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1.
Silicified specimens of the Vendian (late Precambrian) "index fossil" Conophyton gaubitza from South Kazakstan contain a diverse assemblage of well-preserved cyanophytic and apparently eukaryotic algae, the first stromatolitic microbiota to be reported from the Soviet Union. Unlike the stromatolites in which they occur, the microorganisms that apparently built this form of Conophyton did not become extinct at the end of the Precambrian. 相似文献
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Carbonaceous shales of the late Precambrian Chuar Group of the Grand Canyon, Arizona, contain abundant and well-preserved chitinozoans. The occurrence of these distinctive, tear- and flask-shaped microfossils, the oldest chitinozoans now known and the first to be reported from the Precambrian, seems to suggest that heterotrophic protists (or primitive metaozoans) were extant at least as early as about 750 +/- 100 million years ago. 相似文献
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Glauconite from the upper part of the Missoula Group of the Belt Series, Flathead County, Montana, has been dated at 1070 million years by potassium-argon and rubidium-strontium analyses. This is the first glauconite of Precambrian age reported in North America. 相似文献
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在野外调查、标本鉴定以及文献资料查阅的基础上,运用植物区系地理学研究方法,对秦岭地区的豆科植物区系进行了分析。结果表明:1）秦岭地区共有豆科植物57属172种5亚种8变种,其中自然分布的种有44属144种5亚种6变种,生活型以草本和灌木为主,主要分布在海拔500～2 000 m的混交林带;2）该区的豆科植物区系成分复杂,具有较强的温带性质,含有温带属27属,占总属数的61.4%,温带分布种76种,占总种数的49.1%,中国特有种67种,占总种数的43.2%,中国特有种的分布类型体现了秦岭豆科植物区系与川滇地区的亲缘关系;3）秦岭豆科植物区系具有明显的过渡性,从秦岭南坡到北坡由亚热带性质向温带性质过渡,从秦岭西段到东段由中国—喜马拉雅植物成分向中国—日本植物成分过渡;4）通过与黄土高原、中国帕米尔高原、长白山、南岭及横断山区的豆科植物组成比较,发现秦岭豆科植物区系与黄土高原相似性最高,与帕米尔高原相似性最低。 相似文献
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虎灰蝶属是基于虎灰蝶Yamamotozephyrus kwangtungensis而建立的单种属,报道了产自广东南岭的虎灰蝶幼期.该蝶寄主植物为壳斗科白锥Castanopsis sp.,年发生1个世代,成虫出现于5-6月. 相似文献
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The stratigraphic distribution in Australian Precambrian rocks of columnar stromatolites, organosedimentary structures formed by blue-green algae, has been investigated. Their morphology is being studied according to methods developed in Russia. The discovery of successive different assemblages supports not only regional but also intercontinental stratigraphic correlations which are in agreement with available isotopic datings. 相似文献
7.
Rock avalanches blocked streams in the Olympic Mountains southwest of Puget Sound during the past few thousand years. Limiting radiocarbon ages indicated that three or four of six avalanches occurred from 1000 to 1300 years ago or shortly thereafter. Most of the dates were from the outer preserved rings of trees drowned behind avalanche dams. These three or four avalanches may be coeval not only with one another but also with abrupt tectonic deformation in western Washington. No rock avalanches in the Olympic Mountains are known to have resulted from storms or earthquakes during the past century. The avalanches strengthen the case that a large prehistoric earthquake occurred in the Puget Sound region. 相似文献
8.
记述了福建省武夷山缓步动物的一个新记录种细齿大生熊虫(Macrobiotus crenulatus Richters,1904),该种隶属缓步动物门(Tardigrada)、真缓步纲(Eutardigrada)、并爪目(Parachela)、大生熊虫科(Marcobiotidate)、大生熊虫属(Macrobiotus)。 相似文献
9.
An assemblage of cellularly well-preserved, filamentous and spheroidal plant microfossils has been detected in a cherty pisolite bed of the late Precambrian Chuar Group from the eastern Grand Canyon of the Colorado River. This newly discovered microflora, probably among the youngest Precambrian biological communities now known, appears to be of both evolutionary and biostratigraphic significance. 相似文献
10.
Organically preserved algal microfossils from the Ringwood evaporite deposit in the Gillen Member of the Bitter Springs Formation (late Precambrian of central Australia) are of small size, low diversity, and probable prokaryotic affinities. These rather primitive characteristics appear to reflect the stressful conditions that prevailed in a periodically stagnant, hypersaline lagoon. This assemblage (especially in comparison with the much more diverse assemblages preserved in the Loves Creek Member of the same formation) illustrates the potential utility of Proterozoic microbiotas for basin analysis and local stratigraphic correlation and demonstrates the need to base evolutionary considerations and Precambrian intercontinental biostratigraphy on biotas that inhabited less restricted environments. 相似文献
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长白山区野生芳香植物资源评价与利用对策 总被引：10，自引：2，他引：10
周繇 《安徽农业大学学报》2004,31(2):212-218
长白山区属温带气候,野生芳香植物资源十分丰富.经过3年的调查研究,报道了长白山区野生芳香植物共有40科、108属、174种.其中乔木15科、19属、27种;灌木9科、13属、25种;木质藤本2科、2属、3种;多年生草本19科、57属、91种;一、二年生草本8科、18属、27种;草质藤本1科、1属、1种.介绍了长白山区36种主要野生芳香植物以及野生芳香植物在5个不同景观带的分布和其它方面的用途.提出了开发利用和保护的具体建议. 相似文献
13.
