-Las caracteristicas Geodinamicas comienzan a ser mas pasivas. -Primero formacones cristalinas en continentes y formaciones basalticas en. Convert documents to beautiful publications and share them worldwide. Title: Conclusiones Eon Proterozoico, Author: wilo bope, Length: 7 pages, Published. First, a few words about the Precambrian, an informal name for the vast expanse of time prior to the Phanerozoic Eon (which includes the Paleozoic, Mesozoic.
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Proterozoic Eonthe younger of the two divisions of Precambrian timethe older being the Archean Eon. The Proterozoic Eon extended from 2.
Proterozoic rocks have been identified on all the continents and often constitute important sources of metallic ores, notably of irongoldcopperuraniumand nickel. During the Proterozoic, the atmosphere and oceans changed significantly.
Proterozoic rocks contain many definite traces of primitive life-forms—the fossil remains of bacteria and blue-green algaeas well as of the first oxygen-dependent animals, the Lroterozoico fauna.
What happened geologically at the time of the Archean-Proterozoic boundary 2. It seems to have been a period of little tectonic activity, and so it is possible that the earlier intensive Archean crustal growth had caused the…. Priterozoico is a by-product of photosynthesis. Free oxygen in the atmosphere increased significantly as a result of biological activity during the Proterozoic. The most important period of change occurred between 2.
Oxygen levels fluctuated during this time, coinciding with the peak deposition period of banded-iron formationswhich removed surplus oxygen from the atmosphere throughout protwrozoico world.
Continued biological activity allowed atmospheric oxygen concentrations to increase.
Conclusiones Eon Proterozoico
By the time eukaryotes became established in the environmentatmospheric oxygen pressure had risen pdoterozoico low values to about 10 percent of the present atmospheric level PAL. Megascopic eukaryotes first appeared about 2. Eukaryotes employed a form of respiration and oxidative metabolism; they had a central nucleus that could split into separate sex cells, and so for the first time a mixed and variable genetic code could be passed to younger generations.
Early organisms on Earth flourished most easily in the shallow water of continental margins. Such stable continental shelf environmentswhich were rare in the Archean, proterozojco after 2. Evidence of the rapid rise in the oxygen content includes the first appearance on continental margins of red sandstones.
Their colour is caused by the coating of quartz grains with hematite. Other evidence proterozoick provided by the occurrence of hematite-rich fossil soil beds that date to about 2. The formation of these beds is consistent with a drastic rise in oxygen pressure to 0. By million to million years ago, the multicellular Porterozoico fauna had appeared; these were the first metazoans animals made up of more than one type of cell that required oxygen for growth.
The soft-bodied Ediacara fauna were the precursors of organisms with skeletons, the appearance of which marked the end of the Proterozoic and the beginning of the Phanerozoic Eon.
The history of the Proterozoic Eon is dominated by the formation and breakup of supercontinents. By the time of the Archean-Proterozoic boundary about 2. The breakup of this landmass is indicated by the intrusion of abundant transcontinental swarms of dolerite a type of fine-grained igneous rock dikes during the period of 2.
These dikes resulted from the impingement of mantle plumes onto the base of the continental crust. This was the fundamental cause of the breakup of the initial supercontinent. During the period between 2. Modern plate-tectonic processes were in operation by at least 2. The fragmentation of Columbia gave rise to many smaller continents that had eventually assembled into another supercontinent, or a group of several large continental pieces in close proximity to one another, by about 1.
This assemblage is called Rodinia. Rodinia was intruded by many basaltic dikes after 1. Other indications of plume activity and continental breakup are vast piles of basalts and transcontinental rifts.
A key example is the 1. This rift, which is 2, km about 1, miles long and km miles wide, contains a pile of basaltic lavas 25 km about 16 miles thick. Many mountain belts formed during the Proterozoic, in particular during the intervals between 2.
New ocean basins were created by the rifting apart of the continents and were subsequently destroyed in subduction zones similar to those under modern-day Japan. The closure of these oceans enabled continental blocks to collide, giving rise to major mountain belts such as the Grenville belt in eastern North America.
This belt, which is 1. Other major Proterozoic mountain belts created by continental collisions include the Wopmay Orogen in northwest Canada 2. In contrast, mountain belts such as the 2. pdoterozoico
Primicias Arrecifes » Eón Proterozoico
Proteeozoico, they include many island arcs similar to those found in modern-day Japan as well as many ophiolite sequences. Many Phanerozoic basins contain thick piles of sediments and lie partly to completely on top of Proterozoic mountain belts, obscuring the underlying geological relationships. Some Phanerozoic mountain belts such as the Himalayas contain blocks of Proterozoic rocks many tens of kilometres in size that have been heavily reworked by later tectonic activity.
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Learn More in these related Britannica articles: The lines of weakness within the mosaic later guided stresses that pulled the blocks apart or pushed them together. The Proterozoic fold belts that bounded the western and…. In Asia rocks of Archean age are found in the Angaran and Indian platforms, in the North China and the Yangtze paraplatforms, and in smaller fragments caught up in younger orogenic belts such as the North….
The Proterozoic Eon 2. For the Hadean Eon, the only record comes from meteorites and lunar rocks. No rocks of Hadean age survive on Earth. In the figure, eons are divided…. After the Precambrian, geologic time intervals are commonly subdivided on the basis of the fossil record. The paucity of Precambrian fossils, however, precludes the creation of small-scale subdivisions epochs and ages in this time….
Geologic record Precambrian time In Precambrian time: Major subdivisions of the Precambrian System In Precambrian time: Proterozoic rock types stratigraphic classification of Africa In Africa: General considerations Asia In Asia: The Precambrian Australia In Australia: Help us improve this article! Contact our editors with your feedback. You may find it helpful to search within the site to see how similar or related subjects are covered.
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