2 d tomographic imaging of velocities in the wichita uplift anadarko basin region of southwestern oklahoma in january of 1985 a densely recorded wide aperture seismic experiment was performed by the university of texas at el paso and at dallas across the southwestern oklahoma aulacogen a two dimensional p wave velocity distribution is estimated for the wichita uplift the anadarko basin and the interface between them by iterative tomographic imaging of travel time picks from seven shots located near the 100 km long recording line the region that is imaged is roughly triangular in shape with depth 0 km at the ends of line and 15 km near its center the main features that are revealed are a high velocity 6 8 km sec central core in the wichita uplift and an asymmetrical anadarko basin with decreasing velocities toward the basin axis there are indications within the uplift of local high velocity sills and a local low velocity region that may be a remnant of normal crustal material

models for midcontinent tectonism an update during the past decade significant progress has been made in defining the nature of midcontinent tectonism as a result of an improved geophysical geologic data base which permits an integration of seismicity data crustal structures and current stress directions critically placed microseismic networks have shown that many earthquakes with common focal mechanisms occur in specific spatial patterns the direction of the maximum horizontal compressive stress is generally directed east northeast which supports an origin associated with ridge push forces related to movement of the north american plate crustal structures have been mapped locally by seismic studies and regionally by extensive gravity and magnetic anomaly data these data have been used to relate current seismicity and associated tectonism to one of two models increasing evidence from across the midcontinent supports reactivation of preexisting zones of crustal weakness appropriately oriented with respect to the prevailing stress field the zone of weakness model as the dominant control on contemporary tectonism and the local basement inhomogeneity model as a mechanism for minor low energy release earthquake activity

historical evolution and extreme climate events during the last 400years on the rhone prodelta nw mediterranean abstract the rhone river is the most important source of freshwater and sediment to the western mediterranean sea deltaic lobes and littoral prisms compose the sedimentary units that make up the whole rhone subaqueous delta which reaches up to 50 m in thickness individual lobes that accompanied the retreat of the rhone during sea level rise and the subsequent westward then eastward shift of the main outlet display averaged sedimentation rates in excess of 1 cm yr 1 containing both continental and marine material during the industrial period most of the river flow was delivered through the pegoulier and roustan distributary channels which evolved under human influence within the prodeltas associated to these distributaries very expanded sedimentation rates 10 cm yr 1 allow the documentation of historical extreme climate events a 7 71 m long piston core rhs ks57 was retrieved from the distal prodelta 79 m water depth a multi proxy study was carried out using microfossil assemblages ostracods benthic foraminifera and coccoliths in combination with sedimentological and geochemical proxies our results show that 1 four different intervals i iv spanning a time range comprised between 1600 ad and present day have been differentiated from this multi proxy analysis they correspond to a different position of distributary channels each interval correlates with the different phases of channel avulsion induced by climate events or by human activity 2 the signature of extreme floods that can be identified by the punctuated occurrence of freshwater continental ostracods e g candona spp ilyocypris sp correlating with increases in grain size and or organic carbon content they correspond to decadal scale increased runoffs reported in historical archives our study demonstrates the relevance of benthic microfossil studies for reconstructing paleoenvironmental changes in transitional marine continental settings

chromium and nickel as indicators of source to sink sediment transfer in a holocene alluvial and coastal system po plain italy abstract a reliable quantitative estimate of changes in source to sink sediment transfer requires that high resolution stratigraphic studies be coupled with accurate reconstructions of spatial and temporal variability of the sediment routing system through time source to sink patterns from the contributing upland river catchments to the deltaic and coastal system are reconstructed from the holocene succession of the po plain on the basis of selected geochemical indicators sediment supplied to the delta area by the major trunk river the po exhibits naturally high cr and ni values which invariably exceed the maximum permissible concentrations for unpolluted sites this anomaly reflects remarkable sediment contribution from ultramafic ophiolitic parent rocks cropping out in the po drainage basin western alps and nw apennines in contrast alluvial and coastal plain deposits supplied by ophiolite free apenninic catchments invariably display lower cr and ni contents for constant sediment provenance domain cr and ni distribution is observed to be controlled primarily by hydraulic sorting clay silt deposits floodplain swamp and lagoon bay facies associations invariably show higher metal concentrations than their sandy counterparts fluvial channel distributary channel and beach ridge facies associations from a stratigraphic perspective in sedimentary basins characterized by strong differences in sediment composition geochemical fingerprinting of individual facies associations framed by surfaces of chronostratigraphic significance is proposed as an invaluable approach towards an accurate quantitative assessment of sediment storage in alluvial and coastal depositional systems as opposed to volumetric reconstructions based on lithologic or geometric criteria alone

wave field processing of data from a large aperture seismic experiment in southwestern oklahoma data from a wide aperture survey performed in january 1985 in southwestern oklahoma have been processed using prestack imaging and the images are interpreted to reveal a new picture of the crustal structure in the wichita uplift and the anadarko basin as the data were in recording apertures of approximately 90 km it was necessary to develop new processing concepts and software a complete new imaging system based on common source gathers was conceived implemented tested and applied to these data the heart of the system consists of velocity estimation by slant stacking and acoustic prestack reverse time finite difference migration the migration produces reflectivity images in regions of 50 km 100 km has no dip restrictions and operates in an arbitrarily complicated two dimensional velocity distribution for comparison the data were also processed using standard common midpoint processing but this is a less valid approach for wide aperture data the main ambiguities and limitations in processing and interpretation are a consequence of the small number of shots processing and interpretation of the data provide a new picture of the subsurface structure of southwestern oklahoma the environment is clearly compressive with thrust faulting as the main accommodating mechanism in the upper and central crust beneath a possible detachment zone at 30 km depth the lower crust has responded to the compression by thickening by 50 the moho is interpreted to be 45 km in depth beneath the thrust zone shallowing to 40 km beneath the wichita uplift and the anadarko basin

origin and accumulation of trace elements in sediments of the northwestern mediterranean margin continental margins receive natural and anthropogenic trace elements tes from direct atmospheric deposition of aerosols onto the sea surface and from advection of riverine suspended particles and or resuspended sediments from the continental shelf slope when the margin is incised by submarine canyons as for example in the northwestern mediterranean sea most of these particles are preferentially transferred via these topographic features towards their final repositories in the abyssal plain the gulf of lions gol shelf receives the largest particulate riverine input to the western mediterranean with its associated chemical contaminants originating from the industrialized and urbanized rhone valley sediments samples grabs cores and moored traps collected in the cap de creus cdc canyon and its adjacent areas at the southwestern exit of the gol were analyzed to explore the origin dispersion transfer and accumulation of a suite of tes ag cd co cr cu ni pb zn and v from the gol shelf to the adjacent continental rise distributions of cu cr ni pb zn and v in the surface sediments of the shelf confirm their terrigenous origin in association with clay minerals whereas ag and cd are more associated with organic matter om all these tes are anthropogenically enriched in the rhone prodelta sediments anthropogenic influence remains clearly discernible in the gol shelf surface sediments for ag pb and zn hydrodynamical resuspension and sorting of shelf sediments occur at the head of the cdc canyon during dense shelf water cascading events during these events the material collected in moored sediment traps contains a higher coarse carbonate fraction slightly impoverished in tes compared to the clays of the nepheloid layer and the organically rich particles deposited before and at the end of the cascading period upper and middle canyon sediments are characterized by high sedimentation rates 0 2 cm yr 1 of fine clay material conversely sediments from the lower continental slope and rise exhibit low sedimentation rates 0 06 cm yr 1 and receive carbonaceous planktonic detritus from the water column at the lower continental slope coarse material includes foraminifers and pteropods whereas at the continental rise finer planktonic derived material is more abundant both in the cdc canyon and in its adjacent lower continental slope rise sediments co cu cr ni and v are associated with clay whereas ag cu and pb are preferentially associated with om cadmium cr and zn are also associated with om in canyon sediments carbonaceous plankton appears to be especially efficient for scavenging ag

long term erosion of the tidal flats king sound north western australia abstract king sound in northwestern australia with a tropical semi arid climate is situated in a macrotidal tide dominated regime the shores of king sound are bordered by tidal flats that exhibit a considerable variation in geomorphology and stratigraphy erosion is the dominant geomorphic process forming the tidal flats today three types of erosion are important these are sheet cliff and tidal creek erosion tidal flat geomorphology at the local scale is an expression of which erosion type is dominant the geomorphology at regional scale is largely an expression of the extent that erosion has gone to completion in removing holocene pleistocene and bedrock stratigraphic units determination of erosion rates over the past few decades extrapolation of these rates into the past together with stratigraphic and diagenetic data point to a long term erosional history for king sound king sound itself appears to be formed largely as a result of long term lateral erosion

