应用线性光谱分离技术研究喀斯特地区土地覆被变化——以贵州省关岭县为例   总被引：24，自引：3，他引：21  

万军  蔡运龙 《地理研究》2003,22(4):439-446

喀斯特地区土地覆被主要类型除了和非喀斯特地区一样的植被和裸露土壤外,还存在一个广泛分布的裸露基岩,一般遥感处理方法不具备直接定量提取这三类土地覆被参数的能力。基于地物光谱线性混合模型的线性光谱分离技术,可以在亚象元的尺度上直接获取植被覆盖、裸露土壤和裸露基岩等在各象元区域内的比例,非常适合用于喀斯特地区的土地覆被变化的研究。本文利用1987年2月17日和1999年12月27日LandsatTM各6波段遥感影像,使用ENVI软件,分离出植被、裸露土壤、裸露岩石和阴影等土地覆被丰度和RMS的空间分布。对比结果表明,研究区1987～1999年,植被覆盖率上升593%,裸露土壤面积下降1215%,裸露基岩面积上升408%。表明研究区尽管植被在恢复、水土流失总量在减少,但石漠化面积在明显上升,生态形势依旧严峻。  相似文献   

晚震旦世陡山沱期后生生物群的古生态环境探讨   总被引：2，自引：1，他引：1  

杨瑞东 《沉积与特提斯地质》1999,19(5):53-59

早期后生生物群是当前古生物学研究热点之一。我国上扬子区的庙河生物群和瓮安生物群是震旦纪的重要生物群,而生物群是怎样繁盛和埋藏保存是研究早期后生生物群的一个重要方面。作者研究认为瓮安生物群是由于洋流上升提供了大量的ＳｉＯ２ 和Ｐ２Ｏ５ 等养分,使生物在台地边缘大规模繁盛,其海水由于富ＳｉＯ２ 和Ｐ２Ｏ５ 所引起强烈的磷酸岩化及硅化作用,使大量的生物尸体被快速矿化,形成具有抗水动力强的骨架,避免水动力和氧化作用的破坏,因此,矿化作用是生物体保存为化石的另一个重要因素。最后,提出上扬子区陡山沱期为有利于生物群繁盛和保存区域  相似文献   

晚震旦世陡山沱期后生生物群的古生态环境探讨   总被引：1，自引：0，他引：1  

杨瑞东 《沉积与特提斯地质》1999,19(5):53-59

早期后生生物群是当前古生物学研究热点之一。我国上扬子区的庙河生物群和瓮安生物群是震旦纪的重要生物群,而生物群是怎样繁盛和埋藏保存是研究早期后生生物群的一个重要方面。作者研究认为翁安生物群是由于洋流上升提供了大量的ＳｉＯ２和Ｐ２Ｏ５等养分,使生物在台地边缘大规模繁盛,其海水由于富ＳｉＯ２和Ｐ２Ｏ５所引起强烈的磷酸岩化及硅化作用,使大量的生物尸体被快速矿化,形成具有抗水动力强的骨架,避免水动力和氧化作  相似文献   

Cretaceous tectonic and biotic evolution of the southeastern Russian continental margin          下载免费PDF全文

Galina L. Kirillova 《Island Arc》2018,27(2)

The Cretaceous tectonic and geodynamic settings of the southeastern Russian continental margin are discussed using data generated during several recent geological studies. The structural patterns of the East Asian Cretaceous continental margin are the result of the influence of global and regional processes. The interaction and reorganization of the Eurasian, Pacific and other related plates induced intraplate tectonic processes such as rifting, subduction, collision, transform faulting, and basin formation. Three major basin types are recognized in this area: (i) mainly marine active continental margins associated with shear components (Sangjian–Middle Amur Basin); (ii) passive continental margins (Bureya, Partizansk, and Razdolny basins); (iii) intracontinental basins (Amur–Zeya Basin). The evolution of the biota in this region allows the examination of Early and Late Cretaceous biostratigraphy, faunal and floral changes, and the phytogeography of the southeastern Russian continental margin.  相似文献   

Dimorphism of Bivalved Arthropod Branchiocaris? Yunnanensis from the Early Cambrian Chengjiang Biota, South China     

WU Yu  FU Dongjing  ZHANG Xingliang  Allison C. DALEY  SHU Degan 《《地质学报》英文版》2016,90(3):818-826

The bivalved arthropod Branchiocaris? yunnanensis Hou, 1987 is redescribed on the basis of new fossil material from the early Cambrian Chengjiang biota, South China. In total, 81 specimens have been examined. The carapace comprises two identical valves, each valve are sub-circular in outline, ranging from 24 mm to 58 mm in length, and from 15 mm to 46 mm in height. The dorsal margin is straight and bears two short cardinal spines. The valve surface is either smooth or ornamented with polygonal reticular structures, which may result from different preservation conditions. Two morphotypes have been recognized based on the presence or absence of a subdorsal swelling of the valve, which is convex dorsolaterally and extends beyond the dorsal margin when it appears. Statistic and ontogenetic analyses show both morphotypes grow isometrically and have the same growth trajectory. Therefore, the two morphotypes are interpreted as dimorphism within the same species. Our results are helpful for investigating the taxonomy and ontogeny of arthropod fossils and suggest that dimorphism might be fairly common in these early arthropods.  相似文献   

