how heterogeneous coseismic slip affects regional probabilistic tsunami hazard assessment a case study in the south china sea rupture complexity typically in the form of heterogeneous slip distribution pattern significantly affects the local tsunami wave field however the effect of rupture complexity is not commonly considered in any form of tsunami hazard assessment taking rupture complexity into account significantly increases the computational load particularly in regional scaled probabilistic tsunami hazard assessments pthas that usually require a large number of simulations based on synthetic scenarios in this study we investigate how the heterogeneous slip distribution affects the regional scaled ptha by taking the south china sea scs as an example by doing this we update ptha for the scs by incorporating the best available information of seismic tsunamigenic sources along the manila megathrust we integrate a stochastic source model into a monte carlo type simulation in which a broad range of slip distribution patterns is generated for large numbers of synthetic earthquake events green s function technique is employed to efficiently calculate the nearshore tsunami wave amplitude along the scs coastlines our result suggests that for a relatively small and confined region like the scs the commonly used approach based on the uniform slip model significantly underestimates tsunami hazard not only in the near source region like west luzon as expected but also in the relative far field such as south china and central vietnam additionally our sensitivity test of the patch size effects suggests that large patch size is unable to adequately resolve the details of heterogeneous seafloor deformation and such approaches considerably underestimate the potential tsunami hazard for the scs coasts

remarkable bathymetric change in the nearshore zone by the 2004 indian ocean tsunami kirinda harbor sri lanka we investigated bathymetric data obtained at kirinda harbor sri lanka one month before and 2 and 11 months after the 2004 indian ocean tsunami our bathymetric surveyed data and numerical modeling results suggest that the first run up tsunami wave transported huge amounts of offshore sea bottom sediment and deposited it in a layer up to 4 m thick along the shoreface slope in some places this accreted sediment was not eroded by the backwash because of the particular arrangement of artificial structures and sand dunes especially the sedimentation process and the volume of the sediment transported by the run up waves can be examined where the influence of the backwash flow was very minor remarkable sedimentation attributable to the run up wave would have occurred mainly by the deposition of the sediment particles along the slope by the run up waves the slope was developed toward the stoss side rather than by the settlement of the sediment from the suspension load we estimated that considerable amounts of sediment were transported by the tsunami from the offshore sea bottom but most were deposited not on land but in the sea eleven months after the tsunami the harbor bathymetry had almost undergone complete reversion to its pre tsunami condition implying that the tsunami impact on permanent geomorphological landforms was limited at this harbor

large bedform generated by the 2011 tohoku oki tsunami at kesennuma bay japan abstract the 11 march 2011 m w 9 0 tohoku megathrust earthquake off the pacific coast of japan was a salient event in the history of japan the resultant huge tsunami the 2011 tohoku oki tsunami inundated a vast coastal area of northeastern japan causing widespread devastation twenty days after the tsunami we analyzed the impact of the tsunami on the sea bottom of the kesennuma inner bay using side scan sonar to explore the damage and bathymetric change in the harbor herein we present the first direct evidence that the sea bottom sediments of around 10 15 m were largely reworked by the tsunami to thickness of a few meters and that large dunes were formed by the tsunami considering that the sea wave influence is as weak as it is inside the inner bay the potential exists that even meter thick paleo tsunami deposits are preserved in shallow sea bottoms with large bedforms this finding will be a stepping stone to future geological studies of tsunami effects in shallow sea regions

unexpected uses for obsidian experimental replication and use wear residue analyses of chopping tools abstract large flaked stemmed artefacts with a morphological resemblance to axes or adzes have been recovered from stone quarries in west new britain papua new guinea but they are made from obsidian a volcanic glass generally considered too brittle for tasks demanding tough long lasting edges such as chopping wood to evaluate the potential of obsidian for percussive woodworking 11 replica obsidian tools were used as axes and adzes although breakage was common and the tools suffered extensive edge damage they were surprisingly effective as chopping tools the patterns of use wear and residue traces on the experimental tools informed the analysis of 27 archaeological artefacts which were found to have been used as axes or adzes with the addition of sawing in a few cases as these tools have not been found outside the quarries their occurrence suggests that during this period some forms of woodworking took place only where there was an abundant supply of raw material the limited spatial distribution of obsidian chopping tools raises questions about the nature of forest clearance and woodworking in this tropical environment

a remarkable pulse of large scale volcanism on new britain island papua new guinea new studies of the deposits from the latest caldera forming eruption the dk event at dakataua volcano new britain island papua new guinea help identify an intense space time concentration of large scale volcanism during the 7th century ad on new britain radiocarbon dating of charcoal from the dk deposits yields an age of 1 383 28 bp calibration of this result gives an age in the range ad 635 670 at 1 s d at about the same time two other volcanoes on new britain rabaul and witori also produced very large eruptions very high acidity levels in ice cores from antarctica and greenland at ad 639 and ad 640 respectively may be linked to either or both of the dakataua and rabaul eruptions another ice core high acidity level at ad 692 may be associated with the witori eruption significant volcanic risk within the new britain region is indicated by its late cenozoic history of relatively frequent large scale eruptions from as many as 8 caldera systems within an arc parallel zone about 380 km long over the last 20 ka the return period for major vei 5 eruptions in this region was about 1 0 ka and individually high frequencies of major eruptive activity were experienced at witori and rabaul the relatively short return period for major eruptions in the region would tend to increase the chance that such events could cluster in time

integrating phytoliths within use wear residue studies of stone tools abstract analyses of phytolith assemblages extracted from residues on obsidian artefacts and from the surrounding soil matrix of two sites in papua new guinea address two important methodological issues first multivariate analysis of phytolith assemblages extracted from the edges of stone artefacts from soil directly in contact with the artefact and from soil derived from the same archaeological context demonstrates the integrity of phytolith residues second reconstructions of tool use based on the analysis of phytoliths are compared with results from an independent use wear residue study the interpretation of phytolith assemblage variability enhances and strengthens the use wear residue results finally integrating the phytolith data within the broader use wear residue study produces significant new findings about changes in obsidian tool use in prehistoric papua new guinea

studies of late prehistoric and modern opal phytoliths from coastal sand dunes and machair in northwest britain abstract this paper investigates the possibilities of identifying the origins of and classifying modern and prehistoric sand samples from coastal dune environments based on a study of their phytolith content a simple conservative classification of phytolith morphotypes has been developed for specimens from this type of sedimentary environment this classification has facilitated the recognition of anthropogenic and non anthropogenic depositional levels in ancient sand dunes on the basis of their contained phytolith suites areas of ancient human occupation and activity are shown to be characterized by phytolith concentrations which are larger by orders of magnitude than those that occur naturally in these coastal dune systems correspondence analysis has been used to investigate the extent to which some specific aspects of past human activity can be distinguished specifically the introduction of cut peat plant and animal waste and possible differences in the character of grazing or pasture in the dune systems

the heat flow of europa the heat flow from europa has profound implications for ice shell thickness and structure as well as for the existence of an internal ocean which is strongly suggested by magnetic data the brittle ductile transition depth and the effective elastic thickness of the lithosphere are here used to perform heat flow estimations for europa results give preferred heat flow values for a typical geological strain rate of 10 15 s 1 of 70 110 mwm 2 for a brittle ductile transition 2 km deep the usually accepted upper limit for the brittle ductile transition depth in the ice shell of europa 24 35mwm 2 for an effective elastic thickness of 2 9 km supporting a plateau near the cilix impact crater and 130 mwm 2 for effective elastic thicknesses of 0 4 km proposed for the lithosphere loaded by ridges and domes these values are clearly higher than those produced by radiogenic heating thus implying an important role for tidal heating the 19 25 km thick ice shell proposed from the analysis of size and depth of impact structures suggests a heat flow of 30 45 mwm 2 reaching the ice shell base which in turn would imply an important contribution to the heat flow from tidal heating within the ice shell tidally heated convection in the ice shell ould be capable to supply 100 mwm 2 for superplastic flow and at the cilix crater region 35 50 mwm 2 for dislocation creep which suggests local variations in the dominant flow mechanism for convection the very high heat flows maybe related to ridges and domes could be originated by preferential heating at special settings

forward mechanical modeling of the amenthes rupes thrust fault on mars amenthes rupes overlies one of the largest thrust faults on mars with structural topography accurately measured by mola forward mechanical models successfully predict the surface topography across this large contractional structure the best fitting fault parameters are fault dip angle 25 30 depth of faulting 25 30 km and fault offset 1 5 km these first order results are insensitive to either the offset distribution along the fault or crustal material properties both very shallow e g 15 km and very deep 45 km depths of faulting can be ruled out as can significantly different dips and offset magnitudes amenthes rupes may span the ancient seismogenic lithosphere in the martian noachian highlands implying maximum values at the time of faulting for heat flux of 54 70 mw m 2 and paleogeothermal gradient of 15 20 k km 1

