middle and late jurassic radiolarian palaeoecology versus carbon isotope stratigraphy abstract jurassic radiolarians are sensitive to palaeoclimatic palaeoceanographic changes recorded by the stable carbon isotope curve carbon isotopic variations have been linked to changes in ocean structure productivity and concentrations of greenhouse gases in the atmosphere in the middle upper jurassic terminilletto section of the umbria marche sabina apennines central italy well preserved radiolarians are present in a sequence of cherty limestones interbedded with platform derived carbonates the 13 c curve in the aalenian kimmeridgian interval indicates three main positive 13 c events in the lower bajocian late bathonian lower callovian and middle oxfordian the positive 13 c shifts are correlated to increases in visible chert in the outcrop and may represent periods of increased biological productivity of surface sea water spumellaria nassellaria ratios and the fluctuations of relative abundance of selected genera tend to correlate with 13 c and chert abundance values and seem to be related to episodes of high nutrient mobilisation from the base of the bajocian the radiolarian associations show a slight tendency towards diversification coincident with increasing 13 c values in the upper part of the middle bajocian last appearances prevail over first appearances associated with the peak of the 13 c event this may indicate maximum eutrophic conditions coincident with the late bathonian early callovian positive 13 c shift the radiolarian associations record a different trend with respect to the bajocian event when the 13 c values are increasing to a maximum radiolarian associations tend to be reduced in species diversity followed by a small diversification trend when the 13 c values are decreasing we speculate that during the callovian a more stressful palaeoenvironment due to high level of eutrophication is indicated by the combination of high productivity of biogenic silica and low carbonate input although varying preservational conditions may have influenced the observed trends in the radiolarian associations the good correlation between changes of sedimentation patterns radiolarian assemblages and 13 c positive anomalies open interesting avenues for further investigations concerning the palaeoecology of mesozoic radiolarians

searching for eustasy in deglacial sea level histories abstract perturbations to the earth s gravity field and solid surface associated with glacial isostatic adjustment gia cause the total observable sea level change to depart from the eustatic curve which is defined as a spatially uniform height shift of the ocean surface to accommodate any mass gained lost from grounded ice in this study we apply a state of the art model of gia induced sea level change to quantify the magnitude and spatial form of this departure at the global scale for a range of model parameters with an aim to identify regions that are well suited to obtain accurate and precise estimates of eustatic sea level and therefore past grounded ice volume in general our results indicate that eustatic sea level is not a directly measurable quantity and so must be estimated by subtracting a model derived estimate of non eustatic contributions from observations in this regard we use our results to isolate regions where this procedure can be applied with optimal accuracy and precision that is where 1 the gia predictions are relatively insensitive to plausible ranges in input parameters and 2 where the non eustatic contribution is small i e the predicted sea level closely approximates the eustatic value we present maps that can be employed by the field community to identify areas where sea level reconstructions would be well suited to arrive at robust estimates of eustatic sea level note that sea level changes associated with tectonic motion and changes in ocean water temperature salinity which also lead to departures from eustasy are not considered in this analysis

rapid flooding of the sunda shelf a late glacial sea level record the increase in sea level from the last glacial maximum has been derived from a siliciclastic system on the tectonically stable sunda shelf in southeast asia the time from 21 to 14 thousand calendar years before the present has been poorly covered in other records the record generally confirms sea level reconstructions from coral reefs the rise of sea level during meltwater pulse 1a was as much as 16 meters within 300 years 14 6 to 14 3 thousand years ago

post glacial sea level rise from a coral record at huon peninsula papua new guinea dating of coral reef terraces can provide a record of changes in sea level which should be pronounced during the transition between glacial and interglacial periods cores drilled from coral reefs at barbados in the equatorial west atlantic1have revealed the sea level changes that occurred during the younger dry as event at the end of the last glacial maximum 11 000 yr bp it has not been known however whether pacific coral reefs can grow at a rate sufficient to keep up with the rise in sea level during such a transition here we report results obtained from a 52 m drill core from the post glacial reef at huon peninsula papua new guinea spanning the interval from 7 000 to 11 000 14c yr bp which show that coral growth kept pace while the relative sea level rose by 50m although the tectonic environment is very different from that at barbados the two records compare well when corrections are made for local tectonic uplift showing that sea level rise was similar at both locations the rate of rise was greatest between 9 000 and 10 00014c yr bp corresponding to the time of the younger dryas

acid processing of pre tertiary radiolarian cherts and its impact on faunal content and biozonal correlation the numbers of radiolarians visible in thin sections of chert rich rocks are commonly an order of magnitude greater than the numbers observed on the surfaces of fragments etched by hydrofluoric acid hf and typically orders of magnitude greater than the numbers of individuals found in hf processed residues destruction of radiolarians during both diagenesis and hf processing severely reduces faunal abundance and diversity and affects the taxonomic and biostratigraphic utility of chert residues the robust forms that survive the processing represent only a small fraction of the death assemblage and delicate skeletal structures used for species differentiation commonly preserved in limestone radiolarian faunas are either poorly preserved or dissolved in many coeval chert residues first and last occurrences of taxa in chert sequences are likely to be coarse approximations of their true stratigraphic ranges precise correlation is difficult between biozonations based solely on index species from cherts and those constructed from limestone faunas careful selection of samples in sequence use of weaker hf solutions and study of both chert and limestone faunas should yield better biostratigraphic information

patterns of biotic change in middle jurassic to early cretaceous tethyan radiolaria abstract the rate of taxic turnover of nearly 400 radiolarian species subspecies is analyzed in order to document long term biotic change of plankton during the middle jurassic to early cretaceous aalenian to aptian the pattern and dynamic of diversity change is described using four indices rate of species first and last occurrence rate of diversification and rate of turnover plots of cumulative sampling effort suggest that the analyzed data represent an adequate sample of total standing diversity for most examined stages rates of species first occurrence exceed rates of last occurrence for most of the middle jurassic except for the middle bajocian in contrast the late jurassic was a time of decreasing radiolarian diversity and the kimmeridgian records the lowest rate of diversification it is followed by a dramatic increase in first occurrences near the jurassic cretaceous boundary with as a result the highest rate of diversification recorded in the late tithonian regional radiolarian diversity was stable throughout most of the early cretaceous a stratigraphic permutation test was performed to assess the influence of uneven sampling on the observed pattern of taxic turnover and identified the intervals for which randomly obtained patterns are significantly different from the observed pattern the kimmeridgian and late tithonian events coincide with substantial climate derived perturbations in water cycling nutrient supply and oceanic productivity they point to a negative relationship between radiolarian macroevolution and changes in the state of nutrient availability although further work is needed to refine the temporal resolution of this relationship and to explore ecological aspects of its causal link with respect to radiolarian evolution

oxygen isotopes and sea level from the time that detailed oxygen isotope records derived from foraminifera living in the constant temperature environment of the abyssal ocean became available there has been a discrepancy between the ice volume record that these records imply and that derived from the altitude of dated coral terraces around the world here we re examine the data and conclude that the temperature of the abyssal ocean has been an actively varying component of the climate system

