isotope geochemical characteristics of auriferous quartz veins from medium and great depths of xiaoqinling area central china and their significance h o s he and ar isotopes of gold bearing quartz veins from the medium and great depths of xiaoqinling area in central china were studied in this paper the data obtained indicate that the ore forming fluids were dominantly derived from the upper mantle and gradually mixed with crustal fluids along with the metallogenic process according to the temporal and spatial link between the gold mineralization and the tectonic evolution of regional extension in combination with other researchers achievements the authors hold that the main gold mineralization in xiaoqinling area occurred at the post collisional stage of late mesozoic being products of the regional extension resulting from the deep process the extensional tectonic system provided dilatational space for migration mixing and water rock interaction of the ore forming fluids as well as gold enrichment and deposition

unprecedented erosion of the upper texas coast response to accelerated sea level rise and hurricane impacts the upper texas coast is an ideal location to examine coastal response to global change over geologic and historic time here we quantify the long term sequestration for sand eroded from an island into two main sinks offshore galveston island and san luis pass tidal delta in order to compare long term and short term erosion we determine the average storm related offshore sand fl ux for the middle part of the holocene ca 5240 5040 2 cal yr b p to present to be 4200 4400 670 m 3 yr with a decrease in the offshore sand fl ux to 920 970 270 m 3 yr during the latter part of the holocene ca 2730 2610 2 cal yr b p to present the tidal delta initially formed ca 2100 1 median cal yr b p when the rate of sealevel rise slowed from 2 0 mm yr to 0 60 mm yr we calculate the sand fl ux from galveston island into san luis pass from ca 2100 1 median cal yr b p to 200 yr ago to be 4700 m 3

ice sheet sources of sea level rise and freshwater discharge during the last deglaciation we review and synthesize the geologic record that constrains the sources of sea level rise and freshwater discharge to the global oceans associated with retreat of ice sheets during the last deglaciation the last glacial maximum 26 19 ka was terminated by a rapid 5 10 m sea level rise at 19 0 19 5 ka sourced largely from northern hemisphere ice sheet retreat in response to high northern latitude insolation forcing sea level rise of 8 20 m from 19 to 14 5 ka can be attributed to continued retreat of the laurentide and eurasian ice sheets with an additional freshwater forcing of uncertain amount delivered by heinrich event 1 the source of the abrupt acceleration in sea level rise at 14 6 ka meltwater pulse 1a 14 15 m includes contributions of 6 5 10 m from northern hemisphere ice sheets of which 2 7 m represents an excess contribution above that derived from ongoing ice sheet retreat widespread retreat of antarctic ice sheets began at 14 0 15 0 ka which together with geophysical modeling of far field sea level records suggests an antarctic contribution to this meltwater pulse as well the cause of the subsequent younger dryas cold event can be attributed to eastward freshwater runoff from the lake agassiz basin to the st lawrence estuary that agrees with existing lake agassiz outlet radiocarbon dates much of the early holocene sea level rise can be explained by laurentide and scandinavian ice sheet retreat with collapse of laurentide ice over hudson bay and drainage of lake agassiz basin runoff at 8 4 8 2 ka to the labrador sea causing the 8 2 ka event

winter storm induced hydrodynamics and morphological response of a shallow transgressive shoal complex northern gulf of mexico abstract using extended deployments during seasons of low and high discharge from the atchafalaya river meteorological hydrodynamic and bottom boundary layer parameters were monitored from tiger and trinity shoal complex off louisiana coast usa during winter storms the surface current speed measured at both shoals exceeded 0 5 m s and the entire water column followed the prevailing wind direction the current speed close to the bottom exceeded 0 3 m s during high energy northerly winds the mean water level in the shoal complex increased during southerly winds and decreased during northerly winds such that the difference between wind set up and set down exceeded 0 7 m in tiger shoal and 0 6 m in trinity shoal during high energy frontal passages the swell height was inversely correlated with mean water level and increased during pre frontal phase and decreased during post frontal phase of winter storms the sea short waves height responded quickly to wind direction and speed and within a few hours after the wind shifted and blowing from the north the sea height increased during both deployments bimodal wave frequency spectrum was observed during wind veering from southerly to northerly when both sea and swell intensities were significant the tiger shoal bed sediment texture transformed drastically from mud to shell and shell hash assemblage within a period of two weeks during the december 2008 deployment backscatter signal intensity from a pulse coherent acoustic doppler profiler pcadp and its velocity estimates were used to determine the vertical extend and timing of mud resuspension and their eventual flushing out from the shoal environment when exposed to high energy winter storm passages the computed time frame for a total transformation of bottom sediment texture from muddy bottom to shell and shell hash assemblage was supported by the combined wave and bottom current induced shear stress at shoal bed the bed samples collected from tiger shoal before and after the deployment in spring 2009 consisted of more than 80 shell and shell hash which again confirmed a stable bottom as predicted from the pcadp data however the fine sand and mud dominated bed at trinity shoal was highly dynamic and experienced a few cm of ephemeral sediment deposition during the passage of each cold front as revealed from the analysis of acoustic backscatter data from the pcadp suspended sediment concentration estimated from optical backscatterance sensors obs and pcadp were in good agreement during low river discharge events in december 2008 but significantly diverged during the spring 2009 deployment when a high suspended sediment load was discharged into the shelf from the atchafalaya river and subsequently pushed farther offshore into the deployment sites by wind induced strong currents during the passage of cold fronts

beach ridges and prograded beach deposits as palaeoenvironment records abstract beach ridges are landforms commonly developed on prograded coasts with beach shorelines a sequence of beach ridges coupled with their subsurface deposits can be regarded as a time series of coastal evolution methodological advances in field surveying and chronology applicable to beach ridges have led to detailed palaeoenvironmental reconstructions to be derived from such sequences this paper reconsiders the basic aspects of beach ridges and deposits which need to be properly understood for their comprehensive interpretation in a palaeo environmental context it also reviews case studies in which beach ridge sequences have been used to unveil past sea level history catastrophic events and climate changes proposed formative processes of beach ridges include 1 progradation of sandy beach and berm formations in relation to fairweather waves coupled with aeolian foredune accumulation 2 building of gravel ridges by storm waves 3 welding of longshore bars beach ridge formation through sea level oscillation is thought to be questionable and caution is suggested for this process when undertaking palaeoenvironmental reconstruction beach deposit stratification is known to dip either landwards or seawards but landward dips are uncommon seaward dipping stratification is formed in relation to beachface progradation and is usually dissected in places by erosion surfaces resulting from episodic beach retreat the boundary between the foreshore and the underlying shoreface is well defined only in the case that longshore bars lead to complex bedding structure relative to that of the foreshore reliable chronology of beach ridges can be determined by radiocarbon and optically stimulated luminescence osl dating radiocarbon dating of articulated shells which are considered not to be extensively reworked provides robust results but osl dating is more useful as it enables direct dating of sediment grains it is noted that there are restrictions in chronological resolution and continuity inherent to beach ridge and beach deposits the plan view geomorphic expression of beach ridges typically consists of ridge sets with multi decadal intervals whereas their internal sedimentary structures define shorter time scales records of beach sedimentation and erosion are likely to be reworked by episodic high magnitude beach retreat and the resultant record of the net progradation is likely to be sporadic and discontinuous the height of sandy beach ridges is often variable due to differing degrees of aeolian sand accumulation and they are thus not used as sea level indicators unless purely wave built gravel ridge height is a relatively reliable indicator of sea level but can vary in response to storminess fluctuations subsurface sediment facies boundaries are preferred as sea level indicators and those proposed include boundaries of aeolian beach foreshore shoreface and upper lower shorefaces catastrophic events are expressed in both erosional and depositional records erosion surfaces or scarp imprints revealed in a cross section of beach deposits indicate storm or tsunami events however erosional events are likely to rework previous records of sedimentation and even other erosional events and thus the apparent history decoded from the resultant deposits tends to be biased several attempts for estimating the frequency and intensity of prehistoric cyclones rely on assumed relationships between the level of coarse sand beach ridges and cyclone inundation the formative process of coarse sand ridges remains uncertain and needs to be clarified as it constitutes the fundamental basis of these attempts the growth rates of beach ridge systems are expected to reflect fluctuations in river sediment discharge to the coast and in aeolian sand flux due to onshore winds both of which are affected by climate change assessment of the growth rate is potentially improved by ground penetrating radar survey of subsurface structure and by detailed chronology orientation of beach ridges reflects long term trends in wave direction inferred relationships between beach ridges and cyclic fluctuations of sea level and climate rely on weak assumptions and are not substantiated by rigid chronological evidence and thus remain highly questionable correlation between the inherently decadal signal of beach ridge intervals and possible climate cycles such as sunspot activity is probably coincidental as it lacks causal explanations

