a new hypothesis for the holocene appearance of coccolithophores in the black sea a recent accelerator mass spectrometer ams radiocarbon study of black sea holocene sediments has resolved a long standing chronology controversy involving radioisotope and varve counting methodologies the revised chronology combined with model results of the salinity evolution of the black sea since the last glacial maximum does not support the hypothesis of a salinity controlled holocene invasion of the black sea by coccolithophores a planktonic golden brown unicellular marine algae rather evidence presented here is used to suggest these organisms were inadvertently transported from the mediterranean sea by sailing vessels during the greek exploration and colonization of the black sea in the seventh and eighth centuries bc as such this may be one of the earliest examples of anthropogenic transport of marine organisms between ocean basins and a good example of the difficulties inherent in distinguishing natural from anthropogenic effects when studying holocene biological systems

osseous skeletal material and fish scales in marine sediments under the oxygen minimum zone off northern and central chile abstract the significance of whale falls for the study of the biogeography evolution and biodiversity of deep sea biota has been recently recognized by international programs since large carcasses are known to give rise to biogenic chemosynthetic ecosystems however the plain accumulation of smaller bone material in the shallower settings of the continental shelf and upper slope under the hypoxic conditions of the oxygen minimum zone omz has received much less attention here we describe new findings of skeletal material and fish scales in marine sediments under the omz off northern and central chile which combined with previous reports for the study area lead us to suggest the existence of a band in the benthos of accumulation of bones and scales extending at least twenty degrees in latitude 18 38 s future studies should focus on the characterization of biotic communities living upon these resources in order to elucidate their peculiarities and importance in the eastern south pacific

remobilization of authigenic uranium in marine sediments by bioturbation uranium behaves as a nearly conservative element in oxygenated seawater but it is precipitated under chemically reducing conditions that occur in sediments underlying low oxygen bottom water or in sediments receiving high fluxes of particulate organic carbon sites characterized by a range of bottom water oxygen bwo and organic carbon flux ocf were studied to better understand the conditions that determine formation and preservation of authigenic u in marine sediments our study areas are located in the mid latitudes of the northeast pacific and the northwest atlantic oceans and all sites receive moderate 0 5 g cm2 kyr to high 2 8 g cm2 kyr ocf to the sediments bwo concentrations vary substantially among the sites ranging from 3 to 270 m a mass balance approach was used to evaluate authigenic u remobilization at each site within each region studied the supply of particulate nonlithogenic u associated with sinking particles was evaluated by means of sediment traps the diffusive flux of u into sediments was calculated from pore water u concentration profiles these combined sources were compared with the burial rate of authigenic u to assess the efficiency of its preservation a large fraction one third to two thirds of the authigenic u precipitated in these sediments via diffusion supply is later regenerated even under very low bwo concentrations 15 m bioturbating organisms periodically mix authigenic u containing sediment upward toward the sediment water interface where more oxidizing conditions lead to the remobilization of authigenic u and its loss to bottom waters

rhenium and molybdenum enrichments in sediments as indicators of oxic suboxic and sulfidic conditions of deposition abstract the trace elements re and mo both behave conservatively in seawater yet are strongly enriched in reducing sediments their potential for authigenic enrichment above crustal concentrations is greater than for many other elements due to the high ratio of metal sw metal crust we present sedimentary re and mo data from box and multi cores spanning a range of redox conditions from well oxygenated sites to locations with substantial sulfide concentrations at the oxic sites re and mo as expected accumulate at concentrations close to their crustal abundances re shows substantial enrichment in suboxic absence of o 2 and h 2 s sediments of the sea of japan in sediments within the oxygen minimum of the pakistan margin as well as in sediments underlying the sulfide bearing waters of the black sea and saanich inlet re enrichment occurs in these cores just below the depths of fe and u reduction only in the sediments underlying the sulfidic waters of the black sea and saanich inlet is there substantial authigenic mo accumulation absence of re and mo enrichments in sediment trap samples from the sulfide bearing basins suggests that the addition of both metals occurs at or below the sediment water interface the re and mo concentration profiles are modeled to hindcast the removal depth of re and mo in the sediments which along with the re mo ratio determine whether oxic suboxic or sulfidic conditions were present in the water column or in the sediments in the past using this approach historical redox conditions can be inferred even in environments such as continental margins where a substantial lithogenic component can obscure authigenic enrichments of other metals

