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

Abstract

The northern Flinders Ranges and eastern Willouran Ranges, South Australia, expose Neoproterozoic salt diapirs, salt sheets, and associated growth strata that provide a natural laboratory for testing and refining models of allochthonous salt initiation and emplacement. The diapiric Callanna Group (∼850-800 Ma) comprises a lithologically diverse assemblage of brecciated rocks that were originally interbedded with evaporites that are now absent. Using stereonet analysis to derive three-dimensional information from two-dimensional outcrops of stratal geometries flanking salt diapirs and beneath salt sheets, we evaluate 10 examples of the transition from steep diapirs to salt sheets, 3 of ramp-to-flat geometries, and 2 of flat-to-ramp transitions.Stratal geometries adjacent to feeder diapirs range from a minibasin-scale megaflap to halokinetic drape folds to high-angle truncations and appear to have no relationship to subsequent allochthonous salt development. In all cases, the transition from steep diapirs to salt sheets is abrupt and involved piston-like breakthrough of thin roof strata, which permitted salt to flow laterally. We suggest two models to explain the transition from steep diapirs to subhorizontal salt: (1) salt-top breakout, where salt rise

Numerical modelling study of mechanisms of mid‐basin salt canopy evolution and their potential applications to the Northwestern Gulf of Mexico

“…Here, salt can either move directly along the surface or seafloor or, as is more common in submarine conditions, move under and together with its sedimentary roof (Hudec & Jackson ; Hearon et al . ).…”

“…; Giles & Rowan ; Hearon et al . ). Significant developments have been made in understanding the mechanisms of salt‐sheet advance through the wealth of data collected in the last decades (Hudec & Jackson ; Hearon et al .…”

“…Significant developments have been made in understanding the mechanisms of salt‐sheet advance through the wealth of data collected in the last decades (Hudec & Jackson ; Hearon et al . ). Salt‐sheet advance, which follows the earlier ‘extrusion’ phase, is primarily controlled by the basal slope, the salt viscosity, and the ratio between salt‐supply rate and sediment accumulation rate (Fletcher et al .…”

The transition from salt diapir to weld and thrust: Examples from the Northern Flinders Ranges in South Australia

“…The interested reader will find thorough sedimentary and stratigraphic descriptions in publications covering the regional geology of the area: Dalgarno and Johnson (1968), Dalgarno (1998), Preiss (1990, 1993, 2000), Preiss and Cowley (1999), Hearon, Rowan, Giles, et al. (2015). However, a general overview of the stratigraphic record found in Warraweena is offered for completeness (Figure 3).…”

“…Researchers have been studying shortened salt structures for decades. There is a plethora of examples in convergent‐margin fold‐and‐thrust belts detached in salt: the Alps (Graham et al., 2012; Granado et al., 2018), the Parentis basin (Ferrer et al., 2012), the Pyrenees (García‐Senz, 2002; Saura et al., 2016), the Zagros Mountains (Callot et al., 2012; Jahani et al., 2009), La Popa Basin (Rowan et al., 2003), the Betics (Escosa et al., 2018), the Atlas in Morocco (Saura et al., 2014; Vergés et al., 2017), the Sivas Basin in Turkey (Callot et al., 2014; Kergaravat et al., 2016; Ringenbach et al., 2013), the Kuqa fold‐and‐thrust belt in NW China (Izquierdo‐Llavall et al., 2018; Li et al., 2014; Pla et al., 2019), the Flinders and Willouran ranges of South Australia (Hearon, Rowan, Giles, et al., 2015; Rowan et al., 2019; Rowan & Vendeville, 2006) and the Eastern Cordillera in Colombia (Parravano et al., 2015). There are also numerous studies of deep‐water salt provinces and fold‐and‐thrust belts on passive margins (see Rowan et al., 2004), such as the northern and southern Gulf of Mexico (Duffy et al., 2020; Rowan & Ratliff, 2012), the Espirito Santo basin in Brazil (Fiduk et al., 2004) and offshore Angola (Brun & Fort, 2004; Gottschalk et al., 2004).…”