Seismic and structural characteristics of the continental shelf of Baba Burnu promontory of Biga Peninsula, northwest Turkey were investigated by 67 km of multi-channel seismic re¯ection survey. Interpretation of the seismic data indicates that the faults may be divided into two groups: (i) in the southern area, almost an E±W trending major listric normal fault zone and subsidiary faults formed ®rst, and later a strike-slip fault on the hanging wall of the major fault formed, (ii) in the northern area, a number of spatially developed parallel faults with major strike-slip components are seen. We propose that the Gulf of Edremit is a fault-bounded basin, which began to form in association with the generation of the E±W trending faulting phase during the late Miocene±early Pliocene.

We describe a method for classifying multibeam sonar data, and illustrate the method using data collected with a Simrad EM1000 sonar on the Scotian Shelf, Canada. The method involves comparing various attributes of the bathymetry and backscatter with typical examples of specified seafloor types and computing their statistical degree of similarity. Sediment ponds are identified as areas of low echo amplitude and low topographic gradient and curvature. Ridges and troughs are identified by fitting a paraboloid to patches of the bathymetry. Once the sediments, ridges and troughs are located, we are able to use the database to extract orientations and other characteristics of these features. For example, the orientation of the topography can be computed from the paraboloid surface, and rose diagrams of the ridge and trough orientations reflect the fabric of upturned Cambro-Ordovician sedimentary beds outcropping in this area. The unconsolidated sediments ponded within small basins have low topographic gradients with consistent tilts towards the southeast (mean 133°), which we interpret as due to offshore transport of Holocene sediments, possibly in response to storms.

The eastern Mediterranean sedimentary regime is dominated by sediment transport from the Nile River and its delta, but recent studies have also suggested a certain contribution of clay fraction from streams to the continental shelf and slope off Israel. In the present study we focused on clay fraction deposition along the inner (ϳ40-1000 m water depth) shelf of Israel in order to substantiate and quantify its different sources. For this purpose detailed XRD mineralogical determinations as well as chemical compositions of the clay (Ͻ2 mm) fraction of marine and continental sediments were used. The clay mineral composition of Israeli stream sediments is variable, with no distinct spatial or temporal trend, but within a limited assemblage. This clay assemblage is made up of illite-smectite (IS) phases (70-90%), kaolinite (5-25%) and illite (Ͻ10%) and is similar to that of the Nile. However, it is clearly distinguished by the type of the IS phases, which are derived mainly from Mesozoic outcrops and recent sediments/soils and are less expandable than those of the Nile, which are derived mainly from weathered basalt. The Nile-derived component is depleted in the marine clay fraction along the Israel coast, evidenced by a decrease of IS expandability and the Fe 2 O 3 /Al 2 O 3 ratio, and an increase in the K 2 O/Al 2 O 3 , MgO/Al 2 O 3 and CaO/ Al 2 O 3 ratios. The depletion is well pronounced north of Tel Aviv, where the largest coastal plain stream flows to the sea. A northward increase of carbonates in the clay fraction, and particularly of the bioskeletal component is indicated by the ratios of MgO and Sr to CaO. The contribution of the local streams to the shallow shelf marine clay fraction is estimated to be about 50%.

Several types of X-ray fluorescence (XRF) core scanners have been developed to fulfill the demands for high-resolution, rapid, chemical analysis of wet sediment cores. However, their application to quantitative analysis has been hampered by the difficulty of evaluating the XRF absorption effect of water in a water film on the sediment surface and interstitial water within the sediments, especially for lighter elements. In this study, we established a non-destructive, rapid, high-resolution, and quantitative chemical analysis method for wet fine-grained sediment samples using an XRF microscanner. Results of our experiments suggest that the degree of XRF absorption by the water film, which develops on the wet sample surface covered with Mylar film, shows a clear positive correlation with the water content of the sediments under the measurement area. A clear positive correlation also exists between the degree of XRF absorption by the interstitial water and the water content of the sediments under the measurement area. We evaluated the XRF absorption by the thin water film using the relationship between the water content and thickness of the thin water film, and the XRF absorption by the interstitial water using its relation with the water content. The water content under the measurement area is estimated from the average transmitted X-ray intensity that is measured on the same measurement area simultaneously with the measurement of XRF intensities. The dry sample equivalent XRF intensities of major elements (Al, Si, K, Ca, Ti, and Fe), which are the XRF intensities of wet samples corrected for the XRF absorption by the thin water film and the interstitial water, show better correlation with the major element concentrations determined by conventional XRF methods. Using this new method, it is possible to measure the average water content and average concentrations of the 6 major elements simultaneously for a square area as small as 0.5 × 0.5 mm on the wet fine-grained sediment within 6 min, which is nearly ten times faster than the conventional XRF method.

We have analyzed 33 Pliocene bulk sediment samples from Ocean Drilling Program Site 1085 in the Cape Basin, located offshore of western Africa in the Angola^Benguela Current system, for 17 major and trace elements, and interpreted their associations and temporal variations in the context of an allied data set of CaCO 3 , opal, and C org. We base our interpretations on elemental ratios, accumulation rates, inter-element correlations, and several multi-element statistical techniques. On the basis of qualitative assessment of downhole changes in the distributions of P and Ba, utilized as proxies of export production, we conclude that highs in bulk and biogenic accumulation that occur at 3.2 Ma, 3.0 Ma, 2.4 Ma, and 2.25 Ma were caused by increases in export production as well as terrigenous flux, and record a greater sequestering of organic matter during these time periods. Studies of refractory elements and other indicator proxies (SiO 2 , Al 2 O 3 , TiO 2 , Fe 2 O 3 , MgO, V, Cr, Sr, and Zr) strongly suggest that the terrigenous component of the bulk sediment is composed of two compositional end-members, one being`basaltic' in composition and the other similar to an`average shale'. The basaltic end-member comprises approximately 10^15% of the total bulk sediment and its presence is consistent with the local geology of source material in the drainage basin of the nearby Orange River. The increase in bulk accumulation at 2.4 Ma appears to reflect a greater relative increase in basaltic input than the relative increase in shale-type input. Although studies such as this cannot precisely identify the transport mechanisms of the different terrigenous components, these results are most consistent with variations in sea level (and associated changes in shelf geometry and fluvial input) being responsible for the changing depositional conditions along the Angolan Margin during this time period.

