aridity driven decoupling of δ13c between pedogenic carbonate and soil organic matter pedogenic carbonate is an invaluable archive for reconstructing continental paleoclimate and paleoecology the c of pedogenic carbonate c c has been widely used to document the rise and expansion of c plants over the cenozoic this application requires a fundamental presumption that in soil pores soil respired co dominates over atmospheric co during the formation of pedogenic carbonates however the decoupling between c c and c of soil organic matter c som have been observed particularly in arid regions suggesting that this presumption is not always valid to evaluate the influence of atmospheric co on soil c c here we performed systematic c analyses of paleosols across the chinese loess plateau with the sample ages spanning three intervals the holocene the late pleistocene and the mid pliocene warm period our paired c c and c som data reveal broadly divergent trending patterns using a two component co mixing model we show substantial incorporations of atmospheric co up to 60 into soil pore space during carbonate precipitation this result readily explains the enrichment of c c and its divergence from c som as a consequence c of pedogenic carbonates formed under semiarid and or arid conditions are largely driven by regional aridity through its control on soil co composition and thus cannot be used to evaluate the relative abundance of c versus c plants nonetheless these carbonates can be applied for atmospheric co reconstructions even for periods with low co levels

drastic climatic shift at 2 8ma as recorded in eolian deposits of china and its implications for redefining the pliocene pleistocene boundary there has been a long running debate over the position of the pliocene pleistocene boundary i e 1 8 ma versus 2 6 ma this study presents litho and pedo stratigraphic characteristics grain size magnetic susceptibility and dust sedimentation rates for red clay loess sequences over northern china in order to assess the drastic climatic event s recorded in the quasi continuous eolian deposits and to readdress the position of the pliocene pleistocene boundary in complete chinese loess sequences 33 soil loess couplets have been identified and labeled with si li system traditionally the base of chinese loess has been designated at the bottom of loess unit l33 however a typical loess layer within the uppermost red clay is identified and formally designated here as l34 and the soil unit between l33 and l34 as s33 which lowers the basal age of chinese loess from 2 6 ma to w2 8 ma although the neogene red clay and the overlying quaternary loess are both of windblown origin they have quite different pedogenic characteristics the loess consists of alternating reddish soil and yellowish loess layers while the red clay is composed of soils with much redder colour and carbonate nodule layers in general the red clay has been subjected to stronger pedogenic processes than the overlying loess and can be regarded as an extremely thick soil complex the alternation of loess and soils reflects large scale oscillations between glacial and interglacial conditions whereas the well developed red clay deposition indicates a relatively stable climate condition at w2 8 ma shortly before the gauss matuyama boundary the eolian sequences show a sedimentary transition from the well weathered red clay to the alternating loess and paleosol deposits accompanied by coarser particle size increased dust accumulation rates and change of magnetic susceptibility signature these indicate a large climatic shift from long lasting warm humid conditions to large amplitude cold dry and warm humid fluctuations around 2 8 ma and a dramatic increase in aridity over the dust source region in contrast such a drastic event is not identified around the top of the olduvai event or at any other time of the past 7 7 ma as the gauss matuyama boundary offers a sound foundation for global time correlation and chronostratigraphic classification these results still support the proposal of ics and inqua that the conventional pliocene pleistocene boundary should be lowered from 1 8 ma to 2 6 ma

late cretaceous and cenozoic tectonics of the malay peninsula constrained by thermochronology abstract new thermochronological analyses of granites from the malay peninsula record the region s thermal history during the late mesozoic and cenozoic 40 ar 39 ar and u th sm he analyses are combined with existing fission track data to provide a comprehensive set of temperature and time data fully and partially reset k feldspar and biotite mica 40 ar 39 ar analyses indicate a significant period of thermal perturbation between 100 and 90 ma and a second lesser perturbation between 51 and 43 ma zircon u th sm he analyses and existing fission track data indicate exhumation of the malay peninsula in the cretaceous and renewed localised exhumation in the early paleogene apatite u th sm he and fission track data indicate rapid exhumation of the region in the late eocene and oligocene late cretaceous tectonism is linked to the reversal of a regional dynamic topographic low following the cessation of subduction along the sundaland margin in the late cretaceous causing regional uplift and exhumation and the addition of significant heat into the crust via mantle upwelling early paleogene exhumation may reflect the continuation of cretaceous tectonism or a discrete phase of paleocene exhumation linked to localised transpressional tectonics eocene tectonism is coincident with major subsidence offshore of the malay peninsula interpreted to reflect regional block faulting in response to north south compression driven by the resumption of subduction along the southern margin of sundaland in the eocene

late miocene palaeoecological evolution of the tianshui basin ne tibetan plateau evidence from stable organic carbon isotope record abstract the spatial and temporal variations and the driving mechanisms of c3 c4 vegetation evolution throughout the miocene have been a matter of long standing debate a continuous lacustrine fluvial sediment sequence widely exposed in the tianshui basin ne tibetan plateau provides great potential for deciphering the c3 c4 vegetation dynamics during the miocene based on the measurements of 13corg c n and c n ratios of organic matter of this sediment sequence here we present a new perspective on vegetation history in inland asia during the period from 17 1 to 6 1 ma the organic matter preserved in the tianshui basin is most likely a mixture of terrestrial and aquatic origins the lack of correlation between organic 13corg and carbonate 13ccarb indicates that terrestrial plants made a dominant contribution to the organic matter the 13corg of organic matter shows negative values between 24 1 and 28 3 along the sequence from 17 1 to 6 1 ma indicating a predominance of c3 plants more specifically our results indicate that the 13corg values of organic matter show a significant increase by ca 1 4 from 26 6 to 25 2 from 7 1 ma onwards equivalent to ca 10 increase in c4 plants reflecting the initial occurrence of c4 plants the occurrence and expansion of the c4 component in the study area is supposed to be a result of increasing summer precipitation due to the enhanced asian summer monsoon since that time

stable and clumped isotopes in shell carbonates of land snails cathaica sp and bradybaena sp in north china and implications for ecophysiological characteristics and paleoclimate studies knowledge of ecophysiological characteristics of different land snail species is crucial for defining climatic significance of snail faunal assemblages however little work has been done in this aspect hindering our obtaining unambiguous paleoclimatic information using these proxy indicators here we document for the first time the different ecophysiological characteristics of cathaica sp and bradybaena sp land snails using the stable isotopes and clumped isotope 47 of the shell carbonates the 47 derived temperatures for both species revealed a robust correlation with environmental temperatures moreover the temperatures for cathaica sp are 3 5 c higher than those for bradybaena sp land snails indicating different ecophysiological adaptations or growing seasons of the two species specifically cathaica sp snails prefer living in a warm humid summer whereas bradybaena sp snails are active in the relatively cool arid spring and or autumn the result testifies to the 47 in snail shell carbonates as a promising paleothermometer in monsoonal region and presents new insight into paleoclimatic explanation of these land snail species this finding highlights the importance of climatic seasonality in the changes of the faunal assemblages of land snails

prospect of hydrocarbon associated with fossil rift structures of the southern indus basin pakistan the southern indus basin 550 x 250 km is characterized by tectonic upwarping on the western margin of the indo pakistan subcontinent several hypotheses have so far been proposed to explain the origin of these crustal features but these basement upwarps remain puzzling aeromagnetic data have been analyzed and interpreted supplemented with seismicity and geological information from the integrated study we inferred basement configuration and developed models for tectonic evolution of these exotic crustal features and their impact on hydrocarbon potential associated with the southern indus basin the southern indus basin is identified as an extension basin resulting from an inferred fossil rift crustal feature overlain by a thick sedimentary sequence extension was a consequence of temporal divergence of the indo pakistan subcontinent from gondwanaland during the early paleozoic based on magnetic anomaly trends the indus basin fossil rift feature is characterized by horst and graben structures together with a system of transcurrent faults the association of seismicity events and basement crustal features suggests that tertiary reactivation of individual segments of the inferred rift structure has deformed overlying sequences of the indus basin and also the surrounding areas particularly the fold and thrust belt of pakistan on the western side of the basin the proposed geological models also illustrate the potential for appropriate environments for development of hydrocarbon source rocks sufficient heat for thermal maturity and structures for reservoirs and seals suggesting more bright prospects in the southern indus basin

reconstruction of the vegetation distribution of different topographic units of the chinese loess plateau during the holocene abstract soil erosion and related ecological restoration present a tremendous challenge to the socioeconomic development of the chinese loess plateau clp although the chinese government has addressed the problem of soil erosion via an afforestation programme there have been several negative outcomes one of the reasons for this is our incomplete understanding of the past natural vegetation distribution in the various topographic units of the clp under different climate scenarios consequently we used fossil pollen data from 41 sites from different topographic units together with the biomization method to reconstruct the holocene vegetation distribution of the clp the results demonstrate significant differences in vegetation types between different topographic units forest was distributed in mountainous areas steppe was dominant in yuan areas and desert vegetation was distributed in the transition zone between loess and desert the vegetation in the gully areas exhibited significant spatial differences during the mid holocene in addition the vegetation on the various topographic units was well developed during the interval from 9 to 4 ka b p when regional moisture levels reached a maximum this suggests that the east asian summer monsoon was one of the main factors controlling the evolution of vegetation patterns during the holocene in addition our results confirm that both topography and human activity were fundamental factors determining the vegetation distribution of the region against a background of ongoing global warming we advocate a program of vegetation restoration including planting trees and shrubs in the mountainous areas and promoting the growth of grasses in the yuan areas and in the transitional zone between loess and desert in the gully areas the planting of trees and shrubs is appropriate for reducing soil erosion caused by human activities

