the early permian floras of prince edward island canada differentiating global from local effects of climate change new permian plant specimens are described from prince edward island canada they include attached specimens of leaf and stem genera walchia and tylodendron enabling reconstruction of this early permian conifer al though poorly preserved the study of these floras extends our knowledge of diversity and climate conditions in the re gion by placing these findings in a broader stratigraphic and geographic framework we can document the phytogeographic and climate trends through the carboniferous and permian in the maritimes basin combined data on temporal trends in climate sensitive sediments as well as macrofloral and microfloral diversities generally match the independently derived paleolatitudinal estimates these show the region migrating from the southern subtropics across the equator and into the northern subtropics between the early carboniferous and early permian evaporites and pedogenic carbonates together with low diversity floras match its subtropical position in the early carboniferous in contrast coals are present in the late carboniferous accompanied by high diversity macro and microfloral remains when the region was on or near the equator however the subsequent transition to pedogenic carbonates eolian sands and lower diversity floras is not matched by significant poleward latitudinal motion we ascribe these changes to a de crease in moisture availability as transgressions of epeiric seas became less frequent and finally stopped altogether causing an increase of continentality in euramerica resume cet article decrit de nouveaux specimens de plantes datant du permien provenant de l ile du prince edouard canada ils comprennent des specimens de feuilles et de tiges rattachees de genre walchia et tylodendron permettant la reconstruction de ce conifere du permien precoce bien que ces flores soient mal preservees leur etude etend nos connaissances de la diversite et des conditions climatiques de la region en placant ces decouvertes dans un cadre stratigraphique et geographique plus large nous pouvons documenter les tendances phytogeographiques et clima tiques du carbonifere et du permien dans le bassin des maritimes des donnees combinees sur les tendances temporel les dans des sediments sensibles au climat et des diversites relatives a la macro et a la microflore concordent generalement avec les estimations de paleoaltitude derivees de facon independante ces donnees montrent qu entre le carbonifere precoce et le permien precoce il y eut une migration des regions subtropicales meridionales par dela l equateur vers les regions subtropicales septentrionales des evaporites et des carbonates pedogenetiques avec des flo res faiblement diversifiees correspondent a sa position subtropicale au carbonifere precoce par contre on retrouve des charbons au carbonifere tardif accompagnes de restes de macro et de microflores grandement diversifiees lorsque la region etait a ou pres de l equateur toutefois la transition subsequente a des carbonates pedogenetiques a des sables eoliens et a une diversite florale moindre n est pas correlee par un mouvement meridien significatif vers le pole nous attribuons ces changements a une reduction de l humidite disponible alors que les transgressions des mers epicontinen tales devenaient de moins en moins frequentes et qu elles ont finalement cesse tout a fait causant une augmentation de la continentalite en euramerique

calcretes at sequence boundaries in upper carboniferous cyclothems of the sydney basin atlantic canada abstract nodular and associated groundwater calcretes in coal bearing cyclothems of the sydney basin mark the boundary between underlying marginal marine and overlying alluvial deposits they are inferred to represent lowstand surfaces sequence boundaries the host sediments include both sand siltstones and palustrine limestones microfabrics of calcretes with detrital hosts show evidence of replacement displacement and shrinkage alpha fabrics suggesting that the calcretes formed under relatively arid conditions in contrast microfabrics of nodular calcretes with limestone hosts exhibit predominantly beta fabrics with root induced brecciation and subordinate shrinkage fabrics the calcretes and host limestones are inferred to have formed in topographic lows thick alluvial sediments with red calcic vertisols overlie the calcretes and formed within the transgressive systems tract under conditions of abundant sediment supply coals and associated hydromorphic palaeosols lie near the transgressive maximum and in the highstand systems tract the presence of calcareous palaeosols on lowstand surfaces suggests that the lowstands were times of relative climatic aridity

milankovitch forcing of fluctuations in the level of tropical lakes from 18 to 0 kyr bp an atmospheric general circulation model has been used to simulate the climates of january and july at 3 000 yr intervals from 15 kyr bp onwards the model simulates a strengthened monsoon circulation and increased precipitation in the northern hemisphere tropics culminating at 9 6 kyr bp the computed hydrological budgets were used to estimate the area of closed lakes between 8 9 and 26 6 n giving with minor exceptions results in good agreement with geological evidence

the influence of changing orbital parameters and surface boundary conditions on climate simulations for the past 18 000 years abstract general circulation model experiments at 3000 year intervals for the past 18 000 years were made to estimate the magnitude timing and pattern of the climatic response to prescribed changes of orbital parameters date of perihelion axial tilt eccentricity and glacial age lower boundary conditions ice sheets land albedo sea ice and sea surface temperature the experiments used the community climate model ccm of the national center for atmospheric research ncar the response of monsoon circulations and tropical precipitation to the orbitally produced solar radiation changes was much larger than the response to changes of glacial age boundary conditions the continental interior of eurasia was 2 4 k warmer in summer and summer monsoon precipitation of north africa south asia was increased by 10 20 between 12 000 and 6000 yr bp before present when perihelion occurred during northern summer rather than in winter as now and the earth s axial tilt was larger than now southern hemisphe

prediction of modern bauxite occurrence implications for climate reconstruction abstract the formation of bauxite and laterite strongly depends on prevailing climate we use modern climate and bauxite distribution data to investigate quantitatively the role of climate in bauxite formation and to develop a method for testing general circulation models gcms we find that a very satisfactory prediction for potential bauxite formation can be achieved using two different sets of criteria the first requires the mean annual temperature to be greater than 22 c with annual mean precipitation greater than 1200 mm and 6 or fewer months when the rainfall is less than 60 mm the alternative model requires precipitation greater than evaporation for at least 6 months per year and monthly mean temperatures greater than 23 c for at least 8 months these proxy models are also used with simulations of the present day using a general circulation model the results show that the climate models are robust suggesting that bauxitization can be used to evaluate quantitatively such climate models for ancient times we also show that based on climate model predictions the regions favourable for bauxitization have remained stable through the holocene but with the exception of the malay peninsula bauxite formation would have ceased at the last glacial maximum

dynamics of the india eurasia collision zone we present simple new dynamic calculations of a vertically averaged deviatoric stress field over a depth average of 100 km for asia from geodetic geologic topographic and seismic data a first estimate of the minimum absolute magnitudes and directions of vertically averaged deviatoric stress is obtained by solving force balance equations for deviatoric stresses associated with gravitational potential energy differences within the lithosphere plus a first order contribution of deviatoric stresses associated with stress boundary conditions this initial estimate of the vertically averaged deviatoric stress field is obtained independent of assumptions about the rheology of the lithosphere absolute magnitudes of vertically averaged deviatoric stresses vary between 5 and 40 mpa assuming bulk viscous behavior for the lithosphere the magnitudes of deviatoric stresses together with the magnitudes of strain rates inferred from quaternary fault slip rate and gps data yield vertically averaged effective viscosities for tibet of 0 5 5 1022 pa s compared with 1 2 5 1023 pa s in more rigid areas elsewhere in the region a forward modeling method that solves force balance equations using velocity boundary conditions allows us to refine our estimates of the vertically averaged effective viscosity distribution and deviatoric stress field the total vertically averaged deviatoric stress and effective viscosity field are consistent with a weak lower crust in tibet they are consistent with some eastward motion of tibet and south china lithosphere relative to eurasia and they confirm that gravitational potential energy differences have a profound effect on the spatially varying style and magnitude of strain rate around the tibetan plateau our results for the vertically averaged deviatoric stress argue for a large portion of the strength of the lithosphere to reside within the seismogenic upper crust to get deviatoric stress magnitudes there to be as high as 100 300 mpa in accord with laboratory and theoretical friction experiments indicating that stress drops in earthquakes are small fractions of the total deviatoric stress

