aeolian sand sea development along the mid cretaceous western tethyan margin spain erg sedimentology and palaeoclimate implications the existence of a mid cretaceous erg system along the western tethyan margin iberian basin spain was recently demonstrated based on the occurrence of wind blown desert sands in coeval shallow marine deposits here the first direct evidence of this mid cretaceous erg in europe is presented and the palaeoclimate and palaeoceanographic implications are discussed the aeolian sand sea extended over an area of 4600 km2 compound crescentic dunes linear draa and complex aeolian dunes sand sheets wet dry and evaporitic interdunes sabkha deposits and coeval extradune lagoonal deposits form the main architectural elements of this desert system that was located in a sub tropical arid belt along the western tethyan margin sub critically climbing translatent strata grain flow and grain fall deposits pin stripe lamination lee side dune wind ripples soft sediment deformations vertebrate tracks biogenic traces tubes and wood fragments are some of the small scale structures and components observed in the aeolian dune sandstones at the boundary between the aeolian sand sea and the marine realm intertonguing of aeolian deposits and marine facies occurs massive sandstone units were laid down by mass flow events that reworked aeolian dune sands during flooding events the cyclic occurrence of soft sediment deformation is ascribed to intermittent marine flooding of aeolian dunes and associated rise in the water table the aeolian erg system developed in an active extensional tectonic setting that favoured its preservation because of the close proximity of the marine realm the water table was high and contributed to the preservation of the aeolian facies a sand drift surface marks the onset of aeolian dune construction and accumulation whereby aeolian deposits cover an earlier succession of coastal coal deposits formed in a more humid period a prominent aeolian super surface forms an angular unconformity that divides the aeolian succession into two erg sequences this super surface formed in response to a major tectonic reactivation in the basin and also marks the change in style of aeolian sedimentation from compound climbing crescentic dunes to aeolian draas the location of the mid cretaceous palaeoerg fits well to both the global distribution of other known cretaceous erg systems and with current palaeoclimate data that suggest a global cooling period and a sea level lowstand during early mid cretaceous times the occurrence of a sub tropical coastal erg in the mid cretaceous of spain correlates with the exposure of carbonate platforms on the arabian platform during much of the late aptian to middle albian and is related to this eustatic sea level lowstand

a model based interpretation of low frequency changes in the carbon cycle during the last 120 000 years and its implications for the reconstruction of atmospheric δ14c a main caveat in the interpretation of observed changes in atmospheric d14c during the last 50 000 years is the unknown variability of the carbon cycle which together with changes in the 14c production rates determines the 14c dynamics a plausible scenario explaining glacial interglacial dynamics seen in atmospheric co2 and d13c was proposed recent ly kohler et al 2005 a similar approach and expanding its interpretation to the 14c cycle is an important step towards a deeper understanding of d14c variability this approach is based on an ocean atmosphere biosphere box model of the global carbon cycle bicycle to reproduce low freque ncy changes in atmospheric co2 as seen in antarctic ice cores the model is forced forward in time by various paleo climatic records derived from ice and sediment cores the simulation results of our proposed scenario match a compiled co2 record from various ice cores during the last 120 000 years with high accuracy r2 0 89 we analyze scenarios with different 14c production rates which are either constant based on 10be measured in greenland ice cores or the recent high resolution geomagnetic field reconstruction glopis 75 and compare them with the available d14c data covering the last 50 000 years our results suggest that during the last glacial cycle in general less than 110 o oo of the increased atmospheric d14c are based on variations in the carbon cycle while the largest part 5 6 of the variations has to be explained by other factors glacial atmospheric d14c larger than 700 o oo cannot not be explained within our framework neither through carbon cycle based changes nor through variable 14c production superimposed on these general trends might lie positive anomalies in atmospheric d14c of 50 o oo caused by millennial scale variability of the northern deep water production during heinrich events and dansgaard oeschger climate fluctuations according to our model the dominant processes that increase glacial d14c are a reduced glacial ocean circulation 40 o oo a restricted glacial gas exchange between the atmosphere and the surface ocean through sea ice coverage 20 o oo and the enrichment of dic with 14c in the surface waters through isotopic fractionation during higher glacial marine export production caused by iron fertilization 10 o oo

changes in atmospheric co2 and its carbon isotopic ratio during the penultimate deglaciation abstract the largest natural increases in atmospheric co 2 concentration as recorded in ice cores occur when the earth climate abruptly shifts from a glacial to an interglacial state open questions remain regarding the processes at play the sequences of events and their similarities along different glacial interglacial transitions here we provide new combined data of atmospheric co 2 and its carbon isotopic ratio 13 co 2 for the penultimate glacial interglacial transition termination ii from the antarctic epica dome c ice core together with the strongest antarctic warming this transition bears the largest co 2 increase 104 ppmv of the last nine terminations ending with an overshoot of 21 ppmv occurring within 300 y and leading to higher levels than those of the late pre industrial holocene the full co 2 rise is accompanied by an overall decrease of the 13 co 2 minimum values on which three positive excursions are superimposed peak to peak 13 co 2 changes in our record can reach 1 the ice core atmospheric 13 co 2 appears more depleted by 0 2 during termination ii compared to termination i paralleling a similar carbon isotopic depletion recorded in marine data during both terminations most of co 2 and 13 co 2 variations are attributed to southern ocean stratification breakdown and decreased efficiency of the biological pump compared to termination i termination ii ice core data point to different timings of decrease in iron supply and sea ice extent suggesting that they could account for distinct patterns of the carbon cycle

glacial to holocene implications of the new 27000 year dust record from the epica dome c east antarctica ice core insoluble dust concentrations and volume size distributions have been measured for the new 581 m deep dome c epica ice core antarctica over the 27000 years spanned by the record microparticle measurements from 169 levels to date confirm evidence of the drastic decrease in bulk concentration from the last glacial maximum lgm to the holocene interglacial by a factor of more than 50 in absolute value and of about 26 in flux unique new features revealed by the epica profile include a higher dust concentration during the antarctic cold reversal phase acr by a factor of 2 with respect to the holocene average this event is followed by a well marked minimum that appears to be concomitant with the methane peak that marks the end of the younger dryas in the northern hemisphere particle volume size distributions show a mode close to 2 m in diameter with a slight increase from the lgm to the holocene the lgm holocene concentration ratio appears to be dependent on particle size and for diameters from 2 to 5 m it changes from 50 to 6 glacial samples are characterised by well sorted particles and very uniform distributions while the interglacial samples display a high degree of variability and dispersion this suggests that different modes of transport prevailed during the two climatic periods with easier penetration of air masses into antarctica in the holocene than during glacial times assuming that southern south america remained the main dust source for east antarctica over the time period studied the higher dust content recorded during the acr which preceded the younger dryas period represents evidence of a change in south america environmental conditions at this time a wet period and likely mild climate in south america is suggested at circa 11 5 11 7 kyr bp corresponding to the end of the younger dryas the holocene part of the profile also shows a slight general decrease in concentration but with increasingly large particles that may reflect gradual changes at the source

dependence of ice core relative trace element concentration on acidification to assess the role of methodological differences on measured trace element concentrations in ice cores we developed an experiment to test the effects of acidification strength and time on dust dissolution using snow samples collected in west antarctica and alaska we leached antarctic samples for 3 months at room temperature using nitric acid at concentrations of 0 1 1 0 and 10 0 v v at selected intervals 20 min 24 hours 5 days 14 days 28 days 56 days 91 days we analyzed 23 trace elements using inductively coupled plasma mass spectrometry concentrations of lithogenic elements scaled with acid strength and increased by 100 1380 in 3 months incongruent elemental dissolution caused significant variability in calculated crustal enrichment factors through time factor of 1 3 pb to 8 0 cs using snow samples collected in alaska and acidified at 1 v v for 383 days we found that the increase in lithogenic element concentration with time depends strongly on initial concentration and varies by element e g fe linear regression slope 1 66 r 0 98 our results demonstrate that relative trace element concentrations measured in ice cores depend on the acidification method used

links between iron supply marine productivity sea surface temperature and co2 over the last 1 1 ma received 3 july 2008 revised 9 october 2008 accepted 27 october 2008 published 14 february 2009 1 paleoclimatic reconstructions have provided a unique data set to test the sensitivity of climate system to changes in atmospheric co2 concentrations however the mechanisms behind glacial interglacial g ig variations in atmospheric co2 concentrations observed in the antarctic ice cores are still not fully understood here we present a new multiproxy data set of sea surface temperatures sst dust and iron supply and marine export productivity from the marine sediment core ps2489 2 odp site 1090 located in the subantarctic atlantic that allow us to evaluate various hypotheses on the role of the southern ocean so in modulating atmospheric co2 concentrations back to 1 1 ma we show that antarctic atmospheric temperatures are closely linked to changes in so surface temperatures over the last 800 ka and use this to synchronize the timescales of our marine and the european project for ice coring in antarctica epica dome c edc records the close correlation observed between iron inputs and marine export production over the entire interval implies that the process of iron fertilization of marine biota has been a recurrent process operating in the subantarctic region over the g ig cycles of the last 1 1 ma however our data suggest that marine productivity can only explain a fraction of atmospheric co2 changes up to around 40 50 ppmv occurring at glacial maxima in each glacial stage in this sense the good correlation of our sst record to the edc temperature reconstruction suggests that the initial glacial co2 decrease as well as the change in the amplitude of the co2 cycles observed around 400 ka was most likely driven by physical processes possibly related to changes in antarctic sea ice extent surface water stratification and westerly winds position