2012年夏季北极浮冰生物群落结构及垂直分布特征研究          下载免费PDF全文

贾书磊 张芳林凌  贾睿何培民  何剑锋 《极地研究》2016,28(1):25-33

海冰生物群落是北极生态系统的重要组成部分,在北冰洋初级生产和碳循环中扮演着重要角色。本文利用荧光显微分析技术对2012年度夏季采集于北冰洋中心区的浮冰生物群落进行了分析,结果显示：柱总生物量平均为105.85±53.41 mgC •m^-2,其中细菌占生物量的47.2%,而后依次是硅藻（26.7%）,鞭毛虫（18.2%）,鞭毛藻（6.9%）和纤毛虫（1.0%）。最高纬站位（123°43.454′E 87°39.598′N）出现冰底鞭毛藻藻华现象,生物量可达329.6 μg C•L^-1,该站位生物群落处于硅藻藻华后期,海冰上层存在较大程度的融冰作用,底部冰芯营养盐N/P比较高,可能形成有利于鞭毛藻生长的小生境。与已有研究结果的对比表明,近年来夏季北极海冰的快速融化对浮冰生物群落结构产生了明显影响,异养类群生物量升高,细菌取代硅藻成为优势类群。  相似文献   

贵州新民石门坎三叠系关岭组底部火山凝灰岩锆石U-Pb年龄及意义     

柴珺  江大勇  周敏  孙作玉  齐宁远  Ryosuke MOTANI  Andrea TINTORI 《地质论评》2022,68(1):2022020001-2022020001

华南地区三叠系地层发育,安尼阶底界（即下—中三叠统界线）附近广泛发育浅绿色火山凝灰岩或凝灰质碎屑岩,俗称 “绿豆岩”。国际安尼阶底界界线层型候选剖面——位于南盘江盆地内的贵州关刀剖面和广西湾头剖面,已获得可对比的“绿豆岩”锆石U-Pb年龄,但在相邻的上扬子台地上尚缺少对安尼阶底界测年的可对比数据。本研究采集了贵州省盘州市新民镇石门坎剖面三叠系关岭组底部的多层“绿豆岩”,利用LA-ICP-MS获得锆石的U-Pb年龄。结果显示,石门坎剖面关岭组底部的锆石结晶年龄为246.9±1.1 Ma,可与南盘江盆地内及上扬子台地区出露安尼阶底界的剖面相对比。其绝对年龄为上扬子台地区内的安尼阶底界年龄对比提供了参照,有助于限定中三叠世海生爬行动物群所代表的海洋生态系统的复苏时间。石门坎剖面地层沉积连续,未来有望继续开展综合地层学的研究。  相似文献   

Temporal trends of mercury in marine biota of west and northwest Greenland     

Rigét F  Dietz R  Born EW  Sonne C  Hobson KA 《Marine pollution bulletin》2007,54(1):72-80

Temporal trends in mercury concentrations ([Hg]) during the last two to three decades were determined in liver of shorthorn sculpin, ringed seal and Atlantic walrus from northwest Greenland (NWG, 77 degrees N) and in liver of shorthorn sculpin and ringed seal from central west Greenland (CWG, 69 degrees N) during the last decade. Stable-nitrogen (delta(15)N) and carbon (delta(13)C) isotope values were determined in muscle of ringed seals to provide insight into potential trophic level changes through time. Log-linear regressions on annual median [Hg] did not reveal any temporal trend in shorthorn sculpin from CWG and NWG and walrus from NWG. In ringed seals from NWG, an increase in [Hg] of 7.8% per year was observed. When based on delta(15)N-adjusted [Hg] this rate increased to 8.5% but was still non-significant. In ringed seal from CWG no trend was found in [Hg] during the period 1994-2004. However, during the last part of the period (1999-2004) the [Hg] increased significantly. Including tissue delta(15)N values as a covariate had a marked effect on these results. The annual changes in delta(15)N-adjusted [Hg] was estimated to -5.0% for the whole period and 2.2% during the last 5 years compared to -1.3% and 12.4%, respectively, for the non-adjusted [Hg].  相似文献   

A Fresh Look at Dickinsonia： Removing It from Vendobionta     

ZHANG Xingliang Joachim REITNER 《《地质学报》英文版》2006,80(5):636-642

The Ediacaran Dickinsonia is well-known for being the only fossil to be assigned to many phyla, ranging from lichens, Cnidaria, Piatyheiminthes, Annelida, and a phylum of its own to a nonmetazoan kingdom. A new specimen from the Ediacaran fine-grained sandstone on the Winter Coast of the White Sea in northern Russia, which has an age of -555 million years ago, preserved convincing internal anatomies of definite animals, comparable with meridionai canals of extant ctenophores （comb jellies）. Additionally, we reconsidered Dickinsonia as a biradiaily symmetrical animal rather than a bilateral one as previously thought. The animal nature of Dickinsonia is, thus, well established and its affinities are most probably allied to ctenophores. This research is not only removing Dickinsonia from Vendobionta, but also bringing the fossil record of ctenophores forward to 20 million years before the Cambrian ＂explosion＂.  相似文献   

从事件地层学角度探讨东亚陆相侏罗、白垩系界线   总被引：13，自引：0，他引：13  

刘本培  陈芬  王五立 《地球科学》1986,(5)

本文将广义的热河生物群进一步划分为晚侏罗世热河动物群（狭义）和早白垩世阜新生物群,并讨论了上述生物群的演替与侏罗、白垩纪之交古气候、海平面变化地质事件之间的关系。  相似文献