vegetation zones and diagnostic pollen profiles of a coastal peat swamp bocas del toro panama abstract a survey of the dominant vegetative cover of a large domed coastal swamp near changuinola in the province of bocas del toro panama has been undertaken as an initial step in reconstructing the holocene history of peat accumulation on this coast seven phasic communities of peat forming vegetation are defined and mapped 1 rhizophora mangle mangrove swamp 2 mixed back mangrove swamp 3 raphia taedigera palm swamp 4 mixed forest swamp 5 campnosperma panamensis forest swamp 6 sawgrass stunted forest swamp 7 myrica cyrilla bog plain pollen extracted from surface peat samples and collected from dominant vegetation at representative sites is used to prepare a pollen profile of each phasic community these profiles are then compared to pollen distribution in 2 peat cores one from the deep central part of the deposit and the second from a site near the marine margin in order to construct a history by floral succession of the 4000 year evolution of the deposit the changuinola mire originated as freshwater palm and hardwood forest swamps that developed in close proximity to both the changuinola river mouth probably behind a barrier bar and freshwater lagoon system adjacent to a low energy mangrove dominated bay the early swamp was likely drained to the southeast by brackish blackwater creeks much as it is today and formerly extended considerably farther in the direction of almirante bay the palm swamp was succeeded by hardwood forest swamp dominated by a very limited number of specialized species only one of which campnosperma panamensis is prone to forming monospecific stands increasing accumulation of woody peat promoted by the everwet climate impeded drainage of the mire leading to doming increased oligotrophy and establishment of bog plain conditions in a manner similar to that described by the anderson model of succession in the coastal swamps of malaysia and indonesia development of the changuinola mire did not require the initial mangrove phase which is common to the peat swamps of southeast asia as the palm raphia taedigera is able to colonise and institute peat accumulation in a variety of freshwater and brackish environments

a comparison of gcm simulated cretaceous greenhouse and icehouse climates implications for the sedimentary record abstract two general circulation model simulations of mid cretaceous climate are presented one representing a greenhouse and the other representing an icehouse world through a comparison of greenhouse and icehouse palaeoclimates differences in processes which are intrinsically linked with climate such as continental weathering and snow and ice accumulation may be observed a number of conspicuous and discrete climatic differences can be seen between the two simulations which may be translated into a number of identifiable signatures in the sedimentary record the climate at mid high latitudes in the icehouse simulation was more arid than the greenhouse simulation and could result in deposition of smectite dominated clay suites in contrast the climate of low latitudes of the icehouse simulation resulted in a moister climate than the greenhouse simulation which could affect the weathering regimes and result in deposition of kaolin dominated clay suites thus cool climate episodes do not necessarily result in a global increase in aridity the icehouse simulation predicts a small permanent icecap at high latitudes which could account for the origin of dropstones in marine sediments furthermore a sea level fall as a consequence of an accumulation of ice at high latitudes may also increase continentality and surface albedo which may also contribute to the causes of the drier climate at high latitudes hurricanes are likely to be more frequent in greenhouse than icehouse climates mid latitude depressions also important for generating storms are likely to be both intense and frequent during icehouse and greenhouse periods of the middle cretaceous

block kinematics of the pacific north america plate boundary in the southwestern united states from inversion of gps seismological and geologic data 1 the active deformation of the southwestern united states 30 41 n is represented by a finite number of rotating elastic plastic spherical caps gps derived horizontal velocities geologic fault slip rates transform fault azimuths and earthquake derived fault slip vector azimuths are inverted for block angular velocities creep on block bounding faults permanent strain rates within the blocks and the rotations of 11 published gps velocity fields into to a common north american reference frame gps velocities are considered to be a combination of rigid block rotations recoverable elastic strain rates resulting from friction on block bounding faults and nonrecoverable strain rates resulting from slip on faults within the blocks the resulting pacific north america angular velocity is similar to some published estimates and satisfies transform azimuths and one spreading rate in the gulf of california earthquake slip vectors in the gulf of california and alaska and gps velocities along coastal california and within the pacific basin published fault slip rates are satisfied except in the southern mojave desert where the motion of the mohave block relative to north america is faster than can be explained by mapped faults the largest blocks the sierra nevada great valley and the eastern basin and range show permanent strain rates after removing elastic strain of only a few nanostrain per year demonstrating approximately rigid behavior observed horizontal strain rates correlate strongly with predicted strain rates from known faults suggesting that the short term strains evident in gps velocities are largely elastic in only about 20 of the region is distributed deformation needed to match the data indicating that a plate tectonic style description of the deformation of the western united states is plausible most blocks rotate about vertical axes at approximately the same rate as the pacific relative to north america suggesting that locally spin rates are communicated from block to block arguing against both floating block and ball bearing mechanisms of block rotation the similarities of the blocks spin rates to that of the pacific suggests that the pacific strongly influences their motions through edge tractions however it is shown that the blocks cannot rotate about the pacific north america pole without spinning counter to the sense of pacific north america shear unlike some other broad plate boundaries in the western united states vertical axis rotations take up very little of the slip rate budget across the region

permian phytogeographic patterns and climate data model comparisons abstract the most recent global icehouse hothouse climate transition in earth history began during the permian warmer polar conditions relative to today then persisted through the mesozoic and into the cenozoic we focus here on two permian stages the sakmarian 285 280 ma and the wordian 267 264 ma also known as the kazanian integrating floral with lithological data to determine their climates globally these stages postdate the permo carboniferous glaciation but retain a moderately steep equator to pole gradient judging by the level of floral and faunal differentiation floral data provide a particularly useful means of interpreting terrestrial paleoclimates often revealing information about climate gradations between dry and wet end member lithological indicators such as evaporites and coals we applied multivariate statistical analyses to the permian floral data to calibrate the nature of floral and geographical transitions as an aid to climate interpretation we then classified sakma

the late cretaceous environment of the arctic a quantitative reassessment based on plant fossils abstract late cretaceous megafossil floras from the palaeo arctic of northeastern russia and northern alaska are reviewed in respect of their age composition structure and floral dynamics palaeofloral correlations and comparisons are made between the two regions nine angiosperm rich predominantly cenomanian to coniacian floras from the palaeo arctic are re evaluated using climate leaf analysis multivariate program clamp calibrated using a global gridded 0 5 0 5 climate data set derived from that used in climate modelling additional floras from lower palaeolatitudes were used to derive latitudinal temperature gradients seven from n america five from around 30 n palaeolatitude in europe and one from kazakhstan the arctic climatic determinations similar to previous estimates support the existence of a northern pacific ocean cold gyre and a warm arctic ocean at palaeolatitudes greater than 80 n floras are insufficiently diverse in woody dicot taxa to use clamp but using clamp derived latitudinal temperature gradients arctic ocean coastal environments at 70 ma and 82 n and which supported a diverse dinosaur magafauna are predicted to have experienced a mean annual temperature of 6 3 2 2 c a warm month mean of 14 5 3 1 c and a cold month mean no colder than 2 0 3 9 c all uncertainties are 2 the new estimates are in good agreement with a wide range of non palaeobotanical climate proxies and render as an outlier warmer temperature estimates for the arctic ocean derived from the tex 86 proxy modelling however shows that land to ocean temperature gradients could have been steep the clamp estimates also suggest high values for humidity and precipitation consistent with sedimentological indicators and coupled with warm temperatures support the existence of a persistent polar cloud cap that helped maintain high terrestrial air temperatures throughout prolonged periods up to 5 months of winter darkness

an 18 million year record of vegetation and climate change in northwestern canada and alaska tectonic and global climatic correlates abstract we reconstruct long term vegetation paleoclimatic trends spanning the last 18 million years in alaska yukon and far western northwest territories twenty one average percentage spectra for pollen and spores are assembled from eight surface subsurface sections the sections are dated independently or by correlation pollen and spore ratios indicate the direction of change in vegetation and climatic parameters growing season temperature test tree canopy density cest and paludification at study sites pest a global warm peak ca 15 ma is shown by the abundance of thermophilous taxa including fagus and quercus a temperature decline immediately following 15 ma parallels climatic reconstructions based on marine oxygen isotopes subsequent declines correlate to the messinian event and the onset of late pliocene pleistocene glaciation after 7 ma herbs and shrubs become more important elements of the palynological assemblages suggesting a more continental colder drier climate however a late pliocene warm interval is evident vegetation climatic changes during the early to late miocene show synchrony with and are most economically attributable to global events after 7 ma vegetation climate change is attributed primarily to latest miocene to pleistocene uplift of the alaska range and st elias mts the continuing influence of global climatic patterns is shown in the late pliocene warm interval despite uplift to the south the opening of the bering strait ca 3 ma may have moderated the climate in the study area