yangtze delta eastern china 1 geometry and subsidence of holocene depocenter abstract stratigraphic analysis of 59 borings serves to define the subsurface configuration of late quaternary deposits of the outer yangtze delta including both subaerial lower plain and its contiguous submerged sector isopachous maps of the holocene sediment section reveal a linear thickened trend parallel to the lower yangtze estuary chongming island which extends seaward southeast to the mid shelf maps depicting depths of the holocene to late pleistocene contact also highlight this thickened northwest to southeast trend and a deep downward bowing depression formed by the sedimentary sequence seaward of the yangtze mouth radiocarbon dated facies in the cores serve to calculate long term averaged subsidence rates for the holocene section 0 1 to 3 0 mm year on land and 1 6 to 4 4 mm year at sea this preliminary information is vital for planning coastal protection erosion salt water intrusion in this densely populated low lying region vulnerable to marine inundation

quantifying holocene lithospheric subsidence rates underneath the mississippi delta abstract the pattern of holocene relative sea level rsl change on the us gulf coast has been a long standing subject of debate featuring opposing scenarios of continuous submergence versus one or more holocene rsl highstands the significance of this debate is that the relative role of eustasy glacial isostatic adjustment gia and lithospheric flexural subsidence associated with mississippi delta sediment loading remains unresolved here we present a new rsl record from the louisiana chenier plain 100 km west of the mississippi delta margin based on ams 14 c dated marsh basal peat this enables us to provide for the first time constraints on holocene lithospheric subsidence rates underneath one of the world s major deltas our new record conclusively shows that no middle holocene rsl highstands occurred on the central us gulf coast rather it exhibits a pattern of progressive rsl rise comparable to that from the mississippi delta suggesting that long wavelength gia is a dominant deformational process driving lithospheric subsidence in the entire region by means of forebulge collapse nevertheless a 0 15 0 07 mm yr differential rate of subsidence between the chenier plain and key portions of the mississippi delta including the new orleans metropolitan area exists this shows that while the sediment loading effect is real it is about an order of magnitude smaller than recent studies have postulated

deciphering holocene sea level history on the u s gulf coast a high resolution record from the mississippi delta published holocene relative sea level rsl curves for the u s gulf coast are in mutual conflict with some characterized by a smooth rsl rise akin to widely accepted eustatic sea level curves versus others including several recent ones that are characterized by a conspicuous stair step pattern with prolonged millennium scale rsl stillstands alternating with rapid meter scale rises in addition recent work in texas and alabama has revitalized the notion of a middle holocene rsl highstand estimated at 2 m above present mean sea level an extensive sampling program in the mississippi delta louisiana focused on the collection of basal peats that accumulated during the initial transgression of the pre existing consolidated pleistocene basement we used stable carbon isotope ratios to demonstrate that many of these samples accumulated in environments affected by frequent saltwater intrusion in the 30 cm zone between mean spring high water and mean sea level and we selected plant macrofossils that were subjected to ams 14c dating nearly 30 sea level index points from a 20 km2 study area on the eastern margin of the delta suggest that rsl rise followed a relatively smooth trend for the time interval 8000 3000 cal yr b p thus questioning the occurrence of major rsl stillstands alternating with abrupt rises given the narrow error envelope defined by our data set any sea level fluctuations if present would have amplitudes of 1 m although a true middle holocene highstand never occurred in the mississippi delta the high level of detail of our time series enables a rigorous test of this hypothesis correction of our data set for a hypothetical tectonic subsidence rate of 1 1 mm yr 1 assuming a constant subsidence rate compared to the tectonically relatively stable adjacent coast of texas leads to sea levels near 2 m above present during the time interval 6000 4000 cal yr b p however this model also implies a rsl position near 2 m around 8000 cal yr b p which is inconsistent both with data of this age from texas as well as with widely accepted sea level data from elsewhere we therefore conclude that a middle holocene highstand for the u s gulf coast is highly unlikely and that the entire area is still responding glacio isostatically by means of forebulge collapse to the melting of the laurentide ice sheet

the earthquake and tsunami of 1865 november 17 evidence for far field tsunami hazard from tonga summary historical reports of an earthquake in tonga in 1865 november identify it as the only event from that subduction zone which generated a far field tsunami observable without instruments run up heights reached 2 m in rarotonga and 80 cm in the marquesas islands hydrodynamic simulations require a moment of 4 1028 dyn cm a value significantly larger than previous estimates of the maximum size of earthquake to be expected at the tonga subduction zone this warrants an upwards re evaluation of the tsunami risk from tonga to the cook islands and the various polynesian chains which had hitherto been regarded as minor

far field simulation of tsunami propagation in the pacific ocean impact on the marquesas islands french polynesia the islands in the marquesas archipelago are most exposed to far field tsunamis in french polynesia four recent earthquakes located at the pacific rim kurile 1994 chile 1995 mexico 1995 and peru 1996 earthquakes generated trans pacific tsunamis and caused contrasting inundations in several inhabited marquesian bays the aim of this study is to better understand the amplification phenomena observed in the marquesas islands and to improve the risk assessment we present here numerical simulations of these four tsunamis by means of a finite difference model solving the equations of tsunami propagation at different scales the water heights computed in the bays are in excellent agreement with the available observations and thus validate our numerical method these numerical results allow us to determine 1 which propagation azimuths are dangerous for the whole marquesas archipelago and 2 the behavior of each studied bay amplitude frequency in response to tsunami waves we observe that the seismogenic subduction zone along south america is likely to define one of the most dangerous tsunami generation areas for the marquesas archipelago owing to the source geometries and to the trapping of the tsunami energy by bathymetric features in the southern pacific ocean fracture zones seamount chains

how stable is the mississippi delta large deltas are commonly believed to exhibit rapid rates of tectonic subsidence largely due to sediment loading of the lithosphere as a result deltaic plains are prone to accelerated relative sea level rise coastal erosion and wetland loss hurricane katrina s devastation testifies to the severe threat that these processes pose to the mississippi delta but the relative role of tectonics versus other mechanisms causing land subsidence remains elusive relative sea level records derived from basal peat have the potential to quantify differential crustal movements over holocene time scales with exceptionally high accuracy and precision here we present new sea level index points from two study areas in the southwestern mississippi delta that essentially coincide with a recently published detailed relative sea level record from the eastern part of the delta our results show that differential vertical movements among the three study areas have been only 0 1 mm yr 1 w e compare our evidence with a recent sea level compilation from the caribbean to a large extent based on data from areas that are tectonically stable our sea level index points nearly coincide with the caribbean data showing surprising tectonic stability for considerable sections of the mississippi delta however the well documented high subsidence rates in and near the birdfoot of the mississippi delta indicate that different conditions prevail there the rapid wetland loss in coastal louisiana is likely due to a considerable extent to the compaction of holocene strata

