a high resolution record of the last deglaciation in the central mediterranean sea palaeovegetation and palaeohydrological evolution abstract a high resolution palynological and stratigraphical record of a marine deep sea core in the adriatic sea documents marine and continental palaeoenvironmental changes in the basin during the last deglaciation and early holocene a chronology is derived from the oxygen isotope stratigraphy three periods of aridity marked by the development of a semi desert rich in artemisia occurred between 18 5 and 16 kyr between 14 4 and 12 7 kyr and between 11 1 and 9 7 kyr consistent with the last glacial maximum the oldest dryas and the younger dryas they are correlated with increases in productivity and intensification of the levantine water formation in the eastern mediterranean basin during the warmer bolling allerod 12 7 11 1 kyr the presence of the cold temperate dinocyst bitectatodinium tepikiense is interpreted as indicating the establishment of a strong seasonal thermal gradient probably linked to seasonal cold freshwater runoff from the po river attested by the unique presence of pollen of freshwater plants the expansion of forest and the development of the warmer dinocysts start with termination ib during the holocene three tree phases are recognized and are contemporaneous with the preboreal boreal and atlantic chronozones of europe the two phases of sapropel deposition are marked by higher pollen and dinocyst concentrations and a high representation of brigantedinium spp which indicate higher preservation of organic material and or freshwater runoff of the po river

late glacial to holocene planktic foraminifera bioevents and climatic record in the south adriatic sea quantitative analyses of planktic foraminifera sea surface temperatures ssts oxygen isotope and radiocarbon dating from a deep sea core recovered in the south adriatic sea have been used to reconstruct a subcentennial climatic and biochronological record since the late glacial the last 24 cal ka bp the identification and relative abundance of 25 species of planktic foraminifera along the core have provided a continuous record of the faunal changes over this time interval these results have permitted the establishment of 10 biozones in the south adriatic sea based on the appearance and or disappearance of the main specific taxa from peaks of abundance and or by modification in marine conditions the robust chronology of the south adriatic core allowed correlation of sst estimates to the gisp2 ice core record indicating that the main climate changes recorded in greenland ice cores over the last 24 ka are recorded and globally synchronous with those observed in the south adriatic sea this finding further allows comparison of the planktic foraminifera record with the event stratigraphic scheme proposed by the intimate group in order to better identify the relationship between past climatic changes and the response of microfaunal assemblages in the south adriatic copyright 2010 john wiley sons ltd

sedimentology of a glaciofluvial deposit at ekeby east central sweden abstract the ekeby site south of stockholm has been chosen to elucidate glaciofluvial sedimentation processes soon after the end of the younger dryas detailed lithofacies and grain size analyses of gravel sand and fine sediment sequences in a gravel pit reflect changes in the depositional environment four main facies assemblages have been distinguished the lowermost part of the sequence was probably deposited in a subglacial conduit environment the middle part of the sequence reflects a transition to a proglacial subaqueous environment the upper part of the latter sequence probably occurred during increased melting of the ice the sequence was then covered by beach gravel formed during the regression after the drainage of the baltic ice lake

hydrological changes in the mediterranean sea over the last 30 000 years sea surface temperatures were reconstructed over the last 30 000 years from alkenone paleothermometry sst alk and planktonic foraminifera assemblages using the modern analog technique mat sst foram along two cores of the mediterranean sea md84 632 levantine basin and md04 2797 siculo tunisian strait oxygen isotope of planktonic foraminifera g bulloides for core md04 2797 and g ruber for core md84 632 were also determined sst alk in the levantine basin indicate colder values at the last glacial maximum lgm 14 c than earlier established from mat and a cooling amplitude of 6 7 c comparable to the central mediterranean sea climatic events such as the younger dryas yd and heinrich events 1 and 2 h1 and h2 were times of significant cooling in the two cores in the eastern basin values of local seawater oxygen isotope w indicate relatively saltier waters during the lgm and deglaciation than today with increasing w values higher salinity in the eastern basin and decreasing ones lower salinity in the central mediterranean sea during cold stadials the observed alterations of surface water properties t and w in the central and eastern mediterranean at the lgm are consistent with model experiments showing slightly lower evaporation in the mediterranean than today except for the eastern basin