river channel changes in the rhone delta france since the end of the little ice age geomorphological adjustment to hydroclimatic change and natural resource management abstract this study provides a representative example of a river affected by artificial width contraction and consequent bed incision in a context of sea level rise geomorphological adjustment in the rhone catchment since the final stage of the little ice age has been induced by hydroclimatic change and human disturbances these adjustments are examined to highlight the response of two sand bed distributary channels of the rhone delta by using methods such as sedimentological evidence historical sources planimetric resurvey repeated longitudinal and cross profiling and hydraulic data the geomorphological and hydraulic responses to channel changes are characterised and their consequences assessed it is shown that the reduction of sediment yield is a combined effect of a decrease of flood frequency sediment dredging and building of dams on the rhone river and its tributaries the combination of decreased catchment sediment yield artificial width contraction increased stream power and boundary shear stress is the cause of channel incision of the rhone river in the coastal zone the increase of the rhone river s stream power has facilitated the transport of sediment down to the subdeltas engineering works designed to stabilise the planform and to limit overbank flooding caused 1 channel entrenchment thus 2 the destabilization of infrastructure e g bridges quays along the river 3 the lowering of the phreatic water table in the floodplain which in turn induced 4 soil salinization change in salt wedge position eventually the channelization led to 5 an increase of the flood hazard and risks because although more rare the inundations have become more destructive however the contribution of the large flood events is negligible in terms of progressive channel in filling because of their low frequency finally no relation exists between the vertical adjustment of the rhone channel through entrenchment and relative sea level which rose at a rate of up to 2 mm year 1 during the 20th century clearly natural resource management in particular engineering activities were the main cause of the river channel changes that occurred during the last century

sources and exchanges of mercury in the waters of the northwestern mediterranean margin abstract ocean margins are focal regions in terms of mercury hg exchanges between the continent and the open sea the aim of this paper is to describe the distribution and partition of hg between the gaseous dissolved and particulate phases in the waters of the northwestern mediterranean nwm margin in order to assess the hg sources and exchanges within the continuum between the continental shelf gulf of lions and the open sea northern gyre mean standard deviation of total hg species hgt concentrations in unfiltered water samples were 1 52 1 00 pmol l 1 n 36 in the inner shelf 1 09 0 15 pmol l 1 n 30 along the slope and 1 10 0 13 pmol l 1 n 99 in the northern gyre the dissolved phase the hg from the open sea water is the largest hg input to the gulf of lions 5 7 kmol yr 1 whereas inputs from the riverine source account for 3 4 kmol yr 1 and atmospheric deposition for less than 0 5 kmol yr 1 the hg accumulated in the sediments of the shelf is 4 5 kmol yr 1 including 0 6 1 7 kmol yr 1 in the rhone prodelta sediments the evasion to the atmosphere represents a hg flux of 2 6 kmol yr 1

how did the meers fault scarp form paleoearthquake or aseismic creep a soil mechanical perspective abstract studies confirm that the meers fault in southwestern oklahoma has been active in recent times the most recent movement occurred about 1100 y ago in late holocene there is as much as 5 m vertical and possibly appreciably more left lateral strike slip displacements on the fault during faulting the quaternary soils 1 along the fault were folded as well as ruptured in some places almost all of the deformation is accommodated by ductile folding of the soils having this kind of deformation with no record of an earthquake associated with the meers fault during historical times raises the question whether the present scarp was formed seismically by earthquake event s or aseismically by slow deformation aseismic fault creep to determine how the scarp was formed i have developed a multidisciplinary study which involved geological soil mechanical and soil micromorphological techniques geological mapping delineated the deformation stratigraphy and any features that might be associated with the faulting the mapping was also needed to reconstruct the sequence of events that formed the scarp at the study site consolidation tests using the casagrande 1936 method for finding maximum effective stresses were used to determine the states of stresses imposed on the soil deposits when they were first faulted these states of stresses were then compared to the states of stresses needed to slowly deform or shear the soils in triaxial and direct drained shear tests the direction of maximum principal stress was determined by mohr s circle and soil micromorphological analyses the results of soil mechanical analysis show that the faulting of the quaternary soils along the fault had to be sudden or fast which indicates that the scarp was probably created seismically during faulting the soils were anisotropically consolidated or compacted thereby recording in their structure the states of stresses that caused faulting to occur the direction of the maximum principal horizontal stress is between n62 e and n72 e indicating rotation of principal stress axes the technique developed for this study can be used in similar areas where active faults offset quaternary soils with relatively unchanging moisture contents below some depth also for shallow depths this technique might give more reliable young tectonic stress measurements both magnitude and orientation than other techniques such as overcoring hydraulic fracturing and wellbore breakouts because it is used on geologically recent units which unlike lithified rocks have not yet existed through millions of years of deformation

cocorp profiling across the southern oklahoma aulacogen overthrusting of the wichita mountains and compression within the anadarko basin cocorp consortium for continental reflection profiling deep reflection profiles recorded across the wichita mountains and anadarko basin suggest that significant crustal shortening occurred in the final stages of the evolution of the southern oklahoma aulacogen the crystalline rocks of the wichita mountains were thrust in pennsylvanian time northeastward over sedimentary rocks of the anadarko basin along a series of faults with moderate average 30 to 40 and southwesterly dips these faults can be traced possibly as deep as 20 to 24 km listric thrust faults and hanging wall anticlines developed in the sedimentary rocks of the basin these features contrast with conventional interpretations of pennsylvanian structures as the result of predominantly vertical movements along high angle faults and they suggest that pennsylvanian downwarping of the anadarko basin was at least partially due to thrust loading truncations of reflections from cambrian ordovician rocks in the deepest part of the basin suggest normal faulting which would support ideas of an early extensional stage in the aulacogen cycle the distinctive precambrian layering seen on earlier cocorp data recorded south of the wichita mountains cannot be recognized under the anadarko basin and the proterozoic basin containing that layering may have been bounded on its north side by a precambrian fault this inferred fault was probably twice reactivated during formation of the southern oklahoma aulacogen once during late precambrian early cambrian extension and again during pennsylvanian compression the popular view that aulacogens originated from radial rifting of updomed homogeneous continental crust is probably too simplified and a more important constraint on their location and development may be the nature of pre existing lines of weakness

timing and chemistry of igneous events associated with the southern oklahoma aulacogen abstract igneous activity in the southern oklahoma aulacogen of north america was concentrated in the early rifting stages of aulacogen development the time span over which liquids rose may not have exceeded 50 m y and certainly terminated before the upper cambrian igneous activity began with three basaltic liquids stratigraphically identifiable but perhaps not all distinct genetically this was followed by one large rhyolitic granitic episode of a type character one final basaltic event ended the activity all the basaltic types seem to be tholeiitic showing more kinship with either the older proterozoic north american midcontinental rift or the northern part of the cenozoic rio grande rift than the cenozoic east african rift two major uplifts occurred one between the earlier basalts and the rhyolite and one much later after all igneous activity was over in the pennsylvanian

heat flow and thermal history of the anadarko basin and the western oklahoma platform abstract the average geothermal gradient in the anadarko basin and the oklahoma platform estimated from 856 corrected bottom hole temperatures bhts is 21 c km analysis of previously published thermal maturation data indicates that the anadarko basin has undergone from 1 to 3 km of erosion starting about 40 to 50 ma the average thermal gradient at the time of maximum burial was in the range of 22 to 25 c km there is no evidence that the thermal state of the anadarko basin has changed significantly since the late paleozoic 250 ma to estimate heat flow in the anadarko basin and the oklahoma platform we made 652 thermal conductivity measurements on drill cuttings from 9 oil and gas wells all measurements were corrected for the effects of anisotropy temperature and porosity matrix conductivities perpendicular to bedding at 22 c range from 1 7 w m 1 k 1 for permian age sandstone and shale to 2 6 w m 1 k 1 for devonian silurian age limestone and shale in situ thermal conductivities vary from 1 3 w m 1 k 1 to 1 9 w m 1 k 1 estimated heat flow 20 ranges from 30 mw m2 to 42 mw m2 with a mean of 36 mw m2 we found no evidence for heat flow to increase significantly from the anadarko basin in the south to the oklahoma platform to the north these results contradict a previous study which found heat flow increases from south to north with heat flow in the oklahoma platform as much as 50 greater than heat flow in the anadarko basin at the present time we do not know if these differences are related to spatial variations or reflect methodological errors if our results are averaged with those reported in previous work mean heat flows in the anadarko basin and oklahoma platform are 39 mw m2 and 51 mw m2 respectively

thermal structure of the anadarko basin the anadarko basin of oklahoma is a two stage paleozoic cratonic basin with as much as 12 km 7 5 mi or more of sedimentary fill we present a present day thermal model of the basin based on lithologic analysis at 3 m 10 ft intervals in 63 wells heat flow measurements at seven sites and in situ thermal conductivity calibration of the sediment section at two sites we do not use bht bottom hole temperature information in the process but we do at the end of the process compare the independently predicted temperatures to bht information the in situ calibration of thermal conductivity was accomplished using detailed temperature logs and represents a new practical application for evaluating basin thermal characteristics shale exerts the most control on the temperature distribution because it is the most abundant lithology and has the lowest thermal conductivity shale comprises 47 by volume of rock in the basin and represents 75 of total thermal resistance directly related to temperature gradient therefore shale dominates the thermal structure of the basin thus the problems in sampling and in characterizing the in situ thermal conductivity of shale from laboratory measurements represent a major limitation in basin thermal analysis we use the in situ calibration approach as a way to address the difficulty the temperatures calculated do not mimic the structure of the sediments i e the hottest area on a given age horizon in the lower paleozoic is not in the most deeply buried part of the anadarko basin the combination of decreasing heat flow toward the wichita mountains and the facies changes in the pennsylvanian units from marine shale low thermal conductivity in the basin to the granite wash high thermal conductivity toward the uplift results in the highest temperatures being displaced about 50 km 31 mi northward into the basin the pattern of vitrinite reflectance in the woodford shale is virtually identical to the present day reconstructed temperature pattern therefore we conclude that the thermal pattern is and has been dominated by conductive heat transport