226ra in the black sea and sea of marmara water column distributions of226ra were determined at stations in the sea of marmara and the black sea as part of the 1988 joint u s turkish black sea expedition black sea surface water226ra concentrations were a factor of three to four lower than measurements made 20 years earlier the most likely cause is increased removal of226ra and ba 35 due to increased surface biological activity a secondary effect is decreased fluvial discharge and related dimunition of inputs by desorption from fluvial suspended sediments the amount of226ra missing from the surface waters of the black sea over this period is accounted for in the high porosity surficial fluff sediment layer throughout the black sea depth profiles of226ra exhibited pronounced maxima of approximately 25 dpm 100 l at about 16 2 16 3 in the vicinity of a bacterial maximum but slightly shallower than the total dissolved mn and fe maxima 16 4 16 5 reported by lewis and landing 38 while the226ra maximum may in part be linked to the cycling of mn and fe oxyhydroxides near theo2h2s interface its distribution appears to be more plausibly explained as a result of the microbial breakdown of particulate organic matter and the subsequent release and partial dissolution of associated barite in this region a simple steady state two model has been used to obtain a semiquantitative understanding of the behavior of226ra in the black sea by incorporating reasonable estimates for the input and removal of226ra in the black sea an excellent agreement between predicted and observed 1988 226ra concentrations was achieved the model suggests that the dominant variables controlling the distribution of226ra in the black sea are riverine input and cycling with ba

a high resolution historical record of holocene anoxygenic primary production in the black sea i reconstruct the historical record of anoxygenic primary production in the black sea over the last 8200 years by an analysis of chlorobium carotenoids in sediments anoxygenic photosynthesis in the black sea occurs only when hydrogen sulfide containing deep water penetrates the euphotic zone the data show that the black sea has experienced large fluctuations in the extent of anoxygenic primary production and therefore the depth of the h2s chemocline throughout much of the holocene changes in the depth of the h2s chemocline also shift the dominant phytoplankton populations in the water column to noncarbonate bearing species and result in the formation of intense dark bands in sediments

sulfur isotopic trends and pathways of iron sulfide formation in upper holocene sediments of the anoxic black sea down core trends for extents of iron sulfidation in upper holocene microlaminated deposits of the black sea abyssal plain imply that most of the pyrite in these sediments is formed in the sulfidic water column and or very close to the sediment water interface sulfur isotopic data for pyrite within microlaminated muds from two localities in the deep basin show striking uniformity between sites and down core with a mean 34scdt value of 37 2 0 9 1 n 18 these isotopic trends support the hypothesis of early pyrite formation isotopic compositions of pyrite sulfur in the microlaminated bottom sediments are similar to those reported for particulate reduced sulfur collected in middepth sediment traps and to 34s values for water column dissolved sulfide within a narrow zone immediately below the o2 h2s interface these three sulfur reservoirs are distinctly different from the isotopic composition of ambient dissolved sulfide of the deep water column 175 m with 34s values for the deep dissolved sulfide reservoir being consistently lower by 2 to 4 these isotopic relationships suggest that iron sulfidation is occurring dominantly within a narrow shallow region at the top of the sulfidic water mass isotopic data from a fine grained turbidite collected in the deep basin and from rapidly accumulating iron monosulfide rich muds on the anoxic upper slope are enriched in34s relative to the microlaminated deposits the enrichments on the basin margin reflect a large component of iron sulfide formed during rapid burial a broad suite of geochemical data including sulfur isotopic results are consistent with an upper slope sediment source for the ubiquitous muddy turbidites of the deep basin the collective effects of reworking transport and redeposition result in a complete conversion of avs to pyrite with little additional iron sulfidation this conclusion is supported by a detailed isotopic mass balance the present isotopic study also highlights fundamental differences in the reactivities of the iron reservoirs distributed throughout the anoxic basin sediments of the upper slope and the genetically linked turbidites of the deep basin show similar extents of iron sulfidation that are significantly lower than those of the microlaminated deposits of the deep basin floor suggesting dramatically shorter timescales of iron reactivity for the microlaminated sediments of the deep basin importantly isotopic patterns from the modern black sea should assist greatly in the recognition and interpretation of ancient anoxia in the stratigraphic record

