coarse clastic barrier environments evolution and implications for quaternary sea level interpretation abstract this paper reviews recent work particularly from eastern canada on the dynamics and evolution of coarse clastic barriers it is argued that an understanding of quaternary coastal changes on paraglacial glacially influenced coasts can only be achieved with a knowledge of gravel barrier morphodynamics and sedimentation gravel barriers are distinctive coastal forms in which morphological inheritance and sediment sorting provide major behavioral controls spatially adjacent gravel barriers may display different depositional tendencies prograde seawards migrate landward or aggrade vertically such inconsistent spatial behaviour must be considered in terms of an erosional front advancing landward under stationary or rising sea level redistribution of sediment across or along the erosional front supplies sediment for the development of gravel barriers which in turn provides environments for fine grained deposition which is favourable for further barrier migration an example of an erosional front is given from chezzetcook inlet nova scotia three stages are recognized in the development of gravel barriers starting with the initiation of small drift aligned forms at the leading edge of the erosional front as sea level rises this is followed by a period of consolidation and stabilization when drift aligned forms may become swash aligned conditions for this transition are discussed under rising sea levels it is difficult to explain the conditions leading to the formation of multiple parallel swash aligned ridges although three hypotheses are advanced all of which may operate in different locations the third stage is associated with the breakdown of barriers as sediment supply fails and or sea level rises drift aligned forms are inherently unstable and show signs of pre breakdown stress in the form of reworking and remobilization of proximal sediments into cells swash aligned barriers may be breached revert to drift alignment become segmented or be overstepped some gravel is re incoporated in barriers farther landward while other material is passed seaward of the erosional front and becomes abandoned on the shoreface gravel barriers may exert a major influence on estuary and back barrier environments especially where they control the depositional record the implications for the reconstruction and interpretation of quaternary environments are summarized

precessional climate cyclicity in late cretaceous early tertiary marine sediments a high resolution chronometer of cretaceous tertiary boundary events we report well dated late cretaceous and early tertiary precessional climatic cycles recorded by rhythmic carbonate maxima and minima in south atlantic deep sea sites spectral analyses of digitized sediment color a suitable carbonate proxy show prominent regularities in the spacing marl carbonate beds magnetostratigraphic dating over a number of magnetic chrons constrains the duration of the cycles which can be detected over at least 20 myr of sedimentation at 7 coring locations their mean absolute period of23 5 4 4kyr agrees closely with the predicted late cretaceous precessional period of 20 8 kyr because they can be matched to a physical forcing mechanism with a known repeat time the cycles offer a new high resolution tool to measure rates of climate change before and after the cretaceous tertiary k t boundary from counts of carbonate cycles we derive the position of the k t boundary within c29r at 350 kyr after the base of the reversal the constancy of cycle thickness linearly related to sedimentation rate and amplitude up to the boundary clay does not give evidence for climate instability preceding the boundary orbital chronometry records a step function decrease in sediment accumulation rate at the cretaceous tertiary boundary that is consistent with a geologically instantaneous event

coastal management and sea level rise abstract the predicted rise in sea level due to global warming has given rise to much speculation as to the impact on erosion and accretion rates at the coast as well as increases in hazards to coastal users this paper focuses on the spatial adjustments that coastal landforms will exhibit in response to changing energy gradients both normal to and parallel to the shore these adjustments in many cases will take the form of the migration of landforms in order that they maintain their position within the coastal energy gradient prediction of the rates of such migration will be fundamental to the future management of the changing coastal environment the paper discusses the impact of sea level rise on the two basic coastal landform assemblages those in estuaries and those on the open coast and then goes on to examine the effect on ebb tidal deltas that are located at the critical junction between estuaries and open coasts in each case the rates of landform migration under an accelerated sea level rise are predicted and compared with existing rates using examples from the east coast of britain assuming a sea level rise of 6 mm year the paper predicts that estuaries will migrate landwards at rates of around 10 m year open coast landforms can exhibit long shore migration rates of 50 m year while ebb tidal deltas may extend laterally along the shore at rates of 300 m year the implication for the management of such dynamic coastal systems including such issues as coastal defence and conservation are discussed

chromium and nickel as indicators of source to sink sediment transfer in a holocene alluvial and coastal system po plain italy abstract a reliable quantitative estimate of changes in source to sink sediment transfer requires that high resolution stratigraphic studies be coupled with accurate reconstructions of spatial and temporal variability of the sediment routing system through time source to sink patterns from the contributing upland river catchments to the deltaic and coastal system are reconstructed from the holocene succession of the po plain on the basis of selected geochemical indicators sediment supplied to the delta area by the major trunk river the po exhibits naturally high cr and ni values which invariably exceed the maximum permissible concentrations for unpolluted sites this anomaly reflects remarkable sediment contribution from ultramafic ophiolitic parent rocks cropping out in the po drainage basin western alps and nw apennines in contrast alluvial and coastal plain deposits supplied by ophiolite free apenninic catchments invariably display lower cr and ni contents for constant sediment provenance domain cr and ni distribution is observed to be controlled primarily by hydraulic sorting clay silt deposits floodplain swamp and lagoon bay facies associations invariably show higher metal concentrations than their sandy counterparts fluvial channel distributary channel and beach ridge facies associations from a stratigraphic perspective in sedimentary basins characterized by strong differences in sediment composition geochemical fingerprinting of individual facies associations framed by surfaces of chronostratigraphic significance is proposed as an invaluable approach towards an accurate quantitative assessment of sediment storage in alluvial and coastal depositional systems as opposed to volumetric reconstructions based on lithologic or geometric criteria alone

shoreline response to submerged structures a review abstract submerged coastal structures are widely perceived to be capable of providing beach protection without the adverse impacts including loss of beach amenity and aesthetic considerations often associated with more conventional structures such as revetments and groynes in addition there is growing interest in the concept that the layout and cross section of submerged coastal protection structures can be optimised to also enhance local surfing conditions however as submerged structures have only rarely been adopted for beach protection the shoreline response to these structures is not well understood at present therefore this review of the available published literature was undertaken with the aim of investigating the environmental and structural parameters governing shoreline response to submerged structures gleaned from the results of field laboratory and numerical studies undertaken to date the review reveals that contrary to expectations a majority of the submerged structures constructed to date have resulted in shoreline erosion in their lee furthermore the key environmental and structural parameters governing the mode i e erosion or accretion and the magnitude i e size of salient of shoreline response to submerged structures are yet to be identified although submerged coastal structures offer the potential for low aesthetic impact incorporating multi function design until the response of the adjacent shoreline to submerged structures is better resolved their use is likely to remain relatively limited

controls on focused flow and dispersed flow deepwater carbonates miocene agua amarga basin spain abstract common models for carbonate slope or basin margin sedimentation emphasize the contrasts between linear sediment sources and point sediment sources geologic mapping and high resolution stratigraphic study of a set of miocene outcrops exceptional for their three dimensional exposure and preservation of paleotopography demonstrates that paleotopographic focus or lack thereof may be a dominant control on geometries and sediment character of sediment gravity flow deposits in line sourced systems in the agua amarga basin se spain basin topography is initially modified by subaerial exposure and erosion of volcanic basement to form paleovalley systems after late miocene marine inundation topography is partially modified by infilling of high energy shallow water heterozoan deposits units 1 and 2 that subdued topography in one area to produce a ramp like surface but did not significantly infill a large paleovalley located in another area further relative rise in sea level resulted in an extensive reefal platform that formed along a paleo high adjacent to both features la rellana platform subsequent sediment gravity flow deposits shed from this reefal platform followed two pathways down the ramp like surface dispersed flow or into the large flooded paleovalley focused flow deposits within each system display contrasting lithofacies architectures these deepwater deposits units 3 7 in this study consist of carbonate breccia facies coarse facies graded skeletal packstone facies coarse facies and planktonic foraminifera rich facies fine facies that are interpreted as sediment gravity flow deposits and pelagic sediments relative sea level fluctuations resulted in deepwater facies variations in the large paleovalley as a result of significant backstepping and progradation of the rellana reefal platform on a gently sloping surface fining of basinal deposits and shelfward migration of the locus of deposition for sediment gravity flows is associated with sea level rise coarsening of basinal deposits and basinward migration of the locus of deposition for sediment gravity flows is associated with stillstand and relative fall in sea level both relationships demonstrate a direct link between the locus of reefal platform growth and style of basin sedimentation early parts of relative rises in sea level late parts of highstands and falling stages led to transport of abundant coarse sediment into the basin focused flow deposits were line sourced and funneled into the axis of a large margin parallel paleovalley and confined to a channel volume ratio of coarse facies to fine facies is estimated at 0 7 deposits in proximal paleovalley locations display compensation geometries around positive relief on debrites channelization erosional truncation lapout against paleovalley walls and some drape as a result of lateral confinement and proximity to the sediment source deposits in distal paleovalley locations display increasingly tabular geometries as a result of decreasing lateral confinement and concentration of coarse grained sediment gravity flows down depositional dip dispersed flow deposits were line sourced into the basin along a gently inclined ramp like surface that lacked paleotopographic focus volume ratio of coarse facies to fine facies is estimated at 0 1 the less complex sheet like depositional geometries and locations of these deposits result from the absence of lateral confinement and subtle changes in substrate slope focused flow sediment gravity flow deposits that are confined by topographic elements such as channels are most likely to form sizeable accumulations of coarse facies with characteristics most appropriate for conventional oil and gas exploration there are many paleotopographic configurations that can lead to focusing of flows so this deepwater carbonate system may be more common than previously recognized

