relation between depositional environment and the elemental composition of early diagenetic siderite early diagenetic siderites from marine and fresh water depositional environments are characterized by distinctive compositional trends siderite from fresh water environments is often relatively pure i e greater than 90 mol feco sub 3 and commonly attains end member composition siderite from marine environments however is always extremely impure and has extensive substitution of mg up to 41 mol and to a lesser extent ca up to 15 mol for fe in the siderite lattice in addition marine siderite generally contains less mn and has a higher mg ca ratio than fresh water siderite this compositional variation appears to result from differences in the chemistry of early marine and meteoric pore waters inasmuch as early marine pore waters generally have a higher mg sup 2 ca sup 2 ratio and contain less mn sup 2 and fe sup 2 and more ca sup 2 and mg sup 2 than meteoric waters

a novel multiproxy approach to reconstruct the paleoecology of extinct cephalopods abstract reconstructing marine paleoenvironments from the skeletal hardparts of nektic organisms is often hampered by their unknown migrational pathways involving different water masses and their corresponding physico chemical parameters despite significant progress over the last years the reconstruction of migration patterns of extinct ammonoids is difficult because both vertical and horizontal ones lead to an intricate combination of reconstructed seawater temperatures paleonvironmental data retrieved from exceptionally well preserved lower albian douvilleiceras mammillatum ammonite zone uppermost cc8a nannofossil zone 110 5 111 0 ma cephalopod shells from madagascar mahajanga basin 40 42 southern latitude are reconstructed based on a novel multi proxy approach here we combine and contrast i nacre tablet paleobathymetry ii westermann morphospace and iii shell isotope geochemistry analysis results obtained allow for a robust reconstruction of habitat depth paleo seawater temperatures and paleoecology of extinct cephalopod taxa the discocone nautiloid cymatoceras is regarded as vertical migrant with a maximum habitat depth of 250 m and a mean habitat water temperature of 20 21 c all three ammonoid taxa cleoniceras desmoceras and eogaudryceras share a platycone to planorbicone shell shape suggesting a demersal life habit at maximal water depths of 450 500 m and temperatures of 19 21 c for cleoniceras and desmoceras and the deepest 525 m and coolest 14 c habitat for eogaudryceras circumstantial evidence from benthic mollusk shells from the same stratigraphic interval as well as sedimentological and paleopathological data provide further support for habitat reconstructions reconstructed paleotemperatures shown here provide well constrained evidence for the thermal structure of past oceanic water masses and have significance for cretaceous paleoceanography in general

de glauconiarum origine the glauconitic facies is widespread on present day continental shelves from 50 s to 65 n and at water depths between 50 and 500 m and is in particularly great abundance on the upper slope and outer shelf between 200 and 300 m it is also common in many ancient rocks of post late precambrian age it occurs as sand to pebble sized essentially green particles granular facies but also as a surface coating on particles and hardgrounds and as a diffuse impregnation film and diffuse facies we suggest the replacement of the term glauconite which has been interchangeably used to designate a morphological form and a specific mineral by glaucony facies and glauconitic smectite and glauconitic mica as end members of the glauconitic mineral family the widely accepted model of burst and hower for glauconitization requires a degraded micaceous 2 1 layer lattice structure parent clay mineral however detailed analysis of numerous samples of recent glaucony reveals that such a parent substrate is exceptional the model therefore requires modification generally the parent material is carbonate particles argillaceous kaolinitic faecal pellets infillings of foraminiferal tests various mineral grains and rock fragments that pass gradually into the commonly occurring green grains we show that the process of glauconitization is achieved by de novo authigenic growth of automorphous crystallites in the pores of the substrate accompanied by progressive alteration and replacement of the substrate it is this two fold evolution that causes the verdissement of granular substrates macrofossils and hardgrounds the authigenic mineral is an iron rich and potassium poor glauconitic smectite while new smectites are growing into the remaining pore space the earlier smectites are modified by incorporation of potassium producing decreasingly expandable minerals with a non expandable glauconitic mica as the end member this mineralogical diversity of the glauconitic mineral family explains the highly variable physical and chemical properties of glaucony four categories nascent little evolved evolved and highly evolved glaucony are distinguished glauconitization appears to be controlled by a delicate balance between degree of physical confinement of a particle and the amount of ionic exchange between the micro environment and ambient open marine sea water the optimum conditions for glauconitization are those of semi confinement as a result the interior of a grain is more glauconitized than its less confined periphery similarly for identical substrate types large grains 500 m provide more favourable substrates for glauconitization than lesser confined small grains on a larger scale the formation of glaucony is governed by the availability of iron and potassium and the balance between detrital influx and winnowing low accumulation rates expose grains to the open marine environment for sufficiently long times 105 106 years for highly evolved glaucony

conditions of formation and diagenetic evolution of upper proterozoic phosphate nodules from southern sweden evidence from petrology mineral chemistry and isotopes abstract dark gray to black cryptocrystalline francolite occurs as nodules 2 8 cm in diameter which are embedded in organic matter rich mudstones of the visingso group upper proterozoic southern sweden the 13cpdb values 18 4 to 0 98 of structural co2 complemented by studies of the petrographic character and strontium isotopic composition of francolite indicate precipitation in the suboxic and sulfate reduction zones francolite is intergrown with berthierine that has formed in the suboxic fe reduction zone calcite enriched in mn and to a lesser extent fe occurs as fracture and void fillings and as replacement of francolite mn and mg rich calcian siderites have precipitated as pseudomorphs after bacteria in the zone of microbial methanogenesis the carbon 13 c pdb 0 75 to 7 04 and oxygen 18 o pdb 14 21 to 10 58 isotopes of calcite suggest derivation of carbonate ions from microbial methanogenesis and from thermal decarboxylation of organic matter at temperatures of 60 to 80 c some of the void and fracture filling calcites 13 c 20 8 to 18 63 18 o 5 46 to 5 21 have however precipitated at lower temperatures 25 30 c in the sulfate reduction zone

erosion of modern terrestrial organic matter as a major component of sediments in fjords fjords have recently been recognized as hotspots of carbon burial in this study we investigated organic carbon oc and biomarker radiocarbon values in fjord sediments from new zealand our results showed that oc was mostly modern with the most aged oc in middle reaches of fjords likely related to hydrodynamic sorting and inputs along adjacent slopes radiocarbon ages of sedimentary oc increased from north to south consistent with the fiordland regional gradients of lower fjord slopes and less rainfall our biomarker results suggested that lignin and long chain fatty acids were preferentially linked with fresh terrestrial debris and degraded soil respectively likely due to their chemical and physical properties finally we propose that fjords are a significant sink of modern oc in contrast to large lowland coastal systems as a major sink of pre aged oc overall this study indicated that radiocarbon techniques are critical in investigating carbon dynamics in coastal systems

characteristics of the atlantic storm track eddy activity and its relation with the north atlantic oscillation abstract this study focuses on feedbacks of the high frequency eddy activity onto the quasi stationary circulation particularly with regard to the north atlantic oscillation nao the methodology consists of analyzing ncep ncar reanalysis data and sensitivity runs from a high resolution nonhydrostatic regional model consistent with recent studies results show that the jet displacement characteristic of the nao phenomenon depends strongly on the dynamics of the synoptic scale waves and the way they break positive and negative phases of the nao are closely related to anticyclonic and cyclonic wave breaking respectively indeed the high frequency momentum flux whose sign is directly related to the type of wave breaking is correlated with the nao index over the atlantic the peak of the momentum flux signal precedes that of the nao by a few days suggesting that wave breaking is triggering nao events two examples illustrate the significant impact of single storms in particular those occurring in the e

efficient sequestration of terrigenous organic carbon in the new britain trench abstract the fate of terrigenous organic carbon octerr in the ocean remains an enigma for four decades hadal trenches the deepest ocean realm 6 11 km deep were recently proposed to be oc depocenters but whether and how much octerr was sequestrated there remain elusive here we conducted comprehensive analyses for four sediment cores from the new britain trench nbt close to papua new guinea to assess source translocation and burial of oc the bulk and molecular radiocarbon data suggest that the nbt landward slope and axis sediments mainly receive young and biogenic rather than petrogenic oc the three endmember mixing model based on 14c 13c and oc contents reveals that sediments of the nbt axis 8225 m comprise relatively high oc contents 0 66 0 08 of which biogenic octerr accounts for 62 10 the high proportion of biogenic octerr was attributed to the selective translocation of octerr enriched coarse particles and rapid delivery of sediments supported by unique v shape feature of the trench in contrast the sediment oc at the oceanward slope is primarily of a marine origin suggesting that octerr was efficiently trapped in the trench bottom it is estimated that the burial rate is 2 75 0 32 g c m 2 yr 1 for oc and 1 69 0 41 g c m 2 yr 1 for octerr in the nbt given a fact that many trenches are close to the landmasses we propose that the hadal trenches may contribute significantly to the burial of octerr in the ocean

burial of organic carbon and pyrite sulfur in sediments over phanerozoic time a new theory in present day marine sediments almost all of which are deposited in normal oxygenated seawater rates of burial of organic carbon c and pyrite sulfur s correlate positively and bear a constant ratio to one another c s 3 on a weight basis by contrast calculations based on the isotopic model of garrels and lerman 1981 indicate that at various times during the phanerozoic the worldwide burial ratio must have been considerably different than the present day value this ratio change is caused by the requirement that increases in the worldwide mass of organic carbon must be accompanied by equivalent decreases in the mass of sedimentary pyrite sulfur in order to maintain a roughly constant level of o2 in the atmosphere such apparently contradictory behavior can be explained if the locus of major organic carbon burial has shifted over time from normal marine environments as at present to non marine freshwater or to euxinic environments in the geologic past a shift to predominantly freshwater burial can help explain predicted high c s ratios in permo carboniferous sediments and a shift to euxinic environments can help explain predicted low c s ratios during the early paleozoic it is demonstrated that the three environments today exhibit distinguishably different average c s ratios

carbon isotopic evidence for coupled sulfate reduction methane oxidation in amazon fan sediments abstract carbon isotope ratios of dissolved inorganic carbon were measured on porewaters from amazon fan sediments collected on ocean drilling program leg 155 values as low as 49 6 vs pdb were recorded with the lowest values coinciding with the base of the sulfate reduction zone at each site the values indicate that on the order of 50 85 of sulfate reduction in amazon fan sediments takes place by methane oxidation estimated rates of methane oxidation range from 0 3 1 0x10 5 moles l yr the reasons for the high percentage of sulfate reduction taking place by methane oxidation are thought to be the large decrease in fan sedimentation rates in the early holocene and the terrestrial source of organic matter in fan sediments

