high latitude lower thermospheric neutral winds at eiscat and sondrestrom during ltcs 1 the incoherent scatter radar located at sondre stromfjord greenland 67 n 51 w 74 5 and the eiscat incoherent scatter facility located in northern scandinavia 69 5 n 19 e 66 3 both obtained e and f region measurements during the first campaign of the lower thermosphere coupling study ltcs 1 september 21 25 1987 neutral winds deduced from these measurements have been analyzed for their mean flow and tidal components a number of the altitude profiles for the mean winds and the diurnal and semidiurnal wave components at the two radar locations show similar variations with height indicating that latitudinal rather than longitudinal effects are dominant in determining the observed wind field diurnal tidal amplitudes and phases are reasonably well represented by theoretical model results forbes 1982 the semidiurnal amplitudes and phases although somewhat consistent between the two radars are not well represented in equinox tidal model results forbes and vial this issue results from both radars indicate a vertical wavelength for the zonal semidiurnal oscillation of approximately 60 km during a period of impulsive magnetospheric forcing september 22 23 winds deduced from measurements at both radars show enhanced eastward flows near midnight accompanied by equatorward winds at sondrestrom comparison with the results of a national center for atmospheric research thermosphere ionosphere general circulation model tigcm simulation of the ltcs 1 interval shows generally better agreement with the observations at eiscat than at sondrestrom during the period of activity on september 22 23 the tigcm is reasonably successful at simulating the eastward surge near midnight in the eiscat but not in the sondrestrom observations and the equatorward flow after midnight in the sondrestrom results the observed winds in magnetic latitude and magnetic local time coordinates indicate the presence of anticyclonic divergent flow near dusk and cyclonic converging flow near dawn

core based evidence for sandy slump and sandy debris flow facies in the pliocene and pleistocene of the gulf of mexico implications for submarine fan models examination of nearly 3 500 feet of conventional core from pliocene and pleistocene deep water reservoirs cored in 25 wells in 8 different areas covering the eastern central and western gulf of mexico reveals that the reservoirs are predominantly composed of mass transport deposits mainly sandy slumps and sandy debris flows 60 100 of cored intervals bottom current reworked sands are common 10 50 of importance to existing submarine fan models is that turbidities are extremely rare 1 of all cores sedimentary features indicative of slump and debris flow origin include sand units with sharp upper contacts slump folds discordant steeply dipping layers up to 60 degrees glide planes shear zones brecciated clasts rafted mudstone clasts planar clast fabric inverse grading of clasts and moderate to high matrix content 5 20 these reservoirs have been interpreted by others to represent turbidite dominated basin floor fans and slope fans of the often used sequence stratigraphic model however our core data do not show a dominance of turbidities sandy debris flows exhibit a variety of log motifs e g blocky fining up and coarsening up due to changes in concentration of midstone clasts and a variety of internal seismic facies e g parallel continuous irregular discontinuous chaotic discontinuous and lateral pinch out perhaps due to changes in stacking patternsmore of debris flows and slumps classic submarine fan models commonly advocated for these reservoirs may not be appropriate we propose a slump and debris flow dominated slope model in which sea floor topography and depositional freezing i e plastic flows control sand distribution and geometry contrary to popular belief sandy debris flows can be thick areally extensive and excellent reservoirs less

mass transport processes on amazon cone western equatorial atlantic three large mass transport deposits occur on the upper to middle amazon cone these slump debris flow complexes have been mapped from 3 5 khz echograms and cover approximately 75 000 sq km or about 10 of the cone the debris flows traveled down slopes with gradients as low as 1 90 to 1 165 0 3 to 0 6 for distances up to 300 km these deposits average 10 to 50 m in thickness and the total amount of sediments displaced may exceed 3 800 cu km the upslope parts of these complexes generally consist of hummocky slump or slide deposits which are commonly bounded by scarps of varying relief downslope from this zone of removal the deposits consist of thin the occurrence of such widespread mass movements on the amazon cone indicates that mass transport is probably an important sedimentation process on deep sea fans however most studies and models of modern deep sea fans have minimized or ignored the potential importance of mass transport processes in fan development we suggest that in the future both ancient and modern deep sea fans be more closely examined for mass transport deposits so that the importance of this process to overall fan development can be more accurately assessed

the bouma division a and the possible duration of turbidity currents abstract experimental data arnott and hand 1989 combined with theoretical arguments suggest that the transition in a turbidite from division a to division b occurs at a deposition rate of unsupported grains of about 6 7 10 4 m s 1 in the case of fine medium quartz sand a second rate may be calculated from properties measured at the transition from division b to division c allen 1971b these rates together permit an estimate to be made of the order of magnitude of the duration of deposition from a turbidity current the calculated order of a few tens of minutes for a mio pliocene turbidite described and interpreted hydraulically by komar 1985 is in broad agreement with his independent estimate based on the sequenc of sedimentary structures

