seafloor morphology of the montenegro n albania continental margin adriatic sea central mediterranean abstract high resolution multibeam morpho bathymetric maps and a dense grid of seismic reflection profiles show relict and palimpsest geomorphologic features along the montenegro northern albanian continental margin this sector of the eastern adriatic shelf at the external front of the dinarides chain is characterized by highly variable seafloor patterns and depositional styles and shows a peculiar alternation of large scale troughs and ridges probably caused by tectonic compressive deformations these tectonically controlled morphologies are overprinted by the result of sedimentary processes such as progradation at river outflows erosion and reworking of sediments by longshore currents as well as gravity driven process caused by sediment loading and seismic shaking physiographic domains along this shelf slope margin include i an inner and an outer shelf separated by two major topographic highs the kotor and the bar ridges ii a drowned lobate delta formed during the last phase of sea level fall likely fed by the buna bojana drainage basin and iii a continental slope affected by gravity driven faulting and mass wasting processes seafloor reflectivity maps ground truthed by grain size analysis of bottom sediments reveal that fine grained deposits accumulate in the inner shelf while other sectors appear starved the effects of the last sea level rise is testified by the presence of seabed forms diagnostic of erosion or depositional processes such us large dunes sediment ridges and sediment waves which were studied to infer the effect of bottom currents under the present day oceanographic regime and in the recent past this paper presents a first description of geomorphologic features observed along the montenegro northern albanian continental margin in the context of late quaternary sea level changes

sandy contourite drift in the late miocene rifian corridor morocco reconstruction of depositional environments in a foreland basin seaway abstract the rifian corridor was a seaway between the atlantic ocean and the mediterranean sea during the late miocene the seaway progressively closed leading to the messinian salinity crisis in the mediterranean sea despite the key palaeogeographic importance of the rifian corridor patterns of sediment transport within the seaway have not been thoroughly studied in this study we investigated the upper miocene sedimentation and bottom current pathways in the south rifian corridor the planktic and benthic foraminifera of the upper tortonian and lower messinian successions allow us to constrain the age and palaeo environment of deposition encased in silty marls deposited at 150 300 m depth there are i 5 to 50 m thick mainly clastic sandstone bodies with unidirectional cross bedding and ii 50 cm thick mainly clastic tabular sandstone beds with bioturbation mottled silt lack of clear base or top and bi gradational sequences furthermore seismic facies representing elongated mounded drifts and associated moat are present at the western mouth of the seaway we interpret these facies as contourites the products of a westward sedimentary drift in the south rifian corridor the contourites are found only on the northern margin of the seaway thus suggesting a geostrophic current flowing westward along slope and then northward this geostrophic current may have been modulated by tides by comparing these fossil examples with the modern gulf of cadiz we interpret these current dominated deposits as evidence of late miocene mediterranean overflow into the atlantic ocean through the rifian corridor this overflow may have affected late miocene ocean circulation and climate and the overflow deposits may represent one of the first examples of mainly clastic contourites exposed on land

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

land sea correlation between late holocene coastal and infralittoral deposits in the se iberian peninsula western mediterranean the well exposed systems of prograding beach ridges on the carchuna calahonda granada and campo de dalias roquetas almeria coastal plains continue offshore as infralittoral prograding wedges ipw the holocene ipw is a narrow morpho sedimentary unit up to 2 5 km wide which develops seaward from the lower edge of the shoreface to 15 20 m depth extending to a well defined break of slope at water depths of 35 40 m these ipws have been recognized and studied using very high resolution seismic profiles topas and multibeam data em 3000d in detail they are complex morpho sedimentary units in which internal structures are closely linked to the pattern of progradation of the adjacent coastal plains when longshore currents produce significant littoral drift the ipws are composed of several minor units arranged in offlap which accrete parallel or oblique to the main shoreline therefore it is possible to correlate progradational units in the coastal plain h units sensu goy j l zazo c dabrio c j 2003 a beach ridge progradation complex reflecting periodical sea level and climate variability during the holocene gulf of almeria western mediterranean geomorphology 50 251 268 and subunits in the ipw but special care is required depending on the local arrangement of morpho sedimentary units besides it is not realistic to draw conclusions regarding the age of the subunits inside a given ipw without adequate dating as the number of subunits will greatly vary from place to place depending on local factors magnitude of sea level oscillations and sediment supply

paleo sea levels reconsidered from direct observation of paleoshoreline position during glacial maxima for the last 500 000 yr the drastic climatic changes which characterise the cooling trend of the last few million years of earth history led to variations in eustatic sea level that had tremendous impact on the geology and ecology of continental margins reconstructing a sea level curve back in time is not an easy task observations of shoreline positions are always a local measurement of relative sea level that needs to be corrected from the effect of tectonic and thermal subsidence sediment loading compaction and glacio hydro isostasy extensive studies have been done for the last deglaciation and for the last 100 000 yr cycle but very few studies deal with position of sea level during earlier cycles simply because conditions are very rarely favourable for the preservation of such witnesses the shelf of the golfe du lion western mediterranean reveals a unique record of shoreline paleopositions during glacial maxima of at least the last five circa 100 kyr glacial interglacial cycles in fact it is the entire glacial deltaic lobe of up to 50 m thick from delta front or shoreface to prodelta that has been preserved in place and which provides direct and independent constraints for relative sea level minima we measure a relative sea level of 112m 128 134 246 and 262 m for mis 2 6 8 10 and 12 respectively after corrections taking into account postdepositional movement of strata subsidence we find that sea level dropped to a depth of 102 6 m during the last three glaciations mis2 mis6 mis8 but reached exceptionally low values of more than 150 10 m during the preceding glaciations mis10 and mis 12 at about 340 and 434 kyr bp this general time framework and sedimentological interpretation has been confirmed by preliminary results from two deep drillings during the promess cruise july 2004 which validate our methodology however no detailed and absolute datings of such witnesses are available so far so that we cannot prove that these levels are the lowest ever reached during each glacials but they correspond undoubtedly to the last preserved shoreface before rapid sea level rise we also suggest that the abrupt change in sea level maxima might be the overprint of 400 kyr orbital periodicity cycles last but not least these results prove that the golfe du lion is indeed a unique laboratory to study paleoclimates and sea level variations on a larger time scale further work is needed for a complete glacio hydro sedimento isostatic modelling of each sequence and each glacial to further constraint local sea level versus global sea level and quantify in particular the relative effect of glacio hydro isostatic effect which differ according to ice sheet extend but also of erosion sedimentation isostatic effect erosion on land and deposition on the outer shelf and slope

