geochemistry of central tethyan upper permian and lower triassic strata abadeh region iran nearly 2 km of upper permian to lower triassic limestones are exposed in the hambast mountain abadeh region iran lime mud matrix and most bioclasts of permian age are recrystallized into large calcite crystals and contain 600 4000 ppm sr suggesting a probable aragonite precursor low bulk rock 18 o values 7 to 10 pdb and recrystallized textures are also indicative of diagenetic alteration within the murghabian and abadehian two gradual upward increases in carbonate and organic matter 13 c compositions each roughly 3 pdb in magnitude are documented both are attributed to increased organic productivity and sequestration of organic matter in sediments within the julfian and across the permian triassic p t boundary two sharp upward decreases in carbonate and organic matter 13 c values each 4 pdb in magnitude are observed both are best explained by mixing of a deep water mass having low 13 c values and a shallow water mass having high 13 c compositions early triassic 13 c values initially low 1 pdb increase to 3 pdb within 100 m above the p t boundary variations in 13 c compositions of carbonate and organic matter and changes in 13 c 13 ccar 13 corg indicate that early triassic 13 c values were controlled by productivity cycles

sea levels during late marine isotope stage 3 or older reported from the red river delta northern vietnam and adjacent regions abstract a 60 m long sediment core from the lower red river delta in northern vietnam contains three depositional sequences consisting mostly of regressive shallow marine sediments bounded by unconformities the youngest unit represents the modern red river delta the second unit a facies succession comparable to the overlying deltaic succession formed during an earlier sea level highstand as indicated by the marine isotope stage mis 3 age obtained by radiocarbon dating the third undated unit might reflect earlier high sea levels of the middle to late pleistocene the mis 3 ages derived from shoreline related sedimentary facies are supported by records from adjacent mega deltas and shelf sites with paleoshoreline facies proximal sites from the central indochina craton show high sea levels during late mis 3 whereas distal sites from the open continental shelf indicate much lower sea levels at the same time independent globally relevant sea level reconstructions suggest that both positions have been affected by later vertical movement this discrepancy between sea level records from central cratonic sites and the continental margin can be explained by a balanced response to locally differentiated sediment loading and compaction on the shelf as is supported by published seismic data however if the complete set of radiocarbon dates is contaminated by younger material then the second recorded sea level highstand may be associated with mis 5 as no marine deposits have yet been reported in any of the three indochinese mega deltas for this time interval

the permian triassic boundary event a geochemical study of three chinese sections abstract trace elements were determined in two well documented chinese permian triassic p tr boundary sections meishan and shangsi and in a new section liangfenya iridium concentrations range from 3 to 87 pg g at or below levels in common sedimentary rocks the results contrast with previous reports of high ir concentration in the meishan and shangsi sections and offer no support to suggestions of a major meteoroid impact at the end of the permian a notable feature in each of these widely separated p tr sections 500 1500 km is the existence of 2 5 light colored clay layers at and near the boundary these clay layers are strongly enriched in cs zr hf ta and th and depleted in cr co and ir indicating that they are altered ash apparently from the same massive silicic volcanic eruptions we estimate the magnitude of these eruptions to be a few thousand km3 of magma a volume comparable to the great toba eruption

sea level changes in the tectonically stable malay thai peninsula abstract the malay thai peninsula is part of sundaland a geological region of relative crustal stability therefore the positions of old shorelines of the past 20 000 years or so can be considered to indicate positions of actual past sea levels over 200 shoreline indicators at positions below as well as above present sea level have been radiocarbon dated these dated positions indicate that prior to 6 ka the sea rose from at least 90 m below present sea level at rates that initially amounted to 15 mm year and later became 6 mm year at ca 6 ka the rising sea surpassed its current position and at ca 5 ka it reached 5 m during this maximum marine inundation the peninsula was narrower since the low coastal plains did not yet exist in the period following this maximum transgression the available shoreline data indicate that regional sea level subsided through a series of fluctuations that were characterized by amplitudes of 2 m and periods of about 2000 years the peaks and troughs of the fluctuations became progressively lower the latest peak was at about 1 7 m or 0 7 m above present high tide a few hundred years ago the cause of these fluctuations is not yet known but the trend suggests that in the near future regional sea level may subside at annual rates between 1 5 mm and 2 mm this rate of descent is 25 to 30 of the estimated rate of sea level rise that may result from global warming in other words for the malay thai peninsula the effect of sea level rise on account of manmade greenhouse gases will be partly compensated by actual subsidence of regional sea level

sem image analysis for characterization of sand grains in thai paddy soils abstract this study presents a detailed characterization of sand grains in 34 samples of thai paddy soils mostly alfisols and ultisols that have formed from diverse parent materials computer analysis of sem images of thin sections provided a novel and reliable method to analyse the size and shape of quartz grains using the software imagej 1 34s sand grain size expressed as the feret value showed a log normal distribution for 16 samples whereas for the other samples the distribution was positively skewed a logit transformation of grain circularity values generated a normal distribution for 26 samples and eight samples had bimodal distributions these granulometric data indicate the diversity of the soil parent materials and the observed soil layers represent discrete sedimentary events with materials of different origins or different depositional energies pedogenesis including pedoturbation has not disrupted these sedimentary layers some sand grains consist of gold brass copper ilmenite zircon magnetite barite or monazite the diversity of these grains reflects the complex geology of the catchments providing the sediments and some anthropogenic materials may have been incorporated into the soils

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

positive europium anomaly at the permo triassic boundary spiti india a limonitic layer at the base of the otoceras ophiceras zone in the lalung section in spiti valley shows a significant positive europium anomaly with maximum eu eu 1 9 this layer defines the contact between the earliest griesbachian and the permian productus shale sequence the layer shows a small cerium anomaly having the maximum value of ce la n 1 4 the iridium concentration in this layer at 73 pg g is only marginally above the levels found in the adjacent shales although higher than that found in the overlying limestones another horizon having 114 pg g of ir occurs 70 cm below this limonitic layer in the shale sequence these observations have important implications both for the terrestrial mainly volcanic and extra terrestrial impact hypotheses for the permo triassic transition which are discussed

intrabasin variability of the carbon isotope record across the permian triassic transition sverdrup basin arctic canada abstract a major late paleozoic depocentre the sverdrup basin canadian high arctic has been largely left out of the latest permian extinction debate as early workers presumed middle to late permian strata were absent basin scale sequence stratigraphic and chemostratigraphic correlations indicate late permian strata are only missing on the basin margins where they were removed by sub triassic erosion whereas continuous deposition is recorded in the basin centre the varying degree of sub triassic erosion has significant impact on the carbon isotope record across the latest permian extinction event where both the apparent rate and magnitude of carbon isotope shift vary as a function of basin position the intrabasin variability in apparent 13corg shift across the event is equivalent to that observed globally in contrast to the abrupt isotope shifts recorded on the basin margin similar to many records reported globally the basin centre section shows a systematic shift associated with the latest permian extinction the earth likely underwent a prolonged period of increasing environmental stress leading up to the event

