direct determination of the timing of sea level change during termination ii an outcrop within the last interglacial terrace on barbados contains corals that grew during the penultimate deglaciation or termination ii we used combined 230th and231pa dating to determine that they grew 135 8 0 8 thousand years ago indicating that sea level was 18 3 meters below present sea level at the time this suggests that sea level had risen to within 20 of its peak last interglacial value by 136 thousand years ago in conflict with milankovitch theory predictions orbital forcing may have played a role in the deglaciation as may have isostatic adjustments due to large ice sheets other corals in the same outcrop grew during oxygen isotope 18o substage 6e indicating that sea level was 38 5 meters below present sea level about 168 0 thousand years ago when compared to the 18o signal in the benthic v19 30 v19 28 record at that time the coral data extend to the previous glacial cycle the conclusion that deep water temperatures were colder during glacial periods

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

the chronology of speleothem deposition in northern yukon and its relationships to permafrost in the northern yukon there is a significant group of limestone caves in an area that was not glaciated during the quaternary permafrost appears to have played an important role in restricting calcite speleothem deposition in the caves u th dating and stable isotopic studies indicate that the deposits form two distinct groups a first group younger than 350 ka and a second group older than the 350 ka bp limit of the conventional u th alpha spectrometric dating method two large samples from the second group yield sequences of magnetic declinations and inclinations with reversed and normal polarity perhaps from the tertiary the pollen content of five speleothems the modes of calcite deposition and stable isotopic analyses indicate that the speleothems were deposited under a cold regime it is suggested that the ancient speleothems were deposited at a time when permafrost was absent during the later tertiary or at the beginning of the quaternary period the establishment and maintenance of permafros

quaternary environmental evolution in the south carpathians reconstructed from glaciokarst geomorphology and sedimentary archives abstract the carpathian island type glaciokarst has a great potential of preserving signals of past environments archived in cave deposits like speleothems and clastic infills we present here the geomorphology and structural control of several relict alpine caves and the surrounding glaciated marble karst in the f g ra mountains four truncated and partially unroofed caves remained on the ridge top of mu eteica mountain above the glacial cirque while a ponor cave that developed on the cirque bottom could be related to the last glacial period structural measurements and cave morphology showed that the conduits formed at the intersection of foliation planes and tectonic fractures on the ne sw and nw se directions cave development reflects three speleogenetic stages 1 texture and fabric controlled dissolution and distension 2 structurally controlled breakdown and 3 truncation unroofing and cave infilling with sediments slow diffuse dissolution was typical for the ridge top caves whereas m1 cave developed by pressure flow further we report the first u th speleothem ages related to the evolution of alpine caves and island glaciokarst in the south carpathians during the middle and late pleistocene dating results show a minimum estimated age of 560 ka for the ridge top caves and that speleothem deposition met optimal conditions only during warmer periods largely corresponding to interglacials stable carbon isotope values in speleothems range between 9 96 and 4 11 indicating the presence of plant and soil organic activity at the time of deposition in total five speleothem growth phases were distinguished during the last 560 ka we excavated the sediment infill of a ridge top doline down to a 2 m depth radiocarbon dating revealed that it was deposited during the late holocene and preliminary pollen analysis identified a plant assemblage dominated by grasses using the relationships between karst development glaciation and cave sedimentary archives we present a time slice chronology of alpine landscape evolution at 560 ka 400 ka 330 ka the last glacial period 70 12 ka and the late holocene our geomorphological isotopic and geochronological results also support the existing hypothesis that the south carpathians may have experienced at least two glacial phases during the pleistocene glacial erosion rate during the last glacial period and most likely during the penultimate glaciation averages around 0 6 mm yr 1

start of the last interglacial period at 135 ka evidence from a high alpine speleothem a detailed study of growth periods of a flowstone from spannagel cave in the zillertal alps austria at 2500 m above sea level a site highly sensitive to climate changes offers unprecedented new insights into pleistocene climate change in central europe flowstone sample spa 52 has a high u content to 116 ppm analyses of this sample reveal that episodes of calcite deposition started at 204 3 ka 135 1 2 ka and 122 ka suggesting that at these times the mean air temperature at this high alpine site was within 1 5 c of the present day condition the beginning of growth at 135 ka corresponds to the ending of the last glaciation and is concordant with a midpoint age for the penultimate deglaciation at 135 2 5 ka as deduced from the absolutely dated oxygen isotope curve in sediments from the bahamas as well as with recent coral evidence from barbados indicating a high sea level already by 135 8 0 8 ka this set of data supports evidence against northern hemisphere forcing of termination ii because the insolation maximum is at 127 ka

