Central Zagros fold-thrust belt (Iran): New insights from seismic data, field observation, and sandbox modeling

摘要

We present five generalized cross sections across the central Zagros fold-and-thrust belt (Iran). These sections show that the fold geometry varies significantly both horizontally and vertically. The style is closely related to the changes in the mechanical behavior of the lithostratigraphic horizons and, in particular, to the presence of intermediate decollements within the sedimentary pile. Restoration of the sections shows amounts of shortening of the same order from one section to the other. However, it appears to be unequally distributed, suggesting variations in basal decollement shear strength. Analogue modeling has been performed to systematically investigate the effect of an intermediate decollement level at different depths on the style of folding. The models demonstrate that the position of intermediate decollements is an important factor controlling both structural style and fold wavelength. Models with shallow intermediate decollement show regularly and widely spaced anticlines.