Evolution of fluid pathways along fracture controlled faults in fold-thrust belt carbonate strata

Aquifers and reservoirs in fold-thrust belt carbonate often have low matrix-porosity and permeability, where fluid pathways depend on high porosity and permeability fracture and fault zones. Evolution of fluid pathways along fracture controlled faults has been determined in platform carbonates of the Maiella Mountain, Italy, and in basinal carbonates of the External Albanides, Albania, where stratigraphic fabric, fracture systems, folds, and faults were investigated from thin-section to fold-thrust belt scale.; Fault formation in thrust front platform carbonates initiated and grew through formation of pressure-solution surfaces and their subsequent shearing. Through mapping in the field, detailed architecture of faults ranging from incipient to ∼50 meters of normal offset are documented. A conceptual model for fault growth details evolution of the structural system through pre-tilting pressure solution surface formation, and four stages of syn-tilting fault development.; Evolution of fracture controlled faults in carbonate of the Albanides fold-thrust belt has been systematically documented using hierarchical development of structural elements. The role of fractures and faults in fluid migration was elucidated using bitumen within these structures as a paleoflow indicator. Pre-folding and folding related fracture assemblages together formed fragmentation zones within mechanical layers, and are the sites of incipient fault localization. Further deformation was accommodated by rotation and translation of fragmented rock, which formed breccia and facilitated fault offset across multiple mechanical layers. By systematic identification of fractures and faults, their evolution, and their cement and bitumen contents, along with subsurface core and well log data, NE-SW trending strike-slip faults and the associated structures at high-angle to the fold-thrust belt are identified as dominant fluid pathways.; Depositional setting and sedimentary fabric play a critical role in the localization, geometry, and distribution of bed-parallel pressure solution surfaces (PS1) in peritidal and basinal carbonate. Upon shearing, PS1 provide a major flow pathway in fold-thrust belt carbonate aquifers. A conceptual model emphasizes the link between sedimentary and structural fabric, where solution seams localize in mud-rich intervals, and the resulting PS1 geometry is influenced by sedimentary geometry. As layer-parallel slip increases to accommodate shear strain in the fold-thrust belt, more PS1 behave as mechanical layer boundaries.