aeolian sand sea development along the mid cretaceous western tethyan margin spain erg sedimentology and palaeoclimate implications the existence of a mid cretaceous erg system along the western tethyan margin iberian basin spain was recently demonstrated based on the occurrence of wind blown desert sands in coeval shallow marine deposits here the first direct evidence of this mid cretaceous erg in europe is presented and the palaeoclimate and palaeoceanographic implications are discussed the aeolian sand sea extended over an area of 4600 km2 compound crescentic dunes linear draa and complex aeolian dunes sand sheets wet dry and evaporitic interdunes sabkha deposits and coeval extradune lagoonal deposits form the main architectural elements of this desert system that was located in a sub tropical arid belt along the western tethyan margin sub critically climbing translatent strata grain flow and grain fall deposits pin stripe lamination lee side dune wind ripples soft sediment deformations vertebrate tracks biogenic traces tubes and wood fragments are some of the small scale structures and components observed in the aeolian dune sandstones at the boundary between the aeolian sand sea and the marine realm intertonguing of aeolian deposits and marine facies occurs massive sandstone units were laid down by mass flow events that reworked aeolian dune sands during flooding events the cyclic occurrence of soft sediment deformation is ascribed to intermittent marine flooding of aeolian dunes and associated rise in the water table the aeolian erg system developed in an active extensional tectonic setting that favoured its preservation because of the close proximity of the marine realm the water table was high and contributed to the preservation of the aeolian facies a sand drift surface marks the onset of aeolian dune construction and accumulation whereby aeolian deposits cover an earlier succession of coastal coal deposits formed in a more humid period a prominent aeolian super surface forms an angular unconformity that divides the aeolian succession into two erg sequences this super surface formed in response to a major tectonic reactivation in the basin and also marks the change in style of aeolian sedimentation from compound climbing crescentic dunes to aeolian draas the location of the mid cretaceous palaeoerg fits well to both the global distribution of other known cretaceous erg systems and with current palaeoclimate data that suggest a global cooling period and a sea level lowstand during early mid cretaceous times the occurrence of a sub tropical coastal erg in the mid cretaceous of spain correlates with the exposure of carbonate platforms on the arabian platform during much of the late aptian to middle albian and is related to this eustatic sea level lowstand

palaeoseismology review of the state of the art abstract historical seismicity provides only a partial indication of the seismotectonic character i e earthquake potential of a given region even in italy where a relatively long historical record exists available catalogues are generally unsatisfactory for this purpose fortunately strong earthquakes often leave geological evidence herein referred to as seismites that are mainly related to surface faulting folding or other deformation and occasionally to secondary ground failures e g landslides liquefaction features etc these features may be preserved and therefore palaeoseismological studies may detect and date them thereby permitting extension of knowledge beyond the local historical threshold up to 2000 years in the most fortunate cases this paper provides a summary of criteria which may aid in the identification of areas suitable for palaeo earthquake investigation historical seismicity and the presence of well developed tectonic geomorphic features are recognized as the most reliable criteria for identifying active faulting however lack of these characteristics cannot be considered conclusive evidence for lack of activity palaeoseismological techniques aim at identifying not only the obvious effects of surface faulting such as offset of young geologic units but also the more subtle tectonic or non tectonic features including liquefaction structures gravity features and coseismic uplift and or subsidence finally we discuss some questions that pertain to palaeoseismicity evaluation techniques among these are the reliability of the quaternary dating techniques the evaluation of the seismic energy released minimum magnitude and principally the unequivocal identification of a seismic origin for the considered geological structures

timing of recovery from the end permian extinction geochronologic and biostratigraphic constraints from south china four volcanic ash beds bracket the early middle triassic boundary as defined by conodont biostratigraphy in a stratigraphic section in south china high precision u pb dates of single zircons allow us to place the early to middle triassic olenekian anisian boundary at 247 2 ma magnetic reversal stratigraphy allows global correlation the new dates constrain the early triassic interval characterized by delayed biotic recovery and carbon cycle instability to 5 m y this time constraint must be considered in any model for the end permian extinction and subsequent recovery

postapocalyptic greenhouse paleoclimate revealed by earliest triassic paleosols in the sydney basin australia the permian triassic boundary in the sydney basin of australia is coincident with a pronounced decrease in 13 c isotopic values of organic carbon the last coals anywhere in the world for all of the early triassic ca 6 m y time and extirpation of the glossopteris flora at the top of the illawarra and newcastle coal measures coal bearing paleosols of the latest permian represent extensive swamplands of the seasonally deciduous glossopteris flora in a humid cold temperate lowland southwest of an andean style volcanic arc stone rolls large ribs of floor rock up into the coal within some of the uppermost coals of the permian coal measures can be interpreted as string bogs of a kind now found in cold climates at latitudes of 68 70 which is compatible with a paleomagnetically estimated paleolatitude of 65 85 s for the sydney basin paleolatitude was not much different for earliest triassic time but paleosols of that age include inceptisols and entisols showing substantial chemical and textural weathering more like soils now forming at latitudes of 40 58 than those within polar circles this anomalous high latitude warmth set in at the permian triassic boundary sedimentation rates increased at the boundary marked by geochemically unusual acidification of clay and a dramatic carbon isotopic excursion these changes in environments and ecosystems can be explained by soil erosion following deforestation implied by the plant extinctions and abundant fungal remains at the permian triassic boundary evidence from paleosols can now be added to that from paleontological and isotopic studies showing that disruption of the carbon cycle at the permian triassic boundary resulted in a co 2 or ch 4 post apocalyptic greenhouse paleoclimate

an integrated model of extrusive sand injectites in cohesionless sediments clastic injection and surface expression of subsurface sediment remobilization is a phenomenon which is becoming increasingly recognized however understanding of the physical mechanisms that control these features remains limited dominated by inference from outcrop and seismic studies here this limitation is addressed through a set of experiments focused on the development and evolution of fluidization features in non cohesive bedded sequences fluidization and the onset of piping are shown to occur progressively through a sequence of discrete phases with initial void formation development of infiltration horizons rupture and finally pipe formation critically the style of piping the stability of piping and the temporal evolution of venting are shown to exhibit considerable variability in particular pipes may either be stable or very mobile migrating laterally over large distances these produce deposits that are typically interpreted in outcrop as being the product of en masse liquefaction rather than localized dynamic fluidization these differing elements are synthesized to produce a model of sand extrudites in addition the implications of this model are explored

diagenetic origin of carbon and oxygen isotope compositions of permian triassic boundary strata bulk carbonate 13 c and 18 o compositions of profiles across permian triassic p t boundary sections in china italy austria and iran show wide varieties of trends the 13 c depletions occur in all sections and range from 2 to 8 pdb in magnitude these excursions take place over intervals ranging from less than 0 1 to more than 40 m the 18 o values may increase or decrease toward the p t boundary but decrease sharply by 2 9 pdb at or above the boundary cross plots of 13 c and 18 o values from all sections show positive covariance wide differences in magnitudes trends and position of the excursions relative to the boundary as well as the covariance patterns suggest that p t boundary 18 o and 13 c values are partially or entirely diagenetic in origin formed in association with exposure surfaces this interpretation implies that p t boundary sections studied till date were subaerially exposed before during and after the mass extinction resulting in the removal of strata containing key information about the extinction mechanism this inference is consistent with the paleontological studies that have shown the presence of gaps at the boundary and further supported by the sharp lithologic changes observed at virtually all p t boundary sections subaerial exposures are documented by detailed sedimentologic and isotopic studies from central tethyan sections in abadeh and shah reza in iran proposed p t boundary extinction models are based on isotopic values that are diagenetic in origin and stratigraphic sections that are incomplete leading to extinction mechanisms with little physical supporting evidence

lower triassic peritidal cyclic limestone an example of anachronistic carbonate facies from the great bank of guizhou nanpanjiang basin guizhou province south china abstract most shallow marine sections described from the lower triassic formed in mixed carbonate siliciclastic systems shallow marine limestones from an isolated carbonate platform the great bank of guizhou in the nanpanjiang basin south china provide a unique opportunity to examine a pure peritidal carbonate depositional system the platform had a low relief bank profile in the early triassic with oolite shoals at the margin shallow subtidal and peritidal deposits in the interior and pelagics debris flow deposits and turbidites on gentle basin margin slopes interior strata are 265 m thick beginning in the lowermost triassic with renalcis biostromes followed by lime mudstone oolite and cyclic peritidal limestone the cyclic limestone is olenekian in age 164 m thick and contains up to 83 cycles parasequences parasequences are 0 2 7 4 m thick and typically shallow upward from subtidal oolite grainstone and skeletal packstone facies followed by renalcis reef mounds or biostromes and capped by intertidal flaser bedded ribbon rock the skeletal packstone and reef mounds contain a low diversity biota of cyanobacteria echinoderms bivalves gastropods lingulid brachiopods spirorbids and ostracodes ribbon rock contains alternating lime mud and fine peloidal packstone and grainstone laminae scour surfaces ripple cross lamination lime mud drapes and minor prism cracks parasequence stacking patterns exhibit gradual increase and decrease of parasequence thickness defining a third order sequence boundary and several 4th order parasequence sets that correlate between interior sections parasequence stacking patterns similar to those of lower palaeozoic green house sequences and different from ice house sequences the lower triassic platform interior parasequences represent an anachronistic facies in that they are strikingly similar to the common renalcis mound ribbon rock parasequences of the lower palaeozoic and different from other permo triassic parasequences e g capitan shelf parasequences or loferites facies similarities such as renalcis mounds and flaser bedded intertidal ribbon rock reflect anomalous oceanic conditions resulting in low biodiversity and low intensity of bioturbation after the end permian extinction similarities in parasequence stacking patterns reflect low amplitude high frequency sea level fluctuations resulting from green house conditions common to the early palaeozoic and early triassic

earthquake magnitude frequency epicentral distance and soft sediment deformation in sedimentary basins abstract empirical equations available for earthquake magnitude frequency and the maximum epicentral distance of liquefied sites versus magnitude are combined with the characteristic instantaneous sediment deposition rate at a station in a sedimentary basin to form a model for the local stratigraphic frequency of earthquake induced soft sediment deformation structures both the style of sedimentation and the characteristics of the earthquake source combine to determine the pattern of incidence of the structures in a basin the model is probably most directly applicable to the geodynamic interpretation of fluvial basins in which substantial volumes of readily liquefied sands accumulate at high local short term rates

