EGU22-1844, updated on 06 May 2022
https://doi.org/10.5194/egusphere-egu22-1844
EGU General Assembly 2022
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

Multi-proxy evidence for the denudation of Taiwan at the start of the Pliocene

Amy I. Hsieh1,2, Shahin E. Dashtgard1, Pei-Ling Wang3, Chorng-Shern Horng4, Chih-Chieh Su3, Andrew T. Lin5, Romain Vaucher6, and Ludvig Löwemark2
Amy I. Hsieh et al.
  • 1Simon Fraser University, Earth Sciences, Burnaby, Canada
  • 2Department of Geosciences, National Taiwan University, Taipei, Taiwan
  • 3Institute of Oceanography, National Taiwan University, Taipei, Taiwan
  • 4Institute of Earth Sciences, Academia Sinica, Taipei, Taiwan
  • 5Department of Earth Sciences, National Central University, Taoyuan, Taiwan
  • 6Institute of Earth Sciences, University of Lausanne, Switzerland

Collision between the Philippine Sea Plate and the Eurasian Plate in the late Miocene-early Pliocene resulted in the uplift of Taiwan, and lithospheric flexure to the west formed the adjacent Western Foreland Basin (WFB). Petrographic studies of late Miocene to Recent sediment and sedimentary strata in the WFB indicate that Taiwan was the main sediment source to the WFB in the early- to mid-Pleistocene, and prior to this, sediments were assumed to be derived primarily from the Eurasian continent. However, uplift of Taiwan began significantly earlier, and sediment derived from the island should reflect the onset and acceleration of uplift and subsequent erosion.

To resolve the timing of changes in sediment sources in the WFB, we present clay mineralogy, carbon and nitrogen geochemistry, and magnetic susceptibility data from the late Miocene to late Pliocene Kueichulin Fm that outcrops along the Da’an River in western Taiwan. This formation is composed of the lower Kuantaoshan Member, the middle Shihliufen Shale, and the upper Yutengping Sandstone. Clay mineralogy shows an upward increase in illite and illite crystallinity, and a decrease in chlorite and kaolinite starting at the base of the Shihliufen Shale, and this suggests that rapid erosion of Taiwan became a major sediment source to the WFB between the late Miocene and early Pliocene (Shihliufen Shale). δ13Corg­­­ and C/N ratios preserve the dominance of Taiwan-derived sediment in the early Pliocene where there is a marked change from dominantly marine- to dominantly terrestrially sourced carbon at the transition from the Shihliufen Shale to the overlying Yutengping Sandstone. Finally, a rapid decrease (>50%) in magnetic susceptibility across the Shihliufen/Yutengping boundary indicates a significant dilution of magnetic minerals deposited in the WFB by the high flux of non-magnetic minerals delivered from the Taiwan orogenic belt. Together, these datasets record a major shift in sediment source to the WFB during the late Miocene to early Pliocene, and that Taiwan became the dominant source of sediment supply to the WFB by the early Pliocene, approximately two million years earlier than previously thought.

How to cite: Hsieh, A. I., Dashtgard, S. E., Wang, P.-L., Horng, C.-S., Su, C.-C., Lin, A. T., Vaucher, R., and Löwemark, L.: Multi-proxy evidence for the denudation of Taiwan at the start of the Pliocene, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1844, https://doi.org/10.5194/egusphere-egu22-1844, 2022.

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