early diagenetic reactions in interbedded pelagic and turbiditic sediments in the nares abyssal plain western north atlantic consequences for the composition of sediment and interstitial water abstract measured pore water concentrations of iron in interbedded pelagic and turbiditic sediments from the nares abyssal plain are in excellent agreement with sediment colour and measured redox potential the organic carbon content of these sediments appears to define the redox conditions and consequently the porewater and solid phase concentration of constituents that are involved in early diagenetic reactions in the turbiditic sediments the concentration of no 3 generally goes to zero within a sediment depth of 1 m whereas at 8 m in a pelagic core from the same area the concentration of no 3 is still higher than it is in the bottom water the pore water concentration of mn 2 in the turbiditic sediments increases sharply down to a depth of approximately 3 m and from thereon remains nearly constant due to saturation with respect to mn ca co 3 the pore water of the turbiditic sediments is also saturated with respect to calcite the few diagenetic spikes in the pore water concentration of no 3 and mn 2 and the concentration depth profile of dissolved iron h 4 sio 4 and phosphate all clearly demonstrate the inhomogeneous nature of interbedded pelagic and turbiditic sediments the simultaneous occurrence of peaks of dissolved iron silica and of sediment intervals with a relatively high organic carbon content is attributed to enhanced early diagenetic reactions associated with the decomposition of organic matter in these specific intervals linked with these reactions is the irregular pore water concentration of phosphate which is shown to originate partly from the oxidation of organic matter but mainly from the desorption of phosphate from iron oxide potential concentrations of phosphate are calculated from the stoichiometric early diagenetic reactions and compared with measured concentrations due to the unique combination of low porosity and relatively high sedimentation rates the sediments from the nares abyssal plain are an ideal basis for the study of such interbedded sequences of pelagic and turbiditic deposits

biological processes on glacier and ice sheet surfaces glacial ice covers around 10 of the earth s continents a review of the literature suggests that microbes living on glaciers and ice sheets are an integral part of both the glacial environment and the earth s ecosystem

recycling of graphite during himalayan erosion a geological stabilization of carbon in the crust at geological time scales the role of continental erosion in the organic carbon oc cycle is determined by the balance between recent oc burial and petrogenic oc oxidation evaluating its net effect on the concentration of carbon dioxide and dioxygen in the atmosphere requires the fate of petrogenic oc to be assessed here we report a multiscale nanometer to micrometer structural characterization of petrogenic oc in the himalayan system we show that graphitic carbon is preserved and buried in marine sediments while the less graphitized forms are oxidized during fluvial transport radiocarbon dating indicates that 30 to 50 of the carbon initially present in the himalayan rocks is conserved during the erosion cycle graphitization during metamorphism thus stabilizes carbon in the crust over geological time scales

a sequence stratigraphic interpretation of a mudstone dominated succession the lower jurassic cleveland ironstone formation uk microfacies analysis using optical and backscattered electron imagery has been undertaken on 37 samples from the cleveland ironstone formation staithes yorkshire uk four lithofacies were encountered clay rich mudstones silt rich mudstones sand rich mudstones and concretionary carbonates two types berthierine siderite rich ironstones and apatite rich concretionary horizons successive units were found to stack systematically into upward coarsening units on a small 0 1 1 0 m scale upward coarsening and upward fining packages were also found on a larger 1 0 3 0 m scale the small scale upward coarsening units are interpreted to be parasequences while the large scale upward fining and upward coarsening packages are interpreted to be retrogradational and progradational parasequence sets respectively the ironstones occur at the level where the stacking patterns change from being overall progradational to retrogradational while the apatite rich concretionary units occur at the level where the stacking patterns change from being retrogradational to progradational the concretionary carbonates are interpreted to have formed close to at major stratal surfaces the ironstones are interpreted to be either the correlative equivalent of sequence boundaries or part all of the forced regressive system tract while the apatite rich units are interpreted to have precipitated close to at maximum flooding surfaces condensed sections and or major transgressive surfaces

a novel proxy for terrestrial organic matter in sediments based on branched and isoprenoid tetraether lipids we propose a novel tracer for terrestrial organic carbon in sediments based on the analysis of tetraether lipids using high performance liquid chromatography mass spectrometry hplc ms analysis of terrestrial soil and peats shows that branched tetraether lipids are predominant in terrestrial environments in contrast to crenarchaeol the characteristic membrane lipid of non thermophilic crenarchaeota which is especially abundant in the marine and lacustrine environment based on these findings an index was developed the so called branched and isoprenoid tetraether bit index based on the relative abundance of terrestrially derived tetraether lipids versus crenarchaeol this bit index was applied to surface sediments from the angola basin where it was shown to trace the outflow of the congo river furthermore analyses of particulate organic matter from the north sea showed relatively higher bit indices in water column particulate organic matter near large river inputs a survey of globally distributed marine and lacustrine surface sediments shows that the bit index in these environments correlates with the relative fluvial input of terrestrial organic material making this index generally applicable the new proxy allows the rapid assessment of the fluvial input of terrestrial organic material in immature sediments up to 100 ma old

circumglobal teleconnections the jet stream waveguide and the north atlantic oscillation abstract monthly and seasonally averaged upper tropospheric northern hemisphere winter fields are examined to determine whether the waveguiding effect of the time averaged tropospheric jets on low frequency disturbances that is predicted by theory does affect the behavior of these disturbances it is found that indeed disturbances in the vicinity of the mean jets particularly the jet that stretches across south asia are fundamentally different from those that reside in regions where the mean winds have weaker meridional gradients like the mid pacific patterns of variability in the jets tend to be smaller scale and to consist of zonally oriented chains of anomalies while variability in the mid pacific is composed of patterns with distinct meridional orientation because they are meridionally trapped and zonally elongated patterns associated with the jet stream waveguide connect activity at points that are much farther apart than do patterns in other regions of the globe within the south asian waveg

characteristics of wave packets in the upper troposphere part i northern hemisphere winter abstract gridded data produced by the ecmwf reanalysis project have been analyzed to document the properties of wave packets in the northern hemisphere winter midlatitude upper troposphere based on results from earlier investigations 300 hpa meridional wind variations were chosen for analysis wave packet envelopes were also defined by performing complex demodulation on the wind data the properties of the wave packets are mainly illustrated using time lagged one point correlation maps performed both on and wave packet envelopes the results show that over most regions in the northern hemisphere winter with the exception of the deep tropics and near the aleutian low medium scale waves dominant wavenumber 5 8 exhibit the characteristics of downstream development and occur within wave trains that propagate with eastward group velocities much faster than the phase speeds of individual phases of the waves their group velocity is highly correlated with the local time mean 200 400 hpa wind while the

whence the gosport sand upper middle eocene alabama the origin of glauconitic shell beds in the paleogene of the u s gulf coastal plain abstract an explanation for the depositional history of the gosport sand has proven to be as puzzling as its diverse mollusk fossils is beguiling we propose that shifting delta lobes produced patchy environments which accumulated to form the gosport sand and likely other glauconite and fossil rich shell beds of the gulf coastal plain of the paleogene we present facies and mineralogical data to suggest glauconite in the gosport sand was deposited during relatively stable environmental conditions increased glauconite maturity and taphonomic alteration in the gosport sand are attributed to eustatic transgression resulting in decreased deposition enhanced winnowing and increased exposure at the sediment water interface increased fossil diversity and abundance likely result from time averaging and accumulation of shells from ancient patchy habitats analogous to modern inner shallow shelf and open sound environments delta progradation and subsidence would have determined the migration of these environments we evoke a similar depositional model for glauconite rich shell beds distributed throughout the paleocene and eocene of the gulf coastal plain based on their transgressive nature and roughly equivalent facies these shifting environmental conditions may have played a partial role in generating the high molluscan diversity of the gulf coastal plain of the paleogene

the association between enso and winter atmospheric circulation and temperature in the north atlantic region the association among enso the northern hemisphere sea level pressure slp and temperatures in europe has been analyzed during the period 1873 1995 in the first part the sst of the nino 3 region has been used to select extreme cold and warm enso events and periods that can be regarded as normal the study was carried out for winter with the constraints that the enso events were well developed during the winter of study and that they are extreme events composites of winter slp and temperatures have been made for the selected cold and warm events as well as for normal cases and compared with each other in the north atlantic area no statistically significant slp anomaly patterns were found associated with warm events while during cold events a statistically significant anomaly pattern resembling the positive phase of the north atlantic oscillation nao was found the temperature analysis shows statistically significant negative anomalies during cold events over the iberian peninsula and positive anomalies over the british isles and southern scandinavia consistent with the slp anomalies the slp and temperatures have also been analyzed for spring the patterns resemble those found for winter but the anomalies have lower amplitudes for the completion of the composite analysis the consistency among events of the relationship between enso and slp as well as between enso and temperatures was examined the results show that the significant patterns found in the composite analysis in the north atlantic area are not the result of a few major events but rather because both the slp and temperature anomalies in this area during cold enso events are stable and qualitatively similar to those found during the positive phase of the nao the possible physical basis for this association between nao and enso is discussed

paleoecology of the eocene wheelock member of the cook mountain formation in western houston county texas abstract eighty five species of foraminifera and forty nine molluscan species were recovered from the wheelock member of the cook mountain formation in the porter springs area of houston county texas and along the little brazos river in brazos county texas the wheelock member is primarily a regressive unit a thin shell lag deposit at the base of the member is all that remains of the transgressive part of the sequence above the shell lag deposit the lower part of the member consists dominantly of bioturbated glauconitic fossiliferous mudstone the percentage of planktic foraminifers and the diversity of benthic foraminifers suggests deposition in an inner or inner middle shelf environment the low diversity and equitability of the molluscan population and the abundance of opportunistic corbulid bivalves suggest that the environment was at least periodically unstable the upper part of the wheelock member consists dominantly of regularly layered or laminated mudstone and siltstone and contains only a low diversity assemblage of agglutinated foraminifera this part of the member was probably deposited in a shallow brackish water environment with a high sedimentation rate planktic foraminifers recovered from the wheelock member support an age correlation with the late middle eocene morozovella lehneri or orbulinoides beckmanni zones according to berggren and others 1985 this corresponds to an absolute age of between 42 and 46 million years b p

