deposit from a giant wave on the island of lanai hawaii limestone bearing gravel the newly named hulopoe gravel blankets the coastal slopes on lanai the deposit which reaches a maximum altitude of 326 meters formerly was believed to have been deposited along several different ancient marine strandlines but dated submerged coral reefs and tide gauge measurements indicate that the southeastern hawaiian islands sink so fast that former worldwide high stands of the sea now lie beneath local sea level evidence indicates that the hulopoe gravel and similar deposits on nearby islands were deposited during the pleistocene by a giant wave generated by a submarine landslide on a sea scarp south of lanai

coral ages and island subsidence hilo drill hole a 25 8 m thick sedimentary section containing coral fragments occurs directly below a surface lava flow the 1340 year old panaewa lava flow at the hilo drill hole ten coral samples from this section dated by accelerator mass spectrometry ams radiocarbon and five by thermal infrared multispectral scanner tims 230th u methods show good agreement the calcareous unit is 9790 years old at the bottom and 1690 years old at the top and was deposited in a shallow lagoon behind an actively growing reef this sedimentary unit is underlain by a 34 m thick lava flow which in turn overlies a thin volcaniclastic silt with coral fragments that yield a single 14c date of 10 340 years the age depth relations of the dated samples can be compared with proposed eustatic sea level curves after allowance for island subsidence is taken island subsidence averages 2 2 mm yr for the last 47 years based on measurements from a tide gage near the drill hole or 2 5 2 6 mm yr for the last 500 000 years based on the ages and depths of a series of drowned coral reefs offshore from west hawaii the age depth measurements of coral fragments are more consistent with eustatic sea levels as determined by coral dating at barbados and albrolhos islands than those based on oxygen isotopic data from deep sea cores the panaewa lava flow entered a lagoon underlain by coral debris and covered the drill site with 30 9 m of lava of which 11 m was above sea level this surface has now subsided to 4 2 m above sea level but it demonstrates how a modern lava flow entering hilo bay would not only change the coastline but could extensively modify the offshore shelf

tropical atlantic coral oxygen isotopes glacial interglacial sea surface temperatures and climate change abstract we have generated a detailed oxygen isotope time series from the fossil coral reefs from offshore barbados the barbados coral based record is a unique paleoceanographic data set with an equivalent sedimentation rate in excess of 600 cm kyr where not only is the annual signal uniquely preserved but seasonality as well oxygen isotope values during the late glacial and lgm 16 20 14c kyrs 19 24 calendar kyrs are 2 3 heavier than corresponding living specimens and indicate a regional cooling on the order of 4 5 c there is also an isotopic expression of the bolling pre boreal climate oscillation with values reflecting a cooling during the younger dryas seasonality a key diagnostic of the state of the climate system remained the same or slightly less than present and indicates that the observed coolings were a change in the mean state of the western tropical atlantic pan tropic cooling during the last glaciation is best explained by a change in the radiative balance of the tropics variable tropical sea surface temperatures during climate oscillations such as the younger dryas challenge the paradigm that climate change only cascades from variations in north atlantic deep water production

the morphology and distribution of submerged reefs in the maui nui complex hawaii new insights into their evolution since the early pleistocene reef drowning and backstepping have long been recognised as reef responses to sea level rise on subsiding margins during the late pleistocene 500 14 ka hawaiian reefs grew in response to rapid subsidence and 120 m 100 kyr sea level cycles with recent work on the submerged drowned reefs around the big island of hawaii and in other locations from the last deglacial providing insight into reef development under these conditions in contrast reefs of the early pleistocene 1 8 0 8 ma remain largely unexplored despite developing in response to significantly different 60 70 m 41 kyr sea level cycles the maui nui complex mnc forming the islands of maui molokai lanai and kahoolawe provides a natural laboratory to study reef evolution throughout this time period as recent data indicate the reefs grew from 1 1 to 0 5 ma we use new high resolution bathymetric and backscatter data as well as sub bottom profiling seismic data and field observations from rov and submersible dives to make a detailed analysis of reef morphology and structure around the mnc we focus specifically on the south central region of the complex that provides the best reef exposure and find that the morphology of the reefs varies both regionally and temporally within this region barrier and pinnacle features dominate the steeper margins in the north of the study area whilst broad backstepping of the reefs is observed in the south within the au au channel in the central region between the islands closely spaced reef and karst morphology indicates repeated subaerial exposure we propose that this variation in the morphology and structure of the reefs within the mnc has been controlled by three main factors the subsidence rate of the complex the amplitude and period of eustatic sea level cycles and the slope and continuity of the basement substrate we provide a model of reef development within the mnc over the last 1 2 ma highlighting the effect that the interaction of these factors had on reef morphology

the ancient shorelines of lanai hawaii revisited abstract three ancient shorelines the mahana kaluakapo and manele have been described at elevations of 365 190 and 170 m in the kaluakapo crater lanai hawaii bernice p bishop mus bull 237 1978 1 stearns original observation of a fossil bearing outcrop at 326 m was interpreted as an ancient shoreline subsequently moore and moore 1984 1988 science 226 1984 1312 geol soc am spec pap 229 1988 101 argued that stearns fossil evidence represented the highest inundation of tsunami waves associated with the collapse of the flanks of the hawaiian islands chain the giant wave hypothesis gwh subsequently stearns fossil bearing swale site has never been observed geological field studies of kaluakapo crater were conducted to clarify the nature of the highest coral bearing outcrops preserved on lanai these field studies found no support for a shoreline at 326 m however the field studies did document a shingle terrace with numerous coral clasts at 190 m elevation we find in situ fossil bearing marine deposits at 170 m elevation within kaluakapo crater furthermore we observe the undisturbed nature of marine deposits at 190 m the preservation of fine grained materials at 170 m the absence of in situ deposits with a biological component between 200 and 365 m the dearth of rounded boulders lacking weathering rinds between 200 and 365 m and the lack of post depositional burial of the terrace deposit despite loose debris being present on the high ground surrounding the 190 m terrace these observations lead us to believe that erosion by the hypothesized giant waves did not take place our observations are inconsistent with the giant wave tsunami inundation of the kaluakapo crater area thus we concur with stearns 1938 1978 geol soc am bull 49 1938 615 bernice p bishop mus bull 237 1978 1 jones 1993 jones a t 1993 elevated fossil coral deposits in the hawaiian islands a measure of island uplift in the quaternary phd dissertation department of oceanography university of hawaii 1 274 and grigg and jones 1997 mar geol 141 1997 11 that the coral bearing deposits on lanai represent ancient shorelines and reflect a history of uplift of the island associated with lithospheric deformation of the sea floor around the hawaiian hot spot

magma chamber evolution prior to the campanian ignimbrite and neapolitan yellow tuff eruptions campi flegrei italy the campi flegrei campanian region italy experienced two cataclysmic caldera forming eruptions which produced the campanian ignimbrite 39 ka ci and the neapolitan yellow tuff 15 ka nyt we studied the minor eruptions before both these large events to understand magma chamber evolution leading towards such catastrophic eruptions major trace element and sr and nd isotope compositions of pre campanian ignimbrite and pre neapolitan yellow tuff products define distinct geochemical groups which are here interpreted as distinct magma batches these batches do not show any transitional trend towards the ci and nyt eruptions the ci and nyt systems are decoupled geochemically and isotopically at least one of the pre ci and one of the pre nyt erupted magma batches qualifies as mixing endmembers for the large ci and nyt eruptions and thus must have been stored in reservoirs for some time to remain available for the ci and nyt eruptions the least evolved isotopically distinct magma compositions that are typical of the last phases of the nyt and ci eruptions did not occur before caldera forming events based on the new data we propose the following scenario multiple magma chambers with distinct compositions existed below the campi flegrei before the ci and nyt eruptions and remained generally separated for some time unless new magma was recharged in each case one of the residing magma reservoirs was recharged by a new large volume magma input of intermediate composition from a deeper differentiating magma reservoir this may have triggered the coalescence of the previously separated reservoirs into one large chamber which fed the cataclysmic caldera forming eruption large magma chambers in the campi flegrei may therefore be ephemeral features interrupted by periods of evolution in individual separated magma reservoirs

sea level and reef accretion history of marine oxygen isotope stage 7 and late stage 5 based on age and facies of submerged late pleistocene reefs oahu hawaii abstract in situ pleistocene reefs form a gently sloping nearshore terrace around the island of oahu tims th u ages of in situ corals indicate that most of the terrace is composed of reefal limestones correlating to marine oxygen isotope stage 7 mis 7 190 245 ka the position of the in situ mis 7 reef complex indicates that it formed during periods when local sea level was 9 to 20 m below present sea level its extensiveness and geomorphic prominence as well as a paucity of emergent in situ mis 7 reef framework deposits on oahu suggest that much of mis 7 was characterized by regional sea levels below present later accretion along the seaward front of the terrace occurred during the latter part of mis 5 i e mis 5a 5d 76 113 ka the position of the late mis 5 reefal limestones is consistent with formation during a period when local sea level was below present the extensiveness of the submerged pleistocene reefs around oahu compared to the relative dearth of holocene accretion is due to the fact that pleistocene reefs had both more time and more accommodation space available for accretion than their holocene counterparts

