evidence from u th dating against northern hemisphere forcing of the penultimate deglaciation milankovitch proposed that summer insolation at mid latitudes in the northern hemisphere directly causes the ice age climate cycles1 this would imply that times of ice sheet collapse should correspond to peaks in northern hemisphere june insolation but the penultimate deglaciation has proved controversial because june insolation peaks 127 kyr ago whereas several records of past climate suggest that change may have occurred up to 15 kyr earlier2 3 4 5 6 7 8 there is a clear signature of the penultimate deglaciation in marine oxygen isotope records but dating this event which is significantly before the 14c age range has not been possible here we date the penultimate deglaciation in a record from the bahamas using a new u th isochron technique after the necessary corrections for recoil mobility of 234u and 230th and a small age correction for sediment mixing the midpoint age for the penultimate deglaciation is determined to be 135 2 5 kyr ago this age is consistent with some coral based sea level estimates but it is difficult to reconcile with june northern hemisphere insolation as the trigger for the ice age cycles potential alternative driving mechanisms for the ice age cycles that are consistent with such an early date for the penultimate deglaciation are either the variability of the tropical ocean atmosphere system or changes in atmospheric co2 concentration controlled by a process in the southern hemisphere

u th ages obtained by mass spectrometry in corals from barbados sea level during the past 130 000 years the study of the sea level record during the last glacial cycle has primarily proceeded indirectly by means of oxygen isotope measurements on foraminifera from deep sea sediments1 2 the direct approach of dating sea level indicators stagnated during the past decade mainly because the samples required to complete our knowledge of the past glaciations are below the present day sea level3 7 using the 14c ages of acropora palmata samples collected by drilling offshore the island of barbados fairbanks8 presented the first detailed chronology for the last deglaciation this radiocarbon chronology is limited to the past 30 kyr because of the short half life of 14c 5 730 yr we must therefore rely on other dating methods to obtain information for the whole last glacial cycle during the past four years 230th 234u dating of corals by thermal ionization mass spectrometry has been shown to be significantly more precise and accurate than the classical counting method9 14 we have used this technique to measure u th ages in coral samples from the barbados collection and from subaerially exposed outcrops see also ref 15 here we present results bearing on the sea level record for the past 130 000 years we conclude that the last deglaciation started 3 000 years earlier than previously thought and confirm that there were two surges in melt water8 at about 11 kyr and 14 kyr bp before present

uranium 234 anomalies in corals older than 150 000 years we present new precise u th ages of well preserved coral specimens collected from the island of barbados west indies and the atoll of mururoa french polynesia our new data confirm the ages attributed to oxygen isotope stage 7 in the framework of the milankovitch theory berger 1978 mar tinson et al 1987 by using thermal ionization mass spectrometry tims it is also possible to quantify precisely the 234u238u ratios in corals samples older than 150 kyr b p are shown to be characterized by significant excesses of 234u relative to the uranium isotopic composition expected if the corals grew in present day sea water assuming that the 230th ingrowth ages are accurate these anomalies translate into high initial 234u238u ratios about 1 2 at 200 kyr and up to 1 5 at about 450 kyr b p we propose that the anomalies result from both diagenetic addition and replacement of u and possibly from global changes in the 234u238u composition of sea water through time the 234u anomalies cast doubt on the accuracy of the classical 230th ingrowth dating method in old corals and in particular for the use of measured 234u238u ratios alone to date corals older than 150 kyr

recognition of non milankovitch sea level highstands at 185 and 343 thousand years ago from u th dating of bahamas sediment abstract thirty one new bulk sediment u th dates are presented together with an improved 18o stratigraphy for odp site 1008a on the slopes of the bahamas banks these ages supplement and extend those from previous studies and provide constraints on the timing of sea level highstands associated with marine isotope stages mis 7 and 9 ages are screened for reliability based on their initial u and th isotope ratios and on the aragonite fraction of the sediment twelve reliable dates for mis 7 suggest that its start is concordant with that predicted if climate is forced by northern hemisphere summer insolation following the theory of milankovitch but u th and 18o data indicate the presence of an additional highstand which post dates the expected end of mis 7 by up to 10 ka this event is also seen in coral reconstructions of sea level it suggests that sea level is not responding in any simple way to northern hemisphere summer insolation and that tuned chronologies which make such an assumption are in error by 10 ka at this time u th dates for mis 9 also suggest a potential mismatch between the actual timing of sea level and that predicted by simple mid latitude northern hemisphere forcing four dates are earlier than that predicted for the start of mis 9 although the most extreme of these dates may not be reliable based on the low aragonite content of the sediment the other three appear robust and suggest that full mis 9 interglacial conditions were established at 343 ka this is 8 ka prior to the date expected if this warm period were driven by northern hemisphere summer insolation

a high relative sea level stand in the middle holocene of southeastern tunisia abstract study of the marine holocene deposits in southeastern tunisia shows bioclastic beaches at elevations ranging between 0 and 100 cm above high tide level a h t l depending on the elevation of these fossilized shorelines the ages obtained are different the age of the older deposits ranges between 5900 and 4000 14cc yr b p 6400 4300 calendar yr b p there deposits consist of bioclastic beaches attaining an elevation of about 40 to 100 cm a h t l the younger deposit is dated at around 2100 14c years ago 1850 calendar yr b p and is found today at the same elevation as the present sea level this deposit also consists of bioclastic beach material and contains pottery fragments postglacial melting should not be responsible for this observed higher relative sea level stand because deglaciation ended about 7000 6000 14c years ago fairbanks 1989 furthermore the regularity of the paleobeach deposit elevation over a broad area in southeastern tunisia suggests that tectonics cannot explain the emergence the emergence of up to 1 m of marine deposits dating back to between 5900 and 4000 14c yr b p should rather be interpreted as the result in the region of a postglacial hydro isostatic rebound as predicted in the theological models of continental margins by for example clark et al 1978 and lambeck 1993 the present situation was reached 2100 14c years ago

establishing rates of karst landscape evolution in the tropics a context for the formation of archaeological sites in western flores indonesia tropical landscapes evolve at a rapid rate creating stepped alluvial terraces dense basin and cone topographies and multilevel cave systems an understanding of the rate of landscape evolution is crucial for understanding how landscapes respond to tectonic instability and for reconstructing landscapes that have changed over archaeological timescales the rate of landscape incision as a proxy for karst landscape evolution in indonesia a key region in the path of human dispersal has been established using the rate of karstification by estimating a chronology for stages of cave development using thermal ionisation mass spectrometry u series dating on flowstones and the rate of downcutting by establishing a chronology for a series of alluvial terraces using red thermoluminescence dating using these techniques we have determined that the estimated rate of karstification 113 26 mm ka 1 is slower than the average rate of downcutting 305 24 mm k 1 and the combined rate of landscape incision 217 18 mm ka 1 is slower than the known rate of tectonic uplift for this region derived from raised coral terraces 450 50 mm ka 1 this suggests that rivers are quicker to respond to tectonic instability but both cave and river systems display a slower rate of incision and karstification than uplift correlations between these components of the landscape system reveal a strong interacting relationship where defined phases of uplift are reflected in the pattern of karstification and cycles of downcutting an understanding of this relationship has been pivotal in reconstructing the formation and geomorphic history of archaeological caves such as liang bua copyright c 2010 john wiley sons ltd

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

tims u series dating and stable isotopes of the last interglacial event in papua new guinea the extensive flight of uplifted reef terraces which occurs along the vitiaz strait on the northern flank of the huon peninsula in png papua new guinea contains a particularly good record of sea level changes in the last 250 ky the huon terraces were the target of an international expedition which took place in july august 1988 in particular we searched for suitable samples for u series dating in a reef complex designated as vii which is correlated with the last interglacial episode and high sea level stand this complex is composed of a barrier reef viib a lagoon and a fringing reef viia twelve corals from these terraces and two corals from the older reef complex viii were selected for analysis the petrography oxygen and carbon isotope compositions and magnesium and strontium concentrations were determined along with the concentrations and isotopic compositions of uranium and thorium 230 th 234 u ages of the corals with 99 aragonite having primary textures and which show u sr ratios around 0 4 10 3 and initial 234 u values close to that of present seawater appear to be reliable the most reliable ages from complex vii corals fall in two tight groups centered at 118 ky and 134 ky corals with 234 u t values higher than 160 and u sr ratios substantially lower than seawater are assumed to have undergone diagenetic alteration which appears to be common in this area the simplest model for sea level height for terrace vii is a continuous rise between 134 and 118 ky alternatively there may have been two periods of rapid sea level rise in contrast in the bahamas there is evidence that sea level remained rather constant over the time interval 132 to 120 ky the absence of ages between 132 and 120 ky in png could be the result of changes in the local tectonic uplift rates during that time or erosion that disrupted the continuous record in any event we find no basis for accepting a single brief time for the age of the last interglacial and applying this age as a precise chronometer for worldwide correlation or as a test of climatic models the older ages reported here precede the milankovitch solar insolation peak at 128 ky and the younger ages are 10 ky after this peak if the present high precision data are correct then it will be necessary to reassess the validity of the milankovitch theory of climatic changes the fundamental issue which must now be resolved is a means of identifying coral samples that have not been disturbed by diagenetic processes

record of mis 5 sea level highstands based on u th dated coral terraces of haiti abstract new geomorphologic investigations and new u th series dates from haiti northwestern peninsula confirm the age of coral reef terraces assigned to mis 5 5 130 ka mis 5 3 107 ka and mis 5 1 83 ka sea level peaks they also provide evidence for a second high sea level occurring some thousand years before 118 ka and indicate a second mis 5 1 sea level stand at about 76 ka these results are in agreement with the raised terraces of barbados although the staircase of haiti consists of four steps compared to eight the haitian sequence can be compared with the maximal number of distinct mis 5 sea level highstands recorded in the world from coral reef tracts and their relative height above or below present sea level three mis 5 5 sea level changes have been recognized with sea level oscillating above or near the present level until 122 ka only dropping then rising to 11 m below present sea level at 120 ka three high frequency sea level oscillations occurred during mis 5 3 and a fourth during mis 5 3 5 2 two or three events may have occurred during mis 5 l according to whether the 73 ka event is considered to belong to mis 5 1

