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Topic: Proterozoic

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Precambrian era

Archaean

1 E16 s

Precambrian

Paleoproterozoic

Mesoproterozoic

Neoproterozoic

Hadean

Geologic timescale

Cambrian

Cambrian Explosion

Snowball Earth

Ice age

Geology of the United Kingdom

Paleozoic

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	Proterozoic - Wikipedia, the free encyclopedia
		In geology, the Proterozoic is an eon prior to the first abundant complex life on Earth.
		The Proterozoic consists of 3 geologic eras, from oldest to youngest:
		Classically, the boundary between the Proterozoic and the Paleozoic was set at the base of the Cambrian period when the first fossils of animals known as trilobites and archeocyathids appeared.
	en.wikipedia.org /wiki/Proterozoic (304 words)

	Proterozoic (Site not responding. Last check: 2007-11-05)
		The debate extends into the early Archaean, however it is clear that by roughly 3600Ma temperatures were stable at near modern levels, continental crusts were in place, oceans of liquid water existed, and simple lifeforms either had appeared or would appear shortly.
		The major well identified events were the transition to an Oxygenated atmosphere that probably occurred in the Mesoproterozoic and several glaciations the most severe of which took place in the late Neoproterozoic.
		The Proterozoic Era An overview of the era from the UC Berkeley Museum of Paleontology.
	www.serebella.com /encyclopedia/article-Proterozoic.html (335 words)

	Anorthosite - Wikipedia, the free encyclopedia
		However, most Proterozoic anorthosites are deformed, and such large plagioclase crystals have recrystallized to form smaller crystals, leaving only the outline of the larger crystals behind.
		While many Proterozoic anorthosite plutons appear to have no large-scale relict igneous structures (having instead post-emplacement deformational structures), some do have igneous layering, which may be defined by crystal size, mafic content, or chemical characteristics.
		The composition of plagioclase feldspar in Proterozoic anorthosites is most commonly between An and An This compositional range is intermediate, and is one of the characteristics which distinguish Proterozoic anorthosites from Archean anorthosites.
	en.wikipedia.org /wiki/Anorthosite (1912 words)

	IRSPS - Proterozoic Stratigraphy
		Proterozoic lithostratigraphy and sedimentation of Sariola and Jatuli-type rocks in the Nunnanlahti - Koli - Kaltimo area, eastern Finland; implications for regional basin evolution models.
		Early Proterozoic Stratigraphy of the SalahmiPyhäntä Area, Central Finland, with an Emphasis on Applying the Principles of Lithodemic Stratigraphy to a Complexly Deformed and Metamorphosed Bedrock.
		Lithostratigraphy of the early Proterozoic Kainuu Schist Belt in the KurkikyläSiikavaara area, northern Finland, with emphasis on the genetic approach.
	irsps.sci.unich.it /education/pastactiv/proterozoic.html (1375 words)

	The Proterozoic Era (Site not responding. Last check: 2007-11-05)
		The period of Earth's history that began 2.5 billion years ago and ended 543 million years ago is known as the Proterozoic.
		With the beginning of the Middle Proterozoic comes the first evidence of oxygen build-up in the atmosphere.
		The Proterozoic Era occurs between the Archaean and the Paleozoic.
	www.ucmp.berkeley.edu /precambrian/proterozoic.html (257 words)

	Proterozoic (Site not responding. Last check: 2007-11-05)
		In geology, the Proterozoic is an era prior to the first abundantcomplex life on earth.
		Classically, the boundary between the Proterozoic and the Paleozoic was set atthe base of the Cambrian period when the first fossils of animals known as trilobites and archeocyathids appeared.
		The major well identified events were thetransition to an Oxygenated atmosphere that probably occurred in the Mesoproterozoic and several glaciations the most severe of which took place in the late Neoproterozoic.
	www.therfcc.org /proterozoic-80688.html (220 words)

	Proterozoic: Facts and details from Encyclopedia Topic (Site not responding. Last check: 2007-11-05)
		(the Proterozoic is an eon prior to the first abundant complex life on earth.
		The cambrian is a major division of the geologic timescale that begins about 542 million years before the present (bp) at the end of the proterozoic eon and...
		The paleoproterozoic is the first of the three sub-divisions of the proterozoic occurring between 2500 to 1600 million years ago....
	www.absoluteastronomy.com /encyclopedia/p/pr/proterozoic.htm (1076 words)

	Proterozoic (Site not responding. Last check: 2007-11-05)
		Dillip is a professional Geologist with work experience in gold exploration from the Archean Greesntone and Proterozoic belts of Tanzania.
		All modern plants carry out photosynthesis, but in the Proterozoic (the geologic period of time), cyanobacteria were the only organisms that could do this.
		Host rocks are weakly to moderately metamorphosed, Proterozoic age deep-marine sediments; the presence of these lithologies suggests potential for a Sedex-type...
	www.wikiverse.org /proterozoic (363 words)

