facies and sequence controls on the appearance of the cambrian biota in southwestern mongolia implications for the precambrian cambrian boundary neoproterozoic cambrian rocks of the zavkhan basin govi altay western mongolia com prise large scale alternations of siliciclastic and carbonate dominated units cf grand cycles analysis of such dcpositional sequences near the base of the cambrian confirms that the distribution of trace fossils small shelly fossils and calcimicrobial structures was strongly controlled by ecology and taphonomy corre sponding to specific points in a sea level cycle evolution of the cambrian biota is thus viewed through a series of narrow time windows once only for each dcpositional cycle correlation of the precambrian cambrian boundary level on the basis of the first appearance of the phycodes pedum assem blage is also fraught with difficulty since stratigraphic resolution may be limited to a single sea level cycle c 1 5 ma it is suggested that in many cases basin analysis will need to be undertaken before this bound ary can be drawn

proterozoic supercontinent its latest precambrian rifting breakup dispersal into smaller continents and subsidence of their margins evidence from asia several large cratons and numerous smaller blocks all with precambrian sialic crust are seen clearly in the present day structure of asia the outer parts of larger precambrian terranes and entire smaller ones are covered with vendian early paleozoic shallow water carbonate sedimentary rocks coupled with the so called old late vendian early cambrian phosphorites in siberia southern china india kazakhstan and mongolia these sedimentary rocks are interpreted to represent a global belt of near equatorial sedimentation on passive continental margins of numerous vendian early paleozoic continents with free access to the world ocean later precambrian rifting is recorded clearly in many precambrian terranes of asia rifting was repeated during cenozoic time with the same pattern and in the same places it was preceded and accompanied by various magmatic activity from 750 to 600 ma tillites filling rifts are about 650 ma and are believed to be a feature of a single proterozoic super continent rift to drift transition as attested by the beginning of thick and laterally continuous carbonate sedimentation on passive margins seems to be diachronous it started in early vendian time or even earlier in some places but not earlier than cambrian in others

fossil microbial communities in neoproterozoic interglacial rocks maikhanuul formation zavkhan basin western mongolia abstract glaciogenic deposits are widely distributed in the neoproterozoic successions around the world but only few of them are associated with occurrences of authentic macroscopic fossils problematical circular remains recovered from intertillite beds of the neoproterozoic maikhanuul formation zavkhan basin western mongolia may be a new record of biogenic structures in ancient glacial rocks the maikhanuul tillites were deposited between 732 and 777 ma the underlying volcanic rocks of the neoproterozoic dzabkhan formation and 632 14 ma the overlying limestones of the ediacaran nemakit daldynian tsagaanolom formation the assemblage of microfossils from the tsagaanolom formation is comparable to the assemblage known from the 635 551 ma doushantuo formation of south china the maikhanuul glacial event may therefore be correlated with the 635 ma nantuo glaciation morphological taphonomic biometric and geochemical observations have allowed us to interpret the problematical circular remains from the maikhanuul tillites as microbial communities preserved in situ on the floor of an ancient glacial basin many discoidal fossils from precambrian strata have been compared with extant microbial colonies that have a similar external morphology however ultrastructure of the hypothetical precambrian microbial communities to the best of our knowledge has not previously been reported scanning electron microscopy of the circular remains from the maikhanuul tillites revealed rod shaped filamentous and star shaped bacteriomorph structures some microremains and especially the star shaped particles are considerably enriched in iron up to 50 that may be attributed to bacterial activity furthermore the star shaped microremains can be compared with modern star shaped bacteria known from freshwater and terrestrial environments and with aggregates of biogenic nanohematite although the presence of microbial communities could not be used for global correlation it does provide information on prokaryotic diversity and ecology as well as on palaeoenvironmental conditions

the heterodonty of albertosaurus sarcophagus and tyrannosaurus rex biomechanical implications inferred through 3 d modelsthis article is one of a series of papers published in this special issue on the theme albertosaurus the objective of this study is to analyze how different crown morphologies and different root lengths respond to stresses generated by the bite forces of albertosaurus sarcophagus and tyrannosaurus rex six well preserved teeth of a sarcophagus from the albertosaurus bonebed in dry island park southern alberta were selected to study their biomechanics and t rex teeth were included for comparison the three dimensional 3 d models were obtained through computerized tomography ct scanning and 3 d digitizing finite element analyses were performed in strand7 bite forces for albertosaurus and tyrannosaurus were calculated based on cranial and jaw proportions the results were viewed with the tresca yield criterion the ratios of shear stresses observed along the mesio distal versus labio lingual axes of all models allows the identification of similar stress distribution patterns in the upper and lower jaws of albertosaurus and the upper jaws of tyrannosaurus with a higher amount of shear along the

gravitational slope deformation of a resurgent caldera new insights from the mechanical behaviour of mt nuovo tuffs ischia island italy abstract ischia island italy is an impressive example of the rare phenomenon of caldera resurgence the emplacement and replenishment of magmas at shallow depth resulted in a vertical uplift of about 900 m concentrated in the western portion of mt epomeo 789 m a s l as a consequence of this uplift the island has experienced several slope instabilities at different scales since the holocene from shallow mass movements to large rock and debris avalanches these mass wasting events which mobilised large volumes of greenish alkali trachytic tuff the mt epomeo green tuff megt were strictly related to volcano tectonic activity and the interaction between the volcanic slopes and the hydrothermal system beneath the island deep seated gravitational slope deformation dsgsd at mt nuovo located adjacent to densely populated coastal villages is an ongoing process that covers an area of 1 6 km 2 the mt nuovo dsgsd involves a rock mass volume of 190 mm 3 and is accommodated by a main shear zone and a series of sub vertical fault zones associated with high angle joint sets to improve our understanding of this gravity induced process we performed a physical porosity and permeability and mechanical uniaxial and triaxial deformation experiments characterisation of two ignimbrite deposits both from the megt that form a significant component of the nw sector of mt epomeo the main conclusions drawn from our experiments are twofold first the presence of water dramatically reduces the strength of the tuffs suggesting that the movement of fluids within the hydrothermal system could greatly impact slope stability second the transition from brittle dilatant to ductile compactant behaviour in the tuffs of the megt occurs at a very low effective pressure analogous to a depth of a couple of hundred metres and that this transition is likely moved closer to the surface in the presence of water we hypothesise that compactant porosity decreasing behaviour at the base of the layer could therefore facilitate slope instability although our results show that transient exposure to 300 c does not influence the short term strength of the tuff we speculate that the high in situ temperature could increase the efficiency of brittle and compactant creep and therefore increase the rate of slope deformation taken together our experimental data highlight a potentially important role for the hydrothermal system that reaches a minimum depth of 1 km in dictating the dsgsd at mt nuovo an understanding of this deformation process is not only important for the proximal coastal villages at risk of engulfment by a large debris avalanche but also for the towns and cities along the coast of the gulf of naples that are at risk to a secondary consequence of such an avalanche a tsunami wave

the significance of the theropod collections of the royal tyrrell museum of palaeontology to our understanding of late cretaceous theropod diversity1 significant specimens of theropod dinosaurs were part of the collections that were transferred to the royal tyrrell museum of palaeontology when it split off from the provincial museum of alberta in 1981 collecting activity of the institution increased dramatically in the period leading up to the opening of the building and displays in 1985 and resulted in the recovery and preparation of many fine theropod skeletons new specimens have been added to the collection every year since the museum opened several mostly small taxa are only represented by isolated bones partial skeletons and or teeth theropod specimens also include footprints coprolites eggs and feathers in amber although theropods are relatively rare in comparison with herbivorous dinosaurs the tyrrell has managed to build one of the finest research collections of late cretaceous forms thirty seven species of theropods in the tyrrell are currently accepted as being valid of which 30 are from the upper cretaceous deposits of alberta

glacial facies associations in a neoproterozoic back arc setting zavkhan basin western mongolia diamictites many of glacial origin are globally distributed in the neoproterozoic recently two relatively thin diamictites in the maikhan uul member at the base of the neoproterozoic tsagaan oloom formation from the zavkhan basin of western mongolia have been identified as being of glacial origin the mongolian diamictites form a series of backstepping units within the transgressive systems tract of two major depositional sequences associated with sea level changes in each case the diamictites of the transgressive systems tract are abruptly overlain by deeper water upward shoaling highstand systems tracts consisting of thinly bedded sandstones and shales in sequence 1 and thinly bedded dark carbonates in sequence 3 the fact that the sequences conform closely to depositional models established at other localities suggests that all are related to major ice ages and that the depositional sequences they have generated provide a valuable tool for global correlation in this part of the stratigraphic column available stratigraphic and isotope geochemical information presented by brasier et al 1996 this issue suggests that both diamictites are likely to be of sturtian age a riftogenic setting and sturtian age for the diamictites provide a link with eastern australia and western america it is possible therefore that these diamictites formed during the breakup of a supercontinental assembly including siberia australia and laurentia c 750 725 ma bp

systematics of chlorite alteration at the phelps dodge massive sulfide deposit matagami quebec hydrothermal alteration at the phelps dodge archcan volcanogenic massive sulfide deposit has converted rhyodacite and rhyolite footwall rocks into the following mineral assemblages quartz chlorite albite epidote or sericite quartz chlorite or sericite chlorite or sericite and chlorite talc or stilpnomelane alteration at constant al was initiated by hydration addition of fe mg silicification and leaching of ca na which produced al saturated chlorites with a wide range of fe fe mg ratios within the assemblage quartz chlorite albite epidote or sericite with continued addition of fe and less mg combined with extensive leaching of quartz the chlorite became al undersaturated quartz chlorite talc assemblage and ultimately formed a rock composed essentially of chlorite the chlorite talc or stilpnomelane assemblage is stable in late crosscutting veinlets and in the ore zone chlorites in the si al mg fe system form a rectangular solid solution plane with limited substitution of al for si and extensive substitution of fe for mg in si al space the solid solution plane is outlined by al saturation presence of other al rich mineral and al undersaturation presence of al poor or al free mineral boundaries al iv substitution for si in the chlorites increases from 2 3 to 3 01 formula units based on 8 si al iv with fe fe mg whereas al iv occupancy decreases from 2 88 to 2 65 the valence charge balance is compensated by octahedral site vacancies or by the conversion of fe super 2 to fe super 3 the al iv content of chlorite also increases with temperature chlorites on the al saturated boundary of the solid solution field form a potentially useful geothermometer t degrees c 106 al iv 18 al iv is corrected for changes with the fe fe mg ratio as al iv corrected al iv 0 7 fe fe mg the fe fe mg ratios of bulk rock and contained chlorite correlate well birefringence colors of the chlorite change from green to brown violet and berlin blue as fe fe mg changes from 0 18 to 0 64 the fe fe mg variation apparently depends largely on the proportions of mg rich seawater and fe rich hydrothermal fluid in the altering brine

