paleoclimatology and paleoecology across the eocene oligocene boundary thrace basin northeast aegean sea greece abstract the detailed biostratigraphic and ichnological analysis of the upper eocene lower oligocene forearc sedimentary sequence in the southern greek part of the thrace basin on lemnos island reveals a relationship between eco sedimentary factors and the base level dynamics influencing calcareous nannofossils and trace fossil assemblages the lower part of the 350 m thick succession was deposited in a sand rich submarine fan system and upper part in a shelf environment it contains nannofossil assemblages and distributions typical of the np19 np21 biozones the eocene oligocene e o boundary top of np20 biozone is clearly distinguished within the upper parts of the turbidite system where a decrease in water temperature salinity nutrient supply and oxygenation level is also revealed additionally 19 ichnospecies mostly graphoglyptids typical of deep sea fan deposits have been distinguished the trace fossil diversity and abundance decrease upward reflecting the impact of the changing depositional environments from basin floor fans to slope systems and then shelfal environments the regional basin fill history rather than global climatic changes was probably the fundamental controlling factor on the distribution of graphoglyptids and other trace fossils across the e o boundary

deep sea carbonates reading the carbon isotope signal the carbon isotope signal in deep sea sediments reflects a mix of 1 global changes in the rates of exchange of the ocean s carbon reservoir with biosphere soil and sediments 2 global and regional changes in surface water productivity 3 internal shifts in water mass structure and circulation basin basin fractionation oxygen minimum development and 4 organism specific fractionation effects due to changes in micro habitat and or ontogenic fractionation vital effects additional complications arise from differential preservation it is impossible to entirely isolate these various factors as a rule of thumb long period signals that are parallel for planktonic and benthic data reflect external global fractionation patterns whilst short period signals are more likely tied to internal patterns water mass fractionation the various approaches to interpretation are illustrated with three case studies the glacial holocene transition the messinian carbon shift and the miocene monterey excursion

late quaternary spatial and temporal variability in arctic deep sea bioturbation and its relation to mn cycles changes in intensity and composition of bioturbation and trace fossils in deep sea settings are directly related to changes in environmental parameters such as food availability bottom water oxygenation or substrate consistency because trace fossils are practically always preserved in situ and are often present in environments where other environmental indicators are scarce or may have been compromised or removed by diagenetic processes the trace fossils provide an important source of paleoenvironmental information in regions such as the deep arctic ocean detailed analysis of x ray radiographs from 12 piston and gravity cores from a transect spanning from the makarov basin to the yermak plateau via the lomonosov ridge the morris jesup rise and the gakkel ridge reveal both spatial and temporal variations in an ichnofauna consisting of chondrites nereites phycosiphon planolites scolicia trichichnus zoophycos as well as deformational biogenic structures the spatial variability in abundance and diversity is in close correspondence to observed patterns in the distribution of modern benthos suggesting that food availability and food flux to the sea floor are the most important parameters controlling variations in bioturbation in the arctic ocean the most diverse ichnofaunas were observed at sites on the central lomonosov ridge that today have partially ice free conditions and relatively high summer productivity in contrast the most sparse ichnofauna was observed in the ice infested region on the lomonosov ridge north of greenland since primary productivity and therefore also the food flux at a certain location is ultimately controlled by the geographical position in relation to ice margin and the continental shelves temporal variations in abundance and diversity of trace fossils have the potential to reveal changes in food flux and consequently sea ice conditions on glacial interglacial time scales down core analysis reveal clearly increased abundance and diversity during interglacial interstadial intervals that were identified through strongly enhanced mn levels and the presence of micro and nannofossils warm stages are characterized by larger trace fossils such as scolicia planolites or nereites while cold stages typically display an ichnofauna dominated by small deep penetrating trace fossils such as chondrites or trichichnus the presence of biogenic structures in glacial intervals clearly show that the arctic deep waters must have remained fairly well ventilated also during glacials thereby lending support to the hypothesis that the conspicuous brown layers rich in mn which are found ubiquitously over the arctic basins are related to input from rivers and coastal erosion during sea level high stands rather than redox processes in the water column and on the sea floor however the x ray radiograph study also revealed the presence of apparently post sedimentary diagenetically formed mn layers which are not directly related to mn input from rivers and shelves these observations thus bolster the hypothesis that the bioturbated brownish mn rich layers can be used for stratigraphic correlation over large distances in the arctic ocean but only if post sedimentary diagenetic layers can be identified and accounted for in the mn cycle stratigraphy

an ichnological model for a deltaic depositional system new insights from the neogene siwalik foreland basin of darjeeling sikkim himalaya abstract trace fossils being almost always in situ yield information about the organism s behaviour in response to its ambient environment largely controlled by the hydrodynamic conditions salinity and bathymetry the neogene siwalik succession exposed in the tista valley the southern part of the darjeeling sikkim himalaya contains fifteen ichnogenera sporadically distributed generally in suites of low abundance although at places the bioturbation index is high three major ichnofacies namely scoyenia skolithos and cruziana have been recognised based on the association of different kinds of ichnogenera preserved in dominantly wave reworked delta front open marine bay fill and prodelta deposits the overall characters of the siwalik trace fossils are i low diversity ii low abundance iii diminutive size iv paucity of suspension feeding structures v co occurrence of both vertical and horizontal trace fossils and vi predominance of simple structures formed by trophic generalists a predominance of drifted plant litter synsedimentary deformation structures hyperpycnites and rare structures of suspension feeding organisms is consistent with a deltaic depositional environment the overall diminutive size of trace fossils their low diversities and low abundances are attributed to a stressful environment caused by freshwater influx these characteristics of siwalik ichnogenera probably mark the distinctions likely to be observed between trace fossils of deltaic and non deltaic shoreline deposits it thus appears that the riverine discharge during floods followed by post flood recovery of normal marine conditions might have been a key controlling factor in shaping the ichnological characteristics in the river wave interactive deltaic system of the siwalik sea the findings of ichnogenera typical of marine affinity unequivocally establishes a marine deltaic depositional environment negates the exclusively continent interior alluvial fan fluvial interpretation for this succession of earlier workers

trace fossils biology and taphonomy 1990 special topics in palaeontology 3 280 pp e17 95 pbk e40 00 hbk unwin hyman london isbn 004445 6867 pbk 3035 hbk

ichnofabric characterization of a deep marine clastic system a subsurface study of the middle eocene ainsa system spanish pyrenees this paper documents a subsurface trace fossil and ichnofabric study of the proximal parts of a structurally confined and channelized sand rich lower slope and proximal basin floor deep marine system in the middle eocene ainsa basin spanish pyrenees five depositional environments are recognized based on sedimentary facies associations depositional architecture and stratigraphic context channel axis channel off axis channel margin levee overbank and interfan as well as a channel abandonment phase each environment is characterized by distinct and recurring ichnofabrics ichnological measurements and observations were recorded from six cores recovered from six wells drilled at a spacing of between 400 m and 500 m at outcrop and totalling 1213 m in length from channel axis to levee overbank environments there is a trend of increasing bioturbation intensity and ichnodiversity ichnofabrics in channel axis and channel off axis environments are characterized by low bioturbation intensity and low ichnodiversity thalassinoides dominated firmground ichnofabrics associated with erosive sediment gravity flows are common in these environments in contrast channel margin and levee overbank environments are characterized by ichnofabrics associated with high bioturbation intensity and ichnodiversity sediments of the interfan are characterized by the highest bioturbation intensity associated with burrow mottling and an absence of primary sedimentary structures this paper demonstrates that in core based studies ichnofabric analysis is an important and valuable tool in discriminating between different environments in channelized deep marine siliciclastic systems the results of this study should find wide applicability in reservoir characterization studies in the petroleum industry in field based analogue ichnofabric studies and other core based studies in deep water siliciclastic systems worldwide such as the integrated ocean drilling program

the youngest known dictyodora from the late permian lopingian deep sea in west qinling central china abstract dictyodora has been generally considered an ichnogenus with a restricted temporal range from the cambrian to the mississippian until now there have been no reports of dictyodora after the mississippian here we report on well preserved and abundant dictyodora from deep sea sediments of the lopingian maomaolong formation in west qinling central china which is hitherto the youngest occurrence of dictyodora and extends the stratigraphic range of dictyodora to the late permian two ichnospecies of dictyodora are distinguished d zimmermanni and d cf scotica unlike the small sized dictyodora in the pre pennsylvanian the three dimensional morphology of dictyodora studied here shows larger amplitudes and longer limbs with clearly inclined walls and basal burrows which are interpreted to have been made by a soft bodied worm like organism with a snorkel like organ as similarly documented in previous studies detailed systematic ichnological features and sem and eds results indicate that dictyodora here is not simply a respiration structure made during the locomotion of the trace maker but resulted from active filling by the trace maker dictyodora is probably not a good indicator of the deep marine environment in the paleozoic from our dataset dictyodora originated from the shallow marine environment in the early cambrian then migrated into the deep sea in the ordovician and the marginal marine setting in the wenlock and was finally restricted to the deep marine environment in the carboniferous and permian both psammichnites and dictyodora are structures made by organisms with snorkel like organs and both were eliminated during the end permian mass extinction

multiple monsoon controlled breakdown of oxygen minimum conditions during the past 30 000 years documented in laminated sediments off pakistan abstract late holocene laminated sediments from a core transect centred in the oxygen minimum zone omz impinging at the continental slope off pakistan indicate stable oxygen minimum conditions for the past 7000 calendar years high sw monsoon controlled biological productivity and enhanced organic matter preservation during this period is reflected in high contents of total organic carbon toc and redox sensitive elements ni v as well as by a low diversity high abundance benthic foraminiferal buliminacea association and high abundance of the planktonic species globigerina bulloides indicative of upwelling conditions surface water productivity was strongest during sw monsoon maxima stable omz conditions reflected by laminated sediments were found also during warm interstadial events preboreal bolling allerod and dansgaard oeschger events as well as during peak glacial times 17 22 5 ka all ages in calendar years sediment mass accumulation rates were at a maximum during the preboreal and younger dryas periods due to strong riverine input and mobilisation of fine grained sediment coinciding with rapid deglacial sea level rise whereas eolian input generally decreased from glacial to interglacial times in contrast the occurrence of bioturbated intervals from 7 to 10 5 ka early holocene in the younger dryas 11 7 13 ka from 15 to 17 ka heinrich event 1 and from 22 5 to 25 ka heinrich event 2 suggests completely different conditions of oxygen rich bottom waters extremely low mass and organic carbon accumulation rates a high diversity benthic fauna all indicating lowered surface water productivity during these intervals the omz was very poorly developed or absent and a sharp fall of the aragonite compensation depth favoured the preservation of pteropods the abundance of lithogenic proxies suggests aridity and wind transport by northwesterly or northeasterly winds during these periods coinciding with the north atlantic heinrich events and dust peaks in the tibetan loess records the correlation of the monsoon driven omz variability in the arabian sea with the rapid climatic fluctuations in the high northern latitudes suggests a close coupling between the climates of the high and low latitudes at a global scale

organic carbon and sedimentation rate further evidence for anoxic deep water conditions in the cenomanian turonian atlantic ocean abstract the relationship between organic carbon content and sedimentation rate based on data derived from recent to miocene sediments deposited under oxic and anoxic sea water conditions is used to characterize the different depositional environments these data are compared with data of cenomanian turonian dsdp sediments from the atlantic ocean the results may support deposition in anoxic environments due to extremely reduced deep water circulation as the main cause for the formation of cenomanian turonian black shales in the north atlantic rather than increased supply of organic matter due to higher oceanic productivity

