landslide generated tsunamis at reunion island 1 landslides that occur on oceanic volcanoes can reach the sea and trigger catastrophic tsunamis reunion island has been the location of numerous huge landslides involving tens to hundreds of cubic kilometers of material we use a new two fluid seawater and landslide numerical model to estimate the wave amplitudes and the propagation of tsunamis associated with landslide events on reunion island a 10 km3 landslide from the eastern flank of piton de la fournaise volcano would lift the water surface by about 150 m where it entered the sea the wave thus generated would reach saint denis the capital of reunion island population of about 150 000 people in only 12 min with an amplitude of more than 10 m and would reach mauritius island in 18 min although mauritius is located about 175 km from the impact waves reaching its coast would be greater than those for reunion island this is due to the initial shape of the wave and its propagation normal to the coast at mauritius but generally coast parallel at reunion island a submarine landslide of the coastal shelf of 2 km3 would trigger a 40 m high wave that would severely affect the proximal coast in the western part of reunion island for a landslide of the shelf of only 0 5 km3 waves of about 2 m in amplitude would affect the proximal coast

tsunami of december 26 2004 on the southwest coast of india post tsunami geomorphic and sediment characteristics this paper discusses the impact of the december 26 2004 tsunami on the geomorphic features and sediment characteristics along the southwest coast of india the data used include field observations made after the tsunami and the inferences drawn from the satellite imagery taken before and after the tsunami sediment samples collected from the inner shelf beach and estuarine environments were analyzed to understand post tsunami changes in grain size characteristics the tsunami eroded and transported landwards significant volumes of distinct black sands rich in heavy minerals from the shelf onto the beaches of the kerala region and up to 500 m inland of the present coast

chaotic deposition by a giant wave molokai hawaii a coral basalt breccia conglomerate is exposed 60 m above present sea level and nearly 2 km inland from the present shoreline on the southwest side of east molokai volcano molokai the conglomerate is preserved mantling interfluves between gullies and forms a blanket like deposit 0 5 to 3 m thick no evidence of a wavecut terrace either within the blanket or at its upper or lower limits of exposure can be found no coral was found in growth position unsorted basalt clasts as large as boulder size are subrounded to angular randomly oriented and vary from 2 3 to 50 volume of the deposit the size of the largest basalt and coral fragments shows almost no systematic variation with elevation distance inland or lateral position parallel to the shore two indistinct rock units are present in a few places a lower carbonate rich unit that we interpret as an onwash facies and an upper basalt rich unit an offwash facies the carbonate rich onwash facies is dominated by biogenic debris especially fragments of coral and beach rock and gastropod and bivalve shells the offwash facies contains 40 to 90 basalt cobbles and boulders in a matrix of finely broken biogenic fragments where the distinct facies are lacking the proportion of basalt clasts increases crudely from the lower to the upper part of the conglomerate at a single place and from lower to higher elevation out crops where the deposit overlies a cinder cone several carbonate bearing elastic dikes extend from the conglomerate as much as 10 m down into the basalt cinders this deposit was apparently laid down by a giant wave that broke over an outer reef similar to the present fringing reef and advanced as a turbulent bore over the back reef flat picking up a slurry of carbonate rich debris and depositing it on the slopes inland as the wave advanced the offwash picked up loose basalt debris on its return flow u series dating of coral fragments indicates that the age of this deposit is 240 200 ka indicating the wave is distinct from that which produced a similar deposit on lanai about 100 ka this giant wave was most likely caused by one of the many large submarine landslides that have been identified on the lower slopes of the major hawaiian islands

boulders as a signature of storms on rock coasts this paper is the first review of coastal boulder studies it serves as a peer reviewed introduction to a special issue on the topic of boulders as a signature of storms on rock coasts since 2004 and the indian ocean tsunami most coastal boulder research has been focused on using boulders as sedimentary signatures of palaeo tsunami events and the most commonly used transport equations typically suggest that large boulder deposits are products of tsunami rather than storms there is growing empirical evidence demonstrating on inter annual to century timescales that storm waves are capable of transporting and depositing boulders of significant size at elevations well above sea level current process studies of how boulders are eroded transported and deposited have not received wide attention by rock coast geomorphologists or palaeoenvironmental reconstruction scientists this special issue is framed around the goal of highlighting our current understanding of the role of storm waves as a driving mechanism for boulder erosion transport and deposition here we review the current state of knowledge about boulder dynamics boulder responses to storms and boulders as sedimentary signatures of storm events we identify gaps in our conceptual and quantitative understanding lastly we propose means of addressing research gaps improving consistency between researchers and collecting multi purpose data this review and the papers contained within the special issue provide an improved understanding of coastal dynamics particularly the role storms can play in influencing erosion rates and depositional patterns of coarse material i e boulders or larger which has hitherto been under represented in the literature

natural hazards extreme events and mountain topography the hazard of any natural process can be expressed as a function of its magnitude and the annual probability of its occurrence in a particular region here we expand on the hypothesis that natural hazards have size frequency relationships that in parts resemble inverse power laws we illustrate that these trends apply to extremely large events such as mega landslides huge volcanic debris avalanches and outburst flows from failures of natural dams we review quantitative evidence that supports the important contribution of extreme events to landscape development in mountains throughout the world and propose that their common underreporting in the quaternary record may lead to substantial underestimates of mean process rates we find that magnitude frequency relationships provide a link between quaternary science and natural hazard research with a degree of synergism and societal importance that neither discipline alone can deliver quaternary geomorphology stratigraphy and geochronology allow the reconstruction of times magnitudes and frequencies of extreme events whereas natural hazard research raises public awareness of the importance of reconstructing events that have not happened historically but have the potential to cause extreme destruction and loss of life in the future

