9:30 AM - 9:45 AM
[MIS04-03] Quantification of Asian dust multi-source contributions to silt and clay fractions in the Japan Sea sediments at IODP Site U1425 since 10 Ma by the Parallel Factor (PARAFAC) end-member modelling
Keywords: aeolian accumulation rate, Parallel factor analysis , Miocene to Pleistocene, Taklimakan Desert, Gobi Desert, Ordos Plateau
A complete aeolian accumulation rates in silt and clay fractions from the Late Miocene to Pleistocene were reconstructed at the Integrated Ocean Drilling Program (IODP) Site U1425 in the Japan Sea. A total of 180 samples were collected from the Hole 1425D, which had 354 m in length and covered the last 9.76 m.y. Grain size separation was conducted to evaluate the mineral composition in silt (>4 μm) and clay (<4 μm) fractions by X-ray diffractometer (XRD). Mineral composition suggests the source variabilities in silt and clay fractions, which could be interpreted as provenance shifts occurring in 8 and 2.7 Ma.
Parallel factor analysis (PARAFAC) was applied to decompose X-ray diffractograms into individual subcomponents to identify the sources and quantify their contributions. Six-components PARAFAC model was established and 3 Asian dust sources (Taklimakan Desert, Gobi Desert and Ordos Plateau), a riverine source of Japan Island Arc, and 2 biogenic sources of Opal-A and Opal-CT were identified.
In the late Miocene, high riverine flux from Japan Islands reflected strong summer monsoon during 9.7-8 Ma. Provenance shift occurred between 8 and 7 Ma from Japan Islands source to aeolian source for a short period. Flux of materials from Japan decreased to the lowest of 0.2 g/cm2/kyr in 8 Ma and aeolian flux was higher from 7.5 to 7 Ma. These data implied that Asian aridification was intensified at about 8 Ma coinciding with the late Miocene cooling. During this period, eolian flux was generally low with occasional increases to 1.4 and 1 g/cm2/kyr in 6.7 and 5.64 Ma, respectively, indicating sporadic aridification of Asian interior and the intensification of the winter monsoon.
Aeolian flux increased dramatically in Pleistocene to the maximum of 4 g/cm2/kyr, where the Gobi Desert, Taklimakan Desert and Ordos Plateau were the 3 main contributors of the aeolian flux to the Japan Sea since then. The abrupt increases of aeolian flux in Japan Sea were related to the Northern Hemisphere Glaciation (NHG) which established a very cold and dry environment to accelerate sediment erosion in the Central Asia Mountain ranges and strengthened the atmospheric circulation systems in northern hemisphere. However, aeolian flux decreased to 2.8 g/cm2/kyr during Holocene due to decreasing fluxes from Gobi and Ordos Plateau.
The contribution of Taklimakan source to Japan Sea ranged from 10 to 50% and the dust flux increased gradually in Pleistocene to the highest of 1.74 g/cm2/kyr at 0.13 Ma. Lower flux occurred in the Late Miocene to Pliocene of <0.6 g/cm2/kyr. Mass accumulation rate (MAR) of Taklimakan aeolian in silt fraction was generally higher than clay fraction. The contribution of Gobi dust to Japan Sea ranged from 20 to 50% since 10 Ma. The highest MAR of 2.42 g/cm2/kyr occurred in 1.02 Ma and the lowest in Pliocene. The MAR of Gobi dust in clay fraction was higher than silt fraction from 9.24 to 0.75 Ma. Taklimakan dust showed higher grain size index than Gobi, which could be controlled by the different pathways of westerly jet and winter monsoon from the source regions to the site.
Parallel factor analysis (PARAFAC) was applied to decompose X-ray diffractograms into individual subcomponents to identify the sources and quantify their contributions. Six-components PARAFAC model was established and 3 Asian dust sources (Taklimakan Desert, Gobi Desert and Ordos Plateau), a riverine source of Japan Island Arc, and 2 biogenic sources of Opal-A and Opal-CT were identified.
In the late Miocene, high riverine flux from Japan Islands reflected strong summer monsoon during 9.7-8 Ma. Provenance shift occurred between 8 and 7 Ma from Japan Islands source to aeolian source for a short period. Flux of materials from Japan decreased to the lowest of 0.2 g/cm2/kyr in 8 Ma and aeolian flux was higher from 7.5 to 7 Ma. These data implied that Asian aridification was intensified at about 8 Ma coinciding with the late Miocene cooling. During this period, eolian flux was generally low with occasional increases to 1.4 and 1 g/cm2/kyr in 6.7 and 5.64 Ma, respectively, indicating sporadic aridification of Asian interior and the intensification of the winter monsoon.
Aeolian flux increased dramatically in Pleistocene to the maximum of 4 g/cm2/kyr, where the Gobi Desert, Taklimakan Desert and Ordos Plateau were the 3 main contributors of the aeolian flux to the Japan Sea since then. The abrupt increases of aeolian flux in Japan Sea were related to the Northern Hemisphere Glaciation (NHG) which established a very cold and dry environment to accelerate sediment erosion in the Central Asia Mountain ranges and strengthened the atmospheric circulation systems in northern hemisphere. However, aeolian flux decreased to 2.8 g/cm2/kyr during Holocene due to decreasing fluxes from Gobi and Ordos Plateau.
The contribution of Taklimakan source to Japan Sea ranged from 10 to 50% and the dust flux increased gradually in Pleistocene to the highest of 1.74 g/cm2/kyr at 0.13 Ma. Lower flux occurred in the Late Miocene to Pliocene of <0.6 g/cm2/kyr. Mass accumulation rate (MAR) of Taklimakan aeolian in silt fraction was generally higher than clay fraction. The contribution of Gobi dust to Japan Sea ranged from 20 to 50% since 10 Ma. The highest MAR of 2.42 g/cm2/kyr occurred in 1.02 Ma and the lowest in Pliocene. The MAR of Gobi dust in clay fraction was higher than silt fraction from 9.24 to 0.75 Ma. Taklimakan dust showed higher grain size index than Gobi, which could be controlled by the different pathways of westerly jet and winter monsoon from the source regions to the site.