stable isotopic signatures of tertiary lake carbonates eastern ebro basin spain abstract the tertiary ebro basin spain was a region of internal drainage fed by rivers emanating from the fringing pyrenees catalanides and iberian chains the stable isotopic composition of bulk carbonates deposited in diverse late eocene to oligocene lakes within the eastern part of this endorheic region are investigated carbon and oxygen isotopes fall into several distinct hydrographic provinces which are partly palaeogeographical and partly biostratigraphical the isotopic signatures of the lake carbonates primarily reflect the nature of the river input duration seasonality catchment geology and autochthonous processes within the lake biological productivity evaporation but diagenetic changes may further complicate interpretations seasonal changes in precipitation rates are picked out by light dark variations in single lithological cycles

sedimentology of quaternary perched springline and paludal tufas criteria for recognition with examples from guadalajara province spain outcrop scale geometries and bed relationships of ambient temperature freshwater carbonates are poorly understood because many described tufas have been dismantled by erosion and present only part of a particular depositional model at the field scale four end member models encompass the tufa continuum 1 perched springline 2 paludal 3 fluvial and 4 lacustrine tufas individual bed types can occur with variable dominance within several of these models but one or more beds are characteristically dominant only within a single tufa model so it can be differentiated from relatively isolated outcrop fragments two models perched springline tufas and paludal tufas are known in outline only in the literature despite being present within the quaternary deposits of most karstic regions perched springline tufas generally form lobate fan shaped mound morphologies on hillslopes and develop from single or multiple spring resurgences mature deposits show a subhorizontal top and a steep face on the downflow side the steep outer zones of tufa mounds may be developed into cascades with moss curtains or can be dominated by shallow rimstone pools according to face angle tufa deposits lying downslope of the mounds are usually detrital in nature especially if some dismantling of the mound has occurred the relatively thin subhorizontal lobe top deposits commonly contain organic rich deposits paludal tufas develop predominantly in waterlogged valley bottom situations where line sourced waters emerge from valley side and bottom aquifers lime mud precipitation predominates in these sites mud is deposited as subhorizontal laminites that thin towards the valley axis and downstream of resurgences tufa spring mounds may form where lesser volumes of water are involved individual tussocks phytoherm cushions of grasses and rushes are the most diagnostic feature of the model but sapropels and peats may be intercalated diagenesis in both models is rapid lithification of individual beds is virtually instantaneous and always occurs before the decay of the associated living vegetation the resulting highly porous and permeable fabrics remain fresh in holocene tufas but aggrading neomorphism and partial spar infill of vegetation moulds is common in older deposits dissolution in many perched springline tufas is small scale many large cavities are primary but with later coatings of speleothems early removal of organics from paludal tufas is responsible for autobrecciation and differential compaction

palustrine carbonates and the florida everglades towards an exposure index for the fresh water environment abstract palustrine carbonates are shallow fresh water deposits showing evidence of subaqueous deposition and subaerial exposure these facies are common in the geological record the intensity of modification is highly variable depending on the climate and the length of emergence palustrine limestones have previously been interpreted as marginal lacustrine deposits from fluctuating low salinity carbonate lakes but several problems remain with existing facies models 1 palustrine carbonates possess a lacustrine biota but commonly display fabrics similar to those of calcretes and peritidal carbonates 2 the co occurrence of calcrete horizons and karst like cavities is somewhat unusual and appears to indicate contemporaneous carbonate precipitation and dissolution in the vadose zone 3 the dominance of gray colors indicates water saturation apparently inconsistent with the evidence for strong desiccation overprint 4 profundal lake deposits are generally absent from palustrine sequences and sublittoral facies commonly make up only a small proportion of total thicknesses 5 no good modern analogue has been identified for the palustrine environment analogy with the florida everglades suggests a re interpretation of palustrine limestones not as pedogenically modified lake margin facies but as the deposits of extensive very shallow carbonate marshes the distribution of environments in the everglades is determined by the local hydrology reflecting the control of seasonal water level fluctuations and topography climate and topography were the main controls on deposition of ancient palustrine carbonates as in peritidal sequences aggradational cycles are capped by a range of lithologies evaporites desiccation and microkarst breccias calcretes lignite or coal horizons etc permitting interpretation of the climate careful analysis of lateral facies variations may permit reconstruction of subtle topography consideration of the florida everglades as a modern analogue for the palustrine environment has suggested the development of an exposure index for fresh water carbonates

carbonate deposition physical limnology and environmentally controlled chert formation in paleocene eocene lake flagstaff central utah abstract lake flagstaff paleocene eocene of central utah owed its existence large size shallowness and low clastic content to its tectonic setting but the climate controlled its mostly autochthonous sediments during the first and most humid of the three lake phases the lake was fresh calcareous large and highly productive with abundant vegetation and snails the first deposits were limestones with gradually increasing detrital dolomite eroded from lake marginal carbonate mudflats that were undergoing penecontemporaneous dolomitization continuous fluctuation in lake level produced many secondary dewatering and pedogenic paludine fabrics the lake developed into a playa lake during the very arid second phase becoming restricted in area and fauna the water was saline and alkaline and twice became a gypsum precipitating brine frequent exposure of the lake beds resulted in much calichification and in rapid and complete dolomitization under the intermediate climate of the third phase the lake reexpanded and freshened snails returned and many limestones escaped dolomitization each phase defines a member of the flagstaff formation chert absent in the oldest beds increases up section the lowest chert forms minor small spheres and linings in voids near the top of the lowest member suggesting limited silica input and post dolomitization precipitation in areas of greatest groundwater movement the base of the middle member contains horizons of atextural chert mudcrack fillings and nodules that appear to have been an inorganically precipitated gel most of the middle member however contains abundant chert nodules that replaced limestone prior to dolomitization the nodules grew prior to burial some even prior to mudcrack formation by the movement of dissolved silica to areas of relatively low ph in the upper member chert is even more prevalent entire thin beds were pervasively but incompletely silicified prior to dolomitization probably by vertical evaporative pumping of siliceous groundwater moving under mudflats toward the lake

the stable isotopic composition of modern soil carbonate and its relationship to climate the oxygen isotopic composition of modern soil carbonate is well correlated with the isotopic composition of local meteoric water the carbon isotopic cycle for co 2 in soils can be described in terms of the proportion of biomass using the c 4 photosynthetic pathway and the co 2 respiration rate of the soil at low soil respiration rates significant atmospheric co 2 mixing can occur in general the carbon isotopic composition of soil carbonate is related to the proportion of c 4 biomass present in soil but soils that freeze to the depth of carbonate formation often have a significant atmospheric component this suggests that freezing of the soil solution should be considered as another important mechanism for soil carbonate formation because of these relationships the isotopic composition of soil carbonate may be a paleoclimatic and paleoecologic indicator in cases in which diagenetic alteration has not occurred

distribution of very low frequency earthquakes in the nankai accretionary prism influenced by a subducting ridge abstract we investigated the distribution of very low frequency earthquakes vlfes that occurred in the shallow accretionary prism of the eastern nankai trough during one week of vlfe activity in october 2015 they were recorded very close from the sources by an array of broadband ocean bottom seismometers bbobss equipped in dense oceanfloor network system for earthquakes and tsunamis 1 donet1 the locations of vlfes estimated using a conventional envelope correlation method appeared to have a large scatter likely due to effects of 3d structures near the seafloor and or sources that the method could not handle properly therefore we assessed their relative locations by introducing a hierarchal clustering analysis based on patterns of relative peak times of envelopes within the array measured for each vlfe the results suggest that in the northeastern side of the network all the detected vlfes occur 30 40 km landward of the trench axis near the intersection of a splay fault with the seafloor some likely occurred along the splay fault on the other hand many vlfes occur closer to the trench axis in the southwestern side likely along the plate boundary and the vlfe activity in the shallow splay fault appears less intense compared to the northeastern side although this could be a snap shot of activity that becomes more uniform over longer term the obtained distribution can be reasonably explained by the change in shear stresses and pore pressures caused by a subducting ridge below the northeastern side of donet1 the change in stress state along the strike of the plate boundary inferred from the obtained vlfe distribution should be an important indicator of the strain release pattern and localised variations in the tsunamigenic potential of this region

palaeoenvironmental significance of palustrine carbonates and calcretes in the geological record interest in palustrine carbonates and calcretes has increased over the last 20 years since they contain significant environmental information much of the work performed in this area has focused on either of two types of terrestrial carbonate palustrine carbonates or calcretes pedogenic and groundwater yet their simultaneous study shows there may be a gradual transition from one form to the other revealing the interplay between pedogenic sedimentary and diagenetic processes three main factors control the formation of these carbonates the position of the water table the host rock and the period of sub aerial exposure in pedogenic calcretes precipitation of carbonate takes places mostly in the vadose zone above the water table and within a previous host rock or sediment in groundwater calcretes the precipitation of carbonate also occurs within a previous host rock and around the groundwater table in palustrine carbonates however the precipitation of lime mud occurs in a lacustrine water body palustrine carbonates necessarily form on previous lacustrine mud whereas both types of calcretes may form on any type of sediment or soil the sub aerial exposure time needed to form palustrine carbonates may by relatively short even a season whereas pedogenic calcretes need more time several years to millions of years groundwater calcretes do not form on the topographic surfaces so there is no need of sub aerial exposure however stable surfaces favour the development of thick groundwater calcretes small fluctuations in the water table cause gradual transitions of these three types of terrestrial carbonates and the subsequent mixture of their characteristic features causing difficulties in the interpretation of these carbonates the formation of these carbonates is controlled by palaeoenvironmental factors both commonly form in semi arid climates arid climates are also suitable for calcretes but sub humid conditions are more suitable for palustrine carbonates more indications of climatic conditions may be obtained through the analysis of the d18o content of both calcretes and palustrine carbonates and from the depth of the horizon containing carbonate nodules in pedogenic calcretes vegetation is also important in the formation of these types of carbonates data on the prevailing vegetation can be obtained from the analysis of the micro and macrofabric as well as from the d13c signal of the primary carbonates which in pedogenic carbonates has also been used to estimate atmospheric pco2 during the phanerozoic these terrestrial carbonates are widely distributed on floodplains and distal areas of alluvial basins their presence and characteristics can be used as indicators of aggradation subsidence or accommodation rates and therefore as indicators of different tectonic regimes even though the study of these carbonates has notably increased in recent years much less is known about them than about marine carbonates presently there is much emphasis on obtaining a general model for sequence stratigraphy in terrestrial basins with a need to include the carbonates analysed in this paper

quaternary palaeolakes in the evolution of semidesert basins with special emphasis on lake bonneville and the great basin u s a abstract this paper reviews attributes of quaternary lakes and lake basins which are often important in the environmental prehistory of semideserts basin floor and basin closure morphometry have set limits on palaeolake sizes lake morphometry and basin drainage patterns have influenced lacustrine processes and water and sediment loads have influenced basin neotectonics information regarding inundated runoff producing and extra basin spatial domains is acquired directly from the palaeolake record including the littoral morphostratigraphic record and indirectly by reconstruction increasingly detailed hypotheses regarding lake bonneville the largest late pleistocene palaeolake in the great basin are subjects for further testing and refinement oscillating transgression of lake bonneville began about 28 ka the highest stage occurred about 15 ka and termination occurred abruptly about 13 ka a final resurgence of perennial lakes probably occurred in many subbasins of the great basin between 11 and 10 ka when the highest stage of great salt lake successor to lake bonneville developed the gilbert shoreline and when the russell shoreline formed 500 600 km away in the carson desert of the lake lahontan basin the highest post gilbert stage of great salt lake which has been one of the few permanent lakes in the great basin during holocene time probably occurred between 3 and 2 ka a set of eighteen general observations regarding geologic aspects of the palaeolake record in semidesert basins is helping to guide quaternary studies in the great basin

