Cambrian Evolutionary Radiation: Context, correlation, and chronostratigraphy—Overcoming deficiencies of the first appearance datum (FAD) concept

摘要: Abstract Use of the first appearance datum (FAD) a fossil to define global chronostratigraphic unit's base can lead intractable correlation and stability problems. FADs are diachronous—they reflect species' evolutionary history, dispersal, biofacies, preservation, collection, taxonomy. The Cambrian Evolutionary Radiation is characterised by diachronous FADs, biofacies controls, provincialism taxa ecological communities that confound stable Lower chronostratigraphy. series stage definitions require greater attention assemblage zone successions non-biostratigraphic, particularly carbon isotope, techniques such as those Ediacaran System base. A redefined, basal Trichophycus pedum Assemblage Zone lies above highest Ediacaran-type biotas (vendobionts, putative metazoans, calcareous problematica Cloudina ) Asteridium tornatum–Comasphaeridium velvetum (acritarchs). This definition likely close correspondence origin local FAD T. preserves Fortune Head, Newfoundland, GSSP allows presence sub-Cambrian, branched ichnofossils. sub-Tommotian-equivalent Stage 2 (a suggested “Laolinian Stage”) should be defined I′/L4/ZHUCE δ 13 C positive peak, bracketed lower ranges Watsonella crosbyi Aldanella attleborensis (molluscs) Skiagia ornata–Fimbrioglomerella membranacea W. A. cannot they even in Newfoundland “type” Zone. Series based on owing skeletalised metazoans Terreneuvian–Series boundary interval heterochrony oldest trilobites. 3 “Lenaldanian Series” “Zhurinskyan Stage,” new) proposed at Siberian Atdabanian IV peak—which correlates into South China, Avalonia, Morocco assigns trilobites terminal Terreneuvian Series.