Age, distribution, tectonics, and eustatic controls of the Paranense and Caribbean marine transgressions in southern Bolivia and Argentina

Marine transgression onto the South American continent took place at least twice in the Miocene along distinct paleogeographic corridors. The first event occurred between 15 and 13 Ma and the second between 10 and 5? Ma. Each event has particular dominant variables (tectonism, eustacy, sediment accumulation rate) that permitted the preservation of the record and development of the sea on the continent. The 15–13 Ma transgression was tectonically and eustatically controlled, flooding older sedimentary accommodation zones on the South American plate during a global high sea level, whereas the 105? Ma event was predominantly tectonically controlled, generated by tectonic loading created in the Cordillera Oriental fold-and-thrust belt. A new 7.72±0.31 Ma ⁴⁰Ar/³⁹Ar date from the Río Parapetí in Bolivia suggests that the 15–13 Ma transgression registered in Argentina produced no continental connection to the Caribbean transgression, registered in Bolivia, because of temporal constraints.     

Riddle of arsenic in groundwater of Bengal Delta Plain—role of non-inland source and redox traps

In the Bengal Delta Plain (BDP) the primary arsenic sourcing appears to be different from the global scenario. Here, the Terminal Pleistocene–Holocene depositional platform, the interactive early Holocene depositional morphology with fluvio-estuarine and marine incursions played a crucial role for arsenic sourcing and enrichment. The lenticular silt-fine sand layer between anoxic clay beds favoured entrapment of dissolved organic carbon with decayed phyto-planktons debris. The Terminal Pleistocene–Holocene transgression and regression processes may have acted as major events in the BDP. Interestingly, at the end of the last glacial maxima, the Pleistocene delta had undergone block movements, wherein some parts of the platform were raised above the level of Holocene deposition. Those blocks were found to be free from arsenic in the groundwater. The sea, during re-emerging inundation (10–7 ka BP), has witnessed a monsoon-induced environment in the BDP with the resultant oscillation of sea level leading to higher upsurge towards the north. This might have resulted in the marine incursion and inundation in pre-existing land depressions. Meanwhile arsenic entrapments through marine incursion as well as enrichment in the presence of organic carbon/DOC and/or Fe/Mn/Al catalytic agents could have developed into localised redox traps. It may be of relevance that due to the repetitive transgressive–regressive phases in Holocene, resulting in periodic exposure and weathering of iron-bearing minerals and consequent iron enrichment in the aquifer system. The iron, thus present, had free charge to host arsenic as a sink. It appears that arsenic, wherever found, would likely be of atypical localised exhaustible phenomenon, both in horizontal and vertical context. It also rationalises the cause of the absence of arsenic in the other nearby Pleistocene platform, which has not come across Holocene interaction and marine incursion, as to the likely limiting condition for the search for arsenic in the BDP or beyond.     

Vegetation history of the penultimate glacial period (Marine isotope stage 6) at Ioannina,north‐west Greece

The vegetational history of the penultimate glacial period, Marine Isotope Stage (MIS) 6 (c. 185–135 ka), has remained relatively unexplored. Here we present a new record from the Ioannina basin, north‐west Greece, which constitutes the highest‐resolution terrestrial pollen record for this interval produced to date. It shows that the vegetation history of MIS 6 in this region can be divided into two parts: an early period (185–155 ka) with pronounced oscillations in tree population extent, and a later period (155–135 ka) with much smaller tree populations and subdued oscillations. This pattern is analogous to the MIS 3/MIS 2 division during the last glacial in the same sequence, although the early part of MIS 6 had larger Pinus populations and fewer temperate trees relative to the equivalent interval in MIS 3. This implies cooler and wetter conditions, which is somewhat counterintuitive given the high summer insolation during MIS 6e, but is in line with other palaeoclimatic evidence from the Mediterranean. Comparison with North Atlantic records suggests that despite the absence of pronounced iceberg discharges during MIS 6, North Atlantic millennial‐scale variability had a significant downstream impact on tree populations in north‐west Greece. Copyright © 2011 John Wiley & Sons, Ltd.     