hydrogeological constraint on nitrate and arsenic contamination in asian metropolitan groundwater a total of 243 groundwater samples from five asian metropolitan areas bangkok jakarta manila seoul and taipei were analysed to determine the status and mechanism of groundwater nitrate no3 and arsenic as pollution the samples were divided into three groups based on the no3 versus as high no3 10 150 mg l as no3 with low as 0 5 g l low no3 0 10 mg l with high as 5 120 g l and low no3 0 10 mg l and as 0 5 g l groundwater from the seoul hard rock and jakarta unconfined aquifer belonged to the first group while that of the confined aquifer of jakarta manila and bangkok belonged to the second group and the taipei groundwater belonged to the last group comparison of the hydrogeological parameters and groundwater geochemistry among cities demonstrated that the redox conditions defined the behaviour of contaminants in groundwater from manila and bangkok where impermeable marine clay deposits comprise a large proportion of the surface geology no3 was depleted due to denitrification while the as levels were higher as a result of the reducing conditions of the aquifer conversely the relatively oxic environments in the jakarta unconfined aquifers and the seoul crystalline rock aquifer resulted in less denitrification and as dissolution the results of this study suggest that no3 versus as diagrams are a useful method of evaluating the pollution types and contamination processes among the different urban groundwater systems while considering the hydrogeological settings copyright 2011 john wiley sons ltd

geochronological constraints on the age of a permo triassic impact event u pb and 40ar 39ar results for the 40 km araguainha structure of central brazil abstract impact cratering has been a fundamental geological process in earth history with major ramifications for the biosphere the complexity of shocked and melted rocks within impact structures presents difficulties for accurate and precise radiogenic isotope age determination hampering the assessment of the effects of an individual event in the geological record we demonstrate the utility of a multi chronometer approach in our study of samples from the 40 km diameter araguainha impact structure of central brazil samples of uplifted basement granite display abundant evidence of shock deformation but u pb ages of shocked zircons and the 40ar 39ar ages of feldspar from the granite largely preserve the igneous crystallization and cooling history mixed results are obtained from in situ 40ar 39ar spot analyses of shocked igneous biotites in the granite with deformation along kink bands resulting in highly localized partial resetting in these grains likewise spot analyses of perlitic glass from pseudotachylitic breccia samples reflect a combination of argon inheritance from wall rock material the age of the glass itself and post impact devitrification the timing of crater formation is better assessed using samples of impact generated melt rock where isotopic resetting is associated with textural evidence of melting and in situ crystallization granular aggregates of neocrystallized zircon form a cluster of ten u pb ages that yield a concordia age of 247 8 3 8 ma the possibility of pb loss from this population suggests that this is a minimum age for the impact event the best evidence for the age of the impact comes from the u th pb dating of neocrystallized monazite and 40ar 39ar step heating of three separate populations of post impact inclusion rich quartz grains that are derived from the infill of miarolitic cavities the 206pb 238u age of 254 5 3 2 ma 2 error and 208pb 232th age of 255 2 4 8 ma 2 error of monazite together with the inverse 18 point isochron age of 254 10 ma mswd 0 52 for the inclusion rich quartz grains yield a weighted mean age of 254 7 2 5 ma 0 99 2 error for the impact event the age of the araguainha crater overlaps with the timing of the permo triassic boundary within error but the calculated energy released by the araguainha impact is insufficient to be a direct cause of the global mass extinction however the regional effects of the araguainha impact event in the parana karoo basin may have been substantial

influences of tropical monsoon climatology on the delivery and dispersal of organic carbon over the upper gulf of thailand abstract organic carbon cycling in se asia is data sparse and poorly studied although high sediment yield and organic carbon intensity occur in the tropical region in the present study we evaluated the role of tropical monsoon pertaining to fluvial discharge sediment load coastal current and water stratification on seasonal organic carbon dynamics during four sampling campaigns in the upper gulf of thailand ugot this study demonstrates that particulate organic carbon poc is closely correlated with the river influx of suspended sediment which is generally regulated by the local rainfall higher poc is found near the large estuarine section chao phraya river chao during southwest monsoon period and the small estuarine section mae klong river mk during november 2013 when tropical cyclones impacted poc in the estuarine sections is more significantly influenced by the seasonal shift compared with the coastal sections land derived organic matter prevails in the small estuarine and coastal sections while marine derived organic matter dominates in the estuarine sections impacted by chao and mk anthropogenic inputs and dam regulation also influences the river export of organic matter during the high precipitation periods total organic carbon toc however displays less significant seasonal monsoon variations than poc further toc tends to accumulate in the sub silt fraction of sediments which mainly occurs in the small estuarine and eastern coastal sections and is more obviously influenced by marine derived factors toc in sediment of the chao and mk influenced sections however displays more seasonal variations with prevailing river input evidenced by coarser sediment and higher c n ratios moreover the almost year round water stratification across the region acts as the barrier in retaining organic carbon in the estuaries and their vicinities from dispersal into the lower portion of gulf of thailand high sedimentation rate 1 1 cm yr 1 further facilitates the organic carbon burial in the study area the delivery dispersal and burial of organic carbon are closely associated with the climate controlled precipitation and thus the tropical monsoon climatology under the global warming in particular is an important factor influencing the organic carbon in the ugot

sequencing events across the permian triassic boundary guryul ravine kashmir india abstract the permian triassic boundary ptb section at guryul ravine kashmir india comprises a 100 m thick apparently conformable succession of mixed siliciclastic carbonate sediments deposited in a deep shelf or ramp setting this section although long important in debates concerning placement of the ptb has not previously been the focus of an integrated chemostratigraphic study in the present study samples from a 20 m thick interval straddling the ptb were analyzed for major and trace element concentrations toc tic rees and organic 13c 15n to investigate contemporaneous environmental changes the guryul ravine section exhibits a sequence of discrete events that provide potentially important information about the character and cause s of the ptb two transient negative c isotopic excursions within the upper changxingensis zone predate the late permian event horizon lpeh i e the global mass extinction event by 200 400 kyr and are associated with the onset of a major eustatic rise and with secondary extinction peaks these excursions may record minor environmental disturbances prior to the main end permian crisis supporting an intrinsic mechanism such as volcanism and climate change rather than an extrinsic mechanism such as a bolide impact the onset of a large 4 0 to 4 5 sustained negative c isotope shift marks the lpeh which is located at the zewan khunamuh formation contact 260 cm below the biostratigraphically defined ptb the guryul ravine section exhibits a stepwise extinction pattern with the largest peak between the lpeh and ptb and a secondary peak just above the ptb a pattern similar to that observed in the meishan d gssp

the permo triassic extinction the end permian mass extinction brought the palaeozoic great experiment in marine life to a close during an interval of intense climatic tectonic and geochemical change improved knowledge of latest permian faunas coupled with recent advances in isotopic studies and biostratigraphy have greatly enhanced our understanding of the events of 250 million years ago and have begun to provide answers to many questions about the causes of extinction

