reconstructing the pre quaternary landscape in agnew lawlers area western australia with emphasis on the permo carboniferous glaciation and post glacial weathering the pre quaternary stratigraphic section in agnew lawlers area consists of permo carboniferous glacial sediments unconformably overlain by tertiary clastics of palaeochannel sequence and quaternary alluvial and colluvial sediments the unique permo carboniferous glacial sedimentary succession in the yilgarn craton has not been studied in detail in terms of vertical chemostratigraphic variations basin and landscape evolution diagenesis and post permian weathering overprints in agnew lawlers district continental facies of glacial diamictites glaciofluvial sandstones and glaciolacustrine rhythmites vary in thickness from 28 m to 181 m and is preserved beneath cenozoic sediments as relict landforms in highly irregular asymmetrical and poorly drained basins the permo carboniferous sediments were mechanically weathered and eroded by glaciers from the surrounding archaean basement palaeohighs under a cold arid climate textural relationships of diamictites indicate that they were derived from proximal and distal source rocks the denuded palaeotopography of the basement palaeohighs source rocks and permo carboniferous sediments were subjected simultaneously to an intensive post permian chemical weathering the exposed basement rocks were deeply weathered into residual saprolite whereas the permo carboniferous sediments were differentiated into three chemostratigraphic units the diamictite and rhythmite of the lower unit are unweathered and preserves the signature of the glacial interglacial weathering mineralogical and geochemical changes dominated in this unit are related mainly to diagenesis at shallow depth eogenesis with no significant compaction the formation of a paragenetic diagenetic sequence of chlorite ferroan dolomite and pyrite indicates diagenesis has occurred under reducing and alkaline conditions below the permafrost and modern water table mineralogical and geochemical changes dominated in the middle unit are linked mainly to eogenetic redox reactions the formation of smectite and ferruginous cements in this unit is attributed to weathering of ferromagnesian and opaque heavy minerals under oxic and slightly alkaline conditions mineralogical and geochemical changes dominated in the upper unit is related mainly to post permian chemical weathering where almost all rock forming minerals are altered to kaolinite and alkali and alkaline earth elements are leached forming bleached white saprolitic diamictites a change in clay minerals from kaolinite in the weathered permo carboniferous succession to smectite in the overlying cenozoic succession demarcates the unconformity and probably reflects a change to an arid climatic condition chemically the cenozoic succession shows a sharp increase in ti al and la ce ratios and a decrease in ce anomaly that remain constant in the permo carboniferous section these mineralogical and chemical variations through the phanerozoic stratigraphic section can be used to follow the landscape and climatic evolution since the late palaeozoic glaciation

late paleozoic glacial episodes in gondwanaland reflected in transgressive regressive depositional sequences in euramerica the late paleozoic glaciation of gondwanaland comprised two short episodes in the famennian i and visean ii confined to brazil and adjacent northwest africa and a long episode that started in the namurian iiia of eastern australia and bolivia argentina expanded to cover much of gondwanaland in the stephanian asselian iiib and collapsed in the early sakmarian iiic dropstones in eastern australia indicate that small ice centers lingered to the kazanian across the belt of low latitudes north of gondwanaland short ranging fossils in widespread shallow marine and paralic deposits indicate synchronous deposition of transgressive regressive sequences in different parts of euramerica these sequences correlate with glacial events in gondwanaland at three levels a four major regressions in euramerica in the famennian 1 visean 2 namurian 3 stephanian 4 and the tastubian transgression that preceded the sterlitamakian regression 5 also recorded in gondwanaland correlate with glacial episodes i ii and iiia iiib and iiic b the time interval of cyclothemic deposition in euramerica brigantian or latest visean to sterlitamakian correlates with that of glacial episode iii and c the dominant period of the euramerican cyclothems as estimated from the middle and late pennsylvanian deposits of the mid continent of north america and of the thickest known gondwanaland glacigenic sediment the earliest permian lyons group of western australia is 0 4 ma equivalent in turn to the long orbital eccentricity period of the quaternary ice age and the dominant period of fluctuation of the late miocene antarctic ice cap the three levels of correlations confirm wanless and shepard9s 1936 hypothesis that the late paleozoic cyclothems are controlled largely by sea level fluctuations related to the gondwanaland glaciation

an example of alternative correlation techniques in a low accommodation setting nonmarine hydrocarbon system the lower cretaceous mannville basal quartz succession of southern alberta chemostratigraphy and heavy mineral techniques have been applied to the lower cretaceous basal quartz in the western canada sedimentary basin the aim of the study is to demonstrate that these two techniques can be used to help understand the complex stratigraphy of reservoirs deposited in low accommodation fluvial settings the basal quartz is an ideal unit to demonstrate their applicability in stratigraphic studies of hydrocarbon reservoirs because extensive mapping and petrographic studies have enabled the establishment of a rigorous stratigraphic framework despite its complexity resulting from deposition in a low accommodation fluvial setting the three component units analyzed in the basal quartz horsefly unit bantry alderson taber bat unit and ellerslie unit each have unique geochemical and heavy mineral characteristics chemostratigraphic analysis shows that silty claystones from the horsefly bat and ellerslie units have distinctly different geochemistry from one another with the variations being caused by changes in clay mineralogy and other components such as feldspar apatite and zircon the geochemistry also suggests periodic volcanogenic input influenced the silty claystones of the basal quartz heavy mineral analysis shows that sandstones from the three units can be distinguished on the basis of ratio parameters such as apatite tourmaline rutile zircon and zircon tourmaline which are controlled by differences in provenance and intensity of weathering during transport

paleoenvironmental evolution of central paratethys sea and lake pannon during the cenozoic abstract deep wells penetrated cenozoic sedimentary record of two different basins 1 oligocene retro arc basin which is buried under the 2 miocene back arc danube basin this study is focused on biotic and abiotic proxies discussed in terms of existing biostratigraphical paleoenvironmental and sedimentological data biotic proxies are represented by palynofacies and biomarkers palynomorphs aom phytoclasts toc pr ph ratio steranes abiotic proxies are represented by inorganic geochemistry e g cia sr ba ga rb th u sio2 al2o3 corg p and enrichment factors the biotic and abiotic proxies helped to refine the knowledge about the changes in redox conditions salinity depositional system and paleoclimate in the study area five temporally different environments are observed 1 sedimentation in the oligocene fragment of the retro arc hungarian paleogene basin that took place on a highly proximal part of the shelf a major dysoxic event connected with humid marsh environment is documented within last rupelian transgression ru4 ch1 ch2 2 after a hiatus the danube basin initiated with early badenian langhian stable oxic to slightly dysoxic shelf with minor salinity changes lan2 ser1 ser2 transgression 3 late badenian early serravallian dysoxic deposition similar in all basins of the central paratethys was influenced by upwelling connected with the ser2 ser3 transgression 4 sarmatian late serravallian dysoxic event associated with subsequent flooding ser3 ser4 tor1 which created shallow marginal marine environment 5 pannonian tortonian messinian sedimentation took place on an oxic shelf of the lake pannon near a fluvio deltaic source most likely represented by the paleo danube delta system

the permian triassic transition in ocean island setting environmental disturbances and new high resolution carbon isotope record from the qiangtang basin nw china abstract the permian triassic boundary ptb events such as carbon isotope excursion volcanism and environmental disturbances are not well understood in an ocean island setting here we develop a new case study for the permian triassic transition in the qiangtang basin tibet by combining existing biostratigraphy new carbon isotope data sedimentological data u pb zircon age mineralogical and geochemical data these new data defined the permian triassic transition age as about 252 3 0 9 ma corresponding to the lowermost sea level a long term negative carbonate carbon isotope trend is present at the same stratigraphic level in different depositional environments strongly suggesting its global nature however our new ocean island setting is characterized by an abrupt shift in carbon isotope values across the level which is different from many chemostrtigraphic studies that show a gradual shift in carbon isotope values across the event horizon the most likely explanation for the abrupt shift in 13c values is a sedimentary hiatus at this level in the study section three stage climatic models through the ptb in the ocean island setting are identified stage 1 is characterized by a warm and humid climate with moderate chemical weathering while a hot and humid climate with intense chemical weathering dominates stage 2 the climate in stage 3 is a relatively hot and arid climatic condition with weak chemical weathering

carbon isotope chemostratigraphy and implications of palaeoclimatic changes during the cisuralian early permian in the southern urals russia abstract in order to meet the requirements for potential gssps in the cisuralian series early permian isotopic chemostratigraphy from the carboniferous permian boundary to middle artinskian using bulk carbonates was investigated under high resolution biostratigraphical and new geochronologic constrains from three gssp candidate sections at usolka kondurovsky and dal ny tulkas in the southern urals russia a gradually increasing trend in carbonate carbon isotope 13 c has been observed in the interval from the base of asselian to early sakmarian which is generally consistent in timing with the increasing development of glacial iii or p1 from the latest carboniferous to early sakmarian early permian which prevailed in southern gondwana an excursion with double negative shifts in 13 c value is present around the asselian sakmarian boundary in both the usolka and kondurovsky sections which may have great potential to serve as chemostratigraphical marks for intercontinental correlation the following highly positive excursion of 13 c in early sakmarian indicates the maximium expansion of glacial iii or p1 the negative 13 c shift in the middle sakmarian is possibly related to the quick collapse of glacial iii or p1 on the gondwanaland this negative shift is largely correlative with those documented in other areas of russia the north american craton and south china but further precise biostratigraphical and geochronologic constrains are neccessary to confirm this global signal the late sakmarian is characterized by a strong oscillation stage of 13 c which probably indicates a complex climate transition marked by smaller alternating glacial interglacial transitions during glacial p2 superimposed on an overall warming trend the sharp negative 13 c shift around the sakmarian artinskian boundary at the dal ny tulkus section is difficult to interpret this is followed by long term low values 13 c values in the artinskian at the dal ny tulkas section might result regionally from the enhanced input of organic carbon after the melt out of ice sheets and the subsequent degradation and isotopic refractionation of the microbial chemosynthetic processes on the buried organic matter

