Origin of mud in turbidites and hybrid event beds: Insight from ponded mudstone caps of the Castagnola turbidite system (north-west Italy)

The partitioning of different grain-size classes in gravity flow deposits is one of the key characteristics used to infer depositional processes. Turbidites have relatively clean sandstones with most of their clay deposited as part of a mudstone cap or as a distal mudstone layer, whereas sand-bearing debrites commonly comprise mixtures of sand grains and interstitial clay; hybrid event beds develop alternations of clean and dirty (clay-rich) sandstones in varying proportions. Analysis of co-genetic mudstone caps in terms of thickness and composition is a novel approach that can provide new insight into gravity flow depositional processes. Bed thickness data from the ponded Castagnola system show that turbidites contain more clay overall than do hybrid event beds. The Castagnola system is characterized by deposits of two very different petrographic types. Thanks to this duality, analyses of sandstone and mudstone composition allow inference of which proportion of the clay in each of the deposit types was acquired en route. In combination with standard sedimentological observations the new data allow insight into the likely characteristics of their parent flows. Clean turbidites were deposited by lower concentration, long duration, erosive, muddy turbidity currents which were more efficient at fractionating clay particles away from their basal layer. Hybrid event beds were deposited by shorter duration, higher-concentration, less-erosive sandier flows which were less efficient at clay fractionation. The results are consistent with data from other turbidite systems (for example, Marnoso-arenacea). The approach represents a new method to infer the controls on the degree of clay partitioning in gravity flow deposits.     

From marine bands to hybrid flows: Sedimentology of a Mississippian black shale

Organic-rich mudstones have long been of interest as conventional and unconventional source rocks and are an important organic carbon sink. Yet the processes that deposited organic-rich muds in epicontinental seaways are poorly understood, partly because few modern analogues exist. This study investigates the processes that transported and deposited sediment and organic matter through part of the Bowland Shale Formation, from the Mississippian Rheic–Tethys seaway. Field to micron-scale sedimentological analysis reveals a heterogeneous succession of carbonate-rich, siliceous, and siliciclastic, argillaceous muds. Deposition of these facies at basinal and slope locations was moderated by progradation of the nearby Pendle delta system, fourth-order eustatic sea-level fluctuation and localized block and basin tectonism. Marine transgressions deposited bioclastic ‘marine band’ (hemi)pelagic packages. These include abundant euhaline macrofaunal tests, and phosphatic concretions of organic matter and radiolarian tests interpreted as faecal pellets sourced from a productive water column. Lens-rich (lenticular) mudstones, hybrid, debrite and turbidite beds successively overlie marine band packages and suggest reducing basin accommodation promoted sediment deposition via laminar and hybrid flows sourced from the basin margins. Mud lenses in lenticular mudstones lack organic linings and bioclasts and are equant in early-cemented lenses and in plan-view, and are largest and most abundant in mudstones overlying marine band packages. Thus, lenses likely represent partially consolidated mud clasts that were scoured and transported in bedload from the shelf or proximal slope, as a ‘shelf to basin’ conveyor, during periods of reduced basin accommodation. Candidate in situ microbial mats in strongly lenticular mudstones, and as rip-up fragments in the down-dip hybrid beds, suggest that these were potentially key biostabilizers of mud. Deltaic mud export was fast, despite the intrabasinal complexity, likely an order of magnitude higher than similar successions deposited in North America. Epicontinental basins remotely linked to delta systems were therefore capable of rapidly accumulating both sediment and organic matter.     

巴东新城区紫红色泥岩工程地质性质研究

通过地质调查及大量岩土力学试验,对巴东新城区中三叠统巴东组二段T2b2紫红色泥岩工程地质性质进行了综合研究。测定了岩石的矿物成分及微观结构和岩石的物理及水理性质参数。由不同含水状态下的室内崩解试验发现,紫红色泥岩具有较强的崩解特性,且与岩石的物理状态密切相关,试验得到岩块的力学性质指标和变形特征。进行了点荷载试验,对不同风化程度和不同物理状态下的岩石的工程地质性质进行了分析,并指出其对工程的影响。     

METAMORPHIC PETROLOGY

正20140751 Guo Xincheng(Geological Party,BGMRED of Xinjiang,Changji 831100,China);Zheng Yuzhuang Determination and Geological Significance of the Mesoarchean Craton in Western Kunlun Mountains,Xinjiang,China(Geological Review,ISSN0371-5736,CN11-1952/P,59(3),2013,p.401-412,8     

青西凹陷下白垩统含白云质泥岩与泥质白云岩储集层微观孔喉特征及控制因素

岩石类型中的孔喉特征对储集层的研究具有重要意义。对青西凹陷下白垩统储集层中的含白云质泥岩和泥质白云岩进行薄片观察、矿物X衍射定量分析、场发射扫描电镜观察、Qemscan系统分析和压汞分析,结果发现,含白云质泥岩中黏土矿物含量高,发育黏土矿物层间孔,含部分黄铁矿晶间孔及微裂缝,粒内孔数量较少,微米级孔隙(孔径10~200μm)数量居多;泥质白云岩中白云石含量高,以矿物颗粒粒缘缝、粒间孔、微裂缝及有机质收缩缝为主,偶见有机质溶蚀孔、黄铁矿晶间孔,纳米级孔隙较多,主要为20~200μm。通过两类岩性中孔喉特征差异初步分析,认为矿物组成、压实作用、有机质成熟度是其主要影响因素。     