morphodynamic evolution self organisation and instability of coarse clastic barriers on paraglacial coasts abstract beaches and barriers on many mid to high latitude coasts comprise mixtures of fine and coarse clastic materials forming a distinctive morphodynamic environment in many cases the sediments are derived primarily from limited glacigenic deposits and the coasts are considered paraglacial over relatively long time scales decades to centuries coarse clastic barriers on such coasts show evidence of self organisation through large scale morphological evolution and facies differentiation this process involves gradual reworking partitioning and textural sorting of material toward transport minima long intervals of slow evolution are punctuated by episodes of rapid reorganisation involving breakdown of stable barrier structures and facies patterns remixing of sediment and accelerated migration of transgressive systems drift aligned systems develop longshore cell structure sometimes leading to breaching and segmentation and may evolve toward progressively greater swash alignment under appropriate circumstances swash aligned systems may experience catastrophic transformation when appropriate environmental triggers lead to threshold exceedance in the morphodynamics of the shore system adjacent barriers may show quite different behaviour depending on the antecedent states of individual coastal cells while appropriate parameterisations and sediment budget formulations allow us to model the long term evolution of some barrier structures the non linear dynamics that appear to dominate large scale behaviour may limit predictability the identification of stability threshold criteria remains an important research priority

laminated bioturbated cycles in maastrichtian chalk of the north sea oxygenation fluctuations within the milankovitch frequency band the maastrichtian chalk of the southern central graben danish north sea is a homogeneous pure white coccolithic chalk mudstone deposited in a deep epeiric shelf sea which covered large parts of northern europe the sediment displays a pronounced cyclicity marked by decimetre thick bioturbated beds alternating with slightly thinner non bioturbated mainly laminated beds the laminated half cycles consist of alternating millimetre thick graded high porosity laminae and non graded low porosity laminae the cyclicity has been interpreted previously as caused by periods of slow background sedimentation and bioturbation interrupted by periods of rapid deposition of laminated beds with the latter reflecting random and local resedimentation processes based on textural and structural analysis the millimetre scale non graded laminae are interpreted as having been deposited directly from pelagic rain of pelleted coccoliths representing the primary production the graded laminae were deposited from small volume low density turbidity currents and suspension clouds the sedimentation rates of the cyclical chalk are similar to those known elsewhere and the lamination is interpreted as having been preserved from destruction through bioturbation by anoxic conditions at the seafloor bioturbated laminated cycles are thus formed by slow sedimentation during alternating seafloor redox conditions probably on a milankovitch scale a direct implication of this interpretation is that the cycles are areally widespread probably extending throughout the southern central graben area and may be useful for correlation and high resolution cyclostratigraphy in the chalk fields of the danish north sea if the laminated half cycles represent a few rapid resedimentation events with a high sedimentation rate as suggested by most workers then the sediment would not be truly cyclic but would represent event sedimentation within a pelagic background represented by the bioturbated beds in this case the cycles would have very limited potential for correlation

magnetic susceptibility as carrier of a climatic signal in chalk abstract the composition and the magnetic properties of the insoluble residue of maastrichtian chalk from the north sea have been investigated in order to get a better understanding of the cyclic signals in chalk carbonates and the depositional processes that have contributed to the pattern the insoluble residue of the maastrichtian north sea chalk contains quartz dolomite pyrite organic material ferrimagnetic minerals and clay minerals smectite illites the concentration and in particular the type of clay minerals determine the variations in the magnetic properties of the insoluble residue and the bulk magnetic susceptibility of the chalk the existence of a detrital component in the insoluble residue suggests that the cyclic variations in the bulk magnetic susceptibility and consequently in the composition of the chalk are controlled by changes in the runoff from land into the basin

pelagic carbonate chemostratigraphy sr mg 18o 13c abstract a synthesis of the elementary sr and mg and isotopic 18 o and 13 c geochemistry of mesozoic to recent bulk pelagic carbonates suggests that the influence of late burial diagenesis is considerably less than was previously thought and that bulk carbonate geochemistry could be important for both paleoceanography and stratigraphy numerous chemical fluctuations in sr ca mg ca and 13 c 12 c ratios have occurred in the ocean during the last 140 ma the main factors responsible are 1 variations in submarine hydrothermal activity and 2 sea level fluctuations the validity of the chemostratigraphic methodology can be demonstrated by the synchroneity and the worldwide occurrence of various geochemical shifts

a model of coastal evolution in a transgressed thermokarst topography canadian beaufort sea abstract the coast of the southern canadian beaufort sea consists of bluffs of ice bearing quaternary sediments and of spits and barrier islands enclosing more or less completely lagoons and complex embayments formed by the breaching of thaw lakes the study of the evolution of this coast developed in a thermokarst topography and of the shallow stratigraphy of the inner continental shelf has resulted in the development of a conceptual model of coastal evolution five stages have been defined in this model which form an idealized continuum of coastal evolution according to the model the formation of embayments spits and barrier islands is primarily controlled by the pre existing topography relative sealevel rise and local sediment supply sealevel rise over a topography of thermokarst basins formed in ice bearing sediments leads to the formation of embayments and rapidly eroding headlands from which spits develop geomorphic evidence suggests that barrier islands mainly form by spit breaching or by erosion of tundra islands breached lake basins act as sediment sinks and may restrict the development of coastal accumulation features spits and barrier islands are rapidly retreating landward the mean retreat rates being 2 2 m a 1 and 3 9 m a 1 respectively on an annual time scale spits and barrier islands retreat in response to episodic storm generated overwash events but on a geologic time scale relative sealevel rise in the major forcing mechanism of landward migration while retreating landward these coastal accumulation features may be drowned and possibly partially preserved in breached lake basins during the holocene transgression the shoreface has undergone erosional retreat partly eroding the pre existing topography but preserving the bottom of some breached thaw lakes and lagoons which are now overlain by a transgressive sand sheet on the inner shelf our observations provide the basis of a semi quantitative model of shoreline changes for the barrier coast of the canadian beaufort sea which relates coastal stability to bluff erosion ground ice content sediment texture offshore sediment supply wave energy volume of breached lake basins relative sealevel rise and regional slope

geological and mechanical study of argillaceous north sea chalk implications for the characterisation of fractured reservoirs abstract argillaceous chalk intervals from the north sea are characterised by matrix permeabilities lower than 0 2 md and therefore they are defined as tight chalks hence fracture networks within these chalks are of major importance to predict fluid flow and reservoir or seal behaviour this study aims to understand the geological parameters controlling the chalk petrophysical and mechanical properties using the outcrop analogue of the cenomanian chalk at cap blanc nez northern france sedimentological petrographic and petrophysical analyses were performed and show that the combination of the depositional environment and diagenetic imprint control the microtexture non carbonate content is ranging from 5 to 40 within the studied samples and is critical for the diagenetic imprint the fracture behaviour of the chalk was studied using a mechanical stratigraphy approach throughout the 70 m thick succession where a transition between lower cenomanian argillaceous chalk and middle upper cenomanian pure chalk is exposed twenty two mechanical units are distinguished and the amount of fractures crosscutting initiating and terminating on mechanical interfaces quantified manual scanlines show that fracture spacing ranges from 17 to 232 cm mechanical interfaces are associated with lithological heterogeneities with strong microtextural contrasts related to the non carbonate content and or degree of cementation the mechanical units are thus defined either by deposition or diagenesis the fracturing behaviour of about 10 m homogeneous pure chalk interval units defined as dfz densely fractured zones differs significantly from the rest of the succession large sigmoidal shaped fractures are confined to those intervals and a dense fracture network developed because of their plastic behaviour clay layers are able to accommodate part of the stress whereas homogeneous pure chalk show a more brittle behaviour

isotopic variation in rhythmically bedded chalks paleotemperature variation in the upper cretaceous detailed sampling at 2 cm intervals of a rhythmically bedded chalk marl sequence in southeast england has revealed a cyclic variation in oxygen isotopic composition of the carbonate component these changes are most consistent with paleotemperature fluctuations of up to 4 5 c contrary to some recent models chalk horizons are interpreted to reflect periods of warmer temperature and higher primary productivity than those responsible for marl deposition the effects of different faunal content diagenesis and variations in the water chemistry can all be discounted

