ring index a new strategy to evaluate the integrity of tex86 paleothermometry the tex86 tetraether index of 86 carbon atoms sea surface temperature proxy has been increasingly applied in the reconstruction of mesozoic and cenozoic ocean temperatures however the archaeal lipids that compose tex86 indices glycerol dialkyl glycerol tetraethers gdgts can derive from water column production terrestrial sources and or within sediments tex86 sea surface temperature estimates can also be influenced by non temperature factors such as growth phase and nutrient levels here we show that the weighted average of cyclopentane moieties known as the ring index ri can be used to determine if tex86 temperature estimates are influenced by non thermal factors and or deviate from modern analogues we demonstrate that ri and tex86 indices from the published global core top data set and mesocosm cultures are significantly correlated as predicted through the influence of temperature on lipid biochemistry we further show that when ri and tex86 indices in modern or ancient records deviate from the modern global tex86 ri relationship gdgt distributions are not solely controlled by environmental temperature and or tex86 based temperature reconstructions are questionable

correlation of 1 to 10 hz earthquake resonances with surface measurements of s wave reflections and refractions in the upper 50 m resonances observed in earthquake seismograms recorded in seattle washington the central united states and sherman oaks california are correlated with each site s respective near surface seismic velocity profile and reflectivity determined from shallow seismic reflection refraction surveys in all of these cases the resonance accounts for the highest amplitude shaking at the site above 1 hz these results show that imaging near surface reflections from the ground surface can locate impedance structures that are important contributors to earthquake ground shaking a high amplitude s wave reflection recorded 250 m northeast and 300 m east of the seattle kingdome earthquake recording station with a two way travel time of about 0 23 to 0 27 sec about 18 to 22 m depth marks the boundary between overlying alluvium v s 180 m sec and a higher velocity material v s about 400 m sec this reflector probably causes a strong 2 hz resonance that is observed in the earthquake data for the site near the kingdome in the central united states s wave reflections from a high impedance boundary an s wave velocity increase from about 200 m sec to 2000 m sec at about 40 m depth corresponds to a strong fundamental resonance at about 1 5 hz in sherman oaks strong resonances at about 1 0 and 4 hz are consistently observed on earthquake seismograms a strong s wave reflector at about 40 m depth may cause the 1 0 hz resonance the 4 0 hz resonance is possibly explained by constructive interference between the first overtone of the 1 0 hz resonance and a 3 25 to 3 9 hz resonance calculated from an areally consistent impedance boundary at about 10 m depth as determined by s wave refraction data

weights of evidence and logistic regression modeling of magmatic nickel sulfide prospectivity in the yilgarn craton western australia abstract bayesian weight of evidence and logistic regression models are implemented in a gis environment for regional scale prospectivity modeling of greenstone belts in the yilgarn craton western australia for magmatic nickel sulfide deposits the input variables for the models consisted of derivative gis layers that were used as proxies for mappable exploration criteria for magmatic nickel sulfide deposits in the yilgarn about 70 of the 165 known deposits of the craton were used to train the models the remaining 30 was used to validate the models and therefore had to be treated as if they had not been discovered the weights of evidence and logistic regression models respectively classify 71 4 and 81 6 validation deposits in prospective zones that occupy about 9 of the total area occupied by the greenstone belts in the craton the superior performance of the logistic regression model is attributed to its capability to accommodate conditional dependencies amongst the input predictor maps and provide less biased estimates of prospectivity

lithology and shear wave velocity in memphis tennessee we have derived a new three dimensional model of the lithologic struc ture beneath the city of memphis tennessee and examined its correlation with measured shear wave velocity profiles the correlation is sufficiently high that the better constrained lithologic model may be used as a proxy for shear wave velocities which are required to calculate site amplification for new seismic hazard maps for memphis the lithologic model and its uncertainties are derived from over 1200 newly compiled well and boring logs some sampling to 500 m depth and a moving least squares algorithm seventy six new shear wave velocity profiles have been measured and used for this study most sampling to 30 m depth or less all log and velocity observations are publicly available via new web sites

seismic velocity model of the central united states version 1 description and simulation of the 18 april 2008 mt carmel illinois earthquake abstract we have developed a new three dimensional seismic velocity model of the central united states cusvm that includes the new madrid seismic zone nmsz and covers parts of arkansas mississippi alabama illinois missouri kentucky and tennessee the model represents a compilation of decades of crustal research consisting of seismic aeromagnetic and gravity profiles geologic mapping geophysical and geological borehole logs and inversions of the regional seismic properties the density p and s wave velocities are synthesized in a stand alone spatial database that can be queried to generate the required input for numerical seismic wave propagation simulations we test and calibrate the cusvm by simulating ground motions of the 18 april 2008 m w 5 4 mt carmel illinois earthquake and comparing the results with observed records within the model area the selected stations in the comparisons reflect different geological site conditions and cover distances ranging from 10 to 430 km from the epicenter the results based on a qualitative and quantitative goodness of fit gof characterization indicate that both within and outside the mississippi embayment the cusvm reasonably reproduces 1 the body and surface wave arrival times and 2 the observed regional variations in ground motion amplitude cumulative energy duration and frequency content up to a frequency of 1 0 hz in addition we discuss the probable structural causes for the ground motion patterns in the central united states that we observed in the recorded motions of the 18 april mt carmel earthquake online material simulated and observed waveforms and response spectral acceleration ground motion prediction equation comparison

archaeal ammonia oxidation plays a part in late quaternary nitrogen cycling in the south china sea abstract thaumarchaeota as an ammonia oxidizing archaea aoa is crucial for modern marine nitrogen cycling however little is known about its history during the quaternary climate change here isoprenoidal glycerol dialkyl glycerol tetraethers gdgts biomarkers of thaumarchaeota were used to trace the role of aoa in the south china sea scs for the past 160 kyr the gdgt 2 3 ratio was firstly argued as an indicator of contribution of shallow thaumarchaeota cluster that is more active in ammonia oxidization ao than the deep cluster and then was used to reconstruct ao in the past the inferred ao exhibited intensification in the interglacials and moreover showed strong precessional cycles with enhancements at the precessional maxima when boreal winter insolation was the highest the aoa record varied in line with isotope record of organic nitrogen 15 norg that is modulated by the strength of diazotroph n2 fixation nf suggesting a close coupling of increased ao with enhanced nf during periods of weak east asian winter monsoon eawm and hence increase of upper water stratification ao intensification a step of a series of dissolved oxygen consuming processes is hereby hypothesized to encourage nf when the eawm weakens this result might be a reference for the future nf trend in the current situation of enhanced ocean deoxygenation due to global warming

seismic ground motions from a bolide shock wave 1 an intensely brilliant bolide accompanied by an audible sonic boom occurred on the night of 3 november 2003 2150 lt or 4 november 2003 0350 ut in northeastern arkansas the sonic boom was well recorded by 22 three component stations of the center for earthquake research and information cooperative seismic network arrival times and wave polarizations were used to reconstruct the acoustic wave front propagating across the network and to estimate trajectory parameters of the bolide a grid search location technique constrains the trajectory and gives a reference height of 50 100 km above the southern edge of the network an azimuth of propagation of 270 290 toward the northwest and a plunge of 38 48 downward the trajectory and date of the bolide event are consistent with a taurid shower meteor transient ground motions from the sonic boom were studied using plane wave cagniard dehoop and propagator matrix theory for an incident pressure pulse impinging on a layered elastic earth model general characteristics of the vertical and radial polarization and wave frequency content require acoustic coupling within a thin 10 m near surface layer with low p wave 0 25 km s and s wave 0 125 km s velocities ground motions are generally confined to this near surface layer are not sensitive to deeper earth structure within the mississippi embayment unconsolidated sediments and display both leaky mode pl a type of dispersed p type seismic wave and locked mode rayleigh wave propagation acoustic wave ground motion coupling studies may be a useful way to analyze near surface site responses to determine velocity structure in earthquake shaking hazard studies

ground motion simulations of 1811 1812 new madrid earthquakes central united states we performed a suite of numerical simulations based on the 1811 1812 new madrid seismic zone nmsz earthquakes which demonstrate the importance of 3d geologic structure and rupture directivity on the ground motion response throughout a broad region of the central united states cus for these events our simulation set consists of 20 hypothetical earthquakes located along two faults associated with the current seismicity trends in the nmsz the hypothetical scenarios range in magnitude from m 7 0 to 7 7 and consider various epicenters slip distributions and rupture characterization approaches the low frequency component of our simulations was computed deterministically up to a frequency of 1 hz using a regional 3d seismic velocity model and was combined with higher frequency motions calculated for a 1d medium to generate broadband synthetics 0 40 hz in some cases for strike slip earthquakes located on the southwest northeast striking nmsz axial arm of seismicity our simulations show 2 10 s period energy channeling along the trend of the reelfoot rift and focusing strong shaking northeast toward paducah kentucky and evansville indiana and southwest toward little rock arkansas these waveguide effects are further accentuated by rupture directivity such that an event with a western epicenter creates strong amplification toward the northeast whereas an eastern epicenter creates strong amplification toward the southwest these effects are not as prevalent for simulations on the reverse mechanism reelfoot fault and large peak ground velocities 40 cm s are typically confined to the near source region along the up dip projection of the fault nonetheless these basin response and rupture directivity effects have a significant impact on the pattern and level of the estimated intensities which leads to additional uncertainty not previously considered in magnitude estimates of the 1811 1812 sequence based only on historical reports the region covered by our simulation domain encompasses a large portion of the cus centered on the nmsz including several major metropolitan areas based on our simulations more than eight million people living and working near the nmsz would experience potentially damaging ground motion and modified mercalli intensities ranging from vi to viii if a repeat of the 1811 1812 earthquakes occurred today moreover the duration of strong ground shaking in the greater memphis metropolitan area could last from 30 to more than 60 s depending on the magnitude and epicenter online material tables of 1d velocity models used to generate the high frequency synthetics and figures of source models and peak ground motion synthetics

microtremor recordings in northern mississippi abstract this paper presents the results of 305 single point microtremor recordings covering northern mississippi that is situated within the upper mississippi embayment area both long and short term recordings were obtained by a le 3d 20s seismometer over a large network of points where the unconsolidated sediment thickness ust varies from zero to 1400 m applying the nakamura method the recordings were processed to determine predominant frequency f0 and its relation to ust initial results of wind influence on the frequency spectra particularly in low frequency band 0 05 0 2 hz and dominant vibration direction are also presented it is shown that analysis of systematic microtremor recordings can provide a stable and reliable estimation of the predominant frequency from which estimates of average shear wave velocity of overall sediment profile can be derived predominant frequency and average shear wave velocity is reasonably well correlated with ust wind and human activities are found to produce peaks over the low frequency band

