faulting pattern along slow spreading ridge segments a consequence of along axis variation in lithospheric rheology abstract we present here results from an analogue model designed to test the relative influence of along axis variations of the crustal thickness and of the thermal structure of the lithosphere on the geometry and on the faulting pattern of the axial rift of a slow spreading ridge rheologically calculated layered models are employed using quartz sand and silicone putty as analogues of the brittle and ductile components of the lithosphere respectively two parameters have been analysed in detail 1 the thickness of the brittle layer and 2 the viscosity of the ductile layer this study shows that the thickening of the brittle layer and the increase of the viscosity of the ductile layer bring about a widening of the axial valley associated with an increase of the number of faults a decrease of the depth of the axial valley and of the vertical throw of the faults is observed with an increase of the viscosity of the ductile layer and a decrease of the thickness of the brittle layer these results are consistent with observations along mid atlantic ridge segments for segment ends the fault pattern obtained in the models is similar to that described on both sides of the axis for segments bordered by a zero offset discontinuity and on outside corners for segments bordered by a lateral offset discontinuity our results suggest that the viscosity of the ductile layer plays a more important role in the fault pattern than the thickness of the brittle layer the influence of segment length offset length and temporal variation in thermal input could explain the more or less important along axis variation in the deformation pattern observed along segments of slow spreading ridges

rheological modelling and deformation instability of lithosphere under extension ii depth dependent rheology summary bassi bonnin 1988 have recently discussed the stability of continental lithosphere in extension they examine the hypothesis that thickness inhomogeneities can be amplified during extension and be responsible for lithospheric necking we carry our analysis one step further by accounting for the increase of strength with depth in brittle layers namely the upper crust and in some cases the upper part of the mantle this variation had been neglected in the previous study to simplify the mathematical formulation rather than a constant the equivalent viscosity is now a linear function of depth as predicted by byerlee s friction law which is postulated to control the mechanical behavior of brittle layers this more realistic rheological model confirms the results of the original analysis specifically that the interfaces between layers tend to flatten during extension unless they correspond to an inversion of density therefore extension of continental lithosphere appears to be stable if there is no other initial defect susceptible of localizing the deformation

the largest local tsunami in 20th century hawaii abstract the 1975 kalapana tsunami had waves that ran up to 14 6 m high it deposited a discontinuous basalt boulder and carbonate sand veneer on the halape apua point coast of the island of hawaii these deposits fine up to 320 m inland and 10 4 masl the deposit is an unusual sedimentary association in which sand sized material is a minor component both boulders and sand fine inland over the same distance not in a continuum and they terminate at approximately the same point boulders were transported and deposited by only one wave the second whereas the sand deposit was in part reworked by subsequent smaller waves boulder transport by one wave in association with a relative paucity of finer sediment reduced internal clast interference and helped to impart a marked fining inland sequence this fining inland sequence is at odds with work that proposes a chaotic or random nature of boulder emplacement by tsunamis where there is abundant sediment clast interference during entrainment will impede the fining inland of larger material in cases where it is difficult to determine the nature of inundation or the number of tsunamis a chaotic pattern may simply reflect deposition by storm tsunami or a combination of the two

modelling the processes of cliff top erosion and deposition under extreme storm waves at exposed sites on the deep water coasts of the british isles cliff top storm deposits ctsds occur on cliffs at a variety of elevations above sea level and may occasionally reach up to 50 m above sea level time series field mapping of ctsds has demonstrated their formation over the historical period and their continued modification during major past storms this paper seeks to clarify the morphogenetic context of ctsds model the wave conditions and forces encountered at the cliff face and cliff top platform and propose mechanisms to link wave processes to cliff face quarrying and landwards cliff top transport of quarried blocks to deposition zones at the rear of the cliff top platform we report on wave tank experiments using scaled cliff and wave conditions from a cliff in the shetland islands to focus on three situations incident waves lower than the cliff edge height at the same height as the cliff edge height and higher than the cliff edge height the modelling suggests that steep waves of 10 m and above impacting on a 15 m high cliff will result in impact pressures sufficient to promote crack propagation block detachment and lifting of large blocks large but not necessarily steep waves of the same height as the cliff edge produce sufficient impact pressures and water flow over the cliff edge and platform to entrain blocks transport and deposit them on the cliff top where cliff top height is below wave crest elevation green water bore flow occurs sufficient to force rotation or lifting of blocks out of cliff top and cliff top platform sockets high flow velocities rapidly accelerate and transport blocks inland until the flow attenuation results in deposition of blocks at the limit of run up the model results provide a good explanatory framework to account for the quarrying of the upper part of the cliff face and cliff top platform under storm wave conditions and provide an insight into the exceptional velocities experienced over the cliff top platform under bore flow conditions the modelling results show that extreme storm waves are capable of quarrying transporting and depositing large blocks at altitude and significant distances inland and so present serious questions about the use of such deposits as diagnostic of palaeo tsunami

rheological stratification of the lithosphere abstract the rheology of the lithosphere is estimated on the basis of pore pressure dependent frictional failure in the brittle regime and power law steady state creep in the ductile regime different petrological models of the continental and oceanic lithosphere combined with different geotherms and thicknesses are used to generate models covering a variety of geodynamic situations results show that the depth dependence of lithospheric rheology varies with the tectonic province and that in many instances the continental lithosphere has one at the bottom of the crust or two the previous one plus another at mid crustal levels soft ductile layers sandwiched between brittle layers the depth distribution of geophysical parameters seismicity seismic wave velocity and electrical conductivity matches the theological predictions well the lithospheric rheological profiles are used to analyze observed variations in the structural style of deformed continental margin and oceanic terranes in the southeastern canadian cordillera the large scale characteristics of the system show a satisfactory agreement with the inferred rheological structure sub horizontal decollements should be the rule rather than the exception where the lithospheric rheology is strongly stratified

boulders transport by catastrophic waves along the ionian coast of apulia southern italy abstract several tracts of the ionian coast of apulia southern italy are characterized by large boulders up to 80 t in weight scattered some meters above present sea level the largest boulder is about 80 t in weight and slid for about 40 m from the mean sea level up to about 1 8 m of altitude elongated boulders show a remarkably narrow range of orientation of the long axis as well as of the imbrication axis suggesting that they had been transported by a single catastrophic event most likely a tsunami connected to a wave train approaching the coast from the south stratigraphic morphological and historical data suggest that this event occurred during the late holocene conventional radiocarbon age determination performed on lithophag shells collected from a large boulder yielded a calibrated age between 1421 and 1568 a d then the catastrophic wave train probably a tsunami could be a local effect of the strong earthquake which hit southern italy on december 5th 1456