benthic foraminiferal response to changes in bottom water oxygenation and organic carbon flux in the eastern mediterranean during lgm to recent times abstract we present a high resolution study of benthic foraminiferal abundances in 4 cores from the central aegean and ne levantine seas spanning the interval from 30 ka bp to the present the benthic foraminiferal faunas indicate that during lgm times bottom waters were well ventilated while organic flux to the sea floor was significantly higher than today from 30 to 10 2 ka bp faunal density and composition suggest a gradual decrease in organic flux to the sea floor this trend is interrupted by a short return to higher organic flux levels during the younger dryas 12 8 11 5 ka bp the faunas immediately preceding the early to middle holocene organic rich layer sapropel s1 are very similar to late holocene faunas indicating oligotrophic conditions the transition from well ventilated bottom waters to anoxic levantine basin or strongly dysoxic aegean sea bottom waters appears to take place within a time span of only 600 years from 10 8 to 10 2 ka bp sapropel s1 10 2 6 4 ka bp is characterized by extended periods of bottom water anoxia in the levantine basin and by strongly dysoxic conditions punctuated by episodic re ventilation events in the aegean sea re establishment of fully oxygenated bottom water conditions after sapropel s1 was extremely rapid the ensuing late holocene faunas are very similar to recent faunas found in the aegean sea suggesting much lower fluxes of organic matter to the sea floor than during glacial times

a stratigraphically controlled multiproxy chronostratigraphy for the eastern mediterranean 1 an accelerator mass spectrometry ams 14c dated multiparameter event stratigraphy is developed for the aegean sea on the basis of highly resolved centimeter to subcentimeter multiproxy data collected from four late glacial to holocene sediment cores we quantify the degree of proportionality and synchroneity of sediment accumulation in these cores and use this framework to optimize the confidence levels in regional marine radiocarbon based chronostratigraphies the applicability of the framework to published lower resolution records from the aegean sea is assessed next this is extended into the wider eastern mediterranean using new and previously published high resolution data from the northern levantine and adriatic cores we determine that the magnitude of uncertainties in the intercore comparison of ams 14c datings based on planktonic foraminifera in the eastern mediterranean is of the order of 240 years 2 se these uncertainties are attributed to synsedimentary and postsedimentary processes that affect the materials dated this study also offers a background age control that allows for vital refinements to radiocarbon based chronostratigraphy in the eastern mediterranean with the potential for similar frameworks to be developed for any other well studied region

a centennial scale organic walled dinoflagellate cyst record of the last deglaciation in the south adriatic sea central mediterranean abstract a high resolution study of sea surface temperature sst and primary productivity changes during the last deglaciation in the south adriatic sea is presented on the basis of organic walled dinoflagellate cysts dinocysts compared with stable oxygen and carbon isotope records derived from globigerina bulloides two more defined warming phases between 14 75 and 14 10 cal kyr bp gi 1e and between 13 85 and 13 25 cal kyr bp gi 1c and perhaps a mild one between 12 95 and 12 60 cal kyr bp gi 1a interrupted by two cold events between 14 10 and 13 85 cal kyr bp gi 1d and between 13 25 and 12 95 cal kyr bp gi 1b are highlighted weaker sst oscillations occurred within the relatively stable periods gs 2a 17 00 14 75 cal kyr bp gs 1 or younger dryas 12 60 11 60 cal kyr bp and early holocene several dinocyst proxies used to evaluate surface primary productivity suggest that the cold events gi 1d and gi 1b are associated with episodes of both enhanced primary productivity and perhaps improved organic matter preservation due to reduced deep water formation phases of more pronounced increased surface primary productivity without stagnation in bottom waters are recorded during gi 1c and early gs 1 freshwater po river discharge seems to be the cause of enhanced productivity during event gi 1c at 13 4 cal kyr bp and probably during gi 1d