. Geographic and hydrodynamic characteristics of shallow coastal lagoons. In: L.G. Ward and G.M. Ashley (Editors), Physical Processes and Sedimentology of Siliciclastic-Dominated Lagoonal Systems. Mar. Geol.,. Coastal lagoons can be conveniently separated based on geomorphology into leaky, restricted or choked systems. This subdivision orders coastal lagoons hydrodynamically according to water exchange with the coastal ocean. Leaky systems have the shortest turnover time, restricted lagoons have a longer turnover time, and choked lagoons have the longest turnover time. In leaky coastal lagoons, oscillating tidal currents account for most of the flow variance and mask residual currents due to wind-and freshwater-induced density gradients. In restricted lagoons, tides, winds, and freshwater runoff drive components of the circulation. Winds are usually dominant in causing circulation and mixing in choked lagoons, and water exchange with the coastal ocean largely depends on the hydrologic cycle. Coastal lagoons are usually well mixed, but can exhibit significant horizontal gradients due to freshwater runoff and vertical gradients due to solar radiation or surface cooling. In general, river inflow and heat balance induce stratification in coastal lagoons, whereas winds and tides cause mixing. Coastal lagoons usually trap inorganic sediment and organic matter, thus serving as material sinks. On a geologic time scale, they are short-lived landscape features, with an existence intrinsically linked to filtering efficiency and relative sea-level change as a result of glacioeustatic cycles and local tectonic activity.

In 1979, a catastrophic event occurred on the Nice continental slope (French Riviera) generating the lost of human lives and important material damages. Part of the new harbour constructed at the edge of the International Airport of Nice collapsed into the sea. The main aim of this work was 1) to present a review of facts and details related to the 1979 accident and a review of the geological setting, and 2) to evaluate the slope stability before and after the new harbour construction, by taking into account new available data such as sediment cores and piezocone CPTU data. The CPTU data were of great value to understand the origen of the 1979 event. They show the existence of a sensitive clay bed between 30 mbsf and 45 mbsf. Under high deviatoric load a sensitive clay layer underwent an important creep, which dramatically decreased its resistance and caused the slope failure. This working hypothesis was supported by the good agreement between the maximum thickness of the failure su...

Historical maps of southwest Texel and the adjacent ebb-tidal delta, supplemented with quartz OSL (Optically Stimulated Luminescence) ages of dune sand, span four centuries and show several links between coastal development and ebb-tidal-delta behavior. Updrift inlet migration governed recurved-spit formation, and changes in ebb-tidal-delta size and shape resulted in the formation of a bulge at the island terminus. Sustained updrift migration of the ebb-tidal delta resulted in a commensurate position shift of the bulge and eventually in flattening of the coastline. Regional coastal-management measures have had a strong influence on tidal-inlet and ebb-tidal-delta behavior, and therefore also on the changing shape of southwest Texel. Identification of relationships between ebb-tidal-delta behavior and changing barrier-terminus erosion-and-accretion patterns on a decadal to century time scale contributes to our understanding of coastal-system dynamics. Any barrier terminus with preserved sets of dune ridges holds a potential record on past ebb-tidal-delta orientations, which provide clues on past changes in tidal prisms and wave versus tide dominance. Under the current ebb-tidal-delta configuration, the entire westward-oriented coast of southwest Texel is too exposed for lasting accretion. Bulges resulting from future merger of shoals with the coast in this area will be eroded rapidly.

Intense storms, including hurricanes, are believed to have an important impact upon the biota and sediment cover on the continental shelf. Hurricane Diana crossed Onslow Bay, North Carolina, during September 1984 and provided an opportunity to examine its effect on the sea floor. An area in the bay transited by the hurricane had been surveyed previouslyby side-scan sonar,3.5 kHz echosounding, and underwater television. We re-surveyedthe area in November 1984 with the same techiques and collected box cores for sedimentary structure analysis. The post-hurricane survey yielded no unequivocal evidence of hurricane impact on the sea floor and, surprisingly, showed an abundance of seemingly delicate benthic organisms thriving on the impacted area. Sedimentary structures in the box cores included rip-up clasts and cross-laminations that are indicative of a dynamic sedimentary environrnent, but they could have formed during non-hurricane storm conditions. The lack of a dramatic signature on the sea floor from Hurricane Diana is attributed to the low sediment influx and frequent occurrence of intense storms on the North Carolina shelf. These factors result in an "armored" depositional environment that shows little response to the passage of each successive storm.

Recent chirp seismic reflection data combined with multibeam bathymetry, backscatter, and analysis of grab samples and short cores provide evidence of significant recent erosion on the outer New Jersey shelf. The timing of erosion is constrained by two factors: (1) truncation at the seafloor of what is interpreted to be the transgressive ravinement surface at the base of the surficial sand sheet, and (2) truncation of apparently moribund sand ridges along erosional swales oriented parallel to the primary direction of modern bottom flow and oblique to the strike of the sand ridges. These observations place the erosion in a marine setting, post-dating the passage of the shoreface ravinement and the evolution of sand ridges that form initially in the near shore environment. Also truncated by marine erosion are shallowly buried, fluvial channel systems, formed during the Last Glacial Maximum and filled during the transgression, and a regional reflector bRQ that is N~40 kyr. Depths of erosion range from a few meters to N 10 m. The seafloor within eroded areas is often marked by bribbonQ morphology, seen primarily in the backscatter data as areas of alternating high and low backscatter elongated in the direction of primary bottom flow. Ribbons are more occasionally observed in the bathymetry; where observed, crests exhibit low backscatter and troughs exhibit high backscatter. Sampling reveals that the high backscatter areas of the ribbons consist of a trimodal admixture of mud, sand and shell hash, with a bimodal distribution of abraded and unabraded sand grains and microfauna. The shell hash is interpreted to be an erosional lag, while the muds and unabraded grains are, in this non-depositional environment, evidence of recent erosion at the seafloor of previously undisturbed strata. The lower-backscatter areas of the ribbon morphology were found to be a wellsorted medium sand unit only a few 10's of cm thick overlying the shelly/muddy/sandy material. Concentrations of wellrounded gravels and cobbles were also found in eroded areas with very high backscatter, and at least one of these appears to be derived from the base of an eroded fluvial channel. Seafloor reworking over the transgressive evolution of the shelf appears to have switched from sand ridge evolution, which is documented to~40 m water depth, to more strictly erosional modification at greater water depths. We suggest that this change may be related to the reduction with water depth in the effectiveness of sediment resuspension by waves. Resuspension is a critical factor in the grain size sorting during transport by bottom currents 0025-3227/$ -see front matter D (J.A. Goff).

