geology and tectonics of the betic zone se spain abstract the southern margin of the iberian continent comprises a complex geological history which can be traced back into the proterozoic when a gneissic basement was formed a cover of nevado filabride rocks was deposited onto this proterozoic basement during the palaeozoic the permian intrusion of the bedar granite suggests that the palaeozoic sedimentary rocks now exposed in the betic cordilleras have been affected by the hercynian orogeny similar to that of palaeozoic rocks in the adjoining ossa morena zone the hercynian basement was probably covered by alpujarride carbonates in the mesozoic when rifting opened tethys and intruded 140 ma old basic dyke swarms the palaeozoic basement of the betic cordilleras comprises a suture of late cretaceous subduction 80 85 ma b p this can be inferred from hp lt metamorphic facies obducted in coeval thrust slices of nevado filabride rocks the nevado filabride nappes include mesozoic carbonates transformed into marbles macael the suture was probably annnealed after the closure of tethys the mesozoic boundary between africa and europe and the rifting in tethys ceased during the palaeogene when the atlas mountains were formed 36 ma b p subsequently relative movements between africa and europe in the neogene were accommodated by strike slip faults these define the iberian microplate moving eastward by atlantic spreading and possibly subducting under italy neogene deformation of iberia is most intensive in southeastern spain due to emplacement of a mantle diapir under the alboran area this occurred early in the neogene aquitanian and caused nappe spreading involving alpujarride and malaguide rocks the subsequent neogene history has now been studied in great detail and is reviewed here it involves clear examples of calc alkaline volcanism most probably not related to subduction seismic motion along strike slip faults within the iberian microplate and syntectonic deposition in intermontane neogene basins

the influence of whitecapping waves on the vertical structure of turbulence in a shallow estuarine embayment abstract the vertical distribution of the turbulent kinetic energy dissipation rate was measured using an array of four acoustic doppler velocimeters in the shallow embayment of grizzly bay san francisco bay california owing to the combination of wind and tide forcing in this shallow system the surface and bottom boundary layers overlapped whitecapping waves were generated for a significant spectral peak steepness greater than 0 05 or above a wind speed of 3 m s 1 under conditions of whitecapping waves the turbulent kinetic energy dissipation rate in the upper portion of the water column was greatly enhanced relative to the predictions of wind stress wall layer theory instead the dissipation followed a modified deep water breaking wave scaling near the bed bottom 10 of the water column the dissipation measurements were either equal to or less than that predicted by wall layer theory stratification due to concentration gradients in suspended sediment was identified as the likely cause for t

geomorphic characterization of four shelf sourced submarine canyons along the u s mid atlantic continental margin abstract shelf sourced submarine canyons are common features of continental margins and are fundamental to deep sea sedimentary systems despite their geomorphic and geologic significance relatively few passive margin shelf breaching canyons worldwide have been mapped using modern geophysical methods between 2007 and 2012 a series of geophysical surveys was conducted across four major canyons of the us mid atlantic margin wilmington baltimore washington and norfolk canyons more than 5700 km2 of high resolution multibeam bathymetry and 890 line km of sub bottom chirp profiles were collected along the outer shelf and uppermost slope depths of 80 1200 m the data allowed us to compare and contrast the fine scale morphology of each canyon system the canyons have marked differences in the morphology and orientation of canyon heads steepness and density of sidewall gullies and the character of the continental shelf surrounding canyon rims down canyon axial profiles for washington baltimore and wilmington canyons have linear shapes and each canyon thalweg exhibits morphological evidence for recent relatively small scale sediment transport for example washington canyon displays extremely steep wall gradients and contains 100 m wide 5 10 m deep v shaped incisions down the canyon axis suggesting modern or recent sediment transport in contrast the convex axial thalweg profile the absence of thalweg incision and evidence for sediment infilling at the canyon head suggest that depositional processes strongly influence norfolk canyon during the current sea level high stand the north walls of wilmington washington and norfolk canyons are steeper than the south walls due to differential erosion though the underlying cause for this asymmetry is not clear furthermore we speculate that most of the geomorphic features observed within the canyons e g terraces tributary canyons gullies and hanging valleys were formed during the pleistocene and show only subtle modification by holocene processes active during the present sea level high stand

submarine canyons and channels in the lower st lawrence estuary eastern canada morphology classification and recent sediment dynamics abstract series of submarine canyons and channels observed in the lower st lawrence estuary lsle provide an opportunity to analyze in great detail the morphology spatial distribution and modern activity of such systems in a relatively shallow 300 m semi enclosed basin based on their geomorphology and physical settings the canyons and channels were classified into four categories according to their feeding sources ancient or recent glacially fed river fed longshore drift fed and sediment starved systems their activity was interpreted based on geomorphological characteristics such as the presence of bedforms related to gravity flows backscatter intensity axial incision and the presence of rapidly deposited layers in surficial sediments river fed deltas were interpreted as inactive mainly because suspended sediment concentrations at river mouths are low preventing the generation of hyperpycnal currents or delta lip failures related to high sediment supply longshore drift fed canyons present where the coastal shelf narrows were found to be episodically active probably due to earthquakes or extreme storm events unlike other longshore drift fed canyons observed elsewhere in the world they are active infrequently because of the modern low rates of sediment supply to their heads the most active canyons are the sediment starved type and were observed near pointe des monts their activity is probably due to slope failures and to the presence of strong hydrodynamic processes therefore sediment supply is not the main mechanism responsible for modern canyon and channel activity in the lsle however sediment supply has been an important factor during the formation of the submarine channels and canyons their quasi exclusive occurrence on the quebec north shore is attributed to its larger watershed and important sedimentary delivery during deglaciation the quebec north shore watershed is 20 times greater than the quebec south shore watershed which favored the transport of greater volumes of sediment during the early holocene moreover the slope proximity to the shore led to the formation of longshore drift fed systems on the north shore when sediment supplied to rivers were transferred on a narrow shelf

geomorphology and neogene tectonic evolution of the palomares continental margin western mediterranean abstract the palomares continental margin is located in the southeastern part of spain the margin main structure was formed during miocene times and it is currently part of the wide deformation zone characterizing the region between the iberian and african plates where no well defined plate boundary occurs the convergence between these two plates is here accommodated by several structures including the left lateral strike slip palomares fault the region is characterized by sparse low to moderate magnitude mw

