time scales of sedimentary transfer and weathering processes from u series nuclides clues from the himalayan rivers abstract in order to define time scales of erosion and sedimentary transfer in the himalaya 238 u 234 u 230 th disequilibria have been analysed in river bank sediments and in bedloads collected along the kali gandaki river one of the main nepalese rivers and in the ghaghara and gandak rivers two major plain tributaries of the ganges the th activity ratios and u th ratios in river sediments of the two ganges tributaries constantly decrease from upstream to downstream this is related to the maturation of sediments by weathering during their transfer to the plain the u series data allow to calculate a transfer time for the sediments in the alluvial gangetic plain from the chain front to the confluence with the ganges of about 100 kyr for both rivers the kali gandaki river sediment data highlight a decrease of both the th isotopic and u th ratios which is explained by a mixing between two sources with similar u th ratios but having suffered a different u th fractionation history interpretation of the u series data in the frame of this scenario gives long time scales of weathering of several 100 s kyr for the himalayan terranes the results imply that himalayan bedrocks are submitted to a long in situ stage of weathering before their erosion and transfer into the rivers in addition occurrence of similar u sr signatures in dissolved i e

the lost paleosols masked evidence for emergence and soil formation on the kimmeridgian jura platform nw switzerland abstract lagoonal carbonates of kimmeridgian age in nw switzerland formed in a tropical epeiric sea and exhibit indicators of subaerial emergence such as tidal biolaminites desiccation cracks flat pebble conglomerates and fenestral structures additionally 30 dinosaur tracksites from at least six stratigraphic intervals indicate repeated formation of land bridges between the platform and adjacent massifs populations of herbivorous and carnivorous dinosaurs necessitate substantial vegetation and consequently a soil cover but no striking evidence of paleosols have been found within the track bearing sequences however two stratigraphic levels exposed in nine outcrops exhibit distinctive hardgrounds that experienced early meteoric diagenesis during times of emergence initial induration began with the precipitation of thin micritic meniscus cements contemporaneously meteoric waters completely dissolved all aragonite leaving large voids iron hydroxides were precipitated in the uppermost 7 10 cm where they impregnated the porous micrite and constituted a separate cement generation which caused a penetrative dark red staining these aspects are suggestive of the formation of mediterranean type red soils on the emerged platform during transgression the soil was eroded and wave cut hardgrounds were superimposed on the hardgrounds formed during regression erosion is evidenced by micro karst truncated gastrochaenolites isp borings and the physical removal of steinkerns the eroded material including floral remains provided surplus nutrients leading to eutrophication this food rich environment supported the mass occurrence of gastropods in the nerineoid limestones and oysters nanogyra sp in the virgula marls

chemical weathering indices applied to weathering profiles developed on heterogeneous felsic metamorphic parent rocks abstract chemical weathering indices are commonly used for characterizing weathering profiles by incorporating bulk major element oxide chemistry into a single metric for each sample generally on homogeneous parent rocks weathering indices change systematically with depth however the weathering of heterogeneous metamorphic rocks confounds the relationship between weathering index and depth in this paper we evaluate previously defined chemical weathering indices for their suitability in characterizing weathering profiles developed on felsic heterogeneous metasedimentary bedrock from coweeta hydrologic laboratory north carolina usa among the weathering indices evaluated here the weathering index of parker wip is the most appropriate for application to weathering profiles on heterogeneous and homogeneous parent rock because the wip includes only the highly mobile alkali and alkaline earth elements in its formulation it yields values that differ greatly from those of the parent rock in addition the wip allows for aluminum mobility unlike other weathering indices these characteristics combine to make the weathering index of parker the most applicable index for studying the weathering of heterogeneous metasedimentary rocks however the wip should be applied judiciously as alkali and alkaline earth metals may be readily depleted during weathering in addition to reflecting weathering the chemical index of alteration cia chemical index of weathering ciw plagioclase index of alteration pia and vogt s residual index v may be sensitive to subtle geochemical changes such as hydrothermal alteration along a fault and or alteration at the water table weathering indices that include iron in their calculations were not included in this study because they do not distinguish between ferric and ferrous iron the oxidation state and distribution of iron in a weathering profile is influenced by the proportion of oxidation states in the pre weathered metamorphic rock and interaction with groundwater during weathering

holocene carbonate sedimentation on the west eucla shelf great australian bight a shaved shelf the southern continental margin of australia is a cool water carbonate sedimentary province located in a high energy swell dominated oceanographic setting a vibrocore transect of 14c dated sediments across the centre of the eucla shelf is the first record of holocene shelf deposition in the great australian bight much of the seafloor shallower than 70 m water depth the base of wave abrasion is bare cenozoic limestone in some places encrusted by late pleistocene coral rich limestone that is cemented by high magnesium calcite 12 mole mgco3 the areally extensive 100 km wide hard bored substrate supports an epibiota of coralline algae minor bryozoans and soft algae or is covered by patches of holocene sediment up to 1 5 m thick generally a basal bivalve lag 3 ka overlain by quartzose bioclastic palimpsest sand this pattern of active carbonate production but little accretion on the wave swept mid to inner shelf is similar to that on other parts of the southern australian continental margin the term shaved shelf is proposed for this style of carbonate platform formed by alternating periods of sediment accretion cementation and erosion the palimpsest sand is typically rich in bivalves coralline algae and locally detrital dolomite outer shelf holocene sediment below the base of wave abrasion but inboard of the shelf edge is a metre thick unit of fine microbioclastic muddy sand with minor delicate bryozoans overlying a 9 13 ka rhodolith gravel some of this outer shelf sediment appears to have been resedimented the shelf edge is a sandy and rocky seafloor with active bryozoan growth and sediment production the holocene sediments are enriched in coralline algal particles and conspicuous large foraminifers cf marginopora and depleted in bryozoans as compared to coeval deposits on the lacepede and otway shelves off southeastern australia these differences are interpreted to reflect warmer waters of the leeuwin current and prevalent downwelling in this area as opposed to the general upwelling and colder waters in the east

unravelling the origin of a paleogene unconformity in the latium abruzzi carbonate succession a shaved platform the latium abruzzi carbonate platform constitutes the sedimentary record from the triassic to the late miocene of the southern tethyan margin outcropping in the apennines this sedimentary succession is punctuated by an important hiatus between the end of the cretaceous and the early miocene this paleogene hiatus has long been interpreted as the result of prolonged subaerial exposure however no evidence of such exposure has ever been documented on the latium abruzzi platform this is contrary to the coeval and adjacent apulia and lessini carbonate platforms where a broadly developed paleokarst system formed between the eocene and the early miocene the assumption that the miocene marine transgression deeply eroded a karstified cretaceous substrate on the latium abruzzi platform is not supported because this surface appears in the field as a perfectly flat bioeroded paraconformable surface in this work a marine origin is proposed for this unconformity from late paleocene to early miocene the latium abruzzi carbonate platform was a shaved isolated platform exposed to wave action in the middle of the proto mediterranean area bioclastic sediment accumulated during transgressive and sea level highstand phases whereas in the following falling and lowstand stages sediment was eroded as the seafloor came into the zone of wave abrasion the sediment eroded from the platform was shed into the basin where it produced coarse bioclastic intercalations in the hemipelagites of the scaglia formation at the end of the oligocene when the adjacent basin was filled a small ramp was established in the transitional zone between the platform and the basin there cross bedded carbonates accumulated in middle to outer ramp environments the inner ramp remained within the zone of wave abrasion such that sediment generated there was washed out into the middle and outer ramp environments finally in the early burdigalian the mediterranean progressively evolved into closed sea during the initial stages of the closure of indo pacific connection the reduction of the wave base depth typical of an enclosed sea created increased accommodation space allowing sediments to accumulate and form the complete inner to outer ramp facies belts of the miocene latium abruzzi ramp

the monterey event within the central mediterranean area the shallow water record the middle miocene is an important time to understand modern global climate evolution and its consequences on marine systems the mid miocene climatic optimum between 17 0 ma and13 5 ma was the warmest time interval of the past 35 million years during which atmospheric co2 concentrations were lower than today in the mid miocene climatic optimum a significant carbon cycle perturbation occurred expressed as a last long term positive carbon isotope shift known in literature as the monterey carbon isotope excursion and recorded in open ocean settings in this work the lower to middle miocene carbon isotope records from three different domains of the central mediterranean are analyzed with the aim of identifying the local carbonate platform response to the major global carbon cycle perturbation of the monterey event carbon and oxygen isotope ratios have been measured on samples belonging to three different stratigraphic sections two of them representative of shallow water settings latium abruzzi and apula platforms and the latter of a hemipelagic setting umbria marche basin a well defined monterey carbon isotope excursion is recorded also in these shallow water sections despite their expected problematic stratigraphic constraints a reliable age model is provided by calcareous nannofossil biostratigraphy and strontium isotope stratigraphy in both carbonate platform successions examined the monterey carbon isotope excursion coincides with a spread of bryozoans over other carbonate producing biota the high productivity of the bryozoan dominated factory in the aphotic zone had an important control on the platform depositional profile the high rates of sediment production in the deeper aphotic and oligophotic zones produced a depositional profile of a low angle ramp this article is protected by copyright all rights reserved

pleistocene chemical weathering history of asian arid and semi arid regions recorded in loess deposits of china and tajikistan quaternary loess soil sequences in china and tajikistan are valuable archives of the chemical weathering history for arid and semiarid regions of asia the development of new proxies independent of grain size are vital to reconstruct the long term chemical weathering history of eolian deposits in this study we analyze major elemental and rb sr and ba concentrations of decarbonated residue from representative loess and soil units along a north south transect on the chinese loess plateau and compare these concentrations among different grain size fractions results show that most of the elemental abundances and ratios vary considerably among different grain size fractions for both loess and paleosols indicating transport driven compositional differentiation of minerals during subaerial transport however cao na2o mgo tio2 ratios show little variation among different size fractions for the loess soil transect loess soil sequences at lingtai northern china and chashmanigar southern tajikistan for the past 1 50 1 77 ma show lower cao na2o mgo tio2 ratios in soil units than in adjacent loess horizons in good agreement with greater weathering intensity in soils than in loess units the cao na2o mgo tio2 ratio of the decarbonated residue is therefore a reliable proxy for chemical weathering of loess deposits that is independent of grain size the cao na2o mgo tio2 ratios of the lingtai and chashmanigar sections display a relatively regular oscillation within a narrow range in the early pleistocene and a rapid increase in average values and in variance from 0 85 0 6 ma to the present indicating lowered chemical weathering intensity in both the dust source regions and the depositional areas this event may be causally related to the expansion of northern hemisphere ice and or the regional tectonic uplift of high mountains in asia since the mid pleistocene

