山东平邑盆地古近系湖相核形石的沉积环境分析

山东省平邑盆地古近系官庄组湖相碳酸盐岩露头发育有大量的核形石。为分析其沉积环境,采用野外观测、地球化学测试、偏光显微镜和扫描电镜观察等方法,研究其岩性背景、伴生的生物、沉积构造以及元素地球化学特征。研究表明,核形石主要发育于浅水、中等偏低能量的环境。有少量陆源碎屑物的环境有利于核形石生长;但较多的陆源碎屑物则对其不利。将核形石分为3类:规则泥晶纹层核形石(简称A类核形石),具有大颗粒、多层的规则纹层、复合核心等特点,可以指示浅水、中能、低陆源环境;规则微亮晶纹层核形石(B类),以色浅、粒径小、分选好、微亮晶纹层为特点,可指示浅水、较高能环境;不规则泥晶纹层核形石(C类),以色深、外形不规整、凝块状不规则纹层为特征,指示较深水、低能环境。发育A类和C类核形石的岩石,孔隙发育较差;发育B类核形石的岩石,孔隙发育较好,表现出相对较好的储层潜力。     

平邑盆地下第三系官中段核形石成因分析

平邑盆地下第三系官中段核形石较为发育,类型多样。通过对其内部结构的研究发现核形石单元纹层有六种类型,作为核心的藻类仅在顶端发生碎屑粘结效应,而其底部则发育厚度小,规则的暗色纹层。纹层组合类型多样,主要受藻类发育程度,水动力强度和藻类种属的控制,是不同水动力环境下的产物。根据颗粒大小、纹层组合类型纹层层数、填隙物将核形石分为浅水高能成因核形石和较深水低能成因核形石。核形石成因分析和分类对沉积环境的判     

川西北杨坝剖面埃迪卡拉系灯影组核形石组构特征

埃迪卡拉系灯影组核形石研究对揭示该期古环境特征及演化具有重要意义。在杨坝剖面埃迪卡拉系灯影组2段核形石发育段的宏观及微观描述（564块薄片）的基础上,分析了核形石组构、类型及垂向分布。该剖面核形石发育段共分为上、下两个亚段,厚度分别为109.53 m、126.2 m,核形石累积厚度分别为22.6 m、49.5 m。核形石核心及壳层的成分、组构、形态多样;核形石类型包括不规则状核形石、椭圆状核形石、次圆状—圆状核形石、帽状核形石等4种,每种类型的粒径、形态、层位分布、形成环境不同;粒度在垂向上表现为10个反旋回。整体上核形石发育不够完善,以薄皮核形石、弥散粒为主,代表着核形石发育的最初阶段。不规则状、次圆状、帽状核形石形成于弱搅动的浅水低能环境,包括潮下低能带、潮间带等;椭球状、圆状核形石形成于连续搅动的潮下高能带。核形石粒度差异大、形态多样、垂向多旋回变化的特征反映了埃迪卡拉纪灯影期海水受限、水体相对深浅及能量频繁动荡,同时受一定物源影响的特征。     

松辽盆地早白垩世青山口组核形石的特征及其环境意义

在松辽盆地中央坳陷带龙虎泡-大安阶地与西部泰康隆起的交界处青山口组二三段高二、高一砂岩组发现了一种特殊的沉积——核形石,最典型的核形石产在杜30井的青山口组二三段（Qn2+3）段。发育核形石的层段厚度约40cm,产出深度为1415.36-1415.77m。核形石颜色以灰色、棕褐色为主,有球状、椭球状、扁球状和不规则状。通过研究认为,本区核形石形成环境主要有两种：三角洲前缘水下分流间湾相带及滨浅湖滩坝相带。青山口组沉积期为湖盆萎缩期,随着相带向湖盆内（研究区东南方向）的迁移,核形石发育层位也向上迁移,表现出良好的环境指示意义。较少的陆源供给、较深的水体、温暖的气候、波动的水体环境都为介形虫的发育及核形石的物质沉淀、滚动生长提供了优良的条件。于是,核形石在小林克-齐家地区青山口组大量成层发育。     