numerical analysis of boulder transport by the 2004 indian ocean tsunami at pakarang cape thailand at pakarang cape thailand we conducted field observations and numerical modeling of the spatial and grain size distributions and sources of boulders deposited by the 2004 indian ocean tsunami the boulders are a very rare example of boulders for which a tsunami origin is well confirmed numerical modeling of the tsunami s boulder transport revealed that the grain size and spatial distributions of boulders are explainable by the initial distribution of boulders at the source and the tsunami s local behavior which is controlled strongly by the tsunami hydrodynamic features and local topography soon after the bore front reached at the beach the tsunami s hydraulic force on the tidal bench decreased suddenly below the critical force necessary to displace the boulder because of the seaward propagation of the reflected wave that had been generated at the beach slope consequently all boulders were deposited below the high tide line and subsequently concentrated at the western coast of the cape absence of boulders that had been originally deposited deeper than 10 m water depth is also explained by this reflected wave because the wave passed over boulders that had been originally deposited at 10 m water depth before the boulder crossed the reef edge our well tuned model elucidates how the tsunami was able to deposit large boulders on the tidal bench at the cape the results demonstrate that theoretically up to 250 tons of boulders might have been emplaced on the tidal bench by the 2004 indian ocean tsunami at the cape approximately 7 m wave height the calculated maximum weight is of comparable order to that of boulders around the world that are inferred to be of tsunami origin although we infer that the weight is determined based on the sensitive balance of the local topography hydrodynamic features of the tsunami and the initial distribution of boulders at the source

burial history and kinetic modeling for hydrocarbon generation part i the galo model this paper discusses the principles and applications of the galo computer program which generates numerical simulations of the evolution of a sedimentary basin the program calculates variations in the sedimentary bed thickness predicts the thermal regime in the sedimentary cover or in the basement and estimates the potential hydrocarbon yield of the source rocks alternative methods for determining the magnitude of tectonic subsidence of the basement surface within the framework of a local isostasy model are applied to provide a detailed model of the sequential tectonic thermal events involved in the development of the basin the program determines reaction parameters controlling the maturation of the organic matter in source rocks these parameters are based largely on the hydrocarbon pyrolysis yield data and the stage of maturation of the organic matter entered into the program neglecting this stage drastically displaces the reaction spectrum toward higher energies leading to considerable underestimation of hydrocarbon output

the strength of the continental crust detachment zones and the development of plastic instabilities abstract the maximum strength of the continental crust is constrained by the geothermal gradient the lithological make up of the crust and whether or not the byerlee relation holds to the base of the continental crust if this linear byerlee relation holds then maximum shear stress levels sustained at low geothermal gradients 10 20 c km 1 could be as high as 300 mpa in the upper part of the mantle for strike slip regimes and up to 700 mpa in thrust regimes towards the base of the crust however if byerlee s relation breaks down at moderate temperatures and pressures and if such breakdown is associated with the transition from unstable to stable sliding on pre existing faults then the maximum stress levels in the crust being set by the shear stress at the breakdown depth are much lower ca 300 mpa for low geothermal gradients and thrust regimes the lithosphere is quite weak below the crust for geothermal gradients greater than 20 c km 1 so attempts to treat the lithosphere as an elastic slab for time scales for which plastic flow contributes significantly to the deformation should be questioned for a geothermal gradient of 10 c km 1 the entire continental crust and part of the upper mantle behave as an elastic brittle slab at higher geothermal gradients the distribution of strength is variable vertically according to the magnitude of the geothermal gradient and the lithological make up large contrasts in strength occur across rheologically defined boundaries as well as across lithological boundaries at these higher geothermal gradients such contrasts in strength could act as nuclei for detachment zones within the continental crust and upper mantle detachment at or near the moho is to be expected only for low geothermal gradients lateral variations in the geothermal gradient produce shallowly dipping zones of highly contrasting strength throughout the continental crust and uppermost mantle possibly resulting in flat lying thrusts and normal faults which may ramp upwards through the crust instabilities leading to seismic events which occur solely during plastic shearing should be common in thrust terranes where the stresses are relatively high ca 100 200 mpa for geothermal gradients ranging from 10 to 50 c km 1 and for quartz rich felsic mafic and peridotitic rock types thrust terranes are therefore predicted to be characterized by coseismic plastic instabilities on all detachment zones throughout the crust and into the uppermost mantle but embryonic rift zones should be aseismic at depth ca 10 km

reply to comments by kelletat 2008 comments to dawson a g and stewart i 2007 tsunami deposits in the geological record sedimentary geology 200 166 183

geological and hydrodynamical examination of the bathyal tsunamigenic origin of miocene conglomerates in chita peninsula central japan a conglomerate appears on a rocky coast called tsubutega ura coast located on the southwestern coast near the southern tip of the chita peninsula aichi prefecture central japan the conglomerate belongs to miocene sedimentary rocks termed the morozaki group the conglomerate includes meter scale boulders indicating that it was formed by an extraordinary event in the geological investigation we observed that the conglomerate shows alternate changes of paleocurrent directions between seaward and landward this feature is supposed to be formed by tsunami currents in the hydrodynamical investigation we obtained following results 1 the lowest limit of a current velocity to move a boulder of about 3 m in diameter would be about 2 3 m s 2 the speed of tsunami currents reproduced by tsunami simulation exceeds 3 m s at 300 m in depth when the tsunami is generated by a gigantic earthquake with magnitude 9 0 or more 3 the transport distance of the boulder would be several hundred meters to several kilometers by one tsunami event caused by a gigantic earthquake we conclude that tsunamis best explain the formation of the conglomerate deposited in upper bathyal environments about 200 400 m depth both from geological and hydrodynamical viewpoints

characteristics and hydrodynamics of boulders transported by storm waves at kudaka island japan abstract this study investigates the size position and the long axis orientation of 210 boulders at kudaka island japan these boulders were deposited from the reef crest to the slope of the back reef moat distributed within 275 m from the reef edge most boulders were rectangular to ellipsoidal without sharp broken edges they are reef rock fragments estimated as

comments to dawson a g and stewart i 2007 tsunami deposits in the geological record sedimentary geology 200 166 183

extremely high energy wave deposits inside the great barrier reef australia determining the cause tsunami or tropical cyclone abstract a hydrodynamic approach is used to determine whether tsunami or cyclone generated waves were responsible for the deposition of fields of well imbricated rock boulders up to 290 tonnes along the coast of cairns inside the great barrier reef australia calculations of the overturning moments show that only tsunami are capable of moving such large boulders in this environment it is hypothesised that large tsunami 11 m have been able to penetrate the great barrier reef through wide 5 10 km 50 70 m deep passages between individual reefs three such passages each approximately 35 km apart and oriented in the same direction exist in the cairns region it is possible that these passages have funnelled and amplified palaeotsunamis the preferential location of eroded coral boulders up to 3 m in length on reef flats alongside these passages and their absence on other reefs throughout the region provide further evidence that extremely high energy waves have been able to penetrate the great barrier reef into the inner channel adjacent to the mainland carbon 14 ages of the coral boulders on these reef flats matches closely the ages of coral fragments pinned below the very large rock boulders along the coast these ages suggest that the cairns region has experienced large tsunami twice over the last millennium

