the permian triassic transition and the onset of mesozoic sedimentation at the northwestern peri tethyan domain scale palaeogeographic maps and geodynamic implications the main aim of this paper is to review middle permian through middle triassic continental successions in european secondly areas of middle late permian sedimentation the permian triassic boundary ptb and the onset of triassic sedimentation at the scale of the westernmost peri tethyan domain are defined in order to construct palaeogeographic maps of the area and to discuss the impact of tectonics climate and sediment supply on the preservation of continental sediment at the scale of the western european peri tethyan basins the upper permian is characterised by a general progradational pattern from playa lake or floodplain to fluvial environments in the northern variscan belt domain areas of sedimentation were either isolated or connected to the large basin which was occupied by the zechstein sea in the southern variscan belt during the late permian either isolated endoreic basins occurred with palaeocurrent directions indicating local sources or basins underwent erosion and or there was no deposition these basins were not connected with the tethys ocean which could be explained by a high border formed by corsica sardinia palaeorelief and even parts of the kabilia microplate the palaeoflora and sedimentary environments suggest warm and semi arid climatic conditions at the scale of the whole study area an unconformity more or less angular is observed almost everywhere between deposits of the upper permian and triassic except in the central part of the germanic basin the sedimentation gap is more developed in the southern area where in some basins upper permian sediment does not occur the large sedimentary supply erosion and or lack of deposition during the late permian as well as the variable palaeocurrent direction pattern between themiddle late permian and the early triassic indicate a period of relief rejuvenation during the late permian during the induan all the intra belt basins were under erosion and sediment was only preserved in the extra belt domains the northern and extreme southern domains in the northern domain the central part of the germanic basin sediment was preserved under the same climatic conditions as during the latest permian whereas in the extreme southern domain it was probably preserved in the tethys ocean implying a large amount of detrital components entering themarinewaters mesozoic sedimentation began in the early olenekian the ephemeral fluvial systems indicate arid climatic conditions during this period three distinct areas of sedimentation occur a northern and southern domain separated by an intra belt domain the latter accumulated sediments during the early middle permian and experienced erosion and or no deposition conditions between the middle late permian and the beginning of mesozoic sedimentation dated as anisian to hettangian at the top of the lower triassic another tectonically induced more or less angular unconformity is observed the hardegsen unconformity which is dated as intra spathian and is especially found in the north european basins this tectonic activity created new source areas and a new fluvial style with marine influences at the distal part of the systems during the anisian and ladinian continental sedimentation was characterised by a retrogradational trend in other words the fluvial system evolved into fluvio marine environments attesting to a direct influence of the tethys ocean in the southern and northern domains both at the end of the olenekian spathian and during the anisian the presence of palaeosols micro andmacrofloras indicate less arid conditions throughout this domain

a 1000 year history of large floods in the upper ganga catchment central himalaya india abstract determining the frequency magnitude and causes of large floods over long periods in the flood prone himalaya is important for estimating the likelihood of future floods a thousand year record with some information from 2600 years ago of the frequency and some estimates of velocities and discharges of large floods has been reconstructed in the upper ganga catchment india using written reports litho stratigraphy and sedimentology and dated by optical and radiocarbon methods in the upper ganga catchment rainfall triggers large landslides that dam rivers and release large amounts of water when they burst thereby amplifying the effects of rainfall the large floods in the catchment may be the result of landslide dam bursts rather than glacial lake bursts and these are likely to continue and possibly worsen as the monsoon intensifies over the next century however preliminary information suggests that the recent devastating flood of june 2013 was the result of heavy rainfall not landslide dam bursts the frequency record is non random and shows a high frequency between ad 1000 and ad 1300 omitting uncertainties then a low frequency until a cluster of floods occurred about 200 years ago then increased frequency this temporal pattern is like but not identical with that in peninsular india and both appear to be the result of variations in the monsoon

facies and facies architecture of paleogene floodplain deposits willwood formation bighorn basin wyoming usa abstract paleogene deposits of the willwood formation were analyzed in two areas of the bighorn basin to provide a better understanding of the facies and facies arrangement of floodplain deposits and the various processes that influence floodplain construction and facies variability despite similar facies and facies organization floodplain deposits in the two areas differ in grain size hydromorphy and maturity of the paleosols and scale and organization of ribbon sandstones in the avulsion deposits these differences appear to be controlled by basin position of the study areas and differences in avulsion between the areas two kinds of cumulative floodplain paleosols red and purple paleosols formed on overbank deposits the red paleosols were better drained and formed on less clay rich parent material intense mottling and iron oxide nodules indicate that the purple paleosols which formed on more clay rich parent material were poorly drained the grain size differences reflect basin position in particular distance from a local sediment source avulsion deposits are volumetrically important comprising about half of the floodplain deposits in both areas the avulsion deposits resemble the stage iii splays described by smith et al 1989 smith n d cross ia dufficy j p clough s r 1989 anatomy of an avulsion sedimentology 36 1 24 in terms of characteristics of their ribbon sandstones and the presence of thin sheet sandstones or siltstones paleosols that formed on the fine grained facies show morphologic differences interpreted as developmental differences and attributed to differing rates of avulsion in the two study areas this study shows that avulsion belt paleosols provide a key to understanding avulsion rate in the stratigraphic record other differences between the willwood avulsion deposits in the two areas and between these ancient deposits and the modern avulsion deposits described by smith et al may reflect 1 problems in clearly recognizing ancient avulsion deposits in the field and 2 sampling bias resulting from the areally restricted view provided by the stratigraphic record of an areally extensive modern depositional feature at the same time because exposures are three dimensional the willwood strata reveal aspects of the facies and facies arrangement of avulsion belts not readily observed in the modern ones

lacustrine record of high magnitude flood events and climate variability during mid to late holocene in the semiarid alluvial plains western india abstract long term data on flooding events are necessary for understanding the flood frequency and magnitude variations but the available instrumental records span only a few decades recently lake sediment sequences have emerged as a relatively untapped archive for high magnitude floods over longer timescales in the present study multi proxy data from a lacustrine sequence at timbi in the dhadhar river basin were analysed to determine high magnitude floods in this semi arid region of western india in response to southwest monsoon variability the results indicate the occurrence of discreet high magnitude flood events and depositional phases corresponding to different climatic conditions during the mid to late holocene three large flash floods between 4830 and 2730 cal yr b p phase i have been identified as coeval with flood events from fluvial archives and correlated to the widespread period of aridity and weak monsoon recorded in the lakes of north western india a shift in the depositional environment from fluvial to lacustrine occurred around 2730 cal yr b p as inferred from an abrupt change in the sediment character and palynofacies caused by high intensity flash floods and high sediment influx phase ii 2730 1730 cal yr b p was marked by periodic erosion and deposition in the catchment and sediment influx during pulses of higher precipitation as evident in the dominance of glomus sp and alternaria sp and relatively low values in concentration related magnetic parameters and s ratio a high magnitude flood event occurred at 1770 cal yr b p towards the end of phase ii during phase iii 1730 880 cal yr b p the monsoon was enhanced and climate was warmer as suggested by low fd sirm s ratio higher ba sr ratio and presence of aquatic palynomorphs a high percentage of structured organic matter om low fungal remains and increased ba sr ratios between 880 and 360 cal yr b p indicate higher lake waters and better monsoon condition during phase iv the phase v 360 0 cal yr b p corresponds to lake level lowering soil formation and eutrophication the timbi lake sediments demonstrate the potential for lakes in semi arid alluvial plains of western india to preserve proxy flood records providing additional archives for generating long term datasets the flood record generated substantiates palaeoflood data from the fluvial archive suggestive of regional scale southwest monsoon variability low frequency high magnitude floods occurred during arid periods and low magnitude high frequency events during relatively strengthened monsoon and thus have implication for linking the palaeoflood events to the southwest monsoon intensity in the semi arid continental regions

climate control on erosion distribution over the himalaya during the past 100 ka sediment samples from a 50 m long core representing 100 ka of deposition taken from the ganga plain on the campus of the indian institute of technology kanpur were analyzed for sr and nd isotope compositions both 87 sr 86 sr and nd vary significantly with depth in the core 0 72701 0 76708 and 14 4 to 16 6 respectively within the range for silicate rocks of the higher and the lesser himalaya the variations in the isotope compositions reflect variations in the mixing proportion of sediments from the higher and lesser himalaya the two major sediment sources to the ganga the opposite trends in 87 sr 86 sr and nd depth profiles further confirm this hypothesis the isotope profiles exhibit two major excursions ca 20 ka and ca 70 ka ago coinciding with periods of precipitation minima and larger glacial cover these excursions are the result of a decrease in the proportion of sediment from the higher himalaya due to a decrease in monsoon precipitation and an increase in glacial cover that are in turn caused by lower solar insolation this study highlights the significant influence of climate on erosion in the himalaya