cooling rates of plinian fall and pyroclastic flow deposits in the bishop tuff inferences from water speciation in quartz hosted glass inclusions cooling rates inferred from water speciation in rhyolitic glass inclusions in quartz phenocrysts from the bishop tuff california vary over more than 5 orders of magnitude from about 10 to 10 4 c s 1 many of the cooling rates are within the previously published experimentally calibrated range of this technique but the slowest rates 10 4 c s 1 are extrapolated such extrapolation suggests cooling rates as low as 10 8 c s 1 0 3 c year 1 for the interiors of thick pyroclastic flow deposits the temperatures at which oh and molecular h2o species would be in equilibrium range from 400 c for glass inclusions from plinian fall deposits to 250 c for the most slowly cooled glassy inclusions from pyroclastic flow deposits notwithstanding appreciable uncertainties cooling rates correlate with depositional process fall vs flow deposition and distance above the cold ground or below overlying hot pyroclastic flow deposits plinian inclusions within 2 5 m of the cold pre bishop ground cooled at 1 10 c s 1 consistent with thermal modeling of small pumice clasts falling through cold air very slow inferred cooling rates for pyroclastic flow deposits 10 6 to 10 8 c s 1 also agree with thermal conduction models faster cooling rates 10 1 to 10 4 c s 1 for inclusions in the lowermost 0 5 m of pyroclastic flow deposits reflect the effect of quenching against the cold ground at blind spring hill east of long valley caldera intermediate cooling rates 10 3 to 10 6 c s 1 are observed in plinian deposits overlain by and partially interbedded with pyroclastic flow deposits indicating that reheating of rapidly cooled plinian inclusions can reset water speciation melt inclusions in pyroclastic flow deposits are quenched to glass only if the deposit is relatively thin or has a relatively low emplacement temperature in relatively thick or hot deposits inclusions may be quenched to glass at the base of the deposit where it is more rapidly cooled by contact with the pre eruption ground

exhumation of an active magmatic hydrothermal system in a resurgent caldera environment the example of ischia italy abstract ischia is a rare case of a well exposed caldera system that has experienced rapid recent resurgence which can be used to dissect the anatomy of an otherwise inaccessible active hydrothermal system developed in a caldera forming environment integrated analyses of melt and fluid inclusions mineralogy and stable isotopic compositions of pumices tuffs and syenitic xenoliths of the ischia volcanic system provide strong physico chemical constraints on the shallow magmatic reservoir and the hydrothermal system the hydrothermal system has been exposed by the rapid uplift of the mt epomeo resurgent block the engine of the hydrothermal system of ischia can be identified in the shallow magmatic system at around 2 km depth that hosts hot c 1000 c trachytic magma the hydrothermal system developed principally within thick intracaldera ignimbrite deposits and extended to a depth of at least 1 km defining a series of facies characterized by associations of alteration mineral assemblages typical of a seawater dominated high temperature geothermal system supplementary material sample descriptions and analytical methods are available at http www geolsoc org uk sup18371

shear wave velocity and attenuation structure of ischia island using broad band seismic noise records abstract in volcanic areas accurate localization of earthquakes requires detailed velocity and possibly attenuation models taking into account wide lithological variability and high geothermal gradients ischia island campania region italy is a seismically active volcano recently affected by a mw 3 9 event casamicciola august 21 2017 1 km depth due to the lack of a specific velocity model the earthquakes occurred on the island were localized using the one developed for the nearby campi flegrei caldera the aim of this work is the definition of a mean representative 1d shear wave velocity vs and attenuation q model of the shallower crust up to 2 km depth of ischia seismic noise array and spectral ratios techniques were applied to broad band seismic signals recorded by temporary and permanent networks updated after the august 2017 earthquake the values of both shear wave velocity vs and quality factor q are realistic with q values comparable with those obtained for campi flegrei and stromboli volcanic areas by taking into account stratigraphic information from deep wells and ultrasonic measurements of velocity on granite and trachytic lava samples a geological interpretation of the resulting velocity model is provided such a model can have significant implications for understanding the dynamics of a volcano mainly those leading to seismic activity

the postcranial skeleton of monolophosaurus jiangi dinosauria theropoda from the middle jurassic of xinjiang china and a review of middle jurassic chinese theropods the middle jurassic was a critical time in the evolution of theropod dinosaurs highlighted by the origination and radiation of the large bodied and morphologically diverse tetanurae middle jurassic tetanurans are rare but have been described from europe south america and china in particular china has yielded a number of potential basal tetanurans but these have received little detailed treatment in the literature here we redescribe the postcranial skeleton of one of the most complete chinese middle jurassic theropods monolophosaurus several features confirm the tetanuran affinities of monolophosaurus but the possession of primitive traits such as a double faceted pubic peduncle of the ilium and a hood like supracetabular crest suggest a basal position within tetanurae this conflicts with most published cladistic analyses that place monolophosaurus in a more derived position within allosauroidea we review the middle jurassic record of chinese theropods and compare monolophosaurus to other middle jurassic theropods globally these comparisons suggest that monolophosaurus and chuandongocoelurus formed an endemic theropod clade limited to the middle jurassic of asia other middle jurassic chinese theropods deserve further study

taphonomy of jack s birthday site a diverse dinosaur bonebed from the upper cretaceous two medicine formation of montana jack s birthday site is a diverse vertebrate assemblage from the upper two medicine formation of western montana age is roughly 74 ma the site covers roughly 3000 m2 and excavations over 140 m2 a large bone sample 1600 skeletal elements allowed statistical evaluation of the preservational and compositional variation within the site evidence including sedimentary facies plant and invertebrate fossils and bone orientation and condition indicates jack s birthday site represents part of a small shallow floodplain lake lithologies and fossil preservation vary from northwest to southeast over a distance of 50 m this variation represents a transition from lake through shoreline to marginal shoreline floodplain environments containing ten dinosaur taxa and a variety of non dinosaurs jack s birthday site provides one of the best single faunal samples of the region the vertebrate assemblage includes two taphonomic fractions the first consisting of attritional predominantly isolated and allochthonous elements represents a time averaged assemblage the other consists of associated parautochthonous remains restricted to a single horizon taxa represented by associated remains include three iguanodontoids hypacrosaurus prosaurolophus and gryposaurus and the theropod troodon associated individuals of these taxa have non random distributions within the site fisher s exact test p 0 01 and observed taxonomic clustering may reflect group behavior and or event mortality the four or more troodon represent the first described multi individual troodontid occurrence the diversity and spatial complexity of the parautochthonous fraction of the birthday site assemblage is difficult to explain discussion of possible event mortality mechanisms focuses on three drought botulism and cyanobacterial toxicosis these share an ability to act over an ecologically significant period of time affect a variety of species and concentrate mortality along water sources aspects that may have been important in generating the birthday site assemblage evidence at the site favors drought or perhaps a drought botulism hypothesis however taxonomic clusters could represent completely separate events with a variety of causes

the ischia volcanic island southern italy inferences from potential field data interpretation abstract in this paper we present a study of the structural setting of the volcanic island of ischia by the analysis and interpretation of high resolution aeromagnetic and self potential data recently acquired over the island the magnetic data allowed us to locate the main anomaly sources and lineaments of the island and its offshore surroundings while the self potential sp data provided information on both the structural pattern of the resurgent caldera and the high temperature fluid circulation an inversion of the acquired magnetic and sp data and a joint modelling of the magnetic data and of a previous gravity data set along a sw ne profile allowed us to build a model of the island the model is characterized by the presence of an igneous very likely trachytic structure whose top is located at 1200 1750 m b s l such a body possibly formed by several neighbouring intrusions has a density contrast with the pyroclastic cover of about 0 4 gr cm 3 and its central western part below mt epomeo seems to be demagnetized the demagnetization should be connected to the high geothermal gradient measured in this portion of the island and may be due to hydro chemical alteration processes and or to the possible presence of partially melted spots within the intrusion our outcome is consistent with the results of previous geophysical geo volcanological and geothermal studies

the crystallization of shoshonitic to peralkaline trachyphonolitic magmas in a h2o cl f rich environment at ischia italy with implications for the feeder system of the campania plain volcanoes abstract bulk rock and mineralogical characterization of massive samples lava flows lava domes scoria spatter chosen to be representative of different activity periods and of the whole known compositional range of ischia island roman magmatic province campanian district is reported in this paper the rocks vary in composition from shoshonites to peralkaline trachyphonolites crystallization started with al rich chromite inclusions and their host magnesian olivine in shoshonites and latites and ended with lavenite rinkite kochite hiortdahlite hainite mn aenigmatite britholite and ti zr rich aegirine in the groundmass of the peralkaline trachyphonolites removal of feldspar bearing assemblages with calcic to sodic plagioclase in shoshonites and latites sodic sanidine and anorthoclase in trachytes and trachyphonolites is established throughout the compositional range and is accompanied by interaction between variably evolved magmas with their differing phenocryst assemblage mostly in mafic and intermediate compositions this led to enrichment in mn alkalis zr nb ree rb th u cl and f and depletion in mg fe v ca ba sr and eu in the most evolved magmas the ischian rocks have a tendency to sodic affinity and by peculiar mineral compositions and compositional trends which do not indicate extremely oxidizing conditions the ischian rocks thus differ from the phlegrean fields analogues and the ultrapotassic more silica undersaturated rocks of somma vesuvius overall variations in the chemical compositions of the rocks and their trends imply unrelated feeding systems and thus are inconsistent with the hypothesis of a common magma reservoir beneath the main volcanic areas of the campanian plain

the sequence stratigraphy of fluvial depositional systems the role of floodplain sediment storage abstract the currently used model for alluvial sequence stratigraphy has been criticised miall 1991 and an alternative model is offered here in this model alluviation mainly takes place during transgressive and not highstand phases when accommodation space allows sediment storage the high capacity for some river systems to store floodplain sediments is a critical consideration the effects of climatic and intrinsic geomorphic changes during fluvial deposition are likely to greatly complicate simple base level controlled sequence models and recognising higher order fourth and fifth order cycles will be particularly difficult

palaeopathological changes in a population of albertosaurus sarcophagus from the upper cretaceous horseshoe canyon formation of alberta canadathis article is one of a series of papers published in this special issue on the theme albertosaurus over the past decade excavations of a monodominant theropod bonebed from the lower maastrichtian beds of the horseshoe canyon formation have recovered a minimum number of 26 individuals of the tyrannosaur albertosaurus sarcophagus examination of skeletal elements from the bonebed revealed a small number of abnormalities from at least two individuals these include bony spurs enthesophytes of unknown origin on three pedal phalanges well healed fracture calluses are present on two rib shafts and a gastralia element the left dentary of one adult preserves both healed and unhealed parallel bite marks and a perforative lesion attributable to a partially healed mechanically induced puncture wound unfortunately the limited range in the types and frequencies of pathological changes provides only little information on the distribution of such phenomena but may be suggestive of the overall health of the population

further shrimp geochronology on the early cambrian of south china zircon 206pb 238u ages are reported for bentonites from two cambrian sections in south china the meishucun and the fandian the analyzed zircons vary widely in age because of the presence of detrital and altered grains spot ages were corrected for calibration drift during analysis and the age of reference zircon sl13 was calibrated as 580 ma against other standards using sims use of mixture modeling was essential to resolve the different age components and to identify the volcanic ages two age groups occur within the meishucun bed 5 bentonite of which the larger at 518 7 2 5 ma is interpreted as a post depositional zircon growth event and the other at 539 4 2 9 ma as the volcanic age bentonites from the meishucun bed 9 and its fandian equivalent have two age groups 526 5 1 1 ma and 540 2 1 0 ma we interpret the younger of these as the tuff magmatic age and the older as detrital small shelly fossils indicate meischucunian bed 5 is an equivalent of the late nemakit daldynian and its 539 4 2 9 ma age both closely times the base of the cambrian and is a maximum for the basal tommotian the 526 5 1 1 ma for bed 9 and its equivalents approximates the close of the tommotian

