sedimentology and isotope geochemistry of carnian deep water marl limestone deposits from the sicani mountains sicily environmental implications and evidence for a planktonic source of lime mud abstract the upper triassic halobia bearing marl limestone deposits from the sicani mountains sicily record the sedimentary evolution of the sicanian basin through the middle and late carnian time dark marls and interbedded grey calcilutites of julian age are characterized by abundant pyrite sparse bioturbation and negative carbonate carbon 13c values they accumulated in a basin with dominantly anoxic to dysaerobic bottom waters lower tuvalian dark grey pyritic marls and calcilutites which contain carbonate minerals with relatively high mn contents and widely fluctuating 13c signatures were deposited under dysaerobic conditions middle and upper tuvalian cherty limestones show intense bioturbation and nearly invariable positive 13c values around 2 for calcite they form a thick and monotonous succession accumulated in a deeper and more oxygenated basin the halobia bearing deposits preserve some calcareous nannoplanktonic forms the nannofossils varying in size from 7 to 32 m are significantly abundant in the cherty limestones pointing to a notable role of the calcareous nannoplankton as a source of carbonate mud in the deep water basins of the southern tethys during the late triassic time

differences in el nino response over the southern hemisphere southern hemisphere sh circulation conditions during austral springs of enso events are examined based on previous knowledge that sst variations over the subtropical south central pacific sscp region are linked to differences among el nino en events a stratification of the springs associated with en events was performed according to sst conditions over the el nino 3 4 sector and over the sscp region the en events associated with cold conditions in the sscp wc exhibit enhanced convection not only in the intertropical convergence zone over the central equatorial pacific but also in the south pacific convergence zone spcz extended south eastward into the subtropical regions the resulting heating forcing intensifies a localized overturning cell which is associated with an anomalous rossby wave source in the central south pacific extratropical region neither the rossby wave source nor the associated wave pattern is evident during en events associated with warm conditions in the sscp and inactive spcz ww the basic features that characterize the differences in the en response over the south pacific can also be identified through the analysis of the spcz activity over the central south pacific the fact that variations in spcz activity lead sst anomaly changes in the sscp would indicate that the differences in the en response over the sh might be mainly driven by atmospheric changes which induces extratropical sst anomalies the differences in the circulation anomalies that characterize both types of en response over the sh were further explored through the analysis of the activity of the three leading modes of circulation variability the combined effect of the three leading patterns describes in some extent the intensification weakening of the cyclonic circulation anomaly observed over the southeastern pacific in wc ww associated with an active inactive spcz in particular the interdecadal variability observed in the pacific by many previous studies influences the circulation response to enso over the sh mainly through changes in the activity of the sh annular mode

tertiary uplift and inversion history in the north celtic sea basin and its influence on source rock maturity abstract tertiary uplift and basin inversion have been widely recognized in the area of the north celtic sea basin offshore ireland but the magnitude and timing of the various events have not been well documented an understanding of these events is important because recent basin history generally has a major influence on hydrocarbon source rock maturity levels a multi disciplinary approach was used to investigate the timing and nature of uplift in the north celtic sea basin involving seismic data interpretation well log correlation vitrinite reflectance measurement apatite fission track analysis and a cretaceous chalk group isopach and velocity study both regional uplift and compressive inversion can be interpreted to have occurred based on missing geological section compressive reactivation of earlier normal faults and basin centred uplift two tertiary erosion events are recognized a regional uplift in the palaeocene and compressive inversion characterized by basin doming and fault reversal probably associated with an oligo miocene phase of the alpine orogeny separating these was a period of basinal deposition in the eocene to oligocene a map of the magnitude of erosion generated as a result of the two events shows that the amount of uplift is quite variable in the northeast part of the basin where the later event was most severe uplift was as much as 1100 m reconstruction of the basin geometry before inversion together with thermal modelling at selected well locations suggests that upper jurassic source rocks reached maturity for oil generation only in the central portion of the basin whereas lower jurassic source rocks entered the gas window in much of the basin prior to tertiary uplift

