Cenozoic Eucla Basin and associated palaeovalleys, southern Australia — Climatic and tectonic influences on landscape evolution, sedimentation and heavy mineral accumulation

Transcontinental Cainozoic paleovalleys of Western Australia

“…The recent age of endorheism development, limited sediment influxes over the period, and limited aeolian reworking altogether explain the preservation of paleovalleys in the topography of Western Australia (Alley et al, 2009;Beard, 2002;Beard, 1973;Bunting et al, 1973;de Broekert and Sandiford, 2005;Hou et al, 2008;van de Graaf, 1977). Analysis of the drainage pattern indicates that the network of flow lines has remained stable since its formation during the Albian emergence, with only sporadic changes in the connectivity of flow lines due to river diversions.…”

“…The goal is to explore the consequences of a diminishing water balance (gains minus losses) on river incision, sediment deposition, and the size of lakes produced over time (Figure 2). This step is constrained 1) by various independent environmental proxies of precipitation and temperature Martin, 2006;McGowran et al, 2004;McLaren et al, 2014), 2) by the erosional response of rivers to post Middle Miocene tectonic deformation (Bunting et al, 1973;Cope, 1974;McGowran et al, 2004;Müller et al, 2012;Whitney et al, 2016) and erosional shoreline formation during the Middle Miocene north of the GAB (Hou et al, 2003;Hou et al, 2008), inferred from the present-day topography (see following section), 3) by the amount of sediment stored within valleys (Alley et al, 2009;Beard, 2002;Clarke, 1994a;de Broekert and Sandiford, 2005;Jones, 1990), and 4) by the evolution of lake salinity (Clarke, 1994b;English et al, 2001;Zheng et al, 1998).…”

“…Aridification of the continental interior initiated between the Late Eocene and the Late Miocene (Martin, 2006;McLaren et al, 2014) inducing a decrease in terrigenous sediment and freshwater delivery to the shelves, with sediment retention on land, before complete drying of the valleys in the Late Pliocene to Early Quaternary (Chen and Barton, 1991;Dodson and Macphail, 2004;English et al, 2001;Zheng et al, 1998). This evolution thereby influenced the formation of potential hydrocarbons traps and seals in the Cenozoic series on the shelves (Romine et al, 1997;Sit et al, 1994), the accumulation of heavy mineral placers along paleoshorelines and paleovalleys (Hou et al, 2003;Hou et al, 2008), and the retention of dissolved uranium in phreatic calcretes in drying valley floors (Jaireth et al, 2010). Besides, increased dominance of groundwater over surface routing in the context of an almost passively deforming surface has probably changed groundwater redistribution across the continental interior.…”

Cenozoic post-breakup compressional deformation and exhumation of the southern Australian margin

“…The Eucla Basin extends ~2000 km from west to east and ~500 km from north to south, thereby constituting the largest Cenozoic basin on the southern margin (Hou et al, 2006(Hou et al, , 2008. Though extensive, the Eucla Basin succession is relatively thin (up to 800 m) (James et al, 2006).…”

“…A number of recent studies have identified post-breakup uplift and tilting of these sediments through examination of palaeo-shoreline associated with carbonate deposition that are preserved on the Nullarbor Plain (Fig. 4) (Hou et al, 2006(Hou et al, , 2008Sandiford, 2007). Sandiford (2007) reports the occurrence of mid-late Eocene (~41-39 Ma) palaeo-shoreline features including offshore barrier systems, marginal lagoons and inundated valleys that extend up to ~400 km inland of the present-day shoreline.…”