deep sea records of the continental weathering and erosion response to east asian monsoon intensification since 14 ka in the south china sea we analyzed sediment from ocean drilling program odp site 1144 in the northern south china sea to examine the weathering response of se asia to the strengthening of the east asian monsoon eam since 14 ka our high resolution record highlights the decoupling between continental chemical weathering physical erosion and summer monsoon intensity mass accumulation rates ti ca k rb hematite goethite and sr 87 sr 86 show sharp excursions from 11 to 8 ka peaking at 10 ka clay minerals show a shorter lived response with a higher kaolinite illite chlorite ratio at 10 7 9 5 ka however not all proxies show a clear response to environmental changes magnetic susceptibility rises sharply between 12 and 11 ka grain size becomes finer from 14 to 10 ka and then coarsens until similar to 7 ka but is probably controlled by bottom current flow and sealevel sr and nd isotopes show that material is dominantly eroded from taiwan with a lesser flux from luzon while clay mineralogy suggests that the primary sources during the early holocene were reworked via the shelf in the taiwan strait rather than directly from taiwan erosion was enhanced during monsoon strengthening and caused reworking of chemically weathered pleistocene sediment largely from the now flooded taiwan strait which was transgressed by similar to 8 ka cutting off supply to the deep water slope none of the proxies shows an erosional response lasting until similar to 6 ka when speleothem oxygen isotope records indicate the start of monsoon weakening although more weathered sediments were deposited from 11 to 8 ka when the monsoon was strong these are reworked and represent more weathering during the last glacial maximum lgm when the summer monsoon was weaker but the shelves were exposed c 2012 elsevier b v all rights reserved

long term cooling drying record of north china since the middle pleistocene from geochemical evidence of a 150 m deep drill core beijing plain china the quaternary strata in north china primarily consist of fluvial sediments which react strongly to east asian monsoon circulation however the records of the quaternary climate change history in terms of these fluvial sedimentations were limited which impeded understanding the east asian monsoon evolution in north china thus a 150 m deep drill core was collected from changping in the beijing plain to reconstruct the quaternary palaeoenvironmental changes the core was chronologically well constrained using palaeomagnetic and thermoluminescence dating the magnetostratigraphic result indicated that the brunhes matuyama boundary is at 134 2 m 0 78 ma and the age at the bottom of the core is 1 07 ma the thermoluminescence tl dating of the upper sand at similar to 2 m was 10 4 ka the chemical weathering history since the middle pleistocene in beijing plain was reconstructed by using geochemical proxies including selected major element pairs chemical index of alteration and al2o3 cao na2o k2o diagrams the cia value of the changping core ranged from 50 3 to 69 4 average 59 2 which indicated that the sediment has experienced incipient to intermediate chemical weathering during the middle pleistocene the result of a cn k figure shows a high plagioclase to k feldspar ratio in the source which would be indicative of a granodiorite gd source from jundu mountains north of the beijing plain all the geochemical results revealed a long term gradual decrease of weathering since the middle pleistocene which implied a long term increasing aridification cooling in the beijing plain c 2014 elsevier ltd and inqua all rights reserved

cratered cobbles in triassic buntsandstein conglomerates in northeastern spain an indicator of shock deformation in the vicinity of large impacts comment and reply ernstson et al 2001 1 discuss the origin of cratered cobbles in triassic buntsandstein conglomerates in northeastern spain they conclude that the indentations on the cobbles were induced by shock deformation in the vicinity of large impacts they report that pebbles are radially cracked at

dynamics of tethyan carbonate platforms tethyan carbonate platforms are relatively short lived depositional systems which were born developed died and sometime resurrected in a tectonically active area in contrast with pericratonic platforms which are generally huge in size hundreds of kilometers across and show wide facies belts very gentle slopes ramps and transitional boundaries tethyan carbonate platforms are smaller tens of kilometers and have steep slopes generally faulted boundaries and abrupt facies changes it appears clear that the overall control on these two contrasting systems is the geodynamic milieu relatively stable in the first case where eustatic oscillations and long term subsidence are probably the main dictators quite dynamic and aggressive in the second one where carbonate platforms developed through the entire geodynamic spectrum rifting transtension transpression and collision of the wilson cycle primary controls on tethyan carbonate platforms appear to be tectonics most important and eustatic sea level oscillations which determine their emplacement growth and decay their overall shape and architecture are a function of these factors secondary factors affecting tethyan carbonate platform evolution are physiography oceanographic conditions and biology as a function of geologic time especially across the mesozoic tertiary boundary facies and facies distribution and to a lesser extent their shape are controlled by thesemore variables less

late holocene forcing of the asian winter and summer monsoon as evidenced by proxy records from the northern qinghai tibetan plateau abstract little is known about decadal to centennial scale climate variability and its associated forcing mechanisms on the qinghai tibetan plateau a decadal resolution record of total organic carbon toc and grainsize retrieved from a composite piston core from kusai lake nw china provides solid evidence for decadal to centennial scale asian monsoon variability for the northern qinghai tibetan plateau during the last 3770 yr intensified winter and summer monsoons are well correlated with respective reductions and increases in solar irradiance a number of intensified asian winter monsoon phases are potentially correlated with north atlantic climatic variations including bond events 0 to 2 and more recent subtle climate changes from the medieval warm period to the little ice age our findings indicate that asian monsoon changes during the late holocene are forced by changes in both solar output and oceanic atmospheric circulation patterns our results demonstrate that these forcing mechanisms operate not only in low latitudes but also in mid latitude regions the northern qinghai tibetan plateau

linkage between lake xingkai sediment geochemistry and asian summer monsoon since the last interglacial period in this study we present the element geochemical data of core xk08 a2 drilled from lake xingkai khanka northeast china the study aims to examine the changes of sediment provenance and geochemical composition in response to asian summer monsoon variability since the last interglacial period major elemental analyses on lacustrine samples and sand samples from lake xingkai and the surrounding sandy ridges in northeast china indicate that their abundance varied in relatively narrow ranges the samples had only undergone the primary stage of chemical weathering similar ti al and k al ratios between the lacustrine samples from lake xingkai and the loess paleosol samples in north china were observed which suggests that they come from broadly similar desert sources due to the significant dependence on grain size and influence of sediments recycling chemical index of alteration of the lacustrine sediments could not be regarded as sensitive indicators of source regions weathering on the glacial interglacial timescale alternatively the geochemical proxies of the lacustrine sediments could be linked to the asian summer monsoon through the development of runoff and physical erosion in the catchment weakened asian summer monsoon caused more fine particles transported to the lake basin by reduced runoff in the last glacial period in contrast coarser and less weathered detritus are transported into the lake accompanying strengthened asian summer monsoon during the warm periods

middle eocene seagrass facies from apennine carbonate platforms italy abstract two stratigraphic sections located in the latium abruzzi monte porchio central apennines central italy and in the apulian carbonate platform s cesarea torre tiggiano salento southern italy were measured and sampled to document the sedimentological characteristic and the faunistic assemblages of middle eocene seagrass deposits the faunistic assemblages are dominated by porcellaneous foraminifera orbitolites alveolina idalina spiroloculina quinqueloculina triloculina and abundant hooked shaped gypsinids associated with hooked red algae and green algae halimeda fabiania rotaliids and textulariids as well as nummulitids are subordinated the samples were assigned to lutetian sbz13 16 according to the occurrence of nummulites cf lehneri alveolina ex gr elliptica idalina berthelini orbitolites complanatus slovenites decastroi and medocia blayensis at santa cesarea reticulate nummulites occur in association with alveolina spp and halkyardia minima marking the lower bartonian sbz17 three main facies associations have been recognised i larger porcellaneous foraminiferal grainstones with orbitolitids and alveolinids deposited into high energy shallow water settings influenced by wave processes that reworked the sediments associated with a seagrass ii grainstone to packstone with small porcellaneous foraminifera and abundant permanently attached gypsinids deposited in a more protected e g small embayment in situ vegetated environment iii bioclastic packstone with parautochthonous material reworked from the seagrass by rip currents and accumulated into rip channels in a slightly deeper environment the biotic assemblages suggest that the depositional environment is consistent with tropical to subtropical vegetated environments within oligotrophic conditions

a 6 ma chemical weathering history the grain size dependence of chemical weathering intensity and its implications for provenance change of the chinese loess red clay deposit abstract major element chemical analyses of the baishui loess red clay sequence 35 24 10 n 106 54 43 e gansu province china reveal that the chemical weathering intensities inferred from cia chemical index of alteration values have progressively weakened and increased in amplitude with decreasing age the general trend of the cia can be correlated well with the oxygen isotope variations of the deep sea sediments analyses of multiple size fractions

the ti al molar ratio as a new proxy for tracing sediment transportation processes and its application in aeolian events and sea level change in east asia abstract ti al molar ratios of sediments in various sedimentary environments are used to explain sediment transportation from source regions to sink areas samples were collected from outcrops soils fluvial lake and marine sediment environments initial ti al molar ratios of sediments are controlled by those of parent soils or rocks these ratios tend to decline gradually as a result of heavy mineral gravity fractionation during transportation sedimentary ti al molar ratios in sink areas such as lakes and pelagic environments are lower than those in source regions in this study for the changjiang river huanghe river and kaoping river ti al molar ratios decline considerably from downstream to estuary environments additionally well sorted aeolian sands have extremely low ti al molar ratios in northern china the ti al molar ratios of aerosol particles found in taiwan and the east china sea show reduced ratios as a result of asia dust storm episodes furthermore lower ti al molar ratios in deep ocean sediments were discovered by tracing the distribution of sedimentary ti al molar ratios in the south china sea when sea levels dropped during glacial periods the river estuary was closer to deep marine areas and carried more terrestrial sediments into deep marine environments the closer estuary with relatively higher ti al ratio would lead increase of ti al molar ratios in deep sea sediments in this study ti al molar ratio is promoted as a new proxy to help with understanding changes in sedimentary environments

geochemical and grain size evidence for the provenance of loess deposits in the central shandong mountains region northern china abstract widespread loess deposits in the central shandong mountains yield valuable paleoclimatic records for this currently semi humid monsoonal region of northern china the grain size distribution and major element composition for bulk samples and two grain size fractions

impact of carbonate producing biota on platform architecture insights from miocene examples of the mediterranean region abstract different types of carbonate platforms formed in the mediterranean during the miocene low angle homoclinal types of ramp distally steepened ramps flat topped platforms and reef rimmed shelves the critical differences between these platforms result from differences in the capacities of the carbonate systems to accumulate sediments above hydrodynamic base level ecologically controlled accommodation the various depositional profiles and facies belt distributions resulted from the interplay between different sediment production and redistribution processes and the internal architectures resulted from the response of each type of platform to changes in accommodation heterogeneities driven by high frequency sea level cycles are maximized in platforms ruled by shallow water euphotic framework dominated production and minimized in low angle ramps where sediment resulted from aphotic and oligophotic carbonate production in the mediterranean region there is no direct relationship between type of platform and global temperature as shown by the coeval occurrence of different platforms in similar latitudinal settings although temperature is a key limiting factor other paleoceanographic factors such as trophic resources may have also been along with biological evolution important factors influencing different types of carbonate producing biotas

