塔中I号坡折带上奥陶统台缘礁滩复合体建造模式   总被引：3，自引：0，他引：3  

王振宇  孙崇浩  杨海军  周成刚  张正红 《地质学报》2010,84(4):546-552

塔中Ⅰ号坡折带的台缘高能区发育上奥陶统良里塔格组礁滩体,主要包括生物礁丘、灰泥丘、粒屑滩、滩间海等沉积类型,纵向上表现为粒屑滩、灰泥丘、礁丘的多旋回组合。单个礁滩复合体下部发育粒屑滩,上部为灰泥丘和(或)礁丘,之上为下一旋回的粒屑滩亚相所覆盖。横穿宽3～10km的区域,特别是台地边缘向陡坡转折的高地为礁生长相对集中区,而向内侧则更多出现滩相。不同沉积期礁滩单元分布范围不同,从良三段到良一段沉积期间内呈现逐步向塔中Ⅰ号坡折带迁移的缩减趋势。经后期多次成岩作用和构造破裂的改造,形成沿台缘分布且具有非均质性变化的礁滩型储层。  相似文献   

Latitudinally different responses of Tethyan shoal‐water carbonate systems to the Early Aptian oceanic anoxic event (OAE 1a)     

STEFAN HUCK  NIELS RAMEIL  TVRTKO KORBAR  ULRICH HEIMHOFER  THOMAS D. WIECZOREK  ADRIAN IMMENHAUSER 《Sedimentology》2010,57(7):1585-1614

Ocean‐wide anoxic events represent intensively investigated anomalies in the global carbon cycle. Most previous research has focussed on hemipelagic and pelagic settings and on the relationship between black‐shale deposition and carbon‐isotope excursions. The study of ocean‐wide anoxic events and coeval shallow‐water settings is now increasingly seen as an interesting complementary approach, but one that is not without problems. Whereas platform drowning characterizes the Early Aptian of the northern Tethyan margin, Lithocodium–Bacinella‐rich facies and ongoing shoal‐water sedimentation at the southern Tethyan margin (Oman) bears important information on potential causes of carbon‐cycle perturbations. The present paper seeks to test the supra‐regional relevance of the Oman data by investigating coeval central Tethyan limestones. Three Lower Aptian shoal‐water sections in Istria (Croatia), deposited on the isolated Adriatic Carbonate Platform, are investigated applying chemostratigraphy (carbon and strontium) and detailed sedimentological analysis. The focus is on peritidal to lagoonal facies characterized by mass occurrences of Lithocodium–Bacinella, an enigmatic microencruster community. Lithocodium–Bacinella facies occurs predominantly in layers ranging from one to several centimetres in stratigraphic thickness, with several layers merging to metre‐thick packages. Growth fabrics within the layers include oncoidal morphotypes, lumps, interconnected patches and columns, layers and rare nodular to massive bindstone facies. These growth patterns show a remarkable regional extent and consistency over study sites distributed several kilometres apart. This widespread distribution suggests that specific Lithocodium–Bacinella morphotypes might serve as regional stratigraphic markers. The high‐resolution carbon‐isotope chemostratigraphy presented here is based on pristine rudist shells and matrix micrite samples and calibrated against strontium‐isotope data obtained from screened rudist low‐Mg calcite. The chemostratigraphic data are consistent with existing biostratigraphic data and place the studied strata at the onset of Early Aptian oceanic anoxic event 1a. Moreover, results indicate the near‐coeval nature of Lithocodium–Bacinella bloom facies in Istria and Oman. The outcomes of this study point to latitudinally different responses of Tethyan shoal‐water carbonate systems (platform drowning versus Lithocodium–Bacinella blooms) to the ocean‐wide anoxic event 1a.  相似文献   

Increased terrigenous influx but no drowning: palaeoenvironmental evolution of the Tunisian carbonate platform margin during the Late Aptian     

