the role of earthquakes in inducing sediment mass movements in the eastern korinthiakos gulf an example from the february 24 march 4 1981 activity abstract korinthiakos gulf is a narrow arm of the sea connecting the ionian and the aegean seas through the rion antirion strait and the korinth canal respectively the eastern part of korinthiakos was surveyed by the marine geology department of the institute of geology and mineral exploration of greece using a 3 5 khz subbottom profiler the survey was carried out a short time after intensive earthquake activity which occurred in the area from february 24 to march 4 1981 during this activity three major shocks of magnitudes ranging from 6 4 to 6 7 took place the subbottom profiles reveal a sediment mass which was deposited by submarine slumping in the alkyonides basin which lies at the eastern end of the studied area the slump is about 10 km long 1 5 to 2 0 km wide and its areal extent is about 16 km2 the scarp area occurs at a bathymetric depth of about 100 to 250 m in the northeastern part of the basin the scarp faces are from 10 to 15 m high and have a total areal extent of about 4 km2 the destruction of fishing nets of trawling boats and other evidence indicates that the triggering of the mass flow was effected by the earthquake activity and probably by the first major shock scarp areas and scarp faces from which sediment masses have been removed were detected in other shallow and deep sectors of the studied area indicating that mass transport processes are very common in this area of high seismicity

sedimentary processes on the atlantic continental slope of the united states abstract until recently the sedimentary processes on the united states atlantic continental slope were inferred mainly from descriptive studies based on the bathymetry and on widely spaced grab samples bottom photographs and seismic reflection profiles over the past 6 years however much additional information has been collected on the bottom morphology characteristics of shallow subbottom strata velocity of bottom currents and transport of suspended and bottom sediments a review of these new data provides a much clearer understanding of the kinds and relative importance of gravitational and hydrodynamic processes that affect the surface sediments on the rugged slope between georges bank and cape lookout n c these processes include 1 small scale mass wasting within submarine canyons and peripheral gullies 2 density flows within some submarine valleys 3 sand spillover near the shelf break 4 sediment creep on the upper slope and 5 hemipelagic sedimentation on the middle and lower slope the area between georges bank and hudson canyon is further distinguished by the relative abundance of large scale slump scars and deposits on the open slope the presence of ice rafted debris and the transport of sand within the heads of some submarine canyons between cape lookout and southern florida the slope divides into two physiographic units and the topography is smooth and featureless on the florida hatteras slope offshelf sand spillover and sediment winnowing related to gulf stream flow and possibly to storm driven currents are the major processes whereas hemipelagic sedimentation is dominant over the offshore slope along the seaward edge of the blake plateau north of the blake spur slumping generally is absent south of cape lookout although one large slump scarp related to uplift over salt diapirs has been identified east of cape romain future studies concerning sedimentary processes on the atlantic slope need to resolve 1 the ages and mechanisms of mass wasting 2 the accumulation rates and thicknesses of hemipelagic sediments and 3 the causes and variability of offshelf sand spillover sediment winnowing and canyon transport

processes and rates of recent holocene basin filling in an active transform margin santa monica basin california continental borderland abstract santa monica basin an inner basin of the california continental borderland is a deep margin basin presently receiving sediments under high sea level conditions since the slowing of the last transgression the basin has been receiving primarily suspended load contributions with rare turbidites except in the most headward parts of the two principal canyons one turbidite found throughout the basin was laid down about 200 years bp and was probably deposited by a turbidity current generated by mass movement of slope sediments in the slope apron adjacent to the major active canyons similar basin wide events have occurred throughout holocene time at intervals of about 500 1000 years and these represent the effects of big earthquakes major floods or other exceptional happenings not commonly recorded in historic time except for these exceptional events the basin has received fine clastic sedimentation derived from the mainland rivers and transported by nepheloid plumes near bottom and in the surface mixed layer biogenic carbonate and organic carbon input from areas of high productivity fed by upwelling is masked by the fine detrital influx over the major fans by dilution from the rain of particulates from the major surface and near bottom turbid plumes that pass over the basin center a maxima of carbonate and organic content occurs in the basin floor sediments most distant from the combined diluting effects of these two major detrital inputs the basin slope fan and shelf bank top sediments are differentiated on the basis of mean particle size and skewness changes in sand and silt content are related to the pattern of the prevailing surface and near bottom water circulation with their reservoirs of fine suspended particulates the principal process removing the fine particles from the surface plumes is biological filtering and pelleting sedimentation rates of major sediment components show that near bottom nepheloid plumes are trapped by the closed deep basin and their load settles out as the turbid waters circle over the central basin floor sedimentation rates vary from 40 80 cm 1000 years average sediment delivery is about 106 tons but exceptional floods can deliver several fold more sediment at 10 30 year intervals

