Gravity Cores Research Articles

Sediment transport mechanisms from the slopes and canyons to the deep basins south of Crete Island (southeast Mediterranean)

Sediment transport processes from the slopes to the deep basins were studied in the southern Cretan margin (Eastern Mediterranean) by means of swath bathymetry, seismic reflection (airgun) profiling, and gravity coring. Mud/silt turbidites, developed in structureless or laminated patterns, appear to dominate the continental slope and the 2700–3600-m deep depressions of Samaria, Messara, and Gortys. These deposits are the result of successive mass transport events and turbidity currents. Over-steepening caused by strike–slip shearing associated with extensional tectonic activity in the shallow crustal levels, shaking due to significant seismic activity, and the presence of weak sediment layers are responsible for frequent triggering of slope failures and the subsequent formation of turbidity currents on the Gavdos slope. On the Cretan slope, sediments channeled as turbidity currents through canyons proved to be the major delivery mechanism, together with debris flows. Subordinate contributions of hemipelagic sediments occur only in the Messara basin. Moreover, steep non-incised slope areas and slope-confined canyons of the Gavdos slope were found to provide comparable sediment contribution with the fluvially connected canyons of the Cretan slope.

The Bortoluzzi Mud Volcano (Ionian Sea, Italy) and its potential for tracking the seismic cycle of active faults

Abstract. The Ionian Sea in southern Italy is at the center of active interaction and convergence between the Eurasian and African–Adriatic plates in the Mediterranean. This area is seismically active with instrumentally and/or historically recorded Mw>7.0 earthquakes, and it is affected by recently discovered long strike-slip faults across the active Calabrian accretionary wedge. Many mud volcanoes occur on top of the wedge. A recently discovered one (called the Bortoluzzi Mud Volcano or BMV) was surveyed during the Seismofaults 2017 cruise (May 2017). High-resolution bathymetric backscatter surveys, seismic reflection profiles, geochemical and earthquake data, and a gravity core are used here to geologically, geochemically, and geophysically characterize this structure. The BMV is a circular feature ≃22 m high and ≃1100 m in diameter with steep slopes (up to a dip of 22∘). It sits atop the Calabrian accretionary wedge and a system of flower-like oblique-slip faults that are probably seismically active as demonstrated by earthquake hypocentral and focal data. Geochemistry of water samples from the seawater column on top of the BMV shows a significant contamination of the bottom waters from saline (evaporite-type) CH4-dominated crustal-derived fluids similar to the fluids collected from a mud volcano located on the Calabria mainland over the same accretionary wedge. These results attest to the occurrence of open crustal pathways for fluids through the BMV down to at least the Messinian evaporites at about −3000 m. This evidence is also substantiated by helium isotope ratios and by comparison and contrast with different geochemical data from three seawater columns located over other active faults in the Ionian Sea area. One conclusion is that the BMV may be useful for tracking the seismic cycle of active faults through geochemical monitoring. Due to the widespread diffusion of mud volcanoes in seismically active settings, this study contributes to indicating a future path for the use of mud volcanoes in the monitoring and mitigation of natural hazards.

Sediment Provenance of the Nansha Trough Since 40 ka B.P. in the South China Sea: Evidence From δ13Corg, TOC and Pollen Composition

Geochemical proxies in organic matter (OM) are considered to be reliable proxies for deciphering types of paleo-vegetation (C3 plants and C4 plants) and their abundance. The contributions of total organic carbon (TOC), stable carbon isotopes (δ13Corg), total nitrogen (TN) and organic carbon to total nitrogen ratios (C/N) were obtained from a gravity core NS07-25 (6°39.945′ N, 113°32.936′ E, water depth 2006 m), extracted from the southern South China Sea (SCS). These data were used to reconstruct the climate changes of the Nansha Trough since 40ka B.P. by comparing them with pollen data from the same core, and this comparison provides better sediment provenance details in the study area. During the periods between 37ka to 27ka, and from 12.5ka to modern day, the majority of terrestrial sediment received from Borneo, and some climatic events have been governed by aeolian fluxes from mid-latitude areas (mainland China). These periods were relatively humid, compared to 27ka to 12.5ka, where the majority of terrestrial sediment came from the Sunda Shelf through riverine pathways. This study serves as the first study to correlate deep oceanic pollen and geochemical proxies in order to identify the weaken terrestrial OM signals in the deep ocean.

