A depositional model for seismo-turbidites in confined basins based on Ionian Sea deposits

Abstract

This study investigates Ionian Sea seismo-turbidite (ST) deposits that we interpret to be triggered by major historic earthquakes and tsunamis in the Calabrian Arc. ST beds can be correlated with the AD 1908 Mw 7.24 Messina, AD 1693 Mw 7.41 Catania, and AD 1169 Mw 6.6 Eastern Sicily earthquakes while two previously unknown turbidites might have been generated by the AD 1818 Mw 6.23 Catania and AD 1542 Mw 6.77 Siracusa earthquakes.\ud Textural, micropaleontological, geochemical and mineralogical signatures of STs reveal cyclic patterns of STa, STb, STc and STd sedimentary units for each earthquake with an associated tsunami. The STa unit contains multiple ST stacks with different mineralogy, geochemistry foraminiferal assemblages and sedimentary structures that are deposited from synchronous multiple slope failures and turbidity currents. The STb homogenite graded mud unit overlying the STa unit is deposited by the waning flows of the multiple turbidity currents that are trapped in the\ud Ionian Sea confined basin. The STc laminated and marine-sourced unit results from seiching of the confined water mass that appears to be generated by earthquake ruptures combined with tsunami waves. The STd unit is a tsunamite cap deposited by the slow settling suspension cloud created by tsunami wave backwash erosion of the shoreline and continental shelf. This tsunami process interpretation is based on the textural gradation of the upper unit and a more continental source of the tsunamite cap which includes C/N >10 and the presence of inner shelf foraminifera with a lack of abyssal species. This interpretation is in agreement with the lack of a tsunamite cap for the turbidite likely linked to the AD 1542 historic earthquake that is not associated with a tsunami. The new sedimentologic criteria identifies the final seiche and tsunamite cap deposits of STs and provides a model that can now be tested in other locations to better understand the different depositional processes of seismo-turbidites in confined basins

Gravity‐Driven Deposits in an Active Margin (Ionian Sea) Over the Last 330,000 Years

“…Previous studies on the Holocene showed that the gravity‐driven deposits have a co‐seismic origin (Polonia et al, a, b, ; San Pedro et al, ). The large majority of the seismo‐turbidite deposits present amalgamated or stacked beds, characteristic of the deposition by multiple quasi‐synchronous flows (Gutiérrez‐Pastor et al, ; Migeon et al, ; Nelson et al, ; Polonia et al, ) and the presence of liquefaction figures and faults should be the witnesses of a co‐seismic origin.…”

“…The formation of these two accretionary wedges over a million years scale (Coy et al, ; Dewey & Sengör, ; Gallais et al, ; van Dijk & Scheepers, ; Truffert, ) as well as their morphology and present day functioning have been widely studied (D'Agostino et al, ; Gutscher et al, ; Huguen et al, ; Kreemer & Chamot‐Rooke, ; Polonia et al, ; Tortorici et al, ). For the last thousand years, Polonia et al (b, ) has focused initially on the Holocene's palaeoseismology based on turbidite record and, more recently, studies have been extended to the last 60 ka (Köng et al, ). Between these two time scales (million years and the last thousand years) few studies deal with the turbidite record in active margin.…”

“…This study try to reconstruct the turbidite activity over a span of hundred thousand years on the wedges in the Ionian Sea. This area have been described as a good place to conduct palaeoseismologic studies for three reasons: (1) the majority of debris flows, turbidites and sliding seem to be distinctive earthquakes‐triggered structure (Kastens, ; Köng et al, ; Polonia et al, a, b, ; San Pedro et al, ), (2) sapropels and tephra provide a suitable means of dating events (Kastens, ; Löwemark et al, ), (3) glacio‐eustatism influence is expected to be minor if the area is disconnected from the shelf (Kastens, ). This study attempts to decipher which control factor (sea level changes, earthquakes and volcanism) dominates the triggering of gravity‐driven sedimentation recorded on ridge and slope basins of the Calabrian Arc and the Mediterranean Ridge over the last 330,000 years.…”

The Bortoluzzi Mud Volcano (Ionian Sea, Italy) and its potential for tracking the seismic cycle of active faults

“…This plateau is, however, dissected by long normal and strike-slip fault zones mostly striking NW-SE. The inner plateau is characterized by chaotic units (Rossi and Sartori, 1981) and many mud volcanoes (Praeg et al, 2009;Ceramicola et al, 2014;Gutscher et al, 2017;Loher et al, 2018) including the BMV that is studied in this work.…”

“…Many mud volcanoes occur on active accretionarysedimentary prisms (Cita, 1981;Kopf, 2002;Panieri et al, 2013;Ceramicola et al, 2014), where their degassing activity is at least in part connected with active compression and associated faulting and fracturing (Camerlenghi et al, 1995;Kopf, 2002;Chamot-Rooke et al, 2005;Mazzini et al, 2007;Panieri et al, 2013). It is also noteworthy that, in these active tectonic settings, the longevity of mud volcanoes may even exceed 1 Ma (Cita et al, 1989;Camerlenghi et al, 1992Camerlenghi et al, , 1995Robertson, 1996;Kopf et al, 1998;Praeg et al, 2009;Somoza et al, 2012). All together the known submarine mud volcanoes release about 27 Mt methane a −1 (plus other gases ;Milkov, 2004;Etiope and Milkov, 2004).…”