龙永煤田吕凤煤矿区童子岩组地层特征及聚煤环境讨论

本文首先归纳了龙永煤田吕凤煤矿区下二叠统童子岩组各段的地层特征主要为细粒的碎屑岩和煤层等;在此基础上浅析了吕凤煤矿区童子岩组的聚煤环境,主要为浅海-滨海-三角洲相为主;最后将其环境与整个龙永煤田区域上的该组地层沉积环境进行对比。     

《中国煤田地质》1992年总目录

第一期华北聚煤区南部滑脱构造系统的构造环境研究…………………………………………曹代勇、高文泰(1)从鄂东南二叠系的岩相分布对淮阳古陆的质疑…………………………………………………王文海(7)福建下二叠统童子岩组层序与对比………………………………………………………………林水霖(11)福建茅口期生物生态特征与生境解释……………………………………………………………林向星(15)福建童子岩组沉积环境及其演化规律……………………………………………………………张仰钰(20)福建下二叠统童子岩组的聚煤作用…………………………………     

西藏拉萨地块西部下二叠统昂杰组—下拉组底部沉积特征与沉积环境

拉萨地块作为组成青藏高原的众多板块之一,其古地理演化是学术界关注的焦点,识别拉萨地块晚古生代冰期—冰后期地层和沉积的变化对于了解和认识拉萨地块古环境变化有重要的指示意义。前人对于拉萨地块下二叠统沉积环境研究较少,且主要集中在拉萨地块中部。本文通过详细测制西藏拉萨地块狮泉河地区羊尾山剖面下二叠统,依据邓哈姆碳酸盐岩分类方案及威尔逊碳酸盐岩相带划分模式,查明了昂杰组上部至下拉组底部的岩石类型、组合及沉积环境。昂杰组以生物碎屑灰岩夹碎屑岩沉积为特征,代表了晚古生代大冰期衰退后的碳酸盐岩中缓坡下部环境;下拉组底部岩性以富含生物碎屑的泥粒灰岩为特征,沉积环境为碳酸盐岩中缓坡上部环境。研究认为,狮泉河地区与拉萨地块中部下二叠统的沉积背景大体相同,表现出由碳酸盐岩中缓坡下部逐渐向碳酸盐岩中缓坡上部过渡的特征,以及海平面变浅的趋势,同时指示拉萨地块早二叠世时是一个稳定的地块。     

福建的童子岩组沿革补遗

对福建童子岩组（煤系）如何由上二叠统改为下二叠统以及为何采用这一岩石地层名称作了一些历史细节的报道。     

龙永煤田滑脱断层特征及其控煤作用

龙永煤田中二叠统童子岩组煤系的顶底部广泛发育着一种缓倾角的断裂构造,这种地质构造主要特征之一就是造成地层的缺失,对煤系的赋存影响较大。在福建煤田地质界将其称之为"滑脱断层"。这种断层的发育具一定的层位性,在剖面上沿多个固定的层位顺层发育,上下叠置,相互平行、成组出现。发育层位从老至新主要有:栖霞组灰岩与下伏上泥盆系-石炭系之间的F_0下断层;二叠统栖霞组灰岩和童子岩组煤系间的F₀断层;童子岩组煤系一段与三段直接的F₀₁断层;童子岩组煤系与上二叠统屏山组之间的F₀₂断层;翠屏山组与下三叠统溪口组的F₀₃断层等滑脱断层。龙永煤田滑脱断层的成因机制为:在晚古生代,存在一些大背斜,并且在印支期进一步隆升,造成岩层重力不稳定趋势;岩层从高处向低处脱离有个力学性质软弱面;外来的触发因素如地震、火山喷发等促使岩层从高处向低处滑动;由于断层发育的层位不同,其对煤系的影响作用也不同。若发育于煤系的底部,对煤系起破坏作用,不利于地质找煤。若发育于煤系的顶部,则对煤系起保护作用,使煤系的埋藏相对变浅,利于深部找煤。      