234u 238u mass spectrometry of corals how accurate is the uth age of the last interglacial period direct measurement of u and th by mass spectrometry recently provided a spectacular improvement in the precision of coral dating by the uth disequilibrium method 1 mass spectrometric data also provide a much better resolution for the examination of subtle diagenetic effects revealed by small variations of the 234u 238u ratio such perturbations may strongly affect the accuracy of the uth chronometer a compilation of all the corals analyzed to date by mass spectrometry shows that most of the corals from terraces of the last interglacial have initial 234u 238u ratios higher than present day seawater in contrast to modern holocene and last glacial corals some samples that have very high 234u 238u initial ratios up to 1 2 and high u concentrations up to 4 ppm were probably contaminated by continental groundwaters however even apparently pristine samples have 234u 238u initial ratios which are still slightly higher than present day seawater mean value 1 160 compared to 1 140 1 150 2 with little overlap between the two distributions this difference in the u initial ratio raises some uncertainty about the accuracy of the uth age determinations of these corals in spite of the fact that the 234u230th ages cluster in a narrow range between 122 and 133 kyr the data could also be interpreted as resulting from slight contamination of corals that are significantly older than 125 kyr two possible explanations may explain these data 1 all these samples may have been diagenetically altered since they all come from surface outcrops which have been directly exposed to precipitations or soil waters for 125 kyr in this case the true age of these corals remains uncertain depending on the timing of the alteration process i e initial late or continuous 2 the second possibility is that some of the differences in 234u 238u ratios measured in 125 kyr cold corals compared to modern seawater may be due to a higher 234u 238u ratio in seawater 125 kyr ago this could result from temporal variations in the weathering regimes of continental land masses

holocene late pleistocene non tropical carbonate sediments and tectonic history of the western rift basin margin of the southern gulf of california abstract using high resolution seismic reflection profiling and dating of 1 shallow marine vibracores and 2 sediments collected from uplifted marine terraces we reconstruct the tectonic history and sediment accumulation patterns of holocene to late pleistocene warm temperate to subtropical carbonates in the southern gulf of california mexico the study was conducted in the vicinity of la paz where carbonates form along the fault bounded narrow western shelf of the tectonically active gulf of california rift basin the non tropical nature of the setting is responsible for 1 poor cementation of the bioclastic carbonates and 2 a composition which is dominated by rhodoliths coralline red algae corals and mollusks unrimmed carbonate flats forming in small pocket bays and a rhodolith bioherm which has a surface area of more than 20 km2 and is up to 16 m thick constitute the major carbonate factories holocene carbonate accumulation rates were deduced from seismic and core data and are highest on the rhodolith bioherm 260 cm ka and in subtidal zones of pocket bays 210 cm ka and lowest on the inner and middle shelf 100 cm ka taken together rates of carbonate accumulation are intermediate in magnitude between higher rates recorded in fully tropical carbonate settings and lower rates typical of cool water carbonates seismic reflection profiles demonstrate that isla espiritu santo in the center of the study area is a west dipping fault block which is tectonically influenced by two distinct faults the la paz and espiritu santo faults the latter fault accommodates at least 700 m of east side down normal offset and forms a steep eastern escarpment leading into the la paz slope basin some of the sediments produced in the shallow carbonate factories of the narrow la paz shelf are transported across this escarpment and are redeposited in the slope basin at a water depth of 750 m uranium series dates of marine terraces exposed on isla espiritu santo indicate that late pleistocene uplift along the eastern side of the island could be as high as 310 mm ka whereas downdropping along the western side of the island occurred at a rate of up to 15 mm ka isla espiritu santo therefore constitutes part of the uplifted shoulder of the western margin of the gulf of california rift basin patterns of vertical tectonic movements of isla espiritu santo together with fault offsets on the surrounding seafloor and slump features on steep submarine slopes point to continuous activity of the la paz and espiritu santo faults results of this study will assist in recognizing and interpreting similar settings along ancient non tropical rift basin margins worldwide and especially in the neogene of the gulf of california

the last glacial interglacial transition lgit in the western mid latitudes of the north atlantic abrupt sea surface temperature change and sea level implications abstract high resolution reconstructions of sea surface temperature uk 37 sst coccolithophore associations and continental input total organic carbon higher plant n alkanes n alkan 1 ols in core d13882 from the shallow tagus mud patch are compared to sst records from deep sea core md03 2699 and other western iberian margin cores results reveal millennial scale climate variability over the last deglaciation in particular during the lgit in the iberian margin heinrich event 1 h1 and the younger dryas yd represent two extreme episodes of cold sea surface condition separated by a marine warm phase that coincides with the bolling allerod interval b a on the neighboring continent following the yd event an abrupt sea surface warming marks the beginning of the holocene in this region ssts recorded in core d13882 changed however faster than those at deep sea site md03 2699 and at the other available palaeoclimate sequences from the region while the sst values from most deep sea cores reflect the latitudinal gradient detected in the iberian peninsula atmospheric temperature proxies during h1 and the b a the tagus mud patch core d13882 experienced colder ssts during both events this is most certainly related to a supplementary input of cold freshwater from the continent to the tagus mud patch a hypothesis supported by the high contents of terrigenous biomarkers and total organic carbon as well as by the dominance of tetra unsaturated alkenone c37 4 observed at this site the comparison of all western iberia sst records suggests that the sst increase that characterizes the b a event in this region started 1000 yr before meltwater pulse 1a mwp 1a and reached its maximum values during or slightly after this episode of substantial sea level rise in contrast during the yd holocene transition the sharp sst rise in the tagus mud patch is synchronous with meltwater pulse 1b the decrease of continental input to the mud patch confirms a sea level rise in the region thus the synchronism between the maximum warming in the mid latitudes off the western iberian margin the adjacent landmasses and greenland indicates that mwp 1b and the associated sea level rise probably initiated in the northern hemisphere rather than in the south

variable methane fluxes in shallow marine systems over geologic time abstract carbon cycling is an important but poorly understood process on passive continental margins in this study we use the ionic and stable isotopic composition of interstitial waters and the petrology mineralogy and stable isotopic composition of authigenic carbonates collected from ocean drilling program odp leg 174a sites 1071 and 1072 to constrain the origin of the carbonates and the evolution of methane on the outer new jersey shelf the pore fluids of the new jersey continental shelf are characterized by 1 a fresh brackish water plume and 2 organic matter degradation reactions which proceed through sulfate reduction however only minor methanogenesis occurs the oxygen isotopic composition of the pore fluids supports a meteoric origin of the low salinity fluids authigenic carbonates are found in nodules thin 1 cm layers and carbonate cemented pavements siderite is the most common authigenic carbonate followed by dolomite and calcite the oxygen isotopic composition of the authigenic carbonates i e 1 3 6 5 peedee belemnite pdb indicates an origin in marine pore fluids the carbon isotopic composition of dolomite cements range from 16 4 to 8 8 pdb consistent with formation within the zone of sulfate reduction siderite 13c values show a greater range 17 67 16 4 but are largely positive mean 2 8 and are interpreted to have formed throughout the zone of methanogenesis in contrast calcite 13c values are highly negative as low as 41 7 and must have formed from waters with a large component of dissolved inorganic carbon derived from methane oxidation pore water data show that despite complete sulfate reduction methanogenesis appears not to be an important process presently occurring in the upper 400 m of the outer new jersey shelf in contrast the carbon isotopic composition of the siderites and calcites document an active methanogenic zone during their formation the methane may have been either oxidized or vented from shelf sediments perhaps during sea level fluctuations if this unaccounted and variable methane flux is an areally important process during neogene sea level fluctuations then it likely plays an important role in long term carbon cycling on passive continental margins

diagenesis and sea level change lessons from moruroa french polynesia an inclined borehole through the margin of moruroa atoll french polynesia in which the ages of units are constrained by radiometric dates provides a unique opportunity to examine the relationship between sea level change and diagenetic history the oldest rocks encountered are dated at 355 840 yr bp and the overlying succession records five cycles of deposition and emergence culminating in the deposition of the holocene sequence successive intervals of emergence provided the driving force for diagenetic change promoting the through flow of chemically aggressive fresh waters that were at times either pervasive or confined within relatively isolated pathways on a millimetre to metre scale these locally varying flows and flow rates defined restricted zones characterized by differences in water chemistry and diagenetic signatures in contrast to some sequences elsewhere the upper part of the moruroa atoll succession is typified by alternations of intervals in which either several generations of cement growth are represented or only one or two cements are present three distinct diagenetic signatures can be recognized as follows i fresh water phreatic zones are reflected in neomorphism and the deposition of cements that occluded porosity thus preventing the deposition of later cements and conferring relative stability ii vadose zones are characterized by more complex diagenetic sequences reflecting multiple phases of dissolution and cement growth attesting to the relative duration of exposure and the conditions of ground water flow and iii deep in the core sequences reflect lowstand deposits that suffered sub sea diagenesis generating pores in which multi layered marine cements apparently formed at more frequent intervals than those subject to subaerial processes all cements appear to be of narrowly constrained ages these results highlight the contentious issue of whether the distributions of former diagenetic environments can be related to specific sea level stands and erosion surfaces it seems that in the moruroa core some cycles of sea level change are reflected in distinctive packages of diagenetic features that have not been overprinted by cement growths during later sea level stands

ice age paleotopography a gravitationally self consistent theory of postglacial relative sea level change is used to infer the variation of surface ice and water cover since the last glacial maximum lgm the results show that lgm ice volume was approximately 35 percent lower than suggested by the climap reconstruction and the maximum heights of the main laurentian and fennoscandian ice complexes are inferred to have been commensurately lower with respect to sea level use of these ice age boundary conditions in atmospheric general circulation models will yield climates that differ significantly from those previously inferred on the basis of the climap data set

block rotation by strike slip faulting structural and paleomagnetic evidence geometric analysis shows that motion of sets of strike slip faults should cause block rotation otherwise the distorted fault domain would not fit with its surrounding the sense of the block rotation depends on the sense of fault slip and the spacing and orientation of the faults all of which can be obtained from structural data the predictions of the geometric model can then be independently tested by paleomagnetic measurements the model was tested in northern israel structural data reveal several domains of contemporaneous right and left lateral strike slip faults paleomagnetic measurements show that in a domain of nnw trending left lateral faults blocks rotated 23 3 8 2 clockwise and in a domain of right lateral faults blocks rotated 22 4 9 0 anticlockwise these results are in agreement with the prediction of the geometric analysis of the structure the combined results of the heterogenous deformation of the area resembles a pure shear which allows n s extension by about 1 3 in other domains rotations of 34 6 9 1 and 53 1 11 0 were found in their original orientation the left and right lateral faults intersected at angles of 60 70 enclosing the principal axis of shortening in accordance with theories of brittle failure as a result of block rotations this angle is now larger and may reach 110 the results demonstrate large block rotations in different senses in domains of strike slip faults the independent structural and paleomagnetic data can be interpreted within the framework of a simple geometric model northern israel is considered to be a good model for this efficient mechanism of intraplate deformation which is expected to occur in similar tectonic settings elsewhere

deglacial sea level record from tahiti corals and the timing of global meltwater discharge the timing of the last deglaciation is important to our understanding of the dynamics of large ice sheets1 and their effects on the earth s surface2 3 moreover the disappearance of the glacial ice sheets was responsible for dramatic increases in freshwater fluxes to the oceans which probably disturbed the ocean s thermohaline circulation and hence global climate4 7 sea level increases bear witness to the melting of continental ice sheets but only two such records from barbados8 9 and new guinea10 11 corals have been accurately dated but these corals overlie active subduction zones where tectonic movements are large and often discontinuous especially in new guinea so the apparent sea level records may be contaminated by a complex tectonic component here we date fossil corals from tahiti which is far from plate boundaries and thus is likely to be tectonically relatively stable and remote from the locations of large former ice sheets the resulting record indicates a large sea level jump shortly before 13 800 calendar years bp which corresponds to meltwater pulse 1a in the barbados coral records8 9 the timing of this event is more accurately constrained in the tahiti record revealing that the meltwater pulse coincides with a short and intense climate cooling event12 15 that followed the initiation of the bolling allerod warm period12 16 but preceded the younger dryas cold event by about 1 000 years

genesis and architecture of sequences of quaternary coral reef terraces insights from numerical models the variety of coral reefs morphologies highlights their sensitivities to several forcings fossil reefs stack in sequences that are accordingly diverse in order to understand their genesis and architectures we devised a numerical approach accounting for quaternary sea level oscillations vertical land motion initial slope wave erosion and reef growth we first test our model on the subsiding sequence of hawaii and on the uplifting sequence of wangi wangi sulawesi that bears active barriers we then construct a parametric study that we analyze based on a comprehensive yet compact description of sequences as barcodes that depict the vertical distribution of a few geometrical characteristics number width and height of the terraces and barriers we find that geological factors suffice to explain the variety of architectures of reefal sequences at first order regardless of additional ecosystemic processes vertical land motion and foundation slopes are the prime players while reef growth rates only play a minor role barriers may develop both in uplift and subsidence mode and their preservation attests for the erosional power last we reappraise the genesis of sequences and find that sequences do not fingerprint discrete events of sea level oscillations but a continuous process harrowed by stochastic events major sea level fluctuations can be overrepresented by several terraces or conversely absent reoccupations may yield composite terraces representing multiple events overall sequences shall not be regarded as stacks of reef bodies forming during sea level highstands which implies that the commonly assumed bijective relationship between sea level highstands and terraces shall be abandoned

