淮北煤田早二叠世化石植物古生态     

杜美利 《中国煤田地质》1994,6(4):21-25

淮北煤田早二叠世化石植物丰富，其形成于炎热多雨的热带滨海三角洲沉积体系中。下三角洲平原是该区化石植物最宜生长的地方。早二叠世该区化石植物常形成四类植物群落：森林沼泽植物群落、沿岸水生植物群落、高地植物群落、三角洲平原真蕨及种子蕨混生植物群落（早期）、树蕨－大羽羊齿类雨林植物群落（晚期）。随着时间的推移，这四类植物群落的结构及面貌发生着不断的变化；其演替显示，早二叠世晚期该区气侯更加湿热，雨林气侯更为普遍。  相似文献   

中国沙漠植物学术语注释   总被引：1，自引：0，他引：1  

刘Ying心 《中国沙漠》1995,15(2):191-195

注释并举例说明我国沙区植物常用术语，如短生植物、类短生植物、替代种、特有种、属的起源中心、发展中心、演替、顶极、偏途顶极等。  相似文献   

Variation among fossil chironomid assemblages in surficial sediments of Bodensee-Untersee (SW-Germany): implications for paleolimnological interpretation     

Alexandra Schmäh 《Journal of Paleolimnology》1993,9(2):99-108

In paleolimnology, subfossil head capsules of chironomids play an important role as ecological indicators of lake history. It is important to determine, therefore, whether fossil assemblages are representative of former biocoenoses. There is evidence that headcapsules washed in from other places can make up a significant percentage of the total. As interpretations are usually drawn from the examination of a single core, it is of special interest to know whether a fossil assemblage of a single site properly reflects limnological conditions of the whole lake. This study examined the taxonomic distribution of subfossil chironomids in the surficial sediments of the Bodensee-Untersee, with the aim of assessing the variability in chironomid assemblages. Apparently, most of the head capsules of the profundal fossil assemblages in the Untersee had been washed in from the littoral zone or from the slope. Although the Bodensee-Untersee is a rather large lake, variability is surprisingly low among all samples. Therefore a correct interpretation from a single core may be possible.  相似文献   

西藏申扎永珠乡晚石炭世和早二叠世的腕足动物化石     

刘发 《吉林大学学报(地球科学版)》1991,(3)

申扎地区石炭二叠系发育良好,化石丰富。本文描述的化石采自上下两个层位,下部化石少,以石燕贝类为主, 其组合特征反映了石炭纪腕足类的特点与改则县玛米雪山地区上石炭统所产相似;上部化石丰富,以石燕贝类的Spiriferella和Syrin-gothyris的出现为特征,共生还有长身贝类的Chonetinella,Echinauris,Tylo-pecta等。这个化石组合与西藏其他地区相同时代的化石组合不同。特别是Syringothy-ris在下二叠统的发现具有重要意义。  相似文献   

Definition of subfossil meandering palaeochannels     

Karol Rotnicki  Ryszard K. Borwka 《地球表面变化过程与地形》1985,10(3):215-225

The determination of the bottom of a subfossil meandering palaeochannel is important for investigations of the palaeohydrology of valley bottoms, and crucial for the quantitative estimation of past river discharges. The authors present a procedure on the basis of which the bottom of a palaeochannel can be precisely determined. It is based on an analysis of the stratigraphic variability of such features of deposits as: mean diameter, standard deviation of the grain-size composition, the percentage of sand, and ignition loss.  相似文献   

Structures caused by repeated freezing and thawing in various loamy sediments: A comparison of active,fossil and experimental data     

Brigitte Van Vliet-Lanoë  Jean-Pierre Coutard  Albert Pissart 《地球表面变化过程与地形》1984,9(6):553-565

In this paper, the authors present the results of both macroscopic and microscopic investigations on structure development created by repeated ice lensing in various loamy experiments. Experimental data are compared with observations performed on active forms in High Arctic and Alpine Mountain environments. Those observations are also compared with phenomena observed in fossil periglacial formations of Western Europe. Platy and short prismatic structure formation is bonded to the hydraulic and thermal conditions during ice segregation. When a long series of alternating freezing and thawing affects platy structures, the fabric evolves, also being influenced by slope and drainage conditions: cryoturbations, frostcreep, and gelifluction can appear. They are characterized by specific microfabrics which are better developed with an increasing number of cycles: this is clear in experiments where hydraulic and thermal parameters are better controlled. Vesicles are also a prominent characteristic of the surface horizon in experiments and arctic soils. The genesis of vesicles is discussed on the basis of new observations and is related to the mechanical collapse of frost-created aggregates under the mechanical work of soil air escape during soil saturation by water at thaw.  相似文献   

