Characteristics of Macroelements and Revealed Evolution of Weathering Intensity in Sediments of Chaohu Lake,Anhui,China
Holocene is an important period for the formation and development of human civilization.Study on the laws of climate change since Holocene will help to understand global climate change and scientifically respond to abrupt events.The major element contents and ratio characteristics in core SZK1507 of Chaohu Lake were conducted;combined with AMS 14C dating,the evolution process of weathering intensity in Chaohu Basin since 10.8 cal.ka B.P.was rebuilt,and the process of climate and environmental change in the basin and possible climate abrupt events were revealed,while the possible influencing factors of chemical weathering intensity were preliminarily explored.The results show that ① the valley values of environmental substitution index,such as chemical index of alteration(CIA)and Ki,as well as the peak values of Ba and w,both appear in the sand layers and silt layers,indicating that the chemical weathering degree is weaker than that of other layers.② During the period I(10.8-9.9 cal.ka B.P.)and the period Ⅲ(9.3-5.7 cal.ka B.P.),the chemical weathering intensity is strong;and weaker chemical weathering intensity occurs in the period Ⅱ(9.9-9.3 cal.ka B.P.);during the period Ⅳ(5.7-2.3 cal.ka B.P.),the chemical weathering intensity gradually weakens;during the period Ⅴ(from 2.3 cal.ka B.P.to the present),the chemical weathering intensity changes frequently,showing an overall weakening feature;in addition,there is a good consistency between the intensity of chemical weathering and climate change,revealing that Chaohu Basin has undergone a climate and environmental evolution process since Holocene,which is relatively wet → relatively dry→ wet → wet to dry → dry.③ The variation of weathering intensity also effectively records 9.3,8.2,4.2,and 2.8 ka B.P.abrupt events.By combining with the CIA,summer solar insolation since Holocene at 30°N,δ18O records of Sanbao Cave in Shennongjia Mountains,δ13 C of Dajiu Lake peat section in Shennongjia Mountains and other comprehensive comparisons since 11 000 cal.a B.P.,it is found that the tectonic uplift movement provides stable terrestrial debris material,and the climatic and environmental conditions of the watershed are the controlling factors for the intensity of chemical weathering.The vegetation succession under the background of climate change also affects the strength of weathering,while the particle size mainly affects the chemical element composition of sediment.
Holoceneweathering intensityenvironmental evolutionclimate eventinfluencing factormajor elementAMS 14C datingChaohu Lake
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