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

response of coral reefs to climate change expansion and demise of the southernmost pacific coral reef received 21 may 2010 revised 20 june 2010 accepted 6 july 2010 published 3 august 2010 1 coral reefs track sea level and are particularly sensitive to changes in climate reefs are threatened by global warming with many experiencing increased coral bleaching warmer sea surface temperatures might enable reef expansion into mid latitudes here we report multibeam sonar and coring that reveal an extensive relict coral reef around lord howe island which is fringed by the southernmost reef in the pacific ocean the relict reef in water depths of 25 50 m flourished in early holocene and covered an area more than 20 times larger than the modern reef radiocarbon and uranium series dating indicates that corals grew between 9000 and 7000 years ago the reef was subsequently drowned and backstepped to its modern limited extent this relict reef with localised re establishment of corals in the past three millennia could become a substrate for reef expansion in response to warmer temperatures anticipated later this century and beyond if corals are able to recolonise its surface citation woodroffe c d b p brooke m linklater d m kennedy b g jones c buchanan r mleczko q hua and j zhao 2010 response of coral reefs to climate change expansion and demise of the southernmost pacific coral reef geophys res lett 37 l15602 doi 10 1029 2010gl044067

the last interglacial sea level change new evidence from the abrolhos islands west australia u series ages measured by thermal ionisation mass spectrometry tims are reported for a last interglacial li fossil coral core from the turtle bay houtman abrolhos islands western australia the core is 33 4 m long the top of which is approximately 5 m a p s l above present sea level from the232th concentrations and the reliability of the u series ages two sections in the core can be distinguished calculated u th ages in core section i 3 3 m a p s l to 11 m b p s l vary between 124 1 7 ka bp 3 3 m a p s l and 132 5 1 8 ka 4 m b p s l i e below present sea level and those of section ii 11 23 m b p s l between 140 3 and 214 5 ka bp respectively the ages of core section i are in almost perfect chronological order whereas for section ii no clear age depth relationship of the samples can be recognised further assessments based on the 234u t criteria reveal that none of the samples of core section ii give reliable ages whereas for core section i several samples can be considered to be moderately reliable within 2 ka the data of the turtle bay core complement and extend our previous work from the houtman abrolhos showing that the sea level reached a height of approximately 4 m b p s l at approximately 134 ka bp and a sea level highstand of at least 3 3 m a p s l at approximately 124 ka bp sea level dropped below its present position at approximately 116 ka bp although the new data are in general accord with the milankovitch theory of climate change a detailed comparison reveals considerable differences between the holocene and li sea level rise as monitored relative to the houtman abrolhos islands these observation apparently add further evidence to the growing set of data that the li sea level rise started earlier than recognised by specmap chronology a reconciliation of these contradictionary observations following the line of arguments presented by crowley 1994 are discussed with respect to the milankovitch theory

mid to late holocene geomorphological and hydrological changes in the south taihu area of the yangtze delta plain china abstract the taihu plain of the lower yangtze valley china was a centre of rice agriculture during the neolithic period reasons for the rapid development of rice cultivation during this period however have not been fully understood for this coastal lowland which is highly sensitive to sea level change to improve understanding of the geomorphological and hydrological context for evolution of prehistoric rice agriculture two sediment cores dtx4 and dtx10 in the east tiaoxi river plain south taihu plain were collected and analysed for radiocarbon dating diatoms organic carbon and nitrogen stable isotopes 13c and 15n grain size and lithology these multiproxy analyses revealed that prior to ca 7500 cal yr bp the east tiaoxi river plain was a rapidly aggrading high salinity estuary the palaeo taihu estuary after ca 7500 cal yr bp low salinity conditions prevailed as a result of strong yangtze freshwater discharge subsequently seawater penetration occurred and saltmarsh developed between ca 7000 and 6500 cal yr bp due to accelerated relative sea level rise this transgression event influenced a large area of the taihu plain during the holocene as shown by multiple sediment records from previous studies persistent freshwater marsh or subaerial land formed due to dramatic shrinkage closure of the palaeo taihu estuary after ca 5600 cal yr bp when sea level was relatively stable we speculate that geomorphological and hydrological changes of the east tiaoxi river plain played an important role in agricultural development across the taihu plain during the neolithic period the closure of the palaeo taihu estuary and the formation of stable freshwater marsh or subaerial land after ca 5600 cal yr bp were critical preconditions encouraging the rapid rise of rice productivity in the liangzhu period 5500 4500 cal yr bp this development changed the landscape and river systems and thus provided adequate freshwater supply to the taihu plain

low latitudinal standard permian radiolarian biostratigraphy for multiple purposes with unitary association graphic correlation and bayesian inference methods abstract the ideal goal of biostratigraphic studies is to make stratigraphic ranges of all species clear and to fix globally synchronous biohorizons as age controls however it is difficult to achieve this goal in simple traditional ways and so a new solution is proposed for permian radiolarian biostratigraphy to achieve this goal including to establish a globally applicable biostratigraphy to estimate the numerical age of biohorizons and to determine stratigraphic ranges at species level all 400 known permian radiolarian species approximately 70 stratigraphic sections and 1560 samples from 350 previously published papers about the low latitude tethys and panthalassa oceans were analyzed issues of permian studies are summarized and a solution is proposed from the cenozoic point of view considering traditional methods as well as successful methods in cenozoic radiolarian studies here we implement newly proposed methods that have never been used for permian radiolarian studies unitary association method uam minimum disordered biohorizon algorithm mdba graphic correlation gc and reiteration estimation rounds rer of these our proposed rer is a new method to predict the probability of the estimated age for a sample by bayesian inference and joint probability both statistical methods as these four methods are applicable to any biostratigraphic study the principals and practical applications of these methods are carefully explained so non specialists can understand the logical procedure as a result 15 unitary association zones uazs are established for the entire permian biostratigraphic scheme by uam the numerical ages of 42 first occurrences fos are estimated from non parametric data from the middle guadalupian middle permian to the uppermost lopingian uppermost permian by mdba and gc and the statistical likelihood uaz ranges of 165 species in the entire permian were obtained using the rer procedure a usability test of our uazs shows that 97 96 of the 933 tested samples from previously published papers are well correlated and without contradiction within the statistical error of cenozoic synchronous biohorizons at 1 4 myr 23 of 42 fos are potentially regarded as synchronous events as the statistical likelihoods of uaz ranges are estimated by bayesian inference these ranges can be updated by anyone

