Paleo- to Eoarchean crustal evolution in eastern Hebei,North China Craton: New evidence from SHRIMP U–Pb dating and in-situ Hf isotopic study of detrital zircons from paragneisses

In the Caozhuang complex in eastern Hebei, North China Craton, the Paleo- to Eoarchean crustal evolution was earlier revealed by the preservation of detrital zircon grains older than (or as old as) 3.8 Ga in fuchsite-quartzite. In order to test if the Eoarchean antiquity is also preserved in rocks other than the fuchsite quartzite, we collected two paragneisses, a hornblende gneiss and a garnet–biotite gneiss, from Huangbaiyu village and dated their detrital zircon grains. The zircon dating of the hornblende gneiss yielded concordant ²⁰⁷Pb/²⁰⁶Pb ages ranging from 3684 to 3354 Ma. However, an older date of 3782 Ma with 18% discordancy was also obtained. Detrital zircon grains from the garnet–biotite gneiss gave a similar ²⁰⁷Pb/²⁰⁶Pb age range, from 3838 to 3342 Ma. The metamorphic domains of the zircon grains from both samples, including the strongly recrystallized cores and rims, recorded an overprinting metamorphism at ca. 2.5 Ga, which correlates with the most widespread tectono-thermal event in the North China Craton. In situ zircon Hf-isotope analyses on the dated zircon grains yielded a wide range of model ages (T_DM1) from 4.0 to 3.3 Ga with corresponding ε_Hf(T) from −36.0 to +4.8. This suggests that the evolution of the crustal segment in this area has involved multiple phases of juvenile crustal addition as well as recycling of older crustal rocks. The new geochronological results imply the presence of a significant amount of Eoarchean crustal fragments in the eastern Hebei area. The sedimentary protoliths of the paragneisses and other high-grade metamorphic rocks in the Caozhuang complex were probably deposited between 3.4 and 2.5 Ga.     

Coral communities and reefs from Guerrero,Southern Mexican Pacific

Corals in the Eastern Pacific extend south from the Gulf of California to Ecuador and oceanic Chile, and west from Colombia to Clipperton Atoll. Nevertheless, large stretches of the Mexican Pacific remain fundamentally unstudied. Therefore, to assess the current conditions of coral communities, a coastal fringe ～300 km long (17°40′ N, 101°39′ W to 16°46′ N, 99°49′ W) was surveyed within the Southern Mexican Pacific, between 2005 and 2009. Fifteen stony coral species were identified at 13 coral communities and six Pocillopora‐dominated fringing reefs, with Pocillopora verrucosa and Pocillopora damicornis the primary contributing taxa. Reef development was identified in embayments or behind rocks or islands that offered shelter from northern and northwestern winds. Observations of Pocillopora effusus, Pocillopora inflata, Porites lobata, Pavona clavus, and Pavona varians expanded the species known geographic ranges by several degrees of latitude, suggesting reef building fauna comprised a mixture of widespread and relatively rare Eastern Pacific corals. Results indicated greater live coral cover in the Ixtapa‐Zihuatanejo area (15–73%) than in the Acapulco localities, which had high algal dominance; the reefs in the latter region exhibited high erosion. Regional differences are likely the result of long‐standing anthropogenic pressures around Acapulco since 1950, when it became an important tourist destination. This paper is the first detailed report of ecologically stressed corals and coral reefs from the state of Guerrero on the Mexican Southern Pacific coast.     

