statistical probability distribution of snow depth at the model sub grid cell spatial scale comprehensive snow depth data collected using georadar and hand probing were used for statistical analyses of snow depths inside 1 km grid cells the sub grid cell spatial scale was 100 m statistical distribution functions were found to have varying parameters and an attempt was made to connect these statistical parameters to different terrain variables the results showed that the two parameters mean and standard deviation of snow depth were significantly related to the sub grid terrain characteristics linear regression models could explain up to 50 of the variation for both of the snowcover parameters mentioned copyright 2004 john wiley sons ltd

a tsunami deposit at the cretaceous tertiary boundary in texas at sites near the brazos river texas an iridium anomaly and the paleontologic cretaceous tertiary boundary directly overlie a sandstone bed in which coarse grained sandstone with large clasts of mudstone and reworked carbonate nodules grades upward to wave ripple laminated very fine grained sandstone this bed is the only sandstone bed in a sequence of uppermost cretaceous to lowermost paleocene mudstone that records about 1 million years of quiet water deposition in midshelf to outer shelf depths conditions for depositing such a sandstone layer at these depths are most consistent with the occurrence of a tsunami about 50 to 100 meters high the most likely source for such a tsunami at the cretaceous tertiary boundary is a bolidewater impact

persistence in intra annual snow depth distribution 1 measurements and topographic control 1 terrestrial and airborne laser scanning tls and als techniques have only recently developed to the point where they allow wide area measurements of snow distribution in varying terrain in this paper we present multiple tls measurements showing the snow depth development for a series of precipitation events we observe that the pattern of maximum accumulation is similar for the two years presented here correlation up to r 0 97 storms arriving from the northwest show persistent snow depth distributions and contribute most to the final accumulation pattern snow depth patterns of maximum accumulation for the two years are more similar than the distribution created by any two pairs of individual storms based on the strong link between accumulation patterns and terrain we investigated the ability of a model based on terrain and wind direction to predict accumulation patterns this approach of winstral et al 2002 which describes wind exposure and shelter was able to predict the general accumulation pattern over scales of slopes but failed to match observed variance furthermore a high sensitivity to the local wind direction was demonstrated we suggest that winstral et al s model could form a useful tool for application from hydrology and avalanche risk assessment to glaciology

reworked tsunami deposits by bottom currents circumstantial evidences from late pleistocene to early holocene in the gulf of cadiz abstract younger sand layers ysls have been identified in drill cores of a late glacial to early holocene muddy contourite succession from the gulf of cadiz in this study we evaluate the grain size characteristics of the ysl which display bi gradational grading with inverse grading from silt to fine or medium grained sand followed by normal grading from fine or medium grained sand to silt radiocarbon dating shows that the ysl formed at three distinct times 1 the bolling allerod sites u1387 and u1386 2 the younger dryas site u1390 and 3 the beginning of the boreal site u1389 ichnological analyses and radiocarbon dating of cores from drill site u1389c indicate that the ysls consist of reworked materials deposited at a high sedimentation rate the results of sedimentological analyses ichnological treatment spatial distributions and radiocarbon dating of the ysls suggest that the possibility of an origin of the ysls is tsunami related but later reworked by bottom current however the source areas of the sandy sediments remain unclear although our results show them to be variable and area dependent some sandy deposits are transported by the mediterranean outflow water mow from the proximal sector of the gulf of cadiz contourite depositional system cds which is close to the strait of gibraltar however in other cases it is more probable that local gravity flows which are the result of instability on adjacent margins provide the sandy material

numerical forward modelling of fluxoturbidite flume experiments using sedsim abstract delta front fluxoturbidity deposits in rift basin margins as well as sand avalanches are influenced by topography water level fluctuation and wave action instability of prior sediments deposited on the delta front is a prerequisite for the generation of fluxoturbidity in this study sedsim a three dimensional numerical stratigraphic forward model is used to replicate and extend a set of physical flume tank experiments investigating the formation of fluxoturbidites from different initial conditions this study has investigated the influence of topographic slope relative water level change and wave action on the formation of fluxoturbidites and hopefully improves our understanding and insight into the dynamic processes of fluxoturbidity resulting from different initiation mechanisms the study also illustrates the value of numerical modelling in complementing and extending physical flume tank studies we show that at least at the scale of a flume tank there exists an optimum window of topographic slopes within which fluxoturbidites arise due to slumping this window ranging from 9 to 18 may be useful in distinguishing the effects of topographic slope from other fluxoturbidite causal mechanisms the amplitude and frequency of water level oscillation appears to be a significant control on fluxoturbidite thickness while wave attributes especially wave angles appear to affect fluxoturbidite locality relative to the sediment source

sedimentary structures tentatively attributed to seismic events abstract fingerprints of earthquakes in the sedimentary record are as yet difficult to identify this is particularly true for failure phenomena dewatering slumping fault graded and turbidite structures that could have been triggered also by other kinds of energy input other promising candidates are strange biostratinomic features convex down stacking of shells current orientation in wave ripple accumulations as well as certain preservational features found in geosynclinal pelagic limestones but in every case verification of the seismic origin is still needed

sedimentary features of tsunami backwash deposits in a shallow marine miocene setting mejillones peninsula northern chile abstract miocene shoreface sandstones in the caleta herradura half graben northern chile contain an exceptionally coarse deposit that based on sedimentologic and stratigraphic features is regarded as having been laid down during a tsunami event by non cohesive and sediment laden subaqueous density flows interpretations of the principal sediment depositing mechanisms effective in the tsunami surges rely largely on field observations of deposit geometry and internal sedimentary characteristics this example comprises two erosively based sedimentation units that were probably deposited by successive waves in the tsunami wave train the lower unit consists of a clast supported polymodal boulder bearing breccia composed mostly of angular clasts and fewer well rounded clasts framework components are mostly chaotic but may also exhibit either inverse to normal grading or crude normal grading laterally changes in characters of depositional facies are common and abrupt the sand sized bioclastic rich matrix is poorly sorted and very similar to the underlying lower shoreface bioclastic sandstone implying that soft sediments eroded at the lower erosional surface contributed to the tsunami deposit the bulk of the upper unit is a poorly sorted breccia bearing sandstone pebbles and cobbles are scattered massive or normally graded sporadic outsized boulders emplaced as debris fall deposits may occur along the erosional base an array of signatures such as unusually coarse grain size in comparison to the surrounding deposits erosional bases the mixed sources of sediments multiple erosional and depositional events normal size grading or massive texture are all considered distinctive features of tsunamigenic deposits backwash deposition is indicated by the incorporation within the tsunami deposits of sediments derived from mixed sources such as angular clasts from nearby subaerial settings rounded clasts reworked from beach gravels and bioclastic sand eroded from older and unconsolidated shoreface deposits notwithstanding the absence of soft sediment deformation features the marked facies change from a lower shoreface into an upper shoreface environment through the tsunamiites provides directional information about the origin of the tsunami wave it was most likely produced by a sea floor fault displacement associated with an episode of sudden probably coseismic coastal uplift

reply to the discussion by roger higgs on hummocky cross stratification like structures in deep sea turbidites upper cretaceous basque basins western pyrenees france by mulder et al sedimentology 56 997 1015

numerical modelling of tsunami propagation with implications for sedimentation in ancient epicontinental seas the lower jurassic laurasian seaway abstract tsunamis are frequent events in modern marine environments but evidence of their passing in subtidal ancient epicontinental sea deposits is elusive it has been suggested that this is due to mis identification or poor preservation potential herein a numerical modelling approach is used to show that tsunami propagation in one large ancient epicontinental sea was hindered by the damping effect of shallow bathymetries and reflection refraction and diffraction from emergent landmasses the imperial college ocean model icom is used for this study and is first validated against data from the sumatra andaman tsunami of december 2004 a palaeobathymetric dataset is then presented for the hettangian lower jurassic laurasian seaway with idealised tsunami sources situated on the continental shelf and within the adjacent oceanic basin results show that tsunamis forced from within ocean basins adjacent to the epicontinental sea are rapidly attenuated over the continental slope and fail to propagate great distances onto the shelf similarly the sedimentological effect of tsunamis forced from within the epicontinental sea is also restricted it is concluded that tsunami deposits in ancient epicontinental seas are most likely to occur in relative proximity to the source region and this must contribute to their scarcity in the geological record