constraint of the co2 rise by new atmospheric carbon isotopic measurements during the last deglaciation 1 the causes of the 80 ppmv increase of atmospheric carbon dioxide co2 during the last glacial interglacial climatic transition remain debated we analyzed the parallel evolution of co2 and its stable carbon isotopic ratio 13co2 in the european project for ice coring in antarctica epica dome c ice core to bring additional constraints agreeing well but largely improving the taylor dome ice core record of lower resolution our 13co2 record is characterized by a w shape with two negative 13co2 excursions of 0 5 during heinrich 1 and younger dryas events bracketing a positive 13co2 peak during the bolling allerod warm period the comparison with marine records and the outputs of two c cycle box models suggest that changes in southern ocean ventilation drove most of the co2 increase with additional contributions from marine productivity changes on the initial co2 rise and 13co2 decline and from rapid vegetation buildup during the co2 plateau of the bolling allerod

zircon u pb geochronology and hf isotopes of major lithologies from the jiaodong terrane implications for the crustal evolution of the eastern block of the north china craton abstract as an important component of the western shandong complex in the eastern block of the north china craton the yishui terrane consists of neoarchean high grade supracrustal rocks granitoid gneisses and charnockites la icp ms zircon u pb dating and hf isotopic analyses on these lithologies have been carried out and the results provide new insights into the neoarchean crustal evolution of the eastern block of the north china craton new zircon dating results reveal that the magmatic precursors of the supracrustal metapelites and granitoid gneisses were generated at 2 54 2 53 ga and 2 57 2 55 ga respectively and the charnockites were emplaced contemporaneously around 2 56 2 53 ga single metamorphic zircon grains and overgrowth rims from these rocks document consistent metamorphic ages at 2 50 ga suggesting that the yishui terrane experienced a high grade metamorphic event at the end of the neoarchean detrital zircons from pelitic gneisses yield 207pb 206pb ages of 2 89 2 65 ga with a major age peak at 2 53 ga and a subordinate age peak at 2 70 ga implying that the sedimentary protoliths of the pelitic gneisses may have been sourced from 2 53 ga rocks in the yishui terrane and 2 70 ga rocks in the adjacent luxi granite greenstone terrane hf isotopic compositions show that the neoarchean magmatic zircons have positive ehf t values ranging from 1 4 to 7 8 and depleted mantle model ages of 2 92 2 60 ga with a prominent peak at 2 8 2 7 ga suggesting that the neoarchean crust was derived mainly from juvenile sources and partly from the recycling of old continental crust in the yishui area combined with previous data from the adjacent luxi granite greenstone terrane and other complexes in the eastern block it is concluded that the neoarchean was an important period of crust accretion in the eastern block of the north china craton

early proterozoic stream deposits braided or meandering evidence from central australia abstract it has been suggested that meandering stream deposits should be rare in proterozoic rocks this question was addressed during study of the early proterozoic hatches creek group in central australia as the lower part of the group includes up to 4000 m of fluvial sediments most of the 3000 m thick kurinelli sandstone appears to result from braided streams but there is evidence for the existence of meandering stream deposits in the overlying taragan sandstone and in sediments within the treasure volcanics the basal taragan sandstone consists of a fining up cycle in part of which lateral accretion surfaces are present a 28 m thick sedimentary member in the treasure volcanics contains preserved bedforms form sets which provide indirect evidence for the existence of meandering streams the bedforms including dunes 0 1 1 m high are preserved beneath a mudstone layer as a result of a very sudden drop in current velocity during deposition the observed structures can be explained by neck cut off in a meandering stream although the damming or diversion of a stream by lava flows cannot be discounted the hatches creek group thus contains evidence consistent with the existence of meandering stream deposits at two stratigraphic levels meandering streams should form when suitable combinations of bed and suspended load material are available for transport and discharge and slope parameters are within certain limits evidently the lack of land vegetation has not totally precluded the development of meandering streams in the proterozoic

shrimp u pb zircon ages of granitoid rocks in the luliang complex implications for the accretion and evolution of the trans north china orogen abstract the luliang complex is situated in the central segment of the trans north china orogen tnco a continent continent collisional belt along which the discrete eastern and western blocks amalgamated to form the basement of the north china craton the complex consists of supracrustal and granitoid rocks of which the latter can be subdivided into pre tectonic ttg gneisses including the yunzhongshan guojiazhuang and chijianling guandishan gneisses syn tectonic gneissic granites represented by the huijiazhuang gneissic granite and post tectonic granites including the luyashan charnockite luchaogou porphyritic granite and tangershang guandishan massive granite the pre tectonic ttg gneisses are mostly calc alkaline and considered to have formed in a magmatic arc environment shrimp u pb analyses reveal that the yunzhongshan gneisses were emplaced at 2499 9 ma representing the earliest arc related magmatic event in the luliang complex this was followed by the intrusion of the guojiazhuang gneisses at 2375 10 ma the most widespread arc related magmatic event in the region was the emplacement of the chijianling guandishan granitoid gneisses of which the tonalitic granodioritic and monzogranitic gneisses were emplaced at 2199 11 ma 2180 7 ma and 2173 7 ma respectively metamorphic zircon overgrowth rims from a tonalitic gneiss yielded a weighted mean 207 pb 206 pb age of 1872 7 ma consistent with the metamorphic age range of 1880 1820 ma defined by metamorphic zircons from various high grade rocks in the tnco thus the evolution of the luliang complex involved emplacement of the yunzhongshan granitoids at 2499 ma the guajiazhuang granitoids at 2375 ma and the chijianling guandishan granitoids at 2199 2173 ma with the final collision between the eastern and western blocks in this area occurring at 1872 7 ma the whole series of magmatic events lasting nearly 650 ma this suggests that the trans north china orogen represents a long lived magmatic arc the new shrimp zircon data combined with structural and petrological studies also reveal the existence of both syn and post collisional granites in the luliang complex the former is represented by the huijiazhuang gneissic granite that was emplaced at 1832 11 ma whereas the latter include the 1815 5 ma luyashan charnockite 1807 10 ma luchaogou porphyritic granite 1798 11 ma guandishan massive granite and 1790 14 ma tangershan massive granite

eight glacial cycles from an antarctic ice core the antarctic vostok ice core provided compelling evidence of the nature of climate and of climate feedbacks over the past 420 000 years marine records suggest that the amplitude of climate variability was smaller before that time but such records are often poorly resolved moreover it is not possible to infer the abundance of greenhouse gases in the atmosphere from marine records here we report the recovery of a deep ice core from dome c antarctica that provides a climate record for the past 740 000 years for the four most recent glacial cycles the data agree well with the record from vostok the earlier period between 740 000 and 430 000 years ago was characterized by less pronounced warmth in interglacial periods in antarctica but a higher proportion of each cycle was spent in the warm mode the transition from glacial to interglacial conditions about 430 000 years ago termination v resembles the transition into the present interglacial period in terms of the magnitude of change in temperatures and greenhouse gases but there are significant differences in the patterns of change the interglacial stage following termination v was exceptionally long 28 000 years compared to for example the 12 000 years recorded so far in the present interglacial period given the similarities between this earlier warm period and today our results may imply that without human intervention a climate similar to the present one would extend well into the future

structural pattern of the wutai complex and its constraints on the tectonic framework of the trans north china orogen abstract wutai complex is a key to test controversial models for the tectonic evolution of the trans north china orogen tnco along which the eastern and western blocks amalgamated to form the north china craton three stages of deformation d 1 to d 3 were identified in the wutai complex d 1 is characterized by ne sw trending foliations s 1 and nw se orientated lineations l 1 indicating an initial nw se directed compression associated with d 1 was prograde metamorphism m 1 d 2 progressively overprinted d 1 and generated z shaped folds and nee sww trending ductile shear zones d 2 resulted in a fan shaped structural pattern of the complex with top to the nw thrusting in the northwestern part and opposite top to the se thrusting in the southeastern part during d 2 the crust was doubled through thickening leading to peak metamorphism m 2 d 3 developed during post collision exhumation and deformed the early fabrics to be open folds resulting in near isothermal decompression m 3 and late cooling metamorphism m 4 the overall structure of the wutai complex is characterized by a fan shaped pattern with structural divergence structural features of the wutai complex combined with those of the adjacent hengshan and fuping complexes indicate that the tnco is characterized by a fan shaped orogenic wedge with opposite senses of thrust this orogenic wedge could have resulted from an eastward subduction and collision between the western and eastern blocks to finally form the tnco at 1 85 ga

dust impact on marine biota and atmospheric co2 during glacial periods 1 we assess the impact of high dust deposition rates on marine biota and atmospheric co2 using a state of the art ocean biogeochemistry model and observations our model includes an explicit representation of two groups of phytoplankton and colimitation by iron silicate and phosphate when high dust deposition rates from the last glacial maximum lgm are used as input our model shows an increase in the relative abundance of diatoms in today s iron limited regions causing a global increase in export production by 6 and an atmospheric co2 drawdown of 15 ppm when the combined effects of changes in dust temperature ice cover and circulation are included the model reproduces roughly our reconstruction of regional changes in export production during the lgm based on several paleoceanographic indicators in particular the model reproduces the latitudinal dipole in the southern ocean driven in our simulations by the conjunction of dust sea ice and circulation changes in the north pacific the limited open ocean data suggest that we correctly simulate the east west gradient in the open ocean but more data are needed to confirm this result from our model data comparison and from the timing of the dust record at vostok we argue that our model estimate of the role of dust is realistic and that the maximum impact of high dust deposition on atmospheric co2 must be 30 ppm