M. HELDT  J. LEHMANN  M. BACHMANN  H. NEGRA  J. KUSS 《Sedimentology》2010,57(2):695-719

During the Aptian, some carbonate platforms of the sub‐tropical realm (for example, on the northern Tethys margin or in the Gulf of Mexico) were affected repeatedly by severe perturbations in the carbonate production factory and drowning, preferentially during global warming events such as the Early Aptian Oceanic Anoxic Event 1a and a prominent mid‐Late Aptian warming interval. These platform growth crises have been explained mainly by strongly increased coastal runoff (for example, siliciclastics and nutrients) in combination with pronounced eustatic sea‐level rises. In the last few years, increasing evidence suggests that carbonate platforms of lower latitudes were generally less or even not affected by environmental perturbations during these events. This raises the question as to the responsible factors that promoted platform growth or decline in different latitudinal areas. In this study, Upper Aptian (Middle Gargasian to Uppermost Clansayesian) inner‐tropical carbonate ramp deposits of the Serdj Formation at Djebel Serdj, north‐central Tunisia are studied in detail with regard to microfacies, lithology, biostratigraphy and chemostratigraphy. These data allow reconstruction of the palaeoenvironmental evolution of the Tunisian carbonate platform margin and investigation of its response to the prominent mid‐Late Aptian warming interval. The unusually expanded, 600 m thick Serdj Formation consists of limestones, marlstones and siltstones, suggesting deposition within mid‐ramp to inner‐ramp palaeoenvironments. Deposits of the mid‐Late Aptian are represented by quartz‐rich platform carbonates and siltstones, probably resulting from increased coastal runoff on the Tunisian shelf as a response to global warming and accelerated water cycling. The siliciclastic input was accompanied by elevated nutrient levels as indicated by a partial decline in the abundance of oligotrophic biota and mass occurrences of orbitolines and green algae. Carbonate platform drowning during the mid‐Late Aptian, as reported from the sub‐tropical realm, has not been identified. A comparison with other tropical river‐influenced platforms suggests that none of them drowned during the mid‐Late Aptian. One important reason might be widespread arid to semi‐arid climatic conditions within lower latitudes during that time, promoting platform growth due to comparably low nutrient runoff.  相似文献   

碳酸盐岩中锶元素地球化学特征及其指示意义   总被引：7，自引：0，他引：7  

倪善芹  侯泉林  王安建  琚宜文 《地质学报》2010,84(10):1510-1516

应用锶指示古环境的方法很多,其中以锶的含量和与Sr配对的相应的元素比值作为指示剂,具有典型代表性。本文以北京下古生界碳酸盐岩为研究对象,采用ICP-MS分析技术测试了49件样品中Sr、Ba、Cu的含量。以锶的含量、Sr/Ba、Sr/Cu比值作为地化指标,深入探讨了锶的地球化学特征。系统的分析了Sr含量,Sr/Ba、Sr/Cu比值对不同的沉积环境的地质响应。指出从浅海环境到深海环境Sr含量及其相应的元素比值增加趋势明显,对沉积环境具有重要的指示作用。并且,Sr的分布还受到不同沉积旋回的影响,研究沉积作用对Sr分布的影响时,应在同一沉积旋回中进行。此外还深入研究了不同岩性、不同沉积旋回中Sr的分布特征,探讨了影响Sr分布的不同因素。归纳了锶对沉积环境的指示作用。就成岩作用对碳酸盐岩中锶分布的影响,结合前人的工作,进行了探索性的分析。  相似文献   

深层超深层碳酸盐岩优质储层发育机理和“三元控储”模式——以四川普光气田为例   总被引：6，自引：0，他引：6  

马永生  蔡勋育  赵培荣  张学丰 《地质学报》2010,84(8)

优质储层发育与分布是深层、超深层碳酸盐岩勘探的关键。近几年四川普光、通南巴和元坝等一系列深层超深层气田的发现,不断在深度上突破早期的认识,探索这类极限条件下优质储层发育机理,成为勘探的热点和难点。本文根据普光气田主要钻井的岩芯观察、薄片、孔渗、电子显微镜、同位素分析等数据资料的分析与统计,探讨普光气田优质碳酸盐岩储层发育的主控因素,提出沉积-成岩环境控制早期孔隙发育、构造-压力耦合控制裂缝与溶蚀、流体-岩石相互作用控制深部溶蚀与孔隙的保存的"三元控储"机理。  相似文献   

四川东部华蓥山三叠系海相碳酸盐岩对海水信息的保存性评估   总被引：3，自引：0，他引：3       下载免费PDF全文

胡作维黄思静  黄可可孙 伟 龚业超 《中国地质》2010,37(5):1374-1382

海相碳酸盐成岩蚀变及其对海水信息保存程度的认识与评估在古海洋学和沉积地质学等学科领域研究中有着重要意义,尤其对于沉积地球化学和化学地层学等方面的研究是必不可少的基础工作。笔者通过对四川东部华蓥山仰天窝剖面三叠系海相碳酸盐岩样品的微观组构观察、阴极发光和微量元素等分析表明,大多数的样品保留了较好的原始沉积组构,具有极弱和弱的阴极发光强度、较低的Mn含量和较高的Sr含量,同时也具有较小的Mn/Sr值。只有6个样品被认为遭受了较大的成岩蚀变而对海水信息的保存程度较差,需要被剔除,而大多数的样品只遭受了较小的成岩蚀变作用,较好地保留了当时海水的信息,仍然在很大程度上代表了当时的海水。  相似文献   

Geochemistry of meteoric diagenesis in carbonate islands of the northern Bahamas: 1. Evidence from field studies     

