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71.
H. S. Goldie 《Environmental Geology》1993,21(3):160-166
The Wildlife and Countryside Act 1981 was passed to provide strengthened legal protection for threatened wildlife and environmental features in Britain. Limestone pavements were included specifically in section 34 of this act because their unique features were being damaged or destroyed through various causes. Limestone Pavement Orders (LPOs) are made under this act. This review considers why this protection became necessary, how the legislation is being implemented, what problems have arisen during implementation, and what progress has been made in making LPOs. Enforcement of the law, monitoring of sites after LPOs have been made, and management of pavement sites are discussed with reference to limestone pavements in NW England. Effectiveness of the legislation is difficult to assess because legal processes are incomplete, but there are indications that it is being effective in Britain. However, commercial threats to these landforms may simply have been shifted to Eire. The British experience with legal protection of these fragile karst features may aid conservationists in other nations. 相似文献
72.
Mongkol Udchachon Punya Charusiri Hathaithip Thassanapak Clive Burrett 《Proceedings of the Geologists' Association. Geologists' Association》2018,129(2):215-226
Lower Palaeozoic rocks have been mapped in Kayin State in an area previously shown on published maps as either metamorphic or possibly Lower or Upper Palaeozoic rocks. Three new formations, with a total thickness of over 900?m, apparently overlain by an, at least, 100?m thick Upper Palaeozoic formation are mapped along the Salween River and along the road from Yinbaing, in Myanmar, to Tha Song Yang, in Thailand. The Lower Palaeozoic succession consists of the predominantly siliciclastic Kyaukpulu and Kushwe–e–we formations and an overlying, predominantly carbonate Meseik Ashe Formation which contains Middle Ordovician (Darriwilian) conodonts. The older two formations are probable correlates of the Ngwetaung and Lokeypin formations of the southern Shan State of Myanmar and the Lower Ordovician siliciclastics of western Thailand. The overlying, peritidal to shallow subtidal carbonates of the Meseik–Ashe Formation are correlates of the Wunbye and Sitha formations of Shan State, Myanmar. The thick–bedded, quartz arenites of the Nyaungwiang Formation are faulted against the Ordovician carbonates and are probable lithological correlates of the Carboniferous Taungnyo Formation. The folds in the Lower Palaeozoic rocks are overturned to the northeast and deformation was in one major phase between the Tournaisian and the Early Permian. The Lower Palaeozoic strata may probably be followed as a ridge for at least 100?km towards the NNW, close to the western border of the Sibuma Block which is separated by a postulated cryptic suture from the Irrawaddy Block to the west. 相似文献
73.
The Ching-dar syncline is located to the west of the city of Birjand, in the east of han. The ca. 500 m thick studied section at the eastern flank of the syncline contains a sequence of almost continuous shallow- marine limestones that exhibit no major sedimentary breaks or evidence for volcanic activity. Skeletal grains consist of large benthic foraminifera and green algae whereas non-skeletal grains are mostly peloids and intraclasts. They were deposited on a shallow-marine carbonate ramp. The limestones have undergone extensive diagenetic processes with varying intensities, the most important of which are micritization, cementation, compaction (chemical and mechanical), internal filling and stylolitization. Chemical analysis of the limestone samples revealed high calcium and low magnesium content. Major and minor element values were used to determine the original carbonate mineralogy of these lime- stones. Petrographic evidence and elemental values indicate that calcite was the original carbonate mineral in the limestones of the Ching-dar syncline. The elemental composition of the Ching-dar car- bonates also demonstrates that they have stabilized in a meteoric phreatic environment. Variation of Sr/ Ca vs. Mn values suggests that diagenetic alteration occurred in an open geochemical system. 相似文献
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76.
安徽巢北地区栖霞组臭灰岩段富有机质成因探讨 总被引:3,自引:0,他引:3
以安徽巢北地区二叠纪栖霞组臭灰岩段为研究对象,从岩石学、古生物学及沉积学特征出发,探讨臭灰岩段富有机质与风暴事件沉积之间的关系。臭灰岩段岩性整体为灰黑色中厚层状石灰岩,层间夹数毫米至数厘米厚灰黑色钙质泥岩,整套岩层富含有机质;其中生物化石丰富,整体为热带、亚热带正常盐度浅水生物组合为特征;为正常浅海碳酸盐岩台地沉积,沉积期表现为一个明显的海侵过程,并受风暴作用的频繁扰动。臭灰岩段沉积环境并非“贫氧或缺氧”条件,而是正常富氧环境。富有机质特征一方面得益于沉积期较高的生物产率,同时还与风暴事件沉积作用密切相关,即在风暴作用下,沉积物发生快速堆积,有机质未来得及与富氧水体发生长期接触即被埋藏覆盖,从而导致有机质被良好保存,形成臭灰岩段富有机质特征。风暴作用频发与研究区臭灰岩段沉积期所处的低纬度特征有关。 相似文献
77.
