PALINSPATIC RECONSTRUCTION OF THE BIRD HEAD POP-UP STRUCTURE AS A NEW MECHANISM OF THE SORONG FAULT

摘要

The main concerns of this research are the occurrence of NE-SW trending Sorong Fault to the northwest of the Bird's Head of Papua and its activities. The researched area is bounded by Waigeo Island on the northwest, Ayamaru Platform, Salawati Basin and Batanta Island on the southeast, south and southwest respectively. This fault is a left lateral fault system which cuts along the northern margin of the Bird's Head since Miocene, confirmed by its activities during the deposition of Miocene sequence. Sorong Fault is the main structural control for hydrocarbon play in Salawati basin.More than 100 seismic lines have been interpreted along the offshore of NW Bird Head area. These interpretations showed the development of pop-up structure at NW Bird Head area as the evidence of the Sorong Fault activities, which cut Palaeozoic through the Tertiary rocks. Grabens development at the Eocene through the Oligocene sequence was related with passive margin NW shelf Australia rifting since the Mesozoic. Therefore, palinspatic reconstructions will be used to evaluate this fault and its correlation with hydrocarbon play in NW Bird Head.This pop-up feature becomes an interesting subject because it was formed at an extreme depth in the basin. This is a unique feature that is not observed in other place. They are well developed in the northern part of the area, trending to the southwest and are associated with the morphologically high area in the North of Bird Head, known as Mar High, which has been reported to have a series of Mesozoic to Miocene sequence in outcrop.Seismic interpretations and palinspatic reconstructions suggest that there is another strike slip fault to the North of the Bird's Head area that couples with the well known Sorong Fault. Both have been active since the Miocene related to convergent plate interaction between Pacific Plate and NW Australian Passive Margin.