Analysis of systematic fracturing in Eocene flsch of the Slovenian coastal region

We analyse systematic fractures occurring in sandstone beds in Eocene flsch of the Slovenian coastal area.\udTwo nearly perpendicular fracture sets were identifid: fractures F1 are generally NW-SE oriented, wellexpressed and predominately planar, whereas fractures F2 are NE-SW-striking, shorter, more irregular in shape,\udand terminate against the F1 set. The average orientation of both sets does not change signifiantly in a coastal\udtransect crossing all principal structural domains of the area. We analysed fracture spacing with respect to layer\udthickness and determined fracture spacing index for both fracture sets. We interpret both fracture sets as tensional\ud(Mode I) joints originating in two distinct extensional episodes. Set F1 is older and formed in NE-SW directed\udtension which we correlate with the well-documented regional post-Dinaric orogen-perpendicular extension of\udpresumably mid-Miocene age. Set F2 formed in NW-SE oriented tension, which is compatible with previously\uddocumented NE-SW-striking normal faults occurring in the area, but was so far not documented elsewhere. We\udinterpret that F1 fractures predate folding and thrusting in the coastal belt. Earlier, Eocene-Oligocene Dinaric\udthrusting therefore did not signifiantly affect the coastal area, whereas post-F1 shortening, associated with\udnorthward indentation and underthrusting of the Adria microplate, did not commence before late Miocene