Growing algal and bacterial stromatolites composed of nearly amorphous silica occur around hot springs and geysers in Yellowstone National Park, Wyoming. Some Precambrian stromatolites may be bacterial rather than algal, which has important implications in atmospheric evolution, since bacterial photo-synthesis does not release oxygen. Conophyton stromatolites were thought to have become extinct at the end of the Precambrian, but are still growing in hot spring effluents. 相似文献
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报道了陕西秦岭苔草属Cyperaceae一新记录种——匿鳞苔草(Carex aphanolepis Franch.)。该种与秦岭地区日本苔草(Carex japonica Thunb.)相近,所以比较了两者的形态特征,并对该新记录种的形态特征进行了描述。 相似文献
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兴安落叶松生长变异及早期选择 总被引：1，自引：0，他引：1
通过对大、小兴安岭６块天然兴安落叶松（Ｌｉｒｉｘ ｇｍｅｌｉｎｉｉ）林１８株解析木的研究表明：兴安落叶松不同地点之间在生长性状上有差异。兴安落叶松天然林树高、胸长条积的随年龄的增大而减小、２５ａ（大兴安岭）和１２ａ（小兴安岭）是生长由剧烈分化到稳定的转折年龄。此时树高和胸径与晚期材积的相关性达到极显著水平、选择效率也达最高、所以２５ａ（大兴安岭）和１２ａ（小兴安岭）是兴安落叶松早期选择的最佳实质上 相似文献
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介绍了大秦岭地区的地理概况及水资源状况,并分析了陕西秦岭地区资源保护和发展中存在的问题、措施和政策;在此基础上,提出建议国家级生态示范区是大秦岭保护与发展的必由之路。 相似文献
17.
安徽贝母药用资源的分布及其利用 总被引：4，自引：0，他引：4
安徽产１１种、２变种、１变型贝母属植物，其中有７种、２变种、１变型为安徽特有的种质资源．其种质资源仅次于新疆和四川，居全国第三位。笔者认为，皖南山区和大别山区是我国贝母群南方种系的重要分布和分化中心。这种分化与分布区边缘种系的基因因其所受环境负荷大而频发突变有关。文中还对安徽贝母的生产与药用现状及问题进行了讨论。 相似文献
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More than 40 base metal porphyry ore deposits in southwestern North America are associated with the Laramide orogeny (about 90 million to 50 million years ago). Rhenium-osmium dates on molybdenite, a rhenium-enriched sulfide common in many of the deposits, reveal that in individual deposits mineralization occurs near the final stages of magmatic activity irrespective of the time of inception, magnitude, or duration of magmatism. Deposits that differ widely in location and in the extent and timing of magmatism have nearly identical ages for mineralization. Rhenium-osmium-ages suggest that mineralization occurred during two distinct intervals from about 74 million to 70 million years ago and from 60 million to 55 million years ago. Most deposits that formed in the oldest interval are within the older Precambrian basement of northwestern Arizona, whereas the younger deposits are restricted to the younger Precambrian basement in southern Arizona and northern Mexico. Synchronous, widespread mineralization indicates that similar crust-mantle interaction occurred on a regional scale for ore deposits once thought to be the product of localized processes. 相似文献
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为了揭示滇中地区降水的时空分异特征,以哀牢山区7年(2008-2014年)来110个模拟气象站点逐日降水数据为基础,运用普通克里金插值、T检验等方法对哀牢山区降水的时空格局进行多尺度分析,并探讨了哀牢山降水阻隔效应.结果表明:①从降水站点尺度看,哀牢山西侧站点的降水量均高于东侧对应站点,哀牢山北端和中部两侧降水差异最小,南段两侧降水差异最大;②从等降水量线尺度看, 800 mm与1 200 mm等降水量线在不同降水类型年份走势存在差异,降水偏多年份等降水量线分布杂乱,降水偏少年份等降水量线与哀牢山走势相近;③从降水量插值面尺度看,哀牢山区降水的空间分异特征可划分为东部高原区、中西部三角岭谷区、以及南部水平丘陵区.总体上看,哀牢山北段较南段降水阻隔效应更明显,体现了较高的时空异质性. 相似文献
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[目的]优化台蘑小香蕈液体发酵培养基的最佳配方。[方法]通过单因素试验考察葡萄糖、蔗糖、马铃薯汁、无机盐等常用碳源与氮源对台蘑液体发酵菌丝生物量的影响。[结果]台蘑小香蕈液体发酵培养基的最佳配方为蔗糖3.0%、麸皮汁3.0%、玉米粉5.0%、马铃薯汁30%、植被汁10%、NaNO_3 0.3%、K_2HPO_40.1%、KCl 0.1%、FeSO_4 0.001%,pH 7。[结论]优化后的培养基配方能明显提高台蘑液体发酵的菌丝生物量,配方经济合理。 相似文献