global sea level control on local parasequence architecture from the holocene record of the po plain italy abstract holocene deposits exhibit distinct predictable and chronologically constrained facies patterns that are quite useful as appropriate modern analogs for interpreting the ancient record in this study we examined the sedimentary response of the po plain coastal system to short term millennial scale relative fluctuations of sea level through high resolution sequence stratigraphic analysis of the holocene succession meters thick parasequences form the building blocks of stratigraphic architecture above the younger dryas paleosol a prominent stratigraphic marker that demarcates the transgressive surface early holocene parasequences s 1 3 record alternating periods of rapid flooding and gradual shoaling and are stacked in a retrogradational pattern that mostly reflects stepped post glacial eustatic rise conversely middle to late holocene parasequences s 4 8 record a complex pattern of coastal progradation and delta upbuilding that took place following sea level stabilization at highstand starting at about 7 cal ky bp the prominent transgressive surface at the base of parasequence 1 correlates with the period of rapid global sea level rise at the onset of the holocene mwp 1b whereas flooding surfaces associated with parasequences 2 and 3 apparently reflect minor early holocene eustatic jumps reported in the literature changes in shoreline trajectory parasequence architecture and lithofacies distribution during the following eustatic highstand had instead an overwhelming autogenic component mostly driven by river avulsions delta lobe switching local subsidence and sediment compaction we document a 1000 year delayed response of the coastal depositional system to marine incursion farther inland from the maximum landward position of the shoreline a dramatic reduction in sediment flux due to fluvial avulsion resulted in marine inundation in back barrier position whereas coastal progradation was simultaneously taking place basinwards we demonstrate that the landward equivalents of marine flooding surfaces parasequence boundaries may be defined by brackish and freshwater fossil assemblages and traced for tens of kilometers into the non marine realm this makes millennial scale parasequences whether auto or allogenic in origin much more powerful than systems tracts for mapping detailed extents and volumes of sediment bodies the holocene parasequences of the po coastal plain with strong age control and a detailed understanding of sea level variation may provide insight into the driving mechanisms and predictability of successions characterized by similar depositional styles but with poor age constraint resulting in more robust interpretations of the ancient record

control of alongshore oriented sand spits on the dynamics of a wave dominated coastal system holocene deposits northern gulf of lions france article the maguelone shore extends along the northern coast of the gulf of lions west of the rhone delta and east of high gradient coastal streams that have provided most of the clastic sediments to the gulf of lions margin since the early miocene this 10 km wide area is constituted by a small coastal watershed 15 km long in low lying carbonate hills a kilometre wide marsh a sandy beach barrier and a shoreface experiencing local low sedimentation rates this onshore offshore transition zone is a key area to understand the relationships between erosion by pass deposition and preservation processes unlike the neighbouring rhone deposits that display numerous thick deltaic sequences related to a continuous sediment flux the maguelone shore exhibits peculiar sedimentary bodies the analysis of about 250 km of new vhr seismic profiles acquired over the study area 9 short cores and outcrops data allowed us to determine the three dimensional high resolution geometry of the coastal system tracts from quaternary to present day this revealed dominant denudation processes in the upstream catchments associated with the formation of incised valleys during quaternary lowstands in addition this study investigates the erosion and deposition mechanisms controlled by littoral hydrodynamics that have been taken place on this shore since the last transgression in particular metre high and hundreds of metre long sandy bodies constructed by alongshore hydrodynamics were identified and their effect on the morphodynamics of the whole littoral system is discussed the maguelone shore can be used as an experimental study for onshore offshore dynamics under the influence of microtidal wave current hydrodynamics and very low river derived sediment flux during a eustatic cycle geometry of system tracts across flood plain to shoreface is usually considered to be controlled by relative sea level changes and is successfully analysed with 2d sequence stratigraphy cross shore models it is observed that in areas like the maguelone shore traditional sequence stratigraphy methods might not be fully relevant and need to integrate alongshore hydrodynamical processes

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

aeolianite and barrier dune construction spanning the last two glacial interglacial cycles from the southern cape coast south africa the southern cape region of south africa has extensive coastal aeolianites and barrier dunes whilst previously reported limited knowledge of their age has precluded an understanding of their relationship with the climatic and sea level fluctuations that have taken place during the late quaternary sedimentological and geomorphological studies combined with an optical dating programme reveal aeolianite development and barrier dune construction spanning at least the last two glacial interglacial cycles aeolianite deposition has occurred on the southern cape coast at ca 67 80 88 90 104 128 160 189 and 200 ka before the present using this and other published data coupled with a better understanding of late quaternary sea level fluctuations and palaeocoastline configurations it is concluded that these depositional phases appear to be controlled by interglacial and subsequent interstadial sea level high stands these marine transgressions and regressions allowed onshore carbonate rich sediment movement and subsequent aeolian reworking to occur at similar points in the landscape on a number of occasions the lack of carbonates in more recent dunes oxygen isotope stages 1 2 and 4 5 is attributed not to leaching but to changes to carbonate production in the sediment source area caused by increased terrigenous material and or changes in the balance between the warm agulhas and nutrient rich benguela ocean currents

evolution of mid cretaceous radiolarians in response to oceanic anoxic events in the eastern tethys southern tibet china abstract oceanic anoxic events oaes are well known from their widespread black shale and carbon isotopic excursions in the western and eastern tethys and atlantic ocean however the weakest link in the studies of the oaes is biological evolution sedimentological biostratigraphical and geochemical data from albian to coniacian strata in southern tibet recorded turnover events and fluctuations in diversity of the radiolarian fauna within the eastern tethys during oae 1d and oae 2 abundant radiolarian fossils were obtained from the gyabula formation with 93 species from 43 genera identified and assigned to the mid to upper cretaceous acaeniotyle umbilicata archaeospongoprunum tehamaensis crucella cachensis alievium superbum and dictyomitra formosa zones the association of carbon isotopic excursions black shale and radiolarian turnover indicates extensive changes in the ocean climate system nutrients are made increasing available to the marine plankton through submarine volcanic activity and rising sea level which were a likely cause of radiolarian turnover at or near the oaes active submarine tectonism volcanism leads to the expansion of the hypoxic zone and may cause many deeper dwelling forms to become extinct whereas most of the shallower dwelling radiolarians survive radiolarian evolution thus provides a useful record with which to seek understand relationships between climate paleoceanographic processes and plankton evolution