characteristics of high resolution hydraulic head profiles and vertical gradients in fractured sedimentary rocks summary accurately identifying the position of vertical hydraulic conductivity k v contrasts is critical to the delineation of hydrogeologic units that serve as the basis for conceptual and numerical models of groundwater flow high resolution head profiles have identified the position and thickness of k v contrasts in clayey aquitards but this potential has not yet been thoroughly evaluated in sedimentary rocks this paper describes an experiment in which head profiles with the highest technically feasible resolution were obtained using westbay multilevel systems mls installed in 15 cored holes at three sedimentary rock research sites with contrasting geologic and flow system conditions mlss were installed to maximum depths between 90 and 260 m with 2 5 monitoring zones per 10 m head profiles were measured over multiyear periods the vertical component of hydraulic gradient i e vertical gradient was calculated for each pair of adjacent monitoring intervals in every mls and then categorized based on its repeatability to facilitate interpretation of k v contrasts and comparisons within boreholes between boreholes at the same site and between sites the head and vertical gradient profiles from all three sites display systematic i e simple geometric shapes defined by repeatable intervals of no to minimal vertical gradient indicating relatively high k v units bounded by shorter depth intervals with large up to 50 m m vertical gradients indicating relatively low k v units the systematic nature of the profiles suggests flow in regular and interconnected fracture networks rather than dominated by a few key fractures with irregular orientations the low k v units were typically thin with their positions and thicknesses not predicted by lithostratigraphy or detailed lithologic geophysical and horizontal hydraulic conductivity data hence the position and thickness of units with contrasting k v would not be evident if mlss with the conventional number of monitoring zones had been used furthermore the detailed profiles can be strongly diagnostic of hydrogeologic unit boundaries or layers and can be used to improve the quantitative assessment of flow system conditions that is foundational to understanding contaminant plume migration

advances in the study of mega tsunamis in the geological record abstract extreme geophysical events such as asteroid impacts and giant landslides can generate mega tsunamis with wave heights considerably higher than those observed for other forms of tsunamis in this paper we review recent advances in the study of mega tsunamis in the geological record focusing on well documented examples that have captured particular attention over the past decade we provide up to date background on the source mechanisms of tsunami generation during asteroid impacts and ocean island landslides which are the largest landslides on earth we also discuss the main sources of uncertainty for modelling such mega tsunamis and for addressing associated hazards

structures uplift and magmatism of the western myanmar arc constraints to mid cretaceous paleogene tectonic evolution of the western myanmar continental margin abstract knowledge of trans himalayan tectono magmatic evolution is critical to understanding the complex pre collisional history of southern eurasia active continental margin it has been proposed that magmatic rocks of the trans himalayan batholith extending from southern tibet to southeast asia are now exposed as the western myanmar arc and central granite belt in myanmar yet origin emplacement and relationships of the two juxtaposed belts remain poorly constrained in this study 2d seismic and drilling data for the western myanmar arc zircon u pb age and hf isotope and whole rock geochemical data for magmatic rocks from the arc have been applied our seismic profiles borehole stratigraphic sequences and zircon u pb data show that a typical arc basin system was well developed along the western myanmar continental margin the magmatic arc has experienced at least three igneous events in the mid cretaceous 110 90 ma latest cretaceous early paleocene 69 64 5 ma and eocene 53 38 ma as well as three associated uplift processes in the late cretaceous eocene and late oligocene whole rock geochemical characteristics and zircons showing variable but predominately positive e hf t values suggest a significant juvenile mantle source involving a proportion of ancient subducted sediments and juvenile crustal materials for these typical arc related magmatic rocks the identification of mid cretaceous to paleogene magmatic rocks having positive e hf t values from the western myanmar arc 1 indicates that the magmatism can be correlated with the gangdese arc within the lhasa terrane of the southern tibetan plateau 2 provides evidence for the proximal derived model that paleogene sediments in the central myanmar basin were from the western myanmar arc but were not delivered by the paleo yarlung tsangpo irrawaddy river system from the gangdese arc and 3 enables a model of eastward subduction of the neo tethyan indian oceanic crust to reflect onset of the magmatism at the mid cretaceous and a long existed back arc extension in western myanmar

tsunami deposits in santiago island cape verde archipelago as possible evidence of a massive flank failure of fogos volcano abstract massive flank failures of volcanic edifices generate tsunami waves these low frequency but high magnitude hazards remain poorly documented because of the scarcity of observations offshore deposits are studied only by geophysical surveys and the failure rheologies are poorly constrained marine conglomerates found at unusually high elevations in hawaii and in the canary islands were previously interpreted as being the result of giant tsunami waves generated by massive flank failures this study focuses on the search for and interpretation of sedimentary evidence of a tsunami around the coastline of santiago island which is located 55 km east of the active fogo volcano the bordeira caldera in fogo island which opens to the east was formed by the monte amarelo flank collapse and the active edifice is now nested in the failure s scar the only evidence of a tsunami was found north of tarrafal bay the deposits display many similarities with the tsunami conglomerate described in hawaii and the canary islands erosive contact with the substratum rip up clasts of paleo soil marine bioclasts never found in growth or live position internal organisation into different facies with distinct characteristics of clast size up to boulders sorting from moderately to very poorly sorted and clast fabrics landward or seaward orientations this organisation suggests that the tsunami consisted of two main waves the absence of tsunami deposits elsewhere on santiago island coupled with the relatively low elevation of the conglomerate in tarrafal

