alkane terpene and polycyclic aromatic hydrocarbon geochemistry of the mackenzie river and mackenzie shelf riverine contributions to beaufort sea coastal sediment abstract to study the largest source of river sediment to the arctic ocean we have collected suspended particulates from the mackenzie river in all seasons and sediments from the mackenzie shelf between the river mouth and the shelf edge these samples have been analyzed for alkanes triterpenes and polycyclic aromatic hydrocarbons pahs we found that naturally occurring hydrocarbons predominate in the river and on the shelf these hydrocarbons include biogenic alkanes and triterpenes with a higher plant peat origin diagenetic pahs from peat and plant detritus petrogenic alkanes triterpenes and pahs from oil seeps and or bitumens and combustion pahs that are likely relict in peat deposits because these components vary independently the season is found to strongly influence the concentration and composition of hydrocarbons in the mackenzie river while essentially the same pattern of alkanes diagenetic hopanes and alkyl pahs is observed in all river and most shelf sediment samples alkane and triterpene concentration variations are strongly linked to the relative amount of higher plant peat material polycyclic aromatic hydrocarbon molecular mass profiles also appear to be tied primarily to varying proportions of peat with an additional petrogenic component which is most likely associated with lithic material mobilized by the mackenzie river at freshet consistent with the general lack of alkyl pahs in peat the higher pahs found in the river are probably derived from forest and tundra fires a few anthropogenic pyrogenic compounds are manifest only at the shelf edge probably due to a weakening of the river influence we take this observation of pyrogenic pahs and the pronounced source differences between two sediment samples collected at the shelf edge as evidence of a transition from dominance by the mackenzie river to the geochemistry prevalent in arctic regions far removed from major rivers

arsenic trace metals and organic micro contaminants in sediments from the pechora sea russia grain size material 63 m toc tn pahs and organochlorines and the major al and fe and trace as cd cr cu hg li mn ni pb v and zn elements have been determined for grab and core samples from the southeast part of the barents sea known as the pechora sea russia most of the organic matter appears to be of marine origin but a terrestrial origin for om is indicated for the coastal areas in the vicinity of the pechora estuary all organic micro contaminant concentrations except lindane were low lithium normalization of cd cr cu hg ni pb v and zn concentrations indicates that they are at or near natural levels as a result of natural granular and mineralogical variability in the sediments high levels of arsenic however occur in fine grained surface and subsurface sediments the as enrichment is most likely due to the deposition and post depositional modification of as rich radioactive particulate material dispersed into the pechora sea by underwater nuclear explosions in guba chernaya on the southwest coast of novaya zemlya during the 1950s and 1960s

hydrocarbons in recent sediment of the monterey bay national marine sanctuary a complex mixture of hydrocarbons is present in the recent sediment of the monterey bay national marine sanctuary eighteen samples from the continental shelf between san francisco and monterey contain aliphatic and aromatic hydrocarbons showing biological contributions from both marine and terrigenous sources with the terrigenous indicators more pronounced near monterey of particular interest however is a low level background of petroleum related compounds including 28 30 bisnorhopane and 18 h oleanane which are characteristic of many crude oils from the monterey formation of california thus the sediments are overprinted by a regional chemical signature which may be derived from eroded monterey formation rocks and from onshore and offshore seeps releasing petroleum from monterey formation source rocks

calcimicrobial stromatolites at the permian triassic boundary in a western tethyan section bukk mountains hungary basal triassic carbonates of the gerennavar formation bukk mountains northern hungary were studied the succession was deposited in an open marine deep ramp environment of the western tethys and can be divided into three parts on the basis of the dominant microfacies the lowermost 0 5 m thick interval is made up by thin bedded and bioturbated mudstones which contain ostracods and earlandia along with relict skeletal fragments the successive 8 m thick deposits consist of planar stromatolites with well preserved microfabrics the most characteristic microfabric elements are sphere clusters in a dense micrite groundmass bushy aggregates of micrite clots bundles of prostrate micrite threads and peloids the formation of the spheres and the surrounding dense micrite is attributed to calcification of a coccoid cyanobacteria dominated mat community the tufted micrite clot clusters crudely resemble angusticellularia a filamentous microbial origin is likely for the thread bundles the peloids are interpreted either as reworked pieces of calcified mat or rolled microbial clumps the reduced preservation of microfabric components in the upper unit refers to less favourable condition for mat development which is probable due to deepening of the depositional environment the overlying mudstone unit is very poor in fossils the preservation of microbial microfabrics in the stromatolites indicates that early lithification by carbonate precipitation was widespread and intense even in open marine environments following the end permian boundary events this supports the assumption that significant changes took place in geochemistry of seawater during the late permian early triassic time interval d 2006 elsevier b v all rights reserved

210pb derived sediment accumulation and mixing rates for the washington continental slope abstract total sediment accumulation rates g yr in four canyons indenting the washington continental shelf are about twice those on the nearby open slope even though canyons comprise less than 40 of the depositional area of the entire slope this is because 210 pb derived sediment accumulation rates g cm 2 yr for astoria and quinault canyons are 3 4 times greater than those for willapa and grays canyons and intermediate open slope areas supporting the hypothesis that columbia river derived solids are preferentially transported to these two canyons quinault canyon currently appears to be accumulating solids at rates much greater than its low long term accumulation rate which is attributed to turbidity currents transporting solids down this canyon roughly every 500 years the following four different approaches all show that mixing may cause 210 pb derived sediment accumulation rates for slope and canyon sediments to be 2 3 times higher than true accumulation rates 1 comparison between accumulation rates calculated from 210 pb profiles with and without surface zones in which mixing has obviously affected 210 pb distributions 2 comparison between 210 pb derived and independently determined long term accumulation rates 3 comparison between 210 pb derived accumulation and modern columbia river discharge rates 4 comparison between two and three layer steady state one dimensional diffusion advection decay models mixing coefficients for surface sediments calculated using a one dimensional two layer vertical eddy diffusion model show large differences within the region with most in the 3 30 cm 2 yr range mixing rates are several times larger in canyon sediments from 0 2 1 1 km water depth probably due to physical reworking processes erroneously neglected mixing at depth of no more than 5 of that calculated for the surface mixed layer can cause the 2 3 fold calculated overestimation of true sediment accumulation rates and 2 4 fold calculated underestimation of true mixing coefficients

a biomarker perspective on paleoproductivity variations in two late quaternary sediment sections from the southeast atlantic ocean abstract sedimentary inventories of selected molecular biomarkers in two sediment sections from the african continental margin below highly productive surface waters in the southeast atlantic ocean each spanning the last 76 kyr were investigated and compared to each other a principal component analysis of the stratigraphic data separated groups of biomarkers representing different assemblages of biological sources and or different diagenetic histories related to their chemical structures and their metabolic role in the food chain the concentrations of long chain n alkenones n diols the major n ketool and loliolide and its epimer isololiolide are correlated with paleoproductivity estimates that were calculated from organic carbon contents this group of relatively refractory compounds very likely represents those planktonic communities which contributed significantly to surface water productivity and subsequent burial of organic carbon during the considered time interval concentrations of dust transported terrigenous long chain fatty acids c24 to c28 are interpreted to be related to the intensity of upwelling driving winds and are also significantly correlated with high contents of organic matter concentrations of cholesterol and the major short chain fatty acids are not related to the marine paleoproductivity signal most likely as a consequence of their nonspecific origin and their metabolic role during heterotrophic feeding processes abundances of 24 ethylcholest 5 en 3 ol and its saturated counterpart 24 ethyl 5 cholestan 3 ol the major steroid alcohols in both sedimentary environments appear not to be related to any of the above mentioned components and probably represent the contribution of algal species adapted to nutrient conditions different from those of other major primary producers differences between both environments the angola dome and the benguela coastal upwelling are evident in the relative distribution of major components and the stratigraphic behavior of selected compounds relative to other variables these differences are discussed in relation to specific characteristics of both oceanographic environments 1999 elsevier science ltd all rights reserved

hydrocarbon geochemistry of the puget sound region iii polycyclic aromatic hydrocarbons in sediments abstract polycyclic aromatic hydrocarbon pah distributions and sources are characterized in 96 sediment samples from 24 210 pb dated cores collected at locations in the greater puget sound the highest pah concentrations are found within a few kilometers of several sources including industrial facilities in northern puget sound urban areas in central puget sound and river systems draining coal bearing strata regional patterns of combustion derived pah in surficial sediments indicate little atmospheric or waterborne exchange of pah between different regions of the sound significant subsurface maxima in combustion derived pah concentrations 210 pb dated at the 1950s occur only in sediment cores collected near urban centers perylene apparently derives from erosion of a terrestrial source with little or no evidence of in situ production at depth in sediment cores coal fragments are carriers of a characteristic suite of alkylated phenanthrene chrysene and picene derivatives concentrated near river mouths in central and southern puget sound

palaeoenvironmental changes in the padul basin granada spain over the last 1 ma based on the biomarker content the n alkane components of sediments were measured in 530 samples taken from a 107 m long core in the padul basin andalusia spain covering from the lower pleistocene ca 1 ma to the mid holocene ca 4 5 ka b p we show that the relative percentages of the high molecular weight n alkanes c27 c29 and c31 are useful tools to reconstruct the ancient vegetation and palaeoclimatological evolution of this basin on the basis of these proxies we distinguished twelve long term climatic periods linked to alternating dry humid scenarios 6 dry episodes alternating with 5 humid episodes were interpreted in the pleistocene record together with a final episode covering the holocene dry scenarios produced the recession of forests and the development of grasses whereas the inverse pattern was interpreted during humid phases the good correlation with the guadix baza basin record showed that in most cases dry periods coexisted with warm conditions while humid ones were linked to temperate colder conditions only during the last long term dry episode of the pleistocene which coincided with the end of the last glacial period did low temperatures concur the relative percentages of the high molecular weight n alkanes also indicate rapid changes in vegetation produced by short scale arid cycles during the last glacial period 100 ka b p which are linked to the heinrich events and younger dryas this interpretation has been confirmed by previous pollen analysis performed in the padul basin likewise a correlation was observed with marine isotope stages mis these results show that vegetation responds to long term cycles orbital scale and millennial scale global cycles therefore climatic variations in the padul basin responded to global climatic changes although with local climatic effects good correspondence was also observed with elemental isotopic and other molecular organic proxies thereby amplifying the palaeoclimatological knowledge of the padul basin during the pleistocene especially in some spans that were previously unclear