3500 year western pacific storm record warns of additional storm activity in a warming warm pool abstract frequent storm surges often cause catastrophic impacts on human lives and the global economy however these phenomena are not well understood in this study a regional storm reconstruction is performed based on a grain size analysis and stratigraphic modelling of the accelerator mass spectrometry radiocarbon dates of benthic foraminifera from two neighbouring lagoon cores from lingyang reef in the xisha islands located in the northern south china sea of the western pacific the dating results from the lagoon cores reveal a 3500 year depositional history three different depositional units are recognized based on a time series of distinct grain size variations that correspond to the following three stages of storm activity intense and frequent storms from 3500 to 3100 cal yr bp and 1800 cal yr bp to present and weak and infrequent storms from 3100 to 1800 cal yr bp a high sedimentation rate remarked by reverse and chaos age is observed from 2800 to 2600 cal yr bp in both cores and it was likely associated with a tsunami event in addition grain size variability may be associated with changes over time caused by the synchronous asian monsoon and may also be correlated with climate records retrieved from the ice cores from greenland thus this variability could indicate pervasive global climatic teleconnections the overall temporal patterns of the isolated coral branches and shells from the sediment sequences are well correlated with the high sea surface temperatures in the western tropical pacific we suggest that increasing sea surface temperatures in the future may lead to more intense storm activity in the western pacific warm pool as the planet warms

heterogeneities in the thickness of the elastic lithosphere of mars constraints on heat flow and internal dynamics derived values of the thickness of the effective elastic lithosphere on mars are converted to estimates of lithospheric thermal gradients and surface heat flow by finding the thickness of the elastic plastic plate having the same bending moment and curvature subject to assumed strain rates and temperature dependent flow laws for crustal and mantle material local thermal gradients and heat flow values so estimated were 10 14 k km 1 and 25 35 mw m 2 respectively at the time of formation of flexurally induced graben surrounding the tharsis montes and alba patera while gradients and heat flow values of less than 5 6 k km 1 and 17 24 mw m 2 respectively characterized the lithosphere beneath the isidis mascon and olympus mons at the time of emplacement of these loads on the basis of the mean global thickness of the elastic lithosphere inferred to support the tharsis rise and estimates of mantle heat production obtained from snc meteorites it is suggested that the present average global heat flux on mars is in the range 15 25 mw m 2 approximately 3 5 of this heat flux during the amazonian epoch has been contributed by excess conducted heat in the central regions of major volcanic provinces most likely this excess heat flux has been delivered to the base of the lithosphere by mantle plumes the fractional mantle heat transport contributed by plumes during the last 2 b y on mars is therefore similar to that at present on earth

discerning use related micro residues on tools testing the multi stranded approach for archaeological studies abstract in this paper i explore how post depositional contaminants and non use related ancient residues may be distinguished from use related residues directly associated with the application of ancient artefacts it is assumed that contaminant and unintentional remains have a random distribution over a tool s surface preserved use related residues however are expected to have a consistent spatial distribution around a working edge to test this residues on used and unused experimental flakes were recorded after they underwent weathering the surfaces of the experimental flakes were divided in four quadrants of roughly equal size the surface coverage of the residue types per quadrant was then recorded on used flakes with well preserved residues the use related residues are more abundant on portions associated with the sharp edge than on portions associated with blunt sides on the samples without identified use related remains and on the unused sample the distribution of micro remains is more uniform this study confirms that by using a contextual approach it is possible to distinguish use related remains from non use related and co incidental remains

coastal lake sediments reveal 5500 years of tsunami history in south central chile abstract we present an exceptionally long and continuous coastal lacustrine record of 5500 years from lake huelde on the west coast of chiloe island in south central chile the study area is located within the rupture zone of the giant 1960 ce great chilean earthquake mw 9 5 the subsequent earthquake induced tsunami inundated lake huelde and deposited mud rip up clasts massive sand and a mud cap in the lake long sediment cores from 8 core sites within lake huelde reveal 16 additional sandy layers in the 5500 year long record the sandy layers share sedimentological similarities with the deposit of the 1960 ce tsunami and other coastal lake tsunami deposits elsewhere on the basis of general and site specific criteria we interpret the sandy layers as tsunami deposits age control is provided by four different methods 1 210pb dating 2 the identification of the 137cs peak 3 an infrared stimulated luminescence irsl date and 4 22 radiocarbon dates the ages of each tsunami deposit are modelled using the bayesian statistic tools of oxcal and bacon the record from lake huelde matches the 8 regionally known tsunami deposits from documented history and geological evidence from the last 2000 years without over or underrepresentation we extend the existing tsunami history by 9 tsunami deposits we discuss the advantages and disadvantages of various sedimentary environments for tsunami deposition and preservation e g we find that lake huelde is 2 3 times less sensitive to relative sea level change in comparison to coastal marshes in the same region

depositional evidence for the kamikaze typhoons and links to changes in typhoon climatology in the late 13 th century kublai khan ruler of the mongol empire launched one of the world s largest armadas of its time in an attempt to conquer japan early narratives described the decimation and dispersal of these fleets by the kamikaze of 1274 ce and 1281 ce a pair of intense typhoons divinely sent to protect japan from invasion these historical accounts are prone to exaggeration and significant questions remain regarding the occurrence and true intensity of these legendary typhoons to provide independent insight we present a new 2000 yr sedimentary reconstruction of extreme coastal flooding from a coastal lake near the location of the mongol invasions two marine sourced flood deposits date to the kamikaze typhoons and are the events of record in the reconstruction the complete reconstruction indicates periods of greater flood activity relative to modern beginning ca 250 ce and extending past the timing of the kamikaze events to 1600 ce comparisons with additional reconstructions are consistent with greater regional typhoon activity during the mongol invasions due to the preferential steering of storms toward japan and driven by greater el nino activity relative to modern results are consistent with the paired kamikaze typhoons being of significant intensity and support accounts of them playing an important role in preventing the conquering of japan by mongol fleets the kamikaze typhoons may therefore serve as a prominent example for how past increases in severe weather associated with changing climate have had significant geopolitical impacts

exploring typhoon variability over the mid to late holocene evidence of extreme coastal flooding from kamikoshiki japan sediment cores from two coastal lakes located on the island of kamikoshiki in southwestern japan lake namakoike and lake kaiike provide evidence for the response of a backbarrier beach system to episodic coastal inundation over the last 6400 years sub bottom seismic surveys exhibit acoustically laminated parallel to subparallel seismic reflectors intermittently truncated by erosional unconformities sediment cores collected from targeted depocenters in both lakes contain finely laminated organic mud interbedded with coarse grained units with depths of coarse deposits concurrent with prominent seismic reflectors the timing of the youngest deposit at kamikoshiki correlates to the most recently documented breach in the barrier during a typhoon in 1951 ad assuming that this modern deposit provides an analog for identifying past events paleo typhoons may be reconstructed from layers exhibiting an increase in grain size a break in fine scale stratigraphy and elevated sr concentrations

change in morphology and modern sediment thickness on the inner continental shelf offshore of fire island new york between 2011 and 2014 analysis of hurricane impact abstract seafloor mapping investigations conducted on the lower shoreface and inner continental shelf offshore of fire island new york in 2011 and 2014 the period encompassing the impacts of hurricanes irene and sandy provide an unprecedented perspective regarding regional inner continental shelf sediment dynamics during large storm events analyses of these studies demonstrate that storm induced erosion and sediment transport occurred throughout the study area in water depths up to 30 m acoustic backscatter patterns were observed to move from 1 m to 450 m with a mean of 20 m and movement tended to decrease with increasing water depth these patterns indicate that both of the primary inner continental shelf sedimentary features in the study area linear sorted bedforms offshore of eastern fire island and shoreface attached sand ridges offshore of central and western fire island migrated alongshore to the southwest the migration of the sorted bedforms represents the modification of an active ravinement surface and is thought to have liberated a significant volume of sediment comparison of isopach maps of sediment thickness show that the volume of modern sediment composing the lower shoreface and shoreface attached sand ridges decreased by 2 8 10 6 m 3 across the 73 km 2 of common seafloor mapped in both surveys however a similar analysis for the relatively calmer 15 yr period prior to 2011 revealed significant accretion this allows speculation that the shoreface attached sand ridges are maintained over decadal timescales via sediment supplied through erosion of pleistocene outwash and lower holocene transgressive channel fill deposits exposed on the inner continental shelf but that the sand ridges also periodically erode and move to the southwest during large storm events analyses show that significant storm induced erosion and sediment transport occurs far seaward of the 5 to 9 m depth of closure assumed for fire island where it is thought that an onshore directed sediment flux from the inner continental shelf to the littoral system is required to balance the coastal sediment budget it is also thought that the morphology of the shoreface attached sand ridges controls the persistent shape of the adjacent shoreline through modification of incident waves thus we suggest that the sediment dynamics of the inner continental shelf and both storm induced and anthropogenic modification of the field of shoreface attached sand ridges be considered in future coastal resiliency planning

thickness of the martian crust improved constraints from geoid to topography ratios 1 the average crustal thickness of the southern highlands of mars was investigated by calculating geoid to topography ratios gtrs and interpreting these in terms of an airy compensation model appropriate for a spherical planet we show that 1 if gtrs were interpreted in terms of a cartesian model the recovered crustal thickness would be underestimated by a few tens of kilometers and 2 the global geoid and topography signals associated with the loading and flexure of the tharsis province must be removed before undertaking such a spatial analysis assuming a conservative range of crustal densities 2700 3100 kg m 3 we constrain the average thickness of the martian crust to lie between 33 and 81 km or 57 24 km when combined with complementary estimates based on crustal thickness modeling gravity topography admittance modeling viscous relaxation considerations and geochemical mass balance modeling we find that a crustal thickness between 38 and 62 km or 50 12 km is consistent with all studies isotopic investigations based on hf w and sm nd systematics suggest that mars underwent a major silicate differentiation event early in its evolution within the first 30 ma that gave rise to an enriched crust that has since remained isotopically isolated from the depleted mantle in comparing estimates of the thickness of this primordial crust with those obtained in this study we find that at least one third of the martian crust has an origin dating from the time of accretion and primary differentiation subsequent partial melting of the depleted mantle would have given rise to the remaining portion of the crust while we predict that a large portion of the crust should be composed of ancient enriched materials a representative sample of this primordial crust does not currently exist among the known martian meteorites index terms 6225 planetology solar system objects mars 5417 planetology solid surface planets gravitational fields 1227 5430 planetology solid surface planets interiors 8147 1227 geodesy and gravity planetary geodesy and gravity 5420 5714 6019 keywords mars crustal thickness crustal evolution geoid topography

clues to stone tool function re examined comparing starch grain frequencies on used and unused obsidian artefacts the identification of plant residues observed on prehistoric stone artefacts has often been used to inform on tool function without adequate consideration of potential contamination due to post depositional processes the paper redresses this balance by proposing a methodology which combines use wear and residue analyses with systematic testing of depositional context to distinguish residues formed during tool use from accidental contamination a case study involving obsidian artefacts from an open site in papua new guinea is used to illustrate the new approach starch grains a class of residue which has had little attention outside australia were chosen as the focus of study because of their abundance at this site the frequency of starch grains extracted from residues on stone artefacts was compared with those in sediments adhering to and adjacent to the artefact a use wear study conducted as a blind test provided an independent measure of whether the artefacts had been used the frequency of starch grains was shown to be significantly correlated with used artefacts and not correlated with unused artefacts or the sediments the case study demonstrates the importance of testing for contamination and also illustrates the benefit of studying starch grains as a class of plant residue

