reflection and tunneling of ocean waves observed at a submarine canyon 1 ocean surface gravity waves with periods between 20 and 200 s were observed to reflect from a steep walled submarine canyon observations of pressure and velocity on each side of the canyon were decomposed into incident waves arriving from distant sources waves reflected by the canyon and waves transmitted across the canyon the observed reflection is consistent with long wave theory and distinguishes between cases of normal and oblique angles of incidence as much as 60 of the energy of waves approaching the canyon normal to its axis was reflected except for waves twice as long as the canyon width which were transmitted across with no reflection although waves approaching the canyon at oblique angles cannot propagate over the canyon total reflection was observed only at frequencies higher than 20 mhz with lower frequency energy partially transmitted across analogous to the quantum tunneling of a free particle through a classically impenetrable barrier

south polar residual cap of mars features stratigraphy and changes abstract the south residual polar cap of mars rich in co2 ice is compositionally distinct from the north residual cap which is dominantly h2o ice the south cap is also morphologically distinct displaying a bewildering variety of depressions formed in thin layered deposits which have been observed to change by scarp retreat over an interval of one mars year malin et al 2001 science 294 2146 2148 the climatically sensitive locale of the residual caps suggests that their behavior may help in the interpretation of recent fluctuations or repeatability of the mars climate we have used mars global surveyor mars orbiter camera moc images obtained in three southern summers to map the variety of features in the south residual cap and to evaluate changes over two mars years mars y the images show that there are two distinct layered units which were deposited at different times separated by a period of degradation the older unit 10 m thick has layers approximately 2 m thick the younger unit has variable numbers of layers each 1 m thick the older unit is eroding by scarp retreat averaging 3 6 m mars y a rate greater than the retreat of 2 2 m mars y observed for the younger unit the rates of scarp retreat and sizes of the different types of depressions indicate that the history of the residual cap has been short periods of deposition interspersed with longer erosional periods erosion of the older unit probably occupied 100 150 mars y one layer may have been deposited after the mariner 9 observations in 1972 residual cap layers appear to differ from normal annual winter deposits by having a higher albedo and perhaps by having higher porosities these properties might be produced by differences in the depositional meteorology that affect the fraction of high porosity snow included in the winter deposition

clinoforms and clinoform systems review and dynamic classification scheme for shorelines subaqueous deltas shelf edges and continental margins abstract clinoforms are inclined and normally basinward dipping horizons developed over a range of spatial and temporal scales in both siliciclastic and carbonatic systems the study of clinoform successions underpins sequence stratigraphy and all efforts to reconstruct the relative partitioning of reservoir seal and source rocks along shoreline to basin floor profiles here we review clinoform research and propose a more systematic description and classification of clinoforms this is a crucial step to improve predictions of facies and lithology distribution within shoreline to continental shelf and abyssal plain successions together with the genesis drivers and dynamics of their constituent sedimentary units four basic clinoform types are here distinguished in delta shorelines lacustrine and marine environments on the basis of their overall spatial and temporal scale morphology outbuilding dynamic and geodynamic and depositional setting 1 2 delta scale clinoforms which in turns are sub divided into shoreline and delta scale subaqueous clinoforms 3 shelf edge clinoforms and 4 continental margin clinoforms delta scale clinoform sets are tens of metres high and typically represent 1 103 kyr with progradation rates ranging from 1 000 100 000 m kyr for shorelines and subaerial deltas to 100 20 000 m kyr for subaqueous deltas shelf edge clinoform sets are hundreds of metres high and are nucleated and accreted in 0 1 20 myr usual progradation rates of 1 100 m kyr by successive cross shelf transits of delta scale clinoforms continental margin clinoform sets are thousands of metres high hallmark key geodynamic crustal boundaries e g continent ocean transition and slowly prograde basinwards in ca 5 100 myr with typical rates of 0 1 10 m kyr as a consequence of the very different progradation rates and of the difficulty of large scale clinothems to backstep during transgressions shorelines are the most dynamic clinoforms with regards to position continental margins the least and shelf edges are intermediate shortly after a transgression therefore the four clinoform types may prograde synchronously along shoreline to abyssal plain transects forming compound clinoform systems during the subsequent regressive cycle however due to the dissimilarity in progradation rates different clinoform types will normally merge progressively with each other giving rise to hybrid clinoforms e g shelf edge deltas and fewer depositional breaks in slope are distinguished along a single shoreline to abyssal plain transect overall all clinoform systems are the result of the dynamic evolution of compound and hybrid clinoforms along a temporal and spatial continuum regulated by the cyclical backstepping of the smaller scale system within natural progradational retrogradational cycles of larger scale clinothem outbuilding all clinothem types may show either an accretionary active or draping passive style depending on the proximity to the sediment source draping clinothems are nearly always composed of condensed fine grained sediments while actively accreting clinothems can be composed of predominantly coarse grained i e reservoir forming or predominantly fine grained i e non reservoir lithotypes a novel hierarchical classification scheme for both recent and ancient clinoforms is here proposed consisting of 12 classes the four basic clinoform types delta scale shoreline delta scale subaqueous shelf edge and continental margin are sub divided into eight accretionary active and draping passive sub types 8 division each accretionary sub type is then sub divided into a sandstone prone and mudstone prone variant 12 division which can be at least tentatively predicted on the basis of the clinoform morphology even in the absence of direct stratigraphic logs

hyperspectral imaging of convective co2 ice clouds in the equatorial mesosphere of mars 1 a unique feature of the martian climate is the possibility for carbon dioxide the main atmospheric constituent to condense as ice co2 ice is usually detected as frost but is also known to exist as clouds this paper presents the first unambiguous observation of co2 ice clouds on mars these images were obtained by the visible and near infrared imaging spectrometer omega on board mars express the data set encompasses 19 different occurrences compositional identification is based on the detection of a diagnostic spectral feature around 4 26 m which is produced by resonant scattering of solar photons by mesospheric co2 ice particles in a spectral interval otherwise dominated by saturated gaseous absorption observed clouds exhibit a strong seasonal and geographic dependence concentrating in the near equatorial regions during two periods before and after northern summer solstice ls 45 and 135 radiative transfer modeling indicates that the 4 26 m feature is very sensitive to cloud altitude opacity and particle size thereby explaining the variety of spectra associated with the cloud images on two orbits the simultaneous detection of clouds with their shadow provides straightforward and robust estimates of cloud properties these images confirm the conclusions established from modeling clouds are thick with normal opacities greater than 0 2 in the near infrared and are lofted in the mesosphere above 80 km the mean radius of co2 ice crystals is found to exceed 1 m an unexpected value considering this altitude range this finding implies the existence of high altitude atmospheric updrafts which are strong enough to counteract the rapid gravitational fall of particles this statement is consistent with the cumuliform morphology of the clouds which may be linked to a moist convective origin generated by the latent heat released during co2 condensation

sublacustrine gravity induced deposits the diversity of external geometries and origins abstract our current knowledge of deep water depositional systems is mainly built of extensive achievements obtained from marine basins although lacustrine basins are important oil gas productive areas of the world gravity induced deposits in these basins are poorly understood in the literature when compared with those documented in marine basins based on new insights from 3d seismic data this paper attempts to investigate the effect of the interaction between gravity induced flows and lake floor topography on the resulting external geometry of gravity induced deposits in the cretaceous qingshankou and nenjiang formations of the songliao basin slb eight different shapes of gravity induced deposits were identified in the slb and which were in turn grouped into four distinct categories according to external shape internal architecture and spatial assembly 1 channel fan complexes 2 fan form complexes 3 strip form complexes and 4 pond form complexes furthermore fan form complexes can be subdivided into four subcategories isolated fan with compressional ridges isolated fan without compressional ridges mother son fans and stacked fans strip form complexes can be subdivided into two subcategories including strip form controlled by gully system and strip form controlled by growth faults sediment transport mechanism density flows or mass transport flows and lake floor topography together influence the pathways runout distances discharge places and internal characteristics of gravity induced deposits which could ultimately influence external geometries of gravity induced deposits in the slb consequently sublacustrine gravity induced deposits does not exhibit classic fan like geometry frequent and powerful hyperpycnal flows associated with flood events are fairly common and develop channel distal fan complexes mtds exhibit various external geometries which are significantly affected by growth faults slope gullies gradient and basin floor irregularities the new depositional model built from the slb is vital to understanding the distribution of gravity flow deposits in a sublacustrine slope