ice age initiation by an ocean atmospheric circulation change in the labrador sea abstract the contrast between the large greenland ice sheet and the nearly ice free area of canada to the west exemplifies the critical role of the moisture supply in glaciation the trigger for new ice sheet growth in canada at the end of the last interglacial was probably an increase in the moisture supply rather than regional cooling triggering is attributed to stronger storm activity in the labrador baffin area caused by warming in the labrador sea and cooling in the greenland norwegian sea the key to this temperature and circulation change may have been an increase in the hydrologic deficit of the mediterranean sea a larger hydrologic deficit would have increased mediterranean salinity and consequently the volume of mediterranean overflow water a resulting increased upwelling of mediterranean overflow water from the lower thermocline off scotland would have diverted additional warm north atlantic drift water westward via the irminger current thus warming the labrador sea the underlying cause of the hydrologic deficit increase was diminishing milankovitch summer insolation in lower latitudes this reduced african monsoon intensity and nile river discharge in modern times nearly all nile discharge to the mediterranean has been lost due to irrigation practices culminating with the completion of the aswan high dam in 1968 the total increase in the hydrologic deficit due to nile discharge loss is now 8 in the next 70 100 years the nile loss added to larger evaporative losses due to co 2 warming may increase the deficit as much as 22 above the inferred deficit at the beginning of the last glaciation thus further warming the labrador sea consequently the triggering of major ice sheet growth in canada 100 years from now is possible

chemical signatures of palaeotsunamis a forgotten proxy article i nfo article history a range of diagnostic criteria are required to help identify palaeotsunami deposits although chemical signatures have long been used as indicators of palaeosalinity in sedimentary sequences their use in the studies of palaeotsunami deposits is rarely applied and is yet to be widely recognised the chemical composition of interstitial water in coastal ponds and sedimentary sequences in coastal marshes and lagoons has been used successfullyasanindicatoroftsunamiinundation chemicalsignaturescanalsoprovidecluesaboutthelandward limit of runup of a tsunami beyond the area of sediment deposition like most palaeotsunami proxies however the preservation of chemical signatures varies with environmental conditions

numerical modelling of the tsunami triggered by the guimar debris avalanche tenerife canary islands comparison with field based data abstract some tsunami deposits have been previously identified 41 188 m asl in the agaete valley on the northwest coast of the island of gran canaria in the canary islands in this paper the guimar sector collapse tenerife 0 83 ma and its expected associated tsunami that is thought to be at the origin of these tsunami deposits are tentatively reproduced using a two fluid numerical code two failure processes are considered 1 the whole 44 km 3 volume is released in one go or 2 the 44 km 3 are released in five retrogressive failures of equal volume occurring each 120 s in both cases two rheologies are used to simulate the landslide propagation the mohr coulomb frictional law and a constant retarding stress two hypotheses concerning the origin of the offshore mapped deposits are also considered 1 the mapped deposits are the direct result of a single collapse event occurring either in one go or by near retrogressive failures or 2 the mapped deposits result from a collapse followed by later partial remobilization of its deposits in all scenarios the subaerial destabilisation spreads out eastwards into the sea triggering waves 390 500 m high when considering a collapse in one go and 225 380 m when considering successive retrogressive failures the first wave reaches the coast of gran canaria located at 70 km from the scar 495 560 s after the collapse onset whatever the scenario considered water enters the agaete valley on gran canaria 555 690 s after the onset of collapse reaching up to 9 1 km inland for a collapse in one go and 5 0 km when considering five retrogressive failures in this valley the simulated waves inundate all the locations where tsunami deposits were identified with the flow depth measured reaching a maximum of 50 m collapse by retrogressive failures to 150 m collapse in one go at these particular places the directions of maximum kinetic energy as a function of time for the simulated waves are consistent with the current directions recorded by the cobble fabrics present in the run up and backwash layers of the tsunami deposits at one outcrop this study shows that the major source of uncertainty when reproducing landslide triggered tsunamis is linked to the way the landslide happens failure mechanisms that should be thus more precisely taken into account for landslide triggered tsunamis hazard assessment the rheology chosen to simulate the landslide propagation has only a second order impact on the produced waves

tsunami deposits related to flank collapse in oceanic volcanoes the agaete valley evidence gran canaria canary islands abstract enigmatic marine conglomerates are attached at 41 188 m asl to the walls of the valley of agaete on the northwest coast of gran canaria canary islands they are formed by heterogeneous angular to rounded heterometric volcanic clasts roundness and maximal size decreasing with altitude and fossils rhodolites and marine shells never found in growth position and often broken the deposits are internally stratified into several layers most of them showing very poor sorting matrix supported and reverse grading they present lenticular morphologies with poor lateral continuity in transversal and longitudinal sections slopes show values and orientations similar to those of the relief of the substratum to which they seem to adapt although they show clear evidence of erosive contact with the substratum rip up clasts they do not tend to form horizontal terraces soft materials soils and colluviums are preserved in the contact with the substratum in outcrops with deposit slopes of up to 15 the age of the deposits is constrained between 1 75 ma and 32 ka their altitude and slope distributions are not related to pleistocene interglacial sea level changes storm deposits or isostatic movements all the above suggests that the agaete marine deposits were generated by tsunami waves the most probable source being a flank failure at least nine major such events having occurred in the canary islands during the pleistocene the guimar sector collapse east coast of tenerife 30 km 3 is the closest possible source for the tsunami and the sole flank failure that is directed towards another island in the canaries

