DYNAMICS and ACTIVE PROCESSES - International Lithosphere ...

ILP TASK FORCE on SEDIMENTARY BASINS
2010 International Workshop
November 7-12, 2010, Tirana (Albania)
On the LINK between OROGENIC SHORTENING and “BACK-ARC”
EXTENSIONAL COLLAPSE in LOW TOPOGRAPHY OROGENS
Liviu MATENCO 1 and M. DUCEA 2
1 Netherlands Research Centre for Integrated Solid Earth Science, VU University Amsterdam,
De Boelelaan 1085, 1081 HV Amsterdam, The Netherlands,
2 University of Arizona, Department of Geosciences, Tucson, AZ, USA
Classical models of orogenic evolution assume that back arc basins form in the hinterland of
orogens, collapsing the upper plate above oceanic subduction zones. This is a common
characteristic of all low-topography orogens of Mediterranean type, driven by the fast rollback
of subducted slabs. This extension may take place far at the interior of the upper plate, as
is the case in various segments of the Carpathians, but in most cases of the Dinarides,
Apennines or Hellenides it take place superposed or far into the foreland of oceanic susture
zones. Therefore, the term back-arc extension is misleading, as exhumation along major
detachment zones takes place in the core of the orogen (Rif, Betics), in the accreted crustal
material of the lower plate (Apennines, Dinarides) or even in the fore-arc (Aegean). The
present-day Mediterranean Sea with its oceanic crust does not contain the main subduction
zone which formed these mountain chains. Western Mediterranean formed in response to the
rapid roll-back of the Calabrian slab, while Eastern Mediterranean is a remnant of an older
oceanic domain, the Neotethys. The Mediterranean orogens formed in response to the
subduction and collision of the Alpine Tethys (senso largo) during post-Early Cretaceous
times. The Hellenides are a particular situation, where the continental crust has been scraped
between the point of Alpine Tethys collision and Neotethys, initiating subduction in the latter.
This means that collision has largely duplicated crustal blocks from the lower plate and has
gradually shifted subduction zone far towards the lower plate. Amounts of lower plate
shortening in these orogens range from >120km in the Dinarides,