comparison of an optimized resistivity array with dipole dipole soundings in karst terrain wereporttheresultsofafieldcomparisonof2dresistivity data collected using both the traditional dipole dipole array and a new computer optimized array recently described in literature the study was conducted at a karst site in eastern pennsylvania computer simulations suggested that for a given line length the optimal array and the dipole dipole arraywouldbeequallyeffectiveatimagingshallowtargetsbut the optimal array would provide better resolution at depth ourfield test results showed that the two arrays imaged karst bedrock topography equally well when the full grid of 2d lines were combined and analyzed using 3d inversion however theoptimalarraywasabletoresolveacrosscuttingbedrock fracture system that was not visible in the dipole dipole data the existence of the fracture system was confirmed by drilling because the optimal array requires roughly three times as many measurements per line we conclude that the optimalarrayispreferabletotraditionaldipole dipolesoundings only when the slight improvement in resolution at depth ismoreimportantthanrapiddatacollection

permeability and voids influence on the thermal signal as inferred by multitemporal uav based infrared and visible images abstract this work presents for the first time associated thermal anomalies and deformations over subsurface cavities voids located within two harbour quays in le havre harbourg normandy france an u a v unmanned aerial vehicle was used to acquire visible and thermal images over a diurnal cycle from 7 a m to 5 p m the visible images were processed to realize an altimetric model of the platforms by mean of the photogrammetric method while the thermal infrared tir images were used to study the evolution of their surface temperatures the obtained 3d model shows the location of five topographic depressions on both quays the analysis of the evolution of the surface thermal field leads to the detection of cold thermal anomalies that are 1 not correlated to surface properties and 2 spatially associated to the flanks of the five topographic depressions using a 2d conductive radiative model we show that these anomalies are not directly due to the thermally insulating effect of an air filled area finally we conclude that preferential infiltration and subsequent evaporation in the micro fracturation present within the flanks of the depressions may be responsible for the strong cooling of these zones

increased productivity in the eastern equatorial pacific during the last glacial maximum 19 000 to 14 000 yr b p a widespread pronounced enrichment in the organic carbon content occurs at shallow depths in eastern equatorial pacific sediments the c org peak is shown by radiocarbon dating to be temporally coincident with the last stage 2 or wisconsin glacial maximum in contrast caco 3 profiles show less overall variation which appears to be partly a function of the location of the sediments relative to the lysocline consideration of the iodine c org ratio in the sediments rules out enhanced preservation as a cause of the stage 2 organic carbon enrichment the peak instead must have resulted from a significant increase in productivity during the glacial maximum

molecular and stable carbon isotopic compositions of saturated fatty acids within one sedimentary profile in the shenhu northern south china sea source implications abstract this study examined the distributions and stable carbon isotopic compositions of saturated fatty acids safas in one 300 cm long sedimentary profile which was named as site4b in shenhu northern south china sea the concentrations of total safas in sediments ranged from 1 80 to 10 16 g g g fa g dry sediment and showed an even over odd predominance in the carbon chain of c12 to c32 mostly with n c16 and n c18 being the two major components the short chain fatty acids scfas n c12 to n c18 mainly from marine microorganisms had average 13c values of 26 7 to 28 2 whereas some terrigenous sourced long chain fatty acids lcfas n c21 to n c32 had average 13c values of 29 6 to 34 1 the other lcfas n c24 n c26 n c28 average 13c values are 26 1 to 28 0 as well as n c19 and n c20 safas average 13c values are 29 1 and 29 3 respectively showed a mixed signal of carbon isotope compositions the relative bioproductivity calculation marine vs terrigenous demonstrated that most of organic carbon accumulation throughout the sedimentary profile was contributed by marine organism the high marine productivity in shenhu south china sea may be related to the hydrocarbon seepage which evidenced by diapiric structures interestingly there is a sever fluctuation of terrigenous inputs around the depth of 97 cm below the seafloor bsf probably resulting from the influence of the dansgaard oeschger events and the younger dryas event as revealed by 14c age measurements

factors influencing cavity detection in karst terrain on two dimensional 2 d direct current dc resistivity survey a case study from the western part of thailand to create a three dimensional 3 d cave and cavity network model in karst terrain from two dimensional 2 d direct current resistivity dcr profiles we first need to recognize their effects on the inversion results from a number of special cases 2 d and 3 d cavity models are created to demonstrate effects from 1 depth of the cavity 2 size and shape 3 distance to the edge of the cavity 4 orientations inclination and declination of the cavity and 5 several smaller cavities lying in an array for other complicated models combinations of these factors can be used to infer the results two parallel dcr profiles from the western part of thailand were first inverted with the 2 d inversion for interpretation knowledge gained from the numerical modeling on these special cases is helpful to constrain the interpretation and also to extend the interpretation to 3 d this gives us a picture of the 3 d cave and cavity networks beneath the area of study two main connected cavities between these two profiles can be inferred from the data along with several local cavities near the surface

recent sedimentary hopanoids in the northwestern pacific alongside the japanese islands their concentrations and carbon isotopic compositions two hopanoids 17b h 21b h hop 22 29 ene diploptene and 17b h 21b h bishomohopanoic acid bbc32ha are the most abundant among the pentacyclic triterpenoids found in recent sediments of the pacific ocean alongside the japanese islands the concentration of diploptene normalized to organic carbon content is higher in sediments where c37 polyunsaturated alkene a biomarker of haptophytes is in high concentration suggesting that the diploptene may be associated with the accumulation of marine organic matter in open marine settings d 13 c values of bbc32 ha range from 23 8 to 19 4 relative to pdb being enriched in 13 c relative to diploptene 31 6 to 26 3 by 5 9 the isotopic diaerence indicates the presence of at least partially diaerent sources for the two hopanoids while diploptene is derived from cyanobacteria and chemotrophic bacteria in the water column or sediment bishomohopanoic acid may be produced mainly by heterotrophs in the sediment using marine organic matter in contrast the d 13 c values of the two hopanoids from river and bay sediments are similar 31 to 29 indicating a common source derived from soil components terrestrial plants or bacteria in soils 2000 elsevier science ltd all rights reserved

post glacial microbialite formation in coral reefs of the pacific atlantic and indian oceans abstract the occurrence of microbialites in post glacial coral reefs has been interpreted to reflect an ecosystem response to environmental change the greater thickness of microbialites in reefs with a volcanic hinterland compared to thinner microbial crusts in reefs with a non volcanic hinterland led to the suggestion that fertilization of the reefal environment by chemical weathering of volcanic rocks stimulated primary productivity and microbialite formation using a molecular and isotopic approach on reef microbialites from tahiti pacific ocean it was recently shown that sulfate reducing bacteria favored the formation of microbial carbonates to test if similar mechanisms induced microbialite formation in other reefs as well the tahitian microbialites are compared with similar microbialites from coral reefs off vanuatu pacific ocean belize caribbean sea atlantic ocean and the maldives indian ocean in this study the selected study sites cover a wide range of geological settings reflecting variable input and composition of detritus the new lipid biomarker data and stable sulfur isotope results confirm that sulfate reducing bacteria played an intrinsic role in the precipitation of microbial carbonate at all study sites irrespective of the geological setting abundant biomarkers indicative of sulfate reducers include a variety of terminally branched and mid chain branched fatty acids as well as mono o alkyl glycerol ethers isotope evidence for bacterial sulfate reduction is represented by low 34s values of pyrite 43 to 42 enclosed in the microbialites and compared to seawater sulfate slightly elevated 34s and 18o values of carbonate associated sulfate 21 9 to 22 2 and 11 3 to 12 4 respectively microbialite formation took place in anoxic micro environments which presumably developed through the fertilization of the reef environment and the resultant accumulation of organic matter including bacterial extracellular polymeric substances eps coral mucus and marine snow in cavities within the coral framework tof sims analysis reveals that the dark layers of laminated microbialites are enriched in carbohydrates which are common constituents of eps and coral mucus these results support the hypothesis that bacterial degradation of eps and coral mucus within microbial mats favored carbonate precipitation because reefal microbialites formed by similar processes in very different geological settings this comparative study suggests that a volcanic hinterland is not required for microbialite growth yet detrital input derived from the weathering of volcanic rocks appears to be a natural fertilizer being conductive for the growth of microbial mats which fosters the development of particularly abundant and thick microbial crusts

a comprehensive approach to karst identification and groutability evaluation a case study of the dehou reservoir sw china abstract yunnan province in sw china has one of the most developed karst terrains in china and has been historically affected by sinkholes and other instability phenomena caused by unpredictable cavity formation and well developed underground hydraulic conduits during construction of a karst seepage control reservoir project grouting of a 4 6 km long anti seepage curtain in yunnan province some typical detection methods electromagnetic and water injection tests failed to map the complex geo structural karst zones clearly resulting in considerable grout loss and excessive leakage during the grouting phase of this project to deal with this limitation a comprehensive approach including a new drilling process monitoring system borehole electrical resistivity tomography borehole sonic logging and water injection tests is employed to identify the general characterization geometry and spatial distribution of karst zones along the anti seepage curtain additionally a deep belief network dbn model replaced the empirical relationships typically used to predict the grouting quantity for groutability evaluation in karstified areas the dbn algorithm is trained by data collected using this comprehensive approach rate of penetration rock permeability resistivity and p wave velocities and two previous grouting quantities as input data the lessons learned in this case study permit us to define an effective comprehensive approach for delineating the general characterization of karst zones between two boreholes and locations of potential conduits for grout flow through the borehole the proposed dbn model can predict the grouting quantity for karst regions and the accuracy of prediction is greatly affected by previous grouting quantity rather than the collected parameters

an organic geochemical assessment of oceanographic conditions at manop site c over the past 26 000 years eleven sediment samples taken downcore and representing the past 26 kyr of deposition at manop site c 0 57 2 n 138 57 3 w were analyzed for lipid biomarker composition biomarkers of both terrestrial and marine sources of organic carbon were identified in general concentration profiles for these biomarkers and for total organic carbon toc displayed three common stratigraphic features in the time series 1 a maximum within the surface sediment mixed layer 4 ka 2 a broad minimum extending throughout the interglacial deposit and 3 a deep pronounced maximum within the glacial deposit using the biomarker records a simple binary mixing model is described that assesses the proportion of terrestrial to marine toc in these sediments best estimates from this model suggest that 20 of the toc is land derived introduced by long range eolian transport and the remainder is derived from marine productivity the direct correlation between the records for terrestrial and marine toc with depth in this core fits an interpretation that primary productivity at site c has been controlled by wind driven upwelling at least over the last glacial interglacial cycle the biomarker records place the greatest wind strength and highest primary productivity within the time frame of 18 to 22 kyr b p diagenetic effects limit our ability to ascertain directly from the biomarker records the absolute magnitude that different types of primary productivity have changed at this ocean location over the past 26 kyr

the record of late pleistocene biogenic sedimentation in the eastern tropical pacific ocean we have generated 300 kyr records of biogenic opal calcite and organic carbon corg for three cores in the eastern and central equatorial pacific ocean and have compared the records to determine whether common periods of biogenic sedimentation have occurred throughout the region we find that corg has been deposited in common pulses throughout the area while opal has a much more local pattern of variation calcite varies regionally but the record is shaped by superimposed dissolution and productivity processes the most intense corg peak occurs at 18 ka and can have greater than 2 times the holocene corg content other major corg peaks occur 150 ka and perhaps at 280 ka we have compared the corg record in one of the cores v19 28 to a model deepwater oxygen record developed from 13c data in the nearby v19 30 to test whether the corg record has been mostly shaped by degradation or by the rain of organic matter from the euphotic zone we found no coherence between the two records implying that the corg record is primarily a measure of productivity by comparing the opal calcite and corg records in v19 28 a core which is at or above the lysocline we found that both increased calcite and opal deposition matches high corg accumulation we also found however that the calcite and opal records were uncorrelated so that episodes of high opal deposition do not necessarily accumulate calcite rapidly we hypothesize that at least two different plankton communities have been dominant in the waters above this site one rich in opal secreting plankton and one more dominated by calcite producers the opal rich plankton community was dominant during the intervals 10 15 ka and 35 60 ka supplement data table 2 is available with entire articleon microfiche order from american geophysical union 2000 florida avenue n w washington dc 20009 document p88001 2 50 payment must accompany order

