organic geochemical proxies of paleoceanographic paleolimnologic and paleoclimatic processes abstract organic matter constitutes a minor fraction of marine and freshwater sediments yet its important contribution to the sedimentary record can be used to reconstruct marine and continental paleoenvironments the organic matter content of sediments is the residue of past biota the amounts and types of organic matter present in sediments consequently reflect environmental conditions that impacted ecosystems at different past times general sources of the organic matter are inferred from bulk properties such as elemental compositions carbon and nitrogen stable isotope ratios rock eval pyrolysis data and organic petrography details of organic matter origins are refined by analyses of biomarker molecular compositions source changes are proxies for fluctuations in sea level oceanic surface currents and continental climates algal paleoproductivity rates are indicated by organic carbon mass accumulation rates and carbon and nitrogen stable isotopic compositions these parameters record past availability of nutrients and therefore are proxies of surface mixing in the oceans and amount of land runoff to lakes sea surface paleotemperatures are recorded by the number of carbon carbon double bonds in lipid biomarkers produced by marine algae larger proportions of the double bonds are proxies for the cooler surface waters that accompanied periods of global glaciation and intervals of enhanced upwelling the 13c and d values of plant organic matter record past concentrations of carbon dioxide in the atmosphere and changes in delivery of atmospheric moisture respectively diagenesis which causes the concentration and composition of organic matter in sedimentary settings to differ from those of the original biologically synthesized materials can bias organic geochemical paleoenvironmental records the magnitude of this potential source of misinformation must always be considered and evaluated comparison of multiple organic geochemical proxies of past conditions helps to compensate for the effects of diagenetic alterations and thereby to improve interpretations of paleoenvironmental change

coseismic slip distribution of the 1999 chi chi taiwan earthquake deduced from inversion analysis of gps data the 1999 chi chi earthquake m w 7 6 was the largest thrust type earthquake that occurred in taiwan in the twentieth century following the event large horizontal and vertical coseismic displacements were observed at gps stations near the fault region the observed maximum horizontal displacement uplift and subsidence were 9 1 4 0 and 0 7 m respectively in order to estimate coseismic slip distribution geodetic data inversion was carried out based on the gps displacement data total numbers of horizontal and vertical data used here are both 118 taking the shape of the surface rupture aftershock distribution and centroid moment tensor solutions into account a gently curved fault plane with a fault size of 70 km 50 km a dip angle of 31 and strike of n9 e was constructed the results show that the amount of average slip is 5 1 m and the average slip direction is n55 w on the fault plane seismic moment estimated from the geodetic data inversion is 5 4 1020 n m the amount of slip gradually increases toward the northwest on the fault plane reaching 13 8 m the spatial distribution of the coseismic slip is consistent with that estimated from inversion analysis of teleseismic and near source strong motion data whereas the amount of slip of the former is larger than that of the latter this may suggest that slow large afterslips occurred on the northwestern part on the fault plane within one month of the event and or the fault dip adopted in this study was larger than the actual dip indicating disagreement of coseismic fault plane with one of the nodal planes estimated from the cmt solutions and the aftershock distribution manuscript received 31 july 2000

the use of hydroxyacids as geochemical indicators abstract the distributions of hydroxyacids in a variety of recent and ancient sediments have been determined by gas chromatography mass spectrometry a lacustrine sediment rostherne mere u k and two marine situations cariaco trench black sea were analyzed as examples of recent depositional environments hydroxyacids occurred in all of the recent sediments consistent with their presumed microbial origin whereas di and trihydroxyacids were present in the sediments with a significant higher plant input black sea and rostherne mere sediments the two ancient eocene sediments examined viz the greene river u s and messel germany oil shales contained only trace amounts of hydroxyacids these results provide evidence that hydroxyacids are in general not well preserved over geological time

