Potential Cretaceous-Paleogene boundary tsunami deposit in the intra-Tethyan Adriatic carbonate platform section of Hvar (Croatia)

Abstract

An exceptional 47-m-thick succession of Maastrichtian to Paleocene inner-platform carbonates is exposed in the Dalmatian island of Hvar (Adriatic Sea, Croatia) in a seaside locality called Majerovica. The middle part of this succession comprises a ~5 m thick intraformational massive deposit, which is underlain by well-bedded peritidal inner-platform limestones containing latest Maastrichtian rudists and shallow water benthic foraminifera. This deposit includes a polygenic, matrix-supported carbonate breccia characterized by ripped-up platform limestone lithoclasts, up to boulder sized, and polygenic microbreccia in a muddy matrix. The microbreccia contains rare small intraclasts of pelagic mudstone containing terminal Maastrichtian planktonic foraminifera. The deposit is overlain in turn by mudstone containing a planktonic foraminiferal association belonging to the P0 and P Zones of the basal Paleogene, and by shallow-water muddy limestones containing planktonic foraminifera belonging to the P1 Zone. While facies suggest that the deposit was emplaced over the inner platform by a single large tsunami, the biostratigraphic assessment of this section and the presence of enhanced concentrations of platinum group elements, such as iridium in the topmost part of the massive deposit, lend support to the hypothesis that this tsunamite is related to the K-Pg event, triggered by the Chicxulub impact in Yucatán. This is potentially the first case of a tropical carbonate platform sedimentary succession recording the K-Pg event, which provides a new constraint for modeling both the western Tethyan paleogeography and the catastrophic aftermaths of the Chixculub impact at the Cretaceous-Paleogene boundary.

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

“…Korbar, McDonald, Fućek, Fuček, and Posilović () report a tsunamite, triggered by the Chicxulub impact on Yucatan, from the Likva Cove carbonate platform of the Island of Brač, Croatia, which is similar to that in an earlier report from the nearby Island of Hvar (Korbar et al., ). If true, such deposits in the Adriatic Sea would be truly anomalous given that no tsunamites are identified in well‐preserved Cretaceous–Palaeogene (K–Pg) sections from the Basque‐Cantabric Basin (Bidart, Zumaia, Hendaye and Sopelana sections), which are located more proximal and towards the hypothetical tsunami wave propagation front.…”

“…The K-Pg boundary age tsunami interpretation of Korbar et al (2017) and an earlier study from Hvar (Korbar et al, 2015) hinges on precise age control based on planktic foraminifera, but good age control is lacking and most species are misidentified. For example, in (Keller et al, 2003(Keller et al, , 2013.…”

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

“…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.…”

“…() is that there is no modern analogue for an isolated carbonate platform tsunamite (e.g. Korbar et al., ; Shiki, Tsuji, Yamazaki, & Minoura, and references therein). Major modern tsunamis are documented either from coral‐reef dominated atolls and small intra‐oceanic islands or from coastal regions encompassing broad open shelves (Shiki et al., ).…”

“…) in the sedimentological records from very distal K-Pg deep-marine successions. We discussed that issue in Korbar et al (2015), especially with respect to Gubbio as the closest reported deep-marine K-Pg record to the Adriatic platform and the shallow-marine K-Pg successions of Hvar and Likva. Thus, neither the giant hydrodynamical perturbations expected in a K-Pg tsunami nor attenuated seismic energy would be expected to affect the deepwater sediments in very distal regions.…”