uranium series dating of fossil coral reefs extending the sea level record beyond the last glacial cycle abstract absolutely dated records of past sea level change are extremely important for understanding the advance and retreat of the large ice sheets when combined with other complementary climate archives and climate models such records offer the potential to gain an improved understanding of earth s natural climate cycles providing a firmer basis for assessing the role of anthropogenic effects such as greenhouse gas emissions in modifying climate the u series dating of fossil coral reefs has been widely utilized to provide absolutely dated records of past sea level change and numerous observations now exist for the past 130 000 years spanning the last glacial cycle despite this controversies still exist regarding the exact timing and character of sea level events within this time interval and extending the sea level history further back in time on the basis of robust and independent age constraints for older fossil reefs remains very elusive this is primarily due to a progressive loss in the resolution of the u series chronometer as one goes further back in time coupled to a lack of well preserved dateable coral in older fossil reefs to overcome these limitations the primary challenges are three fold first new analytical protocols are required to improve the resolution of the u series chronometer enhanced analytical precision must be coupled to accuracy through continued refinement of the u series decay constant determinations and via the implementation of rigorous inter laboratory calibration exercises second efforts should continue to be focussed on gaining an improved understanding of the mechanisms controlling open system exchange of the u series isotopes in fossil reef systems this will allow the number of reliable u series observations to be extended third alternative dateable archives of past sea level change must continue to be emphasized to further complement the coral reef database these limitations are discussed in the context of current developments that further advance the application of u series chronology to older fossil reef systems formed prior to the last glacial cycle

234u 238u ratios and230th ages for hateruma atoll corals implications for coral diagenesis and seawater234u 238u ratios published results for corals that are more than ca 50 ka old from for example barbados and vanuata often yield initial 234u 238u activity ratios that are significantly greater than 1 144 0 004 the value for modern seawater this study reports results for corals from hateruma atoll japan and investigates the effects of diagenesis on the initial 234u 238u ratios of the corals hateruma consists of over 95 reef material of less than 500 ka in age because groundwaters associated with recent carbonates tend not to have elevated 234u 238u ratios the scope for increasing the 234u 238u ratios of hateruma corals through groundwater interaction should be minimal the corals examined range from those which show no petrographic or x ray evidence for diagenetic alteration and are pristine to those containing secondary cements of either aragonite or high or low mg calcite these various phases have been mechanically separated and analysed in agreement with previous assertions the analyses of these separates demonstrates that the presence of calcite should be a cause for rejection of coral samples it is also shown that aragonite cement can form later than coral death and may bias estimates of age and initial 234u 238u ratios of the six pristine corals three have anomalous 230th 238u ratios requiring u loss and or230th addition the remaining fifteen of the eighteen total analyses reported here yield ages from 1 6 ka to 260 ka no evidence for an increase in 234u 238u ratios in past seawater from this period has been found the best estimates for 234u 238u ratios are close to the current seawater value

sea level during the penultimate interglacial period based on a submerged stalagmite from argentarola cave italy accurate constraints are presented for the absolute age duration and sea level for the highstand corresponding to marine isotope stage mis 7 1 our work is based on a stalagmite collected in a currently submerged cave from italy argentarola cave flooding of this coastal cave is clearly marked within the stalagmite by a thick marine overgrowth of serpulid worms precise uranium thorium u th ages measured by thermal ionization mass spectrometry suggest that the stalagmite growth varied in phase with climate during mis 7 2 and mis 6 the penultimate glacial period in addition the period of marine transgression is bracketed between 202 and 190 kyr bp defining a mis 7 1 duration of 11 2 kyr comparison with previous studies provides a new constraint on the sea level during mis 7 1 that has approximately remained between 318 and 39 m relative to present sea level the timing of the mis 7 1 highstand is in full agreement with the specmap chronology which contrasts with the growing body of evidence showing a significant phase difference for mis 5 5 a tempting conclusion is that second order sea level highstands such as mis 7 1 may be purely driven by astronomical changes in contrast with major terminations such as termination ii atmospheric co2 levels may partly explain this contrast since the two sea level transitions mis 7 2 7 1 and mis 6 5 5 are characterized by very different co2 rises 20 vs 100 ppm fl 2002 elsevier science b v all rights reserved

quaternary slope development of the western leeward margin of the great bahama bank abstract to date work on the great bahama bank s western leeward margin has centred chiefly on seismic scale expressions of carbonate sequences and systems tracts however periplatform slope sediments also exhibit very well developed cyclicity on scales of decimetres to several metres it is these small scale high frequency cycles within the larger scale facies successions of the quaternary which form the main topic of this paper previous studies have shown that the small scale cycles correlate to the orbitally forced high frequency sea level changes therefore these cycles should indicate how sea level has affected the slope development and thus platform margin evolution during this period through detailed high resolution sequence stratigraphy of the great bahama bank s leeward margin obtained via 18o isotope and mineralogical xrd analyses confined by u th dating and nannofossil bioevents a greater understanding of the bedding geometries within the pleistocene holocene seismic sequences and clues as to the nature of the slope development has been achieved the high resolution seismic profiles indicate that since the plio pleistocene change in geometry in which the great bahama bank developed into a rimmed platform continued steepening and subsequent progradation of the leeward margin has typified slope development during the quaternary which is described as an accretionary slope however on the basis of our observations we conclude that only the early to lower middle pleistocene section isotope stages 45 20 and the holocene isotope stage 1 of the leeward margin is accretionary this indicates that a degree of erosion and or by passing has occurred on the leeward margin since the lower middle pleistocene isotope stage 19 during the first part of this period isotope stages 19 12 erosion and or by passing occurred in the middle to lower slope regions and toe of slope by the end of the upper middle to late pleistocene phase isotope stages 11 2 erosion also occurred on the upper slope this erosion by currents at the toe of slope and oversteepening of the upper and middle slopes have led to back cutting upslope and resulted in the progressive retreat of the toe of slope towards the platform to the east however the rise in sea level since the last glacial maximum to its present day level has allowed high productivity on the platform top during the holocene and the deposition of a thick sediment wedge on the slope and sedimentation across the entire leeward flanks this has led to the redevelopment of an accretionary slope and continued westward progradation of the great bahama bank s western leeward margin

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

structural expression of forearc crust uplift due to subducting asperity abstract new structural observations and mapping of reefal terraces carried out both on the field and on satellite remote sensing data indicate that sumba island is presently undergoing a large amount of extension associated with a significant regional uplift this crustal uplift may have been created by a major thrust emerging in the south of the island the uplift which partly accommodated the australian plate south west banda arc convergence is associated with the general northeastward tilt of the island the consequent anomalous positive topography along the southern coast of the island is being compensated by significant tectonic erosion along large scale curvilinear normal faults in the southeastern half of the island the most important expression of this gravitational collapse is located at the receding side of an advancing circular dome showing striking similarities with accretionary wedges being affected by seamount subduction the part of the forearc basin known as the savu basin is moderately deformed mostly in its central part and appears to act as a rigid buttress in the convergence between the banda arc and the australian plate as a result the convergence appears to be transferred northward within the actively shortening back arc domain which goes from the north of the flores island to the southwest of the timor block the convergent plate boundary shows a transition between a stable domain west of sumba and a tectonized domain east of sumba the latter coinciding with the subduction of the outer australian passive margin the subduction of the ocean continent boundary of the austral indian plate below the banda arc since the lower pliocene may have incorporated some crustal fragments in the plunging benioff zone most likely the integration of the stretched continental lithosphere in the subduction zone caused the uplift the entire forearc domain exhibiting inherited structures of the upper plate

a one million year long sequence of marine terraces on sumba island indonesia abstract an exceptional sequence of raised coral reef terraces is visible at cape laundi on the north coast of the island of sumba in the savu sea in which at least eleven terraces wider than 100 m six of them even being over half a kilometer wide are geomorphologically distinguishable between an ancient patch reef now at 475 m and the present sea level esr date estimations of almost unrecrystallized corals most of them in situ make possible a tentative identification of the terraces corresponding to isotope stages 15 ca 600 ka ago and 9 ca 330 ka ago when the uplift trend deduced from the present altitude of dated terraces 0 49 0 01 mm yr is extrapolated to the whole raised section most geomorphological features appear to correspond to interglacial stages of the astronomically calibrated oxygen isotope record up to stage 27 ca 0 99 ma beyond the matuyama jaramillo geomagnetic boundary the upper terraces would in this case be twice as old as previously estimated ca 0 5 ma main terraces seem to correspond to high sea levels at certain interglacial stages and substages but in some cases the action of low sea levels at glacial stages cannot be ruled out for terraces between 30 and 70 m in altitude th u and esr dates reveal that aragonitic corals at similar elevations may differ in age as much as 100 ka this can be explained by taking into account a polycyclic origin for several terraces reconstructions available of changes in the eustatic sea level during the last 250 kyr and the fact that coral reef development may have been scattered at some periods only without totally covering subjacent older formations the sumba sequence of marine terraces at cape laundi is among the longest and most complete for the past million years reported in the literature its relatively good state of preservation will probably give impetus to a number of new studies on the chemical physical isotopic morphological palaeoclimatic pedological ecological and diagenetic changes which have occurred during the past one million years

late quaternary sea level history of saipan commonwealth of the northern mariana islands usa a test of tectonic uplift and glacial isostatic adjustment models

a discontinuous climatic record from 187 to 74 ka from a speleothem of the clamouse cave south of france this study presents a continental paleoclimatic record in the south of france based on n 18 o n 13 c and the 234 u 238 u activity ratio dated by the 230 th 234 u disequilibrium method with thermal ionization mass spectrometry a stalagmite cla4 from the clamouse cave offers a discontinuous stable isotopic record between 189 ka and 74 ka which covers marine isotope stages mis 7 6 4 5 5 5 3 and 5 1 the growth phases of the cla4 stalagmite correspond to high sea level stages except during mis 6 4 169 162 ka all the growth phases of cla4 correspond to humid periods corresponding to the sapropel events observed in the eastern mediterranean basin thus the influence of a strong hydrological activity in the eastern mediterranean basin during these periods prevailed as far west as the south of france because the karstic system studied strongly buffers the isotopic composition of water isotopic variations of the calcite deposited in the cave represent mainly global and large scale environmental variations when isotopic equilibrium conditions prevailed for calcite crystallization sub stage 5 3 the end of 5 5 and mis 7 were colder by about 4 6 c calculated temperature compared to present day temperature while the growth phases of substages 5 1 and the beginning of 5 5 reflect environmental conditions close to present ones the n 18 o and n 13 c values of cave deposits of the sub stage 6 4 are 1 strongly marked by kinetic fractionation processes such as evaporation due to moisture deficit within the cave atmosphere during the first step of this growth phase and 2 related to higher humidity due to a second period of enhanced rainfall during the second step of growth this study shows that even if calcite has not been deposited at isotopic equilibrium its isotopic composition can give insights into the environmental conditions at the time of deposition 2002 elsevier science b v all rights reserved

