calibration of the planktonic foraminiferal mg ca paleothermometer sediment trap results from the guaymas basin gulf of california 1 the mg ca ratio has been measured in two surface dwelling species of planktonic foraminifera globigerinoides ruber and globigerina bulloides from biweekly sediment trap samples collected in guaymas basin gulf of california between august 1992 and november 1997 the guaymas basin experiences significant seasonal changes in sea surface temperature sst 16 33 c and thus is an ideal location for testing the temperature dependence of mg incorporation into foraminiferal calcite the planktonic foraminiferal mg ca ratios are directly compared with concurrent temperature measurements from the study site the results from the sediment trap study reveal a strong positive correlation between sst and the mg ca ratio in both g ruber r2 0 86 and g bulloides r2 0 90 the mg ca ratio increases exponentially by 7 per 1 c change in temperature for g ruber and by 6 for g bulloides these results indicate that the mg ca ratio in g ruber and g bulloides accurately records the measured seasonal surface temperature cycle and interannual variability in the guaymas basin within 1 c the greatest deviation between mg ca estimated sst and observed sst occurs in the spring and fall for both species this variability is attributed to rapidly changing hydrographic conditions and possible offset between the time of calcification and the temperature measurements in addition g ruber and g bulloides exhibit very high mg ca ratios during the strong el nino southern oscillation years of 1992 and 1997 verifying their potential to record sst up to 33 c and 28 c respectively the trace metal data are compared with foraminiferal oxygen isotope and alkenone measurements made on the same suite of sediment trap samples to assess the internal consistency of these temperature proxies strong correlations exist between the 18o and mg ca for g ruber r2 0 86 and g bulloides r2 0 79 similarly sea surface temperature estimates from mg ca ratios are in good agreement with alkenone derived temperature estimates r2 0 89 for g ruber and r2 0 81 for g bulloides

open system coral ages reveal persistent suborbital sea level cycles sea level is a sensitive index of global climate that has been linked to earth s orbital variations with a minimum periodicity of about 21 000 years although there is ample evidence for climate oscillations that are too frequent to be explained by orbital forcing suborbital frequency sea level change has been difficult to resolve primarily because of problems with uranium thorium coral dating here we use a new approach that corrects coral ages for the frequently observed open system behavior of uranium series nuclides substantially improving the resolution of sea level reconstruction this curve reveals persistent sea level oscillations that are too frequent to be explained exclusively by orbital forcing

anatomy of a late quaternary carbonate island constraints on timing and magnitude of sea level fluctuations west caicos turks and caicos islands bwi abstract the data set of the island of west caicos consists of a combination of high resolution lidar and digital imagery radiometric data and amino acid racemization aar d l values as well as extraordinary preservation of sedimentary and bio constructed deposits on the island together with a well established regional stratigraphic framework from the neighboring bahamian island chain and detailed field mapping the west caicos data set provides an opportunity to advance our understanding of the link between carbonate stratigraphy and the controlling parameters of sea level sediment supply tectonics and climate the exceptionally well preserved stratigraphic record of the mid late pleistocene from west caicos allows recognition of marine isotope stages mis 9 11 5e and holocene the west coast of the island provides a continuous 8 4 km exposure of the mis 5e record that enhances our understanding of the intra mis 5e bipartite succession in this region and supports a sea level lowering that occurred during the last interglacial lig west caicos accreted as a series of eolian foreshore shoreface barrier reef and fringing reef facies shoreline positions for all but the mis 7 and mis 5a c deposits are now captured in the sub meter geodetic quality topobathy lidar survey the star town unit of mis 9 11 age forms the southern margin of the island as well as the central karst modified spine with uranium thorium u th coral ages of between 368 and 365 thousand years ago ka and a d l glu average of 0 60 early mis 5e strata include the railroad ridge unit in the center of the island which was previously identified as one of the older units the railroad ridge unit is a north south linear dune ridge that has a d l glu average of 0 52 and indicates the onset of sediment sources from the east associated with a flooded central caicos platform approximately synchronously the early mis 5e south reef unit 3 75 4 m sea level elevation nucleated on the western coast of west caicos attached to the middle pleistocene star town unit the south reef corals yield an average coral u th age of 126 5 ka with an average d l glu from skeletal matrix of 0 46 this transitional barrier fringing reef is unconformably overlain by the late mis 5e boat cove unit corals in the basal transgressive phase of this upper mis 5e boat cove unit yield an average 120 6 ka u th and average d l glu of 0 45 shallow marine foreshore and eolian facies of the late mis 5e rest on a wave cut terrace that cuts the early mis 5e south reef unit by as much as 3 m down to a 0 5 m above present sea level elevation the upper mis 5e boat cove unit displays a maximum of 4 5 m elevation above present day sea level measured from the middle of the foreshore this estimate may be a minimum value as the exposures on the west coast are part of a forced regressive foreshore sequence last stages of the upper mis 5e deposition are seen in a series of regressive dune beach ridge deposits referred to as the northeast ridges unit with sea level positions ranging from 4 5 m early in the central part of west caicos to 0 5 m on the far northeast coast eventually building down below present day sea level this sea level history fits well with previously documented records in the bahamas and globally and the extensive erosion supports a short lived between 126 and 120 ka intra mis 5e relative sea level fall holocene deposition on west caicos is restricted to northern and eastern margins of the island as a combination of strandplain and dune ridge mixed skeletal oolitic units using the high resolution digital elevation model dem and linked digital geologic map makes it possible to compare areas of the different pleistocene and holocene units quantitatively and to constrain volumetric assessments and accumulation rates on the island for different units the peak sediment volume production accumulation rate between 6 5 and 8 106 m3 or between 2 2 and 2 7 106 m3 per ka is observed in the upper mis 5e unit this rate is 5 times greater than the 0 5 106 m3 per ka estimated for the holocene ooid dune ridge strandplain complex suggesting that the combination of higher sea level greater wave and wind energy and warmer ocean temperatures may have fostered the higher rate of chemically precipitated sediment supply