surfaces with a long history the aptian top shu aiba formation unconformity sultanate of oman discontinuity surfaces in shallow marine carbonate successions may represent significant time gaps in the geological record of ancient epeiric neritic seas understanding the hidden geological information contained in major discontinuities is thus of key significance in palaeo environmental analysis sequence stratigraphy reconstructions of sea level change and basin evolution in the present paper the aptian top lower shu aiba formation discontinuity in the sultanate of oman is taken as a prominent example of a regionally extensive 100 000 km2 surface with a long up to 10 myr and complex geological history the top shu aiba discontinuity formed on the topographically elevated domain of the oman platform and represents in essence the late aptian time interval coeval carbonates in the intrashelf bab basin and oceanic rim indicate forced regression and sequence wise gradual down stepping available regional sedimentological sequence stratigraphic petrographic palaeontological and geochemical evidence from outcrops and cored wells in oman is summarized in part complemented by new data and reviewed in a process oriented context in the field the discontinuity is expressed as a low relief stained surface with evidence for a marine hardground stage being dominant indistinct features that indicate a transient meteoric precursor stage isotope shifts meteoric cements circumgranular cracks etc are present but their interpretation requires careful and detailed work this feature is remarkable as a series of relative sea level falls with amplitudes of up to several tens of metres from the early to late aptian boundary to the end of the aptian are reported from the middle east and elsewhere despite the palaeogeographic position of the study area in the tropical climate zone evidence of deep cutting karst features characteristic for many long term exposure surfaces worldwide is scarce acknowledging the fact that the modern world offers no genuine analogues for the lower aptian carbonate system in oman morphological similarities between actualistic wave eroded coastal terraces and the top shu aiba discontinuity are discussed critically this discussion may imply that during an exposure time of several million years the top shu aiba discontinuity experienced repeated stages of shallow flooding and emergence with each transgression removing portions of the underlying rock record the data shown here exemplify the complexity of hiatal surfaces in epeiric neritic carbonates and may serve as a case example for other major discontinuities

controls on the erosion of cenozoic asia and the flux of clastic sediment to the ocean rates of continental erosion may be reconstructed from variations in the rate of accumulation of clastic sediment most of which lies offshore global rates of marine sedimentation are usually considered to have reached a maximum after 3 4 ma driven by enhanced erosion in a variable glacial interglacial climate however a new compilation of seismic data from the marginal seas of asia now shows that only the red river reached its historic peak after 4 ma sediment flux from asia first peaked in the early middle miocene 24 11 ma well before the initiation of a glacial climate indicating that rock uplift and especially precipitation are the key controls on erosion at least over long periods of geologic time reconstructions of weathering in east asia show that faster erosion correlates with more humid warm climates in the early middle miocene changing to less erosive drier climates after 14 ma when antarctic glaciation begins average rates of sedimentation on most east asian continental margins since 1 8 ma are 5 6 times less than the modern fluvial flux implying that the flux to the oceans varies sharply on short timescales and is not always buffered over timescales of 10 4 yr by storage in flood plains

geochemical evidence of windblown origin of the late cenozoic lacustrine sediments in beijing and implications for weathering and climate change abstract the origin of lacustrine sediments in the middle latitudes of asia remains controversial in this study we conducted major and trace element analyses on 86 lacustrine samples from the x5 core in beijing to determine their origin and provenance the results indicate that their abundances all varied in relatively narrow ranges similar to those of the samples in the chinese loess plateau clp a high correlation of major and trace element abundances exists between our lacustrine samples and the clp samples ucc normalized major and trace element abundances also have a similar pattern between the lacustrine and the clp samples with the exception of a few elements with high solubility such as mg in the ternary diagrams of a cn k la th sc and zr 10 th sc and the correlation maps of major trace elements and their ratios four groups of the x5 lacustrine samples with different sedimentation stages 3 16 2 7 ma 2 7 1 8 ma 1 8 0 9 ma and 0 9 0 ma overlap well with each other and with the clp samples indicating that the x5 lacustrine samples are likely of windblown origin and possibly shared common unchanged dust source regions with the clp since the late pliocene this interpretation is supported by the overlap of the lacustrine samples from beijing with the clp samples in the correlation maps of ms vs sorting ms vs skewness ms vs kurtosis and kurtosis vs skewness analysis of the frequency and cumulative frequency curves indicates that the x5 lacustrine sediments were dominantly transported by the winter monsoon and the westerly circulation given more scattered distributions of different elemental ratios and grain size parameters of the x5 core lacustrine sediments compared to those of the clp samples local dust particles must have contributed occasionally which deserves further investigation in the future several chemical ratios such as rb sr na 2 o al 2 o 3 cao al 2 o 3 and chemical index of alteration cia were calculated for the lacustrine samples in beijing comparison of these ratios variations with those of the sea level of the south china sea and the global benthic 18 o record indicates that na 2 o al 2 o 3 and cia can be regarded as sensitive indicators of chemical weathering of lacustrine dust sediments in the mid latitudes of northern hemisphere

variation of rb sr ratios in the loess paleosol sequences of central china during the last 130 000 years and their implications for monsoon paleoclimatology abstract rb sr and magnetic susceptibility have been measured in the last interglacial glacial loess profiles at luochuan and huanxian central china a high degree of similarity between the parameters in both profiles suggests that variations of rb sr ratios in the sequence can be regarded as an indicator of east asian summer monsoon strength matching the rb sr record with the specmap 18o curve suggests that the rb sr ratio responds sensitively to changes of the east asian monsoon induced by global ice volume variation

pop up structure in massive carbonate hosted fold and thrust belt insight from field mapping and 2d kinematic model in the central apennines abstract fold and thrust belts are characterized by the occurrence of foreland verging thrusts and antithetic backthrust which develop in the hangingwall of thrust sheets both thrust and backthrust bound the so called pop up structure which is a deformed zone characterized by thrust and backthrust related anticlines pop up structures mainly develop in fold and thrust belts characterized by a multilayered sedimentary sequence consisting of limestones marls and shales deformed above a weak decollement such as evaporites however in this work we combine field mapping stratigraphic constrains and structural analysis with 2d kinematic forward modeling to document a pop up structure developed within limestones dolostones deformed above a strong decollement consisting of dolostones in the central apennines italy in particular we describe a sw verging anticline and a ne verging anticline in the sw and ne margin of the serra lunga ridge respectively such folds were generated by a ne dipping backthrust and by sw dipping forethrust respectively therefore we suggest that the serra lunga ridge represents a pop up structure showing geometries similar to other pop up structures observed within fold and thrust belts characterized by a multilayered sedimentary sequence in addition backlimb tilting of backthrust related anticlines generates the forelandward dipping monoclines observed within thrust sheets in the central apennines and in several fold and thrust belts worldwide

grain size and accumulation rate records from late cenozoic aeolian sequences in northern china implications for variations in the east asian winter monsoon and westerly atmospheric circulation we attempt to reconstruct the history of westerly and monsoonal circulations in northern china using variations in sediment grain size and accumulation rate at four loess sections in the central chinese loess plateau the initiation of aeolian accumulation at about 7 6 ma in the main part of the chinese loess plateau probably marked the onset of the monsoonal circulation both the monsoonal and westerly circulations weakened from 7 6 to 5 2 ma subsequently the monsoonal circulation strengthened progressively from 5 2 ma to the present in addition the westerly circulation strengthened from 5 2 to 0 6 ma but then weakened thereafter and especially during the last 0 6 ma comparison of our aeolian records and the deep sea sediment record suggests that the strengthening trends of the monsoonal and westerly circulations were associated with the progressive development of global ice sheets during the late cenozoic abrupt changes of both the monsoon and westerly circulations occurred at 7 6 3 4 and 1 2 0 9 ma together with a weakening trend of the westerly circulation in the last 0 6 ma and are interpreted as the consequence of the episodic uplift of the tibetan plateau spatial differences in the grain size characteristics amongst the four sections suggest that the circulation intensity and variability decreased from west to east across the loess plateau due to the topographic effect of the tibetan plateau in addition some spatial differences may have been the result of local topographic effects c 2008 elsevier b v all rights reserved

high resolution osl dating of a late quaternary sequence from xingkai lake ne asia chronological challenge of the mis 3a mega paleolake hypothesis in china in this paper a combined osl 49 samples and 14c 14 samples dating study was conducted on a sediment core from xingkai lake ne asia a single aliquot regenerative dose protocol was used to determine the equivalent dose dede of the extracted fine grained fg quartz fraction the suitability of the measurement procedure was confirmed by a set of luminescence tests e g preheat plateau and dose recovery measurements in addition a post ir infrared stimulated luminescence protocol at 290 c pirir290 was applied to the polymineral fg fraction of seven samples our results can be summarized as follows 1 the uppermost sample was dated to 110 a indicating that the osl signal of fg quartz has been well bleached this has been further confirmed by the consistency of osl ages and pirir290 ages within 80 ka the resulting osl ages generally increased with depth and the lowermost samples of core xk08 reached back to the last interglacial although the pirir290 dating suggested that the quartz osl ages likely begin to be underestimated beyond 80 ka 2 the comparison of osl and 14c ages suggested that the radiocarbon dating technique may significantly underestimate the age of sediments for samples older than 30 cal ka bp corresponding to 25 14c ka bp and thus it is necessary to pay attention when using such old 14c dates for paleoclimatic archaeological interpretation 3 this study challenges the radiocarbon based chronology of the mis 3a mega paleolake hypothesis which had been reiterated for many years and extensively reported across northern and western china and 4 the current high resolution osl dating record one age 5 10 cm showed clear sedimentation rate changes down the core the identified variations in the sedimentation processes at the orbital timescale may be related to regional global climatic changes during the past 130 ka and the high sedimentation rate during the last 0 4 ka has probably been caused by intensified human activities in the xingkai lake catchment

lake qinghai sediment geochemistry linked to hydroclimate variability since the last glacial abstract geochemistry of basin sediments from semi arid regions is valuable to understand past hydroclimatic changes here we investigate the links of sedimentary geochemistry rb sr ca zr toc and caco 3 carbonate mineralogy and ostracod shell 18 o of lake qinghai a basin proximal to major dust production centers at mid latitudes of the northern hemisphere to changes in depositional conditions and hydroclimate during the past 32 ka surface lacustrine sediments are characterized by low rb high sr low rb sr high caco 3 and high ca zr values in contrast to the chemical compositions of eolian loess high rb low sr high rb sr low caco 3 and low ca zr a direct comparison of soluble ca and sr in two short cores with instrumental water discharge data suggests that lacustrine precipitates in lake qinghai are dominated by authigenic aragonite formed under ca 2 limited water conditions and that the accumulation rate of aragonite dominantly depends on solute fluxes into the lake during the rainy seasons late may to september our high resolution down core records show that sediments during the last glacial 32 19 8 ka had high rb low sr low caco 3 and low ca zr indicating eolian dust loess accumulation in a desiccated basin under dry glacial conditions further supported by grain size and pollen results this type of sedimentation was maintained during the last deglacial 19 8 11 5 ka but interrupted by episodic lacustrine precipitates with high sr high caco 3 high ca zr and low rb at 11 5 ka sedimentary rb sr ca zr caco 3 and toc show dramatic and permanent changes implying an abrupt shift in the atmospheric circulation at the onset of the holocene in the lake qinghai region lacustrine precipitates have persisted throughout the holocene with a maximum during the early to mid holocene 10 5 8 0 ka since 8 0 ka the gradual and significant decreases in aragonite and sr accumulations in tandem with increasing dust deposit and more positive ostracod 18 o may be linked to a weakening of asian summer monsoons during the mid to late holocene overall our records appear to show a high sensitivity of sediment development and geochemistry in lake qinghai to the regional hydroclimate changes since the last glacial

apatite fission track data for the miocene arabia eurasia collision the collision between the eurasian and arabian plates along the 2400 km long bitliszagros thrust zone isolated the mediterranean from the indian ocean and has been linked to extension of the aegean rifting of the red sea and the formation of the north and east anatolian fault systems however the timing of the collision is poorly constrained and estimates range from late cretaceous to late miocene here we report the fi rst apatite fi ssiontrack aft ages from the bitlis zagros thrust zone the aft samples are distributed over the 450 km length of the bitlis thrust zone in southeast turkey and include metamorphic rocks and eocene sandstones despite the disparate lithology and large distance the aft ages point consistently to exhumation between 18 and 13 ma the aft ages along with a critical appraisal of regional stratigraphy indicate that the last oceanic lithosphere between the arabian and eurasian plates was consumed by the early miocene ca 20 ma the results imply that aegean extension predated the arabia eurasia collision