post lgm upward shift of the mediterranean outflow water recorded in a contourite drift off nw spain abstract the nw iberian continental margin is characterised by a complex morphology and by a sedimentary system which was highly dynamic over glacial to interglacial times the sedimentary history of the continental slope was strongly influenced by the interaction of bottom currents with topographic highs of structural origin leading to the accumulation of several sediment drifts a combined analysis of gravity cores from different water depth with hydroacoustic data reveals the vertical behaviour of the upper mediterranean outflow water mow core after the last glacial maximum lgm a coarser grained interval during deglacial and early holocene times 17 2 to 9 9 cal ka bp points to an increase in bottom current strength this increase in velocity was probably related to oceanic density fronts which migrated through the 300 m thick transition zone between the underlying labrador sea water and the overlying mow radiocarbon dates timed the current strengthening to 17 2 cal ka bp and a following weakening of the bottom current to 13 3 cal ka bp at 1965 m water depth and to 9 9 cal ka bp at 1885 m water depth the depth dependent current weakening suggests an upward shifting of the transition zone by 80 m that was related either to an overall shallowing of mow or a vertical contraction of this water mass the upward movement happened over a time interval of approximately 3 4 thousand years in addition sediment core analysis reveals significant lateral heterogeneities within cm to dm thick sediment layers in the contourite drift these heterogeneities suggest a need of a detailed core coverage across current influenced deposits for palaeoceanographic studies to minimize misinterpretations

impact of the paleocene eocene thermal maximum on the macrobenthic community ichnological record from the zumaia section northern spain article i nfo trace fossil assemblages from the latest paleocene to the earliest eocene were significantly affected by the environmental perturbation of the paleocene eocene thermal maximum petm high resolution ichnolo gical analysis shows well marked different ichnological features pre syn and post event a well developed normal tiered burrowing community is present in the sediments below the petm indicating oxic conditions and normal benthic food availability during the petm the record of trace fossil producers disappeared gradually but rapidly reflecting the global increase in temperature and the concentration of benthic food in the very shallow surface layer and probably the local depletion of oxygen within the sediments although probably not true anoxia the environmental perturbation significantly affected the whole benthic habitat as shown by the correspondence with the main phase of the benthic foraminiferal extinction after the petm the normal tiered burrowing community recovered gradually and slowly in a delayed return to pre petm environmental conditions the changes in the trace fossil assemblage thus document the impact of the petm on the macrobenthic community a decline in oxygen levels during the petm in a globally perturbed habitat due to global warming and the similarities and differences in the response of micro and macrobenthic communities to global phenomena thus ichnological analysis reveals as a very useful additional tool to understanding atmosphere ocean dynamic during petm and a potential way in future climate research 2011 elsevier b v all rights reserved

paleoenvironmental analysis of the ichnogenus zoophycos in the lower devonian tempestite sediments of the longmenshan area sichuan china abstract the trace fossil zoophycos is characteristic of the lower devonian in the longmenshan area of southeastern china three distinct storm generated or induced types of sedimentary sequences bearing zoophycos have been identified in shallow marine deposits of the bailiuping formation and the yangmaba formation the type a deposit is composed of siltstones with shell concentrations and wave ripples and small zoophycos at the top the type b deposit is characterized by fine graded sandstone with long wavelength hummocky cross stratification and black gray mudstone as well as the largest and densest zoophycos at the top the type c deposit has graded bioclastic limestone with short wavelength hummocky cross stratification muddy wackestone and large zoophycos at the top based on the features of the types of zoophycos the distribution zone of the zoophycos ichnogenus that preserved in tempestite sequence was built between the fair weather wave base and storm wave base in the lower devonian this research suggests that the distribution patterns of zoophycos formed in storm induced deposits may not provide significant clues for the estimation of relative water depths the hydrodynamic conditions and sedimentation rate are two important environmental factors of the development of the zoophycos in the lower devonian shallow marine deposits where it was mainly affected by storms between the fair weather and storm wave bases the abundance of zoophycos at the top of locally frequent storm deposits could indicate a fairly opportunistic behavior and they were formed in the early hst deposit which had a relatively stable environment with low energy and higher sedimentation rate

three dimensional to two dimensional cross strata transition in the lower pleistocene catanzaro tidal strait transgressive succession southern italy sandstone tidal cross strata are the predominant sedimentary feature of strait fill stratigraphic successions however although widely described in numerous studies tidal strait fill two dimensional and three dimensional cross strata have rarely been reported to occur in discrete intervals which are laterally adjacent or vertically stacked and the meaning of this stratigraphic architecture has not yet been fully investigated understanding of the processes responsible for changes in the internal features of modern and ancient tidal bedforms is essential in order to predict lateral and vertical heterogeneities in analogous reservoir strata this facies based study aims to interpret the three dimensional to two dimensional cross strata transition observed in the lower pleistocene mixed siliciclastic bioclastic sandstone filling the catanzaro strait in southern italy during a continuous phase of tectonically driven marine transgression tidal cross strata disappear in the uppermost interval of the studied succession where mudstone strata prevail this stratigraphic trend is interpreted as the evidence of an important change in the tidal strait hydrodynamics due to a phase of relative sea level rise at the beginning of the transgression three dimensional tidal dunes migrated throughout the ca 3 to 4 km wide and ca 30 km long wnw ese oriented catanzaro strait due to strong tidal currents amplified through the seaway and flowing in semi diurnal phase opposition as the intermediate phase of transgression enlarged the seaway width the tidal current strength decreased as tidal water exchange occurred over a larger cross sectional area the progressive reduction of the bed shear stress modified three dimensional tidal dunes into an extensive two dimensional bedform field at the end of the transgression the further widening of the catanzaro strait into a ca 10 to 12 km wide marine passageway changed the tidally dominated strait into a non tidal open shelf the results of this research suggest the presence of a critical cross sectional area in the narrowest strait centre zone which controls the activation and deactivation of tidal current amplification along a marine seaway

a zoophycos carnival in devonian beds paleoecological paleobiological sedimentological and paleobiogeographic insights abstract devonian occurrences of zoophycos are often observed in successions representing shelfal deposits and have been interpreted as the first expansion of this trace fossil during the paleozoic dense zoophycos occurrences in storm generated paleozoic beds have been interpreted as the result of ecological opportunist strategy when the tracemaker exploited quiet nutrient garden substrates after storms in the devonian ponta grossa formation pragian to frasnian of the parana basin brazil zoophycos is both preserved in storm generated strata indicating oxyc substrates and in association with chondrites and phycosiphon suggesting dysoxic offshore deposition this study focuses on the analysis of zoophycos observed in the devonian strata to understand the depositional context reflected by paleoecologic strategies and taphonomic signatures we analyzed the ichnofabrics and sedimentary facies of devonian sections from the parana basin focusing on the occurrences of zoophycos the tiering structure involving dense zoophycos ichnofabrics demonstrated that shallower burrows e g asterosoma palaeophycus cylindrichnus schaubcylindrichnus skolithos reworked deep tier burrows chondrites phycosiphon and zoophycos indicating erosion of surficial levels the dense zoophycos ichnofabric representing the fair weather suite obliterated primary sedimentary structures of storm deposits which favored the visibility of deep tier structures in a lam scram pattern in this sense dense zoophycos ichnofabric from parana basin cannot be linked to an opportunistic behavior but to an over represented occurrence in space and time being a taphonomic artifact related to low accommodation space in prograding context the association with other trace fossils allowed the attribution of zoophycos as a component of distal and archetypal expressions of cruziana ichnofacies rather than zoophycos ichnofacies concerning the vertical distribution of zoophycos in the parana basin this trace appears in strata related to the first occurrence of land plants being common in the pragian eifelian interval and declining in upper strata this decline might be related to a potential structural change of the parana basin during middle devonian

milankovitch forcing of bioturbation intensity in deep marine thin bedded siliciclastic turbidites abstract trace fossils have been used to infer a milankovitch type control on pelagic and hemipelagic sediments but there have been no comparable studies in deep marine siliciclastic turbidite successions here we present the results of a quantitative analysis of trace fossil abundance and intensity in an essentially continuous middle eocene 230 m long well a6 core comprising very thin and thin bedded siliciclastic turbidites in the deep marine ainsa basin spanish pyrenees after removing the sediment slides and debris flow deposits as these represent geologically instantaneous events approximately two orders of magnitude thicker than the typical laminated turbiditic sediments in the core spectral analysis was conducted on the bioturbation intensity data spectral analysis of bioturbation intensity in the a6 core suggests for the first time from a siliciclastic turbidite succession at a tectonically active plate margin thrust top basin in a foreland basin a cyclicity that is interpreted to reflect the 41 kyr and an 112 kyr possibly an average of the 95 and 125 kyr milankovitch frequencies we propose that this drove environmental changes in bottom water conditions in the ainsa basin most likely leading to critically varying levels of oxygenation stratification of bottom waters our age model for the ainsa basin 4 km of deep marine sediments in 10 myr yields an average sediment accumulation rate of 40 cm kyr 1 that is consistent with that inferred from the spectral analysis 30 cm kyr 1 for fine grained sedimentation an implication of these results is that global environmental change probably glacio eustasy acted as a driver on deep marine siliciclastic sedimentation patterns during the middle eocene

physicochemical and biological influences on sedimentary fabric formation in a salinity and oxygen restricted semi enclosed sea gotland deep baltic sea two ca 8000 year long sediment cores from the gotland deep the central sub basin of the baltic sea were studied by means of digital images x radiographs and scanning electron microscopy energy dispersive x ray mineralogical analysis to gain understanding of the physicochemical and biological influences on sedimentary fabric formation in modern and ancient seas with a high flux of organic carbon and associated oxygen stress and depauperate ichnofauna four lithofacies were recognized i sharply laminated mud ii biodeformed mud iii burrow mottled mud and iv sedimentation event bed the sharply laminated and burrow mottled facies dominate the cores as alternating long intervals whereas the biodeformed and sedimentation event facies occur as thin interbeds within the sharply laminated intervals the sharply laminated mud comprises alternating diatom rich and lithic laminae with occasional mn carbonate laminae lamination discontinuity horizons within the laminites where the regular lamination is overlain sharply by gently inclined lamination challenge the traditional view of mud accumulation by settling from suspension but indicate localized accumulation by particle trapping microbial mats and potentially by the rapid lateral accretion of mud from bedload transport the biodeformed interbeds record brief few years to few decades oxic dysoxic conditions that punctuated the anoxic background conditions and permitted sediment surface grazing and feeding by a very immature benthic community restricted to the surface mixed tier the likely biodeformers were meiofauna and nectobenthic pioneers passively imported with currents the sedimentation event interbeds are distal mud turbidites deposited from turbidity currents probably triggered by severe storms on the adjacent coastal areas the turbidite preservation was favoured by the anoxic background conditions the long burrow mottled intervals are characterized by intensely bioturbated fabrics with discrete planolites rare arenicolites polykladichnus and very rare lockeia trace fossils as well as bivalve biodeformational structures which represent shallowly penetrating endobenthic feeding and grazing strategies and permanent dwellings these burrowed intervals represent longer periods several years to few centuries of oxic dysoxic conditions that permitted maturation in the benthos by means of larval settling of opportunistic worm like macrofauna and bivalves resulting in the development of a transition tier these observations imply more dynamic and oxic depositional conditions in gotland deep than previously thought comparison to previous zoobenthic studies in the area allowed discussion of the benthic dynamics and the identification of probable biodeforming and trace producing species implications for current biofacies and trace fossil models are discussed