the geomorphic evolution and sediment balance of the lower rhone river southern france over the last 130 years hydropower dams versus other control factors article i nfo atthe end of thelittleice age lia agriculturalpractices and successive phasesof channel management involv ing embankments and dams however the respective roles of these various control factors in modifying sedi ment storage and channel stability are often difficult to identify the aim of this paper is to determine the main factors that have driven morphological changes over the past 130 years on the 120 km long downstream reach of the rhone river a gis based analysis of maps and aerial photographs available since 1860 coupled with chrono stratigraphic data on the river s alluvial deposits has enabled quantification of sediment storage and erosion in different morphological units changes measured include riverbed incision narrowing of the main channel in relation with accumulation of fine sediments along the channel margins and reduction of sed iment input at the mouth on the basis of local and reach scale sediment balances we show that these changes are synchronous with engineering works carried out at the end of the nineteenth century and beginning of the twentieth century a period that coincided with a decline in river sediment inputs largely generated by human activities the early stabilisation of mountain slopesresulting from a decline inrural agriculture rural exodus re forestation and engineered torrent control has had a much greater impact in geomorphically transforming the rhone than dams and gravel mining the major identified causes of river destabilisation in the world this calls for caution in the all too common and wholesale attribution of declining sediment budgets of european rivers

post depositional migration of elements during diagenesis in brown clay and turbidite sequences in the north east atlantic abstract two cores from a ne atlantic pelagic clay area of low accumulation rate each contain a single turbidite with different age thickness and composition diagenesis following introduction of exotic turbidite material into the pelagic clay sequence has resulted in distinctive colour changes the diagenetic process is thought to be driven by bacterially mediated organic oxidation and compositional differences in the turbidites and clays allow examination of the effects on metal concentrations of this process in one core a long turbidite section emplaced 330 000 years ago is overlain by clay organic oxidation has apparently proceeded from the turbidite top downwards and has maintained a u concentration peak below the oxidation front marked by a colour change the u source is believed to be u initially associated with the organic matter in the oxidised section of the turbidite vanadium and cu behave similarly but upward migration of the redox sensitive metals mn and ni is also seen in the second core an 8 cm turbidite section was emplaced about 170 000 years ago in a clay column in this case organic consumption now appears complete but evidence for diagenetic effects is found in a 16 cm compositional alteration halo of the underlying pelagic clay fe ii has been enriched and the hydrogenous component of mn co ni and cu removed from the pelagic clay to form the halo

shallow structure from a seismic reflection profile across the borah peak idaho fault scarp this is the publisher s version also available electronically from http onlinelibrary wiley com

a shallow seismic reflection survey in basalts of the snake river plain idaho the objective of this feasibility study was to determine if the seismic reflection method could help to optimize placement of water quality monitoring wells near a radioactive storage facility seismic reflections from depths less than 30 m were recorded along a 500 m long line over a basalt rhyolite and sedimentary sequence in the snake river plain some shallow reflections at 40 to 50 ms on the field files are of exceptional quality with frequency exceeding 150 hz reflections and refractions from selected seismograms along the line possess vastly different normal moveout nmo and apparent velocities as well as wavelet characteristics extreme variations in quality seismic character and reflector geometries observed on seismograms give the appearance of varying geologic settings and are uncommon for such short distances severe surgical muting was necessary for accurate velocity and statics analyses the seismic reflection data show apparent structural lows in a sedimentary layer sandwiched between

morphodynamics of a macrotidal beach abstract an intensive field investigation of hydrodynamic processes processes of sediment entrainment and suspension and morphologic change was carried out on an unprotected macrotidal beach near broome in northwestern australia the spring tide range was 9 5 m waves had heights of 0 5 1 2 m and periods of 9 13 s the beach had an overall concave upward profile with low gradient and dissipative subtidal and low tidal zones and steeper more reflective mid tidal and high tidal zones direct measurement of energy flux dissipation over the intertidal profile showed dissipation rates on the order of 1 2 w m 2 of bed and indicated an approximate balance between shoaling and dissipation of unbroken waves so as to maintain a constant wave height time averaged predictive estimates of wave work over the lunar half cycle for different points on the intertidal profile show similar dissipation rates and reveal a relatively uniform distribution of work over most of the profile but with maxima in the middle of the low tidal zone and over the lower part of the high tidal zone most of the work over the low and mid tidal zones was performed by unbroken shoaling waves rather than by surf zone processes surf zone processes only dominate over the high tidal zone the nature of the surf zone processes varied across the profile as local gradient and degree of reflectivity changed with changing tide level the growth of standing waves and infragravity surf beat oscillations as identified from spectra and cross spectra of surface elevation and currents u and v was inhibited over most of the profile however well developed secondary standing wave energy particularly at infragravity frequencies was observed over the high tidal zone at spring high tide and over the mid tidal zone at neap high tide over the low tidal and subtidal zones strong shore parallel tidal currents were subordinate only to the orbital velocities of unbroken incident waves over the subtidal zone asymmetrical tidal currents skewed toward the north attained maximum speeds of 0 5 m s 1 just after high water field measurements of suspended sediment concentration profiles under broken and unbroken waves showed very good fit to a diffusion model for wave induced sediment suspension and suggested that sediment suspension was probably attributable largely to waves northerly advection of wave suspended sediment by asymmetrical tidal currents over the subtidal and low tidal zones accounted for a net northerly longshore transport the greatest morphologic mobility of the intertidal profile occurred over the lower high tidal and upper mid tidal zones corresponding to the position of the coarsest material and secondary maximum of time averaged wave work and to a beach state intermediate between the reflective and dissipative extremes temporally the greatest mobility of the profile as a whole was observed on the short within tidal cycle time scale net changes over the longest time scale of a lunar half cycle were negligible

dynamics of the turbidity maximum in king sound tropical western australia king sound is a 100 km long embayment located in tropical northwestern australia with a spring tidal range of 11 m this is the second largest tide in the world after the bay of fundy in canada intertidal areas cover about 800 km2 the upper reaches of the sound are turbid with fine suspended sediment concentration reaching 3 kg m 3 field studies of the dynamics of water and fine sediment were carried out in the dry seasons of 1997 and 1998 the tide was a propagating wave shoaling and dissipating by friction as it entered the sound this mode of propagation generated an asymmetric tidal current with a stronger current at flood than at ebb an evaporation driven salinity maximum zone was found in the upper reaches of the sound and this was also where the turbidity maximum occurred tidal pumping by the tidal asymmetry and possibly the biological filter formed by muddy marine snow trapped the fine sediment in the upper regions of king sound wind driven waves contributed significantly to entrainment of bottom fine sediment possibly through wave pumping of the sediment and not wave induced orbital velocities field data suggest that erosion of bottom fine sediment was proportional to the sixth power of the tidal current and the third power of the wave height

late proterozoic to early palaeozoic supracrustal succession of sierra leone an aulacogen at the western margin of the west african craton three parallel zones of upper proterozoic to lower palaeozoic sedimentary volcanic cover rocks have been recognized in western sierra leone the kasila group m the sw ist metamorphosed to the granulite facies and grades into the marampa schist group and this in turn grades into the unmetamorphosed rokel river group in the ne prior to this investigation these rocks were thought to belong to different ages the most highly metamorphosed was thought to be the oldest and the unmetamorphosed the youngest this view is unrealistic since field mapping has failed to reveal any sharp contacts between them and all available age data indicate their involvement in the pan african ca 550 ma orogeny a model is proposed involving an intracontinental graben aulacogen extending from western sierra leone into the adjacent territories developed about 1000 ma ago during the pan african orogeny a portion of the aulacogen fill overlying the remobilized basement was subjected to a regional metamorphism and deformation the grade of metamorphism and the degree of deformation decreased steadily from the centre of the pan african domain to the contact with the west african craton the unmetamorphosed and mildly deformed to undeformed equivalent rests on the craton

