stretching overall the early carboniferous granitic rocks show a west to east mineralogical and isotopic zonation indicating that magma genesis involved a greater contribution of juvenile material of mantle character to the west based on the observed patterns of geochronology geochemistry and field relationships we suggest that a type magma genesis in the eastern sierras pampeanas was linked to an andean type margin where the lithospheric mantle played a role in its generation

a depositional and sequence stratigraphic model for cold water spiculitic strata based on the kapp starostin formation permian of spitsbergen and equivalent deposits from the barents sea this article summarizes the lithostratigraphy of two sections through the kapp starostin formation on spitsbergen having contrasting distal and proximal depositional settings these outcrop sections are compared with an approximately age equivalent spiculitic unit penetrated in two exploration wells 800 km to the southeast on the finnmark platform eight main facies associations comprise these strata including limestones matrix rich matrix poor and mudstone siliciclastics shale and sandstone spiculite dark tight and light colored porous and phosphatized surfaces a sequence stratigraphic model is proposed wherein siliciclastic limestone intervals represent lowstands of relative sea level and the spiculites are mainly highstand deposits based on this model seven depositional cycles sequences are recognized in the distal high accommodation locality on spitsbergen akseloya four in the proximal locality dickson land and two on the finnmark platform a speculative model for correlation between these localities is presented wherein lateral amalgamation of sequences due to landward pinch out of some lowstand intervals results in recognition of fewer sequences in areas of lower accommodation on both dickson land and the finnmark platform an upward change in spiculite lithology from dark tight to light porous is shown and dickson land also shows an upward change in siliciclastic lithology from shale to glauconitic sandstone these changes record a long term shoaling trend approaching the permian triassic boundary this model provides a basis for interpreting the basin scale begin page 2062 distribution of lithofacies and predicting the occurrence of porous zones representing potential hydrocarbon reservoirs

causes and consequences of extreme permo triassic warming to globally equable climate and relation to the permo triassic extinction and recovery permian waning of the low latitude alleghenian variscan hercynian orogenesis led to a long collisional orogeny gap that cut down the availability of chemically weatherable fresh silicate rock resulting in a high co2 atmosphere and global warming the correspondingly reduced delivery of nutrients to the biosphere caused further increases in co2 and warming melting of polar ice curtailed sinking of o2 and nutrient rich cold brines while pole to equator thermal gradients weakened wind shear and associated wind driven upwelling lessened further diminishing productivity and carbon burial as the earth warmed dry climates expanded to mid latitudes causing latitudinal expansion of the ferrel circulation cell at the expense of the polar cell increased coastal evaporation generated o2 and nutrient deficient warm saline bottom water wsbw and delivered it to a weakly circulating deep ocean warm deep currents delivered ever more heat to high latitudes until polar sinking of cold water was replaced by upwelling wsbw with the loss of polar sinking the ocean was rapidly filled with wsbw that became increasingly anoxic and finally euxinic by the end of the permian rapid incursion of wsbw could have produced 20 m of thermal expansion of the oceans generating the well documented marine transgression that flooded embayments in dry hot pangaean mid latitudes the flooding further increased wsbw production and anoxia and brought that anoxic water onto the shelves release of co2 from the siberian traps and methane from clathrates below the warming ocean bottom sharply enhanced the already strong greenhouse increasingly frequent and powerful cyclonic storms mined upwelling high latitude heat and released it to the atmosphere that heat trapped by overlying clouds of its own making suggests complete breakdown of the dry polar cell resulting rapid and intense polar warming caused or contributed to extinction of the remaining latest permian coal forests that could not migrate any farther poleward because of light limitations loss of water stored by the forests led to aquifer drainage adding another 5 m to the transgression non peat forming vegetation survived at the newly moist poles climate feedback from the coal forest extinction further intensified warmth contributing to delayed biotic recovery that generally did not begin until mid triassic but appears to have resumed first at high latitudes late in the early triassic current quantitative models fail to generate high latitude warmth and so do not produce the chain of events we outline in this paper future quantitative modeling addressing factors such as polar cloudiness increased poleward heat transport by deep water and its upwelling by cyclonic storms and sustainable mid latitude sinking of warm brines to promote anoxia warming and thermal expansion of deep water may more closely simulate conditions indicated by geological and paleontological data