morphometric analysis and genetic implications of pro deltaic sea floor undulations in the northern alboran sea margin western mediterranean basin abstract several fields of seafloor undulations from pro deltaic wedges in the northern margin of alboran sea western mediterranean basin are described in this paper a series of elongated subparallel bathymetric undulations are distinguished in the foreset to bottomsets regions of the holocene pro deltaic wedges related with the guadalfeo and verde seco rivers multibeam data surficial sediment samples and high resolution seismic profiles have been used in this study and integrated in a geographical information system quantitative measurement of key morphometric parameters wave length height asymmetry length and wave form index was performed on multibeam data and seismic profiles using the arcgis software wave form index and depth data were analysed statistically and a cluster analysis was carried out in each area according to these results we infer that sea floor undulations in the study areas are best explained by the influence of strong sediment flows normal to bathymetric contours probably coupled with the effect of subsequent slow sediment deformation processes such as sediment creeps the influence of bottom current activity is considered less likely as the position of river mouths and the very high slope gradients seems to be the key factors which control the development of these sea floor undulations the alboran sea sea floor undulations are compared with those of other fields in shallow water environments and the different processes of formation evaluated

a walk down the cap de creus canyon northwestern mediterranean sea recent processes inferred from morphology and sediment bedforms the cap de creus canyon northwestern mediterranean sea belongs to a complex network of submarine canyons cutting the western gulf of lion continental shelf and opening into the larger sete canyon swath bathymetry data mak 1m deep towed side scan sonar imagery and 5 khz high resolution seismic reflection profiles show striking morphologies in the cap de creus canyon floor and walls as a consequence of the canyon head and the upper reach severe incision the continental shelf dramatically narrows in front of the creus cape promontory the upper canyon has a flat bottomed thalweg incised in a mega scale sediment furrow field displaying hyperbolic seismic facies the tens of kilometres long linear furrows extend also over the middle canyon down to 1400 m of water depth the furrows on either side of the canyon are not parallel but oblique and display varying degrees of excavation mid channel sediment bars are locally present in the thalweg which is made of sandy lag deposits as revealed by its acoustic response and verified by sediment samples the middle canyon is linear and steep with an up to 700 m high southern wall contrasting with the sinuous smooth lower canyon which is controlled by flowage of the underlying messinian evaporites large sections of the canyon are affected by sediment instability processes the lower cap de creus canyon hangs up to 260 m over its distalmost reach and the sete canyon through a narrow less than 1 km wide gorge numerous scours up to 10 m deep suggesting bed load transport occupy the lower sete canyon immediately downstream of the cap de creus canyon mouth the data set provides the first complete very high resolution imaging of a submarine canyon from its upper part down to its distalmost reach the observations evidence a wide set of erosion transport and deposition processes along the cap de creus canyon including sediment entrapment at the canyon head furrow generating dense water cascading through the southern wall along channel currents strong enough to excavate specific sections of the channel floor and bed load sediment transport as demonstrated by the presence of mega ripples crescent scours and grooves in the lower canyon

large scale sediment waves and scours on the modern seafloor and their implications for the prevalence of supercritical flows large scale 20 m to 7 km wavelength bedforms are common on the seafloor yet there is a lack of consensus on how they form and thus what to call them we conducted statistical analysis on a dataset of 82 seafloor bedforms that span a range of water depths and environments the data form three distinct groups 1 small scale 20 300 m wavelength sediment waves with mixed relief made of medium sand to cobble sized sediment that form in confined settings which we call small sediment waves 2 large scale 300 7000 m wavelength sediment waves with mixed relief made of fine grained sediment that form in relatively unconfined settings which we call large sediment waves and 3 large scale fully enclosed depressions in the seafloor which we call scours there is a statistically significant data gap in the size of bedforms between small sediment waves and large sediment waves that does not appear to be a sampling artefact this data gap probably results from the environments in which sediment waves form being either confined e g channel or canyon or unconfined e g open slope bedform migration direction is available for 36 of the data and includes small and large scale sediment waves of these examples all are shown to migrate up current up current migration is indicative of supercritical flow thus this data suggests that supercritical flows operate in a wide range of environments and can generate both small and large sediment waves therefore we suggest that small and large sediment waves form by similar processes despite the gap in bedform wavelength and sediment size the migration direction for scours remains unknown scours may form from similar processes to small and large sediment waves or alternatively they may be a completely separate bedform type that form when erosive flows exploit pre existing defects in the seafloor this novel statistical analysis of a global database shows that up current migrating bedforms associated with supercritical flow are unusually widespread and are recognised at two distinct scales

semiannual patterns of erosion and deposition in upper monterey canyon from serial multibeam bathymetry recently acquired 3 m resolution 244 khz multibeam seafloor bathymetry 0 5 m depth precision reveals geomorphology at sufficient detail to interpret small scale features and short term processes in the upper 4 km of monterey canyon california the study area includes the continental shelf and canyon features from 10 m to 250 m depth the canyon floor contains an axial channel laterally bounded by elevated complex terrace surfaces sand waves with 2 m height and 35 m average wavelength dominate the active part of the canyon floor the sand waves are strongly asymmetrical indicating net down canyon sediment transport in this reach terraces including a broad 25 m tall terrace complex near the head of the canyon bear evidence of recent degradation of the canyon floor slump scars and gullies having a variety of sizes and relative ages shape the canyon walls serial georeferenced digital elevation models were analyzed to detect net changes in bathymetry or morphology occurring during both a six month period september 2002 to march 2003 and a 24 h period 24 march to 25 march significant changes over the six month period include 1 complete reorganization of the sand waves on the channel floor 2 local channel degradation creating new 2 m tall erosional terraces on the channel margins 3 local channel widening that laterally eroded older channel margin terraces and 4 60 m extension of one minor gully head on a steep canyon wall there were no discernable changes in morphology during the 24 h study period raster subtraction of serial bathymetric grids provides estimates of sediment erosion and deposition that occurred between the canyon head and a point 2 km down canyon during the six month study erosion of 320 000 m 3 80 000 m 3 of sediment occurred mainly in the tributaries along the margins of the axial channel and in the lowest 700 m of the analyzed reach this eroded volume was approximately balanced by 260 000 m 3 70 000 m 3 of sediment deposition that was concentrated in the nearshore region along the rim of the canyon head there was no measurable sediment gain or loss during the 24 h study period