foraminiferal ecozones a high resolution proxy for the late quaternary biochronology in the central mediterranean sea the planktic foraminiferal distribution identified in 60 cores collected in different basins of the mediterranean sea allowed to establish an ecostratigraphical scheme which provides a very important tool for the biochronological subdivision of the uppermost quaternary we identified a succession of ten ecozones during the last 23 ka in the tyrrhenian basin and eight ecozones in the adriatic sea during the last 15 ka the ecozones boundaries have been calibrated by 14c ams radiometric data and by the stable oxygen isotope record the chronological framework defined by the successive bioevents shows a very high resolution millenary scale and evidences that the changes in the planktic microfauna occurred more or less synchronously throughout the central mediterranean sea differences due to different oceanographic settings of the basins do not affect the general distributional pattern of planktic foraminifera

reconstruction of the last deglaciation deconvolved records of δ18o profiles micropaleontological variations and accelerator mass spectrometric14c dating bioturbation acts as a low pass filter in displacing and reducing the amplitudes of stratigraphic signals this often leads to a loss of high frequency events in the stratigraphic record in addition when considering an isotopic signal 18o 14c measured in stratigraphic carriers such as foraminifera bioturbation and carrier abundance changes can create artifacts which may be falsely interpreted as leads or lags in the paleoclimatic record

abrupt increase in greenland snow accumulation at the end of the younger dryas event the warming at the end of the last glaciation was characterized by a series of abrupt returns to glacial climate the best known of which is the younger dryas event1 despite much study of the causes of this event and the mechanisms by which it ended many questions remain unresolved1 oxygen isotope data from greenland ice cores2 4 suggest that the younger dryas ended abruptly over a period of about 50 years dust concentrations2 4 in these cores show an even more rapid transition 20 years this extremely short timescale places severe constraints on the mechanisms underlying the transition but dust concentrations can reflect subtle changes in atmospheric circulation which need not be associated with a large change in climate here we present results from a new greenland ice core gisp2 showing that snow accumulation doubled rapidly from the younger dryas event to the subsequent preboreal interval possibly in one to three years we also find that the accumulation rate change from the oldest dryas to the bo11ing allerod warm period was large and abrupt the extreme rapidity of these changes in a variable that directly represents regional climate implies that the events at the end of the last glaciation may have been responses to some kind of threshold or trigger in the north atlantic climate system

short term climate changes during the last glacial holocene transition comparison between mediterranean records and the grip event stratigraphy this paper presents biostratigraphical and stable isotope data obtained from core cm92 43 which was recovered from the central adriatic as part of a comprehensive investigation of the palaeoenvironmental history of the basin the data span the period of the last glacial holocene lg h transition ca 18000 to 8000 grip ice core yr bp regional biozones are defined on the basis of characteristic assemblages of planktic foraminifera and these are compared with other foraminiferal biostratigraphical schemes from the southern adriatic and the tyrrhenian sea variations in relative abundance of selected planktic foraminifera and in selected pollen types are shown alongside variations in 18o and 13c obtained from globigerina bulloides and relative abundance of globigerinoides ex gr ruber the data are compared with the grip ice core record and the event stratigraphy scheme based on this record and it is concluded that the climate forcing mechanisms that controlled climate variations in the north atlantic region during the lg h transition also extended their influence into the mediterranean region over the same period copyright 1999 john wiley sons ltd

calcareous nannofossils planktonic foraminifera and oxygen isotopes in the late quaternary sapropels of the ionian sea core m 25 4 12 a long piston core 12 20 m recovered in the ionian sea during cruise m25 4 of the r v meteor summer 1993 at a water depth of 2467 m shows an almost complete sequence of sapropels s 1 s 3 to s 10 over the last 330 ka this paper presents the results of an integrated study based on quantitative biostratigraphic analyses performed on both calcareous nannofossils and planktonic foraminifera coupled with the 18o record a decrease in syracosphaera sp 1 and an increase in the abundance of the genus rhabdosphaera and of helicosphaera carteri florisphaera profunda and of the reworked specimens has been found in the calcareous nannofossil assemblage within the sapropels the planktonic foraminiferal assemblage of the sapropels is characterized by a peak in the frequency of globigerinoides ruber var alba and rosea and neogloboquadrina dutertrei the 18o record of globigerinoides ruber and globigerina bulloides allows recognition of isotope stages 1 to 9 and shows a negative fluctuation that corresponds to the sapropel layers these features support the idea of increased productivity coupled to the presence of reduced salinity surface waters that caused the deposition of the sapropels however the need for a good understanding of the ecological requirements of modern assemblages is stressed this is necessary to correctly interpret fossil assemblages this in turn will allow a better understanding of the palaeoceanographic conditions leading to sapropel deposition