atmospheric circulation features associated to argentinean andean rivers discharge variability 1 winter atmospheric circulation patterns and their relationship to runoff variability in the atuel and chubut rivers of argentina are analyzed the most important atmospheric low levels condition associated with high low atuel discharges is the weakening strengthening of the mean atmospheric flow while the same feature is displaced 5 southward for chubut at high levels results suggest the existence of a nw se direction wave pattern extending from australia to the south atlantic favoring positive negative pressure anomalies west of the drake passage which deflect the storm tracks northward southward and hence increase decrease precipitations and subsequent atuel discharges in contrast chubut discharges are mainly controlled by a shorter wave pattern along the subtropical pacific which zonally crosses south america this pattern helps to maintain low high pressure anomalies off the chilean coast at the upper river basin latitude for high low chubut runoffs

extension tectonics in the wessex basin southern england the permian to cretaceous tectonic evolution of the wessex basin was controlled by horizontal tensional and vertical isostatic forces within the lithosphere the gross morphologies of its constituent structures were governed by the location of variscan thrust and wrench faults in the upper and middle crust which suffered extensional reactivation in tensional stress fields oriented approximately nw se several episodes of crustal extension can be resolved in early permian early triassic early jurassic and late jurassic early cretaceous times these were characterized by the rapid subsidence of fault bounded basins and commonly by erosion of adjacent upfaulted blocks superimposed upon the fault controlled subsidence dominant during periods of fault quiescence and becoming increasingly important with time a component of regional subsidence is considered to have a thermal origin this suggests that crustal extension was accompanied by some form of not necessarily uniform lithospheric thinning subsidence analyses assuming local airey isostasy give cumulative crustal extension factors of 20 28 beneath the grabens a more reasonable assumption of regional airey compensation indicates basinwide crustal extension of 13 17 which is consistent with birps offshore deep seismic reflection data

the structure and evolution of the wessex basin southern england an example of inversion tectonics abstract the wessex basin of southern england consists of four main sub basins each sub basin is thought to be fundamentally controlled by the normal reactivation of hercynian basement thrust and wrench or transfer faults post hercynian polyphase reactivation of both east west thrust and northwest southeast transfer faults tended to compartmentalise the basement thereby leading to the initiation of discrete permian cretaceous depocentres while rifting was confined to the western portions of the area during the permo triassic easterly migration in the mesozoic allowed the initiation of the weald and channel basins the sub basins represent therefore simple sinistral pull apart basins opening along northwest southeast faults this same fault direction is postulated to have also played a major role in controlling and or modifying the development of european basins in general major pre aptian uplift and erosion is largely attributed to the thermal effects and hence the isostatic uplift of the basin associated with continental rifting of the bay of biscay and the north atlantic margins major inversion and hence basin destruction began in the late cretaceous early tertiary with the uplift of the channel weald and vale of pewsey basins and culminated in the oligocene miocene synchronous with the helvetic phase of alpine deformation wessex basin inversion was facilitated by the thrust reactivation of variscan faults above an intracrustal detachment surface the same surface which allowed upper crustal extension and hence basin initiation in the permo triassic the structural development of the wessex basin both during extension basin formation phase and compression inversion phase was ultimately controlled by the plate motion of africa relative to europe such plate motions successfully predict the observed nw se sinistral motion from the stephanian to the aptian e w sinistral motion during the aptian cenomanian and largely nw se dextral motion from the cenomanian to the present day

the control of sedimentary facies by climate during phases of crustal extension examples from the triassic of onshore and offshore england and northern ireland crustal extension controls the tectonic accommodation space available for sediments in rift settings and may be defined by the structural and depositional geometry of sedimentary successions observed on seismic data and the rate of subsidence through time as represented by the accommodation of sediment the characteristic features of each are dependant on three variables the time taken for deposition the interplay between tectonics and eustasy and the lithology thus facies of the succession observed the sherwood sandstone group has been considered to represent a syn rift phase of fluvial deposition throughout europe with the overlying mercia mudstone group interpreted as the succeeding phase of deposition in an evaporitic seaway during post rift thermal subsidence more recently however there has been the recognition that it is the mercia mst gp which is seen to thicken markedly into faults imaged on seismic data rather than the sherwood sandstone group this work demonstrates the mercia mst gp to be a syn rift phase of deposition with the fine grained nature of the sedimentary record at this time controlled by the prevailing arid climate such conditions were not conducive to the large scale and rapid movement of sediments from the hinterlands raised by relative footwall uplift thus the sediments are fine grained the minor thickening of the sherwood sst gp into faults is interpreted to be a combination of minor extension in the early triassic superimposed on thermal subsidence inherited from the important regional phase of extension in the early permian analysis of the timing of fault growth indicates a larger proportion of fault controlled synsedimentary movement occurred during the mid to late triassic mercia mst gp rather than the early triassic sherwood sst gp