pigment preservation and remineralization in oxic coastal marine sediments abstract complex mixtures of sedimentary chlorophyll degradation products were measured using high performance liquid chromatography hplc in 210 pb dated box and piston core sediments sediments were collected from dabob bay washington a coastal marine fjord conducive to studies yielding an understanding of the remineralization and diagenesis of organic carbon greater than 99 of the pheopigment flux out of the water column does not accumulate in the top 2 cm of sediment surface sediment pigment profiles indicate that pheophorbides are the dominant pheopigments observed with concentrations decreasing rapidly with depth concentrations of chlorophyll c derivatives also decrease rapidly but ratios of a c pheopigments remain within ranges reported for natural and cultured phytoplankton sharp pheopigment concentration decreases within the bioturbated surface sediments as defined by 210 pb activities were modeled using a one dimensional mixing model the in situ pheopigment decomposition rate corrected for bioturbation and sediment accumulation corresponds to an approximate half life of 40 days sedimentary humic acid fulvic acid and residual humin associated pheopigments in sediments which had been previously acetone extracted to remove the lipophilic pheopigment fraction were typed by chromic acid oxidation and release of pyrrole derived maleimides this humic associated pyrrole derived nitrogen while a small fraction of total sedimentary or humic nitrogen accounted for 16 75 of the total sedimentary pheopigment accumulation and may be significant in understanding the diagenetic fate and transformation of pheopigments to petroporphyrins

distribution of terrigenous lipids in marine sediments off northeastern taiwan surface sediments on the continental margin off northeastern taiwan have been analyzed for terrigenous lipids including n alkanes n fatty alcohols and sterols marine input to the sediments is particularly low based on the average n c17 n c29 alkane and n c16 n c28 fatty alcohol ratios 0 15 0 13 and 0 13 0 06 respectively this may be due to the fact that marine lipids are more prone to degradation than terrestrial ones the study area has the highest plant wax n alkane contribution average carbon preference index 3 9 1 2 among the coastal marine areas surrounding taiwan lateral particle transport from the southern east china sea shelf and river runoff from the east taiwan coast are considered to be the major contributors the distributions of plant wax n alkane and n alkanol concentrations normalized to total organic carbon toc in the study area generally show maximum values on the upper slope of the southernmost okinawa trough but not for phytosterols linear regression of toc versus plant wax n alkane concentrations show a weak relationship r 0 64 p 0 001 and an even weaker relationship r 0 42 p 0 05 between toc and plant wax n fatty alcohol concentrations is found this could be attributed to several factors 1 a complex input not a point source of terrigenous organic matter to the study area 2 toc also including marine organic matter 3 temporal variations in river flow due to flooding and 4 different rates of degradation for toc and individual biomarkers however in spite of those factors toc and phytosterol concentrations are positively linearly correlated r 0 85 p 0 001 implying that the dilution of phytosterols in terrigenous organic carbon with marine organic carbon with or without the phytosterols follows a nearly constant ratio which is remarkable in addition the predominant source of diploptene in the sediments does not appear to be of higher plant origin

microbial carbonates the geological record of the calcified bacterial algal mats and biofilms summary deposits produced by microbial growth and metabolism have been important components of carbonate sediments since the archaean geologically best known in seas and lakes microbial carbonates are also important at the present day in fluviatile spring cave and soil environments the principal organisms involved are bacteria particularly cyanobacteria small algae and fungi that participate in the growth of microbial biofilms and mats grain trapping is locally important but the key process is precipitation producing reefal accumulations of calcified microbes and enhancing mat accretion and preservation various metabolic processes such as photosynthetic uptake of co2 and or hco3 by cyanobacteria and ammonification denitrification and sulphate reduction by other bacteria can increase alkalinity and stimulate carbonate precipitation extracellular polymeric substances widely produced by microbes for attachment and protection are important in providing nucleation sites and facilitating sediment trapping microbial carbonate microfabrics are heterogeneous they commonly incorporate trapped particles and in situ algae and invertebrates and crystals form around bacterial cells but the main component is dense clotted or peloidal micrite resulting from calcification of bacterial cells sheaths and biofilm and from phytoplankton stimulated whiting nucleation interpretation of these texturally convergent and often inscrutable fabrics is a challenge conspicuous accumulations are large domes and columns with laminated stromatolite clotted thrombolite and other macrofabrics which may be either agglutinated or mainly composed of calcified or spar encrusted microbes stromatolite lamination appears to be primary but clotted thrombolite fabrics can be primary or secondary microbial precipitation also contributes to hot spring travertine cold spring mound calcrete cave crust and coated grain deposits as well as influencing carbonate cementation recrystallization and replacement microbial carbonate is biologically stimulated but also requires favourable saturation state in ambient water and thus relies uniquely on a combination of biotic and abiotic factors this overriding environmental control is seen at the present day by the localization of microbial carbonates in calcareous streams and springs and in shallow tropical seas and in the past by temporal variation in abundance of marine microbial carbonates patterns of cyanobacterial calcification and microbial dome formation through time appear to reflect fluctuations in seawater chemistry stromatolites appeared at 3450 ma and were generally diverse and abundant from 2800 to 1000 ma inception of a proterozoic decline variously identified at 2000 1000 and 675 ma has been attributed to eukaryote competition and or reduced lithification thrombolites and dendrolites mainly formed by calcified cyanobacteria became important early in the palaeozoic and reappeared in the late devonian microbial carbonates retained importance through much of the mesozoic became scarcer in marine environments in the cenozoic but locally re emerged as large agglutinated domes possibly reflecting increased algal involvement and thick micritic reef crusts in the late neogene famous modern examples at shark bay and lee stocking island are composite coarse agglutinated domes and columns with complex bacterial algal mats occurring in environments that are both stressed and current swept products of mat evolution ecological refugia sites of enhanced early lithification or all three

anomalously diverse early triassic ichnofossil assemblages in northwest pangea a case for a shallow marine habitable zone early triassic trace fossil assemblages from the northwest margin of pangea record a diverse suite of postextinction infauna these ichnofossil assemblages occurred within well oxygenated shallow marine refuges in a panthalassa ocean otherwise characterized by widespread anoxia we propose an environmentally controlled model for their distribution in which wave aeration enhanced by frequent storms gave rise to an optimal zone for benthic colonization within this habitable zone extinction pressures were ameliorated and postextinction recovery duration was minimized

isotopic chemostratigraphy of the microbialite bearing permian triassic boundary section in the zagros mountains iran carbon isotopic chemostratigraphy and a sr isotope datum provide age constraints to the uppermost permian lowermost triassic section in central zagros mountains iran the 77 m thick carbonate dominated section contains two microbialite beds that consist of abiotic carbonate crystals and possible calcimicrobes the textures resemble those reported from the lowermost triassic elsewhere which were likely developed under unusual environmental and ecological conditions after the end permian extinction our results show that the lower section up to the lower microbialite bed has high 13 c values of 3 to 4 which are typical values for the latest permian from 3 m above the base of the lower microbialite the values abruptly decreases to 0 3 in the upper section the 13 c curve records another negative excursion and gradual increase to 2 0 the curve coincides with the global trend from other permian triassic boundary sections and places the chemostratigraphic boundary within the lower microbialite the 13 c negative excursion postdates geochemical and or ecological changes that triggered the microbialite development if the trigger was increased alkalinity by a vast carbon flux the source carbon should not have significantly light value of 13 c

evidence for rapid precipitation of calcium carbonate in south china at the beginning of early triassic abstract anachronistic facies are sedimentary features and fabrics that are very common in the early history of the earth but mainly occur following mass extinctions during the phanerozoic anachronistic facies are typically found in carbonates commonly have a microbial origin and reflect an unusual oceanic chemistry the aftermath of the end permian mass extinction is one of the periods when anachronistic facies were common and occur in sedimentary rocks from around the world in south china different types of anachronistic facies appear in an orderly succession over time microbialites are often the first anachronistic sediments that formed after the end permian mass extinction in shallow platform settings and are subsequently followed by oolites and oncolites which are sometimes intercalated with vermicular limestones because different types of anachronistic facies represent different depositional environments this succession pattern in the strata records the evolution of marine environments following the end permian mass extinction based on sedimentological analysis of the yangjiawan section hunan province south china this study suggests that the transition from microbialite to oolitic limestone was associated with a rise of sea level and an increase in hydrodynamic energy the shift from oolite to oncolite reflects a sustained rapid rise of sea level the occurrence of vermicular limestone is considered to be the product of an ephemeral restricted environment anachronistic facies reach a thickness of 75 m at the yangjiawan section while over nearly the same time interval argillaceous limestone reaches a thickness of only 40 cm of beds 27 29 at the global stratotype section and point gssp section at meishan in zhejiang province this difference in thickness indicates strongly elevated sedimentation rates in shallow water platform settings after the end permian mass extinction high rates of carbonate precipitation are indicative of calcium carbonate supersaturation within shallow watermasses which may have resulted from the upwelling of alkaline anoxic deep waters accompanied by high rates of evaporation as a consequence of extremely high temperatures at the time nevertheless it is the global sea level rise in the early triassic that provided the accommodation space necessary for the precipitation of the great thickness of anachronistic carbonate sediments at the yangjiawan section

