hillslope infiltration planar slopes the solution of the full nonlinear unsaturated flow equation is given for a problem of infiltration and associated subsurface flows into a planar hillslope of a homogeneous isotropic soil with uniform initial moisture content the solution uses the assumption that at some distance below the slope crest a spatial equilibrium is approached with the moisture content and other properties independent of downslope coordinate x and dependent only on the normal coordinate z and time t the analysis is found to be generally applicable beyond a small distance from the slope crest or from a point of slope change for slope angles less than 30 infiltration normal to the slope differs relatively little from infiltration from a horizontal surface interesting aspects of the solution include a time independent total horizontal flow into the slope and a time dependent downslope total flow component which behaves as t1 2 at small t and as t at large t previously hillslope flows in these directions have been discussed in terms of soil anisotropy and layering but these flows in a homogeneous isotropic soil are simple physical consequences of capillarity and gravity the analysis applies with minor modification to two simple types of hillslope anisotropy 1 anisotropy parallel to the slope and 2 horizontal anisotropy type 1 yields a complicated time dependence of the horizontal flow and type 2 affects downslope flow similarly these flow directions will commonly reverse during the course of the infiltration process

sediment transport patterns in the san francisco bay coastal system from cross validation of bedform asymmetry and modeled residual flux abstract the morphology of 45 000 bedforms from 13 multibeam bathymetry surveys was used as a proxy for identifying net bedload sediment transport directions and pathways throughout the san francisco bay estuary and adjacent outer coast the spatially averaged shape asymmetry of the bedforms reveals distinct pathways of ebb and flood transport additionally the region wide ebb oriented asymmetry of 5 suggests net seaward directed transport within the estuarine coastal system with significant seaward asymmetry at the mouth of san francisco bay 11 through the northern reaches of the bay 7 8 and among the largest bedforms 21 for 50 m this general indication for the net transport of sand to the open coast strongly suggests that anthropogenic removal of sediment from the estuary particularly along clearly defined seaward transport pathways will limit the supply of sand to chronically eroding open coast beaches the bedform asymmetry measurements significantly agree up to 76 with modeled annual residual transport directions derived from a hydrodynamically calibrated numerical model and the orientation of adjacent flow sculpted seafloor features such as mega flute structures providing a comprehensive validation of the technique the methods described in this paper to determine well defined cross validated sediment transport pathways can be applied to estuarine coastal systems globally where bedforms are present the results can inform and improve regional sediment management practices to more efficiently utilize often limited sediment resources and mitigate current and future sediment supply related impacts

submerged karst landforms observed by multibeam bathymetric survey in nagura bay ishigaki island southwestern japan abstract submerged tropical karst features were discovered in nagura bay on ishigaki island in the southern ryukyu islands japan the coastal seafloor at depths shallower than 130 m has been subjected to repeated and alternating subaerial erosion and sedimentation during periods of quaternary sea level lowstands we conducted a broadband multibeam survey in the central area of nagura bay 1 85 2 7 km and visualized the high resolution bathymetric results over a depth range of 1 6 58 5 m various types of humid tropical karst landforms were found to coexist within the bay including fluviokarst doline karst cockpit karst polygonal karst uvalas and mega dolines although these submerged karst landforms are covered by thick postglacial reef and reef sediments their shapes and sizes are distinct from those associated with coral reef geomorphology the submerged landscape of nagura bay likely formed during multiple glacial and interglacial periods according to our bathymetric results and the aerial photographs of the coastal area this submerged karst landscape appears to have developed throughout nagura bay i e over an area of approximately 6 5 km and represents the largest submerged karst in japan

detrital sediment supply in the southern okinawa trough and its relation to sea level and kuroshio dynamics during the late quaternary abstract during leg 195 of the ocean drilling program site 1202 was drilled in the subtropical northwestern pacific ocean beneath the kuroshio black current between northern taiwan and the ryukyu island arc on the northern flank of the i lan ridge at 1274 m water depth the upper 110 m of the site 1202 section composed of dark grey calcareous silty clay provide an expanded record of environmental changes during the last 28 kyr the sediments were deposited at high sedimentation rates between 3 0 and 5 0 m kyr and peak values of 9 0 m kyr between 15 1 and 11 2 ka bp variations in the modes and sources of detrital sediment input as inferred from sediment granulometry mineralogy and elemental xrf scanner data reflect changes in environmental boundary conditions related to sea level changes kuroshio variability and the climate driven modes of fluvial runoff the provenance data point to increased sediment supply from northwestern taiwan between 28 and 19 5 ka bp and from east china sources between 19 5 and 11 2 ka bp the change in provenance at 19 5 ka bp reflects increased fluvial runoff from the yangtze river and strong sediment reworking from the east china sea shelf in the course of increased humidity and postglacial sea level rise particularly after 15 1 ka bp the holocene was dominated by sediments that originated from rivers in northeastern taiwan for the pre holocene period prior to 11 2 ka bp low portions of sortable silt 63 10 m show that the kuroshio did not enter the okinawa trough because of low sea level in turn high proportions of sortable silt and sediment provenance from northeastern taiwan point to strong ocean circulation under the direct and persistent influence of the kuroshio during the holocene the reentrance of the kuroshio to the okinawa trough was heralded by two pulses in relative current strengthening at 11 2 and 9 5 ka bp as documented by stepwise increases in sortable silt in the lower holocene section from a global perspective environmental changes in the southern okinawa trough show affinities to climate change in the western pacific warm pool with little influence of climate teleconnections from the north atlantic realm otherwise seen in many other marine and terrestrial palaeoclimate records from southeastern asia