mediterranean moisture source for an early holocene humid period in the northern red sea paleosalinity and terrigenous sediment input changes reconstructed on two sediment cores from the northernmost red sea were used to infer hydrological changes at the southern margin of the mediterranean climate zone during the holocene between approximately 9 25 and 7 25 thousand years ago about 3 per thousand reduced surface water salinities and enhanced fluvial sediment input suggest substantially higher rainfall and freshwater runoff which thereafter decreased to modern values the northern red sea humid interval is best explained by enhancement and southward extension of rainfall from mediterranean sources possibly involving strengthened early holocene arctic oscillation patterns and a regional monsoon type circulation induced by increased land sea temperature contrasts we conclude that afro asian monsoonal rains did not cross the subtropical desert zone during the early to mid holocene

african monsoon variability during the previous interglacial maximum abstract little is known about centennial to millennial scale climate variability during interglacial times other than the holocene we here present high resolution evidence from anoxic unbioturbated sediments in the eastern mediterranean sea that demonstrates a sustained 800 yr climate disturbance in the monsoonal latitudes during the eemian interglacial maximum 125 ka bp results imply that before and after this event the intertropical convergence zone itcz penetrated sufficiently beyond the central saharan watershed 21 n during the summer monsoon to fuel flooding into the mediterranean along the wider north african margin through fossil river wadi systems that to date have been considered only within a holocene context relaxation in the itcz penetration during the intra eemian event curtailed this flux but flow from the nile with its vast catchment area was not affected previous work suggests a concomitant eurasian cooling event with intensified impact of the higher latitude climate on the mediterranean basin the combined signals are very similar to those described for the holocene cooling event around 8 ka bp the apparent type of concurrent changes in the monsoon and higher latitude climate may reflect a fundamental mechanism for variability in the transfer of energy latent heat between the tropics and higher latitudes

variability of mg ca and sr ca between and within the planktonic foraminifers globigerina bulloides and globorotalia truncatulinoides the variability in mg ca and sr ca within individual tests and chambers of tests and samples consisting of differing numbers of individuals was determined for globigerina bulloides and globorotalia truncatulinoides in a north atlantic core top sample 52 918 n 16 917 w the variability in mg ca and sr ca within individual tests and chambers was determined by electron microprobe and samples consisting of variable sample size were measured using inductively coupled plasma optical emission spectrometer icp oes large compositional heterogeneity was found within individual chambers and within the test as a whole of the two species and the presence of regions with up to 10 mmol mol mg ca especially in g bulloides mean mg ca decreases in successive chambers of g bulloides especially the 300 355 m fraction and is accompanied by decreasing variance but is not statistical significant sr ca is much more homogeneously distributed with a normal distribution and shows no differences from chamber to chamber the variability of mg ca and sr ca decreases with increasing sample size from single to five to twenty tests per sample approximately as for a normal distribution with greater variability for g bulloides than for g truncatulinoides equivalent to uncertainties in temperature n 20 of 1 1 c and 0 7 c for the two species within the whole of the sediment mixed layer

timing of meltwater pulse 1a and climate responses to meltwater injections the temporal relationship between meltwater pulse 1a mwp 1a and the climate history of the last deglaciation remains a subject of debate by combining the greenland ice core project d18o ice core record on the new greenland ice core chronology 2005 timescale with the u th dated barbados coral record we conclusively derive that mwp 1a did not coincide with the sharp bolling warming but instead with the abrupt cooling of the older dryas to evaluate whether there is a relationship between meltwater injections north atlantic deep water nadw formation and climate change we present a high resolution record of nadw flow intensity from eirik drift through the last deglaciation it indicates only a relatively minor 200 year weakening of nadw flow coincident with mwp 1a our compilation of records also indicates that during heinrich event 1 and the younger dryas there were no discernible sea level rises and yet these periods were characterized by intense nadw slowdowns shutdowns clearly deepwater formation and climate are not simply controlled by the magnitude or rate of meltwater addition instead our results emphasize that the location of meltwater pulses may be more important with nadw formation being particularly sensitive to surface freshening in the arctic nordic seas

three hundred eighty thousand year long stable isotope and faunal records from the red sea influence of global sea level change on hydrography stable isotope and faunal records from the central red sea show high amplitude oscillations for the past 380 000 years positive 18o anomalies indicate periods of significant salt buildup during periods of lowered sea level when water mass exchange with the arabian sea was reduced due to a reduced geometry of the bab el mandeb strait salinities as high as 53 and 55 are inferred from pteropod and benthic foraminifera 18o respectively for the last glacial maximum during this period all planktonic foraminifera vanished from this part of the red sea environmental conditions improved rapidly after 13 ka as salinities decreased due to rising sea level the foraminiferal fauna started to reappear and was fully reestablished between 9 ka and 8 ka spectral analysis of the planktonic 18o record documents highest variance in the orbital eccentricity obliquity and precession bands indicating a dominant influence of climatically driven sea level change on environmental conditions in the red sea variance in the precession band is enhanced compared to the global mean marine climate record specmap suggesting an additional influence of the indian monsoon system on red sea climates

