川北旺苍唐家河剖面仙女洞组灰泥丘沉积特征及造丘环境分析

目前川北地区早寒武世微生物藻与古杯参与的生物礁(丘)发育特征存在较大争议。通过实测剖面与镜下分析,川北旺苍县鼓城乡唐家河剖面仙女洞组发育三期灰泥丘。对该剖面灰泥丘沉积特征进行精细研究认为:第一期灰泥丘发育在滑塌角砾灰岩之上,造丘生物主要为枝状和房室状附枝藻,主要岩性为砾屑灰岩、藻格架凝块灰岩和含云生物碎屑灰岩,发育丘基、丘核、丘盖和丘翼,后期演化为钙质砂泥岩结束生长。第二期生物丘发育在鲕粒滩间生屑灰岩之上,造丘生物主要为肾状藻,次为附枝藻,主要岩性为生物碎屑灰岩、藻格架凝块灰岩、漂浮砾岩和亮晶鲕粒灰岩,纵向上发育丘基、丘核、丘坪、丘盖和丘翼,最终再度沉积鲕粒灰岩。第三期灰泥丘发育在藻叠层灰岩之上,造丘生物为古杯和微生物藻,岩性主要为古杯灰岩、生物碎屑泥晶灰岩、藻格架凝块灰岩和藻叠层灰岩,发育丘基、丘核和丘盖。进一步分析三期灰泥丘的成丘环境认为第一期灰泥丘属于台缘斜坡环境内的斜坡灰泥丘低能沉积,经历三个演化阶段;第二期属于台地边缘灰泥丘,经历四期演化阶段;第三期为台缘高能鲕粒滩向陆一侧能量相对较低的台缘古杯灰泥丘沉积,经历三个演化阶段。剖面中灰泥丘多与鲕粒滩共存,构成丘滩复合体,为后期研究储集性能和油气富集关系具有重要的油气地质意义。     

四川盆地古生代生物礁滩特征及发育控制因素

在古生代,生物礁从老到新主要发育在早寒武世、早志留世及晚二叠世地层中。地理分布上,它们分别产于四川盆地北、东北缘大巴山、米仓山地区（早寒武世礁）、四川盆地南北缘（早志留世礁）以及鄂西渝东、川东北地区（晚二叠世礁）。早寒武世礁滩组合包括古杯礁、灰泥丘及鲕粒滩,造礁生物为古杯、蓝藻类微生物,附礁生物有三叶虫、腕足类、海百合及海绵等。由于受海平面波动的控制,生物礁具有旋回性,并从西向东,层位逐渐抬升。早志留世礁有点礁、灰泥丘及层状礁等,其分布受古陆影响的陆源碎屑-碳酸盐缓坡的控制,也与海平面波动有关。晚二叠世生物礁有点礁、台缘礁及灰泥丘,其分布也受古地貌格局和海平面波动的控制。     

世界石炭纪生物礁发育基本特征

石炭纪生物礁在晚古生代礁体演化序列中处于特殊地位。石炭纪是生物礁地史演化过程中一个非常关键的时期,发育的生物礁类型有:(1)叶状藻礁丘;(2)叠层石礁丘;(3)珊瑚礁;(4)Waulsortian灰泥丘;(5)Chaetetes礁丘;(6)钙质微生物—藻礁丘。石炭纪生物礁总体上表现为礁相结构、造礁群落组成及礁体建造阶段的造礁作用相对比较简单,这些都体现出生物礁在石炭纪的发展受到生物灭绝事件的影响。在以藻礁占主导地位的宾夕法尼亚亚纪,中国后生动物骨架礁发育,尤其是发育有Fomitchevella大型珊瑚礁,成为世界石炭纪生物礁的一个亮点。从石炭纪整个生物礁的发展情况来看,后生动物骨架礁与以微生物和钙藻为主导的生物礁或许是两个平行发展的礁系统,后生动物骨架礁的发展在大规模生物灭绝事件之后有明显的演化滞后现象,以钙藻和微生物为主导的造礁群落的复苏在生物灭绝事件之后更为迅速。从石炭纪生物礁古地理分布来看,石炭纪生物礁基本上分布在南北纬30°之间的区域,因此,它们代表了在相对温暖的气候条件下生长的礁体,与现代珊瑚礁的分布相近似。     