temperate glacimarine varves an example from disenchantment bay southern alaska abstract the sediment record of disenchantment bay southern alaska a large marine calving embayment contains distinctive annual deposits each year a glacimarine couplet forms with a clast rich stratified to massive diamicton deposited in winter by intense iceberg rafting and a summer meltwater deposit of thinly laminated mud and turbidite sand beds although iceberg rafting occurs throughout the year coarse debris is deposited in high concentrations and forms diamicton only during the winter because of minimal fine sediment from meltwater discharges and a longer residence time of icebergs in the bay due to winter fjord circulation and meteorological factors when meltwater discharge commences in summer laminated mud with dropstones is deposited spring and fall conditions are recorded a transitional phases between winter and summer by clast poor diamictons average sediment accumulation rates calculated from varve thicknesses range from 48 cm yr 3 4 km from hubbard glacier at the head of the bay to 14 cm yr 15 km away sediment accumulation rates estimated from 210pb dating of core sediments are in the same range deposits from the 1986 russell fiord outburst flood are identified from anomalously high 210pb activities in sediments indicating an alternative sediment source to disenchantment bay glacimarine varves are a dating tool for the barren proximal sediments commonly deposited near calving glacier termini they yield paleoclimatic information because they are a product of both glacial ice in the sea and laminated sediments deposited from significant melt water discharge found in a temperate to subpolar climate

two paradigms of baroclinic wave life cycle behaviour two idealized baroclinic wave 6 life cycles examined here suggest a framework of opposite extremes a in which to view the behaviour of real synoptic scale disturbances in middle latitudes and b in which to interrelate the synoptic and wave theoretic viewpoints using the saturation propagation saturation sps picture of wave 6 life cycle behaviour the two life cycles dented by lc1 and lc2 are higher resolution versions of the simmons hoskins basic and anomalous cases showing strong and weak late decay of eddy kinetic energy eke they illustrate in varying degrees two extreme types of behaviour here disignated anticyclonic and cyclonic and epitomized by strongly contrasting upper air trough behaviour anticyclonic behaviour dominates the late stages of lc1 and is characterized by backward tilted thinning troughs being advected anticyclonically and equatorward as in the commoner cases of planetary scale mid stratospheric rossby wave breaking cyclonic behaviour dominates lc2 and is characterized by forward tilted broadening troughs wrapping themselves up cyclonically and poleward producing major cut off cyclones in high latitudes these morphologies are visualized by upper air maps of potential temperature on the nominal tropopause defined as a constant potential vorticity surface some atmospheric mid latitude disturbances examined here using the same visualization applied to operational analyses show the same two extreme types of trough behaviour together with intermediate cases the sps picture is re examined using eliassen palm and refractive index cross sections it is shown in particular by reference to a wave activity theorem of haynes that the late stages of lc2 can be looked upon as a remarkably clear and morphologically novel large amplitude counterpart of the nonlinear reflection scenario of rossby wave critical layer theory the late stages of lc1 by constrast look more akin to an nonlinear critical layer absorption scenario lc2 exhibits region of largely undular pv contours adjacent to a nonlinear of irreversiby deformen pv contous in the latter region pv rearrangement and hence absorption of rossby wave activity has largely ceased this accounts for the more persistent ekee in the lc2 case

nonlinear planetary wave reflection in an atmospheric gcm the nonlinear behavior of planetary waves excited by midlatitude topography is considered in an atmospheric gcm the gcm is run at standard resolution t42 and includes all of the complexity normally associated with a gcm only two simplifications are made to the model first it is run in perpetual january mode so that the solar radiation takes the diurnally varying value associated with 15 january second the lower boundary is simplified so that it is entirely ocean with zonally symmetric ssts planetary waves are excited by gaussian shaped topography centered at 45 n 90 w as in earlier studies the excited wave train propagates toward low latitudes where for sufficiently large forcing amplitude i e height of topography the wave will break several different experiments are run with different mountain heights each experiment is run for a total of 4015 days the response of the model depends on the height of the mountain for the small amplitude mountain 500 m the wave is dissipated at low latitudes near its critical latitude for large amplitude mountains 2000 3000 and 4000 m wave breaking and nonlinear reflection out of the wave breaking region is observed the spatial character of the reflected wave train is similar to that detected in earlier studies with more idealized models

abstract lower claiborne regional stratigraphic architecture southeast texas to east central louisiana abstract the lower claiborne section and its units discussed and illustrated here of lutetian age middle eocene figure 1 are recognized as a series of marine shelf marginal marine and deltaic strandline deposits regional closely spaced well log cross sections extending for almost 500 miles from south texas to eastern louisiana updip of the claiborne shelf margins clearly show the regional stratigraphic architecture along depositional strike from southeast central texas through east central louisiana ewing 1994 ewing and vincent 1997 the obvious internal forms when viewing the lower claiborne at such great scale are large very low angle sigmoidal clinoform sets delineated by regional flooding surfaces see figure 2 below the flooding surfaces fs are depicted as the flat to sigmoidal lines seen in that cross sectional diagram major fs s shown by heavier lines lesser fs s by thin and or dashed lines these large downlaps are roughly oriented from nw to se across coastal texas and into central louisiana demonstrating the time transgressive nature of the entire lower claiborne the downlaps proceed from oldest to youngest coming from west to east contrast with perkins and hobday 1980 and fisher 1964 basin analysis and subsurface exploration rely on the identification of genetic units or sequences because they are time bounded units which unite all of the co occurring processes and their resulting deposits genetic stratigraphic units are defined and bounded by key flooding surfaces which approximate time lines genetic sequences of galloway 1989a b these units combining progradational and transgressive elements have the advantage of being bounded by surfaces which on the shelf at least are continuous are easy to recognize have associated biozonations and are verifiably correlatable on well logs unconformities which may be detectable in up dip positions in these dynamic basin margin settings are for all practical purposes difficult to impossible to find in the down dip conformable portions of these units and for simplicity s sake are not shown on the accompanying cross section fig 2

centers of organic carbon burial and oxidation at the land ocean interface abstract continental margin systems collectively receive and store vast amounts of organic carbon oc derived from primary productivity both on land and in the ocean thereby playing a central role in the global carbon cycle the land ocean interface is however extremely heterogeneous in terms of terrigenous input marine primary productivity sediment transport processes and depositional conditions e g such as bottom water oxygen level continental margins are also highly dynamic with processes occurring over a broad range of spatial and temporal scales the rates of oc burial and oxidation are consequently variable over both space and time hindering our ability to derive a global picture of oc cycling at the land ocean interface here we review the processes controlling the fate of organic matter in continental margin sediments with a special emphasis on hot spots and hot moments of oc burial and oxidation we present a compilation of compositional data from a set of illustrative settings including fjords small mountainous river margins large deltaic systems and upwelling areas bulk oc stable isotope and radiocarbon compositions reveal the diversity and complexity characteristic of oc buried in marginal seas this primarily relates to differences in marine and terrestrial inputs the composition of the terrestrial component e g vascular plant oc soil and petrogenic oc inputs and processes modulating the fate of oc within the marine environment e g priming this widely contrasting behavior of oc among these systems illustrates that the reactivity of oc is a product of its chemical composition and regional conditions interpreted in the context of bulk compositional data as well as that obtained on specific molecular markers e g lignin derived phenols the possibility exists to tease apart complex mixtures of terrestrial and marine inputs and to shed light on the role of the myriad of depositional and post depositional processes finally we discuss a set of hot topics that warrant further investigation such as the role of photochemistry fungi halogenation and reactive iron in dictating the fate of oc in the changing coastal ocean

classification seasonality and persistence of low frequency atmospheric circulation patterns abstract orthogonally rotated principle component analysis rpca of northern hemisphere 1 month mean 700 mb heights is used to identify and describe the seasonality and persistence of the major modes of interannual variability the analysis is detailed and comprehensive in that 1 a high resolution approximately equal area 358 point grid is used for the virtually maximum possible 35 year period of record 2 a positive bias in the nmc data base in the early 1950s in the subtropics is largely eliminated for the first time and 3 homogeneous separate analyses of each month of the year are carried out detailing the mouth to month changes in the dominant circulation patterns winter results are similar to those of other recent rpca and teleconnection studies except that some less obvious patterns are identified and further detail of the better known patterns is provided two north south dipole patterns are found over the pacific ocean west pacific oscillation and east pacific pattern and over the atla

petrology and palaeoenvironmental significance of authigenic iron rich clays carbonates and apatite in the claiborne group middle eocene ne texas the claiborne group eocene in north east texas consists of clayey sandstones and mudrocks both with variable proportions of dark green to brown clay pellets deposited in a marginal to open marine setting on the gulf coast margin the composition of concretionary carbonate and clay pellets from 5 localities has been investigated using a wide variety of analytical techniques our palaeontological sedimentological c s and stable isotope data support an interpretation of marginal marine facies with limited freshwater input for the claiborne group dark green mature pellets are predominantly associated with transgressive bioturbated marine sediments from the weches formation through to the youngest crockett formation there is a trend from pellets composed mostly of dark green serpentine rich mixed layer clay to those of mostly brown immature nontronite rich mixed layer clay the serpentine is intermediate between odinite and berthierine and may have been originally odinite that has undergone partial transformation to berthierine pellet maturity apparently corresponds with the degree of winnowing and sedimentation rate it does not appear to correspond with global temperature fluctuations though the serpentine rich rather than glauconite rich composition may do siderite cement mostly in the form of concretions post dates the iron rich clay pellets and pre dates calcite cement carbonate and apatite concretions show a wide range of mineral cement textures reflecting variation in sedimentary environment and early diagenetic processes based on water temperatures derived from verneriacardia bivalves a precipitation temperature of 20 c is assumed for the concretionary siderite using this temperature we surmise that the siderite precipitated from marine pore waters with intermittent meteoric water mixing