豫西前寒武纪汝阳群遗迹化石   总被引：18，自引：3，他引：18  

杨式溥  周洪瑞 《地质论评》1995,41(3):205-210

本文研究的遗迹化石：Ｒｕｙａｎｇｉｃｈｎｕｓ ｌｏｙｕｅｎｓｉｓ ｉｃｈｎｏｇｅｎ，ｅｔ ｉｃｈｎｏｓｐ．ｎｏｖ．，Ｔｏｒｒｏｗａｎｇｅａ ｒｏｓｅｉ ｗｅｂｂｙ，Ｃｈａｎｇｃｈｅｎｇｉａ ｉｃｈｎｏｓｐ．，Ｓｑｕａｍｏｄｉｃｔ ｙｏｎ（？）ｉｃｈｎｏｓｐ．等发现于河南西部鲁山县和汝阳县的汝阳群云梦山组和北大尖组。根据同位素年龄值，微古植物和叠层石资料，产遗迹化石的汝阳群应相当于中元古代，可以和蓟  相似文献   

南山坪古油藏的形成及其破坏因素分析   总被引：1，自引：0，他引：1  

凡元芳  丰勇 《矿产与地质》2005,19(3):296-298

南山坪古油藏以南山坪背斜(圈闭)为依托，油藏的形成、破坏与背斜(圈闭)的形成及演化息息相关。加里东晚期-海西早期的构造运动形成了南山坪背斜的雏形，与之对应的是最初的油藏形成；南山坪背斜在印支运动得到加强，形成构造圈闭，与之对应的是原油藏裂解生气及烃源岩进入生气阶段，形成气藏及部分沥青。之后的燕山运动Ⅱ幕使得南山坪背斜(圈闭)被褶皱和断层复杂化，形成由东南向北西的逆冲断裂，其上覆盖层抬升、剥蚀，原油藏彻底破坏，成为古油藏。分析认为，南山坪古油藏的破坏因素主要是印支期的热裂解和燕山运动Ⅱ幕的构造抬升、剥蚀，且后者更为主导因素。比较南山坪古油藏、余杭泰山古油藏及威远气藏，力图寻找其共性及差异性，从而为中国南方的油气勘探提供借鉴意义。  相似文献   

Seismic anisotropy beneath Dronning Maud Land, Antarctica, revealed by shear wave splitting   总被引：1，自引：0，他引：1  

Bettina Bayer  Christian Müller  David W. Eaton  Wilfried Jokat 《Geophysical Journal International》2007,171(1):339-351

Shear wave splitting analyses have been carried out using teleseismic data from broad-band seismograph stations deployed at temporary and permanent locations in Dronning Maud Land (DML), Antarctica. In most cases, the observed anisotropy can be related to major tectonic events that formed the present-day Antarctic continent. We rule out an anisotropic contribution from recent asthenospheric flow. At the Russian base Novolazarevskaya near the coast in central DML, waveform inversion suggests a two-layer model where the fast direction of the upper layer is oriented parallel to Archean fabrics in the lithosphere, whereas the anisotropy of the lower layer is interpreted to have been created during the Jurassic Gondwana break-up. Recordings at the South African base Sanae IV, however, show enigmatic results. For narrow backazimuthal segments, splitting parameters show strong variations together with a multitude of isotropic measurements, indicative of complex scattering that cannot be explained by simple one- or two-layer anisotropic models. In the interior of the continent, the data are consistent with single-layer anisotropy, but show significant spatial variations in splitting parameters. A set of temporary stations across the Heimefront shear zone in western DML yield splitting directions that we interpret as frozen anisotropy from Proterozoic assembly of the craton. An abrupt change in fast axis direction appears to mark a suture between the Grunehogna craton, a fragment of the Kalahari–Kaapvaal craton in southern Africa and the Mesoproterozoic Maudheim Province.  相似文献   

藏南岗巴—定日地区始新世化石碳酸盐岩微相与沉积环境   总被引：8，自引：0，他引：8       下载免费PDF全文

李国彪万晓樵  其和日格梁定益  刘文灿 《中国地质》2002,29(4):401-406

藏南岗巴-定日地区发育着西藏最晚期的海相沉积，对这套海相沉积的研究，可提供关于西藏特提斯演化晚期的良好信息，本文对岗巴-定日地区始新世遮普惹组的化石碳酸盐岩微相进行了较为详细的分析和研究。参考Wilson(1975)的标准微相，初步识别出10种微相和5种生物相类型。同时对遮普惹组中的砾状灰岩的成因机制作了有益的探讨，它完全是由沉积作用而成；胶结物不是源于物质的重新分配，而是台地边缘斜坡的等深流沉积。以此为基础，对西藏特提斯晚期沉积环境的演变进行了较为详细的分析。笔者认为：岗巴-定日盆地在始新世Ypresian-Lutetian早期接受海侵；自Lutetian晚期开始，区内总体处于一种海退环境，但由于受板块碰撞作用的影响，岗巴地区在Lutetian晚期-Bartonian晚期成为-深水坳陷盆地；至Priabonian早期，海水完全退出本区。  相似文献