[MIS05-08] Reconstruction of asian dust flux variability since 10 Ma based on grain size specific mineral composition at IODP Site U1425 in the Japan Sea
Keywords:Aeolian dust , Mass accumulation rate , Flux, illite crystallinity (FWHM), Quartz,plagioclase (albite)and illite
Terrigenous sediments at Site U1425 in Japan Sea receiving significant amount of mixture dust materials from Taklamakan desert, Gobi deserts and Chinese Loess. Japan Sea is located approximately 4000 km, 2800 km, and 2400 km to the east of Taklimakan Desert, Gobi Deserts, and Chinese Loess Plateau respectively, which are the main areas of dust emission in Asia.
In this research, total 180 samples obtained from IODP Site U1425 Hole D (354m depth) were measured for mineral composition of their silt and clay fractions by using X-ray diffraction analysis. The half height width (FWHM) and chemical index of illite were also examined.
The mineral assemblages indicate that the provenances of silt and clay may be different. The mineral composition of Chinese Loess is generally characterized by higher quartz and plagioclase. Illite is the dominant clay mineral in the Chinese Loess (Sun 2011). This suggests that higher ratios of quartz, plagioclase and illite indicate as same detrital origin as the Chinese Loess.
Quartz, plagioclase (albite), and illite are the main components of Asian desert dust minerals. According to the albite (Ab) /quartz (Q) ratio and illite crystallinity (FWHM), Asian dust within the sediment at Site U1425 can be successfully distinguished from riverine input from the Japan Island arc.
The Gobi dust significantly contributed to the Pleistocene sediments with 52% at 0.57 Ma, while Taklimakan dust was a major contributor to the Pliocene and Miocene sediment with 20-40% at Site U1425 in the Japan Sea. Contribution of riverine input from Japanese Island arc was dominant in late Miocene and decreased to less than 20% after 5 Ma.
The total mass accumulation rate (MAR) of Asian dust at Site U1425 showed a decreasing trend from Miocene to Pliocene and a increasing trend from Pleistocene to Present. The highest MAR is 3.96 g/cm2/kyr at 1.02 Ma and another peaks with 3.63 g/cm2/kyr at 9.7 Ma. The lowest MAR of Asian dust is found in Pliocene with 0.5-1.5 g/cm2/kyr.
Gobi dust showed the highest MAR during Pleistocene than others source areas after 2 Ma in Pleistocene. The highest MAR of Gobi dust is 2.79 g/cm2/kyr at 1.02 Ma while the lowest value with 0.12 to 1.0 g/cm2/kyr occurred in Pliocene. Taklimakan dust showed the highest MAR in late Miocene of 1.83 g/cm2/kyr at 9.5 Ma and slightly lower MAR in Pleistocene with 1.3 g/cm2/kyr. Riverine input of Japanese Island arc showed the lowest MAR with less than 0.5 g/cm2/kyr at Site U1425 during Pliocene to Pleistocene except for 1.02 Ma. During late Miocene, riverine input shows higher MAR from 0.5 to 2.0 g/cm2/kyr.
Asian dust and fluvial input shows different grains sizes. Grain size of riverine input at Site U1425 is finer than dust, and mostly contained in clay fraction, which is consistent with previous researches in this region. Gobi dust grain size in general is coarser than Taklimakan dust, and fluvial input of Japan Island Arc from Miocene to Pliocene. Silt size fraction dominates in Gobi dust at 4, 6.5, 8.3 and 9.5 Ma which may be related to the global cooling and strengthening of winter monsoon that could bring coarser dust particles. After 3.5 Ma, Gobi dust becomes finer than Taklimakan dust. The reason may be the increasing supply of dust from the northern Chinese Loess Plateau which is a main dust source of fine silt and clay.
In this research, total 180 samples obtained from IODP Site U1425 Hole D (354m depth) were measured for mineral composition of their silt and clay fractions by using X-ray diffraction analysis. The half height width (FWHM) and chemical index of illite were also examined.
The mineral assemblages indicate that the provenances of silt and clay may be different. The mineral composition of Chinese Loess is generally characterized by higher quartz and plagioclase. Illite is the dominant clay mineral in the Chinese Loess (Sun 2011). This suggests that higher ratios of quartz, plagioclase and illite indicate as same detrital origin as the Chinese Loess.
Quartz, plagioclase (albite), and illite are the main components of Asian desert dust minerals. According to the albite (Ab) /quartz (Q) ratio and illite crystallinity (FWHM), Asian dust within the sediment at Site U1425 can be successfully distinguished from riverine input from the Japan Island arc.
The Gobi dust significantly contributed to the Pleistocene sediments with 52% at 0.57 Ma, while Taklimakan dust was a major contributor to the Pliocene and Miocene sediment with 20-40% at Site U1425 in the Japan Sea. Contribution of riverine input from Japanese Island arc was dominant in late Miocene and decreased to less than 20% after 5 Ma.
The total mass accumulation rate (MAR) of Asian dust at Site U1425 showed a decreasing trend from Miocene to Pliocene and a increasing trend from Pleistocene to Present. The highest MAR is 3.96 g/cm2/kyr at 1.02 Ma and another peaks with 3.63 g/cm2/kyr at 9.7 Ma. The lowest MAR of Asian dust is found in Pliocene with 0.5-1.5 g/cm2/kyr.
Gobi dust showed the highest MAR during Pleistocene than others source areas after 2 Ma in Pleistocene. The highest MAR of Gobi dust is 2.79 g/cm2/kyr at 1.02 Ma while the lowest value with 0.12 to 1.0 g/cm2/kyr occurred in Pliocene. Taklimakan dust showed the highest MAR in late Miocene of 1.83 g/cm2/kyr at 9.5 Ma and slightly lower MAR in Pleistocene with 1.3 g/cm2/kyr. Riverine input of Japanese Island arc showed the lowest MAR with less than 0.5 g/cm2/kyr at Site U1425 during Pliocene to Pleistocene except for 1.02 Ma. During late Miocene, riverine input shows higher MAR from 0.5 to 2.0 g/cm2/kyr.
Asian dust and fluvial input shows different grains sizes. Grain size of riverine input at Site U1425 is finer than dust, and mostly contained in clay fraction, which is consistent with previous researches in this region. Gobi dust grain size in general is coarser than Taklimakan dust, and fluvial input of Japan Island Arc from Miocene to Pliocene. Silt size fraction dominates in Gobi dust at 4, 6.5, 8.3 and 9.5 Ma which may be related to the global cooling and strengthening of winter monsoon that could bring coarser dust particles. After 3.5 Ma, Gobi dust becomes finer than Taklimakan dust. The reason may be the increasing supply of dust from the northern Chinese Loess Plateau which is a main dust source of fine silt and clay.