spring sapping on the lower continental slope offshore new jersey undersea discharge of ground water during periods of lower sea level may have eroded valleys on part of the lower continental slope offshore new jersey steep headed basins cliffed and terraced walls and irregular courses of these valleys may have been produced by sapping of exposed near horizontal tertiary strata joints in eocene calcareous rocks would have localized ground water movement some karstlike features of the submarine topography and the outcrops suggest that solution of the calcareous rocks also took place

hyperpycnal plume formation from riverine outflows with small sediment concentrations a series of laboratory experiments has been conducted in order to elucidate the sediment induced mixing processes accompanying riverine outflows specifically the discharge of a warm fresh particle laden fluid over a relatively dense cool brine in a parameter regime analogous to recently acquired field measurements hypopycnal surface plumes were subject to a convective instability driven by some combination of heat diffusing out of the warm fresh sediment laden plume and particle settling within it convection was robust in the presence or absence of intense turbulence at sediment concentrations as low as 1 kg m 3 and took the form of millimetre scale sediment laden fingers descending from the base of the surface plume a consequence of the convective instability of the original hypopycnal plume is the generation of a hyperpycnal bottom riding flow the experiments presented here indicate that natural river outflows may thus generate hyperpycnal plumes when sediment concentrations are 40 times less than those required to render the outflow heavy relative to the oceanic ambient the resulting hyperpycnal plumes may play an important role in transporting substantial quantities of sediment to the continental slope and beyond

high resolution morphobathymetric analysis and evolution of capbreton submarine canyon head southeast bay of biscay french atlantic coast over the last decade using descriptive and numerical modeling abstract in this study the capbreton canyon head just off the coast is investigated using high resolution multibeam bathymetry datasets sediment samples and numerical modeling the hr bathymetry analysis reveals a morphological connection between the longshore trough and the head of the canyon the analysis of recent sediment samples shows a clear correlation between the sediment of the canyon head and that of the nearshore hydrodynamic modeling a coupled wave flow model shows that for high energy waves the rotational nature of surf zone circulation reverses and wave induced currents have the potential to transport large quantities of nearshore sands toward the canyon head all these arguments support the assumption that the canyon head captures a part of the sand transported by longshore drift over the 15 years of observation 1998 2013 time lapse bathymetry shows that the floor of the canyon head and one lateral gully network experienced significant morphological reworking in terms of hazards despite this strong activity the position of the canyon head and the profile of its longitudinal slope remained stable and appear as a comforting factor however the activity of unusual lateral erosions needs to be monitored

seasonal variations of sediment transport to a canyon and coastal erosion along the shimizu coast suruga bay japan abstract we examined seasonal variations in offshore and longshore sediment transport along the shimizu coast suruga bay central japan facing the pacific ocean and considered the relationship between these variations and coastal erosion based on coastal topographic data and detailed bathymetric data acquired by narrow multi beam echo soundings in 2004 2007 and analyses of material collected in 2004 2005 combined with wave data in the nearshore zone sediment transport in the study area is divided into two seasonal modes in winter spring a period dominated by the winter monsoon littoral drift is recognized but offshore directed sediment transport is minimal sediment is deposited around coastal structures during this period consequently tombolos are formed from gravelly deposits and offshore banks which represent the bulges of the seafloor in water depths of 3 7 m are formed seaward of the structures due to the deposition of sandy sediment in summer autumn when typhoons commonly strike the coast we observe pronounced longshore and offshore sediment transport consequently the deposits that form tombolos and offshore banks are intensely eroded the bulk of the eroded sediments are transported into the submarine canyons in the case that a canyon is located close to the coastline and the shelf is narrow as a result of this transport sand ridges and depressions are formed from sandy and gravelly deposits respectively the amount of erosion 34 000 m 3 from the seafloor where most of the active transport occurred in the study area during summer autumn approximately corresponds to the amount of nourishment 35 000 m 3 recorded throughout the entire study area corresponding to about 50 of the amount of the sediment carried by longshore transport 70 000 m 3 year long period deep water waves and high incident waves generated by typhoons during summer autumn are essential in transporting sediment from the coast to offshore areas the winter monsoon makes only a minor contribution in this regard the amount of sediment outflow generated by high energy waves appears to increase with the accumulation of sediment around offshore breakwaters built in regions with a narrow shelf research on offshore directed sediment transport as in this study is important for managing and preserving the nearshore environment e g to examine the budget between supply and outflow as deposits that flow out into the deep ocean never return to the beach

morphology of turbidite systems within an active continental margin the palomares margin western mediterranean abstract the palomares margin an nne ssw segment of the south iberian margin located between the alboran and the algerian balearic basins is dissected by two major submarine canyon systems the gata in the south and the alias almanzora in the north new swath bathymetry side scan sonar images accompanied by 5 khz and topas subbottom profiles allow us to recognize these canyons as mediterranean examples of medium sized turbidite systems developed in a tectonically active margin the gata turbidite system is confined between residual basement seamounts and exhibits incised braided channels that feed a discrete deep sea fan which points to a dominantly coarse grained turbiditic system the alias almanzora turbidite system larger and less confined is a good example of nested turbiditic system within the canyon concentric sediment waves characterize the alias almanzora deep sea fan and the size and acoustic character of these bedforms suggest a fine grained turbidite system both canyons are deeply entrenched on a narrow continental shelf and terminate at the base of the continental slope as channels that feed deep sea fans while the alias almanzora turbidite system is the offshore continuation of seasonal rivers the gata turbidite system is exclusively formed by headward erosion along the continental slope in both cases left lateral transpressive deformation influences their location longitudinal profiles incision at the upper sections and canyon bending associated with specific fault segments

