Cross section balancing across the Taiwan fold-and-thrust belt for improving palaeogeographic reconstructions of the Eurasian passive margin
Final Report Abstract
The main results of our project are as follows: • We constructed three new crustal-scale geological cross-sections at various latitudes of the Taiwan fold-and-thrust belt, on the basis of the surface geology and crust-mantle interfaces constrained from a 3D-model employing seismological data. • We infer that three basement-rooted thrusts, namely the Infra-Pilu Tunnel Thrust, the Pilu Tunnel Thrust and the Shoufeng Fault, form the structural base of three basement imbricates consisting of Eurasian pre-Cenozoic basement. Possibly, these thrust faults originated as riftrelated extensional faults related to Paleogene segmentation of the passive margin preceding the opening of the South China Sea. • The three basement imbricates overthrust the Cenozoic passive margin series and are, in turn, tectonically overlain by the upper-plate-derived Coastal Range series. • On the scale of the entire Taiwan fold-and-thrust belt, two deformation phases are of paramount importance: an older deformation phase D1 associated with W-directed transport and nappe stacking is followed and overprinted by a younger deformation phase D2 that is associated with eastward crustal-scale backfolding at a later stage. • Restorations of our cross sections yield minimum shortening estimates between 120 and 140 km in the Eurasian passive margin series, with about 50% of the basement, on top of which the accreted material was initially sitting, already subducted below the Philippine Sea Plate. • When put into paleogeographic maps, these findings imply that the Eurasian passive margin likely formed a slightly eastward-convex salient prior to plate convergence that created the Taiwan fold-and-thrust belt.
Publications
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(2017): New views on the crustal-scale geometries of the Taiwan fold-thrust belt. Annual DGGV meeting 2017, GeoBremen
Ustaszewski K., Suppe J., Zhang Y.
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(2018): New views on the crustal-scale geometries of the Taiwan fold-thrust belt. 17th Symposium of Tectonics, Structural Geology and Crystalline Geology (TSK), Jena
Ustaszewski K., Suppe J., Zhang Y.
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(2018): The Yuli Belt in the eastern Taiwan fold-andthrust belt: A Miocene accretionary prism separating Eurasian and Philippine Sea Plates. Annual DGGV meeting 2018, GeoBonn
Zhang Y., Froitzheim N., Tsai C.-H., Ustaszewski K.
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(2020): The Yuli Belt in Taiwan: part of the suture zone separating Eurasian and Philippine Sea plates. Terrestrial, Atmospheric and Oceanic Sciences, 31, 415-435
Zhang, Y., Tsai, C.-H., Froitzheim, N., Ustaszewski, K.
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(2020): Yuli Belt in the eastern Taiwan orogen: a part of suture zone separating Eurasian and Philippine Sea plates. Online conference, EGU General Assembly 2020
Zhang, Y., Tsai, C.-H., Froitzheim, N., Ustaszewski, K.
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2021: Structural evolution of the Taiwan fold-and-thrust belt gleaned from balanced cross sections and tectono-metamorphic studies in the Central Range, 140 pp. PhD thesis, Friedrich-Schiller-Universität Jena, 157 p.
Zhang, Y.