Late Glacial and Holocene vegetation patterns of Attica: A high-resolution record from Elefsis Bay, southern Greece

The present study focuses on the palynological investigation of a sediment core (S2P) recovered from Elefsis Bay, in the western part of Attica Peninsula (southern Greece). Until now, there is quite scarce knowledge about the vegetation history of southern Greece during Late Glacial and Holocene due to a deficiency of long high-resolution pollen records. The analyzed gravity core is a unique continuous and well-dated pollen archive, providing the opportunity for the reconstruction of the plant landscape succession in southern Greece since Late Glacial. In order evidence for the vegetation response to climate oscillations and human impact to be derived, detailed analyses were conducted throughout the sedimentary sequence, spanning the last 13,500 years. The pollen data suggest that temperate deciduous, open oak woodlands of Late Glacial were fully expanded during the onset of Holocene, without any pronounced setback due to climate oscillations as it has been previously indicated by pollen archives from northern Greece. Following this period, Middle Holocene is characterized by the establishment of complex vegetation patterns, partly as the result of human activities, which seem to be the dominant vegetation shaping factor during Late Holocene. Overall, our pollen record highlights the vegetation transition during Late Glacial and Holocene in southern Greece, while offering valuable insight into the plant landscape prior to the first signs of human impact on the environment.

Quantification of diagenetic transformation of continental margin sediments at the Holocene time scale

Early diagenesis processes in the Bay of Biscay have been studied previously on short interface cores. In order to complete the data base and to characterize anoxic biogeochemical processes that affect Quaternary deposits, 1–3 m long gravity cores were collected at 150, 550, 1000 and 2000 m water depth on the continental slope of the south-eastern part of the Bay of Biscay. The aim of this work was to determine how a recorded signal could be changed in the several thousand-year situation of the Holocene period. For that, we determined radiocarbon and 210Pb dating, sedimentological characteristics, and the vertical distribution of particulate and pore water biogeochemical compounds. The sediment consists of a muddy facies deposited continuously during the Holocene. Results show that the distribution of redox sensitive compounds follows the well-established depth sequence of diagenetic reactions governed by the preferential use of the electron acceptor for the bacterially mediated oxidation of organic matter. Mineralization of organic matter occurs down to the bottom of the cores studied, indicating that Holocene sediment of the Bay of Biscay are in a transient state and they keep on being diagenetically transformed today. Effects of anoxic processes on buried sediments were estimated from fluxes induced by chemical gradients in pore waters. Anoxic processes consume up to 3.6 mg particulate organic carbon (POC) per g of dry sediment. They yield also precipitation of secondary calcium carbonate, which represent up to 5% of total buried carbonates. Early diagenetic reactions, which affect proxies commonly used in paleo-oceanography, such as POC, carbonates, phosphorus, or manganese, should be quantified in order to distinguish the part of a sedimentary record being the result of past environmental conditions from that due to post-depositional diagenetic processes. Diagenesis of Holocene deposits also contributes to a low, but significant fraction of N and P flux to the Bay of Biscay sea water.

Staged fine-grained sediment supply from the Himalayas to the Bengal Fan in response to climate change over the past 50,000 years

The Bengal Fan, as the largest submarine fan in the world, receives a large amount of sediments discharged from the Himalayas through the Ganges-Brahmaputra (G-B) river system. However, previous studies of this system seldom focused on the role of channels, which are widely developed in the Bengal Fan, in sediment transportation over the last glacial cycle. Here, we discuss the coupled sedimentary archive in two gravity cores along the Active Channel in the Bengal Fan. Our findings are based on grain size, clay minerals, and Sr and Nd isotope compositions of these two sediment cores. End-member modeling of grain-size data reveals that the intermediate end-member represents the flux of distal fluvial particles from the G-B river system, the fine end-member denotes regional sediment supply of weathered volcanic materials, especially from the eastern Indian Peninsula, and the coarse end-member probably reflects nearby terrigenous input, aeolian input and/or volcanic glass. Sediment provenance analysis based on clay minerals, and Sr and Nd isotopes confirmed sediment supply from the G-B river system which was characterized by high illite percentage, high 87Sr/86Sr ratios and low εNd values, especially during five stages (50–45 ka, 42–37 ka, 31–28.5 ka, 24–20 ka and 14–9 ka). During these stages, heavy fine-grained sediment supply from the G-B river system was discharged into the study area under the influence of climate change rather than sea-level fluctuation, additionally emphasizing the importance of channels in the sediment transport process. Moreover, we find a significant alteration of sediment sources at ∼26 ka, which may be related to conversion of the deep-water currents in the Bay of Bengal.

