巴西中部元古代Parano和Bambu′i群叠层石的古生态和构造背景(英文)

叠层石的形态和它们与陆源沉积的关系反映了沉积盆地的构造背景。在巴西中部地区 ,叠层石出现在中元古和新元古代的 Paranoa′群、Vazante群和 Bambui′群。根据沉积学和矿物学的研究分析 ,Paranoa′群形成于被动边缘盆地 ,而另外两个群形成于前陆盆地。Vazante群沉积在形成巴西褶皱带的山脉附近 ,然而 Bam bui′群的大部分都形成于克拉通地区。通常远离山脉褶皱带的 Paranoa′群和 Bambui′群内的叠层石建造的形态和规模的改变与环境的变化有关。在柱状生长方向的频繁变化和不规则的丰富陆源物质的夹层进入叠层石 ,表征活跃的构造背景 ,例如在Vazante,Paranoa′群和 Bam bui′群的西部     

微体古生物学报第20卷2003年总目次

第 1期No.1绪论 :化石藻类和叠层石穆西南　袁训来 (1)………………………………………………………Introduction to Fossil Algae and Stromatolites MU X i- nan and YUAN Xun- lai (1)………………………………………中国叠层石研究的历史和现状曹瑞骥　袁训来 (5 )…………………………………………………………Brief History and Current Status of Strom atolite Study in China CAO Rui- ji,YUAN Xun- lai (5 )………………………巴西中部元古代 Paranoa′和 Bambui′叠层石的古生态和构造背景…………………………………     

河南卫辉地区寒武系苗岭统馒头组二段中的铁质叠层石

河南卫辉地区寒武系馒头组二段顶部发育连续沉积的铁质叠层石。本文综合运用沉积学与沉积古地理、矿物学和地球化学方法,对卫辉罗圈村剖面馒头组二段的铁质叠层石进行了详细的分析。研究区铁质叠层石形成于潮间-浅潮下带滩后微生物丘礁,发育有大量铁矿化的葛万菌(Girvanella)丝状体。地球化学测试显示铁质叠层石中的含铁矿物为赤铁矿;叠层石样品的主量元素Ca、Al、P和Ti含量较高且Al、Fe和Ti元素之间有显著的正相关;微量元素呈现与地壳类似的丰度和变化规律;稀土元素总量较高,总体偏向于轻稀土相对亏损,重稀土相对富集且无明显Eu异常;这些特征说明铁质叠层石的含铁矿物来自陆源。沉积古地理分析表明,含铁矿物很可能来自鄂尔多斯陆的陆源风化产物随陆地径流南下进入研究区。铁质叠层石中铁含量与葛万菌的密集程度呈正相关关系,反映出赤铁矿的沉淀与葛万菌的发育密切相关。葛万菌的光合活性通过增加pH值和氧气浓度来提高铁氧化速率,其细胞外聚合物吸引三价铁离子,为铁矿物的积累提供成核位点,丝状体的运动性有助于捕获沉淀物,从而形成明暗交替纹层的铁质叠层石。     

叠层石衰减事件

“叠层石”这一术语是1908年Kalkowsky首先定义的,用来描述具有多少近似平面状、生物成因细纹层构造的灰岩体。叠层石这个词的使用和定义经历了逐渐的变化,现在大家一致认为叠层石是蓝细菌等微生物群体形成的一种层状的生物沉积构造,如下图所示。近代叠层石主要形成于清水环境、海边缘、潮间带的浅水环境。叠层石并不一定是碳酸盐岩,也可以是硅质岩、蒸发岩或磷酸盐。许多金属矿沉积都与叠层石有密切联系,尤其是叠层石礁。在叠层石形成过程中,微生物对于各种自生矿物的沉淀起到了重要作用,包括碳酸盐、磷酸盐、氧化物、硫化物和硒酸盐。微…     

新元古代奇异叠层石和凝块石中可疑的动物活动证据

在湖北保康马桥地区,新元古代神农架群石家冲组产出一套奇异的叠层石,凝块石和叠层石－凝块石联合体。其中叠层石具类似于食草和钻孔动物破坏的疤痕,通过对上述构造形态和特征分析,这些构造可能与后生动物的活动有关,但也不排除它们是非生物成因的可能。这些后生动物似乎已显示高度发育的行为。当前的资料表明,在凝块石构造与食草和钻孔动物生态效应之间似乎存在着一种紧密的联系,在生物进化史上,寒武纪生命大爆发似乎仅是一     