evolution of continental slope gullies on the northern california margin abstract a series of subparallel downslope trending gullies on the northern california continental slope is revealed on high resolution seismic reflection profiles imaging the uppermost 50 m of sediment the gullies are typically 0 m wide and have 1 to 3 m of relief they extend for 10 to 15 km down the slope and merge into larger channels that feed the trinity canyon in the lower half of the 50 m stratigraphic section the gullies increase in both relief and number up section to maxima at a surface 5 to 10 m below the last glacial maximum lowstand surface gully relief increased as interfluves aggraded more rapidly than thalwegs erosion is not evident in the gully bottoms therefore gully growth was probably due to reduced sediment deposition within the gullies relative to that on interfluves as the gullies increased in relief their heads extended upslope toward the shelfbreak at all times a minimum of 10 km of non gullied upper slope and shelf stretched between the heads of the gullies and the paleo shoreline the gullies did not connect with a subaerial drainage network at any time gully growth occurred when the gully heads were in relatively shallow water 200 m paleo water depth and were closest to potential sediment sources we suggest that prior to the last glacial maximum the mad river then within 10 km of the gully heads supplied sediment to the upper slope which fed downslope eroding sediment flows these flows removed sediment from nearly parallel gullies at a rate slightly slower than sediment accumulation from the eel river 40 km to the south the process or processes responsible for gully growth and maintenance prior to the last glacial maximum effectively ceased following the lowstand when sea level rose and gully heads lay in deeper water 300 m water depth farther from potential sediment sources during sea level highstand the mad river is separated from the gully heads by a shelf 30 km wide and no longer feeds sediment flows down the gullies which fill with sediment from the distal eel river approximately one half of the subsurface gullies have no expression on the seafloor because they have completely filled with sediment following the last glacial maximum lowstand of sea level

geomorphology of the oceans abstract we present the first digital seafloor geomorphic features map gsfm of the global ocean the gsfm includes 131 192 separate polygons in 29 geomorphic feature categories used here to assess differences between passive and active continental margins as well as between 8 major ocean regions the arctic indian north atlantic north pacific south atlantic south pacific and the southern oceans and the mediterranean and black seas the gsfm provides quantitative assessments of differences between passive and active margins continental shelf width of passive margins 88 km is nearly three times that of active margins 31 km the average width of active slopes 36 km is less than the average width of passive margin slopes 46 km active margin slopes contain an area of 3 4 million km2 where the gradient exceeds 5 compared with 1 3 million km2 on passive margin slopes the continental rise covers 27 million km2 adjacent to passive margins and less than 2 3 million km2 adjacent to active margins examples of specific applications of the gsfm are presented to show that 1 larger rift valley segments are generally associated with slow spreading rates and smaller rift valley segments are associated with fast spreading 2 polar submarine canyons are twice the average size of non polar canyons and abyssal polar regions exhibit lower seafloor roughness than non polar regions expressed as spatially extensive fan rise and abyssal plain sediment deposits all of which are attributed here to the effects of continental glaciations and 3 recognition of seamounts as a separate category of feature from ridges results in a lower estimate of seamount number compared with estimates of previous workers

alboran basin southern spain part i geomorphology abstract bathymetric 3d relief and shaded relief maps created from multibeam echo sounding data image the morphology of the alboran basin a structural low along the east west trending eurasian african plates boundary topographic features in the basin are the consequence of volcanism associated with miocene rifting rift and post rift sedimentation and recent faulting resulting from the convergence of the african eurasian plates pleistiocene glacially induced regressions transgressions when the sea level dropped to about 150 m below its present level gas seeps and bottom currents recent faulting and the pleistocene transgressions regressions led to mass wasting formation of turbidity currents and canyon erosion on the basin s slopes recent fault traces at the base of the northern basin slope have also served as passageways for thermogenic methane the oxidation of which by bacteria led to the formation of carbonate mounds along the fault intercepts on the sea floor expulsion of thermogenic or biogenic gas has led to the formation of pockmarks erosion by bottom currents has resulted in the formation of moats around seamounts and erosion of the seafloor of the alboran ridge and kept the southern edge of the 36 10 n high sediment free

submarine deltaic geometries linked to steep mountainous drainage basins in the northern shelf of the alboran sea filling the gaps in the spectrum of deltaic deposition abstract a comprehensive analysis of small deltaic environments linked to short mountainous and seasonal fluvial systems in the northern shelf of the alboran sea was undertaken in order to define the controlling parameters of the geomorphological variability the database includes multibeam and backscatter imagery surficial sediment samples and high resolution seismic profiles additionally geomorphological and hydrodynamic modeling and statistical analysis principal component and cluster analysis of hydrological and physiographic variables were performed most of the studied deltaic systems have high gradient coarse grained deposits with preferential development of the submarine portions to the detriment of the deltaic plains the geomorphological analysis identified three basic types of plan view distributions according to the length to width ratios elongate linguoid and lobate cross slope profiles evidence dominant concave upward geometries fewer occurrences of planar geometries and no sigmoid profiles sediment depocenters are extremely thick in proximal locations but thin out rapidly seawards the geometric distribution patterns of the deltaic systems are characterized by a predictable pattern in plan view according to the type of fluvial system ranging from a relatively large river to ephemeral creeks prevailing concave and secondary planar profiles support strong sediment progradation in the submarine realm and low sediment retention in the emerged deltaic environment two different types of systems are distinguished 1 larger rivers where deltaic deposition is largely controlled by basin dimensions ultimately dictating the magnitude of water and sediment discharges and 2 smaller rivers and creeks where deltaic geometries are related to the basin slopes the influence of hydrodynamic variables on defining the submarine deltaic geometry has been observed in the case of concave upward geometries where geomorphological boundaries are defined by medium and high energy wave conditions

morphodynamics in sediment starved inner shelf submarine canyons lower st lawrence estuary eastern canada abstract the contemporaneous activity and sedimentary processes in a series of inner shelf submarine canyons located in the lower st lawrence estuary were examined using high resolution multibeam bathymetry and backscatter data the presence of crescent shaped bedforms csbs displaced upslope at the bottom of the canyons between 2007 and 2012 indicates that they are currently active through the remobilization of sediment by gravity flows however the shelf and shores of the region are characterized by the absence of sediment our results indicate that gravity flows currently eroding the canyon floors do not transport new material downslope coming from the shelf but rather remobilize in situ deglacial sediments within the canyon thalweg we suggest that slope failures and internal tides waves are responsible for sediment remobilization in these canyons although their role in the upslope migrating csbs is unclear this paper provides evidence that sediment supply is not a prerequisite for the modern activity of inner shelf submarine canyons when processes such as slope failures and internal tides waves are frequent enough to remobilize in situ sediments