the permian to jurassic stratigraphy and structural evolution of the central cheshire basin new seismic reflection data reveal details of the permo triassic basin fill in the central cheshire basin the seismic stratigraphy indicates that the permian and triassic succession is far thicker than previously estimated seismic data and backstripping of the preserved permian to early jurassic sedimentary succession suggest that at least two phases of fault controlled subsidence occurred in early permian and early triassic times an intra triassic unconformity is seen on the seismic data near the top of the sherwood sandstone group this may equate with the hardegsen unconformity it is possible that this unconformity was generated by syn extensional regional uplift accompanying lithospheric thinning the gross morphology and location of the faults on the eastern margin of the cheshire basin are interpreted to be at least locally controlled by extensional re activation of a westwards dipping reverse fault possibly an extension of the pontesford linley lineament

relationships between low frequency variability in the southern hemisphere and sea surface temperature anomalies abstract long term trends and interannual variations of circulation anomalies in the southern hemisphere are examined using the national centers for environmental prediction national center for atmospheric research reanalysis from 1949 to 1998 the changes in planetary circulation regimes are linked to global sea surface temperature anomalies sstas empirical orthogonal function eof analysis was performed on 500 hpa height anomalies the leading mode eof1 shows a strong zonal symmetry with a phase reversal between height anomalies in high and midlatitudes apart from zonal symmetry a zonal wavenumber 3 is evident with three centers located in three southern oceans in the low frequency band with fluctuations longer than 60 months eof1 is associated with the second rotated eof mode of sstas with positive loadings over three southern oceans and negative loadings in the north pacific and the north atlantic the next two modes are the pacific south american psa patterns they depict wave 3 patterns in

redox dependent distribution of early macro organisms evidence from the terminal ediacaran khatyspyt formation in arctic siberia abstract the ediacaran period witnessed the first appearance of macroscopic animal life in earth s history however the biogeochemical context for the stratigraphic occurrence of early metazoans is largely uncertain in part due to the dearth of integrated paleobiological and chemostratigraphic datasets in this study a comprehensive geochemical analysis was conducted on the fossiliferous khatyspyt formation in arctic siberia in order to gain insights into the ediacaran paleoenvironments this study was designed to specifically address the relationship between paleoredox conditions and ediacaran fossil occurrences in the khatyspyt formation our data reveal a dramatic shift in pyrite sulfur isotope compositions 34 s pyrite from ca 20 to ca 55 and this shift is intriguingly associated with the first occurrence of ediacara type macrofossils at the studied section suggesting a possible link between seawater redox conditions and distribution of early macroscopic organisms based on multiple lines of sedimentological and geochemical evidence we propose that the development of oceanic euxinia which may be widespread in the continental margins due to enhanced oxidative weathering in the terminal ediacaran period may have locally prohibited the colonization of ediacara type organisms and resulted in low 34 s pyrite values in the lower khatyspyt formation in the middle and upper khatyspyt formation progressive secular transition from euxinic to non euxinic and more habitable conditions may have allowed for the colonization of ediacara type and other macro organisms