simulating arctic climate warmth and icefield retreat in the last interglaciation in the future arctic warming and the melting of polar glaciers will be considerable but the magnitude of both is uncertain we used a global climate model a dynamic ice sheet model and paleoclimatic data to evaluate northern hemisphere high latitude warming and its impact on arctic icefields during the last interglaciation our simulated climate matches paleoclimatic observations of past warming and the combination of physically based climate and ice sheet modeling with ice core constraints indicate that the greenland ice sheet and other circum arctic ice fields likely contributed 2 2 to 3 4 meters of sea level rise during the last interglaciation

high precision u series dating of corals from western australia and implications for the timing and duration of the last interglacial abstract u series ages using methods of thermal ionisation mass spectrometry tims are reported for last interglacial fossil reefs along the stable coastal margin of western australia thorium isotope ratios were measured with superior precision using methods of charge collection high levels of precision in the measurement of both uranium and thorium isotopes has reduced the age uncertainty due to analytical errors excluding the uncertainty in the decay constants by a factor of four over the precisions reported by many earlier tims workers uncertainties in 234u t determined from both 230th 238u and 234u 238u are also significantly smaller than previously reported allowing samples which have undergone diagenetic exchange of uranium and thorium to be more easily identified strict criteria were adopted to screen the new western australian data reliable ages range from 127 to 122 ka published tims observations from other localities have been assessed using the same strict criteria when these are combined with glacio hydro isostatic sea level models they indicate that the last interglacial period occurred from at least 130 to 117 ka however these age constraints are largely determined from single data points and need to be verified with additional ages before considering them to be robust estimates for the timing of onset and termination of the last interglacial globally the main episode of reef growth appears to be confined to a narrow interval occurring from 127 to 122 ka in direct agreement with the narrow range in ages obtained from the western australian sites this may indicate that the last interglacial was of short duration extending from 127 to 122 ka only alternatively this interval may reflect a major reef building event in the middle of a longer duration 130 117 ka interglacial interval

reef drowning during the last deglaciation evidence for catastrophic sea level rise and ice sheet collapse elevations and ages of drowned acropora palmata reefs from the caribbean atlantic region document three catastrophic metre scale sea level rise events during the last deglaciation these catastrophic rises were synchronous with 1 collapse of the laurentide and antarctic ice sheets 2 dramatic reorganization of ocean atmosphere circulation and 3 releases of huge volumes of subglacial and proglacial meltwater this correlation suggests that release of stored meltwater periodically destabilized ice sheets causing them to collapse and send huge fleets of icebergs into the atlantic massive inputs of ice not only produced catastrophic sea level rise drowning reefs and destabilizing other ice sheets but also rapidly reduced the elevation of the laurentide ice sheet flipping atmospheric circulation patterns and forcing warm equatorial waters into the frigid north atlantic such dramatic evidence of catastrophic climate and sea level change during deglaciation has potentially disastrous implications for the future especially as the stability of remaining ice sheets such as in west antarctica is in question

planktonic foraminiferal and alkenone records of the last deglaciation from the eastern arabian sea the oxygen isotope record of planktonic foraminifera from tropical core md77194 eastern arabian sea exhibits a clear two step deglaciation with a brief 18o transient event in the tropics this 18o maximum could correspond to a cooling or to a change in the 18o content of sea water in this study past sea surface temperature sst and primary production pp are reconstructed from foraminiferal transfer functions and compared to values estimated from alkenone measurements sst and pp records from both proxies indicate a 1 5 2 5 c deglacial warming coupled with a pp decrease and a 0 5 1 c cooling during the younger dryas yd a detailed comparison between independent micropaleontological and geochemical proxies helps us identify potential biases and thus strengthen the paleo reconstructions

variations in mg ca and sr ca ratios of planktonic foraminifera caused by postdepositional dissolution evidence of shallow mg dependent dissolution a comparative study has been made of two species of planktonic foraminifera g tumida and g sacculifer in a depth transect on the ontong java plateau western equatorial pacific g tumida tests from core top sediments showed decreasing mg ca 2 65 1 25 mmol mol and sr ca 1 50 1 16 mmol mol ratios with increasing water depth 1600 4400 m while no such variation was found in g sacculifer tests in excess of 355 m average mg ca 3 6 mmol mol sr ca 1 4 mmol mol artificial dissolution of g tumida tests led to a decrease in both mg ca and sr ca but in g sacculifer there was no significant change in the ratios analyses by electron microprobe revealed that mg ca of the inner chamber calcite in g tumida tests was much higher than that of the calcite crust keel whereas sr ca was only slightly elevated there were no consistent spatial differences in either mg ca or sr ca for g sacculifer tests dissolution in the oceans gives rise to the removal of the chamber calcite in g tumida about 30 of the total calcite leaving the keel calcite although g tumida is thought of as a dissolution resistant form the majority of mg ca and sr ca depletion and chamber loss occurs above the lysocline it is also possible that much of the mg enriched gametogenic calcite has been lost by dissolution from g sacculifer above 1600 m mg content has a significant effect on the dissolution susceptibility of planktonic foraminifera calculations show that the saturation horizon for mg rich parts of tests may be elevated by several hundred meters compared with normal calcite