immobility of 210pb in black sea sediments we measured 210pb in a core from the deep black sea which contained a turbidite of low 210pb activity surrounded above and below by pelagic sediments of much higher activity to evaluate in situ210pb mobility under the anoxic moderately sulfidic conditions by measuring at millimeter scales across the distinct laminae turbidite contacts and modeling the observed profile we estimated a lower limit of the kd of 107 deff 5 10 13 this result increases confidence in sediment chronologies from the black sea based on 210pb because it implies that profiles will not be altered significantly by diffusive transport of 210pb below the turbidite the 210pb inferred accumulation rate was 50 g m2 a which is lower than laminae based estimates by a factor of 3 4

sediment accumulation in the central western black sea over the past 5100 years the postdepositional particle flux accumulation rate over the last 5100 years was studied in the anoxic sediment units i and ii from the central western black sea deposition of unit ii sapropel in the deep black sea basin was divided further into two subunits the beginning of the deposition of the sapropel in the black sea 5100 3100 years b p subunit iib was characterized by higher organic carbon accumulation rates due largely to higher primary production accumulation rates of lithogenic matter were at a minimum compared to younger units during the subsequent 2100 years 3100 1000 years b p subunit iia organic carbon accumulation rates decreased considerably while accumulation rates of lithogenic matter increased to the present level at 1000 years b p unit i total mass accumulation rates increased by a factor of 3 this increase was largely a result of an increase in carbonate accumulation rates by a factor of 11 which was caused by the rapid appearance of emiliania huxleyi in the black sea higher carbonate accumulation rates in unit i are mainly the cause for the considerably lower organic carbon content compared to unit ii since the organic carbon accumulation rate in unit i did not decrease general correspondence of accumulation rates of lithogenic matter in different cores through time suggests overregional long term 100 year scale climatic effects on the terrigenous particle supply to the black sea

variation in biogenic and detrital fluxes and formation of laminae in late quaternary sediments from the peruvian coastal upwelling zone abstract studies of laminated sediments from the peru margin using back scattered electron imagery bsei provide a high resolution record of variation in detrital and biogenic fluxes and highlight the uncertainty involved in preserving a record of surface processes in bottom sediments intermittently laminated sediments which predominate in the peru forearc basins record episodic major diatom bloom events from which there was adequate flux to counteract water column processes of dissolution and comminution a distinctive sub millimetre lamination with a limited occurrence during isotope stage 5 comprises a regular alternation between silt rich and clay rich couplets which may represent annual deposition with irregularly interlaminated diatom ooze containing near monospecific bloom assemblages the absence of diatom ooze layers between silt clay couplets may be controlled by variation of either the intensity of upwelling and or the nutrient content of upwelled waters macroscopically obvious 0 5 3 cm thick pelleted or homogeneous zones which occur throughout the sub millimetre laminated sequence represent periods of increased oxygenation with a probable 8 16 year duration occurring at irregular intervals of a few years to a few hundred years a slight but pervasive microscopic bioturbation is common within laminated intervals which would macroscopically be described as anaerobic sediments

iunconsistencies in accumulation rates of black sea sediments inferred from records of laminae and 210pb recently published estimates for the age of the unit 1 unit 2 contact in black sea sediments based on accelerator mass spectrometry ams 14c measurements jones 1990 calvert et al 1991 appear to be older than those based on the previously published chronology based on lamina couplets degens et al 1980 hay 1988 by a factor of 2 to 3 to help reconcile the differences we compare sediment accumulation rates based on the 210pb method with estimates based on lamina counts for two cores from the black sea abyssal plain accumulation rates estimated using the 210pb technique have varied little over the last 150 years from the averages of 55 and 50 g m 2 yr 1 at stations in the western and eastern basins respectively these values are about a factor of 2 lower than accumulation rates derived by counting lamina couplets over the dated intervals close examination of the laminae suggests that the discrepancy exists both because it is difficult to count the very fine laminae and because a complete couplet is not deposited every year in order to provide a useful stratigraphic horizon for future investigators studying sedimentary records of the black sea we estimate the age of a distinct black marker horizon which can be easily identified across the entire abyssal plain to be 150 8 years deposited in 1838 8 a d