u pb zircon geochronology and tempo of the end permian mass extinction the mass extinction at the end of the permian was the most profound in the history of life fundamental to understanding its cause is determining the tempo and duration of the extinction uranium lead zircon data from late permian and early triassic rocks from south china place the permian triassic boundary at 251 4 0 3 million years ago biostratigraphic controls from strata intercalated with ash beds below the boundary indicate that the changhsingian pulse of the end permian extinction corresponding to the disappearance of about 85 percent of marine species lasted less than 1 million years at meishan a negative excursion in 13 c at the boundary had a duration of 165 000 years or less suggesting a catastrophic addition of light carbon

seismically induced soft sediment deformation structures in an active seismogenic setting the plio pleistocene karewa deposits kashmir basin nw himalaya abstract recent uplift in the nw himalaya has exposed more than 1000 m of the plio pleistocene so called karewa deposits in kashmir these deposits mostly consist of horizontal stratified sand silt clay conglomerates and lignite beds the sedimentary succession belongs to the kashmir basin that is located in a seismically active zone the area was previously affected by large earthquakes the observed soft sediment deformation structures ssds are predominantly developed in the sand silt and clay beds and include load and water escape structures intrusive sedimentary bodies convolute bedding disturbed laminites and slump structures deformation mechanism and driving forces of the ssds were seismic shock waves sediment loading and storm events as driver for the ssds are less likely and the proximity of the ssds to faults underlines the seismic origin of these structures syn and post depositional faults and deformation bands developed in the karewa deposits support the interpretation of neotectonic activity and point to an earthquake of magnitude 5 5 that struck the kashmir basin in the plio pleistocene

transient response of an atmospheric gcm to north atlantic sst anomalies abstract a high resolution atmospheric general circulation model gcm is used to evaluate the atmospheric response to north atlantic sea surface temperature sst anomalies the transient evolution of the response is studied in detail the linear and nonlinear effects can thus be contrasted and separated by their different time scales baroclinic patterns related directly to the surface anomalies quickly reach their maximum manifestation however barotropic patterns related to the mid and upper troposphere eddy vorticity fluxes have longer time scales with much more important amplitude able to gradually replace the initial baroclinic response this study thus provides an evolutional picture of the two types of response in a gcm

circumglobal teleconnections the jet stream waveguide and the north atlantic oscillation abstract monthly and seasonally averaged upper tropospheric northern hemisphere winter fields are examined to determine whether the waveguiding effect of the time averaged tropospheric jets on low frequency disturbances that is predicted by theory does affect the behavior of these disturbances it is found that indeed disturbances in the vicinity of the mean jets particularly the jet that stretches across south asia are fundamentally different from those that reside in regions where the mean winds have weaker meridional gradients like the mid pacific patterns of variability in the jets tend to be smaller scale and to consist of zonally oriented chains of anomalies while variability in the mid pacific is composed of patterns with distinct meridional orientation because they are meridionally trapped and zonally elongated patterns associated with the jet stream waveguide connect activity at points that are much farther apart than do patterns in other regions of the globe within the south asian waveg

mid cretaceous aeolian desert systems in the yunlong area of the lanping basin china implications for palaeoatmosphere dynamics and paleoclimatic change in east asia abstract the mid cretaceous constitutes a period of worldwide atmospheric and oceanic change associated with slower thermohaline circulation and ocean anoxic events possible polar glaciations and by a changing climate pattern becoming controlled by a zonal planetary wind system and an equatorial humid belt during the mid cretaceous the subtropical high pressure arid climate belt of the planetary wind system controlled the palaeolatitude distribution of humid belts in asia as well as the spatial distribution of rain belts over the massive continental blocks at mid low latitudes in the southern and northern hemispheres additionally the orographic effect of the andean type active continental margin in east asia hindered the transportation of ocean moisture to inland regions with rising temperatures and palaeoatmospheric conditions dominated by high pressure systems desert climate environments expanded at the inland areas of east asia including those accumulated in the mid cretaceous of the simao basin the sichuan basin and the thailand s khorat basin and leading the late cretaceous erg systems in the xinjiang basin and jianghan basin this manuscript presents evidences that allow to reinterpret previously considered water laid sediments to be accumulated as windblown deposits forming part of extensive erg sandy desert systems using a multidisciplinary approach including petrological sedimentological and architectural observations the mid cretaceous albian turonian nanxin formation from the yunlong region of lanping basin formerly considered to aqueous deposits is here interpreted as representing aeolian deposits showing local aeolian fluvial interaction deposits the palaeowind directions obtained from the analysis of aeolian dune cross beddings indicates that inland deserts were compatible with a high pressure cell hpc existing in the mid low latitudes of east asia during the mid cretaceous compared with the early cretaceous the mid cretaceous had extremely lower temperatures and pressure gradients more arid climate which is in accordance with the existing morphology of hpc and the hpc was stable with little movement simultaneously the deserts controlled by the mid cretaceous hpc were closer to the equator indicating the shrinkage of the hadley cell relative to the early cretaceous

geometry and origin of large scale deformation structures in some ancient wind blown sand deposits large scale deformational features that disrupt the cross bedded strata of some ancient wind blown dune sand deposits jurassic aztec and navajo sandstones u s a can betraced laterally for at least tens of metres information from four exposures leads to an idealized deformation style characterized by 1 a head portion marked by collapse features 2 a middle portion marked by a thrust ramp or a large recumbent fold and 3 a toe portion marked by a planar shear zone with small recumbent folds drag folds and possibly small horizontal shear faults an hypothesis involving earthquake induced liquefaction and collapse of the dunes is proposed sands liquefied during earthquakes cannot support an unequal surface load resulting in the collapse of surface dunes above the liquefied substrate compensatory lateral squeezing of liquefied sand and buried strata produces the shear zone in the toe portion engineering studies suggest that buried strata underlying interdunal lows where over burden stress is least will be most susceptible to liquefaction other considerations suggest that it will be the steeper lee sides of advancing surface dunes that collapse squeezing liquefied sand forward or downwind i e away from the lee slope of surface dunes if the liquefied condition persists load structures can be formed when unliquefied layers founder into the liquefied substrate

changes in the global carbon cycle occurred as two episodes during the permian triassic crisis coeval records of ocean atmosphere and terrestrial change are crucial to understanding the pattern and causes of global mass extinction across the permian triassic boundary ptb however relationships among changes in different settings remain largely unclear primarily due to the challenges associated with the correlation among disparate records here we compare marine carbon isotopic records with marine and terrestrial environmental and biotic events recorded in sediments from the meishan ptb section of south china time scaled carbonate carbon isotopes exhibit two gradual major shifts across the ptb at meishan and these are duplicable elsewhere around the tethys ocean the two shifts are associated with two episodes of enhanced terrestrial weathering indicated by an increased abundance of 13 c enriched moretanes relative to hopanes and an elevated abundance of black carbon fragments key marine events previously reported for the ptb including photic zone euxinia faunal mass extinction and cyanobacterial expansion also occur as two episodes coinciding with both of the progressive shifts to negative 13 c values and enhanced weathering the temporal sequence of the duplicable events suggests that the biotic crisis was a consequence of prolonged and episodic changes in the marine and continental systems and argues against an extraterrestrial impact as the main cause

the unusual sedimentary rock record of the early triassic a case study from the southwestern united states abstract sedimentary systems as well as the earth s biota changed dramatically following the end permian mass extinction this global sedimentological transformation is reflected in the widespread occurrence of flat pebble conglomerates subtidal wrinkle structures microbialites and carbonate seafloor fans in various lower triassic sections as a case study a facies analysis of the lower triassic virgin limestone member of the moenkopi formation and the middle and upper members of the union wash formation southwestern united states was conducted and all unusual facies were documented within a palaeoenvironmental framework the occurrence of the flat pebble conglomerates and wrinkle structures is significant because these reflect a long term reduction in vertical bioturbation in the case of the subtidal microbialites and carbonate seafloor fans their formation is linked to an increase in alkalinity the presence of these facies in the uppermost lower triassic strata of the southwestern united states indicates that reduced levels of infaunal bioturbation as well as and perhaps a consequence of unusual ocean chemistry extended for 5 6 million years after the end permian mass extinction suggesting that depositional environments as well as the biota were significantly affected by the extinction event

seismically induced deformation structures in oligocene shallow marine and aeolian coastal sands paris basin abstract soft sediment deformation structures have been identified in the oligocene coastal sand body in the southern part of the paris basin stampian sables de fontainebleau formation these coastal barrier sediments are characterized by pure fine grained sands the deformed beds are observed over some 60 110 km2 and are present either in foreshore sands or aeolian sand dunes convoluted laminations of an average amplitude around 0 70 m were identified in the foreshore or interdune sediments these are interpreted as the result of liquefaction conversely deformed sets of aeolian dune sand often involve large amounts of sediment these large scale contorted laminae several metres thick with minor internal faulting suggest deformation by slope failure under wet conditions such large scale soft sediment deformations may have been generated by storm surges and earthquakes which have similar liquefaction potentials we propose that the deformation structures were created by a single triggering event because of the absence of superposition of deformed layers over the study area the earthquake triggering hypothesis is supported by the large amount of sand involved in the slope failure features and the persistence of the contorted laminations over a wide area