云南保山地块香山组和丁家寨组沉积序列与碳同位素研究

通过对保山地块北部西邑地区下石炭统香山组和下二叠统丁家寨组详细的野外剖面实测与钻孔编录,并结合层序地层学、沉积相以及碳氧同位素分析结果认为,下石炭统香山组自下向上可分为三个岩性段,分别对应台前斜坡下部、台前斜坡上部、碳酸盐岩台地三种沉积环境。下二叠统丁家寨组为滨岸冰水沉积,下部为冰碛含砾钙质杂砂岩,发育落石构造。下石炭统香山组δ13C_PDB值自下而上逐渐升高,环境可能较稳定,有机质埋藏增加。综合前人古地磁、生物区系对比、大地构造学等研究成果认为早石炭世保山地块较稳定,仍属冈瓦纳大陆北缘。丁家寨组冰碛含砾钙质杂砂岩结束后δ13C_PDB值出现强烈负偏,与研究区冰期结束、早二叠世初次温度上升、大量玄武岩喷发等时限高度一致,共同说明了保山地块在早二叠世开始从冈瓦纳大陆北缘裂解出来,并开始向北漂移。该项研究的开展为探讨Submasu地块晚古生代的古海洋、古地理和气候演化具有重要意义,为全球同时期碳氧同位素数据库提供了新资料。     

鄂尔多斯盆地东南缘下二叠统沉积相

近几年的勘探开发发现,鄂尔多斯盆地东南缘下二叠统具有巨大的非常规天然气资源潜力。为探明其沉积环境,在详细的岩心、测井及室内分析化验的基础上,运用沉积学理论,对鄂尔多斯盆地东南缘下二叠统沉积相进行研究。研究结果表明:太原组发育障壁岛、泻湖、潮坪、浅海陆棚沉积,山西组发育三角洲、湖泊沉积;自太原组至山西组沉积环境经历了由海陆过渡相至陆相的演化过程。     

华北盆地西部太原组遗迹化石组合对古水深变化的响应

通过对豫西—晋中南地区上石炭统—下二叠统太原组碳酸盐岩中遗迹化石的组成、产状及分布特征的研究,结合部分生物潜穴中Sr含量、Sr/Ba值、1000×(Sr/Ca)值和δ13C值,得到不同地区太原组沉积期古水深的变化曲线,建立了3种不同水深的遗迹组合:(1) Nereites-Chondrites遗迹组合,产生于氧化还原界面附近水体相对较深的浅海下部环境;(2) Zoophycos-Teichichnus遗迹组合,形成于浪基面至氧化还原界面之间的浅海中部沉积环境;(3) Zoophycos-Thalassinoides遗迹组合,出现在平均海平面至浪基面之间的浅海上部或较为闭塞的海湾潟湖沉积环境。依据这3种遗迹组合在各剖面上的变化特征和古水深,认为在豫西—晋中南地区太原组沉积期发生过2次较大规模的海侵。这一成果为精细研究华北西部地区太原期沉积环境演变规律及对比地层提供了生物遗迹学方面的依据。     

贵州平塘地区上二叠统长兴组沉积相与层序地层特征

本文应用沉积学和层序地层学的基本原理和方法,采取野外实测与室内微观研究结合,利用区域钻井资料对比层序地层,对贵州平塘地区中上二叠统长兴组的沉积相特征、层序地层特征以及岩相古地理平面展布进行了研究和总结。结果表明,贵州平塘地区上二叠统长兴组发育开阔台地、台地边缘浅滩以及台盆3种沉积环境。长兴组可划分为2个Ⅲ级层序PSQ1和PSQ2,且均由海侵体系域(TST)与高水位体系域(HST)两部分组成,且皆为TST>HST。对比邻区沉积相和层序地层特征,说明纵向上长兴组的沉积环境是由开阔台地、台地边缘浅滩沉积变为深水台盆沉积;横向上自西向东从安顺到甘寨一带在上二叠统层序PSQ2时期,构成了由浅水碳酸盐台地到深水台盆沉积的廊带。且黔南坳陷在晚二叠世,海水总体为由南向北迁徙海侵。     

论东吴运动构造事件与二叠系分统界线问题

根据华南二叠系海水进退、沉积旋回、岩相变化、生物变革及火山活动等事件研究，东吴运动是存在的，位于翠屏山组与童子岩组、龙潭组与堰桥组、吴家坪组与茅口组之间，以假整合、整合或不整合而显现其不平衡性。它是属一种以升降为主振荡性质的地壳运动，并可与新疆北山运动和欧洲萨尔运动相对比。东吴运动所造成的这一事件界线是由早二叠世海退线和晚二叠世海进线重合而成，前者是穿时的，后者则是近等时的。因此，以其作为二叠系分统的界线，应是一条比较理想的自然界线。     

