oa Fractures as Indicators to 4D Fold Development within the Zagros Fold-and-Thrust Belt, Iran

The Zagros fold and thrust belt represents progressive deformation of Palaeozoic to Cenozoic<br>sediments above a salt detachment, which in turn overlays inverted extensional faults in the<br>metamorphic basement. The Cenozoic sediments of the Zagros contain some fine examples of exposed<br>fractured carbonate sequences.<br>Using Landsat 7 ETM+ imagery data, regional scale fracture sets have been interpreted across the<br>anticlines of Kuh-e Khurgu, Kuh-e Devin, Kuh-e Finu and Kuh-e Ginau in the Laristan domain, SE<br>Zagros. Using Quickbird imagery data, field-scale fracture sets have also been interpreted across Kuh-e<br>Khurgu. The results of the regional and field-scale fracture analysis show dominant fold axis-parallel,<br>fold axis-orthogonal, and conjugate NW-SE and NE-SW fold axis-oblique orientations.<br>Utilising the 0.67m resolution of the Quickbird data allows rapid, field-scale identification of fracture<br>patterns. Mapping the fracture and joint sets alongside fold aspect ratio analysis illustrates the<br>deformation evolution of the folds, including the presence of, and disturbance by, reactivated basement faults.<br>NW-SE orientated fracture patterns dominate anticlinal rose diagrams regardless of fold size, axial<br>orientation or shape. This abundance confirms a local underlying basement trend striking roughly NWSE.<br>A balanced cross-section of the area was constructed, using the Landsat 7 ETM+ imagery and the<br>newly released 30m Global ASTER DEM data, showing salt-cored detachment folds above a series of<br>reactivated basement thrusts that indicate both thin and thick-skinned deformation.<br>The results of the satellite image interpretation are then integrated in 3-D Move and a geological model<br>built. The restoration tools are used to validate the geological model and suggest alternatives where<br>appropriate. Once a “best fit” structural history has been identified, the data are then used to capture<br>the geometric strain history through time in 3-D Move. The strain information and other attributes<br>(e.g. curvature) are used to generate a discrete fracture network that is controlled by the observed data.<br>A multi-stage, 4-dimensional fracture model is proposed for all four folds of the area. This takes into<br>account the incremental and progressive development of fractures as strain indicators within the fold.