postglacial evolution of coastal barriers along the west pomeranian coast ne germany abstract the aim of this study is to present an evolutionary model of the coastal barriers in west pomerania regarding both morphological development and chronostratigraphy the study area is situated on the islands of rugen and usedom in the tideless sw baltic to reconstruct the geological setting 250 cores were collected 20 new radiocarbon dates allow a description of the late pleistocene to holocene evolution of the barriers in all areas investigated the lithofacies sequences are similar which enables the derivation of a general evolutionary model for the sw baltic sea coasts the controlling factors are the relief of the early holocene landscape as well as the sea level history of the baltic sea the base is made up of a pleistocene till the deposition of this till had already determined the configuration of the present day coast late pleistocene to early holocene freshwater deposits follow in the columnar section often overlain by peat during the main phase of the transgression 8000 6000 before present bp the early holocene landscape was drowned and mud accumulated in the depressions beach ridges attached to pleistocene headlands began to develop at 6000 bp simultaneously landward of the beach ridges sediment accumulated in wind flats this depositional environment which can still be recognised along the coast today is controlled by wind driven currents a second peat layer younger than 1000 bp makes up the uppermost part of the sequence in most of the lowland sites the evolution of the coastal barriers in west pomerania follows the scheme developed for tidal paraglacial coasts this study adjusts the scheme to the regional stratigraphy and extends it with regard to tideless conditions and the evolution of wind flats

paleoclimatic evidence for future ice sheet instability and rapid sea level rise sea level rise from melting of polar ice sheets is one of the largest potential threats of future climate change polar warming by the year 2100 may reach levels similar to those of 130 000 to 127 000 years ago that were associated with sea levels several meters above modern levels both the greenland ice sheet and portions of the antarctic ice sheet may be vulnerable the record of past ice sheet melting indicates that the rate of future melting and related sea level rise could be faster than widely thought

coastal retreat and shoreface profile variations in the canadian beaufort sea the coastline of the southern canadian beaufort sea consists primarily of unconsolidated bluffs although the sea is ice free for 3 months of the year and wave energy is restricted by pack ice the coast is undergoing regional retreat with erosion rates as high as 10 m a 1 in some locations simple and multiple regression analyses were carried out to determine the degree of correlation between the mean retreat rate measured at various locations and the different parameters that may control shoreline recession sediment texture ground ice content cliff height wave energy and shoreface gradient revealed medium to poor correlation with erosion rates showing that the recessive evolution of the coastline can not be explained solely by wave induced and subaerial processes the comparison of nearshore echo sounding records from 1987 with bathymetry from 1971 showed substantial erosion up to 1 m of the submarine profile between 12 and 15 m of water there is strong evidence that this erosion has been caused by sea ice gouging on the seafloor from depths of 5 to 9 m accretion has taken place possibly induced by ice push processes and inshore of the 5 m isobath wave and current erosion of the shoreface has occurred these results suggest that the erosion of the inner shelf by ice gouging drives the erosion observed inshore on the coastal bluffs and nearshore zone as the shoreface profile strives for a state of dynamic equilibrium

succession of late pleistocene and holocene ostracode assemblages in a transgressive environment a study at a coastal locality of the southern baltic sea germany abstract the present study documents the hydrological and coastal evolution of a southern baltic sea lagoon by analyzing ostracode associations six ostracode zones were distinguished from a 13 5 m long vibro core in the pudagla lowland ne germany using splitinf binary divisive clustering zonation sediments of a pleistocene freshwater stage are overlain by deposits of a preboreal brackish water environment which are not related directly to the development of the baltic sea different boreal freshwater habitats developed in the study area until marine water protruded the pudagla site in the course of the littorina transgression a gradual succession in the species assemblage reflects the subsequent transgression freshwater species i e metacypris cordata fabaeformiscandona protzi and herpetocypris sp are substituted in pre littorina inland waters ca 7 2 14 c ka bp by halotolerant species i e candona angulata sarscypridopsis aculeata and plesiocypridopsis newtoni ca 6 5 14 c ka bp and finally the ostracode fauna is dominated by cyprideis torosa associated with cytheromorpha fuscata and loxoconcha elliptica when brackish marine water conditions are established ca 6 4 14 c ka bp

anoxic events productivity rhythms and the orbital signature in a mid cretaceous deep sea sequence from central italy albian pelagic sediments from the umbrian apennines exhibit rhythmic bedding in outcrop high temporal resolution 4 kyr spacing sampling of carbonate si and al along a 1 6 m y interval of core demonstrates that changes in accumulation rate of calcareous and siliceous microorganisms were controlled by insolation cycles optical densitometry logging correlates variations of geochemical parameters to episodes of deep sea anoxia indicated by numerous black laminated zones black shales harmonic analysis of data shows oscillations at three frequencies which correspond closely in estimated duration and ratio to the modern eccentricity and precessional orbital cycles as in pleistocene marine sequences the eccentricity approximately 100 kyr term dominates the sedimentary variance in the umbrian cycles anoxic episodes occur in phase with a limestone marl repetition and reflect minima of the precessional 21 kyr cycle the covariance of carbonate and silica with estimates of foraminiferal abundances suggest that carbonate cycles are the result of changes in surface productivity of calcareous organisms rather than an effect of dissolution or diagenesis recognition of orbital cyclicity provides a tool for making quantitative estimates of these changes productivity during anoxic events was uniformly low 0 4 0 5 g cm2 kyr carbonate 0 05 g cm2 kyr silica but it rose to high levels during oxygenated periods 1 2 5 g cm2 kyr carbonate 0 1 0 3 g cm2 kyr silica vertical overturning and organic carbon flux decreased during anoxic episodes but decreased oxygenation of the deep water led to enhanced preservation of the organic matter delivered the degree of paleoceanographic variability indicated by this study requires that accepted notions of climate stability and oceanic quiescence during nonglacial times be reassessed

coastline evolution at different time scales examples from the pomeranian bight southern baltic sea sedimentological and morphological changes on the upper and lower shoreface during relatively stable sea level highstand conditions have been investigated in the pomeranian bight southern baltic sea at time scales ranging from storm events to millennia in order to cover that variety of time scales different methods have been applied seasonal variations in the morphology of the upper shoreface were measured accurately using the tracer stick method the ratio of breaking waves and energy dissipation due to wave breaking are the main forces controlling redeposition on the upper shoreface with the depth of disturbance up to three times the net change the impact of single storm events can be observed from sidescan sonar mosaics to remain on the decadal scale aerial photographs covering the upper shoreface show that the location of gates channel like systems where water masses move offshore created during storm events also remain stable over decades sedimentological and geomorphological variations and changes on the lower shoreface are only measurable on the century to millennium scale because the main driving forces are longlasting processes like sea level fluctuations or neotectonics data on these scales have much more uncertainty in their relationship to forcing functions than data at shorter time scales because the effects of coastal processes active on different time scales can interact comprehensive understanding of large scale coastal behavior requires investigations from short events to long term processes c 2002 elsevier science b v all rights reserved

closed system marine burial diagenesis isotopic data from the austin chalk and its components the carbon and oxygen isotopic composition of the austin chalk was examined in cores representing a range of depths from surface to 3000 m in order to document the effects of burial diagenesis on carbon and oxygen isotopic composition low magnesium calcite oysters were separated from 500 pm wide areas and analysed to estimate the starting composition of cretaceous marine sediment these gave an average value of 2 5 6 o 2 0 6i3c pdb the compositions of micrite intergranular cement and fracture cement were analysed and their deviation from this original marine composition was evaluated to document the progression of chalk diagenesis interestingly micrite exhibits only minor variation in composition from marine values despite present burial depth ranges in excess of 3000 m the average deviation from 6 o marine is less than 1 5 o furthermore intergranular cement and particularly fracture cements which occur only in the deepest cores and which clearly post date micrite lithification are generally indistinguishable from micrite in composition isotopic compositions exhibit no correlation with depth of burial despite abundant petrographic ev idence of deep burial diagenesis this uniformity in composition is interpreted as reflecting a closed rock dominated diagenetic system in which the compositionsof precipitated carbonate cements were controlled by the composition of dissolving carbonates during lithification as such the composition of burial cement is not representative of the rock water temperatures during precipitation thus in the context of isotopic analyses from other carbonate systems unless the degree of openness of the diagenetic system is known oxygen isotopic signatures of cements cannot directly be converted to the rock water temperatures at which they were precipitated unless the composition of the ambient porefluid is also known

lateglacial and holocene water level variations along the ne german baltic sea coast review and new results abstract a comprehensive overview is given of the current knowledge regarding the lateglacial and holocene water table evolution along the west pomeranian coast which is related to the four evolutionary stages of the baltic sea the baltic ice lake the yoldia sea the ancylus lake and the littorina sea the first three stages were characterized by intensive water table fluctuations in the baltic basin the balance between glacio isostatic uplift and water table rise due to meltwater and river discharge produced either a temporary connection with the ocean or isolation from it new findings are presented on the water levels reached during the different stages only at about 8 ky bp did the baltic obtain a permanent connection with the ocean the first marine sediments in the recent coastal zone ca 7 8 ky old are found at 15 m and are related to the initial littorina sea the maximum of the main littorina transgression was reached at 1 5 m to 2 0 m ca 5 8 ky bp the course of the sea level reveals that later only some minor oscillations took place correlated with climatic fluctuations these indicate a control by regional changes in the north atlantic circulation rather than by global sea level alterations isostatic movements were determined by comparing the reconstructed relative sea level curve with curves assumed as nearly eustatic the resulting isostatic curve shows uplift at 11 5 ky bp of about 55 m which decreased until 7 8 ky bp to 6 m and ceased at ca 3 ky bp currently the coastal zone experiences a slight tilting with uplift in the northeastern part and inundation in the southwestern area