radiolarian diversity patterns in the latest jurassic earliest cretaceous abstract the global diversity patterns of latest jurassic earliest cretaceous tithonian berriasian radiolarian faunas were analyzed based on samples from the european alps oman philippines and antarctica and an extensive literature survey several measures of diversity were applied to faunas from tropical oman mexico pacific subtropical alps california philippines japan and subpolar antarctic peninsula new zealand northern russia localities original diversity patterns are obscured by taxonomic sedimentological and preservational biases qualitative and quantitative corrections of these biases indicated a significant diversity gradient from tropical subtropical to subpolar latitudes but no significant difference between tropical and subtropical assemblages the latitudinal diversity gradient was apparently asymmetrical being steeper in the northern hemisphere than in the southern hemisphere in the southern hemisphere the diversity gradient was similar to the one observed in modern radiolarian sedimentary assemblages considering the more equable climate of the tithonian berriasian it appears unlikely that temperature was the only control of the observed diversity patterns the results substantiate the notion of latitudinal diversity gradients as a time invariant feature of the earth possibly driven by gradients in biome size

the quaternary eolian sequence of madeira stratigraphy chronology and paleoenvironmental interpretation a thick ca 40 m sequence of coastal eolian sediments occurs on a narrow peninsula on the eastern end of the island of madeira located in the eastern atlantic at 33 n latitude the sediments consist of black volcanic sands with or without bioclasts as well as clay units up to 2 m thick a series of inceptisols eutrochrepts and one alfisol a hapludalf are developed in these sediments land snail shells and secondary carbonates in the form of well developed rhizoliths calcretes fissure fills and soil nodules are present in abundance the chronology of the sequence was determined by 14c and u th analyses of land snail shells and secondary carbonates and amino acid epimerization analysis of land snail shells all sediments including the clay units are originally of eolian origin derived from the beach to the south of the deposit but some have been redeposited by colluviation temporal variation in the lithology of the sediments relates to variations in sea level with black sands being deposited during lower sea level stands and clays at the lowest it is suggested that fine marine sediments exposed during low sea level stands may also be the dominant source of silty or clayey units in other coastal eolian deposits in the subtropical atlantic and mediterranean the sequence spans from 200 000 300 000 years ago up to the 20th century sedimentation was discontinuous and often rapid erosional hiatuses are present during the holocene eolian sands started accumulating at 8200 yr b p during a transgressive phase and stopped at 4500 yr b p as sea level approached its present height colluviation increased dramatically following the first human settlement of the island in the 15th century and continued up to the 20th century as dated by amino acid epimerization analysis of land snails earlier periods of colluviation were identified from the age distribution of land snail shells redeposited in younger colluvium paleoenvironmental reconstruction was based mainly on soil and sediment features including rhizolith morphology and land snail faunas but also on stable isotope variations 13c 18o in land snails and secondary carbonates pollen generally not well preserved and phytoliths most of the portion of the middle pleistocene represented in the sequence was characterized by moderately dry conditions in comparison to the late pleistocene and holocene during the last interglacial relatively wet conditions occurred wetter than during the holocene interglacial moderately moist conditions were present during the accumulation of the thick unit dating to ca 80 000 yr b p as sea level fell subsequent to this period conditions appear to have become drier starting ca 50 000 55 000 yr b p conditions were especially wet but prior to the last glacial maximum markedly arid conditions ensued toward the end of the last glacial wet conditions returned and produced the best developed soil preserved in the sequence moderately moist conditions occurred during the early to middle holocene but apparently become slightly drier after 4500 yr b p the impact of human settlement can be seen in the loss of woody vegetation and enhanced gullying and colluviation during the last ca 500 years

assessing subsidence rates and paleo water depths for tahiti reefs using u th chronology of altered corals we present uranium thorium chronology fora 102 m core through a pleistocene reef at tahiti french polynesia sampled during iodp expedition 310 tahiti sea level we employ total and partial dissolution procedures on the older coral samples to investigate the diagenetic overprint of the uranium thorium system although alteration of the u th system cannot be robustly corrected diagenetic trends in the u th data combined with sea level and subsidence constraints for the growth of the corals enables the age of critical samples to be constrained to marine isotope stage 9 we use the ages of the corals together with o based sea level histories to provide maximum constraints on possible paleo water depths these depth constraints are then compared to independent depth estimates based on algal and foraminiferal assemblages microbioerosion patterns and sedimentary facies confirming the accuracy of these paleo water depth estimates we also use the fact that corals could not have grown above sea level to place a maximum constraint on the subsidence rate of tahiti to be 0 39 m ka with the most likely rate being close to the existing minimum estimate of 0 25 m ka

development of palaeozoic mesozoic radiolaria in the northwestern pacific rim abstract investigations of radiolaria allow us to trace the evolutionary trends and rates of these siliceous microorganisms within the northwestern pacific there are several phases or megacycles in the development of radiolarian fauna in northeastern and eastern russia in ascending order these are ordovician silurian devonian carboniferous early permian late permian triassic middle jurassic middle callovian barremian aptian early campanian late campanian early paleocene and late paleocene to recent no evidence has been found for mass extinction at higher taxonomic levels or for instantaneous catastrophic extinction several of the cycles are characterised by increased diversity and morphological specialization immediately prior to extinction recognition of megacycles permits us to hypothesize a close relationship between radiolarian events and palaeoceanographic palaeoclimatic and tectonic changes which took place in the pacific probably a sharp change of palaeohydrography and the opening of the new submarine seaways led to the appearance and radiation of new higher taxa including the order nassellaria in the early mesozoic

evolution of the rhone delta plain in the holocene abstract the delta plain of the rhone shows many sandy beach ridges cropping out at the surface we propose here a radiocarbon chronology for the accumulation of the sedimentary bodies and an interpretation of the morphology of the mouth lobes that they form morphologies of the lobes depend on four principal factors 1 the variation of the relative sea level which constitutes the morphogenic base level 2 the fluvial input volume of water discharge and sedimentary input number and position of the mouths 3 marine dynamics volume and direction of the longshore drift dominant wave direction 4 the accommodation space created by the rise of relative sea level along with the paleobathymetry onto which the lobe will prograde immediately in front of the delta and at sea our conclusions are the main holocene paleo delta lobes of ulmet and saint ferreol were contemporaneous being deposited from 4000 to 2000 yr bp however the fluvial style of their downstream channel meandering for ulmet channel and linear for saint ferreol and the lobe morphologies of both channels are contrasted rounded in the case of ulmet and elongated for saint ferreol the role of the accommodation space is confirmed by two recent drillholes traversing the entire holocene succession which reveal a prior stage of sedimentary filling in the case of the saint ferreol lobe thus limiting the accommodation space and favouring a rapid and pointed progradation of this lobe the decoupling between hydrological activity and progradation of lobe indicates the complexity of mechanisms in the large catchment basin of rhone however the high rate of progradation of saint ferreol lobe after 2900 bp is probably a consequence of the increase of human activity after this date the variation of relative sea level remains an important factor controlling the evolution of the rhone delta after 6000 bp the local stabilization of the relative sea level between 4585 bp and 3520 bp played an important role in the triggering of coastal progradation saint ferreol lobe eastern margin rhone delta