influence of holocene stratigraphic architecture on ground surface settlements a case study from the city of pisa tuscany italy abstract the holocene stratigraphic architecture of modern coastal and deltaic plains has peculiar characteristics that may influence ground surface settlements in the pisa urban area the inhomogeneous spatial distribution of geotechnically weak layers typically formed during the mid late holocene highstand coastal progradation is inferred to be responsible for urban ground settlement and building damage as evidenced by the tilt of several surface structures among which the famous leaning tower of pisa is the most prominent on the basis of integrated stratigraphic sedimentological and geotechnical data from a wide georeferenced database three facies associations with high deformability potential units 1 3 are identified in the uppermost 30 m as opposed to depositional facies units 4 5 with higher geotechnical strength whereas unit 1 represents a thick laterally extensive lagoonal clay deposit the overlying highly deformable units units 2 3 show more discontinuous spatial distribution controlled by the holocene paleohydrographic evolution of the arno coastal plain unit 2 dated between the neolithic and the etruscan age ca 5000 2000 yr bp is composed of swamp clays and silty clays recording lagoon infilling due to arno delta progradation units 3 and 4 which consist of wet levee deposits and stiff floodplain clays respectively formed during the subsequent phases of alluvial plain construction started around the roman age from ca 2000 yr bp whereas units 3 and 4 are recorded within the uppermost 5 m fluvial and distributary channel sands unit 5 cut the underlying deltaic alluvial succession at various stratigraphic levels down to unit 1 the spatial distribution of these units gives rise to three locally juxtaposed stratigraphic motifs in pisa underground reflecting different potential risks for settlement under building loads we show how lateral changes in stratigraphic architecture account for the irregular spatial distribution of geotechnically weak layers that are responsible for building damage and ground settlement

the geochemistry of thai paddy soils abstract this study has determined the elemental composition of uncontaminated thai paddy soils and identified whether variations in chemical composition within and between profiles are sedimentological in origin or due to pedogenic processes the chemical composition of the paddy soils is highly diverse in comparison to typical values for soils worldwide the median concentrations of zn rb sr pb as and cd in thai paddy soils are lower concentrations of si al fe k ca mg na mn ti s v p li ni cu ga co ag be and u are comparable and concentrations of cr are higher using factor analysis two affinity groups of elements and properties are recognized the first group consists of sand si and cr and relates to the sand content of the soils which includes chromium magnetite grains the second group is diffuse and consists of clay silt cec ph h 2 o ph kcl al fe k ca mg na mn ti s v p zn rb li ni sr cu ga pb co as be u ag and cd factor analysis indicates that the compositions of individual horizons in each soil are highly diverse resulting in substantial overlaps in composition between different horizons and soil profiles the large variations of chemical composition within and between thai paddy soils are due to the presence of discrete depositional layers within soil profiles with differences in texture of the soil controlling the variations in chemical composition pedogenic processes have modified original depositional properties to only a moderate extent but may have included the genesis of smectite microprobe analysis of thin sections has shown that the chemical composition of clay coatings is similar to that of the clay matrix and is consistent with the smectitic kaolinitic or mixed clay mineralogies of particular soils the composition of clay minerals in iron oxide rich mottles is similar to that of the clay matrix for kaolinitic soils iron oxide rich nodules in smectitic soils are also kaolinitic rather than smectitic indicating that the smectite formed in the matrix but not in the nodules which are original sedimentary features

petrogenesis of the flood basalts from the early permian panjal traps kashmir india geochemical evidence for shallow melting of the mantle article i nfo the early permian panjal traps of northern india represent a significant eruption of volcanic rocks which occurred during the opening of the neotethys ocean basaltic basaltic andesites dacitic and rhyolitic rocks collected from guryal ravine and pahalgam show evidence for subaerial and subaqueous eruptions indicating that they are contemporaneous with the formation of a shallow marine basin the major and trace element geochemistry of the basalts is consistent with a within plate setting and there are basalts which have high ti tio2 n 2 0 wt and low ti tio2 b 1 8 wt compositions the high ti basalts are similar to oib whereas the low ti basalts are similar to continental tholeiites the identification of high and low ti basalts within the panjal traps is analogous to other large igneous provinces e g karoo deccan parana emeishan the sr nd isotopic values end t 5 3 to 1 3 isr 0 70432 to 0 71168 of both types of basalts overlap indicating that the rocks may have originated from the same ancient subcontinental lithospheric i e emii like mantle source tdm 2000 ma the two groups of basalts can be modeled by using a primitive mantle source and different degrees of partial melting where the high tirocksare producedby 1 partial melting of a spinel peridotite source where as the low ti rocks are produced by 8 partial melting trace elemental and isotope modeling indicatesthat some of the basalts assimilated 10 crustal material in contrast the basaltic andesites are likely formed by mixing be tween basaltic magmas and crustal melts which produced rocks with higher sio2 55 wt content and enriched isotopic signatures end t 6 1 isr 0 70992 the panjal trap volcanism was likely due to partial melting of the sclm within a passive extensional setting related to the rifting of cimmeria from gondwana contemporaneous volcanic and plutonic granitic rocks throughout the himalaya are probably not petrogenetically related but are likely part of the same regional tectonic regime

different isotopic evolutionary trends of δ34s and δ18o compositions of dissolved sulfate in an anaerobic deltaic aquifer system abstract concentration and isotope ratios 34sso4 and 18oso4 of dissolved sulfate of groundwater were analyzed in a very large anaerobic aquifer system under the lower central plain lcp 25 000 km2 in thailand groundwater samples were collected in two different kinds of aquifers type 1 with a saline water contribution and type 2 lateritic aquifers with no saline water contribution two different isotopic compositional trends were observed in type 1 aquifers sulfate isotope ratios range from low values 2 2 for 34sso4 and 8 0 for 18oso4 to high values 49 9 for 34sso4 and 17 9 for 18oso4 in type 2 aquifers sulfate isotope ratios range from low values 0 1 for 34sso4 and 12 2 for 18oso4 to high 18oso4 ratios 18 4 but with low 34sso4 ratios

close up of the end permian mass extinction horizon recorded in the meishan section south china sedimentary elemental and biotic characterization and a negative shift of sulfate sulfur isotope ratio abstract the permian triassic p tr boundary beds of the meishan section south china have been re studied in detail based on complete samples across the p tr transition under the microscope the end permian mass extinction horizon is calibrated to a 12 mm stratal interval the top being 19 mm below the top of bed 24e of the changhsing formation this abrupt disappearance of skeletal fragments of major benthos characterizes the end permian extinction event suggesting a catastrophic event an abrupt decrease in the 34s 32s ratios of seawater sulfate is confirmed to coincide with the end permian event horizon the sulfur isotope event is thought to have been caused by an overturn of a stratified ocean dominated by h2s implying coincidence of the oceanic mixing and the mass extinction coincident siberian flood volcanism may have triggered a long term 103 years cooling leading an ocean mixing a presumed comet impact to the ocean could have directly caused ocean mixing and the mass extinction

