sedimentary facies of the eastern pacific s northernmost reef like setting cabo pulmo mexico abstract cabo pulmo mexico is often cited as the eastern pacific s northernmost coral reef we investigated sedimentary dynamics to verify whether the system functions sedimentologically as a reef which would mean that it retained internal sediment in a framework and exported peri reefal sediment creating clearly identifiable facies dominated by reefal fauna we mapped distribution of sediments using grab samples the acoustic ground discrimination systems qtc view and echo plus at 50 khz signal frequency and an ikonos satellite image morphologically the bay of cabo pulmo can be divided into intrusive dikes and rocky hardgrounds in less than 10 m depth and a sandy interior with rocky outcrops sloping to over 40 m reefal fauna without lasting framework building but with production of typically reef associated carbonate sediments as well as a patch reef facies were found on the dikes and hardgrounds sediments in the bay were a mixture of carbonates and siliciclastics and were influenced by a seasonal river near the bay s center that imported siliciclastic material to the north and south sediments had a higher carbonate content although overall the bay was characterized by 50 siliciclastics the shallower subtidal sands were dominated by mollusk fragments whereas in depths 30 m planktonic foraminiferal sand was found acoustically and optically remote sensed maps were used to differentiate between the rocky and sandy areas and to identify the presumed off shelf transport pathway of reef derived carbonates overall the sedimentary system is characterized by carbonate production but the coarser reef derived carbonates coral and reef dwelling mollusks are transported off shelf along a steep depth gradient and little typical peri reef sediment remains this transport is likely aided by storms since no sediment retaining frameworks are formed the dikes cannot retain internal sediment and the reefal fauna was not dominant in sediments throughout the bay we conclude that cabo pulmo sedimentologically functions only in a limited way like a coral reef

a study on the regulation of the concentrations of some trace metals rb sr zn pb cu v cr ni mn and mo in saanich inlet sediments british columbia canada abstract bulk metal concentrations were measured in the sediments of saanich inlet in an attempt to establish the occurrence of trace metal enrichment in the anoxic central basin ba ni v cr zn pb cu and mo were found to be enriched in the anoxic ooze over the possible contributions from lithogenic sources spatial and seasonal variations in the chemical composition of the settling particulates collected with interceptor traps gave further indications of the mode of incorporation of these metals biogenic ba and cr appeared to be associated with opaline silica although alternative explanations are also possible particularly for ba zinc seemed to be added to the sediment essentially in association with planktonic materials while cu required an additional source directly linked to the anoxic environment similarly ni v and mo were added to the anoxic sediments by reactions occurring at the sediment water interface in the nearshore environment studied here these metals particularly ni and mo were not associated to any significant extent with planktonic materials of all the elements analyzed mo showed the largest enrichment in the anoxic sediments of saanich inlet

a young multilayered terrane of the northern mare imbrium revealed by chang e 3 mission china s chang e 3 ce 3 spacecraft touched down on the northern mare imbrium of the lunar nearside 340 49 e 44 12 n a region not directly sampled before we report preliminary results with data from the ce 3 lander descent camera and from the yutu rover s camera and penetrating radar after the landing at a young 450 meter crater rim the yutu rover drove 114 meters on the ejecta blanket and photographed the rough surface and the excavated boulders the boulder contains a substantial amount of crystals which are most likely plagioclase and or other mafic silicate mineral aggregates similar to terrestrial dolerite the lunar penetrating radar detection and integrated geological interpretation have identified more than nine subsurface layers suggesting that this region has experienced complex geological processes since the imbrian and is compositionally distinct from the apollo and luna landing sites

sediment properties along gradients of siltation in south east asia marine sediment properties were quantified along se asian siltation gradients and across different habitat types to assess the extent of terrestrial sediment influence and derive indicators of of terrestrial sediment input three sites in the andaman sea ranong phuket and trang thailand one site in the gulf of thailand pak phanang thailand and three sites in the south china sea bolinao at the luzon island puerto galera at the mindoro island and el nido at the palawan island all in the philippines were studied the following main habitat types were covered mangroves seagrass beds coral reefs mud flats river mouths and deep channels particularly in bolinao and el nido distinct fronts in siltation were identified at about 7 km from the source mud 250 m total and inorganic carbon as well as calcium interstitial ammonia and phosphate varied with the fine sand fraction along the second axis two way analysis of variance showed that water depth distance from silt source site and habitat type all contributed to the variance but site explained most linear regressions showed positive correlations between silt and water content organic matter total nitrogen total phosphorus and iron but negative correlations with calcium suggesting iron and calcium as markers for terrigeneous and marine origin respectively the composition of the sediment particulate matter groups the habitat types in two clusters 1 silty types as river mouths shallow mud bottoms deep channels and mangrove stands with high contents of organic matter and nutrients versus 2 non silty types as seagrass beds and coral reefs with low contents of nutrients and organic matter median settling velocities of the silt loads varied from 0 6 m d 1 to 27 m d 1 experimentally determined susceptibility to resuspension identified a critical water content of 50 2002 elsevier science ltd