an open system model for u series age determinations of fossil corals the source of excess 234u in fossil corals and its relationship to u series age determinations has been an outstanding problem in geochronology for more than 20 years with increasing numbers of u series isotope measurements in corals and significant improvements in analytical precision through mass spectrometry it is increasingly apparent that a substantial fraction of observed isotope ratios cannot be reasonably explained by closed system decay moreover observations of a positive correlation between 234u 238u and 230th 238u ratios in corals from the same terrace are difficult to explain however the decay of dissolved uranium and recoil mobilization of uranium daughters produce particle reactive 234th and 230th and the coupled addition of these th isotopes could simultaneously increase coral 234u 238u and 230th 238u here we present a quantitative model based on decay dependent redistribution of 234th and 230th permitting calculation of open system coral ages these equations provide a general solution to the recoil redistribution problem applicable to any alpha decay series while measured isotope ratios of corals from the three youngest stratigraphically defined barbados terraces are inconsistent with closed system decay they fall in broadly linear arrays agreeing with model predictions isotopic arrays of older barbados corals and corals from terraces around the world are also consistent with model predictions suggesting the open system model is generally applicable corals with extreme isotopic compositions that are impossible to produce by closed system decay are consistent with the limited range of isotopic compositions predicted by the model at ages older than 600 ka for corals from a single terrace 234th and 230th redistribution appears to be a source of systematic conventional age error even for corals with slightly elevated 234u however open system ages are consistent even for corals with extremely elevated 234u for the youngest three barbados terraces mean open system terrace ages are consistent with mean conventional terrace ages calculated from pristine samples if the most accurate conventional ages are from corals with an initial 234u 238u identical to modern seawater then the open system model will improve the accuracy of coral u series age determinations and dramatically increase the number of reliable ages

early middle holocene relative sea level oscillation events recorded in a submerged speleothem from the yucatan peninsula mexico geomorphological and biological archives of relative sea level change in the western north atlantic caribbean region following the last glacial maximum have traditionally supported the hypothesis o

late miocene magnetostratigraphy biostratigraphy and cyclostratigraphy in the mediterranean a new chronology for the late miocene of the mediterranean is presented by combining magnetostratigraphic biostratigraphic planktonic foraminifera and dinoflagellates and cyclo stratigraphic data long and continuous upper miocene sections on gavdos metochia section and sicily gibliscemi section display cyclic alternations of homogeneous marls and sapropels and can be correlated on the basis of their distinct cyclic patterns the metochia section yields a good paleomagnetic signal and the position of 17 polarity reversals can be determined the resulting polarity sequence allows an unambiguous correlation to the geomagnetic polarity time scale gpts the paleomagnetic signal in the gibliscemi section is too weak to determine a reliable polarity sequence except for the lowermost part of the section detailed biostratigraphic analysis results in the identification of 13 planktonic foraminiferal and 9 dinoflagellate bioevents which can all be accurately dated the tortonian messinian boundary defined by the first regular occurrence fro of the g conomiozea group is determined in chron c3br 1r with an age of 7 12 ma according to the gpts ck95 of cande and kent 1

uranium series dating of marine and lacustrine carbonates of the possible uranium series dating schemes the most important and most widely applied to marine carbonates is 230th dating with 231pa dating playing an increasingly important role for this reason this review will focus on these two methods 230th dating also referred to as u th dating or 238u 234u 230th dating involves calculating ages from radioactive decay and ingrowth relationships among 238u 234u and 230th 232th is also typically measured as a long lived essentially stable index isotope over the time scales relevant to 230th dating at present 230th dating can in principle be used to date materials as young as 3 years and in excess of 600 000 years edwards et al 1987a 1993 edwards 1988 see stirling et al 2001 for an example of dating corals in excess of 600 000 years old 231pa dating also referred to as u pa dating involves calculating ages from the ingrowth of 231pa from its grandparent 235u at present 231pa dating can be used to date materials as young as 10 years and as old 250 000 years edwards et al 1997 230th dating covers all of the 231pa time range and more with somewhat higher precision and is therefore the method of choice if a single method is applied however the combination of 231pa and 230th dating is of great importance in assessing possible diagenetic mobilization of the pertinent nuclides and thereby the accuracy of the ages allegre 1964 ku 1968 even if the primary age exceeds the 250 000 year limit of 231pa dating the combined methods can be used to assess the degree to which the samples have remained closed over the past 250 000 years e g edwards et al 1997 thus

quaternary raised coral reef terraces on sumba island indonesia a spectacular sequence of coral reef terraces six steps broader than 500 meters and many minor substeps is developed near cape laundi sumba island between an ancient patch reef 475 meters high and sea level several raised reefs have been dated with the electron spin resonance and the uranium series dating methods the uplift trend deduced from these reefs is 0 5 millimeter per year most terraces although polycyclic in origin appear to correspond to specific interglacial stages with the oldest terrace formed 1 million years ago this puts them among the longest and most complete mid quaternary terrace sequences

a new geomagnetic polarity time scale for the late cretaceous and cenozoic we have constructed a magnetic polarity time scale for the late cretaceous and cenozoic based on an analysis of marine magnetic profiles from the world s ocean basins this is the first time since heirtzler et al 1968 published their time scale that the relative widths of the magnetic polarity intervals for the entire late cretaceous and cenozoic have been systematically determined from magnetic profiles a composite geomagnetic polarity sequence was derived based primarily on data from the south atlantic anomaly spacings in the south atlantic were constrained by a combination of finite rotation poles and averages of stacked profiles fine scale information was derived from magnetic profiles on faster spreading ridges in the pacific and indian oceans and inserted into the south ariantic sequence based on the assumption that spreading rates in the south atlantic were smoothly varying but not necessarily constant a time scale was generated by using a spline function to fit a set of nine age calibration points

moissanite sic with metal silicide and silicon inclusions from tuff of israel raman spectroscopy and electron microscope studies abstract here we present studies of natural sic that occurs in situ in tuff related to the miocene alkaline basalt formation deposited in northern part of israel raman spectroscopy sem and fib assisted tem studies revealed that sic is primarily hexagonal polytypes 4h sic and 6h sic and that the 4h sic polytype is the predominant phase both sic polytypes contain crystalline inclusions of silicon sio and inclusions of metal silicide with varying compositions e g si58v25ti12cr3fe2 si41fe24ti20ni7v5zr3 and si43fe40ni17 the silicides crystal structure parameters match si2tiv5 pm 3m space group cubic fesi2ti pbam space group orthorhombic and fesi2 cmca space group orthorhombic respectively we hypothesize that sic was formed in a local ultra reduced environment at respectively shallow depths 60 100 km through a reaction of sio2 with highly reducing fluids h2o ch4 h2 c2h6 arisen from the mantle hot spot and passing through alkaline basalt magma reservoir sio2 interacting with the fluids may originate from the walls of the crustal rocks surrounding this magmatic reservoir this process led to the formation of sic and accompanied by the reducing of metal oxides to native metals alloys and silicides the latter were trapped by sic during its growth hence interplate hot spot alkali basalt volcanism can now be included as a geological environment where sic silicon and silicides can be found

geologic evidence for prehistoric tsunamis and coseismic uplift during the ad 1854 ansei tokai earthquake in holocene sediments on the shimizu plain central japan this study examines geological evidence for earthquakes and tsunamis based on data obtained from 14 sediments cores and one trench in the coastal area of the shimizu plain japan the shimizu plain

timing of the last interglacial high sea level on the seychelles islands indian ocean abstract corals from the seychelles islands indian ocean occur mainly as small coralline algae vermetid remnants found in cavities adhering to the rock surface and they rarely attain more than 2 m 2 in area samples of goniastrea and porites from elevations between 1 7 and 6 m above present mean sea level were dated by tims 238 u 234 u 230 th techniques the ages from well preserved corals lie between 131 000 and 122 000 yr b p in agreement with most other observations of the last interglacial sea level field evidence and dating from high marine limestones from two sections at la digue island indicate a period of coral buildup until 131 000 yr b p followed by a drop in sea level between 131 000 and 122 000 yr b p

high precision u series measurements of more than 500 000 year old fossil corals robust independent age constraints on the absolute timing of climate events based on the u series dating of fossil coral are sparse before the last glacial cycle using multiple collector inductively coupled plasma mass spectrometry with multiple faraday protocols we are able to date 600 ka samples with an uncertainty of better than 15 ka 2 representing a three fold improvement in precision compared with previous techniques using these methods we report u series measurements for a suite of 500 thousand year old ka corals from henderson island an emergent atoll in the south central pacific ocean the fossil corals show extraordinarily little diagenetic alteration for their age and the best preserved sample yields a u series age of 600 15 ka 2 which overlaps with the timing of the warm marine isotope stage mis 15 interglacial the open system model of villemant and feuillet villemant b and feuillet n 2003 dating open systems by the 238u 234u 230th method application to quaternary reef terraces earth and planetary science letters 210 1 2 105 118 and the linear regression or open system isochron is clearly limited for such old samples however the open system model developed by thompson et al thompson w g spiegelman m w goldstein s l and speed r c 2003 an open system model for u series age determinations of fossil corals earth and planetary science letters 210 1 2 365 381 appears to reliably correct for open system effects in roughly half of the corals giving a mis 15 origin for these thus the data provide evidence that the systematic addition of 230th and 234u through recoil is a dominant open system process occurring in the henderson island fossil reef system several coral samples yield significantly older thompson et al open system ages between 650 and 750 ka the uncertainty on these ages typically 30 kyrs is too great for precise assignment but most data overlap with the mis 17 interglacial the reliability of these ages is currently unclear it is shown that separate aliquots of the same coral can yield different thompson model ages therefore there appear to be additional diagenetic mechanisms that create further anomalous excursions in the u series systematics limiting the reliability of the thompson et al open system model

messinian events new constraints from sedimentological investigations and new 40ar 39ar ages in the melilla nador basin morocco abstract new 40ar 39ar ages obtained both from within a platform and from the adjacent basin allow through the extension of a previous argon dataset the establishment of a chronological framework for the messinian carbonate complex of melilla morocco in the platform prograding bioclastic deposits began around 6 87 0 02 ma whereas the youngest preserved deposits are 5 77 0 04 ma old the southern part of the basin was uplifted and emergent prior to 6 23 0 03 ma the tortonian messinian and the messinian pliocene boundaries have not yet been identified in the melilla region durations of the prograding bioclastic deposits ca 410 ka the prograding porites reefs ca 360 ka and the preserved part of the terminal carbonate complex tcc ca 330 ka can be estimated sedimentological and geochronological investigations do not indicate any major subaerial unconformity nor any major time gap if a major sea level fall did exist during messinian times it developed after 5 77 0 04 ma chronological correlations show that the onset of the sorbas gypsum deposition southern spain considered as the marker of the messinian salinity crisis onset is contemporaneous with aggrading porites reef building of the terminal carbonate complex of melilla a major paleoceanographic change in the marginal areas of the mediterranean with the cessation of upwelling systems could be partly coeval with the onset of the messinian salinity crisis

