Carboniferous conodont biostratigraphy of the Dianzishang section, Zhenning, Guizhou, South China

A preliminary summary of the lower Visean to uppermost Moscovian (Carboniferous) conodont succession and biostratigraphy of the Dianzishang section in Zhenning, Guizhou, South China is presented. Eleven conodont zones, in ascending order, can be recognized:Gnathodus praebilineatus,Gnathodus bilineatus,Lochriea ziegleri,Declinognathodus noduliferus,Neognathodus symmetricus, ‘Streptognathodus’expansus(primitive form), ‘Streptognathodus’expansus,Mesogondolella donbassica – Mesogondolella clarki,Idiognathodus podolskensis,Swadelinafauna andIdiognathodus swadeizones. The first occurrences ofLochriea ziegleriat the base of the Serpukhovian Stage,Declinognathodus noduliferus noduliferusat the base of the Bashkirian Stage and ‘Streptognathodus’expansusat the base of the Moscovian Stage are recognized. The definitions of these stage boundaries, as well as that of the base of the Kasimovian Stage are discussed. Correlations with the Naqing section in South China, Russian and North American sections, as well as other important sections in the world, are considered.

New occurrences of the Pennsylvanian index ammonoidDunbaritesfrom the North American midcontinent

Ten newly recoveredDunbaritesspecimens significantly extend the known stratigraphic range ofDunbarites.These include the first documented Midcontinent Basin records of the Missourian type speciesDunbarites rectilateralis(Miller, 1930) from north-central Oklahoma. Additional species ofDunbaritesfrom south-central Oklahoma and north-central and West Texas are described asDunbarites wewokensisn. sp. andDunbarites boardmanin. sp. AlthoughDunbaritesis an extremely rare component (~0.025 percent) of Middle and Upper Pennsylvanian ammonoid assemblages, Ruzhencev and Bogoslovskaya (1971, 1978) suggested thatDunbaritesandParashumarditesRuzhencev, 1939 be used as genozone markers for the Kasimovian [Zhigulevian] Stage (Missourian in North America). As demonstrated by this report, the range ofDunbaritesis not confined to the Kasimovian, thereby precluding its use as a Kasimovian Stage indicator.