震旦系灯影组核形石白云岩成因机制及其意义：以柳湾剖面为例

震旦系灯影组核形石白云岩作为典型的前寒武纪微生物碳酸盐岩,是我国古老深层油气勘探的岩石类型之一.核形石成因模式的研究,对研究古水体、恢复古环境及其成储模式有重要指导意义.根据核形石结构特征和成因机制将灯影组核形石分为6类,结合岩石学、沉积学和地球化学等研究手段,开展了四川盆地北缘核形石分布特征和沉积过程的综合研究.结果显示：灯影组二段核形石发育于潮下带-潮间坪环境下,水动力和微生物条件的差异影响着微生物生长、自身钙化作用、微生物膜粘结和捕获作用、化学沉淀作用4种核形石纹层形成机理;进一步体现在水动力条件控制着核形石纹层发育厚度、形态特征和伴生岩石类型,而微生物活动习性控制影响着核形石主微量、稀土元素分异特征：贫藻纹层较富藻纹层有较高的Fe/Mn比、实体藻较非实体藻有较高Cu/Zn比,纹层稀土元素富集度一般低于核心.综上所述,灯二段核形石的形成存在4种机理,且它们被海平面变化下的微生物和水动力条件联合控制.     

塔里木盆地塔中台地上奥陶统良里塔格组核形石成因研究

塔里木盆地塔中台地上奥陶统良里塔格组礁滩相中核形石大量发育。本文选取5口钻井取心样品,从核形石形态、粒径大小、纹层磨损度、圆度几个方面进行镜下统计分析。镜下观察核形石有长条状、扁平状、偏心椭圆形、椭圆形、卵圆形、圆形等形状,平均粒径在0.1～2.5 cm之间,核心颗粒以生屑颗粒为主。核形石的纹层磨损度在泥粒岩中为轻度,在颗粒岩中为重度,泥粒—颗粒岩居中。研究认为,促使塔中台地上奥陶统核形石形成的因素包括水动力能量、微生物、碎屑颗粒的累积量等,其中水动力能量占主导地位。能量过低,核形石扁平;能量适合,核形石纹层均匀且厚;能量过强,核形石处于磨蚀状态。水流的强烈冲刷作用会破坏微生物对颗粒的黏附作用,使砂屑生屑核形石滩转变为砂屑生屑滩。     

四川龙门山区中泥盆统金宝石组核形石岩石学特征及其成因*

四川龙门山区甘溪剖面中泥盆统金宝石组顶部发育一套核形石灰岩。通过野外剖面实测和镜下详细观察,认为该套核形石灰岩垂向上可分为3个沉积旋回,每个旋回均由核形石灰岩和泥晶灰岩组成。葛万藻(Girvanella)丝状体在核形石的核心和包壳中均有发育,对核形石的形成具有重要的作用。结合核形石中的纹层类型、Girvanella丝状体形态以及渗滤砂与核形石纹层的关系,认为核形石是在浅滩和礁后潟湖环境中沉积形成的,核形石及其围岩中赋存的粒内渗滤砂和粒间渗滤砂,形成于核形石沉积之后的大气水淋滤作用。通过对核形石形成环境的分析可知,龙门山区甘溪剖面中泥盆统金宝石组顶部核形石灰岩形成的水动力条件从下到上逐渐减弱,反映了当时相对海平面由低到高的变化特点。     

湖北震旦系磷块岩中的藻类化石

湖北荆襄地区震旦系陡山沱组磷块岩特别发育,含丰富的藻类化石。陡山沱组有四层磷块岩,第一层含叠层石和核形石,第三、四层含核形石。叠层石柱体被磷酸岩紧密包裹者,品位较高;基本层理由磷灰石与白云石交替组成亮层和暗层者,品位较低;柱体中仅含团粒状磷灰石者,品位更低。     