interactions between human activity volcanic eruptions and vegetation during the holocene at garua and numundo west new britain png this paper reviews recent fossil phytolith analysis from wet tropical west new britain papua new guinea the holocene vegetation has been influenced by spatially and temporally diverse patterns of both prehistoric human settlement and catastrophic volcanic events we have hypothesized different landscape responses and recovery pathways to events during the last six millennia phytolith sequences on the coastal lowlands the willaumez peninsula and nearby island of garua provide details of vegetational change and human interactions at different landscape scales since c 5900 cal yr b p during this period four major volcanic eruptions c 5900 3600 1700 and 1400 cal yr b p have disrupted the landscape the evidence provides detailed descriptions of temporal and spatial patterning in the impacts and changes in the vegetation in particular vegetation responded differently from one event to another reflecting both forest recovery from seed bank and shooting and the influence of prehistoric people on recovering vegetation furthermore after some events landscape recovery was moderately uniform while after others there was considerable landscape partitioning although these differences largely relate to airfall tephra type distribution and magnitude the partitioning is more strongly influenced by human activity

internal structure and early thermal evolution of mars from mars global surveyor topography and gravity topography and gravity measured by the mars global surveyor have enabled determination of the global crust and upper mantle structure of mars the planet displays two distinct crustal zones that do not correlate globally with the geologic dichotomy a region of crust that thins progressively from south to north and encompasses much of the southern highlands and tharsis province and a region of approximately uniform crustal thickness that includes the northern lowlands and arabia terra the strength of the lithosphere beneath the ancient southern highlands suggests that the northern hemisphere was a locus of high heat flow early in martian history the thickness of the elastic lithosphere increases with time of loading in the northern plains and tharsis the northern lowlands contain structures interpreted as large buried channels that are consistent with northward transport of water and sediment to the lowlands before the end of northern hemisphere resurfacing

evaluating the usefulness of phytoliths and starch grains found on survey artifacts abstract archaeologists use survey artifacts to study any number of interesting topics the focus of this study is to test the usefulness of starch grains and phytoliths found on artifacts recovered during archaeological survey phytolith and starch grain analysis was used to determine the level of environmental contamination on three types of medieval ceramics collected during survey work from plowed fields in the parish of wicken northamptonshire england the plant residues found on these artifacts were compared with their surrounding soil and with contemporaneous excavated artifacts recovered from under the floorboards of a medieval house in nearby wyton cambridgeshire england through the use of the piggyback approach pioneered by chandler ezell and pearsall phytoliths and starch grains were systematically removed from the artifacts surface residues associated with contamination were removed from the outermost layer of the artifact surface while potentially uncontaminated residues were removed from the innermost layer of the artifact surface matching phytoliths and starch grains were found on the outermost surface of the survey artifacts and in the surrounding soils no phytoliths and starch grains were found on the innermost surface of the survey artifacts suggesting that residues from the surrounding soils did not penetrate into the pores and crevices of the artifacts the overall results suggest that although they are preliminary there is potential for plant residue analysis of survey artifacts

martian surface heat production and crustal heat flow from mars odyssey gamma ray spectrometry 1 martian thermal state and evolution depend principally on the radiogenic heat producing element hpe distributions in the planet s crust and mantle the gamma ray spectrometer grs on the 2001 mars odyssey spacecraft has mapped the surface abundances of hpes across mars from these data we produce the first models of global and regional surface heat production and crustal heat flow as previous studies have suggested that the crust is a repository for approximately 50 of the radiogenic elements on mars these models provide important directly measurable constraints on martian heat generation our calculations show considerable geographic and temporal variations in crustal heat flow and demonstrate the existence of anomalous heat flow provinces we calculate a present day average surface heat production of 4 9 0 3 10 11 w kg 1 we also calculate the average crustal component of heat flow of 6 4 0 4 mw m 2 the crustal component of radiogenically produced heat flow ranges from 1 mw m 2 in the hellas basin and utopia planitia regions to 13 mw m 2 in the sirenum fossae region these heat production and crustal heat flow values from geochemical measurements support previous heat flow estimates produced by different methodologies

lake sediment record of late holocene hurricane activities from coastal alabama coastal lake sediments contain a stratigraphically and chronologically distinct record of major hurricane strikes during late holocene time frederic a category 3 hurricane that struck the alabama coast on the gulf of mexico in 1979 left a distinct sand layer in the nearshore sediments of lake shelby as a result of storm tide overwash of beaches and dunes sediment cores taken from the center of lake shelby contain multiple sand layers suggesting that major hurricanes of category 4 or 5 intensity directly struck the alabama coast at ca 3 2 3 0 2 6 2 2 1 4 and 0 8 ka 14 c yr with an average recurrence interval of 600 yr the alabama coast is likely to be struck by a category 4 or 5 hurricane within the next century

holocene sea level history of the northern coast of south china sea abstract this study has collected and analyzed seven sediment cores from the pearl river delta from which 16 new and high quality sea level index points are generated using a new approach this study has also re checked and re calibrated the previously published sea level data from china s southeast coast with corrections made for tectonic subsidence and sediment compaction factors these sea level data indicate a rise of relative sea level from 49 3 0 8 m to the present height between 10 500 and 7000 cal a bp this sea level history is similar to those recorded from other far field locations and ice volume equivalent sea level models the early to early middle holocene sea level history in the study area shows a phase of accelerated rise at a rate increasing rapidly from 16 4 6 1 mm a at 10 500 cal a bp to 33 0 7 1 mm a at 9500 cal a bp this phase was followed by a period of rapid decrease in the rate of sea level rise to 8 8 1 9 mm a at 8500 cal a bp and 1 7 1 3 mm a at 7500 cal a bp during the past 7000 years the relative sea level in the study area changed very little this new and complete history of holocene sea level change supports the following findings 1 no obvious higher than present sea level highstand in the holocene is found from the northern south china sea 2 certain proportion of the effects of the predicted glacial isostatic adjustment were cancelled out by the effects of the weak upper mantle viscosity in the study area 3 meltwater pulse 1b likely exists spanning into the early holocene 4 there are significant misfit between sea level data and glacial isostatic adjustment models and a revision to the existing ice melting history for the early holocene is possibly needed

storm cycles in the last millennium recorded in yongshu reef southern south china sea large storm relocated porites coral blocks are widespread on the reef flats of nansha area southern south china sea detailed investigations of coral reef ecology geomorphology and sedimentation on yongshu reef indicate that such storm relocated blocks originated from large porites lutea corals growing on the spurs within the reef front living coral zone because the coral reef has experienced sustained subsidence and reef development during the holocene dead corals were continuously covered by newly growing coral colonies for this reason the coral blocks must have been relocated by storms from the living sites and therefore the ages of these storm relocated corals should approximate the times when the storms occurred rapid emplacement of these blocks is also evidenced by the lack of coral overgrowth encrustation or subtidal alteration u series dating of the storm relocated blocks as well as of in situ reef flat corals suggests that during the last 1000 years at least six strong storms occurred in 1064 30 1210 5 1201 4 1336 9 1443 9 1685 8 1680 6 1872 15 ad respectively with an average 160 year cycle 110 240 years the last storm which occurred in 1872 15 ad also led to mortality of the reef flat corals dated at similar to 130 years ago thus the storm had significant impacts on coral reef ecology and morphology c 2004 elsevier b v all rights reserved

depth of faulting on mercury implications for heat flux and crustal and effective elastic thickness 1 topographic profiles across a lobate fault scarp on mercury have been used to constrain the depth of faulting to 30 40 km here we use this depth to place constraints on the crustal thickness and heat flow into the base of the crust with no crustal heat production the mantle heat flux on mercury at the time of scarp formation was 30 50 mwm 2 however higher crustal heat production rates allow significantly lower mantle heat fluxes in all cases the mantle heat flux exceeds the likely radiogenic heat flux 4 gyr ago it is likely that secular cooling accounted for the remainder irrespective of crustal heat generation a crustal thickness of 140 km is required to satisfy both the faulting observations and the requirement that the base of the crust does not melt the effective elastic thickness of the lithosphere at the time of faulting is predicted to be 25 30 km

density and lithospheric structure at tyrrhena patera mars from gravity and topography data the tyrrhena patera highland volcano mars is associated with a relatively well localized gravity anomaly and we have carried out a localized admittance analysis in the region to constrain the density of the volcanic load the load thickness and the elastic thickness at the time of load emplacement the employed admittance model considers loading of an initially spherical surface and surface as well as subsurface loading is taken into account our results indicate that the gravity and topography data available at tyrrhena patera is consistent with the absence of subsurface loading but the presence of a small subsurface load cannot be ruled out we obtain minimum load densities of 2960 kg m 3 minimum load thicknesses of 5 km and minimum load volumes of 0 6 106 km3 photogeological evidence suggests that pyroclastic deposits make up at most 30 of this volume such that the bulk of tyrrhena patera is likely composed of competent basalt best fitting model parameters are a load density of 3343 kg m 3 a load thickness of 10 8 km and a load volume of 1 7 106 km3 these relatively large load densities indicate that lava compositions are comparable to those at other martian volcanoes and densities are comparable to those of the martian meteorites the elastic thickness in the region is constrained to be smaller than 27 5 km at the time of loading indicating surface heat flows in excess of 24 mw m 2

