benefits of freeze drying sediments for the analysis of total chlorins and alkenone concentrations in marine sediments abstract long chain alkenones and photosynthetic pigment derivatives chlorins are commonly employed biomarkers in the reconstruction of past sea surface temperatures ssts and organic carbon export from the surface to the deep ocean for these studies marine sediment samples are often available which have been air dried or freeze dried given that these are common methods for removing water from sediments prior to microfossil analysis we compared both drying procedures by analysing samples from two sediment cores odp 1087 southeast atlantic and m36 2 mc435 north atlantic we found that significant losses of chlorins 25 and alkenones up to 75 occur with air drying relative to freeze drying changes in the composition of pigments are also likely the alkenone unsaturation index u 37 k is sensitive to the drying method showing an increase of up to 0 02 units relative to freeze drying however this represents a maximum increase in sst estimates of only 0 5 c the tests suggest that freeze dried samples rather than air dried sediments should preferably be used to determine the sedimentary concentration of biomarkers however if chlorins are the main target compounds wet extraction with acetone of sediment results in ca 12 higher yield than the extraction of freeze dried sediments with acetone water

alkenone molecular stratigraphy in an oceanic environment affected by glacial freshwater events the sedimentary record of a ratio uk37 of long chain c37 unsaturated alkenones is a useful indicator of glacial interglacial climatic change in the late quaternary northern gulf of mexico where a planktonic foraminiferal 18o caco3 record is complicated by meltwater and or fluvial events williams and kohl 1986 application of a laboratory temperature calibration of the uk37 ratio prahl and wakeham 1987 to a pigmy basin hydraulic piston core record deep sea drilling project core 619 suggested that the minimum glacial surface mixed layer sml temperature was 8 1 c colder than the holocene high sml temperature of 25 6 0 5 c this predicted glacial interglacial temperature difference was significantly larger than the differences predicted by either the foraminiferal 18o or foraminiferal assemblage temperature methods 0 8 2 0 c this large difference may be caused by local prymnesiophyte assemblage changes in response to climatically induced hydrographic changes interglacial periods may be dominated by pelagic prymnesiophyte assemblages while glacial periods may be dominated by neritic assemblages a combined mechanism of both climatically varying prymnesiophyte species assemblage and depth of alkenone biosynthesis may account for the large difference between the temperature methods

frictional viscous flow of phyllosilicate bearing fault rock microphysical model and implications for crustal strength profiles it is widely believed that around the brittle ductile transition crustal faults can be significantly weaker than predicted by conventional two mechanism brittle ductile strength envelopes factors contributing to this weakness include the polyphase nature of natural rocks foliation development and the action of fluid assisted processes such as pressure solution recently ring shear experiments using halite kaolinite mixtures as an analogue for phyllosilicaterich rocks for the first time showed frictional viscous behavior i e both normal stress and strain rate sensitive behavior involving the combined effects of pressure solution and phyllosilicates this behavior was accompanied by the development of a mylonitic microstructure a quantitative assessment of the implications of this for the strength of natural faults has hitherto been hampered by the absence of a microphysical model in this paper a microphysical model for shear deformation of foliated phyllosilicate bearing fault rock by pressure solution accommodated sliding along phyllosilicate foliae is developed the model predicts purely frictional behavior at low and high shear strain rates and frictional viscous behavior at intermediate shear strain rates the mechanical data on wet halite kaolinite gouge compare favorably with the model when applied to crustal materials the model predicts major weakening with respect to conventional brittle ductile strength envelopes in particular around the brittle ductile transition the predicted strength profiles suggest that in numerical models of crustal deformation the strength of high strain regions could be approximated by an apparent friction coefficient of 0 25 0 35 down to depths of 15 20 km

temperature and salinity effects on alkenone ratios measured in surface sediments from the indian ocean abstract we compare alkenone unsaturation ratios measured on recent sediments from the indian ocean 20 n 45 s with modern sea oceanographic parameters for each of the core sites we estimated average seasonal cycles of sea surface temperature sst and salinity which we then weighted with the seasonal productivity cycle derived from chlorophyll satellite imagery the unsaturation index u37k ranges from 0 2 to 1 and correlates with water temperature but not with salinity theu37k versus sst relationship for indian ocean sediments u37k 0 033 sst 0 05 is similar to what has been observed for core tops from the pacific and atlantic oceans and the black sea a global compilation for core tops givesu37k 0 031 t 0 084 r 0 98 which is close to a previously reported calibration based on particulate organic matter from the water column for temperatures between 24 and 29 c however the slope seems to decrease to about 0 02u37k unit c for indian ocean core tops the ratios of total c37alkenones total c38alkenones and the slope of theu37k sst relationship are similar to those previously observed for cultures ofemiliania huxleyibut different from those previously published forgephyrocapsa oceanica eithere huxleyiis a major producer of alkenones in the indian ocean or strains ofg oceanicaliving in the northern indian ocean behave differently from the one cultured in contrast with coccolithophorid assemblages the ratios of c37alkenones to total c38alkenones lack clear geographic pattern in the indian ocean

detection and correlation of tephra derived smectite rich shear zones by analyzing glass melt inclusions in mineral grains abstract shear zones rich in the clay mineral smectite are significant geological features because of the particular physicochemical properties of this mineral however predicting the distribution of such shear zones using limited borehole data is a challenge for geoscientists and geoengineers here we present detailed mineralogical and geochemical analyses of clay rich shear zones 30 cm thick that are associated with bedding parallel or bedding oblique faults in drill cores of a siliceous mudstone containing mainly opal cristobalite tridymite from the horonobe area northern hokkaido japan the bedding parallel shear zones are rich in smectite and some shear zones are characterized by melt inclusions hosted by plagioclase and quartz the chemical compositions of melt inclusions in six shear zones are very similar but distinct from those of melt inclusions in other shear zones these six shear zones consistently occur in horizons 350 m shallower than a known tephra layer these mineralogical characteristics and stratigraphic positions suggest that the six shear zones occur within the same tephra layer and that the smectite formed as a result of burial diagenesis of volcanic glass tephra derived smectite rich shear zones can be detected and correlated by analyzing melt inclusions preserved in mineral grains the distribution of such shear zones can be predicted in a similar way to tephra layers

sulphur and oxygen sequestration of n c37 and n c38 unsaturated ketones in an immature kerogen and the release of their carbon skeletons during early stages of thermal maturation sedimentary rock from the gessoso solfifera formation messinian in the vena del gesso basin northern italy containing immature ro 0 25 s rich organic matter was artificially matured by hydrous pyrolysis at temperatures from 160 to 330 c for 72 h to study the diagenetic fate of n c37 and n c38 di and tri unsaturated methyl and ethyl ketones alkenones biosynthesised by several prymnesiophyte algae during early diagenesis the alkenones are incorporated into the kerogen by both sulphur and oxygen cross linking as indicated by chemical degradation experiments with the kerogen of the unheated sample heating at temperatures between 160 and 260 c which still represents early stages of thermal maturation produces large amounts up to 1 mg g toc of s bound o bound and both s and o bound n c37 and n c38 skeletons saturated n c37 and n c38 methyl ethyl and mid chain ketones c37 and c38 mid chain 2 5 di n alkylthiophenes c37 and c38 1 2 di n alkylbenzenes and c37 and c38 n alkanes with increasing thermal maturation three forms of the n c37 and n c38 skeletons are relatively stable saturated hydrocarbons 1 2 di n alkylbenzenes and saturated ketones whereas the s and o bound skeletons are relatively labile these results suggest that in natural situations saturated ketones with an n c37 and n c38 skeleton can be expected as well as the corresponding hydrocarbons