changing fluvial environments across the permian triassic boundary in the karoo basin south africa and possible causes of tetrapod extinctions abstract the karoo supergroup is a 12 km thick succession of sedimentary rocks that accumulated in a large intracratonic retroarc foreland basin in southwestern gondwana the strata record 100 million years of almost continuous sediment accumulation from the permo carboniferous 300 ma through to the early jurassic 190 ma under a range of climatic regimes and within several tectonically controlled sub basins alluvial sediments dominate the succession from the late permian onwards fossils of synapsid reptiles and early dinosaurs are sufficiently common to be used in a ten fold biostratigraphic subdivision of these strata the permian triassic boundary in the karoo succession is marked by a major extinction of the herbivorous dicynodonts which co incides with a rapid change in fluvial facies this study uses field observations of the sedimentary facies palaeosols and in situ fossils of well exposed p tr boundary sequences in the southern karoo basin to provide evidence of environmental changes that may have caused the tetrapod extinctions in the main karoo basin below the p tr boundary sequence the sediments comprise drab greenish grey mudrocks with a few thick 3 12 m multistoried laterally accreted fine grained sandstone bodies the mudrocks host hydromorphic palaeosols with palustrine carbonate horizons and mostly disarticulated skeletal remains of dicynodon assemblage zone fauna above a transition zone of approximately 20 m thickness these strata change into reddish brown mudrocks with numerous thin 0 5 5 m ribbon sandstone bodies and more continuous sheet sandstones calcic palaeosols with rhizocretions nodular horizons and pervasive calcareous encrustation of articulated skeletons of lystrosaurus and associated fauna of the lystrosaurus assemblage zone within a 20 m thick interval of the transitional strata fossils of dicynodon and lystrosaurus occur together the facies transition that co incides with the latest permian dicynodont extinction is interpreted as a change in fluvial style from meandering to low sinuosity channels with general drying of the floodplain habitats and redistribution of vegetation belts the horsetails in particular became significantly reduced in areal distribution the changes in fluvial style in the karoo basin at the end of the permian were triggered by a pulse of thrusting in the southerly source area dated at 247 ma 2 ma which brought about rapid progradation of a large sandy braided fan system the katberg sandstone fm into the central parts of the basin a concomitant basinward migration of depositional environments allowed the lystrosaurus communities that were adapted to dry floodplains to colonise the entire basin to the detriment of most of the wet floodplain dicynodon fauna that lived there

palaeoenvironment of braided fluvial systems in different tectonic realms of the triassic sherwood sandstone group uk abstract fluvial successions comprising the fills of sedimentary basins occur in a variety of tectonic realms related to extensional compressional and strike slip settings as well as on slowly subsiding passive basin margins a major rifting phase affected nw europe during the triassic and resulted in the generation of numerous sedimentary basins in the uk much of the fill of these basins is represented by fluvial and aeolian successions of the sherwood sandstone group additionally regions that experienced slow rates of mesozoic subsidence unrelated to triassic rifting also acted as sites of accumulation of the sherwood sandstone group one well exposed example being the eastern england shelf the fluvial depositional architecture of deposits of the sherwood sandstone group of the eastern england shelf a shelf edge basin is compared with similar fluvial deposits of the st bees sandstone formation eastern irish sea basin a half graben the two studied successions represent the preserved deposits of braided fluvial systems that were influenced by common allogenic factors climate sediment source delivery style differences in preserved sedimentary style principally reflect their different tectonics settings analysis of lithofacies and architectural elements demonstrates that both studied successions are characterized by amalgamated channel fill elements that are recorded predominantly by downstream accreting sandy barforms the different tectonic settings in which the two braided fluvial systems accumulated exerted a dominant control on preserved sedimentary style and long term preservation potential on the eastern england shelf the vertical stacking of pebbly units and the general absence of fine grained units reflect a slow rate of sediment accommodation generation 18 19 4 m myr in this shelf edge basin successive fluvial cycles repeatedly reworked the uppermost parts of earlier fluvial deposits such that only the lowermost channel lags tend to be preserved by contrast in the eastern irish sea basin of west cumbria the rate of sediment accommodation generation was substantially greater 119 m myr such that space was available to preserve complete fluvial cycles including silty drape units that cap the channelized deposits

sr and nd isotopes in river sediments from the ganga basin sediment provenance and spatial variability in physical erosion 1 sr and nd concentrations and isotope compositions in sediment of the ganga river from gangotri to rajmahal and its tributaries have been measured to determine provenance and the spatial variability in physical erosion among the ganga subbasins sr and nd in silicates range from 37 to 138 and from 10 to 36 g g with 87sr 86sr and nd of 0 7474 0 8428 and 25 5 to 15 5 respectively the results suggest that 65 of ganga mainstream sediments are derived from the higher himalayan crystallines highlighting intense physical erosion in this region the 87sr 86sr values of sediments in the gangetic plain show nearly identical trends during two seasons with a sharp and significant decrease at barauni downstream of gandak confluence this brings out the major impact of the sediment contribution from the gandak to the ganga mainstream model calculation suggests that about half of the ganga sediment at rajmahal is sourced from the gandak the erosion rates in the himalayan subbasins of the ganga range between 0 5 and 6 mm a where a is years with the gandak having the highest erosion rate high relief and intense precipitation over the headwater basins of the gandak appear to drive the rapid and focused erosion of this basin the results of this study and those in literature suggest that the eastern syntaxis brahmaputra the western syntaxis indus and the gandak have much higher physical erosion rates than the other himalayan basins focused erosion in the hot spots of these river basins contributes significantly to the global riverine sediment budget and influence regional tectonics

identifying the causes of sea level change global mean sea level change has increased from a few centimetres per century over recent millennia to a few tens of centimetres per century in recent decades a review of the latest work shows that global mean sea level rise is unlikely to exceed one metre over the twenty first century but regional departures from this global mean could reach several decimetres

sequence stratigraphy of continental triassic strata of southernmost brazil a contribution to southwestern gondwana palaeogeography and palaeoclimate abstract the continental triassic succession of southernmost brazil comprises two second order depositional sequences the sanga do cabral early triassic and the santa maria middle to late triassic supersequences the first one includes ephemeral low sinuosity fluvial deposits developed on a low gradient plain based on fossil tetrapods especially procolophonids an upper induan age is estimated for this sequence facies association of the santa maria supersequence indicates low sinuosity fluvial rivers deltas and lakes this supersequence can be further subdivided into three third order sequences age provided by palaeovertebrate biostratigraphic data as follows santa maria 1 ladinian santa maria 2 carnian to early norian and santa maria 3 probably raethian or early jurassic sequences the gondwanides paroxysms i and ii in the sierra de la ventana cape fold belt are directly related to the development of both supersequences the source area of the sanga do cabral supersequence was located to the south it consisted of an uplifted peripheral bulge situated landward of the retro foreland system from where older sedimentary rocks were eroded the source area of the santa maria supersequence was also positioned southwards and related to the uplifted sul rio grandense and uruguayan shields the santa maria supersequence stratigraphic architecture is comparable to the triassic rift basins of western argentina diagenesis facies and palaeontology of the studied succession suggest a dominantly semiarid climate during the triassic

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

changes in the magnitude and frequency of late holocene monsoon floods on the narmada river central india during the past three decades the narmada river of monsoon dominated central india has undergone extraordinarily large floods that rank among the highest recorded rainfall runoff discharges per drainage area in the world the floods on this river are a direct result of intense tropical cyclones embedded within the summer monsoon circulation the cluster of extreme floods in the past few decades represents an anomalous increase in both the magnitude and frequency of large floods when compared with the 1700 yr record of paleoflood deposits on this river sand deposits from recent floods consistently blanket older flood deposits at numerous slack water paleoflood sites along a 15 km reach of the narmada river at the site of the highest flood deposits 4 5 sandy flood deposits yielding post a d 1950 14c dates cap an underlying sequence of 7 10 silty flood deposits with a minimum 14c age of 650 70 b p and a maximum age older than 1720 185 b p the post a d 1950 floods are thus the largest in at least the past several hundred years an undisturbed surface archaeological site of microlithic artifacts 0 5 m above the post 1950 flood sands provides further evidence that no significantly larger floods have occurred in at least the past 3000 yr incipient soil development on the buried surfaces of some of the higher paleoflood deposits indicates long intervals in the past when no floods reached the highest slack water site the largest flood in the 1951 1991 gaged record of the narmada river at mortakka 55 323 m3s 1 in 1961 is equivalent to a 1000 yr flood in a probability distribution based on the 1700 yr paleoflood record but is less than a 50 yr flood based on the 1951 1991 gaged record alone demonstrating the enormous recent increase in the frequency of severe floods this cluster of severe floods could reflect changes in either climate or land use a number of paleoflood studies in tropical storm regions show a similar increase in high magnitude floods within the past four decades suggesting a widespread climatic cause for this pattern

sedimentology of cold climate aeolian sandsheet deposits in the askja region of northeast iceland active aeolian sandsheets cover an area of 270 km2 in the askja region of ne iceland the sandsheet is divided into i a deflationary upwind part that is characterised by deflation lags ventifacted boulder fields and restricted aeolian sand patches in the lee of obstacles ii an accumulating central part that is characterised by continuous aeolian sand cover up to 10 m thick where three scales of aeolian ripples are evident along with larger scale forms including longitudinal zibars and iii a downwind part that is currently subject to aeolian bypass with only localised accumulation occurring in topographic hollows between basaltic lava fields trains of aeolian granule megaripples are a characteristic landform of the downwind part of the sandsheet these sinuous crested oblique bedforms attain heights of 0 35 m and downwind spacings of 6 m they are composed principally of low density pebble grade pumice clasts and other reworked volcaniclastic detritus derived from the nearby askja volcanic centre the distribution of landforms across the sandsheet reflects a regional aeolian sediment budget that is controlled by dynamic interactions between glacial ice margin fluvial aeolian and volcaniclastic processes under the influence of a distinctive climatic regime sediment supply at the upwind sandsheet margin adjacent to the dyngjujokull glacier increases during summer periods when rates of glacial ablation are at a maximum longer term controls on sediment supply rate are determined by episodes of glacier surging and retreat and by periodic eruptions of volcaniclastic debris from the askja volcanic centre the availability of sediment for aeolian transport is controlled by the level of the groundwater table the depth and continuity of the permafrost layer in the proglacial area the degree of development of armoured pebble lags and freezing of the sandsheet surface during winter months the transport capacity of the wind varies on a seasonal basis with mean wind velocities and wind gustiness reaching a maximum during winter periods both winter and summer mean wind velocities have been steadily increasing since formal records began in 1969 the suite of aeolian landforms developed within the askja region as defined by sediment texture and composition and bedform scale morphology and spatial distribution reflects a special set of controlling circumstances which mean that the askja sandsheet deposits differ significantly from those described from elsewhere