the neoproterozoic lower cambrian in northern govi altay western mongolia regional setting lithostratigraphy and biostratigraphy this paper provides a framework for the stratigraphy and correlation of key sections through the neoproterozoic lower cambrian of the govi altay area western mongolia studied by members of igcp project 303 dzabkhan formation volcanic rocks at the base of the succession are suggested to have formed during rifting of the baydrik tarbagatay microcontinent in the baykalian interval c 850 650 ma pre vendian accretion transformed this rift and adjacent microcontinental fragments into a marginal marine back arc basin in which accumulated relatively uninterrupted neoproterozoic and earliest palaeozoic sediments lithostratigraphy for the latter is defined with detailed maps at five sections bayan gol northern and southern blocks tsagaan gol salaany gol and tayshir the tsagaan oloom formation lower member contains two diamictites of possible sturtian age middle and upper carbonates are compared with the yudomian vendian of siberia the former ending with a unit of boxonia grumulosa stromatolites in the upper member phosphorite shale is followed mainly by limestones with the earliest skeletal fauna the bayan gol formation comprises siliciclastic limestone intercalations with increasingly diverse invertebrate biota correlation of lithological marker beds across the study area produces a composite stratigraphic section to which the earliest skeletal fossil occurrences are tied the anabarites trisulcatus zone of the nemakit daldynian stage begins near the base of the tsagaan oloom formation upper member unit 11 the purella antiqua zone begins near the base of the bayan gol formation unit 18 assemblages typical of the nochoroicyathus sunnaginicus zone base of the tommotian stage range through units 19 to 23 elements typical of the dokidocyathus regularis zone middle tommotian appear in unit 24 near the top of the bayan gol formation

the ischia debris avalanche first clear submarine evidence in the mediterranean of a volcanic island prehistorical collapse sector or flank collapse with related debris avalanches is increasingly recognized as a relatively common volcanic behaviour in particular for large hot spot related oceanic islands here we report the case of a catastrophic collapse that occurred at ischia volcanic island in prehistorical times and was driven by the volcano tectonic uplift of mt epomeo the major relief of the island the collapse left a subaerial to submarine horseshoe scar on the southern flank of the island and generated a debris avalanche incorporating thousands of giant blocks dispersed as far as 50 km from the island during the emplacement part of the debris avalanche evolved into a debris flow covering an area of 250 300 km2 this constitutes the first clear evidence of a submarine debris avalanche in the mediterranean sea the major collapse was followed and probably also preceded by recurrent less catastrophic terrestrial and underwater failures two other undersea hummocky deposits are found north and west of the island and might tentatively be correlated to the major southern collapse such volcanic behaviour previously unknown for ischia volcano has likely triggered tsunami waves over the entire bay of naples raising the question of their impact on prehistorical historical communities

stratigraphic analysis of upper cretaceous rocks in the mahajanga basin northwestern madagascar implications for ancient and modern faunas abstract upper cretaceous strata of the mahajanga basin northwestern madagascar yield some of the most significant and exquisitely preserved vertebrate fossils known from gondwana the sedimentology of these strata and their stratigraphic relations have been the focus of renewed geological investigations during the course of five expeditions since 1993 we here designate stratotypes and formalize the terrestrial maevarano formation with three new members masorobe anembalemba miadana and the overlying marine berivotra formation the maevarano formation accumulated on a broad semiarid alluvial plain bounded to the southeast by crystalline highlands and to the northwest by the mozambique channel the berivotra formation was deposited in an open marine setting that evolved from a clastic to a carbonate dominated shelf resulting in deposition of the overlying betsiboka limestone of danian age new stratigraphic data clearly indicate that the maevarano formation correlates at least in part with the

carbonate carbon isotope evolution of seawater across the ediacaran cambrian transition evidence from the keping area tarim basin nw china sedimentary rocks from the ediacaran cambrian boundary record important biological climatic and geotectonic changes during this time to date only few geochemical investigations on the upper ediacaran upper cambrian rocks in the tarim basin have been carried out here we report high resolution 13 c carb records from the penglaiba the wushi phosphorite and the dongergou sections from ediacaran cambrian series 3 in the keping area of the tarim basin the sections display several obvious 13 c carb shifts 13 c carb values increased from 3 to 6 7 across the qigebulage formation moreover a negative 13 c carb shift across the ediacaran cambrian boundary is apparent 13 c carb values decreased to a minimum of 9 8 in the wushi phosphorite section 7 7 in dongergou section and 5 4 in penglaiba section followed by a positive carbonate carbon isotopic excursion across the yuertusi formation into the middle of the overlying xiaoerbulak formation furthermore more or less invariable positive 13 c carb values characterize the middle and upper xiaoerbulak formation the most negative 13 c carb value 14 3 occurred near the base of the shayilik formation which is the absolute minimum value among the studied sections of the cambrian series 2 to cambrian series 3 transition in the world the 13 c data from keping tarim basin are in good agreement with carbon isotope profiles recorded in south china and these events may reflect the perturbation of the carbon cycle in the tarim basin during the ediacaran cambrian and the cambrian series 2 cambrian series 3 transitions

rolling bones taphonomy of jurassic dinosaur bones inferred from diagenetic microcracks and mineral infillings abstract dinosaur bones from the upper jurassic shishugou formation near qitai in the junggar basin nw china show black manganese oxide and light quartz infillings in the bone pore space such as haversian canals and diagenetic cracks the manganese oxides are identified by x ray diffraction as pyrolusite some haversian canals are only partially filled with pyrolusite which forms miniature geologic spirit levels the orientations of these spirit levels have been measured and several generations of pyrolusite infillings determined indicating that the bones were turned around once or several times during their fossilization characteristic desiccation cracks in the dinosaur bones indicate deposition on the soil surface and early diagenesis under dry climate conditions in the upper jurassic in nw china during dry season evaporation and resulting capillary forces drove the groundwater with dissolved manganese ii ions towards the soil surface and further into the capillary system of the bones hence the capillary system of the bones was already in contact with that of the sediment when the bones were still lying on the surface and were not yet totally embedded in the sediment mn oh 2 precipitated under high ph conditions in the pore space of the bones such as haversian canals and cracks during late diagenesis the mn oh 2 was oxidized to mno2 and transformed into pyrolusite mineral infillings and desiccation cracks in fossil bones thus can yield valuable insights into the taphonomic history of skeletal remains such as environmental conditions during diagenesis and fossil reworking

agglutinated tests in post sturtian cap carbonates of namibia and mongolia abstract paleomagnetic data suggest that the early cryogenian sturtian glaciation extended to sea level at low latitude the impact of this dramatic environmental change on biota and the composition of ecosystems in the immediate aftermath of the sturtian glaciation remain virtually unknown here we report the discovery of abundant agglutinated tests in organic rich carbonates directly overlying sturtian glacial deposits from two different paleocontinents the rasthof formation of the congo craton in northern namibia and the tsagaan oloom formation of the dzabkhan terrane in mongolia the most abundant tests preserve morphological and compositional characters consistent with those found in at least two different families of modern lobose testate amoebae amoebozoa a group of heterotrophic microbial eukaryotes the presence of spatially and compositionally variable clay minerals quartz and microcline on the test walls is a signature of widespread biological agglutination the post glacial fossil assemblages differ from the most common pre sturtian vase shaped fossil testate amoebae perhaps as a result of different preservational mechanisms or of the appearance of new forms after the glaciation the apparent local abundance of eukaryotic body fossils in the post sturtian carbonates suggests that the cryogenian limestones and dolostones may host a currently unexplored fossil record of modern eukaryotes

33 000 yr k ar dating of the volcano tectonic horst of the isle of ischia gulf of naples the gulf of naples corresponds to a tectonic sink connected with recent volcanic activity in the south campanian area phlegrean fields ischia and vesuvius at its extreme northwest the isle of ischia was early recognized as a volcano tectonic horst by rittmann1 previous data2 concluded that its uplift ended around 300 000 yr and that the green tuff formation of which it is predominantly composed had an age of some 700 000 yr but tectonic and morphological studies together with original tephrostratigraphical observations on the slope of the horst led us to do some new k ar datings these revealed that the 780 m uplift of the horst from the sea level is younger than 33 000 yr the green tuff which was considered to be the oldest volcanic unit in the island is now dated at 56 000 yr its eruption following the dismantlement of a first volcanic complex now dated as not older than 130 000 yr

biostratigraphy of the vendian cambrian beds and the lower cambrian boundary in siberia general agreement exists that the position of the base of the cambrian precambrian cambrian boundary should coincide with a biostratigraphic marker that can be widely traced and is linked to the evolution of the small shelly fauna on the siberian platform the presence of distinct facies during the vendian cambrian interval has made biostratigraphic correlation based on palaeontological data highly contentious a solution to this problem appears to exist with the recognition of an almost uninterrupted profile in the aldan uchur watershed where key sections expose the eastern and transitional facial region on this basis we present a general biostratigraphic scheme for the vendian cambrian across the southern siberian platform that connects separate facies further correlation with key sections in northern siberia leads to the recognition of three biostratigraphic zones for the vendian cambrian interval these are anabarites trisulcatus zone purella antiqua zone aldanocyathus sunnaginicus zone the abundance of chinese type small shelly fossils in the region of the eastern facies suggest correlation of the a sunnaginicus zone with the siphogonuchites paragloborilus zone of china and the p antiqua zone with the circotheca anabarites protohertzina zone in places at the base of the circotheca anabarites protohertzina zone in china analogies to the a trisulcatus zone can be identified it is proposed that in siberia the base of the a sunnaginicus zone base of tommotian stage be taken as the base of the cambrian this would correspond with marker b of the meishucunian in china

magma chamber of the campi flegrei supervolcano at the time of eruption of the campanian ignimbrite a supereruption that occurred in the campi flegrei area italy ca 39 ka had regional and global scale environmental impacts and deposited the campanian ignimbrite ci we attempt to shed light on critical aspects of the eruption depth of magma chamber intensive pre eruptive magma conditions and the large volume magma plumbing system on the basis of information derived from analyzing melt inclusion mi data to achieve these aims we provide new measurements of homogenization temperatures and values of dissolved h2o within phenocryst hosted mis from pumices erupted during different phases of the ci eruption the mi data indicate that a relatively homogeneous overheated trachytic magma resided within a relatively deep magma chamber dissolved water contents in mis indicate that prior to the eruption the magma chamber underwent radical changes related to differential upward movement of magma decompression of the rising trachytic magma caused a decrease in water solubility and crystallization and trachytic bodies were emplaced at very shallow depths the proposed eruptive model links portions of the main magma chamber and apophyses with specific eruptive units

palaeomagnetic study of vendian and early cambrian rocks of south siberia and central mongolia was the siberian platform assembled at this time abstract a palaeomagnetic study of vendian and early cambrian sediments from the angara block of the siberian platform shaman 52 08 n 108 83 e and minya 58 0 n 110 0 e formations and the tuva mongolian block tsagan olom and bayan gol formations 46 76 n 96 37 e isolated three different components of magnetization through thermal demagnetization the stable high temperature characteristic remanence directions show both normal and reverse polarities the mean palaeopoles computed after these high temperature components are 32 0 s 71 1 e dp dm 6 9 13 8 for the vendian shaman formation 10 sites 80 samples 33 7 s 37 2 e dp dm 8 6 14 7 for the vendian minya formation 12 samples 22 8 s 28 4 e dp dm 10 8 21 6 for the vendian tsagan olom formation 4 sites 25 samples and 21 4 s 167 1 e dp dm 9 6 19 1 for the early cambrian bayan gol formation 6 sites 49 samples from a compilation of vendian and early cambrian palaeopoles from the anabar angara and aldan blocks of the siberian platform and tuva mongolia block we propose a model where these blocks were situated in an equatorial to low south palaeolatitude position with their present day southern boundaries facing the north pole from the analysis of the scatter of these poles we conclude that the siberian platform might not have fully amalgamated by this time and that significant rotations occurred after the early cambrian our new palaeopoles for the tuva mongolia block together with previously published ones show that this block was already adjacent to siberia by the vendian and early cambrian we propose that the large counterclockwise rotation of the tuva mongolia block with respect to angara block could mark the end of the closure of the part of the palaeo asian ocean separating these two blocks and could account for the occurrence of vendian early cambrian ophiolites in the region

trace fossils and biofabrics at the precambrian cambrian boundary interval in western mongolia a small suite of trace fossils from the zavkhan basin govi altay includes many of the ichnotaxa typical of the nemakit daldynian tommotian and younger cambrian stages and other indeterminate forms the traces are almost entirely from the sandstone intervals of the large scale alternations of carbonate and siliciclastic sediments thus emphasizing the facies and taphonomic controls on trace fossil distribution and hence the inherent difficulties in using trace fossils in detailed global correlation especially in using first appearances the assemblage of traces and biofabrics is seen as resulting from the partly non uniformitarian non actualistic sedimentary environments that pertained over the boundary interval rather than as evolutionary failures and subsequently vacated environments

gregarious behaviour among non avian theropods inferred from trackways a case study from the cretaceous cenomanian candeleros formation of patagonia argentina abstract gregarious behaviour among dinosaurs has been inferred from several lines of evidence monospecific bonebeds skeletal morphology phylogenetic inferences comparison with modern ecosystems and parallel trackways with particular characteristics but is relatively poorly documented for non avian theropods here we report five parallel theropod trackways of large track size average length of 28 cm in the cretaceous cenomanian candeleros formation from northwestern patagonia argentina the tracks are provisionally assigned to aff asianopodus pulvinicalx and considering the autopod morphology of the theropod taxa documented in the candeleros formation abelisaurid theropods are suggested as trackmakers the trackways possess similar stride speed estimation direction and preservational features and track show uniform depth and do not overlap physical barriers i e large fluvial channels or perennial lake that could influence the direction of the theropod trackmaker gaits were not recognized in the section taking into account these considerations a gregarious behaviour for the abelisaurid theropod trackmakers is proposed the tracks are preserved as shallow undertracks in a medium grained sandstone bed deposited in a floodplain setting the tracking surface is interpreted as the overlaying layer of muddy siltstone the occurrence of swelling clays and microbial mats in the track bearing level could have contributed to the substrate stabilization and their role in the preservation is discussed

early cambrian chronostratigraphy and geochronology of south australia abstract the most successful chronostratigraphic correlation methods enlist multiple proxies such as biostratigraphy and chemostratigraphy to constrain the timing of globally important bio and geo events here we present the first regional high resolution shelly fossil biostratigraphy integrated with 13c chemostratigraphy and corresponding 18o data from the traditional lower cambrian terreneuvian and provisional cambrian series 2 of south australia the global zhuce shice positive excursions ii and iii and the care are captured in lower cambrian successions from the arrowie and stansbury basins the south australian shelly fossil biostratigraphy has a consistent relationship with the 13c results bolstering interpretation identification and correlation of the excursions positive excursion ii straddles the boundary between the kulparina rostrata and micrina etheridgei zones and the care straddles the boundary between the m etheridgei and dailyatia odyssei zones peaking in the lower parts of the latter zone new ca tims zircon dates from the upper hawker group and billy creek formation provide geochronologic calibration points for the upper d odyssei zone and corresponding chemostratigraphic curve embedding the lower cambrian successions from south australia into a global chronostratigraphic context this multi proxy investigation demonstrates the power of integrated methods for developing regional biostratigraphic schemes and facilitating robust global correlation of lower cambrian successions from south australia part of east gondwana with coeval terranes on other cambrian palaeocontinents including south and north china siberia laurentia avalonia and west gondwana

evidences for disruption of a crystallizing front in a magma chamber during caldera collapse an example from the breccia museo unit campanian ignimbrite eruption italy abstract this work is focused on juvenile components and some cognate xenoliths of the breccia museo bm unit the bm is a coarse grained proximal unit of the caldera forming phase of the ignimbrite campana ic eruption southern italy the bm products show some peculiar characteristics that distinguish them from the other ic deposits in particular different types of pumice fragments constitute the juvenile fraction and their crystal contents are remarkably higher than the other ic units slightly porphyritic and highly porphyritic trachytic to phonolitic pumices were distinguished in each sample and investigated separately for mineralogy matrix glass composition melt and fluid inclusion studies most feldspar crystals may have formed at the margins of the magma chamber and the crystal content of both types of pumice fragments can be ascribed to variable entrainment of these crystals from the solidification front by the melt variably porphyritic

neoproterozoic 800 ma orogeny in the tuva mongolia massif siberia island arc continent collision at the northeast rodinia margin abstract the tuva mongolia massif is a composite precambrian terrane incorporated into the palaeozoic sayany baikalian belt its neoproterozoic amalgamation history involves early 800 ma and late baikalian 600 550 ma orogenic phases two palaeogeographic elements are identified in the early baikalian stage the gargan microcontinent and the dunzhugur oceanic arc they are represented by the gargan glyba block and the island arc ophiolites overthrusting it the gargan glyba is a two layer platform comprising an early precambrian crystalline basement and a neoproterozoic passive margin sedimentary cover the upper part comprises olistostromes deposited in a foreland basin during the early baikalian orogeny the dunzhugur arc ophiolite form klippen fringing the gargan glyba and show a comprehensive oceanic arc ophiolite succession the dunzhugur arc faced the microcontinent as shown by the occurrence of forearc complexes the arc continent collision followed a pattern similar to phanerozoic collisions when the marginal basin lithosphere had been completely subducted the microcontinental edge partially underthrust the arc and the forearc ophiolite overrode it continued convergence caused a break of the arc lithosphere resulting in the uplift of the submerged microcontinental margin with the overthrust forearc ophiolites sliding into the foreland basin owing to the lithospheric break a new subduction zone inclined beneath the gargan microcontinent emerged initial melts of the newly formed continental arc are represented by tonalites intruded into the gargan microcontinent basement and its cover and into the ophiolite nappe the tonalite rb sr mineral isochron age is 812 18 ma which is similar to a u pb zircon age of 785 11 ma a period of tonalite magmatism in meso cenozoic orogenic belts is recognized some 1 10 m y after the collision accordingly the dunzhugur island arc gargan microcontinent collision is conventionally dated at around 800 ma it is highly probable that in the early neoproterozoic the gargan continental block was part of the southern in modern coordinates margin of the siberia craton it is suggested that a chain of precambrian massifs represents an elongate block separated from siberia in the late neoproterozoic the tuva mongolia massif is situated in the northwest part of this chain these events occurred on the ne neoproterozoic margin of rodinia facing the world ocean

geothermal assessment of the island of ischia southern italy from isotopic and chemical composition of the delivered fluids abstract the ischia geothermal system is hosted by silicic rocks of the quaternary potassic roman province in southern italy exploration drilling down to 1156 m depth in the mid 1950s provided information on boiling profiles up to 250 c and on the depth and permeability of the potential reservoirs discharge fluid samples were collected and analyzed to define the inflow of surrounding seawater c1 ranges from 2 5 to 20 g kg into the system analyses of samples from surface manifestations and shallow wells collected during 1983 and 1988 point to the existence of three distinct mixing regimes involving three water components a dishomogeneous body of diluted water cl less than 2 5 g kg that occurs at depths 700 m and reequilibrates at 240 c at least is overlain by an aquifer of groundwater variably mixed with variably seawater cl from 4 to 10 g kg which tends to reequilibrate at 160 c steam heated waters locally develop and act as dilutants of the rising geothermal fluids dilution mixing and evaporation of the ascending chloride fluids are supported by oxygen and hydrogen isotopic data the thermal waters being enriched in 18 o and d with respect to local meteoric water by up to 7 and 30 respectively the relative composition of the major cations in thermal solutions was used to discriminate the two main groups of thermal waters the reservoir temperatures of which are estimated from the na k gethermometer k mg geothermometer indicates reequilibration in near surface conditions the isotopic composition of the fumarolic steam varies from 7 to 12 in 8 o and from 35 to 70 in d in agreement with a deep mixed fluid that boils adiabatically from 240 to 80 c the deuterium content of the h 2 o h 2 pair gives enrichment factor of about 830 corresponding to equilibrium temperature conditions slightly higher than the surface boiling temperatures the 13 c of co 2 is almost constant at 4 5 1 0 4 suggesting an important magmatic contribution and the 18 o values of co 2 appears to in equilibrium with accompanying steam at the measured temperatures the co 2 ar and h 2 ar chemical ratios have been used to derive aquifer temperatures the values obtained being consistent with those of solute geothermometers

volcanoes interpreting inclusive evidence crystallization of ascending magma may affect the style of volcanic activity pockets of melt incorporated into crystals provide windows on processes that occur several kilometres below earth s surface

variation in sericite compositions from fracture zones within the coso hot springs geothermal system two types of white micas are found in drillhole samples within the geothermal system at coso hot springs low permeability zones of the crystalline basement contain coarse grained relict muscovite whereas rock alteration near fracture zones at temperatures 150 c is characterized by abundant finegrained sericite in association with secondary calcite and quartz and unaltered relict microcline in this hydrothermal sericite there is an increase in interlayer k octahedral mg fetotal and tetrahedral al with increasing temperature between 215 to 250 c thermodynamic activity of the al2si4o10 oh 2 component of serielles calculated using site mixing approximations of helgeson and aagaard 1985 decreases with increasing temperature between 215 and 250 c as a consequence of the observed variations in the interlayer octahedral and tetrahedral site occupancies the activity of kal2 alsi3o10 oh 2 is essentially constant in the coso seriates over this temperature range the calculated equilibrium distribution of aqueous species in the hydrothermal solutions produced from well 16 8 together with cation activity phase diagrams that account for variations in sericite composition requires a ph of 6 7 6 8 at temperatures between 236 and 250 c comparison of predicted and observed phase relations with fluid compositions indicate that seriates are in local equilibrium with the geothermal reservoir fluid whereas relict metamorphic muscovites are metastable although the compositions of hydrothermal sericites are a complex function of temperature pressure and geothermal fluid composition compositional relations observed at coso together with published compositions of hydrothermal dioctahedral layer silicates from the salton sea geothermal system demonstrates that elemental compositions of interlayer k and tetrahedral al increase systematically with increasing temperature despite the dramatic differences in fluid compositions between these two geothermal systems this suggests that the observed variations in interlayer and tetrahedral site occupancy is largely dependent on the enthalpy of hydrolysis reactions representing equilibrium between sericite solid solutions and the geothermal reservoir fluids

late ediacaran boxonia bearing stromatolites from the gobi altay western mongolia abstract a couplet comprising a boxonia bearing stromatolite unit and phosphatic layers occurs widely at the base of the zuun arts formation in the zavkhan terrane of gobi altay province western mongolia the stromatolite unit is late ediacaran in age and forms bioherms of several kilometres in lateral extent the stromatolites consist of two parts the lower columnar boxonia stromatolites ca 7 m thick change abruptly into the upper domed stromatolites ca 4 5 m thick in the bayan gol gorge the columnar stromatolites are made up of columnar structures 2 6 cm in diameter formed by the accumulation of upward convex laminae and partly protrude laterally to form bridges between neighbouring columns in contrast the domed stromatolites 30 60 cm in width are composed of accumulations of low convex laminae both types of stromatolite are characterized by alternating darker and lighter laminae which consist of peloids two types of micritic clot homogeneous lime mud and spar filled fenestral fabrics these stromatolites are inferred to have been deposited in a subtidal setting below the wave base with no evidence of sediment displacement by strong currents the stratigraphic transition from columnar to domed growth forms reflects deepening of the basin the change in column diameter observed within the columnar stromatolites might reflect fluctuations in microbial activity the appearance of inter columnar bridges in the columnar stromatolites might indicate more active colonization of microbial mats which expanded into the inter columnar areas neither type of stromatolite includes microbial remains such as filamentous or coccoidal cells however the various micritic components of the stromatolites clots peloids and homogeneous lime mud originated from in situ precipitation through microbial activity and reflected differences in the timing and intensity of microbial calcification and degradation these stromatolites including the variety of micritic components may provide clues to the variations in microbial metabolic activity and degradation processes that were associated with stromatolite formation

