THE HAMMERHEAD DELTA—DEEPWATER FOLD-THRUST BELT, BIGHT BASIN, AUSTRALIA: 2D GEOMECHANICAL AND KINEMATIC RECONSTRUCTIONS
Here, we have interpreted a regional two-dimensional seismic dataset in order to construct a three-dimensional geological model of the Hammerhead Delta—Deepwater Fold-Thrust Belt. This model was used to constrain the structural geometry of the system, and to determine if the amount of observed extension could be balanced against the amount of observed shortening in the system.
Two different restoration techniques were applied to the Hammerhead Delta—Deepwater Fold-Thrust Belt, a Finite Element Method-based two-dimensional geomechanical restoration (using Dynel) and a geometric-based two-dimensional kinematic restoration (using MOVE). Both modelling techniques indicate that the Hammerhead Delta—Deepwater Fold-Thrust Belt system is a near-balanced system, demonstrating approxmiately equal amounts of up-dip extension and down-dip compression during formation.
Although the system is nearly balanced, the models demonstrate slightly more extension than compression (< 2%), a result that is unusual for a passive margin delta—deepwater fold-thrust belts. Other passive margin systems demonstrate larger amounts of extension compared to shortening, due to the regional-scale progradational nature of the systems. These results suggest that the near-balanced geometry of the Hammerhead Delta—Deepwater Fold-Thrust Belt is consistent with a sudden decrease in sediment supply during the upper Maastrichtian, resulting in a cessation of prograding fault activity. Thus, the system failed to develop into an extensive passive margin delta—deepwater fold-thrust belt.