sea bottom classification across a shallow water bar channel and near shore shelf using single beam acoustics an acoustic ground discrimination system qtc view series iv was used to identify and map the bottom acoustic diversity in the bar channel of ria de aveiro western portugal the majority of the survey area presented shallow depth for this type of equipment ranging mainly from 5 to 15 m depth occasionally reached 25 m in specific areas located across the entrance channel dug by the strong tidal currents reaching 3 m s the acoustic data were submitted to manual and auto cluster and the results obtained from both procedures were coherent using aids to the acoustic classification and ground truth sediment data a final solution consisting of four acoustic classes was reached their geographical distribution was coincident with the spatial distribution of the major bottom types and sediment groups hard bottom coarse sand medium sand and fine sand identified through multivariate analysis of the grain size data and reflected the complex hydrodynamics of the entrance channel the acoustic pattern was coincident at the intersections of the acoustic survey lines assuring the repeatability of the acoustic procedure overall the acoustic approach showed consistent results for the assessment and mapping of the benthic habitats in this shallow water coastal area providing a very valuable tool in an area where conventional sediment sampling is less favourable namely due to strong tidal currents and frequent ship traffic such as the entrance channel of ria de aveiro and the near shore adjacent shelf

macrobenthic community structure over the continental margin of crete south aegean sea ne mediterranean macrobenthic faunal composition abundance biomass and diversity together with a suite of sedimentary environmental parameters were investigated on a seasonal basis in order to determine factors regulating faunal distribution over the oligotrophic continental margin of the island of crete south aegean sea north eastern mediterranean macrofaunal species composition was similar to that of the western mediterranean and the neighboring atlantic having several common dominant species mean benthic biomass abundance and diversity decreased with depth with a major transition zone occurring at 540 m beyond which values declined sharply at comparable depths biomass and abundance values were considerably lower to those found in the atlantic high lighting the extreme oligotrophy of the area the continental margin of crete was characterised by a high diversity upper continental shelf environment dominated by surface deposit feeding polychaetes and a very low diversity slope and deep basin environment dominated by carnivorous and filter feeding polychaetes classification and ordination analyses revealed the existence of four principle clusters divided by a faunal boundary between 200 and 540 m as well as beyond 940 m depth significant correlations between macrofauna and sediment parameters led to the conclusion that besides depth food availability as manifested by the concentration of chloroplastic pigments is the principle regulating factor in the system such being the case the prevailing hydrographic features that structure the pelagic food web and are directly responsible for the propagation of organic matter to the benthos also affect its community structure

spatial variation of intertidal macrofauna on a sandy ocean beach in australia abstract spatial variation of macrofauna on a sandy beach was examined simultaneously over two scales across shore among and within zones and three nested scales along shore over the entire length of the beach prior to the main study pilot studies were performed to determine 1 the relative efficiency accuracy and precision of combinations of core size depth of sampling and sieve mesh size and 2 the likely distribution of macrofauna across shore so that stratification of sampling in the main study would be meaningful from this three zones were defined across shore namely 1 the high shore zone which extended 10 m downshore of the drift line and was dominated by two species of isopod 2 the mid shore zone which extended across the beach from the bottom of the high shore zone to the top of the swash zone and was dominated by the glycerid polychaete hemipodus sp and 3 the swash zone which contained more species than the other two zones and was dominated by amphipods hemipodus sp the bivalve donax deltoides and a species of cumacean in the main study multivariate analyses confirmed that assemblages of macrofauna varied significantly among zones despite smaller scale variation within zones and along shore variation significant along shore variation was detected in assemblages of macrofauna from each zone and occurred at different scales for different zones only assemblages in the swash zone showed a pattern of along shore variation that was consistent with a gradient in wave exposure along the beach univariate analyses showed that significant variation in populations of individual taxa occurred at both large and small scales significant variation was detected across shore within zones for nearly all variates and this demonstrated the importance of formally assessing variation within zones when making comparisons among zones significant variation was also detected along shore in analyses of particular taxa and interactions of across and along shore variation also occurred these results illustrate the necessity of considering both across and along shore variation for describing spatial patterns in assemblages or individual species of macrofauna unfortunately sampling a single transect across a beach which is common in many published descriptions of spatial patterns will not provide an adequate nor representative description of the macrofauna of that beach because this approach fails to consider all important sources of variation and confounds large and small scale variation the authors conclude that a better understanding of small scale variation both along and across shore within beaches is required in order to provide better descriptions of patterns provide a basis for larger scale studies allow unconfounded comparisons among beaches and ultimately to improve our understanding of the ecology of sandy beaches

benthic habitat mapping of sorted bedforms using hydroacoustic and ground truthing methods in a coastal area of the german bight north sea abstract the continuously influence of human impacts on the seafloor and benthic habitats demands the knowledge of clearly defined habitats to assess recent conditions and to monitor future changes in this study a benthic habitat dominated by sorted bedforms was mapped in 2010 using biological sedimentological and acoustic data this approach reveals the first interdisciplinary analysis of macrofauna communities in sorted bedforms in the german bight the study area covered 4 km2 and was located ca 3 5 km west of island of sylt sorted bedforms formed as sinuous depressions with an east west orientation inside these depressions coarse sand covers the seafloor while outside predominantly fine to medium sand was found based on the hydroacoustic data two seafloor classes were identified acoustic class 1 was linked to coarse sand type a found inside these sorted bedforms whereas acoustic class 2 was related to mainly fine to medium sands type b the two acoustic classes and sediment types corresponded with the macrofauna communities 1 and 2 the aoinides paucibranchiata goniadella bobretzkii community on coarse sand and the spiophanes bombyx magelona johnstonii community on fine sand a transitional community 3 scoloplos armiger ophelia community with species found in communities 1 and 2 could not be detected by hydroacoustic methods this study showed the limits of the used acoustic methods which were unable to detect insignificant differences in the fauna composition of sandy areas