climatic dependence of the organic matter contributions in the north eastern norwegian sea over the last 15 000 years abstract lipids are used for the evaluation of the different organic matter contributions in the north eastern norwegian sea m23258 site 75 n 14 e over the last 15 000 years development of a mass balance model based on the down core quantification of the c 37 alkenones the odd carbon numbered n alkanes a odd and the unresolved complex mixture of hydrocarbons ucm has allowed three main organic matter inputs involving marine continental and ancient reworked organic matter to be recognized the model shows good agreement between measured and reconstructed toc values similarly a strong parallelism is observed between predicted components such as marine toc and carbonate content which was determined independently representation of the model results within a time scale based on 15 ams 14 c measurements shows that the main changes in organic matter constituents are coincident with the major climatic events of the last 15 000 years thus the predominance of reworked organic matter is characteristic of termination ia up to 70 continental organic matter was dominant during the bolling allerod b a and younger dryas yd periods about 85 and a strong increase of marine organic matter occurred in the holocene between 50 and 75 this agreement reflects the main hydrographic changes that determined the deposition of sedimentary materials between 0 and 15 cal ka ice rafted detritus from the barents continental platform ice melting waters from the arctic fluvial system discharging into the barents sea and dominance of north atlantic currents respectively in this respect the high resolution down core record resulting from the mass balance and lipid measurements allows for the identification of millennial scale events such as the increase of reworked organic matter at the final retreat of the barents ice sheet at the end of the deglaciation period termination ib

factors controlling the types of microbial consortia in cold seep environments a molecular and isotopic investigation of authigenic carbonates from the south china sea authigenic carbonates were recovered from several locations of the south china sea continental slope at a 470 m to 770 m water depth the sources of seeping fluids the time involved in carbonate formation and the potential driving forces are increasingly understood but little is known about the biogeochemical processes that occur during this type of carbonate precipitation here a molecular and isotopic investigation of authigenic carbonates was conducted to determine the factors controlling the types of microbial consortia in cold seep environments the studied carbonates were one aragonitic crust and three high mg calcitic tubular concretions from specific sites a significant input of biogenic methane to the carbon pool during the precipitation of the carbonates was suggested by the presence of c 13 depleted molecular fossils of methanotrophic archaea with delta c 13 values as negative at 141 5 and sulfate reducing bacteria with delta c 13 values as negative at 128 5 the methane was primarily oxidized in an anaerobic process the predominant consortia were anme 2 assemblages in the aragonitic carbonate sample tvg3 c2 whereas high mg calcitic carbonates samples tvg14 c2 and tvg8 c5 were dominated by anme 1 assemblages according to the specific biomarkers observed taking the favored environments for specific aom consortia and crystallization conditions for aragonite and calcite together the factors selecting for specific aom communities appear to be constrained by their biogeochemical settings accordingly higher alkalinity abundant sulfate concentration and being closer to the water sediment interface conditions favor the precipitation of aragonite over high mg calcite c 2013 elsevier b v all rights reserved

biomarker temperature estimates for modern and last glacial surface waters of the california current system between 33 and 42 n sea surface temperature sst estimates were made using data for c37 39 alkenones analyzed in modern and glacial age intervals of sediment cores collected along an east west 42 n from 125 to 132 w and a north south 41 33 n transect of the california current system ccs the prymnesiophyte biomarker results suggest that surface waters warmed significantly throughout this region since the last glacial maximum lgm but the magnitude of warming varied spatially stratigraphic profiles from four sediment cores along the north south transect indicate the warming period was confined to the glacial interglacial transition 15 10 ka with sst reaching a maximum value at 10 ka and maintaining a uniformly high value throughout the holocene comparison of estimates derived from analysis of modern and lgm sediment intervals indicates the magnitude of the sst change was minimal for locations south of about 36 n 1 2 c and increased significantly 3 5 c north of this latitude using a simple heat balance model we calculate from the latitudinal gradient in sst that southward flow in the california current system during the lgm was about 60 of that measured today at 36 n our findings support the conclusion of others based on pollen data that coastal upwelling in the region of the northeast pacific off northern california was significantly reduced or even completely shutdown during the lgm

compositional similarities of non solvent extractable fatty acids from recent marine sediments deposited in differing environments abstract five recent sediment samples from a variety of north american continental shelves were analyzed for fatty acids fas in the solvent extractable solex lipids as well as four types of non solvent extractable nonex lipids the nonex lipids were operationally defined by the succession of extraction procedure required to recover them the complete procedure included i very mild acid treatment ii hf digestion and iii saponification of the sediment residue following exhaustive solvent extraction the distribution pattern and various compositional parameters of solex fas in the five sediments were divided into three different groups indicating the difference of biological sources and also diagenetic factors and processes among the three groups of samples nevertheless the compositions of the corresponding nonex fas after acid treatment were surprisingly very similar this was also true for the remaining nonex fa groups in the five sediment samples the findings implied that most of the nonex fas reported here are derived directly from living organisms it is also concluded that a large part of nonex fas are much more resistant to biodegradation than we have thought so that they can form the large percentage of total lipids with increasing depth of water and sediments

stable carbon isotopic variation of long chain n alkanoic acids in the equatorial pacific sediments over the last 40 ma implications for expansion of c4 grassland in south america abstract the stable carbon isotope ratio 13 c values of sedimentary long chain c 20 n alkanoic acids from the equatorial pacific iodp sites u1331 1338 were measured for historical reconstruction of c 4 plant contribution from south america over the last 40 ma the values for c 30 and c 32 acids ranged between 36 9 and 25 4 suggesting that they likely originated from higher plant wax associated with c 3 dominated vegetation the molecular distribution of alkanoic acids in the sediments showed a marked change across the intertropical convergence zone itcz indicating a potential contribution from the northern hemisphere to the sediments located at 10 n in contrast the abundances of n alkanoic acids significantly decreased in the sediments at 13 c values suggest that the differences in the core locations possibly caused north and southward shifts of ca 1 0 n and ca 0 5 s from the equator respectively the corrected 13 c values of c 30 and c 32 acids did not cross the c 3 end member threshold until 1 7 ma despite the onset of c 4 plants in central south america at ca 7 ma this implies that vegetation in the low latitudes of south america was less affected by hydrological changes induced by the uplift of the andes during the late miocene

comparative molecular biomarker assessment of phytoplankton paleoproductivity for the last 160 kyr off cap blanc nw africa abstract we report high resolution molecular abundance data for alkenones dinosterol long chain diols and n alkanols from odp site 658 20 45 n 18 35 w 2263 m water depth these data are compared with previously reported data for toc chlorins opal and long chain n alkanes the contents and mass accumulation rates mars of chlorins are used as total phytoplankton productivity proxies while the contents and mars of opal dinosterol alkenones and diols are used as productivity proxies for diatoms dinoflagellates haptophytes and eustigmatophytes diatoms respectively five high productivity intervals hpis are identified two at the glacial interglacial transition boundaries of 132 122 and 15 8 ka two within the warmer periods of mis 3 50 30 ka and the late holocene 4 0 ka and one within the glacial period of mis 4 67 60 ka productivity was lowest during both the penultimate glacial maximum of mis 6 150 140 ka and the last glacial maximum 22 18 ka as revealed by both the total phytoplankton and individual phytoplankton productivity indicators phytoplankton community structure changed significantly over the last 160 kyr the termination i ii hpis were characterized by higher opal content possibly reflecting increased diatom contributions to total productivity eustigmatophyte diatom and haptophyte contributions were higher during mis 5 but decreased toward the holocene dinosterol revealed an opposite trend with the highest contribution in the holocene we ascribe such changes in phytoplankton communities to the effects brought about by the varying amounts and nature of nutrient inputs contributed regionally by eolian dusts river influxes ocean currents and upwelling water masses

the organic geochemistry of peru margin surface sediments i a comparison of the c37 alkenone and historical el nino records abstract the alkenone u k 37 paleothermometer has potential as a sedimentary marker for el nino southern oscillation enso events in the peru upwelling regime we assessed this potential by comparing the historical enso record with detailed u k 37 profiles for 210 pb dated cores from the peru margin oxygen minimum zone omz sediments with the greatest potential for holding a sedimentary u k 37 record of el nino events are sediments from the center of the omz sectioned at intervals the yearly sedimentation rate the u k 37 signals of individual el nino events were substantially attenuated in the sediments we examined and periods of frequent enso activity e g 1870 1891 were more readily identified than isolated enso events in periods of less frequent enso activity detailed depth profiles of the c 37 alkenones in a core from 253 m o 2 k 37 values for the five 2 mm sections from 0 1 cm suggests that the u k 37 may be unaffected by the alkenone loss correlation between the c 37 alkenone concentration profiles in two cores from 15 s collected nine years apart are consistent with the use of these compounds for molecular stratigraphy

small changes in the sea surface temperature during the last 20 000 years molecular evidence from the western tropical pacific one of the most controversial problems of glacial paleoclimatology is the conservative change in tropical sea surface temperature sst in contrast with the large high altitude temperature change in the western tropical pacific in this report sst was estimated for the last 20 000 years using alkenones preserved in marine sediments recovered from a site 800 km north of new guinea the uk37 unsaturation degree of long chain alkenones synthesized by planktonic prymnesiophyte algae record suggests that sst decreased at most 1 5 c at the last glacial maximum this small changes in sst of the western tropical pacific is concordant with results previously reported in uk37 studies from the eastern equatorial pacific and the equatorial atlantic the uk37 based sst estimates are in good agreement with the climap results and planktonic foraminifera 18o but much smaller than those ca 5 c obtained from coral sr ca and 18o thermometries and glacial vegetation reconstruction

global variations of surface ocean productivity in low and mid latitudes influence on co2 reservoirs of the deep ocean and atmosphere during the last 21 000 years based on detailed reconstructions of global distribution patterns both paleoproductivity and the benthic 13c record of co2 which is dissolved in the deep ocean strongly differed between the last glacial maximum and the holocene with the onset of termination i about 15 000 years ago the new export production of low and mid latitude upwelling cells started to decline by more than 2 4 gt carbon year this reduction is regarded as a main factor leading to both the simultaneous rise in atmospheric co2 as recorded in ice cores and with a slight delay of more than 1000 years to a large scale gradual co2 depletion of the deep ocean by about 650 gt c this estimate is based on an average increase in benthic 13c by 0 4 0 5 the decrease in new production also matches a clear 13c depletion of organic matter possibly recording an end of extreme nutrient utilization in upwelling cells as shown by sarnthein et al 1987 the productivity reversal appears to be triggered by a rapid reduction in the strength of meridional trades which in turn was linked via a shrinking extent of sea ice to a massive increase in high latitude insolation i e to orbital forcing as primary cause

