Temporal constraints on fracturing associated with fault-related folding at Sant Corneli anticline, Spanish Pyrenees

摘要

We mapped fractures at Sant Corneli anticline, an E-W trending non-cylindrical, fault-related anticline in the Spanish Pyrenees. Fracture mapping in syn-tectonic strata directly links fold-related fracturing to fold evolution because the relationship of fractures to syn-tectonic strata can constrain structural timing. Rather than using absolute fracture orientation as a primary means of grouping fracture sets, we used relative fracture timing, mineral fill, fracture size (length and height), and orientation with respect to bed strike to delineate five bed-orthogonal fracture sets that we interpret to be associated with folding and faulting events. We observe several early sets of joints with calcite fill (J1, J2, J3) many of which are interpreted to be related to fold axis perpendicular normal faulting of the anticline. Two late-stage joint sets with associated iron oxide mineralization in the surrounding wall rock (J4, J5) are oblique to bedding, maintain orientation with respect to bed strike, and are interpreted to result from flexure of the anticline. We infer the timing of J4/J5 jointing relative to syn-tectonic events. This research demonstrates how fracture studies that integrate syn-tectonic strata and distinguish fracture sets on the basis of multiple characteristics can better constrain the timing of fracturing relative to regional deformation events.