sedimentology and acoustic mapping of modern rhodolith facies on a non tropical carbonate shelf gulf of california mexico abstract rhodolith facies are characterized by an abundance of free living coralline red algae and are a common feature of modern and ancient carbonate shelves worldwide rhodolith communities contribute significantly to the global calcium carbonate budget and fossil rhodoliths are commonly used to obtain paleoecologic and paleoclimatic information few attempts have been made to quantify the spatial extent of modern rhodolith facies despite their importance and common occurrence combining sediment sampling with acoustic facies mapping this study provides the first set of quantitative data on rhodolith facies distribution in the warm temperate southwestern gulf of california mexico though rhodoliths were the main carbonate producers other important calcareous biota were bivalves 19 bryozoans 13 and corals 6 based on cluster analysis biota were grouped into a rhodolith a rhodolith bivalve coral and a bivalve bryozoa biofacies the acoustic seafloor classification distinguished four acoustic facies which were confirmed by ground truthing an outer shelf silt facies a biogenic sand facies a peripheral rhodolith facies and a central rhodolith facies rhodolith facies covered approximately 40 of the surveyed seafloor 45 km2 results from quantitative analysis of sediment samples and acoustic mapping showed a significant correlation between grain size biofacies and acoustic seafloor facies we successfully applied an acoustic device to provide highly resolved continuous coverage of the seafloor and discriminate modern rhodolith facies from surrounding sediment this has important implications for quantifying rhodolith carbonate production in other regions as well as for ecological and conservation studies

mobile sand deposits and shoreface sediment dynamics in the inner german bight north sea abstract this paper presents a conceptual model for the net bedload transport regime on the shoreface of the german bight the model is based on the spatial distribution of the surficial sediment cover north sea sands which is identical to the uppermost layer in the seismic recordings sediment thickness was measured using very high resolution seismic profiling chirp sonar and vibrocoring the three dimensional sediment distribution was estimated using geostatistical methods cokriging the results demonstrate a longshore sand distribution with three distinct zones in zone 1 0 10 m water depth the sediments attain their maximum thickness of 10 2 5 m between 10 and 15 m water depth a relatively thin sand layer of 0 4 1 5 m is observed within zone 2 the seaward adjacent zone 3 15 20 m water depth is characterized by an averaged sand thickness of 2 3 m with local maxima of 5 6 m further offshore the sand layer decreases to about 1 2 m thickness the net bedload transport directions inferred from this sediment zonation comprise a longshore sediment bypassing in zone 1 which results in a substantial sediment supply to the innermost part of the german bight due to bedload convergence shore normal bedload transport shifts sand to and fro across the coastal profile although the net directional transport is seawards this results in sediment depletion between the 10 and 15 m isobaths zone 2 and an adjacent sediment accumulation in deeper waters zone 3

the morphodynamic effects of incident wave groupiness and tide range on an energetic beach abstract the roles played by daily tide range and incident wave groupiness in affecting the short term morphodynamic responses of an energetic beach are examined demodulation of original tide and wave time series from the moderate energy narrabeen beach australia resulted in new time series of daily tide range and a daily grouping factor which expresses the relative amplitude of the alternation between groups of high and low waves using these new time series together with time series of daily beach state and changing breaker conditions statistical analyses were performed aimed at determining the contributions made by tide and groupiness in explaining time varying beach state additional to those made by time varying wave conditions eigenvector analyses of monthly surveyed beach and surf zone profiles provided a set of time series on modes of profile configuration change which were also analyzed to determine the relative effects of waves and tide range on profile shape both tide range and groupiness are significant determinants of beach state the six beach states are reflective low tide terrace transverse bar and rip rhythmic bar and beach longshore bar trough and dissipative wright and short 1984 provided that wave conditions are within the appropriate range to favor beach states at the reflective end of the sequence spring tides will tend to favor the low tide terrace over the transverse bar and rip state higher tide ranges are also associated with more subdued bar trough topography the more accentuated bar trough profiles are developed when tide range is minimal overall higher relative incident wave groupiness favors the more dissipative states incident wave groupiness is the dominant factor determining whether the low tide terrace state or transverse bar and rip state prevails provided incident wave steepnesses permit one or the other of these states groupiness is also important in discriminating between the transverse bar and rip and rhythmic bar and beach states

benthic habitat mapping concerns using a combined approach acoustic sediment and biological data abstract near shore benthic biotopes in the 2 30 m depth range were analyzed and mapped using a combination of biological sedimentary and acoustic data to interrogate the utility of these methods the surveyed area covered approximately 270 km 2 along 80 km of the southeast coast of portugal the acoustic data were acquired with a single beam ground discrimination system qtc view series v connected to a dual frequency echo sounder 50 and 200 khz sediment grain size and macrofaunal community data were obtained by grab sampling at 88 sites the sedimentary and the biological data were subjected to classification and ordination analysis and the acoustic data obtained with the two frequencies were analyzed individually with the qtc impact v3 4 software and classified into acoustic classes the affinity groups obtained with the three datasets were mapped using a geographic information system the study area showed an inshore offshore pattern with sands ranging from very fine to very coarse revealing a sediment distribution in the near shore shelf comprised by two main areas a very fine fine sand area up to 7 10 m depth and a very coarse coarse sand area offshore in turn the biological data also showed an inshore offshore pattern identifying two main biological assemblages fine very fine sand and coarse very coarse sand communities furthermore the biological pattern clearly reflected the hydrodynamic conditions of the area from highly hydrodynamic shallow depth to the calmer deeper areas accordingly species richness and densities were lower at shallow areas than at deeper depth the acoustic data identified the prevailing biosedimentary gradients along the inshore offshore direction overall the results obtained here showed that the acoustic system could identify two main areas based on sediment grain size which closely related to the two main biological communities groups a and b this study indicates the importance of combining several layers of information in order to increase the spatial resolution of the main biotope distribution validating the acoustic data and detail their sub divisions ground truth sampling furthermore we show that designing ground truth samples on the basis of the acoustic diversity data allows the biological data to speak for itself in general acoustic techniques are used as a means to optimize ground truth sampling this will only be valid if acoustics can capture all the essence of biotope heterogeneity if this is not the case special attention should be given when using broad scale methods acoustic remote sensing devoted to biotope mapping