coastal staircase sequences reflecting sea level oscillations and tectonic uplift during the quaternary and neogene many coasts feature sequences of quaternary and neogene shorelines that are shaped by a combination of sea level oscillations and tectonics we compiled a global synthesis of sea level changes for the following highstands mis 1 mis 3 mis 5e and mis 11 also we date the apparent onset of sequences of paleoshorelines either from published data or tentatively extrapolating an age for the uppermost purported oldest shoreline in each sequence including the most documented mis 5e benchmark we identify 926 sequences out of which 185 also feature holocene shorelines six areas are identified where elevations of the mis 3 shorelines are known and 31 feature elevation data for mis 11 shorelines genetic relationships to regional geodynamics are further explored based on the elevations of the mis 5e benchmark mean apparent uplift rates range from 0 01 0 01 mm yr hotspots to 1 47 0 08 mm yr continental collision passive margins appear as ubiquitously uplifting while tectonic segmentation is more important on active margins from the literature and our extrapolations we infer ages for the onset of formation for 180 coastal sequences sea level fingerprinting on coastal sequences started at least during mid miocene and locally as early as eocene whether due to the changes in the bulk volume of seawater or to the temporal variations in the shape of ocean basins estimates of eustasy fail to explain the magnitude of the apparent sea level drop thus vertical ground motion is invoked and we interpret the long lasting development of those paleoshore sequences as the imprint of glacial cycles on globally uplifted margins in response to continental compression the geomorphological expression of the sequences matches the amplitude and frequency of glacial cyclicity from middle pleistocene to present day moderately fast 100 000 yrs oscillating sea levels favor the development of well identified strandlines that are distinct from one another pliocene and lower pleistocene strandlines associated with faster cyclicity 40 000 yrs are more compact and easily merge into rasas whereas older cenozoic low frequency eustatic changes generally led to widespread flat lying coastal plains

coseismic event of may 15 1992 huon peninsula papua new guinea comparison with quaternary tectonic history the may 15 1992 earthquake on the huon peninsula papua new guinea resulted in the uplift and large scale mortality of intertidal fringing coral reefs reduction in the highest level of survival of intertidal massive corals was used as a proxy for assessing the amount of coseismic uplift over 45 km of the huon coastline measurements were gathered from three sites one and three months after the earthquake sea level pressure gauges in place in the northern end of sialum lagoon showed not uplift but subsidence from the earthquake uplift ranged from 7 to 13 cm and subsidence ranged from 8 to 14 cm the may 15 1992 earthquake corroborates the coseismic origin of the raised reef terraces of the huon peninsula greater uplift of the land in the southeast relative to the northwest is consistent with the regional quaternary uplift pattern the close proximity of subsidence shown by sea level gauges to uplift shown by coral mortality is a manifestation of the abundant fault blocks in the area uplift rates of 3 0 5 2 m ka calculated from the earthquake are only marginally higher than previous estimates based on radiometric age dates and terrace geomorphology the first directly observed earthquake uplift event on the huon peninsula has yielded only centimetre scale coseismic uplift thus individual holocene and pleistocene terraces thought to have been the result of metre scale displacement from single earthquakes may rather have been due to successive episodes of centimetre scale uplift on constructional reef platforms the clustered history of earthquakes on the huon peninsula throughout the past 100 years indicates the complexity involved in assessment of seismic risk throughout the world

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

evidence for local shifting of the main fault and changes in the structural setting kinarot basin dead sea transform two new high resolution seismic reflection profiles from the kinarot valley dead sea rift analyzed with older conventional oil exploration profiles throw light on the quaternary evolution of the african arabian transform type plate boundary in the area the present en echelon main faults of the dead sea transform are observed in the seismic data as wide zones of deformation rather than as distinct fault planes a similar zone of deformation is observed in the center of the kinarot basin and may be associated with an extinct trace of the main fault the zemah structure previously mapped and drilled is shown by the new data to be an inactive anticline compression within the basin is suggested as being the result of motion along the now inactive main fault observed in the center of the basin compression and shortening started some 2 m y ago and ended late in the quaternary as a result of changes in the geometry of the transform at present the kinarot basin is subsiding

computer simulation of reef growth light is one of the major controls on reef growth and carbonate production the growth of present reef builders depends largely upon the amount of light available for photosynthesis as light decreases with water depth so does reef growth the computer model presented extends this principle by combining two functions one for photosynthesis and the other for the extinction of light in water the model is used to simulate the growth of alacran reef mexico two reefs of the great barrier reef and the reefs of the windward platform of st croix us virgin islands the model also gives an accurate simulation of the growth of fore reef walls in belize in agreement with the accretion hypothesis developed for this feature

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

active faulting in the dead sea rift abstract manifestations of late quaternary and holocene faulting were studied in a 500 km long segment of the dead sea transform rift most prominent are left slip faults whose characteristic physiographic features are recognizable along most of the studied segment where these faults bend or are stepped to the left rhomb shaped grabens or pull aparts are produced forming depressions in the reverse situation compressional features such as pressure ridges domes and folds form positive topographic features such structures are combined on a variety of scales ranging from a few hundred meters long to tens of kilometers normal faults sub parallel to the left slip faults produce a trough like valley along much of the dead sea transform but are most prominent along the margins of the large rhomb grabens e g the dead sea trough they apparently record a small component of transverse extension generally their motion is slow young slip did not occur along some segments during the last few 10 4 y elsewhere throws of 10 20 m at least occurred in this period the dead sea transform is seismically active the instrumental and historic records indicate a seismic slip rate of 0 15 0 35 cm y during the last 1000 1500 y while estimates of the average pliocene pleistocene rate are 0 7 1 0 cm y either much creep takes place or the slip rate varies over periods of a few 10 3 y

adjustment of the ventilated thermocline the time dependence of the ventilated thermocline is examined via analytical and numerical means the original henderschott model is modified such that the outcrops all occur on the same geopotential surface rather than at staggered geopotential surfaces this model has the advantage that the ocean interior can be ventilated directly by the sverdrup flow rather than by western boundary processes the propagation of disturbances governed by linearized forms of the three layer or four layer modified henderschott model nonlinear solutions of the full modified henderschott model and numerical solutions of the planetary geostrophic equations are considered low frequency disturbances are predicted by the linear models to move on characteristics jointly set by advection and wave dynamics it is shown that perturbations due to wind stress anomalies project strongly onto the first mode and propagate westward similarly to the classical first baroclinic rossby mode they do not experience much interaction with the mean flow the so called non doppler effect on the other hand perturbations generated by buoyancy anomalies have strong projections onto the second or third modes and propagate along pathways very close to the mean circulation their speed is somewhat slower than the current speed however these properties appear in the linearized and simplified nonlinear models and their occurrence in planetary geostrophic results argues the relevance of the henderschott model also these properties are consistent with results from other studies

the timing of sea level high stands during marine isotope stages 7 5 and 9 constraints from the uranium series dating of fossil corals from henderson island direct dating of fossil coral reefs using the u series chronometer provides an important independent test of the milankovitch orbital forcing theory of climate change however well dated fossil corals pre dating the last interglacial period 130 thousand years ago ka are scarce due to 1 a lack of sampling localities 2 insufficient analytical precision in u series dating methods and 3 diagenesis which acts to violate the assumption of closed system u series isotopic decay in fossil corals here we present 50 new high precision u series age determinations for fossil corals from henderson island an emergent coral atoll in the central south pacific u series age determinations associated with the marine isotope stage mis 9 interglacial and mis 7 5 interstadial periods are reported the fossil corals show relatively little open system u series behaviour in comparison to other localities with fossil coral reefs formed prior to the last glacial cycle however open system u series behaviour is still evident in most of the dated corals in particular percent level shifts in the 230th 238u act composition are observed leading to conventional u series ages that are significantly younger or older than the true sample age this open system u series behaviour is not accounted for by any of the open system u series models indicating that new models should be derived the new u series ages reported here support and extend earlier findings reported in stirling et al 2001 providing evidence of prolific coral reef development on henderson island at not vert similar320 ka most likely correlated with mis 9 3 and subsequent reef development at not vert similar307 ka during mis 9 1 while relative sea level was potentially not vert similar20 m lower than during mis 9 3 the u series ages for additional well preserved fossil corals are suggestive of minor reef development on henderson island during mis 7 5 245 230 ka at 240 3 0 8 and 234 7 1 3 ka all u series observations are consistent with the milankovitch theory of climate change in terms of the timing of onset and termination of the dated interglacial and interstadial periods the best preserved samples also suggest that the oceanic 234u 238u during mis 9 and mis 7 5 was within five permil of the modern open ocean composition

duration and structure of the past four interglaciations reanalysis and additional dating of the devils hole 18o paleotemperature record confirm that the last interglaciation in the great basin the continental analog of marine isotopic substage 5e lasted 22 000 yr consistent with the vostok paleotemperature record which suggests a duration of 19 000 yr for this event in antarctica the three preceding interglaciations in the devils hole record analogs of marine isotopic substages 7e 9c and 11c range from 20 000 to 26 000 yr in duration a 20 000 yr duration for the last interglaciation is consistent with tims uranium series dated sea level high stands thus the widely held view that interglaciations were of 11 000 to 13 000 yr duration and constituted only about 10 of mid to late pleistocene climatic cycles needs reexamination the warmest portion of each interglaciation in the devils hole time series is marked by a 18o plateau signifying apparent climatic stability for periods of 10 000 to 15 000 yr duration

the tectonic framework of a complex pull apart basin seismic reflection observations in the sea of galilee dead sea transform abstract a multi channel seismic reflection survey consisting of 20 lines with a total length of 180 km was conducted in the sea of galilee the data provide new insights into the pliocene quaternary evolution of the kinarot beit shean pull apart basin kbsb along the dead sea transform two distinct zones are defined beneath the lake 1 a graben that underlies most of the lake bounded by steep north south longitudinal strike slip faults and 2 shallow pre rift units underlying the northwestern wider part of the lake we suggest that before approximately 4 ma the kbsb grew due to northward movement of the korazim plateau and by crustal stretching along the rift axis since the pliocene 4 ma lateral slip has been transferred from the southern segment of the basin s western marginal fault to normal faults in the galilee and to the eastern margin of the korazim plateau by the newly formed almagor fault which makes a restraining bend along the transform n s lithospheric stretching below the kbsb has diminished and the korazim plateau has changed from being a detached block to a compressional saddle a phase of rapid subsidence and formation of a half graben structure in the northern part of the basin approximately 1 ma ago was coeval with major deformation in areas adjacent to the kbsb indicating major reorganization of the plate boundary in the region currently most transform motions are probably taken up along a single fault on the eastern side of the kbsb implying that the main trough under the sea of galilee is in a late stage of growth as a pull apart

sea surface temperature during the quaternary at odp sites 976 and 975 western mediterranean abstract based on the relative abundances of the planktonic foraminifera species found in quaternary samples from odp sites 976 alboran sea and 975 menorca rise and using a modern analog technique winter and summer sea surface temperatures were estimated frequency distributions of temperatures are asymmetrical more so at odp site 976 where there is a greater abundance of samples from the warm part of the temperature range during the quaternary there is a general tendency for temperatures to fall with an overall diminution of 1 c for the winters and of more than 2 c for the summers overall mean temperatures and those of the biostratigraphic intervals identified are higher at odp site 975 than at 976 when differences are statistically significant the q1 interval i e the oldest in the quaternary is colder than the upl i e terminal pliocene and the q2 interval the q3 interval is also colder than the q2 interval and the q4 interval i e the most recent interval differences between intervals general trends and the asymmetries of frequency distributions cannot be explained as linear responses to insolation the stratigraphic series from odp site 976 was dated by correlating the relative maxima and minima of the summer temperature series with those of insolation during the month of july at 65 n it was found that 26 2 of the variance of the time series of temperatures was concentrated in the harmonics related to precession and obliquity while 19 was located in those related to eccentricity there are indications of the need to add lags and leads to the age of temperature spikes with respect to insolation but such delays and leads cannot be quantified precisely

