萬(wàn)物簡(jiǎn)史 第85期:敲石頭的人們(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.

接著就是萊爾所謂的“世”——更新世、中新世等——這些名稱(chēng)僅僅用來(lái)指最近的(但又是古生物學(xué)研究很活躍的)6500萬(wàn)年;最后，便是一大堆更細(xì)的分類(lèi)，名叫“期”或“代”。其中大多數(shù)以地名命名，讀起來(lái)幾乎總是很拗口：伊利諾期、得梅因期、克羅伊期、金默里奇期等等，都具有同一特色。據(jù)約翰·麥克菲說(shuō)，這類(lèi)名稱(chēng)總共多達(dá)"幾百個(gè)"。幸運(yùn)的是，除非把地質(zhì)學(xué)作為你的專(zhuān)業(yè)，你從此以后再也不大可能聽(tīng)到這些名稱(chēng)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.

更加混亂的是，北美的“期”或“代”跟歐洲的說(shuō)法不一，在時(shí)間上往往只是大體交叉。因此，北美的辛辛那提期在很大程度上相當(dāng)于歐洲的阿什吉利期，再加上一點(diǎn)兒稍早的喀拉多克期。

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，這一切，不同的教科書(shū)、不同的人都有不同的叫法，因此有的權(quán)威提出7個(gè)代，而有的權(quán)威滿(mǎn)足于4個(gè)代。在有的書(shū)里，你還會(huì)發(fā)現(xiàn)不用第三紀(jì)和第四紀(jì)，而是用不同長(zhǎng)度的系來(lái)取而代之，稱(chēng)做下第三系和上第三系。有的人還把前寒武紀(jì)分成兩個(gè)代，即非常古老的太古代和較近的元古代。有時(shí)候，你還可看到"顯生宙"這個(gè)詞，用來(lái)涵蓋新生代、中生代和古生代。