formation age and genesis of the gongchangling neoarchean banded iron deposit in eastern liaoning province constraints from geochemistry and shrimp zircon u pb dating abstract the gongchang iron deposit a typical algoma type banded iron formation bif deposit located in the eastern block of the north china craton ncc is hosted in neoarchean metamorphic rocks including amphibolite biotite leptynite garnet biotite schist plagioclase hornblende schist garnet chlorite schist muscovite quartz schist and actinolite magnetite quartzite geochemical data suggest that protoliths of the amphibolites and biotite leptynite should be basalt and dacite respectively shrimp u pb dating of zircons from the plagioclase hornblende schist shows that the gongchangling iron deposit was formed at 2554 12 ma major elements and ree data of the ores indicate that the gongchangling bif precipitated from seawater and the ultimate iron and silica origins may have been related to nearby volcanic activity the 18o values of quartz from the bifs range between 9 1 and 12 9 suggesting that exotic high 18o fluids were involved during metamorphism the pyrite have 34s values of range between 3 5 and 14 7 suggesting that mineralization were originally from metamorphism comparison of the mineralization age of the gongchangling bif with those of other local bifs in north china and other cratons throughout the world indicates that the gongchangling bif formed coevally with the global bif mineralization at 2 5 ga taken together these data suggest that the gongchangling iron deposit was formed in a volcanic submarine environment in which hydrothermal fluids associated with volcanic activity supplied both iron and silica for the banded iron formations

a new 27 ky high resolution east antarctic climate record the ice core recently drilled at the dome concordia site on the east antarctic plateau provides a new high resolution isotope record covering part of the last glacial the last transition and the holocene the two step shape of the deglaciation is remarkably similar for all the ice cores now available on the east antarctic plateau the first warming trend ends about 14000 years ago and is followed by the well marked antarctic cold reversal acr with a secondary peak common to all records during the deglaciation there are more similarities between the near coastal site of taylor dome and inland east antarctica than between taylor dome and central greenland however the results for epica do appear to confirm the taylor dome timescale after about 14 ka showing cooling into the acr roughly in phase between greenland and antarctica while the overall deglacial pattern is asynchronous this suggests that the now classical picture of a temperature seesaw between antarctica and greenland may be too simplistic

formation mechanism of gongchangling high grade magnetite deposit hosted in archean bif anshan benxi area northeastern china abstract banded iron formations are main resources of global iron ore in which high grade ore is mainly composed of martite goethite and hematite they are also the major resource of iron ore in china mainly distributing in liaoning and hebei province in china the iron ore with fe greater than 50 is classified as high grade iron ore the high grade iron ore mainly consists of magnetite and displays its unique characteristics gongchangling iron deposit is one typical bif iron deposit which contains 150 mt of high grade iron ore in china the high grade magnetite ore bodies mainly occur around magnetite quartzite faults and the cores of folds and show positive relation to the development of the altered rocks in this deposit this research shows that high grade magnetite comes from magnetite quartzite and they are both formed with little or no addition of aluminum containing detrital material by marine chemical deposition in reduced environment and they are closely related to seafloor hydrothermal activity muddy silty rocks are original rocks of altered rocks of which the primitive mantle normalized ree pattern except eu is consistent with that of iron ore reflecting that their formation is related to the formation of high grade magnetite ore therefore the formation mechanism of high grade iron ore is proposed as following the regional metamorphism provides storage space for the formation of high grade magnetite ore and required temperature and pressure conditions for the mineral transformation the regional metamorphic hydrothermal fluid leaches feo out of magnetite quartzite when it passes by and the feo that leached out moves near faults or cores of folds together with the metamorphic hydrothermal fluid and aluminum containing rocks of which the original rocks are muddy silty in the formation of high grade iron ore aluminum containing rock appears in the intervals of sedimentation of iron containing rock series and consumes the silicon leached out of magnetite quartzite and forms garnet chlorite and biotite

eolian dune degradation and generation of massive sandstone bodies in the paleoproterozoic makgabeng formation waterberg group south africa abstract massive sandstone bodies in the 1 85 ga makgabeng formation south africa are located within the middle and upper part of the formation and are associated with the oldest reported deposits of barchan and barchanoid ridge dunes bases of massive sandstone bodies are channelized or planar channel based bodies typically overlie low angle or up to 26 inclined wind ripple strata channel margins vary from low angle to vertical rarely massive sandstones at channel margins display vague horizontal stratification and or contain ripped up fragments of wind ripple strata planar based massive sandstone bodies are lenticular and characteristically are interbedded with low angle to horizontal dune toesets these lobate massive sandstone bodies vary from 5 cm to 6 m in thickness and from 3 m to possibly over 50 m in width some of the sandstone bodies onlap dune reactivation surfaces rare dewatering structures parting lineations and adhesion structures occur at tops of the massive sandstone bodies lower boundaries of massive sandstone bodies change from channelized to planar based down the dune foresets massive sandstones were generated by two different mechanisms which are inferred to have been triggered by significant precipitation events the presence of steep margins channeling rip up fragments and dewatering features and a lack of tractional structures indicate that most massive sandstones were deposited from hyperconcentrated flows down the dune lee face flows were initially turbulent analogous to hyperconcentrated flows resulting in scouring of wind ripple strata as hyperconcentrated flows migrated onto the dune plinth rapid deposition produced lobate massive sandstone deposits with planar bases this sedimentation is linked to development of a hydraulic jump at the slipface plinth intersection which increased flow depth and reduced flow velocity some flows maintained their turbulence onto the dune plinth resulting in erosion of the plinth and scouring into the underlying preserved dune deposits massive sandstone bodies linked to reactivation surfaces are more likely a result of partial lee face collapse which generated translational slides

coastal dune facies permian cutler formation white rim sandstone capitol reef national park area southern utah abstract the permian cutler formation white rim sandstone in the capitol reef national park area in southern utah is an excellent example of a coastal dune complex subjected to periodic flooding by marine waters wind ripple grainfall and grainflow laminae compose the cross sets deposited by eolian dunes however wave reworked structures such as oscillation ripples the occurrence of the characteristically marine trace fossils thalassinoides and chondrites and interfingering marine carbonate beds of the kaibab formation collectively indicate marine interaction with the eolian environment four facies are distinguished cross stratified sandstone burrowed to bioturbated sandstone brecciated and deformed sandstone and ripple laminated sandstone and thin carbonate beds one unusual aspect of the cross stratified sandstone facies is the abundance of coarse grained sand coarse grained sand is atypical in many ancient eolian slipface deposits but occurs here in large slipface foresets as both grainflow and wind ripple deposits no water laid structures are found in these slipface deposits coarse grained sand was probably transported to the cutler shoreline by fluvial systems draining the uncompahgre uplift to the east and then concentrated as coarse grained ripples in interdune areas some of these coarse grained ripples migrated up the stoss side of the dunes and accumulations of coarse grained sand avalanched down the crest to form grainflow deposits an extensive amount of soft sediment deformation is indicated by the presence of convolute bedding and brecciation these features occur near the zone of interfingering with marine carbonate beds of the kaibab formation the water saturated and moist conditions required for extensive deformation may have been controlled by the proximity of these sandstones to the shoreline and fluctuations in the associated groundwater table

glacial interglacial co2 change the iron hypothesis several explanations for the 200 to 280 ppm glacial interglacial change in atmospheric co2 concentrations deal with variations in southern ocean phytoplankton productivity and the related use or nonuse of major plant nutrients an hypothesis is presented herein in which arguments are made that new productivity in today s southern ocean 7 4 1013g yr 1 is limited by iron deficiency and hence the phytoplankton are unable to take advantage of the excess surface nitrate phosphate that if used could result in total southern ocean new production of 2 3 1015 g c yr 1 as a consequence of fe limited new productivity holocene interglacial co2 levels preindustrial are as high as they were during the last interglacial 280 ppm in contrast atmospheric dust fe supplies were 50 times higher during the last glacial maximum lgm because of this fe enrichment phytoplankton growth may have been greatly enhanced larger amounts of upwelled nutrients may have been used and the resulting stimulation of new productivity may have contributed to the lgm drawdown of atmospheric co2 to levels of less than 200 ppm background information and arguments in support of this hypothesis are presented

geochronological and geochemical constraints on the luliang group in the luliang complex implications for the tectonic evolution of the trans north china orogen abstract the luliang complex is located at the western margin of the middle segment of the trans north china orogen along which the western and eastern blocks amalgamated to form the basement of the north china craton the complex consists of the late neoarchean to paleoproterozoic granitic plutons and meta supracrustal rocks of which the latter are subdivided into the jiehekou luliang yejishan and heichashan lanhe groups the luliang group is composed mainly of siliciclastic rocks in the lower part and volcanic rocks in the upper part all of which have been metamorphosed from greenschist to amphibolite facies u pb ages of detrital zircons from meta sedimentary rocks in the luliang group yield four populations of 3061 2920 ma 2790 2600 ma 2599 2280 ma and 2211 2202 ma suggesting that their provenances were derived mainly from the luliang and taihua complexes in the trans north china orogen the meta volcanic rocks give igneous zircon u pb ages of 2209 2178 ma and e hf t values of 0 8 to 3 6 geochemically they are subalkaline basalts and andesites that can be classified into two groups of which one group has flat lrees weak enrichment in lrees relative to hrees and flat hrees and displays e morb like spider diagrams with the exception of insignificantly negative nb ta zr hf and ti anomalies in contrast the other group displays stronger lree fractionation stronger enrichment in lrees relative to hrees and mildly fractionated hrees and is characterized by spiky spider diagrams similar to arc volcanic rocks the first group is interpreted to have originated from a neoarchean e morb source whereas the second group shows inputs of newly subduction derived fluids in the mantle source these geochronological and geochemical signatures indicate the existence of an 2 2 2 1 ga continental back arc system in the luliang complex of the trans north china orogen which is consistent with the model that the collision between the eastern and western blocks to form the coherent basement of the north china craton in the paleoproterozoic not at the end of neoarchean