ecologic interpretation of deep sea trace fossil communities abstract trace fossil types and their vertical arrangement tiering are closely related to the biotope and hence can provide information on ecological conditions especially on oxygenation benthic food content sedimentation rate and substrate consistency however to use the full potential of trace fossils for environmental analyses various ichnologic criteria are necessary in addition to trace fossil taxonomy based on a taxonomically oriented ichnologic evaluation of modern deep sea environments six ichnologic aspects to ecologic changes have been found to be of major importance 1 1 penetration depth of burrows is influenced by oxygenation benthic food availability and substrate consistency 2 2 the number and vertical extension of tiers varies due to environmental changes a decrease in the vertical extension of tiers telescoping indicates a decrease in oxygenation benthic food content and or sedimentation rate if shallow penetrating traces disappear oxygen may be depleted and if the deepest tiers disappear the benthic food content may be lowered 3 3 the size diameter of specific trace fossils can indicate oxygen and benthic food availability 4 4 degree of bioturbation is related to sedimentation rate and benthic food content and the diversity of the whole ichnocoenoses or within a specific tier is affected by oxygenation benthic food content sedimentation rate and substrate consistency 5 5 the type of burrow wall unlined mucus lined pellet lined mainly refers to substrate consistency and subordinately to pore water oxygenation 6 6 the type of sediment displacement by body appendages used for excavation ingestion sideward pressing or outside pumping is related to substrate consistency and grain size

trace fossils indicating bottom aeration changes folusz limestone oligocene outer carpathians poland abstract bioturbation sequences in the pelagic folusz limestone indicate deposition under decreasing bottom aeration possibly in association with the development of microbial mats u shaped burrows diplocraterion and arenicolites exclusively were produced in the laminated limestone and they represent the only colonizers sessile suspension feeders of the oxygen deficient sediment

pyrite framboids interpreted as microbial colonies within the permian zoophycos spreiten from southeastern australia two types of pyrite framboids pf probably sulphate reducing bacteria have been found within the zoophycos spreiten hosted in the guadalupian middle permian glaciomarine greywacke of the westley park sandstone member within the broughton formation from the southern sydney basin of southeastern australia they are composed of non sheathed pf1 and sheathed pf2 sub micron balls respectively chemically the sub micron balls consist of iron sulphur carbon and oxygen both pf1 and pf2 occur in rhythmic alternation within the thick light grey and thin dark grey minor lamellae of zoophycos spreiten the framboids from the minor lamellae are highly abundant and occur in an orderly arrangement of equal density and in a good state of preservation within zoophycos spreiten no homogeneous filling fecal pellets or any sign of re exploitation of the minor lamellae have been recognized no similar framboids have been observed outside zoophycos spreiten therefore the framboids are interpreted as the pyritized remains of microbial colonies within zoophycos spreiten the trace zoophycos would be a multifunctional garden that may have been carefully constructed by the zoophycos maker where different microbial colonies were orderly and carefully planted and cultured within different minor lamellae further it is proposed that the zoophycos maker had a symbiotic relationship with microbial colonies on the mutual basis of food supply and redox conditions the fact that the overlying spreiten cut the underlying ones indicates that the zoophycos from the study area is of an upward construction the rhythmic alternation of both the thick light grey and thin dark grey minor lamellae within zoophycos spreiten may be suggestive of a gardening manner of the zoophycos maker responding to the warm and cold changes food supply in pulses and variations of sedimentation rate for planting and culturing microbial colonies under the conditions of a glaciomarine environment at the high latitudes

paleoethologic implications of zoophycos from late cretaceous and paleocene limestones of the venetian prealps northeastern italy large specimens of zoophycos are abundant in paleocene pelagic limestone successions in the vicinity of feltre and belluno in northeastern italy these burrow systems are familiar examples of the strongly ribbed downwardly spiralling version of the ichnogenus containing well developed primary and secondary lamellae marginal tunnels and poorly preserved axial structures some of the specimens contain fecal pellets rich in non carbonate mud and carbonized phytodetritus suggesting surface deposit feeding and organized subsurface storage of fecal material by the zoophycos producer other examples of the burrows record a departure from the normal behavioral pattern in the form of conspicuous radial tunnels that diverge from the axial region cut across structural elements and follow the laminae exactly to the outer margin this special feature of fully developed zoophycos appears to represent the last time the trace producers recycled the banks of fecal material possibly during long intervals of meager food supply at the deep ocean floor

environmental factors affecting the development of the zoophycos ichnofacies in the lower cretaceous rio mayer formation austral basin patagonia abstract the rio mayer formation berriasian albian is part of the basal infill of the austral basin southwestern gondwana in the los glaciares national park santa cruz province seven sections were sedimentologically studied in detail the investigated interval is mainly composed of black mudstones and shales interbedded with marls and fine grained sandstones the vertical distribution of these lithologies provided the basis to distinguish three major units lower middle and upper in general within the rio mayer formation two different developments of the zoophycos ichnofacies were recognized first in the middle unit valanginian hauterivian this ichnofacies shows a high degree of bioturbation having a bioturbation index bi between 3 and 4 zoophycos specimens are of large size the spreiten are nearly 1 cm in height and more than 1 m in width this ichnogenus is associated with chondrites and bergaueria perata environmentally this ichnofacies formed during a transgression the sedimentation rates were very low and promoted the accumulation of benthic food in the outer shelf second the zoophycos ichnofacies in the upper unit albian exhibits a less intense degree of bioturbation bi between 0 and 1 and zoophycos is of relatively small size the spreiten are 0 3 cm high and short typically are associated ophiomorpha chondrites palaeophycus and teredolites when this ichnofacies formed the prodelta margin prograded across the outer shelf and led to enhanced sedimentation rates further offshore resulting in the dilution of the nutrients

bias in foraminiferal multispecies reconstructions of paleohydrographic conditions caused by foraminiferal abundance variations and bioturbational mixing a model approach abstract a simple box model was applied to study the combined effect of bioturbation and foraminiferal abundance variations using synthetic isotope records constructed from the greenland oxygen isotope record gisp2 apart from the well known general smoothing of the signal the attenuation of peak heights and the up or downwards shift of the proxy records at intervals of changing abundance the modeling results draw attention to two effects of special importance to climatic reconstructions based on the comparison of proxy signals from two or more planktonic foraminifer species first the bioturbational mixing of tests out of abundance maxima and into over and underlying sediment can lead to the introduction of stratigraphic shifts between different species when species with opposing abundance patterns are used this shifting of the signals can easily result in apparent increases or decreases in the isotopic gradients between different species especially at intervals of rapidly changing climate conditions second in intervals with rapidly changing environmental conditions such as dansgaard oeschger cycles where species with different preferences often show opposing abundance patterns the mixing of foraminifer tests out of their respective abundance maxima can result in a general but artificial offset between the two species this offset then may disappear during intervals of slower variability these artifacts have the potential of seriously biasing any paleoceanographic and paleoclimatic reconstructions based on multispecies analysis where the studied species show opposing abundance patterns it is therefore highly recommended that species with as low abundance variations as possible or at least with similar abundance variations are used whenever multispecies reconstructions are attempted

ethology of the trace fossil chondrites form function and environment abstract the behaviour of the iconic ichnogenus chondrites is re evaluated based on review of existing literature and analysis of novel data macroscopic thin section and esem edx observations ct scans and resin peels of modern analogues computer controlled serial grinding morphometric analysis and theoretical morphology the bedding plane expression of chondrites is well constrained by morphometry 1 the angle of dichotomy formed by a pair of adjacent branches is typically between 30 and 56 interquartile range mean 47 2 branching order is between 1 and 9 3 branches are on average nine times longer than wide in the third dimension downward branching is dominant but bundled shafts and upward branching may be present the size of chondrites increased markedly from the late jurassic to the late cretaceous suggesting that the tracemakers became larger and larger microfabric analysis of chondrites shows active fill or alternatively passive fill of empty tunnels by currents or clay percolation a new mechanism proposed herein the tracemakers built chondrites to obtain food 1 vermiform deposit feeders produced chondrites for searching for food in the sediment fodinichnion 2 asymbiotic bivalves built chondrites for cultivating and directly ingesting bacteria agrichnion 3 chemosymbiotic bivalves produced chondrites to provide symbionts with chemical agents chondrites was modified through the life of the tracemaker or it represented a part of the producer s lifespan chondrites and its modern tracemaker s is associated with a range of marine settings including well oxygenated dysoxic and space limited nucleocave environments as such chondrites is regarded as an extremotolerant ichnotaxon

an aberrant helicoidal trace fossil chondrites sternberg a helicoidal specimen of chondrites sternberg from upper cretaceous marly flysch in switzerland is interpreted as a deep tier trace fossil its producer reworked the filling of a shallow tier helicoidal burrow that was emplaced earlier but the earlier trace fossil is not preserved the aberrant chondrites was formed by the same tracemaker as the adjacent chondrites intricatus brongniart 1999 elsevier science b v all rights reserved

modelling of outbursts at 26 colliery glace bay nova scotia part 1 outburst history and field data abstract the outbursts experienced at 26 colliery glace bay nova scotia originated from within sandstone river channels just above and sometimes penetrating the coal seam these outbursts caused delays in driving the main headings a considerable loss of revenue and threatened the closure of some areas of the mine a major mine fire has since closed this mine however other mines in the sydney coal field are expected to experience similar problems part 1 of this paper summarises the geology of the sydney coal basin and the geology associated with the outbursts a brief description of the 37 recorded outbursts is presented little data is available to classify the conditions at the outbursts sites but that available on the rock properties gas pressures and field stress conditions is summarised here a better understanding of the mechanisms of these outbursts could pave the way to creating a safer and more profitable operation at neighbouring mines part 2 of this paper proposes a mechanism that explains these occurrences and a model is developed to analyse the influencing parameters part 3 compares the results of the model studies with field observations

ichnological trends along an open water transect across a large marginal marine epicontinental basin the modern baltic sea article i nfo late holocene sediments in the baltic sea provide an opportunity to study lateral changes in the assemblages of identifiable biogenic sedimentary structures ichnofossils in a large high latitude semi enclosed sea with instrumentally determined gradients in biodiversity and environmental factors such as salinity and ox ygen availability integrated sedimentological and ichnological analysis is carried out on 6 long cores collect ed along an open sea declining salinity transect across the basin muddy sediments in euhaline kattegat and polyhaline mecklenburg bight sites are characterized by the archetypal cruziana ichnofacies portrayed by subsurface deposit feeding structures scolicia and planolites surface deposit feeding structures sko lithos and structures that reflect both these feeding strategies palaeophycus arenicolites polykladichnus and unnamed biodeformational structures produced by bivalves the ichnofossils are tiered to 3 levels the cruziana ichnofacies is impoverished in the higher mesohaline arkona basin and even more so with de clining salinity farther inland the deepest oxygen restricted study sites gotland deep and the western gulf of finland below a permanent halocline are characterized by very small and shallow deposit feeding struc tures planolites and rare flat arenicolites polykladichnus and poorly developed tiering the nearly freshwa ter eastern gulf of finland is characterized by the cenozoic archetypal mermia ichnofacies dominated by narrow and shallow subsurface and surface deposit feeding structures planolites and flat arenicolites polykladichnus large planolites 3 7 mm in diameter at this site are untypical of mermia ichnofacies assem blages these results confirm the earlier observations that marine forms dominate brackish water ichnoas semblages with the ichnofossil size and diversity decreasing with declining salinity the results also confirm the predicted decreases in the ichnofossil size and vertical extent at low oxygen levels poorly devel oped tiering is a particularly useful indicator of oxygen stress in the salinity restricted system