u series dating of diagenetically altered fossil reef corals initial 234u 238u activity ratios higher than those expected from closed system evolution of seawater are an outstanding problem in u series dating of fossil reef corals the increased activity ratios are ascribed to post depositional diagenesis we analysed six last interglacial and one holocene coral of the genus porites collected near the northern end of the gulf of aqaba northern red sea together with three recent corals from this location as a modern reference while the values measured on the recent samples show no deviation from expected values the holocene and last interglacial corals display highly elevated 234u 238u activity ratios as well as increased 238u and 232th concentrations 234u 238u activity ratios are strongly correlated with 230th 238u and total uranium content a model assuming different degrees of uranium addition and subsequent loss in different sub samples of one coral produces straight lines isochrons on a 234u 238u 230th 238u plot and predicts that the true age of the coral can be calculated by intersecting this isochron with the seawater evolution curve we used the strong correlation detected in the aqaba corals to calculate isochron ages the isochron age of the holocene coral 3116 167 156 yr is concordant with its calibrated 14c age 2963 92 103 yr the ages of the last interglacial corals are between 121 6 7 5 3 and 121 9 7 0 6 3 kyr for a higher terrace 7 10 m asl and 106 4 8 9 8 1 and 117 1 19 7 15 3 kyr for a lower terrace 4 5 m asl one last interglacial coral with an aragonite content of 85 could not be dated the elevation and ages of the fossil terraces are consistent with existing sea level reconstructions from the red sea

high rates of sea level rise during the last interglacial period sea level during the last interglacial stood at least 4 m higher than at present with evidence of short term fluctuations of up to 10 m a new continuous sea level record from the red sea and coral ages suggest that during these fluctuations sea level changes were on the order of 1 6 m per century

precise chronology of the last interglacial period 234u 230th data from fossil coral reefs in the bahamas a detailed study of 238 u 234 u 230 th ages was made for different coral species from two bahamian reefs to determine the time scale of the sea level high during the last interglacial period using recently developed mass spectrometric techniques for the measurement of u and th isotopes thirty seven coral samples were analyzed in replicate typical errors at 125 ky are 1 5 ky 2 and 3 ky time intervals appear to be well resolved this high precision permits detailed chronologic study with time resolution adequate to define stages of the reef s history these data demonstrate that the time between transgression and regression of the ocean in the last interglacial was about 12 ky after which sea level fell rapidly at more than 2 m ky the high sea level stand began possibly by 132 ky and certainly by 129 ky ago when sea level reached 6 m above present mean low sea level high sea level was sustained until 120 ky and then fell rapidly this time period covers the milankovitch insolation peak at 65 n but is not sharply defined and the sea level high lasted from about 4 ky before the insolation peak to 8 ky after it we find no evidence for a double peak of sea level rise in the last interglacial episode that is high stands at both 125 and 142 ky there appears to be some discrepancy between this precise chronology for a coral reef on a tectonically stable platform and the chronology assigned to deep sea sediments the present results show that the duration of the last interglacial led to a 12 ky period of high sea level stand which is much longer than the insolation peak the study area consists of two sizeable bank barrier coral reefs of sangamon age that crop out along the coast northwest of cockburn town on san salvador island and at devil s point on great inagua island the initial stage of reef development is not revealed at either site but the main parts of both reefs are well preserved at cockburn town the beginning of the reef was marked by colonization of acropora palmata on hardground areas and possibly other corals at 132 ky ago patch reefs at the southeastern flank of the developing reef were growing by 129 to 126 ky ago by 126 to 123 ky ago the crest of the reef was formed by the frame building coral a palmata and associated patch reefs flourished along its flanks a palmata coral heads grew upward to a mean low sea level 6 m above the present one the reef began to decline as sea level dropped at about 123 to 120 ky ago near two measured profiles at devil s point the top of a rubblestone dominated by a cervicornis and patch reef corals preserved in growth position have been beveled off and represent an ancient wave cut surface 230 th ages on corals below and above this surface indicate that it was cut at about 125 1 ky ago

a revised morpho and chronostratigraphy of the late and middle pleistocene coral reef terraces on southern barbados west indies the barbados coral reef terraces are one of the few type localities worldwide that provide insights into interglacial sea level change during the late and middle pleistocene several sea level estimates have been established since the late 1960s and each has contributed to the barbados model of sea level change this paper presents new morpho and chonostratigraphic data from the barbados coral reef terraces developed over the last 12 years the work is based on significant advances in electron spin resonance esr dating of fossil coral air photo interpretation and a greatly improved geomorphic map of preserved fossil beach formations and reef terraces above present sea level the need for a revision of past published morpho and chronostratigraphies is best demonstrated on the southern part of the island the morpho and chronostratigraphic sequence in this region is both more complex and diverse than has been assumed so far the revised morphostratigraphy presented here includes a differentiation of coral reef terraces wave cut platforms and other erosive features such as notches and cliffs our study of these geomorphic features combined with new numeric dating results esr u th enable a revised estimate of the spatial and temporal variation in tectonic uplift rate within south barbados these new rates are an essential requirement for more precise glacio eustatic sea level reconstructions during the late and middle pleistocene from this region