the tributary valley systems of the almeria canyon alboran sea sw mediterranean sedimentary architecture three tributary valley systems of the almeria canyon dalias andarax and gata located on the almeria margin alboran sea sw mediterranean were studied using high resolution techniques including swath bathymetry and topas seismic reflection profiles a detailed morphological and seismic stratigraphy study shows that the tributary valley systems tvs are formed by two types of valleys gullies and leveed channels dalias tvs is the best developed system covering an area of more than 300 km 2 from the shelf edge off cabo de dalias to the almeria canyon 100 1500 m depth andarax tvs covers about 65 km 2 from the shelf off the andarax river mouth to the westernmost branch of the almeria canyon 40 300 m depth gata tvs covers more than 100 km 2 from the shelf edge off cabo de gata to the almeria canyon 200 650 m depth tributary valley systems can be divided into two models based on the detailed morpho seismic study the sea level controlled model and the sediment supply controlled model the sea level controlled model includes the dalias and gata tvs this model is mainly governed by sea level fluctuations and the valleys grow as a result of the activity of turbidity currents and hemipelagic sedimentation displaying a retrogressive upslope pattern the valleys development would have been favoured by glacio eustatic oscillations during the late quaternary a tentative chronostratigraphic correlation has been made relating the evolution of dalias and gata tvs with the marine isotopic stages and sea level curves tectonics and margin physiography play a secondary role in the development of this type of valley the sediment supply controlled model is applicable to the andarax tvs the growth of the valleys is controlled by the ephemeral sediment discharges from the andarax river the valleys are small scale gullies located on the shelf and slope which would grow as a result of the turbidity currents which channel the fluvial sediment supplied in form of hyperpycnal currents this model would have been developed during the last highstand of sea level once the coast line reached its present situation d 2005 elsevier b v all rights reserved

submarine canyon head morphologies and inferred sediment transport processes in the alias almanzora canyon system sw mediterranean on the role of the sediment supply abstract canyon head regions are key areas for understanding the shelf to canyon sedimentary dynamics and assessing the predominant hydrodynamic and sedimentary processes shaping their morphology high resolution multibeam bathymetry surveys conducted on the shelf upper slope and along the main thalwegs of the alias almanzora submarine canyon system were used to recognize the specific morphological features of the various canyon heads and infer the main sediment transport mechanism operating through them off the almanzora river different canyon head morphologies were observed at 65 90 m water depth incising the outer prodeltaic deposits a direct connection from the river supply is evidenced by the presence of a large radial field of sediment waves on the prodelta presumably related to hyperpycnal flows during flash flood events and their continuation towards trains of cyclic steps that merge into the almanzora canyon head processes linked to seepage and groundwater sapping also seems apparent in the prodeltaic deposits which results in pockmark alignments and formation of elongated narrow canyon heads at the southern limit of the almanzora prodelta another type of canyon head results from the formation and merging of linear gullies these have been interpreted as the morphological expression of the distal off shelf transport of flood related hyperycnal flows however most of the canyon heads of the main tributaries of this canyon system i e garrucha cabrera and alias are found at much shallower water depths 7 20 m they generally show a continuation in land with rivers or intermittent creeks known as ramblas that also experience flash flood events but some of them are disconnected from any river source these canyon heads cut into the infralittoral prograding wedge displaying feeder channels that tend to oriented against the direction of the prevalent long shore current some canyon head tributaries show sediment waves along their axis interpreted as the result of hyperpycnal flood events or storm induced turbidity flows this study focusses on the diversity of sediment transport processes that can co exist in the various canyon tributaries of a given submarine canyon system stressing on the importance of the canyon heads location with respect to the principal sedimentary source which ultimately determines their main geomorphological traits

pleistocene raised marine terraces of the spanish mediterranean and atlantic coasts records of coastal uplift sea level highstands and climate changes detailed geological mapping morphostratigraphic palaeontological and geochronological uranium series analyses were undertaken on the raised marine terraces and interbedded terrestrial deposits along the spanish peninsular and insular atlantic and mediterranean coasts several sets of pleistocene shallow marine to coastal deposits exposed in a staircase arrangement are interpreted as being emplaced during sea level highstands coeval with interglacials or interstadials correlating with marine oxygen isotopic stages ois 5a 5c 5e 7 9 11 and older up to three highstands have been identified in deposits formed during ois 5e close to the end of ois 5e there is a record of sudden changes in sea surface conditions and climate marked by the disappearance of a major proportion of the warm senegalese fauna switches from oolitic to non oolitic facies and accumulation of boulder beaches dating of the coral cladocora caespitosa found in a layer that also contains strombus bubonius confirms the occurrence of warm fauna in the mediterranean basin during ois 7 as previously suggested by hillaire marcel et al 1986 goy et al 1986a b zazo and goy 1989 also the occurrence of warm faunas in deposits corresponding to an older interglacial probably ois 9 or 11 in the balearic islands suggests similar oceanographic conditions sea surface temperature assuming constant salinity during the last interglacial and at least two interglacials of the middle pleistocene in the western mediterranean a 2002 elsevier science b v all rights reserved

sediment grains moved by passing tsunami waves tsunami deposits in deep water abstract tsunamis propagating in the open ocean have associated horizontal particle velocities that do not change with depth yet the limiting water depth where a tsunami of given characteristics will initiate sediment motion remains unknown based upon linear wave theory and a parametrization of the shields curve equations are derived and solved using an iterative scheme to address the topic of grain movement by tsunami waves as a function of water depth and wave amplitude the focus is on waves in deep water where tsunami waves behave linearly and on non cohesive sediment grains furthermore the question is addressed of which grain sizes are picked up on a sloping beach as the wave shoals according to the results even the boxing day tsunami in 2004 was incapable of moving fine sand in water deeper than 985 m in the bay of bengal and 335 m in the indian and pacific oceans the results suggest that tectonic tsunamis of size equal to or smaller than the boxing day tsunami cannot initiate motion of deep water cohesionless sediments that can be correlated on an oceanic basin wide scale