depositional model for a prograding oolitic wedge upper jurassic iberian basin abstract facies architecture and bedding patterns of the kimmeridgian pozuel formation iberian basin evidence that this 50 70 m thick oolitic grainstone unit conforms to the infralittoral prograding wedge ilpw model instead of the classic models used for interpreting oolitic grainstones sandbodies on carbonate ramps or platforms i e bank margin shoal complexes beaches and beach ridges ten lithofacies have been distinguished in the pozuel formation 5 10 dipping clinobedded oolitic grainstone foresets passing to tabular oolitic packstones grainstones which interfinger the muddy basinal bottomsets landwards the clinobeds pass into subhorizontal topsets composed of trough cross bedded to structureless oolitic grainstones oolitic skeletal grainstones with stromatoporoids and coral stromatoporoid microbial mounds siliciclastic lithofacies and oncolitic peloidal packstones occur at the innermost position these lithofacies stack in strike elongated 5 20 m thick 0 5 2 km dip oriented wide aggradational progradational packages with complex sigmoid oblique geometries lithofacies depositional geometries and stacking pattern permit to summarize the main characteristic of such upper jurassic oolitic infralittoral prograding wedge potentially to be applied in other oolitic sandbodies both in outcrops and subsurface 1 sediment production within the wave action zone 2 grainstone dominated textures 3 prograding basinward onto basinal muds 4 laterally strike extensive paralleling the shoreline 5 variable thickness commonly of few tens of meters 6 broadly sigmoidal to oblique internal architecture with topsets foresets and bottomsets 7 dip of foresets close to the angle of repose 8 topsets deposited in shallow water extending through the shoreface from the shoreline down to the wave base 9 mounds either microbial or skeletal may occur in the topsets the coated grains factory was along the high energy wave dominated outer platform topset beds from where the mud was winnowed and the grains transported both landward to the platform interior and seaward to the platform edge from were the grains cascaded down the slopes as grain flows and mass flows forming clinobeds this genetic model can be applied to other grain dominated lithosomes some of them forming hydrocarbon reservoirs e g the jurassic hanifa formation and some arab d e g qatif field in arabia the smackover formation in northern louisiana and south arkansas the aptian shuaiba formation e g bu hasa field and the cenomanian mishrif formation e g umm adalkh field of the arabian gulf

forecasting and hindcasting waves with the swan model in the southern california bight abstract the naval research laboratory created a wave forecasting system in support of the nearshore canyon experiment ncex field program the outer nest of this prediction system encompassed the southern california bight this forecasting system is described in this paper with analysis of results via comparison to the extensive buoy network in the region there are a number of potential errors two of which are poor resolution of islands in the bight which have a strong impact on nearshore wave climate and the use of the stationary assumption for computations these two problems have straightforward solutions but the solutions are computationally expensive so an operational user must carefully consider their cost the authors study the impact of these two types of error relative to other errors such as error in boundary forcing using several hindcasts performed after the completion of ncex it is found that with buoy observations as ground truth the stationary assumption leads to a modest increase in root mean square error this is due to relatively poor prediction of the timing of swell arrivals and local sea growth decay the model results are found to be sensitive to the resolution of islands however coarse resolution does not incur an appreciable penalty in terms of error statistics computed via comparison to buoy observations suggesting that other errors dominate inaccuracy in representation of the local atmospheric forcing likely has a significant impact on wave model error perhaps most importantly the accuracy of directional distribution of wave energy at the open ocean boundaries appears to be a critical limitation on the accuracy of the model data comparisons inside the bight

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

the influence of shelf indenting canyons and infralittoral prograding wedges on coastal morphology the carchuna system in southern spain abstract submarine canyons and progradational sedimentary bodies are common features of continental margins worldwide few studies have analyzed the relationship between the coastal morphology and the morphology and sedimentary characteristics of the adjacent shelf in wave dominated coasts or the potential role played by shelf indenting canyons as inducers of sediment deposition in shallow waters this work presents a study that correlates the coastal morphology with the characteristics of the adjacent offshore shallow shelf in an area with a complex inner bathymetry the carchuna system spain the study area is characterized by large scale non rhythmic cuspate features in the coastline whereas the inner bathymetry exhibits a shallow water infralittoral prograding wedge ipw and a shelf indenting canyon that has tributaries located a short distance from the coastline using detailed bathymetric measurements observational data and wave propagation modeling the influence of the different bathymetric elements was quantified and a mechanism proposed for the generation of the carchuna ipw the wave propagation results show that the canyon is the main source of the alongshore modulation of nearshore waves and that it plays a major role in the generation of the large scale cuspate features in the shoreline additionally these results suggest that the long term coastal erosion associated with extreme storms yielded sufficient sediment which when subsequently transported eastward the dominant littoral drift direction formed the ipw once formed the ipw modified the wave propagation patterns and contributed to the development and reinforcement of the shoreline features

