Spider impact structure, Kimberley Plateau, Western Australia: interpretations of formation mechanism and age based on integrated map-scale data

Mousso structure: A deeply eroded, medium-sized, complex impact crater in northern Chad?

“…However, a pronounced central peak would be consistent with observations at some proven terrestrial impact structures, e.g., the BP impact structure, Libya, or the Gweni Fada impact structure, Chad, where central uplifts are less eroded than other parts of the structures and form prominent topographic features (e.g., Koeberl et al, 2005a;Koeberl et al, 2005b). Abels (2005) recently pointed out that the structural type of central uplift, as represented by that of the Spider impact structure (a system of about 20 imbricated, radiating, and overlapping thrusts), is unique among the deeply eroded impact structures known on Earth. However, the detailed structural investigation of the central uplift of the Upheaval Dome impact structure, Utah, USA, by Kenkmann et al (2005) shows an analogous structural arrangement.…”

“…As regards the conspicuous arrangement of arcuate ridges within the central peak of the Mousso structure (Figs. 2 and 5), a striking similarity to the central uplift of the Spider impact structure, Western Australia, can be observed (see Shoemaker and Shoemaker, 1996;Abels et al, 2000;Abels, 2001;Abels, 2005; see Fig. 6 for comparison), which further supports a possible impact origin of the Mousso structure.…”

“…A similar deformation pattern has also been reported from the central uplifts of the Sierra Madera impact structure, Texas, USA (Wilshire and Howard, 1968) and the Gosses Bluff impact structure, central Australia (Milton et al, 1996;Scherler et al, 2006). The central uplifts of the Spider, Upheaval Dome, and Gosses Bluff impact structures are characterised by bilateral symmetry in their complex fault systems and show central anticlines as common structural features (Milton et al, 1972;Abels, 2005;Kenkmann et al, 2005). The central uplift of the Sierra Madera impact structure exhibits several NW-SE trending central anticlines (see Wilshire and Howard, 1968).…”

Liquefaction of sedimentary rocks during impact crater development

“…E-H: Scanning electron microscopy, backscattered electron images detailing shear zone in D. Shear zone walls vary from irregular to sharp and record intense grain size reduction through cataclasis or wear abrasion. Australia; Abels, 2005;Salisbury et al, 2008;Vredefort in South Africa;Wieland et al, 2005;Lana et al, 2003aLana et al, , 2003bLana et al, , 2008 describe rather smooth and continuous fold geometries, which are consistent with a viscous rock deformation. Outcrop, petrography and modeling all suggest that at least part of the large-scale folding in sedimentary strata is accompanied by intense brittle fracturing (Nicolaysen and Reimold, 1999;Collins et al, 2004;Grieve et al, 2008), faulting and block rotation (Wieland et al, 2005;Grieve et al, 2008;Lana et al, 2008).…”

“…The nature of this process is unknown to any tectonic environment operative on Earth and, consequently, the mechanism that best explains the sudden reduction in rock strength remains obscure. One explanation is that and the Araguainha structure in central Brazil (Lana et al, 2003a(Lana et al, , 2004(Lana et al, , 2006(Lana et al, , 2008Abels, 2005;Wieland et al, 2005;Salisbury et al, 2008;Tohver et al, 2013). These folds are the best expression of extreme compressional strain recorded in central uplifts of a number of complex craters in sedimentary and mixed (sedimentary+crystalline) target rocks (e.g., Lana et al, 2003aLana et al, , 2006Wieland et al, 2005).…”