Evidence for an Extended Scattered Disk

By telescopic tracking, we have established that the transneptunian object (TNO) 2000 CR₁₀₅ has a semimajor axis of 220±1 AU and perihelion distance of 44.14±0.02 AU, beyond the domain which has heretofore been associated with the “scattered disk” of Kuiper Belt objects interacting via gravitational encounters with Neptune. We have also firmly established that the TNO 1995 TL₈ has a high perihelion (of 40.08±0.02 AU). These objects, and two other recent discoveries which appear to have perihelia outside 40 AU, have probably been placed on these orbits by a gravitational interaction which is not strong gravitational scattering off of any of the giant planets on their current orbits. Their existence may thus have profound cosmogonic implications for our understanding of the formation of the outer Solar System. We discuss some viable scenarios which could have produced these objects, including long-term diffusive chaos and scattering off of other massive bodies in the outer Solar System. This discovery implies that there must be a large population of TNOs in an “extended scattered disk” with perihelia above the previously suggested 38 AU boundary. The total population is difficult to estimate due to the ease with which such objects would have been lost. This illustrates the great value of frequent and well time-sampled recovery observations of trans-neptunian objects within their discovery opposition.     

内蒙古北山及邻区金属矿床类型及其时空分布

依据金属矿床围岩岩性组合和成矿作用特征，将内蒙古北山及邻区分布的各类金属矿床(点)划分为6种类型，即①斑岩型钼—金和铜矿床(点)；②夕卡岩型铁—铜矿床(点)；③火山气液型铁和锑矿床(点)；④热液脉型钨、锡和稀有金属矿床(点)；⑤岩浆岩型铬和钒—钛—铁矿床(点)和⑥变质热液型金和铁矿床(点)。在较详细剖析各类金属矿床(点)基本地质特征的基础上，划分了4个成矿带和9个矿化集中区，并且讨论了区域地壳演化与金属成矿作用的关系。研究结果表明：尽管本区金属矿床(点)成矿作用分别发生在前寒武纪和晚古生代，但是大规模成矿作用发生的时间与海西期板块活动高峰期相吻合，是地壳特定演化阶段构造—岩浆活动的产物。     

中轴构造带(南段)的变形及缩短速率计算

中轴构造带是欧亚大陆的一个重要的构造带 ,具有地震震中密集分布、重力梯级、岩石圈厚度或结构变异等特点 ,但没有突兀连贯的山链 ,其原因是多地块的大规模走滑活动的抑制。以往对于中轴构造带的宏观运动和块体之间的相对运动研究得比较深入 ,但是对其缩短变形的研究尚有明显欠缺 ,这使得在讨论青藏高原东向运动是任其“自由逃逸”还是有阻挡性约束的问题时缺乏必要的依据。针对此问题 ,笔者以地块的宏观变形与块体内变形的透入程度为切入点 ,通过编绘横切中轴构造带的平衡剖面 ,计算出该带的缩短率为 2 2 .37% 7.4 3% ,中新世以来的平均缩短速率为 3.6 34.4 5mm/a ,并对中轴构造带形成的变形机制进行了初步探讨。提出青藏高原东向运动受阻 ,中轴构造带内块体东向汇聚下 ,上下地壳拆离并呈现出上叠式仰冲褶皱缩短的认识。     

Paleomagnetism of the Upper Proterozoic and Devonian rocks from the K odzko Metamorphic Complex in the West Sudetes (SW Poland): tectonic implications for the Variscan belt of Central Europe

The K odzko Metamorphic Complex (KMC) consists of Upper Proterozoic metaigneous and metasedimentary rocks forming a stack pile thrusted over the Givetian and overlain by Frasnian–Fammenian sediments. Magnetomineralogical experiments show that the magnetic minerals are secondary. The paleomagnetic experiments identified three components of the Natural Remanent Magnetization; labeled A1, A2 and M. The mean pole positions calculated in situ correspond with the Baltica Upper Devonian (A1: PlatS=−18°, PlongE=317°), Permo-Carboniferous (A2: PlatS=−39°, PlongE=2°) and Triassic–Jurassic (M: PlatS=−60°C, PlongE=308°) segments of the Apparent Polar Wander Path (APWP) for Baltica. This indicates that the region studied was situated close to the Baltica plate at least since the Upper Devonian and was not folded after this period.     

Early Cretaceous sinistral shearing and associated folding in the South Kitakami Belt, northeast Japan

Abstract   Early Cretaceous structural development of the southern part of the South Kitakami Belt, northeast Japan, is discussed through precise structural mapping and the measurement of semiquantitative strain. The mapping and measurement revealed that wide north- to northeast-trending sinistral shear zones occupied by the 'slate' with higher strain than the surrounding rocks run from the axial part to the western limb of major synclines, with the wavelength of 5–10 km. The major synclines with a U-shaped rock distribution opening to the south are interpreted to be drag folds along the sinistral shear zones. These structures were modified by a second stage of Early Cretaceous sinistral shearing characterized by localized high-temperature mylonite zones along the rim of some of the 120 Ma granitoids that cut the major folds and baked the 'slate' in the older shear zones mentioned above. The rocks of the South Kitakami Belt, which had undergone two stages of shearing, were rapidly exhumed before the deposition of the Late Aptian–Albian Miyako Group. Finally, a restoration model is presented of the Early Cretaceous sinistral displacement and deformation in the study area.     