mineralogical constraints on the genesis of the dahu quartz vein style au mo deposit xiaoqinling gold district china implications for phase relationships and physicochemical conditions abstract the quartz vein style dahu au mo deposit with an average grade of 6 8 g t for 38 tons au and an average grade of 0 24 for 100 000 tons mo is situated in the xiaoqinling region in the northernmost part of qinling orogen in china it is characterized by enrichment of native gold molybdenite telluride and bi sulfosalt the current understanding of telluride and bi sulfosalt mineralization in the dahu au mo deposit is very poor and this paper is the first systematic study of these minerals in this deposit the au mo ores occur mainly as veins and stockworks as well as disseminated in quartz veins and they are hosted by biotite plagioclase gneiss amphibole plagioclase gneiss and amphibolite of the archaeozoic taihua group four paragenetic stages of mineralization are recognized that reflect early formation of sulfide minerals and subsequent precipitation of telluride minerals i quartz k feldspar pyrite molybdenite ii quartz pyrite molybdenite iii sulfide telluride sulfosalt gold and iv carbonate barite the telluride minerals are mainly altaite tellurobismuthite and tetradymite and to a minor extent calaverite petzite hessite and stutzite some bi sulfosalt minerals also exist in the deposit including aikinite lindstromite saddlebackite krupkaite and hammarite of these minerals saddlebackite krupkaite and hammarite are reported in this deposit for the first time herein the au ag te bi s minerals substantially formed in the dahu au mo deposit under conditions of t 260 c p 100 mpa ph 3 9 to 7 9 log o2 40 9 to 33 8 log te2 12 5 to 7 5 log s2 13 5 to 8 2 log h2s 2 4 to 0 3 and log au aq ag aq 6 7 to 6 2 the deposit formed from an ore forming fluid dominated by hte or and te22 in which au was transported in the forms of au hs 2 and or an unknown aqueous te species e g aute2 furthermore during the mineralization stages of the dahu deposit the ore forming fluid evolved from an initial oxidation type to a later relative reduction type and the telluride minerals bi sulfosalt minerals and native gold were formed in a relatively reduced condition the au ag te mo bi metal associations in the dahu au mo deposit were derived from a magmatic hydrothermal system during the late triassic

spectral analysis of tsunami waves separation of source and topography effects a new approach is proposed to separate the influence of source and topography in observed tsunami spectra and to reconstruct the initial source spectrum the method assumes a linear tide gauge response to external forcing and is based on comparative analysis of tsunami and background spectra evaluation of the ratio of tsunami to background spectra gives functional characteristics that are invariant of station location and dependent only on the source parameters three events the urup tsunami of december 22 1991 northwest pacific the hokkaido southwest okushiri tsunami of july 12 1993 sea of japan and the shikotan tsunami of october 4 1994 northwest pacific are used as examples of the proposed approach the source spectra reconstructed from the analysis of different tide gauges were found to be in good agreement with each other and with the seismological geodetic and field survey data

transient response of harbours to long waves under resonance conditions abstract this paper presents the results of a study aimed at quantifying the time response of harbour basins to long waves under resonance conditions on the basis of numerical simulations reproducing long waves in the yacht harbour of rome ostia italy it shows that the results valid for periodic forcing waves acting for an infinitely long time as those provided by models based on elliptic equations like the helmoltz and the mild slope equations can be misleading with respect to the more realistic ones that can be obtained using time varying wave equations taking advantage of the similarity between the processes studied here and a simple one dimensional resonator a method is also proposed to roughly estimate a time response parameter of each mode of the harbour using results from steady state numerical model results commonly applied for studying harbour resonance in engineering practice on the basis of further numerical simulations aimed at reproducing schematic harbour layouts the effect on resonance of the position of the entrance and of an outer harbour is studied the results indicate that the effects of design solutions to reduce resonance by placing the entrance at the middle of the harbour or using the outer harbour as a resonator can be correctly evaluated only when considering the time needed for the oscillations to fully develop

far field simulation of the 1946 aleutian tsunami summary we present hydrodynamic far field simulations of the aleutian tsunami of 1946 april 1 using both a dislocation source representing a slow earthquake and a dipolar one modelling a large landslide the earthquake source is derived from the recent seismological study by lopez and okal while the landslide source was previously used to explain the exceptional run up at scotch cap in the near field the simulations are compared to a field data set previously compiled from testimonies of elderly witnesses at 27 far field locations principally in the austral and marquesas islands with additional sites at pitcairn easter and juan fernandez we find that the data set is modelled satisfactorily by the dislocation source while the landslide fails to match the measured amplitudes and to give a proper rendition of the physical interaction of the wavefield with the shore in particular at nuku hiva marquesas the emerging picture is that the event involved both a very slow earthquake responsible for the far field tsunami and a major landslide explaining the near field run up but with a negligible contribution in the far field

origin of the ore forming fluids and metals of the hetai goldfield in guangdong province of south china constraints from c h o s pb he ar isotopes abstract the hetai goldfield located in the southern segment of the qinzhou bay hangzhou bay juncture orogenic belt qhjb is one of the largest gold mining districts in south china although the goldfield shares some similarities in ore geology and geochemistry to orogenic gold deposits there has been controversy on the origin of the ore forming fluids and metals an integrated analysis on c h o s pb he ar isotopes has been carried out to trace the origins of the ore fluids and metals thereby to evaluate the genesis of the hetai goldfield the 3 he 4 he and 40 ar 36 ar ratios of fluid inclusions in sulfides from the hetai ores exhibit a range of 0 27 0 62 ra and 932 4 6324 2 with the 4 he and 40 ar concentrations varying from 1 99 to 96 80 10 7 cm 3 stp g and 0 51 7 75 10 7 cm 3 stp g respectively this suggests a dominant crust derived fluid mixed with significant mantle derived fluids for the hetai gold mineralization the calculated 18 o h2o vsmow and measured d h2o vsmow values of fluid inclusions in gold bearing quartz range from 0 5 to 10 4 and from 83 1 to 52 4 respectively the 13 c pdb and 18 o pdb of calcite range from 3 53 to 1 91 and 21 21 to 19 67 respectively suggesting a deep seated source of the c bearing portion of the fluid the 34 s cdt values of sulfides intergrown with native gold range from 4 0 to 1 3 with an average of 2 8 indicating that the majority of the sulfur came from granitic magma by partial melting of the host rocks but likely with minor input from the mantle the pb isotopic components of sulfides from the hetai ores have 206 pb 204 pb 207 pb 204 pb and 208 pb 204 pb ratios of 18 044 19 404 15 568 15 793 and 38 426 39 597 respectively indicating a main upper continental crust source of ore metals but probably with minor contribution from the mantle linked to the ore geology and regional tectonomagmatic events the integration of the isotopic compositions obtained in this study with previously published fluid inclusion and geochronologic data suggests that the ore fluids and metals may have undergone two stages of evolution i e from the indosinian metamorphic water dominated fluids mixed with minor magmatic waters to the yanshanian magmatic water dominated fluids mixed with mantle derived fluids and meteoric waters

