Mapping Regional Sedimentary Horizons in the Onshore Baram Delta, Sarawak, from Magnetic and Graviti Data Using Energy Spectral Analysis

Aeromagnetic and airborne gravity data acquired over part of the Baram Basin, Sarawak, Malaysia, was used to estimate depth to economic basement that is the Top Cretaceous (Horizon-1), and depth to three intra-sedimentary horizons: Top and Base of Carbonates (Horizon-2 and Horizon-3), and the top of an additional shallower interface (Horizon- 4). Depths to these horizons were calculated through the analysis of energy spectra of the observed magnetic and gravity fields, while faults and magnetic lineaments were derived through the application of an automatic curve matching (ACM) method based on the Naudy technique. The project involved the application of a new spectral technique, termed the Multi-Window-Test (MWT). The application of the MWT allowed quick estimation of depth to multiple horizons (skeleton maps) and also provided a set of optimal window sizes used for detailed mapping. The potential field derived results correlate well with both seismic and well data. Spectral methods have been successfully applied in the Baram Basin, and the MWT has proved itself a valuable tool in producing a robust interpretation of potential field data.