structural profiles of ouachita mountains western arkansas the ouachita mountains of oklahoma and arkansas are the largest exposure of the pennsylvanian age orogen rimming the southern margin of north america the exposure consists of a thick carboniferous flysch sequence overlying a thin early paleozoic deep water sequence and is generally interpreted to have been deformed in a south dipping subduction zone two balanced cross sections 40 km apart of the ouachita mountains in western arkansas are presented here illustrating the regional structural style major features of the cross sections include from north to south 1 triangle zones along the northern border of the frontal thrust zone produced by imbrication at depth 2 large scale 10 km wavelength fault propagation folds in the frontal thrust zone formed prima ily above normal faults that offset the basement and act as buttresses at depth 3 a late stage basement uplift along the reactivated johns valley normal fault system resulting in the antiformal structure of the benton uplift and backthrusts in the northern benton uplift and 4 small scale 1 3 km heavily faulted folds in the early paleozoic deep water rocks exposed in the benton uplift greenschist metamorphism in these rocks is attributed to the estimated 13 km of carboniferous overburden which was later eroded reconstructions of the late paleozoic continental margin are made from the two cross sections the reconstructed shelf to slope transition is interpreted to underlie the southern flank of the benton uplift using modern analogs for the across strike width of the shelf to slope transition a minimum regional shortening estimate of 30 50 110 155 km is obtained for deep water rocks currently exposed in the benton uplift

a preliminary experimental study of turbidite fan deposits discussion parsons et al 2002 have discussed an experimental study of turbidite fan deposits for understanding lobe switching because of the perceived importance of turbidite lobes in hydrocarbon reservoirs shanmugam and moiola 1991 this experimental study could be of value to the oil industry also experimental studies are the primary means of unraveling the complexities of the process dynamics of turbidity currents and their deposits this is because the other two options namely 1 direct observations of turbidity currents in the deep sea e g shepard et al 1979 and 2 attempts to understand turbidity currents and their fan deposits on the basis of outcrop study on land e g mutti and ricci lucchi 1972 have proven to be unsuccessful e g mutti 1992 shanmugam 2002 therefore the experimental study by parsons et al 2002 requires close scrutiny i would like to debate the following issues discussed in the paper 1 reynolds number 2 grain size variation 3 depositional bedforms and 4 importance of mud proper scaling of experimental flows to natural turbidity currents is vital according to parsons et al 2002 p 626 the reynolds number of bottom boundary layer in natural turbidity currents is often greater than 100 whereas the reynolds number of experimental turbidity currents was always much less than unity parsons et al 2002 p 626 also acknowledged that the particle reynolds number in these experiments is not compatible with values of natural flows the authors attributed these scaling difficulties to the density of the particles and the viscosity of the fluid used in their

slope turbidite packets in a fore arc basin fill sequence of the plio pleistocene kakegawa group their formation and sea level changes discussion

comparison of depositional elements of an ancient and a modern submarine fan complex early pennsylvanian jackfork and late pleistocene mississippi fans normark urged that all future meaningful deep sea fan comparisons be confined to key depositional elements common to most turbidite systems these elements should include basin size tectonic and eustatic setting and depositional process indicators a test case for elemental comparisons between two widely studied fan complexes is presented and evaluated the lower pennsylvanian morrowan jackfork submarine fan complex extends from central arkansas to northeast texas sequence analysis suggests that the jackfork is composed of four to seven depositional episodes and occupies the floor of a deep basin bordered to the north and east by a passive carbonate siliciclastic shelf margin and to the south and east by a northward advancing orogenic belt the jackfork apparently unrestricted to the west and southwest the mississippi submarine fan complex extends from the submerged continental shelf of southern louisiana to the abyssal depths between yucatan and florida the fan complex is primarily pleistocene in age with the present morphologic fan being late wisconsinian the mississippi fan is composed of 17 depositional episodes it occupies the floor of a deep basin bordered on the north and west by quiescent halokinetic siliciclastic shelf margins and to the east and south by passive carbonate margins elemental comparisons between themore mississippi fan and a palynspastically restored jackfork fan complex suggest that both are quite similar even though the mississippi fan is up to three times larger in some categories comparative study of key depositional elements facilities a more complete understanding of both modern and ancient submarine fans less

internal waves in the strait of messina studied by a numerical model and synthetic aperture radar images from the ers 1 2 satellites a new numerical two layer model is presented which describes the generation of internal tidal bores and their disintegration into internal solitary waves in the strait of messina this model is used to explain observations made by the synthetic aperture radar sar from the european remote sensing satellites ers 1 and ers 2 the analysis of available ers 1 2 sar data of the strait of messina and adjacent sea areas show that 1 northward as well as southward propagating internal waves are generated in the strait of messina 2 southward propagating internal waves are observed more frequently than northward propagating internal waves 3 sea surface manifestations of southward as well as northward propagating internal waves are stronger during periods where a strong seasonal thermocline is known to be present 4 southward propagating internal bores are released from the sill between 1 and 5 hours after maximum northward tidal flow and northward propagating internal bores are released between 2 and 6 hours after maximum southward tidal flow and 5 the spatial separation between the first two internal solitary waves of southward propagating wave trains is smaller in the period from july to september than in the period from october to june the numerical two layer model is a composite of two models consisting of 1 a hydrostatic generation model which describes the dynamics of the water masses in the region close to the strait s sill where internal bores are generated and 2 a weakly nonhydrostatic propagation model which describes the dynamics of the water masses outside of the sill region where internal bores may disintegrate into internal solitary waves due to a technique for movable lateral boundaries the generation model is capable of simulating the dynamics of a lower layer that may intersect the bottom topography the proposed generation propagation model depends on one space variable only but it retains several features of a fully three dimensional model by including a realistic channel depth and a realistic channel width it is driven by semidiurnal tidal oscillations of the sea level at the two open boundaries of the model domain numerical simulations elucidate several observed characteristics of the internal wave field in the strait of messina such as north south asymmetry times of release of the internal bores from the strait s sill propagation speeds and spatial separations between the first two solitary waves of internal wave trains

