Peri-Adriatic mélanges and their evolution in the Tethyan realm

Abstract

In the peri-Adriatic region, mélanges represent a significant component of the Apennine and Dinaride–Albanide–Hellenide orogenic belts as well as ancient and present-day accretionary wedges. Different mélange types in this broad region provide an excellent case study to investigate the mode and nature of main processes (tectonic, sedimentary, and diapiric) involved in mélange formation in contrasting geodynamic settings. We present a preliminary subdivision and classification of the peri-Adriatic mélanges based on several years of field studies on chaotic rock bodies, including detailed structural and stratigraphic analyses. Six main categories of mélanges are distinguished on the basis of the processes and geodynamic settings of their formation. These mélange types are spatially and temporally associated with extensional tectonics, passive margin evolution, strike-slip tectonics, oceanic crust subduction, continental collision, and deformation. There appears to have been a strong interplay and some overlap between tectonic, sedimentary, and diapiric processes during mélange formation; however, in highly deformed regions, it is still possible to distinguish those mélanges that formed in different geodynamic environments and their main processes of formation. This study shows that a strong relationship exists between mélange-forming processes and the palaeogeographic settings and conditions of mélange formation. Given the differences in age, geographic location, and evolutionary patterns, we document the relative importance of mélanges and broken formations in the tectonic evolution of the peri-Adriatic mountain belts

Late Oligocene–early Miocene olistostromes (sedimentary mélanges) as tectono-stratigraphic constraints to the geodynamic evolution of the exhumed Ligurian accretionary complex (Northern Apennines, NW Italy)

“…The trace of the geological cross sections is shown in Figure 1A. Koons, 1994) in late Eocene times (modified after Castellarin, 1994;Festa et al 2010bMosca et al 2010). …”

“…2), including olistostromes, occur at different stratigraphic levels, within the episutural/wedge-top basin succession (e.g., Bettelli et al 1989aBettelli et al , 1989bCastellarin and Pini, 1999;Mutti et al 1995;Martelli et al 1998;Pini, 1999;Panini et al 2002bPanini et al , 2013Papani et al 2002;Pini et al 2004;Festa et al 2010aFesta et al , 2010bFesta 2011;Remitti et al 2011;Ogata et al 2012a;. Particularly, the occurrence of olistostromes in the late Oligocene -early Miocene time interval (i.e., Val Tiepido -Canossa argillaceous breccias of Panini et al 2002b; Canossa Olistostrome of Fazzini and Tacoli 1963, Papani 1963, Bettelli et al 1987; Val Tiepido-Canossa sedimentary mélange of , Bettelli et al 1989a, 1989b; see also Castellarin and Pini, 1987;Pini, 1999;Balatri et al 2002;Benini et al 2002;Bettelli et al 2002;Papani et al 2002;Gasperi et al 2005aGasperi et al , 2005bMartelli et al 2009;Remitti et al 2011) show a significant regional scale distribution (about more than 300 km long by 10-15 km wide) in almost all the outer part of the present-day Northern Apennines (Fig.…”

“…1A, 1D and 2), which, in turn, overthrust the deformed Adria continental margin causing the Apenninic prowedge (sensu Koons 1994) to develop. During the progressive incorporation into the accretionary wedge, a consistent part of the External Ligurian Units (i.e., Lower-to Upper Cretaceous "Basal Complex") was strongly deformed by tectonic processes forming broken formations and tectonic mélanges (e.g., Pini 1999;Bettelli and Vannucchi, 2003;Cerrina Feroni et al 2004;Festa et al 2010bMarroni et al 2010;Remitti et al 2011;Codegone et al 2012b;. Since middle-late Eocene, different episutural and wedge-top basins (i.e., Tertiary Piedmont Basin and Epiligurian Units, respectively) unconformably covered the Ligurian accretionary complex (Fig.…”

Formation of Taconic mélanges and broken formations in the Hamburg Klippe, Central Appalachian Orogenic Belt, Eastern Pennsylvania

“…Their internal structure and architecture display strong evidence for those geological processes that operated in certain tectonic setting(s) and along plate boundaries. The structure and stratigraphy preserved in chaotic rock bodies can also allow us to better understand the tectonostratigraphic evolution of orogens in which they are preserved (e.g., Ogawa, 1998;Festa et al, 2010aFesta et al, , 2010b. This is the case of different orogenic belts and accretionary complexes around the world where mélanges and olistostromes occur, for example in the Alpine-Himalayan belt (e.g.…”

“…This is the case of different orogenic belts and accretionary complexes around the world where mélanges and olistostromes occur, for example in the Alpine-Himalayan belt (e.g. Ring et al, 1990;Trommsdorff, 1990;Liu and Einsele, 1996;Federico et al, 2007), circum-Mediterranean orogens (e.g., Elter and Trevisan, 1973;Dilek et al, 1999Dilek et al, , 2007Pini, 1999;Okay, 2000;Robertson et al, 2009;Camerlenghi and Pini, 2009;Ghikas et al, 2010;Festa et al, 2010b), Appalachians (e.g., Lash, 1987a;Rast and Horton, 1989;Cousineau and St-Julien, 1992;Tremblay et al, 1995;Ganis and Wise, 2008), circum-Pacific regions (e.g., Hsü, 1968;Matsuda and Ogawa, 1993;Cowan, 1985;Cloos, 1982;Wakabayashi, 1992;Kimura et al, 1996;Kusky and Bradley, 1999;Ikesawa et al, 2005;Yamamoto et al, 2009;Wakabaysahi et al, 2010) and many others.…”