The Style and Evolution of Foreland Structures: An Example from the Sulaiman Lobe, Pakistan

Abstract

 Structural cross sections constrained with seismic reflection, borehole, Landsat, and surface geology in the foreland of the Sulaiman lobe provides data on the style and evolution of a specific foreland structures. Seismic reflection profiles show about 10 km thick stratigraphic section at the deformation front. Nearly all of the stratigraphic section is detached from the crystalline basement, suggesting a deep decollement at the base of the wedge.: Structural uplift of 4-8 km is observed in the seismic reflection profiles, without emergent thrusts in the fureland. This is interpreted to be related to passive-roof duplex style of deformation. Duplex sequence is consists of Juras-sic and older strata with a floor thrust taeco\lemen,t) at the base of the section and a roof thrust (passlve tsxckthrust) in thick Cretaceous shales.
Three cross sections across the foreland show the structural variations from: (1) two broad (half-wavelength about 25 km), low amplitude (1-1.5 krn) folds in front of the duplex; (2) a small wavelength (about 3.5), low amplitude (about 1 km) fault- propagation fold ahead of a broad fold and the duplex; and (3) a duplex respectively at the deformation front. This data suggests chronology of foreland structures from a fault-propagation fold to a broad concentric buckle fold to a duplex.