南海大洋钻探及海洋地质与地球物理前沿研究新突破

南海是西太平洋地区规模最大且具有代表性的边缘海盆地之一。经过近几十年的研究积累,尤其是通过实施5个国际大洋钻探航次(1999–2018年)与国家自然科学基金委“南海深海过程演变”重大研究计划(2011–2019年),我国科学家获得了大量宝贵的第一手资料,取得了一系列创新进展与重大突破,标志着南海海洋地质与地球物理研究正走向国际前沿。重要研究成果包括:(1)新提出南海是“板缘张裂”盆地,与经典的大西洋型陆缘模式不同;(2)大洋钻探首次获取了基底玄武岩样品,结合中国在南海首次深拖地磁测量实验,精确测定了南海海盆玄武岩年龄,揭示南海海盆从东向西分段扩张;(3)大洋钻探结果发现南海陆缘岩石圈减薄之初岩浆迅速出现,未发现缓慢破裂造成的蛇纹岩出露;(4)发现南海扩张结束后仍存在大量岩浆活动,可能受控于多种构造与地幔因素;(5)地球化学证据与地球动力学模拟都显示南海岩浆的形成受到周边俯冲带的影响。目前我国的海洋地球科学正在进入崭新的发展阶段,有望以南海为基点,开始拓展到周边大洋,通过主导大型研究计划以及建设我国大洋钻探平台,以提升我国在南海、西太平洋与印度洋海洋地质科学研究的实质性影响力与引领地位。     

Is the ocean floor a fractal?

The topographic structure of the ocean bottom is investigated at different scales of resolution to answer the question: Can the seafloor be described as a fractal process? Methods from geostatistics, the theory of regionalized variables, are used to analyze the spatial structure of the ocean floor at different scales of resolution. The key to the analysis is the variogram criterion: Self-similarity of a stochastic process implies self-similarity of its variogram. The criterion is derived and proved here: it also is valid for special cases of self-affinity (in a sense adequate for topography). It has been proposed that seafloor topography can be simulated as a fractal (an object of Hausdorff dimension strictly larger than its topological dimension), having scaling properties (self-similarity or self-affinity). The objective of this study is to compare the implications of these concepts with observations of the seafloor. The analyses are based on SEABEAM bathymetric data from the East Pacific Rise at 13°N/104°W and at 9°N/104°W and use tracks that run both across the ridge crest and along the ridge flank. In the geostatistical evaluation, the data are considered as a stochastic process. The spatial continuity of this process is described by variograms that are calculated for different scales and directions. Applications of the variogram criterion to scale-dependent variogram models yields the following results: Although the seafloor may be a fractal in the sense of the definition involving the Hausdorff dimension, it is not self-similar, nor self-affine (in the given sense). Mathematical models of scale-dependent spatial structures are presented, and their relationship to geologic processes such as ridge evolution, crust formation, and sedimentation is discussed.     

天然气水合物开发安全检测技术应用研究

中国近年来先后在南海北部和祁连山南缘青海省天峻县永久冻土带中发现天然气水合物,这是一种新能源,它将对中国能源结构的调整和能源紧张的缓解起到非常重要的作用。但是,天然气水合物开采安全是个大问题,已经引起了国际上专家们的极大关注。俄罗斯南方国立技术大学地球物理、探矿工程和石油钻采教研室开发出来的天然气水合物开发安全检测技术和方法,可以准确确定出射孔部位的位置、检查射孔部位是否阻塞和如何解阻等关键技术,对天然气水合物开采安全提供了技术支撑,对此应该进行研究。     

Dynamic link between the level of ductile crustal flow and style of normal faulting of brittle crust

In a rheologically layered crust, compositional layers have an upper, elasto-plastic part and a lower, viscous one. When broken, the upper elastic part undergoes flexure, which is upward for the foot-wall and downward for the hanging wall. As a consequence of bending, stresses will develop locally that can overcome the strength of the plate and, therefore, impose the migration of active fault. In the lower, viscous part of each compositional layer, rocks can potentially flow. Numerical modelling of the behaviour of a crust made up of two compositional layers, during and following extension, shows that flow can take place not only in the lower crust but also, and more importantly, in the lower part of the upper crust. The ability of crustal rocks to flow influences the style and kinematics of rifted regions. When no flow occurs, subsidence will affect the extending areas, both hanging wall and foot-wall will subside with respect to an absolute reference frame such as sea level, and there will be a strict proportionality between extension and thinning. In addition, the downward movement of the fault blocks will decrease the local stresses created in the foot-wall and increase those of the hanging wall, thereby imposing a migration of fault towards the hanging wall. This is the behaviour of extensional settings developed on stabilised crust and which evolved in a passive margin. When flow does take place, middle crustal rocks will move towards the rifting zone causing isostatically driven upward movements that will be superimposed on movements associated with crustal and lithospheric thinning. Consequently, fault blocks will move upwards and the crust will show more extension than thinning. The upward movements will decrease the stresses developed in the hanging walls and increase those of the foot-wall. Faults will then migrate towards the foot-wall. Such a mode of deformation is expected in regions with thickened crust and has its most apparent expression in core complexes.     