the submerged paleolandscape of the maltese islands morphology evolution and relation to quaternary environmental change after the end of the last glacial maximum 450 km2 of former terrestrial and coastal landscape of the maltese islands was drowned by the ensuing sea level rise in this study we use high resolution seafloor data multibeam echosounder data seismic reflection profiles and remotely operated vehicle imagery and bottom samples to reconstruct 300 km2 of this submerged maltese paleolandscape the observed paleolandscape is exceptionally well preserved and comprises former coastal landforms i fault related escarpments ii paleoshore platforms and associated shorelines iii paleoshoreline deposits and iv mass movement deposits and former terrestrial landforms v river valleys vi alluvial plains vii karstified limestone plateaus and viii sinkholes these elements indicate that the paleolandscape has been primarily shaped by tectonic activity combined with fluvial coastal slope instability and karstic processes these are the same processes the shaped the current terrestrial and coastal landscape by correlating the identified landforms with the timing of known changes in sea level during the last glacial cycle we infer that the alluvial plains and the shallowest limestone plateaus had up to 100 kyr to develop whereas the paleoshoreline deposits are likely to have formed between 28 kyr and 14 kyr the most prominent paleoshore platforms shorelines and river valleys were generated between 60 kyr and 20 kyr fluvial erosion is likely to have been prevalent during periods of low sea level last glacial maximum and stadial conditions during mis 3 whereas karst processes should have been more effective during warm and humid interstadial periods our results have implications for improving the characterization of past environments and climates as well as providing a much needed background for prehistoric and geoarcheological research in the central mediterranean region

sediment surface effects on methane hydrate formation and dissociation abstract the effects of sediment surfaces on methane hydrate formation and dissociation were investigated using colloidal suspensions and new experimental methods developed for a large volume 72 liters temperature controlled pressure vessel hydrates were formed by bubbling methane gas through test solutions at temperatures and pressures within the hydrate stability field hydrate formation was visually detected by the accumulation of hydrate encrusted gas bubbles to measure hydrate dissociation conditions the pressure vessel was warmed while temperature was monitored within a zone of previously formed hydrate encrusted gas bubbles hydrate dissociation was indicated by a distinct plateau in the hydrate zone temperature while temperatures of the gas and liquid phases within the vessel continued to rise the dissociation plateau appears to be a phenomenon that is unique to the large volume of the pressure vessel used for the experiments in experiments where hydrates were formed in pure water temperature and corresponding pressure conditions measured during the temperature plateau matched model predicted values for hydrate stability in water thus confirming the validity of this new method for measuring hydrate dissociation conditions formation and dissociation conditions were measured for methane hydrates in colloidal suspensions containing bentonite hydrate formation experiments indicated that the presence of bentonite in water at 200 mg l significantly decreased pressures required for hydrate formation relative to formation in pure water alone on the other hand hydrate dissociation conditions measured in bentonite and silica suspensions with solids concentrations of 34 g l did not differ significantly from that of water these results are relevant to the origin and stability of natural gas hydrate deposits known to exist in deep permafrost and marine sediments where the effects of sediment surfaces are largely unknown