climate instability during the penultimate glaciation evidence from two high resolution loess records china the xinzhuangyuan and lijiayuan loess sections in the northwestern part of the chinese loess plateau were studied down to paleosol unit s2 which probably formed during marine oxygen isotopic stage 7 200 000 years b p the thickness of the loess soil sequence above s2 is 63 m at xinzhuangyuan and 43 m at lijiayuan a 2 cm sample spacing yields a mean depositional resolution of 50 80 years for the last and penultimate glacial loess units l1 and l2 and 200 years for the last interglacial soil unit sl thus enabling us to reconstruct high resolution climatic changes during the last two glacial interglacial cycles the grain size records of the two sections are regarded as a proxy for changes in the monsoon desert system over northern china results show that frequent large amplitude climatic oscillations on millennial timescales occurred during the penultimate glaciation in a manner similar to that during the last glaciation suggesting that suborbital scale climatic variations may be a common feature of the climate system during glacial periods of the pleistocene the last interglacial soil s1 is composed of three individual soils and two thin intervening loess horizons in both of the sections short term variations in grain size are not prominent within the soil complex implying the absence of strong millennial scale climatic oscillations during the last interglaciation in northern china

proxy of monsoon seasonality in carbon isotopes from paleosols of the southern chinese loess plateau soil organic matter som and soil carbonate sc are common constituents in soils and are directly related to plant growth som accumulates gradually from the decomposition of plant material over time whereas sc formation is biased to dry season soil dissolved co 2 that derives from plant respiration during a drying phase of the growing season in some mixed c 3 c 4 environments the peak of c 3 and c 4 plant metabolism differs seasonally and the carbon source that contributes to the som and sc can be different consequently 13 som values reflect an annual average of the floral biomass but 13 sc values reflect a seasonal aspect of the plant community the relationship between 13 c sc and 13 c som is mainly controlled by how different the seasonal conditions are our results suggest that the relationship is a seasonal proxy that can be used to differentiate the seasonality effects of indian east asian and siberian monsoons on the chinese loess plateau during the last interglacial glacial cycle

systematic variations in the carbon and oxygen isotopic composition of pedogenic carbonate along elevation transects in the southern great basin united states stable carbon and oxygen isotope variations in holocene soil carbonates that formed in the unsaturated zone were examined along several elevation transects in the southern great basin united states a region with a semi arid climate our intent was to study the relationship between the stable isotopic composition of pedogenic carbonates and climate ecological variations differences in parent material and soil depth 13 c of pedogenic carbonate in three different soil profiles from different elevations decreases with soil depth indicating a decrease in the ratio of atmospheric to plantderived co 2 downprofile pedogenic carbonate at the soil air interface approaches a 13 c value in equilibrium with atmospheric co 2 in all three soils observed 13 c profiles for pedogenic carbonate can be described using a one dimensional model for 12 co 2 and 13 co 2 assuming isotopic equilibrium between soil co 2 and soil carbonate the modeled best fit to observed isotopic profiles suggests that the profile differences in part result from differing soil respiration rates at each site 13 c in deep pedogenic carbonate 50 cm varies by about 12 per mil over a 2 440 m elevation range being enriched in 13 c at the lowest elevations the slope of 13 c for these carbonates versus elevation is very similar for soils developed on carbonate and on noncarbonate parent materials depletion by 4 6 to 4 7 per mil per 1 000 m increase in altitude between 300 to 2 740 m above mean sea level for the localities studied this concordance makes it likely that there has been complete isotopic exchange between hco 3 in solution and soil co 2 prior to carbonate precipitation soil co 2 and soil respiration rates increase systematically with elevation the plantderived component of soil co 2 indicates that c 3 plants dominate the biomass at most measured sites in agreement with plant surveys calculated equilibrium fractionation factors between soil co 2 and soil carbonate are very similar to those observed again indicating complete isotopic exchange between carbon species in all the soil co 2 and soil carbonate data suggest that the 13 c variation with elevation observed in the soil carbonates results from differing soil respiration rates at each site as well as from variations in the proportion of c 3 to c 4 and cam plants in each site9s surface biomass 18 o values in pedogenic carbonates are higher at lower elevations due in part to the more positive 18 o values for meteoric waters at lower elevations the average 18 o value of deep 50 cm pedogenic carbonate at all sites however is enriched 2 4 to 3 7 per mil with respect to values we predict should be in equilibrium with the isotopic composition of local meteoric waters this suggests that evaporative isotopic enrichment of soil waters may have occurred at all elevations prior to precipitation of carbonate or that seasonal differences in the isotopic composition of meteoric waters coupled with differential infiltration may be taking place one or both of these processes also may explain the 18 o decrease in soil carbonate with depth observed in two of three soil profiles

hydrocarbon plays and global basin classification hydrocarbon plays and the global basin classification system have important connections after a basin has been classified its similarities or differences with other basins may be compared prolific hydrocarbon basins are categorized and the plays are compared to specific tectonic and depositional events some plays are controlled by basin initiating tectonic events such as interior fracture or interior sag and the type of sedimentation inherent in each basin type in more complex polyhistory basins oil and gas plays are commonly associated with combinations of various cycles or by basin modifying tectonics such as episodic wrenching subsidence foldbelts and basin tilt

loessic palaeolith discovery at the beiyao site luoyang and its implications for understanding the origin of modern humans in northern china abstract the excavation at beiyao palaeolithic site during 2007 2008 uncovered a number of lithics including 49 cores 180 flakes 3 tools and 486 pieces of knapping debris making a total of 719 artefacts research conducted on these finds produced two main points the first was that a new cultural layer was discovered in the loess layers dating to mis3 mis2 in this cultural layer some of the raw material had been transported over considerable distances the second aspect of this research focused upon the relationship between the temporal distribution of the lithics and the changing climate although human activities took place at the site during both cold or warm weather periods human activities during warm periods were much more intense than in cold periods before mis3 from mis3 human activities were obviously intensified during cold periods this shift may have some relationship with the emergence of modern humans

soil nitrogen isotopic composition of the xifeng loess paleosol sequence and its potential for use as a paleoenvironmental proxy abstract the isotopic composition of soil nitrogen soil 15 n values has been widely used to explore the soil biogeochemical cycle and study land vegetation conditions however the 15 n values in the loess paleosol sequence have not been thoroughly studied in this study we provide the first report of 15 n values from the xifeng loess paleosol profile which spans the last 130 ka the 15 n values show great variation 2 1 6 1 in the xifeng loess sequence according to these results the 15 n values have a similar pattern with changes in the magnetic susceptibility ms and exhibit significant differences within the glacial interglacial cycle over the last 130 ka we hypothesize that climate conditions and land vegetation conversion could be reflected by the changes in the 15 n values within the glacial interglacial cycle 1 the 15 n values are positively correlated with the reconstructed mean annual temperature mat and mean annual precipitation map on the glacial interglacial time scale moreover it appears that the mat may be more effective than the map for the 15 n changes in the xifeng loess paleosol sequence 2 vegetation changing from grasses to shrubs may cause 15 n depletion during the glacial period in addition increasing grass groups may cause 15 n enrichment of the soil during the interglacial stage in the xifeng loess paleosol sequence because nitrogen is one of the most significant nutrient elements for vegetation paleovegetation changes may be the main controlling factor for 15 n values in the loess paleosol section therefore 15 n values have the potential for use as a proxy in paleoenvironmental reconstructions of the chinese loess plateau

extensional model for the subsidence of the northern united states atlantic continental margin the simple extensional model for the subsidence of the northern united states atlantic continental margin attributes subsidence which results in sedimentary basin formation to extension and thinning of continental lithosphere the model is used to predict the tectonic subsidence histories that would be associated with various amounts of extension actual tectonic subsidence history curves are calculated from data collected in the continental offshore stratigraphic test cost wells b 2 b 3 g 1 and g 2 and are found to be consistent with the predictions

dolomite abundance in chinese loess deposits a new proxy of monsoon precipitation intensity dolomite of detrital origin in carbonate rich soil can help indicate the intensity of carbonate dissolution and leaching processes using fourier transform infrared spectroscopy we generated a high resolution record of dolomite and calcite contents from eight sections on the chinese loess plateau spanning the last 130 kyr based on the relative abundance of calcite and dolomite four dissolution phases of carbonate minerals related to summer monsoon sm variations are identified as follows 1 coexistence of dolomite and calcite indicating a very weak sm with a mean annual precipitation map 725 mm

multiple expansions of c4 plant biomass in east asia since 7 ma coupled with strengthened monsoon circulation the expansion of plants using the c4 photosynthetic pathway is one of the most prominent changes in the global ecosystem during the cenozoic era a significant late miocene expansion is well documented however the existence and cause of subsequent expansions are still not clear owing in part to the lack of long continuous climate vegetation records here we present two high resolution carbon isotope time series covering the past 7 m y derived from eolian deposits on the chinese loess plateau the data indicate three intervals of significant c4 plant expansions within the semiarid monsoonal region of east asia ca 2 9 2 7 ma 1 3 0 9 ma and 0 6 ma present these expansions covary with strengthened east asian summer monsoon circulation we conclude that in east asia large scale late miocene c4 c3 vegetation changes in semiarid areas have been primarily driven by warm seasonal precipitation and temperature variations associated with changes in monsoon circulation