statistical analysis of the surface circulation of the california current we use a set of mixed layer drifting buoy trajectories from the california current 20 n 40 n during 1985 1990 to obtain statistically reliable estimates of the mean currents the mean variance field and the geographically varying diffusivity integral timescales and integral space scales typical values for the diffusivity are 1 1 8 7 107 cm2 s 1 while the timescales and space scales are 2 1 7 1 days and 16 59 km respectively the variance field displays a strong westward gradient out to 125 w and diffusivity shows a tendency to decrease toward the southwest part of the domain significant anisotropy is found in the variance field near the coastal boundary and at 30 n 130 w which is the region where the subarctic and northern subtropical fronts approach the california current the antisymmetric component of the diffusivity tensor indicates that cyclonic eddies dominate the mesoscale signature of drifters in this region we seek simple parameterizations to relate the scales of motion of the random velocity field to the diffusivity by testing least squares fits to u02t and u0l where u02 is the velocity variance we found no cases for which these two hypotheses could be distinguished for the meridional component the linear regressions are not successful which suggests that the meridional departure velocities result from a flow regime that is significantly organized by for example waves or coherent structures a subset of the drifters measured temperature along their tracks and we use the resultant data to produce the first direct estimates of the horizontal eddy heat flux divergence based on lagrangian estimates in addition we separately compute the eddy diffusivity parameterization of the eddy heat flux divergence u using our diffusivity estimates and a sea surface temperature climatology the two independent terms agree well which provides a measure of reassurance about the diffusivity estimates the eddy heat flux divergence in the california current is very small 5 w m 2 and does not appear to be significant in the long term heat budget of the upper ocean in this region

topographic meteorologic and canopy controls on the scaling characteristics of the spatial distribution of snow depth fields 1 in this study lidar snow depths bare ground elevations topography and elevations filtered to the top of vegetation topography vegetation in five 1 km 2 areas are used to determine whether the spatial distribution of snow depth exhibits scale invariance and the control that vegetation topography and winds exert on such behavior the one dimensional and mean two dimensional power spectra of snow depth exhibit power law behavior in two frequency intervals separated by a scale break located between 7 m and 45 m the spectral exponents for the low frequency range vary between 0 1 and 1 2 for the one dimensional spectra and between 1 3 and 2 2 for the mean twodimensional power spectra the spectral exponents for the high frequency range vary between 3 3 and 3 6 for the one dimensional spectra and between 4 0 and 4 5 for the mean two dimensional spectra such spectral exponents indicate the existence of two distinct scaling regimes with significantly larger variations occurring in the larger scale regime similar bilinear power law spectra were obtained for the fields of vegetation height with crossover wavelengths between 7 m and 14 m further analysis of the snow depth and vegetation fields together with wind data support the conclusion that the break in the scaling behavior of snow depth is controlled by the scaling characteristics of the spatial distribution of vegetation height when snow redistribution by wind is minimal and canopy interception is dominant and by the interaction of winds with features such as surface concavities and vegetation when snow redistribution by wind is dominant

scaling properties and spatial organization of snow depth fields in sub alpine forest and alpine tundra this paper reports on a study analysing the spatial distribution functions the correlation structures and the power spectral densities of high resolution lidar snow depths 1 m in two adjacent 500 m 500 m areas in the colorado rocky mountains one a sub alpine forest the other an alpine tundra it is shown how and why differences in the controlling physical processes induced by variations in vegetation cover and wind patterns lead to the observed differences in spatial organization between the snow depth fields of these environments in the sub alpine forest area the mean of snow depth increases with elevation while its standard deviation remains uniform in the tundra subarea the mean of snow depth decreases with elevation while its standard deviation varies over a wide range the two dimensional correlations of snow depth in the forested area indicate little spatial memory and isotropic conditions while in the tundra they indicate a marked directional bias that is consistent with the predominant wind directions and the location of topographic ridges and depressions the power spectral densities exhibit a power law behaviour in two frequency intervals separated by a break located at a scale of around 12 m in the forested subarea and 65 m in the tundra subarea the spectral exponents obtained indicate that the snow depth fields are highly variable over scales larger than the scale break while highly correlated below based on the observations and on synthetic snow depth fields generated with one and two dimensional spectral techniques it is shown that the scale at which the break occurs increases with the separation distance between snow depth maxima in addition the breaks in the forested area coincide with those of the corresponding vegetation height field while in the tundra subarea they are displaced towards larger scales than those observed in the corresponding vegetation height field

storm generated episodic sediment movements off kahe point oahu hawaii abstract the area off kahe point oahu hawaii has been the focus of recent oceanographic research in preparation for a large scale ocean thermal energy conversion otec project underwater instrument arrays moored to the bottom in this area were damaged shifted or lost during hurricane iwa in 1982 four underwater telephone cables located at greater depths were severed during the same period seamarc ii images show that most of the sea floor in this area is represented by light gray tones cores collected from this smooth sediment cover contain thick sequences of hemipelagic silt and clay darker acoustic reflection patterns trend downslope across this light gray background cores containing coarse sands and gravels and displaced shallow benthic foraminifera were collected from rough bottom represented by these patterns the pattern configurations sediment types within them and their benthic foraminiferal content indicate that these darker tones represent downslope sediment flow telephone cables were damaged and instrument arrays moved during hurricane iwa in places and along trajectories coincident with the orientation of the dark tones

coconuts in miocene turbidites in new zealand possible evidence for tsunami origin of some turbidity currents fossil coconuts are recorded in proximal turbidites of middle miocene age in eastern north island new zealand this is apparently the first record of coconuts in turbidites the rocks can be assigned to a mid submarine fan environment and are part of the accretionary prism of the late cenozoic volcanic arc in northern new zealand the climate was marginally tropical these turbidites may have been formed by the surge of sediment and debris carried offshore by tsunamis

duplex like structures in submarine fan channels ouachita mountains arkansas submarine fan channel sequences of the jackfork formation lower pennsylvanian at degray dam section in the ouachita mountains arkansas contain discrete units 10 75 cm thick with moderately dipping 25 40 sigmoidal imbricate slices adjacent units with opposing imbricate slices are common the sigmoidal structures are similar in geometry to a tectonic feature known as a duplex a tectonic origin of sigmoidal structures however seems unlikely because opposing directions of imbrication in adjacent units would require an unrealistic tectonic movement history for the area we propose that the jackfork sigmoidal structures were formed by a process kinematically similar to that responsible for generating duplex structures unlike tectonic duplexes however the sigmoidal structures were formed by soft sediment deformation of sand and mud layers as high energy sediment gravity flows glided over these layers sediment gravity flows responsible for forming the sigmoidal deformation were probably generated by slumping of adjacent channel walls dip direction of sigmoidal slices is perpendicular to channel axes thus recognition of sigmoidal deformation structures may be useful in inferring the trend of channels in ancient submarine fan complexes

hurricane induced sediment transport in open shelf tropical systems an example from st croix u s virgin islands hurricane hugo passed directly over st croix on 17 september 1989 sustained winds in excess of 110 knots gusts to 165 knots and waves 6 7 m in height accompanied the storm along the north coast wave height was lower ca 3 4 m due to the leeward position of the shelf in the deeper reefs at cane bay and salt river damage was confined primarily to the soft bodied benthic community e g sponges gorgonians coral damage was much less severe largely because of the buffering effects of the water column the greatest change observed after the storm was wholesale flushing of sand from shelf edge areas in salt river submarine canyon a minimum of 2 million kg of sediment were flushed into deeper water the transport rate associated with the storm was eleven orders of magnitude above that measured during fair weather and the volume of sediment that was removed from the canyon equalled roughly a century of normal sediment accumulation at cane bay 336 000 kg of sediment were flushed from a single channel with similar amounts removed from adjacent breaks in the shelf edge reef a current meter in salt river submarine canyon provided information on the timing and intensity of the oceanographic processes related to hurricane hugo as the storm approached waves piled water against the shoreface and in salt river bay as the storm passed over st croix the change in wind direction followed by a decrease in wave height triggered a release of water trapped in the bay and along the adjacent shoreline by waves earlier in the storm for a period of 4 6 hours net down canyon currents reaching 2 m s and oscillatory flows up to 4 m s occurred along the base of the western canyon wall removing up to 2 m of sand similar events were likely responsible for the wholesale removal of sand in eastern cane bay the paradoxical concurrence of wholesale sediment transport and low level reef damage is related to the protection from waves but not wind afforded by the north coast of st croix facing away from the direction of storm approach these observations and measurements provide our first opportunity to relate sediment export in such a high energy event to the physical processes that were responsible calculations based on post hugo measurements are in agreement with an earlier sediment budget for salt river canyon sediment export in cane bay exceeded the volume similarly predicted because such events are probably common on all exposed carbonate shelf margins storms like hurricane hugo are among the most important factors in the cycling of sediment through exposed open marine environments both now and in the geologic past the patterns of reef damage and sediment transport are much more complicated than previously envisioned and more thoughtful consideration of their variability and the processes responsible is essential to an understanding of the signature that will be left by major storms