reappraisal of the cambrian glauconite bearing anse maranda formation quebec appalachians from deep sea turbidites to clastic shelf deposits the cambrian anse maranda formation is a glauconite bearing clastic succession within the quebec reentrant it is part of the appalachians humber zone particularly of the shale feldspathic sandstone assemblage which represents the rift to drift deposits of the laurentian margin the massive sandstones of the anse maranda were originally interpreted as the proximal turbidites of a deep sea fan the occurrence of glauconite and the high degree of bioturbation which give the sandstones a massive aspect suggest a different depositional environment detailed ichnology and lithofacies descriptions indicate that the anse maranda predominantly represents shelf sediments deposited in storm influenced environment and that intense bioturbation destroyed most of the sedimentary structures the paleo geographic reconstruction suggests that the anse maranda was deposited seaward of a headland identified as the montmorency promontory along a narrow shelf with an irregular topography some coeval turbidites of sim

ichnology of american chalks the selma group upper cretaceous western alabama chalk facies within the selma group most of them impure crop out only in a relatively small area of western alabama and eastern mississippi and grade laterally into calcareous terrigenous clastics body fossils and skeletal borings described in a separate paper are diverse and abundant in some units especially the impure chalks major burrow forms also distributed unequally among these units include chondrites sp cylindrichnus pustulosus n sp planolites beverleyensis skolithos sp teichichnus rectus teichichnus zigzag n sp thalassinoides paradoxicus thalassinoides suevicus trichichnus linearis zoophycos sp and mineralized burrows minor forms include palaeophycus sp rosselia spp and mantled burrows characteristic trace fossil distributions especially include the striking dominance of thalassinoides paradoxicus in chalk hardgrounds of the arcola member of the mooreville chalk and successive patterns of bioturbation in the lower unnamed member of the demopolis chalk in purer chal

global variations of surface ocean productivity in low and mid latitudes influence on co2 reservoirs of the deep ocean and atmosphere during the last 21 000 years based on detailed reconstructions of global distribution patterns both paleoproductivity and the benthic 13c record of co2 which is dissolved in the deep ocean strongly differed between the last glacial maximum and the holocene with the onset of termination i about 15 000 years ago the new export production of low and mid latitude upwelling cells started to decline by more than 2 4 gt carbon year this reduction is regarded as a main factor leading to both the simultaneous rise in atmospheric co2 as recorded in ice cores and with a slight delay of more than 1000 years to a large scale gradual co2 depletion of the deep ocean by about 650 gt c this estimate is based on an average increase in benthic 13c by 0 4 0 5 the decrease in new production also matches a clear 13c depletion of organic matter possibly recording an end of extreme nutrient utilization in upwelling cells as shown by sarnthein et al 1987 the productivity reversal appears to be triggered by a rapid reduction in the strength of meridional trades which in turn was linked via a shrinking extent of sea ice to a massive increase in high latitude insolation i e to orbital forcing as primary cause

zoophycos distribution and sequence stratigraphy examples from the jurassic and cretaceous deposits of southeastern france the trace fossil zoophycos is characteristic in certain jurassic and cretaceous basinal deposits of southeastern france these deposits are cyclic marl limestone alternations in which depositional sequences can easily be recognized two kinds of sequence have been studied the marl limestone couplet and the third order sequence detailed observations show that zoophycos has a particular position in the sequences in the marl limestone couplet the trace is concentrated towards the upper part of the calcareous beds the burrow is also present in the lower part of the beds and at the top of the underlying marls but is less abundant the same kind of burrow distribution occurs in the third order sequences zoophycos is concentrated in the upper part of the calcareous bundles which are interpreted as lowstand systems tracts while it is totally lacking in the superimposed more marly sequence which probably corresponds to the lower part of the transgressive systems tracts the burrow may be present throughout the highstand systems tracts which overlie the maximum flooding surfaces but is less abundant the particular distribution of zoophycos is related to the fluctuations of certain environmental factors the most important of which are the carbonate productivity the sedimentation rate and the substrate consistency zoophycos can be proposed as a useful marker of sequence boundaries and of the transgressive surfaces in distal deposits where other signals for sequence analysis are often lacking

the former presence of organic matter caused its later absence burn down of organic matter in oceanic red beds enhanced by bioturbation eocene variegated shale carpathians eocene oceanic red beds that formed in a well oxygenated setting at low sedimentation rates below the calcite compensation depth are effectively barren of organic carbon in the present state recurrent distal low erosive turbidites preserve the bioturbated zone underneath that documents seasonal and long term fluctuating accumulation of considerable amounts of organic matter on the sea floor as evidenced by scolicia the producers of this trace fossil exploited nutritious organic matter conserved in turbidite buried sea floor deposits over the long term slow average sedimentation of hemi pelagic oxic red mud led to long oxygen exposure times and low burial of organic matter consequently trace fossils representing persistent sediment feeding modes are of small size although the food limited setting appears appropriate for producers of graphoglyptids such stationary burrows have not been encountered because seasonal deposition of organic matter fostered at least temporary surface layer feeding organisms for instance producers of nereites irregularis that intensively reworked the sediment and hence hindered graphoglyptid production these findings confirm palaeoceanographic modelling results that suggest upwelling in the study area during the eocene this article is protected by copyright all rights reserved

the plume of the yukon river in relation to the oceanography of the bering sea abstract physical and biological oceanography of the northern bering sea including the plume of the yukon river were studied using satellite data in conjunction with shipboard measurements the satellite data recorded by the noaa very high resolution radiometer vhrr and advanced very high resolution radiometer avhrr and the landsat multispectral scanner mss and thematic mapper tm sensors were used to detect sea surface temperatures and suspended sediments shipboard measurements of temperature salinity and chlorophyll were acquired by the inner shelf transfer and recycling ishtar project and were compared to digitally enhanced and archived satellite images sea surface temperatures derived from satellite data were generally higher than field measurements this difference was the likely result of microscale stratification of the water column although other factors could have been involved also satellite data confirmed the known distribution of water masses in the region coachman et al 1975 upwelled water of oceanic origin anadyr water was visible as a cold surface plume running from anadyr strait north through western bering strait in the east warm alaskan coastal water was prominent along the alaskan coast including norton sound and the southeastern chukchi sea areal patterns of temperature salinity and phytoplankton distribution determined from field measurements agreed reasonably well with patterns of water mass distribution obtained from satellite images archived satellite images 1974 1978 were used to investigate the variability of the distribution of sea surface temperature and of the turbid plume of the yukon river alaskan coastal water acw first warms near the coast in june and the process extends seaward as summer progresses turbid water associated with discharge of the yukon river progresses in the same fashion extending northward across the entrance to norton sound maximum extent of the plume occurs in october anadyr water flows north through anadyr strait past st lawrence island its extent is variable depending on mesoscale pressure and local wind fields

unbioturbated sediments on a muddy shelf hypoxia or simply reduced oxygen saturation abstract x radiographs of sediment box cores acquired from the western gulf of mexico reveal limited bioturbation in sediment deposited in bathymetries greater than 35 m between 15 and 35 m sediments are thoroughly bioturbated with averaged bioturbation indices for all beds in a core between 2 1 and 5 6 and trace diversities between 2 and 9 distinct burrow forms below 35 m water depth box cores exhibit trace diversities of 1 3 and core averaged bioturbation indices range between 0 3 and 3 6 there is an overall decrease in trace diversity and bioturbation indices in the offshore direction cross shore ichnological trends are compared to dissolved oxygen contents of bottom waters above 35 m dissolved oxygen do contents show pronounced variability ranging from 100 do saturation through to hypoxia the data reveal a direct correlation between a the density of infauna and the diversity and density of burrows and b do of bottom water the degree of bioturbation is significantly reduced in waters that are oxic but below 80 do saturation based on these observations we suggest that it is inappropriate to link low bioturbation intensities and diversities to hypoxia

mechanism of instantaneous coal outbursts thousands of mine workers die every year from mining accidents and instantaneous coal outbursts in underground coal mines are one of the major killers various models for these outbursts have been proposed but the precise mechanism is still unknown we hypothesize that the mechanism of coal outbursts is similar to magma fragmentation during explosive volcanic eruptions i e it is caused by high gas pressure inside coal but low ambient pressure on it breaking coal into pieces and releasing the high pressure gas in a shock wave hence coal outbursts may be regarded as another type of gas driven eruption in addition to explosive volcanic lake and possible ocean eruptions we verify the hypothesis by experiments using a shock tube apparatus knowing the mechanism of coal outbursts is the first step in developing prediction and mitigation measures the new concept of gas driven solid eruption is also important to a better understanding of salt gas outbursts rock gas outbursts and mud volcano eruptions

trace fossil model for reconstructing oxygenation histories of ancient marine bottom waters application to upper cretaceous niobrara formation colorado abstract trends of decreasing trace fossil diversity burrow size and penetration depth with diminishing oxygen availability in contemporary marine settings have been incorporated with the concept of trace fossil tiering to develop a model for reconstructing the oxygenation history of ancient basin bottom waters more sensitive than traditionally employed criteria the model permits detailed evaluation of relative degree of oxygenation through the recognition of oxygen related ichnocoenosis ori units or units of strata deposited under similar levels of bottom water oxygenation when employed in detailed vertical sequence analyses the model may also be used to construct interpreted oxygenation curves that reflect rates and magnitudes of temporal change in redox conditions the utility of the model is demonstrated by its application to rhythmically bedded calcareous strata of the niobrara formation upper cretaceous exposed in colorado non laminated strata of the niobrara are characterized by four recurring trace fossil suites referred to as the 1 chondrites 2 zoophycos teichichnus 3 planolites and 4 thalassinoides assemblages on the basis of trends in trace fossil diversity burrow diameter and penetration depth these assemblages are recognized as oxygen related ichnocoenoses interpreted oxygenation curves for the basal fort hays member reflect high magnitude redox cycles characterized by rapid deoxygenation events followed by gradual reoxygenation phases curves for the overlying smoky hill member reflect an overall lower degree of oxygenation with more irregular lower magnitude redox fluctuations significant correlation between interpreted levels of paleooxygenation and organic carbon content illustrate the model s potential for evaluating the distribution of organic rich fine grained strata co interpretation of these variables with carbonate content supports the premise that deposition was controlled by paleoceanographic perturbations modulated by milankovitch like climatic cycles comparison with traditionally emphasized macroinvertebrate body fossil criteria clearly demonstrates the greater utility of the trace fossil approach for evaluating paleo oxygenation

bioturbational structures record environmental changes in the upwelling area off vietnam south china sea for the last 150 000 years the sediments in the upwelling area off central vietnam are totally bioturbated and display a low diverse assemblage of bioturbational structures during interglacial times marine isotope stage mis 1 5a 5c 5e summer monsoon leads to pronounced upwelling and seasonally pulsed arrival of organic matter on the seafloor these deposits are characterized by a 4 tier bioturbated zone with zoophycos zoophycos producers used this seasonal food source and show a cache behavioral strategy during glacial periods upwelling was weak and oxygenation of bottom water decreased as evidenced by bioturbational structures that show a decrease in size penetration depth and diversity enlarged freshwater influx during glacial times fuelled primary production and led to estuarine circulation the resultant oxygen minimum layer favored an increased deposition of organic matter that in turn affected sediment properties during mis 2 and 5b oxygenation was probably a little lower than today during mis 3 and 5d chondrites like burrows point to a stronger oxygen deficiency during mis 4 bottom water oxygenation was even lower and only biodeformational structures occur in soft sediment rich in benthic food based on these findings an ichnofabric model for food rich fairly soft deposits experiencing oxygen deficiency is suggested having biodeformational structures as low oxygen end member