the oldest evidence of bioturbation on earth detailed study of the khatyspyt formation in arctic siberia has shown that contrary to common expectations the earliest ichnofabric is of late ediacaran age records a food seeking behavior and is found in a distal carbonate ramp setting where it co occurs with fossils of avalon type ediacaran soft bodied organisms preserved depth of bioturbation reaches 5 cm the ichnofabric solely comprises nenoxites the oldest known meniscate trace fossil which is interpreted as burrows with terminal backfill structure formed as a result of active displacement of sediment to form a tunnel within the substrate followed by emplacement of the material behind the animal as it progressed through the sediment in addition to being the most reliable paleontological evidence for the existence of bilaterians at ca 555 ma the late ediacaran bioturbation is regarded as a key step in the escalatory engineering of phanerozoic ecospace leading to sudden diversification of macroscopic organisms and macrocommunities

predictive model for the development and distribution of triassic reservoir sands offshore southeast ireland based on seismic sequence geometries at the variscan unconformity

the variscan fold thrust belt of southeast ireland and its control on early mesozoic extension and deposition a method to predict the sherwood sandstone

the stable isotope altimeter do quaternary pedogenic carbonates predict modern elevations stable isotope altimetry is a useful tool for estimating paleoelevation in sedimentary records yet questions remain regarding how source moisture climate and local topography can influence these estimates here we present stable isotope altimetry results on late quaternary pedogenic carbonates of known elevation on both flanks of the andean orogen at 33 s we measured 18 o values of pedogenic carbonates and river water samples from small drainages at regular elevation increments within the rio aconcagua chile and rio mendoza argentina catchments the 18 o values of river waters correlate well with elevation and show similar isotopic gradients between the chilean 3 7 km and argentine 4 8 km sides of the range uncertainties associated with scatter in the river water data and assumptions about the temperature of carbonate formation indicate that elevation estimates have 1 errors of 350 450 m we estimate the isotopic composition of soil water from pedogenic carbonates on both sides of the range by assuming mean annual temperatures based the modern temperature lapse rate from meteorological station data combined our data show that stable isotope altimetry produces reasonable estimates of modern elevation with the majority of our samples 60 within the 1 uncertainties and 77 within 2

seasonality of the enso related rainfall variability in central chile and associated circulation anomalies the seasonality of the enso rainfall relationship in central chile 308 418s and associated circulation anomalies are studied using correlation and compositing techniques during el nino episodes there is a tendency for the occurrence of above average precipitation between 308 and 358s in winter june july august jja and from 358 to 388s in late spring october november on while rainfall deficit is typically observed from around 388 to 418s during the following summer january february march jfm when el nino reaches its maximum development opposite rainfall anomalies are characteristic during la nina events this study confirms results from previous investigations indicating that enhanced blocking activity over the amundsen bellings hausen seas area in the southeastern se pacific during el nino is a key feature explaining the wet conditions in winter it is also shown that the same circulation anomaly explains the relatively wet conditions in late spring in the 358 388s region during el nino episodes furthermore the southward displacement from winter to late spring of the area with significant enso related rainfall anomalies seems associated with the seasonal migration of the boundary separating the region under the influence of the subtropical domain from the extratropical domain where the westerly regime and associated disturbances prevail blocking episodes in the se pacific during el nino seem to be part of a wave structure particularly intense during spring characterized by a sequence of positive and negative quasi barotropic height anomalies stretching southeastward from the equator toward the se pacific and back to the southwestern atlantic on the other hand anomalously dry conditions in winter and late spring during la nina are favored by long lasting and intense ridges at subtropical latitudes over the se pacific and south america resulting in a southward migration of the midlatitude storm tracks in summer a higher frequency of ridges in the southern tip of the south america during el nino episodes presumably contributes to reinforcement of the southern edge of the subtropical anticyclone in the se pacific which at this time of the year reaches its southernmost position resulting in the annual rainfall minimum on the other hand an increased frequency of cyclonic circulation anomalies crossing the southern tip of the continent is associated with relatively wet conditions in southern central chile particularly during la nina events

