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Gondwana
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Des chitinozoaires au Cambrien

L'apparition des chitinozoaires, groupe énigmatique de microfossiles marins, doit être reculée dans le temps jusqu'à l'explosion cambrienne, il y a environ 510 millions d'années (Ma). C'est ce qu'indique la découverte de spécimens du groupe dans une formation du sud de la Chine, décrits par une équipe de chercheurs chinois de l'Université de Yunnan en collaboration avec des paléontologues de l'Université de Leicester (Royaume Uni) et du laboratoire Géosystèmes (CNRS-INSU, Université de Lille 1) dans la revue Geology, doi: 10.1130/G33763.1.
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Great Unconformity
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 Evidence for a geologic trigger of the Cambrian explosion

The results of this Cambrian explosion are well documented in the fossil record, but its cause - why and when it happened, and perhaps why nothing similar has happened since - has been a mystery.
New research shows that the answer may lie in a second geological curiosity - a dramatic boundary, known as the Great Unconformity, between ancient igneous and metamorphic rocks and younger sediments.

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RE: Gondwana
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Scientists have discovered two huge sunken islands in the Indian Ocean west of Perth.
The islands, about the size of Tasmania, were once part of the supercontinent Gondwana and are more than 1.5km underwater.
Researchers from the University of Sydney, Macquarie University and the University of Tasmania say the islands were once above water and formed part of the last link between India and Australia.
They made the discovery while mapping the seafloor of the Perth Abyssal Plain.

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Oldest Fossils of Large Seaweeds, Worm-like Animals Tell Story of Ancient Oxygen

Almost 600 million years ago, before the rapid evolution of life forms known as the Cambrian explosion, a community of seaweeds and worm-like animals lived in a quiet deep-water niche near what is now Lantian, a small village in south China.
Then they simply died, leaving some 3,000 nearly pristine fossils preserved between beds of black shale deposited in oxygen-free and unbreathable waters.
Scientists from the Chinese Academy of Sciences, Virginia Tech in the United States and Northwest University in Xi'an, China report the discovery of the fossils in this week's issue of the journal Nature.

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Cambrian Explosion
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New Timeline for Appearances of Skeletal Animals in Fossil Record Developed by UCSB Researchers

Beginning around 542 million years ago, a profusion of animals with shells and skeletons began to appear in the fossil record. So many life forms appeared during this time that it is often referred to as the "Cambrian Explosion."
Geologists at UC Santa Barbara and a team of co-authors have proposed a rethinking of the timeline of these early animal appearances. Their findings are published in the latest issue of the Geological Society of America Bulletin.

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RE: Gondwana
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Late Paleozoic Glacial Events & Postglacial Transgressions

This collection of papers covers state-of-the-art critical topics related to the Late Paleozoic Glaciation and deglaciation-triggered sea-level rise that affected Gondwana. Those topics include the sequence stratigraphic framework of postglacial transgressions and their influence on the salinity of the postglacial coastlines, faunas (including the Levipustula Fauna) and floras associated with the Late Paleozoic Glaciation, ichnofacies related to this paleoclimatic episode, and relatively less known glacial deposits in some Gondwanan regions. One chapter challenges the popular interpretation that there was a single massive ice sheet over much of Gondwana during the late Paleozoic glaciation.
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Posts: 131433
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Cambrian Explosion
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The Chengjiang fossils, first unearthed in 1984, are particularly important because they open up a window onto one of the most important events in the history of life: the so-called Cambrian 'explosion' when most of the major animal groups we know today first appeared in the fossil record.
The big question has always been: where did this dazzling variety of animals come from? Did they suddenly develop or were earlier examples of complex animals simply never preserved?
These particular fossils have survived because of an amazing stroke of luck: "The preservation of all the soft tissues is a result of the organic materials of these animal bodies being replaced by 'fool's gold' - iron pyrites".

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RE: Gondwana
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The Congo Basin - with its massive, lush tropical rain forest - was far different 150 million to 200 million years ago.
At that time Africa and South America were part of the single continent Gondwana. The Congo Basin was arid, with a small amount of seasonal rainfall, and few bushes or trees populated the landscape, according to a new geochemical analysis of rare ancient soils.
The geochemical analysis provides new data for the Jurassic period, when very little is known about Central Africa's paleoclimate, says Timothy S. Myers, a palaeontology doctoral student in the Roy M. Huffington Department of Earth Sciences at SMU.

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Cambrian Explosion
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La première « explosion » de vie date du Cambrien (-542 à - 488 millions d'années), avec l'émergence des principaux embranchements animaux actuels qui vivaient essentiellement sur les fonds marins. Ce n'est que plus tard entre -489 à -443 millions d'années, à l'Ordovicien, que les océans se remplissent réellement de vie avec une multiplication exceptionnelle du nombre de familles et de genres d'organismes marins. La diversification rapide des groupes planctoniques a engendré le développement des organismes benthiques et des premiers grands prédateurs nageurs, comme les poissons et les céphalopodes. L'étude des raisons de cette "Grande Biodiversification Ordovicienne" a fait l'objet d'un programme international, l'International Geoscience Programme (IGCP) 503, Ordovician Palaeogeography and Palaeoclimate, auquel plusieurs équipes françaises ont participé. Une synthèse des résultats vient d'être publiée dans la revue GSA Today. Les causes de cette expansion de la vie marine à l'Ordovicien sont multiples, mais un facteur essentiel aurait été l'augmentation des surfaces de plateformes continentales et des hauts niveaux marins qui ont favorisé le développement du plancton et de l'ensemble des organismes marins.

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Ferrar basalts
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The longest lava flows in the solar system formed mountain ranges across three continents, according to new geological research.
Called the Ferrar basalts, the rocks formed by the cooling lava are now found in mountain ranges across Antarctica, South Africa, Australia and New Zealand.
The lava came to the surface in volcanic eruptions around 183 million years ago, when Gondwana, the ancient super-continent, was still a single land-mass - although a rift was already opening across it that would eventually form the split between modern Africa and Antarctica.
In the months after the eruptions, the lava flows moved around 4100 kilometres, although along most of this length they were only around 160km wide. Researchers think the lava travelled by forcing surface rocks up and flowing laterally in the space below to form what geologists call 'sills' - horizontal incursions of lava into older rocks.

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