sondrestrom incoherent scatter radar observations during the lower thermosphere coupling study september 21 26 1987 the incoherent scatter radar located at soendre stroemfjord greenland obtained e and f region measurements during the first lower thermosphere coupling study ltcs 1 september 21 26 1987 lower thermospheric neutral winds deduced from these measurements show that the neutral dynamics are influenced by both tidal oscillations and magnetospheric forcing during an interval which was relatively quiet geomagnetically september 23 24 a semidiurnal oscillation dominated the neutral motion the model equinox tidal amplitudes and phases of forbes 1982 for the diurnal tide are roughly in agreement with the observed diurnal oscillation for the first four days of the experiment vertical variations in the observed diurnal phases are consistent with the results of forbes and hagan 1988 and may provide evidence of dissipation of the propagating 1 1 tidal mode the semidiurnal motion observed during this period is not well represented by the recent theoretical results for the amplitude and phase of the semidiurnal tide forbes and vial this issue neutral winds obtained during a geomagnetically active interval september 25 26 displayed a flow pattern that was significantly distorted from that observed during the preceding relatively quiet interval although the changes in the zonal winds throughout this active interval were consistent with the directionmore of the ion drag force at 115 km and above the variations in the meridional winds suggest that other forces such as pressure gradients driven by joule heating need to be considered to explain the observations less

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

mesosphere thermosphere tidal coupling during the september 21 25 1987 ltcs 1 campaign the thermosphere ge 90 km is dynamically coupled to the mesophere and lower atmospheric regions by gravity waves tides and planetary waves which propagate upward from below and often undergo dissipation in the 80 to 150 km region this paper focuses on the mesosphere thermosphere coupling due to the solar semidiurnal atmospheric tide during the first lower thermosphere coupling study ltcs campaign interval of september 21 25 1987 during this period determinations of semidiurnal eastward u and northward v velocity components and temperature delta t are available within the 80 to 150 km region from a total of 13 incoherent scatter meteor and spaced antenna radars a new method is developed and reported here for assimilating such data sets into a self consistent global empirical description of the tidal dynamics between 80 and 150 km using a set of numerically generated hough mode extension hme functions for u v and delta t corresponding to the 2 2 2 3 2 4 and 2 5 semidiurnal tidal modes a least squares fit to the radar data is performed the fit results in a single complex normalizing factor for each hme from which globally continuous and internally consistent semidiurnal oscillations in u v and delta t as well as vertical velocity and density canmore be derived the quality of fit to these data from various height regions including both northern and southern hemispheres establishes the internal consistency between these measurements as well as the applicability of the method to future data sets the resulting empirical model reproduces the data significantly better than recent theoretical models suggesting use of the method for deriving tidal boundary conditions for thermospheric general circulation models less

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

thermospheric extensions of the classical expansion functions for semidiurnal tides solutions to the thermospheric tidal equations are described that define the extensions into the thermosphere of normalized wind and temperature structures associated with the 2 2 2 3 2 4 and 2 5 semidiurnal propagating tidal modes sample figures are presented that illustrate the degree of alteration of vertical structures with latitude and the change in horizontal shapes with height corresponding to semidiurnal oscillations in northerly westerly and vertical velocity and temperature in the thermosphere additional figures and tables covering the 80 to 400 km altitude region for five levels of solar activity at 6 latitude increments are available on microfiche for potential users the structures can be used to extend meteor wind 80 100 km and partial reflection drift 60 100 km measurements to heights above 100 km for consistency checks with tidal winds and temperatures from thomson scatter measurements at possibly different latitudes or to simultaneously fit data covering these height regions for modeling purposes supplementary figures and tables are available with entire article on microfiche order from american geophysical union 2000 florida avenue n w washington d c 20002 document j82 003 1 00 payment must accompany order

on the coupling between the lower and the upper thermosphere during the first lower thermosphere coupling study simultaneous observations of the neutral winds and temperatures and electron densities in the upper and lower thermosphere are presented the measurements were made at arecibo and millstone hill during the first lower thermosphere coupling study ltcs 1 campaign in september 1987 the observations show a great deal of day to day variability possibly due to the geomagnetic activity which occurred during the period storm effects are discernible in the data at low altitudes near 120 km even at low latitudes near 18 n theoretical simulations of the period were attempted by the national center for atmospheric research thermosphere ionosphere general circulation model a novel development was the use in the model of lower boundary conditions representative of the upward propagating semidiurnal tides based on the ltcs 1 mesosphere lower thermosphere observations the upward propagating diurnal 1 1 mode was also included in the model simulations of the low and mid latitudes did not substantially improve with the use of lower boundary conditions derived from the measurements the model was also unable to reproduce the observations in both the lower and upper thermosphere this may be partially due to the effects of geomagnetic activity on the atmospheric fields since the observational period included two intervals of geomagnetic disturbances in the lower thermosphere resolution of the discrepancies between the data and model predictions may require the extension of the model to lower altitudes at present the model predictions in the lower thermosphere are strongly dependent on the lower boundary conditions the model predicts that diurnal waves are not negligible in analysis of lower thermosphere data indeed near 100 km at the model location of arecibo the diurnal wave amplitudes of the meridional winds were predicted to be greater than the semidiurnal investigation of the model predictions awaits the development of techniques to obtain observations of at least 24 hours duration in the lower thermosphere and the extension of the theoretical models to lower altitudes