	Proterozoic Geology of CAP LTER
		The oldest bedrock in the greater Phoenix area is principally composed of rocks of the Proterozoic (1.7-1.4 billion years ago).
		The earlier Proterozoic rocks are various metamorphosed sedimentary, metamorphic, and igneous rocks (both volcanic and intrusive).These rocks are present in all of the major mountain ranges in and around Phoenix (the Sierra Estrella, McDowell, Phoenix, San Tan, South, and White Tank Mountains).
		The plate tectonic setting interpreted for the formation of the Proterozoic rocks is one similar to that currently found in association with the Andes of South America - oceanic crust being subducted beneath continental crust in a southeasterly direction with attendant volcanism, intrusion of magmas, and folding of sediments shed into the subduction zone.
	caplter.asu.edu /home/capltertour/proterozoic_geo.htm (247 words)

	proterozoic rocks
		Proterozoic rocks of the southwestern United States are found in Arizona, New Mexico, and Colorado.
		Proterozoic rocks are the basis of many current research projects involving rocks in Colorado, Arizona, and New Mexico.
		The primary objective is to obtain knowledge of the structural geology of the Proterozoic rocks in western Colorado, eastern Utah, Arizona, and New Mexico, and to interpret the differences in deformation between the Paleoproterozoic and Mesoproterozoic rocks, the forces required for the deformation, and their general location.
	www.mesastate.edu /snsm/geology/classes/seminar/ahosack/protrx.html (1833 words)

	Proterozoic Eon
		During the Proterozoic time, the area that was to become the Ozarks became a part of the future North American continent.
		The proterozoic rocks under the Bryant area are known only from a few deep drill holes in the area and from interpretation of other geophysical data.
		The area during the Proterozoic was a "hot" place; presumably along the margin of a growing continent.
	www.watersheds.org /earth/gtime01c.htm (481 words)

	Palaeos Proterozoic: The Proterozoic Era
		The Proterozoic is, roughly speaking, the time when plate tectonics began to govern over other processes in determining the form of the Earth's crust.
		As Dr. Christopher Scotese notes on his paleomap site: "With available data, 650 million years is about as far back as we can go." Of course, this has not stopped him (or many others) from pushing the paleomap envelope to about 750 Mya.
		The Proterozoic of the Eastern Midcontinent and Beyond: abstracts from a recent conference.
	www.palaeos.com /Proterozoic/Proterozoic.htm (868 words)

	Proterozoic (Site not responding. Last check: 2007-11-05)
		In geology the Proterozoic is an eon prior to the abundant complex life on earth.
		Classically the boundary between the Proterozoic and Paleozoic was set at the base of Cambrian period when the first fossils of known as trilobites and archeocyathids appeared.
		The debate into the early Archaean however it is clear that by 3600Ma temperatures were stable at near modern continental crusts were in place oceans of water existed and simple lifeforms either had or would appear shortly.
	www.freeglossary.com /Proterozoic (376 words)

	Life of the Proterozoic Era
		Their importance for understanding Proterozoic life is tremendous; stromatolites that have been silicified (forming a type of rock known as stromatolitic chert) often preserve exquisite microfossils of the microbes that made them.
		However, the oldest relatively non-controversial, well-studied animal fossils appear in the last hundred million years of the Proterozoic, just before the Cambrian radiation of taxa.
		The time from 600-650 million years ago to 543 million years ago, known as the Vendian period, saw the origin and first diversification of soft-bodied organisms known collectively as the "Vendian fauna" or "Ediacara fauna" (after the Ediacara Hills of southern Australia, where the first abundant and diverse fossils of this kind were found).
	www.ucmp.berkeley.edu /precambrian/proterolife.html (460 words)

	Colorado Geology Overview
		The stalwart Wyoming craton played a pivotal role in the Early Proterozoic assemblage of Colorado's Precambrian basement by serving as a backstop for a long series of juvenile Early Proterozoic island arcs and more mature terranes rafted in from the south along a 1,300 km-wide, east northeast-trending convergent plate margin active around 1.78-1.65 Ga.
		Since its Early Proterozoic assembly via subduction, Colorado has been far removed from active plate boundaries, but far-field effects from subsequent plate interactions to the west, south and east continued to play an important role in Colorado's evolution, both at the surface and at depth.
		Late Proterozoic rifting must have interrupted the process at times, but by Late Cambrian time, statewide erosion had exposed a featureless expanse of planed off crystalline basement rocks originally hailing from a variety of mid-crustal levels, judging from their mineral assemblages.
	www.cliffshade.com /colorado/geo_overview.htm (10393 words)

	Stratigraphy of the Proterozoic Era (Site not responding. Last check: 2007-11-05)
		The period of Earth's history that began 2.5 billion years ago and ended 544 million years ago is known as the Proterozoic; it is divided up, rather arbitrarily, into the Paleoproterozoic (2.5 to 1.6 billion years ago), Mesoproterozoic (1.6 billion to 900 million years ago) and Neoproterozoic (900 to 543 million years ago).
		Near the beginning of the Proterozoic, stable continents first appeared and began to accrete, a long process taking about a billion years.
		Organisms had to evolve biochemical methods for rendering oxygen harmless; one of these methods, oxidative respiration, had the advantage of producing large amounts of energy for the cell, and is now found in most eukaryotes.
	www.ucmp.berkeley.edu /precambrian/proterostrat.html (320 words)

