Jane Cunneen¹, Myra Keep²

(1) The University of Western Australia, Nedlands, Australia
(2) University of Western Australia, Perth, Australia

ABSTRACT: Analysis of Neogene Structures as a Tool for Determining Trap Breach in the Timor Sea, Northwest Australia

Neogene deformation in the Timor Sea has caused significant left-lateral transtensional reactivation of Mesozoic rift structures. Given that some hydrocarbon traps in the Timor Sea have been charged in the past 3 Ma, the Neogene structural history and fault linkage are crucial in understanding structural controls on trap formation and breaching in this area.

Fault growth curves from the Laminaria basement high area show several pulses of movement during the Neogene, with the youngest faults occurring adjacent to the Timor Trough. Structural styles include net normal and left-lateral strike-slip faults, as well as controversial "hourglass" faults. The hourglass faults, which appear to cross each other within the early Tertiary horizons, may be related to detachments within the Neogene section, with the crossover points representing areas of high strain.

Although most of the faulting is confined to the Neogene section, some faults form a hard link with reactivated Mesozoic structures. The proportion of hard linkage increases with the amount of strain and is dominant on the northern margins of basement highs that flank the Timor Trough. Regional 2D and detailed analyses of 3D seismic data suggest that the displacement sense and amounts vary with proximity to the Laminaria basement high. Contemporary stress orientations also vary locally around the Laminaria high, and the effects of present day stress in reactivating faults is important in understanding the structural controls on the Laminaria/Corallina fields. Smaller than expected offsets on major faults in the area indicate that significant deformation may also be distributed on sub-seismic scale faults.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado