塔里木盆地西南部早白垩世风成沙丘古风向测量与古风带恢复

本文通过对塔里木盆地西南部早白垩世风成沙丘的前积层产状的测量,恢复了当时的古风向和古风带。研究结果表明:当时盛行东北风,研究区属于东北信风带,正好位于北半球中低纬度沙漠带之中。     

四川盆地东部中二叠统茅口组顶部钙结壳的发现及其发育模式

对四川盆地东部涪陵地区角帮沟剖面中二叠统茅口组顶部钙结壳进行的岩石学和矿物学系统分析发现,该剖面中钙结壳的矿物组成和含量呈规律变化,可分为基岩带、过渡带及钙结带。岩石学分析表明,基岩带为灰白色中厚层泥晶生物灰岩,其内发育碳酸盐岩砂和岩溶角砾充填的岩溶系统;过渡带为黄白色、黄褐色、褐红色含燧石条带或团块状泥晶生物灰岩,其内发育钙质胶结的原地角砾充填的侵蚀漏斗;钙结带为局部钙结岩化的灰色亮晶生屑灰岩叠覆土黄色多孔块状钙结岩,其内发育多期裂缝、根模、肺泡结构和次生碳酸钙胶结物等典型钙结壳结构。矿物学分析表明,自过渡带至钙结带CaCO₃含量呈逐渐上升的趋势,推测内部次生碳酸钙逐步胶结富集是钙结岩形成的主要原因。结合四川盆地茅口组顶部以发育铝土质泥岩和铝土岩的岩石组合为特征,且其与中二叠世上扬子地区位于赤道附近的古地理背景相吻合,表明四川盆地东部地区茅口组顶部钙结壳形成于湿热气候条件下;并通过与经典钙结壳特征的比较,总结出湿热气候条件下的钙结壳发育模式。该研究成果不仅是对四川盆地中二叠统茅口组表生成岩作用产物的补充,而且还可为国内外同类型钙结壳研究提供详实的材料。     

Geochemical characteristics and depositional environment of the Middle Permian mudstones from central Qiangtang Basin,northern Tibet

Geochemical characteristics of the Middle Permian mudstones from the Longge Formation in the Jiaomuri area, central uplift zone of Qiangtang Basin have been analysed to constrain their provenance, tectonic setting, depositional redox condition and palaeoclimate. Based on the geochemical parameters like CIA, PIA, ICV values and Th/U, K/Rb ratios indicate that the source rocks were affected by low degree weathering conditions. The U/Th, V/Cr, Ni/Co, V/Sc ratios and U_au, C‐values of samples suggest that the mudstones were formed in an oxic environment, with arid palaeoclimate. Bulk‐rock geochemistry analysis indicates that they are mainly arkose and subarkose, derived from dominantly andesitic rocks, probably a mixing of felsic and mafic provenance. The CIA, PIA and ICV values of these samples suggest that the Longge mudstones are compositionally immature and related to moderate weathering. The tectonic discrimination diagrams, as well as critical trace and REE characteristic parameters imply an oceanic arc or continental arc setting for the depositional basin of mudstones from the Longge Formation, probably back‐arc basin. This study supports an occurrence of archipelagic oceanic basins in the Jiaomuri area in the Middle Permian, which provides evidence for the research of the Longmu Co–Shuanghu–Lancangjiang Suture. Copyright © 2015 John Wiley & Sons, Ltd.     

Tephras in lacustrine sediments of the Sarliève marsh (French Massif Central): age and preservation

The Sarliève marsh sediments (Massif Central, France) contain two tephras. The first tephra [, ca. 12 000 BP], regionally well known, enables to date the beginning of lacustrine infill to the Lateglacial. The second tephra, the ‘tephra de Sarliève’, the emitting volcano of which is unknown, would be dated to around the Early Subboreal from pollen data. This occurrence, after the discovery of the ‘tephra de Beaunit’, emphasizes that volcanic eruption(s) occurred in the ‘Chaîne des Puys’ or in the volcanic Cézallier more than 1000 years after the last known eruption (Pavin) in the ‘Chaîne des Puys’ at around 6.6/6.7 ka (5800/5900 BP). In the Sarliève piles, these tephras, well preserved in thick and more silicated deposits of deltas, were not observed in carbonated basin sediments where they were altered. The abundance of authigenic zeolites formed during the Lateglacial in restricted depocentre lacustrine waters allows us to detect initial CF1 tephra occurrence. To cite this article: A. Fourmont et al., C. R. Geoscience 338 (2006).     

