Imaging continental shelf shallow stratigraphy by using different high-resolution seismic sources: an example from the Calabro-Tyrrhenian margin (Mediterranean Sea)

Abstract

A B S T R A C THigh-resolution seismic reflection profiles of the Calabro-Tyrrhenian continental shelf were collected using different seismic sources (Sub-Bottom Profiler, Uniboom, Sparker 0.5-1-4.5 kJ). Noticeable differences and results were obtained both from a geophysical and geological-interpretative point of view. The availability of different sources permitted the definition of the most suitable seismostratigraphic characterization in terms of resolution, penetration and acoustic facies. Very high resolution stratigraphy was defined through profiles produced by different seismic systems used in parallel. This permitted the application of sequence-stratigraphy concepts with the reconstruction of a thick postglacial depositional sequence, formed by a transgressive and a high-stand systems tract. The thickness distribution of postglacial deposits reveals that the main depocenter (55-65 m) is located offshore of the Coastal Range, along a stretch of coast supplied by several small and seasonal streams ("fiumare") and characterized by the lack of a coastal plain. This suggests the greater efficiency of sediment supply and bypass in this area relatively to sectors located offshore of the main rivers. The transgressive systems tract, usually thin or nearly absent, is particularly well developed (up to 33 m) and is composed of up to three parasequences with a retrogradational stacking pattern. The high-stand systems tract, up to 30 m thick, is made up of two parasequences and has a quite regular geometry and acoustic facies. R E S U M OPerfis de reflexão sísmica de alta resolução da plataforma continental tirreniana de Calabro foram obtidos utilizando-se recursos sísmicos diversos (Perfilador de Sub-superfície, Uniboom, Sparker 0.5-1-4.5 kJ). Diferenças evidentes foram encontradas sob o ponto de vista geofísico e geológico-interpretativo. A disponibilidade de diferentes fontes permitiu a definição de uma caracterização sismo-estratigráfica mais acurada em termos de resolução, penetração e facies acústica. Uma estratigrafia de resolução bastante alta pôde ser obtida através de perfis produzidos por diferentes sistemas sísmicos utilizados em paralelo. Este fato possibilitou o emprego de conceitos de sequência-estratigrafia para a reconstrução de uma espessa sequência deposicional pós-glacial formada por um trato de sistemas transgressivo e de nível de base alto. A espessura dos depósitos pós-glaciais revela que o principal centro de deposição (55-65 m) está localizado ao largo da serra costeira, ao longo de uma costa distendida e alimentada por pequenos filetes sazonais ("fiumare"), sendo caracterizado pela falta de uma planície costeira. Os dados sugerem a existência de um suprimento de sedimentos bastante eficiente nessa área, em relação a setores localizados ao largo dos rios principais. O trato de sistemas transgressivo, geralmente estreito ou ausente, é aqui particularmente bem desenvolvido (acima de 33 m) e composto por até três parasequências com padrão de empilhamento retrogradacional. O trato de sistemas d...

Episodic, rapid sea-level rises on the central Mediterranean shelves after the Last Glacial Maximum: A review

“…Composite post-LGM transgressive deposits inferred to be related to a stepped relative sealevel rise were also recognized by Amorosi et al (2009) in the Arno incised valley fill, Italy and by Martorelli et al (2010) on the Tyrrhenian margin of Calabria. Prograding wedges inferred to have accumulated during periods of relative sea-level still-stand or slow rise punctuating the post-LGM transgression were recognized in the western Mediterranean shelves, in particular in the Gulf of Valencia, in the area around Malaga and in the Gulf of Lions, as well as in the Gulf of Cádiz (Hernández-Molina et al, 1994;Somoza et al, 1997;Berné et al, 2007;Labaune et al, 2008;Albarracín et al, 2014).…”

“…However, several morpho-bathymetric and seismo-stratigraphic studies have highlighted submerged features, such as palaeo-coastal cliffs, barrier beaches and sedimentary wedges which may be the result of discontinuous post-glacial relative sea-level rise (Hernández-Molina et al, 1994;Somoza et al, 1998;Lobo et al, 2005;Massari and Chiocci, 2006;Berné et al, 2007;Labaune et al, 2008;Storms et al, 2008;Martorelli et al, 2010;Schattner et al, 2010;Maselli et al, 2011;Zecchin et al, 2011). Barrier islands and coastal cliffs may have been drowned and partially preserved in relation to rapid rates of relative sea-level rise, according to the 'in place drowning' and the 'cliff overstep' transgressive models, respectively (Sanders and Kumar, 1975;Zecchin et al, 2011).…”

“…Barrier islands and coastal cliffs may have been drowned and partially preserved in relation to rapid rates of relative sea-level rise, according to the 'in place drowning' and the 'cliff overstep' transgressive models, respectively (Sanders and Kumar, 1975;Zecchin et al, 2011). Sedimentary wedges, usually staked in a backstepping way, likely developed during episodes of relative sea-level still-stand or slow rise that punctuated the post-LGM transgressive phase (Hernández-Molina et al, 1994;Massari and Chiocci, 2006;Martorelli et al, 2010).…”

Chapter 12 Overview of the variability of Late Quaternary continental shelf deposits of the Italian peninsula

“…12.5) are relatively uncommon; they have been identified in the Ligurian shelf (Corradi et al 2004), the central-southern Tyrrhenian shelf (Martorelli et al , 2010 and the central Adriatic shelf (Cattaneo et al 1997;Cattaneo & Trincardi 1999). As indicated by the sequence stratigraphy model, transgressive deposits are usually organized in backstepping parasequences, bounded at their top by the maximum flooding surface and at their base by the transgressive surface or (more commonly) by the erosional unconformity.…”

“…The best examples of thick backstepping sandy parasequences come from the narrow Calabro-Tyrrhenian shelf, where they developed under high sediment supply conditions and on a high-gradient shelf (Chiocci et al 1989;Martorelli et al 2010). Similarly, the central Adriatic shelf is characterized by thick muddy parasequences in response to its higher gradient than the northern counterpart (Cattaneo & Trincardi 1999).…”