塔木察格盆地塔南凹陷下白垩统层序结构特征及控制因素分析

摘要:应用层序地层学原理对塔南凹陷下白垩统地层进行了划分和对比,建立了等时的层序地层格架,分析了不同级别层序界面的特征。对层序结构特征的研究表明,不同沉积期的层序类型、沉积体系的空间展布和配置关系有明显区别。SQ1层序为初始裂谷期湖泊层序,发育冲积扇、滨浅湖等沉积组合; SQ2层序为裂谷高峰早期湖泊层序,发育冲积扇、扇三角洲、滨浅湖等沉积组合;SQ3层序为裂谷高峰中晚期湖泊层序,发育扇三角洲、湖底扇、浅湖、深湖等沉积组合;SQ4层序为裂谷后期过渡层序,发育半深湖一深湖,大型长轴三角洲、滨浅湖、等沉积组合。不同层序发育期各层序的结构特征决定着特定沉积相带的展布,沉积体系域的沉积相构成也有变化。     

Metamorphic garnet pyroxenite from the 540-600 m main borehole of the Chinese Continental Scientific Drilling (CCSD) project

Compared to other mafic and ultramafic rocks from the CCSD main borehole as well as from the outcrops, rocks from the 540-600 m section is extraordinary in terms of its geophysical as well as geochemical properties. It consists of > 70% hematite-ilmenite garnet pyroxenite (HI-GPX) and < 30% intercalated rutile garnet pyroxenite (R-GPX). Whole-rock geochemical data show that HI-GPXs have: (1) relatively high V with an average of 606 ppm, but lower Nb and Ta; (2) highest TFeO, Fe₂O₃/FeO ratio, and highly variable but strong positive Eu anomalies with Eu/Eu? up to 2.9; (3) anomalously high V/Sc ratios ranging from 8.39 to 43.23, average 15.03; and (4) high amounts of hematite-ilmenite solid solutions with a very fine intergrowth structure down to nanometer scale. V/Sc ratios in the CCSD garnet pyroxenites are correlated negatively with MgO, but positively with Fe₂O₃/FeO ratios. Both suites of pyroxenites have similar rare earth elements and high field strength elements geochemistry. These features demonstrate that these pyroxenites were formed from metamorphism of high-Fe and/or -Ti gabbroic cumulates. This can account not only for low high field strength elements (HFSE) and rare earth elements (REE) but also low Nb/Ta and Zr/Hf ratios in these rocks. Seemingly negative correlation between Nb/Ta and Zr/Hf in the CCSD metabasites, not significantly affected by UHP metamorphism, is also consistent with the silicate differentiation trend in a basaltic magma chamber.     

Holocene environmental change inferred from the loess–palaeosol sequences adjacent to the floodplain of the Yellow River, China

Chinese loess deposits are generally considered to be the product of dust storms and dust falls from the central Asia arid zones that were transported across China by the northwesterly continental monsoon. In contrast, the Zhengzhou Loess found southeast of the Loess Plateau, adjacent to the floodplain of the Yellow River, records a different eolian regime and dust source. The Zhengzhou Loess was investigated by field observations, measurements of magnetic susceptibility, particle-size distribution, loss-on-ignition, CaCO₃ and chemical contents. Both field observations and the laboratory results indicate that, during the last glacial, the Zhengzhou Loess was supplied by two different eolian regimes and dust sources, one was from the fresh flood deposits of the Yellow River driven by the northeast winds from the low-lying floodplain, and the other was from the dust storms and dust falls that traveled across the Loess Plateau driven by the northwesterly continental monsoon from the central Asian arid lands. The early Holocene, 11,500–8500 a BP, was a transition during the change in eolian regime and dust source because of the weakened northwesterly monsoon along with the global climatic amelioration. Following the retreat of the northwesterly monsoon from the onset of the mid-Holocene Climatic Optimum at 8500 a BP, dust supply from the drifting sand zone on the Yellow River floodplain became dominant because of the intensified strength of the northeast winds from the Bohai Sea. From 3100 a BP onwards, climatic aridity and extensive human disturbance have resulted in intensive eolian processes causing the incursion of the drifting sand into the Zhengzhou Loess zone. These results show that loess accumulation is more complex than traditionally assumed. The origin of loess deposits elsewhere outside the Loess Plateau may be related to dust sources derived from alluvial sediments of major river systems.     