the cilicia adana basin complex eastern mediterranean neogene evolution of an active fore arc basin in an obliquely convergent margin abstract detailed interpretation of multi channel seismic reflection profiles showed that the deposition of the miocene successions in the cilicia adana basin complex occurred within a foredeep south of the arcuate tauride fold thrust belt the misis kyrenia fault zone defined the northernmost of a number of smaller thrust culminations developed within this foredeep fluvio deltaic successions suggest that the adana and inner cilicia basins became emergent during the tortonian when the western portion of the piggy back basin retained a marine connection the entire region became emergent during the messinian salinity crisis and up to 1000 m of evaporites were deposited in the cilicia and southern adana basins stratigraphic and structural relationships demonstrated that the late plio quaternary cilicia adana basin complex evolved as an asymmetric piggy back basin on the hanging wall of the large south verging misis kyrenia thrust culmination on the misis kyrenia segment of the culmination thrust activity ceased in early messinian whereas on the kyrenia segment it continued to the present the shift in the kinematics is expressed by the development of the ne sw trending steep faults with extensional separations bounding the plio quaternary depocentre in the adana and inner cilicia basins these basement rooted faults are incompatible with the contractional regime that existed in this part of the basin complex during the miocene in the outer cilicia basin the incompatibility between a domain of continued south directed fold thrust activity and uplift on the kyrenia range and a domain of extension associated with the development of plio quaternary depocentre indicates that strain is strongly partitioned across the e w trending southern basin bounding fault system along the southern margin of the outer cilicia basin progressive westward displacement of the tauride block within the aegean anatolian microplate created a localised transtensional regime within the inner cilicia and adana basins suggesting the presence of hard intra plate fault boundaries centred along the misis kyrenia horst block and the southern basin bounding fault system the northern basin bounding fault system including the kozan fault in the cilicia basin is a set of large antithetic structures linked to the master faults the westward pull out of the tauride block is related to the overall westward escape of the aegean anatolian microplate during the latest miocene to early pliocene whereas the continued contraction south of the basin complex across cyprus is related to the evolving collision and under plating of the continental micro fragment the eratosthenes we propose that the southern master fault of the outer cilicia basin primarily functions as a boundary separating a contractional microplate domain to the south from a transtensional microplate domain to the north

mars aerosol studies with the mgs tes emission phase function observations optical depths particle sizes and ice cloud types versus latitude and solar longitude 1 emission phase function epf observations taken in 1999 2001 by mars global surveyor thermal emission spectrometer mgs tes support the broadest study of martian aerosol properties to date tes solar band and infrared ir spectral epf sequences are analyzed to obtain first time seasonal latitudinal distributions of visible optical depths particle sizes and single scattering phase functions this combined angular and wavelength coverage enables identification of two distinct ice cloud types over 45 s 45 n type 1 ice clouds exhibit small particle sizes reff 1 2 m and a distinctive backscattering increase they are most prevalent in the southern hemisphere during aphelion but also appear more widely distributed in season and latitude as topographic and high altitude 20 km ice hazes type 2 ice clouds exhibit larger particle sizes reff 3 4 m a distinct side scattering minimum at 90 100 phase angles characteristic of a change in particle shape relative to the type 1 and appear most prominently in the northern subtropical aphelion cloud belt the majority of retrieved dust visible to ir optical depth ratios are indicative of reff 1 5 0 1 m consistent with pathfinder and viking mariner 9 reanalyses however increased ratios 2 7 versus 1 7 appear frequently in the northern hemisphere over ls 50 200 indicating substantially smaller dust particles sizes reff 1 0 0 2 m at this time in addition larger reff 1 8 2 5 m dust particles were observed locally in the southern hemisphere during the peak of the 2001 global dust storm detailed spectral modeling of the tes visible band pass indicates agreement of epf derived dust single scattering albedos 0 92 0 94 with the spectrally resolved results from pathfinder observations

moc observations of four mars year variations in the south polar residual cap of mars abstract the residual south polar cap of mars rspc is distinct from the residual north polar cap both in composition and in morphology co 2 frost in the rspc is stabilized by its high albedo during southern spring and summer despite the relatively large insolation during that period the morphology of the rspc in summer displays a bewildering variety of depressions that are formed in relatively thin layers of co 2 the increase of the size of these depressions between each of the first three years of mars global surveyor mgs observations may possibly signal some sort of climate change on the planet for example the erosion of the bright plateaus might reduce the rspc albedo and affect the energy balance the mars orbiter cameras moc on mgs observed mars for four consecutive martian years before contact with the spacecraft was lost in late 2006 during this period coverage of the polar regions was particularly dense because mgs flew over them on every orbit in this paper we report on the four year behavior of the morphological features in the rspc and on the large scale variability in rspc albedo over the period the changes in the size of the surface features in the rspc due to backwasting that were first observed between mars years my 24 and 25 and subsequently between my25 and m26 was observed to continue at the same rate through my 27 the results indicate that on average thicker layers in the rspc retreat faster than thinner ones roughly in proportion to their thickness we argue that a simple difference in porosity between the a and b layers can explain this difference although other factors could be involved the large scale albedo of the rspc decreases as the depressions are uncovered by sublimation of seasonal co 2 however any interannual differences in albedo due to the backwasting process are masked by interannual differences in the summer dust opacity in the rspc region

submarine depositional terraces in the tyrrhenian sea as a proxy for paleo sea level reconstruction problems and perspective abstract in the last decade great effort was put in the study of relative sea level changes on mediterranean coastlines through the integration of geophysical modelling and proxy data of paleo shorelines in this paper we show potential and limitations of using additional marine geomorphic sedimentary markers for earlier and lower sea levels these markers are submarine depositional terraces sdts i e deposits formed by a set of small prograding sedimentary wedges having a terraced shape and found at variable shallow water depths mainly the first 150 m on continental and insular shelves in the tyrrhenian sea the shallowest terraces near shore have their edges at depths between 10 m and 30 m approximating the modern local storm wave base level their formation is thought to be associated with the modern sea level highstand and thus can be used as the modern analogue for deeper terraces formed in the past when the sea level was on the middle and outer shelf mid shelf terraces have their edges at variable depths between 40 m and 90 m and probably formed during the last sea level rise they show a patchy spatial distribution and a large variability in their internal structure so that they are not suitable for correlation on a regional scale shelf edge terraces have their edges at depths between 120 m and 170 m which is close or deeper than the last glacial maximum lgm sea level stand they show a remarkable lateral continuity and a prograding internal structure similar to those at shallower depth and thus represent a proxy for the sea level position at around 20 ka however the position of sdts edges is not a direct measure of paleo sea level positions because their depth depends on a complex interplay of several factors such as the base of the storm wave and its variation in response to coastal physiography as well as the occurrence of subsequent erosional or depositional processes depending on the geophysical and mapping methods used to determine their depth the associated error range can also differ based on the analysis of these complexities and a wide range of physiographic settings of the tyrrhenian sea we discuss these error ranges in order to assess potential and limitation of the sdt for analyses of vertical mobility of an area