a major glacial interglacial change in aeolian dust composition inferred from rare earth elements in antarctic ice we present the first rare earth elements ree concentration record determined in 294 sections of an antarctic ice core epica dome c covering a period from 2 9 to 33 7 kyr bp ree allow a detailed quantitative evaluation of aeolian dust composition because of the large number of variables i e 14 elements ree concentrations match the particulate dust concentration profile over this period and show a homogeneous crustal like composition during the last glacial stage lgs with only a slight enrichment in medium ree this signature is consistent with the persistent fallout of a mixture of dust from heterogeneous sources located in different areas or within the same region e g south america starting at not vert similar15 kyr bp there was a major change in dust composition the variable character of which persisted throughout the holocene this varying signature may highlight the alternation of single dust contributions from different sources during the holocene we observe that the frequent changes in ree composition at the onset of the holocene 10 13 5 kyr bp are linked to dust size and in turn to wind strength and or the path of the atmospheric trajectory this may indicate that atmospheric circulation dictated the composition of the dust fallout to east antarctica at that time although the dust concentrations remained fairly low a notable return towards more glacial dust characteristics is recorded between 7 5 and 8 3 kyr bp this happened concomitantly with a widespread cold event around 8 kyr bp that was 400 600 years long and suggests a moderate reactivation of the dust emission from the same potential source areas of the lgs

biogeochemistry of iron in australian dust from eolian uplift to marine uptake 1 dust is an important vector for iron supply to the ocean which subsequently impacts ocean productivity atmospheric co2 concentrations and hence global climate here we synthesize the processes influencing the biogeochemistry of australian dust and compare them with those from other southern hemisphere dust sources our observations range from soil and dust physical properties to abrasion and cloud chamber chemistry experiments to dust storms and their dispersion and deposition we then present satellite observations of the impact of episodic dust deposition events on the productivity of low iron oceanic waters north i e low nitrate low chlorophyll lnlc and south i e high nitrate low chlorophyll hnlc of australia dust deposition from the largest dust storm in over 40 years did not result in iron mediated algal blooms in either oceanic region a comparison of australia with other southern hemisphere source regions reveals that the relatively well sampled australian system is a poor generic model furthermore there are marked distinctions between southern and northern hemisphere iron dust biogeochemistry that must be recognized by modelers and included in future simulations better information is required on the relative role of the atmosphere and ocean on influencing iron biogeochemistry and how their relative influences might change in the future due to climate change

windblown desert sands in coeval shallow marine deposits a key for the recognition of coastal ergs in the mid cretaceous iberian basin spain introductionthe action of the wind in ancientsedimentary records is commonlybased on the direct observations ofdune and interdune deposits within ahierarchy of aeolian bounding surfa ces a direct observation of ancientaeolian systems is not always possibleas they are prone to erosion and to theremoval of sand into other uvial andmarine systems although the aeoliandeposits may no longer be present their former existence can be inferredon the basis of grain size characteris tics and aeolian features on grainsurfaces aeolian sediments indeedconstitute an important source formarine deposits kukal and saadal lah 1973 fryberger et al 1983 widespread ne grained very well sorted quartz sandstones characterizeshallow marine facies in the mid cre taceous of the eastern spain iberianbasin the good sorting and round ness of the grains hint at the presenceof a nearby erg system suggestive ofan arid climatic zone along the west ern tethyan margin during the mid cretaceous geological settingthe mesozoic iberian basin along thewestern tethyan margin has one ofthe more complete lower middle cre taceous sedimentary records in eur ope the iberian range is a nw sestriking intraplate fold belt generatedby the tectonic inversion of theiberian basin during the palaeogene fig 1a b salas and casas 1993 capote et al 2002 this basin wasformed by crustal thinning duringthe late permian triassic and latejurassic early cretaceous rift stages salas and casas 1993 arche andlo pez go mez 1996 during thesecond rift stage extensional sub basins were formed as part of thelarger maestrazgo basin i e the east ern sector of the iberian basin fig 1b soria 1997 sands of boththe last synrift unit of these sub basins the escucha formation and of the rst post rift unit of the iberian basin the utrillas formation were depos ited across the estuarine deltaic and uvial environments fig 1c quer ol et al 1992 the sands are domi nantly ne grained show excellentsorting and as they consist almostpurely of quartz they are mineralog ically very mature the escucha and the utrillasformationsthe upper aptian middle albian es cucha formation aguilar et al 1971 sole de porta et al 1994 fig 1c was formed during the last phases ofthe second rift stage that a ected theiberian basin salas and casas 1993 it is a tidally in uenced heterolithicunit dominated by very well sorted ne sand and clay with coal bearingdepositsinitslowerpart andlocallyinthe basal part coarse grained siliciclas tic levels it lies upon the limestonesand marls of the urgonian platform aptian and is covered by sandstonesof the utrillas formation fig 1c pardo 1979 querol 1990 the es cucha formation was interpreted as adeltaic estuarine succession querolet al 1992 with a barrier island sys tem in the northern part of the olietesub basin rodri guez lo pez et al 2005 it was deposited in extensionalsub basins bounded by palaeogeo graphic thresholds produced by listricand block rotation faults the utrillasformation overlies the escucha for mation and is late albian early cen omanian in age and represents uvialdeposits pardo 1979 however theabstract

ammonium and non sea salt sulfate in the epica ice cores as indicator of biological activity in the southern ocean sulfate so42 and ammonium nh4 flux records over the last 150 000 years from both antarctic epica ice cores european project for ice coring in antarctica are presented the ice core record from dome c is influenced by the indian sector of the southern ocean so whereas dronning maud land is facing the atlantic sector generally they reflect the past atmospheric aerosol load and thus potentially reveal the fingerprint of marine biogenic sources from the so the most important feature of both the nssso 4 2 as well as nh4 flux records is the absence of any significant glacial cycles in contrary to the distinct transitions for mineral dust and sea salt aerosol over the last 150 000 years this finding challenges the iron fertilization hypothesis on long time scales as the significant changes in dust e g from the last glacial maximum toward the holocene have neither an impact on nssso 4 2 nor on nh4 fluxes found in interior antarctica the inter site correlation of both species is weak r 2 0 42 for the nssso 4 2 flux and r 2 0 12 for the nh4 flux respectively emphasizing the local source characteristics of biogenic aerosol from the so millennial variability in nh4 and nssso 4 2 is within the uncertainty of our flux estimates correlation with mineral dust and sea ice derived sodium shows only a very weak influence of dust deposition on those insignificant changes in nssso 4 2 flux for the atlantic sector of the southern ocean but also small transport changes or terrigeneous sulfate contributions may contribute to those variations at edml c 2009 elsevier ltd all rights reserved

was the deposition of large precambrian iron formations linked to major marine transgressions geochemical evidence suggests the iron and silica rich precipitates that compose large neoarchean and paleoproterozoic iron formations formed along a chemocline between iron rich deep water and iron poor surface water sedimento logical evidence indicates many large iron formations accumulated in marine shelf environments during major transgressions we suggest this occurred because the chemocline could only impinge on continental shelves during times of sea level rise or highstand on the other hand the stratigraphic record indicates that deposition of iron formations ceased during regressions in some basins and transgressions in others to explain this we propose that iron concentrations in the precambrian ocean were greatest at mid water depths in a zone on the order of 100 m thick radiometric age dates from the hamersley basin of western australia suggest major iron formation deposition had a periodicity of ca 20 to 125 m y close to second order cycles in phanerozoic sea level driven by long te

defining the geochemical composition of the epica dome c ice core dust during the last glacial interglacial cycle the major element composition of the insoluble windborne long range dust archived in the european project for ice coring in antarctica dome c ice core has been determined by particle induced x ray emission analyses the geochemistry of dust from the last glacial maximum lgm and from the holocene is discussed in terms of past environmental changes throughout the last climatic cycle antarctic dust from glacial and interglacial climate clearly reveals different geochemical compositions the weathered crustal like signature of lgm dust is characterized by a low compositional variability suggesting a dominant source under the glacial regime the close correspondence between the major element composition of antarctic glacial dust and the composition of southern south american sediments supports the hypothesis of a dominant role of this area as major dust supplier during cold conditions conversely the major element composition of holocene dust displays high variability and high al content on average this implies that an additional source could also play some role comparison with size selected sediments suggests that a contribution from australia is likely during warm times when a reduced glacial erosion decreases the primary dust production and a more intense hydrological cycle and larger vegetation cover inactivates dust mobility in a large part of southern south america weakening its contribution as a massive dust supplier to antarctica

