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pedum ichnofossil assemblage that is now formally used to correlate the base of the Cambrian.The ash horizon in Oman from which this date was recovered corresponds to a marked fall in the abundance of carbon-13 that correlates to equivalent excursions elsewhere in the world, and to the disappearance of distinctive Ediacaran fossils (Namacalathus, Cloudina).Because the international stratigraphic subdivision is not yet complete, many local subdivisions are still widely used.In some of these subdivisions the Cambrian is divided into three epochs with locally differing names – the Early Cambrian (Caerfai or Waucoban, mya; also known as Late Cambrian, Merioneth or Croixan).However, average temperatures were 7 degrees Celsius higher than today.There were likely polar ice caps and a series of glaciations, as the planet was still recovering from an earlier Snowball Earth.

Discovery of this fossil a few metres below the GSSP led to the refinement of this statement, and it is the T.The Cambrian marked a profound change in life on Earth; prior to the Cambrian, the majority of living organisms on the whole were small, unicellular and simple; the Precambrian Charnia being exceptional.Complex, multicellular organisms gradually became more common in the millions of years immediately preceding the Cambrian, but it was not until this period that mineralized—hence readily fossilized—organisms became common.The lower boundary of the Cambrian was originally held to represent the first appearance of complex life, represented by trilobites.The recognition of small shelly fossils before the first trilobites, and Ediacara biota substantially earlier, led to calls for a more precisely defined base to the Cambrian period.

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