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

holocene highstand deposits in the gulf of cadiz sw iberian peninsula a high resolution record of hierarchical environmental changes a comparison of the internal structure of holocene highstand shallow marine deposits with emerged spit bar systems in the gulf of cadiz margin sw iberian peninsula is presented in order to increase the knowledge about the patterns of environmental fluctuations of sub milankovitch periodicity during the recent highstand period a high resolution seismic database of boomer profiles was interpreted focusing on shallow marine deposits of the gulf of cadiz shelf such as the guadalquivir river prodelta the guadiana river depositional system and the faro tavira infralittoral prograding wedge the results indicate that the internal architecture of recent highstand shelf deposits is complex as the recognition of three main types of seismic unit motifs suggests the existence of a hierarchical pattern of environmental fluctuations a major scale motifs the most significant feature observed in the seismic records is the pervasive occurrence of two major scale motifs lower and upper within the holocene highstand systems tract b intermediate scale motifs each major scale motif is composed of two intermediate scale motifs defining four intermediate scale motifs h1 to h4 c minor scale motifs the internal structure of major and intermediate scale motifs reveals a high degree of environmental variability during the recent highstand probably led by climatic cyclicities of submillenial scale the lower major scale motif is characterised by alternating progradational aggradational minor scale motifs whereas the upper major scale motif presents a more uniform internal structure dominated by progradational units the influence of two distinct trends or asymmetric cycles of sea level change seems to have been significant in the generation of the major scale architecture the transition between both major phases was probably related with a major sea level rise other factors such as changes in the magnitude and or direction of storm events and climatically induced changes of sediment supply are proposed to have controlled the generation of intermediate and minor scale architectures

observations of the semidiurnal internal tide on the southern california slope and shelf 1 we give a detailed description of the semidiurnal band current and temperature variability observed during the internal waves on the continental margin iwaves field experiments of 1996 and 1997 off of mission beach california this variability was dominated by the internal tide and the structure of the internal tide on the slope and shelfbreak region was different from that on the narrow shelf on the slope and shelfbreak the internal tide was dominated by alongshore propagating coastal trapped waves in this region semidiurnal band currents were predominantly oriented in the alongshore direction in the lower half of the water column at a water depth h of 350 m current and temperature variability were consonant with a short wavelength 8 km bottom trapped wave propagating in the alongshore direction to the north in the upper 120 m of the water column above the depth of the shelfbreak slope and shelfbreak currents were highly coherent with a zero phase lag that is there was no phase propagation in the cross shore direction on the narrow 10 km shelf cross shore currents u were much more energetic than on the slope and had the structure of a mode one internal wave the alongshore currents v decreased monotonically from the surface to the bottom of the water column with a phase that did not change with depth the near bottom u signal propagated toward the coast during all mooring deployments faster in the summer than in the fall the near bottom u and mid column temperature relative phase was neither consistent with a purely progressive nor a purely standing mode one internal wave we conclude that the internal tide on the shelf was partially reflected

late quaternary subsidence of santa catalina island california continental borderland demonstrated by seismic reflection data and fossil assemblages from submerged marine terraces

the shaping of continental slopes by internal tides the angles of energy propagation of semidiurnal internal tides may determine the average gradient of continental slopes in ocean basins 2 to 4 degrees intensification of near bottom water velocities and bottom shear stresses caused by reflection of semi diurnal internal tides affects sedimentation patterns and bottom gradients as indicated by recent studies of continental slopes off northern california and new jersey estimates of bottom shear velocities caused by semi diurnal internal tides are high enough to inhibit deposition of fine grained sediment onto the slopes

global ocean mean wave period data validation and description a global comparison of altimeter and era 40 mean wave period data is performed for the first time altimeter and era 40 mean wave period are shown to compare well in non swell dominated conditions triply collocated altimeter buoy and era 40 data show that the variance of the random errors is bigger for the era 40 data and smaller for the buoy data a new expression is given to relate altimeter data to wave period in wind dominated conditions provided this correction is applied altimeter data are adequate for the most needed validation of global model mean wave period data in non swell dominated conditions triply collocated altimeter buoy and era 40 also reveal that altimeter mean wave period is reliable even in swell conditions for moderate to high winds in contrast to previous suggestions which limited its validity to wind dominated seas