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

geochemical investigation of dry and wet deposited dust during the same dust storm event in harbin china constraint on provenance and implications for formation of aeolian loess abstract a strong dust storm event occurred in harbin china on may 11 2011 the dry and wet deposited dust depositions in this dust storm event together with the surface sediments from the potential sources were collected to study grain size distributions carbonate content and carbon isotopic composition of carbonate major element trace element and rare earth elements ree and sr nd isotopic compositions the results indicate as follows the dry deposited dusts are characterized by bimodal grain size distributions with a fine mode at 3 6 m and a coarse mode at 28 m whereas the wet deposited dusts are indicative of unimodal grain size modes with a fine mode at 6 m the dust storm depositions are influenced to a certain extent by sedimentary sorting and are of a derivation from the recycled sediments based on identifying the immobility of element pairs before constraining sources of dust storm deposits using geochemical elements in conjunction with ree and especially sr nd isotopic compositions the primary and strengthening sources for the dust storm event were detected respectively the hunsandake sandy land as the primary source and the horqin sandy land as the strengthening source were together responsible for the derivation of dust depositions during dust storm event the hunsandake sandy land however contributes less dust to the dust storm event in harbin compared to the horqin sandy land and the hulun buir sandy land is undoubtedly excluded from being one of the sources for dust storm depositions in harbin there are not notable differences in geochemical especially sr nd isotopic compositions between dry and wet deposited dusts indicating that the wet deposited dust is of identical derivation to the dry deposited dust based on our observations it is of interest to suggest that fine and coarse particles in the clp chinese loess plateau loess possibly have the same sources

tertiary palaeogeography and tectonostratigraphic evolution of the northern and southern peri tethys platforms and the intermediate domains of the african eurasian convergent plate boundary zone abstract the increasing effects of african eurasian convergence during the tertiary resulted in the uplift and emergence of the northern and southern peri tethys platforms palaeogeographic maps covering six selected time slices including the middle eocene late early oligocene late early miocene early middle miocene early late miocene and middle to late pliocene illustrate that environmental and depositional differentiations on the northern platform and along the bordering domains of the convergence zone were more pronounced than on the southern platform and its adjacent areas the tectonic evolution of the northern platform included an overall eastward directed trend in the onset of basin uplift and emergence which started at about the eocene oligocene transition at 34 ma tectonostratigraphic analyses indicate a striking contemporaneity of the events which defined the temporal and spatial development of both the domains of the convergent plate boundary zone and the bordering platforms five episodes of major regional change in palaeogeographic and tectonic setting are distinguished they occurred in the late eocene 37 34 ma early late oligocene 30 27 ma latest early to earliest middle miocene 17 15 ma early late miocene 9 8 ma and late early to early middle pliocene 4 3 ma these episodes encompassed changes which were most probably induced by geodynamic events primarily related to the relative motions of the african arabian and eurasian plates in turn the plate motions are assumed to have triggered discrete steps in the regional kinematics and geodynamics that governed the palaeogeographic evolution of the peri tethys platforms and the intermediate domains of the african eurasian plate boundary zone

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

magnetic susceptibility evidence of monsoon variation on the loess plateau of central china during the last 130 000 years the magnetic susceptibility of loess and paleosols in central china represents a proxy climate index closely related to past changes of precipitation and vegetation and thus to summer monsoon intensity time series of magnetic susceptibility constructed for three loess paleosol sequences in the southern part of the chinese loess plateau document the history of summer monsoon variation during the last 130 000 yr they correlate closely with the oxygen isotope record of stages 1 to 5 in deep sea sediments soils were forming during intervals of strong summer monsoon whereas loess units were deposited at times of reduced monsoon intensity the chinese loess paleosol sequence can thus be viewed as a proxy record of asian monsoon variability extending over the last 2 5 myr

accommodation and supply a dual control on stratigraphic sequences abstract it is widely accepted that both eustatic and tectonically controlled regional changes of sea level have contributed to the record of stratigraphic sequences i suggest that environmental change be added as a third autonomous control sedimentologic principles clearly indicate that sequences and their systems tracts are controlled by the interplay of two rates the rate of change in accommodation space available for sedimentation and the rate of sediment supply sea level has direct control on accommodation but its influence on sediment supply is remote and easily overshadowed by environmental factors for instance the record of the most recent sea level rise is a transgressive systems tract where supply is low it is a prograding highstand systems tract in deltas where the supply is high examples of sequence boundaries generated by changes in sediment supply include tectonically driven shifts in sediment input into basins changes in ocean currents pulsating supply from failure of submarine slopes and drowning of carbonate platforms by environmental stress furthermore the stratigraphic sequences in fluviatile continental basins are physically removed from sea level induced changes in accommodation and must have formed by changes in the rate and pattern of supply subaerial exposure of marine sediments at the sequence boundary is a most important criterion for recognizing sea level cycles as opposed to supply cycles other criteria include downstepping of shelf breaks and characteristic patterns in the spacing of time lines within sequences some third order cycles ca 0 5 3 ma duration meet these criteria others do not cycle stacking patterns and the shifting facies belts on cratons indicate that many second and third order cycles lack pronounced exposure unconformities and represent gradual changes superimposed on more rapid shorter oscillations seismic data yield poor images of these gradational changes because they lack resolution seismic models of outcrops show that near the limits of resolution the seismic tool tends to portray rapid changes in facies and bed thickness i e lateral variations in supply as unconformities seismic unconformities do not necessarily correspond to unconformities in outcrop the succession of stratigraphic sequences is best considered a composite record of sea level and environmental change separating the various controls requires carefully planned experiments work on the oxygen isotope curve another proxy for sea level has set an example in this respect

weathering and global denudation a negative correlation between sediment yield and weathering history as measured by the chemical alteration cia of the suspended sediment is observed for many of the world s major rivers and other regions of denudation the weathering history is a first order control on the sediment yield of such areas termed equilibrium denudation regions for other areas data scatter with either apparent increases or decreases of sediment yield for given cia values these areas are termed nonequilibrium denudation regions low sediment yields can be attributed to moderated erosion either natural or human induced and or the incorporation of unweathered glacial debris accelerated erosion resulting in high sediment yield is primarily human induced and results from cultivation and other land use each of these effects has a profound influence on global sediment discharge from the continents pre human suspended sediment discharge from the continents is estimated to be 12 6 times 10 15 g yr or about 0 6 the

east asian monsoon variation during the last 130 000 years evidence from the loess plateau of central china and lake biwa of japan abstract the loess paleosol sequence on the loess plateau of central china constitutes an excellent proxy record of variations in asian monsoon climate over the past 2 5 ma magnetic susceptibility of loess and paleosols has been used as a proxy indicator for summer monsoon intensity while the median diameter of quartz isolated from the loess and paleosols has been regarded as a proxy index of the strength of winter monsoon winds that were responsible for most of the dust transport the eolian quartz flux to lake biwa of central japan during the last 130 000 yr provides direct information on variations of the east asian winter monsoon whereas the fluvial quartz flux reflects significant changes in paleoprecipitation over the lake area the intervals of high eolian quartz flux values during marine oxygen isotope substages 5d and 5b and stages 4 and 2 correspond to the periods of large quartz median diameter values of the chinese loess and paleosols indicating strengthened winter monsoon winds whereas the intervals of high fluvial quartz flux values during isotope substages 5e 5c and 5a and stages 3 and 1 correlate to the periods of high magnetic susceptibility values of the chinese loess and paleosols suggesting increased summer monsoon intensity variations in winter monsoon strength indicated by the eolian quartz flux and quartz median diameter proxies bear a general inverse relation to those in summer monsoon intensity inferred from the fluvial quartz flux and magnetic susceptibility proxies

dust transport and the question of desert loess formation although contemporary dust storms are frequent in arid and semi arid areas desert loess deposits are poorly developed much of the world s loess occurs in mid latitude areas which experienced glaciation during the pleistocene ocean core evidence indicates that dust transport from sub tropical deserts increased during cold stages of the pleistocene but loess formed only on certain desert margins for reasons which have not been fully explained this paper re examines the mechanisms of dust transport and deposition and the circumstances leading to the accumulation of thick loess typical loess is composed mainly of medium silt grains which are transported in short term suspension a few metres above the ground significant thicknesses of loess form only when dust is trapped within a limited area often relatively close to the source dust particles finer than 20 m are transported mainly in long term suspension over a greater height range and may be widely dispersed the availability of silt and the frequency magnitude and direction of dust transporting winds are important factors governing the potential for loess formation but the existence of a suitable dust trap is particularly important traps may be formed by topographic obstacles areas of moist ground or vegetated surfaces vegetation adjacent to glacial outwash plains and braided meltwater streams trapped dust in mid latitudes during the pleistocene dust blown during glacial periods from certain deserts notably in sinai soviet central asia and china accumulated as loess in neighbouring semi arid regions on the margins of other deserts loess formation was inhibited partly by the absence of vegetation traps during most of the holocene net dust deposition rates in all desert marginal areas have been too low for significant loess accumulation this is mainly due to a reduction in silt availability and a tendency towards landscape stability reported dust storm frequencies during the past 50 years over estimate the longer term holocene dust flux due to the effects of human activities much modern dust owes its origin to erosion of cultivated soils in semi arid areas and is finer than typical loess

