02254nas a2200181 4500008004100000245010600041210007300147260005000220300001200270490002800282520160900310100001401919700001601933700002001949700001601969700001901985856006802004 2016 eng d00aThe Precambrian–Phanerozoic and Ediacaran–Cambrian Boundaries: A Historical Approach to a Dilemma0 aPrecambrian–Phanerozoic and Ediacaran–Cambrian Boundaries A Hist aLondon, EnglandbGeological Society of London a311-3490 vSpecial Publication 4483 a

The Cambrian was originally defined as a rock interval with a trilobite-dominated fauna that overlay a presumed biologically barren Precambrian epoch. Work to formally define the Cambrian base arose after the discovery of Precambrian macrofossils in South Australia. The Working Group on the Precambrian–Cambrian Boundary (set up in 1972) promoted an emphasis on an extended pre-trilobitic interval with mineralized skeletal elements (small shelly fossils or early skeletal fossils). The study of early skeletal fossils made the Ulakhan-Sulugur (Siberia) and Meishucun (South China) sections candidates for the basal Cambrian Global Stratotype Section and Point (GSSP), but difficulties in correlation and the taxonomy of early skeletal fossils did not allow the selection of a reliably correlative horizon. Bilaterian ichnofaunas below the first diverse early skeletal fossils suggested the definition of a Cambrian base GSSP below the early skeletal fossils. Work on the thick, stratigraphically continuous and fairly unifacial sections in the Burin Peninsula, southeastern Newfoundland led in 1992 to an ichnofossil-defined GSSP at Fortune Head. Despite arguments for a revision and redefinition of the lower boundary of the Cambrian System, the best definition of the basal Cambrian GSSP is at Fortune Head and does not rely on the Treptichnus/Trichophycus pedum (abbreviated below as T. pedum) first appearance datum, but rather on the base of the T. pedum Assemblage Zone at the highest occurrence of Ediacaran taxa and in the lower range of T. pedum.

1 aGeyer, G.1 aLanding, E.1 aBrasier, A., T.1 aMcIlroy, D.1 aMcLoughlin, N. uhttp://sp.lyellcollection.org/content/early/2016/11/01/SP448.10