macrobenthic zonation patterns along a morphodynamical continuum of macrotidal low tide bar rip and ultra dissipative sandy beaches the species composition densities biomass and zonation patterns of the macrobenthos of sandy beaches are greatly influenced by the morphodynamics and morphology of the beaches macrobenthic zonation patterns along a small scale morphodynamic gradient comprising eight belgian beach sites were investigated by taking into account the dimensionless fall velocity and the relative tidal range the beach sites were ordered along the gradient from the ultra dissipative beach type ud to the low tide bar rip beach type ltbr the resulting beach state index varied between 1 8 and 4 2 and the beach profiles were related with the beaches morphodynamic state in total 35 macrobenthic species mainly polychaetes and crustaceans were encountered varying between 19 and 23 species per beach site the species composition was quite similar among beach sites with scolelepis squamata being abundant at all eight sites furthermore the macrobenthic distribution patterns were mainly related to elevation at all beach sites some remarkable difference in metrics largely related to the beach morphodynamics and the consequent hydrodynamics were found at the hydrodynamically benign and consequently macrobenthos rich ud beaches the highest macrobenthic densities and biomass occurred on the upper beach while at the hydrodynamically harsh and thus macrobenthos poor ltbr beaches the maximum densities and biomass occurred lower on the beach species typically occurring on the upper ud beaches such as eurydice pulchra s squamata and bathyporeia sarsi were restricted to the sub optimal middle and lower beach zone at ltbr beaches only bathyporeia pilosa was found on the upper beach of both ud and ltbr beaches the more robust polychaete ophelia rathkei and the interstitial polychaete hesionides arenaria were exclusively found in the hydrodynamically harsh conditions of the middle ltbr beach zone

mobility of maerl siliciclastic mixtures impact of waves currents and storm events abstract maerl beds are free living non geniculate coralline algae habitats which form biogenic reefs with high micro scale complexity supporting a diversity and abundance of rare epifauna and epiflora these habitats are highly mobile in shallow marine environments where substantial maerl beds co exist with siliciclastic sediment exemplified by our study site of galway bay coupled hydrodynamic wave sediment transport models have been used to explore the transport patterns of maerl siliciclastic sediment during calm summer conditions and severe winter storms the sediment distribution is strongly influenced by storm waves even in water depths greater than 100 m maerl is present at the periphery of wave induced residual current gyres during storm conditions a combined wave current sediment mobility index during storm conditions shows correlation with multibeam backscatter and surficial sediment distribution a combined wave current mobilization frequency index during storm conditions acts as a physical surrogate for the presence of maerl siliciclastic mixtures in galway bay both indices can provide useful integrated oceanographic and sediment information to complement coupled numerical hydrodynamic sediment transport and erosion deposition models

response of infaunal macrobenthos to the sediment granulometry in a tropical continental margin southwest coast of india abstract surficial sediment samples collected from the continental margin of the southwest coast of india in july 2004 were examined for the grain size and soft bottom macrobenthic fauna to understand the sediment granulometry and its effect on the faunal distribution samples were collected using smith mcintyre grab from 20 to 200 m depth range consisting of mid shelf outer shelf and slope fine grained sediment located in the mid shelf and supported low faunal abundance polychaetes constituted the bulk of the fauna feeding guild changed with depth and sediment granulometry coexistence of deposit feeders and carnivores in outer shelf and deposit feeders and filter feeders in the slope region indicated the effective utilization of different food resources in general richness and diversity were high in the southern region depth wise the diversity and abundance were relatively high in the 50 75 m depth range correlation and bio env analysis showed that combination of different factors such as sediment texture sediment sorting and depth were found to influence the distribution of macrobenthos hence spatial variations observed in benthic community were presumably linked to the variations in sediment granulometry and the energy level conditions prevailing in the area

diversity and distribution of echinoderms in the south eastern arabian sea shelf under the influence of seasonal hypoxia abstract the south eastern arabian sea seas margin represents a tropical eastern boundary upwelling system which is subjected to intense seasonal hypoxia in the continental shelf and impingement of oxygen minimum zone omz along the continental slope this paper provides the first comprehensive information on abundance diversity and distribution patterns of echinoderms which are highly sensitive to oxygen deficiency and anthropogenic disturbances in the continental shelf 20 250 m of the seas results are based on depth stratified and seasonally resolved sampling at 241 sites representing 8 latitudinal grids 4 depth strata from inner shelf to shelf edge using naturalist dredge and smith mcintyre grab echinoderms were the numerically dominant group among epifauna 42 with significant seasonal variations in relative abundance 71 during winter and 17 during summer monsoon fifty five species of echinoderms were identified among which ophiuroids showed highest diversity 24 species followed by echinoids 11 species and asteroids 8 species species richness of echinoderms was higher in the inner and mid shelf 20 80 m while the group was nearly absent in the shelf edge 150 250 m a significant negative correlation was noted between species richness and latitude and three distinct sub regions could be delineated based on species diversity and abundance the observed distribution patterns were found to be determined chiefly by sediment texture and bottom water dissolved oxygen along with anthropogenic disturbances bottom trawling echinoderms showed maximum abundance and species richness in the well oxygenated sandy sediments of the southern seas and very low species richness and abundance in relatively silty sediments of the northern seas which were characterised by high seasonal fluctuations in dissolved oxygen seasonal hypoxia the near absence of echinoderms in the shelf edge despite the availability of sandy substrates indicates that this group is more sensitive to the perennially low oxygen conditions prevailing here