western mediterranean planktonic foraminifera events and millennial climatic variability during the last 70 kyr abstract detailed study of associations of planktonic foraminifera in cores md95 2043 and odp 977 located in the alboran sea mediterranean sea has allowed the identification of 29 new faunal events defined by abrupt changes in the abundances of neogloboquadrina pachyderma right and left coiling turborotalita quinqueloba globorotalia scitula globorotalia inflata globigerina bulloides and globigerinoides ruber white and pink varieties the age model for odp 977 was based on that of md95 2043 cacho et al 1999 paleoceanogr 14 698 705 on the isotopic stratigraphy and on two ams 14c measurements sea surface temperatures ssts were estimated for the last 54 kyr using the modern analog technique mat and were compared with the ssts provided by the uk 37 method the uk 37 record is very similar to the mat annual mean temperature record for the last 8 kyr however for older times alkenone derived temperatures are consistently higher than the annual mat temperatures this offset may be due to an underestimation of the sst provided by the planktonic foraminiferal method for glacial times to an overestimation of the uk 37 record or to changes in the seasonal production of alkenones most of the variability in the fauna is related to the millennial variability of heinrich and dansgaard oeschger d o events during heinrich events hes and most of the other d o stadials g bulloides t quinqueloba and g scitula increased while n pachyderma right coiling g inflata and g ruber decreased by contrast n pachyderma left coiling was only abundant in the hes the main component of the associations n pachyderma right coiling follows a general trend similar to that of sea level and 18o this species reached its highest abundance during the last glacial maximum when sea level was at a lower position the occurrence of a shallower nutricline owing to a shallowing of the interface between atlantic inflowing and mediterranean outflowing waters could have favoured the development of neogloboquadrinids in the vicinity of the strait of gibraltar

morphological and microtectonic analysis of quaternary deformation from puna and santa clara islands gulf of guayaquil ecuador south america abstract this paper presents the neotectonic study of santa clara and puna islands sited in the gulf of guayaquil eastern part both islands are located on the south western segment of the fault zone bounding to the east the north andean block fault motion and morphostructural analysis were carried out from pleistocene age terrain a two step deformation characterises the south puna tectonics the first step involves the zambapala cordillera uplift that post dates pleistocene sediments and pre dates a marine terrace correlated with the m i s 11 or 13 440 550 ka the second step is the formation of a pull apart that shows evidence of 2 9 km dextral offset since the m i s 11 or 13 giving an offset mean rate of 5 3 to 6 6 mm yr this rate is higher than the one calculated on the pallatanga fault northeast of the study area in the western andean cordillera suggesting that deformation is split in different fault segments from the gulf of guayaquil to the continent the zambapala cordillera uplift and transpression deformation requires a compressive event that may have been induced by the subduction process during the early pleistocene

