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It is crucial to establish a robust chronology for understanding late Quaternary sedimentation processes and environment changes in response to sea-level fluctuation on shelves. The shelf of the East China Sea (ECS) is featured by huge terrigenous sediment input and striking land -sea interaction during the late Quaternary. However, there remains controversy in chronostratigraphic rebuilding of transgression and regression deposits during eustatic-glacial cycles, mainly due to a lack of reliable dating data. In this study, an extensive comparison of 17 optically stimulated luminescence (OSL) and 15 AMS 14C ages from core TBF-1 (upper 40 m) provides a constraint in chronostratigraphic reconstruction since Marine Isotope Stage (MIS) 5. OSL ages range from 9.5 ± 0.7 to 67.3 ± 4.8 ka at depths from 2.00 to 28.00 m, while 14C ages range from 6645 to 41435 cal a BP at depths from 0.02 to 17.52 m. Regression analysis demonstrates a high level of agreement between OSL and 14C ages, with r2 values of 0.91 and 0.90, respectively. For Holocene sediments (U1), both OSL and 14C methods are applicable in tidal sand ridges, however, it should be noted that 14C ages may exhibit a young bias of up to 3 ka. For pre-Holocene sediments (U6-U2), OSL ages are robust within saturation limitation of OSL signal (D e up to ca. 166 Gy), cross-checked by feldspar post-IR IRSL (pIRIR) dating protocol. Nevertheless, the shell 14C ages (11620 and 10390 cal a BP at depths of 13.95–14.56 m) in Last Glacial Maximum (LGM) fluvial sediments of U2 are significantly underestimated, because of their susceptibility to recrystallization and overgrowth, resulting in carbon exchange with environment. While the peaty layer's14C age in deltaic deposition (17.50 m, U5) was determined to be 36420 cal a BP, coincided with OSL age of 39.6 ± 3.9 ka. The chronostratigraphy since MIS 5 for core TBF-1 exhibits a significant correlation with previously published cores SFK-1, DZQ4, and DH02, on the ECS outer shelf. Through the evaluation of those underestimated 14C ages and saturated OSL ages, we re-elucidated the primary sedimentary facies and their respective formation periods. This sedimentary stratigraphic illustration exhibits significant consistency with eustatic-glacial cycles. The renewed chronological framework for ECS shelf allows better correlation between the late Quaternary sedimentary evolution and the land-sea interaction on open shelves dominated by siliciclastic sedimentation. [ABSTRACT FROM AUTHOR]

The East China Sea (ECS) is featured by a broad continental shelf, huge terrigenous sediment input, and striking river-sea interaction during the Quaternary. Despite previous studies, mostly on the littoral areas and inner shelf, the late Quaternary stratigraphy and sedimentary environment on the mid-outer ECS shelf were poorly documented. In particular, it is still controversial in critical issues such as the recognition of marine transgression deposits in the interglacial period and the occurrence and ages of deposits in the glacial period [1, 2, 3, 4], mainly due to the limited robust chronological data. This study presents new data on geochronology and lithology of a borehole on the outer shelf of the ECS, aiming to revisit the sedimentary stratigraphic evolution since the Marine Isotopic Stage 5 (MIS5). A comprehensive analysis of 19 luminescence and 17 AMS 14C ages provides a strong constraint for the chronostratigraphy since MIS5. The marine regression/transgression cycles were identified using sedimentological analysis, which primarily constrained the environmental change over the past 100 kyrs, including tidal sand ridge, tidal flat, tidal estuary, fluvial channel, shallow sea. Although the borehole was characterized by the strong river-sea interaction accompanied with sea level fluctuations, this study clearly identified the stratigraphic boundaries between MIS1 and MIS 5 by luminescence dating, as well as by lithology. The data confirmed the tide-influenced fluvial deposition formed during the Last Glacial Maximum on the outer shelf. We infer that tidal forcing significantly superimposed its influence on sea level change and thus formed the most striking feature on the late Quaternary stratigraphy of the open ECS shelf. The major findings of this study may allow better understanding of the Quaternary sedimentary evolution and river-sea interaction on open shelves dominated by siliciclastic sedimentation, as well as for regional stratigraphic correlation. [ABSTRACT FROM AUTHOR]

Heavy mineral assemblages have been widely used to effectively trace sediment sources. Heavy mineral assemblages are rarely used in research to trace sediment sources in the southern Okinawa Trough compared with geochemical proxies. In this study, the TESCAN Integrated Mineral Analyzer (TIMA) revealed the full-size heavy mineral assemblages in the five layers of the core sediment H4-S2 in the southern Okinawa Trough. During the past 700 years, the heavy mineral assemblages in the sediments of the southern Okinawa Trough were very similar to the East China Sea shelf/Yangtze River, mainly composed of mica and chlorite; dolomite; actinolite; and hematite/magnetite. The grain size distribution of heavy minerals is in the clay–sand range and mainly in silt. Actinolite and hornblende can indicate the supply of sediments from the East China Sea shelf/Yangtze River to the southern Okinawa Trough. Due to their complex sources, pyrite, epidote, and hematite/magnetite are not adequate indicators for distinguishing between the different provenance areas. Because previous studies have used a variety of analytical methods, especially using heavy liquids with different densities, dolomite cannot be used as a marker for sediments on the Yangtze River/East China Sea shelf. Therefore, the East China Sea shelf/Yangtze River is a vital provenance of sediments from the southern Okinawa Trough since the late Holocene period. [ABSTRACT FROM AUTHOR]