development of a largely anoxic stratified ocean and its temporary massive mixing at the permian triassic boundary supported by the sulfur isotopic record systematic sulfur isotope data for whole rock sulfides have been obtained from the chert dominated continuous pelagic sedimentary sequences spanning the permian triassic p tr boundary at tenjinmaru in the chichibu terrane and at sasayama in the tanba terrane in japan the p tr boundary is characterized by the occurrence of siliceous shales in association with a carbonaceous black mudstone which is similar in appearance to the worldwide distributed cretaceous tertiary k t boundary claystone the observed data clearly demonstrate a significant bimodalism the 34s 32s ratios with respect to cdt are generally low throughout the middle permian ca 39 to 25 0 and show a remarkable increase beginning in the lower upper permian and persisting into the lower triassic ca 20 to 2 0 with a temporary and drastic negative shift down to roughly the same isotopic level as in the middle permian just at the suspected p tr boundary ca 41 to 23 0 interestingly the mode of isotopic excursion across the p tr boundary is in striking contrast to that across the k t boundary which was recently described at kawaruppu in hokkado japan the apparent extent of fractionation with respect to contemporaneous seawater sulfate in the high 34s 32s group lies within the range of 25 10 0 which is quantitatively equivalent to the currently confirmed range of kinetic isotope effect during bacterial dissimilatory sulfate reduction and that in the low 34s 32s group mostly exceeds this range giving the values typically in the range of 45 10 0 which is similar to what is generally observed in the present day oceanic sediments the present data would provide strong evidence for the development of a largely stagnant anoxic stratified ocean which presumably began to form in the lower upper permian and persisted into the lower triassic and for a brief episode of its temporary massive mixing just at the suspected p tr boundary such an oceanic oxic anoxic history may account to some extent for the relatively high enrichments of chalcophile elements in basal triassic sediments in the world and add a significant constraint to the current arguments on the cause and consequence of the terminal permian mass extinction

seismites in the lokapur subgroup of the proterozoic kaladgi basin south india a testimony to syn sedimentary tectonism abstract syn sedimentary deformation structures ssds can indicate disturbance caused by autogenic or allogenic processes affecting the depositional system such structures are prolific in the proterozoic shallow marine sediments of kaladgi basin especially in the basal part of the succession lokapur subgroup in both clastics and carbonates widespread distribution lateral traceability of the deformed horizons across several hundreds of meters their occurrence between undeformed beds and proximity to nw se to e w trending faults and shears are used to attribute a seismic origin to some of these ssds release of accumulated stresses in the basin floor undergoing extension caused the episodic seismic activity producing the seismites these seismites record the syn sedimentary tectonism that controlled facies distribution patterns in the mesoproterozoic bagalkot group in conjunction with sea level fluctuations on one hand this is a contribution towards recognition of seismic events during the mesoproterozoic a period from which few seismites have been recorded on the other hand recognizing that the crustal processes that operated in brittle regimes during the creation of this extensional supracrustal basin around 1800 ma were comparable to those operating in present day extensional systems opens a window of understanding how the proterozoic platform basins hosting thick shallow marine sequences evolved

sea surface temperature anomalies planetary waves and air sea feedback in the middle latitudes the mechanisms that contribute to the generation and damping of large scale mid latitude sea surface temperature sst anomalies are discussed the sst anomalies reflect primarily the response of the upper ocean to the changes in air sea fluxes that are associated with daily weather fluctuations heat flux forcing is dominant in the lower middle latitudes while wind driven entrainment may be most effective in the high latitudes advection by anomalous ekman current is generally less important and ekman pumping is negligible the sst anomalies decay in part because of entrainment effects associated with mixed layer deepening and oceanic mixing and in part because of heat exchanges with the atmosphere the three approaches commonly used to model the evolution of sst anomalies are reviewed case studies based on monthly or seasonal anomaly maps of the large scale sst and atmospheric anomalies numerical simulations with one dimensional mixed layer models and stochastic forcing models we stress the similarities in the different approaches and discuss their main advantages and limitations the response of the atmosphere to mid latitude sst anomalies is considered first we discuss the poorly known relationship between sst anomalies and diabatic heating using a crude assumption for the air sea coupling we consider a two layer quasi geostrophic channel model and discuss the stationary wave response to sst anomaly forcing and the resulting air sea feedback it is found that the back interaction of the sst anomalies onto the atmosphere causes a weak sst anomaly damping at large scales and a strong one at small scales the air sea coupling should also act as an eastward propagator for the sst anomalies the response of more realistic linear wave models to prescribed diabatic heating is then reviewed and it is suggested that realistic mid latitude sst anomalies have a weak influence on the atmospheric circulation corresponding to changes in the geopotential height of 10 30 m at most this order of magnitude is consistent with the results of general circulation model experiments and with the limited climate predictability associated with mid latitude sst anomalies

large scale atmospheric response to eastern mediterranean summer autumn sst anomalies and the associated regional impact since the mediterranean sea is halfway between subtropical and middle latitudes and it represents a marginal oceanic region research has tended to focus on how large scale modes of atmospheric variability modulate its surface temperature conversely the present study examines the potential influence of the mediterranean sea surface temperature sst anomalies on the northern hemisphere atmospheric circulation in particular this work explores the large scale changes in the global circulation forced influenced by the eastern mediterranean summer autumn sst pattern to isolate the atmospheric response agcm sensitivity experiments with prescribed sst over the mediterranean sea and climatology elsewhere are analysed observational diagnostics upon the period used to define the boundary conditions 1979 2002 are also interpreted our results support the hypothesis of an atmospheric pattern initiated in the mediterranean basin pointing out both a local baroclinic response and a barotropic circumglobal anomaly this atmospheric teleconnection pattern projects onto a hemispheric wave like structure reflecting the waveguide effect of the westerly jets results suggest thereby that the recurrent summer autumn circumglobal teleconnection pattern can be excited locally by changes in the atmosphere over the mediterranean region a linear behaviour is found upon a regional impact over northeastern africa the remote impacts present however a nonlinear signature anomalous warm conditions influencing on northern europe and euro asia whereas anomalous cold conditions impacting more on the north pacific basin limitations in our model setup are also discussed

simulation of the east asian summer monsoon using a variable resolution atmospheric gcm the east asia summer monsoon easm is simulated with a variable resolution global atmospheric general circulation model gcm developed at the laboratoire de meteorologie dynamique france the version used has a local zoom centered on china this study validates the model s capability in reproducing the fundamental features of the easm the monsoon behaviors over east asia revealed by the ecmwf reanalysis data are also addressed systematically providing as observational evidence the mean state of the easm is generally portrayed well in the model including the large scale monsoon airflows the monsoonal meridional circulation the cross equatorial low level jets the monsoon trough in the south china sea the surface cold high in australia and the upper level northeasterly return flow while the performance of simulating large scale monsoonal climate is encouraging the model s main deficiency lies in the rainfall the marked rainbelt observed along the yangtze river valley is missed in the simulation this is due to the weakly reproduced monsoonal components in essence and is directly related to the weak western pacific subtropical high which leads to a fragile subtropical southwest monsoon on its western flank and results in a weaker convergence of the southwest monsoon flow with the midlatitude westerlies the excessively westward extension of the high together with the distorted indian low also makes the contribution of the tropical southwest monsoon to the moisture convergence over the yangtze river valley too weak in the model the insufficient plateau heating and the resulting weak land sea thermal contrast are responsible for the weakly reproduced monsoon it is the deficiency of the model in handling the low level cloud cover over the plateau rather than the horizontal resolution and the associated depiction of plateau topography that results in the insufficient plateau heating comparison with the simulation employing regular coarser mesh model reveals that the local zoom technique improves in a general manner the easm simulation

thin skinned deformation of sedimentary rocks in valles marineris mars deformation of sedimentary rocks is widespread within valles marineris characterized by both plastic and brittle deformation identified in candor melas and ius chasmata we identified four deformation styles using hirise and ctx images kilometer scale convolute folds detached slabs folded strata and pull apart structures convolute folds are detached rounded slabs of material with alternating dark and light toned strata and a fold wavelength of about 1 km the detached slabs are isolated rounded blocks of material but they exhibit only highly localized evidence of stratification folded strata are composed of continuously folded layers that are not detached pull apart structures are composed of stratified rock that has broken off into small irregularly shaped pieces showing evidence of brittle deformation some areas exhibit multiple styles of deformation and grade from one type of deformation into another the deformed rocks are observed over thousands of kilometers are limited to discrete stratigraphic intervals and occur over a wide range in elevations all deformation styles appear to be of likely thin skinned origin crism reflectance spectra show that some of the deformed sediments contain a component of monohydrated and polyhydrated sulfates several mechanisms could be responsible for the deformation of sedimentary rocks in valles marineris such as subaerial or subaqueous gravitational slumping or sliding and soft sediment deformation where the latter could include impact induced or seismically induced liquefaction these mechanisms are evaluated based on their expected pattern scale and areal extent of deformation deformation produced from slow subaerial or subaqueous landsliding and liquefaction is consistent with the deformation observed in valles marineris

recent changes in deep water formation and spreading in the eastern mediterranean sea a review abstract observations of the last decade testify that the characteristics of the deep thermohaline circulation in the eastern mediterranean sea have changed thoroughly the source of the most dense waters of the basin has moved from the adriatic to the aegean sea this new source has proved to be very efficient since the estimated formation rate for the period 1989 95 was more than 1 sv about three times more than the dense water formation rate of the adriatic sea these new waters with hydrological characteristics that are warmer and more saline have replaced almost 20 of the older deep waters of the basin and have uplifted the deep isopycnals by about 500 m this major event can be attributed to important meteorological anomalies in the eastern mediterranean and to changes of circulation patterns the extended dry period of 1988 93 and the exceptionally cold winters of 1987 and 1992 93 created favorable conditions for increased formation of dense water in the aegean furthermore changes in the circulation patterns in the intermediate water range levantine intermediate water liw and cretan intermediate water themselves possibly linked to meteorological anomalies appear to have played an important role in the redistribution of salt as a result of an interruption to exchanges between the ionian and levantine basin the salinities in the latter started to rise high salinity waters were diverted into the aegean malanotte rizzoli p manca b b ribera dacala m theocharis a 1998 the eastern mediterranean in the 80s and in the 90s the big transition emerged from the poem bc observational evidence rapport du commission international de la mer medittanee 35 174 175 and the westward transport of liw was reduced an additional effect of the deep water discharge from the aegean and the resulting uplifting of mid depth waters was to lower salinities in the liw layer this effect is most strongly felt in the ionian sea a 3 d primitive equation numerical model for the eastern mediterranean with a 20 km grid size is used to simulate the observed changes and understand the basic mechanisms which caused them under appropriate atmospheric forcing the model successfully reproduces the main characteristics of the transient these results indicate that the observed changes can be at least partially explained as a response of the eastern mediterranean and more specifically of the aegean to atmospheric forcing variability

asian jet waveguide and a downstream extension of the north atlantic oscillation abstract anomalous atmospheric fields associated with the north atlantic oscillation nao are analyzed on interannual and intraseasonal time scales in order to examine the extent to which the nao is a regional phenomenon analyses on the interannual time scale reveal that the nao signal is relatively confined to the euro atlantic sector in december while it extends toward east asia and the north pacific in february the difference is most clearly seen in the meridional wind anomaly which shows a wave train along the asian jet collocated with an anomalous vorticity source near the jet entrance diagnoses using a linear barotropic model indicate that this wave train is interpreted as quasi stationary rossby waves trapped on the asian jet waveguide and effectively excited by the anomalous upper level convergence over the mediterranean sea it is found that when the nao accompanies the mediterranean convergence mc anomaly most frequently seen in february the nao indeed has a much wider horizontal str

the western mediterranean deep water a proxy for climate change reconstructions of mediterranean ocean temperature fields back to 1950 show a proxy relationship between heat content changes in the north atlantic and the western mediterranean deep water wmdw formed in the gulf of lions in winter because of consistent air sea heat fluxes over these areas strongly correlated to the north atlantic oscillation nao