burial of terrestrial organic matter in marine sediments a re assessment 1 calculations based on recent observations indicate that approximately one third of the organic matter presently being buried in marine sediments may be of terrestrial origin with the majority of this terrestrial organic matter tom burial occurring in muddy deltaic sediments these calculations further suggest that the remineralization of terrestrial organic matter in the oceans is also much less efficient than that of marine organic matter these two underappreciated observations have important implications in terms of our understanding of the controls on the global carbon cycle from a paleoceanographic perspective the results presented here also suggest that changes in tom burial on glacial interglacial timescales have the potential to impact the global carbon cycle i e atmospheric co2 levels

sedimentary organic matter geochemistry of clayoquot sound vancouver island british columbia surface sediment samples from three interconnected fjords of clayoquot sound british columbia were density fractionated 1 6 g cm 3 to isolate discrete organic debris od from mineral associated organic matter mom total organic carbon oc values varied greatly ranging from 0 1 to 8 8 by weight with a general decreasing trend from fjord head to the continental shelf within the sediment terrestrial om was present either as vascular plant debris or soil mom down fjord the woody vascular plant material in the od fraction acquires nitrogen which is hypothesized to be due to the bacterial incorporation of nitrogen from the water terrestrial oc in the mom is incompletely replaced by marine oc within the fjords resulting in a 65 net loss of mom sediments deposited under oxic and intermittently anoxic water column conditions have organic carbon to surface area ratios oc sa ranging from 0 4 to 1 2 mg c m 2 similar to that of typical continental margin sediments given that temperate fjords contain an estimated 12 of the continental margin sediment deposited during the last 100 000 yr and that they bury at least a margin equivalent amount of oc either weight or surface area normalized we hypothesize that temperate fjords may contain 12 or more of the sedimentary oc buried during this time

integrating satellite observations and modern climate measurements with the recent sedimentary record an example from southeast alaska 1 assessments of climate change over time scales that exceed the last 100 years require robust integration of high quality instrument records with high resolution paleoclimate proxy data in this study we show that the recent biogenic sediments accumulating in two temperate ice free fjords in southeast alaska preserve evidence of north pacific ocean climate variability as recorded by both instrument networks and satellite observations multicore samples ew0408 32mc and ew0408 43mc were investigated with 137cs and excess 210pb geochronometry three dimensional computed tomography high resolution scanning xrf geochemistry and organic stable isotope analyses ew0408 32mc 57 162 n 135 357 w 146 m depth is a moderately bioturbated continuous record that spans ad 1930 2004 ew0408 43mc 56 965 n 135 268 w 91 m depth is composed of laminated diatom oozes a turbidite and a hypopycnal plume river flood deposit a discontinuous event based varve chronology indicates 43mc spans ad 1940 1981 decadal scale fluctuations in sedimentary br cl ratios accurately reflect changes in marine organic matter accumulation that display the same temporal pattern as that of the pacific decadal oscillation an estimated sitka summer productivity parameter calibrated using seawifs satellite observations support these relationships the correlation of north pacific climate regime states primary productivity and sediment geochemistry indicate the accumulation of biogenic sediment in southeast alaska temperate fjords can be used as a sensitive recorder of past productivity variability and by inference past climate conditions in the high latitude gulf of alaska

non pelletal glauconite from the campanian qusseir formation egypt implication for glauconitization abstract glauconitization processes proposed in the literatures include the layer lattice theory in which glauconite formed through k uptake by a detrital smectite precursor and the neoformation theory that does not require a smectite like precursor the non pelletal glauconite bed in the uppermost part of the campanian qusseir formation at the abu tartur area and the underlying smectite rich beds provided a potential example for the glauconitization process the glauconite occurs as fine clayey moderately hard and homogeneous bed ranges in thickness from 2 to 3 m under the optical microscope glauconite occurs in a unique morphology as very fine green clayey matrix which differs from the typical pelletal shape of many glauconites under the scanning electron microscope it appears as dense uniform and very fine flakes that are composed of si al fe and k x ray diffraction analysis of both bulk samples and clay fractions indicates that the glauconite bed is composed entirely of glauconite geochemical analysis suggested that the investigated glauconites belong to the 2nd stage of the maturity scale i e moderate maturity or they can be alternatively ranked as evolved chondrite normalized ree patterns exhibit lree enrichment relative to hree la yb n ratios vary from 5 to 8 and slightly negative eu anomalies eu eu from 0 7 to 0 8 clay beds that underlie the glauconite bed are composed of two types of smectites smectite of low k 2 o and fe 2 o 3 contents and smectite of high k 2 o and fe 2 o 3 contents smectite of low k 2 o and fe 2 o 3 contents is considered in this study as the initial precursor of glauconite while smectite of high k 2 o and fe 2 o 3 represents the transitional phase between smectite and glauconite this in turns supports the layer lattice theory in which glauconite formed by k diffusion to a detrital smectite precursor from the sea water due to transgression absence of mixed layer minerals suggests that the diffusion process was active and continuous until reaction completion was reached i e formation of glauconite maturity and ree patterns suggest the possible formation of the studied glauconite probably at shelf environment at approximately 100 m water depth the occurrence of glauconite indicates a marine invasion of the upper part of the qusseir formation which was considered previously as non marine sediments

geomorphic tectonic control of sediment discharge to the ocean the importance of small mountainous rivers analysis of data from 280 rivers discharging to the ocean indicates that sediment loads yields are a log linear function of basin area and maximum elevation of the river basin other factors controlling sediment discharge e g climate runoff appear to have secondary importance a notable exception is the influence of human activity climate and geology on the rivers draining southern asia and oceania sediment fluxes from small mountainous rivers many of which discharge directly onto active margins e g western south and north america and most high standing oceanic islands have been greatly underestimated in previous global sediment budgets perhaps by as much as a factor of three in contrast sediment fluxes to the ocean from large rivers nearly all of which discharge onto passive margins or marginal seas have been overestimated as some of the sediment load is subaerially sequestered in subsiding deltas before the proliferation of dam construction in the latter half of this century rivers

asian jet waveguide and a downstream extension of the north atlantic oscillation abstract anomalous atmospheric fields associated with the north atlantic oscillation nao are analyzed on interannual and intraseasonal time scales in order to examine the extent to which the nao is a regional phenomenon analyses on the interannual time scale reveal that the nao signal is relatively confined to the euro atlantic sector in december while it extends toward east asia and the north pacific in february the difference is most clearly seen in the meridional wind anomaly which shows a wave train along the asian jet collocated with an anomalous vorticity source near the jet entrance diagnoses using a linear barotropic model indicate that this wave train is interpreted as quasi stationary rossby waves trapped on the asian jet waveguide and effectively excited by the anomalous upper level convergence over the mediterranean sea it is found that when the nao accompanies the mediterranean convergence mc anomaly most frequently seen in february the nao indeed has a much wider horizontal str

spatial and temporal variations in early diagenetic organic matter oxidation pathways in lower jurassic mudstones of eastern england abstract the lower liassic succession of the east midlands platform eastern england comprises shallow marine mudstones and oolitic ironstones in these sediments temporal and spatial variations in the relative importance of early diagenetic anaerobic organic matter oxidation pathways are recorded the ironstones are stratigraphically condensed and were deposited upon the market weighton swell mws a topographic high in the basin in shallow water and high energy conditions at times of low relative sea level at times of higher sea level stratigraphically condensed mudstones were deposited upon the mws away from the mws stratigraphically expanded mudstones were deposited throughout the lower liassic the ironstones contain berthierine ooids and pore filling cement and siderite pore filling cement with rare pyrite replacing berthierine and siderite mudstones deposited away from the mws contain pyrite as the sole early diagenetic iron mineral contrastingly mudstones deposited upon the mws contain both early diagenetic pyrite and mn rich siderite the presence of berthierine and siderite in the ironstones indicates that sulphide was absent from early diagenetic pore waters and that fe iii reduction dominated anaerobic organic matter oxidation in contrast in mudstones deposited away from the mws the presence of pyrite indicates that sulphate reduction was a predominant pathway for anaerobic organic matter oxidation in mudstones deposited upon the mws the presence of both pyrite and mn rich siderite suggests that both sulphate reduction and fe iii reduction were important during early diagenesis it is proposed that this spatial and temporal variation in relative importance of early diagenetic anaerobic organic matter oxidation reactions was a result of variation in physical sedimentary parameters sediment accumulation rate and energy of environment at times of low net sediment accumulation rates in shallow water high energy environments suboxic diagenesis fe iii and mn iv reduction dominated giving rise to the characteristic berthierine siderite ironstone assemblage at times of higher sedimentation accumulation rates in deeper lower energy environments sulphate reduction dominated leading to pyrite formation at intermediate conditions fe iii mn iv and sulphate reduction were all important leading to precipitation of both pyrite and mn rich siderite

early diagenesis and its relationship to depositional environment and relative sea level fluctuations upper cretaceous marshybank formation alberta and british columbia early diagenesis of the upper cretaceous late coniacian to early santonian marshybank formation was controlled by depositional environment composition of depositional water fe and organic content of the sediment sedimentation rate proximity to the shoreline and influx of meteoric water related to relative sea level fall five depositional environments each characterized by a distinct early diagenetic mineral assemblage have been recognized offshore shelf sediments that were deposited in a dysaerobic environment are characterized by abundant framboidal pyrite and rare septarian concretions composed of early calcite and siderite intense sulphate reduction promoted by the dysaerobic depositional water was the primary influence on early diagenesis offshore shelf sediments deposited under aerobic conditions are characterized by abundant concretions composed of two generations of siderite s1 and s2 in this environment methanogenesis rather than sulphate reduction was more important early diagenesis of the inner shelf sands was generally limited however in sands deposited proximal to the shoreline mixing of marine and meteoric waters promoted crystallization of fe rich chlorite and siderite the shoreface was characterized by dissolution of detrital minerals in the upper portion and precipitation of kaolinite or illite smectite in the lower portion in the coastal plain environment brackish water and early reducing conditions resulted in formation of abundant euhedral pyrite ankerite rather than siderite is the typical early diagenetic carbonate the 18o values of the earliest cements i e early calcite siderite s1 inner shelf siderite indicate crystallization from a low 18o marine derived porewater assuming crystallization at 25 c a 18o value of about 7 smow can be estimated for the seaway during marshybank formation time similar calculations for the overlying dowling member puskwaskau formation suggest that the 18o value of the seaway increased to about 4 smow consistent with its transgressive nature very low 18o values are exhibited by siderite s2 these results indicate crystallization during intermediate diagenesis 60 c from meteoric water 15 smow that entered the marshybank formation during sea level lowstand