Characteristics of Albaillella （ Albaillellarian ,Radiolarian） Fauna from Guadalupian to Lopingian Series in Permian, South China

On the basis of establishment of radiolarian biostratigraphy and conodont biostratigraphy,a radiolarian Albaillella fauna in the transitional environment from Guadalupian to Lopingian Series in Permian was found at a pelagic chert section in southeast Guangxi, South China. Radiolarian Albaillella is one of the most sensitive biology to the transitional environment. The Albaillella fauna shows an ecological evolutionary process from Guadalupian to Lopingian: declined stage-recovery stage-flourishing stage. The study of characteristics of the Albaillella fauna in the transitional environment may provide more information, not only for the subdivision and correlation of a high-resolution biostratigraphy, but also for influence of radiolarian Albaillella fauna on the pre-Lopingian mass extinction.     

新疆乌鲁木齐二叠系湖相微生物白云岩成因

新疆乌鲁木齐地区养牛场剖面中二叠统芦草沟组以发育浅湖至半深湖背景下的中层深灰色、灰色碳酸盐岩、粉砂岩、细砂岩与中、厚层灰黑色泥岩、油页岩的互层沉积为特点.湖相碳酸盐岩以微晶白云岩为主体,其次为微晶灰岩.微晶白云岩主要由白云石、铁白云石及少量方解石等组成,常混有泥质组分且富含有机质.镜下观察白云石主要为微晶(＜4μm)及微亮晶(4-10 μm),极少数为亮晶(＞10μm).扫描电镜分析发现微晶白云岩中存在微球状(直径约9μm)、微棒状(长度约0.3～1.2μm)及微米级它形(＜ 5μm)等3种微形貌的白云石,其中微米级它形白云石在白云岩中占绝大多数.在微晶灰岩中还发现了直径约70-150nm,形态与球菌相似的纳米微粒,具有微生物矿化的特征.研究区白云岩Sr丰度及Sr/Ca比总体持平或略高于微晶灰岩,Mn丰度远高于微晶灰岩,C、O同位素均高于微晶灰岩,暗示了白云岩可能形成于比微晶灰岩更深及盐度更大的水下还原环境,二者之间缺乏明显的交代关系.芦草沟组白云岩的δ13CPDB介于9.2 ‰～15.6‰,强烈正偏的δ13CPDB可能是产甲烷古菌的代谢活动引起有机质碳同位素分馏的结果.以上特征表明,研究区芦草沟组白云石的沉淀可能与产烷带厌氧微生物的代谢活动引起的甲烷生成作用有关.     

Geochemistry of Miocene lacustrine sediments from the Sokolov Coal Basin (Czech Republic)

Sediments of the upper part of the Sokolov Formation of the Sokolov Brown Coal Basin consist mostly of brown lacustrine clays and claystones enriched in organic matter (2–18% TOC). The lower portion of the stratigraphic profile is formed mostly by kaolinite–illite clays and claystones, while the montmorillonite content increases in the upper portion. The change in the lithology of sediments is caused by the gradual erosion of the weathering crust in the source areas of the clastic material. Inversion of the weathering profile during erosion is manifested geochemically in a decrease in the Al₂O₃/Na₂O ratio and an increase in the SiO₂/Al₂O₃, Na₂O/K₂O and K₂O/TiO₂ ratios from the base to the top of the studied part of the Sokolov Formation. The amounts of trace elements (La, Ce, Nb, Zr, Cr, V, Sn) also decrease in the same direction. On the other hand, the amounts of Rb and Sr increase. The organic matter of the upper part of the Sokolov Formation consists primarily of Types I and II kerogen. Only near the base of the studied part of the formation, i.e., in the coal stringer, kerogen of Type III prevails. The extremely low degree of thermal maturity permits determination of the source of the organic matter and characterization of its accumulation environment. The organic material in the sediments is predominantly of algae origin. Relatively high amount of pentacyclic triterpanes of the hopane series indicates either the occurrence of cyanobacteria as primary producers or bacterial reworking during sedimentation and diagenesis. Organic matter accumulated under the conditions of a fresh-water lake or lake with slightly elevated salinity, in a dysoxic aqueous environment. The alternation of organic carbon-rich layers with layers low in organic matter is explained in terms of changes in the degree of dysoxia of the aqueous environment and a variation in the intensity of oxidation and mineralization of the organic material.     