anthropogenic changes in a confined groundwater flow system in the bangkok basin thailand part ii how much water has been renewed excessive groundwater pumping from the sedimentary basin underlying the bangkok metropolitan area thailand has caused not only piezometric level decline but also enhancement of groundwater recharge although groundwater renewal has accelerated it remains unclear how much water in confined aquifers has been renewed owing to the excessive pumping to reveal the details of the groundwater renewal process we performed a water budget analysis and virtual tracer experiment using a numerical model of groundwater flow and solute transport mean turnover time was 45600 yr prior to the beginning of significant pumping in 1954 which then shortened to 3500 yr in 2001 the renewed water fraction since 1954 was estimated to be only 0 78 in 2007 on average over the whole basin this is a reflection of the huge storage capacity of the basin relatively low recharge rate due both to existence of a thick clay bangkok clay and low plain gradient the spatially distributed renewed water fraction which was obtained from the virtual tracer experiment was no more than 1 in most aquifers except for basin margins where the aquifers are exposed while in the uppermost bk aquifer it exceeded 5 over a wide extent and reached more than 20 at an alluvial fan the estimated fraction of renewed water was generally consistent with measured 3h concentrations demonstrating in part the validity of the numerical model used the results from our studies indicate that modern waters recharged since 1954 have minimal affect on water quality in the main production aquifers however water storage and pressure in aquifers respond quickly to increase in pumping rate potentially affecting land subsidence thus we have to focus on different time scales between groundwater quantity and quality management copyright 2011 john wiley sons ltd

permian triassic boundary interval in the middle east iran and n oman progressive environmental change from detailed carbonate carbon isotope marine curve and sedimentary evolution abstract the end permian negative 13c excursion is well known but its cause and chronology are still in question in an attempt to decipher the timing and reasons for this strong decrease we established high resolution sedimentological biostratigraphical and carbonate carbon isotopic studies in four sections in iran abadeh shareeza zal and djulfa and two in oman wadi sahtan the position of the sections on two different margins of the neotethys has allowed us to distinguish between local and global signals this high resolution chemostratigraphy tested for isochrony on the basis of an updated high resolution conodont and ammonoid biostratigraphy allows the discrimination of nine successive isotopic events ie 0 8 for the permian triassic boundary interval ptbi the negative excursion of the ptbi has been separated into four distinct parts a first drop ie 0 occurs in the late wuchiapingian with an amplitude of around 1 3 a second decrease begins ie 1 2 at the base of the dzhulfites ammonoid beds changhsingian and continues gradually until the extinction event top jolfensis conodont interval without important second order variations its amplitude varies between 1 5 and 2 8 and its duration has been estimated around 2 2 ma revealing a non catastrophic phenomenon the lower meishanensis praeparvus conodont zone records stationary to slightly increasing values ie 3 the interval of the curve after the extinction event between the upper meishanensis praeparvus zone and the base of the i isarcica zone records numerous second order variations ie 4 7 its amplitude is of 1 2 3 1 these second order variations are correlatable in iran but with some uncertainty with oman poor correlation of these small peaks with others published sections might be due to a higher sensitivity to local perturbations and a lower buffer capacity of the whole ocean we assume that the processes leading to the extinction event also caused the isotopic decrease before the extinction level with a maximal amplitude of only 2 8 this allows consideration of some possible mechanisms that were rejected as unrealistic to cause a 4 6 excursion

association of 34s depleted pyrite layers with negative carbonate δ13c excursions at the permian triassic boundary evidence for upwelling of sulfidic deep ocean water masses 1 a marine permian triassic boundary ptb section at nhi tao vietnam contains a series of at least 9 pyritic horizons characterized by concurrent decreases in pyrite s 34spy and carbonate c isotopic compositions 13ccarb the first and largest of the events that precipitated these pyritic horizons was coincident with the late permian mass extinction while subsequent events were generally smaller and occurred at quasiperiodic intervals of 20 to 30 ka a near complete lack of organic carbon to drive bacterial sulfate reduction in sediment pore waters among other considerations argues against a diagenetic control for these relationships rather the covariant patterns documented herein are most easily explained as the product of recurrent upwelling of anoxic deep ocean waters containing 34s depleted hydrogen sulfide and 13c depleted dissolved inorganic carbon the sulfide 34s record of the study section represents a mixture of a small amount of isotopically heavy authigenic pyrite formed via in situ bacterial sulfate reduction with a generally larger quantity of isotopically light syngenetic pyrite precipitated within the water column during upwelling episodes although upwelling of toxic deepwaters has been invoked in earlier studies as a mechanism for the late permian marine mass extinction this is the first study to 1 document patterns of pyrite 13ccarb covariation that strongly support upwelling as a major process at the ptb and 2 provide evidence of multiple quasiperiodic upwelling events that may reflect reinvigoration of global ocean overturn following a prolonged interval of late permian deep ocean stagnation

mass extinctions and sea level changes abstract review of sea level changes during the big five mass extinctions and several lesser extinction events reveals that the majority coincide with large eustatic inflexions the degree of certainty with which these eustatic oscillations are known varies considerably thus the late ordovician and end cretaceous extinctions are associated with unequivocal major regressions demonstrated from numerous widespread regions in contrast the multiple high frequency sea level changes reported for the frasnian famennian crisis based on the supposed depth preferences of conodont taxa have little support from sequence stratigraphic analyses which reveals the interval to be one of highstand the end permian mass extinction has long been related to a severe first order lowstand of sea level newell n d 1967 revolutions in the history of life geol soc am spec pap 89 63 91 based primarily on the widespread absence of latest permian ammonoid markers but field evidence reveals that the interval coincides with a major transgression newell s hypothesis that marine extinctions are related to shelf habitat loss during severe regression remains tenable for the end guadalupian and end triassic extinction events but not for other crises rapid high amplitude regressive transgressive couplets are the most frequently observed eustatic changes at times of mass extinction with the majority of extinctions occurring during the transgressive pulse when anoxic bottom waters often became extensive the ultimate cause of the sea level changes is generally unclear a glacioeustatic driving mechanism can only be convincingly demonstrated for the end ordovician and end devonian events at other times it is speculated that they may relate to the widespread regional doming and subsequent collapse caused by the impingement of superplumes and ultimate eruption on the base of the lithosphere

methane driven oceanic eruptions and mass extinctions focusing on the permian triassic boundary ca 251 ma i explore the possibility that mass extinction can be caused by an extremely fast explosive release of dissolved methane and other dissolved gases such as carbon dioxide and hydrogen sulfide that accumulated in the oceanic water masses prone to stagnation and anoxia e g in silled basins the mechanism of the explosive release is the same as in the lake nyos disaster of 1986 i e a water column eruption caused by the interplay of buoyancy forces and exsolution of dissolved gas the eruption brings to the surface deep anoxic waters that cause extinctions in the marine realm terrestrial extinctions are caused by explosions and conflagrations that follow the massive release of methane the air methane mixture is explosive at methane concentrations between 5 and 15 and by the eruption triggered floods this scenario accounts well for the available data and may be relevant to other phenomena

