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2009-02-03 – La tartaruga fossile e il polo “tropicale” (Turtle fossil and tropical Artic)

CLIMA: CANADA; FOSSILE TARTARUGA PROVA ANTICO EFFETTO SERRA

L’Artide 90 milioni di anni fa era un posto molto piu’ temperato: senza ghiacci e con passaggio migratorio degli animali preistorici. Lo sostengono alcuni scienziati dopo la scoperta di un fossile di tartaruga asiatica nell’Artide canadese. Secondo i ricercatori, tra cui Donald Brinkman del Royal Tyrell Museum dell’Alberta, la tartaruga tipica della Mongolia, chiamata ‘tartaruga aurora’, con il guscio quasi perfettamente rotondo, esistente all’epoca dei dinosauri e da tempo estinta, avrebbe percorso migliaia di chilometri dal suo habitat originario nelle acque dolci dell’Asia passando non dall’Alaska ma direttamente dal polo Nord. Questo proverebbe che nel polo Nord le temperature in passato erano molto piu’ temperate, al punto da rendere l’Artide un percorso migratorio delle creature preistoriche. Secondo i ricercatori un ‘super effetto serra’, forse originato da eruzioni vulcaniche, causo’ 90 milioni di anni fa un’enorme emissione di anidride carbonica scaldando i poli ed aprendo nuovi passaggi per gli animali migratori, comprese le tartarughe. (ANSA). COR-DI
02/02/2009 19:47

fonte: http://www.ansa.it/ambiente/notizie/notiziari/natura/20090202194734816739.html

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Turtle fossil shows how ‘super-greenhouse effect’ created tropical Arctic

The discovery of a fossilised ancient turtle reveals the North Pole was once “extremely” warm and tropical, scientists said.

Turtle fossil shows how 'super-greenhouse effect' created tropical Arctic
The North Pole: “extremely” warm and tropical millions of years ago Photo: GETTY IMAGES

Animals migrated from Asia to North America directly across the formerly frost-free Arctic Ocean, new evidence shows.

Geologists made the breakthrough after discovering the fossil of a freshwater Asian turtle – dating back millions of years – in Canada.

John Tarduno, a US-based professor of geophysics at the University of Rochester, said: “We’ve known there’s been an interchange of animals between Asia and North America in the late cretaceous period, but this is the first example we have of a fossil in the High Arctic region showing how this migration may have taken place.

“We’re talking about extremely warm, ice-free conditions in the Arctic region, allowing migrations across the pole.”

Numerous rivers from the adjacent continents would have poured fresh water into the ancient Arctic sea, he said.

Fresh water, which is lighter than marine water, may have rested on top of the salty ocean water allowing animals such as the turtle to migrate with relative ease.

The professor, who published his findings in the journal Geology, added: “We found this turtle right on top of the last flood basalts – a large stretch of lava from a series of giant volcanic eruptions.

“That leads us to believe that the warming may have been caused by volcanoes pumping tremendous amounts of carbon dioxide into the Earth’s atmosphere.

“There is evidence that this volcanic activity happened all around the planet – not just the Arctic.

“If it all happened on a short-enough timescale, it could cause a super-greenhouse effect.”

The research team plans to return to the Arctic to look for more fossils.

source: http://www.telegraph.co.uk/earth/environment/climatechange/4419843/Turtle-fossil-shows-how-super-greenhouse-effect-created-tropical-Arctic.html

febbraio 3, 2009 - Posted by | - Rettili, 1 Cretaceo, An. Vertebrates, Antartide, Lang. - Italiano, Mesozoic, P - Paleoclimatologia, Paleontology / Paleontologia | , , , , , , , , ,

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