FOLD AMPLIFICATION AND PARASEQUENCE STACKING PATTERNS IN SYNTECTONIC SHOREFACE CARBONATES

Kinematic models for fault-related folding may be examined by estimati ng amplification and limb-tilt rates using the stratigraphies of synde formational strata, The methodology behind such analyses is described with reference to a case study from the Maghrebian thrust belt of Neog ene age from central Sicily, High biostratigraphic resolution is provi ded by Pliocene strata that were deposited across the Marcasita anticl ine during deformation, The coastal carbonate facies of the rocks reco rd variations of relative base-level and tilt histories, Foraminifera and nannoplankton faunal assemblages, from interbedded and laterally c ontinuous pelagic sediments, bracket the age of the strata, and sequen ce stratigraphic boundaries are used to correlate relative time lines through the depositional architecture, These chronostratigraphic data are incorporated into a depositional model to quantify the rates of up lift and sedimentation. Offlapping parasequences record progressive ti lting of the fold limb. Regionally, other sections also show this offl apping relationship, but the rate of offlap varies, thus putting const raints on the uplift history across several profiles of the fold. Tilt rates for late Pliocene time, based on an astronomically calibrated t ime scale, are estimated at 1 degrees/28 ky. with uplift rates (relati ve to long-term sea level) of 1 m/k.y. The methodology may be applied to study along-axis variations in fold amplification or regional varia tions in deformation rate. The parasequence stacking patterns and thei r implied deformation rates are inconsistent with simple fault-bend fo ld and kink-band models. They are better explained by detachment foldi ng and tightening of a preexisting anticline in conjunction with conti nued propagation of an underlying thrust.