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

the role of the global carbonate cycle in the regulation and evolution of the earth system we review one of the most ancient of all the global biogeochemical cycles and one which reflects the profound geochemical and biological changes that have occurred as the earth system has evolved through time that of calcium carbonate caco3 in particular we highlight a mid mesozoic revolution in the nature and location of carbonate deposition in the marine environment driven by the ecological success of calcareous plankton this drove the creation of a responsive deep sea sedimentary sink of caco3 the result is that biologically driven carbonate deposition provides a significant buffering of ocean chemistry and of atmospheric co2 in the modern system however the same calcifying organisms that under pin the deep sea carbonate sink are now threatened by the continued atmospheric release of fossil fuel co2 and increasing acidity of the surface ocean we are not yet in a position to predict what the impact on caco3 production will be or how the uptake of fossil fuel co2 by the ocean will be affected this uncertainty in the future trajectory of atmospheric co2 that comes from incomplete understanding of the marine carbonate cycle is cause for concern

controls on facies architecture of a large triassic carbonate platform the great bank of guizhou nanpanjiang basin south china abstract the great bank of guizhou gbg is an exceptionally well exposed isolated triassic platform in the nanpanjiang basin of south china the platform is exhumed with its depositional profile preserved and is dissected by a faulted syncline that exposes a complete and uncomplicated cross section providing a unique opportunity to evaluate mechanisms involved in its birth evolution and demise the gbg formed near the southern margin of the yangtze platform during a deepening event that expanded the nanpanjiang basin and drowned the region surrounding the gbg in the latest permian initial accumulation of the gbg began in the latest permian with small reef mounds and open marine skeletal packstones following the end permian extinction cyanobacterial boundstones grew over the bank top during the early triassic the gbg developed a low relief bank profile with mobile oolite shoals at the margin shallow subtidal and peritidal deposits in the interior and gentle slopes dominated by pelagics debris flow deposits and turbidites at the basin margin in the middle triassic anisian the gbg developed a progressively steepening profile rimmed with massive tubiphytes reefs the platform was flat topped with tidal flat deposits across the interior basin margin deposition was dominated by turbidites and debris flow deposits but eventually shifted to avalanche and rock fall deposits as the slopes steepened to the angle of repose in the middle triassic ladinian an erosional escarpment up to 1700 m high developed at the margin platform margin strata are bedded packstones similar to interior strata whereas breccias at the basin margin contain coral boundstone clasts suggesting erosion of reefs from the escarpment a restricted subtidal lagoon formed in the interior producing an atoll like morphology later a flat topped profile was restored as tidal flats spread across the interior in the beginning of the late triassic deepening contributed to termination of the gbg before siliciclastic turbidites and shales were deposited over the platform in contrast with the well known platforms of the dolomites of northern italy the gbg contains abundant muddy carbonates and a progressively steepening bank to reef rimmed and escarpment architecture the italian platforms contain little mud and have angle of repose pinnacle geometries the gbg s larger size increased mud production and protected it from extensive winnowing of mud which in turn resulted in off bank shedding of muddy sediments that were stable on relatively gentle basin margin slopes which progressively steepened and ultimately led to avalanche deposits and a high relief erosional escarpment in contrast the lesser mud content of the dolomites platforms forced avalanche and talus deposition to dominate throughout deposition of basin margins which in turn produced their angle of repose geometries

glacial mediterranean sea surface temperatures based on planktonic foraminiferal assemblages we present a new reconstruction of mediterranean sea surface temperatures sst during the last glacial maximum lgm a calibration data set based on census counts of 23 species of planktonic foraminifera in 129 north atlantic and 145 mediterranean core top samples was used to develop summer winter and annual average sst reconstructions using artificial neural networks anns and the revised analogue method ram prediction errors determined by cross validation of the calibration data set ranged between 0 5 and 1 1 c with both techniques being most successful in predicting winter ssts glacial reconstructions are based on a new expanded data set of 273 samples in 37 cores with consistent minimum level of age control the new lgm reconstructions suggest that the east west temperature gradient during the glacial summer was 9 c whereas during the glacial winter the gradient was 6 c both some 4 c higher than that existing today in contrast to earlier studies our results tend to suggest much cooler sst estimates throughout the glacial mediterranean particularly in the eastern basin where previous sst reconstructions indicated a decrease of only 1 c our new sst reconstructions will provide the modelling community with a detailed and updated portrayal of the mediterranean sea during the lgm setting new targets on which glacial simulations can be tested

permian triassic boundary interval in the abadeh section of iran with implications for mass extinction part 1 sedimentology the uppermost permian strata of the abadeh section in iran consist of 56 m of skeletal limestone abadehian that grades upward into 18 m of grey bioturbated lime mudstone djulfian which in turn grades upward to 18 m of red nodular wackestone dorashamian containing an abundant pelagic fauna the overlying lowermost triassic includes two enigmatic layers at its base immediately above the boundary is a 1 m thick layer of inorganically precipitated synsedimentary carbonate cement the cement is composed of 10 20 cm long crystals oriented either perpendicular to the bedding or as dome shaped features resembling botryoids about 0 5 m of wackestone overlies the cement layer the second layer is a 1 5 m thick grainstone overlying the cement horizon and consists of recrystallised spherical grains ooids or peloids the remainder of unit a is composed of 100 m of grey bioturbated to nodular lime mudstone the lithofacies succession of the uppermost permian is interpreted to represent deposition under increasing water depth related to rising of relative sea level which led to drowning of the carbonate platform to below storm wave base sedimentologic characteristics lithology wide distribution and slow sedimentation rates indicate that strata immediately below the permian triassic p t boundary dorashamian interval were deposited in deep oxygenated waters the enigmatic lowermost triassic synsedimentary carbonate cement and grainstone layers are interpreted to have been deposited in shallow waters indicating a rapid and major drop in relative sea level at the end of permian time in this area followed by a relative sea level rise during the earliest triassic precipitation of synsedimentary cement immediately above the p t boundary in iran and elsewhere south china suggests a global change in ocean chemistry one possible explanation is that dissolved calcium and bicarbonate concentrations in seawater increased sufficiently to promote spontaneous carbonate precipitation a rare event in the phanerozoic but common during precambrian time alternatively a massive heating event could have resulted in co2 degassing and decreases in oceanic carbonate solubility both leading to inorganic synsedimentary carbonate precipitation inorganic precipitation of synsedimentary carbonate cement may indicate that biochemical production of carbonate was halted due to the p t boundary events our study indicates that shallow and moderately deep waters during the latest permian were well oxygenated in the open ocean setting of the central tethys sea in iran therefore p t mass extinction scenarios that invoke upon widespread marine anoxia should be viewed with caution

δ13c and δ18o values of triassic brachiopods and carbonate rocks as proxies for coeval seawater and palaeotemperature abstract a dataset of 160 isotope 13c and 18o values from anisian ladinian carnian and rhaetian articulate brachiopod shells complemented by 158 carbon and oxygen isotope values from whole rock carbonates define the first continuous stable isotope baseline trends for the triassic seawater the carbon isotope data suggest the existence of several short term high amplitude excursions in the early triassic followed by a predominance of values around 0 5 1 during the middle triassic a rise to 3 5 during the carnian plateau at this level during the late carnian to early norian and a 1 5 decline in the middle norian to values around 2 during the late norian rhaetian interval the causation scenarios for these rapid oscillations are at present equivocal but may in part reflect a biological instability of the carbon cycle following the recovery from the end permian extinction event and or an input of mantle derived co2 from enhanced volcanic activity the 18o values from well preserved brachiopods from the tethyan realm range from 3 9 to 0 6 v pdb these values require open marine triassic seawater 18o values close to 0 v smow for the calculated temperatures to be within the range of tolerance of the coexisting reef building corals a 2 18o increase within the uppermost cordevolian and early julian suggests either a distinct temperature decline in the southern alps during that time interval an increase in seawater salinity or their combination oxygen isotope values for the muschelkalk brachiopods range between 6 2 and 2 0 and likely reflect a strong influx of meteoric waters into the germanic basin that shifted the oxygen isotopes to more negative values

mechanisms determining the atmospheric response to midlatitude sst anomalies abstract previous gcm experiments demonstrated that a model atmosphere produces two different responses to a midlatitude warm sst anomaly over the pacific under perpetual january and february conditions to elucidate the mechanisms responsible for the different gcm responses and their dependence on the background flow experiments with two idealized models are conducted experiments with a linear baroclinic model reveal that the gcm responses at equilibrium are primarily maintained by the anomalous eddy forcing the anomalous flow induced directly by an idealized initial heat source exhibits little sensitivity to the background flow eddy feedbacks on the heating induced anomalous flow are examined using a linear storm track model the anomalous eddy forcing produced by the storm track model is sensitive to the basic state the eddy forcing in january acts to shift the heating induced upper level ridge toward the northeast of the gulf of alaska while in february it acts to reinforce the ridge this sugge

