Search

A comprehensive study of the Maastrichtian–Danian boundary rocks in the Klementyev Mountain section (eastern Crimea) was carried out. The lithological characteristics of carbonate, carbonate–clayey, and clastic rocks are scrutinized. The dynamic of changes in the benthic and planktonic foraminiferal assemblages is analyzed. The geochemical and isotopic data were obtained for this section for the first time. The stratigraphic range of the upper Maastrichtian and lower Danian has been specified. The late Campanian–early Maastrichtian age of the underlying rocks has been confirmed for the first time. Sediments of the Klementyev Formation were deposited in a deep-sea pelagic paleoenvironment on the submerged part of the outer shelf, whereas the overlying Lower Danian sediments were deposited in shallow waters of the inner shelf with terrigenous sedimentation and high hydrodynamic activity. [ABSTRACT FROM AUTHOR]

Increasing interest in high‐tech metals (e.g., rare earth elements and yttrium, REY) has triggered extensive research on the enrichment of these metals in pelagic sediments. In the sediments collected worldwide, Ca‐phosphate and Fe‐Mn (oxyhydr)oxides are targeted as the two most important REY carriers based on multiple geochemical and mineralogical analyses. However, the formation of the REY‐rich stratum remains enigmatic as the influences of diagenesis and the local restrictions of different oceanic basins are complex, which require further investigation. In our study, we analyzed four sediment cores from the Western, Central North, and Eastern South Pacific (WP, CNP, and ESP), which are three of the most promising REY‐rich regions in global oceans. Sequential leaching quantifies the dominance of Ca‐phosphate by controlling ∼73.9%–93.3% of ΣREY and the secondary role of Fe‐Mn (oxyhydr)oxides by holding up to ∼97.8% of Ce and ∼4.82%–13.9% of ΣREY. The shallowly and deeply buried sediments show similar features regarding the REY proportions hosted by different phases, which indicates that the REY accumulation by Ca‐phosphate might majorly occur on the seawater‐sediment interface. The geochemistry of the studied sediment cores reveals that (a) REY enrichment in ESP is affected by hydrothermal Fe‐Mn (oxyhydr)oxides which can promote adsorptions of P and REY. (b) The Fe and Mn contents in WP sediments show an inverse relationship against REY enrichment which might be explained by the dust input from Central Asia. (c) The slow sedimentation rate of CNP enables the extraordinary REY‐uptake by Ca‐phosphate, but the low flux of phosphorus constrains the formation of high‐grade REY deposits. Plain Language Summary: Rare earth elements and yttrium (REY) are useful for geological studies and valuable materials for cutting‐edge technologies. Recently, scientists found high REY contents in deep‐sea sediments, which could be future resources. However, its enriching mechanism is not fully understood. Here, we analyze the geochemistry of four sediment cores across the Pacific. The samples were sequentially leached with chemical solutions to separate different mineral phases. The results reveal that Ca‐phosphate (e.g., fish fossils) is the main carrier holding ∼73.9%–93.3% of REY, and Fe‐Mn (oxyhydr)oxides (e.g., small Fe‐Mn nodules) hold ∼4.82%–13.9%. The proportions of REY hosted by the carriers are similar among the layers ranging from the surface to 8‐m depth. This indicates that the REY accumulation mostly happens on the seafloor surface. Additionally, this study reveals that the REY‐rich sediments in the Eastern South Pacific are likely related to underwater hot vents that release more Fe and Mn to accumulate P and REY. In the Western Pacific, the levels of REY seem to be affected by dust coming from Central Asia. In the Central North Pacific with slow sedimentation rates, fish fossils can take up high REY, but their low amount limits the formation of high‐quality REY deposits. Key Points: The rare earth elements and yttrium (REY) held by Ca‐phosphate and Fe‐Mn (oxyhydr)oxides in pelagic sediments are quantified by sequential extractionCa‐phosphate mainly scavenges REY at the seawater‐sediment interface on the seafloorLocal constraints on REY‐rich sediments from different pelagic basins relate to their material sources (e.g., eolian dust and hydrothermal vent) [ABSTRACT FROM AUTHOR]