the fluvial geochemistry contributions of silicate carbonate and saline alkaline components to chemical weathering flux and controlling parameters narmada river deccan traps india abstract the narmada river in india is the largest west flowing river into the arabian sea draining through the deccan traps one of the largest flood basalt provinces in the world the fluvial geochemical characteristics and chemical weathering rates cwr for the mainstream and its major tributaries were determined using a composite dataset which includes four phases of seasonal field spot samples during 2003 and 2004 and a decade long 1990 2000 fortnight time series multiannual data here we demonstrate the influence of minor lithologies carbonates and saline alkaline soils on basaltic signature as reflected in sudden increases of ca2 mg2 and na contents at many locations along the mainstream and in tributaries both spot and multiannual data corrected for non geological contributions were used to calculate the cwr the cwr for spot samples cwrspot vary between 25 and 63 ton km 2 year 1 showing a reasonable correspondence with the cwr estimated for multiannual data cwrmulti at most study locations the weathering rates of silicate silwr carbonate carbwr and evaporite sal alkwr have contributed 38 58 28 45 and 8 23 respectively to the cwrspot at different locations the estimated silwr 11 36 ton km 2 year 1 for the narmada basin indicates that the previous studies on the north deccan rivers narmada tapti godavari overestimated the silicate weathering rates and associated co2 consumption rates the average annual co2 drawdown via silicate weathering calculated for the narmada basin is 0 032 1012 moles year 1 suggesting that chemical weathering of the entire deccan trap basalts consumes approximately 2 0 24 1012 moles of the annual global co2 drawdown the present study also evaluates the influence of meteorological parameters runoff and temperature and physical weathering rates pwr in controlling the cwr at annual scale across the basin the cwr and the silwr show significant correlation with runoff and pwr on the basis of observed wide temporal variations in the cwr and their close association with runoff temperature and physical erosion we propose that the cwr in the narmada basin strongly depend on meteorological variability at most locations the total denudation rates tdr are dominated by physical erosion whereas chemical weathering constitutes only a small part

intensifying aeolian activity following the end permian mass extinction evidence from the late permian early triassic terrestrial sedimentary record of the ordos basin north china

sr and nd isotopes as tracers of clastic sources in lake le bourget sediment nw alps france during the little ice age palaeohydrology implications geochemical methods major elements and sr nd isotopes have been used to 1 characterize lake le bourget sediments in the french alps 2 identify the current sources of the clastic sediments and estimate the source variability over the last 600 years major element results indicate that lake le bourget sediments consist of 45 clastic component and 55 endogenic calcite in addition several individual flood levels have been identified during the little ice age lia on the basis of their higher clastic content 70 potential sources of lake le bourget clastic sediments have been investigated from sr and nd isotope compositions the sediments from the sierroz river and leysse river which are mainly derived from the mesozoic calcareous massifs are characterised by lower 87sr 86sr ratios and slightly lower nd 0 ratios than the arve river sediments which are derived from the palaeozoic mont blanc external crystalline massifs the rhone river appears to have been the main source of clastic sediments into the lake for the last 600 years as evidenced by a similar sr and nd isotopic compositions analyzed in core b16 sediments 87sr 86sr 0 719 nd 0 10 and in the sediments of the rhone river 87sr 86sr 0 719 nd 0 9 6 the isotopic signatures of flood events and background samples from core b16 in lake le bourget are also similar this indicates that prior to 1800 the inputs into the lake have remained relatively homogeneous with the proportion of clastic component mainly being a function of the palaeohydrology of the rhone river early human modification deforestation and agriculture of the lake catchment before the 1800s appears to have had little influence on the source of clastic sediments

tracing the distribution of erosion in the brahmaputra watershed from isotopic compositions of stream sediments bank sediments and suspended loads of the brahmaputra river and its important tributaries were collected from the himalayan front to bangladesh along with most of the important tributaries chemical and isotopic compositions of the sediments are used to trace sediment provenance and to understand erosion patterns in the basin overall isotopic compositions range from 0 7053 to 0 8250 for sr and nd from 20 5 to 6 9 this large range derives from the variable proportions of sediments from himalayan formations with high sr isotopic ratios and low nd and transhimalayan plutonic belt with lower sr isotopic ratios and higher nd the latter are exposed to erosion in the tsangpo and in the eastern tributary drainages overall erosion of the himalayan rocks is dominant representing ca 70 of the detrital influx compositions of the brahmaputra main channel are rather stable between 0 7177 and 0 7284 for sr and between 14 4 and 12 5 for nd throughout its course in the plain from the siang tsangpo at the foot of the himalayan range down to the delta this stability despite the input of large himalayan rivers suggests that the siang tsangpo river represents the major source of sediment to the whole brahmaputra geochemical budget implies that erosion of the namche barwa zone represents about 45 of the total flux at its outflow before confluence with the ganga from only 20 of the mountain area higher erosion rates in the eastern syntaxis compared to the other himalayan ranges is related to the rapid exhumation rates of this region possibly triggered by higher precipitation over the far eastern himalaya and the high incision potential of the tsangpo river due to its very high water discharge

clay minerals and sr nd isotopes of the sediments along the western margin of india and their implication for sediment provenance mineralogy and sr nd isotopic composition of the 2 m fraction of the holocene and late pleistocene sediments from 12 gravity cores collected along the western margin of india were used to delineate the provenance and understand the response of isotopes with respect to the source rock composition holocene sediments show distinct clay mineral associations representing three major sources illite chlorite rich sediments from the indus smectite dominated sediments from the deccan traps and kaolinite and smectite enriched sediments from gneissic rocks the mixing of indus derived sediment with the deccan traps derived sediment or the deccan traps derived sediment with gneissic rock derived sediment occurs in the deeper water cores sr isotopes are very sensitive to weathering and laterization weathering does not influence nd isotopes the 87sr 86sr ratios of the holocene sediments in shallow water cores are higher and fluctuated widely than those in deeper water cores nd correlates well with the clay mineral associations indicating source rock composition or mixing of source sediments kaolinite enriched sediments coupled with high sr ratios and low nd on the sw margin of india suggest intense chemical weathering in the hinterland the influence of the sediment from the ganges brahmaputra transported by the bay of bengal waters during the ne monsoon surface current or sw monsoon underwater current on the composition of the sediments of the sw indian margin is insignificant the late pleistocene sediments reflect a decrease of hydrolytic processes resulting in decrease of smectite and sr isotopic ratio clay minerals and nd values suggest that the provenance and transport pathways of the late pleistocene sediments are the same as those of the holocene for each region

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

archean to recent aeolian sand systems and their sedimentary record current understanding and future prospects the sedimentary record of aeolian sand systems extends from the archean to the quaternary yet current understanding of aeolian sedimentary processes and product remains limited most preserved aeolian successions represent inland sand sea or dunefield erg deposits whereas coastal systems are primarily known from the cenozoic the complexity of aeolian sedimentary processes and facies variability are under represented and excessively simplified in current facies models which are not sufficiently refined to reliably account for the complexity inherent in bedform morphology and migratory behaviour and therefore cannot be used to consistently account for and predict the nature of the preserved sedimentary record in terms of formative processes archean and neoproterozoic aeolian successions remain poorly constrained palaeozoic ergs developed and accumulated in relation to the palaeogeographical location of land masses and desert belts during the triassic widespread desert conditions prevailed across much of europe during the jurassic extensive ergs developed in north america and gave rise to anomalously thick aeolian successions cretaceous aeolian successions are widespread in south america africa asia and locally in europe spain and the usa several eocene to pliocene successions represent the direct precursors to the present day systems quaternary systems include major sand seas ergs in low lattitude and mid latitude arid regions pleistocene carbonate and holocene modern siliciclastic coastal systems the sedimentary record of most modern aeolian systems remains largely unknown the majority of palaeoenvironmental reconstructions of aeolian systems envisage transverse dunes whereas successions representing linear and star dunes remain under recognized research questions that remain to be answered include i what factors control the preservation potential of different types of aeolian bedforms and what are the characteristics of the deposits of different bedform types that can be used for effective reconstruction of original bedform morphology ii what specific set of controlling conditions allow for sustained bedform climb versus episodic sequence accumulation and preservation iii can sophisticated four dimensional models be developed for complex patterns of spatial and temporal transition between different mechanisms of accumulation and preservation and iv is it reasonable to assume that the deposits of preserved aeolian successions necessarily represent an unbiased record of the conditions that prevailed during episodes of earth history when large scale aeolian systems were active or has the evidence to support the existence of other major desert basins been lost for many periods throughout earth history