苏、皖北部震旦纪叠层石及其沉积环境学意义

根据苏、皖北部震旦纪叠层石的外形、大小、颜色及纹层特征,结合其它沉积构造特征,探讨水体能量、光照及沉积作用等环境因素对叠层石生长的影响,以此找出叠层石上具有指相意义的某些生态学特征。目前发现,大型层状、层柱状叠层石往往与浅水低能沉积物共生;分叉不发育的大、中型柱状叠层石则与具周期性变化的浅水高能沉积物共生;分叉发育的柱状叠层石与变化不定的浅水高能沉积物共生;平行分叉的小型柱状叠层石则与中-次中等能量沉积物共生。值得注意的是,环境的变化使一些叠层石形态也随之变异,形成一系列过渡类型,引起分类上的混淆。叠层石纹层表面积与水深往往成反比梯变,这也许与藻席受光照的充足程度有关。叠层石及其围岩的原生色也可作为了解当时水体化学性质及生物对矿物的富集作用的线索。     

淮南地区新元古代九里桥组叠层石成礁过程及其影响因素

淮南地区新元古代九里桥组中段灰岩中发育有形态多变的叠层石礁体,具有与显生宙生物礁相似的相分异特征,基底、礁核、盖层、礁前、礁后、礁翼等不同微相可以明确区分,定殖期、拓殖期、泛殖期和衰亡期等不同造礁阶段的叠层石柱体变化特征明显。该组叠层石礁体自下而上分别为分散分布的小型丘状礁体、连绵分布的大型丘状礁体和分散分布的小型丘状礁体或透镜状礁体,该变化趋势指示了九里桥组沉积时期海平面先升高后降低的变化趋势,结合该组沉积期沉积环境变化特征可将该组叠层石礁体划分为风暴环境型礁体、海进环境型礁体和海退环境型礁体三种类型。对九里桥组沉积学、古生物学等研究表明,该组沉积时期造叠层石生物与其它生物之间存在较强的生存竞争关系,但更能适应风暴沉积环境,叠层石在该组沉积晚期的消失很可能与以海平面变化为特征的沉积构造环境变化有关。     

末前寒武纪叠层石衰退事件的研究

叠层石是前寒武纪最为常见的生物化石之一,它经历了从开拓性发育→广泛繁盛→急剧衰退的一个明显的发展过程.叠层石是微生物和沉积双重作用下形成的一种生物——沉积建造体.它在地质历史上的盛衰不仅与地球早期微生物群的演化有关,而且与地表环境的深刻变化(包括大气圈和水圈的变化)有着密切的联系.在整个发展阶段中,叠层石(主要指柱叠层石)由繁盛向衰退的转变几乎是全球性和突发     

云南东川前寒武纪叠层石类型与找矿意义

根据云南东川矿区前寒武纪地层中叠层石的形态,按叠层石的总貌、主要分型特征和细微结构,提出了在野外较易分辨的类、型、体三级命名方案。通过分析东川地区前寒武纪叠层石形成环境、矿体特征、与"东川式"铜矿有关的岩相特征,以及在不同的沉积环境内,叠层石组合和相应的沉积相的变化规律,提出潮间环境及浅水泻湖环境是成矿重要的有利区域,叠层石组合和沉积相对于"东川式"铜矿空间分布具有指示意义。     

北京永定河谷中新元古界雾迷山组叠层石生长控制因素探讨

北京永定河谷庄户洼剖面中新元古界雾迷山组产出大量叠层石。本文对其形态进行分析测量,获得叠层石优势生长方向的雷达图,结合雾迷山组时期古板块方位、波痕构造所指示古水流方向及当时的构造应力方向等信息进行分析,对叠层石形态生长控制因素进行综合探讨。分析表明,因雾迷山组形成时期华北板块位于赤道附近,永定河谷庄户洼剖面雾迷山组叠层石形态不受阳光控制,控制其形态的主要因素是古水流。另外,构造应力活跃所引起的古地震频发导致了软沉积物向深海滑塌也影响了叠层石的生长形态,硅质填充物在后期破坏了叠层石的形态。对叠层石形态生长控制因素进行分析探讨,可帮助理解叠层石形态生长机理和古环境,具有重要的地球生态学意义。     

南海莺琼盆地渐新世—上新世孢粉组合序列及其古环境意义

本文对莺琼盆地新生代的孢粉资料进行了综合梳理,划分出6个特征明显的孢粉组合。根据孢粉组合的特征及具有时代意义的化石分子对地层的时代进行划分,探讨了各个时代的植被类型、气候条件及沉积环境。孢粉组合显示,莺琼盆地陵水组/三亚组出现的孢粉组合差异大,气候条件发生了较大突变,由偏凉干向偏暖湿变化,是古近纪/新近纪的界线。     

ULTRASTRUCTURE AND CYTOCHEMISTRY OF SPERMATANGIAL DEVELOPMENT AND FERTILIZATION IN AGLAOTHAMNION OOSUMIENSE (CERAMIACEAE, RHODOPHYTA)

Freshwater dinoflagellates have not previously been reported from Belize, although there has been extensive work with marine dinoflagellates and some work with other freshwater groups. Freshwater dinoflagellates are more frequently observed in standing water and none have been observed in the several streams and rivers sampled since 1990. The goal in 1998 was to examine water samples from small ponds within hours of collection to improve the chance of observing swimming dinoflagellates. A plankton net was used and whole water samples also were collected. A small brown water pond on a peninsula and 30m from the Caribbean yielded a bloom of Thompsodinium intermedium. Dinoflagellates, including Peridinium centenniale , Katodinium sp., and Peridinium sp. in the Umbonatum Group, were observed within "Crocodile pond" and "Lily pond" on the mainland.     