early middle triassic stromatolites from the luoping area yunnan province southwest china geobiologic features and environmental implications abstract an early middle triassic stromatolite deposit is documented from the guanling formation of the luoping area yunnan sw china the luoping stromatolite shows five types of constructional microbial forms in various magnifications 1 typical stratified columnar structures up to 20 cm high with crinkled laminae dark coloured laminae 1 mm thick are composed of upright filamentous tubes averagely 29 4 m in diameter showing a vertical growth fabric 2 laminoid fenestrae 0 5 1 mm wide and 3 prostrate filaments which are reflected by strong fluorescence in sharp contrast to dolomite cement in fluorescent images 4 rod like aggregates 4 6 18 m in diameter composed of minute dolomite rhombs are very common in stromatolitic laminae they resemble present day cyanobacterial trichome and thus may represent putative fossilized cyanobacteria 5 moreover small pits coccoid like spheroids calcified biofilms and fibrous structures are also common in stromatolitic laminae the last two may represent calcified extracellular polymeric substances eps that contributed to the development and lithification of stromatolites authigenic quartz grains are common and may also have involved biological processes in stromatolite formation of these microbial functional groups driving accretion and lithification processes of stromatolite documented in literature both lithified cyanobacteria oxygenic phototrophs and possible sulfate reducing bacteria srb which induced microbial formation of dolomite and contributed to the accretion of the luoping stromatolite are suggestive of biogenic origin the luoping stromatolite differs from the permian triassic boundary microbialites ptbms in having abundant filamentous structures and growing in an oxic marine environment both sedimentary facies analysis and abundant fossilized cyanobacteria may indicate proliferation of oxygenic phototrophs in a normal oxic habitat during the middle anisian early middle triassic a period when hospitable environments coupled with biotic diversification prevailed in south china and set an agenda for the full recovery of marine ecosystems in middle late anisian however the post extinction stromatolites and other anachronistic facies are not necessarily indicative of anoxic or oxic conditions and their environmental settings are much more complex than previously thought

upper lower triassic stromatolite from anhui south china geobiologic features and paleoenvironmental implications abstract widespread stromatolites and other microbialite deposits characterize lower triassic marine successions worldwide this study documents a stromatolite deposit 1 1 m thick from the upper spathian lower triassic of the susong area south china the stromatolite comprises distinct laminated domes in the basal part and columns at the upper part dark laminae are loosely spaced and interlayered with thicker light colored laminae diffusive dark colored laminae are composed of peloidal micrite that grade locally into microclotted structures and yield copies of bacteria clump like and coccoid like spheroid aggregates the former are characterized by cloudy micrite nuclei rimmed by coarse grained euhedral sparry calcite crystals while the latter are comprised of solid calcite crystal nuclei coated with rather thin micrite envelopes the cloudy micrite nuclei resemble bacteria clump like structures observed in present day travertine both the coccoid like spheroids and bacteria clump like structures are surrounded by coarse grained euhedral calcite crystals suggesting a similar accretion mechanism both spherical structures therefore could be crucial in the accretion of the susong stromatolite the laminated microclotted structures are interpreted as the result of variation in timing of lithification relative to the timing of the decay of microbes micro analysis also unravels the common occurrence of authigenic micro quartz crystals in association with fe bearing illite clay minerals in the stromatolite columns their coalescing nature with each other together with the associated pyrite grains strongly support the formation of micro quartz crystals from microbial reduction of an fe bearing smectite precursor by sulfate reducing bacteria a comparison of the susong stromatolite with its counterparts from the upper lower triassic strata in dajiang south china reveals many similarities in stromatolite microstructures suggesting that a harsh euxinic anoxic environment resulting in the bloom of sulfate reducing bacteria most likely extended into the latest spathian in south china

earliest triassic microbialites in curuk dag southern turkey composition sequences and controls on formation the permian triassic boundary sequence at curuk dag near antalya turkey begins with a major erosion surface interpreted as being the late permian lowstand on which lies ca 0 4 m of grainstone packstone composed of ooids peloids and bioclasts most ooids are superficial coats on fragments of calcite crystals presumed to be eroded from crystal fans which are no longer present the erosion surface is smooth and shows no evidence of dissolution the grainstone packstone contains intraclasts of the underlying wackestone proving erosion next are 15 m of microbialite comprised of interbedded stromatolites thrombolites plus beds of planar limestones with small scale erosion the latter comprise a complex interlayering of stromatolitic thrombolitic and peloidal fabrics and precipitated crystal fans which form a hybrid of microbialite and inorganic carbonate together with bioclastic debris and micrite the curuk dag microbialite sequence is repetitious the lower part is more complex with abundant stromatolites and hybrid microbialites some of the stromatolites are themselves hybrids composed of peloids and crystal fans in the upper part of the sequence stromatolites are missing and the rock is composed mostly of recrystallized thrombolites that develop upwards from tabular to domal form the domes form directly below small breaks in microbialite growth where very thin shelly micrites and grainstones packstones are deposited repetition of facies may be controlled by sea level change a deepening up model is consistent with the evidence stromatolites with abundant crystal fans dominate in shallower water deepening through hybrid microbialite and interlayered sediments to thrombolite probably no more than a few tens of metres deep followed by breaks and renewal of microbialite growth an interpretation of open marine fully oxygenated waters for microbialite growth is consistent with ongoing parallel work that has identified bairdioid ostracods in the microbialite a group known to be open marine however other researchers have proposed low oxygen conditions for permian triassic boundary facies globally so work continues to confirm whether the curuk dag microbialite grew in dysoxic or normally oxygenated conditions the principal stimulus for post extinction microbialites is likely to be carbonate supersaturation of the oceans the microbialite sequence is overlain by a further 25 m of grainstone packstone without microbialite followed by early triassic shales overall microbialites form a thin aggradational sequence during an overall relative sea level rise consistent with global eustatic rise following the late permian lowstand

the use of radon 222 as a tracer of sediment irrigation and mixing on the washington continental shelf abstract observations of the natural radioisotope rn 222 were used in conjunction with radiochemical biological and sedimentological techniques to investigate the irrigation and mixing of sediment at three sites about 90 m water depth along the washington continental shelf the rn 222 deficit difference between observed and predicted concentrations within the seabed was greatest near the columbia river during the summer molecular diffusion at most locations and times could account for only a portion of the deficit irrigation and mixing of the seabed explain the remainder biological mixing bioturbation and physical irrigation wave and tidal pumping have relatively little effect on the rn 222 deficit physical mixing erosion and deposition has a significant effect soon after a major erosion event storm however no such event occurred prior to the observations the conclusion is that biological irrigation and molecular diffusion are the primary causes of the rn 222 deficit and that biological irrigation is responsible for the observed spatial and temporal variations in the deficit therefore biological irrigation is greatest near the columbia river during the summer the spatial increase of irrigation near the columbia is probably due to a relatively large population of tube dwelling filter feeding polychaetes the temporal increases of irrigation during the summer is probably due to annual growth cycles of the benthic community and is not due to water temperature changes

organic markers as source discriminants and sediment transport indicators in south san francisco bay california sediment samples from nearshore sites in south san francisco bay and from streams flowing into that section of the bay have been characterized in terms of their content of biogenic and anthropogenic molecular marker compounds the distributions input sources and applicability of these compounds in determining sediment movement are discussed by means of inspection and multivariate analysis the compounds were grouped according to probable input sources and the sampling stations according to the relative importance of source contributions a suite of polycyclic aromatic hydrocarbons pahs dominated by pyrene fluoranthene and phenanthrene typical of estuarine environments worldwide and suites of mature sterane and hopane biomarkers were found to be most suitable as background markers for the bay a homologous series of long chain n aldehydes c12 c32 with a strong even over odd carbon number dominance in the higher molecular weight range and the ubiquitous n alkanes n c24 c34 with a strong odd over even carbon number dominance were utilized as terrigenous markers several ratios of these terrigenous and bay markers were calculated for each station these ratios and the statistical indicators from the multivariate analysis point toward a strong terrigenous signal in the terminus of south bay and indicate net directional movement of recently introduced sediment where nontidal currents had been considered to be minimal or nonexistent and tidal currents had been assumed to be dominant

onset development and cessation of basal early triassic microbialites betm in the nanpanjiang pull apart basin south china block abstract new investigations in the nanpanjiang basin indicate that the onset of the iconic microbialites associated with the paleozoic mesozoic boundary was early triassic in age bathymetry water agitation oxygenation light penetration and clastic load are shown to have exerted a direct control on the growth of microbialites carbonate supersaturation is also required for the deposition of the microbialites bathymetric control is further corroborated by the inheritance of the topography of a latest permian pull apart basin into early triassic times with a distribution of basal early triassic microbialites betm restricted to uplifted blocks and the accumulation of carbonaceous black shales in adjacent troughs the geographically most extensive nanpanjiang betm bloomed on a large nw se trending uplifted block exceeding 12 000 km 2 luolou platform centered on northwestern guangxi post triassic displacements along the youjiang fault obscure the paleogeographic relation of betm exposed west of this fault triassic foraminifers occur in the basal most betm episode which is locally bracketed by high energy grainstones made of reworked permian foraminifers therefore the permian triassic boundary ptb is within the unconformity that separates the late permian heshan fm from the basal most betm where accommodation space was sufficient up to five event surfaces are associated with the unconformity microfacies analysis supports chemical dissolution but did not reveal evidence for subaerial erosion although intercalated grainstone made of permian foraminifers indicate reworking chemical dissolution and mechanical erosion both conceivably contributed to the genesis of the unconformity the upward shift from tabulated to domical microbial build ups is accompanied by accumulation of coquinoid lenses between domes which indicates deepening of the luolou platform betm the main drowning resulting from both regional tectonic subsidence and a global sea level rise led to the cessation of the betm that were buried under predominant fine siliciclastics any concomitant change in sea water chemistry appears unlikely

a 220 ka palaeoenvironmental reconstruction of the fuentillejo maar lake record central spain using biomarker analysis abstract the sedimentary record of the volcanic lake known as the fuentillejo maar central spain offers the opportunity to determine the palaeoenvironmental evolution of the central southern part of the iberian peninsula during the middle and upper pleistocene a total of 439 samples from the upper 88 m of a ca 142 m long core spanning the last ca 355 ka were examined the interval corresponds to the last 220 ka of the record high n alkane cpi values and the presence of sulfur revealed that little diagenetic signal attenuation or modification had occurred a number of n alkane based indices e g predominant n alkane acl paq and tar hc ratios and the proportion of c 27 c 29 and c 31 n alkanes with respect to the summed c 27 c 29 c 31 alkanes showed changing conditions in the organic matter input to the maar lake over time with episodes involving a major input of terrestrial vegetation alternating with others in which algae or a mixed input of terrestrial plants aquatic macrophytes and algae occurred the proportions of c 27 c 29 and c 31 were useful for reconstructing the palaeoenvironmental evolution of the basin as they allowed assignment of several dry intervals during which grasses developed while during humid phases trees expanded at the expense of grasses in general we found good correspondence between these episodes and the climatic cycles observed in 18 o records from ices cores in greenland and antarctica as well as from marine cores thus we conclude that global palaeoclimatological changes were recorded in the maar record likewise heinrich events appeared to be reflected in the n alkane indices this was confirmed by single spectral analysis and cross spectral analysis with the insolation curve on 21 july at a latitude of 65 n the approach revealed that the cycles interpreted in the fuentillejo record 103 41 23 and 19 ka showed evidence of orbital influence related to the astronomical cycles of the eccentricity variation in the earth s orbit the earth s obliquity oscillation and the precession variation milankovitch theory