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

the geomorphology of the flanks of the lord howe island volcano tasman sea australia abstract the flanks of mid ocean volcanoes are inherently unstable features especially in the constructional phase of development when the volcano is active lateral and vertical stresses are placed on the volcanic edifice as it builds with the flanks continuing to be unstable up to at least 1 ma after volcanism has ceased the flanks of the lord howe island volcano record this period of greatest instability and a subsequent period in which marine and subaerial erosion have dominated its geomorphic evolution lord howe island lies in the tasman sea of the southern pacific region and is the subaerial remnant of a miocene mid ocean volcano the island has only recently entered reef building seas and therefore has been subject to marine erosive processes over the past 5 6 ma the island is unique as it sits on the stable drowned continental crust of the lord howe rise rather than oceanic crust like many other mid plate basaltic islands multibeam sonar bathymetry data were collected to a depth of 3500 m where the island flanks grade into the surrounding planar sea floor several slump features are evident the largest being over 130 km2 in area these features are inferred to be old late tertiary based on an extensive cover of marine sediment as indicated by low multibeam backscatter intensity and subdued topography most likely the slumps formed during the immediate post eruptive stage of volcano evolution before the bulk of the subaerial portion of the volcano was removed by marine erosion flank processes are now dominated by the deposition of carbonate sediment composed of mollusc and foraminiferal remains based on radiocarbon and stable isotope analyses of a sediment core 760 m depth collected on a trough in the centre of the volcanic edifice quaternary sediment was likely deposited predominantly during glacial periods the erosional morphology sediment cover and tectonic stability of the region suggest that the flanks of the volcano are at present relatively stable

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

carbonate rocks matrix permeability estimation carbonate rocks store half of the world s proven oil reserves genesis and postdepositional diagenetic processes define the porous network topology and the matrix permeability this study compiles a database of porosity specific surface mercury porosimetry and permeability values extracted from published sources and complements the database through a focused experimental study specific surface and porosity combine to estimate the pore size dsur permeability versus dsur data cluster along a single trend with a slope of 2 in a log log scale which is in agreement with the kozeny carman model discordant data points correspond to samples with dual porosity or broad pore size distributions with long tails where flow channels along larger interconnected pores indeed the detailed analysis of all the porosimetry data in the database shows that permeability correlates best with the pore size d80 that is the 80th percentile in pore size distributions once again the best fit is a power function in terms of d80 2 analogous to kozeny carman the prediction uncertainty using d80 is one order of magnitude and has the same degree of uncertainty as more complex models and analyses this observation suggests an irreducible uncertainty of one order of magnitude in permeability estimation from index properties such as porosity mercury porosimetry and specific surface probably resulting from specimen preparation effects inherent physical differences in permeation versus invasion and difficulties in data interpretation these estimates of permeability are most valuable when specimens are limited to small sizes such as cuttings

reply to mega highstand or megatsunami discussion of mcmurtry et al elevated marine deposits in bermuda record a late quaternary megatsunami sed geol 200 2007 155 165 by paul j hearty and storrs l olson our recent paper mcmurtry g m tappin d r sedwick p n wilkinson i fietzke j and sellwood b 2007a elevated marine deposits in bermuda record a late quaternary megatsunami sedimentary geol 200 155 165 critically re examined elevated marine deposits in bermuda and concluded that their geological setting sedimentary relations micropetrography and microfaunal assemblages were inconsistent with sustained intertidal deposition instead we hypothesized that these deposits were the result of a large tsunami that impacted the bermuda island platform during the mid pleistocene hearty and olson hearty p j and olson s l in press mega highstand or megatsunami discussion of mcmurtry et al elevated marine deposits in bermuda record a late quaternary megatsunami sedimentary geology 200 155 165 2007 aug 07 sedimentary geol 200 155 165 in their response attempt to refute our conclusions and claim the deposits to be the result of a 21 m eustatic sea level highstand during marine isotope stage mis 11 in our reply we answer the issues raised by hearty and olson hearty p j and olson s l in press mega highstand or megatsunami discussion of mcmurtry et al elevated marine deposits in bermuda record a late quaternary megatsunami sedimentary geology 200 155 165 2007 aug 07 sedimentary geol 200 155 165 and conclude that the bermuda deposits do not provide unequivocal evidence of a prolonged 21 m eustatic sea level highstand rather the sediments are more likely the result of a past megatsunami in the north atlantic basin

combining high resolution vertical gradients and sequence stratigraphy to delineate hydrogeologic units for a contaminated sedimentary rock aquifer system summary hydrogeologic units hgus representing subsurface contrasts in hydraulic conductivity form the basis for all conceptual and numerical models of groundwater flow however conventionally delineation of these units relies heavily on data sets indirect with respect to hydraulic properties here we use the spatial and temporal characteristics of the vertical component of hydraulic gradient i e vertical gradient as the primary line of evidence for delineating hgus for cambrian ordovician sedimentary rocks at a site in dane county wisconsin the site includes a 16 km2 area encompassing a 3 km long mixed organic contaminants plume the vertical gradients are derived from hydraulic head profiles obtained using high resolution westbay multilevel systems installed at 7 locations along two orthogonal 4 km long cross sections and monitoring to depths between 90 and 146 m with an average of 3 4 monitoring zones per 10 m these vertical gradient cross sections reveal 11 laterally extensive hgus with contrasting vertical hydraulic conductivity kv the position and thickness of the kv contrasts are consistently associated with sequence stratigraphic features maximum flooding intervals and sequence boundaries distinguished at the site using cores and borehole geophysical logs the same sequence stratigraphic features are also traceable across much of the cambrian ordovician aquifer system of the midwest us the vertical gradients and sequence stratigraphy were arrived at independently and when combined provide a hydraulically calibrated sequence stratigraphic framework for the site this framework provides increased confidence in the precise delineation and description of the nature of hgu contacts in each borehole reduced uncertainty in interpolation of the hgus between boreholes and some capability to predict hgu boundaries and thickness in offsite areas where high resolution hydraulic data sets are not available consequently this hgu conceptual model will serve as a better basis for numerical simulations of groundwater flow and contaminant transport needed for continued risk assessment and to evaluate potential remedial technologies for the site more broadly the association between kv contrasts and sequence stratigraphy demonstrated at this site provides valuable insight into the relationship between geology and hydraulic contrasts that can be transferred to other areas of the upper midwest us and perhaps elsewhere to strata deposited in similar settings