准噶尔盆地吉木萨尔凹陷芦草沟组湖相云质致密油储层特征与分布规律

准噶尔盆地东南缘吉木萨尔凹陷中二叠统芦草沟组新近发现了独特的湖相云质混积岩致密油储层,不同于传统的海/湖相硅质/灰质致密油储层,展示出重要的学科研究意义。本文报道了这类储层的基本特征与分布规律。结果表明,这类储层岩性主要由砂屑白云岩、粉砂质白云岩/白云质粉砂岩和微晶白云岩组成,见少量粉砂岩和凝灰岩;储集空间以次生粒间溶蚀孔隙和部分剩余粒间孔隙为主,微裂缝仅在少数样品中发育。储层含油性与物性呈正相关,据此将储层分为三类:一类储层孔隙度12%,渗透率0.1m D;二类储层孔隙度7%~12%,渗透率0.01m D;三类储层孔隙度以4%~7%,渗透率0.001m D。前两类是相对优质储层,分布特征表现为南厚北薄,物性南好北差。这种特点受控于沉积相及其物源,南部是主物源区。据此预测了有利储层分布区,其中芦草沟组上甜点段优质储层主要分布在吉32-吉171-吉31井区,下甜点段优质储层主要分布在吉174-吉251-吉36井区。这些认识还可供区域油气勘探参考。     

Petrography and geochemistry of the Lopingian (upper Permian)-Lower Triassic strata in the southern Junggar and Turpan basins,NW China: implications for weathering,provenance, and palaeogeography

ABSTRACT

This study investigates three Lopingian (upper Permian)-Lower Triassic terrestrial successions in northwest China, namely the Urumqi and Jimsar sections in the southern Junggar Basin (SJB), and the Taodonggou section in the Turpan Basin (TB). Stratigraphy studies suggest that, in all three sections, the Lopingian-Lower Triassic strata are represented by mixed fluvial and lacustrine deposits. The lithofacies and geochemical indicators (CIA, PIA) suggest that, in all three sections, the Wutonggou Formation (Wuchiapingian) was deposited under subhumid conditions. The Guodikeng Formation (Changhsingian-early Induan) represents subhumid to semiarid conditions. The Jiucaiyuan and Shaofanggou formations (mid-to-late Induan to Olenekian) in the SJB show highly variable subhumid-semiarid conditions, while the two formations in the TB display early episode of fluctuating subhumid-semiarid and later semiarid-arid conditions. Within each section, all four formations display similar petrographic and geochemical characteristics, suggesting consistency in provenance during deposition. However, the provenance characteristics of the Urumqi and Jimsar sections differ from those of the Taodonggou section. Relative to the Taogonggou section, the two sections in the SJB contain more felsic and recycled sedimentary components. This suggests that the greater Junggar-Turpan Basin was in a partitioned setting during the Lopingian-Early Triassic, when different subbasins have relatively independent provenance systems.     