compound specific radiocarbon dating of the varved holocene sedimentary record of saanich inlet canada 1 the radiocarbon contents of various biomarkers extracted from the varve counted sediments of saanich inlet canada were determined to assess their applicability for dating purposes calibrated ages obtained from the marine planktonic archaeal biomarker crenarchaeol compared favorably with varve count ages the same conclusion could be drawn for a more general archaeal biomarker gdgt 0 although this biomarker proved to be less reliable due to its less specific origin the results also lend support to earlier indications that marine crenarchaeota use dissolved inorganic carbon dic as their carbon source the average reservoir age offset r of 430 years determined using the crenarchaeol radiocarbon ages varied by 110 years this may be caused by natural variations in ocean atmosphere mixing or upwelling at the ne pacific coast but variability may also be due to an inconsistency in the marine calibration curve when used at sites with high reservoir ages

teleconnections between enso and north atlantic in an echo g simulation of the 1000 1990 period 1 the north atlantic sea level pressure anomalies slpa associated with el nino southern oscillation enso have been analyzed in a quasi millennial 1000 1990 simulation with the echo g model in november december the enso related slpa over the north atlantic area are weak while a realistic pattern already appears over the north pacific and north america in january march the slpa over north atlantic are stronger and realistic from the north pacific to europe the aleutian low is strengthened weakened slpa are positive negative over the north central and north eastern parts of north america and slpa display a negative positive nao like pattern over north atlantic during warm cold enso events as in observations the results also confirm the existence of a strong inter event slpa associated with warm and cold enso events especially over the north atlantic while the relationship is stationary at multidecadal timescales it seems that neither the intensity nor geographical longitude of the equatorial pacific sea surface temperature anomaly ssta and intensity of tropical atlantic ssta nor the volcanic forcing simply introduced here as a decrease of the solar constant significantly induce an inter event variability which seems in this run mostly of atmospheric origin

stability and facies association of early diagenetic mineral assemblages an example from a jurassic ironstone mudstone succession u k abstract sedimentological and petrographic data from two lower liassic ooidal ironstones the frodingham and pecten ironstones and associated mudstones from eastern england have been collected within these ironstones early diagenetic berthierine siderite and minor glauconite have a limited lateral extent associated with an intrabasinal high the market weighton swell this mineral assemblage passes laterally and vertically into mudstones and silty mudstones within which pyrite is the dominant early diagenetic iron mineral the ironstones are stratigraphically condensed having experienced low net sediment accumulation rates and shallow high energy conditions thermodynamic considerations indicate that berthierine and siderite should be stable in anoxic environments where sulfide activity is negligible pyrite is rare within the ironstones suggesting that sulfate reduction was a negligible process during ironstone formation where pyrite is present it postdates berthierine and siderite indicating that sulfate reduction may have been a later process in some beds we propose that berthierine and siderite were precipitated during suboxic diagenesis where sulfate reduction was inhibited and iron reduction was the dominant process of organic matter oxidation suboxic diagenesis resulted from the extended periods of physical and biological sediment reworking during ironstone deposition which favored the oxidation of iron minerals and aerobic egradation and loss of organic matter berthierine formed during early suboxic diagenesis at the expense of detrital clays and iron oxides during later suboxic diagenesis pore water bicarbonate activities increased leading to siderite precipitation early glauconite also formed in places and it seems likely that it formed close to the oxic suboxic interface the predominance of pyrite in the mudstones indicates that sulfate reduction was the major process of organic matter oxidation during early diagenesis

phase asymmetric downstream development of the north atlantic oscillation and its impact on the east asian winter monsoon 1 the phase asymmetry in a downstream pattern of the north atlantic oscillation nao is examined during boreal winter time we compared the downstream anomaly patterns associated with the positive and negative persistent nao events over several days both phases of the persistent nao events accompany quasi stationary wave trains in downstream upper levels however a distinct low level anomaly appears only for the negative persistent nao events the low level anomaly migrates eastward as a surface anticyclone that is confined to the low troposphere a few days later the surface anticyclone reaches central siberia and induces cold advection over east asia therefore the phase dependent downstream development of the nao expands the impact of the nao to the east asian region we also discuss the possible interaction between the upper and lower level anomalies a necessary condition for the amplification of the siberian high

early diagenetic phosphate cements in the albian condensed glauconitic limestone of the tatra mountains western carpathians early diagenetic phosphate cements are described from the albian condensed glauconitic limestone of the tatra mountains western carpathians with regard to their macro and micromorphology distribution classification and genesis the cements occur within stratigraphically condensed semi pelagic foramini feral glauconitic layers and are associated with mature hardgrounds within the tatra albian limestone phosphate cement fabrics consist of crypto to microcrystalline carbonate fluorapatite and they occur as i rim envelopes ii infillings of intraparticle porosity iii rim cement iv multiple rim cement v palisade fabric and vi cluster cement micromorphological variability of the cement fabrics results from varying texture of the cemented sediment the nature of original porosity as well as from presence of associated microbial fabrics the microbial fabrics are interpreted as fossilized coccoid cyanobacteria phosphate cementation developed under peculiar early diagenetic conditions within semi closed microenvironments rich in organic matter in the marine phreatic environment the cementation contributed to the formation of phosphatic fossils and hardgrounds the accretion of the cements was due to concentration of biologically uptaken phosphorus near the sediment water interface enrichment of pore fluids with respect to phosphate and its precipitation within restricted microenvironments phosphate cementation post dated seafloor formation of pelletal glauconite but predated partial decomposition of organic matter as well as dissolution or neomorphism of aragonite and high mg calcite phosphate cementation occurred on a carbonate platform following the submersion of urgonian reefal build ups episodes of phosphate cementation were repeated during the sedimentation of the tatra albian limestone as a response to rapid relative sea level rises and increased influence of nutrient rich tethyan waters

determination of the content and distribution of fixed ammonium in illite smectite by x ray diffraction application to north sea illite smectite a new x ray diffraction method for the determination of the amount and distribution of fixed nht in illite smectite has been developed illite smectite was saturated with k and heated at iso c the 002 and 005 reflections were recorded with steps of 0 01028 and the experimental d values and the values for full width at half height fwhh were determined using a peak profile fitting procedure peak profiles were calculated with the newmod program for illite structures having different amounts of nh and different patterns for the distribution of nh in interlayers for upper jurassic illite smectite from north sea oil source rocks the amount and the distribution of nh in illite interlayers were determined by comparing the experimental values for doo5 and fwhh with the values calculated for the selected illite structures the amounts of nh determined in this manner correlate well with the amounts determined by an isotopic dilution method the results demonstrate that these illite smectite samples have k end member illite and nh4 endmember illite tobelite layers and that the illite layers formed during diagenesis and oil generation actually are tobelite layers

carbon cycling and burial in new zealand s fjords understanding carbon cycling in continental margin settings is critical for constraining the global carbon cycle here we apply a multiproxy geochemical approach to evaluate regional carbon cycle dynamics in six new zealand fjords using carbon and nitrogen concentrations and isotopes lipid biomarkers and redox sensitive element concentrations we show that the new zealand fjords have carbon rich surface sediments in basins that promote long term storage i e semirestricted basins with sediment accumulation rates of up to 4 mm yr 1 using 13c distributions to develop a mixing model we find that organic carbon in fjord sediments is well mixed from marine and terrestrial sources in down fjord gradients this is driven by high regional precipitation rates of 6 m yr 1 which promote carbon accumulation in fjord basins through terrestrial runoff in addition we have identified at least two euxinic subbasins based on uranium molybdenum iron and cadmium enrichment that contain 7 organic carbon because the strength and position of the southern hemisphere westerly winds control precipitation and fjord circulation carbon delivery and storage in the region are intimately linked to westerly wind variability we estimate that the fjord region 759 km2 may be exporting up to 1 4 107 kgc yr 1 outpacing other types of continental margins in rates of carbon burial by up to 3 orders of magnitude

optimized sequential extraction for carbonates quantification and δ13c analysis of calcite dolomite and siderite siderite is present in diverse types of rocks and sediments but its quantification is cumbersome when present in relatively low contents a new analytical method for the sequential separation of different carbonate phases is presented the separation quantification and characterization of the carbonates is based on different kinetic reactions during acid digestion in combination with monitoring the solution composition and the concomitant release of co2 trapping the released gasses permits the isotopic characterization 13c of the different phases based on published rate laws an idealized model was built to identify ph and temperature conditions for optimal separation of the various carbonates by taking the size distribution of carbonate particles into consideration results from the theoretical survey were implemented in an extraction scheme which was optimized and evaluated by tests on pure mineral phases and their mixtures further tests on a diverse array of sediment and rock samples validated the specificity and reproducibility of the method

the dynamics of nao teleconnection pattern growth and decay this investigation performs both diagnostic analyses with ncep ncar re analysis data and forced barotropic model calculations to examine the dynamical mechanisms associated with the growth and decay of the north atlantic oscillation nao teleconnection pattern the diagnostic calculations include projection and composite analyses of each term in the stream function tendency equation the results of the analyses reveal a complete life cycle of growth and decay within approximately two weeks the positive nao phase is found to develop after anomalous wavetrain propagation across the north pacific to the east coast of north america this contrasts with the negative nao phase which appeared to develop in situ both high frequency period 10 days transient eddy fluxes drive the nao growth after the nao anomaly attains its maximum amplitude the high frequency transient eddy fluxes continue to drive the nao anomaly in a manner that is consistent with a positive feedback process the decay of the nao occurs through both the divergence term and the low frequency transient eddy fluxes the temporal and spatial properties of the divergence term are found to be consistent with ekman pumping these results illustrate many important differences between the nao and pacific north american pna teleconnection patterns perhaps most striking being that the nao life cycle is dominated by nonlinear processes whereas the pna evolution is primarily linear in addition the relation between the nao and the zonal index is discussed copyright 2003 royal meteorological society