国外景观演化研究的最新进展

景观演化与全球构造、生物演变和主要气候变化具有相同的时间尺度 ,是长期全球变化的一个重要方面。最近 ,地表过程在地壳变形中的作用已经引起了广泛的注意 :一方面努力从景观中模拟地形演化或演绎地壳过程 ;另一方面试图通过地壳变形和地表过程的型式和速度来研究隆起、海平面变化、侵蚀、气候和地势之间的动力学关系。文中旨在介绍和评述国外关于会聚边缘和裂开边缘山脉尺度景观演化研究 ,包括高原边缘地形演化、前陆盆地的沉积型式、景观切割、古地形复原以及质量流动和平衡等方面的最新进展 ,以及地表过程和地壳过程相互作用中的反馈机制、均衡效应和岩石圈强度效应以及调整和平衡等几个理论问题。目前已经普遍认为 ,把地表过程纳入地球动力学模型之中 ,无疑对于认识造山带的发育和裂开边缘的演化是一个巨大的进步。     

内蒙古桌子山中奥陶统的“特殊”浊积岩系

内蒙古桌子山中奥陶统拉什仲组是由鲍马层序清晰的多层浊积岩组成的浊积岩系,然而其沉积序列总厚度以及浊积岩内部特征等诸多方面,又与那些形成于不稳定或次稳定型外陆架边缘直至深海盆内的巨厚浊积岩系有着明显的差异,因此将拉什仲组以“特殊”浊积岩系称之。文中在对这两种浊积岩系进行多方面的对比研究后,进而从沉积相、相组合、浊流的古流向以及遗迹化石群落的生态特征等方面,阐述了形成拉什仲组浊流盆地的特征,并认为:充填这套“特殊”浊积岩系的海盆是位于稳定地块之间、盆地地形简单、坡度不大、海水深度在浪基面以下200m左右、含氧量较充足的深水浊流盆地。     

山东中新世山旺组生物群的古生态

山东临朐产出的中新世山旺组化石群,保存精美、属种分异度高。50多年来,经发掘和研究,目前已从约30余米的硅藻页岩沉积中报导了真菌、硅藻、介形虫、孢粉、昆虫、鱼类、两栖动物、爬行类、鸟类、哺乳动物及遗迹化石等十几个门类的化石,共计400余属700多种。本文总结了化石与周围无机界的关系、化石的埋藏特征、形成原因以及相关古生态学问题――古气候、古温度、古纬度、古地形、山旺湖的水文性质、湖水的季节性变化与硅藻页岩的纹层、动植物群的营养结构以及山旺盆地的沉积历史。     

Variations in Isochore Thickness of the Ecca Sediments in the Eastern Cape Province of South Africa, as Deduced from Gravity Models

Gravity modelling was carried out along five profiles that traverse the Eastern Cape Province of South Africa in order to determine the depositional surface and isochore thickness of the Ecca sediments.Gravity models of the subsurface rock density reveal that the Ecca Group has a maximum vertical thickness of about 3215 ± 160 m.The maximum depositional surface(elevation)above sea level for the Ecca sediments is about 500 m,whilst the depth below sea level reaches about10000 m.Correlation of the isochore thickness maps with the depositional surfaces shows that the sediments in the basement highs were subsided,deformed,eroded and deposited in the basement lows.The basement highs served as the source area(s) for the sediments in the basement lows,thus basement highs are characterized with thin sediment cover whilst the lows have thick sediment cover.     

Late Miocene freshwater mussels from the intermontane Chota Basin,northern Ecuadorean Andes

Prior to the development of the modern Amazonian drainage network during the Late Miocene-Early Pliocene, large areas of western Amazonia may have been occupied by an extensive lacustrine and wetland environment known as the Pebas and Acre systems. These depositional systems are thought to have formed in response to foreland subsidence east of the uplifting Andes. Based on the occurrence at a present-day elevation of 1600 m of fossil pearly freshwater mussels of the genus Anodontites (indet. species) in intermontane Chota Basin of northern Ecuador (the westernmost South American fossil record for this genus), we discuss their potential implications for understanding of westernmost limit of the Miocene wetland ecosystem and consequently a later timing for the regional uplift of the Eastern Cordillera.     