coordinated incoherent scatter radar observations of the semidiurnal tide in the lower thermosphere the incoherent scatter radars at arecibo 18 3 degree n millstone hill 42 6 degree n and sondrestrom 67 degree n simultaneously observed the thermal structure and dynamics of the earth s lower thermosphere during the period september 21 25 1987 as part of the lower thermosphere coupling study plasma spectral measurements were used to derive ion temperatures and horizontal neutral wind velocities in the altitude region 90 140 km and semidiurnal harmonics were determined from the data sets the daily mean temperatures were found to be within 40 degree k at the three stations and the largest semidiurnal temperature amplitudes exceeding 70 degree k above 115 km were recorded at arecibo mean winds were about plus minus 30 m s at most altitudes shifting from eastward to westward directions at 115 km and the semidiurnal amplitudes were in the range 20 70 m s phase variations with height reveal reasonable consistency among the three stations within 3 4 hours and indicate an average vertical wavelength of 40 70 km however a strong variation is seen in the vertical structure in the 110 to 130 km region suggesting the presence of different tidal modes comparison with the most current tidal propagation model by forbes and vial this issue indicates that the model tends to underestimate the amplitudes for this time period particularlymore above 110 km by virtue of the latitudinal distribution of the three radars their coordinated observations of the lower thermosphere serve to constrain numerical models and improve their understanding of this important yet complex region of the atmosphere less

reinterpretation of depositional processes in a classic flysch sequence pennsylvanian jackfork group ouachita mountains arkansas and oklahoma discussion the pennsylvanian jackfork group in the ouachita mountains of arkansas and oklahoma has conventionally been interpreted by many workers including us as a classic flysch sequence dominated by turbidites in a submarine fan setting however normal size grading and bouma sequences indicative of turbidite deposition are essentially absent in these sandstone beds they appear massive i e structureless in outcrop but when slabbed reveal diagnostic internal features these beds exhibit sharp and irregular upper bedding contacts inverse size grading floating mudstone clasts a planar clast fabric lateral pinch out geometries moderate to high detrital matrix up to 25 sigmoidal deformation duplex structures and contorted layers all these features indicate sand mplacement by debris flows mass flows and slumps mud matrix in these sandstones was sufficient to provide cohesive strength to the flow discrete units of current ripples and horizontal laminae have been interpreted to represent traction processes associated with bottom current reworking the dominance of sandy debris flow and slump deposits nearly 70 at degray spillway section and bottom current reworked deposits 40 at kiamichi mountain section and the lack of turbidites in the jackfork group have led us to propose a slope setting our rejection of a submarine fan setting has important implications for predicting sand body geometry and continuity because deposits of fluidal turbidity currents in fans are laterally more continuous than those of plastic debris flows and slumps on slopes a turbidite dominated fan model would predict an outer fan environment with laterally continuous sheetlike sandstones for the jackfork group in southern oklahoma and western arkansas whereas a debris flow slump model would predict predominantly a slope environment with disconne ted sandstone bodies for the same area

determination of offset across the northern margin of the wichita uplift southwest oklahoma the wichita uplift represents a tectonic element within the ancestral rocky mountains a series of basement involved uplifts and associated basins within the foreland of the ouachita orogen contrasting tectonic models for the evolution of the wichita uplift are evaluated by i analyzing the suite of structures within the frontal fault zone which separates the uplift from the adjoining anadarko basin and ii undertaking a palinspastic restoration of houton group late ordovician devonian thickness trends between the basin and the frontal fault zone to estimate the magnitude and sense of offset across the principal uplift bounding faults cross sections from uplift to basin show basement involved thrusts and folds similar to those recognized within the laramide late cretaceous tertiary foreland of the rocky mountains structural patterns in map view possess elements that have been previously interpreted as resulting from reverse slip and or left slip on the uplift bounding faults palinspastic restoration of isopach patterns between the frontal fault zone and anadarko basin indicates that offset across the frontal faults may be explained by oblique slip left reverse slip on the uplift bounding faults the component of left slip is nearly an order off magnitude less than proposed in some previous models of carboniferous tectonism within the foreland of the ouachita orogen

coordinated global radar observations of tidal and planetary waves in the mesosphere and lower thermosphere during january 20 30 1993 a multi instrument global campaign involving incoherent scatter medium frequency and meteor wind radars was conducted during the period of january 20 30 1993 to study the dynamics of the mesosphere and lower thermosphere data obtained from 15 radar stations covering a wide latitude range have been used to determine the global distribution of planetary and tidal waves during this 10 day campaign spectral analysis of the neutral winds measured by the radars in the altitude range from 80 to 130 km indicates the existence of a strong 48 hour wave near 90 km at latitudes between 40 n and 40 s that is present up to 108 km at 18 n the semidiurnal tide is large at middle and high latitudes near 90 km and is predominant above 110 km while the diurnal tide is observed to be particularly important in the upper mesosphere near 40 latitude a least squares fit to the radar data is performed to obtain the amplitudes and phases of the tidal and 48 hour waves comparison with national center for atmospheric research thermosphere ionosphere mesosphere general circulation model shows that the predictions from the model agree reasonably well with the observed global morphology of tidal wave amplitudes