hydrocarbons in washington coastal sediments the sources and distributions of polycyclic aromatic hydrocarbons pah and aliphatic hydrocarbons are characterized in seventeen sediments from a highly river influenced sedimentary environment off the southwestern coast of washington the major hydrocarbons are land derived introduced as preformed compounds and display long term stability in sediment cores a series of pah of anthropogenic origin and two naturally derived compounds retene and perylene dominate the pah composition in these sediments plantwax n alkanes are the major aliphatic hydrocarbon constituents aliphatic hydrocarbons of marine origin pristane and a series of four acyclic multibranched c25 polyolefins are also observed in many sediments the concentrations of these marine derived hydrocarbons decrease to negligible levels rapidly with sediment depth from the sea sediment interface suggesting degradation in general the major land derived hydrocarbons are concentrated in the midshelf silt deposit which extends northwestward along the continental shelf from the columbia river mouth a quantitatively more minor natural series of phenanthrene homologs also of terrestrial origin is preferentially advected further offshore and deposited in continental slope sediments these distributions are consistent with recognized particle associations for these compounds and sediment dispersal processes in this coastal environment sediment core records suggest the present pattern of dispersal has persisted for at least the past century and possibly since the late pleistocene

aliphatic hydrocarbons in surface sediments from the north queensland coast and great barrier reef effects of tropical cyclone winifred abstract aliphatic hydrocarbons were determined in inner shelf and reef lagoon surface sediments off the north queensland coast near innisfail in february 1986 immediately after tropical cyclone winifred passed through the region causing severe rainfall runoff and disturbance of bottom sediments lagoon sediments from feather gilbey and potter reefs 25 50 km offshore were characterized by a suite of c 15 c 25 n alkanes and alkenes derived predominantly from algal sources terrestrial hydrocarbons were not present in contrast inner shelf sediments contained relatively large amounts of terrestrial derived c 25 c 33 n alkanes which decreased in concentration with distance from the coast inner shelf sediments collected after the cyclone also contained a suite of petroleum derived hydrocarbons the concentrations of terrestrial derived hydrocarbons increased in samples collected from the inner shelf after the cyclone however the distribution of terrestrial hydrocarbons was largely confined to the inner shelf after the cyclone and only occurred in trace concentrations in midshelf sediments these results indicate that cyclone related outwelling of suspended sediments and presumably nutrients from rivers was confined to the inner shelf and did not reach the reef zone the post cyclone phytoplankton bloom was probably caused by resuspension of bottom sediments and release of porewater nutrients rather than advection of river plumes to the offshore reefs

sources and distributions of sedimentary organic matter in the columbia river drainage basin washington and oregon1 nonwoody angiosperm tissues and gymnosperm woods are the major types of vascular plant debris in bottom sediments from 16 sites within the columbia river and its tributaries in tributary sediments relative abundances of these types of tissue vary regionally and are consistent with drainage basin vegetation within the extensively dammed main river vascular plant debris mixtures are more uniform indicating downstream mixing of sedimentary material from reservoir to reserwoir vascular plant tissues account for an average of a third of the total sedimentary organic matter at the 16 river sites the remaining organic material has an atomic c n of 10 l 5 and a stable carbon isotope composition similar to average land plants organic matter in sediments of the columbia river system is generally enriched in nonwoody angiosperm tissues and ligninpoor organic matter in comparison to columbia river derived organic matter in modern marine sediments from the southern washington continental shelf

impacts of late quaternary fluctuations in water level on the accumulation of sedimentary organic matter in walker lake nevada meyers p a 1990 impacts of late quaternary fluctuations in water level on the accumulation of sedimentary organic matter in walker lake nevada palaeogeogr palaeoclimatol palaeoecol 78 229 240 walker lake a terminal saline lake in western nevada has experienced major fluctuations in its water level due to changes in regional climate and river diversions during the late quaternary change in the degree of preservation of sediment organic matter has accompanied the lake level fluctuations and changes in the biotic sources of organic matter to the lake sediments have occurred in response to the climate changes and water diversions the record of these events has been studied using organic matter c n ratios and carbon isotope contents and employing molecular compositions of geolipids extracted from the sediment modern sediments contain mostly lake derived organic matter which has been altered by microbial reworking decreasesin the degree of preservation of organic matter indicate lake lowstands increases in the proportion of land plant components in sediment organic matter also indicate lowstand conditions

anachronistic facies and carbon isotopes during the end permian biocrisis evidence from the mid tethys kisejin iran abstract late permian mass extinction lpme research has focused primarily on tethyan sections because it is believed that these successions are more complete than those from other localities and provide a more comprehensive record of the largest most devastating extinction event in earth history the kisejin section a previously undocumented mid tethyan upper permian lower triassic succession located in the central iran plate the kisejin section contains a continuous permian triassic sequence with only small breaks in sedimentation and was examined in order to determine sedimentologic biostratigraphic and carbon isotopic trends across the permian triassic transition abnormal anachronistic carbonates developed in the study area following the lpme and include microbialites edgewise conglomerates sparitic microspheres and microbially coated grains microbialites occur as thrombolites stromatolites and as agglutinated forms renalcis type calcimicrobes are documented for the first time from permian triassic boundary microbialites ptbms of iran coated grains fall into two groups and include pre ptbm ooids which are dense and cloudy and possibly microbial in origin and post ptbm cortoids with destructive and constructive micrite envelopes latest permian conodonts h praeparvus m ultima coupled with carbon isotopic values place the permian triassic boundary within the lowermost thrombolite unit about 2 1 m above the boundary between the nessen formation and the elika formation and indicate that microbialite growth began during the latest permian our study of this previously unknown section shows that unlike other well known ptb sections from iran the microbialite pattern is complicated and is more similar to ptbm successions from turkey in addition we note a similarity between the unusual facies of the kisejin section and those of eastern tethyan sections from china i e sparry microspheres and renalcis type calcimicrobes these unusual facies have not been previously reported from other well known iranian sections including julfa and abadeh which are thick and have been extensively studied

microbially induced sedimentary structures misss from the lower triassic kockatea formation northern perth basin western australia palaeoenvironmental implications abstract like microbialites microbially induced sedimentary structures misss are commonly observed in siliciclastic and mixed carbonate siliciclastic settings in the lower triassic and are represented by several morphological types including wrinkle structures however their origin and their role in the early triassic ecosystem recovery is currently a hot topic of debate herein we report and describe abundant wrinkle structures from the smithian kockatea shale formation of northampton area in the perth basin western australia on the basis of detailed field observations as well as petrographic and sem examinations of rock thin sections the surficial morphologies of wrinkles are characterized by closely spaced crests and ridges on the upper bedding surfaces together with other forms such as pitted bulges and reticulated ridges detailed petrologic analysis revealed that the smithian wrinkle structures from the northern perth basin possess a distinct vertical profile 1 cross stratified lamianted sandstone 2 alternating laminated layers and sandstone 3 laminated layers and 4 wrinkled layers in an ascending order the wrinkled layers are overlain by thin shale laminated layers beneath wrinkled surfaces comprise densely packed pronounced wavy laminae mica flakes in laminations show a preferred alignment parallel to bedding under sem imaging suggesting the binding and trapping of the former presence of a microbial matground these evidences support that the early triassic wrinkle structures from the smithian kockatea formation are biogenic in origin close association of both trace and body fossils with the wrinkle structure bearing layers is interpreted to indicate the presence of a matground ecosystem in which some small gastropods and various trace making animals lived possibly taking the habitat as a refuge the global temporal and spatial occurrences of early triassic miss were tabulated and analyzed revealing a wide range of palaeoenvironmental distributions and the seemingly selected association between metazoans and certain miss as to why only some misss have been found together with metazoans remains as an open question it will require further investigation especially with regard to the specific type of microbes that had built the microbial matground ecosystems and their interplay with the hosted metazoans in the aftermath of the end permian mass extinction

hydrocarbon geochemistry of the puget sound region ii sedimentary diterpenoid steroid and triterpenoid hydrocarbons cyclic components of the aliphatic hydrocarbon mixtures extracted from puget sound sediment cores include a suite of c19 and c20 diterpenoid hydrocarbons of which fichtelite sandaracopimaradiene and isopimaradiene have been identified although apparently also derived from vascular plants these diterpenoid hydrocarbons have relative abundances distinctly different from the co existing plant wax n alkane suite five c27 c28 and c29 diasteranes and four c29 c30 and c31 17 h 21 h hopanes occur in relatively constant proportion as components of a highly weathered fossil hydrocarbon assemblage these chromatographically resolved cycloalkanes along with the strongly covarying unresolved complex mixture have been introduced to puget sound sediments from adjacent urban centres at increasing levels over the last 100 yr in the absence of any major oil spill naturally occurring triterpenoid hydrocarbons including hop 22 29 ene diploptene are also present a new group of c30 polyenes has been detected which contains compounds apparently structurally related to a co existing bicyclic c25 diene and to c20 and c25 acyclic multibranched hydrocarbons described in a previous paper barrick et al 1980

early triassic environmental dynamics and microbial development during the smithian spathian transition lower weber canyon utah usa the early triassic biotic recovery following the end permian mass extinction is well documented in the smithian spathian thaynes group of the western usa basin this sedimentary succession is commonly interpreted as recording harsh conditions of various shallow marine environments where microbial structures flourished however recent studies questioned the relevance of the classical view of long lasting deleterious post crisis conditions and suggested a rapid diversification of some marine ecosystems during the early triassic using field and microfacies analyses we investigate a well preserved early triassic marine sedimentary succession in lower weber canyon utah usa the identification of microbial structures and their depositional settings provide insights on factors controlling their morphologies and distribution the lower weber canyon sediments record the vertical evolution of depositional environments from a middle smithian microbial and dolosiliciclastic peritidal system to a late smithian early spathian bioclastic muddy mid ramp the microbial deposits are interpreted as microbially induced sedimentary structures miss that developed either 1 in a subtidal mid ramp where microbial wrinkles and chips are associated with megaripples characterizing hydrodynamic conditions of lower flow regime or 2 in protected areas of inter to subtidal inner ramp where they formed laminae and domal structures integrated with other published data our investigations highlight that the distribution of these microbial structures was influenced by the combined effects of bathymetry hydrodynamic conditions lithology of the substrat physico chemical characteristics of the depositional environment and by the regional relative sea level fluctuations thus we suggest that local environmental factors and basin dynamics primarily controlled the modalities of microbial development and preservation during the early triassic in the western usa basin