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

palaeoclimate of the late jurassic of portugal comparison with the western united states investigation of the palaeoclimatic conditions associated with upper jurassic strata in portugal and comparison with published palaeoclimate reconstructions of the upper jurassic morrison formation in western north america provide important insights into the conditions that allowed two of the richest terrestrial faunas of this period to flourish geochemical analyses and observations of palaeosol morphology in the informally named upper jurassic lourinhaformation of western portugal indicate warm and wet palaeoclimatic conditions with strongly seasonal precipitation patterns palaeosol profiles are dominated by carbonate accumulations and abundant shrink swell vertic features that are both indicative of seasonal variation in moisture availability the d 18 osmow and ddsmow values of phyllosilicates sampled from palaeosol profiles range from 22ae4 to 22ae7 and 53ae0 to 37ae3 respectively these isotope values correspond to temperatures of formation between 32 c and 39 c 3 with an average of 36 c which suggest surface temperatures between 27 c and 34 c average 31 c on average these surface temperature estimates are 1 c higher than the highest summer temperatures modelled for late jurassic iberia using general circulation models elemental analysis of matrix material from palaeosol b horizons provides proxy chemical index of alteration minus potassium estimates of mean annual precipitation ranging from 766 to 1394 mm year with an average of approximately 1100 mm year palaeoclimatic conditions during deposition of the lourinhaformation are broadly similar to those inferred for the morrison formation except somewhat wetter seasonal variation in moisture availability does not seem to have negatively impacted the ability of these environments to support rich and relatively abundant faunas the similar climate between these two late jurassic terrestrial ecosystems is probably one of the factors which explains the similarity of their vertebrate faunas

universality of slow earthquakes in the very low frequency band deep tectonic tremors have been observed together with signals in the very low frequency vlf band from 0 02 to 0 05 hz which have been identified as vlf events in limited regions of subduction zones by stacking broadband seismograms relative to the timing of tremors we have detected similar signals in all regions where tremors occur in western japan these signals are inverted to obtain the moment tensor and the fault normal and slip vectors are generally consistent with the geometry of the plate interface and the direction of plate motion therefore these signals are probably radiated by shear slip on the plate interface the ratio between the seismic energy rate estimated from the tremors and seismic moment rate in the vlf band is almost proportional with a proportionality constant i e scaled energy of around 5 10 10 the spatial distribution of scaled energy may reflect spatial variations in the frequency dependent characteristics of slow deformation

recurring and triggered slow slip events near the trench at the nankai trough subduction megathrust the discovery of slow earthquakes has revolutionized the field of earthquake seismology defining the locations of these events and the conditions that favor their occurrence provides important insights into the slip behavior of tectonic faults we report on a family of recurring slow slip events sses on the plate interface immediately seaward of repeated historical moment magnitude mw 8 earthquake rupture areas offshore of japan the sses continue for days to several weeks include both spontaneous and triggered slip recur every 8 to 15 months and are accompanied by swarms of low frequency tremors we can explain the sses with 1 to 4 centimeters of slip along the megathrust centered 25 to 35 kilometers km from the trench 4 to 10 km depth the sses accommodate 30 to 55 of the plate motion indicating frequent release of accumulated strain near the trench

climatic and tectonic controls on carbonate deposition in syn rift siliciclastic fluvial systems a case of microbialites and associated facies in the late jurassic this work provides new insights to assess the factors controlling carbonate deposition in the siliciclastic fluvial systems of rift basins sedimentological and stable isotope data of microbialites and associated carbonate facies along with regional geological information are shown to reveal the influence of climate and tectonics on the occurrence and attributes of carbonate deposits in these settings the vega formation a 150 m thick lower kimmeridgian siliciclastic fluvial sequence in asturias province northern spain constitutes a candidate for this approach this unit includes varied facies stromatolites rudstones packstones and wackestones containing oncoids intraclasts charophytes and shell bioclasts marlstones and polygenic calcareous conglomerates that formed in a low gradient fluvial lacustrine system consisting of shallow low sinuosity oncoid bearing channels and pools within marshy areas with sporadic coarse alluvial deposition the sedimentological attributes indicate common erosion by channel overflow and rapid lateral changes of subenvironments caused by water discharge variations the carbonate fluvial lacustrine system developed near uplifted marine jurassic rocks the occurrence of the system was conditioned by normal faults active during the deposition of the unit that favoured i springs of hco3 ca rich water from a rhaetian sinemurian carbonate rock aquifer and ii carbonate deposition in areas partially isolated from the adjacent siliciclastic fluvial system the microbialite 13c and 18o values support deposition in a hydrologically open system fed by ambient temperature meteoric water with riparian vegetation three types of lamination in the stromatolites and oncoids reflect distinct morphological types of cyanobacterial communities the textural pattern of lamination parallels 13c and 18o changes suggesting short term cycles of precipitation and temperature a moderately to strongly contrasted seasonal and or pluriannual precipitation regime is inferred from the cyclic 13c pattern of the lamination and from the discontinuous and asymmetrical growth of oncoids thus the isotopic and sedimentological attributes of the carbonate deposits were linked to short term climate changes associated with semi arid conditions consistent with the studied climatic zone

a palaeoclimate model for the kimmeridgian abstract most attempts at using numerical general circulation model gcm to simulate mesozoic climates have studied the late cretaceous and have focused on the enigmaof apparently equable global climates however this climate regime lasted throughout the mesozoic and it is of interest to examine other periods we present the results of an integration for the late jurassic using a relatively detailed and high resolution model there is generally good agreement between the model climate and the existing geological data in particular the simulation predicts no permanent ice cover near either pole arid conditions over the southwestern usa seasonally arid climate over southern europe and winter storminess over europe and australia however the surface temperatures over siberia and southeastern gondwanaland drop below zero for a significant part of the winter

very low frequency earthquakes off the pacific coast of tohoku japan we found very low frequency earthquakes vlfes at a shallow subduction zone close to the japan trench off the pacific coast of tohoku japan centroid moment tensor solutions of vlfes showed reverse fault mechanisms with a compression axis in the east west direction a cross correlation analysis of seismograms with template events between 2005 and 2013 revealed three major vlfe clusters and their temporal evolution a vlfe cluster in the central off tohoku region located in the large slip area of the 2011 tohoku earthquake was detectable only before the tohoku earthquake however vlfes in the northern and southern off tohoku regions at the rim of the large slip area were activated after the tohoku earthquake the change in the activity may reflect the stress redistribution by the coseismic and or afterslip processes of the tohoku earthquake

petrography and diagenesis of cherts from lake magadi kenya pleistocene cherts from alkaline lake magadi kenya are believed to have formed inorganically from sodium silicate precursors magadiite nasi 7 o 13 oh 3 3h 2 o and or kenyaite nasi 11 o sub 20 5 oh 4 3h 2 o they have been cited as modern analogs for cherts found in both ancient lacustrine deposits and precambrian iron formations but few criteria exist to distinguish magadi type chert from other cherts in the geological record we studied approximately twenty chert samples and one magadiite sample from lake magadi to develop such criteria and to shed light on the mechanism of the magadiite quartz conversion characteristics of the type magadi cherts are 1 a groundmass mosaic of fine quartz crystals that vary in orientation from random to rectilinear 2 finely disseminated inclusions of silicate clays zeolites and or carbonates predominantly calcite 3 large crystal molds probably after trona concentrated near sample margins and 4 inward directed shrinkage cracks and or more irregular internal voids filled with chalcedony silicate clays zeolites and or carbonates predominantly calcite shrinkage cracks which define surface reticulation patterns are frequently cited as evidence of a magadi type origin for ancient lacustrine cherts but they are not unique to alkaline lake cherts based on a reconnaissance of ancient cherts of various origins no single characteristic appears to be unique to magadi type chert with the possible exception of the rectilinear or grid work orientation of the quartz crystals this texture appears to be inherited from the precursor magadiite which displays a similar extinction pattern due to the presence of 10 20 mu m spherical aggregates of plate like crystals this pseudomorphing implies direct volume for volume replacement of magadiite by quartz void filling chalcedony and the high densities of the cherts however indicate that silica was added during and after the conversion from magadiite to chert petrographic observations suggest the magadiite quartz conversion takes place in multiple stages with early conversion in brines and later leaching by more dilute meteoric water a reconnaissance of 35 chert samples from 16 different formations ranging in age from pleistocene to archean yielded only two samples with convincing grid work fabrics both of which had already been interpreted as magadi type chert on the basis of other characteristics this suggests that the distinctive textures which characterize the type magadi cherts may be useful for recognizing other inorganic alkaline lake cherts in the stratigraphic record

influence of a subducted oceanic ridge on the distribution of shallow vlfes in the nankai trough as revealed by moment tensor inversion and cluster analysis

