黔东北伊迪卡拉纪陡山沱组的宏体藻类

宏体生物广泛地生活于扬子地区伊迪卡拉纪陡山沱期的海洋中,它们为后生动物的快速发展和演化奠定了一个崭新的环境和一个新生态链的基础.产自于黔东北伊迪卡拉系陡山沱组的瓮会生物群生活环境应在贫氧的、透光性良好的浅海低能环境,以宏体藻类为主,共描述15属18种(其中包括3个新属、5个新种、2个修定属和4个修定种)和1个未命名藻以及不明藻类固着器,另包含有宏体后生动物,可能的后生动物以及遗迹化石.瓮会生物群不但含有鄂西庙河生物群和皖南蓝田植物群的分子,也有南澳大利亚Ediacara生物群和俄罗斯WhiteSea生物群的分子,而且具有自已的特征而有别于其他伊迪卡拉期的生物群.其宏体藻类形态变化较大,组织器官和功能已出现明显的分化,并与高等植物之间存在一定的演化关系.宏体藻类多为直立固着于海底,提高了光合作用的效率,增加了水体中的含氧量.同时,宏体藻类作为生态系统中的初级生产者成为一种新的食物,改变了后生动物的食谱.因此,陡山沱期的宏体植物不仅改善了环境,为依赖一定氧而生活、生长和繁殖的后生动物给予了必要的支持,而且作为生态系统中的必要基础,为宏体后生动物的快速发展和演化提供了一个新的食物源.另外,宏体生物群的繁盛不仅提高了有机质的生产率,而且促进了富有机碳的沉积和保存.     

封闭系统中多孔介质甲烷水合物的CT实验研究

阐述了在封闭系统中的查理模型,建立了利用查理定律计算分析甲烷水合物生成和分解的方法。通过实验,对封闭系统中不同含水量多孔介质甲烷水合物生成、发育和分解的实验方法、相平衡条件、生成量关系等进行了探讨。在一定温度差的介质里,水分克服重力向冷端迁移并生成水合物。实验中利用查理数的改变计算水合物的生成量变化,连通性好的含水多孔介质有很好的水—气结合条件,达到平衡条件后迅速生成水合物,在240分钟内完成,含水量线性地影响甲烷水合物的生成量。同时,利用CT扫描方法直接观测含水粗砂在低温—高压环境下的甲烷水合物生成和分解过程,并可以利用CT图像数据计算出多孔介质中水分迁移、区域密度改变和砂体的移动、及分解后介质密度分布变化特征。     

河北宣化土城子组恐龙足迹化石新发现

本文报道了新近发现于河北宣化地区土城子组的恐龙足迹化石及沉积环境。为确定足迹化石的地质年代、土城子组的沉积环境及足迹化石属种,本文在对恐龙足迹化石层及其上、下地层进行剖面测制、沉积相划分和沉积环境分析的基础上,对化石层上覆凝灰岩层进行了LA-ICPMS锆石U-Pb测年,并对保存较好的足迹化石进行了测量和对比研究工作。研究结果表明,土城子组底部为冲积扇扇中沉积环境,足迹化石上、下地层则表现为河流相沉积环境,而足迹化石的赋存层位形成于滨湖相沉积环境,发育暴露构造并含有大量裸子植物碎屑化石。凝灰岩锆石U-Pb加权平均年龄为152.3±0.3 Ma(MSWD=0.00106),说明化石层位于土城子组一段,时代属于晚侏罗世钦莫利期(Kimmeridgian)中晚期。已发现的足迹化石以兽脚类三趾型足迹为主,包括跷脚龙足迹属(Grallator)、安琪龙足迹属(Anchisauripus)和实雷龙足迹属(Eubrontes),其次为一些疑似蜥脚类恐龙足迹,是华北北缘土城子组中群落丰富度最高的恐龙足迹点,其中一处或许为中国北方面积最大的恐龙足迹点。因此,我们认为宣化-下花园盆地土城子组一段以河流、湖泊...     