origin of florida canyon and the role of spring sapping on the formation of submarine box canyons florida canyon one of a series of major submarine canyons on the southwestern edge of the florida platform was surveyed using gloria seabeam and deep tow technologies and it was directly observed during three dsrv alvin dives florida canyon exhibits two distinct morphologies a broad v shaped upper canyon and a deeply entrenched flat floored u shaped lower canyon the flat floored lower canyon extends 20 km into the florida platform from the abyssal gulf the lower canyon ends abruptly at an 3 km in diameter semicircular headwall that rises 750 m with a 60 slope angle to the foot of the upper canyon the sides of the lower canyon are less steep than its headwall and are characterized by straight faces that occur along preferred orientations and indicate a strong joint control the upper canyon is characterized by a gently sloping straight v shaped central valley cut into a broad terrace the flat floor of the upper canyon continues as terraces along the upper walls of the lower canyon on the flanks of the upper canyon there are five 50 m deep 0 5 km wide closed sink hole like depressions which indicate subsurface dissolution within the platform the origin of the lower canyon is difficult to explain with traditional models of submarine canyon formation by external physical processes the movement of ground water probably with high salinities and reduced compounds along regional joints may have focused the corrosive force of submarine spring sapping at the head of the lower canyon to produce the canyon9s present shape

tectonic origin and evolution of a transverse drainage the rio almanzora betic cordillera southeast spain abstract the rio almanzora forms one of the larger drainage systems within the betic cordillera southeast spain in its distal reaches prior to joining the mediterranean sea the rio almanzora cuts across a major topographic barrier the sierra almagro forming drainage that is transverse to the regional geological structure the long term drainage evolution of the rio almanzora and its creation as a transverse drainage across the sierra almagro has been examined by reconstruction of an evolving basin scale drainage network using a combination of the geological and geomorphological record the early stages of drainage evolution late miocene pliocene and plio pleistocene reveals the emergence of marine basins to the north and south of the sierra almagro and the development of unconnected drainage systems this emergence records the development of the proto rio almanzora on the south side of the sierra almagro as a prograding fan delta and alluvial fan system expansion of this drainage network via incision and headward erosion across the sierra almagro took place during the pleistocene during the early mid pleistocene the proto rio almanzora became fully transverse across the sierra almagro and linked the endorheic almanzora huercal overa basin with the vera basin a tectonically induced lowering of regional base level is proposed for the incision headward erosion and drainage network expansion that has resulted in the creation of the rio almanzora as a transverse drainage differential uplift between the huercal overa almanzora and vera basins has resulted in southwards tilting and the creation of a regional gradient the fluvial response to tilting was for incision into the steepened regional surface gradient via an increase in stream power the incision headward erosion and drainage network expansion by the proto rio almanzora and its creation as a transverse drainage appears to be part of a regional response by fluvial systems to differential uplift recorded throughout the betic cordillera of southeast spain during the plio pleistocene

macrofaunal communities within and adjacent to a detritus rich submarine canyon system abstract macrofaunal abundance biomass diversity and species assemblages within scripps and la jolla submarine canyons are compared with those on the nearby continental shelf and slope our primary objective was to examine the effect of detrital aggregates on infaunal communities within canyons two submarines a remotely operated vehicle rov and a soutar box corer were used to collect samples within the canyons organic enrichment by macrophyte detritus was evident from canyon heads down to 550 m and evidence of strong currents coarse sediment was found down to 700 m infaunal density and biomass were higher in the canyons than outside at all depths where comparative data were available 100 500 m infaunal assemblages in canyons were distinct from those at reference stations both the canyon and non canyons samples showed community differentiation with depth species diversity was generally high but decreased with depth outside of canyons and increased with depth within the canyons low diversity at shallow depths within the canyon is attributed to a combination of organic enrichment and physical disturbance submarine canyons are commonly found to contain distinct species assemblages or higher faunal densities and or biomass than nearby non canyon regions at similar depths canyons are regular features along most ocean margins and appear to be important as sites of enhanced secondary production provide diverse habitats and act as conduits of coastal detritus to the deep sea

crustal scale transcurrent fault development in a weak layered crust from an integrated geophysical research carboneras fault zone eastern betic cordillera spain new magnetotelluric and receiver transfer function studies provide insights from the upper to the lower crust of the eastern betic cordillera which is deformed by large folds normal faults and a major transcurrent left lateral fault the carboneras fault zone cfz receiver function analysis determines a nnw dipping moho reaching 20 that increases in depth from 20 km south of the cfz up to 34 km in the sierra de los filabres in addition seismic discontinuities determined in the upper crust are interpreted as major contacts between metamorphic complexes that are detached and folded the mt inversion model reveals a conductive zone also representing a crustal seismic discontinuity associated with the alpujarride nevado filabride contact and fitting the n vergent geometry of the sierra alhamilla antiform a small flexure at moho coincides with the cfz as revealed by the bouguer anomaly trend in agreement with the receiver function results moreover the bahr strike and tipper angle at the stations placed closest to the cfz clearly reveal the continuity of the cfz at least down to approximately 15 km in depth crossing all the detected crustal discontinuities up to the moho the lack of a clear moho offset associated with the carboneras fault supports the idea that some large strike slip faults tend to accommodate the deformation by a broadening fault zone at lower crustal levels its nucleation could occur at the base of a thin crust where melting processes critically reduced the lithospheric strength during the late miocene to then propagate upward reaching the topographic surface northward the lithosphere comprised moderately larger strength and the crustal discontinuities favored the development of larger folds with kilometric amplitude instead of strike slip faults since the late miocene

crustal types and tertiary tectonic evolution of the alboran sea western mediterranean multichannel seismic reflection images across the transition between the east alboran and the algero balearic basins show how crustal thickness decreases from about 5 s two way traveltime twtt 15 km thick in the west east alboran basin to 2 s twtt typical of oceanic crust 6 km thick in the east algero balearic basin we have differentiated three different crustal domains in this transition mainly on the basis of crustal thickness and seismic signature boundaries between the three crustal domains are transitional and lack evidence for major faults tilted blocks related to extension are very scarce and all sampled basement outcrops are volcanic suggesting a strong relationship between magmatism and crustal structure stratigraphic correlation of lithoseismic units with sedimentary units of southeastern betic basins indicates that sediments onlap igneous basement approximately at 12 ma in the eastern area and at 8 ma in the western area linking seismic crustal structure with magmatic geochemical evidence suggests that the three differentiated crustal domains may represent from west to east thin continental crust modified by arc magmatism magmatic arc crust and oceanic crust middle to late miocene arc and oceanic crust formation in the east alboran and algero balearic basins respectively occurred during westward migration of the gibraltar accretionary wedge and shortening in the betic rif foreland basins arc magmatism and associated backarc oceanic crust formation were related to early to middle miocene subduction and rollback of the flysch trough oceanic basement subduction of this narrow slab beneath the alboran basin was coeval with collision of the alboran domain with the iberian and african passive margins and subsequent subcontinental lithosphere edge delamination along the betic rif margins