revised neoproterozoic and terreneuvian stratigraphy of the lena anabar basin and north western slope of the olenek uplift siberian platform abstract the early to mid neoproterozoic pre glacial sedimentary succession of the lena anabar basin northeast siberian platform records protracted faulting and subsidence possibly as part of the widespread continental rifting and the break up of rodinia there is a significant stratigraphic unconformity separating the pre glacial neoproterozoic strata and the overlying upper ediacaran succession in the lena anabar basin with the terreneuvian strata most likely to be deposited in a foreland of the central taimyr accretionary belt the cryogenian sensu strictum i e younger than 720 ma and lower ediacaran deposits are missing in the area in this study we assess the palaeontological content of the precambrian and terreneuvian strata of the lena anabar basin and the adjacent north western slope of the olenek uplift and revise the chronostratigraphy of the region with special emphasis to biostratigraphic index taxa for the pre glacial neoproterozoic section we establish the new tukulan kulady taimylyr formations and redefine the khastakh formation we also refine the ediacaran and terreneuvian stratigraphy by formalising the maastakh khatyspyt and turkut formations of the khorbusuonka group whereas the kessyusa formation is raised to group rank and subdivided into the syhargalakh oppokun mattaia and chuskuna formations the proposed stratigraphic correlation scheme is based upon depositional unity and is consistent both lithologically and biostratigraphically providing a robust framework for future stratigraphic sedimentological and palaeobiological studies

seismic reflection investigations into the stratigraphy and structural evolution of the worcester basin two seismic reflection lines recently shot in the western part of the worcester basin suggest that its western boundary is defined by major syn depositional normal faults downthrowing to the east and active throughout permo triassic times farther east other faults can be seen within the basin these moved at various times during the permian and triassic and profoundly affected patterns of sedimentation the subsidence history of the basin can be explained by two phases of lithospheric stretching one in the permian and the second in early triassic times giving a cumulative stretching factor of about 1 2 this is consistent with the regional pattern of normal faulting provided that stretching was either one dimensional oblique to the n s and e w directions or two dimensional

neoproterozoic substrate condition vis a vis microbial mat structure and its implications sonia sandstone rajasthan india dst fast track project young scientist scheme no sr ftp es 03 2011 cas phase v upe ii programme of jadavpur university national research foundation and university of pretoria south africa

the oldest evidence of bioturbation on earth reply brasier et al 2012 1 raise concerns over our interpretation of the meniscate structure in the late ediacaran carbonates of the khatyspyt formation of siberia rogov et al 2012 2 although serial sectioning or ct scanning would no doubt reveal the three dimensional morphology of the

rainfall patterns and the distribution of coals and evaporites in the mesozoic and cenozoic abstract paleoclimatologists have adequately demonstrated over the last twenty years that the distribution of climatically sensitive sediments can be related to present day climatic zones that are roughly parallel to latitude for example coals were deposited at paleolatitudes that correspond to the present day rainy zones at the equator and at about 55 n and 55 s indicating that those zones were present in the past from this it can be concluded that atmospheric circulation has not been radically different from its present configuration despite some apparently great differences in some climatic parameters such as the equator to pole temperature gradient nevertheless the zonal model for predicting the distribution of climatically sensitive sediments is not wholly adequate although general atmospheric circulation may not have been radically altered from its present pattern it would have differed in some respects because the paleogeography was different from the present geography therefore we have constructed what we believe are more realistic maps of the distribution of rainfall through time these maps are based on maps of atmospheric circulation that have been successfully used to predict the distribution of some petroleum source beds and phosphorites we have compared the predicted distribution of rainfall to the distribution of coals and evaporites for each of seven geologic stages the circulation rainfall maps were more successful than the zonal model for predicting the distribution of evaporites and coals for times when the paleogeography would have maximized the development of a monsoonal circulation which most effectively disrupts the general zonal pattern for times when a monsoonal circulation would not have been important the zonal model adequately predicted the distribution of these rocks

