stabilization of the coupled oxygen and phosphorus cycles by the evolution of bioturbation animal burrowing and sediment mixing bioturbation began during the run up to the ediacaran cambrian boundary1 2 3 initiating a transition4 5 between the stratified precambrian6 and more well mixed phanerozoic7 sedimentary records against the backdrop of a variable8 9 global oxygen reservoir probably smaller in size than present10 11 phosphorus is the long term12 limiting nutrient for oxygen production via burial of organic carbon13 and its retention relative to carbon within organic matter in marine sediments is enhanced by bioturbation14 15 16 17 18 here we explore the biogeochemical implications of a bioturbation induced organic phosphorus sink in a simple model we show that increased bioturbation robustly triggers a net decrease in the size of the global oxygen reservoir the magnitude of which is contingent upon the prescribed difference in carbon to phosphorus ratios between bioturbated and laminated sediments bioturbation also reduces steady state marine phosphate levels but this effect is offset by the decline in iron adsorbed phosphate burial that results from a decrease in oxygen concentrations the introduction of oxygen sensitive bioturbation to dynamical model runs is sufficient to trigger a negative feedback loop the intensity of bioturbation is limited by the oxygen decrease it initially causes the onset of this feedback is consistent with redox variations observed during the early cambrian rise of bioturbation leading us to suggest that bioturbation helped to regulate early oxygen and phosphorus cycles

distribution of anthropogenic co2 in the pacific ocean 1 this work presents an estimate of anthropogenic co2 in the pacific ocean based on measurements from the woce jgofs oaces global co2 survey these estimates used a modified version of the c technique modifications include a revised preformed alkalinity term a correction for denitrification and an evaluation of the disequilibrium terms using an optimum multiparameter analysis the total anthropogenic co2 inventory over an area from 120 e to 70 w and 70 s to 65 n excluding the south china sea the yellow sea the japan east sea and the sea of okhotsk was 44 5 5 pg c in 1994 approximately 28 pg c was located in the southern hemisphere and 16 5 pg c was located north of the equator the deepest penetration of anthropogenic co2 is found at about 50 s the shallowest penetration is found just north of the equator very shallow anthropogenic co2 penetration is also generally observed in the high latitude southern ocean one exception to this is found in the far southwestern pacific where there is evidence of anthropogenic co2 in the northward moving bottom waters in the north pacific a strong zonal gradient is observed in the anthropogenic co2 penetration depth with the deepest penetration in the western pacific the pacific has the largest total inventory in all of the southern latitudes despite the fact that it generally has the lowest average inventory when normalized to a unit area the lack of deep and bottom water formation in the north pacific means that the north pacific inventories are smaller than the north atlantic

neritic and pelagic carbonate sedimentation in the marine environment ignorance is not bliss synthesis of available data allows us to define general patterns of late quaternary carbonate production and sedimentation in the global ocean during high stands of sea level the neritic and pelagic environments appear to sequester approximately similar amounts of carbonate whereas during low stands of sea level the decreased neritic zone produces and accumulates approximately an order of magnitude less carbonate assuming that global accumulation of deep sea carbonates remains more or less constant during glacially induced changes in sea level the ocean becomes depleted with respect to calcium carbonate during high stands and recharges during low stands before we can achieve a better understanding of the global carbonate system however we need a better understanding of key environments and processes a production and accumulation on continental shelves both as potential sinks accumulation and as sources export to the deep sea b a better measure of pelagic carbonate production and c late quaternary late pleistocene and holocene mass accumulation rates in the deep sea

martin brasier s contribution to the palaeobiology of the ediacaran cambrian transition martin brasier s work spanned almost the entire geological column but the origin of animals and the nature of the cambrian explosion were areas of particular interest to him martin adopted a holistic approach to the study of these topics that considered the interplay between multiple geological and biological phenomena and he sought to interpret the fossil record within the broad context of geological biogeochemical and ecological changes in the earth system here we summarize martin s main contributions to this area of research and assess the impact of his findings on the development of this field karl popper would have said that palaeontology is not real science because you can t go out and sample it i think absolutely the opposite i think this is actually where science is it s trying to guess what lies over the hill and map terra incognita when people come in and colonize that s just technology martin brasier 2013 excerpt from a phone interview in moor 2016

an oceanographic nowcast forecast system for the red sea we describe the application of a nowcast forecast system for three dimensional currents temperature and salinity to the red sea the modeling system is constructed around a high resolution 6 7 km primitive equation numerical circulation model with complete thermodynamics and an imbedded turbulence closure submodel it is coupled to near real time databases containing meteorological forecasts and remotely sensed and in situ temperature and salinity data the temperature and salinity data are ingested into the model daily using a nudged objective analysis technique because the red sea is a relatively narrow basin bounded by typically high and complex orography a single layer atmospheric boundary layer submodel has been used to increase the effective resolution of the original 40 km resolution meteorological fields by taking into account orographic steering of the low level winds in order to validate the modeling system two very complete hydrographic surveys of the red sea were undertaken and their results are described both the surveys and the modeling system nowcasts demonstrate that the circulation pattern of the red sea is variable and often composed of a series of eddies or subgyres mainly anticyclones immediately before one survey the winds tended to be along axis while just before the second they tended to be cross axis the red sea circulation was much more eddy like when the winds were cross axis by forcing the modeling system with and without orographically steered winds we were able to establish that the complex eddy structure is a response to a wind field which can be highly structured and vorticity rich because of interaction with the high and variable adjacent orography when the winds are more along axis there is less interaction with the adjacent orography and consequently there are fewer eddies in the red sea

oxygen facies and secular controls on the appearance of cryogenian and ediacaran body and trace fossils in the mackenzie mountains of northwestern canada the causes behind the appearance of abundant macroscopic body and trace fossils at the end of the neoproterozoic era remain debated iron geochemical data from fossiliferous ediacaran successions in newfoundland suggested that the first appearances correlated with an oxygenation event a similar relationship was claimed to exist in the mackenzie mountains canada although later stratigraphic studies indicated that the sections analyzed for geochemistry were incorrectly correlated with those hosting the fossils to directly connect fossil occurrences with geochemistry in the mackenzie mountains we conducted a multiproxy iron carbon sulfur and trace element geochemical analysis of stratigraphic sections hosting both the cryogenian twitya discs at bluefish creek as well as ediacaran fossils and simple bilaterian traces at sekwi brook there is no clear oxygenation event correlated with the appearance of macroscopic body fossils or simple bilaterian burrows however some change in environment a potential partial oxygenation is correlated with increasing burrow width higher in the blueflower formation data from sekwi brook suggest that these organisms were periodically colonizing a predominantly anoxic and ferruginous basin this seemingly incongruent observation is accommodated through accounting for differing time scales between the characteristic response time of sedimentary redox proxies versus that for ecological change thus hypotheses directly connecting ocean oxygenation with the appearance of macrofossils need not apply to all areas of a heterogeneous ediacaran ocean and stably oxygenated conditions on geological time scales were not required for the appearance of these avalon assemblage ediacaran organisms at least in the mackenzie mountains the appropriate facies for fossil preservation appears to be the strongest control on the stratigraphic distribution of macrofossils

eddies in the red sea a statistical and dynamical study sea level anomaly sla data spanning 1992 2012 were analyzed to study the statistical properties of eddies in the red sea an algorithm that identifies winding angles was employed to detect 4998 eddies propagating along 938 unique eddy tracks statistics suggest that eddies are generated across the entire red sea but that they are prevalent in certain regions a high number of eddies is found in the central basin between 18 n and 24 n more than 87 of the detected eddies have a radius ranging from 50 to 135 km both the intensity and relative vorticity scale of these eddies decrease as the eddy radii increase the averaged eddy lifespan is approximately 6 weeks aes and cyclonic eddies ces have different deformation features and those with stronger intensities are less deformed and more circular analysis of long lived eddies suggests that they are likely to appear in the central basin with aes tending to move northward in addition their eddy kinetic energy eke increases gradually throughout their lifespans the annual cycles of ces and aes differ although both exhibit significant seasonal cycles of intensity with the winter and summer peaks appearing in february and august respectively the seasonal cycle of eke is negatively correlated with stratification but positively correlated with vertical shear of horizontal velocity and eddy growth rate suggesting that the generation of baroclinic instability is responsible for the activities of eddies in the red sea

the evolutionary significance of a lower cambrian trace fossil assemblage from the meguma terrane nova scotia we report a diverse assemblage of trace fossils from the lower cambrian high head member of the church point formation near yarmouth nova scotia based on the presence of sharp based beds load casts and flute casts along with other sedimentological criteria the strata are interpreted to have a turbidite origin other characteristics including wrinkle structures and high fidelity of trace fossil preservation suggest that the inter episode biotope was influenced by the presence of biomats the trace fossil assemblage includes in approximate order of abundance planolites helminthopsis oldhamia chondrites gordia cladichnus psammichnites gigas treptichnus phycodes lorenzinia palaeophycus and teichichnus trace fossils are increasingly abundant upwards in the section but they are ultimately mitigated by an increase in inferred sedimentation rates the trace fossil assemblage which bears many similarities to other lower cambrian locales e g puncoviscana formation of northwest argent