progressive shape evolution of a mineral inclusion under differential stress at high temperature example of garnet inclusions within a granulite facies quartzite from the lutzow holm complex east antarctica due to the size independency of dislocation creep assuming ggrtqtz 1 0 nm 1 dgb a 1 0 10 12 m 2 s 1 dgb b 1 0 10 11 m 2 s 1 and sa 1 0 mpa the garnet data are fitted to a theoretical curve under condition of sb 1 4 10 2 mpa ta 0 5 myr and

evolution of veatch washington and norfolk submarine canyons inferences from strata and morphology abstract investigations of veatch washington and norfolk submarine canyons on the eastern continental margin of the united states resulted in a detailed assessment of their past and present geologic processes norfolk and washington canyons share such characteristics as similar levee geometry stratigraphy and mineralogy veatch canyon differs from norfolk and washington canyons in these respects seismic reflection profiles of all three submarine canyon heads indicate an erosional origin seismic profiles of veatch canyon s lower continental slope indicate a formation by depositional processes in contrast the continental slope profiles of washington and norfolk canyons reveal a history of alternating episodes of deposition and erosion cored sediments from washington and norfolk canyons disclose recent intermittent down canyon transport of sand to the continental rise bathymetric and seismic profiles suggest veatch washington and norfolk canyons have all been subjected to a minimum of two periods of development similar axial trends of washington and norfolk canyons imply a common structural influence

a petrologic and ion microprobe study of a vigarano type b refractory inclusion evolution by multiple stages of alteration and melting abstract usnm 1623 8 is a type b vigarano inclusion 6 mm in diameter consisting of melilite ak12 72 fassaite 17 23 a12o3 5 17 tio2 anorthite and spinel secondary alteration is negligible and consists of diopside and sparse nepheline melilite is normally zoned and contains up to 0 35 wt na2o higher than generally seen in melilite from other refractory inclusions a strong correlation between akermanite content and na2o in 1623 8 melilite suggests that the na was present during igneous crystallization rather than introduced later by diffusion anorthite in 1623 8 is coarse grained but commonly has an irregular border with neighboring melilite crystals many spinel grains enclosed within anorthite have selvages of melilite around them which in places are continuous with melilite exterior to the anorthite the anorthite appears to be replacing melilite ion microprobe analyses of anorthite in 1623 8 show that there is no detectable excess 26mg in nine anorthite crystals that have 27 al 24 mg as high as 970 implying an upper limit of 26 al 27 al 0 7 one crystal was found that has excess 26mg consistent with 26 al 27 al 0 3 10 6 melilite in the outer portion of the inclusion 27 al 24 mg 2 7 11 5 contains excess 26mg that considered together with spinel and pyroxene defines an isochron consistent with the canonical early solar system value of 26 al 27 al 0 4 5 10 5 melilite near an anorthite 27 al 24 mg 1 6 5 9 has 26mg values in excess of those predicted from 26 al 27 al 0 4 5 10 5 presumably caused by redistribution of radiogenic 26mg from adjacent anorthite the high na2o inferred to have been present in the melt suggests that the precursor solids were na bearing such as for example refractory material having an allende like overprint of feldspathoid bearing secondary alteration the melting event must have been brief in order that not all of the na was vaporized during melting the isotopic composition of the anorthite relative to melilite indicates a subsequent much later after the decay of most or all 26a1 episode of partial melting or solidstate recrystallization that did not affect the al rich melilite but reset most of the anorthite and some mg rich melilite near anorthite because the inclusion is both rimmed and slightly altered this late resetting event appears to have been a nebular one an assumption of homogeneously distributed 26a1 in the regions of the nebula where the inclusion formed and was later modified implies a several millionyear interval between condensation of the precursors and final melting of 1623 8

active geologic processes in barrow canyon northeast chukchi sea abstract circulation patterns on the shelf and at the shelf break appear to dominate the barrow canyon system the canyon s shelf portion underlies and is maintained by the alaska coastal current a c c which flows northeastward along the coast toward the northeast corner of the broad chukchi sea offshelf and onshelf advective processes are indicated by oceanographic measurements of other workers these advective processes may play an important role in the production of bedforms that are found near the canyon head as well as in processes of erosion or non deposition in the deeper canyon itself coarse sediments recovered from the canyon axis at 400 to 570 m indicate that there is presently significant flow along the canyon the canyon hooks left at a point north of point barrow where the a c c loses its coastal constriction the left hook as well as preferential west wall erosion continues down to the abyssal plain of the canada basin at 3800 m a possible explanation for the preferential west wall erosion along the canyon at least for the upper few hundred meters is that the occasional upwelling events which cause nutrient rich water to flow along the west wall would in turn cause larger populations of burrowing organisms to live there than on the east wall and that these organisms cause high rates of bioerosion this hypothesis assumes that the dominant factor in the canyon s erosion is biological activity not current velocity sedimentary bedforms consisting of waves and furrows are formed in soft mud in a region on the shelf west of the canyon head their presence there perhaps reflects a the supply of fine suspended sediments delivered by the a c c from sources to the south probably the yukon and other rivers draining northwestern alaska and b the westward transport of these suspended sediments by the prevailing beaufort gyre which flows along the outer shelf