fringing reef growth and morphology a review abstract fringing reefs are generally not simple veneers of coral growth along tropical shorelines extensive research over the past few decades based on radiocarbon dating of holocene reef deposits has indicated that they can develop in a complex variety of ways even though the surface morphology may appear relatively simple the principal factor that appears to determine the growth and morphology of fringing reefs is the available accommodation space sea level fluctuations are important primarily because the sea surface determines the absolute accommodation space for a given reef this means that a reef established during a period of sea level rise will be able to accrete vertically as space is created above it if however the reef establishes at or grows to the sea surface thereby occupying all the available accommodation space it can no longer accrete vertically and begins to build laterally the morphology and chronostratigraphy of a range of holocene fringing reefs are described on the basis of which six fringing reef growth models are identified in model a the fringing reef is established at depth and primarily accretes vertically towards the sea surface reef growth in model b initiates at sea level and due to the lack of vertical accommodation space grows laterally model c has a similar morphology to model b however the reef progrades over a non reefal sediment wedge episodic lateral and vertical growth occurs in model d with a stepwise progradation of the reef front the remaining models are characterised by seaward reef framework behind which unconsolidated sediments accumulate in model e reef crest growth forms a barrier leading to the development of a backreef lagoon model f has a similar morphology to model e except that the reef crest is formed by hurricane rubble accumulation rather than framework accretion and is periodically reworked

the sea level record of the last deglacial in the shinano river incised valley fill echigo plain central japan abstract the echigo plain on the japan sea coast is in a sedimentary basin governed by subsidence controlled by the echigo plain western margin fault zone the glacial incised valley in the echigo plain filled with the sediment discharge of the shinano river as the sea level rose during the last deglacial the incised valley fill allows us to reconstruct the detailed sea level record because the plain is still interseismically subsiding at a rate of about 3 mm yr and the present tidal range along the japan sea coast is less than 0 3 m in this study we reconstructed a centennial scale sea level record for the deglacial period 12 000 9000 cal bp on the basis of the sedimentary facies and 54 radiocarbon dates from a sediment core obtained from the echigo plain near the western margin fault zone in this core the interval from 95 to 55 m below the present sea level consists of floodplain and salt marsh sediments deposited aggradationally during 11 600 9000 cal bp as a result of transgression taking into account the holocene subsidence rate of 2 7 mm yr at the core site the relative sea level rise during the period of core deposition can be divided into the periods of rapid and slow rates sea level rose rapidly 23 mm yr during 11 600 11 100 cal bp followed by a slow rate of sea level rise 2 mm yr during 11 200 10 300 cal bp another period of rapid sea level rise 11 mm yr during 10 500 9400 cal bp was followed by a slow rate of rise 2 mm yr during 9600 9000 cal bp this record of relative sea level rise indicates that the rapid rate of sea level rise during 11 600 11 100 cal bp is consistent with meltwater pulse 1b

new evidence for episodic post glacial sea level rise central great barrier reef australia abstract we present an extensive database of 364 radiocarbon dates from coastal and marine sediments of the central great barrier reef gbr shelf of which 110 are previously unpublished the elevation data have been reduced to a common datum australian height datum ahd and the various sources of error have been assessed using modern lithological and biological relationships with sea level the elements of the radiocarbon database have been converted into sea level indicators the upper bound of the assembled dataset corresponds to a best estimate sea level curve and the full dataset provides a narrow envelope for sea level rise on the gbr shelf for the last 11 12 kyr not including hydro isostatic crustal flexing the envelope is consistent with episodic rise in post glacial sea levels the rising post glacial sea level probably included stillstands or minor falls at ca 45 m ahd at ca 10 5 kyr b p 5 m 7 8 kyr b p 2 m ca 6 kyr b p and 1 7 m 5 5 kyr b p there is evidence for a significant fall in sea level between stillstands at 11 m 8 5 kyr b p and 17 m 8 2 kyr b p stillstand durations apparently ranged between the vertical spread in the derived sea level data is very wide the use of shell material for dating seems unreliable and prone to large and unpredictable errors data from bulk mangrove muds appear reliable for determination of ancient sea level but may at times result in sea level being placed up to 4 m below the true level in situ biogenic carbonates such as preserved oyster beds and coral micro atolls are the most reliable indicators of sea level position while deposits of mangrove mud give a useful first order approximation of ancient sea levels caution should be used in drawing sea level curves from few data points we conclude that the post 11 12 kyr b p relative rise in sea level was episodic on the central gbr continental margin more data are required to define clearly sea level change up to ca 20 m at 9 kyr b p

origins and development of holocene coral reefs a revisited model based on reef boreholes in the seychelles indian ocean until recently concepts of coral reef growth and accumulation have been predominantly based on a darwinian model in this the upwards and outwards growth of a reef core a coral framework takes place over a foreslope consisting of reef talus with the simultaneous filling of the back reef lagoon by reef derived debris the principal adaptations of this pattern relate to the influence of relative changes in sea level and commonly ignore oceanographic factors such as storm frequency and severity boreholes through the outer edge of a fringing reef in the seychelles western indian ocean reveal a record of holocene sediment accumulation first established approximately 8 ka ago faunal and floral associations show that growth of this body began in relatively deep water but that this shallowed to 5 m within 1 ka subsequent accumulation was of keep up style but as the rate of sea level rise slowed shoaling became more frequent and aggradation was limited by reducing accommodation space constructional facies are characterised either by massive corals including leptastrea porites and faviids or by branching corals typically acropora of the danai robusta group coral surfaces may be encrusted by red algae foraminifera and vermetids and are commonly bored by filamentous algae clionids and molluscs however detrital facies are volumetrically dominant and the paucity of a constructional framework requires a re evaluation of models of reef accretion new models relate the geometry of accretion to the interplay between extreme storm events and fairweather hydrodynamic conditions these suggest that a contiguous framework forms in areas of moderate fairweather energy without extreme storm events severe storms destroy the continuity of reef structures and generate increasing volumes of coarse detritus low storm severity coupled with low fairweather hydrodynamic energy may promote the accumulation of fine grained reef derived sediments that inhibit framework growth while ecology reflects year by year sea conditions lithology and structure are controlled by exceptional storms with the effects of changing sea level superimposed