Oxygen is essential for marine ecosystems, and it is linked by respiration to carbon storage in the deep ocean. Reconstructing oxygen concentrations in the past has been limited by the absence of quantitative, rather than qualitative, proxies, but several new (semi-) quantitative oxygen proxies have recently been developed. In this study we explore the possibility of adding bulk sedimentary uranium (U) to this list by normalizing it to barium (Ba). First, U/Ba and bottom water oxygen concentrations are compared on a global scale, using a core top database, in pelagic environments greater than 200 m water depth. Then, the relationships between U/Ba and bottom water oxygen are examined on smaller spatial scales: within each ocean basin and regionally within the Eastern Equatorial Pacific, the Arabian Sea, and Western Equatorial Atlantic. At this regional scale, where secondary influences on the behavior of both U and Ba may be more spatially uniform, empirical piecewise linear calibrations are developed and subsequently tested on downcore records. U/Ba-based oxygen reconstructions generally agree with those derived from previously published alkenone preservation and benthic foraminiferal surface porosity records. Several limitations to the utility of U/Ba as a proxy for oxygen have also been identified. The proxy should only be applied in the uppermost sedimentary intervals that contain porewater sulfate to minimize barite diagenesis, and phosphorus contents should be monitored for the potential influence of apatite on uranium content. U/Ba is more successful at recording oxygen concentrations during mean glacial and interglacial periods than during climate transitions, when the timing and amplitude may be more sensitive to burndown and smoothing. Conservative errors on the calibrations result in the greatest utility of U/Ba in regions with relatively high oxygen concentrations (e.g., >50 μmol/kg) and large oxygen variability (±10 s of μmol/kg). Even with these caveats, U/Ba is only one of two quantitative oxygen proxies potentially capable of recording variability above 50 μmol/kg, and further investigation into its functionality in different environmental settings is worthwhile in the endeavor to reconstruct the full marine range of oxygen concentrations in the past. [ABSTRACT FROM AUTHOR]

The Sulu Sea is a marginal spreading basin in the triple junction of Euro-Asia/Indian/Pacific plates. The genesis of seafloor basalts is crucial for understanding the nature and evolution history of the underlying mantle in this region. Nevertheless, the mantle source of the Sulu Sea remains unclear due to limited geochemical data. In this study, we report a complete set of whole-rock major and trace elements and Sr-Nd-Pb-Hf isotopes for the volcanic rocks at Ocean Drilling Program Site U768 in the Southeast Sulu Sea. These volcanic rock samples are characterized by transitional trace element compositions between mid-ocean ridge basalts (MORBs) and island arc basalts (IABs). A subduction modified depleted mantle source is indicated by their higher Th/Yb ratios than the MORB-OIB array and trace element patterns. We propose that the pelagic sediments contributed to the mantle source of the Southeast Sulu Sea based on the plots of 206Pb/204Pb vs. Ce/Pb and Th/Nb. Based on the decoupled Hf–Nd isotopes and the variation of Pb isotopes for Site U768 volcanic rocks, we suggest that subducted pelagic sediments contributed to the origin of the Indian-type mantle of the Southeast Sulu Sea.

Fine-peloidal- to coarse oolitic-bioclastic grainstones with hummocky cross stratification (HCS) occur interbedded in Jurassic pelagic lime-mudstone successions (Subbetic, Betic ranges, Southern Spain). These strata were deposited in pelagic troughs and swells, away from continental areas, in the Southern Iberian Paleomargin of the Western Tethys. Selected examples presented in this study include: a) coarse oolitic grainstones, encased in pelagic marls, holding characteristics similar to the ridge-berm-swash zone of modern beaches; b) peloid grainstones with HCS interbedded with radiolarite marls deposited on the flanks of volcanic guyots. The interbedded lime muds and marls contain "filaments", sponge spicules and radiolarians; c) peloid-bioclastic (radiolarians, "filaments", etc.) grainstone beds with HCS, interbedded with pelagic lime muds; d) crossbedded peloidal-skeletal (Saccocoma) grainstones with HCS and wave ripples on top, interbedded with pelagic mudstones and wackestones with abundant bioturbation and ammonites (Ammonitico Rosso facies). All the examples here presented share: 1) grainstone beds are interbedded with pelagic mudstones and marls; 2) grainstone components were reworked by oscillatory flows superimposed to unidirectional tractive flows (unidirectional ripple lamination and HCS); 3) components, either derived from shallow-water environments (e.g., ooids) or produced in pelagic conditions (e.g., radiolarians, Saccocoma , "filaments", peloids, etc) were reworked by high-energy processes unrelated to surface storm waves; 4) Internal waves (IWs) propagating along a pycnocline and breaking against a sloping surface are the best candidates to induce the sedimentary structures and sediment organization that characterize these grainstone beds. Coarser sediments "trapped" at the breaker zone form sediment accumulations similar to the sediments caught by the "littoral fence" in the surface beach. This scenario evidences the HCS not to be necessarily linked to the surface storms but to the pycnocline bathymetry, solving the problem of having HCS in pelagic zones where the storm and hurricanes wave action can be considered "out-of-context". • Grainstones with hummocky cross-stratification occur in a Jurassic pelagic basin. • These are interpreted as the product of breaking internal waves on sea bottom. • Alternative interpretation of the "rare" presence of grainstones between pelagics. • It can provide models to explain and predict the occurrence of oil and gas resources. [ABSTRACT FROM AUTHOR]