bathymetry and sediment dispersal dynamics along the yallahs fan delta front jamaica abstract the shallow offshore yallahs fan delta serves as a model for the interaction of littoral processes and bathymetry and how they influence sedimentation on steep submarine slopes and in deep marine basins in tectonically active areas bottom reflection profiles show that the yallahs delta front is characterized by two bathymetric zones a narrow island shelf and a steep slope dissected by the heads of at least three submarine canyons the refraction and diffraction of waves across these canyons and shelf control sediment distribution and the alternation of erosional and depositional beaches a dominantly westward longshore drift transports coarse grained sediments until they are trapped in the heads of the submarine canyons or temporarily stored on steep unstable slopes between the canyons mass gravity processes presumably move these sediments downslope where they are deposited as turbidites in the yallahs basin and out onto the colombian abyssal plain

eocene fan delta submarine fan deposition in the wagwater trough east central jamaica the wagwater trough is a fault bounded basin which cuts across east central jamaica the basin formed during the late palaeocene or early eocene and the earliest sediments deposited in the trough were the wagwater and richmond formations of the wagwater group these formations are composed of up to 7000 m of conglomerates sandstones and shales six facies have been recognized in the wagwater group facies i unfossiliferous massive conglomerates facies ii channelized non marine conglomerates sandstones and shales facies iii interbedded fossiliferous conglomerates and sandstones facies iv fossiliferous muddy conglomerates facies v channelized marine conglomerates sandstones and shales and facies vi thin bedded sheet sandstones and shales the wagwater and richmond formations are interpreted as fan delta submarine fan deposits facies associations suggest that humid region fan deltas prograded into the basin from the adjacent highlands and discharged very coarse sediments on to a steep submarine slope at the coast waves reworked the braided fluvial deposits of the subaerial fan delta into coarse sand and gravel beaches sediments deposited on the delta front slope were frequently remobilized and moved downslope as slumps debris flows and turbidity currents at the slope basin break submarine fans were deposited the submarine fans are characterized by coarse inner and mid fan deposits which grade laterally into thin bedded turbidites of the outer fan and basin floor

tectonics and sedimentation in the gulf of corinth and the zakynthos and kefallinia channels western greece abstract single channel seismic reflection profiling data are presented from the gulf of corinth and from the continental margin outside the gulf of patras different tectonic styles are exhibited in the two regions the gulf of corinth is occupied by a complex asymmetrical graben structure with major faults trending nearly perpendicular to the local tectonic zones of the internal hellenides the gulf is interpreted to have formed during the quaternary in response to approximately north south extensional stress the deep floor of the gulf is underlain by a sequence of turbidites up to 1 km thick affected by normal growth faulting that extends up to the sea floor the sea areas inside the ionian islands of zakynthos and kefallinia zakynthos and kefallinia channels occupy a broad structural depression that trends parallel to the local tectonic zones of the external hellenides and is situated on the continental side of the strophades continental margin rise the channels contain local nw se trending structural basins zakynthos and kefallinia basins whose geometry is controlled by reverse faults or thrusts with associated diapirism in triassic evaporites hydra bank is interpreted as a tilted fault block with a diapiric core and its faulted western margin can be traced into the zone of thrusting and diapirism in southeast kefallinia at the boundary between the ionian and pre apulian paxos zones of the external hellinides the zakynthos and kefallinia structural basins are filled with a variety of sediments including prodeltaic deposits in front of the modern delta complex of the acheloos river slumped masses and debris flow deposits and in the zakynthos basin occasional turbidites the boundary separating zones of extensional and compressional focal mechanisms for shallow earthquakes crosses the gulf of patras the inner part of which exhibits wnw ese trending graben tectonics apparently related to the gulf of corinth tectonic province onshore neotectonic studies around the gulf of patras are required in order to understand the nature and cause of the westward tectonic transition from wnw ese graben structures in the gulfs of corinth and patras to nw se oriented zones of subsidence with associated compressional tectonics and diapirism in the zakynthos and kefallinia channels