structures and textures in triassic braided stream conglomerates bunter pebble beds in the sherwood sandstone group north staffordshire england in the northern parts of the needwood and stafford eccleshall basins england the pebble beds of the sherwood sandstone group contain thick successions of texturally mature fluvial pebble cobble conglomerates which are organized into either horizontal or cross stratified sets the horizontally lying sets generally coarser grained and more poorly sorted than the cross bedded sets are usually disorganized and either matrix or clast supported although thin lenses of well sorted occasionally openwork units interpreted as falling stage phenomena are often present the cross stratified conglomerates have foresets exhibiting remarkable textural organization with a coarse bimodal sometimes matrix supported part grading upwards or being abruptly overlain by a finer well sorted occasionally openwork part and finally capped by sandstone these rhythmic textural changes are attributed partly to an avalanche process at high stage and partly to falling stage conditions the most common types of vertical association are thick successions of horizontally bedded conglomerates up to 20 m and sequences of an upwards coarsening nature 2 12 m in which cross stratified sets are overlain by flat lying sets the environment of deposition of the gravels is interpreted as one in which water depths at high stage were greater than depths in most modern braided stream plains proglacial or alluvial fan but shallower than depths associated with the pleistocene catastrophic floods from which texturally mature giant gravel bars have been recorded recent braided streams with relatively confined channels and considerable bar channel relief are better analogues in particular medial or mid channel bars with a two tier structure subaqueous and partly emergent portions may explain the upward coarsening sequences in which horizontally lying conglomerates overlie cross stratified conglomerates the thicker sequences of horizontally stratified conglomerates represent proximal longitudinal bar deposits sheets of pebbly sandstone and argillaceous sandstone lying between the conglomerates and commonly occurring towards the top of the succession largely represent deposition from sandwaves and dunes finer interbedded argillaceous sandstones siltstones and mudstones are interpreted as overbank and waning flood deposits basin forming tectonism of increasing intensity probably caused the initial coarsening upwards of the lower part of the succession whilst more stable tectonic conditions and decreasing relief on the margins of the basins and in the areas of provenance in the midlands and the hercynides account for the upwards fining of the upper part of the succession

the oldest evidence of bioturbation on earth comment recently rogov et al 2012 1 discovered dense bioturbation fabrics the preserved depth of which reached 5 cm from the ediacaran khatyspyt formation of the northern siberian platform the age of the bioturbated beds is estimated at ca 555 ma the ichnotaxon itself is attributed to the

the south celtic sea bristol channel basin origin deformation and inversion history abstract the south celtic sea bristol channel basin is a relatively narrow and elongated sedimentary trough located within the northern part of the hercynian fold belt and filled with permo triassic redbeds to jurassic marine sediments its present configuration is the result of a three fold sequence of tectonic phases initiated during the late palaeozoic the origin of the basin appears to be related to localised extensional reactivation of hercynian thrust zones during the permian and early triassic followed by regional subsidence during the late triassic and jurassic uplift of the basin margins together with dextral strike slip movements in an east west sense and large scale erosion during the late jurassic to early cretaceous resulted in the present elongated configuration of the lower mesozoic basin regional subsidence from aptian time onwards resulted in widespread deposition of a relatively thin section of wealden elastics and upper cretaceous chalk unconformably overlying folded pre cretaceous strata sedimentation was interrupted during the early tertiary by a series of tectonic events that included emplacement of the lundy igneous mass during the early eocene and mild basin inversion during the oligo miocene inversion was accompanied by dextral reactivation of the nw se oriented sticklepath fault zone the total amount of uplift probably not exceeding 350 m reflects the rather stable configuration of the underlying lithospheric crust as indicated by seismic reflection and refraction data

