Abstract

A late Oxfordian to early Berriasian nannofossil biostratigraphic framework has been developed from research on D.S.D.P Site 534 and composite outcrop sections in southeastern France and central Portugal. It is built on published nannofossil biostratigraphic studies of the same deep-sea site, as well as those from outcrop sections in both southeastern France and northern Italy.

These results were first applied to the subsurface in 16 wells in the East Texas Basin (Leon and Robertson Counties) during the 1990s and then in six wells in the Haynesville Basin in northeastern Texas in 2009. The relative stasis in nannofossil evolution during the middle Oxfordian to Kimmeridgian and subsequent major Tithonian radiation necessitated the unconventional use of fossil appearances (i.e., bases) during our examination of mostly ditch-cutting samples from these onshore wells. Nannofossil biostratigraphic resolution was further challenged by sparse nannofossil recoveries, which were exacerbated in the older carbonates.

The reliability of the individual nannofossil events are assessed for both the research and subsurface sections. Two new Kimmeridgian species, Bucanthus lusitanicus and Calcivascularis cassidyi, are described herein. One new combination is also introduced.