Depositional and halokinetic-sequence stratigraphy of the Neoproterozoic Wonoka Formation adjacent to Patawarta allochthonous salt sheet, Central Flinders Ranges, South Australia

Abstract

Parts of two third-order Neoproterozoic (Marinoan) depositional sequences are documented in the Wilpena Group (Wonoka Formation and Bonney Sandstone) at Patawarta diapir, located in the central Flinders Ranges, South Australia. These sequences represent an overall regressive succession transitioning upwards from outer to middle wave-dominated shelf deposits to a tidally dominated barrier bar to coastal plain. The lower, middle, upper limestone and green mudstone informal members of the Wonoka Formation comprise the Highstand Systems Tract of the lower sequence. The Sequence Boundary is at the top of the Wonoka green mudstone member and is overlain by the Lowstand Systems Tract of the upper sequence, which includes the lower dolomite, sandstone and upper dolomite beds of the Patsy Hill Member of the Bonney Sandstone. The upper sequence Transgressive Systems Tract comprises the Bonney Sandstone. These units comprise one complete tapered composite halokinetic sequence (CHS). The lower halokinetic-sequence boundary is associated with the Maximum Flooding Surface of the lower depositional sequence and the upper halokinetic-sequence boundary is interpreted as the Transgressive Surface of the overlying depositional sequence where an angular truncation of up to 90° is documented.

Allochthonous salt initiation and advance in the northern Flinders and eastern Willouran ranges, South Australia: Using outcrops to test subsurface-based models from the northern Gulf of Mexico

“…The identification of the breccia at Pinda as relict evaporite bodies was later corroborated by Dyson (1997Dyson ( , 1998, who was also the first to suggest the presence of allochthonous salt in the eastern Willouran Ranges (Dyson, 2004b) and in the northern Flinders Ranges, including Patawarta and Loch Ness diapirs (Dyson, 2005). More recently, our research team has extensively investigated these and other allochthonous salt bodies (Hearon, 2008;Hannah, 2009;Rowan et al, 2010;Hearon et al, 2010a, b;Kernen, 2011;Kernen et al, 2012;Hearon et al, 2012Hearon et al, , 2014.…”

“…Whereas a tectonic (Delamerian) origin has been suggested for deformation of the Callanna Group breccia by some workers (e.g., Mount, 1975;Burns et al, 1977;Mendis, 2002), many others have cited evidence for long-lived passive growth of salt diapirs (e.g., Coats, 1965;Dalgarno and Johnson, 1968;Lemon, 1985;Preiss, 1987;Dyson, 1996Dyson, , 1998Lemon, 2000;Rowan and Vendeville, 2006;Hearon et al, 2010aHearon et al, , b, 2014Kernen et al, 2012). Studies of diapirs in the eastern Willouran and northern Flinders Ranges have yielded abundant evidence, including halokinetic growth strata and unconformities, pseudomorphs after evaporite minerals, and diapir-derived detritus in adjacent strata.…”

“…Geologic map of the southeastern end of the Patawarta diapir based onCoats (1973),Hall et al (1986), and and modified with new field work byKernen (2011) andKernen et al (2012). Black lines with pairs of dots denote salt welds.…”

Evolution of fluvial systems in salt-walled mini-basins: A review and new insights

“…Numerous studies have been previously conducted to demonstrate how various sedimentary environments are influenced by coeval halokinesis that results in high rates of basin subsidence (e.g., Prather, 1998), diversion of sediment transport pathways by uplifting topography (e.g., Kneller and McCaffrey, 1995;Banham and Mountney, 2013a), and reworking of uplifted sediments or diapir-derived detritus (e.g., Lawton and Buck, 2006). Numerous studies show how the effects of these phenomena are expressed in the preserved stratigraphic record: in deep-water environments, turbidity currents can be deflected, diverted or reflected by uplifting salt topography resulting in a complex 3 arrangement of turbidite deposits (Kelling et al, 1979;Kneller and McCaffery, 1995;Byrd et al, 2004;Kane et al, 2012); in shallowmarine environments, enhanced rates of subsidence can locally increase sediment accumulation rates (Dyson, 2004;Kernen et al 2012); in aeolian environments, surface topography arising from saltwall growth can encourage dune-field construction, accumulation and preservation by shielding such environments from reworking by fluvial processes (Venus, 2013). Of these and other studies, only a modest number have attempted to document and account for the style of accumulation of fluvial successions in salt-walled mini-basins and show how fluvial systems can be diverted by salt-wall-generated topography.…”

Geology and tectonics of Neoproterozoic salt diapirs and salt sheets in the eastern Willouran Ranges, South Australia

“…Rowlands et al, 1980;Preiss, 1987;Hearon, 2008;Hannah, 2009;Fig. Dalgarno & Johnson, 1968;Lemon, 1985;Dyson, 1998Dyson, , 2004Rowan & Vendeville, 2006;Hearon et al, 2010a,b;Kernen et al, 2012). Similar lithologies and textures within the Roan Group breccia of the Central Aftrican Copperbelt also suggest an origin as a former layered evaporite sequence (e.g.…”