Late Holocene Changes in Erosion Patterns in a Lacustrine Environment: Landscape Stabilization by Volcanic Activity Versus Human Activity

AbstractThe most recent eruption of Mount Fuji (Japan), the VEI 5 Hōei plinian eruption (CE 1707) heavily impacted Lake Yamanaka, a shallow lake located at the foot of Mount Fuji. Here we discuss the influence of the Hōei eruption on the lacustrine sedimentation of Lake Yamanaka using high‐resolution geophysical and geochemical measurements on gravity cores. Hōei scoria fallout had two major impacts on Lake Yamanaka: (i) reduction of the sedimentation rate (from ~0.16 to ~0.09 cm/year) and (ii) the increase of in situ lake productivity. Sedimentation rates after the eruption were relatively low due to the thick scoria layer, trapping underlying sediments in the catchment. The lacustrine system took more than ~170 years to begin to recover from the Hōei eruption: most recently sedimentation recovery has been accelerated by changes in land use. Since the beginning of the twentieth century, vegetated strips delimited cultivated parcels, trapping sediment and minimizing anthropogenic impacts on the sedimentation rate. Over the last decade, the decline of agriculture and the increase of other human activities has led to an increase in the sedimentation rate (~1 cm/year). This study highlights the effect of the grainsize of the volcanic ejecta on the sedimentation rate following a volcanic eruption. Coarse‐grained tephra are difficult to erode. Therefore, their erosion and remobilization is largely limited to intense typhoons when porous scoria deposits are saturated by heavy rains. Moreover, this study suggests that recent anthropogenic modifications of the catchment had a greater impact on the sedimentation rate than the Hōei eruption.

New coring study in Augusta Bay expands understanding of offshore tsunami deposits (Eastern Sicily, Italy)

AbstractTsunami deposits present an important archive for understanding tsunami histories and dynamics. Most research in this field has focused on onshore preserved remains, while the offshore deposits have received less attention. In 2009, during a coring campaign with the Italian Navy Magnaghi, four 1 m long gravity cores (MG cores) were sampled from the northern part of Augusta Bay, along a transect in 60 to 110 m water depth. These cores were taken in the same area where a core (MS06) was collected in 2007 about 2·3 km offshore Augusta at a water depth of 72 m below sea level. Core MS06 consisted of a 6·7 m long sequence that included 12 anomalous intervals interpreted as the primary effect of tsunami backwash waves in the last 4500 years. In this study, tsunami deposits were identified, based on sedimentology and displaced benthic foraminifera (as for core MS06) reinforced by X‐ray fluorescence data. Two erosional surfaces (L1 and L2) were recognized coupled with grain‐size increase, abundant Posidonia oceanica seagrass remains and a significant amount of Nubecularia lucifuga, an epiphytic sessile benthic foraminifera considered to be transported from the inner shelf. The occurrence of Ti/Ca and Ti/Sr increments, coinciding with peaks in organic matter (Mo incoherent/coherent) suggests terrestrial run‐off coupled with an input of organic matter. The L1 and L2 horizons were attributed to two distinct historical tsunamis (ad 1542 and ad 1693) by indirect age‐estimation methods using 210Pb profiles and the comparison of Volume Magnetic Susceptibility data between MG cores and MS06 cores. One most recent bioturbated horizon (Bh), despite not matching the above listed interpretative features, recorded an important palaeoenvironmental change that may correspond to the ad 1908 tsunami. These findings reinforce the value of offshore sediment records as an underutilized resource for the identification of past tsunamis.