environmental change in yellow sea during the last deglaciation to the early holocene 15 000 8 000 bp abstract this study is the first reconstruction of the paleoenvironment and paleovegetation during the holocene interglacial and last deglaciation periods of the yellow sea carbon isotope and biomarker n alkane and alkenone compositions of organic carbon matter om from core 11 ys pcl14 collected from the central yellow sea recorded past changes in east asian monsoon eam climates the result shows the variability of the eam affected the sedimentary profile of total organic carbon toc the stable isotopes of bulk organic carbon 13 c org the atomic ratio of carbon and nitrogen c n ratio and biomarker content the oscillations of toc along the sediment core might be associated with the paleoceanographic conditions changes in the sea level related to the contribution of the autochthonous and allochthonous om input two climatic conditions were distinguished warm humid and cold dry based on the n alkane proxy and the observed changes in 13 c of individual n alkane 13 c alk between the holocene and last deglaciation were attributed to changes in plant distribution type a shift in vegetation type between climatic periods occurred as a result of different photosynthetic response to co 2 and temperature among c 3 and c 4 plants the most interesting new finding of this work is the fact that alkenone derived temperature changed independently with global climate change which might be related to the influence of the kuroshio current in the yellow sea the variations in the intensity of the eam could be the main mechanism accounting for the paleoenvironmental and paleoceanographic variation observed in the central yellow sea

negative δ18o δ13c relationship of pedogenic carbonate from northern china indicates a strong response of c3 c4 biomass to the seasonality of asian monsoon precipitation abstract evaluating how future climate changes may impact c3 c4 biomass in east asia depends largely on the understanding of the relationship between past c3 c4 variations and asian monsoon circulation the glacial interglacial variations in c3 c4 biomass have been readily ascribed to the summer monsoon however the internal processes governing the link of c3 c4 vegetation to the asian monsoon have not been clearly described here we present isotopic results of pedogenic carbonate from northern china for the holocene the last and penultimate interglacial periods comparison of the observed and predicted 18o values of modern soil carbonate from gravelly soils suggests that pedogenic carbonate forms mainly in warm rainy season carbonate nodules from the chinese loess demonstrate a distinct negative 18o 13c relationship and a wider scatter of isotopic values in the southern loess plateau than in the northern part by combining rainfall 18o of precipitation and the peak of c3 and c4 plant metabolism we develop a conceptual model to explain the isotopic signatures of the carbonate nodules our model shows that a narrowly focused season of monsoon precipitation at a specific site produces low 18o values of soil water and simultaneously favors c4 over c3 plants our model further suggests that the scattered isotopic values of soil carbonate reflect a strong summer monsoon while the focused values indicate a weak summer monsoon 13c values of soil carbonate indicate a striking pattern of northward increasing c4 vegetation for the last interglacial while a flat spatial pattern is seen for the penultimate interglacial and the holocene it is inferred that the summer monsoon was stronger during the last interglacial than during the penultimate interglacial and the holocene leading to a northward displacement of c3 forest ecosystems into the southern loess plateau in addition an in phase relationship between intra nodule 13c and 18o values suggests a strong and possibly rapid response of c3 c4 biomass to the seasonality of asian monsoon precipitation in this context if the last interglacial period mis 5 is taken as an analog for the projected near future then c3 plants may be favored in the south while c4 plants may be efficient in the north

stacked 2 6 ma grain size record from the chinese loess based on five sections and correlation with the deep sea δ18o record 1 this study aims to establish a stacked climate record of the quaternary period from the chinese loess sequence and to address the forcing mechanisms for the regional climate history of the loess plateau by correlating the stacked record with a composite 18o record in deep sea sediments a total of 18 352 samples were obtained from five loess sections located at baoji lingtai jingchuan puxian and pingliang in the southern and middle loess plateau these yielded high resolution grain size records between section correlation of these shows that although small depositional hiatuses are present in places within a single section most parts of the sections display near continuous dust deposition throughout the quaternary the grain size records were tuned simultaneously to the theoretical variations in obliquity and precession of the earth s orbit the grain size records plotted on their orbital timescales were then averaged to form a stacked loess grain size time series termed the chiloparts record this resolves most of the orbital timescale paleoclimate events buried in the loess soil sequences of the southern and middle loess plateau and can be used as a regional archive of the pleistocene climate history in the loess plateau comparison of the chiloparts record with a composite marine 18o record shows that for the past 1 8 ma the loess paleosol record can be correlated almost cycle by cycle with the marine record several discrepancies in the climatic events between the two records have also been identified implying that regional forcing mechanisms may have played a part in the climatic evolution of the chinese loess plateau

advance retreat history of the east asian summer monsoon rainfall belt over northern china during the last two glacial interglacial cycles abstract in northern china the history of desert migration provides a good measure of the east asian summer monsoon variations since the desert margin environment is very sensitive to changes in summer monsoon rainfall desert margin migration can be well documented in the downwind loess deposits since the grain size of chinese loess is principally controlled by source to sink distance and hence the loess grain size is an effective proxy for reconstructing the history of the east asian summer monsoon in order to investigate the pattern and migration of the summer monsoon rainfall belt over northern china during the past two glacial interglacial cycles contour maps of loess grain size were constructed for mis 2 3 4 5 6 and 7 all the grain size isolines show a near north south gradient for both glacials and interglacials indicating a dominant dust source region in north and an approximately north south dust transport pathway for dust deposits in the main body of the loess plateau at least for the past two glacial interglacial cycles the reconstructed southeast desert margin for mis 2 3 4 5 6 and 7 roughly parallels the present isohyets implying that the pattern of the east asian summer monsoon rainfall belt during the past two glacial interglacial cycles is similar to the present i e a northeast southwest trend for the isohyets of the summer monsoon despite the glacial interglacial cycles using the grain size isolines of mis 2 as a reference we derive a northerly desert retreat of 160 km 19 km 225 km and 223 km for mis 3 4 5 and 7 respectively and a southerly desert advance of 29 km for mis 6 that could be preliminarily regarded as the relative migration distance for the east asian summer monsoon rainfall belt in addition the inferred climate conditions in mis 3 are cool and humid in northern china while the driest and coldest interval of the last two glacial periods occurs in mis 6

color reflectance of chinese loess and its implications for climate gradient changes during the last two glacial interglacial cycles 1 to examine the relationship between color changes of loess deposits and paleoclimate conditions a north south transect consisting of twelve loess sections were studied color reflectance was measured on loess paleosol samples from the loess transect which accumulated over the last two glacial interglacial cycles the redness value a shows an overall southward increase for both loess and soil units coinciding with the pattern of a southerly increase in pedogenic development and the present north south climatic gradient the redness of loess deposits is linearly correlated with latitude values implying that this parameter is an efficient proxy for the weathering intensity of loess deposits the gradient of weathering intensity is much steeper during interglacials than in glacials by comparison of color records for different time interval

global geologic history and distribution of hydrocarbon reserves a review of global geologic history during seven major periods between the cambrian and the holocene reveals the principal factors influencing the distribution of world hydrocarbon reserves the paleozoic reserves located mainly in north america and europe are mostly related to stable platform environments the mesozoic and tertiary reserves are found in more diverse tectonic environments represented mainly by the mesogean tethyan realm passive margins and the western american mobile belts the mesogea tethys formed a latitudinal feature separating gondwana and laurasia the mesogean realm contains 69 of the world oil and gas reserves divided almost equally between the gondwana and laurasia areas the voluminous reserves in the mesogean realm reflect the history of repeated opening and closing of the mesogea ocean that resulted in several phases of basin development the comparative isolation of the basins from the global ocean circulation favored preservation f organic matter because of diagenesis the thermal history and migration the ultimate hydrocarbon reserves generally decrease as the ages of the reservoir and source rocks increase migration is usually directed toward the higher parts of the stratigraphic section concentrations of reserves within particular age ranges apparently reflect development of two major categories of basins 1 marine platform basins which were dominant in the devonian jurassic and cretaceous periods and 2 rapidly subsiding basins which were dominant in the late tertiary and probably during the late carboniferous pennsylvanian the middle east has an exceptional volume of sediments prolific source rocks and well preserved hydrocarbons and it is not likely that another hydrocarbon province of comparable importance will be found moreover these middle east reserves do not give any anomalous weight to the total reserves of the gondwanian areas when compared to those in the laurasian areas

oxygen isotope variations in rainfall drip water and speleothem calcite from a well ventilated cave in texas usa assessing a new speleothem temperature proxy abstract measurements of the oxygen isotopic composition 18o value of rainfall drip water and associated calcite grown on artificial substrates and in a natural speleothem at multiple drip sites in a well ventilated cave in central texas were conducted to investigate the potential use of speleothem 18o for quantitative temperature reconstructions from 2009 to 2011 rainfall 18o varied by 11 5 10 5 to 1 0 v smow whereas drip waters had a much narrower range of 0 3 4 7 to 4 4 v smow this contrast indicates that mixing processes along flow paths in the vadose zone above the cave produce a well homogenized water reservoir that supplies drip water to the cave the 18o values for calcite grown on substrates over the same time period show seasonal variations summer 6 winter 3 that are strongly correlated with surface air temperatures ta at all three monitored sites r2 0 88 0 96 p