morphological changes and sedimentary processes induced by the december 2003 flood event at the present mouth of the grand rhone river southern france the study which is based on repetitive bathymetric surveys assesses changes and effects of one of the most important floods recorded in the rhone delta area bottom morphology and sediment distribution in the rhone outlet after the december 2003 flood are discussed by comparison between digital terrain maps dtms of november 2003 and january 2004 the post flood morphology shows that the whole of the system is active mainly in the east the channel of the rhone has been hollowed out on the left bank by more than 5 m the eastern coast of the mouth has retreated 400 m the mouth bar has prograded 200 m and the slope of the delta front has increased by 0 19 the overlay of pre and post flood dtms makes it possible to estimate the total volume deposited in the 0 to 20 m zone as 7 8 10 the acquisition of bathymetric measurements immediately before and after a major flood allows more than a simple morphological description in addition an analysis of the solid load transfer processes towards the prodelta is achievable three mechanisms are highlighted most of the material eroded in the channel and supplied to the delta front corresponds to fine sediment that drape homogeneously over the pre flood morphology of the delta front the transit of the coarsest sediment primarily sand is slowed down in the channel of the rhone this sediment builds up in relatively small areas leading to the formation of gullies on the prodelta slope the gullies have fixed positions and disappear gradually towards the west following the progressive migration of the active band towards the east these old features are not reactivated by floods occurring after their formation during the flood only a small volume of coarse sediment bypasses through the gullies and the fine deposits are remobilised rapidly or compacted flood input concerns essentially the delta front which traps 90 of the fluvial solid discharge between 0 and 20 m depth the coarse prodelta supply is then due mainly to mass movements of unconsolidated material deposited beforehand on the top of the delta front consequently the main nourishment of the prodelta does not occur directly during and or immediately after a flood event but is delayed by sediment being temporarily trapped on the delta front

shallow seismic reflection mapping of the overburden bedrock interface with the engineering seismograph some simple techniques where unconsolidated overburden exceeds 20 m in thickness the reflection method may be efficiently used with a 12 channel engineering seismograph to map topography on the overburden bedrock interface as well as possible structure within the overburden the two techniques we suggest are the simplest forms of reflection profiling which can be applied with a minimum amount of equipment which we suggest is a 12 channel enhancement seismograph a 12 geophone array and a hammer source these techniques require good transmission characteristics of the overburden as well as a sharp velocity discontinuity at the overburden bedrock interface for data processing and display a microcomputer is essential

early diagenetic processes in coastal marine sediments disturbed by a catastrophic sedimentation event abstract following a catastrophic flash flood in july 1996 as much as 50 cm of post glacial clays were deposited in less than 2 days in the upper reaches of the saguenay fjord quebec canada disrupting the normal sedimentation and diagenetic regimes we report detailed geochemical analyses of sediments porosity eh organic and inorganic carbon fe and mn reactive solid phases and acid volatile sulfide and porewaters salinity dissolved organic carbon doc fe ii mn ii nitrate ammonium and sulfate for seven stations located in the saguenay fjord three of these sag 05 sag 09 and sag 30 were visited in 1996 and once per year thereafter to document the chemical evolution of the sediment toward a new steady state the flood deposits contain less organic carbon and more inorganic carbon than the indigenous fjord sediments the flood deposit modified the distribution patterns of reactive mn and fe as a result of the reduction of mn and fe oxides delivered with the deposit and those concentrated at the now buried former sediment water interface most of the mn ii migrated to the new sediment water interface where a mn rich layer was formed in contrast much of the fe ii was precipitated as sulfides and remained trapped at or close to the old interface a nitrate peak developed in the porewater at the old sediment water interface possibly because of the oxidation of ammonia by mn oxides the distributions of porewater doc within the flood deposit correlate with the distributions of dissolved mn ii and fe ii suggesting that adsorbed doc was released when metal oxides were reduced

radionuclide deposition in the rhone river prodelta nw mediterranean sea in response to the december 2003 extreme flood the extreme rhone river flood that peaked in early december 2003 with water discharges as high as 11 500 m 3 s 1 induced major damage in southern france and transferred large amounts of radionuclides that were associated with suspended particulate matter such as be 7 cs 137 and pb 210 specific marine locations in the close vicinity of the rhone river mouth were sampled three times in december 2003 february 2004 and april 2004 in order to quantify the consequences of flood events in the rhone river prodelta and to investigate the sedimentary depositional patterns through time the pb 210 xs profile analyses in sediment revealed the existence of two particulate matter inputs one that was related to the december extreme flood and the other to a peak flood of 4000 m 3 s 1 of water discharge that occurred in january 2004 the december event net deposition was assessed at 75 19 gbq of pb 210 xs and 27 2 gbq of cs 137 the net deposition in response to the january 2004 flood event although less damaging is of the same order of magnitude to the december 2003 deposition i e 71 21 gbq of pb 210 xs and 16 5 gbq of cs 137 the sedimentary records of the december flood exhibited from the cores collected in december 2003 february 2004 and april 2004 are similar arguing for good environmental signal preservation through time but the standard deviation of flood deposition estimate increases with time after the december flood event indicating a loss of accuracy with time c 2006 elsevier b v all rights reserved

two dimensional synthetic seismogram modeling of wide angle seismic data from the wichita uplift oklahoma abstract in conjunction with the 1979 cocorp wichita uplift survey wide angle reflection refraction data were recorded on a fixed array the object of the present study is to model and interpret these wide angle data to add independent constraints on the deep structure of the wichita uplift three common receiver profiles were extracted from the data recording apertures were 3 2 to 23 4 km to the north of the array 4 2 to 14 9 km to the east and 4 2 to 12 6 km to the west these profiles are modeled by iterative fitting of high frequency synthetic seismograms computed by asymptotic ray theory the model derived contains low velocity 2 0 to 2 16 km sec surficial sediments that vary in thickness these account for strong local travel time variations of 0 05 sec and for a small but persistent ghost arrival that follows all the main branches with a delay of 0 2 sec the basement granites rhyolites and gabbros are very near the surface throughout the study area both granite and gabbro outcrops are seen basement p wave velocities are therefore relatively high representative velocities are 4 7 km sec at 0 8 km depth 6 2 at 1 8 6 4 at 2 8 and 6 5 at 4 0 local velocities as high as 7 4 km sec may be present the basement is fairly transparent beneath the wichita uplift with only a few local reflectors present this is consistent with the cocorp results

mapping shallow faults at the evrona playa site using high resolution reflection method a shallow high resolution seismic reflection survey was carried out at the evrona playa site in the southern arava valley israel the aim of the survey was to detect and map faults in the shallow subsurface upper 100 150 m and establish the relationship of the morphological features revealed by aerial photographs and surface geological mapping with the faults detected in the subsurface the survey included three seismic lines shot using the p wave technique and one sh wave line which overlapped one of the p wave lines the seismic energy source on all the lines was a sledge hammer the acquired reflection data were of good quality and did not require special processing efforts the seismic sections along the lines show a sequence of reflected events within the 8 150 m range at several locations continuity of the events is interrupted by a system of faults these faults form flower structures apparently related to strike slip motions typical of the region comparison of the faults mapped on the seismic sections with those expressed by surface morphological features generally show good correspondence the results of the seismic survey provide important information for the study of paleoseismicity and seismic hazards in the investigated area

usarray shear wave splitting shows seismic anisotropy from both lithosphere and asthenosphere north america provides an important test for assessing the coupling of large continents with heterogeneous archean to cenozoic aged lithospheric provinces to the mantle flow we use the unprecedented spatial coverage of the usarray seismic network to obtain an extensive and consistent data set of shear wave splitting intensity measurements at 1436 stations overall the measurements are consistent with simple shear deformation in the asthenosphere due to viscous coupling to the overriding lithosphere the fast directions agree with the absolute plate motion direction with a mean difference of 2 with 27 standard deviation there are however deviations from this simple pattern including a band along the rocky mountain front indicative of flow complication due to gradients in lithospheric thickness and variations in amplitude through the central united states which can be explained through varying contributions of lithospheric anisotropy thus seismic anisotropy may be sourced in both the asthenosphere and lithosphere and variations in splitting intensity are due to lithospheric anisotropy developed during deformation over long time scales

manganese rich brown layers in arctic ocean sediments composition formation mechanisms and diagenetic overprint we present inorganic geochemical analyses of pore waters and sediments of two late quaternary sediment cores from the western arctic ocean southern mendeleev ridge rv polarstern expedition ark xxiii 3 focussing on the composition and origin of distinct brown colored mn rich sediment layers carbonate enrichments occur in association with these layers as peaks in ca al mg al sr al and sr mg suggesting enhanced input of both ice rafted and biogenic carbonate for the first time we show that the mn rich layers layers are also consistently enriched in the scavenged trace metals co cu mo and ni distinct bioturbation patterns specifically well defined brown burrows into the underlying sediments suggest these metal enrichments formed close to the sediment water interface the geochemical signature of these metal and carbonate rich layers most probably documents formation under warmer climate conditions with an intensified continental hydrological cycle and only seasonal sea ice cover both rivers and sea ice delivered trace metals to the arctic ocean while enhanced seasonal productivity exported reactive organic matter to the sea floor the coeval deposition of organic matter mn oxyhydr oxides and trace metals triggered intense diagenetic mn cycling at the sediment water interface these processes resulted in the formation of mn and trace metal enrichments and the degradation of labile organic matter with the onset of cooler conditions reduced riverine runoff and or a solid sea ice cover terminated the input of riverine trace metal and fresh organic matter resulting in deposition of grayish yellowish metal poor sediments oxygen depletion of arctic bottom waters under these cooler conditions is not supported by our data and did not cause the sedimentary mn distribution while the original composition and texture of the brown layers resulted from specific climatic conditions and corresponding diagenetic processes pore water data show that diagenetic mn redistribution is still affecting the organic poor deeper sediments given persistent steady state conditions purely authigenic mn rich brown layers may form while others may be partly or completely dissolved the degree of diagenetic mn redistribution largely depends on the depositional environment the mn and organic matter availability and apparently affected the co mo ratios of mn rich layers thus brown arctic layers are not necessarily synchronous features and should not be correlated across the arctic ocean without additional age control