flexure of the continental lithosphere with multilayered rheology summary in this paper a model of flexure of the continental lithosphere is derived taking into account crustal and mantle rheologies bending of the continental lithosphere is modelled with a double yield stress envelope three layers brittle elastic and ductile for the crust and three analogous layers for the mantle portion the deformation of the layers is controlled by the rheological properties of quartz rich crustal rocks and olivine rich mantle rocks the influence of various factors such as the depth of moho strain rates thermal structure of the lithosphere boundary conditions and topographic load is examined results show that the mechanical strength of the continental lithosphere in the horizontal and vertical directions is primarily controlled by the present thermal structure of the plate boundary forces and moments and the applied topographic load this explains why mountainous regions may be more locally compensated than adjacent regions we also thus are able to explain why many continental plates have apparent effective rigidities much smaller than those predicted on the basis of their geological ages the model is then applied to the tien shan tarim area central asia and original topography and gravity data are used to constrain parameters of the model we found that the model satisfactorily matches the data and is also able to predict the thermal state of the plate and the location of the deep seismicity

variations of elastic plate thickness at continental thrust belts after examining 15 reliable estimates of the elastic thickness of the lithosphere where it underthrusts mountain belts in europe asia and the americas we conclude that the strength of continental lithosphere as a function of depth must be very different from that of oceanic lithosphere depending on the state of stress continental lithosphere may be either very much stronger or very much weaker than would be predicted for oceanic lithosphere of the same thermal age we explain this observation as the result of two competing effects a thicker thermal plate beneath the continents which allows a deeper elastic ductile transition for plates more than 100 million years old and a low activation energy for ductile creep in the continental crust which leads to massive failure of the upper elastic lithosphere at high bending stresses the 100 km values for elastic plate thickness of billion year old lithosphere require a thermal plate thickness of at least 250 km the magnitude of apparent thinning of the elastic plate at high stress is consistent with that calculated from a simple yield envelope which includes a ductile zone in the lower crust the low yield strength of continental materials leads to correlations between effective elastic plate thickness and all of the following dip of the underthrust plate radius of curvature of the thrust front in map view and total length of the mountain belt using insight derived from laboratory experiments on the buckling of spherical shells and drawing analogies with the geophysical characteristics of oceanic subduction zones we arrive at the following sequence of causes and effects the primary variable is the dip of the downgoing plate presumably prescribed by its own excess mass and pressure exerted by dynamic flow in the mantle where this dip is steep the rigidity of the plate is weakened due to inelastic yielding the weakened plate can then buckle at small wavelengths into short arcuate mountain belts thus we believe that the mantle ultimately controls the pattern of surface tectonics but that the nonelastic rheology of the lithosphere is the mechanism by which that control is imposed

martian wrinkle ridge topography evidence for subsurface faults from mola mars orbiter laser altimeter mola topography shows distinct elevation offsets across wrinkle ridges that can be explained simply by subsurface thrust faults mola has provided the first reliable topographic data of wrinkle ridges to test models for their origin although previous work has shown that wrinkle ridges result from compressional folding and faulting of near surface units the role of thrust faulting and its depth penetration have been argued topographic profiles across wrinkle ridges in solis planum lunae planum tempe terra xanthe terra arcadia terra sirenum thaumasia planum arabia terra syrtis major and hesperia planum show characteristic features such as superposed hills crenulations and elevation offsets between the plains on either side of the ridge the characteristic elevation offsets between plains surfaces on either side of the ridges shown by mola are easily explained by subsurface thrust faults that underlie the ridges and produce the offset in solis dorsa wrinkle ridges are 10 20 km wide well resolved by the 300 m spaced mola elevations have a total relief of 80 250 m and have elevation offsets of 50 180 m well above the uncertainty in the mola elevations mola topography shows that the plains decrease in elevation toward the southeast and are deformed into folds or arches not visible in images that are parallel to and in between the ridges the elevations of the plains on either side of the ridges in solis and lunae plana are characteristically down to the southeast and east respectively suggesting that faults beneath the wrinkle ridges offset the plains this offset indicates underlying thrust faults that dip to the northwest and west respectively and systematically lower the southeast side of the plains the observation that the elevation offsets across the ridges are maintained to the next ridge implies that the thrust fault penetrates to depths of tens of kilometers and thus well into the mechanical lithosphere small foreland basement uplifts on earth in which slip on shallowly dipping thrust faults in the crystalline basement is accommodated by folding in the overlying sedimentary rocks appear to be broadly analogous to these groups of wrinkle ridges and suggest that they are examples of thick skinned compressional deformation on mars these observations are not consistent with models for the formation of wrinkle ridges that involve folding of near surface layers only or subsurface thrust faults that flatten into decollements at shallow depths

shoreface ravinement evolution tracked by repeat geophysical surveys following hurricane ike bolivar peninsula texas 2008 2013 we have investigated the impact of hurricane ike on the shoreface of the bolivar peninsula texas using three nearsurface marine geophysical surveys during a five year span following the storm which made landfall in september of 2008 multibeam bathymetry sidescan backscatter and chirp subbottom reflection data were collected during each survey the first survey in november 2008 discovered the presence of an erosional landward facing scarp across a broad of the barrier spit shoreface at approximately 3 5 m water depth the erosion incised into a shallow reflection horizon interpreted as the holocene shoreface ravinement exposing lag deposits that were truncated at the scarp and forming a thin high backscatter anomaly up to 1 0 m of material was excavated shoreward of the scarp including up to 0 5 m of shoreface sand above the shoreface ravinement and another 0 5 m of indeterminate

post 19 ka b p eruptive history of ulleung island korea inferred from an intra caldera pyroclastic sequence ulleung island is a quaternary volcanic island located in the mid western part of the east sea sea of japan back arc basin which has erupted from the pliocene until the late holocene this study focuses on reconstructing the latest eruptive history of the island by describing the sedimentological and stratigraphic characteristics of the most recent trachytic phonolitic pyroclastic sequence named the nari tephra formation this formation is preserved as a succession of unwelded pyroclastic and epiclastic deposits within an embayed margin of the nari caldera the embayment acted as a topographic trap for proximal pyroclastic deposits and contains a complete record of the past 19 000 years of eruption history the formation includes evidence for five separate eruptive episodes member n 1 to n 5 with intervening weathered and or soil horizons indicating hundreds to thousands of years of repose between each eruption eruption styles and depositional mechanisms varied between and during individual episodes reflecting changing dynamics of the magma plumbing system magmatic gas coupling and a variable role of external water extra caldera sequences show that only a few of these eruptions generated sustained eruption columns or pyroclastic density currents pdcs large enough to overtop the caldera wall thus tephra sequences outside the caldera provide an underestimate of eruption frequency and care needs to be taken in the interpretation and correlation to distal tephra sequences recognized in marine and terrestrial records in addition topographic effects of caldera structures should be considered for the assessment of pdc related hazards in such moderately sized pyroclastic eruptions

depositional events and their records an introduction abstract event deposits of some lateral extent as defined here occur almost in all types of sedimentary basins the reflect either local intra basinal processes or they are associated with regional or global mechanisms some types of event beds such as sediment gravity flows sandy and muddy turbidites are common and usually well preserved they make up large proportions of basin fills whereas others e g tsunami deposits and in situ earthquake structures appear to be less frequent or rare in the geological record volume frequency and facies of event deposits are controlled by several processes pre event sediment accumulation triggering and transport mechanisms and mode of final deposition

the gravitational signature of martian volcanoes by modeling the elastic flexure of the martian lithosphere under imposed loads we provide a systematic study of the old and low relief volcanoes 3 2 ga 0 5 to 7 4 km and the younger and larger prominent constructs within the tharsis and elysium provinces 3 2 ga 0 5 to 7 4 km and the younger and larger constructs clustered in the tharsis and elysium provinces 3 ga 5 8 to 21 9 km the observed topography is used to define the load and to derive a simulated gravity field that is compared to the observed gravity the bulk density of the lava that composes all volcanoes is found to be 3 200 kg m 3 which is representative of iron rich basalts as sampled by the martian basaltic meteorites the elastic part of the lithosphere that is the part maintaining loads over geologic time is found to have been thin when the small old volcanoes formed which implies that the lithosphere was hot early in geologic history conversely larger volcanoes are found to have been emplaced on a cold and thicker elastic lithosphere

technological and behavioural complexity in expedient industries the importance of use wear analysis for understanding flake assemblages abstract expedient lithic technology has been described as unchanging and without or very limited presence of formal tool types however this premise seems to limit the discussion on technological and behavioural complexity when studying amorphous flake industries to address this issue we employed multi stage use wear analysis to identify features that are not detectable through macroscopic approach our analysis of chert tools from leang sarru north sulawesi indicated the use of both unmodified flakes and retouched tools for plant processing and we detected evidence for the manufacture of composite tools microscopic wear traces on unretouched flakes show that these were attached to shafts for possible use as hafted tools but not necessarily as projectiles our results suggest that simple flake assemblages can be part of complex tool production and present an alternative view on the seemingly unchanging lithic technology from the late pleistocene to the holocene furthermore our current understanding of expedient lithic technology should be reassessed as features that are not observable with standard morphological and technological analyses may be detected through use wear analysis overall the applied methodology and results of this study are relevant to pleistocene and early holocene archaeological sites and assemblages that exhibit the dilemma of inferring technological and behavioural complexity through the analysis of simple stone tools

thermal and compositional evolution of the martian mantle effects of phase transitions and melting abstract we present new numerical models for the thermochemical evolution of the mantle of mars over the past 4 gy specifically we have developed a parameterized model of composition and thermoelastic properties of mantle material and combined it with a two dimensional anelastic compressible convection and melting algorithm in a spherical annulus geometry these models include a detailed treatment of the effects of solid solid phase transitions and of compositional changes that accompany generation and removal of mantle partial melt during magmatism among other questions we examine if a perovskite ferropericlase layer pv fp exists at the base of the martian mantle if long lived plumes can explain the volcanic provinces under which circumstances mars may still be volcanically active and how iron and radionuclide rich mars is results of the models are compared with geophysical and chemical observations from spacecraft and information from martian meteorites most models yield crustal thicknesses between 75 and 90 km ancient depths for the curie temperatures of possible magnetic carriers that include the entire crust and mechanical lithosphere thicknesses that increased from less than 100 km in the noachian to 200 250 km now generally models with a large core mg 0 75 and radionuclide contents derived from those suggested by wanke and dreibus chemistry and accretion history of mars philos trans r soc lond a 349 285 293 1994 tend to explain observations best but none of the models reproduces the full range of concentrations found in martian meteorites thus implicitly supporting the idea that ancient chemical heterogeneities survive in the mantle only a subset of the models develops a pattern of mantle convection that evolves towards two or three large long lived plumes and it takes at least 2 gy before this stage is reached whereas models with a larger number of plumes or with plumes that are less stationary are more common as tharsis and probably elysium are older than 2 5 3 gy either model assumptions more complex than those made in this study or a dynamical mode different from low degree convection with long lived large plumes is required to explain these major volcanic provinces the effect of the mid mantle phase transitions on mantle dynamics is rather weak so that whole mantle convection prevails however a basal pv fp layer would form a dynamically separate unit and decouple the mantle and core to some extent