A Group I Intron in the Nuclear Small Subunit rRNA Gene of Cryptendoxyla hypophloia, an Ascomycetous Fungus: Evidence for a New Major Class of Group I Introns

The ascomycetous fungus Cryptendoxyla hypophloia contains an insertion of 433 base pairs in the genes encoding nuclear small subunit ribosomal RNA. Secondary structure analyses of the insert reveal characteristics indicative of a Group I intron, including elements P, Q, R, and S; however, the sequences of these conserved regions deviate significantly from recognized consensus sequences for Group I introns. Principal-components analysis, based on 79 nucleotide positions from the conserved core sequences of 93 Group I introns, identified 17 introns similar to that of C. hypophloia. This grouping, which includes inserts from phylogenetically diverse organisms, cannot readily be classified in any previously recognized major group of Group I introns. We propose the creation of a new group, IE, to accommodate these sequences, and discuss the evolutionary relationships between group IE and other major groups of Group I introns. Received: 11 January 1998 / Accepted: 12 October 1998     

Phytoplankton chlorophyte structure as related to ENSO events in a saline lowland river (Salado River,Buenos Aires,Argentina)

We analyzed the phytoplankton present in the lower sector of the Salado River (Buenos Aires, Argentina) for 10 years (1995–2005) and detected significant changes occurring in chlorophyte abundance and species richness during La Niña event (1998–1999), which period was analyzed throughout the entire basin (main stream and tributaries). We compared the physicochemical and biologic variables between two El Niño–La Niña–Southern Oscillation (ENSO) periods – El Niño (March 1997–January 1998) and La Niña (May 1998–May 1999) – to identify possible indicators of a relationship between climatic anomalies and chlorophyte performance. Chlorophyte density increased during the La Niña. Under normal or extreme hydrologic conditions, mobile (Chlamydomonas spp.) and nonmobile (Monoraphidium spp.) chlorophytes codominated. These species belonged to Reynolds's functional groups X1 and X2, those typical of nutrient‐enriched environments. Comparative analyses between El Niño and La Niña periods indicated significant differences in physicochemical (K⁺, dissolved polyphenols, particulate reactive phosphorus, alkalinity, pH) and biologic (species diversity and richness, phytoplankton and chlorophyte total densities) variables between the two periods at all basin sites. During the La Niña condition, species richness was greater owing to interconnected shallow lakes and drainage‐channel inputs, while the Shannon diversity index was lower because of the high abundance values of Monoraphidium minutum. A detailed analysis of the chlorophytes in the entire basin, indicated that changes in density and species dominance occurred on a regional scale although diverse chlorophyte assemblages were identified in the different sectors of the Salado River basin. After La Niña event, the entire basin had the potential to revert to the previous density values, showing the resilience to global environmental changes and the ability to reestablish the general conditions of stability.     

Is high-frequency repetitive transcranial magnetic stimulation of the left primary motor cortex superior to the stimulation of the left dorsolateral prefrontal cortex in fibromyalgia syndrome?

Objective: To investigate effectiveness of two different high-frequency repetitive transcranial magnetic stimulation (rTMS) protocols on pain, fatigue, quality of life (QoL) and depression in female patients with fibromyalgia.

Methods: Thirty patients were randomized into three groups. Fifteen sessions of 10?Hz (90% resting motor threshold-RMT, 1200 pulses) rTMS were applied to left primary motor cortex and left dorsolateral prefrontal cortex (DLPFC) in Group M1 (n:10) and Group DLPFC (n:10), respectively. Group sham (n?=?10) received 15 sessions of sham rTMS over 3?weeks. Visual Analogue Scale, Fibromyalgia Impact Questionnaire, Fatigue Severity Scale, Short-form 36, and Beck Depression Inventory were assessed at baseline and at the end of the treatments by a blinded-experienced assessor.

Results: Significant improvements in pain, QoL, and depression scores were observed in three groups. However, improvements in depression, physical functioning, physical role functioning, and general health perceptions were greater in active rTMS groups than in sham group. Emotional role functioning was only improved in Group M1. The decrease in VAS scores was significantly greater in Group M1 when compared to sham group. Change in physical role functioning was significantly greater in Group DLPFC than in Group M1.