assessment of the eruptive activity and identification of the mud breccia s source in the olimpi mud volcano field eastern mediterranean abstract even though the intensity and frequency of the eruptive episodes of deep sea mud volcanoes mvs substantially regulate the methane fluxes into the hydrosphere and the development of the near seafloor sulfate zone that affects the position of the gas hydrate stability zone these factors are not yet adequately investigated moreover the evaluation of the eruptive sediment s thermal maturity may provide solid documentation of the petroleum generation potential in high depths below seafloor bsf hence the present study through the integration of sedimentary facies analysis with hydrocarbon biomarker analysis based on the concentrations of long chain c25 c35 n alkanes hopanes and steranes supported by swath bathymetry data examined five sediment cores recovered from the gelendzhik moscow milano leipzig and heraklion mvs of the olimpi mud volcano field omvf on the central mediterranean ridge the main objective of this investigation was to assess the modern eruptive activity in the omvf and identify the mud breccia s origin and mobilization depth based on its maturity level and the ages of the source beds among the studied mvs milano leipzig and heraklion appear recently active while moscow perhaps remains in dormancy for at least one century the eruptive activity in the omvf seems to be generally vigorous and persistent while it is linked with several source beds of variable stratigraphy or environmental condition the multiple eruptive episodes occurring as uninterrupted events or via pulses create conditions that perhaps favour high releases of methane into the water column as well as the growth of the gas hydrate phase near the seafloor the identified modern mudflows appear thermally immature for oil generation while they most probably originate from terrestrial source beds located not deeper than 2 km bsf a messinian age could be suggested for the principal sources of the very soft to soft mud breccias of the omvf while stratigraphic horizons of early middle miocene might be proposed as the likely major sources for the firm to very stiff mud breccias of the area

a late silurian extinction event and anachronistic period resurgence of microbialites and anachronistic facies in the aftermath of phanerozoic extinction events has hitherto only been documented among the major five based on the classical silurian carbonate platform strata of gotland sweden a minor biotic event is herein for the first time related to a substantial increase in anachronistic facies strata deposited during and shortly after the lau event in the baltic paleobasin eke and burgsvik formations include evidence for reduced grazing and infaunal activity in contemporaneous shallow low latitude seas e g flat pebble conglomerates normal marine stromatolites mass occurrence of oncoids and subtidal wrinkle structures e g kinneyia and microripples the latter structures have recently been suggested to be restricted to proterozoic cambrian and early triassic time and therefore are regarded as anomalous for the phanerozoic the co occurrence of these facies and global extinctions among pentamerid brachiopods and conodonts suggests that minor extinction events also resulted in anachronistic periods less devastating but fully comparable to those in the aftermath of the end ordovician and end permian mass extinctions a global positive stable carbon isotope excursion and the last appearance datum of the conodont polygnathoides siluricus may facilitate identification of the late silurian anachronistic period elsewhere less

the palaeoenvironmental and palaeohydrological evolution of padul peat bog granada spain over one million years from elemental isotopic and molecular organic geochemical proxies abstract the elemental concentration of organic carbon atomic h c and c n ratios isotopic 13 c values of organic matter and molecular predominant n alkane chain length and carbon preference index cpi organic components were measured for 600 samples taken from a 107 m long core from the padul basin andalusia spain the record runs from the lower pleistocene ca 1 ma b p to the mid holocene ca 4 5 ka b p with in general little diagenesis removal of components two markedly different hydrogeological scenarios were interpreted 1 from ca 1 ma to ca 400 ka b p run off recharge was significant and water depths were greater lacustrine scenario from ca 400 to 4 5 ka b p the padul basin became a peat bog s s with the major water input coming from groundwater inflow from ca 400 to ca 180 ka b p alternating episodes with either predominant grasses trees or aquatic macrophytes which were linked to wet dry phases took place an important deglaciation episode has been interpreted to occur between ca 180 and 170 ka b p the global climatic changes occurring from ca 170 to 25 ka b p were not recorded in the proxies though they do show important variations linked to the last glacial maximum and the beginning of the holocene ca 25 10 ka b p 2 cold phases coexisting with dry periods produced the recession of forests and the development of grasses after these periods as both temperature and precipitation increased forests expanded and the water level linked to thaw rose especially at ca 20 ka b p few changes occurred during the holocene although there were short alternations between wet and dry episodes overall the techniques applied proved to be excellent palaeoenvironmental proxies for studying the basin s palaeoclimatological and palaeohydrological evolution

geochemistry of c25 and c30 biogenic alkenes in sediments of the narragansett bay estuary abstract the distributions of a series of structurally related c 25 and c 30 biogenic alkenes in sediments of the narragansett bay estuary have been determined the suite of alkenes detected differs both quantitatively and qualitatively from those previously reported in other estuanne and coastal regions four c 25 mono and dienes and one c 30 diene comprise 73 91 of the total alkenes in all surface upper 2 5 5 cm sediments analyzed however significant geographic variations exist in the relative abundance of these five compounds throughout the estuary a comparison of alkene concentrations with 13 c of the bulk sedimentary organic matter has shown that the geographic variations of some alkenes reflect the distribution of marine organic matter suggesting a marine source for these compounds the distributions of other alkenes are not similarly correlated in particular concentrations of the c 30 diene are relatively constant and exhibit no dependence on the origin of organic matter in these sediments this distribution implies an in situ production of this alkene throughout the estuary analysis of several sediment cores reveals that alkene concentrations are generally highest at the surface and decrease to low constant values within the upper 25 cm an exception is the subsurface concentration of one c 25 diene which exhibits an increase at the same depth in two separate upper bay cores

chemical evidence of differential particle dispersal in the southern washington coastal environment aliphatic hydrocarbons cupric oxide oxidation products of lignin and polycyclic aromatic hydrocarbons pah were analyzed by capillary gas chromatography in sediments from the southern washington continental shelf and slope the concentration of diploptene relative to plantwax n alkanes increased systematically in surface sediments with distance offshore along east west transects of the study area and remained constant in surface sediments along the midshelf silt deposit analogous trends were also observed for the concentration of cinnamyl phenols relative to vanillyl phenols and total methylphenanthrenes relative to phenanthrene these changes in sedimentary composition are evidence that diploptene from some terrestrial source lignin characteristic of non woody vascular plant tissue and a fossil organic material contained within weathered rock debris disperse across the washington continental shelf and slope in geographic patterns distinct from that for other river derived chemically related materials the compositional variations are explained by the particulate associations of the land derived chemicals and differential hydraulic dispersion of their respective carrier particles after discharge at the mouth of the columbia river

a microbialite carbonate crust at the permian triassic boundary in south china and its palaeoenvironmental significance a 1 m thick carbonate crust layered and commonly domal caps crinoidal limestones on reef complexes of the top permian changxing formation in the huaying mountains eastern sichuan china the crust s stratigraphic level lies at a sharp change in facies and is overlain by poorly fossiliferous laminated micrites and shales of the lower triassic feixianguan formation the crust therefore appears to coincide with the end permian extinction event although the dating of the strata is currently imprecise the crust is composed mostly of digitate carbonate locally thrombolitic with remnant lobate fabric and resembles microbialites but is mostly recrystallised and a microbial origin is unconfirmed it is enclosed in micrite with pyrite crystals ostracode and other shell debris the crust is absent from interreef areas previous interpretations of karstification and calcrete formation are not upheld and the facies were deposited under water overlying sediments are low energy with abundant ferroan calcite and pyrite reflecting anoxia associated with rising sea level various interpretations of the crust are possible 1 it was organic and microbia grew preferentially on topographic highs of reef tops 2 microbia were a disaster biota in the absence of grazers 3 microbia took advantage of favourable conditions for calcification associated with a rapidly rising environmental co2 content during the late permian 4 the crust was an inorganic precipitate associated with co2 rich water microbial crusts are rare after the cambrian but whether this crust is organic or not its presence in these strata reinforces the view that oceanic atmospheric conditions in the permian triassic boundary interval were unusual

excavation and analysis of layered tektites from northeast thailand results of 1994 field expedition we have analyzed the size shape composition and spatial distribution of 6 kg of layered tektite fragments excavated from a 3 m 3 m area near the town of ban huai sai in northeast thailand our analysis suggests that these fragments represent a single homogeneous mass that underwent fragmentation far in the past and has undergone little disturbance since its deposition we have also studied the stratigraphic occurrence of layered tektites exposed in situ near the town of ban huai om tektites were found along a disconformable paleo erosion surface covered by recent aeolian sand similar to other occurrences throughout southeast asia this stratigraphic relationship provides little chronostratigraphic information and thus does not support a stratigraphic age paradox for the australasian tektites the present day surface density of layered tektites in this area is 2 to 20 g m2

the formation of sedimentary strata in an allochthonous shelf environment the washington continental shelf nittrouer c a and sternberg r w 1981 the formation of sedimentary strata in an allochthonous shelf environment the washington continental shelf mar geol 42 201 232 models of fine scale 120 m shelf regions the inner shelf sand and mid shelf sandy silt are the predominant accretionary deposits on the shelf important sedimento logical observations obtained by boxcoring the upper 1 2 m of these deposits are a progressive decrease in grain size with distance from the columbia b downward coarsening within the seabed c loss of distinct sedimentary structure homogenization of sediment with distance from the columbia non dimensional parameters based on sediment transport and benthic biological studies can be used to relate rates of sediment mixing re working to rates of accumulation these parameters have the potential for quantitative prediction of strata formation from measurements of active processes physical and biological mixing can be assumed to remain relatively constant in an alongshelf direction on the washington shelf and accumulation rate is known from pb 210 geochronology to decrease away from the columbia together these factors tend to increase the ratio of mixing to accumulation with distance from the columbia and predict the sedimentological observations listed above

