Foreland basin stratigraphic control on thrust belt evolution
The link between orogenic activity and foreland basin stratigraphy is well established; however, potential controls by foreland basin stratigraphy on thrust belt architecture have not been fully evaluated. Mechanical properties of typical foreland basin stratigraphic successions influence the structural development of fold-thrust belts in predictable ways. Fundamental features of foreland basins include the onset of rapid subsidence and deposition of a coarsening-upward sedimentary succession. In the lower part of this succession are fine-grained, distal foreland basin deposits. Enlargement of the orogenic wedge through frontal accretion incorporates the foreland basin strata into the thrust belt, and distal foreland basin depositional units may be preferentially exploited as a thrust detachment zone, resulting in multiple detachment levels. We propose that foreland basin stratigraphic architecture has significant influence on the structural development of thrust belts and that, by extension, processes that influence foreland basin sedimentation may ultimately influence orogenic evolution far removed in time and space.
Figure 1. A: Schematic forward model for shortening in a thrust belt with an intermediate-level detachment. During orogenic loading, an undeformed, rheologically layered foreland basin develops (time,T = 0). As the foreland is caught up in thrust belt deformation, shortening steps up from the basal décollement to an intermediate-level detachment that is located in fine-grained, distal foreland depositional units (T = 1). With continued shortening, the stratigraphic succession below the intermediate-level detachment is also deformed resulting in a duplex and a folded fault surface (T = 2). B: Examples of thrust belts that display the geometry and detachment positions described in A. The frontal Himalaya (modified from DeCelles et al.,1998) corresponds to stage T = 1 and the Marathon segment of the Ouachita (southern United States) (modified from Chapman and McCarty, 2013) corresponds to stage T = 2. MBT—Main Boundary thrust; MFT—Main Frontal thrust; VE—vertical exaggeration.
GSA Geology. First published online May 19, 2015, doi: 10.1130/G36597.1 v. 43 no. 7 p. 579-582.