the preservation potential of ash layers in the deep sea the example of the 1991 pinatubo ash in the south china sea following the eruption of mount pinatubo on 15 june 1991 volcanic ash was transported westward to the south china sea in an atmospheric plume falling out and settling to the sea floor within days and forming an up to 10 cm thick layer on an area 400 000 km 2 immediately after deposition surviving deepburrowing animals re opened their connection to the sea floor to obtain water for respiration and or food take up later small sized meiofauna and then macrofauna re colonized the sea floor mixing newly deposited organic fluff with the underlying ash consequently ash deposits thinner than 1 mm have not often been observed as a continuous layer when cored six years after the eruption while ash about 2 mm thick is now patchily bioturbated in areas covered by ash thicker than 5 mm mixing by benthic animals is controlled mainly by the adaptation of the burrowing fauna to variations in grain size the rate of background sedimentation the availability of benthic food on and within the sediment and pore water oxygen levels with respect to these factors four provinces can be distinguished i along the philippines margin run off from land fuels primary production that in turn leads to a high benthic food content the benthic fauna is adapted to a variable grain size and rapid sedimentation therefore mixing is intense and the preservation potential of the ash layer is low ii in areas affected by deposition of hyperpycnites and turbidites i e in canyons in front of river mouths and in the manila trench the ash layer is preserved due to rapid burial iii the area to the west to about 116 e receives low amounts of benthic food benthic mixing is less intense and the preservation potential of the ash is high iv the central south china sea where the ash is thinner than 3 cm is affected by intense wind mixing and upwelling and the benthic food content is high thus the chance that the ash will be preserved as a sharp based layer is low consequently the style of ash preservation has palaeo environmental significance older buried and burrowed event layers provide further information to elucidate the fate of the 1991 pinatubo ash layer in general their appearance fits with observations in the recent

application of satellite visible band data to high latitude oceans abstract remote sensing of high latitude oceans differs from oceans of tropical and subtropical latitudes because of the decoupling of the water s temperature structure from the flow dynamics at low water temperatures sea surface thermal patterns are useful here as tracers of the flow only without a direct link to the circulation dynamics oceanic flow responds to water density contrasts and at high latitudes the density is controlled by salinity distributions though density contrasts are not ordinarily detectable with remote sensors freshwater discharge in the northeast pacific contains very fine sediments glacial flour that can be detected using landsat thematic mapper tm and multi spectral scanner mss imagery from the tm data we have discovered several new coastal circulation features in the northern gulf of alaska flow around a coastal island produces a myriad of dipole eddies which are important to the cross shelf transport of salt and heat they also serve as sites to test numerical models to allow a better understanding of coastal flows and eddy formation elsewhere detection of these dipole eddies from their sediment distributions has allowed the comparison of different spectral bands from six imaging satellite sensors for their abilities to describe these features we conclude that in addition to the tm sensor s capability the sediments can be detected with the mss and coastal zone color scanner czcs sensors but not with avhrr or defense meteorological satellite program dmsp as a consequence of this comparison of satellite visible data we have confirmed that the dipole eddies here exist under low flow conditions 3 s

tiering in suspension feeding communities on soft substrata throughout the phanerozoic tiering of benthic marine suspension feeding communities on soft substrata has varied throughout the phanerozoic epifaunal tiering was most developed during the middle and late paleozoic and the triassic to jurassic with large scale reductions in tiering occurring during the permian triassic extinctions and after the jurassic infaunal tiering reached its highest level of organization after the paleozoic

sapropel burn down and ichnological response to late quaternary sapropel formation in two 400 ky records from the eastern mediterranean sea two approximately 400 ky long sedimentary records from the eastern mediterranean sea were used to study the factors determining why some sapropels are more or less completely erased while others are preserved x ray radiographs bulk density organic carbon content fe al and mn al ratios were used to reconstruct initial thickness and burn down ratios of sapropels s1 to s11 the results show that at the low sedimentation rate open ocean settings studied initial carbon content of the sapropel as well as post sapropel sedimentation rate and carbon flux have had only limited influence on the preservation of sapropels in contrast the regional position relative to the deep water source controlling bottom water current intensity and bottom water oxygenation played a major role in the preservation of the sapropels furthermore orbitally controlled variations in the intensity of subsequent summer insolation maxima also seem to play an important role in the preservation potential of sapropel layers subsequent strong insolation maxima resulting in thick sapropels tend to act as a lid preventing further burn down of the older sapropels below the long and well dated records also offer an opportunity to study the response of the benthic fauna to the drastic environmental changes related to the formation of sapropels the sediment in the two cores is generally characterized by mottled burrows with only scarce occurrences of distinct trace fossils such as scolicia thalassinoides chondrites and trichichnus the meager ichnofauna is attributed to the well oxygenated and warm bottom waters in an oligotrophic environment typical for non sapropel times the sparse ichnofauna and the lack of tiered ichnocoenosis render existing models of bioturbational response to changes in bottom water oxygenation unsuitable for this kind of environments however observations on individual traces support earlier studies that suggest that the trace fossils trichichnus and chondrites are the result of chemosymbiotic activities that benefit from reducing conditions in the pore water and that the producers of scolicia have a preference for well oxygenated conditions and sandy substrates c 2006 elsevier b v all rights reserved

feeding traces related to shells from the prague basin czech republic tremadocian to early darriwilian ordovician abstract post mortem feeding activities along or within the interiors of shallowly buried shells can be preserved by sediment infilling and be visible on internal moulds of shelly fossils almost no such activities were recorded in three lowermost ordovician formations t enice milina and klabava tremadocian to dapingian of the prague basin in the barrandian area czech republic in contrast a distinct increase occurs in the sarka formation early and middle darriwilian sarka feeding traces are common in shells preserved within siliceous nodules they are associated with almost all taxonomic groups composing a rich and diversified fossil assemblage within that formation but there is no evidence of similar traces produced by feeding on soft bodied fauna arachnostega pilichnus and palaeophycus are the most abundant ichnogera observed their trace makers selectively oriented on decaying soft tissues palaeophycus producers apparently preferred an easily accessible and nourishing food that was easily consumed these traces typically intersect a digestive tract especially the gut the arachnostega and pilichnus traces are oriented in a manner suggesting systematic feeding these tracemakers spent more time in a carcass reaching lower nutrient tissues including various membranes that degraded more slowly and were more difficult to access the preferential distribution of feeding traces in each shell reflects the topology of the soft tissues serving as a food all studied feeding traces were found in nodules never in shales of the sarka formation this reflects a taphonomical bias influencing occurrences of these traces therefore a lack of the feeding traces in the units underlying the sarka formation could be the result of taphonomic differences related to depositional conditions and diagenetic processes nevertheless the abundance of those traces in the sarka formation illustrates the prosperity of this feeding behavior during the darriwilian an increase in the abundance diversity and complexity of communities that fed within the internal ecospace of shells while utilizing feeding strategies developed during previous periods is considered to be a primary effect related to increased ecosystem complexity during the great ordovician biodiversification event

biogenic structures in modern slope to deep sea sediments in the sulu sea basin philippines abstract slowly accumulated slope and rise sediments 5 20 cm 1000 yr are totally bioturbated as compared to only 10 30 in rapidly deposited abyssal plain sediments 100 200 cm 1000 yr in contrast to a decrease in degree of bioturbation biogenic trace diversity increases with water depth all ichnocoenoses are clearly influenced by the low oxygen content of the bottom water caused by minimal circulation and restricted water exchange oxygen deficiency and relatively high sedimentation rates have created nutrient rich sediments thus there is no need for optimal fractionation into individual ecological niches and behavioral programs are not highly developed 1 in slope and rise sediments animal traces are associated with biodeformational structures 2 in slope to abyssal plain sediments trace assemblages are dominated by burrows with open tubes for circulation of respiration water 3 in abyssal plain sediments small diameter biogenic traces common in turbidite sequences graphoglyptids e g paleodictyon are absent this may be due to rapid sedimentation leading to inefficiency of graphoglyptid behavior where graphoglyptids are lacking ichnocoenoses are dominated by forms like phycosiphon in slope and rise sediments graphoglyptids may have been destroyed by deeper burrowing organisms

iron nutrients and humic type fluorescent dissolved organic matter in the northern bering sea shelf bering strait and chukchi sea 1 the concentrations of dissolved fe dfe total dissolvable fe humic type fluorescence intensity humic f intensity as humic type fluorescent dissolved organic matter humic type fdom and nutrients were determined vertically in the northern bering sea shelf yukon river estuary region and st lawrence island polynya region the eastern chukchi sea shelf chukchi shelf polynya region and the central bering strait during 30 july to 12 august 2007 and 30 june to 12 july 2008 in early july 2008 with a nearly peak river water discharge period remarkably high humic f intensity and high dfe were found with a decrease in salinity s 26 30 in the surface water of the yukon river estuarine region these results suggest that riverine humic type fdom is responsible for dfe in coastal waters with natural organic ligand complexation of fe iii apparently playing an important role in iron transport to the northern bering sea shelf in the st lawrence island and chukchi shelf polynya regions cold dense waters t 1 5 to 1 7 c and 26 2 to 26 7 were found in deep and bottom waters the cold waters are characterized by high nutrient and iron concentrations and high humic f intensity probably resulting from two main processes brine rejection during sea ice formation and transport across the sediment water interface during early diagenesis in the central bering strait the waters are vertically uniform with high salinity s 32 5 and high nutrient and iron concentrations these waters appear to originate from the outer shelf of the bering sea and are not affected by denitrification occurring in bottom sediments of the bering shelf

brines in the carboniferous sydney coalfield atlantic canada abstract formation waters within upper carboniferous sandstones in the sub sea prince and phalen coal mines nova scotia originated as residual evaporative fluids probably during the precipitation of windsor group lower carboniferous salts which underlie the coal measures salinity varies from 7800 to 176 000 mg l and the waters are na ca cl brines enriched in ca sr and br and depleted in na k mg and so4 relative to the seawater evaporation curve br cl and na cl ratios suggest that the brine composition corresponds to an evaporation ratio of as much as 30 the brines lie close to the meteoric line on h o isotopic plots but with a compositional range of 18o from 4 18 to 6 99 and of d from 42 4 to 23 5 distant from modern meteoric or ocean water mine water composition contrasts with that of nearby salt spring brines which are inferred to have originated through dissolution of windsor group evaporites by modern meteoric waters however a contribution to the mine waters from halite dissolution and from br in organic matter cannot be ruled out present concentrations of several elements in the brines can be explained by water rock interaction the original windsor brines probably moved up into the overlying coal measure sandstones along faults prior to the late triassic the high salinity and irregular salinity distribution in the phalen sandstones suggests that the brines have undergone only modest dilution and are virtually immobile in contrast prince waters show a progressive increase in salinity with depth and are inferred to have mixed with surface waters basinal brines from which these modern formation fluids were derived may have been important agents in base metal and ba mineralisation from the mid carboniferous onwards as saline fluid inclusions are common in zn pb sulphide deposits in the region

