Contemporaneous thrusting and large-scale rotations in the western Sicilian fold and thrust belt

The present structural framework of the Kala Chitta Range evolved through movement between two detachment surfaces. The Precambrian Attock Slates acted as a basal detachment surface above which large scale horizontal compression took place to produce the main structural framework of the Kala Chitta Range. The Middle Eocene argillaceous and gypsiferous Kuldana Formation behaved as the upper detachment surface giving rise to blind thrusts which were later exposed due to the intense erosion of the overlying folded Miocene strata.

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Analogue modeling and tectono-stratigraphic evolution of the eastern Sicilian fold-and-thrust belt

10.5194/egusphere-egu2020-5573 ◽

2020 ◽

Author(s):

Maxime Henriquet ◽

Stéphane Dominguez ◽

Giovanni Barreca ◽

Jacques Malavieille ◽

Carmelo Monaco

Keyword(s):

Large Scale ◽

Middle Miocene ◽

General Structure ◽

Foreland Basin ◽

Accretionary Wedge ◽

Thrust Belt ◽

Central Mediterranean ◽

Fold And Thrust Belt ◽

Structural Architecture ◽

Back Arc

&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160; In Central Mediterranean, the Sicilian Fold and Thrust Belt (SFTB) and Calabrian Arc, as well as the whole Apennine-Maghrebian belt, result from the subduction and collision with drifted micro-continental terranes. These terranes detached from the European margin and migrated southeastward in response to Neogene slab roll-back and associated back-arc extension. From N to S, the SFBT is divided in 4 main tectono-stratigraphic domains: (1) the Calabro-Peloritani terrane, drifted from the European margin and detached from the Corso-Sarde block since the back-arc opening of the Tyrrhenian basin, (2) the Neotethyan pelagic cover, constituting the remnants of the Alpine Tethys oceanic accretionary wedge, (3) the folded and thrusted platform (Panormide) and basinal (Imerese-Sicanian) series of the down-going African margin, and (4) the undeformed african margin foreland (Hyblean).&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160; The scarce good quality outcrops of key tectono-stratigraphic units and crustal scale seismic lines makes the structural architecture of the SFTB very controversial, as testified by the wide variety of tectonic interpretations (Bianchi et al., 1987; Roure et al., 1990; Bello et al., 2000; Catalano et al., 2013). Major outstanding issues particularly concern: (1) the occurence of Alpine Tethys units far from the region where the remnants of the Tethyan accretionary wedge outcrop (Nebrodi range); in a forearc position above the Peloritani block north of the SFTB and in an active foreland context along the southern front of SFTB; (2) the diverging suggested tectonic styles, from stacked large-scale tectonic nappes to foreland imbricated thrust systems rooted into a main basal d&#233;collement; and (3), the deposition environnement of substantial units such as the widespread Numidian Flyschs, from syntectonic foreland basin to wedge-top sedimentation.&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160; We used 2D analogue models to investigate the mechanical processes involved in the formation of the SFTB starting from the Oligocene Tethys subduction to the Middle Miocene - Late Pliocene continental collision with the African paleo-margin. Based on a detailed tectono-stratigraphic synthesis, complemented by field observations, we reproduce the first-order mechanical stratigraphy of the sedimentary and basement units involved in the SFTB as well as the structural inheritance of the African margin. Our models also include: syntectonic erosion and sedimentation, syn-orogenic flexure and adjustable material output via a &#8220;subduction channel&#8220;.&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160; The analog models succeed in reproducing the general structure of the SFTB and main tectono-stratigraphic correlations. For instance, the Panormide platform is underthrusted beneath the Alpine Tethys accretionary wedge, then stacked above the Imerese basinal units and belatedly exhumed in response to basement anticlinal stack. Our results also suggest that the Alpine Tethys units couldn&#8217;t overthrust the whole African foreland in the Middle Miocene, nor be back-thrusted over the forearc basin during the Burdigalian. We rather favor a gravity-induced sedimentation process inducing reworking of the tethysian sediments at specific building stages of the accretionary wedge. The structural architecture of the modeled orogenic wedge is also consistent with a SFTB growing by frontal accretion and basal underplating of mechanically resistant stratigraphic units rather than by large-scale nappe overthrusting.&#160;&#160;

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Constraining the timing of crustal thickening using garnet geochronology – An argument against subduction-driven orogenesis in the Dom Feliciano Belt, Brazil

10.5194/egusphere-egu21-9547 ◽

2021 ◽

Author(s):

Jack Percival ◽

Jiří Konopásek ◽

Robert Anczkiewicz

Keyword(s):

Large Scale ◽

Crustal Thickening ◽

Granitic Rocks ◽

Garnet Growth ◽

Thrust Belt ◽

Research School ◽

Fold And Thrust Belt ◽

Granitic Magmatism ◽

Granite Belt ◽

Dom Feliciano Belt

Metamorphic minerals in the Brusque Complex of the northern Dom Feliciano Belt, Brazil, provide new insights into the timing and mode of regional convergence, challenging a long-lived subduction-collision model for orogenesis. The key evidence for subduction is an extensive linear belt of granitic rocks (the Granite Belt) that intruded the length of the hinterland of the Dom Feliciano Belt between ~630&#9472;580 Ma, and that is inferred to represent arc magmatism above the subducting Adamastor Ocean prior to continental collision. The study area comprises supracrustal units of a foreland fold-and-thrust belt outcropping along the western edge of the symmetric Kaoko&#9472;Dom Feliciano orogenic system. The integrated study of primary metamorphic mineral assemblages and associated deformation fabrics support the interpretation of a fold-and-thrust belt environment, with early tectonic movement top-to-NW away from the hinterland. P&#9472;T estimates constrained by garnet compositions indicate peak metamorphic conditions of 540&#9472;570&#176;C and 5.5&#9472;6.5kbar, in line with typical geothermal gradients associated with orogenic metamorphism. The timing of early garnet growth, and by inference the early stages of crustal thickening in the foreland, is constrained by Lu&#9472;Hf garnet geochronology at ~660&#9472;650 Ma. The data indicate that the onset of metamorphism and deformation in the orogenic foreland occurred ~20&#8211;30 m.y. prior to intrusion of extensive granitic magmatism into the orogenic hinterland. The timing of early orogenic thickening in the foreland precludes the interpretation of the Granite Belt as an arc above a large-scale subduction zone in the lead up to orogenesis. Instead, it is interpreted to represent syn-orogenic magmatism typical for hinterland domains in other ancient and recent orogenic systems.We appreciate financial support from Diku Norway and CAPES Brazil (project UTF-2018-10004), and from the Czech Science Foundation (project no. 18-24281S). This work was partly supported by the Research Council of Norway through the funding to The Norwegian Research School on Dynamics and Evolution of Earth and Planets, project number 249040/F60.

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