乌尔逊凹陷西部边界断裂的幕式演化模式及其对含油气系统的控制作用

海拉尔盆地乌尔逊凹陷西部的边界断层-乌西断裂, 对该凹陷的构造演化具有明显的控制作用。研究发现该断裂的生长发育有着明显的幕式演化特点: 经历了分段连锁、宁静、活化和反转等4 个演化阶段, 每一阶段都有不同的构造和沉积特点。其中, 分段连锁和活化阶段是凹陷的主要生长期, 分段连锁阶段以发育张性断块构造样式为特征, 活化阶段则以发育盖层滑脱型构造样式为主。乌西断裂的幕式演化对乌尔逊凹陷烃源岩演化、储盖系统的分布及含油气系统具有一定的控制作用。     

GPS在胶济铁路勘测定界工程中的应用

根据胶济客运专线工程勘测定界工作的成功施测经验,探讨了GPS在狭长带状工程中的应用。针对狭长带状控制网,探讨了如何合理布设GPS点,使控制网更趋于合理,各项指标更完备,同时最大程度地节省人力、物力和时间。     

Integrated “plume winter” scenario for the double-phased extinction during the Paleozoic–Mesozoic transition: The G-LB and P-TB events from a Panthalassan perspective

The event across the Paleozoic–Mesozoic transition involved the greatest mass extinction in history together with other unique geologic phenomena of global context, such as the onset of Pangean rifting and the development of superanoxia. The detailed stratigraphic analyses on the Permo-Triassic sedimentary rocks documented a two-stepped nature both of the extinction and relevant global environmental changes at the Guadalupian–Lopingian (Middle and Upper Permian) boundary (G-LB, ca. 260 Ma) and at the Permo-Triassic boundary (P-TB, ca. 252 Ma), suggesting two independent triggers for the global catastrophe. Despite the entire loss of the Permian–Triassic ocean floors by successive subduction, some fragments of mid-oceanic rocks were accreted to and preserved along active continental margins. These provide particularly important dataset for deciphering the Permo-Triassic paleo-environments of the extensive superocean Panthalassa that occupied nearly two thirds of the Earth’s surface. The accreted deep-sea pelagic cherts recorded the double-phased remarkable faunal reorganization in radiolarians (major marine plankton in the Paleozoic) both across the G-LB and the P-TB, and the prolonged deep-sea anoxia (superanoxia) from the Late Permian to early Middle Triassic with a peak around the P-TB. In contrast, the accreted mid-oceanic paleo-atoll carbonates deposited on seamounts recorded clear double-phased changes of fusuline (representative Late Paleozoic shallow marine benthos) diversity and of negative shift of stable carbon isotope ratio at the G-LB and the P-TB, in addition to the Paleozoic minimum in ⁸⁷Sr/⁸⁶Sr isotope ratio in the Capitanian (Late Guadalupian) and the paleomagnetic Illawarra Reversal in the late Guadalupian. These bio-, chemo-, and magneto-stratigraphical signatures are concordant with those reported from the coeval shallow marine shelf sequences around Pangea. The mid-oceanic, deep- and shallow-water Permian records indicate that significant changes have appeared twice in the second half of the Permian in a global extent. It is emphasized here that everything geologically unusual started in the Late Guadalupian; i.e., (1) the first mass extinction, (2) onset of the superanoxia, (3) sea-level drop down to the Phanerozoic minimum, (4) onset of volatile fluctuation in carbon isotope ratio, 5) ⁸⁷Sr/⁸⁶Sr ratio of the Paleozoic minimum, (6) extensive felsic alkaline volcanism, and (7) Illawarra Reversal.The felsic alkaline volcanism and the concurrent formation of several large igneous provinces (LIPs) in the eastern Pangea suggest that the Permian biosphere was involved in severe volcanic hazards twice at the G-LB and the P-TB. This episodic magmatism was likely related to the activity of a mantle superplume that initially rifted Pangea. The supercontinent-dividing superplume branched into several secondary plumes in the mantle transition zone (410–660 km deep) beneath Pangea. These secondary plumes induced the decompressional melting of mantle peridotite and pre-existing Pangean crust to form several LIPs that likely caused a “plume winter” with global cooling by dust/aerosol screens in the stratosphere, gas poisoning, acid rain damage to surface vegetation etc. After the main eruption of plume-derived flood basalt, global warming (plume summer) took over cooling, delayed the recovery of biodiversity, and intensified the ocean stratification. It was repeated twice at the G-LB and P-TB.A unique geomagnetic episode called the Illawarra Reversal around the Wordian–Capitanian boundary (ca. 265 Ma) recorded the appearance of a large instability in the geomagnetic dipole in the Earth’s outer core. This rapid change was triggered likely by the episodic fall-down of a cold megalith (subducted oceanic slabs) from the upper mantle to the D″ layer above the 2900 km-deep core-mantle boundary, in tight association with the launching of a mantle superplume. The initial changes in the surface environment in the Capitanian, i.e., the Kamura cooling event and the first biodiversity decline, were probably led by the weakened geomagnetic intensity due to unstable dipole of geodynamo. Under the low geomagnetic intensity, the flux of galactic cosmic radiation increased to cause extensive cloud coverage over the planet. The resultant high albedo likely drove the Kamura cooling event that also triggered the unusually high productivity in the superocean and also the expansion of O₂ minimum zone to start the superanoxia.The “plume winter” scenario is integrated here to explain the “triple-double” during the Paleozoic–Mesozoic transition interval, i.e., double-phased cause, process, and consequence of the greatest global catastrophe in the Phanerozoic, in terms of mantle superplume activity that involved the whole Earth from the core to the surface biosphere.     