late quaternary geology of the lower central plain thailand abstract the lower central plain or chao phraya plain located in the upper gulf of thailand has an average elevation of 2 m above the present mean sea level it is a fault bounded basin developed in the plio pleistocene epoch consequently the basin has been filled with quaternary sediment reaching a thickness of almost 2000 m of which only the upper 300 m is known the pleistocene deposits of the lower central plain represent a complex interplay of alluvial fluvial and deltaic environments of the chao phraya river and its tributaries the upper sequence of sand and stiff clay with iron oxide concretions on the surface was deposited in a fluviatile environment subjected to a regressive period in the late pleistocene the term chao phraya delta is used to define the landform where the chao phraya river interacted with marine processes as the sea level changed during the holocene transgression these strata indicated that the holocene sea reached its maximum height of 4 m above the present mean sea level around 6000 years b p from then on sea level fluctuated until it reached its present level around 1500 years b p this complex sea level history has caused the progradation of tidal flat and tide dominated delta deposits consisting of soft marine clay that covered the lower central plain to an average depth of 15 m in the bangkok area the soft marine clay or bangkok clay is the most important unit in the stratigraphic sequence in terms of land subsidence in the lower central plain evidence of coastal erosion is also considerable in the low tidal flat area on the west bank of the chao phraya river mouth and adjacent coast

natural surface rebound of the bangkok plain and aquifer characterization by persistent scatterer interferometry we estimated recent surface displacements around bangkok by means of persistent scatterer interferometry with alos palsar images acquired from november 2007 to december 2010 land subsidence due to excessive groundwater pumping has been reported in this region however we detected ground surface uplift around the mega city along with seasonal surface displacement with high spatial resolution we then discriminated long term natural rebound and seasonal displacement by fitting exponential and sinusoidal functions to displacement time series and mapped their spatial distributions this mapping allowed us to infer that the second and third shallowest aquifers are laterally continuous whereas the shallowest aquifer has lateral discontinuities the temporal decay rate of the long term rebound might reflect spatial changes of the chao phraya river watershed or the magnitude of the preceding groundwater extraction we demonstrated that our method of decomposing the displacement time series into different spatial and temporal patterns is useful for understanding aquifer connectivity and the elastic response pattern in an aquifer system

stratigraphy and holocene evolution of the mud dominated chao phraya delta thailand abstract the central plain of thailand was formed over the last 8 7 kyr mainly by the deltaic processes of two major rivers the chao phraya and the mae klong the delta plain is the third largest delta plain in southeast asia after that of the mekong and the irrawaddy on the basis of sedimentological and paleontological analyses of samples from three boreholes and an open pit survey the evolution of the delta was clarified with high resolution 14 c dating after the maximum transgression at between 8 and 7 cal kyr bp the delta system migrated southward into the paleo gulf of ayutthaya a large mud shoal the sananivate mud shoal formed near the mouth of the paleo gulf between 7 and 3 cal kyr bp and facilitated its infilling as a result the delta has prograded rapidly particularly during the last 2 kyr deltaic sediment volume for the last 7 5 0 5 kyr shows that the average rate of sedimentation was 23 1 3 6 million t yr which is nearly the same as the present total sediment discharge from both rivers the comparatively wide delta plain relative to sediment discharge resulted from the stable sea level the shallow paleo gulf acting as a receiving basin and effective sediment trapping because of the mud shoal

origin of the silicic volcanic rocks of the early permian panjal traps kashmir india abstract the panjal traps of kashmir india represent a significant outpouring of mafic and silicic volcanic rocks during the early permian and are synchronous with the opening of the neotethys ocean previous studies have suggested that the silicic volcanic rocks are derived by differentiation of mafic magmas dacites and rhyolites collected from the lower portions of the volcanic pile near pampore kashmir are peraluminous anck 1 0 in composition their calculated whole rock i sr values are variable i sr 0 69307 to 0 71825 and indicate open system behavior of either rb or sr or both whereas their nd isotope compositions end t 8 6 to 8 9 are nearly uniform the end t values and trace element th nb pm 4 nb u 8 ratios suggest the rocks are derived partially or wholly from the crust least squares and melts modeling indicate that the likely source of the silicic rocks is the middle crust rather than the lower or upper crust furthermore the silicic panjal traps have trace element compositions similar to some felsic volcanic rocks and a type granitic rocks from other large igneous provinces e g karoo parana and camp the paleoproterozoic t dm ages t dm 1836 to 1937 ma indicate that the rocks were likely derived from an ancient crustal source which experienced multiple episodes of recycling in contrast to silicic volcanic rocks from other lips the silicic panjal traps are unusual in that they did not involve mantle source material the heat required to melt the crust was likely due to the continuous injection of contemporaneous basaltic magmas which formed the majority of the mafic panjal traps

age and timing of the permian mass extinctions u pb dating of closed system zircons the age and timing of the permian triassic mass extinction have been difficult to determine because zircon populations from the type sections are typically affected by pervasive lead loss and contamination by indistinguishable older xenocrysts zircons from nine ash beds within the shangsi and meishan sections china pretreated by annealing followed by partial attack with hydrofluoric acid result in suites of consistent and concordant uranium lead u pb ages eliminating the effects of lead loss the u pb age of the main pulse of the extinction is 252 6 0 2 million years synchronous with the siberian flood volcanism and it occurred within the quoted uncertainty

carbon sulfur oxygen and strontium isotope records organic geochemistry and biostratigraphy across the permian triassic boundary in abadeh iran pelagic deposits at abadeh represent a complete biostratigraphic record across the permian triassic boundary ptb the presumed water depth during deposition of these sediments was between 60 and 90 m similar to other permian triassic boundary sections the succession at abadeh is characterised by a negative carbon isotope shift of approximately 4 the values start to decrease in the lower c changxingensis c deflecta s l zone reach 0 12 v pdb in the uppermost permian just below the ptb remain low to the early i isarcica zone 0 32 and increase subsequently in the upper i isarcica zone for the time interval of the ptb negative carbon isotope excursion between the c iranica and the i isarcica zones no correlation exists between the 13ccarb and the 18ocarb the above observations argue against the conclusion of heydari et al 2001 that the carbon isotope event at the p t transition is an alteration artefact and not a global signal the decrease in 13ccarb is accompanied by a 5 and potentially up to 10 increase in 34ssss together these features are thought to reflect a complex global event notably the development of widespread anoxic oceans with anoxic bottom layers rising onto the shelves for the carbon isotope drop other factors such as the collapse of ocean primary productivity may also have played a role the 87sr 86sr ratios of dzhulfian seawater show only a minor increase from 0 70705 to 0 70710 reaching 0 70720 in the dorashamian the increase becomes steeper in the early triassic reaching 0 70754 in the n dieneri zone the rise of the strontium isotope values is thought to be related to enhanced continental weathering under humid climatic conditions in the uppermost permian c meishanensis h praeparvus zone and the lack of a dense land vegetation in the early triassic prior to the spathian upper olenekian