华北克拉通大青山-集宁地区古元古代变质沉积岩的锆石氧同位素组成:SHRIMP微区原位分析

在已获得锆石U-Pb年龄基础上,我们首次对孔兹岩带典型出露区大青山和集宁土贵乌拉地区古元古代变质沉积岩进行了锆石SHRIMP氧同位素研究。锆石具有复杂的内部结构和年龄分布。大青山地区古元古代早期变质沉积岩4个样品碎屑锆石的δ18O为5.52‰~7.11‰,部分重结晶锆石的δ18O为7.22‰~7.90‰,变质新生锆石的δ18O为6.37‰~8.31‰。大青山地区古元古代晚期变质沉积岩2个样品的锆石O同位素组成特征与古元古代早期的类似,另外2个样品的锆石O同位素组成与之不同,碎屑锆石、部分重结晶锆石和变质新生锆石的δ18O分别为6.26‰~10.80‰、9.00‰~11.20‰和9.66‰~11.90‰。集宁土贵乌拉地区古元古代晚期超高温变质沉积岩4个样品不存在碎屑锆石,变质锆石的δ18O变化范围为11.41‰~13.57‰。主要认识如下:1)大青山地区碎屑沉积物主要来自新太古代晚期-古元古代早期成熟度不高的TTG花岗质岩石物源区,与之相比,集宁土贵乌拉地区古元古代晚期超高温岩石的变质原岩成熟度更高;2)不同类型变质沉积岩变质新生锆石的δ18O和变质新生锆石与碎屑锆石的Δ18O存在明显区别,主要反映了岩石体系和变质流体的O同位素组成不同;3)大青山地区高角闪岩相-麻粒岩相变质沉积岩,重结晶锆石的O同位素完全重置,但U-Th-Pb体系未完全重置,集宁土贵乌拉地区超高温变质沉积岩的重结晶锆石O和U-Th-Pb同位素体系都完全重置。变质作用强度不同是主要原因。     

塔北哈拉哈塘地区奥陶系碳酸盐岩古地貌及岩溶储层发育特征

为了研究哈拉哈塘地区奥陶系碳酸盐岩岩溶古地貌及岩溶储层发育规律,基于地震、钻井、岩心、薄片分析,采用"残厚与地层古构造趋势面结合"方法对古地貌、古水系进行恢复刻画,划分为3种二级地貌类型,6种三级地貌类型和若干微地貌形态。在岩石化学特征及储层物性研究基础上结合古岩溶缝洞充填方解石碳氧同位素特征,对古岩溶发育及充填期次进行分析。结果表明:后期溶蚀孔、溶洞和溶蚀裂缝是该区主要储集空间;充填方解石δ~(13)C和δ~(18)O值变化范围较大,δ~(13)CPDB值为-4.17‰~1.59‰,平均值为-1.05‰;δ~(18)O_(PDB)值为-15.71‰~-5.17‰,平均值为-11.15‰。并划分为海相沉积充填环境、大气淡水充填环境、浅埋藏沉积充填环境和深部埋藏高温环境4种不同的古岩溶作用期次。     