Conclusions: Significant improvements in physical role functioning, physical functioning, depression, and general health perceptions were achieved in active rTMS groups. Further clinical studies on larger samples involving both sexes with longer follow-up durations are needed.     

云南原缨口鳅属鱼类不同地理居群形态差异及分化

将采自中国云南的249尾原缨口鳅属鱼类标本以采集地分为13组,共测量20个常规性状,应用多变量形态度量学方法比较其形态差异。结果表明,全部标本可以水系分为3群,分别命名为澜沧江群、李仙江群和元江群。它们之间的差异系数均超过亚种水平的临界值(1.28),而且各群间的主成分分值散点间没有过渡中间类群。所以,3群应是3个不同的物种。根据原始文献描述的越南行政分区,推测李仙江分布的原缨口鳅属鱼类应为Vanmanenia tetraloba(Mai,1978),而元江分布的应为Vanmaneniastriata Chen(1980)。澜沧江中分布的原缨口鳅属鱼类标本以体型扁平、偶鳍宽大和头部骨骼小等特征组合区别于V.tetraloba和V.striata。经验证保存于中国科学院昆明动物研究所的唯一标本证实,采自禄劝掌鸠河的原缨口鳅属标本不是V.tetraloba,而应是平舟原缨口鳅V.pingchowensis。     

SUMMER HOME RANGE AND HABITAT SELECTION OF HARBOR SEAL (PHOCA VITULINA) PUPS

We studied the summer home range and habitat selection of harbor seal pups tracked using VHF radio telemetry along the coast of central Norway in 1997 and 1998. Median fixed kernel home range of six pups tracked in 1998 was 10.4 km² and the median core area was 1.2 km². One particular deep basin (>100 m deep) was highly selected, and extensively used by four of the pups, probably for feeding. An area adjacent to the deep basin also was selected, probably for haul outs. One pup spent most of the time in inshore, kelp forest areas. Shallow areas without kelp forest and exposed land were used least frequently, possibly because they did not provide suitable areas for feeding and to haul out. The seals hauled out more during calm wind and low tide than during rough wind and high tide. Seals seemed to haul out on intertidal rocks associated with islands, and alternated between several haul-out sites. We found no pattern in haul-out activity associated with age, time of day, air/sea temperature, cloud cover, or rainfall. In 1997, seven pups were tracked manually. These data were associated with methodological limitations, and they were used only to illustrate that these seals stayed mainly within the shallow, inshore, kelp forest area, indicating a possible difference in habitat use between years.     

Middle and Late Triassic radiolarians from northern Tibet: Implications for the Bayan Har Basin evolution

During the Triassic, the Bayan Har Basin is a huge triangular basin surrounded by the North China Platform, South China Platform and Qingtang Terrane. It is filled by a Triassic turbidite sequence, the Bayan Har Group. For a long time, the series of Bayan Har Group in the eastern part of the basin were considered to be a Lower to Upper Triassic sequence, and in the western part, was attributed to the Upper Triassic. A well-preserved diversified radiolarian fauna was recovered from radiolarian chert and tuffite interbeds of the Bayan Har Group turbidites and adjacent stratigraphic units in the Hoh Xil area, northern Tibet. Sixty-seven species are identified and subdivided into two assemblages: late Anisian and early Carnian. Combined with the discovery of the Late Permian and Early Triassic turbidite in the Bayan Har Group in this area by Huang et al., it proves that all the Triassic is also present in the Bayan Har Group sequence in the western part. The evolution of the Bayan Har Basin may be traced back to the Late Permian. The massive sequence of the Bayan Har Group and its provenance indicate that the Kunlun and Qinling orogenic belts rapidly rise during the Middle-Late Triassic. The basin extended to the end of the Triassic, possibly locally to the Jurassic.     

Topographical pattern of the forest vegetation on a river basin in a warm-temperate hilly region,central Japan

The relationship between tree distribution and topography was examined in a small river basin (3.4 ha) comprising a complex mosaic of topographical units at 10² to 10³ m² order, each of which had a shallow valley bordered by small ridges or breaks of slopes. Twenty-five major woody species were divided into two groups (groups A and B) based on a cluster analysis using the distribution data in the basin. Group A, which mainly consisted of early-successional species, was distributed around the valley sites of the topographical units, while group B, which mainly consisted of late-successional species, was distributed around the ridge sites of the topographical units. This vegetation pattern coincided with erosional condition in the basin. That is, the valley sites were eroded more actively than the ridge sites, as soil depth tended to be thin in the valley sites and thick in the ridge sites, and because large (canopy) trees were restricted in the ridge sites. There was no tendency that group B was replacing group A, and hence it was suggested that repeated disturbance by slope failures or small-scale shallow landslides have prevented compositional change from the early-successional (group A) to the late-successional (group B) species by preventing the invasion of the latter into valley sites.