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

karst controlled reservoir heterogeneity in ellenburger group carbonates of west texas petroleum production from restricted shelf carbonates of the lower ordovician ellenburger group is commonly considered to have been a result of a pervasive relatively homogeneous tectonic fracture system within the reservoir rock however regional facies and diagenetic paleokarst studies of ellenburger strata based on cores and wireline logs have demonstrated that significant reservoir compartmentalization was caused by karst modification in the upper part of the unit ellenburger group carbonates which attain a thickness of over 1 700 ft 520 m record sedimentation on a shallow water restricted shelf occupying most of west texas logging of over 10 000 ft 3 050 m of core from 63 wells has allowed recognition of six facies assemblages 1 lithic arenite 2 mixed siliciclastic carbonate packstone grainstone 3 ooid peloid grainstone 4 mottled mudstone 5 laminated mudstone and 6 gastropod intraclast packstone grainstone these facies assemblages record initial transgression and subsequent progradation and aggradation paleoslope was generally south and east from the texas arch toward the ouachita and marathon orogenic belts all facies assemblages with the local exception of the ooid peloid grainstone assemblage are characterized y very low intergranular and intercrystalline porosity porosity development in ellenburger group carbonates is directly related to a prolonged period of subaerial exposure that coincided with a middle ordovician eustatic lowstand prior to transgression of simpson group siliciclastics during this episode a widespread system of caves sinkholes joint controlled solution features and collapse breccias developed of particular importance to reservoir development was the formation of a regionally extensive cave system between 100 and 300 ft 30 and 90 m beneath the exposed ellenburger surface infill of this cave system by simpson group sand and clay segmented the upper ellenburger into three karst facies which are in descending order 1 cave roof dolomites fracture and mosaic breccias 2 laterally persistent cave fill facies siliciclastic matrix supported and carbonate matrix supported breccias and 3 lower collapse facies chaotic clast supported breccias of the cave floor pronounced vertical segregation of permeable zones defined by the three karst facies is evident in the emma andector martin block 13 and several other major ellenburger reservoirs lateral reservoir heterogeneities formed by localized laterally extensive collapse structures such as in the shafter lake reservoir also contribute to compartmentalization of producing zones within the upper ellenburger group secondary and tertiary recovery programs in these ellenburger reservoirs can be optimized by integrating concepts of lateral and vertical heterogeneity predicted by the karst model

the giant coastal landslides of northern chile tectonic and climate interactions on a classic convergent plate margin abstract documented for the first time are an extensive suite of late neogene giant terrestrial coastal landslides along the classic convergent margin of western south america 18 to 24 south these are remarkable in terms of their unusual abundance and atypical setting such failures previously being linked with oceanic volcanic edifices or over steepened glaciated coastlines located within the hyper arid coastal cordillera of the atacama desert of northern chile we report the presence of more than 60 individual large scale landslides with individual volumes up to 9 km 3 developed over a horizontal coastline distance of some 650 km these landslides were emplaced as a combination of rock avalanches and multiple rotational failures the majority terminated directly into the pacific likely generating significant tsunami hazard to the chilean and south peruvian coastline in a region which is today considered to be part of a notorious seismic gap the proliferation and scale of these late neogene giant landslides in this actively uplifting hyperarid terrain suggests they are the main geomorphic agent for relief reduction probably triggered by megathrust earthquakes and potentially providing a unique palaeoseismic archive the temporal and spatial distribution of these giant landslides corresponds with a period of surface steepening of the forearc wedge in the central andes and south to north differential uplift associated with factors such as aseismic ridge subduction the resulting surface gradient increases combined with the persistent climatic aridity of the region have served to limit effective relief reducing geomorphic processes in this oversteepened terrain to large scale landsliding the phenomena documented here geospatially link previously recognised large scale slope failures from the off shore environment and higher altitude areas of the andean forearc suggesting that large scale landsliding is capable of transferring sediment on a regional scale to the off shore peru chile trench this has implications for the friction of the subducting nazca plate and associated seismicity and uplift

geological and historical records of tsunami in australia abstract the indian ocean tsunami iot of 2004 has resulted in significant interest within australia about the record of tsunami for the continent because an understanding of tsunami hazard begins with a catalogue of past events here a preliminary catalogue of tsunami affecting australia is presented the catalogue contains entries for 57 tsunami events the oldest event is dated at 3 47 ga the most recent is the july 17th 2006 forty four tsunami were recorded on the new south wales coast although the nw coast of western australia records a significant number of events forty seven events have affected australia since ad1858 maximum run up for an historic event is 6 m asl whilst the maximum run up for a palaeotsunami event is reported at an elevation of at least 100 m asl twenty three percent of historic australian tsunami were generated by unknown causes and papua new guinea the solomon islands and indonesia collectively represent the most important source area of historic tsunami for australia geological records for palaeo and historic tsunami are identified and summarised the geological record of tsunami represents a potentially important source of information for australian tsunami however at the present time the geological record is both limited and controversial and future research should seek to re examine proposed geological evidence of tsunami from an analysis of this preliminary catalogue of australian tsunami a series of key research priorities have been identified to guide future research in the region

