Effects of wave breaking on wave statistics for deep-water random wave train

The experimental studies of the breaking effects on wave statistics for deep-water random waves are presented. It is especially focused on the behavior of kurtosis of surface elevations due to wave breaking. Wave breaking suppresses the maximum limit of kurtosis of the surface elevation, although skewness depends on characteristic wave steepness. The mean instantaneous wave steepness of breaking waves defined using the zero-down-crossing method was much lower than expected from the Stokes waves.     

法向承力锚(VLA)--一种适用于深海工程的新型系泊基础

深水系泊基础是深水系泊系统的重要组成,随着海洋油气资源开发的加速发展,深水系泊系统的关键技术成为国际海洋油气资源开发的重要研究领域.法向承力锚（VLA）是一种崭新的适用于深海油气资源开发的系泊基础形式,论文对其应用、性能特点、工作原理、安装与回收以及计算分析方法等进行了全面介绍,以期对科研人员进一步认识深水系泊系统的关键技术有所帮助,并对国内深水系泊系统的研发起到一定的借鉴作用.     

Sedimentation styles and depositional processes in a Middle to Late Jurassic slope environment, Bowser Basin, northwestern British Columbia, Canada

The Middle to Upper Jurassic Todagin assemblage in northwestern British Columbia, Canada, was deposited in the Bowser Basin above arc-related rocks of the Stikine terrane. Sedimentary structures indicate that a variety of gravity flow processes were involved in transport and deposition in deep-water slope environments. At Mount Dilworth, laterally continuous and channelized turbidites are interbedded with and overlain by mass-transport deposits in which sedimentary clasts are supported in a mudstone matrix. More than 50% of the succession consists of mass-transport deposits, indicating significant slope instability. A 300 m thick mass-transport complex exposed near the top of the succession is interpreted to result from tectonic activity, which triggered a major change in sediment supply from a local source area. At Todagin Mountain, a channel complex displays three successive channel-fills with associated overbank sedimentation units. Mass-transport deposits are rare, and confined to channel axes. Channels 1 and 2 are characterized by 40-50 m thick, ungraded pebble clast-supported conglomerate while the uppermost Channel 3 contains graded beds and occasional traction structures. The gradual change from erosive and amalgamated channel deposits at the base, to more aggradational channels at the top, is related to elevation of the equilibrium profile. Creation of accommodation favored aggradation on the mud-dominated slope succession and construction of well-developed channel-levee systems. The vertical succession exposed at Todagin Mountain is consistent with normal progradation of the slope under high sedimentation rates. In the Mount Dilworth area, extensional faulting associated with development of the restricted Eskay rift in the early Middle Jurassic produced a dissected basement above which the Todagin assemblage was deposited. These structures were inverted during collision of the Stikine and Cache Creek terranes, and likely played a major role in the stratigraphic evolution of the deep-water architectures.     

Topographically constrained deep-water flows in the Baltic Sea

Density-driven currents have a significant impact on the deep-water characteristics of the Baltic Sea since they account for the water exchange between the deeper parts of neighbouring basins. The essential quantitative problem is to determine the flow rates in relation to a set of external parameters such as the strait topography, the stratification, and the internal circulation of the upstream basin. Using hydraulic theory it is possible to accomplish this by analysing the dynamical constraints that limit the deep-water flux between adjacent basins. On the basis of these results, the deep-water flows through the Bornholm Channel and the Irbe Strait are compared.     

Is Centrophorus squamosus a highly migratory deep-water shark?