准噶尔盆地玛湖凹陷下二叠统风城组碱湖岩石特征与成因*

风城组作为准噶尔盆地下二叠统优质烃源岩,一直是盆地油气勘探的重点。但因其埋藏深、岩性复杂、全球可对比研究实例少,也一直是研究的难点。文中以精细的岩性研究为基础,利用岩心描述、薄片观察、SEM、X衍射、TOC含量测定、包裹体测温及地化分析等手段,深入分析玛湖凹陷风城组碱性矿物特征和地质背景,探讨了碱湖成因与形成过程,得出: (1)风城组岩石可细分为5种主要类型,其中碱性岩为碱湖标志性岩类,富硅硼纳石岩类与火山喷发或热液作用相关;(2)风城组存在5种主要的岩石组合类型,从近源区至湖区依次为: 河流-冲积平原发育的组合类型Ⅴ、滨浅湖环境发育的组合类型Ⅲ与类型Ⅳ、深湖-半深湖环境发育的组合类型Ⅰ与类型Ⅱ,其中类型Ⅰ与类型Ⅲ为碱湖特有岩石组合,含优质烃源岩;(3)碱湖形成主要受火山活动和气候控制,前者为碱湖形成提供了Na⁺溶质,后者促进了淡水湖咸化,最终演化成碱湖。     

Permian bimodal dyke of Tarim Basin, NW China: Geochemical characteristics and tectonic implications

This study reports for the first time the occurrence of bimodal dyke in the Shuigongtuan area of Bachu County, Tarim Basin, NW China. Here, quartz syenite porphyry and diabase dykes occur in direct contact showing bimodal feature. The quartz syenitic porphyry is metaluminous, enriched in K₂O + Na₂O (10–11 wt.%) and total rare earth elements (REE), with low Mg/(Mg + Fe) ratios, high LREE/HREE, and negative Eu anomalies. The chemical characteristics and tectonic discriminative diagrams show that the rocks have geochemical affinity with A-type granites. The diabase dyke shows 45–52 wt.% SiO₂ and Mg/(Mg + Fe) ratio in the range of, with high total REE, high LREE/HREE ratios and lack of Eu anomalies, broadly corresponding to tholeiitic composition. Based on low Y/Nb (as low as 0.4, and less than 1.2), enrichment in LILE and HFSE, and uniform Nb-enrichment patterns in spider diagram for the quartz syenitic porphyry, together with the geochemical patterns of the diabases, this biomodal association is interpreted to be derived from a mantle source and formed under typical within-plate environment. The quartz syenitic porphyry and diabase have Daly gap of 46 wt.%–67 wt.% in SiO₂, which is explained through formation under bimodal rifting. The quartz syenitic dyke probably formed during Early Permian (277 Ma) and has geochemical affinity with the Xiaohaizi syenitic body. We propose that magmas sourced from the mantle intruded into middle–upper crust and were emplaced as dykes, which indicate large-scale extension during the Permian in Tarim Basin. The bimodal dyke has genetic affinity with the huge volume of Permian basalts and igneous rocks (248–292 Ma) that occur in the Tarim Basin. The magmatism manifests the culmination of the major thermal event in the Tarim Basin.     

New chondrichthyans from the Irati Formation (Early Permian,Paraná Basin), Brazil: origin,paleoenvironmental and paleogeographical considerations

Three genera, known by dorsal finspine, are reported from conglomeratic sandstone at the base of the Lower Permian (Kungurian) Irati Formation (Paraná Basin) near Rio Claro, São Paulo State, Brazil, noteworthy for the great richness of vertebrate fossils. The fossils include: (1) the previously known Sphenacanthus with the species Sphenacanthus sanpauloensis and an indeterminate species; (2) the Permian – Carboniferous genus Amelacanthus; (3) a new indeterminate Chondrichthyes. These fossils are found together with: continental, fresh-water and salt-water vertebrates. The analysis of this assemblage allows inference about the origin of Paraná Basin Chondrichthyes as well as reconstruction of the paleoenvironment and the possible geographic isolation of these fishes during the Permian in Brazil.     