diagenesis and geochemistry of porites corals from papua new guinea implications for paleoclimate reconstruction coral proxy records of sea surface temperature sst and hydrological balance have become important tools in the field of tropical paleoclimatology however coral aragonite is subject to post depositional diagenetic alteration in both the marine and vadose environments to understand the impact of diagenesis on coral climate proxies two mid holocene porites corals from raised reefs on muschu island papua new guinea were analysed for sr ca 18 o and 13 c along transects from 100 aragonite to 100 calcite thin section analysis showed a characteristic vadose zone diagenetic sequence beginning with leaching of primary aragonite and fine calcite overgrowths transitional to calcite void filling and neomorphic fabric selective replacement of the coral skeleton average calcite sr ca and 18 o values were lower than those for coral aragonite decreasing from 0 0088 to 0 0021 and 5 2 to 8 1 respectively the relatively low sr ca of the secondary calcite reflects the sr ca of dissolving phases and the large difference between aragonite and calcite sr ca partition coefficients the decrease in 18 o of calcite relative to coral aragonite is a function of the 18 o of precipitation carbon isotope ratios in secondary calcite are variable though generally lower relative to aragonite ranging from 2 5 to 10 4 the variability of 13 c in secondary calcite reflects the amount of soil co 2 contributing 13 c depleted carbon to the precipitating fluids diagenesis has a greater impact on sr ca than on 18 o the calcite compositions reported here convert to sst anomalies of 115 c and 14 c respectively based on calcite sr ca compositions in this study and in the literature the sensitivity of coral sr ca sst to vadose zone calcite diagenesis is 1 1 to 1 5 c per percent calcite in contrast the rate of change in coral 18 o sst is relatively small 0 2 to 0 2 c per percent calcite we show that large shifts in 18 o reported for mid holocene and last interglacial corals with warmer than present sr ca ssts cannot be caused by calcite diagenesis low level calcite diagenesis can be detected through x ray diffraction techniques thin section analysis and high spatial resolution sampling of the coral skeleton and thus should not impede the production of accurate coral paleoclimate reconstructions copyright 2003 elsevier science ltd

early pleistocene origin of reefs around lanai hawaii a sequence of submerged terraces l1 l12 offshore lanai was previously interpreted as reefal and correlated with a similar series of reef terraces offshore hawaii island whose ages are known to be 500 ka we present bathymetric observational lithologic and 51 87sr 86sr isotopic measurements for the submerged lanai terraces ranging from 300 to 1000 m l3 l12 that indicate that these terraces are drowned reef systems that grew in shallow coral reef to intermediate and deeper fore reef slope settings since the early pleistocene age estimates based on 87sr 86sr isotopic measurements on corals coralline algae echinoids and bulk sediments although lacking the precision not vert similar 0 23 ma to distinguish the age depth relationship and drowning times of individual reefs indicate that the l12 l3 reefs range in age from not vert similar 1 3 0 5 ma and are therefore about 0 5 0 8 ma older than the corresponding reefs around the flanks of hawaii these new age data despite their lack of precision and the influence of later stage submarine diagenesis on some analyzed corals clearly revise the previous correlations between the reefs off lanai and hawaii soon after the end of major shield building not vert similar 1 3 1 2 ma the lanai reefs initiated growth and went through a period of rapid subsidence and reef drowning associated with glacial interglacial cycles similar to that experienced by the hawaii reefs however their early pleistocene initiation means they experienced a longer more complex growth history than their hawaii counterparts

the impact of the mid pleistocene transition on the composition of submerged reefs of the maui nui complex hawaii the submarine reef terraces l1 l12 of the maui nui complex mnc the islands of lanai molokai maui and kahoolawe in hawaii provide a unique opportunity to investigate the impact of climate and sea level change on coral reef growth by examining changes in reef development through the mid pleistocene transition 900 800 ka we present an analysis of the biological and sedimentary composition of the reefs that builds directly on recently published chronological and morphological data we define nine distinct limestone facies and place them in a spatial and stratigraphic context within 12 reef terraces using rov and submersible observations these include oolitic two coral reef two coralline algal nodule algal crust hemi pelagic mud bioclastic and peloidal mud facies these facies characterise environments from high energy shallow water coral reef crests to low energy non reefal deep water settings combining the bottom observations and sedimentary facies data we report a shift in the observed sedimentary facies across the submerged reefs of the mnc from dominant shallow coral reef facies on the deep reefs to coralline algae dominated exposed outcrop morphology on the shallower reefs we argue that this shift is a reflection of the change in period and amplitude of glacioeustatic sea level cycles 41 kyr and 60 70 m to 100 kyr and 120 m during the mid pleistocene transition mpt 800 ka coupled with a slowing in the subsidence rate of the complex the growth of stratigraphically thick coral reef units on the deep pre mpt reefs was due to the rapid subsidence of the substrate and the shorter smaller amplitude sea level cycles allowing re occupation and coral growth on successive cycle low stands longer larger amplitude sea level cycles after the mpt combined with greater vertical stability at this time produced conditions conducive to deep water coralline algae growth which veneered the shallower terraces additionally we compare reef development both within the mnc and between the mnc and hawaii finally we suggest that climatic forcings such as sea surface temperature and oceanographic currents may also have influenced the distribution of coral species within the sample suite e g the disappearance of the acropora genus from the maui nui complex in the middle pleistocene

the alban hills and monti sabatini volcanic products used in ancient roman masonry italy an integrated stratigraphic archaeological environmental and geochemical approach abstract the rocks of alban hills and monti sabatini volcanoes central italy and their associated epiclastic deposits have been extensively used as building material in ancient rome from about viiith century bce to ivth century ce however the identification of the source areas of these rocks is difficult due to the lack of an integrated stratigraphic and geochemical analysis of the relationships between the two volcanic districts and to the alteration affecting the primary products as consequence of weathering and pedogenetic processes here a comprehensive upgraded stratigraphic and geochronological review of the two volcanic districts corroborated by new geochronological data for several eruptive units and altered deposits is presented coupled to a complete geochemical background achieved by means of newly determined major and trace element analyses for all the main eruptive units a study of the alteration processes of the primary products is also presented and the age of the main weathering and pedogenetic phases associated to quaternary climatic changes are also investigated the results are integrated with those from literature in order to construct discriminant diagrams based on selected trace elements and allow us to characterize the primary and altered volcanic deposits in the rome area distinguish products of different volcanic districts discuss the effects of different weathering processes on the mobility of some elements and provide a reference frame for the provenance of the volcanic materials employed in ancient roman masonry the interdisciplinary data set and results presented here provide groundwork for volcanological climate pedological and archaeological provenance studies

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

genesis of zeolites in the neapolitan yellow tuff geological volcanological and mineralogical evidence the study proposes a model by which a thick succession of volcanic tuffs can be zeolitized by alteration of pyroclastic material in the presence of sufficient eruptive water and at temperatures close to water vapour condensation in the case of phreatomagmatic products the model simplifies interpretation of problematic deposits that exhibit pronounced vertical and lateral variation in lithification grade a major feature of the model is that thick zeolitized tuffs can be formed during emplacement of pyroclastic products in marked contrast to later alteration in an open hydrologic system geological volcanological and mineralogical data for the neapolitan yellow tuff a widespread trachytic pyroclastic deposit outcropping around campi flegrei southern italy have been used to infer the physico chemical conditions that determined mineral genesis this tuff shows a reduction in lithification grade towards the base top and with distance from the vent and very variable zeolitization within the lithified portion we suggest that during initial emplacement the erupted products chilled against the ground inhibiting zeolite crystallization during rapid deposition of the thick wet succession thermal insulation allowed the persistence of elevated temperatures for a time sufficient for enhancement of hydration dissolution processes in the volcanic glass the highly reactive alkali trachytic glass quickly buffered the acid ph of the system favouring phillipsite crystallization followed by chabazite nucleation the variable zeolite content reflects fluctuating emplacement conditions e g changes in water content and temperature cooling of the upper and relatively thin distal deposits inhibited the zeolitization process thereby preserving the primary unlithified deposit

age of tilted reefs hawaii submerged carbonate reefs are preserved as a series of submarine terraces between molokai and hawaii along a 200 km span of the southeastern hawaiian ridge limestones from two of the terraces have been sampled from submersibles and dated radiometrically at 13 and 120 ka recognition that the terraces are tilted permits assignment of about a dozen terraces from 150 to 1300 m depth to eight general reef platforms these reefs were drowned by the combined effects of island subsidence and sea level rise at the end of successive glacial stages from 13 to 647 ka the platforms are tilted 5 m km southeast toward the locus of volcanic loading centered on the island of hawaii the end of the active period of volcanic shield building is represented on each nonactive volcano by a submerged change in slope dating of this slope change by reference to the dated reefs provides independent evidence that shield building ended at about the same time that the volcano changed from eruption of tholeiitic to alkalic basalt the variation in depth of the dated tilted reefs along the ridge indicates that the end of subsidence follows the end of shield building by about one half million years the present northwest margin of major subsidence probably crosses southeast maui during the last half million years the rate of southeast migration of the beginning of both subsidence and of tholeiitic volcanism does not appear to have increased however the rate of southeast migration of the end of both subsidence and of tholeiitic volcanism has apparently increased this shortening of the life history of the younger volcanoes implies an increase in eruption rates

strontium isotope stratigraphy of enewetak atoll sup 87 sr sup 86 sr ratios determined for samples from a 350 m core of neogene lagoonal shallow water limestones from enewetak atoll display a remarkably informative trend like the recently published data for deep sea drilling project dsdp carbonates sup 87 sr sup 86 sr at enewetak increases monotonically but not smoothly from the early miocene to the pleistocene the data show intervals of little or no change in sup 87 sr sup 86 sr punctuated by sharp transitions to lower values toward greater core depths the sharp transitions correlate with observed solution disconformities caused by periods of subaerial erosion whereas the intervals of little or no change in sup 87 sr sup 86 sr correspond to intervals of rapid accumulation of shallow water carbonate sediments when converted to numerical ages using the published dsdp 590b trend the best resolved time breaks are at 282 m 12 3 to 18 2 ma missing and 121 6 m 3 0 to 5 3 ma missing below the lagoon floor at enewetak sr isotopes offer a stratigraphic resolution for these shallow marine neogene carbonates comparable to that of nannofossil zonation in deep sea carbonates 0 3 3 m y in addition the correlation of times of sr isotope breaks at enewetak with times of rapid sr isotope change in the dsdp 590b samples confirms the importance ofmore sea level changes in the evolution of global marine sr isotopes and shows that the sr isotope response to sea level falls is rapid less

