The evolution of a model trap in the central Apennines, Italy: Fracture patterns, fault reactivation and development of cataclastic rocks in carbonates at the Narni Anticline

Citation
F. Storti et F. Salvini, The evolution of a model trap in the central Apennines, Italy: Fracture patterns, fault reactivation and development of cataclastic rocks in carbonates at the Narni Anticline, J PETR GEOL, 24(2), 2001, pp. 171-190
Citations number
51
Categorie Soggetti
Earth Sciences
Journal title
JOURNAL OF PETROLEUM GEOLOGY
ISSN journal
01416421 → ACNP
Volume
24
Issue
2
Year of publication
2001
Pages
171 - 190
Database
ISI
SICI code
0141-6421(200104)24:2<171:TEOAMT>2.0.ZU;2-#
Abstract
Recent hydrocarbon discoveries in the Southern Apennines of Italy have focu ssed attention on the importance of studying fracturing and cataclasis in c arbonate rocks because of their fundamental impact on reservoir permeabilit y and connectivity The Narni Anticline in the central Apennines consists of a stack of easterly-verging carbonate thrust sheets compartmentalized by e xtensional and strike-slip fault zones. The structure provides afield analo gue for studying the evolution of superimposed fold-and-fault-related fract ures in carbonate reservoir rocks. The fracture pattern at the Narni Anticline developed as a result of three mechanisms. (a) layer-parallel shortening predating folding and faulting; ( b) thrust-related folding and further thrust breakthrough; and (c) extensio nal and strike-slip faulting. Along-strike (longitudinal) fractures develop ed during progressive rollover fault-propagation folding, and their intensi ty depends on the precise structural position within the fold: fracture int ensity is high in the forelimb and low in the crest. The 3-D architecture o f the mechanical anisotropy associated with thrusting folding and related f racturing constrained the location and geometry of subsequent extensional a nd strike-slip faulting. The superimposition in damage zones of a fault-rel ated cleavage on the pre-existing fracture pattern, which is associated wit h layer-parallel shortening and thrust-related folding, resulted in rock fr agmentation and comminution, and the development of cataclastic bands. The evolution of fracturing in the Narni Anticline, its role in constrainin g thrust breakthrough trajectories and the location of extensional and stri ke-slip faults, and the final development of low-permeability cataclastic b ands, will be relevant to studies of known oilfields in the Southern Apenni nes, as well as for future exploration.