molecular records of twentieth century el nino events in laminated sediments from the santa barbara basin organic molecules preserved in sediments especially long chain alkenones can preserve and record evidence of past climate variations1 5 a dependence of alkenone distributions on temperature has been recognized in cultures of the unicellular coccolithophorid alga emiliania huxleyi1 6 which survives in sediments and water column participates6 through this dependence stratigraphic profiles of the degree of alkenone unsaturation expressed asuk37 values1 have been shown in several oceanic settings to reflect long term changes in sea surface temperatures associated with glacial interglacial cycles1 5 here we show that annual variations in alkenone unsaturation in laminated sediments from the santa barbara basin off the shore of california reveal increases in water temperatures which can be linked directly to the observed sequence of el nino events in the twentieth century7 the range and variations in water temperatures calculated from uk37 values 12 8 15 2 c using the relationship established from culture experiments6 8 broadly correspond to the annually averaged temperatures 11 3 15 2 c measured intermittently by the calcofi programme at 20 m depth between 1953 and 1984 these results show that in favourable settings alkenone unsaturation profiles can provide an annually resolved record of oceanic temperaturechanges and may constitute a valuable tool for describing and evaluating the history of global climate variability and change

bacterial and algal hydrocarbons in sediments from a saline antarctic lake ace lake capillary gas chromatography mass spectrometry c gc ms and iatroscan thin layer chromatography flame ionisation detection tlc fid were used to study hydrocarbon distributions in a sediment core from ace lake a saline meromictic lake in the vestfold hills of antarctica hydrocarbons were abundant in most core sections up to 125 g g dry wt particularly in near surface samples and the distributions were very complex major constituents were identified as phytane 2 6 10 15 19 pentamethyleicosane tetrahydrosqualene a mixture of phytenes cholesta 3 5 diene and fern 7 ene smaller amounts of sterenes and hopenes were also present the predominance of the first 3 acyclic isoprenoids in sediments buried less than 30 cm is consistent with high populations of methanogenic bacteria known to be present phytenes were abundant in all core sections and there was no relationship between their abundance and that of phytane which suggests that they were not derived from methanogenic bacteria phytadienes were minor constituents at all depths studied an unusual feature of some distributions was the high concentrations of fern 7 ene which was the major hydrocarbon in the 20 25 cm core section this alkene was only abundant in sediments which contained high concentrations of methanogen markers suggesting that it may also be indicative of anoxic depositional environments a possible source might be from purple non sulphur bacteria high concentrations of straight chain c29 and c34 alkenes were also found in these sediments but their origin has not been determined major changes in the hydrocarbon distributions with depth indicate that the depositional environment in the lake has altered dramatically since the lake was formed less than 8000 years ago the present condition of permanent anoxic bottom waters probably developed only in the last 1000 years

slickenside and fault surface kinematic indicators on active normal faults of the alpine betic cordilleras granada southern spain abstract twenty four mesoscopic slickenside kinematic indicators are described here for the pliocene quaternary active normal faults of the alpine betic cordilleras granada southern spain the indicators are classified into twelve groups depending on the down or up slope asymmetric orientation of features such as concavities damaged versus sharp grain borders or step edges v shaped markings fractures and trailed material seventeen of the indicators were not previously described in the literature the new kinematic indicators include two types of asymmetric grains a carrot shaped marking six substructures of congruous and incongruous steps trailed fault material a drop shaped figure a v shaped marking three types of synthetic hybrid fractures with congruous steps and two varieties of pluck holes we think that some of these kinematic indicators provide information on the amount of displacement aseismic versus seismic slip rates cataclastic flow frictional wear or surface polishing

diagenesis of biomarkers in biwa lake sediments over 1 million years abstract lipid biomarker compounds n alkanoic acids n alkanols sterols n alkanes chlorophyll derivatives and total lipid carbon in a chloroform extractable fraction isolated from sedimentary deposits up to 2 ma old of a 1400 m core sample of lake biwa were analyzed by gas chromatography gas chromatography mass spectrometry and a thin layer chromatography flame ionization detection analyzer tlc fid to investigate their diagenesis and their utilities as biomarkers the samples are divided into two parts at a depth of 911 4 m the samples below 911 4 m are basement rock the upper core is composed of clay from the surface to 249 5 m in depth and alternated with slit clay and gravels from 249 5 to 911 4 m the organic compound carbon obtained by hydrolysis of the lipid fraction by alkali solution comprised from 11 to 35 of the total lipid carbon tlc fid analysis indicated that significant amounts about 70 80 of the total lipid carbon were present in the polar fraction and small proportions were simple lipids the amounts of n alkanols were comparable to those of n alkanoic acids and sterols while contemporary lacustrine sediments usually contain a larger amount of n alkanoic acids than of n alkanols normal alkanes maximizing in abundance at c 27 or c 29 were most abundant among the lipid compounds variation in the distributions of sterols and stanols seemed to preserve the information of input sources and the c 27 c 29 ratios were correlated to the c n of the sediments the composition of n alkanols maximizing at c 24 or c 18 appeared to indicate an aquatic paleoenvironment a paleowater depth at least in the upper 250 m ratios of shorter to longer chain n alkanoic acids which had been believed to be an indicator of autochthonous to allochthonous origins clearly increased with time a marked correlation between chlorophyll derivatives ratio of chlorophyll derivatives to total lipid carbon and paleotemperature was found

slickenside kinematic indicators abstract a new classification of slickenside kinematic indicators is presented based on 61 criteria these slickensides have been subdivided into eleven major groups v or crescentic markings steps fractures trains of inclined planar structures trailed material asymmetric elevations deformed elements mineralogical crystallographic orientations asymmetric plan view features asymmetric cavities and asymmetric folds this classification constitutes a useful tool for geologists interested in the determination of the shear sense in fault surfaces bearing slickensides examples of application of this classification to natural fault surfaces at different scales are presented

major factors controlling lamina induced fractures in the upper triassic yanchang formation tight oil reservoir ordos basin china abstract lamina induced fractures lf are abundant in lacustrine formations playing an important role for the tight oil resource exploration studies of controlling factors of the lf are still lacking especially for the heterogeneous formations characterized with complex combinations of the lamina and surrounding rock therefore 28 long column samples for triaxial compression tests 37 short column samples for brazil split tests and 12 powder samples for mineral component analysis and isotopes analysis carbon and oxygen are made from 6 cores in 4 petrophysical faces the experiments are designed to study the lf propagation process considering the controlling factors in terms of mineral component the lamina angle and the petrophysical faces our results show that clay content and dolomite cement degree more significantly control the lf propagation than the other minerals the lf propagation is not only dependent on the mineral component in the lamina but even more on the mineral component difference between the lamina and the surrounding rock i e the l s values where l represents the lamina and s represents the surrounding rock adjacent to the lamina the lf tended to propagate in a middle lamina angle range approximately 10 60 in shear properties and characterized with lower compression strength values all the lf observed in the thin sections were associated with oil although there was no obvious oil shown in the study cores the 13c and 18o values of lamina samples varied with the lamina mineral component for the complex organic matter oxidation and degradation reactions additionally the hydrocarbon flow parameter phf has been proposed on the carbon and oxidation isotope trace lines to indicate the oil rock reactions during the lf open period