geochemical and b sr nd isotopic evidence for mingling and mixing processes in the magmatic system that fed the astroni volcano 4 1 3 8 ka within the campi flegrei caldera southern italy abstract the astroni volcano was built through seven eruptions that generated pyroclastic deposits and lava domes within the campi flegrei caldera southern italy 4 1 3 8 ka bp whole rock geochemical and b sr nd isotopic investigations were carried out on representative samples of all seven eruptions the products vary from tephriphonolites to phonolites and from latites to trachytes they show textural mineralogical and isotopic evidence of disequilibrium including distinct clinopyroxene populations rounded and or resorbed plagioclase and alkali feldspar and reverse zoned phenocrysts of all these mineral phases the sr nd and b isotopic composition of whole rocks is variable and correlated with the degree of chemical evolution suggesting open system processes in addition to fractional crystallisation moreover significant sr isotopic disequilibrium between the phenocrysts and glass has been documented for one sample the chemostratigraphy of the products indicates that astroni eruptions 1 through 5 were fed by magmas of trachytic to phonolitic composition that were less enriched in radiogenic sr and 11b up section this variability has been interpreted as the result of mingling between at least two distinct magmatic end members one more evolved and the other less evolved another heterogeneous batch of magma resulting from almost complete mixing between the same two end members was drained during eruptions 6 and 7 the more evolved end member characterised by 87sr 86sr 0 7075 143nd 144nd 0 51247 and 11b 8 was very similar to the magma that fed the final phases of the agnano monte spina eruption which occurred a few centuries earlier in the astroni vent area the less evolved end member had 87sr 86sr 0 70726 143nd 144nd 0 51251 and 11b 10 and was likely derived by fractional crystallisation of a mantle derived magma an abrupt decrease in both the sr isotope ratio and the th content detected at the transition between unit 4 and 5 suggests that another magma with a 87sr 86sr ratio intermediate between those of the two identified end members may have been involved in astroni activity the more evolved end member is interpreted as a residue of the agnano monte spina eruption that was invaded by either the intermediate or the less evolved magmatic end member promoting mingling and triggering astroni activity this study of astroni provides insights for both short and long term volcanic hazard assessment as the astroni volcano is the best example of a very close sequence of eruptions from the same vent area in the campi flegrei caldera

signatures of the 3 day wave in the low latitude and midlatitude ionosphere during the january 2010 ursi world day campaign 1 recent studies of the equatorial ionosphere have found evidence of forcing by atmospheric ultra fast kelvin ufk waves this study investigates the quasi 3 day ufk wave and its effects on the variations of the ionosphere at low latitudes and midlatitudes using coordinated observations of both the atmosphere and ionosphere during the january 2010 ursi world day campaign the global maps of tec from the igs ground based gps product demonstrate a 3 day periodic variation during january 15 25 this variation has the largest amplitude at 15 magnetic latitude and extends into lower latitudes simultaneously a 3 day wave is observed in the mesosphere in the zonal wind measurements by a meteor radar at the magnetic equator the latitudinal range of the tec variation 20 s 20 n is also consistent with that of the 3 day wave the incoherent scatter radar isr observations show a 3 day signature in vertical ion drifts over jicamarca 11 9 s 76 w and in the electron densities in the top side of ionosphere measured from millstone hill 42 6 n 71 5 w this signature is consistent with the fountain effect in the equatorial region and shows the impact on the topside ionosphere at midlatitudes the ufk wave is trapped within 30 geographic latitude but this study shows that the effects of the wave could reach the ionosphere at the higher latitude even as high as 40 n 50 n magnetic latitude

unlocking the secrets of al tobermorite in roman seawater concrete ancient roman syntheses of al tobermorite in a 2000 year old concrete block submerged in the bay of pozzuoli baianus sinus near naples have unique aluminum rich and silica poor compositions relative to hydrothermal geological occurrences in relict lime clasts the crystals have calcium contents that are similar to ideal tobermorite 33 to 35 wt but the low silica contents 39 to 40 wt reflect al 3 substitution for si 4 in q 2 1al q 3 1al and q 3 2 al tetrahedral chain and branching sites the al tobermorite has a double silicate chain structure with long chain lengths in the b 020 crystallographic direction and wide interlayer spacing 11 49 a na and k partially balance al 3 substitution for si 4 poorly crystalline calcium aluminum silicate hydrate c a s h cementitious binder in the dissolved perimeter of relict lime clasts has ca si al 0 79 nearly identical to the al tobermorite but nanoscale heterogeneities with aluminum in both tetrahedral and octahedral coordination the concrete is about 45 vol glassy zeolitic tuff and 55 vol hydrated lime volcanic ash mortar lime formed 10 wt of the mix trace element studies confirm that the pyroclastic rock comes from flegrean fields volcanic district as described in ancient roman texts an adiabatic thermal model of the 10 m 2 by 5 7 m thick baianus sinus breakwater from heat evolved through hydration of lime and formation of c a s h suggests maximum temperatures of 85 to 97 c cooling to seawater temperatures occurred in two years these elevated temperatures and the mineralizing effects of seawater and alkali and alumina rich volcanic ash appear to be critical to al tobermorite crystallization the long term stability of the al tobermorite provides a valuable context to improve future syntheses in innovative concretes with advanced properties using volcanic pozzolans

drowned coralline algal dominated deposits off lanai hawaii carbonate accretion and vertical tectonics over the last 30 ka we present detailed bathymetry remotely operated vehicle rov and submersible observations and sedimentary and radiocarbon age data from carbonate deposits recovered from two submerged terraces at 150 m t1 and 230 m t2 off lanai hawaii the tops of the terraces are veneered by relatively thin b5 m in situ accumulations of coralline algal nodule coralgal nodule halimeda and a derived oolitic facies deposited in intermediate 30 60 m to deep fore reef slope settings 60 120 m the data are used to develop a sedimentary facies model that is consistent with eustatic sea level variations over the last 30 ka both nodule facies on t1 and t2 initiated growth 30 29 ka following a fall in sea level of 50 m and increase in bottom currents during the transition from marine isotope stage 3 to 2 the nodules accreted slowly throughout the last glacial maximum when sea level was relatively stable drowning occurred during the early deglaciation 17 16 ka and was marked by the complete drowning of coralline algal nodules facies on t2 and incipient drowning of coralgal facies on t1 abrupt sea level rise during the middle deglaciation perhaps associated with global meltwater pulse 1a 14 15 ka finally drowned the coralgal facies on t1 which in turn was overlain by a deep water halimeda facies or an oolitic facies derived from upslope our data indicates that lanai has experienced relatively little vertical tectonic movement over the last 30 ka using paleobathymetric data derived from the sedimentary facies age vs depth relationships and published sea level curves we estimate that lanai could be either slowly uplifting or subsiding but at rates b0 1 m kyr uplift or b0 4 m kyr subsidence over this 30 kyr period d 2005 elsevier b v all rights reserved

marine and meteoric diagenesis of pleistocene carbonates from a nearshore submarine terrace oahu hawaii abstract the nearshore slope of oahu consists of a shallowly dipping shelf extending from the shoreline out to the 20 m contour where there is a sharp break in slope down to 30 m limestones recovered in a series of short cores taken from this nearshore terrace are typical of shallow marine reef environments and comprise either a branching coral or massive coral facies the composition as well as shoreward zonation of facies suggests that the terrace represents an in situ fossil reef complex th u ages of in situ corals are all pleistocene and suggest that the bulk of the feature formed during marine oxygen isotope stage 7 later accretion along the seaward front of the terrace occurred during marine oxygen isotope substages 5a and or 5c deposition during these interglacial highstands has not previously been documented in the sea level record on oahu although the diagenetic record in the cored samples is incomplete three periods of diagenesis are identified early shallow marine meteoric and post meteoric shallow marine early shallow marine diagenesis includes cementation by aragonite and mg calcite in an active marine phreatic zone and predominantly micritization in a stagnant marine phreatic zone meteoric processes occurred in the vadose zone and include precipitation of calcite needle fibers meniscus cements micritic networks neomorphism and dissolution all limestones are now in an active marine phreatic zone evidence of post meteoric shallow marine diagenesis is found in last generation mg calcite cements and internal sediments occurring directly on limestone substrates that have otherwise been stabilized to calcite the present seafloor is undergoing extensive biological and physical erosion no holocene limestones were recovered petrographic and geochemical signatures of subaerial exposure and meteoric diagenesis are recognized within the upper several centimeters of all cores thus the present seafloor in the study area is a flooded pleistocene subaerial exposure surface

deleterious reactions of aggregate with alkalis in concrete concrete in the built environment the word concrete is derived from the latin concretus compact condensed representing a conjunction of con together and the past participle of cresco to grow compare crescendo thus concrete could be liberally translated as grown solid together alluding to the consolidation of a particulate aggregate material with a cement binder of some sort concrete containing aggregate has been used in construction by the ancient greek and romans possibly as a further development of clay initially used by the assyrians and babylonians as a binder later superseded by burnt lime and gypsum by the egyptians as a construction material concrete allows architects and engineers to design a structure with only minimal constraints to its form a complicated shape requiring great effort to chisel out from a piece of stone can simply be poured in a mold and reproduced as often as desired also ex situ both the invention of ordinary portland cement opc first patented by british bricklayer joseph aspdin in 1824 and of reinforced concrete first patented by parisian gardener joseph monier in 1867 for making durable flower pots contributed to the development of mechanically stronger concrete allowing yet slimmer and taller structures to be built today concrete is the most popular building and construction material with an annual production volume exceeding 7 5 km3 or about 20 billion tonne concrete is the prime ingredient in the world s largest and most prominent structures and landmark edifices including hydropower dams e g three gorges dam yichang cn also see charlwood and solymar 1995 coastal defense works e g delta works nl telecommunication e g cn tower toronto ca office skyscrapers e g burj khalifa dubai uae theatres e g opera house sydney au hotels and casinos e g marina bay area singapore sg nuclear power plants oil and gas drilling and productions rigs e g sakhalin ru sea ports and harbors e g

