early pleistocene climate changes in the central mediterranean region as inferred from integrated pollen and planktonic foraminiferal stable isotope analyses vegetation inherited from a pliocene subtropical climate evolved through obliquity oscillations and global cooling leading to modern conditions an integrated highly time resolved record of pollen and stable isotopes 18o and 13c of globigerina bulloides was obtained to understand vegetation responses to early pleistocene climate changes continental and marine responses are compared in the central mediterranean region with a particular consideration of environmental changes during anoxic events pollen data illustrate vegetation dynamics as follows 1 development of mesothermic elements warm and humid conditions 2 expansion of mid and high altitude elements cooler but still humid conditions and 3 strengthening of steppe and herb elements cooler and dry conditions these successions correlate with precession 18o variations recorded by globigerina bulloides define two cycles mis 43 40 related to obliquity at northern low to mid latitudes the pollen signal records temperature and wetness changes related to precession even during global climate changes induced by obliquity this may result in unexpected increasing wetness during glacial periods which has to be considered specific to the central and eastern mediterranean region lastly an analysis of anoxic events reveals that enhanced runoff is indicated by increasing frequency of the riparian trees liquidambar and zelkova

paleohydrology of the upper miocene bicorb lake eastern spain as inferred from stable isotopic data from inorganic carbonates abstract the hydrological evolution of the upper miocene bicorb lake eastern spain has been established based on sedimentology carbonate mineralogy and stable isotopic data from inorganic carbonates from the upper lacustrine unit three main subunits have been recognized in subunit a the sedimentological features suggest a hydrologically closed lake although the isotopic data are not conclusive the isotopic compositions of primary carbonates from subunit b display a distribution typical for a hydrologically closed lake and allow the differentiation of four developmental stages the first stage was defined by the deposition of gypsum lmc dolomite and aragonite indicating large variations in the water mg ca ratio during the second and third stages only lmc was deposited suggesting only minor mg ca fluctuations the 13c and 18o pattern of the second stage shows a well defined covariance r 0 8 while in the third stage the isotopic data display a negative covariant relationship r 0 8 changes in dissolved inorganic carbon composition are considered the main factor to explain the variations from positive to negative covariance in the fourth stage the lake waters underwent large mg ca fluctuations as indicated by the deposition of lmc hmc and aragonite the isotopic trend is also covariant finally subunit c is characterized by lmc and minor amounts of hmc suggesting minor changes in mg ca ratio the isotopic features of this subunit are more congruent with a hydrologically open lake the lowest 13c and 18o values are very similar in the three subunits reflecting the most dilute conditions of the lake water and a uniform isotopic composition of the local meteoric water during these periods the changes in water balance and solute inputs recorded in the mineralogy and isotopic signatures of carbonates were controlled by the diapiric evolution and changes in the e p balance

palaeoenvironmental reconstruction of a middle miocene alluvial fan to cyclic shallow lacustrine depositional system in the calatayud basin ne spain the middle miocene sedimentary fill of the calatayud basin in north eastern spain consists of proximal to distal alluvial fan floodplain and shallow lacustrine deposits four main facies groups characteristic of differentsedimentary environments are recognized 1 proximal and medial alluvial fan facies that comprise clast supported gravel and subordinate sandstone and mudstone the latter exhibiting incipient pedogenic features 2 distal alluvial fan facies formed mainly of massive mudstone carbonate rich palaeosols and local carbonate pond deposits 3 lake margin facies which show two distinct lithofacies associations depending on their distribution relative to the alluvial fan system i e front lithofacies a comprising massive siliciclastic mudstone and tabular carbonates or lateral lithofacies b showing laminated and or massive siliciclastic mudstone alternating with tabular and or laminated carbonate beds and 4 mudflat shallow lake facies showing a remarkable cyclical alternation of green grey and or red siliciclastic mudstone units and white dolomitic carbonate beds the cyclic mudflat shallow lake succession as exposed in the orera composite section ocs is dominantly composed of small scale mudstone carbonate dolomite cycles the mudstone intervals of the sedimentary cycles are interpreted as a result of sedimentation from suspension by distal sheet floods the deposits evolving either under subaerial exposure or water saturated conditions depending on their location on the lacustrine mudflat and on climate the dolomite intervals accumulated during lake level highstands with mg rich waters becoming increasingly concentrated lowstand to highstand lake level changes indicated by the mudstone dolomite units of the small scale cycles reflect a climate control from dry to wet conditions on the sedimentation in the area the spatial distribution of the different lithofacies implies that deposition of the small scale cycles took place in a low gradient shallow lake basin located in an interfan zone the development of the basin was constrained by gradual alluvial fan aggradation additional support for the palaeoenvironmental interpretation is derived from the isotopic compositions of carbonates from the various lithofacies that show a wide range of 1 8 o and 1 3 c values varying from 7 9 to 3 0 pdb and from 9 2 to 1 7 pdb respectively more negative 1 8 d and 1 3 c values are from carbonate rich palaeosols and lake margin carbonates which extended in front of the alluvial fan systems whereas more positive values correspond to dolomite beds deposited in the shallow lacustrine environment the results show a clear trend of 1 8 o enrichment in the carbonates from lake margin to the centre of the shallow lake basin thereby also demonstrating that the lake evolved under hydrologically closed conditions

late cenozoic sedimentation of nihewan basin central north china and its tectonic significance abstract late cenozoic sediments of the nihewan basin in the northeastern part of the shanxi graben north china craton include buried late neogene rocks and exposures of the pliocene yuxian formation the pleistocene nihewan formation and xiaodukou formation with the age at least from 3 6 to 0 11 ma the sedimentary succession records the tectonic processes of the graben in the eastern nihewan basin on the basis of sedimentary facies and provenance analysis we have identified three main evolution stages during the late cenozoic the first stage was rapid expansion of the basin in the neogene which is thought to have commenced at least from 3 6 ma and lasted until 2 6 ma this stage is characterized by lacustrine facies dark colored mud and silt in depocenter of the basin with a potential source area from the northeast of the basin the following stage was a period of contraction at 2 6 1 8 ma characterized by deltaic deposits in depocenter of the basin and braided fluvial deposits in northeast margin of the basin and the deposition of cross bedded sands that were derived from erosion of archean proterozoic paleozoic and jurassic rocks from the north northwest and south of the basin the last stage was one era of gradually extinction of the basin from 1 8 to 0 11 ma followed by dried up of the basin and replaced by loess sediments were deposited in deltaic in depocenter of the basin and alluvial fan in northeast margin of the basin these coarse grained sands and pebbles were derived mainly from north and north northeast of the basin and generally from archean proterozoic and paleozoic rocks these three stages and the conversion ages 2 6 1 80 and 0 11 ma are largely consistent with three episodes of tibetan plateau rapid uplift therefore we infer that the evolution of the nihewan basin was predominantly influenced by the far field effect of the progressive uplift and northeastward expansion of the tibetan plateau

identifying space time clustering properties of the 1983 1997 irpinia basilicata southern italy seismicity abstract the fractality of the earthquake sequence 1983 1997 of irpinia basilicata southern italy one of the most seismically active regions of the mediterranean area has been analysed by temporal and spatial fractal tools the fractal exponent estimated by the allan factor method characterises the time clustering behaviour of the set of earthquakes while the correlation dimension d c calculated by means of the correlation integral method gives information on the space clustering behaviour of the sequence of seismic events analysing the variations of both the parameters we recognised the presence of a strong space time clusterisation associated with the major events that occurred in the investigated area

systematic survey of high resolution b value imaging along californian faults inference on asperities understanding and forecasting earthquake occurrences is presumably linked to understanding the stress distribution in the earth s crust this cannot be measured instrumentally with useful coverage however the size distribution of earthquakes quantified by the gutenberg richter b value is possibly a proxy to differential stress conditions and could therewith act as a crude stress meter wherever seismicity is observed in this study we improve the methodology of b value imaging for application to a high resolution 3 d analysis of a complex fault network in particular we develop a distance dependent sampling algorithm and introduce a linearity measure to restrict our output to those regions where the magnitude distribution strictly follows a power law we assess the catalog completeness along the fault traces using the bayesian magnitude of completeness method and systematically image b values for 243 major fault segments in california we identify and report b value structures revisiting previously published features e g the parkfield asperity and documenting additional anomalies e g along the san andreas and northridge faults combining local b values with local earthquake productivity rates we derive probability maps for the annual potential of one or more m6 events as indicated by the microseismicity of the last three decades we present a physical concept of how different stressing conditions along a fault surface may lead to b value variation and explain nonlinear frequency magnitude distributions detailed spatial b value information and its physical interpretation can advance our understanding of earthquake occurrence and ideally lead to improved forecasting ability

progressive development of the buyuk menderes graben based on new data western turkey oblique and normal fault systems exposed in the buyuk menderes graben bmg region record two successive and independent complex tectonic events the first group tectonic event is defined by an e w extension related to n s contraction and transpression this group is responsible for the development of nw and ne trending conjugate pairs of oblique faults which controlled early middle miocene basin formation between the early middle miocene and plio quaternary strata exists an unconformity indicating a period of folding uplift and severe erosion associated with n s shortening the second group of events was the change in tectonic regime from e w extension to n s extension which controlled the formation of the buyuk menderes graben by three progressive pulses of deformation the first pulse of extensional deformation was initially recorded in the region by the exhumation of the deep part of the menderes massif mm with the development of the e trending buyuk menderes detachment fault bmdf the minimum age of this pulse is constrained by the older plio quaternary fluviatile deposits of the buyuk menderes graben that range in age from the plio pleistocene boundary interval to late pleistocene the second pulse which is marked by the rapid deposition of alluvial deposits initiated the formation of approximately e w trending high angle normal faults synthetic and antithetic to the buyuk menderes detachment fault on the northern margin during holocene times these faults are interpreted as secondary steeper listric faults that merge with the main buyuk menderes detachment fault at depth the third pulse was the migration of the buyuk menderes graben depocentre to the present day position by diachronous activity of secondary steeper listric faults these steeper faults are the most seismically active tectonic elements in western turkey according to the stratigraphic and structural data the n s extension in the buyuk menderes graben region produced a progressive deformation phase with different pulses during its plio quaternary evolution with migration of deformation from the master fault to the hangingwall the formation of diachronous secondary synthetic and antithetic steeper faults on the upper plate of the buyuk menderes detachment fault hence the southward migration of the deformation and of the buyuk menderes graben depocentre should be related to the evolution of detachment in the region the presence of the seismically active splays of secondary faults implies an active detachment system in the region this young plio quaternary n s extension in the buyuk menderes graben may be attributed to the combined effects of the two continuing processes in aegean region the first process is back arc spreading or probably the roll back of african slab below the south aegean arc which seems to be responsible for the change in the stress tensor from e w extension to n s extension the second and later event is the southwestward escape of the anatolian block along its boundary fault that is the north anatolian fault naf

paleoclimatic significance of late quaternary lacustrine and alluvial stratigraphy animas valley new mexico lacustrine and alluvial stratigraphic sequences in the southern animas valley of new mexico allow reconstruction of late quaternary climates four separate stands of late quaternary lake cloverdale in the southern animas valley are recorded by lacustrine shoreline deposits soils and stratigraphic evidence show that three young lake highstands occurred during the holocene and that a higher lake stand occurred 18 000 to 20 00014c yr b p fluvial systems aggraded the southern animas valley during the middle to late holocene the late quaternary stratigraphy shows that several periods during the late holocene were characterized by higher effective precipitation than at any time since the last glacial maximum