eastern mississippi delta late wisconsin unconformity overlying transgressive facies sea level and subsidence abstract analysis of 92 engineering core logs located in the balize sector of the eastern mississippi delta focuses on the late wisconsin unconformity and lithofacies of strata lying immediately below and above this stratigraphic horizon this major sequence boundary is a key feature used to correlate strata across shelf and slope to the basin observations emphasize lithofacies distributions of the latest pleistocene sediments underlying the unconformity the late pleistocene to early holocene transgressive facies and the immediately overlying deltaic deposits maps and a cross section compiled with this information highlight the critical relation between lithofacies distributions and late wisconsin sea level oscillations core analysis reveals that the transgressive facies comprises distinct environments of deposition offshore to onshore findings identify criteria to determine the approximate position of the shoreline at the late wisconsin maximum sea level lowstand and at the extent of early holocene maximum marine inundation in the balize complex mapping of lithologies along the late wisconsin unconformity serves to improve correlation of sediment facies with changes in acoustic response along high resolution seismic profiles an estimate of long term averaged land subsidence suggests lowering of at least 1 mm year near the shelfedge during the past 18 000 years this mapping also refines sea level response models for the mississippi delta including criteria to locate key paleogeographic features such as shelfedges and maximum flooding surfaces in other recent marine deltas and in older stacked deltaic sequences

the early cretaceous yangzhaiyu lode gold deposit north china craton a link between craton reactivation and gold veining the yangzhaiyu gold deposit is one of numerous lode gold deposits in the xiaoqinling district southern margin of the north china craton gold mineralization is hosted in neoarchean to early paleoproterozoic amphibolite facies metamorphic rocks and consists of auriferous quartz veins and subordinate disseminated ores in the vein proximal alteration zone ore related hydrothermal alteration is dominated by sericite quartz sulfide assemblages close to gold veins and biotite quartz pyrite chlorite epidote alteration generally distal from mineralization pyrite is the predominant sulfide mineral locally coexisting with minor amounts of chalcopyrite sphalerite and galena gold occurs mostly as free gold enclosed in or filling microfractures of pyrite and quartz and is also present in equilibrium with au bearing tellurides mainly petzite and calaverite coexisting with hessite tellurobismuthite and altaite fluid inclusion studies suggest that gold veins were deposited at intermediate temperatures 175 313 c from aqueous or aqueous carbonic fluids with moderate salinity 5 14 wt nacl equiv 34s values of sulfide minerals range mainly from 2 0 to 4 4 whereas auriferous quartz vein samples have 18o values of 12 4 to 9 6 with calculated 18oh2o values of 6 0 to 3 2 gold related pyrite grains yield elevated 3he 4he ratios 1 51 0 32 ra relative to crustal reservoirs and mantle like 20ne 22ne and 21ne 22ne ratios 9 90 9 68 and 0 029 respectively the stable and noble gas isotopes thus suggest deep seated most likely magmatic and mantle derived sources for the ore fluids sulfur and by inference other components in the ore system 40ar 39ar dating of ore related sericite and biotite separates indicates two episodes of gold genesis at 134 5 to 132 3 and 124 3 to 123 7 ma the mineralization ages overlap zircon u pb ages of 141 0 1 6 to 125 8 1 4 ma 2 for the wenyu and niangniangshan monzogranite plutons and a number of mafic to intermediate dikes intruding these plutons all being proximal to the yangzhaiyu gold deposit the synchronism of gold genesis and magmatism provides additional weights of evidence for a magmatic derivation of ore fluids and sulfur the geochronologic data also suggest that gold veining took place billions of years after the stabilization of the north china craton and associated metamorphism in the late archean to early paleoproterozoic this contrasts sharply to lode gold deposits in other precambrian cratons that formed predominantly in late archean to paleoproterozoic temporarily and genetically related to regional high grade metamorphism and compressional or transpressional tectonism available data have demonstrated that the north china craton was reactivated in the late mesozoic as marked by voluminous igneous rocks faulted basin formation high crustal heat flow and widespread metamorphic core complexes in the eastern part of the craton it is thus suggested that the yangzhaiyu gold deposit together with other deposits of similar ages in the xiaoqinling district were products of this craton reactivation event lithospheric extension and extensive magmatism related to the craton reactivation may have provided sufficient heat energy fluid and sulfur required for the formation of the gold deposits

subsidence of the texas coast inferences from historical and late pleistocene sea levels abstract changes in sea level observed at tide gauges are caused by actual changes in water level and by changes in elevation at the observing station recent research has focused on the relationship between climatic change and sea level but vertical land movement can be just as important particularly in subsiding sedimentary basins the purpose of this study is to compare long term rates of subsidence estimated from upper pleistocene strata along the central texas coast with historical subsidence rates from the same area obtained from geodetic surveys and tide gauge data this comparison shows that historical subsidence rates are much greater than long term averages and are equal or greater than actual sea level change along the texas coast south of galveston bay long term 10 5 yr subsidence rates were estimated by establishing the extent of marine marine influenced and nonmarine strata within the upper pleistocene beaumont formation in the copano bay area of the central texas coast and comparing the maximum elevation of in place marine influenced deposits with published maximum sea level estimates of 5 8 m above mean sea level msl from correlative well dated coral terraces from stable and uplifted areas in place shell bearing horizons deposited at or below sea level occur no higher than 2 m msl in the copano bay area suggesting that there has been no more than 6 m of subsidence since the probable time of deposition during the sangamon interglacial at 120 ka the long term average subsidence rate for this part of the texas coast is thus 0 05 mm yr or less historical subsidence rates were obtained by 1 1 calculating relative elevation changes between national geodetic survey first order leveling surveys conducted in the early 1950s with those conducted in the late 1970s to early 1980s 2 2 normalizing the relative elevation differences between surveys to annual rates of change relative to an arbitrarily chosen benchmark 3 3 referencing these lines to sea level at three tide gauges and 4 4 comparing calculated rates of relative sea level rsl rise along the lines with estimates of eustatic sea level esl rise rates of rsl rise for the texas coast south of galveston bay were generally 4 8 mm yr locally rates were as high as 23 mm yr these rates are significantly higher than global averages of 1 mm yr much of the difference is probably caused by subsidence of the texas coastal zone at rates of 1 22 mm yr or 20 440 times the long term average of 0 05 mm yr the highest subsidence rates were found locally where there has been historical water level decline in shallow aquifers lower subsidence rates of 3 7 mm yr occur regionally where groundwater decline is minimal or nonexistent increased subsidence over the long term average in these areas may be caused by pressure decline in underlying oil and gas reseivoirs

shelf resonance and impact of near field tsunami generated by the 2010 chile earthquake 1 the 2010 chile earthquake of mw 8 8 generated a destructive tsunami in the near field that resulted in warnings across the pacific numerical modeling shows trapping and amplification of the energy over the continental shelf and slope a spectral analysis of the computed surface elevation reveals resonance oscillations with periods up to 129 min along the central chile coast the temporal and spectral data provides an explanation for the long period waves recorded by dart buoys and the prolonged wave activities and belated impacts reported by residents and survey teams the present study of the 2010 chile tsunami together with those of the 2006 kuril and 2009 samoa tsunamis has directly associated shelf resonance with impacts on insular and continental coasts and provided a tool to identify at risk localities in tsunami hazard assessment