late quaternary paleoclimatic and paleoenviromental changes in the tyrrhenian sea abstract paleoclimatic and paleoenvironmental changes that occurred in the tyrrhenian sea during the last 26 kyr are investigated in this paper isotopic and micropaleontological studies on foraminifers supported by radiometric and sedimentological analyses are carried out in a high resolution core from the upper continental tyrrhenian slope near the ombrone river mouth the location of the studied core allows us to obtain both paleoclimatic data and results concerning the transgression caused by the last deglaciation while previous paleotemperature reconstructions are based on deep sea or on coastal proxies like coral reefs and spelean serpulids cumulative curves of cold and warm water species presented were derived from hierarchical cluster analysis hca comparing these curves with those of globigerina bulloides 18 o and 13 c results on paleoclimatic events of the late quaternary were obtained faunal and isotopic proxies concur and were used to isolate seven climatic zones corresponding to the well known climatic episodes of the last glacial post glacial cycle during the late glacial three main climatic episodes were recognised last glacial maximum lgm centred at about 22 5 kyr bp during which our proxies indicate the lowest temperatures bolling allerod between 15 0 and 12 5 kyr bp characterised by rapid climatic fluctuations younger dryas yd centred at about 11 4 kyr bp with sea surface temperature sst not dissimilar to that of lgm a brief time span of about only 500 years separates the yd climax from the first appearance of seasonality that is typical of holocene on the whole the transition between glacial peak and full holocene conditions spans about 1000 years foraminiferal isotopic and sedimentological data agree in excluding important bathymetric changes during glacial times a rapid sea level rise is recorded at the onset of the holocene with a mean rate of about 23 mm yr calculated between 10 9 and 8 3 kyr bp three distinct phases of water circulation regimes were evidenced in the course of holocene during pre boreal and boreal chronozones 10 9 8 3 kyr bp a marked seasonality has been recognised it corresponded to a homogeneous water column favoured by efficient vertical mixing during the winter and by warm stratified water column and oligotrophic surface waters during the summer both faunal and isotopic record indicate from 8 3 to 5 2 kyr bp well stratified water column with a low salinity layer in surface waters probably marking its climax at 6 2 kyr bp such conditions correspond to the deposition of sapropel s1 in the eastern mediterranean sea the subsequent paleoceanography is characterised by the establishment of the winter convection and vertical mixing typical of the modern tyrrhenian sea

a new greenland ice core chronology for the last glacial termination 1 we present a new common stratigraphic timescale for the north greenland ice core project ngrip and grip ice cores the timescale covers the period 7 9 14 8 kyr before present and includes the bolling allerod younger dryas and early holocene periods we use a combination of new and previously published data the most prominent being new high resolution continuous flow analysis cfa impurity records from the ngrip ice core several investigators have identified and counted annual layers using a multiparameter approach and the maximum counting error is estimated to be up to 2 in the holocene part and about 3 for the older parts these counting error estimates reflect the number of annual layers that were hard to interpret but not a possible bias in the set of rules used for annual layer identification as the grip and ngrip ice cores are not optimal for annual layer counting in the middle and late holocene the timescale is tied to a prominent volcanic event inside the 8 2 kyr cold event recently dated in the dye 3 ice core to 8236 years before a d 2000 b2k with a maximum counting error of 47 years the new timescale dates the younger dryas preboreal transition to 11 703 b2k which is 100 150 years older than according to the present grip and ngrip timescales the age of the transition matches the gisp2 timescale within a few years but viewed over the entire 7 9 14 8 kyr section there are significant differences between the new timescale and the gisp2 timescale the transition from the glacial into the bolling interstadial is dated to 14 692 b2k the presented timescale is a part of a new greenland ice core chronology common to the dye 3 grip and ngrip ice cores named the greenland ice core chronology 2005 gicc05 the annual layer thicknesses are observed to be log normally distributed with good approximation and compared to the early holocene the mean accumulation rates in the younger dryas and bolling periods are found to be 47 2 and 88 2 respectively

enhanced rainfall in the western mediterranean during deposition of sapropel s1 stalagmite evidence from corchia cave central italy a stable isotope record from a stalagmite collected from antro del corchia cave apuan alps central italy supported by 17 uranium series ages indicates enhanced regional rainfall between ca 8 9 and 7 3 kyr cal bp at the time of sapropel s1 deposition within this phase the highest rainfall occurred between 7 9 and 7 4 kyr cal bp comparison with different marine and lake records and in particular with the soreq cave record israel suggests substantial in phase occurrence of enhanced rainfall between the western and eastern mediterranean basins there is no convincing evidence for major climatic change at the time of the 8 2 kyr event

tephrostratigraphy study for the last 18 000 14 c years in a deep sea sediment sequence for the south adriatic abstract a detailed tephrostratigraphy supported by accelerator mass spectrometry ams 14c dating and isotopic and geochemical analyses has been carried out for a deep sea core collected from the southern adriatic sea which spans the last 18 14c kyr fourteen ash layers have been recognized in the marine core and the origin was determined by comparing their age and geochemistry with tephra detected in terrestrial deposits the geochemical signatures of marine ash layers indicate a prevailing campanian and subordinate etnean and eolian provenances collectively they are attributed to sources in the phlegraean fields lam lagno amendolare ln1 ln2 gm1 c 2 nyt neapolitan yellow tuff c 1 agnano pomici principali ams pf agnano monte spina ast astroni somma vesuvius l9 pomici di base l8 greenish mount etna et1 y1 biancavilla ignimbrite lipari e 1 gabellotto fiumebianco and palinuro seamount pal 1 some of these eruptions have been detected for the first time in marine cores astroni lam l9 l8 and three were detected and dated by marine tephra ln1 ln2 and pal 1 providing new more precise stratigraphic markers for the last 18 kyr in the south adriatic marine record