major element and ree compositions of pliocene sediments in southwest japan implications for paleoweathering and paleoclimate abstract the history of the east asian monsoon and the relationship between the development of the monsoon climate tectonics and global climate are complicated and controversial earlier studies have indicated that the east asian monsoon fluctuated in the asian interior during the pliocene thus the chemical weathering record in coastal regions of east asia can be the key to elucidating its evolution as well as the kuroshio current variability the present study clarifies the chemical weathering conditions in southwest japan based on the concentrations of major elements and rare earth elements rees in lacustrine muddy sediments the chemical weathering was moderate between 4 4 and 3 8 ma between 3 8 and 3 4 ma chemical weathering significantly intensified as indicated by the high values of the chemical index of alteration that reached a maximum of 98 as well as the high concentrations of rees and light rees against heavy rees and kaolinite rich clay mineral compositions despite the wide variation in source rock compositions and grain sizes the degree of chemical weathering remained moderate during the early pleistocene the intense chemical weathering on land in southwest japan from 3 8 to 3 4 ma may have been regulated by alternating periods of warm and humid climate brought by the invasion of the kuroshio current and the intensification of the east asian summer monsoon

maastrichtian oil shale deposition on the southern tethys margin egypt insights into greenhouse climate and paleoceanography abstract a comprehensive set of organic and inorganic geochemical proxies clay mineralogy and molecular fossils are presented from two biostratigraphically well dated oil shale horizons of egypt within the upper cretaceous duwi and dakhla formations the studied oil shales were deposited within intracratonic sedimentary basins in a broad northern african epeiric sea calcareous nannofossil biostratigraphy indicates that the oil shales range from early to late maastrichtian in age covering nannofossil zones uc18 uc19 and uc20 the oil shales contain smectite and kaolinite as the main clay minerals that formed by weathering of precursor basement rocks the relative abundances of clay minerals and several geochemical proxies e g c value cia ga rb rb sr and sr cu along with the occurrence of warm water nannofossil taxa demonstrate that the maastrichtian oil shales accumulated under a warm arid to humid greenhouse climate during a general maastrichtian cooling trend this episode of oil shale deposition in egypt coincided with the first potential imprint of the global warming that has been recorded during early to late maastrichtian times 70 6 67 7 ma elevated eolian terrigenous input was recorded within the duwi formation oil shales shown by high ti al si al zr al and low la lu ratios the duwi formation environment was characterized by enhanced salinity and a stratified water column compared to that of the dakhla formation shown by elevated values of the gammacerane index tetracyclic terpane carotene and sr ba ratio the caco3 content and carbonate siliciclastic ratio indicate that the dakhla formation oil shales were deposited during a relative sea level rise in a deeper marine setting than the duwi formation oil shales the data further imply a wind driven upwelling scenario of nutrient input s that simulated primary production and increased organic matter fluxes thus paleoclimate and paleoceanography had a considerable impact on organic matter enrichment

tectonic subsidence modelling and gondwana source rock hydrocarbon potential northwest bangladesh modelling of kuchma singra and hazipur wells abstract the northwestern part of bangladesh is in terms of hydrocarbon exploration still under explored this paper presents the basin development from a structural point of view and includes the results of thermal and maturity modelling using numerical tools of basin modelling one regional seismic section and three exploration wells have been investigated to unravel a conceptual model for the subsidence and thermal history of the region according to the findings it is very likely that up to 2900 m of triassic jurassic and partly permian sediments have been eroded prior to the break up of gondwana during continental break up a peak heat flow is considered this was necessary for calibrating maturity profiles using vitrinite reflectance vr derived from modelled wells a significant gas generation phase during lower jurassic is predicted at modelled well locations although renewed subsidence occurred during tertiary to present day a second phase of gas generation has not occurred as past maximum temperatures were not exceeded according to the interpreted regional seismic sections in the region the area southeast of the hinge zone can be regarded as the main kitchen area for gas generation from the gondwana source rock the petroleum system in the northwestern part of bangladesh remains high risk due to uncertainties in source rock distribution and generation

late paleozoic detrital history of eastern gondwanaland petrofacies and detrital geochronology of permo carboniferous intracratonic sequences of the northwest bengal basin

geochemical petrographic and grain size variations within single turbidite beds pronounced changes in chemical composition were detected upwards within single turbidite beds with sio2 contents deceasing by as much as 20 all other major elements and eighteen trace elements increase in abundance upwards enrichment factors from bed base to top range from 1 2 na2o to 5 7 cu these changes are related to textural and mineralogical grading that in turn were the result of turbidity current action before and during the deposition of the bed we found only slight changes in the modal petrographic composition of the sandstone fractions although this technique is operator dependent and only semi quantitative in nature chemical analysis appears to be a more sensitive more rapid and less subjective method of determining provenance and the compositional contrasts within beds chemical anomalies produced by dilution effects from quartz overgrowths and intrabasinal material however show the need for utilisation of a combination of techniques and for an appreciation of the interdependence of texture framework modes and bulk chemistry the chemical variations we detect in single beds also reflect the variation in a suite of representative samples collected from within a confined several km2 geographic area hence either sampling over a given area or specific sampling of individual beds provided that the bed is typical of the succession as a whole can be used to determine the compositional variations within a succession as a whole

trace and rare earth element ree characteristics of mudstones from eocene pinghu formation and oligocene huagang formation in xihu sag east china sea basin implications for provenance depositional conditions and paleoclimate abstract the interpretation of depositional conditions provenance and paleoclimate provide important information to understand hydrocarbon source rock formation and distribution the concentrations of trace elements and rare earth elements rees of fifty mudstone samples from eocene pinghu formation and oligocene huagang formation in xihu sag east china sea basin were determined by inductively coupled plasma mass spectrometry icp ms to test the depositional conditions provenance and paleoclimate evidences from the visual comparisons of the simple bivariate plots diagrams and statistical comparisons of the mann whitney rank sum test suggest that there may be a common source for the pinghu formation and huagang formation mudstones sedimentary provenance from bivariate plots diagrams of hf versus la th and la sc versus co th shows that pinghu formation mudstones are mainly composed of mixed felsic basic source and acidic source whereas huagang formation is mainly acidic source additionally the ree vs la yb discrimination diagram shows that the property of the provenance for the pinghu formation mudstones consists sedimentary rock alkaline basalt and a small amount of continent tholeiitic basalts whereas that of the huagang formation is mainly alkaline basalt and sedimentary rock discriminant diagrams consisting of la th sc and th co zr 10 suggest that the mudstones of two formations were deposited in continental island arc and active continental margin tectonic setting redox proxies v ni v v ni and ce indicate that most of the mudstones of two formations were deposited in a relatively dysoxic anoxic condition the cool and humid climate represented by sr cu and rb sr ratios were prevailing in xihu sag during the eocene and oligocene period and the oligocene was cooler than eocene moreover five long term base level cycles siii1 siii5 and four sequence boundaries sb2 sb5 were recognized in the pinghu formation and huagang formation based on the previous research we find that the abnormal surfaces of geochemical parameters such as v ni sr ba u ti v ti ti and ree to some extent agree with sequence boundaries sb2 sb3 sb4 and sb5 in mudstones additionally the increment of ti and ree concentrations and the decrease of sr ba v ni u ti and v ti ratios above the sb4 indicates that terrigenous clast grew significantly and the sea level dropped after late eocene which is related with the late eocene tectonic movement

effects of chemical weathering and sorting on the petrogenesis of siliciclastic sediments with implications for provenance studies the bulk chemical compositions mineralogy and mineral proportions of sands and muds of the mallacoota basin in southeastern australia reflect the composition of weathering profiles mantling source rocks rather than bedrock muds contain abundant clay minerals that are virtually absent from the source rocks but abundant in the weathering profiles sands are strongly enriched in quartz relative to source rocks even in the headwaters of the fluvial system demonstrating that feldspar destruction occurs by in situ chemical weathering within profiles and before detritus enters the fluvial system k feldspar is proportionally more abundant in fluvial sands than in source rocks because plagioclase is more rapidly destroyed than either quartz or k feldspar in weathering profiles subsequent erosion and sorting produce sands enriched in quartz with high k feldspar plagioclase ratios relative to source rocks the composition of plagioclase incorporated into the fluvial sands is also controlled by chemical weat