Abstract We performed high pressure and high temperature (HPHT) experiments on NH 4 -doped montmorillonite (~2 wt% of NH 4) under pressures of 2.5, 4.0, and 7.7 GPa and temperatures from 200 to 700 °C. Each experiment was analyzed with XRD, FTIR, CHN elemental analysis, and SEM in order to determine the NH 4 -Smectite phase changes and their morphology, and the presence of ammonium in the runs. Our results show that smectite can easily transport nitrogen, speciated as ammonium (NH 4 +), incorporated into the smectite interlayer in mildly reducing environments to deeper levels in the Earth through cold thermal regime subduction zones. NH 4 -Smectite transforms into NH 4 -enriched micaceous phase (tobelite) through a NH 4 +-enriched interlayered I/S phase in relatively low pressures and temperatures (around 2.5 GPa and 500 °C). Tobelite is stable until more extreme conditions (7.7 GPa and 700 °C), together with lesser amounts of buddingtonite (an ammonium-bearing feldspar) kyanite, and garnet. Our experiments also show the effect of nitrogen in the feldspar stability, as potassic and sodic feldspar are stable up to ~5 GPa, while buddingtonite, is observed to be stable up to 7.7 GPa. Nitrogen can return to the surface once the stability of these nitrogen-enriched minerals is reached due to pressure or temperature increasing. [ABSTRACT FROM AUTHOR]

The application of thermal methods, such as Rock−Eval 6 pyrolysis or differential thermal analysis, provides complex information about sediment and rock properties, including thermal behaviour, degree of maturity, alteration of organic matter, and high temperature combustion synthesis mineral products. In this study, thermal methods included experiments on the thermokinetics of modern deep-sea sediments of the Northeast Pacific Basin. For experimental the procedure, twelve samples of siliceous clayey silts collected from the Clarion−Clipperton Fracture Zone (CCFZ), Interoceanmetal claim area, were analysed. CCFZ is highly prospective as a giant marine polymetallic deposit which contains several economically valuable metals, such as Ni, Cu, or Co. Hydrocarbon potential, thermal maturity, and roasting products were investigated. Mineralogical characteristics of thermal products were investigated. The obtained results of thermal experiments were compared with sedimentological, mineralogical, and geochemical data of bulk sediments. The total enthalpy ΔHTot. and activation energy Ea were proposed as a new lithogeochemical proxies of oxygen depletion during oxic−suboxic diagenesis. The distinctive increase in positive enthalpy (or heat transmission) was observed with the burial depth, where pelagic sediments showed strong oxygen depletion and consumed more energy during phase transformations.

Four isochronous Oligocene coccolith limestone horizons from the Carpathians were examined in order to reconstruct paleoceanographic conditions in the Central Paratethys. The dominance of small and size-uniform pyrite framboids, the occurrence of low-diversity dinoflagellate cysts and coccolithophorids and the presence of biomarker molecule 28,30-dinorhopane indicate that the water column was stratified with the upper water column being relatively well‑oxygenated, but the bottom water being anoxic. The latter is confirmed by the fine and consistent horizontal laminations in various parts of the basin, scarcity of benthic organisms and their trace fossils. The limestones exhibit typical marine δ 13 C values, but are significantly depleted in 18 O and enriched in 87 Sr relative to contemporaneous ocean water. These isotopic compositions result from a decreased salinity of the surface waters caused by an increased riverine input. This is confirmed by the lack or impoverishment of planktonic foraminifers, presence to abundance of goniodomid dinoflagellate cysts and massive occurrence of low-diversity nannoplankton assemblages, which indicates decreased salinities as low as 17‰ and high productivity in the upper water column. These observations indicate that the limestones were formed during periods when connection of the Central Paratethys with the global ocean was limited, which impeded water exchange causing the development of low-salinity conditions of surface water and bottom-water anoxia. During the deposition of the oldest Tylawa horizon, primary productivity was enhanced and chemocline was positioned exceptionally high in the water column. Moreover, decreased δ 13 C values in both carbonates and organic matter of this horizon suggest that widespread methane venting took place in the basin during NP23. All these data show that during the Oligocene the Central Paratethys experienced similar conditions to those of the current Black Sea, which can be used as a modern analogue, especially for the Tylawa horizon. Therefore, the Tylawa horizon can be perceived as a potential effect of future post-depositional processes of coccolith marls analogous to those having been deposited in the Black Sea for 2.7 kyr. [ABSTRACT FROM AUTHOR]