the bering sea and paleoceanography abstract this paper serves as an introduction to the bering sea preceding the 14 contributed papers contained in this volume several parts of the paper are allocated for current reviews of the bering sea included in the review topics are geomorphology surface water circulation and the importance of the formation of intermediate waters representative results of previous paleoceanographic studies are also presented in particular focusing on spatial and temporal distributions of biosiliceous microfossils as well as isotopic analyses of carbon and nitrogen concerning changes in productivity and nutrients motivations behind the scientific expeditions conducted which resulted in the many papers included here are briefly discussed in order to illustrate the recent trend in paleoceanography in the bering sea and the adjacent regions brief summaries or highlights of each of the contributed papers are given in order to provide an overview of the volume

in situ calcium carbonate dissolution in the pacific ocean over the past several years researchers have been working to synthesize the woce jgofs global co2 survey data to better understand carbon cycling processes in the oceans the pacific ocean data set has over 35 000 sample locations with at least two carbon parameters oxygen nutrients cfc tracers and hydrographic parameters in this paper we estimate the in situ caco3 dissolution rates in the pacific ocean water column calcium carbonate dissolution rates ranging from 0 01 1 1 mmol kg1 yr1 are observed in intermediate and deepwater beginning near the aragonite saturation horizon in the north pacific intermediate water between 400 and 800 m caco3 dissolution rates are more than 7 times faster than observed in middle and deep water depths average 0 051 mmol kg1 yr1 the total amount of caco3 that is dissolved within the pacific is determined by integrating excess alkalinity throughout the water column the total inventory of caco3 added by particle dissolution in the pacific ocean north of 40s is 157 pg c this amounts to an average dissolution rate of approximately 0 31 pg c yr1 this estimate is approximately 74 of the export production of caco3 estimated for the pacific ocean these estimates should be considered tomore be upper limits for in situ carbonate dissolution in the pacific ocean since a portion of the alkalinity increase results from inputs from sediments less

smothering of microbial mats by macrobiota implications for the ediacara biota abstract recent advances in understanding the preservation of the soft bodied neoproterozoic ediacara biota have centred upon the role of microbes in casting the morphologies of static or dead macrobiota on the precambrian sea floor this experimental study explores the preservational effects brought about by the passive movement of dead macro organisms upon a pre established marine microbial mat under laboratory conditions this demonstrates the potential for making multiple impressions of body tissues on the surface of microbial mats by means of passive transport alone this throws doubt on the evidence for active feeding in ediacaran fossils such as dickinsonia and yorgia supplementary material methods are available at http www geolsoc org uk sup18375

assemblage palaeoecology of the ediacara biota the unabridged edition fossils of the ediacara biota offer our earliest insight into diverse macroscopic life on this planet in particular given the diversity and range of exquisite soft bodied preservation the potential for unraveling aspects of the paleobiology and paleoecology is great clearly however there can be a taphonomic overprint that dictates how complete the assemblage is new diversity data including richness and evenness from south australia is compared to previously published data from newfoundland and the white sea and is within the range of values for both modern and phanerozoic assemblages however missing from our current understanding of ediacaran ecosystems is a full description and interpretation of the many problematica structures and organic surfaces

hydraulic sediment penetration and seasonal growth of petalonamean basal discs from the vendian of ukraine abstract around the ediacaran cambrian transition about 540 million years ago marine organisms began to dig in the sediment that has resulted in its better ventilation and further expansion of infaunal life few vertical infaunal burrows are known from the precambrian and they are usually attributed to sea anemones here we show that the enigmatic ediacaran petalonamean sea pens were able to penetrate sediment for more than one centimetre depth while anchoring the body in the microbial mat their growth as evidenced by numerous well preserved basal discs from the late ediacaran lomoziv member of the mohyliv formation in podolia ukraine was under control of rhythmic sedimentation events and periodic microbial mat development size frequency distribution in classes of both the final disc size and growth retention stages show that their size increase was stepwise each discrete stage corresponds to deposition of a thin sediment layer and development of the microbial mat at its top podolia was located near the south pole in the ediacaran vendian and such rhythmic sedimentation was probably connected with the local climate seasonality

microbial origin of early animal trace fossils abstract elongate surface trails that abound in late ediacaran and early paleozoic sandstone and siltstone are often attributed to early animals these trails commonly exist on the same beds as wrinkle structures millimeter to centimeter size ridges and pits that are interpreted as evidence of the former presence of microbial mats here we show that interactions between oscillatory flow and centimetric microbial aggregates produce elongate trails on the surface of a sediment bed trails left by moving microbial aggregates share a number of characteristics with some presumed trace fossils of the earliest animals elevated edges zig zag patterns smooth curves reversals intersections with other trails series of pits and paths that terminate abruptly and restart nearby under the same flow conditions millimetric microbial aggregates generate wrinkle structures thus the interaction between flow and microbial aggregates on a sediment bed can produce a number of structures that are commonly interpreted as evidence of early animal locomotion

decadal changes in the aragonite and calcite saturation state of the pacific ocean 1 based on measurements from the woce jgofs global co2 survey the clivar co2 repeat hydrography program and the canadian line p survey we have observed an average decrease of 0 34 yr 1 in the saturation state of surface seawater in the pacific ocean with respect to aragonite and calcite the upward migrations of the aragonite and calcite saturation horizons averaging about 1 to 2 m yr 1 are the direct result of the uptake of anthropogenic co2 by the oceans and regional changes in circulation and biogeochemical processes the shoaling of the saturation horizon is regionally variable with more rapid shoaling in the south pacific where there is a larger uptake of anthropogenic co2 in some locations particularly in the north pacific subtropical gyre and in the california current the decadal changes in circulation can be the dominant factor in controlling the migration of the saturation horizon if co2 emissions continue as projected over the rest of this century the resulting changes in the marine carbonate system would mean that many coral reef systems in the pacific would no longer be able to sustain a sufficiently high rate of calcification to maintain the viability of these ecosystems as a whole and these changes perhaps could seriously impact the thousands of marine species that depend on them for survival

pore water evolution during sediment burial from isotopic and mineral chemistry of calcite dolomite and siderite concretions abstract coal measures often contain concretions segregations of diagenetic minerals originally formed within unconsolidated sediments three different types calcite pyrite dolomite pyrite and siderite occurring spatially quite close together in the central pennine region of england vary widely in carbon isotope composition 10 35 13c 21 49 and in major cation chemistry ca mg fe mn within some siderite concretions very high mn fe ratios were found in central subsamples these were also most enriched in 13c the fe mg ratio decreases systematically from centre to edge early shallow to deeper later precipitation the calcite pyrite and dolomite pyrite concretions developed completely prior to significant burial both have high mn fe ratios but negative 13c values calcite 21 49 dolomite 8 67 to 10 48 all of these patterns can be equated precisely with theories of pore water evolution developed on the basis of geochemical investigations of modem sediments microbial processes sulphate reduction methanogenesis contributed significantly as did thermal decarboxylation to siderite precipitated at considerable burial depth mn iv and fe iii acted differentially as oxidants producing co2 and increasing alkalinity the interplay of fresh and marine depositional waters is seen most obviously in the presence or absence of sulphate reduction this controlled mineral type iron sulphide or carbonate as well as isotopic and mineral chemistry

on the origin of a chain of eddies in the gulf of eilat aqaba abstractthe gulf of eilat aqaba is a terminal elongated basin that exchanges water with the northern red sea via the straits of tiran this study used energy budgets of mean kinetic energy mke and eddy kinetic energy eke differentiated by a simple horizontal averaging filter instability analysis and numerical simulations to study the horizontal circulation of the gulf which is characterized by the existence of a chain of eddies along its main axis the kinetic energy is predominantly in the form of eke energy conversion between mke and eke is negligible where the main sources for both energy reservoirs are the conversions from the available potential energy ape this term is balanced by the work done by pressure at the straits in case of mke and by dissipation in the case of eke the mke balance represents the coupling between the exchange flow at the straits and the wintertime dense water formation the dense water exits through the straits while sinking adiabatically along the gulf the stro

evolutionary relationships within the avalonian ediacara biota new insights from laser analysis abstract we report new high resolution laser scanning of the type material for the earliest complex ediacaran genera charnia bradgatia charniodiscus and ivesheadia from charnwood uk and compare these with beothukis mistakensis gen et sp nov and the recently described taxa charnia wardi charnia antecedens and fractofusus spp from broadly coeval strata in newfoundland we use the laser and other techniques to map the similarities and differences in morphology between these ediacaran rangeomorphs key features are suggested to include the number of growth axes the number and placement of growth tips the presence of radiating or subparallel axes for the first and higher order branches the extent of displayed or undisplayed leaf like rangeomorph9 architecture and the extent of furling of the margins of these leaf like elements these features are then used to propose suggested homologies between these taxa leading to a preliminary phylogenetic hypothesis for the evolution of the avalonian ediacara biota

two layer hydraulics a functional approach a new approach for investigating two layer hydraulic exchange flows in channels is introduced the approach is based on the functional formalism of gill 1977 and applied to the flow through a contraction in width and to flow over a simple sill the sill geometry is an extension of that looked at by earlier workers in particular farmer armi 1986 who used a froude number plane approach in the present paper a simple relationship between the composite froude number and the hydraulic functional is derived though the functional approach may also be applied to channels where a froude number is not readily defined the ability to trace roots of this functional from one reservoir to the other is a prerequisite for the flow to be realizable two hydraulic transitions are required for the flow to be fully controlled and the exchange flow rate to be maximal if only one hydraulic transition is present the flow is governed by the conditions in one of the reservoirs and the exchange flow rate is found to be submaximal the flow along a channel is found to be very sensitive to small departures from symmetry about a horizontal plane the response of the interface to the introduction of a net barotropic flow is found to be a discontinuous function of the strength of the forcing for some range of sill heights

