Ecostratigraphy and sequence biostratigraphy, with a neritic formaminiferal example from the Miocene in Southern Australia

Abstract

The Miocene oscillation is a second order interruption of Cainozoic cooling and falling sea level with a time of warming and relatively high sea level at its zenith, the Miocene climatic optimum. The second order trajectories in putative global sea level, in oceanic δ18O (a proxy for climate change) and δ13C (a proxy for major change in nutrient regime), are punctuated by third order changes, including the Mi glacials. Southern-temperate foraminiferal assemblages provide a profile of neritic biofacies through the oscillation. Plankton and benthos fit the second order and third order scenarios well: there are numerous resonances from the global ocean in this regional neritic realm. The cycle TB2 is a biofacies entity as well as a physical entity, and so too are most of its third order components. The influence of the Monterey carbon excursion and the climatic optimum are visible in this biotic succession. We corroborate the prediction that a trophic resource continuum expands in a warming and transgressive trend and, at the same time, responding more strongly to environmental fluctuations. We cannot corroborate the notion of coherent biofacies recurring through the succession as the environment shifts from warming to upwelling and back. There is a strong sense of a community "evolving" through time whilst spreading and adapting ad hoc to the shifts in physical environment, rather than of discrete communities tracking those shifts.