tsunami induced conglomerates in miocene upper bathyal deposits chita peninsula central japan abstract the tsubutegaura conglomeratic tsunamiites occur in the middle section of the miocene storm related sand silt alternation system in the chita peninsula central japan deposition of the system in the upper bathyal environment in a bay and synsedimentary seismic activity has been elucidated by palaeontological palaeogeographical and sedimentological studies two coupled units each built up by a conglomerate layer with an overlying sandstone layer and the alignment of lenticular sedimentary bodies are exceptional in this sequence some typical lenticular bodies confined within sedimentary troughs consist of a boulder bearing conglomerate layer and calcareous sandstone layer of the lower couple and another conglomerate layer of the upper couple the tuffaceous sandstone layer of the upper couple is distributed more widely than the other lithologies the framework gravels in the coupled conglomerates form a clast supported fabric and are quite notably monomictic the clasts are angular and imbricated partly forming peculiar gravel clusters due to traction current transportation conspicuous laminations develop in the coupled sandstone layers antidunes with chute and pool structure in the upper couple sandstone layer indicate deposition from an upper flow regime current on the other hand the calcareous composition of the lower couple sandstone layer reveals shallow water provenance thixotropic deformations and diastasis cracks in the siltstone bed immediately beneath the layers of the couples show that a severe earthquake tremor and a rapid change of water pressure occurred just before the deposition of the tsunamiites submarine debris flows due to collapse of a fault scarp in a shallow bank and the ensuing wash by two pulses of the tsunami induced ebb current comprise the scenario for the formation of the tsubutegaura conglomeratic tsunamiites

deep marine tidal bottom currents and their reworked sands in modern and ancient submarine canyons abstract submarine canyons provide a unique setting for tidal processes to operate from shallow marine to deep marine environments in modern canyons current meter measurements at varying water depths 46 4200 m show a close correlation between the timing of up and down canyon currents and the timing of semi diurnal tides these tidal bottom currents in submarine canyons commonly attain maximum velocities of 25 50 cm s based on core and outcrop studies of modern and ancient deep marine deposits it is proposed here that sand mud rhythmites double mud layers climbing ripples mud draped ripples alternation of parallel and cross laminae sigmoidal cross bedding with mud drapes internal erosional surfaces lenticular bedding and flaser bedding can be used to interpret deposits of deep marine tidal currents this approach is an alternative to the conventional approach in which most deep water traction structures e g climbing ripples and cross bedding would be attributed to deposition from turbidity currents underwater photographs show active mass flows i e slides slumps grain flows and debris flows in modern canyons box cores taken from modern submarine canyons e g la jolla california and conventional cores and outcrops of ancient canyon fill facies oua iboe pliocene nigeria and the annot sandstone eocene oligocene se france contain deposits of both tidal processes and mass flows this facies association in the rock record can be used as a criterion for recognizing submarine canyon settings in a channel mouth environment deep marine tidal deposits are likely to develop elongate bars that are aligned parallel to the channel axis within the channel whereas turbidites are more likely to develop depositional lobes that are aligned perpendicular to channel axis turbidite depositional lobes are much larger than the channel width whereas tidal sand bars are much smaller than the channel width therefore the wrong use of a turbidite lobe model with sheet geometry in lieu of a tidal bar model with bar geometry will result in an unrealistic overestimation of sandstone reservoirs in deep water exploration

ten turbidite myths abstract during the past 50 years the turbidite paradigm has promoted many myths related to deep water turbidite deposition john e sanders 1926 1999 a pioneering process sedimentologist first uncovered many of these turbidite myths this paper provides a reality check by undoing 10 of these turbidite myths myth no 1 turbidity currents are non turbulent flows with multiple sediment support mechanisms reality turbidity currents are turbulent flows in which turbulence is the principal sediment support mechanism myth no 2 turbidites are deposits of debris flows grain flows fluidized flows and turbidity currents reality turbidites are the exclusive deposits of turbidity currents myth no 3 turbidity currents are high velocity flows and therefore they elude documentation reality turbidity currents operate under a wide range of velocity conditions myth no 4 high density turbidity currents are true turbidity currents reality ph h kuenen 1950 introduced the concept of turbidity currents of high density based on experimental debris flows not turbidity currents high density turbidity currents are sandy debris flows myth no 5 slurry flows are high density turbidity currents reality slurry flows are debris flows myth no 6 flute structures are indicative of turbidite deposition reality flute structures are indicative only of flow erosion not deposition myth no 7 normal grading is a product of multiple depositional events reality normal grading is the product of a single depositional event myth no 8 cross bedding is a product of turbidity currents reality cross bedding is a product of traction deposition from bottom currents myth no 9 turbidite facies models are useful tools for interpreting deposits of turbidity currents reality a reexamination of the annot sandstone in se france which served as the basis for developing the first turbidite facies model suggests a complex depositional origin by plastic flows and bottom currents myth no 10 turbidite facies can be interpreted using seismic facies and geometries reality individual turbidity current depositional events commonly centimeters to decimeters in thickness cannot be resolved in seismic data all turbidite myths promote falsehood and should be abandoned

submarine paleoseismology of the northern hikurangi subduction margin of new zealand as deduced from turbidite record since 16 ka abstract paleoseismic studies seek to characterise the signature of pre historical earthquakes by deriving quantitative information from the geological record such as the source magnitude and recurrence of moderate to large earthquakes in this study we provide a 16 000 yr long paleo earthquake record of the 200 km long northern hikurangi margin new zealand using cm thick deep sea turbidites identified in sediment cores cores were collected in strategic locations across the margin within three distinct morphological re entrants the poverty ruatoria and matakaoa re entrants the turbidite facies vary from muddy to sandy with evidence for rare hyperpycnites interbedded with hemipelagites and tephra we use the oxal probabilistic software to model the age of each turbidite using the sedimentation rate of hemipelagite deduced from well dated tephra layers and radiocarbon ages measurements on planktonic foraminifera turbidites are correlated from one core to the other using similarity in sedimentary facies petrophysical properties and ages results show that 46 turbidites are synchronous along the entire margin amongst them 41 are interpreted as originating from the upper continental slope in response to earthquake triggered slope failures between 390 170 to 16 450 310 yr bp using well established empirical relationships that combine peak ground acceleration magnitude and location of earthquakes we calculate that synchronous slope failures were triggered by the rupture of 3 of the 26 known active faults in the region each capable of generating mw 7 3 to 8 4 earthquakes two are crustal reverse faults and one is the subduction interface the 41 mw 7 3 earthquakes occurred at an average recurrence interval of 400 yr over the last 16 000 yr among them twenty are interpreted as subduction interface earthquakes that occurred at an average recurrence interval of 800 yr with alternating periods of high activity and low return times 305 610 yr and quiescence periods with high return times 1480 2650 yr based on turbidite paleoseismology we propose that subduction interface earthquakes were of lower magnitude during active periods mw 7 5 than during quiescence periods mw 8 2