three dimensional surface displacements and rotations from differencing pre and post earthquake lidar point clouds 1 the recent explosion in sub meter resolution airborne lidar data raises the possibility of mapping detailed changes to earth s topography we present a new method that determines three dimensional 3 d coseismic surface displacements and rotations from differencing pre and post earthquake airborne lidar point clouds using the iterative closest point icp algorithm tested on simulated earthquake displacements added to real lidar data along the san andreas fault the method reproduces the input deformation for a grid size of 50 m with horizontal and vertical accuracies of 20 cm and 4 cm values that mimic errors in the original spot height measurements the technique also measures rotations directly resolving the detailed kinematics of distributed zones of faulting where block rotations are common by capturing near fault deformation in 3 d the method offers new constraints on shallow fault slip and rupture zone deformation in turn aiding research into fault zone rheology and long term earthquake repeatability

preparation and analysis techniques for studies of laminated sediments laminated sediments commonly represent the highest resolution continuous records available of marine and lacustrine variability to exploit this information effectively careful sampling and preparation procedures must be followed thus the method of analysis chosen must have sufficient resolution to recover the data the scanning electron microscope because of its good spatial resolution is an ideal tool for analyzing laminated sediment fabric backscattered electron imagery produces preserved flux data on intra annual time scales which enables high resolution fabric studies palaeoenvironmental reconstructions and compilation of data for time series analysis this contribution summarizes the techniques used for laminated sediment fabric investigation and discusses the use of the scanning electron microscope including the best preparation method for thin sections and the procedure for backscattered electron imagery analysis

tephra from the minoan eruption of santorini in sediments of the black sea the explosive eruption of santorini volcano in the aegean sea about 3 300 years ago is of considerable archaeological and volcanological significance1 5 here we report the discovery of tephra from this minoan event in laminated sediments of the black sea this finding provides constraints on the distribution of debris from the eruption we estimate a minimum fallout area of 2 l06 km2 extending from the black sea in the north to the southeastern mediterranean sea the main dispersal axis trends through southern turkey in agreement with other studies of minoan tephra6 7 the tephra deposits should provide a useful reference horizon for assessing the chronology of black sea sediments which has been much debated8 15

export fluxes of calcite in the eastern equatorial pacific from the last glacial maximum to present 1 the eastern equatorial pacific eep is an important center of biological productivity generating significant organic carbon and calcite fluxes to the deep ocean we reconstructed paleocalcite flux for the past 30 000 years in four cores collected beneath the equatorial upwelling and the south equatorial current sec by measuring ex230th normalized calcite accumulation rates corrected for dissolution with a newly developed proxy for fraction of calcite preserved this method produced very similar results at the four sites and revealed that the export flux of calcite was 30 50 lower during the lgm compared to the holocene the internal consistency of these results supports our interpretation which is also in agreement with emerging data indicating lower glacial productivity in the eep possibly as a result of lower nutrient supply from the southern ocean via the equatorial undercurrent however these findings contradict previous interpretations based on mass accumulation rates mar of biogenic material in the sediment of the eep which have been taken as reflecting higher glacial productivity due to stronger wind driven upwelling