two step deglaciation at the oxygen isotope stage 6 5e transition the zeifen kattegat climate oscillation comparison of marine lacustrine and terrestrial records from twenty four sites suggests the existence of a younger dryas type climate oscillation just prior to the oxygen isotope stage 6 5e boundary these records include results from biostratigraphic pedostratigraphic and speleothem studies as well as analyses of stable isotope compositions of marine records and ice cores the climate oscillation is named after the warm zeifen interstadial and the cold kattegat stadial the zeifen interstadial may be related to a major meltwater pulse in the baffin bay labrador sea norwegian sea region the climate oscillation is presumably in part a result of a variation in ocean circulation especially in the strength of the north atlantic drift but changes in the atmospheric circulation also played an important role the geographically widespread distribution of the oscillation suggests that the two step deglaciation influenced both the northern and southern hemispheres c 1996 elsevier science ltd

the quaternary glaciations of switzerland with special reference to the northern alpine foreland summary 1 the quaternary glaciations of the swiss alpine foreland comprise at least five major glacial advances beyond the northern border of the alps within the time span of the classical chronology of the alps however only two full interglacials are known hitherto between the glacigenic accumulations this paucity of inter glacial records and the lack of radiometric dates causes problems in correlation of the swiss glacial sequence with neighbouring areas or with the deep sea oxygen isotope record 2 the thalgut section to the south of berne is the most complete lithogenetic quaternary succession available the discovery of pterocarya beanng inter glacial deposits there is of regional importance hoistein interglacial sensu welten this discovery implies that the most intensive erosion of the perialpine valleys must have taken place before the riss glaciation of the classical chronology this observation and the absence of glacigenic deposits at meikirch and niederweningen question the traditionally held view that the penultimate glaciation riss was the most extensive glaciation of the swiss alps the big event antedates the holstein interglacial sensu welten 3 during the early stages of the second before last glaciation mindel or even before that event a change in the morphogenetic behaviour of the swiss plain occurred predominant erosion of the main valleys is followed after that time by predominant accumulation of glacigenic glacilacustrine and fluvial and lacustrine sediments this morphodynamic change is most probably related to crustal movements because a change in fluvial or glacial dynamics alone cannot explain this evolution 4 traces of glaciations in the alpine foreland which antedate the fundamental morphogenetic change and the time period of the classical four glaciations are recorded in the cover gravels of ne switzerland and in the wanderblockformation of the northern tabular jura mountains but these events may be pre quaternary in age 5 a schematic chronology of the glaciations recorded in the quaternary sediments of the swiss alpine foreland is given in fig 6

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

warm period growth of travertine during the last interglaciation in southern germany abstract late quaternary travertine at two sites near stuttgart formed entirely during interglacial periods the travertine contains structures from growth induced by bacteria and such structures have been dated by 230th u mass spectrometry the resulting ages from both sites imply growth episodes of short duration with growth rates up to 5 mm yr 1 at 99 800 1300 yr b p 2 n 8 and 105 900 1300 yr b p 2 n 7 these episodes were likely part of marine isotope stage mis 5 3 deposition of silt interrupted travertine growth at one of the sites 105 000 yr b p likely correlatives of this silt are the st germain i b stade recorded in the grand pile peat bog and a cold episode 1000 yr long recorded by 18o values in the grip ice core travertine also formed during stage 5 5 115 000 yr and during the early holocene we found no evidence for travertine accumulation in stages 2 3 4 and 5 1 at both sites the sr u ratio and the initial 234u 238u activity ratio resemble those of modern spring water however the sites differ in the chemical composition of spring water and in stratigraphic sequence of travertine accumulation

