Abstract

A new understanding of Southeast Asian Cenozoic biostratigraphy has resulted from integrated studies following recent extensive deepwater drilling activity. Previous biostratigraphy of the region has more often than not been focused on shelf sediments where transgressive and highstand systems tracts tend to be predominant. Such proximal sediments are by their nature subject to periods of erosion or non-deposition, and much of geological time is consequently not represented. Furthermore, local and regional tectonics can result in even more pronounced 'missing sections' in proximal settings, as well as extensive redeposition of reworked continental material in marine and deepwater marine settings.

Widespread unconformities and hiatuses are a challenge to complete integration of biostratigraphy and chronostratigraphy, especially in coastal plain and shelf settings where, typically, insufficient consideration has previously been given to understanding gaps in the stratigraphic record. It can, however, be just as important to understand what is missing from a particular stratigraphic section, as it is to analyze and understand what is present. In contrast the more distal deepwater sediments, which have recently been the focus of much attention, are proving to contain relatively complete stratigraphic sections.

Deepwater sections might typically consist of thick lowstand facies and condensed transgressive and highstand facies. Close biostratigraphy and palynofacies sample spacing enables the recognition of significant stratal surfaces and subsequent calibration with globally-significant sequence boundaries and maximum flooding events.