elemental geochemistry of river sediments from the deccan traps india implications to sources of elements and their mobility during basalt water interaction abstract the abundances of several major na ca mg k al ti fe and minor elements sr ba mn p v cr ni cu and zn have been measured in twenty eight sediment samples from seventeen rivers belonging to the krishna headwaters and west flowing western ghat rivers all of which drain the deccan trap basalts these results particularly those of na ca mg and sr coupled with those reported for these elements in the dissolved phase of the same rivers provide an assessment of their relative mobility and insight into the nature of chemical weathering of deccan basalts the sediments are heavily depleted in na ca mg and sr relative to parent basalts by 60 the abundance ratios of these elements in sediments are roughly the same as those in basalts and in dissolved phases of these rivers das a krishnaswami s sarin m m pande k 2005a chemical weathering in the krishna basin and the western ghats of the deccan traps rates of basalt weathering and their controls geochim cosmochim acta 69 2067 2084 suggesting their near congruent release from basalts to water during chemical weathering both at present and over the residence time of particles in the basin k and ba show limited mobility relative to the above four elements the abundances of k and ba are strongly correlated most likely due to their association in rock forming minerals al fe and ti are generally enriched in the sediments resulting from the loss of more mobile elements from basalts and their association with secondary minerals formed during weathering the data also provide evidence for the fractionation of fe and al during chemical weathering and erosion fe and ti exhibit significant correlation attributable either to their co occurrence in weathering resistant minerals and or due to scavenging of ti by fe oxy hydroxides formed during weathering of basalts the abundance of minor elements mn p v cr ni cu and zn and their ratios with al show significant scatter by and large bracketing the range reported for deccan basalts the wide and overlapping ranges in the concentration of these elements and their ratios relative to al between sediments and basalts place severe constraints in assessing their mobility during weathering and erosion and in judging the role of anthropogenic sources in contributing to their abundances among the minor elements there is a hint that zn concentration may have been influenced by anthropogenic inputs mn v and ni analogous to ti show significant correlation with fe either due to their association with fe ti minerals or their sequestration by fe oxy hydroxides the mobility of elements during weathering and erosion of deccan basalts follows the trend na ca mg sr k ba al fe ti there is considerable spatial variability in the intensity of chemical weathering of deccan basalts the cia chemical index of alteration values for the sediment range between 42 and 92 compared to 37 for the deccan basalts the lower cia values are in sediments richer in caco 3 this may be a result of semi arid climate of the region which facilitate caco 3 precipitation and restrict chemical weathering erosion higher cia values are generally associated with sediments from basins with higher runoff modeling the major element composition of sediment and water yields estimates of particulate abundances in water these estimates agree with the measured values within a factor of 2 for some of the rivers whereas in some others they differ by more than a factor of 3 4 the use of sediment composition instead of that of the suspended matter spatial and temporal variations in sediment flux and non steady state erosion all can contribute to this discrepancy these factors also seem to be contributing to difference in co 2 consumption estimated from sediment composition and that reported based on dissolved phase data

deposition in the kuznetsk basin siberia insights into the permian triassic transition and the mesozoic evolution of central asia abstract this paper describes the permian mesozoic stratigraphy of the kuznetsk basin southern siberia which is adjacent to the vast and hydrocarbon rich west siberian basin and on the edge of the siberian flood basalts the basin fill is permian to cretaceous in age and is dominated by non marine siliciclastics up to 7 km thick palaeocurrent indicators show dominant flow to the north northeast during the permian to jurassic fourteen lithofacies are grouped in three facies associations fluvial channel belt overbank and floodplain floodplain pond coal bearing permian siliciclastics are interpreted as meandering river deposits in a foreland basin with subsidence generated by thrust sheet loading from at least three basin margins these sediments pass abruptly but conformably upwards into coal barren sandstones and conglomerates and siltstones interpreted as braided river deposits two basalt flows occur within the coal barren succession a recently published precise ar ar age of 250 3 0 7 ma for the lower of these basalts

temporal variations in 87sr 86sr and ɛnd in sediments of the southeastern arabian sea impact of monsoon and surface water circulation sr and nd isotopic composition of silicate fractions of sediments have been measured in two well dated gravity cores from the eastern arabian sea archiving a depositional history of 29 and 40 ka the 87 sr 86 sr and e nd in the northern core ss 3104g 12 8 n 71 7 e ranges from 0 71416 to 0 71840 and 8 8 to 12 8 these variations are limited compared to those in the southeastern core ss 3101g 6 0 n 74 0 e in which they vary from 0 71412 to 0 72069 and 9 0 to 15 2 respectively this suggests that the variation in the relative proportions of sediments supplied from different sources to the core ss 3104g are limited compared to core ss 3101g the 87 sr 86 sr and e nd profiles of ss 3101g exhibit two major excursions ca 9 ka and 20 ka coinciding with periods of holocene intensified monsoon phase imp and the last glacial maximum lgm respectively with more radiogenic 87 sr 86 sr and lower e nd during these periods these excursions have been explained in terms of changes in the erosion patterns in the source regions and surface circulation of the northern indian ocean resulting from monsoon intensity variations the intensification of north east ne monsoon and associated strengthening of the east indian coastal current in southwest direction during lgm transported sediments with higher 87 sr 86 sr and lower e nd from the western bay of bengal to the arabian sea in contrast enhanced south west sw monsoon at 9 ka facilitated the transport of sediments from the northern arabian sea particularly indus derived to the southeastern arabian sea this study thus highlights the impact of monsoon variability on erosion patterns and ocean surface currents on the dispersal of sediments in determining the sr and nd isotopic composition of sediments deposited in the eastern arabian sea during the last 40 ka

the terminal paleozoic fungal event evidence of terrestrial ecosystem destabilization and collapse because of its prominent role in global biomass storage land vegetation is the most obvious biota to be investigated for records of dramatic ecologic crisis in earth history there is accumulating evidence that throughout the world sedimentary organic matter preserved in latest permian deposits is characterized by unparalleled abundances of fungal remains irrespective of depositional environment marine lacustrine fluviatile floral provinciality and climatic zonation this fungal event can be considered to reflect excessive dieback of arboreous vegetation effecting destabilization and subsequent collapse of terrestrial ecosystems with concomitant loss of standing biomass such a scenario is in harmony with predictions that the permian triassic ecologic crisis was triggered by the effects of severe changes in atmospheric chemistry arising from the rapid eruption of the siberian traps flood basalts

nd isotopes in indian ocean sediments used as a tracer of supply to the ocean and circulation paths abstract neodynium isotopic compositions of eighteen sediments from the indian ocean were measured these quaternary marine sediments were collected in different physiographic provinces with samples being taken from the abyssal plain ridge submarine fan fracture zone and aseismic ridge environments the main results is that there are large areas in the indian ocean which are isotopically homogeneous although the results also enforce the idea that in marine sediments the continent derived material exerts an important control on the nd budget the northeastern part of the indian ocean is influenced by erosion of the indonesian arc the values between e 0 7 and e 0 8 observed in samples from the central indian ocean are nearly constant both in the eastern and western parts of the indian ocean this was interpreted as mixing between two major inputs firstly material coming from the erosion of the indian shield e 0 14 to 17 and secondly from the indonesian arc e 0 0 subsequently all the material is then homogenized by the oceanic circulation the western indian ocean values are more variable perhaps because of the proximity of old continental terrains i e southern africa and the influence of atlantic waters the highest value e 0 2 93 observed in the southern part of the indian ocean may be explained by the influence of the erosion of the crozet basaltic plateau indeed the two samples which exhibit positive nd isotopic values correspond geographically to the area of erosion of the crozet and possibly the kerguelen basaltic plateaus the location of the sample with the lowest isotopic value e 0 18 88 close to antarctica implies that this sediment might have included an old continental component of precambrian or even archaen age this result traces in the case of particle transport the circulation of water masses from antarctica to northern parts of the indian ocean which are known for their deep waters with the exception of the samples located near the crozet plateau where probable destruction of the plateau is occurring we do not observe any nd isotopic variations related to the specific physiographic location of any one sample consequently the nd isotopic variations are principally due to the pathways of water circulation and possibly winds over the indian ocean

implications of palaeohydrological proxies on the late holocene indian summer monsoon variability western india abstract in this paper we identify changes in the indian summer monsoon ism intensity during the late holocene as revealed by palaeohydrological proxies in the fluvial archives of western india proxy indices including the geomorphological sedimentological geochemical and biological evidence along with chronology have been employed to highlight the trend in ism intensity over the late holocene it is inferred that on a longer timescale the indian summer monsoon weakened during the late holocene however short pulses of ameliorated monsoon occurred around 3 1 6 and 0 3 cal ka bp clustering of flood events is seen to occur at 3 2 8 2 2 1 6 1 3 1 1 and 0 65 0 2 cal ka bp not necessarily coinciding with strengthening of the ism palaeoflood data with regard to the ism variability shows that the two most prevalent flood events at 0 5 and 1 7 cal ka bp coincide with the weak monsoon period climatic transition in this region the occurrence of high magnitude flood events during weak monsoon periods is also reflected in the modern flood and rainfall data it is surmised that high magnitude flood events may represent peak monsoon periods however cannot be singularly considered as indicators for enhanced monsoon conditions in a region only a more robust database of palaeohydrological proxies can further validate their implications on the monsoonal changes over western india