watershed reconstruction of a paleocene eocene lake basin using sr isotopes in carbonate rocks provenance studies have used sr isotopes 87 sr 86 sr of silicate source rocks as a link to their eroded basinal equivalents this technique however cannot identify the proportional inputs from different watersheds or define more precisely sedimentation events due to tectonic or climatic change erosion of carbonate rocks dominates the sr input within basin drainage and potentially can be used through 87 sr 86 sr ratios to reconstruct paleohydrology of the entire basin and trace watershed inputs and depositional patterns in continental basins the sr isotopic ratios from waters of the source area allowing for the mixing of shallow groundwater and surface water along the transport path are homogenized in the basinal carbonate sediments mineralogy and diagenesis of carbonate rocks generally do not affect the sr isotopic signal in a near surface system lacking external influence by volcanism eolian dust or deep geothermal waters the 87 sr 86 sr ratios from the source area are directly comparable to those in the receiving continental basin the sr isotopic signal of the paleocene eocene flagstaff formation central utah a carbonate lake deposit in a foreland basin is compared to that of projected source waters draining its thrust front the sevier fold thrust belt freshwater carbonates compose a large portion of the lowermost ferron mountain and uppermost musinia peak members of the formation whereas gypsum and carbonates predominate in the middle cove mountain member previous research had attributed gypsum deposition to the deposition of the middle cove mountain member to either climatic change or unroofing of diapirs of jurassic gypsiferous carbonates to examine more closely the influence of climate versus tectonics on flagstaff sedimentation as well as the efficacy of provenance studies using carbonates we collected rock samples from the three members of the formation on the wasatch plateau of central utah in addition to sampling stream water associated with pennsylvanian permian and jurassic carbonate terrains from the nearby thrust front the 87 sr 86 sr ratios in carbonates and gyprock belonging to the flagstaff formation remained unchanged during deposition the average sr isotope composition of the flagstaff rocks being identical to that of sampled waters draining the projected provenance area there was little change in source rock weathering as the thrust front evolved deposition of gypsum occurred in the basinal lake only during the deposition of the middle cove mountain member despite its constant exposure in the drainage area suggesting a changing balance of tectonic and climatic controls during lake sedimentation the 87 sr 86 sr isotopic studies targeting carbonate rocks and their presumed source waters are a simple but accurate method for reconstructing the paleohydrology of lake basins

tidal response in shallow tectonic tremors various types of slow earthquakes e g tectonic tremors and slow slip events have been reported in tectonic zones especially in the subduction zone the tidal response of a tremor is considered to be strongly related to the weak friction state of the plate interface and many studies have reported observational evidence of such correlation between tides and deep tremor activity here we used the modified frequency scanning method at a single station to detect micro tectonic tremors that have not been previously reported in southern kyushu in the early stage of the tremor activity tremors are mostly modulated by slow slip events in contrast we found a seismic response to ocean tides during the later stage in the shallower part of the subduction zone this might indicate that the tremors are triggered by tidal changes caused by fault weakening due to slow slip events as same as deeper condition

the synchronous occurrence of shallow tremor and very low frequency earthquakes offshore of the nicoya peninsula costa rica 1 the occurrence of transient shallow slow slip at seismogenic zones has important implications for earthquake and tsunami hazards here we provide evidence that a tremor and slow slip event occurred at shallow depth offshore of the nicoya peninsula costa rica in august 2008 the temporal coincidence of offshore tremor very low frequency earthquakes vlfes motions consistent with slow slip on the plate interface on western coastal gps stations and a pressure transient in an iodp borehole all indicate slow slip occurring at shallow depths large ocean loading stresses on the shallow plate interface modulate tremor activity with the peak coulomb stress forced by semi diurnal ocean tides correlating with tremor productivity based on beamforming data we constrain that the vlfe activity occurs in the same region as the tremor and slow slip the presence of slow slip at shallow depth has important implications for the up dip extent of earthquake rupture the proximity of the 5 september 2012 mw 7 6 megathrust earthquake to slow slip tremor and vlfe activity in the 2008 event suggests abrupt frictional transitions from locked to conditionally stable behavior on the plate interface offshore of the nicoya peninsula

a chronostratigraphic framework for the upper jurassic morrison formation western u s a the attached document is the authors final accepted submitted version of the journal article you are advised to consult the publisher s version if you wish to cite from it

lithofacies associations and stable isotopes of palustrine and calcrete carbonates examples from an indian maastrichtian regolith detailed information on semi arid palustrine carbonate calcrete lithofacies associations in a sheetwash dominated regolith setting is sparse this is addressed by studying the lower limestone of the lameta beds a well exposed maastrichtian regolith in central india the general vertical lithofacies assemblage for this unit comprises a basal calcareous siltstones and marls with charophytes ostracods and gastropods b buff micritic limestones associated in their upper parts with calcretized fissure fill sandstones c sheetwash as fissure fill diamictites and thin pebbly sheets locally developed over a few metres and d sandy nodular brecciated and pisolitic calcretes at the top the sequence is regressive with upsection filling of topographic lows by increased sheetwash lateral lithofacies change is marked but there are no permanent open water lake deposits in topographic lows close to the water table marshy palustrine or groundwater calcretes formed whereas on better drained highs brecciation and calcretization occurred prolonged exposure is implied suggesting that shrinkage was the main cause of brecciation evidence for rhizobrecciation and other biological calcrete fabrics is sparse contrasting with the emphasis on root related brecciation in many studies of palustrine lithofacies stable isotope d18o and d13c values are consistent with the palustrine limestones being fed from meteoric derived groundwater with a strong input of soil zone carbon there is overlap of both d18o and d13c values from the various palustrine and calcrete fabrics co occurring at outcrop this suggests that in groundwater supported wetlands conversion from palustrine carbonate to calcrete need not show isotopic expression as the groundwater source and input of soil zone carbon are essentially unchanged cretaceous tertiary d18o and d13c values from palustrine lithofacies and associated calcretes appear to be strongly influenced by the inherited values from lakes and wetlands hydrologically closed lakes and marine influenced water bodies tend to result in low negative palustrine d18o and d13c values during brecciation and calcretization the degree of isotopic inheritance depends on whether or not alteration occurs in waters that are different from those of the original water body or wetland marked biological activity e g rhizobrecciation or root mat development during calcretization may lower d13c values where c3 plants are abundant but in shrinkage dominated systems d13c values will be largely inherited from the palustrine limestones

source rock deposition controlled by tectonic subsidence and climate in the western pearl river mouth basin china evidence from organic and inorganic geochemistry abstract interest in factors controlling lacustrine source rock deposition has increased over the last few decades because this type of deposits contain significant petroleum resources generally tectonic subsidence and climate are the two root causes as they control the accommodation potential water column properties and sources of organic matter in this study coupling organic geochemical and elemental geochemical data two potential source rocks i e the eocene wenchang formation e 2 w and oligocene enping formation e 3 e were investigated two models were finally raised to explain deposition of the two set of source rocks according to their paleoclimatic and tectonic properties the source rock potential shows a strong heterogeneity the second member of the eocene wenchang formation e 2 w 2 is characterized by high organic matter content and oil prone kerogen type in contrast the first member of the eocene wenchang formation e 2 w 1 and the oligocene enping formation e 3 e are characterized by low organic matter content and gas prone kerogen type the primary productivity and depositional environment exhibit notable differences between the two potential source rocks horizons and show an obvious variation from the depocenter to the slope and can be best explained by the coevolution of tectonic subsidence and climate during the e 2 w depositional stage low sediment supply led to mudstone deposited in deep lacustrine environment and resulted in underfilled lake basin the low water inflow provided little terrigenous organic matter low bicadinane perylene and floranthene contents and oxygen besides the low area depth ratio impeded the water circulation thus resulted in shallow thermocline and anoxic suboxic bottom environment abundant dibenzothiophene and high c 35 c 31 22s hopane ratios therefore abundant algae which contributed to the high amorphous organic matter aom content can be preserved the warm and wet climate high mn mg ratios gave birth to autochthonous organism such as dinoflagellates and pavlova gyrans abundant 4 methyl sterane during the e 3 e depositional stage the sufficient sedimentary supply resulted in expanding shallow lacustrine and swamp environment the higher area depth ratio and high sediment supply made environment unstable and can be strongly influenced by external environment broader range of mn mg ratios enough terrigenous organic matter tom was transported to the slope but little to the depocenter the slightly hot and dry climate low mn mg ratios led to decreasing autochthonous organism and evaporation environment the shallow water depth and relative dry climate resulted in saline suboxic dysoxic acid bottom environment the co variation of organic and inorganic indexes indicates the combination is a valid method in reconstructing source rock depositional models

reconnaissance of upper jurassic morrison formation ichnofossils rocky mountain region usa paleoenvironmental stratigraphic and paleoclimatic significance of terrestrial and freshwater ichnocoenoses seventy five types of ichnofossils documented during a four year reconnaissance study in the upper jurassic morrison formation demonstrate that highly diverse and abundant plants invertebrates and vertebrates occur throughout most of the morrison or equivalent strata invertebrate ichnofossils preserving the most environmentally and climatically sensitive in situ behavior of morrison organisms are in nearly all outcrops terrestrial ichnofossils record biotic processes in soil formation indicating soil moisture and water table levels freshwater ichnofossils preserve evidence of water depth salinity and seasonality of water bodies ichnofossils categorized as epiterraphilic terraphilic hygrophilic and hydrophilic new terms reflect the moisture regime where they were constructed the ichnofossils are vertically zoned with respect to physical chemical and biological factors in the environment that controlled their distribution and abundance and are expressed as surficial shallow intermediate and deep the sedimentologic stratigraphic and geographic distribution of morrison ichnofossils reflects the environmental and climatic variations across the basin through time marginal marine tidal to brackish water ichnofossils are mainly restricted to the windy hill member very large to small termite nests dominate the salt wash member similar size ranges of ant nests dominate the brushy basin member soil bee nests dominate in the salt wash decreasing in abundance through the brushy basin deeper and larger insect nests indicate more seasonal distribution of precipitation and rainfall shallower and smaller insect nests indicate either dry or wet substrate conditions depending on the nest architecture and paleopedogenic and sedimentologic character of the substrate trace fossil indicators of flowing or standing water conditions are dominant in the tidwell member and in fluvial sandstones of the salt wash and brushy basin members large communities of perennial freshwater bivalve traces are abundant in the tidwell and brushy basin members but to a lesser extent in the salt wash member shallow crayfish burrows indicating a water table level close to the surface 1 m are restricted to channel bank and proximal alluvial deposits in the salt wash recapture and brushy basin members sauropod theropod pterosaur and other vertebrate tracks occur throughout the morrison formation associated with alluvial lacustrine and transitional marine shoreline deposits ichnofossils and co occurring paleosols in the morrison reflect the local and regional paleohydrologic settings which record the annual soil moisture budget and were largely controlled by the climate in the basin contributions to near surface biologic systems by groundwater from distant sources were minor except where the water table perennially seasonally or ephemerally intersected the ground surface the jurassic morrison formation in the southern portion of the basin experienced a mosaic of seasonal climates that varied from a drier tidwell windy hill deposition to a wetter lower and middle salt wash deposition and slightly drier upper salt wash deposition tropical wet dry climate returning to a wetter tropical wet dry climate near the end of morrison deposition brushy basin deposition the northern part of the basin experienced similar trends across a mosaic of mediterranean climate types the range and mosaic pattern of wet dry morrison climates is analogous to the range of climates and their seasonal variability that dominates the african savanna today