羌塘盆地半岛湖地区上侏罗—下白垩统礁灰岩地球化学特征和成岩流体性质

半岛湖地区生物礁以发育灰岩为主,包括以造礁生物为主的骨架岩和非礁碳酸盐岩,针对生物礁相碳酸盐岩的显微组构分析和阴极发光分析,测得不同点礁各类礁相碳酸盐岩的常微量元素和碳、氧同位素组成,分别为:35件样品Mn,Sr,Fe元素平均质量分数为129×10-6,270×10-6和1 320×10-6,具有较低的Mn含量、较高的Sr含量、Fe含量,表明在成岩过程中海源流体发挥了主导作用,同时遭受了不同程度的大气淡水成岩流体的影响;碳同位素值变化不大且都为正值,变化区间为1.4‰~3.5‰,平均值为2.61‰;氧同位素值变化区间为-7.4‰~-2.7‰,平均值为-5.25‰,古海水盐度指数Z值变化较小,为126.6~132.7,平均值为130.5。结果表明,成岩流体盐度较高,溶蚀孔洞较为发育的颗粒灰岩和礁灰岩具有相对更低的δ18 O值,晚侏罗—早白垩世时期,羌塘盆地北部大量有机碳被高速埋藏是导致半岛湖地区礁相碳酸盐岩碳同位素值普遍偏高的首要原因。     

塔中地区礁滩储集体形成条件及分布规律

奥陶纪时期，塔中地区发育生物礁、丘和滩等不同类型的碳酸盐岩建隆生物礁丘发育层位主要集中在上奥陶统．塔中地区的礁滩相包括灰泥丘、中物礁、粒屑滩和地质异常体等4种类型，沉积古地理、构造作用、陆源碎屑物注入和海平面变化是控制生物礁发育的主要因素．塔中地区生物礁的分布环境主要有2个相带：一是台地内，尤其是半局限台地与开阔台地的转折处或台内缓坡上，如塘参1井、塔中23井上奥陶统的生物礁：另一个是台地边缘，如塔中45井-塔中44井-塔中24井-带为台缘外带，以发育中高能粒屑滩和骨架礁组合为特色，而大致在塔中35井-塔中12井-塔中15井-塔中161井-带为台缘内带，发育中低能粒屑滩、灰泥丘及障积礁组合．     

四川盆地早古生代灰泥丘中的微生物及其造岩和成丘作用

作为生物礁的特殊类型,灰泥丘在古生代十分发育,许多学者都认为它们是通过微生物造岩作用而形成的,而且,也在现代湖泊中发现了由兰菌藻的生命活动所形成的灰泥沉积物及灰泥丘。但是国际上一直没有在古生代灰泥丘中发现过细菌等微生物的实体化石,微生物促使碳酸钙沉淀、聚集的能力和机理也不明确。四川盆地北缘寒武纪和志留纪灰泥丘发育,笔者通过扫描电镜及能谱分析,在国际上首次发现了 (川西北志留纪 )灰泥丘中菌藻类微生物的实体化石及其特征的造岩成丘现象,发现的菌藻类微生物实体化石有三种类型 :1.表面光滑的卵形球体型;2.表面粗糙的椭球体型;3.网状结构型。而且,对寒武纪和志留纪灰泥丘凝块石作生物标志化合物分析也证明了其有机质生源为菌藻类微生物。这些凝块石灰泥丘中的菌藻类实体化石都显示了不同的沉积、造岩和成丘功能,因而证实了微生物在形成古生代灰泥丘中具重要作用。     

塔里木盆地麦盖提斜坡群古三维区奥陶系碳酸盐岩古岩溶储层特征

和田河气田、玉北1井油藏的发现证实了和田古隆起作为塔里木盆地三大古隆起之一有着广阔的勘探前景,但研究程度较低。基于地震、钻井、岩心、薄片等资料综合分析,对麦盖提斜坡群古三维区奥陶系碳酸盐岩古地貌、古水系及岩溶储层发育规律进行了研究;结合古岩溶缝洞系统充填方解石碳氧同位素特征,对古岩溶储层发育及充填期次进行了分析。结果表明:后期溶蚀孔、溶洞和溶蚀裂缝是该区主要储集空间;充填方解石δ13C和δ18 O的变化范围较大,δ13 CPDB为-10.22‰~3.06‰,平均值为-0.89‰,δ18 OPDB为-15.53‰~-6.21‰,平均值为-9.72‰;可划分为古风化壳裸露岩溶期、埋藏岩溶期和较晚岩溶作用期3期不同的古岩溶作用期次。     