molecular paleoclimatology reconstruction of climate variabilities in the late quaternary abstract lipid class compounds were studied in the deep sea surface sediments from the central pacific across a latitudinal transect at 175 e 48 n 15 s and a box core from the western tropical pacific to discuss their utility as paleoclimatological indicators higher concentrations of c25 c35 n alkanes were observed in the higher latitudes in the north pacific their latitudinal distributions are similar to the spatial distributions of the observed soil dust concentrations observed in the central north pacific atmosphere suggesting that the sedimentary c25 c35 n alkanes are atmospherically transported from terrestrial higher plants and can be used as an indicator of terrestrial input to ocean environments downcore distributions of total c25 c35 n alkanes suggest that terrestrial input doubled over the western tropical pacific at the lgm and decreased by a factor of two at the last deglaciation period in comparison with the holocene the latitudinal distributions of c17 c20 n alkanes and pristane are higher in the high latitudes and equatorial region probably reflecting the higher primary productivity in surface waters of these oceans the downcore profiles of these compounds as well as total organic carbon long chain alkenones and dinosterol suggest that biological production decreased significantly during the deglaciation period and slightly increased during the lgm compared with that of the holocene the downcore uk37 record suggests that the sst was almost constant over the last 20 000 y which agrees well with the climap results and foraminifera 18o although it disagrees with results from coral sr ca ratios and 18o records

sediment core profiles of long chain n alkanes in the sea of okhotsk enhanced transport of terrestrial organic matter from the last deglaciation to the early holocene 1 terrestrial plant derived n alkanes c25 c35 w ere measured in three piston cores pc1 pc2 and pc4 in the sea of okhotsk covering the last 30 kyrs down core profiles of the n alkane concentrations and mass accumulation rates mar were characterized by deglacial maxima in particular cores pc2 and pc4 which were collected from the central and western sea of okhotsk respectively show a two step increase around the meltwater pulse events mwp 1a 14 5 13 5 kyr bp and 1b about 10 kyr bp this finding was interpreted by the outflow of terrestrial organic matter from the submerged land shelf to the sea of okhotsk through the east sakhalin current this study demonstrated that the sea level rise forced by global warming in the deglaciation period may have caused the enhanced transport of terrestrial organic matter in marginal seas index terms 3022 marine geology and geophysics marine sediments processes and transport 4267 oceanography general paleoceanography 1055 geochemistry organic geochemistry citation seki o k kawamura t nakatsuka k ohnishi m ikehara and m wakatsuchi sediment core profiles of long chain n alkanes in the sea of okhotsk enhanced transport of terrestrial organic matter from the last deglaciation to the early holocene geophys res lett 30 1 1001 doi 10 1029 2001gl014464 2003

distribution of lipid class compounds in bottom sediments of freshwater lakes with different trophic status in japan abstract unbound and bound lipid class compounds mono and di carboxylic acids and hydroxy acids n alkanes n alcohols and perylene were studied in bottom sediments collected from four freshwater lakes in japan with different trophic status lakes motosu biwa haruna and suwa concentrations of some lipid components relative to total organic carbon toc showed positive or negative correlations with the primary productivity of the lakes n saturated c12 c19 fatty acids fa s branched chain fa s unsaturated fa s and c14 c19 fatty alcohols which are probably of autochthonous origin appear to increase with an increase in primary productivity whereas n saturated c20 c32 fa s c20 c30 fatty alcohols dicarboxylic acids n alkanes and perylene which are probably of terrestrial origin appear to decrease with an increase in primary productivity these results indicate that primary productivity of lakes is an important factor controlling the distributions of organic molecules in the bottom sediments on the other hand concentrations of hydroxy acids relative to toc did not show a correlation with primary productivity because these acids are derived from bacterial activity their distributions may be controlled by sedimentary environments such as oxic or anoxic rather than primary productivity

fatty acid geochemistry of a 200 m sediment core from lake biwa japan early diagenesis and paleoenvironmental information abstract fatty acids fas and hydroxy acids dicarboxylic acids and n alkanes were studied in a 200 m sediment core taken from lake biwa japan fas showed bimodal distribution with peaks at c 16 and c 22 c 28 their distribution patterns clearly changed with depth from lower molecular weight c 12 c 19 predominance to higher molecular weight c 20 c 32 predominance in the upper 20 m interval analyses of related compounds and hydroxy acids and dicarboxylic acids suggest that and oxidative degradation of c 12 c 19 fas has occurred in the sediments the ratio of bound c 12 c 19 to unbound fas increases with depth in the upper 0 1 m sediments suggesting that unbound fas are more labile however the ratio varies significantly in deeper sections and may be associated with water temperature in the sediments deeper than 20 m in depth c 12 c 19 fas gradually decrease on the other hand higher molecular weight fas hfas c 20 c 32 which were probably derived from terrestrial plants increase in concentration from 20 m to 100 m suddenly decrease at 100 m and show progressively lower concentration in deeper sediments these fluctuations are interpreted in relation to paleolimnological changes of the lake and the drainage basin hydroxy c 20 c 30 acids and c 20 c 30 dicarboxylic acids show a distribution pattern similar to hfas branched chain fas hydroxy acids and c 9 c 19 dicarboxylic acids show a major peak around 3 15 m in depth this peak is probably caused by increased bacterial activity in the water column and surface sediments in the past which may be associated with an increase in primary production of the lake