iron in ice cores from law dome a record of atmospheric iron deposition for maritime east antarctica during the holocene and last glacial maximum total dissolvable iron tdfe was measured in sections of ice cores recovered from law dome on the coast of wilkes land east antarctica these samples include ice dating from the last glacial maximum lgm the last deglaciation and the early and mid holocene as well as samples from the anthropocene that have been dated with seasonal to annual resolution combining our tdfe concentration data with estimates of the ice accumulation rate we estimate the atmospheric iron deposition for law dome and the adjacent southern ocean during these periods our results indicate that the atmospheric iron deposition flux to this region during the lgm 8 mol fe m 2 yr 1 was an order of magnitude higher than the average holocene deposition flux 0 8 mol fe m 2 yr 1 this holocene flux estimate is significantly higher than recent estimates of atmospheric iron deposition based on the analysis of iron in samples of the dome c epica ice core implying that there are significant meridional gradients in eolian iron flux to the antarctic region our data also suggest that there have been significant variations in atmospheric iron deposition to law dome and adjacent ocean waters over seasonal to decadal timescales during the past century analysis of ice samples dating from calendar years 1927 to 1928 indicates an anomalously high flux of tdfe to the law dome region amounting to around half the maximum lgm flux possibly as a result of severe drought conditions on the australian continent given that chronic iron deficiency is thought to limit phytoplankton production in much of the ocean around antarctica such large secular variations in atmospheric iron supply are likely to have had profound impacts on year to year primary production and ecosystem structure in antarctic waters

archaean gneisses amphibolites and banded iron formations from the anshan area of liaoning province ne china their geochemistry metamorphism and petrogenesis an investigation of the trace element geochemistry and geothermobarometry of amphibolites and banded iron formations bif of the anshan group and of associated amphibolite facies orthogneisses in the anshan area of liaoning province of ne china has been carried out with a view to understanding the petrogenesis and evolution of this archaean high grade terrain which is unique for its abundance of bif the anshan supracrustal group which has a sm nd isochron age of 2 79 ga comprises bif metavolcanic amphibolites quartzites phyllites and schists the bif actinolite cummingtonite magnetite quartz stilpnomelane occurs in kilometre long beds up to 80 m thick which contain very low contents of total ree co2 s cu pb zn mn ni p ti v and cr s34 is near chondritic and o18 approximates the calculated primary o18 of sio2 deposited from archaean sea water the amphibolites hornblende plagioclase quartz epidote tourmaline form beds up to 1 km thick range from quartz to olivine and hyperthene normative and have low zr and ti abundances and trace element patterns that are most similar to those of basalts derived from sub continental mantle or to those of modern island arc tholeiites metasediments are muscovite tourmaline quartzites quartz muscovite chlorite phyllites quartz biotite muscovite garnet staurolite schists quartz garnet biotite schists quartz garnet cumming tonite gedite rocks and quartz k feldspar plagioclase biotite sillimanite gneisses the tiejiashan orthogneisses which have rb sr and pb pb isotopic ages of 2 83 2 86 ga probably represent basement to the anshan group they range from granites to trondhjemites and consist of quartz plagioclase biotite and microcline the anshan orthogneisses have a sm nd isochron age of 2 53 ga and range in composition from granites to tonalites they intruded the anshan supracrustals with the result that the bif and associated supracrustal rocks now form lenses of up to several kilometres in the gneisses the most common assemblage is quartz k feldsparplagioclase biotite both the tiejiashan and anshan gneisses have high sr rb and k sr and low ca and thus are similar to amphibolite facies gneisses in many high grade terrains and to modern volcanic arc granites geothermometry of metasediments suggests that t increased from 500 550 c in the south to 600 c in the north of the area these temperatures are consistent with the presence of amphibolites sillimanite in gneisses and staurolite in schists no assemblages are suitable for estimating pressure combined geological geochronological and geochemical data suggest to us that the anshan group was deposited in a shallow water basin on or against a continental margin or basement and close to a magmatic arc during the accretion events associated with the 2 5 ga anshan orogeny arc driven granitic rocks intruded the basin and engulfed the supracrustal rocks leaving the bif etc as enclaves in ductile orthogneisses

stratigraphic architecture of alluvial aeolian systems developed on active karst terrains an early pleistocene example from the ebro basin ne spain abstract during the early pleistocene fluvial alluvial and aeolian depositional systems interacted in the central ebro basin spain constructing wide alluvial plains over a neogene evaporite substratum fluvial sediments mainly longitudinal gravel bars and channels are interdigitated with gravel mass flow and distal mudflat deposits aeolian sedimentation is registered as aeolian dunes and sand sheets episodes of fluvial deposition alternated with periods of alluvial fan progradation and aeolian deposition these changes are related to climate driven water availability stratigraphic units and deformation structures show synsedimentary karstification of the evaporite substratum that although karst was not restricted to any particular climate scenario was probably favoured during periods of high water availability karstification conditioned the development of local sedimentary depocentres which in turn influenced the distribution of sedimentary subenvironments as well as the accumulation and preservation of aeolian dunes and lacustrine palustrine deposits stratigraphic architecture shows that thickening of the series due to karst subsidence did not occur homogeneously but was controlled by diachronous subsidence resulting in numerous angular unconformities in subsiding karst areas transport capacity was reduced and sediment preservation increased

tectonothermal history of the basement rocks in the western zone of the north china craton and its tectonic implications the basement of the north china craton can be divided into the eastern central and western zones based on lithological structural metamorphic and geochronological data the western zone comprises two different petrotectonic units archaean tonalitic trondhjemitic granodioritic ttg grey gneisses and metamorphic mafic rocks and palaeoproterozoic khondalite series the former is characterized by isobaric cooling ibc type anticlockwise p t paths in the north northwestern part of the zone and near isothermal decompression itd type clockwise p t paths in the eastern part adjacent to the central zone on the other hand the tectonothermal evolution of palaeoproterozoic khondalite series rocks is characterized exclusively by nearly isothermal decompression following the peak of metamorphism and then cooling defining clockwise p t paths the archaean ttg gneisses and associated mafic rocks with anticlockwise metamorphic p t paths reflects an origin related to underplating and intrusion of mantle derived magmas which may be derived from mantle plumes they represent a late archaean continental block in the western part of the north china craton the palaeoproterozoic khondalite series rocks represent passive continental margin deposits they were metamorphosed and deformed in the late palaeoproterozoic during the amalgamation of the western continental block with another continental block in the east part of the north china craton the itd type clockwise p t t paths of the palaeoproterozoic khondalite series rocks record the tectonothermal histories of the collision of the western and eastern continental blocks which resulted in the final assembly of the north china craton at c 1800 ma

marine destruction of eolian sand seas origin of mass flows abstract the basal marine sandstone of the upper jurassic curtis formation of northeastern utah was deposited in a shallow tide dominated sea during marine transgression across the entrada eolian sand sea entrada dunes within the study area are interpreted to have been over 100 m in height eolian paleotopographic highs along the entrada curtis contact however are only up to 7 m high clearly indicating that major portions of entrada dunes were destroyed within the transgressive marine deposits are abundant massive sandstone beds up to 12 m thick that are interpreted as mass flow deposits derived from the marine destruction of the large entrada dunes these massive sandstones are lenticular and locally contain clay and sandstone clasts faint horizontal and contorted laminae and dish s ructures some massive sandstones were emplaced with significant scour of underlying deposits but others show nonerosional basal contacts that bury and perfectly preserve underlying marine megaripples and trains of megaripples most mass flows were probably initiated during marine storm events surges that undercut dunes and resulted in slumpage followed immediately by liquefaction and flowage liquefaction in water saturated basal portions of dunes probably also resulted in failure and flowage interpreted travel distances of a few kilometers over the gently sloping curtis shelf suggest that liquefied flows evolved into high density turbidity currents characteristics of the massive sandstone deposits however indicate that final deposition was from liquefied flows the flows there ore apparently evolved from liquefied flows to high density turbidity currents and then back to liquefied flows as momentum was lost we suggest that slumping liquefaction and mass flowage of dune sands which are very prone to liquefaction commonly occur along the coastlines of some eolian sand seas and are significant mechanisms for the destruction of dunes during marine transgressions and for offshore transport of sand to the shelf these mechanisms can also operate in flooded interdune areas during major storms available literature suggests that massive sandstones are abundant along eolian marine contacts where dune topography has been largely destroyed and are relatively uncommon where dunes are preserved nearly intact the primary factors that control the frequency of mass flow events during marine transgression and similarly whether dune topography is preserved or destroyed are 1 the energy and nature f the transgressing marine environment 2 the rate of transgression and 3 the abundance of sand stabilizing early cements

the contribution of aeolian sand and dust to iron fertilization of phytoplankton blooms in southwestern ross sea antarctica iron is a limiting micronutrient for primary production in the ross sea antarctica recent observations reveal low dissolved fe dfe concentrations in the ross sea polynya following high initial rates of primary production in summer after the dfe winter reserve has been consumed significant new sources of dfe are therefore required to further sustain phytoplankton blooms iron from aeolian sand and dust asd released from melting sea ice is one potential source to constrain aeolian fe inputs we determined asd mass accumulation rates and the total and soluble fe content of asd on sea ice in mcmurdo sound southwestern sw ross sea the mean mass accumulation rate was 1 5 g m 2 yr 1 total fe content of this asd was 4 1 wt and the percentage of soluble fe was 11 1 our mean estimate of the bulk aeolian dfe flux of 122 1 mol m 2 yr 1 for the mcmurdo sound region suggests that aeolian fe can support between 9 0 109 and 4 1 1011 mol c yr 1 0 1 4 9 tg c yr 1 of new primary production this equates to only 15 of new primary production in the sw ross sea suggesting that aeolian dfe is a minor component of seasonal fe supply the very high asd accumulation on sea ice in mcmurdo sound compared to other regions of antarctica suggests that our results represent the upper limit of dfe supply to the ocean from this source in the ross sea