estimation of the highest potential transmissivity of discrete shear fractures using the ductility index abstract previous studies indicated that the highest potential transmissivities of fractures in fault zones might be well estimated by a mechanical indicator the ductility index di the di is defined as the effective mean stress normalized to the tensile strength of the intact rock mass the mechanism of formation and preservation of pore structures in fault zone fractures can be explained by local shear induced tensile stresses and pore structures in discrete shear fractures may form in the same way i investigated therefore whether the di model can correctly predict the highest transmissivities of shear fractures recorded in fractured neogene diatomaceous mudstone koetoi formation where fault zones and joints are rare but discrete shear fractures without mineral fillings are abundant analyses of the shear fractures reveal that the detected states of paleostress are nearly equal to the current stress state implying the shear fractures have potentially been tectonically active thus the highest transmissivities detected at fractures by flowing fluids electric conductivity ffec borehole logging may potentially be treated as the highest potential transmissivities in terms of the given dis relationships between the transmissivities of flow anomalies and dis fit the existing di model well which suggests the model is applicable to discrete shear fracture systems as well as fault zones

long chain alkenones preserved in miocene lake sediments abstract over the last few decades the occurrence of long chain alkenones lcas in quaternary lacustrine settings has been reported the distributions being remarkably different from those of open ocean settings we report here the occurrence of lcas with modern lake type composition from middle miocene sedimentary strata in the dahonggou section qaidam basin northern tibetan plateau this is the first report of lcas with preserved lake compositions in pre quaternary lacustrine sediments the discovery implies that the producers of modern lacustrine lcas could originate from similar lake species living at least as far back as the miocene epoch it also sheds new light on the potential of alkenones as palaeotemperature indicators in lacustrine systems back to at least 10 5 ma

incremental fold test for paleostress analysis using the hough transform inverse method abstract an incremental fold test method for the paleostress inversion of a fault slip dataset obtained from folded sedimentary rock is proposed the method provides not only the orientations of the three principal stress axes and the stress ratio but also the relative timing of folding and faulting the method is based on the stepwise backtilting of strata significant stresses are identified by simply comparing peak values of total goodness of fit for the paleostress inversion technique and the stress differences among peaks detected from each step of backtilting of a fault slip dataset to assess its validity the method is applied to artificial fault slip datasets generated with hypothetical histories of folding and faulting and with known paleostresses the proposed method successfully recovers the artificial stress tensors and the relative ages of folding and faulting second the method is applied to a natural fault slip dataset obtained for eocene sedimentary strata in kyushu southwest japan folded around ne sw trending axes in the miocene the analysis yields three significant paleostresses a normal faulting stress that occurred before folding and two syn folding stresses indicating the existence of a spatially and temporally varying stress field during folding

silica diagenesis of neogene diatomaceous and volcaniclastic sediments in northern japan marine diatomaceous siliceous sediments in neogene sections of northern japan contrast with the monterey shale of california in containing many intercalations of acidic volcaniclastic sediments diagenesis of these sediments from deep boreholes and surface sections was investigated three diagenetic zones biogenic opal opal ct and quartz zones are recognized in siliceous sediments corresponding roughly to amorphous silica low cristobalite and quartz zones in acidic vitric volcaniclastic sediments opal ct consists almost exclusively of silica and water while low cristobalite contains appreciable amounts of a1 ca na and k in subsurface sections values of d 101 spacing of opal ct decrease progressively with increasing burial depth the progressive ordering is not associated with additional silica cementation in surface sections the behaviour of d 101 spacing is complicated owing to the modification of the progressive ordering developed during burial diagenesis by later silica cementation during uplift the cementing opal ct is probably precipitated from percolating groundwater which dissolves siliceous skeletons in porous diatomaceous mudstones overlying the opal ct porcellanite opaline cherts that form during burial diagenesis are designated as early opaline chert while those which form during uplift are later opaline chert the later opaline chert contains two groups of opal ct one is progressively ordered opal ct and the other is additionally cemented opal ct with higher d 101 spacing than that in the host porcellanite in diatomaceous siliceous sediments early opaline chert is scarce most if not all opaline cherts in surface sections are of later origin

long chain alkenones and alkyl alkenoates and the fossil coccolith record of marine sediments long chain n c37 c39 alkenones and alkyl alkenoates are biological markers for sediment inputs of algae from the class prymnesiophyceae which includes the coccolithophorids these compounds have been recognized in many recent and ancient marine sediments but in only a few living algal species notably the ubiquitous coccolithophorid emiliania huxleyi the proven value of long chain alkenones in palaeotemperature assessment prompts an evaluation of their sedimentary record especially their correspondence with coccolithophorid fossils in ancient marine sediments synthesis of available micropalaeontological and molecular data suggests that morphologically related species of the genera crenalithus dictyococcites emiliania gephyrocapsa pseudoemiliania and reticulofenestra all belonging to the family gephyrocapsaceae were potential biological sources of alkenones and alkyl alkenoates in marine sediments deposited since the eocene 45 ma the occurrence of alkenones in cenomanian and albian sediments devoid of nannofossils may be presumed to reflect contributions from ancestors of the gephyrocapsaceae although an investigation of cretaceous samples containing both coccoliths and alkenones would provide further evidence of this proposed correspondence the combination of palaeontological and molecular chemotaxonomic information offers a novel approach to the evaluation of the phylogenetic lineages that link living and extinct algae

dating of a late quaternary loess section from the northern slope of the tianshan mountains xinjiang china and its paleoenvironmental significance abstract late quaternary loess deposits from the tianshan mountains are potentially valuable archives for the study of environmental change however the reported chronologies of the loess deposits in this area are still controversial previous studies have shown that there remain discrepancies between the optically stimulated luminescence osl ages and accelerator mass spectrometry ams 14c ages of the loess deposits from the yili valley to establish a robust chronological sequence of the shichengzi section scz17 from the northern slope of the tianshan mountains in xinjiang we adopted both ams14c and quartz osl dating methods and the dates based chronology was further refined by correlating sedimentary proxies loss on ignition and grain size with the proxy information from other sequences comparison of the ams 14c and quartz osl ages suggests that the ams 14c ages of bulk organic matter are generally younger than the quartz osl ages with the maximum age discrepancy reaching up to 10 ka regional correlation of the holocene lithology of the scz17 section with other holocene lithologies from the tianshan mountains reveals that the holocene paleosol formation occurred in the late holocene the analyzed proxy data e g grain size carbonate content indicate a cold and dry climate from 21 6 to 10 ka and a persistent wetting trend during the past 10 ka this study provided interesting and new evidence of late quaternary environmental changes in arid central asia

