[U-03] 人新世・第四紀の気候および水循環

[U03-03] Evolution of a rapidly uplifting orogen and the preservation of paleoenvironmental proxy records

★Invited Papers

*Amy Hsieh^1,2、Shahin E. Dashtgard¹、Peter D. Clift³、Li Lo²、Romain Vaucher⁴、Christian Zeeden⁵、Ludvig A Lowemark² (1.Paleoclimate Records in Shallow Marine Strata (PRISMS) Research Group, Department of Earth Sciences, Simon Fraser University, Burnaby, Canada、2.Department of Geosciences, National Taiwan University, Taipei, Taiwan、3.Department of Earth Sciences, University College London, London, United Kingdom、4.Department of Earth Sciences, University of Geneva, Rue des Maraichers 13, 1205 Geneva, Switzerland、5.Leibniz Institute for Applied Geophysics (LIAG), Geozentrum Hannover, Hannover, Germany)

キーワード：Source-to-sink, Cyclostratigraphy, East Asian Summer Monsoon, Paleoclimate proxies, Taiwan

The rapid uplift and erosion of the Taiwan orogen since the early Pliocene resulted in exceptionally high sedimentation rates and increasing basin accommodation space, which provided ideal conditions for the preservation of climate signals in its shallow-marine strata. Time-series analysis of gamma-ray records through the late Miocene¬–early Pliocene Kueichulin Formation confirmed the presence of orbital climate cycles imprinted in the rock record, and show that the evolution of the Taiwan orogen influenced the preservation of different orbital frequencies at different stages of its uplift. The growth of Taiwan also resulted in the formation of a semi-sheltered strait, which, in addition to increased sediment supply and basin accommodation, served to enhance preservation of precession-driven hydroclimate variability.

The uplift and southwest migration of Taiwan and northwest migration of Luzon during this time period also resulted in the formation of southwest-flowing currents that transported sediment from Taiwan towards the South China Sea. The influx of Taiwan-sourced sediment is recorded in East Asian Summer Monsoon proxy records in the South China Sea, as far as >1000 km southwest from the orogen. Overall, the findings of this study confirm that shallow-marine sedimentary archives can be used for resolving orbital climate oscillations, and demonstrates how different orbital signals are imprinted in the shallow-marine record at different stages of orogenesis. Additionally, this research also demonstrates that climate-independent controls, such as tectonic- and geodynamic-driven shifts in sediment transport mechanisms and sediment source, have the potential to produce “false” climate signatures, and must be considered in order to properly interpret paleoclimate records.