chondrites a trace fossil indicator of anoxia in sediments the trace fossil chondrites a highly branched burrow system of unknown endobenthic deposit feeders occurs in all types of sediment including those deposited under anaerobic conditions in some cases such as the jurassic posidonienschiefer formation of germany chondrites occurs in black laminated carbonaceous sediment that was deposited in chemically reducing conditions in other cases such as numerous oxic clastic and carbonate units throughout the geologic column chondrites typically represents the last trace fossil in a biotutbation sequence this indicates that the burrow system was produced deep within the sediment in the anaerobic zone below the surficial oxidized zone that was characterized by freely circulating and oxidizing pore waters

structure and function of large lobed zoophycos pliocene of rhodes greece abstract in the kolymbia limestone facies upper pliocene of the rhodes formation of rhodes greece a study was made of a large spiral form of zoophycos named herein zoophycos rhodensis in the small bay south of cape vagia two individuals were excavated and dissected while several more were serially sectioned in a vertical plane the upper parts of the zoophycos were missing through modern beach erosion but in one individual the two lowest whorls were almost completely exposed these comprised a skirt like zone of spreite surrounded by a zone of 63 marginal lobes the diameter of the trace fossils was about 1 m vertical sections demonstrated that the spreiten were composed of material advected downward from a higher horizon indicating that the spreite was produced nearly 1 m below the sea floor the skirt like zone of the spreite was constructed of sigmoidal minor lamellae in bundles separated by major lamellae the radiating major lamellae are not replaced by ridges such as is the case in many other lobed spiral zoophycos the marginal tube and to a lesser extent the spreite are mineralised with an oxidised iron mineral probably once pyrite the marginal tube is completely filled with sediment and shows no signs of collapse or compaction this is taken to indicate active backfilling and that the operative burrow was thus j shaped and not u shaped the two zones of the spreite are considered to represent two different modes of behaviour the skirt like zone probably represents deposit feeding the mineralised marginal tube and lobes possibly represent sulphide wells connected with chemosymbiosis between the trace making animal and sulphide oxidising bacteria

characteristic trace fossil associations in oxygen poor sedimentary environments the sedimentologic record of oxygen poor depositional environments typically includes trace fossils produced by deposit feeding organisms we propose an oxygen controlled trace fossil model in which increasing oxygen concentration of interstitial water in sediment parallels a transition from fodinichnia dominated through pascichnia dominated to domichnia dominated trace fossil associations in certain places such as parts of the late paleozoic oquirrh basin in utah this model provides a reasonable alternative to the more traditional depth controlled model of trace fossil distribution

paleoecology of the marine endobenthos endobenthic animals which reside within the sea bottom include stationary suspension feeders mobile deposit feeders and both stationary and mobile carnivores their activities especially with regard to dwelling feeding walking crawling and resting nesting are recorded as trace fossils abundance diversity and density of some kinds of trace fossils allow interpretation of the population strategies of the trace makers in terms of opportunistic r selected and equilibrium k selected strategies opportunistic ichnotaxa tend to be faciesbreaking traces which are highly localized in low diversity high density trace fossil associations in rocks representing environmental extremes e g variable salinities harsh temperatures low oxygen levels or shifting substrates equilibrium ichnotaxa usually are restricted to particular sedimentary facies and are characteristic of high diversity low dominance trace fossil associations in sediments reflecting stable predictable environmental conditions the most important environmental factors influencing the composition of trace fossil assemblages in marine settings are bathymetry substrate oxygen and hydrodynamic energy the four factors are closely interrelated because as water depth increases there is a general decrease in sediment grain size and hydrodynamic energy of the depositional environment as depth below the water sediment interface increases the firmness of the sediment due to compaction and dewatering increases and the oxygen content of interstitial waters drops drastically marine ichnofacies are largely substrate controlled soupgrounds are water saturated incompetent substrates typified by highly compressed and usually unidentifiable burrows softgrounds commonly contain numerous distinctive burrows and are zoned bathymetrically by the skolithos cruziana zoophycos and nereites ichnofacies firmgrounds are characterized by stiff compacted sediments in which traces of the glossifungites ichnofacies are excavated hardgrounds are cemented substrates in which bioerosion traces of the trypanites ichnofacies are bored woodgrounds are woody materials that have been exposed to the sea and bored by bivalves which produce characteristic traces of the teredolites ichnofacies tiering of endobenthic communities is common and is related to substrate preference of the burrowers and oxygen stratification of interstitial waters

baffin bay paleoenvironments in the lgm and hs1 resolving the ice shelf question abstract core hu2008029 12pc from the disko trough mouth fan on the central west greenland continental slope is used to test whether an ice shelf covered baffin bay during the last glacial maximum lgm and at the onset of the deglaciation we use benthic and planktic foraminiferal assemblages stable isotope analysis of planktic forams algal biomarkers ice rafted detritus ird lithofacies characteristics defined from ct scans and quantitative mineralogy to reconstruct paleoceanographic conditions sediment processes and sediment provenance the chronology is based on radiocarbon dates on planktic foraminifers using a r of 140 30 14 c years supplemented by the varying reservoir estimates of stern and lisiecki 2013 that provide an envelope of potential ages hu2008029 12pc is bioturbated throughout sediments between the core base at 11 3 m and 4 6 m lgm through hs1 comprise thin turbidites plumites and hemipelagic sediments with greenlandic provenance consistent with processes active at the greenland ice sheet margin grounded at or near the shelf edge abundance spikes of planktic forams coincide with elevated abundance of benthic forams in assemblages indicative of chilled atlantic water meltwater and intermittent marine productivity ird and ip 25 are rare in this interval but brassicasterol an indicator of marine productivity reaches and sustains low levels during the lgm these biological characteristics are consistent with a sea ice covered ocean experiencing periods of more open water such as leads or polynyas in the sea ice cover with chilled atlantic water at depth rather than full ice shelf cover they do not support the existence of a full baffin bay ice shelf cover extending from grounded ice on the davis strait initial ice retreat from the west greenland margin is manifested by a pronounced lithofacies shift to bioturbated diatomaceous mud with rare ird of greenlandic origin at 467 cm 16 2 cal ka bp r 140 yrs within hs1 a spike in foraminiferal abundance and ocean warmth indicator benthic forams precedes the initial ice retreat from the shelf edge at the end of hs1 ip 25 brassicasterol and benthic forams indicative of sea ice edge productivity increase indicating warming interstadial conditions within the bolling allerod interstadial a strong rise in ip 25 content and ird spikes rich in detrital carbonate from northern baffin bay indicate that northern baffin bay ice streams were retreating and provides evidence for increased open water advection of atlantic water in the west greenland current and formation of an ird belt along the w greenland margin

trace fossils as indicators of environmental change in holocene sediments of the archipelago sea northern baltic sea abstract biogenic structures in holocene sediments from the archipelago sea northern baltic sea were characterized through the analysis of x ray images of four cores collected from water depths between 32 and 66 m in the area initial colonization of endobenthic invertebrates occurred at 7800 80 calendar years bp the trace assemblage at this level is low diversity small diameter shallowly tiered and palaeophycus dominated rare arenicolites are also observed early colonization coincides with increasing marine influence in the post glacial lacustrine setting just before the dramatic onset of brackish water conditions established after 7600 bp the post incursion brackish water assemblage possesses a higher diversity of traces planolites arenicolites lockeia teichichnus which is taken to reflect the enhanced salinity and trophic state of the basin the shift from palaeophycus mottling to a planolites dominated fabric represents changed behavioural patterns in the endobenthic community due to changed substrate properties the ethology of the succeeding trace assemblage also represents a switch from domicile based activities such as predation scavenging and interface dominated deposit feeding to shallow tier deposit feeding finally traces are excluded from thinly laminated intervals demonstrating that seafloor oxygen deficiency commonly reached levels that were detrimental to colonization of the sediment substrate

vertical open burrows in deep sea sediments 2 m in length previous studies of the mixed layer in deep sea sediments suggest a maximum burrowing depth of about 10 30 cm ref 1 however we now report that two recently obtained cores from the north east atlantic s126 2 and s126 4 display open burrows to a depth of 214 cm within a distal pelagic turbidite an organic lining in one of the burrows indicates a modern origin many of the burrows are less than 0 5 mm across and are only visible on fractured surfaces their effects on sediment mixing are probably minimal but they provide a network of open vertical channels which considerably increases the permeability this is of crucial importance to studies involving pore water movement such as those associated with the radioactive waste disposal project the effect of the burrows changes the calculated permeability from the equivalent of a clay to that of a coarse sand the delicate structure of the burrows may result in their closure during handling thus requiring their effect on pore water fluxes to be studied in situ

the ichnogenus teichichnus seilacher 1955 the ichnotaxonomy of the phanerozoic trace fossil teichichnus seilacher 1955 is revised and its ethology producers and environmental affiliation are re evaluated newly studied material reveals that teichichnus is a sub vertical spreite burrow with an arcuate shape containing stacked laminae and a passively filled terminal causative burrow funnel like extension of the terminal causative burrow and wall ornamentation may occur high variation of burrow morphology is common and has resulted in the erection of 18 ichnospecies of which only four are herein regarded as valid teichichnus rectus t zigzag t patens and t duplex these ichnospecies are characterised by their overall burrow shape spreite morphology and more subordinate occurrence of branching and sculpture as recommended ichnotaxobases combined modes of feeding become evident including deposit and suspension feeding suggesting that teichichnus is a dwelling trace rather than a feeding trace aside from the classical interpretation of polychaetes as producers many features accord with an interpretation of dwelling echiurans and holothurians this interpretation may apply for many post palaeozoic t rectus and t zigzag whereas t duplex and partly t patens are likely produced by arthropods i e trilobites and crustaceans bivalves are also considered for producing teichichnus like traces teichichnus is a marine trace fossil with predominance in shallow marine environments low diversity and high density occurrences of teichichnus characterise marginal marine paralic environments with reduced salinity i e brackish water and oxygen i e dysoxia whereas in shoreface and offshore settings teichichnus occurs in association with many other ichnotaxa and in low density deep marine occurrences of teichichnus are comparably sparse and isolated records may indicate dysoxic bottom conditions

phanerozoic history of deep sea trace fossils the phanerozoic diversity of deep sea trace fossils based on 151 flysch formations displays distinct non linear changes through the phanerozoic with peaks in the ordovician early silurian and early carboniferous lowered in the permian older late jurassic a peak in the tithonian aptian lowered in the albian and the maximum in the eocene the contribution of graphoglyptids in trace fossil assemblages rises gradually up to the end of the cretaceous shows a peak in the palaeocene eocene but a depression in the oligocene all the changes were probably influenced by competition for food and food supply bottom water temperatures and oxygenation and frequency of flysch habitats there is no clear influence of major biotic crises ordovician silurian cretaceous tertiary palaeocene eocene on the diversity of deep trace fossils except the eocene oligocene crisis

