Eocene to Miocene stratigraphic controls in the far East Java Sea: Implications for stratigraphic studies

摘要

A comparison is made between an existing stratigraphic model and new data in the same area of southeast Sundaland; the composite tectonic plate that underlies much of SE Asia. A previous view that the Neogene eustatic stratal signature was detectable is refuted with new well data. A new interpretation of stratigraphy and regional geology is made through an evidence-based, inductive approach. Care is taken in assessing the precision and accuracy of observational inputs, similar to confidence ranges declared by other sciences, especially in determining geological age and fades. At a low resolution the new interpretation appears to match the expected rift phase which gradually faded to basinal sag, then mild compression in Miocene times. However it also identifies distinct episodes of sedimentation, separated by times of rapid change in the basin morphology. These times of change correlate over a wide area, and appear to be the primary controls on sedimentation. Their highly variable geographic intensity identities them as having been produced by tectonic movements. The previous model-based and deductive interpretation of the area can be summarised as being introspective, with the focus being on the idealised, technical model rather than a wider reality. The evidence-based, inductive approach is outward looking as it is built on, and seeks verification through, cross-checking data types. It is also predictive and potentially falsifiable, that is, it has a stronger emphasis on science rather than technique. For example, a sudden reduction in rates of sedimentation coinciding with the Eocene to Oligocene boundary predicts the sudden appearance and growth of sediment traps (new basins) in a proximal location, and the variable polarity of vertical movement through the Oligocene and up to the Oligo-Miocene boundary predicts non-epeirogenic type tectonic movement. Both these hypotheses can be tested and augmented. This review argues that a change from model-based and deductive approaches to an inductive method, as well as more qualified descriptions of data reliability, is necessary to develop a better understanding of tectonically active and complex regions. The currently popular method of having a stratigraphic summary based on a poorly described relative sea-level curve and an un-evaluated rift to sag basin genesis is neither rigorously deductive nor properly inductive, and has little scientific (predictive) value. A new tectono-stratigraphic method is needed to improve our understanding of both stratigraphy and the Cenozoic tectonic processes that developed SE Asia.