High-resolution sedimentary record of lead in the coastal mud of the East China Sea in the past one hundred and fifty years

In the East China Sea （ECS）, there are some mud areas, including the south coastal mud area, the north coastal mud area, and the mud area to the southwest of Cheju Island. X-ray fluorescence （XRF） techniques and Thermal Ionization Mass Spectrometry （TIMS） were used to study the high-resolution sedimentary record of Pb concentrations and Pb stable isotopic compositions in the past one hundred and fifty years in the coastal mud of the ECS. Pb concentrations of a ^210Pb dating S5 core in the study area have increased rapidly since 1980, and reached the maximal value with 65.08 μg/g in 2000, corresponding to the fast economic development of China since the implementation of the ＂Reform and Open Policy＂ in 1978; ^206Pb/^207Pb ratios generally had stabilized at 1.195 from 1860 to 1966, and decreased gradually from 1966 to 2000, indicating that the anthropogenic source Pb contribution to the ECS has increased gradually since 1966, especially since 1980. Pb concentrations decreased distinctly from 2000 to 2003 and ^206Pb/^207Pb ratios increased from 2001 to 2003, corresponding closely to the ban of lead gasoline from 2000 in China. From 1950 to 2003, there occurred four distinct decrease events of ^206Pb/^207Pb, possibly responding to the Changjiang River （Yangtze River） catastrophic floods in 1998, 1991, 1981 and 1954; from 1860 to 1966, there were two decrease periods of ^206Pb/^207Pb, which may respond to the catastrophic floods of Changjiang River in 1931 and 1935, and 1870. As a result of the erosion and drowning by the catastrophic floods, the anthropogenic lead accumulated in soil and water environments over a long period of time was brought into the Changjiang River, then part of them was finally transported into the ECS, which leads to changes in Pb stable isotopic composition.     

Early diagenesis of nurtrients （C, N, P and Si） stored in sediments of two reservoirs in southwestern China

Damming is a common anthropogenic intervention along the course of rivers, which is defined as ＂artificial-lake effect＂, both in China and across the world. Today as many as 48000 dams and/or reservoirs are in operation in the Changjiang River （Yangtze River） drainage area, and more are being constructed. While damming is well known to affect riverbome nutrient loads, and thus the riverine ecosystems owing to removal of carbon fixation, and removal of particles in reservoir sediments, there is limited information on the detailed early diagenesis of sediments in reservoirs including the regeneration processes of nutrients deposited in sediments and exchange flux across the sediment-water interface, which is important for mass balance of riverbome nutrients. In the present study, two large-size reservoirs, Wujiangdu Reservoir （WJDR） and Dongfeng Reservoir （DFR）, located on the main steam of the Wujiang River and with uniformity hydrography and discrepancy biogeochemical activity （e. g. primary production）, were selected for a comparative study on the detailed processes of nutrient regeneration. Water, pore water and sediment were sampled from these two reservoirs and dissolved organic carbon （DOC）, NH4^＋, NO3^-, PO4^3-, dissolved silica （DSi） in the overlying water and pore water, and total organic matter in sediments were determined. The results of correlation analysis suggested that in these two reservoirs, processes of nutrient regeneration near the sediment-water interface were significantly different. As a result of rapid decomposition of algae-derived ＂labile＂ organic matter in upper sediments, nutrient regeneration processes and upward fluxes in WJDR are dramatically stronger than those of DFR. NH4^＋ upward flux from sediment in WJDR was about 17 times higher than that in DFR. PO4^3- flux in WJDR is about 13 times above that in DFR. DOC flux in WJDR is larger that in DFR by 5 times, and DSi by 1 time.     

Aragonite cycles: diagenesis caught in the act

Organic biomarker and nannofossil assemblages are used in combination with sedimentary petrology to identify the role of diagenesis for the formation of a rhythmic calcareous succession. A record from the Early Pliocene of the Maldives (Ocean Drilling Program, ODP Leg 115) is presented containing precession and eccentricity cycles expressed as variable aragonite content. Additional sub‐Milankovitch cycles are caused by rhythmic precipitation of calcite cement in the lower part of the interval. Comparison with palaeo‐productivity indicators (nannofossils, chlorin, total organic carbon) suggests that cementation occurs preferentially in intervals characterized by increasing or decreasing productivity. The coupled variability in productivity and carbonate diagenesis is attributed to the effect of organic matter degradation in the sediment. The observed combination of primary and diagenetic factors hampers the interpretation of the cyclicity on Milankovitch and sub‐Milankovitch scales. Diagenetically stable proxies for palaeo‐productivity, such as nannofossil assemblage data, were used to distinguish between palaeoclimate and diagenetic influences.     