depth to pedogenic carbonate horizon as a paleoprecipitation indicator an analysis of 1168 modern soil profiles from the u s natural resources conservation service yields no correlation between mean annual precipitation and depth to the top of the carbonate horizon r 2 0 03 p 0 001 parent material and soil texture both play negligible roles in this regression when combined with similar published studies n 1481 r 2 improves slightly r 2 0 31 p 0 001 caution is therefore advised in using this or any previously published regression for inferring paleoprecipitation from paleosols however in the combined data set carbonate horizon bearing soils correlate with a mean annual precipitation of 760 mm p 0 05 thus the presence vs absence of pedogenic calcium carbonate is a good indicator of paleoprecipitation above or below this value

c3 c4 vegetation evolution over the last 7 0 myr in the chinese loess plateau evidence from pedogenic carbonate δ13c the stable carbon and oxygen isotopic compositions of soil carbonate were measured on an eolian loess and red clay sequence at lingtai the chinese loess plateau this sequence is composed of 130 m of tertiary red clay deposits with a basal age of 7 05 ma overlain by 175 m of pleistocene loess in the field we identified ca 110 carbonate nodule horizons in the red clay and 27 nodule horizons in the loess these carbonate nodule horizons are formed by leaching and re precipitation of carbonate from the eolian material the d13c record of soil carbonate indicates a major expansion of c 4 plants at ca 4 0 myr in the loess plateau this event is comparable in timing with the expansion of c 4 plants in northern north america cerling et al 1997 nature 389 153 158 but is ca 3 million years later than the c 4 biomass expansion in pakistan quade et al 1989 nature 342 163 166 the pedogenic characteristics of the soils and the d18o record in the red clay suggest that the c 4 plant expansion in the loess plateau was not driven by local climatic changes which may support cerling et al s 1997 assertion that the decline of atmospheric co 2 levels in the neogene is responsible for this global vegetation change our record also implies that the tibetan plateau could have been uplifted to a critical height in the late miocene thus resulting in the formation of the atmospheric great east asia trough 2000 elsevier science b v all rights reserved

stable isotope composition of the carbonate concretion in loess and climate change carbonate concretions are commonly found in the loess in china oxygen and carbon isotopic compositions of carbonate concretions collected from 14 different paleosols s1 s14 in the lishi formation of luochuan loess section china were analysed the isotopic compositions of concretion in loess are useful tools in paleoclimatic study usually the more developed the paleosol is the less negative the 18o values and the more negative the 13c values are the oxygen isotopic composition of these paleosols varies within a range of about 1 3 the carbon isotopic composition however shows larger variations from one paleosol to the other within a range of 5 3 an attempt was made to semi quantitatively estimate the paleosol formation temperature and precipitation based on the carbon and oxygen isotopic data obtained

leaf wax n alkane distributions in chinese loess since the last glacial maximum and implications for paleoclimate abstract leaf wax n alkanes have been recently introduced into loess deposits for paleovegetation and paleoclimate reconstruction however the paleoclimate significance of some n alkane parameters such as chain length ratios l h c 27 c 31 c 29 c 31 and c 27 c 29 c 31 c 33 remains to be clarified in order to evaluate the validity of those proxies in loess deposits leaf wax n alkanes were analyzed from a northwest southeast transect on the chinese loess plateau since the last glacial maximum lgm the n alkanes show a bimodal distribution between c 14 and c 33 with carbon number maxima c max at c 14 or c 16 and at c 31 or c 33 indicative of both terrestrial plant and microbial origin l h variations are in good agreement with climate changes both temporally and spatially i e the higher l h ratio the warmer and wetter climate and vice versa therefore the l h ratio in chinese loess can serve as an efficient proxy for paleoclimate by comparing long chain n alkane ratios with pollen records we suggest that the generally used woody plant proxies c 27 and c 29 and grass proxies c 31 and c 33 are not applicable to chinese loess as the chinese loess plateau was dominated by herbs in both the lgm and the holocene the long chain n alkane ratios may mainly reflect changes in the species composition of local vegetation for a better understanding of leaf wax n alkanes in chinese loess further studies are required to investigate the n alkane distributions in both the major plant species and their associated surface soils on the chinese loess plateau

carbon and oxygen isotopes of calcified root cells carbonate nodules and total inorganic carbon in the chinese loess paleosol sequence the application of paleoenvironmental studies abstract the continuous loess paleosol sequence on the chinese loess plateau clp is a major terrestrial archive of paleoclimate changes the carbon and oxygen isotopes of soil carbonate in the sequence have long been applied to reconstruct quaternary climate changes yet which soil carbonates has the integrity to signify the climate variability still remains a controversy hence in this study we compared carbon and oxygen isotopic compositions of soil inorganic carbon tic carbonate nodules and calcified root cells crcs found in the xifeng loess profile on the clp to test their significance as paleoclimate indicators the x ray diffraction and scanning electron microscope analysis performed on crcs prove that they are pure micro scale calcite minerals with distinct epidermal cell structures of plant rootlets the results of 14c dating show that crcs and nodules have evident translocation of younger carbon while the tic appears more or less consistent with the model ages the 13ccrc values vary from 18 2 to 11 6 while the 18ocrc values range from 13 7 to 9 2 on the v pdb scale spanning 6 6 and 4 5 respectively the contrast shows that 13ccrc values are more negative than those of nodules and tic and the 13ccrc values disperse within a large spectrum which reflects a rapid germination of root cell calcification with little or even no time for diffusion process within individual c3 plant roots we argue that pure secondary micro carbonates like crcs are closely associated with the plant genic carbon their isotope values carry seasonal or even single event based climate signals our study also suggests that stable isotope compositions of carbonate nodules and tic are interfered by primary carbonate minerals thus it should be used with caution when applying those materials for researches of paleoclimate changes

strengthening of the east asian summer monsoon revealed by a shift in seasonal patterns in diet and climate after 2 3 ma in northwest china article i nfo to examine climate variability in northwest china in the late cenozoic and to test hypotheses regarding the development of c4 ecosystems and the dynamics of the asian monsoons the carbon and oxygen isotopic compositions of 32 bulk and 368 serial tooth enamel samples from herbivores in the linxia basin gansu province ranging in age from 25 ma to the present were determined the results corroborate and improve the record previously obtained from the area showing that all mammals in the linxia basin lived in habitats consisting primarily of c3 vegetation prior to 2 3 ma and that c4 grasses did not become a significant component of local ecosystems until the quaternary the data also show that shifts in climate to drier and or warmer conditions after about 14 9 5 7 and 2 5 ma as indicated by positive 18 o excursions in the bulk enamel 18 o record were accompanied by increased seasonality whereas negative 18 o shifts in the bulk

lower temperature as the main cause of c4 plant declines during the glacial periods on the chinese loess plateau abstract the distribution of c3 and c4 plants changed in regionally contrasting ways during the last glacial period c4 plant expansion in low latitude africa and america coincided with c4 plant decreases in mesoamerica and the us great plains this c4 plant expansion has been attributed to lower pco2 and increased aridity and the decline in c4 plants is believed to have been caused by increased winter precipitation and lower temperatures however it is still difficult to generalize whether pco2 temperature or aridity was mainly responsible for c3 vs c4 vegetation changes during glacial periods paleoclimate conditions on the chinese loess plateau clp offer opportunities to further evaluate the role of temperature in the c3 vs c4 competition detailed climate records have shown that the clp region was drier and colder during glacial periods with aridity favoring c4 expansion and lower temperatures favoring c3 expansion here we present two high resolution compound specific carbon isotope records of n alkanes from the clp as vegetation biomarkers to estimate the relative abundance of c4 plants during the last two glacial interglacial transitions more negative 13c values during the glacial periods from two clp sites clearly show that in contrast with low latitude sites c4 plants declined this decrease in c4 abundance was caused by lower temperature despite the lower pco2 and increased aridity on the clp during glacial time

stable carbon isotope records of black carbon on chinese loess plateau since last glacial maximum an evaluation on their usefulness for paleorainfall and paleovegetation reconstruction abstract stable carbon isotope composition of soil organic matter 13 c som has been widely used to infer past environmental or vegetation c 3 c 4 changes however as a carbonaceous product of incomplete burning of biomass the carbon isotope signature of black carbon bc has received little study and a limited usage on this purpose moreover the environmental or vegetation indication of bc carbon isotope composition 13 c bc in sedimentary records remains ambiguous although the 13 c bc is supposed to reflect carbon isotope composition of vegetation being burnt this deserves site specific studies here we analyzed 13 c bc and 13 c som on loess paleosol samples from lijiayuan and yangling sections on chinese loess plateau clp spanning the last glacial maximum to decipher the environmental or vegetation meaning of 13 c bc at each study site opposite changing patterns were observed on the 13 c bc values for the two sections the 13 c bc at yangling in southern part of the clp varied from 19 18 to 21 93 mean 20 62 with more positive values occurred during the middle holocene than those during the lgm demonstrating more c 4 plants occupied in the region during the warm humid middle holocene this is consistent with the changing pattern widely documented in 13 c som records over the clp during the same period by contrast the 13 c bc at lijiayuan in northwestern part of the clp changed within the range of 21 83 24 64 mean 23 34 and displayed more negative values during the early middle holocene with respect to the lgm period the 13 c bc at lijiayuan were about 2 5 lower than those at yangling indicating a northward decrease of c 4 plants on the clp the anti phased changes of 13 c bc at lijiayuan were considered to reflect variations in paleorainfall because the vegetation is dominated by c 3 plants at the study site and carbon isotope compositions of c 3 plants decrease as rainfall increases compared with 13 c som record at the same profile 13 c bc seem biased against capturing c 4 signal during mid holocene possibly due to dominance of c 3 plants at the study site during fire seasons and a potentially extra source of bc from forest fires occurred on surrounding mountains by contrast 13 c bc tend to exaggerate c 4 signal during the lgm attributed to a possible shift of fire season from spring to summer these findings suggest that we probably underestimate the abundance of c 4 plants during mid holocene and overestimate c 4 biomass during the lgm using bc carbon isotope composition

