古生代

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古生代(Paleozoic,符号PZ)是地质时代中的一个,开始于同位素年龄542±0.3百万年(Ma),结束于251±0.4Ma。

古生代是显生宙的第一个代,上一个代是元古宙新元古代,下一个代是中生代。古生代包括寒武纪奥陶纪志留纪泥盆纪石炭纪二叠纪。其中寒武纪、奥陶纪、志留纪又合称早古生代,泥盆纪、石炭纪、二叠纪又合称晚古生代

古生代意為遠古的生物時代,持續约3亿年。對動物界來說,這是一個重要時期。它以一場至今不能完全解釋清楚的進化拉開了寒武紀的序幕。寒武紀動物的活動範圍只限於海洋,但在古生代的廷續下,有些動物的活動轉向乾燥的陸地。古生代後期,爬行動物和類似哺乳動物的動物出現,古生代以迄今所知最大的一次生物絕滅宣吿完結。

早古生代稱為無脊椎動物時代。 晚古生代稱為魚類兩棲類時代。

古生代各时期[编辑]

古生代各時期
[1] 重大事件 年代[2]
n亿年前
二叠纪 地球上的大陸全部合併變成超級大陸(盤古大陸),形成了阿巴拉契亞山脈。二疊系-石炭紀的冰河時期結束。合弓綱爬蟲類(盤龍目pelycosaur和獸孔目therapsid)生長繁盛,同時副爬行動物離片錐目的兩棲動物也仍非常普遍。在二疊紀中期,成煤森林英语coal forest的植物逐漸開始被取代為苔蘚植物松球(地球上第一個出現的裸子植物)。甲蟲蒼蠅開始演化。在溫暖的淺珊瑚礁有各式各樣的海洋生物, 有長身貝目(productida)和石燕貝目英语spiriferida的腕足動物、雙殼類、有孔蟲菊石都非常的多。在2.25億前發生了二疊紀-三疊紀滅絕事件,造成地球上有95%的生物都滅絕,包括三葉蟲筆石海蕾北美洲沃希托造山運動英语Ouachita orogeny茵勒溫薰造山運動英语lnnuitian orogeny亞洲阿爾泰造山運動(Altaid orogeny)「參考:阿爾泰」。烏拉爾造山運動使歐洲亞洲逐漸減少。在澳大利亞大陸上,逐漸開始亨特-鮑文造山運動英语Hunter-Bowen orogeny,形成了麥克唐奈爾山脈。(c. 2.6億–2.25億) 2.9~2.5
石炭纪 宾夕法尼亚纪/
上石炭紀[3][4]
飛行的昆蟲突然顯露,有一些昆蟲(例如:原蜻蜓目Protodonata和古網翅目Palaeodictyoptera)都變得特別的大。兩棲動物的種類變得多樣化。首次出現爬蟲類成煤森林英语Coal forest (例如:鱗木屬英语Lepidodendron蕨類植物封印木屬英语Sigillaria蘆木屬英语Calamites科達木屬英语Cordaites…等。)。這段期間,地球上大氣的含氧量是有史以來最高的。海洋有很豐富的棱菊石目生物、腕足動物外肛動物門(Bryozoa)、雙殼類和珊瑚。有殼有孔蟲激增。烏拉爾造山運動發生在當時的歐洲亞洲法利斯葛造山運動英语Variscan orogeny大約發生在密西西比紀的中期至晚期之間。 3.3~2.9
密西西比纪/
下石炭紀[3][4]
大型树形石松门植物(如“磷木”)形成森林。第一代四足类动物和两栖鲎类动物(如广翅鲎,Euripterid)登陆并在成煤海岸边的一些咸水坑(Brackish water)附近生活。 此时占据主宰地位的大型掠食鱼类是肉鳍鱼中的根齿鱼。在大洋中,早期软骨鱼Chondrichthyes,如鲨鱼)趋于常见并且呈多样化发展;棘皮动物(尤其是海百合海蕾)繁荣兴盛。珊瑚外肛门动物,棱菊石目动物和腕足门动物(如长身贝--productida、石燕贝--spiriferida 等)已经十分常见,但是三叶虫鹦鹉螺渐趋衰落。在下石炭纪时期冈瓦那大陆东部开始进入冰川时期。位于新西兰北部的马约尔岛造山运动Mayor Island / Tuhuaorogeny)进入尾声。 3.6~3.3
泥盆纪 First clubmosses, horsetails and ferns appear, as do the first seed-bearing plants (progymnosperms), first trees (the progymnosperm Archaeopteris), and first (wingless) insects. Strophomenid and atrypid brachiopods, rugose and tabulate corals, and crinoids are all abundant in the oceans. Goniatite ammonoids are plentiful, while squid-like coleoids arise. Trilobites and armoured agnaths decline, while jawed fishes (placoderms, lobe-finned and ray-finned fish, and early sharks) rule the seas. First amphibians still aquatic. "Old Red Continent" of Euramerica. Beginning of Acadian Orogeny for Anti-Atlas Mountains of North Africa, and Appalachian Mountains of North America, also the Antler, Variscan, and Tuhua Orogeny in New Zealand. 4.1~3.6
志留纪 First Vascular plants (the rhyniophytes and their relatives), first millipedes and arthropleurids on land. First jawed fishes, as well as many armoured jawless fish, populate the seas. Sea-scorpions reach large size. Tabulate and rugose corals, brachiopods (Pentamerida, Rhynchonellida, etc.), and crinoids all abundant. Trilobites and mollusks diverse; graptolites not as varied. Beginning of Caledonian Orogeny for hills in England, Ireland, Wales, Scotland, and the Scandinavian Mountains. Also continued into Devonian period as the Acadian Orogeny, above. Taconic Orogeny tapers off. Lachlan Orogeny on Australian Continent tapers off. 4.4~4.1