seismogenically induced fluidization of jurassic erg sands south central utah large bodies of fluidized sandstone occur in the jurassic entrada carmel page and navajo formations at several locations in south central utah they are most abundant in the entrada sandstone where they commonly occur in clusters have a cylindrical form and have a sharp contact with their cross bedded host rock these clastic pipes are as wide as 75 m and have exposed heights of as much as 100 m some of the entrada pipes extend well into the underlying carmel redbeds other clastic pipes in the entrada sandstone are less deformed and display various degrees of brittle to hydroplastic deformation and liquefaction clastic pipes in the page and navajo sandstones are less common but are similar in size and form to those in the entrada and carmel and probably have a similar origin some massive sandstone bodies are irregular in form and have tongue like projections into the host rock implying forcible injection of fluidized sand several pipe host contacts in the entrada sandstone display small scale ring faults where relative displacement can be clearly demonstrated pipe sandstones are invariably down faulted locally as much as 5 m at two sites carmel host rock is upwarped around the entrada pipes stratified and cross bedded breccia blocks occur in many entrada pipes and preliminary petrographic analysis indicates that at least some of these breccia blocks are derived from the host rock homogeneous pipe sandstones are also petrographically similar to their entrada host rock suggesting that some pipes originate through fluidization of the fine grained entrada fluidization of the entrada must have occurred in a water saturated environment during early diagenesis but before complete lithification most probably under considerable porewater pressure although there are no known modern analogues to these huge masses of structureless sandstone they may have a small scale modern counterpart in earthquake induced sandblows these features were most probably caused by large magnitude seismic events during the middle jurassic although other possibilities cannot be ruled out at this point

coherent composition of glacial dust on opposite sides of the east antarctic plateau inferred from the deep epica ice cores 1 the dust provenance identification through isotopic and geochemical tracers focused mostly on ice cores drilled in the pacific indian sector of antarctica where a common provenance of dust from southern south america during glacial ages was demonstrated conversely in other areas of the east antarctic plateau as dronning maud land provenance was deduced indirectly from back trajectory analyses and soluble chemistry records in this work we present the first comparison of major elemental composition of dust archived in two ice cores from opposite sides of antarctica in the framework of the epica project mineral particles extracted from the edc and edml cores date back to glacial mis 2 4 and 6 over the last 200 kyr results reveal a coherent geochemical dust composition at both locations providing experimental evidence of a common provenance over the wide area of east antarctica during glacials and key analytical constrains for atmospheric general circulation models

a tentative chronology for the epica dome concordia ice core a tentative age scale edc1 for the last 45 kyr is established for the new 788 m epica dome c ice core using a simple ice flow model the age of volcanic eruptions the end of the younger dryas event and the estimated depth and age of elevated 10be about 41 kyr ago were used to calibrate the model parameters the uncertainty of edc1 is estimated to 10 yr for 0 to 700 yr bp up to 200 yr back to 10 kyr bp and up to 2 kyr back to 41 kyr bp the age of the air in the bubbles is calculated with a firn densification model in the holocene the air is about 2000 yr younger than the ice and about 5500 yr during the last glacial maximum

atmospheric iron fluxes over the last deglaciation climatic implications a decrease in the micronutrient iron supply to the southern ocean is widely believed to be involved in the atmospheric co2 increase during the last deglaciation here we report the first record of atmospheric iron fluxes as determined in 166 samples of the dome c ice core and covering the last glacial interglacial transition 22 9 kyr b p it reveals a decrease in fallout flux from 24 10 2 mg fe m 2 yr 1 during the last glacial maximum to 0 7 10 2 mg fe m 2 yr 1 at the onset of the holocene the acid leachable fraction of iron determined in our samples was the 60 of the total iron mass in glacial samples about twice the value found for holocene samples this emerging difference in iron solubility over different climatic stages provides a new insight for evaluating the iron hypothesis over glacial interglacial periods

complexities in eolian and marine interactions processes and eustatic controls on erg development abstract the interplay between eolian and marine realms includes process interactions cycles of transgression and regression and possible inland effects of marine coastal events process interactions are geologically common and most obvious where eolian and marine environments are adjacent these interactions include sediment exchange between the two environments the supply of marine ions to the erg for surface and near surface cementation and the control directly or indirectly of marine events on the sediment budget of an erg regression accompanied by erg progradation over marine deposits occurs with both onshore and offshore winds marine transgression of ergs varies from producing a planar marine scoured surface to a planar deflation surface that precedes the transgression to varying degrees of paleotopographic dune preservation and a variety of transitional facies the extent of paleotopographic dune preservation is largely a function of the energy level of the transgressing marine realm the rate of the transgression and potential for early dune cementation general correlations between ergs and global eustatic sea level and coastal onlap curves occur for coastal and near coastal cyclic erg sequences eustatic control of inland ergs exists to the extent that sea level controls in large measure the extent of the basin exposed to subaerial processes i e regional base level and probably to a lesser extent the sediment supply to the erg direct correlation of inland erg events to coastal onlap curves is dubious at present but an indirect relationship may exist

synchronous deposition of volcanic ash and sulfate aerosols over greenland in 1783 from the laki eruption iceland 1 sulfate aerosols from the 1783 1784 a d laki eruption are widely used as a reference horizon for constraining greenland ice core time scales yet the timing of the arrival of the sulfate remains under discussion two ice cores from western greenland analyzed with high temporal resolution confirm that sulfate aerosols arrived over greenland late in 1783 concomitant with the tephra elevated concentrations of cd bi and tl all indicators of volcanic emissions and with a short lived rare earth elements anomaly thereafter sulfate deposition declined rapidly very modest concentrations of sulfate in 1784 snowfall evident in six greenland cores suggest a relatively short less than 1 year atmospheric residence time and an injection height limited to the lower stratosphere an improved estimate of the associated stratospheric sulfate burden is calculated and provides an important input for models assessing climatic impacts of this volcanic eruption

mass and hyperconcentrated flow deposits record dune damming and catastrophic breakthrough of ephemeral rivers skeleton coast erg namibia channel shaped deposits of well sorted sand with only 2 4 fine grained material being either massive and structureless or upward fining with basal lag are found interbedded with aeolian sand in the skeleton coast erg namibia detailed analyses of the channel shaped deposits suggest that they are formed as hyperconcentrated flows within the erg grain size analysis and whole rock geochemical modeling revealed that some of the fluvial sediments contain up to 70 aeolian sand interpreted as a result of dune collapse into the fluvial system in certain cases this instantaneous supply of sand resulted in generation of sandy mass flows with laminar flow behaviour the presence of smectite as dominant clay mineral proved to be of crucial importance in formation of mass flow deposits these mass flows had no erosional capacity and drape the palaeotopography they are comparable to those generated by catastrophic collapse of dunes described in the literature this paper suggests that all these deposits should be termed intra erg mass flows as several of them carry little if any debris based on their origin intra erg mass flows can be divided into two groups

archean blocks and their boundaries in the north china craton lithological geochemical structural and p t path constraints and tectonic evolution an examination of lithological geochemical geochronological structural and metamorphic p t path data suggests that the basement of the north china craton can be divided into eastern and western blocks separated by major crustal boundaries that roughly correspond with the limits of a 300 km wide zone called the trans north china orogen the eastern block consists predominantly of late archean domiform tonalitic trondhjemitic granodioritic ttg batholiths surrounded by anastomosing networks and linear belts of open to tight synforms of minor volcanic and sedimentary rocks metamorphosed from greenschist to granulite facies at 2 5 ga with anticlockwise p t paths some early to middle archean rocks are locally present in the eastern block but their tectonic history is unclear due to reworking by the 2 5 ga tectonothermal event the western block has a late archean assemblage structural style and metamorphic history similar to that of the eastern block but it differs in the absence of early to middle archean assemblages and in being overlain by and interleaved with paleoproterozoic khondalites which were affected by a 1 8 ga metamorphic event involving clockwise p t paths a mantle plume model is proposed for the formation and evolution of late archean basement rocks in the eastern and western blocks based on a combination of extensive exposure of ttg gneisses affinities of mafic rocks to continental tholeiitic basalts presence of voluminous komatiitic rocks dominant diaprism related domiform structures anticlockwise p t paths and a short time span from the primary emplacement of ttg and ultramafic to mafic rocks until the onset of regional metamorphism between the two blocks is the trans north china orogen which is bounded by two major fault systems and is composed of late archean to paleoproterozoic ttg gneisses and granitoids interleaved with abundant sedimentary and volcanic rocks that are geochemically interpreted as having developed in magmatic arc and intra arc basin environments these rocks underwent multiple phases of compressional deformation and peak high pressure metamorphism followed by rapid exhumation during the late paleoproterozoic at 1 8 ga as a result of collision between the eastern and western blocks resulting in the amalgamation of the north china craton