hypautochthonous allochthonous coal deposition in the permian south african witbank basin no 2 seam a combined approach using sedimentology coal petrology and palaeontology abstract a suite of techniques including coal petrology micropalynology mesofossil analysis and macroscopic appearance has been used to examine the early permian south african witbank basin no 2 seam from a sample locality near ogies this coal appears to be similar in its palynological and petrographic composition to other coals of this interval from this basin however its accumulation appears to have been largely hypautochthonous or allochthonous evidenced by erosive contacts small scale cross laminations and fine lenticular bodies being recognised within the coal seam profile this ex situ deposition probably in part relates to frequent wildfire activity which may have promoted subsequent run off and erosion and led to the numerous mineral rich horizons observed in the sample seam profile in addition to the sedimentological characters described above the petrology of the seam and its mesofossils most particularly megaspores from a lycopsid parent vegetation indicate saturated peat forming conditions however examination of charred mesofossil fragments indicates periods of low humidity and even drying of the peat itself rendering it liable to combustion these contradictory characters may indicate seasonality and suggest a coldness of the climate at least for part of the year that could account for the retardation of peat decay during these drier intervals these characters can be reconciled with deposition during an interglacial phase as the dwyka glaciation terminates as has previously been proposed for the witbank basin no 2 seam

holocene vegetation dynamics in response to climate change and human activities derived from pollen and charcoal records from southeastern china abstract our knowledge about the holocene evolution of the east asian summer monsoon easm and its relation to human activities remains incomplete a detailed palynological investigation of two sediment sections from the daiyun mountain nature reserve ca 25 38 25 44 n 118 05 118 21 e fujian province suggests easm controlled subtropical climate conditions that were wetter and warmer than present over the early and middle holocene after 5700 cal yr bp steadily increasing non arboreal pollen and fern spore percentages imply an attenuation of the easm the general climate trend is interrupted by several century scale changes in composition and concentration of arboreal pollen taxa around 8200 7200 6300 and 4400 cal yr bp coinciding with weaker precipitation and lower temperature as suggested by the easm oxygen isotope record our results further support the hypothesis that the natural vegetation cover of southern china was not markedly affected by human activities until 3000 cal yr bp the pollen records suggest a quick decrease in the forest cover ca 3000 2450 cal yr bp followed by a generally open agricultural landscape and spread of secondary pine forests this pattern is in line with a major population growth promoted by the southward expansion of rice based agriculture across the region that postdates the widely accepted holocene climate optimum by several millennia this highlights the multidimensional significance of this term which is commonly used in palaeoenvironmental and archaeological studies and should be consequently applied with respect to the specific issue under consideration

three dimensional velocity field of present day crustal motion of the tibetan plateau derived from gps measurements 1 using the measurements of 750 gps stations around the tibetan plateau for over 10 years since 1999 we derived a high resolution 3 d velocity field for the present day crustal movement of the plateau the horizontal velocity field relative to stable eurasia displays in details the crustal movement and tectonic deformation features of the india eurasia continental collision zone with thrust compression lateral extrusion and clockwise rotation the vertical velocity field reveals that the tibetan plateau is continuing to rise as a whole relative to its stable north neighbor however in some subregions uplift is insignificant or even negative the main features of the vertical crustal deformation of the plateau are the following a the himalayan range is still rising at a rate of 2 mm yr the uplift rate is 6 mm yr with respect to the south foot of the himalayan range b the middle eastern plateau has a typical uplift rate between 1 and 2 mm yr and some high mountain ranges in this area like the longmen shan and gongga shan have surprising uplift rates as large as 2 3mm yr c in the middle southern plateau there is a basin and endorheic subregion with a series of ns striking normal faults showing obvious sinking with the rates between 0 and 3 mm yr d the present day rising and sinking subregions generally correspond well to the cenozoic orogenic belts and basins respectively e at the southeastern corner of the plateau there is an apparent trend that the uplift rate is gradually decreasing from between 0 8 and 2 3 mm yr in the inner plateau to between 0 5 and 1 6 mm yr outside the plateau with the decrease of terrain height

high latitude meteoric δ18o compositions paleosol siderite in the middle cretaceous nanushuk formation north slope alaska siderite bearing pedogenic horizons of the nanushuk formation of the north slope alaska provide a critical high paleolatitude oxygen isotopic proxy record of paleoprecipitation supplying important empirical data needed for paleoclimatic reconstructions and models of greenhouse world precipitation rates siderite 18 o values were determined from four paleosol horizons in the national petroleum reserve alaska npr a grandstand 1 core and the values range between 17 6 and 14 3 peedee belemnite pdb with standard deviations generally less than 0 6 within individual horizons the 13 c values are much more variable ranging from 4 6 to 10 8 pdb a covariant 18 o versus 13 c trend in one horizon probably resulted from mixing between modified marine and meteoric phreatic fluids during siderite precipitation groundwater values calculated from siderite oxygen isotopic values and paleobotanical temperature estimates range from 23 0 to 19 5 standard mean ocean water smow minor element analyses show that the siderites are impure having enrichments in ca mg mn and sr minor element substitutions and mg fe and mg ca mg ratios also suggest the influence of marine fluids upon siderite precipitation the pedogenic horizons are characterized by gleyed colors rare root traces abundant siderite abundant organic matter rare clay and silty clay coatings and infillings some preservation of primary sedimentary stratification and a lack of ferruginous oxides and mottles the pedogenic features suggest that these were poorly drained reducing hydromorphic soils that developed in coal bearing delta plain facies and are similar to modern inceptisols model derived estimates of precipitation rates for the late albian of the north slope alaska 485 626 mm yr are consistent with precipitation rates necessary to maintain modern peat forming environments this information reinforces the mutual consistency between empirical paleotemperature estimates and isotope mass balance models of the hydrologic cycle and can be used in future global circulation modeling gcm experiments of greenhouse world climates to constrain high latitude precipitation rates in simulations of ancient worlds with decreased equator to pole temperature gradients

climate model predictions for the latest cretaceous an evaluation using climatically sensitive sediments as proxy indicators to date many general circulation model gcm experiments have failed to reproduce the warm high latitude temperatures suggested for the cretaceous by geological proxy climate indicators especially for the northern hemisphere and within continental interiors the vast majority of these proxies are biologically based and it is important to determine whether alternative sedimentologically based proxies indicate similar cold biases in models therefore we have performed an evaluation of the very latest generation of climate model predictions for terrestrial sites using climatically sensitive sediments as palaeoclimate indicators evidence from the geological record comprising coal peat evaporites bauxite and laterite deposits are portrayed on a series of palaeoclimate data maps these are then compared with the global distributions of potential deposits generated from model simulations of the maastrichtian using versions of the hadley centre climate model the maastrichtian was chosen because of the greater range and sophistication of gcms adapted for its climate simulation and sediment prediction than for other cretaceous stages this thus represents the first attempt at comparing such state of the art models to lithological climate indicators and quantifying their relative performances for peat coal there is generally good correspondence between maastrichtian model predictions for predicted potential deposits and the observed record for evaporites there is also very close agreement between predictions by the models and the geological record minor differences between the individual model versions resulting from their differing levels of atmospheric co2 and the different palaeogeographical representations of intracontinental seaways in the northern hemisphere for bauxites and laterites the models predict less than half of the documented deposits successfully portraying equatorial accumulations but omitting the majority of mid to high latitude deposits the main discrepancy is therefore identified as the failure of all models to predict bauxite and laterite deposits corresponding with recorded accumulations within the mid to high latitudes of europe and asia in many cases the effects of co2 have minimal impact on the skill of model prediction however for evaporite distributions the low co2 model is appreciably worse in general the best match across the geological data and models is achieved by the simulation with open northern hemisphere seaways overall these results confirm those inferred from biological proxies showing that climate models have a serious cold bias in high latitudes and continental interiors during the cretaceous and that the latest generation of climate models still produces results which are incompatible with the geological data levels of atmospheric co2 and uncertainties in palaeogeography cannot explain the discrepancy the cold bias is common to many climate models and suggests that a process or mechanism is poorly represented or omitted in the current generation of climate models or that we are failing to recognise a major boundary condition change in the cretaceous if the former this implies that we may be underestimating the extent of extreme future climate change at high latitudes and in continental interiors