illite smectite patterns in sheared pleistocene mudstones of the southern apennines and their implications regarding the process of illitization a multiscale analysis abstract the transformation of water rich smectite clay minerals into relatively anhydrous illite is a common reaction in sedimentary basins it is commonly thought to be driven by temperature increase with increasing burial depth this mineral transformation is also observed in the gouge of large faults and because it releases bound water from smectite it is thought to be a key control in hydrologic and mechanical processes at subduction complexes in this work the distribution of smectite and illite within a large fault zone of the southern apennines of italy is analysed at scales varying from outcrop to sub millimetre x ray diffraction analyses indicate a direct link between the darkening in colour of the sheared mudstone and the illitization of smectite the heterogeneous distribution of illite and smectite within this shear zone was studied by integrating outcrop scale observations with a peeling technique that allows microscope and sem observations to be made over areas in excess of 60 cm2 the observed patterns of smectite illitization suggest that temperature is not the primary cause of the mineral transformation inside the fault the distribution of illite along planes of the p foliation and in the infill of shears indicates that shear stress facilitates the mineral transformation

reaction kinetics of alkenone and n alkane thermal alteration at seismic timescales recent experiments and field observations have indicated that biomarker molecules can react over short timescales relevant to seismic slip thereby making these compounds a useful tool in studying temperature rise in fault zones however short timescale biomarker reaction kinetics studies have previously focused on compounds that have already experienced burial heating here we present a set of hydrous pyrolysis experiments on pleistocene aged shallow marine sediment to develop the reaction kinetics of long chain alkenone destruction change in the alkenone unsaturation ratio uk 37 and change in the n alkane chain length distribution our results show that biomarker thermal maturity provides a useful method for detecting temperature rise in the shallow reaches of faults such as subduction zone trench environments through the course of our work we also noted the alteration of total alkenone concentrations and uk 37 values in crushed sediments stored dry at room temperature for durations of months to years but not in the solvent extracts of these materials this result though parenthetical for our work in fault zones has important implications for proper storage of sedimentary samples to be used for alkenone paleotemperature and productivity analysis this article is protected by copyright all rights reserved

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

chlorin index a new parameter for organic matter freshness in sediments 1 total chlorins comprising degradation products of chlorophyll have been used recently to reconstruct paleoproductivity from marine sediment cores here we report on a new index the chlorin index ci that proves to be a helpful tool for rapidly estimating organic matter freshness in marine sediments the ci is a ratio between the fluorescence intensity of a sediment extracted with acetone and treated with hydrochloric acid and the original sediment extract it represents the ratio of chlorophyll and its degradation products deposited in the sediments that could still be chemically transformed and those that are inert to chemical attack the ratio is lower in sediments that include freshly deposited phytoplankton material and higher in older more degraded sediments we measured this new parameter on surface sediments and sediments from several short and a long sediment core from different oceanic settings ci values range from 0 2 for chlorophyll a to 0 36 0 56 for fresh material deposited on the shelf off namibia to values around 0 67 in sediments off chile and peru to values up to 0 97 for sediments in a deep core from the northeastern slope of the arabian sea we have compared the ci to rates of bacterial sulfate reduction as a direct measure of organic matter reactivity and to other degradation indices based on amino acid composition we conclude that the ci is a reliable and simple tool for the characterization of organic material freshness in sediments in respect to its degradation state

paleoenvironmental and paleoclimatic variations around lake van eastern turkey recorded by sedimentary source specific biomarkers 250 130 ka mis7 and mis6 abstract paleoclimatic changes during mis7 and mis6 remain poorly described in the near east we quantified source specific biomarkers in lake van sediments during the interglacial glacial cycle mis7 mis6 long chain n alkanes produced by land derived vegetation as well as long chain alkenones and sterols namely brassicasterol and dinosterol produced by aquatic algae were investigated stable hydrogen isotopic measurements 2h on n c29 alkanes were used as a proxy for aridity and revealed three wetter periods interrupted by two drier intervals during mis7 in contrast during the mis6 glaciation a generally drier climate was predominant during the warmer and wetter periods of mis7 a higher input of aquatic organic matter to lake van sediments was recorded by higher concentrations of long chain alkenones dinosterol and brassicasterol long chain alkane abundances do not show a pattern related to aridity and were observed in higher concentrations in wetter as well as drier periods generally in the eastern mediterranean a wetter interglacial interrupted by drier episodes followed by a dry glacial period was the common feature observed during the mis7 mis6 interglacial glacial cycle however in comparison to the last interglacial glacial cycle the extreme dry glacial period registered around lake van from mis5d to mis2 was apparently unique and not equaled by a similar event within the last 250 ka

shear fractures in anisotropic ductile materials an experimental approach abstract analogue models have been used to investigate the influence of planar mechanical anisotropy on the orientation of shear fractures in an elastoviscous brittle material multilayered models consisting of a mixture of plasticine vaseline and preferentially oriented paper flakes have been coaxially deformed for this purpose the evolution of the orientation length and connectivity of fracture sets has been systematically analysed with progressive coaxial deformation the experimental results show that the orientation of fractures with respect to the deformation axes depends on the orientation of transverse anisotropy two symmetrical sets of shear fractures are formed in models with layering parallel to the extension axis x while the fracture network is asymmetrical with respect to the deformation axes for cases with oblique anisotropy the average dihedral angles between fracture sets are higher than 100 with the obtuse bisector between the two sets oriented perpendicular to layers the stress fields calculated from fracture data differ from the boundary conditions applied by the deformation apparatus this misorientation is related to the degree of anisotropy in models with high oblique anisotropy both fracture arrays rotate in a dextral sense together with layers towards the x axis indicating that the presence of a strong anisotropy controls their evolution with progressive deformation

climatic changes in the upwelling region off cap blanc nw africa over the last 70 kyear a multi biomarker approach abstract molecular statigraphic records of core su94 11k 21 n 18 w 1200 m water depth were reconstructed for organic carbon oc carbonates alkenones n alkanols and sterols over the last 70 ky to study past changes of production and paleoceanographic conditions in the coastal upwelling of northwest africa u k 37 derived sea surface temperatures sst show a 2 5 c warming during the last deglaciation surprisingly they also indicate that during the last glacial period between 24 and 15 kyear sst rose by 1 c it can be seen from the values of marine and terrigenous biomarker mass accumulation rates mar that this time interval was also the period of lowest marine production and dust supply suggesting a major change in the north east trade winds system this situation would have lasted until the onset of the deglaciation from which upwelling progressively intensified to produce highest marine biomarker mar at the holocene our data also show a reduced terrigenous supply in late holocene sediments that may reflect lower emission rates from the vegetation and or changes in the wind conditions