back arc extension in the okinawa trough the okinawa trough lying to the east of china is a back arc basin formed by extension within continental lithosphere behind the ryukyu trench arc system middle to late miocene uplift associated with normal faulting of the initially adjacent ryukyu nonvolcanic arc and the taiwan sinzi folded belt corresponds to the first rifting phase the timing of rifting is supported by the presence of marine sediments of corresponding age drilled in the northern okinawa trough the rifting occurred after a major early miocene change in the motion of the philippine plate with respect to eurasia and ceased during the pliocene a second rifting phase started about 2 m y ago at the plio pleistocene boundary and has continued until the present time it has proceeded to a more advanced stage in the middle and southern okinawa trough than it has farther north detailed bathymetric sea beam seismic reflection and magnetics data collected during the pop 1 cruise of the r v jean charcot reveal the principal features of the extensional processes the back arc spreading phase started very recently in the southern and middle okinawa trough as exemplified by several en echelon and in some cases overlapping active central graben oriented n70 e n80 e some of these depressions are intruded by volcanic ridges of fresh back arc basalt with associated large magnetic anomalies transform faults between these en echelon active rifts are not obvious we suggest that the major part of the southern okinawa trough is underlain by a thinned continental crust and that except for the system of en echelon rifts of the southern okinawa trough the back arc basin oceanic domain is limited to a width of a few tens of kilometers or less in the axial portion of the trough the system of axial back arc volcanic ridges that occur in the rifts ends at the latitude of okinawa island whereas active volcanoes in the ryukyu arc occur only north of okinawa island we refer to this transition between active arc and back arc volcanism as the volcanic arc rift migration phenomenon vamp globally back arc volcanism propagated from the southern okinawa trough to the okinawa vamp area rifting continues to occur in the northern okinawa trough but is not yet accompanied by associated volcanism the okinawa vamp area is characterized by a series of parallel basaltic ridges oriented n75 e with associated linear magnetic anomalies characteristic of dyke intrusions we suggest that the formation of the back arc oceanic domain took place along the axial back arc extensional zone trending n75 e and that this zone presently ends at the southern extremity of the active volcanic chain the initial phase of formation of back arc basin oceanic crust is non steady state and is characterized by the lack of a developed fracture zone pattern the termination of the vamp area in the direction of the volcanic zone of the arc is consistent with the suggestion of molnar and atwater that the volcanic arc is a fundamental line of weakness which determines where initial back arc spreading occurs apparently back arc extension initially occurred within the continental lithosphere located westward of the ryukyu arc along its whole length but the subsequent back arc volcanism was initiated in the southernmost portion of the region and then moved northward this migration was accompanied by the shutting down of volcanic activity along the abandoned portions of the arc it is this transfer of volcanism that we call the vamp process thus arc and back arc basin volcanism seem to be associated in such a manner that spreading tends to migrate simultaneously with a cessation in volcanic activity along the arc this interplay of arc and back arc activity is probably linked to changes in the parameters of plate convergence since the plate motion in the phillippine sea is oblique to the trench at least in the southern part of the okinawa trough we suggest that the oblique resisting force applied to the edge of the overriding plate engenders the development of en echelon extensional features within and behind the arc the motion of the ryukyu platelet with respect to eurasia is consequently an extensional strike slip motion trending roughly parallel to the okinawa trough

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

holocene coral reef development under windward and leeward locations at ishigaki island ryukyu islands japan abstract coral reef growth is largely controlled by the wave energy associated with ocean swells and local winds this growth has responded to changes in wave conditions that evolved in concert with holocene sea level changes we analyzed holocene facies of the ibaruma and fukido reefs of ishigaki island southern ryukyu islands in the context of temporal and spatial changes in wave conditions by comparing present day coral assemblages and internal fossil reef facies four major coral assemblages that developed under different wave energy conditions were recognized six cores recorded a holocene reef sequence consisting of four sedimentary facies that differed in the relative volumes of four coral taxa acropora digitifera and acropora hyacinthus and lesser amounts of favia stelligera and montastrea curta holocene windward reef growth began at 7820 cal years bp after flooding of the pleistocene reef limestone surface the ensuing reef growth kept up with the rapid sea level rise a vertical growth rate of 7 5 m 1000 years during reef nucleation and early growth stages decreased to 3 5 m 1000 years during the main stage of reef framework development the uppermost part of the windward reef consisted of a very robust framework unlike the open framework of the leeward reef ages indicated that the uppermost leeward reef was ca 3000 years younger than the uppermost windward reef these variations in facies development and timing were caused by differences in local wind driven wave conditions

new evidence for drowned shelf edge reefs in the great barrier reef australia we present four new high resolution multibeam bathymetry datasets from the shelf edge of the northern great barrier reef gbr analysis of these data combined with chirp sub bottom profiles and existing submersible observation data provides a fresh insight into the detailed morphology and spatial distribution of submerged reefs and terraces at the shelf edge an extensive and persistent line of drowned shelf edge reefs exist on the gbr margin in about 40 to 70 m they appear as barrier reefs up to 200 m wide and comprising twin parallel ridges of rounded pinnacles subtle yet consistent terrace and step features lie between 78 and 114 m seaward of the shelf edge reefs in the southern study area submersible observations confirm that the drowned reefs now provide a favorable hard substrate for live soft corals and algae they form a consistent and extensive seabed habitat that extends for possibly 900 km along the gbr shelf edge the submerged reef and terraces features may reflect a complex history of growth and erosion during lower sea levels and are now capped by last deglaciation reef material

karstic uvala revisited toward a redefinition of the term abstract uvalas are a particular type of karst closed depression while other types of closed depression dolines and poljes are regularly listed and relatively well defined in overviews of karst surface morphology uvalas are either excluded or their vague identification is stressed the leading idea of this paper is to obtain a clearer meaning of the term uvala and prevent its abandonment from karstology and general geomorphology within the study 43 examples of uvalas have been selected the studied uvalas are located in the dinaric karst and karst of the carpatho balkanides all the case examples have been digitally processed in the same way creation of high resolution digital elevation models enabled quantification of morphometric parameters generation of inclination maps and cross sections as well as application of statistical analyses formation of the geographical information system of the studied uvalas was done using raster based and vector based gis software packages in 12 studied uvalas detailed structural geological mapping has been carried out which revealed dominant development of uvalas along regional scale tectonically broken zones a revised definition of the term uvala is suggested leaving the opportunity for further discussion