evolution of the late miocene mediterranean atlantic gateways and their impact on regional and global environmental change marine gateways play a critical role in the exchange of water heat salt and nutrients between oceans and seas as a result changes in gateway geometry can significantly alter both the pattern of global ocean circulation and associated heat transport and climate as well as having a profound impact on local environmental conditions mediterranean atlantic marine corridors that pre date the modern gibraltar strait closed during the late miocene and are now exposed on land in northern morocco and southern spain the restriction and closure of these miocene connections resulted in extreme salinity fluctuations in the mediterranean leading to the precipitation of thick evaporites this event is known as the messinian salinity crisis msc the evolution and closure of the mediterranean atlantic gateways are a critical control on the msc but at present the location geometry and age of these gateways are still highly controversial as is the impact of changing mediterranean outflow on northern hemisphere circulation here we present a comprehensive overview of the evolution of the late miocene gateways and the nature of mediterranean atlantic exchange as deduced from published studies focussed both on the sediments preserved within the fossil corridors and inferences that can be derived from data in the adjacent basins we also consider the possible impact of evolving exchange on both the mediterranean and global climate and highlight the main enduring challenges for reconstructing past mediterranean atlantic exchange

mechanisms and controls on the formation of sand intrusions sandstone intrusions are found in all sedimentary environments but have been reported most commonly from deep water settings they also appear to be more frequently developed in tectonically active settings where applied tectonic stresses facilitate development of high fluid pressures within the sediments a variety of mechanisms have been cited as triggers for clastic intrusions these include seismicity induced liquefaction application of tectonic stresses excess pore fluid pressures generated by deposition related processes and the influx of an overpressured fluid from deeper within the basin into a shallow sand body the formation of sandstone dykes and sills is investigated here by considering them as natural hydraulic fractures when the seal on an unconsolidated overpressured sand body fails the resulting steep hydraulic gradient may cause the sand to fluidize the fluidized slurry can then inject along pre existing or new fractures to form clastic intrusions the scale and the geometry of an intrusive complex is governed by the stress state depth and pre existing joints or faults within the sedimentary succession as well as the nature of the host sediments for the simplest tectonic setting where the maximum stress in a basin is vertical gravitational loading small irregular intrusions commonly result in the formation of sills at shallow depths within a few metres of the surface whereas at greater depth dykes and sills forming clastic intrusion networks are more typical a simple relationship is derived to calculate the maximum burial depth at which a dyke sill complex forms as a function of the source bed to sill height the bulk density of the surrounding sediments and the ratio of the vertical to horizontal effective stresses k 0 when applied to three examples of large scale dyke sill complexes developed within paleocene and eocene deep water reservoir sand bodies of the north sea maximum burial depths in a range of 375 to c 500 m 450 700 m and 550 850 m are estimated for intrusion of each of the three complexes

altered river morphology in south africa related to the permian triassic extinction the permian triassic transition in the karoo basin of south africa was characterized by a rapid and apparently basin wide change from meandering to braided river systems as evidenced by preserved sedimentary facies this radical changeover in river morphology is consistent with geomorphic consequences stemming from a rapid and major die off of rooted plant life in the basin evidence from correlative nonmarine strata elsewhere in the world containing fluvial permian triassic boundary sections suggests that a catastrophic terrestrial die off of vegetation was a global event producing a marked increase in sediment yield as well as contributing to the global 13 c excursion across the permian triassic boundary

non annular hemispheric signature of the winter north atlantic oscillation sensitivity experiments with an atmospheric general circulation model agcm without a proper stratosphere are performed to locally force a north atlantic oscillation nao like response in order to analyse the tropospheric dynamics involved in its hemispheric extent results show that the circulation anomalies are not confined to the north atlantic basin not even within the first 10 days of integration where the atmospheric response propagates downstream into the westerly jets at this linear stage transient eddy activity dominates the emerging regional nao like pattern while zonal eddy coupling may add on top of the wave energy propagation later at the quasi equilibrium nonlinear stage the atmospheric response emphasizes a wavenumber 5 structure embedded in the westerly jets associated with transient eddy feedback upon the atlantic and pacific storm tracks this agcm waveguided structure rightly projects on the observational nao related circumglobal pattern providing evidence of its non annular character in the troposphere these findings support the view on the importance of the circumglobal waveguide pattern on the development of nao related anomalies at hemispheric level it could help to settle a consensus view of the arctic oscillation which has been elusive so far

a microbialite carbonate crust at the permian triassic boundary in south china and its palaeoenvironmental significance a 1 m thick carbonate crust layered and commonly domal caps crinoidal limestones on reef complexes of the top permian changxing formation in the huaying mountains eastern sichuan china the crust s stratigraphic level lies at a sharp change in facies and is overlain by poorly fossiliferous laminated micrites and shales of the lower triassic feixianguan formation the crust therefore appears to coincide with the end permian extinction event although the dating of the strata is currently imprecise the crust is composed mostly of digitate carbonate locally thrombolitic with remnant lobate fabric and resembles microbialites but is mostly recrystallised and a microbial origin is unconfirmed it is enclosed in micrite with pyrite crystals ostracode and other shell debris the crust is absent from interreef areas previous interpretations of karstification and calcrete formation are not upheld and the facies were deposited under water overlying sediments are low energy with abundant ferroan calcite and pyrite reflecting anoxia associated with rising sea level various interpretations of the crust are possible 1 it was organic and microbia grew preferentially on topographic highs of reef tops 2 microbia were a disaster biota in the absence of grazers 3 microbia took advantage of favourable conditions for calcification associated with a rapidly rising environmental co2 content during the late permian 4 the crust was an inorganic precipitate associated with co2 rich water microbial crusts are rare after the cambrian but whether this crust is organic or not its presence in these strata reinforces the view that oceanic atmospheric conditions in the permian triassic boundary interval were unusual

late cretaceous climbing erg systems in the western xinjiang basin palaeoatmosphere dynamics and east asia margin tectonic forcing on desert expansion and preservation abstract this study reassesses the terrestrial deposits of the late cretaceous tangbian formation in the western xinjiang basin of the south china block originally considered to be aqueous deposits we reinterpret these strata as representing an extensive aeolian system in a desert environment this paper suggests that the development of aeolian deposits in the tangbian fm represents the culmination of the late cretaceous desertification that followed the relatively humid early late cretaceous epoch in the interior of south china the area was dominated by subtropical high pressure systems on a planetary scale combined with coastal mountains caused by sustained orogenic activity the interaction between subtropical high pressure systems and topographic conditions ultimately caused the development of a tropical desert climate characterized by an extensive dry climbing aeolian dune system we propose that the coastal mountains not only blocked moisture transport from the ocean and led to the aridification of south china interior but also exerted a control and transformed the original prevailing surface wind pattern

chronology causes and progression of the messinian salinity crisis the messinian salinity crisis is widely regarded as one of the most dramatic episodes of oceanic change of the past 20 or so million years 1 3 earliest explanations were that extremely thick evaporites were deposited in a deep and desiccated mediterranean basin that had been repeatedly isolated from the atlantic ocean1 2 but elucidation of the causes of the isolation whether driven largely by glacio eustatic or tectonic processes have been hampered by the absence of an accurate time frame here we present an astronomically calibrated chronology for the mediterranean messinian age based on an integrated high resolution stratigraphy and tuning of sedimentary cycle patterns to variations in the earth s orbital parameters we show that the onset of the messinian salinity crisis is synchronous over the entire mediterranean basin dated at 5 96 0 02 million years ago isolation from the atlantic ocean was established between 5 59 and 5 33 million years ago causing a large fall in mediterranean water level followed by erosion 5 59 5 50 million years ago and deposition 5 50 5 33 million years ago of non marine sediments in a large lago mare lake sea basin cyclic evaporite deposition is almost entirely related to circum mediterranean climate changes driven by changes in the earth s precession and not to obliquity induced glacio eustatic sea level changes we argue in favour of a dominantly tectonic origin for the messinian salinity crisis although its exact timing may well have been controlled by the 400 kyr component of the earth s eccentricity cycle

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

ocean stagnation and end permian anoxia ocean stagnation has been invoked to explain the widespread occurrence of organic carbon rich laminated sediments interpreted to have been deposited under anoxic bottom waters at the time of the end permian mass extinction however to a first approximation stagnation would severely reduce the upwelling supply of nutrients to the photic zone reducing productivity moreover it is not obvious that ocean stagnation can be achieved numerical experiments performed with a three dimensional global ocean model linked to a biogeochemical model of phosphate and oxygen cycling indicate that a low equator to pole temperature gradient could have produced weak oceanic circulation and widespread anoxia in the late permian ocean we find that polar warming and tropical cooling of sea surface temperatures cause anoxia throughout the deep ocean as a result of both lower dissolved oxygen in bottom source waters and increased nutrient utilization buildup of quantities of h2s and co2 in the late permian ocean sufficient to directly cause a mass extinction however would have required large increases in the oceanic nutrient inventory

seismites in continental sand sea deposits of the late cretaceous caiua desert bauru basin brazil abstract two large scale sediment deformation structures minor fold occurrences in cross bedded sand dune deposits and complex convolute folds are observed in red sandstones in a zone about 1 5 km long in floodway cuts at the sergio motta porto primavera dam sao paulo state brazil the most important structures are confined to planar zones up to 10 m thick in undeformed dune foreset strata were they can be traced laterally for about 50 60 m the sandstones are part of the rio parana formation caiua group which accumulated in a great sand sea of about 100 000 km2 the caiua desert developed during the late cretaceous in the southern part of the bauru basin an intracontinental subsiding area in the central southern part of the south american platform the basin was filled by a sandy sequence about 300 m thick the sand sea deposits correspond to the caiua group and comprise a deposits of dry sand sheets santo anastacio formation b deposits of medium sized dunes and humid interdunes of the sand sea peripheral zones goio ere formation and c deposits of large sized complex aeolian dunes and draas that correspond to the central part of the inland sand sea rio parana formation the deformations in the sediments are attributed to the effects of fluidization liquefaction and shear stress which are interpreted as being earthquake induced structures mainly because 1 the deformed horizons are confined between undeformed cross bedded strata 2 the complex convolute folds sometimes include nappe like structures that overlie foreset facies 3 during the bauru basin infilling there was tectonic activity associated with alkaline volcanism on the borders of the basin and related silicification in the central southern part the main silicification zones are aligned to regional lineaments that cross the area near the large scale sedimentary deformation structures