Late Holocene Pollen Record of Environmental Changes in Karimata Strait, Sunda Shelf Region

DOI: 10.17014/ijog.6.1.41-55Pollen analysis has been conducted on a 90 cm gravity core taken from the Karimata Strait to reveal pollen facies in marine sediment and Late Holocene environmental changes in the central Sunda Shelf region. The core site is at 32 m water depth and located about 170 km northwest of Bangka Island, Indonesia. Ten samples were collected at 10 cm intervals through the core. The total number of pollen grains counted in the samples varies between very low (<50 grains) to abundant (>200 grains). High frequencies (50 - 70%) of mangrove pollen are found at 90 to 40 cm indicating that pollen facies in offshore marine sediment may be comparable with those in mangrove forest floor sediment. The core site has been in a neritic environment since its early deposition ca. 1,800 yr B.P. (~150 A.D.) when mangroves vastly grew on the tidal flats of the surrounding islands and they persisted to ca. 700 yr B.P. (~1,250 A.D.). In the middle of this period, a catastrophic event speculatively due to the 535 A.D. Krakatau eruption might have responsible for the decrease of mangroves and the disappearance of benthic foraminifers. The deposition of silicious materials (tephra) due to this eruption might have provided an opportunity for benthic foraminifers to increase their population subsequently. From ca. 700 yr B.P. (~1,250 A.D.) mangroves declined, as indicated by lower frequencies of pollen grain in samples from 30 cm deep upward. It occurred simultaneously with the deposition of coarser sediment and the increase of benthic foraminifer abundance. Interplay of anthropogenic activities, strengthening ENSO cycle, and lowering erosion base level might have been responsible for these environmental changes.

Geochemistry of core sediments along the Active Channel, northeastern Indian Ocean over the past 50,000 years: Sources and climatic implications

Major and trace elements of sediments from two gravity cores (10YDY09 and 12I712) in the northeastern Indian Ocean have been analyzed for sediment provenance and the relationship of the sediments with climate change since 50 ka. The rare earth element (REE) compositions were analyzed, and the sediment contributions were estimated for the major potential sources, including the Ganges-Brahmaputra (G-B), Godavari-Krishna (G-K) and Mahanadi Rivers. Our results showed that the sediments in the study area were a mixture of sediments discharged from the above three rivers. The sediment contribution of the G-K Rivers increased notably during the Holocene when the rainfall increased, which may be caused by the strengthening of the East Indian Coastal Current (EICC) and the resulting large amounts of sediments supplied by the G-K Rivers. The higher sediment contribution from the G-B Rivers demonstrated the role of the Active Channel in transporting sediments to the distal Bengal Fan. During the last glacial maximum (LGM), especially in the late period, the Indian summer monsoon weakened, but the winter monsoon strengthened, resulting in a decrease in chemical weathering and elemental enrichment in the northeastern Indian Ocean. Conversely, when the rainfall was low, the chemical weathering strengthened and K2O/TiO2 ratios were lowered due to the longer weathering time and resulting sediment potassium loss. However, when the sea level reached a certain height during the Holocene, the fluvial sediments could not easily enter deep-water environments through submarine channels, which were well developed in the Bengal Fan.

Variations in trace metal concentrations and Sr, Nd isotopic compositions in sediments from two contrasting settings in the Eastern Arabian Shelf: Implications for provenance and paleoclimate reconstruction