decadal changes in the caco3 saturation state along 179 e in the pacific ocean 1 to assess degrees of ocean acidification we mainly investigated decadal changes in the saturation state of seawater with respect to aragonite arg which is a more vulnerable mineral form of caco3 along the 179 e meridian woce p14n in the pacific ocean we found a maximum decrease of arg of 0 48 0 034 a 1 at 200 300 dbar isopycnal surfaces of 24 0 25 8 kg m 3 at 20 n between 1993 and 2007 the saturation horizon rose by 17 dbar 1 2 dbar a 1 at latitudes 10 n 50 n although arg mostly reflected changes in normalized dissolved inorganic carbon nct it was larger than could be explained by anthropogenic co2 storage alone decomposition of nct revealed that argwas enhanced by approximately 50 by a non anthropogenic co2 contribution represented by changes in apparent oxygen utilization our results suggest that ocean acidification can be temporarily accelerated by temporal changes in oceanic conditions

stepwise seasonal restratification and the evolution of salinity minimum in the gulf of aqaba gulf of eilat 1 the gulf of aqaba gulf of eilat is a terminal elongated basin that exchanges water with the northern red sea via the straits of tiran the gulf s hydrography exhibits strong seasonal variability with deep mixing in february march and stable stratification afterward recently using an oceanic model that simulated the seasonal conditions in the gulf we demonstrated that a relatively large advected heat and water influx through the straits are responsible for most of the observed rises in temperature and increase in volume of the surface layer during the restratification phase april august here we investigate the restratification process in the surface layer by using the same oceanic model with the aid of passive tracers that allow tracking the water entering through the straits as it flows northward we show that the time varying surface hydrography in the northern red sea has a significant influence on the seasonal hydrographic conditions in the gulf the northern red sea water warms monotonically during the restratification phase as a result new water that enters the gulf during this phase is warmer than the water that entered previously and therefore the stratification is built up gradually layer by layer the phase difference between minimal salinity may and maximal temperature september in the northern red sea is responsible for the evolution of subsurface salinity minimum level along the gulf we also explain the transition to a four layer exchange flow between august and november

shallow depth caco3 dissolution evidence from excess calcium in the south china sea and its export to the pacific ocean national basic research program of china 973 program 2009cb421201 2009cb421206 national science foundation of china nsfc 40821063 90711005 south china sea institute of oceanology the chinese academy of sciences

an oceanic general circulation model ogcm investigation of the red sea circulation 2 three dimensional circulation in the red sea 1 the three dimensional circulation of the red sea is studied using a set of miami isopycnic coordinate ocean model micom simulations the model performance is tested against the few available observations in the basin and shows generally good agreement with the main observed features of the circulation the main findings of this analysis include an intensification of the along axis flow toward the coasts with a transition from western intensified boundary flow in the south to eastern intensified flow in the north and a series of strong seasonal or permanent eddy like features model experiments conducted with different forcing fields wind stress forcing only surface buoyancy forcing only or both forcings combined showed that the circulation produced by the buoyancy forcing is stronger overall and dominates the wind driven part of the circulation the main circulation pattern is related to the seasonal buoyancy flux mostly due to the evaporation which causes the density to increase northward in the basin and produces a northward surface pressure gradient associated with the downward sloping of the sea surface the response of the eastern boundary to the associated mean crossbasin geostrophic current depends on the stratification and b effect in the northern part of the basin this results in an eastward intensification of the northward surface flow associated with the presence of kelvin waves while in the south the traditional westward intensification due to rossby waves takes place the most prominent gyre circulation pattern occurs in the north where a permanent cyclonic gyre is present that is involved in the formation of red sea outflow water rsow beneath the surface boundary currents are similarly intensified southward undercurrents that carry the rsow to the sill to flow out of the basin into the indian ocean index terms 4243 oceanography general marginal and semienclosed seas 4255 oceanography general numerical modeling 4532 oceanography physical general circulation keywords red sea marginal sea oceanic general circulation model water mass formation

evidence for cnidaria like behavior in ca 560 ma ediacaran aspidella the first appearance of animals in the geological record is a matter of continuing debate how deep were the roots of the cambrian explosion molecular clock estimates indicate that the deepest divergences of the metazoa had occurred by the ediacaran period 635 541 ma yet evidence of animal activity from well below the ediacaran cambrian boundary has been rare and often questionable meanwhile the ediacaran macrobiota has remained enigmatic as emphasized by recent controversial claims that south australia ediacaran forms were not marine animals at all but land based lichens and microbial colonies here we report evidence for animal like behavior in a submerged setting in a key ediacaran form aspidella terranovica billings 1872 a discoidal fossil from the ca 560 ma fermeuse formation of newfoundland canada we describe sedimentary fabrics indicating progressive vertical movement of an organism through sediment in response to an aggrading sediment water interface such equilibrium traces are familiar from the phanerozoic and are observed in partially buried marine animals such as tube anemones today furthermore horizontal trails closely comparable to trails previously described from 565 m y old mistaken point newfoundland are now linked to aspidella our findings constitute evidence of both vertical and horizontal movement in a key ediacaran taxon consistent with an animal of cnidarian grade moreover because aspidella is also reported from the rawnsley quartzite of south australia our evidence conflicts with the proposed radical interpretation of that ediacaran fossil assemblage we demonstrate that at least some ediacaran forms were probably early animals and that they lived underwater

biogeochemical changes across the ediacaran cambrian transition in south china abstract the late neoproterozoic successions of south china comprise some of the most complete and well preserved records of the ediacaran cambrian transition the articles in this special issue provide a snapshot of ongoing research that is helping us to understand early stages in the development of the modern earth system these studies illustrate the transitional character of the ediacaran cambrian interval from the evolution and early extinctions of the first bilaterian metazoans during the ediacaran period to their dominance of pelagic and benthic realms by the end of the early cambrian geochemical data reveal a noisy transition of increasing baseline 13c values punctuated by extreme isotopic oscillations it is evident that highly negative 13c values and large amplitude 13c swings ceased once modern marine ecosystems had become firmly established by 520 ma we postulate that sub surface bioturbation helped to strengthen the relationship between benthic oxidation state and p retention thus tightening an important negative feedback that helps to stabilize productivity climate and oxygen levels in the modern earth system the disappearance of negative excursions after 520 ma might also suggest a key role for methanogenesis which would have declined following the rise of in sediment sulphur cycling due to bioturbation further insight into this fascinating interval is needed before we can disentangle the complex interactions between biological evolution and biogeochemical cycling during the emergence of the modern earth system

a modeling study of circulation and eddies in the persian gulf abstract the circulation and mesoscale eddies in the persian gulf are investigated using results from a high resolution 1 km hybrid coordinate ocean model hycom the circulation in the persian gulf is composed of two spatial scales basin scale and mesoscale the progression of a cyclonic circulation cell dominates the basin scale circulation in the eastern half of the gulf 52 55 e during march july this is primarily the consequence of density driven outflow inflow through the strait of hormuz and strong stratification a northwestward flowing iranian coastal current icc 30 40 cm s 1 between the strait of hormuz and north of qatar 52 e forms the northern flank of the cell between july and august the icc becomes unstable because of the baroclinic instability mechanism by releasing the potential energy stored in the cross shelf density gradient as a result the meanders in the icc evolve into a series of mesoscale eddies which is denoted as the iranian coastal eddies ice the ice have a

the oldest evidence of bioturbation on earth detailed study of the khatyspyt formation in arctic siberia has shown that contrary to common expectations the earliest ichnofabric is of late ediacaran age records a food seeking behavior and is found in a distal carbonate ramp setting where it co occurs with fossils of avalon type ediacaran soft bodied organisms preserved depth of bioturbation reaches 5 cm the ichnofabric solely comprises nenoxites the oldest known meniscate trace fossil which is interpreted as burrows with terminal backfill structure formed as a result of active displacement of sediment to form a tunnel within the substrate followed by emplacement of the material behind the animal as it progressed through the sediment in addition to being the most reliable paleontological evidence for the existence of bilaterians at ca 555 ma the late ediacaran bioturbation is regarded as a key step in the escalatory engineering of phanerozoic ecospace leading to sudden diversification of macroscopic organisms and macrocommunities

volcanosedimentary paleoenvironments of ediacaran fossils in newfoundland a new perspective on paleoenvironments of ediacaran fossils of the upper conception group newfoundland comes from geochemical and sedimentological study of volcanic tuffs and sedimentary rocks tuffs in the conception group have major and trace element compositions and u pb ages comparable with those of source volcanics on the nearby burin and bonavista peninsulas and the islands of st pierre and miquelon loss of silica and alkalies in some ashes indicates weathering on land not marine diagenesis volcanic crystal and lapilli tuffs fail to show grading and have lapilli and highly vesicular scoria scattered in a fine grained matrix and so they were deposited on land not in water these as well as block and ash flows volcanic spindle bombs and degassing features are evidence of eruptions from nearby subaerial volcanic edifices the fossiliferous conception group accumulated within a forearc basin formed on continental crust inboard of the holyrood horst and uplifted as part of an ancient subduction complex or accreted terrane like analogous forearc basins in oregon washington southern chile and japan the conception group includes not only marine bay turbidites but also a variety of intertidal and terrestrial tsunamites seismites tempestites and paleosols traditional marine turbidite models explain deposition of the mall bay lower drook and lower briscal formations of the conception group but the gaskiers upper drook upper briscal and mistaken point formations were deposited in coastal plains and intertidal zones paleoenvironments of vendobiont fossils preserved in life position in newfoundland were terrestrial to marginal marine not deep sea