Fiona F. Whitaker  Peter L. Smart 《水文研究》2007,21(7):949-966

Processes driving carbonate diagenesis in islands of the northern Bahamas are investigated using major ion, dissolved oxygen and dissolved organic carbon analyses of water samples from surface and ground waters, and measurements of soil gas P. Meteoric waters equilibrate with aragonite, but reactions are water controlled rather than mineral‐controlled and drive dissolution rather than concurrent precipitation of calcite. Surface runoff waters equilibrate with atmospheric P and rapidly recharge the vadose zone, limiting subaerial bedrock dissolution to only 6·6–15 mg l^?1 Ca. P of soil gas measured in the summer wet season ((7·4 ± 3·7) × 10^?3 atm) is elevated compared with that of the atmosphere, despite the thin skeletal organic nature of the soil and the discontinuous soil cover. Soil waters retained in surface pockets are equilibrated with respect to aragonite and have dissolved 51 ± 19 mg l^?1 Ca. This is substantially less than the 93 ± 18 mg l^?1 Ca in samples from pumping boreholes that sample meteoric waters from the freshwater lens. The high P of the freshwater lens ((16 ± 8·3) × 10^?3 atm for pumping boreholes) suggests that significant additional CO₂ may be derived by oxidation of soil‐ and surface‐derived organic carbon within the lens. The suboxic nature of the majority of the freshwater lens and the observed depletion in sulphate support this suggestion, and indicate that both aerobic and anaerobic oxidation may take place. Shallow lens samples from observation boreholes are calcite supersaturated and have a lower P than deeper lens waters, indicating that CO₂ degasses from the water table, driving precipitation of calcite cements. We suggest that the geochemical evolution of waters in the vadose zone and upper part of the freshwater lens may be determined by the presence of a body of ground air with P controlled by production in the freshwater lens and soil and by degassing to the atmosphere. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

山西王家岭矿区奥陶系碳酸盐岩溶蚀规律研究   总被引：2，自引：0，他引：2  

桂辉  许进鹏 《中国煤炭地质》2010,(1):46-49

为研究王家岭矿区奥陶系碳酸盐岩的溶蚀规律,模拟造成差异性溶蚀的主要因素进行了实验。在常温常压、溶蚀液碳酸水的pH值为6.5～6.9、每次溶蚀时间控制在24h左右的条件下,对矿区不同层段的碳酸盐岩进行溶蚀实验。实验发现,碳酸盐岩的成分和结构是影响溶蚀指标的重要因素,比溶蚀度和比溶解度总体趋势是白云岩灰岩膏岩;不溶物含量的增大使比溶蚀度和比溶解度下降,机械破坏量呈非线性增加;相同情况下方解石溶解速度快于白云石2～3倍。该实验结果为矿区进行水文地质研究提供了基础数据。  相似文献   

The Origin of Pb-Zn Deposits in the Northern Kuandian Area, Liaoning Province     

Qu Yajun  Wang Changfeng 《东北亚地学研究》2001,(1)

1 Regional geologyThere are a series of lead -- zinc deposits in theLiao-ji paleo-rift, for exarnple, the Kumduk Pb -- Zndeposit of Korea, the Huanggoushan Pb -- Zn depositof Jilin Province, the Qingchengzi Pb -- Zn dePOsitand Beiwagou Pb -- Zn deposit of…  相似文献   

碳酸盐岩团簇同位素约束下的川东地区二叠系热演化     

刘鑫  邱楠生  冯乾乾  宋佳霖  李才俊 《地质学报》2023,97(8):2676-2689

有效古温标的缺乏制约了碳酸盐岩层系热史的研究,团簇同位素作为一种新兴古温标,对碳酸盐岩层系热史重建具有重要意义。四川盆地二叠系是天然气勘探开发的重点层系,本文通过对川东地区二叠系碳酸盐岩样品进行团簇同位素测试,联合镜质组反射率重建了二叠纪以来的热史,在此基础上明确了二叠系烃源岩的热演化,并讨论了峨眉山地幔柱对川东热体制的影响。川东地区碳酸盐岩的团簇同位素温度在101. 7~178. 7℃,利用交换/扩散模型进行热史模拟认为：川东地区晚白垩世古温度最高,最高古温度在213~225℃,古地温梯度在23~33 ℃/km;川东地区二叠纪古热流最高,最高古热流约为55~70 mW/m 2,二叠纪之后热流逐渐降低至现今大地热流。烃源岩热演化分析认为：川东地区二叠系烃源岩热演化具有阶段性,热演化受控于构造运动,受印支期运动和燕山 喜马拉雅期运动影响存在两期热演化停滞,晚白垩世达到最高古温度后停止生烃,现今处于生气阶段。川东地区二叠纪热流值和烃源岩热演化主要受到地壳拉张减薄作用的影响,受峨眉山地幔柱的影响较小且具有局限性。  相似文献