mega tsunami conglomerates and flank collapses of ocean island volcanoes abstract marine conglomerates at high elevation on the flanks of ocean islands are usually interpreted as evidence of mega tsunamis generated by volcano flank collapses although their origin is sometimes debated elevated littorals vs tsunami in this review we introduce case studies of well documented examples of tsunami conglomerates in hawaii pacific ocean the canary and cape verde islands atlantic ocean and mauritius island indian ocean other less documented marine conglomerates are also presented as tsunami candidates then we build a comprehensive picture of the general characteristics of these conglomerates and the different methods that can be applied to date them different perspectives of research are proposed especially on the use of tsunami conglomerates as proxies for better constraining numerical models of ocean island flank collapses and associated tsunamis we also discuss the possible links between volcano growth flank instability and climate

uplift caused by lithospheric flexure in the hawaiian archipelago as revealed by elevated coral deposits the presence of definitive indicators of sea level such as corals found in growth position coralline beach deposits wave cut notches and wave eroded terraces all at elevations above known levels of eustatic sea level during the past 500 ka provides strong evidence that uplift has occurred in the central high hawaiian islands lithospheric flexure is proposed as the mechanism for uplift the modelled wavelength and amplitude of flexure roughly correspond to the distance and height of elevated coral rich deposits a trend of increasing age of coralline beach deposits with elevation on oahu and molokai adds support to the uplift hypothesis data and observations presented in this paper are inconsistent with a tsunami origin for most elevated deposits on lanai molokai and oahu a giant wave origin may only apply to scattered and localized deposits concentrated in low lying gulches 100 m such as those on lanai

the averno 2 fissure eruption a recent small size explosive event at the campi flegrei caldera italy the averno 2 eruption 3 700 50 a b p was an explosive low magnitude event characterized by magmatic and phreatomagmatic explosions generating mainly fall and surge beds respectively it occurred in the western sector of the campi flegrei caldera campanian region south italy at the intersection of two active fault systems oriented ne and nw the morphologically complex crater area largely filled by the averno lake resulted from vent activation and migration along the ne trending fault system the eruption generated a complex sequence of pyroclastic deposits including pumice fall deposits in the lower portion and prevailing surge beds in the intermediate upper portion the pyroclastic sequence has been studied through stratigraphical morphostructural and petrological investigations and subdivided into three members named a through c member a was emplaced during the first phase of the eruption mainly by magmatic explosions which generated columns reaching a maximum height of 10 km during this phase the eruption reached its climax with a mass discharge rate of 3 2 106 kg s intense fracturing and fault activation favored entry of a significant amount of water into the system which produced explosions driven by variably efficient water magma interaction these explosions generated wet to dry surge deposits that emplaced member b and c respectively isopachs and isopleths maps as well as areal distribution of ballistic fragments and facies variation of surge deposits allow definition of four vents that opened along a ne oriented 2 km long fissure the total volume of magma extruded during the eruption has been estimated at about 0 07 km3 dre the erupted products range in composition from initial weakly peralkaline alkali trachyte to last emplaced alkali trachyte isotopic data and modeling suggest that mixing occurred during the averno 2 eruption between a more evolved less radiogenic stored magma and a less evolved more radiogenic magma that entered the shallow reservoir to trigger the eruption the early phases of the eruption during which the vent migrated from sw to the center of the present lake were fed by the more evolved uppermost magma while the following phases extruded the less evolved lowermost magma integration of the geological and petrological results suggests that the averno 2 complex eruption was fed from a dyke shaped shallow reservoir intruded into the ne sw fault system bordering to the west the la starza resurgent block within the caldera floor

crustal subsidence rate off hawaii determined from 234u 238u ages of drowned coral reefs a series of submerged coral reefs off northwestern hawaii was formed during largely glacial intervals when the rate of local sea level rise was less than the maximum upward growth rate of the reefs mass spectrometric sup 234 u sup 238 u ages for samples from six such reefs range from 17 to 475 ka and indicate that this part of the hawaiian ridge has been subsiding at a roughly uniform rate of 2 6 mm yr for the past 475 ka the sup 234 u sup 238 u ages are in general agreement with model ages of reef drowning based on estimates of paleo sea level stands derived from oxygen isotope ratios of deep sea sediments but there are disagreements in detail the high attainable precision plus minus 10 ka or better on samples younger than approximately 800 ka large applicable age range relative robustness against open system behavior and ease of analysis for this technique hold great promise for future applications of dating of 50 1 000 ka coral

petro chemical features and source areas of volcanic aggregates used in ancient roman maritime concretes abstract we present and discuss data from petrographic observation at the optical microscope electron microprobe analyses on selected glass shards and trace element analyses on 14 mortar aggregates collected at the ancient harbors and other maritime structures of latium and campania spanning the third century bce through the second ce aimed at identify the volcanic products employed in the concretes and their area of exploitation according to latin author vitruvius assertion about the ubiquitous use of campanian pozzolan in the ancient roman sea water concretes results of this study show a very selective and homogeneous choice in the material employed to produce the concretes for the different investigated maritime structures evidencing three main pumice compositions all corresponding to those of the products of the post neapolitan yellow tuff activity of the phlegraean fields and a systematic use of the local neapolitan yellow tuff to produce the coarse aggregate of these concretes however mixing with local products of the colli albani volcanic district located 20 km east of rome has been evidenced at two fishponds of latium in punta della vipera and torre astura based on these petrographic and geochemical data we conclude that the selective use of pozzolan from campania rather than of unproved different chemical properties was the consequence of a series of logistic economic industrial and historical reasons

assessment of material characteristics of ancient concretes grande aula markets of trajan rome abstract the grande aula or great hall of the markets of trajan ad 96 to 115 is an intact example of the domed concrete architecture of imperial rome petrographic x ray diffraction chemical and sem analyses demonstrate that wall mortars contain pozzolane rosse volcanic ash aggregate harenae fossiciae and stratlingite a complex calcium aluminate cement hydrate c 2 ash 8 that gives modern cements good durability and compressive strength specific gravity tests and a new petrographic method for assessing bulk densities indicate unit weights of about 1750 kg m 3 for the wall mortars and 1430 1640 kg m 3 for the pumice bearing vaulted ceiling mortars innovative point load source tests record the tensile strengths f t of the aggregate and interfacial elements of the conglomeratic concrete fabric these suggest f t of about 2 7 mpa for brick 1 2 mpa for tufo lionato tuff and 0 9 mpa for tufo giallo della via tiberina tuff coarse aggregate caementa based on a tentative approximate correlation with splitting brazilian tests the pozzolanic mortar and interfacial zones have lower f t in the range of 0 8 mpa to 0 5 mpa the relatively low mortar strength and its somewhat tenuous adhesion to the coarse aggregate suggests that the caementa may have arrested the propagation of tensile microcracks that formed in the mortar thereby increasing the composite tensile strength of the concrete roman builders selected the complex aggregate mixes to optimize the performance of the wall and vault concretes

postglacial sediment deposition along a mixed carbonate siliciclastic margin new constraints from the drowned shelf edge reefs of the great barrier reef australia a seismic stratigraphy analysis was conducted at two sites hydrographers and noggin passages separated by about 540 km on the shelf edge of the central great barrier reef gbr australia we used recently available seismic and bathymetry data and a new synthesis of downhole logs and lithological petrophysical and radiometric data from cores recovered by the integrated ocean drilling program expedition 325 great barrier reef environmental changes we compared the stratigraphy of both sites identifying a full depositional sequence with deposits from at least 28 ka bp to 7 ka bp bounded by two marine flooding surfaces within this sequence each systems tract is represented by unique depositional features characteristic of the shelf edge systems despite the broad environmental and geomorphic similarities between the two sites differences in postglacial reef development were remarkable these contrasts can be explained as a result of 1 local antecedent substrate variations and 2 the interplay of shelf physiography with late quaternary sea level fluctuations which favoured changes in biological production and sediment flux as the palaeo shoreline evolved from linear to complex during intermediate sea levels during these intermediate sea levels the northern estuarine coast and its steep substrate at shelf edge locations contrasted strongly with the protected palaeo lagoons and the extensive gentle marginal terraces found at the southern central gbr this setting enhanced the regional differences in sediment transport and reef development through the last transgression the conceptual model presented here provides a broader depositional framework and improves the understanding of the main processes controlling the spatial and temporal depositional patterns on the shelf edge of mixed siliciclastic carbonate margins

age of 360 m reef terrace hawaii and the rate of late pleistocene subsidence of the island observations from a manned submersible vehicle indicate that the 360 m reef terrace northwest of the island of hawaii is a drowned coral reef the preferred uranium series age of coralline algae collected from the reef face is 120 5 ka this age agrees with the notion that the reef was drowned during the sea level rise following the major lowstand of the sea that occurred at 145 ka oxygen isotope stage 6 this drowning pattern is similar to the previously determined radiocarbon age of 13 ka for drowning of the 150 m reef off west hawaii which drowned during the sea level rise following the last major lowstand of the sea at 18 ka oxygen isotope stage 2 estimated average subsidence of the reef site off northwest hawaii is 2 7 mm yr since final drowning of the 360 m reef

palaeoenvironmental records from fossil corals the effects of submarine diagenesis on temperature and climate estimates the geochemistry of coral skeletons may reflect seawater conditions at the time of deposition and the analysis of fossil skeletons offers a method to reconstruct past climate however the precipitation of cements in the primary coral skeleton during diagenesis may significantly affect bulk skeletal geochemistry we used secondary ion mass spectrometry sims to measure sr mg b u and ba concentrations in primary coral aragonite and aragonite and calcite cements in fossil porites corals from submerged reefs around the hawaiian islands cement and primary coral geochemistry were significantly different in all corals we estimate the effects of cement inclusion on climate estimates from drilled coral samples which combine cements and primary coral aragonite secondary 1 calcite or not vert similar2 aragonite cement contamination significantly affects sr ca sst estimates by 1 c and 0 4 to 0 9 c respectively cement inclusion also significantly affects mg ca b ca and u ca sst estimates in some corals x ray diffraction xrd will not detect secondary aragonite cements and significant calcite contamination may be below the limit of detection not vert similar1 of the technique thorough petrographic examination of fossils is therefore essential to confirm that they are pristine before bulk drilled samples are analysed to confirm that the geochemistry of the original coral structures is not affected by the precipitation of cements in adjacent pore spaces we analysed the primary coral aragonite in cemented and uncemented areas of the skeleton sr ca b ca and u ca of primary coral aragonite is not affected by the presence of cements in adjacent interskeletal pore spaces i e the coral structures maintain their original composition and selective sims analysis of these structures offers a route to the reconstruction of accurate ssts from altered coral skeletons however mg ca and ba ca of primary coral aragonite are significantly higher in parts of skeletons infilled with high mg calcite cement we hypothesise this reflects cement infilling of intraskeletal pore spaces in the primary coral structure