四川龙门山区中泥盆统金宝石组核形石岩石学特征及其成因

四川龙门山区甘溪剖面中泥盆统金宝石组顶部发育一套核形石灰岩。通过野外剖面实测和镜下详细观察,认为该套核形石灰岩垂向上可分为3个沉积旋回,每个旋回均由核形石灰岩和泥晶灰岩组成。葛万藻(Girvanella)丝状体在核形石的核心和包壳中均有发育,对核形石的形成具有重要的作用。结合核形石中的纹层类型、Girvanella丝状体形态以及渗滤砂与核形石纹层的关系,认为核形石是在浅滩和礁后潟湖环境中沉积形成的,核形石及其围岩中赋存的粒内渗滤砂和粒间渗滤砂,形成于核形石沉积之后的大气水淋滤作用。通过对核形石形成环境的分析可知,龙门山区甘溪剖面中泥盆统金宝石组顶部核形石灰岩形成的水动力条件从下到上逐渐减弱,反映了当时相对海平面由低到高的变化特点。     

四川江油马角坝地区船山组核形石基本特征及其环境意义

四川江油马角坝地区船山组核形石十分发育,类型多样。基于对其内部显微结构的研究发现核形石核心和纹层各有5种类型,并伴随有3种圈层"构造"。基于对其核心、纹层和形态的研究将研究区核形石分为大球状核形石、小球状核形石、长棒状核形石、帽状核形石、不规则状核形石和复合核形石等6大类,并将它们划分成3种沉积环境,即台地边缘滩、开阔台地和局限台地,并探讨了碳酸盐岩地层中核形石的分布、形成环境和沉积环境的耦合关系。高含量、大颗粒、纹层厚度大于核心厚度、纹层复杂、核心组分与基质组分存在较大差异,亮晶胶结的核形石的形成环境与沉积环境不一致,即核形石形成于水动力较弱的局限台地或开阔台地环境,强水动力使核形石发生磨圆,基质生物碎屑破碎,进而沉积于水动力较大的台地边缘滩环境。中等含量、中等粒度、纹层简单、与完整生物碎屑共存且粒径类似、亮晶胶结的核形石的形成环境与沉积环境类似,即部分生物碎屑在中等水动力条件下,处于悬浮状态,捕获和粘附碳酸盐质点,当个体增大和水体环境变化时,核形石就地沉积于中等能量的开阔台地环境。含量低、粒径变化大、纹层厚度小于核心厚度、纹层简单、形状易受核心的影响,纹层外壳凹凸不平,基质生物含量低、泥晶基质含量特别高的核形石的形成环境与沉积环境一致,即形成并沉积于水动力偏弱的局限台地环境。     

松辽盆地白垩系青山口组核形石的发现及其环境意义

在松辽盆地上白垩统青山口组中首次发现核形石灰岩,见于细砂岩、粉砂岩和泥质岩层系中。核形石有三种类型：环状、石笋状和姜状核形石。多数核形石由核心和多环纹层组成,少数具不明显核心或呈单层环状。该套核形石形成于湖泊三角洲前缘分流河口砂坝侧翼的水下分流间湾环境。地形坡度和三角洲前缘的生长,致使核形石普遍发生准同生变形。由于核形石出现于青山口组二、三段,处于温湿向干热气候转变时期,因此核形石可能作为重要的古气候变迁标志。     

Oncolites of the Lower Permian ChuanshanFormation in South China and Their Geologicaland Economic Significance

A large amount of oncolites popularly named " Chuanshan balls" occur universally in the Lower Permian Chuanshan Formation in South China. These kinds of oncolites have the following characteristics: wide distribution, huge quantities, large sedimentary thickness and similar characters, which constitute a specific " fashion fades" in geological history. The authors consider that these kinds of oncolites were due to the intense differentiation of the global climate at that time, which resulted in a universal descent of the sea level and breeding of a large amount of algae in sea water over low-latitude areas. According to the distribution and characteristics of the oncolitic, relative relationships between different tectonic blocks may be inferred, diagenetic strength indicated and diagenetic history recovered, and more important, oncolites serve as a favourable reservoir rock, so their study is of great theoretical and economic significance.     