handbook of environmental isotope geochemistry vol 1 the terrestrial environment a p fritz and j ch fontes editors elsevier amsterdam 1980 xii 532 pp u s 90 25 dfl 185 00

spatial patterns of vegetation and climate on the chinese loess plateau since the last glacial maximum abstract in order to identify the spatial patterns of vegetation and climate on the chinese loess plateau since the last glacial maximum lgm pollen analysis was conducted for loess deposits from seven sites which constitute two north south and west east transects across the plateau results show that steppe prevailed both in the lgm and the holocene optimum during the lgm vegetation in the northwest mainly consisted of artemisia echinops type taraxacum type and chenopodiaceae and vegetation in the southeast was characterized by the same types but with a slight increase in poaceae during the holocene optimum vegetation was more diverse with poaceae artemisia echinops type and chenopodiaceae dominant in the northwest and pinus corylus poaceae artemisia and selaginella sinensis dominant in the southeast our records also show that from the lgm to the holocene optimum the presence of echinops type and taraxacum type pollen decreased while poaceae pollen became more prevalent as it has been found that most species of poaceae prefer relatively humid conditions and abundances of echinops type and taraxacum type increase in desert vegetation a new proxy poaceae echinops type taraxacum type ratio p e t was thus developed to compare the spatial differences in climate between the lgm and the holocene optimum with high p e t values indicating relatively warm and wet conditions the p e t ratio shows an overall southward and eastward increase for both the lgm and the holocene optimum furthermore it exhibits a prominent north south and west east gradient during the holocene optimum but displays a flat one during the lgm indicating more pronounced spatial contrasts in climate during the holocene than in the lgm this phenomenon may be attributed to the unique geographic location of the loess plateau which was located in the marginal zone of the east asian summer monsoon during interglacials but was dominated by the winter monsoon during glacials due to a southward displacement of climate zones

pedostratigraphy of chinese loess deposits and climatic cycles in the last 2 5 myr summary the pedostratigraphy and magnetostratigraphy of several sections in the loess plateau of north central china have been investigated and correlated the most complete and distinct loess paleosol sequence occurs in the baoji section of the southern part of the plateau thirty seven pedostratigraphic units are identifiable in the baoji section and correlated with those in other parts of the plateau the sequence represents thirty seven major cold to warm climatic cycles in the last 2 5 myr at about the time of the matuyama gauss magnetic reversal an abrupt climatic event occurred in north china represented by the shift of the well weathered red clay formation below the m g boundary to the alternating loess and paleosol units above marking the beginning of a new epoch in the course of climatic evolution in addition there are two other major shifts of dominant periods of climatic cycles recorded in the loess paleosol sequences one occurring at about 1 5 myr and another at about 0 8 myr the pedostratigraphy of loess deposits in north central china provides an independent measure of the world wide climatic fluctuations and is now the most complete and reliable record of the major climatic cycles in the last 2 5 myr

seasonal bias in the formation and stable isotopic composition of pedogenic carbonate in modern soils from central new mexico usa in order to better calibrate pedogenic carbonate as a proxy for past environments we compared the stable isotopic composition of soil co 2 soil water and pedogenic carbonate in young soils from central new mexico usa seasonal changes in the 13 c value of soil co 2 the 18 o value of soil water and the soil temperature were monitored to establish the timing of isotopic equilibrium with the carbonate calcite solubility was calculated from measured temperatures and co 2 concentrations in the soil this approach allowed us to determine the conditions associated with pedogenic carbonate formation carbon isotope equilibrium oxygen isotope equilibrium and minimum calcite solubility all occurred simultaneously during warm dry conditions in may 2008 when soil co 2 concentrations were low it is therefore concluded that pedogenic carbonate forms during warm dry periods and does not record mean growing season conditions as typically assumed the seasonal bias in pedogenic carbonate formation may explain the occurrence of pedogenic carbonate in monsoon climates and its absence in regions where annual precipitation is more uniformly distributed the implications of the seasonal bias for stable isotope based paleoenvironmental reconstructions are that paleoelevations may have been previously over or underestimated paleoatmospheric co 2 concentrations likely have been signifi cantly overestimated and pedogenic carbonate provides a c 4 biased record of paleovegetation especially in dry soils

acetic acid leachable elements in pedogenic carbonate nodules and links to the east asian summer monsoon carbonate nodules at the base of paleosols within chinese loess are products of pedogenic neoformation and thus have great potential to document the summer monsoon history here we present mineralogical and elemental compositions of carbonate nodules from a north south loess transect of northern china for the last and penultimate interglacials x ray diffraction patterns show that the nodules are composed mainly of calcite together with some silicate minerals such as quartz plagioclase orthoclase illite and kaolinite elemental composition of the acetic acid leachable fraction is characterized by extremely high ca concentration and modest k and mg content followed by al si sr mn fe p na ba pb th and u based on the mineralogical data and relationship between carbonate and the leachable element content we suggest that k mg sr ba and u mainly come from clay minerals na from highly soluble salts trapped by calcite particles and al and si from amorphous phases of pedogenic origin for both the last and penultimate interglacials the na content decreases from north to south while the al si and u concentrations show a southward increasing pattern these characteristics all suggest a southward decrease in aridity across the chinese loess plateau for both interglacials consistent with the pattern of a southerly increase in pedogenic development for the two interglacial soils and with the pattern of the present north south rainfall gradient therefore na al and na si ratios in the acetic acid extract are efficient proxies for aridity and are ultimately controlled by the summer monsoon precipitation i e high ratios indicate weakened summer monsoon intensity in addition the significant content of highly soluble na salts in carbonate nodules highlights soil dewatering as an important mechanism for the formation of pedogenic carbonate at least in the case of the northern loess plateau

petroleum geology and potential hydrocarbon plays in the gulf of suez rift basin egypt the gulf of suez in egypt has a north northwest south southeast orientation and is located at the junction of the african and arabian plates where it separates the northeast african continent from the sinai peninsula it has excellent hydrocarbon potential with the prospective sedimentary basin area measuring approximately 19 000 km 2 and it is considered as the most prolific oil province rift basin in africa and the middle east this basin contains more than 80 oil fields with reserves ranging from 1350 to less than 1 million bbl in reservoirs of precambrian to quaternary age the lithostratigraphic units in the gulf of suez can be subdivided into three megasequences a prerift succession pre miocene or paleozoic eocene a synrift succession oligocene miocene and a postrift succession post miocene or pliocene holocene these units vary in lithology thickness areal distribution depositional environment and hydrocarbon importance geological and geophysical data show that the northern and central gulf of suez consist of several narrow elongated depositional troughs whereas the southern part is dominated by a tilt block terrane containing numerous offset linear highs major prerift and synrift source rocks have potential to yield oil and or gas and are mature enough in the deep kitchens to generate hydrocarbons geochemical parameters sterane distribution and biomarker correlations are consistent with oils generated from marine source rocks oils in the gulf of suez were sourced from potential source rock intervals in the prerift succession that are typically oil prone type i and in places oil and gas prone type ii or are composites of more than one type multiple types i ii or iii for oil prone oil and gas prone or gas prone respectively the reservoirs can be classified into prerift reservoirs such as the precambrian granitic rocks paleozoic cretaceous nubian sandstones upper cretaceous nezzazat sandstones and the fractured eocene thebes limestone and synrift reservoirs such the miocene sandstones and carbonates of the nukhul rudeis kareem and belayim formations and the sandstones of south gharib zeit and

stable isotope geochemistry of pedogenic carbonates in loess derived soils of northeastern iran paleoenvironmental implications and correlation across eurasia despite the occurrence of pedogenic carbonates in loess paleosol sequences of northern and northeastern iran there is no information about stable isotope geochemistry of pedogenic carbonates in these regions this paper presents the first stable isotope data on pedogenic carbonates in loess derived soils of northeastern iran southern eurasian loess belt carbon and oxygen stable isotope values of pedogenic carbonates in different landforms were measured using mass spectrometry based on climatic data there is no possibility for soil leaching and pedogenic carbonate formation under the present arid conditions stable oxygen and carbon isotopic data suggest two separate periods of carbonate formation these periods are characterized by either lower or higher temperatures during post glacial than today and paleoecological conditions dominated by c3 and c4 plants respectively hemispheric correlation of loess deposits based on isotopic data of pedogenic carbonates shows a strong positive correlation for the post glacial carbonates nodules of northeastern iran and european russia this suggests a similar mechanism of carbonate formation and also the impact of westerlies in these regions we present the first quantitative isotopic data for paleoenvironment of northeastern iran however more quantitative investigations about the holocene and the last interglacial paleoenvironments of northeastern iran are needed