吉尔嘎朗图凹陷宝饶洼槽下白垩统层序地层与沉积体系

运用高分辨率层序地层学原理和方法,通过对钻井和地震资料的综合分析,在二连盆地吉尔嘎朗图凹陷下白垩统中识别出1个超长期基准面旋回(二级层序)SSC1和5个长期基准面旋回(三级层序):LSC1,LSC2,LSC3,LSC4,LSC5,分析了各旋回的发育特征。识别出五种类型的沉积体系:滨浅湖近岸水下扇、较深水湖浊积扇、滨浅湖扇三角洲、滨浅湖辫状河三角洲和河流沉积体系,并在等时地层格架内分析了各基准面旋回的沉积体系构成和储层砂体的发育情况。综合分析生、诸、盖条件后认为,在垂向上,LSC3旋回为本区最有利的储集层段,在平面上,本区的油气勘探应主要寻找宝饶构造带辫状河三角洲前缘砂体,主要储层砂体类型为前缘分流水道砂和前缘席状砂。     

塔里木盆地阿克库勒地区石炭系卡拉沙依组成岩作用

阿克库勒地区卡拉沙依组碎屑岩储层的成分成熟度和结构成熟度均较低．储层的次生溶蚀孔隙所占比例远高了：原生孔隙，次生孔隙是储层的主要储集空间．样品数据统计显示，卡拉沙依组储层属于低孔、低渗储层类型．根据岩石薄片、铸体薄片观察及储层样品的扫描电镜和阴极发光分析结果，本区石炭系储层主要经历的成岩作用有压实（压溶）作用、胶结作用、溶蚀作用和交代作用，其中碳酸盐矿物的沉淀和溶蚀作用是本区卡拉沙依组储层所经历的最重要的成岩作用．成岩作用已达到晚成岩B期，早期方解石交代石英颗粒并发生大量溶蚀，生成大量次生孔隙，晚期方解石没有发生溶蚀．     

辽河盆地冷家油田沙河街组三段储层岩相古地理

辽河盆地在沙河街组三段早期水体较深,主要形成扇三角洲及盆底扇;沙三晚期水体较浅,发育湖泊砂体.依据沉积相分布规律,沙三早、中、晚3个时期可进一步分别划分出湖泊扩张和收缩阶段.盆地西部凹陷的冷家油田为东陡西缓的箕状洼陷.研究区内沙三段的古地理格局是决定相分布的关键因素,河流和湖泊能量相对强弱决定扇体沉积的规模.受相对湖平面变化的影响,纵向扇三角洲主要形成于湖泊扩张时期,并且有相带窄、过渡快、以粗碎屑沉积为主的特点.扇体沉积中主要发育前缘分流河道充填沉积,但位于河口前缘或侧缘的滩坝及前三角洲中的盆底扇局部也较发育.     

胜利油田车镇凹陷沙河街组二、三段沉积相

车镇凹陷古近系沙河街组三段上亚段-二段下亚段是较为典型的深断陷型三级层序.层序的发育主要受控于幕式断陷作用,可进一步划分出低位体系域、湖侵体系域和高位体系域.通过岩心观察、薄片镜下鉴定、粒度分析、古生物及遗迹化石分析,并综合利用测井曲线和地震相特征,认为该时期主要发育有扇三角洲、三角洲、近岸水下扇、湖底扇、滨浅湖滩坝等骨架砂体相,以及滨浅湖、半深湖-深湖等沉积相及其亚相.综合考虑物源特征、沉积环境、沉积体系平面展布以及生、储、盖组合关系,认为有利的沉积相带主要是三角洲、扇三角洲前缘、湖底扇、近岸水下扇的中扇和外扇以及滨浅湖中发育的滩坝和砂坝.     

河南省平顶山盐田盐矿床成矿特征探讨

以现有钻孔及区域资料为基础，对平顶山盐田盐矿床形成的构造条件和盐湖的沉积模式、沉积类型成矿物源进行了分析，为平顶山盐田的进一步勘查和开发提供了宝贵资料。     

山东车镇凹陷东部古近系沙河街组成岩作用

车镇凹陷沙河街组的沉积体系受控于盆地内的构造、物源供给以及沉积时的气候环境。以岩石学特征为基础，描述了成岩过程中压实与压溶作用、胶结作用、溶解作用与次生孔隙的特征，以及次生孔隙带在本区的分布。论述了碳酸盐胶结物与粘土矿物胶结作用的特点。粘土矿物蒙脱石-伊利石转变具有明显的渐变与突变交替的演化程式，其演化经历了蒙脱石带、渐变带、迅速转化带和伊利石带以及蒙脱石向伊利石的转变带。沙河街组的成岩作用划分为早期成岩阶段（A期、B期）和晚期成岩阶段（A期、B期、C期），并提出了成岩阶段的划分标志。     

泌阳凹陷安棚油田深层系成岩作用研究及其在成岩圈闭预测中的应用

深层系一般指沉积盆地中埋藏深度在2 500～2 700 m以下的地层,其储集物性普遍很差,但在一定条件下,深部溶蚀作用可产生优质储层,形成成岩圈闭.然而这种成岩圈闭的预测一直是一个难题.安棚油田位于河南泌阳凹陷东南部,勘探成果表明,在该油田深层系下第三系核桃园组核三段下部(简称(核三下)席状的扇三角洲砂体中存在成岩圈闭.本次通过定量的成岩作用研究和成岩阶段划分,对成岩圈闭的形成机理和分布进行了探讨.研究表明,该区核三下的砂体经历了压实、胶结、溶蚀等多种成岩作用,不同的成岩作用发生于不同的埋藏深度.2 700～3 100 m之间以胶结强烈为特征,属于胶结带.3 100～3 900 m之间以次生溶蚀孔隙发育为特征,尤其是3 200～3 600 m之间, 属于深部溶蚀带.本区核三下砂体自南而北埋藏深度逐渐变浅,其上倾方向处于胶结带的部分由于强烈胶结而变成致密层,可封堵油气,而下倾方向处于溶蚀带的部分由于次生溶蚀孔隙发育而成为良好储层,从而形成成岩圈闭.根据不同埋藏深度、不同成岩阶段孔隙发育和保存的特征,可预测成岩圈闭分布。