A study on hydrocarbon generation potential of deep source rocks and gas sources in Changling Fault Depression,Songliao Basin

Through natural gas exploration in the Changling Fault Depression,abundant natural gas flows were obtained and high-quality source rocks were also reveiled.Based on bulk analyses,organic matter abundance,organic matter type and thermal maturity of the source rocks were studied systematically.At the same time,gas gener-ating intensity and gas generating quantity were quantitatively analyzed by using basin modeling technologies.The results indicated that gas source rocks of the Shahezi Formation are characterized by abundant organic matter and dark mudstone distributions and high-over thermal maturity.They possess high gas generating intensity with the biggest value surpassing 500×108 m3/km2,and large gas generating quantity,accounting from 74.40% of the total amount.The Yingcheng Formation has good gas-source rocks with moderate dark mudstone and relatively high organic matter.It has type-Ⅲ organic matter and low-over thermal maturity.The gas generating intensity is moderate,between 20×108 and 60×108 m3/km2.The gas generating quantity is 13.63% of the total amount.The Huoshiling Formation has relatively good source rocks with limited dark mudstone and low organic matter.It has type-Ⅲ kerogen and over-thermal maturity.The gas generating quantity is 7.10% of the total amount.The Denglouku Formation has poor-gas source rocks,and is characterized by undeveloped dark mudstone and low organic matter abundance.It has type-Ⅲ organic matter and low-high thermal maturity.Hydrocarbon gases in the Changling Fault Depression mainly originated from the Shahezi Formation,and secondarily from the Yingcheng Formation.The contribution of the Huoshiling Formation gas source rocks is relatively small.     

淮北五沟煤矿F_（14）断层导水特征研究

五沟煤矿的F14断层为矿区内二采区的边界断层,落差较大且切割了多个含水层,造成主采10煤层、部分81、82煤在断层处与灰岩含水层＂对口＂接触。因此,在井巷工程揭露F14断层时,灰岩水有直接进入矿坑的可能性。在分析矿区地质及水文地质条件的基础上,根据断层带的岩性特征、抽水试验成果、物探及井下实际揭露等资料,并运用泥岩涂抹系数法,对F14断层的导水特征和封闭性进行了综合分析,得出了F14断层的导水性较差,断层封闭性较好的结论,为后续煤矿的安全生产提供了理论依据。     

盐源地区古生界页岩气地质条件分析

为了进一步探索我国西南地区的页岩气资源潜力,中国地质调查局成都中心对盐源地区开展公益性页岩气基础地质调查。在系统的地质调查和沉积学、石油地质学研究的基础上,对盐源地区进行页岩气地质条件分析。发现盐源地区早古生代发育志留系龙马溪组和泥盆系坡脚组两套富有机质页岩层系。志留系龙马溪组以碳质硅质泥页岩和碳质粉砂质泥页岩为主,以富有机质、硅质含量高、笔石发育为主要特征,发育于深水陆棚环境中。泥盆系坡脚组以含钙质碳质泥岩和钙质碳质粉砂质泥岩为主,以富有机质、黏土含量高、竹节石发育为主要特征,主要发育于潟湖环境中。两套富有机质页岩层系均具有有机质含量高,沉积厚度大,热演化程度高,脆性指数较高,低孔低渗的特征。盐源地区发育大量宽缓向斜,具备较好的页岩气保存条件。在志留系稗子田组和泥盆系坡脚组的勘探获得了油气显示,表明盐源地区页岩气具备良好的勘探潜力,研究成果为区域油气勘探评价提供借鉴与参考。     

克拉玛依油田二厂八区套管破损机制研究

克拉玛依油田二厂八区井区经过长期开采出现了大量的套管破损问题。对套管破损位置进行总结归纳发现,套管破损主要存在于白垩系吐谷鲁群、侏罗系齐古组、二叠系乌尔禾组等地层中。对研究区连井进行地层对比、地震数据体进行波阻抗反演和砂体分析,发现研究区内白垩系吐谷鲁群和侏罗系齐古组的砂体十分发育,广泛存在于整套地层中。砂体中流体的渗流作用对套管的腐蚀为套管破损的主要因素。泥岩吸水蠕变膨胀、油层出砂和固井质量不合格为套管破损的其他因素。     

Discovery of Potassium-Bearing Cuttings from the Well Yangta 4 in the Kuqa Depression and Seam Division

正The world petroleum exploration suggests that,about70%of the world’s potash resources were discovered during oil and gas exploration(Zheng et al.,2007).The Kuqa depression in the Tarim basin is abundant with petroleum exploration data,and