3d computational simulation based mineral prospectivity modeling for exploration for concealed fe cu skarn type mineralization within the yueshan orefield anqing district anhui province china abstract the yueshan orefield is one of the best known fe cu orefields in china and is located within the central yangtze metallogenic belt ofin anhui province china the recent discovery of the skarn type zhuchong fe cu deposit at depth within the orefield has highlighted the prospectivity of this area to host deep seated skarn type mineralization however the effectiveness of traditional geophysical exploration techniques is reduced with increasing depth this combined with recent developments in 3d mineral prospectivity modeling has led to the use of a 3d targeting approach for exploration for deep seated and concealed mineralization in this area however to date the usefulness of this approach has been limited by a lack of an approach that could generate more useful 3d predictive maps this study presents a 3d computational simulation based mineral prospectivity modeling approach that identified several exploration targets for concealed and deep seated skarn type mineralization within the yueshan orefield these prospective targets include areas of known mineralization as well as a number of new targets for future mineral exploration in addition the analysis of the resulting data using a capture efficiency curve indicates that these 3d computational simulation approaches can provide additional predictive information for mineral exploration indicating that 3d computational simulation should have a key role in the development and use of future 3d prospectivity modeling techniques during exploration targeting

evidence for deep water deposition of abyssal mediterranean evaporites during the messinian salinity crisis scientific drilling of the abyssal evaporites beneath the deepest parts of the mediterranean basin gave rise to the idea that the mediterranean sea completely evaporated at the end of the messinian herein we show using new organic geochemical data that those evaporites were deposited beneath a deep water saline basin not in a subaerial saltpan as originally proposed abundant fossil organic lipids were extracted from evaporites in mediterranean deep sea drilling project cores the archaeal lipid distribution and new analyses using the ace salinity proxy and tex86 temperature proxy indicate that surface waters at the time of evaporite deposition had normal marine salinity ranging from 26 to 34 practical salinity units and temperatures of 25 28 c these conditions require a deep water setting with a mixed layer with normal marine salinity and an underlying brine layer at gypsum and halite saturation after correction for isostatic rebound our results indicate maximum drawdown of 2000 m and 2900 m relative to modern sea level in the western and eastern mediterranean basins respectively our results are consistent with previously proposed scenarios for sea level drawdown based on both subaerial and submarine incision and backfilling of the rhone and nile rivers which require messinian sea level drops of 1300 m and 200 m respectively this study provides new evidence for an old debate and also demonstrates the importance of further scientific drilling and sampling of deeper part of the abyssal messinian units

archaeal tetraether membrane lipid fluxes in the northeastern pacific and the arabian sea implications for tex86 paleothermometry the newly introduced temperature proxy the tetraether index of archaeal lipids with 86 carbon atoms tex86 is based on the number of cyclopentane moieties in the glycerol dialkyl glycerol tetraether gdgt lipids of marine crenarchaeota the composition of sedimentary gdgts used for tex86 paleothermometry is thought to reflect sea surface temperature sst however marine crenarchaeota occur ubiquitously in the world oceans over the entire depth range and not just in surface waters we analyzed the gdgt distribution in settling particulate organic matter collected in sediment traps from the northeastern pacific ocean and the arabian sea to investigate the seasonal and spatial distribution of the fluxes of crenarchaeotal gdgts and the origin of the tex86 signal transported to the sediment in both settings the tex86 measured at all trap deployment depths reflects sst in the arabian sea analysis of an annual time series showed that the sst estimate based on tex86 in the shallowest trap at 500 m followed the in situ sst with a 1 to 3 week time delay likely caused by the relatively low settling speed of sinking particles this revealed that the gdgt signal that reaches deeper water is derived from the upper water column rather than in situ production of gdgts the gdgt temperature signal in deeper traps at 1500 m and 3000 m did not show a seasonal cyclicity observed in the 500 m trap but rather reflected the annual mean sst this is probably due to a homogenization of the tex86 sst signal carried by particles as they ultimately reach the interior of the ocean our data confirm the use of tex86 as a temperature proxy of surface ocean waters

paleoenvironmental changes in the northern south china sea over the past 28 000years a study of tex86 derived sea surface temperatures and terrestrial biomarkers abstract we have generated a record of tex86 tex 86 h derived sea surface temperatures ssts over the last 28 ka for core md97 2146 from the northern south china sea scs the tex 86 h derived temperature of a core top sample corresponds to the ssts in warmer seasons the sst record shows a drop during the oldest dryas period an abrupt rise at the onset of the bolling allerod period a plateau across the younger dryas period and an abrupt rise at the beginning of the holocene the glacial interglacial contrast in tex 86 h derived temperature is almost the same as that in foraminiferal mg ca ratio derived temperature but it is larger than those in u 37 k and transfer function derived temperatures possible interpretations are 1 the seasonal shift of glycerol dialkyl glycerol tetraether gdgt production 2 the overestimation of temperature change by tex 86 h and 3 the underestimation of temperature change by u 37 k and transfer function approaches the similar variation in tex 86 h derived temperature at the study site and chinese stalagmite 18o during the last deglaciation suggests that changes in tex 86 h derived temperature in this period reflected atmospheric and oceanic reorganization on a millennial timescale the long chain n alkanes are mainly of higher plant origin before 14 ka and a mixture of higher plant and lithic origins after 14 ka the abundance ratio of long chain to short chain n fatty acids decreases at 15 ka suggesting a drastic change in sediment sources at 14 15 ka we attribute the higher content of fresh higher plant n alkanes and long chain n fatty acids before 14 15 ka to enhanced aeolian transportation and or arid environments increased precipitation likely due to intensified summer monsoon after 14 15 ka enhanced the erosion of sedimentary rocks and increased the contribution of lithic n alkanes

alkenone temperature and carbon isotope records temporal resolution offsets and regionality 1 over the last decade the number of paleoceanographic studies presenting and discussing alkenone derived sea surface temperature sst records and carbon isotope ratios of alkenones 13calkenones has increased rapidly this short review paper summarizes the state of knowledge about sst variability determined by alkenone paleothermometry in sediment trap studies and investigations of marine sediments for timescales of single to millions of years in particular from the evaluation of quaternary records characteristic temperature pattern have emerged that mismatch with sst curves estimated by other methods e g foraminiferal stable oxygen isotopes and transfer functions in future studies the spatial distribution of such variance patterns typically observed in alkenone sst curves should be checked in order to better understand their meaning for ocean circulation changes and a possible relationship to global climate change on the other hand certain physical and biological processes have the potential to put the reliability of alkenone sst curves into question accordingly examples for possible effects of bioturbational mixing lateral transport of remote alkenones diagnetic alteration and degradation of alkenone composition biogeographic and temporal diversity changes in alkenone producing algae as well as the influence of changes in salinity and nutrient conditions on the alkenone paleotemperature signal are briefly mentioned highlighting the need for more detailed future studies on these issues finally a short summary on the status of the use of the 13calkenones signal as a proxy for past variations in the carbon dioxide pressure pco2 in ocean surface waters and related problems is given

variations in gdgt distributions through the water column in the south east atlantic ocean abstract the tetraether index of 86 carbon atoms tex 86 temperature proxy is widely used in reconstructions of past sea surface temperature most current calibrations are based on surface sediment distributions of the glycerol dialkyl glycerol tetraether lipids gdgts that comprise tex 86 and assume that these gdgts are exported from the upper mixed layer however gdgt export from deeper waters could impact sedimentary gdgt distributions and therefore tex 86 paleothermometry here we examine gdgt distributions in suspended particulate matter spm and underlying sediments collected from the southeast atlantic ocean our results reveal different gdgt distributions specifically the ratio between gdgts bearing 2 vs 3 cyclopentyl moieties 2 3 ratios between surface subsurface 50 200 m and deep water 200 m spm which suggests the occurrence of in situ deep production that is not apparent when considering tex 86 the gdgt distributions in sediments match those of subsurface waters rather than surface waters suggesting that they have not been preferentially derived from the upper mixed layer this is consistent with gdgt abundances being highest in shallow subsurface spm 100 to 200 m it remains unclear what governs the different 2 3 ratios throughout the water column but it is likely related to a combination of temperature and thaumarchaeotal community structure