plates and their motions the last reviews which covered research in plate motions were those of herron and pitman 1975 on marine magnetic anomalies and dewey 1975 on plate tectonics both reporting on research for the period 1971 1974 in the last 12 years there has been considerable refinement of relative motion models as well as further development of global models also major effort has gone into defining reference frames for the study of plate motions and discriminating between them more recently the role of errors in individual plate rotations and the associated uncertainties in reconstructions have received attention in this report i concentrate on work published in the last 4 years 1983 1986 citing a minimum of publications from previous years however some papers in press for early 1987 have been included this report first reviews work on relative plate motions for the present and past and reconstructions and then models for these motions global ones for driving forces and local ones determining subduction history and back arc spreading the problem of reference frames both hotspot and paleomagnetic is discussed next i end with a review of work on the errors in plate motions

in situ spectral measurements of space weathering by chang e 4 rover abstract space weathering introduces confounding effects on visible and near infrared reflectance spectra of airless bodies which considerably darkens the reflectance reddens the continuum slope and suppresses absorption features it s mainly attributed to the gradual formation and accumulation of submicroscopic metallic iron smfe on regolith grains in situ spectral measurements from chang e 4 rover provide a unique opportunity to investigate the space weathering effects on the intact lunar farside regolith smfe abundance at the landing site which is 0 32 0 06 wt is retrieved from in situ measured reflectance spectra by using hapke model the derived is feo maturity index 82 15 indicates the finsen crater ejecta sourced regolith is mature which is consistent with the geologic background that it had experienced about 3 7 ga space weathering

macrobenthic community structure of soft bottom sediments at the belgian continental shelf within the frame of different research projects a large number of sites at the belgian continental shelf bcs have been sampled for the macrobenthos between 1994 and 2000 these samples cover a diverse range of habitats from the sandy beaches to the open sea from the gullies between the sandbanks to the tops of the sandbanks and from clay to coarse sandy sediments to investigate the large scale spatial distribution of the macrobenthos of the belgian continental shelf the data of all these research projects 728 samples were combined and analysed by means of several multivariate techniques 10 sample groups with similar macrobenthic assemblage structure were distinguished each sample group is found in a particular physico chemical environment and has a specific species composition four sample groups differ drastically both in habitat and species composition and are considered to represent four macrobenthic communities 1 the muddy fine sand abra alba mysella bidentata community is characterized by high densities and diversity 2 the nephtys cirrosa community occurs in well sorted sandy sediments and is characterized by low densities and diversity 3 very low densities and diversity typify the ophelia limacina glycera lapidum community which is found in coarse sandy sediments and 4 the eurydice pulchra scolelepis squamata community is typical for the upper intertidal zone of sandy beaches these macrobenthic communities are not isolated from each other but are linked through six transitional species assemblages the transition between the a alba m bidentata community and the n cirrosa community is characterized by a reduction in the mud content and is dominated by magelona johnstoni the transition between the n cirrosa and the o limacina g lapidum community is distinctive by decreasing densities and coincides with a gradual transition between medium and coarse sandy sediments from the n cirrosa to the e pulchra s squamata community transitional species assemblages related to the transition from the subtidal to the intertidal environment were found each community or transitional species assemblages was found over a specific range along the onshore offshore gradient four types can be discerned 1 almost restricted to the near shore area but possible wider distribution 2 distributed over the full onshore offshore gradient 3 restricted to the near shore area and 4 restricted to the sandy beach environment the diversity pattern on the bcs follows this division with species rich and poor assemblages in the near shore area to only species poor assemblages more offshore the distribution and diversity patterns are linked to the habitat type distinguished by median grain size and mud content

tectonic evolution of the pacific ocean since 74 ma abstract a recent re evaluation of the late mesozoic and cenozoic sea floor spreading data in the eastern pacific has allowed us to make a new interpretation of the timing and sequence of the tectonic events which produced the present configuration of the plates whitman and harrison 1981 whitman 1981 rotation parameters specifying the relative motion between all pairs of plates in the ocean basin have been calculated from the best fit of oceanic magnetic anomalies with additional input from bathymetry and crustal ages of the deep sea drilling project sites the rotation parameters for the relative motion between the pacific and antarctic plates are taken from weissel et al 1977 and the continental rotation parameters are from barron et al 1981 plate motions have been determined back to 74 ma this time marks the initiation of spreading at the pacific antarctic ridge which caused the separation of the campbell plateau from antarctica barron et al 1981 thus this time is the earliest fix on the position of the pacific plate relative to the continents surrounding the pacific ocean basin using sea floor spreading since it is not possible to derive quantitative information about the relative motion between two plates separated by a trench all rotations for the oceanic plates of the pacific basin have been calculated relative to the pacific plate and then relative to north america through the plate circuit pacific antarctica africa north america since we also know the relative position of north america with respect to the other continents we can show the relative position of the pacific plate and the other oceanic plates with respect to all of the continental plates surrounding the pacific ocean basin

