What are Some Paleogene Organisms?

Precambrian

Precambrian stratolithic reefs are formed by microbial communities, and the microstructural characteristics of stratolithic reefs formed by different microbial compositions are also different. Stratoliths are mainly formed by benthic bacteria, cyanobacteria and some bacteria and algae in the shallow water light zone due to the growth of photosynthetic circadian cycles and metabolism, and precipitate carbonate deposits in water. Microbial sedimentary structure. Because these microbial activities caused carbonate deposits, the carbon dioxide content in the atmosphere decreased, and their photosynthesis released huge amounts of oxygen into the atmosphere, so it had an important impact on the evolution of the early Earth's atmosphere and biosphere. This period was the period when stromatolites flourished. Coastal, lagoon, tidal flat, and shoal environments were spread throughout the world. Large-scale barrier reefs, embankment reefs, point reefs, atolls, and biological layers were built, which constituted the vast continental shelf and the continental An important part of slopes and platform edges. Shallow water environment under the tide is most suitable for the growth of reef-forming stromatolites. Shallow water environment with high energy or frequent turbulence is more favorable for the formation of small stromatolite reefs (Cao Ruiyu, 1997). Reef-forming microbial stromatolites have strong adaptability and can respond to environmental changes in a timely manner. Only in the case of sudden changes in the environment, reef-forming stromatolitic microorganisms may suspend reef-making activities because they do not adapt to environmental mutations. Once the environment suitable for its existence appears, the reef-forming stromatolite microorganisms multiply and form reef bodies quickly. ^[1]

The Early Cambrian ancient cup reef mound is the biological reef formed by the oldest metazoan in the history of geology. The main reef-creating creatures in this type of reef are paleo cup animals and algae. This type of biological reef system is mainly distributed in the tropical warm water inland shelf, open shelf, and shelf edge shallows within 10 ° -20 ° on both sides of the ancient equator. The ancient cup animals became the main body of biological reefs in the middle and late period of the Early Cambrian. In the reef-building community of the ancient cup reef hills, it is generally mainly constructed by 3 to 4 ancient cup animals of different genera, and they often coexist with reef-making cyanobacteria. Regular cups and trilobites, brachiopods, sea lilies The other two formed the reef biota. The ancient cup is a multi-cellular animal with a warm-water benthic fixed life. The buds reproduce, reproduce and progeny. Different protrusions on the surface of the cup body are often connected to each other. The new cup body grows around to form a dendrite. group. This ecological characteristic plays a role in strengthening the strength of the group structure and competing for living space; it plays a role in blocking and stabilizing sediments such as stucco during the reef making process, and acting as a barrier to stucco accumulation. The calcified cyanobacteria that are closely symbiotic with the ancient cup animals are mainly epiphytic algae, kidney-shaped algae, and Kuwan algae, of which epiphytic algae alone can form barrier rocks. ^[1]

In the early Early Ordovician in China, the main microorganisms Queqiu and stromatolite reefs were mainly formed by cyanobacteria and calcified cyanobacteria. Since the early Ordovician period, bryophytes and sponges have been added to the reef-building community, and many bottlenite-sponge-algal reefs have developed during the Southern Red Garden period. The unique feature of the Early Ordovician reefs in the Ordovician reef system is that sponges and bottle stones have become important reef-building organisms. Middle Ordovician corals were added to the reservoir-building system. During this period, some coral-layer foraminiferous reefs and coral-calcified cyanobacterial barrier reef mounds developed in the area north of the Weihe River in Shaanxi. In the Late Ordovician, coral-layer foraminifera reef-building activities strengthened. Typical coral-layer foraminifera skeleton reefs developed in Tazhong, Tarim Basin, Zhaquan, north of the Weihe River, and Sanshan, on the border of Zhejiang and Jiangxi. The turn of the Middle and Late Ordovician period is a turning point for the substantial renewal of the reef community. Previously, the Ordovician stratified foraminifera, planktonic corals, and Middle Ordovician-derived corals from the local benthic community To play a major role, he began to reach the reef-building stage on a large scale to form a large coral-layer foraminifera reef (Qi Wentong, 2002). ^[1]

The Silurian mainly developed the layer foraminifera-coral reef system. Compared with the previous biological reefs, the nutritional structure of the Silurian alkaloid fauna has not been significantly reorganized (Jin Shanyu et al., 1996, Qi Wentong, 2002). In the Late Ordovician, the foraminifera-sponge-slatted coral-tetraradial coral reef fauna has basically continued, and the main changes have been the increase in genera and species composition. The structure of the Silurian alkaloid fauna is closer than that of the Ordovician, and the differentiation is more obvious. Fixed-dwelling filter-eating animals are predominant, including sea lilies that feed from higher waters, but also striatomes, bed corals, tiny corals, four-shot corals, brachiopods and Moss, etc. Active predators such as nautilus and stationary predators such as large complex corals and single corals are located on the second level of the food chain. Gastropods and other food-eating animals are common in some reef parts, and swallows and scavengers are also widely distributed. ^[1]