大庆油田勘探50年：陆相生油理论的伟大实践

文章系统分析了陆相生油理论和大庆油田的勘探实践,总结了大庆油田的勘探历程并划分为三大阶段：构造油藏勘探阶段,岩性油藏勘探的探索阶段,岩性油藏勘探大发展阶段。详细阐述了“十五”以来,大庆油田依靠创新理论与技术,丰富完善了大型陆相坳陷盆地岩性油藏勘探理论与配套技术,深层火山岩气藏勘探理论与配套技术,复杂断陷盆地油气勘探理论与配套技术,从而带来了松辽盆地北部中一浅层、深层和海拉尔盆地油气勘探的大发展,大庆油田再次进入油气储量增长高峰期。在详细分析大庆探区的勘探实际和资源潜力的基础上,提出了“百年油田”勘探的工作思路,通过扎实推进科学勘探,努力为油田可持续发展提供有力资源保障的勘探战略。     

A preliminary study of early agriculture practices at the Haojiatai site in Luohe city,Henan Province

As the most fundamental economic sector of human societies,farming has played a significant role in interactions between humans and the environment.The study of crop patterns in various regions could not only clarify the economic foundations of early societies,but also greatly improve our understanding of interactions among human beings,the environment,and other creatures.In this regard,this study focuses on early agriculture practices at the Haojiatai site,situated in the cultural and natural transitional region between North and South China.Macro plant remains from this site reveal that foxtail millet was the most important staple crop here during the Longshan and Xinzhai periods(4300–3800 cal.yr BP),along with common millet and a small amount of rice and soybean.This crop pattern is in contrast to the ancient environmental conditions of this region,and cultural factors such as agriculture traditions and food preferences may have been more important in the formation process of this crop pattern.     

青藏高原河流网络高分CubeSat遥感监测

河流网络是地表水循环的重要组成部分,如何实现河流网络动态监测已成为河流遥感研究的热点。近年来,以PlanetScope为代表的CubeSat小卫星已具备了米级空间分辨率、1 d重访周期的优势,这为河流网络高时空分辨率动态监测提供了可能。本文以青藏高原长江源区的通天河流域（227 km²）为研究区,选取2017-05—2017-10 5期3 m空间分辨率CubeSat遥感影像,增强河流横纵剖面特征自动化提取了河流网络,研究了通天河流域河流网络动态变化,对比分析了3 m CubeSat与30 m Landsat 8、10 m Sentinel-2所提取的河流网络,以及5种现有水体数据集（GRWL,GSW,FROM-GLC 2017,OpenStreetMap,HydroSHEDS）。研究结果表明：（1）研究区内河流网络5月水系密度较低（0.38 km^-1）,7—8月河流网络进入丰水期,水系密度显著增加至0.61 km^-1,9月河流网络进入平水期,水系密度趋于平稳（0.53 km^-1）,随后迅速退化并于10月开始冻结,水系密度迅速降低至0.37 km^-1;（2）采用高空间分辨率CubeSat所提取的河流网络能够识别更多细小河流（河宽3—30 m）,CubeSat所提取的河流总长分别为Landsat 8、Sentinel-2所提取河流总长的1.6倍和1.3倍;（3）CubeSat所提取的河流网络水系密度高于现有水体数据集（2.9—12.4倍）,弥补了现有水体数据集无法反映细小河流的不足。     

AO0235＋164射电波段宽带谱指数周期性变化的研究

收集了AO0235＋164天体射电4．8GHz和14．5GHz波段的光变测量数据,并获得了长期的光变曲线,从光变曲线可以看出其活动是非常剧烈的。利用Jurkevieh方法和自相关函数方法分别对AO0235＋164射电波段宽带谱指数进行周期性分析,并对流量和谱指数进行相关性分析,研究结果表明：（1）AO0235＋164天体射电波段4．8GHz-14．5GHz对应的宽带谱指数,可能存在5．30年的光变周期,与Liu等人用功率谱法在射电波段发现其流量密度可能存在5．59±0．47年的光变周期基本吻合;（2）宽带谱指数与流量密度之间存在相关性。