Implications of Middle Devonian deformation of the eastern part of the Hill End Trough, Lachlan Orogen, New South Wales

The Hill End Trough is a mid-Silurian to Early Devonian sedimentary basin t hat formed during middle Palaeozoic regional extension in the Eastern Belt of the Lachlan Orogen. Recent mapping suggests that in the Sofala area, the Hill End Trough extends east of the Wiagdon Thrust towards Sunny Corner an d Portland. This means that the eastern part of the trough ts bounded to th e north by Lower-Middle Ordovician turbidites and Upper Ordovician volcanic s. Ordovician basement and fill of the Hill End Trough are juxtaposed acros s a west-northwest-trending fault system that can be traced for 35 km along strike. This fault system, the Wattle Flat-Portland Fault System, is inter preted to be a Middle Devonian north-dipping thrust that carried Ordovician rocks southwards over Lower Devonian rocks of the Hill End Trough during t he first phase of basin deformation. Subsequent east-west folding and parti al reactivation of this fault system followed, either in the Middle Devonia n during regional east-west shortening or in the Carboniferous Kanimblan de formation, after these structurally juxtaposed units had been eroded down t o sea-level and before deposition of the unconformably overlying Upper Devo nian Hervey Group. On a wider scale, there is now accumulating evidence tha t the Middle Devonian Tabberabberan deformation affected a large part of th e Lachlan Orogen.