the role of porosity in discriminating between tsunami and hurricane emplacement of boulders a case study from the lesser antilles southern caribbean coastal boulder deposits are a consequence of high energy wave impacts such as storms hurricanes or tsunami parameters useful for distinguishing between hurricane and tsunami origins include distance of a deposit from the coast boulder weight and inferred wave height in order to investigate the role of porosity on boulder transport and elucidate the distinction between tsunami and hurricane impacts we performed archimedean and optical 3d profilometry measurements for the determination of accurate physical parameters for porous reef and coral limestone boulders from the islands of aruba bonaire and curacao abc islands netherlands antilles leeward islands subsets of different coral species and lithotypes constituting the boulders were sampled the physical parameters of boulders were analyzed and each boulder component was attributed to a certain range of porosity and density lowest porosities were observed in calcarenite 5 8 whereas highest porosities were measured for serpulid reef rock 47 68 porous serpulid reef rock 0 8 1 2 g cm 3 and the coral diploria sp 0 6 1 0 g cm 3 possess the lowest bulk densities while less porous calcarenite 2 0 2 7 g cm 3 and the coral montastrea cavernosa yield the highest bulk density values 1 6 2 7 g cm 3 the obtained physical parameters were used to calculate boulder weights and both hurricane and tsunami wave heights necessary to initiate transport of these boulders boulders are up to 5 6 times lighter than given in previously published data and hence required minimum hurricane or tsunami waves are lower than hitherto assumed the calculated wave heights the high frequency of tropical storms and hurricanes in the southern caribbean and the occurrence of boulders exclusively on the windward sides of the islands implicate that for boulders on the abc islands a hurricane origin is more likely than a tsunami origin 2008 elsevier b v all rights reserved

thermal and compaction processes in a young rifted basin containing evaporites gulf of lions france the gulf of lions northwestern mediterranean is a young oligocene miocene rifted basin characterized by the presence of a thick evaporitic sequence observed data surface heat flow well temperatures geopressures below the evaporites crustal thinning are used to model 1 the basin forming mechanisms and 2 the intrasedimentary processes that influence the temperature history and thus the maturation of source rocks a two dimensional finite difference basin model temispack simulates the sedimentation compaction and overpressures related to the low permeability of the post rift sequence the heat transfer from the rifted lithosphere into the sediments and the level of maturation by using a kinetic approach the classic passive margin model which relates the history of heat flow and the rate of subsidence to a uniform thinning factor yields subsidence and heat flow predictions that agree with observations the recently accelerated subsidence observed in the deep margin is probably an effect of recent regional compression rather than the consequence of alternative rifting mechanisms the history of maturation of organic matter was influenced by the variation of the regional heat flow due to the rifting the effect of sedimentation or blanketing and the variability of the lithologies and porosities the undercompaction of sediments underlying the evaporites is accounted for by the model which suggests that hydraulic fracturing is taking place at present in the overpressured sediments fluid flow associated with the compaction disequilibrium has negligible thermal effect undercompacted shales below the evaporites have lower thermal diffusivity and thus higher temperatures which has a significant effect on maturation

tsunami deposits on the coastline of west crete greece abstract the eastern mediterranean and the aegean sea in particular are the most active seismic regions in europe historically numerous earthquakes have occurred in this part of the world and comprehensive tsunami recordings exist nevertheless field evidence of tsunamis is rare although many neotectonic movements certainly must have triggered very strong tsunami waves along the coastlines of western crete we found evidence for tsunami impacts such as 1 bimodal deposits large clasts floating in sands comprised of shell fragments 2 dislocation of large boulders with tilting of biogenous notches and 3 boulders with lithophaga or cliona borings weighing up to 75 tons thrown onshore and imbedded in strata of marine shells this paper documents these deposits and discusses whether they originated from the sudden uplift that occurred in 365 ad moreover numerical radiocarbon ages reveal the occurrence of two tsunamis dated to 5660 yrs bp and 500 yrs bp evidence for other tsunami impacts is discussed but not supported by numerical dating due to the lack of suitable material

field signatures of the se asian mega tsunami along the west coast of thailand compared to holocene paleo tsunami from the atlantic region the andaman sumatra tsunami of dec 26 2004 was by far the largest tsunami catastrophe in human history an earthquake of 9 to 9 3 on the richter scale the extension of waves over more than 5000 km of ocean and run ups up to 35 m are its key features these characteristics suggest significant changes in coastal morphology and high sediment transport rates a field survey along the west coast of thailand phuket island khao lak region including some similan islands nang pha mangrove areas and phi phi don islands seven to nine weeks after the tsunami however discovered only small changes in coastal morphology and a limited amount of dislocated sediments restricted to the lower meters of the tsunami waves this is in striking contrast to many paleo tsunami s events of the atlantic region explanations for this discrepancy are sought in a mechanics of the earthquake a rather slow shock impulse on the water masses over the very long earthquake zone b shallow water in the earthquake zone and c bathymetry of the foreshore zone at the impacted sites shallow water west of thailand has diminished wave energy significantly the differences in geomorphological and sedimentological signatures of this tsunami compared with many paleo tsunami worldwide makes it unsuitable to be used as a model for old and future tsunami imprints by an event of this extreme energy and extension

distribution origin and transport process of boulders deposited by the 2004 indian ocean tsunami at pakarang cape thailand abstract the tsunami of 2004 in the indian ocean transported thousands of meters long boulders shoreward at pakarang cape thailand we investigated size position and long axis orientation of 467 boulders at the cape most of boulders found at the cape are well rounded ellipsoid in shape without sharp broken edges they were fragments of reef rocks and their sizes were estimated to be 3 22 7t the distribution pattern and orientation of long axis of boulders reflect the inundation pattern and behavior of the tsunami waves it was found that there is no clear evidence indicating monotonous fine coarse shoreward trends of these boulders along each transect line on the other hand the large boulders were deposited repeatedly along the three arcuate lines at the intertidal zone with a spacing of approximately 136m interval this distribution pattern may suggest that long lasting oscillatory flows might have repositioned the boulders and separated the big ones from small no boulders were found on land indicating that the hydraulic force of the tsunami wave rapidly dissipated on reaching the land due to the higher bottom friction and the presence of a steep slope we further conducted numerical calculation of tsunami inundation at pakarang cape according to the calculation the sea receded and the major part of the tidal bench area with boulders at present was exposed above the sea surface before the arrival of the first tsunami wave the first tsunami wave arrived at the cape from west to east at approximately 130min after the tsunami generation and then inundated inlands our calculation shows that tsunami wave was focused around the offshore by a small cove at the reef edge and spread afterwards in a fan like shape on the tidal bench the critical wave velocities necessary to move the largest and average size boulders by sliding can be estimated to be approximately 3 2 and 2 0m s respectively the numerical result indicates that the maximum current velocity of the first tsunami wave was estimated to be from 8 to 15m s between the reef edge and approximately 500m further offshore this range is large enough for moving even the largest boulder shoreward these suggest that the tsunami waves that were directed eastward struck the reef rocks and coral colonies originally located on the shallow sea bottom near the reef edge and detached and transported the boulders shoreward

