The present paper aims to show, both from a stratigraphic and structural points of view, the main features ofa wedge-top syntectonic basin which evolved recording polyphase and non-coaxial tectonics. The study areais the Scillato Basin (SB), a roughly N–S-oriented structural depression located in the central-northern sectorof the Sicililian Maghrebides. There, an approximately 1300 m-thick upper Serravallian to upper Tortoniansuccession of clastic units outcrops as a portion of the Neogene syntectonic covers of the Sicilian fold andthrust belt. Within the outcropping succession the upper Tortonian Terravecchia Fm represents the maintopic of this paper. A multidisciplinary approach was carried out through an integration of sedimentology, facies,stratal pattern and structural analyses; this was applied to the formation enabling one to recognize inthe Scillato Basin aﬁning to coarsening upward succession, deposited recording an early transgressive anda late regressive depositional stage. In our model these two main depositional stages developed and are directlyrelatable to a two-step structural evolution of the basin. During theﬁrst step, a NW–SE-oriented structuraldepression existed, enclosed between structural highs and accommodating the lower and middleportion of the upper Tortonian succession. Subsequently, during the second step, the NW–SE depressionwas non-coaxially deformed by superimposition of high-angle transpressive faults (many of which wereSE-dipping), developed in response to the upward propagation of structures enucleated at deeper structurallevels. This step was recorded in the basin by development of both depositional and structural interferencesrecognizable along the upper portion of the Scillato Basin succession. A comparison betweenﬁeld data anddeep geophysical data interpreted at the preliminary stage, raises questions about the late Miocene geologicalevolution of this sector of the Sicilian chain, including: (i) the syn-tectonic deposition of the TerravecchiaFm. in the Scillato Basin clearly recorded the interference of two main and non-coaxial tectonic events;(ii) the younger of these two events has a clear tranpressional character and was active during the verylate Tortonian; (iii) as also indicated by many authors in neighboring orogenic wedges, the main controlon the location, geometry and depositional evolution of the Scillato wedge-top Basin was carried out by compressionaland transpressional structures developed at a deeper structural level. Their deformation propagatedupward both into the shallow structural level and sedimentary covers; therefore (iv) the late Miocenestructural scenario here depicted is not consistent either with the back-arc-related extension or with thelate orogenic gravitational collapse models previously invoked by other authors with regard to this sectorof the Sicilian thrust belt.
|Numero di pagine||18|
|Stato di pubblicazione||Published - 2012|
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