a sediment and organic carbon budget for the canadian beaufort shelf abstract the arctic ocean accounts for 20 of the world s continental shelves because the arctic is sensitive to global change budgets of organic carbon for its shelves are of immediate interest the mackenzie shelf of the canadian beaufort sea is the best north american proxy for the enormous eurasian shelves large area large river input and the only site for which a complete organic carbon budget can be attempted due to an extensive data base a mass balance for the mackenzie shelf has been constructed for sediments terrestrial organic carbon and primary produced carbon we have considered allochthonous inputs from the mackenzie river from coastal erosion from smaller rivers from groundwater from the atmosphere and import by ice the mackenzie river dominates the supply to the beaufort shelf of inorganic sediment 127 mt a 1 and paniculate and dissolved terrestrial carbon 2 1 mt a 1 poc 1 3 mt a 1 doc the combined input from all other sources contributes only about 5 of the mackenzie load using sediment accumulation data we estimate that about half of the sediment supply is trapped in the delta about 40 on the shelf and the remainder escapes the shelf edge by various processes autochthonous primary production in the delta and on the shelf adds a further 3 3 mt a 1 of particulate organic carbon a box model has been constructed to account for sediment terrestrial organic carbon and primary produced carbon whereas about 60 of the terrestrial poc is preserved in delta and shelf sediments it appears that most 97 of the primary produced carbon is recycled and not preserved in sediments confidence in the budget should be improved by focusing future research on the determination of modern sedimentation rates on the delta and shelf measurement of organic carbon content of deltaic sediments determination of primary production on the shelf and determination of the relative proportions of terrestrial and marine organic carbon preserved in sediments

modelling of chalk diagenesis eldfisk field norwegian north sea using whole rock and laser ablation stable isotopic data laser ablation techniques permit the determination of the stable isotopic ratios of finely crystalline calcite cements in chalks for the first time modelling of fluid rock interaction using whole rock and laser ablation stable isotopic data indicates that carbonate mineral diagenesis in the eldfisk field consisted largely of the dissolution and reprecipitation of calcite with little associated loss of porosity cementation by calcite derived from stylolites apparently occurred throughout the eldfisk field chalk but had only a subsidiary effect on whole rock isotopic ratios oxygen isotopic data indicates a pore water temperature of 50 80 c during the bulk of chalk recrystallization increases in whole rock 13 c values with depth are likely the result of bacterial methanogenesis during chalk recrystallization

signal analysis of cyclicity in maastrichtian pelagic chalks from the danish north sea abstract low field bulk magnetic susceptibility has been determined on maastrichtian chalk samples from a drill core from the dan field in the danish north sea fast fourier transformations fft have been used to detect possible cycles in the magnetic susceptibility data power spectra from the complete section and from sub sections of the magnetic susceptibility reveal two cyclicities of ca 0 4 cycles m and ca 1 7 cycles m which are present on a 90 confidence level signal analysis of natural gamma ray wire line log data supports these findings sedimentation rate estimates place the cycles in the milankovitch frequency band artificial time series are used to study the applicability of the fft to identifying cyclicity in chalks expected geological distortions e g hiati and sedimentation rate variations are introduced into the time series to investigate the response of the frequency spectra different methods of handling missing data intervals are also examined

new insight into the microtexture of chalks from nmr analysis an integrated petrographical and petrophysical study was carried out on a set of 35 outcrop chalk samples covering a wide range of lithologies and textures in this study various chalk rock types have been characterized in terms of microtextures and porous network by integrating both geological sediment petrological and petrophysical data including porosity permeability low field nmr nuclear magnetic resonance micp and specific surface area bet measurements the data allow an in depth understanding of the nmr signal of chalks with a focus on tight chalks including all low reservoir quality chalks independently of their sedimentological and or diagenetic history the study aims to develop an nmr based approach to characterize a broad range of chalk samples the provided laboratory low field nmr chalk classification can be used as a guide to interpret nmr logging data based on the petrographical and petrophysical analysis 6 groups of samples were identified each of them characterized by a unique nmr signature 1 micritic chalks 2 grainy chalks 3 cemented chalks 4 marl seam chalks 5 argillaceous chalks and 6 silicified chalk nmr t2 distributions were linked to pore body size and t2 logarithmic t2lm was calculated it is apparent that tight chalks whether their characteristics are sedimentological or diagenetic yield smaller pore body sizes t2lm 60 ms and pore throats average radius 290 nm and higher permeabilities up to 13 md the marl seam chalk samples yield bimodal t2 distributions with a first peak related to the micritic matrix pores and a second peak related to intraparticle pores within fossils for all samples permeability was inferred from nmr spectra using sdr schlumberger doll research model

north sea chalk diagenesis cementation of chalks and healing of fractures abstract petrological and geochemical studies have been carried out on the chalk matrix and the fracture filling calcite from several oil fields in the great ekofisk area of the central graben norwegian north sea in order to understand the mechanism of chalk cementation and fracture healing a hypothesis involving an episode of ascending hot water from the underlying permian evaporites has been postulated by some workers to explain the healing of similar fractures in the chalk reservoirs of the norwegian and danish north sea and the danish sub basin however the results presented in this paper including cathodoluminescence microscopy major and trace element geochemistry c o and sr isotope composition and modelling of heating and compactional water flow rates suggest that the ascending hot water hypothesis does not satisfactorily explain the required water budget rate of flow and the source of the calcite cement heat flow simulations demonstrate that a fluid flow rate of 7 5 cm yr is required by the ascending hot water hypothesis this is much higher than the flow rates calculated for this and other sedimentary basins an alternative model is proposed which can account for the observed 18o values of the fracture filling calcite 12 7 to 8 5 pdb the chalk matrix 7 4 to 4 1 pdb and the formation water 4 smow in terms of closed to semi closed system diagenesis in this model calcite from the chalk matrix dissolves congruently and cement precipitates with an isotope ratio governed by the geothermal gradient similarity in the cathodoluminescence trace element composition and carbon isotope values between the fracture filling calcite and the chalk matrix also suggests that the cements in the fractures and the chalk matrix are similar and were probably derived locally by pressure solution processes

geometry of allochthonous chalk group members central trough north sea abstract the temporal and spatial distribution of the hydrocarbon bearing late cretaceous and early tertiary allochthonous chalk is of economic importance examination of cores from the uk sector of the central trough has confirmed the correlation of major allochthonous chalk units to wireline log responses dependent on high porosity allochthonous units were recognized from wireline log coverage of over 100 exploration wells in the central trough area correlation indicated extensive apparent lateral continuity of allochthonous sediment packages enabling the establishment of an event stratigraphy a minimum of nineteen major redeposition events were recognized within the late cretaceous maastrichtian and early palaeocene danian chalks essentially synchronous sourcing and redeposition occurred on both margins of the central trough but with a marked dominance of activity along the eastern margin in terms of incorporated sediment volume the described core material was placed in a regional context by means of the event stratigraphy and confirmed a previously proposed relationship of depositional rock type and transport distance this study recognizes five principal mass flow complexes named after their dominant sediment source areas jaeren north hidra south hidra lindesnes and auk the jaeren north hidra and auk flow complexes are here documented for the first time as are other less extensive deposits

sediment budget calculation to estimate holocene coastal changes on the southwest baltic sea germany abstract the tide less sw baltic sea has a paraglacial coast alternating pleistocene cliff sections and holocene barrier systems separate shallow lagoons from the open sea more than 300 cores penetrating the holocene coastal sequence allowed for detailed reconstruction of the palaeogeographic evolution the sequence formed in response to transgression in the early holocene 8000 year bp the barrier cliff system evolution is described as four stages over these stages dependencies of sedimentation processes to the rate of sea level rise are obvious to reconstruct palaeo coast configurations mass balance calculations were applied retreating cliff sections are seen as the main source for coastal sediment starting from mapped volumes of sand incorporated in barriers cliff retreat in the last 8000 years is calculated to total 2400 m at maximum sediment supply to the coastal zone averaged over the larger part of the holocene is approximately three times smaller than for the last hundreds years this signals accelerated rise of sea level since c 1000 years and hints on what to expect when sea level rises faster in the future such will cause intensified coastal erosion and eventually the formation of new inlets a general drowning of the coastal landscape as observed in the early holocene is unlikely