geochemical characterisation of early cretaceous lacustrine sediments of bima formation yola sub basin northern benue trough ne nigeria organic matter input preservation paleoenvironment and palaeoclimatic conditions the bima formation is the oldest lithogenetic unit occupying the base of the cretaceous successions in the yola sub basin of the northern benue trough it is differentiated into lower b1 middle b2 and upper b3 bima members integrated organic and inorganic geochemical studies were applied on the lacustrine sediments of the bima formation with the aim of reconstructing the palaeodepositional environment and organic matter input in response to climate and tectonism the analysed sediments were deposited in a freshwater lacustrine environment with a low salinity stratified water column and suboxic to relatively anoxic conditions as indicated by the bulk geochemical parameters the biomarkers provide evidence for a contribution of aquatic algae and microorganisms with a significant amount of terrigenous organic matter input the preservation of the organic matter is possibly attributed to the stratified water column with low salinity and suboxic to relatively anoxic conditions based on the geochemistry of major and trace elements the sediments were deposited during semi arid climatic conditions within passive continental margin setting this agrees with the tectonic events in the west and central african rift system wcars during the early cretaceous period

geochemical evolution of the tertiary succession of the nw shelf bengal basin bangladesh implications for provenance paleoweathering and himalayan erosion abstract whole rock major trace and rare earth element ree compositions of paleogene to neogene sedimentary rocks of the nw shelf succession province 1 of bangladesh contain a record of interaction of the india and asian plates himalayan tectonism and climatic development analyses of 66 sandstones and mudrocks from the tertiary succession of bangladesh were made to examine provenance source weathering and the influence of paleoclimate and tectonism the sediments display linear geochemical trends due to quartz dilution and varying quartz clay ratios produced by hydrodynamic sorting chondrite normalized ree patterns for both sandstones and mudrocks from different groups are similar to upper continental crust with moderate to high lree enrichment lithotypes within formations average lan ybn 5 31 11 41 and marked negative eu anomalies eu eu 0 51 0 69 based on geochemical criteria the succession can be divided into three parts jaintia barail surma and dupi tila very high silica contents in jaintia tura sandstones and high chemical index of alteration cia indices in kopili mudrocks fe shales suggest derivation from a deeply weathered and stable cratonic source india the tura sandstones are interpreted as first cycle quartz arenites produced while the indian plate drifted across equatorial regions during the paleocene eocene thermal maximum petm the barail surma and dupi tila sediments were derived from a felsic orogen the himalaya the barail surma sediments were mainly derived from the trans himalayan batholith and associated granitoids with significant contribution from the lesser himalaya mafic input is also evident probably from intraoceanic arc material within the himalaya barail mudrocks have uniformly high cia values 92 95 suggesting intense steady state weathering of their proto himalayan source and warm and humid climate in contrast cia values of surma mudrocks range from 66 to 93 average 84 suggesting non steady state weathering related to active uplift in the himalaya the dupi tila sediments were derived from a more felsic lesser himalaya source with significant contribution from the trans himalaya and very little or no ophiolitic or arc material dupi tila mudrocks have cia ratios of 62 99 average 72 also indicating non steady state weathering in the rising himalayan source geochemical compositions of the nw shelf sediments are comparable to coeval successions in the surma basin province 2 of bangladesh and the siwaliks india indicating similar source evolution of the indian monsoon and associated high precipitation caused intense chemical weathering of the surma and dupi tila source despite rapid uplift the surma group thus bears the signature of evolution of the asian monsoon in the bengal basin at 21 ma simultaneous with the development of the east asian monsoon this supports proposals that both monsoon systems developed at the same time

the relationship between major element concentration and grain size within sandstones from four turbidite sequences in japan abstract there are few systematic investigations of variation in major element concentration with varying grain size in sandstone in this study we examine the relationship between grain size and major element composition for four suites of sandstone each with different modal composition and sio2 content the sandstones are sampled from permian cretaceous and paleogene turbidite sequences in japan we found that the effect of grain size on sandstone chemistry is related to the mineral composition of the sandstone itself in commonly occurring sandstones that are composed mainly of quartz feldspar and felsic intermediate volcanic rock fragments a decrease in grain size is accompanied by a gradual decrease in sio2 content and increase in tio2 al2o3 fe2o3 mgo k2o and p2o5 the relationships can be largely explained by relative increases in the abundance of illite and chlorite in the fine grained sediments in contrast sandstones that are derived mainly from basic volcanic rocks and that contain a high proportion of mafic minerals show different major element trends in response to grain size variation in this group sio2 and k2o contents increase gradually with decreasing grain size whereas tio2 fe2o3 mgo cao and p2o5 decrease the major element trends observed in these sandstones are related to syn depositional hydraulic sorting of heavy mafic minerals from light felsic minerals such as quartz and feldspar

chemo sedimentary facies analysis of fine grained sediment formations an example from the lucaogou fm in the jimusaer sag junggar basin nw china abstract fine grained sedimentary formations occupy about two thirds of the entire sedimentary sequences in nature they have recently received great attention owing to the boom of shale oil and gas exploration unlike their coarse counterparts detailed depositional features of fine grained sedimentary rocks are quite difficult to recognize directly by visual inspection at core or hand specimen scales a chemo sedimentary facies analysis csfa procedure has been developed by incorporating high resolution down to 30 m 2d elemental maps of rock slabs obtained by in situ xrf scanning with high resolution optical images the method enables one to unambiguously differentiate rock compositions and fine sedimentary structures and to generate core scale chemo sedimentary facies images the 2d chemo sedimentary facies map contains major elements with atomic numbers greater than 12 and some trace elements including ba v cr ni cu zn rb sr y zr nb mo th and u at individual pixels the csfa procedure was applied to study the lucaogou formation a key shale oil producing interval in the jimusaer sag junggar basin nw china to illustrate three key advantages of csfa in studying fine grained sedimentary formations 1 recognizing invisible sedimentary structures 2 determining sediment provenances 3 identifying subtle paleo environmental changes the lucaogou formation has been characterized in unprecedented fine details with sedimentary heterogeneities at centimeter millimeter scales seven chemo sedimentary facies were delineated in the lucaogou formation among them facies cs 1 was deposited under a relatively deep fresh to brackish water with strong energy and moist climate facies cs 2 was deposited under relatively shallow brackish water with weak energy arid climate facies cs 6 was deposited under relatively shallow brackish water arid climate with intermittent hydrodynamic enhancement facies cs 7 was deposited in semi deep fresh water with strong energy and moist climate facies cs 1 and cs 7 have relatively high porosities the dolomitic fragments in facies cs 6 was originally deposited in facies sc 2 but has higher porosities than that of facies cs 2 facies cs 6 and facies cs 7 commonly occur together the interval with well developed facies cs 1 facies cs 6 and facies cs 7 are identified to be the most favorable exploration intervals in the lucaogou formation

organic geochemical characteristics and depositional setting of paleogene oil shale mudstone and sandstone from onshore penyu basin chenor pahang malaysia abstract the eastern chenor pahang area of the penyu basin contains an untapped potential in part due to poor knowledge of its organic facies characteristics the sedimentary succession of eastern chenor pahang area is dominated by fine to coarse grained sandstone occurring in association with oil shale and mudstone in a predominantly fining upward sequence detailed geochemical and petrographic characterization was carried out on oil shale and mudstone samples to evaluate the origin and type of organic matter om as well as the paleoenvironmental conditions and organic richness of the paleogene sedimentary succession the facies are only enriched in total organic carbon toc potential hydrocarbon yield s2 and extractible organic matter eom the types of organic matter are important index reflecting the potential of the source rock s based on elemental ratios the analyzed samples are shown to contain types i and ii kerogens this finding is supported by the high hydrogen index hi of 300 mg hc g toc and the presence of abundant liptinitic materials biomarker signatures n alkanes n c25 high c29 c30 17 h hopane ratios 0 8 3 3 and high c29 steranes 49 78 low total sulfur and v v ni ratio suggest a predominantly terrestrial source input with some contribution from aquatic microorganisms as indicated by the common occurrence of amorphous organic matter combining this results with n alkane patterns kerogen types and organic petrography predominance of c29 sterane probably indicates a contribution of aquatic organisms such as green and brown algae consistent with botrycoccus braunii race a and pediastrum contribution and some influence of higher plants om integration of biomarker studies with bulk geochemical and petrographic analysis suggests that the analyzed samples were deposited under suboxic conditions in a fresh water lacustrine environment this finding is corroborated by the ratios of pristane phytane v ni and sr br high bioproductivity and a stratified fresh water column with suboxic bottom water condition enhanced om preservation in the analyzed mudstone and shale facies the high om content in these samples maybe related to the fine grained matrix of the mud rocks and the paleoclimate in the area

prediction of some weathering trends of plutonic and volcanic rocks based on thermodynamic and kinetic considerations abstract the exposed crust consists mainly of plagioclase 35 quartz 20 k feldspar 11 volcanic glass 12 biotite 8 and muscovite 5 quartz is a resistate thus feldspars and glass represent approximately 75 percent of the labile minerals the weathering characteristics of these constituents are summarized in the context of thermodynamic mass balance and kinetic considerations experimentally determined release rate constants were used to predict the proportions of ca na and k released by feldspars of plutonic rocks granites to gabbros to weathering solutions the chemical weathering trends of the weathered residues calculated from the kinetic data conform closely to the initial trends observed in some recent weathering profiles demonstrating the accuracy of the predictions since the weathering of feldspars is controlled by processes that should not change through geological time the relative release rates of ca na and k from the feldspars of granitic rocks can be calculated for future and past episodes of continental weathering experimentally determined release rate constants are not available for a wide range of volcanic glass compositions but the limited data indicate that compositional trends are predictable in weathering profiles developed on volcanic rocks the kinetic data available for rhyolitic glasses accurately predict the initial weathering trends observed in a recent rhyolite weathering profile

