| Popis: |
The Columbus Basin offshore Trinidad is a thin-skinned detached basin characterised by large-scale, syn-depositional gravitational extensions faulting and rapid creation of accommodation filled by thick sedimentary sequences since the Late Miocene. The investigation of extensional growth faults using fault displacement back-stripping is based on faults and horizons mapped on a high-quality 3D seismic survey. The study area contains three major block-bounding normal faults, with maximum throws of 1400-2500 m. Smaller fault systems show various evolutionary patterns, including (1) fault linkage after breaching of a relay ramp, and (2) upward splaying into several fault segments from a continuous fault at depth. This suggests that geometric linkage and kinematic linkage are not necessarily simply related. Most faults have higher throw rates during their early stages that decrease until their deaths. The largest faults have throw rates of up to 2.5-3.5 mm/a, whilst the smaller ones are generally below 1 mm/a. Variations from this general trend are attributed to fault Interaction, non-uniform basin extension and the migration of the deltaic depocentre, which governs the location of primary sediment deposition and, therefore, gravitational collapse. Fault activity was reconstructed for successive time intervals from 2.78 Ma to the present- day. The data show pronounced seaward migration of fault activity for progressively younger horizons which is attributed to the progradation of the shelf-edge delta. Initiation of a major block-bounding fault results in numerous smaller faults in its hanging wall, whose activity rapidly decreases as soon as the next major basinward fault becomes active. The total throw rate across the study area varies over the investigated time span. This may reflect broader regional variations of fault activity that might be controlled by the rate of sediment supply and the location and migration of the centre of gravitational collapse. A series of vertically persistent, small-scale hanging wall anticlines that are located at kinks in the fault plane and associated with the largest faults in the study area are interpreted as remnants of fault linkage. In this study, the fault interaction and evolution of several extensional faults in the Columbus Basin were investigated and the throw rates at which these faults moved were determined. Within the study area, the temporal and spatial migration of active faulting in a detached gravitational basin was quantified. Open Access |