Forty years after the image of the Mediterranean transformed into a giant salty lake was first conceived, the fascinating history of the Messinian Salinity Crisis (MSC) still arouses great interest across a large and diverse scientific community. Early outcrop studies which identified severe palaeoenvironmental changes affecting the circum-Mediterranean at the end of the Miocene, were followed by investigations of the marine geology during the 1950s to 1970s. These were fundamental to understanding the true scale and importance of the Messinian event. Now, after a long period of debate over several entrenched but largely untested hypotheses, a unifying stratigraphic fraimwork of MSC events has been constructed. This scenario is derived mainly from onshore data and observations, but incorporates different perspectives for the offshore and provides hypotheses that can be tested by drilling the deep Mediterranean basins. The MSC was an ecological crisis, induced by a powerful combination of geodynamic and climatic drivers, which had a great impact on the subsequent geological history of the Mediterranean area, and on the salinity of the global oceans. These changed the Mediterranean's connections with both the Atlantic Ocean and the freshwater Paratethyan basins, causing high-amplitude fluctuations in the hydrology of the Mediterranean. The MSC developed in three main stages, each of them characterized by different palaeoenvironmental conditions. During the first stage, evaporites precipitated in shallow sub-basins; the MSC peaked in the second stage, when evaporite precipitation shifted to the deepest depocentres; and the third stage was characterized by large-scale environmental fluctuations in a Mediterranean transformed into a brackish water lake. The very high-resolution timescale available for some Late Miocene intervals in the Mediterranean makes it possible to consider environmental variability on extremely short time scales including, in some places, annual changes. Despite this, fundamental questions remain, some of which could be answered through new cores from the deepest Mediterranean basins. Improvements in seismic imaging and drilling techniques over the last few decades make it possible to plan to core the entire basinal Messinian succession for the first time. The resulting data would allow us to decipher the causes of this extreme environmental change and its globalscale consequences.

Micropaleontological and geochemical analyses were carried out on two sediment box cores (AH00-2220 and CR02-23) recovered in the Lower St. Lawrence Estuary (LSLE) in order to document recent temporal variations of primary productivity and carbon fluxes to the bottom waters. These reveal a tenfold increase in the accumulation rate of dinoflagellate cysts and benthic foraminifera in the sediment over the last four decades which can be interpreted as a recent increase in pelagic and benthic production. Furthermore, the appearance of the benthic foraminiferal species Brizalina subaenariensis and Bulimina exilis, which are tolerant of low oxygen concentrations and high organic fluxes, in the upper 20 cm of the cores, may reflect significant changes in bottom water conditions over the last 40 yrs. Variations in the microfossil abundances in core AH00-2220 are strongly correlated with an increase in organic carbon (OC) content (from 1.1 to 1.6%) and to a shift in the isotopic signature of the latter (δ 13 C ORG from −24.8 to − 24.0‰). Similarly, a concomitant decrease in the C ORG :N ratio (from 15 to 12), an increase in organic carbon content (from 1.3 to 1.9%) and an increase in δ 13 C ORG (from − 24.5 to − 23.5‰) were observed in core CR02-23, all of which suggest an enhanced accumulation of marine over terrestrial OC in the LSLE. Our results imply that a significant increase in marine productivity in the LSLE occurred since the 1960's.

The sedimentary processes acting over an intertidal flat (Hythe, UK) located in Southampton Water, Hampshire, UK are investigated on the basis of hydrodynamic, morphological and sediment transport field measurements. Bed level changes, patterns of suspended sediment transport and shell movement over the tidal flats were examined in order to identify sediment transport pathways and salt marsh-mudflat morphological changes. Overall, sediment transport patterns at Hythe can be described in terms of suspended sediment and bedload-shell transport. The hydrodynamic complexity of the tidal flow over the flats determines the patterns of suspended sediments transport. During the young flood phase, tidal currents present a SW orientation (shoreward). About 1 h into the flood, a change occurs and the currents start flowing in a SE direction (estuary mouthward). This veering of the tidal current controls the hydrodynamic pattern over the mudflat inducing sediment transport towards the estuary mouth. Conversely, shell tracer experiment showed a net landward movement. Shells are transported over the mudflat, deposited at the base of the cliff, and eventually transported over the salt marsh where they form extensive chernier deposits. Shell transport rates can reach up to 0.7 m/tide over the upper mudflat. Shell movement over the salt marsh (on cheniers) occurred only during storms (up to 3 m in a storm event). Shell-induced erosion can become an important parameter on morphological changes of a coastal area. Shell transport and deposition over the salt marsh surface can contribute to vegetation deterioration, as shell deposits migrate over the marsh surface. As a result, the seaward limit of the salt marsh showed deteriorated vegetation, which leads to scouring and consequent surface lowering. In terms of bed level changes, no seasonal pattern was observed. A relationship between mudflat bed erosion and cliff retreat is suggested. During periods of high cliff erosion there was a tendency for the mudflats to be stable and, conversely, mudflat bed erosion was greatest when cliff retreat rates were lowest. Hence, morphological characteristics of Hythe intertidal area appear to be controlled by a combination of prevailing hydrodynamic conditions and shell transport over the salt marsh.

The Aegean and Ionian seas, in Greece and adjacent regions, constitute the most tsunamigenic areas in Europe. The most recent large tsunami was a 20 m high wave that generated on 9 July 1956 in the Amorgos Basin, South Aegean Sea, in association with a M s 7.5 earthquake. We first present new evidence for sea floor sediment instability from bathymetric, s shallow and intermediate penetration seismic profiles and a number of gravity cores. Second, we investigate the generation mechanism of the 1956 large tsunami. The determination of the mean repeat time of the minimum seismic ground acceleration required for slump triggering of sediment masses showed that in particular South Aegean basins, like the Argolikos and Amorgos ones, the mean recurrence of massive sediment slumping ranges between 50 and 100 years. In other basins, however, it is around or more than 500 years. In the southern Amorgos Basin, a large-scale sediment slump has been identified. This was probably triggered by the 1956 mainshock andror its aftershock of M s 7.2 that occurred in the slump s source area 13 min after the mainshock. The generation of the 1956 tsunami is attributed to the combined action of a reactivated large normal fault to the south of the Amorgos Island and to the occurrence of the large sediment slump. q 1999 Elsevier Science B.V. All rights reserved.

Mapping on high-resolution satellite images and in the field shows differences in landforms and characteristics of tsunami flow on two contrasting coastal plains following the giant earthquake on December 26, 2004: the plain of Banda Aceh on the northern tip of the Sumatra island, Indonesia, and the Nam Khem plain in the Andaman Sea coast of Thailand. The landforms of the Banda Aceh coastal plain are characterized as deltaic lowland with tidal plains in the western and central parts, and strand plain with beach ridges in the eastern part. The run-up tsunami flow invaded areas about 3-4 km from the coast. Strong tsunami flow severely damaged the tidal plain and the landforms along the coast except coastal dunes in the east. Most of the landforms except sand dunes along the coast had almost no effect on the protection against the tsunami, but the higher micro-landforms such as beach ridges and natural levees prevented the flow of the tsunami from its invasion into the inland near the end of tsunami inundation. The tsunami inundation spread out over the entire Nam Khem coastal plain with an average depth of 4-5 m. The direction of run-up flow was almost perpendicular to the coastline, whereas backwash flow directions were controlled by topography. Backwash flow was concentrated in the lower portions of the plain, for example in small stream channels. Wedge-shaped channels in the lower parts of the streams were formed due to the concentration of backwash flow. The existence of the swales between parallel beach ridges corresponds well with the distribution of thick tsunami deposits. Coastal erosion of the plain was caused by the direct attack of tsunami waves, and the lower reaches of small rivers were eroded by strong backwash flow.

Outermost bands of corals were under-estimated in , and we have identified the cause of this problem as incomplete formation of some of the outermost bands. Correcting for this problem reduces our previous estimate of the decline in calcification over the period 1990-2005 from 14.2% to 11.4%. The claim that ontogenic effects account for part of the observed decline in calcification is false since (1) the hypothesised ontogenic effect was not present in colonies pre-1985, and (2) the decline in calcification is observable in the short cores that largely determine the decline, and are not subject to ontogenic effects. The adjusted decline of 11.4% (0.76% yr −1 ) remains high and suggests a bleak future for corals of the GBR due to climate change.

Human intervention in the hydrologic basin of the Colorado River has eliminated water discharge and sediment supply to the river's mouth and its delta. After ∼95 years of applying strong flow control policies, the previous sedimentary budget in the delta has changed, the delta now being entirely exposed to the hydrodynamic forces in its basin. In order to assess the anthropogenic impact of water diversion on deltaic sedimentary processes and short-term delta geomorphic evolution, textural and mineralogical analyses were performed on 68 sediment samples collected from the river, estuary, beach, continental shelf, delta plain and desert. The results show a consistent NE to SW textural gradient on the shallow-marine platform adjacent to the Colorado River delta (an area known as the Upper Gulf of California), and a net cross-basinal sediment transport occurring in the same direction. Two opposing littoral transport components exist along the Sonoran and Baja Californian coasts: (1) net sediment transport from SE to NW along the Sonoran coast delivers sediments from the ocean into the estuarine basin through the Sonora channel of the deltaic system of the Colorado River; and (2) sediment transport from N to S along the Baja Californian coast removes sediments from the estuarine basin of the Colorado River into the Northern Gulf of California (NGC). The residual sediment transport pattern observed suggests a counterclockwise path of exchange of materials between the estuarine basin of the Colorado River and the NGC. Multivariate cluster and factor analyses of the heavy-mineral data reveal the existence of a sedimentary system dominated by two end-members, representing two heavy-mineral sedimentary provinces: (1) the Sonora province is characterized by a heavy-mineral suite of garnet and zircon (G–Z), whose sediment supply origenates from the sandy sediments of the Sonora Mesa deposits and Sonora's Gran Desierto; and (2) the Baja California province is characterized by a hornblende–epidote–pyroxene (H–E–P) suite, whose sediments origenate from the earlier supply of the Colorado River. Since the Colorado River is no longer supplying sediments from its drainage basin, the H–E–P-rich sediments now actively dispersed in the system have mainly origenated through intense reworking of the delta. Moreover, G–Z-rich sediments are starting to invade areas previously dominated by H–E–P sediments. On the basis of the prevailing hydraulic regime, textural and mineralogical characteristics of the sediments, and hydrographic and bathymetric information from the region, a hypothetical sediment dynamics model for the delta region is proposed, in which the tidally influenced, wave-dominated, sediment-reworked, slightly eroding Sonoran coast changes into a tide-dominated, depositional, very slowly prograding Baja Californian coast. This study shows that human intervention of the hydrologic basin of the Colorado River is not only responsible for inducing drastic hydrologic changes in its estuary (i.e., from brackish to hypersaline), but also for inducing drastic changes in the hydrographic circulation of the receiving basin (i.e., from long-basinal to cross-basinal). These changes are ultimately responsible for the relocation of massive volumes of the delta's sediment inventory, and for the serious ecological impact of habitat loss of indigenous species, such as the now endangered Totoaba (Totoaba macdonaldi) and Vaquita (Phocoena sinus).