depositional environments and ichnology of the deep marine succession of the amiran formation upper maastrichtian paleocene lurestan province zagros fold thrust belt iran abstract the paleoenvironmental significance of deep marine trace fossil assemblages in the upper maastrichtian paleocene amiran formation has been done for the first time in lurestan province nw zagros from the zagros fold thrust belt a semi quantitative study of trace fossil abundance bioturbation indices in the amiran formation shows that trace fossil assemblages can be very powerful discriminators of deep marine clastic fan and related environments the amiran formation is a sand rich thick bedded and coarse grained turbidite succession deep marine paleoenvironments from basin slope to basin floor settings are preserved these strata contain a diverse and abundant pre and post depositional ichnofauna proximal and axial parts of the sandy systems show low diversity and low density trace fossil assemblages dominated by post depositional trace fossils but distal environments show a general increase in trace fossil diversity abundance and number of pre depositional trace fossils the post depositional association essentially consists of dwelling feeding and grazing traces the pre depositional assemblage is rich in graphoglyptids and grazing trails and feeding structures also occur the ichnodiversity composition ethology and morphologic complexity of the pre depositional association of the heterolithic successions of thin to thick bedded turbidite sandstone and inter turbidite mudstone are characteristic of three ichnosubfacies of the nereites ichnofacies these ichnosubfacies are identified in amiran formation deposits the typical succession of ichnosubfacies can express a bathymetric trend from shallower to deeper parts and from higher to lower hydrodynamic conditions they are 1 the ophiomorpha rudis ichnosubfacies the proximal and axial parts with thick bedded channel and lobe related environments 2 the paleodictyon ichnosubfacies channel lobe transition in the distal lobe facies and 3 the nereites ichnosubfacies distal part of off axis lobe or fan fringe basin floor transition and overbank settings there is also mixed o rudis to paleodictyon ichnosubfacies channel margin lobe fringe in the proximal lobe facies the dominance of zoophycos and chondrites in poor oxygen basin floor facies may represent zoophycos ichnofacies the number of graphoglyptids increases from distal basin floor to proximal fan fringe basin floor transition fan fringe lobe complex fringe lobe complex off axis settings they are absent in the most proximal axial lobe environments due to increased volume frequency erosive power of turbidity current events and sedimentation rate grain size decreased preservation potential of shallow tier and pre turbidite trace fossils the ichnosubfacies method used here as utilized by other authors has the potential to improve paleoenvironmental analysis of other deep marine depositional settings and in outcrop investigation of turbidite systems

middle holocene to present sedimentary environment in the easternmost gulf of finland baltic sea and the birth of the neva river abstract the easternmost gulf of finland is the recipient of the neva river the largest river draining to the baltic sea the depositional history and endozoobenthic activity in the area have not been studied before based long sediment cores although such studies are desirable to provide a paleoenvironmental context for the recent environmental changes and the ecosystem projections for the future baltic sea two replicate long sediment cores from the easternmost gulf of finland record brackish water mud accumulation beginning at 5900 60 calendar years before present cal bp the brackish water muds are characterized by thin beds with erosional bases fining upward grain sizes and increasing upward organic contents a storm induced flow origin is inferred for the thin mud beds contrasting with previous interpretations that these muds accumulate by quiescent suspension settling the bed primary microstructures are overprinted by biodeformation and burrow mottling by incipient small planolites and arenicolites polykladichnus ichnofossils of the continental skolithos ichnofacies left behind by endobenthic oligochaetes and chironomid larvae the depositional succession is cut by a strong erosional hyperpycnal flow event at 3320 40 cal bp caused by the birth of the neva river which is now documented offshore for the first time mineral magnetic properties show pseudosingle domain magnetite as the main magnetic mineral present increased magnetic grain sizes and reduced loi values indicate a strong lithic influx immediately after the neva river birth the dominance of riverborne material in the accumulating sediments ever since highlights the strong influence of reworking in the shallow sea area increased diameters and the deeper penetration of biogenic sedimentary structures demonstrate improved seafloor oxygenation after the river birth during the medieval warm period ca 1000 700 cal bp and the last century increased sedimentary lithic contents and magnetic grain sizes indicate an elevated riverine influx due to increased precipitation and or the increased reworking of sediments by storms the results provide a paleoenvironmental context for the study area and deepen the understanding of storm induced sediment dispersal and the formation of sedimentary fabric in shallow wave dominated sea areas

ichnological and sedimentological features of the hongguleleng formation devonian carboniferous transition from the western junggar nw china abstract two sections of the late devonian to early carboniferous hongguleleng formation in the sha erbuerti and xiemisitai mountains of western junggar nw china were logged in detail and studied with particular reference to their trace fossil content and sedimentary features the hongguleleng formation is composed essentially of shallow marine deposits formed in a volcanic arc related setting it contains trace fossils including indeterminate ellipsoid structures indeterminate shallow pit structures chondrites intricatus chondrites targionii chondrites isp dolopichnus gulosus multina isp nereites missouriensis nereites isp palaeophycus tubularis phycosiphon isp phymatoderma isp rhizocorallium commune rosselia cf socialis teichichnus rectus teichichnus ispp thalassinoides isp and zoophycos ispp these ichnofossils and related bioturbation structures constitute five distinct groups of ichnofabrics chondrites phymatoderma rhizocorallium commune anemone dwelling burrowing teichichnus and zoophycos ichnofabrics conforming to an upward trend from the cruziana to zoophycos ichnofacies the volcanic arc setting provides a natural laboratory to investigate the colonisation styles of benthic faunas during the devonian especially for environments with widespread and relatively frequent depositional events disturbing background deposition the distal event beds are especially suitable for the distinction of the relationship between background and post event ichnofaunas simple and composite ichnofabrics have been distinguished the simple ichnofabrics are typified by the indeterminate ellipsoid ichnofabric made by sea anemones representing short colonisation event and in situ death and burial resulted from relatively high sedimentation rates even during the periods between volcanic explosions the composite ichnofabrics are characterised by the chondrites phymatoderma multina zoophycos and multi tier zoophycos ichnofabrics representing vertical migration of benthic faunas in pace with either distal event deposition or steadily accreted sea floor the colonisation window in the arc related setting is closely related to sedimentation rates and frequency of depositional events determining the completeness of burrow system structure and maturity of benthic communities

neoichnology at lake margins implications for paleo lake systems abstract neoichnological studies provide significant information that can aid in the interpretation of ancient ichnological assemblages here we examine for the first time the pattern in both vertebrate and invertebrate trace distribution and abundance that can be seen in two geographically separate but broadly analogous contemporary semi arid climate lake margin settings in an effort to describe taphonomic processes relevant to paleo lake systems lake margin to supralittoral zone transects were made at ruby reservoir montana usa and la sotonera spain and vegetation cover trace cover trace diversity and substrate characteristics were recorded similar patterns in trace distribution were seen through the eulittoral to supralittoral zones with the majority of traces identified within a single transect present at both sites however a few traces attributed to larger organisms were found to be unique to each and in some instances could to be assigned to a specific trace maker the eulittoral zone was considered to have characteristics attributable to the scoyenia ichnofacies however analysis of the supralittoral zone shows some characteristics of both the coprinisphaera and the mermia ichnofacies in addition a transitional zone between a scoyenia like ichnofacies and a fully terrestrial assemblage was found which may enable continental ichnofacies to be further refined for application to paleo lake systems study of the distribution of traces with distance along the transects also suggests taphonomic biases against the preservation of certain types of traces e g avian due to seasonal fluctuations of the lake level and the subsequent reduced preservation potential for lake proximal traces

trace fossil model for reconstruction of paleo oxygenation in bottom waters recognition of fluctuations in the degree of paleo oxygenation of bottom waters recorded in fine grained pelagic strata is important for interpretation of paleoceanographic and paleoclimatologic conditions general sedimentary fabric composition of trace fossil assemblages and burrow size and crosscutting relationships have been incorporated into a trace fossil tiering model that permits detailed reconstruction of changes in paleo oxygenation of bottom waters applications of this model to the miocene monterey formation california and the cretaceous niobrara formation colorado indicate that the ichnologic approach is more sensitive to both magnitude and rates of change in oxygenation levels compared to macrobenthic body fossil information

sequential colonization of muddy turbidites in the eocene beloveža formation carpathians poland abstract a 100 350 m thick succession of centimeter thick fine grained turbidites form the lower mud dominated part of a prograding deep sea fan in the eocene belove a formation in the carpathian mountains of poland these strata contain over 50 ichnotaxa only six of which are common phycosiphon nereites chondrites scolicia halopoa ophiomorpha polished slabs and examination of cross cutting relationships show that post event colonization was sequential using modern analogues it can be shown that the colonization of different depth levels in the sediment at different times reflects changing geochemical conditions especially the re adjustment and re establishment of the redox boundary modern analogues allow an assessment of the timing of each colonization phase the phycosiphon producers entered first and occupied the well oxygenated muds 5 40 mm below the sediment surface as the redox boundary reformed nereites producers entered and probably utilized microbial matter just above the redox boundary about 15 30 mm below the sediment surface subsequently chondrites producers penetrated down to the oxygen deficient layers of the event bed or even deeper levels the halopoa producers entered with phycosiphon but reworked coarser layers contemporaneously with this sequential colonization deep permanent bioturbators which were unaffected by the event cross cut the post depositional suite the variability of the resultant ichnofabrics can be attributed in part to a patchy distribution of the benthos and the relative frequency of turbidite events five ichnofabrics which reflect the successive colonization episodes are recognized each was modified by elements of the permanent infauna

sedimentologic significance of turbidite ichnofacies in the saraceno formation eocene southern italy abstract mixed siliciclastic carbonate and siliciclastic turbidites of the saraceno formation eocene in calabria southern italy contain diverse trace fossil associations the depositional setting appears to have been a small tectonically isolated rapidly subsiding borderland basin into which turbidity currents dumped a variety of sediments the formation comprises four sedimentary facies each of which is characterized by a distinctive ichnofacies from bottom to top facies i alternating calcarenite and thick bedded shale chondrites muensteria rhizocorallium facies ii alternating calcarenite and thin bedded shale chondrites muensteria zoophycos facies iii thin bedded siliciclastic sandstone zoophycos helminthoida palaeophycus facies iv alternating sili iclastic sandstone and shale zoophycos helminthoida phycosiphon the trace fossil associations are dominated by fodinichnia such as chondrites in the lower part of the formation facies i and ii and zoophycos in the upper part facies iii and iv the agrichnia graphoglyptids and pascichnia that usually dominate turbidite ichnofacies are uncommon perhaps owing to a a fairly shallow water depth b an extremely high frequency of turbidity currents and or c dysaerobic or anaerobic interstitial conditions within the sediment

coastal sediments and patterns of bioturbation eastern buzzards bay massachusetts abstract coastal sequences of eastern buzzards bay exhibit characteristic suites of physical and biogenic sedimentary structures related to energy gradients geomorphology and distributions of palimpsest glacial debris in beach to offshore sequences unbioturbated planar to ripple laminated or cross bedded pebbly sands of the foreshore and shoreface give way abruptly to thoroughly bioturbated poorly sorted sediments of the offshore zone preserved biogenic sedimentary structures first appear at water depths of 1 to 2 m below mlw and bioturbation of sediments is complete at depths of 2 to 4 m offshore the seaward shift from physical to biogenic structures is a pivotal point almost equally discernible among modern and ancient beach to offshore deposits sequences in harbors and embayments intergrade with those of such allied environments as salt marsh estuaries tidal flats and the offshore zone tidal creek deposits within salt marshes range from sparsely bioturbated cross bedded sand to completely bioturbated impure sand most streamside marsh deposits consist of thoroughly bioturbated root bound muddy sand or sandy mud collectively these bay marsh sequences are reminiscent of albeit at a much smaller scale than estuarine sequences of the georgia bight

