Biostratigtaphical correlations around the Oxfordian/Kimmeridgian boundary

Andrzej Wierzbowski


Within the ammonite faunas occurring in the Bimammatum and the Planula Zones of the Upper Oxfordian in Central Poland, there occur aside of the overdominating Submediterranean forms, also those of the Subboreal/Boreal affinity. The oldest are some Ringsteadia and Amoeboceras indicating the approximate correlation of the lowermost part of the Bimammatum Zone with a lower, but possibly not the lowest, part of the Pseudocordata Zone. The younger is Amoeboceras bauhinia (OPPEL) occurring from the lower part of the Planula Zone which indicates the correlation of the major part of the Planula Zone with a lower part of the Baylei Zone. This shows that the boundary of the Oxfordian and Kimmeridgian in the Submediterranean zonal scheme runs relatively too high when compared with that of the Subboreal/Boreal zonal schemes.

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