tsunami and palaeotsunami depositional signatures and their potential value in understanding the late holocene tsunami record in recent years much research on modern and palaeotsunami deposits has been published from these studies a range of signature types has been identified identifying and dating such deposits is an important element in understanding late holocene tsunami hazard and risk however important questions such as do modern and palaeotsunami leave similar or dissimilar traces do tsunami leave the same signatures all around the world or are there significant variations and what is the actual record of tsunami in different parts of the world still remain answering these questions is not an easy task but examining megatsunami flood deposits should shed some light on these questions because such high magnitude events should leave very clear and detailed traces within the coastal landscape the coast of se australia is reported to have been affected by numerous palaeomegatsunami in the late holocene as such the coast of new south wales offers an important natural laboratory to examine in detail deposits associated with such events here we summarize the published characteristics of modern and palaeotsunami deposits globally and within australia we briefly outline the tsunami risk to australia before examining a site called minnamurra point on the coastline of se australia south of sydney that has previously been described as containing evidence for a palaeomegatsunami of an unknown age we describe the results of a detailed coastal survey field stratigraphic investigation and various standard laboratory analyses surprisingly we are unable to replicate the previously reported findings of tsunami deposits whilst we prefer the interpretation that the sequence is an in situ soil the sediment sequence examined contains none of the usually reported lines of evidence to demonstrate tsunami provenance we recognize and discuss the significance and difficulty of identifying tsunami deposits in the field and consider the implications of our findings to the wider debate about the preservation of tsunami deposited sediments

relating small scale sedimentary structures and permeability in a cross bedded aquifer summary the objective of this study is to investigate the relation between small scale sedimentary structures and permeability in the brussels sands formation an early middle eocene shallow marine sand deposit in central belgium that constitutes a major groundwater source in the region a field campaign was carried out consisting of field observations of the sedimentary structures and in situ measurements of air permeability the sedimentary structures were interpreted sketched digitally photographed and measured in a representative outcrop additionally a total of 2750 cm scale air permeability measurements were carried out in situ analysis of the spatial distribution of sedimentary structures and permeability shows that clay rich sedimentary features such as bottomsets and distinct mud drapes exhibit a different statistical and geostatistical permeability distribution compared to the other lithofacies in the cross bedded sands spatial analysis of the air permeability data shows that permeability anisotropy in the cross bedded lithofacies is dominated by the foreset lamination orientation these results show that small scale sedimentary heterogeneity strongly influences the local spatial distribution of the hydraulic properties and results in permeability heterogeneity and stratification that would produce anisotropy in upscaled permeability values

evidence for hydraulic heterogeneity and anisotropy in the mostly carbonate prairie du chien group southeastern minnesota usa abstract in southeastern minnesota paleozoic bedrock aquifers have typically been represented in groundwater flow simulations as isotropic porous media to obtain a more accurate hydrogeologic characterization of the ordovician prairie du chien group a new approach was tested combining detailed geologic observations particularly of secondary porosity with hydraulic data lithologic observations of the depositional and erosional history of the carbonate dominated bedrock unit constrained characterization of both primary matrix and secondary porosity from outcrops and core hydrostratigraphic data include outcrop and core observations along with core plug permeability tests hydrogeologic data include discrete interval aquifer tests borehole geophysics water chemistry and isotope data and dye trace studies results indicate that the prairie du chien group can be subdivided into the shakopee aquifer at the top consisting of interbedded dolostone sandstone and shale and the underlying oneota confining unit consisting of thickly bedded dolostone the boundary between these two hydrogeologic units does not correspond to lithostratigraphic boundaries as commonly presumed groundwater flow in the shakopee aquifer is primarily through secondary porosity features most commonly solution enlarged bedding planes and sub horizontal and vertical fractures regional scale preferential development of cavernous porosity and permeability along specific stratigraphic intervals that correspond to paleokarst were also identified along with a general depiction of the distribution of vertical and horizontal fractures the combination of outcrop and core investigations along with borehole geophysics discrete interval aquifer tests water chemistry and isotope data and dye trace studies show that the prairie du chien group is best represented hydrogeologically as heterogeneous and anisotropic furthermore heterogeneity and anisotropy within the prairie du chien group is mappable at a regional scale 15 000 km2

landward fining in onshore gravel as evidence for a late pleistocene tsunami on molokai hawaii a conglomerate on the south coast of molokai hawaii has simple trends in carbonate clast abundance and size that are explained better by tsunami deposition than by shoreline uplift the conglomerate extends as much as 2 km inland and to 72 m above present sea level it consists mainly of basalt boulders derived from underlying bedrock but also contains carbonate pebbles and cobbles derived from coral reefs whereas basalt clasts display no vertical or lateral trend in size carbonate clasts decrease in abundance and get smaller with elevation and distance from shore the origin of the conglomerate is controversial it may have been produced by either a single tsunami or by wave action at multiple higher sea levels on molokai the deposit is best explained as the result of a single tsunami because only such a tsunami could move large grains so far inland and produce a simple trend in carbonate clasts while imparting no trend to the basalt clasts

sedimentologic and geomorphologic tsunami imprints worldwide a review abstract tsunami events with extreme effects on sedimentary transport or considerable alterations of the coastal configuration are rather rare regarding human history but considering geological timescales they occur frequently at least 100 megatsunami in different parts of the world have been recorded in the past 2000 years but presumably far more have failed to be noticed during historical times and are not mentioned either in written or oral ancient records therefore the topic of paleotsunami requires inevitable sedimentological and geomorphological research however field research concerning paleotsunami is astonishingly rare within the scientific approach and only 5 of the existing tsunami literature is related to this subject future efforts in paleotsunami research should focus on the geological evidence of these mega events to clarify their contribution to coastal forming processes this paper reviews the state of the art knowledge of sedimentologic and geomorphic imprints of tsunami along the world s coastlines in order to highlight the need for more detailed studies of paleotsunami depositional and geomorphological traces

tsunami sediments and their foraminiferal assemblages abstract tsunami hazard assessment begins with a compilation of past events that have affected a specific location given the inherent limitations of historical archives the geological record has the potential to provide an independent dataset useful for establishing a richer chronologically deeper time series of past events recent geological studies of tsunami are helping to improve our understanding of the nature and character of tsunami sediments wherever possible geologists should be working to improve the research tool kit available to identify past tsunami events marine foraminifera single celled heterotrophic protists have often been reported as present within tsunami deposited sediments but in reality little information about environmental conditions and by analogy the tsunami that deposited them has been reported even though foraminifera have an enormous capacity to provide meaningful palaeo environmental data here we review what foraminifera are describe their basic form and significance summarise where they have been reported in tsunami sediments and identify what can be learnt from them we review the gaps in our understanding and make recommendations to assist researchers who examine foraminiferal assemblages in order to enhance their use within tsunami geology

