Structural overprinting criteria determined from regional aeromagnetic data: An example from the Hill End Trough, East Gondwana

Abstract

Determining overprinting relationships in the geological record has underpinned our understanding of the evolution of the Earth and has provided the context in which to interpret geoscientific datasets. Geological overprinting relationships are generally determined from outcrop relationships. When outcrop is absent or limited, overprinting relationships using geological observations is often ineffective or ambiguous. We show how aeromagnetic data can be used to inform superposition of geological structures using a combination of folded stratigraphy, faults (both high angle and low angle), and plutons from the well-exposed Hill End Trough, in the Phanerozoic eastern Lachlan Orogen. Overprinting relationships reveal episodic inversion of the Late Silurian to Early Devonian back arc basin succession, preserved within the Hill End Trough, occurred during superimposed shortening events. The first event resulted in the development of regional folds associated with the Tabberabberan Orogeny and the second event resulted in the development of overprinting north-south and north-northwest trending faults during the Early Carboniferous Kanimblan Orogeny. Inversion structures are overprinted by a Carboniferous granite, which is overprinted by previously unrecognised northeast- and northwest conjugate faults, which we interpret to be related to the Permo-Triassic Hunter Bowen Orogeny.