alkenone based temperature and climate reconstruction during the last deglaciation at lake dangxiong co southwestern tibetan plateau the climate of the tibetan plateau is influenced by the monsoons and the westerlies due to land sea thermal contrasts however few quantitative temperature reconstructions have been made for the region and this hinders our ability to validate climate models and to understand the coupling process between monsoon ocean and ice sheets through time here we report a quantitative temperature reconstruction for the last deglaciation from a terrace of lake dangxiong co in the southwestern tibetan plateau based on the unsaturation index of long chain alkenones the reconstructed mean annual air temperature during the late last glacial maximum was about 0 2 c while the bolling allerod b a period was characterized by a rapid increase in temperature from 0 8 c to 2 4 c 2 9 followed by an abrupt decrease in temperature to 0 9 c in the early younger dryas yd the alkenones and n alkanes record indicates that dangxiong co experienced a cold and wet climate in the early part of the last deglaciation after the last glacial maximum a warm dry b a and a cold and dry yd our temperature reconstruction confirms that the thermal and dynamical effects of the tibetan plateau are one of the main elements contributing to abrupt changes in the indian summer monsoon

experimental investigation into the microstructural and mechanical evolution of phyllosilicate bearing fault rock under conditions favouring pressure solution abstract mature crustal fault zones are known to be zones of persistent weakness this weakness is believed to result from microstructural modifications during deformation such as grain size reduction and foliation development around the brittle ductile transition phyllosilicates are expected to have a significant effect on fault strength in particular under conditions favouring pressure solution to study such effects we performed rotary shear experiments on brine saturated halite kaolinite mixtures aimed at investigating the relation between microstructural and mechanical evolution in a system where pressure solution and cataclasis dominate the results show significant strain weakening and a transition with progressive strain towards more rate sensitive and less normal stress sensitive behaviour this was accompanied by a microstructural evolution from a purely cataclastic microstructure to a mylonitic microstructure consisting of elongate asymmetric clasts in a fine grained foliated matrix the results demonstrate that strain weakening and the development of a typical mylonitic microstructure can occur as a consequence of grain size reduction by cataclasis and a transition to pressure solution accommodated deformation even in the absence of dislocation creep the data raise questions regarding the reliability of microstructures as rheology indicators as well as on the use of low strain monomineralic flow laws for modelling crustal dynamics

long chain unsaturated ketones and esters in living algae and marine sediments abstract series of c37 c39 di and triunsaturated ketones and methyl and ethyl esters of hexatriacontadienoic acid c36 2 have been previously identified in marine sediments and the coccolithophorid emiliania huxleyi these compounds have now been found in four further species of the isochrysidales prymnesiophyta which are not known to bear coccoliths suggesting that they are more widely distributed in living algae than previously thought in addition the ketones have been recognised in sediments of eocene age ca 45 ma which greatly extends their known geological time range and increases their potential as molecular markers for algal input heptatriacontatetraen 2 one c37 4 octatriacontatetraen 3 one c38 4 methyl and ethyl esters of hexatriacontatrienoic acid c36 3 and the ethyl ester of hexatriacontatetraenoic acid c36 4 have also been identified in varying amounts in these algae by gas chromatography and computerised gas chromatography mass spectrometry

uk 37 temperature estimates from eemian marine sediments in the southern coast of hainan island tropical china abstract this study concerns high resolution sea surface temperature sst changes for the eemian interglacial period reconstructed from the southern coast of hainan island china the lower marine unit in the sediment core is composed of monotonous mud 31 m thick dated to be from the eemian interglacial period or lower part of marine isotope stage 5 mis 5 determined by optically stimulated luminescence osl the high sedimentation rate and the richness of organic matter and marine fossils provide good opportunity for the study of palaeo environments in the northern margin of the south china sea scs sediment grain size foraminifer sediment color index and long chain alkenone were used to reveal the near shore sedimentary environments and temperature at millennial scale specifically a high resolution uk 37 sst record was reconstructed for the eemian interglacial period the new evidence in northwestern margin of scs shows that the maximum value of sst during the eemian interglacial is approximately 29 c and the lowest is 26 5 c the trend of decreasing sst from 29 c throughout the marine sequence is consistent with the variations in sediment grain size reflecting the cooling trend of sst and sea level lowering tendency during the last interglacial period this new eemian sst result agrees with other records in the region of scs showing a coherent descending trend but spatial heterogeneity exists in timing and amplitude the insolation changes might be the main force for initiating the sst evolution during the penultimate interglacial period

atlantic core top calibration of the u37k index as a sea surface palaeotemperature indicator abstract a field calibration of the uk index with sea surface temperature is discussed through analysis of an extensive suite of surface sediments n 109 from the northeastern atlantic 2 s 75 n values of u 37 k are compared with sea surface temperatures for overlying waters measured at different depths and seasons to obtain a correlation suitable for palaeotemperature reconstructions the best fit is obtained using surface 0 m temperatures corresponding to caloric winter and autumn months however the annual average spring and summer surface temperature equations also have high correlation coefficients and are also appropriate for climatic studies the results further validate the general applicability of the u 37 k as a climatic proxy because the calibration equations are valid over a wide range of surface water temperatures 0 28 c for different algal populations and are representative of the average contribution of alkenones to sediments as found in sediment cores

the origin of ridge in groove slickenside striae and associated steps in an s c mylonite abstract a three dimensional study of an s c mylonite reveals that the s surfaces anastomose around porphyro clasts and c surfaces are not truly planar but curvi planar with the linear generator parallel to the movement direction it is suggested that it may be common for shear surfaces at all scales to take this form in the material studied surfaces exposed by parting primarily along c surfaces which are a product of ductile deformation and are penetrative have all the characteristics of classic slickensides on the slickensides striae of the ridge in groove type and steps of both congruous and incongruous types are developed the ridge in groove shape of the striae is directly related to the curvi planar shape of the c surfaces incongruous steps are smooth they are the result of parting along s surfaces congruous steps are rough first order congruous steps are formed by fracturing between individual c surfaces whereas second order congruous steps form by breaking off the tips of the dihedra between s and c surfaces thus the smoothness roughness technique can be used to determine the sense of shear in strongly deformed rocks where the angle between s and c surfaces is too small to be recognized in the field this may prove to be a useful shear sense indicator

the influence of salinity on d h fractionation in alkenones from saline and hypersaline lakes in continental north america abstract we present a preliminary assessment of the hydrogen isotopic composition of individual alkenones c 37 39 di tri and tetra unsaturated methyl and ethyl ketones purified from surface lake sediment from sites spanning a range of salinities from 20 to 133 ppt combining these measurements with measurements of the hydrogen isotopic composition of modern lake water we estimate the magnitude of d h fractionation across our sample set and observe reduced sensitivity to salinity compared to observations from emiliania huxleyi and gephyrocapsa oceanica this lends support to the hypothesis that d h fractionation during biosynthesis is less sensitive to changes in salinity in alkenone producers from continental interior sites than in producers from open marine environments we also observe stronger correlations between the tetra unsaturated alkenone d values with water d values and associated values with salinity than we do for the di and tri unsaturated compounds and suggest that this may result from increased number of lacustrine haptophyte species producing the di and tri unsaturated as compared to the tetra unsaturated