Timing and magnitude of tetrapod extinctions across the Permo-Triassic boundary

A review of the tetrapod (amphibian and amniote) record across the Permo-Triassic boundary (PTB) indicates a global evolutionary turnover of tetrapods close to the PTB. There is also a within-Guadalupian tetrapod extinction here called the dinocephalian extinction event, probably of global extent. The dinocephalian extinction event is a late Wordian or early Capitanian extinction based on biostratigraphic data and magnetostratigraphy (the extinction precedes the Illawara reversal), so it is not synchronous with the end-Guadalupian marine extinction. The Russian PTB section documents two tetrapod extinction events, one just before the dinocephalian extinction event and the other at the base of the Lystrosaurus assemblage. However, generic diversity across the latter extinction remains essentially the same despite a total evolutionary turnover of tetrapod genera. The Chinese and South African sections document the stratigraphic overlap of Dicynodon and Lystrosaurus. In the Karoo basin, the lowest occurrence of Lystrosaurus is in a stratigraphic interval of reversed magnetic polarity, which indicates it predates the marine-defined PTB, so, as previously suggested by some workers, the lowest occurrence of Lystrosaurus cannot be used to identify the PTB in nonmarine strata. Correlation of the marine PTB section at Meishan, southern China, to the Karoo basin based primarily on magnetostratigraphy indicates that the main marine extinction preceded the PTB tetrapod extinction event. The ecological severity of the PTB tetrapod extinction event has generally been overstated, and the major change in tetrapod assemblages that took place across the PTB was the prolonged and complex “replacement” of therapsids by archosaurs that began before the end of the Permian and was not complete until well into the Triassic. The tetrapod extinctions are not synchronous with the major marine extinctions at the end of the Guadalupian and just before the end of the Permian, so the idea of catastrophic causes of synchronous PTB extinctions on land and sea should be reconsidered.     

Conodont biostratigraphy across the Permian–Triassic boundary at the Dawen section, Great Bank of Guizhou, Guizhou Province, South China: Implications for the Late Permian extinction and correlation with Meishan

Several continuous Permian–Triassic boundary (PTB) sections are well exposed in the interior of the Great Bank of Guizhou (GBG) on the east limb of the Bianyang syncline, Luodian County, Guizhou Province, South China. Fourteen conodont taxa are identified, including Clarkina kazi, Clarkina lehrmanni n. sp., Clarkina taylorae, Clarkina zhejiangensis, Hindeodus eurypyge, Hindeodus inflatus, Hindeodus sxlatidentatus, Hindeodus parvus erectus, Hindeodus parvus parvus, Hindeodus postparvus, Hindeodus praeparvus, Hindeodus typicalis, Isarcicella staeschei, and Merrillina ultima based on a detailed study of the Permian-Triassic interval at the Dawen section. The first occurrence (FO) of H. parvus parvus in the lower Daye Formation, at about 7.45 m above the contact surface between the Upper Permian skeletal packstone and a calcimicrobial framestone unit, is correlated with the Permian–Triassic boundary; the occurrence of H. eurypyge, H. praeparvus and M. ultima immediately below and H. postparvus above the interval supports this interpretation. A morphometric analysis of 31 Hindeodus specimens helped distinguish H. parvus erectus from H. parvus parvus and H. postparvus. Correlation with the Meishan section (PTB GSSP) using both conodont biostratigraphy and carbon isotopes, indicates that the major extinction at the two localities is simultaneous and coincides with the top of the skeletal packstone at Dawen. The contact between the skeletal packstone and the calcimicrobialite is very irregular and has previously been interpreted as a dissolution surface and correlated with a surface in the lower part of bed 27 at Meishan. Our results confirm this interpretation and reveal that the dissolution event postdated the extinction.     