subaerial debris flow deposition in the upper paleozoic cutler formation western colorado abstract outcrops of the lower part of the cutler formation near gateway colorado contain proximal alluvial fan deposits of two principal lithofacies the diamictite lithofacies d consists of a variety of sharply bounded massive muddy beds which are interpreted as deposits of subaerial debris flows the gravelly sandstone lithofacies s consists of amalgamated beds of laminated and cross bedded conglomeratic sandstones which are interpreted as water deposited sediments clasts in s are rarely larger than 0 5 m in maximum diameter but clasts in d are commonly much larger up to 8 m both normal and inverse grading are visible in d but grading is generally not well developed in either lithofacies imbrication of clasts although more pronounced and more consistent in s is fairly commo in both lithofacies four subfacies of diamictite are distinguishable on the basis of clast packing and grading massive matrix supported dram graded matrix supported dmg inversely graded clast supported dci and massive clast supported dcm given the hydrodynamic and rheologic properties of debris flows as reported by previous workers four debris flow regimes are postulated on the basis of varying water content and clast interaction subfacies dram and drag typify deposits of flows having viscous clast interactions subfacies dci represents deposits of flows having inertial or colliding clast interactions subfacies dram comprises deposits of flows with demonstrably high yield strengths subfacies dcm represents deposits of flows in which yield strength was insufficient to support most clasts this classification specifically recognizes turbulence selective deposition and bedload transport of clasts as essential characteristics of certain dilute debris flows it also accommodates as debris flow deposits some beds which have features usually associated with aqueous deposition including clast frameworks channelization imbrication and normal grading

subsurface structure of the eastern arkoma basin analysis of 425 km of seismic reflection data in the eastern arkoma basin reveals a structure and history quite different from those previously reported for the arkoma basin the eastern arkoma basin has three structural styles that formed in the following chronological order deep steep normal faults shallow listric normal faults and thrust faults the origin of the structural styles and the paleozoic history of the eastern arkoma basin may be summarized as follows late proterozoic or early cambrian rifting was followed by deposition of cambrian through upper mississippian strata on a passive plate margin the mississippian pennsylvanian boundary marks a time of major down to the south normal faulting with coincident folding of the footwall blocks and truncation of t e faulted and folded terrain by a pre morrowan mississippian pennsylvanian unconformity the unconformity slopes southward and steepens locally across the erosionally truncated footwall blocks during the pennsylvanian down to the south listric normal faults cut the atokan and morrowan sections and merged with but did not displace the steeper segments of the sub morrowan unconformity surface folds north of the ross creek thrust are rollover anticlines overlying these listric normal faults major deformation in the eastern arkoma basin terminated with emplacement of the ross creek thrust in the late pennsylvanian

upper pleistocene turbidite sand beds and chaotic silt beds in the channelized distal outer fan lobes of the mississippi fan cores from a mississippi outer fan depositional lobe demonstrate that sublobes at the distal edge contain a complex local network of channelized turbidite beds of graded sand and debris flow beds of chaotic silt off lobe basin plains lack siliciclastic coarse grained beds the basin plain mud facies exhibit low acoustic backscatter on seamarc ia sidescan sonar images whereas high acoustic backscatter characteristic of the lobe sand and silt facies the depth of the first sand silt layer correlates with relative backscatter intensity and stratigraphic age of the distal sublobes i e shallowest sand highest backscatter and youngest sublobe the high proportion 50 of chaotic silt compared to graded sand in the distal outer fan sublobes may be related to the unstable muddy canyon wall source areas of the extensive mississippi delta fed basin slope a predominace of chaotic silt in cores or outcrops from outer fan lobes thus may predict similar settings for ancient fans

the bouma sequence and the turbidite mind set abstract conventionally the bouma sequence bouma a h 1962 sedimentology of some flysch deposits a graphic approach to facies interpretation elsevier amsterdam 168 pp composed of ta tb tc td and te divisions is interpreted to be the product of a turbidity current however recent core and outcrop studies show that the complete and partial bouma sequences can also be interpreted to be deposits formed by processes other than turbidity currents such as sandy debris flows and bottom current reworking many published examples of turbidites most of them hydrocarbon bearing sands in the north sea the norwegian sea offshore nigeria offshore gabon gulf of mexico and the ouachita mountains are being reinterpreted by the present author as dominantly deposits of sandy debris flows and bottom current reworking with only a minor percentage of true turbidites i e deposits of turbidity currents with fluidal or newtonian rheology in which sediment is suspended by fluid turbulence this reinterpretation is based on detailed description of 21 000 ft 6402 m of conventional cores and 1200 ft 365 m of outcrop sections the predominance of interpreted turbidites in these areas by other workers can be attributed to the following 1 loose applications of turbidity current concepts without regard for fluid rheology flow state and sediment support mechanism that result in a category of turbidity currents that includes debris flows and bottom currents 2 field description of deep water sands using the bouma sequence an interpretive model that invariably leads to a model driven turbidite interpretation 3 the prevailing turbidite mind set that subconsciously forces one to routinely interpret most deep water sands as some kind of turbidites 4 the use of our inability to interpret transport mechanism from the depositional record as an excuse for assuming deep water sands as deposits of turbidity currents 5 the flawed concept of high density turbidity currents that allows room for interpreting debris flow deposits as turbidites 6 the flawed comparison of subaerial river currents fluid gravity flows dominated by bed load transport with subaqueous turbidity currents sediment gravity flows dominated by suspended load transport that results in misinterpreting ungraded or parallel stratified deep sea deposits as turbidites and 7 the attraction to use obsolete submarine fan models with channels and lobes that require a turbidite interpretation although the turbidite paradigm is alive and well for now the turbidites themselves are becoming an endangered facies