Depositional environments of Late Eocene lignite-bearing strata, east-central Texas

Late Eocene lignites in the Brazos River Valley area occur in parasequence-scale cycles containing mostly marine sediments. Lignite is present at the base of the marine interval and forms the base of the cycle in a majority of cases. Less frequently, lignite is underlain by a thin interval of nonmarine deposits that form the base of the cycle. In both situations, the lignite is part of a thin transgressive interval. Cycles are separated by an exposure surface, usually marked by plant rooting and/or development of a paleosol in the top of the underlying sediments. Peat accumulated on top of these exposure surfaces and lignite is preserved where marine flooding allowed ocean waters to cover the peat deposits with fine grained sediments, producing high-ash lignite horizons of great lateral extent but variable thickness and quality. This strandplain model of lignite occurrence provides a better understanding of Late Eocene lignites in Texas than the deltaic or fluvial-deltaic models previously used. The strandplain model of lignite occurrence is appropriate for most of the Yegua-Jackson lignites (Middle-Late Eocene) of Texas and should be considered when evaluating depositional conditions of Paleogene lignites in the northern Gulf Coast region. A re-evaluation of Late Eocene stratigraphy of the Brazos Valley area accompanies the documentation of depositional environments.     

Strontium isotopic composition of the Madera Formation (Pennsylvanian) near Albuquerque,New Mexico

⁸⁷Sr/⁸⁶Sr ratios of fourteen unaltered limestone and six fossil samples show a range of 0.7066-0.7118 for the depositional water of the Middle to Upper Pennsylvanian Madera Formation. The variation of these ⁸⁷Sr/⁸⁶Sr ratios may be due to the restricted depositional basin and nature of the source of the Madera Formation.While fossil and limestone samples are equally good for determination of strontium isotopic composition of depositional waters, leaches of calcareous shales contain significant amount of ⁸⁷Sr leached from the noncarbonate fraction during acid treatment.     

Palaeoenvironmental Reconstruction of the Early to Middle Miocene Sequence in West Central Sinai,Egypt, as Revealed from Fossil Diatoms

A detailed analysis of the diatoms from the sedimentary sequence exposed in Abu Qada basin, west central Sinai, was used to determine the palaeoenvironmental changes during the Lower to Middle Miocene. A total of 85 diatom species and varieties belonging to 37 genera were identified from 154 samples collected throughout the stratigraphic succession. The lithological characters of the studied samples varied between sandstone, silty interbeds, sandy shales, shales, and terminated with anhydrite and limestones. These rock units are included in two lithostratigraphic formations (Rudies and Kareem), which are separated by a marked unconformity. The distribution and preservation of fossil diatoms in the sedimentary record are examined with the aim of outlining the temporal and spatial variation in the composition of the diatom assemblages, in order to estimate the changes in depositional environments during the Lower to Middle Miocene. The distributional pattern of the recorded diatom taxa distinguished four diatom eco-zones. The environment of each eco-zone is deduced and a proposed paleobathymetric change and depositional history of the Miocene sediments in the studied area are given.     

化石群落演替与环境变化

本文对湖南孟公坳组Ｃｙａｏｐｈｒｅａｔｉｓ－Ｃｈｏｎｅｔｉｐｕｓｔｕｌａ群落和刘家塘组ＦｉｎｏｓｐｉｒｉｆｅｒＭａｒｇｉｎａｔｉａ群落进行了生态演替过程分析．研究表明,化石群落的生态演替体现了当时生活在相同或相似环境中若干生物群落的动态发展．化石群落演替过程的形成和保存与生活环境和沉积环境有直接的关系．分析化石群落的演替过程可以恢复当时沉积环境的变化幅度和变化趋势,有助于研究群落与环境在时空上的变化,有利于提高地层划分和对比的精度．     

Impressions of algal mats from the Middle Proterozoic Belt Supergroup, northwestern Montana, U.S.A.

Irregular, low relief bedding-plane markings which probably represent impressions of thin, wrinkled algal mats have recently been detected in mudstones from the 1100 m.y. old Snowslip Formation, Belt Supergroup, Glacier National Park, Montana. Algal-mat impressions are rarely reported from ancient strata, yet algal mats are common in certain modern environments. Originating primarily in moist settings and in relatively quiescent shallow-water settings, such structures may be of some value in interpreting ancient depositional environments.