Late Devonian–Early Carboniferous structure and tectonics of part of the northeast sector of the Darling Basin Conjugate Fault System, western New South Wales

Abstract

The Darling Basin, located in the northern part of the Lachlan Orogen, is cut by the 1000 km long east-northeast-trending Darling Lineament (Fault) which intersects the Koonenberry Fault to the north and the Mt Wintlow High (fault) to the south. During the Lachlan Orogeny these faults formed the Darling Basin Conjugate Fault System (DBCFS) in which the four sectors (NW, NE, SE, SW) showed alternate compression/uplift, and tension/subsidence. The DBCFS underwent five phases of development. During orogenic Phase 5, the northeast sector was in compression, and thick distal braidplains, deposited during orogenic Phase 4, when the sector was in tension, and underlying the older strata, were deformed. The study area has a 4–10 km wide concave northeast-facing fault zone, largely comprising, dextral faults, which is consistent with some tectonic transport of the fault blocks of the zone, largely to the southwest. Faulting followed an earlier period of east–west and southeast–northwest folding. This structure overprints unexposed strata deposited during orogenic phases 1, 2 and 4 in the Lachlan Orogeny as well as pre-Late Ordovician structure (Delamerian Orogeny).

Key Words:

• Darling Basin Conjugate Fault System
• Early Carboniferous deformation
• northeast sector
• Lachlan Orogen
• Delamarian Orogeny

Acknowledgements

Barry Angel and John Sutton, then of Mt Jack and Talalara Stations, respectively, Maurice Jones of Momba Station, and Bill Pick and Alan Harbour of the Paroo National Park are thanked for hospitality and assistance. The National Parks awarded a scientific licence valid for the park. Kevin Morgans, Jack O'Toole, Jack Willoughby and especially Jeff Vaughan assisted in the field (field assistance was essential for the conclusion of the fieldwork); Dr Peter Rickwood kindly reviewed the manuscript; and Mathew Hunt and Chris Meyers are thanked for technical assistance. The journal reviewers, Evan Leitch and Kingsly Mills are thanked for their extensive constructive reviews, which greatly improved the paper.