revisiting the paleogene climate pattern of east asia a synthetic review abstract east asian paleogene climates have long been regarded as controlled by the planetary wind system which might result in a climate pattern with three latitudinally distributed zones two humid zones located separately in the north and south were lithologically designated by coals and oil shales while an arid zone in the middle was represented by red beds and evaporites because the middle arid zone was located along 30 n paleolatitude its presence had been further linked with a then subtropical high however this long standing model has recently been challenged by growing evidence from petrology sedimentology paleontology paleobiogeography paleoclimatology and climate modeling here we review the primary data from these disciplines and reinterpret their climate significances to revisit the east asian climate pattern during the paleogene petrologically while the occurrence of coals and or oil shales is accepted as an indicator for overall humid climates that of red beds and or evaporites is highly equivocal to exclusively indicate perennial arid climates unless their origins are carefully investigated in reality generic red beds merely represent an oxidizing environment not essentially associated with a single specific climate type meanwhile evaporites although typically precipitated in arid environments may be deposited in either perennial dry or seasonal monsoonal climates there is no solid evidence so far to convincingly support that the landscape of the so called middle arid zone was dominated by desert and or steppe under a then subtropical high during most of the paleogene the plant function type study additionally suggests that the middle arid zone appears to be lack of xerophytic vegetation even though some xerophytic or sclerophyllous plant taxa did sporadically occur interestingly paleozoological data show that the paleogene mammalian faunas were somewhat equably distributed over east asia strongly suggesting the evident absence of a critical biogeographical or climatic barrier stretched across the middle arid zone as the planetary wind model implied in contrast to the planetary wind model monsoonal or monsoon like paleogene climates have been broadly reported from the northern middle and southern east asia as well as adjacent regions of russia and kazakhstan if only the indicators for humid climates are considered simply due to the uncertainty of those for perennial arid climates east asia must have had a relatively dry region in the continental interior during the late eocene to oligocene transition likely caused by the continentality and or the rain shadow effect along with the global cooling the monsoonal interpretation is highly in agreement with the evidence from floras faunas basin analyses and modeling experiments and well explicates the paleogene climate distribution and seasonal dynamics of east asia however further studies will be largely needed to verify whether uniformly according to the modern criteria the paleogene climates of the east asia interior can be accurately attributed to the arid category

the formation of inertinite rich peats in the mid cretaceous gates formation implications for the interpretation of mid albian history of paleowildfire abstract image analysis and standard point count petrographic data are used to interpret the amount source and variation of inertinite in coal seams of the mid cretaceous gates formation rocky mountain foothills northeastern british columbia inertinite on average is abundant between 40 60 by seam by volume and higher in some zones and within seams fluctuates cyclically the inertinite is interpreted to be almost exclusively fire derived suggesting that fire was a relatively common occurrence in the original peat forming wetlands inertinite enrichment in the gates coals appears to have resulted from preferential destruction of vitrinite precursors by either low temperature decomposition processes or burning rather than by formation of inertinite by a microbial process the position of the gates formation depositional setting east of the rising canadian cordillera is interpreted to have resulted in overall drier conditions in the region and periodic drought in the wetland settings cyclic variation in inertinite vitrinite composition within some of the seams is primarily attributed to climatic variations although variation in subsidence rates could also have been responsible

jurassic savannah plant taphonomy and climate of the morrison formation upper jurassic western usa abstract the morrison formation contains six plant taphofacies wood whole leaf leaf mat root common carbonaceous debris and rare carbonaceous debris none of these taphofacies is common in the morrison particularly striking is the paucity of wood even in more reducing environments the flora of the morrison formation is distinct in the kimmeridgian and tithonian parts of the section the plant taphofacies are consistent with a predominantly herbaceous vegetation evidence from the plant taphofacies floras and sedimentology of the morrison is consistent with a warm seasonal semi arid climate throughout changing from dry semi arid to humid semi arid from the kimmeridgian to the tithonian parts of the formation

forest dynamics and tip up pools drive pulses of high carbon accumulation rates in a tropical peat dome in borneo southeast asia singapore national research foundation singapore mit alliance for research and technology

experiments on a turbulent plume shape analyses 1 we report the results of laboratory experiments on a turbulent plume a simplified model of a positively buoyant volcanic plume with a small content of fine ash to study how the shape of the plume changes as a function of time to model such plumes we continuously inject a dense fluid downward at a constant exit velocity and study how the plume shape changes with time as vortices develop from flow instability and entrainment here a series of experiments are conducted with exit velocity and the density difference as the changeable parameters and the jet plume transition is realized in the laboratory initially the plume has a finger like shape which becomes unstable and forms a plume head and later transforms into a cone like self similar shape we also find that when the buoyancy becomes sufficiently large compared to inertia there is a temporary deviation from the cone like shape to form a headed cone we devise new methods to quantitatively characterize these changes of shape and define four regimes as a function of time we find that the onset times of the flow instability and the regimes have negative power law dependence on the initial re or the exit velocity and that buoyancy causes the regime transitions to become earlier our experiments suggest that monitoring the change of the shape of the rising volcanic plumes and analyzing the regime onset times can be used as a measure to constrain their buoyancy

the influence of vegetation cover on soil organic matter preservation in antarctica during the mesozoic a possible biological component of the explanation for the lack of substantial coal formation on antarctica between the late jurassic and late cretaceous is hypothesised forcing a process based terrestrial biogeochemistry model with climate model simulations for three successive intervals of the mesozoic late jurassic 150 ma mid cretaceous 100 ma and late cretaceous 65 ma predicts the establishment of productive terrestrial ecosystems with substantial soil carbon pools throughout the land surface of antarctica between 150 and 65 million years ago sensitivity analyses indicate the annual land surface hydrological budget of antarctica 150 65 ma was largely balanced due to the effects of canopy transpiration on soil moisture post depositional erosion and tectonic setting must have played an important role in determining coal preservation on the continent however the model results indicate that an active vegetated land surface precluded the preservation of the substantial soil organic carbon inputs by minimising the potential for anaerobic preservation i e water logging

development of potential acid sulfate paleosols in paleocene floodplains bighorn basin wyoming usa abstract floodplain paleosols in the paleocene fort union formation in the bighorn basin are distinguished by a dark claystone interval with yellow jarosite mottles relatively high total organic carbon values and woody debris and leaves along bedding planes the paleosols also have various redoximorphic features including low matrix chromas grey root mottles and local concentrations of goethite and hematite especially associated with roots and other organic matter jarosite is usually an oxidation product of pyrite which forms under waterlogged conditions when sulfate and organic matter are available the former presence of pyrite and the redoximorphic features suggest that the fort union paleosols first developed as potential acid sulfate soils brinkman and pons 1973 the dark claystones with jarosite are interpreted as permanently reduced or gr horizons the gr horizon is overlain by mudstone that is lighter colored and lacks jarosite this represents an ancient bg horizon or a bg sequence the jarosite indicates that the paleosols underwent a subsequent episode of oxidation and acidification those processes require that the soils be drained which probably did not occur during paleocene time and may be a recent event rather the soils were probably buried as the fort union formation continued to aggrade and the waterlogged soils were pushed even farther below the groundwater table only with late cenozoic excavation of strata in the basin and exposure of the fort union deposits did jarosite precipitate pedogenic and paleobotanical features suggest that the soils formed in floodplain swamps dominated by coniferous trees the high organic content and clay rich nature of the gr horizons suggest that the floodplain swamps were not close to the active channel the bipartite nature to the profiles bg horizon or a bg sequence above a gr horizon probably resulted from two different kinds of floodplain deposition grain size trends indicate that the gr horizons formed on sediment deposited by overbank flooding the impermeable fine grained sediment and its low topographic position led to waterlogging the overlying a bg or bg horizons formed on coarser sediment that was probably deposited during channel avulsion the greater permeability and higher topographic position of this sediment caused it to be better drained than the gr horizon the paleosols are unusual because they formed in a freshwater setting whereas modern potential acid sulfate or acid sulfate soils form in coastal areas where sulfate is readily available the source of the sulfate may have been cretaceous marine shales exposed along the flanks of mountains rising around the bighorn basin during paleocene time other upper cretaceous and paleocene formations in the rocky mountain area contain similar rocks suggesting that sulfidic soils were relatively common in the mid continent at this time most of these other examples probably reflect deposition associated with the retreating western interior seaway and humid climates

