Radiometric dating of ordovician period
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).
The Cambrian is divided into four epochs (series) and ten ages (stages).
Currently only two series and five stages are named and have a GSSP.
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.
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).
pedum in Namibia, Spain and Newfoundland, and possibly, in the western USA. pedum overlaps the range of the Ediacaran fossils in Namibia, and probably in Spain.
The Cambrian Period followed the Ediacaran Period and was followed by the Ordovician Period.