Deep-water sharks are considered highly vulnerable species due to their life characteristics and very low recovery capacity against overfishing. However, there is still limited information on the ecology or population connectivity of these species. The aim of this study was to investigate if the species Centrophorus squamosus could make long displacements and thus confirm the existence of connectivity between different deep-water areas. In addition, the study was the first attempt to use tagging techniques on deep-water sharks, since it has never been undertaken before. Five C. squamosus were tagged with satellite tags (PAT) in the El Cachucho Marine Protected Area (Le Danois Bank) located in waters of the North of Spain, Cantabrian Sea (NE Atlantic). Data from four of these tags were recovered. One of the sharks travelled approximately 287 nm toward the north east (French continental shelf) hypothetically following the continental slope at a mean depth of 901±109 m for 45 days. Two other sharks spent almost 4 months traveling, in which time they moved 143 and 168 nm, respectively, to the west (Galician coast). Finally, another leafscale gulper shark travelled to the NW (Porcupine Bank) during a period of 3 months at a mean depth of 940±132 m. Depth and temperature preferences for all the sharks are discussed. Minimum and maximum depths recorded were 496 and 1848 m, respectively. The temperature range was between 6.2 and 11.4 °C, but the mean temperature was approximately 9.9±0.7 °C. The sharks made large vertical displacements throughout the water column with a mean daily depth range of 345±27 m. These preliminary results support the suggestion of a whole population in the NE Atlantic and confirm the capacity of this species to travel long distances.     

Geochemical evolution of Oligocene–Middle Miocene sediments in the deep-water area of the Pearl River Mouth Basin,northern South China Sea

The deep-water area of the Pearl River Mouth Basin in the South China Sea has received much scientific attention since the Ocean Drilling Program (ODP) Leg 184 in 1999 due to its potential economic prospects and distinct tectono-sedimentary evolutionary processes. In this study, we present the composition of major and trace elements from two newly sampled deep-water boreholes (BY6 and LW3) in the Baiyun Sag of the southern Pearl River Mouth Basin. The geochemical evolution in the Oligocene–Middle Miocene, as well as potential controlling factors, are investigated based on a comparative study with previous data from ODP site 1148 and borehole PY33. The Chemical Index of Alteration (CIA) and A–CN–K plot reveal that the observed weathering trends are not compatible for the four discussed boreholes. Sedimentary sorting is primarily observed in borehole PY33, where data trend away from the A apex to the feldspar join in the A–CN–K plot and show a spread of Al₂O₃/SiO₂ and Nb/Zr ratios. Compared to chemical weathering and hydrodynamic sorting, provenance has a greater impact on sediment composition of the deep-water area. From the north, the Pearl River was the primary sediment supply. However, a positive Eu anomaly and the provenance discrimination diagrams (i.e., La/Th versus Th/Yb and Zr/Co versus Th/Co) reveal the mafic nature of borehole BY6 sediments in the Zhuhai–Lower Zhujiang (32.0–18.5 Ma) and Upper Hanjiang (13.8–10.5 Ma) formations. These compositions are unusual and differ from the well-defined felsic sources in the majority of the Baiyun Sag; these discrepancies are likely related to multistage magmatism. The sediments at site 1148 are characterized by slightly enriched heavy rare earth elements and relatively high Zr/Co ratios, which could possibly be caused by zircon enrichment from local sources.     

Late Quaternary sedimentation on the Mid-Atlantic Reykjanes Ridge: clay mineral assemblages and depositional environment