lowstand carbonates highstand sandstones the sedimentary facies sediment dynamics and sequence architecture of modern high energy shelves in the mid and high latitudes are largely governed by wave abrasion processes cool water carbonates may form there if the influx and or net accretion of siliciclastics is kept at a minimum little dilution of the carbonate produced in situ is generally promoted by a wide epicontinental shelf subdued topography of the adjacent mainland the predominance of limestone outcrops and an arid climate the aforementioned requirements are rarely met and thus will automatically lead to the formation of mixed siliciclastic cool water carbonates such an example is found in the early to mid miocene lagos portimao formation algarve s portugal which formed on a narrow high energy shelf of the atlantic ocean that was bounded by a mountain range the sediments of the formation consist of fossiliferous sandstone fs shell beds and rhodolith blankets along strike the stratification of the formation is monotonous for tens of kilometres and well exposed in coastal cliffs whereas no outcrops of dip sections exist the bulk skeletal composition of the sediments is typical for the warm temperate climatic zone various endo and epibenthic bivalves bryozoans coralline algae echinoderms gastropods and large foraminifers heterostegina in some very rare beds a few isolated not framework forming specimens of zooxanthellate corals porites tarbellastrea indicate temporally elevated surface water temperatures close to the lower threshold of the coral reef ecosystem in sandstones the fauna is well preserved and burrowing bivalves are commonly found in life position in limestone beds the state of preservation of the grains ranges from intact to disintegrated and abraded specimens we infer an accumulation of the shell beds through winnowing of fine materials siliciclastic sand and carbonate mud at wave abrasion depth and concentration of calcareous skeletons associated with the subsequent attraction of new epibiota in a complex shell bed the vertical alternation of fossiliferous sandstone and shell beds and in phase variations of the photo index photic biota vs bryozoans and bryozoan index bivalves vs bryozoans is envisaged to document variations of water depth and sea level sandstone units built up when wave abrasion depth wad rose above the sea floor during tst and early hst whereas the shell beds formed during lst when the wad for sand intersected with the sea floor clastic sediments were probably brought on the outer shelf during early transgression and by longshore currents sea level signatures inferred in the mixed siliciclastic cool water carbonate shelf setting of s portugal therefore significantly deviate from conventional concepts of carbonate sequence stratigraphy which were developed for flat topped platforms successful interpretations of ancient mixed sequences must therefore take into consideration the processes of production concentration and accretion of the carbonate sediments

the lake baikal drilling project in the context of a global lake drilling initiative abstract records of the tectonic and climatic evolution of continental interiors are important for understanding the dynamics of the earth s climate system evolutionary processes within the terrestrial biosphere and human origins sediment drill cores recovered from lake baikal provide essential records not only for comparison with oceanic records of marine processes but also benchmarks which can be used to help interpret other continental records including other lake archives scheduled to be drilled in the near future drilling of lake baikal made it possible for the first time to have a continental archive with the same scientific and chronostratigraphic integrity as marine records to address critical questions of the quaternary and pliocene the lake baikal drilling project bdp rapidly progressed from piston coring and seismic reflection studies to conducting the first scientific drilling in 4 short years and to very deep drilling in over 8 years bdp has taken advantage of the harsh siberian winters by using the frozen surface of lake baikal as a drilling platform the positioning of the drill sites was selected using seismic and piston coring surveys by continuously improving the drilling operations and technology bdp has achieved new core recovery and depth records over the last ten years and become the world s leader in pioneering the recovery of high quality extremely long lacustrine sediment sequences from deep water the success of bdp came at a time of growing interest in lake drilling among members of the paleoclimate community with few recent large scale coordination efforts to draw upon at the organizational technological and financial levels some recent changes are favorable for the development of a global lake drilling initiative which could become as successful and efficient as the ocean drilling program

constraining the onset of flexural subsidence and peripheral bulge extension in the miocene foreland of the southern apennines italy by sr isotope stratigraphy abstract in fold and thrust belts developing at convergent margins the migration of the advancing wedge is accompanied by bulging of the downgoing plate followed by the development of a foredeep basin filled by a thick succession of syn orogenic sediments the transition from forebulge to foredeep marks a key moment in the evolution of the orogenic system in deep water environments the record of this transition is typically complete and progressive conversely in the shallow water continental environment of many collisional systems the uplift of the forebulge area can imply emersion and erosion obliterating the stratigraphic record of key steps of the evolution of the orogenic system the southern apennines constitute one of these collisional fold and thrust belts where the development of the forebulge has implied emersion and erosion with the development of a miocene forebulge erosional unconformity accompanied by extensional deformation associated with the bending of the lithosphere during the forebulge stage in this paper we use strontium isotope stratigraphy to constrain with unprecedented time resolution the age of the forebulge unconformity in areas presently incorporated in the northern sector of the southern apennines fold and thrust belt integration of our results and those of previous studies indicates at the regional scale a younging toward the foreland of the forebulge unconformity across the belt our high resolution ages also reveal a diachronous onset of the flexural subsidence over short distances associated with the occurrence of horst and graben structures possibly resulting from inherited paleotopography along with forebulge extension this work highlights how high resolution dating is critical to unravel the evolution of foreland basin systems at different scales

significance of the sedimentary al ti ratio as an indicator for variations in the circulation patterns of the equatorial north atlantic this paper presents results of geochemical investigations conducted on three gravity cores recovered along an e w transect 3 5 n in the equatorial atlantic considering the high terrigenous content of the sediments approximately 12 74 wt al and ti concentrations are predominantly associated with the input of lithogenous phases the terrigenous fraction of western equatorial atlantic sediments is more influenced by material derived from the amazon river than by deposition of african dust particles as a possible route of transport the north equatorial countercurrent is considered fluctuations in al ti records generally reflect changes in the low latitude insolation cycle 19 23 kyr and thus indicate a close coupling to variations of the trade wind systems and continental climate changes however characteristics of the terrigenous signals in the eastern and western equatorial atlantic differ significantly while the precessional signal in the al ti record and low latitude portion in the 18o record are in phase in the eastern equatorial atlantic variations in the terrigenous fraction westward of the mid atlantic ridge precede the marine signal by 2 3 kyr which we ascribe to a shift between trade wind systems of the northern and southern hemispheres

response of silicate weathering to monsoon changes on the chinese loess plateau abstract eolian deposits of loess on the chinese loess plateau are investigated to decipher the influence of sequentially changed monsoon climate on silicate weathering process detailed hydrochloric acid dissolution experiments are applied to establish a sensitive proxy for silicate weathering combined elemental and mineralogical studies show that the minerals which are susceptible to incipient chemical weathering can be totally dissolved in hot hydrochloric acid 80 c 3mol l after 4h while other stable minerals are nearly unaffected thus the hydrochloric acid dissolvable fractions adf of loess and paleosol are more sensitive than bulk samples in the weathering reaction since mg is tend to be leached out from the adf while al is conserved during the incongruent weathering mg al ratio of the adf mg al adf could indicate the weathering intensities of the mg bearing minerals mainly chlorite the mg al adf of the modern soils on the chinese loess plateau is closely correlated to the local precipitation amounts suggests that the intensity of summer monsoon is a key factor in the weathering of mg silicate the silicate weathering intensity of the loess paleosol deposits of past 130kyrs shows strong procession cycle of 23kyrs coupled by glacial interglacial variation the 23krys cycles are coherent to the variations of the intensity of summer monsoon while the 100kyrs glacial interglacial variation may relates to the changes in winter monsoon phased intensification of east asian summer monsoon and thus enhanced silicate weathering and atmosphere co 2 drawdown in response to the uplift of tibetan plateau may be another mechanism relating the late cenozoic tectonics to global cooling

a proposal for the kinematic modelling of w dipping subductions possible applications to the tyrrhenian apennines system in w dipping subduction zones there is a general eastward progression of the back arc basin accretionary wedge foredeep complex with the forward progression early stages of the complex are revealed by slices of upper crust and sedimentary cover abandoned to the west left floating above a new section of mantle a major shear zone should form at the new moho separating upper crust slices of earlier accretionary stages and the eastward flowing mantle the mantle wedging at the top of the subduction plane could be responsible for the uplift of the central parts of the belt the retreating of the subduction hinge is interpreted as due to the push generated by the eastward mantle flow detected in the hot spot reference frame the foredeep depth is mainly a function of the radius of curvature of the subduction hinge the frontal wedge is constructed from the stacking of the upper layers of the subducting plate and the syntectonic clastics that fill the foredeep which are progressively involved in thrusting and later by extension in order to preserve volume balance the lithosphere of the eastern plate before subduction has to be the same size as that which has been subducted due to the longer length of the arc with respect to the original length of the linear margin between the two converging plates laterally stretched subducted lithosphere is predicted at depth w dipping subductions usually have a short life probably due to their inherent capability to produce new lateral heterogeneities of the lithosphere the thin back arc which are a key factor in controlling and generating new subductions both e and w dipping this model is applied to the apennines tyrrhenian sea system

chemical weathering of monsoonal eastern china implications from major elements of topsoil major element compositions of 36 bulk samples and 41 clay samples which were obtained from 47 topsoils collected in monsoonal eastern china were investigated with conventional wet chemistry and x ray fluorescence xrf spectrometry respectively based on major element analyses the mobility of major elements and latitudinal distributions of sio2 al2o3 ratio chemical index of alteration cia chemical index of weathering ciw and weathering index of parker wip were analyzed meanwhile the suitability of these chemical weathering indices to topsoils in monsoonal eastern china and its controls were discussed these investigations indicate that na k ca mg and si are relatively depleted while mn p fe and ti are relatively enriched in topsoils of the study area by comparison with their contents in the upper continent crust ucc and that alkali metal na k and alkaline earth metal ca mg elements are generally easier to be depleted from their parent materials than other major elements during chemical weathering the latitudinal distributions of cia ciw and wip show that they are suitable to both bulk and clay samples but sio2 al2o3 is only suitable to clay samples not suitable in bulk ones all these investigations indicate a significant dependence of grain size in major element abundance and latitudinal distributions of sio2 al2o3 cia ciw and wip but parent rock type has little effect on them except its impact on the latitudinal distribution of wip in clay samples the significant grain size dependence probably indicates the presence of unaltered minerals in bulk samples thus we suggest that clay samples are more suitable to investigating chemical weathering of sediments on continents than bulk samples the trivial effect of parent rock type probably indicates a relatively uniform chemical weathering on various parent rocks correlation analyses indicate that climate is the dominant control of chemical weathering of topsoils in the study area and the significant latitude effect indicated by the spatial distributions of chemical weathering indices actually reflect the climate control on chemical weathering of topsoils chemical weathering indices actually reflect the integrated weathering history in the study area besides the dominant control of climate other factors like tectonics parent rock biology landform and soil depth and age might also have some effect on the chemical weathering of topsoils in the study area which needs further research c 2013 elsevier ltd all rights reserved

two unique weathering regimes in the changjiang and huanghe drainage basins geochemical evidence from river sediments the present research reconstructs the histories of chemical weathering in the drainage basins of the changjiang and huanghe based on the chemical compositions of the river sediments the silicate weathering of the changjiang basin is strong and naand ca silicate minerals are considerably dissolved while other silicate minerals are less attacked in comparison the huanghe basin is characterized by very weak silicate weathering and the weathering degree corresponds well with that of the loess which is the predominant source of the huanghe sediment overall the changjiang and huanghe basins constitute a consistent weathering spectrum from the early to intermediate stage the similarity of chemical compositions between upper continental crust and the huanghe sediments as well as the low degree of chemical weathering in the huanghe basin imply that the river sediments can be considered to be the representative of ucc and are suitable for studying the evolution of continental crust our observations indicate that climate is the predominant factor controlling silicate weathering in both river basins while controls by source rocks and relief are subordinate highly erosive river basins such as the huanghe produce poorly weathered materials which casts doubt on the idea that strong physical weathering naturally contributes much to chemical weathering differences in silicate weathering processes between the changjiang and huanghe basins may provide more constraints in estimating atmospheric co2 budget in china d 2003 elsevier b v all rights reserved