Major and trace elements concentrations as well as Nd and Sr isotopic ratios were measured in sediments from two gravity cores (GC17 and GC19) deposited in the high-sediment flux regime of the Eastern Arabian Shelf (EAS). The core-sampling locations are close to the mouths of the geochemically and isotopically well-characterized Rivers Mandovi and Zuari and are overlain by water columns of contrasting redox conditions. Given the available knowledge of bottom water oxygen concentrations in the studied locations, the compositions of the Mandovi and Zuari sediments as well as the lithology of the drainage basin, the goal of this study was to test the efficacy of different paleo-redox proxies and provenance indicators in a high-sediment flux regime of the ocean.The variations of immobile elements like Al, Ti, Th, and Zr in the studied samples suggest lack of sediment reworking and sorting. Provenance proxies such as Th/Co, La/Sc ratios and variations in La-Th-Sc concentrations suggests a dominantly silicic source rock of granitic to granodioritic composition for these sediments, which is consistent with the dominant lithology of the drainage basins of the Mandovi and Zuari Rivers. Minor contributions from a mafic source (basalt or metabasalt) cannot be ruled out. The chemical index of alteration (CIA) and plagioclase index of alteration (PIA) values of the samples suggest low to moderate weathering of the source rocks. While the Sr isotopic compositions of the GC17 and GC19 sediments overlap with that of the gneissic basement rocks from the Mandovi and Zuari drainage basins, the εNd(0) of the sediments (average −13.72) show significantly more radiogenic values compared to the gneissic basement rocks (average −36). This difference in the Nd isotopic compositions is explained by early selective weathering and removal of rock-forming minerals like plagioclase in the source rocks which results in the supply of radiogenic Nd isotopic composition bearing sediments to the ocean. This argument is consistent with the overlapping εNd(0) of the GC17 and GC19 sediments and suspended particulate matter (SPM) of the Mandovi and Zuari Rivers. Although, the Nd isotopic compositions overlap, the less radiogenic Sr isotopic compositions of the GC17 and GC19 sediments compared to the SPM of the Mandovi and Zuari Rivers suggests the influence of organic matter, formation of authigenic clay and carbonates, as well as the contribution of Sr from submarine groundwater discharge.Trace metal concentrations and ratios were measured in the bulk sediments as well as in the leached authigenic and residual detrital-rich fractions of selected samples. For the GC19 sediments overlain by oxygenated waters, these geochemical proxies correctly infer their deposition under oxic conditions. In contrast, most of these proxies, barring those involving U and Mo, erroneously infer oxic depositional conditions for the GC17 sediments which are overlain by an oxygen minimum zone (OMZ) of the eastern Arabian Sea. We believe that the high sedimentation rate and large terrigenous flux possibly prohibits the equilibration of some of these trace metals in the sediments with the ambient seawater. Our study suggests that U and Mo-based proxies for inferring paleo-redox conditions are robust even under high sedimentation conditions. Overall, this study provides useful insights into the behaviour of redox-sensitive elements and provenance indicators in a continental margin setting impinged by an OMZ.

New archive of another significant potential sediment source in the South China Sea

Sediment provenance is an important part of the sediment source-to-sink transport process from land to sea. However, we sometimes cannot explain some contradictory problems well when assessing sediment sources in certain areas. The northern South China Sea (SCS) is currently considered to be dominantly supplied with sediments from the Pearl River, Taiwan and Luzon. For smectite (one type of clay mineral), Luzon is normally thought to be a significant source when considering only the high smectite percentages in Luzon-derived sediments and neglecting their limited sediment discharge into the sea and longer transport distance of its sediments from this island. Recently, clay mineral compositions of the Pearl River originated sediments were reported to change from rich in smectite from ~2500 years ago due to the anthropogonic activities. By contrast, the wide area in the east of the Pearl River (EPR) is similarly characterized by sediments with high smectite percentages and a shorter transport distance than those from Luzon. However, a previous study showed that surface sediment samples with high smectite percentages were occasionally distributed in bays. Here, we present a sediment archive of 16 gravity cores from neighboring bays/harbors along the northern SCS coast. Unlike surface sediments with low smectite percentages, core sediments from the coastal bays/harbors of the EPR show high smectite percentages, indicating that the EPR besides the Pearl River and/or Luzon might be as another potential sediment source for the northern SCS. In South China, widely distributed igneous rocks/volcanic materials are prodigious sources for sediments in the northern SCS slope. In future work, weathering of local materials must be considered when differentiating various sediment sources.

Advanced passive residual heat removal system for high power pool-type research reactor

A novel passive residual heat removal system is proposed to enhance the safety and cost effectiveness of open pool-type research reactor with high power. As the pool-type research reactors typically have forced downward flow through the reactor core, a stagnant coolant in the middle of flow transition from forced to natural circulation can cause damage to fuel bundles. The main strategy of the proposed system is to delay the flow inversion time by prolonging the core downward flow until the decay heat is significantly calmed down. A gravity core cooling tank is devised to drag the downward flow on by gravity. To demonstrate the new system with the gravity core cooling tank, experimental results from a small-scale facility were compared with results from theoretical analysis and CFD simulation. The theoretical prediction of a 15 MWt real scale system shows that the advanced passive residual heat removal system can perform as an intermediate heat removal system to natural convection by providing sufficient mass flow to remove decay heat from a high power research reactor.

