专业英语-地史古生物学

Historical geology examines the origin and evolution of Earth, including its continents, atmosphere, oceans, and life history. Historical geology is, however, more than just a recitation of past events. It is the study of a dynamic planet that has changed continuously during the past 4.6 billion years. In addition to determining what occurred in the past, geologists are also concerned with interpreting how and why past events happened.

–––––“Historical Geology”, 2004, Reed Wicander & James Monroe

① The Earth accreted from planetesimals and differentiated into a core and mantle, and at least some crust was also present.

②Like the other terrestrial planets, the Earth was bombarded by comets and meteorites, and volcanic activities were ubiquitous.

③Furthermore, a primitive atmosphere formed, although it was quite different from the oxygen-rich one we have today.

①The oldest known organisms occur as fossil prokaryotes (anaerobic and autotrophic bacteria and cyanobacteria) from the 3.5-billion-year-old Warrawoona Group, western Australia.

Other than the origin of life itself, the most significant biological event of the Archean was the development of photosynthesis. The oldest known undisputed stromatolites were found in 3.0-billion-year-old rocks in South Africa.

②The Archean rock associations mainly consist of greenstone belts（绿岩带）and granite-gneiss complexes（花岗片麻杂岩）. Actually, granite-gneiss complexes have rocks varying form granite to peridotite to various sedimentary rocks, all of which have been metamorphosed.

③Some primitive cratons or continental nuclei (including North China nucleus ) formed and grew by continental accretion during this Eon. By the end of the Archean, perhaps 30% to 40% of the present volume of continental crust existed.

④Archean mineral resources: Gold is the mineral most commonly associated with Archean rocks.

Though 92% of the Earth’s Banded Iron Formations (BIFs, from 3.8 to 1.8 Ga in age) were deposited during the Proterozoic (2.5~2.0Ga), the Archean is the most important period for China’s iron ore deposits (especially in Anshan, Benxi, eastern Hebei, etc.).

Archean sulfide deposits of zinc, copper, and nickel are well known in Australia, Zimbabwe, and Canada. About one-fourth of Earth’s chrome reserves are in Archean rocks, esp. in Zimbabwe.

① The appearance of eukaryotic cells（真核细胞）about 2.1 billion years ago marks a milestone in biological evolution comparable to the development of complex metabolic mechanisms such as photosynthesis（光合作用）during the Archean.

Multicellular organisms also appeared in the Proterozoic. The most remarkable Ediacaran fauna was originally discovered as impressions of soft-bodied animals in the Pound Quartzite in the Ediacara Hills, southern Australia. The Ediacara-type faunas were found from all continents except Antarctica ca. 620Ma ago. But the great majority of these organisms did not survive the beginning of the Cambrian Period.

②Deducing form the Grenville Orogenic Belt, the Proterozoic supercontinent known as “Rodinia” assembled between 1.3 and 1.0 billion years ago, consisting of all or at least much of the present continents, and then began breaking up ca. 750 million years ago.

③V ast glacial deposits were found from Early Proterozoic localities. Two worldwide glaciers are most acceptable during the Neoproterzoic, i.e., the Sturtian glaciation (730~700Ma) and the Marinoan glaciation (665~635Ma), resulting in the coeval hypothetical “Snowball Earth”.

④With gradual increase of free oxygen, the Proterozoic atmosphere evolved from a chemically reducing one to an oxidizing one. Two widespread types of Proterozoic sedimentary rocks serve as the evidence, i.e., Banded Iron Formations (BIFs) and Continental Red Beds.

⑤Proterozoic mineral resources: Most of the world’s iron ore comes from Paleoproterozoic

(2.5~2.0Ga) banded iron formations. Substantial nickel, copper and PGE are mined from Proterozoic rocks especially in Sudbury of Canada. The Bushveld Complex of South Africa yields most significant platinum and chromite. Economically significant oil and gas have been discovered in Proterozoic rocks in China and Siberia. The most important phosphorite was deposited during the Ediacaran (Sinian) of Neoproterozoic, esp. in Yunnan and Guizhou.

①There are six major continents (Gongdwana, Laurentia, China, Siberia, Baltica and Kazakhstania) existed at the beginning of the Paleozoic.

②Animals with skeletons, the so-called Small Shelly Fossils (SSFs), appeared abruptly at the beginning of the Paleozoic Era and experienced a short period (less than 5 Ma) of rapid evolutionary diversification, i.e., the evolutionary “Big Bang” or the Cambrian Explosion represented by the Chengjiang Biota, the Burgess Shale Biota, and the Sirius Passet Biota.

The Cambrian Period was a time of many evolutionary innovations during which almost all the major modern invertebrate phyla appeared and evolved. Remarkably, the earliest vertebrates, agnathous (jawless 无颌) fish, emerged from the Early Cambrian in South China, whereas the well-known jawless fish ostracoderms (甲胄鱼) were found in the Upper Cambrian.

③The Ordovician Period witnessed striking changes in the marine community, resulting in a drastic increase in the diversity of invertebrates (无脊椎动物), esp. corals (珊瑚), trilobites (三叶虫), brachiopods (腕足类), cephalopods (头足类), and graptolites (笔石), followed by a mass extinction (集群绝灭) at the end of the Ordovician.

Bryozoans (苔藓动物) and tabulate and rugose corals (横板珊瑚和皱襞珊瑚) rose in Ordovician and acted as major reef builders.

④The earliest jawed fish (acanthodians 棘鱼) and first seedless vascular land plants (psilophytes 裸蕨类) appeared in the Early and Late Silurian respectively.

⑤ The Lower Paleozoic rocks contain a variety of important mineral resources. The Early Cambrian is also an important time for the deposition of phosphorite (磷灰岩) in China. Industrial limestone and sandstone, strata-bound lead and zinc deposits, rock salt and rock gypsum etc. are