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Boundaries of dating book

The boundaries between the continents of Earth are generally a matter of geographical convention. The number of continents is most commonly considered seven but may range as low as four when the Americas and Afro-Eurasia are each considered a single continent.

According to the definition of a continent in the strict sense, an island cannot be part of any continent, but by convention and in practice most major islands are associated with a continent.

Therefore, the age range of 635 to 542 million years is based on correlations to other countries where dating has been possible.

The base age of approximately 635 million years is based on U-Pb (uranium-lead) isochron dating from Namibia Applying this age to the base of the Ediacaran assumes that cap carbonates are laid down synchronously around the world and that the correct cap carbonate layers have been selected in such diverse locals as Australian and Namibia.

It is named after the Ediacara Hills of South Australia.

The Ediacaran Period's status as an official geological period was ratified in 2004 by the International Union of Geological Sciences (IUGS), making it the first new geological period declared in 120 years.

Although the period takes its name from the Ediacara Hills where geologist Reg Sprigg first discovered fossils of the eponymous Ediacara biota in 1946, the type section is located in the bed of the Enorama Creek The Ediacaran Period overlaps, but is shorter than the Vendian Period, a name that was earlier, in 1952, proposed by Russian geologist and paleontologist Boris Sokolov.

The Vendian concept was formed stratigraphically top-down, and the lower boundary of the Cambrian became the upper boundary of the Vendian.

At its nearest point, Morocco and the European portion of Spain are separated by only 13 kilometres (8.1 miles).

The Portuguese Atlantic island possession of the Azores is 1,368 km (850 mi) from Europe and 1,507 km (936 mi) from Africa, and is usually grouped with Europe if grouped with any continent.

This is controversial because an age of about 580 million years has been obtained for glacial rocks in Tasmania which some scientists tentatively assign to those just beneath the Ediacaran rocks of the Flinders Ranges.

The fossil record from the Ediacaran Period is sparse, as more easily fossilized hard-shelled animals had yet to evolve.

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