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

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

cenozoic global sea level sequences and the new jersey transect results from coastal plain and continental slope drilling the new jersey sea level transect was designed to evaluate the relationships among global sea level eustatic change unconformity bounded sequences and variations in subsidence sediment supply and climate on a passive continental margin by sampling and dating cenozoic strata from coastal plain and continental slope locations we show that sequence boundaries correlate within 0 5 myr regionally onshore offshore and interregionally new jersey alabama bahamas implicating a global cause sequence boundaries correlate with 18o increases for at least the past 42 myr consistent with an ice volume glacioeustatic control although a causal relationship is not required because of uncertainties in ages and correlations evidence for a causal connection is provided by preliminary miocene data from slope site 904 that directly link 18o increases with sequence boundaries we conclude that variation in the size of ice sheets has been a primary control on the formation of sequence boundaries since 42 ma we speculate that prior to this the growth and decay of small ice sheets caused small amplitude sea level changes 20 m in this supposedly ice free world because eocene sequence boundaries also appear to correlate with minor 18o increases subsidence estimates backstripping indicate amplitudes of short term million year scale lowerings that are consistent with estimates derived from 18o studies 25 50 m in the oligocene middle miocene and 10 20 m in the eocene and a long term lowering of 150 200 m over the past 65 myr consistent with estimates derived from volume changes on mid ocean ridges although our results are consistent with the general number and timing of paleocene to middle miocene sequences published by workers at exxon production research company our estimates of sea level amplitudes are substantially lower than theirs lithofacies patterns within sequences follow repetitive predictable patterns 1 coastal plain sequences consist of basal transgressive sands overlain by regressive highstand silts and quartz sands and 2 although slope lithofacies variations are subdued reworked sediments constitute lowstand deposits causing the strongest most extensive seismic reflections despite a primary eustatic control on sequence boundaries new jersey sequences were also influenced by changes in tectonics sediment supply and climate during the early to middle eocene low siliciclastic and high pelagic input associated with warm climates resulted in widespread carbonate deposition and thin sequences late middle eocene and earliest oligocene cooling events curtailed carbonate deposition in the coastal plain and slope respectively resulting in a switch to siliciclastic sedimentation in onshore areas oligocene sequences are thin owing to low siliciclastic and pelagic input and their distribution is patchy reflecting migration or progradation of depocenters in contrast miocene onshore sequences are thicker reflecting increased sediment supply and they are more complete downdip owing to simple tectonics we conclude that the new jersey margin provides a natural laboratory for unraveling complex interactions of eustasy tectonics changes in sediment supply and climate change

sedimentologic character of ancient muddy subaqueous deltaic clinoforms down cliff clay member bridport sand formation wessex basin u k abstract muddy subaqueous clinoforms are a common feature of many modern deltas particularly those developed in basins with strong waves tides or oceanographic currents ancient examples have only rarely been reported implying that they are under recognized herein the sedimentological characteristics of muddy subaqueous deltaic clinoforms from the lower jurassic down cliff clay member of the bridport sand formation wessex basin uk are described and interpreted as a reference to re evaluate other ancient shallow marine mudstone successions deposits below the down cliff clay clinoforms consist of erosionally based bioclastic sandy limestone beds intercalated with upward thickening fossiliferous claystones and siltstones facies association a which record upward increasing water depth under conditions of minor input of clastic sediment and reworking by storm waves these deposits are downlapped by foreset to toeset deposits of the subaqueous deltaic clinoforms which comprise claystones and siltstones that contain calcareous nodules and are variably bioturbated by a low diversity trace fossil assemblages dominated by chondrites facies association b these foreset to toeset deposits record slow deposition undecompacted sediment accumulation rate of c 4 4 m myr from suspension fall out and distal sediment gravity flows under conditions of intermittent and or poor oxygenation of bottom waters clinoform foreset deposits dip paleoseaward at 2 and consist of siltstones and sandy siltstones that are moderately to completely bioturbated by a high diversity trace fossil assemblage facies association c thin

local wave climate and long term bed shear stress characteristics in monterey bay ca abstract five and a half years of wave measurements at two stations in monterey bay ca show that the local wave climate at the south marina station is markedly different from that at the north santa cruz harbor station measured significant wave heights at the marina station are profoundly greater than at the santa cruz harbor station especially during winter during summer southerly or southwesterly pacific ocean swells can be dominant and therefore the peak wave periods at the marina station protected from these swells by the monterey peninsula headland are much shorter than at the santa cruz station this disparity of wave characteristics at the two stations are the direct causes of the difference in the long term probability of sediment suspension and transport sheet flow conditions under which significant sand transport events presumably take place occur about 20 to 40 times more often at the marina station than at the santa cruz harbor station

holocene sand beaches of southern california enso forcing and coastal processes on millennial scales abstract a proxy record of sand beach accretion for the past 10 000 years has been assembled from radiocarbon dates on the pismo clam tivela stultorum in archaeological sites along the southern california coast when this record is compared with numerous climate proxies it appears that el nino southern oscillation enso controls on wave climate and sediment flux have acted upon regional geomorphology at different sea levels to either accrete or erode the holocene beaches of southern california tivela dates from the santa maria coast indicate that perennial sand beaches built by 9000 years ago in response to abundant riverine sediment contained by the natural groin at point sal wave sheltering by the massive headland of point buchon and early holocene el nino events on the western santa barbara coast sand beaches were forming by 7000 years ago in response to high sand fluxes from the santa ynez mountains to the many small littoral catchments possibly aided by high local rates of uplift decline of these sand beach habitats 5000 4000 years ago coincides with increased el nino driven wave energy in accord with slowing in sea level rise ca 6000 years ago sand beaches were most widespread in the period 6000 5000 years ago on estero bay the western santa barbara coast and west of point dume however tivela dates first appear 5000 years ago in the oceanside and silver strand littoral cells of the san diego region this lag coincides with the middle holocene shift to a more variable climate and modern periodicity in el nino events that increased sediment supply to the southern coast the ontogeny of the littoral cells provides timelines for modeling coastal evolution with implications for sand beach ecology prehistoric human coastal adaptations and coastal planning for future climate change