barrier and lagoon coast evolution under differing relative sea level regimes examples from ireland and nova scotia abstract although the coasts of southern ireland and eastern nova scotia possess many basic similarities especially in terms of geology glacial history sediment character resistance to erosion and wave and tide regimes there is a fundamental contrast in holocene sea level history in ireland recent the past 4000 years sea level rise has been limited to less than 1 mm year by contrast the atlantic coast of nova scotia has been experiencing sea level rises up to three to five times greater over the same period under these markedly differing relative sea level rise regimes barrier and lagoon evolution has varied considerably in ireland barrier lagoon form is controlled by local basement expression particularly through the emergence of headlands creating largely closed sediment systems and the requirement to maintain cross shore drainage it is this latter factor that leads to a simple four fold categorization of the irish barriers and lagoons from freshwater seepage to open tidal environments the nova scotian examples are associated with rapidly moving erosional fronts with local basement control relegated to a subordinate role at the expense of rapid changes in sediment supply barriers can both grow and decay under these conditions subject to certain critical but as yet ill defined thresholds simultaneously forcing development and destruction of adjoining lagoons these major differences also find expression in sedimentary sequences

bed scale cyclicity of pelagic cretaceous successions as a result of world wide control abstract in many cretaceous pelagic successions the bed scale cyclicity termed currently marl limestone alternations displays common characters related to duration composition mineralogical and microfaunal content as for post cretaceous alternations climatic variations milankovitch s cycles are assumed to have controlled their deposition the lower cretaceous at dsdp sites 534 blake bahama basin north atlantic 535 and 540 gulf of mexico exhibit major and minor marl limestone cycles which have been used for an accurate description of lithological couplets and of their main parameters thickness and frequency the frequency of minor cycles per drilling core varies parallel at different sites distributed within the north and south atlantic as well as in the central pacific the curves illustrating these variations are used as a tool for stratigraphic correlations they also point out changes of the sedimentation rate the latter being dominated essentially by planktonic production consequently the fertility of cretaceous sea surface water was submitted to long term variations of global nature of climatic or eustatic character some arguments seem to favor the latter

stratal geometries facies and sea floor erosion in upper cretaceous chalk normandy france unusual lenticular stratal geometries and facies of the upper cretaceous chalk of coastal haute normandie france are described and interpreted thirteen facies within these chalks are described and illustrated on the basis of field thin section and sem investigations nannofossil mudstones nannofossil hardgrounds echinoderm wackestones and packstones echinoderm hardgrounds bryozoan mudstones and wackestones bryozoan hardgrounds bryozoan packstones and wackestones inoceramid wackestones inoceramid hardgrounds sponge hardgrounds marly chalks conglomeratic chalks and debris flow chalks these facies occur within lenticular bedded structures with both concave up and concave down geometries which have been previously interpreted as megaripples mud mounds or tectonic structures detailed examination of the structures and the associated facies indicates that the concave up geometries were formed from submarine erosion and redeposition in nw se longitudinal channels the concave down geometries developed between adjacent channels assessment of the regional and temporal setting indicates that the erosion occurred in the armorican cornubian straits of the anglo paris basin during sea level lowstands within these straits channelling is preferentially developed on the positive south western block to the lillebonne fecamp cotentin fault

formation and diagenesis of bedding cycles in uppermost cretaceous chalks of the dan field danish north sea metre scale lithologic cycles visible in core and on logs from maastrichtian chalks of the dan field were examined to determine their mechanisms of deposition and relation to hydrocarbon production the lower parts of cycles consist of porous cream coloured largely non stylolitic commonly laminated chalk with limited bioturbation mainly escape burrows cycles are capped by thinner intervals of white to grey hard stylolitic chalk with concentrations of bioclastic material intense burrowing and few preserved primary sedimentary structures the cycle caps contain nearly twice as much mg as compared to the more porous parts of cycles and also have slightly larger 18o values 4 1 for the caps 4 4 for porous zones there is a significant reduction of average cycle thickness as well as total thickness of the maastrichtian chalk section from sw to ne across the dan field the cycle thinning largely results from a reduced thickness of porous chalks from the lower parts of cycles and thus is reflected in lower average porosity and permeability on the ne side of the field these data indicate that episodic winnowing removed fine grained constituents from highstanding northeastern areas porous cycle bases were deposited at relatively high rates that precluded complete bioturbation preserved laminae coupled with escape burrows reflect episodic sediment influx in areas that flank the seafloor highs cycle tops apparently accumulated more slowly throughout the region but especially on seafloor highs perhaps because of reduced productivity of planktic organisms slower sedimentation allowed more complete bioturbation and destruction of sedimentary structures and also led to incipient high magnesium calcite seafloor cementation sufficient to yield firmer sediment and enhanced burrow preservation but not to form true hardgrounds thus the elevated magnesium contents and reduced porosity of the cycle caps reflect very early diagenetic processes that were only partially modified by burial diagenesis rates of chalk deposition as inferred from physical and geochemical evidence appear to be a significant control on reservoir characteristics in north sea chalks the highest average porosities and permeabilities are found in areas with the highest sediment accumulation rates where seafloor diagenesis is minimized topographic depressions at the time of sedimentation can thus be expected to have the best production characteristics and synsedimentary topographic highs should have the thinnest sections and the poorest petrophysical properties

petrography and environmental controls on the formation of phanerozoic marine carbonate hardgrounds early marine seafloor lithification of carbonate sediments leads to the formation of hardgrounds and is known from rocks as old as the proterozoic hardground surfaces however are more commonly recorded in the phanerozoic sedimentological archive while ecological studies of hardground biota abound the environmental and physico chemical parameters leading to the development of seafloor lithification remain in many cases poorly understood and documented this paper reviews published evidence on the petrography mineralogy and geochemistry of phanerozoic carbonate hardgrounds within a process oriented context of their environmental controls hardgrounds typically develop in warm and shallow agitated tropical waters that are saturated with respect to caco3 but are also reported from hemi pelagic to bathyal realms and from cool water temperate settings a range of early marine cement types are documented from present day hardgrounds whereas preserved cement fabrics and related mineralogies are less diverse in early phanerozoic hardgrounds carbonate hardgrounds are widespread during calcite sea periods e g ordovician and cretaceous as opposed to some preservation bias ancient aragonite seas e g permian and triassic obviously the relation between seawater chemistry and hardground abundance and attributes is not an easy one here the concept of aragonite versus calcite seas serves as a first order template for the sake of a structured discussion whereas modern aragonite mode oceans document a significant diversity in spatial and bathymetric seawater properties this spatio temporal complexity is perhaps reflected in the scarce record of calcite sea hardgrounds from the devonian or paleogene rock record contrasted by the abundance in aragonite holocene and recent seas holocene hardgrounds allow for the direct assessment of rates of and reasons for early subaquatic lithification and in most cases escaped subsequent non marine diagenetic overprint conversely studies of ancient hardgrounds are often biased by early biological and mechanical erosion the degree of diagenetic overprint and tectonic to orogenic processes the formation distribution and physical properties of hardgrounds depend on the global climatic context greenhouse icehouse modes on sea level changes on ocean stratification on the spatial extent of epicontinental seas and carbonate depositional environments and on the spatially different mineralogies and rates of carbonate production the fabrics and mineralogies of early hardgrounds cement seem to substantially hinge on variations in atmospheric co2 thus the application of lessons from modern to ancient hardground case examples is not straightforward a holistic model explaining the full variability of controls on submarine hardground formation and their cement petrography throughout the phanerozoic is as yet lacking a more critical view on secular changes in hardground formation patterns is clearly needed future work should rely on the combination of sedimentological stratigraphic palaeoecological petrographic and geochemical approaches specific emphasis should be given to time intervals triassic carboniferous cambrian etc where the bulk of reported case studies is at best scarce

mass transport in european cretaceous chalk fabric criteria for its recognition although it is a pelagic sediment fine grained calcareous ooze may be mobilized prior to general lithification and redeposited as allochthonous units numerous occurrences of allochthonous chalk have been reported in recent years having been recognized by large scale bedding features seen in outcrop smaller scale internal features such as contorted laminae and larger features such as smeared burrows and imbricated flint nodules attest to a significant amount of soft sediment deformation and synsedimentary slumping in european chalk sections of late cretaceous age truly autochthonous chalks contain complex tiered ichnofabrics and in some cases exhibit a diagenetic nodular fabric that is undisturbed by transport in some situations such as stagnant water conditions autochthonous chalks may exhibit primary lamination although this is very uncommon in european chalk sequences different types of redepositional processes produce an array of varied allochthonous fabrics glide and slump units for example contain internal deformational features produced during sliding ooze flow causes plastic deformation of chalk units internally as well as externally resuspension and fluid flow of chalk sediment produces a deposit having a totally new fabric such as a conglomerate composed of detrital chalk clasts in this paper typical macroscopic sedimentary fabric types are illustrated and the means of identifying them are discussed in terms of bioturbation features in situ diagenetic nodules versus detrital clasts physical deformation structures and development of flints