interplay between river discharge and topography of the basin floor in a hyperpycnal lacustrine delta basin floor topography influences the flow path of hyperpycnal plumes and delta morphology during progradation of the red river delta in lake texoma usa the red river discharge is typically a hyperpycnal plume due to elevated total dissolved solids because the river plume is a bottom hugging hyperpycnal flow lake bathymetry and topography strongly influence deposition and subsequent delta morphology in addition to elevated total dissolved solid concentrations compared with lake texoma water the density contrast of the red river outflow is increased by high suspended sediment concentrations during high discharge events steep lateral slopes in the lake texoma basin deflect hyperpycnal river plumes and subsequently change the delta progradation direction before the delta reaches the opposite bank of the lake analysis of multi temporal aerial and satellite images indicates that the hyperpycnal delta follows the steepest lake bottom gradients corresponding to the pre impoundment river thalweg i e bypassing shallow parts of the lake an analytical model for the hyperpycnal plume trajectory indicates plume deflection during low discharge or high discharge events towards the deepest part of the basin the magnitude of plume deflection is a function of river discharge and basin margin gradients plume deflection can vary between 10 and 80 from the channel axis towards the old river thalweg the high deflection appears in the case of maximum basin side gradients of 12 8 and in conditions of low river discharge during low discharge periods the red river delta builds a lobate shape with multiple terminal distributary channels whereas during high discharge periods the red river delta builds an elongate shape with a single large distributary channel the elongate morphology of the delta is formed through the development of a single distributary channel and abandonment of the other distributaries therefore the lobate shaped delta is expected to be preserved in the rock record

dispersion of bauxitic red mud in the gulf of corinth greece abstract bauxitic red mud slurry discharged by an aluminium processing factory on the shelf of the gulf of corinth greece is used as a tracer to examine sediment transport and dispersion processes in a tectonically active deep basin the gulf of corinth is a silled elongate basin with a maximum depth of 860 m it is characterised by high seismicity the red mud is discharged through a pipeline at a depth of 100 m where it forms an extensive deposit grab sampling has shown that the red mud extends over the slope and the abyssal plain up to a distance of 17 km from the mouth of the pipeline it forms small scattered sheet like deposits of up to 3 cm in thickness the structures observed in the scattered patches of the red mud which in some places are overlain by a thin veneer of grey olive green natural sediments suggest that the red mud is transported from the shelf to the abyssal plain by gravitative sediment flows the flows are triggered by earthquakes granulometric and geochemical analyses of the red mud samples show that the red mud during its transport from the shelf to the abyssal plain is subjected to mixing with the surrounding sediments a different mixing ratio is determined however by reference to the various trace metals fe ni co pb

morphology and sedimentology of two contemporary fan deltas on the southeastern baja california peninsula mexico abstract the san juan de los planes drainage basin is located on the southeastern margin of the baja california peninsula approximately 20 km southeast of the city of la paz pleistocene alluvial fans have been built into the basin from the surrounding areas of high relief and are presently being eroded at the fan apex the dissection depth ranges from 20 to 40 m and is 6 to 15 m at the coast the sediments have been redeposited in several active modern fan deltas built out into the narrow shelf of la ventana bay shelf width ranges from 0 to 5 km average 3 km wave energy is delivered from southeasterly storms and from the local sea breeze winds the respective wave heights average 2 and 1 m the agua caliente and las canoas fan deltas the subjects of this paper are located on the active el sargento fault zone and are fed by channels that deeply dissect the older fan surfaces the agua caliente fan delta is a classic gilbert type delta with a steeply inclined delta front wave reworking and redistribution of the sediments at the delta face are important and a wave cut terrace has developed at about 6 m depth the las canoas fan delta is a shoal water profile hjulstrom type with a gently inclined delta front wave energy is less important the alignments of the coasts of both fans are controlled by the fault line sediment supply is largest for the las canoas fan delta the fan deltas are examples of this depositional form as it has developed in an arid tectonically active high relief and narrow neo trailing edge margin

the seismicity geomorphology and structural evolution of the corinth area of greece in the eastern gulf of corinth geological structure is closely reflected in the topography in the 1981 corinth earthquakes ground deformation accentuated existing geomorphological patterns we explore the relationship between seismicity and landforms in space and time the area examined extends beyond the epicentral region of the 1981 events and its evolution is traced over the last 40000 years to understand the relation between deep and superficial structures we discuss processes that occurred in the 1981 earthquakes and go on to propose that surface faulting appears only above linear faults at depth that move in earthquakes with magnitudes m s greater than six where faults at depth intersect or bend the faulting becomes distributed and prim ary faulting does not reach the surface here the surface manifestation of faulting at depth is surface folding and secondary faulting such regions are identified in maps of the eastern gulf of corinth evidence for the evolution of the fault systems is provided by eyewitness accounts of shoreline changes following the recent earthquakes historical and archaeological data pertaining to old sea levels and 14 c dates for molluscs collected from fossil shorelines the results of these studies broadly confirm an earlier view of j a jackson et al earth planet sci lett 57 377 397 1982 that motion has shifted from faulting south of the city of corinth to faulting in the perachora peninsula but the transfer is not complete areas lying between the two fault systems have moved up and down in historical and archaeological times indicating that both systems are still active the evidence for activity of the northern system points to a repeat time of 300 years for earthquakes com parable with those of 1981 the work discussed in this paper suggests that some of the features previously described as m arine terraces are fault controlled continental surfaces furtherm ore beach deposits at a num ber of different levels long regarded as successive shorelines are in fact contemporaneous the critical ages were obtained by radiocarbon dating of shell carbonate a technique which yields dependable results if applied to samples which have been carefully selected and pretreated palaeontological dating of the terraces in contrast is found to be misleading because the faunas are environm entally controlled and consequently diachronous