loess stratigraphy in central china abstract the loess deposits in central china record world wide climate changes of the last 2 5 ma numerous climatic oscillations are marked by alternating loess and soil units with continuous coverage of the matuyama and brunhes epochs magnetic susceptibility of the deposits correlates closely with the oxygen isotope record of the deep sea sediments and provides an independent measure of climate and time the key marker bed of the chinese loess sequence is the paleosol s5 the time equivalent of the mid brunhes oxygen isotope stages 13 14 and 15 it marks a prolonged interval of warm humid climate lasting from approximately 615 to 470 thousand years ago several episodes of river downcutting coincide with deposition of the exceptionally thick loess units l1 oceanic oxygen isotope stages 2 to 4 l2 stage 6 l5 stage 12 l6 stage 16 l9 stage 22 l15 stage 38 about 1 15 ma and ws4 about 2 3 ma these erosional events are interpreted as a result of episodic uplift of the loess plateau the deposition of the earliest loess layers between 2 5 and 2 3 ma ago marks a first order shift from warm and humid environments toward harsh continental steppes comparable to those of the middle and late pleistocene little if any lithologic or paleontologic changes were noted within or above the olduvai magnetozone so that the proposed plio pleistocene boundary at approximately 1 65 ma has no lithostratigraphic and biostratigraphic representation in the chinese loess series comparison with the deep sea drilling program core 552a in the north atlantic and with the santerno river section near bologna shows that the occurrence of the earliest loess in china coincides with the timing of the first significant ice rafting in the north atlantic and with the appearance of cold water foraminifers in the marine deposits of northern italy an extension of the stage system of the oxygen isotope signal extended back to the gauss matuyama boundary is proposed

chinese loess and the paleomonsoon abstract this paper presents a general review of the recent research advances of the east asian paleomonsoon based mainly on studies of the loess soil sequences in the chinese loess plateau in the last 2 6 million years the paleomonsoonal history may be divided into about 166 events on a time scale of the earth s orbital variations during the last glacial period millenial scale oscillations of the monsoon system were prominent which can be fairly well correlated with the dansgaard oeschger cycles recognized in the greenland ice cores the monsoonal rainfall belt has experienced a wide repeated advance retreat change during the glacial interglacial cycles of the pleistocene both temporal and spatial changes of the monsoon system in the quaternary could have been linked closely to global ice volume variations

baoji type pedostratigraphic section loess plateau north central china abstract the baoji section is judged to be the most complete pedostratigraphic section on the loess plateau of north central china it is located about 5 km north of the city of baoji and consists of 37 paleosols formed during more than the last 2 5 ma it is designated here as the type pedostratigraphic section with formally named geosols following the rules of the north american commission on stratigraphic nomenclature geochronological control is based largely on magnetostratigraphy with the brunhes matuyama and gauss epochs and jaramillo and olduvai events clearly recognized the baoji geosols can be correlated with equivalent pedostratigraphic units throughout the loess plateau by a combination of magnetostratigraphy and character position and the association of the pedostratigraphic units within the quaternary succession the variation of the geosols suggests climatic cycles of varying intensity and duration but generally warmer and moister conditions when compared with the loess units that suggest colder and drier periods

changes in plant richness and evenness since marine isotope stage 2 on the chinese loess plateau the warming period from marine isotope stage 2 mis 2 to the mid holocene provides a useful analog for assessing the impact of global warming on plant diversity previously published pollen records from ten loess sections across the chinese loess plateau clp have shown that herbs were dominant during both mis 2 and the mid holocene during mis 2 the vegetation in the eastern part was characterized mainly by artemisia together with taraxacum type echinops type and chenopodiaceae and by echinops type chenopodiaceae nitraria ephedra and picea in the western part during the mid holocene artemisia remained dominant while echinops type chenopodiaceae nitraria ephedra and picea decreased and poaceae became more prevalent from west to east during the mid holocene corylus quercus and pinus increased while artemisia and taraxacum type decreased in the present study two indices of plant diversity richness and evenness were analyzed using these published pollen data the results demonstrate that from mis 2 to the mid holocene plant richness increased at most of the studied sites while plant evenness decreased the increase in plant richness during the warming interval is in accordance with numerous geological records but differs from modern observations of the response of biodiversity to ongoing global warming the decrease in plant evenness is attributed to the increase in precipitation associated with the intensification of the east asian summer monsoon which resulted in an increase in the dominance of artemisia and the corresponding inhibition in the growth of other species therefore our results imply that plant richness in northern china would be expected to increase in a climate warming scenario while changes in plant evenness would largely depend on interspecific competition within a plant community

summer monsoon intensity controls c4 c3 plant abundance during the last 35 ka in the chinese loess plateau carbon isotope evidence from bulk organic matter and individual leaf waxes the natural abundance of c3 and c4 plants is affected by multiple environmental factors including temperature moisture balance and atmospheric pco2 the relative importance of these factors is a subject of considerable debate and may vary in different natural ecosystems previous studies generally focus on single loess sequences in the chinese loess plateau and conflicting conclusions on c4 c3 have been reached when studying carbon isotope ratios in carbonate and organic matter in this paper we report a comprehensive carbon isotopic characterization of total organic carbon toc and individual higher plant leaf waxes from five loess sequences spanning the last 35 ka from the chinese loess plateau clp the five coring sites encompass large gradients of annual mean temperature 9 2 13 9 c and precipitation 402 673 mm allowing us to assess the controlling mechanisms on c4 c3 plant ratios glacial interglacial sequences provide carbon isotope data for comparison with other climatic and environmental proxies such as lithology and magnetic susceptibility our results demonstrate that increased c4 c3 ratios are positively correlated with higher temperature and increased summer rainfall which characterize stronger summer monsoon in all five sites we conclude c4 abundance increases from the last glacial to the holocene in response to greater monsoon activity and that the c4 expression is suppressed in the cold and drier intervals

vegetation and climate changes in the western chinese loess plateau since the last glacial maximum abstract pollen analysis was conducted for loess deposits from three sites in the western chinese loess plateau i e the loess area west of the liupan mountains results show that during the last glacial maximum lgm in situ vegetation was dominated by artemisia and some drought tolerant species such as echinops type chenopodiaceae nitraria and ephedra while coniferous forest mainly picea flourished in nearby river valleys during the holocene optimum picea almost disappeared and echinops type chenopodiaceae nitraria and ephedra decreased vegetation was characterized by artemisia taraxacum type polygonaceae and leguminosae implying the climate was warmer and wetter than during the lgm during the late holocene chenopodiaceae indicator of human managed habitats increased in the study area indicating enhanced human activity the climate was warmer and more humid in the loess areas east of the liupan mountains than in the west during both the lgm and holocene optimum likewise a significant difference in specific plant types was observed between the east and west since the lgm during the lgm pinus and some broadleaf trees emerged but no picea forest grew while in the west vegetation was characterized by desert shrub and desert steppe in situ and by dark coniferous forests mainly picea in nearby river valleys during the holocene optimum treeline advanced upward as a result of increased temperature picea thus withdrew from the western loess areas therefore temperature is the major factor controlling the growth of picea in the chinese loess plateau

paleosol nodules as pleistocene paleoclimatic indicators luochuan p r china abstract loess deposits with their interbedded paleosols in central china record the world wide climatic changes of the past 2 5 ma the carbon and oxygen isotopic compositions of carbonate nodules in a loess profile at luochuan record paleoclimatic and paleoecologic conditions of paleosol formation interglacial periods during the past several 100 000 years it appears that the climatic and ecologic conditions during different periods of paleosol s 1 s 8 formation interglacial periods were very similar at luochuan and are marked by a presence of a mixed c 3 and c 4 type flora or mixed grass and wood and or shrublands

a model based determination of spatial variation of precipitation δ18o over china abstract many works show the dependence of precipitation 18o on altitude and latitude as a result of air temperature change the assumption that these quantitative relations can hold across a large geographical region can be used to give a rough estimation of local precipitation 18o where there is on direct observation of precipitation 18o although there truly exists uncertainty in the estimation an effect was made in this paper to establish the precipitation 18o pattern over the whole china based on regional topography and the 18o of meteoric precipitation this paper established a quantitative relationship between 18o in precipitation and latitude and altitude using the existing 18o data from 55 sites over china the model describes as 18oppt 0 0073lat2 0 3261lat 0 0015alt 9 7776 and was used to generate a higher resolution map of mean annual 18o for precipitation over china using geographic information system software integrating with latitude altitude and the moisture cycle this determination of the spatial distribution of 18o in modern precipitation of china provides important information for ancient climate and stable isotope hydrology studies