comment on record of mis 5 sea level highstands based on u th dated coral terraces of haiti by dumas et al quaternary international 2006 106 118 abstract the opening sentence of the introduction dumas b hoang c t raffy j 2006 record of mis 5 sea level highstands based on dated coral terraces of haiti quaternary international 145 146 106 118 quaternary sea level changes are mainly deduced from the study of raised coral terraces involves a flawed premise as two undefined variables operate simultaneously sea level changes and vertical tectonic motion both perhaps having up and down components to produce a succession of terraces it is impossible to solve the equation without supplying real numbers for either variable hence to deduce sea level history either largely unprovable assumption about constant uplift and or featureless sea level histories are required or a model of sea level must be imported from regions that have not experienced tectonic displacement furthermore coral reefs are less than ideal monitors of sea level change rather they might be preferred as monitors of sea level stability as their response time and depositional tempo may be measured in hundreds or thousands of years reefs may grow and flourish during slow rise of sea level once accommodation space is filled vertical growth ceases and only erosion and diagenesis of the reef occurs until sea level changes once more major intervals of sea level change may thus be lost or never recorded in the rocks

quaternary changes in the egyptian shoreline of the northwestern red sea and gulf of suez abstract on the nw egyptian shoreline of the red sea remarkably preserved pleistocene holocene marine reefs beaches mangrove swamps gypsum salinas and non marine alluvial fans and wadi terraces deposits are located within a complex neogene rift frame the early and middle pleistocene reefs are uplifted to a maximum of 40 m subsequent movement being limited to a few metres except on the s gulf of suez shores which suggests a decreasing tectonic activity of the northern part of the rift a new series of radiometric dates and precise levelling have demonstrated a short lived low stand of relative sea level during the last interglacial high stand 5e at that time flooding of the isthmus of suez has enabled exchanges between mediterranean and indian ocean faunas and the biogeographic limit was temporarily located in the southern gulf of suez thus explaining the late quaternary introduction of potamides conicus into the indian ocean subprovince

the coral record of last interglacial sea levels and sea surface temperatures abstract the rise and fall of the last interglacial li sea levels and sea surface temperatures ssts are evaluated using u series dating combined with sr ca ratios in corals from both stable and tectonically uplifted sites along the stable coastal margin of western australia an extensive series of li coral reefs occur at heights of 2 3 m above present day sea level these corals have a very tight cluster of 234u 230th ages ranging from 129 1 to 119 1 ka as well as a narrow range of initial 234u values of 150 5 similar to modern seawater bahamas which is also a stable site has an essentially identical pattern of u series ages from 130 1 to 120 1 ka barbados and huon peninsula are tectonically active sites where the li terraces are found at elevations of 50 and 200 m respectively u series ages from corals exposed in the lower footwall of these uplifted reefs allow better constraints to be placed on the rate of sea level rise which initiated the li corals from the huon peninsula constrain sea level at 80 10 m at 131 2 ka and from barbados at 30 5 m at 129 1 ka combined with constraints from stable sites these observations require an exceedingly rapid rise in sea level of 30 50 m per 1000 years at 130 1 ka this indicates that large scale catastrophic melting of the once massive continental ice sheets occurred in phase with the rapidly increasing northern hemisphere nh summer insolation consistent with the orbital forcing being the main driver of glacial interglacial climate change there is also some evidence from huon peninsula although still not conclusive for a precursor oscillation in sea level during the penultimate deglaciation that may have been within 20 m of present day levels at 135 ka ssts for the li porites corals from the huon peninsula and western australia have mean annual temperatures and seasonal ranges that are remarkably similar to present day patterns the tropical site of huon peninsula has ssts of 29 1 c which is indistinguishable from the ssts given by modern corals at ningaloo reef in western australia similar mean annual 24 c and summer maximum ssts of 27 29 c are found in both li and modern corals the only significant difference is the 1 c cooler winter minimum ssts of 21 c for the li compared to present day minimums of 22 c li ssts from these southern hemisphere sh sites were thus very similar or at most only slightly cooler than today despite sea levels being up to 4 m higher this maybe indicative of asymmetric warming of the earth with the increased nh insolation during the li period being responsible for the extensive melting of the mainly nh based ice sheets and hence higher global sea levels the observation of relatively high sea levels in the li together with the rapid pulses of sea level rise indicates that the potential now exists for greenhouse warming to initiate increases in sea level of at least several metres on relatively short time scales 102 years

timing and duration of the last interglacial evidence for a restricted interval of widespread coral reef growth abstract we report new mass spectrometric u series ages for eight last interglacial fossil reefs along the continental margin of western australia corals were selected in growth position from localities that are characterized by apparently low levels of diagenesis and relative tectonic stability so that the fossil reefs provide critical information on last interglacial sea levels without requiring corrections for tectonic movements in addition we have improved the constraint on the timing of onset of reef growth by recovering drill core coral from the base of the reefs uranium and thorium isotopes were measured with high levels of precision leading to improvements in age resolution and allowing samples which have undergone diagenetic exchange of uranium and thorium to be more easily identified and discarded these data supplement our previous results for rottnest island and leander point leading to more than seventy mass spectrometric u series ages from which constraints can be placed on the timing duration and character of the last interglacial sea level highstand reliable ages show that reef growth started contemporaneously at 128 1 ka along the entire western australian coastline while relative sea levels were at least 3 m above the present level because western australia is located far from the former penultimate glacial maximum ice sheets and are not significantly effected by glacial unloading these data constrain the timing of onset of the last interglacial period to 128 1 ka assuming reef growth started soon after sea level approached interglacial levels a unique regressive reef sequence at mangrove bay constrains the timing of termination of the last interglacial period to 116 1 ka the major episode of reef building however both globally and locally along the western australian coast is restricted to a very narrow interval occurring from 128 ka and 121 ka suggesting that global ocean surface temperatures were warm and or sea levels were stable enough to allow prolific reef growth only during the earlier part of the last interglacial