600 year sedimentary archive of hurricane strikes in a prograding beach ridge plain southwestern louisiana abstract this study tests a novel approach to paleotempestology substituting the lateral time depth of a prograding beach ridge plain for the vertical time depth of an aggrading coastal lake pond lagoon swamp or marsh trenching and coring of a beach ridge plain in southwestern louisiana revealed six sand beds and one shell bed interpreted as hurricane washover deposits the sand beds are readily distinguished from enclosing marsh sediments by their higher sand content lower organic content and contrasting microfossil assemblages based on the modern analogs of hurricanes audrey 1957 rita 2005 and ike 2008 and consideration of nearby landfalling hurricanes in the historical record it was determined that the storm intensity threshold of the study site is equivalent to a category 3 hurricane there is a wide variation in hurricane strike frequency between this site and other sites bordering the gulf of mexico this variation results from differences in site sensitivity and the nature of geologic or geochemical proxies used to derive hurricane strike records the approach demonstrated by this study could have applicability at other sites around the world where beach ridge plains are subject to tropical cyclone strikes

natural and human impacts in a 35 000 year vegetation history in central new britain papua new guinea abstract phytoliths and micro charcoal from the yombon airstrip archaeological site in central new britain papua new guinea provide the longest vegetation history record yet available for the new guinea islands the record begins about 35 kya with the first evidence for human presence at the site and with the exception of the last glacial maximum period is continuous to the present three other sites provide supplementary evidence including plant macro remains from the early holocene onwards the record is punctuated by a series of volcanic events which are reflected in the vegetation record by alternating frequencies of closed forest and regrowth elements micro charcoal is present from the oldest levels and fluctuates in frequency throughout the sequence increasing substantially from the terminal pleistocene early holocene onwards this coincides with the first appearance of panicoid grasses and a range of potential cultivars including bananas and saccharum increased levels of burning coinciding with the appearance of potential plant cultivars may indicate shifts in plant food production leading to cultivation from the early holocene onwards this compares favourably with previously reported evidence from garua island off the north coast of new britain the combination of trends in burning vegetation clearance and appearance of potential cultivars on new britain appears to parallel changes in the papua new guinea highlands at a similar time and suggests regional similarities in subsistence and vegetation management practices from before the lgm onwards further studies are needed to clarify the timing and extent of these shifts across the region and to provide a vegetation picture for the period before human colonisation of new britain

finding resolution for the howiesons poort through the microscope micro residue analysis of segments from sibudu cave south africa in this paper i present the results of a micro residue analysis of stone segments the type fossils of the howiesons poort technocomplex in south africa with an age of more than 60 ka at sibudu cave kwazulu natal fifty three segments were systematically analysed and 1826 organic micro residue occurrences were documented on the sample the distribution patterns of micro residues and other use traces are interpreted in terms of hafting and function it is shown that most of the tools were indeed hafted and most were probably used as inserts for hunting weapons there is evidence for differences and changes over time in haft materials and hafting configurations of the segments the study demonstrates how functional studies could improve our understanding of change and variability in human behaviour during the middle stone age a period that used to be portrayed as static or slow changing

holocene hydrological and sea surface temperature changes in the northern coast of the south china sea abstract in order to reconstruct the holocene environmental history of a coastal site in the northern south china sea this study analysed the organic carbon isotope ratios 13corg and alkenone unsaturation ratios uk 37 from a 36 5 m long sediment core drilled at seabed in the mouth region of the pearl river estuary and generated a coupled hydrological and temperature record this record reveals changes of monsoon induced sediment discharge and sea surface temperature of the holocene in four stages in stage i the site was under fluvial conditions prior to postglacial marine transgression stage ii saw an increase of sea surface temperature from c 23 0 c to 27 0 c associated with a strengthened summer monsoon from c 10 350 to 8900 cal years bp this was also a period of rapid sea level rise and marine transgression during which the sea inundated the palaeo incised channel i e the lower part of the t shape accommodation space created by the rising sea in these 1500 years fluvial discharge was strong and concentrated within the channel and the high sedimentation rate 11 8 mm year was very close to the rate of sea level rise in the subsequent 2000 years stage iii sea level continued to rise and the sea flooded the broad seabed above the palaeo incised channel resulted in fluvial discharge spreading thinly across the wide accommodation space and a much reduced sedimentation rate 1 8 mm year sea surface temperature in this stage reached 27 3 c initially but dropped sharply to 26 1 c towards c 8200 cal years bp the final stage covers the last 7000 years and the site was under a stable sea level sedimentation in this stage varied a little but averaged at 1 8 mm year whilst fluvial discharge and sea surface temperature didn t change much two short periods of hydrological and temperature change were observed which are related to the climatic cooling events of c 4200 cal years ago and the little ice age

heat flows through the ice lithosphere of europa some of the geological features on the surface of europa s ice shell suggest the existence of a brittle lithosphere that in some regions is no more than 2 km thick the surface heat flow needed to put the brittle ductile transition in ice at a depth of 2 km is at least 100 mw m 2 much higher than predicted by tidal heating models for a purely conductive ice shell a possible explanation lies in the probable existence of a convective layer beneath the brittle lithosphere which owing to tidal dissipation in warm ice could contribute to higher heat flows if a convective subsurface layer and grain size dependent flow behavior of ice are admitted the grain size at brittle ductile transition depth cannot be 1 mm which is consistent with the required value for the onset of convection in an ice shell thinner than 20 km

emplacement and movement of boulders by known storm waves field evidence from the okinawa islands japan abstract field observations from previous studies of boulder movements were compiled to augment our own work on boulders that have been displaced by storm waves during recent typhoon events in the okinawa islands japan to elucidate the ability of storm waves to move boulders our observations reveal that recent storm waves displaced by sliding and overturning 100 ton boulders emplacing them on the reef or high cliff tops and that storm waves might also be capable of displacing 200 ton boulders on the reef the weights of storm wave boulders at the okinawa islands are of comparable order to those boulders displaced by historical tsunami origins consequently boulder weight alone is an inappropriate parameter to discriminate between tsunami or storm wave processes however these heavy storm wave boulders are close to the reef and cliff edges while tsunami boulders can be deposited much further inland hence horizontal displacement distance of boulders could be a useful parameter to discriminate boulders deposited by the tsunami and storm waves on the wide fringing reef the storm wave boulders were characteristically concentrated on the southeastern pacific ocean sides of each island but large boulders are rarely found on the northwestern east china sea side this is probably because the storm wave intensities are generally stronger at the southeastern side than at the northwestern side although differences of reef strength and initial condition of boulders should also be taken into account consideration of the high frequency of typhoons at the area suggests that effects of the storm waves and the consequent displacement of boulders on the reef might have contributed to the formation of the reef moat framework that typifies the okinawa islands especially if the moat is located within the transport limit of the storm wave boulders approximately 300 m from the reef edge at the islands

reconstruction of prehistoric landfall frequencies of catastrophic hurricanes in northwestern florida from lake sediment records abstract sediment cores from western lake provide a 7000 yr record of coastal environmental changes and catastrophic hurricane landfalls along the gulf coast of the florida panhandle using hurricane opal as a modern analog we infer that overwash sand layers occurring near the center of the lake were caused by catastrophic hurricanes of category 4 or 5 intensity few catastrophic hurricanes struck the western lake area during two quiescent periods 3400 5000 and 0 1000 14 c yr b p the landfall probabilities increased dramatically to ca 0 5 per yr during an hyperactive period from 1000 3400 14 c yr b p especially in the first millennium a d the millennial scale variability in catastrophic hurricane landfalls along the gulf coast is probably controlled by shifts in the position of the jet stream and the bermuda high

holocene indian ocean tsunami history in sri lanka sediment cores from karagan lagoon in southeastern sri lanka retrieved deposits from the a d 2004 indian ocean tsunami and older similar deposits that provide evidence for a tsunami 2417 152 cal calendar yr b p to 2925 98 cal yr b p and for six tsunamis between 4064 128 cal yr b p and 6665 110 cal yr b p a period for which the sediment record appears continuous radiocarbon dating indicates that the recurrence interval is variable ranging from 181 517 yr to 1045 334 yr with a mean recurrence interval of 434 40 yr during the ca 4000 7000 cal yr b p continuous interval assuming that these tsunamis were generated by giant earthquakes along the sumatra andaman subduction zone a reasonable assumption for this far field transoceanic location this record extends the giant earthquake history for the indian ocean region the longest recurrence interval of more than 1000 yr implies that earthquakes along the subduction zone may reach twice the size of the 2004 earthquake

crustal heat flow a guide to measurement and modeling g r beardsmore and j p cull cambridge university press 2001 324 p 100 00 hardback 37 95 paperback crustal heat flow 2001 cambridge university press is an engaging volume an inexpensive introduction to geothermal techniques and applications this text was intended by the authors to be a handbook for geologists and geophysicists who manipulate thermal data particularly for petroleum exploration it is also considered by the authors to be a text that would form the basis of a course on these topics the book provides important information in a format accessible to specialists and lay scientists interested in thermal methods but suffers from some inconsistent handling of basic concepts the book is divided into three primary sections the thermal state of the earth measurement techniques and modelling techniques the first section includes background information on the origin and thermal evolution of our planet units and fundamental theory and mechanisms by which heat is created and transported the second section describes methods for measuring thermal gradients thermal properties and paleo thermal indicators thermal maturity the third section of the book describes calculation of heat flow from field and lab measurements common corrections correlations between heat flow and other geological parameters models for lithospheric creation and evolution numerical methods and sedimentary basins is there a need for a book like this

