Radiaxial fibrous calcites as low-magnesian calcite cement precipitated in a marine-meteoric mixing zone

Abstract Radiaxial fibrous calcite (RFC) has previously been interpreted as a marine or replacive cement. Study of the Dongjeom Formation (Early Ordovician), Korea, shows that RFC can form in marine‐meteoric mixing zones as a low‐magnesian calcite (LMC) cement. RFC in the shallow‐marine Dongjeom Formation occurs in arenaceous limestones at the top of a transgressive facies overlying a regressive facies. It shows well‐developed growth zonation, and lighter oxygen isotope values and more radiogenic strontium isotope ratios than those of Early Ordovician marine calcite. Such petrographic and chemical evidence indicates that the RFC was precipitated as a primary LMC cement in a marine and meteoric mixing zone. Owing to the unique environment of formation, the Dongjeom RFC is characterized by growth zonal fabric comprising alternating subzones, which may indicate precipitation from varying fluids. In addition, this study documents the importance of substrate for development of RFC. Early ‘nucleation’ for RFC occurred mainly on microcrystalline skeletal grains and internal sediments, whereas on homogeneously altered substrates, thin‐coated banding structure developed, ultimately forming coarse crystalline spar. This suggests that microcrystalline substrates are preferred sites for nucleation of RFC.     

Nutrient control of the global occurrence of isolated carbonate banks

The growth and origin of the world's isolated carbonate banks are as yet not completely understood. This paper presents a comparison of the areas, depths, and latitudinal distribution of the world's carbonate banks. These are then compared with chemical parameters of seawater in the upper mixed zone of the oceans and at depth. The results allow large-scale inferences to be made on the interacting controls on bank growth and distribution. The data support the hypothesis that nutrient-rich waters commonly control bank depth and size.     

Scenarios for the Future Population of Sydney

The period 1996-2001 has witnessed a refocusing of population growth on Sydney and Melbourne as both cities have developed significant concentrations of so-called 'new economy' jobs and taken on, to greater or lesser extents, the characteristics of global cities. The consequence of these trends, for Sydney most particularly, is population growth. This paper establishes this demographic reality by describing recent demographic trends in Sydney and possible future scenarios for Sydney's population, given differing levels of fertility, internal migration and international migration. A related future trend is also traced--that the number of households in Sydney will grow more rapidly than the population due to changes in household structure. This raises the issue of how and where these households will be accommodated, given the relative land shortage in the Sydney Statistical Division and given that there is no doubt that planners in New South Wales will be attempting to maintain and enhance Sydney's status as a global city. In sum, the paper argues that Sydney planners should be preparing for growth of around one million people in the next 20 years and a further one million in the following 30 years. To maintain that potential future residents of Sydney can be redirected to other parts of New South Wales is a vain hope.     

汇聚造山带变质矿物冠状反应边及生长环带

哀牢山、澜沧江、高黎贡山、念青唐古拉山等汇聚造山带变质岩中,发现一些标型或特征变质矿物间形成冠状反应边或生长环带。它们是变质过程的真实记录,反映了变形变质环境条件的不断变化,完整或直观地表现了不同地体或构造带PTt轨迹特征。可帮助恢复汇聚造山带中不同地体构造属性,为研究造山带PTtD轨迹和PTDX轨迹,提供准确资料。可从另一侧面了解汇聚造山带的演化史。     

新旧动能转换视角下山东省土地资源保障能力研究

充分认识山东省土地资源利用所面临的形势,是保障经济社会新旧动能有序转换的基本问题。土地资源与新旧动能转换存在着相互渗透、相互促进的关系,土地资源以宏观调控的方式,促进新旧动能的有序转换,是保障新旧动能有序转换的有效手段;新旧动能转换又是土地资源管理、利用和保护的内在需求。该文从新旧动能转换基本概念出发,深入剖析了二者之间的相互关系,从土地利用方式、土地利用结构和布局、土地质量和土地生态环境四个方面,分析了新旧动能转换对土地保障能力的要求,探究了土地资源利用管理中的旧动能和新动能,总结归纳土地资源管理、利用和保护对经济发展的新旧动能转换的作用,提出了保障新旧动能有序转换的措施。     

Growth structures and growth strata of the Qianjiadian Basin in the western Yanshan fold and thrust belt,North China