molecular fossils in a pleistocene river terrace in southern china related to paleoclimate variation abstract the red paleosols oxisols in southern china provide a record of global climate oscillation during at least the last 0 80 ma here we present a correlation between the marine oxygen isotope record stage 11 21 and the paleosol molecular fossil signature in the fourth xiushui river terrace in southern china temporal variations seen in two molecular ratios c15 21 c22 33n alkanes and pristane to phytane pr ph down the paleosol profile are postulated to have arisen from variations in biological input and subsequent pedogenesis in response to the changing strength of the east asian summer monsoon climate the preliminary findings suggest strong couplings among the soil vegetation and climate and provide a basis for a correlation between the terrestrial and oceanic records

molecular isotopic stratigraphy of long chain n alkanes in lake baikal holocene and glacial age sediments the molecular distribution and the carbon isotopic composition d 13 c of n alkanes extracted from a lake baikal core spanning the last 20 kyr of sediment accumulation have been investigated a terrestrial origin has been inferred for the odd carbon numbered long chain c27 n alkanes on the basis of the observed high cpi27 33 values range 8 7 10 8 typical of n alkanes derived from leaf waxes of higher plants a shift in the abundance of n c27 alkane relative to n c31 homologue is observed across the late pleistocene glacial holocene interglacial climate change perhaps indicative of the climate induced vegetational change previously deduced from palynological analyses compound specific isotope analyses indicate remarkably uniform d 13 c values in the range of 31 0 to 33 5 for the leaf wax c27 c33 nalkanes in the entire cored sequence such an isotopic compositional range is characteristic for n alkanes biosynthesized by plants utilizing the c3 photosynthetic pathway our data suggest that the observed 13 c enrichment in the bulk organic matter in the glacial age sediments relative to d 13 c values of total organic carbon in the holocene section is therefore unlikely to be attributed to an expansion of c4 type vegetation in the baikal watershed during the late pleistocene glacial interval 2000 elsevier science ltd all rights reserved

anthropogenic influences on hydrocarbon contents of sediments deposited in eastern lake ontario since 1800 the amounts and types of extractable hydrocarbon components in sediment cores from the rochester basin of eastern lake ontario provide a record of environmental changes that have accompanied the settlement and population growth of the surrounding land areas sediments deposited prior to the mid 1800s contain low concentrations of hydrocarbons that are dominated by land plant wax components concentrations begin to rise in the late 1800s as erosion of soil and nutrients from watershed areas accelerated this pattern continues into modern times episodes of enhanced aquatic productivity are sometimes recorded in twentieth century sediments by the dominance of algal hydrocarbons but land plant components typically predominate petroleum residues begin to appear in sediments deposited in the late 1800 s but remain minor constituents of the hydrocarbon contents of modern sediments in the rochester basin

insights into the origin of perylene from isotopic analyses of sediments from saanich inlet british columbia perylene is an abundant and common polycyclic aromatic hydrocarbon in sedimentary settings yet its origin remains puzzling we have investigated the relation of perylene to the amount and type of organic matter in the sediments of saanich inlet a coastal marine anoxic basin organic matter is predominantly marine in origin but the proportions of marine and land derived components have varied perylene concentrations generally increase with sediment depth relative to toc which indicates continued formation of this compound by microbially mediated diagenesis perylene 13c values range between 27 7 and 23 6 whereas toc 13c values vary narrowly from 21 7 to 21 2 over the same sediment depth interval the variation in isotopic difference suggests that perylene originates from more than one precursor material both aquatic and continental organic matter different microbial processes or some combination of these possibilities