the final miocene carbonate crash in the atlantic assessing carbonate accumulation preservation and production abstract in many palaeoceanographic studies low carbonate contents in neogene deep sea sediments are interpreted as dissolution events related to prominent shifts in intermediate and deep water circulation in the middle to late miocene such carbonate crash events were a widespread phenomenon throughout the world s ocean basins however low carbonate contents may also derive from terrigenous dilution and carbonate production changes in surface waters as shown for late miocene records of the south atlantic diester haass et al 2004 westerhold et al 2005 in order to contribute to solve this question we investigated the youngest of the miocene crash events 10 5 ma to 9 0 ma at a prominent key location of global deep water circulation i e the equatorial atlantic ceara rise depth transect odp sites 926 927 and 928 by analysing different carbonate preservation proxies like carbonate content silt grain size parameters sand content fragmentation index and mass accumulation rates we were able to quantify dissolution dilution and production and to assess previous conflicting interpretations critical evaluation of the different dissolution proxies and comparison to former studies revealed that silt preservation proxies do not entirely reproduce the depth dependant dissolution in the miocene sediments as indicated by foraminifer fragmentation in the investigated late miocene time slice three minima of carbonate accumulation were detected the predominant control on these events changed from dissolution of carbonate to lowered production the last event at 9 6 ma is accompanied by an increased preservation but reduced carbonate accumulation during this time the first prominent pulses of northern component water ncw occurred sourced most probably from the labrador sea this may be understood as a first short term precursor of long time persistent and much stronger ncw production that is characteristic for younger periods and marks the turnover to the modern type of basin to basin fractionation between the atlantic and pacific furthermore preservation trends of caribbean and ceara rise records were in phase in contrast to former hypotheses that suggested antithetical preservation during carbonate crash events the similarity of the preservation records in the studied ocean basins in conjunction with the inconsistency in timing of the cc events and proposed ncw estimates indicates that changes in the carbon cycle other than dissolution controlled the cc events prior to 9 9 ma

temporal and bathymetric resolution of nautiloid death assemblages in stratigraphically condensed oozes new caledonia cephalopod shells can be affected by postmortem transport and biostratigraphic condensation but direct estimates of the temporal and spatial resolutions of cephalopod assemblages are missing amino acid racemisation calibrated by 14c demonstrates a centennial scale time averaging 500 years of nautilus macromphalus in sediment starved epi and mesobathyal pelagic environments the few shells that are thousands of years old are highly degraded the median occurrence of dead shells is at 445 m depth close to the 300 400 m depth where living n macromphalus are most abundant therefore dead shells of this species accumulate at a centennial temporal resolution and with excellent bathymetric fidelity dead nautilus shells exist for only a few hundred years on the seafloor in contrast to the biostratigraphically condensed mixture of extant foraminifers and foraminifers that went extinct during the pleistocene cephalopod shells that do not show any signs of early diagenetic cementation are unlikely to be biostratigraphically condensed

trace fossil preservation and the early evolution of animals abstract the trace fossil record is an important element in discussions of the timing of appearance of bilaterian animals a conservative approach does not extend this record beyond about 560 555 ma crucial to the utility of trace fossils in detecting early benthic activity is the preservational potential of traces made close to the sediment water interface our studies on the earliest cambrian sediments suggest that shallow tiers were preserved to a greater extent than typical for most of the phanerozoic this can be attributed both directly and indirectly to the low levels of sediment mixing the low levels of sediment mixing meant that thin event beds were preserved the shallow depth of sediment mixing also meant that muddy sediments were firm close to the sediment water interface increasing the likelihood of recording shallow tier trace fossils in muddy sediments preservation of surficial trace fossils in this type of setting remains problematic but the above factors suggest that also these can be expected to have left a reasonable record overall the trace fossil record can be expected to provide a sound record of the onset of bilaterian benthic activity the lack of convincing trace fossils significantly before the cambrian supports models of late appearance of macroscopic benthic bilaterians

tilting marks a wave produced tool mark resembling a trace fossil abstract small waves can move by repeated tilting objects over considerable distances oblique to nearly parallel to wave crests this was observed for dead gaping articulated bivalves of the genus mytilus only larger than average waves about every 20th wave affected the shells but even these waves did not actually reach the sediment surface the wave energy led to a right left tilting and a small lateral shift of the bivalve producing a sedimentary structure tilting mark by pushing aside the sediment when tilted tilting marks typically consist of symmetrical walls and a central furrow displaying a transverse ornamentation tilting marks resemble the lower part of the trace fossil scolicia and could be misinterpreted as such tilting marks were observed in very shallow water

prediction of sea of japan east sea acidification over the past 40 years using a multiparameter regression model 1 a multiparameter linear regression model mlr of aragonite saturation state arg as a function of temperature pressure and o2 concentration in the upper 1 000 m of the sea of japan east sea was derived with an uncertainty of 0 020 1 the arg data n 1 482 used to derive the basin wide arg prediction model were collected during a field survey in 1999 and were corrected for anthropogenic co2 some biases were resolved by addition of a pressure and o2 concentration interaction term to the proposed model correlation between the two predictor terms caused by addition of this term was minimized by centering the data for the three variables thus subtracting the mean from each individual data point validation of the model against data sets obtained in 1992 and 2007 yielded correlation coefficients of 0 995 0 013 for 1992 n 64 p 0 001 and 0 995 0 009 for 2007 n 137 p 0 001 and root mean square errors of 0 064 for 1992 and 0 050 for 2007 the strong correlation between measurements and predictions suggests that the model can be used to estimate the distribution of arg in the sea of japan east sea including dynamic coastal waters on varying time scales when basic hydrographic data on temperature pressure and o2 concentration are available application of the model to past measurements for the sea of japan east sea indicated that interdecadal variability 2 from the mean in arg corrected for anthropogenic co2 was generally high 0 1 0 7 in the upper water layer 200 m depth and decreased 0 05 0 2 with depth for waters deeper than 500 m the interdecadal variability is largely controlled by variations in the degree of water column ventilation superimposed on this natural variability the input of co2 derived from fossil fuels has markedly acidified the upper water layers during the anthropocene and thereby moved the aragonite saturation horizon upward by 50 250 m the impact of co2 derived from fossil fuels on upper ocean acidification will increase in the future the present study indicates that in combination with other easily measurable parameters a multifunctional model can be a powerful tool for predicting the temporal evolution of arg in the ocean including coastal waters that are highly likely to be susceptible to ocean acidification in the future

abyssal water carbon 14 distribution and the age of the world oceans the carbon 14 distribution in the abyssal waters of the world oceans indicates replacement times for pacific indian and atlantic ocean deep waters more than 1500 meters deep of approximately 510 250 and 275 years respectively the deep waters of the entire world ocean are replaced on average every 500 years

sources of eddy kinetic energy in the labrador sea experiments with a suite of north atlantic general circulation models are used to examine the sources of eddy kinetic energy eke in the labrador sea a high resolution model version 112 quantitatively reproduces the observed signature a particular feature of the eke in the labrador sea is its pronounced seasonal cycle with a maximum intensity in early winter as already found in earlier studies based on altimeter data in contrast to a previously advanced hypothesis the seasonally varying eddy field is not related to a forcing by high frequency wind variations but can be explained by a seasonally modulated instability of the west greenland current wgc the main source of eke in the labrador sea is an energy transfer due to reynolds interaction work barotropic instability in a confined region near cape desolation where the wgc adjusts to a change in the topographic slope geostrophic contours tend to converge upstream of cape desolation such that the topographically guided wgc narrows as well and becomes barotropically unstable the eddies spawned from the wgc instability area dominating the eke in the interior labrador sea are predominantly anticyclonic with warm and saline cores in the upper kilometer of the water column while the few cyclones originating as well from the instability area show a more depth independent structure companion experiments with a model exhibit the strength of the wgc influenced by either changes in the wind stress or heat flux forcing as a leading factor determining seasonal to interannual changes of eke in the labrador sea

neoproterozoic substrate condition vis a vis microbial mat structure and its implications sonia sandstone rajasthan india dst fast track project young scientist scheme no sr ftp es 03 2011 cas phase v upe ii programme of jadavpur university national research foundation and university of pretoria south africa

production and accumulation of calcium carbonate in the ocean budget of a nonsteady state present day production of caco3 in tne world ocean is calculated to be about 5 billion tons bt per year of which about 3 bt accumulate in sediments the other 40 is dissolved nearly half of the carbonate sediment accumulates on reefs banks and tropical shelves and consists largely of metastable aragonite and magnesian calcite deep sea carbonates predominantly calcitic coccoliths and planktonic foraminifera have orders of magnitude lower productivity and accumulation rates than shallow water carbonates but they cover orders of magnitude larger basin area twice as much calcium is removed from the oceans by present day carbonate accumulation as is estimated to be brought in by rivers and hydrothermal activity 1 6 bt suggesting that outputs have been overestimated or inputs underestimated that one or more other inputs have not been identified and or that the oceans are not presently in steady state one missing calcium source might be groundwater although its present day input is probably much smaller than that of rivers if as seems likely caco3 accumulation presently exceeds terrestial and hydrothermal input this imbalance presumably is offset by decreased accumulation and increased input during lowered sea level shallow water accumulation decreases by an order of magnitude with a 100 m drop in sea level while groundwater influx increases because of heightened piezometric head and the diagenesis of metastable aragonite and magnesian calcite from subaerially exposed shallow water carbonates