泰国呵叻盆地二叠系碳酸盐岩元素地球化学特征与古环境意义

采用电感耦合等离子体发射光谱和同位素质谱等测试方法,对泰国呵叻盆地中部二叠系浅海相碳酸盐岩进行了微量元素与碳氧同位素组成及指标分析,讨论了研究区二叠系沉积古环境及其与碳酸盐岩烃源岩发育的控制关系。通过δ~(13)C/δ~(18)O指标及Sr/Ba、V/Ni、V/(V+Ni)比值等综合判别表明,研究区二叠系帕诺考组碳酸盐岩浅水斜坡亚相以淡-微咸水为主,属弱氧化-弱还原环境。深水斜坡亚相位于浪基面以下,以半咸水-咸水为主,属于缺氧的还原环境,为有机质保存提供了有利条件,是研究区碳酸盐岩烃源岩发育的有利相带。     

Paleo-environmental reconstruction of Lopingian (upper Permian) sediments in the Galilee Basin,Queensland, Australia

The recent review of the Lopingian (upper Permian) stratigraphic framework of the Galilee Basin, prompted a reconsideration of the paleo-environments of deposition. This study interpreted the distribution of sedimentary facies from geophysical logs across the basin complemented by detailed logging from four key wells (GSQ Tambo 1-1A, OEC Glue Pot Creek 1, CRD Montani 1 and GSQ Muttaburra 1). Seven facies associations were identified: terrestrial fluvial, floodplain, lacustrine and mire; and paralic to marine estuarine shoreline, delta and restricted marine. Coal measures (mire facies) are best developed in the northeastern margin of the basin, whereas the southern Springsure Shelf was dominated by marine conditions throughout the Lopingian, only developing terrestrial facies towards the very uppermost Lopingian. The ‘Colinlea Sandstone equivalent’ was deposited in a fluvial system, with tidal influence exhibited in the southern part of the basin, which decreases further north as lacustrine environments become common. The regional transgression represented by the Black Alley Shale can be mapped into the central part of the basin, but based on new exploration data its northern extent is more limited than previously thought. The ‘Burngrove Formation equivalent’ and Bandanna Formation represent a southerly prograding fluvial-deltaic system during the regional regression in the upper part of the Lopingian.     

New Materials of the Shanita-Hemigordius Assemblage (Permian Foraminifers) from the Baoshan Block, Western Yunnan

Fossil materials of Shanita and Hemigordius from a section northeast of the Woniusi (the Woniu Temple) of Baoshan, western Yunnan are described and figured in this paper. Field investigation indicates that fossils of these two foraminifer genera are extremely abundant and form a typical Shanita-Hemigordius assemblage in the so-called "Cracked Limestone" in the Baoshan area. Preliminary study has revealed that the features of this assemblage, which includes Shanita amosi, S. chagouensis, Hemigordius renzi and H. biconcavus, are similar not only to the Shanita fauna previously reported from the Shazipo Formation in the Zhengkang area, west Yunnan, but also to those from the Permian of Burma, Thailand, Iran and Turkey.     

贵州六枝—盘县地区早二叠世隆林期类组合与沉积环境

六枝-盘县地区的早二叠世隆林期地层,相区分异明显、篮类化石数量巨大。各相区篮类化石群落特征差异较大：半局限台地相为Staffella—Nankinella—Pisolina;台地边缘生物滩（礁）相为Parafusulina—Pseudofusulina;斜坡-盆地相为Pseudofusulina,进一步划分为近岸碳酸盐上缓坡环境的Staffella-Parafusulina-Wentzellophyllum群落、远岸碳酸盐上缓坡环境的Pamirina-Schwagerina-Pseudofusulina群落、碳酸盐下缓坡环境的Pseudofusulina Robustoschwagerina-Kepingophyllum群落和盆地环境的Pseudofusulina-Schwagerina-Verbeekiella群落。     

