Figure 10: (A and B) Plots showing how deep (A) or how many seismic cycles (B) pit crater centroids are beneath the Base Cretaceous unconformity along dyke-strike (Supporting Table 1). Inset into (B): schematic depicting what constitutes a seismic cycle. (C) Plot of cone height along dyke strike (Supporting Table 1). See Figure 3B for explanation of measured parameters.
For each pit crater chain situated within dyke-induced graben, the depth of their pit crater centroids beneath the Base Cretaceous unconformity varies by ≲60 m along their length (Fig. 10A). Several pit crater chains (A, D, F, G, and I) show a broad northwards increase in centroid depth (Fig. 10A). Above some dykes, pit crater centroids all occur along the same stratigraphic reflection (i.e. D and G), even though the number of cycles between their level and the Base Cretaceous unconformity may vary (i.e., the post-overburden varies in thickness over a length-scale longer than that of an individual crater or chain of craters Figs 6D, 7B, and 10B). For other chains, pit crater centroids coincide with different (deeper or shallower) reflections along their length (i.e. A, B, C, E, F, H, and I; Figs 6, 7, and 10B). The pit craters associated with tectonic normal faults have centroids that occur at the same stratigraphic reflection above the Top Athol Formation, except forX3 which is the only pit crater to terminate below the Top Athol Formation (Fig. 8).
The total height of the pit craters varies across the data, with most extending down into the Mungaroo Formation (Figs 4A and 6-8); pit craters G5, G11, and G12 appear to terminate at or above the Top Mungaroo Formation (Fig. 7C). Our measurements show pit crater total height ranges from 114–868 m (Supporting Table 1). In places, mapped bases of pit crater pipes coincide with the upper tips of underlying dykes (G2, G4, G6, G10a, G12, and H2) or dyke-induced fault planes (B/C2, C2, C3, F9, F13, I2, and I3) (Figs 6-7). The X1 -X5pit crater pipes all extend down to tectonic faults (e.g., Fig. 8). Where the base of pit crater pipes intersect dyke-induced or tectonic faults, they typically do so where the fault planes are relatively steep or sub-vertical (e.g., Figs 6C, 7B, F, 8B, and C). Other pit craters appear to terminate within strata overlying dyke upper tips or fault planes (Figs 4A and 6-8).
Where pit craters display a funnel-like morphology, we measure the height of their inverted cone section and occasionally the deflection of the uppermost stratigraphic reflection within them (i.e. the deflection height) (Fig. 3B). We show inverted cone heights are ~18–245 m, with slopes of 7–51°, and that these values vary across the study area and along individual pit crater chains (Figs 10C, 11A, and B; Supporting Table 1). The corresponding pipe height of these funnel-like pit craters are 27–789 m (Fig. 11A; Supporting Table 1); the heights of pipe-like pit craters are 107–254 m (Table 2). There is no correlation between cone height and total height or pipe height for pit craters within dyke-induced graben (either those above dykes or dyke-induced faults), or for those associated with tectonic normal faults (Figs 11A and B; Supporting Table 1). Deflection heights are ~4–21 m, with slopes <12°, and do not correlate with either total height or cone height (Figs 11C and D; Supporting Table 1).