soils at the hyperarid margin the isotopic composition of soil carbonate from the atacama desert northern chile we evaluate the impact of exceptionally sparse plant cover 0 20 and rainfall 2 114 mm yr on the stable carbon and oxygen composition of soil carbonate along elevation transects in what is among the driest places on the planet the atacama desert in northern chile d 13 c and d 18 o values of carbonates from the atacama are the highest of any desert in the world d 13 c vpdb values from soil carbonate range from 8 2 at the wettest sites to 7 9 at the driest we measured plant composition and modeled respiration rates required to form these carbonate isotopic values using a modified version of the soil diffusion model of cerling 1984 earth planet sci lett 71 229 240 in which we assumed an exponential form of the soil co2 production function and relatively shallow 20 30 cm average production depths overall we find that respiration rates are the main predictor of the d 13 c value of soil carbonate in the atacama whereas the fraction c3 to c4 biomass at individual sites has a subordinate influence the high average d 13 c value 4 1 of carbonate from the driest study sites indicates it formed perhaps abiotically in the presence of pure atmospheric co2 d 18 o vpdb values from soil carbonate range from 5 9 at the wettest sites to 7 3 at the driest and show much less regular variation with elevation change than d 13 c values d 18 o values for soil carbonate predicted from local temperature and d 18 o values of rainfall values suggest that extreme 80 in some cases soil dewatering by evaporation occurs at most sites prior to carbonate formation the effects of evaporation compromise the use of d 18 o values from ancient soil carbonate to

the epicontinental subsiding margin of the triassic in northern israel north arabian plate abstract the triassic sedimentary pattern of the north arabian margin represents a transition from continental to deep marine we here present a transect part of this suite from southern to northern israel cuttings from the ramalla s and devora n boreholes were studied by petrographic and cathodoluminescence microscopy biotic and sedimentological components were grouped into microfacies upon which a carbonate evaporitic depositional facies model was based mid to inner ramp conditions persisted along the transect essentially following a s n depositional strike with outer ramp to basinal facies to the west five low order lo cycles were identified and integrated into a sequence stratigraphic model with eustatic tectonic and differential subsidence components lo cycle 1 is late anisian pelsonian cycle 2 is late anisian to longobardian cycle 3 is early carnian cycle 4 is late carnian and cycle 5 is at the carnian norian transition facies range from supratidal via lagoonal facies in late hst or lst to calcarenitic shoals and short term deepening to offshore at maximum flooding cycles 1 and 2 are non evaporitic with a clastic influx event in cycle 2 cycles 3 and 4 contain sabkha or salina evaporites in the lagoonal facies that end in the lower part of cycle 5 these facies group into a higher order cyclicity with discrete events that can be correlated between the boreholes depositional and burial history were correlated to alpine and arabian plate stratigraphy over 20 myr from the anisian pelsonian to the norian siliciclastic carbonate and evaporite dominated environments indicate climates ranging from relatively humid to extremely arid rapid subsidence in the late anisian is attributed to neotethyan rifting of northeastern gondwana from latest anisian to early carnian reduced subsidence took place in the face of eustatic sea level rise renewed subsidence in the carnian is attributed to further neotethyan rifting subsidence terminated in the norian with uplift to the north attributed to pre volcanic doming

hydrogen isotope ratios of leaf wax n alkanes in loess and floodplain deposits in northern china since the last glacial maximum and their paleoclimatic significance abstract the hydrogen isotopic composition of leaf wax n alkanes d n alkane is increasingly used as a proxy for estimating d of past precipitation d p however aridity can also affect sedimentary d n alkane complicating the interpretation of paleo d n alkane records in order to evaluate the effects of the complex interactions and balance between precipitation hydrogen isotope composition and aridity on sedimentary d n alkane records we present two d n alkane records from the north china plain and the western chinese loess plateau across a steep east west climatic gradient in the east asian summer monsoon area since the last glacial maximum the estimated d p changes based on a present day relationship between d p and rainfall amounts can explain much of the d n alkane variations in the north china plain but do not explain the large variations of d n alkane in the western chinese loess plateau comparison of d n alkane records with observed d n alkane values in modern plants and published pollen data indicates that changes in vegetation play a minor role in the variations of d n alkane instead d n alkane values are coincident with aridity both temporally and spatially i e the higher d n alkane values the drier climate and vice versa aridity effects are more evident in the western chinese loess plateau than in the north china plain therefore on glacial interglacial scale sedimentary d n alkane records from the north china plain mostly reflect changes in d p values whereas those from the western chinese loess plateau largely reflect the effects of aridity mainly due to a greater evapotranspirational deuterium enrichment caused by a drier climate in the western chinese loess plateau than in the north china plain further calibrations from modern sediments are required to better define the quantitative relationship between the d n alkane and climate in northern china

pedostratigraphy and paleomagnetism of a 7 0 ma eolian loess red clay sequence at lingtai loess plateau north central china and the implications for paleomonsoon evolution abstract a 305 m thick loess red clay sequence was discovered recently at lingtai which is located in the middle part of the chinese loess plateau it consists of a complete pleistocene loess soil sequence with a thickness of about 175 m and 130 m of tertiary red clay deposits the red clay sequence at lingtai is the thickest one presently known in the loess plateau field observations show that the lingtai red clay contains over 110 couplets of pedogenic b horizons and horizontal carbonate nodule horizons and that it can be regarded as an extremely thick soil complex paleomagnetic studies of 680 samples suggest that the basal age of the lingtai loess red clay sequence is about 7 05 ma grain size analysis of samples taken at 3 3 cm intervals indicates that the red clay has the same sedimentological characteristics as those observed in the loess thus suggesting a wind blown origin of the tertiary red clay and continuous atmospheric dust deposition in the loess plateau during the last 7 05 ma the pedogenic characteristics of the paleosols within the pleistocene loess and the b horizons in the red clay suggest that the east asia summer monsoon in the latest miocene may have already been slightly stronger than that during the holocene this implies that at about 7 5 ma bp the tibetan plateau could have been uplifted to a critical height in maintaining the east asia summer monsoon system observations of the loess red clay sequence also suggest that the long term changes in the east asia summer monsoon strength have been nonlinear since the latest miocene

microcodium in chinese loess as a recorder for the oxygen isotopic composition of monsoonal rainwater abstract records of asia summer monsoon asm from the chinese loess and the speleothem display distinct features the very different proxies that were applied to the two archives may be responsible for this discrepancy a direct comparison between the speleothem and the loess records under the same proxy system of rainwater 18o may help to resolve this puzzle here we show that the calcified microcodium in the loess deposits may record the oxygen isotopic composition of the summer rainwater a microcodium based 18o record covering the past 140 kyrs was generated which shows similar magnitude of the overall variation to that of the speleothem records however much weaker precession variability was registered in the microcodium record during the last interglacial period instead the microcodium 18o record is more consistent with the widely used summer monsoon proxy of magnetic susceptibility in the loess deposits with clear glacial interglacial pattern this similarity may originate from the low sedimentation rate of the interglacial paleosol layer that preferentially record the peak asm signals on the precession band it is also possible that the orbital variability of asm between the north china and south china is inherently different with more ice volume related influence in the north a longer microcodium 18o record in sequences of higher sedimentation rate and a reliable record of summer rainfall may help to resolve these possibilities

global basin classification system a proposed system classifies sedimentary basins worldwide into specific as well as general categories the geologic history of each basin may be subdivided into cycles using three parameters basin forming tectonics depositional sequences and basin modifying tectonics sedimentary basins may be simple with one or two tectonic sedimentary cycles or they may be complex polyhistory basins with many different cycles and events there are eight simple cycle types in this classification which cover continental continental margin and oceanic areas the eight basic cycle types their depositional fills and tectonic modifiers have been given letter and number symbols so that the specific geologic history of each basin may be written as a formula these formulas may then e compared and similarities or differences between basins noted

a new osl chronology for dust accumulation in the last 130 000 yr for the chinese loess plateau abstract a sensitivity corrected multiple aliquot regenerative dose protocol has been developed for fine grained quartz osl dating of chinese loess its reliability has been assessed on the basis of the methodology and by dating reference samples of known age close to the transition from the last interglacial paleosol s 1 to the last glacial loess l 1 which corresponds to the marine oxygen isotope stage mis 5 4 transition on the basis of the fine grained quartz osl age estimates for 33 loess samples from the upper part of the luochuan profile a detailed chronostratigraphy of continuous dust accumulation in the past 130 ka has been proposed changes in the accumulation rate occurred during the last glacial period mis 4 to mis 2 unexpectedly high accumulation rates were found in the weakly developed l 1 2 s paleosol of the last interstadial mis 3 rather than in the classic l 1 1 and l 1 3 loess of the cold dry glacial condition mis 2 and 4 the osl ages show some disagreement with the previous numerical chronology for the loess paleosol sequence based on correlation of variations in grain size with sedimentation rate the latter method resulted in an almost constant accumulation rate from 72 to 12 ka

climatically driven glacial interglacial variations in c3 and c4 plant proportions on the chinese loess plateau high resolution 13c records of bulk organic matter om from three loess paleosol successions from the central chinese loess plateau document systematic fluctuations in c3 and c4 plant abundance for certain intervals during the past 620 k y measured 13c values of om in paleosols are less negative by 0 5 4 and total organic carbon toc contents are higher by up to 0 5 wt relative to corresponding values in loess deposits the 13com and toc decrease from peak values in paleosols progressively into overlying and underlying loess deposits integrated 13com toc and magnetic susceptibility rec ords indicate an increase in c4 vegetation to 50 during peak paleosol formation and a decrease in c4 vegetation to 30 during loess deposition for three of the past glacial interglacial cycles these results indicate that c4 plant abundance declined during glacials in this mid latitude region driven primarily by a shift to enhanced winter precipitation and lower temperatures and further contribute to the rapidly growing body of evidence that low p co2 during pleistocene glacials was insufficient to trigger c4 plant expansion without coincident favorable climatic conditions