tsunami sedimentary facies deposited by the storegga tsunami in shallow marine basins and coastal lakes western norway sedimentary successions in small coastal lakes situated from 0 to 11 m above the 7000 year bp shoreline along the western coast of norway contain a distinctive deposit very different from the sediments above and below the deposit is interpreted to be the result of a tsunami inundating the coastal lakes an erosional unconformity underlies the tsunami facies and is traced throughout the basins with most erosion found at the seaward portion of the lakes the lowermost tsunami facies is a graded or massive sand that locally contains marine fossils the sand thins and decreases in grain size in a landward direction above follows coarse organic detritus with rip up clasts here termed organic conglomerate and finer organic detritus the tsunami unit generally fines and thins upwards the higher basins 6 11 m above the 7000 year shoreline show one sand bed whereas basins closer to the sea level 7000 years ago may show several sand beds separated by organic detritus these alternations in the lower basins may reflect repeated waves of sea water entering the lakes in basins that were some few metres below sea level at 7000 years bp the tsunami deposit is more minerogenic and commonly present as graded sand beds but also in some of these shallow marine basins organic rich facies occur between the sand beds the total thickness of the tsunami deposit is 20 100 cm in most studied sites an erosional and depositional model of the tsunami facies is developed

deep sea tsunami deposits in the eastern mediterranean new evidence and depositional models the tsunami wave induced by the collapse of the santorini caldera after the bronze age minoan eruption 3500 bp produced turbidites and large volume mega turbidites in the abyssal plains of the ionian sea as well as on the floor of small basins of the mediterranean and calabrian ridges characterized by the so called cobblestone topography since the first discovery in 1978 a holocene mud layer which has been termed homogenite and which typically shows a graded interval at its base has been identified and correlated in over 50 deep sea cores recovered in the eastern mediterranean four types of homogenite can be distinguished each related to a particular depositional setting 1 a closed cobblestone these are from a few decimetres to several metres thick pelagic turbidites of local provenance exclusively found at the bottom of small sized ponded basins of the mediterranean and calabrian ridges a debris flow may be present at the base of the turbidite where the vertical relief of the basins is over 200 m 2 b abyssal plain a 10 to 20 m thick megaturbidite recorded in the ionian and sirte abyssal plains the source area is the african continental margin possibly the continental shelf it can be easily identified as a transparent acoustic layer that shows recent deformation across the deformation front of the mediterranean ridge accretionary prism the volume of the minoan homogenite in the ionian abyssal plain has been calculated at a minimum of 11 km3 3 c open cobblestone this type is exclusively found on the outer slope of the mediterranean ridge near the deformation front unlike types a and b the base of the turbidite here is erosional instead of depositional this homogenite has been deposited in small basins and occasionally on topographic highs of the mediterranean ridge by the up slope flow of turbidity currents of african provenance that formed the abyssal plain deposit type b 4 d a fourth depositional model has been identified homogenites present in deep anoxic basins of the mediterranean ridge this setting is substantially similar to type a but the vertical relief of the basin is much higher up to 800 m and the deposition occurs in high density anoxic brines which modify the settling rate and hence the resulting sedimentological characters

interannual persistence of the seasonal snow cover in a glacierized catchment knowledge of the spatial snow distribution and its interannual persistence is of interest for a broad spectrum of issues in cryospheric sciences in this study snow depths derived from airborne laser scanning are analyzed for interannual persistence of the seasonal snow cover in a partly glacierized mountain area 36 km2 at the end of five accumulation periods the snow covered area varied by 16 of its temporal mean mean snow depth of the total area ranged by a factor of two 1 31 2 58 m with a standard deviation of 0 42 m interannual correlation coefficients of snow depth distribution were in the range 0 68 0 84 of the investigated area 75 was found to be interannually persistent the remaining area showed variable snow cover from year to year caused by occasional avalanches and changes in surface topography as a result of glacier retreat snow cover underwent a change from a homogeneous distribution on the former glacier surface to a more heterogeneous snow cover in the recently deglaciated terrain a geostatistical analysis shows interannual persistence in scaling behavior of snow depth in ice free terrain with scale break distances at 20 m scale invariant behavior of snow depth is indicated over 100 m on smooth glacier surfaces

tsunami induced sediment transport in the abyssal mediterranean sea an unusual stratigraphic unit nicknamed homogenite fills topographic lows in the complex ridge and trough bathymetry at two survey sites on the western mediterranean ridge and the calabrian ridge on near bottom 4 khz seismic reflection profiles this unit us an acoustically transparent near surface flat lying layer whereas in cores it is a homogeneous gray marl as much as 7 m thick grain size decreases upcore within the unit implying that it was deposited in a single event controlled by gravitational settling the stratigraphic position of the homogenite relative to a firmly dated sapropel bed suggests emplacement between 4400 and 3100 yr b p the source of the homogenite is inferred to be the nearby basin walls farther east two other sites with similar rugged topography lack homogenite entirely a triggering mechanism is required which is capable of initiating massive sediment transport simultaneously in many separate basins at the western two survey sites but which is not effective at the eastern sites a large archeologically recorded earthquake of the correct age is considered and rejected because its epicenter is closer to the nonhomogenite bearing sites than to the sites where this sediment type was observed and because several other earthquakes of comparable magnitude have since been recorded in the area whereas the homogenite is unique the 3 500 yr b p collapse of the caldera of the volcano of santorini caused a huge tsunami which is recorded archeologically and geologically around the eastern mediterranean because of refraction of the tsunami by the bathymetry and because the caldera collapsed in its southwest corner a disproportionate amount of tsunami energy was directed toward the western area where homogenite is observed in contrast the homogenite free sites were relatively sheltered an order of magnitude calculation shows that the near bottom oscillating currents accompanying the santorini tsunami were at or above the threshold erosion velocity at the homogenite bearing sites in addition the near bottom pressure pulse under the tsunami at the homogenite bearing sites was sufficient to cause liquefaction of sediments neither mechanism was adequate to cause sediment transport or slope failure at the homogenite free sites

deep sea tsunami deposits triggered by the explosion of santorini 3500 y bp eastern mediterranean abstract the collapse of the santorini caldera after the catastrophic eruption of the bronze age 3500 y bp caused a tsunami wave that had catastrophic effects in the ionian basin including its deepest parts pelagic turbidites of local origin were deposited on the bottom of small perched basins of the southern calabrian western and central mediterranean ridges type a homogenite whereas a megaturbidite of distal origin presumably triggered by the tsunami wave hitting the shoreline of the sirte gulf was deposited on the ionian and sirte abyssal plains extending eastwards as far as the western herodotous trough depositing a thick acoustically transparent layer type b homogenite three core transects crossing the deformation front of the mediterranean ridge are presented and discussed a fourth transect of giant piston cores was collected on the abyssal plains located to the south of the mediterranean ridge all those to the west of the collision zone contain the holocene homogenite with a thickness in excess of 20 m whereas the cores taken from the herodotous abyssal plain east of the collision zone are devoid of the homogenite sedimentological analyses were performed on the only giant core that penetrated the sandy base of the homogenite and the underlying pelagic sediments of late pleistocene last glacial age the african provenance of this typical type b homogenite is corroborated by shallow water fauna derived from the north african shelf no sedimentological characteristics peculiar to tsunamiites are observed in the deep sea homogenite of the eastern mediterranean

sedimentary features of seismoturbidites triggered by the 1983 and older historical earthquakes in the eastern margin of the japan sea abstract both mass failure deposits and turbidites are widely distributed in the epicentral area of the 1983 earthquake mw 7 9 in the eastern margin of the japan sea this basin is semi enclosed with no active conduits for the entrance of coarse detrital sediments seismic reflection surveys and sediment cores reveal that mass failure deposits which are distributed on the continental slopes merge into turbidites in the basin plain hence the mass wasting process is a major transportation process in this region one gravity core gh93 816 was recovered from the southeastern margin of the japan basin close to the epicentral area of the 1983 japan sea earthquake sedimentological results show that five turbidite beds are intercalated in the top 68 cm of the column occurrence of the b tm tephra at the depth of 68 71 cm indicates that these turbidite beds were developed during the last 1000 years the high 137cs concentration in the top 20 cm of the core implies that the uppermost turbidite bed was deposited after 1954 based on these age limits for the top and the bottom of the studied interval we estimate the recurrence intervals of turbidites as 160 330 years we suggest that these turbidites were generated by submarine slides which were triggered by the 1983 and older historical earthquakes in this region these seismoturbidites are characterized by amalgamated beds irregular structure sequences grain size breaks fluctuations abrupt changes in composition within bed and variable composition among beds from these features we infer that deposition resulted from a series of turbidity currents associated with multiple or line sources for example multiple shallow slides that were regionally initiated by the same earthquake the sedimentary features described herein may be useful as criteria for identifying modern seismoturbidites in other settings as well as seismoturbidites in the geologic record however further study is needed for the distinction of this type of turbidites from other types e g tempestites reflected turbidites