provenance and depositional conditions of fluvial conglomerates and sandstones and their controlling processes in a rift setting mid permian lower and upper quanzijie low order cycles bogda mountains nw china abstract this study investigates how provenance lithology transport distance and depositional and paleoclimatic conditions had affected the composition and texture of fluvial conglomerates and sandstones in the middle permian lower and upper quanzijie low order cycles bogda mountains greater turpan junggar intracontinental rift basin nw china composition and texture of gravels in conglomerates and sandstones define two conglomerate and two sandstone petrofacies respectively in tarlong taodonggou area in southern bogda and dalongkou area 70 km to the north in northern bogda conglomerate petrofacies i occurs in tarlong taodonggou and is dominated by basaltic gravels whereas conglomerate petrofacies ii occurs mainly in dalongkou and is dominated by sedimentary gravels sandstone petrofacies i occurs in tarlong taodonggou and contains dominantly basaltic lithics few sedimentary lithics and minimal quartz it is compositionally immature and texturally immature to submature the compositional maturity increases upsection conglomerate petrofacies i and sandstone petrofacies i both indicate the young tian shan arc to the south as the main sediment source and rift shoulders as a local source sandstone petrofacies ii occurs in dalongkou and contains dominantly sedimentary lithics and abundant and well developed pedogenic clay coats the petrofacies in dalongkou indicate older rift sedimentary rocks exposed at rift shoulders as the main sediment source and distant suture zones as a minor source in summary the composition and texture of quanzijie conglomerates and sandstones are mainly controlled by provenance lithology and secondarily depositional and paleoclimatic conditions and transport distance the results substantiate the rift origin of the turpan junggar basin in middle permian which had many half grabens and grabens and was bordered by a volcanic arc at the southern basin margin

snowpack density retrieval using fully polarimetric terrasar x data in the himalayas this paper focuses on the development of a novel algorithm for deriving snowpack density over the snow covered region of the himalayas the analysis utilizes fully polarimetric terrasar x synthetic aperture radar data sets field observations and other ancillary information for the retrieval of snowpack density the algorithm involves the development of a new generalized hybrid decomposition model the generalized volume scattering parameter from the decomposition model is inverted for snow density estimation a few field data measurements campaigns were carried out within near real time of satellite passing over the area to collect various parameters such as temperature water content and the density of the snowpack at varying depths these field observations are further used for validation of the results obtained from the inversion algorithm it is also found that the model estimated snowpack density is highly congruent with the field measured snowpack density the mean absolute error of snowpack density root mean square error and index of agreement are found to be 9 9 kg text m 3 10 kg text m 3 and 0 96 respectively which are well within the acceptable range

continental records of organic carbon isotopic composition δ13corg weathering paleoclimate and wildfire linked to the end permian mass extinction abstract the late permian was the acme of pangea assembly with collision and subduction of global plates accompanied by major changes in atmospheric composition paleoclimates and paleoenvironments of the earth s surface system these events are extensively recorded in marine successions from the tethys but much less are known from continental successions that typically lack high resolution stratigraphic control in order to reveal these fluctuations in terrestrial strata and their relationship with the end permian mass extinction epme we investigate continental 13corg mercury and nickel concentrations wildfire and climate change proxies from the late permian changhsingian stage to early triassic induan stage in the yuzhou coalfield in the north china plate ncp results show two negative organic carbon isotope excursions cie within the changhsingian aged sunjiagou formation the first cie i 2 2 during mid changhsingian and a second larger excursion cie ii 2 7 near the end of the changhsingian that coincides with the peaks in the chemical index of alteration cia value and extinction of plant species we infer cie ii to be the global negative excursion of 13corg associated with the epme arid climates prevailed in the study area from the changhsingian to the early induan inferred from the low kaolinite contents and weak continental weathering except for two short duration episodes with higher humidity that correspond with cie i and cie ii extremely high fusinite content x 63 1 and its increasing abundance through the changhsingian indicates that frequent wildfires may have been a direct cause for both the destruction of terrestrial vegetation ecosystems and the rapid decline of terrestrial biodiversity at the epme we consider that terrestrial ecosystems may have played an important role in the extinction of marine communities at the epme this represents the first time the empe has been demonstrated in the ncp based on combined evidence from negative carbon isotope excursion concurrent weathering trends ni al ratio and biotic extinctions representing an important step in accurately identifying and correlating the epme in continental settings from the ncp

geochemistry of permo triassic mudstone of the satpura gondwana basin central india clues for provenance abstract major and trace element data of the permo triassic mudstones from the intracratonic satpura gondwana basin central india have been used to investigate provenance the satpura succession 5 km thick unconformably overlies the precambrian basement sediment dispersal pattern suggests that the precambrian rocks straddling the southern margin of the satpura basin were the most probable source for the sediments the lowermost unit of the satpura succession comprises glacio marine and glacio fluvial deposits the rest of the succession largely represents a variety of fluvial depositional systems with some records of fluvio deltaic and fluvio lacustrine sedimentation under a climatic spectrum of temperate humid to warm semi arid the present study is confined to the lower six formations namely talchir barakar motur bijori pachmarhi and denwa arranged in that order from bottom to top the oldest rocks of this sequence the talchir formation are enriched in mobile elements such as na ca and mg depleted in alumina and have high icv 0 93 1 29 and lower cia values 61 82 74 89 compared to those of the younger mudstones k 2 o al 2 o 3 ratios of the talchir mudstones 0 24 0 28 are higher than the younger mudstones in this sequence these results suggest that the talchir mudstones were weathered less intensely and are thus more immature than the younger mudstones this is consistent with the prevailing cold climate and relatively higher rate of basin subsidence in contrast the majority of the mudstones from the younger formations are depleted in mobile elements have relatively low icv 0 18 0 87 and k 2 o al 2 o 3 values 0 07 0 26 higher cia values 76 99 92 86 and appear compositionally more mature reflecting moderate to high intensity source rock weathering among them the barakar mudstones likely have been more intensely weathered than mudstones from any of the other formations the trace element compositions and ratios are consistent with most mudstones being derived from a felsic source with some mudstones being derived from a more mafic source for example la sc 0 805 and 0 114 la th 6 245 5 072 7 418 6 245 and 5 072 and eu eu 1 431 0 868 and 0 805 of some mudstones indicate mafic source bivariate plot of th sc and zr sc indicates considerable enrichment of zircon that suggests recycling from meta sedimentary rocks prominent negative eu anomaly high lree hree and flat hree pattern reflect sediment derivation from predominantly felsic rocks of the old upper continental crust sio 2 al 2 o 3 versus k 2 o na 2 o plot for the mudstones suggests that they formed in a passive margin also total ree content of most of the mudstones is conformable with passive margin tectonic setting and craton interior type of provenance plotting in la th sc th sc zr 10 and la sc versus ti zr diagrams largely indicates continental margin settings for majority of the mudstones but fails to differentiate between active and passive continental margins

characterization of depositional conditions for lacustrine oil shales in the eocene jijuntun formation fushun basin ne china abstract the strike slip fushun basin hosts a lacustrine oil shale interval of ca 50 300 m in the eocene lutetian jijuntun formation the oil shale deposits consist of the lower lean oil shale unit losu and the upper rich oil shale unit rosu in outcrop areas the identified depositional cycles of ca 8 10 m and 5 8 m in thickness record the stacking of massive and non laminated oil shales in the losu and fine and coarse laminated oil shales in the rosu respectively depositional conditions in the paleo jijuntun lakes were synoptically reconstructed based on sedimentary features trace element and organic geochemical proxies oxic to suboxic fresh water conditions were prevailing in the paleo jijuntun lakes during deposition of the losu and then evolved into oxygen deficient fresh to mildly brackish water conditions during deposition of the rosu as revealed by the concentrations of redox and salinity sensitive trace elements e g v ni v cr ni co and sr ba ratios and boron content in the oil shales warm to cool and humid to arid climate represented by e g sr cu and rb sr ratios could result in the deepening of water column from ca 20 30 m to ca 100 m and saline stratification superposed on pre existing thermal stratification in the paleo jijuntun lakes a systematical decrease approximately one order of magnitude in the concentrations of most trace elements except for boron and co in the coaly oil shale in the lowermost losu relative to those in the other oil shales in the jijuntun formation indicates the significant change of organic matter om input from higher plant especially coaly materials to aquatic plankton this is partly consistent with the variations of om input from terrestrial higher plant and aquatic organisms type ii kerogen in the losu to lacustrine algae type i kerogen in the rosu as revealed by biomarkers the slight to significant enrichment or depletion of few trace elements i e mn and mo in these immature to low mature oil shale deposits may be associated with low to moderate productivities of aquatic plankton and or incompletely oxygen free conditions in the paleo jijuntun lakes

global continental weathering trends across the early permian glacial to postglacial transition correlating high and low paleolatitude sedimentary records time equivalent early permian sedimentary successions from high latitude gondwana basins and from equatorial accumulations in north china covering the glacial to postglacial transition display correlatable trends in continental weathering intensity based on chemical index of alteration cia values the successions display a pattern of cia values that varies with latitude similar to modern estuarine suspended sediments based on the modern day cia temperature correlation the glacial early permian low to high latitude land surface temperature gradient is estimated as 20 c slightly higher than the calculated values for the contemporaneous sea surface temperature gradient