human influence in geomorphology abstract the human influence in geomorphology has a long history and major contributions have for example been made by shaler mcgee gilbert and marsh however in the last two decades concern with global environmental change has brought the role of anthropogeomorphology into sharper focus global warming if it occurs will have important implications for many geomorphological processes and phenomena as a result of the direct effects of warming as a consequence of other related climatic changes e g precipitation change and as a result of climatically moderated changes in major geomorphologically significant variables e g vegetation cover large uncertainties exist with respect to such matters as hydrological response the frequency of tropical cyclones the speed and degree of permafrost degradation the response of glaciers and ice caps the extent of sea level rise the reaction of beaches to rising sea levels and the state of wetlands deltas and coral reefs other human activities may serve to compound the effects of global geomorphological proccesses given the uncertainties of so many of the environmental changes there is a great need to obtain a greater understanding of the rates and mechanisms of landform response geomorphologists need inter alia to establish long term study sites that will generate base line data to monitor the location and rate of change using sequential cartographic and remote sensing materials to determine information on natural background levels and long term trends by means of data gained from cores to gain a more profound understanding of the operation of geomorphological systems particularly with regard to sensitivities and thresholds and to appreciate the consequences of deliberate manipulation of environmental systems by humans

early paleozoic radiolarian biozonation current knowledge of early paleozoic radiolarians permits the recognition of faunal assemblages and zones that constitute a biozonation this new zonation utilizes robust and relatively common easily recognized morphotypes it will facilitate rapid acquisition of previously unavailable age constraints for marine siliceous sedimentary successions in hitherto poorly understood early paleozoic orogenic collages

contrasting holocene sedimentary geologies of lower daly river northern australia and lower sepik ramu papua new guinea abstract the estuarine plain of the macrotidal daly river in monsoonal northern australia is underlain by extensive mid holocene mangrove swamp sediments which accumulated during the last stages of post glacial sea level rise sediment yield from the catchment is too low to account for the volume which accumulated during sea level rise and onshore transport is invoked this is supported by radiocarbon ages and facies analysis of the transgressive sediment tract beneath the maximum flooding surface mfs and of the tract of vertical sedimentation which extends from the mfs to the surface of estuarine fluvial transition the eft the eft occurred about 5000 to 6000 bp throughout the estuarine plain a contrasting situation exists in the lowland holocene basin of the microtidal sepik and ramu rivers in papua new guinea which derive sediment from highly tectonic catchments a tectonic basin which was a shallow brackish inland sea after post glacial transgression is separated by a low divide from a deltaic plain progradation of the deltaic plain commenced about 3500 bp after regressive sedimentation eclipsed the inland sea in the tectonic basin contrasting organic facies mangrove in the daly and freshwater swamp deposits in the sepik ramu highlight differences between facies models of the two systems differences between fluvio tidal regimes are reflected by the eft which is synchronous in the daly and diachronous in the sepik ramu and possibly by the mfs which is diachronous in the daly and may be synchronous in the sepik ramu

calibration of the c 14 timescale over the past 30 000 years using mass spectrometric u th ages from barbados corals uranium thorium ages obtained by mass spectrometry from corals raised off the island of barbados confirm the high precision of this technique over at least the past 30 000 years comparison of the u th ages with 14c ages obtained on the holocene samples shows that the u th ages are accurate because they accord with the dendrochronological calibration before 9 000 yr bp the 14c ages are systematically younger than the u th ages with a maximum difference of 3 500 yr at 20 000 yrbp the u th technique thus provides a way of calibrating the radiocarbon timescale beyond the range of dendrochronological calibration

are catch up reefs an artefact of coring drill cores through modern coral reefs commonly show a time lag in reef initiation followed by a phase of rapid accretion to sea level from submerged foundations the so called catch up response but because of the difficulty of drilling in these environments core distribution is usually restricted to accessible areas that may not fully represent reef history especially if the reef initiated in patches or developed with a prograde or retrograde geometry as a consequence core data have the potential to give a misleading impression of reef development particularly with respect to the timing of initiation and response to sea level rise here we use computer models to simulate keep up reef development and from them quantify variations in the timing of reef initiation and accretion rate using mock cores taken through the completed simulations the results demonstrate that cores consistently underestimate the timing of reef initiation and overestimate the reef accretion rate so that statistically a core through a keep up reef will most likely produce a catch up pattern an initiation lag followed by a phase of rapid accretion to sea level this implies that catch up signatures may be an artefact of coring and that keep up reefs are significantly more common than previous core studies claim

palynomorph evidence for tropical climate stability in the gulf of papua papua new guinea over the latest marine transgression and highstand 14 500 years bp to today abstract three sediment cores mv 41 mv 46 and md 50 from the gulf of papua gop papua new guinea were analyzed to assess changes in climatic oceanographic and sedimentological conditions over the last 14 5 kyr palynomorphs which were isolated from sediment core samples were collected at approximately 0 5 m intervals using a strong acid and oxidant md 50 non oxidant mv 41 mv 46 procedure radiocarbon 14c stable isotope geochronology magnetic susceptibility stable isotope analysis md 50 only oxygen 18 18o and carbon 13 13c and clay mineral maturity analysis were also completed for each core palynological data indicate that climatic conditions at sea level have remained warm wet and stable for the past 14 5 kyr with sea surface temperatures in the gop above 14 c potential decreases in vegetative cover marked the younger dryas interval 12 5 11 5 kyr bp as indicated by reduced pollen and spore recovery the end of the latest marine transgression and the subsequent return to eustatic sea level highstand is clearly delineated by increases in marine palynomorph recovery and decreases in mangrove pollen at approximately 5 kyr bp an increase in seasonality and potential el nino southern oscillation variability is observed in md 50 s oxygen isotope results at 5 kyr bp this is not supported by the palynomorph record likely because of the sampling interval and dilution by tropical pollen flora which indicates stable climatic conditions throughout the last 14 5 kyr sediment transport pathways in the gop remained fairly constant throughout the time interval which is supported by the lack of major changes in palynomorph assemblage composition