influence of strike slip fault segmentation on drainage evolution and topography a case study the palomares fault zone southeastern betics spain abstract the palomares fault zone pfz is one of the main sinistral strike slip faults in the betics se spain with approximately 16 km of north south displacement the pfz initiated during the tortonian messinian as a transfer structure linking areas subject to nw se shortening during the plio quaternary the fault zone lengthened cutting previous fold structures and widened towards the east displacing the active mountain front to the western border of sierra almagrera sierra almenara these sierras which show moderate uplift rates of 0 05 0 15 m ka formed in response to the oblique slip regime of the pfz the drainage system in the vicinity of the pfz is asymmetric with respect to a main axial valley that runs parallel to the pfz on the downthrown fault block in this block the drainage density is lower and the streams are longer than in the uplifted block furthermore west of the main axial valley the streams describe eastward directed deflections indicating the progressive eastward migration of the main axial valley during the pleistocene the drainage system on the uplifted ranges shows a consequent pattern indicating recent uplift and folding under nnw sse convergence recent activity along segments of the pfz has increased topographical gradients favouring dissection of previous streams by headward erosion of streams transverse to the active fault segments

direct sediment transfer from land to deep sea insights into shallow multibeam bathymetry at la reunion island abstract submarine canyon heads are key areas for understanding the triggering factors of gravity currents responsible for the transfer of detrital sediment to the deep basins this contribution offers a detailed picture of canyon heads off la reunion island with high resolution multibeam bathymetry in the water depth range of 4 220 m the present feeding of the cilaos turbidite system one of the largest modern volcaniclastic systems in the world is deduced from morphological and sedimentological interpretations of newly acquired data the study highlights small scale sedimentary features indicating hydrodynamic and sedimentary processes a direct connexion between the saint etienne river mouth and submarine canyons is evidenced by the complete incision of the shelf and the presence of canyon heads connected to the modern deltaic bar this direct connection supplied by river torrential floods cyclonic floods every two or three years suggests the continuity of high density fluvial flows to submarine gravity flows forming hyperpycnal flows in the canyon the initiation of secondary submarine gravity flows by storm waves large austral waves and cyclonic waves is also proposed for submarine canyons with large canyon heads developed in the surf zone from a sandy coastal bar bedforms in active canyon axis are considered as an indicator of the frequent activity of high density turbidity currents moreover a morphological record of last glacial and deglacial sea level variations is preserved and particularly the last glacial maximum sea level with the presence of small vertical cliffs observed in this bathymetric data which likely corresponds to a paleo shoreline or paleo reefs

physiography of the monterey bay national marine sanctuary and implications about continental margin development abstract combined em 300 multibeam bathymetric data and satellite photography reveal the physiography of the continental margin between 35 50 and 37 03 n and from the shoreline west of 122 40 and 122 37 w which includes monterey bay in a previously unprecedented detail patterns in these images clearly reveal the processes that are actively influencing the current geomorphology of the monterey bay region including the monterey bay national marine sanctuary mbnms our data indicates that seafloor physiography within the mbnms results from plate margin tectonic deformation including uplift and erosion along structural lineaments and from fluid flow mass wasting is the dominant process active within the ascension monterey and sur partington submarine canyon systems and along the lower slopes meanders slump dams and constricted channels within the submarine canyons especially within monterey canyon slow and interrupt down canyon sediment transport we have identified for the first time thin sediment flows rotational slumps rills depressions that may be associated with pipes and other fluid induced features we call scallops off the ascension slope and suggest that fluid flow has sculptured the seafloor morphologies here these unusual seafloor morphologies are similar to morphologies found in terrestrial areas modified by ground water flow

near synchronous and delayed initiation of long run out submarine sediment flows from a record breaking river flood offshore taiwan subsea fiber optic telecommunication cables can break under fast sediment flows that travel 100s of kilometers through the deep ocean in response to earthquakes and submarine landslides similar flows are inferred to form from major river floods whose sediment laden waters plunge and travel along the seabed however the complex initiation of flood related flows and their hazard potential have not been observed until now here we use cable fault data from the gaoping canyon manila trench off taiwan to show that a major river flood formed during typhoon morakot 2009 generated two long run out destructive sediment flows one during peak flood and the other 3 days later the latter flow was more damaging with speeds and run out similar to that of landslide triggered turbidity currents formed in the same catchment if the second flow was due to remobilized canyon sediment it occurred during low earthquake mw 2 0 activity suggesting other triggering mechanisms

geomorphic and sedimentary response of rivers to tectonic deformation a brief review and critique of a tool for recognizing subtle epeirogenic deformation in modern and ancient settings abstract rivers are extremely sensitive to subtle changes in their grade caused by tectonic tilting as such recognition of tectonic tilting effects on rivers and their resultant sediments can be a useful tool for identifying the often cryptic warping associated with incipient and smaller scale epeirogenic deformation in both modern and ancient settings tectonic warping may result in either longitudinal parallel to floodplain orientation or lateral normal to floodplain orientation tilting of alluvial river profiles alluvial rivers may respond to deformation of longitudinal profile by 1 deflection around zones of uplift and into zones of subsidence 2 aggradation in backtilted and degradation in foretilted reaches 3 compensation of slope alteration by shifts in channel pattern 4 increase in frequency of overbank flooding for foretilted and decrease for backtilted reaches and 5 increased bedload grain size in foretilted reaches and decreased bedload grain size in backtilted reaches lateral tilting causes down tilt avulsion of streams where tilt rates are high and steady down tilt migration combing where tilt rates are lower each of the above effects may have profound impacts on lithofacies geometry and distribution that may potentially be preserved in the rock record fluvial sedimentary evidence for past tilting is traditionally based on the assumption that depositional features reminiscent of modern fluvial tectonic effects are evidence for past tectonic effects where it is closely associated with historically active structures or where non tectonic causes cannot be invoked however caution must be exercised when using these effects as criteria for past or current tectonic warping as these effects may be caused by non tectonic factors these non tectonic causes must be eliminated before tectonic interpretations are made

