Chemical Weathering And Its Implications To Provenance And Climate Changes Of Core ZK2 In The Liaohe Delta Since Holocene

The modern estuary delta is one of the most intense and sensitive areas of sea-land interaction.It usually preserves relatively complete information on sea level change,climate change and river change history.The Liaohe Delta is one of the four major estuary deltas in China.It is a combination of Liaohe River,Daliaohe River and Daling River,and it is a climate sensitive area.By studying the chemical composition and mineral composition characteristics of sediments in the Liaohe Delta,it can provide a basis for determining the source and evaluating the paleoclimate environment,so that we can deeply understand the evolution history of the Bohai Sea since the Holocene,and provide a basis for analyzing and predicting the future climate change.The sample in this paper is core ZK2 in the Liaohe River Delta area,Which is located at the mouth of the Daliao River in Yingkou City,Liaoning Province.The depth of the core is 41.4 m,the elevation is 4.24 m,and the rate is>90%.According to foraminifera characteristics,stratigraphic elevation,grain size,and dating data,the core ZK2 in the Liaohe Delta are divided into three sedimentary environmental evolution models:U1 lacustrine sedimentary facies,which is 11000-8820 cal a BP;U2 marine sedimentary,dating from 8820 to 1295 cal a BP,and also dividing U2 into five sedimentary subfacies:U2-1 tidal flat deposit;U2-2 shallow sea deposit;U2-3 front Delta;U2-4 delta front;U2-5 lower delta plain facies deposition;The U3 deposition unit mainly consists of a stratum since 1295 cal a BP,which is deposited on the upper delta plain.The provenances of the area was different since the Holocene by analysis the clay minerals(ISKc)?detrital minerals(quartz/feldspar,ATi index,GZi index and cluster analysis)and REE characteristic parameters[(La/Yb)ucc and 8 Eu]of core ZK2,but in general,it mainly come from the Liaohe River,followed by the Daliao River,and other rivers around the Liaohe River Delta is weak,the source is relatively stable.The chemical weathering characteristics of the Liaohe River Delta since the Holocene studied by chemical weathering parameters CIA,n(Na)/n(K),A-CN-K and A-CNK-FM triangle diagrams shows that it has undergone a process of enhancement-strongest-stronger-weakening-enhancement.we compare the chemical weathering parameters CIA,([I/S+I]/K),n(Fe)/n(Mg),and the ?18O curve of the Dongge Cave of Guizhou,nuanhuo Cave of Liaoning,the 42°N solar radiation in the Northern Hemisphere.We found that the climate change process reflected between them is basically consistent,and has a good correspondence with the climate events on the time scale.Therefore,based on the correspondence between the degree of chemical weathering and the stalagmite data,we also combine the sporopollen data in this area.Five stages of the paleoclimate changes were divided since the Holocene in this area,namely:Early Holocene(11.0?8.8 cal ka BP):the intensity of chemical weathering gradually enhanced,highly concentrated with herbal pollen,and the climate gradually turned into warm-wet conditions;Early and mid-Holocene(8.8?6.9 cal ka BP):the intensity of chemical weathering was the strongest in the Holocene,a large number of temperate broadleaf species and fern spores exhibit high levels and the climate was hot and wet;Mid?Holocene(6.9?4.6 cal ka BP):the intensity of chemical weathering was strong,but with a weakening trend,and the climate was warm and wet;Middle and late Holocene(4.6?1.3 cal ka BP):the intensity of chemical weathering was the weakest,the broadleaf plant content decreased and the climate turned cold and dry;Late Holocene(1.3 cal ka BP-present):the climate was warm and dry with an enhancing intensity of the chemical weathering.In general,the climate change process reflected by the major elements in this area is basically consistent with the stalagmite ?18O curve,revealing that the major elements have a certain role in the process of inversion of climate change.