麦盖提斜坡奥陶系碳酸盐岩碳氧同位素特征及其意义

依据实测的塔里木盆地麦盖提斜坡玉北地区41个碳酸盐岩碳氧同位素数据,结合岩石学方法,研究了碳氧同位素的组成、演化及其地质意义。数据显示,δ~(13) C值主要分布在-2.6‰~0.7‰,均值为-1.0‰;δ~(18) O值分布在-9.4‰~-3.5‰,均值为-6.9‰。玉北地区古盐度为118.39~126.34,平均为121.94。奥陶系碳酸盐岩淡水改造作用明显。碳氧同位素的组成和演化不但可以指示沉积环境,而且还与生物生产率以及古海平面变化呈正相关性:δ~(13) C的低值对应于局限台地台内滩亚相沉积环境;δ~(13) C的高值对应于开阔台地滩间海、台内滩亚相沉积环境。碳氧同位素组成还对成岩环境有明显响应:鹰山组δ~(13) C与δ~(18) O均向高负值偏移,表明经历过强烈的表生岩溶作用;蓬莱坝组δ~(13) C低—中负值,δ~(18) O表现为高负值,在白云岩储层中可见鞍状白云石及燧石,主要为深埋藏成岩环境;良里塔格组同位素特征为δ~(18) O高负值,δ~(13) C低正值,并且在进入埋藏岩溶阶段之前还经历过风化壳岩溶作用。     

The terrestrial fauna of the Late Triassic Pant-y-ffynnon Quarry fissures,South Wales,UK and a new species of Clevosaurus (Lepidosauria: Rhynchocephalia)

Pant-y-ffynnon Quarry in South Wales yielded a rich cache of fossils in the early 1950s, including articulated specimens of new species (the small sauropodomorph dinosaur Pantydraco caducus and the crocodylomorph Terrestrisuchus gracilis), but no substantial study of the wider fauna of the Pant-y-ffynnon fissure systems has been published. Here, our overview of existing specimens, a few described but mostly undescribed, as well as freshly processed material, provides a comprehensive picture of the Pant-y-ffynnon palaeo-island of the Late Triassic. This was an island with a relatively impoverished fauna dominated by small clevosaurs (rhynchocephalians), including a new species, Clevosaurus cambrica, described here from a partially articulated specimen and isolated bones. The new species has a dental morphology that is intermediate between the Late Triassic Clevosaurus hudsoni, from Cromhall Quarry to the east, and the younger C. convallis from Pant Quarry to the west, suggesting adaptive radiation of clevosaurs in the palaeo-archipelago. The larger reptiles on the palaeo-island do not exceed 1.5?m in length, including a small carnivorous crocodylomorph, Terrestrisuchus, and a possible example of insular dwarfism in the basal dinosaur Pantydraco.     

Définition d'une limite multicritère ; stratigraphie du passage Campanien–Maastrichtien du site géologique de Tercis (Landes,SW France)Definition of a multi-criteria boundary; stratigraphy of the Campanian–Maastrichtian interval of the geological site at Tercis (Landes,SW France)

Lithostratigraphy, physicochemical stratigraphy, biostratigraphy, and geochronology of the 77–70 Ma old series bracketing the Campanian–Maastrichtian boundary have been investigated by 70 experts. For the first time, direct relationships between macro- and microfossils have been established, as well as direct and indirect relationships between chemo-physical and biostratigraphical tools. A combination of criteria for selecting the boundary level, duration estimates, uncertainties on durations and on the location of biohorizons have been considered; new chronostratigraphic units are proposed. The geological site at Tercis is accepted by the Commission on Stratigraphy as the international reference for the stratigraphy of the studied interval. To cite this article: G.S. Odin, C. R. Geoscience 334 (2002) 409–414.     