sediment transport processes on an active submarine fault escarpment gulf of corinth greece abstract sediment transport processes on the escarpment of a listric fault in the tectonically active and terrigenous sediment dominated corinth graben in greece are studied using 3 5 khz and airgun profiles and sidescan sonar images the whole of the slope area is affected by gravitational mass movements slumps debris mud flows and liquified and turbidity flows in canyon fan systems large volumes of sediment are transported through slumping debris mud and turbidity flows into the basin here they build coalescing fans which consist of intercalations of debris flow deposits and turbidites in delta front slope fan apron systems sediments are transported radially downslope through slumping debris mud flows liquified flows and high density turbidity flows into the basin where they build coalescing fan aprons these consist of massive homogenized deposits fluxoturbidites in shelf slope systems retrogressive rotational slumping is the dominant instability feature however due to the sharp increase in the slope gradient caused by the slumping debris and turbidity flows are triggered the major factors responsible for triggering gravitational mass movements in the region are earthquakes high sedimentation rates off the river mouths and heavy rainfalls and high seas these mass movements appear to occur at least once every 2 yrs as indicated by the failure of submarine cables

morphology of a submarine slide kitimat arm british columbia a digitally acquired scale corrected side scan sonar survey yielded high resolution imagery of a submarine landslide in british columbia the landslide in a fjord head setting at kitimat was last active in 1975 and created a wide area of deformed sea floor the sediment failure involved shallow rotational movements on the slopes of a fjord head delta marginal tearing translational sliding compressional folding and block gliding of fjord bottom marine clays the slide is shallow and elongate and appears to have been produced by failure in mobile low strength sediments

crystal chemical effects on the partitioning of trace elements between mineral and melt an experimental study of melilite with applications to refractory inclusions from carbonaceous chondrites the partitioning behavior of the trace elements be sc ba la ce and tm between melilite and liquid has been determined using stepwise integration of a rayleigh fractionation equation for ion microprobe analyses of synthetic zoned melilite crystals distribution coefficients between melilite and liquid d mel l i were determined over the entire range of melilite spinel crystallization for one bulk composition corresponding to that of an average type b inclusion from the allende c3v carbonaceous chondrite beryllium is incompatible in gehlenitic meliliters e g d mel l b e 0 5 for x ak 0 3 but compatible in akermanitic melilites e g d mel l b e 1 9 for x ak 0 75 barium d mel l b a 0 04 0 05 sc d mel l s c 0 01 0 02 la d mel l l 0 07 0 29 ce d mel l c e 0 05 0 21 and tm d mel l t m 0 03 0 14 are all incompatible in melilites in the range ak25 ak75 variations in d mel l i as a function of x ak are explicable in terms of a simple thermodynamic treatment of trace element partitioning based on crystal chemical considerations characteristic trace element zoning patterns are predicted for early crystallizing melilite from meliliterich type b inclusions for example concentrations of the rees in melilite should continually decrease with increasing degrees of crystallization opposite the behavior normally expected of an incompatible element concentrations of be should rise with increasing degrees of crystallization even when the element is compatible again opposite the behavior normally expected of compatible elements in general zoning patterns of trace elements in melilite from type b inclusions are consistent with those predicted for fractional crystallization from a melt in a closed system trace element zoning patterns in meteoritic melilite crystals constrain the origin and thermal histories of ca al rich inclusions from carbonaceous chondrites

morphological analysis of olivine grains annealed in an iron nickel matrix experimental constraints on the origin of pallasites and on the thermal history of their parent bodies two types of pallasites can be distinguished on the basis of the grain shape of olivine rounded or angular it has been suggested that these two types of textures resulted from different degrees of annealing at high temperature in the parent body in order to characterize the kinetics of rounding of olivine grains in an fe ni matrix we carried out a series of annealing experiments using a mixture of olivine and fe ni powder we were able to reproduce at a miniature scale the range of textures in pallasites the rate of rounding was rapid enough to be observed and measured at the scale of a few micrometers to 20 m even though the experiments were performed below the solidus of the fe ni metal for instance grains 14 m in diameter became nearly spherical within 7 days at 1400 oc for the morphological analysis of olivine grains we used two independent techniques the critical diameter method and the gaussian diffusion resample method a new technique specially developed for our study both techniques indicate that the rounding time scale is proportional to the cube of the grain size and that morphological adjustments in our experiments occurred by volume diffusion in the olivine lattice not by surface diffusion along the olivine metal boundaries we used our experimental data to estimate the time scales required for the development of olivine metal textures in natural pallasites we determined that small scale rounding of olivine grains in a solid metal matrix can be produced within relatively short time intervals 100 years to produce rounded olivine grains 0 1 mm in radius at 1300 1400oc