the 2010 and 2011 tsunamis in french polynesia operational aspects and field surveys we present a detailed timeline of the warning procedures as they unfolded at the laboratoire de geophysique in papeete tahiti during the nights of 26 27 february 2010 maule chile tsunami and 10 11 march 2011 tohoku tsunami in particular we discuss how the flow of information available to the warning center including seismic evaluations obtained both locally and from other warning centers as well as maregraph and dart buoy data built up and eventually led to red alerts which the local authorities used in both cases to impose an evacuation of low lying areas on 68 islands while the alerts were successful in polynesia a difficulty arose in 2011 when the alert had to be reinstated immediately as the all clear was being declared since the maximum amplitude was carried by the fourth wave packet we also present a complete dataset of 119 values of run up and inundation surveyed in the aftermath of the two tsunamis principally in the marquesas islands where their effects were maximal and on tahiti and moorea for the 2011 event the highest run up 4 45 m was observed in 2011 in the bay of taipivai on nuku hiva where seven houses were flooded we find no clear correlation between run up values at the same locations in 2010 and 2011 suggesting that local responses are controlled by details specific to each tsunami in 2010 in the village of puamau on hiva oa marquesas a delayed harbor response probably due to resonance of the bay upon arrival of short period components dispersed outside the shallow water approximation flung a launch onto a wharf 7 h after the first arrivals and 2 5 h after issuance of the all clear

breaching of mustang island in response to the 8 2 ka sea level event and impact on corpus christi bay gulf of mexico implications for future coastal change the results from an investigation of the coupled mustang island corpus christi bay complex gulf of mexico shows that the island was eliminated as an effective salinity barrier between 8 86 and 8

on the origin of late holocene sea level highstands within equatorial ocean basins abstract late holocene sea level highstands of amplitude 3 m are endemic to equatorial ocean basins these highstands imply an ongoing and moderate sub mm yr sea level fall in the far field of the late pleistocene ice cover that has long been linked to the process of glacial isostatic adjustment gia clark et al 1978 mitrovica and peltier 1991 coined the term equatorial ocean syphoning to describe the gia induced sea level fall and they provided the first physical explanation for the process they argued that water migrated away from far field equatorial ocean basins in order to fill space vacated by collapsing forebulges at the periphery of previously glaciated regions we provide a complete physical explanation for the origin of equatorial ocean syphoning and the associated development of sea level highstands using numerical solutions of the equation that governs meltwater redistribution on spherical viscoelastic earth models in particular we separate the total predicted sea level change into contributions associated with ice and meltwater loading effects and by doing so isolate a second mechanism that contributes significantly to the ocean syphoning process ocean loading at continental margins induces a levering of continents and a subsidence of offshore regions that has also long been recognized within the gia literature walcott 1972 we show that the influx of water into the volume created by this subsidence produces a sea level fall at locations distant from these margins indeed over the major ocean basins that is comparable in amplitude to the syphoning mechanism isolated by mitrovica and peltier 1991

kuril islands tsunami of november 2006 1 impact at crescent city by distant scattering 1 a numerical model for the global tsunami computation constructed by kowalik et al 2005 2007a is applied to the tsunami of november 15 2006 in the northern pacific with spatial resolution of one minute numerical results are compared to sea level data collected by pacific dart buoys the tide gauge at crescent city cc recorded an initial tsunami wave of about 20 cm amplitude and a second larger energy packet arriving 2 hours later the first energy input into the cc harbor was the primary direct wave traveling over the deep waters of the north pacific interactions with submarine ridges and numerous seamounts located in the tsunami path were a larger source of tsunami energy than the direct wave travel time for these amplified energy fluxes is longer than for the direct wave prime sources for the larger fluxes at cc are interactions with koko guyot and hess rise tsunami waves travel next over the mendocino escarpment where the tsunami energy flux is concentrated owing to refraction and directed toward cc local tsunami amplification over the shelf break and shelf are important as well in many locations along the north pacific coast the first arriving signal or forerunner has lower amplitude than the main signal which often is delayed understanding this temporal distribution is important for an application to tsunami warning and prediction as a tsunami hazard mitigation tool we propose that along with the sea level records which are often quite noisy an energy flux for prediction of the delayed tsunami signals be used

late mesozoic felsic magmatism and mo au pb zn mineralization in the southern margin of the north china craton a review abstract the widespread large scale mo au pb zn mineralization in the southern margin of the north china craton ncc is spatially and temporally associated with the voluminous late mesozoic granitic magmatism relationship between the granitic magmatism and ore mineralization has been extensively investigated in the last decade however controversy still exists regarding the magma source metallogeny and geodynamic settings this paper systematically reviews the major features of the mesozoic granitic magmatism and associated mo au pb zn mineralization in the southern margin of the north china craton including temporal and spatial variations of magmatic rocks composition of ore fluids sources of ore metals and metallogeny the granitic rocks were mainly formed in late mesozoic and emplaced in two stages the early stage 158 128 ma granites are of typical i type derived from remelting of ancient crust of the southern margin of the ncc with input of mantle material under lithospheric thinning tectonic regime the late stage 127 112 ma granites include a type and or highly fractionated i type granites which commonly contain more fractions of mantle materials as exhibited by more depleted isotopic signatures suggestive of an intracontinental extensional setting mo mineralization 155 130 ma related to the early stage granitic magmatism includes mainly of porphyry or porphyry skarn type with ore metals mainly derived from the mixed source of the mantle and crust whereas the late stage mo mineralization 127 116 ma is mainly of porphyry type with the ore metals from similar sources with more input of mantle materials pb zn deposits 144 130 ma associated with the early stage granitic magmatism are mainly of hydrothermal vein and skarn types whereas those 125 117 ma related to the late stage granites are of hydrothermal vein type the pb zn deposits are most likely distal products of the mo deposits together forming a metallogenic system au deposits are located in the xiaoqinling and xiong ershan areas and were formed during middle jurassic to early cretaceous 163 118 ma mostly from 132 to 120 ma the ores mainly occur in quartz veins and altered rocks and are hydrothermal magmatic in origin with au derived from a mixed source of crust and mantle

secular bathymetric variations of the north channel in the changjiang yangtze estuary china 1880 2013 causes and effects abstract as the interface between the fluvial upland system and the open coast global estuaries are facing serious challenges owing to various anthropogenic activities especially to the changjiang estuary since the establishment of the three gorges dam tgd currently the world s largest hydraulic structure and certain other local hydraulic engineering structures the changjiang estuary has experienced severe bathymetric variations it is urgent to analyze the estuarine morphological response to the basin wide disturbance to enable a better management of estuarine environments north channel nc the largest anabranched estuary in the changjiang estuary is the focus of this study based on the analysis of bathymetric data between 1880 and 2013 and related hydrological data we developed the first study on the centennial bathymetric variations of the nc it is found that the bathymetric changes of nc include two main modes with the first mode representing 64 of the nc variability which indicates observable deposition in the mouth bar and its outer side area lower reach the second mode representing 11 of the nc variability which further demonstrates channel deepening along the inner side of the mouth bar upper reach during 1970 2013 further recent erosion observed along the inner side of the mouth bar is caused by riverine sediment decrease especially in relation to tgd induced sediment trapping since 2003 while the deposition along the lower reach since 2003 can be explained by the landward sediment transport because of flood tide force strengthen under the joint action of tgd induced seasonal flood discharge decrease and land reclamation induced lower reach narrowing generally the upper and lower nc reach are respectively dominated by fluvial and tidal discharge however episodic extreme floods can completely alter the channel morphology by smoothing the entire channel the results presented herein for the nc enrich our understanding of bathymetric variations of the changjiang estuary in response to human activities which can be well applied to other estuaries subject to similar interferences