earthquakes recurrence and interoccurrence times the purpose of this paper is to discuss the statistical distributions of recurrence times of earthquakes recurrence times are the time intervals between successive earthquakes at a specified location on a specified fault although a number of statistical distributions have been proposed for recurrence times we argue in favor of the weibull distribution the weibull distribution is the only distribution that has a scale invariant hazard function we consider three sets of characteristic earthquakes on the san andreas fault 1 the parkfield earthquakes 2 the sequence of earthquakes identified by paleoseismic studies at the wrightwood site and 3 an example of a sequence of micro repeating earthquakes at a site near san juan bautista in each case we make a comparison with the applicable weibull distribution the number of earthquakes in each of these sequences is too small to make definitive conclusions to overcome this difficulty we consider a sequence of earthquakes obtained from a one million year virtual california simulation of san andreas earthquakes very good agreement with a weibull distribution is found we also obtain recurrence statistics for two other model studies the first is a modified forest fire model and the second is a slider block model in both cases good agreements with weibull distributions are obtained our conclusion is that the weibull distribution is the preferred distribution for estimating the risk of future earthquakes on the san andreas fault and elsewhere

loess stratigraphy in central china abstract loess sequences in central china provide a detailed record of climate changes during the last 2 5 million years at least 44 major shifts from glacial to interglacial conditions occurred during this time in china prolonged loess deposition lasting more than 40 millennia occurred eleven times with only four of these intervals in brunhes chron the climate oscillations took place with increased frequency between 2 4 and 0 5 ma compared to the last half million years major shifts toward cooler and drier climates occurred at about 2 4 ma 1 2 ma and 0 5 ma while less pronounced shifts are dated to 1 65 ma 0 8 ma and 0 2 ma three of the last four reversals of the earth s magnetic field whose lithostratigraphic position has been detail are recorded in a glacial deposit the low field magnetic susceptibility of loess and soils which reflects the concentration of ultrafine magnetite is related to the degree of pedogenesis and serves as a proxy measure of climate the accumulation rate of the magnetite was fairly constant throughout the last 1 2 million years and can serve as a measure of time susceptibility records from localities near xifeng and luochuan located 160 km apart are compared and used to define informal lithostratigraphic units in the loess plateau of china

investigating non uniform scaling behavior in ultra low frequency ulf earthquake related geomagnetic signals abstract the scaling properties of the time dynamics of 2000 2001 ulf geomagnetic data in the frequency range between 1 mhz and 10 hz observed at izu peninsula in japan were investigated on the basis of detrended fluctuation analysis dfa which is a powerful method to detect scaling in non stationary time series deviations from uniform power law scaling were identified and quantified our results suggest that a significant non uniform scaling behavior in ulf geomagnetic data could be related to the occurrence of intense seismic clusters these first results could be useful in the framework of short term earthquake prediction

carbonate replacement of lacustrine gypsum deposits in two neogene continental basins eastern spain abstract bedded nonmarine gypsum deposits in the miocene teruel and cabriel basins eastern spain are partly replaced by carbonate the libros gypsum teruel graben is associated with fossiliferous carbonate wackestones and finely laminated organic matter rich mudstones which accumulated under anoxic conditions in a meromictic permanent lake the gypsum is locally pseudomorphed by aragonite or less commonly replaced by calcite low 13c values indicate that sulphate replacement resulted from bacterial sulphate reduction processes that were favoured by anacrobic conditions and abundant labile organic matter in the sediments petrographic evidence and oxygen isotopic composition suggest that gypsum replacement by aragonite occurred soon after deposition a subsequent return to oxidising conditions caused some aragonite to be replaced by diagenetic gypsum native sulphur is associated with some of these secondary gypsum occurrences the los ruices sulphate deposits cabriel basin contain beds of clastic and selenitic gypsum which are associated with limestones and red beds indicating accumulation in a shallow lake calcite is the principal replacement mineral bacterial sulphate reduction was insignificant in this basin because of a scarcity of organic matter stable isotope composition of diagenetic carbonate indicates that gypsum replacement occurred at shallow burial depths due to contact with dilute groundwaters of meteoric origin depositional environment evidently has a major influence upon the diagenetic history of primary sulphate deposits the quantity of preserved organic matter degradable by sulphate reducing bacteria is of particular importance and along with groundwater composition is the main factor controlling the mechanism of gypsum replacement by carbonate

sedimentology and isotope geochemistry of lacustrine carbonates of the oligocene campins basin north east spain the non marine campins basin developed in the oligocene during a period of early rifting of the catalan coastal ranges lacustrine deposits interbedded between two alluvial units comprise shallow and deep lacustrine facies the lower shallow lacustrine facies are made up of microbialite buildups and thin limestone beds in the studied area these facies are overlain by deep lacustrine facies which consist of alternations of several metre thick carbonate and mudstone dominated intervals in addition to calcite which is characteristic of the shallow lacustrine facies aragonite and abundant dolomite are present in the deep lacustrine facies this mineralogical change in the sequence reflects an overall increase in the mg ca ratio of the lake waters the deep lacustrine sequences are interpreted as having formed in a hydrologically closed basin that was subject to changes in the mg ca ratio of the water probably related to variations in the evaporation precipitation rate the sedimentological mineralogical and isotopic characteristics of the campins basin dolomites suggest that in general they are primary in origin the stable isotope data show an approximate covariance between 13c and 18o in the lower shallow lacustrine carbonates calcite which suggests that they formed during the onset of closure of the lake the 13c and 18o values of the deep lacustrine carbonates display three different clusters that are roughly related to the carbonate mineralogy normalisation with respect to calcite of the isotopic compositions of dolomite and aragonite from the deep lacustrine carbonates allows the integration of all these isotope values into one covariant trend the sequential appearance of different carbonate minerals and the isotopic covariant trend may indicate an overall evaporative concentration of the lake waters the change in slope of the covariant trend for the isotope values between the shallow and the deep lacustrine carbonates might reflect the change in the waterbody morphology recorded in the basin fill sequence

sedimentology diagenesis and ichnology of cretaceous and palaeogene calcretes and palustrine carbonates from uruguay abstract the cretaceous mercedes formation and paleogene queguay formation deposits cropping out in w and s uruguay comprise two terrestrial limestone units that are very rich in trace fossils the study of these units permits to propose a sedimentological model for palustrine limestones and calcretes in which the distribution of different types of trace fossils is considered the study units include three main types of deposit lacustrine limestones palustrine limestones and calcretes the lacustrine limestones are relatively homogeneous and contain gastropods charophytes and ostracods but no trace fossils they were deposited in a relatively more perennial lacustrine environment the palustrine limestones include four different facies desiccated mudstones nodular limestones granular limestones and gravel sheets the desiccated mudstones indicate a lesser degree of pedogenic modification and the granular limestones a higher degree the gravel sheets are an indication of the reworking of previous limestones deposits during low lakewater levels most of the palustrine limestones except the gravel sheets contain the same bioclasts as the lacustrine limestones plus a variety of trace fossils such as rebuffoichnus sciuttoi fictovichnus gobiensis and different ichnospecies of celliforma the calcretes are either massive groundwater or laminar the massive calcretes are sandy limestones made up of a carbonate matrix and cements the laminar calcretes root mats which contain alveolar septal structures occur as centimetre thick layers and can be seen in all types of deposit they contain the same trace fossil association as the palustrine limestones the massive calcretes are poorer in such fossils the distribution of trace fossils in these environments is under strong facies control and provides good evidence of subaerial exposure and semi arid climates all the limestones are partially replaced and cemented by opal and quartz but in all cases the primary structure is preserved silicification occurred under groundwater meteoric conditions overall the limestones facies calcretes palustrine and lacustrine and their lateral distribution likely reflect the existence of wetland environments in semiarid to sub humid climates these climatic conditions were interrupted by a period of increased precipitations probably the early eocene climatic optimum

multiparametric statistical investigation of seismicity occurred at el hierro canary islands from 2011 to 2014 abstract a detailed statistical investigation of the seismicity occurred at el hierro volcano canary islands from 2011 to 2014 has been performed by analysing the time variation of four parameters the gutenberg richter b value the local coefficient of variation the scaling exponent of the magnitude distribution and the main periodicity of the earthquake sequence calculated by using the schuster s test these four parameters are good descriptors of the time and magnitude distributions of the seismic sequence and their variation indicate dynamical changes in the volcanic system these variations can be attributed to the causes and types of seismicity thus allowing to distinguish between different host rock fracturing processes caused by intrusions of magma at different depths and overpressures the statistical patterns observed among the studied unrest episodes and between them and the eruptive episode of 2011 2012 indicate that the response of the host rock to the deformation imposed by magma intrusion did not differ significantly from one episode to the other thus suggesting that no significant local stress changes induced by magma intrusion occurred when comparing between all them therefore despite the studied unrest episodes were caused by intrusions of magma at different depths and locations below el hierro island the mechanical response of the lithosphere was similar in all cases this suggests that the reason why the first unrest culminated in an eruption while the other did not may be related to the role of the regional local tectonics acting at that moment rather than to the forceful of magma intrusion

the weibull log weibull transition of interoccurrence time for synthetic and natural earthquakes abstract we study the interoccurrence time distributions of events by analyzing synthetic catalogues and three natural catalogues of the japan meteorological agency jma the southern california earthquake data center scedc and the taiwan central weather bureau tcwb we find a universal feature i e the weibull log weibull transition in the interoccurrence time statistics this transition demonstrates that the interoccurrence time statistics of earthquakes possess the hybrid weibull and log weibull statistics we further find that the crossover magnitude m c from the superposition regime to the pure weibull regime is averagely proportional to the plate velocity in the end of this paper we summarize a region independent relation i e m c m max 0 54 0 06 which represents a novel empirical relation related to the weibull log weibull transition for earthquake processes

microbially mediated carbonates in the holocene deposits from sarlieve a small ancient lake of the french massif central testify to the evolution of a restricted environment both the mineralogy and facies of lacustrine bio induced carbonates are controlled largely by hydrological factors that are highly dependent upon climatic influence as such they are useful tools in characterizing ancient lake environments in this way the study of the sedimentary record from the small ancient sarlieve lake limagne massif central france aims to reconstruct the hydrological evolution during the holocene using petrographical mineralogical and geochemical analyses the fine grained marls mainly calcitic display numerous layers rich in pristine ca dolomite with small amounts of aragonite which are clearly autochthonous as these minerals are rather unusual in the temperate climatic context of western europe the question arises about their forming conditions and therefore that of the lacustrine environment ca dolomite prevails at the base of the sequence as a massive dolomicrite layer and in the middle part it builds up most of the numerous laminae closely associated with organic matter scanning electron microscope observations reveal the abundance of tiny crystals tens to hundreds of nanometres mainly organized as microspheres looking like cocci or bacilli such a facies is interpreted as resulting from the fossilization of benthic microbial communities by dolomite precipitation following organic matter consumption and extracellular polymeric substance degradation these microbial dolomites were precipitated in a saline environment as a consequence of excess evaporation from the system as is also suggested by their positive 18o values the facies sequence expresses the following evolution i saline pan i e endorheic stage with a perennial lowstand in lake level boreal to early atlantic periods ii large fluctuations in lake level with sporadic freshening of the system atlantic iii open lake stage sub boreal and iv anthropogenic drainage sub atlantic

multiple rifting pulses and sedimentation pattern in the cameli basin southwestern anatolia turkey abstract the neotectonic development of western anatolia was characterized by the formation of numerous graben type basins which have been well documented by general mapping although the cause and timing of the neogene regional tectonic extension remain controversial previous interpretations of the origin and evolution of these neogene basins were based mainly on regional scale tectonic inferences rather than detailed basin fill analysis the present study of the terrestrial intramontane cameli basin in the western taurides combines detailed facies analysis with biostratigraphic dating mammalian and molluscan fossils and documents three pulses of crustal extension that are reflected in changes in the palaeogeography and sedimentary architecture of the basin development of the cameli graben commenced in the vallesian time early tortonian and is marked by alluvial fan fluvial and lacustrine depositional systems with freshwater molluscan fauna a second pulse of tectonic extension occurred in the late ruscinian time early middle pliocene producing a new normal fault that split the basin longitudinally into two compartments the lake environment expanded and deepened coastal peat forming mires developed and abundant mammal fauna appeared by the early villanian time middle pliocene with the lacustrine deposits onlapping the basin margin and intrabasinal fault escarpments the lacustrine environment subsequently shrank as the progradation of axial river deltas and basin margin fan deltas caused water shallowing and shoreline regression a third pulse of extension occurred at the end of villanian time late pliocene when the development of a new generation of normal faults further split the basin into still narrower half graben compartments the third pulse of rifting is estimated to have accounted for little more than 10 of the sub basinal crustal extension but caused the most striking changes in the basin palaeogeography and drainage pattern the inward development of the successive normal faults indicated a high rate crustal extension this is the first regional case study of a terrestrial neotectonic graben employing detailed sedimentary facies analysis and mammal biostratigraphy and providing a time stratigraphic framework for the rifting pulses in western anatolia