reconstruction of holocene monsoon history from the pearl river estuary southern china using diatoms and carbon isotope ratios this study employs a multiproxy approach in the reconstruction of holocene monsoon history from sedimentary sequences obtained from the pearl river estuary southern china a set of modern surface sediment samples were collected within and outside the estuary and a sediment core was obtained from the mouth of the estuary a range of modern environmental variables were recorded including water salinity summer winter and annual average and water depth the diatom results show a good relationship with water salinity with marine diatoms dominating the more distal samples from outside the main estuary and freshwater diatoms dominating the proximal samples influenced by higher freshwater flux this pattern is matched by the bulk organic carbon isotopes the isotope values vary between 21 1 0 3 0 for samples from the fully marine environment between 23 2 0 8 and 23 7 0 8 for samples from the mid to outer estuary brackish water environment and less than 24 7 1 3 for samples from the inner estuary close to the freshwater sources similarly the c n ratios vary from below 7 0 6 in the marine end members to over 14 8 3 0 in the freshwater end members both the diatom and carbon data from the sediment core reveal a significant increase in freshwater flux from 8500 cal yr bp resulting from the enhanced summer monsoon regime in early holocene the strength of freshwater flux reached its highest between 7500 and 6000 cal yr bp in the last 6000 years freshwater flux decreased towards present reflecting a gradual weakening of the summer monsoon

the early thermal and magnetic state of the cratered highlands of mars surface heat flows are calculated from elastic lithosphere thicknesses for the heavy cratered highlands of mars in terms of the fraction of the surface heat flow derived from crustal heat sources previous heat flow estimations for mars used linear thermal gradients which is equivalent to ignoring the existence of heat sources within the crust we compute surface heat flows following a methodology that relates effective thickness and curvature of an elastic plate with the strength envelope of the lithosphere and assuming crustal heat sources homogeneously distributed in a radioactive element rich layer 20 or 60 km thick the obtained results show that the surface heat flow increases with the proportion of heat sources within the crust and with the decrease of both radioactive element rich layer thickness and surface temperature also the results permit us to calculate representative temperatures for the crust base rock strength for the upper mantle and lower and upper limits to the crustal magnetization depth and intensity respectively for terra cimmeria an effective elastic thickness of 12 km implies between 30 and 80 of heat sources located within the crust in this case the uppermost mantle would be weak at the time of loading and temperatures in the lower crust cold enough to favor unrelaxed crustal thickness variations and to permit deep curie depths in the highlands as suggested by the observational evidence d 2005 elsevier b v all rights reserved

a decadally resolved paleohurricane record archived in the late holocene sediments of a florida sinkhole article i nfo a 4500 year record of hurricane induced storm surges is developed from sediment cores collected from a coastal sinkhole near apalachee bay florida recent deposition of sand layers in the upper sediments of the pond was found to be contemporaneous with significant historic storm surges at the site modeled using slosh and the best track post 1851 a d dataset using the historic portion of the record for calibration paleohurricane deposits were identified by sand content and dated using radiocarbon based age models marine indicative foraminifera some originating at least 5 km offshore were present in several modern and ancient storm deposits the presence and long term preservation of offshore foraminifera suggest that this site and others like it may yield promising microfossil based paleohurricane reconstructions in the future due to the sub decadal 7 years resolution of the record and the site s high susceptibility to hurricane generated storm surges the average local frequency of recorded events approximately 3 9 storms per century is greater than that of previously published paleohurricane records from the region the high incidence of recorded events permitted a time series of local hurricane frequency during the last five millennia to be constructed variability in the frequency of the largest storm layers was found to be greater than what would likely occur by chance alone with intervals of both anomalously high and low storm frequency identified however the rate at which smaller layers were deposited was relatively constant over the last five millennia this may suggest that significant variability in hurricane frequency has occurred only in the highest magnitude events the frequency of high magnitude events peaked near 6 storms per century between 2800 and 2300 years ago high magnitude events were relatively rare with about 0 3 storms per century occurring between 1900 and 1600 years ago and between 400 and 150 years ago a marked decline in the number of large storm deposits which began around 600 years ago has persisted through present with below average frequency over the last 150 years when compared to the preceding five millennia

sedimentary responses to holocene sea level change in a shallow marine environment of southern china abstract this study has examined how the sedimentary processes in the prevalent non deltaic coastal marine environments along the southeast coast of china have responded to sea level change and other environmental drivers during the holocene three sediment cores collected from a shallow marine embayment of the lantau island hong kong on the northern coast of the south china sea were analyzed the results of particle size total organic carbon content organic carbon and nitrogen ratios organic carbon stable isotope ratios abundance of alkenones and radiocarbon dating of these cores have helped reconstruct the sedimentary history of this site this history shares the similarity in sedimentary processes within the deltaic environment for the early holocene because palaeo incised channels exist in both environments the first 1500 years of deposition involved rapid channel infill caused by the rapidly rising sea level and strong monsoon driven discharge this was followed by a period of decelerated sedimentation under strong marine influence as the sea flooded the wide accommodation space in the subsequent two millennia major differences between the two environmental settings occur in the past 7000 years vertical accretion was seen in the non deltaic coastal environment whilst lateral shoreline advance was the dominant process in the deltaic basin the progressively slowing down in sedimentation rate in the non deltaic site during the middle and late holocene was caused by the reduced monsoon discharge intensified disturbance from tropical cyclone activity and coastal currents

tsunami hazard and early warning system in south china sea abstract in this paper we discuss the potential tsunami hazard in the south china sea region we focus our discussions on the characteristics of tsunamis generated from earthquakes along the manila subduction zone a procedure is presented for establishing a tsunami early warning system in the region a scenario case is used to demonstrate the feasibility of the early warning system

reconstructing late holocene palaeoenvironments in bangladesh phytolith analysis of archaeological soils from somapura mahavihara site in the paharpur area badalgacchi upazila naogaon district bangladesh palaeoenvironmental reconstruction based on phytolith analysis of late holocene aged soils in and around the somapura mahavihara archaeological monastery site in the paharpur area badalgacchi upazila of naogaon district in northwestern bangladesh was undertaken results indicate five climate zones marked by alternatively cool and temperate events the phytolith assemblages of zones 1 3 and 5 are clearly characterized by a higher proportion of pooideae phytoliths the climate indices for these zones are all greater than 50 indicating cooler climatic conditions in contrast the phytolith assemblages of zones 2 and 4 are typified by a higher proportion of panicoideae phytoliths their climate indices are 42 and 44 respectively indicating the presence of a warmer more temperate climate in general the dominance of grasses over broad leaved trees throughout the sequences suggests that generally cool to temperate and dry conditions with some cyclical variability persisted around paharpur and the surrounding region throughout the pala dynasty from ad 730 to 1080 the question of whether these shifts in vegetation might be linked with el nino southern oscillation events and whether these might in turn have cultural responses is raised

holocene explosive eruptions of witori and dakataua caldera volcanoes in west new britain papua new guinea abstract witori and dakataua caldera volcanoes have been very active in the middle to late holocene using tephrochronology this paper establishes the chronostratigraphy of these eruptions and their magnitude and the frequency of explosive volcanism at witori and dakataua after a long dormancy witori started explosive activity at ca 5600 conventional radiocarbon years bp producing in the next 4500 years five major tephra layers w k1 to w k4 w g with veis of 5 to 6 after the w g eruption at around 1200 bp the activity decreased in magnitude but increased in frequency with some eruptions forming central cones the major eruption of dakataua began with alternating ejections of phreatomagmatic ashfalls and plinian deposits followed by the cataclysmic eruption resulting in lithic rich pyroclastic flows ca 1100 1200 bp the major tephra layers cover extensive areas in west new britain due to their large volumes and the prevailing easterly winds providing valuable time markers for establishing holocene chronology the largest eruption the w k2 event of ca 3300 bp shaped much of the present landscape with an extensive area significantly devastated by tephra falls and pyroclastic flows obsidian and other artefacts buried by the tephras indicate that the area was repeatedly occupied the major tephra events formed new coastal plains favourable for human occupation

the history of water salinity in the pearl river estuary china during the late quaternary this research reconstructed the late quaternary salinity history of the pearl river estuary china from diatom records of four sedimentary cores the reconstruction was produced through the application of a diatom salinity transfer function developed based on 77 modern surface sediment samples collected across the estuary from shallow marine environment to deltaic distributaries the statistical analysis indicates that the majority of sediment samples from the cores has good modern analogues thus the reconstructions are reliable the reconstructed salinity history shows the older estuarine sequence formed during the last interglacial was deposited under similar salinity conditions to the younger estuarine sequence which was formed during the present interglacial further analysis into the younger estuarine sequence reveals the interplays between sea level monsoon driven freshwater discharge and deltaic shoreline movement key factors that have influenced water salinity in the estuary in particular a core from the delta plain shows the effects of sea level change and deltaic progradation while cores from the mouth region of the estuary reveal changes of monsoon driven freshwater discharge this study demonstrates the advantages of quantitative salinity reconstructions to improve the quality of reconstruction and allow direct comparison with other quantitative records and the instrumentally observed values of salinity copyright 2010 john wiley sons ltd

crustal heat production and the thermal evolution of mars the chemical composition of soils and rocks from the pathfinder site and phobos 2 orbital gamma ray spectroscopy indicate that the martian crust has a bulk composition equivalent to large ion lithophile lil and heat producing element k th u enriched basalt with a potassium content of about 0 5 a variety of radiogenic isotope data also suggest that separation of lil enriched crust and depleted mantle reservoirs took place very early in martian history 4 0 ga accordingly if the enriched martian crust is 30 km thick it is likely that a large fraction up to at least 50 of the heat producing elements in mars was transferred into the crust very early in the planet s history this would greatly diminish the possibility of early widespread melting of the martian mantle