stratigraphically controlled silicification in danian chalk and its implications for reservoir properties southern danish central graben abstract the effect of silica on reservoir quality in chalk is subject to continuing debate in particular the stratigraphic variations in silica content within the chalk matrix have not been addressed sufficiently in this study a new approach is applied to constrain silica variability in reservoir chalk utilizing hand held x ray fluorescence hh xrf on samples from four maastrichtian danian cores from hydrocarbon producing fields in the southern danish central graben the results indicate a significant lateral and stratigraphic variability in silica concentrations across the study area data display a common stratigraphic signature in all wells however with maximum silica concentrations and minimum porosities occurring in the lower part of the danian ekofisk formation correlation between hh xrf quantified silica concentrations and biostratigraphic data indicates the synchronous onset of an at least semi regional silica event during the mid danian nannofossil zones nntp2f g to nntp4a d whereas the upper boundary of the peak silica unit is poorly constrained generally stratigraphic trends in silica concentrations appear to be negatively correlated with porosity trends however comparison between the hh xrf quantified silica content and reservoir data porosity permeability estimated pore radius and calculated specific surface area shows poor correlation indicating that silica content within the ekofisk reservoir is not the only factor controlling the reservoir quality unknown complex diagenetic interactions between calcite silica and clay probably influence the reservoir properties by promoting calcite cementation in stratigraphically controlled zones making the ekofisk reservoir much less predictable than the underlying maastrichtian tor formation

a predictive mesoscale model of the erosion and profile development of soft rock shores the development application and behaviour of a generic model of retreating soft rock e g clay shores is described this represents a broad system in coastal modelling terms comprising shore platform beach tidal range wave transformation cliff and talus the coast is divided into a series of representative cross shore profiles each of which is discretised into a column of elements erosion of a platform element at each timestep depends on its gradient material strength is dealt with as a calibration constant wave forces are averaged over durations of a tide or hour and sediment transport is represented in bulk terms attention has been focussed on interaction between system parts and the emergence of system properties in particular profile shape this is allowed to develop towards dynamic equilibrium and is the principal means of model validation the emergence of the profile shape is dominated by the distribution of wave scour by the tide and by interaction with a beach if present because the model is process based it may be used to model the effects of climate change and engineering intervention yet it is also computationally inexpensive so may be used to explore uncertainty through probabilistic application the breadth of the included system coupled with short run times enables predictions over timescales of decades which we refer to as the mesoscale the model is used to explore the dynamics of retreating soft rock shore profiles and to predict future behaviour of a study site

spatial variability in petrophysical properties in upper maastrichtian chalk outcrops at stevns klint denmark abstract the spatial variability of porosity and permeability was determined for a section in the uppermost maastrichtian chalk exposed in the sigerslev quarry at stevns klint the aims were threefold 1 to quantify the spatial variability pattern and its link to geology by applying systematic variogram analysis procedure 2 to detect potential cyclicity in the petrophysical properties in this pure and overtly homogeneous chalk and 3 to compare the section with chalk reservoirs in the north sea in order to asses to what extent this onshore sequence has a potential as an analogue of the offshore more deeply buried chalk reservoirs the interval is of comparable stratigraphic age to the uppermost reservoir zones in the tor formation of the north sea chalk reservoirs the variability and spatial correlation of porosity and permeability in both horizontal and vertical directions are interpreted in a geological context and show indications of small scale heterogeneity at 15 25 cm scale but the clear cyclic layering described from other chalk deposits is not recognised at this locality the investigated outcrop is not a close analogue to north sea reservoir chalk but some aspects are common including basic material properties porosity permeability trends and the variability pattern the outcrop has a potential as analogue for some of the onshore subsurface chalk successions at shallow burial depth that form important aquifers

upper cretaceous marl limestone sequences of alabama possible products of sea level change not climate forcing marl limestone sequences in the arcola limestone member campanian of alabama have been cited as key examples of climate forced sedimentation resulting from cycles of production and dilution however sedimentologic and stratigraphic data from the arcola presented herein suggest a more probable link between short term sea level changes and marl limestone sequence genesis either relative sea level change caused by intraplate deformation or short term eustatic sea level change is suggested as the causative mechanism for deposition of the marl limestone sequences

cretaceous rhythmic bedding sequences a plausible link between orbital variations and climate abstract simple oscillation cycles have been recognized in cretaceous pelagic sequences as a marked periodicity in carbonate and or organic carbon content the estimated periodicities of these cycles resemble milankovitch type variations in orbital elements however during warm geologic periods the nature of the link between orbital variations and the sedimentary record has been problematic climate model studies show that the intensity of continental margin precipitation in specific low latitude regions is a function of land sea thermal contrast which is sensitive to orbital variations cretaceous climate model simulations are characterized by regions of intense precipitation the locations of which are controlled by geographic configuration in particular in the model simulation the northern margin of the tethys ocean has all the climatic characteristics necessary to exhibit a sensitivity to orbital variations detailed studies of the biota sedimentology and geochemistry of the bedding rhythms in greenhorn cyclothem in the western interior seaway of north america are best interpreted in terms of variations in precipitation runoff and stable stratification of the seaway combined the geologic and model studies support a link between orbital periodicities variations of intense precipitation associated with specific paleogeographic situations and cretaceous bedding patterns this hypothesis has important implications for the sensitivity of the atmosphere hydrosphere lithosphere system to external forcing

a milankovitch scale for cenomanian time a detailed cyclostratigraphy is present in the rhythmically bedded cenomanian hemipelagic chalks of the northern anglo paris basin which can be correlated over 100 000 km2 individual decimetre scale couplets probably represent the precession cycle modes at 18 or 23 kyr and can be readily grouped in sets averaging five indicative of the short cycle of eccentricity 100 kyr a composite cyclostratigraphy for the basin is presented here and is used as the basis for a cenomanian time scale 20 and 100 kyr units the total duration of the cenomanian thus obtained 4 4 myr compares well with recent radiometric dates of 4 0 4 5 myr the time scale is used to estimate the length of ammonite inoceramid and planktonic foraminiferal zones the rates of formation of authigenic minerals glauconite sedimentation rates and the duration of transgressions and anoxic events

sedimentology geochemistry and origin of phosphatic chalks the upper cretaceous deposits of nw europe santonian lower campanian and lower maastrichtian phosphatic chalks in northern france southern england and belgium are europe s largest sedimentary phosphatc deposits the stratigraphy sediment ology petrography mineralogy and geochemistry of the lithofacies are reviewed and new data presented depositional and diagenetic models for phosphatic chalk deposits are developed using published experimental work and from observations of modern high and low productivity phosphogenic systems it is concluded that phosphatic chalks were deposited in well oxygenated current swept environments phosphatization required a delicate balance to be maintained between moderate organic carbon and carbonate sedimentation rates reduced bulk sediment accumulation rate and an enhanced rate of bioturbation precipitation of carbonate fluorapatite francolite accompanied the bacterially mediated decomposition of organic matter occurring within centimetres of the sediment seawater interface and taking place preferentially within microbial bodies and coatings in addition to the organically derived component pore water phosphate levels were enhanced by phosphate absorbed on ferric oxyhydroxides which was liberated during iron reduction mineralization was probably a dominantly post oxic process but occurred in a thick sediment mixed layer in which marine organic matter was undergoing intense mixed aerobic and anaerobic microbial degradation phosphogenesis occurred predominantly on the ne margins of the anglo paris basin where shallower sea floors and suitable palaeoceanographic conditions prevailed phosphogenic episodes were limited by sea level fluctuations which controlled the effectiveness of the erosional currents that formed and maintained the phosphatic basins and may have stimulated local productivity

geochemical constraints on the origin of enigmatic cemented chalks norfolk uk very hard cemented chalk stacks and crusts found locally in the upper part of the cretaceous chalk of north norfolk uk are related to solution features the solution features mainly pipes and caves formed after deposition of the overlying middle pleistocene wroxham crag probably by routing of sub glacial or glacial melt waters derived from late pleistocene glaciers new geochemical particularly stable isotope data shows that cementation of the chalks although related spatially to the solution features was not caused by glacier derived waters the carbon isotope composition of the chalk cements is typically around 9 5 indicative of biologically active soils moreover the oxygen isotope compositions of the cements around 5 are incompatible with water 18 o values much below 9 to 10 which probably precludes isotopically negative glacier derived water as resulting palaeo temperatures are below zero taken together the isotope data suggest chalk cementation occurred under interglacial conditions similar to the present dissolved calcium carbonate for cementation came from dissolution of reworked chalk in overlying mis 12 glacial tills

