changes of environments and climate during the late pleistocene and holocene reconstructed from aeolian and colluvial deposits of the zaktui site tunka rift valley baikal region abstract integrated study of the multilayer zaktui site supplied a large volume of paleontological materials and a series of radiocarbon dates falling within the mis 3 mis 1 interval multidisciplinary data provided evidence of the past dynamics of environments and climate paleontological data point to a mosaic structure of landscapes and suggest a temperate warm and humid climate in the south western baikal region during mis 3 interval with some regional deviations

sedimentary impacts of anthropogenic alterations on the yeongsan estuary south korea abstract over the last half century coastal zones within the republic of korea s korea have experienced a wide range of engineered coastal modifications including construction of seawalls extensive land reclamation and installation of estuarine dams the yeongsan estuary has experienced all of these modifications and provides an ideal case study on how sedimentation changes within a macrotidal estuary in response to these alterations combined these alterations have considerably modulated the timing and intensity of river discharge prevented natural tidal exchange modified the shoreline profile and altered the transport of sediment and organic matter within the coastal zone these impacts have been investigated using 30 gravity cores analyzed for 210 pb radioisotope geochronology laser diffraction particle size analyses 13 c and 15 n isotope ratio mass spectrometry and x radiography average sediment accumulation rates range from 0 9 0 6 cm yr 1 to 10 0 2 9 cm yr 1 with the highest rates proximal to the downstream side of the dam and some areas determined to be either actively eroding or recently dredged these results are supported by comparison of multiple bathymetric surveys and chirp seismic data suggest an order of magnitude increase from average holocene sediment accumulation rates side scan sonograms collected adjacent to the dam reveal distinctive scouring transitioning to areas accumulating fine grained sediments shifts in the organic matter source inputs are apparent in pre post dam sediments and reflect the occluding of tidal influence above the dam resulting in increasingly terrestrial dominated signatures additionally a time series of cores collected during periods of limited and high discharge analyzed for 7 be indicates sediment deposition occurs episodically corresponding to high discharge dam releases our observations record a shift in depositional environments as a response to an extensive array of anthropogenic alterations ultimately land reclamation and dam construction have severely altered the fate and transport of sediment within the estuarine system as a consequence sedimentation rates have increased dramatically and depositional events are primarily controlled by discharges from the estuarine dam

environmental and climate reconstructions of the fore baikal area during mis 5 1 multiproxy record from terrestrial sediments of the ust oda section siberia russia abstract the ust oda section exposes the structure of a 25 m terrace of the kitoy river the eroded surface of the jurassic sandstones is overlain by the heterogeneous primarily aeolian alluvial upper pleistocene holocene deposits that include buried soils the quaternary part of the section exhibits five main stratigraphic subdivisions ranging from isotopic stage mis 5 to mis 1 reconstructed vegetation composition of the unit 1 formation age is typical for late quaternary interglacial periods and suggests moderately cool and moderately humid climate unit 2 sediments yielded small mammal remains of taiga steppe tundra and hydrophilic species characterizing the fauna as ecologically mixed or disharmonic typical of cold pleistocene epochs in eurasia for example lagurus lagurus and dicrostonyx sp are animal species whose current habitats do not cross and are substantially distant from each other microtheriofauna species composition and structure imply unit 2 formation under the conditions of cold and arid climate together with 14c dating of the overlying strata suggesting its mis 4 age unit 3 sediments contain spore pollen spectra typical for mis 3 interstadial of the pribaikalye area mis 3 climate substantially differed from the modern one average january temperatures might have been 15 c lower than the modern ones and the mean july temperatures 2 3 c lower mean annual precipitation value could be lower than the modern one by 100 mm yr the analysis of the small mammal species ecological requirements suggests domination of tundra steppe landscapes in the area during the formation of the unit 3 theriofauna of the unit 5 allows reconstruction of paleoecological conditions close to modern ones in humidity and temperature

pleistocene permafrost in western transbaikalia abstract progressive cooling of the pleistocene climate led to the formation of permafrost in the southern part of eastern siberia in particular in low mountains and valley floors of the transbaikal area it was thought that in western transbaikalia the permafrost first appeared in the middle pleistocene and was related to the maximum riss samarovo glaciation ravsky et al 1964 anthropogene deposits of the southern east siberia nauka press moscow p 105 in russian bazarov d b 1968 the quaternary deposits and the main stages of the selenginskoye midland development ulan ude p 166 in russian and others earlier investigators found evidence of two cold stages in the tologoi key section alexandrova l p vangengeim e a gerbova v g golubeva l v ravsky e i 1963 new data on the anthropogene deposits of the tologoi section western transbaikalia quaternary commission of the ussr bulletin 28 84 101 in russian bazarov 1968 new research in this area in particular at the tologoi key section resulted in the discovery of cryogenic deformation levels which were older than those previously described they are found below the brunhes matuyama boundary although above the jaramillo event of normal magnetization between 0 78 and 0 99 ma bp eight levels of cryogenic deformations have been established in the tologoi key sections with three dated to the early pleistocene and five to the middle pleistocene in total in the transbaikal area not less than 10 levels of pleistocene cryogenic deformations are recognized at the present time

sedimentary facies and radiocarbon dates of the nam dinh 1 core from the song hong red river delta vietnam abstract the song hong red river delta which is located on the western coast of the gulf of bac bo gulf of tonkin in the south china sea is characterized by three morphological systems that are clearly distinguished spatially fluvial tidal and wave dominated we obtained a 70 m long core of sediments the nam dinh 1 core from the central part of the delta in 1999 this paper presents the first detailed description of sedimentary facies with high resolution radiocarbon dating for the latest pleistocene holocene sediments of the song hong delta the core sediments were divided into three units on the basis of the sediment facies in ascending order unit 1 fluvial sediments consisting of fining upward gravels to clay unit 2 coarsening upward marine clay to shelly sand and unit 3 coarsening upward marine clay and laminated sand twenty one radiocarbon dates showed that the core succession was deposited after the last glacial maximum lgm the ages were 15 11 cal kyr bp for unit 1 11 9 cal kyr bp for unit 2 and 8 0 cal kyr bp for unit 3 these data indicate that sediments were deposited in transgressive fluvial estuarine to regressive deltaic environments formed in the central delta plain of the song hong after the lgm in response to sea level changes

fluctuations of eolian flux and ocean productivity in the mid latitude north pacific during the last 200 kyr abstract in order to understand fluctuations in terrestrial and marine environments a sedimentary core h3571 was investigated from the hess rise located in the mid latitude north pacific under the north westerly wind system the 18 o grain size and grain shape of type 1 quartz suggest that this quartz is of aerosol origin good correlation between al and aerosol quartz in content and mass accumulation rate mar indicates that the alumino silicate minerals in the sediments are mainly transported by wind mar of mineral aerosol maraerosol varies from 156 to 732 mg cm 2 kyr 1 during the last 200 kyr the maraerosol maxima occur in oxygen isotope stage ois 4 to latest ois 5 middle ois 6 moderate maxima occur in early ois 1 2 late ois 3 and middle ois 3 these maxima are ascribed to reduced precipitation during the summer monsoon and to strengthened wind speed during the winter monsoon the mean organic carbon total nitrogen atomic ratio is 7 2 suggesting that the organic matter in the core h3571 is also mainly of marine origin the mar of organic carbon marorganic exhibits two prominent maxima in ois 2 and 4 and relatively high values in middle and late ois 6 enhanced primary productivity is most likely to be responsible for the high burial rate of organic carbon in the sediments carbonate and phosphorus inputs with aerosol into sea surface have played a minor role through dissolution in diminishing pco2 in surface water during glacial times on the other hand the aerosol silica supply to the ocean may have some potential to affect the burial of biogenic silica into sediments the effect of mineral aerosol on the ocean carbon cycle would be greater in the coastal and hemipelagic regions of the western pacific and equatorial atlantic as compared with that in the hess rise regime