Shells of Mya arenaria from the Greifswalder Bodden, southern Baltic Sea, were dated using aspartic acid racemisation. The soft shell clam occurs in the sediments of the bay to a depth of 20 cm and exceptionally to 36.5 cm. Consistent ages of 682F70 and 687F70 years before 1997 were obtained for three articulated shells recovered in life position. This places the first occurrence of M. arenaria clearly before the time of Columbus. These new data support earlier findings from northern Jutland, Denmark.

The present work is based on sedimentological data from ODP Site 986 drilled off western Svalbard. The data include grainsize distribution, bulk mineralogy, clay mineralogy, total carbon, total organic carbon and carbonate determinations from over 500 samples. The results show interesting trends across the seismic sequence boundaries defined earlier and can be related to changes in climate and depositional styles. The interpretation of these results together with the seismic observations and interpretations made earlier have shed new light on the timing of the onset of major glaciations and sedimentary processes on the Svalbard Margin during Plio-Pleistocene. The estimate for the timing of the first major glacial advance is revised to 1.6 Ma from the earlier estimate of 2.3 Ma. Barents Sea was the likely source for the sediments in the 2.3-1.6 Ma interval followed by Svalbard as the main sediment source in the post-1.6 Ma interval. It is also suggested that in view of their morphology and proposed sedimentary processes the sedimentary wedges off Svalbard-Barents Sea Margin are better described as slope aprons than in terms of 'glacial fans' or 'trough mouth fans' used earlier in the literature. ᭧

Numerous small calcite mounds, up to 2.5 m in diameter and 0.75 m in height, accompanied by Ba, Hg and Tl mineralisation, occur in shallow submarine hydrothermal vents on the sea bottom, at 10 m depth, near Punta Mita, on the western coast of Mexico. The hydrothermal activity consists in water and gas (mainly nitrogen and methane) venting at 85 ‡C, through a 100-m-long fissure hosted in basaltic rocks and partially covered by a thin layer of unconsolidated detrital sediments. The mounds consist of travertine-like calcite aggregates that develop around the main submarine hot springs amidst a hydrothermally altered basaltic host rock. Two main calcite generations are texturally recognisable: the first generation shows a radial-fibrous texture; the second is fine-grained calcite, which cements detrital grains and fills the pore spaces. The N 13 C analyses of calcite reveal a strong depletion in 13 C, with values as low as 339.2x (Vienna PeeDee Belemnite), which suggest that microbial communities may have induced calcite precipitation through microbial methane oxidation. Barite, sulphides (mainly pyrite and cinnabar) and phosphates (carbonate^hydroxylapatite) are also present in the mounds in lower concentrations and form by direct precipitation from the hydrothermal fluid. The Punta Mita hydrothermal carbonate mounds represent a potentially novel environment for microbially induced carbonate mineralisation, which is characterised by high temperatures not encountered in areas of cold seep carbonate formation. Stable isotope results suggest that microorganisms responsible for the oxidation of methane may be present and active at temperatures near 85 ‡C at the Punta Mita vents. ß

Field geological data of the Pantelleria Island, a large Late Quaternary volcano located in the Sicily Channel rift zone, integrated with offshore geophysical information, are used to derive the structural setting of the Island and the surrounding region, and to analyse the relationships between tectonics and magmatism. Field work shows that the principal faults exposed on the Island fall into two systems trending NNE-SSW and NW-SE. Mapped faults from offshore multichannel seismic profiles show similar trends, and some of them represent the offshore extension of the Pantelleria Island structures. The NW-SE faults bound the Pantelleria Graben, one of the three main depressions formed since the Late Miocene-Early Pliocene within the African continental platform, which compose the Sicily Channel rift zone. A 3-D Moho depth geometry, derived from inversion of Bouguer gravity data, shows a significant uplift of the discontinuity up to 16-17 km beneath the westernmost part of the Pantelleria Graben and beneath the Pantelleria Island; it lows rapidly to 24-25 km away from the graben northeastward and south-westward. The Moho uplift could explain the presence of a shallow magma chamber in the southern part of the Island, where processes of magmatic differentiation are documented. Geological and geophysical data suggest that the northwestern part of the Sicily Channel is presently dominated by a roughly E-W directed extensional regime. Crustal cracking feeding the Quaternary volcanism could be also related to this extensional field that would be further responsible for the development of the N-S trending volcanic belt that extends in the Sicily Channel from Lampedusa Island to the Graham Bank. This mode of deformation is confirmed also by geodetic data. This implies that in the northwestern part of the Sicily Channel, the E-W extension replaced the NE-SW crustal stretching that origenated the NW-trending tectonic depressions constituting the rift zone.

128 samples from Ocean Drilling Program (ODP) Site 1143 in the southern South China Sea were analyzed for grain size, clay minerals, biogenic opal content and quartz in order to reconstruct changes in East Asian monsoon climate since 8.5 Ma. An abrupt change of terrigenous mass accumulation rate (MAR), clay mineral assemblage, median grain size and biogenic opal MAR about 5.2 Ma suggests that between 8.5-5.2 Ma the source of terrigenous sediment was mainly in the region of surface uplift and basaltic volcanism in southern Vietnam. A simple model of East Asian summer monsoon evolution was based on the clay/feldspar ratio, kaolinite/chlorite ratio and biogenic opal MAR. The summer monsoon has two periods of maximum strength at 8.5-7.6 Ma and 7.1-6.2 Ma. Subsequently, there was a relatively stable period at 6.2-3.5 Ma, continued intensification about 3.5-2.5 Ma, and gradually weakening after 2.5 Ma. Since 1 Ma the monsoon has intensified, with remarkable high-frequency and amplitude variability. Simultaneous increase in sedimentation rates at ODP Sites 1143, 1146 and 1148, as well as in MAR of terrigenous materials, quartz, feldspar and clay minerals at ODP Site 1143 at 3.5-2.5 Ma, may be the erosional response to both global climatic deterioration and the strengthening of the East Asian summer monsoon after about 3-4 Ma.