annual sst cycle in the eastern mediterranean red sea and gulf of elat 1 the summer to winter sst difference in the eastern mediterranean red sea and gulf of elat vary from 6 c in the red sea and gulf of elat to 12 c in the eastern mediterranean this dramatic difference occurs despite the similar monthly mean values of heat flux components that prevail in these seas we show that direct mixing by the wind stress fresh water influx or upwelling cannot account for this difference instead we demonstrate the crucial role of the deep water temperature in determining the amplitude of the annual sst changes via its effect on the temperature gradient above the base of the permanent thermocline since the deep water in the eastern mediterranean is formed in the aegean or adriatic seas and not in situ it is much colder than in the red sea and the gulf of elat this low temperature of the deep water causes the observed large sst annual signal

calcium carbonate budget in the atlantic ocean based on water column inorganic carbon chemistry 1 recent independent lines of evidence suggest that the dissolution of calcium carbonate caco3 particles is substantial in the upper ocean above the calcite 100 saturation horizon this shallow water dissolution of carbonate particles is in contrast with the current paradigm of the conservative nature of pelagic caco3 at shallow water depths here we use more than 20 000 sets of carbon measurements in conjunction with cfc and 14c data from the woce jgofs oaces global co2 survey to estimate in situ dissolution rates of caco3 in the atlantic ocean a dissolution rate is estimated from changes in alkalinity as a parcel of water ages along an isopycnal surface the in situ caco3 dissolution increases rapidly at the aragonite 100 saturation horizon estimated dissolution rates north of 40on are generally higher than the rates to the south which is partly attributable to the production of exported caco3 being higher in the north atlantic than in the south atlantic as more caco3 particles move down the water column more particles are available for in situ dissolution the total water column caco3 dissolution rate in the atlantic ocean is determined on an annual basis by integrating estimated dissolution rates throughout the entire water column and correcting for alkalinity input of approximately 5 6 1012 mol c yr 1 from caco3 rich sediments the resulting water column dissolution rate of caco3 for the atlantic ocean is approximately 11 1 1012 mol c yr 1 this corresponds to about 31 of a recent estimate 35 8 1012 mol c yr 1 of net caco3 production by lee 2001 for the same area our calculation using a large amount of high quality water column alkalinity data provides the first basin scale estimate of the caco3 budget for the atlantic ocean

inorganic carbon in the indian ocean distribution and dissolution processes 1 this study uses nearly 25 000 carbon measurements from the woce jgofs global co2 survey to examine the distribution of dissolved inorganic carbon dic and total alkalinity ta in the indian ocean shallow and intermediate distributions of inorganic carbon do not strictly follow temperature and salinity because of differing surface gradients and vertical biological processes that work to modify the circulation derived features anthropogenic co2 has increased the shallow dic by as much as 3 decreasing the vertical dic gradient deep ocean dic and ta increase toward the north because of the decomposition and dissolution of organic and inorganic particles calcite saturation depths range from 2900 3900 m with the deepest saturation depth in the central indian ocean variations of aragonite saturation depth 200 1400 m are similar to calcite but the deepest saturations are in the southwestern indian ocean the shallowest aragonite saturation depths are found in the bay of bengal in the northern arabian sea and bay of bengal the current aragonite saturations are 100 and 200 m shallower respectively than in preindustrial times estimates of carbonate dissolution rates on isopycnal surfaces range from 0 017 to 0 083 mol kg 1 yr 1 in deep waters upper water column dissolution rates range from 0 to 0 73 mol kg 1 yr 1 with a local maximum occurring in intermediate waters just below the aragonite saturation horizon dissolution is also generally higher north of the chemical front at 10 20 s there is some evidence for significant sedimentary sources in the northern indian ocean

first evidence for locomotion in the ediacara biota from the 565 ma mistaken point formation newfoundland evidence for locomotion in the precambrian fossil record is scant reliable ediacaran trace fossils are all younger than 560 ma and consist of relatively simple horizontal burrows and trails from shallow water deposits here we describe an assemblage of macroscopic locomotory traces from deep water environments at mistaken point southeastern newfoundland canada dated to ca 565 ma these trails extend the record of complex trace fossils back into the earliest avalonian biota our new evidence for large motile organisms on the seafloor at this time suggests that at least some of these early ediacaran organisms whose biological affinities are widely debated could have been muscular and of metazoan grade

postindustrial enhancement of aragonite undersaturation in the upper tropical and subtropical atlantic ocean the role of fossil fuel co2 the dissolution of aragonite particles in the ocean primarily depends on the degree of undersaturation of seawater with respect to that mineral most of the upper atlantic ocean particularly north of 308s and at depths of less than 2000 m is supersaturated with respect to aragonite whereas much of the deep atlantic is undersaturated here we report for the first time shallow layers of aragonite undersaturated water between 208s and 158n in the eastern tropical atlantic these layers are centered at 800 m and are surrounded by aragonite supersaturated water above and below this feature most likely results from a combination of chemical and biological processes including the uptake of anthropogenic co2 and the oxidation of organic matter falling from the highly productive overlying surface water reaction with protons resulting from these processes decreases the carbonate ion concentration and consequently the saturation state of the waters with respect to aragonite the oceanic uptake of anthropogenic co 2 during the industrial era has caused a significant increase in the size of the undersaturated layers future expansion will likely occur laterally to the west and south where the degree of supersaturation is low compared to waters to the north this expansion of the undersaturated layers is a prime example of how human activity during the industrial era has altered the upper ocean chemistry by injecting fossil fuel co 2 into the ocean

trace fossils in the ediacaran cambrian transition behavioral diversification ecological turnover and environmental shift abstract after taxonomic revision trace fossils show a similarly explosive diversification in the ediacaran cambrian transition as metazoan body fossils in shallow marine deposits of ediacaran age trace fossils are horizontal simple and rare and display feeding strategies related to exploitation of microbial matgrounds equally notable is the absence of arthropod tracks and sinusoidal nematode trails this situation changed in the early cambrian when a dramatic increase in the diversity of distinct ichnotaxa is associated was followed by the onset of vertical bioturbation and the disappearance of a matground based ecology agronomic revolution on deep sea bottoms animals have been present already in the ediacaran but ichnofaunas were poorly diverse and dominated by the horizontal burrows of undermat miners as shown by the ichnogenus oldhamia this life style continued to be predominant into the early and to a lesser extent middle cambrian nevertheless there was an explosive radiation of behavioral programs during the early cambrian when exactly the bioturbational revolution arrived in the deep sea is uncertain in any case the nereites ichnofacies was firmly established in the early ordovician the rich ichnofauna in the early cambrian guachos formation of northwest argentina probably marks a first step in this ecological onshore offshore shift

spindle shaped ediacara fossils from the mistaken point assemblage avalon zone newfoundland the mistaken point assemblage of the ediacara fossils is dominated by rangeomorphs with homologous fractal branching elements the most distinctive are the fusiform fossils herein named fractofusus misrai n gen and n sp and fractofusus andersoni n gen and n sp although endemic to the newfoundland portion of the avalonia terrane they dominated deep sea floor communities below the photic zone in the mid ediacaran period ca 575 560 ma their biological affinities remain uncertain but their architecture suggests a phylogenetic position near the base of the metazoa

tilting marks observations on tool marks resembling trace fossils and their morphological varieties abstract tilting marks defined here as linear tool marks having transverse ornamentation are produced in shallow water when the oscillatory action of waves of short wavelength tilt grounded objects rhythmically in such a way that they move and push sediment aside these tool marks can resemble trace fossils particularly if they are bilaterally symmetrical even asymmetrical objects can produce symmetrical tilting marks because the shape of the mark only depends on the geometry of the ground touching part of the object which may be partially floating objects of either soft or hard consistency such as jellyfish or wood respectively can produce tilting marks tilting marks are normally produced linearly parallel or at an angle to the direction of wave propagation and do not show sharp bends or curves tilting marks can be formed on plane beds as well as rippled surfaces tilting marks can be distinguished from trace fossils by taking into account the geometry symmetry the direction of movement and the mainly linear course and the internal pattern

uranium and molybdenum isotope evidence for an episode of widespread ocean oxygenation during the late ediacaran period abstract to improve estimates of the extent of ocean oxygenation during the late ediacaran period we measured the u and mo isotope compositions of euxinic anoxic and sulfidic organic rich mudrocks orm of member iv upper doushantuo formation south china the average 238 u of most samples is 0 24 0 16 2sd relative to standard crm145 which is slightly higher than the average 238 u of 0 02 0 12 for restricted black sea deep water unit i euxinic sediments and is similar to a modeled 238 u value of 0 2 for open ocean euxinic sediments in the modern well oxygenated oceans because 238 u is preferentially removed to euxinic sediments compared to 235 u expanded ocean anoxia will deplete seawater of 238 u relative to 235 u ultimately leading to deposition of orm with low 238 u hence the high 238 u of member iv orm points to a common occurrence of extensive ocean oxygenation ca 560 to 551 myr ago the mo isotope composition of sediments deposited from strongly euxinic bottom waters h 2 s aq 11 m either directly records the global seawater mo isotope composition if mo removal from deep waters is quantitative or represents a minimum value for seawater if mo removal is not quantitative near the top of member iv 98 mo approaches the modern seawater value of 2 34 0 10 high 98 mo points to widespread ocean oxygenation because the preferential removal of isotopically light mo to sediments occurs to a greater extent in o 2 rich compared to o 2 deficient marine environments however the 98 mo value for most member iv orm is near 0 relative to standard nist srm 3134 0 25 suggesting extensive anoxia the low 98 mo is at odds with the high mo concentrations of member iv orm which suggest a large seawater mo inventory in well oxygenated oceans and the high 238 u hence we propose that the low 98 mo of most member iv orm was fractionated from contemporaneous seawater possible mechanisms driving this isotope fractionation include 1 inadequate dissolved sulfide for quantitative thiomolybdate formation and capture of a seawater like 98 mo signature in sediments or 2 delivery of isotopically light mo to sediments via a particulate fe mn oxyhydroxide shuttle a compilation of mo isotope data from euxinic orm suggests that there were transient episodes of extensive ocean oxygenation that break up intervals of less oxygenated oceans during late neoproterozoic and early paleozoic time hence member iv does not capture irreversible deep ocean oxygenation instead complex ocean redox variations likely marked the transition from o 2 deficient proterozoic oceans to widely oxygenated later phanerozoic oceans