resolving original signatures from a sea of overprint the geochemistry of the gungri shale upper permian spiti valley india abstract the geochemistry of black shales can faithfully record paleoenvironmental conditions however the original geochemical signatures are obscured by post depositional events such as diagenesis and weathering resolving the relative influence of these processes on the geochemistry of shales requires a combination of geochemical and chemometric chemical statistics approaches to data analysis that identify the sources of variance in major and trace element geochemistry the permian gungri shale kuling group at attargoo spiti valley himachal pradesh india is a gray to black shale capped unconformably by an iron rich pebble sand layer ferruginous layer marking ostensibly the permian triassic boundary high resolution analysis of the gungri at attargoo 3 cm intervals reveals a geochemical record complicated by low grade metamorphism diagenesis and modern weathering using multivariate chemometric techniques e g principal component analysis we identified variance in the geochemical record associated with the original detrital and depositional conditions we also identified 4 beds within the gungri that mark depositional events which may correlate to those identified in other pt sections e g guryul ravine kashmir identification of sources of variance allowed us to identify geochemical signatures that can be used for paleooceanographic reconstruction the attargoo section records a sequence of discrete events including transient iron enrichments attributed to euxinic depositional conditions and late diagenetic formation of siderite and regression condensation surfaces associated with pulsed transgression regression towards the uppermost permian our results show that chemometric analysis of geochemical data enables the resolution of paleoenvironmental conditions in shales impacted by post depositional alteration

hydrogeochemical and isotopic characterization of groundwater salinization in the bangkok aquifer system thailand the deterioration of groundwater quality particularly due to salinization because of the overexploitation of groundwater in the lower central plain of thailand remains a major concern with increasing demand for water there is a growing need for sustainable management of the resource which would benefit from an improved understanding of the sources of chloride contamination thus a hydrochemical and isotopic study was carried out to chemically characterize groundwater and to investigate possible sources of salinization and in particular of chloride contamination in the multi layered bangkok aquifer system groundwater samples were taken from four topmost aquifers bangkok phra pradaeng nakhon luang and nonthaburi additionally short term rainwater sampling as well as river and seawater sampling was performed and later analyzed for ionic composition and stable water isotopes ionic and isotopic data indicate at least three different recharge sources for groundwater the major recharge source is rainwater the influence of seawater is limited to the coastal region and tidally influenced areas of the two main rivers chao phraya and tha chin bromide data also suggest the influence of saline water in deeper aquifers due to trapped water most importantly although the influence of seawater on groundwater is recognizable the surrounding geology contributes a significant number of dissolved ions detected in the groundwater

tracing a confined groundwater flow system under the pressure of excessive groundwater use in the lower central plain thailand excessive groundwater pumping from deep wells in the bangkok metropolitan area bma since the 1950s has induced piezometric drawdown land subsidence and probably remarkable disturbance in confined groundwater flow to trace the large scale groundwater flow system in the lower central plain lcp of thailand and to detect its disturbance we carried out isotopic and hydro chemical investigations of surface subsurface waters as well as hydrometric measurements at 98 observation wells isotopic compositions of the water d and 18o reflected significant seawater mixing and evaporative enrichment the cl br mass ratio suggested that halite dissolution is negligible and spatial distributions of and cl concentration implied that saline water is mainly remnant seawater in addition the cl relationship indicated that the remnant seawater may have been concentrated in part by transpiration from mangrove forests during delta formation after a period of maximum transgression the original d of the source water was estimated by correcting for the effects of seawater mixing and evaporative enrichment using the cl concentration and 18o respectively and its three dimensional distribution revealed that the water originating from precipitation over the lcp during the post glacial age was drawn down to a maximum depth of 240 m by groundwater pumping at two large depressions in the east and west of the bma water recharged during the last glacial age and or originating at higher elevations outside the lcp is drawn from suburban areas laterally or through underlying aquifers in contrast in the central bma groundwater within major productive aquifers is mainly replenished by downward leakage across confining layers copyright 2011 john wiley sons ltd

catastrophic environmental transition at the permian triassic neo tethyan margin of gondwanaland geochemical isotopic and sedimentological evidence in the spiti valley india abstract interpreting global consequences of the permian triassic p tr extinction requires examination across paleogeographic realms of pangaea the spiti valley in india remnant of the peri gondwanan shelf preserved trails of this environmental catastrophe in the neo tethys ocean we document new sedimentological observations and high resolution trace element concentrations and carbon oxygen lead isotope data across the p tr boundary in spiti framboidal pyrites fossils and laminated lithology of the late permian shales indicate deeper anoxic depositional environment while 13 c org excursions of 2 4 and 3 1 in atargu and guling outcrops respectively identify the p tr transition across a clayey partly gypsiferous ferruginous layer sedimentological similarities of this layer to other neo tethyan sections from transcaucasia and iran indicate subaqueous oxidation of shallow marine sediments on a regional scale light rare earth element enriched late permian shales with conspicuous ce eu anomalies reflect their source from the adjacent panjal trap basalts ca 289 ma of kashmir continental crustal nb ta and zr hf anomalies appear at the p tr boundary sediments and prevail through the overlying early triassic carbonates original pb isotope ratios along with an increasing pb abundance closer to the p tr boundary distinguish the volcanic source of the late permian shales from the continental crustal siliciclastic signature of the early triassic carbonates our 13 c org trace element and pb isotope record from spiti indicate catastrophic changes in sediment sources and facies with effects on carbon cycle and are consistent with an abrupt episode of marine regression and erosional forcing also observed elsewhere along northern gondwanaland simultaneous eruption of siberian volcanics and bolide impacts in parana basin of brazil and elsewhere implicating impact triggered volcanism left catastrophic regional global imprints on sea level climate marine anoxia and tectonic stability that connected the p tr crisis across terrestrial and marine realms worlwide

evidence for ca 7 ka maximum holocene transgression on the peninsular malaysia east coast in situ fossil coral and shelly marine deposits occur up to 50cm above mean sea level in north east peninsular malaysia the fossil reef comprises over 15 coral species and associated molluscs radiocarbon ages of corals range from 7238 to 6909 cal a bp the reef occurs adjacent to bedrock hills that formed a mainland peninsula when the coral was living abundant well preserved fossil molluscs with bivalves commonly articulated occur in ditch tailings from coastal plains flanking these hills landward a sand ridge represents part of the maximum transgression shoreline when alive the fossil coral reef required clear water and full marine conditions seaward of the peninsula the maximum transgression here occurred ca 7 ka with stable environmental conditions persisting long enough for diverse coral reef development assuming a similar tidal range to today relative sea level ca 7 ka would have been between 1 4 and 3m above present between then and ca 6 ka abundant sediment supply resulted in barrier beach construction seaward of the coral reef converting the area to a lagoonal environment unsuitable for coral and burial by muddy deposits assuming that regional relative sea level data indicate maximum holocene highstand up to 5m between 6 and 4 ka are correct then the maximum transgression preceded maximum sea level by at least 1000 years copyright 2014 john wiley sons ltd

