Controls on the Geometry and Evolution of Deep-water Fold Thrust Belt of the NW Borneo.

The key driving mechanisms for establishing deep-water fold-thrust belt are either lithospheric stress or gravity-driven associated with margin instability or a combination of both. Despite long academic interest, we still lack of detailed understanding of the interaction between the deformation mechanisms (gravity- and tectonic-driven). The results of an evaluation of the interaction between the deformation mechanisms, with focused attention upon the NW Borneo deep-water fold-thrust belt, are reported. A methodology integrating a detailed structural analysis of the deep-water fold-thrust belt from the available subsurface data and equivalent onshore outcrop is utilized in this study. Detailed structural analysis of 2D seismic profiles is used to present a basin-scale seismic-stratigraphic framework and detailed description of the general appearance of the deformational style along the deltaic system. Sub-seismic scale investigation of well-exposed outcrops onshore NW Sabah is used to extract information on onshore tectonic deformation, making it possible to evaluate the differences of structural architecture related to different deformation mechanisms. The result has led to an improved understanding of the regional-scale structural geometry along the NW Borneo margin. Regional scale cross-sections are used to demonstrate a regional-scale analysis of the NW Borneo margin that includes structural restoration. The results allow an assessment of the relative timing of deformation, the domain interaction and the possible processes and parameters that control deformation. This has led to an improved insight relating to the kinematic nature of the allochthon and the interaction between the deformation mechanisms. Structural restorations are also used to evaluate of areas of compressionally and extensionally dominated systems, in order to verify the main proses responsible for the margin evolution. This study illustrates outcrop-scale to seismic-scale analysis and quantitative measurements combined with seismic interpretations, with the aim to identify the interaction between gravity-and tectonic-driven deformation, and their controls on the geometry and evolution of deep-water fold-thrust systems. Additionally, the margin evolution and the implications on NW Borneo are evaluated.