综合工程物探在上海地铁四号线抢险工程中的应用

在上海地铁四号线抢险工程中,综合工程物探快速、准确地圈定了受地面沉降影响,周边土体的扰动范围及深度,并对江底隧道的状况进行了调查。文章介绍了用地质雷达、高分辨率SH波浅层反射波法、瞬态瑞雷面波法勘探及水上高密度多波列地震影像法等综合工程物探方法在该工程中的应用前提及效果。     

地理信息系统GIS在地籍、地形测量中的运用

本文利用地理信息系统(GIS)对测绘地形、地籍以及生成土地证、房产证等一些图件进行说明，并作相应的转换处理，满足了地籍管理工作的需要。     

Dislocation generation, slip systems, and dynamic recrystallization in experimentally deformed plagioclase single crystals

Three samples of gem quality plagioclase crystals of An60 were experimentally deformed at 900 °C, 1 GPa confining pressure and strain rates of 7.5–8.7×10⁻⁷ s⁻¹. The starting material is effectively dislocation-free so that all observed defects were introduced during the experiments. Two samples were shortened normal to one of the principal slip planes (010), corresponding to a “hard” orientation, and one sample was deformed with a Schmid factor of 0.45 for the principal slip system [001](010), corresponding to a “soft” orientation. Several slip systems were activated in the “soft” sample: dislocations of the [001](010) and 110(001) system are about equally abundant, whereas 110{111} and [101] in ( 31) to ( 42) are less common. In the “soft” sample plastic deformation is pervasive and deformation bands are abundant. In the “hard” samples the plastic deformation is concentrated in rims along the sample boundaries. Deformation bands and shear fractures are common. Twinning occurs in close association with fracturing, and the processes are clearly interrelated. Glissile dislocations of all observed slip systems are associated with fractures and deformation bands indicating that deformation bands and fractures are important sites of dislocation generation. Grain boundaries of tiny, defect-free grains in healed fracture zones have migrated subsequent to fracturing. These grains represent former fragments of the fracture process and may act as nuclei for new grains during dynamic recrystallization. Nucleation via small fragments can explain a non-host-controlled orientation of recrystallized grains in plagioclase and possibly in other silicate materials which have been plastically deformed near the semi-brittle to plastic transition.     

Provenance, environmental and paleogeographic controls on sandstone composition in an incised-valley system: the Eocene La Meseta Formation, Seymour Island, Antarctica

The Eocene La Meseta Formation is the youngest exposed unit of the back-arc James Ross Basin, Antarctic Peninsula, cropping out in Seymour (Marambio) Island. The formation comprises 720 m of clastic sedimentary rocks of deltaic, estuarine and shallow marine origin. It was subdivided into six unconformity-based units (Valle de Las Focas, Acantilados, Campamento, Cucullaea I, Cucullaea II and Submeseta Allomembers) grouped into three main facies associations. Facies association I represents valley-confined deposition in a progradational/aggradational tide-dominated and wave-influenced delta front/delta plain environment. Facies association II includes tidal channels, mixed tidal flats, tidal inlets and deltas, washover and beach environments. Facies association III represents nonconfined tide- and storm-influenced nearshore environments. La Meseta Formation sandstones are quartzofeldspathic with some hybrid arenites (glauconite and carbonate bioclasts-rich). Sandstone detrital modes are subdivided into two distinctive petrofacies: the low quartz petrofacies (petrofacies I, Q<55% and L>12%), interpreted to retain the original provenance signal, and the high quartz petrofacies (petrofacies II, Q>55% and L<12%), representing the reworking product of the former after selective elimination of the more labile components. Petrofacies I sandstone framework grains were mainly derived from a dissected magmatic arc and an associated metamorphic belt. Textural evidence for recycling of some grains (e.g. garnet) from older sedimentary units during valley incision is not conclusive. Changes in the relative participation of source areas during the evolution of the incised-valley system are evaluated from the relative proportions of lithic fragments and monomineralic clasts derived from each rock type. Two lithic assemblages were recognized. The mixed lithic assemblage (Rv/Rm+Rp<1.4) shows participation of all rock types; it represented valley-confined environments, either during the initial stage of valley development, or after main episodes of incision. The volcanic lithic assemblage (Rv/Rm+Rp>1.4) is clearly dominated by volcanic-derived clasts; it developed at times of high sea level and/or during later stages of the valley fill, when an “energy fence” at the shoreline prevented delivery of sediment from the Antarctic Peninsula, thus enhancing the relative participation of local volcanic sources.     

Lithofacies and palaeosol analysis of the Middle and Upper Siwalik Groups (Plio–Pleistocene), Haripur-Kolar section, Himachal Pradesh, India

The Middle–Upper Siwalik Groups (Plio–Pleistocene) are exposed at Haripur-Kolar, Himachal Pradesh, India. The succession is 2800-m thick and has been subdivided into Unit M1 of the Middle Siwalik and four units U1–U4 of the Upper Siwalik Group, on the basis of facies associations, and type and degree of development of palaeosols. The available magnetostratigraphic ages for bases of Units U1, U3 and U4 are 5.5, 2.6 and 1.77 Ma, respectively. The top of the section has been dated as 19 ka.