Fusulinoidean faunal succession of a Paleo–Tethyan oceanic seamount in the Changning–Menglian Belt, West Yunnan, Southwest China: An overview

Abstract   Fusulinoidean faunal succession from Paleo–Tethyan seamount-type carbonates of the Yutangzhai section in the Central zone of the Changning–Menglian Belt of West Yunnan, Southwest China, is presented for the first time. The Changning–Menglian Belt is one of the orogenic belts that represent the closed main Paleo–Tethys in East Asia. The Yutangzhai section is represented by basalts and overlying carbonates, about 1100 m thick. It exhibits a continuous faunal succession composed of 17 fusulinoidean assemblages ranging from the Serpukhovian (late Mississippian/late Early Carboniferous) to Midian/Capitanian (late Middle Permian/late Guadalupian). No significant faunal break can be recognized in this section. The generic and some specific composition of the Yutangzhai assemblages indicates that the faunal succession is similar to those observed in Tethyan and Panthalassan areas and is of tropical Tethyan type although their generic diversity is definitely lower than those of Paleo–Tethyan shelves, such as South China, Indochina, and Central Asia. Throughout the Yutangzhai section, the carbonate rocks are essentially massive, very pure in composition, and devoid of terrigenous siliciclastic inputs. These lithologic characters are identical to those observed in accreted shallow-marine carbonate successions of seamount origin in Permian and Jurassic accretionary complexes of Japan, for example the Akiyoshi Limestone. This evidence further demonstrates the seamount origin of the basalt–limestone succession in the Central zone of the Changning–Menglian Belt from the viewpoint of lithofacies. In middle Mississippian (middle Early Carboniferous) time, oceanic submarine volcanism that was probably related to hot spot activities formed a number of seamounts and oceanic plateaus. It was active not only in the Panthalassa, but also in the Paleo–Tethys.     

基于GIS的交通经济带空间边界界定方法研究--以沪宁杭高速公路经济带为例

随着经济的发展，交通运输系统对生产力发展的贡献日益增强，一种以交通运输干线为发展轴线，以周边大中城市与城镇群为依托，不断集聚和扩散人流、物流、信息流的带状空间经济综合体——交通经济带不断生长并迅速发展，本文首先阐述了交通经济带的基本模式，重点分析了高速公路经济带的特点。在此基础上，以沪宁杭高速公路经济带为例，运用GIS专题地图叠加、缓冲区等空间分析功能，建立了一种界定交通经济带空间边界的方法。     

Late Paleozoic brachiopod faunas of the South Kitakami Belt, northeast Japan, and their paleobiogeographic and tectonic implications

Abstract    Late Paleozoic (Middle Devonian, Early Carboniferous and Middle Permian) brachiopod faunas of the South Kitakami Belt, northeast Japan, are closely related paleobiogeographically to those of the Xinjiang–Inner Mongolia–Jilin region, northwest–northeast China. This relationship suggests that the South Kitakami Belt was part of the trench or continental shelf bordering the northern and eastern margins of North China (Sino-Korea) during the Middle Devonian to Middle Permian times. Among the three models on the origin and tectonic development of the South Kitakami Belt, the strike–slip model is most consistent, but both the microcontinent model and the nappe model have considerable inconsistencies with the above paleobiogeographic and paleogeographic evidence.     

Transpressional deformation in northwestern Sardinia (Italy): insights on the tectonic evolution of the Variscan BeltDéformation transpressive dans le Nord-Ouest de la Sardaigne (Italie) : considérations sur l'évolution tectonique de la chaı̂ne Varisque

Structural investigations in northwestern Sardinia highlight the occurrence of a regional D2 transpressional deformation related both to NNE–SSW direction of compression and to a NW–SE shear displacement. The deformation is continuous and heterogeneous, showing a northward strain increase, indicated by progressively tighter folds and occurrence of F2 sheath folds. D2 transpression is characterised by the presence of a crustal-scale shear deformation overprinting previous D1 structures, related to nappe stacking and top-to-the-south and southwest thrusting. The L2 prominent stretching lineation points to an orogen-parallel extension and to a change in the tectonic transport from D1 to D2. It is attributed to the position of Sardinia close to the northeastern part of the Cantabrian indenter during the progressive evolution of the Ibero-Armorican Arc. D1 phase developed during initial frontal collision, whereas D2 deformation characterised the progressive effect of horizontal displacement during the increasing curvature of the arc. To cite this article: R. Carosi, G. Oggiano, C. R. Geoscience 334 (2002) 287–294.