surface lowering rates of uplifted limestone terraces estimated from the height of pedestals on a subtropical island of japan in kikai jima south western japan many pedestal rocks have developed on the surface of holocene raised coral reef terraces with known dates of emergence pedestals are formed just under boulders which are considered to have been transported by tsunami and settled on a reef flat before emergence on the assumption that boulders protect the underlying limestone terrace from rainfall solution the rate of surface lowering of these limestone terraces was evaluated from the height of pedestals and the period of their formation the result showed that the mean lowering rate over 6000 years is 205 mm ky copyright 2007 john wiley sons ltd

late glacial to post glacial sea levels in the western indian ocean late glacial to post glacial sea level changes provide direct evidence of the progress of melting of large ice sheets during the last deglaciation but although the correlation between ice and ocean volumes is incontrovertible the causal link is commonly obscured local effects including tectonics isostatic and hydroisostatic responses and equatorial ocean syphoning impose additional signals that hide the true picture a detailed regional study of the western indian ocean based on the analysis of drill cores carried out through modern reefs in combination with observations and sampling of reef foreslopes and investigations of outcrops provides a comprehensive data base sites from a range of tectonic settings include the microcontinental margins of madagascar the granitic seychelles and the isolated volcanic islands of reunion mauritius and the comoros in which the effects of subsidence can be shown to be small these cover a range of latitudes and comparisons with adjacent sites on continental margins allow the construction of sea level curves that closely reflect the eustatic response and disengage this from the effects of other mechanisms the mayotte foreslope in the comoro islands provides the first coral reef record of sea level change during the early deglaciation in the indian ocean 110 115 m below present sea level between 18 000 and 17 000 yr bp two distinctive reef terraces at 90 and 60 m water depth are dated at 13 600 yr bp and partly attributed to the younger dryas period 12 700 11 600 cal yr bp reef drowning at around 13 500 yr bp may correspond to meltwater pulse 1a and although there were surges in the rate of sea level rise most notably between 11 950 and 11 350 yr bp there is little evidence to support a well defined meltwater pulse 1b reconstructed holocene sea level curves are in good agreement and reflect a rapid sea level rise of about 6 mm yr 1 between 10 000 and 7500 yr bp followed by a clear inflection around 7500 yr bp when the rate fell to 1 1 mm yr 1 modern reefs started to grow 8000 9000 years ago in the post glacial period the rate of sea level rise was 1 1 5 mm yr 1 before stabilization at its present level 3000 2500 years ago curves for the 10 000 6000 yr 1 bp interval correspond closely with those predicted by theoretical models but lie below these in the subsequent period in particular and with the exception of the margins of the madagascar microcontinent influenced by hydroisostatic processes they do not reflect predicted higher sea level stands during the late holocene

laboratory study of methane hydrate formation kinetics and structural stability in sediments abstract the natural gas hydrate deposits in the offshore of india are embedded in different sediments namely clay rich silts and sands coarse grain sand and volcanic fly ash the variations in gas hydrate concentrations at different geological locations shows dependency on sediment mineralogy it is also known that the particle size of the sediments plays an important role in hydrate formation and gas hydrate concentrations in sediments we carried out systematic studies on the methane hydrate formation kinetics and methane hydrate volumetric yields in stirred reactor experiments using suspensions of synthetic silica and natural sediment from krishna godavari kg basin the hydrate formation behavior in silica and kg basin sediment is also compared with the formation of methane hydrates in a pure system without sediment or added silica grains our results show that the hydrate formation kinetics is faster in 50 m silica system followed by that in natural marine sediment observed methane hydrate yield in the laboratory is higher 39 in both the pure no sediment and 1 m silica suspensions the gas intake is much quicker 375 min in the suspension of 50 m silica system while the hydrate yield is noticeably less 29 38 the methane hydrates are characterized by raman spectroscopy and they show characteristic structure i si methane hydrate signatures with a hydration number in the range 5 93 6 12