remote imaging of internal solitons in the coastal ocean abstract during a combined in situ and airborne remote sensing exercise off oceanside ca a compact airborne spectrographic imager casi observed alongshore lineations which were associated with an internal soliton packet accompanying a tidally generated internal solitary wave solibore the soliton packets were most evident in the images at green wavelengths which penetrate the deepest into the water column and only weakly evident at optical wavelengths with shallower penetration we believe that this is the first observation of internal soliton packets determined from remotely sensed upwelled radiance we hypothesize that the lineations were produced by changes in the upwelling radiance from the interior of the water column not by changes in surface reflectance using a simulation it is demonstrated that such lineations can be produced by vertical modulation of the inherent optical properties iops during the passage of the internal soliton packet since surface manifestations are not always present this opens the potential for broadly based inventories of internal solitons in coastal waters

slump dominated upper slope reservoir facies intra qua iboe pliocene edop field offshore nigeria abstract an integration of sedimentologic and 3d seismic data provides a basis for unraveling complex depositional processes and sand distribution of the intra qua iboe iqi reservoir pliocene edop field offshore nigeria nearly 3 000 feet of conventional core was examined in interpreting slump slide debris flow bottom current turbidity current pelagic hemipelagic wave and tide dominated facies the iqi was deposited on an upper slope in close proximity to the shelf edge through time as the shelf edge migrated seaward deposition began with a turbidite channel dominated slope system iqi 1 and 2 and progressed through a slump debris flow dominated slope system iqi 3 the principal reservoir to a tide and wave dominated collapsed shelf edge deltaic system iqi 4 using seismic time slices and corresponding depositional facies in the core a sandy open quotes fairway open quotes has been delineated in the iqi 3 because of differences in stacking patterns of sandy and muddy slump intervals seismic facies show 1 both sheet like and mounded external forms geometries and 2 parallel continuous as well as chaotic hummocky internal reflections in wireline logs slump facies exhibits blocky coarsening up fining up and serrated motifs in the absence of conventional core slump facies may be misinterpreted and even miscorrelated because seismic facies and log motifsmore of slumps and debris flows tend to mimic properties of turbidite fan deposits the slump dominated reservoir facies is composed of unconsolidated fine grained sand thickness of individual units varies from 1 to 34 feet but amalgamated intervals reach a thickness of up to 70 feet and apparently form connected sand bodies porosity commonly ranges from 20 to 35 horizontal permeability commonly ranges from 1 000 to 3 000 md less

sediment resuspension and mixing by resonantly generated internal solitary waves the observation of internal solitary waves isws propagating upstream along a strongly stratified bottom layer on the california shelf is reported an increased concentration of particulates in the water column accompanies the passage of these isw packets the estimated local richardson number in the bottom vicinity is around 1 4 and a vertical coefficient of eddy diffusivity of order 1022 m2 s21 is associated with the upstream propagating leading isw the leading isw gave rise to reversed flow in an 8 m layer above the bottom it is argued that the upstream propagating isws were generated by resonant flow over bottom topography internal waves generated in this way seem to be frequent in the record of a month long experiment model results suggest that the isws can carry up to 73 of such generated long wave energy the ocean conditions at the site are similar to those of other coastal sites which suggests that the phenomenon described here may be common

lunar tidal winds at adelaide and saskatoon at 80 to 100 km heights 1985 1990 winds data from the two sites were analyzed for lunar tides in 2 year groups the variation with height of the phase and amplitude of the tide showed considerable variability from year to year yet in general seasonal variations at particular heights were similar to those determined previously phases of the tide at the two sites were compared in order to estimate whether the tide was symmetric or antisymmetric for this purpose it was found necessary to use only 1 year data sets the predominance of symmetric tides during solstice months and antisymmetric tides at the equinox came as a surprise yet the result is in broad agreement with phase relations of the lunar geomagnetic tide

carbonate debris flows cow head group western newfoundland abstract the cow head group is an allochthonous cambro ordovician sequence of deep water limestone conglomerates mudstones to grainstones minor quartz sandstones siltstones and shales platy clast conglomerates and boulder rich megaconglomerates as much as 100 m thick exhibit features similar to those described for subaerial debris flows that is flat sharp bases with only minor evidence for erosion poorly developed clast fabric with tilting of platy clasts at right angles to the flow direction boulders floating within flows or projecting above the tops of flows irregular flow tops indicating primary relief above the sea floor and tapered flow margins snouts snout geometry and the extent of boulder projection both allow calculation of debris static strength these results combined with measured flow thickness permit calculation of minimum and maximum paleoslope gradients original debris static strengths were in the range of 103 to 105 dynes cm2 similar to the observed range in subaerial flows calculations yield bottom gradients of l l 8 but independent field data suggest that the paleoslope dip was on the order of only a few degrees this constraint suggests that debris strength was substantially reduced during flow probably by excess pore fluid pressures thus permitting flow on very gentle slopes the paleoslope orientations used in this study are substantially different from those previously published by hubert et at 1977