understanding the red sea response to sea level here we outline a new pragmatic methodology to derive relative sea level estimates from central red sea oxygen isotope records based on a previously published model in this paper the methodology is described in detail and it is shown that sea level change is the dominant factor responsible for the recorded variability in red sea 18o pdb for sea level changes greater than 12 m variables such as temperature or net evaporation are shown to have relatively small effects on the oxygen isotope record the modelled 18o pdb to sea level relationship is given in terms of a fifth order polynomial which may be used to describe relative sea level from central red sea oxygen isotope records we show how established sea level records from fossil reef terraces for the last 20 kyr are successfully simulated from central red sea oxygen isotope records we also examine the spatial variability of 18o pdb in the basin over the last 13 kyr

increased seasonality in middle east temperatures during the last interglacial period the last interglacial period about 125 000 years ago is thought to have been at least as warm as the present climate owing to changes in the earth s orbit around the sun it is thought that insolation in the northern hemisphere varied more strongly than today on seasonal timescales which would have led to corresponding changes in the seasonal temperature cycle here we present seasonally resolved proxy records using corals from the northernmost red sea which record climate during the last interglacial period the late holocene epoch and the present we find an increased seasonality in the temperature recorded in the last interglacial coral today climate in the northern red sea is sensitive to the north atlantic oscillation a climate oscillation that strongly influences winter temperatures and precipitation in the north atlantic region from our coral records and simulations with a coupled atmosphere ocean circulation model we conclude that a tendency towards the high index state of the north atlantic oscillation during the last interglacial period which is consistent with european proxy records contributed to the larger amplitude of the seasonal cycle in the middle east

sea level reversal during termination ii the termination of the penultimate glacial period tii shows both similarities and differences to the last termination ti both terminations show significant cold reversals in the postglacial warming trend ti consists of a continuously increasing sea level trend whereas tii may demonstrate a sea level reduction midway through the termination we present a new continuous sea level record for tii derived from red sea 18 o records that supports the existence of the tii sea level reversal the record gives an unprecedented look at the structure of the tii sea level reversal which consists of an early highstand lasting several millennia in duration followed by a 30 12 m to 40 12 m reduction in sea level and a stillstand of several millennia before the final sea level rise to the marine oxygen isotope stage mis 5e interglacial we suggest that there is a link between the sea level reversal and internal millennial scale variability in the climate system

from unthinned continent to ocean the deep structure of the west iberia passive continental margin at 38 n abstract the crustal and lithospheric mantle structure at the south segment of the west iberian margin was investigated along a 370 km long seismic transect the transect goes from unthinned continental crust onshore to oceanic crust crossing the ocean continent transition oct zone the wide angle data set includes recordings from 6 obss and 2 inland seismic stations kinematic and dynamic modeling provided a 2d velocity model that proved to be consistent with the modeled free air anomaly data the interpretation of coincident multi channel near vertical and wide angle reflection data sets allowed the identification of four main crustal domains i continental east of 9 4 w ii continental thinning 9 4 w 9 7 w iii transitional 9 7 w 10 5 w and iv oceanic west of 10 5 w in the continental domain the complete crustal section of slightly thinned continental crust is present the upper ucc 5 1 6 0 km s and the lower continental crust lcc 6 9 7 2 km s are seismically reflective and have intermediate to low p wave velocity gradients the middle continental crust mcc 6 35 6 45 km s is generally unreflective with low velocity gradient the main thinning of the continental crust occurs in the thinning domain by attenuation of the ucc and the lcc major thinning of the mcc starts to the west of the lcc pinchout point where it rests directly upon the mantle in the thinning domain the moho slope is at least 13 and the continental crust thickness decreases seaward from 22 to 11 km over a 35 km distance stretched by a factor of 1 5 to 3 in the oceanic domain a two layer high gradient igneous crust 5 3 6 0 km s 6 5 7 4 km s was modeled the intra crustal interface correlates with prominent mid basement 10 15 km long reflections in the multi channel seismic profile strong secondary reflected pmp phases require a first order discontinuity at the moho the sedimentary cover can be as thick as 5 km and the igneous crustal thickness varies from 4 to 11 km in the west where the profile reaches the madeira tore rise in the transitional domain the crust has a complex structure that varies both horizontally and vertically beneath the continental slope it includes exhumed continental crust 6 15 6 45 km s strong diffractions were modeled to originate at the lower interface of this layer the western segment of this transitional domain is highly reflective at all levels probably due to dykes and sills according to the high apparent susceptibility and density modeled at this location sub moho mantle velocity is found to be 8 0 km s but velocities smaller than 8 0 km s confined to short segments are not excluded by the data strong p wave wide angle reflections are modeled to originate at depth of 20 km within the lithospheric mantle under the eastern segment of the oceanic domain or even deeper at the transitional domain suggesting a layered structure for the lithospheric mantle both interface depths and velocities of the continental section are in good agreement to the conjugate newfoundland margin a 40 km wide oct having a geophysical signature distinct from the oct to the north favors a two pulse continental breakup