organic geochemistry and origin of late glacial holocene sapropelic layers and associated sediments in marmara sea abstract organic geochemistry of two sapropel sapropelic sediment units dated 10 6 6 4 and 3 8 3 2 kyr bp and associated sediments in two gravity cores from the marmara sea were studied to characterize the organic matter and discuss its paleoceanographic implications vertical trends of c n ratio 13c and hydrogen indices show that the flooding of the marmara sea by the mediterranean waters at 12 kyr bp and onset of deposition of the lower sapropelic layer at 10 6 yr bp are characterized with a high input of terrestrial organic matter this terrestrial input decreased and marine organic matter contribution increased in time towards the top of the upper sapropelic layer at 3 2 kyr bp the lower sapropelic layer is broadly the same age and has a similar distribution of organic matter type as the s1 sapropel of the aegean sea suggesting their depositions may have been controlled by the same events both the lower marmara sapropelic layer and the aegean s1 sapropel were probably deposited during a time of high influx of organic rich river waters from the black sea this influx of black sea water could have induced water stratification in the marmara sea and aegean sea and lead to the deposition of the sapropels

late and postglacial sea level change and paleoenvironments in the oder estuary southern baltic sea abstract knowledge of sea level change in the southern baltic sea region is important for understanding the variations in late pleistocene and holocene sea level change across northern europe these variations are a consequence of the response of the earth s crust to the deglaciation of fennoscandia and of the water added to the oceans from the melting of all pleistocene ice sheets the sedimentological and geochemical composition of five sediment cores from the lagoonal oder estuary offers new observational evidence for sea level change and coastal development in the southern baltic sea region the combined use of several geochemical proxies organic carbon nitrogen calcium carbonate and biogenic opal contents corg s and corg n ratios 13c values of organic matter and 15n values is a new approach for the study area the chemical evidence of this multiproxy approach allows clear identification of several stages in the development of the lagoonal environment postglacial lake stages with sandy sedimentation during the older dryas and the allerod stades lacustrine phases with high autochthonous productivity during the atlantic stade terrestrial stages with peat formation at the beginning of the subboreal stade sedimentation as a result of marine transgression and brackish sedimentation after the formation of sand spits and barrier islands during the subatlantic stade the stages are the result of regional sea level change owing to complex shoreline development they support the tentative sea level curve proposed nearly 20 years ago for the region in addition changes in oder river input in response to climate conditions is monitored whereas high terrigenous input of organic matter from the oder river occurred during periods of humid climate during the allerod atlantic and subatlantic stades oder river discharge decreased with drier and cooler climate conditions during the subboreal stade furthermore the geochemical evidence points to local anomalies such as the significance of river input and additional sulfate supply into the oder lagoon for the composition of the sediments overall the results provide a framework for future studies which would allow for a more detailed comparison with other similar environments

holocene rhythms of soil formation and sedimentation in the central russian upland abstract for the first time the rhythms of soil formation and accumulation of sediments in holocene in the central russian upland were determined on the basis of radiocarbon analysis of slope balka and floodplain soils and deposits buried paleosols of different ages were distinguished early atlantic pd5 7600 6700 yr bp late atlantic pd4 6180 4800 yr bp subboreal pd3 4150 3000 yr bp subatlantic pd2 2380 1050 yr bp buried allerod preboreal and boreal paleosols and modern 200 yr old soil on newly deposited sediments were studied the paleosols were formed within long more than 1200 yr phases of geomorphological stability and buried in transitional accumulative landscapes alluvial proluvial deluvial and other holocene deposits were accumulated within shorter phases of morpholithogenesis these pedogenetic and morpholithogenetic phases follow a 1850 yr cycle

sedimentary facies of the tide dominated paleo changjiang yangtze estuary during the last transgression abstract a large estuary was formed by marine inundation of the paleo changjiang yangtze incised valley during the transgression after the last glacial maximum this paper presents the sedimentary facies and architecture of the estuary fill based on the analysis of three sediment cores cm97 js98 and hq98 obtained from the present changjiang delta plain estuary fill deposits showing an upward fining succession were grouped into five depositional facies tidal river distributary channel muddy intertidal to subtidal flats transgressive lag and estuary front based on sedimentary textures lithology and physical sedimentary structures sand mud couplets are common in these deposits indicating that tides played a significant role in producing these sedimentary structures and that the estuary type was tide dominated some of the successive sand mud couplets probably recorded neap spring cycles as well as semidiurnal tidal cycles the nature of the estuary was very different from other representative tide dominated estuaries in sediment facies its distribution and sediment source for estuarine fill unlike the other estuaries that receive sediments mainly from the sea the paleo changjiang estuarine fill deposits were supplied largely from the river this difference would also have a great influence on the sedimentological and morphological component in the estuary the sediment distribution of the estuary showed fining seaward and estuary mouth sand bodies fed by marine source sand were absent the architecture model of tide dominated estuaries should be divided into two types by the degree of fluvial sediment supply the paleo changjiang estuary shows a good example for an estuary of large rivers

source mechanism of volcanic tremor low frequency 10 hz volcanic earthquakes originate at a wide range of depths and occur before during and after magmatic eruptions the characteristics of these earthquakes suggest that they are not typical tectonic events physically analogous processes occur in hydraulic fracturing of rock formations low frequency icequakes in temperate glaciers and autoresonance in hydroelectric power stations we propose that unsteady fluid flow in volcanic conduits is the common source mechanism of low frequency volcanic earthquakes tremor the fluid dynamic source mechanism explains low frequency earthquakes of arbitrary duration magnitude and depth of origin as unsteady flow is independent of physical properties of the fluid and conduit fluid transients occur in both low viscosity gases and high viscosity liquids a fluid transient analysis can be formulated as generally as is warranted by knowledge of the composition and physical properties of the fluid material properties geometry and roughness of the conduit and boundary conditions to demonstrate the analytical potential of the fluid dynamic theory we consider a single phase fluid a melt of mount hood andesite at 1250 c in which significant pressure and velocity variations occur only in the longitudinal direction further simplification of the conservation of mass and momentum equations presents an eigenvalue problem that is solved to determine the natural frequencies and associated damping of flow and pressure oscillations for a simple constant pressure reservoir conduit orifice fluid system a change in orifice size can cause the source signal duration due to a single disturbance to change from several seconds to in excess of an hour fluid kinematic viscosity 0 412 m2 s is both included and neglected in the analysis to illustrate its effect upon system damping tremor magnitude is related to the magnitude of the conduit wall motion occurring in response to oscillating fluid pressures the entire volcanic fluid system does not generally experience a transient flow condition at a given time closed end and constant pressure fluid system boundaries reflect pressure waves and isolate components of the fluid system total fluid movement may not be accurately monitored by tremor data alone since steady state and slowly changing flows are aseismic

the link between tectonic and paleoclimatic events at 2 8 2 5mabp in the lake baikal region abstract the records of diatom abundance clay fraction content and magnetic susceptibility from lake baikal drill core bdp 96 1 reflect the climate driven plio pleistocene evolution of the lake baikal sedimentation system in addition to the dramatic variations in the proxy records in response to the northern hemisphere ice ages the baikal record also indicates climatic deterioration from 2 8 to 2 5 ma bp with evidence for an early siberian glaciation around the matuyama gauss paleomagnetic reversal boundary the drill core data also allow correlation of this early glacial interval with the basin wide seismic sequence boundary b10 which marks the unconformity produced by the active neotectonic phase in the baikal rift zone at the bdp 96 drill site however the strong b10 acoustic reflection was produced not by an erosional boundary but instead by deposition of glacial clay layers the paleomagnetic age scale of bdp 96 1 constrains the upper age of the neobaikalian uplift subsidence phase in the baikal sayan region at ca 2 5 ma bp the coincident timing of the paleoclimatic and tectonic events recorded in lake baikal sediments suggests a close causal link between regional tectonics and climate and indicate that the late pliocene uplift contributed to the initiation of the early glaciation in southeast siberia between 2 8 and 2 6 ma bp by creating an elevated terrain with lower snowline favorable for alpine glaciation and by changing the heat balance of the region

bubble collapse as the source of tremor at old faithful geyser old faithful geyser yellowstone was used as a natural laboratory for fluid flow induced seismic activity pressure measurements within the geyser s water column obtained simultaneously with seismic measurements on the surface demonstrated that the tremor observed at old faithful results from impulsive events in the geyser tremor intensity is controlled by the rate of occurrence of these impulsive events there is no resonance observed within the water column the impulsive events are modeled by a collapse of a spherical bubble including the effects of residual non condensible gas and damping the pressure data can be explained by a collapse of a 5 cm radius bubble driven by a pressure difference of p 0 3 10 5 pa and effective viscosity e 0 04 m 2 s using a quasi static geyser model we treat the individual bubble collapses as cooling events that occur when the water column reaches a critical temperature their rate of occurrence is controlled by the heating rate dt dt of the water column as a result the intensity of the hydrothermal and seismic activities is determined by the heat and mass input rate into the geyser it is demonstrated that a sharp widening of the conduit can cause the number of events per unit time to drop as observed while the water level is still rising and heat is being input and thus the tremor intensity can be modulated by variations in the conduit shape