Tracing dissolved organic matter cycling in the eastern boundary of the temperate North Atlantic using absorption and fluorescence spectroscopy

Apparent oxygen utilization (AOU), dissolved organic carbon (DOC), coloured dissolved organic matter (CDOM) absorption spectra, and CDOM fluorescence characteristic of aromatic amino acids (excitation/emission 280 nm/320 nm; F(280/320)) and marine-humic like substances (320 nm/410 nm; F(320/410)) were measured in full depth during a cruise in the temperate Eastern North Atlantic (ENA). An optimum multi-parameter (OMP) inverse method was run to calculate water mass proportion-weighted average (archetypal) concentrations of these chemical parameters for all water masses and samples. Archetypal concentrations retain the variability due to water mass mixing and basin scale mineralization from the water mass formation sites to the study area. Conversely, the difference between measured and archetypal concentrations, retain the variability due to dissimilarities in mineralization processes within the study area. Our analysis indicates that DOC supported 26±3% of the AOU in the dark temperate ENA and that basin scale processes occurring at and from the formation area of the water masses explained 63% of the total DOC variability. Our data also suggests that DOC remineralized at the basin scale was of lower molecular weight, and with a lower proportion of fluorescent aromatic amino acids than found within the study area. The relationship between the absorption coefficient at 254 nm (a_CDOM(254)) and AOU indicates that a_CDOM(254) was consumed during organic matter remineralization in the dark ocean, with 55% of the variability being explained by basin scale processes. The relationships of F(320/410) with AOU and DOC confirmed that marine humic-like substances are produced by microbial degradation processes, at a rate of 6.1±0.9×10⁻³ mg equivalents of QS mol AOU⁻¹. Our results also indicate that basin-scale remineralization processes account for 85% of the total variability of F(320/410), emphasizing that large scale processes control the formation of humic-like substance in the dark ENA.     

更新世以来南海表层水温变化及其古气候意义

南海南部2Ma以来古温度记录显示该海域更新世以来海水表层温度的不断降低,并且以冰期降低为特征,间冰期温度变化不大。南海南北经向表层海水温差的大小,反映了东亚冬季风的强弱变化,2 Ma以来的温差变化说明东亚冬季风在中更新世之前的持续强化,中更新世之后不断减弱,而在晚第四纪时又再次转为增强,同时叠加在长期变化趋势之上的是轨道时间尺度上冰期增强间冰期减弱的循环波动。青藏高原构造作用可能对中更新世时期东亚冬季风强化产生重要影响,而更新世以来东亚冬季风变化的整体趋势及轨道尺度变化主要受全球冰量变化和低纬ENSO影响。     

A review of eastern tropical Pacific oceanography: Summary

The collection of articles in this volume reviewing eastern tropical Pacific oceanography is briefly summarized, and updated references are given. The region is an unusual biological environment as a consequence of physical characteristics and patterns of forcing – including a strong and shallow thermocline, the ITCZ and coastal wind jets, equatorial upwelling, the Costa Rica Dome, eastern boundary and equatorial current systems, low iron input, inadequate ventilation of subthermocline waters, and dominance of ENSO-scale temporal variability. Remaining unanswered questions are presented.     