irregular glacial interstadials recorded in a new greenland ice core the greenland ice sheet offers the most favourable conditions in the northern hemisphere for obtaining high resolution continuous time series of climate related parameters profiles of 18o 16o ratio along three previous deep greenland ice cores1 3 seemed to reveal irregular but well defined episodes of relatively mild climate conditions interstadials during the mid and late parts of the last glaciation but there has been some doubt as to whether the shifts in oxygen isotope ratio were genuine representations of changes in climate rather than artefacts due to disturbed stratification here we present results from a new deep ice core drilled at the summit of the greenland ice sheet where the depositional environ ment and the flow pattern of the ice are close to ideal for core recovery and analysis the results reproduce the previous findings to such a degree that the existence of the interstadial episodes can no longer be in doubt according to a preliminary timescale based on stratigraphic studies the interstadials lasted from 500 to 2 000 years and their irregular occurrence suggests complexity in the behaviour of the north atlantic ocean circulation

sub millennial scale climatic oscillations in the central adriatic during the lateglacial palaeoceanographic implications abstract a multi proxy study of a sedimentary core obtained from the central adriatic basin provides evidence of short term events of palaeoceanographic variability during the last glacial lateglacial period grip event stages gi 1 and gs 1 comparison of the adriatic results with other mediterranean records reveals a common sequence of changes in palaeoceanographic conditions variations in foraminiferal assemblage data and in stable isotopic compositions indicate two short term cold oscillations which interrupted an overall cooling trend that commenced at the beginning of the greenland gi 1 episode bolling allerod episode these cold events considered to be contemporaneous with gi 1b and gi d of the grip ice core record are indicated by distinctive foraminiferal assemblages which reflect episodes of high productivity under relatively restricted water circulation with in particular reduced vertical mixing during winter differences in the foraminiferal assemblages indicate that the younger of the two cold spells is characterized by reduced ventilation of bottom waters our results combined with published data from neighbouring marine basins suggest a widespread reduction in deep water formation in the central mediterranean which commenced during the gi 1b episode and reached its maximum effect during the onset of the gs 1 younger dryas episode moreover three intervals with reduced vertical mixing correspond to the two cold spells during gi 1 and the lower phase of the gs 1 episode and show close similarities with the palaeoceanographic changes reported for the north atlantic this similarity indicates that the mediterranean and north atlantic may have been responding more or less synchronously to common forcing mechanisms

quantitative interpretation of fossil pollen spectra dissimilarity coefficients and the method of modern analogs abstract dissimilarity coefficients measure the difference between multivariate samples and provide a quantitative aid to the identification of modern analogs for fossil pollen samples how eight coefficients responded to differences among modern pollen samples from eastern north america was tested these coefficients represent three different classes 1 unweighted coefficients that are most strongly influenced by large valued pollen types 2 equal weight coefficients that weight all pollen types equally but can be too sensitive to variations among rare types and 3 signal0to noise coefficients that are intermediate in their weighting of pollen types the studies with modern pollen allowed definition of critical values for each coefficient which when not exceeded indicate that two pollen samples originate from the same vegetation region dissimilarity coefficients were used to compare modern and fossil pollen samples and modern samples so similar to fossil samples were found that most of three late quaternary pollen diagrams could be reconstructed by substituting modern samples for fossil samples when the coefficients indicated that the fossil spectra had no modern analogs then the reconstructed diagrams did not match all aspects of the originals no modern analogs existed for samples from before 9300 yr b p at kirchner marsh minnesota and from before 11 000 yr b p at wintergreen lake michigan but modern analogs existed for almost all holocene samples from these two sites and brandreth bog new york