facies and architecture of an estuarine tidal bar the trompeloup bar gironde estuary sw france abstract this study describes the sedimentary facies and internal architecture of a modern estuarine tidal bar present in the bay head delta of a wave and tide dominated estuary the gironde estuary in southwest france based on 51 cores 2 to 5 m long this work demonstrates that such bars are composite sedimentary bodies made up of individual sigmoidal sand units isolated from one another by thick muddy layers the bar appeared in the study area around 1874 since then its evolution has been characterized by phases of rapid downstream bar migration alternating with periods of bar abandonment during the periods of active bar progradation which commonly last between 10 and 20 years the bar progrades up to 7 km seaward and forms a narrow 200 800 m wide sand ridge up to 6 m thick during abandonment phases which also last around 10 20 years the bar is starved of sand and a mud layer 1 to 3 m thick is deposited the vertical succession formed by the seaward progradation of the tidal bar records these alternating phases of growth and abandonment a typical vertical succession in the bar system is 8 m thick and comprises several superimposed upward coarsening units of cross stratified sand deposited during phases of seaward progradation separated by a thick layer of thinner bedded mud and sand laminae deposited during phases of bar abandonment when a tidal bar builds up to the supratidal zone marshes accumulate and the bar becomes a permanent island in the estuary the large scale architecture of the bar is thus made of an alternation of potential sandy reservoir units and muddy internal seals the reservoir units are characterized by a sigmoidal shape the muddy layer which is deposited between the two sigmoidal units is a thick continuous potential internal seal this complex internal architecture is due to the fact that there is a considerable amount of mud present in the bay head delta of the gironde estuary it is thought to be representative of the architecture of tidal bars in the inner part of wave and tide dominated estuaries

large scale facies sequences in alluvial overbank environments abstract gradational coarsening upwards or fining upwards sequences order of meters thick in overbank environments can be produced by progressive crevasse splay levee progradation or abandonment while the channel belt remains unchanged in position in contrast meter scale facies sequences related to periodic channel bell avulsion may show relatively abrupt changes in facies and paleocurrent direction simulation models suggest that the number of such avulsion related facies changes in any overbank sequence bounded above and below by channel belt deposits is on the order of 1 to 10 this is confirmed using an ancient example in this example the average thickness of each avulsion bounded overbank facies sequence was 3 m assuming an average recurrence interval for avulsions of about 1 000 ye rs the mean overbank deposition rate was about 3 mm per year

stratigraphy and paleoenvironmental changes in the yangtze delta during the late quaternary the yangtze delta area may be subdivided into paleo valley and paleointerfluves of the last glaciation the postglacial transgressive sedimentary cycle ptsc on the front zones of the paleointerfluves is composed of marsh nearshore and barrier lagoon shallow marine and nearshore tidal flat units with a basement in stiff clay the ptsc in back zones of the paleointerfluves consists of lacustrine marsh deposits the ptsc in the incised valley contains river channel floodplain estuary estuarine shallow marine and deltaic units with an erosional surface at its bottom the stiff clay and the erosional surface constitute the ptsc lower boundary the stiff clay consisting of a paleosol experienced deposition alternating with pedogenesis during the falling of sea level during 18o stage 3 ongoing pedogenesis in the sea level lowstand of 18o stage 2 and early diagenesis after paleointerfluve inundation by the sea level rise of 18o stage 1 the climate during the paleosol formation was temperate with more than 500 mm a 1 rainfall and frequently fluctuating groundwater the yangtze river incised its course during falling sea level of stage 3 and a huge incised valley was formed during the sea level lowstand stage 2 the filling of the incised valley took place during the postglacial sea level rise and delta formation occurred at a late stage of ptsc development

tidal bedding and tidal cyclicities within the intertidal sediments of a microtidal estuary dyfi river estuary west wales u k abstract in the microtidal dyfi river estuary west wales the characteristic sedimentary structure within the intertidal sediments is tidal bedding this consists of sand mud couplets by means of thickness measurements and detailed observations the following conclusions can be drawn 1 the thicknesses of and structures in both mud layer and sand layer of each couplet vary systematically downward in the studied cores and trenching profiles variations are mainly due to differences in the current speed and tidal range between tides to difference of individual neap spring tides and to the possible effect of filtering of currents due to being in the intertidal zone 2 the patterns of sand mud couplet thickness variations reflect two main types of tidal cyclicities diurnal inequality and the neap spring neap tidal cycle which is in turn related to the lunar cycle 3 the mud layer of each couplet represents deposition from suspension at times of tidal slack no ebb slack water period during low tide in the intertidal zone thus no ebb mud deposition during low water whilst the sand layer is deposited by asymmetrical bidirectional tidal currents in either the ebb or flood half of a tidal cycle 4 the tidal regime derived from these variation patterns is characterized by a mixed predominantly semi diurnal form which is comparable with the present tidal regime 5 finally it can be concluded that tidal bedding patterns are the structural expressions of tidal cyclicity

what is a fluvial levee abstract fluvial levees are elevated partitions between channels and floodplains because of their character and position levees may provide critical controls on and insights into geomorphic processes that determine the distribution of water and sediment within river systems few studies have analysed the character distribution sedimentology and processes that form levees in modern depositional environments characterisation of levee deposits from the mississippi river continues to form the basis for most levee interpretations from the rock record this discussion paper assesses the reliability of interpretations of levee deposits in numerous examples from the rock record and their associated inferences for river style this uncertainty reflects the lack of definitive sedimentological attributes for levee deposits their limited preservation potential and the fact that levee identification in the rock record is inhibited by the reliance on geometric descriptors or indirect associations between channel and floodplain facies given these concerns it is suggested that geomorphologists and sedimentologists need to recognise the limitations of our present knowledge of levees and work towards a more systematic understanding of these significant fluvial landforms in the full spectrum of modern and ancient river settings

radiocarbon dating and the reconstruction of late quaternary sea level changes in hong kong abstract radiocarbon dating is used widely for the reconstruction of late quaternary sea level changes in the present study eight case studies in hong kong have been chosen to highlight the difficulty in obtaining reliable radiocarbon dates pre holocene radiocarbon dates exceeding about 8100 yr bp have been found to show a young age bias a shell sample dated by two separate radiocarbon laboratories gave last interstadial ages differing by almost 9500 years while an oxygen isotope stage 5e age was obtained using uranium series dating other evidence including stratigraphy have shown that only the last interglacial age is acceptable the young age bias is attributed mainly to the post depositional introduction of young carbon into the sample for the reconstruction of sea level changes it is essential to select samples immediately above of the base of the holocene transgressive unit in offshore boreholes and excavations to satisfy the criteria of rapid burial these samples should preferably include mud plant matter and shells to facilitate interpretation furthermore as many samples as possible from a range of water depth down to about 130 m below the present sea level should be dated to reduce error introduced by counting statistics so the true signal of sea level changes can be reflected

in situ observations of old faithful geyser in a series of experiments from 1983 to 1993 four probes were carefully lowered into old faithful geyser yellowstone national park wyoming at different times these probes variously recorded pressure temperature time conditions to nearly 22 m depth and video probes showed the conduit geometry and processes of recharge to 13 m depth temperatures recorded were within experimental error the same as those recorded in 1942 with a peak bottom temperature t of 118 c processes observed include fog formation in the upper levels of the conduit owing to wind and entrainment of cool air bank storage of hot water that splashes to high levels cools and recharges recharge of cooler ground water into the conduit superheated steam expansion into the conduit t 129 5 c periodic temperature fluctuations and exsolution of bubbles of noncondensable gas which we propose are co 2