overlapping of pedogenesis and meteoric diagenesis in distal alluvial and shallow lacustrine deposits in the madrid miocene basin spain the miocene distal alluvial fan and palustrine deposits of the madrid basin paracuellos de jarama area were examined to establish the sequence of its pedogenic diagenetic processes and the main factors controlling them in this area the diagenetic processes operated not only on carbonates as commonly studied but also in high magnesium clays and opaline cherts this paper provides a dynamic model for saline alkaline lake margins that complements the existing freshwater palustrine model three sections ber pel and upc containing limestones sepiolite dolostones and opaline cherts were examined these represent the entire transition from alluvial fan deposit to lake environment the alluvial fan deposits pel section show the most complex sequence of processes after a weak edaphic imprint the primary mudstone and siltstones are affected by silicification opaline levels formed mainly by selective replacement of sepiolites and later dolomitization several types of dolomite are present rounded crystals spherules and globular bodies being the most characteristic in the ponds situated at the foot of the alluvial fans or in interfan areas sepiolite precipitated within free water bodies ber section and an intense pedogenesis led to the formation of palustrine sepiolite deposits later the intense silicification of the sepiolite produced lenticular opaline levels that were locally transformed to quartz by aging in the shallow lakes upc section palustrine limestones and sepiolite were deposited the carbonates are partially affected by silicification the sepiolite becoming completely silicified the opaline levels clearly preserve the structure of the limestones and sepiolite host rocks all the opaline levels show local aging processes the silicification processes were different in the three settings due to the interplay of groundwater with sedimentary environments and facies in the distal alluvial fan sediments of the pel section the initial host rock affected by silicification is not preserved due to the later dolomitization that erased both it and its textures the silicification environment was therefore not easy to determine in the ber and upc section the main silicification took place in groundwater influenced environments but evidence was seen of cements and silicifications in vadose environments in all study settings the overlapping of pedogenic vadose and groundwater processes was controlled by changes in the position of the water table four stages were concluded to explain the transformation from the primary deposits to the later dolomitization process and the formation of vadose cements the majority of the silicifications seen occurred as responses to changes in the water table position linked to the aggradation of this closed basin in all the studied environments the sepiolite deposits were preferentially silicified their fibrous structure and high absorption capacity helping to retain interstitial fluids moreover sepiolite and opal are stable under relatively similar geochemical conditions in arid environments the dissolution of the sepiolite caused an increase in silica in the interstitial fluids favouring silicification and ruling out the need of a biogenic source the replacement of limestones by silica is usually driven by variations in ph and salinity which are very common in surface environments such as shallow lakes and soils

stream response to quaternary tectonic and climatic change evidence from the upper weihe river central china abstract seven terraces of upper weihe river in the longxi basin on the north flank of the qinling mountains are capped with a succession of loess units and paleosols that correlate with the standard marine isotope chronology based on fieldwork and terrace ages which were determined using loess paleosol stratigraphy paleomagnetic optical stimulated luminescence osl and radiocarbon dating the results show that the fluvial fills were deposited during marine oxygen isotope stages miss 22 20 18 16 12 6 4 and 2 respectively whereas terracing occurred during glacial interglacial transitions this in turn points to eccentricity related climatic changes that may have driven recurrent incision and aggradation processes and significantly influenced the formation of staircase terraces of weihe river through the direct and indirect influence of both temperature and precipitation on fluviatile activity on the basis of terrace ages and its heights incision rates were enhanced from 865 to 412 ka 0 27 m ka decreased from 412 to 128 ka 0 09 m ka and increased from 128 ka to present 0 32 m ka

cenozoic calcretes from the teruel graben spain microstructure stable isotope geochemistry and environmental significance in the teruel graben northeast spain laminar and nodular calcretes formed in a variety of cenozoic deposits ranging in age from palaeogene to pleistocene these calcretes developed in a relatively small area under the influence of the same highlands consequently differences in their microstructure and isotopic composition c and o must be related to differences in host rock climate vegetation and duration of development nine profiles developed in different sedimentary settings from proximal areas to lacustrine environments were studied to determine whether the microstructure and stable isotope composition changed during the cenozoic these characteristics might be used as indicators of the prevailing climate and vegetation and reveal any changes that occurred during this time most of the laminar calcretes studied are compound profiles that formed on hard substrates e g jurassic limestones or coarse detrital deposits e g palaeogene pliocene and plio pleistocene sandstones and conglomerates these profiles formed in proximal areas of the basin and also in fluvial terraces microstructures include biogenic features such as alveolar septal structures root tubes calcified root cells and calcified organic filaments underside coatings of micrite and fibrous vadose cements are common around gravel clasts on the other side spherulites are only preserved at the very top of the youngest calcretes nodular calcretes developed on fine detrital substrates e g on palaeogene miocene and pliocene red mudstones and sandy mudstones of distal alluvial and floodplain environments and in some places grade vertically into palustrine limestones the nodules consist of micrite and were elongated vertically show desiccation cracks and mottling micritic coatings some alveolar septal structures and root traces microcodium of type 1 occurs in both laminar and nodular calcretes but only in those of palaeogene age while calcified root cells microcodium of type 3 are seen in the pliocene calcretes the stable isotope composition covers a wide range 8 23 18o 4 29 pdb and 7 29 13c 3 42 pdb nodular laminar and palustrine facies occupy overlapped isotopic fields displaying an overall negative covariant trend location within the basin prevailing climate and density of vegetation are responsible for differences in isotope values the palaeogene samples show a wide range of values and are difficult to separate from the others however there is as significant change to lighter carbon values from the miocene to the pliocene profiles this change may be related to the cooler climatic conditions that prevailed during the pliocene and is reverse to the expected shift to heavier 13c values which is related to the increase of c4 vegetation that occurred in many areas of the world during the miocene or to the transit to the pliocene the formation of these calcretes seems to have occurred in semi arid conditions with prevailing c3 vegetation

cyclic quaternary alluviation and terracing in a nonglaciated drainage basin on the north flank of the qinling shan central china abstract pleistocene alluvial terraces of the nonglaciated ba river drainage basin on the north flank of the qinling shan are capped by a succession of loess units and paleosols that correlate with the standard marine isotope chronology and are used to date the subjacent alluvial gravels alluvial fills were deposited during isotope stages 2 6 8 12 and 16 whereas terracing occurred during interglacial stages 1 5 7 11 and 15 the apparent absence of terraces dating to stage 14 and stage 4 may be due to the lesser intensity of these glaciations compared to that of stage 2 although disruption of the alluvial regime by local tectonism is a likely alternative for the lack of a stage 4 terrace a stage 10 terrace was not positively identified from available exposures its possible absence could be related to post stage 12 uplift aggradational episodes correlate with glaciations and loess deposition whereas degradational episodes correlate with interglaciations or interstades and soil formation implying that climate is the primary control on quaternary paleohydrology this in turn points to variations in the earth s orbital geometry as the major factor that modulates both climate and ultimately the fluvial system in the qinling shan in this region glaciations were dominated by a cold dry winter monsoon climate whereas during interstades and interglaciations a warmer and wetter climate prevailed implying strengthening of the summer monsoon both the loess paleosol and the alluvial records are consistent with climate model simulations spanning the last 18 000 yr that show a change from cold dry conditions during the last glacial maximum to a climate warmer and wetter than present during the first half of the holocene

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

paleohydrology of an upper aptian lacustrine system from northeastern brazil integration of facies and isotopic geochemistry abstract the codo formation records the initial evolutionary stages of an intracontinental rift system formed along the brazilian equatorial margin in the late aptian deposits of this unit exposed on the eastern margin of the grajau basin include gypsum bituminous black shales and limestones these lithologies were formed in a low energy well stratified anoxic and hypersaline lake system developed in a dominantly arid semi arid climate this lacustrine succession is internally organized into three categories of shallowing upward cycles with the first and second order cycles being related to seismic activity associated with fault reactivations and the third order cycles recording climatic fluctuations studies emphasizing petrography and analysis of the geochemical tracers fe mg sr mn na and ca helped to identify the sedimentary facies that kept a primary signal which were thus appropriate for isotopic investigations aiming paleoenvironmental and paleohydrologic reconstructions the results of this study revealed a wide distribution of dominantly low carbon and oxygen isotope values in carbonates ranging from 5 69 to 13 02 and from 2 71 to 10 80 respectively this paper demonstrates that at least in the particular case of oxygen the isotope ratios vary according to seismically induced shallowing upward cycles with values in general lower at their bases where central lake deposits dominate and progressively higher upward where marginal lake deposits are more widespread in addition to confirming a depositional signature for the analysed samples this behavior allowed the development of a seismic induced isotope model the lighter isotope ratios appear to be related to flooding events promoted by subsidence which resulted in the development of a perennial lake system while heavier isotope values are related to ephemeral lake phases favored by uplift and or increased stability furthermore the results show that a closed lake system dominated as indicated by the overall good positive covariance i e 0 42 to 0 43 between the carbon and oxygen isotopes though open phases are also recorded by negative covariance values of 0 36 during closed phases the 18 o displayed the highest range of variation i e 3 63 to 4 89 due to increased residence time while this variation was low i e 0 09 to 1 87 during open lake phases when there was a balance in the water isotope composition maintained by continuous basin inflow

evolution of the late cenozoic tectonic stress regime in the shanxi rift central north china plate inferred from new fault kinematic analysis abstract the shanxi rift an intracontinental belt along the eastern margin of the ordos block north china plate has undergone multi stage extensional deformation during the late cenozoic in this study new fault kinematic analysis of boundary faults in the shanxi rift constrained by geochronological data defines a three stage tectonic stress regime since the late miocene providing new structural evidence for deciphering the northeastward growth of the tibetan plateau the earliest stage involved a transtensional stress regime of nw se extension and ne sw compression in the late miocene early pleistocene ca 10 1 8 ma and characterized by mean principal stress axes of 1 at 344 7 87 2 2 at 217 6 01 1 and 3 at 128 1 01 0 the early transtensional stress regime was responsible for the opening of the shanxi rift and was very likely associated with intensive right lateral pull apart activity in the eastern ordos block due to the northeastward growth of the tibetan plateau during the second stage the stress regime changed to less intense ne sw extension with mean stress orientations of 323 3 85 2 for 1 127 5 02 9 for 2 and 214 9 02 6 for 3 in the early late pleistocene ca 1 8 0 11 ma this stage is marked by a distinct shift from fluvio lacustrine to fluvio piedmont sedimentary facies at the end of the early pleistocene and the widespread eruption of basalt in the datong basin north of the shanxi rift this short lived extension appears to be the result of relaxation in the midst of crustal shortening during growth of the tibetan plateau the third stage was transtensional characterized by nnw sse extension and wnw ese compression 1 at 060 88 9 2 at 074 9 03 9 and 3 at 164 00 since the late pleistocene ca 0 11 ma causing dextral shear deformation in the shanxi rift and the disappearance of its paleo lake this stage resulted from regional ene wsw shortening due to northeastward growth of the tibetan plateau