sedimentological evaluation of general circulation model simulations for the greenhouse earth cretaceous and jurassic case studies abstract conceptual climate models based on the workings of the present day climate system provided a first order approach to ancient climate systems they are potentially very subjective in character their main drawback was that they involved the relocation of continents beneath a stable atmospheric circulation modelled upon that of the present general circulation models gcms use the laws of physics and an understanding of past geography to simulate climatic responses they are objective in character however they require super computers to handle vast numbers of calculations nonetheless it is now possible to compare results from different gcms for a range of times and over a wide range of parameterisations gcms are currently producing simulated climate predictions which compare favourably with the distributions of climatically sensitive facies e g coals evaporites and palaeosols they have been used effectively in the prediction of oceanic upwelling sites and the distribution of petroleum source rocks and phosphorites parameterisation is the main weakness in gcms e g sea surface temperature orography cloud behaviour sensitivity experiments can be run on gcms which simulate the effects of milankovitch forcing and thus provide insights into possible patterns of climate change both globally and locally i e provide predictions that can be evaluated against the rock record future use of gcms could be in the forward modelling of sequence stratigraphic evolution and in the prediction of the diagenetic characteristics of reservoir units in frontier exploration areas the sedimentary record provides the only way that gcms may themselves be evaluated and this is important because these same gcms are being used currently to predict possible changes in future climate

deformation during the 12 november 1999 duzce turkey earthquake from gps and insar data only 87 days after the mw 7 5 17 august 1999 izmit earthquake the duzce earthquake ruptured a ca 40 km long adjoining strand of the north anatolian fault naf system to the east we used displacements of 50 global positioning system gps sites together with interferometric synthetic aperture radar insar range change data spanning the event to estimate the geometry and slip distribution of the coseismic rupture postseismic deformation transients from the duzce earth quake and the preceding i zmit event that are included in some of the measurements are corrected for using dislocation models fit to gps data spanning the various time periods nonlinear inversions for fault geometry indicate that the rupture occurred on a ca 54 north dipping oblique normal right lateral fault distributed slip inver sions indicate maximum strike slip near the center of the duzce fault close to the earthquake hypocenter slip magnitude and depth of faulting decrease to the west and east of the hypocenter both gps and insar data suggest that normal slip is restricted to the shallow portion of the rupture the duzce earthquake had the highest slip to rupture length ratio of any historic earthquake along the naf

the 2011 tohoku oki earthquake displacement reaching the trench axis we detected and measured coseismic displacement caused by the 11 march 2011 tohoku oki earthquake moment magnitude mw 9 0 by using multibeam bathymetric surveys the difference between bathymetric data acquired before and after the earthquake revealed that the displacement extended out to the axis of the japan trench suggesting that the fault rupture reached the trench axis the sea floor on the outermost landward area moved about 50 meters horizontally east southeast and 10 meters upward the large horizontal displacement lifted the sea floor by up to 16 meters on the landward slope in addition to the vertical displacement

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

sedimentology of fraser river delta peat deposits a modern analogue for some deltaic coals abstract on the recent lobe of the fraser river delta peat accumulation has actively occurred on the distal lower dilta plain the transition between upper and lower delta plains and the alluvial plain distal lower delta plain peats developed from widespread salt and brackish marshes and were not influenced appreciably by fluvial activity lateral development of the marsh facies were controlled by compaction and eustatic sea level rise the resulting thin discontinuous peat network contains numerous silty clay partings and high concentrations of sulphur freshwater marsh facies formed but were later in part eroded and altered by transgressing marine waters the peats overlie a thin fluvial fining upward sequence which in turn overlies a thick coarsening upward prodelta delta front succession lower delta plain upper delta plain peats initially developed from interdistributary brackish marshes and were later fluvially influenced as the delta prograded the thickest peats occur in areas where distributary channels were abandoned earliest sphagnum biofacies replace sedge grass dominated communities except along active channel margins where the sedge grass facies is intercalated with overbank and splay deposits the peats are underlain by a relatively thin sequence of fluvial deposits which in turn is underlain by a major coarsening upward delta front and pro delta sequence alluvial plain peats accumulated in back swamp environments of the flood plain earliest sedge clay and gyttjae peats developed over thin fining upward fluvial cycles or are interlaminated with fine grained flood deposits thickest accumulations occur where peat fills small avulsed flood channels overlying sedge grass and sphagnum biofacies are horizontally stratified and commonly have sharp boundaries with fine grained flood sediments at active channel margins however sedge grass peats are intercalated with natural levee deposits consisting of silty clay these levees reduce both the number and size of crevasse splay deposits coal originating from peats of the different environments of the fraser delta would vary markedly in character peats of the lower delta plain will form thin lenticular coal seams with numerous splits and have a high ash and sulphur content peats from the lower to upper delta plain will be laterally extensive and of variable thickness and quality basal portions of the seams will contain numerous splits and have a high sulphur content whereas upper portions will be of higher quality peats from the upper delta plain alluvial plain will form thick isolated and laterally restricted coal seams characterized by low ash and sulphur contents

facies analysis of the balta formation evidence for a large late miocene fluvio deltaic system in the east carpathian foreland abstract deposits of the balta fm are preserved in a large arcuate sediment body that covers about 60 000 km 2 and is up to 350 m thick the balta fm spans ca 5 ma as constrained by underlying tortonian bessarabian and overlying messinian early pontian paratethys strata it contains frequent terrestrial mammal fossils and fresh as well as brackish water paratethys molluscs and ostracods over the past 140 years our understanding of the sedimentary architecture of the formation and its origins has remained in its infancy which has limited insight into the evolution of the east carpathian foreland here we provide the first modern sedimentary facies analysis of the balta fm which is integrated with an extensive review of previously published local literature it is supported with micropalaeontological results and a wealth of historical borehole information we show that the balta fm has a tripartite vertical division its lowermost part is clay dominated and consists of subordinate delta front sand bodies interspersed between muds the middle unit contains separate delta plain channels or channel belts encased in thick muds these are overlain by a unit with amalgamated delta plain channel deposits with only minor amounts of associated mud the abundance of upper flow regime sedimentary structures in channel sands the absence of peats or coals and the presence of calcareous nodules suggest a strongly seasonal and relatively dry climate with a flashy discharge regime deposition of the balta fm in an area previously characterized by distal shelf and prodelta environments indicates large scale progradation triggered by high sediment volume from the uplifting carpathian orogen and enhanced by a general lowering of paratethys sea level the tripartite internal architecture of the balta fm indicates that progradation continued during deposition its wedge shaped geometry suggests that tectonic activity in the carpathians generated a 300 km wide foreland basin that allowed for significant delta plain aggradation despite of the generally regressive trend in paratethys sea level

simulated warm polar currents during the middle permian 1 during permian stage 6 wordian kazanian the pangaean supercontinent was surrounded by a superocean panthalassa an ocean general circulation model has been coupled to an atmospheric energy balance model to simulate the sensitivity of the wordian climate 265 million years ago to changes in greenhouse gas concentrations high latitude geography and earth orbital configurations the model simulates significantly different circulation features with different levels of greenhouse gas forcing ranging from a strong meridional overturning circulation in the southern hemisphere at low co2 concentration present level to more symmetric overturning circulation cells with deep water formation in polar latitudes of both hemispheres at high co2 concentration 8 times present level the simulated climate with 4 times present level co2 concentration agrees generally well with climate sensitive sediments and phytogeographic patterns the model simulates strong subtropical gyres with similarities to the modern south pacific circulation and moderate surface temperatures on the southern continent gondwana resulting from a strong poleward heat transport in the ocean an even more moderate climate is generated if high latitude land is removed from the southern continent so that ocean currents can penetrate into the polar regions of gondwana

oblique stepwise rise and growth of the tibet plateau two end member models of how the high elevations in tibet formed are i continuous thickening and widespread viscous flow of the crust and mantle of the entire plateau and ii time dependent localized shear between coherent lithospheric blocks recent studies of cenozoic deformation magmatism and seismic structure lend support to the latter since india collided with asia 55 million years ago the rise of the high tibetan plateau likely occurred in three main steps by successive growth and uplift of 300 to 500 kilometer wide crustal thrust wedges the crust thickened while the mantle decoupled beneath gently dipping shear zones did not sediment infilling bathtub like of dammed intermontane basins formed flat high plains at each step the existence of magmatic belts younging northward implies that slabs of asian mantle subducted one after another under ranges north of the himalayas subduction was oblique and accompanied by extrusion along the left lateral strike slip faults that slice tibet s east side these mechanisms akin to plate tectonics hidden by thickening crust with slip partitioning account for the dominant growth of the tibet plateau toward the east and northeast

