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 Precambrian rocks of Madagascar were formed and/or modified during continental collision known as the Pan‐African orogeny. Aborted Permo‐Triassic Karoo rifting and the subsequent separation from Africa and India resulted in the formation of sedimentary basins in the west and volcanic activity predominantly along the margins. Many geological studies have documented the imprint of these processes, but little was known about the deeper structure. We therefore deployed seismic stations along an SE‐NW trending profile spanning nearly all geological domains of southern Madagascar. Here we focus on the crustal structure, which we determined based on joint analysis of receiver functions and surface waves derived from ambient noise measurements. For the sedimentary basin we document a thinning of the underlying crystalline basement by up to ∼60% to 13 km. The crustal velocity structure demonstrates that the thinning was accomplished by removal or exhumation of the lower crust. Both the Proterozoic and Archean crust have a 10 km thick upper crust and 10–12 km thick midcrust. However, in contrast to the typical structure of Proterozoic and Archean aged crust, the Archean lower crust is thicker and faster than the Proterozoic one, indicating possible magmatic intrusions; an underplated layer of 2–8 km thickness is present only below the Archean crust. The Proterozoic mafic lower crust might have been lost during continental collision by delamination or subduction or thinned as a result of extensional collapse. Finally, the Cretaceous volcanics along the east coast are characterized by thin crust (30 km) and very large VP/VS ratios.
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