Primary production in the eastern tropical Pacific: A review

The eastern tropical Pacific includes 28 million km² of ocean between 23.5°N and S and Central/South America and 140°W, and contains the eastern and equatorial branches of the north and South Pacific subtropical gyres plus two equatorial and two coastal countercurrents. Spatial patterns of primary production are in general determined by supply of macronutrients (nitrate, phosphate) from below the thermocline. Where the thermocline is shallow and intersects the lighted euphotic zone, biological production is enhanced. In the eastern tropical Pacific thermocline depth is controlled by three interrelated processes: a basin-scale east/west thermocline tilt, a basin-scale thermocline shoaling at the gyre margins, and local wind-driven upwelling. These processes regulate supply of nutrient-rich subsurface waters to the euphotic zone, and on their basis we have divided the eastern tropical Pacific into seven main regions. Primary production and its physical and chemical controls are described for each.Enhanced rates of macronutrient supply maintains levels of primary production in the eastern tropical Pacific above those of the oligotrophic subtropical gyres to the north and south. On the other hand lack of the micronutrient iron limits phytoplankton growth (and nitrogen fixation) over large portions of the open-ocean eastern tropical Pacific, depressing rates of primary production and resulting in the so-called high nitrate-low chlorophyll condition. Very high rates of primary production can occur in those coastal areas where both macronutrients and iron are supplied in abundance to surface waters. In these eutrophic coastal areas large phytoplankton cells dominate; conversely, in the open-ocean small cells are dominant. In a ‘shadow zone’ between the subtropical gyres with limited subsurface ventilation, enough production sinks and decays to produce anoxic and denitrified waters which spread beneath very large parts of the eastern tropical Pacific.Seasonal cycles are weak over much of the open-ocean eastern tropical Pacific, although several eutrophic coastal areas do exhibit substantial seasonality. The ENSO fluctuation, however, is an exceedingly important source of interannual variability in this region. El Niño in general results in a depressed thermocline and thus reduced rates of macronutrient supply and primary production. The multi-decadal PDO is likely also an important source of variability, with the ‘El Viejo’ phase of the PDO resulting in warmer and lower nutrient and productivity conditions similar to El Niño.On average the eastern tropical Pacific is moderately productive and, relative to Pacific and global means, its productivity and area are roughly equivalent. For example, it occupies about 18% of the Pacific Ocean by area and accounts for 22–23% of its productivity. Similarly, it occupies about 9% of the global ocean and accounts for 10% of its productivity. While representative, these average values obscure very substantial spatial and temporal variability that characterizes the dynamics of this tropical ocean.     

Effects of wind waves of the Pacific westerly on the eastern Pacific wave transport

There exists a tongueshaped swelldominance pool known as Swell Pool (SP) in the Eastern Pacific region. The monthlymean wave transports (WT) for each month of 2000 is computed using the wave products of ECMWF reanalysis data. By comparing the 2000 monthlymean WT and monthlymean wind field from QUICKSCAT, large differences are found between the wave transport direction and the wind direction over the Eastern Pacific. This may serve as an evidence for the existence of the SP in this region. The work done in this study indicates that the sources of swell in the Tropical Eastern Pacific (TEP) are in the westerly regions of the Southern and Northern Pacific.     

临清坳陷东部三叠系沉积岩地球化学特征及构造意义

碎屑沉积岩的物质组成对其形成的构造背景具有重要的指示作用。通过对临清坳陷东部三叠系碎屑沉积岩样品地球化学主量和微量元素分析表明：三叠系岩石样品主要为成熟度较低的杂砂岩和长石砂岩;碎屑沉积岩的母岩总体上与大陆地壳组成基本一致,原岩以沉积岩和花岗岩为主;临清坳陷东部中生代早—中三叠世处于靠近大陆岛弧的活动大陆边缘构造环境,其动力学机制与早期秦岭洋壳向华北板块俯冲、晚期扬子板块和华北板块碰撞作用有关。研究结果为确定三叠纪时期华北东部南侧的构造环境提供了地球化学方面的证据。     

Fishermen responses on marine protected areas in the Baltic cod fishery

Much of the research that concerns the impacts of management measures in the eastern Baltic cod fishery has focused on fish stock rather than understanding fishermen's attitudes towards regulations. Hence, there is little information available on fishermen's responses although they are the ones whom the regulations affect most profoundly. This study analyses the views of fishermen towards management measures with an emphasis on fishing closures (marine protected areas, MPAs). Swedish log-book data from 1996 to 2005 were used to describe MPA induced fishing effort displacements. Fishermen argued that MPAs have been inefficient in conservation of cod stock. The enlargement of Bornholm MPA in 2005 caused substantial effort displacement towards areas dominated by smaller sized fish. This contributed to the increased discarding of juvenile cod. Enlarged MPAs also intensified competition between different fleet segments and reallocated fishing areas. To reduce fishing mortality, fishermen suggested days-at-sea (effort) regulation and an effective landings control system for all fleets that exploit cod stocks in the Baltic Sea Main Basin. These measures would better motivate fishermen for mutual rule compliance, which is a prerequisite for a sustainable cod fishery.