reconstruction of environmental changes during the late glacial and holocene reflected in a soil sedimentary sequence from the lower selenga river valley lake baikal region siberia assessed by lipid molecular proxies abstract sediments of lake baikal and smaller lakes in its surroundings have been frequently used to trace paleoenvironmental changes however these sediments integrate environmental proxies over large areas and the processes leading to alteration of terrestrial signals are not fully understood more specific information can be derived from terrestrial archives such as alternating soil sediment sequences near the village of burdukovo southeast of lake baikal such sequences are accessible along the 5 m high right terrace of the selenga river however terrestrial archives can be associated with degradation of organic matter therefore lipid molecular proxies were applied in the current study to trace environmental and vegetation shifts as well as incorporation and degradation of organic matter alkane and fatty acid molecular proxies as part of the lipid fraction are well known for their diagnostic character to trace sources of organic matter and its degradation several parameters including the carbon preference indices of alkanes and fatty acids indicated a well preservation of the organic matter in the investigated sequence furthermore the organic matter in the c horizons of the terrestrial upper part of the sediments was most likely overprinted by rooting of the plants growing on respective overlaying soils as reflected by the average chain length of fatty acids and alkanes and the relative composition of long chain n alkanes c 25 33 the 3 5 m thick sequence enabled tracing of vegetation shifts the alkane composition argued for changes in the grass dominated vegetation cover within the different phases of the holocene until today whereas a birch and willow dominated deciduous forest vegetation as traced in other archives of the larger baikal area could not be determined in the burdukovo sequence by lipid molecular proxies the scatter in the alkane and fatty acid composition revealed only minor vegetation shifts throughout the holocene nevertheless some changes in the lipid composition indicated a change in the plant community as coniferous trees have often similar alkane patterns to grass vegetation it cannot be excluded that conifers also contributed to a certain degree to the molecular record in the burdukovo sequence the general decrease in the carbon preference index of alkanes since approximately 4 ka bp until recent times further argues for an increasing admixture of coniferous lipids to the record lipid molecular proxies of sediment that formed 2 8 2 6 ka bp revealed the incorporation of deciduous tree derived organic matter most likely originating from birch that grew elsewhere in the catchment of the selenga river the proxies enabled an assessment of site specific vegetation shifts and degradation of organic matter in the soil sediment sequence of the burdukovo area and thus provide more specific information related to a certain area than lacustrine sediments integrating over larger catchments

steppe species in the late pleistocene and holocene small mammal community of the urals abstract finds of steppe mammal fossils in pleistocene dated deposits in regions situated hundreds thousands kilometers apart from their modern distributions are considered as markers of certain events in climate and landscape dynamics in north eurasia during the late pleistocene fossil data were used to examine peculiarities of area shifting in several species of the steppe mammal communities in response to the climate and landscape dynamics of the late pleistocene and holocene intervals the main attention was paid to the data from the ural region the main idea of this study was to reveal regularities of distribution concerning some species of small mammals representing steppe biota found in late pleistocene and holocene sediments in the urals the research concentrated mainly on the northern border position limiting these species ranges during different time intervals

deep volcanic tremor and magma ascent mechanism under kilauea hawaii deep harmonic tremor originating at depths around 40 km under kilauea was studied using records accumulated since 1962 at the hawaii volcano observatory of the u s geological survey the deep source of the tremor was determined by onset times and confirmed by the relative amplitude across the island wide network of seismometers the period of tremor was conclusively shown to be determined by the source effect and not by the path or station site effect because the period would change considerably in time but maintained uniformity across the seismic net during the tremor episode the tremor appeared to be primarily composed of p waves we interpret the observed period and amplitude in terms of the stationary crack model of aki et al 1977 and find that the seismic moment rates for deep tremors are considerably larger than those for shallow tremors suggesting more vigorous transport for the former we propose a kinematic source model which may be more appropriate for deep tremor according to this model a measurable quantity called reduced displacement is directly proportional to the rate of magma flow a systematic search for deep tremor episodes was made for the period from 1962 through 1979 and the amplitude period and duration of the tremor were tabulated we then constructed a cumulative reduced displacement plot over the 18 year period the result shows a generally steady process which does not seem to be significantly affected by major eruptions and large earthquakes near the surface the total magma flow estimated from the reduced displacement is however one order of magnitude smaller than that estimated by swanson 1972 it may be that most channels transport magma aseismically and only those with strong barriers generate tremor

geology and fauna and preliminary correlation of sediments of the main late cenozoic sites of the transbaikal area abstract the pliocene and pleistocene sediments exposed in eight sections of transbaikalia have been correlated using geological and palynological data together with information on fossil mammals and some paleomagnetic characteristics the most complete sequence of fossiliferous deposits spanning the time interval from the middle pliocene to the late pleistocene is exposed in the tologoi key section the sequence was correlated with other sections primarily on the basis of mammal faunas during deposition of the chikoi suite udunginian chikoian and itantsinian faunal complexes appeared in succession four successive stages in mammal evolution are recognized within the early pleistocene deposition of the krivoyarskaya suite proceeded throughout the time when the tologoi faunistic complex ivolginian and other pleistocene faunas followed each other in the transbaikalian region

isotopic and geomorphic evidence for holocene climate southwestern kansas abstract the cimarron bend of southwestern kansas is characterized by loess dunes and sand sheets that reflect a complex eolian alluvial history stratigraphic evidence indicates that at least two major dune and sand sheet reactivation episodes occurred these follow intervals of alluviation stability and soil development in the holocene radiocarbon ages from paleosol horizons bracket these periods and their 13 c values provide evidence of a shift from a cooler wetter climate in the late pleistocene and early holocene dominated by c 3 plants to a warmer drier middle holocene period characterized by an increase in c 4 plants stable isotopic results for late holocene soils may reflect local rather than regional climatic conditions our results compare favorably with studies in the central and southern great plains together these results imply that a regional change toward a warmer drier climate occurred from the early to the middle holocene on the southern great plains

late pleistocene and holocene environmental peculiarity of the baikalian region based on mammal associations and deposits abstract changes of paleoclimates and paleoenvironments in the lake baikal region including transbaikalia and prebaikalia are traced through the late pleistocene holocene on the basis of small mammal faunal succession the deposit structure and pollen assemblages paleoenvironments and biota of the two regions became increasingly different since the end of middle pleistocene in prebaikalia tundra steppe non analog faunas appeared and were dominant through the late pleistocene although there was alternation of faunas indicative of colder and warmer interglacial conditions in the transbaikalian region faunas typical of arid landscapes were characteristic of both cold and warm periods they were similar in the species composition although differing noticeably in proportion of individual taxa

new data on the late pleistocene stratigraphy and paleoenvironment of the southwestern baikal area siberia abstract this paper presents an overview of study of the upper pleistocene key sections of the southwestern baikal area tunka rift valley baikal rift zone and prebaikalia south of siberian platform geochemical data have revealed some paleoclimatic variations in the region during the late pleistocene the highest values of the lithochemical moduli are present in kazantsevo deposits of the ust odinsky section they indicate a high degree of chemical transformation of rocks and accumulation of alumina and iron which is characteristic of warm humid climate the upper part of all studied sections including the holocene horizon mis 1 shows a significant decrease of all moduli values a result of climate deterioration from kazantsevo time mis 5 through sartanian time mis 2 moreover there are two peaks of modulus values corresponding to the karginsky mis 3 paleosols the analyses of the mammal faunal composition of the studied regions have revealed that in the tunka rift valley the dominant forms of both large and small mammals are central asian species arid open landscape dwellers in contrast in the pebaikalian fauna the inhabitants of tundra tundra steppe are predominant the fauna of ust odinsky section murukta time mis 4 contains the representatives of a disharmonious fauna lagurus lagurus and dicrostonyx sp the mammal assemblages of the kazantsevo mis 5 suggest rather humid and warm paleoenvironmental conditions in contrast to the karginsky mis 3 interval which is characterized by drier moderate cold climate with steppe biotopes

is chemical index of alteration cia a reliable proxy for chemical weathering in global drainage basins the chemical weathering of silicate rocks in continents as an important sink of atmospheric co2 is of great significance for global environmental change rivers play a key role in earth surface processes and are regarded as the most important carrier of terrigenous materials into the sea the chemical index of alteration cia has been widely used as a proxy for chemical weathering in sediment source area in this paper the cia values of suspended particulate matters from 44 rivers worldwide are recalculated the cia values vary significantly with the highest average value occurring in african rivers and the lowest in north american rivers the correlation analyses suggest that on a global scale the cia is sensitive to land surface temperature latitude at river mouth and soil depth in the drainage basins but poorly correlated with drainage area precipitation average elevation and runoff however the cia of the rivers draining east china are closely related to temperature precipita tion latitude and runoff primarily reflecting the dominant control of monsoon climate on chemical weathering in the catchments it is therefore unrealistic to find a simple law of regulating chemical weathering in continents the cia actually reflects the integrated weathering history in the drainage basins and therefore caution should be taken while using it as a direct and quantitative proxy for evaluating the intensity of instantaneous chemical weathering in continents