regional paleoclimatic and stratigraphic implications of paleosols and fluvial overbank architecture in the morrison formation upper jurassic western interior usa abstract paleosols in the morrison formation upper jurassic from the western interior and colorado plateau regions occur in fluvial overbank and marginal lacustrine depositional facies associated with aggradational settings and at sequence bounding unconformities that mark divisions between major aggradational and degradational successions pedogenic features within these horizons preserve important contextual information about the local and regional paleoclimate and paleoenvironment in which the soils formed floodplain and lake margin paleosols show evidence that most of the morrison basin was characterized by a semi arid to tropical wet dry paleoclimate with fluctuating groundwater conditions a low precipitation to evaporation ratio and weak to moderately seasonal precipitation paleosol ichnofauna show evidence of a diverse and opportunistic flora and fauna that exploited changing conditions and existing nutrient and moisture regimes changes in paleosol type and degree of development over the basin indicate the overall regional paleoclimate was drier in the western and southern portions of the basin vertical trends indicate paleoclimatic conditions over the basin became steadily more humid through time laterally continuous well developed deeply weathered paleosols formed during times of little or no deposition and mark regional unconformities the paleosols at these sequence bounding unconformities serve as useful regional stratigraphic markers to trace genetic packages across the morrison depositional basin and to determine regional accommodation trends

climatic vs tectonic signals in a continental extensional basin teruel ne spain from stable isotope δ18o and sequence stratigraphical evolution alluvial fans and shallow carbonate lakes interfered in the teruel half graben during the late miocene pliocene tectonic influence is recorded in alluvial and lacustrine palustrine successions with long term climate changes being recorded in detail in the isotopic signatures of carbonates episodes of tectonic activity induced alluvial fan progradation and lake retraction in the whole basin three lacustrine stages have been identified which support the idea that climate also exerted an important control on sedimentation the transition between stages 1 and 2 occurred during a tectonically calm episode due to an increase in aridity in the early turolian small fans with source areas next to the lake margin prograded inducing lake shore retraction the transition from stage 2 to 3 was caused by the superimposition of increasing tectonic activity and aridity effects our study demonstrates that discrimination of allogenic factors controlling sedimentation in continental closed basins is possible using sequence stratigraphy in combination with other techniques such as geochemistry of carbonates

late pleistocene holocene palaeoenvironmental evolution of the anamaza river valley iberian range ne spain multidisciplinary approach on the study of carbonate fluvial systems abstract the uppermost pleistocene and holocene palaeoenvironmental evolution of the anamaza river valley iberian range ne spain is deduced using multidisciplinary approach including stratigraphical mineralogical palynological geochemical geophysical methods and drilling main changes were registered in distinct subenvironments of a carbonate fluvial system including the channelled zone and wetlands in the floodplain tufa barrages dominated although pools also existed geophysical survey and coring reveal tufa build ups and pool facies also in the subsoil lower water temperature and scarce evaporation are deduced for the pleistocene fluvial system that progressively changed through the holocene with more hydrologically closed areas and higher evaporation influence a general aggrading evolution during warm stages related with increasing base level and damming due to fast carbonate precipitation characterised the holocene detrital tufa indicates erosive high energy floods or colder stages when water level would decrease favouring erosion 14 c and 230 th 234 u dating reveal high sedimentation rates and three main discontinuities related with cold episodes younger dryas middle part of the holocene climate optimum and iron age epoch during the uppermost pleistocene tufa growth would be enhanced during warmer episodes as the bolling allerod in the younger dryas scarce vegetation favoured erosion of both slopes and tufa constructions subsequent warmer temperatures during the first part of the holocene favoured vegetated slopes enhanced tufa growing although interrupted in the middle part of the holocene climate optimum and development of wetlands with riparian vegetation in the floodplain where either siliciclastics or detrital tufa incoming alternated with low energy waters stages and mud settling progressive decline in tufa is deduced for the upper holocene but it is not possible to determine whether this and other palaeoenvironmental changes were related either to climate or increasing human activities during the roman and medieval warm periods more oxidizing conditions in the wetlands and increasing erosion prevailed probably conditioned by human activities the pollen record shows for the early holocene development of pinus forest with betula and expansion of deciduous quercus xerophilous and heliophilous grassland subsequent increasing moisture supported open forests with deciduous quercus ulmus corylus and evergreen quercus ilex pistacia species from ca 4000 yrbp a dominant deciduous quercus forest with groves of corylus ulmus acer fagus and taxus expanded and human activities grazing occurred from 1200 yrbp dry grassland expanded due to intensive land use agropastoral activities almost completely deforested plateaus surround the site today with slopes covered by patchy grass with junipers groves and screeds with little soil

site amplification of coda waves from local earthquakes in central california the goals of this study are two fold 1 to examine the site effect of coda waves believed to be the average site effect of shear waves in order to understand its spatial and frequency dependent behavior and 2 to learn what we can about the processes that generate the coda itself we use digital data from over 90 earthquakes each recorded by a subset of some 150 stations in the coast ranges of central california between san francisco and san luis obispo results from the band 1 5 to 24 hz indicate that site amplification depends strongly on surface geology and frequency at low frequencies 1 5 to 3 0 hz changes in amplification up to a factor of 20 are observed amplification generally varies inversely with deposit age at sediment sites and is lowest at granite and franciscan basement sites at high frequencies 6 to 24 hz the pattern changes many granite sites the majority in the gabilan range exhibit increasing amplification with frequency relative to the average station this behavior differs strikingly from that observed at sediment and franciscan sites which roll off at an intermediate rate and many sediment sites adjacent to the san andreas fault zone which decay away even more rapidly with frequency these results can be explained qualitatively by appealing to variable near site impedance and attenuation however complicating phenomena such as mode excitation in valley sediments must exist at low frequencies peaked behavior at a few hard rock sites at high frequency 12 hz currently lacks explanation at a few sediment sites the low frequency excitation is so strong that the coda envelopes begin to take on different shapes this contradicts the assumption based on previous observations that the coda shape is independent of source receiver location thus some site measurements may be artificially high the working model of coda waves as body wave energy backscattered from randomly distributed inhomogeneities must be modified to include the possibility of efficient near site resonance excited by incident direct and coda wave energy

lacustrine carbonates and pedogenesis sedimentology and origin of palustrine deposits from the early cretaceous rupelo formation w cameros basin n spain the berriasian rupelo formation of the w cameros basin consists of a 2 200 m thickness of marginal and open lacustrine carbonate and associated deposits open lacustrine facies contain a non marine biota with abundant charophytes both stems and gyrogonites ostracods gastropods and rare vertebrates carbonate production was mainly biogenic the associated marginal lacustrine palustrine facies show strong indications of subaerial exposure and exhibit a wide variety of pedogenic fabrics silicified evaporites found near to the top of the sequence reflect a short hypersaline phase in the lake history the succession was laid down in a low gradient shallow lake complex characterized by wide fluctuations of the shoreline carbon and oxygen stable isotope analyses from the carbonates show non marine values with ranges of 13 from 7 to 11 and 18 from 3 to 7 5 differences in the isotopic composition of open lacustrine carbonates are consistent with sedimentary evidence of variation in organic productivity within the lake analyses from the entire sample suite plot on a linear trend isotopic compositions become lighter with increasing evidence of pedogenic modification this suggests progressive vadose zone diagenesis and influence of meteoric waters rich in soil derived co2 the stable isotope data thus support evidence from petrography and facies relations that palustrine limestones form through pedogenic modification of lake carbonates

the slow earthquake spectrum in the japan trench illuminated by the s net seafloor observatories investigating slow earthquake activity in subduction zones provides insight into the slip behavior of megathrusts which can provide important clues about the rupture extent of future great earthquakes using the s net ocean bottom seismograph network along the japan trench we mapped a detailed distribution of tectonic tremors which coincided with very low frequency earthquakes and a slow slip event compiling these and other related observations including repeating earthquakes and earthquake swarms we found that the slow earthquake distribution is complementary to the tohoku oki earthquake rupture we used our observations to divide the megathrust in the japan trench into three along strike segments characterized by different slip behaviors we found that the rupture of the tohoku oki earthquake which nucleated in the central segment was terminated by the two adjacent segments

climate of the supercontinent pangea numerous climate models predict that the geography of the supercontinent pangea was conducive to the establishment of a megamonsoonal circulation in general geologic evidence supports the hypothesis of a megamonsoon that reached maximum strength in the triassic pangea in the late carboniferous had widespread peat formation in what is now central and eastern north america and europe and relatively dry conditions on the colorado plateau the equatorial region of the continent became drier through the end of the carboniferous by the permian the equatorial region of pangea was dry and indicators of aridity and rainfall seasonality became more widespread wind directions from colorado plateau eolian sandstones are consistent with an increasing influence of monsoonal circulation at this time in the triassic climate in the colorado plateau region became relatively wet though still seasonal and the few eolian sandstones indicate a major shift in wind direction at that time in addition sedimentation

diagenesis of late miocene micritic lacustrine carbonates madrid basin spain mud grade lacustrine limestones of miocene age from the madrid basin spain reveal varied and complex diagenetic histories microporous micrites occur as well as micrites with anhedral mosaics the micrites have recrystallized from a metastable precursor in part under sub oxic meteoric diagenetic conditions probably before extensive karstification in the pliocene the absence of aragonite relics their mainly micritic microfabric low sr content and covariant trend of sr and mg suggest that the micrites formed from mainly high magnesian calcite muds lacustrine micrites can be compared to marine forms and criteria used to assess the composition of the marine precursor muds can be applied to lacustrine limestones to complement other techniques to identify original lake water compositions

paleoenvironmental reconstruction of jurassic dinosaur habitats of the vega formation asturias spain jurassic aged strata of asturias spain contain trace fossils including sauropod theropod and ornithopod dinosaur footprints but their paleoenvironmental context has been relatively unstudied a coastally exposed continuous section at playa de vega shows a clear transition from the marine middle jurassic rodiles formation to the terrestrial upper jurassic vega formation within the 100 m of vega formation stratigraphy that was logged there four distinct types of paleosols were identified 1 entisols 2 inceptisols 3 vertisols and 4 composite or cumulative paleosols the paleosol types and their features indicate a floodplain depositional setting with short stature shrubby vegetation theropod and ornithopod tracks have been identified at the base of the section indicating that a dinosaurian fauna was present at playa de vega during the jurassic results from well characterized climofunctions based on modern soils and paleosol b horizon chemical composition of the inceptisols and vertisols yield mean annual precipitation estimates of 400 980 mm yr 1 and mean annual temperature estimates of 8 15 c the presence of vertisols with both evidence for shrink and swell behavior and dispersed pedogenic carbonate is consistent with a strongly seasonal precipitation regime the 13 c analyses of pedogenic carbonates yield values that range from 7 09 to 8 88 relative to vienna peedee belemnite vpdb and indicate carbon dioxide levels about six times pre industrial levels consistent with previous results the asturian vertebrate track assemblage is remarkably similar to that of the morrison formation western united states but it has greater overall richness the pattern is reversed for body fossils the reconstructed paleoenvironmental and paleoclimatic conditions indicate similar depositional settings in both places but with a cooler wetter more seasonal environment in asturias the greater seasonality indicated by the vega formation relative to the morrison formation may explain the observed differences in richness