response of quaternary fluvial systems to differential epeirogenic uplift aguas and feos river systems southeast spain the geomorphic expression of two fluvial systems the rio de aguas and the rambla de los feos in southeast spain reflects their adjustment to differential epeirogenic uplift and local tectonic activity during the quaternary regional uplift of a depositional marine surface resulted in the development of a southward flowing drainage network during late pliocene early pleistocene time disruption of this consequent drainage began as the alhamilla cabrera sierras and the sorbas basin were differentially uplifted relative to the surrounding basins the ancestral feos drainage responded by incision across the uplift through a combination of superimposition and antecedence differential uplift of the sorbas basin enhanced headward erosion of strike oriented drainages and promoted capture of the ancestral feos drainage by the rio de aguas during the late pleistocene stratigraphic relations and soil development indicate that epeirogenic uplift and local tectonics together with climatic fluctuations have influenced the development of the drainage systems throughout the quaternary

correlation of sidescan backscatter with grain size distribution of surficial seabed sediments the dependence of acoustic backscatter on sediment grain size distribution is examined using dual frequency 100 and 410 khz sidescan sonar and 22 sediment grab samples from the loch linnhe artificial reef site on the west coast of scotland the sidescan data were processed to remove an empirically estimated average grazing angle dependence on backscatter the processed data were analysed by forming histograms of pixels extracted from a 20 m 2 box around each ground truth site a positive correlation r 0 73 between mean backscatter intensity and mean grain size was obtained i e the coarsest samples had the brightest backscatter a positive correlation r 0 59 was also found between the standard deviations of the backscatter and grain size distributions i e poorly sorted sediments gave the most variable backscatter the performance of the sidescan data was compared to results from a co incident single beam echo sounder roxann survey the roxann roughness index e1 compared well with the sidescan whilst the roxann hardness index e2 did not this may be due to a physical link between the acoustic measures the comparison showed the sidescan to have delivered a significantly higher resolution image of the seabed for a similar amount of ship time imaging of the artificial reef modules themselves was found to be frequency dependent d 2004 elsevier b v all rights reserved

e w opening of the algerian basin western mediterranean we present geophysical and geological evidence of fast 2 cm yr 1 in the east and 5 cm yr 1 in the west e w spreading between 16 and 8 ma in the region behind the gibraltar arc in the algerian basin

rupture lengths and temporal history of significant earthquakes on the offshore and north coast segments of the northern san andreas fault based on turbidite stratigraphy piston gravity and jumbo kasten cores were collected from channel and canyon systems draining the northern california continentalmargintoinvestigatetherecordofperiodicholoceneturbiditesforpossibleconnectiontolargemagnitudeearthquakeson the adjacent northern san andreas fault poorly known channel systems were mapped with multibeam sonar to define pathways and channel confluences cores sampled all major and many minor channel systems extending from cape mendocino to just north of monterey bay sampling both along and across channels was done and particular attention was paid to channel confluences as these areas afford opportunities to test for synchronous triggering of turbidity currents while at sea all cores were scanned using a geotek multisensor core logger mscl which collects high resolution photography p wave velocity gamma ray density and magnetic susceptibility data from the unsplit cores lithology was logged visually and cores were later imaged with x radiography we use 14 c ages relative dating tests at channel confluences and stratigraphic correlation using physical properties to determine

classification of submarine canyons of the australian continental margin abstract submarine canyons influence oceanographic processes sediment transport productivity and benthic biodiversity from the continental shelf to the slope and beyond however not all canyons perform the same function the relative influence of an individual canyon on these processes will in part be determined by its form shape and position on the continental margin here we present an analysis of canyon geomorphic metrics using an updated national dataset of 713 submarine canyons surrounding mainland australia these metrics attributes for each canyon are used to classify them into canyon types across a hierarchy of physical characteristics separately for shelf incising n 95 and slope confined blind n 618 canyons we find that the canyon metrics describe a wide variety of canyon form and complexity that is consistent with a population of canyons that has evolved at different rates around the australian margin since the break up of gondwana the large number of slope confined canyons is interpreted to reflect dominance of slope mass wasting processes over erosive turbidity flows from fluvial and shelf sources on an arid continent the distribution of submarine canyons around the australian margin is not regular with clusters occurring in the east southeast west and southwest where the margin is steepest the classification result provides a quantitative framework for describing canyon heterogeneity for application in studies of geological controls on individual canyons canyon oceanography and canyon biodiversity

the morpho tectonic setting of the southeast margin of iberia and the adjacent oceanic algero balearic basin abstract multi beam bathymetry and high resolution low penetration seismic reflection profiles of the offshore extensions of the betic internal zone off sierra de cartagena la union margin along its south side and the mar menor margin along its east side the mazarron escarpment forming its southern boundary and the adjacent oceanic algero balearic basin have provided images of the neo tectonic structures of the region equal to those provided by subaerial photography for the first time we mapped with unprecedented detail the mazarron escarpment and the southeast margin of iberia the first order structures of the region are due to the consequence of the collision of the african and eurasian plates during the alpine orogeny in late oligocene middle miocene the westward migration of the alboran plate in the middle miocene and the desiccation of the mediterranean in the messinian late miocene that led to the deposition of evaporites in the algero balearic basin and erosion of the mazarron escarpment the sierra de cartagena la union shelf the mar menor margin and the adjacent coast our data images second order tectonic features neo tectonic features superimposed on the larger structures these include the deformation of the strata in the algero balearic basin by the gliding of the plio quaternary sediments on messinian halite on the margins of the basin and sediment loading in its center the late miocene quaternary deformation of the area north of the mazarron escarpment resulting from the continuous oblique convergence of the african and eurasian plates in a nnw sse direction the miocene to pleistocene volcanic edifices and pinnacles dikes the pockmarks formed by the extrusion of gas water via faults and the massive gravitational failure of the mazarron escarpment triggered by this plate convergence the data also show in detail features formed on the mazarron escarpment during the messinian pliocene and pleistocene regressions and those on the shelf formed during the pleistocene glacially induced regressions transgression and sediment drifts generated by modern currents