岩溶生态系统中的土壤 总被引:149,自引:2,他引:149
在偏碱富钙的岩溶生态系统中,其土壤具以下特征:①形成速率十分缓慢,形成1 m厚的土层需要250~7 880 ka,因而对岩溶区土壤侵蚀的评价应有新的认识;②高含量的钙离子使土壤腐殖质中胡敏酸的含量比例较高,且稳定性好,不易分解的腐殖质使石灰土供应营养元素具缓效性;③微量营养元素含量及有效态具有不平衡性,且随钙镁含量的降低,其有效率显著提高;④粘粒含量高,当有机质含量高时,具有良好的团粒结构,有较好的供水、供肥能力,反之其团粒结构就失去稳定性,使土壤有效水含量、抵御水土流失的能力降低;⑤岩溶地貌制约石灰土的类型及分布,并延缓其向地带性土壤演化。因此石灰土资源的有效利用应从岩溶学、土壤学与植物学相互协调的角度进行生态经济规划。 相似文献
78.
白云石化是碳酸盐典型的成岩作用类型之一,中-下奥陶统鹰山组浅海碳酸盐岩是塔河地区重要的含油气储层,普遍发育多种类型的白云石化作用。本文针对塔河地区鹰山组灰岩中沿缝合线分布这一特定类型的白云石化进行了研究。岩石学基础上的阴极发光分析、86Sr/87Sr比值以及δ13C-δ18O 的研究表明,这种类型的白云石化发育于相对还原的浅埋藏成岩环境,孔隙中的残留海水是主要的白云石化流体来源,碳酸盐矿物(主要是高镁方解石)稳定化过程中释放的Mg2+ 可能是白云石化主要的物质来源,而埋藏过程中逐渐升高的温度一定程度上也促进了白云石化的发生。成岩流体及Mg2+ 有限的供给量限制了白云石化作用的整体规模。显微结构与岩石物性分析表明,该类白云石化对储层物性参数的绝对贡献相对有限,但可能成为小规模油气运移以及深部热流体活动的潜在通道。 相似文献
79.
Limestones in the Palmers Oakey District, N.S.W., range in age from Middle Silurian to Early Devonian. They occur as sheet‐like, bioclastic beds and/or isolated clasts in three facies: a volcaniclastic facies, a mudstone‐limestone facies, and a limestone‐mudstone breccia facies. Multielement conodont taxa, not previously reported from Australia, include Kockelella absidata, Kockelella stauros, Ozarkodina asymmetrica, Ozarkodina stygia, Ozarkodina transitans, Pseudooneotodus bicornis, and Pseudooneotodus tricornis. 相似文献
80.
The Ordovician Daylesford Limestone at Bowan Park and the Fossil Hill Limestone at Cliefden Caves have diagenetic and pedogenic features of microkarst, paleosols and calcrete associated with subaerial disconformities in their stratigraphic sequences, all of which, as an ensemble, have global geoheritage significance. The original shelly limestones, lime mudstones, and coralline limestones have selectively dissolved to form vugular limestone whose cavities have filled with sparry calcite and/or crystal silt. The limestones also have been calcretised to develop massive and laminar calcrete and calcrete ooids. Below disconformity surfaces are bleached limestone, crystal-silt and spar-filled fossil moulds and enlarged moulds, micro-breccia-filled moulds and fissures filled with crystal silt, calcrete pellets and calcrete ooids. The disconformity surfaces are irregular or undulating interfaces between lithologies, fissures and fissure-fills, and calcrete. Above disconformities there are limestone lithoclasts, remanié fossils, calcreted limestone, veined limestone, calcrete ooids, laminated calcrete, lithoclast grainstone, or calcrete-ooid grainstone, and lithoclasts with fossils moulds filled with crystal silt and/or spar. The lithological, stratigraphic and possibly landscape differences, make the subaerial diagenesis/pedogenesis in the Daylesford Limestone subtly different to that of the Fossil Hill Limestone. Subaerial disconformities and associated diagenesis/pedogenesis, as recorded in these formations, are not widely reported globally nor well represented in Ordovician limestones. The microkarst features provide insights into the types of subaerial diagenesis/pedogenesis during the Ordovician and into climate, landscape setting, paleohydrology, and groundwater/rainwater alkalinity. Consequently, the story of the Ordovician microkarst, paleosols and calcrete ooids is unique and globally of geoheritage significance as examples of subaerial alteration in an ancient high-rainfall, tropical climate volcanic island environment in a tectonically active region. 相似文献