continental shelf landscapes of the southeastern united states since the last interglacial abstract the wide sediment starved continental shelf and modern coastal areas of the southeastern united states retain well preserved but scattered remnants of a submerged paleolandscape this paper presents a conceptual model of stratigraphic deposition and landscape formation since the last interglacial on the continental shelf of south carolina with portions of north carolina georgia and florida usa data for this study include multibeam bathymetry surveys sidescan sonar mosaics high resolution subbottom profiles and ground truth surveys from 250 m to the modern tidewater region four bathymetric zones are recognized with eleven landforms and landform indicators the described zones range in depths from the modern shoreline across the shelf and over the shelf edge to 250 m msl relative sea level curves are presented for the area and discussed in conjunction with cultural and climatic events the potential for preservation of paleoamerican sites is high at the shelf edge between 130 m and 45 m with archaic and later occupations likely in depths of less than 25 m prominent vantage points for paleoamericans 11 kya would have existed at the shelf edge and tidewater resources would have been available nearby for a period of almost 6 ka rapid transgression rates 60 km ka after the sea level rose over the shelf edge make preservation of tidewater sites less likely on the outer and middle shelf searches for the earliest paleoamericans should focus on promontories at the edge of the shelf and along future discoveries of paleoincisions on the shelf mapping and delineating this paleolandscape and associated unconsolidated sedimentary deposits interspersed with rocky plains and ledges will continue to be a priority to marine archeologists coastal managers fishery scientists and marine spatial planners over the next several decades

discrimination of boulders deposited by tsunamis and storm waves at ishigaki island japan abstract the ryukyu islands japan where numerous boulders are deposited on the reef and on land might be ideal research fields of boulders deposited by tsunami and storm waves because many typhoons and several tsunamis attacked the same area during its history this study investigates the size position and the long axis orientation of 626 boulders at ibaruma and shiraho reefs at ishigaki island japan to elucidate the sedimentary differences of boulders deposited by tsunamis and storm waves in one area two distinct groups of boulders were found at these reefs boulders on the reef crest group 1 and along the shoreline group 2 boulders in group 1 porites sp of moat origin the group 2 boulders were remarkably heavier 14 c age based on results of this study we infer that tsunami boulders in these islands so called tsunami ishi can be discriminated from boulders of storm wave origin based on their sedimentary differences this sedimentological approach is expected to be applicable to other boulder fields throughout the world our results further suggest that the spatial and grain size distribution of tsunami boulders are very useful to elucidate local flow characteristics of the tsunami for example the group 2 tsunami boulders were deposited below the high tide line irrespective of size some were split into several pieces they were probably deposited below the high tide line by the remarkable reduction of the current velocity of the tsunami because of the local topography the reduction of the current velocity must have been drastic to have made the boulders hit the ground with sufficient force to split them

submarine geomorphology and glacial history of the sea of the hebrides uk the sea of the hebrides is an island studded region of complex bathymetry on the uk continental shelf west of the scottish mainland an extensive area 2200 km2 of recently collected multibeam bathymetry data combined with seismic reflection profiles reveal this part of the shelf to have been extensively modified by both glacial and modern processes our new geomorphological evidence strongly supports the contention that an ice stream drained ice from western scotland and the inner hebrides towards the barra fan at the continental shelf break at the height of the last glaciation marine isotope stage 2 3 convergent seabed glacial lineations and other subglacially streamlined features eroded in bedrock around the islands of canna and rum preserve the direction of ice sheet movement and strongly suggest the onset of ice streaming in a southwesterly direction on the continental shelf in the sea of the hebrides region this fast flow zone formed part of a larger convergent ice stream system draining much of western scotland and the north of ireland the southern part of which has been postulated already a number of rock basins linear troughs and deeps west and south of muck kept sediment free by the dominant modern tidal regime are interpreted as being at least partly subglacial in origin similarly a large complex of buried deeps between eigg and arisaig are interpreted as an overdeepened glacial drainage network it is suggested that intense bedrock erosion by focused subglacial abrasion and subglacial meltwater discharge over multiple glacial advance and decay cycles led to significant modifications of the pre quaternary bedrock surface other features such as moraines are only found in shallower water typically 50 m west of canna west of rum and south of skye their relative paucity indicates that the modern tidally dominated environment of the area may have removed much of the localised geomorphological evidence of offshore glacial limits within the sea of the hebrides or alternatively that the ice sheet margin was floating and retreated predominantly by calving leaving little geomorphological evidence of its retreat

hillslope infiltration and lateral downslope unsaturated flow lateral downslope vadose flow occurs in hillslopes with deep homogeneous soils when and why this happens has been partially answered by past experimental numerical and quasi analytical studies what has been overlooked however is that lateral downslope flow in unlayered soils is largely a drainage phenomenon driven by the changing character of the boundary condition at the soil surface numerical simulations show that when rainfall ceases the near surface head gradient in a hillslope becomes nearly parallel to the slope as a simple consequence of the surfaces becoming a no flow boundary neglecting evaporation during rainfall infiltration is nearly vertical for most soils except those with high constant anisotropy