Karl Andrée began studying questions of sedimentology and oceanography in 1908 when working as an assistant at the University of Marburg and he remained faithful to these subjects until his death in 1959. The vast majority of his scientific contributions, however, were published during his time at the University of Königsberg (1915-1945). There he published his fundamental papers on marine geology, all of which adhered strictly to the principles of uniformitarianism, and helped improve our understanding of sedimentary processes and the stratigraphic record. His scientific work has enormous breadth. In the course of 55 years, he published 124 individual papers and books, some of which became classic textbooks. His versatility is particularly evident in his book 'Geology of the Seafloor', which contains many pertinent observations and descriptions still relevant today, even if it has fallen out of fashion. This scientist and university teacher was the first to successfully present the huge field of marine geology in all its facet and to consider the deposition of marine sediments as a function of their geographical distribution. [ABSTRACT FROM AUTHOR]

Copyright of Revue de Micropaleontologie is the property of Elsevier B.V. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This research deals with a regional comparative analysis of nodule morphology and texture with pelagic sediment distribution. Samples were collected on board of R/V El Puma during oceanographic cruise MIMAR VI. The study area is located in the northeastern portion of the Clarion Fracture Zone in the Economic Exclusive Zone of Mexico. The more abundant nodules sizes are smaller than 2 cm and discoid form with smooth and rough surfaces were dominant. Small sizes occur in the southern study area, while nodules larger than 4 cm are found in the northern portion. Sediments are enriched in Si, Al, Na, K, and Ti; in contrast the nodules are richer in Mn, Fe, Mg, Ca, Ni, Co, and Cu. Most of the Si and Al seem to be terrigenous probably due to the influence of winds carrying small particles from Vizcaino and Sonora deserts. Nodules are hydrogenic in the northern study area and diagenetics towards the south. [ABSTRACT FROM PUBLISHER]

The 34-million-year (My) interval of the Late Triassic is marked by the formation of several large impact structures on Earth. Late Triassic impact events have been considered a factor in biotic extinction events in the Late Triassic (e.g., end-Triassic extinction event), but this scenario remains controversial because of a lack of stratigraphie records of ejecta deposits. Here, we report evidence for an impact event (platinum group elements anomaly with nickel-rich magnetite and microspherules) from the middle Norian (Upper Triassic) deep-sea sediment in Japan. This includes anom-alously high abundances of iridium, up to 41.5 parts per billion (ppb), in the ejecta deposit, which suggests that the iridium-enriched ejecta layers of the Late Triassic may be found on a global scale. The ejecta deposit is constrained by microfossils that suggest correlation with the 215.5-Mya, 100-km-wide Manicouagan impact crater in Canada. Our analysis of radiolarians shows no evidence of a mass extinction event across the impact event horizon, and no contemporaneous faunal turnover is seen in other marine plank-tons. However, such an event has been reported among marine faunas and terrestrial tetrapods and floras in North America. We, therefore, suggest that the Manicouagan impact triggered the extinction of terrestrial and marine organisms near the impact site but not within the pelagic marine realm. [ABSTRACT FROM AUTHOR]