recognition and implications of eocene tufas and travertines in the chadron formation white river group badlands of south dakota there are few descriptions of pre quaternary tufa or travertine yet these deposits have important climatic hydrological and tectonic implications in the badlands of south dakota the late eocene chadron formation contains a variety of tufa fluvial lacustrine paludal and perched springline types travertine and calcrete pedogenic and non pedogenic types in fluvial channels tufas and tufa barrages oncolites tufa lithoclast conglomerates and phytoherms are transitional to travertines pseudostromatolitic boundstone gravels and small pinnacle resurgences with rimstone edges and pools lacustrine tufas formed in small ponds adjacent to other types of tufas and are similar to the low energy bench margin facies types observed in modern groundwater fed temperate zone hardwater lakes paludal tufas are laterally discontinuous sheets of pisoid intraclast wackestone that fill palaeotopography distal perched springline tufas are mounds of numerous sloping tufa sheets concretions and rhizoliths associated with palaeosols are recognized as pedogenic calcretes whereas non pedogenic calcretes are variably cemented vertically oriented conduits for palaeogroundwater discharge that are located in fault zones these deposits resulted from palaeogroundwater discharge along faults during the late eocene coeval unroofing of the black hills uplift created a regional groundwater flow system through karsted palaeozoic limestones exposed in the black hills the chadron formation is an avulsion dominated siliciclastic unit yet important bodies of carbonate accumulated in it as a result of groundwater processes

spatial and frequency dependent properties of site amplification factors in japan derived by the coda normalization method we have estimated broadband f 0 5 8 hz site amplification factors at 1800 sites in japan based on the coda normalization method using 4001 seismograms obtained from 48 events the results show that in the low frequency band f 0 5 1 hz the site amplification factor varies over a wide range from 4 to 24 db with larger site amplification factors 8 db in such major basins as kushiro rumoi sapporo aomori sendai niigata tokyo toyama nagoya osaka oita and kagoshima on the other hand the site amplification factor in the high frequency band f 4 8 hz varies over a relatively narrow range from 0 to 18 db at each station and has no clear correlation with the surface geology of each station we then examined the contribution of the site amplification at each station to the anomalous distribution of the intensity pattern during large earthquakes by correcting the observed ground accelerations at each k net and kik net station with their corresponding estimated site amplification factors the corrected pattern of intensity shows simple concentric isoseismal intensity contours around the hypocenter indicating the applicability of our estimates to strong motion predictions we confirmed that our estimates are superior to those derived from geology such as those based on the regression of the averaged s wave velocity from the surface to a depth of 30 m graphic 1 with a smaller standard deviation of intensity variations based on a standard decay function of intensity versus hypocentral distance 1 embed inline graphic 1 gif

sedimentology of ancient coastal wetlands insights from a cretaceous multifaceted depositional system coastal wetlands are prominent modern environments widely studied in geomorphology and ecology but the term coastal wetland is still barely used for the sedimentological classification of ancient deposits the depositional system studied here leza formation cameros basin early cretaceous n spain includes diverse carbonate and clastic facies deposited at the sea land transition and is an illustrative example of the wide array of sedimentary environments that may occur in coastal wetlands systems the studied system was composed mainly of carbonate water bodies whose salinity ranged from fresh to brackish and near marine and which had variable input of clastic material due to their lateral connection with alluvial fans in addition the system also included carbonate water bodies with stronger marine influence tide influenced oolitic areas and relatively restricted evaporative settings the deposits of all these environments occur alternating with each other throughout a unit 30 280 m thick and they range from continental to marine conditions in a relatively small area approximately 10 km 3 30 km thus this sedimentological study of the leza fm provides an ideal opportunity to investigate challenging ancient deposits with both continental and marine features comparison with other modern and ancient coastal settings allows the conclusion that coastal wetland may be the most accurate sedimentological classification for the leza fm since it was not part of a major coastal system e g delta or estuary a series of general sedimentological characteristics of coastal wetland deposits are gathered from the cretaceous case study and from the modern and ancient examples examined these characteristics include predominance of shallow water facies common subaerial exposure and edaphic features great variety of interrelated continental transitional and marine environments with contrasting hydrodynamic and hydrochemical conditions and low diversity biotic communities including both continental and marine fossils as well as fossils of ambiguous affinities

concretion formation in volcaniclastic host rocks evaluating the role of organics mineralogy and geochemistry on early diagenesis abstract the upper part of the brushy basin member of the jurassic morrison formation in the four corners regions of the u s was deposited in an ephemeral alkaline saline lake system with copious input of volcanic ash that resulted in dynamic fluid rock interaction during early diagenesis three broad diagenetic facies defined by color and associated bioturbation features are interpreted red green and intermediate diagenetic facies reflect meter scale paleotopography red facies represent shallow water to subaerial oxidizing conditions green facies reflect saturated conditions and reducing pore water chemistry shortly after deposition and intermediate facies represent a combination of or rapid transition between the previous two conditions three categories of concretions are characterized based on mineralogy carbonate iron oxyhydr oxide and phosphate concretions variation in concretion mineralogy and morphology in the brushy basin member suggests that alkaline saline fluid chemistries created diagenetic microenvironments within a larger lake system to influence concretion precipitation however porosity and permeability are more important factors affecting concretion size morphology and mineralogy than host rock composition diagenetic fluid rock interactions in volcaniclastic sediments can be spatially variable even on tens of centimeters scale

dynamic deformation of the accretionary prism excites very low frequency earthquakes 1 we have detected anomalous very low frequency earthquakes within the accretionary prism along the nankai trough southwestern japan centroid moment tensor inversion analysis reveals that the earthquake hypocenters are distributed at 10 km depth above the upper surface of the subducting philippine sea plate and within 50 70 km landward of the trough axis the focal mechanisms indicate reverse faulting their hypocenters are distributed beneath a deformation zone of an accretionary prism in sea floor topography these observations suggest that the occurrence of very low frequency earthquakes is related to numerous reverse fault systems within the accretionary prism and that the earthquakes reflect the dynamics of deformation within this accretionary prism

recurrent slow slip events as a barrier to the northward rupture propagation of the 2016 pedernales earthquake central ecuador the northern ecuador segment of the nazca south america subduction zone shows spatially heterogeneous interseismic coupling two highly coupled zones 0 4 s 0 35 n and 0 8 n 4 0 n are separated by a low coupled area hereafter referred to as the punta galera mompiche zone pgmz large interplate earthquakes repeatedly occurred within the coupled zones in 1958 mw 7 7 and 1979 mw 8 1 for the northern patch and in 1942 mw 7 8 and 2016 mw 7 8 for the southern patch while the whole segment is thought to have rupture during the 1906 mw 8 4 8 8 great earthquake we find that during the last decade the pgmz has experienced regular and frequent seismic swarms for the best documented sequence december 2013 january 2014 a joint seismological and geodetic analysis reveals a six week long slow slip event sse associated with a seismic swarm during this period the microseismicity is organized into families of similar earthquakes spatially and temporally correlated with the evolution of the aseismic slip the moment release 3 4 1018 nm mw 6 3 over a 60 40 km area is considerably larger than the moment released by earthquakes 5 8 1015 nm mw 4 4 during the same time period in 2007 2008 a similar seismic aseismic episode occurred with higher magnitudes both for the seismic and aseismic processes cross correlation analyses of the seismic waveforms over a 15 years long period further suggest a 2 year repeat time for seismic swarms which also implies that sses recurrently affect this area such sses contribute to release the accumulated stress likely explaining why the 2016 pedernales earthquake did not propagate northward into the pgmz

fresh water carbonates from the lower freshwater molasse oligocene western switzerland sedimentology and stable isotopes abstract the lower freshwater molasse of western switzerland comprises a thick series of continental deposits of late oligocene early miocene age fresh water carbonates occur at two main horizons within this succession lower chattian palustrine carbonates calcaires inferieurs show a shallow fresh water fauna flora of ostracods and charophytes but display clear evidence of subaerial exposure in the form of glaebule pisoid formation circumgranular cracking rhizoliths and microkarstic cavities repeated desiccation led to locally intense modification by pedogenesis these horizons record the development of shallow ephemeral lakes at the northern margin of the swiss molasse basin stable isotope analyses were carried out on 46 calcite samples data from matrix and intraclasts reveal typical fresh water compositions 13c 5 to 7 5 18o 5 5 to 9 a weak co variant trend suggests deposition in hydrologically closed lakes although the range of 13c values recorded is also consistent with pedogenetic overprinting associated with subaerial exposure spar cements and vadose crystal silts display 13c compositions from 6 to 7 but show light 18o values from 10 to 11 recording formation from meteoric waters upper chattian carbonates calcaires d eau douce et dolomie include algal ostracodal laminites interpreted as profundal lake deposits as well as bioturbated shallow lake charophyte ostracod mudstones and wackestones sandy wackestones and white dolomite stable isotope analyses 20 calcites 2 dolomites show 13c values from 2 to 6 and 18o from 6 to 11 data for laminites and biomicrites plot in different fields variations in carbon isotopic composition may be attributable to higher organic productivity during high lake stands the laminites show heavier 13c values or to areal differences in the proportions of biogenic authigenic and detrital carbonate 13c values are generally higher in areas of greater detrital carbonate supply the heavier 18o values shown by the dolomites 13 c 3 18 o 0 to 1 suggest formation from evolved evaporitic lake waters these carbonates record deposition in an extensive possibly deeper lake complex subject to clastic input from the alps in the south

paleohydrology of the late miocene ridge basin lake california uppermost miocene lacustrine deposits of the ridge basin california contain benthic microbial carbonates as fragmentary crusts on clasts in resedimented conglomerates of the violin breccia deposited adjacent to the fault controlled southwestern margin of the basin and as fragments and more extensive in situ stromatolitic units within the ridge route formation around the northeastern part of the basin ridge route microbialites formed in the open waters of the ridge basin paleolake and have 18 o values that are significantly higher than those from the violin breccia the latter may have formed in warm littoral pools or in streams maintained by local runoff their 18 o compositions are consistent with carbonate precipitation from meteoric waters supplied by rainfall dominated by 67 75 winter precipitation at temperatures of 16 17 c ridge route formation microbialites have a wide range of 13 c and 18 o values and indicate that the lake fluctuated between hydrologically open and closed conditions light carbon isotopic compositions for carbonate that precipitated during periods of open basin conditions suggest that inflow waters came from a fluvial system with a well vegetated flood or delta plain relatively high 18 o values imply that the lake was not maintained by local rainfall but depended on inflow that came either from an upstream lake or from a region to the east or northeast where the rainfall regime was dominated by isotopically heavy summer precipitation