奥陶纪 最古老的脊椎動物甲冑魚 Invertebrates diversify into many new types (e.g., long straight-shelled cephalopods). Early corals, articulate brachiopods (Orthida, Strophomenida, etc.), bivalves, nautiloids, trilobites, ostracods, bryozoa, many types of echinoderms (crinoids, cystoids, starfish, etc.), branched graptolites, and other taxa all common. Conodonts (early planktonic vertebrates) appear. First green plants and fungi on land. Ice age at end of period. 4.9~4.4
寒武纪 寒武紀大爆發,生物群以海生无脊椎动物为主,特别是三叶虫奇蝦、低等腕足类和古环动物;红藻绿藻等开始繁盛。 Numerous fossils; most modern animal phyla appear. First chordates appear, along with a number of extinct, problematic phyla. Reef-building Archaeocyatha abundant; then vanish. Trilobites, priapulid worms, sponges, inarticulate brachiopods (unhinged lampshells), and many other animals numerous. Anomalocarids are giant predators, while many Ediacaran fauna die out. Prokaryotes, protists (e.g., forams), fungi and algae continue to present day. Gondwana emerges. Petermann Orogeny on the Australian Continent tapers off (550–535 Ma). Ross Orogeny in Antarctica. Adelaide Geosyncline (Delamerian Orogeny), majority of orogenic activity from 514–500 Ma. Lachlan Orogeny on Australian Continent, c. 540–440 Ma. Atmospheric CO2 content roughly 20–35 times present-day (Holocene) levels (6000 ppmv compared to today's 385 ppmv) 寒武紀-奧陶紀滅絕事件 5.4~4.9

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参考文献[编辑]

  1. ^ Paleontologists often refer to faunal stages rather than geologic (geological) periods. The stage nomenclature is quite complex. For an excellent time-ordered list of faunal stages, see The Paleobiology Database. [2006-03-19]. 
  2. ^ Dates are slightly uncertain with differences of a few percent between various sources being common. This is largely due to uncertainties in radiometric dating and the problem that deposits suitable for radiometric dating seldom occur exactly at the places in the geologic column where they would be most useful. The dates and errors quoted above are according to the International Commission on Stratigraphy 2004 time scale. Dates labeled with a * indicate boundaries where a Global Boundary Stratotype Section and Point has been internationally agreed upon: see List of Global Boundary Stratotype Sections and Points for a complete list.
  3. ^ 3.0 3.1 In North America, the Carboniferous is subdivided into Mississippian and Pennsylvanian Periods.
  4. ^ 4.0 4.1 上石炭紀地質在歐美及中國均以盛產煤炭著名,因此便以石炭紀為此時代地層的名稱,但在美國則以密士西必紀作為下石炭紀,另以賓夕法尼亞紀稱上部石炭紀。[1]

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