observations of nearshore circulation rip currents a sector scanning doppler sonar was deployed at the end of the scripps institution of oceanography pier aimed in toward the surf zone estimates of acoustic backscatter intensity and radial velocity were obtained seaward of the break point over a wedge with an arc of about 45 and a radius of 200 to 400 m the acoustic intensity is proportional to some combination of the bubble density and the suspended sediment in the water well defined jets of water extending seaward from the surf zone or rip currents were observed these rip currents occurred episodically recurred aperiodically one to four times per hour or so and lasted several minutes each the water transported offshore within the rips was rich in suspended sediment and bubbles producing distinctive bright patterns that can be easily recognized in successive images of backscatter intensity from the sonar fluid velocities were estimated from the doppler shift of the sonar signal approaching 0 7 m s in some of the events simultaneously a transect of temperature density and turbidity within the rip current was obtained with conductivity temperature depth ctd and optical backscatter strength obs sensors these data describe the ejection of warm turbid water from the surf zone and provide a comparison between the acoustic intensity and the optical turbidity of the fluid the horizontal extent of the sonar measurements and the vertical resolution of the ctd obs measurements complement each other in the study of the dynamics of the nearshore environment exchange rates are not fully resolved here since only one seaward jet is contained within the field of view however these observations suggest that rip currents could cause significant exchange between the nearshore and offshore waters

tectonic controls on nearshore sediment accumulation and submarine canyon morphology offshore la jolla southern california chirp seismic and swath bathymetry data acquired offshore la jolla california provide an unprecedented three dimensional view of the la jolla and scripps submarine canyons shore parallel patterns of tectonic deformation appear to control nearshore sediment thickness and distribution around the canyons these shore parallel patterns allow the impact of local tectonic deformation to be separated from the influence of eustatic sea level fluctuations based on stratal geometry and acoustic character we identify a prominent angular unconformity inferred to be the transgressive surface and three sedimentary sequences an acoustically laminated estuarine unit deposited during early transgression an infilling or healing phase unit formed during the transgression and an upper transparent unit beneath the transgressive surface steeply dipping reflectors with several dip reversals record faulting and folding along the la jolla margin scripps canyon is located at the crest of an antiform where the rocks are fractured and more susceptible to erosion la jolla canyon is located along the northern strand of the rose canyon fault zone which separates cretaceous lithified rocks to the south from poorly cemented eocene sands and gravels to the north isopach and structure contour maps of the three sedimentary units reveal how their thicknesses and spatial distributions relate to regional tectonic deformation for example the estuarine unit is predominantly deposited along the edges of the canyons in paleotopographic lows that may have been inlets along barrier beaches during the holocene sea level rise the distribution of the infilling unit is controlled by pre existing relief that records tectonic deformation and erosional processes the thickness and distribution of the upper transparent unit are controlled by long wavelength tectonically induced relief on the transgressive surface and hydrodynamics

submerged paleoshoreline mapping using high resolution chirp sub bottom data northern channel islands platform california usa high resolution chirp sub bottom data were obtained offshore from the northern channel islands nci california to image submerged paleoshorelines and assess local uplift rates although modern bathymetry is often used for modeling paleoshorelines chirp data image paleoshorelines buried beneath sediment that obscures their seafloor expression the nci were a unified landmass during the last glacial maximum lgm 20 ka when eustatic sea level was 120 m lower than present we identified seven paleoshorelines ranging from 28 to 104 m in depth across this now submerged lgm platform paleoshoreline depths were compared to local sea level curves to estimate ages which suggest that some were reoccupied over multiple sea level cycles additionally previous studies determined conflicting uplift rates for the nci ranging from 0 16 to 1 5 m ka our results suggest that a rate on the lower end of this range better fits the observed submerged paleoshorelines using the uplift rate of 0 16 m ka we estimate that paleoshorelines formed during marine oxygen isotope stage 3 the lgm and the younger dryas stade are preserved on the nci platform these results help clarify uplift rates for the nci and illustrate the importance of sub bottom data for mapping submerged paleoshorelines

improved general circulation models of the martian atmosphere from the surface to above 80 km we describe a set of two new generation general circulation models of the martian atmosphere derived from the models we originally developed in the early 1990s the two new models share the same physical parameterizations but use two complementary numerical methods to solve the atmospheric dynamic equations the vertical resolution near the surface has been refined and the vertical domain has been extended to above 80 km these changes are accompanied by the inclusion of state of the art parameterizations to better simulate the dynamical and physical processes near the surface boundary layer scheme subgrid scale topography parameterization etc and at high altitude gravity wave drag in addition radiative transfer calculations and the representation of polar processes have been significantly improved we present some examples of zonal mean fields from simulations using the model at several seasons one relatively novel aspect previously introduced by wilson 1997 is that around northern winter solstice the strong pole to pole diabatic forcing creates a quasi global angular momentum conserving hadley cell which has no terrestrial equivalent within such a cell the coriolis forces accelerate the winter meridional flow toward the pole and induce a strong warming of the middle polar atmosphere down to 25 km this winter polar warming had been observed but not properly modeled until recently in fact thermal inversions are generally predicted above one and often both poles around 60 70 km however the mars middle atmosphere above 40 km is found to be very model sensitive and thus difficult to simulate accurately in the absence of observations

meteorological predictions for 2003 mars exploration rover high priority landing sites 1 the mars regional atmospheric modeling system is used to predict meteorological conditions that are likely to be encountered by the mars exploration rovers at several proposed landing sites during entry descent and landing seven areas five of which contain specific high priority landing ellipses are investigated hematite two sites isidis planitia elysium planitia two sites valles marineris and gusev crater the last two locations are in regions of extreme topography and the local and regional thermal circulations that result are equally extreme horizontal wind speeds near the floor of valles marineris exceed 50 ms 1 vertical velocities near the walls exceed 40 ms 1 and penetrate 10 km in altitude above the rim of the canyon thermal convection is suppressed within valles marineris by subsidence that forms in response to the upslope flows along the canyon walls wind magnitudes at gusev crater are approximately one third of those at the canyon but horizontal wind shear is greater deep convective thermals are noted at the relatively flat hematite site where 10 ms 1 updrafts rising to heights of 5 km are not uncommon during the midafternoon linearly organized convective updrafts superimposed on upslope circulations dominate over most of isidis planitia hexagonal and linearly organized convection predominates at elysium planitia afternoon circulations at all sites pose some risk significant risk in some cases to entry descent and landing most of the atmospheric hazards are not evident in current observational data and general circulation model simulations and can only be ascertained through mesoscale modeling of the region

late holocene sediment accumulation on the northern california shelf oceanic fluvial and anthropogenic influences the late holocene sedimentary record of the northern california continental shelf archives the combined influences of fluvial and oceanic mechanisms of land to ocean sediment flux and provides perspective on the cumulative impacts of major floods and land use change in the drainage basin during historical time piston cores collected on the shelf 50 150 m water depths off the eel and klamath rivers were analyzed to identify lithologies indicative of depositional processes over the past 5 k y and dated using 137cs and 14c methods to resolve spatial patterns in sediment accumulation rates sediment accumulation rates averaged over the past several millennia display along and across shelf gradients that reflect interactions between the shelf flow field and antecedent tectonically produced topography the highest rates 3 6 mm yr 0 4 0 8 g cm2 yr are associated with structural lows on the middle shelf whereas the lowest rates 0 2 0 6 mm yr 0 03 0 05 g cm2 yr occur at structural highs and at the shelf edge this accumulation pattern is spatially coincident with postglacial sediment thicknesses on the shelf and with depocenters that form on shorter time scales in response to oceanic flood events the sediment column exhibits an upward fining sequence consistent with increased bypass of river silt and clay as delta plains progressively filled during the holocene transgression sedimentary event beds indicative of major river floods including two probable hyperpycnal discharges of the eel river within the past 1 k y are preserved stratigraphic evidence of accelerated sediment delivery to the shelf during historical time in the form of increased burial of fluvial mud relative to fine grained sand is superimposed on this natural record this change is concordant with the regional history of forest clearing and related land use practices in the watershed after the early 1800s and appears to record the combined impacts of timber harvesting and several extreme floods after ca a d 1950

long term tectonic control on holocene shelf sedimentation offshore la jolla california a high resolution compressed high intensity radar pulse chirp survey reveals shore parallel variations in the holocene sediment thickness offshore la jolla california sediment thicknesses decrease from 20 m in the south near scripps canyon to zero in the north approaching torrey pines in addition to the south to north variation in sediment thickness the transgressive surface observed in seismic lines shoals from scripps canyon to the north despite these dramatic shore parallel subsurface changes the nearshore bathymetry exhibits little to no change along strike a left jog i e a constraining bend along the rose canyon fault causes local uplift in the region and appears to explain the northward shoaling of the transgressive surface the decrease in relief on the transgressive surface away from the left jog and the holocene sediment thickness variation this tectonic deformation is shore parallel and thus the accommodation can be separated into its tectonic and eustatic components

durable terrestrial bedrock predicts submarine canyon formation though submarine canyons are first order topographic features of earth the processes responsible for their occurrence remains poorly understood potentially analogous studies of terrestrial rivers show that the flux and caliber of transported bedload are significant controls on bedrock incision here we hypothesize that coarse sediment load could exert a similar role in the formation of submarine canyons we conducted a comprehensive empirical analysis of canyon occurrence along the west coast of the contiguous united states which indicates that submarine canyon occurrence is best predicted by the occurrence of durable crystalline bedrock in adjacent terrestrial catchments canyon occurrence is also predicted by the flux of bed sediment to shore from terrestrial streams surprisingly no significant correlation was observed between canyon occurrence and the slope or width of the continental shelf these findings suggest that canyon incision is promoted by a greater yields of durable terrestrial clasts to the shore

depths of modern coastal sand clinoforms abstract clinoforms are classical geological features examples in the rock record or in seismic reflection data that originally formed in shallow water can potentially help to locate paleo sea level but their precise links with sea level need to be established using modern examples before such inferences can be made accurately some near shore areas of high wave energy and steep coasts host sand bodies with upwards convex surfaces these clinoforms have been suggested to have been created from sand exported from the upper shoreface during stormy conditions and deposited at depths where wave action diminishes below the threshold of motion field and roy 1984 hernandez molina et al 2000 we have compiled the shapes of these bodies in a variety of wave environments in order to test this idea the interpreted depths at which the sand surface steepens i e the clinoform rollover vary from 21 m off southern california to deeper than 50 m off se australia to assess the link with wave action rollover depths were compared with adjacent deep water wave properties over the period 1992 2001 in the era 40 reanalysis dataset rollover bed shear stresses were computed from properties representing average wave conditions and from properties associated with upper percentile conditions stresses were found to reach 0 1 0 5 pa during upper 5 percentile wave conditions exceeding the sediment threshold of motion estimated from reported grain size data sediment to below the rollover is therefore mobile during extreme wave conditions

breaching in fine sands and the generation of sustained turbidity currents in submarine canyons natural moderately loosely packed sands can only erode from the surface of the bed after an increase in pore volume because of this shear dilatancy negative pore pressures are generated in the bed in cases of low permeability these negative pressures are released relatively slowly which retards the maximum rate of erosion this effect is incorporated in a new analytically derived pick up function that can explain the observation of gradual retrogressive failure of very steep subaqueous slopes sometimes more than 5 m high in fine non cohesive sands this process termed breaching in the field of sediment dredging may produce large failures in sand bars or river banks the analytical function that describes the breaching process in fine sand is incorporated in a one dimensional steady state numerical model of turbidity currents describing the spatial development of flow this model is applied to simulate a large flushing event in scripps submarine canyon pacific coast of california breach retrogradation and the successive evolution in time of the resulting turbidity current in the canyon are predicted in a sequence of discrete steps predicted velocities are compared with values measured during a flushing event implications for the interpretation of deep water massive sands are discussed

unusual marine erosion in san diego county from a single storm abstract observations of wave induced geological damage were made along the san diego coastline to a depth of 25 m following the storm of 17 18 january 1988 massive damage to limestone reefs occurred including the shearing of individual sections with in water weights of over 20 tonnes at the remarkable depth of at least 22 m large sections of the walls of a submarine canyon were broken off at a depth exceeding 20 m the drag and inertial forces from the waves in this storm are shown to be about twice those in the largest previous storms of the century and it appears to be a 200 year event in addition to the kelp mortality reported in seymour et al 1989 there was extensive mortality among encrusting algal and animal communities the apparent age of the mature successional communities in the deeper sites supports the engineering estimates of the rarity of this event the movement of cobbles and boulders at depths almost twice as great as the previously assumed limits on effective sediment transport may require coastal engineers to revise cross shore transport models

modern sedimentation on the shoreface and inner continental shelf at wrightsville beach north carolina u s a abstract the geologic framework and surficial morphology of the shoreface and inner continental shelf off the wrightsville beach north carolina barrier island were mapped using high resolution sidescan sonar bathymetric and seismic reflection surveying techniques a suite of over 200 diver vibracores and extensive seafloor observations by divers the inner shelf is a sediment starved active surface of marine erosion modern sediments where present form a patchy veneer over tertiary and quaternary units the lithology of the underlying units exerts a primary control on the distribution texture and composition of surficial sediments as well as inner shelf bathymetry the shoreface is dominated by a linear cross shore morphology of rippled scour depressions rsds extending from just seaward of the surf zone onto the inner shelf on the upper shoreface the rsds are incised up to 1 m below surrounding areas of fine sand and have an asymmetric cross section that is steeper sided to the north on the inner shelf the rsds have a similar but more subdued cross sectional profile the depressions are floored primarily by shell hash and quartz gravel vibracore data show a thick up to 1 5 m sequence of rsd sediments that unconformably overlies ancient coastal lithosomes in this sediment starved inner shelf setting rippled scour depressions probably form initially on preexisting coarse sediment substrates such as modern lag deposits of paleofluvial channel lithosomes or ancient tidal inlet thalwegs interannual observations of seafloor morphologic change and the longer term record contained in vibracores suggest that the present seafloor morphology is either relatively stable or represents a recurring preferential morphologic state to which the seafloor returns after storm induced perturbations the apparent stability is interpreted to be the result of interactions at several scales that contribute to a repeating self reinforcing pattern of forcing and sedimentary response which ultimately causes the rsds to be maintained as sediment starved bedforms responding to both along shore and across shore flows sediment accumulation from over 30 years of extensive beach nourishment at wrightsville beach appears to have exceeded the local shoreface accommodation space resulting in the leaking of beach and shoreface sediment to the inner shelf a macroscopically identifiable beach nourishment sediment on the shoreface and inner shelf was used to identify the decadal scale pattern of sediment dispersal the nourishment sediment is present in a seaward thinning wedge that extends from the beach over a kilometer onto the inner shelf to waters depths of 14 m this wedge is best developed offshore of the shoreline segment that has received the greatest volume of beach nourishment

effect of the northward migrating mendocino triple junction on the eel river forearc basin california structural evolution offshore northern california the gorda plate is subducting obliquely beneath north america the resulting complicated tectonic setting forms the southern end of the cascadia subduction zone the southern cascadia subduction zone and overlying eel river forearc basin lie just north of the unstable mendocino triple junction the neogene strata of the eel river basin record structural deformation caused by the underthrusting of the gorda plate as well as deformation generated by northward migration and encroachment of the mendocino triple junction three distinct deformation regimes are present in the eel river forearc basin 1 along the western margin of the forearc basin and within the foreslope of the accretionary prism thrust faults and anticlines record pliocene pleistocene shortening caused by subduction of the gorda plate 2 the southern part of the basin rotated counterclockwise in the late pleistocene resulting in modern transpressional deformation offshore humboldt bay the rotation and deformation are caused by north south convergence across the boundary between the pacific plate and the southernmost part of the forearc basin at the triple junction 3 the northeastern margin of the eel river basin is deformed by high angle faults with a component of strike slip motion that may represent the incipient northward propagation of the pacific north american transform system north of the triple junction