the thermal and mechanical development of the wessex basin southern england summary the wessex basin of southern england is an e w trending late palaeozoic to tertiary extensional basin formed on early palaeozoic variscan crust extension occurred over a protracted period from late carboniferous to cretaceous times resulting in the evolution of four main depocentres or sub basins the channel basin winterborne kingston trough vale of pewsey and weald basins each sub basin was controlled fundamentally by the normal reactivation of basement thrust faults and wrench or transfer faults the basement faults represent primary structures associated with the fold and thrust terrain of the devonian carboniferous variscan orogeny subsequent but synchronous reactivation of both thrust and transfer faults tended to compartmentalize the basement leading to discrete depocentres and the production of general rhomboidal shaped sub basins characteristic of pull apart basins in strike slip terrains to investigate the thermo mechanical properties of the lithosphere during basin formation 50 boreholes within the wessex basin were back stripped to isolate the driving tectonic subsidence responsible for basin formation the resultant driving subsidence is characterized by a gentle sometimes negative exponential form with superimposed rapid discrete subsidence events as the geological development of the wessex basin was characterized by polyphase extension and the utilization of crustal detachments the lithospheric model used to determine crustal extension above the detachment and stretching below the detachment included the effects of depth dependent stretching and finite re rifting from the back stripping analysis the basin wide averaged upper crustal extension and lower crustal sub crustal lithospheric stretching were 11 and 5 respectively the distribution of is strongly influenced by the location of growth faults and hence basement thrust fault reactivation suggesting that is reflecting the brittle failure and collapse of hanging wall blocks repeated slip and block collapse resulted in the polyphase extension responsible for renewed basin subsidence in contrast is uniformly distributed across the basin suggestive of a ductile failure of the lower crust and responsible for the low magnitude thermal subsidence strain compatibility between the upper crust and lower crust sub crustal lithosphere is maintained partly within the basin 5 and partly external to the basin as the variscan basal thrust was the fundamental relay in the sense of wernicke responsible for the wessex basin formation we postulate that strain balancing induced a cumulative essentially thermal isostatic uplift of 60 m under the northern margin of the armorican massif

climatic and biotic change in the late triassic generally arid conditions that pervaded much of europe and north america during the late triassic were interrupted by a wet monsoonal climatic phase during middle and late carnian times extensive fluviatile sandstones deposited at this time throughout the region occur within a thick sequence of playa lake mudstones the sandstones occasionally contain kaolinite suggesting a humid climate an extreme 13 c depletion in a shallow marine sequence of this age in israel has been interpreted as evidence for an influx of freshwater a widespread change from carbonates to clastics in marine sequences at this time may also be climate related water course cave systems in limestone areas exposed during the late triassic indicate high levels of runoff during the middle and late carnian the marine invertebrate fauna shows a significant turnover at the end of the early carnian the terrestrial fauna and flora were relatively unaffected at this time but subsequently diversified prior to a major biotic turnover at the carnian norian boundary these periods of biotic change appear to be synchronous with the onset and cessation of a carnian humid phase the change to a monsoonal climate during this interval has been documented over more than 90 of longitude between 5 and 50 north of the triassic equator it may have been caused by rising atmospheric co 2 levels due to volcanism associated with the incipient dispersal of pangaea

first finds of problematic ediacaran fossil gaojiashania in siberia and its origin we describe the first occurrence of the problematic fossil gaojiashania outside china in the ediacaran yudoma group of the siberian platform in both areas gaojiashania characterizes the lower upper ediacaran strata and precedes the appearance of cloudina and other skeletal fossils which highlights its significance for the ediacaran subdivision and correlation features of this fossil such as indeterminate length the absence of a distinct growth pattern and self avoiding behaviour indicate its trace fossil origin but do not necessarily imply metazoan affinities for its producers several organisms including stem group social amoebozoans and unicellular protists may have been proterozoic trace fossil producers

development of small gas fields in the kinsale head area a number of potential development prospects have been identified in the area of the kinsale head gas field in the celtic sea using the recent development of the ballycotton gas field as a model this paper discusses how similar fields might be developed as satellites of the existing production platforms the ballycotton gas field was discovered in march 1989 by an exploration well drilled in block 48 20 by the western pacesetter iv a further two wells confirmed the extent of the gas accumulation see taber et al 1995 the field is located approximately 25 miles off the coast of cork and 8 miles north of the kinsale head gas field fig 1 which up to that time was ireland s only producing gas field colley et al 1981 the existence of gas processing facilities relatively close to the discovery well was a major factor in determining the technical and commercial viability of the ballycotton gas field owing to the relatively small size of the field and the predicted initial flow rate of over 50 mmscfd which could be obtained from the primary lower cretaceous a sandstone reservoir it was decided to tie the discovery well 48 20 2 back to one of the kinsale head platforms this was made possible by means of sub sea completion techniques whereby the necessary production equipment is installed underwater at the well site and the well is remotely controlled from a mother platform which also processes the gas this obviates the need for a permanent platform or a floating production system both