estimating palaeobathymetry of wave graded continental shelves from sediment texture the concept of the wave graded continental shelf with sea floor sediment coarsening from offshore mud to shoreface sand has been well known from the time of johnson 1919 although most of the modern shelf shows textures unrelated to water depth on account of relict features or sediment starvation the geological record is more likely to preserve sites where sediment is being fed to a subsiding inner shelf these consistently show the landward coarsening pattern of the wave graded shelf recording past water depth history in accumulated sea floor sediment the landward coarsening pattern is driven primarily by wave induced bed shear stress which increases shoreward exponentially although it also varies from place to place with wave climate and can be influenced by sediment concentration and currents in this study the relationship between bed shear stress sediment texture and water depth has been investigated by comparing per cent mud and wave climate data from shore normal transects of three modern wave graded coastal settings wellington harbour low energy and the manawatu coast moderate energy in new zealand and monterey bay in california moderate high energy samples from all three locations show a progressive change from poorly sorted mud offshore to well sorted fine sand nearshore with the sand mud transition ranging from 3 m low energy to 50 m moderate high energy reflecting differences in average bed shear repeat measurements of per cent mud on seasonal annual and decadal time scales along a manawatu coastal transect showed no measurable change demonstrating equilibrium between sediment supply wave energy water depth and sediment texture a simple model based on the relationship between wave climate shear stress and per cent mud and using data and conditions from the modern manawatu coast is applied to two mid pliocene cyclothems exposed 50 km inland giving results comparable with estimates from foraminifera and the deep sea isotope record per cent mud offers more detail for palaeobathymetric trends in shallow water shelf strata than other proxy depth recorders although it is limited to depths above wave base and requires an independent estimate of wave climate if depths are to be quantified

fluvial and marine controls on combined subaerial and subaqueous delta progradation morphodynamic modeling of compound clinoform development 1 fluviodeltaic systems commonly display a compound clinoform geometry that consists of a subaerial subaqueous delta couplet the extent of subaqueous delta development varies significantly and in modern systems is a function of fluvial input and basin hydrodynamics we present a model of fluviodeltaic progradation in which the repeated occurrence of characteristic terrestrial floods and large coastal storms drives fluvial and shallow marine morphodynamics respectively we couple fluvial and shallow marine sediment dynamics via the surf zone which we collapse to a shock condition and treat as a moving boundary with steady sediment supply and sea level and simple basin geometry our model naturally develops prograding deltas with compound clinoform geometries the subaerial delta grows via fluvial aggradation and shoreface progradation whereas the subaqueous delta expands through foreset progradation with only minor topset aggradation the interplay of fluvial input with the wave current field controls the basic partitioning of sediment between subaerial and subaqueous deltas and by extension the compound clinoform geometry increasing the frequency or magnitude of coastal storms decreasing flood frequency or discharge and reducing grain size all increase the fraction of sediment delivered to the shallow marine environment and the extent of subaqueous delta progradation relative to subaerial delta development our model which emphasizes the intrinsic coupling of fluvial and shallow marine sediment dynamics and downplays the importance of allogenic fluctuations can explain many of the first order morphologic features of natural delta systems including significant lateral separation of the shoreline and clinoform rollover and differing rates of subaerial and subaqueous delta progradation

clinoform development by advection diffusion of suspended sediment modeling and comparison to natural systems clinoforms are the building blocks of prograding stratigraphic sequences these sig moid shaped surfaces can be found forming today on modem deltas sedimentation rate profiles over the clinoform surface of these deltas show low rates of sediment accumulation on both topset and bottomset regions with a maximum accumulation rate on the upper foreset region we pres ent a model for the formation of clinoforms that relies on the interpretation of modem clinoform sedimentation as a result of the distribution of shear stresses at the mouth of a river model clino form surfaces are generated using an equation for the conservation of suspended sediment concentration together with a conservation of fluid equation for simple time averaged flow velocity fields in the model suspended sediment is advected horizontally into a basin and gravitational settling of sediment particles is counteracted by vertical turbulent diffusion in shallow water shear stresses are too large to allow deposition and sediment bypasses the topset region with increasing water depth near bed shear stresses decrease and sediment is allowed to deposit at the foreset region with gradually decreasing rates toward deeper water this sedimentation pattern leads to progradation of the clinoform surfaces through time the clinoform surfaces produced by the model capture the fundamental morphological characteristics of natural clinoforms these include the gradual slope rollover at the topset and bottomset steeper foreset slopes with increased grain size and an increase in foreset slope through time as clinoforms prograde into deeper water because the parameters controlling the model clinoforms have a direct relation to physical quantities that can be measured in natural systems the model is an important step toward unraveling the physical processes associated with these deposits

analyses of a large scale depositional clinoformal wedge along the italian adriatic coast abstract the processes controlling the formation of the late holocene high stand systems tract along the central adriatic coast a prograding clinoformal sediment wedge have been diagnosed using a large scale behavior oriented numerical model this model is based on time averaged marine sediment dynamics allowing it to represent processes acting over millennial time spans river derived sediment is redistributed by the combined action of littoral shoreface and shelf processes in this application the numerical model successfully simulates both the overall geometry of the deposits and the internal time line stratigraphy the simulation of this prograding clinoform with the numerical model clearly shows that the growth of these deposits depends on the combined effect of a strong and persistent coast parallel advection and cross shelf dispersion related to a large number of sediment re entrainment events this means that this clinoform is in the process of forming a new shelf surface with an offshore profile that is in adjustment with the present wave and current climate along with the relative stability of sea level over the past six millennia