deposition of ungraded muds from high density non turbulent turbidity currents turbidity current deposits of mud have recently been found up to 10m in thickness resulting from single depositional events1 2 turbidites 1 5 m thick from the madeira abyssal plain3 4 display long segments with little vertical change of grain size5 6 this suggests that the currents froze in some way making them unable to sort sediment here we suggest that a decline in flow speed of these currents led to a concentration gradient in silt close to the bed that was sufficiently steep to stratify the flow a concentration gradient of 18 kg m 3 over 1 5 m height gives a layer richardson number above the critical value of 0 25 for damping of turbulence we propose that with turbulence severely damped a dense suspension of fine material consolidates like a static suspension while continuing to flow downslope the current changes from a fully turbulent flow to a decelerating flow with suppressed turbulence and increasing density in the latter state interparticle forces prevent differential settling of the coarser grains

semidiurnal tidal climatology of the e region theoretical predictions of global monthly and seasonally averaged semidiurnal temperatures and winds between 80 and 150 km are presented and compared with seasonal means from measurements at the arecibo chatanika millstone hill and sondrestrom incoherent scatter radars the model values above 100 km are obtained by utilizing a set of tabulated hough mode extension functions to extrapolate the 2 2 2 3 2 4 and 2 5 propagating tidal modes at 100 km from a spectral model not valid in the e region due to the way molecular dissipation is parameterized to higher altitudes and by superimposing a component driven by in situ excitation important mainly above 140 km the monthly simulations demonstrate the close coupling that exists between seasonal and latitudinal structures and argue for an observational program emphasizing adequate seasonal and latitudinal coverage despite constraints imposed by the distributions of existing data with respect to month and year comparisons with the model reveal several trends that appear to be real 1 the model amplitudes are usually 20 50 smaller than those observed 2 vertical wavelengths are well predicted by the model but model phases generally lead the observations at middle and low latitudes by approximately 2 3 hours at all heights for both winds and temperatures 3 semidiurnal temperatures at middle and low latitudes in both the observations and model indicate significant seasonal changes in the phase of the temperature oscillation but not in the winds and 4 the seasonal trends in the model and observations are consistent with summer leading winter at millstone hill while the reverse is true at arecibo the sources of the absolute amplitude and phase discrepancies in the model which are probably connected with the adopted mean wind and thermal excitation specifications need to be investigated in addition a concerted effort must be made within the coupling energetics and dynamics of atmospheric regions cedar program to better delineate the seasonal latitudinal thermal structure and dynamics of the e region following the example of the extensive f region observational data base which has been accumulated over the last decade

traction carpet stratification in turbidites fact or fiction abstract the spaced stratification that characterizes some thick deep water sandstones consists of a stack of layers 5 10 cm thick that are inversely graded at their base and structureless at their top these layers have been attributed to deposition from a succession of collapsed inertia layers traction carpets prior to collapse each layer was believed to have been maintained by shear from the overriding turbidity current this depositional model is based on the mistaken assumption that the distribution of shear stress in such a traction carpet is indistinguishable from the distribution of shear stress in a grain flow on a steep slope instead shear stress in an externally sheared traction carpet should be approximately constant from the top to the base of the layer and deposition sho ld be a gradual process leaving no record of sequentially active inertia layers inertia layers that do form under large turbidity currents are probably never as thick as 5 10 cm based on available data from shear cell experiments instead inertia layers are probably about 1 cm thick similar to the thickness of the inversely graded basal part of each layer in field examples of spaced stratification the rest of each inversely graded stratum probably forms due to rapid fallout from suspension the basal inversely graded 1 cm is believed to record strong shear that may accompany impingement on the bed of large turbulent eddies hence spaced stratification may not be a structure produced beneath steady flows but may record strong y fluctuating hydrodynamic conditions and vigorous burst sweep cycles in large turbidity currents

atmospheric tide 2 the solar and lunar semidiurnal components solar and lunar semidiurnal wind and temperature oscillations from the surface to 400 km are simulated for average solar activity conditions utilizing the numerical tidal model described in part 1 hough mode decomposition of the solstitial solar semidiurnal tide excited by h2o and o3 insolation absorption below 80 km indicates that it is characterized by a predominance of 2 2 below 60 km about equal contributions of 2 2 2 3 and 2 4 between 70 and 90 km mostly 2 4 with some 2 5 and 2 2 between 90 and 120 km and a predominance of 2 2 above 140 km with secondary contributions from 2 3 and 2 5 the solstitial lunar semidiurnal tide is characterized by a predominance of 2 2 below 70 km 2 4 with secondary contributions from 2 2 2 3 and 2 5 between 80 and 110 km and by 2 2 with a fairly strong secondary contribution from 2 3 above 120 km similar descriptions for both the solar and lunar oscillations apply at equinox except that the asymmetric 2 3 and 2 5 modes are absent relative to the solar component lunar temperature and wind amplitudes are sufficiently large 20 in the lower and upper thermosphere to account for some of the observed variability previously attributed to the solar tide amplitudes of the 2 4 and 2 5 modes above 100 km are significantly affected by mesospheric eddy diffusion coefficients in excess of 2 106 cm s 1 the total solar semidiurnal exospheric temperature oscillation for average solar conditions ranges from 10 20 k poleward of 40 n to 40 60 k equatorward of 30 n and has its origin in three sources of excitation all of comparable importance 1 euv solar radiation absorption in the lower thermosphere 100 200 km 2 in situ momentum coupling due to the interaction of diurnal winds and diurnally varying ion drag and 3 tides propagating upwards from below 100 km in addition the calculations are compared with rocket meteor radar partial reflection thomson scatter and satellite data to evaluate the consistency of the model with observations