中国东部降水年际变化的随机动力诊断

利用一个具有门限的非线性随机动力气候模式对中国东部江淮流域的降水进行了分析。结果表明：在不同的门限域中,降水对外部强迫的响应有明显差异,呈现出一定的非线性特征;模式能较好地拟合降水的变化趋势。     

基于地理学科核心素养的高中地理教材活动栏目比较 ——以人教版和中图版必修《地理二》为例

本文选取新版人教版与中图版高中必修《地理二》的活动栏目作为研究对象,在划分活动考察的核心素养内容和水平的基础上,对比活动栏目的编排方式和问题设置方式。中图版教材活动栏目中核心素养的渗透面向课堂教学各个环节,且活动考察核心素养的难度水平呈现阶梯上升的趋势,略高于课标要求;问题设置形式丰富,既有独立设问的活动,随知识点设计以夯实基础,也有问题链形式的活动以激发学生学习潜能,提升能力。人教版教材活动栏目中核心素养考察多设计在节中,辅助课堂教学,帮助学生内化核心素养,考察水平满足课标要求,减轻学生学习负担;问题设置以问题链形式为主,在单个活动栏目中呈现从较低水平到较高水平递进的趋势。     

The effect that coarse particles have on estimates of both optical and radiation characteristics of dust aerosol

Based on mathematical simulation, quantitative estimates of the effect that coarse dust particles have on the accuracy of retrieving the optical characteristics of aerosol have been obtained from the results of ground-based measurements of the spectral fluxes of both direct and scattered solar radiations. The results of verifying a retrieval algorithm (used at the AERONET ground-based network) based on special test models showed that the aerosol characteristics retrieved with this algorithm are unsuitable for calculating integral solar fluxes and for simulating space spectrometric IR measurements when the concentration of dust particles in the atmosphere exceeds their concentration in the well-known CONT model of continental aerosol by a factor of two or more.     

A note on the useable dynamic range of accelerographs recording translation

Since the late 1970s, the dynamic range and resolution of strong motion digital recorders have leaped from 65 to 135 dB, opening new possibilities for advanced data processing and interpretation. One of these new possibilities is the calculation of permanent displacement of the ground or of structures, associated with faulting or with non-linear response. Proposals on how permanent displacements could be recovered from recorded strong motion have been published since 1976. The analysis in this paper concludes that permanent displacements of the ground and of structures in the near-field can be calculated provided all six components of strong motion (three translations and three rotations) have been recorded, and the records are corrected for transducer rotation, misalignment and cross-axis sensitivity.     

Fossil cyclic calcrete in the Kuwait Group clastic deposits (Mio-Pleistocene) of Kuwait,Arabian Gulf

An investigation of the upper Kuwait Group clastic sequence (Mio-Pleistocene) exposed along the Jal Az-Zor escarpment in north Kuwait revealed several horizons of fossil calcrete. Field occurrences and textural characteristics of the studied sequence indicated that the fossil calcrete was hosted in cyclic fluviatile muddy sandstones and developed through diagenesis during inter-fluvial periods. Depositional and diagenetic features of the calcretized fluviatile sandstone units suggested that each cycle started with the deposition of a fluviatile muddy host sandstone during a humid period. This was followed by a period of semi-aridity during which calcrete profiles developed. The upper part of the calcrete profiles was weathered and terra rosa type soil was formed during wet seasons. This was succeeded by a severe arid climate and the deposition of desert aeolian sand sheets. Fossil nodular calcrete was only developed within the fluviatile muddy sandstones. The calcretized sandstones were lithified in two stages of diagenesis-an early stage that was responsible for the authigenesis of microcrystalline calcite and the development of calcrete nodules, and a later stage during which macrocrystalline calcite cement was precipitated as an intergranular cement displacing and replacing the clay matrix of the host sediments and filling fractures and cavities in the calcrete nodules. The findings and conclusions of the present study will help in understanding the lithostratigraphic setting of the Kuwait Group clastic sequence in the northern Arabian Gulf region.