latest oligocene late miocene lacustrine systems of the north central part of the ebro basin spain sedimentary facies model and palaeogeographic synthesis abstract in the central part of the ebro basin spain north of the ebro river three allostratigraphic or tectosedimentary units differentiated within the latest oligocene late miocene upper agenian vallesian interval are sedimentologically characterized these deposits represent carbonate and sulphate lacustrine environments fed by pyrenean alluvial systems luna system and huesca system in each unit several facies associations or lithofacies were mapped these interfinger through time gypsum lithofacies occupy the southernmost part of the study area and are surrounded by carbonate and or detrital lithofacies to the north each lithofacies consists of different carbonate sulphate and or detrital facies arranged in simple sequences decimetres to metres thick the four types of sequences characterized reflect a complex shallowing evolution involving carbonate or sulphate contexts thus each lithofacies represents the sedimentation in a particular lacustrine or alluvial subenvironment a single lacustrine system is proposed for the central part of the basin its evolution followed cycles of water level variations which caused kilometre scale migrations of the lake shoreline in this model two distinct situations or lakes alternated through time a one represents high levels associated with a single body of dilute carbonate water where massive carbonate facies formed influenced by organism proliferation these lakes had wide palustrine vegetated margins in which bioturbated facies developed b the other represents low levels that correspond to a playa lake model laminated sulphate deposits formed in the lake waters while nodular gypsum originated in the surrounding saline mud flats and within the exposed previously deposited carbonate sediments transitions from one situation to the other including minor water level fluctuations within carbonate sedimentation conditions were marked by the development of laminated and stromatolitic facies lake level variations were caused by climatic cycles and gave rise to the simple sequences and to the lithofacies lateral relationships recognized in this study correlation among tectosedimentary units in the studied pyrenean domain and in the iberian domain of the ebro basin shows that for units n1 and n2 the facies that resulted from dilute carbonate waters are rare in the lacustrine areas of the iberian margin this indicates that a strong hydrological contrast existed between both regions on this basis a theoretical asymmetrical facies model is proposed for the single lacustrine basin that extended over these regions

from palaeotectonics to neotectonics in the neotethys realm the importance of kinematic decoupling and inherited structural grain in sw anatolia turkey abstract in order to asses young i e neotectonic fault kinematics and the relation with plate tectonic processes in sw turkey we focused on the questions 1 what produced the structural grain i e how and when are faults generated 2 what was is the kinematic behaviour of these faults and 3 during which period s were these faults active firstly the distribution of faults has been investigated using a lineament analysis performed on satellite imagery and digital elevation models we define five main tectonic domains in sw turkey 1 and 2 the northern and southern western anatolian extensional provinces 3 the eastern hellenic arc including rhodes island and the submarine anaximander mountains 4 the lycian taurides and 5 the western limb of the isparta angle lineament analysis reveals dominance of three lineament groups i e nne ene and wnw trending in all identified domains variations in the relative importance of lineament groups exist and are attributed to the specific tectonic evolution of each domain a synthesis of recently published field data shows that the onset of activity of related fault groups is neither synchronous nor uniform the structural grain for the neotectonic deformation in sw turkey is formed during the last stage of palaeotectonic deformation stage 1 which is dominated by the onset of the menderes massif exhumation along a top n major detachment the datca break away fault seyitoglu g isik v and cemen i 2004 complete tertiary exhumation history of the menderes massif western turkey an alternative working hypothesis terra nova 16 358 364 and related se ward sliding of the lycian nappes in the footwall of this fault this stage is characterized by spatially variable types of deformation that are delineated by from nw to se the datca fault around the menderes lycian contact zone and the lycian frontal thrust zone respectively the kinematic decoupling along these structures explains the co existence of top n detachment type extension in the western anatolian extensional province and ongoing nappe emplacement and piggy back development in the lycian taurides the decoupling also explains the lateral complexity of deformation associated with later neotectonic deformation from late miocene onward stage 2 nne ssw extension dominated the western anatolian extensional province influenced by combined anatolian extrusion and hellenic subduction roll back contemporaneously bidirectional ese wnw and nne ssw extension controls the lycian taurides due to the effects of hellenic arc expansion superposed on extrusion roll back extension the zone of kinematic decoupling is characterized by structural complexity with local transpressional features during stage 3 post late pliocene the same types of extension prevail in the western anatolian extensional province and the lycian taurides although a third tectonic regime becomes gradually more important this regime is associated with a tectonic escape in the hellenic arc that induced forearc slivers to be sheared of the expanding arc along mostly sinistrally displacing ene trending strike slip zones several of these zones have been identified in the coastal zones of sw turkey either through recent seismicity or field observations and are especially focused in the lycian taurides domain here they form what is classically referred to as the fethiye burdur fault zone which becomes gradually penetrated from the sw by oblique or strike slip zones exemplifying the time transgressive nature of the tectonic escape mechanism zones of kinematic decoupling remain persistent throughout the entire early miocene recent tectonic evolution of sw turkey and explain the existence of differently deforming tectonic domains

variable style of transition between palaeogene fluvial fan and lacustrine systems southern pyrenean foreland ne spain two palaeogene fluvial fan systems linked to the south pyrenean margin are recognized in the eastern ebro basin the cardona su ria and solsona sanau ja fans these had radii of 40 and 35 km and were 800 and 600 km2 in area respectively during the priabonian to the middle rupelian the fluvial fans built into a hydrologically closed foreland basin and shallow lacustrine systems persisted in the basin centre in the studied area both fans are part of the same upward coarsening megasequence up to 800 m thick driven by hinterland drainage expansion and foreland propagation of pyrenean thrusts fourteen sedimentary facies have been grouped into seven facies associations corresponding to medial fluvial fan channelized terminal lobe nonchannelized terminal lobe mudflat deltaic evaporitic playa lake and carbonate rich shallow lacustrine environments lateral correlations define two styles of alluvial lacustrine transition during low lake level stages terminal lobes developed whereas during lake highstands fluvial dominated deltas and interdistributary bays were formed terminal lobe deposits are characterized by extensive 100 600 m wide sheet like fine sandstone beds formed by sub aqueous quasi steady hyperpycnal turbidity currents sedimentary structures and trace fossils indicate rapid desiccation and subaerial exposure of the lobe deposits these deposits are arranged in coarsening fining sequences metres to tens of metres in thickness controlled by a combination of tectonics climatic oscillations and autocyclic sedimentary processes the presence of anomalously deeply incised distributary channels associated with distal terminal lobe or mudflat deposits indicates rapid lake level falls deltaic deposits form progradational coarsening upward sequences several metres thick characterized by channel and friction dominated mouth bar facies overlying white grey offshore lacustrine facies deltaic bar deposits are less extensive 50 300 m wide than the terminal lobes and were also deposited by hyperpycnal currents although they lack evidence of emergence sandy deltaic deposits accumulated locally at the mouths of main feeder distal fan streams and were separated by muddy interdistributary bays whereas the terminal lobe sheets expand from a series of mid fan intersection points and coalesced to form a more continuous sandy fan fringe

late quaternary records of the atmospheric input of eolian dust to the center of the chinese loess plateau abstract the concentrations of 15 elements and mineral grain size distributions were determined for late quaternary loess sediments from the chinese loess plateau particle size distributions of the loess were approximately log normal for each of three modes i e 0 04 to 1 m diameter 2 to 20 m and 20 to 200 m that integrate the transport and deposition of eolian dust the mass particle size distributions of typical crustal elements si ca fe ti k mn and v in paleosol and loess samples show patterns similar to those of mineral aerosols but higher concentrations occur in the submicrometer sediment particles absolute principal component analysis of the elemental data suggests that the loess can be described in terms of synsedimentary and postdepositional concentration and subvertical migration of caco3 and various elements through the deposit a variety of geochemical indicators in the loess are apparently sensitive to asian monsoon variations these include the mass ratio of course to fine particles the concentration ratios of certain trace elements the elemental fluxes associated with eolian dust and the bulk concentration of ca in the sediments

holocene geomorphic evolution and settlement distribution patterns in the mid lower fen river basins china abstract holocene geomorphic changes have fundamentally shaped the spatial temporal distributions of prehistoric and historical settlements in north china through intensive field surveys and careful field examination of typical sedimentary sequences we reconstructed the late pleistocene and holocene geomorphic history in the two major basins of the mid lower fen river central south shanxi china our first hand data provides crucial information for reconstructing the dynamic relationship between the characteristics of holocene geomorphic changes and settlement distribution patterns in the two basins from the neolithic period to the bronze age xia shang dynasties in the taiyuan basin due to river downcutting processes from the end of the late pleistocene to the early holocene edge of the basin emerged and evolved into tablelands the elevation of the flat lands atop the tablelands that was significantly above the level of floodwater provided an ideal environment for early settlements the holocene geomorphic changes are characterized by continous fluvio lacustrine aggradation and the central basin became void of human settlements due to uninhabitable hydrological and gemorphic conditions and especially due to frequent floods instead most settlements were located along the basin displaying a unique around basin distribution pattern in the linfen basin following large scale incision of the main channels and branches of the fen river during the late pleistocene platform type plain with deep incised valleys was formed similar to the surrounding loess tableland the central basin became an optimal environment for human activities and settlement construction forming a full basin like settlement distribution pattern that is distinctively different from the around basin distribution pattern in the taiyuan basin

orbit related long term climate cycles revealed in a 12 myr continental record from lake baikal quaternary records of climate change from terrestrial sources such as lake sediments1 2 and aeolian sediments3 4 in general agree well with marine records5 6 but continuous records that cover more than the past one million years were essentially unavailable until recently when the high sedimentation rate site of lake baikal was exploited1 2 7 8 because of its location in the middle latitudes lake baikal is highly sensitive to insolation changes9 and the entire lake remained uncovered by ice sheets throughout the pleistocene epoch making it a valuable archive for past climate here we examine long sediment cores from lake baikal that cover the past 12 million years our record reveals a gradual cooling of the asian continental interior with some fluctuations spectral analyses reveal periods of about 400 kyr 600 kyr and 1 000 kyr which may correspond to milankovitch periods reflecting orbital cycles our results indicate that changes in insolation were closely related to long term environmental variations in the deep continental interior over the past 12 million years

generic dependence of the frequency size distribution of earthquakes on depth and its relation to the strength profile of the crust 1 we explore the idea that the relative size distribution of earthquakes quantified using the so called b value is negatively correlated with differential stress because the maximum possible differential stress increases linearly in the brittle upper crust we expect to find a decrease of b with depth we test this expectation for seven continental areas around the world each of which is described by a regional earthquake catalog we find a monotonic decrease in b value between 5 and 15 km depth the decrease stops near the brittle ductile transition we specifically focus on the high quality catalogs of earthquakes in california to perform a sensitivity test with respect to depth uncertainty we also estimate the probability depth gradient for the occurrence of a target magnitude event and study the behavior of b with depth in near and off fault zones we also translate the observed b depth gradients into b differential stress gradients our findings suggest that b values are negatively correlated with differential stress and hus have the potential to act as stress meters in the earth s crust

variations in earthquake size distribution across different stress regimes the earthquake size distribution follows in most instances a power law1 2 with the slope of this power law the b value commonly used to describe the relative occurrence of large and small events a high b value indicates a larger proportion of small earthquakes and vice versa statistically significant variations of b values have been measured in laboratory experiments mines and various tectonic regimes such as subducting slabs near magma chambers along fault zones and in aftershock zones3 however it has remained uncertain whether these differences are due to differing stress regimes as it was questionable that samples in small volumes such as in laboratory specimens mines and the shallow earth s crust are representative of earthquakes in general given the lack of physical understanding of these differences the observation that b values approach the constant 1 if large volumes are sampled4 was interpreted to indicate that b 1 is a universal constant for earthquakes in general5 here we show that the b value varies systematically for different styles of faulting we find that normal faulting events have the highest b values thrust events the lowest and strike slip events intermediate values given that thrust faults tend to be under higher stress than normal faults we infer that the b value acts as a stress meter that depends inversely on differential stress