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

sedimentology of pennsylvanian quartzose sandstones of the lee formation central appalachian basin fluvial interpretation based on lateral profile analysis abstract lateral profiling including bounding surface and architectural element analyses are utilized to demonstrate a fluvial origin for the quartzose sandstones of the lee formation internal architecture of the sandstones consists primarily of multistorey and multilateral channel bodies individual channel elements up to 20 m thick contain a complex hierarchy of bedform deposits the primary depositional elements within the channels were downstream accreting mid channel macroforms channel elements frequently contain deposits of more than one macroform reconstruction of the macroforms reveals accretion primarily by superposed bedforms that migrated down a low angle front steeper giant foresets transitional along flow with the low angle facies indicate that the macroform episodically developed a steep slipface the uppermost channels within the rockcastle member contain macroform elements with components of lateral accretion interpreted as deposits of alternate bank attached macroforms other depositional elements recognized within channel fill deposits are minor channel sandy bedform gravity flow attributed to bank slumping and channel bottom elements the latter element is contained within a facies sequence that suggests rising to flood to waning stage deposition in general deposition probably occurred during relatively high stage little evidence of low stage flow was recognized subordinate fine grained facies are interpreted as levee and overbank deposits the greater part of the lee formation was deposited in deep low sinuosity bedload dominated fluvial channels strongly unimodal paleocurrents lack of facies that suggest low stage reworking and paucity of lateral accretion features indicate deposition in a single channel system i e a low braiding index

a revised 30 000 year paleoclimatic and paleohydrologic history of lake albert east africa abstract new geochemical and palynological data and a sedimentological reinterpretation of two cores from lake albert allow a revision of the paleoclimatic and paleohydrologic history of northwest uganda over the last 30 000 14 c yr bp our findings document one and possibly three periods of significantly reduced inflow to the nile river system from the white nile based on sediment fabric and mineralogy shifts in percentages of total organic carbon toc and total organic nitrogen ton hydrogen index hi and 13 c and 15 n as well as poor preservation of sporopollenin and siliceous microfossils we recognize two mature paleosols that formed between 18 000 and 12 500 14 c yr bp at the surface of exposed lacustrine muds a thin fossiliferous zone between the two soils documents a brief period of flooding lake albert was below the level of the coring site and thus a closed basin for several thousand years during the late pleistocene around 12 500 14 c yr bp the younger vertisol was flooded by a major rise in lake level relatively deep water conditions were established soon after this transgression but an apparent change in sedimentation rate sometime between 8 000 and 3 400 14 c yr bp may reflect another briefer period of low water which resulted in interruption of sedimentation at the coring site palynological data document a rapid and abrupt shift to drier conditions around lake albert from 11 400 to 9 900 14 c yr bp coincident with the cool younger dryas event of the northern hemisphere geochemical evidence suggests that throughout the terminal pleistocene and early holocene and again in the late holocene the water column was relatively well mixed with little tendency to persistent anoxia

preservation of elemental and isotopic source identification of sedimentary organic matter the amount and type of organic matter in the sediments of lakes and oceans contribute to their paleoenvironmental and paleoclimatological records only a small fraction of the initial aquatic organic matter survives destruction and alteration during sinking and sedimentation selective degradation modifies the character of the surviving small fraction of organic matter which becomes incorporated in bottom sediments organic matter alterations can continue to sub bottom depths of hundreds of meters corresponding to millions of years source and paleoenvironmental information nonetheless remains preserved in the molecular elemental and isotopic compositions of organic matter c n and 13c values of total organic matter in particular appear to retain paleoenvironmental information for multi myr time periods

radiocarbon dating of palaeosol components in moraines in lapland northern sweden abstract accurate geochronologies are the key for comparison of palaeoclimate records in order to clarify problems concerning the geochronology of glacier fluctuations we dated palaeosols in moraines in the kebnekaise mountain region of swedish lapland these palaeosols already have been dated several years ago using bulk samples of the palaeosols and yielded ages of 6180 5790 and 2750 2100 cal yr bp in an attempt to evaluate the sources of contamination associated with bulk samples these soils were re dated by using coleoptera fragments cenococcum geophilum spores humic acids and woody plant tissues the new dates reveal that the two palaeosols found within the moraines represent much longer periods of time than was previously assumed soil formation periods can be distinguished for periods 7800 7580 6300 4080 2450 2000 and 1170 740 cal yr bp these age groups point to differentiated soil formation processes resedimentation bioturbation and or cryoturbation the results show that dated terrestrial macrofossils from glacial moraines indicate climate changes that are in accordance with other proxy records in northern and central scandinavia and in certain times off phase with glacier fluctuations in southern maritime norway this throws light on possible changing interaction of forcing factors during the holocene

processes facies and architecture of fluvial distributary system deposits abstract there is evidence from the stratigraphic record of examples of fluvial deposits that were the products of deposition from river systems which had decreasing discharge down flow and transitions from proximal channelised to distal unconfined flow these deposits form fan shaped bodies several tens of kilometres in radius and their stratigraphic architecture is aggradational with no evidence of deep incision driven by base level fall the fluvial systems that generated these deposits formed under conditions for which there is no complete analogue today an endorheic basin with a relatively arid climate adjacent to an uplifted area with higher precipitation a conceptual model for fluvial systems of this type has therefore been built on the basis of outcrop examples and a consideration of the controls on sedimentation proximal areas are characterised by amalgamated coarse pebbly and sandy channel deposits with little preservation of overbank facies channel dimensions are generally smaller in the medial areas but sizes are variable deposits are of braided meandering and simple channels which show varying degrees of lateral migration the channel fills may be mud or sand with overbank flow processes playing an important role in filling channels abandoned on the floodplain after avulsion the proportion of overbank deposits increases distally with sheets of sand deposited as lateral and terminal splays by unconfined flow interconnection of sandstone bodies is poor in the distal areas because channel fill bodies are sparse small and are not deeply incised the radial pattern of the sediment body forms by the repeated avulsion of channels active channels build up lobes on the alluvial plain and rivers switch position to follow courses on lower lying areas the term fluvial distributary system is here used to describe a river system which has a downstream decrease in discharge and has a distal zone which is characterised either by terminal splays on to a dry alluvial plain or a lake delta during periods of lake highstand

changes in tidal characteristics as a result of the construction of sea dike sea walls in the mokpo coastal zone in korea abstract it is shown by numerical analysis via the adoption of a fully implicit scheme that the tidal choking is much less significant after the construction of sea dike sea walls in the mokpo coastal zone tidal records show an amplification of tidal range extreme high tide is 60 cm higher and extreme low tide is 43 cm lower this amplification may cause serious inundation in the event of a typhoon another problem is the reduction in tidal velocity which may cause deterioration of the coastal environment in order to determine the ebb dominance near the mokpo coastal zone the extent of ebb dominance of each region was quantified by analyzing the m 2 and m 4 tidal constituents and in addition the variation of ebb dominance in mokpo harbor was observed after the construction of the sea dike sea walls ebb dominance appears to be more serious with each successive construction this is probably caused by the elimination of tidal choking at mokpogu the transport mechanism of sediment and pollutants has been altered because of increased ebb dominance however ebb dominance will be somewhat lessened after the construction of the fourth sea wall

ecosystem analysis of baikal siberia using palaeolithic faunal assemblages to reconstruct mis 3 mis 2 environments and climate abstract integrated studies of the geological context and fauna of palaeolithic sites made it possible to reconstruct climate and environments of baikal siberia during mis 3 mis 2 the main constituents of the faunal assemblages are small mammals which are a reliable bioindicator of landscapes and climates of the past in the fore baikal area fauna recovered from archaeological sites presents a mixture of ecological indicators its components presently inhabiting different natural zones the sediments studied at the bol shoi naryn and gerasimov s sites and dated to mis 3 yielded fauna with a large proportion of tundra species its composition suggests mosaic landscapes of tundra forest meadow steppes and a cold humid climate at the time of human habitation fauna from the malta site mis 2 is indicative of tundra steppe and harsh climate at the beginning of the sartan glaciation evidence from the end of the pleistocene and postglacial indicates the climate becoming warmer and wetter tundra animals are absent from mis 3 sites of transbaikalia according to faunal evidence dry steppe and arid climates existed at the early sartan mis 2 and taiga animal species appeared and increased in importance towards the end of pleistocene when the forests had wide distribution fauna from mis 3 sites in the southwestern baikal area near baikal area is similar to transbaikalia lacking tundra species and dominated by indicators of dry steppe and arid climates the southwestern baikal is more similar to fore baikal area both having a higher proportion of forest species than in transbaikalian assemblages the fauna distribution displays features of mosaic landscapes with distinctly identified zones forest and meadow steppe along rivers and dry steppe and semi desert on south facing slopes of mountains the climate was milder than in the transbaikal and warmer than in the fore baikal area unfortunately we have little data on the fauna of mis 2