the lower triassic sedimentary and carbon isotope records from tulong south tibet and their significance for tethyan palaeoceanography abstract the lower triassic sedimentary and carbonate organic carbon isotope records from the tulong area south tibet are documented in their integrality for the first time new age control is provided by ammonoid and conodont biostratigraphy the basal triassic series consists of griesbachian dolomitic limestones similar to the kathwai member in the salt range pakistan and to the otoceras beds in spiti india the overlying thin bedded limestones of dienerian age strongly resemble the lower ceratite limestone of the salt range they are followed by a thick series of dark green silty shales of dienerian early smithian age without fauna that strikingly resemble the ceratite marls of the salt range this interval is overlain by thin bedded light grey fossil rich limestones of middle to late smithian age resembling the upper ceratite limestone of the salt range these are followed by a shale interval of early spathian age that has no direct counterpart in other tethyan sections carbonate production resumes during the late early and middle spathian with the deposition of red bioclastic nodular limestone ammonitico rosso type facies apart from its colour this facies is similar to the one of the niti limestone in spiti and of the spathian nodular limestone in guangxi south china as in other tethyan localities such as spiti the early middle anisian part of the tulong section is strongly condensed and is characterized by grey thin bedded limestones with phosphatized ammonoids as for many other tethyan localities the carbon isotope record from tulong is characterized by a late griesbachian dienerian positive 13ccarb excursion 2 and a very prominent positive excursion 5 at the smithian spathian boundary thus confirming the well documented perturbations of the global carbon cycle following the permian triassic mass extinction event

no link between the panjal traps kashmir and the late permian mass extinctions 1 voluminous late permian flood basalt eruptions are contemporaneous with the mid capitanian 260 ma and end permian 251 ma mass extinction events the panjal traps of kashmir are thought to be correlative to the mid capitanian mass extinction however no radiometric age has been determined we report a single zircon u pb laser ablation icp ms date of a rhyolite from the lower middle part of the volcanic sequence twenty four individual zircon crystals yield a mean 206u 238pb age of 289 3 ma the results show that the panjal traps are considerably older than previously interpreted and not correlative to post neo tethys rifting of the gondwanan margin or the mid capitanian mass extinction and are in fact correlative to the opening of the neo tethys ocean in contrast to other similarly size large igneous provinces the panjal traps are not coincident with a mass extinction event and therefore casts doubt on the direct relationship between continental flood basalt volcanism and ecosystem collapse

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

search for evidence of impact at the permian triassic boundary in antarctica and australia life on earth was almost destroyed some 250 m y ago in the most profound of all known mass extinction events we investigated the possible role of impact by an extraterrestrial bolide through chemical and mineralogical characterization of boundary breccias search for shocked quartz and analysis for iridium in permian triassic boundary sections at graphite peak and mount crean antarctica and wybung head australia thin claystone breccias at the isotopically and paleobotanically defined boundary at all three locations are interpreted as redeposited soil rather than impact ejecta the breccias at all three locations also yielded shocked quartz but it is an order of magnitude less abundant 0 2 vol and smaller only as much as 176 micrometers m diameter than shocked quartz at some cretaceous tertiary boundary sites faint iridium anomalies were detected up to 134 pg g 1 these values are an order of magnitude less than iridium anomalies at some cretaceous tertiary boundary sites furthermore peak iridium values are as much as 1 m below the isotopically and paleobotanically defined boundary the idea that impact caused the extinctions thus remains to be demonstrated convincingly

pyrite framboids in the permian triassic boundary section at meishan china evidence for dysoxic deposition pyrite framboid evidence from the permian triassic global stratotype at meishan china indicates the late permian mass extinction is closely associated with a dramatic decline of benthic oxygen levels sizes and abundances of the framboids were determined from acid residues and in situ on polished sections of the samples the framboids are abundant in the thin pyrite lamina on the top of bed 24e the upper layer of bed 24 and beds 25 26 and 29 rare in bed 24e and bed 28 but absent in bed 27 they have narrow size distributions with average diameters from 4 6 mu m to 8 7 mu m which are similar to those formed under anoxic dysoxic conditions the abundances and mean diameters of the pyrite framboids indicate redox conditions of deposition changing from upper dysoxia bed 24e and lower dysoxia pyrite lamina beds 25 and 26 to oxygenation bed 27 and again to upper dysoxia bed 28 and lower dysoxia bed 29 our discovery confirms a worldwide dysoxic marine event during the permian triassic transition suggestive of a direct relationship with the permian triassic marine mass extinction c 2007 elsevier b v all rights reserved

a comparative study on hydrochemical evolution and quality of groundwater in coastal areas of thailand and bangladesh abstract in recent years thailand and bangladesh have been drawing more attention due to groundwater pollution but there is rarely a comparative study on hydrochemical evolution and quality assessment of groundwater in the areas in this paper end member mixing and gibbs model are used to study the evolution of groundwater hydrochemistry based on the 74 water samples due to the seawater intrusion the evolution path of groundwater in bangkok bay is ca mg hco3 na ca mg hco3 and na ca mg cl na cl which led to increased na k and hco3 concentrations in groundwater and enrichment of fluorine in groundwater caused fluorine pollution in contrast although the evolution path of groundwater in southern bangladesh shows a similar pattern as ca mg hco3 na ca mg hco3 and ca mg cl na cl the principal influence factors are residential agricultural and industrial pollutants the scope of seawater intrusion is only limited to estuary areas of the southern estuary whereas most groundwater is received recharge of polluted surface water which resulted in the enrichment of fe and mn in addition compared with shallow groundwater deep groundwater is updated slowly and evolved to higher degree and is in the na ca mg hco3 and ca mg cl stage for improving groundwater conditions in southern bangladesh enhancing the supply capacity of surface potable water and significantly reducing groundwater exploitation are priority strictly controlling the generation storage and treatment of domestic waste industrial and agricultural pollutants are also important in bangkok bay reducing the groundwater exploitation and dispersing the exploitation area is required

anthropogenic changes in a confined groundwater flow system in the bangkok basin thailand part i was groundwater recharge enhanced in many asian megacities the excessive use of confined groundwater has caused drastic decline of piezometric level with succeeding severe problems such as land subsidence and groundwater salinisation at the same time it may have enhanced groundwater recharge via an increase in vertical and or lateral hydraulic gradient the strength and spatiotemporal variation of the enhanced recharge are expected to depend on geographical and or hydrogeological settings of an area in question in the present study the bangkok basin in thailand was selected to examine characteristics of enhanced recharge due to excessive pumping we carried out numerical experiments on this phenomenon for half a century using a three dimensional groundwater flow model the model reproduced well observed hydraulic head variations model outputs showed clearly that confined groundwater recharge under natural conditions e g without pumping occurred only in suburban hilly areas corresponding to deep aquifer outcrop areas while recharge was enhanced due not only to suburban pumping urban areas mantled in thick clay i e bangkok metropolitan area recharge flux response to temporal variation in groundwater pumping was faster in urban areas and slower in remote hilly areas on the plain enhanced recharge was more distinct at locations where the bangkok clay is relatively thin these results suggest that piezometric level decline can be mitigated if appropriate sites are selected for groundwater pumping copyright 2011 john wiley sons ltd