a numerical study of the climate response to lowered mediterranean sea level during the messinian salinity crisis abstract roughly six million years ago tectonic movements isolated the mediterranean sea ms from the atlantic ocean an event known as the messinian salinity crisis msc subsequent evaporative drawdown of the ms resulted in a subaerial depression with a depth between 1500 and 2500 m in this study five simulations are run using the national center for atmospheric research ncar community atmosphere model version 3 cam3 configured with the slab ocean model three simulations have been performed to test the climate impacts to desiccation and to changing the ms base level in this study the ms base level is reduced 750 m in the half land simulation hl and 1500 m in the lowered sea ls and lowered land ll simulations the hl and ll simulations differ from the ls in that the surface is converted to land representing the complete desiccation of the ms the substantial ms depression generates planetary scale atmospheric waves responsible for significant climate effects throughout the northern hemisphere a notable deepening of the aleutian low and a significant equatorward shift in the atlantic jet stream are evident in djf vertical ascent at the northern margin of the ms results in a 1 5 2 5 mm day 1 precipitation anomaly in the ls run over the alps consistent with proxy data annual mean area averaged ms evaporation is slightly higher than control conditions except when salinity is a substantial barrier to evaporation our results suggest that a partially filled basin cannot exist in equilibrium and the ms must either be partly connected to the atlantic ocean or completely desiccated base level lowering which alters the water budget must be taken into account when considering the freshwater budget during the msc

the transient atmospheric response to midlatitude sst anomalies abstract to study the transient atmospheric response to midlatitude sst anomalies a three layer quasigeostrophic qg model coupled to a slab oceanic mixed layer in the north atlantic is used as diagnosed from a coupled run in perpetual winter conditions the first two modes of sst variability are linked to the model north atlantic oscillation nao and eastern atlantic pattern eap respectively the dominant atmospheric modes in the atlantic sector the two sst anomaly patterns are then prescribed as fixed anomalous boundary conditions for the model atmosphere and its transient responses are established from a large ensemble of simulations in both cases the tendency of the air sea heat fluxes to damp the sst anomalies results in an anomalous diabatic heating of the atmosphere that in turn forces a baroclinic response as predicted by linear theory this initial response rapidly modifies the transient eddy activity and thus the convergence of eddy momentum and heat fluxes the latter transforms t

recurrent deformations of aeolian desert dunes in the cretaceous of the south china block trigger mechanisms variability and implications for aeolian reservoirs abstract deposits of aeolian dunes accumulated in cretaceous intramontane deserts in the south china block underwent recurrent deformation processes affecting their toesets and foreset sediments the mid cretaceous matoushan formation preserves examples of soft sediment deformation deformations associated with theropod tracks in aeolian dune apron sandstones the late cretaceous tangbian formation in the xinjiang basin shows i seismites associated with dry interdune laminated deposits and sand injection into the interdune laminated facies generating intraclast breccias ii mass flow deposits associated with heavy rains generating interbedding of non deformed and deformed intervals in aeolian dune foresets deformed intervals display a variety of deformation styles including thrust duplexes upturned and deformed stratification recumbent folds and microfolds and liquefied intervals covered by overlying draa mega cross bedded sets animal tracks seismites monsoon rains and earthquakes are proposed as the main trigger mechanisms of the failures that led to deformation hydroseismicity associated with monsoon rains is a probable but difficult to prove trigger mechanism this process could be an important deformation agent in the case of large scale deformation recorded in ancient erg sequences mass wasting deposits in ancient erg extensive sandy deserts characterized by aeolian dunes sequences constitute significant heterogeneities for hydrocarbon migration and its architectural variability could determine the development of effective sedimentary traps in aeolian reservoirs

δ13c depth profiles from paleosols across the permian triassic boundary evidence for methane release stable carbon isotopic analyses of organic carbon 13 c in individual paleosol profiles from permian triassic sequences of antarctica reveal systematic isotopic variations with profile depth these variations are in many cases analogous to those in modern soils which are functions of redox conditions soil development and degree and type of microbial decay in modern soils these isotopic depth functions develop independently from vegetation changes c 3 versus c 4 vegetation and can be diagnostic of soil orders this study shows that soil intrinsic functions can be preserved in the 13 c values of paleosols as old as 260 ma and constitute valuable data for paleoecological interpretations a large carbon isotopic offset of as much as 10 in whole paleosol profiles across the permian triassic boundary indicates significant changes in the soil biogeochemistry and the soil atmosphere system early triassic paleosols are distinctive in their extremely low 13 c values to 42 and often show an anomalous 13 c depth distribution compared to both permian paleosols and modern soils highly depleted 13 c values as the ones in early triassic paleosols are suggested to be associated with microbial methane oxidation methanotrophy this hypothesis implies increased methane concentrations in the early triassic soil atmosphere system increased atmospheric methane was probably partly responsible for the global carbon isotopic shift documented in marine and terrestrial sediments across the permian triassic boundary

anoxia as a cause of the permian triassic mass extinction facies evidence from northern italy and the western united states facies faunal and geochemical evidence from the permian triassic boundary sediments of the dolomites and idaho indicates a major anoxic event in the earliest triassic in both regions the basal beds consist of finely laminated micrites with common syngenetic pyrite the only fauna consists of occasional bedding plane assemblages of lingula or clacaria a typical lower dysaerobic assemblage this is a level where previous studies have shown a major negative carbon isotope excursion and a cerium anomaly in the dolomites the pyritic micrite directly overlies strata containing a diverse and typically permian marine fauna of algae foraminifers including fusulinids and articulate brachiopods implying an abrupt extinction in contradiction to many previous views sequence stratigraphic analysis of the dolomite boundary sediments reveals a minor sequence boundary in the late permian followed by extremely rapid transgression leading to the development of the relatively deep water pyritic micrite a maximum flooding surface at the permo triassic boundary a further pulsed deepening in the lower griesbachian recorded in both the dolomites and idaho lead to the widespread establishment of dysaerobic facies it is clear that most of the extinctions occurred at the erathem boundary although the subsequent failure of the marine benthos to fill the empty ecospace in the ensuing griesbachian may have been due to the widespread development of dysaerobic conditions

atmospheric gcm response to an idealized anomaly of the mediterranean sea surface temperature the atmospheric response to an idealized 2 k cooling of the mediterranean sea is studied in a general circulation model gcm in the downstream region from the eastern mediterranean basin to the whole asian continent following the sub tropical jet stream a baroclinic response is produced with high pressure near the surface and low pressure in the upper layers it is the direct response to the mediterranean cooling and it needs only a few days to be established teleconnections with strong zonal characteristics are found following the sub tropical jet stream to the north pacific and north america propagating further across the north atlantic towards northern europe two remarkable remote features are the deepening of the aleutian low in the north pacific and the weakening of the icelandic low in the north atlantic these two teleconnections form and grow in several days in the north pacific and several tens of days in the north atlantic both have a quasi barotropic vertical structure it is believed that they are the consequence of complex interactions between the mean flow and the transient eddies in the atmosphere

erosional truncation of uppermost permian shallow marine carbonates and implications for permian triassic boundary events on shallow marine carbonate buildups in south china turkey and japan uppermost permian skeletal limestones are truncated by an erosional surface that exhibits as much as 10 cm of topography including overhanging relief sedimentary facies microfabrics carbon isotopes and cements together suggest that erosion occurred in a submarine setting moreover biostratigraphic data from south china demonstrate that the surface postdates the uppermost permian sequence boundary at the global stratotype section and truncates strata within the youngest known permian conodont zone the occurrences of similar truncation surfaces at the mass extinction horizon on carbonate platforms across the global tropics each overlain by microbial buildups and their association with a large negative excursion in 13 c further suggest a causal link between erosion of shallow marine carbonates and mass extinction previously proposed to account for marine extinctions the hypothesis of rapid carbon release from sedimentary reservoirs or the deep ocean can also explain the petrographic observations rapid unbuffered carbon release would cause submarine carbonate dissolution accounting for erosion of uppermost permian skeletal carbonates and would be followed by a pulse of high carbonate saturation explaining the precipitation of microbial limestones containing upwardgrowing carbonate crystal fans models for other carbon release events suggest that at least 5 10 18 g of carbon released in 100 k y would be required of previously hypothesized permian triassic boundary scenarios thermogenic methane production from heating of coals during siberian traps emplacement best accounts for petrographic characteristics and depositional environment of the truncation surface and overlying microbial limestone as well as an associated carbon isotope excursion and physiologically selective extinction in the marine realm

climate induced sediment palaeosol cycles in a late cretaceous dry aeolian sand sheet marilia formation north west bauru basin brazil aeolian sand sheets which are characterized by low relief surfaces that lack dunes are common in arid and semi arid climatic settings the surface of an aeolian sand sheet can either be stable and subject to pedogenetic effects or unstable such that it is affected by deflation or sedimentation the maro lia formation late cretaceous may be interpreted as an ancient aeolian sand sheet area where alternating phases of stability and instability of the accumulation surface have been recorded detailed field studies were carried out in several sections of the maro lia formation where cyclic alternations of palaeosols and aeolian deposits were evident using palaeopedological and facies analysis methods supported in the laboratory by the analysis of rock samples cut and polished in slabs thin sections scanning electron microscope images and x ray diffraction data from the clay minerals the deposits comprise three lithofacies that in order of abundance are characterized by i translatent wind ripple strata ii flood deposits and iii ephemeral river channel deposits palaeosols constitute on average 65 of the vertical succession three types of palaeosols pedotypes are recognized i aridisols ii entisols and iii vertisols erosional surfaces due to aeolian deflation divide the top of the palaeosol profiles from the overlying aeolian deposits the palaeoenvironmental interpretation of the deposits and the palaeosols allows the depositional system of the maro lia formation to be defined as a flat area dominated by aeolian sedimentation with subordinate ephemeral river sedimentation and characterized by a dry climatic setting with occasional rainfall the climate is the main forcing factor controlling the alternation between episodes of active sedimentation and periods of palaeosol development a climate controlled model is proposed in which i the palaeosols are indicative of a stable surface that is developed during the more humid climatic phases and ii the erosional surfaces and the overlying aeolian sediments attest to periods of deflation and subsequent sedimentation thereby increasing the availability of sediment during the drier climatic phases the ephemeral fluvial deposits mark the more humid climatic conditions and contribute to the lagged sediment influx caused during the drier periods by the erosion of previously stored sediment