volcanic earthquakes and their relationship to eruptions at ruapehu and ngauruhoe volcanoes abstract crustal earthquakes near ruapehu and ngauruhoe fall into two classes each of which can be subdivided on the one hand there are high frequency events 3 hz with sharp well defined phases mainly concentrated beneath ruapehu crater lake low frequency events the low frequency events resemble minakami s b type and explosion earthquakes but sometimes occur where no vent exists and rather deeper than his formal definition difficulty in applying minakami s classification rigorously and the fact that low frequencies may be due to abnormal attenuation of higher frequencies along the path rather than to their suppression or absence at the source has led to reclassification of earthquakes near the volcanoes into two broad groups tectonic and volcanic the former includes all high frequency earthquakes and those discrete events in which dominant low frequencies are due to path effects the latter includes multiple and emergent events which show evidence of prolonged or repetitive source mechanism dominant low frequencies are ascribed to occurrence in heat weakened material and high frequencies to instantaneous source mechanisms operating in competent rock the term volcano tectonic describes tectonic earthquakes within some arbitrary distance of a volcano at ngauruhoe and ruapehu volcanic earthquakes accompany explosive vent clearing eruptions subsequent open vent degassing and ash emission however although often powerful and prolonged usually occurs without earthquakes such activity is however frequently accompanied by volcanic tremor at ruapehu under closed vent conditions when lake temperature is low low frequency earthquakes up to magnitude ml 3 4 have occurred without any eruption five types of phreatic eruptions are identified at ruapehu each having a distinctive seismic pattern the three most explosive types appear to be generated by a chain reaction process and all involve flashing of water to steam the first by failure of the roof with little precursory seismicity after a closed vent period during which lake temperature decreases the second after prolonged heating of the lake and much preliminary volcanic tremor interpreted as due to rising magma and the third under open vent conditions in the wake of one of the two preceding types a fourth probably occurs in wet sediments near the base of the lake as a result of upward migration of hot gas and a fifth aseismic or accompanied by very weak volcanic tremor is associated with convective overturn within crater lake

stratigraphy and subaerial exposure of late quaternary tidal deposits in haenam bay korea south eastern yellow sea late quaternary stratigraphy of the coastal deposits in haenam bay south western coast of korea south eastern yellow sea consists of two depositional units a holocene intertidal deposit unit i and an underlying late pleistocene tidal deposit unit ii both of which are distinguished by distinct unconformity the yellowish colour and more consolidated and oxidized nature are characteristics of the sediments in the upper part of unit ii in spite of the lack of primary sedimentary structures a conspicuous cryogenic structure was found in the upper part of unit ii reflecting cold and dry conditions the magnetic susceptibility enhancement in the upper part of unit ii added the possibility of pedogenesis during subaerial exposure the upper part of unit ii is characterized by the deficiency of smectite and chlorite in contrast to the clay mineral suites of unit i and lower part of unit ii which may be attributed to post depositional and diagenetic alteration the degree of weathering measured by the chemical index of alteration shows that the removal of labile minerals by leaching also occurred in the upper part of unit ii thus the upper part of this unit appears to have undergone subaerial exposure and weathering during low sea level stands the supporting evidence of the sediment properties including sediment colour and structure water contents and shear strength geochemical and clay mineralogical data and magnetic susceptibility provides the potential signature of the subaerial exposure and weathering of late pleistocene sediments in the tidal dominated haenam bay sedimentary basin

yangtze offshore china highly laminated sediments from the transition zone between subaqueous delta and the continental shelf abstract this study examines the deposition of highly laminated muddy sediment in vibrocores recovered from a depth of 40 55 m of water and located 120 km east of the yangtze river mouth x radiographs show numerous sharp based sedimentary rhythmics with nearly parallel and undulated laminations interbedded with silty lenses and interbeds the laminated sediment varies from clayey silt to silty clay ams radiocarbon dates on well preserved bivalves are primarily younger than 5500 y bp indicating the formation of the laminated sediment under the present sea level conditions macro and microfossils in the sediments are consistent with the modern offshore sedimentary setting the laminated sediment originated from the yangtze estuary but the sedimentation processes were not deltaic the highly laminated sediment that lies below the normal wave base of 10 m was deposited on the seaward margin of the yangtze subaqueous delta closely associated with submarine tidal and storm generated currents

microearthquakes in the black smoker hydrothermal field east pacific rise at 21 n in july and august 1980 an array of five ocean bottom seismographs was deployed within 3 km of the 350 c hydrothermal vents at the rivera submersible experiment rise site at 21 n on the east pacific rise two of these instruments were placed within 600 m of the vents using a transponder navigation network the array detected four basic types of events the first type consisted of local very small microearthquakes locations obtained for 11 of these events place three within 1 km of the vents with the others elsewhere along the rise crest they appear to originate either from movement on the faults in the area or from the hydrothermal system beneath this area a study of the s p times of this type indicates a maximum hypocentral depth of 2 3 km implying a similar limit to the depth of hydrothermal circulation and brittle fracturing in the vicinity of the vents the second type of event found consisted of emergent earthquakes that have many of the characteristics of volcanic harmonic tremor the frequency of these events falls in the 1 5 hz range and are similar in appearance to those seen at mount st helens prior to and during its may 1980 eruption they may be either hydrothermal or volcanic in origin the third type of event produced a very monochromatic high frequency seismogram with the energy concentrated at 20 hz these events also appear to have a local origin the particle motion of these earthquakes shows almost pure stonely wave propagation and they appear to originate from a regularly oscillating dilatational source the nature of the source of event types two and three is clearly not the usual sort of motion on a fault and is still not understood the fourth type of earthquake recordings were regional events apparently from the nearby rivera and tamayo fracture zones the low frequency acoustic noise in the water was 16 64 times higher within 300 m of the vents than it was 2 km away this implies that the black smoker vents may be generating a large acoustical disturbance as the 350 c water pours into the ocean the observations are among the first of seismicity on moderate to fast spreading ridges and many of the events appear to be related to the hydrothermal activity found there

late quaternary stratigraphy of the yeongsan estuary southwestern korea abstract the 18 820 m long sediment core mw 1 from the yeongsan estuary consists of five primary unconsolidated to semi consolidated units ranging in age from late pleistocene to holocene overlying a cretaceous aged basement from oldest to youngest these units include units 1 2 3 fluvial units unit 4 paleosol unit and unit 5 holocene estuarine deposits units 1 2 and 3 are interpreted as in channel or overbank deposits plant materials included within the units and the toc tn total organic carbon total nitrogen ratios 11 14 are also indicative of terrestrial origin unit 2 yields radiocarbon date of 37 700 14 c yrbp unit 4 the paleosol unit is estimated to be originally deposited in fluvial setting such as the area of floodplain or backswamp away from the main channel based on the sporadic distribution of the stagnant freshwater acritarch pseudoschizaea and algae spirogyra the timing of deposition of the original sediments of the paleosol unit is constrained by radiocarbon age of underlying fluvial sediments unit 2 the timing of pedogenesis is around the last glacial maximum when sea level of the yellow sea was lowered temperature was lowered rainfall was reduced and the inland was sparsely vegetated estuarine deposits unit 5 are interpreted to be deposited during the holocene marine transgression

late pleistocene silty tidal rhythmites in the macrotidal flat between youngjong and yongyou islands west coast of korea abstract late pleistocene silty tidal rhythmites developed in the macrotidal flat between youngjong and yongyou islands demonstrate hierarchical tidal cycles ranging from daily to monthly variations associated with synodic tropical and anomalistic cycles on the basis of rhythmicities and textural composition the rhythmites were likely deposited in an upper intertidal flat under a mixed dominantly semi diurnal tidal regime the rhythmites showing gradational contact with overlying cryoturbated silty facies indicating subaerial exposure and subsequent weathering during the last glacial maximum represent the tidal environment during the last highstand or ensuing regression phase of sea level in the late pleistocene

