Three-Dimensional Structural and Hydrologic Evolution a Reservoir Scale Fault-Cored Fold

J. Ryan Shackleton, Department of Geosciences, University of Massachusetts, Amherst, Massachusetts, USA, [email protected]

The Sant Corneli Anticline is a well-exposed example of a fault-cored fold whose hydrologic evolution and structural development are directly linked. The E-W striking anticline is ~5 km wide with abrupt westerly plunge, and formed in response to thrusting associated with the upper Cretaceous to Miocene collision of Iberia with Europe. The fold’s core of fractured carbonates contains a variety of west dipping normal faults with meter to decameter scale displacement and abundant calcite fill.  This carbonate unit is capped by a marl unit with low angle, calcite filled normal faults.  The marl unit is overlain by clastic syn-tectonic strata whose sedimentary architecture records limb rotation during the evolution of the fold.  The syn-tectonic strata contain a variety of joint sets that record the stresses before, during, and possibly after fold growth. Faulting in the marl and calcite-filled joints in the syn-tectonic strata suggest that normal faults within the carbonate core of the fold eventually breached the overlying marl unit. This breach may have connected the joints of the syn-tectonic strata to the underlying carbonate reservoir and eliminated previous compartmentalization of fluids.  Furthermore, breaching of the marl units probably enhanced joint formation in the overlying syn-tectonic strata.  Preliminary three-dimensional finite element restorations using Dynel have allowed us to test our hypotheses and constrain the timing of jointing and marl breach.  Future geochemical studies of calcite compositions in the three units will address this hypothesis.