geotherms evolution of the lithosphere and plate tectonics abstract for the purpose of calculating precambrian geotherms modern average geotherms need to be defined curves calculated from estimated plate sections are close to those of clark and ringwood 1964 thicknesses of lithospheric plates at any time in the past can be estimated from fossil geotherms because subduction of oceanic plates depends upon their density average densities of precambrian plates should place important constraints on the beginning of subduction this method however only indicates that in all probability subduction did not begin before 1000 ma ago geological data suggest a date of about 800 or 900 ma ago formation of archean continents would have proceeded from partial melting of basaltic crust and the end of that phase of earth s evolution would be a thermally controlled feedback mechanism lowering geothermal gradients in sub continental mantle the beginning of subduction was also thermally controlled and probably accompanied the increasing stability of eclogite in the upper mantle

multiple dating approach 14c 230th u and 36cl of tsunami transported reef top boulders on bonaire leeward antilles current achievements and challenges abstract dating the transport deposition time of supratidal coarse clast deposits is difficult limiting their value for inferring frequency magnitude patterns of high energy wave events on bonaire leeward antilles caribbean these deposits form prominent landforms and transport by one or several holocene tsunamis is assumed at least for the largest clasts although a large dataset of 14c and electron spin resonance esr ages is available for major coral rubble ridges and ramparts it is still debated whether these data reflect the timing of major events and how these datasets are biased by the reworking of coral fragments as an attempt to overcome the current challenges for dating the dislocation of singular boulders three distinct dating methods are implemented and compared i 14c dating of boring bivalves attached to the boulders ii 230th u dating of post depositional secondary calcite flowstone and subaerial microbialites at the underside of the boulders and iii surface exposure dating of overturned boulders via 36cl concentration measurements in corals approaches ii and iii have never been applied to coastal boulder deposits so far the three 14c age estimates are older than 40 ka i e most probably beyond the applicability of the method which is attributed to post depositional diagenetic processes shedding doubt on the usefulness of this method in the local context the remarkably convergent 230th u ages all pointing to the late holocene period 1 0 1 6 ka are minimum ages for the transport event s the microbialite sample yields an age of 1 23 0 23 ka and both flowstone samples are in stratigraphic order the older onset of carbonate precipitation and younger flowstone layers yield ages of 1 59 0 03 and 1 23 0 03 ka respectively four coral samples collected from the topside of overturned boulders yielded similar 36cl concentration measurements however the computed ages are affected by large uncertainties mostly due to the high natural chlorine concentration after correction for the inherited component and chemical denudation since platform emergence inducing additional uncertainty the calculated 36cl ages cluster between 2 5 1 3 and 3 0 1 4 ka for three of four boulders whilst the fourth one yields an age of 6 1 1 8 ka probably related to a higher inheritance these 230th u and 36cl age estimates are coherent with a suggested tsunami age of

the experimental deformation of dunite deformation experiments have been carried out on two dunites anita bay of 100 m grain size and aheim of 900 m grain size at strain rates from 10 3 to 10 6 s 1 and temperatures from 1000 c to 1300 c in a gas medium deformation apparatus at 300 mpa confining pressure most of the tests were under wet conditions defined by the presence of small amounts of water from hydrous minerals initially present constant strain rate and relaxation experiments covering ranges of flow stress down to about 70 mpa and 7 mpa respectively show that there is a change in flow law in going below about 100 mpa differential stress and that the coarser grained rock is stronger than the finer grained one power law parameters above the transition are n 4 48 0 31 and q 498 38 kj mol 1 for aheim dunite and n 3 35 0 17 and q 444 24 kj mol 1 for anita bay dunite while below the transition relaxation tests on anita bay dunite give n 2 44 0 18 and q 386 27 kj mol 1 it is concluded that there is a weakening effect of water that this effect is mainly in the grain boundaries and that grain boundary sliding is probably a significant deformation mechanism at the lower stresses under wet conditions

the geology petrology and geochemistry of coal seams from the st rose and chimney corner coalfields cape breton nova scotia canada abstract seams from the st rose and chimmey corner coalfields nova scotia canada were sampled and examined for petrographic and geochemical composition rank determinations indicate a rank of high volatile c b bituminous seams show regular alternations of dull and bright microbanded lithotypes with dull lithotypes predominant in the central portion of the main seam no 5 seam brighter lithotypes are dominated by vitrinite 80 with minor inertinite avg 12 and minor liptinite duller lithotypes contain greater amounts of inertinite up to 40 and liptinite primarily sporinite mineral matter consists of epigenetic pyrite with lesser amounts of clay and quartz cabonates are common in the chimney corner seams elemental composition of the seams is similar to other canadian coals and fall within world coal ranges with the exception of high concentrations of cl zn ni mo pb cu and as depositional environment of the seams as indicated by maceral composition lithotypes and geology suggest a predominance of wet forest to reed moor conditions in a fluvial lacustrine setting periodic episodes of flooding and drying are indicated by lithotype maceral and mineral variations

the main tectonic events depositional history and the palaeogeography of the southern urals during the riphean early palaeozoic abstract investigation of former and new sections in the classic riphean region of the bashkirian anticlinorium ba revealed that this palaeozoic segment of the passive margin of the east european platform eep during its proterozoic history was initially formed as an intracratonic aulacogen basin which developed as an inter cratonic half structure only after the early ordovician opening of the uralian palaeo ocean the originally opposite half structure of this riphean basin may have been located either on the afro european part of gondwana or along the margins of the siberian craton or elsewhere but definitely not along the conjugate permian collision suture with the kazakh block or the mugodzhary microcontinent the ca 1150 ma 1635 to 488 ma depositional history of the bashkirian basin was punctuated several times due to major tectonic events folding downfaulting uplift magmatic intrusions metamorphism which may have caused extended periods of erosion and non deposition furthermore numerous cyclothems of unknown regional extent are incorporated into the enormous time span involved in the evolution of the ca 12 15 km thick riphean sequence the riphean vendian sedimentary assemblages reflect alternating shallow marine to peritidal and continental fluviatile environments the regional distribution of which is illustrated in sets of palaeogeographic maps angular unconformities are seen at the base of the lower riphean ai formation dated at 1635 ma at the base of the middle riphean mashak formation dated at 1340 ma at the base of the upper riphean zilmerdak formation approx 1000 ma and below the middle ordovician quartzites containing shelly fossils which overlie steeply folded and slightly metamorphosed proterozoic suites along the southeastern margin of the bashkirian anticlinorium during the vendian to ordovician interval major eastern parts of the bashkirian anticlinorium as well as regions further north along the european margin of the urals were subjected to strong diastrophism probably related to the cadomian or baikalian orogeny later on during the ordovician the western half part of the bashkirian basin turned into a marginal basin of the east european platform and thus was modified by the early stages of the uralian oceanic development