基于凸壳构造技术的领海基点选取问题研究

领海基点的选取数量及其空间点位分布的不同,对海域划界结果有着重要的影响.在传统的领海基点选取工作中缺乏一种有效的用于检验选取方案优劣的数学模型,因而这一工作中存在着不确定性因素.为了解决这个问题,提出了利用最小凸包(凸壳)构造技术实现领海基点最优选取的思路和方法,并在此基础上对某群岛的领海基点选取方案作了实例分析.     

Beyond the epsilon band: polygonal modeling of gradation/uncertainty in area-class maps

A spatial modeling technique is proposed to represent boundary uncertainty or gradation on area-class maps using a simple polygon tessellation with designated zones of indeterminacy or transition zones. The transition zone can be conceptualized as a dual of the epsilon band, but is more flexible and allows for a wide range of polygonal configurations, including polygons with sinuous boundaries, spurs, three-way transition zones, and null polygons. The model is specified using the medial axis to capture the general shape characteristics of a transition zone. Graph theoretic representation of an extended version of the medial axis captures key junctions in both shape and classification and is used to identify well-formed transition zones that can be logically and unambiguously handled by the model. A multivariate classification surface is specified by first defining degrees or probabilities of membership at every point on the medial axis and transition zone boundary. Degrees or probabilities of membership at all other points are defined by linear interpolation. The technique is illustrated with an example of a complex transition zone, and a simple isoline representation that can be derived from the model is presented. The proposed modeling technique promises to facilitate expert characterization of soil formations, ecological systems, and other types of areal units where gradation and/or boundary uncertainty are prevalent.     

利用重磁资料研究莺-琼盆地构造分界及其两侧断裂特征

莺-琼盆地(即莺歌海盆地和琼东南盆地)位于印支地块与华南大陆交汇处,该区域地质构造复杂,为南海西北走滑型和伸展型陆缘的交汇区,也是印澳-欧亚板块碰撞“挤出-逃逸构造区”和“古南海俯冲-拖曳构造区”.莺-琼盆地的北部以红河断裂带中1号断裂为界,前人对其认识比较统一,但莺-琼盆地南部由于地质和地球物理资料较少、研究程度低,以致其构造格局及分界位置不明确.通过对重、磁资料的处理,认为在莺-琼盆地分界的北段存在明显的重力异常和磁力异常梯级带,该梯级带与1号断裂位置相对应;在其南段存在明显的重力异常和磁力异常高值带,推断该高值带为一“中建凸起”,结合重、磁对应分析技术确定了该“中建凸起”的分布范围.采用重、磁异常归一化总水平导数垂向导数技术识别出控制莺-琼盆地分界两侧的断裂构造,在分界以西断裂走向主要为北北西向,分界以东主要为北东向.通过地质和地球物理综合研究认为莺-琼盆地的北段以1号断裂为界,南段以“中建凸起”为界.     

Dynamic interaction numerical models in the time domain based on the high performance scaled boundary finite element method

Consideration of structure-foundation-soil dynamic interaction is a basic requirement in the evaluation of the seismic safety of nuclear power facilities. An efficient and accurate dynamic interaction numerical model in the time domain has become an important topic of current research. In this study, the scaled boundary finite element method （SBFEM） is improved for use as an effective numerical approach with good application prospects. This method has several advantages, including dimensionality reduction, accuracy of the radial analytical solution, and unlike other boundary element methods, it does not require a fundamental solution. This study focuses on establishing a high performance scaled boundary finite element interaction analysis model in the time domain based on the acceleration unit-impulse response matrix, in which several new solution techniques, such as a dimensionless method to solve the interaction force, are applied to improve the numerical stability of the actual soil parameters and reduce the amount of calculation. Finally, the feasibility of the time domain methods are illustrated by the response of the nuclear power structure and the accuracy of the algorithms are dynamically verified by comparison with the refinement of a large-scale viscoelastic soil model.     

Condensed hyperelements method of non-vertical consistent boundaries for wave propagation analysis in irregular media

The study of wave propagation in finite/infinite media has many applications in geotechnical and structural earthquake engineering and has been a focus of research for the past few decades. This paper presents an analysis of 2D anti- plane problems （Love waves） and 2D in-plane problems （Rayleigh waves） in the frequency domain in media consisting of a near-field irregular and a far-field regular part. The near field part may contain structures and its boundaries with the far-field can be of any shape. In this study, the irregular boundaries of the near-field are treated as consistent boundaries, extending the concept of Lysmer＇s vertical consistent boundaries. The presented technique is called the Condensed Hyperelements Method （CHM）. In this method, the irregular boundary is limited to a vertical boundary at each end that is a consistent boundary at the far-field side. Between the two ends, the medium is discretized with hyperelements. Using static condensation, the stiffness matrix of the far-field is derived for the nodes on the irregular boundary. Examples of the application of the CHM illustrate its excellent accuracy and efficiency.