the adriatic sea general circulation part ii baroclinic circulation structure abstract in the second part of the paper dedicated to the adriatic sea general circulation the horizontal structure of the hydrographic parameters and dissolved oxygen fields is described on a seasonal timescale maps of temperature and salinity climatological fields reveal the enhanced seasonal variability of the adriatic sea which at the surface is associated with the major dilution effects of river runoff the density and derived dynamic height fields show for the first time the baroclinic geostrophic structure of the general circulation winter is dominated by compensation effects between temperature and salinity fronts along the western coastline the resulting baroclinic circulation is weak and suggests the presence of barotropic current components not accessible by the dataset spring and summer seasons have the smallest spatial scales in the temperature and salinity fields and stronger subbasin scale gyres and current systems which have been classified in a schematic representation of the circu

factors influencing the degree of saturation of the surface and intermediate waters of the north pacific ocean with respect to aragonite new carbonate chemistry data obtained during a 1982 cruise have been combined with earlier ge osecs and indopac data to determine the degree of aragonite saturation of surface and intermediate waters of the north pacific large gradients in saturation state occur in the region of the subarctic front in the north south direction and across the subtropical gyre in the east west direction these gradients are primarily due to the extensive mixing that occurs in the intermediate waters of the western north pacific the major variations in saturation state were primarily related to the carbonate ion concentration which in turn is primarily a function of mixing and biological processes the present aragonite saturation depth at our northernmost station in the western north pacific was calculated to be within 120 m of the surface this result was directly corroborated by observations of aragonite dissolution under in vitro conditions our calculations show that one possible effect of fossil fuel derived co2 on the surface of the north pacific will be a steady progression of undersaturation from the northern to southern and western areas with the first sign of undersaturation possibly occurring as early as the second half of the next century

charnia and sea pens are poles apart c harnia from the ediacara biota is here examined in terms of its growth and development the ediacara biota comes from the critical period of evolution just before the cambrian explosion and is key to our understanding of the origin of animal life we show that charnia cannot be related to the modern cnidarian group the sea pens pennatulacea with which it has for so long been compared as generative zones cannot be homologized between these forms

first evidence for locomotion in the ediacara biota from the 565 ma mistaken point formation newfoundland comment liu et al 2010 1 claim to have found the first evidence for locomotion in the form of putative locomotion traces from the ediacaran 565 ma mistaken point formation of newfoundland if by first they mean the geologically most ancient evidence of animal locomotion they should have discussed

paleoenvironmental analysis of the late neoproterozoic mistaken point and trepassey formations southeastern newfoundland the mistaken point and trepassey formations conception and st john s groups respectively comprise a terminal neoproterozoic deep marine succession of fine grained turbidites and volcanogenic deposits that are part of the avalonian terrane debris flow beds slumped units the low dispersion of turbidity current paleoflow directions and the absence of wave generated structures together indicate that the sediment was deposited on a deep water southeast facing slope channels were not present in the study area the upward increase in the abundance of slump structures suggests that these units represent toe of slope and mid slope environments respectively these units prograded over basin floor deposits of the drook and briscal formations which have axial paleocurrent directions that are orthogonal to the inferred downslope flow that characterized the overlying deposits within the mistaken point and trepassey formations a diverse assemblage of soft bodied non phototrophic ediacaran organisms is

the early paleozoic development of bioturbation evolutionary and geobiological consequences abstract bioturbation the physical and chemical mixing of sediments by burrowing animals is a critical engineering process in modern seafloor environments and exerts an important control on not only benthic ecology and sediment properties but also ocean wide biogeochemical cycling well mixed sediments have long been assumed to appear at the precambrian cambrian boundary with the first occurrence of the index fossil and three dimensional burrow treptichnus pedum however field based analyses synthesizing ichnological stratigraphic sedimentological and taphonomic data collected from lower paleozoic successions worldwide indicate that sediment mixing in marine shelf environments remained limited until at least the late silurian 120 million years after the precambrian cambrian transition in spite of early advances in complex modes of infaunalization mixed layer development had a much more gradual trajectory and did not occur in step with the first appearance of three dimensional burrows the delayed appearance of modern style intensities of sediment reworking postdating both the cambrian explosion and the great ordovician biodiversification event may be due to the late stage radiation of mobile infaunal deposit feeders biological bulldozers the organisms which are in modern marine settings the most efficient bioturbators the protracted development of the sediment mixed layer holds important implications for contemporaneous biogeochemical cycling and oxygenation of the ocean atmosphere system the delayed development of intensive sediment mixing may have also mediated exceptional preservation of both fossilized soft tissues and shallow tier trace fossils and may therefore have contributed to the anomalous preponderance of konservat lagerstatten and exceptionally preserved shallow tier trace fossils and bioglyphs characteristic of the lower paleozoic stratigraphic record

evidence for cnidaria like behavior in ca 560 ma ediacaran aspidella comment menon et al 2013 1 regard wrinkles at the base of discoid fossils aspidella terranovica and deformation of laminae in cut slabs as evidence for upward migration of a cnidarian polyp in marine shales but their observations are better explained by a sessile growing organism with growth

astronomical time scale for the middle upper doushantuo formation of ediacaran in south china implications for the duration of the shuram wonoka negative δ13c excursion abstract the ediacaran period 635 541 ma of the neoproterozoic records the advent of multi cellular life on earth the ediacaran doushantuo formation dst fm contains records of some phases of this bio evolution and profound perturbations to the global carbon cycle but the timing and the duration of these events are still unclear the jiulongwan jlw roadcut in south china is a well studied reference section for these ediacaran events including the major en3 shuram wonoka negative carbon isotope excursion spectral analysis of geochemical data through the middle upper dst fm indicates that the sedimentary cycles correspond to 405 kyr long eccentricity and 100 kyr short eccentricity periods tuning the dst fm at jlw section to the 405 kyr long eccentricity cycles yielded a 30 myr long astronomical time scale member dst 4 black shale of the uppermost dst fm spans 7 5 myr and the negative 13c excursion en3 shuram wonoka has a duration of 20 myr relative to a u pb date of 551 1 0 7 ma near the top of the dst fm the onset of member dst 4 is at 557 8 0 8 ma and the projected basal age of member dst 3 is 579 3 0 8 ma the onsets of positive ep2 and negative en3 13c excursions were ca 578 1 ma and 571 1 ma respectively therefore both excursions occurred after the termination of the gaskiers glaciation 581 ma thereby these ages and astronomical time scale provide important new constraints on the subdivision of ediacaran strata and have implications for our understanding the character of the 13c excursions orbital forcing may be important to the co evolution of life the global carbon cycle and sedimentary environments

the puzzle assembled ediacaran guide fossil cloudina reveals an old proto gondwana seaway abstractduring the ediacaran the clymene ocean separated the lau rentia amazonia and rio apa cratons from several landmasses to the west forming the proto gondwana supercontinent however no clear evidence about the existence of ediacaran epeiric seas over those landmasses has been found here we report and discuss the discovery of the ediacaran guide fossil cloudina sp associated with other metazoan body and trace fossils in the bambui group central eastern brazil the ediacaran age of the bambui group and the paleogeographic position of cloudina bearing successions in brazil antarctica namibia and argentina suggest a scenario of ocean con nectivity among coeval intracratonic basins of south america africa and antarctica at the end of neoproterozoic time the new nding epitomizes one of the most important paleontological discoveries ever made in south america helping to solve an old paleogeographic puz zle of the gondwana supercontinent introduction the bambui group crops out in central eastern brazil and is one of the most studied neoproterozoic sedimentary successions in south america it comprises an extensive at lying cratonic cover in erosional contact with paleoproterozoic and archean basement rocks of the sao francisco craton in its eastern and westernmost occurrences the bam bui group is deformed and metamorphosed by the brasilia and aracuai mobile belts respectively fig 1a the regional tectonostratigraphy has been interpreted as re ecting deposition in a foreland basin related to gondwanan collisions involving the sao francisco craton pimentel et al 2011 the bambui group bg overlies rocks of the macaubas group and jequitai formation and the carrancas conglomerate units supposedly de posited during sturtian glaciation the unit is 700 1000 m thick misi et al 2007 and comprises limestones and dolomites of the sete lagoas for mation at the base that grade upward to shales and siltstones of the serra de santa helena formation followed by marls siltstones limestones and sandstones of the lagoa do jacare serra da saudade and tres marias formations fig 1b the precise age of the bg is not well established precluding accurate correlation with other supposedly coeval successions such as the corumba group brazil itapucumi paraguay arroyo del soldado uruguay si erras bayas argentina and nama group namibia the presence of