formation and evolution of the nova scotian rifted margin evidence from deep seismic reflection data a deep marine seismic reflection profile was obtained across the mesozoic rifted continental margin off nova scotia eastern canada this profile crosses the seotian basin one of the deepest basins on the margin of eastern north america and it complements other deep crustal seismic data on this margin the seismic data have been interpreted in conjunction with gravity anomaly and subsidence data they show significant thinning of the continental crust over a zone about 200 km wide the mode of extensional deformation is probably a combination of pure and simple shear there is evidence for simple shear in the crust the continent ocean boundary lies near the seaward edge of synrift salt below the continental rise a 100 km wide zone of very thin approximately 9 km or less continental or transitional crust extends seaward from the outer shelf to this boundary reflectivity of the oceanic crust adjacent to the margin shows evidence of progressive igneous construction perhaps modified by extensional faulting this margin is nonvolcanic and the transition to the volcanic margin off the eastern united states occurs about 500 km southwest of the seismic line the width of the zone of crustal extension is much greater on this nonvolcanic margin segment than it is on the volcanic margin to the south it seems likely that the prerift fabric of the continental lithosphere controls this width a narrow rift may be prone to vigorous asthenospheric convection and therefore to more voluminous volcanism however significantly narrower zones of crustal extension occur on other nonvolcanic margins so factors in addition to rift width such as the rate of rifting may also be important

climatological evaporation seasonality in the northern red sea 1 the dynamic and thermodynamic processes that underlie the exceptionally high evaporation over the northern red sea are examined through a combination of data analysis and a simple numerical model we show that the key boundary layer dehumidifier is ageostrophic cross channel sea breezes this circulation develops semidiurnally in response to thermal gradients across the red sea s coasts because of disparate land ocean heat capacities during the summer day the thermally induced high pressure center over the red sea axis results in near surface flows from the red sea toward the neighboring deserts the strong divergence associated with these flows is maximized along the red sea axis and is accompanied by strong subsidence that suppresses boundary layer relative humidity by both reducing specific humidity and increasing temperatures because the summer nighttime reversed thermal gradients are smaller in magnitude the daytime circulation dominates over the nighttime in summer and thus dominates over the daily and seasonal means following similar reasoning we also devise a winter dehumidifier we conclude by advancing a simple means of estimating red sea evaporation under diverse paleoinsolation regimes and we show small but clear evaporation changes during the course of the holocene our estimates represent lower bounds and we plan to refine them in follow up work

quaternary isotope stratigraphy and paleoclimate of coral reef terraces gulf of aqaba south sinai egypt five quaternary coral reef terraces have been recognized along sharm elsheikh ras mohammed coast of which terraces v to ii form a well developed staircase at um seed while recognized separately at ras mohammed terrace i was only observed as a reef pathches at sharm elsheikh ras mohammed road terraces v to i exist at elevations of 1 b s 1 to 0 m 3 6 m 10 12 m 15 20 m and 25 35 m a s 1 respectively uranium series dates of samples representing terraces v iv iii ii and i show ages grouped as ka 118 125ka 200ka 280 300ka and older 300ka which are related to isotope stages 1 5e 7 9 and 11 respectively the variation of 18o for samples from these terraces show evidence of at least four major warm wet climatic periods in relationship to high sea level and contemporaneous with the formation of the reef terraces faulting affects only the older terraces i and ii and along with the occurrence of terrace iv of last interglacial age at elevation of 3 6 m suggest that the coastal area has not been subjected to major tectonic activities at least with the last 125 ka

influence of northern hemisphere climate and global sea level rise on the restricted red sea marine environment during termination i 1 we present high resolution paleoceanographic records of surface and deep water conditions within the northern red sea covering the last glacial maximum and termination i using alkenone paleothermometry stable oxygen isotopes and sediment compositional data paleoceanographic records in the restricted desert surrounded northern red sea are strongly affected by the stepwise sea level rise and appear to record and amplify well known millennial scale climate events from the north atlantic realm during the last glacial maximum lgm sea surface temperatures were about 4 c cooler than the late holocene pronounced coolings associated with heinrich event 1 2 c below the lgm level and the younger dryas imply strong atmospheric teleconnections to the north atlantic owing to the restricted exchange with the indian ocean red sea salinity is particularly sensitive to changes in global sea level paleosalinities exceeded 50 psu during the lgm a pronounced freshening of the surface waters is associated with the meltwater peaks mwp1a and mwp1b owing to an increased surface near inflow of normal saline water from the indian ocean vertical 18o gradients are also increased during these phases indicating stronger surface water stratification the combined effect of deglacial changes in sea surface temperature and salinity on water column stratification initiated the formation of two sapropel layers which were deposited under almost anoxic condition in a stagnant water body

stratigraphy palaeoenvironments and model for the deposition of the abdur reef limestone context for an important archaeological site from the last interglacial on the red sea coast of eritrea stone tools discovered within uplifted marine terraces along the red sea coast of eritrea at the abdur archaeological site dated to 125 7 ka the last interglacial marine isotope stage 5e show that early humans occupied coastal areas by this time walter et al 2000 nature 405 65 69 in the present paper the stratigraphy facies types and faunal composition from 25 measured sections of the tool bearing abdur reef limestone arl are documented in detail and interpreted to provide a palaeoenvironmental context for the stone artefacts and a model for the deposition of the arl the arl represents a complex marine terrace sequence erosional surfaces indicative of interrupted sedimentation are locally observed at two levels within the arl they subdivide the complex into three subunits named 5e1 5e2 and 5e3 representing different stages of the marine isotope stage 5e sea level highstand comprising six depositional phases i vi of the arl subunit 5e1 begins with the initial transgression of the 5e sea level highstand leading to the deposition of widespread lag gravels on which rich oyster beds developed in shallow water phase i it further records rapid deepening accompanied by the deposition of low energy carbonates with scarce corals phase ii and later shoaling characterised by local development of a fringing reef tract in a sedimented environment phase iii subunit 5e1 is capped locally by a burrowed hardground that is laterally equivalent to depositional discontinuities interpreted as caused by a globally recognised mid 5e sea level low stand phase iv extensive reef build up in response to sea level rise and improved conditions for coral growth characterises subunit 5e2 phase v a possible second sea level drop during the 5e highstand is inferred from the oyster encrusted upper surface of subunit 5e2 subunit 5e3 encompasses restricted coral patches that developed on the upper surface of the underlying subunit during the last stage of the 5e marine high stand phase vi two different toolkits are found in the arl one consists of bifacial hand axes and cores of the acheulian industry typically associated with the oyster beds encrusted on the transgressive lag deposits the other consists of middle stone age msa type obsidian flakes and blades mainly found in the nearshore and beach environments alongside debris from marine invertebrates and large land mammals the distribution of these tools suggests that foraging activities of early humans varied with environmental setting the abdur archaeological site represents a late example of the acheulian msa transition seen as a benchmark for early modern human behaviour and is to date the earliest well dated example of early human adaptation to marine food resources