the reduction effects of mangrove forest on a tsunami based on field surveys at pakarang cape thailand and numerical analysis abstract using an integrated approach including satellite imagery analysis field measurements and numerical modeling we investigated the damage to mangroves caused by the 2004 indian ocean tsunami at pakarang cape in pang nga province thailand comparing pre and post tsunami satellite imagery of the study area we found that approximately 70 of the mangrove forest was destroyed by the tsunami based on field observations we found that the survival rate of mangroves increased with increasing stem diameter specifically we found that 72 of rhizophora trees with a 25 30 cm stem diameter survived the tsunami impact whereas only 19 with a 15 20 cm stem diameter survived we simulated the 2004 indian ocean tsunami using the nonlinear shallow water wave theory to reproduce the tsunami inundation flow and investigated the bending moment acting on the mangrove trees results of the numerical model showed that the tsunami inundated areas along the mangrove creeks and its current velocity reached 5 0 m s 1 based on the field measurements and numerical results we proposed a fragility function for mangroves which is the relationship between the probability of damage and the bending stress caused by the maximum bending moment we refined the numerical model to include the damage probability of mangrove forests using the obtained fragility function to investigate the tsunami reduction effect of mangrove forest under simple numerical conditions related to the mangrove forest ground level and incident wave the model showed that a mangrove forest of rhizophora sp with a density of 0 2 trees m 2 and a stem diameter of 15 cm in a 400 m wide area can reduce the tsunami inundation depth by 30 when the incident wave is assumed to have a 3 0 m inundation depth and a wave period of 30 min at the shoreline however 50 of the mangrove forest is destroyed by a 4 5 m tsunami inundation depth and most of the mangrove forest is destroyed by a tsunami inundation depth greater than 6 m the reduction effect of tsunami inundation depth decreased when the tsunami inundation depth exceeded 3 m and was mostly lost when the tsunami inundation depth exceeded 6 m

numerical simulation of permafrost evolution as a part of sedimentary basin modeling permafrost in the pliocene holocene climate history of the urengoy field in the west siberian basin present day temperature profile may be used as an important constraint for reconstruction of the thermal regime in sedimentary basin modeling this type of profile is significantly non steady state especially for basins located at high and middle latitudes however estimations of past thermal regimes are indefinite and often limited by knowledge of past glaciations and by the simple two layer model usually employed in this paper permafrost modeling was carried out as a continuation of basin modeling of the sedimentary section of urengoy field of the west siberian basin 66 n 77 e consideration of surface temperatures beginning with the triassic a refined initial temperature distribution permafrost modeling for the past 3 4 ma and use of a real lithological cross section distinguish this approach from previous studies depth and time variations in thermophysical parameters of rocks heat conductivity heat capacity unfrozen water content salt content and porosity had a considerable influence

waves coastal boulder deposits and the importance of the pre transport setting the pre transport environment of a coastal boulder along with its shape size and density determines the height of wave required for it to be transported different forces act on sub aerial boulders as opposed to submerged boulders when struck by a wave boulders derived from joint bounded blocks on shore platforms predominantly experience lift force and require a wave of greater height to be transported than boulders in other environments no one equation is applicable to determine the height of palaeo waves responsible for depositing a field or ridge of imbricated coastal boulders a range of equations and their derivation is presented here which can be applied to the respective pre transport environment of a boulder such an approach is necessary when attempting to reconstruct the frequency and magnitude of past coastal wave hazards and for differentiating between tsunami and storm wave deposited boulder fields

the tectono metamorphic evolution of gneiss complexes in the middle urals russia a reappraisal abstract the middle urals are characterized by a major virgation in the linear trend of the urals orogen and represent the most highly contracted part of the late palaeozoic collisional belt this part of the orogen is dominated by metamorphic complexes and major fault and shear zones the main uralian fault zone muf the east dipping suture of the orogen containing low grade metamorphic rocks separates the sysert complex in the east from the ufaley complex in the west the sysert complex in the hanging wall of the muf consists of intensely deformed gneisses granitic intrusions and a metamorphosed melange zone tectonic and isotopic investigations suggest the following stages for the evolution of the sysert complex a pre orogenic rifting and magmatism during ordovician and silurian times b oceanic closure island arc formation related to convergence and subduction during devonian times c major ductile deformation under amphibolite facies conditions related to nw directed thrusting associated with crustal stacking during collision in carboniferous times d exhumation and contractional intracontinental tectonics during permian times and e closing of isotope systems related to cooling and the end of orogenic shortening through triassic times the ufaley complex in the footwall of the muf is interpreted as an east dipping crustal stack that records an amphibolite facies uralian metamorphism lithologically the complex can be divided into pre orogenic european basement west ufaley and intensely deformed palaeozoic metasediments and amphibolites east ufaley high pressure relics in the east ufaley complex are interpreted to be the result of subduction whereas intense ductile deformation is related to overthrusting onto west ufaley the west ufaley complex is composed of gneisses amphibolites migmatites and granitic intrusions and has been thrust onto devonian limestones along a major shear zone in both sysert and ufaley complexes nw trending stretching lineations and top to the nw kinematic indicators suggest an oblique plate convergence with a significant sinistral component the muf is interpreted as a major normal fault that developed congruent with continental subduction and that compensated lithospheric thickening and the rapid exhumation of subducted crust in the footwall

the geosynclinal development of the urals abstract on the basis of the regularities occurring in sedimentation development of magmatism metamorphism and tectonic structure a model for the geological evolution of the urals is suggested the authors show that the geosynclinal process was due to the active overthrusting of oceanic masses onto the continental margin resulting in tectonic and geochemical interactions of sialic continental and basic oceanic crusts the main points of the model are as follows ultrabasic belts have been exposed by the frontal zones of large allochthonous plates of the crust which were overthrust onto the east european platform there were three main stages of overthrusting the late ordovician middle devonian and lower carboniferous as evidenced by the glaucophane bearing metamorphic complexes the belts are rejuvenated in the eastern direction geosynclinal magmatism whose main characteristic features are the evolution of chemical composition in time and the lateral migration of volcanism in space develops with cyclic recurrence of vertical formation groups in three time intervals the ordovician middle devonian the middle devonian early tournaisian and the late tournaisian visean each new tectonic cycle begins after each succeeding ultramafic belt has been overthrusted and has been developed at the tangential compression of the earth s crust in this case the volcanic part of the formation group comes into being first evolving from its basic composition to an acidic one with an increased amount of alkali and then the sedimentary part appears represented by flysch thus lateral migration in the eugeosynclinal uralian zone of both volcanism and flysch accumulation is caused by the mechanism of rock masses from the uralian paleoocean successively overthrusting onto the east european platform and it is this mechanism which created geosynclinal formation groups changing one another in time and space