evidence for a regional warm bias in the early cretaceous tex86 record abstract the cretaceous period 145 66 ma provides an opportunity to obtain insights into the adaptation of the climate system to increased atmospheric greenhouse gas concentrations the organic paleothermometer tex86 is one of the few proxies available for reconstructing quantitative estimates of upper ocean temperatures of this time period here we show that the sedimentary tex86 signal in the early cretaceous north and south atlantic shows systematic differences to other cretaceous samples in particular the relative increase in the fractional abundances of the crenarchaeol isomer compared to crenarchaeol exhibits similarities with surface sediments from the modern mediterranean and red sea dedicated climate model simulations suggest that the formation of warm and saline deep waters in the restricted north and south atlantic may have influenced tex86 export dynamics leading to a warm bias in reconstructed upper ocean temperatures applying a regional calibration from the modern mediterranean and red sea to corresponding tex86 data significantly improves the model data fit for the aptian oceanic anoxic event 1a and the overall comparison with other temperature proxies for the early cretaceous our results demonstrate the need to consider regional and temporal changes of the tex86 temperature relation for the reconstruction of deep time ocean temperatures

dense array recordings in the san bernardino valley of landers big bear aftershocks basin surface waves moho reflections and three dimensional simulations abstract fourteen geos seismic recorders were deployed in the san bernardino valley to study the propagation of short period t 1 to 3 sec surface waves and moho reflections three dense arrays were used to determine the direction and speed of propagation of arrivals in the seismograms the seismograms for a shallow d 1 km m 4 9 aftershock of the big bear earthquake exhibit a very long duration 60 sec of sustained shaking at periods of about 2 sec array analysis indicates that these late arrivals are dominated by surface waves traveling in various directions across the valley some energy is arriving from a direction 180 from the epicenter and was apparently reflected from the edge of the valley opposite the source a close in aftershock 25 km depth 7 km displays substantial short period surface waves at deep soil sites a three dimensional 3d finite difference simulation produces synthetic seismograms with durations similar to those of the observed records for this event indicating the importance of s wave to surface wave conversion near the edge of the basin flat layered models severely underpredict the duration and spectral amplification of this deep soil site i show an example where the coda wave amplitude ratio at 1 to 2 hz between a deep soil and a rock site does not equal the s wave amplitude ratio because of the presence of surface waves in the coda of the deep soil site for one of the events studied 90 km there are sizable phases that are critically reflected from the moho pmp and sms at one of the rock sites the sms phase has a more peaked spectrum that the direct s wave

merging late holocene molecular organic and foraminiferal based geochemical records of sea surface temperature in the gulf of mexico 1 a molecular organic geochemical proxy tex86 for sea surface temperature sst is compared with a foraminifera based sst proxy mg ca in a decadal resolution marine sedimentary record spanning the last 1000 years from the gulf of mexico we assess the relative strengths of the organic and inorganic paleoceanographic techniques for reconstructing high resolution sst variability during recent climate events including the little ice age lia and the medieval warm period mwp sst estimates based on the molecular organic proxy tex86 show a similar magnitude and pattern of sst variability to foraminiferal mg ca sst estimates but with some important differences for instance both proxies show a cooling 1 c 2 c of gulf of mexico ssts during the lia during the mwp however mg ca ssts are similar to near modern ssts while tex86 indicates ssts that were cooler than modern using the respective sst calibrations for each proxy results in tex86 sst estimates that are 2 c 4 c warmer than mg ca sst throughout the 1000 year record we interpret the tex86 sst as a summer weighted sst signal from the upper mixed layer whereas the mg ca sst better reflects the mean annual sst downcore differences in the sst estimates between the two proxies t tex86 mg ca are interpreted in the context of varying seasonality and or changing water column temperature gradients

sediment thickness variations of the tangshan fault zone in north china from a dense seismic array and microtremor survey abstract reliable knowledge of sediment thickness is beneficial for investigating buried active faults and improving seismic hazard assessments especially in regions with recent strong earthquakes in this study we investigate the basement of sediments around the 1976 ms 7 8 tangshan earthquake region north china using the microtremor horizontal to vertical spectral ratio h v method for the ambient vibration survey we deploy a dense seismic array comprising 152 seismographs with inter station distances of approximately 1 4 km and obtain the resonance frequency from each seismograph which indicates the sediment thickness the h v method provides a potential tool for inferring the shallow subsurface structure based on the relations between resonance frequency and sediment thickness from permanent borehole seismic stations records we recover the sediment thickness around the tangshan fault zone which varies from less than 200 m in the northern region to more than 800 m in the southern region our results are generally consistent with those of previous drilling and geological studies variations in the thickness of sediments indicate that the buried fault system has experienced significant modifications over time which is partially due to predominant tectonic control by the ne sw trending tangshan fault the obtained thickness of sediments provide an important basis for earthquake strong motion simulations sediment crustal corrections for travel time tomography and active fault investigations in the tangshan fault zone

microtremor observations of deep sediment resonance in metropolitan memphis tennessee we measured site resonance periods throughout metropolitan memphis tennessee the site resonance was derived from recordings of ambient microtremor and is a direct measurement of seismic ground shaking in the memphis metropolitan area the period t0 in s is predicted by the empirical relation t0 0 39899 7 8922 10 3h 3 0634 10 6h2 350 h 1100 m where h is the thickness in m of the unconsolidated sediments that overly hard paleozoic rocks assuming that a quarter wavelength relationship governs the relationship between resonant period sediment thickness and average shear wave speed we estimate the average shear wave speed of unconsolidated sediments as a function of sediment thicknesses vs 521 15 0 37459h 350 h 1100 m the scatter in the observations and discordance with earlier work suggests that caution is warranted in applying these values of wave speed indiscriminately to sites in the absence of further detailed work

miocene to pliocene development of surface and subsurface temperatures in the benguela current system 1 the initiation of the benguela upwelling has been dated to the late miocene but estimates of its sea surface temperature evolution are not available this study presents data from ocean drilling program odp site 1085 recovered from the southern cape basin samples of the middle miocene to pliocene were analyzed for alkenone based u37k sstuk and glycerol dialkyl glycerol tetraether gdgt based tex86 temptex water temperature proxies in concordance with global cooling during the miocene sstuk and temptex exhibit a decline of about 8 c and 16 c respectively the temperature trends suggest an inflow of cold antarctic waters triggered by antarctic ice sheet expansion and intensification of southern hemisphere southeasterly winds a temperature offset between both proxies developed with the onset of upwelling which can be explained by differences in habitat alkenone producing phytoplankton live in the euphotic zone and record sea surface temperatures while gdgt producing thaumarchaeota are displaced to colder subsurface waters in upwelling influenced areas and record subsurface water temperatures we suggest that variations in subsurface water temperatures were driven by advection of cold antarctic waters and thermocline adjustments that were due to changes in north atlantic deep water formation a decline in surface temperatures an increased offset between temperature proxies and an increase in primary productivity suggest the establishment of the benguela upwelling at 10 ma during the messinian salinity crisis between 7 and 5 ma surface and subsurface temperature estimates became similar likely because of a strong reduction in atlantic overturning circulation while high total organic carbon contents suggest a biogenic bloom in the pliocene the offset between the temperature estimates and the cooling trend was reestablished

comparison of 3d prospectivity modeling methods for fe cu skarn deposits a case study of the zhuchong fe cu deposit in the yueshan orefield anhui eastern china abstract three dimensional 3d metallogenic prospectivity modeling has become increasingly important in deep fe cu skarn mineralization prospecting the selection of prediction models and their comparison are of great significance in this paper we integrated the geological and geophysical data from the zhuchong fe cu deposit in the yueshan orefield anhui eastern china to establish the local 3d geological framework we extracted the 3d ore controlling factors quantitatively by means of 3d spatial analysis methods and compared the 3d mineralization locations predicted by the weight of evidence method and the artificial neural network method the results show that both methods can locate most of the known orebodies suggesting that both are relatively reliable in addition the weight of evidence method performed distinctly better than the artificial neural network method in terms of both prediction effectiveness and efficiency therefore the weight of evidence method may be more applicable in 3d prospectivity modelling for fe cu skarn deposits in the region finally the composite area predicted by the two methods is taken as the final prediction result of the mineralization area of the deposit and it is suggested that in the quantitative 3d prediction multiple selection of different methods with good adaptability should be involved in the prediction at the same time and compound prediction method should be used to delineate the target area our work has guiding significance for future deep prospecting and exploitation for other similar fe cu skarn deposits

distribution and export of isoprenoid tetraether lipids in suspended particulate matter from the water column of the western atlantic ocean abstract the tex86 paleotemperature proxy is based on the distribution of archaeal glycerol dibiphytanyl glycerol tetraether gdgt lipids preserved in marine sediments yet both the influence of different physiological factors on the structural distribution of gdgts and the mechanism s by which gdgts is are exported to marine sediments remain s unresolved we investigated the abundance and structural distribution of gdgts in the south west and equatorial atlantic ocean in four water column profiles spanning 48 degrees of latitude the depth distribution was consistent with production by ammonia oxidizing thaumarchaeota maximum gdgt concentration occurred at the base of the no2 maximum core gdgts dominated the structural distribution in surface waters above the no2 maximum and intact polar gdgts potentially indicating live cells were more abundant below the no2 maximum between 0 and1000 m 98 of the integrated gdgt inventory was present in waters at and below the no2 maximum depth profiles of tex86 temperature values displayed local minima at the no2 maximum while the ratio of gdgt 2 gdgt 3 increased with depth a model based on the results predicts an average depth of origin for gdgts exported to sediments between ca 80 250 m in the model exported tex86 values are remarkably insensitive to change in the average depth of origin of gdgts however tex86 values exported from the water column appear to reflect euphotic zone productivity possibly due to the correlative intensity of organic matter remineralization providing substrates for ammonia oxidation predicting the influence of these regional controls on sedimentary tex86 records requires a better understanding of the interaction between gdgt production particle dynamics and the depth of origin for exported organic matter

