志留纪 Silurian

构造运动

With the supercontinent Gondwana covering the equator and much of the southern hemisphere, a large ocean occupied most of the northern half of the globe.

冈瓦纳超级大陆覆盖了赤道和南半球的很大一部分区域，一个巨型海洋占据了绝大部分的地球的北部。

The high sea levels of the Silurian and the relatively flat land (with few significant mountain belts) resulted in a number of island chains, and thus a rich diversity of environmental settings.

志留纪的高海平面和相对平坦的陆地（被大山脉环绕）导致了许多的岛链，也因此形成了复杂多变的环境条件。

During the Silurian, Gondwana continued a slow southward drift to high southern latitudes, but there is evidence that the Silurian icecaps were less extensive than those of the late Ordovician glaciation.

在志留纪时期，冈瓦纳古大陆持续而缓慢地向南漂移一直到南半球高纬度地区，但是有证据表明志留纪的冰盖没有奥陶纪的冰盖延生得广泛。

The southern continents remained united during this period. The melting of icecaps and glaciers contributed to a rise in sea level, recognizable from the fact that Silurian sediments overlie eroded Ordovician sediments, forming an unconformity. The continents of Avalonia, Baltica, and Laurentia drifted together near the equator, starting the formation of a secondsupercontinent known as Euramerica.

南部大陆在这段时期仍旧保持联结状态。我们可以从志留纪的沉积物覆盖在奥陶纪的被剥蚀的沉积层形成的不整合推测出冰盖和冰川的融化导致了海平面的上升。

When the proto-Europe collided with North America, the collision folded coastal sediments that had been accumulating since the Cambrian off the east coast of North America and the west coast of Europe.

当原始欧洲与北美相碰撞，碰撞使得北美的东海岸和欧洲的西海岸自从寒武纪以来沉积的沉积物产生褶皱隆起。

This event is the Caledonian orogeny, a spate of mountain building that stretched from New York State through conjoined Europe and Greenland to Norway.

这个事件被称为加里东造山运动，一连串的造山运动，从纽约连接到欧美，从格陵兰岛连接到挪威。

At the end of the Silurian, sea levels dropped again, leaving telltale basins ofevaporites in a basin extending from Michigan to West Virginia, and the new mountain ranges were rapidly eroded.

在志留纪末期，海平面再次下降，剩下了能够说明问题的从密歇根州延伸到西弗吉尼亚州的盆地，但是新形成的山脉很快被侵蚀。

气候特征

The Silurian period enjoyed relatively stable and warm temperatures, in contrast with the extreme glaciations of the Ordovician before it, and the extreme heat of the ensuing Devonian.

志留纪气温较为稳定而温和，既不像先前奥陶纪冰期的极度寒冷，也不像之后泥盆纪的极度温暖。

During this period, the Earth entered a long, warm greenhouse phase, and warm shallow seas covered much of the equatorial land masses.

志留纪时，地球进入了较长的温暖的温室气体阶段。温暖的浅海上覆盖着许多赤道附近的陆源碎屑。

Early in the Silurian, glaciers retreated back into the South Pole until they almost disappeared in the middle of Silurian. The period witnessed a relative stabilization of the Earth’s general climate, ending the previous pattern of erratic climatic fluctuations.

志留纪早期，冰川再度出现在南极附近，直到志留纪中期才消失。这一时期结束了之前气候不确定的波动模式，见证了地球整体气候的稳定化。

Later in the Silurian, the climate cooled slightly, but in the Silurian-Devonian boundary, the climate became warmer.

志留纪晚期，气候稍稍变冷，但在与泥盆纪的边界时期又变得温暖。

生物特征

笔石动物占主导，保留了双笔石类，新兴的单笔石类也很繁盛；腕足动物内部的构造变得比较复杂，如五房贝目、石燕贝目、小嘴贝目得到了发展；软体动物中头足纲、鹦鹉螺类显著减少，而双壳纲、腹足纲则逐步发展；三叶虫开始衰退，但蛛形目和介形目大量发展；节肢动物中的板足鲎，也称“海蝎”在晚志留世海洋中广泛分布；珊瑚纲进一步繁盛；棘皮动物中海林檎类大减，海百合类在志留纪大量出现。

                                              

脊椎动物中，无颌类进一步发展，有颌的盾皮鱼类和棘鱼类出现，鱼类开始征服水域，为泥盆纪鱼类大发展创造了条件。

植物方面除了海生藻类仍然繁盛以外，晚志留世末期，陆生植物中的裸蕨植物首次出现，植物终于从水中开始向陆地发展。