ostracods and palaeobotany from the middle permian of oman implications on pangaea reconstruction discovery of a middle permian ostracod fauna in the marine khuff formation sultanate of oman combined with palaeobotanical data from the immediately underlying continental gharif formation supports new interpretations of the palaeobiogeography of the tethys during the late palaeozoic a mixed ostracod fauna existed on the arabian platform this new record of permian ostracods combined with recent data obtained in other tethyan areas emphasizes the close relationship between the south western tethys realm and south china the macroand microfloral assemblages of the continental gharif formation demonstrate that this palaeoflora represents a true mixed association in which gondwanan cathaysian and euramerian elements are intermingled two main models exist for the reconstruction of pangaea during the late palaeozoic both ostracods and palaeobotanical evidence favour the reduction of the oceanic area between south china and arabian plate as in the b pangaea model favoured by recent palaeomagnetic data

steep rock lake sedimentology and geochemistry of an archean carbonate platform abstract the 2800 ma mosher carbonate formation at steep rock lake in south central canada is one of earth s oldest limestone deposits it is both thick up to 500 m and relatively well preserved and was one of the first precambrian successions to be noted for evidence of early life it continues to provide information on the antiquity of such processes as photosynthesis the carbonate contains a variety of fabrics and facies from apparently fine grained bedded limestones with domal and columnar stromatolites atikokania radial fans and sheet cracks to closely packed metric scale hybrid domes of originally aragonite seafloor crust interlayered with fenestral fabric here we review previous work provide new observations concerning these sediments and their geochemistry and discuss the inception overall development and ultimate demise of the steep rock platform we divide the mosher carbonate into the lower hogarth member and upper elbow point member these units constitute a shallow water carbonate platform succession the hogarth member overlies eroded 3000 ma tonalite and is at least 120 m thick thin horizons of domal pseudocolumnar columnar and fenestral stratiform stromatolites and occasional layers of atikokania radial crystal fans occur within relatively fine grained thin bedded limestone with iron carbonate horizons in the upper part meter scale domes occur locally with sheet cracks and stromatactis the irregular laminae that build the small domal and columnar stromatolites are interpreted to be lithified mats and biofilms presumably cyanobacteria dominated fine grained well bedded facies of the lower hogarth member and its varied association of small stromatolites is interpreted to have accumulated in a relatively protected inner platform environment numerous very thin horizons of iron carbonate in the lower and upper parts of the hogarth member suggest temporally limited influence of iron rich offshore waters vertical trends in fe mn ba sr ce and 13 c probably reflect progressive restriction of circulation with at least one abrupt but short lived change back to more open seawater conditions the upper hogarth member with large banded domes and fenestral crusts and stromatolites is interpreted as back margin facies the overlying elbow point member is at least 70 m thick and appears to be entirely composed of innumerable juxtaposed elongate smooth and thickly layered domes lacking intervening sediment each dome is typically several meters across and composed of centimetric alternations of cuspate fenestral fabric possibly microbial and crystal fan fabric that is probably abiotic seafloor aragonite precipitate adjacent cuspate fenestral and crystal fan fabric show significant differences in concentration of 13 c sr ba fe and mn this giant dome facies is interpreted as a platform margin deposit in which alternating calcite aragonite mineralogies within each dome reflect a laterally fluctuating offshore redox boundary negative ce anomalies positive gd anomalies and reduced positive eu anomalies relative to laterally correlative deep water iron formation occur in the majority of crystal fan samples and in some cuspate fenestral fabric samples ca carbonate precipitation at the margin of an anoxic iron rich sea would have been promoted by oxygenic removal of iron from seawater otherwise fe carbonate would have been favored over ca carbonate precipitation the mosher carbonate formation is interpreted as an early marine oxygen oasis a shallow platform that favored cyanobacterial productivity was sufficiently isolated from open marine circulation for the seawater to become relatively oxygenated and where carbonate sediment aggradation was a positive feedback that sustained these shallow water conditions limestone accumulation terminated as transgressive suboxic and anoxic seawater deposited first manganese oxide rich and then manganese oxide poor iron formation sediments

global oolite deposits across the permian triassic boundary a synthesis and implications for palaeoceanography immediately after the end permian biocrisis abstract the permian triassic mass extinction ptme is not only a dramatic loss in biodiversity and major change in ecosystem structures but also coincided with the formation of abundant unusual sedimentary structures of these ooids were widespread in shallow marine carbonate settings during the permian triassic p tr transition and giant ooids occurred more frequently at this critical period than any time during the phanerozoic global review of 43 oolite bearing permian triassic boundary ptb sections with reliable biostratigraphic controls indicates that ooids occurred mostly in coincidence with the latest permian extinction lpe and its immediate aftermath ooids became widespread over extensive regions just after the lpe during the interval corresponding to the conodont hindeodus changxingensis zone they persisted into the earliest triassic until the conodont isarcicella isarcica zone in addition oolites are often found in association with microbialites in low latitude shallow marine settings proliferation of ooids over the p tr transition indicates an extensive range of warm waters with high level of carbonate saturation state that prevailed in the oceans during that time the latest permian ooids were usually small 0 3 to 0 7 mm in diameter aragonitic poorly preserved and recrystallized while moderately to well preserved morphology bimineralic and oversized forms usually occurred in the i isarcica zone of the earliest triassic and afterwards widespread aragonitic ooids in the end of the permian reinforce the scenario that an aragonite sea period may have resulted in the dramatic losses of skeletal organisms that precipitated low mg calcite and hampered their recovery in the aftermath the anomalous primary mineralogy of lower triassic ooids implies that previously assumed stable seawater composition during the early triassic needs to be revaluated

factors affecting pore water hydrocarbon concentrations in puget sound sediments abstract polycyclic aromatic hydrocarbon pah and aliphatic hydrocarbon concentrations have been determined for sediments and associated pore waters collected at 2 sites 11 stations in puget sound washington northwest u s a these sediments have been contaminated to varying degrees by hydrocarbons from a creosote plant and from various combustion sources pah were not detected in pore waters of sediments whose pah were primarily derived from combustion and natural sources even though pore water concentrations predicted from sediment concentrations and two phase equilibrium partitioning models were above detection limits from most pah equilibrium partition coefficients calculated from field aqueous and solid phase data from an area contaminated with creosote agreed with laboratory derived coefficients to within a factor of 4 pore water concentrations of creosote derived aliphatic hydrocarbons increase with increasing concentration in bulk sediments however pore water concentrations of natural and contaminant aliphatic hydrocarbons are much higher than predicted by solubility data possibly due to association with nonfilterable dissolved organic matter and colloids other major factors controlling hydrocarbon pore water concentrations include differential hydrocarbon sources specific particle associations and solubility

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

temporal trends of aliphatic and polyaromatic hydrocarbons in the bohai sea china evidence from the sedimentary record abstract this work reports the historical trends and sources of aliphatic hydrocarbons ahs and polycyclic aromatic hydrocarbons pahs in two 210 pb dated sediment cores extracted from the central mud areas of bohai sea bohai the toc tn ratio of the bulk organic matter om and the composition of the n alkanes suggest that the sedimentary organic matter was of mixed marine and terrigenous sources the coarser sediment grain size and decreasing c n ratios since 1976 could be attributed to the relocation of the yellow river mouth causing a decreased influence of yellow river derived sediments and associated om into the central bohai the concentration of total 16 pahs in the two cores ranged from 34 2 202 ng g mean 91 5 for bc1 and from 53 3 186 ng g mean 103 for bc2 with a high abundance of 2 3 ring pahs perylene in the two cores mainly originated from terrigenous sources via riverine discharge and thus could be potentially related to changes in the sediment load from the yellow river into the bohai over time petroleum inputs could be revealed by ratios of methylphenanthrenes to phenanthrene mp p and the patterns of more stable geochemical biomarkers hopanes and steranes along the two cores in addition to the presence of unresolved complex mixtures ucm in the surface layers source diagnostic ratios of pahs indicated a pyrogenic origin from biomass and coal combustion with a minor petroleum contribution downcore trends of compositional pahs profiles were in agreement with the socio economic development in china in the past decades this temporal variation of sedimentary pahs can also reflect a different evolution stage of energy structure in china as compared with those of the western developed countries

natural supply of oil derived hydrocarbons into marine sediments along the california continental margin during the late quaternary abstract sediment samples from three ocean drilling program odp leg 167 sites representing a south north transect along the california continental margin and covering the last 160 ky with selected samples extending in age to 950 ka were analyzed for their bulk and molecular biomarker compositions the aliphatic alicyclic hydrocarbon fractions revealed clear evidence of a largely uniform natural supply of petroleum hydrocarbons during the entire time period the mature fossil hydrocarbons in the sediments from the southern central and central california continental margin can be related to the oil prone rocks of the monterey formation in that area the petroleum hydrocarbon signal on the northern california continental margin differs significantly from that of the two southern sites indicating another presumably more northern source of the oil type hydrocarbons their distribution pattern matches those of eel river basin oils and thus suggests these oils or their source rocks to be the most likely origin of the hydrocarbons

stratigraphic relations of australites in the port campbell embayment victoria abstract in the port campbell embayment of victoria australites have been found in situ in channel deposits of the hanson plain sand of pliocene and pleistocene age the large majority of the australites however occur as a lag deposit at the basal contact of the sturgess sand of late pleistocene and holocene age and are spatially correlated with ferruginous sandstone clasts that are derived from the hanson plain sand some of the tektites are imbedded in or bonded to the ferruginous sandstone clasts but most are found as individual tektite fragments a few percent of the tektites have nearly perfectly preserved complete aerodynamically shaped forms the sandstone clasts and associated tektites have been reworked from the much older underlying hanson plain and have been locally concentrated in the lag deposit some tektites also occur at higher levels in the sturgess sand almost invariably in association with stone flakes exotic stones transported by the aborigines and locally with middens of mollusc shells circumstantial evidence indicates that the aborigines transported the tektites found in the upper part of the sturgess particularly at stanhope bay as port campbell australites unequivocally occur in strata much older than the late pleistocene and holocene sturgess there is no longer any conflict between the apparent stratigraphic age of the tektites and the middle pleistocene ages obtained by various chronometric methods