distributional variations in marine crenarchaeotal membrane lipids a new tool for reconstructing ancient sea water temperatures it has recently been shown that membrane lipids of marine crenarchaeota a ubiquitous and abundant component of plankton occur in relatively high concentrations in recent and ancient sediments in this study we investigated the environmental controls on the relative distribution of these lipids in surface sediments we especially focussed on temperature as it is known from the thermophilic genetic relatives of marine crenarchaetoa that the composition of their membrane strongly depends on growth temperature indeed a significant linear correlation r2 0 92 is found between the number of cyclopentane rings in sedimentary membrane lipids derived from marine crenarchaeota and the annual mean sea surface temperatures this suggests that the mechanism of physical adaptation of their membrane compositions to temperature is identical to that of their thermophilic relatives in turn archaeal lipid distributions in sediments may thus allow the reconstruction of sea water temperatures of ancient marine environments

high temperatures in the late cretaceous arctic ocean to understand the climate dynamics of the warm equable greenhouse world of the late cretaceous period it is important to determine polar palaeotemperatures the early palaeoceanographic history of the arctic ocean has however remained largely unknown because the sea floor and underlying deposits are usually inaccessible beneath a cover of floating ice a shallow piston core taken from a drifting ice island in 1970 fortuitously retrieved unconsolidated upper cretaceous organic rich sediment from alpha ridge a submarine elevated feature of probable oceanic origin a lack of carbonate in the sediments from this core has prevented the use of traditional oxygen isotope palaeothermometry here we determine arctic palaeotemperatures from these upper cretaceous deposits using tex86 a new palaeothermometer that is based on the composition of membrane lipids derived from a ubiquitous component of marine plankton crenarchaeota from these analyses we infer an average sea surface temperature of approximately 15 degrees c for the arctic ocean about 70 million years ago this calibration point implies an equator to pole gradient in sea surface temperatures of approximately 15 degrees c during this interval and by extrapolation we suggest that polar waters were generally warmer than 20 degrees c during the middle cretaceous approximately 90 million years ago

bulk sediment qp and qs in the mississippi embayment central united states we have estimated p wave ands wave anelastic attenuation coefficients for the thick unconsolidated sediments of the mississippi embayment central united states using the spectral distance decay of explosion p and rayleigh waves the sediment trapped p wave psed is observed to ranges of 80 km at 10 hz and 1 hz rayleigh waves are observed out to 130 km from a 5000 lb borehole explosion in the northern part of the embayment rayleigh waves of 4 hz are seen to distances of 3 km from a smaller 50 lb explosion analysis of the group velocity and amplitude distance decay of both waves yields an average qs of 100 and qp of 200 for embay ment sediments that are independent of frequency scatter in the q estimates comes from interference of multiple p wave reverberations and rayleigh wave modes the attenuation model is self consistent in that it is the same as obtained by the analysis of synthetic seismograms using the inferred q values inferred qp and qs values are more than three times higher than previous estimates and imply that unconsolidated sediments of the embayment do not significantly attenuate small strain earthquake ground motions these estimates represent a lower bound to q of the sediments since significant scattering is observed in the waveform data that contributes to the distance decay of wave amplitude higher q values also imply that the unconsolidated sedi ments of the embayment will form an efficient wave guide for surface waves radiated from shallow earthquakes or large earthquakes that rupture into the sediments pro ducing high amplitude long duration wave trains that should be considered in earth quake hazard assessments

variability of site response in seattle washington ground motion from local earthquakes and the ships seismic hazards investigation in puget sound experiment is used to estimate site amplification factors in seattle earthquake and ships records are analyzed by two methods 1 spectral ratios relative to a nearby site on tertiary sandstone and 2 a source site spectral inversion technique our results show site amplifications between 3 and 4 below 5 hz for west seattle relative to tertiary rock these values are approximately 30 lower than amplification in the duwamish valley on artificial fill but significantly higher than the calculated range of 2 to 2 5 below 5 hz for the till covered hills east of downtown seattle although spectral amplitudes are only 30 higher in the duwamish valley compared to west seattle the duration of long period ground motion is significantly greater on the artificial fill sites using a three dimensional displacement response spectrum measure that includes the effects of ground motion duration values in the duwamish valley are 2 to 3 times greater than west seattle these calculations and estimates of site response as a function of receiver azimuth point out the importance of trapped surface wave energy within the shallow low velocity sedimentary layers of the duwamish valley one dimensional velocity models yield spectral amplification factors close to the observations for till sites east of downtown seattle and the duwamish valley but underpredict amplifications by a factor of 2 in west seattle a two dimensional finite difference model does equally well for the till sites and the duwamish valley and also yields duration estimates consistent with the observations for the duwamish valley the two dimensional model however still underpredicts amplification in west seattle by up to a factor of 2 this discrepancy is attributed to 3d effects including basin edge induced surface waves and basin geometry focusing effects caused by the proximity of the seattle thrust fault and the sediment filled seattle basin

an automated purification method for archaeal and bacterial tetraethers in soils and sediments isoprenoid and branched glycerol dialkyl glycerol tetraethers gdgts are archaeal and bacterial polar lipids increasingly used as environmental biomarkers and are studied in a wide range of settings lacustrine and oceanic sediments water column particulate organic matter soils peats sedimentary rocks and extracts from archaeal and bacterial cultures in paleoclimatology for example typical work on a sediment core of several tens of m consists of several hundreds to more than a thousand hplc ms high performance liquid chromatography mass spectrometry analyses the measurements therefore require purification steps from total lipid extracts we propose an automated procedure for obtaining the gdgt core lipid fraction we first evaluate both the yield and efficiency of the separation using different cartridges we then compare the results from automated and classical manual procedures for a soil and a marine sediment as well as for a sedimentary paleosequence

source and site response study of the 2008 mount carmel illinois earthquake abstract two separate inversions are performed using the ground motion data from the 2008 mount carmel illinois earthquake one uses aftershocks as empirical green s functions to determine a finite fault slip distribution the second uses mainshock ground motion spectra to calculate source path and site response parameters the slip inversion reveals a prominent asperity at the hypocenter with an area of approximately 6 km 2 moment of m w 5 20 and stress drop of about 100 bars considering all major and minor slip the total moment is m w 5 45 the rupture velocity is not resolvable due to the small source area after fixing the geometric spreading the source path and site parameter inversion yields a similar moment of m w 5 26 and a corner frequency of 0 89 hz which also give a stress drop of approximately 100 bars our combined geometric and anelastic attenuation function q f r b 1137 f 0 12 r 0 94 fits the regional spectral amplitudes where the data is more plentiful as well as previously derived attenuation relationships site response spectra show prominent resonant frequencies that correlate with the thickness of mississippi river sediments and mississippi embayment deposits in addition higher frequency resonance peaks are observed that most likely represent higher mode resonances and resonances from shallower structure

three dimensional simulation of earthquakes on the los angeles fault system we have used a 3d finite difference method to simulate ground motion from elastodynamic propagating ruptures with constant slip on faults in the metropolitan area of los angeles california simulations are carried out for hypothetical m 6 75 earthquakes on the palos verdes and elysian park faults and for comparison an approximation to the 17 january 1994 m 6 7 northridge earthquake the dominant subsurface features of this area are the deep sedimentary los angeles basin and the smaller and shallower san fernando basin simulated ground motions are restricted to the frequency range 0 0 to 0 4 hz ground motion time histories show that in general sites associated with the largest particle velocities and cumulative kinetic energies are located 1 in the epicentral area 2 above the deepest parts of the basins and 3 near the steepest edges of the los angeles basin we find maximum particle velocities for the palos verdes elysian park and northridge simulations of 0 44 0 67 and 0 58 m sec respectively in each case both the directivity of the rupture and the lower impedance of the basins significantly amplify the ground motion although the gross radiation pattern from these ruptures is observable the 3d basin structure distorts the wave field and becomes a source for edge generated waves signal durations at some basin sites last beyond 90 sec due to love waves and refracted s waves that propagate into the sediments from the basin edges compared with the palos verdes event the durations are generally smaller for the elysian park earthquake due to a smaller amount of love waves generated at the basin edges a simple approximation to the northridge earthquake reproduces the overall spatial pattern of the long period particle velocities successfully predicts the timing of late arriving waves and matches the peak velocities with discrepancies generally less than a factor of 2 however for localized areas immediately north and south of the santa monica mountains the computed ground motion underpredicts the observed horizontal peak velocities but matches the vertical ones the pattern of simulated total cumulative kinetic energies is similar to that for the damage intensities observed near the epicenter of the northridge event while the northridge earthquake caused damage in the los angeles area the 3d simulations show that earthquakes with the same magnitude on the palos verdes or elysian park faults produce more severe ground shaking in the los angeles basin