erosion of deccan traps determined by river geochemistry impact on the global climate and the 87sr 86sr ratio of seawater abstract the impact of the deccan traps on chemical weathering and atmospheric co2 consumption on earth is evaluated based on the study of major elements strontium and 87sr 86sr isotopic ratios of the main rivers flowing through the traps using a numerical model which describes the coupled evolution of the chemical cycles of carbon alkalinity and strontium and allows one to compute the variations in atmospheric pco2 mean global temperature and the 87sr 86sr isotopic ratio of seawater in response to deccan trap emplacement the results suggest that the rate of chemical weathering of deccan traps 21 63 t km2 yr and associated atmospheric co2 consumption 0 58 2 54 106 mol c km2 yr are relatively high compared to those linked to other basaltic regions our results on the deccan and available data from other basaltic regions show that runoff and temperature are the two main parameters which control the rate of co2 consumption during weathering of basalts according to the relationship f r f c 0 exp ea r 1 t 1 298 where f is the specific co2 consumption rate mol km2 yr rf is runoff mm yr c0 is a constant 1764 mol l ea represents an apparent activation energy for basalt weathering with a value of 42 3 kj mol determined in the present study r is the gas constant and t is the absolute temperature k modelling results show that emplacement and weathering of deccan traps basalts played an important role in the geochemical cycles of carbon and strontium in particular the traps led to a change in weathering rate of both carbonates and silicates in carbonate deposition on seafloor in sr isotopic composition of the riverine flux and hence a change in marine sr isotopic composition as a result deccan traps emplacement was responsible for a strong increase of atmospheric pco2 by 1050 ppmv followed by a new steady state pco2 lower than that in pre deccan times by 57 ppmv implying that pre industrial atmospheric pco2 would have been 20 higher in the absence of deccan basalts pco2 evolution was accompanied by a rapid warming of 4 c followed after 1 myr by a global cooling of 0 55 c during the warming phase continental silicate weathering is increased globally since weathering of continental silicate rocks provides radiogenic sr to the ocean the model predicts a peak in the 87sr 86sr ratio of seawater following the deccan traps emplacement the amplitude and duration of this spike in the sr isotopic signal are comparable to those observed at the cretaceous tertiary boundary the results of this study demonstrate the important control exerted by the emplacement and weathering of large basaltic provinces on the geochemical and climatic changes on earth

palaeosols in westphalian coal bearing and red bed sequences central and northern england westphalian a c coal bearing strata and red beds in the pennine basin of central and northern england contain a wide variety of palaeosols in coal bearing facies associations alluvial gley semi gley organic and rare well drained palaeosols reflect the predominance of poor drainage conditions during deposition in red beds more evolved ferruginous and ferallitic palaeosols testify to free drainage conditions during deposition catenary relationships can be inferred between most of the palaeosols in both facies associations providing further information on the palaeogeomorphology of the depositional systems and assisting in the understanding of the environments and conditions of coal seam formation

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

3d mapping hydrodynamics and modelling of the freshwater brine mixing zone in salt flats similar to the salar de atacama chile abstract salt flat brines are a major source of minerals and especially lithium moreover valuable wetlands with delicate ecologies are also commonly present at the margins of salt flats therefore the efficient and sustainable exploitation of the brines they contain requires detailed knowledge about the hydrogeology of the system a critical issue is the freshwater brine mixing zone which develops as a result of the mass balance between the recharged freshwater and the evaporating brine the complex processes occurring in salt flats require a three dimensional 3d approach to assess the mixing zone geometry in this study a 3d map of the mixing zone in a salt flat is presented using the salar de atacama as an example this mapping procedure is proposed as the basis of computationally efficient three dimensional numerical models provided that the hydraulic heads of freshwater and mixed waters are corrected based on their density variations to convert them into brine heads after this correction the locations of lagoons and wetlands that are characteristic of the marginal zones of the salt flats coincide with the regional minimum water brine heads the different morphologies of the mixing zone resulting from this 3d mapping have been interpreted using a two dimensional 2d flow and transport numerical model of an idealized cross section of the mixing zone the result of the model shows a slope of the mixing zone that is similar to that obtained by 3d mapping and lower than in previous models to explain this geometry the 2d model was used to evaluate the effects of heterogeneity in the mixing zone geometry the higher the permeability of the upper aquifer is the lower the slope and the shallower the mixing zone become this occurs because most of the freshwater lateral recharge flows through the upper aquifer due to its much higher transmissivity thus reducing the freshwater head the presence of a few meters of highly permeable materials in the upper part of these hydrogeological systems such as alluvial fans or karstified evaporites that are frequently associated with the salt flats is enough to greatly modify the geometry of the saline interface

geochemical and sr nd isotopic variations in palaeoflood deposits at mainstem tributary junction western india implications on late holocene flood events abstract element geochemistry and sr nd isotopes have been used to characterise the palaeoflood sediments at a tributary junction in lower narmada valley archiving the little ice age lia and to determine the present day sources for the mainstem and the tributary sediments the major and trace element concentrations show minor variations in values post 360 cal yr bp the 87sr 86sr and end values of palaeoflood sediments range from 0 7122 to 0 7191 and 2 89 to 6 28 respectively the bed sediments from the mainstem river narmada and its tributary karjan yield 87sr 86sr values of 0 72394 and 0 7113 and end values of 7 18 and 6 09 respectively potential sources of palaeoflood sediments have been investigated from sr and nd isotope compositions and mixing of the mainstem as well as the tributary sediments is suggested pronounced contribution from the deccan basalt during the early part of the little ice age is inferred the more radiogenic nd values indicate a contribution from the weathering of younger deccan basalts especially the poladpur formations the control of weathering intensity and mineral sorting is observed in higher than the source rock 87sr 86sr ratios of the sediments the major and trace element variations during the last 700 years are not conclusive although isotopic signatures of the flood sediments help in constraining the flux from the tributaries sr and nd isotopic composition of the palaeoflood sediments can be used to track the monsoon intensity and pattern but their concentrations in a fluvial system remain primarily controlled by mineral sorting processes and mixing of sources

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

trace element and nd isotopic evidence for sediment sources in the mid proterozoic vindhyan basin central india abstract ancient sediments reflect the compositions of old eroded continental crustal material and preserve geochemical signatures of paleo tectonic and volcanic events geochemical study of such sediments provides insight into tectonic events that shaped the face of the earth nd isotopes are best suited for such studies because rare earth elements ree specifically sm and nd are not fractionated during post depositional processes such as erosion transportation and diagenesis of organic poor sediments and hence reflect the source composition of these sediments sedimentation in the proterozoic vindhyan basin of central india with a 4 km thick succession of unmetamorphosed and mostly undeformed sediments lasted over 1000 ma from 1630 ma up to the precambrian cambrian boundary these sediments provide an ideal opportunity to study the evolution of ancient continental crust as well as the tectonic evolution of peninsular india the occurrence of porcellanites in the lower part of the basin indicates active volcanism during deposition of the vindhyan sediments these tuffs show large ion lithophile element lile enrichment as well as depletions in nb and ta in primitive mantle normalized plots characteristic of an arc volcanic source in combined trace element ratio plots these volcanic rocks indicate mixing between mantle derived melts and the continental crust and overlap with the composition of global arcs their initial nd at 1630 ma ranging from 5 7 to 0 9 is similar to those observed in andean type continental margin arcs trace element concentration patterns as well as nd isotopic compositions of the clastic and non clastic sediments of the vindhyan basin from one of the type localities of the vindhyan stratigraphy in the son valley are vastly different from those of the bundelkhand granite which is the basement for these sediments indicating that these granitic rocks were not a major source of sediments for the vindhyan basin our nd isotopic study clearly indicates that sedimentation in the vindhyan basin which lasted over 1 ga was not continuous the boundaries between the semri and kaimur groups as well as the rewa and bhander groups are characterized by abrupt changes in the nd isotopic compositions indicating changes in provenance with sediments in the kaimur and bhander groups being derived from more juvenile sources compared to the semri and rewa groups respectively this inference is also supported by changes in t dm and f sm nd for the sediments across these boundaries the strikingly different trace element patterns of the rewa group sediments compared to the underlying kaimur sediments indicates that sediment sources also changed across the kaimur rewa boundary multiple changes in provenance in the vindhyan sediments indicate that this basin was tectonically active during the entire span of sedimentation while there is some uncertainty in determining the exact sources of sediments for the vindhyan basin we argue on the basis of our geochemical in particular nd isotopic ratios data and available paleocurrent data that majority of the sediments were derived from a now extinct andean type arc source in the south that resulted from a southerly dipping subduction prior to the collision of the bhandara and bundelkhand cratons according to this reconstruction the vindhyan basin was initiated as a foreland basin after the collision of these two cratons

geochemistry of flood basalts of the toranmal section northern deccan traps india implications for regional deccan stratigraphy unpublished data 1998 andthe southeastern deccan particularly the poladpur andambenali formations mitchell widdowson 1991 bilgrami 1999 for as much as 350 km from their south western type sections in addition lavas isotopically andchemicallyequivalenttothoseoftheambenaliformation fm arepresentinthenortheastern sectoroftheprovinceas far as 900 km from their southwesternmost counter parts mahoney 1988 deshmukh

paleoflood hydrology and extraordinary flood events paleoflood hydrology is the study of past or ancient flood events the most accurate technique involves the analysis of slackwater deposits and paleostage indicators swd psi slackwater deposits are sand and silt emplaced from suspension in exceptionally deep high velocity floods that characterize narrow deep canyons in resistant geologic materials these and other paleostage indicators are used to establish hydraulic grade lines for the generating flow events favorable sites for slackwater deposition include channel margin areas where stresses and velocities are reduced below critical values necessary to maintain fine grained bedload material sand and silt in suspension computerized procedures for hydraulic flow modeling are used to tie the elevations of the highest slackwater deposits to surveyed river cross sections the flood discharges calculated by this method can be calibrated through the study of modern floods on gaged rivers correlation of multiple swd psi sites along a river reach is used to identify the maximum paleostage achieved by a given flood advances in the dating of flood deposits permit estimates of flood frequency to be made extending over a data base of thousands of years the major geochronologic tool is radiocarbon dating of various kinds of organic matter intercalated with the slackwater deposits an important development is the use of the tandem accelerator mass spectrometer for direct measurement of 14c tiny blebs of charcoal seeds and other organics can be analyzed in order to date ancient flood deposits of hydrologic significance since swd psi studies yield very accurate determinations of paleoflood ages and magnitudes there is a pressing need for new statistical procedures that make optimum use of the information content in paleoflood records for flood frequency analysis nevertheless swd psi paleoflood hydrology has moved beyond the research phase its use should be encouraged in evaluating past experience of extraordinary floods at appropriate hazardous sites