Sediment samples from the Mid-Atlantic Reykjanes Ridge (59°N) were taken to get information about sediment genesis and to identify different sources during the late Quaternary. Samples were investigated by X-ray diffraction and grain-size analyses. The clay mineral assemblages in sediments of the Reykjanes Ridge reflect paleoceanographic changes during the late Quaternary. Holocene sediments are characterized by high contents of smectite, mainly of less developed crystallinity. In the spatial distribution of clay minerals high smectite concentrations on the eastern flank and slightly decreasing concentrations on the western flank of the Reykjanes Ridge indicate the action of bottom-water transport. The smectite originates mainly from the volcanogenous Icelandic shelf and reflects the influence of Iceland-Scotland Overflow Water (ISOW). Stratigraphic variability in the clay mineral composition reflects predominantly the influence of different sources, resulting from oceanographic and glacial transport processes. During glacial time sediment transport is due mainly to input by icebergs. Increasing amounts of illite, chlorite, and kaolinite characterize ice-rafted sediments of the “Heinrich layers”. In these sediments smectite crystallinity is well developed. In contrast, several other ice-rafted layers contain smectite with low crystallographic order, similar to smectites of Holocene age. The icelandic source was proved by distinct amounts of basaltic glass in the coarse-grained sediment. At approximately 55 ka increasing amounts of chlorite and kaolinite suggest an enhanced influx of warm North Atlantic surface waters. This hypothesis is supported by a high carbonate shell production at this time. Relative low concentrations and the well-developed crystallinity of smectite minerals characterize the Last Glacial Maximum (LGM; 18–16 ka), indicating a reduced supply of fine icelandic material. Shortly after the LGM, at the beginning of termination IA, a distinct increase in fine-grained quartz (<2μm) and smectite are visible, which are proposed to reflect a supply of fine-grained ice-rafted material. At 13 ka linear increasing smectite concentrations of lower crystallographic order indicate increasing supply of fine-grained material from Iceland, linked to reinitiation of bottom currents of the ISOW. Full reinitiation is indicated at around 10 ka, where a strong increase in smectite of low crystallographic order is detected.     

Numerical Simulation of Deep-Water Convection in the Gulf of Lion

The unsteady-state process of deep-water convection in the Gulf of Lion has been observed and investigated in recent decades. However, the mechanisms of the uncertainty and irregularity of the deep-water convection in this region have not yet been fully understood. In this study, the effects of time variation of the surface buoyancy flux on the formation of the deep-water convection are examined. Numerical simulations using the Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS^®) with the NRL Coastal Ocean Model (NCOM) as an oceanic component were conducted for the period from October 1998 to September 2000 to cover two winters, 1998–1999 and 1999–2000, over the Gulf of Lion region. The results show large differences in the deep-water convection between the two winters, even though the total surface heat fluxes during the two winter seasons are similar. The differences are related to the time variation of the surface buoyancy flux that causes large differences in the preconditioning and mixing stages of the convection.     

南海珠江深水扇系统的层序地层学研究

位于古珠江大河及其浅海陆架富砂珠江三角洲下方的陆坡深水区白云凹陷是沉积大型深水扇的有利地域,宏观认识的进展指导了白云深水陆坡区系统的层序地层学研究,并因此发现了多层序叠置的南海珠江深水扇系统,使其成为具有油气勘探潜力的新领域。南海珠江深水扇系统的层序地层学研究包含了以下关键内涵层序地层学解释中在承认各种资料的分辨率、多解性和局限性的同时,强调多学科资料的综合应用、相互印证,强调周期性海平面变化对沉积的控制作用研究,强调地震反射相位等时界面确认的有效性,强调层序界面的反复确认,强调生物地层时代、相对海平面、全球海平面与层序界面的响应研究,强调层序格架内各沉积体的相互响应关系研究等。层序地层格架的建立导致了珠江深水扇系统的发现,揭示了珠江大河流域、陆架区大型珠江三角洲系统与陆坡区珠江深水扇系统的耦合关系,揭示了珠江深水扇与海平面变化的响应关系,揭示了珠江深水扇与古地理的响应关系。珠江深水扇系统的发现有力地推动了南海陆坡深水区的油气勘探。     

Confined channel-levee complex development in an elongate depo-center: Deep-water Tertiary strata of the Austrian Molasse basin

A basin axial-channel belt was largely responsible for the observed distribution of coarse-grained gravity-flow deposits in the Tertiary Puchkirchen and basal Hall formations of the Molasse foreland basin in Upper Austria. Elements of this depositional system, mapped in three-dimensional (3D) seismic-reflection data, include channel-belt thalweg, mass-transport complexes, overbank wedge, overbank lobe, and tributary channel. The primary objective of this paper is to develop a comprehensive understanding of the sedimentary processes that were prevalent in the channel-belt complex through the analysis of well data, including drill cores and wireline logs, in conjunction with 3D seismic interpretations.