very high resolution side scan sonar mapping of biogenic reefs of the tube worm lanice conchilega reefs of the tube building polychaete lattice conchilega are known to represent hotspots of biodiversity within inter and subtidal soft sediments of the north sea however because of their patchy distribution point sampling does not appropriately map their subtidal spatial distribution this study evaluated the feasibility to detect l conchilega reefs by very high resolution side scan sonar imagery a subtidal very high resolution 410 khz side scan survey combined with grab sampling revealed high densities of l conchilega up to 1979 ind m 2 to coincide with a higher reflectivity patchy and grainy acoustic facies from the side scan sonar imagery individual reefs were estimated to reach a maximum size of 15 m 2 to ground truth the acoustic facies the distribution of intertidal l conchilega reefs was mapped at low tide and side scan sonar imagery was recorded during the following high tide intertidal l conchilega reefs had a patch size of 0 8 m 2 up to 11 6 m 2 elevated 7 5 to 11 5 cm above the surrounding seafloor and covered approximately 10 of the selected area the very high 445 khz resolution side scan sonar imagery revealed a similar acoustic facies as in the subtidal lower resolution 132 khz side scan sonar imagery was less efficient to detect physically less developed l conchilega reefs we conclude that 1 there are no major technical restrictions to map l conchilega reefs using side scan sonar 2 the developmental stage of l conchilega reefs impacts the detectability of the reefs and 3 very high resolution side scan sonar imagery is considered a necessity when mapping small scale structures such as l conchilega reefs c 2008 elsevier inc all rights reserved

the influence of sedimentary heterogeneity on within maerl bed differences in infaunal crustacean community a study was undertaken of the crustacean community associated with maerl habitats in mannin bay ireland based on a visual classification of sedimentary fractions eight sedimentary facies could be distinguished these ranged from live maerl banks and seagrass covered live maerl banks in the shallow low energy parts of the inner bay to maerl debris facies mixed with varying proportions of sand mud and shell gravel in the more exposed high energy parts of the bay amphipoda dominated the crustacean fauna accounting for more than 95 of total numerical abundance overall the crustacean fauna occurring in the studied maerl habitats is similar to the fauna occurring in subtidal gravel habitats with little evidence of elective species only the mud maerl debris facies and the seagrass covered live maerl banks appear to harbour a relatively different crustacean fauna from the remainder of the sedimentary facies these differences were mainly changes in the numerical abundance of dominant species rather than species displacements

small scale mapping of sea bed assemblages in the eastern english channel using sidescan sonar and remote sampling techniques abstract a survey was conducted in the eastern english channel to investigate the use of sidescan sonar used in conjunction with traditional biological sampling methods to map the variety and distribution of benthic biotopes i e sea bed habitats and their associated biological communities an area of sea bed approximately 28 km 12 km in size offshore from shoreham u k was surveyed using a digital sidescan sonar system and a mosaic of the output was produced covering 100 of the survey area this was used to divide the area into acoustically distinct regions around which subsequent benthic ground truth surveys were designed benthic communities and sediment types within each of the these regions were sampled using a hamon grab fitted with a video camera and using a heavy duty 2 m beam trawl further information concerning the sea bed was obtained through the application of additional video and photographic techniques substrates within each acoustic region were generally homogeneous in distribution and sediment types ranged across the survey area from cobbles and coarse gravel through to muddy sands analysis of the faunal data revealed the presence of statistically distinct biological assemblages within most of the acoustic regions although species similarity between samples collected from within each acoustic area was often low using a combination of all the data sets five discrete biotopes could be identified and mapped across the area the application of acoustic techniques used in conjunction with biological sampling techniques to map the distribution of sea bed habitats and associated benthic communities is discussed

an evaluation of acoustic seabed classification techniques for marine biotope monitoring over broad scales 1 km2 and meso scales 10 m2 1 km2 abstract acoustic seabed classification is a useful tool for monitoring marine benthic habitats over broad scales 1 km 2 and meso scales 10 m 2 1 km 2 its utility in this context was evaluated using two approaches by describing natural changes in the temporal distribution of marine biotopes across the broad scale 4 km 2 and by attempting to detect specific experimentally induced changes to kelp dominated biotopes across the meso scale 100 m 2 for the first approach acoustic backscatter mosaics were constructed using sidescan sonar and multibeam echosounder data collected from church bay rathlin island northern ireland in 1999 2008 and 2009 the mosaics were manually segmented into acoustic facies which were ground truthed using a drop video camera biotopes were classified from the video by multivariate exploratory analysis and cross tabulated with the acoustic facies showing a positive correlation these results were integrated with bathymetric data to map the distribution of seven unique biotopes in church bay kappa analysis showed the biotope distribution was highly similar between the biotope maps possibly due to the stability of bedforms shaped by the tidal regime around rathlin island the greatest biotope change in this approach was represented by seasonal and annual changes in the growth of the seagrass zostera marina in the second approach sidescan sonar data were collected before and after the removal of 100 m 2 of kelp from three sites comparison of the data revealed no differences between the high resolution backscatter imagery it is concluded that acoustic seabed classification can be used to monitor change over broad and meso scales but not necessarily for all biotopes its success depends on the type of acoustic system employed and the biological characteristics of the target biotope

