美国西部干燥的山脉包含了距今4.4亿至5.1亿年前的奥陶纪岩石，其中充斥着热带海洋生物生存的迹象。
The dry mountain ranges of the western United States contain rocks dating back 440 to 510 million years, to the Ordovician period, and teeming with evidence of tropical marine life.
在奥陶纪，大多数生命都生活在海洋里，所以海洋生物，例如三叶虫、腕足类动物与笔石动物的数量在此时急剧减少。
During the Ordovician, most life was in the sea, so it was sea creatures such as trilobites, brachiopods and graptolites that were drastically reduced in number.
然而，有一些研究者认为，大约4.5亿年前的奥陶纪大灭绝是伽马射线爆引起的。
However, some researchers believe that a GRB was responsible for the Ordovician mass extinction approximately 450 million years ago.
其它四次大灭绝对生物进化产生了巨大的影响，动物因此逐渐处于优势地位，但是，奥陶纪末期大灭绝发生前后，处于支配地位的动物物种没有发生变化。
Although the four other Big Five extinction events led to huge changes in which animals rose to prominence, the same animals that dominated before the end-Ordovician dominated afterward.
五次大灭绝中发生最早的一次是奥陶纪末期或者奥陶纪-志留纪大灭绝事件，发生在大约4亿4千4百万年前。许多科学家估计这次规模是五次当中第二大的。
The earliest of the Big Five, the end-Ordovician or Ordovician-Silurian extinction events some 444 million years ago, are reckoned by many to be the second largest.
(古生)板足鲎目的：一种巨大的、有节的，属于板足鲎目的水生节肢动物，生存于奥陶纪到二叠纪时期。
Eurypterid: any of various large segmented aquatic arthropods of the order eurypterida that existed from the ordovician period to the Permian period.
笔者1992年在汶川下庄的结晶灰岩中采到了海百合茎化石，证实其时代属奥陶纪。
In 1992, the author found fossil crinoid stems in crystalline limestone at Xia-zhuang, Wenchuan, which were determined to be of Ordovician age.
鲁西地块的寒武-奥陶纪地层出露连续，露头较好。
The Cambrian - Ordovician strata in Luxi Block are very continuous and well exposed.
这标志着塔里木地区寒武纪和奥陶纪海进海退旋回的终结。
It was an important evolution and marked the end of transgression and regression cycle of the Cambrian and Ordovician in Tarim area.
奥陶纪时期，本区处于北为汉南古陆与巴山隆起，南为广阔的陆表海盆地的古地理环境。
The natural geography of the Ordovician period is that: the Hannan paleocontinent and the Bashan Mountain rise at the north, and the wide epicontinental sea basin lies in the south.
羌南地区奥陶纪—泥盆纪生物和地层的发现，为与邻区地层划分对比和探讨羌塘构造演化提供了重要依据。
The discovery of Ordovician-Devonian biotas and strata provide new important evidence for the stratigraphic division and correlation and the study of the tectonic evolution of the Qiangtang area.
华北石炭纪岩溶型铝土矿的主要物质来源为下伏的晚寒武世—中奥陶世碳酸盐岩。
The material source of the Carboniferous karst type bauxite in North China mainly came from the underlying Late cambrian-middle Ordovician carbonate rock.
国际地层学委员会上关于奥陶纪边界的争论也一般不会占据新闻头条。
Tussles at the International Commission on Stratigraphy over the boundaries of the Ordovician era do not normally capture headlines.
扬子地区奥陶纪古地理条件有利于含油气系统生储盖层的发育。
In the Yangtze region, Ordovician paleogeographic conditions were favorable to the development of source, reservoir and seal rocks in petroleum systems.
在露头和单井层序地层分析的基础上，为了更好地探讨研究区寒武-奥陶纪地层的时空展布，从北往南进行了多条露头和连井剖面的对比分析。
The detailed sequence stratigraphic research about Cambrian-Ordovician in Awati depression has been done on the basis of the outcrop sections and the well logs.
北祁连山石灰沟地区发育一套完整的奥陶纪岛弧火山岩系。
The Middle Ordovician submarine spilite-alkaline volcanic rock association in the Shihuigou area in the Northern Qilian mountains was the product of island arc volcanism.
北祁连山石灰沟地区发育一套完整的奥陶纪岛弧火山岩系。
The Middle Ordovician submarine spilite-alkaline volcanic rock association in the Shihuigou area in the Northern Qilian mountains was the product of island arc volcanism.
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