records of continental slope sediment flow morphodynamic responses to gradient and active faulting from integrated auv and rov data offshore palos verdes southern california borderland abstract variations in seabed gradient are widely acknowledged to influence deep water deposition but are often difficult to measure in sufficient detail from both modern and ancient examples on the continental slope offshore los angeles california autonomous underwater vehicle remotely operated vehicle and shipboard methods were used to collect a dense grid of high resolution multibeam bathymetry chirp sub bottom profiles and targeted sediment core samples that demonstrate the influence of seafloor gradient on sediment accumulation depositional environment grain size of deposits and seafloor morphology in this setting restraining and releasing bends along the active right lateral palos verdes fault create and maintain variations in seafloor gradient holocene down slope flows appear to have been generated by slope failure primarily on the uppermost slope 100 200 m water depth turbidity currents created a low relief

geologic control in the nearshore shore oblique sandbars and shoreline erosional hotspots mid atlantic bight usa abstract beach and nearshore morphology defined primarily by slope and sandbar development is very dynamic and is largely controlled by waves currents and regional sediment characteristics results presented here challenge this long established concept and suggest that underlying framework geology may also exert a first order control on nearshore morphology by influencing the stability and or persistent re establishment of large scale sandbar morphology and position as well as surface sediment characteristics repeated sub bottom chirp and swath bathymetry surveys of the nearshore 2 10 m depths covering over 56 km of the north carolina outer banks and southeastern virginia indicate the following 1 development of shore oblique sandbars adjacent to large gravel outcrops that are surface exposures of the underlying geologic strata 2 identical re development or sustained maintenance of large scale sandbar morphology and position before and after very energetic conditions 3 vertical and horizontal heterogeneity of lithology and grain size and a minimum volume of sand ranging from 0 to 1 5 m thick and 4 close spatial alignment between the location of outcrops shore oblique bars and shoreline erosional hotspots a hypothesis is proposed from these findings that links framework geology to bar morphodynamics and sorted bedforms and ultimately erosional hotspots sediment transport and shoreline evolution models based solely on waves and currents and an assumption of unlimited and uniform sediment may be inadequate in similar heterogeneous sand limited regions

late quaternary relative sea level in southern california and monterey bay abstract few records of late quaternary relative sea level rsl are available for the pacific coast of north america south of san francisco bay a region where rsl data would be particularly useful for constraining vertical rates of tectonic motion this paper provides the first regional uplift corrected late quaternary rsl history for southern california derived from a compilation of 132 previously published and unpublished radiocarbon ages from nearshore estuarine and freshwater deposits in sediment cores from coastal southern california we also provide a local uplift corrected rsl history for monterey bay central california generated from 48 radiocarbon ages from elkhorn slough and surrounding environments our resulting compilations show rapid sea level rise from 15 ka which begins to decelerate to present mean sea level pmsl between 6 and 8 ka late holocene

moc observations of the 2001 mars planet encircling dust storm abstract from 15 september 1997 through 21 january 2006 only a single planet encircling martian dust storm was observed by mgs moc the onset of the storm occurred on 26 june 2001 l s 184 7 earliest recorded to date it was initiated in the southern mid to low latitudes by a series of local dust storm pulses that developed along the seasonal cap edge in malea and in hellas basin l s 176 2 184 4 the initial expansion of the storm though asymmetric was very rapid in all directions 3 32 m s 1 the main direction of propagation however was to the east with the storm becoming planet encircling in the southern hemisphere on l s 192 3 several distinct centers of active dust lifting were associated with the storm with the longest persisting for 86 sols syria claritas these regional storms helped generate and sustain a dust cloud haze which reached an altitude of about 60 km and a peak opacity of dust 5 0 by l s 197 0 the cloud had encircled the entire planet between 59 0 s and 60 0 n obscuring all but the largest volcanoes the decay phase began around l s 200 4 with atmospheric dust concentrations returning to nominal seasonal low levels at l s 304 0 exponential decay time constants ranged from 30 117 sols the storm caused substantial regional albedo changes darkening and brightening as a result of the redistribution removal and deposition of a thin veneer of surface dust at least 0 1 11 1 m thick it also caused changes in meteorological phenomena i e dust storms dust devils clouds recession of the polar caps and possibly surface temperatures that persisted for just a few weeks to more than a single mars year the redistribution of dust by large annual regional storms might help explain the long period 30 years between the largest planet encircling dust storms events

the mars regional atmospheric modeling system model description and selected simulations the mars regional atmospheric modeling system mrams is introduced and selected model results are presented and compared with landed meteorological data when possible mrams is descended from a nonhydrostatic earth mesoscale and cloud scale model that is widely used for forecasting weather and simulating atmospheric systems over complex terrain mesoscale models such as mrams are ideal tools for making use of the high resolution data sets arriving from mars global surveyor experiments simulation of the mars pathfinder mpf landing site at lsd 142 using 1 2 degree mars orbiter laser altimeter mola derived topography and thermal emission spectrometer thermal inertia is shown to be in good agreement with observed near surface temperature pressure and wind direction simulations of topographically induced thermal circulations and mountain induced gravity waves are shown to be consistent with theory and earlier studies that tie large amplitude mountain waves to strong winds capable of producing dust streaks and local dust lifting events a large eddy simulation of the convective boundary layer provides estimates of vertical profiles of heat flux momentum flux turbulent kinetic energy and vertical velocity variance the model results suggest that the martian atmosphere is roughly two to three times more turbulent than the terrestrial atmosphere during the afternoon but fluxes are roughly an order of magnitude smaller due to the lower density dust devillike circulations are also predicted in the large eddy simulation finally a simulation that examines atmosphere surface interactions near big crater is discussed predicted surface wind stress patterns are consistent with aeolian processes inferred through mars orbiter camera imagery of big crater located near the mpf landing site c 2001 academic press

continental shelf morphology and stratigraphy offshore san onofre california the interplay between rates of eustatic change and sediment supply abstract new high resolution chirp seismic data acquired offshore san onofre southern california reveal that shelf sediment distribution and thickness are primarily controlled by eustatic sea level rise and sediment supply throughout the majority of the study region a prominent abrasion platform and associated shoreline cutoff are observed in the subsurface from 72 to 53 m below present sea level these erosional features appear to have formed between melt water pulse 1a and melt water pulse 1b when the rate of sea level rise was lower there are three distinct sedimentary units mapped above a regional angular unconformity interpreted to be the holocene transgressive surface in the seismic data unit i the deepest unit is interpreted as a lag deposit that infills a topographic low associated with an abrasion platform unit i thins seaward by downlap and pinches out landward against the shoreline cutoff unit ii is a mid shelf lag deposit formed from shallower eroded material and thins seaward by downlap and landward by onlap the youngest unit iii is interpreted to represent modern sediment deposition faults in the study area do not appear to offset the transgressive surface the newport inglewood rose canyon fault system is active in other regions to the south e g la jolla where it offsets the transgressive surface and creates seafloor relief several shoals observed along the transgressive surface could record minor deformation due to fault activity in the study area nevertheless our preferred interpretation is that the shoals are regions more resistant to erosion during marine transgression the cristianitos fault zone also causes a shoaling of the transgressive surface this may be from resistant antecedent topography due to an early phase of compression on the fault the cristianitos fault zone was previously defined as a down to the north normal fault but the folding and faulting architecture imaged in the chirp data are more consistent with a strike slip fault with a down to the northwest dip slip component a third area of shoaling is observed off of san mateo and san onofre creeks this shoaling has a constructional component and could be a relict delta or beach structure