palaeohurricane reconstructions from sedimentary archives along the gulf of mexico caribbean sea and western north atlantic ocean margins hurricanes annually threaten the atlantic ocean margins historical hurricane records are relatively short and palaeohurricane sedimentary archives provide a geological and climatic context that sheds light on future hurricane activity here we review palaeo trends in hurricane activity elucidated from sedimentary archives we discuss dating methods site selection and stat istics associated with previously published records these archives have been useful for under standing the long term evolution of coastal systems and the response of intense hurricane activity to climatic changes regional shifts in hurricane overwash on centennial to millennial timescales have been linked to various climatic modes of variability including el nino southern oscillation and the north atlantic oscillation but could also reflect regional scale controls on hurricane activity

giant mesozoic gold provinces related to the destruction of the north china craton abstract lode gold deposits in precambrian cratons represent the world s major gold source and were mostly generated during formation and stabilization of the cratons however there is an extraordinary exception in the north china craton ncc where lode gold deposits formed after prolonged stabilization of the craton molybdenite re os and hydrothermal sericite and biotite 40 ar 39 ar dating of major gold deposits from the xiaoqinling district southern ncc bracket their emplacement in the range of 154 1 1 1 to 118 9 1 2 ma n 23 postdating formation of the craton by more than 1 7 billion years fluid inclusions extracted from gold bearing pyrite have elevated 3 he 4 he ratios 1 52 0 22 ra and mantle like ne isotopes 20 ne 22 ne 10 02 9 22 and 21 ne 22 ne 0 033 0 027 indicating presence of mantle derived fluids in the ore system measured 34 s of pyrite and d and 18 o of hydrothermal micas and fluid inclusion waters in auriferous quartz further confirm a magmatic mantle source for sulfur and ore fluids gold deposits of similar ages also widely occur in the eastern and northern margins of the ncc which together with those in the xiaoqinling district have a total reserve of 2500 t gold forming the only known giant late mesozoic gold province in the world s precambrian cratons these deposits formed coevally with extensive felsic to mafic magmatism development of intracontinental rift basins and exhumation of metamorphic core complexes across the eastern ncc events interpreted as indicating thinning and destruction of the lithosphere beneath the craton rising of asthenosphere coupled with destruction of the lithosphere has generated voluminous mafic and felsic magmas that provided sufficient fluids sulfur and by inference other ore components to form the giant gold provinces

modern day tectonic subsidence in coastal louisiana subsidence is leading to the slow inundation of communities and wetlands of louisiana mississippi texas and alabama united states by the gulf of mexico the prevailing paradigm considers subsidence to be the result of young sediment compaction and or consolidation and human activities this paper describes the results of a test of this theory based on an examination of historic motions of benchmark in the michoud area of orleans parish louisiana this methodology allowed for an assessment of vertical change at different levels over time relative to a precise vertical datum north american vertical datum of 1988 navd88 data do not support the current theory on the origins of subsidence they demonstrate that tectonic causes dominate in the study area during 1969 1971 and 1971 1977 tectonism was responsible for 16 9 mm yr and 7 1 mm yr of subsidence respectively these contributions account for 73 and 50 of the total subsidence during these intervals the change in deep subsidence is attributed to renewed motion along a large normal fault michoud fault over the same time intervals intermediate depth subsidence due to compaction of pleistocene to middle miocene strata was constant 4 6 mm yr similarly subsidence due to shallow processes i e sediment compaction and groundwater offtake was 1 5 mm yr and 2 5 mm yr subsidence associated with petroleum extraction was not a factor due to the lack of local production

modelling holocene relative sea level observations from the caribbean and south america abstract holocene data from the caribbean and the atlantic coast of south america have been critically assessed and a subset of the best quality data are presented these data cover a large north south geographic extent and display a distinct spatial variation we make the first comparisons of this data set to predictions based on a realistic model of glaciation induced sea level change with the main aims of understanding the cause of the observed spatial trend and estimating a eustatic signal for the holocene the spatial variation is dominated by the influence of the ice and ocean mass redistribution on sea level change with the ice induced effect dominating the observed north south trend a best fitting model is applied to estimate a holocene eustatic signal from the observations we find that the model corrected data are consistent with a relatively rapid rise of 7 8 mm yr in the early holocene with a marked reduction in this rate around 7 cal kyr bp from this time until present the model corrected data suggest that the volume of mass transfer between ice sheets and oceans was no more than 1 m eustatic sea level equivalent

degradation of the plaquemines sub delta and relative sea level in eastern mississippi deltaic coast during late holocene abstract the stratigraphic architecture of plaquemines sub delta lobe is identified from sedimentary cores and sub bottom seismic data collected at lower breton sound louisiana usa four lithofacies were identified in cores from bottom to top 1 organic poor mud 2 organic poor silty sand 3 massive mud 4 organic rich peat and root rich soft mud overall the lithofacies displays a typical progradational deltaic deposit at bottom with upward coarsening feature and then an upward fining deposit overlying on top stratigraphic position of the organic rich peat facies indicates that it is formed after the fluvial sediment source moves away from this region and it is recognized as a termination of progradation of the plaquemines sub delta dated peat samples show that sub delta progradation stops between 876 and 1384 yr ad during which a 20 70 cm relative sea level rise is detected the geological framework reported in this study provides critical information for future modeling on river diversions the stratigraphic architecture underlying lower breton sound implicates that top three facies of root rich soft mud organic rich peat and massive mud are likely to be eroded away before the development of new crevasse splay or sub delta when sediment diversion is in operation the deeper organic poor silty sand lithofacies however can serve as a firm foundation to build new land

tsunami hazard in la reunion island sw indian ocean scenario based numerical modelling on vulnerable coastal sites several major tsunamis have affected the southwest indian ocean area since the 2004 sumatra event and some of them 2005 2006 2007 and 2010 have hit la reunion island in the southwest indian ocean however tsunami hazard is not well defined for la reunion island where vulnerable coastlines can be exposed this study offers a first tsunami hazard assesment for la reunion island we first review the historical tsunami observations made on the coastlines where high tsunami waves 2 3 m have been reported on the western coast especially during the 2004 indian ocean tsunami numerical models of historical scenarios yield results consistent with available observations on the coastal sites the harbours of la pointe des galets and saint paul the 1833 pagai earthquake and tsunami can be considered as the worst case historical scenario for this area in a second step we assess the tsunami exposure by covering the major subduction zones with syntethic events of constant magnitude 8 7 9 0 and 9 3 the aggregation of magnitude 8 7 scenarios all generate strong currents in the harbours 3 7 m s 1 and about 2 m of tsunami maximum height without significant inundation the analysis of the magnitude 9 0 events confirms that the main commercial harbour port est is more vulnerable than port ouest and that flooding in saint paul is limited to the beach area and the river mouth finally the magnitude 9 3 scenarios show limited inundations close to the beach and in the riverbed in saint paul more generally the results confirm that for la runion the sumatra subduction zone is the most threatening non local source area for tsunami generation this study also shows that far field coastal sites should be prepared for tsunami hazard and that further work is needed to improve operational warning procedures forecast methods should be developed to provide tools to enable the authorities to anticipate the local effects of tsunamis and to evacuate the harbours in sufficient time when such an earthquake occurs