ostracod fauna from the permian triassic boundary interval of south china huaying mountains eastern sichuan province palaeoenvironmental significance thirteen species of ostracods in a sample of 400 specimens were extracted by hot acetolysis from three samples within the earliest triassic hindeodus parvus zone in the permian triassic boundary interval in the huaying mountains eastern sichuan province south china one new species langdaia laolongdongensis n sp was found ostracod preservation is good this study provides ostracod data that demonstrate a confirmation of palaeozoic holdovers in the earliest triassic in south china b consistency between the palaeoecological interpretation of ostracod faunas and previous environmental and oceanic interpretations that suggest poorly oxygenated waters invaded the shelf in the earliest triassic and demonstrate the value of ostracods in the analysis of these rocks and c evidence of palaeobiogeographical links are between south china and turkey and confirm that south china iran and turkey remain close from middle permian until at least the earliest triassic d 2004 elsevier b v all rights reserved

upper devonian reefs and microbialite at maoying south china implications for paleoenvironmental changes abstract reefal carbonate deposits in south china preserve a record of community structure and environmental change across the frasnian famennian boundary and through the late devonian detailing a regional response to one of the largest mass extinction events in earth history the upper devonian frasnian to famennian limestone outcrops in the maoying area of northern ziyun county south china record a carbonate platform depositional setting with some patch reef development the upper devonian carbonate deposits in maoying area are distinctive from those in correlative sections in dushan county with rare argillaceous limestone and dolomitic limestone as well as less dolostone exposures to the south in the guilin area of northeastern guangxi province are similar to those seen in the study area upper devonian carbonates in the maoying area are divided into two lithologic groups reef limestones or dolostone beds composed of five lithologically distinctive intervals the upper devonian strata have a cumulative thickness of 530 m the upper devonian reefs in the maoying area were developed on a shell pavement of brachiopod and bivalve shell shoal packstones and evolved into patch reefs in the interior of the carbonate platform patch reef development was limited to early frasnian time reef building organisms are dominated by massive and tabular stromatoporoids amphipora sp stachyodes sp and coral thamnopora sp while brachiopods and algae accumulated between stromatoporoid skeletal frameworks three evolutionary stages of the frasnian patch reefs including an initial development stage maturity stage and demise stage can be recognized according to sedimentary structures and fossil assemblage characteristics the frasnian strata overlying the patch reefs represent a well bedded back reef depositional setting and are mainly composed of amphipora floatstone and packstone containing a few bulbous stromatoporoids and small fasciculate corals famennian strata are characterized by laminated limestone and fenestrate limestone that are interbedded with infrequent mudstone and argillaceous limestone horizons a prominent microbialite bed developed in the laminated limestone of the famennian carbonate platform consists of stromatolite and thrombolite framestone this bed can be correlated in horizon and age with microbial reefs and mounds in the famennian offshore carbonate platform in the huanan epeiric sea such as famennian microbial reefs and mounds in guilin this represents a biogenic carbonate formation characterized by microbial fabrics that accumulated in a nearshore carbonate platform setting after the global frasnian famennian biotic extinction event which promoted the growth of microbialites during the latest devonian in south china

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

210pb activities in and fluxes to sediments of the washington continental slope and shelf abstract surface sediments of the washington coast have 210 pb activites which average 104 48dpm g for submarine canyon and slope regimes and 18 12dpm g for the continental shelf regime 210 pb sedimentary fluxes are also higher in canyons averaging 18 13dpm cm 2 per yr compared to 5 2 3 1 dpm cm 2 per yr for slope and 4 8 1 8dpm cm 2 per year for shelf regions these 210 pb activities and fluxes are 2 7 times greater than those reported for other coastal regions inputs from the atmosphere and the columbia river are not sufficient to supply the 210 pb but advection of seawater containing dissolved 210 pb produced in situ from 226 ra provides an input several times larger than the sedimentary fluxes the sedimentary 210 pb flux is limited by scavenging reactions rather than by supply of dissolved 210 pb calculations of maximum biological uptake and fluxes of 210 pb and selective chemical leaching experiments all show that the primary scavenging processes are due to hydrous mn and fe oxides rather than biological phases the pattern of higher 210 pb depositional fluxes in canyons than in nearby open slope areas of comparable water depth is most reasonably explained by enhanced scavenging of dissolved 210 pb near the sea floor rather than by processes operating throughout the water column relatively rapid removal of dissolved 210 pb from the near bottom nepheloid layer to slope and canyon sediments is shown by its mean residence time of less than two years in this layer

the importance of site selection sediment supply and hydrodynamics a case study of submarine paleoseismology on the northern cascadia margin washington usa abstract the washington continental margin presents both a classic test of submarine paleoseismology and an opportunity to explore advancement of the field through analysis of sediment dispersal in a heterogeneous system new and archive core bathymetric backscatter and seismic reflection data from the washington cascadia margin show that during high stand conditions the northernmost canyons barkley nitinat juan de fuca jdf and to some extent quillayute are relict systems with little holocene recharge the remaining canyons quinault grays guide and willapa are recharged to a varying degrees by northward transport of columbia river derived sediment all systems are nonetheless active conduits for turbidity currents during the holocene which are weaker and more restricted than their pleistocene counterparts sedimentologic and ct analysis supported by radiocarbon ages micropaleontology and the mazama ash datum show that the holocene sedimentary sequence consists of a series of sand to mud turbidites in the active portions of all systems interbedded with hemipelagic sediment however the pleistocene astoria and nitinat fans are largely inactive in the holocene with turbidity current activity limited to the proximal parts of the main channels within active systems the turbidite record is modulated by local landsliding and growth of active folds and faults in the relict systems the turbidite record begins in the middle canyon reaches as opposed to the actively recharged systems which have a turbidite record in the more proximal canyon reaches deposits in the relict systems increase in thickness and modal grain size downstream suggesting multiple sources and or entrainment of material along the canyon walls hydrodynamic models using monte carlo model searches for best fitting flow parameters show the most likely pathways by which holocene and pleistocene currents flowed through the complex accretionary wedge to the abyssal plain model results supported by heavy mineral distributions show that the northern canyon systems barkley nitinat jdf quillayute are independent of the southern systems quinault guide grays willapa during the holocene supporting the classic confluence test balancing of sediment volumes required suggests sediment supplied to the slope canyons and abyssal channels in turbidity current events is 2 5 times greater than that supplied by recharge to the canyon heads by external sources this implies a process that is independent of recharge that scavenges the plentiful relict and hemipelagic sediment supply on the continental slope lithostratigraphic correlation and age models suggest similar sequences were deposited in most systems independently and likely synchronously the correlated turbidite sequence suggests deposition of 23 holocene and 16 post mazama turbidites in most parts of the canyon systems with only modest variation mostly attributable to evidence of bypassing and erosion the best candidate for triggering of these sequences remains great earthquakes and the sequence correlates well to onshore and other offshore paleoseismologic evidence the new data including new cores in northern oregon suggest revisions to segmented rupture boundaries several partial ruptures segment b likely extended further north to juan de fuca canyon one event was resolved into two and one washington only event was added most segment c ruptures were found to extend further northward to the latitude of astoria canyon mean recurrence times are therefore revised to 434 years for the washington coast and 340 years for the central and northern oregon coast conditional probabilities in the next 50 years also are revised to 10 17 for the washington coast and 16 22 for the central and northern oregon coast in cascadia sumatra and other locales globally core siting spatial sample density high resolution analysis of core and regional geophysics and understanding of flow dynamics are critical to capturing a paleoseismic record sedimentary records vary across turbidity current systems of varying sediment supply physiography and sediment sources variations in the record will reflect these factors yet may still present a consistent paleoseismic history this analysis highlights the importance of a thorough understanding of flow paths hydrodynamics and the interplay of sedimentation and local tectonics when testing for evidence of earthquakes in the sedimentary record of active margins

the evolution of microbialite forms during the early triassic transgression a case study in chongyang of hubei province south china abstract the widespread development of microbialites in shallow areas of the tethys ocean at the start of the early triassic reflects the deterioration of marine ecosystems in the aftermath of the extinction that marked the demise of the majority of palaeozoic marine faunas here we present a study of the evolving microbialite forms and associated biotic assemblages of this pioneering microbialite interval from exposures at chongyang hubei province china this research provides a perspective on the effects of eustatic transgression on marine ecosystems as water depths increased at the beginning of mesozoic through the study of the changing forms microfacies and distribution of microbialites microbialite forms evolved from stratiform stromatolites to a sequence of tabular thrombolites with an intercalated layer of columnar stromatolites followed by domical thrombolites that were overlain in turn by oolites the stratiform stromatolites contain poorly preserved remains of calcified cyanobacteria but microfossils with chambered structure can also be seen metazoan fossils increased from the base of the overlying tabular thrombolite reflecting increasing biodiversity with deepening of seawater the occurrence of columnar stromatolites within the tabular thrombolite may indicate a temporary sea level shallowing foraminiferans and other metazoans are absent within the columnar stromatolites but spherical cyanobacterial remains are extremely abundant well preserved calcified cyanobacteria may reflect an absence of metazoan predation and or carbonate supersaturation of seawater as water deepened domical thrombolites developed and the more complex seafloor relief created varied niches between and within the domes that harboured more ecologically diverse communities during the process of transgression within the microbialite interval carbon isotopes exhibit a negative relationship with biodiversity implying that upwelling of anoxic deep ocean water if associated with the negative excursion of carbon isotope values did not inhibit the diversification of benthic organisms at least on shallow carbonate platforms in the period immediately after the end permian mass extinction

a geochemical study of long chain n aldehydes in washington coastal sediments a series of n aldehydes c20 to c32 with strong even to odd carbon preference was identified in the mixture of solvent extractable lipids isolated from various washington coastal sediments a limited survey of the lipid composition of surface waxes of foliage and cuticular waxes of pollen from several major plant species indigenous to the pacific northwest revealed that similar series of n aldehydes are intrinsic to regional vegetation debris from such plants discharged at the mouth of the columbia river represents a preformed source of the n aldehyde series accumulating in sediments from the washington coastal region although the evidence suggests n aldehydes are largely introduced erosionally to this region as a chemical component of land derived debris and are not formed in situ in the coastal sediments further study is warranted to establish the postdepositional stability of this series of compounds relative to other lipids of higher plantwax origin despite but few literature reports of the occurrence of these geochemicals long chain n aldehydes are very likely common in many sediments from environments that receive an input of detrital organic matter from higher plants