explosive eruption of coal and basalt and the end permian mass extinction the end permian extinction decimated up to 95 of carbonate shell bearing marine species and 80 of land animals isotopic excursions dissolution of shallow marine carbonates and the demise of carbonate shell bearing organisms suggest global warming and ocean acidification the temporal association of the extinction with the siberia flood basalts at approximately 250 ma is well known and recent evidence suggests these flood basalts may have mobilized carbon in thick deposits of organic rich sediments large isotopic excursions recorded in this period are potentially explained by rapid venting of coal derived methane which has primarily been attributed to metamorphism of coal by basaltic intrusion however recently discovered contemporaneous deposits of fly ash in northern canada suggest large scale combustion of coal as an additional mechanism for rapid release of carbon this massive coal combustion may have resulted from explosive interaction with basalt sills of the siberian traps here we present physical analysis of explosive eruption of coal and basalt demonstrating that it is a viable mechanism for global extinction we describe and constrain the physics of this process including necessary magnitudes of basaltic intrusion mixing and mobilization of coal and basalt ascent to the surface explosive combustion and the atmospheric rise necessary for global distribution

tectono stratigraphic evolution of the andean orogen between 31 and 37 s chile and western argentina fil charrier reynaldo universidad de chile facultad de ciencias fisicas y matematicas departamento de geologia chile universidad andres bello chile

the paleocene eocene thermal maximum petm in svalbard clay mineral and geochemical signals abstract for the first time the paleocene eocene thermal maximum petm interval has been identified in drillcores and field outcrops from the paleogene central basin in svalbard based on mineralogical and geochemical information grumantbyen and frysjaodden formations a more than 300 m thick paleogene interval representing deltaic delta influenced marine shelf and deep water slope environments the petm has been recognized in the deepest and most distal deposits in the lower parts of the frysjaodden formation here this global event is displayed in clay mineralogical distributions as significantly increased kaolinite abundances reflecting a period with intensified chemical weathering in the land areas surrounding this paleogene basin the period was characterized by dominantly reducing sea floor conditions as seen in the th u distribution and the well developed parallel lamination in the pyrite rich shales all to be expected during an interval with increased temperature and precipitation

biogeochemical evidence for euxinic oceans and ecological disturbance presaging the end permian mass extinction event article i nfo the permian triassic boundary event at 252 2 ma marks the largest extinction of marine fauna in the phanerozoic and there is a wide consensus that the extinction coincided with an intense oceanic anoxic event thestratotypeofthechanghsingianstage preciselyconstrainedbytheptbglobalstratotypesectionandpoint gssp and the gssp for the wuchiapingian changhsingian boundary both at meishan in southern china is well documented in respect to geochronology and the pattern of extinction here we report secular trends in bulk isotopic parameters and lipid biomarkers in a core spanning 214 m of stratigraphic section across the ptb and through the entire changhsingian interval our analysis of these data viewed in the context of relative sea level change and strontium isotopes reveals distinct shifts in paleoenvironmental conditions and profound changes in plankton ecology well before and following the biological extinction event specifically patterns of steroids and triterpenoids indicate a marine plankton community that was heavily dominated by bacteria during the late wuchiapingian middle changhsingian and early griesbachian stages secular trends in aromatic hydrocarbons diagnostic for anoxygenic green sulphur bacteria chlorobiaceae identify periods when euxinic conditions extended into the photic zone during the entire changhsingian stage here also the 15

