Advances in the research on Carboniferous deep‐water marine deposits in western Junggar,northwestern China

Carboniferous deep‐water marine strata have been insufficiently studied in western Junggar, NW China where the deep‐water facies successions have long been disputed in terms of age constraints, sequence and palaeoenvironmental reconstruction. This paper introduces some views in the light of new materials obtained from this region in recent years. The presence of the Visean plant fossils from the upper Ta'erbahatai Formation in the Tarbgatay Mountains indicates that the formation can be extended to the Early Carboniferous epoch in age. This unit also displays obvious diachroneity, which is of Late Devonian to Early Tournaisian age in the Saur Mountains and Late Devonian to Visean age in the Tarbgatay Mountains. The Xibeikulasi, Baogutu and Tailegula formations are widely distributed in northwestern Karamay areas. The scouring structures and graded bedding near the boundaries between the three formations confirm the stratal sequence that they were originally assigned, namely the Xibeikulasi, Baogutu and Tailegula formations in ascending order. The ‘fossil chaos’ of the three formations is due to mistaking fossils of other stratigraphic units for fossils of these three formations. After revision, only the Early Carboniferous fossils are considered reliable, and combined with the newly found plant fossils, the Xibeikulasi, Baogutu and Tailegula formations are re‐assigned to the early Visean, late Visean, and latest Visean to Serpukhovian ages, respectively. An extension of the lower Hala'alate Formation was recognized in the southwestern Hala'alate Mountains. The presence of the latest Early Carboniferous brachiopods constrains the Hala'alate Formation as late Serpukhovian to Bashkirian in age, bearing the mid‐Carboniferous boundary. Copyright © 2013 John Wiley & Sons, Ltd.     

Ichnofabric characterization of a deep‐marine clastic system: a subsurface study of the Middle Eocene Ainsa System,Spanish Pyrenees

This paper documents a subsurface trace fossil and ichnofabric study of the proximal parts of a structurally confined and channelized sand‐rich, lower slope and proximal basin‐floor deep‐marine system in the Middle Eocene Ainsa basin, Spanish Pyrenees. Five depositional environments are recognized based on sedimentary facies associations, depositional architecture and stratigraphic context (channel axis, channel off‐axis, channel margin, leveé‐overbank and interfan), as well as a channel abandonment phase. Each environment is characterized by distinct and recurring ichnofabrics. Ichnological measurements and observations were recorded from six cores recovered from six wells drilled at a spacing of between 400 m and 500 m at outcrop, and totalling 1213 m in length. From channel axis to levée‐overbank environments, there is a trend of increasing bioturbation intensity and ichnodiversity. Ichnofabrics in channel axis and channel off‐axis environments are characterized by low bioturbation intensity and low ichnodiversity. Thalassinoides‐dominated firmground ichnofabrics associated with erosive sediment gravity flows are common in these environments. In contrast, channel margin and levée‐overbank environments are characterized by ichnofabrics associated with high bioturbation intensity and ichnodiversity. Sediments of the interfan are characterized by the highest bioturbation intensity, associated with burrow mottling and an absence of primary sedimentary structures. This paper demonstrates that in core‐based studies, ichnofabric analysis is an important and valuable tool in discriminating between different environments in channelized deep‐marine siliciclastic systems. The results of this study should find wide applicability in reservoir characterization studies in the petroleum industry, in field‐based analogue ichnofabric studies and other core‐based studies in deep‐water siliciclastic systems worldwide such as the Integrated Ocean Drilling Program.     

