万物简史 第85期:敲石头的人们(17)

Then come Lyell's epochs—the Pleistocene, Miocene,and so on—which apply only to the most recent (butpaleontologically busy) sixty-five million years, andfinally we have a mass of finer subdivisions known asstages or ages. Most of these are named, nearlyalways awkwardly, after places: Illinoian,Desmoinesian, Croixian, Kimmeridgian, and so on inlike vein. Altogether, according to John McPhee,these number in the "tens of dozens." Fortunately,unless you take up geology as a career, you areunlikely ever to hear any of them again.

接着就是莱尔所谓的“世”——更新世、中新世等——这些名称仅仅用来指最近的(但又是古生物学研究很活跃的)6500万年;最后，便是一大堆更细的分类，名叫“期”或“代”。其中大多数以地名命名，读起来几乎总是很拗口：伊利诺期、得梅因期、克罗伊期、金默里奇期等等，都具有同一特色。据约翰·麦克菲说，这类名称总共多达"几百个"。幸运的是，除非把地质学作为你的专业，你从此以后再也不大可能听到这些名称了。

Further confusing the matter is that the stages or ages in North America have different namesfrom the stages in Europe and often only roughly intersect in time. Thus the North AmericanCincinnatian stage mostly corresponds with the Ashgillian stage in Europe, plus a tiny bit of theslightly earlier Caradocian stage.

更加混乱的是，北美的“期”或“代”跟欧洲的说法不一，在时间上往往只是大体交叉。因此，北美的辛辛那提期在很大程度上相当于欧洲的阿什吉利期，再加上一点儿稍早的喀拉多克期。

Also, all this changes from textbook to textbook and from person to person, so that someauthorities describe seven recent epochs, while others are content with four. In some books,too, you will find the tertiary and quaternary taken out and replaced by periods of differentlengths called the Palaeogene and Neogene. Others divide the Precambrian into two eras, thevery ancient Archean and the more recent Proterozoic. Sometimes too you will see the termPhanerozoic used to describe the span encompassing the Cenozoic, Mesozoic, and Paleozoiceras.

而且，这一切，不同的教科书、不同的人都有不同的叫法，因此有的权威提出7个代，而有的权威满足于4个代。在有的书里，你还会发现不用第三纪和第四纪，而是用不同长度的系来取而代之，称做下第三系和上第三系。有的人还把前寒武纪分成两个代，即非常古老的太古代和较近的元古代。有时候，你还可看到"显生宙"这个词，用来涵盖新生代、中生代和古生代。