Organic rich layers (ORLs), deposited in the westernmost Mediterranean over the Last Glacial Cycle, have been studied integrating sedimentological and ichnological information from sediment records recovered at Ocean Drilling Program Leg 161 Sites 976 and 977. The conducted study has served to redefine the ORLs initially differentiated in sediment records from Sites 977 and 976, with seven new ORLs recognized, as well as extensions and subtraction of some parts in the ORLs previously defined. In addition, three different ORL types are distinguished according to sedimentological and ichnological features. Type 1 with intermediate thickness is highly bioturbated, mainly consisting of abundant Scolicia and Planolites , frequent Chondrites , and possible Thalassinoides in the base, which are interpreted as supporting dysoxic conditions during deposition. Type 2, corresponding to thicker intervals, shows alternance of highly to moderately bioturbated parts, revealing variable oxygen conditions —from moderate to extreme dysoxic or even suboxic. Type 3 consists of short, laminated intervals characterized by the absence of bioturbation, indicating anoxic or suboxic conditions and determining unfavourable macro benthic habitat. The amended ORLs show a correlation between the Sea Surface Temperatures and established climatic events over the Last Glacial Cycle in the Western Mediterranean. • An integrated ichnological analysis is performed on ORLs from the westernmost Mediterranean. • Variable bioturbation is recognized in ORLs over for the Last Glacial Cycle. • Trace fossils reveal as a reliable proxy for reconstructing past ocean oxygenation. • Grayscale colour data and bioturbation correlate with ocean dynamic and climatic changes. [ABSTRACT FROM AUTHOR]

Abstract: Bimodal extrusive volcanic rocks in the northeast Greater Antilles Arc consist of two interlayered suites, including (1) a predominantly basaltic suite, dominated by island arc basalts with small proportions of andesite, and (2) a silicic suite, similar in composition to small volume intrusive veins of oceanic plagiogranite commonly recognized in oceanic crustal sequences. The basaltic suite is geochemically characterized by variable enrichment in the more incompatible elements and negative chondrite-normalized HFSE anomalies. Trace element melting and mixing models indicate the magnitude of the subducted sediment component in Antilles arc basalts is highly variable and decreases dramatically from east to west along the arc. In the Virgin Islands, the sediment component ranges between<0.5 to ∼1% in Albian rocks, and between ∼1 and 2% in succeeding Cenomanian to Campanian strata. In comparison, sediment proportions in central Puerto Rico range between 0.5 to 1.5% in the Albian to 2 to>4% during the Cenomanian-Campanian interval. The silicic suite, consisting predominantly of rhyolites, is characterized by depleted Al2O3 (average<16%), low Mg-number (molar Mg/Mg+Fe<0.5), TiO2 (<1.0%), and Sr/Y (<10), oceanic or arc-like Sr, Nd, and Pb isotope signatures, and by the presence of plagioclase. All of these features are consistent with an anatexic origin in gabbroic sources, of both oceanic and arc-related origin, within the sub-arc basement. The abundance of silicic lavas varies widely along the length of the arc platform. In the Virgin Islands on the east, rhyolites comprise up to 80% of Lower Albian strata (112 to 105 Ma), and about 20% in post-Albian strata (105 to 100 Ma). Farther west, in Puerto Rico, more limited proportions (<20%) of silicic lavas were erupted. The systematic variation of both sediment flux and abundance of crustally derived silicic lavas are consistent with current tectonic models of Caribbean evolution involving approximately perpendicular subduction of the Caribbean spur of the mid-Atlantic Ridge, which was located approximately midway between North and South America until Campanian times. Within this hypothetical setting the centrally positioned Virgin Islands terrain remained approximately fixed above the subducting ridge as the Antilles arc platform swept northeastward into the slot between the Americas. Accordingly, heat flow in the Virgin Islands was elevated throughout the Cretaceous, giving rise to widespread crustal melting, whereas the subducted sediment flux was limited. Conversely, toward the west in central Puerto Rico, which was consistently more remote from the subducting ridge, heat flow was relatively low and produced limited crustal melting, while the sediment flux was comparatively elevated. [Copyright &y& Elsevier]

Constraints on the polarity of Cretaceous subduction in the Greater Antilles are provided through geochemical comparison between the erupted island arc lavas in central Puerto Rico and potential pelagic sediment reservoirs in the flanking ocean basins. Early Jurassic to mid-Cretaceous (185- to 65-Ma) sediment from the open Pacific on the southwest is dominated by pelagic chert, which is highly refractory and depleted with respect to incompatible elements. In comparison, mid- to Late Cretaceous (ca. 112- to 65-Ma) sediment from the younger Atlantic basin on the northeast was dominated by mixtures of two end members. These include (1) biogenic clay and carbonates with elevated light rare-earth element (LREE) abundances, negative MORB-normalized, high field-strength element (HFSE) anomalies, and low Zr/Sm; and (2) turbiditic detritus of upper continental crust composition with high LREE, comparatively shallow HFSE anomalies, and high Zr/Sm. Compositions of Puerto Rican arc basalts are inconsistent with incorporation of Pacific pelagic chert. Instead, patterns characteristic of high-Fe island arc tholeiites are reproduced by incorporation of up to 4% of a low-Zr/Sm biogenic sediment component of Atlantic origin, whereas patterns of low-Fe lavas require, in addition to biogenic sediment, introduction of up to 2% of a high-Zr/ Sm crustal turbidite component. The Atlantic origin of all the subducted sediments indicates the polarity of subduction throughout the Cretaceous in the northeast Antilles was persistently southwest dipping. This conclusion is supported by the presence of a low-Zr/Sm suprasubduction zone component of Atlantic origin in Caribbean plateau basalts (91-88 Ma) from southwest Puerto Rico, which were erupted within the broad back-arc region of the Greater Antilles during intermediate stages of arc development. [ABSTRACT FROM AUTHOR]

