Precambrian fossils are no longer to be considered oddities of questionable scientific or practical value. New discoveries, new techniques, and the impact of radiometric dating on Precambrian stratigraphy make it possible to set out for the first time the sequence of fossils through Early, Middle, and Late Precambrian time. They fall into four major classes: microfossils (appearing first), stromatolites (including index fossils of economic importance), megafossils (rich faunas in Late Precambrian, with at least 25 taxa representing 6 phyla of soft-bodied organisms at one locality in Australia), and trace fossils (possibly the earliest remains of animals). These occurrences can be related to the history of the biosphere and to modern studies of biochemical evolution. Place in proper relation to the geotectonic framework of sedimentation they support the view that the search for oil should be extended beyond the Cambrian frontier into at least Late Precambrian sedimentary basins. Considerations of the definition of the base of the Cambrian and of events at that time also support this view.

End_of_Article - Last_Page 341------------