modifications of the c37 alkenone and alkenoate composition in the water column and sediment possible implications for sea surface temperature estimates in paleoceanography 1 the literature pertaining to c37 alkenone and c37 and c38 alkenoate production and diagenesis has been reviewed and evaluated for issues that might jeopardize their usefulness in paleotemperature estimation we also examined the use of the c37 alkenones as paleoproductivity indicators the stability of their 13c isotopic compositions and their incorporation into the nonsolvent extractable organic matter fraction biological transformation of organic matter by bacteria and zooplankton does not appear to cause significant changes to the ratio of c37 2 and c37 3 alkenones but there are major alterations in the relative composition of alkenoates studies of water column processes and postdepositional sedimentary changes indicate overall stability in the c37 2 c37 2 c37 3 ratio leading to effective preservation of the paleotemperature signal this is not the case for alkenoates and there also appear to be some doubts about the dependence between sea surface temperature and the sedimentary abundance of the c37 4 alkenone c37 alkenones may provide useful qualitative estimates of marine paleoproductivity although these compounds are apparently only derived from haptophycea changes in their quantitative composition might reflect changes in nutrient availability that on sedimentary timescales should also be generally significant of other algal species one caveat is that in highly productive upwelling systems productivity may be expressed mostly in diatom growth and thus not measurable by the c37 alkenones no changes in 13c c37 alkenone composition are observed upon zooplankton ingestion although this is expected from a theoretical perspective further studies are encouraged in order to fully assess the stability of the isotopic signal during c37 alkenone diagenesis finally alkenones bound in the nonextractable fraction of sedimentary organics have not been adequately studied and further work is required to clarify any possible correspondence with a temperature signal

high resolution alkenone sea surface temperature variability on the north icelandic shelf implications for nordic seas palaeoclimatic development during the holocene the palaeoceanography of the northern icelandic shelf for the holocene period was reconstructed from alkenone indices measured in core jr51 gc35 this contains a continuous record of holocene sedimentation spanning 0 10 2 cal kyr bp with a resolution of 20 yr cm we have identified a general holocene cooling trend that has superimposed millennial scale oscillations of 28c their timing is in close agreement with the timing of glacier advances in northern iceland for the later half of the holocene the alkenone sea surface temperature sst record from jr51 gc35 correlates with proxy data for the strength of nadw formation recorded in cores south of iceland this is interpreted as evidence of a close connection existing between north icelandic sea surface temperatures and the north atlantic meridonal overturning circulation the timing of the millennial scale sst variability in our core off north iceland is found to be out of phase or anti phased with the sst variability of a record in the eastern nordic seas md952011 this suggests that the evolution of holocene climate in the nordic seas was more complex than previously proposed and it is likely to be caused by differential responses of the irminger and norwegian currents and modulated by changes in atmospheric circulation analogous to the north atlantic oscillation

biogeochemical formation of calyx shaped carbonate crystal fans in the subsurface of the early triassic seafloor abstract the kuh e dena sedimentary section in iran developed on the southwestern margin of the neotethys ocean the fossil and bioturbation lean early triassic section late dienerian to early smithian is typified by finely laminated calcareous shales that are interbedded with laterally extending carbonate beds which are mostly composed of calyx shaped carbonate crystal fans the calyxes consist of fibrous crystals that apparently formed within the subseafloor in soft water saturated sediment by displacive growth rare earth element and yttrium patterns indicate that calyx shaped crystals precipitated from anoxic pore waters biomarker patterns of the carbonate beds reveal major input of lipids from prokaryotes that typically occur within layered benthic microbial mats i e cyanobacteria anoxygenic phototrophic bacteria sulphate reducing bacteria and methanogenic archaea along their length the fibrous crystals of the calyxes reveal a trend of increasing 13 c carb values from 2 7 to 3 3 suggesting that archaeal methanogenesis affected the carbonate pool apart from the putative benthic prokaryotes molecular fossils of halophilic most likely planktic archaea were detected in the carbonate beds low pristane to phytane ratios 0 8 and the presence of halophilic archaea are in accord with the lack of bioclasts and bioturbation which likely reflects increased salinities the former presence of a benthic microbial mat with cyanobacteria underlain by anoxygenic phototrophic bacteria sulphate reducing bacteria and methanogenic archaea is in accordance with studies on living microbial mats in hypersaline low oxygen marine environments the early triassic subseafloor seems to have been a sink for carbon driven by biologically induced formation of secondary diagenetic carbonate

a giant underwater encrusted stalactite from the blue hole lighthouse reef belize revisited a complex history of biologically induced carbonate accretion under changing meteoric and marine conditions a late pleistocene to holocene submerged and encrusted speleothem exhibits a complex history including a meteoric phase and two marine phases a combined study using petrography mineralogy and inorganic and organic geochemistry as well as geochronology has shown that phototrophic and heterotrophic biological activity impacted carbonate precipitation during all phases of carbonate accretion the stalactite formed ca 30 m below modern sea level at a marginal overhang in the blue hole of lighthouse reef atoll unlike purely meteoric speleothems the belize example consists of a meteoric core a marine aragonite crust and a serpulid micrite rich outer crust as a result of postglacial flooding of the karst cave the core of the stalactite has a tufaceous texture containing algal or microbial remains and consists entirely of low magnesium calcite formed 19 55 10 68 kyr bp the texture suggests that the stalactite formed at the cave entrance and hence the former cave ceiling had apparently collapsed earlier during the pleistocene oxygen 18o and carbon 13c isotopes across the core suggest a trend towards drier conditions and reduced soil and plant cover after the last glacial maximum the marine aragonite crust consists of stacked botryoids in which individual crystals up to 700 lm have dark terminations enriched in high magnesium calcite this crust accreted from 10 82 to 9 95 kyr bp in warm shallow water during the early holocene thermal optimum carbonate accretion rates were considerable and averaged 125 m yr the crust has a dense laminated texture on one side and a porous shrubby texture on the other the presence of n c16 1 5 n c17 1 6 and 10me c16 fatty acids in the laminated crust suggests that sulfate reducing bacteria contributed to aragonite formation in an environment that was less open than the formation environment of the porous crust where these biomarkers are lacking n c16 1 5 n c17 1 6 or are less abundant 10me c16 enrichment of 34s and 18o in carbonate associated sulfate cas relative to seawater sulfate also suggests sulfate reduction during carbonate formation the greater contribution of heterotrophic processes to aragonite precipitation in the laminated crust is also reflected in 13c values as low as 1 3 whereas no such depletion is observed in the aragonite of the porous crust 13c values as low as 0 0 a pronounced isotopic variability and excursions to positive 13c values as high as 3 5 0 in the inner half of the laminated crust indicate an episodic local impact of photosynthesis on aragonite precipitation whereas the lack of such excursions in the porous crust 13c values as high as 1 5 0 is again best explained by a more open environment of formation after a ca 5 kyr hiatus from 4 39 kyr bp a biogenic crust of abundant serpulids and finely crystalline microbial and detrital carbonate consisting of high magnesium calcite and aragonite accreted on the outer surface of the stalactite outermost crust accretion was probably influenced by the inundation of the lighthouse reef lagoon that started to shed abundant fine grained carbonate sediment into the blue hole the stalactite broke off the cave ceiling either before or after the formation of the outermost crust likely due to seismic movements along the nearby plate boundary the study demonstrates that like speleothems from the terrestrial realm submerged stalactites may have had complex histories with great potential as paleoenvironmental archives

carbon and hydrogen isotopic compositions of sterols from riverine and marine sediments the sources marine algae terrestrial c3 and c4 plants of sterols deposited to sediments along a riverine marine transect from ohtsuchi river in iwate prefecture japan to the northwestern pacific ocean were estimated using carbon d 13 c and hydrogen isotopic compositions dd in surface sediments in marine sediments algal sterols such as 24 methylcholesta 5 22 dien 3b ol had d 13 c values of 222 7 6 0 4 and dd values of 2292 6 3 in contrast sterols derived from multiple potential sources such as 24 methylcholest 5 en 3 b ol and 24 ethylcholest5 en 3b ol were gradually enriched in 13 c from riverine 230 7 and 230 5 respectively to marine sediments 222 3 and 224 4 respectively but showed little variation in dd values 2262 6 1 these isotopic signatures suggest that 24 methylcholest 5 en 3b ol and 24 ethylcholest 5 en 3b ol are derived from c3 plants 90 and c4 plants 10 in the riverine sediments and marine algae 30 c3 plants 30 and c4 plants 40 in the open marine sediments thus dual isotopic compositions d 13 c dd of sterols allow determinations of the proportions of three biological sources in which the relative contribution of c3 plants decreases while that of marine algae and c4 plants increases from riverine to marine sediments these results indicate that d 13 c dd signatures of sterols provide a useful tool for interpreting the sources of sedimentary organic matter and for understanding the transport and mixing processes of distinct biological sources in riverine marine environments quantitative assessment of organic matter inputs from marine algae and terrestrial plants to riverine and marine sediments is important for understanding the burial and mixing processes affecting organic matter at continental margins and for estimating marine primary productivity and carbon flux associated with biogeochemical cycles in surface environments marine algae and terrestrial c3 and c4 plants are major primary producers and potential sources for sedimentary organic matter in river dominated coastal environments molecular and isotopic compositions of sedimentary organic materials should reflect both variations in the input of marine algae relative to terrestrial plants and in the proportions of c3 and c4 terrestrial plant inputs many previous studies have estimated the relative contribution between two biological sources marine algae vs terrestrial plants or terrestrial c3 vs c4 plants for sedimentary organic materials from riverine or coastal to marine environments based on biomarker assessments e g laureillard and saliot 1993 mannino and harvey 1999 carbon isotopic compositions of bulk organic carbon e g wada et al 1987 carreira et al 2002 and specific biomarkers including lignin derived com1

upwelling and productivity changes inferred from a temperature record in the central equatorial pacific a series of c37 39 alkenones synthesized by prymnesiophyte algae is commonly preserved in marine sediments and can be used for estimating past sea surface temperatures ssts 1 2 here we present an alkenone analysis of sediments taken from the central equatorial pacific ocean core w8402a 14gc 0 57 n 138 57 w which shows that sst varied slightly 2 c but coherently with milankovitch insolation cycles over the past 250 kyr the in phase response of the sst to the precessional component of insolation indicates that this part of the sst time series may be driven by changes in local trade wind strength and the longer 100 kyr eccentricity component indicates a response to basin wide south pacific winds using a simple heat balance model we use our palaeotemperature record to constrain the upwelling rates that have occurred in the past similar sst records from the eastern pacific could constrain the horizontal advection component of the sst record and allow for better estimates of upwelling upwelling and palaeoproductivity then could be compared to determine whether changes in equatorial nutrient levels actually cause equivalent changes in productivity

organic carbon accumulation over the last 16 kyr off vancouver island canada evidence for increased marine productivity during the deglacial abstract the organic carbon content of marine sediments is commonly used as a proxy for export production however in continental margin sediments a large fraction of the organic matter may be of terrestrial origin and it is necessary to correct the total organic carbon data accordingly radiocarbon dating of bulk organic carbon organic geochemistry and isotope data 13c and 15n are used here to characterize the type of organic matter present in core jt96 09 collected at a water depth of 920 m on the slope off western canada the quantities of marine and terrestrial organic carbon are then estimated using the 13c data the 16 kyr record obtained from core jt96 09 suggests that accumulation of total organic carbon was highest during the late glacial and deglacial but geochemical data indicate that as much as 70 of this carbon is terrestrial in origin when the palaeo record is corrected for this terrigenous input it is observed that accumulation of marine organic matter and presumably marine export production increased at the end of the last glacial contemporaneous with the bolling and that it peaked during the allerod data from other palaeoproductivity proxies i e bio barium opal and alkenones also indicate relatively high productivity during the deglacial these results indicate a return to modern upwelling conditions and high marine export production at 14 3 calendar kyr bp and a period of enhanced upwelling relative to the present during the allerod