a new method for measuring deformation on volcanoes and other natural terrains using insar persistent scatterers 1 we present here a new insar persistent scatterer ps method for analyzing episodic crustal deformation in non urban environments with application to volcanic settings our method for identifying ps pixels in a series of interferograms is based primarily on phase characteristics and finds low amplitude pixels with phase stability that are not identified by the existing amplitude based algorithm our method also uses the spatial correlation of the phases rather than a well defined phase history so that we can observe temporally variable processes e g volcanic deformation the algorithm involves removing the residual topographic component of flattened interferogram phase for each ps then unwrapping the ps phases both spatially and temporally our method finds scatterers with stable phase characteristics independent of amplitudes associated with man made objects and is applicable to areas where conventional insar fails due to complete decorrelation of the majority of scatterers yet a few stable scatterers are present

a comparison of temperate and boreal peats from ontario canada possible modern analogues for permian coals abstract peat profiles were sampled from a raised bog and an interior fen located in the boreal james bay lowlands northern ontario and a cold temperate swamp and a cold temperate bog in the great lakes st lawrence lowlands southern ontario an examination of the micromorphology and maceral compositions of the peats indicates that considerable differences exist between environments the boreal bog and fen both consist predominantly of relatively unaltered textinite commonly sphagnum derived with higher liptinite contents in the fen profile attributable to the more diverse vegetation both the cold temperate swamp and bog show high levels of humification at the surface possibly partially attributable to recent climatic warming trends causing a decline in water table elevation in all profiles funginite was persistent ranging from 2 to 10 of the total maceral content indicating that aerobic conditions generally prevailed at the surface at the time of deposition the influence of depositional environment and vegetation type on the resulting peat was born out in plots of tissue preservation index vs gelification index the petrographic study also demonstrated that none of the profiles contained high inertodetrinite semifusinite contents comparable to those within cold climate cratonic permian gondwana coals since the oxidation processes leading to the formation of inertinite are considered to take place at the peat stage if the peats studied were to contain a similar maceral assemblage upon coalification inertinite precursors may be present in the peat the lack of petrographic similarity between the holocene peats and the permian coals may be related to a number of factors the decrease in water table elevation possibly responsible for the inertinization of the permian coals may have occurred following the cessation of peat formation not concurrently with accumulation and is potentially attributable to long term factors such as climatic warming the change in the peat forming vegetation from permian glossopteris and gangamopteris dominated communities to holocene sphagnum and coniferous vegetation alters the characteristics of the initial botanical starting materials and some aspects of the ecology particularly trophic and ph conditions which control the post depositional alteration of the plant materials and the resulting maceral assemblages

the inorganic chemistry of peat from the maunachira channel swamp system okavango delta botswana abstract the okavango delta is a large 18000 km2 low gradient 1 3600 alluvial fan situated in the semi arid kalahari basin of northern botswana seasonal floodwaters from tropical angola disperse on the fan creating both perennial 6000 km2 and seasonal 7000 to 12000 km2 swamps ninety five percent of this water is lost annually by evapotranspiration organic rich sediment peat is a major sediment of the perennial swamps peat formation commences during senescence of the plants when certain nutrients are recycled while others are lost by rainwater leaching further changes in chemistry occur during subaqueous decay of the plants which involve both gains and losses of constituents decaying plants trap detrital mineral matter which becomes an integral part of the peat the main sources and forms of inorganic matter in the peat are allochthonous kaolinite 40 and quartz 20 and both allochthonous and autochthonous phytolithic silica 30 several inorganic components fe k p na ca and mg which make up the remaining 10 are associated with the organic fraction ion exchange plays only a minor part in their uptake and it seems that these metals are taken up during bacterial activity in the peat the weight proportion of inorganic matter ash decreases downstream mainly due to a decrease in allochthonous mineral matter volume percentage also decreases but is low throughout generally less than five percent this study has revealed that the low quantity allochthonous mineral matter is the main reason for the long term survival of this ecosystem uptake of soluble ions by the peat is important in off setting evaporative concentration of metals

reevaluation of surface rupture parameters and faulting segmentation of the 2001 kunlunshan earthquake mw7 8 northern tibetan plateau china the 14 november 2001 m w 7 8 kunlunshan earthquake ruptured the westernmost part of the kunlun fault northern tibetan plateau the main segment affected by this event was the kusaihu segment field investigations allowed us to constrain the length the width and the coseismic horizontal displacement distribution of the kunlunshan earthquake rupture zone the mapped surface rupture zone starts from 90 257 e in the west and ends at 94 795 e in the east with a total length of 426 km it consists of three main sections the western strike slip section the transtensional section and the eastern strike slip section the rupture zone is oriented n100 10 e on average the distribution of the coseismic horizontal displacements is characterized by multiple peaks departing clearly from a general bell shaped distribution reassessment of the maximum coseismic horizontal left lateral displacement yields a value of 7 6 0 4 m at the site 35 767 n 93 323 e consistent with independent measurements derived from interferometric synthetic aperture radar and seismology from this site the horizontal displacement decreases unevenly to both the west and east coseismic vertical reverse displacement is also noted at the eastern end of the rupture but it remains much smaller than the horizontal component the width of the rupture zone varies from site to site from several meters to few kilometers the maximum width measured reaches 8 km along the yuxi feng subsection where a large number of shaking related cracks were well developed

late quaternary caldera forming eruptions in the eastern aleutian arc alaska late quaternary calderas have been identified at 12 of 40 volcanic centers in the eastern aleutian arc and sufficient radiocarbon dates and geologic information have now been obtained to either date or constrain the timing of the climactic caldera forming eruptions at least eight major caldera forming events each characterized by estimated eruption volumes of more than 10 km 3 occurred at seven different volcanic centers in the holocene and as many as six of these had estimated eruption volumes of more than 50 km 3 eruptions of similar magnitude formed two other calderas in wisconsin time the dating of these hitherto little known events adds significantly to the previously existing chronology of large prehistoric eruptions this refined chronology is important in understanding eruption induced climate changes in assessing volcanic hazards and in developing a tephrochronology for northwestern north america

the effect of global warming and global cooling on the distribution of the latest permian climate zones abstract the end permian biotic crisis is commonly associated with rapid and severe climatic changes these climatic changes are commonly suggested to have originated from solid earth carbon degassing leading to global warming but aerosol and ash induced cooling induced by lava degassing has been suggested as well the application of an earth system model of intermediate complexity has enabled a visualisation of the major climatic shifts on the supercontinent pangaea caused by rapid temperature changes due to changed radiative properties from greenhouse gases the reconstructed reference climate was validated by latest permian climate indicative sediments to investigate the possible climatic shifts from a set of 22 reconstructions which varied with temperature a minimum global annual mean temperature of 18 2 c for the late permian climate prior to the climatic perturbation event was determined starting from this pre event setup global warming and global cooling scenarios were simulated the response of the end permian climate system to temperature increase and decrease show marked differences while global cooling is followed by major climatic changes in the high latitudes and replacement of boreal biomes by tundra and polar frost the changes during global warming are less pronounced with only locally increasing aridity compensated by humidisation in other regions the different behaviour of the climatic belts under warm and cold conditions is accompanied by different climate sensitivities caused by different strength of the snow cover albedo feedback thus changes in the energy balance of the latest permian surface troposphere system have a 30 higher perturbation potential during cold climate conditions than during warmhouse conditions therefore substantial global cooling resulting in coldhouse climate conditions and an annual global mean temperature below 18 c is more efficient in perturbing the earth palaeoclimate during the end permian warmhouse the results suggest that global cooling mechanisms as injection of sulphur aerosols and ash particles from the siberian traps large igneous province into the late permian palaeoatmosphere have a higher climate perturbation potential than a warming due to carbon greenhouse gases with a similar magnitude of radiative forcing