sediment budget of the rhone delta shoreface since the middle of the 19th century this study analyses long term 1841 1872 1895 1974 changes in the grand rhone prodeltaic lobe to 1 quantify the accumulation 2 determine the evolution of relict prodeltaic lobes and 3 establish long term relationships between river sediment discharge the shoreface and the continental shelf our results show a reduction of the sedimentation of the prodeltaic lobe at the main river mouth since 150 yr by a factor of 3 7 12 63 to 3 41 10 6 m 3 yr 1 at the minor mouth of the river erosion dominates and speeds up during the same period 0 53 to 1 34 10 6 m 3 yr 1 these changes are found to directly result from the river sediment input decrease related to the natural decreasing of the frequency of major floods end of the little ice age the reforestation in the catchment area the dam construction and the dredging activities since the 1950s our results indicate that while there is large sediment accumulation in the area around a growing prodeltaic lobe there is also a reduced contribution of the river sediments to the non adjacent beaches of the mouth following a shift in the river channel and mouth the relict prodeltaic lobes petit rhone st ferreol bras de fer and pegoulier are reworked by waves and their sediments contribute partially to the growth of the spits espiguette beauduc and gracieuse this suggests that there is a time shift between the input of river sediment to the sea and the build up of a beach the chronic erosion of the coastline is likely to continue in the future since 1 a river shift is not possible because the river channels are controlled by dykes and human intervention 2 the decrease of river sediment input and 3 the relict prodeltaic lobes constitute sedimentary reservoirs that are gradually being used up 2006 published by elsevier b v

recent morphological channel changes in a deltaic environment the case of the rhone river france abstract channel morphological changes were measured at two sites within the rhone delta along the main channel of the rhone river over one century results show an average erosion rate of 2 8 mm year 1 during the 20th century and decreasing to

input of particulate heavy metals from rivers and associated sedimentary deposits on the gulf of lion continental shelf abstract fluxes of the heavy metals chromium cr cobalt co nickel ni copper cu lead pb cadmium cd and zinc zn delivered by rivers to the gulf of lion nw mediterranean sea were estimated over a three year study of the river rhone and its smaller tributaries most of the particulate metal fluxes 80 90 delivered by these rivers occurred within a very short period of time less than 12 a typical trend for the mediterranean environment where highly contrasting hydrological regimes were observed over the year temporal and spatial variations in the fluxes of these particulate metals were driven by the fluxes in both water discharge and suspended particulate matter load on the shelf these particulate metal fluxes largely arising from the rhone watershed were two to ten times more important than those resulting from atmospheric deposition co cr and ni in the rivers and on the shelf surface sediments were mainly natural and associated with the finest particles cd and phosphorus appeared to be associated with the silt fraction and to be enriched in the prodelta areas pb zn and cu were more closely associated with the organic matter content and also showed enrichment in the organic rich prodeltaic sediments anthropogenic influences diminished offshore except for pb and zn which could be supplied from the atmosphere by man made aerosols although most of the metals tended to be enriched in the prodelta areas these did not constitute a permanent sink due to resuspension processes affecting these shallow depths a resuspension experiment conducted on sediment cores from the rhone prodelta demonstrated that metal deposited on the surface layer especially those associated with the organic matter may be resuspended this should be taken into account for a complete understanding of the biogeochemical cycle of these metals

tectonic cycles in southern africa abstract the recurrence of major geological events within the 3600 ma stratigraphic record of southern africa suggests a periodicity of320 25ma for at least the last 3200 ma this periodicity is reflected in major episodes of continental volcanism granitoid plutonism orogeny reciprocity of terrestrial and marine dominated sequences platform carbonate sedimentation glaciation and first order changes in sea level these serve to define 11 completed megacycles each introduced by a major rifting event accompanied by listric faulting alluvial sedimentation in restricted fault bound troughs volcanism and a type granitoid plutonism prior to 3200 ma continental rift magmatism occurred subaqueously due to very high early archean sea levels resulting in pillow lavas and a lack of interbedded terrigenous siliciclastics the long term reciprocity of terrestrial and marine dominated sequences records eustatic first order changes in sea level with highstands characterized by generally humid warm continental climates low relief and tropical afforestation on the other hand lowstand climates were hot and arid with high relief and widespread desertification thick marine sequences accumulate in areally extensive epeirogenic basins without significant volcanism or faulting and commonly are divided into an early phase of open shelf sedimentation followed by deposition in a brackish marine foreland basin within openshelf environments an early phase of biochemical precipitation and or siliciclastic reworking along linear shorelines is separated from a later phase involving rapid deposition of immature siliciclastics along lobate shorelines evolution of the foreland basin is related to orogenic activity and the isolation of an epeiric sea which sometimes developed the characters of a barred basin marine dominated sequences display a deterministic stacking of lithofacies important glacial epochs commonly occur midway through first order regression sometimes with lesser events closely following peak transgression potentially they display 320 ma periodicity but with an unexplained mid proterozoic gap glaciation is related to the combined effect of climatic cooling associated with first order regression and depletion of atmospheric co2 by biological uptake associated with platform carbonate development terrestrial volcanism is believed to be the main contributor of atmospheric co2 climatic change is accompanied by cyclical patterns of cratonic weathering and pedogenesis

environmental history of northwest australia based on phytolith analysis at carpenter s gap 1 examination of a phytolith assemblage from the archaeological site of carpenter s gap 1 provides an hitherto unrecognised source of vegetation history for the tropical savannah region of north western australia two predominant mechanisms contributed to the formation of the phytolith assemblage firstly the introduction of phytoliths in plant materials brought in by humans and secondly the introduction of phytoliths contained in faecal pellets deposited by animals separating the effects of both mechanisms enables local vegetation patterns and by inference climatic conditions to be reconstructed the period ca 40 000 years bp was probably wetter than today allowing the southerly expansion of palms beyond their present day distribution grassland compositional changes occurred by ca 33 000 years bp probably resulting from a combination of lowered rainfall decreased temperatures and possibly aboriginal firing activities a reduction in palm at a similar time followed by its complete disappearance in association with the loss of ulmaceae prior to the last glacial maximum lgm indicates a continued trend in decreasing water availability an abundance of cyperaceae sponge spicules and diatoms during the lgm when considered in conjunction with the other evidence possibly represents altered human behaviour in response to increased aridity

the a type mount scott granite sheet importance of crystal magma traps the presence of rapakivi feldspar and of distinctive porphyritic texture of mount scott granite indicates a period of crystallization prior to final emplacement beneath an extensive penecontemporaneous rhyolite volcanic pile final crystallization conditions are interpreted to have been 50 mpa at depths 1 4 km based on stratigraphic constraints however geobarometry based on the al content of amphibole phenocrysts and comparison of granite compositions with phase relations in the sio2 naalsi3o8 kalsi3o8 ternary system both yield pressure estimates of 200 mpa these pressure estimates are interpreted as plumbing the depth of a temporary storage chamber at 7 8 km this depth coincides in this case both with the probable proterozoic basement cover contact and with the calculated brittle ductile transition at time of ascent of mount scott magma although rising magma that fed the preceeding voluminous carlton rhyolite apparently rose unimpeded past these horizontal anisotropies rising magma that formed mount scott granite temporarily paused at this depth based on magmastatic calculations we suggest that horizontal anisotropies e g brittle ductile transition become crustal magma traps where the magma driving pressure exceeds the lithostatic load when the anisotropy is encountered during rifting initial large influxes of magma may proceed passed crustal anisotropies but have the effect of increasing the relative magma driving pressure through reducing horizontal stress thus magma driving pressure may eventually exceed the lithostatic load at the depth of the brittle ductile transition thereby activating this crustal magma trap ponding of magma at the brittle ductile transition chokes the eruption such a pause in magma supply rate may permit a return to initial stress conditions and deactivate the crustal magma trap once again magma will rise to the surface initiating a new magmatic cycle

natural and anthropogenic trace metals in sediments of the ligurian sea northwestern mediterranean abstract the magnitude and the chronology of anthropogenic impregnation by hg and other trace metals of environmental concern v cr ni cu zn ag cd and pb including its stable isotopes in the sediments are determined at the dyfamed station a site in the ligurian sea northwestern mediterranean chosen for its supposed open sea characteristics the dyfamed site vd is located on the right levee of the var canyon turbidite system at the end of the middle valley in order to trace the influence of the gravity current coming from the canyon on trace metal distribution in the sediment we studied an additional sediment core va from a terrace of the var canyon and material collected in sediment traps at the both sites at 20 m above sea bottom the patterns of hg and other trace element distribution profiles are interpreted using stable pb isotope ratios as proxies for its sources taking into account the sedimentary context turbidites redox conditions and sedimentation rates major element distributions coupled with the stratigraphic examination of the sediment cores point out the high heterogeneity of the deposits at va and major turbiditic events at both sites at the dyfamed site we observed direct anthropogenic influence in the upper sediment layer according to the 210pbxs derived sedimentation rate at the dyfamed site 0 4 mm yr 1 the hg enriched layer of the top core corresponds to the sediment accumulation of the last 50 years which is the period of the highest increase in hg deposition on a global scale with the hypothesis of the absence of significant post depositional redistribution of hg the hg corg ratio changes between the surface and below are used to estimate the anthropogenic contribution to the hg flux accumulated in the sediment the hg enrichment from pre industrial to the present time is calculated to be around 60 consistent with estimations of global hg models however based on the chemical composition of the trapped material collected in sediment traps we calculated that epibenthic mobilization of hg would reach 73 conversely the cd corg ratio decreases in the upper 5 cm which may reflect the recent decrease of atmospheric cd inputs or losses due to diagenetic processes