morpho bathymetric and seismo stratigraphic analysis of the insular shelf of salina aeolian archipelago to unveil its late quaternary geological evolution abstract the distribution and morphological characteristics of the shelves around salina island have been analyzed and integrated with observations from onshore geological field studies in order to improve knowledge about its evolution and to demonstrate how shelf width depth can be used as proxies for reconstructing the development of the volcanic edifice insular shelves form essentially through marine erosion of volcanic centres during stages of reduced or inactive volcanism and are representative of their original extension shelves having larger widths commonly 1000 m and deeper edges over 125 m depth experienced wave erosion during successive cycles of sea level fluctuations and subsidence after their formation thus being indicative of a relatively older age of the eroded volcanic centres accordingly we document offshore salina the occurrence of presently submerged and largely dismantled volcanic centres namely pizzo capo north and fossa delle felci south predating the oldest subaerial products exposed on the adjacent coastal sectors these offshore centres have subsided after their erosion and are no more documented on land furthermore the finding of the largest and deepest shelf around the subaerial remnants of pizzo di corvo volcanic edifice allows relating it to an earlier stage of evolution of salina shedding light on contradictory radiometric ages on land narrower shelves commonly on the whole our results show the importance of integrated field and marine studies to unravel the geological evolution of insular volcanoes and to obtain inferences on their vertical mobility

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

seismic stratigraphic analysis of the middle jurassic krossfjord and fensfjord formations troll oil and gas field northern north sea abstract the syn rift middle jurassic krossfjord and fensfjord formations troll field northern north sea contain a complex distribution of wave and tide dominated deltaic shoreline and shelf depositional environments of varying reservoir potential uncertainty exists in depositional models used to explain the spatial and temporal distribution of these depositional environments and the absence of coeval coastal plain deposits to date the proposed influence of growing rift related structures on stratigraphic architectures and sedimentation patterns in the units has been poorly defined in this study 3d seismic data are integrated with core biostratigraphic and wireline log data to produce a consistent geological interpretation for the formations seismic analysis has identified nine parasequences containing nne ssw striking delta scale clinoforms that prograded westwards over much of the field quantitative analysis highlights an increase in height and dip of clinoforms from proximal to distal locations coincident with an increase in grain size clinoform geometry is sigmoidal with well developed topsets that based on core data lack subaerial deposits these geometrical and sedimentological characteristics suggest that a subaqueous delta depositional system deposited the krossfjord and fensfjord formations in the troll field in the northeast of the field clinoforms exhibit highly variable strike and oblique cross sectional geometries which suggest that sediment was supplied from here and then redistributed through southward directed wave and longshore current activity rift related faulting is recognised to have occurred in the western part of the troll field only during deposition of the youngest fensfjord formation parasequence thus challenging the notion that these units are syn rift seismically imaged clinoforms in the under explored area south of the troll field prograded southward and are interpreted to represent coeval formation of a southward prograding spit that developed landward of the subaqueous delta platform present in the troll field the interpreted long lived subaqueous delta in the troll field constitutes a novel type of shallow marine reservoir

application of singular vector analysis to the kuroshio large meander 1 singular vector analysis is applied to the formation of the kuroshio large meander south of japan we use a simulation run of an ocean general circulation model ogcm in which a large meander occurs as the background state singular vectors are calculated by the lanczos method in which the tangent linear and adjoint models of the ogcm are used we apply an incremental correction approach for setting up the initial perturbation and averaging for the final norm in order to get modes reflecting nonlinear physics by filtering out high frequency variations the perturbation extracted as the leading right singular vector affects the formation of the large meander most if it is set to the background state two months before when the perturbation is added it enhances an anticyclonic eddy southeast of kyushu in the upper layer which induces downwelling north of it and develops an anticyclonic eddy in the deep layer the anticyclonic eddy produces a cold anomaly at the downstream edge and produces baroclinic instability there resulting in further development of the large meander in contrast the anticyclonic eddy in the deep layer is weakened when the perturbation is subtracted the development of the cold anomaly in the deep layer is delayed and consequently the meander is not so well developed thus singular vector analysis reveals the role of the anticyclonic eddy approaching southeast of kyushu in the upper layer and indicates the importance of the anticyclonic eddy in the deep layer

coastal erosion rates of lava deltas around oceanic islands abstract rates of coastal erosion are needed for planning purposes and to improve understanding of how the shelves of islands develop ultimately becoming submerged banks near shore submarine platforms created by erosion of lava deltas of known age provide an opportunity to quantify erosion rates and to investigate how those rates vary between different types and ages of lava flows as well as how they vary with wave climate we have compiled data on deltas formed during historical and holocene eruptions age 6 ka from both a and p hoehoe lava flows and from diverse localities azores and hawaiian islands and ascension island near shore platforms were interpreted from multibeam sonar bathymetric light detection and ranging lidar and historical sounding data from them we estimated time averaged shoreline retreat rates from the seaward distances between the modern coastlines and the submarine platform edges the 35 interpreted platforms have rugged dipping surfaces left behind by erosion with an average gradient of 5 range 2 10 eroded distance of 436 m 78 1119 m and depth of platform edge of 25 m 5 56 m to evaluate the latter depths we computed seabed orbital speeds due to surface waves at the platform edges depths of platform edges correlate only modestly with those speeds suggesting that platform surfaces have adjusted to wave conditions with a wide range of particle sizes and hence thresholds of motion the largest retreat distances 800 m are associated with platforms of the central azores islands which are exposed to higher waves however retreat rates are highly varied 0 08 12 5 m yr and weakly correlated with measures of wave power suggesting that waves are only a secondary influence given that lack of correlation we suspect that the main factor contributing to variability arises from varied cliff resistance to erosion blocks between joints in lava flows and hence resistance to erosion vary greatly in size from the thicker and less densely jointed a flows to the thinner and shell like layered lavas in p hoehoe flows