influence of toe berm geometry on stability of reshaping berm breakwaters reshaping berm breakwaters have been mainly designed and built for water depth less than 20 m in such conditions a toe structure may be needed to reduce bottom settlements and increase geotechnical stability in the loose subsoil condition also a toe berm can be deployed to reduce the berm recession and increase the stability of the reshaping berm breakwater especially in deep water although many studies have been conducted to study the effects of toe berms on stability of conventional breakwaters investigations on the influence of a toe berm on stability of reshaping berm breakwaters are rare this paper presents results of an experimental work that has been carried out to investigate the influence of a toe berm on the hydraulic stability of reshaping berm breakwaters in a 2d physical test setup in a wave flume a total of 207 tests were conducted to systematically examine the effects of toe berm configuration on the reshaping of berm breakwaters with three types of armor stones the experimental program covers the influence of different geometrical parameters of the toe berm on the berm recession under various sea state conditions comparing results of berm recession of the cases having a toe structure with the cases without a toe berm shows that the amount of berm recession with toe berm is considerably less than the analogous amount for without toe structure it is observed that an increasing toe berm width and thickness both have considerable influence on recession reduction however the toe depth has a relatively larger influence on recession than the toe width and the influence is larger for higher stability numbers it is concluded that a toe berm in front of reshaping berm breakwater not only does have influence on recession due to the depth influence and the changing wave conditions but also the toe depth has a direct influence on the reshaped profile by preventing the displaced rocks to fall down to deeper parts using the test results a new formula is developed for estimation of berm recession by taking into account the influence of the toe berm configuration given an acceptable stability number ho as a design criterion for reshaping berm breakwaters the present method predicts that the recession can be reduced up to 35 by the application of a toe berm thus the main berm width can be shortened resulting in reduction of the required armor stones volume so by using a smaller stone size for the toe berm the stability of the structure is secured and also the total cost of the breakwater can be reduced

speleothem evidence from oman for continental pluvial events during interglacial periods growth periods and stable isotope analyses of speleothems from hoti cave in northern oman provide a record of continental pluvial periods extending back over the past four of earth s glacial interglacial cycles rapid speleothem growth occurred during the early to middle holocene 6 10 5 ka b p 78 82 ka b p 120 135 ka b p 180 200 ka b p and 300 325 ka b p the speleothem calcite deposited during each of these episodes is highly depleted in 18 o compared to modern speleothems the d 18 o values for calcite deposited within pluvial periods generally fall in the range of 24 to 28 relative to the vienna peedee belemnite standard whereas modern speleothems range from 21 to 23 the growth and isotopic records indicate that during peak interglacial periods the limit of the monsoon rainfall was shifted far north of its present location and each pluvial period was coincident with an interglacial stage of the marine oxygen isotope record the association of continental pluvial periods with peak interglacial conditions suggests that glacial boundary conditions and not changes in solar radiation are the primary control on continental wetness on glacial interglacial time scales

orbital forcing of the marine isotope stage 9 interglacial milankovitch orbital forcing theory has been used to assign time scales to many paleoclimate records however the validity of this theory remains uncertain and independent sea level chronologies used to test its applicability have been restricted largely to the past approximately 135 000 years here we report u series ages for coral reefs formed on henderson island during sea level high stands occurring at approximately 630 000 and approximately 330 000 years ago these data are consistent with the hypothesis that interglacial climates are forced by northern hemisphere summer solar insolation centered at 65 degrees n latitude as predicted by milankovitch theory

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

potential mio pliocene reef traps in the iron bottom basin solomon islands abstract the iron bottom basin is situated in iron bottom sound north of honiara guadalcanal solomon islands and is the most southerly sub basin of the central solomons trough the basin contains a maximum sedimentary thickness of about 4 5 km of late oligocene to quaternary strata that may have the potential for the generation and entrapment of hydrocarbons we have interpreted commercial multi channel seismic reflection profiles from the southern nearshore part of iron bottom basin and have found mound like anomalies at at least two stratigraphic levels and we believe these anomalies to be mio pliocene and pliocene shelf edge reefs they cover areas of greater than 6 km by 2 5 km and are up to about 200 m thick a smaller patch reef is also described these reef features are overlain by about 1 km of stratified sediments and lie under about 550 650 m of water they form potential traps for hydrocarbons that may have been generated in iron bottom basin

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

high resolution palynological record off the iberian margin direct land sea correlation for the last interglacial complex abstract we present high resolution pollen dinocyst and isotopic data for the last interglacial complex from marine core md952042 southwestern margin of the iberian peninsula 37 48 n 10 10 w 3148 m direct land sea correlation from this core indicates that during this period north atlantic sea surface temperatures were in phase with iberian climate our palynological analysis suggests a younger dryas like event at the marine isotope stage mis 6 5 transition the analysis also indicates that the eemian spans from the lightest isotopic values of mis 5e ca 126 ky bp to the heavier isotopic values towards the mis 5e 5d transition therefore the eemian is not entirely equivalent to mis 5e pollen analysis identifies four climatic phases of low amplitude during the eemian a mediterranean climate in southwestern europe is gradually replaced by oceanic conditions the middle of the eemian is characterized by an increase in precipitation on the land and ocean associated with a slight cooling this seems to be the result of a displacement of the polar front as far south as southern europe during this period after the eemian three relatively short climatic phases on land melisey i st germain ia and montaigu cold event occurred contemporaneously with three shifts of sea surface temperatures the montaigu event first identified in terrestrial pollen sequences is therefore also recorded in core md952042 on the basis of pollen dinocyst and planktonic isotopic data our results also show that the warm periods of mis 5 are not characterized by similar climatic conditions on land