hydrothermal minerals and alteration rates at surtsey volcano iceland the volcanic island surtsey off the south coast of iceland was created by volcanic activity in 1963 1967 core from a 181 m deep hole extending 123 m below sea level shows the results of 12 yr of hydrothermal alteration of basaltic tephra the primary cause of heating of the tephra and of development of the hydrothermal system was the intrusion of dikes below sea level at present the hottest part of the hole at a maximum temperature of 150 c is cooling at 0 9 c per year palagonitization of sideromelane glass a dominant constituent of the tephra is an important alteration process that is strongly temperature dependent the rate doubling for every 12 c increase at 60 c 90 is palagonitized above 120 c olivine crystals are replaced on their edges by nontronite the thickness of clay doubles for each 8 c increase ten hydrothermal minerals have crystallized in the tephra at 25 to 150 c the dominant species are smectite nontronite analcite phillipsite and tobermorite the primary clay species of palagonite is probably nontronite other minerals are halite opal calcite chabazite xonotlite anhydrite and gypsum no major differences in mineral occurrence are noted above and below sea level but phillipsite and tobermorite tend to grow larger below sea level even at the same temperature analcite appears at lower temperature 55 c above sea level than below sea level 75 c anhydrite is most abundant deep in the hole where inflowing cool sea water precipitated sulfate due to reduced sulfate solubility at higher temperatures

safe long term immobilization of heavy metals looking at natural rocks portland cement clinker is primarily used in building and construction with a global annual production of 4 billion tonnes part of it is also used for immobilization of hazardous materials e g industrial slurries harbor bottom sludge shredded tires notably those containing toxic metals like e g zinc cadmium barium trezza and scian 2000 limited amounts may be added to the raw meal and get incorporated into the clinker minerals upon burning taylor 1997 assuming they remain immobilized in the high ph concrete or mortar environment after hydration and setting of the cement extensive laboratory tests seem to confirm effective mobilization but are generally of limited duration for reason of practicality access to sample materials from centennia or millennia old structures is limited for reasons of cultural heritage preservation and none of these structures were originally designed for environmental reasons the paper by khoury et al 2016 analyzes uncommon combustion metamorphic rocks from jordan closely resembling cement immobilized waste exposed to supergene weathering and alteration over time spans far exceeding experimental practicality

megatsunami deposits on kohala volcano hawaii from flank collapse of mauna loa the origin of coastal and high elevation marine gravels on the hawaiian islands of lanai and molokai is controversial because the vertical tectonics of these islands is poorly constrained the gravels are either from eustatic highstands or were left by massive tsunamis from offshore giant landslides in contrast at kohala on the island of hawaii where continuous subsidence is well established lithofacies analysis and dating of a fossiliferous marine conglomerate 1 5 61 m above present sea level support a tsunami origin and indicate a runup of 400 m 6 km inland the conglomerate age 110 10 ka suggests a tsunami caused by the ca 120 ka giant alika 2 landslide from nearby mauna loa volcano

coral reef response to quaternary sea level and environmental changes state of the science there is considerable uncertainty about future sea level projections due to the current poor understanding of the vulnerability and sensitivity of ice sheets to global warming fossil coral reefs represent a unique archive of sea level and associated environmental changes that extend far beyond instrumental records here recent advances in this field are summarized focusing on periods of earth history typified by rapid sea level rise and short term climate excursions sea level and reef response records from the last deglaciation and periods characterized by higher sea level stands and short term and low magnitude sea level oscillations such as the mid to late holocene and the last interglacial are synthesised special emphasis is given to understanding how coral reefs have responded to these changes in terms of reef development architecture and composition finally seven major challenges and future research directions are identified

phillipsite and al tobermorite mineral cements produced through low temperature water rock reactions in roman marine concrete author s jackson md mulcahy sr chen h li y li q cappelletti p wenk hr abstract 2017 by walter de gruyter berlin boston pozzolanic reaction of volcanic ash with hydrated lime is thought to dominate the cementing fabric and durability of 2000 year old roman harbor concrete pliny the elder however in first century ce emphasized rock like cementitious processes involving volcanic ash pulvis that as soon as it comes into contact with the waves of the sea and is submerged becomes a single stone mass fierem unum lapidem impregnable to the waves and every day stronger naturalis historia 35 166 pozzolanic crystallization of al tobermorite a rare hydrothermal calcium silicate hydrate mineral with cation exchange capabilities has been previously recognized in relict lime clasts of the concrete synchrotron based x ray microdiffraction maps of cementitious microstructures in baianus sinus and portus neronis submarine breakwaters and a portus cosanus subaerial pier now reveal that al tobermorite also occurs in the leached perimeters of feldspar fragments zeolitized pumice vesicles and in situ phillipsite fabrics in relict pores production of alkaline pore fluids through dissolution precipitation cation exchange and or carbonation reactions with campi flegrei ash components similar to processes in altered trachytic and basaltic tuffs created multiple pathways to post pozzolanic phillipsite and al tobermorite crystallization at ambient seawater and surface temperatures long term chemical resilience of the concrete evidently relied on water rock interactions as pliny the elder inferred raman spectroscopic analyses of baianus sinus al tobermorite in diverse microstructural environments indicate a cross linked structure with al3 substitution for si4 in q3 tetrahedral sites and suggest coupled al3 na substitution and potential for cation exchange the mineral fabrics provide a geoarchaeological prototype for developing cementitious processes through low temperature rock fluid interactions subsequent to an initial phase of reaction with lime that defines the activity of natural pozzolans these processes have relevance to carbonation reactions in storage reservoirs for co2 in pyroclastic rocks production of alkali activated mineral cements in maritime concretes and regenerative cementitious resilience in waste encapsulations using natural volcanic pozzolans

the 40ar 39ar dating of core recovered by the hawaii scientific drilling project phase 2 hilo hawaii 1 the hawaii scientific drilling project phase 2 hsdp 2 recovered core from a 3 1 km thick section through the eastern flanks of mauna loa and mauna kea volcanoes we report results of 40ar 39ar incremental heating by broad beam infrared laser of 16 basaltic groundmass samples and 1 plagioclase separate mostly from k poor tholeiites the tholeiites generally have mean radiogenic 40ar enrichments of 1 3 and some contain excess 40ar however isochron ages of glass poor samples preserve stratigraphic order in all cases a 246 m thick sequence of mauna loa tholeiitic lavas yields an isochron age of 122 86 kyr all errors 2 at its base beneath the mauna loa overlap sequence lie mauna kea s postshield and shield sequences a postshield alkalic lava yields an age of 236 16 kyr in agreement with an age of 240 14 kyr for a geochemically correlative flow in the nearby hsdp 1 core hole where more complete dating of the postshield sequence shows it to have accumulated at 0 9 0 4 m kyr from about 330 to 200 ka mauna kea s shield consists of subaerial tholeiitic flows to a depth of 1079 m below sea level then shallow submarine flows hyaloclastites pillow lavas and minor intrusions to core bottom at 3098 m most subaerial tholeiitic flows fail to form isochrons however a sample at 984 m yields an age of 370 180 kyr consistent with ages from similar levels in hsdp 1 submarine tholeiites including shallow marine vitrophyres clasts from hyaloclastites and pillow lavas were analyzed however only pillow lava cores from 2243 2614 and 2789 m yield reliable ages of 482 67 560 150 and 683 82 kyr respectively a linear fit to ages for shield samples defines a mean accumulation rate of 8 6 3 1 m kyr and extrapolates to 635 kyr at core bottom alternatively a model relating mauna kea s growth to transport across the hawaiian hot spot that predicts downward accelerating accumulation rates that reach 20 m kyr at core bottom depaolo and stolper 1996 is also consistent with all reliable ages except the deepest

support for the giant wave hypothesis evidence from submerged terraces off lanai hawaii the origin of subaerial coral conglomerate deposits on the hawaiian islands of lanai and molokai is controversial primarily because these deposits are difficult to interpret and the vertical motion of these islands is poorly constrained based on bathymetry dive observations sedimentary and radiocarbon data from coralline algal dominated deposits from two submerged terraces at 150 and 230 m off lanai lanai has experienced relatively little vertical movement over the last 30 ka using internally consistent age versus depth relationships paleowater depths and published sea level data we estimate that lanai has experienced maximum rates of uplift of 0 1 m kyr or subsidence of 0 4 m kyr over this period our analysis of possible uplift mechanisms published geophysical numerical modelling and recent tide data suggests that this is also the maximum uplift rate for the last several hundred thousand years taken together these data support the interpretation that coral conglomerates at elevations higher than 35 m on lanai are tsunami deposits with a minimum wave run up 170 m rather than shoreline deposits formed during the last two interglacials then uplifted to their present elevations

the hulopoe gravel lanai hawaii new sedimentological data and their bearing on the giant wave mega tsunami emplacement hypothesis recognition that many oceanic islands are shaped by giant landslides has highlighted claims that the hulopoe gravel on south lanai hawaii was deposited by giant waves mega tsunami generated by such a landslide this interpretation is controversial resolution of the controversy has global implications because mass wasting of oceanic islands has been a common process for as long as hot spot volcanism has affected the ocean basins thus if mega tsunami are attendant upon the mass wasting process their effect on earth surface processes should be discernible for much of geological time and may be comparable to that resulting from bolide impacts that form astroblemes detailed facies analysis of the pebble cobble and boulder gravels that form the hulopoe gravel type section shows that the gravels are composed predominantly of basalt clasts with appreciable amounts of limestone clasts in 8 of the 14 beds present deposition was not continuous eight disconformities are recognized in the 9 2 m type section three of which are associated with truncated paleosols the hulopoe gravel was not deposited by a single tsunami at 105 ka as has been proposed one bed is clearly an alluvial deposit the origins of others are unclear but the facies data do not exclude tsunami as one of the processes that deposited individual beds within the hulopoe gravel either above or below sea level

