Preliminary report on the Callovian/Oxfordian boundary in the Central Russia

Kiselev D.N., Rogov M.A.

            Last decades there are many papers devoted to biostratigraphy of the Middle-Upper Jurassic boundary beds were published and some good sections for the GSSP were suggested (for review see Page, 2002). Throughout in the Russia as well as in the Europe with rare exception Callovian-Oxfordian boundary traced by the condensed and incomplete deposits (Brochwicz-Lewiński et al., 1984). Only in the temporal quarry near Saratov good and rich by the taxa and individuals ammonite succession through these levels occur (Mitta, 2003; Rogov, Egorov, 2003). As in the Oxford Clay facies in southern England, these beds have the potential to yield information on microfossil assemblages. In our opinion this section is good candidate for the Callovian/Oxfordian boundary GSSP. Ammonite succession consists from taxa of the different palaeobiogeography confined areas. Therefore we can build few independent scales of faunal horizons, based on the Boreal (Cardiocaratid), Subboreal (Kosmoceratid) and Submediterranean (Aspidoceratid and Oppeliid) ammonites. Here we proposed summary of the ammonite succession within faunal horizons (see also Gulyaev et al., 2002):

Upper Callovian, Lamberti Zone, Lamberti Subzone

lamberti horizon Callomon, 1964

Quenstedtoceras lamberti (Sow.), Q. zieteni Maire, Q. brasili R.Douv., Vertumniceras vertumnum (Leck.), Kosmoceras subspinosum (Nik. et Rozhd.), K. duncani (Phill.), Peltoceras sp.

mojarowskii horizon Gulyaev et al., 2002

Cadoceras williamsoni (  ), Kosmoceras rotundum (Quenst.), K. mojarowskii (Nik. et Rozhd.), Sublunuloceras cf. nodosulcatum (Lah.), Putealiceras douvillei Jeannet, Brightia sp., Grossouvria sulcifera (Opp.)

paucicostatum horizon Marchand, 1979

Vertumniceras paucicostatum (Lange), V. mariae (Orb.), Quenstedtoceras orbis Maire, Cardioceras (Scarburgiceras) sp. nov., Choffatia poculum (Leck.), Euaspidoceras sp., Sublunuloceras cf. deperditum (Rollier).

Lower Oxfordian, Mariae Zone

Scarburgense Subzone

scarburgense horizon Buckman, 1913

Cardioceras scarburgense (Young et Bird), Vertumniceras luppovi (Amannijasov), Sublunuloceras deperditum (Rollier), Euaspidoceras sp.

woodhamense horizon Fortwengler & Marchand, 1994

Cardioceras woodhamenseArkell.

Praecordatum Subzone

unnamed horizon

Cardioceras praecordatum R.Douv., Peltoceras sp.

renggeri horizon Loriol, 1898

Creniceras renggeri (Opp.), Richeiceras aff. richei (Lor.), R. dentostriatum (Quenst.), R. sarasini (Lor.), Cardioceras cf. alphacordatum Spath, Peltoceras sp.

References. Brochwicz-Lewiński W. et al. (1984). C.R. Acad. Sc. Paris. 1984. T. 299., sér. II. no.19: 1359-1362; Gulyaev D.B. et al. 6^th International Symposium on the Jurassic System, September 12-22 2002, Palermo. Abstracts and program: 81-82; Mitta V.V. (2003) VM Novitates. no.11. 21 p. [in Russian]; Page K.N. (2002) 6^th International Symposium on the Jurassic System, September 12-22 2002, Palermo. Abstracts and program: 141-142; Rogov M.A. & Egorov E.Yu. (2003) Mat. 3^rd Conf. Lect. in Memory of Yanshine. Moscow: Nauchny Mir: 245-248.