across shelf sediment transport since the last glacial maximum southern california margin correlation of continental shelf slope stratigraphy in santa monica bay southern california with ocean drilling program records for nearby slope basin sites has illuminated the timing and scale of terrigenous sediment dispersal on margin since the last glacial maximum lgm marine flooding surfaces preserved in a transgressive sequence on the santa monica shelf provide a key link between base level elevation and sediment transport across shelf sediment accumulation rates at slope basin sites were maximal ca 15 10 ka well after the lgm decreased during the 12 9 ka transition from fluvial estuarine to fully marine conditions on the shelf and decelerated throughout the holocene to 30 75 of their values at the lgm the deceleration is interpreted to manifest a landward shift in the margin depocenter with the onset of transgressive sedimentation beginning when sea level surmounted the shelf edge ca 13 ka as predicted by sequence stratigraphic models however the records make clear that factors other than base level modulated slope basin accumulation rates during the deglaciation

mars equatorial mesospheric clouds global occurrence and physical properties from mars global surveyor thermal emission spectrometer and mars orbiter camera limb observations 1 we report the occurrence of a new type of cloud in the mars dayside 1300 1400 local time atmosphere apparent as high altitude 60 to 80 km vertically discrete aerosol scattering layers mars global surveyor mgs limb observations from the thermal emission spectrometer tes visible channel indicate peak frequencies at the beginning and end of the aphelion northern summer season ls 30 and 150 where they are confined to equatorial 15 s 15 n latitudes and two longitude ranges 40 e 2 w and 50 w 120 w limb images from the mgs mars orbiter camera moc indicate significant horizontal variations in these mars equatorial mesospheric mem clouds on 20 50 km scales on the basis of the distribution of projected limb heights mem clouds exhibit peak optical depths over 70 75 km altitudes that are substantial nadir vis of order 0 01 for the low pressure region of formation 1 bar averaged tes limb infrared spectral 5 40 m and solarband radiance profiles corresponding to mem occurrence indicate dust aerosols reff 1 5 2 0 m vis 0 4 at 0 25 km altitudes capped by water ice clouds reff 1 5 2 0 m vis 0 2 at 20 45 km altitudes the lack of detectable infrared radiances at mem cloud heights precludes distinction of water versus co2 ice but indicates 1 m particle sizes for water or 1 5 m for co2 ice compositions more recent mars express observations point toward mars mesospheric co2 clouds although current dynamical and radiative models do not indicate sufficiently cold temperatures at mem cloud locations to produce daytime co2 saturation conditions

two dimensional numerical modeling of storm deposition on the northern california shelf abstract a two dimensional across shelf sediment transport model has been developed to simulate storm deposition on continental shelves this paper describes the structure of the model and related algorithms in the model the time dependent sediment resuspension transportation and deposition and across shelf transport gradients are simulated as responses to storm waves on the eel shelf northern california the simulations show that the pattern of storm deposition on the sandy inner shelf is different from that on the muddy middle and outer shelf storm bed thickness decreases seaward across the inner shelf sandy zone as far as the 50 m isobath farther seaward storm bed thickness increases as the mud component in the sea floor becomes abundant then decreases again as the weakening of bottom wave motion with greater depth becomes the dominant control storm bed thickness in the mud zone thus has a nearly symmetrical cross shelf pattern with the maximum thickness at a water depth of 70 m the pattern suggests that while the sequence of new beds found in february 1995 on the eel shelf may have had a flood source their geometry reflects storm resuspension and transport the new muds found in these beds may have been reworked transported and redeposited several times by storm waves and other oceanic forces numerical simulations illustrate that the critical bottom shear stress for mud erosion e and the coefficient for sand resuspension 0 are more important than other parameters in determining storm depositional patterns on the eel shelf

modeling the rollovers of sandy clinoforms from the gravity effect on wave agitated sand abstract clinoforms on coasts exposed to ocean waves form from sand exported from the shoreface during extreme wave conditions and deposited where wave action diminishes elsewhere it is shown that during upper 5 percentile wave conditions wave induced shear stresses exceed the sediment threshold of motion to below the clinoform rollovers experiments and theory suggest that where bed sediments are agitated by waves the effect of gravity should move particles down slope with a flux proportional to the slope combined with considerations of continuity this implies a diffusion of the sediment topography a property that would explain the smooth seabed morphology found at sandy rollovers where recorded with multibeam sonar for situations where this gravity effect dominates a simple analytical expression developed here shows how the rollover curvature should relate to wave properties and to the offshore component of sediment flux more sharply curved rollovers are expected where waves have short periods or where the sediment flux is large relative sediment fluxes were calculated using the model from rollover curvature and wave properties for sites from california southeast australia and atlantic and mediterranean iberia the relative magnitudes of the fluxes are roughly as would be expected from local physiography and coastal erosion rates for sandy clinoforms developed under mainly wave influences the model could be useful for exploring variations within clinoform datasets e g how varied convexity in an area of uniform wave properties reflects varied sediment flux and for interpreting how varied curvatures of rollovers within seismic stratigraphy reflect how wave climate and flux have varied in the past

geomorphological development of the goto submarine canyon northeastern east china sea abstract the geomorphological development of submarine canyons is controlled by multiple factors such as sea level fluctuations tectonic activity and ocean currents but the relative contributions of each factor vary among these canyons the development of submarine canyons along active rift margins is not fully understood because there are relatively few documented examples of such phenomena the goto submarine canyon offers a good example of this type of structure because it is located on the flank of the okinawa trough which is an active back arc basin through multi beam bathymetry multi channel seismic reflection profiling and remotely operated vehicle surveys we reveal that this canyon is more than four times wider than other submarine canyons and has a gradient that is half as deep and a remarkably flat canyon floor a series of upstream facing cliffs with reliefs up to 110 m and longitudinal lineaments are also associated with this canyon these morphological features can mainly be attributed to direct sediment inputs from the yellow river during glacial stages vertical incision prevented by erosion resistant beds and faulting and tectonic tilting of resistant strata the possibility of tidal current induced erosion is also suggested these processes have been influenced primarily by regional factors such as the wide continental shelf carbonate cementation and active rifting of the okinawa trough the contribution of rifting including faults and tectonic tilting to the canyon s morphology is expected to be a general characteristic of submarine canyons along active rifting margins

holocene activity of the rose canyon fault zone in san diego california the rose canyon fault zone in san diego california has many well expressed geomorphic characteristics of an active strike slip fault including scarps offset and deflected drainages and channel walls pressure ridges a closed depression and vegetation lineaments geomorphic expression of the fault zone from mount soledad south to mission bay indicates that the mount soledad strand is the most active a network of trenches excavated across the mount soledad strand in rose creek demonstrate a minimum of 8 7 m of dextral slip in a distinctive early to middle holocene gravel filled channel that crosses the fault zone the gravel filled channel was preserved within and east of the fault but was removed west of the fault zone by erosion or possibly grading during development consequently the actual displacement of the channel could be greater than 8 7 m radiocarbon dates on detrital charcoal recovered from the sediments beneath the channel yield a maximum calibrated age of about 8 1 0 2 kyr the minimum amount of slip along with the maximum age yield a minimum slip rate of 1 07 0 03 mm yr on this strand of the rose canyon fault zone for much of holocene time other strands of the rose canyon fault zone which are east and west of our site may also have holocene activity based on an analysis of the geomorphology of fault traces within the rose canyon fault zone along with the results of our trenching study we estimate the maximum likely slip rate at about 2 mm yr and a best estimate of about 1 5 mm yr stratigraphie evidence of at least three events is present during the past 8 1 kyr the most recent surface rupture displaces the modern a horizon topsoil suggesting that this event probably occurred within the past 500 years stratigraphie and structural relationships also indicate the occurrence of a scarp forming event at about 8 1 kyr prior to deposition of the gravel filled channel that was used as a piercing line a third event is indicated by the presence of several fault strands that displace the channel but did not move during the most recent event other events may also have occurred but these data suggest that the return time for surface rupturing earthquakes is no more than about 4 kyr