evidence for molecular structural variations in the cytoarchitectures of a jurassic plant in this study we investigate the molecular structural characteristics of organic remains in various cellular organelles from a 180 ma jurassic royal fern belonging to the osmundaceae family of ferns and compare their carbon isotopic compositions to a now living species of royal fern osmunda regalis we discovered molecular structural variations indicated by raman and infrared spectral parameters obtained from various fossilized cellular organelles the organic remains preserved in the chromosomes and cell nuclei show marked structural heterogeneities compared to the cell walls during different stages of the cell cycle the fossil and extant fern have similar 13 c values obtained from bulk samples supporting evolutionary stasis in this plant lineage and an unchanged metabolic pathway of carbon assimilation since the jurassic the organic remains in the cellular organelles of the fossil seem to be less heterogeneous than those in the extant fern likely due to the preferential preservation of certain cellular compounds during fossilization taphonomic processes appear to have diminished the subcellular isotopic heterogeneities our research sheds light on the functioning of ancient plant cellular organelles during mitosis provides insights to the taphonomic processes operating at molecular and isotopic levels and shows the practicability of in situ techniques in studying the evolution and behaviors of ancient cells

photosynthetic fractionation of 13c and concentrations of dissolved co2 in the central equatorial pacific during the last 255 000 years carbon isotopically based estimates of co2 levels have been generated from a record of the photosynthetic fractionation of 13c is equivalent to epsilon p in a central equatorial pacific sediment core that spans the last approximately 255 ka contents of 13c in phytoplanktonic biomass were determined by analysis of c37 alkadienones these compounds are exclusive products of prymnesiophyte algae which at present grow most abundantly at depths of 70 90 m in the central equatorial pacific a record of the isotopic composition of dissolved co2 was constructed from isotopic analyses of the planktonic foraminifera neogloboquadrina dutertrei which calcifies at 70 90 m in the same region values of epsilon p derived by comparison of the organic and inorganic delta values were transformed to yield concentrations of dissolved co2 is equivalent to c e based on a new site specific calibration of the relationship between epsilon p and c e the calibration was based on reassessment of existing epsilon p versus c e data which support a physiologically based model in which epsilon p is inversely related to c e values of pco2 the partial pressure of co2 that would be in equilibrium with the estimated concentrations of dissolved co2 were calculated using henry s law and the temperature determined from the alkenone unsaturation index u k 37 uncertainties in these values arise mainly from uncertainties about the appropriateness particularly over time of the site specific relationship between epsilon p and 1 c e these are discussed in detail and it is concluded that the observed record of epsilon p most probably reflects significant variations in delta pco2 the ocean atmosphere disequilibrium which appears to have ranged from approximately 110 microatmospheres during glacial intervals ocean atmosphere to approximately 60 microatmospheres during interglacials fluxes of co2 to the atmosphere would thus have been significantly larger during glacial intervals if this were characteristic of large areas of the equatorial pacific then greater glacial sinks for the equatorially evaded co2 must have existed elsewhere statistical analysis of air sea pco2 differences and other parameters revealed significant p 0 01 inverse correlations of delta pco2 with sea surface temperature and with the mass accumulation rate of opal the former suggests response to the strength of upwelling the latter may indicate either drawdown of co2 by siliceous phytoplankton or variation of co2 si oh 4 ratios in upwelling waters

assessment of sea surface temperature at 42 n in the california current over the last 30 000 years assessment of changes in surface ocean conditions in particular sea surface temperature sst is essential to understand long term changes in climate especially in regions where continental climate is strongly influenced by oceanographic processes to evaluate changes in sst in the northeast pacific we have analyzed long chain alkenones of prymnesiophyte origin at 38 depths in a piston and associated trigger core collected beneath the contemporary core of the california current system at 42 n 270 km off the coast of oregon california the samples span 30 000 years of deposition at this location unsaturation patterns u37k in the alkenone series display a statistically significant difference p 0 001 between interglacial 0 44 0 02 n 11 and glacial 0 29 0 04 n 20 intervals of the cores detailed examination of other compositional features of the c37 c38 c39 alkenone series and a related c36 alkenoate series measured downcore suggests the published u37k temperature calibration u37k 0 034 t 0 039 defined for cultures of a strain of emiliania huxleyi isolated from the subarctic pacific provides best estimates of winter sst at our study site this inference is purely statistical and does not imply however that the phytoplankton source of these biomarkers is most productive in winter or at the ocean surface the temperature record for u37k implies 1 an 4 c shift occurred in winter sst from 7 5 1 1 c at the last glacial maximum to 11 7 0 7 c in the present interglacial period and 2 this warming trend was confined to the time frame 14 10 ka within the glacial to interglacial transition period these conclusions are corroborated entirely by results from an independent sst transformation of radiolarian species assemblage data obtained from the same core materials

the response of benthic foraminifera to productivity cycles in the eastern equatorial pacific faunal and geochemical constraints on glacial bottom water oxygen levels the stage 2 glacial maximum in eastern equatorial pacific ocean sediments is characterized by a pronounced increase in the organic carbon content which has been attributed either to increased upwelling and higher production along the equatorial divergence during the last glacial period or to enhanced preservation as a consequence of a lower concentration of dissolved o2 in glacial bottom water several lines of evidence are presented based on data from two gravity cores collected from the central panama basin which support the former interpretation first both the abundance and the size of benthic foraminifera of the genus uvigerina increase in stage 2 coincident with the increase in organic carbon concentration most probably because of the greater availability of organic detritus during the glacial period the increase in foraminiferal size and associated greater requirement of oxygen for respiration argues against the probability that oxygen was substantially depleted in the upper centimeter where uvigerina spp are thought to live second the number of meiofaunal faecal pellets increases markedly during the stage 2 maximum indicating a more populous and active infauna which again argues against oxygen depletion third there is no significant decrease in the iodine organic carbon i corg ratio in the stage 2 sediments because iodine is depleted relative to carbon in anoxic basins but enriched in association with organic matter in oxic environments the absence of a depletion in the i corg ratio in stage 2 is evidence that bottom water remained oxygen replete during the last glacial fourth molybdenum is not enriched in sediments deposited in stage 2 the presence of anoxic or dysaerobic bottom water or shallow pore waters during that time would have been recorded by the addition of mo to the sediments via coprecipitation with authigenic iron sulphides the combined faunal and geochemical data are consistent with the notion that panama basin deep waters remained oxygen replete during the last glacial maximum it is concluded that the late stage 2 carbon enrichment in the eastern equatorial pacific more probably reflects higher productivity rather than enhanced preservation

exploration for a cave by magnetic and electrical resistivity surveys ayvacik sinkhole example bozdag izmir western turkey abstractgeophysical survey techniques have been successfully applied to near surface cave detection in karstic terrains we used magnetic and electrical resistivity surveys to delineate the karstic structure of the ayvacik sinkhole which may be considered to be a vertical cave the magnetic total field anomaly map helped reveal the metamorphic and sedimentary units in the study area the total horizontal gradient map which was based on a calculated pseudogravity anomaly successfully identified the contact between the limestone unit and the cave system using these results we positioned and carried out a vertical electrical sounding ves survey with a schlumberger array along a line that consisted of 11 stations the ves data were then processed using a 1d global optimization technique which used a genetic algorithm and a 2d linearized least squares algorithm the results were generally in good agreement with each other and together they pointed out three geologic layers 1 an overburden layer 3

hypersaline conditions during deposition of the calcare di base revealed from archaeal di and tetraether inventories abstract the calcare di base is a widespread messinian carbonate formation in the mediterranean especially in sicily and calabria italy the environmental conditions under which these limestones were deposited their formation mechanism and the timing of deposition are a matter of debate in order to shed new light on their formation the lipid biomarker inventories of calcare di base from four locations in sicily and calabria were studied following petrographical and mineralogical characterization of the limestone samples the mineralogy is chiefly calcite the microfabric is mostly peloidal and partly laminated or brecciated deposition took place at high salinity as confirmed by numerous pseudomorphs after halite long chain n fatty acids were the most abundant lipid biomarkers in samples from all sites but isoprenoid alcohols were also abundant the most prominent archaeal compounds were diphytanyl glycerol diethers dgds and glycerol dibiphytanyl glycerol tetraethers gdgts among these archaeol and gdgt 0 caldarchaeol predominated respectively other gdgts were virtually absent minor amounts of c 20 25 dgd extended archaeol a biomarker for halophilic archaea were detected in all samples the 13 c values of caldarchaeol avg 20 and archaeol avg 11 varied widely indicating that these compounds derived from distinct archaeal precursor lipids based on lipid biomarker patterns the calcare di base had been previously considered to represent a normal marine deposit in contrast to the evaporitic gypsum and halite deposits in messinian successions the archaeal biomarker inventories from the calcare di base samples reported here in conjunction with the occurrence of pseudomorphs after halite reveal that deposition took place in a hypersaline environment

coral record of equatorial sea surface temperatures during the penultimate deglaciation at huon peninsula uplifted coral terraces at huon peninsula papua new guinea preserve a record of sea level sea surface temperature and salinity from the penultimate deglaciation remnants have been found of a shallow water reef that formed during a pause similar to the younger dryas in the penultimate deglaciation at 130 000 2000 years ago when sea level was 60 to 80 meters lower than it is today porites coral which grew during this period has oxygen isotopic values and strontium calcium ratios that indicate that sea surface temperatures were much cooler 22 2 c than either last interglacial or present day tropical temperatures 29 1 c these observations provide further evidence for a major cooling of the equatorial western pacific followed by an extremely rapid rise in sea level during the latter stages of termination ii

mid pliocene warmth stronger greenhouse and stronger conveyor abstract three million years ago prior to the onset of northern hemisphere glaciation global mean temperatures may have been as much as 3 5 c warmer than at present we present evidence based on the carbon isotopic composition of marine organic matter that atmospheric co2 levels at this time were on average only about 35 higher than the preindustrial value of 280 ppm we also present carbon isotopic evidence for stronger thermohaline circulation in the atlantic ocean during the warmest intervals and propose that the north atlantic conveyor belt may act as a positive feedback to global warming by enhancing sea ice retreat and decreasing high latitude albedo based on our results it seems unlikely that the mid pliocene warm period was a doubled co2 world

variations of terrestrial input and marine productivity in the southern ocean 48 s during the last two deglaciations various biomarkers n alkanes n alcohols and sterols have been studied in a piston core tsp 2pc taken from the southern ocean to reconstruct the paleoenvironmental changes in the subantarctic region for the last two deglaciations mass accumulation rates of terrestrial higher molecular weight n alkanes and n alcohols and marine dinosterol and brassicasterol biomarkers increased significantly at the last two glacials and stayed low during interglacial peaks early holocene and the eemian these records indicate that the enhanced atmospheric transport of continental materials and the increased marine biological productivity were synchronously linked in the southern ocean at the last two glacials this suggests that increased glacial dust inputs have relieved iron limitation in the subantarctic southern ocean these two processes however were not linked at the cooling phase from the eemian to marine isotope stage mis 5d during this period paleoproductivity may have been influenced by the latitudinal migration of the high production zone associated with the antarctic polar front

factors controlling 13c contents of sedimentary organic compounds principles and evidence the carbon isotopic composition of any naturally synthesized organic compound depends on 1 the carbon source utilized 2 isotope effects associated with assimilation of carbon by the producing organism 3 isotope effects associated with metabolism and biosynthesis and 4 cellular carbon budgets these factors are reviewed and quantitative considerations summarized particularly with regard to active and passive modes of carbon assimilation by phytoplankton and the existence of discernible regularities in isotope effects associated with lipid biosynthesis it is concluded that n alkyl lipids are in general depleted in 13c by about 1 5 relative to polyisoprenoid lipids produced by the same organism the effects of biological reworking on isotopic compositions of organic carbon are examined and it is suggested that enrichment of 13c in sedimentary organic carbon may result from loss of ch4 from zooplanktonic gut communities isotopic methods for estimation of ancient co2 levels are considered and a hyperbolic form favored for the relationship between concentrations of dissolved co2 and isotopic fractionation