variability of early diagenesis in lake sediments evidence from the sedimentary geolipid record in an isolated tarn abstract a 0 5 m long core of sediment from coburn mountain pond maine u s a has provided a virtually undisturbed and continuous record of sediment deposition for the last 200 yr in this small essentially pristine tarn organic carbon concentrations c n ratios carbon isotopic compositions and extractable hydrocarbon molecular compositions indicate subtle differences in the sources of organic matter between sediments deposited before and after ca 1950 but are otherwise constant in contrast total concentrations and molecular distributions of n fatty acids and n alkanols vary considerably the fatty acid and alkanol geolipid fractions are both sensitive to early diagenetic alteration yet the two fractions react differently concentrations and compositional parameters such as long short even odd and branched unbranched ratios fluctuate with sediment depth and reflect amounts of microbial reworking which have varied repeatedly over the depositional history n alkane distributions are relatively unaffected by the short term changes and therefore better preserve the history of biolipid sources to the sediments

lipids of aquatic organisms as potential contributors to lacustrine sediments ii abstract the relationship between the lipid composition of organisms in the water column of an eutrophic lake and the lipid composition of underlying sediments previously examined for n alkanols and steroids is now reported for hydrocarbons ketones and carboxylic acids the n c7 alkane and alkenoic acids from two primary sources are rapidly metabolized in the water column and surficial sediment bacterial biomarkers including hopenes and i ai branched fatty acids were detected in the photosynthetic bacterial layer occurring just above the sediment water interface within the sediment the apparent conversion of free n alkanes alkan 2 ones and hydroxy acids to the corresponding bound form is noted microbiological oxidation of n alkanes to alkan 2 ones is supported by the detection of the intermediate alkan 2 ols with a distribution similar to that of the ketones the geochemistry of sediment deposited c 1900 prior to biological study of the site was interpreted from stable biomarkers and the diagenetic changes recognised in the study of contemporary deposition a qualitative difference in algal input to the older sediment is inferred from the low 7 sterol content and presence of 2 6 10 trimethyl 7 3 methylbutyl dodecane however there was still significant dinoflagellate input as indicated by the presence of 4 methylsterols a difference in higher plant input to the older sediment indicated from the n alkane alkene and triterpenoid ketone distributions is consistent with the recent development of tree cover

subglacial drilling at black rapids glacier alaska u s a drilling method and sample descriptions we employed a commercial wireline drill rig to investigate the subglacial conditions of black rapids glacier a well studied surge type glacier in the central alaska range the four main goals were to assess the capabilities of the commercial drilling industry for sampling subglacial material to investigate the basal morphology to determine the subglacial geology and to emplace borehole instruments the drilling was done in an area where seasonal and secular variations in speed are large and where seismic studies suggested the presence of a till layer four holes were drilled at three locations to a maximum depth of 620 m three holes yielded samples of basal ice and till although recovery of the latter was generally poor bedrock was sampled in one or possibly two of the holes in the area sampled the glacier is underlain by a till layer some 4 7 m thick confirming the seismic interpretation it consists ofa sandy matrix at least 20 30 of which comprises larger clasts limited samples ofthe matrix indicate that near the top ofthe till the porosity is 40 and that some of the pore water is frozen geologic studies suggest that the drilling area lies to the north of the denali fault a major tectonic boundary followed by the glacier and that most of the till is locally derived with transport distances of 2 km

mapping tide water glacier dynamics in east greenland using landsat data landsat multispectral scanner and thematic mapper images were co registered for the kangerdlugssuaq fjord region in east greenland and were used to map glacier drainage basin areas changes in the positions of tide water glacier termini and to estimate surface velocities of the larger tide water glaciers statistics were compiled to document distance and area changes to glacier termini the methodologies developed in this study are broadly applicable to the investigation of tide water glaciers in other areas the number of images available for consecutive years and the accuracy with which images are co registered are key factors that influence the degree to which regional glacier dynamics can be characterized using remotely sensed data three domains of glacier state were interpreted net increase in terminus area in the southern part of the study area net loss of terminus area for glaciers in upper kangerdlugssuaq fjord and a slight loss of glacier terminus area northward from ryberg fjord local increases in the concentrations of drifting icebergs in the fjords coincide with the observed extension of glacier termini positions ice surface velocity estimates were derived for several glaciers using automated image cross correlation techniques the velocity determined for kangerdlugssuaq gletscher is approximately 5 0 km a 1 and that for kong christian iv gletscher is 0 9 km a 1 the continuous presence of icebergs and brash ice in front of these glaciers indicates sustained rates of ice front calving