evaluation of tsunami flooding using geomorphologic evidence abstract whatever the generating mechanism of a tsunami may be this event can discharge destructive energy along coastal areas and produce widespread inundation the presence of large boulders along rocky coasts could be a useful indicator to understand the extent of the impact of past tsunami floods a detailed study of the deposited boulder features size shape and rock density and their initial position prior to the transport is extremely important when reconstructing the possible morphodynamic scenario s applying the appropriate equations is important when aiming to assess the maximum extent of flooding the integration of morphological and hydrodynamic data allows for an estimation of the water level during the tsunami event responsible for boulder transport moreover it is possible to calculate how far the impacting wave flooded inland this is a function of the wave parameters and of the degree of roughness of the flooded terrain that is expressed by the manning number to evaluate its probable average value experimental data computer simulations and post tsunami surveys have been performed in two sectors of the southern apulia coastline characterised by the presence of tsunami boulder fields and or ridges the surveys in each site have allowed for the calculation of the boulder sizes the estimation of their pre transport location and the extent of inland flooding data have been processed using a geographic information system gis as a result a flooding map useful in planning future possible actions for coastal area use has been produced

boulder accumulations produced by the 20th of february 1743 tsunami along the coast of southeastern salento apulia region italy abstract the detachment of large boulders in the nearshore zone and their deposition farther inland are the main morphological effects of tsunamis on rocky coasts along the otranto leuca coast southeastern apulia italy two boulder accumulations have been recognized and studied at the torre sasso locality boulders weighing up to 31 t are scattered from sea level to about 5 m of elevation and clustered in groups of several imbricated elements at torre s emiliano an impressive accumulation made of large boulders has been recognized and studied the accumulation is about 30 m wide and follows the present coastline for about 2 5 km at a variable distance of 15 to 40 m looking closer it is compounded by two ridges the ridge closer to the coastline shows a very steep slope seaward made of very large boulders emplaced in a vertical position its top reaches about 11 m above m s l the inner belt is lower than the outer one and consists of smaller boulders it partly covers a 2 m thick colluvial deposit made of reddish sands huge blocks weighing up to 70 t cover the carved surface stretching from the coastline to the front of the first ridge analysis of the imbrication axes indicates that the catastrophic waves responsible for the development of the boulder accumulations most likely propagated from sse to nnw direction karstic features occurring on the surface of the innermost boulders indicate a very recent age for their deposition as no differences have been found between the aerial exposed surface and the soil covered one three ams radiocarbon age determinations performed on marine shells found landward the boulders have accumulated recently i e within the last three centuries moreover archeological remains in the top layers of the colluvial deposits covered by the boulders can be referenced to 16th 17th centuries this evidence suggests that the 20th of february 1743 earthquake was responsible for the generation of two large tsunami waves which caused the boulder accumulations to deposit this earthquake was particularly violent in the salento region where it reached grade ix on the mcs scale interestingly chronicles of this event record a withdrawal of the sea in the brindisi harbour north of the study area this study highlights the tsunamigenic potential offshore the southeastern salento coast requiring that further strategies be devoted to mitigate the tsunami risk

compensation of paleozoic orogens a comparison of the urals to the appalachians abstract the urals and appalachians are two paleozoic mountain belts with similar geologic and morphologic features we combine geophysical bouguer gravity and deep seismic sounding and geological observations from the ural mountains to test whether the surficial similarities of these paleozoic orogens extend to include deep lithospheric structure and compensation mechanism we find the combined data suggest support of the mountains by a stiff continental slab which is depressed by an effective subcrustal load in addition to the topography as has been recently proposed for the appalachians our preferred model which fits the geophysical data and predicts the presence and shape of the ural foredeep to the west of the mountains requires eastward directed underthrusting of the russian platform behaving as an elastic plate more than 50 km thick it is unlikely that an elastic plate this stiff could have resulted from conductive cooling of a thermal plate only 125 km thick the weight of the existing mountains on such an elastic plate is insufficient to produce the deflection of the moho inferred from seismic and gravity data an additional load on the elastic plate may be provided by a buried mass of similar origin to surface outcrops of dense mafic and ultramafic rocks in the eastern urals alternatively the load may represent the effect of a shallowing of the moho east of the mountains which is a remnant of a buried passive continental margin seismic data and bouguer gravity anomalies suggest that the effect of the subsurface mass anomaly is at least as great as the present day topography and that the russian plate flexurally underthrusts the urals for more than 100 km we speculate that similar effective subsurface loads may exist at younger continental orogens but are obscured by the topographic load in less eroded mountain belts

catastrophic wave erosion on the southeastern coast of australia impact of the lanai tsunamis ca 105 ka sand barriers along the coast of southern new south wales dating from the last interglacial have been almost completely destroyed most probably by a catastrophic tsunami evidence for catastrophic wave erosion can also be traced to heights of at least 15 m above present sea level on coastal abrasion ramps these erosional features lie above the range of effective erosion by contemporary storm waves and cannot be attributed to either eustatic fluctuations or local uplift chronological evidence for the timing of the destruction of the last interglacial barriers suggests that tsunamis generated by the submarine slide off lanai in the hawaiian islands 105 ka traveled across the pacific and eroded this coast

distribution geomorphology and lithofacies of cliff top storm deposits examples from the high energy coasts of scotland and ireland abstract cliff top storm deposits ctsds occur on cliffs at elevations of up to 50 m above sea level at exposed sites on the deep water coasts of the british isles this study examines the distribution geomorphology and lithofacies of ctsds at sites from shetland orkney caithness and the outer hebrides in scotland and from the aran islands in galway bay in ireland ctsds are generated largely by the quarrying of blocks from the cliff top and transported by green water bores across cliff top platforms and ramps to be deposited in backing ridges or as debris spreads maximum boulder sizes reach 48 m 3 but it is likely that much larger blocks can be quarried prior to disintegration during transport eye witness accounts and field mapping demonstrate that formation and modification of ctsds has continued during major storms over recent decades recent ctsds bury a range of man made debris but older deposits lack this and instead show weathering effects that indicate a longer residence time in shetland osl dates on intercalated sands suggest that the oldest ctsds date from 800 ad radiocarbon dates on shell buried inside ctsd ridges relate to major storms between 1700 and 1900 ctsds represent an overlooked archive of storm sedimentation that has great potential for the elucidation of local storm chronologies ctsds also provide evidence of wave impacts on any part of the cliff face or top in fundamental contrast to the concentration of wave action at the cliff foot implicit in traditional models of the erosion of rock coasts