stratigraphic charcoal analysis on petrographic thin sections application to fire history in northwestern minnesota results of stratigraphic charcoal analysis from thin sections of varved lake sediments have been compared with fire scars on red pine trees in northwestern minnesota to determine if charcoal data accurately reflect fire regimes pollen and opaque spherule analyses were completed from a short core to confirm that laminations were annual over the last 350 yr a good correspondence was found between fossil charcoal and fire scar data individual fires could be identified as specific peaks in the charcoal curves and times of reduced fire frequency were reflected in the charcoal data charcoal was absent during the fire suppression era from 1920 a d to the present distinct charcoal maxima from 1864 to 1920 occurred at times of fire within the lake catchment fire was less frequent during the 19th century and charcoal was substantially less abundant fire was frequent from 1760 to 1815 and charcoal was abundant continuously fire scars and fossil charcoal indicate that fires did not occur during 1730 1750 and 1670 1700 several fires occurred from 1640 to 1670 and 1700 to 1730 charcoal counted from pollen preparations in the area generally do not show this changing fire regime simulated sampling of the thin section data in a fashion comparable to pollen slide methods suggests that sampling alone is not sufficient to account for differences between the two methods integrating annual charcoal values in this fashion still produced much higher resolution than the pollen slide method and the postfire suppression decline of charcoal characteristic of my method but not of pollen slides is still evident consideration of the differences in size of fragments counted by the two methods is necessary to explain charcoal representation in lake sediments

carbon sulfur iron systematics of the uppermost deep water sediments of the black sea box cores recovered during leg 4 of the 1988 r v knorr black sea oceanographic expedition from deep water regions of the basin were dominated by coccolith rich microlaminated unit 1 sediment and muddy gray turbidite layers both organic carbon oc and pyrite sulfur values for unit 1 display narrow ranges with mean concentrations of 5 3 1 1 1 wt and 1 3 0 3 wt respectively unit 1 is not enriched in pyrite s relative to sediments deposited under oxygenated bottom waters normal marine sediments with comparable oc concentrations carbon sulfur relationships evaluated on a calcium carbonate free basis to avoid spurious correlations resulting from dilution effects demonstrate that oc and pyrite s are essentially decoupled these observations combined with the persistence of elevated pore water sulfide to depth and a strong correlation between pyrite s and the detrital fe component argue strongly for limitation of pyrite formation in unit 1 by the availability of reactive fe unit 1 fe limitation is further indicated by degree of pyritization dop studies a measure of the extent to which the original potentially reactive fe has been transformed to pyrite these studies show sulfidation of reactive fe ranging from 57 to 78 with dop values independent of oc concentration unit 1 dop profiles suggest that the majority of the pyrite is formed in the sulfidic water column and or very close to the sediment water interface pyrite s concentrations of unit 1 when compared with the particulate reduced sulfur fluxes measured in time series sediment traps are compatible with predominantly water column pyrite formation because of the limitations in the supply of reactive fe associated with the comparatively high supply of oc the microlaminated sediment is characterized by c s ratios greater than those typical of holocene oxically deposited sediments the turbidite muds of the deep basin display high reduced s values relative to holocene normal marine sediments in samples with low oc concentrations low c s ratios this reflects pyrite formation under anoxic sulfidic bottom water conditions in a probable upper slope source region as well as during transport and final deposition intermediate dop values for the turbidites in part a product of their rapid rate of deposition reveal that fe limitation is ultimately not a factor and that further pyrite should form during burial however the very rapid rate at which unit 1 pyrite forms suggests fundamental differences between the overall reactivities of the fe phases associated with the microlaminated and turbiditic sediments the signature of water column anoxia with regard to sedimentary pyrite formation is clearly indicated by the high dop values of unit 1 and the comparatively high levels of s associated with the low concentrations of oc of the turbidite muds this agrees with similar conclusions based on studies of ancient sedimentary rocks

carbon accumulation rates and the origin of the holocene sapropel in the black sea a detailed radiocarbon chronology obtained by accelerator mass spectrometry together with organic carbon and carbonate measurements on two black sea cores has been used to compare and contrast the burial fluxes of organic carbon in the holocene sapropel and the modern sediment at both deep water and eastern slope sites the sapropel is separated from the modern facies by a variable thickness of compositionally homogeneous sediment with low levels of organic carbon and anomalously old radiocarbon ages this homogeneous unit probably represents deposition by slumping or mudflow the age limits of the sapropel are 1600 6600 b p at the deep water site and 4000 6000 b p radiocarbon years before 1950 a d at the shallow water site the carbon accumulation rate in the deep water sapropel is higher than that in the modern deep water facies by a factor of 2 and is approximately the same as that in the modern sediment in shallow water the revised chronology of sapropel formation and the differences in the carbon accumulation rates probably indicate that the sapropel was formed by increased production during the transition from the premodern lake to the modern marine phases of the black sea this conclusion is consistent with the clear marine carbon isotope signal in the organic mattermore in the sapropel in both cores results to be reported elsewhere in contrast to the mixed source of carbon in the other facies less