a unique geochemical record at the permian triassic boundary a 330 metre core drilled through the marine permian triassic boundary in the carnic alps of austria allows closely correlated studies of geochemistry petrography and palaeontology across the boundary the isotope shifts and metal concentrations are extended multiple and complex and do not resemble those seen at the cretaceous tertiary boundary both the carbon isotope shifts and the chemical events including an indium anomaly may have causes related to a major regression of the sea

high resolution surveys along the hot spot affected galapagos spreading center 1 distribution of hydrothermal activity the spatial density of hydrothermal activity along most mid ocean ridges is a robust linear function of spreading rate or magmatic budget but extreme crustal properties may alter this relationship in 2005 2006 we tested the effect of thickened crust on hydrothermal activity using high resolution mapping of plumes overlying the hot spot affected galapagos spreading center from 95 to 89 42 w 560 km of ridge crest plume mapping discovered only two active high temperature vent fields subsequently confirmed by camera tows though strong plume evidence indicated minor venting from at least six other locations total plume incidence ph the fraction of ridge crest overlain by significant plumes was 0 11 0 014 about half that expected for a non hot spot mid ocean ridge with a similar magmatic budget plume distributions on the galapagos spreading center were uncorrelated with abrupt variations in the depth of the along axis melt lens so these variations are apparently not controlled by hydrothermal cooling differences we also found no statistical difference for a significance level of 0 05 in plume incidence between where the seismically imaged melt lens is shallow 2 0 56 km ph 0 108 0 045 and where it is deep 3 4 0 7 km ph 0 121 0 015 the galapagos spreading center thus joins mid ocean ridges near the iceland reykjanes ridge st paul amsterdam south east indian ridge and ascension mid atlantic ridge hot spots as locations of anomalously scarce high temperature venting this scarcity implies that convective cooling along hot spot affected ridge sections occurs primarily by undetected diffuse flow or is permanently or episodically reduced compared to normal mid ocean ridges

formation and fate of sedimentary depocentres on southeast asia s sunda shelf over the past sea level cycle and biogeographic implications abstract sea level variations are the major factor controlling sedimentation as well as the biogeographic patterns at continental margins over late quaternary times fluctuations on millennial time scales produce locally complex deposits in coasts and on shelves associated with short term influence on species development this article reviews the sedimentary and biogeographic history of the tropical siliciclastic sunda shelf as an end member of continental shelves regarding extreme width an enormous sediment supply and highest biodiversity in response to rapid sea level fluctuations we describe particular depositional segments as part of a genetic succession of zones from land to the deep sea based on literature data field observations and calculation of hydro isostatic adjustment effects on changing relative sea level these segments are characterized by individual sedimentary processes and deposits and by a specific potential for material storage and re mobilization long term regressive intervals led to overall sigmoidal promoting extremely thick and wide succeeding units in contrast rapid lateral shifts of defined depocentres over long distances took place in response to short term sea level fluctuations fully isolated small scale sediment bodies formed when sea level changed at exceptionally high rates as a result of the high availability of organic rich sediments mangrove and freshwater peats formed frequently over late quaternary times the appearance of thick massive and widespread peats is mainly linked to time intervals of a sea level rise at slow rates whilst organic matter appears much more dispersely in the sediments during episodes of rapidly changing sea level the preservation potential of the regressive units is generally high due to highest initial sediment supply stabilizing soil formation during exposure and rapid subsidence preservation of depositional elements from other periods is more exceptional and either restricted to local morphological depressions or to episodes of rapid sea level change besides complex channel incision an overall lowering of the sediment surface related to erosion as deep as 20 m or more over wide areas took place mainly during sea level lowering the final export of shelf material is documented by enormous mass wasting packages on the associated continental slope from a palaeogeographic perspective the rapid formation or disappearance of special habitat zones such as mangrove fringes and extended mud flats led to species establishment or truncation in distribution in addition the opening or closure of ocean passages as narrow bridges allowing limited species crossing or as fully colonized corridors had severe impact on eco fragmentation and the expansion or contraction of species independent of such particular conditions sea level changes have been too rapid over the past climatic cycle to allow full regeneration and mature development of coast related ecosystems

a late pleistocene transgression in thailand a marine molluscan fauna from ban praksa samut prakan province abstract a late pleistocene molluscan fauna sampled at ban praksa near the chao phraya river mouth lower central plain of bangkok thailand is herein analyzed and paleoecologically characterized revealing a shallow infralittoral coarse hard bottomed environment the comparison of the ban praksa association with several coeval ones recovered from phra pradaeng formation seems to be evidence of a 10 000 year hiatus between two separate groups of marine faunas possibly belonging to different interstadial transgressive peaks that occurred during the long term sea level regression following the last interglacial

fossil mollusc faunas their bearing on the holocene evolution of the lower central plain of bangkok thailand abstract in this work fossil molluscan assemblages are analyzed in order to reconstruct the evolution of the northern gulf of thailand during the holocene the marine sediments bangkok clay formation of the lower central plain of bangkok and the coastal plain of phetchaburi were sampled at 16 localities obtaining fossil shells and mangrove peat whose 14c ages range from 9000 to 2000 cybp a statistical treatment of abundance data returned four major groups namely the dendostrea rosacea association intertidal mud the corbula fortisulcata mactra luzonica association shallow infralittoral sandy mud the nuculana mauritiana timoclea scabra association infralittoral sand spit and the timoclea scabra arcopagia pudica association infralittoral mud the data allowed both a stratigraphic correlation along two transects covering all of the holocene basin and the creation of digitalized maps showing the presumable extension of the thai paleogulf around the apex of flandrian transgression event about 5500 cybp

palaeoenvironments of the permian triassic transition sections in kashmir india abstract detailed measurements of two permian triassic boundary sections at guryul ravine and pahlgam in kashmir indicate continuous sedimentation across the boundary though with a marked change from shallow storm influenced shelf to deeper shelf below wave base successive shell beds through the 2 5 m thick transitional latest permian section at guryul formed as in situ accumulations with little sign of either erosional breaks or condensation faunal change takes place gradually in the late permian transition beds as elsewhere in the tethyan sections there is no major event layer at the permian triassic boundary and little evidence for dysaerobic conditions both the kashmir and east greenland permian triassic sections have sedimentation rates that are orders of magnitude greater than at the condensed meishan reference section they show that the end permian extinction was associated with transgression but not with immediate onset of anoxic conditions macrofaunal extinction seems associated with reduction in primary production which would also explain the dwarfism of fossils found in all permian triassic sections studied so far