The Gela Nappe of south central Sicily provides an example of a curved segment of an orogenic front that can be examined both onshore and offshore for deformational style and amount of shortening. Synorogenic sediments allow the deformation to be dated. Two distinct structural styles are observed in the Gela Nappe: The central salient part of the nappe (Caltanissetta basin) consists of a single thrust sheet containing a train of continuously tightening folds and the reentrant margins of the nappe (Sciacca and Monte Judica) consist of a stack of several thrust sheets. These different structural styles correspond to the pretectonic Mesozoic stratigraphy of the foreland plate. Carbonate platforms exist on the Adventure bank and Hyblean Plateau ahead of Sciacca and Monte Judica, respectively, while the Caltanissetta basin region appears to have accumulated basinal clay facies. Where the resistant carbonate stratigraphy provides a buttress to the propagation of the thrust front, deformation is taken up by imbrication on‐steep ramps through the carbonates generating a relatively thick orogenic wedge. In the basinal setting, where no strong rheology exists, the low angle of friction on the clay detachment levels requires the growing thrust wedge to be much thinner with a very low foreland dip. Hence the thrust front propagates much farther forward into the basin than it does in the adjacent platformal areas, producing a nonlinear thrust front. In the basinal region, accretion of foreland material to the nappe by imbrication was only prominent during the Messinian when subaerial exposure prevented low‐friction transport of the nappe across the highest levels of the stratigraphy. A steady thickening of the nappe by internal folding suggests an increase in friction along the basal detachment, possibly due to progressive compaction of the clays.

The Tertiary foreland basin of the southern Subalpine chains preserves a stratigraphic record of late Alpine deformation, both ahead of the thrust front in the Valensole basin, and in a series of thrust-sheet-top basin remnants. Stratigraphy and growth structures in these basin remnants have been used to identify the location and timing of deformation and hence to constrain the sequential restoration of a cross section through the region.The thrust belt developed as a single large thrust sheet riding on a weak Triassic evaporite layer. Minor breaching thrusts occur, in particular at Mesozoic normal faults. Kinematic studies of the Digne thrust sheet show a dominantly SW direction of tectonic transport. Where reactivated structures lie at a slightly oblique angle to the transport direction there has been a partitioning of deformation into SW-directed thrusting and a component of dextral strike-slip taken up on minor faults. The total shortening across the fold and thrust belt is 21.5 km, a much lower value than previously estimated but more in line with regional tectonics.The foreland basin stratigraphy demonstrates that deformation within the Digne sheet occurred in three stages. Firstly, during the late Eocene, Alpine collision in the hinterland caused flexure of the foreland plate to generate a simple broad marine foredeep. Slight detachment above the Triassic evaporites allowed gentle buckling of the floor of the foredeep. Secondly, in the Early to Mid-Oligocene overthrust shear associated with the SW emplacement of the internally derived Embrunais-Ubaye nappes into the foredeep caused substantial deformation in the underlying Digne sheet.

The arcuate form of the external western Alps was generated during Tertiary NW-directed collision between the Apulian indentor and the southward-subducting European passive margin. The evolution of peripheral syn-collisional depocentres around this arcuate orogen (in France and Switzerland) is reconstructed using a compilation of stratigraphic and tectonic data. This reveals fundamental changes in the flexural behaviour of the European lithosphere during collision. During early collision (Eocene), an increasingly arcuate, peripheral flexural basin migrated rapidly NW across the European plate. During peak collision (early Oligocene), frontal flexure, recorded in the North Alpine Foreland Basin (NAFB), steepened markedly, while lateral flexure of the European plate, affecting SE France, effectively ceased. Here, Oligocene sedimentation was confined to small thrust-sheet-top basins. Two rift systems initiating in the late Eocene, the West European rift system and the West Mediterranean oceanic basin (that created the Gulf of Lion passive margin), are superimposed in space and time on the outer margins of the alpine flexural depocentres. During waning collision (Mio-Pliocene) the NAFB became overfilled, then uplifted and abandoned while, in SE France, a local depocentre (Digne-Valensole) developed between uplifting blocks and continued to accumulate sediments until the late Pliocene.

Abstract:The integration of structural and stratigraphic data is fundamental for determining rates of deformation in the uppermost continental crust. The high temporal resolution provided by Neogene marine sediments is used here to examine deformation rates in part of a thrust belt chosen from the Maghrebian orogen of Sicily. Conventional biozonal stratigraphy, calibrated against the geomagnetic polarity time scale, shows that individual thrust-fold structures grew steadily over many millions of years. Structures across the thrust belt were active at the same time and accommodated bulk shortening rates of c. 0.5 mm a 1 . In contrast the basal detachment operated about ten times faster. These results are in broad agreement with some theoretical models for orogenic wedge kinematics. Shore-line carbonate successions, calibrated with precession cycles of sea-level change, provide a very high-resolution, temporal scale with which to chart tilt rates on fold limbs (1 /27.6 ka=0.036 ka 1 ). These show that fold amplification was continuous although the rates may have varied with time. Incremental tilting of limbs during fold amplification is not predicted by popular models of fault-bend and 'fault-propagation' folding. Geometric modelling suggests that folding occurred by limb rotation, with minor hinge migration during buckling above buried thrusts. Thus stratigraphic data may be used to examine the kinematic evolution of thrust-fold systems along regional cross-sections, and of local structures. However, the types of structural models that can be tested using estimates of deformation rates depend upon the chrono-stratigraphic resolution available for the syn-tectonic sediments.