variability of the north atlantic oscillation over the past 5 200 years the north atlantic oscillation influences climate in the arctic region and northern europe reconstructions of circulation patterns associated with the north atlantic oscillation from a 5 200 year long lake sediment record suggest that the atmospheric circulation responded to significant transitions in northern hemisphere climate

records of holocene climatic fluctuations and anthropogenic lead input in elemental distribution and radiogenic isotopes nd and pb in sediments of the gulf of lions southern france marine mud belts represent potential continuous high resolution climatic environmental and anthropogenic archives in this study a geochemical record of the gulf of lions mud belt which receives

near surface folding along an active fault seismic or aseismic abstract the meers fault in southwestern oklahoma has been active in recent times the most recent movement occurred about 1100 years ago in the late holocene during the faulting the quaternary age alluvial deposits along the fault were folded as well as ruptured in some places almost all of the deformation is accommodated by ductile folding of these deposits having this type of deformation with no record of an earthquake associated with the meers fault during historical times raises the question whether the present scarp was formed seismically by earthquake event s or aseismically by slow deformation aseismic fault creep triaxial shear tests with various shear rates were run to determine the conditions for brittle ductile and brittle ductile transition type failures relationships between ductility moisture content strain rate shear rate or failure time and confining stress were determined the results show that under the possible field conditions that existed during the faulting the ductile folding of these deposits is possible indicating the meers fault scarp could have been created contemporaneously with earthquake event s

fate of metals in coastal sediments of a mediterranean flood dominated system an approach based on total and labile fractions the dynamics of sediment bound metals cs cu ni pb ti and zn were studied off the tet river western gulf of lion a typical mediterranean coastal river punctuated by short and violent flash floods spatial and temporal sampling strategies were combined to elucidate the fate of these elements in response to both the riverine sediment input and the offshore transport of these sediments through hydrodynamics our results show the temporal entrapment of riverborne particles and associated metals consecutively to a major flood event in the nearshore sedimentary unit called prodelta here deposition and resuspension mechanisms define a sedimentological cycle that could be followed completely in this study in terms of speciation between reactive labile and residual fractions along the fluvio deltaic continuum our results show that cu pb and zn are the most labile potentially mobile metals in the river in accordance with their contributions from anthropogenic sources but in the marine surficial sediments two main behaviours can be discriminated when compared to the riverine suspended particulate matter while pb and zn depict rather a constant labile fraction cu is characterized by decreasing levels up to 50 difference in terms of environmental impact these contrasting trends have direct repercussions for the contaminant dispersal in the coastal area whereas pb and zn conserve their enhanced levels because of their stronger affinity with fine sediments cu is marked by the entire loss of its anthropogenic component that is progressively transferred to the dissolved phase likely mediated by organic ligands we ascribe these behaviours to different post depositional partition mechanisms with respect to oxidation of the particulate organic phase at the bottom sediment water interface also analysis of one sediment core from the prodelta indicates that these early diagenetic processes govern the chemical forms of land derived contaminants sequestrated in the nearshore sedimentary archives c 2011 elsevier ltd all rights reserved

aulacogens of ancient platforms problems of their origin and tectonic development abstract riphean and palaeozoic linear graben like platform depressions aulacogens jointly with linear swell uplifts in a platform cover intraplatform folded zones and meso cenozoic epi platform rift zones are different morphological manifestations of a single group of linear platform structures aulacogens are characterized by the long duration of their development and ability for regeneration their existence is certain mainly since the late proterozoic riphean usually they inherit more ancient linear attenuated tectonic zones of platform basement or adjust to them aulacogens pass through common stages of development forming a single cycle or in many cases even several similar though not identical cycles the cycle starts with the incipience or regeneration of a linear graben like depression limited by normal faults and after a more or less deep and long subsidence accompanied often by basic or alkaline basic volcanism it is completed in many cases by an inversion stage at this stage horst like uplifts appear limited by thrust and overthrusts in the aulacogen basement while linear swell like uplifts or their systems and even linear folded structures occur in its cover the early stages of an aulacogen evolution occur under horizontal extension conditions whereas the inversion stage takes place under a compressional regime cycles of aulacogen development resemble in attenuated miniature form the development cycle of adjacent geosynclinal areas coincide with them in time and many through and penetrating aulacogens are their direct offsets the late proterozoic cycle of aulacogen evolution corresponds to a pre plate stage of the platform history aulacogen stage by bogdanov and is characterized by the widest development of a network of differently oriented aulacogens over the whole area of ancient platforms which have been subjected to some general horizontal extension crawling away and only partially compensated by compression during the inversion stage the subsequent aulacogen development in palaeozoic and on laurasian platforms partly in meso cenozoic was spatially and genetically connected with the history of geosynclinal later orogenic belts bordering these platforms with regard to gondwana platforms and later the north american and siberian the mesozoic saw the development of many aulacogens or rift zones ranging parallel to transversally with respect to the recent margins of platforms this process was connected with the break up of the gondwana supercontinent and the formation of secondary oceanic depressions as a rule it has not been completed by inversion but took place under extension conditions and probably some general expansion of the earth activated during the meso cenozoic

cambrian extensional tectonics and magmatism within the southern oklahoma aulacogen abstract the tectonic evolution of the southern oklahoma aulacogen is partially constrained by the petrological consequences of a bimodal igneous suite associated with the cambrian rift mineralogical and compositional layers and erosional surfaces are recognized as initially subplanar subhorizontal markers the progressive rotation of these horizons can be explained by uniform sense normal faulting magmatism confined to the aulacogen trend elevated the thermal gradient producing a crustal strength anisotropy this ensured the localization of the extension throughout the cambrian rifting event the presence of a substantial volume of mafic igneous rocks within the crust along the aulacogen s trend suggests that crustal attenuation was compensated for by the addition of mantle derived material during extension

lead and its isotopes in the sediment of three sites on the lebanese coast identification of contamination sources and mobility abstract lead concentrations and isotopic composition of sediment samples collected from three sites within the lebanese coastal zones were measured at akkar dora and selaata akkar is located far from any direct source of contamination while dora and selaata receive urban and industrial wastes respectively low pb concentrations 6 16 g g 1 were detected in the akkar sediments and high concentrations of pb 70 101 g g 1 were detected in the dora sediments measuring stable isotope ratios of pb makes it possible to identify the principal sources of pb in the akkar sediments as pb emitted from gasoline combustion and pb originating from natural sources on the other hand pb stable isotopic ratios in dora sediments indicate that they are more highly influenced by anthropogenic sources isotopic pb ratios in the selaata deposits where pb concentrations range between 5 and 35 g g 1 have an exceptional radiogenic signature for marine sediments 1 25 60 after 24 h of extraction and that the extracted pb is less radiogenic than the residual pb

comment on known and suggested quaternary faulting in the midcontinent united states by russell l wheeler and anthony crone abstract studying previously published and other publicly available geologic evidence of quaternary faulting in the midcontinent united states wheeler and crone eng geol 62 2001 51 judged that the 30 km northwest extension of the meers fault in southwestern oklahoma suggested by cetin cetin h 1992 the northwest extension of the meers fault in southwestern oklahoma proc 28th symp eng geology and geotechnical eng university of idaho boise id pp 43 58 is not of quaternary age and claimed that holocene surface rupture has been limited to the previously reported 26 37 km section of the fault to the southeast surface rupture length is one of the most commonly used parameters to infer magnitudes of paleoearthquakes and thus potential future earthquakes in seismic hazard studies as a result underestimating fault dimensions may lead to serious errors in earthquake hazard evaluation evidence for the northwestward extension include displaced terrace deposits of pleistocene age displaced buried and or overthickened soil horizons fault related colluvium deposits colluvial wedges found near and only on the downthrown side of the fault active oil seepage near the fault deflection of stream alignments and the land use pattern along the fault the assessment of the northwestward extension of the meers fault by wheeler and crone thus appears to be mistaken