川中地区中二叠统栖霞组滩控岩溶型白云岩储层特征及主控因素

四川盆地中部地区栖霞组的白云岩是该区主要储层,储层成因的主流观点是热液白云岩化.目前勘探实践发现,优质储渗体形成与早期相控岩溶作用有关.通过取芯及测录井资料进行了详细分析,研究结果表明,该类白云岩储层主要位于栖霞组中上部颗粒滩发育的地层中,按其宏微观产出状态可分为溶斑状云岩、溶洞充填云岩、针孔状基质云岩和致密基质云岩....     

Gas generation and expulsion characteristics of Middle–Upper Triassic source rocks,eastern Kuqa Depression,Tarim Basin,China: implications for shale gas resource potential

Frontier exploration in the Kuqa Depression, western China, has identified the continuous tight-sand gas accumulation in the Lower Cretaceous and Lower Jurassic as a major unconventional gas pool. However, assessment of the shale gas resource in the Kuqa Depression is new. The shale succession in the Middle–Upper Triassic comprises the Taliqike Formation (T₃t), the Huangshanjie Formation (T₃h) and the middle–upper Karamay Formation (T_2–3k), with an average accumulated thickness of 260 m. The high-quality shale is dominated by type III kerogen with high maturity and an average original total organic carbon (TOC) of about 2.68 wt%. An improved hydrocarbon generation and expulsion model was applied to this self-contained source–reservoir system to reveal the gas generation and expulsion (intensity, efficiency and volume) characteristics of Middle–Upper Triassic source rocks. The maximum volume of shale gas in the source rocks was obtained by determining the difference between generation and expulsion volumes. The results indicate that source rocks reached the hydrocarbon expulsion threshold of 1.1% VR and the hydrocarbon generation and expulsion reached their peak at 1.0% VR and 1.28% VR, with the maximum rate of 56 mg HC/0.1% TOC and 62.8 mg HC/0.1% TOC, respectively. The volumes of gas generation and expulsion from Middle–Upper Triassic source rocks were 12.02 × 10¹² m³ and 5.98 × 10¹² m³, respectively, with the residual volume of 6.04 × 10¹² m³, giving an average gas expulsion efficiency of 44.38% and retention efficiency of 55.62%. Based on the gas generation and expulsion characteristics, the predicted shale gas potential volume is 6.04 × 10¹² m³, indicating a significant shale gas resource in the Middle–Upper Triassic in the eastern Kuqa Depression.     

不纯碳酸盐岩的变质作用

不纯碳酸盐岩中的矿物共生组合与变质时的总压和二氧化碳分压密切相关。总压增高促使透闪石、透辉石和橄榄石等矿物生成温度增高。变质过程中岩石中流体成分的变化有两种极端情况,即渗滤作用和缓冲作用。渗滤作用下变质反应,变质矿物界线和变质矿物特征等均与缓冲作用下有所差异,以此可以区别它们。湖北宿松群和河北红旗营子群不纯大理岩是在渗滤作用下变质的。山西五台群板峪口组不纯大理岩是在缓冲加渗滤作用下变质的。     

Relative sea-level fluctuations and brown coal formation around the Early-Middle Miocene boundary in the Lusatian Brown Coal District

The Tertiary sedimentary sequence in the Lusatian Brown Coal District is the result of several transgressive pulses with intercalated regressive phases. Regression repeatedly resulted in the formation of large littoral bogs at the transition between brackish and terrestrial palaeoenvironments. In the lithofacies changes of the Lower-Middle Miocene strata (high energy sands, low energy intertidal silts, paralic peats) long-term changes as well as short-term oscillations of sea level are recorded. The rise of sea level in the upper Lower Miocene (Hemmoorian transgression) is proved in numerous localities of the investigation area. After a regression phase with major peat formation events around the Lower-Middle Miocene boundary, a renewed sea-level rise resulted in the widest extension of marine-brackish beds over pre-Tertiary basement in the south of the region (higher Reinbekian transgression, Middle Miocene). Very differentiated, fine-scaled, probably sea-level induced coastline oscillations could probably be traced even into the coal seams by the recognition of successive bogfacial types possibly showing a groundwater level change in the ancient peat bog (change of topogeneous and ombrogeneous bog types). A biostratigraphic calibration of the decalcified Lower-Middle Miocene sequence with its alternating transgressive and regressive trends to the fully marine sediments of the basinal centre, which are dated by calcareous microfossils, is possible by means of dinoflagellate cysts and pollen and spores. Correspondence to: C. Strauss