paleoenvironmental and basin analysis of the late neoproterozoic ediacaran upper conception and st john s groups west conception bay newfoundland the conception and st john s groups consist of deep marine fine grained siliciclastic volcaniclastic rocks with abundant impressions of ediacaran body fossils based on previous tectonic reconstructions these strata are interpreted to have accumulated during the transition from a fore arc phase 1 ca 630 560 ma to a strike slip pull apart basin phase 2 ca 560 540 ma the drook and mistaken point formations accumulated during phase 1 and are characterized by tabular thick to medium bedded turbidites east southeast paleoflow directions contourites southwest paleoflow directions and volcanic ash beds the high proportion of each bed consisting of te bouma turbidite division mudstone and the lack of correlation between bed thickness and basal grain size suggest ponding of the turbidity currents the differences in paleoflow directions and texture between conception bay and equivalent units at mistaken point imply that the two areas may have been geographically isolated from each other p

in situ calibration of mg ca ratio in planktonic foraminiferal shell using time series sediment trap a case study of intense dissolution artifact in the south china sea this study examines mg ca temperature equations through the use of planktonic foraminifers collected from continuous time series sediment traps at four water depths in the south china sea this deployment provides an opportunity to refine partial dissolution artifacts and to identify responses of shell chemistry to changes in ambient seawater conditions paired mg ca and 18o measurements on shells are strongly correlated with seasonal variability in terms of temperature at specific habitat depths however partial dissolution can significantly alter mg ca ratios even at depths well above the calcite lysocline or carbonate compensation depth of the three species studied neogloboquadrina dutertrei is the most sensitive species to dissolution relative to the other surface dwelling species globigerinoides ruber and globigerinoides sacculifer differences between the mg derived temperature equation here and those from previously established core top or sediment trap calibrations can be attributed to various degrees of dissolution and lateral advection thus highlighting the need for in situ empirical calibration for different ocean basins

the coupling between exchange flux through a strait and dynamics in a small convectively driven marginal sea the gulf of aqaba gulf of eilat 1 we investigate the coupling between the dynamics in the gulf of aqaba gulf of eilat northern red sea and the exchange flow through the straits of tiran in response to seasonally varying surface fluxes and northern red sea hydrographic conditions because the gulf is a relatively small basin winter mixing between the surface and intermediate layers occurs over most places in the gulf including in the vicinity of the straits and leads to a maximal exchange flow in the strait during the spring warming in the red sea forces an influx of warm red sea water into the gulf the surface layer is refilled and consequently the exchange flow in the straits changes from a maximal to a submaximal flow regime as a result the dense wintertime water formation in the gulf and the exchange flow through the strait are strongly coupled on seasonal time scales in addition the hydrographic conditions in the northern red sea undergo strong seasonality these characteristics prevent the direct application of current theories for strait marginal sea systems which commonly assume steady conditions in the open ocean side of the strait and or an annual mean surface flux over the marginal sea we explain why the exchange of volume and heat between the gulf of aqaba gulf of eilat and the northern red sea is larger during spring summer despite the net surface buoyancy input into the gulf and why it diminishes during fall winter despite the large buoyancy loss to the atmosphere the applicability of the results to other systems is discussed

engineering the cambrian explosion the earliest bioturbators as ecosystem engineers by applying modern biological criteria to trace fossil types and assessing burrow morphology complexity depth potential burrow function and the likelihood of bioirrigation we assign ecosystem engineering impact eei values to the key ichnotaxa in the lowermost cambrian fortunian surface traces such as monomorphichnus have minimal impact on sediment properties and have very low eei values quasi infaunal traces of organisms that were surficial modifiers or biodiffusors such as planolites have moderate eei values and deeper infaunal gallery biodiffusive or upward conveying downward conveying traces such as teichichnus and gyrolithes have the highest eei values the key cambrian ichnotaxon treptichnus pedum has a moderate to high eei value depending on its functional interpretation most of the major functional groups of modern bioturbators are found to have evolved during the earliest cambrian including burrow types that are highly likely to have been bioirrigated in fine grained or microbially bound sedimentary environments trace makers of bioirrigated burrows would have had a particularly significant impact generating advective fluid flow within the sediment for the first time in marked contrast with the otherwise diffusive porewater systems of the proterozoic this innovation is likely to have created significant ecospace and engineered fundamentally new infaunal environments for macrobiotic and microbiotic organisms alike

suspected microbial mat related crack like sedimentary structures in the palaeoproterozoic magaliesberg formation sandstones south africa abstract the occurrence of patchy preservation of ripples and of palimpsest ripples on many sandstone bed surfaces of the c 2 1 ga magaliesberg formation pretoria group transvaal supergroup south africa suggests that microbial mats grew within the upper parts of sandy deposits of the braid deltaic tidally controlled epeiric marine coastline palaeoenvironment inferred for this stratigraphic unit recently limited occurrences of petee ridges cracked sand layers elephant skin textures wrinkle structures and manchuriophycus like cracks have been found substantiating the envisaged role for microbial mats binding sandy sediment and providing cohesion during active sedimentation by fluvial and tidal processes ripple marks associated with most of these biogenic sedimentary structures enable evaluation of genetic processes for the ripples currents waves wind as well as estimation of wave heights and water depths cf tanner w f 1967 ripple mark indices and their uses sedimentology 9 89 104 tanner w f 1971 numerical estimates of ancient waves water depths and fetch sedimentology 16 71 88 the petee ridges are interpreted as reflecting spring low tidal desiccation which cracked the mats followed by disruption of sand beneath the mat due to loading from incoming tides or subsequent deposits slightly sinuous sand cracks on ripple crests are related to a similar combination of low tidal desiccation and formation of wind ripples with subsequent high tides providing the deeper water conditions and larger wave heights calculated from the tanner w f 1971 numerical estimates of ancient waves water depths and fetch sedimentology 16 71 88 formula synaeresis cracking is inferred for both elephant skin cracks and manchuriophycus structures these inferred suspect microbial sedimentary structures when studied in relation to data derived from associated ripples thus enable better estimation of depositional conditions within the magaliesberg palaeoenvironment and indicate minimum epeiric tidal ranges of c 112 cm in general these structures are found associated with evidence for shallower water and higher energy conditions which probably protected the microbial mats from degradation by heterotrophic bacteria through fast burial a possible association of such mat related structures with epeiric marine or passive margin coastline conditions may be pertinent for much of the precambrian clastic record

effects of increased horizontal resolution in a simulation of the north atlantic ocean global mean and eddy fields from a four year experiment with a 1 6 1 5 horizontal resolution implementation of the cme north atlantic model are presented the time averaged wind driven and thermohaline circulation in the model is compared to the results of a 1 3 2 5 model run in very similar configuration in general the higher resolution results are found to confirm that the resolution of previous cme experiments is sufficient to describe many features of the large scale circulation and water mass distribution quite well while the increased resolution does not lead to large changes in the mean flow patterns the variability in the model is enhanced significantly on the other hand however not all aspects of the circulation have improved with resolution the azores current frontal zone with its variability in the eastern basin is still represented very poorly particular attention is also directed toward the unrealistic stationary anticyclones north of cape hatteras and in the gulf of mexico

eddy processes in semienclosed seas a case study for the black sea abstract the enclosed boundaries and small scales of some seas lead to the formation of specific physical balances which motivates the oceanographic interest in studying the dynamics of semienclosed ocean basins the focus in the paper is on the specific appearances of eddy processes when the basin scales and the ones of the topographic features are comparable with the baroclinic radius of deformation the black sea is used as a test basin eddy variability is analyzed using simulation results and compared with existing observations the bryan cox model with horizontal resolution 1 10 and 1 6 is forced with annual mean wind stress data buoyancy flux at the sea surface is proportional to the deviation of the model density from the annual mean climatological data sensitivity studies on different forcing and on the topographic control are carried out synoptic periods are estimated to be about 0 5 yr eddies form in the eastern black sea and propagate westward with a speed of about 3 cm s 1 t

post fossilization processes and their implications for understanding ediacaran macrofossil assemblages fossil assemblages from newfoundland s avalon peninsula preserve diverse examples of the enigmatic ediacaran macrobiota offering some of the earliest evidence for large and complex multicellular life these fossils are exposed on extensive coastal bedding planes in extraordinary abundances permitting palaeoecological studies based on census data from spatially extensive palaeocommunities such studies have been used to constrain the reproductive strategy and phylogenetic placement of ediacaran organisms geological mapping and stratigraphic correlation in the mistaken point ecological reserve reveal that some fossil bearing surfaces can be tracked over distances of several kilometres these laterally extensive surfaces reveal that the modern processes by which the sediment overlying a fossil surface is removed may impose important controls on the observed composition of fossil assemblages weathering and erosion along with factors associated with tectonics metamorphism and discovery are here grouped as post fossilization processes and introduce biases that are often not explicitly accounted for in palaeoecological studies specifically post fossilization processes may differentially influence the preservational fidelity of individual specimens on a given surface and generate features that could be mistaken for original morphological characters we therefore recommend that post fossilization processes must be considered when undertaking palaeoecological studies in ediacaran successions in newfoundland and potentially elsewhere