sources of long chain fatty acids in deep sea sediments from the bering sea and the north pacific ocean abstract the distributions and compound specific carbon isotope ratios of long chain n fatty acids and long chain n alkanes in two sedimentary cores collected from the north pacific ocean and the bering sea have been examined long chain fatty acids were further fractionated into three sub fractions esterified free and polar to investigate their sources the 13 c values of these fractions clarified the sources of different fatty acids the esterified fraction had lighter 13 c values 30 1 0 70 similar to those of the long chain n alkanes 30 2 1 08 consistent with a mainly terrestrial plant origin in contrast the long chain fatty acids except c 28 from the polar and free fractions had heavier isotopic values 27 5 1 06 suggesting a mixed origin from terrestrial and marine organisms the esterified fatty acids from the north pacific ocean and the bering sea can be used as terrestrial biomarkers

karst geosites at risk of collapse the sinkholes at nociglia apulia se italy this paper focuses on the impacts of contemporary geomorphological processes on fruition activities in a karst area of salento apulia southeastern italy the work illustrates the results of studies in a sinkhole field at nociglia in the lecce province recently recognized as a geosite and where shallow phreatic speleogenesis operates close to the water table level with the formation of karst caves successive roof collapse formation of wide caverns and sinkhole development at the surface all these features threaten the nearby infrastructures including a province road salento has a great number of active sinkholes related to natural and anthropogenic cavities their presence is at the origin of several problems in the built up environment due to increasing population growth and development pressures in such a context the detection of cavities and the assessment of sinkhole hazards present numerous difficulties to assess the potential danger from sinkholes it is important to identify and monitor the main factors contributing to the formation process a multi disciplinary approach comprising geological geomorphological and geophysical analyses is necessary to obtain a comprehensive knowledge of these complex phenomena in karst areas geophysical methods can be of great help to monitor the processes and for identifying and mapping features related to the underground voids by detecting contrasts in physical properties such as density and electrical resistivity with the surrounding sediments at the same time recognition of the presence of sinkholes by geophysical methods has to adapt to the local geological conditions and take advantage of the integration of the several methodologies available the territory of nociglia demonstrates that monitoring is essential for the safe exploitation of these type of geomorphosites

cave detection using multiple geophysical methods unicorn cave harz mountains germany unicorn cave in the southern harz mountains of germany is a show cave in dolomitic rocks of the zechstein formation the cave s trunk passage is interrupted by larger rooms the overburden is only around 15 m the passages are filled with sediments that can be up to 50 m thick we used gravimetry and electrical resistivity imaging over the cave area to identify the subsurface voids and the extent of the sediment infill of the cave passages our choice of methods was based on several conditions unique to the cave 1 well surveyed 2 shallow overburden 3 large air filled passages and 4 thick sediment cover concealing true passage size using the cave survey as an initial model for the subsurface structure we successfully identified the air filled cave with both methods we then inferred the thickness of the sediment infill by forward modeling and identified a possible southward continuation beyond the currently explored passages

molecular and isotopic abundances of long chain n fatty acids in open marine sediments of the western north pacific abstract molecular abundance and compound specific carbon isotope ratios of long chain n fatty acids lcfas ranging from c20 to c30 are reported for open marine sediments of the western north pacific a positive correlation r2 0 94 is observed between total organic carbon toc and lcfa concentrations although the toc concentrations varied from 0 34 to 2 62 wt in dry sediment the relatively uniform ratio of lcfas to toc 0 74 0 12 mg gc is similar to that of the central pacific reported by ohkouchi et al ohkouchi n kawamura k kawahata h taira a 1997 latitudinal distributions of terrestrial biomarkers in the sediments from the central pacific geochim cosmochim acta 61 1911 1918 and in a core sample from the tropical central pacific by prahl et al prahl f g muehlhausen l a lyle m 1989 an organic geochemical assessment of oceanographic conditions at manop site c over the past 26 000 years paleoceanography 4 495 510 on the other hand lcfa concentrations in riverine and estuarine sediments are apparently higher than in open marine sediments carbon isotopic compositions of individual lcfas in open marine sediments are similar 26 1 for n c24 and n c26 being more enriched in 13 c than bay and riverine sediments by up to 6 terrestrial c3 higher plants commonly have a 13 c value of 26 in bulk organic carbon and because lipid components including fatty acids are known to be depleted in 13 c by several per mil compared to bulk organic matter this study indicates that the open marine sedimentary lcfas are not derived from normal terrestrial c3 higher plants rather the isotopic composition is consistent with a mixed source of c4 and c3 terrestrial higher plants and or marine organisms low carbon preference index cpi values of the lcfas and the isotopic difference between the northern and southern samples suggest that the lcfas of this study are likely to be related to marine primary productivity even though lcfas have often been used to infer a terrestrial higher plant input to marine sediments

practical techniques for 3d resistivity surveys and data inversion1 techniques to reduce the time needed to carry out 3d resistivity surveys with a moderate number 25 to 100 of electrodes and the computing time required to interpret the data have been developed the electrodes in a 3d survey are normally arranged in a square grid and the pole pole array is used to make the potential measurements the number of measurements required can be reduced to about one third of the maximum possible number without seriously degrading the resolution of the resulting inversion model by making measurements along the horizontal vertical and 45 diagonal rows of electrodes passing through the current electrode the smoothness constrained least squares inversion method is used for the data interpretation the computing time required by this technique can be greatly reduced by using a homogeneous half space as the starting model so that the jacobian matrix of partial derivatives can be calculated analytically a quasi newton updating method is then used to estimate the partial derivatives for subsequent iterations this inversion technique has been tested on synthetic and field data where a satisfactory model is obtained using a modest amount of computer time on an 80486dx2 66 microcomputer it takes about 20 minutes to invert the data from a 7 by 7 electrode survey grid using the techniques described below 3d resistivity surveys and data inversion can be carried out using commercially available field equipment and an inexpensive microcomputer

alkenone paleothermometry biological lessons from marine sediment records off western south america an empirical global core top calibration that relates the alkenone unsaturation index u k 0 37 to mean annual sst masst is statistically the same as that defined for a subarctic pacific strain of emiliania huxleyi ccmp1742 grown exponentially in batch culture under isothermal conditions although both equations have been applied widely for paleosst reconstruction uncertainty still stems from two key ecological factors variability in the details of biosynthesis among genetically distinct alkenone producing strains and impacts of nonthermal physiological growth factors on u k 0 37 new batch culture experiments with ccmp1742 here reveal that u k 0 37 diverge systematically from the core top calibration in response to nutrient depletion and light deprivation two physiological stresses experienced by phytoplankton populations in the real ocean other aspects of alkenone alkenoate composition also respond to these stresses and may serve as signatures of such effects providing an opportunity to detect understand and potentially correct for such impacts on the geologic record a test case documents that sediments from the southeast pacific display the alkenone alkenoate compositional signature characteristic of cells physiologically stressed by light deprivation such an observation could be explained if marine snow provided a major vector of sedimentation for these biomarkers late pleistocene u k 0 37 records in the southeast pacific yield plausible paleotemperature histories of ice age cooling but ice age alkenone alkenoate signatures fall outside the range of modern calibration samples of similar u k 0 37 they better match core top samples deposited beneath waters characterized by much cooler masst suggesting key features of ice age ecology for alkenone producing haptophytes were different from today and that the u k 0 37 index taken alone may misgauge the total range of ice age cooling at these locations analysis of the full spectrum of alkenone alkenoate compositions preserved in sediments opens up a new opportunity that may improve the accuracy of paleotemperature estimates based on simple u k 0

fluctuation of biogenic and abiogenic sedimentation on the shatsky rise in the western north pacific during the late quaternary abstract sedimentation of biogenic and abiogenic components was studied in cores ngc108 36 36 85 n 158 20 90 e water depth 3390 m and s2612 32 19 84 n 157 51 00 e water depth of 2612 m from the shatsky rise to understand fluctuations in primary productivity and abiogenic sedimentation in the mid latitude of the western north pacific during the late quaternary the mean c organic n atomic ratio of 6 0 7 8 in both cores indicates that organic matter is mainly marine in origin organic carbon is positively correlated with biogenic opal in core ngc108 in contrast to a weak correlation in core s2612 although the maxima of paleoproductivity estimates in both cores generally occur during glacial times the paleoproductivity estimates biogenic opal carbonate ratios and the c organic c carbonate ratios have always been higher in core ngc108 than in core s2612 during the last 180 kyr suggesting that the surface water at site ngc108 could have been influenced more by subarctic water mass than at site s2612 however the opal carbonate ratio in core s2612 remains fairly constant relative to that in core ngc108 which might mean that the transition zone between subarctic and central water was narrower in latitude in at the oxygen isotope stage ois 2 3 boundary ois 4 and ois 6 sedimentation of 13 inorganic elements has been measured in both cores these elements are classified into four groups based on correlation between each element in content 1 terrigenous components al ti fe 2 biogenic calcareous material ca sr 3 biogenic scavenged elements mg zn cr be and 4 the other elements mn ba cu ni the terrigenous mass accumulation rates were elevated in ois 2 3 and 4 and late ois 6 in core ngc108 while they were higher in early ois 1 ois 2 4 and 6 in core s2612 mno 2 and ba might be redistributed during the sub surface reduced condition especially precipitation of particle reactive be which could be accelerated by both enhanced terrigenous input and biogenic vertical transport has fluctuated largely in response to climatic change because of its short residence time on the order of the oceanic mixing time

habitability of europa s crust the role of tidal tectonic processes jupiter s satellite europa has been identified as one of the most likely sites for life in the solar system the tidal tectonic processes that appear to have governed europa s geology seem to require interaction with an ocean under only a very thin crust providing a variety of evolving environmental niches the mutually dependent relationship between orbital evolution and tidal processes in turn controls europa s rotation heating and stress surface lineaments are correlated with global stress patterns demonstrating that they form by crustal cracking but only if a substantial ocean is present to give adequate tidal amplitude tidal driving of strike slip faulting indicates that cracks penetrate to a fluid layer which is possible only with a very thin ice crust the characteristic ridge sets that cover tectonic terrain are likely built by tidal pumping of fluid and slush to the surface on a daily basis widespread tectonic dilation creates new surface as material rises from below chaotic terrain has morphology and other characteristics indicative of melt through from below surface colorants correlate with locations such as along large scale ridge systems and around chaotic terrain where ocean water reached the surface this model implies that as a result of tides liquid water regularly bathed crustal cracks and surfaces with heat and whatever nutrients are included in the oceanic chemistry creating a variety of habitable environments the processes were recent and thus most likely continue today longer term evolution of environmental conditions provided the need for adaptation and opportunity for evolution

the relationship between sedimentary organic carbon isotopic composition and organic biomarker compound concentration abstract a study of organic biomarker compounds which could serve as tracers of terrigenous and marine sedimentary organic matter sources was performed on samples from a 208 7 m hydraulic piston core hole dsdp hole 619 from the hemipelagic pigmy basin in the northern gulf of mexico organic carbon normalized concentrations of total long chain c37 c39 alkenones and some individual c27 c29 desmethyl sterols were determined to be useful proportional indicators tracers of preserved marine and terrigenous organic carbon respectively the alkenones whose only known source is marine phytoplankton of the class prymnesiophyceae generally occurred in higher concentrations in interglacial isotope stages 1 and 5a b than in the intervening glacial stages sterols c27 c29 apparently of a dominantly terrigenous origin occurred in lower concentrations during interglacial stages than in glacial stages tracers of both terrigenous and marine organic matter appear to be affected by the differential diagenetic alteration of the biomarker corg ratios as indicated by a simple first order kinetic model the lack of any desmethylor 4a methylsterol which is linearly related to the proportion of marine sedimentary organic matter as scaled by 13corg indicates that either 1 1 sedimentary diagenesis has obscured the biomarker corg vs 13corg record 2 2 phytoplanktonic assemblage changes caused variations in the biomarker corg ratio of the primary input preferential preservation of terrigenous sterols may result in a biased sedimentary record of sterol input which could be misinterpreted as indicating solely terrigenous sterol sources a simple model which characterizes the effects of sedimentary diagenesis on the relationship between corg normalized biomarker ratios and 13corg demonstrates the potential problems of long term differential diagenetic skewing on those tracer records

