| Summary: | ‘Rootless’ debris cones (or pseudocraters) occur in platy, patterned ground throughout the Cerberus plains of Mars and are thought to represent the products of explosive magma–ice interaction [Lanagan et al., 2001. Geophys. Res. Lett. 28, 2365–2368; Fagents et al., 2002. In: Smellie, J.L., Chapman, M.G. (Eds.), Volcano–Ice Interaction on Earth and Mars. In: Geol. Soc. Spec. Publ., vol. 202, pp. 295–317]. Requiring lava and water interspersed, they are central to theories of multiple magmatic and aqueous flood events [Burr et al., 2002. Icarus 159, 53–73; Berman, D.C., Hartmann, W.K., 2002. Icarus 159, 1–17] and widespread sheet volcanism [Keszthelyi et al., 2000. J. Geophys. Res. 105, 15027–15049] in the region during the late Amazonian (a region reported to have been occupied by water bodies ranging from lakes to oceans [Scott et al., 1995. Map of Mars showing channels and possible paleolake basins. USGS Miscellaneous Investigations Series, Map I-2461 (1:30,000,000)]). The nature of the platy substrate is the subject of debate, with evidence given for lava [Keszthelyi et al., 2000. J. Geophys. Res. 105, 15027–15049; Plescia, J.B., 2003. Icarus 164, 79–95] and ice [Brakenridge, G.R., 1993. Lunar Planet. Sci. XXIV (Part 1), 175–176; Rice et al., 2002. Lunar Planet. Sci. XXXIII. Abstract #2026; Murray et al., 2005. Nature 434, 352–355]. The superposition relationships of cones and platy deposits in the channels of the Athabasca Valles precludes a magmatic origin, indicating later formation as permafrost mounds (or ‘pingos’), with implications for geologically recent flood volcanism, age constraints on young surfaces and recent climate change on Mars.
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