gravity field over the sea of galilee evidence for a composite basin along a transform fault the sea of galilee lake kinneret is located at the northern portion of the kinneret bet shean basin in the northern dead sea transform three hundred kilometers of continuous marine gravity data were collected in the lake and integrated with land gravity data to a distance of more than 20 km around the lake analyses of the gravity data resulted in a free air anomaly map a variable density bouguer anomaly map and a horizontal first derivative map of the bouguer anomaly these maps together with gravity models of profiles across the lake and the area south of it were used to infer the geometry of the basins in this region and the main faults of the transform system the sea of galilee can be divided into two units the southern half is a pull apart that extends to the kinarot valley south of the lake whereas the northern half was formed by rotational opening and transverse normal faults the deepest part of the basinal area is located well south of the deepest bathymetric depression this implies that the northeastern part of the lake where the bathymetry is the deepest is a young feature that is actively subsiding now the pull apart basin is almost symmetrical in the southern part of the lake and in the kinarot valley south of the lake this suggests that the basin here is bounded by strike slip faults on both sides the eastern boundary fault extends to the northern part of the lake while the western fault does not cross the northern part the main factor controlling the structural complexity of this area is the interaction of the dead sea transform with a subperpendicular fault system and rotated blocks

open system u series ages of corals from a subsiding reef in new caledonia implications for sea level changes and subsidence rate abstract on the amedee islet 4 drill cores were recovered from the barrier reef of western new caledonia the coral reef is slowly subsiding and is thus percolated by sea water during sea level highstands the cores sample a 10 m thick holocene reef overlying a 24 m thick reef of marine isotope stage mis 5 5 which in turn overlies older reef material from mis 7 5 and beyond 234 u 238 u and 230 th 238 u ratios and 232 th were determined by thermal ionization mass spectrometry on aragonitic coral samples that were carefully investigated using x ray diffraction and scanning electron microscopy the petrographic study shows an increasing coral weathering with growing coral age that causes different degree of u series open system behavior and 232 th accumulation holocene corals exhibit a small degree of early diagenesis and yield 230 th 238 u ages according to the holocene sea level rise from 8200 years to 5000 years bp corals from the last interglacial section have experienced more frequent replacement of aragonite fibers and minor dissolution and u series open system behavior is evident to estimate the impact of recoil processes and alteration on the u series system two models by villemant and feuillet b villemant n feuillet dating open systems by the 238 u 234 u 230 th method application to quaternary reef terraces earth and planetary science letters 210 2003 105 118 and thompson et al w g thompson m w spiegelman s l goldstein r c speed an open system model for u series age determinations of fossil corals earth and planetary science letters 210 2003 365 381 have been tested these models yield identical ages within uncertainty which are in agreement to the sea level history of the past 250 000 years as long as physico chemical alteration and re crystallization is small consequently we were able to estimate the subsidence rate from the subsidence observed between the end of mis 5 5 and the early holocene which is 0 16 0 04 m per 1000 years in addition by using this subsidence rate and the sea level highstand of 6 3 m during mis 5 5 we can estimate the sea level highstand at 244 000 mis 7 5 to be between 2 m to 2 m respectively corals from underneath the marine isotope stage 7 5 sequence show more significant dissolution increasing re crystallization elevated 232 th and excess 234 u and 230 th here the villemant and feuillet b villemant n feuillet dating open systems by the 238 u 234 u 230 th method application to quaternary reef terraces earth and planetary science letters 210 2003 105 118 model fails to predict ages but the thompson et al w g thompson m w spiegelman s l goldstein r c speed an open system model for u series age determinations of fossil corals earth and planetary science letters 210 2003 365 381 model was applicable predicting ages between 355 000 to 430 000 years i e coral growth potentially during mis 9 or 11

ice volume and sea level during the last interglacial during the last interglacial period 125 000 years ago sea level was at least several meters higher than at present with substantial variability observed for peak sea level at geographically diverse sites speculation that the west antarctic ice sheet collapsed during the last interglacial period has drawn particular interest to understanding climate and ice sheet dynamics during this time interval we provide an internally consistent database of coral u th ages to assess last interglacial sea level observations in the context of isostatic modeling and stratigraphic evidence these data indicate that global eustatic sea level peaked 5 5 to 9 meters above present sea level requiring smaller ice sheets in both greenland and antarctica relative to today and indicating strong sea level sensitivity to small changes in radiative forcing

evaluation of morphometric proxies for uplift on sequences of coral reef terraces a case study from sumba island indonesia sequences of coral reef terraces characterized by staircase morphologies and a homogeneous lithology make them appropriate to isolate the influence of uplift on drainage morphology along the northern coast of sumba island indonesia we investigated the correlations between landscape morphology and uplift rates which range from 0 02 to 0 6 mm yr 1 we studied eight morphometric indices at two scales whole island 11 000 km2 and within sequences of reefal terraces 3000 km2 at the latter scale we extracted morphometric indices for 15 individual catchments draining mostly the reefal terraces and for 30 areas undergoing specific ranges of uplift rates draining only the reefal terraces indices extracted from digital elevation models include residual relief incision stream gradient indices sl and ksn the hypsometric integral drainage area mean relief and the shape factor we find that sl the hypsometric integral mean relief and the shape factor of catchments positively correlate with uplift rates whereas incision residual relief and ksn do not more precisely we find that only the areas that are uplifting at a rate faster than 0 3 mm yr 1 can yield the extreme values for these indices implying that these extreme values are indicative of fast uplifting areas however the relationship is not bivalent because any uplift rate can be associated with low values of the same indices for all indices the transient conditions of the drainage influence the correlation with pleistocene mean uplift rates illustrating the necessity to extract morphometric indices with an appropriate choice of catchment scale this type of analysis helps to identify the morphometric indices that are most useful for tectonic analysis in areas of unknown uplift allowing for easy identification of short spatial variations of uplift rate and detection of areas with relatively fast uplift rates in unstudied coastal zones

raised coral terraces at malakula vanuatu southwest pacific indicate high sea level during marine isotope stage 3 the occurrence of a series of raised coral reefs from the uplifted island of malakula vanuatu sw pacific provide an opportunity to examine sea level fluctuations over at least the past 120 000 years thirteen fossil coral samples from malakula were analyzed by the thermal ionization mass spectrometry tims u th dating technique yielding information on sea levels during late marine isotope stage 3 and early stage 4 our findings are in good agreement with sea level estimates from raised coral terraces in papua new guinea and the recent sea level reconstruction from the deep sea sedimentary 18o records in particular our coral data appear to confirm that sea levels at about 45 000 50 000 yr b p were only 30 to 60 m below the present level combined with other evidence of sea level change our data provide a strong case for much higher sea levels and therefore markedly reduced continental ice volume at 47 000 to 49 000 years ago

holocene coral reef terraces and coseismic uplift of huon peninsula papua new guinea abstract as many as six levels of emerged holocene coral terraces occur along 40 km of coastline on the huon peninsula papua new guinea recording uplift history since culmination of the postglacial transgression the holocene reef crest ca 6000 yr b p is tilted down to the northwest parallel to the coast and concordant with the deformation of the last interglacial coral reef terrace and descends from 23 to 12 m in the study area the pattern and rate of deformation have been uniform in the late quaternary because average uplift rates have remained the same since the last interglaciation the holocene terraces described here are erosional features with regressive encrusting corals developed upon the holocene transgressive reef the multiple levels represent episodic probably coseismic uplift which has occurred repeatedly in the last ca 6000 yr significant longshore variation in the age of the lowest terrace from 1700 to 2500 yr b p suggests independent coseismic uplift on different sectors of the coast this is supported by age height relationships of the higher holocene terraces nonlinear uplift during the holocene with recurrence intervals increasing toward the present is clearly recorded by the regressive terraces in each subregion some of the holocene regressive terraces grade laterally into fluvial terraces capped with debris flow deposits probably reflecting seismically triggered mass movement

karstification as geomorphological evidence of river incision the karst of cousance and the marne valley eastern paris basin the cousance karst located between the valleys of the saulx and marne has been studied to determine the temporal records of river incision in the eastern paris basin around the andra experimental nuclear waste repository two generations of karst are recognized the first is a palaeophreatic karst indicative of an old base level now uplifted 75 m above the underground streams it is underlain and drained by a second generation of karst with active sinks which records the vertical evolution following the entrenchment of the river marne ten u th dates of speleothems from shafts in the karst show that there were discontinuous growth episodes mainly during isotopic stages 3 and 5 between 102 4 1 2 and 49 4 0 4 ka bp but also during isotopic stage 2 at 16 3 0 1 and 20 9 0 3 ka bp these dates provide an absolute age limit for the start of vertical development of the karst at the latest during isotope stage 5c

east african climate change and orbital forcing during the last 175 kyr bp abstract variations in the temporal and spatial distribution of solar radiation caused by orbital changes provide a partial explanation for the observed long term fluctuations in african lake levels the understanding of such relationships is essential for designing climate prediction models for the tropics our assessment of the nature and timing of east african climate change is based on lake level fluctuations of lake naivasha in the central kenya rift 0 55 s 36 20 e inferred from sediment characteristics diatoms authigenic mineral assemblages and 17 single crystal 40ar 39ar age determinations assuming that these fluctuations reflect climate changes the lake naivasha record demonstrates that periods of increased humidity in east africa mainly followed maximum equatorial solar radiation in march or september interestingly the most dramatic change in the naivasha basin occurred as early as 146 kyr bp and the highest lake level was recorded at about 139 133 kyr bp this is consistent with other well dated low latitude climate records but does not correspond to peaks in northern hemisphere summer insolation as the trigger for the ice age cycles the naivasha record therefore provides evidence for low latitude forcing of the ice age climate cycles

integrated analysis of magnetic paleomagnetic and k ar data in a tectonic complex region an example from the sea of galilee 1 sea of galilee lake kinneret is located in northern israel in the area of complex tectonic setting where the dead sea transform crosscuts other fault systems practical absence of wells in the sea hinders geological geophysical data interpretation map of the total magnetic field shows an intricate pattern of the magnetic field distribution caused by a combined influence of the basalt flows of various age and magnetization in and around the sea the identified magnetic anomalies were analyzed using methods of quantitative interpretation specially developed for complex geological conditions the paleomagnetic stratigraphy of basalt associations around the sea of galilee basin proved to be correlated with the paleomagnetic zones in the sea for the first time was developed the detailed magnetic paleomagnetic scheme with k ar dating unmasking structure of magnetic anomalies in the sea and coordinating the revealed peculiarities with the surrounding anomalies

the timing of high sea levels over the past 200 000 years the 230 th ages and 234 u 238 u ratios were determined for barbados corals that grew during periods of high sea level within the last 200 000 years the similarity of the initial 234 u 238 u ratios of some of the corals to the modern marine value suggests that these samples are pristine and that the marine 234 u 238 u ratio 83 000 and 200 000 years ago was within 2 per mil of the modern value the accuracies of the 230 th ages are evaluated on the basis of the 234 u 238 u values and a model of the behavior of uranium and thorium isotopes during diagenesis for the last three interglacial and two intervening interstadial periods sea level peaked at or after peaks in summer insolation in the northern hemisphere this overall pattern supports the idea that glacial interglacial cycles are caused by changes in earth9s orbital geometry the sea level drop at the end of the penultimate interglacial the last interglacial and a subsequent interstadial period lagged behind the decrease in insolation by 5 000 to 10 000 years