Evolution of the mud patch in the north Yellow Sea and its response to climate change in the past 160 years

As the most important sediment source to the north Yellow Sea (NYS), the sediment discharge from the Yellow River has substantially decreased for at least half a century. The response of the existing mud patches to this decline is not well understood. Here, we present high-resolution grain-size parameters and geochemical composition of one gravity core (B23) collected in the NYS mud patch to investigate the behavior of the mud patch variation in correspondence to the Yellow River’s sediment discharge reduction. The B23 age model is derived by 210Pb dating method, and the average sedimentation rate is estimated to be 0.49 cm/year. Results of a geochemical discrimination analysis suggest that the sediments of B23 were mainly transported from the Yellow River by the strong coastal current along the Shandong Peninsula, whereas the contributions of sediments from Yangtze and Yalu rivers are also measurable. In around 1980, the ratio of sediments from the Yellow River underwent an apparent decrease in the NYS mud. Simultaneous changes include coarsening of grain size and disaccord between East Asia Winter Monsoon intensity and content of sensitive grain size. These are all directly or indirectly due to the decline of the Yellow River’s sediment discharge.

Shelf-edge delta overreach at the shelf break can guarantee the delivery of terrestrial sediments to deep water at all sea-level stands

How and when sediment moves from terrestrial sources to deep-water sinks is a significant area of research. We have used an array of seismic, borehole, and gravity core data sets to explore the timing and magnitude of sediment-routing to Pearl River slope over the last 478 k.y. As predicted by existing sequence stratigraphic models, most sediment dispersal to deep water is shown to have occurred during glacial sea-level falls; however, clastic detritus was still being transported into deep water during interglacial sea-level rises. We suggest that sediment routing to deep water during interglacial sea-level rise is caused by summer monsoon strengthening and resultant warmer and wetter climates, both of which have enhanced effective precipitation and sediment supply. Although some models for the delivery of sediment to deep-water basins stress the importance of proximity of canyon heads and coeval shorelines, we observed that sediment routing to deep water could occur regardless of the distance between channel head and coeval shorelines. In the present case, the success of delivery is related to the combined effects of (1) the short duration and high amplitude of sea-level oscillations during the past 478 k.y. and (2) the enhanced sediment supply caused by more humid climates and greater temperature difference between glacial and interglacial period. This hypothesis is supported by (1) observations that outer Pearl River deltas prograded as an apron over preexisting shelf edges for 10–15 km (6–9 mi) and (2) the occurrence of slope channels extending back to prodelta reaches of Pearl River shelf-edge deltas.

Microbial community composition and diversity in the Indian Ocean deep sea REY-rich muds.

Studies about the composition and diversity of microbial community in the Rare Earth Elements-rich muds are limited. In this research, we conducted a characterization for the composition and diversity of bacterial and archaeal communities from rare earth elements-rich gravity core sediment at approximately 4800 meters deep in the Indian Ocean by Illumina high-throughput sequencing targeting 16S rRNA genes. The results showed that the most abundant bacteria were Proteobacteria, followed by Firmicutes and Actinobacteria. Amongst Proteobacteria, Gammaproteobacteria are present in all sections of this sediment core accounted for a particularly large proportion of bacterial sequences. Candidatus Nitrosopumilus, with a higher relative abundance in our samples, belongs to Thaumarchaeota. This is the first report on the composition and diversity of rare earth elements-rich muds microbial communities in the Indian Ocean deep sea.

Assessment of the high-resolution paleoseismicity record from sediment gravity flows in Prince William Sound, Alaska

Located along the Aleutian Megathrust Boundary, South-Central Alaska is one of the most seismically active areas in the world. Central to this region, Prince William Sound is a glacially carved basin that receives abundant sediment from multiple sources. Primary inputs include the Columbia Glacier and the Copper River, which have diagnostic signatures of Sr/Pb, Cu/Pb, K/Ca, Rb/Sr, and Rb/Ca. As a result, earthquake induced sediment gravity flows originating from different locations deposit event layers that have distinct provenance signatures. A previous study (Kuehl et al., 2017) identified five such event layers preserved in two cores from the southern part of the deep central channel of Prince William Sound that were attributed to large historical earthquakes. To better understand the spatial continuity of these event layers along the entire length of the central channel, seven new gravity cores were collected in a north-south transect. Sedimentation rates were determined by 210Pb, 137Cs, and 239,240Pu geochronology, and cores were assessed for variations in elemental content, grain size patterns, bulk organic and stable isotopic signatures (C/N, δ13C, δ15N). Based on a spatial analysis of these cores, local earthquakes of Mw < 7.0 deposit event layers in the central channel with signatures reflecting the epicenter location, and those of Mw > 7.0 (including an event layer from the 1964 great Alaskan earthquake) have mixed signatures resulting from the widespread generation of numerous flows throughout Prince William Sound. Complete gravity flow records are captured within deep ponded sediment basins and the area spanning the southern end of the central channel. Considering the thick (>100 m) late-Holocene sequence, the approach utilized in this study has the potential to provide a rich record of earthquake recurrence intervals to 4 ka.