combining historical and 14 c data to assess pyroclastic density current hazards in banos city near tungurahua volcano ecuador pyroclastic density currents pdcs from tungurahua volcano ecuador recurrently rush down the northern vazcun valley and threaten the small tourist city of banos located on its mouth estimating pdc hazards i e pdc return rate and extent is difficult in banos and vazcun because data from the literature are rare and debated while geological exposures are few and vegetated to improve our awareness of pdc hazards in the banos area we examined historical documents conducted new geological research in the vazcun valley and obtained additional 14c data we highlight complex radiocarbon results that may lead to difficulties when interpreting the pdc chronology and offer recommendations to improve sampling strategies for 14c age determinations of pdc deposits overall our results show that the 1640 1773 and 1886 pdc forming eruptions are recorded in the valley while products of the 1918 and 2006 events were likely removed through considering recorded unrecorded bias in the reconstruction of past pdc emplacement in vazcun we calculate a minimal average return rate of 18 pdc forming events for pre columbian and historical eruptions since the devastating 3 ka bp eruption which translates into a maximum average return rate of 150 200 years in the valley however the archives suggest that most pdcs did not affected the now urbanized banos area e g 1918 2006 and we estimate that the city is impacted on average every 350 500 years a duration that is likely perceived as fairly long for people living in the area the banos case study thus raises questions on how to communicate on uncertain threats and impacts and how to improve alert messages in a town where economic incomes are essentially based on tourist activities to better address these issues we plan in future works to focus on cognitive perception of risk and volcanic hazard judgment by populations of banos and nearby rural communities

evidence for a differentiated crust in solis planum mars from lithospheric strength and heat flow two independent sets of heat flow estimates provide constraints on the hesperian era surface and mantle heat flows and the thickness of the heat producing elements hpe enriched upper crust in the solis planum region of mars the calculations which use the concentration of uppermost crust heat sources deduced from orbital gamma ray spectroscopy and soils geochemistry are based on the effective elastic thickness of the lithosphere and the minimum depth of faults underlying winkle ridges we find that for the majority of analyzed settings the hpe enriched crust is thinner than the whole crust thickness in this region 65 km thus our results strongly support a differentiated martian crust

assessing bioturbation in archaeological sediments using soil morphology and phytolith analysis abstract analysis of ditch infill at an early modern burial complex dating from the 16th century ad in upland northwestern thailand was undertaken to assess the role of bioturbation in interpreting palaeolandscapes evidence for bioturbation and water percolation is contrasted with ams radiocarbon determinations and a phytolith sequence while more than 50 of the sediment column was disturbed by insect activity the dates and phytolith data suggest soil mixing was localized by understanding the processes of bioturbation a distinctive pattern of swidden agriculture over the last 400 years can be distinguished we conclude that for environments conventionally considered to be prone to bioturbation the combination of soil morphology and phytolith analysis provides a new and effective measure of the extent of vertical movement in a sediment column

clues to the lithospheric structure of mars from wrinkle ridge sets and localization instability 1 wrinkle ridges are a manifestation of horizontal shortening in planetary lithospheres for which deformation is localized on faults that underlie individual ridges in ridged plains of mars such as solis planum or lunae planum wrinkle ridges are spaced 40 km apart whereas in the martian northern lowlands where ridges are identified only in mars observed laser altimeter mola altimetric data the ridge spacing is at least 80 km we attribute ridge spacing to an instability of the lithosphere under horizontal compression the localization instability which results in periodically spaced faults montesi and zuber 2003a links the difference of ridge spacing in the northern lowlands and in the highland ridged plains to the difference of crustal thickness via the depth of the brittle ductile transition bdt in solis and lunae plana where the crust is 50 to 60 km thick the crust may be ductile at depth limiting faulting to the bdt of crustal rocks in the lowlands the crust is only about 30 km thick and may be brittle throughout thus the depth of faulting may be controlled by the bdt of mantle rocks which is roughly a factor of two deeper than that of crustal rocks the geotherm can be identical in both regions at 12 3 k km 1 although differences of a few k km 1 can be accommodated within this model the heat flux implied by this geotherm is similar to the heat produced by radiogenic decay 3 gyr ago our analysis provides a rheological explanation for the difference in spacing between ridges in the highlands and the lowlands in contrast to the suggestion of head et al 2002 who proposed that alternating lowlands ridges are buried by sediments in addition finite element models that use the lithospheric structure deduced from ridge spacing show that modest gradients of crustal thickness or heat flux across a ridged plains favor the formation of faults dipping toward high elevation areas as may be the case in solis planum golombek et al 2001

localization of bedding plane slip and backthrust faults above blind thrust faults keys to wrinkle ridge structure a mechanically based model for wrinkle ridge development is developed that combines wrinkle ridge morphologies regional topographic offsets suggestive of subsurface thrust faults and folding of near surface layers this model provides explicit relationships between observed morphologic elements characteristic of wrinkle ridges and plausible mechanisms in the subsurface a key component that is absent in previous qualitative fault based scenarios for these structures as developed in this paper wrinkle ridges are the surface expression of anticlines that grow above a blind thrust fault as a result of both flexural slip folding of near surface strata and the nucleation and growth of echelon arrays of backthrust faults calculations of displacements both horizontal shortening and vertical uplift and coulomb stress change related to slip along blind thrust faults in the model demonstrate physically important spatial inhomogeneities in these quantities with revealing and useful implications 1 the ratio of shortening due to folding at the surface to the shortening due to faulting at depth is characteristically small for coupled wrinkle ridge blind thrust fault systems and decreases with increasing fault depth the depth of the blind thrust fault s upper tip thus profoundly influences the surface strains 2 folding and uplifted topography forming the topographic ridge are produced above the area of the slipping blind thrust fault plane horizontal and vertical deformation at the surface extend over several ridge widths or a total of at least 50 km for a 10 km wide ridge implying that topographic profiles and geologic studies must extend sufficiently far from the wrinkle ridge to fully characterize the surface deformation 3 calculations of coulomb stress changes suggest that fault slip can localize both bedding plane slip in overlying strata and new backthrust faults that propagate upward to become wrinkles on the trailing side of the ridge initiation of bedding plane slip in association with slip along the blind thrust fault likely determines whether the resulting surface structure becomes a wrinkle ridge or a lobate scarp wrinkle ridge spacing may also be related to stress changes associated with slip along the underlying blind thrust fault

thermal modeling of continental subduction and exhumation constrained by heat flow and seismicity in taiwan abstract the thermal evolution of crustal exhumation subsequent to the subduction of the continental margin is modeled through numerical solutions to the two dimensional heat conduction equation the boundary conditions used in the modeling are basically constrained by available geophysical and geological observations in the taiwan area temperature distributions are calculated at one million year intervals over a 5 ma duration although this study presents a tentative estimation based on some reasonable assumptions the preliminary results not only explain the sharp change in seismicity within the crust but also agree with the general heat flow pattern on the surface of taiwan more specifically both the high heat flow and the aseismic belt beneath the eastern central range which are probably attributed to higher temperatures within the crust are modeled by crustal exhumation after the subduction of the continental margin however the occurrence of deeper earthquakes east of the central range is a result of the lower thermal gradient which is due to the subduction of the cold continental crust into the uppermost mantle in summary preliminary thermal modeling supports the possibility of a tectonic model of active continental subduction and crustal exhumation for the taiwan orogen

lithospheric flexure and thermal anomalies plots of effective elastic thickness te of the oceanic lithosphere as a function of age when elastically deformed show a general increase in te with the square root of age although there is much scatter some of the scatter can be eliminated by correcting for the effect of finite yield strength in rocks which makes te for more sharply bent plates underestimate the true depth tm to the rheological boundary at the base of the high strength mechanical lithosphere after converting effective values te to true thicknesses tm it appears that the mechanical lithosphere is always thinner beneath islands and seamounts compared to lithosphere of similar age flexed at subduction zones from several other lines of evidence such as depth anomalies seamount subsidence and heat flow data it has been suggested that the thermal structure in plates subjected to hot spot type volcanism is reset to values appropriate for much younger lithosphere the reduction in mechanical plate thickness beneath hot spot volcanoes is also consistent with this concept of thermal rejuvenation since the strength of rocks decreases exponentially with rising temperature this dependence implies that variations in mechanical plate thickness can be used to map temperature anomalies in the lithosphere since the mechanical plate thickness depends principally upon the temperature at one depth specifically the depth at which the temperature reaches 550 600 c depending on strain rate flexural data are particularly sensitive indicators of the vertical structure of lithospheric reheating compared to quantities dependent on depth integrals of temperature such as swell height and subsidence the thermal rejuvenation hypothesis predicts that the flexural profile should mimic viscoelastic relaxation in the first 10 ma after loading if initially reheating is confined to depths close to and below the 550 c isotherm the flexural data combined with depth anomaly information for hawaii point to extremely rapid reheating localized in the lower lithosphere rejuvenation in the society islands on the other hand is compatible with slower methods of heat injection involving the entire lithospheric column

correction to localized gravity topography admittance and correlation spectra on mars implications for regional and global evolution 1 in the paper localized gravity topography admittance and correlation spectra on mars implications for regional and global evolution by patrick j mcgovern sean c solomon david e smith maria t zuber mark simons mark a wieczorek roger j phillips gregory a neumann oded aharonson and james w head journal of geophysical research 107 e12 5136 doi 10 1029 2002je001854 2002 the thickness of the lithosphere and lithospheric heat flow for a number of regions of mars and as functions of time were inferred on the basis of gravity topography admittance spectra observed admittances derived from spherical harmonic expansions localized with the scheme of simons et al 1997 were compared with those predicted from models for the flexural response to lithospheric loading e g turcotte et al 1981 gravity was calculated according to the finite amplitude scheme of wieczorek and phillips 1998 estimates for the thickness of the elastic lithosphere te at the time of loading for each region were converted to equivalent thermal gradient dt dz and heat flux q by means of an elastic plastic stressenvelope formalism mcnutt 1984 here we describe a correction required in the calculation of the modeled gravity anomalies we report new estimates of te load density rl dt dz and q from corrected model admittances and we discuss the implications of the new results 2 the source of the required correction is a difference in reference radius values as defined by mcgovern et al 2002 the planetary shape was taken to equal the radius from the center of mass of mars to the martian surface expressed as a spherical harmonic expansion and referenced to the mean equatorial radius req 3396 km