川南地区二叠系沉积环境及其演化特征——以四川古蔺芭蕉村剖面为例

以四川古蔺芭蕉村二叠系剖面为研究对象,在野外沉积特征详细观测的基础上,利用岩石薄片鉴定、全岩X衍射分析、元素地球化学与碳、氧、锶同位素分析,对其地层、沉积环境与演化特征进行研究,为四川盆地二叠系沉积特征研究与天然气勘探提供基础资料。研究表明,四川古蔺芭蕉村地区从中二叠世的梁山—栖霞组沉积时期开始海侵,栖霞组由下向上水体先变深又变浅,呈缺氧—贫氧环境;茅口组底部又一次海侵,以继承栖霞组沉积环境为特征,在茅口组一段水体最深,向上逐渐变浅,呈缺氧—贫氧特征;龙潭组沉积水体最浅,氧化环境为主,局部呈还原环境;长兴组底部沉积水体最深,整体呈缺氧—贫氧特征,其碳酸盐岩沉积的海平面相对中二叠统应较浅。宏观上,四川盆地中二叠统栖霞组、茅口组由东向西为碳酸盐岩缓坡逐渐向台地演化。茅口组三段发育大型的溶蚀孔洞和后期溶蚀缝洞,推测该区茅口组有可能形成岩溶缝洞型储层。长兴组的底部发育水体较深的台盆次相沉积,环台洼或台盆可能是礁滩发育的有利区。见大量的沥青质充填,考虑到川南地区二叠系发育富有机质的碳酸盐岩与黑色页岩及煤层,认为该区二叠系具备形成古油藏的可能。     

桂西南柳桥地区上二叠统大隆组层状硅质岩成因和沉积环境

对桂西南上二叠统大隆组层状硅质岩地球化学的研究发现:陆源主量元素Al、Ti等含量较高,并呈很好的相关性（R>0.90）;热液来源的主量元素Mn和Fe等含量偏低,并具有较小的负相关关系（R=－0.30）;陆源元素(Al、Ti、Hf、Zr、Th等)与总稀土元素含量具有较高正相关性（R为0.70～0.83）;Al Fe Mn三角图解指示研究区的硅质岩为非热液成因。这些说明陆源物质是硅质岩形成的重要物源,结合硅质岩中含有大量的硅质生物（放射虫和海绵骨针等）的事实,我们认为研究区硅质岩是在生物作用为主,并有大量物源物质和少量热液物质（可能与大断裂导致的玄武岩喷发有关）和火山物质混入的条件下形成的。Ce/Ce*、(La/Yb)Shale、(La/Ce)Shale和∑REE与细粒沉积物沉积环境的关系以及(La/Ce)Shale—Al2O3/(Al2O3 +Fe2O3)图解等说明研究区硅质岩沉积环境为大陆边缘的中下部。Th/U和Ceanom指示了硅质岩形成于氧化环境。      

Tectono‐sedimentary evolution of the northernmost margin of the NE German Basin between uppermost Carboniferous and Late Permian (Rotliegend)

The tectono‐sedimentary evolution of the Rotliegend deposits of the northernmost margin of NE German Basin (NEGB) has been analysed on the basis of detailed sedimentary logs of 300 m of core material together with the re‐evaluation of 600 km of seismic lines. Three distinct phases were recognized. During the initial Phase I, basin geometry was largely controlled by normal faulting related to deep‐seated ductile shearing leading to a strong asymmetric shape, with a steep fault‐controlled eastern margin and a gently, dipping western margin. The results of forward modelling along a cross‐section fit the basin geometry in width and depth and reveal a footwall uplift of c. 1000 m. Adjacent to the steep faults, local sedimentation of Lithofacies Type I was confined to non‐cohesive debris flow‐dominated alluvial fans, whereas the gently dipping western margin was dominated by alluvial‐cone sedimentation. During the post‐extensional period (Phase II), cooling of the lithosphere generated additional accommodation space. The sediments of Lithofacies Type II, comprising mainly clast‐supported conglomerates, are interpreted as braided ephemeral stream flow‐surge deposits. Tectonic quiescence and an increase in flood events resulting from wetter climate led to progradation of this facies over the entire region. At the end of this period, the accommodation space was almost completely filled resulting in a level topography. Phase III was controlled by the thermal‐induced subsidence of the southerly located NEGB in post‐Illawarra times. The formerly isolated region tilted towards the SW, thus forming the northern margin of the NEGB during uppermost Havel and Elbe Subgroup times. The sediments of Lithofacies Type III were divided into a marginal sandstone‐dominated environment and a finer‐grained facies towards the SW. The former consists of poorly‐sorted coarse‐grained sandstones of a proximal and medial ephemeral stream floodplain facies. The latter comprise mud flat fines and fine‐grained distal ephemeral stream deposits. The end of the tectono‐sedimentary evolution is marked by the basinwide Zechstein transgression. Copyright © 2001 John Wiley & Sons, Ltd.