temperature and salinity records of the tyrrhenian sea during the last 18 000 years abstract we have used the modern analogue technique to derive sea surface temperature sst records of the last 18 000 years from two well dated deep sea cores recovered in the tyrrhenian sea results show two major cooling events synchronous with the european and north atlantic oldest and younger dryas events a later cooling of lower amplitude is observed between about 8000 and 4500 yr bp tyrrhenian ssts were similar to those of the upper holocene only during the bolling allerod event and at the beginning of the holocene we compared the sst and the planktonic foraminiferal oxygen isotope records to estimate the surface salinity variations our reconstruction shows that salinity decreased in the tyrrhenian sea during the three cold events whereas high ssts correlate with high salinities during most of the last 18 000 years tyrrhenian sea salinity variations were similar to those of the north atlantic ocean near the entrance of the mediterranean sea the salinity gradient between the two basins was thus constant indicating that the western mediterranean circulation pattern and the freshwater budget were not significantly different from the modern one the case was however different during the middle holocene when the strong salinity decrease associated with the sapropel deposit in the eastern mediterranean basin had no equivalent in the north atlantic ocean this peculiar event can only be explained by a local climatic change and an increase of precipitation

synchronisation of palaeoenvironmental events in the north atlantic region during the last termination a revised protocol recommended by the intimate group abstract the north atlantic intimate group of the inqua palaeoclimate commission has previously recommended an event stratigraphy approach for the synchronisation of records of the last termination using the greenland grip isotopic record as the regional stratotype and intcal98 for the calibration of radiocarbon dates lowe j j hoek w intimate group 2001 inter regional correlation of palaeoclimatic records for the last glacial interglacial transition a protocol for improved precision recommended by the intimate project group quaternary science reviews 20 1175 1187 here we present a revised protocol for time stratigraphic correlation in the north atlantic region over a more extended time period 30 8 ka this employs the new ngrip isotopic record and associated greenland ice core chronology 2005 gicc05 as the regional stratotype intcal04 for the calibration of radiocarbon dates bayesian based statistical procedures for the construction of age models and tephrochronology to validate correlations between regional site records

evidence for general instability of past climate from a 250 kyr ice core record recent results1 2 from two ice cores drilled in central greenland have revealed large abrupt climate changes of at least regional extent during the late stages of the last glaciation suggesting that climate in the north atlantic region is able to reorganize itself rapidly perhaps even within a few decades here we present a detailed stable isotope record for the full length of the greenland ice core project summit ice core extending over the past 250 kyr according to a calculated timescale we find that climate instability was not confined to the last glaciation but appears also to have been marked during the last interglacial as explored more fully in a companion paper3 and during the previous saale holstein glacial cycle this is in contrast with the extreme stability of the holocene suggesting that recent climate stability may be the exception rather than the rule the last interglacial seems to have lasted longer than is implied by the deep sea specmap record4 in agreement with other land based observations5 6 we suggest that climate instability in the early part of the last interglacial may have delayed the melting of the saalean ice sheets in america and eurasia perhaps accounting for this discrepancy

hydrological impact of heinrich events in the subtropical northeast atlantic reconstructing the impact of heinrich events outside the main belt of ice rafting is crucial to understanding the underlying causes of these abrupt climatic events a high resolution study of a marine sediment core from the iberian margin demonstrates that this midlatitude area was strongly affected both by cooling and advection of low salinity arctic water masses during the last three heinrich events these paleoclimatic time series reveal the internal complexity of each of the last three heinrich events and illustrate the value of parallel studies of the organic and inorganic fractions of the sediments