development of coral reefs of the ryukyu islands southwest japan east china sea during pleistocene sea level change abstract the pleistocene coral reef deposits called the ryukyu group are widely distributed through the ryukyu islands lithofacies are represented by conglomerate calcareous sandstone and limestones the limestones can be divided into six lithofacies on the basis of macro benthos and large foraminifers they are coral rhodolith cycloclypeus operculina halimeda and poorly to well sorted detrital limestones their depositional environments are reconstructed referring to the depth range of the recent coral reef biota around the ryukyu islands depositional history of the ryukyu group is recorded in a stratigraphic cross section on toku no shima sequence stratigraphical units are recognized in the vertical section of the limestones units 1 and 3 are considered to have been formed when the relative sea level was high while units 2 and 4 were deposited during the low stands of sea level it is noteworthy that the coral limestones of the units 2 and 4 were accumulated during glacial stages the generalized sequence of the limestones is deduced from a transition probability on miyako jima it begins with the cycloclypeus operculina limestone and is followed by rhodolith limestone and ends with coral limestone these facies indicate a shallowing upward succession

the paradox of tropical karst morphology in the coral reefs of the arid middle east despite differences in reef growth between the arabian gulf and the red sea a common distinctive pattern of polygonal sills surrounding ponded depressions consistently occurs in shallow water viewed from a satellite these seafloors are reticulated and maze like despite little current rainfall this patterning is best explained by karst dissolution of limestone during periods of lower sea level this is a paradox since such fine scale karstification is confined to areas with considerably more precipitation than currently observed in arabia we resolve this apparent contradiction by developing a pleistocene holocene chronology of sea level and climate for the red sea and arabian gulf and through the use of pattern analysis and computer simulation reveal the mechanism of formation for these structures we demonstrate that this patterning can be taken as a quaternary signature of paleohumidity in the now hyperarid red sea and arabian gulf

four years of mass balance on chhota shigri glacier himachal pradesh india a new benchmark glacier in the western himalaya little is known about the himalayan glaciers although they are of particular interest in terms of future water supply regional climate change and sea level rise in 2002 a long term monitoring programme was started on chhota shigri glacier 32 2 n 77 5 e 15 7 km2 6263 4050 m a s l 9 km long located in lahaul and spiti valley himachal pradesh india this glacier lies in the monsoon arid transition zone western himalaya which is alternately influenced by asian monsoon in summer and the mid latitude westerlies in winter here we present the results of a 4 year study of mass balance and surface velocity overall specific mass balances are mostly negative during the study period and vary from a minimum value of 1 4 m w e in 2002 03 and 2005 06 equilibrium line altitude ela 5180 m a s l to a maximum value of 0 1 m w e in 2004 05 ela 4855 m a s l chhota shigri glacier seems similar to mid latitude glaciers with an ablation season limited to the summer months and a mean vertical gradient of mass balance in the ablation zone debris free part of 0 7 m w e 100 m 1 similar to those reported in the alps mass balance is strongly dependent on debris cover exposure and the shading effect of surrounding steep slopes

infinite slope stability under steady unsaturated seepage conditions 1 we present a generalized framework for the stability of infinite slopes under steady unsaturated seepage conditions the analytical framework allows the water table to be located at any depth below the ground surface and variation of soil suction and moisture content above the water table under steady infiltration conditions the framework also explicitly considers the effect of weathering and porosity increase near the ground surface on changes in the friction angle of the soil the factor of safety is conceptualized as a function of the depth within the vadose zone and can be reduced to the classical analytical solution for subaerial infinite slopes in the saturated zone slope stability analyses with hypothetical sandy and silty soils are conducted to illustrate the effectiveness of the framework these analyses indicate that for hillslopes of both sandy and silty soils failure can occur above the water table under steady infiltration conditions which is consistent with some field observations that cannot be predicted by the classical infinite slope theory a case study of shallow slope failures of sandy colluvium on steep coastal hillslopes near seattle washington is presented to examine the predictive utility of the proposed framework

the devastating zhouqu storm triggered debris flow of august 2010 likely causes and possible trends in a future warming climate on 8 august 2010 in the northwestern chinese province of gansu a rainstorm triggered debris flow devastated the small county of zhouqu a modeling study using a new multiple phase scalable and extensible geofluid model suggests that the cause is an intersection of several events these were a heavy rainstorm not necessarily the result of global warming which triggered the landslide and followed a drought that created surface cracks and crevasses the geology of the region notably the loess covering heavily weathered surface rock and the bedrock damage that deepened the surface crevasses inflicted by the 7 9 magnitude wenchuan earthquake of 12 may 2008 deforestation and topsoil erosion were critical contributors to the massive size of the debris flow the modeling results underscore the urgency for a high priority program of revegetation of zhouqu county without which the region will remain exposed to future disastrous progressive bulking type landslides debris flows are more predictable types of landslides consequently a series of pseudo climate change model experiments of future extreme precipitation events are carried out using the weather research and forecasting model forced by temperature perturbations from an ensemble of climate models in a possibly future warmer climate extreme precipitation events are anticipated to be more severe and this study has identified an atmospheric blocking pattern that might produce future extreme precipitation events in the peri tibetan plateau tp area located to the northeast of the tp importantly observations from gravity field measuring satellites indicate that the larger geological environment of this region also is becoming increasingly unstable