quantitative ichnology of modern pelagic deposits in the abyssal atlantic abstract quantitative sedimentologic aspects of bioturbation were investigated in a series of deep sea box cores which were collected over a broad latitudinal range 35 n to 30 s and bathymetric range 1 4 to 5 7 km in the central atlantic ocean all cores were thoroughly bioturbated and numerous generations of burrowing could be discerned in many instances preservation of individually distinct burrows ranged from poor to excellent and eight ichnogenera plus several unnamed biogenic structures were recognized the distribution of calcium carbonate organic carbon selected species of planktic foraminifera and sediment grain size were examined in several cores these measurements indicated that the surficial mixed layer which ranged from 3 to 10 cm thick was statistically more homogeneous than the underlying transition layer this relationship is seen most clearly with respect to lateral and vertical variations in the calcium carbonate content of the cores bioturbation of abyssal pelagic deposits appears to be a two phase process consisting of a homogenization of the upper few centimeters i e the mixed layer by shallow burrowing meiofauna and b heterogeneous mixing of the underlying strata i e the transition layer by relatively deep burrowers the heterogeneously mixed transition layer becomes the preserved trace fossil record under normal circumstances the homogenized mixed layer is not preserved

clay mineral dispersal patterns in the north bering and chukchi seas abstract characterization of the clay mineralogic constituents of the m e s d equivalent spherical diameter size fraction of contemporary marine and fluvial sediments from the north bering sea chukchi sea region and adjacent land areas has resulted in delineation of suites dominated by broadly defined illitic and expandable group components with lesser amounts of chlorite and kaolinite distribution patterns elucidated indicate net northward transport of sediments relatively enriched in the expandable group with predominant terrigen ous source from the yukon river system this material is distributed across the study area in a medial zone along a general north south trend with peripherally decreasing relative amounts of this expandable group component and concomitant relative increases in the illitic components these patterns are consistent with known physical oceanographic and regional geologic relationships in terms of sediment sources transport processes and depositional mechanisms the foregoing suggest further that consideration of the stratigraphic relationships of these clay mineral component types as a function of time in relevant marine sediments north and south of the present bering strait should be informative with respect to regional quaternary paleogeography as related to global sea level fluctuations during glacial and interglacial episodes

ichnological analysis the common ground between ichnofacies workers and ichnofabric analysts abstract this work compares the approaches taken by the two schools of applied ichnology ichnofacies and ichnofabric analysts and proposes an integrated approach for future improvement there are many similarities between the two approaches which mainly differ in the resolution at which ichnological analysis is undertaken ichnofabric work is by necessity performed on a bed by bed basis and interpreted at a scale consistent with that of the sedimentologist s facies ichnofacies studies in contrast seldom report bed by bed changes in ichnological content instead highlighting bedset to facies association scale changes in ichnology through comparison with summary models of ichnological trends this work highlights the fact that workers from both schools utilize the same tools with slightly different emphases to reach their ichnological conclusions contention between the two schools has in recent years centred upon which is the better method for studying trace fossils an artificial construct that detracts from the fact that both are extremely useful to sedimentological and palaeoenvironmental studies ichnofabric analysis is in addition a highly effective means of documenting bioturbated sedimentary fabrics as the basis for petrophysical studies ichnofacies and ichnofabric analysts use the same toolbox of ichnological methods to determine ancient palaeoenvironments the scale of observation is generally different but the results closely comparable the recognition of key stratal surfaces on ichnological grounds is also possible with both methodologies ichnofacies analysts look to recognise glossifungites ichnofacies firmgrounds in offshore mudstones ichnofabric studies would look to recognise overprinting of fabrics created by groups of organisms from different palaeoenvironments but associated with the same key surface it is proposed that the terms ichnofacies method and ichnofabric analysis are abandoned in favour of a neutral ichnological analysis method encompassing the approaches and terminology of both to produce a unified scientifically rigorous user friendly methodology

distribution ecology and taphonomy of the organism trace scolicia in northeast atlantic deep sea sediments abstract the organism burrow scolicia was studied in deep sea sediment cores from several regions of the northeast atlantic including the iceland faeroe ridge rockall plateau and reykjanes ridge the data comprised sedimentological and physical measurements and x ray radiographs scolicia generally can be observed only in radiographs grain size and sorting of sediments control the distribution of the echinoids that produce scolicia if developed under optimum ecological conditions in well sorted coarse silts to fine sands scolicia dominates the biogenic structures with its very characteristic ichnofabrics its distribution pattern is influenced mainly by bottom currents sedimentation rate and the faunal association indirectly a dependence on water depth also seems to exist the preservation and recognition of scolicia in lithified sediments needs special conditions these include restricted competition by organisms of the deeper burrowing tiers its generation within the optimum sediment grain size or its production at the sand silt mud interface

discriminating ecological and evolutionary controls during the ediacaran cambrian transition trace fossils from the soltanieh formation of northern iran abstract the nature of the cambrian explosion one of the most critical events in earth history has been a major topic of discussion the trend of increasing morphological complexity and taxonomic diversity of trace fossils within this interval has been used as evidence of the true evolutionary nature of the cambrian explosion however the distribution of trace fossils is controlled by a complex interplay between evolutionary and ecological constraints the pre trilobite soltanieh formation of northern iran displays a significant vertical facies recurrence allowing comparison of identical environments through time therefore its study provides a test case for evaluating the role of evolutionary and ecological controls on lower cambrian trace fossil distribution an integrated study of sedimentary facies small shelly fossil zones sequence stratigraphy and distribution of associated trace fossils indicates a complex interplay of these two sets of factors the distribution and preservation of diagnostic early cambrian trace fossils in the lower shale member of the soltanieh formation is very likely to have been controlled by facies especially within storm generated siltstone shale intercalations providing better preservation potential for interfacial trace fossils therefore delaying the stratigraphic occurrence of treptichnus pedum in contrast evolutionary innovations exerted the primary control on trace fossil distribution in the upper shale member where the vertical distribution of trace fossils strongly matches that observed worldwide this result suggests that although trace fossils provide a valid means of global correlation placing trace fossil assemblages within a paleoenvironmental and sequence stratigraphic framework is a prerequisite of any sound evaluation of the evolutionary and biostratigraphic implications of trace fossils

composite ichnofabrics and tiering of burrows infaunal communities in marine environments typically are tiered that is different taxa live at different depths within the sediment tiered suites of biogenic structures yield complex biogenic sedimentary fabrics ichnofabrics with the traces of deep burrowing organisms overprinted on those of shallow burrowing organisms careful analysis of crosscutting relationships of burrows in such composite ichnofabrics allows reconstruction of the tiered nature of fossil endobenthic communities it is important to recognize that the best preserved and most prominently displayed trace fossils in most assemblages usually represent the deepest tier thus they were farther removed from the sea floor and therefore less indicative of actual sea floor conditions than the more poorly preserved traces of the shallower tiers on which the deeper traces are juxtaposed

stratigraphic completeness tiered trace fossils provide a measuring stick trace fossil associations commonly display a characteristic vertical zonation tiering within the substrate when burrows of a particular tier become truncated by turbidites tempestites or other results of catastrophic events they provide a simple but quantitative caliper for estimating stratigraphic incompleteness the minimum amount of penecontemporaneous sea floor erosion can be determined by types and sequences of trace fossils preserved below event deposits

sand waves echinocardium traces and their bathyal depositional setting monte torre palaeostrait plio pleistocene southern italy stacked cross sets up to 2 5 m thick produced by sand wave migration and meniscate trace fossils produced by echinocardium cordatum both considered in the literature as typical of shallow water marine depositional settings commonly occur in the bathyal plio pleistocene deposits of monte torre calabria southern italy the plio pleistocene sediments form two coarsening upward depositional sequences separated by an unconformity and by a palaeobathymetric gap of at least 300 m the lower sequence passes upwards from hemipelagic marls and thin bedded turbidites to thick bedded sandy turbidites then to sand wave deposits alternated with sandy turbidites and finally to base of slope megabreccias facies characteristics and relationships and the occurrence of deep sea faunal associations indicate deposition in the bathyal zone the facies of the upper sequence reflect a fan delta environment no deeper than a few tens of metres the depositional setting of the lower sequence where the sand wave deposits and meniscate trace fossils occur appears to have been a tectonically controlled seaway connecting the tyrrhenian and ionian seas this seaway became progressively narrower with time evolving into a strait the overall coarsening upward trend reflects the upward transition from a low to a high energy environment possibly caused by the tectonic narrowing of the seaway deposition and erosion from high concentration turbidity currents and from tidal bottom currents were important processes periods of tectonic activity producing first the uplift of the seaway margins and culminating with the uplift of the strait sequence itself are marked by scattered rockfall deposits the strait setting causing the development of powerful oxygenated bottom currents produced optimal conditions in the bathyal zone for the colonization of sandy bottoms by a single infaunal r selected species echinocardium sp

reverse engineering mother nature shale sedimentology from an experimental perspective abstract experimental study of the sedimentology of shales can take a variety of forms at its simplest one can experiment with suspensions in a glass jar and try to understand their settling behavior or one can manipulate mud in a tank or bucket to gain insights into its rheology this approach was championed over a century ago by sorby and the insights gained can be quite profound more recently tank and settling tube experiments of animal sediment interactions compaction behavior and sediment unmixing via re suspension have proven to be highly informative in spite of their simplicity flumes can be used to obtain quantitative information about depositional and erosional parameters and to generate fundamental bedforms in flume experiments however it is of critical importance that the flume be designed in a way that flocculated materials move under shear stress conditions that would be reasonable in natural environments although much flume work on muds has been conducted by hydraulic engineers the transfer of that knowledge to sedimentology is hampered by the fact that engineers and sedimentologists are interested in different though not mutually exclusive products from such experiments engineers and hydrologists are commonly concerned with quantifying fluid flow properties whereas sedimentogists are particularly interested in the sedimentary products that result from a variety of flow conditions recent sedimentologically oriented flume studies have shown that muds can form deposits at flow velocities and shear stresses that would suffice to transport and deposit medium grained sand mud suspensions are prone to flocculation and the resulting floccules travel in bedload and form ripples that accrete into beds the latter finding suggests that many laminated shales were deposited from currents rather than by settling from slow moving or still water there are many other sedimentary features in shales that can potentially be reproduced in flume studies and in the future serve to provide a quantitative basis for shale sedimentology

eustatic signals in deep marine sedimentary sequences recovered at odp site 978 alboran basin western mediterranean sea abstract a continuous section of pliocene marine sediments was recovered at ocean drilling program site 978 located in the alboran sea between spain and morocco three pliocene subunits have been defined at site 978 the lowermost subunit ic 129 2 m thick is characterized by alternating beds of lighter more calcareous and darker less calcareous claystone with bioturbated upper and lower contacts type 1 cycles the middle subunit ib 67 1 m thick is composed of relatively homogeneous nannofossil claystone and the uppermost subunit ia 211 6 m thick contains abrupt based darker terrigenous layers interpreted as turbidites that are interstratified with lighter nannofossil claystone type 2 cycles the rhythmically bedded light and dark layers in subunit ic correlate with those in the rosello composite section of sicily a global reference standard for the pliocene time scale these sedimentary cycles are products of variations in precession and resulting continental runoff missing cycles occur during eustatic highstands the shift to more homogeneous sedimentation in subunit ib is represented in similar aged sequences throughout the mediterranean which display evidence of submarine mass wasting mediterranean wide slope degradation was likely a response to rapid sea level change at approximately 3 ma this change in sedimentation style was accompanied by an upsection increase in sediment accumulation rates associated with turbidite influx in subunit ia turbidite frequency throughout the pliocene section can be linked to eustatic changes in sea level with turbidite maxima corresponding with mid sequence downlap surfaces and their associated condensed sections