Post‐impact event bed (tsunamite) at the Cretaceous–Palaeogene boundary deposited on a distal carbonate platform interior

Abstract

We show crucial evidence for the Cretaceous-Palaeogene (K-Pg) boundary event recorded within a rare succession deposited in an inner-platform lagoon on top of a Mesozoic, tropical, intra-oceanic (western Tethys) Adriatic carbonate platform, which is exposed at Likva cove on the island of Bra c (Croatia). The last terminal Maastrichtian fossils appear within a distinct 10-12 cm thick event bed that is characterised by soft-sediment bioturbation and rare shocked-quartz grains, and is interpreted as a distal tsunamite. Directly overlying this is a 2 cm thick reddishbrown clayey mudstone containing planktonic foraminifera typical of the basal Danian, and with elevated platinum-group elements in chondritic proportions indicating a clear link to the Chicxulub asteroid impact. These results strongly support the first discovery of a "potential" K-Pg boundary tsunamite on the neighbouring island of Hvar, and these two complementary sections represent probably the most complete record of the event among known distal shallow-marine successions.

Reply to Comment on “Post‐impact event bed (tsunamite) at the Cretaceous–Palaeogene boundary deposited on a distal carbonate platform interior”

“…Thirdly, although polychaetes are indeed common in both shallow‐ and deep‐marine environments, we would like to highlight that annelid worms are the dominant macrofauna in modern tropical lagoons (see references and discussion on the topic in Korbar et al. (), while local sediment instability particularly affects the polychaete abundance in tidal flats (Netto, Warwick, & Attrill, ). In addition, there are modern examples showing that polychaetes are the first opportunistic recolonisers of soft bottoms in lagoons after deposition of a sandy tsunamite (Kanaya, Suzuki, & Kikuchi, ).…”

“…() claim that “bed 4 may have accumulated after intermittent bank‐top exposure where intraclasts formed by desiccation and/or bioturbation”. However, there is no sedimentological evidence for the statement, although such features are indeed common deeper downsection (reported in papers referred to by Korbar et al., ). There are also not “just a few angular bioclasts” in the lag, as we reported also on rounded mud intraclasts that originated from bed 3.…”

“…Besides, there are clear soft‐sediment loading structures observed in the lower part of bed 4 (Fig. 2c of Korbar et al., ). It should be highlighted that our study documents a relatively high‐energy event in a very low‐energy setting of a very distal and broad mud‐dominated carbonate platform interior (tidal flat), characterised by rare monospecific skeletal material (requieniid‐rudist bivalves).…”

“…5 of Korbar et al. () of the basal Palaeocene (P0–Pα zones) planktonic foraminifera isolated from the K–Pg boundary “clay” of the Likva section are as follows: (a,b) Guembelitria cretacea CUSHMAN (c) Parvularugoglobigerina cf. longiapertura BLOW (d) Eoglobigerina eobulloides (MOROZOVA) (e) Woodringina claytonensis LOEBLICH and TAPPAN (f) Parvularugoglobigerina cf.…”

“…We disagree with many of the concerns raised by Font et al, () and take this opportunity to clarify matters. We wish to emphasise that in our paper (Korbar et al, ), as well as in the first report on the “potential” Cretaceous–Palaeogene (K–Pg) tsunami in the Adriatic region (Korbar et al, ), we reported on rare shallow marine distal K–Pg records that differ from the dominantly deep marine records commonly reported in other papers. We did not include more references on the latter, since that was not a goal of our paper, and we encourage the authors of the Comment themselves to make additional research of the Likva section, especially the issues that are criticised.…”