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

last interglacial sea stands on barbados and an early anomalous deglaciation timed by differential uplift three major sea level maxima between 137 and 120 kyr b p are documented by surveys of pairs of wave cut notches and other features associated with the broadly defined last interglacial coral terrace on barbados regression analysis of elevation differences between notch pair members as a function of their uplift rates at seven sites yields the age difference between first and third sea stands and their eustatic sea level difference these results when combined with stratigraphic data from the bahamas bermuda and western australia and a chronology based on age limits of corals from the bahamas and western australia yield an endpoint age and eustatic low tide elevation of 136 7 kyr b p and 7 4 m respectively for the first sea stand 126 kyr b p and 5 6 m for the second and 120 5 kyr b p and 3 0 m for the third the first sea stand is the result of an anomalous deglaciation that was completed during low northern summer milankovitch insolation this is contrary to the milankovitch hypothesis that orbitally controlled insolation largely determines the variations of glacial ice volume it implies that internal factors within the earth s climate system can be much stronger than the effects of insolation variations

holocene reef accretion southwest molokai hawaii u s a abstract two reef systems off south molokai hale o lono and hikauhi separated by only 10 km show strong and fundamental differences in modern ecosystem structure and holocene accretion history that reflect the influence of wave induced near bed shear stresses on reef development in hawaii both sites are exposed to similar impacts from south kona and trade wind swell however the hale o lono site is exposed to north swell and the hikuahi site is not as a result the reef at hale o lono records no late holocene net accretion while the reef at hikauhi records consistent and robust accretion over late holocene time analysis and dating of 24 cores from hale o lono and hikauhi reveal the presence of five major lithofacies that reflect paleo environmental conditions in order of decreasing depositional energy they are 1 coral algal bindstone 2 mixed skeletal rudstone 3 massive coral framestone 4 unconsolidated floatstone and 5 branching coral framestone bafflestone at hale o lono 10 cores document a backstepping reef ranging from 8 100 cal yr bp offshore to 4 800 cal yr bp nearshore a depauperate community of modern coral diminishes shoreward and seaward of 15 m depth due to wave energy disrupted recruitment activities and physical abrasion evidence suggests a change from conditions conducive to accretion during the early holocene to conditions detrimental to accretion in the late holocene reef structure at hikauhi reconstructed from 14 cores reveals a thick rapidly accreting and young reef maximum age 900 cal yr bp living coral cover on this reef increases seaward with distance from the reef crest but terminates at a depth of 20 m where the reef ends in a large sand field the primary limitation on vertical reef growth is accommodation space under wave base not recruitment activities or energy conditions interpretations of cored lithofacies suggest that modern reef growth on the southwest corner of molokai and by extension across hawaii in general is controlled by wave induced near bed shear stress related to refracted north pacific swell holocene accretion patterns here also reflect the long term influence of wave induced near bed shear stress from north swell during late holocene time this finding is consistent with other studies e g grigg 1998 cabioch et al 1999 that reflect the dominance of swell energy and sea level in controlling modern and late holocene accretion elsewhere in hawaii and across the pacific and indian oceans notably however this result is refined and clarified for hawaii in the hypothesis of rooney et al 2003 stating that enhancement of the el nino southern oscillation beginning approximately 5000 years ago led to increased north swell energy and signaled the end to net accretion along exposed coastlines in hawaii the exposure of hale o lono to north swell and the age of sea floor there ca 4 800 cal yr bp coupled with the lack of north swell incidence at hikauhi and the continuous accretion that has occurred there over the last millennium strongly supports the enso reef hypothesis as outlined by rooney et al 2003 other factors controlling holocene reef accretion at the study site are relative sea level position and rate of rise and wave sheltering by laau point habitat suitable for reef accretion on the southwest shore of molokai has shrunk throughout the holocene

stratigraphic constraints on the timing and emplacement of the alika 2 giant hawaiian submarine landslide abstract previous work has found evidence for giant tsunami waves that impacted the coasts of lanai molokai and other southern hawaiian islands tentatively dated at 100 and 200 ka by u series methods on uplifted coral clasts seafloor imaging and related work off hawaii island has suggested the alika phase 2 debris avalanche as the source of the 100 ka giant wave deposits although its precise age has been elusive more recently a basaltic sand bed in odp site 842 300 km west of hawaii estimated at 100 20 ka has been suggested to correlate with this or another large hawaiian landslide our approach to the timing and linkage of giant submarine landslides and paleo tsunami deposits is a detailed stratigraphic survey of pelagic deposits proximal to the landslide feature beginning with a suite of seven piston gravity and box cores collected in the vicinity of the alika 2 slide we used u series dating techniques including excess 230 th and 210 pb profiling high resolution paleomagnetic stratigraphy including continuous u channel analysis 18 o stratigraphy visual and x ray sediment lithology and the petrology and geochemistry of the included turbidites and ash layers minimum ages for the alika phase 2a slide from detailed investigation of two of the cores are 112 15 ka and 125 24 ka 2 based on excess 230 th dating a less precise age for the alika phase 1 and or south kona slide is 242 80 ka 2 consistent with previous geological estimates oxygen isotope analyses of entrained planktonic foraminifera better constrain the alika phase 2a maximum age at 127 5 ka which corresponds to the beginning of the stage 5e interglacial period it is proposed that triggering of these giant landslides may be related to climate change when wetter periods increase the possibility of groundwater intrusion and consequent phreatomagmatic eruptions of shallow magma chambers our study indicates the contemporaneity of the alika giant submarine landslides and distal deposits from enormous turbidity currents as well as coral clasts reported to be tsunami deposits on lanai and molokai through direct dating and compositional analysis of the landslide deposits