late cenozoic right lateral strike slip faulting in southern tibet field observations collected during the sino french himalaya tibet cooperation project 1980 1982 show that right lateral faulting between southern and northern tibet roughly along the chord joining the eastern and western syntaxes of the himalayan arc is a major component of the active tectonics north of the himalayas just north of the well developed rifts of southern tibet we studied three right lateral 100 200 km long strike slip faults forming an en echelon array along that chord evidence for earthquake surface breaks was found on each of these faults for the m 8 beng co or damxung strike slip earthquake of november 18 1951 rupture parameters could be constrained to be 8 2 m and l 90 km offset glacial and postglacial morphological markers 105 years and 104 years b p imply displacement rates of the order of 1 2 cm yr on the three faults the en echelon fault zone appears to extend westward 2000 km across the plateau to the karakorum fault and is thus referred to as the karakorum jiali fault zone kjfz fast rates of slip on it and on faults along the northern rim of tibet appear to contrast with the slower rates of deformations in the interior of the plateau our estimates of slip rates on the strike slip and normal faults of southeastern tibet suggest that eastward extrusion of north tibet between the right lateral kjfz and the left lateral altyn tagh and kun lun faults absorbs at least 30 of the present convergence between india and asia we propose an instantaneous velocity model of the active tectonics of asia compatible with such faulting rates and geometries evidence for tertiary right lateral strike slip movements in southern tibet and around the eastern syntaxis of the himalayas is also found in the structural record offsets of various large scale geological features imply that these movements have been large

identifying active faults by improving earthquake locations with insar data and bayesian estimation the 2004 tabuk saudi arabia earthquake sequence abstract a sequence of shallow earthquakes of magnitudes 5 1 took place in 2004 on the eastern flank of the red sea rift near the city of tabuk in northwestern saudi arabia the earthquakes could not be well located due to the sparse distribution of seismic stations in the region making it difficult to associate the activity with one of the many mapped faults in the area and thus to improve the assessment of seismic hazard in the region we used interferometric synthetic aperture radar insar data from the european space agency s envisat and ers 2 satellites to improve the location and source parameters of the largest event of the sequence m w 5 1 which occurred on 22 june 2004 the mainshock caused a small but distinct 2 7 cm displacement signal in the insar data which reveals where the earthquake took place and shows that seismic reports mislocated it by 3 16 km with bayesian estimation we modeled the insar data using a finite fault model in a homogeneous elastic half space and found the mainshock activated a normal fault roughly 70 km southeast of the city of tabuk the southwest dipping fault has a strike that is roughly parallel to the red sea rift and we estimate the centroid depth of the earthquake to be 3 2 km projection of the fault model uncertainties to the surface indicates that one of the west dipping normal faults located in the area and oriented parallel to the red sea is a likely source for the mainshock the results demonstrate how insar can be used to improve locations of moderate size earthquakes and thus to identify currently active faults

cordaiteans in paleotropical wetlands an ecological re evaluation abstract cordaiteans in cordaite dominated permineralized peat from pennsylvanian coals in iowa have been reconstructed as mangroves using root anatomy peat taphonomy and geochemical data macrofloral palynofloral and conodont biostratigraphy indicate that these peats come from the latest atokan blackoak coal and earliest desmoinesian cliffland coal mid moscovian both in the kalo formation thus their depositional setting can be used to evaluate the mangrove hypothesis in recent mires thick mangrove peats have accumulated in tropical to subtropical carbonate systems in contrast thick tropical freshwater peats have accumulated in siliclastic systems kalo formation coals which we interpret as freshwater deposits formed in siliciclastic depositional settings similar to those of modern tropical freshwater peat and to other pennsylvanian coals in north america interpreted as freshwater deposits in the late atokan and earliest desmoinesian mid moscovian cordaiteans and tree ferns predominated in the western interior and illinois basins lycopsids and cordaiteans predominated in the appalachian and donets basins the scarcity of lycopsid only mires in north america during the late atokan earliest desmoinesian mid moscovian suggests drier climates than during the mid to late desmoinesian late moscovian rather than indicating mangrove swamps cordaite dominated peat may indicate climates with a low rain season although most plants in cordaite dominated peat probably grew in freshwater coastal mires in climate zones with seasons of low rain may harbor mangrove taxa the changuinola swamp of panama a modern peat accumulating wetland that has a low rain season is a possible analog of ancient cordaite dominated mires in changuinola most plants require freshwater however mangroves sustained by salt water influx into the swamp grow along the seaward edge and along blackwater creeks the low rain season hypothesis has implications for understanding rainfall amount and continuity during pennsylvanian cyclothem deposition the floral succession in diverse cordaite coals from cordaiteans to tree ferns to lycopsids suggests increasingly wet climate during coal accumulation the position of these coals immediately above the sequence boundary suggests humid climate during early glacial melting for these cyclothems

palaeovalleys and protozoan assemblages in a late carboniferous cyclothem sydney basin nova scotia the early stephanian bonar cyclothem of the sydney basin nova scotia contains an erosional surface cut through coastal plain strata with economic coals and distributary channel bodies the erosion surface is interpreted as a palaeovalley 20 m deep and at least 7 km wide that marks a sequence boundary formed during relative fall in sea level the palaeovalley is filled with stacked alluvial channel bodies which become more isolated as the valley fill passes upward into red alluvial plain deposits probably laid down in an anastomosed river system in an adjacent interfluve area calcretes and red vertic palaeosols cap coastal strata assemblage analysis of agglutinated foraminifera and thecamoebians indicates that the palaeovalley was filled with freshwater sediments before an initial marine transgression flooded the alluvial surface and adjacent interfluve valley incision probably reflects glacioeustatic sea level fall however the alluvial nature of the valley deposits suggests that valley filling reflects an abundant sediment supply during lowstand and or transgressive stages and was not a direct consequence of sea level rise during the subsequent transgression phase aggradation was rapid as sediment supply apparently kept pace with rising sea level features of both channel and extra channel facies suggest that seasonality intensified during the transition from coastal plain to palaeovalley and alluvial plain deposition

carbon cycle perturbation in the middle jurassic and accompanying changes in the terrestrial paleoenvironment abstract carbon isotope analyses of fossil wood from the middle jurassic ravenscar group yorkshire ne england reveal a significant excursion toward light isotopic values 13c change of 3 to 4 at about the aalenian bajocian boundary 174 ma a positive carbon isotopic excursion is also shown for the middle bajocian 170 ma but is less clearly defined these isotopic patterns are very similar to the few published marine carbonate records available for this time in particular one based on belemnites from the hebrides basin nw scotland and others from pelagic limestones in italy the similarity of the terrestrial and marine isotope curves is an indication that the observed isotopic signal is a global phenomenon through parts of the ravenscar group the scarborough formation supplementary data from bulk organic carbon and palynofacies analysis confirm that isotopic curves based on bulk analyses may be strongly influenced by the balance of terrestrial versus marine organic matter present in th

paleoclimatic estimates from tertiary leaf assemblages a primary obstacle to evaluating numerical modeling of tertiary nonmarine climates has been the significance and reliability of proxy data sloan barron 1990 lacking direct measurements of paleoclimatic parameters inferred paleoclimatic values are based on substitute proxy sources such as fossils or isotopes are proxy data significant that is have they been calibrated in modern environments and to what level is the calibration this is the problem of accuracy validity in the statistical sense second are the proxy data reliable can two workers or even the same worker consistently arrive at the same estimates using the same data set this is the problem of precision repeatability can these two problems be resolved quaternary palynologists have used the concept of transfer functions a methodology originally developed for foraminifera imbrie kipp 1971 applied in palynology a response surface for each palynomorph taxon is constructed for the environmental variables under consideration these transformations can then be subjected to a number of different kinds of multivariate analyses including ordination methodologies bartlein et al 1986 webb bryson 1972 these transfer functions can work for quaternary and especially the lateand post glacial of the last 20 to 30 thousand years pollen assemblages because in most regions where the methodology has been applied the flora is of known diversity and the equivalency of a given palynomorph species to one or a few extant species can be reasonably assumed even in the late neogene 1 5 to 10 million years ago however this assumption can no longer be made we know that the palynomorph assemblages contain exotic genera mccartan et al 1990 and the presence of exotic and or extinct species

lower edge of locked main himalayan thrust unzipped by the 2015 gorkha earthquake faults are unlocked by earthquakes analysis of seismic data from the 2015 nepal earthquake shows that only part of the main himalayan thrust fault was unzipped by the quake leaving much of the fault locked and ready to slip in a future event

world peat occurrence and the seasonality of climate and vegetation abstract the climatic controls on present day peat formation are examined in order to develop a uniformitarian tool for refining paleoclimate studies and to create a retrodictive model for the coals of the geologic record a peat database has been compiled for the world and the resulting patterns are compared with aspects of precipitation and temperature drawn from a gridded data set precipitation continuity through the annual cycle is important for biologic productivity in the terrestrial realm it is expressed in terms of the number of months with average precipitation above 40 mm temperature is limiting at higher latitudes where the potential growing season may be defined by the number of months with mean temperature exceeding 10 c a map predicting the growing season has been constructed from these rainfall and temperature statistics which compares very well with actual vegetation persistence through the year as measured directly from satellite instruments however biologic production will not result in peat accumulation unless groundwater levels are maintained through the growing season our peat prediction map therefore shows the percentage of time that precipitation occurs during the potential growing season present day peat accumulations are well predicted by this map