uniquely extensive seismite from the latest triassic of the united kingdom evidence for bolide impact a 2 4 m thick seismite in places overlain by a previously unreported tsunamite can be traced across 250 000 km 2 of the outcrop and subcrop of the latest triassic rhaetian cotham member of the penarth group united kingdom an extent unique for the british phanerozoic its consistent thickness intensity of deformation and preferred orientations of slump fold axes indicate a seismic event of m 10 with an epicenter 600 km w or nw of central britain the magnitude of the event is incompatible with known terrestrial mechanisms fault volcano but is consistent with a major bolide impact a short but unknown interval separates the top of the cotham member seismite from major geochemical and biotic perturbations associated with the end triassic extinction although a direct link between the seismite and these other events remains equivocal the exceptional extent of mega seismites such as this may prove a useful indicator of previously undocumented bolide impacts

tsunami generation potential of different tsunamigenic regions in the pacific abstract the historical tsunami catalog collected within the historical tsunami database htdb pac project contains the most complete parametric tsunami data covering the whole pacific and the full historical period of the available observations from 47 bc to present the collected data provide a possibility to study variability of the tsunami potential of submarine earthquakes over the main tsunamigenic regions in the pacific for each region the tsunami efficiency te is calculated as the ratio between the number of tsunamis of tectonic landslide and unknown origin and the total number of the coastal and the submarine earthquakes with magnitude m 7 0 and focus depth h

lidar measurement of snow depth a review laser altimetry lidar is a remote sensing technology that holds tremendous promise for mapping snow depth in snow hydrology and avalanche applications recently lidar has seen a dramatic widening of applications in the natural sciences resulting in technological improvements and an increase in the availability of both airborne and ground based sensors modern sensors allow mapping of vegetation heights and snow or ground surface elevations below forest canopies typical vertical accuracies for airborne datasets are decimeter scale with order 1 m point spacings ground based systems typically provide millimeter scale range accuracy and sub meter point spacing over 1 m to several kilometers many system parameters such as scan angle pulse rate and shot geometry relative to terrain gradients require specification to achieve specific point coverage densities in forested and or complex terrain additionally snow has a significant volumetric scattering component requiring different considerations for error estimation than for other earth surface materials we use published estimates of light penetration depth by wavelength to estimate radiative transfer error contributions this paper presents a review of lidar mapping procedures and error sources potential errors unique to snow surface remote sensing in the near infrared and visible wavelengths and recommendations for projects using lidar for snow depth mapping

sheet gravel evidence for a late holocene tsunami run up on beach dunes great barrier island new zealand abstract a semi continuous sheet of granule to cobble size clasts forms a distinctive deposit on sand dunes located on a coastal barrier in whangapoua bay great barrier island new zealand the gravel sheet extends from the toe of the foredune to 14 3 m above mean sea level and 200 m landward from the beach clasts are rounded to sub rounded and comprise lithologies consistent with local bedrock terrestrial sources for the gravel are considered highly unlikely due to the isolation of the dunes from hillslopes and streams the only source for the clasts is the nearshore to inner shelf of whangapoua bay where gravel sediments have been previously documented the mechanism for transport of the gravel is unlikely to be storm surge due to the elevation of the deposit maximum recorded storm surge on this coast is 0 8 m above mean high water spring tide aeolian processes are also discounted due to the size of clasts and the elevation at which they occur tsunami is therefore considered the most probable mechanism for gravel transport minimum run up height of the tsunami was 14 3 m based on maximum elevation of gravel deposits optical ages on dune sands beneath and covering the gravel allow age bracketing to 0 4 7 ka within this time frame numerous documented regional seismic and volcanic events could have generated the tsunami notably submarine volcanism along the southern kermadec arc to the east southeast of great barrier island where large magnitude events are documented for the late holocene radiocarbon ages on shell from maori middens that appear to have been reworked by tsunami run up constrain the age of this event to post ca 1400 ad regardless of the precise age of this event the well preserved nature of the whangapoua gravel deposit provides for an improved understanding of the high degree of spatial variability in tsunami run up

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

sedimentary features of seismites seismo turbidites and tsunamiites an introduction abstract catastrophic events such as deposits from sediment flows generated by seismic events or major tempests have not been intensively studied sedimentological procedures for deducing the relationships of seismic foci intensity period and amplitude of the seismic waves have been initiated only recently this special volume arose from a session entitled sedimentary features of seismites seismo turbidites and tsumaniites held at the 15th international sedimentological congress in alicante spain in april 1998 the papers in this volume cover a somewhat broader range of subjects our goal is to stimulate further research on the sedimentary features of seismites seismoturbidites and tsunamiites

scaling properties of wind and snow depth distribution in an alpine catchment 1 the spatial variability of the snow cover is driven by wind induced snow transport processes the main aim of this study is to investigate the link between the scaling behavior of snow depths and the wind induced processes driving the spatial structure of snow depths we used very high resolution atmospheric and snow transport simulations to compare their spatial characteristics with snow depths obtained from airborne and terrestrial laser scans the directions of the strongest autocorrelations of snow depths and wind velocities were predominantly perpendicular to the modeled local flow direction independent of whether more homogeneous lee slope loading in one area was considered or the formation of drifts in another area in the case of homogeneous lee slope loading the same direction of anisotropy was only found in the modeled preferential deposition of precipitation as for both wind and snow distribution this deposition process appears to dominate homogeneous lee slope loading in contrast saltation driven processes seem to dominate the formation of drifts and snow dunes furthermore the fractal analysis suggests similar scale breaks for the modeled wind velocity field and measured snow depths defining the upper scale of landscape smoothing through snow

paleoecology and sedimentary environment of the late devonian coral biostrome from the central devonian field russia the upper frasnian coral biostrome well exposed in the russkiy brod quarry central devonian field russia has been studied in detail with respect to paleoecology and sedimentary environment the biostrome formed by auloporid tabulates and solitary and colonial rugose corals originated in an offshore environment characterized by calmer periods with slow or halted sedimentation and more energetic periods when sedimentation rate increased the episodic higher sediment influx and stronger hydrodynamic regime are not only well expressed in the microfacies but also in the variability of colony integration of the rugose corals observed even within single coralla distinct development of constrictions rejuvenescences and deflection of growth directions in rugose corallites may also indicate unstable sedimentary conditions the latter features however may have in part also resulted from syn vivo biotic interaction with the associated auloporids both the facies and paleontological observations suggest that the biostrome originated by the colonization of deposited bioclasts by pioneering auloporids creating the framework for settlement of later generations of auloporids and rugose corals apart from abundant auloporids representing a single species and associated rugose corals the other encrusters are not numerous and poorly diversified represented by dominating foraminifers followed by single species of productid brachiopods stromatoporoids microconchids and cornulitids the coral associated macrobenthos has similarly a low diversity being represented by single species of spiriferid and rhynchonellid brachiopods and gastropods being developed in an offshore carbonate sedimentary system devoid of any organic rich deposits and characterized by extremely low abundance and diversity of suspension feeding organisms the biostrome is considered to have originated in a low productivity oligotrophic environment strictly dominated by heterozoan coral communities its development in a well oxygenated oligotrophic environment during the time when organic rich black kellwasser facies developed elsewhere additionally attests for multi causal scenarios for the frasnian famennian event during which other factors were responsible in different paleogeographic and facies settings

jurassic flora of the negev desert plant taphonomy paleoecology and paleogeographic inference abstract jurassic fossil plants of makhtesh ramon the northern negev are collected from the early bajocian paralic inmar formation conformably overlain with the marine mahmal formation which contains ammonite markers of the middle upper bajocian age plant remains occur in the thin ferruginous layers traceable all over the questa exposures composed of re deposited sand at the base and the fine grained ferro alumosilicate lamella on top plants are preserved as ferruginous molds of leafy shoots and reproductive material buried by turbid run over sand flows and embedded in the back wash clayey deposits as calcified plant debris on account of their peculiar taphonomy and elementary composition the fossiliferous horizons are interpreted as tsunamites the coastal plant assemblages are endemic at the syntaxonomic level with gondwana affinities extended to insular landmasses north of the tethys the abundance of bennettitalean plants and the inferred proximity of araucaria like brachyphylls give the bajocian inmar flora a thermophilic paratropical aspect while the bathonian flora of sinai is of a more temperate aspect suggesting a major mid jurassic climate change