isotope and fluid inclusion geochemistry and genesis of the qiangma gold deposit xiaoqinling gold field qinling orogen china abstract the qiangma gold deposit is hosted in the 1 9 ga taihua supergroup metamorphic rocks in the xiaoqinling terrane qinling orogen on the southern margin of the north china craton the mineralization can be divided as follows quartz pyrite veins early quartz polymetallic sulfide veinlets middle and carbonate quartz veinlets late stages with gold being mainly introduced in the middle stage three types of fluid inclusions were identified based on petrography and laser raman spectroscopy i e pure carbonic carbonic aqueous co 2 h 2 o and aqueous inclusions the early stage quartz contains pure carbonic and co 2 h 2 o inclusions with salinities up to 12 7 wt nacl equiv bulk densities of 0 67 to 0 86 g cm 3 and homogenization temperatures of 280 365 c the early stage is related to h 2 o co 2 n 2 ch 4 fluids with isotopic signatures consistent with a metamorphic origin 18 o water 3 1 to 5 2 d 37 to 73 the middle stage quartz contains all three types of fluid inclusions of which the co 2 h 2 o and aqueous inclusions yield homogenization temperatures of 249 346 c and 230 345 c respectively the co 2 h 2 o inclusions have salinities up to 10 9 wt nacl equiv and bulk densities of 0 70 to 0 98 g cm 3 with vapor bubbles composed of co 2 and n 2 the isotopic ratios 18 o water 2 2 to 3 6 d 47 to 79 suggest that the middle stage fluids were mixed by metamorphic and meteoric fluids in the late stage quartz only the aqueous inclusions are observed which have low salinities 0 9 9 9 wt nacl equiv and low homogenization temperatures 145 223 c the isotopic composition 18 o water 1 9 to 0 5 d 55 to 66 indicates the late stage fluids were mainly meteoric water trapping pressures estimated from co 2 h 2 o inclusions are 100 285 mpa for the middle stage suggesting that gold mineralization mainly occurred at depths of 10 km fluid boiling and mixing caused rapid precipitation of sulfides and native au through boiling and inflow of meteoric water the ore forming fluid system evolved from co 2 rich to co 2 poor in composition and from metamorphic to meteoric as indicated by decreasing 18 o water values from early to late the carbon sulfur and lead isotope compositions suggest the hostrocks within the taihua supergroup to be a significant source of ore metals integrating the data obtained from the studies including regional geology ore geology and fluid inclusion and c h o s pb isotope geochemistry we conclude that the qiangma gold deposit was an orogenic type system formed in the tectonic transition from compression to extension during the jurassic early cretaceous continental collision between the north china and yangtze cratons

ore genesis of the fancha gold deposit xiaoqinling goldfield southern margin of the north china craton constraints from pyrite re os geochronology and he ar in situ s pb isotopes abstract the fancha gold deposit is one of the representative lode type deposit in the xiaoqinling goldfield four stage mineralization process were identified namely i the barren quartz stage ii the pyrite dominated stage iii the quartz polymetallic sulfides stage and iv the quartz carbonate stage correspondingly pyrite crystal can be divided into three generations i e py1 py2 and py3 according to their different textures and paragenesis during the first three mineralization stages in order to better understand the ore genesis an integrated analysis on re os he ar s pb multi isotopes was carried out for each mineralization stage to delineate the timing of the mineralization and the origins of the ore forming materials in detail gold bearing pyrite yields a re os isochron age of 124 3 2 6 ma mswd 1 9 overlapping with the previous hydrothermal mica 40ar 39ar ages suggesting that gold mineralization occurred in the early cretaceous the 3he 4he r ra and 40ar 36ar values of the py2 are 0 68 to 1 17 and 656 55 to 7384 2 and those of the py3 are 0 20 to 0 33 and 647 67 to 8913 55 respectively which reveal a significant contribution of mantle component in the ore forming fluids and the content of crust fluid is increasing in the later evolution in situ 34s values of the sulfides and tellurides in the auriferous quartz veins including the pyrite py1 py2 and py3 chalcopyrite sphalerite galena bismuthinite and tetradymite display a relatively narrow range 4 9 to 3 6 consistent with magmatic sulfur which are quite different from those of the pyrite in surrounding rock 7 8 to 9 3 in situ pb isotopic compositions of the galena and bismuthinite of stage iii are homogeneous with values of 208pb 204pb 207pb 204pb and 206pb 204pb being 37 482 37 508 15 392 15 523 16 995 17 006 and 39 279 39 287 15 588 15 590 18 283 18 288 respectively indicating a mixed pb sources with obvious proportions of mantle combined with previous data we suggest that the ore forming fluids and metals of the fancha gold deposit stemmed directly from the regional mantle derived magmatic hydrothermal system which is coupled with the large scale lithospheric extension and thinning in the eastern north china craton during the early cretaceous

slip distribution of the february 27 2010 mw 8 8 maule earthquake central chile from static and high rate gps insar and broadband teleseismic data 1 the shallow depth underthrust earthquake of february 27 2010 mw 8 8 ruptured the subduction plate interface in central chile between 34 s and 38 s we retrieve the spatial and temporal distribution of slip during this mega earthquake through a joint inversion of teleseismic records insar and high rate gps hrgps data additionally our model is shown to agree with broadband surface waves rupture initiated at about 32 km depth and propagated bilaterally resulting in two main slip zones located ssw and nne of the hypocenter nucleation did not take place within or at the edge of one of these main asperities but in between during the first 30s slip propagated predominantly southwards later on the rupture evolved more slowly and more symmetrically eventually the northern asperity became predominant with maximum slip reaching about 20 m most of the seismic moment was released within 110s a relatively short time explained by the bilateral propagation the overall average rupture velocity is 2 6 km s but propagation occurred initially faster towards the south 3 2 km s large slip did not reach the trench a result consistent with the moderate size of the tsunami down dip rupture stopped at about 50 km depth in agreement with the lower limit of the locked zone inferred by ruegg et al 2009 from pre seismic gps data

the 26 december 2004 sumatra tsunami analysis of tide gauge data from the world ocean part 1 indian ocean and south africa the m w 9 3 megathrust earthquake of december 26 2004 off the northwest coast of sumatra in the indian ocean generated a catastrophic tsunami that was recorded by a large number of tide gauges throughout the world ocean part 1 of our study of this event examines tide gauge measurements from the indian ocean region at sites located from a few hundred to several thousand kilometers from the source area statistical characteristics of the tsunami waves including wave height duration and arrival time are determined along with spectral properties of the tsunami records

controls on facies distribution and stratigraphic preservation in the ganges brahmaputra delta sequence abundant sediment supply and accommodation space in the bengal basin have led to the development of a major late quaternary delta sequence this sequence has formed in a tectonically active setting and represents an important example of a high energy marine and fluvial high yield continental margin deposit recent studies have detailed the delta s stratigraphy and development noting that tectonics and sediment supply control the ganges brahmaputra more significantly than in many other delta systems these ideas are developed here through a discussion of the effects that spatial and temporal variations in tectonics and sediment supply have had on deltaic processes and sequence character unique and differing stratigraphies are found within thedeltasystem suchthatfine grainedsedimentpreservationisfavoredinareasofactivetectonicprocessessuchasfolding block faulting and subsidence coarse grained deposits dominate the stratigraphy under the control of high energy fluvial processes and mixed fine coarse stratigraphies are found in areas dominantly influenced by eustatic sea level change overlaid upon these spatially varying stratigraphic patterns are temporal patterns related to episodic events e g earthquakes and rivers avulsions and long termchangesinclimate andsediment supply modelingisalsousedtoinvestigatethe influenceofavariable sedimentsupply on sequence character results show that the timing and magnitude of sediment input relative to sea level rise is a significant control on the subaerial extent of the delta and the relative dominance of alluvial and marine facies within the sequence d 2002 elsevier science b v all rights reserved