abrupt changes in the asian southwest monsoon during the holocene and their links to the north atlantic ocean during the last ice age the indian ocean southwest monsoon exhibited abrupt changes that were closely correlated with millennial scale climate events in the north atlantic region1 2 3 suggesting a mechanistic link in the holocene epoch which had a more stable climate the amplitude of abrupt changes in north atlantic climate was much smaller and it has been unclear whether these changes are related to monsoon variability here we present a continuous record of centennial scale monsoon variability throughout the holocene from rapidly accumulating and minimally bioturbated sediments in the anoxic arabian sea our monsoon proxy record reveals several intervals of weak summer monsoon that coincide with cold periods documented in the north atlantic region4 including the most recent climate changes from the medieval warm period to the little ice age and then to the present we therefore suggest that the link between north atlantic climate and the asian monsoon is a persistent aspect of global climate

mid late holocene monsoonal records from the partially active mudflat of diu island southern saurashtra gujarat western india abstract the mid late holocene period is seldom known for any drastic climatic perturbations but witnessed significant anthropogenic growth and thus has been a subject of scientific importance in this study sediment core raised from an active mudflat of diu island southern saurashtra coast gujarat with a climatic history for the last 4100 yr bp has been investigated based on geochemical proxies productivity weathering and detrital results indicate warm and humid conditions during holocene climate optimum hco between 4105 and 2640 cal yr bp as a result of monsoon intensification followed by an arid conditions between 2640 and 1930 cal yr bp later during 1930 355 cal yr bp the region regained warm and humid conditions the mudflat responded in accordance with the global climatic perturbations during last 2000 yr witnessing signatures of roman warm period and medieval warm period additionally cool and humid climatic conditions persisted during little ice age followed by modern warming period witnessed during last 300 yr

geochemical traces of flood layers in the fluvial sedimentary archive implications for contamination history analyses abstract we studied three cores from a well dated sediment archive from an oxbow lake of the river morava czech republic using a high resolution 1 cm multiproxy stratigraphic analysis and a concentration of selected heavy metals the objective was to investigate how the vertical distribution of pollutants could be affected by episodic flood sedimentation in archives with high sedimentation rates stratigraphic proxies magnetic susceptibility ms x ray densitometry and visible light diffuse reflectance spectrometry supported by grain size analyses enabled us to identify relatively coarse grained flood layers and correlate them in the proximal to distal direction in the oxbow lake delta a correlation of the flood layers with the time series of the river discharge was used to improve the age model based primarily on 137cs dating the refined age model is nonlinear and shows periods of lower and higher sediment accumulation rates which coincided with periods of lower and higher frequency of floods in the river respectively concentrations of most heavy metals normalized to lithogenic aluminium revealed vigorous short term variation related to floods whose magnitude exceeds that of long term trends there is a substantial risk that temporal contamination trends even if normalized to lithogenic elements can be strongly influenced by facies which may lead to potential misinterpretations element normalizing to ms which proved to be a good proxy of grain size provided smoother long term trends whose interpretation was less affected by short term variations the long term trends exhibit decreasing concentrations of most heavy metals for the last 25 years most notably between 1987 and 1992 these historical patterns correspond well to the significant improvement in environmental pollution reported elsewhere in central europe in contrast concentrations of na have systematically increased up until the present partly being driven by the widespread use of de icing salt for winter road treatment

terrestrial marine teleconnections in the collapse and rebuilding of early triassic marine ecosystems abstract the latest permian mass extinction lpe just prior to the permian triassic boundary at 252 ma resulted in the disappearance of 90 of skeletonized marine taxa and the replacement of the paleozoic fauna by the modern fauna in the immediate aftermath of the extinction shallow marine ecosystems were dominated by microbial communities and diminutive disaster taxa lilliput faunas and the post crisis period in general was characterized by high abundance low diversity marine communities occupying a reduced ecological space the recovery of marine ecosystems was a protracted process lasting throughout the 5 myr long early triassic some clades failed to recover and subsequently went extinct dead clades walking while others recovered only to suffer secondary crises during the early triassic profound environmental changes accompanied these biotic developments deep oceans experienced sustained hypoxia or anoxia for at least several million years following the boundary event anoxia was also widespread in shallow marine areas especially at the time of the lpe but it was more episodic and abated more rapidly than in the deep ocean making it an unlikely factor in the delayed recovery of early triassic marine ecosystems the development of anoxia was due at least in part to a sharp temperature rise following the lpe but may have been stimulated by changes in marine nutrient inventories and productivity rates as well these conditions may have been the result of a concurrent increase in subaerial weathering rates that was sustained into the early triassic in addition to increasing nutrient fluxes to marine areas rapid weathering caused a massive influx of sediment to shallow marine systems subjecting marine biotas to siltation stress this scenario implies close teleconnections between terrestrial and marine environments during the permian triassic boundary crisis with perturbations of the terrestrial realm contributing to the marine crisis

source and differentiation of deccan trap lavas implications of geochemical and mineral chemical variations the basalt stratigraphy of the deccan trap between mahabaleshwar ghat and belgaum over steps the basement from north to south sr isotope and zr nb ratios and sr rb and ba concentrations correlate portions of the post poladpur stratigraphy over 250 km along the western ghats thereby confirming a southerly component of dip of 0 06 at the southwestern margin the stratigraphy extends upwards from the compositionally uniform ambenali formation cox hawkesworth 1984 into a sequence of grossly heterogeneous flow units which have been allocated to the mahabaleshwar and panhala formations lightfoot hawkesworth 1988 the mahabaleshwar formation is represented only by a sequence of highly fractionated flows termed the kolhapur unit with similar 87sr 86sr0 to the mahabaleshwar 0 7045 but with sr 2 25 succeeding the kolhapur unit are a series of flows with high 87sr 86sr0 0 7045 0 705 zr nb 13 and low sr 230 but trace element concentrations similar to the mahabaleshwar formation these have been allocated to the desur unit of the panhala geochemical variations in flows overlying the ambenali define two distinct trends one is attributed to gabbro fractionation and the other to variations in the compositions of the parental magmas and arguably their source regions there is little evidence for significant crustal contamination in these flows and the degree of fractionation and the composition of the phase extract are shown to vary along strike within the mahabaleshwar formation the high tio2 content of kolhapur unit flows is shown to be the result of shallow level gabbro fractionation rather than the presence of a primitive high ti magma mahabaleshwar formation basalts exhibit a broad negative correlation between the degree of fractionation and sr isotopic composition the endmember with lower 87sr 86sr0 has different zr y from the ambenali basalts and would appear to have been generated by lower degrees of melting of a similar source the other endmember has more radiogenic sr lower zr nb similar zr y but higher mg number the simplest interpretation is that these magmas were more primitive and hence hotter and more able to interact with the lithosphere en route to the surface and that they then mixed to produce the mahabaleshwar array the panhala formation basalts plot on the sr nd array defined by the mahabaleshwar formation and the desur unit basalts plot on an extension of this array this suggests that the source characteristics are also lithospheric the absolute elemental abundances may then be a function of melting and fractionation we are impressed by the apparent switch from crustal lithospheric contributions to mantle lithospheric contributions through the stratigraphy and suggest that this together with the more protracted fractionation of the magma reflects a change in the availability of the lithospheric components accompanying the southerly migration of the volcanic edifice

reconstruction of the variability of the southwest monsoon during the past 3 ka from the continental margin of the southeastern arabian sea from temporal variation in 18o in globigerinoidesruber and g sacculifer and geochemical indices of weathering erosion chemical index of alteration al and ti we infer rapid southwest monsoon swm deterioration with dwindling fluvial and detrital fluxes at ca 450 650 1000 and 1800 2200 cal a bp during the late holocene we have evaluated the role of solar influx reconstructed and high latitude climate variability archived in grip and gisp 2 cores on swm precipitation broadly our 18o climate reconstruction is concordant with grip and gisp 2 and supports a teleconnection through atmospheric connection between the swm and the north atlantic climate albeit temporal extents of the little ice age and medieval warm period from high latitude are not entirely coeval moreover there is a humid climate and enhanced precipitation during the terminal stages of the little ice age the medieval warming ca ad 800 1300 is not synchronous either and is punctuated by an arid event centred at 1000 a bp although the delineation of the specific influence of solar influx on swm precipitation is elusive we surmise that swm precipitation is a complex phenomenon and local orography along southwestern india may have a role on the entrapment of moisture from the southwest trade winds when these hit land copyright 2009 john wiley sons ltd

the end permian regression in south china and its implication on mass extinction abstract records of more than 20 permian triassic boundary ptb sections from south china show that widespread end permian regression took place in whole south china timing of the low ebb of this regression was pinpointed to the clarkina meishanensis and hindeodus changxingensis zones biostratigraphic and paleogeographic studies at conodont zonation level reveal that the yangtze carbonate platform and isolated small carbonate platforms in the hunan guizhou guangxi hgg basin experienced sedimentary hiatus during these two zones which lasted about 50 100 kya meanwhile the basinal areas namely the northern marginal basin of yangtze platform and the hunan guizhou guangxi basin have continuous conodont zonation with silicious and ashbed deposits the basinal areas show two negative 13c shifts during the ptb interval from clarkina yini zone to isarcicella isarcica zone while on the platforms there is usually only one negative shift because the early shift at c meishanensis zone was lost during hiatus the end permian regression and successive rapid transgression taking place at the ptb casted important effects to the pattern and process of the ptb mass extinction the depositional hiatus hitherto underestimated will necessitate reassessment of some interpretations on the causes and results of that extinction