quantitative paleoenvironmental and paleoclimatic reconstruction using paleosols abstract paleosols fossil soils are preserved throughout the geologic record in depositional settings ranging from alluvial systems to between basalt flows until recently paleosols were studied using primarily qualitative methods in recent years paleopedology has shifted from a largely qualitative field based on comparisons with modern analogues to an increasingly quantitative endeavor some of this change has been a result of applying existing techniques to new materials but many of the innovations have been the result of applying new techniques to new materials including thermodynamic modeling of soil formation isotope geochemistry and applications of empirical relationships derived from modern soils a variety of semi quantitative and quantitative tools has been developed to examine past weathering and pedogenesis and to reconstruct both paleoenvironmental and paleoclimatic conditions at the time that the paleosols formed though it is often not possible to achieve the same temporal resolution as with marine records for paleoclimatic reconstructions proxies based on paleosols are potentially a much more direct means of making paleoclimatic reconstructions because soils form at the earth s surface in direct contact with the atmospheric and climatic conditions at the time of their formation paleoclimatic and environmental properties that may be reconstructed using the new proxies include provenance weathering intensity mean annual precipitation and temperature during pedogenesis nutrient fluxes into and out of the paleosols the atmospheric composition of important gases including co2 and o2 the moisture balance during pedogenesis the soil gas composition reconstructed vegetative covering and paleo altitude

reconstructing chemical weathering physical erosion and monsoon intensity since 25 ma in the northern south china sea a review of competing proxies reconstructing the changing strength of the east asian summer monsoon has been controversial because different proxies many being indirect measures of rainfall tell contrasting stories about how this has varied over long periods of geologic time here we present new sr isotope grain size and clastic flux data and synthesize existing proxies to reconstruct changing chemical erosion in the northern south china sea since the oligocene using the links between weathering rates and monsoon strength established in younger sediments as a way to infer intensity chemical proxies such as k rb l al and the chemical index of alteration cia together with clay proxies like kaolinite illite chlorite show a steady decline in alteration after a sharp fall following a maximum at the mid miocene climatic optimum mmco 15 5 17 2 ma probably as a result of cooling global temperatures in contrast physical erosion proxies including bulk ti ca and clastic mass accumulation rates mar show peaks at 21 23 ma similar to 19 ma and 15 5 17 2 ma implying faster run off in the absence of drainage capture rates increase again likely driven by slightly increased run off after 13 ma but decrease after 8 ma which is identified as a period of summer monsoon weakening sr isotope composition correlates with hematite goethite and the spectral proxy crat to show stronger weathering linked to more monsoonal seasonality these proxies argue for a strengthening of the east asian monsoon after 22 23 ma followed by an extended period of monsoon maximum between 18 and 10 ma then weakening there is some suggestion that the summer monsoon may have strengthened since 3 4 ma after reaching a minimum in the pliocene c 2014 elsevier b v all rights reserved

holocene east asian monsoon variability links to solar and tropical pacific forcing 1 sedimentary geochemical records from subalpine retreat lake subtropical taiwan document the unstable east asian monsoon eam climate over the past 10 300 years with a weak eam between 10 3 and 8 6 ky b p eam intensity peaks between 8 6 and 7 7 ky b p and then gradually decrease in response to summer insolation heat and moisture transport our proxy record reveals several weak monsoon intervals that correlate to low sea surface temperatures in the western tropical pacific and cold events in the north atlantic linking the tropical pacific north atlantic and polar climates because weak eam events at 8 2 5 4 and 4 5 2 1 ky b p also correspond to low values of atmospheric methane and periods of reduced north atlantic deep water formation we therefore suggest that centennial to millennial scale monsoon variability during the holocene in the northern subtropics is globally mediated via a sun ocean monsoon north atlantic linkage

variations of illite chlorite ratio in chinese loess sections during the last glacial and interglacial cycle implications for monsoon reconstruction 1 the variations of the clay minerals illite and chlorite were measured by xrd in the 2 m fraction of four loess sections along a north south transect on the chinese loess plateau clp the ratio of illite to chlorite i c provides a tool to evaluate strong monsoon conditions on the clp i c ratios above 2 5 indicate strong chlorite silicate weathering a process that takes place under a regime which at present in the southern clp has annual precipitation and temperature exceeding 600 mm and 10 c respectively the weathering regime during the last previous interglacial period in the southern clp may have been warmer and had higher rainfall during weathering the chlorite may release iron so that nanometer sized iron oxide minerals may form and the free fe2o3 and magnetic susceptibility are increased in the resulting paleosol if that has occurred in the four sections studied it is only in the southern two

development of rudist lithosomes in the coniacian lower campanian carbonate shelves of central southern italy high energy vs low energy settings abstract the late cretaceous shallow water depositional areas of southern tethys were complexes of unprotected shelves occupied by foramol assemblages that produced loose diagenetically stable bioclastic debris not involved in significant in situ cementation processes both storm and wind induced currents and waves exercised a strong control on the distribution of the shifting biogenic sediments which covered the open sea floor constituting large coalescing sheets of winnowed fine to coarse skeletal sands rudists spread over all shelf sectors from more open and external areas to more internal ones occupying different substrata and furnishing the bulk of the skeletal component by means of bioerosion processes they colonised mobile sediments giving rise to complex bodies with peculiar characteristics related to environmental parameters of the different sectors of the shelf on the basis of detailed sedimentological taphonomic and palaeontological data we recognised two main rudist rich depositional settings end members in the southern italy senonian rudist bearing successions in successions pertaining to hypothesised marginal shelf sectors characterised by high energy regime deposits rudist lithosomes are metric in thickness and lateral extent and lens like in morphology rich in bioerosion derived skeletal sand and silt rudists are highly diversified large elongated cylindro conical hippuritids mostly pertaining to the genera hippurites and vaccinites thick shelled radiolitids and plagioptychids largely dominate rudists clustered in life position are subordinate they often form small bouquets more commonly these organisms appear fallen but only barely reworked the rudist rich bodies laterally pass into clean bioclastic grainstone in which sedimentary structures related to current and or storm erosional action are common no evidence of significant original relief of the rudist bodies in respect of the neighbouring sediment can be recognised the submarine erosion and or the high energy processes operating presumably inhibited the aggradation of the tidal sediments above the marginal ones as a consequence the vertical facies organisation shows widespread subtidal cycles as commonly recognised in open shelves with ramp like morphologies in successions pertaining to more internal and or low energy sectors rudist rich beds rhythmically alternate with finer grained foraminiferal limestones small elevator radiolitids with oligospecific diversity are dominant mostly concentrated in clumps rudists in growth position are abundant although a large quantity of shells appear toppled with little reworking they may form laterally continuous biostromal shell beds sedimentary structures such as cross lamination and gradation are only occasionally present the resulting facies are commonly arranged in peritidal shallow subtidal cycles in which evidence of subaerial up to pedogenic modifications on a large and small scale and less frequently submarine exposure is common intermediate successions have been recognised characterised by deposits of silty sand plains which present intercalations of graded bioclastic storm related beds sedimentological characteristics seem to document more open conditions in which submarine erosion was intermittently prevalent in these successions rudist species that are commonly found both in high energy and low energy assemblages coexist

nutrients sea level and tectonics constrains for the facies architecture of a miocene carbonate ramp in central italy in the western part of the central apennines lower middle miocene carbonates were deposited on a tropical subtropical carbonate ramp they record two long term cycles the first of which is illustrated in this paper between 21 and 17 5 ma miocene carbonates paraconformably overlying the cretaceous limestones record a transgressive event during a time of global 2nd order sea level lowstand it is postulated that this deviation is related to an increase in tectonic subsidence between 17 5 ma and 16 15 ma with a progressive relative sea level rise the inner middle ramp facies belt stepped back whereas the bryozoan dominated outer ramp facies belt stepped back but simultaneously prograded this bloom of suspension feeding organisms is interpreted to reflect an increased nutrient availability hence a change from oligotrophic to eutrophic conditions strontium isotope dates constrain correlation of the second phase with a eutrophic event possibly linked to the influence of the neighbouring apenninic accretionary wedge and foredeep system

environmental factors influencing skeletal grain sediment associations a critical review of miocene examples from the western mediterranean the presence of foramol rhodalgal and bryomol skeletal grain associations in ancient shallow marine limestones is commonly interpreted as evidence for non tropical palaeoclimate despite temperature being only one of several factors influencing skeletal grain associations such interpretations neglect the multitude of factors other than temperature that influence carbonate producing biota these include nutrients water energy water transparency depth of the sea floor salinity oxygen ca2 and co2 concentrations mg ca ratio alkalinity substrate requirements competitive displacement as well as biological and evolutionary trends this uniformitarian approach also disregards the probability that conditions of present day biological systems may not be representative of past conditions of analogous systems here the importance of considering these other factors is illustrated through two examples of carbonate platforms in the western mediterranean these platforms are dominated by foramol rhodalgal and bryomol associations of miocene age in spite of having formed in tropical conditions the platforms discussed are 1 the lower tortonian ramp on menorca balearic islands and 2 the lower middle miocene ramps of the central apennines italy evidence for tropical conditions in the mediterranean during the period of growth of these platforms is provided by species of red algae and larger foraminifera by data from coeval continental basins and by global oxygen isotope data

sandy beach ridges from xingkai lake ne asia timing and response to palaeoclimate abstract lake beach ridges and their sediments have been investigated as palaeoenvironmental records robust chronology is crucial to utilize this archive for palaeoenvironmental reconstruction and interpretation this study investigates the optically stimulated luminescence osl dating of quartz in two beach ridges of aeolian origin from xingkai lake ne asia the applicability of the selected measurement procedure is validated by a set of internal tests on luminescence characteristics such as preheat plateau test and dose recovery test and the reliability of the resulting 24 osl ages are also confirmed by agreement with four 14c ages as well as two k feldspar luminescence dates the constructed chronologies are thought to be robust in the stratigraphic and geomorphologic context the two aeolian beach ridges b1 and b2 are dated to 32 15 ka and 1 2 0 5 ka respectively which are interpreted as two distinct periods of lake lowstand that could have caused beach exposure and provided a more extended sand source for foredune formation around xingkai lake these two lowstands could be correlated to the dry cold regional climate including the time span from late mis3 to late glacial and the most recent one at the late holocene

a new proposal for the late cenozoic geodynamic evolution of the western mediterranean a simple mechanism of arcuate fold belt and back arc basin formation is presented based on the opening of mega continental tension gashes along pre existing deep parallel and steep faults that separate lithospheric units with different properties if plate convergence is parallel to these faults the fault bounded units open at right angles to the convergence vector adopting an arcuate shape with thrusting in front of the bowed out units and extensional basin opening between the separated units this model is applied to the cenozoic geodynamic evolution of the western mediterranean after the iberian collision 35 30 ma several ellipsoidal basins valencia alboran north algerian and liguro provencal developed by 10 ma along the eastern margin of the iberian plate the formation of these basins is attributed to an increase in ne sw horizontal tectonic palaeostress during early middle miocene times resulting from the post subduction collision of the tethyan oceanic lithosphere