stable carbon isotope of black carbon in lake sediments as an indicator of terrestrial environmental changes an evaluation on paleorecord from daihai lake inner mongolia china abstract we measured the carbon isotope ratio of black carbon bc from the daihai lake sediment core dh99a in north central china with an objective to examine the effectiveness and sensitivity of the 13c values of bc 13cbc as a potential indicator of terrestrial environmental changes we first performed a statistical study on the available data regarding carbon isotope fractionation cif during the conversion of c3 and c4 vegetation to bc and observed that the mean cif for bc produced from c3 plants is 0 3 whereas that for bc from c4 plants is 1 7 this result provides a solid reference for reconstructing vegetation and environmental changes using the 13cbc values the 13cbc record in the dh99a sediment core spanning the last ca 10 000 years displayed large variations from 23 7 to 29 2 which suggests that c3 plants dominantly occupied the daihai lake region during the holocene the most negative 13cbc peaks coincided with high values of tree percentages and grain sizes which occurred under relatively wetter climatic conditions during the middle holocene ca 6500 3200 cal yr bp and an interval between 1700 and 1350 cal yr bp in contrast the least negative 13cbc values corresponded to low values of tree percentages and grain sizes during relatively drier phases of the early and late holocene the generally negative correlation of the 13cbc values with the tree percentages and grain sizes was thought to reflect a negative correlation of the 13cbc values with the monsoon precipitation this correlation is consistent with the response of carbon isotope in modern c3 plants to precipitation in north china therefore we developed a computational model to reconstruct the changes in annual precipitation over the daihai lake region using the 13cbc values the results indicated that the annual precipitation was highly variable ranging from 170 mm lower to 310 mm higher than that at present during the middle holocene whereas the annual precipitation was generally 70 mm lower than that at present during the early and late holocene the general features of the inferred precipitation changes using the 13cbc values are generally consistent with those reconstructed using pollen data of the same sediment core meanwhile the 13cbc values tend to register some extreme variations of monsoon precipitation which were not reflected in the pollen assemblages we conclude that the 13cbc values in the daihai lake sediments may serve as a sensitive and reliable proxy for monitoring monsoon precipitation

δ18o and δ13c records from a cenozoic sedimentary sequence in the lanzhou basin northwestern china implications for palaeoenvironmental and palaeoecological changes abstract in northwestern china carbonate 18 o variation has been closely associated with evaporation and precipitation whereas the variation of carbonate 13 c generally reflects patterns of palaeovegetation located within the transitional zone between the chinese loess plateau and the tibetan plateau the lanzhou basin has developed a continuous sequence of cenozoic sediments which have been subjected to detailed sedimentological and high resolution magnetostratigraphic analyses in the present study pedogenic carbonate o and c isotopic analyses were obtained throughout the entire cenozoic sequence the 18 o record exhibits a general positive trend with several abrupt changes a dramatic positive shift in the 18 o record at 33 ma indicates the initiation of the aridification process within the basin which was likely associated with the late eocene westward retreat of the tethys sea and global cooling two significant positive shifts in the 18 o record at 22 ma and 3 5 ma are synchronous with major increases in aeolian dust deposition on the chinese loess plateau and in the north pacific ocean suggesting the intensified aridity of the asian interior which is likely related to the stepwise uplift of the tibetan plateau via the blocking of water vapour pathways the 13 c values exhibit a weak positive trend with a remarkable shift at 3 5 ma this trend is likely related to a decrease in vegetation density in response to the ongoing cenozoic aridification whereas the shift at 3 5 ma may reflect the large scale expansion of c 4 plants

investigating the stratigraphy and palaeoenvironments for a suite of newly discovered mid cretaceous vertebrate fossil localities in the winton formation queensland australia the winton formation of central queensland is recognized as a quintessential source of mid cretaceous terrestrial faunas and floras in australia however sedimentological investigations linking fossil assemblages and palaeoenvironments across this unit remain limited the intent of this study was to interpret depositional environments and improve stratigraphic correlations between multiple fossil localities within the preserved winton formation in the eromanga basin including isisford lark quarry and bladensburg national park twenty three facies and six repeated facies associations were documented indicating a mosaic of marginal marine to inland alluvial depositional environments these developed synchronously with the final regression of the eromanga seaway from central australia during the late albian early turonian investigations of regional and local scale structural features and outcrop core and well analysis were combined with detrital zircon provenance signatures to help correlate stratigraphy and vertebrate faunas across the basin significant palaeoenvironmental differences exist between the lower and upper portions of the preserved winton formation warranting informal subdivisions a lower tidally influenced fluvial deltaic member and an upper inland alluvial member this work further demonstrates that the isisford fauna is part of the lower member of the preserved winton formation whereas fossil localities around winton including lark quarry and bladensburg national park are part of the upper member of the winton formation these results permit a more meaningful framework for both regional and global comparisons of the winton flora and fauna

spatial and temporal variability in the stable isotope systematics of modern precipitation in china implications for paleoclimate reconstructions the stable isotopic composition of materials such as glacial ice tree rings lake sediments and speleothems from low to mid latitudes contains information about past changes in temperature t and precipitation amount p however the transfer functions which link 18op to changes in t or p d 18op dt and d 18op dp can exhibit significant temporal and spatial variability in these regions in areas affected by the southeast asian monsoon past variations in 18o and d of precipitation have been attributed to variations in monsoon intensity storm tracks and or variations in temperature proper interpretation of past 18op variations here requires an understanding of these complicated stable isotope systematics since temperature and precipitation are positively correlated in china and have opposite effects on 18op it is necessary to determine which of these effects is dominant for a specific region in order to perform even qualitative paleoclimate reconstructions here we evaluate the value of the transfer functions in modern precipitation to more accurately interpret the paleorecord the strength of these transfer functions in china is investigated using multiple regression analysis of data from 10 sites within the global network for isotopes in precipitation gnip 18op is modeled as a function of both temperature and precipitation the magnitude and signs of the transfer functions at any given site are closely related to the degree of summer monsoon influence 18op values at sites with intense summer monsoon precipitation are more dependent on the amount of precipitation than on temperature and therefore exhibit more negative values in the summer in contrast 18op values at sites that are unaffected by summer monsoon precipitation exhibit strong relationships between 18op and temperature the sites that are near the northern limit of the summer monsoon exhibit dependence on both temperature and amount of precipitation comparison with simple linear models 18op as a function of t or p and a geographic model 18op as a function of latitude and altitude shows that the multiple regression model is more successful at reproducing 18op values at sites that are strongly influenced by the summer monsoon the fact that the transfer function values are highly spatially variable and closely related to the degree of summer monsoon influence suggests that these values may also vary temporally since the southeast asian monsoon intensity is known to exhibit large variations on a number of timescales annual to glacial interglacial and the magnitude and sign of the transfer functions is related to monsoon intensity we suggest that as monsoon intensity changes the magnitude and possibly even the sign of the transfer functions may vary therefore quantitative paleoclimate reconstructions based on 18op variations may not be valid

strengthened east asian summer monsoons during a period of high latitude warmth isotopic evidence from mio pliocene fossil mammals and soil carbonates from northern china the east asian monsoons have fluctuated in concert with high latitude warmth during the past several hundred thousand years with humid summer monsoon dominant climates characterizing warm intervals including interglacials and interstadials and arid winter monsoon dominant climates characterizing cool intervals including glacials and stadials of the states comprising the mid pleistocene to recent climatic regime interglacials are most similar in terms of high latitude ice volumes and temperatures to those extant during the late miocene and early pliocene thus an important question is whether mio pliocene climates in northern china were analogous to a hypothetical prolonged interglacial state with increased summer monsoon precipitation and expansion of forest and steppe environments at the expense of desert environments we utilize new and previously published carbon isotopic data from fossil teeth and soil carbonates to place constraints on paleovegetation distributions and to help infer the behavior of the monsoon system between 7 and 4 ma we find that plants using the c 4 photosynthetic pathway which today are largely grasses found in regions with warm season precipitation were present in northern china by late miocene time demonstrating that the c 4 expansion in china was not significantly delayed compared to the global c4 event during the late miocene early pliocene interval soil carbonate and tooth enamel 13 c data indicate 1 that nearly pure c 3 plant ecosystems existed in the southern chinese loess plateau clp and therefore ecosystems there were dominated by woody dicot herbaceous dicot or cool season grass vegetation or a combination of these and 2 that the clp was characterized by a pattern of northward increasing c 4 vegetation and aridity utilizing a broadened conceptual model for interpreting 13 c data and citing independent faunal floral and lithostratgraphic data we suggest that these patterns reflect northward expansion of forest and steppe ecosystems and relatively humid monsoon climates during the late miocene and early pliocene an important implication of this interpretation is that the forcing mechanism illuminated by the temporal correlation during the pleistocene between warm high latitudes and strong east asian summer monsoons is a robust feature of the eurasian tectonic climatic system that predates the plio pleistocene climatic reorganization