anthropogenic trace metals in the sedimentary record of the llobregat continental shelf and adjacent foix submarine canyon northwestern mediterranean abstract anthropogenic trace metal concentrations and inventories were studied on the llobregat continental margin from the llobregat river mouth to the foix submarine canyon a prodelta sedimentary depocentre was identified along with a previously known canyon depocentre significant upward increases in trace metal contents were detected in sediment cores of the prodelta and upper part of the canyon down to 860 m depth metal enrichment factors ranged between 1 8 and 10 on the continental shelf and between 1 2 and 2 7 in the submarine canyon these metal enrichments occurred during the 20th century and can be correlated with the period of maximum increase of population and industrial activities in the barcelona area and the consequent anthropogenic metal inputs maximum trace metal enrichments are located in the prodelta depocentre and significant enrichments were also measured in the southern prodelta and in the foix upper canyon as a consequence of efficient shelf canyon sediment and metal transfer deeper in the canyon at 1370 m depth no metal enrichments were detected probably because of particle dispersion and dilution with uncontaminated sediment within the canyon this study shows that in some mediterranean sedimentation systems anthropogenic trace metal contamination is affecting not only the littoral and the continental shelf but also the adjacent continental slope sediments through submarine canyons

hydrothermally induced changes in mineralogy and magnetic properties of oxidized a type granites abstract the changes in magnetic mineralogy due to the hydrothermal alteration of a type granitic rocks have been thoroughly investigated in samples from the granite of tana corsica france and compared with other a type granites meruoca ne brazil bushveld south africa mount scott wichita mountains oklahoma usa and the stratoid hypersolvus granites of madagascar the altered red colored samples and their non altered equivalents were magnetically characterized by means of magnetic susceptibility measurements hysteresis loops remanent coercivity spectra and lowrie test it is shown that hydrothermalization in magnetite bearing granites is related to the formation of fine grained magnetite and hematite and to coeval depletion in the content of primary low coercive coarse grained magnetite these mineralogical changes give typical rock magnetic signatures namely lower susceptibility magnitudes and anisotropy degrees prolate ams anisotropy of magnetic susceptibility fabrics and increased coercivities optical microscopy and sem scanning electronic microscopy images suggest that the orientation of the secondary magnetic minerals is related to fluid pathways and micro fractures formed during the hydrothermal event and therefore may be unrelated to magma emplacement and crystallization fabrics changes in magnetic mineralogy and grain size distribution have also to be considered for any paleomagnetic and iron isotope studies in granites

chronology and sources of trace elements accumulation in the rhone pro delta sediments northwestern mediterranean during the last 400years abstract the rhone pro delta sediments receive the particulate inputs from the rhone river the largest freshwater discharge of the western mediterranean sea trace element tes ag cd co cr cu ni pb and zn concentrations and stable pb isotope ratios were determined along a 7 7 m long sediment core collected from the rhone prodeltaic lobe archiving the deposits of the last 400 years trace element mean concentrations during the pre industrialized era before 1850 ce were no different from the average composition of earth s upper crust except for cr principal component analysis performed on tes and tracers suggests three origins for tes that we identified as i marine biogenic material ag cd ii ultramafic rocks li cr ni and iii other clay minerals co cu pb and zn during the pre industrial period several changes in the te al ratios coincided with flood events or and modifications in the channelization of the rhone river mouth some frequencies in the tes temporal variations allow us to hypothesize some influence of climate variation sediments deposited after 1850 ce exhibited concentrations of certain tes exceeding 1 3 3 5 times the concentrations of the pre industrial era ag cd pb cu zn principal component analysis performed on post 1850 ce data allows to distinguish pristine and anthropogenically impacted tes pristine tes such as co cr and ni are linked with clay markers al li and fe co and ni are associated with mn enrichment whereas cr is correlated with fe anthropogenically impacted elements consist of ag cd cu pb and zn vertical profiles show that te contamination has increased dramatically after the iind world war and reached a maximum between 1970 and 1980 consistently with anthropogenic atmospheric emissions changes sediment deposited on the rhone prodelta at the beginning of xviith century have 206 207pb ratios close to values of natural pb 1 200 whereas sediments deposited after 1850 ce are clearly contaminated by european gasoline and industrial pb pools

fertiliser characterisation major trace and rare earth elements abstract in recent years there has been increasing concern regarding the chemical impact of agricultural activities on the environment so it is necessary to identify contaminants and or characterise the sources of contamination in this study a comprehensive chemical characterisation of 27 fertilisers of different types used in spain has been conducted major minor and trace elements were determined including rare earth elements results show that compound fertilisers used for fertigation or foliar application have low content of heavy metals whereas fertilisers used for basal and top dressing have the highest content of both ree and other heavy metals ree patterns of fertilisers have been determined in order for them to be used as tracers of fertilisers in future environmental studies furthermore in this work ree patterns of fertilisers are used as tracers of the source of phosphate in compound fertilisers distinguishing between phosphorite and carbonatite derived fertilisers fertilisers from carbonatites have higher contents of ree sr ba and th whereas fertilisers from phosphorites have higher contents of metals of environmental concern such as cd u and as and the sum of the heavy metals is higher some of the analysed fertilisers have cd concentrations that exceed maximum values established in some countries and can be expected to produce long term soil accumulation furthermore other elements such as u as and cr are 10 50 times higher in concentration than those of cd but there is no legislation regarding them therefore it is necessary to regulate fertiliser compositions in order to achieve environmental protection of soils and waters

suspended sediment and 137cs fluxes during the exceptional december 2003 flood in the rhone river southeast france abstract at the beginning of december 2003 one of the biggest floods for at least 150 yr was recorded on the rhone river in the lower part of the river the peak flood reached 11 000 m 3 s 1 the geomorphological and radioecological consequences of such an event were investigated downstream all the nuclear installations by using measured and calculated fluxes and the total export of suspended sediment and associated 137 cs results pointed out the major role played by large floods in the annual suspended sediment load as 3 70 10 6 tons of silts 0 85 10 6 tons of sands and 0 84 10 6 tons of clays were transferred towards the coastal environment nevertheless these solid loads were found to be lower than those expected as regards the liquid discharge reached during this event and suggested that previous floods that occurred on the river and on its main tributaries during the last decade have probably led to the removal of available sediment from the channels and their banks besides the 137 cs activity measured within the suspended load was estimated at 14 9 0 4 bq kg 1 which is a level characteristic of the suspended sediments from the rhone catchment area and demonstrated that nuclear installations located along the rhone valley did not significantly contribute to any increase in 137 cs activity in the water during the flood the total 137 cs particulate export amounted to 77 17 gbq and was mainly associated with the silt fraction that contributes to around 70 of the total 137 cs export

two dimensional elastic pseudo spectral modeling of wide aperture seismic array data with application to the wichita uplift anadarko basin region of southwestern oklahoma abstract full wave field modeling of wide aperture data is performed with a pseudospectral implementation of the elastic wave equation this approach naturally produces three component stress and two component particle displacement velocity and acceleration seismograms for compressional shear and rayleigh waves it also has distinct advantages in terms of computational requirements over finite differencing when data from large scale structures are to be modeled at high frequencies the algorithm is applied to iterative two dimensional modeling of seismograms from a survey performed in 1985 by the university of texas at el paso and the university of texas at dallas across the anadarko basin and the wichita mountains in southwestern oklahoma the results provide an independent look at details of near surface structure and reflector configurations near surface 70 per cent of the energy in the observed seismograms the interpretation of the data is consistent with the results of previous studies of these data but provides considerably more detail overall the p wave velocities in the wichita uplift are more typical of the middle crust than the upper crust 5 3 to 7 1 km sec at the surface the uplift is either exposed as weathered outcrop 5 0 to 5 3 km sec or is overlain with sediments of up to 0 4 km in thickness ranging in velocity from 2 7 to 3 4 km sec generally increasing with depth the core of the uplift is relatively seismically transparent a very clear coherent reflection is observed from the mountain view fault which dips at 40 to the southwest to at least 12 km depth velocities in the anadarko basin are typical of sedimentary basins there is a general increase from 2 7 km sec at the surface to 5 9 km sec at 16 km depth with discontinuous reflections at depths of 8 10 12 and 16 km

210pb sedimentation rates from the northwestern mediterranean margin abstract a total of 83 cores were collected in the gulf of lions continental margins and analysed for 210 pb xs excess 210 pb in order to understand sedimentation patterns apparent sedimentation rates asr range from 0 65 cm year 1 in the vicinity of the rhone river mouth to 0 01 cm year 1 in the deep basin except for the prodelta area rates decrease with depth linearly with the water depth on the slope asr do not differ between canyons and open slope except for the western area where the rates are slightly higher in the lacaze duthiers canyon compared to its adjacent open slope in the canyon and open slope areas mass accumulation rates determined from 210 pb xs profiles 0 10 and 0 08 g cm 2 year 1 respectively are in good agreement with particulate fluxes calculated from 5 years of near bottom sediment trap data even when the trap particle fluxes and the apparent accumulation rates are overestimated in response to resuspension and bioturbation effects however differences in sediment trap data between west and east portion of the slope are not observed in the sedimentation rates calculated with 210 pb xs the outer shelf area may have an important role in trapping sediment but it is not sufficiently documented sediment surface mixed layer depths decrease with water depth with a mean value for the whole margin of 8 6 cm 210 pb xs inventories in the sediment are systematically higher than the net 210 pb export flux estimated from the above water column over the margin the ratio between accumulated 210 pb and available 210 pb is about 3 suggesting boundary scavenging effects and advective transport