submarine fan sedimentation ouachita mountains arkansas and oklahoma abstract more than 10 000 m 32 800 ft of interbedded sandstones and shales comprise the upper mississippian and lower pennsylvanian flysch succession stanley jackfork johns valley atoka in the ouachita mountains of arkansas and oklahoma deposited primarily by turbidity current and hemipelagic processes in bathyal and abyssal water depths these strata formed major submarine fan complexes that prograded in a westward direction along the axis of an elongate remnant ocean basin that was associated with the collision and suturing of the north american and african south american plates a longitudinal fan system is visualized as the depositional framework for these strata which were deposited in a setting analagous to the modern bengal fan of the indian ocean facies analysis of the jackfork formation indicates that inner fan deposits are present in the vicinity of little rock arkansas middle fan channel and interchannel deposits occur at degray dam and friendship arkansas and outer fan depositional lobe deposits are present in southeastern oklahoma boulder bearing units olistostromes often with exotic clasts were shed laterally into the ouachita basin they occur throughout the flysch succession and in all fan environments i e inner middle and outer this relationship may serve as a useful criterion for recognizing analogous longitudinal fan systems in the rock record

reinterpretation of depositional processes in a classic flysch sequence pennsylvanian jackfork group ouachita mountains arkansas and oklahoma discussion authors reply

is the turbidite facies association scheme valid for interpreting ancient submarine fan environments although turbidite facies reflect only processes of deposition turbidite facies associations are routinely used to identify ancient submarine fan subenvironments e g upper fan channel lobe etc the assumption that process of deposition also reflects environment of deposition may not be valid for the following reasons 1 mutti and ricci lucchi9s facies association scheme for submarine fans has been developed exclusively from ancient turbidite sequences however the true relationship between such turbidite facies associations and related fan subenvironments has not been confirmed from modern fans 2 individual channel levee systems of many modern submarine fans are in many cases large enough to contain the entire ancient fan systems on which these facies associations are based 3 large channel levee systems comparable to those of modern fans have not been recognized in outcrops consequently the validity of turbidite facies associations for interpreting ancient submarine fan subenvironments must be considered tenuous until confirmed in modern fans

ouachita appalachian juncture a paleozoic transpressional zone in the southeastern u s a the northern margin of gondwana collided with the southern margin of the north american craton in the late paleozoic 330 265 ma near normal compressional stresses generated where the trend of the north american margin was nearly perpendicular to gondwana s plate motion vector closure direction caused extensive crustal shortening and decollement thrusting within the sedimentary section the appalachian and ouachita fold belts are the erosional remnants of this collision on the north american margin transecting the ouachita fold belt are several zones of late paleozoic transcurrent faulting the val verde ardmore anadarko and reelfoot zones they occur where the precollision margin of the north american craton was oriented oblique or parallel to the closure direct on with gondwana stresses generated within these zones during the collision were transpressional rather than simply compressional and gave rise to high angle faulting high amplitude vertical displacements and the emplacement of positive flower structures in the val verde and ardmore anadarko basins these features have proven to be major structural traps for oil and gas on the basis of seismic and well data this study identifies a zone of complex structures including positive flower structures in the subsurface paleozoic section of kemper county in east central mississippi the region is considered to be another transpressional zone analogous to the val verde ardmore anadarko and reelfoot zones the kemper county zone separates and truncates the appalachian valley and ridge fo d belt in the subsurface from the mississippi ouachita deformed belt to the west and is therefore also identified as the juncture between the ouachita and appalachian fold belt systems in the southeastern u s a

evidence for carbonate platform failure during rapid sea level rise ca 14 000 year old bioclastic flow deposits in the lesser antilles bioclastic flow deposits offshore from the soufriere hills volcano on montserrat in the lesser antilles were deposited by the largest volume sediment flows near this active volcano in the last 26 kyr the volume of these deposits exceeds that of the largest historic volcanic dome collapse in the world which occurred on montserrat in 2003 these flows were most probably generated by a large submarine slope failure of the carbonate shelf comprising the south west flank of antigua or the east flank of redonda adjacent islands that are not volcanically active the bioclastic flow deposits are relatively coarse grained and either ungraded or poorly graded and were deposited by non cohesive debris flow and high density turbidity currents the bioclastic deposit often comprises multiple sub units that cannot be correlated between core sites some located just 2 km apart multiple sub units in the bioclastic deposit result from either flow reflection stacking of multiple debris flow lobes and or multi stage collapse of the initial landslide this study provides unusually precise constraints on the age of this mass flow event that occurred at ca 14 ka few large submarine landslides have been well dated but the slope failures that have been dated are commonly associated with periods of rapid sea level change