massive expansion of marine archaea during a mid cretaceous oceanic anoxic event biogeochemical and stable carbon isotopic analysis of black shale sequences deposited during an albian oceanic anoxic event 112 million years ago indicate that up to 80 weight percent of sedimentary organic carbon is derived from marine nonthermophilic archaea the carbon 13 content of archaeal molecular fossils indicates that these archaea were living chemoautotrophically their massive expansion may have been a response to the strong stratification of the ocean during this anoxic event indeed the sedimentary record of archaeal membrane lipids suggests that this anoxic event marks a time in earth history at which certain hyperthermophilic archaea adapted to low temperature environments

a study of the tex86 paleothermometer in the water column and sediments of the santa barbara basin california 1 particulate organic matter collected during a 2 year period as part of an ongoing sediment trap study and a high resolution sediment record from 1850 to 1987 a d from the santa barbara basin were analyzed for tex86 a temperature proxy based on marine crenarchaeotal membrane lipids highest fluxes of crenarchaeotal lipids in the water column were found in may june 1996 and from october 1996 to january 1997 and in general showed a good correlation with mass fluxes tex86 reconstructed temperatures from the sediment trap series ranged from 8 to 11 c and were usually substantially lower than sea surface temperatures sst indicating that unlike in previous studies the tex86 corresponds to subsurface temperatures likely between 100 and 150 m tex86 temperature variations observed in trap samples were not coupled to changes in sst or deep water temperatures and only to some degree with crenarchaeotal lipid fluxes this suggests that a complex combination of different depth origins and seasonal growth periods of crenarchaeota contributed to the variations in tex86 signal during the annual cycle tex86 temperatures in the two sediment cores studied 8 13 c were also substantially lower than those of instrumental sst records 14 17 5 c confirming that tex86 records a subsurface temperature signal in the santa barbara basin this result highlights the importance of performing calibration studies using sediment traps and core tops before applying the tex86 temperature proxy in a given study area

noise to signal a microtremor study at liquefaction sites in the new madrid seismic zone understanding how sedimentary basins respond to seismic wave energy generated by large earthquake events is a significant concern for seismic hazard estimation this study explores the use of microtremors or ambient noise for evaluating strong motion site effects the study focuses on the mississippi embayment in the new madrid seismic zone where widespread liquefaction and ground failure occurred during the 1811 1812 earthquake sequence spectral analyses of microtremor data at sites representing different environments of deposition and sedimentary facies different embayment thicknesses and varying liquefaction susceptibility show correlations between 1 calculated vulnerability indices and evidence of liquefaction 2 sediment thickness and fundamental resonant frequency and 3 subsurface stratigraphic boundaries and observed peaks in horizontal to vertical spectral ratios results of the study suggest that the microtremor method could be helpful in identifying those areas most vulnerable to

hydrographic variability in the northern south china sea over the past 45 000 years new insights based on temperature reconstructions by uk 37 and texh86 proxies from a marine sediment core md972146 abstract millennial scale climate variability was persistent feature for greenland ice core and north atlantic marine records during the marine isotope stage mis 3 studying high quality climatic archives outside of the greenland and north atlantic with precise constraint of absolute dating and high resolution sampling is a prerequisite to understand how the millennial scale changes well expressed in north hemisphere nh high latitudes had been propagated out to the other regions here we generated the surface and subsurface hydrography u k 37 and tex h 86 temperatures and terrestrial material input n alkanes records with precise ams 14 c dated control for the 45 ka from a core md972146 retrieved from the northern south china sea scs then we compared our records to the oxygen isotope record from a greenland ngrip ice core and the mean grain size record from a loess sequence at gulang china we found that the millennial scale oscillations of hydrolography and terrestrial material inputs records during the time since the last deglaciation and of 33 45 ka share similar patterns in timing and amplitude of the nh high latitude climate however we found that a non nh pattern of millennial scale oscillations for the late mis 3 20 33 ka of our hydrography and terrestrial material inputs records our studies imply that the changes of obliquity also may be important in determining the timing and amplitude of millennial scale east asian monsoon eam variability expressed in the northern scs hydrography and terrestrial material inputs

site effect evaluation using spectral ratios with only one station the spectral ratio technique is a common useful way to estimate empirical transfer function to evaluate site effects in regions of moderate to high seismicity the purpose of this paper is to show that it is possible to estimate empirical transfer function using spectral ratios between horizontal and vertical components of motion without a reference station the technique originally proposed by nakamura to analyze rayleigh waves in the microtremor records is presented briefly and it is discussed why it may be applicable to study the intense s wave part in earthquake records results are presented for three different cities in mexico oaxaca oax acapulco gro and mexico city these cities are very different by their geological and tectonic contexts and also by the very different epicentral distances to the main seismogenic zones affecting each city each time we compare the results of nakamura s technique with standard spectral ratios in all three cases the results are very encouraging we conclude that if site effects are caused by simple geology a first estimate of dominant period and local amplification level can be obtained using records of only one station

comparison and implication of tex86 and u37k temperature records over the last 356kyr of odp site 1147 from the northern south china sea abstract proxy records from the south china sea scs have played an important role in understanding late quaternary scs environmental changes and the east asian monsoon eam variations but few long sea surface temperature sst records have been generated from the scs the recently established tex86 index provides an opportunity to generate long sst records especially for tropical oceans but the applicability and climatic interpretation of the tex86 index for the scs need further study we report and compare orbital scale resolution ca 5 3 kyr tex86 and u37k temperature records of the past 356 kyr for odp site 1147 from the northern scs both records display clear and similar glacial interglacial patterns the u37k sst fluctuated between 22 3 c and 28 3 c with a glacial interglacial difference of 4 5 c while the tex86 temperature fluctuated between 20 3 c and 25 4 c with a slightly smaller glacial interglacial difference of ca 4 c the tex86 temperature has been consistently lower than the u37k temperature over the past 356 kyr consistent with previous studies suggesting that the u37k index is a proxy for sst but the tex86 index is a proxy for subsurface temperature thus it is proposed that the temperature difference t between the u37k and tex86 records reflects mixed layer depth mld changes in the northern scs which fluctuated between 0 3 and 4 0 c with high values mostly during interglacials and lower values mostly during glacial stages mld changes in the northern scs are interpreted to be driven by eam changes with stronger winter monsoon resulting in a deeper mld and a smaller t thus the combination of u37k and tex86 records and their t can be used to reconstruct east asian winter monsoon variations as well as their influences on the hydrographic structure of the scs

site amplification in the san fernando valley california variability of site effect estimation using the s wave coda and h v methods during the months that followed the 17 january 1994 m 6 7 northridge california earthquake portable digital seismic stations were deployed in the san fernando basin to record aftershock data and estimate site amplification factors this study analyzes data recorded on 31 three component stations from 38 aftershocks ranging from m 3 0 to m 5 1 and depths from 0 2 to 19 km site responses from the 31 stations are estimated from coda waves s waves and ratios of horizontal to vertical h v recordings for the coda and the s waves site response is estimated using both direct spectral ratios and a generalized inversion scheme results from the inversions indicate that the effect of qs can be significant especially at high frequencies site amplifications estimated from the coda of the vertical and horizontal components can be significantly different from each other depending on the choice of the reference site the difference is reduced when an average of six rock sites is used as a reference site in addition when using this multi reference site the coda amplification from rock sites is usually within a factor of 2 of the amplification determined from the direct spectral ratios and the inversion of the s waves however for nonrock sites the coda amplification can be larger by a factor of 2 or more when compared with the amplification estimated from the direct spectral ratios and the inversion of the s waves the h v method for estimating site response is found to extract the same predominant peaks as the direct spectral ratio and the inversion methods the amplifications determined from the hiv method are however different from the amplifications determined from the other methods finally the stations were grouped into classes based on two different classifications general geology and a more detailed classification using a quaternary geology map for the los angeles and san fernando areas average site response estimates using the site characterization based on the detailed geology show better correlation between amplification and surface geology than the general geology classification

archaeal lipids in neogene dolomites monterey and sisquoc formations california planktic versus benthic archaeal sources abstract the distribution of archaeal lipids including archaeol and glycerol dibiphytanyl glycerol tetraethers gdgts in dolomite concretions and surrounding sediment from the monterey formation miocene and the sisquoc formation miocene pliocene were examined to distinguish planktic from benthic contributions for this purpose dolomites with positive 13 c values 7 to 13 were chosen such highly positive values point to pronounced methanogenesis of benthic archaea in the sedimentary column at first glance distributions and relative abundances of gdgts in both dolomites and background sediment were similar resembling patterns of marine planktic crenarchaea a contribution of benthic euryarchaea to the gdgt pool became evident only from variations in the 13 c values of different biphytanes obtained after ether cleavage of gdgts whereas bi and tricyclic biphytanes had an isotopic signal typical of planktic archaea 13 c 23 6 to 20 5 and 23 4 to 21 2 respectively for both dolomite and background sediment acyclic and monocyclic biphytanes showed lower values for dolomite samples 25 1 to 22 6 and 27 6 to 24 7 respectively indicating a contribution of lipids from benthic archaea the isoprenoid diether archaeol 13 c 23 9 to 22 9 assigned to euryarchaea was only detected in dolomite samples also reflecting additional input from sedimentary archaea probably autotrophic methanogens the occurrence of lipids derived from methanogenic archaea agrees with the strong 13 c enrichment of dolomites and with mineral formation taking place in the zone of archaeal methanogenesis this implies that the lipid biomarker inventory of sedimentary strata needs to be interpreted carefully as it is often not straightforward to discriminate between input from the water column and sedimentary microbial activity