lipid distribution in a subtropical southern china stalagmite as a record of soil ecosystem response to paleoclimate change abstract lipid extracts from a 61 7 cm long subtropical stalagmite in southern china spanning the period of ca 10 000 21 000 yr ago as constrained by u th dating were analyzed using gas chromatography mass spectrometry the higher plants and microorganisms in the overlying soils contribute a proportion of n alkanes identified in the stalagmite the occurrence of lmw lower molecular weight n alkanols and n alkan 2 ones in the stalagmite was mainly related to the soil microorganisms we suggest that hmw higher molecular weight n alkanols and n alkan 2 ones identified in the stalagmite originate from soil organics and reflect input from contemporary vegetation shifts in the ratio of lmw to hmw n alkanols or n alkan 2 ones indicative of the variation of soil ecosystems e g microbial degradation of organic matter and or the relative abundance of soil microorganisms to higher plants are comparable with the subtropical alkenone sst sea surface temperature record of the same period the similar trends seen in the 13c data and the lipid parameters in this stalagmite imply that the overlying soil ecosystem response to climate might be responsible for the variation of 13c values

geochemical significance of lipids and lipid derived substructures interlaced in kerogen abstract young kerogens isolated from seven freshwater lakes six river mouths and four marine surface sediments were subjected to pyrolysis in vacuo their pyrolysates were trapped and separated subsequently for determination of hydrocarbons fatty acids and alcohols the abundances carbon number distributions of long c12 polymethylene chain lipid compounds and relative abundances of pristenes are proposed as possible indices applicable to discrimination between young kerogens from freshwater lacustrine and marine sediments some oil shale kerogens of eocene and permian age were pyrolyzed in the same way where the chain length distributions of the pyrolysis products showed similar trends as those observed for the pyrolysis of young kerogens

postglacial climate change record in biomarker lipid compositions of the hani peat sequence northeastern china abstract the peat sequence at hani in northeastern china accumulated over the past 16 cal kyr in a percolation mire in which rain water and ground water seeped through the peat system the molecular compositions of n alkanes n alkanols and n alkanoic acids extracted from the hani peat sequence reveal different responses to the progressive evolution of climate and changes in the nature of the peat forming vegetation long chain length components that originate from the waxy coatings of subaerial vascular plants dominate the n alkane distributions throughout the hani peat sequence the paleoclimate integrity of these biomarker molecules appears to be well preserved most of the n alkanol distributions are similarly dominated by long chain components that indicate their origins from subaerial plants in contrast n alkanoic acid distributions are dominated by secondary components that record the importance of post depositional microbial activity in this peat sequence which evidently can be extensive in a percolation mire elevated n alkane paq values and c23 c29 ratios which are both molecular proxies for water loving plants record an especially moist local climate in the bolling allerod 14 5 to 12 9 ka younger dryas 12 9 to 11 5 ka and pre boreal 11 5 to 10 5 ka portions of the hani peat sequence depressed paq values and c23 c29 ratios and larger n alkane average chain length values indicate that the holocene climatic optimum 10 5 to 6 ka was a period of warmer climate with lower effective precipitation which contrasts with evidence of wetter climates in most of east asia

characterisation of sedimentary organic matter by bulk and molecular geochemical proxies an example from oligocene maar type lake enspel germany abstract characterisation of organic matter composition of fossil lake sediments is important in reconstruction of fossil ecosystems and paleoclimates high time resolved organic matter analysis is needed to characterize sediments from small lake environments due to their rapidly changing environmental conditions a suitable technique for rapid analysis of organic matter in such sediments is rock eval pyrolysis in small lakes however routine interpretation of rock eval data can be misleading lack of tributaries capable of transporting larger woody fragments into small lakes causes a bias towards the input of lipid rich leaf waxes and cuticles this hydrogen rich and oxygen depleted terrigenous organic matter hi 250 600 mg hc g toc and oi 20 40 mg co 2 g toc can easily be misinterpreted as being of algal origin differentiation of terrigenous plant derived hydrogen rich organic matter from algal organic matter is readily achieved by including c n elemental ratios and lipid biomarker data