two phase stratigraphic model of foreland basin sequences application of flexural models to nonmarine foreland basin evolution indicates that two different stratigraphic styles of basin fill may develop over time basin subsidence is most rapid during times of thrust load emplacement associated sedimentation is coarse grained immediately adjacent to the thrust front and grades rapidly into fine grained deposits that cover most of the basin the distal part of the basin may also contain deposits derived from streams that flow from beyond the basin toward the thrust belt subsequent removal of the thrust load by erosion and other processes results in flexural rebound of the thrust belt and adjacent foreland basin during this postorogenic phase of adjustment a regional unconformity develops in the proximal part of the foreland basin proximal deposits along with thrust derived sediment are redeposited in the distal foreland basin and beyond this two phase model of foreland sedimentation predicts that coarsening upward sequences in the proximal and distal parts of the basin have reciprocal significance the proximal sequence represents thrust belt advance whereas the distal sequence represents thrust belt cessation

early cambrian bioconstructions in the zavkhan basin of western mongolia the neoproterozoic cambrian succession in the zavkhan basin of western mongolia preserves early cambrian bioconstructions of nemakit daldynian to botomian age as elsewhere siberia morocco the nemakit daldynian bioconstructions in the upper tsagaan oloom formation to lower bayan gol formation interval were purely calcimicrobial spectacular calcimicrobial patch reefs of presumed tommotian age are present in the lower bayan gol formation in contrast late atdabanian early botomian bioconstructions are varied and well developed in the upper salaany gol formation including in addition to calcimicrobial bioherms gordonophyton razumovskia crusts radiocyathan archaeocyathan bioherms and thickets of the ramose archaeocyath cambrocyathellus these latter zavkhan basin buildups show some ecological and sedimentological features in common with coeval bioconstructions in south australia which also developed under a tectonically active regime

a large crested theropod from the jurassic of xinjiang people s republic of china a skull and partial skeleton of a new genus and species monolophosaurus jiangi n gen n sp of large theropod has been recovered from the middle jurassic beds in the junggar basin of xinjiang c

depauperate skeletonized reef dwelling fauna of the early cambrian insights from archaeocyathan reef ecosystems of western mongolia abstract reef dwelling organisms in the early cambrian include typical members of the cambrian fauna such as trilobites chancelloriids and hyoliths however in comparison to later ordovician reefs cambrian reefs often do not appear as diverse here we investigate early cambrian microbial archaeocyathan reefs of the salaagol formation in the zavkhan basin of mongolia as well as perform a literature survey of 40 early paleozoic reefs to understand the timing of reef biodiversity by using point count analysis we can quantify the carbonate contribution of framework builders and reef dwelling organisms in these ecosystems we find that mongolian reefs contained several genera of framework building archaeocyaths 5 0 by volume and associated microbial forms 5 4 but are unevenly distributed through the formation archaeocyathan contribution increases are potentially concurrent with negative shifts in carbon isotopic composition similar to other localities in gondwana however reef dwelling biota was minimal 0 3 throughout the salaagol formation and did not correlate to changes in framework builders or geochemical proxies such as u v and carbon isotopes a literature survey of ediacaran through ordovician reefs suggests that there is a trend of increasing reef dweller abundance functional richness and skeletonization through time the changes in abundance 17 9 to 28 8 considered frequent and functional richness 3 7 to 6 0 functional groups could be due to an increase in productivity in the oceans during the cambrian thereby expanding the base of the food web during the lead up to the ordovician radiation the trend of increasing skeletonization could be due to the evolution of more robust skeletons among reef dwellers in order to protect themselves from increased predation in reef environments these trends suggest that at least during the early paleozoic increases in biological diversity are not necessarily concurrent with the establishment of a framework reef

stratigraphic and tectonic implications of a newly discovered glacial diamictite cap carbonate couplet in southwestern mongolia we report here the discovery of a new end cryogenian glacial diamictite and an overlying basal ediacaran cap carbonate within the tsagaan oloom formation of southwestern mongolia the identifi cation of the cryogenian ediacaran boundary coupled with new 13 c chemostratigraphic profi les facilitates the integration of the neoproterozoic stratigraphy of mongolia with records elsewhere these correlations indicate that a previously unrecognized 16 cryogenian 13 c anomaly is present in the newly defi ned tayshir member informal of the tsagaan oloom formation furthermore chemostratigraphic and lithostratigraphic relationships suggest an 35 m y depositional hiatus below the phosphorite bearing zunne arts member informal of the upper tsagaan oloom formation and that subsidence renewed in the latest ediacaran early cambrian we propose that the lower 1500 m of the tsagaan oloom formation was deposited on a thermally subsiding passive margin after rodiniaage rifting whereas the zunne arts member and the overlying 1600 m of early cambrian strata were deposited in a foredeep basin that formed as the southern margin of the dzabkhan terrane was subducted beneath the khantayshir dariv arc

integrated stratigraphic geochemical and paleontological late ediacaran to early cambrian records from southwestern mongolia comment global correlation of sedimentary rock successions requires an integrated approach that uses all fossil based and alternative lithostratigraphic geochemical paleomagnetic geochronologic sequence stratigraphic data e g van couvering and berggren 1977 proposed global correlations and their role in interpreting earth and biotic history require a thorough examination of the utility and temporal resolution allowed by each correlation technique in comparison to the others the article by smith et al 2016 is a welcome contribution to understanding the upper ediacaran lower cambrian succession of the zavkhan terrane in the khasagt khairkhan range of southwestern mongolia their work complements earlier syntheses on the zavkhan terrane completed by soviet mongolian teams e g voronin et al 1982 esakova and zhegallo 1996 and under international geoscience programme igcp project 303 late precambrian cambrian event stratigraphy brasier et al 1996a see associated papers in geological magazine v 133 no 4

sequence stratigraphy paleoclimate patterns and vertebrate fossil preservation in jurassiccretaceous strata of the junggar basin xinjiang autonomous region people s republic of china multi kilometre thick jurassic cretaceous age sedimentary successions exposed in the southern northwestern and northeastern regions of the junggar basin display a consistent and correlative stratigraphy comprising four stacked second order megasequences badaowan sangonghe shishugou and kalaza each consists of a basal erosional unconformity or discontinuity surface and lower middle and upper units that are interpreted as forestepping backstepping and aggradational systems tracts respectively each megasequence is interpreted as recording an upsection shift from active tectonism and uplift to tectonic quiescence with associated changes in crustal response and sediment supply basin wide analysis of megasequences indicates that tectonism was intermittent and regionally variable a maximum phase of subsidence and sediment accommodation is recorded in the middle unit of each megasequence and correlates with a notable abundance of fossil vertebrates suggesting a primary tectonic and basin response

first elaphrosaurine theropod dinosaur ceratosauria noasauridae from australia a cervical vertebra from the early cretaceous of victoria abstract elaphrosaurinae is an enigmatic clade of gracile ceratosaurian theropod dinosaurs known from the late jurassic of africa elaphrosaurus bambergi and asia e g limusaurus inextricabilis and the early late cretaceous of argentina huinculsaurus montesi elaphrosaurinae is often placed within noasauridae as the sister taxon to noasaurinae a clade of small bodied theropods that lived in south america africa madagascar and india throughout much of the cretaceous herein we report the first evidence of elaphrosaurinae from australia a nearly complete middle cervical vertebra from the upper lower cretaceous lower albian eumeralla formation of cape otway victoria australia the fact that this site would have been situated at 76 s towards the end of the early cretaceous 110 107 ma implies that elaphrosaurines were capable of tolerating near polar palaeoenvironments whereas its age indicates that elaphrosaurines persisted in australia until at least the late early cretaceous the new australian elaphrosaurine in tandem with the recently described huinculsaurus montesi from the cenomanian turonian of argentina implies that the spatiotemporal distribution of elaphrosaurinae has heretofore been greatly underestimated historic confusion of elaphrosaurines with coelurosaurs especially ornithomimosaurs coupled with our generally poor understanding of noasaurid evolution might explain the apparent dearth of fossils of this theropod clade worldwide

chronology of early cambrian biomineralization data on the first appearances of major animal groups with mineralized skeletons on the siberian platform and worldwide are revised and summarized herein with references to an improved carbon isotope stratigraphy and radiometric dating in order to reconstruct the cambrian radiation popularly known as the cambrian explosion with a higher precision and provide a basis for the definition of cambrian stages 2 to 4 the lophotrochozoa and probably chaetognatha were first among protostomians to achieve biomineralization during the terreneuvian epoch mainly the fortunian age fast evolutionary radiation within the lophotrochozoa was followed by radiation of the sclerotized and biomineralized ecdysozoa during stage 3 the first mineralized skeletons of the deuterostomia represented by echinoderms appeared in the middle of cambrian stage 3 the fossil record of sponges and cnidarians suggests that they acquired biomineralized skeletons in the late neoproterozoic but diversification of both definite sponges and cnidarians was in parallel to that of bilaterians the distribution of calcium carbonate skeletal mineralogies from the upper ediacaran to lower cambrian reflects fluctuations in the global ocean chemistry and shows that the cambrian radiation occurred mainly during a time of aragonite and high magnesium calcite seas

ontogenetic dietary shifts in deinonychus antirrhopus theropoda dromaeosauridae insights into the ecology and social behavior of raptorial dinosaurs through stable isotope analysis abstract the image of the highly intelligent pack hunting raptor has become engrained in scientific literature and popular works alike first proposed to explain the relatively common co occurrence of the large bodied iguanodontian tenontosaurus tilletti and the wolf sized deinonychus antirrhopus from the lower cretaceous of north america a canid like social hunting structure has become the standard depiction of dromaeosaurs in popular works over the last three decades this reconstruction is however problematic largely due to the fact that highly coordinated hunting strategies are rarely observed in modern archosaurs this has led to the alternative hypothesis that d antirrhopus was more analogous to agonistic reptilian carnivores like the komodo dragon varanus komodoensis among the many differences between these two analogs is how social and asocial organisms rear their young producing a diagnostic pattern based on the presence or absence of ontogenetic dietary changes in order to test for dietary changes through growth stable carbon and oxygen isotope 13c 18o analysis was performed on tooth carbonate from small 9 mm crown height d antirrhopus specimens from two microsites from the lower cretaceous cloverly montana and antlers oklahoma formations teeth from goniopholidid crocodylians and tenontosaurus tilletti from the cloverly formation were also tested for comparison the results show that the cloverly goniopholidids like their modern counterparts went through a distinct transition in diet as they grew the smallest teeth were the relatively most enriched in 13c mean 9 32 n 5 the medium sized teeth were the most depleted in 13c mean 10 56 n 5 and the largest teeth were intermediate mean 10 12 n 6 these factors are characteristic of the dietary shifts seen in modern asocial reptiles d antirrhopus showed this same pattern in tooth samples collected from both rock units with small teeth being the more enriched in 13c mean 8 99 n 10 and the large teeth being more depleted in 13c mean 10 38 n 10 these differences suggest that juvenile and adult d antirrhopus from both formations likely consumed different prey hypothetical food sources such as t tilletti are close to the 13c isotopic signal of adult d antirrhopus consistent with the hypothesized trophic relationship predator prey between these two species juvenile d antirrhopus had a diet more enriched in 13c likely composed of smaller bodied but trophically higher species taken together these data add to the growing evidence that d antirrhopus was not a complex social hunter by modern mammalian standards

