Turbidite deposition and the controlling mechanism in the eastern Penghu Canyon System since the Late Holocene

Turbidity currents are a critical mechanism for transporting terrigenous sediments from the northeastern South China Sea to the deep sea via submarine canyons. I This study examines the characteristics, material sources, transport processes, and genetic mechanisms of turbidity current deposits in the eastern Penghu Canyon Group since 1633 cal.aBP, using the DZ35-GC21 core sample located between the Kaoping-Penghu Canyon and the downstream section of the Penghu Canyon Group. The analysis integrates accelerator mass spectrometry (AMS) ¹⁴C dating, sediment grain size, and clay mineral data. Core DZ35-GC21 sediments are mainly clayey silts and some silts, representing an intercalation of hemipelagic deposits and turbidites. Sixty-three turbidite units that are divided by basal erosional surfaces and abrupt grain-size shifts, comprised approximately 40% of the total core length, indicating that turbidity currents exerted a major control on sedimentary evolution in this region. Clay mineral assemblages are dominated by illite and chlorite (average 89%), exhibiting minimal downcore variation in relative abundances, suggesting a persistent sediment source of rivers from the southwestern Taiwan throughout the Late Holocene. Turbidity currents were the main driver of the source-to-sink transport processes in the eastern Penghu Canyon System, while various regional oceanic dynamics—including surface currents, the South China Sea Warm Current, mid-depth circulation, internal waves, internal tides, and contour currents—also exerted supplementary influences on the study area. Comparison in turbidite frequency of core DZ35-GC21 with contemporaneous El Niño-Southern Oscillation (ENSO) variability reveals that turbidity current activity was enhanced in the study area, which was likely triggered by increased frequency of intense typhoon events driven by ENSO. Additionally, the dense medium-fine sandy turbidite layers may be related to the continuous supply of transverse overbank deposits downstream of the Gaoping Canyon.