distributions of uk37 and uk37 in the surface waters and sediments of the nordic seas implications for paleoceanography in this paper we revise the application of the u and u indices as sea surface temperature sst proxies in the nordic seas in the summer of 1999 and 2000 we obtained samples of filtered particulate organic matter pom from surface waters 6 m depth of the nordic seas a number of samples were collected from polar waters with up to 80 of sea ice cover alkenones were detected in all of the major water masses of the nordic seas across a spectrum of sst values from 0 5 to 13 c and sss values from 29 6 to 35 6 psu concentrations of alkenones were similar in magnitude to those reported previously for the north atlantic and the southern ocean values of u from the new nordic seas pom data show no correlation with sst below 8 c in contrast below this temperature a linear correlation exists between u and regional sst supporting previous suggestions that overall u may be a more appropriate sst index for the region it must be noted however that u is calculated using the tetraunsaturated alkenone and the dominant control on this compound is not yet fully understood the new data highlight major differences between distributions of u and u in the water column pom and surficial sediments of the nordic seas we also examine the geographical dependence of the u versus sst relationship in the region s surficial sediments some areas are associated with unreliable sst estimates whereas in others the u versus sst relationship falls within the range of a global core top calibration it is suggested that the breakdown of the u sst relationship in some regions is due to ecological and sedimentological factors the latter relates to the extension of the habitats of alkenone producers in polar waters the former to the resuspension of sediments and laterally transported alkenone inputs this suggests that accurate alkenone derived sst estimates in the nordic seas are geographically constrained

the sources and deposition of organic matter in the late quaternary pigmy basin gulf of mexico abstract the concentration and carbon isotopic composition 13c of sedimentary organic carbon corg n c ratios and terrigenous and marine 13corg endmembers form a basis from which to address problems of late quaternary glacial interglacial climatic variability in a 208 7 m hydraulic piston core dsdp 619 from the pigmy basin in the northern gulf of mexico while interpretations of sedimentary 13corg time series records are often not unique paired analyses of 13corg and n c are consistent with the hypothesis that the corg in the pigmy basin is a climatically determined mixture of c3 photosynthetic terrigenous and marine organic matter confirming the earlier 13corg model of sackett 1964 a high resolution 1 4 2 9 ka sample 13corg record shows that sedimentary organic carbon in interglacial oxygen isotope sub stages 1 and 5a b are enriched in 13c average 1 values are 24 2 1 2 o and 22 9 0 7 o relative to pdb respectively while glacial isotope stage values 2 are relatively depleted 25 6 0 5 concentrations of terrigenous and marine sedimentary organic carbon are calculated for the first time using 13corg and corg measurements and empirically determined terrigenous and marine 13corg endmembers the net accumulation rate of terrigenous organic carbon is 4 3 2 6 times higher in isotope stages 2 4 than in sub stages 1 and 5a b recording higher erosion rates of terrigenous organic material in glacial times the concentration and net accumulation rates of marine and terrigenous corg suggest that the nutrient bearing plume of the mississippi river may have advanced and retreated across the pigmy basin as sea level fell and rose in response to glacial interglacial sea level change

age discrepancy between molecular biomarkers and calcareous foraminifera isolated from the same horizons of northwest pacific sediments abstract recent observations show that establishment of molecular level radiocarbon stratigraphy is increasingly critical for paleoceanographic studies especially to enable comparable discussion about past ocean and climate changes inferred from multiple proxy records based on lipid biomarkers and calcareous foraminiferal microfossils so far although we have interesting evidence that there are temporal and spatial age offsets between the algal alkenone biomarker used for sst sea surface temperature estimates and planktonic foraminifera in regions with high sedimentation rates less is known about such age offsets in the settings of lower sedimentation in this study to investigate the potential of biomarkers as an alternative dating proxy to foraminifera in a low sedimentation rate setting we measured radiocarbon ages of 17 different lipid biomarkers fatty acids fas n alkanes and alkenones bulk total organic matter toc and foraminifera from two sections 12 15 cm and 21 24 cm depth of a surface sediment core in the northwest pacific the sedimentation rate estimated from the toc ranged from 10 5 cm kyr in the core top to 0 9 cm kyr in the lower part of the core the ages of the fas detected at 12 15 cm depth ranged from 530 yr bp c 18 to 3250 yr bp c 28 the 14 c analysis of the fas could be divided into two groups fas c 16 c 18 derived from marine organisms and those c 24 c 26 c 28 derived from terrestrial higher plants the high molecular weight hmw fas ages were older 2550 yr bp c 24 to 3250 yr bp c 28 than those of the low molecular weight lmw fas 530 yr bp c 18 to 1820 yr bp c 16 at 21 24 cm depth the alkenone ages were 7100 7300 yr younger than those of the planktonic foraminifera in this horizon the alkenone 14 c age 7500 yr bp and the alkenone estimated sst 15 3 c suggest that these alkenones were produced in this region during the holocene the alkenone 14 c age was also in good agreement with those of the lmw fas c 14 ic 15 aic 15 c 16 and c 18 1 derived from marine plankton and bacteria similarly the toc age was 5700 yr younger than that of the planktonic foraminifera these age differences are large compared with those estimated for the horizon at 12 15 cm depth which was characterized by a relatively higher sedimentation rate these trends between ages of alkenones toc and planktonic foraminifera are not comparable to the results from sites with high sedimentation rates such as the benguella upwelling system mollenhauer g eglinton t i ohkouchi n schneider r r muller p j grootes p m et al 2003 asynchronous alkenone and foraminifera records from the benguela upwelling system geochim cosmochim acta 67 2157 2171 or the bermuda rise drift deposit ohkouchi n eglinton t i keigwin l d hayes j m 2002 spatial temporal offsets between proxy records in a sediment drift science 289 1224 1227 which are significantly different sedimentary settings from our site the radiocarbon results from these high sedimentation rate regions suggest that the alkenones are several thousand years older than the coexisting planktonic foraminifera on the other hand the age offsets between alkenones and planktonic foraminifera at our site are larger than those from the other sites and the alkenones are younger than the planktonic foraminifera

pendant bioconstructions cemented by microbial carbonate in submerged marine caves holocene se sicily abstract unusual pendant bioconstructions occur within two submerged caves in the plemmirio marine protected area south of syracuse se sicily these cm to dm sized bioconstructions project downward from the cave roofs the main framework builders are serpulids belonging to the genera protula semivermilia and josephella encrusting bryozoans corals hydrozoans and sponges are subordinately present whereas bivalves and brachiopods are overall rare these faunal associations are characteristic of the studied caves but only in some places they form small bioconstructions that are cemented by microbial carbonates made up by autochthonous peloidal to clotted peloidal and aphanitic micrite the autochthonous micrite stabilizes the pendant bioconstructions herein referred to as biostalactites the microbial carbonate reveals high contents of bacterial lipid biomarkers among the most abundant compounds are mono o alkyl glycerol ethers mages and branched fatty acids 10 me c16 0 iso and anteiso c15 0 and c17 0 interpreted as biomarkers of sulfate reducing bacteria other compounds preserved in the autochthonous carbonates include lipids derived from marine zoo and phytoplankton brassicasterol dinosterol and monounsaturated short chain fatty acids unspecified marine bacteria saturated and monounsaturated short chain fatty acids and land plants long chain fatty acids long chain alcohols stigmasterol sitosterol and campesterol the observed lipid biomarker signatures are remarkably similar to those of post glacial reefal microbialites where microbialite formation in cavities of the coral framework was also mediated by sulfate reducing bacteria in the submerged caves of plemmirio marine protected area serpulid colonies apparently occur preferentially where freshwater is seeping through crevices in the limestone the consequent nutrification is believed to favor serpulid aggregation and the growth of other skeletal i e bryozoans and corals and soft bodied organisms i e sponges and ascidiae the resultant accumulation of biomass and its taphonomy provide niches for sulfate reducing bacteria which induce carbonate precipitation cementing and stabilizing the biostalactites the finding of pendant cemented bioconstructions in the mazzere and granchi caves of the plemmirio marine protected area reveals that sulfate reducing bacteria are involved in microbialite formation in various cryptic environments the formation of such peloidal to clotted peloidal microcrystalline carbonates in cryptic ecosystems is a significant factor for the stabilization of different kinds of bioconstructions spanning from small biostalactites to large reefs

fracture zone scale variation of trace elements and stable isotopes in calcite in a crystalline rock setting abstract with an aim to increase the understanding about the isotopic and chemical heterogeneity of calcites in water conducting fracture zones with different crystalline wall rock compositions at different depths we present trace element chemistry isotopic composition 18o 13c 87sr 86sr and biomarkers of euhedral low temperature fracture coating calcite paleohydrogeological fluctuations and wall rock influence on the hydrochemistry in the deep groundwater are explored samples are from several fracture zone sub fractures at 360 to 740 m retrieved during an extensive core drilling campaign in sweden calcite generally showed fracture zone specific values of 13c 18o and 87sr 86sr which indicates precipitation from relatively homogeneous fluid similar to the modern groundwater at the site at the same event in each fracture zone 18o and 13c in the different fracture zones were consistent with precipitation from waters of different salinity and decreasing organic input with depth respectively the latter is also supported by biomarkers showing clear indications of srb related organic compounds e g iso and anteiso c17 0 branched fatty acids except in the deepest zone in contrast to the isotopes variation in trace elements within the fracture zones was generally up to several orders of magnitude manganese and ree as oppose to the other metals were higher in the shallow fracture zones 112 1130 and 44 97 ppm respectively than in the deeper 28 272 and 5 11 ppm respectively in agreement with the groundwater composition although the rock types varied between and within the different fracture zones this had insignificant influence on the trace element chemistry of the calcites co variation was generally relatively large for many trace elements with isometric logratio correlation generally better than 0 75 which indicates that their variation in the calcites is due to variation of ca in the fracture water but other local factors especially uptake in co precipitating minerals clay minerals barite pyrite and zeolites but also microbial activity and metal speciation may have influenced the metal incorporation into calcite these detailed studies of fracture calcite are of importance for the understanding of variation in fluid chemistry and trace metal uptake in fracture zones adding together with hydrochemical studies detailed information optimal for site characterisation

identification of karstic features in lateritic soil by an integrated geophysical approach lateritic soils are widely spread across the southern and central parts of india lateritic formations usually have soft sediments entrapped between hard to medium soft lateritic rock which are leached due to the ingress of water during rainy seasons creating hollow sections or cavities which span over large lengths laterites are highly heterogeneous and prone to cavitation due to its weathering process a sound knowledge of the subsurface condition is required before starting any construction this study presents the application of integrated geophysical investigation for the identification of cavities at a mega construction site in kerala state india geophysical survey methods namely ground penetrating radar gpr and multichannel analysis of surface waves masws techniques are used to identify the heterogeneities in lateritic soils and localized cavities the survey areas identified are critical sections of a mega construction project subjected to heavy dynamic and static loads the preliminary gpr survey is carried out across the study areas at specific interval spacing to identify probable heterogeneities confirmative survey or detailed gpr and masw surveys are carried out at the locations identified in the preliminary survey at close intervals to confirm the presence of an anomaly and identify its location the anomalies in the gpr radargram are identified by visual inspection and trace amplitude approach using masw survey a 2d shear wave velocity profile is generated to identify low shear wave velocity zones which confirm the presence of an anomaly on comparing the data from both gpr and masw survey techniques the underground cavities were successfully identified at multiple locations with further crosschecking with borings the study further provided details on subsurface lithology at survey locations

