Tertiary geodynamics of Sakhalin (NW Pacific) from anisotropy of magnetic susceptibility fabrics and paleomagnetic data

Sakhalin has been affected by several phases of Cretaceous and Tertiary deformation due to the complex interaction of plates in the northwest Pacific region. A detailed understanding of the strain is important because it will provide constraints on plate-scale processes that control the formation and deformation of marginal sedimentary basins. Anisotropy of magnetic susceptibility (AMS) data were obtained from fine-grained mudstones and siltstones from 22 localities in Sakhalin in order to provide information concerning tectonic strain. AMS data reliably record ancient strain tensor orientations before significant deformation of the sediments occurred. Paleomagnetically determined vertical-axis rotations of crustal rocks allow rotation of the fabrics back to their original orientation. Results from southwest Sakhalin indicate a N035°E-directed net tectonic transport from the mid-Paleocene to the early Miocene, which is consistent with the present-day relative motion between the Okhotsk Sea and Eurasian plates. Reconstruction of early–late Miocene AMS fabrics in east Sakhalin indicates a tectonic transport direction of N040°E. In west Sakhalin, the transport direction appears to have remained relatively consistent from the Oligocene to the late Miocene, but it has a different attitude of N080°E. This suggests local deflection of the stress and strain fields, which was probably associated with opening of the northern Tatar Strait. A northward-directed tectonic transport is observed in Miocene sediments in southeast Sakhalin, mid-Eocene sediments in east Sakhalin, and in Late Cretaceous rocks of west and northern Sakhalin, which may be associated with northwestward motion and subduction of the Pacific Plate in the Tertiary period. The boundaries of the separate regions defined by the AMS data are consistent with present-day plate models and, therefore, provide meaningful constraints on the tectonic evolution of Sakhalin.     

活动海岭俯冲与岛弧火山活动的热模拟研究

为解释活动海岭的俯冲会造成岛弧火山活动的间断这一现象,本文采用有限单元法对活动海岭俯冲的热演化过程进行了模拟计算．一般情况下,摩擦剪切生热使岛弧下100km左右深度形成地温反转,俯冲板片海洋地壳内角门岩等含水矿物脱水,释放的水进入其上覆板块,降低了地幔岩石的熔点,使热的地幔楔状体内发生部分熔融,形成岛弧火山活动．高温的活动海岭俯冲时不再出现这种温度反转,俯冲板片在较浅深度达到较高温度而脱水,水进入上覆相对较冷的地幔楔状体不能造成熔融,因此岛弧火山活动会中断．     

青藏高原东南缘现今地球动力学研究

统一的晚第三纪青藏高原面和云南高原面，早更新世后完全分裂解体，海拔高度分别为４５００～５０００ｍ和２０００～２５００ｍ。二者间的北东向块断过渡带，地形自西北向东南层层倾斜、陡降，构成青藏高原东南缘，其鲜明的构造地貌、最新断裂活动、广泛的水热显示、强烈的地震活动表明这是一条现代构造活动带。跨该带的两期ＧＰＳ测量结果（１９９２，１９９４）揭示其为ＮＷ－ＳＥ向拉张性质，地壳与上地幔结构特征支持其属热动力和重力均衡调整边界     

地球动力学的历史和近期发展

地球动力学研究地球的整体运动，地球内部运动及其与地表结构的相互作用和地表大型构造变形和破裂的力学过程。本文给出一个简要历史，从牛顿、泊松、到勒夫是处理均匀球体的，到列宾逊、竹内、迈内兹处理了层状地球，随着板块构造理论的出现。大量应用数值模拟对构造现象的分析，震源机制的研究以及非线性动力学的应用等；讨论了反演问题，对参量及驱动力的反演有较详细的说明；介绍了一些国内有关全球和区域应力场分析，构造现象分     

Some Fundamental Problems of Geodynamics and Application of Earth Observations by Space-Based Measurements

Although great-progress has been made in the earth sciences,some fundamental problems of geodynamics remain unsolved.They are concerned with the whole earth as well as regional tectonics,such as the west Pacific and Qinghai-Xizhang plateau.The new generation of earth observation by space-based measurement will contribute to solving these problems of geodynamics.In this regard,some specific plans about application of these techniques are suggested in this paper.     