chemical weathering since the little ice age recorded in lake sediments a high resolution proxy of past climate because of the different geochemical behaviour of rubidium and strontium in earth surface processes variations of the rb sr ratios in lake sediments were used as a geochemical proxy of chemical weathering and past climate in a single watershed low magnetic susceptibility low caco3 low sr concentration and hence high rb sr ratio in the lake sediments indicate weak chemical weathering under a cold but wet climate during the little ice age lia in the closed daihai lake watershed the concordant change in both sr and caco3 concentrations with 18o values in the dunde ice core suggests that weak chemical weathering during the wet lia was controlled by air temperature after the lia however precipitation played a dominant role in chemical weathering copyright 2001 john wiley sons ltd

u series disequilibria in suspended river sediments and implication for sediment transfer time in alluvial plains the case of the himalayan rivers 238u 234u 230th radioactive disequilibria were analyzed in suspended sediments collected at different depths from the ganges river and one of its main tributaries the narayani gandak river results associated with bedload sediment data suggest that uranium series u series disequilibria in river sediments of the ganges basin vary with grain size and sampling location the range of observed u series disequilibria is explained by a mixing model between a coarse grained sediment end member represented by bedload and bank sediments and a fine grained end member that both originate from himalaya but undergo different transfer histories within the plain the coarse grained sediment end member transits slowly i e several 100 s ky in the plain whereas the fine grained sediment end member is transferred much faster 20 25 ky as indicated by the absence of significant variations in th isotope composition of the fine grained sediment end members these results show that u series isotopes can be used to quantify the various transfer times of river sediments of different sizes and infer that there can be an order of magnitude of difference or more between the transfer time of suspended and bedload sediments this underlines that a good knowledge of the proportion of suspended vs bedload sediments transported in the river is required to accurately assess how fast erosion products are transferred in a catchment and how fast a catchment is likely to respond to external forcing factors

processes controlling the distribution of ti and al in weathering profiles siliciclastic sediments and sedimentary rocks abstract the ratio of ti to al varies greatly in primary igneous source rocks these elements are considered to be relatively immobile in most weathering regimes so that tio2 al2o3 ratios have been used to investigate the provenance of sediments and sedimentary rocks in modern weathering profiles that have undergone moderate weathering ti al ratios remain fairly constant so that siliciclastic sediments derived from them should have ti al ratios like that of the source materials under extreme weathering conditions however the upper most weathered parts of profiles commonly show a marked increase in ti al ratio that is thought to be due to preferential translocation of al rich phases under steady state weathering conditions one particular level of the profile may act as the main source of detrital material and may thus control the ti al ratio of sediments produced from it in a glacio fluvial setting minimum weathering moderate sorting there is considerable variation in ti content but al is nearly constant this is due to concentration of ti bearing mafic minerals such as biotite in the fine fraction in modern sediments derived from moderately weathered and sorted material the ti al distribution reflects mixing of al and ti enriched fine grained materials with sands that are depleted in these elements when a plot of tio2 vs al2o3 is constructed for a suite of such sands and muds the resultant trend differs significantly from that shown by a similar suite of unweathered glacio fluvial sediments comparison of these results with data from sedimentary rock suites suggests that trends shown by plots of tio2 vs al2o3 may provide insight into weathering and depositional history in addition to their use as provenance indicators

discontinuities in carbonate successions identification interpretation and classification of some italian examples abstract the growing use of unconformities as bounding surfaces for new types of stratigraphic units seems not to be matched by a corresponding effort on process oriented researches on unconformities themselves this paper aims at giving a contribution to classification and understanding of discontinuities in carbonate successions from the outcrop perspective based on some italian examples a number of integrated criteria geometry sedimentology diagenesis biostratigraphy is proposed to recognise stratigraphic breaks old terms are discussed and sometimes redefined while some new terms are introduced the term discontinuity surface ds is proposed as a general one to indicate any stratigraphic interface where an interruption of sedimentation can be proved a ds can be characterized as a firm ground or a rock ground depending on its coherence at the moment of the renewal of sedimentation polygenic and simple omission surfaces are separated within firm grounds if a recognizable gap is either present or not a third kind of firm ground revealed only by biostratigraphy has been called hidden discontinuity surface two categories of rock grounds are also distinguished hard grounds and inherited rock grounds if respectively generation of the ds and or deposition of the overlying sediments took place in the same environment of the underlying sediments or not a genetic interpretation for each type of discontinuity is proposed the largest variety of ds s occurs in pelagic sediments some discontinuities hard grounds and simple omission surfaces are attributed to increased bottom current activity during sea level falls others polygenic omission surfaces and hidden ds s are interpreted as submarine slide scars either with or without the overprint due to exposure on the seafloor the ds s separating different facies e g platform and pelagic ones are interpreted to be due to tectonics the relevance of the recognized ds s to sequence stratigraphy is briefly discussed

recognition and documentation of depositional sequences from outcrop an example from the aptian and albian on the eastern margin of the wessex basin stratigraphic data relating to the aptian and albian sediments around folkestone in southeast england on the eastern margin of the wessex basin are plotted graphically to illustrate biostratigraphic gaps and condensed intervals these are then used to suggest candidate sequence boundaries notated lg1 4 and gl 3 which are named after the lower greensand and gault the biostratigraphic subzones apparently unrepresented in the area are lg1 obsoletus and bodei lg2 gracite and debile lg3 schrammeni gl bulliensis candidate sequence boundaries g2 cristatum subzone and g3 auritus subzone are erosion surfaces correlating with probable biostratigraphic gaps elsewhere in the basin the age of lg4 is uncertain but must lie within the mammillatum superzone all candidate sequence boundaries correspond closely to those predicted by recent global sea level cycle charts and additionally there is a close match between predicted maximum flooding surfaces and the occurrence of condensed intervals most of the candidate sequence boundaries could have been formed as a result of rapid and at least regionally extensive relative sea level falls but the sedimentological contexts of lg3 and gl suggest that these may have been generated by transgression related sediment condensation the minor sequence boundary in the loricatus zone intermedius subzone illustrated in the cycle charts cannot be unambiguously recognized at outcrop in the folkestone area additional sequence boundaries not shown in the cycle charts may also be present in the wessex basin

erosion of tortonian phosphatic intervals in upwelling zones the role of internal waves abstract during the miocene the upwelling is assumed to be important in the formation of many mediterranean phosphate deposits in carbonate platform successions there are different types of upwelling mechanisms such as equatorial upwellings ice edge upwellings and coastal upwellings the carbonate platforms are mainly affected by wind driven coastal upwelling systems during upwelling season the seawater in coastal areas is strongly density stratified and the permanent pycnocline rises inshore forming an inclined frontal layer the liaison between upwellings and internal waves is widely documented in the literature internal waves result from perturbations of the hydrostatic equilibrium where balance is sustained between the force of gravity and buoyant restoring force many perturbations of the pycnocline can propagate as an internal wave in a coastal upwelling a key role for wave propagation is played by permanent pycnocline the run up swash currents develop during the break of internal waves and produce erosional processes in particular the backwash return flow may induce the erosion of seafloor sediments and transport these sediments downslope as bedload erosion of phosphate rich intervals has been extensively documented the deposition of gravity flow sediments is followed by intervals of non deposition incipient lithification phosphogenesis and erosion in this work we evaluate the role of internal waves in the formation of the resedimented phosphate rich intervals characterising the basal portion of the hemipelagic orbulina marls these marls are deposited on the low angle latium abruzzi carbonate ramp and represent deposition in a foreland basin during the initial stages of evolution of the central apennine belt during the early tortonian age

a high resolution absolute dated late pleistocene monsoon record from hulu cave china oxygen isotope records of five stalagmites from hulu cave near nanjing bear a remarkable resemblance to oxygen isotope records from greenland ice cores suggesting that east asian monsoon intensity changed in concert with greenland temperature between 11 000 and 75 000 years before the present yr b p between 11 000 and 30 000 yr b p the timing of changes in the monsoon as established with 230th dates generally agrees with the timing of temperature changes from the greenland ice sheet project two gisp2 core which supports gisp2 s chronology in this interval our record links north atlantic climate with the meridional transport of heat and moisture from the warmest part of the ocean where the summer east asian monsoon originates

tracing bottom water oxygenation with sedimentary mn fe ratios in lake zurich switzerland abstract redox dynamics of manganese mn were studied in the sediment of lake zurich using precise sediment core age models monthly long term oxygen o 2 monitoring data of the water column 1936 2010 and high resolution xrf core scanning the age models were based on bi annual lamination and calcite precipitation cycles if present mn exhibits distinct maxima which coincide with the annual maximum deep water o 2 concentrations in spring according to the monitoring data in contrast the iron fe signal is mainly the result of calcite dilution as indicated by a strong negative correlation between fe and calcium ca xrf data the mn fe ratio in the core from the maximum lake depth zh10 15 137 m revealed a moderate correlation with o 2 measurements in the lake bottom water confirming the successful application of the mn fe ratio to semi quantitatively reconstruct bottom water oxygenation in the lake mostly low ratios were observed between 1895 and the mid 1960s as a result of eutrophication however geochemical focusing and sedimentological factors can reduce the applicability of the mn fe ratio in reconstructing o 2 concentrations in the bottom water of lakes

geochemical evidence for the provenance of middle pleistocene loess deposits in southern china the provenance of middle pleistocene loess in the middle and lower reaches of the yangtze river the most intensively investigated loess deposits outside the loess plateau region in china remains controversial identification of the provenance will provide crucial insight into the environmental implications of this valuable sedimentary archive and into the potential role of the east asian winter monsoon in transporting the dust from deserts in the asian interior in this study geochemistry was used to compare the provenance of loess in the lower reaches of the yangtze river in southern china with that inferred for loess deposits on the loess plateau in northern china compared with samples from the loess plateau the 20 mm fraction in the loess deposits of southern china has higher tio2 al2o3 zr nb zr al zr ti zr hf y al and lan smn ratios and lower eu eu th nb y nb and al nb ratios the clear distinction in immobile element ratios between samples from the two regions indicates that the loess deposits in the two regions have different provenances the inferred difference in source area is also supported by variations in the major element composition of bulk samples obtained in this study and collected from published data these lines of evidence indicate that the deserts in the asian interior are not the primary provenance for the southern loess it is suggested that the adjacent floodplains to the north of yangtze river are the dominant dust sources and the occurrence of sustained loess deposits in the lower reaches of the yangtze river currently an area of northern subtropical climate is an indication of local aridification and strengthened winter monsoon activity during glacial periods as a regional response to the middle pleistocene climate transition around 0 8 ma the role of the east asian winter monsoon in transporting the dust from northern deserts to southern china has been overestimated in previous studies