a new isostatic residual gravity map of the conterminous united states with a discussion on the significance of isostatic residual anomalies to display more clearly the gravity anomalies caused by geologic bodies in the upper parts of the crust a new colored isostatic residual gravity map of the conterminous united states has been prepared using the gravity data set compiled for the gravity anomaly map of the united states society of exploration geophysicists 1982 the new isostatic residual gravity map is based on an airy heiskanen model of local compensation in which the surface load requiring compensation is defined by 5 min topographic and bathymetric data sets a colored first vertical derivative map of isostatic residual gravity further enhances the short wavelength anomalies produced by bodies at or near the surface and emphasizes the regional fabrics and trends in the gravity field for the purpose of displaying gravity anomalies caused by shallow bodies of geologic significance the nature of the isostatic model and the values of its parameters are of lesser importance than the application of an isostatic correction of some sort most isostatic models result in residual gravity maps that appear nearly identical in their main patterns and features anomalies on isostatic residual gravity maps should not be casually interpreted in terms of undercompensation or overcompensation because large amplitude anomalies can be produced by crustal bodies in complete local isostatic equilibrium many isostatic residual gravity anomalies less than several hundred kilometers wide can be related to known geologic bodies we present here a classification scheme that attempts to categorize such anomalies on the basis of tectonic environment in general highs correlate with intruded or accreted mafic material or with upthrusted crustal sections whereas lows occur over low density sedimentary or volcanic sections felsic intrusive bodies or down warped crustal sections although some longer wavelength anomalies such as the broad gravity high centered over montana could be manifestations of density contrasts deep in the mantle many such anomalies can also be modeled by geologically reasonable density contrasts that are isostatically compensated and confined to depths of less than several hundred kilometers so that their source bodies need not be deep the fact that certain of these broader anomalies have well defined boundaries which correlate with near surface geologic features increases the likelihood that their sources lie entirely within the lithosphere if so then the density contrasts required to explain the gravity data imply fundamental anomalies in chemical composition or thermal state for the crustal and upper mantle columns under these regions we have investigated spectral analysis as a method to quantitatively characterize regional anomaly patterns contoured plots of normalized amplitude spectra were prepared for various areas of the isostatic residual gravity field of the united states these fourier domain representations show characteristic patterns that can be interpreted in terms of the trends and wavelengths of anomalies and may help to more objectively distinguish geologic basements with different origins or tectonic histories

thermal maturation by vitrinite reflectance of woodford shale anadarko basin oklahoma the woodford shale upper devonian lower mississippian a black shale widely regarded as an important hydrocarbon source rock has attained thermal maturity to postmaturity with respect to the generation of liquid hydrocarbons in most of the anadarko basin in western oklahoma untreated whole rock well cuttings and core material from selected 10 ft intervals of the woodford shale in 28 wells were examined under reflected white light thermal maturation was determined by measuring the reflectance in oil immersion ro of first generation vitrinite particles a minimum of 45 reflectance measurements were recorded for each well representing one or more sample intervals the woodford shale was sampled at depths from 5 060 ft 1 542 m in the northeastern shelf to 25 115 ft 7 655 in the deepest part of the basin a systematic increase in mean vitrinite reflectance meanro with depth was observed over much of the anadarko basin from northeast to southwest across the basin mean ro increases from 0 48 to 2 61 high temperatures have raised the woodford shale to anthracite rank in two wells 4 29 and 4 89 ro in the deep anadarko basin an isoreflectance map for the woodford shale indicates those areas of the basin where the thermal history of the shale is optimum for preserving liquid hydrocarbons mean ro of 0 5 to 2 0 computer generated plots of vitrinite reflectance versus depth provide a regression equation that predicts the vitrinite reflectance of the woodford shale at any depth in the anadarko basin and determines the amount of erosion

shallow seismic reflection profile of the meers fault comanche county oklahoma this is the publisher s version also available electronically from http onlinelibrary wiley com

shallow gas off the rhone prodelta gulf of lions sediment cores acquired in 2004 off the rhone prodelta show consistent anomalous methane concentrations of up to 87 440 ppm methane compositional and isotopic data support a biogenic origin although there are a few sites that show strongly depleted delta c 13 values 53 o pdb suggesting a mixed source for the gas biogenic and thermogenic anomalous methane concentrations samples with more than 90 ppm are discussed and integrated with organic carbon data sedimentary rates and adcp profiles highest gas concentrations were found directly off the river mouth 20 40 m water depth and where the ifremer models point to the thickest accumulation 2 m in response to the rhone flood event in areas unaffected by the high flux of organic matter and rapid thick flood deposition or in between flood events the conditions for methanogenesis and gas accumulation have not been met in these areas the physical and biological reworking of the surficial sediment may effectively oxidize and mineralize organic matter and limit bacterial methanogenesis in the sub surface we propose that in the rhone prodelta flood deposits deliver significant amounts of terrigenous organic matter that can be rapidly buried effectively removing this organic matter from aerobic oxidation and biological uptake and leading to the potential for methanogenesis with burial c 2006 elsevier b v all rights reserved

seismic reflection investigations of a bedrock surface buried under alluvium seismic reflection techniques were used to characterize a bedrock surface buried under alluvium near a construction site on the campus of baylor university in waco texas one of the objectives of the study was to determine if either compressional or shear seismic profiling could be used to reduce the number of engineering boreholes required to determine the bedrock depth and relief prior to building construction the upper few meters of the alluvium is dry but the lower portion is below the water table making the bedrock surface a difficult target for compressional waves the compressional reflection coefficient at the water table is an order of magnitude greater than that at the bedrock surface and the dry alluvium reduces the signal bandwidth such that the two reflections cannot be distinguished also the multimode rayleigh ground roll traveling along the surface at about half the speed of the compressional wave swamps the reflections by using shear waves to profile the alluvium bedrock interface

feasibility of cdp seismic reflection to image structures in a 220 m deep 3 m thick coal zone near palau coahuila mexico the common depth point cdp seismic reflection method was used to delineate subsurface structure in a 3 m thick 220 m deep coal zone in the palau area of coahuila mexico an extensive series of walkaway noise tests was performed to optimize recording parameters and equipment reflection events can be interpreted from depths of approximately 100 to 300 m on cdp stacked seismic sections the seismic data allow accurate identification of the horizontal location of the structure responsible for a drill discovered 3 m difference in coal zone depth between boreholes 150 m apart the reflection method can discriminate folding with wavelengths in excess of 20 m and faulting with offset greater than 2 m at this site

proterozoic basin in the southern midcontinent of the united states revealed by cocorp deep seismic reflection profiling cocorp deep crustal seismic profiles in southwestern oklahoma show strong persistent continuous and undeformed layering in the basement over an area probably very much greater than 2 500 km 2 such layering is very unusual judging by cocorp experience with basement rocks elsewhere in the united states the data can be interpreted as representing a proterozoic basin filled with clastic sedimentary and felsic volcanic rocks 7 to 10 km thick whose base lies 10 to 13 km deep these rocks are believed on the basis of sparse evidence from regional geology to have been deposited or extruded about 1 200 to 1 400 m y ago and some of them may now be metamorphosed this basin lies on the south side of the wichita mountains under the paleozoic hardeman basin and is similar in depth to the paleozoic anadarko basin north of the mountains the deep basement layering is truncated on the south side of the wichita mountains probably by precambrian faults in conjunction with granitic intrusions pennsylvanian compression probably reactivated these precambrian trends extensive precambrian basin deposits in this area were unexpected on the basis of evidence from sparse well control and reports of other layered basement reflections elsewhere in the southern midcontinent suggest that precambrian basins may be an important feature of this region simple models for the evolution of southwestern oklahoma as an aulacogen must be reformulated in the light of these new data

relationship of late quaternary fault scarps to subjacent faults eastern great basin utah high resolution seismic reflection profiles in the sevier desert basin in western utah help clarify the relationship between some late quaternary fault scarps and subjacent faults a profile crossing the clear lake fault confirms that holocene displacement has occurred on a high angle normal fault that is directly connected to the sevier desert detachment if detachment faults can act as seismogenic source zones then the young movement on the normal fault suggests that the sevier desert detachment may be unstable and perhaps the source of future earthquakes a swarm of late quaternary scarps near the drum mountains overlies a network of steep faults in competent rock that have had recurrent movement many subsurface faults are not associated with scarps suggesting that selected faults ruptured during the last episode of surface faulting

inversion of airborne gravity gradient data southwestern oklahoma the diagonal elements of the gravity gradient tensor as recorded by the bell airborne gravity gradient survey system ggss are used to determine the basement topography in southwestern oklahoma this determination is accomplished through a nonlinear inverse procedure based on the conjugate gradient algorithm the resulting model contains a ridge of shallow basement material or 3 0 km deep trending east southeast this ridge is bounded on the north and the south by basement troughs the northern trough extends as deep as 10 0 km the gradient field which results from this model fits most of the ggss observations within their estimated errors of 12 0 e 1 eotvos 10 super 6 mgal cm the model is in general agreement with a set of available oil well depths to the basement and with inferred faults in these igneous rocks to assess the derived solution the problem was linearized about the final model and the linear parameter resolution and parameter covariances were computed generally the basement depths are well resolved and the resolution matrix is diagonally dominant furthermore the parameter standard errors are small 72 parameters out of 98 have errors less than 1 0 km