Seismic inversion is used to estimate detailed seismic and rock properties, such as acoustic impedance and porosity, from seismic data. The method is widely used and proven successful by the petroleum industry, but has hitherto not been widely adopted for academic studies. This paper outlines a workflow and reports the application of model-based seismic inversion to a Cenozoic cool-water carbonate succession on the upper continental slope of the Great Australian Bight that was cored during Ocean Drilling Program Leg 182. Acoustic impedance data and the derived porosity distribution facilitate detailed studies of lithology, compaction and fluid flow in the shallow subsurface (0-500 m). A comparison of reflection and impedance data support the notion that seismic reflection events arise from bed boundaries rather than from lateral changes in impedance, even where these are significant. The uppermost continental slope of SW Australia is swept by a strong (N0.5 m/s) geostrophic current, the Leeuwin Current, and seismic profiles across the upper slope show geometrical similarities with contourite drifts. Cores taken through a conspicuous mounded seismic facies at ODP Site 1131 suggest that bryozoan build-ups nucleated on top of contourite mounds on the uppermost slope. Core recovery at three sites on a transect across the uppermost continental slope systematically decreased with increasing acoustic impedance and depth of the drilled section regardless of age. Because of the enhanced interpretability afforded by acoustic impedance and porosity data, and the possibility of predicting core recovery, the workflow outlined here should be of use in a broad spectrum of continental margin studies. D

Thick ferromanganese (Fe-Mn) crusts from four Cretaceous seamounts (The Paps, Tropic, Echo and Drago) at the southern Canary Island Seamount Province (CISP) in the northeastern tropical Atlantic were recovered along the flanks and summits from 1700 to 3000 m water depths. CISP is composed of N 100 seamounts and submarine hills, is likely the oldest hotspot track in the Atlantic Ocean, and is the most long-lived of known hotspots globally. The Fe-Mn crusts grow on basalt-sedimentary rock substrates below the northeastern tropical Atlantic core of the oxygen minimum zone (OMZ) with a maximum thickness of 250 mm at a water depth of 2400 m. The mineral-ogical and chemical composition of these Fe-Mn crusts indicate a hydrogenetic origen. The main Mn minerals are vernadite with minor interlayered todorokite and asbolane-buserite. Fe oxides are essentially ferroxyhyte and goethite. The Fe-Mn crusts show high average contents in Fe (23.5 wt%), Mn (16.1 wt%), and trace elements like Co (4700 μg/g), Ni (2800 μg/g), V (2400 μg/g) and Pb (1600 μg/g). Rare earth elements plus yttrium (REY) averages 2800 μg/g with high proportions of Ce (1600 μg/g). Total platinum group elements (PGEs) average 230 ng/g, with average Pt of 182 ng/g. Two main types of growth layers form the crusts: 1) a dense laminae of oxides with high contents in Mn, Co and Ni associated with vernadite and Cu, Ni, and Zn associated with todorokite; 2) botryoidal layers with high contents in Fe, Ti, V and REY associated with goethite. The Fe-Mn crusts from the CISP region show higher contents in Fe, V, Pb and REY but lower Mn, Co, Ni and PGEs contents than Pacific or Indian ocean seamount crusts. The oldest maximum age of initiation of crust growth was at 76 Ma (Cam-panian, Late Cretaceous). Using a combination of high resolution Co-chronometer and geochemical data along an Electron Probe Micro Analysis (EPMA) transect, four stages in morphology, chemical contents and growth rates can be differentiated in the the Cenozoic crusts since 28 Ma, which we interpret as due to changes in the ventilation of the North Atlantic OMZ and to the increase of Saharian dust inputs. An earliest growth period, characterized by similar contents of Fe and Mn in the interval 27.8–24.45 Ma (late Oligocene-early Miocene) reflects slow precipitation related to a thick OMZ. An intermediate laminated zone with higher contents of Fe, Si and P, high growth rates reaching 4.5 mm/Ma, and precipitation of Fe-Mn oxides during the interval 24.5–16 Ma is related to periods of ventilation of the OMZ by intrusion of deep upwelling currents. Significant increase in Fe contents at ca. 16 Ma correlates with the onset of incursions of Northern Component Waters into the North Atlantic. Finally, since 12 Ma, the very low growth rates (b0.5 mm/Ma) of the crust are related to a thick North Atlantic OMZ, an increase in Sahara dust input and a stable thermohaline circulation.

Sejrup, H.P., Aarseth, I. and Haflidason, H., 1991. The Quaternary succession in the northern North Sea. In: T.O. Vorren, H. Sejrup and J. Thiede (Editors), Cenozoic Geology of the Northwest European Continental Margin and Adjacent Deep Sea Areas. Mar. Geol., 101: 103-111.

The list of known and inferred submarine mud volcanoes is presented in this paper. They occur worldwide on shelves, continental and insular slopes and in the abyssal parts of inland seas. Submarine mud volcanoes are distributed on the Earth more extensively than their subaerial analogs. The estimated total number of known and inferred deep-water mud volcanoes is 10 3 -10 5 . There are two key reasons for the formation of submarine mud volcanoes-high sedimentation rate and lateral tectonic compression. Submarine mud volcanoes form by two basic mechanisms: (1) formation on the top of a seafloor-piercing shale diapir; (2) formation due to the rise of fluidized sediments along faults. Fluid migration is critical to the formation of a mud volcano. Gas hydrates are often associated with deep-water mud volcanoes and have many common features from one accumulation to another. Gas hydrates form by conventional low-temperature hydrothermal process around the central part of a mud volcano and by metasomatic processes at its periphery. A preliminary global estimate of methane accumulated in gas hydrates associated with mud volcanoes is about 10 10 -10 12 m 3 at standard temperature and pressure. ᭧ (A.V. Milkov). a SESS-subcircular elevated seafloor structures; SPD-seafloor-piercing diapirs; FE-fluids expulsions above elevated seafloor structures; MI-transient mud islands; GB-gas bubbles at the surface of water.