siberian gas venting and the end permian environmental crisis abstract the end of the permian period is marked by global warming and the biggest known mass extinction on earth the crisis is commonly attributed to the formation of the siberian traps large igneous province although the causal mechanisms remain disputed we show that heating of tunguska basin sediments by the ascending magma played a key role in triggering the crisis our conclusions are based on extensive field work in siberia in 2004 and 2006 heating of organic rich shale and petroleum bearing evaporites around sill intrusions led to greenhouse gas and halocarbon generation in sufficient volumes to cause global warming and atmospheric ozone depletion basin scale gas production potential estimates show that metamorphism of organic matter and petroleum could have generated 100 000 gt co2 the gases were released to the end permian atmosphere partly through spectacular pipe structures with kilometre sized craters dating of a sill intrusion by the u pb method shows that the gas release occurred at 252 0 0 4 million years ago overlapping in time with the end permian global warming and mass extinction heating experiments to 275 c on petroleum bearing rock salt from siberia suggests that methyl chloride and methyl bromide were significant components of the erupted gases the results indicate that global warming and ozone depletion were the two main drivers for the end permian environmental crisis we demonstrate that the composition of the heated sedimentary rocks below the flood basalts is the most important factor in controlling whether a large igneous provinces causes an environmental crisis or not we propose that a similar mechanism could have been responsible for the triassic jurassic 200 ma global warming and mass extinction based on the presence of thick sill intrusions in the evaporite deposits of the amazon basin in brazil

acid rain and ozone depletion from pulsed siberian traps magmatism the siberian traps flood basalts have been invoked as a trigger for the catastrophic end permian mass extinction widespread aberrant plant remains across the permian triassic boundary provide evidence that atmospheric stress contributed to the collapse in terrestrial diversity we used detailed estimates of magmatic degassing from the siberian traps to complete the first three dimensional global climate modeling of atmospheric chemistry during eruption of a large igneous province our results show that both strongly acidic rain and global ozone collapse are possible transient consequences of episodic pyroclastic volcanism and heating of volatile rich siberian country rocks we suggest that in conjunction with abrupt warming from greenhouse gas emissions these repeated rapidly applied atmospheric stresses directly linked siberian magmatism to end permian ecological failure on land our comprehensive modeling supplies the first picture of the global distribution and severity of acid rain and ozone depletion providing testable predictions for the geography of end permian environmental proxies

evidence for a diachronous late permian marine crisis from the canadian arctic region a high resolution chemostratigraphic study of a 24 m thick section at west blind fiord on ellesmere island canadian arctic documents stepwise environmental deterioration in the marine sverdrup basin during the late changhsingian late late permian as a result of volcanic disturbances to surrounding landmasses a horizon within the upper lindstrom formation datum a is characterized by increased fe oxyhydroxide fl uxes and weathering intensity as well as modest shifts toward more reducing watermass conditions and higher marine productivity recording an initial disturbance that washed soils into the marine environment the contact between chert of the lindstrom formation and silty shale of the overlying blind fiord formation which is 1 6 m higher and 50 k y younger than datum a records a large increase in detrital sediment fl ux more strongly enhanced marine productivity and a regional extinction of siliceous sponges herein termed the arctic extinction event the horizon equivalent to the latest permian mass extinction of tethyan shallow marine sections is 5 6 m higher and 100 k y younger than the arctic extinction event demonstrating the diachronous nature of the marine biotic and environmental crisis at a global scale it is associated with intensifi ed anoxia and possible changes in phytoplankton community composition in the study section marine environmental deterioration in the sverdrup basin probably triggered by terrestrial ecosystem deterioration and elevated detrital sediment fl uxes was under way by the early part of the late changhsingian well before the onset of main stage siberian traps fl ood basalt volcanism the event sequence at west blind fiord may record the deleterious effects of early stage explosive silicic eruptions that affected the boreal region possibly through deposition of toxic gas and ash within a restricted latitudinal band while having little impact on marine ecosystems in the peri equatorial tethyan region