Abstract: A 328 cm-long piston core (KODOS 02-01-02) collected from the northeast equatorial Pacific at 16°12′N, 125°59′W was investigated for eolian mass fluxes and grain sizes to test these proxies as a tool for the paleo-position of the Intertropical Convergence Zone (ITCZ). The eolian mass fluxes of the lower interval below 250 cm (15.5–7.6 Ma) are very uniform at 5±1 mg/cm2/103 yr, while those of the upper interval above 250 cm (from 7.6 Ma) are over 2 times higher than the lower interval at 12±1 mg/cm2/103 yr. The median grain size of the eolian dusts in the lower interval increases from 8.4ϕ to 8.0ϕ downward, while that of the upper interval varies in a narrow range from 8.8ϕ to 8.6ϕ. The determined values compare well in magnitude to those of central Pacific sediments for the upper interval and equatorial and southeast Pacific sediments for the lower interval. This result suggests a possibility that the study site had been under the influence of southeast trade winds at its earlier depositional period due to the northerly position of the ITCZ, and subsequently of the northeast trade winds for a later period when the upper sediments were deposited. This interpretation is consistent with a mineralogical and geochemical study published elsewhere that assigned the provenance of the study core dust to Central/South America for the lower interval and to Asia for the upper interval. This study suggests that the distinct differences in eolian mass flux and grain size observed across the ITCZ can be used to trace the paleo-latitude of the ITCZ. [Copyright &y& Elsevier]

Abstract: The sediments recovered from two gravity cores of the lower and distal Bengal Fan were investigated for sedimentological properties and Sr–Nd isotopes. Each core exhibits two distinct units, the lower unit 2 and upper unit 1 sediments. The unit 2 sediments are predominantly olive black/grey in colour with abundant finer silt-size fractions, low organic carbon and CaCO3, quartz and mica in the coarse fraction, dominant illite and chlorite in the &#60;2μm fraction and uniform rock-magnetic properties. Biogenic constituents are extremely rare or restricted to the lower part of unit 2. The unit 1 sediments, on the other hand, are moderate brown/yellowish brown in colour with intermittent thin dark-coloured sediment layers. Higher clay, organic carbon, CaCO3, and biogenic constituents in the coarse fraction, and enriched smectite and kaolinite in the &#60;2μm fraction are typical. Magnetic susceptibility values are higher and correlate well with acid-insoluble residue content. Higher Rb, Sr, Sm and Nd concentrations, 87Sr/86Sr ratios and more radiogenic values are characteristic for unit 2 sediments compared to unit 1 in both the cores. The unit 2 sediments represent Pleistocene hemiturbidites, older than 13 14CkyrBP with their source from the northern Bay of Bengal (NBOB), derived from the Himalayas and transported by the Ganges–Brahmaputra (G–B) River system. Unit 1 sediments are calcareous pelagic sediments, which started depositing ∼12 14CkyrBP, with its clastic sediments derived from the Himalayas and SE Indian/Sri Lankan margins. The change in lithofacies from unit 2 to unit 1 suggests that the sediment deposition by turbidity current activity ceased in the distal Bengal Fan at ∼12 14CkyrBP, perhaps because of the rapid rise in sea-level during the melt water pulse 1A and Holocene. [Copyright &y& Elsevier]

