Vines 1 revisited: are older Neoproterozoic glacial deposits preserved in Western Australia?

The stratigraphy in Vines 1, a 2017.5 m-deep cored stratigraphic hole drilled by the Geological Survey of Western Australia in 2001 near the Western Australian – South Australian border, has been reinterpreted with implications for the Neoproterozoic to Cambrian geological history of the Officer Basin. A previous interpretation considered the intersected succession as a conformable stratigraphic package, the Vines Formation. An assemblage of palynomorphs, found throughout the hole and previously used to infer an age of no older than earliest Cambrian, is now thought to consist of contaminants. An older assemblage, which is considered to be reworked and inherited from underlying rocks, provides a new maximum age constraint of mid-Neoproterozoic. Based on sedimentological interpretations and comparisons with other drillholes in the western Officer Basin, and the succession in the eastern Officer Basin, the Vines 1 succession is reinterpreted as four discrete sedimentary packages, the Pirrilyungka (new name), Wahlgu, Lungkarta and Vines (redefined) Formations, in ascending order. The Pirrilyungka and Wahlgu Formations include glacigenic sediments and may correlate with similar glacial successions in Supersequences 2 and 3 (mid to late Cryogenian) of the Centralian Superbasin, and the Sturt Tillite and Elatina Formation and their equivalents in the Adelaide Rift Complex of South Australia, respectively. The eolian Lungkarta Formation and fluvial Vines Formation are considered, on regional evidence, to be most likely of Ediacaran to earliest Cambrian age.     

Characteristics and evolution of lacustrine turbidite of Chang-7 Member of Yanchang Formation in northern Shaanxi

Lacustrine turbidite of Chang-7 Member in the studied area consists of sihstone and fine sandstone with respect to grain size, which is feldspathic lithie sandstone, syrosem arkose and arkose with respect to mineral constitution affected by provenance. There are such apparent signatures as lithology, sedimentary structure, sedimentary sequence and well logs, to recognize turbidite. During the paleogeographic evolution of Chang-7 Member, lake basin and deep lake are both at their maximum extent during Chang-73 stage, resulting in the deposition of Zhangjiatan shale with widespread extent and of turbidite with fragmental-like. Deep lake line is gradually moving toward lake center and turbidite sand bodies are gradually turning better with better lateral continuity, connectivity and more thickness, from stages of Chang-73, Chang-72 and Chang-7t, which can be favorable reservoir in deep-water.     

华北燕山地区雾迷山组疑源类化石组合及其特征

本文通过系统采样,利用化学浸泡法,对冀北坳陷凌源地区和宣龙坳陷北京延庆地区的雾迷山组疑源类进行了研究,并划分出四个化石组合,自下而上分别为:罗庄组合(Asperatopsophosphaera umishanensis-Oscillatori-opsis luozhuangensis)、磨盘峪组合(Stictosphaeridium pectinale-Micrhystridium pallidum)、二十里堡组合(Pale-amorpha punctulata-Orygmatosphaeridium rubignosum)和闪坡岭组合(Microconcentrica cymata-Baltisphaeridium cerinum).通过两个地区疑源类组合特征的对比,认为凌源地区和延庆地区雾迷山组微疑源类化石组合及特征具有可对比性.     

陕西蓝田地区新第三纪地层划分的几点讨论

蓝田地区灞河组和蓝田组的时代归属是我国三趾马动物群分期的关键问题之一。通过与府谷老高川三趾马动物群的对比及古地磁测定，该区新第三纪地层可分为上新统静乐组（原蓝田组上部）、蓝田组（原蓝田组下部）和灞河组．蓝田组的地质时代可归保德期庙梁亚期，地质年龄约为距今５．３—５．０Ｍａ期间．灞河组的地质时代可与喇嘛沟动物群的对比，为保德早期或稍早．     

东营凹陷沙河街组碳酸盐胶结物成因机制

正碳酸盐矿物是砂岩储层中主要的成岩产物之一。碳酸盐胶结物较为活跃,其溶蚀及沉淀广泛发育于砂岩储层内。碳酸盐的溶蚀及沉淀是砂岩储层改造的重要成因之一。明确碳酸盐胶结物的成因机制对预测深部储层具有重要的意义。本次研究,采用铸体薄片及扫描电镜观察,明确碳酸盐胶结物的产状。对不同产状碳酸盐胶结物的分布、     

川西汉旺地区雷口坡组四段风暴岩特征及地质意义

通过野外实测剖面和镜下薄片观察,川西汉旺地区雷口坡组四段发育典型的风暴岩,具有底冲刷—充填构造、风暴砾屑层、菊花构造和丘状交错层理等典型风暴沉积标志。根据该风暴岩岩性、沉积位置、沉积标志组合特征,共识别出三种风暴沉积序列类型：1）序列I由侵蚀底面及砾屑段、粒序段组成,代表靠近风暴浪基面附近的台前缓斜坡下部环境;2）序列Ⅱ由侵蚀底面及砾屑段、粒序段、平行纹层段、丘状纹层段组成,代表靠近正常浪基面附近的台前缓斜坡上部环境;3）序列Ⅲ由粒序段、平行纹层段组成,代表台地边缘环境。风暴层序自下而上的沉积演化为：台前缓斜坡下部—台前缓斜坡上部—台地边缘,整体为一个向上变浅的沉积序列。     

萨拉乌苏河流域萨拉乌苏组沙丘砂沉积特征

萨拉乌苏河流域米浪沟湾剖面萨拉乌苏组含7层古流动沙丘砂、4层古固定-半固定沙丘砂.对这些沙丘砂的沉积构造观察以及粒度、扫描电镜和常量化学元素分析结果表明：（1）这些沙丘砂具有与现代沙丘砂相似的风成沉积构造特征;（2）粒度及其参数——Mz、σ、Sk和Kg,以及主要化学组分SiO2、Al2O3和TOFE也与现代沙丘砂相近;（3）Mz-σ、SiO2-Al2O3＋TOFE散点图和概率累积曲线显示这些沙丘砂与萨拉乌苏组中的河湖相、古土壤差别明显,而与现代沙丘砂一致;（4）石英砂颗粒具有良好的磨圆以及碟形坑、新月形坑、麻坑、上翻解理薄片、硅质沉淀和硅质裂纹等表面结构特征,反映其曾受持久的风力搬运作用.沉积构造、粒度、石英砂颗粒表面结构和化学元素等多个方面具备了与现代沙丘砂类似的风成特征,证明这些沙丘砂的成因是风成的.     

鄂西娄山关组顶部古岩溶不整合面的发现及层序地层学意义

鄂西娄山关组顶部存在古岩溶不整合面,有众多陆上暴露和溶蚀标志,表明其产生受寒武纪末海平面下降事件的控制。它不仅形成了碳酸盐台地上典型的Ⅱ型层序界面,而且恰与寒武—奥陶纪年代地层界线相重合,体现了层序界面、年代界线和事件界线三位一体的有机结合