rock varnish microlamination dating of late quaternary geomorphic features in the drylands of western usa abstract varnish microlamination vml dating is a correlative age determination technique that can be used to date and correlate various geomorphic features in deserts in this study we establish a generalized late quaternary i e 0 300 ka varnish layering sequence for the drylands of western usa and tentatively correlate it with the specmap oxygen isotope record we then use this climatically correlated varnish layering sequence as a correlative dating tool to determine surface exposure ages for late quaternary geomorphic features in the study region vml dating of alluvial fan deposits in death valley of eastern california indicates that during the mid to late pleistocene 5 15 ky long aggradation events occurred during either wet or dry climatic periods and that major climate shifts between glacial and interglacial conditions may be the pacemaker for alteration of major episodes of fan aggradation during the holocene interglacial time however 0 5 1 ky long brief episodes of fan deposition may be linked to short periods of relatively wet climate vml dating of alluvial desert pavements in death valley and the mojave desert reveals that pavements can be developed rapidly

dating open systems by the 238 u 234 u 230 th method application to quaternary reef terraces abstract the sedimentation conditions and diagenetic processes of biogenic and inorganic carbonates are such that the assumptions of a closed system evolution and the absence of initial th invoked in classical 238 u 234 u 230 th dating methods are very often not fulfilled for such material this problem is of interest for all studies requiring accurate dating of corals or aragonite rich sediments as in palaeoclimatology or neotectonics extending the approach of henderson and slowey nature 404 2000 61 66 we propose a consistent model that takes into account possible initial 230 th excess and where continuous selective redistribution gain or loss of 234 u 234 th and 230 th is controlled by recoil processes this model applied to quaternary marine terraces in barbados marie galante lesser antilles arc and pacific islands is able to explain the large scatter in isotopic compositions observed in the series of cogenetic corals or sediments we show that recoil processes generally tend to increase the 234 u 238 u and 230 th 234 u ratios with time leading to an overestimation of the apparent ages calculated using classical methods on the basis of simple assumptions identical marine initial 234 u 238 u 0 and 230 th 232 th 0 ratios we propose a method for calculating a best estimate of the age of cogenetic series our model offers an alternative way to date old reef terraces where corals are almost systematically altered and where classical dating methods do not apply it may also explain the apparent variations of the 234 u 238 u seawater initial ratio estimated from corals formed in the last 300 ka and the apparent uncoupling between sea level highstands and high latitude northern hemisphere summer insolation our set of equations can be applied to all weathering processes where the mobility of u series isotopes is controlled by recoil

rapid fluctuations in sea level recorded at huon peninsula during the penultimate deglaciation about 140 000 years ago the breakup of large continental ice sheets initiated the last interglacial period sea level rose and peaked around 135 000 years ago about 14 meters below present levels a record of last interglacial sea levels between 116 000 years to 136 000 years ago is preserved at reef vii of the uplifted coral terraces of huon peninsula in papua new guinea however corals from a cave situated about 90 meters below the crest of reef vii are 130 000 2000 years old and appear to have grown in conditions that were 6 c cooler than those at present these observations imply a drop in sea level of 60 to 80 meters after 130 000 years sea level began rising again in response to the major insolation maximum at 126 000 to 128 000 years ago the early about 140 000 years ago start of the penultimate deglaciation well before the peak in insolation is consistent with the devils hole chronology

age dating and the orbital theory of the ice ages development of a high resolution 0 to 300 000 year chronostratigraphy using the concept of orbital tuning a continuous high resolution deep sea chronostratigraphy has been developed spanning the last 300 000 yr the chronology is developed using a stacked oxygen isotope stratigraphy and four different orbital tuning approaches each of which is based upon a different assumption concerning the response of the orbital signal recorded in the data each approach yields a separate chronology the error measured by the standard deviation about the average of these four results which represents the best chronology has an average magnitude of only 2500 yr this small value indicates that the chronology produced is insensitive to the specific orbital tuning technique used excellent convergence between chronologies developed using each of five different paleoclimatological indicators from a single core is also obtained the resultant chronology is also insensitive to the specific indicator used the error associated with each tuning approach is estimated independently and propagated through to the average result the resulting error estimate is independent of that associated with the degree of convergence and has an average magnitude of 3500 yr in excellent agreement with the 2500 yr estimate transfer of the final chronology to the stacked record leads to an estimated error of 1500 yr thus the final chronology has an average error of 5000 yr