The nature and origin of bed-parallel slip in Kardia Mine, Ptolemais Basin, Greece

Normal faulting in Kardia Lignite Mine within the Pliocene-Quaternary Ptolemais Basin, Northern Greece, was associated with broadly contemporaneous top to the north bed-parallel slip arising from hangingwall rollover on a km-scale displacement normal fault outside the mine. The direction of bed-parallel slip is perpendicular to the strike of minor normal faults (< 50 m displacement), which therefore provide markers for measuring the magnitude of bed-parallel slip. Associated slip data measured during 6 years of mine extraction provide constraints on the nature and kinematics of slip distributions over bed-parallel slip-surfaces, a generic issue which has previously not been possible to analyse for other extensional fault systems. Bed-parallel slip gradients lie within the range of fault displacement gradients observed in global datasets, but are lower than the gradients developed on normal faults in Kardia mine. Bed-parallel slip-surfaces are segmented both parallel and normal to the slip direction and form both soft- and hard-linked relay zones on a wide range of scales. Zones of layer-bound minor normal faults, forming extensional duplexes or arrays of bookshelf faults between bounding slip-surfaces, accommodate the transfer of slip across associated releasing relay zones.