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At first glance a sedimentary study may seem unsuitable for a paleontological symposium but in this case it is justified by addressing environmental aspects around the last major biotic crisis at the K-Pg mass extinction event. At Elliot´s locality, López de Bertodano Formation (LdB), Seymour Island, Antarctica (Fig. 1; Elliot et al., 1994) and in the section containing the K-P boundary, two of the present authors (EBO and JLK) found in 2008, just above the iridium-enriched layer, a thick sedimentary breccia with abundant mud-chips and shellfragments (Fig. 2). Even though Seymour Island is very distant from the Chicxulub asteroid impact site (Schulte et al., 2010), and consequently the record of the associated tsunami breccia is very unlikely in Antarctica, the location of the discovered breccia just above the iridium layer is very suggestive and deserves proper explanation. Knowing that currentinducederosional or depositional features are difficult to notice in the field due to the friable and homogeneous nature of the mud-dominated LdB, during the 2017 Antarctic field season we made detailed sedimentological observations in the upper part of the LdB trying to detect similar sedimentary breccias. As a result, we found that most of the c. 160 m of the informalUnit 9 (Macellari, 1988) consists of cyclic, asymmetric coarsening-up sedimentary packages that invariably start with concretionary mudstones and end with a coquinoid breccia.Accordingly, the main objective of this presentation is to discuss possible sedimentary processes that may have originated these beds, rather than an impact-generated tsunami.The coarsening-up cyclic packages of Unit 9 (Fig. 3) consist of a basal fine-grained bed,generally micaceous mudstone or sandy siltstone, with abundant fossiliferous glauconite concretions that grade upward to silty fine-sandstone, fine-sandstone and finally to morecoarse-grained beds composed of abundant shell fragments and mud-chips floating in a sandstone matrix. The thickest lower part, dominated by sandy mudstones and fine-grained sandstones is friable and present a characteristic recessive slope. A relatively dense bioturbation of Paradictyodora antarctica and Euflabella multiplex is typical. The coarsest top bed is generally more cemented and characterized by wavy bedding, ripple crosslaminationand trace fossils, dominated by Teichichnus rectus and subordinatedThalassinoides suevicus (Fig. 3B-C). The total thickness of each cyclic package ranges between 3 to 15 m.The cyclic packages of Unit 9 (Fig. 3) are interpreted as prograding parasequences formed during the general regressive trend that characterizes the upper part of the LdB, both in Vegaand Seymour islands (cf. Olivero, 2012). As is typical for siliciclastic wave-dominated shorelines, the basal flooding surface is denoted by a marked shift of sedimentary facies. In Unit 9 of the LdB this facial shift is typified by shallow marine sandstones with wavy ripple cross-lamination and abundant shell fragments and mudstone chips below, and burrowed and fossiliferous offshore mudstone above. Even though the sedimentary breccia was not previously mentioned at Elliot´s locality (it was probably not noticed because of thedominant friable character of the monotonous silty fine-sandstones), Elliot et al. (1994) do interpret a flooding surface above the K-Pg boundary based on a marked shift of dinocyst assemblages, with more offshore marine dinocyst species above the flooding surface. Considering all these pieces of information together, we conclude that the sedimentary breccia found just above the K-P boundarymarks the top of a shallowing upward, asymmetric Maastrichtian parasequence that was followed by a basal Paleogene marine flooding horizon,and not the result of an impact-generated tsunami