the cosmochemical behavior of beryllium and boron abstract the chemistry of be and b in the solar nebula is reinvestigated using thermodynamic equilibrium calculations the dominant be gases are monatomic be at high temperatures and the hydroxides beoh and be oh 2 at lower temperatures beryllium condenses as gugiaite ca 2 besi 2 o 7 in solid solution with melilite with a 50 condensation temperature of 1490 k if an ideal solid solution of chrysoberyl beal 2 o 4 into spinel is assumed most of the be condenses into spinel yielding a 50 condensation temperature of 1501 k however the difference in the crystal structures of spinel and chrysoberyl indicates that their solid solution may be non ideal at high temperatures the dominant b gases are bo hbo and hbo 2 while nabo 2 kbo 2 and libo 2 are dominant at lower temperatures boron is less refractory than be and is calculated to condense into solid solution with feldspar the majority of b condenses as danburite cab 2 si 2 o 8 in solid solution with anorthite at lower temperatures when the feldspar composition is more albitic the remaining b condenses as reedmergnerite nabsi 3 o 8 the 50 condensation temperature of b is 964 k the 50 condensation temperature of b is similar to that of na and much higher than that of s therefore normalized b abundances in chondrites are expected to correlate with na abundances be is predicted to be concentrated in melilite a conclusion which is consistent with the few measurements of be concentrations in calcium aluminum rich inclusions cais boron is predicted to be concentrated in feldspar but no analytical data are available to test this prediction

surface sediments and macrofaunas of the crati submarine fan ionian sea italy abstract five dredge samples 8 grab samples and 18 light gravity cores from the fan delta fed crati submarine fan indicate that the surface cover of the fan is mud dominated comprising muddy turbidites thin bedded silty sandy turbidites and prodelta muds this high mud content does not reflect an abandonment phase of the fan but is the product both of the composition of the sediment load discharged by the crati river and of the littoral processes affecting the constline of the crati fan delta a predominantly northward longshore drift catches most of the coarse bed load and redistributes it along the actively prograding beaches of the fan delta the whole mud reaches the submarine basin via turbidity currents and surficial turbid plumes the biogenic fraction represented by mollusca and benthic foraminifera is scarce because of the high terrigenous input in situ mollusc assemblages which occur only outside the channellized areas vary significantly in composition between the different depositional environments of the fan there is a much higher proportion of filter feeding species in depositional areas more affected by the flow of turbidity currents lobes levees

geomorphology and sedimentary processes of a modern slope type fan delta fujikawa fan delta suruga trough japan abstract the fujikawa fan delta is a slope type fan delta developed on the arc arc collision boundary between the izu bonin and honshu arcs in the east asian monsoon related humid temperature climate region it comprises a stream dominated alluvial fan and a large subaqueous portion that progrades into deep water 1300 m in water depth based on a detailed subaqueous morphology obtained from remote sensing imagery including izanagi deep towing side scan sonar and deep towing video camera images the subaqueous portion is subdivided into delta front upper slope lower slope and prodelta the lower slope comprising three elongate convex upward bulges occupies the largest portion and is the main sedimentation site in the fujikawa fan delta a single feeder channel or canyon is absent instead numerous chutes are developed along the length of the bulge related to the diversion of the river course on the alluvial fan the elongate subaqueous bulge fed directly to the river is formed then switched hence the subaqueous fan shape of the fujikawa fan delta is mainly controlled by the pre existing basin topography and the diversion pattern of the river course on the alluvial fan

