A GLOBAL CORRELATION OF BIOZONES ACROSS THE ORDOVICIAN SILURIAN BOUNDARY

Latest Ordovician to earliest Silurian (through the Hirnantian Substage) strata and fossils are widely distributed on the Yangtze platform. Mu (1974) first erected the Ashgillian graptolite zones in this region. In the recent years, the present authors re studied 4 sections (Wangjiawan and Fengxiang, Yichang; Honghuayuan, Tongzi and Ludiping, Songtao) through this interval with continuous collections. Based on their detailed works the Ashgillian to earliest Llandovery biozones of the Yangtze region have been revised as follows. Llandovery (Silurian) Cystograptus vesiculosus Biozone Parakidograptus acuminatus Biozone Akidograptus ascensus Biozone Ashgillian (Ordovician) N. persculptus Biozone Hirnantia Dalmanitina N. extraordinarius N. ojsuensis Biozone Fauna Paraorthograptus pacificus Biozone Diceratograptus mirus Subzone Tangyagraptus typicus Subzone Un named Subzone Dicellograptus complexus Biozone Dicellograptus complanatus Biozone/ Foliomena Nakinolithus Fauna A global correlation has been discussed in detail and shown in Table Ⅰ among the Yangtze region and Dob's Linn, Scotland, Spain and Portugal, Thuringia Saxonia Bavaria, Germany, Bohemia, Poland, Southern Kazakhstan, Kolyma, Northeastern Siberia, Malaysia Peninsula, Canadian Yukon and Canadian Arctic Islands, Nevada, USA, San Juan and Talacasto, Argentina, and Darraweit Guim, central Victoria, Australia.