environmental processes of the ice age land oceans glaciers epilog knowledge of the state of the earth at the last glacial maximum lgm an interval around 21 000 years ago is an important benchmark for understanding the sensitivity of global environmental systems to change much progress in understanding climates of the lgm has occurred in the 20 years since the end of the climap project of the 1970s climate long range investigation mapping and prediction here we review this progress based on presentations and discussion at a rst open science meeting of the epilog project environmental processes of the ice age land oceans glaciers held in delmenhorst germany may 1999 we outline key controversies and document protocols for epilog contributions so that a new synthesis of the lgm earth can emerge as an open project of the world s community of scientists 2001 elsevier science ltd all rights reserved

mode i microfracturing and fluid flow in damage zones the key to distinguishing faults from slides abstract we have examined the distribution of microfractures in arenites and the evolution of vein forming fluids in the matrix of carbonate breccias within the damage zones of large detached blocks in order to characterize their modes of emplacement previous studies of microfractures in the damage zone associated with tectonic faulting have shown a clear pattern of increasing density as the fault is approached previous studies of carbonate breccia within damage zones of tectonic faults typically document evidence of multiple fluid events representing repeated rupture healing processes however in this study we find no change in the microfracture density with distance from the 45 km displaced gravity driven slide block at heart mountain wyoming in a previous study of the same massive slide block there was no evidence of multiple fluid infiltration events related to emplacement we interpret these observations as indicating the absence of rupture cycling that would be expected in the development of a process zone instead being consistent with catastrophic emplacement of gravity driven slide blocks we use this distinct pattern of microfracture density and fluid infiltration to demonstrate that several large 1 km2 detached blocks in the basin and range previously thought to be allochthons related to hyperextension detachment faults are actually slide blocks whose detachment surfaces represent no crustal extension

mechanical strength of the transition zone at the boundary between opal a and opal ct zones in siliceous rocks abstract in a massive siliceous mudstone at the site of the horonobe underground research laboratory in hokkaido japan a hard part having a very high unconfined compressive strength occurs at the top of siliceous mudstone opal ct zone at the boundary with the overlying diatomaceous mudstone opal a zone bulk chemical data does not indicate additional silica cementation or differences in mineralogy in the hard part compared with the remainder of the siliceous mudstone the hard part corresponds to a transition zone between opal a and opal ct where the two phases coexist sem images show that microcrystalline opal ct precipitates within pore spaces in the pre existing intricate diatom supported framework of the transition zone below this zone the framework is replaced by aggregations of relatively fine and equigranular opal ct the strength of the hard part probably reflects the strong framework cementation due to the coexistence of opal a and opal ct consequently the transition zone between opal a and opal ct is generally strong and brittle and if it tectonically deformed it could act as a fluid conduit

the relationship of strain and preferred orientation of phyllosilicate grains in rocks a review abstract the calculation of strain from the preferred orientation of platy phyllosilicate grains taking strain to be homogeneous is surprisingly often successful from a pragmatic point of view although numerous theoretical objections to this procedure can be and have been raised for the calculation to succeed the original distribution of mica or clay mineral grains must be known or assumed the usual assumption that the starting distribution was random and therefore nearly uniform implies that the strain history of pelitic sediments is taken to start when the watery sediment was last stirred by waves or bioturbation or if it was laid down in still anoxic waters from the moment of first deposition it therefore includes compaction as part of the strain history which is usually neglected by structural geologists originally random distribution of clay flake orientations has been observed in recently deposited sediments in many instances and has been theoretically explained in various ways exceptions probably exist but their frequency has not been estimated biologically disturbed sediments may be brought nearer to a state of random orientation of clay flakes than they were at deposition with the exception of whole beds or concretions in which pores are early filled with cement mudrocks are almost always compacted by the weight of later deposits the strain so induced is axially symmetric about the vertical and thus about the pole of the bedding planes compaction acts on soft unconsolidated rocks but may continue with increasing overburden on rocks strengthened by cementation and by increasing interlocking of grains tectonic deformation may start early before the rock is fully compacted or it may begin only much later and the mechanisms of deformation increase in complexity with the increasing temperature and hydrostatic stress of deeper burial up to a certain level of mild metamorphism however phyllosilicate grains seem to be rather permanent if not as mineral species then at least by preservation of their constituent sheets of silica tetrahedra given this permanence the mechanisms of rock deformation whether intergranular slip cataclasis or dissolution and reprecipitation and various intragranular processes in the non phyllosilicate matrix hardly matter as far as the recording of strain is concerned even a certain amount of stress solution at especially heavily loaded points of the phyllosilicate grains themselves does not destroy their value as strain markers as long as the dissolved material is disposed of mainly by crystallographically continuous overgrowth on existing grains the same holds for local dissolution of phyllosilicates in portions of old grains that have become thermodynamically unstable by bending widespread irregular or random nucleation and growth of newly nucleated phyllosilicate grains at intermediate or high grades of metamorphism can reduce the reliability of the strain record and so can domainal structure of the deformed rock if both the volume fraction of phyllosilicate grains and the intensity of total strain differ sharply from one domain to another if distinct domains are not equant and have themselves a strong preferred orientation of shape nevertheless rocks containing an anastomosing network of zones rich in phyllosilicate grains as slates and other deformed mudrocks commonly do have in many cases been found to have average preferred orientations of mica or chlorite which if used to estimate the strain give results similar to those obtained from independent strain markers in the same rocks thus the most significant verification of the usefulness of strain estimates by measurement of preferred orientation is the mutual confirmation with independently determined strain the limit to such verification is the rarity of strain markers so that the coexistence of two independent ones is exceptionally rare for this reason however it is important to make full use of the orientation of phyllosilicate grains where they are available the alternative to have no strain measurements at all causes structural geologists to miss potential information

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

c axis fabrics and microstructures in a recrystallized quartz vein deformed under fluid rich greenschist conditions the quartz v axis orientations and microstructures have been analyzed in an originally single crystal buckled quartz vein of greenschist metamorphic grade from the sambagawa metamorphic belt southwest japan the basal 0001 plane was inclined by ca 10 20 to the quartz vein surface before deformation and the flexure essentially kink which produced the fold was accomplished by basal 0001 slip alone in the hinges i e flexural slip folding in addition to crystal plasticity dissolution microstructures are ubiquitous in the quartz vein dynamic recrystallization resulted from both subgrain rotation and grain boundary migration rotation recrystallization associated with basal 0001 slip resulted in host controlled v axis orientation distribution along a great circle whereas migration recrystallization perhaps assisted by intergranular fluid resulted in a penetrative development of a weak x elongation maximum v axis fabric nowhere rotated by the folding the migration recrystallization is evidenced by large v axis misorientations across the grain boundaries as well as irregular grain shape based on the weak v axis fabric development and lack of grain shape fabric solution precipitation creep may have dominated in the fluid assisted grain boundary migration regime and hence it is inferred that the transition from rotation to migration recrystallization was caused by a local decrease of differential stress in the buckled quartz vein