towards an orbital time scale for chinese loess deposits abstract in this study we analyzed the grain size of the baoji loess soil sequence at 10 cm intervals results show that grain size variations are very sensitive to loess soil alternations with loess units being much coarser than soils such a change in loess soil grains is interpreted as the result of the glacial interglacial cyclic variations in the intensity of the winter monsoon winds out of siberia the grain size record is thus employed as a proxy indicator of the winter monsoon circulation and tuned to the orbital records calculated recently by berger and loutre 1991 under the control of major magnetic reversals the tuning is independent of any correlation with 18o signals in the deep sea sediments the resulting grain size time scale is tightly constrained as suggested by the following facts 1 the filtered obliquity and precession components from the grain size data on the orbital time scale closely match the theoretical orbital records 2 ages of the major magnetic reversals estimated from the grain size time scale are in good agreement with the k ar dated ages 3 there is close coherence between the baoji grain size time series and the orbital variations at the orbital frequency bands over the entire 0 2 5 ma period and 4 the grain size record on the orbital time scale shows a close similarity to the orbitally tuned dsdp site 607 and odp site 677 18o records examination of time dependent characteristics of the grain size record suggests that there are two major shifts of dominant periodicities in the long term monsoonal cycles one occurring at about 0 8 ma bp and the other around 1 7 ma bp

minimum magnitude of completeness in earthquake catalogs examples from alaska the western united states and japan we mapped the minimum magnitude of complete reporting m c for alaska the western united states and for the junec earthquake catalog of japan mc was estimated based on its departure from the linear frequency magnitude relation of the 250 closest earthquakes to grid nodes spaced 10 km apart in all catalogs studied mc was strongly heterogeneous in offshore areas the mc was typically one unit of magnitude higher than onshore on land also mc can vary by one order of magnitude over distance less than 50 km we recommend that seismicity studies that depend on complete sets of small earthquakes should be limited to areas with similar mc or the minimum magnitude for the analysis has to be raised to the highest com mon value of mc we believe that the data quality as reflected by the mc level should be used to define the spatial extent of seismicity studies where mc plays a role the method we use calculates the goodness of fit between a power law fit to the data and the observed frequency magnitude distribution as a function of a lower cutoff of the magnitude data mc is defined as the magnitude at which 90 of the data can be modeled by a power law fit mc in the 1990s is approximately 1 2 0 4 in most parts of california 1 8 0 4 in most of alaska aleutians and panhandle excluded and at a higher level in the junec catalog for japan various sources such as ex plosions and earthquake families beneath volcanoes can lead to distributions that cannot be fit well by power laws for the hokkaido region we demonstrate how neglecting the spatial variability of m c can lead to erroneous assumptions about deviations from self similarity of earthquake scaling

the taiwan telemetered seismographic network abstract in 1972 the taiwan telemetered seismographic network ttsn was installed to monitor earthquakes occurring in an area from 21 to 26 n latitude and from 119 to 123 e longitude the number of stations increased from six in 1972 to 24 in 1987 the stations are equipped with velocity type seismometers with a natural frequency of 1 hz since 1983 horizontal component sensors have been added at several stations signals recorded by the field stations are transmitted to taipei recording center through telephone lines or radio and then recorded on fm magnetic tapes paper and nine track magnetic tapes through a d converters hypocenters of earthquakes are routinely determined by a hypoc2 computer program the size of an earthquake is estimated from the signal duration moreover a simulated wood anderson seismographic station is in operation at taipei for the determination of local magnitude a seismic work system sws is being established for automatic data acquisition and data processing to avoid clipping of signal amplitude an optimum telemetry system is being linked to the ttsn

tectonically induced climate and its control on the distribution of depositional systems in a continental foreland basin cloverly and lakota formations lower cretaceous of wyoming u s a abstract continental sediments of the cloverly and lakota formations lower cretaceous in wyoming are subdivided into three depositional systems perennial to intermittent alluvial intermittent to ephemeral alluvial and playa chert bearing sandstones conglomerates carbonaceous mudrocks blocky mudrocks and skeletal limestones were deposited by perennial to intermittent alluvial systems carbonaceous mudrocks contain abundant wood fragments cuticle and cortical debris and other vascular plant remains representing deposition in oxbow lakes abandoned channels and on floodplains under humid to seasonal conditions intraformational conglomerates sandstones bioturbated and blocky mudrocks with caliche nodules and bioturbated limestones characterize deposition in intermittent to ephemeral alluvial systems bioturbated limestones are encased in bioturbated mudrocks with abundant pseudo slickensides the presence of caliche nodules in some of the blocky to bioturbated mudrocks is consistent with supersaturation and precipitation of calcium carbonate from groundwater under semi arid conditions caliche nodules pseudo slickensides and carbonate rich floodplain sediments are interpreted to have been deposited by intermittent to ephemeral alluvial systems under seasonal to semi arid climatic conditions laminated mudrocks siltstones vuggy carbonates bedded to nodular evaporites pebbly mudrocks and diamictites were deposited in evaporative alkaline lakes or playas pebbly mudrocks and diamictites are interpreted to represent deposition from channelized and unchannelized hyperconcentrated flows on a playa resulting from intense rain events within the basin the areal abundance and distribution of these depositional systems change systematically across the overfilled portion of the early cretaceous cordilleran foreland basin in wyoming the lower part a interval of the cloverly and lakota formations is characterized by deposits of perennial to intermittent rivers that existed 300 to 1000 km east of the sevier fold and thrust belt proximal to the sevier fold and thrust belt the a interval of the cloverly formation and upper ephraim formation of the gannett group are typified by deposits of intermittent to ephemeral rivers and their associated floodplains in the middle part b interval of the cloverly formation intermittent to ephemeral alluvial systems expand to 600 km into the basin the upper part c interval of the cloverly formation is characterized by playa deposits in the bighorn and wind river basins and intermittent to ephemeral alluvial deposits along the front of the ancestral sevier mountains deposits of perennial to intermittent alluvial systems in the c interval of the cloverly and lakota formations are restricted to the black hills region almost 900 km to the east of the sevier mountains the change in the areal distribution of depositional systems through time within this continental foreland basin may be attributed to the development of a rain shadow associated with the uplift of the sevier mountains in the early cretaceous

antiphase hydrogen and oxygen isotope periodicity in chert nodules abstract oxygen and hydrogen isotope analyses were made of jurassic age chert nodules from the holy cross mountains se poland along radial transects at high spatial resolution there is a radial sigmoidal periodicity for both isotope ratios but the two are out of phase with high d values corresponding to low 18 o values periodicity for a 100 to 120 mm diameter nodule is approximately 16 mm increasing slightly toward the rim with amplitudes approaching 20 and 3 0 for hydrogen and oxygen respectively the combined hydrogen oxygen isotope data for one nodule fall on a published curve for chert forming in equilibrium with seawater knauth and epstein 1976 the range of delta values corresponds to temperature variations of 10 c data for a second chert fall on a subparallel d 18 o line with d values that are almost 50 lower the d 18 o patterns for the nodules cannot be explained by periodic mixing of meteoric and ocean water because the hydrogen and oxygen isotope data are out of phase two possible explanations for the antiphase periodicity are a cyclical temperature variations perhaps related to an unstable convection system e g bolton et al 1999 and b self organizing catalytic precipitation e g wang and merino 1990 the systematic isotopic variations are difficult to explain by diagenesis and strongly suggest that primary isotopic compositions are preserved the isotopic data provide important information on the thermal history of the sedimentary basin if temperature variations are the cause of the isotopic periodicity

calcrete and palustrine assemblages on a distal alluvial floodplain a response to local subsidence miocene of the duero basin spain abstract in the upper miocene of the eastern duero basin two carbonate units cu 1 and cu 2 display a lateral transition from distal alluvial floodplain red mudstones to calcrete and an upwards transition from calcrete to palustrine facies the carbonate content in the calcrete increases upwards as shown in sequences from red or reddish brown mudstones with diffuse calcification to nodular calcrete facies to massive calcretes the palustrine facies display a broad range of textures related to the degree of exposure peloidal intraclast textures formed during the most prolonged phases of exposure and are those most commonly seen in the palustrine facies the transition from calcrete to palustrine facies occurs in two ways 1 as an indurated limestone level with mixed features of calcrete and palustrine facies and 2 a well delimited boundary between the two facies which show very similar characteristics in the vicinity of this boundary the 13cpdb and 18opdb values of the calcretes are similar to those of the palustrine facies this is because their genesis was related to groundwaters which inherited the isotopic signature of meteoric waters good covariance between 13c and 18o palustrine values r 0 78 is typical of lakes in semi arid regions with long water residence times in closed basins the calcrete palustrine association records a progressive decrease in the terrigenous supply and a continuous elevation of the groundwater table until it intersected with the surface to create a pond the rise in the groundwater table resulted from local subsidence that was not compensated by terrigenous supply leading to a lowering of the floodplain changes in the thickness of palustrine facies from central to marginal pond areas with ubiquitous exposure features suggest that the pond was progressively filled up by bio chemical carbonate precipitation balancing the available space created by subsidence this maintained the shallow character of the pond deposits

lacustrine and palustrine facies in the bembridge limestone late eocene hampshire basin of the isle of wight southern england abstract the carbonate lake system represented by the late eocene bembridge limestone formation isle of wight southern england comprises two main facies lacustrine and palustrine these facies are arranged vertically in transgressive regressive cycles corresponding to a model of carbonate lakes of low gradient and fluctuating margins with extensive palustrine fringes these lakes developed in a coastal plain of limited relief where two paleogeographical domains predominate a lacustrine domain is represented in northern and eastern sections in the isle of wight by cycles representing upward passage from central lacustrine sub facies marl marly limestone through marginal lacustrine sub facies biomicrite to sub facies indicative of exposure brecciated nodular limestone a palustrine domain predominant in west wight is represented by a predominantly pedogenic palustrine facies with clotted peloidal to ooidal textures and some intercalated laminated laminar calcrete horizons within the pedogenic facies textures have evolved from those of unaltered biomicrites through clotted peloidal to dense ooidal to open ooidal textures a third domain developed in close geographical proximity to more saline waters is represented by gypsiferous lake margin facies found in north wight in which microlenticular gypsum developed post depositionally as a result of evaporation following subaerial sediment exposure in the lacustrine domain there appears to be an association between cyclicity and changes in base sea level reflecting a likelihood that the lakes were part of a paralic coastal plain complex with distal marine connections alternatively the cyclicity might have developed as a result of the alternation of wetter and drier climatic periods

carbonate deposition in an ephemeral siliciclastic alluvial system jurassic shuttle meadow formation newark supergroup hartford basin usa abstract nonmarine carbonate accumulation from a sedimentologic perspective has multiple possible origins clastic load springs groundwater discharge soil development biochemical seasonal changes cave speleothems and eolian influx many of these carbonates contain diagnostic textures from which origin is easy to ascertain however differentiating between clastic and spring groundwater carbonates especially in depositional systems dominated by siliciclastics is not always simple here criteria for recognition are developed subsurface hydrology and tectonic origin of the depositional basin source rocks surrounding the basin sedimentologic packaging and extent of the carbonates in question as well as their sedimentary structures and fossil content and stable isotopic analyses of the carbonates can all aid in determining carbonate origin and correctly assessing sedimentary and basin evolution the present study focuses on a nonmarine carbonate deposit found within the jurassic shuttle meadow formation of the hartford basin one of many rift basins which formed as a result of the opening of the north atlantic ocean during the late triassic to early jurassic the upper 50 m of the formation at plainville connecticut is interpreted as continental in origin and is composed of five facies red ripple cross laminated muddy siltstones to sandstones fr sr massive red siliciclastic mudstones fm buff fine to medium grained horizontally laminated sandstones sh red to white disrupted calcareous shales fl3 and rare micritic carbonates pm facies fr sr sh and fm are interpreted as an alluvial plain system in an ephemeral setting with bedload sheetflooding as the dominant depositional mechanism similar to the channel country drainage system of central australia in addition preservation of lateral accretion sandstone sheets accretionary benches indicate that the shuttle meadow alluvial system was rapidly accreting the anomalous existence of carbonate beds in facies fl3 and pm in the smf bedload dominated siliciclastic sequence is attributed mainly to the unique nature of the clastic sediment load in the basin no direct evidence for a spring groundwater input is apparent the shallow carbonate lake margin or a pond with vegetation and periodic exposure is envisioned as the depositional environment the intraclastic texture of the micrites with rare primary relict lamination indicates early diagenetic alteration from root penetration desiccation cracks and burrowing

