Palynological evidence for Jurassic strata in the Panagarh area, West Bengal, India

The Rajmahal Traps were discovered in the Panagarh area, West Bengal, during the exploration for coal resources. A Gondwana succession was found beneath the traps, consisting of the Early Cretaceous Intratrappean Rajmahal Formation, the Early Triassic Panchet Formation and the Late Permian coal-bearing Raniganj Formation. The present palynological study was aimed at confirming the age of the Panchet Formation. As a result of this study it has been found that Jurassic sediments are also included in the Panchet Formation. The study has revealed that the Panchet Formation, defined on a lithological basis, is a time-transgressive unit extending from the Early Triassic to the Late Jurassic, with a phase of non-deposition between the Middle Triassic and Middle Jurassic.     

基于小波变换的动态地震活动周期分析

利用Ｍｏｒｌｅｔ小波变换对华北、中国大陆和陕西的地震活动进行了动态周期分析。结果表明，地震活动既存在比较稳定的周期，也有一定时变性，如华北近５００ａ来存在比较稳定的３００ａ周期和６０ａ左右周期，陕西近２０ａ来存在比较稳定的２￣３ａ周期，中国大陆５级以上地震在１９１０￣１９８０年普遍存在３０ａ左右周期，但在１９８０年后变为２０ａ左右周期，小波分析揭示的地震活动周期时变性，一方面提示在依据周期规律外推     

贵州贵阳地区下三叠统凝缩段的遗迹化石特征

贵阳地区下三叠统是一个完整的碳酸盐岩层序（相当于三级旋回层序）．该层序中的凝缩段由深色薄层（单层厚0．5cm～1cm）的泥晶灰岩和泥质条带灰岩组成．凝缩段中产丰富的遗迹化右．该遗迹群落为：Cochlichnus,Cosmorhaphe,Chondrites,Gordia,Huaxich－nus，Oldhamia,Phycosiphon.Protopaleodictyon,Pinnatpedus,Mammillichnus,Neonerites和生物扰动构造．遗迹化石组合与Nereites遗迹相相似。此外，文本还讨论了此遗迹群落的形成原因。     

楚雄复式盆地演化及形成的动力学机制

楚雄盆地处于中国云南省中部，位于扬子板块西南缘，南西界以红河断裂为界与哀牢山造山带相连，北西界为程海断裂，东边为绿汁江断裂。盆地基底包括结晶基底和褶皱基底双重结构。盆地内发育了中三叠世以后的沉积盖层，西部中三叠世和晚三叠世早、中期为海相沉积，晚期为海陆交互相和陆相沉积；盆地东部为陆相沉积。侏罗—白垩纪整个盆地为巨厚的陆相沉积。楚雄盆地的构造格架分为４个带：（１）哀牢山造山带；（２）褶皱逆冲带；（３）中部沉降带；（４）东部隆起带。盆地形成与演化分为六个阶段：（１）被动大陆边缘沉降阶段；（２）拉张热隆起边缘——裂谷盆地阶段；（３）沟－弧－盆系阶段；（４）残洋－周缘前陆盆地阶段；（５）走滑－拉张盆地阶段；（６）走滑－挤压－改造阶段。楚雄盆地的形成与演化体现了盆地动力学性质转化和复合，在多种动力系统作用下或经过多旋回构造阶段产生了复式盆地     

Palynological dating of infra- and intertrappean sediments in the Mesozoic succession of Borehole PGD-6, Domra Sub-basin, West Bengal, India

Palynofloras have been examined from infra- and intertrappean sediments of the Panchet and Rajmahal Formations in the Domra Sub-basin of the Damodar Basin, West Bengal, India. Three distinct palynological assemblages are identified and referred to the following palynozones: (i)Lundbladispora–Verrucosisporites(506.60–505.00 m, late Early Triassic, (ii)Murospora florida(501.65–422.20 m. Late Jurassic, Kimmeridgian–Tithonian), and (iii)Cicatricosisporites australiensis(342.00–229.6 m. Early Cretaceous, Tithonian–Berriasian). The first occurrences ofCallialasporites turbatusandC. dampieriare at 501.65 m.Callialasporitesis a dominant element of the succeeding assemblages from the Panchet Formation and indicates a Jurassic age. The FAD ofCicatricosisporites australiensisandC. augustusat 342.00 m, and inconsistent occurrences ofAequitriradites spinulosus,Crybelosporites stylosusin the overlying sediments indicate Jurassic–Cretaceous transition.     