coupled micro faulting and pressure solution creep overprinted on quartz schist deformed by intracrystalline plasticity during exhumation of the sambagawa metamorphic rocks southwest japan abstract in the sambagawa schist southwest japan while ductile deformation pervasively occurred at d 1 phase during exhumation low angle normal faulting was locally intensive at d 2 phase under the conditions of frictional viscous transition of quartz c 300 c during further exhumation into the upper crustal level accordingly the formation of d 2 shear bands was overprinted on type i crossed girdle quartz c axis fabrics and microstructures formed by intracrystalline plasticity at d 1 phase in some quartz schists the quartz c axis fabrics became weak and finally random with increasing shear accompanied by the decreasing degree of undulation of recrystallized quartz grain boundaries which resulted from the increasing portion of straight grain boundaries coinciding with the interfaces between newly precipitated quartz and mica we interpreted these facts as caused by increasing activity of pressure solution the quartz grains were dissolved mostly at platy quartz mica interface and precipitated with random orientation and pinned by mica thus having led to the obliteration of existing quartz c axis fabrics in the sheared quartz schist the strength became reduced by the enhanced pressure solution creep not only due to the reduction of diffusion path length caused by increasing number of shear bands but also to enhanced dissolution at the interphase boundaries

climatic influences on the paleogene evolution of alkenones application of the alkenone paleotemperature proxy uk 37 for marine sediments is typically constrained by three factors i an absence of alkatrienones in sediments deposited where ocean temperatures exceed 28 c ii loss of alkenones in thermally altered sediments and iii poor preservation of alkenone signals due to oxidative degradation in addition there appears to be a temporal limit on the occurrence of alkatrienones which are conspicuously absent in all alkenone containing sediments from the early aptian to the immediate aftermath of the early eocene climatic optimum eeco when they first appeared in arctic ocean sediments compilation of reported and previously unpublished alkenone distributions for the paleogene coupled with assessment of co occurring calcareous nannoplankton genera within the noelaerhabdaceae provide evidence that evolutionary developments in alkenone occurrences include biosynthetic responses likely triggered by climate change the timing of emergence of alkatrienones post eeco and their subsequent appearance at all latitudes during the middle eocene accompanies expansion of the calcareous nannoplankton genus reticulofenestra coincident with significant climate driven changes in oceanic conditions including i modification of trophic structure associated with weakened thermal stratification ii higher productivity facilitated by enhanced nutrient influx and iii changes in seasonality initially at high latitudes related to greater latitudinal temperature gradients collectively these changes would serve to favor eurythermal eurytrophic algae like reticulofenestra with a biomechanism to store energy through production of lipid bodies rich in alkenones during episodes of higher nutrient availability this ability likely enhanced the viability of this marine haptophyte when nutrients were limiting ultimately ensuring its evolutionary success

palaeoclimatic signals recognized by chemometric treatment of molecular stratigraphic data abstract the high resolution stratigraphy of various marker compounds has been studied using gc hplc and gc ms in a 13 m gravity core recovered from the kane gap region eastern equatorial atlantic which provides a record of the glacial interglacial episodes over the last million years downhole variations in many presumed source specific components are observed e g in n alkanes from terrigenous land plants and dinosterol from dinoflagellates which may be due to perturbations or cyclicities resulting from climatic change fluctuations in the unsaturation of alkenones attributable to variations in water temperatures show correlations with the glacial interglacial cycles recorded in the 18 o values for planktonic foraminifera thereby providing a potential organic geochemical measure of past climates these molecular abundance data can be linked to the palaeotemperature record following computer treatments using principal component and spectral analyses molecular stratigraphy shows promise as a new chemostratigraphical tool where other means of stratigraphy fail for example through calcium carbonate dissolution

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

chemical aspects of alteration of acidic tuffs and their application to siliceous deposits in order to evaluate fundamental chemical characteristics of acidic tuffs and to determine which of these characteristics in volcanogenic sediments is preserved during weathering processes we have analysed 41 pairs of ash samples each pair consists of 1 raw samples obtained from ash layers which consist of a mixture of volcanic glasses and clays and 2 glass shard aggregations extracted from the raw samples the migration of elements in the samples during alteration was examined using the analysed values of these pairs the results showed that certain compositional ratios of the glass shards do not basically change during alteration several diagrams showing these essentially constant ratios in acidic 65 sio2 volcanic glasses are presented these diagrams are helpful in identifying altered siliceous deposits derived from acidic tuffs and in discriminating such deposits from biogenically derived cherts

bedding tilt test for paleostress analysis it is difficult to apply stress inversion to fault slip data obtained from highly tilted sedimentary layers especially in areas where criteria for fault sorting are not available at outcrops this paper shows that a bedding tilt test similar to that used in paleomagnetism allows paleostresses to be inferred in order to assess its validity the testing method was applied firstly to artificial fault slip data generated with a hypothetical history for folding and faulting with known paleostresses the stresses were successfully recovered and the correct timing of faulting relative to tilting could be determined the test procedure was secondly applied to mesoscale faults observed in a mid pleistocene sedimentary unit in central japan which was folded in late pleistocene it was found that the majority of the faults were activated mainly by a strike slip faulting regime of stress at the middle stage of folding

experimental investigation of incipient shear failure in foliated rock abstract it has long been known that rock fabric plays a key role in dictating rock strength and rheology throughout earth s crust however the processes and conditions under which rock fabric impacts brittle failure and frictional strength are still under investigation here we report on laboratory experiments designed to analyze the effect of foliation orientation on the mechanical behavior and associated microstructures of simulated fault rock sheared at constant normal stress of 50 mpa intact samples of pennsylvania slate were sheared with a range of initial fabric orientations from 0 to 165 with respect to the imposed shear direction foliation orientations of 0 30 produce initial failure at the lowest shear stress while samples oriented at higher angles are less favorable resulting in higher peak failure strength in all samples post peak development of through going deformation zones in the r1 riedel orientation results in a residual strength that is lower than that observed for powdered gouge from the same material as shear strain increases all samples approach a residual apparent friction defined by the ratio of shear strength to normal stress of 0 4 however the final deformation microstructure depends strongly on the orientation of the pre existing foliation when fabric is oriented at low angles to the shear direction

diagenetic controls on the structural evolution of siliceous sediments in the golconda allochthon nevada u s a abstract a model is proposed that links the diagenesis of siliceous sedimentary rocks with deformation to explain the heterogeneous structural fabric of radiolarian cherts in the upper paleozoic golconda allochthon of nevada u s a numerous thrust faults slice the cherts into packets each with a unique set of internal structures fold geometries boudin profiles pressure solution features etc vary from packet to packet and layer to layer analogous variations in the diagenetically mixed siliceous sediments of the miocene monterey formation california suggest the cherts of the golconda allochthon were similarly mixed when they were deformed radiolarian sediments composed of biogenic silica opal a developed ductile structures and pressure solution features because of their high porosity weak lithification and the high solubility of disordered silica lowporosity strongly lithified relatively insoluble quartz cherts the final product of silica diagenesis deformed in a brittle fashion and developed fewer pressure solution features diagenetically intermediate ct cherts and ct porcelanites exhibited transitional behavior mixed diagenetic zones produced structures with layer by layer changes in structural style the dehydration of opal a and opal ct helped create the excess pore fluid pressures responsible for thrust faults hydraulic fractures dilation breccias and elastic intrusions the presence of ductile structures and numerous pressure solution features in the oldest cherts of the havallah sequence suggests that these cherts were deformed while diagenetically immature possibly within a long lived upper paleozoic accretionary prism