late miocene to plio pleistocene fluvio lacustrine system in the karacasu basin sw anatolia turkey depositional paleogeographic and paleoclimatic implications abstract the sedimentary record of the late cenozoic karacasu basin a long lived continental half graben from southwestern turkey is characterized by siliciclastic and carbonate deposits sedimentation was controlled by an active nw se trending major normal fault along the basin s southern margin and by climatically induced lake level changes detailed facies analysis subdivides the entire neogene quaternary basin fill into three distinct litostratigraphic units representing paleogeographic changes and sedimentation patterns throughout the basin evolution sedimentation commenced in the late miocene with the deposition of proximal medial alluvial fan and fluvial facies damdere formation fa1 at this stage alluvial fans developed in elevated areas to the south prograding towards the basin center at the beginning of the pliocene fresh to slightly alkaline shallow lake deposits fa2a of the karacaoren formation formed the lake became open and meromictic conditions developed fa2b pollen data from the fa2b facies show that climate was arid to humid climate probably changed cyclically through time producing alternation of artemisia steppe cold and dry periods and more forested vegetation warm and wet the open lake facies passes upwards into lake margin facies fa2c but it was still dominated by alkaline to slightly saline lake conditions sedimentation was almost continuous from the late miocene to pleistocene in the early quaternary the basin was dissected by the re activation of basin bounding faults the unconformable base of the overlying quaternary deposits karacasu formation fa3 reflected the basin s transformation from a half graben into a full graben system oxygen isotope data from carbonates show an alternation of humid climatic periods when freshwater settings predominated and semiarid arid periods in which the basin hosted alkaline and saline water lakes neotectonic activity has rejuvenated many of the basin bounding faults causing development of talus aprons and local alluvial fans the basin was progressively incised by modern rivers that have largely smoothed out the topographic relief of the graben margins

statistical evaluation of characteristic earthquakes in the frequency magnitude distributions of sumatra and other subduction zone regions 1 if subduction zone earthquakes conform to a characteristic model in which persistent segments fail at predictable stress levels due to the steady accumulation of tectonic loading historical seismicity may constrain the occurrence of future events we test this model for earthquakes on the sumatra andaman megathrust and other subduction zones using frequency magnitude distributions using simulations we show that poisson confidence intervals correctly account for the counting errors of histogram data these confidence intervals demonstrate that we cannot reject the gutenberg richter distribution in favor of a characteristic model in any of the real catalogues tested a visual bias in power law count data at high magnitudes combined with a sample bias for large earthquakes is sufficient to explain candidate characteristic events this result implies that historical earthquakes are likely poor models for future events and that monte carlo simulations will provide a better assessment of earthquake and associated hazards

long term earthquake clustering summary we analyse statistically the long term properties of several instrumental earthquake catalogues complete catalogues exhibit both short and long term clustering for earthquakes of all depth ranges after accounting for the effect of short term clustering we find that in residual declustered catalogues long term clustering not periodicity characterizes the occurrence of all earthquakes shallow intermediate and deep the degree of clustering in residual catalogues is the same for earthquakes in different depth ranges circumstantial evidence indicates that the long term v ariation of seismicity is governed by a power law temporal distribution as in short term clustering it is scale invariant the fractal dimension of an earthquake set on the time axis is of the order of 0 8 0 9 therefore mainshock occurrence is closer to a stationary poisson process than standard aftershock sequences of shallow earthquakes

late quaternary dust flow on the chinese loess plateau abstract the dust flux of over 25 g cm2 103yr was reached in the central part of the chinese loess plateau during the last glacial maximum this is more than three times higher than during the last interglacial and early glacial time the grain size of the pleniglacial dust reached a peak shortly after 20 000 years ago and testifies to the occurrence of strong winds and frequent dust storms

grain size of quartz as an indicator of winter monsoon strength on the loess plateau of central china during the last 130 000 yr the chinese loess paleosol sequence constitutes an important record of variations in asian monsoon climate over the past 2 4 myr magnetic susceptibility of loess and paleosols has been used as a proxy for summer monsoon intensity while median grain size has been regarded as a measure of the strength of winter monsoon winds that were responsible for most of the dust transport however median grain size is only an approximate index of winter monsoon strength because both paleosols and loess have been modified to various degrees by weathering processes that have produced pedogenic clay the quartz component of loess and paleosols is largely unaffected by weathering processes and therefore constitutes a more reliable proxy index of monsoon wind strength median grain size qmd and maximum grain size qmax values of monomineralic quartz isolated from the loess paleosol section at luochuan in the central loess plateau are characterized by two main intervals during the last ca 130 000 yr when these parameters were significantly greater than 9 and 85 m respectively and three main intervals when they were lower the data imply that the winter monsoon weakened during the intervals with low qmd and qmax values which coincide with marine oxygen isotope stages 5 3 and 1 and was strongest ca 67 000 and 20 000 yr ago during isotope stages 4 and 2 however both quartz grainsize records display second order high frequency high amplitude variations which are lacking in the magnetic susceptibility record that imply rapid and significant changes in atmospheric conditions that affect dust transport and deposition

the long term paleomonsoon variation recorded by the loess paleosol sequence in central china abstract the loess paleosol sequence in central china during the last 2 5 ma is a good record of the asian monsoon variation which could be considered as the concrete realization of global paleoclimatic cycles the geological and biological evidence of the loess paleosol sequence indicates that the loess was mainly the dust deposits transported by the northerly wind of winter monsoons and also suffered to some extent from pedogenesis caused by weakened summer monsoons and that the paleosol accreted by the rather slow dust accumulation was closely related to strengthened summer monsoons an alternating occurrence of loess and paleosol in the luochuan section implies the variation history of warm humid climate with a summer monsoon dominance and cold dry climate with a winter monsoon dominance the magnetic susceptibility of loess and paleosol can be regarded as a proxy index of asian monsoon variation an analysis of the susceptibility curve and structure characters of luochuan section shows that the asian monsoon circulation was strengthened from early pleistocene to late pleistocene and the 500 ka bp point and 1200 ka bp point seem to be a threshold and a turning point respectively in terms of the long term paleomonsoon variation in asia

tectonic controls for transverse drainage and timing of the xin ding paleolake breach in the upper reach of the hutuo river north china abstract the upper reach of the hutuo river flows along the xin ding basin and cuts a transverse drainage through the xizhou mountain and the taihang range into the north china plain previous studies showed that the xin ding basin was occupied by a lake during the early middle pleistocene however the timing of the paleolake breach and the mechanism for the creation of the transverse drainage are unknown we constructed the fluvial terrace sequence in the upper reach of the hutuo drainage combined with thermoluminescence tl and optically stimulated luminescence osl dating as well as the timescale of the overlying loess paleosol sequence our results reveal that 1 five terraces t5 t1 developed along the upper reach of the hutuo river amongst which terraces t4 t1 were formed synchronously at 600 120 130 20 26 and 6 7 ka respectively 2 the creation of the transverse drainage and breach of the xin ding paleolake occurred between 600 and 130 ka and 3 the mechanism for the creation of the transverse drainage is via river piracy of paleostreams on both sides of the drainage divide localized differential uplift and associated tilting of the xizhou mountain block during the middle pleistocene result in the formation of the transverse drainage and breach of the xin ding paleolake

late miocene and early pliocene environments in the southwestern black sea region from high resolution palynology of dsdp site 380a leg 42b a high resolution palynological study has been performed on late miocene messinian and early pliocene zanclean sediments cored at dsdp site 380a leg 42b a late miocene coastal vegetation has been identified in association with a delta environment the pliocene is characterised by competition between the two most important vegetation components namely humid thermophilous forests and dry steppes with changes driven by large amplitude climatic variations these variations are linked to other european reference pollen records and to the global temperature evolution for the early pliocene and result in climatostratigraphic relationships at large geographic scale an orbital tuning is proposed with respect to new data clarifying time control on the section the black sea appears to have dried up in response to the messinian salinity crisis in the mediterranean with which it might have been connected during periods of high sea level

lacustrine system evolution during early rifting el castellar formation galve sub basin central iberian chain abstract a detailed sedimentological study of the first synrift deposits recorded in the galve sub basin of ne spain during the early cretaceous aided in the reconstruction of climatic and tectonic influences the el castellar formation is composed of siliciclastics and carbonates unit 1 claystones gypsum and carbonates unit 2 and marls and limestones unit 3 unit 1 facies formed in alluvial and palustrine plains a local alluvial fan and low energy shallow lake subenvironments low energy lacustrine facies characterised unit 2 in contrast palustrine low and high energy lake facies were identified for unit 3 the spatial and temporal distribution of lithofacies representing the several environments were used to propose a general lacustrine system evolution from isolated ponds and marshes to low energy shallow lakes and finally to an extensive high energy lake lake evolution is related to changes in the subsidence pattern from local to basin scale subsidence which was ultimately related to the transition from the initial rift to rift climax stage shallowing upwards lacustrine successions have been interpreted as climatically forced and linked to sediment and water supply both tectonics and climate determined the change from an overfilled to a balanced fill lake basin through time

lycian melange southwestern turkey an emplaced late cretaceous accretionary complex the lycian thrust belt is an important part of the tethyan orogenic belt in the eastern mediterranean region it includes a unit of internally disrupted thin skinned thrust sheets layered tectonic melange and a melange rich in ophiolitic material ophiolitic melange the layered tectonic melange is dominated by mesozoic distal deep water sedimentary rocks and the ophiolitic melange includes disrupted thrust sheets of early mesozoic shallow water limestone and blocks of basalt of both mid ocean ridge and within plate geochemical affinities a complete record of closure of a tethyan oceanic basin began with late cretaceous intraoceanic subduction followed by latest cretaceous trench continental collision and ended with mid tertiary continental collision and orogenic collapse

analysis of time dynamical features in intraplate versus interplate seismicity the case study of iquique area chile the intraplate and interplate seismic catalogues of iquique chile area were investigated by using seismological b value of the gutenberg richter law fractal allan factor and detrended fluctuation analysis and topological horizontal visibility graph methods the two catalogues show different stress state indicated by the different b value larger for the intraplate seismicity the interplate seismicity shows significant time clustering behavior of the earthquake occurrence times at large time scales while the time distribution of the intraplate earthquakes seems to be featured by random fluctuations without any significant sign of time clustering different role seems to be played by aftershocks in the two investigated seismic zones revealed by the different time distribution of the aftershock depleted catalogue of the intraplate zone which remains poissonian for most of the time scales and the interplate zone that still keeps its clustering phenomenon but at higher timescales thus shortening its clustering time scale range furthermore the interevent times of the interplate catalogue are characterized by persistent dynamics even after removing the aftershocks while uncorrelated fluctuations characterize the behavior of interevent intervals of the whole as well as aftershock depleted intraplate catalogue additionally the magnitudes of both catalogues are characterized by time reversibility before and after the aftershock removal while the interevent times of intraplate catalogue change their status from time irreversibility to time reversibility after removing the aftershocks the obtained results seem to evidence a different role played by the aftershocks in the intraplate and interplate zones that needs to be further explored

alluvial eolian and lacustrine sedimentology of a paleoproterozoic half graben baker lake basin nunavut canada the northeast trending baker lake sub basin was a volcanically active half graben during deposition of ca 1 85 1 76 ga baker lake group drainage was oriented along transverse and axial directions with flow to playa lake and deeper perennial lacustrine depocentres basin marginal streamflow dominated alluvial fans were concentrated along the southern margin and provided sediment from archean crystalline basement rocks these fed transverse gravel and sand bed braided streams alluvial dynamics were characterized by channel aggradation and abandonment abandoned channel belts were sites of floodplain and eolian deposition basin axial braided streams fed northeast and southwest to a depocentre near christopher island where eolian playa and lacustrine environments were intimately linked felsic minette flows were initially erupted from localized centres contemporaneous sedimentary deposits typically contain minor volcaniclastic components that increase in abundance basinward voluminous and widespread younger minette flows prograded outward from volcanic centres contributing significant additional basin infill