the effect of excess co2 on the calculated calcite and aragonite saturation horizons in the northeast pacific using the tco2 results of chen 1982a obtained during a cruise in the northeast pacific ocean june july 1981 we have calculated preindustrial and 1981 calcite and aragonite saturation horizons for a transect along 150 w between alaska and hawaii uptake of excess co2 by the oceans over the past 130 years has resulted in a significant change in the carbonate chemistry of the northeast pacific ocean the results indicate an apparent reduction in the thickness of the supersaturated lenses and an upward translation of the 100 saturation level by as much as 150 meters for calcite and 70 meters for aragonite in the coldwater region north of the subarctic front

co evolution of eukaryotes and ocean oxygenation in the neoproterozoic era the oxygenation of the earth s deep oceans is often thought to have triggered the evolution of simple animals a review article proposes that instead the evolution of animal life set off a series of biogeochemical feedbacks that promoted the oxygenation of the deep sea

the oldest record of ediacaran macrofossils in gondwana 563 ma itajai basin brazil abstract the avalon biota ediacaran period 570 559 ma marks the first appearance of macroscopic and complex benthic communities in the fossil record this assemblage is known from a few localities worldwide mainly in canada and england here we report for the first time the presence of ediacaran macrofossils in deposits of similar age from gondwana itajai basin southern brazil our new radiometric date 563 ma indicates that the itajai basin can be chronocorrelated with the classic avalonian deposits and thus represents one of the oldest records of the ediacaran biota in gondwana we describe the presence of the ediacaran genus palaeopascichnus as well as discs aspidella and nimbia and other problematic forms contrary to the deep marine macroorganisms of the avalon assemblage the itajai fossils are associated with abundant and exceptionally preserved three dimensional microbial mats and microbially induced sedimentary structures miss in relatively shallow settings upper slope and distal delta front deposits in this sense the itajai biota could represent early adaptations of benthic macrobiota to the shallower and more photic environments that characterize the later white sea assemblage

calcium carbonate dissolution in the upper 1000 m of the eastern north atlantic recent analyses suggest that considerable caco3 dissolution may occur in the upper water column of the ocean 1500 m this study uses the distribution of particulate calcium from high resolution suspended matter sampling along the climate variability and predictability co2 repeat hydrography a16n transect in 2003 to estimate caco3 dissolution in the top 1000 m of the north atlantic dissolution rates were also approximated using changes in total alkalinity measurements along isopycnal surfaces water masses were found to be undersaturated with respect to aragonite at intermediate depths 400 1000 m in the eastern tropical north atlantic the caco3 dissolution rate in this region is estimated to be 0 9 mmol caco3 m 2 d 1 indicating this region is a hotspot for upper water column caco3 dissolution compared to the atlantic basin as a whole dissolution rates calculated from particulate calcium distributions outside of this region were significantly lower 0 2 mmol caco3 m 2 d 1 and are comparable to previous estimates of caco3 dissolution flux for the atlantic ocean the magnitude of upper water column dissolution rates compared to measured surface ocean caco3 standing stocks suggests that biologically mediated caco3 dissolution may be occurring in the top 1000 m of the atlantic

ediacaran biota in the aftermath of the kotlinian crisis asha group of the south urals abstract the asha group of the south urals is dominated by laminated shales and thin siltstone sandstone alternations interpreted as a prograding low energy inner shelf depositional system the succession includes several thick sharp based sandstone bodies comprising interstratified fine to medium grained fine laminated planar laminated hummocky convolute and wave bedded planar and trough cross bedded sandstones occasionally pebble to boulder conglomerates regarded as tidal deltaic and shoreface depositional systems the sandstone shoreface bodies are interpreted as forced regressive deposits stranded in offshore positions during subsequent transgressions although palaeoecological and taphonomic context of the asha group is favourable for the ediacara type biofacies the associated fossil assemblages nevertheless are depauperate and consist of frondomorph holdfast structures palaeopascichnids microbial colonies arumberiamorph structures as well as lithified microbial substrates shagreen texture biolaminites in terms of fidelity and fossil completeness preservation of ediacaran fossils in the asha group is by no means inferior to that seen in other ediacaran macrofossil localities the low biodiversity of ediacaran macrofossils can be attributed to a relatively young ediacaran age of the asha group which is constrained by a u pb zircon date of 547 6 3 8 ma from an ash bed in the lower part of the sedimentary succession the uppermost part of the asha group has yielded bilobed burrows with a backfill structure suggesting an affinity with the ichnogenus didymaulichnus from the ediacaran cambrian boundary strata the asha group therefore offers an important glimpse into the history of the edacaran biota in the aftermath of the kotlinian crisis that caused extinction of dickinsoniomorphs tribrachiomorphs and bilateralomorphs in wave and current agitated shoreface depositional systems 550 million years ago but did not significantly affect frondomorphs and palaeopascichnids

in situ analyses of phosphorus contents of carbonate minerals reconstruction of phosphorus contents of seawater from the ediacaran to early cambrian abstract the ediacaran and cambrian periods were one of the most important periods for the evolution of life the biodiversity drastically expanded in the period however the origins are still ambiguous because surface environmental changes through the time have not been well understood yet we conducted in situ analyses of the phosphorus contents of carbonate minerals with a laser ablation inductively coupled plasma mass spectrometer la icp ms to estimate the phosphorus contents of seawater from the ediacaran to the early cambrian carbonate rocks contain not only the carbonate minerals but also detrital and authigenic materials such as silicate and phosphate minerals therefore the whole rock compositions of carbonate rocks are not directly related with seawater composition to avoid the influence of the involvement of the phosphate minerals we performed the microscopic observation elemental mapping of si ca mg fe and p contents with an electron probe microanalyzer epma and investigation of time profiles of signal intensities of ca sr mn p la and ba with the la icp ms especially samples with low mn sr ratios and primary textures such as oolites are suitable to estimate the primary phosphorus contents of the carbonates the chemostratigraphy of the phosphorus contents of carbonates from the drill core and outcrop samples displays that the phosphorus contents decrease from ca 400 ppm in the ediacaran through ca 200 ppm around the terminal ediacaran and the beginning of the cambrian to ca 50 ppm in the early cambrian previous works on 87sr 86sr chemostratigraphy from the ediacaran to the cambrian sections suggested relatively high continental influx in the middle ediacaran and around the precambrian cambrian pc c boundary the high phosphorus content in the ediacaran was possibly due to the high continental flux on the other hand previous works on chemostratigraphy of carbon isotope values of carbonate carbon from the ediacaran to the cambrian sections showed some large negative anomalies in the ediacaran and around the precambrian cambrian pc c boundary and suggested that the negative anomalies were caused by remineralization and respiration of dissolved organic matter the degradation of the organic matter also accounts for the high phosphorus contents in the ediacaran the high phosphorus content of seawater favors enhancement of primary productivity and formation of phosphorites the high phosphorus contents in the seawater possibly led to the emergence of the large and motile organism through the enhancement of primary productivity and the consequent increase of oxygen content of the seawater

multi layer hydraulic exchange flows flows between ocean basins are often controlled by narrow channels and shallow sills a multi layer hydraulic control theory is developed for exchange flow through such constrictions the theory is based on the inviscid shallow water equations and extends the functional approach introduced by gill 1977 and developed by dalziel 1991 the flows considered are those in rectangular cross section channels connecting two large reservoirs with a single constriction sill and or narrows the exchange flow depends on the stratification in the two reservoirs represented as a finite number of immiscible layers of different uniform density for most cases the flow is controlled at the constriction and often at other points along the channel virtual controls too as with one and two layer hydraulics controls are locations at which the flow passes from one solution branch to another and at which at least one internal wave mode is stationary the theory is applied to three layer flows which have two internal wave modes predicting interface heights and layer fluxes from the given reservoir conditions the theoretical results for three layer flows are compared to a comprehensive set of laboratory experiments and found to give good agreement the laboratory experiments also show other features of the flow such as the formation of waves on the interfaces the implications of the results for oceanographic flows and ocean modelling are discussed

increase of total alkalinity due to shoaling of aragonite saturation horizon in the pacific and indian oceans influence of anthropogenic carbon inputs 1 aragonite saturation horizon ash shallowed significantly by 25 to 155 m and 16 to 124 m in the pacific and indian ocean respectively in two decades apparent oxygen utilization aou increased by 3 to 34 and 0 5 to 31 5 mol kg 1 in the pacific and indian ocean respectively at the depth of ash during this period dic increased by 12 5 to 36 8 and 5 5 to 32 mol kg 1 in the vicinity of ash in the pacific and indian ocean respectively due to combined effect of increased anthropogenic co2 and change in aou ta increased significantly by 5 to 10 and 4 to 9 2 mol kg 1 in the pacific and indian oceans respectively at the ash most likely as a result of aragonite dissolution the upward migration of ash solely due to anthropogenic co2 amounted to 6 to 58 m in the pacific and 4 to 44 m in the indian ocean

observations and modeling of a pulsating density current 1 we investigate density current formation and flow in the northern gulf of eilat red sea using in situ observations and a high resolution nonhydrostatic general circulation model these density currents occur in relatively warm water 20 c and are probably the warmest in the world ocean we demonstrate the intrinsic nonlinearity of density currents by comparing two high resolution simulations forced by different heat flux this nonlinearity which is poorly represented in global models is shown here to affect the properties of simulated density currents such a bias in simulating density currents in global models may lead to significant biases on the larger scale global ocean circulation and water mass distribution