	M. Hitzman - Olympic Dam-type Deposits
		Deposits of this family are found in post-Archean rocks from the Early Proterozoic to the Pliocene.
		We designate this class of deposits as Proterozoic iron oxide (Cu-U-Au-REE) deposits, and propose that the ore deposits generally referred to as "Kiruna-type" should be considered a subset of this larger class.
		The deposits are located in areas that were cratonic or continental margin environments during the late Lower to Middle Proterozoic, and in many cases there is a definite spatial and temporal association with extensional tectonics.
	www.mines.edu /fs_home/mhitzman/olympic.html (769 words)

	LATE PROTEROZOIC CRUSTAL THINNING IN THE ARABIAN SHIELD
		The volcanic activity, represented by the extrusive formations of the Shammar Group, was associated with various intrusive complexes and dike swarms dated between 530 and 590 Ma, whilst gravitational sliding in the uppermost part of the crust is reflected by listric or gently dipping faults.
		By applying these concepts to the Proterozoic formations of the Arabian Shield, we can reinterpret the geodynamic context in which the sedimentary and intrusive formations were deposited between 590 and 530 Ma.
		Ophiolites and the evolution boundaries in the late Proterozoic Arabian-Nubian Shield of Northeast Africa and Arabia.
	www.sgs.org.sa /GIS/Publications/PAPEXTEN.htm (8010 words)

	The Belt Association Home Page
		The Belt Association promotes and co-ordinates geologic study of the Proterozoic Belt Supergroup of the northwestern U.S.A. and the equivalent Purcell Group in southwestern Canada.
		Second is the correlation of faulted and folded blocks to allow piecing together the history of tectonic adjustments.
		Proterozoic sedimentation processes have only poor modern analogues.
	www.idahogeology.org /Belt%20Association/Belt%20Web/thebeltassociation.htm (690 words)

	North Gascoyne Mining Ltd » Welcome to NGM Resources (Site not responding. Last check: 2007-11-05)
		Australian Proterozoic terranes host some of world’s largest mineral deposits, including the iron ore deposits of the Hamersley Basin, world class lead, zinc, silver deposits of Eastern Australia, including Broken Hill and Mt. Isa, and Australia’s largest gold and copper-gold deposits, Telfer and Olympic Dam.
		Proterozoic rocks cover a very large area of the Australian continent, far more than the Archaean terranes of the Yilgarn and the Pilbara in Western Australia, and the Palaeozoic terranes of eastern Australia.
		Much of the Australian Proterozoic is covered with thin sediments and in general the Proterozoic has been less intensely explored for gold than other areas, for example the Archaean of Western Australia.
	www.ngmresources.com.au (533 words)

	Geology of Missouri--Proterozoic/Precambrian
		The Proterozoic is one of the most studied time units in Missouri.
		And finally, the reasonably flat lava flows of Yellowstone extend many hundreds of square miles, similar to the rhyolite which underlies the southern mid-continent.
		A second hypothesis notes the closeness of the Ozarks to the Proterozoic continental margin, and claims that the Ozarks rose somewhat like the Cascade volcanoes of Oregon and Washington, as a result of volcanism related to subduction.
	members.socket.net /~joschaper/proto.html (1001 words)

	Palaeos Proterozoic: The Mesoproterozoic Era
		The Mesoproterozoic Era of the Proterozoic Eon: 1600 to 1000 million years ago
		The Mesoproterozoic was the first period of Earth's history with a respectable geological record.
		Still, it may not be long before we should think about telling Proterozoic time a different way.
	www.palaeos.com /Proterozoic/Mesoproterozoic.html (669 words)

	Harvard Univ., EPS Dept. Faculty
		Members of the Knoll lab are broadly interested in the evolution of life, the evolution of Earth surface environments, and the relationships between the two.
		We are particularly interested in Archean and Proterozoic paleontology and biogeochemistry; however, both past and current projects include investigations of selected problems in Phanerozoic Earth history.
		Grotzinger, J.P., and A.H. Knoll (1999) Proterozoic stromatolites: evolutionary mileposts or environmental dipsticks?
	www.eps.harvard.edu /people/faculty/knoll (449 words)

	Chapter 7, part 1, Lecture Notes, The Proterozoic Eon, Levin: The Earth Through Time - Wiley
		Designation of the beginning of the Proterozoic at 2.5 by is somewhat arbitrary.
		Proterozoic rocks are easier to study than Archean rocks because they are less altered.
		The Paleoproterozoic (or ancient Proterozoic) is the oldest part of the Proterozoic, ranging from about 2.5 by to 1.6 by.
	www3.interscience.wiley.com:8100 /legacy/college/levin/0470000201/chap_tutorial/ch07/chapter07-1.html (588 words)

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