Abstract

Recent uplift in Crete, along the Hellenic trench, has exposed the internal portions of Alpine nappes that were transported south along north-dipping thrusts from the middle Cretaceous to the Oligocene (100–20 Ma). Flysch deposited along the leading, southern edge of the Alpine foreland basin dates the timing of nappe transport and contains twinned calcite in synorogenic limestones and calcite veins that record the stress-strain fields associated with nappe transport and stacking for a 17 Ma period between 35 and 18 Ma. The flysch ages young away from the craton thereby documenting thin-skin thrusting and nappe motion, for the first time, toward the trench.

Fossiliferous marine limestones and calcareous shales were deposited in marginal basins on the leading edges of four thrust-nappes in Crete: the higher and older flysch deposits (Asteroussia, Pindos) are underlain by younger flysch deposits of the Tripolitza and Plattenkalk nappes. The ages of these flysch deposits are well constrained and the flysch sequences are now found deformed between nappes without visible signs of Alpine metamorphism, except the lowest Plattenkalk flysch. Field observations in the flysch deposits include variable bedding, vein, fold axis, and kinematic orientations. Twinned calcite in the flysch limestones (16 samples, n = 425) and veins (23 samples, n = 612) generally preserve subhorizontal, in-transport shortening and vertical extension; where there is a strain overprint (high negative expected values [NEV]), a vertical shortening strain with transport-parallel extension (~N-S) is preserved. Strain magnitudes are greater in the vein sample suite, and differential stress magnitudes responsible for twinning are −230 bars for the entire sample suite. The tectonic evolution of the region involved thin-skinned shortening with south-vergent nappe formation, from north to south, followed by thrust motion on the Cretan detachment. Today, metamorphosed rocks (i.e., Phyllite-Quartzite unit [PQU]) overlie the basal Plattenkalk nappe placing earlier exhumed rocks of the Asteroussia, Tripolitza, and Pindos nappes on top of high-pressure (HP)-metamorphic rocks of the PQU without the deposition of any flysch.

You do not currently have access to this article.