A ∼12 Myr Miocene Record of East Asian Monsoon Variability From the South China Sea

Abstract

 Equable, warm, humid climate over Southeast Asia during Miocene Climatic Optimum due to latitudinal expansion of tropical convection  Intensification of seasonal monsoonal regime linked to stepwise climate cooling during middle Miocene Climatic Transition  Decreased riverine input of alkalinity to ocean due to summer monsoon decline contributed to middle to late Miocene Carbonate Crash Accepted ArticleThis article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record. Please cite this article as

Weakened pacific overturning circulation, winter monsoon dominance and tectonism re-organized Japan Sea paleoceanography during the Late Miocene global cooling

“…In such a situation, PCW possibly influenced the intermediate water depths of the Japan Sea during intervals of the strong Pacific MOC. Additionally, until ~ 7.0 Ma, the East Asian Summer Monsoon (EASM) climate dominated, as suggested by the Tibetan Plateau clay mineral records and XRF scan analysis from sediments collected at ODP 1146 (South China Sea) 58 , 59 . Today, in an area that is influenced by the summer monsoon, such as the East China Sea, productivity is controlled by the upwelling of the NPIW on the slope of the continental shelf e.g., 60 .…”

Enhanced Late Miocene Chemical Weathering and Altered Precipitation Patterns in the Watersheds of the Bay of Bengal Recorded by Detrital Clay Radiogenic Isotopes

“…The upper Miocene sediments of U1443 are nannofossil oozes with variable amounts of foraminifers, detrital clay, biosilica, and volcanic ash (Clemens et al, 2016), and span a composite core depth from 70 to 123 m below seafloor. The age model used in this study is based on the tuning of δ 13 C measurements of monospecific epifaunal benthic foraminifers (Cibicidoides wuellerstorfi) to the reference section of ODP Site 1146 (e.g., Holbourn et al, 2018Holbourn et al, , 2021 and is consistent with Site U1443 calcareous nannofossil biostratigraphy and magnetostratigraphy (Clemens et al, 2016; see Supporting Information S1 for details). Between 6 and 8 well-preserved Cibicidoides wuellerstorfi were picked from the >212 µm fraction and cleaned in ethanol in an ultrasonic bath after being broken into fragments.…”

“…To help improve our current understanding, we present a higher resolution record from a continuous sediment sequence with a well-constrained chronology that was recovered at IODP Site U1443 on the Ninetyeast Ridge in the southern Bay of Bengal. Age control from 9 to 5 Ma is established by tuning a low-resolution benthic stable carbon isotope record from Site U1443 (Data Set S2) to the reference section of ODP Site 1146 (Holbourn et al, 2018(Holbourn et al, , 2021 and is consistent with magneto-bio-stratigraphy (Clemens et al, 2016;Figure S1). This provides a stratigraphic framework with which to compare the evolution of SAM silicate weathering inferred from changes in the clay radiogenic isotopes of Sr, Nd, and Pb with global carbon cycle and climate changes during the late Miocene.…”

Carbonate contourite drifts in the southwest South China Sea: Sedimentary, paleoceanographic and economic implications

“…The Middle Miocene was also a significant period for the onset of the modern-like East Asian monsoon system (Betzler et al, 2016). The intensification of the East Asian monsoon at ~15-10 Ma greatly enhanced the seasonal wind-driven currents Holbourn et al, 2021;Ting et al, 2021). Siliciclastic materials were transported to the ocean, forming carbonate reefs and contourite drifts e.g., in the Maldives and on the proto-Sunda Shelf (Lüdmann et al, 2013;Betzler et al, 2016;Betzler et al, 2018).…”

“…The middle Miocene South China Sea was widely influenced by the monsoonal wind-driven currents (Figure 9A). The enhanced East Asian monsoon promoted surface currents (Farnsworth et al, 2019;Holbourn et al, 2021;Ting et al, 2021), which strongly shaped the morphology of the proto-continental shelves in the northern (Tian et al, 2015), the northwest (Zhuo (Tian et al, 2015), the Zhongjian basin (Yang et al, 2021) and the study area (Figure 11). The development of these contourite features terminated at 10.5 Ma.…”