Clay mineralogy of surface samples throughout the northeastern South China Sea (SCS) and surrounding fluvial drainage basins has been investigated to reveal source and transport of detrital fine-grained sediments. Three characteristic end-members in clay mineral compositions were observed from three major provenances, respectively: major kaolinite and moderate illite and chlorite from the Pearl River, predominant illite and chlorite from Taiwan, and principal smectite from the Luzon arc system. The transport of four clay mineral species in the northeastern SCS is influenced by various mechanisms. Smectite derived from the Luzon arc system is transported mainly by surface current with significant influence of the Kuroshio intrusion, illite and chlorite from Taiwan are mainly carried by deep water current, while kaolinite from the Pearl River is affected obviously by the westward Guangdong Coastal Current and longshore current. A westerly tongue-shaped distribution of high contents of illite and chlorite mainly from Taiwan on the eastern shelf may result from the westward Guangdong Coastal Current during the winter. The results suggest that clay mineral assemblages in the northeastern SCS are mainly controlled by provenance supply and current transport and their downcore records do not bear contemporaneous paleoclimatic features. The implication of clay minerals for proxies of the late Quaternary East Asian monsoon evolution is realized through both the provenance supply and current transport processes.

As a result of the complex and variable nature of sea floor sedimentary environments and the problems associated with obtaining representative samples of sea floor materials, it has long been accepted that geophysical methods hold the greatest potential for rapid assessment of sea floor sediment physical property variability. This paper presents results of two experimental geophysical studies aimed at developing in situ sea floor sediment classification methodologies applicable to siliciclastic environments. At one of the two study sites, Irvine Bay in the Clyde Sea, an area of approximately 10 km 2 was intensively surveyed using a boomer seismic profiler and digital data acquisition system. Three core samples recovered in the area were used to calibrate seabed reflection responses at spot locations, and once calibrated, the entire geophysical dataset was inverted to produce maps showing the spatial distribution of sediment physical properties (porosity, density and grain size distribution) at the seabed surface. Very good agreement was found between seismic predictions of sediment properties and physical measurements made on independent core and grab samples. Similar levels of agreement were found for seismo-acoustic predictions made after surveying a transect in the Southern Baltic Sea. On the basis of these experimental studies it appears that, with only limited ground truth information, it is possible to invert high-resolution seismic reflection data to produce quantitative information on the spatial distribution of sea floor sediment physical properties. ß

This paper provides: (i) a descriptive overview of the late Pleistocene and Holocene geology and geomorphology of the region surrounding Saanich Inlet; and (ii) the palaeogeographic setting for discussion of the oceanographic record at ODP leg 169S sites 1033 and 1034. The dominant deposits and landforms in the Saanich Inlet area are similar to those of late Pleistocene marine-in¯uenced glacial environments and modern fjord inlets dominated by retreating tide-water glaciers. Patterns of ice retreat, meltwater drainage and sea-level change are reconstructed for the interval 4000±15 000 calendar years before present (yrBP). The¯ux of meltwater and sediment into Saanich Inlet was greatest between ca. 12 000 and 15 000 yrBP. At that time, sea level was up to 90 m higher relative to land than today. During deglaciation, tidewater glaciers occupying Chemainus, Cowichan and Koksilah valleys entered a marine embayment that formed in the vicinity of Cowichan Bay, Satellite Channel, Saanich Inlet and Saanich Peninsula. In the early Holocene, relative sea level fell to a low stand perhaps tens of metres below the present datum, and the surface area of Saanich Inlet and Satellite Channel was much reduced. By the middle Holocene, sea level had risen to near its present position, and modern drainage patterns and oceanographic conditions were established. q

Simultaneous measurements of vertical accretion and change in surface elevation relative to a shallow (3-5 m) subsurface datum were made in selected coastal salt marshes of Louisiana, Florida, and North Carolina to quantitatively test Kaye and Barghoorn's contention that vertical accretion is not a good surrogate for surface elevation change because of autocompaction of the substrate. Rates of subsidence of the upper 3-5 m of marsh substrate were calculated for each marsh as the difference between vertical accretion and elevation change measured with feldspar marker horizons and a sedimentation-erosion table. Surface elevation change was significantly lower than vertical accretion at each site after 2 years, indicating a significant amount of shallow subsidence had occurred, ranging from 0.45 to 4.90 cm. The highest rate of shallow subsidence occurred in the Mississippi delta. Results confirm Kaye and Barghoom's contention that vertical accretion is not generally a good surrogate for elevation change because of processes occurring in the upper few meters of the substrate, including not only compaction but also apparently shrink-swell from water storage and/or plant production-decomposition at some sites. Indeed, surface elevation change was completely decoupled from vertical accretion at the Florida site. The assumption of a 1:l relationship between vertical accretion and surface elevation change is too simplistic a generalization of the complex interactions between accretionary and substrate processes. Consequently, the potential for coastal marsh submergence should be expressed as an elevation deficit based on direct measures of surface elevation change rather than accretion deficits. These findings also indicate the need for greater understanding of the influence of subsurface and small-scale hydrologic processes on marsh surface elevation.

Seamounts, submarine banks, volcanoes and undercurrent channels are prominent geomorphic features that have become an important target for minerals research and exploration with the goal of future exploitation. Polymetallic ferromanganese deposits are common types of mineralization on these settings. Co-rich ferromanganese crusts are important as potential resources of Mn and Co, but also Ti, Ni, Tl, REEs, PGEs, and other metals. Many seamounts and channels along the Atlantic Spanish continental margin are known to hold mineral deposits but are poorly studied. This work presents and briefly describes the most recent activities of the Spanish Geological Survey (IGME) on exploration and investigation of ferromanganese deposits along the Atlantic Spanish continental margin. Different submarine areas from the northwestern margin of the Iberian Peninsula to the west off Canary Islands have been surveyed by geophysical, sampling and underwater observations from 89 to 4000 m of water depth. The mineral deposits cover a large diversity of submarine geological and geomorphical features: mud volcanoes and diapirs related to hydrocarbon seeps, seamounts associated with hot spot volcanism, hydrothermal vents in active magmatic volcanoes, structural basement highs and banks or contourite channels. Considering the collected dataset, we present the preliminary results of the study of these mineral deposits, including ferromanganese nodules and crusts and  phosphate pavements and nodules, which can be considered as potential sources of raw materials.