paleoshoreline record of relative holocene sea levels on pacific islands abstract understanding the history of relative holocene sea levels on pacific islands is important for constraining fundamental geodynamic theories interpreting the environments of early human occupation sites and forecasting future environmental conditions on the islands an observational paleoshoreline record is provided by emergent paleoshoreline indicators formed at higher relative sea levels hence standing at higher elevations than modern counterparts emergent paleoshoreline notches in limestone seacliffs record paleo high tide levels and emergent paleoreef flats record paleo low tide levels whereas emergent paleobeachrock locally records paleo intertidal levels both paleonotches and paleoreefs occur along the coasts of high standing islands exposing volcanic bedrock and uplifted reef complexes but low lying coralline atolls lack sufficient relief to preserve paleonotches controls on relative holocene sea level include global eustatic and regional hydro isostatic changes in ambient sea level relative to island landmasses and shifts in the elevations of islands relative to sea level caused by thermal subsidence of the oceanic lithosphere or thermally rejuvenated loci of hotspot volcanism by flexure of the lithosphere under the load of growing volcanic edifices hawaii samoa society islands by arching of the lithosphere over trench forebulges loyalty islands niue bellona rennell and by tectonism within forearc belts between active volcanic chains and trenches mariana islands tonga vanuatu the dominant pattern of relative sea level change where not overprinted by local tectonism or lithospheric flexure was a uniform early holocene rise in eustatic sea level followed by a regionally variable late holocene hydro isostatic drawdown in sea level the resultant was a mid holocene highstand in relative sea level that affected the development of shoreline morphology throughout the tropical pacific ocean the earliest human migrations into intra oceanic island groups of both the northwestern and southwestern pacific ocean followed close on the heels of the mid holocene sea level highstand and took advantage of newly attractive coastal environments engendered by sea level drawdown the effects of the mid holocene highstand were modified to varying degrees in different island groups by geodynamic uplift or subsidence

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

relative sea level change in and around the younger dryas inferred from late quaternary incised valley fills along the japan sea abstract the lastdeglacial sea level change is characterized by episodes of rapid sea level rise such as meltwater pulses mwps and periods of slower sea level rise such as the younger dryas yd period however the existence of mwp 1b which occurred right after the yd at around 11 000 cal bp has been debated for the last decade the echigo plain along the japan sea is governed by an active fault along its western margin and the latest pleistocene to holocene sedimentary fills in the buried incised valley of the shinano river comprise intertidal salt marsh sediments aggraded during the last transgression the present tidal range along the japan sea is less than 0 3 m therefore eustatic sea level trends and events such as mwp 1b are detectable from the incised valley fills if the history of subsidence along the fault is constrained in this study the relative sea level change during 13 000 9000 cal bp is reconstructed on the basis of radiocarbon dates and the depth of salt marsh sediments identified in two sediment cores obtained from the echigo plain if it is assumed that the interseismic subsidence rate with sediment compaction effect of 2 6 3 7 mm yr calculated from the age and depth of sediments in the cores was constant during the valley fill deposition five segments of rapid sea level rise and five segments of slow sea level rise during 13 000 9000 cal bp are detectable comparing relative sea level curves corrected for tectonic movements and sediment compaction effects from the echigo plain barbados and tahiti a rapid sea level rise just before the yd and slow sea level rise during the yd are found as common features of the three sites however three episodes of rapid sea level rise at 11 000 10 900 10 600 10 400 and 9900 9700 cal bp are found only for the echigo plain these provide evidence of coseismic subsidence along the fault the rapid sea level rise during 11 400 11 300 cal bp on the echigo plain is consistent with mwp 1b in barbados but it can just as readily be attributed to coseismic subsidence and if mwp 1b is real its magnitude is only less than 4 m in the japan sea

fluctuations in the late quaternary east asian winter monsoon recorded in sediment records of surface water cooling in the northern japan sea the east asian monsoon climate system involves interactions between land and ocean and is composed of summer and winter monsoons cooling of surface water by the east asian winter monsoon eawm promotes the formation of sea ice and deep water in the northern japan sea modern observations suggest close relationships between intensification of the eawm and both sea ice formation and sea surface temperature sst decrease in the northeastern japan sea records of ice rafted debris ird and alkenone based sst in the northeastern japan sea are examined to clarify the temporal variability of the eawm and its controlling factors close relationships with oxygen isotope records of chinese stalagmites and northern hemisphere summer insolation are observed in the records of ird occurrence and sst during marine isotope stages mis 3 5 the co occurrence of maxima in the abundance of ird and minima in sst in the northeastern japan sea indicates that the intensity of the eawm was enhanced during periods of low summer insolation and high oxygen isotope ratios in chinese stalagmites decoupling between the ird and sst records during mis 2 and mis 6 might be the result of differences in surface water conditions caused by low sea levels and the resultant closure of the tsushima strait during mis 3 and 4 some small but clear maxima in ird and minima in sst occurred at relatively low summer insolation periods some of these peaks co occur with north atlantic heinrich events suggesting a possible climate linkage between the north atlantic and the asian monsoon the presence of finer fluctuations in the occurrence of ird than in summer insolation suggests finer millennial centurial timescale fluctuations in the intensity of the eawm furthermore some ird peaks occurred during periods of high insolation such as 39 86 103 128 145 and 153 ka some of these ird peaks correlate with minima in reconstructed sst and maxima in oxygen isotope ratios of chinese stalagmites this result suggests that extremely cold winters occur even during periods of enhanced east asian summer monsoon intensity and indicates that solar insolation is not the only factor that controls variations in the intensity of the eawm at millennial centurial timescales copyright 2012 john wiley sons ltd

rapid sea level fall and deep ocean temperature change since the last interglacial period we have dated huon peninsula papua new guinea and barbados corals that formed at times since the last interglacial period applying both 230 th and 231 pa dating techniques as a test of age accuracy we show that marine isotope stage mis 5e ended prior to 113 1 8 0 7 kyr when sea level was 319 m during mis 5b sea level was 357 m at 92 6 8 0 5 kyr having dropped about 40 m in approximately 10 kyr during the mis 5c 5b transition sea level then rose more than 40 m during the mis 5b 5a transition also in about 10 kyr mis 5a lasted until at least 76 2 8 0 4 kyr at a level of 324 m at that time combined with earlier data that places mis 4 sea level at 381 m at 70 8 kyr our late mis 5a data indicate that sea level fell almost 60 m in less than 6 kyr 10 6 m kyr during the mis 5 4 transition the magnitude of the drop is half that of the glacial interglacial amplitude and approximatelyequivalent to the volume of the present dayantarctic ice sheet during this interval the minimum average rate of net continental ice accumulation was 18 cm yr likely facilitated by efficient moisture transport from lower latitudes at three specific times 60 6 8 0 3 50 8 8 0 3 and 36 8 0 2 kyr during mis 3 sea level was between 385 and 374 m sea level then dropped to 3107 m at 23 7 8 0 1 kyr early in mis 2 before dropping further to last glacial maximum lgm values and then rising to present values during the last deglaciation times of rapid sea level drop correspond to times of high winter insolation at low northern latitudes and high winter latitudinal gradients in northern hemisphere insolation supporting the idea that these factors mayhave resulted in high water vapor pressure in moisture sources and efficient moisture transport to high latitude glaciers therebycontributing to glacial buildup we combined our sea level results with deep sea n 18 o records as a means of estimating the temperature and ice volume components in the marine n 18 o record this analysis confirms large deep ocean temperature shifts following mis 5e and during termination i deep ocean temperatures changed bymuch smaller amounts between mis 5c and 2 maximum temperature shift in the deep pacific is about 2 whereas the shift at a site in the atlantic is 4 under glacial conditions temperatures at both sites are near the freezing point the shift in the atlantic is likelycaused bya combination of changing proportions of northern and southern source waters as well as changing temperature at the sites where these deep waters form