quaternary deformation at the southeastern margin of the ordos block north china inferred from structural analysis of basin bounding faults abstract the southeastern margin of the ordos block semob is located at the juncture of the north china block the ordos block and the qinling orogen a series of faulted basins has developed in this area since the cenozoic the latest focal mechanism solution and stress field analyses indicate that the semob is located at the adjacent regions of present different stress field although the structural activity and internal mechanisms of this changing remain unclear in this paper we describe the results of a study into the fault systems and quaternary deformation between the linfen and weihe basins on the semob based on the deformation sequences kinematic analyses and activity timing we found that the strain field in semob underwent three evolutionary stages during the quaternary nw se extension in the early pleistocene ne sw extension in the middle pleistocene and ca n s oblique extension from the late pleistocene to the holocene this evolution of the strain field affected both the geomorphic patterns and the activity of paleo earthquake events along the semob during the quaternary quaternary extensional deformation in the upper crust along the semob possibly resulted from crust mantle decoupling which may be related to eastward expansion of the tibetan plateau and subduction of the pacific and philippine sea plates

climatic implications of the s5 paleosol complex on the southernmost chinese loess plateau the s5 is the most prominent paleosol unit in the chinese loess plateau and is distinguished by its great thickness dark color and well developed clay coatings previous studies led to the proposal that the s5 developed under much warmer and wetter conditions than at present implying a climatic optimum however the s5 is a paleosol complex corresponding in time to a period of weak glacial interglacial oscillations as recorded by marine oxygen isotope stages 15 through 13 to understand the character of this climatic interval two profiles of the paleosol s5 in the guanzhong basin were studied with most of the emphasis being placed on the uppermost and best developed pedon s5 i grain size mineralogical and chemical data indicate that the major pedogenic processes experienced by the s5 i included complete decalcification and mechanical translocation of fine particles chemical alteration of silicate minerals has been weak stable carbon isotope analyses of organic matter showed that c4 plant remains are abundant throughout the profiles these results suggest that grasslands dominated the paleovegetation during s5 i development the prominent development of the s5 paleosol complex may reflect a prolonged period of pedogenesis in contrast to previous reports paleoclimatic conditions perhaps even drier than at present are implied by the data for the s5 profiles the relative strength of the glacial interglacial oscillation in this region related to the east asian monsoon was similar to that indicated for global climate during s5 time

regional paleohydrologic and paleoclimatic settings of wetland lacustrine depositional systems in the morrison formation upper jurassic western interior usa abstract during deposition of the upper jurassic morrison formation water that originated as precipitation in uplands to the west of the western interior depositional basin infiltrated regional aquifers that underlay the basin this regional groundwater system delivered water into the otherwise dry continental interior basin where it discharged to form two major wetland lacustrine successions a freshwater carbonate wetland lacustrine succession formed in the distal reaches of the basin where regional groundwater discharged into the denver julesburg basin which was a smaller structural basin within the more extensive western interior depositional basin an alkaline saline wetland lacustrine complex lake t oo dichi formed farther upstream where shallower aquifers discharged into the san juan paradox basin which was another small structural basin in the western interior depositional basin these were both wetlands in the sense that groundwater was the major source of water input from surface and meteoric water was limited in both basins lacustrine conditions developed during episodes of increased input of surface water inclusion of wetlands in our interpretation of what had previously been considered largely lacustrine systems has important implications for paleohydrology and paleoclimatology the distal carbonate wetland lacustrine deposits are well developed in the morrison formation of east central colorado occupying a stratigraphic interval that is equivalent to the lower morrison but extends into the upper morrison formation sedimentologic paleontologic and isotopic evidence indicate that regional groundwater discharge maintained shallow hydrologically open well oxygenated perennial carbonate wetlands and lakes despite the semi arid climate wetland deposits include charophyte rich wackestone and green mudstone lacustrine episodes in which surface water input was significant were times of carbonate and siliciclastic deposition in scarce deltaic and shoreline deposits marginal lacustrine deposits include ooid and skeletal packstone grainstone siltstone and sandstone distal lacustrine units are skeletal mudstone wackestone microbialites and laminated siliciclastic mudstone differentiation between wetlands and distal lacustrine units is not always possible palustrine features magadi type chert mtc and evaporites record episodes of increased aridity and exposure farther upstream during deposition of the upper part of the brushy basin member the ancestral uncompahgre uplift imposed a barrier to shallow eastward flowing groundwater that discharged into the san juan paradox basin on the upstream side of the uplift this created the closed hydrologic setting necessary for development of an alkaline saline wetland lacustrine complex lake t oo dichi silicic volcanic ash delivered by prevailing winds from calderas west and southwest of the basin contributed to the pore water evolution in the sediments a distinctive lateral hydrogeochemical gradient reflecting increasing salinity and alkalinity in the pore waters altered the ash to a variety of authigenic minerals that define concentric zones within the basin the basinward progression of diagenetic mineral zones is smectite clinoptilolite analcime potassium feldspar albite the groundwater fed wetlands were shallow and frequently evaporated to dryness scarce laminated gray mudstone beds record distinct episodes of freshwater lacustrine deposition that resulted from intermittent streams that carried detritus well out into the basin

second order moment of central california seismicity 1969 1982 the second order moment cross correlation function of earthquakes in the u s geological survey central california catalog between 1969 and 1982 was calculated with respect to a magnitude threshold m 4 0 over interevent distances up to 80 km and interevent times up to 320 days the statistical procedure results in a representation of the spatial temporal structure of the catalog associated with m 4 0 earthquakes and is capable of revealing patterns too weak to be detected in the space time distribution of seismicity for individual earthquake sequences a method is introduced for identifying aftershocks based on a physical two parameter model of the earthquake interaction process the results show that the aftershock process dominates the second order moment and may even obscure the statistical expression of a precursory process a concentration of foreshocks within 15 km and 3 days of m 4 0 main shocks exhibits an apparent migration toward the main shock loci with velocity 2 6 5 3 km d this concentration may be related to an observed tendency for m 4 0 events to cluster auto correlate over this interevent range with the identified aftershocks removed the residual catalog is poissonion in space and time when two m 4 0 earthquakes occur within 80 km and 40 days of each other aftershock productivity appears to be relatively enhanced in the earlier sequence this suggests that aftershock populations are not solely dependent on their main shocks and that unusually productive aftershock sequences may be predictors of future moderate earthquakes

fractal and spectral investigation of the shallow seismicity in taiwan abstract we studied the whole and aftershock depleted shallow depth 30 km taiwanese seismicity from 1990 to 2017 by using several independent methods the coefficient of variations and the allan factor have revealed that time clustering characterizes not only the time distribution of the whole seismic catalogue but also that of the aftershock depleted one although this displays time clustering at larger timescales in particular the allan factor shows that at small timescales the seismic process of the whole as well as the aftershock depleted one can be well described by a poisson process the detrended fluctuation analysis clearly evidence persistence in the interevent times and weak persistence or randomness in the magnitudes the singular spectrum analysis of the daily counts in the aftershock depleted catalogue reveals the existence of quasi monthly and bi weekly periodicities furthermore quasi annual and quasi semestral periodicities have been identified that strengthen the link between seismic activity in taiwan and earth s tides

non uniform scaling features in central italy seismicity a non linear approach in investigating seismic patterns and detection of possible earthquake precursors 1 the detrended fluctuation analysis dfa is a powerful method for capturing scaling behavior in nonstationary time series using an appropriate instability index it is possible to identify and quantify deviations from uniform power law scaling which suggest the presence of changing dynamics in the system under study in this context the scaling behavior of the 1981 2007 seismicity in umbria marche central italy which is one of the most seismically active areas in italy was investigated significant deviations from uniform power law scaling in the seismic temporal fluctuations were revealed mostly linked with the occurrence of rather large earthquakes or seismic clusters

palustrine carbonates and pedogenic calcretes in the cal basin of sw anatolia implications for the plio pleistocene regional climatic pattern in the eastern mediterranean abstract sedimentologic and stable isotopic studies in the cal basin fill provide new insights on the late neogene quaternary climatic pattern in the eastern mediterranean long term subsidence and terrestrial sedimentation in the basin beginning in the late miocene are recorded in alluvial fan and fluvial deposits overlain by pliocene palustrine carbonates an erosional unconformity separates the pleistocene siliciclastic and calcrete deposits above as a single sedimentary unit resting on top of floodplain fines and restricted to the basin center the stable isotopic analysis of the palustrine carbonates and pedogenic calcretes displays a wide range of values 7 98

late quaternary variations in the level of paleo lake malheur eastern oregon abstract the highest shoreline features of paleo lake malheur are undated gravelly barrier beaches south of harney lake that lie ca 3 5 m higher than the hydrographic outlet of harney basin at malheur gap 1254 m the earliest quaternary record for lake malheur consists of occurrences of water deposited tephra dated to ca 70 000 80 000 yr ago the next identified lake interval is dated by shells with ages of ca 32 000 and 29 500 yr b p no dates are available for the terminal pleistocene lake malheur lake s were present between ca 9600 and 7400 yr b p although periodic low levels or desiccation are suggested by a paleosol dated as ca 8000 yr b p the lake system probably dried further after 7400 yr b p although dates are lacking for the period between ca 7400 and 5000 yr b p dune deposits on the lake floor are ca 5000 yr old and indicate generally dry conditions fluctuating shallow lakes have probably characterized the last 2000 years a date of 1000 yr b p gives a maximum age for beach deposits at 1254 m near the basin threshold elevation thus the malheur lake system may have drained to the pacific ocean by way of malheur gap during the latest holocene

late pliocene northern hemisphere glaciations the continental and marine responses in the central mediterranean abstract detailed pollen analyses and oxygen isotope records of three foraminiferal species globigerina bulloides uvigerina peregrina and cibicides pachyderma from the semaforo and vrica composite sections crotone southern italy have been compared to the global climatic changes depicted by late pliocene early pleistocene foraminiferal 18o records of site 607 in the north atlantic and hole 653a in the tyrrhenian basin west mediterranean major overturns in the mid altitude vegetation are shown near isotopic stages 82 60 58 and 50 at about 2 03 ma 1 6 ma and 1 37 ma according to the raymo et al 1989 and ruddiman et al 1989 timescales at the same dates glacial 18o maxima either became higher or display step increases in the western mediterranean or in the open ocean as well this suggests that size increases of northern hemisphere ice sheets were the driving factor for regional or local marine and continental environmental changes within the mediterranean basin near isotopic stages 62 60 close to the conventional plio pleistocene boundary the climatic conditions severed enough within the mediterranean basin to modify the continental environment as depicted by a sudden increase of artemisia percentages while the first significant southward migration of the north polar front may have been recorded by an influx of left coiling neogloboquadrina pachyderma in the central mediterranean it also appears that boreal guests entered the mediterranean during phases of 18o enrichment of foraminiferal calcite there does not seem to be any discrepancy between the climatic concept of the pliocene pleistocene boundary and its chronostratigraphic definition

development of gully systems under the combined impact of monsoonal climatic shift and neo tectonic uplift over the chinese loess plateau the surface landscape of the chinese loess plateau features densely developed gully systems gully incision and extension are extremely active over the elevated regions of loess hills ridges and tablelands this paper presents the results of investigations on major gullying phases over the loess plateau during the quaternary the objective is to establish a chronology of gullying events and to examine their relations with monsoonal climatic changes and neo tectonic uplifts results from field observations geomorphologic and pedo stratigraphic analysis indicate that pre historical gullying events are recorded by buried palaeogullies and pedo stratigraphic unconformities preserved in loess sections there were four major gullying phases identified at the loess to palaeosol transitions of l6 s5 l3 s2 l2 s1 l1 s0 in the stratigraphy over the loess plateau the age of a gullying event is closely related with the bottom unit of the palaeosol series in the overlying loess blanket the gullying phases were therefore dated to ca 600 ka 240 ka 125 ka and 11 5 ka respectively by loess chronology this means that gully incision occurred when large scale monsoonal climatic shift met with coincided neo tectonic uplift of the land mass neo tectonic uplift provided the gullying with potential for deep down cutting excessive runoff resulted from precipitation brought on by intensified maritime monsoon was a dynamic forcing of the gullying at the transitions of mis 16 15 8 7 6 5 and 2 1 in response to each wave of gully incision and cross section development occurred the outspreading of the tributary gullies and a new order of gullies formed gully density is therefore increased and the loess land became more dissected hills and ridges these results provide new insights into history of gully erosion and long term landscape development in the semi arid loess regions of the world

