Strike-slip fault-propagation cleavage in carbonate rocks: the Mattinata Fault Zone, Southern Apennines, Italy |
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Authors: | Francesco Salvini Andrea Billi Donald U. Wise |
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Affiliation: | a Dipartimento di Scienze Geologiche, Università Roma Tre, Largo S. L. Murialdo 1, 00146 Rome, Italy;b Department of Geosciences, Franklin and Marshall College, P.O. Box 3003, Lancaster, PA 17604-3003, USA |
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Abstract: | Disjunctive, spaced solution cleavage in carbonate rocks is genetically associated with the propagation of the left-lateral, strike-slip Mattinata Fault in the Gargano Promontory, Italy. Typical cleavage development is restricted within the 200–300-m wide fault zone, which is bounded by virtually unfractured wall rocks. The cleavage consists of sub-parallel solution surfaces, which are often reactivated as sheared solution planes. Geometrical and kinematic relationships exist between the fault and the associated cleavage planes, thus: (1) cleavage–fault intersection lines lie parallel to the fault and the sheared cleavage rotational axes and (2) the cleavage–fault angle is almost constantly equal to 40°. A model for the development of the Mattinata Fault is proposed in which the cleavage surfaces are interpreted as fault-propagation deformations. Cleavage nucleates as solution planes at the front of the advancing fault as the result of stress concentration in this region. Two distinct, time-sequential processes are shown to operate during the fault propagation: (1) typical millimetre- to centimetre-spaced solution surfaces form in the distal tip zone of the advancing fault plane; (2) as the tip advances, the fault plane breaks through the cleavage as minor shear displacements reactivate some of these nascent surfaces. These observations may prove useful in understanding mechanisms for fault-controlled enhanced/reduced permeability and fluid pathways. |
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