Weathering and erosion in central Vietnam over the Holocene and Younger Dryas: Clay mineralogy and elemental geochemistry from the Vietnam Shelf, western South China Sea

Chemical Weathering of the Mekong River Basin With Implication for East Asian Monsoon Evolution During the Late Quaternary: Marine Sediment Records in the Southern South China Sea

“…These suggest a higher contribution from the Mekong River compared to rivers in North Borneo. Second, the illite chemistry index and illite crystallinity of marine sediments have been extensively employed to trace the source of illite in the South China Sea (Liu et al, 2007b;Liu et al, 2008;Liu et al, 2016;Jiwarungrueangkul et al, 2019a;Sang et al, 2019). Illite chemical index and illite crystallinity are determined by the type and intensity of weathering in river basins (Chamley, 1989), but they show no obvious trends between MIS 1, 2, and 3 in this study (Figure 3), implying significant relation to the source of illite instead of the chemical weathering process in the source regions.…”

“…Furthermore, between 9.5 and 8.5 ka, Tjallingii et al (2010) found a rapid migration of the Paleo-Mekong River mouth which was influenced by the enhanced rate of sea-level rise (25 mm/yr) from 34 to 9 m below the modern sea level corresponding to the sea-level jump of the meltwater pulse 1C (MWP-1C). Nevertheless, sea-level fluctuations may not greatly impact terrigenous sediment variations of sediment cores that are close to their sources (e.g., Liu et al, 2010;Wan et al, 2015;Sang et al, 2019). In comparison with sea-level fluctuations in this region, no important variations of clay minerals, major elements, and Sr-Nd isotopic compositions at Core MD05-2896 are observed evidently during the MWP-1A and -1C (Figures 3, 4), suggesting that the sealevel change may not have strongly affected the terrigenous sediment variations of the studied core over the last 45 ka.…”

“…In the source regions, the chemical weathering of the parent rocks generally motivates the enrichment of immobile elements (e.g., Al, Si, Ti, and Fe) and movement of mobile elements (e.g., Ca, Na, K, and Mg) in weathering products (Nesbitt et al, 1980) and their behavior can be conserved in terrigenous sediments in the sea (Clift et al, 2014;Liu et al, 2016). Based on the behavior of major elements during the chemical weathering on the Earth's surface, the chemical index of alteration (CIA) (Nesbitt and Young, 1982), the weathering index of parker (WIP) (Parker, 1970), the plagioclase index of alteration (PIA) (Fedo et al, 1995), the index of compositional variability (CIW) (Harnois, 1988), A-CN-K and A-CNK-FM ternary diagrams (Nesbitt and Young, 1984;Nesbitt and Young, 1989), and their oxide ratios (e.g., Al 2 O 3 /K 2 O, SiO 2 /K 2 O, TiO 2 /K 2 O) have been widely utilized to identify the altered pathway and to evaluate the intensive chemical weathering in the source regions (e.g., Liu et al, 2004;Clift et al, 2014;Wan et al, 2015;Jiwarungrueangkul et al, 2019b;Sang et al, 2019). Nevertheless, the geochemical compositions of fluvial sediments are controlled by complex factors such as provenance geology, weathering and erosion processes, and hydrodynamic sorting (McLennan, 1993;Nesbitt et al, 1996;Garzanti and Resentini, 2016;Guo et al, 2018).…”

“…monsoon evolution, and tectonic activities (e.g., Liu et al, 2003;Liu et al, 2007b;Liu et al, 2010;Schimanski and Stattegger, 2005;Clift et al, 2006;Colin et al, 2010;Tjallingii et al, 2010;Tjallingii et al, 2014;Yan et al, 2011;Sang and Liu, 2021). The East Asian monsoon controls seasonal changes in wind patterns, temperature, and rainfall over Southeast Asia, which strongly impact the weathering process on the land, forcing significantly terrigenous sediment variations in the South China Sea (Webster, 1994;Chu and Wang, 2003;Liu et al, 2004;Liu et al, 2005;Chen et al, 2017;Sang et al, 2019). Clay minerals, major elements, and Sr-Nd isotopes are important compositions of terrigenous sediments in this region and contain valuable information on particular characterizations of their source regions and the weathering process on the Earth's surface (Liu and Stattegger, 2014;Liu et al, 2016).…”

A high-resolution, 1250-year long drought record from Ea Tyn Lake, Central Highlands of Việt Nam

“…The climate of Southeast Asia, including Việt Nam, during the last millennia is largely controlled by the Asian monsoon system (Buckley et al, 2010, 2014; Lieberman and Buckley, 2012; Sang et al, 2019). The Asian monsoon encompasses several implicitly related components, consisting of Indian, East Asian, and Western North Pacific monsoons (Buckley et al, 2014; Wang et al, 2017).…”