model for the sigmoidal curvature of submarine slopes sigmoidal slope profiles are common on the margins of continents and intracratonic basins we propose that these profiles consist of two genetically different segments the lower concave part reflects the exponential decrease of the sedimentation rate with increasing distance from the source at the shelf edge the upper convex part represents the gradational boundary between the shelf domain where sediment is moved by waves and wave induced currents and the slope domain where sediment is moved by gravity the boundary is narrow and the shelf edge is sharp if sedimentary base level remains stationary during progradation the boundary becomes gradational and the shelf edge becomes rounded if storms and sea level cycles induce significant fluctuations of base level this model is supported by observations on holocene sedimentary systems as well as numerical simulations with the program strata based on the diffusion equation for sediment dispersal

subtidal currents over the central california slope evidence for offshore veering of the undercurrent and for direct wind driven slope currents abstract in february 1991 an array of six current meter moorings was deployed for one year across the central california outer shelf and slope the main line of the array extended 30 km offshore of the shelf break out to water depths of 1400 m a more sparsely instrumented line displaced 30 km to the northwest extended 14 km offshore though shorter the northern line spanned similar water depths because the gradient of the topography steepened in the northern region a poleward flow pattern typical of the california undercurrent was seen across both lines in the array over most of the year the poleward flow was surface intensified in general the portion of the undercurrent that crossed the southern line had larger amplitudes and penetrated more deeply into the water column than the portion that crossed the northern line transport over the year ranged from 0 to 2 5 sverdrups sv poleward across the southern line 0 to 1 sv poleward across the northern line we suggest the difference in transport was caused by topographic constraints which tended to force the poleward flow offshore of the northern measurement sites the slope of the topography steepened too abruptly to allow the poleward flow to follow isobaths when currents were strong when current velocities lessened a more coherent flow pattern was seen across both lines in the array in general the poleward flow patterns in the undercurrent were not affected by local winds or by the local alongshore pressure gradient nor was a strong seasonal pattern evident rather unexpectedly a small but statistically significant fraction of the current variance over the mid and outer slope was driven by the surface wind stress an alongshelf wind stress caused currents to flow along the slope parallel to the wind field down to depths of 400 m below the surface and out to distances of 2 rossby radii past the shelf break the transfer functions were weak 3 4 cm s per dyn cm 2 but comparable to wind driven current amplitudes of 4 6 cm s per unit wind stress over the middle shelf equatorward alongshelf winds also caused water from 200 300 m over the slope to upwell onto the shelf as the surface water moved offshore

gravity driven sediment transport on the continental shelf implications for equilibrium profiles near river mouths an analytical model is developed for equilibrium bathymetric profiles off river mouths associated with the shoreward convex upward portion of subaqueous deltas and clinoforms the model builds on recent field results demonstrating that gravity driven flux of suspended mud is important on shelves provided that wave induced suspension of sediment supports the requisite turbid hyperpycnal layer because the maximum sediment load is determined by the critical richardson number the results are independent of the properties of the suspended mud or the bed the model assumes the equilibrium state to represent a balance between the supply of sediment by a river at the coast and the downslope bypassing of sediment to deep water within wave supported turbid near bed layers progressive seaward increases in bed slope across the convex shelf profile allow the attenuation of wave agitation with depth to be compensated for by a downslope increase in the contribution of gravity the model is consistent with shelf profiles off the mouths of the eel california ganges brahmaputra bangladesh waiapu new zealand po italy and rhone france rivers the equilibrium profile is predicted to be a function of wave climate and riverine sediment supply only with deeper and broader profiles associated with decreasing sediment supply increasing wave height and or increasing wave period

an unusual holocene fan shaped subaqueous prograding body at the back of the cies islands ridge ria de vigo nw spain geomorphology facies and stratigraphic architecture abstract the internal structure of a new subaqueous sedimentary body with a 3d morphology of a fan was studied using an interdisciplinary approach based on geophysical geomorphological sedimentological and radiocarbon data the genesis of the sedimentary body is controlled by two main factors 1 the presence of a basement ridge that constitutes the cies archipelago acting as a barrier that protects the ria from high energy marine events and 2 the w sw swell direction under stormy conditions which sweeps the sediment from the platform and introduces it into the ria through the narrow entrance between faro and san martino islands the sedimentary body that has grown inside the ria under low energy conditions progrades in a landward direction from the shelf to the ria sedimentological analysis indicates that the facies associations are coarse grained bioclastics in the proximal areas of this body changing laterally to mixed fine grained sediment in its distal parts the combination of geophysical and radiocarbon data leads us to establish the beginning of the progradation of the sedimentary body subsequent to the younger dryas cold event associated with the holocene sea level rise the seismic analysis of the high resolution seismic records allows us to recognize five main clinoform sets inside the subaqueous prograding sedimentary body which can be attributed to sea level changes during the holocene

exploratory morphodynamic hindcast of the evolution of the abandoned yellow river delta 1578 1855 ce abstract the abandoned yellow river delta ayd which formed when the yellow river flowed into the southern yellow sea between 1128 and 1855 ce is a representative example of the sensitivity of deltas to modifications in their environments in this study we established a process based morphodynamic model to explore the morphological evolution of one such large scale fine grained delta the ayd before 1855 ce the uncertainties in the model settings which are inevitable when historical data are insufficient were assessed together with the corresponding influences on the evolution of the deltaic system by considering a series of scenarios the results indicate that the strength of local tidal forcing is the key factor that determines the shape and evolutionary trend of the delta sediment input discharge and the slope of the initial coastal profile have a considerable effect on the overall size of the delta and the relative ratio between subaerial and subaqueous parts of the delta respectively based on the evaluation of the uncertainties and a comparison with historical maps the simulated ayd was evaluated to be reliable through an analysis of the temporal delta evolution and residual sediment transport the morphological evolution of the ayd before 1855 ce was investigated the southern delta grew as the shoals merged with the mainland which is in agreement with an existing hypothesis zhang 1984 whereas the accretion of the northern delta was independent from the shoals in the northern part additionally suggestions are made regarding the distribution of the ayd at the end of its progradation stage which provides fundamental information for analyzing subsequent erosion processes since 1855 ce this study differs from existing studies on the ayd which are all based on geological approaches it provides insight into the evolution of the ayd through an alternative means viz a process based morphodynamic modeling approach