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

major controls on sedimentation during the evolution of a continental basin pliocene pleistocene of the guadix basin betic cordillera southern spain abstract sequence stratigraphy based on climatic tectonic and base level parameters can be used to understand carbonate sedimentation in continental basins the uppermost continental fill of the guadix basin betic cordillera containing both siliciclastics and carbonates is investigated here in its central sector a thick succession of fluvio lacustrine sediments appear hosting several important pliocene and pleistocene macrovertebrate sites fonelas project the need to characterize the stratigraphic and sedimentologic context of these important paleontologic sites has lead to litho magneto and biostratigraphic studies these data together with the sedimentologic analysis of the pliocene and pleistocene siliciclastic and carbonate successions establish a sedimentary model for the fluvio lacustrine sedimentation of the two last stages of sedimentation in the guadix basin units v and vi unit v comprises mostly fluvial siliciclastic sediments with less abundant carbonate beds interpreted as floodplain lakes or ponds the latter unit vi is dominated by vertically stacked carbonate palustrine successions using two pre existent continental stratigraphic models the influence of climate tectonism and stratigraphic base level during the last 3 5 ma on the sedimentary evolution of the fluvio lacustrine system in the guadix basin especially the carbonate sedimentation patterns is outlined

north america s largest dinosaur trackway site implications for morrison formation paleoecology little known exposures of the upper jurassic morrison formation from the purgatoire valley of southeastern colorado have yielded the world s largest continuously mapped assemblage of dinosaur trackways body fossils include plant invertebrate and vertebrate remains indicative of predominantly fresh water conditions the tracks occur in a lacustrine sequence characterized by 1 shallow water shales 2 micritic shoreface limestones with ooids intraclasts ripple marks mud cracks and 3 minor quartzose sandstone with salt crystal casts analysis of these sedimentary facies suggests that in southeastern colorado lakes were larger and longer lived than in other morrison paleoenvironments trackway orientations and footprint depth contours pinpoint the location of the paleoshoreline at successive levels in the section detailed mapping of 1 300 footprints in bed 2 has revealed more than 100 trackways which testify to the activity of both quadrupedal and bipedal dinosaurs the respective ratio based on trackway counts is 40 60 the quadrupedal tracks are attributed to sauropods and represent the first ever discovered in north america they also exhibit the first known manus claw impressions and are in need of formal description more than 90 of the bipedal tridactyl prints lack claw impressions and are tentatively therefore referred to the ornithopoda cf gypsichnites possibly a camptosaurus the small proportion with distinct claw impressions may represent allosaurus resulting estimates of species diversity 5 and predator prey ratio 1 30 are in general agreement with the estimates of other authors based on skeletal remains and they suggest that the purgatoire river tracks may accurately reflect the composition of the dinosaur fauna distinctive groupings of parallel non overlapping trackways suggest gregarious behavior among sauropods and tridactylous forms

environmental controls on perennial and ephemeral carbonate lakes the central palaeo andean basin of bolivia during late cretaceous to early tertiary times abstract in the central palaeo andean basin potosi basin of bolivia the up to 450 m thick el molino formation campanian maastrichtian to early tertiary includes two main carbonate lacustrine episodes each of different extent and duration these episodes are separated by an extensive development of alluvial facies floodplain deposits and limestones deposited in playa lakes or isolated ponds the el molino formation has been investigated in six different areas of the potosi basin and affords the opportunity to document climatic and tectonic controls on the development of perennial and ephemeral carbonate lacustrine systems the first lacustrine episode originated predominantly in perennial lakes with wave dominated low gradient ramp type margins outer marginal lacustrine facies include winnowed oolitic grainstones ostracod packstones and microbialite bioherms more agitated areas were characterized by nearshore oolitic bars with associated thrombolite mounds the fossil content and the lack of significant precipitation of evaporites indicate that the lake waters were of low salinity probably oligohaline during most of this period after the first lacustrine episode the widespread development of terrigenous alluvial facies floodplain deposits with interspersed playa lakes or isolated ponds in depressions on the floodplain may indicate a change in the net water budget the second lacustrine episode is dominated by dark micritic limestones and to a lesser extent microbialite bioherms which developed under semiarid climatic conditions this episode includes the deposits of ephemeral saline locally alkaline shallow lakes which were characterized by low energy low gradient ramp type margins the stable isotopic analysis of 163 carbonate samples covering the different facies and depositional settings displays a wide range of values 14 2 18 o and 12 9 13 c that is typical of nonmarine environments the distribution of the values indicates that during the deposition of the el molino formation the basin was hydrologically closed and experienced no strong hydrogeographical changes except for variations in the palaeolake level related to fluctuations in the regional p e ratio these are recorded by two main isotopic trends related to changes between perennial and ephemeral lacustrine conditions lacustrine sedimentation was controlled predominantly by climatically driven hydrological changes with repeated oscillations of the water level expansion and contraction and subsequent fluctuations in the width of lacustrine facies belts

taphonomic analysis of an autochthonous fossil concentration in jurassic lacustrine deposits of patagonia argentina abstract a new fossiliferous level from the las chacritas member bajocian callovian of the canadon asfalto formation which crops out in the canadon asfalto basin extraandean chubut argentina was analyzed the study of this assemblage was made on the basis of paleoecological sedimentological and taphonomic criteria this polytypic assemblage is composed mainly of bivalves spinicaudatans gastropods and ostracods associated with plant remains such as brachyphyllum sp charophytes conifers seeds and indeterminate remains the tabular bed of oncolitic packstone facies corresponds to a shallow marginal lacustrine environment of intense organic productivity taphonomic and paleoecological features such as closed articulated valves random orientation and size frequency histograms indicate that the fauna is autochthonous the short life cycle with a quick turnover of the population suggests that the time averaging would only comprise a few years in addition the analysis of energy dispersive x ray spectrometry supports early diagenesis affecting the remains and favoring the dissolution of aragonite calcite as well as the silicification of shells therefore this fossil assemblage can be classified as a sedimentological concentration which could have been originated by seasonal cyclicity in an environment subject to water level fluctuations

pennsylvanian to jurassic eolian transportation systems in the western united states peterson f 1988 pennsylvanian to jurassic eolian transportation systems in the western united states in g kocurek editor late paleozoic and mesozoic eolian deposits of the western interior of the united states sediment geol 56 207 260 the direction of sediment transport in eolian sandstones of permsylvanian to jurassic age was interpreted from crossbedding resultants vector means obtained from studies of eolian rocks in the western u s supplemented by data from the few eolian units of eastern north america these were compiled from the published or unpublished theses hterature from unpublished fidd data contributed by colleagues or from measurements made for this study in addition new paleogeographic maps were compiled to evaluate the influence of geographic features on the atmospheric circulation patterns that are inferred from the crossbedding studies regionally the crossbedding indicates northeasterly northerly or northwesterly winds present coordinates from pennsylvanian through most of middle jurassic time a rather abrupt change in wind directions occurred in late middle jurassic time late part of the cauovian age when westerly wind patterns developed by the late jurassic the winds shifted to southwesterly calculations of the consistency factor vector mean strength made from region wide analyses of the resultants indicate fairly unidirectional winds from the permsylvanian through the early jurassic middle jurassic circulation was more varied judging from crossbedding studies in the lower part of the entrada sandstone crossbedding in upper jurassic eolian rocks of wyoming and south dakota yielded a random pattern but upper jurassic rocks farther south on the colorado plateau and adjoining areas show a return to a fairly unidirectional pattern comparing the resultants with their reconstructed paleogeographic setting shows surprisingly little influence of major geographic features on overall circulation patterns however the greatest amount of local variation occurred at or near highly indented shorelines where the temperature contrast between land and water produces local wind currents that may vary appreciably from regional circulation patterns although they do not cause noticeable horizontal deflections in wind patterns small and low topographic highs appear to be able to promote the development of a dune field if a source of sand is available and if streams do not enter the growing dune field

sedimentology and paleoenvironments of the las chacritas carbonate paleolake canadon asfalto formation jurassic patagonia argentina abstract the las chacritas member is the lower part of the canadon asfalto formation jurassic the unit is a completely continental limestone succession with volcanic contributions that were deposited during the development of the canadon asfalto rift basin chubut province patagonia argentina a detailed sedimentological analysis was performed in the fossati depocenter to determine the paleoenvironments that developed in the context of this rift the las chacritas member represents a carbonate paleolake system with ramp shaped margins associated with wetlands that were eventually affected by subaerial exposure and pedogenesis this process is represented by three main subenvironments a a lacustrine setting sensu stricto lacustrine limestone facies association represented by mudstones wackestones containing porifera spicules f1 intraclastic packstones f6 and tabular stromatolites f10 in which deposition and diagenesis were entirely subaqueous b a palustrine setting palustrine limestone facies association containing microbial mudstones f2 intraclastic sandy packstone with ostracode remains f3 oncolitic packstone f5 brecciated limestone f7 and nodular mottled limestone f8 representing shallow marginal areas affected by groundwater fluctuations and minor subaerial exposure and c a pedogenic paleoenvironment pedogenic limestone facies association including intraclastic limestone f4 and packstones containing microcodium f9 facies displaying the major features of subaerial exposure pedogenic diagenesis and the development of paleosols the fluvial palustrine lacustrine succession shows a general shallow upward trend in which contraction expansion cycles are represented delimited by exposure and surface erosion the variations in the successive formations reflect the responses to fluctuations in a combination of two major controls the tectonic and local climatic variables the predominance of the palustrine facies associations was determined by its accommodation space as well as the local climate conditions the variations in the lacustrine limestone facies associations reflect differential patterns of subsidence within the sub basin the diagnostic features of the palustrine limestone facies associations organic matter om content microinvertebrate fauna abundant mud cracks brecciation presence of evaporitic minerals frame the sub basin in a climatic context intermediate between arid and subhumid conditions

shallow episodic tremor near the nankai trough axis off southeast mie prefecture japan we analyzed long term continuous seismic records from september 2015 to april 2016 of dense ocean floor network system for earthquake and tsunamis an ocean floor observation system deployed around the fore arc slope of the nankai subduction zone to investigate shallow tremor near the trough axis we found that the activity of shallow tremor was concentrated in two time periods 6 days in october 2015 and 2 weeks in april 2016 during the episode in april 2016 migration and triggering of tremor were observed these characteristics are similar to those of tremor in the deeper part of the subduction zone the triggering of tremor indicates that the tremor activity is very sensitive to nearby stress perturbation in the area of this study which is near the initiation points of past large earthquakes along the nankai trough therefore it is very important to monitor tremor activity in this region for understanding the stress accumulation process of megathrust earthquakes