the evolution of the asian plate in burma the post cretaceous evolution of the asian plate in burma is strongly influenced by the spreading of the eastern indian ocean and the movement of greater india northward the western part of burma apparently was an area which received clastic sediments during the early mesozoic times during the end of the mesozoic the eastern part of burma emerged from the ocean the western part formed the shelf area with a slowly westwards migrating geosyncline indoburman geosyncline to the west of it flysch sediments of upper cretaceous age have been found in this area the collision of the indian plate with the asian plate changed the sedimentary conditions in burma the emergence of the indoburman ranges happened during the miocene generating an outer island arc and forming the bay of bengal the subduction along the w coast of burma changed in the n with the approach of continental indian crust and led to thrusts in the n part of the indoburman ranges today subduction appears to be active only s of 18 n in the eastern bay of bengal the opening of the andaman sea fits into the dynamical development of the area

tsunamis as geomorphic crises lessons from the december 26 2004 tsunami in lhok nga west banda aceh sumatra indonesia abstract large tsunamis are major geomorphic crises since they imply extensive erosion sediment transport and deposition in a few minutes and over hundreds of kilometres of coast nevertheless little is known about their geomorphologic imprints the december 26 2004 tsunami in sumatra indonesia was one of the largest and deadliest tsunamis in recorded human history we present a description of the coastal erosion and boulder deposition induced by the 2004 tsunami in the lhok nga bay located to the west of banda aceh northwest sumatra the geomorphological impact of the tsunami is evidenced by beach erosion some beaches have almost disappeared destruction of sand barriers protecting the lagoons or at river mouths numerous erosion escarpments typically in the order of 0 5 1 5 m when capped by soil and more than 2 m in dunes bank erosion in the river beds the retreat along the main river is in the order of 5 15 m with local retreats exceeding 30 m large scars typically 20 50 cm deep on slopes dislodgement of blocks along fractures and structural ramps on cliffs the upper limit of erosion appears as a continuous trimline at 20 30 m a s l locally reaching 50 m the erosional imprints of the tsunami extend to 500 m from the shoreline and exceed 2 km along riverbeds the overall coastal retreat from lampuuk to leupung was 60 m 550 000 m 2 and locally exceeded 150 m over 276 000 m 3 of coastal sediments were eroded by the tsunami along the 9 2 km of sandy coast the mean erosion rate of the beaches was 30 m 3 m of coast and locally exceeded 80 m 3 m the most eroded coasts were tangent to the tsunami wave train which was coming from the southwest the fringing reefs were not efficient in reducing the erosional impact of the tsunami the 220 boulders measured range from 0 3 to 7 2 m large typically 0 7 1 5 m with weights from over 50 kg up to 85 t we found one boulder less than 1 m large at 1 km from the coastline but all the others were transported less than 450 m 30 m and the moderate tsunamis height

integrated geophysical geochemical and hydrogeological investigation of shallow groundwater resources in parts of the ikom mamfe embayment and the adjoining areas in cross river state nigeria information generated from geophysical geochemical and hydrogeological data has been used in assessing the groundwater resource potential quality and usability and in mapping flow directions within the shallow subsurface of the mamfe embayment cross river state nigeria the electrical resistivity technique in which the schlumberger s vertical electrical sounding field procedure has been adopted was the geophysical method employed lithology logs from drilling records discharge rates static water level information were the hydrogeological information utilized while the geochemical techniques involve analyses of water samples apparent resistances were measured using different resistivity meters including oyo mcohm model 2115 abem terrameter sas300b and sas1000 models and igis ssp ats mrp model with maximum current electrode separation reaching 1 km in some communities geological information was used as control in the modelling and interpretation of all geophysical data the physico chemical parameters of the water samples from the different water sources in the area were determined using different analytical techniques and in some cases by in situ direct measurement of some parameters measured values of electrical conductivity static water level available aquifer discharge information and calculated sar and na were integrated into the geophysical and hydrogeological results the shallow subsurface of the area is segmented into four hydrogeological provinces crystalline basement province cbp cross river plain province crpp nkporo afikpo shales province nasp and alluvial buried river province abrp with localized groundwater flow patterns results indicated that the alluvial discharge rate of 3 83 l s fractured sandstone discharge rate of 2 43 l s and basement discharge rate of 1 80 l s aquifers are more yielding than the aquifers in areas covered with deformed shales discharge rate of 0 62 l s and siltstone aquifers discharge rate of 0 97 l s the aquifer horizons are inhomogeneous and anisotropic with topography and lithology exerting significant influence on groundwater flow direction however there appears to be some high yielding aquifers at depths greater than 100 m in the crpp areas although researches on their distribution are still ongoing precipitation is the major source of recharge and the water is enriched with na k ca2 mg2 text hco 3 cl text so 4 2 and text no 3 throughout the year graphical analyses of hydrochemical data using piper and stiff diagrams show that ca mg co3 hco3 is the dominant water facies results from ec sar and na show that the water is fresh and belongs to the good to excellent class and is therefore suitable for domestic agricultural and industrial use

palaeotsunami deposits a new zealand perspective abstract over the past few years geological investigations of coastal sediments in new zealand have provided evidence of past tsunami the identification of palaeotsunami deposits is helping to increase our knowledge about the sources magnitude and frequency of these events this paper briefly outlines both the key diagnostic characteristics used in new zealand to identify palaeotsunami deposits and the emerging findings related to recent research