The Holocene paleo-environmental history of the Gangkou River estuary, Hengchun Peninsula, Taiwan

  • Author(s): Christopher Lüthgens, Lih-Der Ho, Nikolaus Clemenz, Jia-Hong Chen, Chia-Hong Jen, Jiun-Yee Yen, and Shyh-Jeng Chyi
  • DOI: 10.3319/TAO.2018.05.07.01
  • Keywords: Taiwan, Hengchun Peninsula, Quartz and feldspar OSL dating, pIRIR150, Double-SAR, Paleo-environmental reconstruction, Geochronology, Eustatic sea-level, Uplift rate
  • Combined geomorphological, stratigraphical, and geochronological approach
  • Paleo-environmental data reveal eustatic sea level as primary forcing factor
  • Uplift rates for last ~4.5 ka significantly lower than in previous studies
Abstract

The coastal areas of Taiwan are facing the effects of the predicted sea-level rise in the context of global climate change. In that context a better understanding of the mechanisms and forcing factors driving the geomorphological evolution of Taiwan’s coastline is essential. In this study, we highlight the potential of small river estuaries as archives of coastal evolution and provide a paleo-environmental reconstruction of the Gangkou river estuary based on results from a combined methodological approach using geomorphological, sedimentological, and geochronological analyses. A consistent chronology was established by combining Optically Stimulated Luminescence (OSL) dating, as well as radiocarbon dating techniques. A distinct layer of beach-rock allowed firm correlation of six investigated coastal profiles. Eustatic sea level change was identified as the primary forcing factor of coastal and estuarine landscape development in the study area. Tectonic forcing could also be detected from the investigated sites, but has to be regarded as a subordinate secondary forcing factor. The estuary of Gangkou river developed in the early Holocene at about 8 ka and was fully developed by the time the Holocene sea-level maximum was reached. With the sea-level dropping until modern times, a relocation of the estuarine zones and a transition to terrestrial processes was initiated, leading to the development of a coastal dune system since about 2.5 ka. Major dune building phases correlate with the climate change associated with the Little Ice Age (LIA) event and stabilised towards recent times, which is in accordance with regional and over-regional coastal aeolian records in Taiwan.

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