gas hydrates in india potential and development abstract the shallow sediments along the indian continental margin are good hosts for gas hydrates and the methane within gas hydrates has been prognosticated as more than 1500 times of india s present natural gas reserve production of even 10 from this natural reserve is sufficient to meet country s vast energy requirement for about a century hence it was felt necessary to map the most prospective zones of gas hydrates and evaluate their energy potential along the indian margin first of all we have updated the gas hydrates stability thickness map along the indian shelf to provide the spatial and depth domains within which gas hydrates can be looked for we have identified the bottom simulating reflectors bsrs the main marker for gas hydrates in the krishna godavari kg mahanadi andaman kerala konkan and saurashtra regions respectively the total organic carbon content toc sediment thickness and rate of sedimentation indicate that the cauvery and kerala laccadive basins are also prospective for gas hydrates seismic attenuation q 1 reflection strength instantaneous frequency and blanking have been computed to characterize the sediments containing gas hydrates and free gas the faulting or gas chimneys have also been used for the identification of gas hydrates we have developed several approaches based on seismic traveltime tomography full waveform inversion amplitude versus offset avo modeling and avo attributes each coupled with rock physics modeling and utilized them for the quantification of gas hydrates a large volume of multi channel and ocean bottom seismic data have been acquired in 2010 between 500 to 2500 m water depths in kg and mahanadi basins the new data exhibit wide spread occurrences of bsrs reveal new prospective zones of gas hydrates and are being modeled for the delineation of sediments hosting gas hydrates and evaluation of their resource potential efforts are on to develop suitable technology for exploitation we anticipate that free gas lying below gas hydrate bearing sediments can be produced economically in near future however it may take longer time to retrieve gas from gas hydrates

anatomy of a modern coral reef flat a recorder of storms and uplift in the late holocene abstract cores from kabira reef ishigaki island southwest japan reveal the internal structure and temporal changes in sedimentary process of a complete coral reef flat the reef crest caught up with sea level at about 4000 yr bp since then it expanded oceanward and the reef pavement has grown landward the backreef structure is composed of bioclasts derived from the reef framework of all the bioclasts corals and coralline algae are most abundant coral fragments coarser than 3 0 o have dominated the backreef sediments since about 2000 yr bp benthic foraminiferal tests first occurred at about 4000 yr bp and their abundance increased significantly starting around 2000 yr bp shallowing of the reef crest is also indicated by the presence of the shallow water benthic foraminifera baculogypsina sphaerulata tests after 2000 yr bp the date 2000 yr bp is coincident with tectonic uplift at kabira reef kawana 1989 we consider this uplift to have caused a relative sea level fall that aided the deposition of coral fragments transported from the reef pavement by storms the relative sea level fall also caused subaerial exposure of the reef crest during low tides and the transition of reef building organisms from corals to shallow water species of benthic foraminifera resulting in a change noticeable in the constituents of backreef sediments the results of this study suggest that the coral reef flat and especially the backreef can be a faithful recorder of relative sea level changes

hydrate phase equilibria in porous media effect of pore size and salinity considering the ever increasing importance of marine gas hydrates it is crucial to gain a better understanding of clathrate formation and decomposition in porous media it is well established that due to capillary effects small diameter pores similar to those found in natural sediments act to inhibit hydrate stability however accurate data constraining these effects are still lacking here we present experimental methane clathrate dissociation data for 3 5 mass methanol aqueous solutions in confined silica glass pores of narrow distribution 30 6 15 8 and 9 2 nm mean diameters these data have been used to validate a thermodynamic model for clathrate stability porous media experimental data show a marked improvement on literature data which we attribute to the experimental and interpretative methods used and are in good agreement with the model predictions results suggest that mass transfer of inhibitors methanol and dissolved gas during clathrate formation dissociation within the porous network plays an important role in controlling gas hydrate equilibria

timing of the last glacial maximum from observed sea level minima during the last glacial maximum ice sheets covered large areas in northern latitudes and global temperatures were significantly lower than today but few direct estimates exist of the volume of the ice sheets or the timing and rates of change during their advance and retreat here we analyze four distinct sediment facies in the shallow tectonically stable bonaparte gulf australia each of which is characteristic of a distinct range in sea level to estimate the maximum volume of land based ice during the last glaciation and the timing of the initial melting phase we use faunal assemblages and preservation status of the sediments to distinguish open marine shallow marine marginal marine and brackish conditions and estimate the timing and the mass of the ice sheets using radiocarbon dating and glacio hydroisostatic modelling our results indicate that from at least 22 000 to 19 000 calendar years before present land based ice volume was at its maximum exceeding today s grounded ice sheets by 52 5 x 10 exp 6 cu km a rapid decrease in ice volume by about 10 percent within a few hundred years terminated the last glacial maximum at 19 000 250 years