thermal response of the western tropical atlantic to slowdown of the atlantic meridional overturning circulation abstract the western tropical atlantic plays an important role in the interhemispheric redistribution of heat during millennial scale changes in the strength of the atlantic meridional overturning circulation amoc the proper evaluation of this role depends on a clear understanding of sea surface temperature sst variations during amoc slowdown periods like heinrich stadials hs in the western tropical atlantic however published sst records from the western tropical atlantic between ca 4 s and 7 n show inconsistencies that are apparently related to the employed temperature proxy i e mg ca versus alkenone unsaturation index u 37 k in general while mg ca values indicate warming during heinrich stadials u 37 k values show cooling to assess this issue we sampled core geob16224 1 retrieved off french guiana i e 6 39 38 n and reconstructed water temperatures at high resolution using mg ca on the foraminifera species globigerinoides ruber u 37 k tex86 and modern analogue technique mat transfer functions using planktonic foraminifera assemblages calibrated for 50 m water depth our results show that mg ca and tex86 values recorded an increase in sst related to amoc slowdown conversely u 37 k and mat values registered a decrease in temperatures during hs3 and hs1 our u 37 k and mg ca results thus confirm the previously reported inconsistency for the period between 48 13 cal ka bp we suggest that several non thermal physiological effects probably imparted a negative temperature bias on the u 37 k temperatures during heinrich stadials however mat based temperatures show similar variability with u 37 k based temperatures hence we also suggest that during severe slowdown periods of the amoc a steeper meridional temperature gradient together with a southward shift of the intertropical convergent zone produced not only an increase in sst but also a stronger upper water column stratification and a shoaling of the thermocline decreasing subsurface temperatures our new high resolution temperature records allow a better characterization of the thermal response of the upper water column in the tropical western atlantic to slowdown events of the amoc reconciling previously discrepant records

the seismic response of the los angeles basin california using strong motion data recorded in the los angeles region from the 1992 mw 7 3 landers earthquake we have tested the accuracy of existing three dimensional 3d velocity models on the simulation of long period 2 sec ground motions in the los angeles basin and surrounding san fernando and san gabriel valleys first the overall pattern and degree of long period excitation of the basins were identified in the observations within the los angeles basin the recorded amplitudes are about three to four times larger than at sites outside the basins amplitudes within the san fernando and san gabriel valleys are nearly a factor of 3 greater than surrounding bedrock sites then using a 3d finite difference numerical modeling approach we analyzed how variations in 3d earth structure affect simulated waveforms amplitudes and the fit to the observed patterns of amplification significant differences exist in the 3d velocity models of southern california that we tested magistrale et al 1996 graves 1996a hauksson and haase 1997 major differences in the models include the velocity of the assumed background models the depth of the los angeles basin and the depth location and geometry of smaller basins the largest disparities in the response of the models are seen for the san fernando valley and the deepest portion of the los angeles basin these arise in large part from variations in the structure of the basins particularly the effective depth extent which is mainly due to alternative assumptions about the nature of the basin sediment fill the general ground motion characteristics are matched by the 3d model simulations validating the use of 3d modeling with geologically based velocity structure models however significant shortcomings exist in the overall patterns of amplification and the duration of the long period response the successes and limitations of the models for reproducing the recorded ground motions as discussed provide the basis and direction for necessary improvements to earth structure models whether geologically or tomographically derived the differences in the response of the earth models tested also translate to variable success in the ability to successfully model the data and add uncertainty to estimates of the basin response given input scenario earthquake source models

temperature changes reconstructed from branched gdgts on the central loess plateau during the past 130 5 ka abstract this study investigated the glycerol dialkyl glycerol tetraethers gdgts in a loess paleosol sequence lps to quantitatively reconstruct the mean annual air temperature mat on the central chinese loess plateau clp during the past 130 5 ka the results show that 1 mat variations reconstructed by global mbt methylation index of branched tetraethers and cbt cyclisation ratio of branched tetraethers transfer functions at xifeng range from 7 3 c to 28 4 c the mat variation on the central clp xifeng site is between the previously reported mat variations on the western yuanbao site and eastern clp mangshan site in agreement with the pattern that temperature increases from the northwestern clp to the southeastern clp 2 mat variations estimated by transfer functions of global mbt cbt global mbt cbt and chinese mbt cbt for lps are nearly all higher than the modern mat at xifeng indicating that the reconstructed mat values are probably overestimated 3 the maximum value of magnetic susceptibility at xifeng lagged that of the mat derived by mbt cbt proxy during the last interglacial 9 ka lag and since the last deglacial 6 ka lag

occurrence of tetraether lipids in stalagmites implications for sources and gdgt based proxies lipid biomarkers in stalagmites have potential in palaeoenvironmental reconstruction but glycerol dialkyl glycerol tetraethers gdgts in stalagmites have rarely been investigated we report the occurrence of archaeal isoprenoid gdgts and bacterial branched gdgts in heshang cave stalagmites in central china the archaeal component crenarchaeol dominated bacterial branched gdgts in the stalagmites and on the weathered parent rock surface collected inside the cave in contrast the distribution of gdgts in the overlying soil shows that branched gdgts dominated archaeal gdgts hence the majority of archaeal gdgts in stalagmites may be produced by crenarchaeota inhabiting the cave rather than being inherited from the overlying soil bacterial branched gdgt distributions expressed as mbt and cbt indices showed remarkable differences between stalagmite and soil samples implying that most branched gdgts may also be produced in situ in the cave the tex86 or tex86 values were found to increase with more depleted 18o values representing much stronger monsoon and therefore usually higher temperatures in the study region however the mbt cbt index in stalagmites may be influenced by a variety of factors besides palaeotemperature

dynamic deformations of shallow sediments in the valley of mexico part i three dimensional strains and rotations recorded on a seismic array abstract we study the spatial variation in earthquake ground motions or equivalently the dynamic displacement gradient field using a novel analysis procedure borrowed from geodesy seismic data recorded in the valley of mexico by a microarray of three three component surface accelerographs and two three component accelerographs at depths of 30 m and 102 m constrain our estimates of the dynamic displacement gradient field from which strains and rotations derive for four moderate earthquakes at distances of 250 to 300 km our study focuses on the effects of low velocity surface materials on the deformation at the surface the gradients corresponding to deformation across vertical planes dominate and vertical axis rotations are of similar magnitudes as strains the greatest peak surface gradient we observed was 206 strain for the 14 september 1995 m w 7 5 earthquake at a distance of 300 km however much larger gradients occur across horizontal planes u z where u is a horizontal displacement and z is depth at some depth between 0 and 30 m these values are about a factor 10 greater than the corresponding gradient components at the surface u z for the 14 september earthquake equaled or exceeded 665 strain at depth the dynamic deformations experienced in mexico city undoubtedly have occurred before and will occur again in other densely populated areas however in many other regions the sediment response will not remain linear and elastic resulting instead in liquefaction and ground failure

site response models for charleston south carolina and vicinity developed from shallow geotechnical investigations the study models the response of near surface materials in charleston south carolina and the adjacent area geotechnical investigations at 281 locations were made available by local engineering firms the data used for dynamic site response analysis were derived from shear wave velocity measurements at 52 loca tions site response was quantified as the ratio of surface motion to hypothetical hard rock basement outcrop motion scenario earthquake motions were developed with the stochastic model acceleration response ratios for 5 critical oscillator damping were computed for 12 frequencies ranging from 0 1 to 30 hz and for peak ground acceleration two features determine the general nature of site response in the study area the impedance contrast between mesozoic basement and cretaceous sediments and the shallow impedance contrast between quaternary and tertiary sediments average s wave velocities in the quaternary are relatively uniform and range from 150 to 250 m sec they are not strongly correlated with surface geology the velocities of the immediately underlying tertiary sediments range from 300 to 500 m sec because of the uniformity of velocity in the quaternary depth to the quaternary tertiary contact appears to be the most important variable leading to differences in calculated site response this surface is irregular and varies in depth from near surface at inland sites to approximately 30 m at sites near the coast as a consequence estimated site response in the frequency band 1 10 hz varies by as much as a factor of 3 site response at frequencies less than 1 hz is dominated by the first few resonant har monics of the entire sedimentary section with fundamental frequency near 0 2 hz

distribution of glycerol dialkyl glycerol tetraethers in soils from two environmental transects in the usa abstract glycerol dialkyl glycerol tetraethers gdgts of both archaeal and bacterial origin form the basis of new temperature proxies applicable to soil and lake and marine sediments in soil branched gdgts are prevalent and their abundance of methyl or cyclic groups has been calibrated to mean annual temperature mat using mbt and cbt indices however soil ph is also known to be an important variable controlling the distribution of branched gdgts precipitation amount helps control soil moisture as well as ph and soil moisture is a leading variable affecting microbial diversity and activity in soil we have evaluated the distribution of gdgts from two soil transects in the usa a dry western transect covering six western states and a wet east coast transect from maine to georgia in order to assess the effect of precipitation on the distribution of soil gdgts our results show distinctly different gdgt distributions across climatic regions with dry western soils characterized predominantly by thaumarchaeotal isoprenoid iso gdgts and as a consequence low bit index values 0 2 0 6 and moist temperate east coast transect soils expressing mostly branched br gdgts and higher bit values 0 9 1 the predominance of iso gdgts in the western soils is related to the degree of aeration which in turn is related to precipitation amount and also to soil ph we also observed a substantial increase in the offset between measured mat and mbt cbt based mat below an annual precipitation of 700 800 mm yr 1 implying an impact of precipitation amount on mbt cbt based temperature reconstruction the data suggest that while soil tetraethers work well as a temperature proxy in moist temperate regimes they do not produce reliable measurements of temperature in sediments sourced from areas with 1 precipitation moreover erosion of soils with low bit values into lacustrine or marginal marine environments will not be detected via the bit index which can potentially affect paleotemperature reconstruction from sediments and so provide erroneous estimates of soil carbon delivery bit index values also show a correlation with precipitation amount the abundance of iso gdgts in western transect soils allowed calculation of tex 86 values but no correlation was found between tex 86 calculated temperature and mean annual temperature

