Environmental changes in the north‐east Sunda region over the last 40 000 years

Abstract

Pollen and spores from 110 samples from sediment core NS07‐25 from the Nansha Trough in the South China Sea (SCS) were analysed with a particular focus on reconstructing vegetation and climate change and identifying the sources of palynomorphs on the Sunda Shelf during the Last Glacial Maximum (LGM). Palynomorph sources were identified using the Near Analysis function in ArcGIS with 62 data points of the pollen in surface sediment samples from the southern SCS. The results showed that during the LGM, pollen and spores came from the exposed Sundaland, whereas before and after the LGM, pollen and spores came from Borneo. Changes in vegetation and climate were inferred from pollen percentages, concentrations and influx and indicated that during the LGM, ferns, lowland rainforests, upper montane rainforests and lower montane forests were present on the north‐east part of the exposed Sunda Shelf but not over the entire Sunda Shelf. Climate during the LGM was cooler than it is today, but humidity was not substantially lower. During the LGM, grasses and shrubs did not cover the southern continental shelf of the SCS, possibly because they were located in the Intertropical Convergence Zone.

Sediment Provenance of the Nansha Trough Since 40 ka B.P. in the South China Sea: Evidence From δ13Corg, TOC and Pollen Composition

“…This finding may be due to the higher rainfall in the Holocene, which washed large amounts of terrestrial OM from the Borneo region, through the riverine pathway. In addition, the majority of pollen recorded in stage III was received from Borneo region through riverine pathways (Luo et al, 2019). Representing the higher abundance of C3 plants in the terrestrial OM, average δ 13 C org shows a smaller value of−24.01‰, and the signal of C3 plants is more prominent in δ 13 C org records during this stage (Figure 3).…”

“…Aeolian fluxes from an arid land area/deserted area could trigger such a phenomenon with a low nutrient sediment input. When considering stage I, the pollen and spores may have been transported from northern Borneo area (around equator) (Luo et al, 2019) and as Aeolian flux, mainly from the mainland China.…”

Mangrove sediment erosion in the Sunda Shelf during meltwater pulses: Insights from biomarker records

“…The primary objectives are to evaluate: (1) the influence of local sea-level rise on terrestrial deposition, (2) the response of mangrovederived sedimentary organic matter to MWP events, and (3) the deglacial evolution of mangrove ecosystem and implications on the carbon cycle and mangrove conservation. (Sun et al, 2002;Wang et al, 2009;Kumar et al, 2019a;Luo et al, 2019;Yang et al, 2020). The location of paleo-coastline at low sea level during the last glacial period was around the 120 m isobath (solid black line) (Hanebuth et al, 2011).…”

“…Mangroves growing near the shorelines in Southeast Asia account for the most significant proportion of mangrove forests globally (Thomas et al, 2017). However, their response to sea-level fluctuations, especially the global meltwater pulse (MWP) events during the last deglacial period, are not clear, although limited palynological studies have indicated vegetation dynamics and relatively high mangrove percentages during the last glaciation (Sun et al, 2002;Wang et al, 2009;Luo et al, 2019;Kumar et al, 2019b;Yang et al, 2020). Therefore, this study presents record of long-chain alkanes, long-chain alkanols, and taraxerol in sediments from the southern South China Sea to trace changes in the terrestrial input and mangrove carbon reservoirs during the last deglaciation.…”

“…The colored dots in the main map and inserted map indicate the main study sites. The orange squares show sites with records of mangrove pollen during the last glacial period(Sun et al, 2002;Wang et al, 2009;Kumar et al, 2019a;Luo et al, 2019;Yang et al, 2020). The location of paleo-coastline at low sea level during the last glacial period was around the 120 m isobath (solid black line)(Hanebuth et al, 2011).…”