vegetation changeover across the permian triassic boundary in southwest china extinction survival recovery and palaeoclimate a critical review abstract this paper reviews critically the permian triassic p tr fossil plants and microflora recorded in three well studied terrestrial permian triassic boundary ptb sections namely chahe zhejue and jiucaichong and two marine terrestrial transitional ptb sections namely mide and tucheng in western guizhou province and eastern yunnan province wgey southwest china distinct floral composition abundance and diversity across the ptb allow the establishment of two terrestrial macrofloral assemblages the lobatannularia multifolia gigantoclea guiyangensis l g assemblage was recognized from the upper xuanwei formation while the annalepis peltaspermum a p assemblage from the lower kayitou formation the former flora comprises 105 species in 39 genera and is late changhsingian in age the latter assemblage includes 18 species in 14 genera and is induan in age the changhsingian assemblage is characterized by the loss of many wuchiapingian elements of the gigantopteris flora and an increase of the gymnosperms most of the permian type plant taxa were wiped out in the ptb crisis on land with only few relicts persisting into the early triassic which saw the flourishing of annalepis and common presence of peltaspermum and permian relicts of the gigantopterids during the permian triassic transition some rare gigantopterids elements as well as some peltaspermum representatives survived the biocrisis annalepis a pioneering lycopsid genus in the recovery of the triassic land plants and its proliferation marks the recovery of land plants after the ptb crisis on land in wgey accordingly vegetation changeover across the ptb is marked by a dramatic turnover of plants on land from the permian gigantopteris flora to the triassic annalepis dominated assemblage palynofloras are characterized by a dramatic drop of palynomorphs in both abundance and diversity and show a stepwise extinction pattern moreover macro and microfloras of the wgey region indicate that humid and warm climate regime prevailed through the p tr transition in southwest china the coal forming swamps gradually migrated westward due to marine transgressions throughout the late permian the gigantopteris flora also migrated from east to west and a few species can survive into the earliest triassic in the wgey region but disappeared soon after

sr nd and pb isotopic and chemical compositions of central deccan traps lavas and relation to southwestern deccan stratigraphy abstract sr nd and pb isotopic compositions and major and trace element abundances of lavas in five central deccan traps sections are generally very similar to those of lavas in the southwestern deccan western ghats escarpment the combination of strong isotopic and chemical similarities between lavas of the two regions indicates that they shared a closely similar petrogenesis our results indicate that unlike many lavas in the northeastern deccan most of the lavas studied in the central deccan sections can be grouped into different stratigraphic members and chemical types cts belonging to four formations thakurvadi bhimashankar khandala and poladpur present in the type sections of the western ghats bhimashankar and thakurvadi type lavas are found in a section near outram whereas only khandala type lavas make up the mhaishmal ellora and ajanta sections to the east and only poladpur type lavas are present in the easternmost section at lonar this west east sequence is the same as that seen going upward in the western ghats stratigraphy except that bushe type lavas which are located stratigraphically between the khandala and poladpur formations in the western ghats have not been found in this study overall our results indicate that the khandala and poladpur formations extend over west east distances of more than 300 km and some individual members e g the dhak dongar may extend over as much as 500 km the regional dip from igatpuri in the southwest to lonar in the east central deccan is less than 0 5 to the east which is similar to the southward regional dip in the southwestern deccan near horizontal flows in the central and southwestern deccan areas suggest that post deccan tectonic activity has had limited effects on the studied area large volumes of basaltic lavas derived from eruptive centers in the western deccan may have covered both the central and southwestern deccan areas

a 900 year 600 to 1500 a d record of the indian summer monsoon precipitation from the core monsoon zone of india 1 we present a near annually resolved record of the indian summer monsoon ism rainfall variations for the core monsoon region of india that spans from 600 to 1500 a d from a 230th dated stalagmite oxygen isotope record from dandak cave our rainfall reconstruction which spans the medieval warm period mwp and the earliest portion of the little ice age lia indicates that the short instrumental record of ism underestimates the magnitude of monsoon rainfall variability periods of severe drought lasting decades occurred during the 14th and mid 15th centuries and coincided with several of india s most devastating famines

lilliput effect in freshwater ostracods during the permian triassic extinction abstract the lilliput effect following the permian triassic mass extinction and its aftermath has been documented in a variety of marine animal groups but it is less known in terrestrial and freshwater invertebrates here we present new investigations of the size variations of terrestrial ostracods of the genus darwinula based on fossil records from a permian triassic section on the northern limb of the dalongkou anticline section in northwest china quantitative analyses reveal that ostracod test sizes decreased sharply through the terrestrial permian triassic mass extinction interval the lilliput effect in terrestrial ostracods is characterized by the extinction of large taxa and the rise of small sized and elongate new forms coupled with the dramatic loss of conchostracans charophytes and the blooming of lycopod spores the size decrease in terrestrial ostracods following the biotic crisis through the permian triassic interval was probably triggered by several interacting events including global warming anoxia and enhanced sediment input following acid rain and wildfire

evolution of weathering patterns in the indo burman ranges over the last 280 kyr effects of sediment provenance on 87sr 86sr ratios tracer a high resolution study of mineralogy and major element geochemistry combined with sr and nd isotopes has been conducted on high sedimentation rate cores collected off the irrawaddy river mouth in the andaman sea and the bay of bengal to reconstruct the erosional and weathering history of the irrawaddy river basin in both cores nd 0 values imply that both glacial and interglacial sediments share a common crustal source the irrawaddy river strong glacial interglacial cycles are recorded by 87sr 86sr interglacial periods yield values between 0 713 and 0 717 whereas glacial periods show higher values between 0 717 and 0 719 variations of the pedogenic clays smectite and kaolinite to primary mineral feldspar quartz illite and chlorite ratios show strong precessional cycles suggesting a control by past changes in the summer monsoon intensity each increase in pedogenic clays content is also associated with a net loss of labile elements na k and ca from the detrital minerals under chemical weathering wet periods of summer monsoon reinforcement correspond to an increase in weathering of the irrawaddy plain soils and a decrease of 87sr 86sr ratio plotting 87sr 86sr versus 87rb 86sr gives a pseudo isochrons interpreted as a mixing line representing the strength of chemical weathering during glacial stages enhanced physical erosion induced by glacier scour and frost action in the highland of the irrawaddy river basins produced high volumes of unaltered rb rich minerals the low sea level of glacial times constricted the river to the main channel in the lower reaches and permitted an efficient transport of unaltered rb rich minerals with high radiogenic sr composition from the high relief of the indo burman ranges and the tibetan plateau to the indian ocean

chemical weathering in the krishna basin and western ghats of the deccan traps india rates of basalt weathering and their controls rates of chemical and silicate weathering of the deccan trap basalts india have been determined through major ion measurements in the headwaters of the krishna and the bhima rivers their tributaries and the west flowing streams of the western ghats all of which flow almost entirely through the deccan basalts samples n 63 for this study were collected from 23 rivers during two consecutive monsoon seasons of 2001 and 2002 the total dissolved solid tds in the samples range from 27 to 640 mg l 1 the rivers draining the western ghats that flow through patches of cation deficient lateritic soils have lower tds average 74 mg l 1 whereas the bhima except at origin and its tributaries that seem to receive na cl and so4 from saline soils and anthropogenic inputs have values in excess of 170 mg l 1 many of the rivers sampled are supersaturated with respect to calcite the chemical weathering rates cwr of selected basins which exclude rivers supersaturated in calcite and which have high cl and so4 are in range of 3 to 60 t km 2 y 1 this yields an area weighted average cwr of 16 t km 2 y 1 for the deccan traps this is a factor of 2 lower than that reported for the narmada tapti wainganga ntw systems draining the more northern regions of the deccan the difference can be because of i natural variations in cwr among the different basins of the deccan ii selection of river basin for cwr calculation in this study and iii possible contribution of major ions from sources in addition to basalts to rivers of the northern deccan traps silicate weathering rates swr in the selected basins calculated using dissolved mg as an index varies between 3 to 60 t km 2 y 1 nearly identical to their cwr the ca mg and na mg in these rivers after correcting for rain input are quite similar to those in average basalts of the region suggesting near congruent release of ca mg and na from basalts to rivers comparison of calculated and measured silicate ca in these rivers indicates that at most 30 of ca can be of nonsilicate origin a likely source being carbonates in basalts and sediments the chemical and silicate weathering rates of the west flowing rivers of the deccan are 4 times higher than the east flowing rivers this difference is due to the correspondingly higher rainfall and runoff in the western region and thus reemphasises the dominant role of runoff in regulating weathering rates the silicon weathering rate swr in the krishna basin is 15 t km 2 y 1 within a factor of 2 to those in the yamuna bhagirathi and alaknanda basins of the himalaya suggesting that under favourable conditions intense physical weathering high runoff granites and the other silicates in the himalaya weather at rates similar to those of deccan basalts the co2 consumption rate for the deccan is deduced to be 3 6 105 moles km 2 y 1 based on the swr the rate though is two to three times lower than reported for the ntw rivers system it still reinforces the earlier findings that in general basalts weather more rapidly than other silicates and that they significantly influence the atmospheric co2 budget on long term scales

climate and hydrographic variability in the indo pacific warm pool during the last millennium planktonic foraminiferal mg ca and delta o 18 derived sea surface temperature and salinity records from the makassar strait indonesia show a long term cooling and freshening trend as well as considerable centennial scale variability during the last millennium the warmest temperatures and highest salinities occurred during the medieval warm period mwp while the coolest temperatures and lowest salinities occurred during the little ice age lia these changes in the western pacific along with observations from other high resolution records indicate a regionally coherent southern displacement of the inter tropical convergence zone during the lia with more arid conditions in the northern tropics and wetter conditions in the southern tropics