The northwestward subduction of the Izanagi Plate beneath the eastern Eurasian Plate during the Late Mesozoic caused a series of compressional deformation events in the Yanshan fold and thrust belt(YFTB), but the tectonic deformation timing, tectonic properties and relationship between tectonic uplift and sediment accumulation in the intermontane basins continue to be debated. For this reason, the sedimentology, sediment provenance, and basin structure of the Qianjiadian Basin(QJB) in the northern Beijing region during the Late Jurassic and Early Cretaceous were studied in detail. The results suggest that a fault-propagation fold-type(FPFT) growth structure and growth strata developed on the western edge of the QJB and that the top part of Member 2 and Member 3 of the Tuchengzi Formation are growth strata controlled by the limb rotation mechanism. In two small thrust faults in the QJB, the Mesoproterozoic Xiamaling Formation is thrust over the Tuchengzi Formation, and these faults may have controlled the development of the fault-bend fold-type growth strata. An analysis of the "source-to-sink" process suggests that the hanging wall succession of the Shangyi-Pingquan fault(SPF) was the main source area of the Late Jurassic to early Early Cretaceous strata in the QJB. A zircon206 Pb/238 U age of 140.8±2.4 Ma for the volcanic rocks at the bottom of the FPFT growth strata represents the timing of the initiation of FPFT growth structure development. The discovery of the FPFT growth structure and growth strata in the QJB indicate that the QJB was an intermontane flexural basin controlled by fold and thrust structures during the early Early Cretaceous. Near the E-W-trending SPF, the NE-SW-trending Qianjiadian thrust fault(QJTF) and two small intrabasinal thrust faults may constitute a unified right-lateral strike-slip system that formed in response to the northwestward flat subduction of the Izanagi Plate beneath the East Asian continent during the Jurassic-Early Cretaceous.     

里下河古潟湖相软土基本工程特性与形成机理的关系

淮盐高速公路穿越的里下河地区,广泛分布有高含水量、高压缩性古潟湖相软土,工程性质很差,该层软土的工程性质与里下河古潟湖的形成机理密切相关。本文在对潟湖形成一般模式总结的基础上,结合苏北地区第四纪以来沉积环境及区域地质地貌变化情况,得出里下河古潟湖相软土的形成机理,并对淮沿高速公路盐线典型地段土样工程性质进行分析,根据土的工程性质的垂直变化,判断古潟湖相软土的分布情况,进而寻找古潟湖相软土工程性质与其形成机理之间的关系。     

不同饵料对斑节对虾(Penaeus monodon)幼虾的生长及对WSSV 敏感性的影响

采用5种不同饵料投喂斑节对虾幼虾,研究各饵料对幼虾的体长、体重及成活率的影响,实验周期为20天;然后用投喂攻毒的方法分别感染WSSV,观察不同饵料对幼虾WSSV敏感性的影响。实验周期为12天。结果表明,投喂卤虫无节幼体组的幼虾,其体长、体重增长明显优于其它各组（P〈0．01）,随后依次为贝肉组、鱼肉组、人工配合饲料组、虾片组。不同饵料对幼虾WSSV敏感性的影响也有差异：投喂感染WSSV后,卤虫组和鱼肉组成活率最高,明显高于贝肉组、人工配合饲料组和虾片组（P〈0．01）。PCR检测表明,感染后全部幼虾个体为病毒阳性。     

Abundance and growth of larval and early juvenile cod (Gadus morhua) in relation to variable environmental conditions west of Iceland

Around Iceland, the west- and north-flowing coastal current, induced by freshwater runoff, provides a transport mechanism for pelagic eggs and larvae derived from the main spawning grounds off the southwest coast to the main nursery grounds off the north coast. In the present study, abundance and growth of larval and juvenile cod were recorded during a series of cruises conducted in June/July of 1998–2001 along the drift route southwest and west of Iceland. The cruises provided information on approximately 2–8-week-old individuals. Hatch dates and abundance varied greatly between years. Hatch dates ranged from Julian Day 92 to 167. Growth rate differed also between the years studied. Relative abundance was generally greatest in temperatures above 7.5 °C and in low-salinity waters, characteristic for the coastal current. The study demonstrates the link between the coastal current and larval/juvenile distribution, thus providing evidence for its importance in promoting successful recruitment of the Icelandic cod stock.