东营凹陷沙河街组介形虫化石埋藏学研究

东营凹陷古近纪济阳群沙河街组内的介形虫化石在平面上的分布有多种形式；就介形虫化石本身的保存特征而言，壳体充填物有5大类型，壳体颜色丰富多彩。对介形虫化石保存特征进行成因探讨，有助于恢复古环境。     

二纺蛛总科（蜘蛛目：新蛛下目）蜘蛛化石研究进展

二纺蛛总科包括5个现生科、5个化石科以及一些科级位置未定的化石物种,是蜘蛛目中较为古老的一个类群。目前已知最早的二纺蛛总科化石记录可以追溯到早侏罗世,但分子系统发育研究推测其起源时间为二叠纪。二纺蛛总科蜘蛛在中生代最为繁盛,化石物种相对较多,是蜘蛛化石类群的重要组成部分。而现生二纺蛛总科蜘蛛十分稀少,且主要分布在热带和亚热带地区。近年来的系统发育研究认为二纺蛛总科可能是复杂生殖器类的姐妹群,是蜘蛛演化研究的关键类群。因此,本文对二纺蛛总科分类系统的研究历史进行了回顾,总结了二纺蛛总科化石类群在不同地质历史时期的组成和分布,统计了二纺蛛总科蜘蛛化石的名录。目前,二纺蛛总科蜘蛛化石分类研究基础薄弱,部分化石类群的系统位置存疑,二纺蛛总科内部系统发育关系尚不清晰。在将来的研究中,需要利用多种技术手段获取化石材料的形态学信息,打好分类学基础;结合化石类群和现生类群进行系统发育分析;进而联系古地理、古生态、生物学行为等研究,全方位分析二纺蛛总科的自然演化历史。     

豫西苗岭统馒头组二段皱饰构造与遗迹化石共生特征*

埃迪卡拉纪以来,微生物与后生动物之间呈此消彼长的关系,但在寒武纪苗岭世却出现了微生物成因沉积构造和后生动物扰动构造短暂共存的现象。笔者在豫西馒头组二段下部识别出包括皱饰构造与微生物席裂构造在内的2种微生物成因沉积构造,对皱饰构造与遗迹化石的共生关系进行了分类,建立了席上足辙迹(Monomorphichnus henanensis)与牧食迹(Jinningichnus badaowanensis)、席下水平漫游迹(Planolites montanus)、席下深层泥岩中生物扰动共3种微生物席与后生动物的共生模式和生态演化模型。上述研究表明,具有特殊环境耐受性的“机会主义”动物在食物来源较为宽松的潮坪环境中与微生物席共存,这种微生物席与后生动物短暂而“和谐”的共存关系不仅延续了埃迪卡拉纪双方的部分共生特征,且在以混合底为主导的显生宙生态环境中得到了进一步变化与发展。     

西太平洋富钴结壳中钙质超微化石和分子化石研究

本文对西太平洋麦哲伦海山CM3D06富钴结壳进行了钙质超微化石生物地层学研究,发现结壳中有代表白垩纪(晚期)、古新世(晚期)、始新世(早、中、晚期)、中新世(中期)、上新世(晚期)和更新世等各时代的标准钙质超微化石,表明结壳的形成始于白垩纪(晚期);在富钴结壳中检出正构烷烃、类异戊二烯烃、甾烷类等众多分子化石,分子化石组合特征指数、主峰碳、ΣC-23/C+24、CPI、Pr/Ph、Pr/nC17、Ph/nC18和nC31/nC17显示有机质生物母源主要为海洋浮游植物、浮游动物和底栖非光合作用的菌类,而甾烷类的C29、C28和C27含量分布的变化则说明生物种群具有快速演变的特征。此外,还探讨了CM3D06结壳中Pr/Ph和有机碳同位素组成变化与结壳生长过程中的海洋环境演化的关联程度。     

黄土高原区环纹藻化石的发现及其意义

环纹藻化石不仅广泛分布于我国东南部新生界地层，而且笔者近年在黄土高原区晚更新世以来的孢粉中亦有较多发现。在８个化石点共找到环纹藻化石２３７８粒．研究表明，它具有横向和纵向分布规律性。含环纹藻的孢粉组合不仅有喜暧湿的阔叶树种花粉，而且也有喜冷湿的暗针叶树种花粉，反映了环纹藻对气候有很强的适应性．我国西部环纹藻化石种类较东南部单调，其数量从东向西趋于减少。其时代分布，从晚更新世早期到晚全新世，以中全新世最为繁盛。人们可依据它及其共生藻类，追溯到地史时期淡水湖沼的消长。     