burial and thermal history of the west bashkirian sedimentary basins abstract the galo system is applied to the numerical reconstruction of burial and thermal histories of the west bashkirian lithosphere from the riphean to the present an analysis of the variation in tectonic subsidence of the basin during its development is utilized to estimate approximately the mantle heat flow variations our variant of basin evolution suggests that after cooling in the early riphean the rather weak thermal reactivations have not led to considerable heating of the lithosphere in the study region surface heat flow decreased from relatively high values in the early riphean 60 70 mw m 2 in the eastern area and 40 50 mw m 2 in the western part to present day values of 32 40 mw m 2 in spite of the relatively low temperature regime of the basin as a whole a syn rifting deposition of more than 10 km of limestone shale and sandstone in the riphean resulted in rather high temperatures 180 190 c at the base of present day sedimentary blanket in the eastern area in agreement with the observed data computed present day heat flow through the sediment surface increases slightly from 32 to 34 mw m 2 near the west boundary of the region to 42 mw m 2 near the boundary of the ural foldbelt whereas the heat flow through the basement surface decreases slightly from 28 32 to 24 26 mw m 2 in the same direction the mantle heat flow is only 11 3 12 7 mw m 2 which is considerable lower than mean heat flow of the russian platform 16 18 mw m 2 and comparable with the low heat flow of precambrian shields

burial history and thermal evolution of the northern and eastern saharan basins the numerical one dimensional reconstruction of the burial history and thermal evolution of the sedimentary section and basement was conducted for 32 wells in the east algerian basins with the help of the galo basin modeling system these reconstructions allowed the performance of a quasi two dimensional analysis of the burial history of the basins changes in rock temperatures the lithosphere thickness and maturation conditions of organic matter during basin development along the four profiles crossing the study region the modeling assumed that the highest thermal activation in the history of the saharan basins with the heat flow more than 100 mw m2 and the thinnest lithosphere on the order of 25 35 km took place during the late carboniferous to permian in the dahar and oued el mya basins the uplift responsible for this activation caused erosion of 2000 3000 m of ordovician to lower carboniferous strata the ghadames and illizi basins were subjected at the same time to more moderate erosion and thermal activation with heat flow less than 75 mw m2 in the triassic cretaceous interval maximum subsidence occurred in the northern areas which were characterized by maximal thermal activation and the thinnest lithosphere in the permian at present the situation is opposite to that in the permian the highest thermal regime occurs in the southern areas of the study region and especially in the illizi basin where heat flow reaches and even exceeds 100 mw m2 and the thickness of the lithosphere decreases as much as 30 km the modeling also assumes stretching of the lithosphere in the northeastern and central parts of the illizi basin with maximal amplitude of about 1 16 during the cenozoic the analysis shows that the hercynian erosion could account for only a few of the abrupt changes in vitrinite profiles in the saharan basins and that triassic and later intrusive activity and associated hydrothermal heat transfer accurately explain the steplike character of maturation profiles

evolution of temperature maturation level and realization of hydrocarbon potential in subtrappean sedimentary complex of the bombay offshore results of 1 d basin modeling abstract the modified galo program package for basin modeling is used to calculate the temperature and vitrinite reflectance distributions with depth at any time before during and after the decan trap formation an assessment of hydrocarbon generation by kerogen of type iii is carried out for burial history of probable source rocks in the subtrappean sedimentary complex of the western passive margin of india near the bombay offshore duration of trap formation is most critical and indefinite parameter in construction of maturity aureole in the subtrappean sedimentary complex the analysis in the frame of the model of continuous formation of traps suggests that a maturation level of organic matter in sedimentary rocks under the trap depends strongly on duration of the trap formation even for traps thickness of 1 5 km or more maturity level of organic matter in the rocks located on the 100 500 m below the base of the trap can be rather moderate if the trap has been formed over fairly a long time

acceleration of continental rifting due to a thermomechanical instability abstract we have made a numerical experiment on continental rifting based on the rheology of rocks constituting continental lithosphere the model assumes homogeneous pure shear stretching of a three layered lithosphere we also assume constant extensional force in the model to explore acceleration or deceleration of rifting the main parameters which affect the evolution of continental rifting for an initial geotherm are the applied constant extensional force and the thermal diffusivity whereas continental extension elevates the isotherms in continental lithosphere leading to its softening the cooling of the extended continental lithosphere by thermal diffusion leads to its strengthing therefore the applied force and the thermal diffusivity play counteracting roles which cause a stretching instability to separate the final states of rifts i e breakup or failed the transition from the breakup to a failed rift in continental lithosphere is caused by a subtle change in the constant extensional force or in the thermal diffusivity similar to a phase transformation we have shown that a non dimensional number that is modified form the peclet number determines the final state

thermal and maturation modeling of the urengoy field west siberian basin some special considerations in basin modeling present day temperature and vitrinite reflectance ro profiles are considered key factors for calibration in numerical basin modeling therefore it is important to understand how such profiles are generated basin modeling typically considers factors such as rock consolidation depth variation of petrophysical characteristics changes in heat flow and paleoclimate however our basin evaluations have shown that other processes that influence temperature and ro vitrinite reflectance profiles commonly are inadequately studied modeling within the urengoy field of the west siberian basin has allowed numerical estimates of some of these nonstandard processes first a substantial increase in temperature up to 5 10ic is expected from changes in heat conductivity due to the formation of significant free gas gas condensate and condensate second climate variations creating numerous periods of formation and degradation of permafrost zones for the last 3 4 m y could decrease the modern rock temperatures by 10 17ic in the upper 1 5 km of the sedimentary section and up to 10ic at its base due to the short duration of these two processes their effect on organic matter maturation is minimal nevertheless their roles in the formation of present day temperature profiles necessitate their inclusion in basin modeling third modeling results demonstrated that change in heat conductivity of rocks with dispersed organic matter can increase temperature of sedimentary rocks by 3 5ic and rock maturity by not more than 0 02 ro finally the sharp increase in vitrinite reflectance ro with depth typical for the deep sedimentary units of the urengoy field and many other continental rift basins is possible to explain from hydrothermal activity the influence of these processes on subsurface temperatures and maturation of organic matter can vary significantly depending on lithology organic matter content and the location of the modeled section relative to the ancient rift system the results of this study can help one estimate the relative influence of these parameters

a numerical model for the transport of a boulder by tsunami 1 we have conducted hydraulic experiments in an open channel with cubic and rectangular shaped solid blocks on the slope for investigating the boulder transport process by tsunami in our experiments the block was mainly seen to be transported by a bore due to rolling or saltation rather than by sliding previous models for the boulder transport by tsunamis assumed sliding as a mode of transport for the boulder therefore these models underestimated the distance of the boulder moved by the tsunami when it was transported due to rolling or saltation in this study we have developed a practical model for the transport of a boulder by tsunami which takes into account the various transport modes we introduce an empirical variable coefficient of friction by assuming that the coefficient decreases with decrease in ground contact time when the block was transported by rolling or saltation with the aid of this parameter the model can explain various modes of transport i e sliding rolling and saltation and reproduces the experimental results well we further applied this improved model to a tsunami boulder at inoda area in ishigaki island japan which was transported by the 1771 meiwa tsunami the calculated distance of transport of the boulder was approximately 650 m which is consistent with the description in the historical document based on our calculations we estimated hydraulic values of the tsunamis estimation of such hydraulic values is important for understanding the behavior and power of the historical tsunamis besides aiding future disaster mitigation efforts