the plumbing of old faithful geyser revealed by hydrothermal tremor 1 old faithful geyser in yellowstone national park usa has attracted numerous scientific investigations for over two centuries to better understand its geological structure the physics of its eruptions and the controls of its intermittency using data acquired with a seismic array in 1992 we track the sources of hydrothermal tremor produced by boiling and cavitation inside the geyser the location of seismic sources identifies a previously unknown lateral cavity at 15 m below the surface on the sw side of the vent and connected to the conduit this reservoir is activated at the beginning of each geyser eruption cycle and plays a major role in the oscillatory behavior of the water level in the conduit before each eruption

stable vegetation and environmental conditions during the last glacial maximum new results from lake kotokel lake baikal region southern siberia russia abstract this paper presents a new decadal resolution fossil pollen record from lake kotokel 52 47 n 108 07 e 458 m a s l and provides a reconstruction of the last glacial maximum lgm vegetation and environments in the study area during this interval of globally harsh climate lake kotokel is situated close to the eastern shoreline of lake baikal in the boreal forest zone of southern siberia the analysed 190 cm long section 6 of the bottom core ktk10 ktk10 6 consists of compact undisturbed greenish grey to dark grey slightly laminated silty clay indicating continuous lacustrine sedimentation throughout the lgm period ca 26 8 19 1 cal ka bp the age model is supported by 11 calibrated ams dates the results of pollen analysis and pollen based biome reconstruction show that steppe and tundra vegetation composed of grasses and various herbs dominated ca 26 8 19 1 cal ka bp occurrence of conifer tracheids and stomata throughout the record together with small quantities of boreal conifer and broadleaf tree and shrub taxa pollen suggests the presence of single trees or small forest stands in the lake vicinity most likely in the river valleys application of the biomisation method and the resulting numerical scores of the most characteristic biomes steppe tundra and cold deciduous forest show minor fluctuations signifying stability of the regional vegetation cover during the analysed lgm interval in contrast to the regional biomes the local environmental indicators demonstrate greater sensitivity of the lake system to decadal and century scale climate variability the highest pollen percentages of ranunculaceae representing littoral meadow vegetation communities are registered ca 23 8 23 4 cal ka bp this and an increase in coarse grained sand particles together with slightly increased total inorganic carbon tic values representing calcite in the ktk10 6 sediment provide evidence of a much shorter than present distance between the coring site and the shoreline and a reduced lake area in line with a drier than present lgm climate a general stability of the grassland vegetation in the study region ca 26 8 19 1 cal ka bp and relatively constant total organic carbon toc values support the hypothesis that this productive vegetation could stably serve as a perennial food resource for large populations of herbivores thus providing favourable environments for the local hunter gatherers inhabiting the lake baikal region during the lgm interval

volcanic tremors and shocks associated with eruptions at etna sicily september 1980 abstract three strong ash eruptions superimposed on an otherwise rather quiet state of volcanic activity took place from the northeast crater of etna during september 1980 the eruptions lasted only a few hours and were associated with an increase in the amplitudes of volcanic tremors by a factor of 10 compared with the mean value of the preceding months special emphasis in the tremor analysis was given to the eruption of september 26 1980 the time function of the amplitude envelope of the tremors follows a mathematical function which resembles the behaviour of a mechanical oscillator with a resonant period of about 300 s a detailed spectral analysis of the tremors before during and after the eruption reveals factors which seem to be associated with the ascent and descent of the tremor sources in the magma columns the turbulent eruptive magma flow apparently is concentrated in a few dykes and pipes their eigenvibrations during an eruption are observed as spectral peaks of small bandwidth superimposed on the smoother spectrum without a volcanic eruption an analysis of seismicity shows a maximum in august with epicenters clustering along a nw se direction

seasonal variation of sedimentary processes in a semi enclosed bay hampyong bay korea abstract multi annual sedimentological observations on tidal flat sediments were carried out in hampyong bay southeastern yellow sea to infer the budget of modern muddy sediments in the bay sedimentation rates over a four year period show contrasting types of seasonal sedimentary cycles occurring in the tidal flats within the elongated bay both sides of the bay are largely sheltered from winter waves resulting in surface mud deposition during winter and erosion during summer in contrast tidal flats along the head of the bay are influenced by winter waves resulting in a reversed trend where erosion occurs during winter and deposition during summer tidal flats near the bay mouth however show a sedimentary cycle disrupted by the construction of sea walls undergoing consistent erosion throughout the observational period the shoreline artificially straightened seems to cause tidal currents to bypass the tidal flat and hence to be much stronger these differences in sedimentary cycles suggest the critical importance of the orientation of tidal flats relative to the propagating direction from n nw of the monsoon winter storm waves on the tidal flat sedimentation in the eastern coastal area of the yellow sea the preliminary budget estimation for the tidal flat mud suggests that the tidal flats in hampyong bay are subject to the slight but consistent erosion as a whole

paleoenvironments of palaeolithic humans in the baikal region abstract during the last 25 years abundant material on small mammals has been obtained from numerous pleistocene archaeological sites caves and open localities in the baikal region most small mammal fauna localities are dated to sartan time 23 000 10 000 bp with some attributed to karginsk time 50 000 23 000 bp paleontological studies provided a considerable amount of information on environmental changes both in transbaikalia and in the fore baikal region during palaeolithic and mesolithic since the end of middle pleistocene

volcanic tremors at etna a model for hydraulic origin spectral analysis of volcanic tremors at etna reveals 2 characteristic features 1 the escaping vapor and gas streams drive the magma in random turbulent motion generating a seismic wave emission according toa f n exp m f k wherea amplitude f frequency n m k parameters 2 sudden transients in the boundary conditions of the piping system generate hydraulic pressure pulses which in the seismogram appear as wave packages their monochromatic frequency content suggests that their origin is associated with strong resonance phenomena it is conclusive that volcanic eruptions may be distinguished and classified according to different eigenfrequencies of the fissure and pipe network involved in the volcanic activity furthermore positions of active dykes may be traced following the amplitude distributions associated with pronounced spectral lines in the tremor spectra

a buried palaeosol and late pleistocene unconformity in coastal deposits of the eastern yellow sea east asia abstract deep drill core sampling with a high resolution seismic survey was carried out to identify a holocene late pleistocene boundary in the eastern coast of the yellow sea east asia analysis of core sections revealed the existence of an oxidized and desiccated sedimentary layer lying directly below a holocene horizon unit i and being developed at the top of a late pleistocene unit ii possibly last interglacial tidal deposit the buried oxidized sedimentary layer is characterized by semi consolidated yellowish sediments showing signs of desiccation and alteration such as periglacial cryogenic structures lithified trace fossils depletion of smectite and high geochemical weathering index ba sr ratio these features together with radiocarbon ages suggests that the layer defined as a palaeosol developed in marine sediments has formed as a result of prolonged subaerial exposure of unit ii sediments during the wisconsinan sea level lowstand producing a regional unconformity late pleistocene unconformity this unconformable bounding surface corresponds to a prominent near surface reflector r which is observed in seismic profiles obtained across the drilled core sections and further is traced ubiquitously across the yellow sea shelf consequently the buried palaeosol layer associated with the seismic reflector presents a key horizon for the understanding of late quaternary environmental changes and integrated stratigraphical correlation in the east asian marginal seas

pedogenesis of late quaternary deposits northern kyonggi bay korea implications for relative sea level change and regional stratigraphic correlation abstract late pleistocene and early holocene paleosols are described from construction pits and boreholes in the northern kyonggi bay west coast of korea thin section petrography chemistry clay mineralogy and geotechnical properties of the paleosols were examined to infer relative sea level fluctuations during the late quaternary relict laminae and gradational contacts with underlying tidal rhythmites confirm that the late pleistocene paleosol is a pedogenically altered tidal deposit illuvial clay coatings rootlets and enrichment of kaolinite and chemically stable oxides indicate that pedogenesis occurred on a well drained stable surface during the last glacial period redoximorphic features such as drab colored root traces and sphaerosiderite however suggest that waterlogged conditions developed temporarily due to a rise of the water table at the end of the last glacial period as sea level rose an early holocene paleosol formed in freshwater bog deposits burying the late pleistocene paleosol the early holocene paleosol has abundant sphaerosiderites and organic material the presence of weakly developed illuvial clay coatings oxidized siderites and pellets however indicates oxidizing condition associated with water table fall occurred during the early holocene despite the similarity in the degree of chemical and clay mineralogical weathering the late pleistocene paleosol is distinguished from its early holocene counterpart by thicker and more abundant illuvial clay coatings more fe 2 o 3 and a greater degree of consolidation duration of pedogenesis might be a primary cause for the difference of the pedofeatures with climate playing a secondary role the widespread presence of similar late pleistocene paleosols highlights its significance as a key stratigraphic marker for regional correlations along the west coast of korea