release of methane from a volcanic basin as a mechanism for initial eocene global warming a 200 000 yr interval of extreme global warming marked the start of the eocene epoch about 55 million years ago negative carbon and oxygen isotope excursions in marine and terrestrial sediments show that this event was linked to a massive and rapid approximately 10 000 yr input of isotopically depleted carbon it has been suggested previously that extensive melting of gas hydrates buried in marine sediments may represent the carbon source and has caused the global climate change large scale hydrate melting however requires a hitherto unknown triggering mechanism here we present evidence for the presence of thousands of hydrothermal vent complexes identified on seismic reflection profiles from the voring and more basins in the norwegian sea we propose that intrusion of voluminous mantle derived melts in carbon rich sedimentary strata in the northeast atlantic may have caused an explosive release of methane transported to the ocean or atmosphere through the vent complexes close to the palaeocene eocene boundary similar volcanic and metamorphic processes may explain climate events associated with other large igneous provinces such as the siberian traps approximately 250 million years ago and the karoo igneous province approximately 183 million years ago

mid cretaceous desert system in the simao basin southwestern china and its implications for sea level change during a greenhouse climate abstract paleoclimatic indicators suggest that the mid cretaceous was one of the warmest intervals of the phanerozoic the period of the mid cretaceous super greenhouse also experienced an equator to pole temperature gradient much lower than that of the present day implying greater meridional heat transport by the atmosphere and or oceans however reconstructions of cretaceous atmospheric circulation have been hindered by a lack of relevant datasets based on reliable proxies or direct geological evidence aeolian deposits provide direct information about paleoclimate as well as the direction and intensity of paleo wind in the interiors of continents using petrologic and sedimentologic observations this study reassesses the terrestrial deposits of the mid cretaceous mangang formation in the simao basin of southwestern china originally considered to be aqueous deposits we reinterpret these strata as representing aeolian transport in a desert environment we suggest that the development of aeolian deposits in the mangang formation and coeval strata in adjacent basins was a local response to the prevailing desert climate in the mid to low latitudes of the northern hemisphere during the mid cretaceous which were dominated by subtropical high pressure systems on a planetary scale in addition with the closure of the mesotethys ocean the intermontane basins of the south china simao and indochina blocks became more isolated from atmospheric circulation bidirectional subduction of the bangong nujiang oceanic crust and the izanagi plate beneath east asia led to the development of andean type margins which created a rain shadow effect in continental east asia these factors caused the development of a tropical desert climate characterized by aeolian dunes and evaporite deposition we speculate that the severe depletion of groundwater reservoirs via the desertification of east asia may represent a previously unrecognized trigger for short term sea level changes during the ice free cretaceous greenhouse interval

early triassic calcimicrobial mounds and biostromes of the nanpanjiang basin south china stanley s model 1988 proposed that a permiantype reef fauna survived the early triassic reefless period in yet undiscovered refuges in the ancestral pacific ocean and then reappeared as the builders of middle triassic reefs flugel 1994 in contrast suggested that the middle triassic reefbuilding fauna are not holdovers from the permian but bear only a superficial resemblance to permian fossils recent publications reflect a consensus that the early triassic lacked reefs and reef mounds although some authors acknowledged the possibility that reef like structures may have existed in poorly explored areas such as south china and russia senowbari daryan et al 1993 flugel 1994 it is shown herein that calcimicrobial framework mounds and biostromes existed in the early triassic in the nanpanjiang basin of south china organic framework in this paper refers to a three dimensional biologically constructed network of calcified fossils that forms a rigid mass and supports an interconnected network of internal cavities that were open during accumulation although the calcimicrobial frameworks discussed herein are much smaller than frameworks of modern metazoan reefs the term framestone is more appropriate for these fabrics than other reef rock terms such as bindstone or bafflestone embry and klovan 1971 these calcimicrobial mounds and biostromes are important as the first organic framestones documented from the early triassic

pattern of marine mass extinction near the permian triassic boundary in south china the meishan section across the permian triassic boundary in south china is the most thoroughly investigated in the world a statistical analysis of the occurrences of 162 genera and 333 species confirms a sudden extinction event at 251 4 million years ago coincident with a dramatic depletion of 13ccarbonate and an increase in microspherules

seismites in a proterozoic tidal succession singhbhum bihar india abstract early proterozoic metasediments of the chaibasa formation galudih ghatsila dhalbhumgarh region singhbhum bihar india comprise a number of cyclic fining upward prograding successions of tidalites the tidalites show indications for earthquakes in the form of synsedimentary deformation features apart from the structures due to high energy wave action deformed cross bedding convolute laminations synsedimentary faults graben like structures sandstone dykes pseudonodules and slump folds record the seismic activity a gradual decline in the frequency of seismites and tsunami related depositional features in combination with an upward increase in thickness of the tidal cycles are attributed to gradual diminishing of tectonic activity within the basin

seismically induced soft sediment deformation structures seismites around sumdo in the lower spiti valley tethys himalaya abstract soft sediment deformation structures were observed in 120 m thick fluvio lacustrine sediments exposed in the sumdo area in the lower spiti valley tethys himalaya himachal pradesh india these structures vary in their morphology and pattern and occur at eight stratigraphic levels s1 s8 spaced at irregular intervals the deformation structures include over steepened stratification diapiric flame like intrusions of clayey material or complex type recumbent folding of flame like nature pseudonodules large scale soft sediment folding faulting small scale associated with folding and sand dykes these structures are restricted to single stratigraphic layers separated by undeformed beds and can be correlated over a large distance the deformation of the soft sediments is attributed to the combined effects of fluidization liquefaction and shear stress and can be related to past seismic activity in the area recently on 19 january 1975 a major earthquake kinnaur earthquake of magnitude 6 8 caused extensive damage including ground rupturing in the sumdo kaurik area this earthquake has been related to the activation of the kaurik chango fault the deformed layers seismites reported here lie adjacent to this fault zone and can be related with episodic seismicity along this fault it is evident from this study that the kaurik chango fault has been re activated a number of times and that the area suffered at least nine major earthquakes with a magnitude of more than 6 during late pleistocene holocene time including the 1975 kinnaur earthquake

provenance and paleogeographic reconstruction of a mesoproterozoic intracratonic sag basin upper espinhaco basin brazil we would like to thank the capes cnpq grant no 304045 2010 1 and petrobras for their financial support for the field work and analysis

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

linearity of the atmospheric response to north atlantic sst and sea ice anomalies abstract the observations of the ocean atmosphere sea ice have recently revealed that the oceanic surfaces can have a subtle but significant impact on the atmospheric long term fluctuations low frequency variations and long term trends of the north atlantic atmospheric circulation have been partly related to particular sst and sea ice features in this work the influence of typical tripolar sst and dipolar sea ice anomalies in the north atlantic arctic on the atmosphere is investigated a large ensemble of agcm simulations forced by three different anomalous boundary conditions sst sea ice and sst sea ice are used the linearity of the simulated response in the winter season is particularly assessed in these experiments while the winter low level temperature response is mainly symmetric about the sign of the forcing the asymmetric part of the geopotential response is substantial the sea ice forcing maintains a baroclinic response with a strong temperature anomaly in the vicinity of the forcing

impacts of warm and cold situations in the mediterranean basins on the west african monsoon observed connection patterns 1979 2006 and climate simulations using both empirical and numerical ensemble approaches this study focuses on the mediterranean west african relationship in northern summer statistical analyses utilize skin temperature sea surface temperature in situ and satellite rainfall outgoing longwave radiation olr observations and reanalyzed data winds and specific humidity on isobaric surfaces numerical investigations are based on a large set of sensitivity experiments performed on four atmospheric general circulation models agcm arpege climat3 echam4 lmdz4 and ucla7 3 model outputs are compared to observations discussed model by model and with an ensemble multi model approach as in previous studies the anomalous mediterranean warm events are associated with specific impacts over the african monsoon region i e a more intense monsoon enhanced flux convergence and ascendances around the itcz a strengthening of low level moisture advection and a more northward location of ascending motion in west africa the results show also new features 1 thermal variability observed in the two mediterranean basins has unalike impacts i e the western mediterranean covaries with convection in gulf of guinea while the eastern mediterranean can be interpreted as sahelian thermal forcing 2 although observations show symmetry between warming and cooling modelling evidences only support the eastern warming influence 3 anomalous east warm situations are associated with a more northward migration of the monsoon system accompanied by enhanced southwertely flow and weakened northeasterly climatological wind 4 the multi model response shows that anomalous east warm surface temperatures generate an enhancement of the overturning circulation in low and high levels an increase in tej tropical eeasterly jet and a decrease in aej african eeasterly jet

new age constraints on the western betic intramontane basins a late tortonian closure of the guadalhorce corridor several gateways connected the mediterranean with the atlantic during the late miocene but the timing of closure and therefore their role prior to and during the messinian salinity crisis 5 97 5 33 ma is still under debate the timing of closure of the guadalhorce corridor is especially disputed as the common lack of marine microfossils hampers precise age determination here we present new biostratigraphic age constraints on the sediments of the ronda antequera and arcos regions which formed the northern part of the guadalhorce corridor the general presence of globorotalia menardii 4 in the youngest deep marine sediments of all three regions indicates a late tortonian age older than 7 51 ma we conclude that the guadalhorce corridor closed during the late tortonian well before the onset of the messinian salinity crisis and that the late tortonian tectonic uplift of the eastern betics extended into the western betics