the late early miocene acipayam piggy back basin refining the last stages of lycian nappe emplacement in sw turkey abstract alluvial fan to shallow marine sedimentation in the acipayam piggy back basin took place in the hinterland zone of the se facing lycian nappe stack and constrains the age and style of late stage advance of these nappes syn orogenic sedimentation commenced in burdigalian time and is marked by coarse grained alluvial fan deposits that directly overlie mesozoic ophiolitic rocks palaeocurrent data obtained from these coarse clastic units suggest a south southeastward drainage the succession fines upwards and passes into fluvial deposits that become increasingly enriched in carbonate clasts derived from tectonically deeper seated nappes suggesting progressive unroofening of the nappe pile upwards the succession is transitional to a late burdigalian early langhian marginal marine succession consisting of off shore fines with coal seams that overly both the coarse clastic sediments and basement rocks clastic sedimentation ceased at the end of early langhian based on reef carbonates that cap the succession shallow marine deposits and overlying reef carbonates confirm a marine transgression that has been reported from elsewhere in the tauride belt detailed sedimentology of the acipayam basin fill succession its age and overall tectonic setting imply that during burdigalian time the succession was deposited in a piggy back basin located in the hinterland zone of actively moving thrust sheets we propose a model in which thick skinned thrusting invoked inversion of early extensional faults in the autochthon and may explain the generation of large open folds with thick sedimentary sequences in their core the formation of these large folds may have importantly influenced the frontal accretion such that active shortening moved into the hanging wall resulting in episodic nappe advanced of structurally higher nappes in a mode similar to thin skin thrusting the tectonosedimentary evolution of the acipayam piggy back is strongly dependent on its position relative to the hinge of the large open fold the absence of any compressional signatures in the basin fill succession indicates that these thrust translations ceased shortly after aquitanian time by serravallian the succession was interrupted and the region was uplifted to its present elevation probably by gravitationally isostatic orogenic rebound of the nappe stack after these episodes tectonic extension predominated and the succession became dissected by nappe front parallel normal faults that bound the present cameli basin

progressive changes in sedimentary facies and stratal patterns along the strike slip margin northeastern jinan basin cretaceous southwest korea implications for differential subsidence abstract in strike slip basins proximal stratal patterns are a function of displacement on basin bounding faults in order to better understand factors that control changes in sedimentary facies and stratal patterns of the northeastern part of the jinan basin cretaceous a strike slip basin we made a detailed analysis of sedimentary facies depositional architecture and paleoflows the sedimentary successions can be grouped into five facies associations representing five depositional environments 1 facies association fa i alluvial fan 2 fa ii small scale gilbert type delta 3 fa iii large scale steep delta slope 4 fa iv base of large scale steep delta slope and prodelta and 5 fa v lacustrine plain the successions are divided into two distinct sedimentary fills on the basis of facies associations depositional architecture and paleocurrents 1 marginal fill and 2 longitudinal fill the marginal fill ca 3 2 km thick is present along the strike slip basin bounding fault the lower part of the marginal fill ca 1 3 km thick consists of alluvial fan deposits fa i along the bounding fault which are transitional northward to small scale gilbert type delta fa ii and lacustrine plain fa v deposits the upper part of the marginal fill ca 1 9 km thick contains large scale steep delta slope fa iii and base of delta slope prodelta fa iv deposits accompanied with a northward change in facies associations in the marginal fill the successive alluvial fan small scale gilbert type delta and large scale steep delta prodelta deposits are overlapped shingled northeastward the longitudinal fill ca 2 km thick is characterized by eastward overlapped stacks of large scale steep delta slope fa iii and base of delta slope prodelta fa iv deposits with a westward progradation the longitudinal fill was overstepped by the marginal fill the northeastward shingled geometry of the marginal fill was most likely caused by sinistral strike slip displacements on the basin bounding fault the slightly oblique northward progradation of the marginal fill was due to the northward basin floor tilting in the marginal fill the progressive changes in facies and depositional architecture from the lower alluvial fan small scale gilbert type delta to the upper large scale steep delta prodelta are suggestive of increase in basin subsidence along the strike slip basin margin that was closely related to the variation in displacement on the basin bounding fault the sinistral strike slip movements on the bounding fault also caused the eastward overlapping of the longitudinal fill

study of the temporal correlations in the magnitude time series before major earthquakes in japan a characteristic change of seismicity has been recently uncovered when the precursory seismic electric signals activities initiate before an earthquake occurrence in particular the fluctuations of the order parameter of seismicity exhibit a simultaneous distinct minimum upon analyzing the seismic catalog in a new time domain termed natural time and employing a sliding natural time window comprising a number of events that would occur in a few months here we focus on the minima preceding all earthquakes of magnitude 8 and 9 class that occurred in japanese area from 1 january 1984 to 11 march 2011 the day of the m9 tohoku earthquake by applying detrended fluctuation analysis to the earthquake magnitude time series we find that each of these minima is preceded as well as followed by characteristic changes of temporal correlations between earthquake magnitudes in particular we identify the following three main features the minima are observed during periods when long range correlations have been developed but they are preceded by a stage in which an evident anticorrelated behavior appears after the minima the long range correlations breakdown to an almost random behavior possibly turning to anticorrelation the minima that precede m 7 8 earthquakes are distinguished from other minima which are either nonprecursory or followed by smaller earthquakes furthermore it is discussed whether tsallis statistical mechanics in the frame of which it has been suggested that kappa distributions arise can capture the effects of temporal correlations between earthquake magnitudes

facies and basin architecture of the late carboniferous salvan dorenaz continental basin western alps switzerland france the salvan dorenaz basin formed during the late palaeozoic within the aiguilles rouges crystalline basement western alps as an asymmetric intramontane graben elongated in a ne sw direction and bounded by active faults at least 1700 m of fluvial alluvial fan and volcanic deposits provide evidence for a strong tectonic influence on deposition with long term average subsidence rates of 0ae 2m m yr 1 the early basin fill was associated with coarse grained alluvial fans that were dominated by braided channels unit i these issued from the south western margin of the basin the fans then retreated to a marginal position and were overlain by muddy floodplain deposits of an anastomosed fluvial system unit ii that drained towards the ne deposition of thick muds resulted from a reduction in the axial fluvial gradient caused by accelerated tectonic subsidence overlying sand rich meandering river deposits unit iii document a reversal in the drainage direction from the ne to the sw caused by synsedimentary tectonism reflecting large scale topographic reorganization in this part of the variscides with subsidence now preferentially in the w and sw and uplift in the e and ne coarse grained alluvial fan deposits unit iv repeatedly prograded into and retreated from the basin as documented by coarsening upward cycles tens of metres thick reflecting smaller scale tectonic cycles volcanism was active throughout the evolution of the basin and u pb isotopic dating of the volcanic deposits restricts the time of basin development to the late carboniferous 308 295 ma 40 ar 39 ar ages of detrital white mica indicate rapid tectonic movements and exhumation of the nearby basement in unit i youngest ages are close to that of the host sediment but the age spectrum is wide in unit ii high subsidence and or sedimentation rates coincide with very narrow age spectra indicating small homogeneous catchment areas in unit iii age spectra became wider again and indicate growing catchment areas

quaternary paleolake development in the fen river basin north china abstract the taiyuan graben and the linfen graben are two fault controlled grabens in the fen river basin north china broad paleolakes periodically occupied the two grabens during the pleistocene this paper discusses how neotectonic activities and paleoclimate changes may have influenced the development of the paleolakes in the two grabens during the middle to late quaternary based on the lacustrine landforms and sediments the distribution of lake terraces and their correlation with loess paleosol series indicate that three paleolake regressions with vertical drops of about 40 60 m occurred in the two grabens at about 0 76 ma b p 0 55 ma b p and 0 13 ma b p analysis of the factors controlling paleolake development suggests that rapid tectonic uplift may be the main cause of the three paleolake regressions changes in the facies of the lacustrine sediment also suggest that when tectonic movements were relatively weak paleoclimate became the main factor causing 2 3 m fluctuations of the paleolake level

sedimentation of the neogene recent alasehir gediz continental graben system used to test alternative tectonic models for western aegean turkey abstract the alasehir gediz graben exemplifies clastic sedimentation in a long lived continental half graben in a semi arid setting developed within relatively incompetent metamorphic rocks early miocene to recent rift related sediments are exhumed on both flanks of the graben allowing detailed three dimensional study during the early miocene small fan delta lobes were shed northwards from the rugged menderes metamorphic massif into a bordering lacustrine basin during early to mid miocene time large alluvial fans prograded northwards into this basin through drainage to the aegean sea was established as the basin widened and filled discrete lobes of coarse alluvial fan sediments of latest miocene pliocene age also shedding northwards are likely to have been climatically influenced quaternary alluvium party infills the modern alasehir rift basin the sedimentary information can be used to test two alternative tectonic models for the alasehir graben in the first model an e w graben bounded by high angle faults was active during latest miocene recent time whereas earlier miocene sedimentation was controlled by n s faulting related to a n s compressional stress regime in the second hypothesis the alasehir graben was initiated much earlier in the early miocene and was then either continuously or episodically active until recent our results especially facies and palaeocurrent data from alluvial sediments indicate that clastic sedimentation was controlled by mainly e w faulting in a n s stress regime assuming the early miocene clastic sediments are correctly dated this supports the second long lived extension model however rather than steady state extension for ca 15 ma the sedimentary evidence and regional context are consistent with a pulsed extension model whereby initial early to mid miocene extension and related clastic sedimentation was followed by a second phase of extension in latest miocene pliocene time the driving force of initial early miocene extension was probably gravity spreading towards a south aegean subduction zone whereas the inferred second extension pulse is seen as being triggered by westward tectonic escape of anatolia towards the extending aegean back arc region

correlation between climate events in the north atlantic and china during the last glaciation episodes of massive iceberg release heinrich events 1 3 into the north atlantic ocean during the last glaciation were associated with recurring episodes of unusually cold north atlantic surface water bond cycles 4 and cold air temperatures over greenland dansgaard oeschger events 5 6 four of the youngest of these cold events have also been reported in climate records from sites outside the north atlantic region7 but until now the entire suite has been identified only in north atlantic marine sediments greenland ice core records and tentatively in french lake sediments8 here we examine grain size data from chinese loess and intercalated accretionary palaeosols of last glacial age for evidence of similar climate signals remote from the north atlantic region we see grain size maxima with ages that match those of the last six heinrich events which we interpret as an indication of the changing strength of the east asian winter monsoon which largely controls the transport and deposition of central asian aeolian dust thus it seems that these heinrich events have left their signature in the chinese loess record this is consistent with simulations of the glacial climate9 which imply that the climates of the north atlantic and china were linked by the effect of westerly winds

late pleistocene chronology of loess deposition near luochuan china abstract loess near luochuan was sampled for thermoluminescence tl dating simultaneously with magnetic susceptibility measurements to provide the first independent age estimates on a susceptibility record from the loess plateau of china tl age estimates on late pleistocene loess l1 are stratigraphically consistent with no statistical difference in tl ages by the total or partial bleach techniques or by measuring ultraviolet or green wavelengths in the tl analysis loess below the last interglacial soil s1 yielded disparate results and is in many localities in central and eastern china unsuitable for tl dating because of complications of tl saturation and uncertainties in estimating the environmental radiation tl age estimates on the l1 loess are consistent with previously reported tl ages for sites near beijing and xian as well as in general agreement with age models for loess deposition based on paleomagnetics and magnetic susceptibility the convergence of a variety of geochronologic indices indicate that the last major period of loess deposition in central china began 70 000 10 000 yr b p and terminated