primary migration by oil generation microfracturing in low permeability source rocks application to the austin chalk texas fracturing of low permeability source rocks is induced by pore pressure changes caused by the conversion of organic matter to less dense fluids oil and gas these fractures increase the permeability and provide pathways for hydrocarbon migration an equation for the pressure change is derived using four major assumptions 1 the permeability of the source rock is negligibly small 0 01 d 10 20 m2 so that the pore pressure buildup by the conversion is much faster than its dissipation by pore fluid flow 2 the stress state is isotropic so that horizontal and vertical stresses are equal the source rock fails when the pore pressure equals the overburden pressure 3 the properties of the rock organic matter and fluids remain constant during oil generation this assumption is valid when the change in depth i e pressure and temperature is small 4 only two reaction rates are required for the conversions a low temperature reaction rate for the kerogen oil conversion e approx 24 kcal mol a approx 1014 m y and a high temperature reaction rate for oil gas conversion e approx 52 kcal mol a approx 5 5 1026 m y the equations for generation rate and pressure change are applied to the austin source rock by adjusting the several variables to fit geochemical data core saturations and observed levels of oil and gas production this application demonstrates that the equations are easily applied in calculating depths of primary migration for low permeability source rocks

on the three dimensional propagation of stationary waves abstract a locally applicable nonzonally averaged conservation relation is derived for quasi geostrophic stationary waves on a zonal flow a generalization of the eliassen palm relation the flux which appears in this relation constitutes it is argued a useful diagnostic of the three dimensional propagation of stationary wave activity this is illustrated by application to a simple theoretical model of a forced rossby wave train and to a northern hemisphere winter climatology results of the latter procedure suggest that the major forcing of the stationary wave field derives from the orographic effects of the tibetan plateau and from nonorographic effects diabatic heating and or interaction with transient eddies in the western north atlantic and north pacific oceans and siberia no evidence is found in the data for wave trains of tropical origin forcing by the orographic effects of the rocky mountains seems to be of secondary importance

impact of enso on the atmospheric variability over the north atlantic in late winter role of transient eddies abstractthe dynamical mechanism for the late winter teleconnection between el nino southern oscillation enso and the north atlantic oscillation nao is examined using the output from a 2000 yr integration of a coupled general circulation model gcm the coupled model captures many salient features of the observed behavior of both enso and nao as well as their impact on the surface climate in late winter both the observational and model data indicate more occurrences of negative phase of nao in late winter during el nino events and positive nao in la nina episodes the potential role of high frequency transient eddies in the above teleconnection is diagnosed during el nino winters the intensified transient disturbances along the equatorward shifted north pacific storm track extend their influences farther downstream the eddy induced negative height tendencies are found to be more coherent and stronger over north atlantic than that over north pacific these negative height tendencies over the north

petrology and palaeoenvironmental significance of glaucony in the eocene succession at whitecliff bay hampshire basin uk following the investigations of odin and others into the distribution of green granules glaucony has been widely assumed to be a reliable indicator of a fully marine open shelf environment with a low sedimentation rate we have investigated the value of glaucony as a palaeoenvironmental indicator through an investigation of the pellets and their distribution and reworking in the predominantly brackish to shallow marine tertiary sediments of the hampshire basin together with a re evaluation of the sedimentology glaucony has apparently formed in situ in all lithofacies from shallow marine to estuarine of the three highest glaucony concentrations all dominated by in situ glaucony two occur within highstand system tracts the third is at a sequence boundary several important surfaces do not have more than a few percent glaucony with very variable proportions of mature and in situ pellets the correlation between glaucony concentration and sequence stratigraphy is most obvious in the london clay and wittering formations where least reworking of pellets has occurred in the barton group there are no major concentrations of glaucony at any of the important stratal surfaces we believe this more random glaucony distribution is due to limited glaucony formation and reworking of older glaucony in these sediments ideal conditions for glaucony formation are interpreted to have been fully marine 10 30 m water depth a warm temperature plus low sedimentation rate with periodic winnowing to concentrate the pellets although most of these conditions for glaucony formation occurred in the selsey formation and barton group a factor or factors mitigated against glauconitization we suggest that this was lowering of the water temperature the london clay and wittering formations were deposited relatively rapidly 50 60 m ma 1 and include intervals of estuarine sedimentation both factors that we believe inhibited glaucony formation glaucony maturity reflects the minimum length of time spent in surface sediments close to the oxic sub oxic interface point count data and chemical data for glaucony indicate widespread reworking and an overall increase in reworking with time possibly due to uplift on the isle of wight monocline the apparently wide range of conditions in which glaucony will form and the frequency with which it is reworked suggest that it is a less useful indicator palaeo environmental indicator than is commonly supposed

planetary wave breaking and nonlinear reflection seasonal cycle and interannual variability abstract forty six years of daily averaged ncep ncar reanalysis data are used to identify the occurrence of planetary wave breaking pwb in the subtropical upper troposphere as large amplitude waves propagate into the subtropics where the zonal flow is weak they may break pwb is diagnosed by observing the large scale meridional overturning of potential vorticity pv contours on isentropic surfaces near the subtropical tropopause pwb occurs most often during summer and almost exclusively over the subtropical ocean basins in the northern hemisphere the seasonal evolution of the zonal flow and the associated latitudinal pv gradient regulates the location and frequency of pwb significant interannual variability in pwb is associated with well known modes of climate variability one of the most interesting dynamical consequences of pwb is the possibility of nonlinear reflection poleward out of the wave breaking region modeling studies have found nonlinear reflection following pwb observations show

sources of sedimentary organic matter in the mississippi river and adjacent gulf of mexico as revealed by lipid biomarker and δ13ctoc analyses abstract changes in the organic matter om composition c n 13 c toc and lipid biomarker compounds of surface sediments 0 1 cm were examined along the dispersal pathway from mississippi river and marsh estuarine end members to the adjacent shelf and canyon regions of the gulf of mexico organic carbon content decreased fourfold from the marsh to the offshore sites with corresponding changes in organic matter sources biomarkers representing allochthonous higher plant and autochthonous algal plankton bacteria sources demonstrated regional differences in the sources of sediment organic matter som a two end member mixing model using 13 c toc indicated that c 3 vascular plant sources comprised 80 and 50 of the toc at the river and marsh sites respectively however sources of som differed in these regions with contributions of soil organic matter terrigenous plant sources dominant in the river 13 c toc 25 while marsh plants likely contributed to the enriched signatures found in the marsh sediments 13 c toc 18 allochthonous om contributions calculated from fatty acid and sterol biomarkers in the river and marsh regions 39 48 and 50 72 respectively differed from those determined using 13 c toc this was likely due to overlapping 13 c toc values for vascular plants and freshwater microalgae and the higher lipid content of the autochthonous sources although biomarkers representing terrigenous sources decreased with distance offshore they comprised approximately 17 34 of the fatty acid and sterols at even the most distal slope and canyon sites suggesting that these deeper regions could be an important sink for terrigenous carbon in contrast the shelf sites were enriched in algal material 60 78 autochthonous oc with biomarkers for diatoms dominating suggesting that terrigenous carbon is either diluted in or bypasses this region results from this study suggest that processes including hydrodynamic sorting diagenesis and variations in river flow should be considered in future studies investigating the fate of terrigenous om in coastal and shelf regions

barotropic effects on atmospheric storm tracks the effect of barotropic dynamics on atmospheric midlatitude storm tracks is investigated for the northern hemisphere winter season using both observed data analyses and linear barotropic model experiments it is shown that when the model flow is initialized with a realistic wave packet barotropic processes alone can produce key features of the observed storm track structure the author attributes this result both to the barotropic waveguide effect and to the fact that the geographical locations of barotropic growth coincide reasonably well with the baroclinic growth of the atmospheric storm track eddies this study also shows that barotropic dynamics are more relevant for storm tracks in lower latitudes than for those in higher latitudes consistent with the fact that the lower latitude storm tracks are more closely associated with the subtropical jet rather than with the polar front jet that is driven by baroclinic eddies

anatomy and origin of a cretaceous phosphorite greensand giant egypt late cretaceous epicontinental phosphorites porcelanites cherts dark coloured shales glauconitic sandstones and bioclastic and fine grained carbonate rocks in egypt are examined in terms of their overall depositional and diagenetic framework and stable isotopic and organic geochemical characteristics two main depositional realms are interpreted and correlated through sequence stratigraphic analysis 1 a shallow hemipelagic environment accompanying initial stages of marine transgression and conducive to the formation of organic carbon rich shales biosiliceous sediments and thick phosphorites and 2 a relatively high energy depositional regime accompanying sea level fall during which deltas advanced glauconites were reworked seaward and prograding oyster banks became periodically exposed to episodes of fresh water diagenesis thereby promoting solution collapse phenomena in associated cherts lenticular to massive phosphorites are viewed as the result of current winnowing and concentration of authigenic grains initially precipitated in associated reducing shales and biosiliceous sediments in eastern egypt the phosphorites form winnowed lag layers some of which may have been redeposited down slope in structural lows in the west these sands were concentrated into giant phosphorite sand waves built by reworking of penecontemporaneously deposited phosphatic muds during marine transgression carbon isotopic results substantiate interpretations from modern deposits for limitation of phosphate mineral precipitation with depth in sediments as a result of lattice poisoning however direct desorption of phosphorus to pore waters from detrital iron oxyhydroxide phases also may have been important in the cretaceous setting the iron reduced in this process being available for incorporation in glauconites the main locus for authigenic glauconite precipitation appears to be where iron fluxes from regions of lateritic weathering were highest and near the boundary between oxygenated and reduced waters this study suggests a model for the common coexistence of glauconites and phosphorites in the geological record although upwelling is often advocated as the origin of nearly all giant phosphorite deposits we suggest that some of these may have been strongly influenced by fluvially derived phosphorus borne on particulates and desorbed from these compounds upon flocculation and or reduction in bottom waters or pore waters

another look at interannual to interdecadal variations of the east asian winter monsoon the northern and southern temperature modes abstract this study investigates the causes of interannual to interdecadal variability of the east asian ea 0 60 n 100 140 e winter monsoon eawm over the past 50 yr 1957 2006 the winter mean surface air temperature variations are dominated by two distinct principal modes that together account for 74 of the total temperature variance the two modes have notably different circulation structures and sources of variability the northern mode characterized by a westward shift of the ea major trough and enhanced surface pressure over central siberia represents a cold winter in the northern ea resulting from cold air intrusion from central siberia the southern mode on the other hand features a deepening ea trough and increased surface pressure over mongolia representing a cold winter south of 40 n resulting from cold air intrusion from western mongolia the cold northern mode is preceded by excessive autumn snow covers over southern siberia mongolia whereas the cold southern mode is preceded b