continental weathering and palaeoclimatic changes through the onset of the early toarcian oceanic anoxic event in the qiangtang basin eastern tethys abstract the bilong co north section located in the south qiangtang depression northern tibetan plateau provides key information on continental weathering and palaeoclimatic changes through the onset of the early toarcian oceanic anoxic event t oae in the eastern tethys new mineralogical and geochemical data from the bilong co north section suggest that the lower unit of the section corresponds to low chemical index of alteration cia 50 57 and ln al2o3 na2o 0 88 1 16 and high index of compositional variability icv 19 27 indicating a weak weathering and arid climate preceding the onset of the t oae a prominent increase in cia and ln al2o3 na2o values is clearly recorded through the onset of the t oae coinciding with a prominent change in srxs ba and clay fractions suggesting a sharp increase in humidity at the onset of the t oae the palaeoclimatic index of low srxs ba 0 48 4 98 ratios indicates that the climate during the t oae interval was most likely semiarid to semimoist some redox proxies including mo and toc relationships mo u enrichment factors and corg ptotal ratios suggest euxinic conditions during the t oae interval the primary productivity parameters show two main fluctuations within the bilong co north section and their patterns are in good agreement with the observation of palaeoclimatic variation patterns suggesting an influence of palaeoclimate on primary productivity however the palaeoproductivity increase during the t oae in the bilong co north section should mainly be attributed to freshwater inputs rather than solely the result of paleoclimatic change

alluvial sandstone composition and paleoclimate i framework mineralogy abstract systematic variations in compositional maturity of first cycle fluvial sandstones are found in the cutler formation permian and fountain formation permian pennsylvanian in colorado and in the gondwana supergroup permian triassic of peninsular india these variations reflect changing climate during deposition climate is considered to be the critical factor affecting maturity because source rocks granite granite gneiss and tectono environmental setting alluvial systems associated with basement cored block uplifts were similar and remained relatively unchanged throughout deposition of all three of the units the roughly 3 200 m thick gondwana succession consisting of five sandstone petrofacies is characterized by the following sequence of change oldest to youngest in compositional maturity expressed in q f r percentages 54 42 4 88 10 2 62 34 4 82 16 2 99 1 0 this sequence is a function of the changing paleoclimate glacial arid temperate humid warm semiarid warm semihumid warm humid associated with the overall global limatic change and the changing latitudinal location of india as it moved from a location close to the south pole northward during the interval of time represented by gondwana deposition lithologic and fossil evidence indicates that during deposition of the fountain formation climate gradually changed from relatively wet and warm to at least semiarid and warm this climatic change is the main factor responsible for the difference in compositional maturity of the older fountain sandstone q f r 65 26 9 relative to the younger q f r 54 36 10 cutler sandstone was deposited in an arid climate and has maximum compositional immaturity q f r 49 44 7 a log log plot of the ratio of total quartz to total feldspar plus rock fragments against the ratio of total polycrystalline quartz to to al feldspar plus rock fragments is a sensitive discriminator of first cycle sandstones with differing climatic heritage bulk chemical composition data support interpretation of climate from framework mineralogy but by themselves are not sensitive enough to be unequivocal indicators the same is true for the ztr index and observations of degree and abundance of solution pits embayments on detrital quartz results of this study support the conclusion of earlier empirical and theoretical analyses which suggest that the optimum conditions for the production and preservation of a distinctive climatic signature on sand composition are met in extensional plate tectonic settings such settings are characterized by coarse grained crystalline parent rocks short transport distances in low order streams deposition in nonroutine environments and shallow burial diagenesis however even in such optimum settings only rarely will climate be a more important determinant of sandstone composition than the tectonic setting itself

a sar image study of a snow covered area in the french alps abstract two radar experiments were performed in the french alps in december 1989 and april 1990 the main objective was to study the signature of snow covered terrain for different snow conditions the e sar band x from dlr was used and the data were processed by cnes the study area was situated at les arcs a ski resort with elevations ranging from 1600 m to 2600 m ground data included snow depth liquid water content and snow and air temperature a spot image was available for december and aerial photographs for the following july in december there was almost no snow while in april the area was completely snow covered because of the highly varying topography a dem digital elevation model was used to correct the image geometrically and radiometrically a simple scheme was developed for these corrections the snow was slightly wet in april and many features appearing on the image are due to the snow itself or to the snow ground interface in particular the ski runs are clearly visible due to the different structure of the packed snow only a small area could be compared between december and april due to technical problems in december it appears that the snow free and snow covered signatures are very similar for this particular terrain which is a golf course in summer that is smooth wet soil with short grass these experiments show that geometrical corrections are necessary when studying mountainous area furthermore calibrated data are required to compare snow free and snow covered terrain when the snow is slightly wet and therefore slightly absorbant with respect to the electromagnetic waves

co2 forced climate and vegetation instability during late paleozoic deglaciation the late paleozoic deglaciation is the vegetated earth9s only recorded icehouse to greenhouse transition yet the climate dynamics remain enigmatic by using the stable isotopic compositions of soil formed minerals fossil plant matter and shallow water brachiopods we estimated atmospheric partial pressure of carbon dioxide pco2 and tropical marine surface temperatures during this climate transition comparison to southern gondwanan glacial records documents covariance between inferred shifts in pco2 temperature and ice volume consistent with greenhouse gas forcing of climate major restructuring of paleotropical flora in western euramerica occurred in step with climate and pco2 shifts illustrating the biotic impact associated with past co2 forced turnover to a permanent ice free world

petrographic and diagenetic signatures of climatic change in peri and postglacial karoo sediments of sw tanzania abstract the basal idusi formation of the karoo succession in sw tanzania represents deposits of the final late palaeozoic deglaciation event it reflects the change from a cold to a temperate more humid climate the lower unit of the idusi formation lisimba member consists of periglacial deposits with glaciolacustrine diamictites sandstones dropstone bearing mudstones and varvites as well as fluvial and deltaic conglomerates and sandstones the upper unit lilangu member is dominated by organic rich siltstones and sandstones which were accumulated in an eutrophic postglacial lake the petrography of the idusi formation reveals an arkosic composition indicating provenance from cratonic basement rocks the lisimba member is characterized by low mineralogical maturity with a high proportion of garnet fine grained matrix particles in the lisimba member authigenic formation of chlorite corrensite and laumontite at a moderate stage of burial was due to alkaline pore fluid conditions with high ionic strength caused by restricted percolation in the matrix rich sediments and their low mineralogical maturity the postglacial sedimentary rocks are characterized by early diagenetic kaolinite siderite pyrite and barite this paragenesis formed under the influence of acidic meteoric derived pore water and the decay of organic matter such early diagenetic conditions are frequently met in humid continental environments

the chemical index of alteration cia as a proxy for climate change during glacial interglacial transitions in earth history abstract the glacial interglacial transitions of ice ages are associated with large rapid changes in climate which potentially can be reconstructed from stratigraphic profiles of the chemical index of alteration cia here we present a case study based on high resolution cia profiles of neoproterozoic glacial deposits from south china paleolatitude 30 n as a record of the climate transition at the termination of the sturtian glaciation 663 ma drillcore zk2115 gaodi deposit exhibits a progressive upsection increase in mean cia over a 50 m interval from 58 range 52 65 note all ranges are given as 16th 84th percentiles in the synglacial upper tiesi ao formation to 67 range 64 69 in the deglacial basal datangpo formation cap carbonates and to 68 range 66 70 in the postglacial datangpo formation black shales a coeval section from the lijiawan deposit also exhibits an increasing cia trend upsection within shallow water mn carbonate facies these cia patterns show no relationship to lithology and are interpreted to reflect climatic warming and intensified chemical weathering during the sturtian deglaciation similar large increases in postglacial cia values are seen in paleoproterozoic and late paleozoic successions and at least moderate increases in cia values are recorded during warm stages of the late quaternary e g the bolling allerod and holocene relative to the cold stages e g the last glacial maximum and younger dryas the rapidity of cia changes in quaternary systems 1 to 10 kyr suggests that weathering intensity may have changed at similarly rapid rates in more poorly dated deep time glacial successions with potential implications for snowball versus slushball models of cryogenian glaciations these examples show that cia can be a robust proxy for climate changes i e enhanced chemical weathering intensity during glacial interglacial transitions of both ancient and recent ice ages