on gregarious behavior in albertosaurusthis article is one of a series of papers published in this special issue on the theme albertosaurus one century ago a field party from the american museum of natural history discovered a bonebed in the upper cretaceous horseshoe canyon formation of alberta canada excavations by that museum th

quantitative models of hydrothermal fluid mineral reaction the ischia case abstract the intricate pathways of fluid mineral reactions occurring underneath active hydrothermal systems are explored in this study by applying reaction path modelling to the ischia case study ischia island in southern italy hosts a well developed and structurally complex hydrothermal system which because of its heterogeneity in chemical and physical properties is an ideal test sites for evaluating potentialities limitations of quantitative geochemical models of hydrothermal reactions we used the eq3 6 software package version 7 2b to model reaction of infiltrating waters mixtures of meteoric water and seawater in variable proportions with ischia s reservoir rocks the mount epomeo green tuff units megt the mineral assemblage and composition of such megt units were initially characterised by ad hoc designed optical microscopy and electron microprobe analysis showing that phenocrysts dominantly alkali feldspars and plagioclase are set in a pervasively altered with abundant clay minerals and zeolites groundmass reaction of infiltrating waters with megt minerals was simulated over a range of realistic for ischia temperatures 95 260 c and co 2 fugacities 10 0 2 to 10 0 5 bar during the model runs a set of secondary minerals selected based on independent information from alteration minerals studies was allowed to precipitate from model solutions when saturation was achieved the compositional evolution of model solutions obtained in the 95 260 c runs were finally compared with compositions of ischia s thermal groundwaters demonstrating an overall agreement our simulations in particular well reproduce the mg depleting maturation path of hydrothermal solutions and have end of run model solutions whose na k mg compositions well reflect attainment of full equilibrium conditions at run temperature high temperature 180 260 c model runs are those best matching the na k mg compositions of ischia s most chemically mature water samples supporting quenching of deep reservoir conditions for these surface manifestations whilst fe sio 2 and to a lesser extent so 4 contents of natural samples are better reproduced in low temperature 95 c runs suggesting that these species reflect conditions of water rock interaction in the shallow hydrothermal environment the ability of model runs to reproduce the compositional features of ischia s thermal manifestations demonstrated here adds supplementary confidence on reaction path modelling as a realistic and insightful representation of mineral fluid hydrothermal reactions our results in particular demonstrate the significant impact of host rock minerals assemblage in governing the paths and trends of hydrothermal fluids maturation

a revised life table and survivorship curve for albertosaurus sarcophagus based on the dry island mass death assemblagethis article is one of a series of papers published in this special issue on the theme albertosaurus in 1910 a crew from the american museum of natural history discovered a bone bed composed primarily of the large tyrannosaurid albertosaurus sarcophagus in what is now dry island buffalo jump provincial park in alberta canada study of the remains from the site allowed the first life table and survivorship curve for a non avian dinosaur to be created these have served as a model for subsequent studies of dinosaurian population biology since 2006 the discovery and preparation of hundreds of new elements from the bone bed stand to substantially increase the minimum number of individuals mni represented this would allow testing of previous conclusions regarding the population biology of these animals and refinement of our understanding of the patterns of survivorship here four formerly unrecognized individuals from the dry island assemblage are revealed and a revised life table presented as in the previous analysis a left skewed age distribution and sigmoidal survivorship pattern were found annua

new material of xinjiangchelys reptilia testudines from the late jurassic qigu formation shishugou group of the pingfengshan locality junggar basin xinjiang the late jurassic qigu formation of the shishugou group in the pingfengshan locality contains a vertebrate fauna dominated by two taxa of turtles both members of the genus xinjiangchelys one of these xinjiangchelys latimarginalis young and chow 1953 is well represented by a series of specimens the second is specifically indeterminate and is represented by only a single fragmentary specimen but is distinctive in having a long narrow plastral lobe derived features of xinjiangchelys that separate it from plesiochelys include the presence of a loose connection between the plastron and carapace with pegs on the plastron fitting in sockets on the peripherals the extension of the pleural marginal sulcus onto costals one to five the dorsal thickening of the lateral edges of peripherals two to seven the highly expanded seventh to eleventh peripherals the extension of the anal scute to the hypoplastron xiphiplastron suture or onto the hypoplastron a reduction in length of the first dorsal rib and the

associations of vertebrate skeletal concentrations and discontinuity surfaces in terrestrial and shallow marine records a test in the cretaceous of montana abstract although lags of bones and teeth are commonly cited criteria for marine unconformities the consistency of the association of vertebrate fossils and discontinuity surfaces as well as the taphonomic postmortem controls on this relationship are poorly understood a field test across fluvial paralic and shallow marine facies in the campanian two medicine and judith river formations of montana indicates that the distribution of vertebrate skeletal concentrations is poorly correlated with the inferred durations of erosional and omissional hiatuses instead vertebrate concentrations associated with discontinuities of all durations tend to be patchy and closely track the abundance of fossil material in underlying and lateral facies based on the analysis of 83 measured sections we found first that erosional bases of channels and minor scours within channels yield vertebrate lags tidally influenced fluvial deposits are more productive than are upland fluvial deposits second erosional shorefa

the role of central asia in dinosaurian biogeography dinosaurian biogeography may have been largely controlled by the mesozoic fragmentation of pangea and the reassembly of its fragments into a new boreal supercontinent laurasia although late triassic and early jurassic dinosaurs were globally distributed chinese assemblages were dominated by endemic forms from middle jurassic into early cretaceous time the affinities of aptian albian immigrants to asia were strongest with north america and europe rather than gondwana indicating that the northern and southern hemispheres had by then attained their biogeographic identity this distinctiveness was maintained through cretaceous time europe seems to have been a buffer area between paleolaurasia and gondwana of the northern continents it was the most strongly influenced by gondwana dispersants late jurassic dinosaur assemblages in north america exhibited gondwana affinities but by late cretaceous time they were dominated by forms of asian ancestry

palaeomagnetism of the bayan gol formation western mongolia oriented samples of the lower cambrian bayan gol formation from salaany gol mongolia were collected at roughly 5 m stratigraphic intervals for palaeomagnetic analysis progressive alternating field and thermal demagnetization isolated two magnetic components a present field overprint typically removed by 10 mt fields and 200 c heating and a high coercivity high unblocking temperature 550 600 c predominantly single polarity component that was imparted to the rocks prior to early or middle palaeozoic deformation single polarity magnetization at salaany gol contrasts with results from lower cambrian rocks on the siberian platform previously considered correlative with the bayan gol formation which show a prominent change in polarity bias near the top of the tommotian stage two hypotheses can explain this discrepancy first the entire bayan gol formation may correlate with the predominantly reversely polarized lower half of the tommotian stage in siberia this model is consistent with plausible interpretations of 13 c profiles for the zavkhan basin and the siberian platform alternatively the characteristic magnetic direction from our samples may be a pre fold overprint if post accretionary then comparison with siberian palaeomagnetic results suggest a silurian devonian remagnetization age and existing bioand chemostratigraphic correlations provide the most reliable spatial and temporal links between the zavkhan basin and the siberian platform if the observed magnetic directions are primary or an immediate overprint then they may be used to constrain the early cambrian palaeogeography of the zavkhan basin and the palaeo pacific ocean mean inclination of 62 4 corresponds to a palaeolatitude of 44 5 several thousand kilometres from the equatorial siberian craton

engineering the cambrian explosion the earliest bioturbators as ecosystem engineers by applying modern biological criteria to trace fossil types and assessing burrow morphology complexity depth potential burrow function and the likelihood of bioirrigation we assign ecosystem engineering impact eei values to the key ichnotaxa in the lowermost cambrian fortunian surface traces such as monomorphichnus have minimal impact on sediment properties and have very low eei values quasi infaunal traces of organisms that were surficial modifiers or biodiffusors such as planolites have moderate eei values and deeper infaunal gallery biodiffusive or upward conveying downward conveying traces such as teichichnus and gyrolithes have the highest eei values the key cambrian ichnotaxon treptichnus pedum has a moderate to high eei value depending on its functional interpretation most of the major functional groups of modern bioturbators are found to have evolved during the earliest cambrian including burrow types that are highly likely to have been bioirrigated in fine grained or microbially bound sedimentary environments trace makers of bioirrigated burrows would have had a particularly significant impact generating advective fluid flow within the sediment for the first time in marked contrast with the otherwise diffusive porewater systems of the proterozoic this innovation is likely to have created significant ecospace and engineered fundamentally new infaunal environments for macrobiotic and microbiotic organisms alike

braincase structure of the middle jurassic theropod dinosaur piatnitzkysaurus the braincase of the middle jurassic basal tetanuran theropod piatnitzkysaurus floresi is described in detail it exhibits several probable autapomorphic characters of this taxon including the extremely shortened and narrow basipterygoid processes the presence of parasphenoid recesses that seem to communicate with each other and basipterygoid recesses that are approximately as long anteroposteriorly as they are high the braincase of piatnitzkysaurus shows two possible synapomorphies with the enigmatic european middle jurassic theropod piveteausaurus a subrectangular pituitary fossa that is wider than high and the transverse span between the basipterygoid processes being smaller than the width of the basal tubera a noteworthy aspect of the braincase of piatnitzkysaurus is the high number of accessory pneumatic recesses which indicates that the presence of an anterior and dorsal tympanic recess and possibly also of subcondylar and basipterygoid recesses is plesiomorphic for tetanurans in contrast

the neoproterozoic to early cambrian in southwest mongolia an introduction in this collection of papers we attempt to document through interdisciplinary studies in southwest mongolia the interlinked evolution of the biosphere and lithosphere over the neoproterozoic cambrian interval in so doing we bring together the fruits of two expeditions to the altay mountains sponsored by igcp project 303 on precambrian cambrian event stratigraphy both expeditions took place during an interval of great socio economic change in the region the first expedition in 1991 was one of the last in a series of joint soviet mongolian palaeontological expeditions organized by a yu rozanov and r barsbold and led by e a zhegallo and a yu zhuravlev scientists from sweden and the uk also participated the second 1993 expedition was one of the first igcp project meetings organized independently by the mongolian academy of sciences and was led by m d brasier and d dorjnamjaa

first insights on the metallogenic signature of magmatic fluids exsolved from the active magma chamber of vesuvius ad 79 pompei eruption abstract fluid inclusions hosted in sanidine from xenoliths representing the crystallization front of the ad 79 magma chamber of vesuvius offer a rare opportunity to track the composition of magmatic fluids exsolving at the peripheral part of a growing k alkaline magma chamber disrupted by an explosive eruption this work demonstrates that the exsolving magmatic fluids have a complex composition taking in evidence the great capability of metal transport by means of these solutions inclusions are particularly enriched in zn mo w sb bi tl and pb metals display two different positive correlations 1 pb zn tl bi 2 mo w the different trends may reflect the different complexing agent for these elements probably chloride for pb zn tl bi and probably hydroxy for mo w the occurrence of a silicothermal component in these fluids may furthermore favor the metal transport of these solutions this is probably a major previously underestimated process in the enrichment of some metals in magmatic hydrothermal systems this hypothesis may challenge conventional ideas on fluid phase mass transport of components by means of magmatic hydrothermal fluids and should be taken into account in future works on these topics