cyclones and tides as feeders of a submarine canyon off bangladesh extremely high annual sedimentation rates of about 50 cm yr at the head of the submarine canyon swatch of no ground which connects the submarine delta of the ganges brahmaputra to the bengal deep sea fan were estimated by 210 pb and 137 cs gamma spectrometry the sediment in the canyon at 228 m water depth consists of graded sand and silt layers and laminated mud the sand and silt layers are assumed to have been deposited by tropical cyclones whereas the intercalated laminated mud is thought to have been deposited by daily variations of tidal currents the graded layers correlate well with the historical record of cyclones and allow an annual fine tuning the rapid infill of the canyon head is caused by trapping of suspended sediment that has been mobilized by storms and tides on the delta topset the sediment is stored only temporarily in the canyon head slides slumps and earthquakes occasionally remove and transfer it by turbidity currents to the deep sea fan the focusing effect of the canyon and the subsequent stepwise export of sediment probably combined with erosion of the canyon floor explain the long term regional stability of this canyon and probably other shelf canyons

a high energy deposit in the byzantine harbour of yenikapi istanbul turkey abstract a byzantine harbour theodosian harbour has been uncovered during excavations at yenikapi with a stratigraphic sequence spanning the past 7000 bp in the marine part of the sedimentary sequence a high energy deposit has been interpreted as being of tsunami origin and related to the earthquake of 557 ad this paper presents a bio sedimentological analysis of this facies the unit is characterised by coarse sands and gravels containing reworked material such as woods bones marble blocks amphora fragments ceramics coins shells and plant remains the thickness of the facies varies between 10 and 100 cm the sediment matrix is poorly sorted with skewness values indicative of a sub tidal fine sand environment many of the marine taxa have been reworked and diverse ecological assemblages are represented lagoonal coastal and open marine species this unit is divided into three facies consistent with different phases of the tsunami drowning and water retreat the basal facies corresponds to two tsunami wave trains and the upper facies indicates the backwash flow

oceanographic processes and morphosedimentary products along the iberian margins a new multidisciplinary approach abstract our understanding of bottom currents and associated oceanographic processes e g overflows barotropic tidal currents including intermittent processes e g vertical eddies deep sea storms horizontal vortices internal waves and tsunamis is rapidly evolving many deep water processes remain poorly understood due to limited direct observations but can generate significant depositional and erosional features on both short and long term time scales this paper represents a review work which describes for the first time these oceanographic processes and examines their potential role in the sedimentary features along the iberian continental margins this review explores the implications of the studied processes given their secondary role relative to other factors such as mass transport and turbiditic processes and highlights three major results a contourite depositional and erosional features are ubiquitous along the margins indicating that bottom currents and associated oceanographic processes control the physiography and sedimentation b the position of interfaces between major water masses and their vertical and spatial variation in time specifically appears to exert primary control in determining major morphologic changes along the slope gradient including the contourite terraces development and c contourites deposits exhibit greater variation than the established facies model suggests therefore a consistent facies model however faces substantial challenges in terms of the wide range of oceanographic processes that can influence in their development an integrated interpretation of these oceanographic processes requires an understanding of contourites seafloor features their spatial and temporal evolution and the near bottom flows that form them this approach will synthesize oceanographic data seafloor morphology sediments and seismic images to improve our knowledge of permanent and intermittent processes around iberia and evaluate their conceptual and regional role in the margin s sedimentary evolution given their complexes three dimensional and temporally variable nature integration of these processes into sedimentary oceanographic and climatological frameworks will require a multidisciplinary approach that includes geology physical oceanography paleoceanography and benthic biology

basinward transport of chicxulub ejecta by tsunami induced backflow la popa basin northeastern mexico and its implications for distribution of impact related deposits flanking the gulf of mexico ejecta bearing strata are present at the top of cretaceous foreland basin deposits throughout the la popa basin in northeastern mexico in the southeast part of the basin locally thick as much as 4 6 m ejecta rich conglomeratic strata occupy valley like features at a bathymetric break that separated maastrichtian upper shoreface from lower shoreface and prodelta depositional settings clast supported textures normally graded planar conglomerate sandstone couplets upcurrent dipping low angle cross laminae sparse paleocurrent data and transported fossils indicate deposition by south to southeast directed turbulent supercritical flow in the northwest part of the basin ejecta grains are present but less common in correlative deposits sediment ejecta and organisms were eroded from shoreward environments and transported basinward by backflow of run up surge s emplaced against the continent by one or several tsunami s high discharge supercritical offshore directed flow provides a mechanism for transport of voluminous ejecta bearing sediment and late maastrichtian marine organisms into deep water gulf of mexico settings

postglacial after 18 ka deep sea sedimentation along the hikurangi subduction margin new zealand characterisation timing and origin of turbidites recent sedimentation along the hikurangi subduction margin off northeastern new zealand is investigated using a series of piston cores collected between 2003 and 2008 the active hikurangi margin lies along the pacific australia subduction plate boundary and contains a diverse range of geomorphologic settings slope basin stratigraphy is thick and complex resulting from sustained high rates of sedimentation from adjacent muddy rivers throughout the quaternary turbidites deposited since c 18 ka in the poverty ruatoria and matakaoa re entrants are central to this study in that they provide a detailed record of the past climatic conditions and tectonic activity here alternating hemipelagite turbidite debrite and tephra layers reflect distinctive depositional modes of marine sedimentation turbidity current debris flow and volcanic eruption respectively turbidites dominate the record ranging in lithofacies from muddy to sandy turbidites and include some basal reverse graded turbidites inferred to be derived from hyperpycnal flows stacked turbidites are common and indicate multiple gravity flows over short time periods the chronology of turbidites is determined by collating an extremely dense set of radiocarbon ages and dated tephra which facilitate sedimentation rate calculation and identification of the origin of turbidites sedimentation rates range from 285 cm ka during late glacial time 18 5 17 ka to 15 to 109 cm ka during postglacial time 17 0 ka turbidite deposition is controlled by 1 the emplacement of slope avalanches reorganising sediment pathways 2 the postglacial marine transgression leading to a five fold reduction in sediment supply to the slope due to disconnection of river mouths from the shelf edge and 3 the holocene pleistocene boundary climate warming resulting in a drastic decrease in the average turbidite grain size flood induced turbidites are scarce nine hyperpycnites are recognised since 18 ka and the youngest is correlated to the largest enso related storm event recorded onland lake tutira other turbidites contain a benthic foraminiferal assemblage which is strictly reworked from the upper slope and which relates to large earthquakes over the last c 7 ka they yield a shorter return time 270 430 years than the published coastal records for large earthquakes c 670 years but the offshore record is likely to be more complete the deep sea sedimentation along the new zealand active margin illustrates the complex interaction of tectonic and climate in turbidite generation climate warming and glacio eustatic fluctuations are well recorded at a millennial timescale 18 ka while tectonic deformation and earthquakes appear predominant in fostering turbidite production at a centennial timescale 270 430 years

scale of tsunami generated sedimentary structures in deep water to date no attempt has been made to explore possible constraints on maximum water depths for tsunami generated sedimentary structures of various sediment grain sizes in terms of estimated wavelength and amplitude of potential bedforms this paper explores some possible quantitative limits on threshold velocities for sediment movement at specified water depths assuming airy wave theory which treats tsunami waves as shallow water small amplitude long wavelength waves such a treatment suggests that the passage of tsunami waves is unlikely to entrain sediment coarser than line sand to coarse silt in water depths in excess of 200 mm although fraught with theoretical difficulties and a lack of observations of modern sedimentary bedforms attributable to known tsunamis this paper is presented to stimulate debate rather than provide definitive answers

seismoturbidites a new group of resedimented deposits abstract turbidite beds of exceptionally large volume and areal extent occur in both modern and ancient deep water basins these beds which may reach individual volumes in excess of 100 km3 are apparently the product of catastrophic gravity flows triggered by earthquakes along the margins of highly mobile basins most commonly elongate flysch troughs turbidite beds produced by these catastrophic events are generally characterized by very distinctive geometry internal structures and composition and are termed herein seismoturbidites characteristically these sediments lack time persistent features of deep sea fans such as channels and lobes seismoturbidites may occur as scattered intercalations diluted within otherwise normal turbidite sequences thus forming generally excellent markers for basin wide correlations or as closely spaced repetitive units comprising the bulk of the sedimentary fill of certain flysch basins in both cases they may offer a tremendously useful tool for a better understanding of the distribution of paleoseismic zones in time and space