The Devonian biological reef system is characterized by coral-layer foraminifera predominance, and the biological zoning phenomenon is more significant. Biological reefs developed from the Ames period in the late Early Devonian period and continued to Frasska in the early Devonian period. Due to the impact of the extinction of biological extinction in the late Frasnian period, complex corals in shallow sea reefs Almost all foraminifera are extinct, and skeletal reefs of the metazoan zooplankton cease to develop after the Famen period. The Frasian-Falmensional (F / F) biological extinction event caused the Devonian reef-building community to disintegrate, and only some algae were not affected by it. A large number of algae flourished shortly after the extinction time, and various algae and Zaoqiu, with Guilin in Guangxi as its representative (Duan Dewei et al., 1990a, 1990b). ^[1]

Biodiversity between the Frasian and Famen stages of the late Devonian period collapsed the Devonian reef-building community. Entering the Carboniferous Period, a new reef-building community different from the Devonian period appeared. The Early Carboniferous reef-building communities are divided into two types. One is the algae reef-building community, which represents the characteristics of a lower-level reef-building community, which may reflect the impact of the late Devonian biological extinction events on the reef construction. With the rise of new coral communities in the Carboniferous Period, the coral reef-building community of metazoans directly appeared. There is no obvious evolutionary relationship between the two, and they are basically in the same era (Datang period). Parallel developments each form different types of biological reefs. ^[1]

The Permian is an important reef-forming period in the history of the earth's development, and it is also the second reef-growth period in Chinese geological history. During this period, the types of biological reefs were rich, and the reef-building creatures were diverse, forming a unique reef-building community. Common reef-building organisms during this period include sponges, bryozoans, corals, phyllophytes, red algae, and cyanobacteria. Among them, sponges are the main, followed by water snakes. In addition, bryozoans and corals also played an important role in the construction of reefs. . ^[1]

Affected by the Permian biological extinction events, the early Triassic bioreef-making activities were relatively weak, and the distribution of biological reefs was relatively limited. Only in the middle and late stages did a large range of biological reef facies occur. The Permian is a period of resuscitation of reef-building communities. However, the distribution range and size of the reefs in the Triassic are not as good as those in the Permian, and the economic value of the reefs is not as good as that in the Paleozoic (Feng Zengzhao, 1994).

In the early Triassic, biomass and species were at a relatively low level, so there are few examples of biological reef-building, and there is no exact report in China. ^[1]

The Jurassic period was an unprecedented development of marine invertebrates, and various biomes widely appeared in Jurassic strata. However, due to the lack of dominant reef-building organisms, there is no record of reef bodies in the Early Jurassic. Due to the blank history of reef making in this period, Jurassic and Triassic reefs have no obvious inheritance in biological composition. ^[1]

Compared with other Mesozoic periods, there are fewer Cretaceous reefs (Li Xianghui et al., 2001, 2005). The Cretaceous in China mainly developed coral-fixed clam (or thick-shell clam) reef systems. Compared with the Jurassic reefs, the Cretaceous reef-building organisms have certain inheritance and development.

The corals of the Early Cretaceous followed the reef-building model of the Late Paulian corals. Most of the corals reefed with other organisms. Compared with Jurassic bivalves, fixed clams and thick clams are more adaptable. They play a greater role in the construction of the reef, so the reef formation range is wider and can be simultaneously on a section Several biological reefs appeared. Coral reefs mainly occur in the upper part of the Langshan Formation (Chen Ming et al., 2003). The organisms of the Langshan Formation are very prosperous. The reef-building organisms are mainly corals and anchor clams. They are the key species and dominant species of the community, and can be reefs alone. There are also cases of joint reef-building. Attached reefs are mainly foraminifera, bivalves, brachiopods, etc., with various species (Qu Yonggui et al., 2003). ^[1]

Compared with the Cretaceous reefs, there have been new breakthroughs in the types of Paleogene and Neogene reefs. For the first time, lacustrine reefs have appeared (Zhong Jianhua et al., 2004), and reef-building organisms have new development of.

In the Paleogene lacustrine biological reefs in the western Qaidam Basin, algae became the main reef-building organisms, and several biological reef layers were constructed (Zhao Xianzheng et al., 2004). The types of reefs include algae stacked rock reefs, algae clot reefs, and tuber algae, etc. At the same time, lacustrine algae (cyanobacteria) limestones are widely distributed. Stratolithic reefs include two different types of mound-shaped algae reefs composed of short columnar stromatolites and tower-column stromatolite reefs (Guo Zeqing et al., 2004). However, microbial reefs without a typical striation layer (Riding, 2002) are biological reefs formed by microbial capture and binding of sediment particles. The reef algae reefs are mainly irregular reef-shaped, massive algae reefs formed by clade algae. The biocomponents are algae represented by Cladospira, and the reef organisms are mainly mesoderms, followed by snails (Gastropods). They fill the trellis space with a small amount of Burmese, Fecal pellets, algal pellets, broken clots and higher plant debris. ^[1]