geomorphologic controls on the age of particulate organic carbon from small mountainous and upland rivers 1 to assess the role that erosion processes play in governing the character of particulate organic carbon poc discharged from small mountainous and upland rivers a suite of watersheds from oregon california and new zealand was investigated the rivers share similar geology tectonic setting and climate but have sediment yields that range over 3 orders of magnitude the 14c age of the poc loads is highly correlated with sediment yield carbon isotope mass balances reveal that the rivers carry bimodal mixtures of modern plant and ancient rock derived oc at lower yields modern plant oc dominates the material delivered to the river by sheetwash and shallow landsliding with increasing yield a progressively larger part of the poc is contributed directly from bedrock erosion via deep gully incision our results support the inference that active margin watersheds are important sources of aged poc to the ocean

north atlantic oscillation sensitivity to the el nino southern oscillation polarity in a large ensemble simulation a large ensemble modeling experiment with the melbourne university general circulation model is presented thirty 17 year long independent simulations were performed all integrations were forced by the same observed sea surface temperatures obtained from the atmospheric model intercomparison project ii the simulations were analyzed to assess the sensitivity of the north atlantic oscillation nao to the el nino southern oscillation enso polarity the results show signals of the enso phases both in the mean strength of the nao as well as in its internal variability during the cold enso phase the probability density function of the nao index presents a small but positive mean value whereas it is negative during the warm enso phase also the nao variability associated with each enso phase shows a different behavior during the warm phase the probability density function of the nao index presents a larger variance and suggests a bimodality whereas no bimodality is suggested in the cold phase

partitioning of organic carbon among density fractions in surface sediments of fiordland new zealand transport of particles plays a major role in redistributing organic carbon oc along coastal regions in particular the global importance of fjords as sites of carbon burial has recently been shown to be even more important than previously thought in this study we used six surface sediments from fiordland new zealand to investigate the transport of particles and oc based on density fractionation bulk biomarker and principle component analysis were applied to density fractions with ranges of 2 5 g cm 3 our results found various patterns of oc partitioning at different locations along fjords likely due to selective transport of higher density but smaller size particles along fjord head to mouth transects we also found preferential leaching of certain biomarkers e g lignin over others e g fatty acids during the density fractionation procedure which altered lignin based degradation indices finally our results indicated various patterns of oc partitioning on density fractions among different coastal systems we further propose that a combination of particle size density fractionation is needed to better understand transport and distribution of particles and oc

the role of the cryosphere in source to sink systems abstract glacial erosion and sediment production are of interest to diverse scientific communities concerned with the interaction of climatic tectonic and surface processes that influence the evolution of orogens and with the climatic signals archived in glacigenic strata we review the current state of knowledge on the generation transfer and accumulation of glacigenic sediment from land to sea we draw from geomorphology marine geology geochronology numerical modeling of surface processes and landscape evolution and experimental and field observations of glacier erosion and deposition and the interaction of ice with its bed and the ocean boundary our primary goal is to examine glacial systems using a holistic source to sink approach with a focus on describing a how glacial motion produces sediment b how the sediments sink record the dynamic nature of glacial systems under different climatic thermal regimes c the challenges in using the sedimentary record to interpret these dynamics in space and time and d the approaches still needed to further our understanding of how ice and associated sediment fluxes respond to climatic and other perturbations the dynamic state of ice i e the ice flux and ice extent is defined differently between the source and sink communities reflecting the challenges of establishing a stratigraphic signal that volumetrically constrains glacigenic sediment production as a function of the ice response to climate advances in marine geophysics have greatly assisted our understanding of mass transfer pathways and of former ice extents as a measure of ice dynamics and have identified the primary depocenters and key lithofacies of glacial sinks sediment fluxes associated with the dynamic state of the ice are best constrained where sediment volumes derived from key lithofacies and seismic reflection isopachs can be temporally partitioned of which there are few examples rather than from discrete point measures of sediment flux that are subject to sediment transfer biases forward numerical modeling of sediment fluxes as a function of ice dynamics agree with observational data at the continental margin scale but finer time space scale ice dynamic models do not yet recreate observed ice extent or flowpaths future source to sink work in glaciated systems should focus on refining empirical relationships between ice velocity and sediment production and expand the application of existing methods to develop sediment volumes and fluxes in known depocenters of former and modern ice streams

evolution of early cenozoic marine temperatures the equator to high southern latitude sea surface and vertical temperature gradients are reconstructed from oxygen isotope values of planktonic and benthic foraminifers for the following five time intervals late paleocene early eocene early middle eocene late eocene and early oligocene paleotemperatures are calculated using standard oxygen isotope temperature equations with adjustments to account for 1 variations in sea water 18o related to changes in global ice volume over time and 2 latitudinal gradients in surface water 18o these reconstructions indicate that sea surface temperatures sst of the southern oceans in the early eocene were as high as 15 c whereas temperatures during the late paleocene and early middle eocene reached maximum levels of 10 12 c by the late eocene and early oligocene high latitude sst had declined to 6 and 4 c respectively for most of the early paleogene low latitude sub tropical temperatures remained constant and well within the range of holocene temperatures 24 ndash 25 c but by the late eocene and early oligocene declined to values in the range of 18 to 22 c the late paleogene apparent decline in tropical temperatures however might be artificial because of dissolution of near surface foraminifera tests which biased sediment assemblages toward deeper dwelling foraminifera moreover according to recent plate reconstructions it appears that the majority of sites upon which the late eocene and early oligocene tropical temperatures were previously established were located either in or near regions likely to have been influenced by upwelling global deepwater temperature on average paralleled southern ocean sst for most of the paleogene we speculate based on the overall timing and character of marine sea surface temperature variation during the paleogene that some combination of both higher levels of greenhouse gases and increased heat transport was responsible for the exceptional high latitude warmth of the early eocene

biospheric and petrogenic organic carbon flux along southeast alaska abstract holocene fjords store ca 11 12 of the total organic carbon oc buried in marine sediments with fjords along southeast se alaska possibly storing half of this oc smith et al 2015 however the respective burial of biospheric oc bio and petrogenic oc oc petro remains poorly constrained particularly across glaciated versus non glaciated systems here we use surface sediment samples to quantify the sources and burial of sedimentary oc along se alaska fjord coastal systems and conduct a latitudinal comparison across a suite of fjords and river coastal systems with distinctive oc sources our results for se alaska show that surface sediments in northern fjords north of icy strait with headwater glaciers are dominated by oc petro in contrast to marine and terrestrially derived fresh oc in non glaciated southern fjords along the continental shelf of the gulf of alaska terrestrial oc is exported from rivers using end member mixing models we determine that glaciated fjords have significantly higher burial rates of oc petro 1 1 10 3 g oc m 2 yr 1 than non glaciated fjords and other coastal systems making se alaska potentially the largest sink of oc petro in north america in contrast non glaciated fjords in se alaska are effective in burying marine oc oc bio mari 13 82 g oc m 2 yr 1 globally oc in fjord sediments are comprised of a mixture of oc petro and fresh oc bio in contrast to the pre aged oc from floodplain river coastal systems we find that there may be a general latitudinal trend in the role of fjords in processing oc where high latitude temperate glacial fjords e g yakutat bay se alaska rebury oc petro and non glacial mid latitude fjords e g doubtful sound fiordland sequester co 2 from phytoplankton and or temperate forests overall we propose that fjords are effective in sequestering oc bio and re burying oc petro based on our study we hypothesize that climate change will have a semi predictable impact on fjords oc cycling in the near future

intra annual isotopic variation in venericardia bivalves implications for early eocene temperature seasonality and salinity on the u s gulf coast abstract stable isotope compositions were determined for 166 microsamples of aragonite from the bivalve venericardia hatcheplata collected from the early eocene hatchetigbee formation in southwestern alabama these were milled from two transects one across the left valve hinge plate and one along the growth axis amplitude and spacing of about nine years of seasonal variation is very regular with peaks and troughs occurring at equal intervals and reaching consistent compositions except for some attenuation in both parameters during the last three years of life assuming an ice free world with an ocean 18o value of about 1 0 and using the aragonite water fractionation equation of grossman and ku 1986 isotope derived paleotemperatures are somewhat warmer 31 c than temperatures presently recorded anywhere on the earth s surface and exhibit significantly greater seasonality 12 c than regions with the warmest mean temperatures it is therefore likely that these very negative and extremely seasonal 18o values reflect the influence of seasonal discharge of 18o depleted river water into the eocene gulf of mexico comparison of these data with 1 mean annual temperature versus seasonal temperature variation from modern climates 2 isotopic compositions reported from coeval molluscs and 3 isotopic compositions of global meteoric precipitation and united states rivers suggest that mean annual temperature along this portion of the eocene gulf coast was in fact about 26 c and varied seasonally from a winter low of about 25 c to a summer high of 27 c differences between these temperatures and those derived from direct conversion of oxygen isotope values reflect the influence of seasonal influx of fresh 18o value of 4 7 water during deposition of this portion of the hatchetigbee formation ambient water 18o values varied between winter values of about 1 0 to less than 3 5 during the summer freshwater discharge served to seasonally depress salinity to 10 to 16 ppt along this part of the gulf coast the early eocene was perhaps the warmest time interval of the past 65 million years primarily manifest as lower equator to pole temperature gradients in this context an eocene mean annual temperature of 26 c is not much higher than modern surface water temperatures of about 24 c at 29 30 n immediately off the modern alabama coast seasonal temperature variation of 2 to 3 c about a mean of 26 c however is significantly lower than that off coastal alabama 19 to 30 c and occurs only along modern equatorial coasts at latitudes less than 19 this implies that early eocene tropical conditions extended well beyond modern latitudinal limits

