Characteristics Of Clay Minerals In Modern Sediments Between Daling River And Liaohe River

Coastal?coastal lowland?area is population-intensive and also economic-intensive.The vulnerability of coastal environment directly affects human and economic security.The accumulation process of terrigenous materials in coastal zone affect coastal construction and coastal geomorphology.The study area is located between Daling River and Liaohe River in Lower Liaohe Plain and the depositional process in the sedimentary area has been dominated by the Daling River,Liaohe River and Raoyang River in the past 100 years.In order to explore the provenance and evolution of river delta,clay minerals analysis and radioisotopes(²¹⁰Pb,¹³⁷Cs)dating were carried out on 7 sedimentary column cores and 17 river surface samples from the Liaohe-Daling Delta plain.Based on the results,the sedimentary evolution process of the Liaohe-Daling Delta plain was discussed.The main conclusions were summerized as follows:?1?The clay mineral assemblage of the Daling River sediments is montmorillonite-illite-kaolinite-chlorite.The ratio of montmorillonite content to illite content is greater than 1,and the average of illite crystallinity value is 0.41°?2?.The clay mineral assemblage of Liaohe River and Raoyang Riverare illite-montmorillonite-chlorite-kaolinite,and the ratio of montmorillonite to illite is less than 1.The average value of illite crystallinity of Liaohe River is 0.5°?2?,while the average value of Raoyang River is 0.44°?2?.The illite crystallinity of borehole sediments are quite different from that of river surface samples.?2?The characteristics of clay minerals in each river basin indicate that physical weathering is dominant in Daling River Basin,Liaohe River Basin and Raoyang River Basin,while chemical weathering of Liaohe River Basin is stronger than Daling River Basin.Clay minerals are mainly affected by surface rocks and climatic conditions in the source area.?3?According to the analysis of LH34 and LH40 borehole sediments,the supply of sediment materials in the study area from 1846 to 2016 was changed into three periods:?a?1846-1900,the sediments were mainly from the Liaohe River system;?b?1900-1978,the sediments were from Liaohe River and Daling River with dominated by Liaohe River;?c?from 1978 to the present,the sediments are mainly from Daling River.