holocene key coral species in the northwest pacific indicators of reef formation and reef ecosystem responses to global climate change and anthropogenic stresses in the near future abstract the geological record of key coral species that contribute to reef formation and maintenance of reef ecosystems is important for understanding the ecosystem response to global scale climate change and anthropogenic stresses in the near future future responses can be predicted from accumulated data on holocene reef species identified in drillcore and from data on raised reef terraces the present study analyzes a dataset based on 27 drillcores raised reef terraces and 134 radiocarbon and u th ages from reefs of the northwest pacific with the aim of examining the role of key coral species in reef growth and maintenance for reef ecosystem during holocene sea level change the results indicate a latitudinal change in key coral species arborescent acropora acropora intermedia and acropora muricata was the dominant reef builder at reef crests in the tropics whereas porites porites australiensis porites lutea and porites lobata was the dominant contributor to reef growth in the subtropics between 10 000 and 7000 cal years bp when the rate of sea level rise was 10 m ka acropora digitifera acropora hyacinthus acropora robusta a abrotanoides isopora palifera favia stelligera and goniastrea retiformis from the corymbose and tabular acropora facies were the main key coral species at reef crests between 7000 and 5000 cal years bp when the rate of sea level rise was 5 m ka and during the following period of stable sea level massive porites p australiensis p lutea and p lobata contributed to reef growth in shallow lagoons during the period of stable sea level key coral species from the corymbose and tabular acropora facies have the potential to build reefs and maintain ecosystems in the near future under a global sea level rise of 2 6 m ka as do key coral species from the arborescent acropora facies and massive porites facies which show vigorous growth and are tolerant to relatively deep water low energy environments however these species are likely to experience severe mortality in upcoming decades due to natural and anthropogenic stresses consequently this damage will lead to a collapse in reef formation and the maintenance of reef ecosystems in the near future this study emphasizes the need for research into the conservation of key coral species

toarcian radiolaria from mt mangart slovenian italian border and their paleoecological implications abstract diverse and well preserved toarcian radiolarians have been recovered from a succession of organic rich shale with intercalations of siliceous limestone the succession is located at the slovenian italian border in the julian alps and was deposited on a subsided block pertaining to the south tethyan passive continental margin twenty spumellarian and 17 nassellarian genera were found in total thirty six taxa were identified to species level and one new species bistarkum mangartense n sp is described the assemblages show a high predominance of spumellarians over nassellarians spongy spumellarians especially orbiculiforma are markedly abundant pantanelliidae are generally rare but reach a pronounced peak of 13 in one stratigraphic level among nassellarians parahsuum is the most abundant but members belonging to syringocapsidae are scarce to absent in addition to paleolatitude and water column depth ecological conditions accompanying the early toarcian global anoxic event may have to a considerable extent determined the specific taxonomic composition of these radiolarian faunas

drowning of the 150 m reef off hawaii a casualty of global meltwater pulse 1a we present evidence that the drowning of the 2150 m coral reef around hawaii was caused by rapid sea level rise associated with meltwater pulse 1a mwp 1a during the last deglaciation new u th and 14 c accelerator mass spectrometry dates combined with reinterpretation of existing radiometric dates constrain the age of the coral reef to 15 2 14 7 ka u th age indicating that reef growth persisted for 4 3 k y following the end of the last glacial maximum at 19 ka the drowning age of the reef is roughly synchronous with the onset of mwp 1a between 14 7 and 14 2 ka dates from coralline algal material range from 14 to 10 cal ka calibrated radiocarbon age 1 4 k y younger than the coral ages a paleoenvironmental reconstruction incorporating all available radiometric dates high resolution bathymetry dive observations and coralgal paleobathymetry data indicates a dramatic rise in sea level around hawaii ca 14 7 ka paleowater depths over the reef crest increased rapidly above a critical depth 30 40 m drowning the shallow reef building porites corals and causing a shift to deep water coralline algal growth preserved as a crust on the drowned reef crest

paleoseismicity of the north branch of the newport inglewood fault zone in huntington beach california from cone penetrometer test data abstract application of cone penetrometer testing cpt is a promising method for studying subsurface fault zones in stratified unconsolidated sediment where trenching is not feasible analysis of data from 72 cpts spaced 7 5 to 30 0 m apart and 9 borings indicates that the north branch fault the active strand of the newport inglewood fault zone nifz in huntington beach has generated at least three and most likely five recognizable surface ruptures in the past 11 7 0 7 ka additional smaller earthquakes similar to the m w 6 4 1933 long beach earthquake may also have occurred but would not be recognizable with this method the minimum right lateral holocene slip rate of the nifz in the study area is estimated to be 0 34 to 0 55 mm yr the actual slip rate may be significantly higher

continuous reef growth during the last 23 cal kyr bp in a tectonically active zone vanuatu southwest pacific abstract at urelapa island vanuatu sea level rise and a tectonic uplift of 3 mm yr 1 have controlled water depth and the colonization and reef development on a substrate from 23 until 6 cal kyr bp analysis of coralgal assemblages offers insights on the mode of reef growth and on water depth over the reef for the studied period those assemblages precisely dated by the 230 th 234 u method give valuable information on the rate and timing of sea level rise since the last glacial maximum the urelapa reef sequences are characterized by upwards replacement of reef frameworks which indicates changes in wave energy through time the sudden acceleration of sea level rise associated with meltwater pulse 1b at around 11 3 cal kyr bp is marked by a change in reef growth strategy from a keep up mode to a catch up mode we examine the delay in timing of the occurrence of suitable substrates the role of paleoceanographic factors and the influence of possible jumps in sea level