Thermal history of Canadian Williston basin from apatite fission-track thermochronology—implications for petroleum systems and geodynamic history

Apatite fission track (AFT) thermochronology has been applied to a composite depth profile of Precambrian basement rocks underlying the Phanerozoic Canadian Williston Basin. Thermal histories derived from the AFT data record cycles of heating and cooling which follow the pattern of regional burial history, but which also indicate major temporal and geographic variations in the timing and degree of maximum Phanerozoic temperatures. These variations in the thermal history were not previously recognised from organic maturity indicators and subsidence models. Specifically, our study suggests a late Paleozoic heat flow anomaly with a geographic extent closer to that of Middle Devonian–Carboniferous Kaskaskia subsidence patterns than to that of the Williston Basin proper. This thermal anomaly has both economic and geodynamic significance. The recognition that potential Upper Cambrian–Lower Ordovician petroleum source rocks became fully mature during the late Paleozoic distinguishes that petroleum system from others that entered the main hydrocarbon generation stage in latest Cretaceous and Paleogene time. The late Paleozoic heat flow anomaly suggested from the AFT data implies a geodynamic coupling between inelastic Kaskaskia subsidence and previously inferred late Paleozoic lithospheric weakening. While the temporally varying heat flow model is preferred, the lack of independent constraints on the maximum thickness of upper Paleozoic strata precludes the outright rejection of the previous constant heat flow model. The AFT data provide important new constraints on the evolution of the epicratonic Williston Basin and its geodynamic models.     

Origine des variations latérales des dépôts yprésiens dans la zone des dômes en Tunisie septentrionaleOrigin of lateral variations of the Ypresian deposits in the dome zone in northern Tunisia

In the Mejez El Bab–Testour area (northern Tunisia), the Early Eocene extension induced block tilting and salt tectonics of the Triassic evaporites. Tectonic events and halokinesis have determined the organization of Ypresian sediments. Diapiric structures have been generated during Cretaceous along the east–west, north–south and NE–SW major faults and emphasised during Lower Eocene. In this region, the Ypresian deposits constitute a filling sequence and show several thickness and facies variations. They correspond to a Nummulitic and Globigerina mixed facies characterizing a platform-basin transition zone. To cite this article: H. El Ouardi, C. R. Geoscience 334 (2002) 141–146.     

Les manifestations tectono-sédimentaires d'âge Campanien–Maastrichtien en Tunisie : implications sur l'évolution géodynamique de la marge Nord-AfricaineThe Campanian–Maastrichtian synsedimentary tectonic activity: implication in the geodynamic evolution of the North African Margin

The synsedimentary tectonic activity evidenced in central and northern Tunisia points out the fact that the Campanian–Maastrichtian deposits are associated with several NW–SE and east–west normal faults. These results suggest that the east–west transform fault of North African Margin is still active during this stage. These data allow us to discuss a new geodynamic model for the North African Margin. To cite this article: M. Dlala, C. R. Geoscience 334 (2002) 135–140.     

地球重力场的精细频谱结构及其应用

综述了近年内在全球地球动力学合作观测和研究网络框架下开展的重力场观测、频谱结构和应用研究方面的成果. 内容涉及精密大气、海潮负荷信号检测, 重力潮汐和自由核章动参数测定, 海潮模型和重力固体潮模型有效性检验, 重力潮汐实验模型构制, 地球球型基频和低阶震型谱峰分裂现象和地球Chandler摆动等方面. 文章还介绍了综合现代大地测量技术, 全球超导重力仪的长期、连续观测在地表水循环、同震和震后形变、地球慢形变和地壳垂直运动等方面将发挥重要作用的情况.