sea level rise during termination ii inferred from large benthic foraminifers iodp expedition 310 tahiti sea level the course of sea level fluctuations during termination ii tii the penultimate deglaciation which is critical for understanding ice sheet dynamics and suborbital climate variability has yet to be established this is partly because most shallow water sequences encompassing tii were eroded during sea level lowstands of the last glacial period or were deposited below the present sea level here we report a new sequence recording sea level changes during tii in the pleistocene sequence at hole m0005d water depth 59 63 m below sea level mbsl off tahiti french polynesia which was drilled during integrated ocean drilling program expedition 310 lithofacies variations and stratigraphic changes in the taxonomic composition preservation states and intraspecific test morphology of large benthic foraminifers indicate a deepening upward sequence in the interval from core 310 m0005d 26r core depth 134 mbsl through 16r core depth 106 mbsl reconstruction of relative sea levels based on paleodepth estimations using large benthic foraminifers indicated a rise in sea level of about 90 m during this interval suggesting its correlation with one of the terminations assuming that this rise in sea level corresponds to that during tii after correcting for subsidence since the time of deposition a highstand sea level position would be 2 15 m above present sea level masl which is generally consistent with highstand sea level positions in mis 5e 4 2 masl if this rise in sea level corresponds to that during older terminations the subsidence corrected highstand sea level positions 30 15 masl for termination iii and 54 15 masl for termination iv are not consistent with reported ranges of interglacial sea level highstands 18 to 15 masl therefore the studied interval likely records the rise in sea level and associated environmental changes during tii in particular the intervening cored materials between the two episodes of sea level rise found in the studied interval might record the sea level reversal event during tii this conclusion is consistent with u th ages of around 133 ka which were obtained from slightly diagenetically altered i e 1 calcite in situ corals in the studied interval core 310 m0005d 20r core depth 118 mbsl this study also suggests that our inverse approach to correlate a stratigraphic interval with an approximate time frame could be useful as an independent check on the accuracy of uranium series dating which has been applied extensively to fossil corals in late quaternary sea level studies

recent contributions of glaciers and ice caps to sea level rise satellite measurements of earth s gravity field show that the mass loss of glaciers and ice caps contributed to sea level rise by approximately 0 4 millimetres per year between 2003 and 2010 the extent to which mass loss from ice covered land areas contributes to sea level rise is not known accurately in part because previous global estimates use different techniques for glaciers ice caps and ice sheets the gravity recovery and climate experiment grace satellite has provided monthly measurements of the global gravity field since 2002 using grace data jacob et al assess regional mass loss between 2003 and 2010 and conclude that mass loss from ice covered land areas contributed almost 1 5 mm per year to the sea level rise estimated mass loss from the high mountains of asia was negligible in contrast to some other reports glaciers and ice caps gics are important contributors to present day global mean sea level rise1 2 3 4 most previous global mass balance estimates for gics rely on extrapolation of sparse mass balance measurements1 2 4 representing only a small fraction of the gic area leaving their overall contribution to sea level rise unclear here we show that gics excluding the greenland and antarctic peripheral gics lost mass at a rate of 148 30 gt yr 1 from january 2003 to december 2010 contributing 0 41 0 08 mm yr 1 to sea level rise our results are based on a global simultaneous inversion of monthly grace derived satellite gravity fields from which we calculate the mass change over all ice covered regions greater in area than 100 km2 the gic rate for 2003 2010 is about 30 per cent smaller than the previous mass balance estimate that most closely matches our study period2 the high mountains of asia in particular show a mass loss of only 4 20 gt yr 1 for 2003 2010 compared with 47 55 gt yr 1 in previously published estimates2 5 for completeness we also estimate that the greenland and antarctic ice sheets including their peripheral gics contributed 1 06 0 19 mm yr 1 to sea level rise over the same time period the total contribution to sea level rise from all ice covered regions is thus 1 48 0 26 mm 1 which agrees well with independent estimates of sea level rise originating from land ice loss and other terrestrial sources6

reconstruction of the east china sea palaeoenvironment at 16 ka by comparison of fossil and modern faviidae corals from the ryukyus southwestern japan we conducted paired measurements of the sr ca ratio and oxygen and carbon stable isotopes of a fossil faviidae coral specimen myk90 age 16 ka collected from near miyako island the ryukyus southwestern japan our study aimed to reconstruct the palaeoenvironment in the east china sea at 16 ka by comparing the fossil sample with modern faviidae corals our data with annual or longer time resolution may be very suitable for palaeoceanographic reconstruction although no general calibration method for faviidae corals has been reported our calibration showed that the annual mean sea surface temperature was approximately 5 c lower and sea surface salinity sss at the study site was locally higher at 16 ka than at present even though the mouths of the yellow and changjiang rivers were east of their present locations because sea level was much lower our results suggest that the influence of the terrestrial water discharge may not have extended to miyako island weak summer monsoon activity during the last glacial which decreased summer precipitation over the asian continent and an enhanced winter monsoon which may have led to more evaporation likely contributed to the inferred high sss at the study site copyright 2009 john wiley sons ltd