early tertiary rupture of the pacific plate 1700 km of dextral offset along the emperor trough line islands lineament abstract between 67 and 40 ma ago a northwest southeast trending fracture system over 8000 km long split the pacific plate and accumulated at least 1700 km of dextral offset between the east and west portions this system here named the emperor fracture zone efz system consisted of several segments one along the present trace of the emperor trough and another along the line islands joined by short spreading ridges the efz terminated at its northern end against the kula pacific ridge and at its southern end in a ridge transform system called the emperor spreading system which extended to the west north of australia the finite angular velocity vector describing the relative motion between the east and west pacific plates is 0 6 ma about a pole at 36 n 70 w this vector added to the known early tertiary motion of the pacific plate with respect to the global hotspot reference frame accounts in large part for the nnw trend of the emperor seamount chain relative to the wnw hawaiian trend without violation of the integrity of the antarctic plate the meiji emperor and emperor hawaiian bends date respectively the initiation 67 ma ago and cessation 40 ma ago of seafloor spreading on the emperor spreading system the postulated early tertiary relative motion along the efz between the east and west pacific plates explains 1 the present misalignment of the two sets of magnetic bights of the pacific 2 the abrupt truncation of eastern pacific bathymetric lineaments against the emperor trough and line islands 3 the contrast in paleolatitude between the eastern and western pacific as indicated by paleomagnetic and sedimentologic studies and 4 the anomalous gravity signature of the central hawaiian ridge that indicates that the ridge loaded thin hot lithosphere

influence of the upwelling events on the δ13c and δ18o of the benthic bivalve shells of the south western continental margin of india in this study the influence of the spatial and temporal variability of upwelling intensity and the associated biological productivity observed during different phases of summer monsoon along the southwestern continental margin of india swcmi on the 13c and 18o of the inorganic biogenic carbonate shells was investigated multispecies benthic bivalve shells 1 5 mm separated from ten surface sediment samples of swcmi off 12 n 10 n and 9 n collected during the onset osm and peak psm phase of the summer monsoon of 2009 were analysed for 13c and 18o sea surface temperature along the study region indicates prominent upwelling in psm than in osm a comparison of analytical and predicted values for 18o in the bivalve shells confirmed their in situ origin during both the sampling periods during psm the 13c values in the benthic bivalve shells were more depleted in 13c than during osm which recorded lower values of 13c in dissolved inorganic carbon of bottom waters expected in the study region in psm due to the upwelled waters high surface productivity and the associated high degradation of the organic matter in the subsurface and bottom waters however this depletion of 13c was not observed in benthic bivalve shells obtained from 10 n since it is influenced by high export fluxes of carbon from the cochin estuary since early monsoon months

single beam acoustic ground discrimination of shallow water habitats 50 khz or 200 khz frequency survey the single beam acoustic ground discrimination system qtc view series v was used in the bay of cadiz southwest spain for the identification and mapping of the bottom acoustic diversity the acoustic data were obtained through two successive surveys each conducted with one of the following echo sounder frequencies 50 khz and 200 khz the performance of each survey frequency for the identification of the sedimentary gradients was analyzed the surveys were conducted during high tide given that the majority of the surveyed area is shallower than 5 m although depth may occasionally reach 20 m in specific areas located in a navigation channel the acoustic data obtained at the two different frequencies were individually submitted to manual clustering and a final solution consisting of three acoustic classes was reached for both datasets however only the geographical distribution of the acoustic classes obtained with 50 khz echo sounder frequency was coincident with the spatial distribution of the superficial sediment groups silty medium sand very silty fine sand and mud identified through multivariate analysis of the grain size data of ground truth sediment samples the results obtained with the 200 khz echo sounder frequency did not match the sedimentary gradients obtained for the area surveyed not even the separation of muddy and sandy areas

how human activities affect the fine sediment distribution in the dutch coastal zone seabed abstract the fine sediment distribution in the seabed is an important indicator for the ecological functioning of shallow coastal seas in this paper we investigate the processes and conditions that determine the fine sediment distribution in the dutch coastal zone surficial seabed while also assessing the response of the system to human interventions an extensive sediment dataset collected in the dutch coastal zone from 2006 to 2014 is presented these data are used to map the distribution of fines in the seabed of the dcz at unique spatiotemporal scales for the entire dutch coastal zone the distribution of fines generally agrees well with previous studies the recent extension of the port of rotterdam the maasvlakte 2 reclamation was found to locally change the distribution of fines in the sand mining pit and directly south of the reclamation fines percentages in the seabed increased by more than 10 we developed a conceptual framework to analyse the distribution of fines and how it is affected by human interventions three components are distinguished within this framework 1 sources of fines 2 transport pathways and 3 accumulation potential these components are determined both qualitatively and quantitatively based on high resolution bathymetric and hydrodynamic model data the distinction between the three components makes it possible to unravel the contributions of different human interventions to the changes in the fines distribution in the case of maasvlakte 2 the local increase of fines percentage in the seabed could thus be attributed to a temporary additional source of fines and enhanced accumulation potential the high spatiotemporal resolution of the new sediment dataset proved crucial to enable development and testing of the framework to evaluate the impact of large engineering works on the spatial distribution of fines

