The Characteristics And Provenances Of Core S10 Sediments In The Central Okinawa Trough: Constrains On The Index Of Paleoenvironment Since 17000a

Based on precise AMS14 C dating data, we analyzed the grain size, trace elements and clay minerals of sediment core S10, collected from the Central Okinawa Trough. We investigated the sediment provenances of the research region with the rare earth elements data and clay minerals data respectively. The results indicate that core S10 records the evolution of sediment provenances of the Central Okinawa Trough since 17 000 a. Sediments in the study area were mainly composed of terrigenous sediments and igneous materials, with terrigenous sediments predominately came from the Yangtze River and the Yellow River as well as rivers from Taiwan, while the contribution of these provenances varied during the historical sediment periods. During period of 16 500~11 600 a, sediments were mainly terrigenous sediment provenances, coming from the large rivers in East China(the Yangtze River and the Yellow River). In the period of 11 600~7 750 a, although the sea level changed dramatically, sediments remained to be terrigenous sediments from the Yangtze River and the Yellow River. During period of 7 750~6 450 a, the total sediments rare earth elements data reveals that sediments predominately were volcanic materials which were acknowledged as K-Ah ash layer, while clay minerals indicate terrigenous sediment provenance was the Yellow River, which means the coarse grain sediments were mainly from volcanic materials and the fine grain sediments were mainly from the Yellow River. From 6 450 to 3 900 a, the total sediments rare earth elements data shows that terrigenous sediments increased and volcanic materials decreased except for approximate year of 4 000, when another volcanic eruption intruded and clay minerals indicate that fine grain sediments were mainly from the Yangtze River and the Yellow River, with little influence from Taiwan River. In the period of 3 900~1 900 a, terrigenous sediments were mainly from the Yangtze River and the Yellow River, with a little more sediments coming from Taiwan River. Since 1 900 a, the total sediments rare earth elements show terrigenous sediments from Yellow River predominated the sediments of Core S10, while clay minerals indicate that the fine grain sediments were mainly from the Yangtze River as well as the Taiwan River. In this study, discriminant function(DF) data of the Yangtze River and the Yellow River could be used as a new evidence of the East Asian Winter Monsoon evolution since 17 000 a. Furthermore, kaolinite and smectite were generated in the special conditions which made them come from the simplex provenance. And these two clay minerals can be used as another index of the East Asian Winter Monsoon. All these results in this paper demonstrate that rare earth elements and clay minerals study of sediments in the Central Okinawa Trough could help to clarify the evolution of sediment provenances and the East Asian Winter Monsoon since 17 000 a, which will benefit for the reconstruction of the sediment provenance and peoloenvironment evolution history.