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Zusammenfassung Eine Untersuchung der klastischen Sequenz der oberen Kuwait-Gruppe, die entlang der Jal Az-Zor Zone in Nordkuwait aufgeschlossen ist, ergab mehrere Horizonte fossilen Kalksinters. Geländebeobachtungen und texturelle Charakteristik der Sequenz deuten an, daß der fossile Kalksinter in Zyklen eines feinkörnigen fluviatilen Sandsteines eingebettet ist und diagenetisch während interfluviatilen Stadien gebildet wurde. Merkmale der Ablagerungsverhältnisse und der Giagenese des verkalkten fluviatilen Sandsteines sprechen dafür, daß jeder Zyklus mit der Sedimentation des Sandsteines unter humiden Klimabedingungen begann. Auf dieses Stadium folgte eine Phase semiariden Klimas, während dessen sich die Kalksinterprofile entwickelten. Der obere Teil der Kalksinterabschnitte verwitterte in Regenzeiten, dabei bildeten sich »terra rosa«-Böden. Während des folgenden rauhen ariden Klimas wurden wüstenähnliche äclische Sande sedimentiert. Den fossilen knotigen Kalksinter findet man nur innerhalb des fluviatilen Sandsteines. Die Lithifizierung der Sandsteine erfolgte in zwei diagenetischen Phasen: In der frühen Phase wurde auhigener, mikrokristalliner Calcit und die Kalksinterknoten gebildet. Während der späteren Diagenesephase fiel makrokristalliner Calcit als intergranularer Zement aus, der die tonige Ausgangsmatrix substituierte und Klüfte sowie Hohlräume innerhalb der Kalksinterknoten ausfüllte. Beobachtungen und Interpretationen dieser Studie werden das Verständnis um den lithostratigraphischen Zusammenhang der klastischen Sequenz der Kuwait-Gruppe in der Region des nördlichen Arabischen Golfes erleichtern.

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Résumé La série élastique du groupe supérieur du Koweit (MioPleistocène), exposée le long de l'escarpement de Jal Az-Zor (nord du Koweit) montre plusieurs horizons de calcrètes fossiles. Les relations de terrain et les caractères structuraux de cette série montrent que ces calcrètes se sont formées dans des sables argileux fluviatiles cycliques, par un processus de diagenèse intervenu au cours de périodes interfluviales. Les caractères sédimentologiques et diagénétiques de ces roches suggèrent que chaque cycle a débuté par le dépôt, en période humide, des sables argileux fluviatiles et s'est poursuivi en période de semi-aridité par le développement des calcrètes. La partie supérieure des calcrètes a subi une altération atmosphérique avec formation d'un sol de type »terra rossa« au cours des saisons humides. Le cycle se termine par l'installation d'un climat strictement aride, avec dépôt de sables éoliens désertiques. Les calcrètes, nodulaires, se sont formées uniquement dans les sables argileux fluviatiles. Leur lapidification s'est opérée en deux stades: un premier stade responsable de l'apparition de calcite authigène microcristalline et du développement de nodules carbonates; un second stade marqué par la précipitation d'un ciment intergranulaire de calcite macrocristalline qui s'est substitué à la matrice argileuse du sédiment primaire et a rempli les fissures et cavités des nodules. Les résultats de cette étude permettent de mieux comprendre l'édification lithostratigraphique de la série clastique du Groupe du Koweit dans la région septentrionale du Golfe Arabique.

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Generalized geophysical model and dynamic properties of the continental crust

Detailed seismic investigations of the continental crust have produced evidence of definite regularities in the general layering of the consolidated crust despite its high degree of inhomogeneity. Three main layers may be resolved in the inner part of a continent: an upper layer with velocities of 5.8–6.4 km/s and a velocity gradient about 0.04–0.05 s⁻¹, an intermediate layer with velocities of 6.2–6.6 km/s and velocity gradient about zero, and a lower layer with velocities of 6.8–7.2 km/s and a high-velocity gradient of 0.05–0.1 s⁻¹. The intermediate layer is characteristically different not only because of its low average velocity gradient, but also because of its more pronounced horizontal layering, inversion zones, and its higher “transparency” and V_p/V_s ratio. The gravity and magnetic data have shown that basement inhomogeneities disappear at the top of the intermediate layer. Also there are few earthquakes in this layer. These pecularities may be interpreted as the result of partial melting (weakening) of rocks and their possible horizontal mobility inside this layer.Thus, dynamic models of tectonic processes must take into consideration the possible existence of a weak zone in the crust.