palaeoclimate and the formation of sapropel s1 inferences from late quaternary lacustrine and marine sequences in the central mediterranean region abstract synchronous responses to climatic changes during the late pleistocene holocene transition are inferred from marine and lacustrine stratigraphic records in the central mediterranean region new stratigraphic data are presented from well dated sequences in the meso adriatic depression mad two crater lakes in the lazio region and in the tyrrhenian sea the sequences all span the last termination and the holocene but we focus here on the evidence in each record for the time period during which sapropel s1 formed in the mediterranean ca 9 0 to 6 8 cal kyr b p the new records provide evidence of palaeoenvironmental changes on land and sea that can be reconstructed at a high temporal resolution and which throw some light on the processes which led to the formation of s1 the collective evidence indicates that i organic rich sediments occurred in both the marine and the crater lake sites during the time of formation of the s1 sapropel ii there is evidence of increased stratification and anoxia in the sea water column during the period of s1 formation iii the s1 period in the study area is divisible into two sub phases s1a and s1b which reflect short term variations in oceanographic conditions stratification and anoxia iv changes in stratification in the marine column were contemporaneous with regional climate variations that are inferred from the terrestrial records we conclude that the key factor that initiated the formation of s1 was increased discharge of freshwater into the mediterranean following a change post 9 0 cal kyr b p to a warmer and wetter climate furthermore the period of s1 formation was interrupted by a short lived episode ca 500 years of comparatively cooler and drier conditions during the early middle holocene transition emht

benthic foraminiferal successions across late quaternary mediterranean sapropels abstract benthic foraminiferal records across late quaternary mediterranean sapropels s6 s5 and s1 are reviewed and re considered in the light of recent advances in foraminiferal ecology it is suggested that the main factor controlling the foraminiferal successions that occur immediately before and after sapropel deposition is the amount of time involved in the onset of anoxic conditions and in the re oxygenation of the benthic environment faunas dominated by deep infaunal taxa such as globobulimina and chilostomella reflect a very gradual decrease or increase of bottom water oxygenation post sapropel faunas dominated by small biconvex trochospiral taxa which are inferred to have a much more opportunistic life strategy are typical of a very rapid re oxygenation of the benthic environment after sapropel deposition the time involved in re oxygenation depends upon the mechanism causing sapropel formation the faunal succession found above sapropel s5 suggests a basin with a strong density gradient in the upper part of the water column during sapropel deposition followed by a rapid turnover of the following column and quick re oxygenation of the benthic environment in contrast the faunal succession above sapropel s6 suggests a water column with a more gradual density gradient deeper in the basin a progressive deepening of the halocline and a very slow increase of bottom water oxygenation

review and new aspects concerning the formation of eastern mediterranean sapropels abstract in this paper it is proposed that the formation of eastern mediterranean sapropels occurred in an anti estuarine type of circulation which was to some degree weakened relative to the present in response to reduction of the eastern mediterranean excess of evaporation over freshwater input this reduction of excess evaporation would have been imposed by intensifications of 1 the indian ocean summer sw monsoon influencing the eastern mediterranean via increased nile discharge and 2 the system of mediterranean depressions an element of the westerly atlantic system causing increased precipitation and decreased evaporation both the indian ocean summer monsoon and the westerly atlantic system would be intensified in response to the occurrence of distinct minima in the cycle of precession it is demonstrated that reduced excess evaporation whether or not coinciding with global phases of deglaciation would lead to reduction of surface water salinities in the eastern mediterranean causing isolation of previously formed high salinity cooler deep water thus mixing was severely reduced possibly even restricted to eddy diffusion with only occasional convective events that because of the existing density gradient hardly ever would reach the deepest parts of the basin the consequently diminished oxygen advection down from a few hundred meters in the water column favoured preservation of the sinking organic matter this would however suffice only to enable the formation of sapropels with low organic carbon contents the high organic carbon contents observed in various sapropels are argued to reflect superimposed increases of export production the described scenario accounts for previously reported 1 increases of organic carbon content with increasing depth of deposition within individual sapropels and 2 asymmetrical sequences of sapropel deposition characterized by gradual build up and rather abrupt ending it is furthermore in agreement with 3 isotopic and faunal reconstructions of the history of exchange transports through both the strait of sicily and the strait of gibraltar and 4 faunal and floral reflections of the presence or absence of a distinct deep chlorophyll maximum with its associated increases in export production indicating the presence or absence of a shallow pycnocline within the euphotic layer moreover the described scenario 5 is in no way conflicting with the reports of sapropels in the western mediterranean and 6 seems to be endorsed by occasionally intercalated intervals suggestive of somewhat improved oxygenation amidst anoxic benthic desert levels a situation that has been observed in a few quaternary and pliocene sapropels