rhenium in the black sea comparison with molybdenum and uranium rhenium concentrations were measured in the black sea to determine the behavior of this redox sensitive element in an anoxic basin under reducing conditions re is removed from solution leading to its depletion from black sea deep waters compared with uranium water column re and mo profiles show evidence of removal from mid depths suggesting that these elements are scavenged either in the water column or slope sediments to a greater degree than u black sea surface waters are enriched in re reflecting re in rivers draining into the northern black sea that are enhanced up to 80 fold over other large world rivers this enrichment is most likely anthropogenic and may be due to coal burning in the region a simple two box model is used to demonstrate that re concentrations in the black sea are not in steady state with respect to current riverine inputs and authigenic fluxes riverine inputs of u and mo are not as significant perhaps reflecting the fractionation of re from the other elements during a high temperature combustion process re2o7 is volatile above 270 c

holocene history of the baltic sea as recorded in a sediment core from the gotland deep a 4 m long sediment core from the gotland deep baltic sea was investigated by means of biostratigraphical and chemical parameters and c 14 datings this multidisciplinary approach allows us to ev

varve formation in the gulf of california insights from time series sediment trap sampling and remote sensing the varved sediments that accumulate in the central gulf of california guaymas and carmen basins provide a record that allows for the resolution of annual to decadal scale climate variability in this region time series sediment trapping combined with remotely sensed observations of sea surface temperature avhrr and color czcs have been used to examine the mechanism of varve formation in the central gulf sst and surface pigment concentration records for both the mainland and baja sides of the gulf display similar seasonal trends high temperatures and low pigment concentrations occur synchronously on both sides of the central gulf from june through to october in association with the 1991 92 el nino warm temperatures persist in the central gulf until december low ssts typically occur from december through may with high pigment concentrations marking the period from november through april the summer early fall june october is a time of high terrigenous and biogenic sediment fluxes during this time of year the total flux is dominated by eolian transported lithogenic material and dark laminae are deposited during this period during el nino years high terrigenous fluxes may extend into winter light laminae represent deposition from november through may during which time biogenic material dominates the total sediment flux high opal fluxes beginning in november are attributed to seasonal cooling of surface water and upward mixing of nutrients true upwelling conditions do not develop in the gulf until late winter spring during this time the total flux is still dominated by opal but the magnitude of the flux is reduced this may be an artifact of phytoplankton grazing and not lower production rates

holocene and late glacial palaeoceanography and palaeolimnology of the black sea changing sediment provenance and basin hydrography over the past 20 000 years abstract the elemental geochemistry of late pleistocene and holocene sediments of the black sea recovered in box cores from the basin margins and a 5 m gravity core from the central abyssal region of the basin identifies two terrigenous sediment sources over the last 20 kyrs one source region includes anatolia and the southern caucasus the second region is the area drained by rivers entering the black sea from eastern europe alkali metal al and heavy light rare earth element ratios reveal that the relative contribution of the two sources shifted abruptly every few thousand years during the late glacial and early holocene lacustrine phase of the basin the shifts in source were coeval with changes in the lake level as determined from the distribution of quartz and the heavy mineral hosted trace elements ti and zr the geochemistry of the abyssal sediments further recorded a sequence of changes to the geochemistry of the water column following the lacustrine phase when high salinity mediterranean water entered the basin beginning 9 3 kyrs bp bottom water that had been oxic throughout the lake phase became anoxic at approximately 8 4 kyrs bp as recorded by the accumulation from the water column of several redox sensitive trace metals mo re u the accumulation of organic carbon and several trace nutrients cd cu ni zn increased sharply ca 0 4 kyrs later at 8 0 kyrs bp reflecting an increase of primary productivity its increase was coeval with a shift in the dinoflagellate ecology from stenohaline to euryhaline assemblages during this profound environmental change from the lacustrine to the marine phase the accumulation rate of the lithogenous sediment fraction decreased as much as 10 fold in response to the rise of the water level in the basin from a low stand ca 9 3 ka to its current level

