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This paper is intended to compare the sedimentary processes active in the Ritland impact structure with the processes discussed from Gardnos, Kardla, Lockne and Chesapeake Bay marine impact structures. Sedimentary processes, e.g., rock avalanches, slides and slumps, debris and density flows, turbidity and suspension deposition, occur approximately in the same stratigraphical order in all these craters, resulting in comparable crater-infills. The thickness and compositional variations can be explained by differences in crater size, target lithology and water depth. Rock avalanches dominate in crystalline target impact sites with shallow water depth, as observed in the Ritland and Gardnos craters. Impact into deeper water, e.g., Lockne, does not reveal large-scale gravity-driven collapses of the transient sea floor cavity. Crystalline target sites with shallow water depth and thin sedimentary cover, as in the Ritland and Gardnos impact sites, resulted in elevated rim formations, reducing resurge energy, and yielded comparable reduced debris flow events. Impact into thick, stratified sedimentary targets resulted in relatively weaker rim formation in Kardla. The related brim developments in the Lockne and Chesapeake Bay impact structures can be reflected in multiple events of large-scale debris flows. Resurge turbidites are observed in the Kardla and Lockne crater infilling successions. Turbidites in the Ritland and Gardnos are dominantly originated through later slope-failure and reworking of the impact-generated debris. Suspension-dominated late post-impact sedimentation within all the craters is largely controlled by their regional geological settings. |
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