the importance of atmospheric input of terrestrial organic material to deep sea sediments the concentrations of lipids were determined in atmospheric particle gas and rain samples collected from the tropical north pacific to assess lipid sources transport mechanisms and fluxes to the ocean surface four lipid compound classes aliphatic hydrocarbons fatty alcohols fatty acid esters and salts all unequivocally show a terrestrial vascular plant source these aerosol lipids originate from wind erosion of asian and american soils and direct emission from vegetation the major fluxes result from rain rather than dry deposition these fluxes are large enough to have a major potential impact on the inventory of terrestrially derived lipid material found in deep sea sediments this has been showm for n alkanes fatty alcohols fatty acids total lipids and for organic carbon by comparing atmospheric and sediment trap fluxes with sediment accumulation rates it is suggested that some biogenic terrestrial material is more protected from degradation than marine derived material

a multidisciplinary approach in sinkhole analysis the quinis village case study ne italy abstract during the last recent years in quinis a small village sited in the alta val tagliamento valley friuli venezia giulia region ne italy the inhabitants faced with instability phenomena related to the presence of soluble rocks in the subsurface the evaporite bedrock is mainly mantled in fact by high thickness deposit this paper explains the methodological approach that we used to identify the instabilities in a very complex geo structural environment where the urbanization limits the applicability of several investigation techniques different methods were used to define the bedrock morphology to characterize the mantling deposits and to identify the processes behind what emerged from the study is a mandatory multidisciplinary approach to characterize the subsoil because each technique is not able individually to take to a unique result the data collected allowed to draft a geo hydrogeological conceptual model of the quinis village the lessons learned even if with some site specific dependency demonstrate the importance of broad spectrum investigations which are essential to understand the subsurface characteristics avoiding relevant socio economic impact and supporting an adequate future territorial planning

global temperature calibration of the alkenone unsaturation index uk 37 in surface waters and comparison with surface sediments in this paper we compile the current surface seawater c37 alkenone unsaturation uk 37 measurements n 629 1 to 30 c temperature range to derive a global field based calibration of uk 37 with alkenone production temperature a single nonlinear global surface water calibration of uk 37 accurately predicts alkenone production temperatures over the diversity of modern day oceanic environments and alkenone synthesizing populations t 0 957 54 293 uk 37 52 894 uk 37 2 28 321 uk 37 3 r2 0 97 n 567 the mean standard error of estimation is 1 2 c with insignificant bias in estimated production temperature among the different ocean regions sampled an exception to these trends is regions characterized by strong lateral advection and extreme productivity and temperature gradients e g the brazil malvinas confluence in contrast to the surface water data the calibration of uk 37 in surface sediments with overlying annual mean sea surface temperature anno is best fit by a linear model anno 29 876 uk 37 1 334 r2 0 97 n 592 the standard error of estimation 1 1 c is similar to that of the surface water production calibration but a higher degree of bias is observed among the regional data sets the sediment calibration differs significantly from the surface water calibration uk 37 in surface sediments is consistently higher than that predicted from anno and the surface water production temperature calibration and the magnitude of the offset increases as the surface water anno decreases we apply the global production temperature calibration to the coretop uk 37 data to estimate the coretop alkenone integrated production temperature coretop ipt and compare this with the overlying annual mean sea surface temperature anno we use simple models to explore the possible causes of the deviation observed between the coretop temperature signal as estimated by uk 37 and anno our results indicate that the deviation can best be explained if seasonality in production and or thermocline production as well as differential degradation of 37 3 and 37 2 alkenones both affect the sedimentary alkenone signal

carbon chain length distribution in n alkyl lipids a process for evaluating source inputs to lake qinghai abstract lake sediments generally contain a mixture of terrestrial and aquatic source inputs and determining the major inputs is important for understanding geological records in paleoenvironment and paleoclimate research in this study we describe the distribution of n alkanes and n fatty acids fas in representative modern plants from around lake qinghai we found a significant difference in the average length of n fa carbon chains acl fa 16 32 in terrestrial 23 3 and aquatic plants 18 6 the results reveal that acl fa 16 32 may essentially serve as a proxy for evaluating the major source inputs to lake sediments assessment of surface sediments from the lake showed that the fas originated from a mixture of inputs with the aquatic source input predominant at most sites additionally the d values of sediment mid chain n acids c 22 showed a relationship with the acl fa 16 32 proxy an increased fa acl corresponded to more negative hydrogen isotope ratio values we suggest that different sources should be considered and acl fa 16 32 could be a potential calibration proxy before using d values to extract reliable isotopic information from lake water more attention should be paid to source inputs and their relationship to other geochemical proxies in future studies of lake sediments

a numerical study of surface wave based tunnel detection at the black diamond mines regional preserve california author s sherman cs rector j dreger d glaser s abstract 2018 society of exploration geophysicists detecting underground voids such as old mine workings solution cavities in karst terrain or unknown tunnels such as illicit cross border tunnels is a challenging problem for geophysics and an important concern for geotechnical design public safety and domestic security seismic surface wave based detection methods have become increasingly popular for detecting relatively shallow and small targets however the theoretical limitations of these methods have thus far remained unclear we use a suite of 3d numerical simulations inspired by a tunnel detection experiment carried out at the black diamond mines regional preserve bdm in northern california the geophysical anomalies predicted by our numerical simulations at bdm agree with field observations and our estimates for the location of the primary tunnel target agree with historical records in the area using our calibrated numerical model we perform a parametric study to determine the effect of tunnel size depth of burial filling material and source characteristics to determine the range over which surface wave backscattering and attenuation based methods are effective in addition we perform a regression analysis to determine a relationship for the maximum depth at which a tunnel may be detected via these approaches given the target diameter wavelength of interest and the signal to noise ratio

a new energy source for organic synthesis in europa s surface ice 1 colored regions on jupiter s satellite europa and other icy bodies in the outer solar system may be contaminated by organic macromolecular solid material that is produced when surface ices are exposed to electrical energy hypervelocity meteorite impacts and fracture may release tidal and tectonic stresses in icy crusts in the form of electrical discharges which provide the energy for in situ synthesis of the organic solids we report for the first time here on measurements of electrical discharge light emission and magnetic phenomena in hypervelocity impacts into ice with small iron projectiles having velocities 5 km s 1 in these experiments part of the impacting projectile s kinetic energy is converted into electrical potential while the mechanical disruption of the impact also causes the release of stress energy as light heat and electrical and magnetic fields as secondary emissions these new energy sources described here suggest that the dark material in the area of impact craters may be solid phase complex organic material called tholin generated from the energy of the impacts the morphology of europa s impact craters is suggestive of fluidized colored material welling up from the fracture zone probably during crater formation but possibly later large pools of liquid water might persist under the meteorite crater for thousands of years thomson and sagan 1992 with the potential for prebiotic chemistry to take place at an accelerated rate due to energy pumped in from the secondary emissions

terrigenous plant wax inputs to the arabian sea implications for the reconstruction of winds associated with the indian monsoon author posting the authors 2005 this is the author s version of the work it is posted here by permission of elsevier b v for personal use not for redistribution the definitive version was published in geochimica et cosmochimica acta 69 2005 2547 2558 doi 10 1016 j gca 2005 01 001

latitudinal distribution of terrestrial lipid biomarkers and n alkane compound specific stable carbon isotope ratios in the atmosphere over the western pacific and southern ocean abstract we investigated the latitudinal changes in atmospheric transport of organic matter to the western pacific and southern ocean 27 58 n 64 70 s molecular distributions of lipid compound classes homologous series of c15 to c35 n alkanes c8 to c34 n alkanoic acids c12 to c30 n alkanols and compound specific stable isotopes 13c of c29 and c31 n alkanes were measured in marine aerosol filter samples collected during a cruise by the r v hakuho maru the geographical source areas for each sample were estimated from air mass back trajectory computations concentrations of tc and lipid compound classes were several orders of magnitude lower than observations from urban sites in asia a stronger signature of terrestrial higher plant inputs was apparent in three samples collected under conditions of strong terrestrial winds unresolved complex mixtures ucm showed increasing values in the north pacific highlighting the influence of the plume of polluted air exported from east asia n alkane average chain length acl distribution had two clusters with samples showing a relation to latitude between 28 n and 47 s highest acl values in the tropics whilst a subset of southern samples had anomalously high acl values compound specific carbon isotopic analysis of the c29 25 6 to 34 5 and c31 n alkanes 28 3 to 37 revealed heavier 13c values in the northern latitudes with a transition to lighter values in the southern ocean by comparing the isotopic measurements with back trajectory analysis it was generally possible to discriminate between different source areas the terrestrial vegetation source for a subset of the southernmost southern ocean is enigmatic the back trajectories indicate eastern antarctica as the only intercepted terrestrial source area these samples may represent a southern hemisphere background of well mixed and very long range transported higher plant organic material

microgravimetric and gravity gradient techniques for detection of subsurface cavities abstract microgravimetric and gravity gradient surveying techniques are applicable to the detection and delineation of shallow subsurface cavities and tunnels two case histories of the use of these techniques to site investigations in karst regions are presented in the first case history the delineation of a shallow 10 m deep airfilled cavity system by a microgravimetric survey is demonstrated also application of familiar ring and center point techniques produces derivative maps which demonstrate 1 the use of second derivative techniques to produce a residual gravity map and 2 the ability of first derivative techniques to resolve closely spaced or complex subsurface features in the second case history a deeper 30 m deep water filled cavity system is adequately detected by a microgravity survey results of an interval tower vertical gradient survey along a profile line are presented in the second case history this vertical gradient survey successfully detected shallow 6 m anomalous features such as limestone pinnacles and clay pockets but the data are too noisy to permit detection of the vertical gradient anomaly caused by the cavity system interval horizontal gradients were determined along the same profile line at the second site and a vertical gradient profile is determined from the horizontal gradient profile by a hilbert transform technique the measured horizontal gradient profile and the computed vertical gradient profile compare quite well with corresponding profiles calculated for a two dimensional model of the cavity system

does sedimentary organic δ13c record variations in quaternary ocean co2 aq ocean surface water co2 aq variations based on glacial interglacial changes in sediment delta 13corg are shown to compare favorably with reconstructions based on ice core co2 in particular an approximate 80 microatmospheres increase in atmospheric pco2 during the last glacial interglacial transition is calculated to correspond to a 3 4 micromolar increase in ocean surface water co2 aq at atmospheric equilibrium a widespread marine delta 13corg decrease of 1 2 accompanied this event and was not preceded by an equivalent isotopic change in surface water total dissolved inorganic carbon these observations support the hypothesis that co2 aq influences photosynthetic isotope fractionation between marine inorganic and organic carbon pools and therefore that plankton sediment delta 13corg may serve as a proxy for surface water co2 aq

upward decrease of organic c n ratios in the okinawa trough cores proxy for tracing the post glacial retreat of the continental shore line abstract six piston cores were collected along the nw se line in the okinawa trough close to the chinese continental shelf edge and dated by 23 ams 14 c measurements along with planktonic 18 o stratigraphy and an ash layer dated as 6 3 ka on a time scale to 19 ka the ratio of total organic carbon to total nitrogen concentration c n ratio displays gradual decreases toward the present and suggests the decrease of vascular plant fragment input to the trough from continental rivers this suggestion is confirmed by similar decreases of lignin phenol content and ratio of c 28 fatty acid to c 16 fatty acid content in core rn93 pc3 the gradual decrease of land plant fragment input is interpreted to be a consequence of the retreat of the continental coastline during the deglacial period

biomarker stratigraphic records over the last 150 kyears off the nw african coast at 25 n terrigenous and marine biomarkers were investigated in a core oa northwest africa in the northeast atlantic 25n 16w 1445 m depth to assess changes in the sedimentation pattern of organic carbon oc over the last 150 kyears alkenone derived temperatures recorded a warming of 4 5c during the last deglaciation n alkanol mass accumulation rates mar fluctuated in parallel with northeast trade winds netw intensity oc and sterol mar both increased during glacial times indicating enhanced fertility of the ocean in response to intensified netw alkenone oc ratios were higher by a factor of two over stages 4 6 than stages 1 3 thus reflecting distinct coccolithophorid inputs this transition coincides with a major change of alkenone producers inferred from coccolith counts 2000 elsevier science ltd all rights reserved