rapid sea level changes at the close of the last interglacial substage 5e recorded in bahamian island geology rapid and abrupt relative sea level changes within the last interglacial substage 5e are recorded in the island geology of the tectonically stable bahamas from 132 to 118 ka reef growth reached a maximum elevation near 2 m as indicated by fossil reef elevation across the platform whereas bioeroded notches are incised in coastal cliffs as high as 6 m the end of the interval is characterized by voluminous eolianites exhibiting palm tree and frond impressions it is inferred that sea level for most of the interval remained near 2 m restraining reef growth and that the notch at 6 m represents a rapid and brief excursion just before the close of the substage the subsequent fall must have been rapid in order to leave the notch profile intact and mobilize windward lagoon ooids into dunes before cementation could anchor them in order to explain the rapid rise to 6 m glacial surging is invoked the subsequent fall also rapid may be a consequence of the surge flooding high latitudes and providing enough moisture to initiate reglaciation and drawdown

gypsum salina coral reef relationships during the last interglacial marine isotopic stage 5e on the egyptian red sea coast a quaternary analogue for neogene marginal evaporites abstract in the tectonically stable area of the egyptian coast of the red sea the uppermost marine deposits of the last interglacial eemian 5e 5 5 marine isotopic substage consist of two contrasting sedimentary units a subcontinuous fringing coral reef and on its backward side shelly and subaqueous gypsum deposited in erosive depressions elongated parallel to the shore the entrenched geometry and the marine to brackish evolution of the pre evaporite faunas indicate that during this very short period of time a brief sea level drop responsible for the limited erosion separated the succession of reef to marine gypsum and that the coastal area underwent several climatic variations the marine ingression into drowned valleys early mis 5 51 developed khor environments non brackish lagoon on the arabic arid shores which were quickly replaced by highly restricted conditions leading to gypsum precipitation permanence of the salina waters and seasonal lamination interrupting crystal growth suggest an anchialine salina system littoral haline lakes fed by permanent seeping of sea water balanced by refluxing dense brines a semi arid climate is assumed with seasonal rains allowing limited continental sulphate contribution from miocene gypsum outcrops both climate and sea level changes were responsible for the complex evolution of this area compiled data enable generalization concerning the climatic oscillations during the last interglacial sedimentation a model derived from these red sea quaternary deposits as an analogue for the marginal miocene evaporite deposits in the mediterranean and red sea is discussed

dominant northern hemisphere climate control over millennial scale glacial sea level variability abstract based on a radiocarbon and paleomagnetically dated sediment record from the northern red sea and the exceptional sensitivity of the regional changes in the oxygen isotope composition of sea water to the sea level dependent water exchange with the indian ocean we provide a new global sea level reconstruction spanning the last glacial period the sea level record has been extracted from the temperature corrected benthic stable oxygen isotopes using coral based sea level data as constraints for the sea level oxygen isotope relationship although the general features of this millennial scale sea level records have strong similarities to the rather symmetric and gradual southern hemisphere climate patterns we observe in constrast to previous findings pronounced sea level rises of up to 25 m to generally correspond with northern hemisphere warmings as recorded in greenland ice core interstadial intervals whereas sea level lowstands mostly occur during cold phases corroborated by climber 2 model results the close connection of millennial scale sea level changes to northern hemisphere temperature variations indicates a primary climatic control on the mass balance of the major northern hemisphere ice sheets and does not require a considerable antarctic contribution

substantial contribution to sea level rise during the last interglacial from the greenland ice sheet during the last interglacial period the eemian global sea level was at least three metres and probably more than five metres higher than at present1 2 complete melting of either the west antarctic ice sheet or the greenland ice sheet would today raise sea levels by 6 7 metres but the high sea levels during the last interglacial period have been proposed to result mainly from disintegration of the west antarctic ice sheet3 with model studies attributing only 1 2 m of sea level rise to meltwater from greenland4 5 this result was considered consistent with ice core evidence4 although earlier work had suggested a much reduced greenland ice sheet during the last interglacial period6 here we reconsider the eemian evolution of the greenland ice sheet by combining numerical modelling with insights obtained from recent central greenland ice core analyses our results suggest that the greenland ice sheet was considerably smaller and steeper during the eemian and plausibly contributed 4 5 5 m to the sea level highstand during that period we conclude that the high sea level during the last interglacial period most probably included a large contribution from greenland meltwater and therefore should not be interpreted as evidence for a significant reduction of the west antarctic ice sheet