论冷战后国际政治的基本态势及世界政治地理的研究任务与重点

本文立足于政冶地理学的基本理论，从冷战后国际政治基本态势的分析入手，系统阐述了当前世界政治地理研究的基本任务，并在此基础上提出了当前及今后一段时期世界政治地理研究应以世界政治地理格局的演变、国家形成与消亡的地理政治背景、国际领土及边界争端和各国行政区划的基本原则为重点。     

塔里木北部地区三叠系储层溶蚀作用机理

塔里木北部地区三叠系储层在成岩演化过程中曾经历两期溶蚀作用，深埋成岩环境的晚期溶蚀较早期近地表－浅埋成岩环境溶蚀要剧烈得多，溶蚀作用的最大特点是铝硅酸盐矿物较碳酸盐矿物剧烈。溶蚀作用发生的机理是由于三叠系储层处于８０～１２０℃热窗、成岩流体富含低分子量羧酸、碱度由低分子量羧酸控制，铝硅酸盐和碳酸盐矿物均处于去稳定状态。溶蚀作用的发育程度受控于储层砂体的沉积和岩石学特征以及早期成岩发育程度。     

New palaeomagnetic data from Central Iran and a Triassic palaeoreconstruction

New pole positions for Triassic and Cretaceous times have been obtained from volcanic and sedimentary sequences in Central Iran. These new results confirm the general trend of the Apparent Polar Wander Path (APWP) of the Central-East-Iran microplate (CEIM) from the Triassic through the Tertiary as published by Soffel and Förster (1983, 1984). Two new palaeopoles for the Triassic of the CEIM have been obtained; limestones and tuffs from the Nakhlak region yield a mean direction of 094.0°/25.0°, N=12, k=4.1,α ₉₅=24.7°, after bedding correction, corresponding to a palaeopole position of 310.8°E; 3.9°S, and volcanic rocks from the Sirjan regions yield a mean direction of 114.5°/35.1°, N=44, k=45.9,α ₉₅=3.2° after bedding correction and a palaeopole position of 295.8°E; 10.3°N. Combining these with the two previously published results yields a new palaeopole position of 317.5°E; 12.7°N, for the Triassic of the CEIM, thus confirming that large counterclockwise rotations of the CEIM have occurred since the Triassic time. New results have also been obtained from Cretaceous limestones from the Saghand region of the CEIM. The mean direction of 340.7°/26.3°, N=33, k=44.3,α ₉₅=3.8°, and the corresponding palaeopole position of 283.1°E; 64.4°N, is in agreement with previously determined Cretaceous palaeopole positions of the CEIM. Furthermore, results have also been obtained from Triassic dolomite, limestone, sandstone and siltstone from the Natanz region, which is located to the west of the CEIM. A total of 161 specimens from 44 cores taken at five sites gave a mean direction of the five sites at 033.3°/25.1°, N=5, k=69.0,α ₉₅=9.3° and a palaeopole position of 167.2°E; 53.7°N. They pass the positive fold test of McElhinny (1964) on the level of 99% confidence. This pole position is in fairly good agreement with the mean Triassic pole position of the Turan Plate (149°E; 49°N). It indicates that the area of Natanz has not undergone the large counterclockwise rotation relative to the Turan plate since the Triassic, which has been shown for the CEIM. A Triassic palaeogeographic reconstruction of Iran, Arabia (Gondwana) and the Turan Plate (Eurasia) is also presented.