OCEANOGRAPHY & MARINE GEOLOGY

正20141900Lan Xianhong(Key Laboratory of Marine Hydrocarbon Resources and Environmental Geology,Ministry of Land and Resources,Qingdao 266071,China);Zhang Zhixun Geochemical Characteristics of Trace Elements of Sediments from Drillhole SFK-1     

Critical Top Tension for Static Equilibrium Configuration of A Steel Catenary Riser

This paper aims to present the critical top tension for static equilibrium configurations of a steel catenary riser（SCR） by using the finite element method. The critical top tension is the minimum top tension that can maintain the equilibrium of the SCR. If the top tension is smaller than the critical value, the equilibrium of the SCR does not exist. If the top tension is larger than the critical value, there are two possible equilibrium configurations. These two configurations exhibit the nonlinear large displacement. The configuration with the smaller displacement is stable, while the one with larger displacement is unstable. The numerical results show that the increases in the riser＇s vertical distances, horizontal offsets, riser＇s weights, internal flow velocities, and current velocities increase the critical top tensions of the SCR. In addition, the parametric studies are also performed in order to investigate the limit states for the analysis and design of the SCR.     

ROCKS & MINERALS DETERMINATION AND ANALYSIS

正20142093Chen Daohua(Guangzhou Marine Geological Survey,Guangzhou 510075,China);Diao Shaobo The Latest Progress of Geological Marine Testing Technology in China(Rock and Mineral Analysis,ISSN0254-5357,CN11-2131/TD,32(6),2013,p.850-859,105refs.)Key words:chemical analysis,China     

Analysis on Marine Science and Technology Strategy and Key Layout of Japan and the Inspirations to China

The Basic Ocean Law (BOL) and Basic Ocean Plan (BLP) are important guarantee for the maritime strategy of Japan, which has established a complete policy system for the development of marine science and technology. On the other hand, the Japanese Government has started some major marine strategies and plans to promote the BLP. In this paper, the marine science and technology plans launched by the Japanese Government and its participation in the international cooperative research projects were introduced. The research of Japan Marine Science and Technology Center and the University of Tokyo Institute of Oceanography in the long-term planning and focus on the layout features, deep sea research technology layout, contents and advanced equipment were analyzed. At last, some recommendations for China’s development on marine science and technology were proposed, such as strengthening the legislation work and process, carrying out research and development of marine infrastructure with independent intellectual property rights, actively participating in international large-scale ocean plan, improving the discourse right and enhancing national maritime awareness and suggestions and so on.     

Marine riser emergency disconnection analysis using scalar elements for tensioner modelling

This work proposes nonlinear parallel spring-damper scalar elements in series with a rigid beam element to represent drilling riser tensioner behavior during an emergency disconnection scenario in global riser analysis. The software package used was Orcaflex. This is a simpler approach than the more complex, full hydraulic-pneumatic-mechanic dynamic simulation modelling of the tensioning system, commonly used in literature, which can be time consuming and numerically more sensitive. The model can also be used to represent top tension variation in global riser analysis, allowing for more complex and precise simulations, especially for fatigue life and overpull estimations. The results show adequate agreement with the researched bibliography.     

Experimental investigation of the effects of the coverage of helical strakes on the vortex-induced vibration response of a flexible riser

The effects of different helical strake coverage on the vortex-induced vibration (VIV) of a model flexible riser were studied experimentally, with the aim of further improving the understanding of VIV responses. Uniform and linearly sheared currents were simulated to study response parameters such as non-dimensional displacement, fatigue damage, suppression efficiency, and the comprehensive evaluation is further studied. Test results of the bare model for a uniform current showed that the behavior of both the standing wave and traveling wave dominated VIV displacement. However, for a linearly sheared current, traveling wave behavior dominated VIV displacement in the high-velocity range. The results of the straked model tests indicated that the response was strongly dependent upon the amount of coverage of helical strakes. The flexible riser with 75% strake coverage gave the best comprehensive evaluation in a uniform current, and 50% strake coverage gave the best comprehensive evaluation in a linearly sheared current.     

Seeing the ocean through the eyes of seabirds: A new path for marine conservation?

Seeing the ocean through the eyes of seabirds could help meet the challenges of managing common-pool marine resources both in protected and unprotected areas. First, seabirds are top-predators, exposed to all threats affecting the oceans, and this makes them ideal sentinel organisms for monitoring changes within marine ecosystems. Second, seabirds cross both ecological and political boundaries, and following their movements should help making interdependencies within and between marine ecosystems more visible. Third, seabirds are conspicuous and often charismatic animals, which interact differently with different groups of stakeholders and provide the opportunity to acknowledge and discuss each other's values and interests. In this paper, we present these research avenues using a seabirds’ view, for tackling marine conservation and management issues, and we give operational examples of implementation based on our work in the English Channel.