acoustic habitat and shellfish mapping and monitoring in shallow coastal water sidescan sonar experiences in the netherlands sidescan sonar has been applied in a number of shallow water environments along the dutch coast to map and monitor shellfish and seabed habitats the littoral setting of these surveys may hamper data acquisition flying the towfish in zones of turbulence and waves but also offers valuable opportunities for understanding interpreting and validating sidescan sonar images because of the ability to ground truth during low water periods enabling easy identification and validation acoustical images of some of the mussel banks on the tidal flats of the wadden sea recorded at high tide show a marked resemblance with optical google earth images of the same banks these sonar images may thus serve as acoustic type signatures for the interpretation of sonar patterns recorded in deeper water where ground truthing is more difficult and more expensive similarly acoustic type signatures of japanese oyster banks were obtained in the estuaries in the southwest of the netherlands automated acoustic pattern recognition of different habitats and acoustical estimation of faunal cover and density are possible applications of sidescan sonar both require that the backscattering observed on the sidescan sonar images is directly caused by the biological component of the seafloor filtering offers a simple and effective pre processing technique to separate the faunal signals from linear trends such as emanating from wave ripples or the central tracks of the towfish acoustically estimating the faunal density is approached by in situ counting peaks in backscattering in unit squares these counts must be calibrated by ground truthing ground truthing on littoral mussel banks in the wadden sea has been carried out by measuring their cover along lines during low tide due to its capacity of yielding full cover high resolution images of large surfaces sidescan sonar proves to be an excellent cost effective tool for quantitative time lapse monitoring of habitats 2009 elsevier ltd all rights reserved

mesozoic interaction of the kula plate and the western margin of north america abstract oceanic crust west of north america at the beginning of the jurassic belonged to the kula plate the development of the western margin of north america since the jurassic reflects interaction with the kula plate the kula farallon spreading center and the farallon plate the kula plate ceased to exist in the paleocene and later developments were caused by interaction of the farallon plate and subsequently collision with the east pacific rise at the beginning of the jurassic when spreading between north and south america began the kula farallon pacific triple junction moved to the north relative to north america and the eastern end of the kula farallon spreading center swept northwards along the continental margin during the paleocene kula pacific spreading ceased and the kula plate fused to the pacific plate throughout the mesozoic subduction of the kula plate took place along the alaskan continental margin when the kula plate joined the pacific plate a new subduction zone formed along the line of the present aleutian chain wrangellia and stikinia anomalous terrains in alaska and northwestern canada respectively were emplaced by transport on the kula plate from lower latitudes hypotheses which require transport of these plates in the mesozoic from the far reaches of the pacific ignore the problem of transport across either the kula pacific or kula farallon spreading centers the interaction of the kula plate and western north america throughout the jurassic and the cretaceous should result in emplacement of these terrains by motion oblique to the continental margin tethyan faunas in stikinia must come from the western end of tethys between north and south america not the indonesian region at the eastern end of tethys as the northeastern end of the kula farallon ridge moved northward the sense of motion changed from right lateral shear between the kula and north american plates to collision or left lateral shear between the farallon and north american plates left lateral shear along zones analogous to the mojave sonora megashear may have been the means by which anomalous terrains were transported to the southeast into the gap between north and south america forming present day central america such a model overcomes the overlap difficulties suffered in previous attempts to reconstruct the mesozoic paleogeography of central america

chang e 4 initial spectroscopic identification of lunar far side mantle derived materials over 60 years of spacecraft exploration has revealed that the earth s moon is characterized by a lunar crust1 dominated by the mineral plagioclase overlying a more mafic richer in iron and magnesium mantle of uncertain composition both crust and mantle formed during the earliest stages of lunar evolution when late stage accretional energy caused a molten rock magma ocean flotation of the light plagioclase sinking of the denser iron rich minerals such as olivine and pyroxene and eventually solidification2 very large impact craters can potentially penetrate through the crust and sample the lunar mantle the largest of these craters is the approximately 2 500 kilometre diameter south pole aitken spa basin3 on the lunar far side evidence obtained from orbiting spacecraft shows that the floor of the spa basin is rich in mafic minerals4 but their mantle origin is controversial and their in situ geologic settings are poorly known china s chang e 4 lunar far side lander recently touched down in the von karman crater5 6 to explore the floor of the huge spa basin and deployed its rover yutu 2 here we report on the initial spectral observations of the visible and near infrared spectrometer vnis 7 onboard yutu 2 which we interpret to represent the presence of low calcium ortho pyroxene and olivine materials that may originate from the lunar mantle geological context6 suggests that these materials were excavated from below the spa floor by the nearby 72 km diameter finsen impact crater event and transported to the landing site continued exploration by yutu 2 will target these materials on the floor of the von karman crater to understand their geologic context origin and abundance and to assess the possibility of sample return scenarios initial spectral observations by china s chang e 4 far side lunar rover suggest the presence of materials that may originate from the moon s mantle

clay sediment accumulation rates on the monsoon dominated western continental shelf and slope region of india abstract clay accumulation rates shown in sediment cores from the nearshore to outer continental shelf and slope regions in water depths of 10 1246 m on the western continental margins of india were determined by the 210 pb dating technique the 210 pb excess concentration encountered in these regions is about 3 5 dpm g and is independent of water depth the range of clay accumulation rates is from 1 8 to 19 mm yr for the shelf region and decreases southward from the tapti and narbada river confluence in the gulf of cambay this pattern indicates sediment dispersal in the coastal region regulated by southwest monsoon dominated littoral currents the same trend is encountered all along the southwestern traverse this suggests that suspended matter transport across the shelf is minimal since clay accumulation rates on the outer shelf are only 1 8 2 5 mm yr the clay accumulation rate in the slope region is 3 8 mm yr the high accumulation rates encountered on the upper continental slope may be attributed to the terrigenous influx of indus river sediment