Integrated geological and geophysical analysis of the linkage between transverse zones and inherited basement structures in foreland thrust-and-fold belts: the Taiwan example

The baseline assumption being made in this proposal is that heterogeneities (in the form of pre-exisiting faults, zones of sedimentary facies change etc.) in a continental margin that forms the underthrusting plate of a thrust-and-fold belt plays an important role in the development of transverse structures in the upper plate (the thrust-and-fold belt). The hypothesis to be tested is that pre-exisitng faults along the continental margin of southeast Eurasia are being reactivated forming transverse structures in the Taiwan thrust-and-fold belt. The corollary to this hypothesis is that there is a link between these transverse structures and re-activated basement faults during early stages of collision and this therefore affects not only the structure but also the seismicity and the landscape evolution. The main objective of this research is to use an integrated data set consisting of field geology, geophysical, geodetic, and potential field data to further the understanding of the importance of fault reactivation in the formation of transverse zones, to study how the linkage and displacement between these transverse zones and thrusts works, and what the effect is on transient features such as the stress field (calculated from earthquake focal mechanisms), seismicity, and topography. Taiwan is a particularly good place to investigate this process because it is possible to trace the main features of the margin (fault systems, margin morphology) into the undeformed and weakly deformed foreland and, we think, farther into the thrust-and-fold belt itself. Furthermore, the whole (pre-existing fault systems entering the deformation, faults forming the thrust-and-fold belt, and the sedimentary system of the foreland basin) is active, meaning that the transverse structures can be illuminated at depth by earthquakes and, therefore, high-resolution seismic tomography. Taiwan, then, provides an exceptional setting for the study of the causal relationships between the formation of transverse structures in a thrust-and-fold belt and a margin’s morphology and heterogeneities.