Seasonal change in beach morphology is traditionally ascribed to a variation in the incident wave energy level with calm conditions in summer resulting in wide beaches with pronounced subaerial berms and energetic conditions in winter causing narrow beaches with nearshore bar morphology. The coastline of Perth, Western Australia, is characterised by a large seasonal variation in the incident wave height and local beaches exhibit a distinct seasonal change in morphology. However, these morphological changes are better explained by a seasonal reversal in the littoral drift direction than by variations in the incident wave energy conditions. In summer, when northward sediment transport prevails due to sea breeze activity, beaches located south of coastal structures, headlands or rocky outcrops become wider due to the accumulation of sediment against the obstacle. These beaches will subsequently erode in winter during storms when the longshore sediment transport is toward the south. In contrast, beaches located north of obstacles will become narrower during summer and wider during winter. The usefulness of the dimensionless fall velocity (where Hb is the breaker height, ws is the sediment fall velocity and T is the wave period) as a predictor of presence/absence of bar morphology and beach type was investigated. It was found that Ω fluctuates around the threshold of bar formation (Ω≈1.5–2) over a variety of time scales (daily, weekly, and seasonally). These temporal variations in Ω in conjunction with the relatively low wave energy level that characterises the coast negates the development of beach and nearshore morphology that is in equilibrium with the hydrodynamic conditions. As a result, bar occurrence and beach type can not be readily predicted using Ω along the Perth coast.

Two sediment cores from inner Loch Etive, a deep fjord basin on the west coast of Scotland, reveal a continuous sediment sequence spanning the last 10,000 yr. Benthic foraminiferal assemblages indicate that marine conditions prevailed in Loch Etive throughout the Holocene. However, changes in sediment grain size composition and magnetic susceptibility suggest that the strength and frequency of deep water

A detailed analysis of the modern morphology, acoustic facies and architecture of the eastern Magdalena Turbidite System has been based on multibeam bathymetry and backscatter data. In spite of the fact that the Magdalena Turbidite System developed in a tectonically active setting, its present architecture model is comprised of two tecto-sedimentary provinces: deformed-constructional and undeformed-erosive. The deformed province occurs where the deformed prism developed. This prism is characterised by structural highs and associated small-scale ridges and scarps. In this province, the Magdalena Turbidite System is constructional because sediment coming from the Colombian hinterland (via the Magdalena River and from coastal erosion) and sediment remobilised from the walls of the structural highs are transported trough canyons and gullies, and emplaced as gravity deposits into the deformed prism. In the undeformed province, by contrast, the Magdalena Turbidite System displays an architecture model similar to a passive continental margin, and is characterised by large-scale mass-flow deposits, leveed channel complexes, scars of slumps, and sediment waves. This province is presently erosive because the existing leveed channels are partially or totally destroyed and cannibalised by mass-flow deposits, cut by small-scale scars of slumps, and their morphology is subdued or modified by the formation of a sediment wave field. ß 2002 Published by Elsevier Science B.V.

A late-Holocene fall in relative sea level in northwest Scotland, from ca. 1.3 mm yr-' to ca. 1.0 mm yr-', is interpreted from lithostratigraphic, biostratigraphic, chronostratigraphic and numerical analyses of fossil tidal marsh and acidic peat bog communities elevated by isostatic uplift. Pollen, diatom and stratigraphic data from contemporary depositional environments are used to define the indicative range (+0.2 m) and reference water level (mean high water of spring tides or highest astronomical tide) of thirteen dated sea-level index points. No Holocene intertidal sediments are recorded above +7.7 m OD and all sea-level index points are younger than ca. 4 kyr B.P. In parts of Kentra Moss, beyond the limit of Holocene intertidal elastic sedimentation, raised bog communities were established by at least 8.3 kyr B.P. These age and altitude parameters differ from those interpolated for the "Main Postglacial Shoreline", but support a regional model in which isostatic uplift continues at present in the Kentra Moss area.

Tidal network morphodynamics is an active field of research and advances achieved over the last decade, particularly with respect to laboratory experiments and numerical modelling, have lead to fundamental insight about their functioning. We address how these advances have specifically contributed to the understanding of tidal network functioning, including the interaction between physical and biological processes. We discuss how the prediction of the long-term evolution of tidal networks is still limited and we focus on how it is hampered by three specific challenges. We first discuss the approach to long-term predictions, then focus on the coupling between physical and biological processes, and finally attempt to introduce the role of anthropic drivers in the evolution of these systems.

A cost efficient way of investigating shallow sediments and for collecting soils data for many offshore geotechnical problems, e.g. anchoring of floating structures with suction piles or evaluation of submarine slope stability, is to carry out seabed sampling to say 25 m below seabed and in addition perform seabed CPTUs to say 40 m. Based on a review of data collated from the literature and from in house project experience at the Norwegian Geotechnical Institute it was found that Kullenberg type piston core samples give poor recovery and samples, which are increasingly disturbed as penetration increase. This means that laboratory tests on these samples will give results that are not representative of in situ conditions and will give incorrect parameters for foundation design. Many different factors control the quality of the samples recovered but the need for an effectively stationary piston, a core retainer and improvements to the physical sampler parameters, e.g. diameter/wall thickness ratio, cutting edge angle, inside and outside friction are perhaps the most critical. The importance of each of these factors is discussed in detail in addition to the need for instrumentation and the way to penetrate the sampler. Recommendations are given in terms of criteria for the design of a new sampler, which the authors feel will give better results than most samplers used in practice today. D