the composition and early evolution of earth a weighted average composition is suggestd as the best bulk silicate earth bbse bbse thought to represent earth s primitive mantle modern mantle crust is a concept based on analyses of oceanic theoleiites and continental flood basalts oceanic and continental alkali basalts ultramafic ophiolites archean komatiites and spinel and garnet bearing xenoliths from basalts and kimberlites bbse shows the combined effects of core formation and volatility presumably including condensation and sublimation in the solar nebula and volatile loss during the accretion and early evolution of earth the abundances of volatile lithophile elements show a volatility trend vt when plotted against condensation temperature the slope of vt suggests that earth accreted matter that had condensed over a wide range of temperatures consistent with planet formation scenarios of g w wetherill 1988 mercury pp 670 691 univ of arizona press tucson 1990 annu rev earth planet sci 18 205 256 using vt bbse and long standing seismic constraints we infer the composition of the entire earth and its core the bulk earth s vt closely resembles the average composition of h chondrites h3 h6 the 10 most abundant elements in the core nominally include 85 55 mass fe 5 18 o 4 88 ni 2 69 s 0 45 cr 0 41 mn 0 35 p 0 22 co 0 07 cl and possibly 0 02 k the core may contain most of earth s heavy alkali and halogen elements in addition to chalcophiles and siderophiles alternatively depletions of alkali halide components in bbse may have resulted from impact blow off of an early saline ocean it is unclear whether the core contains a significant fraction of earth s k and pb possible partitioning of substantial quantities of o rb and cs into the core and the partitioning behavior of fourth period transition metals suggests that metal silicate equilibration occurred at characteristic pressures of several hundred kilobars or more if correct this implies core formation during or after accretion of earth rather than during the planetesimal stage the inferred partitioning between core and primitive mantle reflects periodic elemental properties such as covalent radius elements that possess covalent radii similar to those of iron are most strongly partitioned into the core the periodic nature of inferred core mantle partioning conflicts with models involving simple addition of siderophile elements and volatiles in a late chondritic veneer however this aspect is in accord with conceptual models involving an approach toward equilibrium partitioning during core formation in one model equilibrium melting and segregation of metal occurs continuously over a range of interior pressures and temperatures as fresh material accretes and mixes into earth bbse may reflect retention of a small amount of the last dregs of metal whose composition was controlled by this dynamic equilibrium

the upper jurassic boulder beds and related deposits a fault controlled submarine slope ne scotland during the late jurassic kimmeridgian rifting in the north sea large scale normal faults developed to form relatively deep marine basins the north western margin of one of these basins defined by the helmsdale fault is described to show the nature of sedimentation associated with a submarine fault scarp subsidence to the se of the helmsdale fault led to a fault scarp down which various sediment mass flows moved including debris flow rockfall high and low concentration turbidity currents and possible storm surge wash over deposits redeposition by soft sediment sliding was important as a slope accretion process deep channels were incised into the slope and infilled by coarse grained elastics contemporaneous small scale submarine fans located farther off in the present north sea may have developed as a result of slope bypassing sediment flows down such channels the succession is characterized by extreme sediment heterogeneity compared to many deep water environments and it may be part of an ancient fan delta the main influences upon slope accretion were the synsedimentary movements on the helmsdale fault and the nature of the available sediment input such that the succession represents structurally controlled and sedimentologically modified slope development

beryllium boron and aluminum magnesium chronology of calcium aluminum rich inclusions in cv chondrites we have made be b measurements in six calcium aluminum rich inclusions cais mostly type b inclusions from cv chondrites and compared them to al mg measurements all cais show 10b excesses in melilite that are correlated with be b ratios the initial 10be 9be ratio inferred from the correlation line is 6 2 times 10 4 in contrast to the be b system in melilite the al mg system in anorthite is disturbed this is probably due to b diffusion in melilite being slow compared with mg diffusion in anorthite this suggests that be b chronology may be useful for measuring time differences of high temperature melting condensation etc events in the early solar system

segregation of core melts by permeable flow in the lower mantle we measured the dihedral angle of molten iron in mg fe sio3 perovskite aggregate with increasing pressure and temperature using laser heated diamond anvil cell results demonstrate that it decreases from 94 at 27 gpa and 2400 k to 51 at 47 gpa and 3000 k this value is smaller than the critical angle of 60 thus allowing iron melt to wet the grain boundaries of silicate perovskite and develop an interconnected melt network within the perovskite dominant matrix even at very small melt fractions the quenched liquid iron contained substantial amounts of oxygen and silicon as pressure and temperature increase such a decrease in the dihedral angle is likely due to a reduction in the iron perovskite interfacial energy by dissolving oxygen and silicon into the liquid iron from coexisting silicate perovskite these suggest that a wetting behaviour of core melts in the solid silicate mantle changes above 40 gpa corresponding to 1000 km depth in the present earth and efficient metal segregation may have proceeded by permeable flow in a late stage of accretion oxygen and silicon incorporated during core formation and later by core mantle boundary process may be important light elements in the earth s core

rounded mineral inclusions in upper mantle peridotite abstract mantle derived peridotite xenoliths contain abundant olivine with rounded spinel and orthopyroxene inclusions and orthopyroxene with rounded olivine and spinel inclusions the shape change of spinel olivine and orthopyroxene inclusions from the primarily polyhedral outline to the spherical outline is governed by interfacial diffusion of oxygen in spinel the most sluggish atom due to reduction of total interfacial energy of the host inclusion system the critical radius of maximum rounded inclusions of spinel in olivine is a function of temperature and annealing time assuming that the activation energy for the interfacial diffusion is 40 70 kcal mol 1 and that the annealing time for the spinel lherzolite from salt lake crater in hawaii is 100 ma the annealing times for perioditites under the island arcs of japan are estimated to be 1 10 ma