Anthropogenically-induced ecological risks in Lake Erikli, NW Turkey

This study examined the vertical distribution of heavy metals in the core sediments of Lake Erikli, Turkey and their potential ecological risks. Two core samples 48 and 34 cm in length were taken with a Kajak gravity core sampler. The samples were divided into 2 cm sub-samples in the laboratory and analyzed using ICP-MS. The enrichment factor (EF), potential ecological risk factor (PERI) and pollution load index (PLI) were calculated to evaluate the environmental quality of the sediment. According to the results, Cu, Pb, Zn, Ni, and Cr come from natural sources in both cores and there is no anthropogenic contribution to the distribution of these elements, while some anthropogenic effects were detected for As, Cd and Hg. According to the calculated risk index (CRI) for each metal, the potential risk of Cu, Pb, Zn, Ni, As and Cr is low. Two metals posing a threat to the ecosystem were identified; Cd and Hg. PLI values significantly increased from the bottom of the slice to the surface in accordance with the EF and PERI values. Continuation of the pumping of domestic waste into Lake Erikli will accelerate the process of deterioration.

Tertiary Deep-Water Coral Supports Cold Seeps in the Ceduna Sub-Basin

The analysis of new 3D seismic and the acquisition of unique core data enables an in-depth interpretation of outboard Eocene mounds in the central Ceduna Sub-basin and a more accurate model of their origin.Seismic attributes and spectral decomposition clearly image the 3D morphology and internal architecture of the mounds and enable building episodes to be defined. Mounds have length of 535km, width of 1-4km and heights of 50-110m and developed at water depth 300-600m. Gravity core of the top of one mound indicates that it consists, at least partly, of corals typical of a deep-water reef. This initial interpretation is based on comparison with modern reef-forming biota, the presence of suspected brachiopods and lack of gastropods.The underlying faults control the initial localisation of the mounds. These faults were active in the Cretaceous and reactivated in the Tertiary and intersect sequences modelled as oil- and gas-mature.One main control for deep-water coral is the need for suitable hard substrates for initial attachment. The distribution of the mounds supports a development mechanism that relies on carbonate hardgrounds produced by chemosynthetic communities metabolizing nutrients from natural hydrocarbon cold seeps along reactivated faults and segments intersections. A hydrothermal feedstock for these communities is possible but less likely due to the distance to the nearest volcanic bodies. Once the substrates are in place the mounds growth is not directly dependant on ongoing cold seeps and could be as well related to the specifics of hydrodynamics in the areas.

Analysis of Physical Distribution of Sediment at Sembrong Reservoir Using GRADISTAT

Sembrong reservoir is a flood-control reservoir which is managed by Syarikat Air Johor since 1984. The reservoir provides clean water supply to 240,000 consumers in the district of Kluang and some parts of Batu Pahat. Reservoir storage is often affected by sedimentation due to soil erosion in the catchment area. As the sediments accumulate, the reservoir gradually loses its ability to store water for the purposes for which it was built. This research is initiated to characterize the sediment which could be used as control in future research in the treatment of contaminated sediment. The objective of this study was to determine the distribution of sediment at Sembrong Reservoir. In this experiment, sediment sampling was done using gravity corer at 6 different points throughout the reservoir. In addition, the physical properties of sediment is investigated by conducted experiments include scanning electron microscope (SEM) and particle size distribution The analysis of sediment distribution was done using GRADISTAT. Results obtained from the analysis shows that the particle in Sembrong reservoir were classified as very coarse sand and sandy gravel.