hydrothermal alteration environments and recent dynamics of the ischia volcanic island southern italy insights from repeated field mineralogical and geochemical surveys before and after the 2017 casamicciola earthquake abstract this study presents the results of repeated surveys conducted in hydrothermally altered areas on the active volcanic island of ischia in the gulf of naples southern italy data were obtained from field work in situ temperature measurements x ray diffraction optical and scanning electron microscopy eds sem micro analysis infrared spectroscopy and whole rock geochemistry analyses on samples collected in october 2016 september 2017 march 2018 and november 2018 both prior to and following the damaging seismic event that occurred in august 2017 at casamicciola mineralogical results point to the evolution of acid sulfate zones along the northern and western flanks of a resurgent block located in the central part of the island in strict relation with endogenous fluid outgassing indicated in the literature mineralogy and whole rock geochemistry of these acid sulfate zones reveal magmatic hydrothermal environments in association with major structures that enable fluid circulation it is interpreted that rare coarser alunites within dominant steam heated and supergene alteration mineral assemblages are associated with environments that are no longer active but which are supplied by magmatic vapours in addition collected data indicate slow endogenous degassing from hydrothermal reservoirs data from september 2017 show variations in the sulfate assemblage within the acidic sulfate zone located near the earthquake s epicentre and acidification and the transitory appearance of alum k is apparent under a nearly unchanged endogenous supply meteorological conditions of late summer could in principle justify the appearance of alum k but its coexistence with alunogen and soil temperatures refute this possibility alum k is interpreted to be the product of alunite decomposition at a local temperature of ca 100 c assuming a correct space time relationship between the appearance of alum k and the earthquake it is thus inferred that mechanical activation by tectonic stress is the possible cause of alunite decomposition

nd isotope composition of early cambrian discrete basins the precambrian cambrian transition is a most dramatic period in the earth s history it is therefore crucial for the understanding of evolutionary changes in the earth s external system including the biosphere one of the most amazing events to take place at the beginning of the early cambrian was the appearance and explosive diversification of small shelly fossils conway morris 1989 small shelly fossils are known from all continents and their wide geographic distribution and rapid evolution may facilitate the reconstruction of the spatio temporal framework of major biotic and abiotic events gubanov 2000 the almost instantaneous appearance of small shelly fossils on all continents and their stable morphological features over all contemporaneous populations suggest the presence of closely related biotopes with extensive genetic exchanges this surprising worldwide

fumarolic and diffuse soil degassing west of mount epomeo ischia italy abstract fumarolic fluid compositions and diffuse soil emissions of hydrothermal fluids of the donna rachele area 0 86 km 2 western flank of mt epomeo ischia island have been studied in order to develop a conceptual geochemical model of the hydrothermal system the degassing area was mapped and the total release of hydrothermal gas and heat associated with the diffuse emission of hydrothermal fluids was estimated a mesostructural study was carried out in order to investigate the relations between the brittle structures and the main pathways of the uprising vapor the fumarolic compositions are typical of hydrothermal fluids and water 99 represents the major component all gas species in the h 2 o h 2 co ch 4 co 2 h 2 s system are close to equilibrium concentrations at temperatures of 300 c and at redox conditions slightly more oxidizing than expected the compositions of the donna rachele fumarolic gas approach the pure liquid equilibrium composition this indicates a high fraction of separated vapor and suggests the presence of a highly energetic hydrothermal system at depth the pure liquid equilibrium compositions of the donna rachele fumaroles along with the historical records of shallow seismicity the explosion of a well in 1995 the occurrence of intense acoustic phenomena and of shallow wells discharging vapor indicate that the internal pressure of the hydrothermal system is occasionally larger than the hydrostatic pressure to quantify the energy dissipated in the donna rachele area by the emission of fumarolic fluids the hydrothermal diffuse degassing was studied by means of 336 soil co 2 flux measurements the highest co 2 fluxes were measured in hydrothermally altered areas along the faults that border mt epomeo structural data indicate that the vapor rises up along nw se striking normal faults related to gravity induced stresses and affecting highly fractured lavas the older faults which are related to the mt epomeo resurgence act as a permeability barrier and bound the donna rachele diffuse degassing structure the total hydrothermal co 2 output was estimated to be 9 t d 1 assuming that the h 2 o co 2 ratio of the fluids that feed the diffuse degassing is the same as that of fumarolic effluents the calculated heat flux is 40 mw this value which represents an important energy release is only a part of the total thermal energy release of ischia where other fumarolic areas occur the results obtained at ischia indicate the importance of thermal energy released by diffuse degassing structures in the energy balance of quiescent volcanoes values of the thermal energy release from the ischia hydrothermal system are comparable with those estimated on other quiescent volcanoes

the vendian system of siberia and a standard stratigraphic scale in siberia vendian is equated with a yudoma complex or yudomian yudomian deposits of the siberian platform and adjacent geosynclines differ greatly in facies and thickness according to the composition and structure of yudomian deposits four facies provinces may be recognized on the platform local stratigraphic charts for each province are presented and their correlation and possibility to subdivide the vendian system in siberia into three horizons or stages are substantiated the upper stage nemakit daldyn on the basis of palaeontological evidence is in its turn subdivided into two zones anabarites trisulcatus and purella antiqua the most important early baikalian rearrangement is proved to take place around 800 50 ma the pre vendian late baikalian movements though less intensive make the determination of the yudomian lower boundary easier the specific character of vendian biostratigraphy is discussed involving all groups of the organic remains that causes the necessity of recognition subdivision and correlation on the basis of the whole complex of data the boundary between the vendian system and the lower cambrian tommotian stage in type section is proved to conform to the base of the pestrozvet formation which divides the a sunnaginicus and p antiqua zones

mantle and crustal processes in the magmatism of the campania region inferences from mineralogy geochemistry and sr nd o isotopes of young hybrid volcanics of the ischia island south italy ischia one active volcano of the phlegraean volcanic district prone to very high risk is dominated by a caldera formed 55 ka bp followed by resurgence of the collapsed area over the past 3 ka the activity extruded evolved potassic magmas only a few low energy explosive events were fed by less evolved magmas a geochemical and sr nd o isotope investigation has been performed on minerals and glass from products of three of such eruptions molara vateliero and cava nocelle 2 6 ka bp data document strong mineralogical geochemical and isotopic heterogeneities likely resulting from mingling mixing processes among mafic and felsic magmas that already fed the ischia volcanism in the past detailed study on the most mafic magma has permitted to investigate its origin the mantle sector below ischia underwent subduction processes that modified its pristine chemical isotopic and redox conditions by addition of 1 of sediment fluids melts similar processes occurred from southeast to northwest along the apennine compressive margin with addition of up to 2 5 of sediment derived material this is shown by volcanics with poorly variable typical 18o mantle values and 87sr 86sr progressively increasing toward typical continental crust values multiple partial melting of this modified mantle generated distinct primary magmas that occasionally assimilated continental crust acquiring more 18o than 87sr at ischia 7 of hercynian granodiorite assimilation produced isotopically distinct k basaltic to latitic magmas a sw ne regional tectonic structure gave these magmas coming from large depth the opportunity to mingle mix with felsic magmas stagnating in shallower reservoirs eventually triggering explosive eruptions

precambrian basement provenance implication and tectonic evolution of the gargan block of the tuva mongolia terranes central asian orogenic belt abstract although the phanerozoic geology of the central asian orogenic belt is extensively studied there is still much to reveal about the initiation and early stages of tectonism the gargan block of the tuva mongolia terranes at the mongolian russian border is one of the archean proterozoic continental crustal fragments that record the earliest evolutionary history of the belt to better constrain the age of its basement extent and provenance in regional tectonic framework we present new zircon u pb geochronologic data from previously undated basement gneisses and the overlying neoproterozoic meta sedimentary rocks of southern part of the gargan block comparison of available basement ages and precambrian detrital zircon spectra from nearby archean proterozoic continental crustal fragments show complex relationship amongst them we propose that the gargan block travelled by itself in most of the proterozoic or was derived from an unknown continental block obtained age confirms the existence of neoarchean neoproterozoic basement in the region however for the first time the 2749 814 ma salig complex reveals multiple stages of neoproterozoic metamorphic events within the central asian orogenic belt older of which at 1 ga may relate to an assembly of several of the pre existing continental crustal fragments in mongolia

a new type of volcano flank failure the resurgent caldera sector collapse ischia italy 1 this study is the first description of recurrent and rapid lateral failure of the resurgent portion of a caldera complex the sliding planes and the characteristics of debris avalanche deposits resemble those of cone sector collapses but the main triggering mechanism proposed at ischia caldera italy is related to intermittent resurgence during the last 33 ka the increase in resurgence rate produced major collapses southward due to three main mechanisms that contributed to an increase in shear stress i magma driven uplift which produced increase in static loading ii faulting and associated deformation which induced tilting and steepening of the original layering and iii earthquake shaking due to coseismic faulting the largest episodes of flank failure occurred in the interval 8 6 5 7 ka bp these were followed by magma eruption and a decrease in the resurgence rate recognition of this phenomenon is particularly important in recent active calderas located near the coast as it can trigger tsunamis

simple shearing block resurgence in caldera depressions a model from pantelleria and ischia abstract similar resurgent blocks occur in caldera depressions at the islands of pantelleria and ischia the two blocks which are tilted show similar deformation patterns and similar distributions of volcanic vents related to resurgence the remaining parts of the floors of the two calderas are not deformed similarities between the two features are so striking that the resurgence mechanism must have been alike a dynamic model for resurgence is presented and called simple shearing block resurgence the triggering mechanism is an increase of the magmatic pressure in the upper part of a shallow magma chamber which results in a vertical direction of the maximum stress applied on the roof rocks the block is first defined by high angle inland dipping marginal detachments and then deformed through a simple shearing mechanism reverse faults on its mostly uplifted side determine an horizontal shortening of the block which is balanced on the opposite side by normal faults oblique movements take place along the other two sides due to this distribution of the stress around the block magmas can reach the surface only through the extensional faults on the less uplifted side

on the mechanics of caldera resurgence the mechanisms suggested to cause caldera resurgence can be categorized as 1 viscous rebound of magma 2 regional detumescence and 3 pressure against the base of the caldera block due to magmatic vesiculation and convection or addition of new magma the critical observation that resurgence takes of the order of 103 105 years insists that the causative mechanism be regulated by a highly viscous e g 1022 pa s structural member of the crust the relatively low viscosity magma and a purely elastic crust cannot be important in achieving this time scale the most likely mechanism is the coupled effect of regional detumescence and magmatic vesiculation detumescence compresses the magma chamber squeezing magma upward against and through the caldera block vesiculation also compresses the chamber and tends to dome the caldera block the times of both detumescence and doming of the caldera block by magmatic pressure are probably inversely proportional to the size of the magma chamber but the rate of cooling of the chamber is proportional to its size because solidification spreads viscous relaxation over a wide region of the crust and curtails resurgence there is likely to be a minimum volume of magma that can undergo resurgent doming it is difficult to be exact about this critical size until more precise models have been developed