dominant influence of volcanic loading on vertical motions of the hawaiian islands abstract rates of island vertical motion above intra plate hotspots record the processes that arise from interactions between lithospheric plates and mantle plumes to assess the contribution of mantle and lithospheric processes to surface motion above the hawaiian hotspot we compare simple models of lithospheric deformation to vertical motion rates measured from dated paleoshorelines and tide gauge records in the hawaiian islands our analysis shows that observed uplift and subsidence rates mainly record the flexural response of the lithosphere to volcanic loads the effective elastic plate thickness that best fits the spatial distribution of subsidence and uplift rates is 40 km consistent with previous estimates based on total vertical deflection because volcanic loading dominates the vertical motion signal hawaiian islands appear to follow a predictable trajectory of vertical motion when they reside within one flexural half wavelength of the active volcanic center islands initially subside at rapid and decreasing rates in the first 1 myr following their construction uplift relatively slowly 1 2 5 myr following their construction and eventually subside again but at slow rates within 5 myr of their construction this observed pattern of uplift and subsidence is consistent with the pattern of vertical motion predicted to result from volcanic loading at the hawaiian hotspot lithospheric migration over the long wavelength topographic swell associated with the hawaiian hotspot has a comparatively minor influence on island uplift and subsidence its contribution to island vertical motion is not readily observed in our data with the possible exception of some uplift observed in the past 500 kyr on o ahu that might correspond to non steady state behavior of the hawaiian plume

strontium isotope stratigraphy of kita daito jima atoll north philippine sea implications for neogene sea level change and tectonic history abstract a detailed chronology of a 432 m core from kita daito jima an atoll on the philippine sea plate has been obtained by strontium isotope stratigraphy the atoll carbonate extends to late oligocene age the top 100 m plio pleistocene section of the core has been dolomitized and dolomite also extends to middle miocene sediments sr isotopes identify two dolomitization events at 2 and 5 ma atoll growth appears to have been continuous between 18 8 and 24 3 ma and the fit of the growth history to a standard model provides a successful confirmation of darwin s subsidence theory the atoll growth appears to have commenced about 42 ma ago 6 ma after volcanism producing a 2 km column of atoll carbonate in agreement with bathymetry the subsidence model defines an apparent loss of 360 m of the sedimentary record since the early middle miocene boundary the amount in excess of the 100 m associated with sea level fall is attributed to plio pleistocene uplift at rates of 20 30 m ma associated with the forebulge of the philippine sea plate prior to its subduction uplift rates have also been estimated using a the heights of dated last interglacial coral reefs on kita daito jima and nearby minami daito jima 17 m ma and 29 m ma b sr isotope ages of calcites from surface samples on minami daito jima 21 m ma and c contrasts in elevation with okino daito jima 100 km away 22 m ma the locations of hiatuses and ages of dolomitization indicate sea level falls of 80 m at 17 16 ma 30 m at 16 15 ma 125 m at 11 ma and 90 m at 5 ma and at 2 ma the data have been combined with those from enewetak atoll to produce a curve of sea level change for the neogene

the restless resurgent campi flegrei nested caldera italy constraints on its evolution and configuration abstract we have collected new stratigraphic data in the campi flegrei caldera through surface geological mapping and study of cores drilled to various depths we integrate these data with geological geochronological and geophysical constraints available in the literature to reconstruct the volcanic and deformational history of the caldera the caldera is a resurgent nested structure resulting from two main collapses related to the campanian ignimbrite 37 ka and the neapolitan yellow tuff 12 ka eruptions while the structure is affected by a broad subsidence ongoing local resurgence and unrest occur inside the younger nested caldera structure although most of the caldera floor consists of multiple structural blocks due to long term deformations magmas were able to erupt only in one sector of the resurgent part the caldera has shown signs of unrest during the past 25 years with short term deformations that have generated a net uplift of 3 5 m the short term deformations are related to the neapolitan yellow tuff caldera resurgence and interpreted as the net result of brittle and ductile components the long term deformations likely represent the sum of the permanent brittle component of each short term deformational event

numerical modeling of the growth and drowning of hawaiian coral reefs during the last two glacial cycles 0 250 kyr 1 drowned coral reefs on rapidly subsiding margins possess a unique archive of sea level and climate changes generally unavailable from stable or uplifting margins using available field observations and sedimentary radiometric age and numerical modeling data we propose a new model of submerged reef development around hawaii during the last two glacial cycles 250 kyr this model provides a quantitative predictive stratigraphy for the reefs that we argue if drilled will yield new information on sea level and climate changes as well as coral reef response over the last 250 kyr comparing the observational and numerical modeling data combined with sensitivity testing we present our best case scenario for the evolution of the drowned lowstand reefs now at 400 h2 and 150 m h1 we find that growth rates of 2 5 2 85 m kyr for the main shallow reef building facies a subsidence rate of 2 5 m kyr and a variable basement substrate configuration best explain the observational data modeling of the internal stratigraphic succession of the reefs shows that the number and thickness of shallow reef units as well as the frequency and duration of subaerial exposure and reef drowning events are sensitive to the frequency and amplitude of eustatic sea level variations but not the rate of subaerial erosion h2 and h1 initiated growth during stable eustatic sea level conditions during highstands circa 222 ka mis7 and circa 126 ka mis5e respectively both h2 and h1 have a long and complex growth history growing episodically for 90 kyr precessional 20 kyr and higher frequency suborbital eustatic sea level fluctuations dominate with each reef experiencing repeated but brief 5 10 kyr drowning and subaerial exposure producing a complex layer cake stratigraphy of shallow 0 30 m coral reef units separated by either subaerial exposure horizons or thin intermediate 30 60 m coralgal units final drowning of h2 and h1 occurs during the penultimate 133 134 ka and last deglaciation 12 14 ka these findings are consistent with available age data and qualitative predictions of previous studies around hawaii

new constraints on the origin of the australian great barrier reef results from an international project of deep coring two new boreholes provide the first direct evidence of the age of the australian great barrier reef an inner shelf sequence total depth 86 m basal age 210 40 ka comprises a dominantly siliciclastic unit thickness 52 86 m overlain by four carbonate units total thickness 0 34 m a shelf edge and slope sequence total depth 210 m reveals three major sections 1 a lower section of resedimented flows deposited on a lower slope 2 a mid section including intervals of corals rhodoliths and calcarenites with low angle graded laminae and 3 an upper section of four shelf margin coral reef units separated by karst surfaces bearing paleosols sr isotope and magnetostratigraphic data indicate that the central great barrier reef is relatively young post bruhnes matuyama boundary time and our best estimate for the onset of reef growth on the outer barrier system is ca 600 280 ka this date suggests that reef initiation may have been related to the onset of full eccentricity dominated glacio eustatic sea level oscillation as inferred from large amplitude saw tooth 100 k y 18o cycles after marine isotope stage 17 rather than to some regional environmental parameter a major question raised by our study is whether reef margins globally display a similar growth history the possibility of a global reef initiation event has important implications for basin to shelf partitioning of caco3 atmospheric carbon dioxide levels and global temperature change during quaternary time

a fossil coral perspective on western tropical pacific climate 350 ka 1 the nature of tropical climate variability 350 ka is addressed using 18o and sr ca records from a modern and a fossil coral from vanuatu southwestern tropical pacific ocean modern el nino events at vanuatu produce positive coral 18o and sr ca anomalies similar anomalies observed in the fossil coral records suggest that el nino was operative 350 kyr ago seasonal variations in coral sr ca a sea surface temperature sst proxy have the same amplitude in both corals whereas seasonal 18o variations are smaller in the fossil coral than in the modern coral this is consistent with displacement of the south pacific convergence zone toward the southwest during the boreal summer 350 ka mathematical modeling results preclude warmer sst and higher sss at vanuatu during this time but permit the surface ocean to be 2 c cooler and 0 2 psu fresher than today assessing the potential of variations in late quaternary seawater sr ca remains the largest obstacle to accurately reconstructing tropical sst using pristine fossil corals

sedimentology of rocky shorelines 4 coarse gravel lithofacies molluscan biofacies and the stratigraphic and eustatic records in the type area of the pleistocene hulopoe gravel lanai hawaii abstract during the pleistocene the south flank of lanai was the site of repeated erosion and deposition as a consequence of glacio eustasy superimposed on tectono isostasy throughout this time terrigenous and bioclastic gravel was generated along mainly rocky shorelines gravelly sediment was deposited in topographically low areas of the shoreface and inner shelf that later were uplifted isostatically the sedimentary lithofacies and biofacies in these deposits are distinctive but they represent a deposystem and suite of environments that hitherto have not been studied systematically these unrecognised circumstances have fuelled controversies about the nature and significance of the hulopoe gravel most notably the claim that it represents a mega tsunami deposit the hulopoe gravel in its type area displays a lithofacies succession that encompasses a complete disconformity bounded transgressive regressive cycle on a sand poor rocky shoreline this succession incorporates not only a distinctive vertical assemblage of rocky shoreline litho and biofacies but also internal disconformities that record episodes of erosion and non deposition during shoreline migration repetition of the lithofacies succession imparts overall stratigraphic order to the hulopoe gravel four unconformity bounded transgressive regressive cycles correspond to eustatic highstands of oxygen isotope stages 5 and 7 superimposed on continuing tectono isostatic uplift driven by growth of the island of hawaii this study of the hulopoe gravel demonstrates that the sedimentary record of mixed volcaniclastic carbonate depositional systems developed on rocky shorelines of tropical and subtropical oceanic island coasts can be preserved this record may include depositional products of both transgressive and regressive shorelines although tsunami and giant submarine landslides are known to occur in the hawaiian islands deposits and features that result from tsunami inundation above the shoreline such as might be expected from landslide related mega tsunami have not been recognised in the type area of the hulopoe gravel rocky palaeoshoreline records on oceanic volcanic islands may yield oceanographic and climatic clues that complement data obtained from other palaeoshoreline types