广西平南县金秀地区寒武纪微古植物群

文章研究了平南县大鹏—金秀六巷地区寒武纪小内冲组、黄洞口组大瑶山微古植物群 ,计有 10 9种 (其中5 4种未定种 ) ,归纳为 3大类 ,并介绍了各类的组合特点。     

南极乔治王岛菲尔德斯半岛西湖柱状剖面藻类化石与环境演变

根据西湖柱状岩芯样品中藻类化石的分布与含量变化,推测本区在3600年前仍为冰川覆盖;距今3600～3000年前为冰缘浅湖期;3000～1200年前湖水稳定,气候环境相对较好;距今1200年至现代气候略有波动。     

Endeavour 42 deposit,Lake Cowal,New South Wales: A structurally controlled gold deposit

Endeavour 42 is a structurally controlled Au deposit with similarities to adularia‐sericite deposits. It is the largest of four gold prospects discovered in the Late Ordovician Lake Cowal volcanic complex, adjacent to the Gilmore Fault Zone, in central New South Wales, Australia. The Lake Cowal volcanic complex consists of calc‐alkaline to shoshonitic volcanic rocks and related sedimentary rocks that were deposited in a relatively deep‐water environment. The volcanic and sedimentary rocks of the Lake Cowal volcanic complex were intruded by diorite and granodiorite. Low‐grade porphyry Cu (0.2–0.35% Cu) mineralisation is developed in parts of the granodiorite intrusion. The gold deposits are developed north of the porphyry Cu mineralisation and occur within a north‐south corridor adjacent to a north‐south‐oriented body of diorite. The Endeavour 42 deposit is hosted by three volcanic units and a diorite. The stratigraphic units at Endeavour 42, consistently strike 215° and dip 50°NW, and comprise an upper unit dominated by redeposited pyroclastic debris and a lower conglomerate unit with clasts of reworked volcanic rocks. Separating these units is a sequence of trachyandesite lava and hyaloclastite breccias. Laminated mudstone and siltstone throughout the sequence are indicative of a relatively deep‐water, below wave‐base, environment. Porphyritic dykes, which are typically associated with zones of faulting, cross‐cut both the volcano‐sedimentary sequence and the diorite. The major fault orientations are 290° and 340°, forming subparallel conjugate fault sets. Both sets of faults are mineralised, contain deformed porphyritic dykes and are associated with sericitic alteration. Endeavour 42 is a sulfide‐poor gold deposit with free native Au and Au associated with pyrite and sphalerite. Minor galena, pyrrhotite and chalcopyrite are also observed. Irregular pyrite veinlets and carbonate‐sulfide veinlets occur in the upper unit of re‐deposited pyroclastic debris. Auriferous veins are parallel‐sided dilatant veins with quartz‐sulfide‐carbonate‐adularia. These veins display a consistent strike of 305° and a dip of 35°SW. Alteration and mineralisation were influenced by host‐rock composition and rheology. A pervasive alteration assemblage of chlorite‐carbonate‐hematite‐epidote is developed throughout the Lake Cowal volcanic complex. This is overprinted by sericite‐silica‐carbonate alteration around fault zones and dykes, with patchy and pervasive alteration of this type developed in the lava sequence and upper volcani‐clastic unit, reflecting permeability and probable alteration zoning. In the lower clastic unit, the diorite and, in parts of the lava sequence, a chlorite‐carbonate‐pyrite assemblage partially overprints sericite‐silica alteration, suggesting an evolving fluid composition, changing physico‐chemical conditions or a different alteration fluid. Age dating of the intrusive phases and sericitic alteration associated with mineralisation at Endeavour 42 yields ages of 465.76 ± 1 and 438.6 ± 0.5 Ma, respectively, suggesting that mineralisation post‐dates the Lake Cowal intrusive event and is related to intrusion of magma during the 440 Ma mineralising event, an important period in the eastern Lachlan Fold Belt.