Middle to Late Devonian distal braidplain deposition in the northeast sector of the Darling Basin Conjugate Fault System, near White Cliffs settlement, western New South Wales

Abstract

Sandstone-rich, 6 km-thick, Eifelian–Frasnian strata of the northeast sector of the Darling Basin Conjugate Fault System, lie north of the Darling River Lineament, east of the Koonenberry Fault, and south of the Olepeloko Fault. Fossils are very rare in the study area: exceptions are in the Skolithos-rich beds of the Paroo National Park, and the early Eifelian fish-fragment horizon near Mt Jack Station. Four marker horizons are known southeast of the Paroo National Park: (i) the Mt Jack fish-fragment horizon; (ii) a Skolithos-rich belt at Momba Station; (iii) the mid-Givetian Keginni Conglomerate Member; and (iv) a ∼20 m-thick vein quartz clast-rich unit that crops out near the base of the Frasnian strata. Four braidplains are mapped: (i) White Cliffs (largest); (ii) Mt Jack; (iii) Bullocky Bore; and (iv) the distal part of the Keginni Conglomerate Member. Sediment derivation was from west of the Koonenberry Fault (White Cliffs Braidplain) from the northwest (Mt Jack Braidplain), from the north (Bullocky Bore Braidplain) and from the southeast (Keginni Conglomerate Braidplain). The braided streams/rivers depositing the sheet braidplains were very shallow, and sheet-flood deposition on the braidplains was widespread.