drowned reefs as indicators of the rate of subsidence of the island of hawaii a major submerged terrace whose seaward edge is at about 150 m depth was investigated in 1983 during 10 dives with the hawaii undersea research laboratory hurl submersible makali i off kealakekua bay hawaii the seaward termination of the terrace is a steep wall of reef limestone that extends from 150 to 250 m below sea level three samples of limestone collected from the reef face at depths of 204 219 m yield a weighted average 14 c age of 13 250 s d 380 years before present the 150 m terrace as well as two deeper terraces off northwestern hawaii at depths of 390 pm 50 m and 580 pm 40 m apparently were formed by the interaction of glacioeustatic sea level changes and island subsidence the best fit of depth age and subsidence data indicates that the northwestern coast of hawaii has subsided at an absolute rate of 1 8 to 3 mm yr and that the rate of subsidence has generally increased over the past 0 3 m y each reef terrace grew intermittently for nearly 0 1 m y the 150 m reef ter

sedimentology of rocky shorelines 5 the marine samples at 326m from stearns swale lanai hawaiʻi and their paleo environmental and sedimentary process implications abstract fossiliferous gravels on lanai one of the smaller hawaiian islands are known collectively as the hulopoe gravel since 1984 several workers have attributed these gravels to deposition from the run ups and retreats of mega tsunami other workers before and since have interpreted the gravels as rocky shoreline deposits exposed by island uplift the existence of harold stearns makana paleoshoreline on lanai at 326 365 m elevation is particularly controversial in 1936 stearns collected some marine molluscan fossils from a site at 326 m elevation on the southern slope of lanai now known as stearns swale details of the site the fossils and his installed markers were recorded in his field note book now held by the us geological survey in honolulu the fossils were lodged in the national museum of natural history in washington d c during ww ii the 326 m site became a military installation and stearns markers and any remaining fossils were destroyed we have examined stearns notebook the 326 m site and the fossils two types of sediment adhere to the fossils a weakly cemented well rounded biocalcarenite grainstones with minor subrounded basalt fragments b calcite cemented sub rounded to well rounded volcanic litharenite or lithrudite with some bioclasts the fossil molluscs and the bioclasts in the adhering sands represent organisms typical of hawaiian rocky shorelines and adjacent submarine slopes these features are consistent with 1 deposition of the sediments on or closely overlying an unconformity surface cut in basalt bedrock in the vicinity of a rocky shoreline they are also consistent with 2 derivation of the materials from rocky shorelines or shorefaces at lower elevations and their transport up slope by waves generated by a category 5 hurricane or by a mega tsunami we prefer the first scenario as lanai s vertical mobility is indicated by at least ten topographically distinct shoreline related deposits located at various elevations on or adjacent to lanai including six submerged terraces on its western flank

lessons from a lost technology the secrets of roman concrete roman concrete was used as building material during roman imperial times for a great number of famous constructions with different functions well known examples are aqueducts for example the pont du gard in france and the aqua alexandrina in rome and numerous monuments such as the famous coliseum and pantheon in rome while visually less apparent today ancient harbors also were an important part of constructions supporting the power of the roman imperial system and were invaluable to control the mediterranean sea trade the article unlocking the secrets of al tobermorite in roman seawater concrete by jackson et al 2013 describes the investigation of several extremely interesting samples drilled from 2000 year old roman maritime concretes in 11 harbors along the mediterranean coast the romacons project 2002 2009 oleson et al 2004

subsidence and volcanism of the haleakala ridge hawaii abstract side looking sonar gloria mapping has revealed a series of four arcuate bands of high sonic backscatter on the crest of the haleakala ridge a major rift zone ridge extending 135 km east of the island of maui dredge recovery indicates that the shallowest of these bands is a drowned coral reef and the deeper bands are also inferred to be coral reefs the reefs occur above a prominent submarine bench 1500 2500 m deep on the ridge h terrace that marks the shoreline at the end of vigorous shield building of haleakala volcano when lava flows ceased crossing and reworking the shoreline since their growth these reefs have subsided as much as 2200 m and have tilted systematically about 20 m km southward as a result of post reef volcanic loading on the island of hawaii whose center of mass is about directly south of the haleakala ridge the 234u 238u age of the dredged coral is 750 13 ka in reasonable agreement with an age of 850 ka for the underlying h terrace previously estimated from its relationship to other dated reefs to the southwest basalt glass fragments dredged from the haleakala ridge below the h terrace are tholeiitic and contain high sulfur indicative of eruption in water deeper than 200 m basalt glass fragments associated with the reefs above the h terrace are dominantly tholeiitic and contain intermediate sulfur contents indicative of subaqueous eruption in shallow near shore conditions one alkalic glass fragment was recovered above the h terrace these relations indicate that the morphologic end of shield building as recorded by construction of the h terrace was not accompanyed by a change from tholeiitic to alkalic basalt instead tholeiite eruptions continued for some time before the erupted lava became alkalic

unraveling the tilting history of the submerged reefs surrounding oahu and the maui nui complex hawaii there is considerable uncertainty concerning the history of lithospheric flexure of oahu and the maui nui complex associated with the hawaiian hot spot previous reconstructions based on models and sparse observational data place the zone of maximum uplift forebulge either under oahu or between oahu and molokai to address this issue we have compiled and analyzed all existing and new high resolution multibeam bathymetry dive observations and chronologic data from submerged terraces in the region we have identified 89 separate submarine terraces and mapped their distribution across the volcanic flanks of oahu and the maui nui complex these data are used to systematically measure the direction and amplitude of terrace tilting within the maui nui complex and to provide new constraints on lithospheric flexure associated with volcanic loading at the hot spot the terraces are divided into six separate geographic regions oahu molokai penguin bank lanai maui and east maui defined by significant discontinuities in either terrace morphology or depth following the sequential development of new substrate as the new volcanoes formed throughout the development of the mnc 18 new and 51 published 87sr 86sr isotopic ages show that the terraces in these regions were also initiated at different times and the tilting data show that they also responded to lithospheric flexure independently the general pattern of terrace tilting records the plate s response to lithospheric flexure with each region continually tilting toward the zone of maximum subsidence since their formation our individual tilt calculations are based on the most complete and highest resolution bathymetric data available and they show that plate response to volcanic loading is a gradual process finally we demonstrate that the shallowest terraces we identified in the oahu and molokai regions tilt toward the north away from the current zone of maximum subsidence indicating that these regions have recently passed the zone of maximum uplift we compare our results with two separate published numerical models and differentiate between these resolving a long standing uncertainty in the position of the forebulge

reef growth and volcanism on the submarine southwest rift zone of mauna loa hawaii a marine sampling program utilizing the pisces 5 submersible operated by the hawaii undersea research laboratory noaa has confirmed the presence of a major submerged coral reef offshore from ka lae south point hawaii the top of the reef is now 150 160 m below sea level radiocarbon and useries dating indicates that it drowned about 13 9 ka by the combined effects of island subsidence 2 5 mm year and the rapid rise of sea level at the end of the last glaciation so that the relative submergence rate of more than 10 mm year exceeded the upward growth rate of the reef the submerged reef caps the offshore part of the southwest rift zone ridge of mauna loa which has apparently undergone little volcanic activity offshore since 170 ka and possibly since 270 ka this fact suggests that rift zone activity is becoming increasingly restricted toward the upper part of the volcano a condition possibly heralding the end of the shield building stage

geochronology of drowned hawaiian coral reefs abstract two deeply submerged coral reefs were sampled with the hurl submersible pisces v off the islands of hawaii and maui an ancient fringing reef at 950 m depth on the kohala slope of hawaii was observed from deep towed camera photographs and during submersible operations a second reef at 1650 m depth on the haleakala slope of maui was observed on side scan images deep towed camera photographs and during submersible observations ages of the two reefs were determined by electron spin resonance dating with a signal intensity for aragonitic coral at g 2 0007 used to ascertain the accumulated dose by the additive dose method uranium concentration was measured by neutron activation analysis the chronology of the reefs indicates that drowning coincided with periods of rapid global climate change at the termination of continental glaciation at approximately 250 ka and 340 ka the drowning events correlate with oxygen isotope stage boundaries 7 8 and 9 10 these data support models of reef drowning on subsiding volcanic edifices

the neapolitan yellow tuff a large magnitude trachytic phreatoplinian eruption eruptive dynamics magma withdrawal and caldera collapse the results of a detailed stratigraphical and volcanological study has allowed the definition of the neapolitan yellow tuff nyt as the largest known trachytic phreatoplinian eruption with an estimated volume of not less than 30 km3 dre the nyt sequence can be subdivided in a lower and an upper member sedimentological and textural variations in time and space indicate that different eruptive and depositional mechanisms operated during the eruption the lower member eruptive phase was characterized by alternating phreatoplinian and magmatic explosions while the upper member eruptive phase was characterized by a random sequence of phreatomagmatic and magmatic explosions particles produced by the same explosion were deposited contemporaneously by fallout and surge mechanisms either at different or at the same distance from the vent compositional variations show that the nyt sequence cannot be modeled as an inverted compositionally zoned magma body with magma becoming more basic in the course of the eruption the chamber composed of three geochemically distinct magma layers was tapped at different depths according to the eruption dynamics each phreatoplinian explosion tapped concurrently all the magma layers while magmatic explosions tapped only one of them the onset of the nyt caldera collapse is well constrained between lower and upper member eruptive phases the collapse which is only gravimetrically detectable occurred inside the larger phlegrean fields caldera which therefore can be defined as a nested caldera