seismic stratigraphy and late quaternary shelf history south central monterey bay california abstract the south central monterey bay shelf is a high energy wave dominated tectonically active coastal region on the central california continental margin a prominent feature of this shelf is a sediment lobe off the mouth of the salinas river that has surface expression high resolution seismic reflection profiles reveal that an angular unconformity quaternary underlies the entire shelf and separates undeformed strata above it from deformed strata below it the salinas river lobe is a convex bulge on the shelf covering an area of approximately 72 km 2 in water depths from 10 to 90 m it reaches a maximum thickness of 35 m about 2 5 km seaward of the river mouth and thins in all directions away from this point adjacent shelf areas are characterized by only a thin 2 to 5 m thick and uniform veneer of sediment acoustic stratigraphy of the lobe is complex and is characterized by at least three unconformity bounded depositional sequences acoustically these sequences are relatively well bedded acoustic foresets occur within the intermediate sequence and dip seaward at 0 7 to 2 0 comparison with sedimentary sequences in uplifted onshore pleistocene marine terrace deposits of the monterey bay area which were presumably formed in a similar setting under similar processes suggests that a general interpretation can be formulated for seismic stratigraphic patterns depositional sequences are interpreted to represent shallowing upwards progradational sequences of marine to nonmarine coastal deposits formed during interglacial highstands and or during early stages of falling sea level acoustic foresets within the intermediate sequence are evidence of seaward progradation acoustic unconformities that separate depositional sequences are interpreted as having formed largely by shoreface planation and may be the only record of the intervening transgressions the internal stratigraphy of the salinas river lobe thus suggests that at least several late quaternary regressions and transgressions may be recorded under the present shelf this record may represent the last major eustatic cycle of sea level an interval not observed in uplifted onshore pleistocene marine terraces

numerical modeling of the cenozoic geomorphic evolution of the southern sierra nevada california abstract recent geomorphic studies suggest that significant 1 5 km late cenozoic surface uplift occurred in the southern sierra nevada a conclusion that is difficult to reconcile with recent stable isotopic paleoaltimetry studies numerical modeling can play an important role in resolving this dispute in this paper i use two models of bedrock channel erosion the stream power model and a sediment flux driven model to test hypotheses for the fluvial cenozoic geomorphic evolution and surface uplift history of the southern sierra nevada cosmogenic data for upland erosion and river incision rates allow each model parameter to be uniquely constrained numerical experiments using the sediment flux driven model suggest that the modern southern sierra nevada was constructed from a 1 0 km pulse of range wide surface uplift in the latest cretaceous 60 ma and a 0 5 km pulse in the late miocene 10 ma the persistent geomorphic response to latest cretaceous uplift in this model is the result of limited cutting tools supplied from the upland low relief boreal plateau this uplift history correctly predicts the modern topography of the range including the approximate elevations and extents of the chagoopa and boreal plateaux and their associated river knickpoints numerical experiments using the stream power model are most consistent with a 1 km pulse of uplift in the late eocene 30 ma and a 0 5 km pulse in the late miocene 7 ma both models suggest that the remaining rock uplift required to produce the 4 km peak elevations of the modern southern sierra nevada was produced by flexural isostatic uplift in response to river incision the balance of evidence including the dominance of sediment flux driven erosion in granitic rocks previous paleoaltimetry studies and the timing of sediment accumulation in the great valley support the conclusions of the sediment flux driven model i e that the sierra nevada experienced range wide surface uplift events in the latest cretaceous and late miocene more broadly these results indicate that nonequilibrium landscapes can persist for long periods of geologic time and hence low relief upland landscapes do not necessarily indicate late cenozoic surface uplift

offshore transport and sand body formation evidence from a steep high energy shoreface southeastern australia abstract elongate shore parallel sand bodies lie on the lower shoreface of the embayed and cliffed coast of central new south wales australia these sand bodies are 10 to 30 m thick extend almost continuously for 40 km parallel to the coast and display a pronounced convexity on the sea floor in profile sediment sampling and detailed seismic reflection and side scan sonar profiling provide evidence that the upper part of these large lobate sand bodies consists chiefly of sand transported downslope from the upper shoreface and surf zone the sand bodies consist entirely of marine sand probably derived locally from retreating embayed beaches and in part from sandstone cliffs channels and sediment lobes oriented normal to the shoreline and internal structure indicate growth by seaward progradation and surface morphology indicates coalescing of lobes and damming of bed load sediment against bed rock ridges in water depths of 70 to 80 m the precise mechanism or mechanisms of seaward transport on the shoreface is unresolved we surmise that during storm events disturbance by large waves and seaward transport by downwelling bottom currents result in sand movement onto and across the sand body surface at depths of 40 to 80 m concurrent modification of the sand bodies by shore parallel processes is suggested by textural trends bed forms and the overall alongshore continuity of the sand bodies