feldspars as a source of nutrients for microorganisms phosphorus and nitrogen are essential macronutrients necessary for the survival of virtually all living organisms in groundwater systems these nutrients can be quite scarce and can represent limiting elements for growth of subsurface microorganisms in this study we examined silicate sources of these elements by characterizing the colonization and weathering of feldspars in situ using field microcosms we found that in carbon rich anoxic groundwaters where p and n are scarce feldspars that contain inclusions of p minerals such as apatite are preferentially colonized over similar feldspars without p a microcline from s dakota which contains 0 24 p 2 o 5 but 1 mu mol g nh 4 super was heavily colonized and deeply weathered a similar microcline from ontario which has no detectable p or nh 4 super was barren of attached organisms and completely unweathered after one year anorthoclase 0 28 p 2 o 5 approximately 1 mu mol g nh 4 super was very heavily colonized and weathered whereas plagioclase specimens 0 01 p 1 mu mmol g nh 4 super were uncolonized and unweathered in addition the observed weathering rates are faster than expected based on laboratory rates we propose that this system is particularly sensitive to the availability of p and the native subsurface microorganisms have developed biochemical strategies to aggressively scavenge p or some other essential nutrient such as fe super 3 from resistant feldspars the result of this interaction is that only minerals containing p will be significantly colonized and these feldspars will be preferentially destroyed as the subsurface microbial community scavenges a limiting nutrient

miocene unconformities in the central apennines geodynamic significance and sedimentary basin evolution abstract this paper shows the results obtained from an integrated study geology biostratigraphy and geochemistry carried out on the miocene edimentary deposits in central italy in order to define the timing of the sedimentary basin evolution this paper deals also with the causes of the unconformities recorded in these basins in the miocene deposits of the latina valley and the ernici simbruini mts several unconformities which distinguish different stratigraphic sequences have been recognized d 0 d 1 d 2 d 3 and d 4 for each unconformity a general description together with a geodynamical significance is provided in particular d 0 unconformity appears to be related to a regional tectonic event adria europe collision as a consequence the adria lithosphere folded and the area underwent a regional erosive event d 1 d 2 and d 3 unconformities have had a more local tectonic control since they represent the stratigraphic record of the migration of the apennines thrust belt foredeep system d 1 and d 2 unconformities are related to the late tortonian foredeep stage whereas d 3 is linked to the early messinian piggy back stage moreover the d 4 unconformity which took place during the messinian piggy back stage is strictly linked to the sea level drop of the messinian salinity crisis in this paper the genesis and evolution of a late tortonian foreland basin is also stressed latina valley foredeep basin finally taking into account sequence boundaries nannofossil biostratigraphy and geochemistry isotopic data a comparison with the curve of the 3rd order of the relative coastal onlap haq et al 1988 has been attempted in order to distinguish the unconformities controlled either by tectonic or eustatic processes

a 2000 year dust storm record from lake sugan in the dust source area of arid china 1 arid northwestern china is considered to be a major source of atmospheric dust supply to the northern hemisphere however dust storm evolution and dust emission processes in the past remain unclear due to the scarcity of geologic archives in this region hydrologically closed lakes in dust source areas act as a trap providing the opportunity to trace the history of dust emission or eolian activity here we present the results of dust storm proxies and a dust storm history from lake sugan in the qaidam basin a dust source area on the northern qinghai tibetan plateau grain size analyses of the materials deposited during modern dust storms and of the lake surface sediments demonstrate that the coarse component of the lake sediments was transported primarily by ambient winds when dust storms occurred in combination with a sediment chronology generated by counting annual laminations a 2000 year dust storm history was reconstructed on the basis of changes in the coarse component and magnetic susceptibility of the lake sediments frequent and or intensive dust storms occurred during the intervals ad 300 500 ad 1180 1240 and ad 1500 1700 the occurrence of dust storms largely coincided with the strengthening of the siberian high with colder air masses from high latitudes such as during the little ice age frequently encroaching into the dust source areas in northwestern china our results suggest that wind strength plays an important role in dust emissions in arid source areas however dust storms in the late 20th century are most likely associated with disturbance of the ground surface caused by petroleum exploitation in the qaidam basin

tectonic control on the architecture of a miocene carbonate ramp in the central apennines italy insights from facies and backstripping analyses abstract analyses of facies associations and biotic assemblages integrated with backstripping analysis are presented to improve understanding of the development of a shallow water miocene carbonate ramp in the central apennines italy with special reference to the relationships between tectonic subsidence and the internal architecture of the ramp subsidence curves were calculated for six measured sections located in different sectors of the platform dating is derived from sr isotope analyses from previous studies and regional correlations corrections for eustasy and paleobathymetry were deduced from biota and facies analyses the subsidence curves show rates that vary both in space and time by analysing the vertical motions in different sectors of the ramp over a fixed time span burdigalian to tortonian it was possible to evaluate the control on platform architecture exerted by tectonically induced changes in sea floor bathymetry and highlight the effects of tectonic migration most analysed sites experienced a short period of tectonic uplift or stability followed by a period of slow subsidence this preceded increased subsidence which resulted in drowning of the shallow water carbonate platform the stability uplift is progressively younger towards the north eastern sectors that correspond to progressively more external zones of the foreland relative to the apenninic orogenic belt the subsequent drowning is related to the diachronous down flexure of the adriatic lithosphere due to its eastward retreating subduction under the apennines the small magnitude of the uplift suggests that the formation of a foreland bulge due to subduction related flexure of the adriatic plate was probably not the responsible mechanism hence this uplift is related to the development of proto thrusts or to the propagation of compressive stresses in the foreland these vertical motions influenced the geometry of the platform during the 17 5 16 ma stage during this period the platform was characterised by exceptional progradation of the bryomol dominated proximal outer ramp facies belt this rapid spreading may be induced by the combined effect of increased eutrophic conditions and a contemporaneous decrease in the sea floor bathymetry resulting from the tectonic uplift from the tortonian onwards when the platform became involved in the eastward migrating foredeep system the tectonic subsidence curve records a short period of fast tectonic subsidence rates followed by a period of slow subsidence or slight uplift during basin drowning and infilling respectively

variations in 87sr 86sr ratios of calcites in chinese loess a proxy for chemical weathering associated with the east asian summer monsoon abstract 87sr 86sr ratios of loess paleosol calcites of luochuan in china over the past 130 ka display a regular change with increasing trend of 87sr 86sr ratios in the following order loess calcite weakly pedogenetic paleosol calcite paleosol calcite pure secondary calcite the observed variations in the 87sr 86sr record of loess paleosol calcites correlate closely with the records of the magnetic susceptibility coarse grain fraction content in the same profile an et al chin sci bull 39 1994 182 184 and the specmap stacked 18o record of global ice volume imbrie et al in berger et al eds milankovitch and climate part i reidel boston 1984 pp 269 305 strata from the last glacial consist mostly of loesses and weakly developed paleosols and have lower 87sr 86sr ratios averaging 0 71079 paleosols which developed during the last interglacial have higher 87sr 86sr ratios averaging 0 71131 the four periods ca 125 110 98 90 80 75 and 9 5 ka b p of increased summer monsoonal rainfall coincide with the four peaks in 87sr 86sr values a series of 87sr 86sr high frequency high amplitude fluctuations is superimposed on the last glacial interglacial cycle over the past 130 ka occurring on millennium timescales with an average time span of about 3 ka during the last glacial the fluctuations of the 87sr 86sr ratios of the luochuan loess paleosol calcites lie in the range 0 71036 0 71176 for the past 130 ka the study shows that the sr isotopic system in loess paleosol calcites may therefore be an excellent proxy of chemical weathering on continents associated with the east asian summer monsoon

weathering of the ganga alluvial plain northern india implications from fluvial geochemistry of the gomati river abstract in the northern part of the indian sub continent the ganga alluvial plain gap feeds its weathering products to the ganga brahmaputra river system one of the world s largest fluvial systems the authors present a geochemical study of the gap weathering products transported by the gomati river the ganga river tributary to understand weathering processes of an alluvial plain in a humid sub tropical climate a total of 28 sediment samples were collected during the monsoon season and were analysed by x ray fluorescence spectrometry for 25 major and trace elements bulk chemistry of the channel flood and suspended sediments mostly consists 90 80 and 75 respectively of three elements al si and fe major element concentrations normalised with respect to upper continental crust ucc show strong depletion of highly mobile elements na ca and enrichment of immobile elements ti si silica enrichment in the sand fraction is probably caused by chemical weathering of feldspar mineral sorting during fluvial transportation acts as the single important factor that controls the geochemistry of these weathering products and also strongly influences major and trace element distribution in the individual sediment samples trace element ba cr cu nb ni pb v and zn concentrations were strongly correlated with major element si al fe mn and k concentrations indicating that the abundance of trace elements is controlled by the same processes that control the major element distribution in these sediments the gap weathering products were geochemically distinguished as arkose to litharenite in rock classification chemical mobility normalised with respect to tio 2 in ucc indicates that si na zr ba and sr mainly derived from feldspar muscovite and biotite are lost during weathering iron and zn remained immobile during weathering and were strongly adsorbed by phyllosilicates and concentrated in fine grained sediment fractions the chemical index of alteration indicates that the gap has experienced chemical weathering of incipient to moderate intensity the gap weathering products also demonstrated a progressive incomplete alteration in the alluvial sequence made up of the himalayan derived sediments a model has been proposed to better understand weathering processes and products of the gap in temporary storage of 50 ka in a humid sub tropical climate

chemical indices cia and wip as proxies for integrated chemical weathering in china inferences from analysis of fluvial sediments abstract rivers play a key role in earth surface processes by weathering and eroding the upper continental crust under variable climate regimes how to quantitatively determine the chemical weathering intensity in the drainage basins using geochemistry of fluvial sediments remains unclear the chemical index of alteration cia and the weathering index of parker wip have been used worldwide as proxies to evaluate the chemical weathering intensity in large watersheds and in specific weathering profiles in this study concentrations of major oxides in the suspended particulate matter spm and fine grained floodplain sediments from 13 major rivers in china from north to south were analysed and compiled for the estimation of chemical weathering in china the gradual increase in cia and decrease in wip values with decreasing latitude of the catchments suggest enhanced weathering intensity in these river basins a combined monsoon climate effect of temperature runoff and precipitation primarily controls the chemical weathering in china the provenance rock types and relief play minor roles in weathering whereas an active tectonic setting and typhoon events play key roles in the weathering process in taiwan the cia values of the finer spm samples within a given river are overall greater than those in the corresponding coarser floodplain sediments underscoring the effect of sediment grain size on cia values the irregular seasonal variation of the cia within a specific river further confirms the notion that the cia does not reflect the instantaneous chemical weathering on continents although it is impossible to build a general model for regulating the chemical weathering of continents this study reveals that the integrated chemical weathering intensity in large latitudinal watersheds can with careful application be quantitatively estimated using the proper geochemical proxies of river sediments

glacial interglacial indian summer monsoon dynamics the modern indian summer monsoon ism is characterized by exceptionally strong interhemispheric transport indicating the importance of both northern and southern hemisphere processes driving monsoon variability here we present a high resolution continental record from southwestern china that demonstrates the importance of interhemispheric forcing in driving ism variability at the glacial interglacial time scale as well interglacial ism maxima are dominated by an enhanced indian low associated with global ice volume minima in contrast the glacial ism reaches a minimum and actually begins to increase before global ice volume reaches a maximum we attribute this early strengthening to an increased cross equatorial pressure gradient derived from southern hemisphere high latitude cooling this mechanism explains much of the nonorbital scale variance in the pleistocene ism record