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

sr isotopic variation in shallow water carbonate sequences stratigraphic chronostratigraphic and eustatic implications of the record at enewetak atoll sr isotope data from two boreholes within the lagoon at enewetak atoll have been used to evaluate the use of such data to correlate date and monitor sea level change in shallow water carbonate sequences correlative stratigraphic intervals of relatively invariant 87sr separated by abrupt transitions to lower 87sr with increasing depth are recognized in both boreholes conversion of 87sr values to age via calibration with the seawater 87sr trend with age indicates that correlative and synchronous deposition of atoll sediments occurred at 0 4 1 2 and 2 1 ma in contrast a 5 m y hiatus is recognized in one borehole but not the other sr isotope stratigraphy sis is a powerful stratigraphic and chronostratigraphic tool in shallow water carbonate sequences only when significant secular variation of 87sr occurs and retention of depositional 87sr values is demonstrated the latter is best demonstrated when 87sr data are integrated with 18o 13c sr content data and petrographic observations several diagenetically altered intervals have greater 87sr values low 13c values and low sr ca ratios relative to adjacent intervals a combination that is consistent with open system meteoric diagenesis calcite cements from these intervals have early pleistocene 1 2 ma 87sr values despite their occurrence well within the late pliocene 2 1 ma sequence thus local sedimentological and diagenetic processes have produced intralagoon variability in the sis of the two boreholes complicating subsurface stratigraphic correlations the occurrence of anomalously young calcite cement relative to adjacent limestone is a direct response of the interaction of sea level change and meteoric phreatic diagenesis whereby overlying metastable carbonates with greater 87sr values are dissolved during periods of atoll emergence and sea level lowstand liberating sr and soil gas co2 to the pore fluid which is then incorporated into downflow meteoric phreatic diagenetic calcite the stratigraphic relation between the sites of carbonate dissolution and diagenetic calcite precipitation suggest an early pleistocene 1 2 ma sea level fall of between 34 and 64 m moreover the stratigraphic position and inferred age of paleophreatic lens calcite when backtracked for subsidence suggest that early pleistocene 1 2 ma sea level was 72 81 m range of 60 100 m below present sea level the enewetak record of early pleistocene sea level lowstand elevation agrees reasonably well with proxy sea level records inferred from sequence stratigraphy and deep sea foraminiferal 18o data however the enewetak record of the amplitude of early pleistocene sea level change is more consistent with the deep sea foraminiferal 18o proxy than the sequence stratigraphy proxy

strontium isotope stratigraphy and paleomagnetic age constraints on the evolution history of coral reef islands northern south china sea understanding the history of the response of coral reefs to past climate changes can provide valuable information for predicting the future response of modern reefs however dating such ancient biotic carbonate is still challenging because of its sensitivity to diagenetic alteration processes scarcity of well preserved fossils and low magnetic mineral content there have been a long debates about the origin and evolutionary history of coral reefs in the northern south china sea mainly due to the lack of direct and reliable age constraints this provides us with a good opportunity to verify the practicability of different dating approaches especially the strontium sr isotope analysis of bulk carbonate here we retrieved a 972 55 m long core from the xisha islands to provide a credible chronologic constraint on the carbonate platform evolution the lithostratigraphy strontium isotope stratigraphy and magnetostratigraphy were analyzed throughout the whole reef sequence the lithostratigraphic results show that the 873 55 m reef sequence developed on an ancient volcaniclastic basement and experienced multiple evolutionary phases the sr 87 sr 86 results of all 100 bulk carbonate samples vary from 0 708506 to 0 709168 and show a monotonic increase with decreasing depth except for a few outliers trace element criteria and stable isotope delta o 18 and delta c 13 methods were applied to these bulk carbonate samples and results imply that the primary or near primary seawater sr 87 sr 86 values were likely preserved although different degrees of diagenetic alteration occurred in addition the paleomagnetic results indicate 10 normal polarity and eight reversed polarity magnetozones based on the sr 87 sr 86 ratios of the selected 58 samples and paleomagnetic reconstruction of polarity reversals the bottom of the reef sequence is dated to 19 6 ma and the observed polarity chronozones extend from chron c6 19 722 18 748 ma at 866 60 m to present at the top based on the new data we propose a new chronologic framework for the evolutionary history of the reef islands where 1 the reefs initiated in the early miocene 19 6 ma and were drowned until 16 26 ma 2 during 16 26 10 66 ma lagoon to lagoon slope environments prevailed 3 the lagoon environment progressively transformed into a reef crest environment from 10 66 to 4 36 ma and 4 36 to 1 59 ma and 4 the reef started to be drowned again during 1 59 0 ma our study provides a new and reliable chronologic constraint on the general evolutionary history of the reef islands in the northern south china sea furthermore the sr 87 sr 86 results from bulk carbonate indicate that strontium isotope stratigraphy is a powerful dating tool only when rigid sample selection sequential leaching procedures and strict trace element and isotopic criteria are applied

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

coral reefs and sea level change abstract coral reefs provide significant evidence for former sea level positions because of their geological preservation and suitability for dating interpretation of this evidence presumes an understanding of reef geomorphology modern reef organism distributions and environmental factors influencing them fossil reef terraces formed during the last interglacial marine oxygen isotope mis substage 5e 128 116 ka are prevalent on many tropical shorelines and there has been ongoing debate as to the height reached by sea level during that highstand observations from numerous last interglacial sites suggest that sea level was at least 3 m above present sea level implying less extensive icesheets than at present an elevation of 6 m has commonly been adopted when correcting tectonically active sites for uplift recent compilations suggest elevations up to 8 9 m but incorporate few observations from reefs where the last interglacial is found below sea level oscillation of sea level during mis 5e has been interpreted from several sites with recent studies inferring rapid rise of several metres at the end of the interglacial these interpretations are at the limits to the precision with which corals can currently be dated and their palaeo water depths inferred it is not surprising that constraining last interglacial sea level changes within uncertainties of less than 1 2 m remains controversial considering sea level variations recognised between reef sites in the holocene and observed geographical variation in isostatic or flexural adjustments fossil coral reefs on uplifting margins also provide clear evidence for mis substages 5c and 5a and those on huon peninsula indicate fluctuations related to heinrich events mis 3 interpretations show considerable variability between sites with still greater uncertainties about sea level timing and elevation during previous interglacials future study of extensive sequences of fossil reefs preserved on rapidly subsiding margins could address these uncertainties submerged reefs have already yielded important information about sea level rise during the last deglaciation coring around barbados and tahiti as well as on the huon peninsula has produced a broadly consistent picture of ice melt reflecting eustatic change since the last glacial maximum these studies have shown the sensitivity of reefs to rapid sea level rise associated with meltwater pulses with some reefs drowning while others back stepped integrated ocean drilling program iodp expeditions to tahiti and recently the great barrier reef extended these records but details of timing nature and impact of deglacial meltwater pulses remain elusive studies of holocene reefs have indicated different growth strategies some kept up with sea level while others caught up when sea level decelerated holocene sea level appears to have experienced a gradual rise up to present across the caribbean providing accommodation space for reefs to accrete vertically whereas in the indo pacific sea level has been near its present level since 7 ka with many reef flats emergent following a slight fall of sea level caused by ocean siphoning microatolls on reef flats provide perhaps the clearest evidence of past sea level position but in their absence novel biological or other sea level indicators are required to better constrain palaeo water depths there is an urgent need for further research from additional key reef locations not only to decipher processes driving past sea level change and its geographical variability but also to better understand how coral reefs will respond in the context of future sea level rise

accelerated pleistocene coral extinctions in the caribbean basin shown by uranium lead u pb dating ages of corals and shallow marine sequences define rates of marine invertebrate evolution tectonic uplift and paleoclimate change yet accurate ages are difficult to obtain prior to the late pleistocene we report a new approach for combining uranium lead u pb and uranium series dating for middle pleistocene corals from the caribbean side of costa rica two corals have 230 th 238 u in secular equilibrium small excesses in 234 u and 206 pb 238 u ages of 1 02 0 07 ma and 1 288 0 034 ma the latter coral age dates a recognized geomagnetic event to ca 1 3 ma a time at which no polarity events had been identified the new ages also show that the major coral extinction in the caribbean basin occurred shortly after 1 0 0 9 ma much more recently than previously thought this coral extinction now coincides with the global change at 1 0 0 8 ma to the current pattern of glacial interglacial cycles and amplified changes in sea level these factors may have provided a new strong environmental mechanism for rapid habitat modification and coral extinction

coral variation in two deep drill cores significance for the pleistocene development of the great barrier reef abstract variations in lithology and coral assemblages in drill cores from outer and inner shelf reefs are used to characterize the pleistocene development of the great barrier reef based on petrographic isotopic and seismic characteristics the outer shelf core from ribbon reef 5 is divided into three sections 1 a main reef section from 0 to 96 m is composed of six reef units 2 a rhodolith section from 96 to 158 m is interbedded with two thin reef units and 3 a basal section from 158 to 210 m is composed of non reefal skeletal grainstones and packstones two distinct coral assemblages identified in this core represent a shallow high energy community and lower energy community these two assemblages are repeated throughout the main reef section with some units recording transitions between assemblages and others composed of only a single assemblage these coral assemblage data also correlate with transitions recorded by coralline algae using similar criteria the inner shelf core from boulder reef is divided into two sections 1 an upper carbonate dominated section from 0 to 34 m is comprised of four reef units and 2 an underlying mud section from 34 to 86 m is composed of siliciclastics and two thin coral bearing units the four reef units in the upper section are dominated by a single coral assemblage representing a community typical of low energy turbid environments taken together these data indicate that 1 reef growth on the inner shelf initiated later than on the outer shelf 2 true reef turn on in outer shelf areas as represented by the main reef section in ribbon reef 5 was preceded by a transitional period of intermittent reef development and 3 the repeated occurrence of similar coral assemblages in both drill cores indicates that the great barrier reef has been able to re establish itself repeatedly producing reefs of similar composition over the last 500 ky despite major environmental fluctuations in sea level and perhaps temperature