a large drop in atmospheric 14c 12c and reduced melting in the younger dryas documented with 230th ages of corals paired carbon 14 14 c and thorium 230 230 th ages were determined on fossil corals from the huon peninsula papua new guinea the ages were used to calibrate part of the 14 c time scale and to estimate rates of sea level rise during the last deglaciation an abrupt offset between the 14 c and 230 th ages suggests that the atmospheric 14 c 12 c ratio dropped by 15 percent during the latter part of and after the younger dryas yd this prominent drop coincides with greatly reduced rates of sea level rise reduction of melting because of cooler conditions during the yd may have caused an increase in the rate of ocean ventilation which caused the atmospheric 14 c 12 c ratio to fall the record of sea level rise also shows that globally averaged rates of melting were relatively high at the beginning of the yd thus these measurements satisfy one of the conditions required by the hypothesis that the diversion of meltwater from the mississippi to the st lawrence river triggered the yd event

paleomagnetic record of the late pleistocene reef sequence of tahiti french polynesia a contribution to the chronology of the deposits abstract rock and paleomagnetic investigations were performed on the late pleistocene reef sequence of tahiti and take part of a multidisciplinary study of the holocene and pleistocene reef sequences carried out by the iodp integrated ocean drilling program expedition 310 the objectives were to characterize the natural remanent magnetization and its mineral carriers in order to identify high resolution magnetostratigraphic markers of the late brunhes chron a series of 85 specimens subsampled within a 79 m thick silty carbonate sequence cored at the maraa site sw of tahiti display a strong and stable natural remanent magnetization nrm carried by titanomagnetite inherited from the basalts which form the bulk of the island the average negative inclination is assignable to the field generated by the normal polarity axial dipole field at the site latitude a few specimens 103 119 m below modern sea level carry a reversed primary magnetization acquired in a weak excursional field based on subsidence rate estimates ranging from 0 25 to 0 4 m kyr this suggests the identification either the laschamp excursion 40 ka or the blake event 115 120 ka radiometric dates of 131 to 134 ka at 117 m below modern sea level confirm that these layers were deposited during the marine isotope stage 5 5 and recorded the direction and intensity anomaly associated with the blake event another sea level highstand reef unit occurring deeper in the pleistocene sequence has seemingly recorded another paleomagnetic intensity anomaly which is not yet definitely identified reef systems which developed around volcanic islands contain geological records of excursions but it is necessary to improve the understanding of nrm acquisition and the role of carbonate diagenesis in order to establish radiometrically dated records of geomagnetic excursions

quaternary marine terraces sea level changes and uplift history of patagonia argentina comparisons with predictions of the ice 4g vm2 model of the global process of glacial isostatic adjustment abstract quaternary marine terraces have been investigated along a 1000 km stretch of the coast of argentinian patagonia fossil mollusc shells most in living position and collected from raised beaches were dated using the u series esr and 14 c methods our analyses show that holocene sea level in this region culminated 7000 to 8000 bp at 6 7 m amsl this beach slightly increases in altitude southward the last interglacial stage 5e was identified at 16 17 m amsl whereas the highest and morphologically most distinctive radiometrically dated terrace at 250 000 to 330 000 bp exists at an elevation of 33 35 m amsl we estimate a constant rate of tectonic uplift of 0 09 m 1000 yr since the middle pleistocene using this estimate of the local rate of tectonic uplift we correct relative sea level r s l observations for the holocene epoch in turn the inferred holocene sea level histories are compared with those predicted using the ice 4g vm2 model of the global process of glacial isostatic adjustment this model accurately predicts r s l history from all sites along the northern part of the east coast of the south american continent venezuela brazil however along the southern part of the coast of argentinian patagonia there is evidence of an influence that is not accurately represented in this version of the model of the global process of glacial isostatic adjustment we suggest that this influence could be connected to the presence of the broad continental shelf that is located offshore of this region but the influence of significant neotectonic uplift cannot be dismissed

evidence of holocene uplift in east new britain papua new guinea 1 we present the first published evidence of uplift along the eastern coast of new britain papua new guinea based upon 230th dating of uplifted holocene coral reefs although uplift rates of the nearby huon peninsula are well constrained 2 3 m ka little is known about vertical motion along the eastern margin of new britain based upon relative sea level curves for papua new guinea present sample elevations and estimates of paleowater depth of four in situ holocene corals we calculate an average uplift rate of 1 6 0 4 m ka for the southeast coast of new britain we suggest underplating of subducted sediment as a possible mechanism for uplift of the reefs

early diagenesis impact on precise u series dating of deep sea corals example of a 100 200 year old lophelia pertusa sample from the northeast atlantic deep sea coral has proved useful for paleoceanographic reconstructions and for documenting 14 c ages of water masses using 230 th ages however for precise and accurate u series dating further information on coral age structure growth rate and diagenetic evolution is still needed to document such processes we used u th 226 ra systematics in a 40 cm diameter lophelia pertusa specimen collected in 1912 from the eastern atlantic sea of the hebrides external parts of the specimen are thought to have been alive when collected whereas more internal parts were likely dead the live collected and dead parts of the skeleton were sampled and analyzed for their 230 th 232 th 234 u 238 u 226 ra and ba contents by thermal ionization and multicollector inductively coupled plasma mass spectrometry 230 th 234 u ratios in the most recent parts yielded ages of 86 6 a and 92 9 a in agreement with the date of recovery the older parts yielded 230 th ages ranging from 169 15 to 211 10 a n 5 but had a 31 higher u content than more recent parts of the skeleton this raises concerns about the possibility of secondary diagenetic u uptake although an environmentally controlled u ca shift between coral growth stages cannot be ruled out 226 ra ba measurements were made and model 226 ra ba ages averaging 250 12 yr were calculated for the older part assuming a constant initial 226 ra ba ratio in bottom waters these ages are slightly older than 230 th ages suggesting either that 226 ra ba ratios of ambient seawater changed over time or that a diagenetic phenomenon have affected the u series system or both scanning electron microscope observations revealed bioerosion and secondary biomineralization in the older part of the coral skeleton supporting the hypothesis that diagenetic processes may have influenced the ages obtained by the u series toolbox modeled u series ages for such an open system are discussed however a comparison between 14 c and 230 th ages performed on both pristine and bioeroded parts of the coral gives coherent values ca 450 a for the preindustrial 14 c reservoir age of north atlantic waters it remains to be determined however whether diagenesis occurs rapidly over a short period of time or whether it continues for longer periods in the latter case diagenetic processes would hamper paleoceanographic interpretations as well as the precise calculation of 14 c ages of deep water masses based on comparative u th and 14 c chronologies copyright 2005 elsevier ltd

aplanktonic zones in the red sea abstract we use micropalaeontological and stable isotope results for a series of cores from north to south through the red sea to assess temporal and spatial patterns of change in planktonic foraminiferal faunas leading up to the remarkable full glacial red sea aplanktonic zones aplanktonic zones reflect salinities in the red sea in excess of the lethal 49 p s u limit caused by reduced exchange transport through the strait of bab el mandab due to glacial sea level lowering concerning the last glacial cycle aplanktonic conditions began at 39 ka bp in the north where salinities eventually reached 55 57 p s u paradoxically planktonic faunas are reported to have survived the last glacial maximum in the northern gulf of aqaba suggesting a poorly understood freshwater dilution at that time aplanktonic conditions s 49 p s u reached the south central red sea by 22 ka bp while planktonic foraminiferal faunas continued albeit in very low abundances and limited diversity s 45 p s u in the southernmost red sea during marine isotope stage mis 6 the 49 p s u isohaline appears to have resided in the central red sea between cores kl11 and md921017 we observe a systematic sequence of species disappearances before all glacial maxima of the last 500 kyr absence of a logical relationship with sea levels suggests that the disappearance sequences are not related to a general salinity increase instead we argue that the sequences were driven by complex reorganisations in hydrography stratification productivity food availability and subsurface oxygenation reproduction habitats the onset is marked by dramatic basin wide expansion of conditions that today are restricted to only the southern red sea suggesting an expansion of the dominance of ne monsoonal circulation over the entire red sea this expansion occurred 15 or more kyr before the aplanktonic zones of mis 12 6 and 2 and also before mis 10 and 8 which never reach the aplanktonic stage regarding the last glacial cycle this event occurred as early as 75 ka bp mis 4 5 boundary after this major climatic reorganisation we reconstruct progressive intensification of the new conditions especially marked by northward expansion and intensification of the subsurface oxygen minimum zone omz during the last glacial cycle a shallow and very distinct omz affected the central red sea as early as 68 ka bp and the north as late as 55 ka bp the omz expansion intensification appears to have been interrupted by episodes of increased ventilation

coral indicators of past sea level change a global repository of u series dated benchmarks fossil corals provide valuable data for reconstructing past sea levels as they are often well preserved in the fossil record and can be dated with u series methods here we present a global and internally consistent database of usingle bondth dated fossil coral sea level indicators including full consideration of all known associated uncertainties both vertical and chronological we include carefully determined taxon specific depth distributions rather than blanket depth uncertainty terms as used in most previous work this is based on a synthesis of extensive modern ecological information on depth ranges these ranges are found to be spatially variable between ocean basins between regions and on sub regional scales because depth itself is not limiting instead depth distributions arise from complex physical chemical and biological interactions with coral reef growth distribution and composition one of the main causes for recognition of the greater depth variability of coral taxa has been the routine inclusion of deep diving and rov surveys in coral ecological studies over the past few decades which has broken through the shallow water bias of early surveys by adding frequent observations on deeper occurrences although more are needed it is also clear from our assessment that coral habitat depth distributions must be determined on the species level to reduce uncertainties in reconstructions of past sea levels and that application to sea level studies then requires these studies also to identify fossil corals to the species level samples identified only to the genus level give rise to wide uncertainties in habitat depth and hence sea level our database contains extensive metadata to assist evaluations of dating quality as well as geomorphic and stratigraphic metadata we demonstrate with examples how such metadata can help to evaluate sea level reconstructions for example by identifying outlier points one example discusses the last interglacial lig where we use the available data with their uncertainties to assess probabilistically the time at which local sea levels exceed that of the present which yields a mean age of 124 6 ka with 95 probability bounds at 118 5 and 129 5 ka we conclude with identification of key outstanding issues relating to i current incomplete understanding of tectonic setting including the current lack of independent verification of uplift subsidence rates and reliance of somewhat unsatisfactory and circular use of the elevation of last interglacial deposits ii the depth distributions of coral taxa and iii the complete documentation of stratigraphic geomorphological and other contextual information with suggestions for strategies to address these issues

the changing architecture of sea level lowstand deposits across the mid pleistocene transition south evoikos gulf greece abstract on subsiding continental shelves the style of stacked coastal and deltaic progradational packages is directly dependent on relative sea level changes in the past 0 6 ma sea level change has been dominated by asymmetric 100 ka eustatic sea level cycles whereas the record of sea level changes in earlier pleistocene progradational sequences is less clear in a steadily subsiding basin in which accommodation balances sediment flux the depth of a eustatic lowstand determines the paleo depth of the deepest clinoform inflection point and the seaward limit of the erosional transgressive surface whereas the duration of a lowstand controls the amount of progradation that takes place we report high resolution seismic profiles of an exceptionally preserved coastal progradational sequence from a coastal embayment in the aegean sea that is subsiding at 100 m ma the seismic profiles show clinoforms of smaller amplitude and volume that were deposited before the 100 ka cyclic progradational units this contrasts with literature reports of complexity in progradational sequences at that time we assume that published stacked benthic foram o isotope records are a good proxy for the duration and a reasonable proxy for the amplitude of pleistocene eustatic sea level cycles the mis 6 5 eustatic sea level rise is recognised based on sedimentation rates from cores the underlying major progradational units are correlated with the long duration extreme lowstand 100 ka cycles of mis 6 12 and 16 changes in the elevation of lowstand inflection points in clinoforms are used to tentatively extend the record back to mis 38 by comparison with the benthic foram proxy the deposits of the higher and longer highstands of mis 25 31 and 37 are also recognised this record provides a testable template for future studies of short early pleistocene sections on land and raises questions of detail about parts of the published 18 o records it independently supports the recent evidence that the mid pleistocene transition was an abrupt event with an extreme lowstand in mis 22