storms versus tsunamis dynamic interplay of sedimentary diagenetic and tectonic processes in the cambrian of montana the upper cambrian deadwood formation of north central montana is composed mainly of fine grained calcareous sandstone and intercalated silty shale and contains scattered intraclastic flat pebble conglomerate these rocks typical of many mixed carbonate siliciclastic subtidal shelf successions of proterozoic through early ordovician age are distal storm deposits in which the conglomerates are conventionally thought to record occasional very high energy events that scoured incipiently cemented layers in the deadwood formation most sandstone beds have a linear to crudely reticulate pattern of vertical cracks filled with injected silt and clay the cracks exhibit a consistent northwest southeast trend and are very shallow burial deformation structures caused by the passage of seismic waves possibly originating from strong earthquakes in idaho most conglomerates are composed of angular to subangular sandstone intraclasts the polygonal plan view of which is similar in outline to the areas between cracks in the sandstones the deformation implied by the cracks sporadic distribution of conglomerates high degree of scouring indicated and angularity of the intraclasts argue that rather than storms the conglomerates were generated by occasional tsunamis the sweep of these tsunamis across the shallow intracratonic sea created extraordinarily strong oscillating bottom currents at the deeper reaches of storm wave base tsunamites are therefore identified with confidence virtually for the first time in shallow subtidal shelf deposits

impact induced sediment deposition on an offshore mud substrate continental shelf cretaceous paleogene boundary brazos river texas u s a abstract data from twenty brazos river stratigraphic sections of the k pg event deposit are compiled to provide a record of changing depositional processes on the texas continental shelf that left a record of disturbance triggered by the chicxulub impact foraminiferal paleobathymetric depth control of enclosing sediments indicates paleo water depths of 75 125 m with gradual deepening above the k pg boundary outcrop scale observations indicate that the most complete deposits have a basal unit of mudstone clast bearing mass flows indicative of movement by noncohesive laminar flow these mudflows were mobilized by impact generated seismic shaking of seafloor sediment the material of the mass flows consists of reworked shell rich mud matrix containing outsize clasts of consolidated mudstone and cemented concretions the upper parts of the k pg event deposit consist of units of high energy upward fining sandstones each with a basal lag layer of spherule rich coarse sandstone lag overlain by poorly or moderately sorted hummocky cross bedded sandstone the last deposited sandstone is capped with a silt mud suspension settling layer that as much as 10 cm thick where cemented with calcite but is much thinner elsewhere the provenance of these k pg brazos river event deposit sediments is offshore marine muds lower units and shallow water sands higher units with admixed impact spherules and no identifiable land derived component deposition was the result of secondary processes activated by energy from seismic disturbance or by atmospheric disturbance with no deposits directly attributable to tsunami wave control

eustatic control of turbidites and winnowed turbidites global changes in sea level primarily the results of tectonism and glaciation control deep sea sedimentation during periods of low sea level the frequency of turbidity currents is greatly increased episodes of low sea level also cause vigorous contour currents which winnow away the fines of turbidites in the rock record the occurrence of most turbidites and winnowed turbidites closely corresponds to global lowstands of paleo sea level this observation may be useful in predicting the occurrence of deep sea reservoir facies in the geologic record

self similarity in glacier surface characteristics catchment wide information on glacier snow cover depth surface albedo and surface roughness is important input data for distributed models of glacier energy balance in this study we investigate the small scale mm to 100 m spatial variability in these properties with a view to better simulating this variability in such models data were collected on midre lovenbreen a 6 km 2 valley glacier in northwest svalbard the spatial variability of all three properties was found to be self similar over the range of scales under investigation snow depth and albedo exhibit a correlation length within which measurements were spatially autocorrelated late winter and summer properties of snow depth differed with smaller depths in summer due to melt and shorter correlation lengths similar correlation lengths for snow depth and surface albedo may suggest that snow depth variation is an important control on the small scale spatial variability of glacier surface albedo for surface roughness the data highlight a possible problem in energy balance studies which use microtopographic surveys to calculate aerodynamic roughness in that the scale of the measurements made affects the calculated roughness value this suggests that further investigations of the relationships between surface form and aerodynamic roughness of glacier surfaces are needed

small scale spatial structure of shallow snowcovers the results of a field study of the small scale spatial structure of the depth of shallow seasonal snowcovers in prairie and arctic environments are presented it is shown that the spatial distribution of snow depth is fractal at small scales becoming random at scales beyond some limiting length this is due to the autocorrelation of depth at small sampling distances the transition of fractal to random behaviour is indexed by a cutoff length which is defined by the intersection of the fractal slope and horizontal tangent of a logarithmic plot of the standard deviation of depth versus sampling distance the magnitude of the cutoff length is related to the degree of macroscopic variability of the underlying topography an increase in length due to the effects of macroscopic topographic variability on snowcover accumulation is confirmed by de trending field measurements the de trended data shown a cutoff length for wheat stubble and fallow surfaces of approximately 30 m which is consistent with the distance determined from measurements on flat fields the implications of the transition of snow depth from fractal to random structure on the scales of snow sampling and modelling are presented the cutoff length may provide a statistic for stratifying shallow snowcovers by linking snowcover properties to the underlying topography

snow depth structure fractal behavior and interannual consistency over haut glacier d arolla switzerland snow depth patterns over glaciers are controlled by precipitation snow redistribution due to wind and avalanches and the exchange of energy with the atmosphere that determines snow ablation while many studies have advanced the understanding of ablation processes less is known about winter snow patterns and their variability over glaciers we analyze snow depth on haut glacier d arolla switzerland in the two winter seasons 2006 2007 and 2010 2011 to 1 understand whether snow depth over an alpine glacier at the end of the accumulation season exhibits a behavior similar to the one observed on single slopes and vegetated areas and 2 investigate the snow pattern consistency over the two accumulation seasons we perform this analysis on a data set of high resolution lidar derived snow depth using variograms and fractal parameters our first main result is that snow depth patterns on the glacier exhibit a multiscale behavior with a scale break around 20 m after which the fractal dimension increases indicating more autocorrelated structure before the scale break than after second this behavior is consistent over the two years with fractal parameters and their spatial variability almost constant in the two seasons we also show that snow depth patterns exhibit a distinct behavior in the glacier tongue and the upper catchment with longer correlation distances on the tongue in the direction of the main winds suggesting spatial distinctions that are likely induced by different processes and that should be taken into account when extrapolating snow depth from limited samples

recent marine lithofacies in cadiz bay sw spain sequences processes and control factors abstract the analysis of the lithofacies preserved in recent marine sediments in cadiz bay shows major fluctuations in the depositional regime which are characterized by significant energy variations drilling and geophysical data indicate the presence of coarse materials such as gravel imbricated shells and plant remains and frequent flow structures which have been interpreted as a result of the action of high energy events while the finest sediments present in the cores are interpreted as a consequence of the ordinary depositional regime fundamentally controlled by normal storm surge and tidal currents three types of sequence are differentiated very high energy vhe sequences high energy he sequences and low energy le sequences the vhe and he sequences were caused by highly energetic oceanic agents such as great waves generated by major storms or tsunamis there is no historical evidence of the action of sufficiently energetic storms while the geological setting of cadiz bay is located near the azores gibraltar fault the limit between the african and european plates points to tsunami action as being the most plausible option to explain the origin of these deposits the radiocarbon age indicates that these high energy events happened between 898 120 bc and 849 121 ad some of which coincide with several historically documented tsunamis affecting the cadiz coast this data indicates that the period from 849 ad to 1200 ad was a time of intense seismic and tsunamigenic activity