molecular stratigraphy a new tool for climatic assessment variations in sea surface temperatures over the past 500 000 years are inferred from the relative abundance behaviour of two organic compounds c37 alkenones over the upper 8 metres of a sediment core from the eastern equatorial atlantic this molecular record ascribed to contributions from prymnesiophyte algae correlates well with the variations in the 18 signal for the calcareous skeletons of certain planktonic foraminifera thus providing the first demonstration of a new stratigraphical technique which may be especially valuable where methods based on carbonate 18 fail

temperature dependent variation in the distribution of tetraether membrane lipids of marine crenarchaeota implications for tex86 paleothermometry 1 recently a new geochemical temperature proxy the tex86 was introduced this proxy is based on the number of cyclopentane moieties in the glycerol dialkyl glycerol tetraethers gdgts of the membrane lipids of marine crenarchaeota which changes as a response to temperature however until now only sediment data have been used to establish this proxy and experimental work is missing we performed mesocosm studies with marine crenarchaeota incubated at temperatures ranging from 5 to 35 c and salinities of 27 and 35 to test the validity of the tex86 proxy growth of marine crenarchaeota in these mesocosms was evident from the substantial increase in the concentration of marine crenarchaeotal membrane lipids with amounts up to 3400 ng l with increasing temperature an increase in the number of cyclopentane moieties in the crenarchaeotal membrane lipids was observed different salinities did not show any effect on the gdgt distribution the tex86 showed a significant linear correlation to incubation temperature tex86 0 015 t 0 10 r2 0 79 this equation has a similar slope to the correlation obtained from core tops but differs in the intersection tex86 0 015 t 0 28 r2 0 92 this difference is mainly determined by the smaller amount of the regioisomer of crenarchaeol in the incubation series compared to core top samples these incubation experiments indicates that water temperature is indeed the major controlling factor for the membrane distribution of marine crenarchaeota and confirms that the tex86 proxy depends on a physiological response to regulate membrane fluidity

are microtremors useful in site response evaluation we have reviewed the applicability of microtremor measurements to evaluate site response of soft soils to this end we evaluated three different techniques commonly used to estimate site effects from microtremor measurements interpretation of fourier amplitude spectra computation of spectral ratios relative to a firm reference station and finally computation of spectral ratios of horizontal components relative to the vertical component of ground motion nakamura s technique these techniques are applied to microtremor records obtained in three cities in mexico mexico city oaxaca and acapulco these cities differ in their local geological conditions and in their seismotectonic environment in order to evaluate the results obtained from microtremor measurements we compare them with standard spectral ratios of the intense s wave part of weak or strong motion records obtained at the same sites our results showed that microtremor measurements can be used to estimate the dominant period of a site with very acceptable reliability in the range 0 3 to 5 hz the best results were obtained with nakamura s technique which also gives a rough estimate of amplification of seismic waves when the local geology is relatively simple simple numerical simulations indicate that the underlying assumptions of nakamura s technique are consistent with the propagation of rayleigh waves these simple numerical simulations also explain why different researchers have been able to successfully characterize 1d site effects using microtremor records regardless of whether they consider microtremors to consist of surface or body waves our results strongly suggest that the technique by nakamura effectively compensates for source effects in microtremor measurements which eliminates a major limitation to their application in earthquake engineering

three dimensional seismic velocity model for the unconsolidated mississippi embayment sediments from h v ambient noise measurements abstract the horizontal to vertical h v technique by nakamura 1989 was applied to data from 30 new field stations and 64 other broadband temporary and permanent seismic stations within the mississippi embayment of the central united states to develop a 3d model of unconsolidated sediment shear wave velocity structure using the dart 1992 map of sediment thickness as a basis two self consistent models of average shear wave velocity versus sediment thickness were developed by utilizing the theoretical linear relationship between the frequency of the h v peak and shear wave velocity one model was based on the observation that the h v peak period t p s versus sediment thickness h m was seen to be approximately linear with the relationship t p 0 003266 h 1 084 the second model was developed by considering peak frequency f p versus sediment thickness parameterized to follow ln f p 8 325 10 7 h 2 0 00232 h 0 01796 overall the models show low average shear wave velocity near the edge of the mississippi embayment with velocities increasing with increasing sediment thickness consistent with increased sediment compaction these models will be useful in studies of site resonance and amplification for earthquake shaking hazards and for wave propagation computations for the region

array observations of microseismic noise and the nature of h v in the mississippi embayment abstract ambient ground motion data were collected using phased seismic arrays in fall 2002 and spring 2007 within the mississippi embayment and at a single station external to the embayment these data allowed us to determine the wave field composition of ambient noise for understanding wave propagation mechanisms giving rise to spectral peaks using nakamura s h v technique ambient ground motions in the frequency band of 0 1 0 33 hz 10 3 sec period were dominated by spatially localized rayleigh and love wave microseisms generated by high ocean waves along the north american seaboard in the time periods of analysis seismic waves important in forming the h v peak near 4 sec period are composed of relatively high phase velocity rayleigh and love waves that convert to propagating homogeneous shear waves in the thick unconsolidated sediments of the embayment the h v resonant period is controlled by both constructive and destructive interference of these shear waves a simple relationship for the h v peak is given using a propagator matrix formulation that predicts the resonance frequency of a layered medium for surface wave motion at the base of the system the amplitude of the observed h v peak however does not give an accurate estimate of shear wave amplification because it depends on the slowness of the incident wave the inconsistency in estimated average shear wave velocities using the h v method and differential travel times of local earthquake sp phases in the mississippi embayment may be explained by misidentification of sp wave conversion points from deeper interfaces

tex86 as a potential proxy of lake water ph in the tibetan plateau abstract water ph represents one of the most important indicators of chemical and biological changes in lacustrine systems however although water ph is also a major influence on inland water bodies and related ecosystems it is not well studied in the lakes of the tibetan plateau tp the applicability of diatom assemblages an effective proxy of variations in water ph in freshwater lakes is greatly limited in the tp because the alkaline environment in most of the lakes is unfavorable for the preservation of diatom frustules isoprenoid glycerol dialkyl glycerol tetraethers igdgts are a series of specific membrane lipids biosynthesized by archaea which appear to be a promising method for reflecting lake water ph variations in this study we analyzed the distribution of igdgts in the surface sediments of 34 alpine tp lakes and combined the data with published igdgts results from across the tp in order to examine the effect of various environmental factors on igdgt cyclization the results show that water ph appears to be the most important factor affecting the degree of cyclization of igdgts in high elevation alkaline lakes this also suggests that the novel temperature proxy tex86 is also a promising water ph proxy for alpine lakes in the region despite a moderate correlation is observed between tex86 and water ph caution is needed in the interpretation of the tex86 records since other factors such as temperature and the dissolved oxygen level may also have an influence nevertheless tex86 appears to be a promising indicator of water ph for the alkaline lakes of the tp and it could be a potentially useful tool for reconstructing ph in alkaline lakes in other areas after regional calibrations

palaeoclimate and palaeoceanographic conditions in the westernmost mediterranean over the last millennium an integrated organic and inorganic approach previous studies have revealed the excellence of the westernmost mediterranean records for reconstructing climate conditions over the last two millennia in particular inorganic and organic proxies have revealed a coherent signal of climate and oceanographic responses during this time here we compare and integrate both proxy records for reconstructing climate and oceanographic conditions with focus on the last millennium the higher temperatures indicated by lipid based proxies during the medieval climate anomaly mca are coincident with drier conditions indicated by inorganic proxies in contrast lower temperatures and humid conditions are indicated during the little ice age lia the industrial period was characterized by increasing humidity in comparison with the previous lia however a progressive aridification occurred since the second half of the twentieth century coexisting with a warming trend and higher contribution of c3 grasses proxy records are also interpreted to show atlantic water inflow at ad 1450 and 1950 and an intensification of the upwelling conditions coinciding with a prolonged positive north atlantic oscillation nao phase in the intervals ad 1000 1450 and 1960 1990 large scale oceanic atmospheric circulation patterns the nao and the atlantic meridional circulation and solar irradiance variations seem to have played the major key role during the last millennium together with anthropogenic contributions in the more recent record