a composite mud volcano system in the chalk group of the north sea central graben abstract the study describes a large kilometre scale composite mud volcano system within the north sea chalk group containing both intrusion and extrusion features the upper part of the system consists of three stacked constructive components at the top a late palaeocene mound shaped extrusion with subtle onlaps is observed below a danian near surface intrusion caused forced folding of the c 100 m thick overburden this is underlain by a shallow intrusion the lower part of the mud volcano system is defined by a depletion related depression and the fluid conduit seismic data suggest that the source unit for the linked intrusion extrusion is to be found either within a lower cretaceous diapiric siliciclastic structure or within the fine grained carbonates of the chalk group the latter is more probable implying that chalk may generate hitherto undocumented intrusions and extrusions comparable with siliciclastic mud volcano systems remobilization is inferred to have been driven by fluidization caused by the influx of mainly pore water expelled from the lower cretaceous succession a distinct depositional variation within the chalk group caused early diagenetic differences in porosity preservation and mechanical properties of the chalk units allowing the remobilization of certain chalk units even at burial depths as great as 200 m

gravel barrier migration and overstepping abstract despite the widespread occurrence of gravel barriers on mid to high latitude coasts understanding of their stability and relationship to gravel deposits on the inner continental shelf remains rudimentary on sand dominated coasts subject to rising relative sea level barrier overstepping has been postulated as a mechanism for preservation of beach deposits on the shelf but direct observation of overstepping events has been lacking observations at a site on the atlantic coast of canada reveal migration of a gravel barrier at 8 m a 1 landward over back barrier mud following abandonment of part of the barrier volume on the shoreface this provides clear evidence for overstepping and suggests that it may play a role in the formation of inner shelf gravel deposits integrity of the migrating stretching barrier depends on continued sediment supply from the headland source to a connecting ridge which must become progressively longer as the landward displacement of the barrier increases

storms and shoreline retreat in the southern gulf of st lawrence abstract storms play a major role in shoreline recession on transgressive coasts in the southern gulf of st lawrence gsl southeastern canada long term relative sea level rise off the north shore of prince edward island has averaged 0 3 m century over the past 6000 years 0 2 m century over 2000 years this has driven long term coastal retreat at mean rates 0 5 m a but the variance and details of coastal profile response remain poorly understood despite extensive sandy shores sediment supply is limited and sand is transferred landward into multidecadal to century scale storage in coastal dunes barrier washover deposits and flood tidal delta sinks charlottetown tide gauge records show mean relative sea level rise of 3 2 mm a 0 32 m century since 1911 a further rise of 0 7 0 4 m is projected over the next 100 years when differenced from tidal predictions the water level data provide a 90 year record of storm surge occurrence combined with wind wave hindcast and sea ice data this provides a catalogue of potentially significant coastal storms we also document coastal impacts from three recent storms of great severity in january and october 2000 and november 2001 digital photogrammetry 1935 1990 and shore zone surveys 1989 2001 show large spatial and temporal variance in coastal recession rates weakly correlated with the storm record in part because of wave suppression or coastal protection by sea ice large storms cause rapid erosion from which recovery depends in part on local sand supply but barrier volume may be conserved by washover deposition barrier shores with dunes show high longshore and interdecadal variance with extensive multidecadal healing of former inlet and overwash gaps this reflects recovery from an episode of widespread overwash prior to 1935 possibly initiated by intense storms or groups of storms in the latter half of the 19th century with evidence from the storms of 2000 2001 this points to the importance of storm clustering on scales of weeks to years in determining erosion vulnerability as well as the need for a long term large scale perspective in assessing coastal stability the expected acceleration in relative sea level rise together with projections of increasing storm intensity and greatly diminished winter ice cover in the southern gsl implies a significant increase in coastal erosion hazards in future

limestone marl alternations as environmental archives and the role of early diagenesis a critical review limestone marl alternations and other micritic calcareous rhythmites have long appealed to sedimentologists as they appeared to directly reflect high frequency environmental change in particular when orbital forcing gained popularity amongst sedimentologists and paleoclimatologists in 1980s such rhythmites seemed to offer an ideal tool for high resolution chronostratigraphy and environmental reconstruction however in spite of the fact that orbital forcing has become a routine interpretation of calcareous rhythmites and that the processes of formation of calcareous rhythmites are considered well understood research in the past 10 years again has questioned their primary origin and their direct interpretability detailed petrographic paleontological and geochemical data from numerous successions through geological time provided the basis for testing whether or not the regular alternation of limestone beds and marl or shale interlayers represents bimodally fluctuating environmental conditions in a direct way in particular these data supplemented by box model simulations imply that post depositional alteration diagenesis has the potential to not only seriously distort primary environmental signals but also to mimic primary signals this questions the use of micritic calcareous rhythmites for high resolution chronostratigraphy and for environmental interpretations where independent data of diagenetically inert parameters are not available diagenetic changes appear to have a yet widely underestimated influence on the appearance of limestone marl alternations and other calcareous rhythmites the aim of the present review is to summarize new approaches and give an overview of our research results in this field of the past decade this review also aims at pointing to still enigmatic aspects that need to be addressed before the interpretation of micritic calcareous rhythmites can be considered a reliable tool for high resolution chronostratigraphy and paleoenvironmental interpretation

recognition of cyclicity in the petrophysical properties of a maastrichtian pelagic chalk oil field reservoir from the danish north sea subdivision of the maastrichtian chalk from the danish north sea has proven difficult because of its homogenous composition which is caused by a fairly stable depositional environment nevertheless the chalk petrophysical properties show cyclic behavior that potentially can be used for subdivision petrophysical properties of a 23 m long succession of maastrichtian chalk from the dan field were examined for cyclicity by spectral analysis magnetic susceptibility values measured on plug samples together with the neutron porosity and natural gamma radiation well log data were analyzed both as complete data sets and in subsets to survey the general existence of cycles in the chalk all three properties contain consistent cycles at approximately 2 m wavelength as well as additional frequencies where the relative dominance of the different frequencies differs cross spectral analyses of subsets of the petrophysical parameters provide substantial evidence for the coexistence of the approximately 2 m cycles in the maastrichtian chalk furthermore the magnetic susceptibility carries spectral evidence for a higher frequency because most power spectra of the subsets from the magnetic susceptibility have a spectral peak in the 1 8 2 0 cycles m interval i e approximately 0 5 m cycle the cycles can be interpreted as resulting from the eccentricity 94 5 k y and the precession 22 5 k y of the milankovitch cycles assuming a sedimentation rate of 2 6 cm k y the existence and the understanding of cycles at a submeter scale yield possibilities for an advantageously precise subdivision of chalk reservoirs and correlation between wells begin page 2004

late glacial and holocene depositional history in the eastern part of the szczecin lagoon great lagoon basin nw poland abstract analyses on 27 sediment cores taken from the bottom of the szczecin lagoon allowed environmental reconstruction of the postglacial main stages of basin development based on detailed sedimentological geochemical diatomological and malacological studies of selected key cores studies revealed that during the late glacial and holocene this area developed in several stages in the late glacial the whole study area constituted a low alluvial plain at the turn from younger dryas to holocene the alluvial plain was cut through by the odra river to a level of 10 11 m below sea level b s l along with the first phases of the holocene marine transgression at the southern baltic sea s coasts the accumulation of the limnic swampy deposits began in this lower part of the odra valley at ca 6 6 5 ka bp the transgression proceeded and littorina sea waters flooded the area at that time the szczecin lagoon constituted a marine embayment in which series of sands partly rich in malacofauna was deposited the development of the swina barrier resulted in the isolation of the embayment from the direct inflow of baltic sea waters

a review of the history of the baltic sea 13 0 8 0 ka bp abstract the dynamic history of the baltic sea during the millennia following the last deglaciation has been one of the main topics for many generations of quaternary geologists around the baltic sea based on the present state of knowledge and certain hypotheses a model for the development during the baltic ice lake yoldia sea and ancylus lake stages are presented the oresund strait was the threshold of the initial stage of the baltic ice lake and was eroded down to bedrock as a result of the isostatic uplift the emerging threshold forced the baltic ice lake to rise above sea level at ca 12 0 ka bp this gradual up damming ended at ca 11 2 ka bp when the large glacial lake was lowered 5 10m by possible subglacial drainage at mt billingen a glacial readvance during the younger dryas ended a ca 400 year long land bridge between sweden and the continent by blocking the former drainage route once again the baltic ice lake had to rise above sea level to be drained over the oresund strait at ca 10 5 ka bp a gradual ice recession began and 200 years later when the receding ice sheet could not withhold the up dammed water masses the final drainage of the baltic ice lake occurred which rapidly lowered the water level within the baltic basin with ca 25 m and ended the baltic ice lake stage the next stage the yoldia sea was characterized by a complex pattern of relative sea level changes with large differences within the baltic basin a very restricted baltic sea in the south and thus an extensive landbridge at ca 9 9 ka bp a short 100 200 years saline ingression is seen in the baltic sediment records from stockholm in the north to the southernmost parts of the yoldia sea the gradually shallower strait in south central sweden the narke strait ended the saline influence 300 400 years later the two remaining outlets west of lake vanern gota alv and otteid steinselva had become too shallow to swallow the outflowing yoldia sea waters at this stage the baltic lake vanern level could thus not fall in pace with the relative sea level fall outside the outlet areas this was the isolation of lake vanern and the baltic from the sea and the beginning of the ancylus lake since the water depth of the larger gota alv outlet had to be more or less maintained the ancylus lake level had to rise in pace with the uplift of the outlet region this caused a significant and rapid transgression 10 30 m in ca 300 years in the southern baltic which flooded large areas with recently immigrated pine forests since the oresund strait during the yoldia sea stage had been uplifted more than southerly areas the ancylus transgression ended with a new drainage pathway at ca 9 2 ka bp through the darss sill area in the southern baltic and northwards through the store belt strait this so called dana river had cut off the former large land bridge the quaternary deposits of this new threshold were eroded and a fairly rapid regression set in at ca 9 0 ka bp the dana river had eroded down to the sea level which isolated lake vanern from the ancylus lake and created a land bridge between southern sweden and northwards ca 800 years later when the sea level rose above the oresund threshold marine water could enter the baltic and at ca 8 0 ka bp brackish water characterized the southern baltic this marks the end of the ancylus lake