ground motion in the near field of a fluid driven crack and its interpretation in the study of shallow volcanic tremor we present a study of the motion of the ground in the near field of a fluid driven tensile crack embedded in a layered half space the source that we consider is the jerky opening of a channel connecting two fluid filled cracks and the cause of this opening is the excess pressure of fluid in one of the cracks we make a complete representation of the three components of ground motion in the space time and frequency domains and analyze the effects of fluid compressibility source depth and medium structure on the ground response the calculations show the presence of a dominant frequency of motion which depends not only on the source geometry and bulk modulus of the fluid but also on medium characteristics receiver position and the component of motion being considered using this source model we view an episode of volcanic tremor as a continuous sequence produced by numerous jerky openings of channels occurring randomly in time along a chain of cracks our results are applied to the october 5 6 1963 east rift eruption of kilauea volcano hawaii and found to be compatible with available seismic data suggesting that magma is transported through an ensemble of cracks with the area of 1 1 km each pair of cracks constituting an individual dike segment which opens in discrete increments at a rate of 1 s we obtain the following parameters for each dike segment opening increase in cavity volume 40 m3 stress drop 0 004 bar seismic moment 1019 dyn cm and force applied by the fluid to open the dike 1014 dyn the total moment integrated over the entire duration of tremor for the eruption is 0 5 1024 dyn cm roughly equivalent to a single magnitude m 5 earthquake the seismic source parameters and other field observations offer constraints on the process of mass transport and are compatible with the excess pressure and viscosity of magma of about 40 bars and 102 p respectively

radiocarbon dating chronologic framework and changes in accumulation rates of holocene estuarine sediments from chesapeake bay abstract rapidly accumulating holocene sediments in estuaries commonly are difficult to sample and date in chesapeake bay we obtained sediment cores as much as 20 m in length and used numerous radiocarbon ages measured by accelerator mass spectrometry methods to provide the first detailed chronologies of holocene sediment accumulation in the bay carbon in these sediments is a complex mixture of materials from a variety of sources analyses of different components of the sediments show that total organic carbon ages are largely unreliable because much of the carbon including coal has been transported to the bay from upstream sources and is older than sediments in which it was deposited mollusk shells clams oysters and foraminifera appear to give reliable results although reworking and burrowing are potential problems analyses of museum specimens collected alive before atmospheric nuclear testing suggest that the standard reservoir correction for marine samples is appropriate for middle to lower chesapeake bay the biogenic carbonate radiocarbon ages are compatible with 210pb and 137cs data and pollen stratigraphy from the same sites post settlement changes in sediment transport and accumulation is an important environmental issue in many estuaries including the chesapeake our data show that large variations in sediment mass accumulation rates occur among sites at shallow water sites local factors seem to control changes in accumulation rates with time our two relatively deep water sites in the axial channel of the bay have different long term average accumulation rates but the history of sediment accumulation at these sites appears to reflect overall conditions in the bay mass accumulation rates at the two deep water sites rapidly increased by about fourfold coincident with widespread land clearance for agriculture in the chesapeake watershed

seismicity at old faithful geyser an isolated source of geothermal noise and possible analogue of volcanic seismicity abstract old faithful geyser in yellowstone national park u s a is a relatively isolated source of seismic noise and exhibits seismic behavior similar to that observed at many volcanoes including bubblequakes that resemble b type earthquakes harmonic tremor before and during eruptions and periods of seismic quiet prior to eruptions although old faithful differs from volcanoes in that the conduit is continuously open that rock fracturing is not a process responsible for seismicity and that the erupting fluid is inviscid h2o rather than viscous magma there are also remarkable similarities in the problems of heat and mass recharge to the system in the eruption dynamics and in the seismicity water rises irregularly into the immediate reservoir of old faithful as recharge occurs a fact that suggests that there are two enlarged storage regions one between 18 and 22 m the base of the immediate reservoir and one between about 10 and 12 m depth transport of heat from hot water or steam entering at the base of the recharging water column into cooler overlying water occurs by migration of steam bubbles upward and their collapse in the cooler water and by episodes of convective overturn an eruption occurs when the temperature of the near surface water exceeds the boiling point if the entire water column is sufficiently close to the boiling curve that the propagation of pressure release waves rarefactions down the column can bring the liquid water onto the boiling curve the process of conversion of the liquid water in the conduit at the onset of an eruption into a two phase liquid vapor mixture takes on the order of 30 s the seismicity is directly related to the sequence of filling and heating during the recharge cycle and to the fluid mechanics of the eruption short 0 2 0 3 s monochromatic high frequency events 20 60 hz resembling unsustained harmonic tremor and in some instances b type volcanic earthquakes occur when exploding or imploding bubbles of steam cause transient vibrations of the fluid column the frequency of the events is determined by the length of the water column and the speed of sound of the fluid in the conduit when these events occur damping is controlled by the characteristic and hydraulic impedances which depend on the above parameters as well as on the recharge rate of the fluid two periods of reduced seismicity of a few tens of seconds to nearly a minute in duration occur during the recharge cycle apparently when the water rises rapidly through the narrow regions of the conduit causing a sudden pressure increase that temporarily suppresses steam bubble formation a period of decreased seismicity also precedes preplay or an eruption this appears to be the time when rising steam bubbles move into a zone of boiling that is acoustically decoupled from the wall of the conduit because of the acoustic impedance mismatch between boiling water c 10 3 g cm 2 s 1 and rock c 3 10 5 g cm 2 s 1 sustained harmonic tremor occurs during the first one to one and a half minutes of an eruption of old faithful but is not detectable in the succeeding minutes of the eruption the eruption tremor is caused by hydraulic transients propagating within a sublayer of unvesiculated water that underlies the erupting two phase liquid vapor mixture the resonant frequencies of the fluid column decrease to about 1 hz when all of the water in the conduit has been converted to a water steam mixture surges are observed in the flow at this frequency but the resonance has not been detected seismically possibly because the two phase erupting fluid is seismically decoupled from the rock on which seismometers are placed if old faithful is an analogue for volcanic seismicity this study shows that because the frequency of tremor depends on the acoustic properties of the fluid and on conduit dimensions both properties must be considered in analysis of tremor in volcanic regions because magma sound speed can vary over nearly two orders of magnitude as it changes from an undersaturated liquid into a saturated two phase mixture tremor frequency might vary by this magnitude and very broad band seismographs may be required if tremor is to be monitored as magma goes from an undersaturated liquid to a vesiculated froth cessation of fluid induced seismicity may indicate that the processes that drive the transients cease but it is also possible that the processes that drive the transients continue but the fluid properties change so that the fluid becomes acoustically decoupled from the rock on which seismometers are placed

development of stratigraphy and sediment distribution in the northeastern yellow sea during holocene sea level rise abstract a succession of holocene deposits in the northeastern yellow sea were interpreted in a sequence stratigraphic context and sedimentology of each deposit was characterized based on analyses of high resolution seismic profiles and sediment cores taken along a transect thin 3 m transgressive sediments that accumulated through shoreface erosion during the rapid sea level rise in the early holocene overlie a subaerially eroded low gradient late pleistocene platform on the present day inner shelf region cores reveal marine sands over tidal estuarine sandy muds with an intervening rather indistinct ravinement surface in the deepest shelf area these early holocene tidal estuarine deposits remain exposed at the seabottom in the mid o late holocene two contrasting deposits of the highstand type deltaic clayey mud and tidal sand ridges began to accumulate in response to slower rates of sea level rise a series of tidal sand ridges in the nearshore area migrated offshore over the transgressive sand sheet and a deltaic watery mud prograded discordantly over consolidated tidal estuarine deposits in the central shelf the transgressive facies relationships present a model for macrotidal epicontinental sea settings subject to low wave energy and reduced sediment supply