Introduction
The Alpine orogenic system stretches along the southern underbelly of Europe and provides a record of the complex interactions between the African and Eurasian plates. The orogenic system is characterized by a number of highly arcuate segments, including, from west to east, the Betic – Rif, the western Alps, the Calabrian Arc, and the Z-shaped bends of the Carpathian – Balkan belt (Fig. 1). The bends characterizing the Alpine system are commonly interpreted as primary features that reflect the paleo-topography of the European southern margin. It is, however, difficult to reconcile models of the bends as primary features with the continuity of the orogenic structures that extend around these bends. An alternative interpretation is that at least some of the arcuate segments of the Alpine system are secondary features that reflect oroclinal buckling of formerly linear segments of the orogen.
Our focus is on the bend pair that constitutes the Carpathian – Balkan belt. The most widely accepted tectonic models for the region focus on the convex to the east Carpathian segment, interpreting it as a primary embayment in the European margin, and invoking differing styles of terrane accretion into the embayment (e.g. Burchfiel, 1980; Channel and Horváth, 1976; Csontos and Vörös, 2004). Burtman (1986), based on preliminary paleomagnetic data, presented an alternative model in which the Carpathian – Balkan bends formed as a result of vertical axis rotation of an originally linear orogen.
Figure 1.
Satellite image of Europe overlain by the approximate traces of major orogenic fronts of the Alpine system (solid upper plate indicators), modern subduction trenches (hollow upper plate indicators) and major transform systems. Imagery courtesy of NASA earth observatory.
None of the published models consider regional paleomagnetic evidence for substantial northward translation, coeval with late-stage Alpine orogenesis, of the Eastern Mediterranean domain immediately to the south and southeast of the Carpathian – Balkan belt. Our goal is to determine if interpretation of the Carpathian - Balkan section of the Alpine orogenic belt as a secondary feature attributable to oroclinal buckling of an originally linear orogen can explain and be reconciled with the Eastern Mediterranean Inclination Anomaly (EMIA). Toward this goal, we (1) summarize the data that constrains the age and aerial extent of the EMIA, (2) assess the structural and available paleomagnetic data in order to test a secondary ‘oroclinal’ interpretation of the curvature through the Carpathian – Balkan belt, and (3) present a geometrically constrained paleogeographic model in which we invoke a cause and effect relationship between the EMIA and oroclinal buckling of an originally linear Carpathian – Balkan belt. Our model suggests that (1) an originally linear Carpathian – Balkan belt was characterized by a northwest-southeast trend, (2) northward translation of the eastern Mediterranean region recorded by the EMIA was accommodated by an equivalent amount of westward translation, and (3) deformation and translation, including oroclinal buckling of the Carpathian – Balkan belt, is explained by and provides a record of ongoing westward tectonic escape of the Aegean – Anatolian region out of the Arabian – Eurasion collision zones.