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

geophysical applications to detect sinkholes and ground subsidence the term sinkhole receives a lot of use and equal amounts of abuse in the popular media generally anytime a hole or depression forms in the land surface sometimes in a short period of time it is called a sinkhole sinkholes are geologic features formed by movement of rock or sediment into voids created by the dissolution of water soluble rock some sinkholes such as the infamous winter park florida sinkhole of 1981 figure 1 capture the attention of society as we view expensive homes and automobiles teetering on a precipice about to disappear into the underworld subsidence features caused by other processes such as mine collapse and washouts resulting from broken water and sewer mains are not true sinkholes but may be equally as damaging these features also result from rock or soil moving into a void but the void was a result of human activities

sedimentary record of marine and terrigenous organic matter delivery to the shatsky rise western north pacific over the last 130 kyr abstract biomarker and carbon isotopic analyses of piston core samples were undertaken to reconstruct changes over the last 130 kyr in the delivery of organic matter from marine plankton and terrestrial sources to sediments on the shatsky rise in the western north pacific marine and terrigenous organic matter delivery was reconstructed from alkenone and n alkane concentrations using multiple regression analysis which gave results consistent with a 13c mass balance model marine organic carbon comprises more than 86 of the total organic carbon throughout the sediment record fluxes of marine organic carbon were higher in glacial times indicating that marine production increased in these periods we conclude that in addition to the southward shift of the subarctic front eolian dust supply at this location played an essential role in enhancing paleoproduction during the last glacial maximum

combined microgravity electrical resistivity tomography and induced polarization to detect deeply buried caves algaidilla cave southern spain abstract the suitability of the combined microgravity and electrical tomography to detect and characterize caves deeply buried in limestones is tested we have selected the buried algaidilla cave in the estepa range western betic cordillera which is partially submerged below the water table and which was intersected between 26 and 66 m in depth by two boreholes at that location microgravity electrical resistivity tomography ert and induced polarization ip data was collected along four profiles algaidilla cave is associated with a 0 5 mgal residual gravity anomaly minimum microgravity models reveal an approximately horizontal n s elongated shape with a maximum length of 150 m and a width of 40 m resistivity variations provide information on the cave sectors remaining above as well as below the water table forward modeling and depth of investigation doi support the suitability of ert to constrain the cave geometry the cave is identified as having an intermediate to low resistivity feature which approximately matches the 250 m contour line along its ceiling in addition induced polarization models show high chargeability anomalies probably associated with decalcification clays the location and approximately geometry of algaidilla cave estimated from geophysical modeling suggests that nearby overburden may develop cave ins and collapse sinkholes microgravity is proved as a powerful tool to detect caves at this depth but this method alone fails to estimate the geometry ert results delineate the cavity both above and below the water table although the deepest sectors of the models should be interpreted with caution since they are less constrained by the data below the water table the cavity shows great resistivity contrast with regard to the background carbonate in addition this study points out the usefulness of the ip method for detecting decalcification clays often present at the base of karstic caves

barium accumulation in the atlantic sector of the southern ocean results from 190 000 year records extensive investigations of sedimentary barium were performed in the southern south atlantic in order to assess the reliability of the barium signal in antarctic sediments as a proxy for paleoproductivity maximum accumulation rates of excess barium were calculated for the antarctic zone south of the polar front where silica accumulates at high rates the correspondence between barium and opal supports the applicability of barium as a proxy for productivity within the antarctic zone north of today s average sea ice maximum interglacial vertical rain rates of excess barium are high with a maximum occurring during the last deglaciation and early holocene and during oxygen isotope chronozone 5 5 during these periods the maximum silica accumulation was supposedly located south of the polar front glacial paleoproductivity instead was low within the antarctic zone north of the polar front significantly higher barium accumulation occurs during glacial times the vertical rain rates however are as high as in the glacial antarctic zone therefore there was no evidence for an increased productivity in the glacial southern ocean

formation of cycloidal features on europa cycloidal patterns are widely distributed on the surface of jupiter s moon europa tensile cracks may have developed such a pattern in response to diurnal variations in tidal stress in europa s outer ice shell when the tensile strength of the ice is reached a crack may occur propagating cracks would move across an ever changing stress field following a curving path to a place and time where the tensile stress was insufficient to continue the propagation a few hours later when the stress at the end of the crack again exceeded the strength propagation would continue in a new direction thus one arcuate segment of the cycloidal chain would be produced during each day on europa for this model to work the tensile strength of europa s ice crust must be less than 40 kilopascals and there must be a thick fluid layer below the ice to allow sufficient tidal amplitude

terrigenous organic matter sources in mid pleistocene sediments from the orphan knoll northwest atlantic ocean abstract the concentration and composition of lignin derived phenols which are often used as biomarkers for terrigenous organic matter om inputs were examined in north atlantic ocean sediments from iodp core u1302a 50 9 985 n 45 38 271 w 3568 m water depth orphan knoll 650 km ne of st john s newfoundland canada for the period of ca 1100 810 ka bp lignin derived phenols were extracted from sediments using cuo oxidation which yielded eight characteristic phenols the majority of sediments have low syringyl phenol to vanillyl phenol s v ratios and high cinnamyl phenol to vanillyl phenol c v ratios suggesting predominant concentrations of gymnosperm derived organic matter inputs from adjacent continents most likely eastern canada and possibly southern greenland the s v values were lower for the period of ca 958 840 ka bp relative to ca 1090 1078 1042 958 and 840 818 ka bp indicating fluctuations in the proportion of angiosperm and gymnosperm derived lignin delivery to the ocean the greater fraction of gymnosperms for the period of 958 840 ka bp likely reflects the response of vegetation in source regions to climate cooling in the early part of the mid pleistocene lignin derived phenol concentrations also displayed high variability during the investigated period which did not show positive correlations with magnetic susceptibility or gamma ray attenuation density considering that a fundamental climate change 41 100 ka cyclicity occurred within the mid pleistocene large variations in abundance and composition of lignin derived phenols in core u1302a is likely indicative of dynamic environmental conditions reflected by the variability in both concentrations and types of vegetation on adjacent continents and or different mechanisms to transport terrigenous organic matter to the deep ocean

mapping of underground cavities by the passive seismic standing waves method the case study of barsukovskaya cave novosibirsk region russia abstract this article presents the results of mapping a karst cave by the passive seismic standing waves method barsukovskaya cave is located about 100 km southeast of the city of novosibirsk russia the total length of the cave s passages and grottoes is estimated at about 200 m the maximum depth from the earth s surface is about 19 m the method for studying underground cavities used is based on the effect of the generation of standing waves by microtremor in the space between the earth s surface and the cave roof the accumulation of amplitude spectra of a large number of microtremor records makes it possible to determine the frequencies of the first few modes of these waves areal passive seismic survey on the earth s surface above the cave made it possible to construct a map of the lowest mode frequency distribution over the cave roof since no standing waves were observed at other points this map reflects the cave structure in plan which confirms the comparison with the cave diagram drawn up earlier by one of the speleologists a schematic map of the depth of the cave roof was constructed using the longitudinal wave velocity vp 3120 m s determined by the rock samples selected near the entrance to the cave this map at a qualitative level also agrees with the data of speleologists which indicate that the cave on average gradually becomes deeper from the entrance to its dead end branches the shallower depths in comparison with the data of speleologists are apparently explained by a very low estimate of the velocity determined from a rock sample taken near the entrance to the cave the reliability of the obtained cave mapping results is confirmed by the numerical simulation results using the finite element method

detection of underground cavities by combining gravity magnetic and ground penetrating radar surveys a case study from the zaragoza area ne spain a geophysical survey routine is proposed to detect underground cavities and dolines it is based on the sequential application of magnetic low frequency ground penetrating radar gpr and microgravity techniques a case study near zaragoza ebro valley spain demonstrates the applicability of these methods the strong contrast of magnetic and electromagnetic properties and to a lesser scale of density between the doline filling and the surrounding stratified tertiary and quaternary rocks allows the shape of filled cavities to be clearly outlined by these methods

tyre and pwyll galileo orbital remote sensing of mineralogy versus morphology at two selected sites on europa observational data from the galileo orbiter s remote sensing instruments including solid state imaging ssi the near infrared mapping spectrometer nims and the ultraviolet spectrometer uvs are analyzed and interpreted in terms of the history of the tyre and pwyll impact sites and the nature of europa s crustal zonal structure material characterized by asymmetric 1 4 and 2 0 xm bands and visible coloration characterizes each site where morphologic evidence suggests disruption of the topmost crust the material is not h20 ice is endogenic and is common to the linea impact basins and dark trailing side terrain differences between tyre and 11 are interpreted in terms of europa s peculiar energy history while other evidence may suggest flooding of the endogenic material as a liquid the pure ice appearance of most of europa s crust is probably superficial while beneath a thin patina of sputtered h20 molecules the crust is everywhere laced with numerous generations of intrusions and extrusions of an aqueous phase our results together with numerous laboratory experiments and theoretical analysis suggest that the aqueous phase is dominated by the so2 anion nothing is rich but the inexhaustible wealth of nature she shows us only surfaces but she is a million fathoms deep

sinkholes subsidence and subrosion on the eastern shore of the dead sea as revealed by a close range photogrammetric survey abstract ground subsidence and sinkhole collapse are phenomena affecting regions of karst geology worldwide the rapid development of such phenomena around the dead sea in the last four decades poses a major geological hazard to the local population agriculture and industry nonetheless many aspects of this hazard are still incompletely described and understood especially on the eastern dead sea shore in this work we present a first low altitude our analysis reveals a kilometer scale sinuous depression bound partly by flexure and partly by non tectonic faults the estimated minimum volume loss of this subsided zone is 1 83 106 m3 with an average subsidence rate of 0 21 m yr 1 over the last 25 years sinkholes in the surveyed area are localized mainly within this depression the sinkholes are commonly elliptically shaped mean eccentricity 1 31 and clustered nearest neighbor ratio 0 69 their morphologies and orientations depend on the type of sediment they form in in mud sinkholes have a low depth to diameter ratio 0 14 and a long axis azimuth of nne ne in alluvium sinkholes have a higher ratio 0 4 and are orientated nnw n from field work we identify actively evolving artesian springs and channelized sediment laden groundwater flows that appear locally in the main depression consequently subrosion i e subsurface mechanical erosion is identified as a key physical process in addition to dissolution behind the subsidence and sinkhole hazard furthermore satellite image analysis links the development of the sinuous depression and sinkhole formation at ghor al haditha to preferential groundwater flow paths along ancient and current wadi riverbeds