sedimentary basin evolution gravity flows volcanism and their impacts on the formation of the lower cretaceous oil shales in the chaoyang basin northeastern china abstract no detailed research has been carried out on the oil shales that are interbedded with gravity flow deposits and volcaniclastic rocks in the third member of the jiufotang formation in order to study the impact of basin evolution gravity flows and volcanism on oil shale formation petrology sedimentology sequence stratigraphy organic geochemistry and elemental geochemistry were used to characterise the oil shales extensional tectonic subsidence is suggested as the controlling factor for basin evolution the predominant maceral in the oil shales is sapropelinite suggesting organic matter was derived from mainly aquatic organism especially algae element indices u cu mo zn sr ba th g g zr g g and the chemical index of alteration cia show that the water conditions during deposition of the oil shales were anoxic and brackish with little terrigenous detrital input and a cold and dry palaeoclimate gravity flows were accompanied by the input of terrestrial detritus and a degree of oxygenation of the bottom waters reducing oil shale formation volcanic eruptions ejected intermediate acidic ashes not only leading to climate cooling but also either enhancing algal blooms by a fertilisation effect due to minor volcanic ash input or inhibiting algal blooms by a poisoning effect due to major volcanic ash input there is synchronicity between the occurrence of rifting gravity flows volcanism and earthquakes the best periods for oil shale formation were during intermissions between tectonic movement when there were few gravity flows volcanic eruptions or earthquakes high bioproductivity and lake expansion along with an anoxic environment were the main controlling factors for high quality oil shale formation there is a series of oil shale bearing rift basins formed in northeastern china that share a similar geological setting so this research provides a useful example for future resource exploration of coeval oil shales in northeastern china

climatic cycles during a neoproterozoic snowball glacial epoch the profound glaciations of the neoproterozoic cryogenian period ca 850 544 ma represent an extreme climatic mode when it is claimed earth was fully or almost completely covered with ice for millions of years we show that the geochemistry and mineralogy of fine grained neoproterozoic sedimentary rocks in oman are best explained by climatic oscillations that drove variations in the intensity of chemical weathering on contemporary land surfaces the cold climate modes of the cryogenian were therefore cyclical punctuated with well defined warm humid interglacial periods the hydrological cycle and the routing of sediment were active throughout the glacial epoch which requires substantial open ocean water this reconstruction represents a significantly different target for numerical climate models at this critical time in the evolution of earth s biosphere

geochemical and nd isotopic compositions of the palaeoproterozoic metasedimentary rocks in the kongling complex nucleus of yangtze craton south china block implications for provenance and tectonic evolution

paleo sedimentary environment in relation to enrichment of organic matter of early cambrian black rocks of niutitang formation from xiangxi area china abstract early cambrian organic rich black rocks are extensively distributed in the southern china in this study we have discussed the relation of paleo sedimentary environments with enrichment of organic matter based on toc data we divided the niutitang formation into three parts upper middle and lower the amount of total organic carbon in the lower 1 55 wt and the upper part 1 35 wt of niutitang formation is significantly smaller than the middle part 8 0 wt which suggest initial transgression and regression stages of the sea level respectively the middle part from both sections longbizui and sancha contains higher toc content which is a clue of intense transgression stage of sea level with high bio productivity kerogen type index kti using different macerals specify the organic matter in these black rock series is mainly type i with a minor amount of type ii1 moreover these black rocks were deposited in weak to moderately restricted hydrographic conditions the heterogenic mineral composition was also observed in these black rocks including quartz clay gypsum pyrite barite dolomite and plagioclase quartz content in the middle part is relatively higher than the upper and the lower part displays a strong positive relation with toc which suggests the main source of quartz during deposition of the middle part was biogenic quartz during early cambrian period due to extension between the yangtze and the cathaysian plate the hydrothermal fluids rich in uranium vanadium molybdenum zinc barium etc from the deeper part of the earth crust and entered the ocean basin through extensional remnant fissures and cracks and due to upwelling phenomena entered to the shelf area these nutrient rich deep crustal fluids at the surface of the sea enhanced the evolution and breeding of planktons and other marine life meanwhile it upsurges the bio productivity additionally it creates bottom water hypoxia which is favourable for the preservation of organic matter in the sedimentary rocks the main factors responsible for the enrichment of organic matter in these early cambrian black rock series of niutitang formation were a hydrographic restriction hydrothermal activities and paleo redox conditions respectively

retrieval of wet snow by means of multitemporal sar data an algorithm has been developed for mapping wet snow in mountainous terrain using repeat pass synthetic aperture radar sar images as a basis for algorithm development backscattering properties of snow free and snow covered alpine surfaces were investigated using ers sar data and field measurements at test sites in the austrian alps the incidence angle dependence of backscattering derived from sar data is compared with simulations for snow free surfaces and for surfaces covered by dry snow and wet snow significant seasonal changes of backscattering are observed which are mainly caused by variations of the snow liquid water content and of the surface roughness the importance of surface roughness for backscattering of wet snow is demonstrated by a surface roughness experiment the algorithm for mapping wet snow applies change detection using ratios of wet snow versus snow free or dry snow surfaces the main steps include coregistration speckle reduction thresholding of ratio images geocoding and optionally combination of crossing passes to reduce the loss of information due to layover a threshold of 3 db was found to be appropriate for both radarsat and ers sar to separate wet snow from other surfaces postprocessing steps based on historic snow maps or topographic information are used to correct for dry snow areas at high elevations effects of imaging geometry are investigated by comparing ers sar images with a look angle of 19 spl deg and radarsat sar beam mode s7 images with a look angle of 40 spl deg the comparison of snow maps from sar and landsat 5 thematic mapper images shows good agreement in areas of closed snow cover whereas near the snow line sar tends to slightly underestimate the snow extent

major element geochemistry and paleoclimatology of the permo carboniferous glacigene dwyka formation and postglacial mudrocks in southern africa abstract a chemical index of alteration cia is used to quantify the degree of weathering of fine grained materials in the glacigenic permo carboniferous dwyka formation and succeeding stratigraphic units of southern africa diamictites in the dwyka formation have low cia values compatible with their glacigenic origin interbedded mudrocks show a wide scatter of values suggesting that at least some of them were deposited during periods when ice had retreated from the source areas samples from the prince albert shale which immediately overlies the dwyka formation show high cia values suggesting a rapid transition to a much more intensive weathering regime warmer climatic conditions samples from the succeeding whitehill shale have a low average value so that weathering was once more inhibited perhaps by a temporary return to a colder climate the highest stratigraphic units sampled the upper shales have an average cia value comparable to that of average shales and suggesting normal weathering conditions major element geochemical data can supplement sedimentological and paleontological information and provide a valuable contribution to the detailed paleoclimatic interpretation of such glacigenic successions

the origin type and preservation of organic matter of the barremian aptian organic rich shales in the muglad basin southern sudan and their relation to paleoenvironmental and paleoclimate conditions barremianeaptian organic rich shales from abu gabra formation in the muglad basin were analysed using geochemical and petrographic analyses these analyses were used to define the origin type of organic matters and the influencing factors of diagenesis including organic matter input and preservation and their relation to paleoenvironmental and paleoclimate conditions the bulk geochemical characteristics indicated that the organic rich shales were deposited in a lacustrine environment with seawater influence under suboxic conditions their pyrolysis hydrogen index hi data provide evidence for a major contribution by type i ii kerogen with hi values of 400 mg hc g toc and a minor type ii iii contribution with hi values 400 mg hc g toc this is confirmed by kerogen microscopy whereby the kerogen is characterized by large amounts of structured algae botryococcus and structureless amorphous with a minor terrigenous organic matter input an enhanced biological productivity within the photic zone of the water columns is also detected the increased biological productivity in the organicrich shales may be related to enhanced semi arid humid to humid warm climate conditions therefore a high bio productivity in combination with good organic matter preservation favoured by enhanced algae

paleoproductivity of the chang 7 unit in the ordos basin north china and its controlling factors abstract primary paleoproductivity provides basic organic matter for the formation of high quality hydrocarbon source rock a progressive method to quantitatively calculate paleoproductivity on the basis of total organic carbon toc has been proposed to evaluate the contribution of primary paleoproductivity to a hydrocarbon source rock with high organic matter abundance in this study pyrite contents organic maceral compositions and high resolution sedimentation rates srs were used to recover the amount of organic matter oxidation and to exclude the effect of terrestrial clastic input during the deposition of the chang 7 sediment multiple calculation methods were used to quantitatively reconstruct paleoproductivity and the results suggest that the ordos basin was a eutrophic lacustrine basin approximately 2 104 mg c cm 2 kyr 1 to 10 104 mg c cm 2 kyr 1 during the chang 7 stage compared with modern lake productivity the paleoclimatic analysis indicates that a warm humid paleoclimate was beneficial for increasing the weathering intensity which could have provided more nutrient inputs to the depositional environment with incoming terrestrial debris in addition the plate collision between the north china block and yangtze block generated moderate volcanic ash that spread to the study area and provided large amounts of essential nutrients for algae blooms moreover a brackish water condition promoted upward mixing of deep water which inhibited water mass stratification and then facilitated primary paleoproductivity in general the chang 7 high quality hydrocarbon source rock is a result of increased paleoproductivity resulting from suitable paleoclimate conditions brackish water masses and abundant essential nutrient inputs

redox conditions and climate control on organic matter accumulation and depletion during the toarcian in the qiangtang basin eastern tethys the toarcian early jurassic sediments are regarded as the most significant hydrocarbon source rocks in the qiangtang basin qinghai tibet plateau in this study geochemical and mineralogical data are reported from the middle to late toarcian organic lean sediments in the qiangtang basin eastern tethys combined with previous studies the factors that control organic matter om accumulation during the toarcian are investigated the early toarcian organic rich sediments were deposited in stratified water column with oxygen deficient bottom water which was conducive to om preservation a warm and humid paleoclimatic condition favored the growth of organisms which in turn could enhance the surficial biotic productivity during the middle to late toarcian oxic waterbody was widely distributed in the qiangtang basin this condition was unbeneficial to the preservation of om during this interval a cold arid climate had an adverse effect on organism growth which in turn would reduce the initial productivity of surface water the consistently low ti al and si al ratios revealed restricted but rather homogeneous clastic influx conditions during the toarcian this may suggest that the dilution of terrigenous material input had a little influence on om accumulation in addition the differential enrichment of om between shales and marls should attribute to carbonate dilution these studies emphasize that redox conditions and paleoclimatic conditions were likely responsible for om accumulation during the toarcian

