Earth and Planetary Science Letters 444 (2016) 192–204

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                                        Earth and Planetary Science Letters

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Quantification of tsunami-induced flows on a Mediterranean carbonate
ramp reveals catastrophic evolution

Arnoud Slootman a,∗, Matthieu J.B. Cartigny b, Andrea Moscariello a, Massimo Chiaradia a,
Poppe L. de Boer c

a Department of Earth Sciences, University of Geneva, Rue des Maraîchers 13, Geneva 1205, Switzerland
b National Oceanography Centre, University of Southampton Waterfront Campus, Southampton SO14 3ZH, UK
c Faculty of Geosciences, Utrecht University, PO Box 80.115, 3508 TC Utrecht, The Netherlands

article info                            abstract

Article history:                        Cool-water carbonates are the dominant limestones in the Mediterranean Basin since the Early Pliocene.
Received 26 August 2015                 Their deposition typically resulted in ramp morphologies due to high rates of resedimentation. Several
Received in revised form 31 March 2016  such fossil carbonate ramps are characterised by a bimodal facies stacking pattern, where background
Accepted 31 March 2016                  deposition of subaqueous dune and/or tempestite deposits is repeatedly interrupted by anomalously
Editor: M. Frank                        thick sedimentary units, dominated by backset-stratification formed by supercritical flows. A multitude
                                        of exceptional triggers (e.g. storms, floods, tsunamis) have been invoked to explain the origin of these
Keywords:                               supercritical flows, which, in the absence of a quantitative analysis, remains speculative as yet. Here,
carbonate ramp                          for the first time, the catastrophic evolution of one such Mediterranean carbonate ramp, on Favignana
Mediterranean                           Island (Italy), is quantified by combining 87Sr/86Sr dating, outcrop-based palaeoflow reconstructions and
tsunami                                 hydraulic calculations. We demonstrate that rare tsunami-induced flows, occurring on average once every
storm                                   14 to 35 kyr, lasting a few hours only, deposited the anomalously thick backset-bedded units that form
supercritical flow                       half of the sedimentary record. In between such events, cumulative two years of storm-induced flows
catastrophic evolution                  deposited the remaining half of the succession by the stacking of subaqueous dunes. The two to four
                                        orders of magnitude difference in average recurrence period between the two flow types, and their
                                        associated sedimentation rates, emphasises the genetic differences between the two styles of deposition.
                                        In terms of sediment transport, the studied carbonate ramp was inactive for at least 99% of the time with
                                        gradual progradation during decennial to centennial storm activity. Carbonate ramp evolution attained a
                                        catastrophic signature by the contribution of rare tsunamis, producing short-lived, high-energy sediment
                                        gravity flows.

                                                                                                                           © 2016 Elsevier B.V. All rights reserved.

1. Introduction                                                       Skeletal sand and gravel produced on the ramp top in the unpro-
                                                                      tected carbonate factory are transported downramp by incidental
    Cool-water carbonates in shallow, temperate seas are charac-      currents, sweeping sediment below wave base. This results in the
terised by the Heterozoan Association of James (1997), consisting     occasional deposition of bioclastic material on the ramp slope,
largely of the remains of red algae, bivalves, bryozoans, echinoids   leading to carbonate ramp progradation through the formation of
and larger foraminifera, in the general absence of non-skeletal       large-scale clinoform units up to tens of metres high.
grains. They lack the major bioconstructions and early cementation
typical of their tropical counterparts (Ahr, 1973; Carannante and         The sedimentary record of the Mediterranean Basin contains
Simone, 1988). The skeletal debris-covered sea floors thus formed      numerous examples of clinoform successions created in this way
are prone to remobilisation and hence have a reduced capacity to      (e.g. Hansen, 1999; Pomar and Tropeano, 2001; Pomar et al., 2002;
accumulate above storm wave base (Pomar and Tropeano, 2001),          Puga-Bernabéu et al., 2010; Massari and D’Alessandro, 2012), form-
which may lead to the development of distally steepened ramp          ing up to six-storey vertical stacks where carbonate ramps orig-
profiles (Pomar et al., 2002; Pedley and Carannante, 2006) (Fig. 1B).  inated in tectonically active areas, such as the Lower Pleistocene
                                                                      foreland and satellite basins of Sicily (e.g. Catalano et al., 1998;
 * Corresponding author.                                              Massari and D’Alessandro, 2012). These clinoform successions,
     E-mail address: Arnoud.Slootman@unige.ch (A. Slootman).          which prograded up to 1–2 km with a maximum height of sev-
                                                                      eral tens of metres, were suggested to correlate with the 41-kyr
http://dx.doi.org/10.1016/j.epsl.2016.03.052                          orbital obliquity-forced oscillation of global sea level related to the

0012-821X/© 2016 Elsevier B.V. All rights reserved.