the role of water in the deformation of dunite specimens of two natural dunites anita bay of 100 m grain size and aheirn of 900 m grain size have been deformed in experiments at temperatures between 1200 and 1400 c and constant strain rates between 10 4 and 10 6 s 1 in a gas medium deformation apparatus at 300 mpa confining pressure prior to these experiments the specimens were given a heat treatment in a controlled oxygen fugacity furnace at 1200 c for 60 hours to dehydrate the trace layer silicate minerals present and drive off adsorbed water the predried specimens are much stronger than specimens tested under wet conditions in an earlier study the predried specimens also do not show the apparent grain size dependence seen under wet conditions infrared absorption measurements on the present specimens and those of the earlier study indicate that for a given rock flow stress can be correlated with the intensity of a residual water related broad absorption the addition of water to a predried specimen results in both a mechanical reweakening and an intensifying of the broadband infrared component the weakening of the dunites under wet conditions is probably strongly influenced by the presence of small amounts of a water related species in the grain boundaries but intragranular weakening may also be contributing it is suggested that the concentration of the water related species in the grain boundaries is governed by its concentration in the small melt fraction present the amounts of water that have been found to be of importance for the strength of these dunites are of the order of 0 01 wt amounts much less than most estimates of the water content of the earth s undepleted upper mantle such water may have an important role in determining upper mantle flow behavior stress strain curves for all experiments are available with entire manuscript on microfiche order from american geophysical union 2000 florida avenue n w washington dc 20009 document b84 008 2 50 payment must accompany order

new perspectives on ancient mars mars was most active during its first billion years the core mantle and crust formed within 50 million years of solar system formation a magnetic dynamo in a convecting fluid core magnetized the crust and the global field shielded a more massive early atmosphere against solar wind stripping the tharsis province became a focus for volcanism deformation and outgassing of water and carbon dioxide in quantities possibly sufficient to induce episodes of climate warming surficial and near surface water contributed to regionally extensive erosion sediment transport and chemical alteration deep hydrothermal circulation accelerated crustal cooling preserved variations in crustal thickness and modified patterns of crustal magnetization

volcanic disasters and agricultural intensification a case study from the willaumez peninsula papua new guinea abstract environments characterized by frequent volcanic activity provide an excellent opportunity to observe interactions between human land use and ecosystem succession as they unfold over time a case study tracing the history of re colonisation by humans and plants following a series of volcanic disasters during the past 40 000 years in the willaumez peninsula papua new guinea investigates the utility of denevan s models describing variation in the intensity of agricultural practices in wet tropical rainforest environments prior to the introduction of metal tools the archaeological and environmental data obtained to date show that people may have taken advantage of the effects of volcanic activity to establish relatively permanent gardens and therefore avoid the costs associated with shifting cultivation archaeological and plant microfossil data show that humans have been interfering with normal vegetation succession from at least the late pleistocene when long term base camps were established that some patches were used intensively from the early holocene and that groups may have been forced to increase the levels of disturbance after the end of a long period of high magnitude volcanic eruptions

the composition and thickness of the crust of mars estimated from rare earth elements and neodymium isotopic compositions of martian meteorites isotopic and trace element compositions of martian meteorites show that early differentiation of mars produced complementary crustal and mantle reservoirs that were sampled by later magmatic events this paper describes a mass balance model that estimates the rare earth element ree content and thickness of the crust of mars from the compositions of shergottites the diverse ree and nd isotopic compositions of shergottites are most easily explained by variable addition of light rare earth element lree enriched crust to basaltic magmas derived from lree depleted mantle source regions antarctic shergottites eet 79001 alh 77005 lew 88516 and que 94201 all have strongly lree depleted patterns and positive initial 143nd isotopic compositions which is consistent with the generation of these magmas from depleted mantle sources and little or no interaction with enriched crust in contrast shergotty and zagami have negative initial 143nd isotopic compositions and less pronounced depletions of the lree which have been explained by incorporation of enriched crustal components into mantle derived magmas jones 1989 longhi 1991 borg et al 1997 the mass balance model presented here derives the ree composition of the crustal component in shergotty by assuming it represents a mixture between a mantle derived magma similar in composition to eet 79001a and a lree enriched crustal component the amount of crust in shergotty is constrained by mixing relations based on nd isotopic compositions which allows the ree pattern of the crustal component to be calculated by mass balance the effectiveness of this model is demonstrated by the successful recovery of important characteristics of the earth s continental crust from terrestrial columbia river basalts self consistent results for nd isotopic compositions and ree abundances are obtained if shergotty contains 10 30 of lree enriched crust with 10 ppm nd this crustal component would have moderately enriched lree sm nd 0 25 0 27 147sm 144nd 0 15 0 17 la yb 2 7 3 8 relatively unfractionated heavy rare earth elements hree and no eu anomaly crust with these characteristics can be produced from a primitive lherzolitic martian mantle by modest amounts 2 8 of partial melting and it would have a globally averaged thickness of 45 km which is consistent with geophysical estimates mars may serve as a laboratory to investigate planetary differentiation by extraction of a primary basaltic crust

reconstruction of storm tsunami records over the last 4000 years using transported coral blocks and lagoon sediments in the southern south china sea large transported coral blocks on reef flats and elevated sedimentation rates in atoll lagoons were demonstrated to be excellent proxies for past strong storms tsunamis in the southern south china sea here we introduce another important proxy coarse fraction contents of lagoon sediments this proxy is based on the principle that coarse fractions of enclosed lagoon sediments are usually controlled by strong sedimentary dynamics on the surrounding reef flat and thus increases in the weight percentages of coarse grained fractions of the lagoon sediments should also reflect strong storm tsunami events or increases in storminess with the size of the content peak as the proxy for the degree of storminess bearing this in mind we measured the contents of the 1 mm grain size fractions referred to as coarse fraction content in an undisturbed lagoon core precisely dated to cover the last 4000 years the decadal resolution data show a systematic variation with some peaks strongly correlated with in timing with strong storm tsunami events dated at ad 1872 15 1685 8 similar to 1680 6 1443 9 1336 9 1210 5 similar to 1201 4 and 1064 30 using wave transported coral blocks using the mean coarsefraction content 9 2 for the entire core as a reference line a total of 77 peaks were identified for the past 4000 years twenty of these peaks are higher than 23 the mean value for peaks that are correlated in age with the six strong storm events identified using independently dated coral blocks among these 23 peaks 13 occurred within the last 1000 years the concentration of contentpeaks in the last millennium could be partially due to higher deposition rates and sampling resolution over the last similar to 4000 years there appears to be a weakly increasing trend in coarse fraction contents towards present time but this trend is not obvious within the last millennium this long term variation may be related to changes in both storminess and reef lagoon morphology however the data do suggest three extremely stormy periods centring around ad similar to 1200 similar to 400 bc and similar to 1200 bc respectively overall this study demonstrates that combined use of transported coral blocks and coarse fraction contents of lagoon sediments provides an excellent means for comprehensive reconstruction of past storm tsunami activity c 2008 elsevier ltd and inqua all rights reserved

metamorphism in the martian crust compositions of basaltic and ultramafic rocks analyzed by mars rovers and occurring as martian meteorites allow predictions of metamorphic mineral assemblages that would form under various thermophysical conditions key minerals identified by remote sensing roughly constrain temperatures and pressures in the martian crust we use a traditional metamorphic approach phase diagrams to assess low grade hydrothermal equilibrium assemblages basaltic rocks should produce chlorite actinolite albite silica accompanied by laumontite pumpellyite prehnite or serpentine talc only prehnite bearing assemblages have been spectrally identified on mars although laumontite and pumpellyite have spectra similar to other uncharacterized zeolites and phyllosilicates ultramafic rocks are predicted to produce serpentine talc and magnesite all of which have been detected spectrally on mars mineral assemblages in both basaltic and ultramafic rocks constrain fluid compositions to be h2o rich and co2 poor we confirm the hypothesis that low grade hydrothermal metamorphism affected the noachian crust on mars which has been excavated in large craters we estimate the geothermal gradient 20 c km 1 required to produce the observed assemblages this gradient is higher than that estimated from radiogenic heat producing elements in the crust suggesting extra heating by regional hydrothermal activity

ancient heat flow crustal thickness and lithospheric mantle rheology in the amenthes region mars surface heat flow calculations for the amenthes region of mars can be independently performed using the depth to the brittle ductile transition and the effective elastic thickness of the lithosphere estimated for the late noachian early hesperian equivalent to an estimated absolute age of 3 6 3 8 ga this along with crustal heat production rates estimated from heat producing elements abundances permits us to put constraints for that particular place and time on both the thermal and mechanical properties of the lithosphere and the crustal thickness the depth to the brittle ductile transition deduced from modeling of the topography of amenthes rupes is 27 35 km and the associated surface heat flow is 26 37 mwm 2 on the other hand the effective elastic thickness in this region is between 19 and 35 km the surface heat flow deduced by considering crustal and lithospheric mantle contributions to the total lithospheric strength as well as wet or dry olivine for lithospheric mantle rheology is 31 49mwm 2 the relatively limited overlap among te andzbdt based heat flowvalues implies a surface heat flowof 31 36mwm 2 with a high fraction originated from crustal heat sources and awet mantle rheology the so obtained local crustal thickness is 43 74 km which suggests an average thickness of 40 75 km for the martian crust for the frequently used crustal density of 2900 kgm 3 our results suggest a crustal thickness of 50 63km for theamenthes region and an average crustal thickness of 45 65 km for mars