The effect of water on accessory phase solubility in subaluminous and peralkaline granitic melts

The solubilities of columbite, tantalite, wolframite, rutile, zircon and hafnon were determined as a function of the water contents in peralkaline and subaluminous granite melts. All experiments were conducted at 1035 °C and 2 kbar and the water contents of the melts ranged from nominally dry to approximately 6 wt.% H₂O. Accessory phase solubilities are not affected by the water content of the peralkaline melt. By contrast, solubilities are affected by the water content of the subaluminous melt, where the solubilities of all the accessory phases examined increase with the water content of the melt, up to 2 wt.% H₂O. At higher water contents, solubilities are nearly constant. It can be concluded that water is not an important control of accessory phase solubility, although the water content will affect diffusivities of components in the melt, thus whether or not accessory phases will be present as restite material. The solubility behaviour in the subaluminous and peralkaline melts supports previous spectroscopic studies, which have observed differences in the coordination of high field strength elements in dry vs. wet subaluminous granitic glasses, but not for peralkaline granitic glasses. Lastly, the fact that wolframite solubility increases with increasing water content in the subaluminous melt suggests that tungsten dissolved as a hexavalent species.     

Quaternary stresses revealed by calcite twinning inversion: insights from observations in the Savonnières underground quarry (eastern France)

Calcite samples were extracted both from the rock matrix and the superficial coating of a karstified fault plane of an underground quarry, located in the eastern border of the Paris basin. The karstification is dated as Quaternary. Analysis of mechanical calcite twinning reveals that only the calcite matrix has also undergone a compression trending WNW that can be attributed to the Mio-Pliocene alpine collision. Both coating and matrix have undergone a strike-slip regime with σ₁ roughly trending north–south, that could correspond to the regional present-day state of stress, a strike-slip compression rather trending NNW, modified by local phenomena. To cite this article: M. Rocher et al., C. R. Geoscience 335 (2003).     

HYDROGEOLOGY

正20141756 Chen Ruige(Mathematical College,China University of Geosciences,Beijing100083,China);Zhou Xun Numerical Simulation of Groundwater Level Fluctuation in a Coastal Confined Aquifer with Sloping Initial Groundwater Level Induced by the Tide(Geological Bulletin of China,ISSN1671-2552,CN11-4648/P,32(7),2013,p.1099-1104,6 illus.,16 refs.) Key words:confined water,groundwater level     

METAMORPHIC PETROLOGY

正20141408 Cai Jia(Institute of Geology,Chinese Academy of Geological Sciences,Beijing100037,China);Liu Fulai Petrogenesis and Metamorphic P-T Conditions of Garnet-Spinel-Biotitebearing Paragneiss in Danangou Area,Daqingshan-Wulashan Metamorphic Complex Belt(Acta Petrologica Sinica,ISSN1000-0569,CN11-1922/P,29(7),     

SERIALS

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GEOPHYSICAL EXPLORATION

正20142386An Guoying(China Aero Geophysical Survey and Remote Sensing Center for Land and Resources,Beijing 100083,China)Application of Satellite Remote Sensing in Regional Hydrogeological Investigation:Taking Cenozoic Strata in Wenquan Sheet(1∶250 000)of Karakoram Range as an Example(Geosci-     

QUATERNARY GEOLOGY & GEOMORPHOLOGY

正20141016An Chengbang(Key Laboratory of Western China’s Environmental Systems,Ministry of Education,Lanzhou University,Lanzhou 730000,China);Zhao Yongtao Lake Records during the Last Glacial Maximum from Xinjiang,NW China and Their Climatic Impli-     

PETROLEUM GEOLOGY

正20141538 Cao Qing(School of Earth Sciences and Engineering,Xi’an Petroleum University,Xi’an 710065,China);Zhao Jingzhou Characteristics and Significance of Fluid Inclusions from Majiagou Formation,Yichuan Huangling Area,Ordos Basin(Advances in Earth Science,ISSN1001-8166,CN62-1091/P,28(7),2013,p.819-828,7 illus.,3 tables,43 refs.)