u pb and hf isotopic study of zircons of the helanshan complex constrains on the evolution of the khondalite belt in the western block of the north china craton abstract the helanshan complex is located at the westernmost segment of the khondalite belt a continent continent collisional belt along which the yinshan block in the north collided with the ordos block in the south to form the western block of the north china craton the complex consists of s type granites and high grade pelitic granulite gneiss felsic paragneiss quartzite calc silicate rock and marble together called the khondalite series rocks la q icp ms u pb geochronology and la mc icp ms lu hf isotopic data of zircons combined with cathodoluminescence cl imaging enable the resolution of magmatic and metamorphic events that can be directed towards understanding the formation and evolution of the khondalite belt in the western block of the north china craton cl images reveal the coexistence of magmatic type detrital zircons and metamorphic zircons in most of the khondalite series rocks of which the metamorphic zircons occur as either single grains or overgrowth rims surrounding and truncating magmatic type detrital zircon cores la q icp ms u pb analyses on magmatic type detrital zircons reveal two distinct age populations with one in the archaean 2 85 2 53 ga and the other in the palaeoproterozoic 2 2 2 0 ga suggesting that the sedimentary protoliths of the khondalite series rocks in the helanshan complex must have been deposited at some time after 2 0 ga the hf analyses show that the archaean detrital zircons possess negative ehf t values from 7 64 to 0 15 with depleted mantle model ages ranging from 3 34 to 3 10 ga this implies the existence of a paleo mesoarchaean 3 34 3 10 ga crust in the western block which underwent a recycling event in the period 2 85 2 53 ga nearly all palaeoproterozoic 2 2 2 0 ga detrital zircons possess positive ehf t values 0 86 9 38 with depleted mantle model ages of 2 45 2 15 ga suggesting a significant crustal growth event in the western block in the palaeoproterozoic metamorphic zircons yield two groups of age with one at 1 95 ga and the other at 1 87 ga of which the former is considered as the timing of the collision between the yinshan and ordos blocks to form the western block whereas the latter is consistent with the age of 1 86 ga from two s type granites which are considered to have formed by the partial melting of pelitic granulites gneisses at the stage of the exhumation of the helanshan complex

multiple sources of soluble atmospheric iron to antarctic waters the ross sea antarctica is a highly productive region of the southern ocean significant new sources of iron fe are required to sustain phytoplankton blooms in the austral summer atmospheric deposition is one potential source the fractional solubility of fe is an important variable determining fe availability for biological uptake to constrain aerosol fe inputs to the ross sea region fractional solubility of fe was analyzed in a snow pit from roosevelt island eastern ross sea in addition aluminum dust and refractory black carbon rbc concentrations were analyzed to determine the contribution of mineral dust and combustion sources to the supply of aerosol fe we estimate exceptionally high dissolved fe dfe flux of 1 2 10 6 g m 2 y 1 and total dissolvable fe flux of 140 10 6 g m 2 y 1 for 2011 2012 deposition of dust fe al and rbc occurs primarily during spring summer the observed background fractional fe solubility of 0 7 is consistent with a mineral dust source radiogenic isotopic ratios and particle size distribution of dust indicates that the site is influenced by local and remote sources in 2011 2012 summer relatively high dfe concentrations paralleled both mineral dust and rbc deposition around half of the annual aerosol fe deposition occurred in the austral summer phytoplankton growth season however the fractional fe solubility was low our results suggest that the seasonality of dfe deposition can vary and should be considered on longer glacial interglacial timescales

zircon geochronology and metamorphic evolution of mafic dykes in the hengshan complex of northern china evidence for late palaeoproterozoic extension and subsequent high pressure metamorphism in the north china craton abstract magmatic and metamorphic zircons have been dated from ductilely deformed gabbroic dykes defining a dyke swarm and signifying crustal extension in the northern part of the hengshan complex of the north china craton these dykes now occur as boudins and deformed sheets within migmatitic tonalitic trondhjemitic granodioritic and granitic gneisses and are conspicuous due to relics of high pressure granulite or even former eclogite facies garnet pyroxene bearing assemblages shrimp ages for magmatic zircons from two dykes reflect the time of dyke emplacement at 1915 ma whereas metamorphic zircons dated by both shrimp and evaporation techniques are consistently in the range 1848 1888 ma the youngest granitoid gneiss yet dated in the hengshan has an emplacement age of 1872 17 ma these results complement recent geochronological studies from the neighbouring wutai and fuping complexes to the se of the hengshan showing that a crustal extension event occurred in the late palaeoproterozoic this preceded a major high pressure collision type metamorphic event in the central part of the north china craton that occurred in the palaeoproterozoic and not in the late archaean as previously thought our data support recent suggestions that the north china craton experienced a major craton wide orogenic event in the late palaeoproterozoic after which it became cratonized and acted as a stable block

comparing the epica and vostok dust records during the last 220 000 years stratigraphical correlation and provenance in glacial periods a new aeolian dust record from the first 2200 m of the epica dome c ice core 75 06 s 123 21 e covering about 220 000 years of climatic history is compared to the vostok 78 28 s 106 48 e ice core nature 399 1999 429 the two dust profiles are very similar and several common dust events allow to establish stratigraphical links the late quaternary period is characterized at both sites and likely overall east antarctic plateau by high dust input during glacial periods in the epica dome c ice core the dust flux rises by a factor of 25 20 and 12 in glacial stages 2 4 and 6 with respect to interglacial periods holocene and stage 5 5 the magnitude and pattern of changes are comparable in the vostok ice core in this study the geographical origin of ice core dust icd in cold periods has been investigated at both sites through 87sr 86sr versus 143nd 144nd isotopic tracers following the previous studies of grousset et al earth planet sci lett 111 1992 175 and basile et al earth planet sci lett 146 1997 573 the new data and the existing ones allow to define the isotopic fields for dust at the two antarctic sites that are almost identical and restricted into the 0 708 87sr 86sr 0 711 and 5 end 0 5 ranges this suggests a common geographical provenance for dust at vostok and dome c and for all the glacial periods of the late pleistocene to decipher the icd provenance more than 50 samples of loess and aeolian deposits sands and fluvioglacial sediments from the potential source areas psas of the southern hemisphere have been collected however the methodology has been refined with respect to former studies first the isotopic fractionation that can occur in function of grain size has been taken into account and the psa s signature has been defined in the 5 m size range within which fine grained dust reaching antarctica is found moreover a possible contribution from carbonates on the samples from psas has also been also considered south africa and australia can be excluded as dominant sources but a partial overlap arises among southern south america new zealand and the antarctic dry valleys isotopic fields these latter two documented for the first time a possible contribution from all these three sources cannot be excluded but complementary arguments suggest the dominant contribution to east antarctic dust in glacial times deriving from the southern south american region of patagonia and the pampas this study shows a first order uniformity in the dust flux and geographical provenance to the east antarctica plateau during glacial periods

implications of the glacial co2 iron hypothesis for quaternary climate change 1 the iron hypothesis posits a role for increased supply of mineral aerosol to the ocean surface during glacial periods in driving atmospheric co2 lower that changes in co2 and climate strongly affect dust supply raises the possibility of feedback here i take a systems view in analyzing the properties and implications of such a feedback and consider three primary state variables that can be related empirically to each other dust supply atmospheric co2 and climate surface air temperature the results of this analysis suggest that the dust co2 climate feedback is primarily an intraglacial phenomenon when it can account for about a third of the temperature variability recorded in antarctic ice cores since glacial interglacial cyclicity prior to ca 800 kyr bp is characterized by the absence of a full glacial state such as the last glacial maximum it is possible that destabilization of climate by the marine iron cycle is fundamental to the differences between 41 kyr and 100 kyr climatic regimes the critical role played by the state of the land surface in this feedback also has implications for the longer term evolution of the earth system during the cenozoic

feedback between aeolian dust climate and atmospheric co2 in glacial time 1 enhanced aeolian supply of iron to the biota of the southern ocean during glacial periods is suspected to be an important contributory mechanism to the concurrently low observed mixing ratios of atmospheric co2 declining rates of dust deposition prior to the glacial terminations may be critical in driving the initial deglacial rise in co2 but the reasons behind the dust decline itself are as yet unknown here we show that the dust record from the vostok ice core can be qualitatively derived from a few general assumptions regarding the formation and aging of patagonian sources of aeolian material and the efficiency with which it is transported through the atmosphere we suggest that during glacial periods this dust supply becomes particularly sensitive to changes in global climate and that in turn climate is responsive to the dust due to iron fertilization this positive feedback may mean that during glacial periods the carbon cycle exhibits two quasi steady states characterized by distinct co2 concentrations recognition of this glacial subcycle may help to account for the timing and sequence of events at the terminations

the role of southern ocean processes in orbital and millennial co2 variations a synthesis abstract recent progress in the reconstruction of atmospheric co 2 records from antarctic ice cores has allowed for the documentation of natural co 2 variations on orbital time scales over the last up to 800 000 years and for the resolution of millennial co 2 variations during the last glacial cycle in unprecedented detail this has shown that atmospheric co 2 varied within natural bounds of approximately 170 300 ppmv but never reached recent co 2 concentrations caused by anthropogenic co 2 emissions in addition the natural atmospheric co 2 concentrations show an extraordinary correlation with southern ocean climate changes pointing to a significant direct or indirect influence of climatic and environmental changes in the southern ocean region on atmospheric co 2 concentrations here we compile recent ice core and marine sediment records of atmospheric co 2 temperature and environmental changes in the southern ocean region as well as carbon cycle model experiments in order to quantify the effect of potential southern ocean processes on atmospheric co 2 related to these orbital and millennial changes this shows that physical and biological changes in the so are able to explain substantial parts of the glacial interglacial co 2 change but that none of the single processes is able to explain this change by itself in particular changes in the southern ocean related to changes in the surface buoyancy flux which in return is controlled by the waxing and waning of sea ice may favorably explain the high correlation of co 2 and antarctic temperature on orbital and millennial time scales in contrast the changes of the position and strength of the westerly wind field were most likely too small to explain the observed changes in atmospheric co 2 or may even have increased atmospheric co 2 in the glacial also iron fertilization of the marine biota in the southern ocean contributes to a glacial drawdown of co 2 but turns out to be limited by other factors than the total dust input such as bioavailability of iron or macronutrient supply