new insights into late pleistocene explosive volcanic activity and caldera formation on ischia southern italy a new pyroclastic stratigraphy is presented for the island of ischia italy for the period 75 50 ka bp the data indicate that this period bore witness to the largest eruptions recorded on the island and that it was considerably more volcanically active than previously thought numerous vents were probably active during this period the deposits of at least 10 explosive phonolite to basaltic trachyandesite eruptions are described and interpreted they record a diverse range of explosive volcanic activity including voluminous fountain fed ignimbrite eruptions fallout from sustained eruption columns block and ash flows and phreatomagmatic eruptions previously unknown eruptions have been recognised for the first time on the island several of the eruptions produced pyroclastic density currents that covered the whole island as well as the neighbouring island of procida and parts of the mainland the morphology of ischia was significantly different to that seen today with edifices to the south and west and a submerged depression in the centre the largest volcanic event the monte epomeo green tuff megt resulted in caldera collapse across all or part of the island it is shown to comprise at least two thick intracaldera ignimbrite flow units separated by volcaniclastic sediments that were deposited during a pause in the eruption extracaldera deposits of the megt include a pumice fall deposit emplaced during the opening phases of the eruption a widespread lithic lag breccia outcropping across much of ischia and procida and a distal ignimbrite in south west campi flegrei during this period the style and magnitude of volcanism was dictated by the dynamics of a large differentiated magma chamber which was partially destroyed during the megt eruption this contrasts with the small volume holocene and historical effusive and explosive activity on ischia the timing and distribution of which has been controlled by the resurgence of the monte epomeo block the new data contribute to a clearer understanding of the long term volcanic and magmatic evolution of ischia

precambrian cambrian boundary global stratotype ratified and a new perspective of cambrian time the precambrian cambrian boundary global stratotype is the base of the phycodes pedum zone at fortune head southeastern newfoundland the initial two stage radiation of the phanerozoic fauna the appearance of phanerozoic aspect trace producers and subsequent origin of diverse skeletalized metazoans was earliest cambrian fossil assemblages with deep complex burrows or originally mineralized skeletal fossils with exception of cloudina are early cambrian or younger correlation into avalon indicates that strata once referred to the proterozoic e g manykaian or nemakit daldynian and rovno stages are lowest cambrian and that the siberian tommotian stage is middle lower cambrian the thick sequence and complex epeirogenic history of the placentian series as compared with the trilobite bearing branchian series suggest that most early cambrian time is represented by the subtrilobitic lower cambrian

taphonomy of the danek bonebed a monodominant edmontosaurus hadrosauridae bonebed from the horseshoe canyon formation alberta the danek bonebed horsethief member horseshoe canyon formation late campanian is dominated by the remains of at least 12 edmontosaurus regalis skeletal remains of a tyrannosaurid and ceratopsid are also known the predominantly disarticulated remains were interred on a periodically inundated floodplain and although the cause of death is unknown a sudden catastrophic death explains the demographic spread faunal diversity rare greenstick fractures and homogeneous weathering abrasion categories of the assemblage the danek bonebed shares a similar taphonomic signature to the liscomb bonebed prince creek formation alaska but it is unique among all other described hadrosaurid bonebeds in the unusually high proportion of bite marked bones 30 suggesting scavenging played a major role in the reworking of the assemblage the highest frequency of bite marks is found on small often unidentifiable and commonly ignored bone fragments underscoring the role that such fragments can play in taphono

re examining ratio based premaxillary and maxillary characters in eudromaeosauria dinosauria theropoda divergent trends in snout morphology between asian and north american taxa abstract the clade eudromaeosauria predominantly comprises medium to large late cretaceous laurasian dromaeosaurids because many specimens are fragmentary the maxilla has frequently been used to infer the proportions of the entire snout given the strong relationship between snout shape and feeding behaviour such inferences have potentially important palaeobiological implications but they should ideally be justified by explicit analysis maxillae have also been hypothesized to have high interspecific variability and are used to erect new taxa however many maxillary characters are based on proportions that may vary ontogenetically sexually and randomly within species as well as phylogenetically proportionate characters are often unjustifiably coded in terms of discrete states even when they represent a continuum of variation in this study eudromaeosaurian maxillae were examined using bivariate least squares regression and multivariate principal component analysis and cluster analysis methods to discern the extent to which this skull element can be used to draw ecological and phylogenetic inferences the length height ratio of the maxilla was found to be a strong predictor of that of the premaxilla justifying inferences about snout morphology from the former element alone pca and cluster analysis show a strong morphological dichotomy between asian and north american taxa and consistently recover congeneric specimens as being most alike maxillary characters from previous analyses were found to be divisible into discrete states but to nevertheless illustrate the potential problems of using such characters in large datasets parsimony analysis of the revised premaxillary and maxillary characters resulted in a different tree topology than the most recent phylogenetic analyses emphasizing the importance of this element in dromaeosaurid phylogenetics evolution of divergent snout morphologies in asian and north american eudromaeosaurians may have been driven by selective pressures resulting from differences in the range of available prey or in environmental variables such as aridity between the two continents

the 21 august 2017 ischia italy earthquake source model inferred from seismological gps and dinsar measurements the causative source of the first damaging earthquake instrumentally recorded in the island of ischia occurred on 21 august 2017 has been studied through a multiparametric geophysical approach in order to investigate the source geometry and kinematics we exploit seismological global positioning system and sentinel 1 and cosmo skymed differential interferometric synthetic aperture radar coseismic measurements our results indicate that the retrieved solutions from the geodetic data modeling and the seismological data are plausible in particular the best fit solution consists of an e w striking south dipping normal fault with its center located at a depth of 800 m moreover the retrieved causative fault is consistent with the rheological stratification of the crust in this zone this study allows us to improve the knowledge of the volcano tectonic processes occurring on the island which is crucial for a better assessment of the seismic risk in the area

chemical and isotopic signatures of the basement rocks from the campi flegrei geothermal field naples southern italy inferences about the origin and evolution of its hydrothermal fluids abstract the campi flegrei naples campanian plain southern italy geothermal system is hosted by quaternary volcanic rocks erupted before during and after the formation of the caldera that represents one of the major structural features in the neapolitan area the volcanic products rest on a mesozoic carbonate basement cropping out north east and south of the area chemical major minor and trace elements and stable isotope c h o analyses were conducted on drill core samples recovered from geothermal wells mf 1 mf 5 sv 1 and sv 3 at depths of 1100 to 2900 m the study was complemented by petrographic and sem examination of thin sections the water which feeds the system is both marine and meteoric in origin mineral zonation typical of a high temperature geothermal system exists in all the geothermal wells measured temperatures in wells are as high as 400 c the chemical composition of the waters suggests the existence of two reservoirs a shallow reservoir depth 2000 m of hypersaline water the drill cores are mainly hydrothermally altered volcanics of trachy latitic affinity but some altered pelites and limestones are also present published na mg and k concentrations of selected geothermal waters indicate that the hydrothermal fluids are in equilibrium with their host rocks with respect to k feldspar albite sericite and chlorite the measured 18 o smow values of rocks range from 4 3 to 16 5 the measured d smow values range from 79 to 46 the calculated isotopic composition of the fluids at equilibrium with the samples vary from 1 to 8 3 18 o and from 52 to 1 d the estimated isotopic composition of the waters at equilibrium with the studied samples confirmed the existence of two distinct fluid types circulating in the geothermal system the shallower has a marine water signature while the deeper water has a signature consistent both with magmatic and meteoric origins in the latter case the recharge of this aquifer likely occurs at the outcrop of the mesozoic limestones surrounding the campanian plain after infiltration the water percolates through evaporitic layers becoming hypersaline and d depleted

hadrosaurid and lambeosaurid bone beds from the upper cretaceous two medicine formation of montana taphonomic and biologic implications numerous dinosaur bone beds have been found in the upper cretaceous two medicine formation taphonomy and size frequency profiles for the most common skeletal elements of six predominantly hadrosaurid and or lambeosaurid assemblages were compared all six localities are single highly concentrated bone horizons within silty mudstones most are monospecific with some degree of skeletal association parautochthonous and likely the result of mass mortality four are associated with small lacustrine or waterhole environments and may be the result of drought related mortality within the two medicine formation drought was apparently a common mechanism for generating fossil assemblages both hadrosaurids and lambeosaurids appear to have been gregarious lack of association between small total length 3 m and larger individuals suggests either that juvenile growth rates were as rapid as large ungulates or less likely that juveniles had a period of noninteraction with adults perhaps dwelling in strictly ju

the affinities of a new theropod from the alxa desert inner mongolia people s republic of china remains of bipedal saurischians from lacustrine strata of albian age in the alxa alashan desert of inner mongolia represent a new taxon and the most complete remains of an early cretaceous ther

introduction to the special issue commemorating the 30th anniversary of the royal tyrrell museum of palaeontology with a summary of the museum s early history and its research contributions located just west of drumheller in southern alberta canada the royal tyrrell museum of palaeontology rtmp is nestled among outcrops of the upper cretaceous horseshoe canyon formation exposed along the red deer river valley fig 1 since it officially opened on 25 september 19851 the museum has become one of alberta s must see tourist attractions a significant contributor to the local economy and earned an international reputation for the quality of its palaeontological collections and the research conducted by its scientists the rtmp is unique within canada in being the only government supported museum dedicated to palaeontology and it is one of the few such institutions in the world fig 1 the royal tyrrell museum of palaeontology a front of museum and main entrance circa 2010 looking westwards and with horizontal beds of the upper cretaceous horseshoe canyon formation exposed in the walls of the red deer river valley in the distance b aerial photograph oblique angle and looking to the north northeast the museum sits on top of the number 7 coal seam sensu gibson 1977 and at the base of the horsethief member of the horseshoe canyon formation d a eberth pers comm 2015 that stratigraphic position correlates with an age of about 71 5 ma i e late campanian and lies within the upper part of the edmontosaurus regalis pachyrhinosaurus canadensis dinosaur assemblage zone see eberth et al 2013 fig 6 c the iconic running theropod logo that until recently graced the exterior of the museum below a life sized tyrannosaurid sculpture by brian cooley one of many such sculptures by cooley that have been featured at the museum since its opening in 1985 and with the education wing opened in 2003 as the atco tyrrell learning centre in the background d the cretaceous alberta life sized diorama opened in 2007 an example of a rtmp exhibit that relies heavily on discoveries and interpretations by museum researchers in this case work done in the albertosaurus bonebed and at other localities throughout the horseshoe canyon formation all photographs courtesy of the royal tyrrell museum of palaeontology this special issue of the canadian journal of earth sciences presents a collection of papers commemorating the rtmp s 30th or pearl anniversary our rationale for doing a 30th anniversary volume was two fold first it is an opportunity to showcase the breadth of research conducted by current and former museum scientists as well as by some colleagues having a history of collaboration with the rtmp the 13 invited papers included in this volume are a mix of review and original research papers all thematically focused on the geology and palaeontology of alberta to varying degrees each contribution is the result of work supported by the rtmp and relies on specimens housed in the museum s collections second the 30th anniversary is an opportunity to reflect on the rtmp s history and its research program as is typical for most institutions the rtmp has done little to formally document its own history this year likely will be the last major milestone for which the original generation of museum staff are still working and available to share their recollections about the museum fieldwork and research already deaths and departures have winnowed away part of the original

some problems concerning the precambrian cambrian transition and the cambrian faunal radiation in siberia the so called khailakh and manykay stages of pre tommotian age are inferred to be partly coeval with the type tommotian and to be based on a misunderstanding about the control of facies on faunal distributions evolutionary patterns are being studied through this interval using a variety of approaches synoptic reviews are presented on diversity changes on changes in skeletal composition and on archaeocyathan morphology the latter group appear to have originated on the siberian platform just prior to the tommotian and migrated globally during the atdabanian and botomian to form secondary centres of diversification olenellid trilobites may have dispersed in a similar pattern but other groups such as volborthella and relatives appear to have had a separate siliciclastic centre of origin the decline in diversity of small shelly fossils after the tommotian and the coeval expansion in archaeocyathans and trilobites may be related to basinal changes connected with the break up of palaeopangea