quaternary hinterland evolution of the active banda arc surface uplift and neotectonic deformation recorded by coral terraces at kisar indonesia abstract coral terrace surveys and u series ages of coral yield a surface uplift rate of 0 5 m ka for kisar island which is an emergent island in the hinterland of the active banda arc continent collision based on this rate kisar first emerged from the ocean as recently as 450 ka these uplifted terraces are gently warped in a pattern of east west striking folds these folds are strike parallel to more developed thrust related folds of similar wavelength imaged by a seismic reflection profile just offshore this deformation shows that the emergence of kisar is influenced by forearc closure along the south dipping kisar thrust however the pinnacle shape of kisar and the protrusion of its metamorphic rocks through the forearc basin sediments also suggest a component of extrusion along shear zones or active doming coral encrusts the island coast in many locations over 100 m above sea level terrace morphology and coral ages are best explained by recognizing major surfaces as mostly growth terraces and minor terraces as mostly erosional into older terraces all reliable and referable coral u series ages determined by mc icp ms correlate with marine isotope stage mis 5e 118 128 ka the only unaltered coral samples are found below 6 m elevation however an unaltered tridacna giant clam shell in growth position at 95 m elevation yields a u series age of 195 31 ka which corresponds to mis 7 this age agrees with the best fit uplift model for the island loose deposits of unaltered coral fragments found at elevations between 8 and 20 m yield u series ages of

pleistocene sea levels and tectonic uplift based on dating of corals from sumba island indonesia we collected and dated fossil corals from the uplifted reef tracts of sumba island mass spectrometry tims and ams was used to obtain reliable and precise radiochronological results it is possible to identify outcrops corresponding to major sea level high stands isotope stage 1 starting at 7 1 kyr bp 5a c a 86 kyr bp 5c c a 105 kyr bp 5e between 119 and 132 kyr bp and 9 c a 305 kyr bp the radiochronological data are thus broadly consistent with the timing of sea level fluctuations predicted by the astronomical theory of paleoclimates comparison with similar data from other terrace sequences and from benthic 18o records indicates that the average tectonic uplift rate at cape laundi sumba is on the order of 0 2 0 5m kyr the lowest values 0 3m kyr lead to the build up of polycyclic topographic terraces in which it is possible to find corals grown during different interstadial or even interglacial times

fossiliferous lana i deposits formed by multiple events rather than a single giant tsunami giant tsunamis generated by submarine landslides in the hawaiian islands have been thought to be responsible for the deposition of chaotic gravels high on the southern coastal slopes of the islands of lana i and moloka i hawaii here we investigate this hypothesis using uranium thorium dating of the hulopoe gravel on lana i and a study of stratigraphic relationships such as facies changes and hiatuses within the deposit the hulopoe gravel contains corals of two age groups representing marine isotope stages 5e and 7 135 000 and 240 000 years ago respectively with significant geographical and stratigraphic ordering we show that the hulopoe gravel was formed by multiple depositional events separated by considerable periods of time thus invalidating the main premise of the giant wave hypothesis instead the gravels were probably deposited during interglacial periods when sea level was relatively high by typical hawaiian shoreline processes such as seasonal wave patterns storm events and possibly normal tsunamis and reached their present height by uplift of lana i

sea level rise during termination ii inferred from large benthic foraminifers iodp expedition 310 tahiti sea level the course of sea level fluctuations during termination ii tii the penultimate deglaciation which is critical for understanding ice sheet dynamics and suborbital climate variability has yet to be established this is partly because most shallow water sequences encompassing tii were eroded during sea level lowstands of the last glacial period or were deposited below the present sea level here we report a new sequence recording sea level changes during tii in the pleistocene sequence at hole m0005d water depth 59 63 m below sea level mbsl off tahiti french polynesia which was drilled during integrated ocean drilling program expedition 310 lithofacies variations and stratigraphic changes in the taxonomic composition preservation states and intraspecific test morphology of large benthic foraminifers indicate a deepening upward sequence in the interval from core 310 m0005d 26r core depth 134 mbsl through 16r core depth 106 mbsl reconstruction of relative sea levels based on paleodepth estimations using large benthic foraminifers indicated a rise in sea level of about 90 m during this interval suggesting its correlation with one of the terminations assuming that this rise in sea level corresponds to that during tii after correcting for subsidence since the time of deposition a highstand sea level position would be 2 15 m above present sea level masl which is generally consistent with highstand sea level positions in mis 5e 4 2 masl if this rise in sea level corresponds to that during older terminations the subsidence corrected highstand sea level positions 30 15 masl for termination iii and 54 15 masl for termination iv are not consistent with reported ranges of interglacial sea level highstands 18 to 15 masl therefore the studied interval likely records the rise in sea level and associated environmental changes during tii in particular the intervening cored materials between the two episodes of sea level rise found in the studied interval might record the sea level reversal event during tii this conclusion is consistent with u th ages of around 133 ka which were obtained from slightly diagenetically altered i e 1 calcite in situ corals in the studied interval core 310 m0005d 20r core depth 118 mbsl this study also suggests that our inverse approach to correlate a stratigraphic interval with an approximate time frame could be useful as an independent check on the accuracy of uranium series dating which has been applied extensively to fossil corals in late quaternary sea level studies

simple models for the geochemical response of the ocean to climatic and tectonic forcing abstract simple models for the geochemical response of the ocean to periodic forcing are used as a framework to discuss the shortest periods of change resolvable by present analytical precision of elemental or isotopic ratio measurements of the chemical evolution of seawater for chemical properties whose budget is dominated by fluxes into and out of the ocean we show that the geochemical response to changing fluxes is strongly attenuated at periods shorter than the residence time and that the response at these periods is also phase shifted so as to lag the forcing by one quarter cycle the amplitude response as a function of period is used to estimate the periods of forcing resolvable by present analytical precision in measuring the 87sr 86sr and 234u 238u evolution of seawater and we find that the shortest periods resolvable are of the order of 1 myr if variations at periods shorter than this are found we would argue that these are very likely of local as opposed to global origin we illustrate the importance of phase shifts as a function of forcing period by discussing some recently published data that show a high degree of correlation over the last 300 kyr between changes in 87sr 86sr and 18o measured in the same sediment core at first sight this correlation might be taken as good evidence that both 87sr 86sr and 18o are responding to some common climatic forcing but given the long residence time of sr in the ocean sr and o should in fact have different phase shifts relative to any proposed common forcing thus the apparent correlation between 87sr 86sr and 18o over the past several 100 ma is not necessarily an indication that they are responding to a common cause amplitude response curves are also used to place limits on permissible global seawater 234u 238u variations and these are then compared with published data to identify local diagenetic effects application to 187os 186os and u records in seawater detectors is proposed

benthic environmental changes in the eastern mediterranean sea during sapropel s5 deposition abstract high resolution benthic foraminiferal analyses of sediment cores collected at different sites in the eastern mediterranean sea revealed that profound changes occurred in deep sea ventilation over the past 124 119 ka bp the three cores sin97 gc01 ban89 gc09 bd02 gc01 were selected in order to investigate middle and deep bathyal ecosystems in the eastern mediterranean basin at site sin97 gc01 933 m water depth urania basin the presence of benthic fauna in the sapropel layer and the gradual increase in benthic foraminiferal abundance from the middle part of the sapropel suggest that the sea floor was partially ventilated and that re oxygenation had increased considerably during the late phase of s5 deposition cores ban89 gc09 2011 m water depth napoli dome and bd02 gc01 2470 m water depth ionian sea show a different pattern during sapropel s5 benthic abundance and diversity strongly decrease and microfauna even disappears in some levels suggesting the establishment and maintenance of stagnant and anoxic conditions at the seafloor until the end of s5 deposition in the deepest part of the basin the re establishment of the benthic foraminiferal community at the top of the s5 layer indicates a relatively slow bottom re oxygenation at the southernmost site the foraminiferal assemblage records a short oxygenation pulse during the deposition of sapropel s5 linked to a short cold spell the results of this study suggest that the evolution of the dysoxic anoxic conditions as well as the re oxygenation pattern at the end of the stagnant period were characterised by spatial and temporal variability possibly controlled by basin physiography

stratigraphic development during the late pleistocene and holocene offshore of the yellow river delta bohai sea abstract a 61 m long sediment core hb 1 and 690 km of high resolution seismic profiles from offshore of the yellow river delta bohai sea were analyzed to document the stratigraphy and sea level changes during the late pleistocene and holocene accelerator mass spectrometry 14c dating and analyses of benthic foraminifera ostracods the mineral composition and sedimentary characteristics were performed for core hb 1 and seven depositional units du 1 du 7 in descending order were identified the seismic reflection data were interpreted in light of the sedimentological data of the core and correlated with other well studied cores obtained previously in the bohai sea area seven seismic units su 1 to su 7 in descending order were distinguished and interpreted as follows su 7 corresponds to marine facies in marine isotopic stage mis 5 su 6 to terrestrial facies in mis 4 su 5 and su 4 to alternating terrestrial and marine facies du 7 du 5 in mis 3 su 3 to terrestrial facies du 4 in mis 2 su 2 to holocene marine facies du 3 and du 2 and su 1 to modern yellow river delta sediments deposited since 1855 du 1 the sedimentary facies from du 7 to du 5 reflect sea level fluctuations during mis 3 and the boundary between du 5 and du 6 which coincides with that between su 4 and su 5 is a distinctive laterally continuous undulating erosion surface with up to 20 m of relief this surface reflects subaerial exposure between transgressions during mis 3 estimated sea levels during mis 3 ranged from 35 5 to 60 5 m or lower with short term fluctuations of 20 m sedimentary environments in the bohai sea area were governed mainly by eustatic sea level changes and the bohai strait topography which controls the entry of sea water into the bohai sea area the mineral composition of the sediment core suggests that the yellow river did not discharge into the bohai sea or at least did not influence the study area significantly during parts of mis 3 and mis 2 to the early holocene 11 8 5 cal kyr bp

glacial rebound and sea level change an example of a relationship between mantle and surface processes lambeck k 1993 glacial rebound and sea level change an example of a relationship between mantle and surface processes in r wortel u hansen and r sabadini editors relationships between mantle processes and geological processes at or near the earth s surface tectonophysics 223 15 37 the problem of glacial rebound provides an outstanding example of the relationship between surface and mantle processes on time scales of 103 to 105 years changes in surface loading of ice and melt water associated with the growth and decay of the great ice sheets deform the surface of the planet and induces flow in the mantle a measure of the earth s response to the changing surface loads and internal deformation is provided by observations of past sea levels relative to the present level and inversion of these observations provides constraints on both the models of the rheological response of the earth to loading and on models of the ice sheets constraints on ice sheet models include the total volume of the grounded ice at the time of maximum glaciation the global rates of melting of the ice sheets the thickness of the ice at maximum glaciation the extent of ice cover over shallow seas such as the north sea and the barents sea and the role of antarctica in the global ice balance constraints on mantle parameters include the effective lithospheric thickness and the effective viscosity of the mantle some recent results for both sets of parameters are discussed