holocene forcing of the indian monsoon recorded in a stalagmite from southern oman a high resolution oxygen isotope record from a thorium uranium dated stalagmite from southern oman reflects variations in the amount of monsoon precipitation for the periods from 10 3 to 2 7 and 1 4 to 0 4 thousand years before the present ky b p between 10 3 and 8 ky b p decadal to centennial variations in monsoon precipitation are in phase with temperature fluctuations recorded in greenland ice cores indicating that early holocene monsoon intensity is largely controlled by glacial boundary conditions after approximately 8 ky b p monsoon precipitation decreases gradually in response to changing northern hemisphere summer solar insolation with decadal to multidecadal variations in monsoon precipitation being linked to solar activity

vertebrate extinction across permian triassic boundary in karoo basin south africa distinct assemblages of paleosols above and below the permian triassic boundary in the karoo basin of south africa are evidence for reorganization of ecosystems following this greatest of all mass extinctions the permian triassic boundary is recognized from the last appearance of dicynodon and from a series of negative excursions in the isotopic composition of carbon within therapsid tusks pedogenic carbonate nodules and organic matter the boundary is also marked by laminated beds with very weakly developed paleosols a change from purple 10r to brownish red 2 5yr paleosols and a thin 10 cm claystone breccia of reworked soil clasts paleoclimatic changes include a shift from arid and highly seasonal paleoclimate inferred from diffuse and shallow calcareous nodules in permian paleosols to semiarid and less seasonal paleoclimate inferred from deep and well focused calcic horizons in triassic paleosols an earliest triassic shift to warmer and wetter paleoclimate is also indicated by increased chemical weathering abundance of lycopsids and diversity of labyrinthodonts permian paleosols have root traces comparable to those of open shrubland and riparian woodland whereas triassic paleosols have root traces and profile forms like soils of open woodland this is a significant paleoenvironmental change but not as dramatic a change as would be expected from the devastating extinctions of 88 of fossil vertebrate genera latest permian therapsid reptiles were diverse and ecologically specialized in contrast the principal earliest triassic therapsid lystrosaurus was a burrower with no specific habitat preference its short internal nares barrel chest and high neural spines would have given it greater aerobic scope than preexisting therapsids and may have been an advantage under conditions of hypercapnia and hypoxia these adaptations and associated ecosystem changes are compatible with widespread vertebrate mortality by acidosis and pulmonary edema in a post apocalyptic greenhouse created by the voluminous release of methane from shallow marine and permafrost clathrates

late pennsylvanian to wuchiapingian palynostratigraphy of the baode section in the ordos basin north china abstract well preserved miospores are recorded and illustrated from the penchi to the lower part of the sunjiagou formations in the baode section of the ordos basin north china eight palynological biozones are proposed for the late pennsylvanian to wuchiapingian interval among them five biozones are refined from pre existing biozones the biozones are comparable throughout the north china craton in contrast long distance palynological correlation between north china and euramerica only extends to the end of the bolsovian early moscovian by reference of associated marine fossils and magnetostratigraphic data approximate stratigraphic correlation with the international stages is possible in ordos basin quantitative abundances of spores and pollen from the late pennsylvanian to wuchiapingian reflect a wet hot palaeoclimate in the ordos basin but with an increasing tendency of palaeoclimatic drying from the early kungurian this drying tendency can be recognized throughout the north china craton and seems to be related to the suturing process between north china craton with the combined northeastern china blocks reduviasporonites which occurs often in relatively high frequencies in many permian triassic boundary sections was recorded for the first time from the early kungurian shansiensis biozone

provenance of proterozoic basal aravalli mafic volcanic rocks from rajasthan northwestern india nd isotopes evidence for enriched mantle reservoirs abstract komatiites komatiitic basalts and tholeiites from nathdwara rajasthan have been investigated for their nd isotopic characteristics 143nd 144nd vary broadly in the komatiites 0 51131 0 51252 and show a restricted range in komatiitic basalts and tholeiites 0 51120 0 51179 and 0 51141 0 51202 respectively the corresponding epsilon nd nd values indicate an enriched source for these rocks the model ages of komatiitic basalts and tholeiites cluster between 2 2 and 3 0 ga the komatiites show older model ages between 3 5 and 3 8 ga if the correlations found between nd and sm isotopic ratios can be interpreted as isochrones then the komatiites point to the age of 2300 ma and the komatiitic basalts and tholeiites constrain the age of 1800 2000 ma the age of 2300 ma for the komatiite samples is similar to the range estimated for the komatiitic basalt and tholeiite samples 1800 2000 ma considering the errors involved collectively the data suggest an age of 2300 1800 ma for the basal aravalli volcanism the variation of nd isotopic ratios between the komatiites and the associated basalts is too large to reflect analytical bias or open system behavior for sm and nd it may be due to significant mantle heterogeneity in the source region isotopically distinct sources for the komatiites and komatiitic basalts are possible but simple mixing between a depleted mantle component and a crustal component in the manner of magmatic assimilation of wall rock material is inconsistent with the observed isotopic ratios the inference of an enriched mantle component appears inevitable as the alternative model of mixing would have generated more siliceous high magnesian boninitic rocks with much lower fe and ti than are observed this enriched material may have been part of the sub continental lithospheric mantle sclm under the aravalli craton which could have generated the basal aravalli magmatic rocks we suggest that during early middle proterozoic the sclm under cratonic regions consisted of relatively fertile mantle capable of generating komatiites tholeiites and alkalic magmas

basalts of the northeastern deccan traps india isotopic and elemental geochemistry and relation to southwestern deccan stratigraphy the northeastern deccan traps include flows with strong isotopic and elemental affinities to lavas in the southwest as far as 900 km away however many of the northeastern flows show a negative correlation of 206pb 204pb with end t and positive correlation of 206pb 204pb with 87sr 86sr t distinct from any of the isotopic fields for the southwestern formations this array from end t 5 87sr 86sr t 0 7041 206pb 204pb 17 9 to end t 0 87sr 86sr 0 7068 206pb 204pb 20 5 overlaps the ambenali formation fm field and runs toward that of the common signature peng et al 1994 that appears to have been an important magma type in several of the lower formations of the southwest this array appears to represent mixing between an ambenali type and 1 a common signature end member or 2 an end member with even higher 206pb 204pb and 87sr 86sr and lower end than the common signature such mixing has been postulated but not documented previously for the deccan lavas isotopically and chemically indistinguishable from the ambenali fm form the tops of sections near jabalpur and chikaldara beneath them are flows that chemically resemble the poladpur fm which sits immediately below the ambenali in the southwest and several lavas similar to the khandala fm beneath the poladpur and intervening bushe fm in the southwest given the general stratigraphic correspondence with the southwestern sequence many of these northeastern flows may be petrogenetically related to the respective southwestern formations lavas with broadly poladpurand khandala like elemental compositions are also abundant in a thick section south of mhow several other mhow area flows resemble the distinctive bushe fm however nearly all of the poladpur and khandala like northeastern deccan lavas analyzed have higher 206pb 204pb man any southwestern poladpur or khandala fm basalts if they indeed are related petrogenetically to these formations many of the northeastern magmas interacted less with low 206pb 204pb continental material and thus must have erupted from different feeder systems

the elemental chemistry of sediments in the krishna river basin india abstract composition of bed core and suspended sediments collected from krishna river sediments were studied and the observations are discussed in the light of other indian rivers world s average river suspended particles surficial rock and soils the contents of v cr co ni cu and zn in the suspended particles are higher in the krishna river than in the world s average indicating pollution inputs suspended sediments are enriched 5 to 10 times in all the elements considered relative to bed sediments downstream profile and metal al ratios of the elements indicate that the mobility of elements within the basin is controlled by basin geology size and mineralogical characteristics good correlations observed for a number of elements point out to their common sink in the clay fraction of the sediments there is no systematic variation with depth for the major elements and most of the elements are considerably higher compared to estuarine or bay of bengal sediments

palaeoproterozoic fluvio aeolian deposits from the lower gulcheru formation cuddapah basin india abstract an analysis of facies was done to understand the depositional environment and the palaeoclimate of the sedimentary succession from the lower part of the palaeoproterozoic 2 0 ga gulcheru formation exposed along the southwestern margin of the cuddapah basin twelve distinct sedimentary facies were identified and grouped into three main facies associations wadi fan ephemeral fluvial and aeolian identification of the fluvial and the aeolian facies allowed a more elaborate interpretation of the depositional environment and its palaeoclimate facies characteristics indicated that the sediments in the beginning were deposited in a dominantly aeolian realm under warm and semiarid climatic condition translatent strata pin stripe lamination zibars high index granule ripples sand sheet deposits grainflow cross strata and grainfall laminae asymptotically down lapping cross strata often with erosional lower bounding surface and massive sand bodies with bimodal fabric the unambiguous evidences of aeolian depositional regime led to this conclusion however the aeolian regime was often punctuated temporarily by fluvial input from ephemeral streams during sudden rainstorm depending upon the size character and availability of sediments relief difference and the sediment water ratio cohesionless debris flow hyperconcentrated flood flow and sheetflood deposits were formed near the basin margin whereas coarse load braided channel deposits were laid further inside the basin ephemeral lakes ponds were formed due to stagnation of floodwater in normally dry interdune lows overbank interdune sediments were deposited in those ephemeral lakes ponds amongst the aeolian facies translatent strata and sand sheet dominate in the west whereas massive beds and dunes with well developed slipfaces dominate in the eastern part the spatial distribution of the aeolian bedforms suggests development of erg apron to the west and dune field erg to the east the aeolian sediments identified in the gulcheru formation may be considered to be amongst the oldest palaeoproterozoic aeolian sediments of the world