mineralogical and chemical distribution of the es3l oil shale in the jiyang depression bohai bay basin e china implications for paleoenvironmental reconstruction and organic matter accumulation abstract the es3l lower sub member of the third member of the eocene shahejie formation shale in the jiyang depression is a set of relatively thick and widely deposited lacustrine sediments with elevated organic carbon and is considered to be one of the most important source rocks in east china we can determine the mineralogy organic and inorganic geochemistry of the es3l shale and calculate paleoclimate indexes by using multiple geochemical proxies based on organic chemistry total organic carbon toc and rock eval pyrolysis major and trace elements x ray diffraction and carbon and oxygen isotope data from key wells alongside ecs elemental capture spectroscopy well log data these indicators can be used to analyze the evolution of the paleoenvironment and provide a mechanism of organic matter om accumulation the es3l oil shale has high toc abundance most samples 3 0 and is dominated by type i kerogens additionally the organic rich shale is rich in cao and enrichment in some trace metals is present such as sr ba and u the positive 13c and negative 18o values high sr ba b ga and ca ca fe ratios and low c s ratios indicate that the es3l shales were mainly deposited in a semi closed freshwater brackish water lacustrine environment the consistently low ti al and si al ratios reflect a restricted but rather homogeneous nature for the detrital supply many redox indicators including the th u v v ni and u ratios pyrite morphology and toc ts fe diagrams suggest deposition under dysoxic to suboxic conditions subsequently the brackish saline bottom water evolved into an anoxic water body under a relatively arid environment during which organic lean marls were deposited in the early stage later an enhanced warm humid climate provided an abundant mineral nutrient supply and promoted the accumulation of algal material om input from algal blooms reached a maximum during the deposition of the organic rich calcareous shale with seasonal laminations high p ti ratios and a strongly positive relationship between the p and toc contents indicate that om accumulation in the oil shale was mainly controlled by the high primary productivity of surface waters with help from a less stratified water column factors such as the physical protection of clay minerals and the dilution of detrital influx show less influence on om enrichment

climatic control on the composition of carboniferous permian gondwana sediments khalaspir basin bangladesh abstract late paleozoic or permo carboniferous gondwana successions world wide are marked by widespread and lengthy glaciation 67 ma and multiple transitions from icehouse to greenhouse state mineralogical and compositional changes in sandstones and mudstones of the gondwana succession in drill hole gdh 45 from the khalaspir basin of bangladesh are interpreted in a climatic framework using the proxies of the mineralogical index of alteration mia and the chemical index of alteration cia low mia

observations on indian permian gondwana coals under fluorescence microscopy an overview abstract macerals like sporinite cutinite suberinite and resinite of the liptinite group have been insufficiently recorded in indian permian gondwana coals until the fluorescence microscopy came into existence with the introduction of this technique macerals like bituminite fluorinite and exsudatinite were convincingly recognized and alginite and liptodetrinite normally mistaken for mineral matter under normal reflected light in routine coal petrographic analysis were identified with certainty thus fluorescence microscopy has added certain new macerals to the tally of the liptinite group and has increased their overall proportion in indian gondwana coals in addition to the liptinite group collodetrinite desmocollinite and a certain fraction of collotelinite telocollinite macerals of the vitrinite group were found to be fluorescing with dull reddish brown to dark brown colours certain semifusinite and inertodetrinite macerals of inertinite group were also found to fluoresce with almost identical intensity and colour as that of the associated perhydrous fluorescing vitrinite contributions of degraded resinite algal matter and bitumen in the formation of perhydrous vitrinite have been established the fluorescence behaviour of inertinite appears to be related with its genesis from partial oxidation of resin bitumen impregnated cell walls

polarimetric synthetic aperture radar study of the tsaoling landslide generated by the 1999 chi chi earthquake taiwan 1 we employ l band airborne synthetic aperture radar sar polarimetry to detect surface changes produced by the tsaoling landslide the largest slope failure triggered by the september 1999 chi chi earthquake in central taiwan imaging polarimeters provide a complete description of the scattering properties of radar target materials resurfacing of forested hillslopes by landslides alters scattering mechanisms from those dominated by backscatter from trees to mechanisms associated with scatter from rough bare surfaces scattering mechanism information on a per pixel basis is extracted by decomposing matrices formed as the outer product of the complex scattering vector measured for each resolution cell we classify surface cover type and thereby identify the extent of the landslide using such polarimetric parameters as scattering entropy anisotropy and pedestal height derived from the eigenvalues of the decomposition as well as the weighted average scattering mechanism derived from the eigenvectors we address the utility of full polarimetry versus dual polarimetry for landslide mapping purposes and show that fully polarimetric sar is necessary for distinguishing water surfaces of varying roughness from the bare surfaces created by landsliding we show that scattering entropy and average scattering mechanism for example can be used to identify the tsaoling landslide source run out area and impounded lakes as proficiently as maps obtained using satellite optical sensors such as landsat and the indian research satellite however the operational advantages of radar over optical sensing techniques namely its day night all weather data acquisition capability suggest that sar polarimetry could play a leading role in the rapid assessment of landslide disasters

large scale climatic fluctuations in the latest ordovician on the yangtze block south china likely under warm and humid conditions low cia values however indicate the near absence of chemical weathering thereby refl ecting cool and or arid conditions in this paper the paleo climatic changes during the ordovician silurian transition were reconstructed in the light of cia values derived from the chemical composition of fi ne grained siliciclastic rocks in the mid upper yangtze river region china the infl u ences of paleoclimatic changes on biota are also discussed abstract the ordovician silurian transition was a critical interval in earth s history marked by dramatic climatic oceanic and biological turnovers here we present the chemical index of alteration cia as a proxy of changes in intensity of chemical weathering and its varia tions across the ordovician silurian boundaries wufeng through guanyinqiao to longmaxi formations from wangjiawan and nanbazi on the yangtze block south china in order to explore the climatic changes our data show that the cia values of sediments commonly range from 75 to 90 in the wufeng and longmaxi formations indicating a high degree of chemical weathering and thus a hot and humid climate during deposition in contrast a sharp drop in cia values most 60 70 in the guanyinqiao formation or hirnantian suggests an overall cold and arid climate interrupted by several intervals of warm climate when deposited the temporal coincidence of two phases of massive biotic extinctions with the beginning and end of the cold climate epoch respectively suggests that the large climatic changes could be one of the main controls on the mass extinctions although other factors may also have played a role

provenance history of a carboniferous gondwana margin forearc basin new england fold belt eastern australia modal and geochemical constraints abstract the visean stephanian myall trough eastern australia formed part of a forearc basin to the east of a magmatic arc situated along the palaeo pacific margin of gondwana petrographic modal whole rock geochemistry and mineral phase chemistry of sandstones siltstones conglomerates and associated igneous rocks provide a consistent and coherent data set which indicate sediment derivation from a magmatic arc of predominantly silicic volcanic composition the low quartz modes of the sandstones the largely volcanic origin of lithic fragments and the overall high sio 2 content of the siliciclastic sediments and igneous rocks require the arc source to be largely dacitic to rhyolitic in composition the predominance of vitric type highly siliceous volcanic rocks lithic fragments suggests a source composed largely of silicic pyroclastics the presence of potassium feldspar as well as the presence of biotite as the principal detrital ferromagnesian phase in the sandstones suggest a source of medium to high k tholeiite composition the high trace element abundances of relatively immobile elements such as zr la ce v nb y and th and corresponding high th u zr y la y la sm ratios and low zr th zr nb la th and ti zr ratios for both the igneous rocks and derived siliciclastic sediments in the myall trough also require a high k and or strongly medium k arc source a lack of temporal or spatial trends in the data indicate that the magmatic arc remained of uniform composition throughout the 25 ma interval of strata preserved within the trough the provenance history of the myall trough requires accumulation along an andean type continental margin rather than an intra oceanic arc outboard of the gondwana margin