a ne trending oblique slip fault responsible for the 2016 zaduo earthquake qinghai china revealed by insar data twelve sentinel 1 images are used to measure the surface displacements caused by the zaduo earthquake on 17 october 2016 in qinghai china comprehensive analysis of the local geologic structure focal mechanisms relocated aftershocks and fault geometrical parameters from nonlinear inversions of the insar data indicates that a ne trending fault with a strike of 61 namely the aduo fault was responsible for this event further geodetic inversions for finite fault models show that the dip angle of this fault is 75 to the se the majority of the slip occurred at the depth from 5 km to 17 km and the normal slip component was comparable to the strike slip component the peak slip of 31 cm occurred at a depth of 10 km the insar determined moment is 9 61 1017 n m with a rigidity of 30 gpa equivalent to mw 5 9 the geological map reveals that the aduo fault was characterized by a left lateral strike slip component in the past as evidenced by the offset of paleogene sedimentary rocks our results for the zaduo earthquake suggest that the qiangtang block probably consists of two or more sub blocks with different eastward extrusion velocities and that the deformation of the qiangtang block is occurring not only along its boundaries but also in its interior

radar interferogram filtering for geophysical applications the use of sar interferometry is often impeded by decorrelation from thermal noise temporal change and baseline geometry power spectra of interferograms are typically the sum of a narrow band component combined with broad band noise we describe a new adaptive filtering algorithm that dramatically lowers phase noise improving both measurement accuracy and phase unwrapping while demonstrating graceful degradation in regions of pure noise the performance of the filter is demonstrated with sar data from the ers satellites over the jakobshavns glacier of greenland

the sedimentary record of carboniferous rivers continuing influence of land plant evolution on alluvial processes and palaeozoic ecosystems abstract evidence from modern rivers and the deep time geological record attests to the fundamental importance of plant life for the construction of physical habitats within fluvial environments data from an extensive literature review and original fieldwork demonstrates that many landforms and geomorphic features of modern river systems appear in the palaeozoic stratigraphic record once terrestrial vegetation had adopted certain evolutionary advances for example stable point bars are associated with the onset of rooted plants in the siluro devonian and avulsive and anabranching fluvial systems become common at the same time as extensive arborescent vegetation in the carboniferous in this paper we demonstrate a correlation between the diversification of physical fluvial environments and the expansion of terrestrial fauna and flora with an emphasis on the culmination of these trends within carboniferous alluvial systems many extrinsic factors have been considered as possible controls on the evolutionary timelines of terrestrialization for organisms however a fundamental prerequisite for achieving terrestrial biodiversity was the variety of physical habitats especially riparian systems available for newly evolved organisms in association with abundant lowland meandering systems the widespread appearance across carboniferous alluvial plains of fixed channel and anabranching reaches created further physical landforms for colonization and would have promoted increasingly complex hyporheic flow regimes furthermore the associated increase in arborescent vegetation and supply of large woody debris to inland and coastal rivers would have created a wealth of microhabitats for continental organisms we argue that the expanding extent and diversity of physical alluvial niches during the palaeozoic is an underappreciated driver of the terrestrialization of early continental life the study of the deep time fossil and stratigraphic record also illustrates that vegetation is a fundamental prerequisite for the creation of biogeomorphic alluvial landforms and physical habitats and microhabitats

2 5 d surface deformation of m6 1 earthquake near mt iwate detected by sar interferometry the two dimensional displacement vector field on the earth s surface associated with a large earthquake near iwate volcano in japan was mapped by combining satellite radar interferometry images from two different track directions the displacement reveals not only large main ruptures but details of many small faults movement of aftershocks and volcanic earthquakes the displacements of the aftershock faults coincide with a stress field reorganized by the main earthquake that accelerated the aftershock fault movements the displacements mimic the topography suggesting that repeated movements of the same faults in the quaternary have led to the presently existing topography

quantitative palaeoclimate gcm validation late jurassic and mid cretaceous case studies using quantitative proxy models of peat and bauxite formation based upon modern analogues predictions of the distribution of peats coals and bauxites for both the late jurassic kimmeridgian and mid cretaceous cenomanian have been made using a general circulation model gcm the predictions have been compared with the known distribution of these deposits such an approach provides a means of identifying and isolating which components of the gcm accurately reflect palaeoclimate the prediction of peats and bauxites for the jurassic and cretaceous show good correspondence with known coals and bauxites and provides otherwise elusive quantitative estimates of high latitude climate the gcm is thus successfully replicating precipitation and mean annual temperatures for both the kimmeridgian and cenomanian investigations of mesozoic palaeoclimate using general circulation models gcms have often focused on qualitative evaluation of results e g barron washington 1982 valdes et al 1995 chandler et al 1992 a number of recent studies have however highlighted the need for gcm predictions to be quantitatively validated against the sedimentological and palaeobiological record e g poore chandler 1994 pollard schulz 1994 price et al 1995 quantitative estimates of terrestrial climate have been produced by physiognomic analysis of floras e g herman spicer 1996 wolfe upchurch 1987 and have also been derived from organisms such as crocodiles e g markwick 1994 comparable results have been used effectively for validating gcm predictions e g sloan barron 1992 but data tend to be restricted to north america and are often latest cretaceous or younger in age

is the greenland ice sheet bistable ice core work on greenland has produced dramatic evidence for an instability of the climate system in the north atlantic sector in this paper we provide climate modeling results indicating another possible example of a multiple equilibrium climate state where such behavior might apply to the ice sheet itself baseline sensitivity experiments in which the greenland ice sheet was removed simulate summer temperatures on greenland of about 10 c this number varied between about 6 and 14 c depending on specification of vegetation type elevation of greenland and orbital forcing the implied hysteresis indicates that the present geographic configuration may have been sufficient to maintain an ice free state prior to formation of the ice cap explanations for formation of the ice sheet therefore present a dilemma four possibilities involve undocumented miocene pliocene co2 excursions to values lower than present a high sensitivity of the climate system a variable sensitivity of the climate system or significant problems with the climate model a variable sensitivity is consistent with our results indicating a multiple steady state climate for greenland although most co2 scenarios do not predict a collapse of the greenland ice sheet in the future our results suggest that if it did present boundary conditions may be sufficient to maintain greenland in an ice free environment even after the greenhouse effect has dissipated

recognizing products of palaeoclimate fluctuation in the fluvial stratigraphic record an example from the pennsylvanian to lower permian of cape breton island nova scotia tectonics and climate are the major extrinsic upstream controls on both the external and internal architectures of fluvial channels while the role of tectonics has been well documented the role of climate has received less attention because both tectonics and climate can produce similar stratigraphic architectures the ability to recognize and differentiate these has major ramifications for the interpretation of fluvial stratigraphy the pennsylvanian to permian succession of the maritimes basin complex on cape breton island is ca 5 km thick and is composed of predominantly non marine strata deposited within a series of depocentres characterized by different subsidence regimes basins in the west are transtensional depocentres characterized by episodic fault movement in contrast basins in the east were formed during prolonged periods of passive thermal subsidence the stratigraphy is composed of four second order sequences a to d each 5 to 10 myr in duration these sequences are composed of amalgamated fluvial channel deposits that fine upwards into extensive mud dominated floodplain deposits with isolated fluvial channel bodies a spectrum of fluvial styles is recorded within the study area including perennial perennial intermittent and ephemeral four stratigraphic intervals e1 to e4 are recognized in which the deposits of strongly seasonal perennial intermittent fluvial deposits are predominant these intervals 2 to 6 myr in duration are correlated across the study area between basins with differing tectonic regimes and do not correlate with a particular position in second order sequences this suggests that climate exerted the dominant influence on the formation of these intervals and can be differentiated from tectonic imprints while the tectonic regime of a particular basin exerted a fundamental control on the external architecture a coherent record of climate change is recognized in the internal architecture of fluvial units this study demonstrates that tectonic and climatic controls can be recognized and differentiated in vertical successions by evaluating the changes in fluvial architecture