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

late quaternary high resolution biomarker and other sedimentary climate proxies in a northeast atlantic core we studied variations in terrigenous input and sea surface temperature over the last 208 ka using a multiproxy approach involving direct comparison of terrigenous and marine molecular biomarker foraminiferal abundance and other sedimentological data for the same horizons in a single northeast atlantic core core t88 9p 48 23 n 25 05 w 3193 m water depth 790 cm core length with a well resolved 18o stratigraphy the abundances of three land derived long chain compound classes the n alkanes c27 c29 and c31 the n alkanoic acids c24 c26 and c28 and the n alkanols c24 c26 and c28 show glacial interglacial related changes in the past 208 ka which generally parallel the weight percent noncarbonate the abundances of these three compound classes are higher in glacial than in interglacial sediments such changes are consistent with the expected higher dust inputs during glaciations as well as enhanced advection of particulate matter in current systems ice rafted debris heinrich events may also contribute to the terrigenous biomarker record the sea surface temperature sst signals derived from the alkenone unsaturation index uk 37 give an average sst during interglacial periods of 13 c which is about 3 4 c higher than the average glacial sst estimate the uk 37 derived sst values dropped markedly in some heinrich layers while sometimes leading the onset of the layer the percent neogloboquadrina pachyderma s which is another frequently used qualitative temperature proxy generally shows maxima coinciding with the layers our results show that most heinrich layers were produced during times of intensely cold waters in the eastern north atlantic they demonstrate that sufficient alkenones are present in the sediments for alkenone stratigraphy to be used as a tool for the assessment of short term variations in sea surface temperatures even in these oligotrophic north atlantic waters

alteration processes of alkenones and related lipids in water columns and sediments 1 alkenones produced by the haptophyte algae are currently being used as indices of sea surface temperature in recent and past ocean environments but limited information is available concerning the impact of biotic and abiotic processes on the integrity of these long chain lipids this synthesis provides selected background information on major alteration processes that must be considered before such indices can be used with confidence a number of processes in the water column and surface sediments have the potential to impact the structural integrity of alkenones and compromise their ability as temperature markers processes discussed include the alteration of alkenone structure during early diagenesis direct biotic and abiotic impacts and the effect of digestive processes by grazers current literature suggests that despite substantial changes in concentration from biological processing the temperature signal is preserved for each of these processes information on the integrity of the alkenone isotopic signature is also needed and limited information available is reviewed in addition to the alkenones related lipids including the long chain alkadienes and akyl alkenoates that might serve as ancillary markers are discussed

the role of bedding in the evolution of meso and microstructural fabrics in fault zones abstract to investigate the role of bedding in the evolution of meso and microstructural fabrics in fault zones detailed microscopic mineralogical and geochemical analyses were conducted on bedding oblique and bedding parallel faults that cut a folded neogene siliceous mudstone that contains opal ct smectite and illite an analysis of asymmetric structures in the fault gouges indicates that the secondary fractures associated with each fault exhibit contrasting characteristics those of the bedding oblique fault are r 1 shears whereas those of the bedding parallel fault are reactivated s foliation the bedding oblique fault shows the pervasive development of s foliation lacks opal ct and has low sio 2 tio 2 ratios only in gouge whereas the bedding parallel fault exhibits these characteristics in both gouge and wall rocks the development of s foliation and the lack of silica can result from local ductile deformation involving the sliding of phyllosilicates coupled with pressure solution of opal ct although such deformation can occur in gouge the above results indicate that it may occur preferentially along bedding planes preceding the formation of a gouge slip surface thus in sedimentary rocks that contain phyllosilicates and soluble minerals bedding can influence the rheological evolution of meso and microstructural fabrics in fault zones

unusual distributions of long chain alkenones and tetrahymanol from the highly alkaline lake van turkey long chain c37 to c40 alkenones with di tri and tetra unsaturation are very abundant in sediment trap material and holocene to late pleistocene core samples from the earth s largest soda lake lake van turkey thus the known distribution range of these typical biomarkers for haptophyte microalgae is extended to highly alkaline environments the observed unsaturation patterns differ strikingly from those found in open marine haptophytes and sediments by an enhanced relative abundance of the tetra unsaturated compounds especially the c37 4 methyl ketone their preponderance is suggested to be a facies marker pattern for lacustrine and marginal marine areas of sedimentation using published u37k calibrations no reliable absolute temperatures were obtained for the lake van samples accordingly marine sea surface temperature determinations based on long chain alkenones should be applied with caution when a contribution of these compounds from coastal or nonmarine sources can not be excluded the presence of tetrahymanol and gammacer 3 one in the lake van materials is attributed to organic matter contributions of ciliates the relative abundance of long chain alkenones and of tetrahymanol gammacer 3 one is considered to reflect changes in the environmental conditions in particular in the hydrological setting we suggest that times of pronounced stagnation are recognised by very high tetrahymanol gammacer 3 one concentrations together with drastically increased stanol stenol ratios and intervals of enhanced convection or of high freshwater input are characterised by high alkenone contributions

late holocene coupled moisture and temperature changes on the northern tibetan plateau the northern tibetan plateau involves complex interactions between the mid latitude westerly circulation and the subtropical asia monsoon circulation acting as a bridge communicating high and low latitude climatic processes previous studies from the region suggest relatively wet conditions in cold periods during the late holocene for instance the little ice age lia however the inference of such temperature moisture association is subject to the large uncertainty in lacustrine 14c chronology due to the particularly large lake reservoir effect in the region here we take a different approach by reconstructing paired temperature and moisture records from the same sediment cores to assess the temperature moisture association independent of chronology uncertainty we use alkenone indices uk 37 and c37 4 to reconstruct high resolution temperature and moisture changes simultaneously from two lakes in the qaidam basin northern tibetan plateau over the last 2500 years characterized by marked climatic variability our paired records confirm the warm dry and cold wet association in arid northwestern china during the late holocene opposite to the warm wet and cold dry association in subtropical asian monsoonal regions our moisture records further suggest substantially drier conditions during the medieval warm period mwp than the current warm period lastly the temperature and moisture changes inferred from our records can be well correlated with solar irradiance changes suggesting a possible link between solar forcing and natural climate variability during the late holocene on the northern tibetan plateau

grain growth and re orientation of phyllosilicate minerals during the development of slaty cleavage in the south kitakami mountains northeast japan abstract using x ray diffraction analysis the mutual relations among illite crystallinity degree of preferred orientation of chlorite grain size change of chlorite and illite during metamorphism and development of slaty cleavage have been investigated for argillaceous rocks in the south kitakami mountains northeast japan the metamorphic grade of ic illite crystallinity index 0 29 is a critical one beyond which the homogenization of chlorite composition coarsening of chlorite and illite grains and degree of preferred orientation of chlorite are abruptly advanced grain coarsening is also promoted by the development of slaty cleavage especially in the range of coarser grain size the oriented growth by the effects of both the anisotropy of intrinsic growth rate of mineral grains and that of the environment in which grains grow is considered to bring about the preferred orientation of chlorite and illite