Lithofacies association and palaeocurrent analysis indicates that the Middle and Upper Siwalik Groups were formed mainly by a basin transverse fluvial system. Two types of river systems, which differ in their size, can be documented in Unit-M1, Unit U1 and Unit-U2: one trunk river system similar to the modern Kosi and the other smaller river system, which formed tributaries to the former. The large rivers were mainly braided in nature. The Unit U3 and lower part of Unit U4 were deposited in the piedmont depositional system mainly by small braided streams and the upper part of the Unit U4 was deposited during a period of arid climate by sediment gravity-flows.

Integration of fluvial lithofacies and pedofacies helps to identify two fluvial depositional systems from the modern Indo-Gangetic Plains. The Lowland System involved deposition on alluvial megafans and interfan areas, which resulted in sand-rich and mud-rich sequences with weekly developed soils. The Upland System allowed large tracts to act as high ground for thousands of years, thereby giving rise to sandstone poor intervals with moderately to strongly developed soils. Occurrence of moderately to strongly developed soils was controlled by uplifting and tilting of large tectonic blocks, without any relation to distance from the main channels. Rate of subsidence apparently controlled the occurrence of Lowland and Upland systems. Deposition of the Unit M1, Unit U1 and Unit U2 took place under Upland and Lowland systems, very similar to those identified from the modern Indo-Gangetic Plains. The warm and humid climate between 5.3 and 2.6 Ma led to the formation of red Alfisols with calcrete nodules at places. Slightly cooler and drier climate starting at about 2.6 Ma and approximately coinciding with the onset of global-scale glaciation, produced poorly developed yellow soil with common development of nodular calcretic horizon and calcitc material disseminated in the groundmass. At ca. 0.9 Ma, a probable significant change to still drier and cooler climate produced typical sediment gravity-flows in the piedmont system, that continued until at least up to 19 ka.     

A Web-based resource discovery facility for a Geo-Data Server

This article deals with the design of a resource discovery system, based on a Web interface, for searching and downloading data stored in a Geo-Data Server. The main features of the Geo-Data Server are the design of a cartographic and image database, following international standards, a relational catalogue, containing meta-information on the archived data, and a high-level interface to access the system. The Geo-Data Server implements a distributed system where data are appropriately organised for remote consultation.     

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.     

Research on Outcrop Sequence Stratigraphy of Permian in Middle—Lower Yangtze Region

According to the latest International Chronostratigraphic Scheme (ICS, 2000), the Permian in the Middle-Lower Yangtze region of South China can e divided into three series and nine stages relevant to the traditional six stages of South China. From Assellian to Changxingian of Permian, 44 Main age range, the strata are composed of 14 third-order sequences, each of which is 3.14 Ma in average age range. There is one third-order sequence of Zisongian, equivalent to middle and upper Chuanshan Formation or equal to Asselian and two thirds of Sakmarian. There are two third-order sequences, corresponding to Liang-shan Formation or Zhenjiang Formation and upper Chuanshan Formation, which are assigned to Longlingian, coinciding with Artinskian and one third of Sakmarian. In addition, three third-order sequences, equal to Qixia Formation, are attributed to Chhsian, corresponding to Kubergandian and one third of Roadian. Four third-order sequences, comprising Gufeng, Maokou, Yanqiao,Yinping and Wuxue formations, are assigned to Maokouan, equivalent to two thirds of Roadian, Wordian and Capitanian. Two third-order sequences, equal to Longtan Formation or Wujiaping Formation, are included in Wuchiapingian. Other two third-order sequences, corresponding to changxing Formation or Dalong Formation, are assigned to Changhsingian. In brief, these above third-order sequences can be incorporated into 4 sequences sets.     

土地划拨中的时空数据模型研究

分析了当前应用在土地划拨中的时空数据模型,阐述了时间作为地理实体的基本特征及GIS中地理时间的模拟方法,并从存储管理和时空语义表现的角度给出了时空数据模型的基本设计思想。     

Ionospheric Signatures Of Bursty Bulk Flows

While the plasma convection in the Earth's magnetosphere was for a long timeconsidered to consist mostly of laminar flows with wide spatial extents, about adecade ago the phenomenon of bursty bulk flows (BBFs), which now could beunderstood as long, but narrow channels of fast earthward plasma flow in thecentral plasma sheet of the magnetospheric tail, was discovered. Soon after thisit became clear that such events are not exceptional, but a large portion of theearthward plasma flow in the inner part of the magnetospheric tail is organisedin this bursty, intermittent mode. Since the Earth's magnetosphere is connectedby highly conducting magnetic field lines with its ionosphere, the next logicalstep was the search for the ionospheric signatures of BBFs. We review the resultsobtained so far in this young field of Space Physics, in terms of theauroral and ground magnetic signatures caused by BBFs, the particle precipitationto the ionosphere, as well as of the ionospheric electrodynamics of the processesassociated with the BBFs in the magnetosphere. Finally, we briefly review somemodels of ionosphere-magnetosphere coupling with respect to their ability to explainthe ionospheric signatures observed.