Abstract: The Bidart section (southwestern France) displays an almost complete Late Maastrichtian–Early Danian transition. As the Cretaceous–Paleocene (K/P) crisis mainly affects carbonate producers, the aim of this study is to precisely evaluate the evolution of pelagic sediments composition across the boundary. A new protocol for separation of fine carbonates into discrete size fractions was used (1) to precisely evaluate (in weight of carbonate and not only number of particles per gram of rock) the contribution of each carbonate component type (foraminifera, calcareous nannofossils and “nonbiogenic” carbonates, calcite microparticles, and calcareous macrocrystals), and (2) to measure their isotopic signature and thus constrain the origin of these carbonate particles. The Maastrichtian pelagic carbonates are mostly biogenic (70% of the bulk carbonate) but also contain “nonbiogenic” carbonates: calcite microparticles (<4 μm) and calcareous macrocrystals (>4 μm). Due to their isotopic signature, calcite microparticles cannot result from fragmentation and partial dissolution of biogenic remains, and the most likely origin appears to be early diagenetic processes and/or export from shallow-water platforms. The calcareous macrocrystals derive from an early diagenetic process. The lowermost Danian sediments are dominated by “nonbiogenic” carbonates (between 50% and 80% of the bulk carbonate). Nevertheless, two kinds of biogenic components are present: Thoracosphaera operculata and Maastrichtian-like calcareous nannofossils. Thoracosphaera operculata is an opportunistic calcareous dinoflagellate, which frequently occurs at high abundances in basal Danian sediments and is certainly in situ, this is confirmed by it showing a Danian isotopic signature. The Maastrichtian-like calcareous nannofossils are nannofossils of taxa that indisputably occur in the Maastrichtian, but which do not occur consistently in later Danian strata, they show a Maastrichtian-type isotopic signature, which strongly supports the inference that they are mainly reworked from the Maastrichtian. This study shows that “nonbiogenic” carbonates are important components of the pelagic carbonate even during periods of normal sedimentation. In the “crisis interval”, the biogenic carbonate production drops sharply, while calcite microparticles and carbonate macrocrystals remain almost unaffected and represent the major part of the carbonate in the earliest Danian sediments. Finally, the sediments return to a composition similar to that of the Maastrichtian in M. pseudobulloides foraminifera zone. [Copyright &y& Elsevier]

Previous studies regarding the depositional pattern and quantity of accumulated seafloor sediment tend to be regional, limited in scope and involving costly and time-consuming geologic field campaigns and laboratory work. Presented herein is a global map of predicted modern (postindustrial, 20th and 21st century) oceanic mass accumulation rates of 5-arc-minute pitch and in log 10 -space, trained on observed marine mass accumulation rates from 43 peer reviewed sources (n = 1744) and predicted using a k-nearest neighbor geospatial algorithm. The resultant model predicts ~3.3 × 104 Mt. yr−1 of sediment accumulating onto the sea floor (R2 = 0.88). Most sediment accumulates proximal to major river outlets and deltas. Continental regions with the highest sediment accumulation are Asia and Oceania. This model is the first of its kind to predict the rate and quantity of sediment accumulating on to the ocean floor, globally, using decades of regional real-world observations. The generated global map of modern, benthic mass accumulation rates also serves to highlight areas of interest for future study in related fields, such as sediment dynamics and seafloor stability. • Predicted sediment mass accumulating onto the sea floor is ~3.3 × 104 Mt. yr−1. • Highest accumulation regions are east and southeast Asia and Oceania. • Large river mouths and deltas are also regions of significant accumulation. [ABSTRACT FROM AUTHOR]

Three instrumented lines were installed on the continental slope and the basin of the Gulf of Valencia for thirteen months (May 2010 to June 2011) aiming to study particle fluxes and their relationship with environmental parameters. Total mass flux varied between 52 mg m−2 d−1 in the central part of the basin and 7199 mg m−2 d−1 in the northern slope sector. The main biogenic constituent was calcium carbonate (estimated fraction) representing more than 26% of the total flux, whereas organic matter and biogenic silica add together <10%. These percentages were similar to the proportional contents in the sea floor sediment and were mainly attributed to advection of particles from the Ebro shelf during wave resuspension events. The coincidence in the temporal variation of the Ebro River discharges with the total mass flux observed in the Gulf of Valencia suggests that the effect of river discharges >400 m−3 s−1 can be detected at least 155 km to the southwest. The temporal variation of satellite-derived chlorophyll-a abundance and organic matter flux indicated that biogenic material collected in the Gulf of Valencia is related to sea surface spring phytoplankton blooms developing in the northwestern Mediterranean. However, the temporal variation of biogenic silica corresponded better with the usual pattern of deep chlorophyll-a maxima reached during the fall season, suggesting that diatoms are a main component in subsurface phytoplankton blooms. • Ebro river discharges and storm-resuspension events control particle fluxes in the Gulf of Valencia. • Degraded organic matter is predominant in the fluxes after storms and high river discharges. • Satellite-derived surface chlorophyll-a biomass signal coincides with organic matter fluxes. • Fresh organic matter settles during the NW Mediterranean spring phytoplankton bloom. • Biogenic silica content increases during the NW Mediterranean deep chlorophyll maximum. [ABSTRACT FROM AUTHOR]