near field observations of an offshore mw 6 0 earthquake from an integrated seafloor and subseafloor monitoring network at the nankai trough southwest japan an mw 6 0 earthquake struck 50 km offshore the kii peninsula of southwest honshu japan on 1 april 2016 this earthquake occurred directly beneath a cabled offshore monitoring network at the nankai trough subduction zone and within 25 35 km of two borehole observatories installed as part of the international ocean discovery program s nantroseize project the earthquake s location close to the seafloor and subseafloor network offers a unique opportunity to evaluate dense seafloor geodetic and seismological data in the near field of a moderate sized offshore earthquake we use the offshore seismic network to locate the main shock and aftershocks seafloor pressure sensors and borehole observatory data to determine the detailed distribution of seafloor and subseafloor deformation and seafloor pressure observations to model the resulting tsunami contractional strain estimated from formation pore pressure records in the borehole observatories equivalent to 0 37 to 0 15 strain provides a key to narrowing the possible range of fault plane solutions together these data show that the rupture occurred on a landward dipping thrust fault at 9 10 km below the seafloor most likely on the plate interface pore pressure changes recorded in one of the observatories also provide evidence for significant afterslip for at least a few days following the main shock the earthquake and its aftershocks are located within the coseismic slip region of the 1944 tonankai earthquake mw 8 0 and immediately downdip of swarms of very low frequency earthquakes in this region illustrating the complex distribution of megathrust slip behavior at a dominantly locked seismogenic zone

abiogenic silica layers within a fluvio lacustrine succession bolzano volcanic complex northern italy a permian analogue for magadi type cherts thin layers of chert occur within a fluvio lacustrine succession sandwiched between acidic volcanic rocks of the lower permian bolzano volcanic complex in northern italy these cherts are interpreted as analogues to magadi type abiogenic chert known from modern volcanic lake settings soft sediment deformation features shrinkage cracks and well preserved palynomorphs document very early diagenetic silica precipitation volume loss by dehydration and consolidation prior to mechanical compaction of the sediment transformation to quartz and concomitant re crystallization resulted in a variety of silica textures dominated by microflamboyant quartz the oxygen isotopic composition of chert samples ranges from 25 4 to 29 0 and is negatively correlated with crystal size and ordering

seasonal wetland carbonate sequences and dynamic catenas a re appraisal of palustrine limestones abstract palustrine carbonate cyclothems are compared directly to well documented peritidal carbonate cyclothems in the case of the latter the trend of increasing degree of exposure seen vertically through a cyclothem has been interpreted as due to the aggradation of the sediment surface relative to the semi diurnal tidal regime palustrine cyclothems also show similar increases in the degree of exposure and this is interpreted as the effect of sediment aggradation in a seasonal wetland regime the resulting changes in the drainage characteristic revealed in a palustrinc cyclothem reflect a type of seasonally variable catenary relationship referred to here as a dynamic catena this model explains the key features of palustrine cyclothems and suggests the importance of seasonal wetland environments in ancient continental settings

tsunamigenic potential of the shallow subduction plate boundary inferred from slow seismic slip at subduction zones slip along the shallowest parts of the plate boundary is generally thought to be aseismic observations of very low frequency earthquakes occurring at shallow levels on the plate boundary of the nankai trough subduction zone imply that slow but seismic slip can occur there and could potentially generate tsunamigenic earthquakes

carbonate lake deposits associated with distal siliciclastic perennial river systems abstract the genesis of thick accumulations of carbonate lake deposits on the siliciclastic floodplains of perennial rivers situated below the regional spring line requires 1 a significant source for calcium in the watershed and 2 a protected area to accumulate calcite the phanerozoic record of fluvial deposits shows that anastomosing rivers with carbonate rich provenance situated in distal areas below the spring line are the best environments for floodplain accumulation of significant carbonate lake deposits anastomosing rivers exist below the regional spring line and have isolated flood basins generally protected from bedload by high levees receiving suspended and dissolved load during flooding events numerical modeling to test the rate of accumulation for these carbonate sediments was performed using stratigraphic data from the pennsylvanian succession containing floodplain limestones of the stewart quadrangle of athens county in ohio usa limestone volumes for six limestone units upper pittsburgh fishpot sewickley benwood arnoldsburg uniontown and waynesburg limestones were calculated with the assumption of overland input of dissolved calcite from carbonate source areas in comparing the calcium input rate to the amount of calcium calculated from limestone unit volumes overland transport of calcium ions not spring input can supply sufficient ions to accumulate thick carbonates over the short lifetime of floodplain lakes within anastomosing river systems

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

isotope signatures associated with early meteoric diagenesis the environments in which carbonate diagenesis proceeds have been documented in previous studies of holocene and late pleistocene sediments and limestones on barbados west indies variations in the carbon and oxygen isotopic composition of limestones produced during early freshwater diagenesis have been observed in this study to occur in specific patterns six potentially useful patterns emerge when one views stable isotope data within a stratigraphic framework 1 the subaerial exposure surface is characterized by strongly 12c enriched limestones 13c compositions of underlying limestones grow progressively heavier with increasing depth 2 the subaerial exposure surface may also be marked by slight 18o enrichment 3 an abrupt shift in 18o values may differentiate sediments above the exposure surface from those below 4 sediments altered in the marine meteoric mixing zone may be characterized by positive covariance between their 18o and 13c compositions 5 the vadose phreatic boundary may be marked by a sharp increase in 13c values in the seaward portions of a fresh groundwater system and 6 samples contemporaneously altered in a single fresh groundwater system within an areally restricted region should display a narrow range of 18o and a wide range of 13c compositions analysis of samples from five palaeozoic and mesozoic formations which contained petrographic evidence of early freshwater diagenesis showed that isotope patterns similar to those observed in barbados limestones have been preserved in rocks as old as mississippian these isotope patterns could prove to be useful for identifying diagenetically induced porosity trends in carbonate rocks they might be used to identify limestones diagenetically altered in meteoric environments to identify mixing zone cements and dolomites and to trace the regional and vertical distributions of early meteoric groundwater systems in ancient carbonate formations

episodic tremor and slip near the japan trench prior to the 2011 tohoku oki earthquake change in the rates of aseismic deformation prior to large earthquakes is a major area of interest in earthquake physics here we present evidence that episodic tremor and slip occurred in the shallow subduction zone within the source region of the 2011 tohoku oki earthquake prior to the main shock ocean bottom seismometers near the japan trench recorded some excitations in amplitude of ambient noise level accompanying both the 2008 and 2011 slow slip events the observed signals show that low frequencies of 5 8 hz dominated suggesting that the excitations were due to small low frequency tremors accompanying the slow slip events the largest amplitude tremor was observed just before the 2011 event the estimated sources of tremors were possibly distributed within the coseismic slip area of the 2011 event suggesting the shallow plate boundary thrust near the trench is a general location of slow earthquakes

distortion of the apparent s wave radiation pattern in the high frequency wavefield tottori ken seibu japan earthquake of 2000 summary the distortion properties of the apparent s wave radiation pattern in the high frequency seismic wavefield of over f 2 hz is investigated using a large number of waveform records of the main shock and 29 aftershocks of the tottori ken seibu japan magnitude mw 6 6 earthquake in 2000 the dense seismic records from the kik net strong motion network show a clear four lobe pattern in the apparent s wave radiation pattern in the low frequency wavefield of f 2 hz and shows an almost isotropic distribution in all directions as the frequency increases above 5 hz the distortion of the apparent s wave radiation pattern in the high frequency wavefield increases as travel distance increases therefore the path effect caused by the scattering of seismic waves due to small scale heterogeneities in the crust is a major cause of distortion of the radiation pattern this hypothesis is examined by a 2 d finite difference method simulation of seismic waves in heterogeneous structure models the results of simulations clearly demonstrate the collapse of the s wave front due to seismic wave scattering in the heterogeneous structure by comparing the observed wavefield and the results of simulations using different sorts of stochastic heterogeneous models the most preferable model that can explain the observation is described by a von karman autocorrelation function with correlation distance of a 3 5 km order of 0 5 and rms value of e 0 07 however our simple stochastic random heterogeneity model proposed herein somewhat overestimates the scattering of low frequency signals below 2 hz

jurassic lake t oo dichi a large alkaline saline lake morrison formation eastern colorado plateau a large alkaline saline lake lake t9oo9dichi9 occupied the entire eastern part of the colorado plateau region during deposition of the brushy basin member of the upper jurassic morrison formation the lake extended from near the site of albuquerque new mexico to near the site of grand junction colorado and occupied a region that encompassed the san juan and ancestral paradox basins making it the largest ancient alkaline saline lake known the lake was typically shallow and frequently evaporated to dryness although the water table was probably never far beneath the surface intermittent streams carried detritus from source areas to the west and southwest far out into the lake basin a reflection of a low depositional gradient and the ephemeral nature of the lake prevailing westerly winds carried silicic volcanic ash to the lake basin from an arc region to the west and southwest a lateral hydrogeochemical gradient characterized by increasing salinity and alkalinity from the margin of the lake to the center developed in pore waters of the lacustrine sediments and resulted in alteration of the ash to a variety of authigenic minerals that define concentric zones within the lake basin the basinward progression of diagenetic mineral zones is smectite clinoptilolite analcime potassium feldspar albite a concomitant lateral zonation of mixed layer illite smectite developed from highly smectitic in the outermost zones to highly illitic in the central zone authigenic albite and illitic mixed layer clay minerals previously thought to require elevated temperatures for formation crystallized during early diagenesis at syndepositional temperatures in the lacus trine sediments of lake t9oo9dichi9 this study presents evidence for a syndepositional origin for both of these minerals these findings have important implications in terms of limiting the use of these minerals as geothermometers recognition of alkaline saline lake deposits in the morrison formation significantly alters interpretations of depositional environments of this formation and it also has important implications for paleoclimatic interpretation late jurassic climate was apparently much more and than had previously been thought in fact sedimentologic evidence suggests that the lake basin was typically dry for extended periods and enjoyed only brief wet intervals this conclusion has important consequences for environmental interpretation of the habitat that was favorable for large herbivorous dinosaurs which thrived in the late jurassic