evolution of long term land subsidence near mexico city review field investigations and predictive simulations 1 aquitard consolidation in the chalco plain is the most recent of a series of major land subsidence problems near mexico city caused by leaky aquifer pumping and involving a complex distribution of basalt flows within a lacustrine sequence this study first conducted a ground magnetic survey combined with lithologic logs to map the extension of basalts then it assessed the evolution of ground surface elevations and updated hydraulic heads in the aquifer and aquitard in order to verify the accuracy of previous simulations and develop new predictions on land subsidence employing a one dimensional nonlinear groundwater flow consolidation model results show the presence of shallow basalts that extend from sierra santa catarina into the chalco plain causing a differential consolidation that controls both the distribution of large scale fractures in the aquitard and the shape of a new lake cumulative land subsidence in the center of the chalco plain reached 13 m in 2006 thus closely matching previous numerical estimations since 1985 the ground surface decline has continued at a rate of 0 40 m yr while the potentiometric surface decline in the aquifer proceeds at an average rate of 1 5 m yr indicating that the flow system has not yet reached steady state conditions numerical predictions show that under current pumping rates where the aquitard is 300 m total land subsidence will reach 19 m by the year 2020 while where the aquitard is 140 m thick total land subsidence will reach 12 m and increase the risk of flooding and aquitard fracturing for nearby urban centers

formation of holocene sedimentary laminae in the black sea and the role of the benthic flocculent layer holocene black sea sediments recovered in 1988 and 1993 from box cores and gravity cores were analyzed geochemically microscopically and with backscattered electron imagery bsei in order to determine the temporal geochemical and sedimentological relationships between the benthic flocculent layer often referred to as the fluff layer and the formation of underlying laminated unit i sediments existence of a permanent benthic fluff layer in the black sea basin is suggested acting as a geochemical transition layer within which all sedimentary particles are hydraulically sorted and particles subject to dissolution or organic remineralization are altered prior to accumulation we propose that particle residence time within the benthic fluff layer is a key factor in determining sedimentary microfabric and geochemical composition of laminated unit i sediments we present a schematic model depicting the above relationships and use it to propose a paleoflux scenario for laminae formation in the unit ii sapropel

quantifying stratigraphic completeness a probabilistic approach using paleomagnetic data although sedimentary hiati of variable magnitude are abundant in most stratigraphic sections quantification of the degree of completeness for individual sections has proven difficult a new method of estimating stratigraphic completeness is developed for sections that preserve a detrital remanent magnetic reversal history because the timing of geomagnetic reversals is independent of sedimentation events the distribution of reversals in a stratigraphic section can be used to evaluate completeness the most direct method in which sections are sampled at the top and base of each stratigraphic unit evaluates the frequency of reversals within units versus at unit contacts the more complete a section the greater the probability that reversals occurred during depositional events and are recorded as within unit reversals the less complete a section the greater the probability that reversals occurred during depositional hiati and are recorded as unit contact reversals monte carlo simulations suggest that

laminated sediments as palaeo indicators as society at large becomes increasingly concerned with the issues surrounding global climate change so the pressure on the scientific community to produce models and predictions of climate variability increases in many respects however that branch of science concerned with climate change is in its infancy while recent meteorological and oceanographic studies have shed light on the processes and mechanisms of atmospheric and oceanic circulation this has produced only a snapshot perspective of global change limited by the range of instrumental or historical records on the other hand palaeoclimatic and palaeoceanographic studies have been mainly on coarser millennial timescales that have a more academic and less immediate appeal the palaeorecords which have the required temporal interannual decadal resolution are limited to tree rings ice cores coral records and laminated marine or lacustrine sediments this volume is concerned with the wide ranging application of lacustrine and marine laminated sediments as palaeo indicators