Henry Lickorish - Structural Geology
Calgary, Canada
tel: +1 250 213 2643
Using high-resolution stratigraphy to date fold and thrust activity: examples from the Neogene of south-central Sicily
Butler R.W.H. and Lickorish W.H. 1997
Journal of the Geological Society , London, 154, 633-643.

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 timescale, shows that individual thrust-fold publications grew steadily over many millions of years. publications across the thrust belt were active at the same time and accommodated bulk shortening rates of c. 0.5mm/a. In contrast the basal detachment operated about ten times faster. These results are in broad agreement with some theoretical models for orogenic wedge kinematics. Shoreline carbonate successions, calibrated with precession cycles of sea-level change, provide a vvery high resolution, temporal scale with which to chart tilt-rates on fold limbs (1/27.6ka=0.036/ka). 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 publications. However, the types of structural models that can be tested using estimates of deformation rates depend on the chronostratigraphic resolution available for the syn-tectonic sediments.