Seven sites were drilled off the eastern shore of New Zealand during Ocean Drilling Program Leg 181 to gain knowledge of southwest Pacific ocean history, in particular, the evolution of the Pacific Deep Western Boundary Current (DWBC). Holes 1123C and 1124C penetrated lower Oligocene to middle Eocene sediments containing moderately to poorly preserved calcareous nannofossils. Nannofossil assemblages show signs of dissolution and overgrowth, but key marker species can be identified. Nannofossil abundance ranges from abundant to barren. The lower Oligocene sediments are distinctly separated from the overlying Neogene sequences by the Marshall Paraconformity, a regional marker of environmental and sea level change. An age-depth model for Hole 1123C through this sequence was constructed using nine nannofossil age datums and three magnetostratigraphic datums. There is good agreement between the biostratigraphy and magnetostratigraphy, which indicates that the Marshall Paraconformity spans ~12 m.y. in Hole 1123C. The same sequence in Hole 1124C is disrupted by at least three hiatuses, complicating interpretation of the sedimentation history. The Marshall Paraconformity spans at least 3 m.y. in Hole 1124C. A 4- m.y. gap separates lower Oligocene and middle Eocene sediments, and a ~15 m.y. hiatus separates middle Eocene mudstones from middle Paleocene nannofossil-bearing mudstones. Nannofossil biostratigraphy from Holes 1123C and 1124C indicates that the Eocene-Oligocene transition was a time of fluctuating biota and intensification of the DWBC along the New Zealand margin.
1McGonigal, K., and Di Stefano, A., 2002. Calcareous nannofossil biostratigraphy of the Eocene-Oligocene transition, ODP Sites 1123 and 1124. In Richter, C. (Ed.), Proc. ODP, Sci. Results, 181 [Online]. Available from World Wide Web: <http://www-odp.tamu.edu/publications/181_SR/207/207.htm>. [Cited YYYY-MM-DD]
2Department of Geological Sciences, 108 Carraway Building, Florida State University, Tallahassee FL 32306, USA. email@example.com
3Dipartimento di Scienze Geologiche, UniversitÓ di Catania, Corso Italia 55, 95129 Catania, Italy.
Initial receipt: 15 October 2001
Acceptance: 5 March 2002
Web publication: 14 August 2002