广西有孔虫藻核形石

一、广西有孔虫藻核形石的特征 Johnso(1946)认为Osagia是由蓝藻(多孔层)和壳层有孔虫组成的。广西有孔虫藻核形石和国外报导的Osagia的特征基本相同,笔者称之为广西Osagia,主要产于广西六寨中泥盆统泥晶灰岩中,单层厚0.5—3m左右。下伏岩层为中泥盆统泥晶灰岩,上覆岩层为中泥盆统珊瑚层孔虫礁灰岩。横向相变为中泥盆统竹节石泥岩或竹节石硅质泥岩。有孔虫藻核形石外形呈椭球状、球状、不规则状,个体大小2—15cm或更大些均有。含量20—70％,呈单体或复体不均匀地埋藏在泥晶基质中。于泥晶基质中尚可见有原地生长     

Oncolites from lacustrine sediments in the Cretaceous of north-eastern Spain

Compact micritic oncolites up to 8 cm in maximum diameter occur within Maestrichtian (Upper Cretaceous) Garumniense continental marls of Sierra del Montsec (Lerida Province) of north-eastern Spain. Synsedimentary development is documented by patches of terrigenous quartz that occur among oncolitic protuberances. Soluble nuclei (limestone fragments and bivalves) further suggest an origin through accretion, rather than that of soil pisolite. Similarities between the petrography and isotopic compositions of the oncolites and those of interbedded Garumniense limestones suggest similar sedimentary origins. However, these lacustrine oncolites, like modern counterparts described by others, probably developed through in situ metabolic precipitation of calcium carbonate. Evidence of this origin is their high degree of concentricity, which is unlikely to have developed through sedimentary accretion, inasmuch as the oncolites ‘float’ in quiet-water marls.     

川西北甘溪地区吉维特阶核形石特征、成因及地质意义

川西北龙门山前甘溪地区吉维特阶发育一套厚2~3m灰-深灰色微生物岩,由直径0.1~4.0cm的核形石组成,其核心皆由早期葛万藻及其他生物碎屑组成,包壳由具同心圈层结构的亮色和暗色含葛万藻的纹层组成,并可分为球状、帽状和变形状3类核形石微生物岩,垂向上可分4个旋回,从底到顶核形石密度和粒径总体变密、变大,平面上呈不均匀发育。核形石样品具不同程度的δ~(13)C、δ~(18)O值负偏移和~(87)Sr/~(86)Sr正偏移特征,表明核形石微生物岩层遭受过古表生期大气淡水的影响,其中亮色纹层与球状核形石微生物岩受大气淡水影响最为强烈,核形石是在葛万藻发育、水流扰动及大气淡水参与的环境下,葛万藻包覆于生屑的外缘而成,藻类越发育、水体能量越高、沉积环境越稳定,形成的核形石粒径越大、丰度越高。核形石微生物岩在纵、横向分布特征,表明在全球中泥盆统艾菲尔期—吉维特期海平面上升背景下,龙门山地区吉维特金宝石组末期表现为至少6期次脉动式且逐渐强烈的构造抬升作用,造成该地区金宝石组末期海平面大幅下降而暴露于地表遭受大气淡水的淋滤作用。     

