Coupled Crust‐Mantle Response to Slab Tearing, Bending, and Rollback Along the Dinaride‐Hellenide Orogen

Abstract

We integrate structural, geophysical, and geodetic studies showing that the Dinarides‐Hellenides orogen along the Adria‐Europe plate boundary in the Western Balkan peninsula has experienced clockwise oroclinal bending since Eocene‐Oligocene time. Rotation of the Hellenic segment of this orogen has accelerated since the middle Miocene and is associated with a north‐to‐south increase in shortening along the orogenic front. Within the Paleogene nappe pile, bending was accommodated by orogen‐parallel extension, clockwise block rotation, and thrusting in the hanging wall of the Skhoder‐Peja Normal Fault (SPNF). The SPNF and related faults cut the older Skhoder‐Peja Transfer Zone with its pre‐Neogene dextral offset of the West Vardar ophiolite nappe. Rotation of the SPNF hanging wall involved Miocene‐to‐recent, out‐of‐sequence thrusting that was transferred to the Hellenic orogenic front via lateral ramps on dextral transfer zones. Along strike of the Dinarides‐Hellenides and coincident with the southward increase in Neogene shortening, the depth of the Adriatic slab increases from ~160 km north of the SPNF to ~200 km just to the south thereof, to several hundreds of kilometers to the south of the Kefalonia Transfer Zone. The geodynamic driver of tectonics since the early Miocene has been enhanced rollback of the Hellenic segment of the Adriatic slab in the aftermath of Eocene‐Oligocene slab tearing and breakoff beneath the Dinarides, which focused slab pull in the south. The SW‐retreating Hellenic slab segment induced clockwise bending of the southern Dinarides and northern Hellenides, including their Adriatic foreland, about a rotation pole in the vicinity of the Mid‐Adriatic Ridge.

The Slab Puzzle of the Alpine‐Mediterranean Region: Insights From a New, High‐Resolution, Shear Wave Velocity Model of the Upper Mantle

“…The fine-scale slab structure in the Mediterranean upper mantle remains uncertain and a matter of heated debates. This concerns, for example, the shallow structure of the Cyprus Slab (e.g., van der Meer et al, 2018), the geometry of the Antalya and Aegean Slabs (e.g., Biryol et al, 2011;Govers & Fichtner, 2016;Salaün et al, 2012), the slab structure and the presence of tears in the transition from the Aegean to the Hellenides and Dinarides (e.g., Handy et al, 2019;Hansen et al, 2019;Šumanovac et al, 2017), the slab configuration and subduction polarity in the Alps (e.g., Hua et al, 2017;Lippitsch et al, 2003;Mitterbauer et al, 2011;Zhao et al, 2016), the shape and presence of slab segments beneath the Apennines and in the transition toward Sicily and the Kabylides in Northern Africa (e.g., Faccenna et al, 2004Faccenna et al, , 2005Faccenna et al, , 2014Fichtner & Villaseñor, 2015;Lucente & Margheriti, 2008), and the slab configuration in the westernmost Mediterranean beneath the Alboran-Betic subduction zone (e.g., Alpert et al, 2013;Bezada et al, 2013;Fichtner & Villaseñor, 2015;Spakman & Wortel, 2004). In summary, a number of slab segments in the Mediterranean upper mantle have been imaged but their configuration, especially down to 300 km depth, remains inconsistently resolved by seismic tomography.…”

“…van der Meer et al (2018) do not mention slabs beneath the Hellenides and the Dinarides explicitly. However, a slab beneath the Hellenides has been suggested by Handy et al (2019) based on the tomographic studies by Piromallo and Morelli (2003), Spakman and Wortel (2004), and Amaru (2007). They favor the presence of a continuous slab beneath the Hellenides.…”

The MW = 5.6 Kanallaki Earthquake of March 21, 2020 in West Epirus, Greece: Reverse Fault Model From Insar Data and Seismotectonic Implications for Apulia-Eurasia Collision

“…The tectonics of Epirus is characterised by on-going compression due to the active collision between the Apulian continental block [1,2,3,4] and the Eurasian (Aegean) plate. The Apulian continental lithosphere subducts beneath Epirus and was imaged at 70-80 km depth by [5].…”

Geodynamics

“…1). The tectonic structures of the region are studied in detail as well as their modern deformations [Caporali, et al, 2009;Meyer, 2011;Nagel, et al, 2011;Jouanne, et al, 2012;Faccenna, et al, 2014;Handy, et al, 2019].…”

“…Carpathian-Balkan region (based on [Caporali, et al, 2009;Faccenna, et al, 2014;Handy, et al, 2019] Another major fault is located between the Adriatic Sea and the Dinarides. The Adriatic plate moves as a whole block to the north-east with the velocity equals 4 mm per year [Altiner et al, 2006].…”