organic matter sources and early diagenetic alterations in arctic surface sediments lena river delta and laptev sea eastern siberia ii molecular and isotopic studies of hydrocarbons abstract the hydrocarbons extracted from three surface sediment samples from the delta of the lena river and adjacent areas of the laptev sea were examined to derive information on their source s natural vs anthropogenic terrestrial vs marine the abundance nature distribution and individual stable carbon isotope ratios of these hydrocarbons were determined it thus appeared that the laptev samples are characterized by i a negligible level of oil pollution due to anthropogenic and or natural petrogenic inputs ii an almost exclusive occurrence of long chain predominantly odd carbon numbered n alkanes and iii some differences in the level of bacterial alteration with a relatively higher degradation of the n alkanes in the seaward sediment a non terrestrial origin is proposed for these n alkanes based on the present results and on previous observations on carboxylic acid moieties and the pyrolysis products of the three surface sediments such hydrocarbons are probably not derived from the epicuticular waxes of higher plants but chiefly correspond to autochthonous products likely of algal origin these observations added to recent results on samples from other types of marine environments stress that an abundance of long chain predominantly odd n alkanes in extracts should not be systematically considered alone as evidence for a major contribution of higher plant waxes the relatively low contribution of terrestrial n alkanes in the laptev sediments should result from the combination of i a major dilution of the terrestrial input due to high primary productivity in summer promoted both by a large influx of nutrients provided by the lena river and by the specific conditions in such an arctic environment and ii the high level of degradation of the organic material transported by the lena river thus the latter probably provided a low input of lipids from terrestrial sources to the laptev samples

the permian triassic boundary at nhi tao vietnam evidence for recurrent influx of sulfidic watermasses to a shallow marine carbonate platform the permian triassic boundary at nhi tao cao bang province vietnam was sampled in a 7 5 m thick outcrop section at high resolution 5 cm intervals for chemostratigraphic and magnetic susceptibility analysis the section consists entirely of slightly argillaceous limestone representing shallow marine facies of the jinxi platform one of several large carbonate platforms within the nanpanjiang basin located on the southern margin of the south china craton upper permian strata beds 1 7 are mainly dark gray cherty fossiliferous wackestones and packstones containing a diverse open marine fauna whereas uppermost permian and lower triassic strata beds 9 and higher are medium gray calcimicrobial framestones containing rare macrofossils these facies are separated by a 12 cm thick oolitic pisolitic grainstone bed 8 that coincides with the disappearance of most late permian faunal elements as well as with the first appearance of various geochemical anomalies that continue into the lower triassic part of the section this late permian event horizon is characterized by 1 an abrupt decline in total organic carbon to near zero values 2 the onset of a sustained decline in carbonate 13c and 3 the first of eight concentration peaks in pyrite sulfur significantly each sulfide peak is associated with lower pyrite 34s values as well as with the onset of a negative carbonate 13c excursion or the acceleration of an excursion already in progress these chemostratigraphic relationships are consistent with multiple episodes of upwelling of sulfidic 34s and 13c depleted deep ocean waters onto the jinxi platform the first upwelling event was the most intense and caused a drastic reduction in primary productivity and the demise of the late permian fauna subsequent episodes were less intense but may have contributed to a delay in recovery of early triassic marine ecosystems a ten fold increase in magnetic susceptibility in bed 9 may record the influx of fine detrital particles following destruction of terrestrial ecosystems and massive soil erosion the terrestrial signal of the end permian catastrophe thus follows the marine signal with a 12 cm lag which may reflect the time of transit of soil derived particles across the nanpanjiang basin suggesting that the marine and terrestrial crises in the nhi tao region occurred more or less synchronously these observations suggest a model in which renewal of global ocean overturn followed a prolonged interval of deep ocean stagnation during the late permian with upwelling intensity modulated by short term 20 kyr climate cyclicity

the record of miocene impacts in the argentine pampas argentine pampean sediments represent a nearly continuous record of deposition since the late miocene 10 ma previous studies described five localized concentrations of vesicular impact glasses from the holocene to late pliocene two more occurrences from the late miocene are reported here one near chasico ch with an 40ar 39ar age of 9 24 0 09 ma and the other near baha blanca bb with an age of 5 28 0 04 ma in contrast with andesitic and dacitic impact glasses from other localities in the pampas the ch and bb glasses are more mafic they also exhibit higher degrees of melting with relatively few xenoycrysts but extensive quench crystals in addition to evidence for extreme heating 1700 c shock features are observed e g planar deformation features pdfs and diaplectic quartz and feldspar in impact glasses from both deposits geochemical analyses reveal unusually high levels of ba 7700 ppm in some samples which is consistent with an interpretation that these impacts excavated marine sequences known to be at depth these two new impact glass occurrences raise to seven the number of late cenozoic impacts for which there is evidence preserved in the pampean sediments this seemingly high number of significant impacts over a 10 6 km 2 area in a time span of 10 myr is consistent with the number of bolides larger than 100 m expected to enter the atmosphere but is contrary to calculated survival rates following atmospheric disruption the pampean record suggests therefore that either atmospheric entry models need to be reconsidered or that the earth has received an enhanced flux of impactors during portions of the late cenozoic evidence for the resulting collisions may be best preserved and revealed in rare dissected regions of continuous low energy deposition such as the pampas additionally the rare earth element ree concentrations of the target sediments and impact melts associated with the chasic event resemble the hna k australites of similar age this suggests the possibility that those enigmatic tektites could have originated as high angle distal ejecta from an impact in argentina thereby accounting for their rarity and notable chemical and physical differences from other australasian impact glasses

reconstructing human landscape interactions in the ancient mediterranean harbour of cartagena spain here we sought to reconstruct the pleistocene and holocene evolution of cartagena bay therefore 16 borehole cores were analysed with the following aims 1 to define a chronological framework 2 to obtain data on the palaeoenvironment and 3 to establish the relationship with human activities especially focused on the reconstruction of the carthago nova also known as qart hadasht conquest a total of 147 samples were recovered for amino acid racemisation aar dating 32 for radiocarbon dating 14c and 159 for sedimentological palaeontological and biomarker determination these approaches allowed us to elucidate the evolutionary phases of the palaeolandscape in cartagena the simultaneous use of aar and 14c dating allowed the discrimination of spurious ages and the establishment of a chronological scale during the marine isotope stages mis 7 and 5 the sea level sl in cartagena bay was almost the same as today an alluvial plain developed in the northern area and a delta was formed by

causes and consequences of extreme permo triassic warming to globally equable climate and relation to the permo triassic extinction and recovery permian waning of the low latitude alleghenian variscan hercynian orogenesis led to a long collisional orogeny gap that cut down the availability of chemically weatherable fresh silicate rock resulting in a high co2 atmosphere and global warming the correspondingly reduced delivery of nutrients to the biosphere caused further increases in co2 and warming melting of polar ice curtailed sinking of o2 and nutrient rich cold brines while pole to equator thermal gradients weakened wind shear and associated wind driven upwelling lessened further diminishing productivity and carbon burial as the earth warmed dry climates expanded to mid latitudes causing latitudinal expansion of the ferrel circulation cell at the expense of the polar cell increased coastal evaporation generated o2 and nutrient deficient warm saline bottom water wsbw and delivered it to a weakly circulating deep ocean warm deep currents delivered ever more heat to high latitudes until polar sinking of cold water was replaced by upwelling wsbw with the loss of polar sinking the ocean was rapidly filled with wsbw that became increasingly anoxic and finally euxinic by the end of the permian rapid incursion of wsbw could have produced 20 m of thermal expansion of the oceans generating the well documented marine transgression that flooded embayments in dry hot pangaean mid latitudes the flooding further increased wsbw production and anoxia and brought that anoxic water onto the shelves release of co2 from the siberian traps and methane from clathrates below the warming ocean bottom sharply enhanced the already strong greenhouse increasingly frequent and powerful cyclonic storms mined upwelling high latitude heat and released it to the atmosphere that heat trapped by overlying clouds of its own making suggests complete breakdown of the dry polar cell resulting rapid and intense polar warming caused or contributed to extinction of the remaining latest permian coal forests that could not migrate any farther poleward because of light limitations loss of water stored by the forests led to aquifer drainage adding another 5 m to the transgression non peat forming vegetation survived at the newly moist poles climate feedback from the coal forest extinction further intensified warmth contributing to delayed biotic recovery that generally did not begin until mid triassic but appears to have resumed first at high latitudes late in the early triassic current quantitative models fail to generate high latitude warmth and so do not produce the chain of events we outline in this paper future quantitative modeling addressing factors such as polar cloudiness increased poleward heat transport by deep water and its upwelling by cyclonic storms and sustainable mid latitude sinking of warm brines to promote anoxia warming and thermal expansion of deep water may more closely simulate conditions indicated by geological and paleontological data

the permian triassic boundary in western slovenia idrijca valley section magnetostratigraphy stable isotopes and elemental variations stable isotope analyses of carbonate 13ccarb and total organic carbon toc 13corg together with geochemical analyses of 54 major minor and trace elements and magnetic susceptibility measurements were carried out on whole rock samples of the undisturbed permian triassic p tr limestone boundary sequence in the idrijca valley w slovenia at the p tr boundary there is a 0 8 cm thick clayey marl layer ptb showing a characteristic magnetic susceptibility pulse and considerable enrichment in most major minor and trace elements the p tr transition is characterized by 1 an abrupt decrease in sedimentation rate from 32 to 5 cm 100 ka 2 a well known prominent negative excursion of 13ccarb and 13corg reflecting global perturbations in the carbon cycle and 3 the drastic disappearance of typically upper permian marine fauna although the shape of the 13ccarb curve indicates gradual long term change across the p tr boundary the sharp negative 13corg anomaly within an interval from 30 cm below to 6 cm above the boundary suggests an interruption of those gradual processes our observations for selected redox sensitive elements mo u v and zn abundances for organic carbon and sulphur and the rare earth elements ree distribution in the boundary sequence as well as the shape of the ce ce curve suggest that oceanic anoxia was typical of the upper permian and that the transition to oxygenated conditions occurred at the p tr boundary oxygenation at the p tr transition is coincidental with the terminal phase of the upper permian marine regression the shape of the ce ce curve indicates that the redox environmental conditions changed again in the earliest triassic resulting once more in oxygen deficient conditions