Influence of inherited basement structures to the development of a sedimentary basin: The Ombilin Basin, Sumatra, Indonesia
Wishnu Triananda Santoso, .
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The Ombilin Basin is one of several Tertiary basins that are presently located in the Sumatran Arc, in close vicinity of the active dextral strike-slip Sumatran Fault System (SFS) and surrounded by an active Quaternary volcanic complex. The Cenozoic geologic history of the basin is subjected to the oblique convergence between the Indo-Australian oceanic plate to the southwestern edge of Sundaland. The Ombilin Basin formed in the Paleogene and as its origin pre-dates the Mid-Miocene SFS, its basin architecture, therefore, forms an excellent recorder of tectonism in the pre- and early history of the SFS. Since the early Paleogene strata are well exposed in this basin, the Ombilin Basin can be considered as an analogue for other Sumatran basins, especially their syn-rift phase. Using surface geology, detailed Digital Elevation Models (DEM), and subsurface data i.e., 2D seismic lines and exploration wells, the study has been conducted to decipher the initial condition, development, and current interior structures of the basin in response to the regional tectonic settings. The research reveals that the Ombilin Basin originated in the extensional phase of Sumatra since the Early Paleogene to the Early Miocene. The geometry and structural development of the basin was then controlled by the NW-SE inherited structural fabrics, which later inverted since the Mid-Miocene onward during the intensive growth of the Barisan Orogeny. A new model for the basin development is then proposed.