A strategy for palinspastic restoration of inverted basins: thermal and structural analyses in SE Australia

Abstract

Abstract Constructing balanced sections across inverted basins is difficult because of the different directions of tectonic transport during extension and compression and the imprecise estimates of the magnitude and timing of inversion events. Sections oriented within 25° of all transport directions can be restored and result in ≤10% error in the amount of extension-compression. Extensional faults are commonly oblique to the transport direction, so the inferred extension direction may be verified by dip analysis of the pre-rift section. Where oblique extensional faults are reactivated during compression, the compressional vector is best determined from the orientation and magnitude of large, curved inversion anticlines. For strongly inverted and eroded anticlines, where T max is not at the present day, palaeotemperature gradients determined regionally from borehole vitrinite reflectance and fission track profiles constrain the amount of denudation allowing reconstruction of the original anticline morphology. The timing of inversion and erosion determined by apatite fission track analysis allow the eroded strata to be replaced on the section and the inversion restored to reveal the amounts of extension and compression and the syn-rift basin morphology, which may constrain hydrocarbon migration paths. For the Otway Ranges in SE Australia 45% Early Cretaceous extension followed by 10% mid-Cretaceous compression are inferred.