martian dust storms 1999 mars orbiter camera observations the mars orbiter camera on board the mars global surveyor from march 9 1999 ls 107 where ls is the areocentric longitude of the sun measured in degrees from mars northern spring equinox to december 31 1999 ls 274 has obtained 7 5 km pixel 1 daily global maps of the martian surface in two wavelength bands blue 400 450 nm and red 575 625 nm visual inspection of these maps during the 1999 dust storm season has resulted in the detection of 783 dust storms ranging in size from local 102 km2 to regional 1 6 106 km2 no global storms were observed the difference in the numbers of dust storms occurring in the two hemispheres north 343 south 440 was not statistically significant fifty percent of the regional size dust storms formed as a result of the merger of two or more smaller local storms the regional storms from ls 207 to ls 223 were observed to move from the northern hemisphere into the southern hemisphere between 30 w and 50 w longitude this cross equatorial transport of dust suggests the location of the low lying southward flowing branch of the hadley circulation observations show that dust storms occur in several regions on mars at the two polar cap edges at the base of high elevation regions in the northern hemisphere near the polar hood during northern fall and at mid latitudes in both hemispheres specific regions such as solis planum and hesperia which were regions of significant dust activity in the past showed almost no dust storm activity in 1999 suggesting that regional dust sources are variable over a 20 year time frame one region of exceptional activity not noted previously was the arcadia amazonis border however other regions such as near elysium mons acidalia chryse hellas noachis argyre cimmeria and sirenum again were active dust storm regions relative dust opacities were modeled for 117 red wavelength events and ranged from 0 54 diffuse haze to 2 13 concentrated local events from the dust opacities we estimated the north polar sedimentation rate to be 6 0 10 10 4 g cm 2 yr 1 a factor of 40 smaller than previous estimates from the two 1977 global dust storms pollack et al 1979 along with the global dust mass loading 2 6 4 0 10 4 g cm 2 and cross equatorial dust mass loading 3 6 10 4 g cm 2 the 1999 cross equatorial mass dust loading suggests that the southern hemisphere subtropical latitudes require at least 2 3 martian years to replenish their dust sources before global storms can form

the role of summer monsoon typhoons in the formation of nearshore coarse grained ripples depression and sand ridge systems along the shimizu coast suruga bay facing the pacific ocean japan abstract coarse grained ripples cgrs develop within the seafloor depression sand ridge systems along the shimizu coast in the northwestern part of suruga bay facing the pacific ocean central japan in this paper we analyze data from high resolution bathymetry seafloor observation by an underwater video camera and high resolution seismic surveys and seafloor trenching of shallow strata obtained between 2005 and 2007 to describe their geomorphological and sedimentological characteristics in detail and to examine the formative processes and maintenance of the systems in water depths of 5 30 m cgrs occur in seafloor depressions that are approximately 40 70 cm deeper than the surrounding sandy seafloor in many cases the ripples develop in depressions between shore normal sand ridges composed mainly of fine sand

transgressive deposits along the actively deforming eel river margin northern california abstract new high resolution chirp seismic data acquired along the eel river margin northern california reveal that stratal architecture and sediment thickness of the holocene transgressive deposits are in large part controlled by tectonic deformation and sediment supply a thick 20 m transgressive deposit is observed across the eel margin a forearc basin that is undergoing active folding perpendicular to the coastline at rates of mm yr the transgressive deposits on the eel margin exhibit marked variations in thickness alongshore being thickest in the eel river syncline and thinnest over the eureka anticline the divergent character of the infill in the syncline suggests that deposition is syntectonic fault displacement and structural relief observed along the transgressive surface are consistent with deformation rates measured onshore the transgressive surface is offset 0 5 m across the eureka anticline suggesting deformation has been active since 10 ka two distinct acoustic units have been identified within the transgressive systems tract a basal deposit that infills relief on the transgressive surface and an upper onlapping unit the basal deposit infills lows along the outer shelf with a maximum thickness of 10 m and appears to be controlled by the early sea level rise 21 7 ka of the last deglaciation it is separated from the overlying acoustically well laminated unit by a pronounced surface of onlap moving shoreward along the inner shelf

intense summer si recycling in the surface southern ocean 1 si cycle in surface waters was investigated in summer 2003 during a transect conducted from south australia to antarctica diatoms dominated the microphytoplankton silicic acid was depleted up to 60 s a subsurface maximum of biogenic silica biosilica was observed in the permanent open ocean zone in the 100 0 01 light zone the ratio of depth integrated biosilica dissolution rate d to depth integrated biosilica production rate p ranged between 0 to 3 1 being 1 for 5 of our 6 stations the biosilica dissolution was related to the percentage of dead diatoms but not to the temperature and might be at least partially under bacteria mediation this study shows that during summer the southern ocean silicate pump can be much less efficient than usually expected existence of scenarios with intense surface si recycling in the southern ocean has major consequences both for modelers and paleoceanographers index terms 4805 oceanography biological and chemical biogeochemical cycles 1615 1615 global change biogeochemical processes 4805 4855 oceanography biological and chemical plankton 4207 oceanography general arctic and antarctic oceanography 4870 oceanography biological and chemical stable isotopes

simulation of the atmospheric thermal circulation of a martian volcano using a mesoscale numerical model mesoscale 100 km atmospheric phenomena are ubiquitous on mars as revealed by mars orbiter camera images numerical models provide an important means of investigating martian atmospheric dynamics for which data availability is limited but the resolution of general circulation models which are traditionally used for such research is not sufficient to resolve mesoscale phenomena to provide better understanding of these relatively small scale phenomena mesoscale models have recently been introduced here we simulate the mesoscale spiral dust cloud observed over the caldera of the volcano arsia mons by using the mars regional atmospheric modelling system our simulation uses a hierarchy of nested models with grid sizes ranging from 240 km to 3 km and reveals that the dust cloud is an indicator of a greater but optically thin thermal circulation that reaches heights of up to 30 km and transports dust horizontally over thousands of kilometres

relative role of accommodation zones in controlling stratal architectural variability and facies distribution insights from the fushan depression south china sea in sedimentary basins a better understanding of the controlling effect of accommodation transfer zones on stratal architecture and facies distribution can improve the success rate of locating hydrocarbon reservoirs the fushan depression is a half graben rift sub basin located in the southeast of the beibuwan basin south china sea in this study comparative analysis of seismic reflection palaeogeomorphology fault activity and depositional facies distribution indicates that three different types of inner basin slopes i e multi level step fault slope in the western area slope flexure zone in the accommodation zone area and gentle slope in the eastern area were developed along the southern slope of the fushan depression together with a large scale accommodation zone located at the intersection of the western and eastern fault systems further analysis shows that the accommodation zone played an important role in controlling not only stratal architectural variability in the southern slope but also depositional facies distribution in the accommodation zone area during the high stand stage the deposition of depositional systems was mainly controlled by sediment supply and the nw trending transfer faults major drainage systems entered the fushan depression through the accommodation zone along the direction of sediment supply and sedimentary flow paths were parallel to the accommodation zone axis with sedimentary flows constrained to the adjacent areas of the nw trending transfer faults by contrast during the low stand stage the transfer faults had little control over depositional facies distribution and the sublacustrine fan sediments diverted away from the accommodation zone and flew down along the northeast oblique to the accommodation zone axis the flow division in the lowstand stage might be greatly influenced by flow type and topography in addition the accommodation zone area demonstrated unique hydrocarbon accumulation models different from the western and eastern areas suggesting that the future exploration should be conducted at different levels in the fushan depression

valles marineris cloud trails 1 distinctive cloud trails are identified in mars reconnaissance orbiter mars color imager marci images over specific locations associated with valles marineris and noctis labyrinthus and at perihelion solar longitudes l s 230 260 high contrast surface shadows are well defined as cast from their eastern margins supporting altitude and optical depth determinations these relatively high altitude clouds 40 50 km exhibit narrow latitudinal widths 25 75 km in comparison to extended longitudinal dimensions 400 1000 km marci multispectral imaging of cloud surface shadows in five wavelength channels 260 320 437 546 and 653 nm yields the wavelength dependence of cloud extinction optical depth revealing a range of small cloud particle sizes r eff 0 2 0 5 m and moderate cloud optical depths 0 03 0 10 visible and 0 1 0 2 ultraviolet local time and temporal sampling characteristics of marci cloud images indicate that these clouds develop very rapidly in afternoon hours 1300 1500 lt reach their full longitudinal extents within 2 h time scales and often reoccur on successive afternoons mars global surveyor mars orbital camera imaging in previous mars years indicates these clouds are annually repeating these observed characteristics suggest a cloud formation mechanism that is specific to 50 km horizontal and vertical scales transports water vapor and dust upward from lower levels exists during the afternoon and is likely associated with the mesoscale atmospheric circulations induced by the near equatorial canyons of mars cloud particles formed in such updrafts would then be rapidly transported westward in the strong retrograde zonal circulation of the subsolar middle atmosphere in this season

on the origin of perennial water ice at the south pole of mars a precession controlled mechanism 1 the poles of mars are known to have recorded recent 107 years climatic changes while the south polar region appears to have preserved its million year old environment from major resurfacing events except for the small portion containing the co2 residual cap the discovery of residual water ice units in areas adjacent to the cap provides compelling evidence for recent glaciological activity the mapping and characterization of these h2o rich terrains by observatoire pour la mineralogie l eau les glaces et l activite omega on board mars express which have supplemented earlier findings by mars odyssey and mars global surveyor have raised a number of questions related to their origin we propose that these water ice deposits are the relics of mars orbit precession cycle and that they were laid down when perihelion was synchronized with northern summer i e more than 10 000 years ago we favor precession over other possible explanations because 1 as shown by our general circulation model gcm and previous studies current climate is not conducive to the accumulation of water at the south pole due to an unfavorable volatile transport and insolation configuration 2 the residual co2 ice cap which is known to cold trap water molecules on its surface and which probably controls the current extent of the water ice units is geologically younger 3 our gcm shows that 21 500 years ago when perihelion occurred during northern spring water ice at the north pole was no longer stable and accumulated instead near the south pole with rates as high as 1 mm yr 1 this could have led to the formation of a meters thick circumpolar water ice mantle as perihelion slowly shifted back to the current value southern summer insolation intensified and the water ice layer became unstable the layer recessed poleward until the residual co2 ice cover eventually formed on top of it and protected water ice from further sublimation in this polar accumulation process water ice clouds play a critical role since they regulate the exchange of water between hemispheres the so called clancy effect which sequesters water in the spring summer hemisphere coinciding with aphelion due to cloud sedimentation is demonstrated to be comparable in magnitude to the circulation bias forced by the north to south topographic dichotomy however we predict that the response of mars water cycle to the precession cycle should be asymmetric between hemispheres not only because of the topographic bias in circulation but also because of an asymmetry in the dust cycle we predict that under a reversed perihelion climate dust activity during northern summer is less pronounced than during southern summer in the opposite perihelion configuration i e today s regime when averaged over a precession cycle this reduced potential for dust lifting will force a significantly colder summer in the north and by virtue of the clancy effect will curtail the ability of the northern hemisphere to transfer volatiles to the south this process may have helped create the observed morphological differences in the layered deposits between the poles and could help explain the large disparity in their resurfacing ages

oceanographic currents differential subsidence and physiography control three dimensional clinothem growth in the gulf of papua papua new guinea abstract a regional high resolution chirp seismic survey in the gulf of papua gop extends the geographic scope of previous studies by 125 km and reveals that the holocene clinothem along margin geometries surfaces of lap and steepness of foreset slopes appear less dependent on eustatic sea level changes and sediment supply than previously suggested clinothems imaged by chirp profiles and sampled by sediment cores include two older relict clinothems and a younger holocene clinothem divided into three units by two surfaces of lap new radiocarbon ages from this study establish that depositional timing is more recent than previously proposed for the transgressive deposits the holocene clinothem units and surfaces of lap while previous ages suggested that observed stratal relationships could coincide with meltwater pulses or sea level stillstands the younger ages from this study question these results and suggest the dominant control on holocene clinothem architecture may be inherited physiography sw ne differential subsidence along margin currents and seasonal variations in wave energy inherited physiography underlying the holocene clinothem consists of valleys incised during relative lowstands of marine isotope stages mis 4 and 2 valleys in the relict clinothem potentially served as across margin conduits for an older holocene clinothem unit after the older holocene unit filled valleys and accommodation younger holocene units preferentially grew along rather than across margin as bottom shear stresses increased relict clinothems have undergone differential subsidence since deposition due to foreland basin loading which has engendered more accommodation in the northeast gop that systematically decreases toward the southwest areas with less accommodation are more likely to experience toplap as they are exposed to increased shear stresses therefore the surfaces of lap are caused by interactions between accommodation and oceanographic currents examining stratal relationships along the holocene clinothem has broad implications for sequence stratigraphy as many clinothems exhibit a three dimensional stacking pattern measurements of seafloor slopes yield complicated results illustrating that seafloor steepness within lobes is influenced by a complex interplay of accommodation sediment supply underlying physiography and oceanographic currents this suggests that clinothem architecture in the gop cannot simply be interpreted as a rate related problem between rates of sediment supply and relative sea level

the effects of tectonic deformation and sediment allocation on shelf habitats and megabenthic distribution and diversity in southern california abstract landscape and seascape structures are typically complex and manifest as patch mosaics within characteristic biomes bordering one another in gradual or abrupt ecotones the underlying patch structure in coastal shelf ecosystems is driven by the interaction of tectonic sedimentary and sea level dynamic processes animals and plants occupy and interact within these mosaics terrestrial landscape ecological studies have shown that patch structure is important for ecological processes such as foraging connectivity predation and species dynamics the importance of patch structure for marine systems is less clear because far fewer pattern process studies have been conducted in these systems for many coastal shelf systems there is a paucity of information on how species occupy shelf seascapes particularly for seascapes imbued with complex patch structure and ecotones that are common globally due to tectonic activity here we present the results of a study conducted along a myriameter scale gradient of bottom and sub bottom geological forcing altered by tectonic deformation sea level transgression and sediment allocation the resulting seascape is dominated by unconsolidated sediments throughout but also exhibits increasing density and size of outcropping patches along a habitat patch gradient forced by the erosion of a sea level transgressive surface that has been deformed and tilted by tectonic forcing a combination of sub bottom profiling multibeam bathymetry and rov surveys of the habitats and the demersal megafauna occupying the habitats indicate 1 significant beta diversity along this gradient 2 biological diversity does not scale with habitat diversity and 3 species occupy the patches disproportionately non linearly with regard to the proportional availability of their preferred habitats these results indicate that shelf habitat patch structure modulates species specific processes and interactions with other species further studies are needed to examine experimentally the mechanics of how patch structure modulates ecological processes in shelf systems our results also provide further support for including multiple spatial scales of patch structure for the application of remote habitat sensing as a surrogate for biological community structure

global patterns in cloud forms on mars abstract mariner 9 images and all viking orbiter images through july 1979 were searched for cloud forms a computer accessible catalog was assembled consisting of a classification of cloud type lee wav wave for example and properties directionality wavelength for example lee wave directionality shows a pattern and seasonal variation at high latitudes which is consistent with predictions of theoretical modeling fog and haze occurrence shows no obvious correlation with water abundance or any other simple causal factor lee waves are rare at equatorial latitudes plumes probably dust occur preferentially at locations where strong boundary layer convection is expected