depositional trends in siliciclastic deposits of the stone city transgressive systems tract middle eocene texas abstract strata exposed at stone city bluff texas contain shelf sediments deposited during progressive marine deepening from shallow water depths and then capped by a maximum flooding horizon they are part of the early bartonian np16 cook mountain transgressive systems tract exposed in the type section of the stone city member of the crockett formation this locality lies on the inner portion of a shelf transect about 175 km 110 mi shoreward of the late eocene shelf slope margin and probably never farther than 80 km 50 mi from the shoreline sedimentary structures in the sediments change upward reflecting a shift from tidal current dominated to storm dominated deposition in lower intervals tidal control is dominant the transition interval contains isolated storm sands as sheets with lenses 40 cm 15 in thick in mudstones with tidal bedding these storm beds contain teeth bone concentrates and some gravel size clasts at the bases of larger lenses in higher intervals storm deposition is dominant in all units mostly as thin distal layers of very fine sand or silt amalgamated storm deposits form larger units e g the moseley bed local hardground surfaces are developed where storm washing exposed concretionary layers or on condensed winnowed zones glauconite occurrence and siderite concretion formation are most common in the upper intervals storm deposits have dual sediment sources and contain 1 skeletal remains shells fish bone and glauconite pellets concentrated by in place winnowing or 2 fine quartzose sand washed in from shallower water settings alternation of amalgamated storm deposits and mudstone units with thin storm deposits indicate a cyclic record of storm activity

zonal asymmetry of the annular mode and its downstream subtropical jet an idealized model study abstractthis study investigates linkages between the zonal asymmetry of the annular mode am zonal pattern and the subtropical jet stj over its downstream regions of the storm track by using an idealized model observational analyses show that the am zonal patterns are more zonally asymmetric during days when the stj downstream of the storm track is unusually strong and vice versa in the idealized model the stj downstream of the storm track is varied by introducing an additional zonally localized tropical heating the model s am variability exhibits a nearly zonally uniform structure when there is no or only weak tropical heating however the signatures of the am are locally strengthened in the heating sector thus the am zonal pattern is zonally asymmetric when the tropical heating is large enough to create a strong stj the model results also show that the percentage of the variance explained by the am the persistence of the am index and the intensity of eddy feedback are also increased when t

rapid wastage of alaska glaciers and their contribution to rising sea level we have used airborne laser altimetry to estimate volume changes of 67 glaciers in alaska from the mid 1950s to the mid 1990s the average rate of thickness change of these glaciers was 0 52 m year extrapolation to all glaciers in alaska yields an estimated total annual volume change of 52 15 km 3 year water equivalent equivalent to a rise in sea level sle of 0 14 0 04 mm year repeat measurements of 28 glaciers from the mid 1990s to 2000 2001 suggest an increased average rate of thinning 1 8 m year this leads to an extrapolated annual volume loss from alaska glaciers equal to 96 35 km 3 year or 0 27 0 10 mm year sle during the past decade these recent losses are nearly double the estimated annual loss from the entire greenland ice sheet during the same time period and are much higher than previously published loss estimates for alaska glaciers they form the largest glaciological contribution to rising sea level yet measured

mudrock hosted carbonate concretions a review of growth mechanisms and their influence on chemical and isotopic composition existing interpretations of cement textures and isotopic compositions may significantly under estimate the depth and duration of concretionary growth minus cement porosities can commonly under estimate depths of concretionary growth for some or all of the following reasons i cements might not passively replace host sediment porosity ii non cement carbonate phases such as replaced bioclastic carbonate can be significant iii sediment compaction models over estimate rates of porosity loss at shallow carbon isotope data from modern sediments show that dissolved carbonate in the methanogenic zone has a continuum of values from 30 to 15 and thus overlaps 13 c depleted values normally considered characteristic of sulphate reduction many concretions previously thought to have grown entirely during sulphate reduction may therefore have continued cementation during methanogenesis indicating a deeper and more prolonged cementation history the necessary carbonate supersaturation for concretionary growth could either occur throughout the porewaters the equilibrium model or be generated in situ by organic matter decay the local equilibrium model or created where external fluids are introduced the fluid mixing model

high and low latitude types of the downstream influences of the north atlantic oscillation using reanalysis data we find that the downstream propagating quasi stationary rossby wave train associated with the north atlantic oscillation nao generally propagates along a high low latitude pathway during warm cold el nino southern oscillation enso boreal winters consistent with the different propagation directions of the nao related downstream wave train during the warm cold enso winters the nao is associated with significant 300 hpa geopotential height anomalies over eastern siberia the arabian sea the east coast of asia at around 40 n and the north pacific and the near surface air temperature perturbations associated with the nao over the high latitudes of asia are relatively strong weak based on these differences we argue that the nao has two distinct types of downstream influence a high latitude type and a low latitude type furthermore we argue that the two types of nao s downstream influence are modulated by the intensity of the subtropical potential vorticity pv meridional gradient over africa when this gradient is weak strong as in the warm cold enso winters the nao s downstream influence tends to be of the high low latitude type these results are further supported by analysis of intraseasonal nao events we separate nao events into two categories in terms of the intensity of the subtropical pv gradient over africa composites of the nao events accompanied by a weak strong subtropical pv gradient show that the nao related downstream wave train tends to propagate along a high low latitude pathway

opposing effects of reflective and nonreflective planetary wave breaking on the nao planetary wave breaking pwb over the subtropical north atlantic is observed over 45 winters december 1958 arch 2003 using ncep ncar reanalysis data pwb is manifested in the rapid large scale and irreversible overturning of potential vorticity pv contours on isentropic surfaces in the subtropical upper troposphere as breaking occurs over the subtropical north atlantic an upper tropospheric pv tripole anomaly forms with nodes over the subtropical midlatitude and subpolar north atlantic the northern two nodes of this tripole are quite similar to the spatial structure of the north atlantic oscillation nao with positive polarity nonlinear reflection is identified in approximately a quarter of all pwb events following breaking two distinct circulation regimes arise one in response to reflective events and the other in response to nonreflective events for reflective events anomalies over the north atlantic rapidly propagate away from the breaking region along a poleward arching wave train over the eurasian continent the quasi stationary wave activity flux indicates that wave activity is exported out of the atlantic basin at the same time the regional poleward eddy momentum flux goes through a sign reversal as does the polarity of the nao for nonreflective events the dipole anomaly over the north atlantic amplifies diagnostics for nonreflective events suggest that wave activity over the azores gets absorbed allowing continued enhancement of both the regional poleward eddy momentum flux and the positive nao

high rates of organic carbon burial in fjord sediments globally fjords have been hypothesized to be hotspots of organic carbon burial a global compilation of organic carbon data and sedimentation rates shows that fjords sequester twice as much carbon as other ocean regions

microbial influence on the oxygen isotopic composition of diagenetic siderite abstract numerous early diagenetic siderite concretions previously described have been interpreted as the results of microbially mediated reactions interpretation of oxygen isotope data for such material requires an understanding of the effect of temperature on fractionation processes however whilst equilibrium fractionation of oxygen isotopes between siderite and water has been measured down to 33 c extrapolation to lower temperatures may be invalid furthermore inorganic measurements may not be applicable to microbial systems the specific iron reducing microorganism geobacter metallireducens has been cultured anaerobically in the laboratory using acetate as an organic substrate and amorphous feooh as an electron acceptor the acetate is oxidised to co2 with concurrent iron reduction and extracellular siderite precipitation rhombohedral siderite crystals up to 25 m in size have been precipitated over a range of temperatures 18 40 c stable isotopic analysis of these crystals and the solutions from which they precipitate shows that this microbial precipitation of siderite has an associated isotopic fractionation different from the published equilibrium and which is not simply a function of temperature in all cases 18o values of siderite are lower than predicted by inorganic equilibrium fractionation data this may explain the numerous anomalously low 18o values reported for early diagenetic marine siderites and previously attributed to mechanisms such as mixing with meteoric water sediment water interaction recrystallisation or variable isotopic fractionation despite a lack of supporting evidence

geochemistry of early siderite cements from the eocene succession of whitecliff bay hampshire basin u k abstract siderite cements in the eocene of whitecliff bay hampshire basin u k occur in a range of depositional facies and morphological associations most siderites are associated with in situ glaucony or occur beneath conspicuous lithological breaks these associations illustrate the importance of slow deposition for early diagenetic carbonate precipitation siderite in the eocene sediments of whitecliff bay is impure and in many cases comprises zoned crystals with an overall decrease in substitution of ca mg and mn for fe from crystal core to rim trends in ca mg and mn from early to later siderite vary between samples with no evident environmental control siderite concretions without calcite cement occur only beneath lithological breaks where meteoric water may have been introduced precipitation temperatures have been calculated from siderite 18o data and are based on the assumption that precipitation occurred from seawater these temperatures are reasonable for typical microbial siderite precipitated in marine sediment but are slightly low for marine siderite where there may have been meteoric overprinting if the precipitation temperature for siderite cements is assumed from 18o data for time equivalent biogenic carbonate rather than the composition of the precipitating fluid the calculated isotopic composition of the precipitating fluid is generally compatible with the inferred marginal marine depositional environments

early diagenesis of organic matter in peru continental margin sediments phosphorite precipitation abstract pore water chemistry total dissolved co 2 nh 4 no 3 no 2 po 4 si oh 4 ca mg fe mn so 4 h 2 s and f and titration alkalinity solid phase chemistry c org p org c tot n tot f si opal and s ii and sediment characteristics porosity dry bulk density and formation factors were determined on a centimeter scale spacing in the upper 20 40 cm of sediments under intense upwelling areas on the peru continental shelf these data demonstrate that carbonate fluorapatite cfa is precipitating from pore waters in the upper few centimeters of a gelatinous mud with high organic carbon content up to 20 c org very high porosity 0 96 ml cm 3 and very low dry bulk density 3 dissolved phosphate concentrations at the sediment water interface range from 20 to 100 m orders of magnitude higher than bottom water concentrations and much higher than predicted from regeneration of organic matter the mechanism of this interfacial phosphate release is unclear but is apparently uncoupled from carbon and nitrogen metabolism and thus may be linked either to dissolution of fish debris or to the presence of a microbial mat in surficial sediments fluoride is incorporated into cfa by diffusion from the overlying seawater and carbonate ions are provided from pore water alkalinity magnesium concentrations in this reaction zone are not significantly different from those of seawater suggesting that magnesium depletion is not a necessary prerequisite for cfa precipitation the environment of precipitation is interface linked rather than driven by organic diagenesis of phosphorus deeper in the sediment most of the cores display a wide range of diagenetic characteristics below the immediate interfacial region but almost all show the precipitation signature near the interface this interface linked early diagenetic porewater environment for the precipitation of cfa explains many of the geochemical characteristics of phosphorites and provides a testable model to compare the modern phosphogenic analog with ancient phosphorite deposits two of the cores display very high solid phase phosphorus and fluoride contents reflecting the presence of apparently modern pelletal apatites