Freshwater oncolites created by industrial pollution, Onondaga Lake, New York

Onondaga Lake is a moderately saline, eutrophic lake characterized by waters rich in calcium, sodium, chloride and bicarbonate. Large quantities of CaCO₃ that are precipitated in the lake result from excess calcium supplied as calcium chloride wastes produced by soda-ash manufacturing to lake waters that are at or near saturation with respect to CaCO₃ from solution of carbonate rocks in the drainage basin. Beaches along the leeward (northeastern) shore of the lake are composed almost entirely of oncolites ranging from a few millimeters to several centimeters in maximum dimension. Offshore, in 1–2 m of water, the oncolites are biscuit-shaped concretions as much as 15 cm in diameter. The oncolites consist mainly of low-magnesium calcite, but dissolution of the carbonate with dilute acid results in a mass of blue-green algal filaments of the same approximate size and shape as the original oncolite. Most oncolites have an obvious nucleus; the most common nucleus is the hollow stem and cortication tubules of charophytes. Charophytes do not occur in Onondaga Lake today although they are common in other limestone-bedrock lakes in central New York State. Charophytes probably were eliminated by the marked increases in salinity of the lake that resulted from the introduction of soda-ash manufacturing on the lake shores around 1880 which means that growth of the oncolites began at least 100 years ago.     

山东省平邑盆地古近系湖相核形石特征及环境意义

山东省平邑盆地古近系官庄组湖相核形石较富集,其特征和分布受古沉积环境的控制。在总结前人研究的基础上,运用野外现场观测、偏光显微镜和扫描电镜观察、地球化学测试等技术手段,研究了本区核形石灰岩的岩石形态、结构、古生物、构造、元素地球化学等具有环境指示意义的特征,并据此将该区核形石分成A、B两类,它们之间根本性区别在于其形成的沉积环境的不同,A类核形石形成于翻转、滚动的强水动力的,水体较浅且较混浊的滨湖岸滩-浅湖浅滩环境;而B类核形石形成于水体较深、较平静的且较清澈的浅湖湖湾环境。研究结果表明,本区的核形石发育于一个处于湖侵体系域阶段的干热湖盆的缓坡地带。     

Pelagic Manganese Nodules--A New Type of Oncolites

Pelagic manganese nodules from the East Pacific Ocean have been studied using polarizing,scanning electron and transmission electron microscopes. It has been revealed that the manganesenodules are composed of cores and stromatolite coatings. The structures and textures of thesenodules are peculiar to oncolite. Consequently, the pelagic manganese nodules are manganeseoncolites. Based on the stromatolites in the coatings, the manganese oncolites from the East Paci-fic Ocean can be divided into two types. One is smooth on surface and dense inside. Its coatingsare composed mainly of Minima. The other has a knobby surface and is loose internally. Itscoatings consist mainly of Admirabilis. The TEM investigation has also revealed that the con-structors of the manganese oncolites are ultra-microbes. The Minima is constructed byMiniactinomyces chinensis sp. nov. and the Admirabilis is built by Spirisosphaerospora pacifica sp.nov.     

More evidence in favour of the biochemical origin of the Mussoorie phosphorite,Kumaon Lower Himalaya,India

Particles of definite skeletal and faecal origin, oncolites and stromatolitic structures from Mussoorie phosphorite, occurring in the Kumaon Lower Himalaya, have been illustrated in the present note with the purpose of providing more evidence in favour of the biochemical mode of origin of these phosphorites.     

沉积鲕石和尿路结石若干特征的对比研究

本文从仿生学的思路出发，将几种沉积鲕石、核形石、结核等从其结构、成分和形成条件等方面与四种常见尿路结石进行对比研究。认为这些产物虽然发生在自然界或人体内两种截然不同的环境中，但是在研究其形成机理时，彼此有许多可以互相借鉴之处。沉积鲕石、核形石的分层结构和再结晶交代现象等，可以对比应用于尿石的形成和发育机理的解释；同时，尿路结石形成理论中的局部过饱和以及取向附生学说，也可引进于沉积鲕石、核形石和结核的形成理论中。此外，本文首次介绍了热发光方法研究沉积鲕石和尿路结石的成果，并认为这一研究方法仍有继续深入探讨其应用范围的潜力。