microseisms observations in the santa clara valley california we have investigated ground motion amplification in the santa clara valley scv using microseisms observed during the 1998 deployment of 41 short period seismometers the santa clara valley seismic experiment scvse lindh et al 1999 fletcher et al 2003 recorded many local regional and teleseismic events in our previous work we investigated the 3d velocity structure of the scv by modeling the teleseismic p waves recorded during the scvse dolenc et al 2005 to complement these results we now focus on the microseisms that were recorded during the same period and relate these observations to local earthquake wave amplification it is found that the seismic noise is related to the ocean wave heights measured on the weather buoy west of half moon bay california the spectral ratio of the horizontal to vertical h v microseisms at each scvse site is stable with time and the period of the dominant peak in the h v ratio is related to the basin depth the results of this study show that seismic noise can be used in the assessment of the effects of deep sediments on long period earthquake ground motions

comparison of instrumental and gdgt based estimates of sea surface and air temperatures from the skagerrak sea surface temperatures ssts and annual mean air temperatures mats are estimated for the last 200 years from glycerol dialkyl glycerol tetraethers gdgts proxies in a marine sediment core from the skagerrak off southern norway the reconstructed values compare well with annual ssts and summer air temperatures obtained from composite regional instrumental records the results provide further confidence in the application of proxies based on gdgts to estimate past temperatures

glycerol dialkyl glycerol tetraethers in surficial coastal and open marine sediments around china indicators of sea surface temperature and effects of their sources accurate reconstruction of past sea surface temperature sst is important for the understanding of past climate and its variations recently the tex86 indicator tetraether index of tetraethers consisting of 86 carbon atoms based on glycerol dialkyl glycerol tetraethers gdgts has been developed into a promising proxy for sst reconstruction in this study we investigated the distribution of gdgts in surficial sea bottom sediments from coastal and open marine settings around china between 18 degrees n and 38 degrees n in water depth of either 1000 m as the distribution patterns of gdgts reflect their biological sources and their respective habitats these can be identified from the sediment samples investigated the distributions of branched gdgts brgdgts in the yellow sea ys was found to be similar to that of the lower yellow river basin indicating that the brgdgts in the ys originated from terrestrial soil while the variability of the cyclisation ratio of branched tetraethers cbt derived ph values in the pearl river estuary pre suggested that brgdgts might also be produced in situ in coastal sediments or in the water column in the shallow areas water depth 1000 m the sst86h matched well the mean annual sst determined by satellite indicating the applicability of the tex86 temperatures for paleodimate investigations in these study areas and potentially in similar settings of deep water these findings provide the basis for application of branched isoprenoid index bit and tex86 as indicators for temperature and paleotemperature in coastal and open marine environments around china c 2013 elsevier b v all rights reserved

quantitative prediction and evaluation of mineral resources based on gis in northern segment of three river sanjiang region southwest china on the basis of geological mineral resources database in the northern part of three river region this research has adopted weights of evidence modeling created by f p agterberg to predicate ore forming anomalies and evaluate mineral resources the result shows that the application of sophisticated mapgisarcview and good mathematical model can certainly raise the accuracy and effectiveness of mineral resource quantitative prediction and evaluation

large temperature variability in the southern african tropics since the last glacial maximum 1 the role of the tropics in global climate change is actively debated particularly in regard to the timing and magnitude of thermal and hydrological response continuous high resolution temperature records through the last glacial maximum lgm from tropical oceans have provided much insight but surface temperature reconstructions do not exist from tropical continental environments here we used the tex86 paleotemperature proxy to reconstruct mean annual lake surface temperatures through the last glacial maximum lgm in lake malawi east africa 9 14 s we find a 3 5 c overall warming since the lgm with temperature reversals of 2 c during the younger dryas 12 5 ka bp and at 8 2 ka bp maximum holocene temperatures of 29 c were found at 5 ka bp a period preceding severe drought in africa these results suggest a substantial thermal response of southeastern tropical africa to deglaciation and to varying conditions during the holocene

large scale 3d mineral prediction methods and channels based on 3d information technology large scale metallogenic prediction methods were important for the exploration of deep hidden deposits in ore field it was a very necessary measurement for research and development of the treatment and information synthesized of the geological explorative data under the condition of 3d visualization as improving 3d geological information technology according to 3d modeling predictions of jiama mine and other ore deposits the authors briefly studied some key technologies i e 3d simulation of ore control structure in ore field 3d visualization of deposit model and 3d information synthesized quantitative evaluation and discussed that the technical difficulties of 3d prediction software exploitation working course of large scale 3d prediction and application effect by using examples

effective use and interpretation of lithogeochemical data in regional mineral exploration programs application of geographic information systems gis technology abstract a geographic information system gis in concert with statistical and geostatistical software has been used to compile manipulate analyze and visualize a large lithogeochemical dataset collected from the archean age swayze greenstone belt sgb located in northern ontario canada altered samples from this database have been identified using a variety of univariate and multivariate statistical and visualization techniques alteration maps are produced for each method and compared to known gold mineralization using the weights of evidence wofe technique major oxide data are interpolated using different sample groups all altered unaltered normalized samples and anomalous concentrations are separated from background using breakpoints on probability plots of the data as well as statistics generated from wofe analysis these maps are also evaluated using wofe analysis with respect to locations of known gold prospects the atypical normative mineral method is more sensitive for identifying alteration in felsic rocks felsic volcanic rocks granitoids whereas the volatile method is more sensitive for detecting alteration in mafic volcanic rocks and sedimentary rocks altered samples are characterized by higher sio2 k2o and mno concentrations and lower mgo and tio2 concentrations areas within the greenstone belt characterized by high concentrations of cao fe k2o and al2o3 were found to the best predictors of the known gold prospects anomalously high concentrations of these oxides reflect carbonatization fe carbonate alteration and potassic alteration trends and indicate that these alteration styles are spatially related to gold mineralization the wofe method is a useful technique with which to evaluate the geochemical maps produced in this paper the wofe technique is useful not only for comparing geochemical anomalies to the location of known gold prospects but also for providing a quantitative measure of association between anomalies and gold prospects furthermore the gold potential maps generated using wofe not only highlight or predict known areas of gold mineralization but also identify high potential areas where no known mineralization occurs a number of areas within the sgb have been identified as having high gold potential on many of the geochemical maps produced in this paper many of these areas coincide with areas of known gold mineralization however others are enigmatic and await follow up exploration

explosion source strong ground motions in the mississippi embayment two strong motion arrays were deployed for the october 2002 embay ment seismic excitation experiment to study the spatial variation of strong ground motions in the deep unconsolidated sediments of the mississippi embayment because there are no comparable strong motion data from natural earthquakes in the area each linear array consisted of eight three component k2 accelerographs spaced 15 m apart situated 1 2 and 2 5 km from 2268 kg and 1134 kg borehole explosion sources respectively the array data show distinct body wave and surface wave arrivals that propagate within the thick unconsolidated sedimentary column the high velocity basement rocks and small scale structure near the surface time domain coherence of body wave and surface wave arrivals is computed for acceleration velocity and displacement time windows coherence is high for relatively low frequency vertical component rayleigh waves and high frequency p waves propagating across the ar ray prominent high frequency ps conversions seen on radial components a proxy for the direct s wave from earthquake sources lose coherence quickly over the 105 m length of the array transverse component signals are least coherent for any ground motion and appear to be highly scattered horizontal phase velocity is com puted by using the ratio of particle velocity to estimates of the strain based on a plane wave propagation model the resulting time dependent phase velocity map is a useful way to infer the propagation mechanisms of individual seismic phases and time windows of three component waveforms displacement gradient analysis is a complementary technique for processing general spatial array data to obtain hori zontal slowness information

broadband microtremor observation of basin resonance in the mississippi embayment central us we report systematic variations in the fundamental period of seismic site resonance within the mississippi embayment the resonance periods are revealed by peaks in horizontal to vertical h v spectral ratios of microtremor measurements and increase with the depth to the sediment basement interface the sediment depth varies slowly enough spatially that at any site it can be modeled as a one dimensional problem revealing structural details of the sedimentary column the strong impedance contrast and gentle dip of the base of the embayment sediments may trap seismic energy within the soft sediments increasing durations and amplitudes of strong ground motions broadband recordings of microtremor within the mississippi embayment provide a simple method to study the seismic response of the basin

isoprenoid and branched gdgt based proxies for surface sediments from marine fjord and lake environments in chile abstract proxies based on glycerol dialkyl glycerol tetraether gdgt lipids from archaea isoprenoid gdgts and bacteria branched br gdgts in 33 surface sediments from marine fjord and lake systems between 25 s and 50 s in chile were analyzed the regional texh86 calibration obtained from the marine and fjord sediments and mean annual surface temperature t 59 6 texh86 33 0 r2 0 9 n 23 is statistically identical to the global ocean calibration based on suspended particulate material in terms of slope but not in terms of intercept the regional surface and subsurface texh86 calibrations were statistically different from the existing global ocean core top calibrations the tex86 calibration model based on most of the relatively large lakes studied here t 50 7 tex86 11 8 r2 0 9 n 5 is statistically identical to the global lake calibration the relatively high tex86 values from smaller lakes suggested an additional source for isoprenoid gdgts likely terrestrial or aquatic methanogenic archaea application of the soil calibrated mbt cbt methylation and cyclization of br gdgts respectively temperature proxy to the marine and fjord sediments resulted in an overestimation of continental mean annual air temperature maat suggesting in situ production of certain br gdgts in the water column or surface sediment for the lakes mbt cbt based surface air temperature estimates were 3 6 c below maat however temperature estimates from the lake specific mbt cbt global calibration were in good agreement with mean annual surface temperature for all the lakes the results highlight the need for testing local vs global calibrations of gdgt based proxies before their application for palaeoenvironmental reconstruction