subcrustal density inhomogeneities of northern eurasia as derived from the gravity data and isostatic models of the lithosphere for the territory of northern eurasia 6 e 165 w 30 75 n the distribution of anomalous masses in the lithosphere has been estimated in accordance with the lithosphere isostatic model the method of model construction is based on the admittance technique the experimental admittance presents a relation between the part of the outer load uncompensated by the moho undulations and the residual gravity field and is used to select the best model the 1 1 averaged values of topography elevations basement and moho depths sedimentary cover density and gravity anomalies have been used as initial data according to the correlation equation relating the outer load and moho depths the mean density contrast between the lower crust and the subcrustal lithosphere is 0 43 g cm3 but the moho undulation can not provide complete isostatic equilibrium in some areas the part of the outer load uncompensated by moho undulations may be as large as 107 kg m2 and the residual gravity field is as intensive as 260 mgal assuming that for loads of wavelength 200 km local isostatic compensation is valid in accordance with the admittance analysis the anomalous masses compensating for the part of the outer load which is not compensated by moho undulations have to be located partly in the lower crust and in the subcrustal layer the regional trend of anomalous compensating masses is negative under western europe the mediterranean eastern asia and adjacent marginal seas and positive under the east european platform and western and central asia the local compensating masses correspond to particular tectonic units the isostatic gravity anomalies of northern eurasia have been determined and the long wave component of the field reflecting anomalous masses under the isostatic compensation level has been evaluated

numerical reconstructions of thermal evolution of sedimentary cover and underlying lithosphere in western part of the south caspian basin abstract thermal evolution of the south caspian sedimentary basin since the upper triassic is numerically reconstructed on the example of the deepest sedimentary sections of the south apsheron and pre alborz depressions the modeling suggests thermally active mantle of the region with present day depth of the asthenosphere top of 50 60 km the temperature at the base of the sedimentary cover at depth of about 20 km is estimated by 400 to 500 c the abnormally low temperatures of sedimentary rocks in the upper 5 6 km of the present day sedimentary cover are in contrast with high temperature regime of the upper mantle in the region these low temperatures are explained by high effective thermal conductivity of the rocks in the upper 5 6 km of sedimentary cover in conditions of avalanche sedimentation it is believed that the considerable increase in effective heat conductivity of sedimentary rocks took place during the last 0 5 1 million years and can be due to contribution of the dispersional heat transfer the latter is effective in deconsolidate upper layer of sediments deposited with high rate of sedimentation during last 2 5 my

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

permafrost heat flow and the geothermal regime at prudhoe bay alaska temperature measurements through permafrost in the oil field at prudhoe bay alaska combined with laboratory measurements of the thermal conductivity of drill cuttings permit an evaluation of in situ thermal properties and an understanding of the general factors that control the geothermal regime a sharp contrast in temperature gradient at approx 600 m represents a contrast in thermal conductivity caused by the downward change from interstitial ice to interstitial water at the base of permafrost under near steady state conditions interpretation of the gradient contrast in terms of a simple mode for the conductivity of an aggregate yields the mean ice content approx 39 and thermal conductivities for the frozen and thawed section 8 1 and 4 7 mcal cm s sup 0 c respectively these results yield a heat flow of approx 1 3 hfu which is similar to other values on the alaskan arctic coast the anomalously deep permafrost is a result of the anomalously high conductivity of the siliceous ice rich sediments curvature in the upper 160 m of the temperature profiles represents a warming of approx 1 8 sup 0 c of the mean surface temperature and a net accumulation of 5 6 kcal cm sup 2 by the solid earth surface during the last 100 years or so rising sea levelmore and thawing of ice rich sea cliffs probably caused the shoreline to advance tens of kilometers in the last 20 000 years inundating a portion of the continental shelf that is presently the target of intensive oil exploration a simple conduction model suggests that this recently inundated region is underlain by near melting ice rich permafrost to depths of 300 500 m its presence is important to seismic interpretations in oil exploration and to engineering considerations in oil production with confirmation of the permafrost configuration by offshore drilling heat conduction models can yield reliable new information on the chronology of arctic shorelines less

sedimentology of rocky shorelines 3 hydrodynamics of megaclast emplacement and transport on a shore platform oahu hawaii abstract megaclasts of well cemented coralgal limestone have been emplaced onto a shore platform by large waves on the north shore of oahu hi emplacement and movements of the largest ca 96 ton megaclast have been dated using aerial photographs hydrodynamic forces at the low submerged shoreline cliff are computed using design wave characteristics based on linear wave theory and experimental results considering the local wave climate and near shore bottom topography force exerted by a tsunami has been estimated based on the 1946 aleutian tsunami the computed forces are evaluated in terms of the initial fracturing along a given failure plane that is required in order for the detachment to occur the analysis shows that tsunami as well as large swell waves are capable of quarrying the megaclast provided that sufficient initial fracturing is present dislodgement and emplacement most likely occurred in a sequence during impact of a single wave on the shoreline cliff swell waves however are seldom capable of emplacing large blocks onto the platform due to their rapid disintegration after breaking so that most blocks quarried from the cliff edge fall back onto the submarine terrace emplacement of large boulders seems to require extreme sea waves with periods longer than storms or north pacific swells usually produce transport mechanisms on the shore platform vary depending on megaclast shape sliding is a common mechanism of transport for larger and irregular megaclasts whereas somewhat smaller and platy megaclasts are occasionally found in overturned positions

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

large boulder accumulations by extreme waves along the adriatic coast of southern apulia italy abstract the adriatic coast of southern apulia italy is marked by the presence of large boulder accumulations boulders are up to 8 t in weight and arranged either in small groups or rows composed of a few imbricated elements the lower surface of some of the boulders is covered by biogenic encrustation which suggests that they were possibly carved from the mid or sublittoral zone and that they capsized during their transport other boulders detached from the supratidal zone have their surface affected by tilted rock pools new horizontal solution pans are continually forming a detailed survey of a large boulder accumulation was carried out at torre santa sabina direct observations were also made concerning the carving out and transportation of one single boulder during the severe storms in that area on january 4th 2002 and on january 12th 2003 collated data from both the survey and the direct observations including some radiocarbon age determinations and hydrodynamic calculations suggest that the studied accumulation was due to the superimposed effects of one or two tsunami as well as of storm waves tsunami would be responsible for the detachment and transportation of the largest boulders while storm waves may have been responsible for the carving out and transportation of the newer smaller blocks and for moving once again the largest boulders it was in this way that a typical boulder accumulation was produced the collated data suggest that two tsunami may have recently struck the adriatic coast of southern apulia the first possibly took place on the dalmatian coast as a result of the earthquake on april 6 1667 which destroyed ragusa modern day dubrovnik the second tsunami would have accompanied the strong earthquake which took place in southern apulia on february 20 1743