The deposition and diagenesis of pelagic marine sediments together play important roles in global geochemical cycles by returning elements, such as silica, from the hydrosphere to the geosphere and stably sequestering them within deep-ocean sedimentary sections around the world. Here, we present new, high-resolution (vertical resolution 2–5 m) seismic reflection data from the northwestern Pacific that we interpret to indicate a period of erosional activity that has returned silica to the hydrosphere and thus represents a departure from uniform sequestration by pelagic sediment deposition. The interpreted erosional features are observed as a ~ 200- to 300-m-wide horizontal variation in reflection character within the ~20-m interval overlying the regional chert/porcellanite layer. This reflection character variation is not consistent with uniform pelagic sedimentation, and it has not previously been noted in the northwestern Pacific, where most seismic data are lower-resolution. Erosion of seafloor sediments may have been caused by bottom-current activity, but the geometry of the observed features suggests that fluid-expulsion erosion from diagenesis of primarily siliceous sediment played some role in driving this mass transfer. This period of erosional activity occurred after this portion of the Pacific plate left the equatorial zone of high biological productivity ~75 Ma, and ended between approximately 35 and 55 Ma. Regardless of the details of the process, erosion of deep-ocean seafloor sediments represents a return of silica and other chemicals from the sediment to the bottom water and, if pervasive in the oceans, these processes should be accounted for in models of global geochemical cycles. • Northwestern Pacific seismic reflection data suggests paleo-seafloor erosion. • Erosion could be caused by fluid expulsion from silica diagenesis. • Seafloor erosion facilitates a return of silica from sediment to bottom water. [ABSTRACT FROM AUTHOR]

The application of thermal methods, such as Rock−Eval 6 pyrolysis or differential thermal analysis, provides complex information about sediment and rock properties, including thermal behaviour, degree of maturity, alteration of organic matter, and high temperature combustion synthesis mineral products. In this study, thermal methods included experiments on the thermokinetics of modern deep-sea sediments of the Northeast Pacific Basin. For experimental the procedure, twelve samples of siliceous clayey silts collected from the Clarion−Clipperton Fracture Zone (CCFZ), Interoceanmetal claim area, were analysed. CCFZ is highly prospective as a giant marine polymetallic deposit which contains several economically valuable metals, such as Ni, Cu, or Co. Hydrocarbon potential, thermal maturity, and roasting products were investigated. Mineralogical characteristics of thermal products were investigated. The obtained results of thermal experiments were compared with sedimentological, mineralogical, and geochemical data of bulk sediments. The total enthalpy ΔHTot. and activation energy Ea were proposed as a new lithogeochemical proxies of oxygen depletion during oxic−suboxic diagenesis. The distinctive increase in positive enthalpy (or heat transmission) was observed with the burial depth, where pelagic sediments showed strong oxygen depletion and consumed more energy during phase transformations. [ABSTRACT FROM AUTHOR]

Multivariate geostatistical methods were employed to describe the local facies of surface pelagic sediments from the Interoceanmetal IOM H11 and H22 perspective areas. Using these methods, we analyze spatial variability in seafloor features, sediment grain size, and mineralogical and geochemical composition. The data were acquired from the seafloor sediments sampled by box corer. Laboratory methods included laser grain size analysis, X-Ray diffractometry and Inducted Coupled Plasma Mass Spectrometry. Universal kriging was applied in order to generate lithofacies maps, following the "classification probability kriging" concept based on a Bayesian theorem. Under this concept, the class membership probabilities are regarded regionalized variables, so that methodical tool of geostatistics can be applied. The final result is a series of thematic maps, showing the spatial distribution of classified sediments facies, expressed by class membership probabilities, which provide information on reliability of mapping. The applied models can be useful for geological exploration of Clarion-Clipperton polymetallic nodules deposit and beyond. The lithofacies maps presented here provide information on formation processes of sediments, induced by several factors, such as diagenetic transformation of sediments and pathways of biogenic, hydrogenous or hydrothermal material. Image 1 • Multivariate regionalized classification for mapping of marine deep-sea sediments. • "Class membership probability kriging" applied for construction of lithofacies maps. • Classified sediments facies maps expressed by class membership probabilities. [ABSTRACT FROM AUTHOR]