petrography and major element geochemistry of the permo triassic sandstones central india implications for provenance in an intracratonic pull apart basin abstract detrital mode composition of feldspars and heavy minerals and major element chemistry of sandstones from the permo triassic succession in the intracratonic satpura gondwana basin central india have been used to investigate provenance the talchir formation the lowermost unit of the succession comprises glacio marine and glacio fluvial deposits the rest of the succession base to top comprising the barakar motur bijori pachmarhi and denwa formations largely represent variety of fluvial depositional systems with minor fluvio deltaic and fluvio lacustrine sedimentation under a variety of climatic conditions including cold warm arid sub humid and semi arid qfl compositions of the sandstones indicate a predominantly continental block provenance and stable cratonic to fault bounded basement uplift tectonic setting compositional maturity of sandstones gradually increases upwards from the early permian talchir to the middle triassic denwa but is punctuated by a sharp peak of increased maturity in the barakar sandstones this temporal change in maturity was primarily controlled by temporal variation in fault induced basement uplift in the craton and was also influenced by climatic factors plots of different quartz types suggest plutonic source rocks for the talchir sandstones and medium to high rank metamorphic plus plutonic source rocks for the younger sandstones composition of alkali feldspars in the permo triassic sandstones and in different precambrian rocks suggests sediment derivation from felsic igneous and metasedimentary rocks compositions of plagioclase in the talchir and bijori sandstones are comparable with those of granite acid volcanic and metasedimentary rocks of the precambrian basement suggesting the latter as possible source rare presence of high k plagioclase in the talchir sandstones however indicates minor contribution from volcanic source rock exclusively plagioclase bearing metasedimentary rock tonalite gneiss and mafic rocks are the probable sources of plagioclase in the upper denwa sandstones quartz rich nature of the sandstones predominance of k feldspar over plagioclase and albite rich character of plagioclase in the sandstones is consistent with deposition in an intracratonic pull apart basin like the satpura gondwana basin composition of garnet and its comparison with that from the precambrian basement rocks suggests mica schist and amphibolite as possible sources predominance of dravite variety of tourmaline in the permian sandstones suggests sediment supply from metasedimentary rocks presence of both dravite and schorl variety of tourmaline in subequal amount in the triassic sandstones indicates sediment derivation from granitic and metasedimentary rocks however schorl bearing rocks are absent in the basement complex of the study area a cn k plot suggests granites acid volcanic rock and meta sediments of the basement as possible sources of the talchir sandstones and metasedimentary rocks for the barakar to pachmarhi sandstones the denwa sandstones were possibly derived from k feldspar free plagioclase bearing metasediments mafic rocks and tonalite gneiss chemical index of alteration cia values suggest low intensity source rock weathering for the talchir sandstones and higher intensity source rock weathering for the others various bivariate plots of major oxides composition of the sandstones suggest passive to active continental margin setting and even arc tectonic setting for a few samples

petrological insights into shifts in eruptive styles at volcan llaima chile tephra and lava pairs from two summit eruptions ad 2008 and 1957 and a flank fissure eruption ad 1850 are compared in terms of textures phenocryst contents and mineral zoning patterns to shed light on processes responsible for the shifts in eruption style during typical eruptive episodes at volcan llaima andean southernvolcanic zone chile the mineralogy and whole rock com positions of tephra and lavas are similar within eruptive episodes suggesting a common magma reservoir for strombolian paroxysms and lava effusion the zoning profiles and textures of plagioclase record successive and discrete intrusions of volatile rich mafic magma accompanied by mixing of these recharge magmas with the resident basaltic andesitic crystal mushes that are commonly present at shallow levels in the llaima system each recharge event destabil izes the plagioclase in equilibrium with the resident crystal mush melt and stabilizes relatively an rich plagioclase as is recorded by the numerous resorption zones lavas typically have 15 20 vol more phenocrysts than the tephra differences in plagioclase and olivine textures and zoning combined with different phenocryst contents indicate that a greater volume fraction of recharge magma is present in the explosively erupted magma than in subsequent effu sively erupted magma we propose that strombolian paroxysms at volcan llaima are triggered by interactions with large volume frac tions of recharge magma which decrease the bulk viscosity and in crease the volatile contents of the erupted magmas leading to the conditions required for the fragmentation of basaltic andesite lava effusion ensues from reduced interactions with the recharge magma after it has partially degassed and crystallized thereby impeding rapid ascent this process could be operating at other steady state basaltic volcanoes wherein shallow reservoirs are periodically re filled by fresh volatile rich magmas

the magnitude of late paleozoic glacioeustatic fluctuations a synthesis a comprehensive literature review shows that the magnitude of eustatic fluctuations varied throughout the carboniferous and permian and that at least eight distinct phases can be recognized facies juxtapositions in carbonate successions and erosional relief in clastic successions indicate that glacioeustatic fluctuations of 20 25 m and occasionally as much as 60 m took place throughout the early mississippian tournaisian a widely recognized glacial period middle mississippian mid chadian through holkerian shallow marine carbonate and clastic successions indicate that eustatic fluctuations were 10 25 m a decrease that matches well with the paucity of coeval glacial deposits late visean asbian through mid brigantian glacioeustatic fluctuations of 10 50 m record the initial phases of ice accumulation in advance of the widespread mid carboniferous glacial event the latest mississippian earliest pennsylvanian mid brigantian through langsettian was a time of widespread glaciation and strata of this age commonly exhibit evidence of glacioeustatic fluctuations of as much as 40 100 m although middle pennsylvanian duckmantian through asturian glacial deposits are present in eastern australia paleovalley depths suggest that coeval glacioeustatic fluctuations were less than 40 m glacioeustatic fluctuations of as much as 100 120 m have been widely reported from late pennsylvanian earliest permian stephanian through mid sakmarian successions in north america an increase that corresponds to the growth of large ice sheets across much of gondwana and the accumulation of ice in the northern hemisphere incision and facies juxtaposition in early middle permian mid sakmarian through kungurian successions in eastern australia indicate that glacioeustatic fluctuations of 30 70 m occurred during the waning stages of major glaciation erosional relief in paleoequatorial carbonates and the presence of coeval glacial deposits in australia suggests that eustatic fluctuations of 10 60 m occurred during the final stages of glaciation in the middle to late permian roadian through capitanian but the modest size of most of these fluctuations makes it difficult to isolate the glacioeustatic signature this review demonstrates that far field cyclic successions record changing glacial conditions in gondwana that the magnitude of glacioeustatic fluctuations was directly related to the volume of glacial ice that carboniferous permian glacioeustasy was more variable than previously recognized and that generalizations from short temporal intervals are probably not representative of the late paleozoic ice age as a whole although any attempt to quantify the magnitude of ancient eustatic changes is based on caveats and assumptions this review incorporates the results of over 100 published papers on the topic in an attempt to minimize the errors inherent in any one study

global changes during carboniferous permian glaciation of gondwana linking polar and equatorial climate evolution by geochemical proxies the most prevalent phanerozoic glaciation occurred during the carboniferous permian on the southern hemisphere gondwana supercontinent sediments from the pennsylvanian dwyka group deposited in the karoo basin of south africa provide a complete record of glaciation and deglaciation phases the direct correlation of glaciation events in southern gondwana basins with the well studied climate evolution of equatorial regions was previously hampered by lack of precise radiometric dating as dating has now become available for the karoo basin the gondwana glaciation can be viewed in a global paleoclimatic framework with high temporal resolution element geochemical proxies cia chemical index of alteration zr ti rb k v cr record three confined shifts in climate and paleoenvironment of the karoo basin these shifts were induced by changes in sea level weathering rate provenance and redox conditions because of the low availability and diagenetic overprint of carbonates ocean and atmosphere pco 2 variations had to be reconstructed from 1 3 c o r g values of marine organic matter the 1 3 c o r g signatures are affected by variable proportions of marine versus terrestrially derived organic matter and its state of preservation organic geochemical investigations toc total organic carbon c n lipid biomarkers indicate the organic matter in the central karoo basin was primarily of algal origin in agreement with element proxies the varying 1 3 c o r g values mirror shifts in pco 2 rather than variations of organic matter type a covariation trend between carbon isotope signatures of equatorial carbonates and 1 3 c o r g values from the karoo basin argues against local forcing factors and instead implies a global climate control mechanism the 5 7 m y duration of a complete glacial cycle is not in tune with any known orbital frequency processes such as changes in equator pole temperature gradients or newly developing atmosphere ocean circulation pathways can be regarded as controlling factors

petrographic and geochemical characterization of the upper cretaceous coal and mudstones of gombe formation gongola sub basin northern benue trough nigeria implication for organic matter preservation paleodepositional environment and tectonic settings abstract under exploration of the upper cretaceous petroleum systems in the northern benue trough nigeria has been attributed largely to lack of subsurface samples and non integration of organic and inorganic geochemical methods recent access to surface sampling from maiganga coalfield revealed a need for detailed evaluation of the sedimentary facies types for better understanding of the hydrocarbon potential of the area detailed maceral point count py gc chnso as well as major oxides and trace element icp ms analysis were used to characterize the gombe formation coals and the mudstones for determination of the organic matter origin preservation paleodepositional environment tectonic setting and paleoclimatic condition during sedimentation evaluation based on the maceral composition tpi gi values plot of trace elements v versus ni and sedimentary succession suggest deposition of predominantly terrigenous organic matter 45 to 73 huminite maceral in an upper deltaic setting for the maiganga facies the maceral analysis associated with py gc studies indicates that the sedimentary facies of gombe formation have potential to generate liquid hydrocarbon this can be estimated from an average of 21 50 liptinite content and the ternary plot of the py gc pyrolysate m p xylene n octene and phenol suggesting presence of type ii and type ii iii kerogen within the basin assessment of the paleodepositional environment based on the trace elements composition indicates a moderate stratified water column and salinity within a relatively sub oxic to oxic conditions during sedimentation the major oxide composition as well as the binary plots of sio2 versus al2o3 k2o na2o and log sio2 versus k2o na2o for the shales and mudstones revealed a predominance of semi arid to slightly humid warm paleoclimatic conditions and a passive continental margin setting this is in accordance with the cretaceous tectonic events of the west and central africa which affected the petroleum system in the entire benue trough