fossil spring deposits in the southern great basin and their implications for changes in water table levels near yucca mountain nevada during quaternary time fossil spring deposits are common in the southern great basin and their distribution provides important constraints on the hydrologic response of the regional water table to climate change this information is crucial because the proposed high level nuclear waste repository at yucca mountain will be located 200 400 m above the modern water table water tables will rise in response to a future return to glacial climates but the magnitude of the change and the consequences for radionuclide travel times and overall repository integrity are key uncertainties increased recharge during past pluvial periods in the spring mountains and sheep range caused water tables to rise and ground water to discharge over broad expanses of the las vegas valley system and in nearby pahrump sandy and coyote springs valleys in contrast other valleys in the region contain only small areas of pleistocene discharge resulting from local damming of ground water by faults that cut valley alluvium in these instances which include the valley wells area and piute and northern coyote springs valleys smaller ranges such as the clark and new york mountains supplied the moisture the change in water table levels since the last full glacial period varies between and within valleys from as little as 10 m in several areas to 95 m in the coyote springs valley at yucca mountain the water table has probably changed by 115 m in response to climate change the spring deposits and the mollusk faunas found with them often misinterpreted as lacustrine in origin share many essential features with active spring systems in northeast nevada deposits associated with discharge mainly consist of pale brown silt and sand that is entrapped by dense stands of phreatophytes covering valley bottoms when water tables are high pale green mud containing a mix of aquatic semiaquatic and moist terrestrial mollusks accumulates in wet meadows and marshes associated directly with spring discharge the record in subbasins of the las vegas valley system is dominated by late wisconsin age sediments although pond sediments and alluvium belonging to at least one older pre wisconsin pluvial period are also locally exposed deposits from two even earlier episodes of spring discharge both of which also occurred during rancholabrean time 10 to 450 ka are exposed in the pahrump chicago piute and coyote springs valleys and in the valley wells the records from the pahrump and coyote springs valleys are especially well exposed and likely extend back to at least early pleistocene time

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

paleoclimate of the kimmeridgian tithonian late jurassic world i results using a general circulation model abstract the kimmeridgian tithonian 154 7 145 6 ma middle and late late jurassic was a time of expanded continental rifting increased sea floor spreading and a relatively high eustatic sea level stand these processes collectively caused the fragmentation and flooding of the megacontinent pangea as well as the alteration of the global paleoclimate using a version of the community climate model ccm from the national center for atmospheric research we report two kimmeridgian tithonian paleoclimate seasonal simulations with geologically inferred paleotopography one using a co 2 concentration of 280 ppm pre industrial level and the other 1120 ppm increasing the co 2 four fold warms virtually the entire planet the greatest warming occurs over the higher latitude oceans and the least over the equatorial and subtropical regions simulation of a warmer planet with an elevated greenhouse effect fits the distribution of paleoclimatically sensitive faunas floras and sedimentary rocks model results indicate that sea ice was restricted to the high latitudes of the boreal and austral seas making landfall only in restricted areas the trade winds bring heavy rainfall in december january february to eastern gondwana and in june july august to the tethys sea margins a strong june july august monsoon occurs over southeast asia the distribution of coals correlates to precipitation sufficient to maintain gymnosperm forests and coastal areas where water saturated sediments are a result of eustatic high stands of sea level evaporites are localized to areas of negative precipitation evaporation runoff is restricted to regions of intense precipitation overall the 1120 ppm co 2 simulation provides a reasonable paleoclimate for the kimmeridgian tithonian and provides a standard until a ccm with oceanic heat transport a coupled atmospheric oceanic model or one with a finer grid cell configuration is available the results need further scrutiny in areas with more detailed geologic information

jurassic early cretaceous paleogeography and paleoenvironments of the north eastern margin of gondwana insights from the carpentaria basin australia abstract although jurassic early cretaceous sedimentary systems were extensively developed on northeastern gondwana deciphering their paleogeography has been complicated by poor exposure and the lack of a robust chronostratigraphic framework the southeastern margin of the carpentaria basin northeastern australia is one of the few regions where these sedimentary systems are extensively exposed employing a combination of facies analysis and new data from paleontology and detrital zircon geochronology we present a temporally and environmentally refined paleogeographic framework for this region a late jurassic southeasterly directed marine incursion invaded northeastern gondwana extending inland across the carpentaria basin as demonstrated by a thin 30 m marine influenced fluvio estuarine stratigraphic succession capped by a sequence bounding 30 myr paraconformity the depositional hiatus marked the late jurassic early cretaceous uplift of the euroka arch with loss of sedimentary and fluvial connectivity between the carpentaria basin and adjoining eromanga basin subsequent deposition by low accommodation fluvial systems resulted in a thin fluviatile depositional package developing during the early cretaceous paleocurrent and provenance data indicate that the middle to late jurassic c 170 160 ma fluvial systems predating the paraconformity extended from the eromanga basin to the south across the southeastern carpentaria basin transporting sediment from distal sources in the lachlan orogen of southeastern australia fluvial systems of the southeastern carpentaria basin post dating the paraconformity and euroka arch uplift show a provenance shift to easterly sources in the mossman orogen and kennedy igneous association previously unrecognised jurassic early cretaceous igneous activity provided a persistent source of sediment to the southeastern carpentaria basin succession due to reworking of air fall tuff from an active magmatic arc located on the continental margin of northeastern gondwana

migrating tremor off southern kyushu as evidence for slow slip of a shallow subduction interface detection of shallow slow earthquakes offers insight into the near trench part of the subduction interface an important region in the development of great earthquake ruptures and tsunami generation ocean bottom monitoring of offshore seismicity off southern kyushu japan recorded a complete episode of low frequency tremor lasting for 1 month that was associated with very low frequency earthquake vlfe activity in the shallow plate interface the shallow tremor episode exhibited two migration modes reminiscent of deep tremor down dip of the seismogenic zone in some other subduction zones a large scale slower propagation mode and a rapid reversal mode these similarities in migration properties and the association with vlfes strongly suggest that both the shallow and deep tremor and vlfe may be triggered by the migration of episodic slow slip events

late jurassic biogeochemical microenvironments associated with microbialite coated unionids bivalvia asturias n spain abstract the vega formation upper jurassic asturias spain contains two kimmeridgian outcrops the abeu and huerres sections with bivalves coated with carbonate microbialites oncoids the bivalve shells in the abeu section were replaced early by calcite while those of the huerres section were dissolved and the moulds filled by late diagenetic cements for the abeu shells there was a loss of sr and a gain of mg fe and mn during the replacement process but much of the original organic matter was retained part of the s present can be linked to this organic matter and part to the sulphate that replaced the carbonate groups in the calcite the thin microbialites inside the shells of some of the huerres bivalves have allowed us to estimate the influence of the growth rate on the incorporation of trace elements in calcite with an approximately six times lower growth rate the internal microbialite incorporates less mg and s and more fe and mn than the external one while maintaining the sr content the trace element content mg s sr fe and mn of the huerres and abeu microbialites are similar these coatings may therefore have been formed in the same type of freshwater but in different microenvironments given the substantial sulphate content of the microbialites from both sections this freshwater probably came from hot springs however the high fe mn ratio of the abeu microbialites suggests a reducing environment during their formation indeed 18o and 13c data confirm that the abeu and huerres microbialites were formed in different microenvironments the positive covariance for 18o and 13c of the abeu microbialites and replaced shells r2 0 83 and the wide range of variation for 18o 2 80 together suggest that the microbialite crusts grew in isolated ponds where evaporation was dominant in the huerres microbialites the positive covariance for 18o and 13c r2 0 59 and the narrow range of variation for 18o 0 74 indicate that the huerres section was formed in a more open environmental system where degassing predominated over evaporation

palustrine sedimentation and associated features grainification and pseudo microkarst in the middle miocene intermediate unit of the madrid basin spain abstract a rather thick sequence 50 75 m of lacustrine limestones forms the uppermost part of the intermediate unit middle miocene in the ne part of the madrid basin central spain a gradual change from distal alluvial to open lake facies is recorded in this area red mudstones passing vertically to strongly mottled limestones are typical of the transition from distal alluvial to marginal lake deposits a wide variety of facies occur in the marginal lacustrine facies association all of them showing pedogenic features e g root traces alveolar septal structures pseudo microkarst micrites and biomicrites are interpreted as open lacustrine deposits although not as strongly pedogenically modified as the marginal lacustrine facies they still show evidence of subaerial exposure the carbonate sequence was deposited in a low gradient shallow lake system in which slight fluctuations in the water level caused extensive emergence pedogenic processes affected most of the lake deposits but modification was more intense in the marginal facies biogenic activity and mechanical reworking at lake margins led to the formation of pedogenic diagenetic pseudo microkarst and peloidal and or intraclastic limestones

low frequency tremors associated with reverse faults in a shallow accretionary prism abstract the shallow part of a seismogenic subduction zone is thought to play an important role in tsunami genesis during large interplate thrust earthquakes near the updip portion of the seismogenic zone along the nankai trough splay faults which are major active reverse faults in the accretionary prism likely rupture during large interplate earthquakes such as the 1944 m w 8 2 tonankai earthquake off kii peninsula we observed low frequency tremors associated with reverse faults in a shallow accretionary prism off kii peninsula at close range by using ocean bottom seismographs the tremors were characterized by a dominant frequency range of 2 8 hz and a lack of energy in the frequency range above 10 hz their duration ranged from tens of seconds to a few minutes their source locations lay in three clusters on the landward slope of the nankai trough activity in each cluster continued for from one day to two weeks many of the low frequency tremors were located near the shallowest part of a major splay fault the episodic activity of low frequency tremors and of previously reported very low frequency earthquakes which indicate reverse faulting in the shallow accretionary prism suggests that the reverse faults in the accretionary prism are conditionally stable faults that can become unstable under sufficiently strong dynamic loading such as that caused by a large earthquake such reverse faults as typified by a splay fault can rupture during large interplate earthquakes and generate large tsunamis

spatial distribution of inter layer shear zones at gaobazhou dam site qingjiang river china abstract the spatial distribution of inter layer shear zones is studied based on the fully mapped inter layer shear zones at the gaobazhou dam site on the qingjiang river in hubei province china the field observations revealed that two types of inter layer shear zone under developed and well developed are distributed differently the former are associated with the incompetent rock layers and the latter are controlled by the inter bed folds and lithological properties of the strata to represent their lithological properties geomechanically data on strength by the schmidt hammer test and thickness of each field identified rock layer were collected to form strength sequences and thickness sequences the adjacent rock layers of similar strength are then grouped and two grouped sequences are combined into a single sequence whose individual term is the strength weighted by the exponential function value of the centralized thickness sct the rescaled range r s analysis results of sct sct r s taking into account the presence of inter bed folds are in good agreement with r s analysis results of the spacing sequence of the well developed inter layer shear zones thus the sct r s model has the potential to predict their spatial distributions