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

effects of rainy season on mobilization of contaminants from tsunami deposits left in a coastal zone of thailand by the 26 december 2004 tsunami study on contamination of tsunami sediments deposited on 26 december 2004 conducted shortly after the tsunami in coastal zone of thailand revealed elevated contents of salts in water soluble and some heavy metals and arsenic in bioavailable fractions szczucinski et al in env geol 49 321 331 2005 few months later rainy season started and effected in total rainfall of over 3 300 mm this paper presents results of survey repeated 1 year after the tsunami to assess the effects of rainy season on mobilization of previously determined potential contaminants the same locations were sampled again and analysed with the same methods the tsunami deposit layer was well preserved but in many locations the sediments were coarser than just after tsunami due to washing out of finer fractions the water soluble salts contents were strongly reduced after the rainy season however the concentrations of acid leachable heavy metals and metalloids were still elevated in comparison to reference sample from an area not impacted by tsunami it is possible that the metals and metalloids are successively moved to more bioavailable fraction from forms which were more resistant to mobilization

shallow marine tsunami deposits in teluk banten nw java indonesia generated by the 1883 krakatau eruption teluk banten tb is a tropical shallow marine embayment with coral reef islands close to the krakatau volcanic complex the 1883 krakatau eruption generated a tsunami which had a devastating effect on the neighboring coastal areas the effects of the 1883 krakatau eruption and the associated tsunami on the bottom sediments in tb are assessed using textural compositional and 210 pb geochronological data an important diagnostic criterion consists of the occurrence of tephra conform descriptions of the 1883 eruption tephra the tsunamite consists of a sandy layer with abundant reworked shell and other carbonate fragments coarse components in the tsunamite consist of locally derived material eroded from the seabed land derived components are incorporated in the tsunamite only in close proximity to the coast the tsunamite is thickest in localized areas of the central part of the bay along the northern open sea facing slope of tb the tsunamite is relatively thin 6 7 cm thick but well preserved as little postdepositional modifications have occurred in the eastern bay area recent erosion since the redirection of the ciujung river in the 1920s has removed the krakatau tsunamite along the west coast of tb the only signature of the 1883 krakatau eruption consists of tephra and evidence for a high energy event is lacking presumably the western area was sheltered from the tsunami wave coming from the northwest at the shallower stations with low accumulation rates the tephra has been thoroughly mixed by bioturbation 2003 elsevier science b v all rights reserved

sedimentary features of tsunami deposits in carbonate dominated beach environments a case study from the 25 october 2010 mentawai tsunami this study provides a case history of tsunami deposition in a carbonate dominated environmental setting we present the results of a sedimentological investigation conducted on deposits formed by the 25 october 2010 mentawai island tsunami and report on deposits analyzed at three sites on north pagai island sabeu gunggung macaroni resort and tumalei the deposits are mainly composed of medium to coarse sand sized fragments of corals shells and foraminifera with thickness ranging from 3 to 26 cm the deposits consist of two to five layers with fining upward trends dominating local topography noticeably affects the thickness number of layers and distribution of tsunami deposits the foraminiferal assemblage and diversity vary at each sample point along transect and between different transects based on the foraminiferal content most of the deposit material likely came from shallower depths in addition density distribution of the tsunami deposit material exhibits some degree of variability in terms of the range of densities in each sample and the trend of the overall density along each transect in contrast to heavy mineral dominated deposits the density of carbonate grains as a function of size may be an important consideration when carbonate dominated deposits are used to interpret hydraulic conditions that created a particular tsunami deposit since there are relatively few studies of tsunami deposits in carbonate dominated environmental settings such as the mentawai islands our study provides a useful case history of tsunami deposition in such an environmental setting

comment on late holocene rupture of the northern san andreas fault and possible stress linkage to the cascadia subduction zone by chris goldfinger kelly grijalva roland burgmann ann e morey joel e johnson c hans nelson julia gutierrez pastor andrew ericsson eugene karabanov jason d chaytor jason patton and eulalia gracia goldfinger et al 2008 conclude that in the northern san andreas fault and cascadia margins holocene turbidites i e deposits of turbidity currents were triggered by earthquakes however their conclusion falters because of 1 selective data sets that were used for establishing seismicity as the sole triggering mechanism of turbidites 2 flawed sedimentological concepts and criteria that were applied for interpreting turbidites and 3 faulty methodologies that were employed for correlating turbidites over long distances this same turbidite i e sedimentological theme has also been published previously by goldfinger et al 2003a b 2006 2007 as with the recent article in bssa their previous publications on the subject matter were published in journals that are concerned primarily with geophysical topics as a result critical sedimentological conclusions which are an integral part of the articles by goldfinger et al have not been subjected to a rigorous scrutiny therefore i would like to comment on the following three issues along the washington oregon california margin potential triggering mechanisms of sediment failures and related turbidity currents are 1 earthquake adams 1990 2 tectonic oversteepening greene et al 2006 3 tsunami adams 1990 geist 2005 4 cyclone adams 1990 shanmugam 2008a fig 4 5 ebb tidal current puig et al 2003 6 submarine volcanic activity davis et al 2002 7 sediment loading adams 1990 and 8 gas hydrates chapman et al 2004 the link between gas hydrate decomposition and mass movements on the norwegian margin was discussed by mienert et al 2005 in the cascadia margin a total of 40 cyclones along the oregon coast were reported for the 1984 2006 period moritz and moritz 2006 a total of 24 tsunamis were reported along the oregon coast for the 1868 1994 period table 1 cyclones and tsunamis are powerful agents of sediment failures shanmugam 2008a on the outer continental shelf of the gulf of mexico for example the

identification of tsunami induced deposits using numerical modeling and rock magnetism techniques a study case of the 1755 lisbon tsunami in algarve portugal abstract storm and tsunami deposits are generated by similar depositional mechanisms making their discrimination hard to establish using classic sedimentologic methods here we propose an original approach to identify tsunami induced deposits by combining numerical simulation and rock magnetism to test our method we investigate the tsunami deposit of the boca do rio estuary generated by the 1755 earthquake in lisbon which is well described in the literature we first test the 1755 tsunami scenario using a numerical inundation model to provide physical parameters for the tsunami wave then we use concentration ms sirm and grain size arm arm b1 2 arm sirm sensitive magnetic proxies coupled with sem microscopy to unravel the magnetic mineralogy of the tsunami induced deposit and its associated depositional mechanisms in order to study the connection between the tsunami deposit and the different sedimentologic units present in the estuary magnetic data were processed by multivariate statistical analyses our numerical simulation show a large inundation of the estuary with flow depths varying from 0 5 to 6 m and run up of 7 m magnetic data show a dominance of paramagnetic minerals quartz mixed with lesser amount of ferromagnetic minerals namely titanomagnetite and titanohematite both of a detrital origin and reworked from the underlying units multivariate statistical analyses indicate a better connection between the tsunami induced deposit and a mixture of units c and d all these results point to a scenario where the energy released by the tsunami wave was strong enough to overtop and erode important amount of sand from the littoral dune and mixed it with reworked materials from underlying layers at least 1 m in depth the method tested here represents an original and promising tool to identify tsunami induced deposits in similar embayed beach environments

the tsunamite problem the genetic term tsunamite is used for a potpourri of deposits formed from a wide range of processes overwash surges backwash flows oscillatory flows combined flows soft sediment deformation slides slumps debris flows and turbidity currents related to tsunamis in lacustrine coastal shallow marine and deep marine environments tsunamites exhibit enormous variability of features e g normally graded sand floating mudstone clasts hummocky cross stratification etc these sedimentary features may also be interpreted as deposits of turbidity currents turbidites debris flows debrites or storms tempestites however sedimentary features play a passive role when these same deposits are reinterpreted as tsunamites on the basis of historical evidence for tsunamis and their triggering mechanisms e g earthquakes volcanic explosions landslides and meteorite impacts this bipartite sedimentological vs historical approach which allows here classification of the same deposit as both turbidite and tsunamite has blurred the distinction between shallow marine and deep marine facies a solution to this problem is to classify deposits solely by a descriptive sedimentological approach the notion that tsunami waves can directly deposit sediment in the deep sea is unrealistic because tsunami waves represent transfer of energy and they are sediment starved during tsunamis and major storms submarine canyons serve as the physical link between shallow water and deep water environments for sediment transport tsunami related deposition involves four progressive steps 1 triggering stage offshore 2 tsunami stage incoming waves 3 transformation stage near the coast and 4 depositional stage outgoing sediment flows in this progression deep water deposition can commence only after the demise of incoming tsunami waves due to their transformation into outgoing sediment flows deposits of these sediment flows already have established names e g debrite and turbidite therefore the term tsunamite for these deposits is obsolete