modeling of the february 1996 peruvian tsunami the february 1996 peruvian earthquake generated a larger tsunami than expected from its surface magnitude this discrepancy as well as the long rupture duration indicate that this event is a tsunami earthquake the associated tsunami was strong locally with runup heights of 1 to 5 meters along a coastline of 400 km it is shown that this tsunami can be modeled for a seismic moment of 2 1020 nm using a rigidity of 2 1010 n m the tsunami propagation is modeled solving long wave equations by a finite difference method the maximum run up heights in the region of chimbote can be simulated using a grid increment of 10 meters the propagation of this small tsunami across the pacific ocean is modeled taking into account frequency dispersion the only notable amplification occurred in the marquesas islands where wave heights of 2 meters were observed and are simulated

improving methodology for high resolution reconstruction of sea level rise and neotectonics by paleoecological analysis and ams 14c dating of basal peats abstract sea level research in several submerging coastal regions has traditionally been based on 14 c dating of basal peats that overlie a compaction free substratum and can be related to paleo ground water levels provided that an unequivocal relationship between ground water level and sea level can be assumed this approach contains two sources of uncertainty 1 the paleoenvironmental interpretation of samples is usually based on inherently inaccurate macroscopic descriptions in the field and 2 14 c ages of bulk peat samples may be erroneous as a result of contamination due to the uncertainties in both the altitude and the age the two crucial sources of evidence necessary to arrive at accurate sea level curves sea level index points are therefore represented by considerable but typically not quantified error boxes accelerator mass spectrometry ams opens new perspectives for this type of sea level research as illustrated by a paleoecological and ams 14 c study of basal peats from a small study area in the rhine meuse delta the netherlands where previous conventional work revealed highly problematic results a detailed macrofossil analysis has two purposes 1 an inferred paleoecological succession indicates a relatively accurate level of paludification of the site and hence rise of the ground water level 2 suitable macrofossils from that specific level are then selected for ams 14 c dating in spite of very small sample sizes our results are consistent and indicate that this approach can constitute a step forward in high resolution reconstruction of sea level rise the new results further enable a revision of holocene ground water gradient lines for the rhine meuse delta a knickpoint in these gradient lines can be related to the effect of faulting this approach therefore also has considerable potential to unravel and quantify neotectonic activity in submerging coastal settings

resonance in hawaii waters from the 2006 kuril islands tsunami 1 the 2006 kuril islands tsunami while not destructive to coastal properties resulted in prolonged oscillations in hawaii waters this study examines the oscillation patterns and amplification through reconstruction of the tsunami using a nonlinear shallow water model after validation with water level measurements a fast fourier transform of the computed surface elevation reveals profound oscillation modes at various periods around the hawaiian islands the oscillation at the regional scale consists of standing waves across the island chain and resonance in interconnected channels embayments and shallow shelves resonance in embayments and standing edge waves dominate the oscillation in coastal waters the results show strong correlation between bathymetric features and resonance oscillations and identify tsunami hazard areas for planning and emergency management

automatic detection location and quantification of earthquakes application to tsunami warning we describe a fully automated seismic event detection and location system providing for real time estimates of the epicentral parameters of both local and distant earthquakes the system uses 12 telemetered short period stations with a regional aperture of 350 km as well as two 3 component broad band stations detection and location of teleseismic events is achieved independently and concurrently on the short period and long period channels the long period data is then used to obtain an estimate of the seismic momentm0 of the earthquake through the mantle magnitudemm as introduced byokal andtalandier 1989 in turn this estimate ofm0 is used to infer the expected tsunami amplitude at papeete within 15 minutes of the recording of rayleigh waves the performance of the method is discussed in terms of the accuracy of the epicentral parameters and seismic moment obtained in real time as compared to the values later published by the reporting agencies our estimates are usually within 3 degrees of the reported epicenter and the standard deviation on the seismic moment only 0 19 unit of magnitude for a population of 154 teleseismic events

could a 1755 like tsunami reach the french atlantic coastline constraints from twentieth century observations and numerical modeling the tsunami generated by the 1 november 1755 earthquake off the coast of portugal affected mainly the coastlines of the iberian peninsula and northwest morocco but was also observed in some places along the north atlantic coasts to determine whether the event could have effected the french coastline we conducted a study to search for signs of the tsunami in historical records from all tide gauge stations off the french atlantic coast during the twentieth century specifically for the 28 february 1969 and the 26 may 1975 tsunamis that were recorded by the portuguese tide gauge network because many recordings are available in la rochelle located on the southwest coast of france we focused our study on this harbor the analysis of the tide gauge data shows no evidence for tsunamis in la rochelle neither in 1969 nor in 1975 to confirm this lack of tsunami signals we used nonlinear shallow water equations to compute the tsunami propagation to the french atlantic coastline for both 1969 and 1975 events results obtained from these simulations confirm otherwise unnoticeable wave amplitudes at la rochelle harbor in a second step tsunamis from three different scenarios for the 1755 earthquake were modeled to estimate the impact of such a tsunami on the french atlantic coast with a focus on la rochelle harbor a comparison of the functions of tide configuration was made in order to analyse the difference in impact the results show that while the harbor is poorly impacted several areas western part of the island of re and northern coast of the island of oleron may have experienced a moderate impact from 0 5 to 1 m especially since the tide was high at the time of arrival possibly causing local inundations in lowland areas

kuril islands tsunami of november 2006 2 impact at crescent city by local enhancement 1 crescent city cc is particularly susceptible to tsunami attack the combination of tsunami signal enhancement by both distant bathymetric features and local nearshore resonance seems to be responsible for this behavior application of global tsunami propagation models to the kuril islands tsunami of november 2006 in the companion paper kowalik et al 2008 delineated the importance of distant bathymetric features for both tsunami wave amplification and for increased duration of the tsunami arriving at cc these distant features were responsible for delivering the late high energy signal which was delayed by 2 hours from the predicted arrival time additional local amplification and increased duration are caused by the shelf bathymetry adjacent to cc as the initial tsunami arrives at cc the shelf trapping mechanism tends to excite the gravest of the natural modes this oscillation is slowly shifted toward the natural mode closest to the period of the incident tsunami wave packet short duration wave trains tend to influence the tsunami response at cc harbor in such a way that 1 hour after the first wave arrival a much stronger wave will be generated owing to the tendency of the shelf to initially ring at the frequency of the gravest mode practical implications of distant and local amplification relate to the potential hazard near cc highlighting the need for awareness of the tsunami signal duration in this respect two timescales are important for this event the 2 hour time delay due to distant bathymetric features and the 1 hour delay due to local offshore bathymetry

subsidence in the northeastern nile delta rapid rates possible causes and consequences holocene fluvial and marine deposits have accumulated in a graben like structure on the northeastern margin of the nile delta this part of the delta which includes lake manzala port said and the northern suez canal has subsided rapidly at rates of up to 0 5 centimeter per year since about 7500 years ago this subsidence has diverted at last four major distributaries of the nile river into this region the combined effects of continued subsidence and sea level rise may flood a large part of the northern delta plain by as much as 1 meter by the year 2100 the impact of continued subsidence now occurring when sediment input along the coast has been sharply reduced because of the aswan high dam is likely to be substantial particularly in the port said area and as far inland as south of lake manzala

resonance and impact of the 2009 samoa tsunami around tutuila american samoa 1 the 2009 samoa tsunami resulted in severe damage and inundation at tutuila american samoa the disparity of the impact and the varying accounts of the tsunami along the coast remain one of the most intriguing aspects of the event we utilize a dispersive wave model to reconstruct the tsunami from the earthquake source for understanding of the wave dynamics around tutuila after validation with water level measurements a fast fourier transform of the computed surface elevation reveals coupled resonance oscillations between 3 and 18 min period over the insular slope and shelf as well as the fringing reefs the resonance which focuses energy according to shelf and embayment configurations provides an explanation of the runup data and eyewitness accounts and identifies the coastal communities prone to tsunami hazards