suturing history of an allochthonous terrane at a modern plate boundary traced by flysch to molasse facies transitions abstract the southern boundary of the south bismarck plate in papua new guinea changes character from west to east as a consequence of oblique collision and suturing of the allochthonous finisterre terrane with the margin of the australian continent and plate plate rearrangements are occurring and a triple junction is migrating eastwards along the plate boundary characterization of modern sedimentary facies leads to the following correlations between facies and tectonic settings tectonic setting sector of plate boundary facies terrane already docked markham valley fluvial molasse terrane now docking huon gulf marine molasse terrane yet to dock western new britain trench conglomeratic flysch these relationships provide the basis for a tectonic depositional model showing the distribution and relationships between facies in time distance space along the plate boundary facies transitions are time transgressive and their trajectories provide a measure of the rate of triple junction migration rapid uplift of the southern margin of the south bismarck plate has exposed older sediments related to this history of terrane suturing their facies characterization provides support for the model but age control is insufficient for conclusive demonstration of its validity

beryllium mineral evolution beryllium is a quintessential upper crustal element being enriched in the upper crust by a factor of 30 relative to primitive mantle 2 1 vs 0 07 ppm most of the 112 minerals with be as an essential element are found in granitic pegmatites and alkalic rocks or in hydrothermal deposits associated with volcanic and shallow level plutonic rocks and skarns because of the extensive differentiation needed to enrich rocks sufficiently in beryllium for beryllium minerals to form these minerals are relative latecomers in the geologic record the oldest known is beryl in pegmatites associated with the sinceni pluton swaziland 3000 ma in general beryllium mineral diversity reflects the diversity in the chemical elements available for incorporation in the minerals and increases with the passage of geologic time furthermore the increase is episodic that is steep increases at specific times are separated by longer time intervals with little or no increase in diversity nonetheless a closer examination of the record suggests that at about 1700 ma the rate of increase in diversity decreases and eventually levels off at 35 species formed in a given 50 ma time interval between 1125 and 475 ma then increases to 39 species at 125 ma except for four spikes before dropping off to 30 species for the last 100 ma these features appear to reflect several trends at work 1 diversifications at 2475 1775 and 525 ma which are associated with highly fractionated rare element granitic pegmatites and with skarns at langban and similar deposits in the bergslagen ore region of central sweden and which are inferred to correspond to the collisional phases of the supercontinents kenorland nuna and gondwana respectively 2 diversification at 1175 ma due to the rich assemblage of beryllium minerals in the ilimaussaq peralkaline complex gardar province west greenland in an extensional environment 3 diversification at 275 ma which is largely attributable to granitic pegmatites appalachian mountains u s a and urals russia and the larvik alkalic complex norway but nonetheless related to continental collision and 4 limited exhumation of environments where beryllium minerals could have formed in the last 100 ma that the maximum diversity of be minerals in any one geologic environment could be finite is suggested by the marked slowing of the increase in the number of species formed in a given 50 ma time interval whereas the drop off at 100 ma could be due to 100 myr being too short a time interval to exhume the deep seated occurrences where many be minerals had formed the relative roles of chance vs necessity in complex evolving systems has been a matter of considerable debate one equally applicable to what extent the temporal distribution of beryllium minerals is a matter of contingency on the one hand the appearance of the most abundant be minerals such as beryl and phenakite early in the history of be mineralization appears to be a deterministic aspect since these minerals only require the abundant cations al and si and crystallize at relatively low concentrations of be in aqueous solution or granitic magmas on the other hand it could be argued that the very existence of most other be minerals as well as the temporal sequence of their appearance is a matter of chance since 55 of the 112 approved be minerals are known from a single locality and many of these phases require an unusual combination of relatively rare elements consequently we cannot exclude the possibility that other equally rare and thus contingent potential be minerals await discovery in as yet unexposed subsurface deposits on earth and we suggest that details of be mineral evolution on other earth like planets could differ significantly from those on earth

mechanisms of sediment transport and dispersion in a tectonically active submarine valley canyon system zakynthos straits nw hellenic trench abstract physical oceanographic and geophysical data sets are used to examine sediment transport processes currents were directed generally along the axis of the valley canyon system and in an area of low tidal range are attributed to regional weather patterns near bed and near surface currents are opposed both in terms of instantaneous observations and net lagrangian drift near bed down canyon water movement provides a mechanism for the offshore movement of fine grained sediment slope failures have been identified in the geophysical records and are considered to be controlled by earthquakes and salt diapirism in a tectonically active area these failures as mass displacement or slow down slope creep result in debris infill and the generation of turbidity currents fine grained sediments resuspended by the turbidity currents would be transported down canyon by the slowly moving near bed residual water movement hence the dominant transport mechanisms in the valley canyon system are 1 frequent mass sediment failure and 2 nearly continuous down channel fine grained suspended sediment movement