The Calabrian Orocline: buckling of a previously more linear orogen
Recent structural studies of the Apennines and the Calabrian orocline and a compilation of structural, stratigraphic, GPS and palaeomagnetic data from the central and western Mediterranean region show that beginning in the Late Miocene a N–S trending ribbon continent that had been previously deformed, and which we now recognize as the Apennine–Sicilian thrust belt, buckled eastward in response to northward movement of Africa relative to stable Europe. A simple geometric model is consistent with available data and shows how eastward buckling of an originally north–south continental beam explains: (1) opening of the Tyrrhenian Sea basin from 7–2 Ma, at which point sea-floor spreading ceases and the basin begins to shrink by southward subduction beneath Sicily; (2) the coeval development of an east-verging fold-and-thrust belt along the length of the Apennine–Sicilian belt in response to overthrusting of the autochthon to the east, followed by extension beginning at 1 Ma as the Apennine portion of the beam begins to retreat to the SW; and (3) subduction of continental and oceanic lithosphere east of the buckling beam into a trench that migrates eastward through time due to ‘push back’ by the buckling upper plate.
Figures & Tables
Plate tectonics provide a unifying conceptual framework for the understanding of Phanerozoic orogens. More controversially, recent syntheses apply these principles as far back as the Early Archaean. Many ancient orogens are, however, poorly preserved and the processes responsible for them are not well understood. The effects of processes such as delamination, subduction of oceanic and aseismic ridges, overriding of plumes and subduction erosion are rarely identified in ancient orogens, although they have a profound effect on Cenozoic orogens. However, deeply eroded ancient orogens provide insights into the hidden roots of modern orogens. Recent advances in analytical techniques, as well as in fields such as geodynamics, have provided fresh insights into ancient orogenic belts, so that realistic modern analogies can now be applied. This Special Publication offers up-to-date reviews and models for some of the most important orogenic belts developed over the past 2.5 billion years of Earth history.