reconstruction of holocene coastal foredune progradation using luminescence dating an example from the świna barrier southern baltic sea nw poland abstract two sandy spits on the wina barrier wolin and uznam provide a very detailed succession of holocene coastal foredunes and dunes and are regarded as key sites along the southern baltic sea coast optically stimulated luminescence osl dating is proven to be a powerful tool for the reconstruction of holocene coastal spit evolution and foredune accretion quartz extracted from the coastal sediments in the study area provides excellent properties for osl dating the osl age from the innermost dune indicates that spit development of the wina barrier started immediately after rapid sea level rise of the littorina transgression decelerated at 6 6 ka a significant change in the foredune progradation rate occurred during the late subatlantic transgression at 1 2 ka 800 ad when migration rates decreased from 2 6 0 7 m a 1 to 1 3 0 4 m a 1 progradation accelerated again during the little ice age between 1550 and 1850 ad the systematic dating of 28 samples reveals six hiatuses during foredune succession at 2100 bc 900 bc 200 bc 200 ad 600 ad 1000 ad and 1600 ad the timing of these hiatuses correlates with the phases of transgressive dune development in the surrounding area troszyn and wina and with phases of increased aeolian activity in other parts of north and west europe we conclude that four of these phases of foredune erosion instability and aeolian sediment mobilisation were caused by general climate shifts to cooler and stormier conditions at 2200 bc 900 bc 600 ad and at 1600 ad the latter corresponding to the little ice age the period of increased aeolian activity around 1000 ad is probably to a phase of intensive forest clearance in central europe in contrast the systematic foredune accretion and foredune plain growth correlates to periods of positive sediment budget milder and calmer climate and an intact vegetation cover

organisational controls typologies and time scales of paraglacial gravel dominated coastal systems abstract the fundamental controls on the initiation and development of gravel dominated deposits beaches and barriers on paraglacial coasts are particle size and shape sediment supply storm wave activity primarily runup relative sea level rsl change and terrestrial basement structure primarily as it affects accommodation space this paper examines the stochastic basis for barrier organisation as shown by variation in gravel barrier architecture we recognise punctuated self organisation of barrier development that is disrupted by short phases of barrier instability the latter results from positive feedback causing barrier breakdown when sediment supply is exhausted we examine published typologies for gravel barriers and advocate a consolidated perspective using rate of rsl change and sediment supply we also consider the temporal variation in controls on barrier development these are examined in terms of a simple behavioural model barch for prograding gravel barrier architecture and its sensitivity to such controls the nature of macroscale 10 2 10 3 years gravel barrier development including inherited characteristics that influence barrier genesis as well as forcing from changing rsl sediment supply headland control and barrier inertia is examined in the context of long surviving barriers along the southern england coastline

morphology of the canadian beaufort sea coast a study of the canadian beaufort sea coast alaskan yukon border to baillie island was conducted to provide a regional summary of a coastal morphology b coastal stability and c coastal processes a total of 2077 km of coastline was mapped using aerial photographs low altitude and oblique aerial video imagery and information from previous field studies the coast can be adequately characterized by six repetitive coastal types four of which are erosional landforms and comprise 60 of the coast ice rich cliffs ice poor cliffs low tundra cliffs and inundated tundra two repetitive coastal types are accretional landforms and comprise 40 of the coast barrier islands and spits and deltas the deltas in the study area are retreating rapidly and therefore over 80 of the coast is considered erosional and less than 20 accretional over 1000 measurements of coastal stability indicate wide scale coastal retreat most sections of the coast show mean coastal retreat rates in excess of 1 m yr 1 despite very low annual wave exposure levels near active areas of the mackenzie river delta mean retreat rates are in excess of 2 m yr 1 and a maximum retreat rate of 18 m yr 1 was documented near shallow bay the presence of significant quantities of ice in the coastal sediments both in the form of pore ice and massive ice beds appears to be the primary cause of the wide scale regional retreat of the coast although a relative sea level rise in the region may also be important

oxygen and carbon isotope compositions of upper cretaceous chalk from the danish sub basin and the north sea central graben the oxygen and carbon isotopic compositions of upper cretaceous chalk have been studied from a large number of outcrops and boreholes in the danish sub basin and the north sea central graben the carbon isotopic compositions vary from 0 50 o to 3 00 o 13c which correspond to the expected carbon isotopic composition of carbonate precipitated from normal sea water the oxygen isotopic compositions of samples from outcrops and near surface drilled sections fall in the range from 0 50 o to 2 00 o 18o which is close to the expected values for carbonate produced by coccoliths in the late cretaceous sea a geographic distribution exists in the danish sub basin showing relatively heavy oxygen isotope values in the centre of the basin and slightly more negative values in the eastern part of the basin primarily the phenomenon is thought to reflect minor variations in the oceanographic parameters in the late cretaceous sea the deep subsurface sections represent a depth interval of 0 3100 m mechanical compaction in the uppermost part of the sequences apparently has no influence on the isotopic composition chemical compaction dominates at greater depth leading to temperature induced isotopic re equilibration in the water rock system in these sequences the oxygen isotope values range from 1 50 o to 7 50 o 18o and are significantly correlated with depth of burial cementation and porosity the data indicate that pressure dissolution recrystallization reprecipitation and ion exchange between solid carbonate phase and pore water are all actively involved in the oxygen isotope re equilibration process this process is believed to take place in a diagenetically closed system and is tentatively divided into two phases 1 an early diagenetic phase which takes place at porosities down to approximately 20 in which the chalk possesses a pore water controlled isotopic re equilibration system and 2 a late diagenetic phase at porosities below 20 in which the re equilibration process increasingly becomes influenced by the rock introduced isotopic change in the composition of the formation water

the shoreline displacement curve of rugen island southern baltic sea abstract rugen island is situated in north east germany at the southern baltic sea coast geological stratigraphical and palaeoecological evidence collected from the schaabe spit in northeast rugen include 167 cores and 46 radiocarbon dates leading to a local shoreline displacement curve which is compared and discussed with morner s eustatic curve of northwest europe and tooley s shoreline displacement curve of northwest england corresponding to these curves the holocene sea level rise occurred in phases on rugen island the undulations found fit temporally well there is a close correlation between the shoreline displacement curves of the lytham area in northwest england and rugen island during the boreal and the atlanticum compared with morner s eustatic curve rugen island was uplifted between about 7000 bp and 5000 bp in a range of 6 m since that time stable conditions or slightly subsidence are presumed on rugen island

a new method of testing periodicity in cyclic sediments application to the newark supergroup abstract we present a new quantitative method for analyzing cyclic sediments the gamma method gamma time thickness tests the assumption that the cycles are periodic and provides quantitative estimates for relative accumulation rates of the different sedimentary facies that compose the cycles as such it provides a means of estimating relative time at very high resolution application of the gamma method to hettangian sediments of the newark supergroup indicates that the primary cycles were deposited in response to precessional climatic forcing and that these cycles were modulated by an eccentricity cycle with period ratios very similar to those of today results of gamma analysis also suggest that relative accumulation rates of the laminated deep water lacustrine facies was about six times slower than that of the shallow water facies

a relative sea level curve for the polish southern baltic sea abstract the relative sea level curve was developed for the southern baltic area based on a set of 315 radiocarbon dates of different terrestrial and marine sediments collected at 164 sites located in the polish part of the southern baltic and in the adjacent coastal land area when developing the curve relicts of various formations related to the shoreline evolution as well as extents of erosional surfaces determined from seismoacoustic profiles were taken into account during the late pleistocene and early holocene i e between 13 0 and 8 5 ka bp the southern baltic sea level rose and fell three times the amplitude of changes extending over 25 27 m in the late boreal c 8 5 ka bp the baltic its water level by about 28 m lower than the present one became permanently connected with the ocean until the onset of the atlantic the sea level had risen to about 21 m below present sea level during 8 0 7 0 ka bp the sea level was rising to reach 10 m subsequently during the atlantic until its end the sea level rose to 2 5 m b s l during the first millenium of the subboreal the sea level rose to about 1 3 1 1 m b s l to become on termination of the subboreal about 0 7 0 6 m lower than present during the subatlantic the sea level changes were minor