stable carbon isotope signature in mid panthalassa shallow water carbonates across the permo triassic boundary evidence for 13 c depleted superocean the jurassic accretionary complex in southwest japan contains exotic blocks of the permo triassic limestone primarily deposited on ancient mid oceanic seamounts in an ancient pacific ocean or superocean panthalassa this study examines stable carbon isotope compositions 13ccarb and 13corg of such open ocean shallow water limestone across the permo triassic boundary ptb at kamura and taho in southwest japan the results show an almost identical secular change in 13ccarb values with a remarkable negative spike across the ptb in both sections this confirms for the first time that the mid panthalassa shallow water carbonates are bio and chemo stratigraphically correlated not with previously studied ptb sections from the peripheries of pangea the negative shift in 13ccarb occurs parallel to that of 13corg in both sections and the difference 13c 13ccarb 13corg remains nearly constant throughout the sections this implies that the 13c depleted water should have developed widely probably in a global extent throughout the superocean panthalassa across the ptb these findings suggest that a large input of 12c enriched carbon into the ocean atmosphere system has occurred and may have caused a global environment change probably relating to the greatest mass extinction in the phanerozoic

stable carbon isotope stratigraphy across the permian triassic boundary in shallow marine carbonate platforms nanpanjiang basin south china a distinct negative 13c excursion is documented in two permian triassic sections heping and taiping in shallow marine carbonate platform deposits in the nanpanjiang basin south china these sections span from the changhsingian to the dienerian and are characterized by a distinct marine boundary facies change from massive skeletal lime packstone in the changhsingian to distinctive calcimicrobial framestone in the griesbachian hindeodus parvus zone the 13corg and 13ccarb excursions occur directly after the onset of the calcimicrobial framestone herein termed the permian triassic boundary event and before the first occurrence of h parvus the isotope shifts are associated with a sharp drop in species abundance and diversity and coincide with a decrease in total organic carbon toc content the shift towards depleted values in 13corg and 13ccarb at the permian triassic boundary event together with low toc contents persists throughout the griesbachian h parvus zone these data document a corresponding negative shift of 13corg and 13ccarb values and low toc contents with the onset of growth of calcified microbial framestones a postextinction disaster facies immediately below the base of the griesbachian h parvus zone based on paleontological evidence the first occurrence of the disaster facies follows the extinction event which implies that the 13c depleted values above this facies postdate the event this suggests that two separate events had to account for the initiation of the extinction and the 13c excursion however the consequences that led to the negative isotopic shift might be linked to the intriguing recovery lag of early triassic ecosystems based on data from ptb sections worldwide of a greater 13c offset in high compared with low latitudes we propose that methane eruptions from thermal destabilization of high latitude clathrate deposits may have led to the negative 13c shift and may have caused long term adverse ecological conditions

deev jahi model of the permian triassic boundary mass extinction a case for gas hydrates as the main cause of biological crisis on earth the smoking gun revealing the secrets of the end permian mass mortality is a unique 1 2 m thick layer consisting of 5 20 cm long crystals of calcite that occurs precisely at the permian triassic boundary ptb in iran armenia turkey and china this layer is interpreted as synsedimentary abiotic seafloor cement indicative of precipitation from a highly carbonate supersaturated seawater its 13 c composition 13 c 0 pdb is 4 to 5 pdb lower than the typical upper permian values 4 to 5 pdb suggesting the involvement of massive amounts of gas hydrate ch 4 13 c 60 pdb the temporal coincidence of the cement layer with the ptb suggests that the process that promoted seafloor cementation was also responsible for the biological crisis a cementation model is developed based on accumulation dissociation cycle of gas hydrates which also explains the mass extinction at the ptb the upper permian accumulation period of gas hydrates ended abruptly adjacent to the ptb and the dissociation event began releasing 3 2 to 4 7 10 18 g ch 4 into the ocean oxidation of ch 4 in the water column created a seawater that was charged with co 2 an oceanic acid bath and had lower than normal o 2 content but not anoxic this oceanic acid bath first dissolved suspended fine grained carbonate particles and small calcareous organisms followed by extensive dissolution of platform carbonates raising ca 2 and hco 3 concentrations of seawater when the release of ch 4 declined the acid bath ocean became a soda ocean precipitating massive amount of seafloor cements observed globally at the ptb the study suggests that prior to cement precipitation the ptb ocean was charged with co 2 warm had low oxygen high ca 2 and high hco 3 concentrations these conditions collectively created stressful conditions causing the marine mass mortality the leakage of ch 4 to the atmosphere produced a super hot climate resulting in the biological devastation on land the proposed kill mechanism is developed on the basis of the physical clue the cement layer left behind by the killing process the change in ocean chemistry the accumulation dissociation cycles of gas hydrates also explain the 13 c pattern of marine carbonates and the periodicity of mass extinction events during the phanerozoic accumulation periods were long 5 to 20 my providing favorable conditions for ecosystem development pardeess phase the dissociation events were short and catastrophic 10 to 500 ky causing low oxygenation super hot climate and biological devastation doozakh phase it appears that most mass extinctions of the phanerozoic have been related to the internal working of the earth system during the phanerozoic methane has played the role of the deev jahi a female demon in persian mythology whose task is to attack the earth every so often to kill life on land and in sea

major perturbation of ocean chemistry and a strangelove ocean after the end permian mass extinction the severe mass extinction of marine and terrestrial organisms at the end of the permian period c 251 ma was accompanied by a rapid 1 ma decrease in sedimentary burial of organic carbon in the early triassic

tempo of the end permian event high resolution cyclostratigraphy at the permian triassic boundary the permian triassic p t boundary is marked by the most severe mass extinction in the geologic record high resolution cyclostratigraphy on a 10 4 yr scale across the p t boundary in a core from the carnic alps austria revealed significant cycles in the ratio 40 10 4 7 2 3 m identified with milankovitch cycles of 412 100 40 20 k y eccentricity 1 and 2 obliquity and precession wavelet analysis indicates continuity of deposition across the boundary with an average accumulation rate of 10 cm k y the dramatic faunal changes at the p t boundary can be constrained within an interval of 60 k y possibly 8 k y with the accompanying sharp negative global carbonisotope shift within 30 k y suggesting a catastrophic cause

spatial variability of iron oxides in soils from brazilian sandstone and basalt abstract iron oxides as goethite gt and hematite hm are key minerals to better understand the soil landscape relationships soil samples were collected at three stages of landscape dissection from the geological formations of vale do rio do peixe sandstone and serra geral basalt in the western paulista plateau wpp brazil both iron oxides were quantified by x ray diffraction xrd and diffuse reflectance spectroscopy drs and the results were subjected to geostatistical analysis in order to assess the usefulness of drs for characterizing the spatial variability in gt and hm the prevalence and spatial variability of hm and gt in the soils were governed by the sandstone basalt lithological contrast and landscape dissection iron oxides in the clay fraction exhibited high spatial variability over a large area and can be robust indicators of geological diversity and landscape dissection in pedoenvironments with low or high contents of iron oxides goethite had the highest spatial variability based on the spatial pattern of the differences between drs and xrd estimates the saturated red color in soil made drs less useful for quantifying hm in environments with high iron oxide contents the maps indicate the sensitivity of xrd and drs techniques to represent hm and gt spatial variability patterns gt was more sensitive to landscape dissection while hm sensitive to lithology thus the drs technique is efficient in characterizing the spatial variability of these soil oxides in large areas even considering the complex relations between soil and landscape

carbon isotope excursions and microfacies changes in marine permian triassic boundary sections in hungary abstract several permian triassic boundary sections occur in various structural units within hungary these sections represent different facies zones of the western palaeotethys margin the gardony core in the ne part of the transdanubian range typically represents the inner ramp while the balvany section in the bukk mountains of northern hungary represents an outer ramp setting the two sections have different patterns for their 13 c values the balvany section shows a continuous change towards more negative 13 c values starting at the first biotic decline followed by a sharp quasi symmetric negative peak at the second decline the appearance of the 13 c peak has no relationship to the lithology and occurs within a shale with low overall carbonate content indicating that the peak is not related to diagenesis or other secondary influences instead the shift and the peak reflect primary processes related to changes in environmental conditions the continuous shift in 13 c values is most probably related to a decrease in bioproductivity whereas the sharp peak can be attributed to an addition of c strongly depleted in 13 c to the ocean atmosphere system the most plausible model is a massive release of methane hydrate the quasi symmetric pattern suggests a rapid warming cooling cycle or physical unroofing of sediments through slope failure and releasing methane hydrate the gardony 1 core shows a continuous negative 13 c shift starting below the p t boundary however the detailed analyses revealed a sharp 13 c peak in the boundary interval just below the major biotic decline although its magnitude doesn t reach that observed in the balvany section based on careful textural examination and high resolution stable isotope microanalyses we suggest that the suppression of the 13 c peak that is common in the oolitic boundary sections is due to combined effects of condensed sedimentation sediment reworking and erosion as well as perhaps diagenesis

lower triassic large sea floor carbonate cements their origin and a mechanism for the prolonged biotic recovery from the end permian mass extinction precipitation of inorganic calcium carbonate is a common occurrence in both modern and ancient marine environments however synsedimentary growth of large 5 10 cm crystalline carbonate cements directly onto the sea floor has been thought to be limited to the proterozoic when seawaters were highly oversaturated with calcium carbonate compared to average phanerozoic values outer shelf to slope deposits of the lower triassic union wash formation in east central california deposited in oxygen restricted settings contain crystalline calcium carbonate cements that appear to have grown directly on the sea floor paleoenvironmental analyses indicate that these large calcium carbonate cements grew under conditions that were similar to those proposed for the precipitation of inorganic calcite in the black sea sulfate reduction of organic matter led to an increase in the amount of bicarbonate ion in deep waters and a concomitant increase in co 2 and alkalinity mixing with surface waters led to co 2 degassing and precipitation of cements from waters supersaturated with calcium carbonate the presence of these cements and associated facies thus provides evidence of harsh environmental conditions in the early triassic at the regional level which may have acted in concert with biotic effects of the end permian mass extinction as well as similar deleterious conditions e g shelf anoxia in other regions to produce a prolonged as well as temporally and geographically variable biotic recovery from this mass extinction