significance of aeolian limestone lenses in quartz sand formations an interdigitation of coastal and continental facies perth basin southwestern australia abstract in the quaternary of the perth basin of southwestern australia the transition from coastal dune ridges to continental siliciclastic sand hinterland is a zone of calcareous sand or limestone lenses on or within siliciclastic sand in the holocene sequences the transition is a zone of landward extended and detached parabolic dunes which in section appear as lenses of calcareous sand resting on pleistocene quartz sand and limestone in the pleistocene sequences aeolian limestone lenses are common in thick sections of yellow quartz sand using the holocene coast to hinterland transition as an analogue the limestone lenses are interpreted to be buried outliers of attenuated parabolic calcareous dunes that migrated inland over an undulating plain of yellow quartz sand from a pleistocene coastal zone these dunes were later buried by influxes of aeolian yellow quartz sand during glacial age desert phases of the pleistocene in section these buried dunes form a zone of limestone lenses within aeolian quartz sand formations thus in a given time interval limestone lenses represent the transition between coastal and hinterland continental desert environments and record the extent that coastal dunes penetrated inland the pleistocene stratigraphic model of aeolian limestone lenses set within a sequence of aeolian siliciclastic sand is a distinctive style of coastal to continental transition which can be used to unravel similar sequences in the stratigraphic record where coastal aeolian calcareous facies interdigitate with desert aeolian siliciclastic facies

paleohydrologic controls on soft sediment deformation in the navajo sandstone abstract many workers have noted the presence of contorted cross strata in the navajo sandstone and other ancient eolianites and have recognized their significance as indicators of sediment saturation during the accumulation history horowitz 1982 proposed a general model for the production of such features in ancient ergs by episodic seismically induced liquefaction of accumulated sand a key feature of that popular model is the prevalence of a flat water table characteristic of a hyper arid climatic regime during deformation under arid climatic conditions the water table is established by regional flow and liquefaction is limited to the saturated regions below the level of interdune troughs however various paleohydrological indicators from navajo sandstone outcrops point toward a broader range of water table configurations during the deformation history of that eolianite some outcrops reveal extensive deformation complexes that do not appear to have extended to the contemporary depositional surface these km scale zones of deformation affecting multiple sets of cross strata and grading upward into undeformed crossbeds may represent deep water table conditions coupled with high intensity triggers which produced exclusively intrastratal deformation such occurrences contrast with smaller scale complexes formed within the zone of interaction between the products of soft sediment deformation and surface processes of deposition and erosion the horowitz model targets the smaller scale deformation morphologies produced in this near surface environment this study examines the implications of a wet climatic regime for the horowitz deformation model it demonstrates how a contoured water table characteristic of humid climates may have facilitated deformation within active bedforms as well as in the accumulation intra dune deformation would enable deflation of deformation features during the normal course of dune migration more parsimoniously accounting for the frequent occurrence of erosionally truncated deformation structures in the navajo sandstone the production of such erosional truncations during bedform climb and aggradation of the accumulation and the dramatic fluctuations in the water table required to deposit dry eolian sand deform those deposits under saturated conditions and then dry the deformed sand to enable deflation

iron speciation in aerosol dust influences iron bioavailability over glacial interglacial timescales 1 iron deposition influences primary production and oceanic sequestration of atmospheric carbon dioxide co2 iron has two oxidation states fe ii and fe iii with fe ii being more soluble and available for oceanic phytoplankton uptake the past proportions of soluble iron in aerosol dust remain unknown here we present iron speciation fe2 and fe3 in the antarctic talos dome ice core over millennial time scales we demonstrate that iron speciation over the last 55 kyr is linked to increasing quantities of fine dust fd 0 7 5 m and intensified long range dust transport we propose that fe ii and fe2 production is principally enhanced in fd by photoreduction although ph and organic complexation may also contribute to the speciation dynamics during the last glacial maximum fe2 concentrations in dust increased by up to seven times more than interglacial levels while fe3 only doubled cold and dusty climatic periods may increase the percentage of biologically available fe ii and fe2 deposited in the nutrient limited southern ocean allowing greater phytoplankton uptake and perhaps increased co2 drawdown

a 220 kyr record of pb isotopes at dome c antarctica from analyses of the epica ice core pb isotopic compositions and pb and ba concentrations are reported in epica dome c ice core samples dating to 220 kyr bp indicating that pb isotopic compositions in antarctic ice vary with changing climate 206pb 207pb ratios decrease during glacial periods with the lowest values occurring during colder climatic periods stages 2 4 and 6 and the holocene low pb concentrations 10 pg g were found during cold climatic periods ba a proxy for mineral dust was used to determine that dust usually accounts for 70 of pb in dome c ice while the remaining 30 was attributed to volcanic emissions pb isotopic compositions at dome c differ from those reported in pre industrial ice from other antarctic locations due to greater proportions of dust pb at dome c

metamorphic p t paths of the zanhuang amphibolites and metapelites constraints on the tectonic evolution of the paleoproterozoic trans north china orogen garnet bearing metapelites and amphibolites are exposed in the south and middle parts of the zanhuang complex which is located in the central segment of the nearly ns striking trans north china orogen these rocks preserve three metamorphic mineral assemblages forming at the prograde peak and post peak decompression stages the prograde metamorphic stage m1 is represented by mineral inclusions within garnet porphyroblasts the peak metamorphic stage m2 is represented by garnet rims and matrix minerals whereas the retrograde stage m3 is represented by amphibole plagioclase symplectite rimming garnet porphyroblasts in the amphibolites and biotite plagioclase symplectite rimming garnet porphyroblasts in the metapelites all garnet porphyroblasts in the metapelites preserve prograde chemical zoning except for the ubiquitous quite narrow zones from the underwent post peak decompression it has been determined through thermobarometric computation that the metamorphic conditions are 650 710 c at 8 2 9 2 kbar for the m1 inclusion assemblages 810 c at 12 5 kbar for the metamorphic peak m2 matrix assemblages and 660 680 c at 4 4 4 5 kbar for the retrograde m3 symplectite assemblages these rocks are thus determined to have undergone metamorphism with clockwise p t paths involving nearly isothermal decompression itd segments which is inferred to be related to the amalgamation of the eastern and western blocks to form the coherent basement of the north china craton along the trans north china orogen in the late paleoproterozoic 1 88 1 85 ga

a comparison of u pb and hf isotopic compositions of detrital zircons from the north and south liaohe groups constraints on the evolution of the jiao liao ji belt north china craton the jiao liao ji orogenic belt is one of the important paleoproterozoic mobile belts in the north china craton ncc and its central segment consists of the north and south liaohe groups and the liaoji granitoids the north and south liaohe groups consist of sedimentary and volcanic successions metamorphosed from greenschist to lower amphibolite facies and the liaoji granitoids are divisible into 2 2 2 1 ga pre tectonic monzogranitic gneisses and 1 88 1 85 ga post tectonic porphyritic monzogranites and alkaline syenites combined with cathodoluminescence cl imaging we report la icp ms laser ablation inductively coupled plasma mass spectrometry u pb and hf isotopic data for detrital zircons from the north and south liaohe groups zircons grains from both groups have igneous zircon cores that yielded two u pb age populations at 2 0 2 2 ga major and 2 5 ga minor indicating that their provenances were similarly dominated by paleoproterozoic liaoji granitoids and late archean basement rocks some structureless zircon rims in both groups yield concordant or upper intercept ages 1 9 ga interpreted as the peak metamorphic age of the two groups these results suggest that both groups were deposited in the period 2 0 1 9 ga shortly after the emplacement of the liaoji granitoids moreover zircons from both groups have similar hf model age peaks t c dm peaks at 2 66 2 75 ga and 2 80 3 00 ga

shrimp u pb zircon geochronology of the huai an complex constraints on late archean to paleoproterozoic crustal accretion and collision of the trans north china orogen

bottomset and foreset sedimentary processes in the mixed carbonate siliciclastic upper jurassic lower cretaceous vaca muerta formation picun leufu area argentina abstract the upper jurassic lower cretaceous vaca muerta formation at the picun leufu area constitutes bottomset and foreset marine deposits comprising open bay siliciclastic basin and mixed carbonate siliciclastic shelf facies detailed sedimentological ichnological and sequence stratigraphic analysis of six stratigraphic sections allows establishing two depositional sequences depositional sequence 1 ds1 begins with lowstand eolian deposits included in the quebrada del sapo formation and continues with thin retrograding transgressive open bay facies of the vaca muerta formation encompassing coastal sand sheet and dune marginal marine bay margin and distal bay facies above the transgressive deposits the regressive hemicycle of ds1 consists of bottomset deposits representing a siliciclastic basin facies association lobe and lobe fringe hyperpycnal flow sedimentation alternated with hemipelagic basinal deposition in an oxygen deficient environment a relative sea level fall generated a sequence boundary which coincides with an angular unconformity that marks the base of depositional sequence 2 ds2 this sea level fall triggered the formation of an extensive lowstand channel fill and lobe complex at the base of the slope followed by retrogradational lobe facies during the subsequent transgression the regressive hemicycle of ds2 represents foreset mixed carbonate siliciclastic shelf facies forming a slope mud belt and slope sand bodies near the top sedimentation in a foreset topset transition resulted in the accumulation of bioturbated mixed slope and sandy shoal deposits sand bars and lagoonal facies occur on top of all sections and are truncated by a sequence boundary the combined analysis provides insights into the sedimentary processes affecting bottomset and foreset deposition underscoring the role of wave influenced hyperpycnal flows and the effect on organic matter dilution in one of the most important unconventional reservoirs from argentina