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结合含水量、TOC含量和TOC/TN比值变化曲线,18·5kaB·P·以来的四海龙湾玛珥湖沉积物全岩有机碳同位素组成(δ13CTOC)记录可划分为3个阶段:1)末次冰期晚期(18·5~14·7kaB·P·),δ13CTOC值偏正,变化范围为-29·50‰~-26·18‰,平均值约为-28·10‰;2)末次冰消期(14·7~11·7kaB·P·),δ13CTOC值显著偏负,变化范围为-33·92‰~-28·40‰,平均值约为-31·75‰,在δ13CTOC值变化曲线上表现为一个低谷,但在类似YoungerDryas的冷干事件期间(12·7~11·7kaB·P·),δ13CTOC值再次显著偏正,最高可达-28·4‰;3)全新世以来(11·7kaB·P.至今),δ13CTOC值变化幅度不大(-30·85‰~-27·37‰),基本上都在平均值-29·1‰左右。研究表明,大气CO2浓度变化是影响18·5kaB·P·以来四海龙湾玛珥湖δ13CTOC值变化的主导因素。
Combined with the curve of water content, TOC content and TOC / TN ratio, the whole-rock organic carbon isotopic composition (δ13CTOC) records of the Four Hailong Maar Lake sediments since 18 · 5kaB · P · can be divided into three stages: 1) In the late stage (18.5 ~ 14.7kaB · P ·), δ13CTOC values were positive with a range of -29 · 50 ‰ -26 · 18 ‰, with an average value of -28 · 10 ‰; 2) (14.7 ~ 11.7kaB · P ·). The δ13CTOC value was significantly negative, with a range of -33 · 92 ‰ ~ -28 · 40 ‰, with an average value of -31 · 75 ‰. On the δ13CTOC value curve (12.7 ~ 11.7kaB · P ·), the δ13CTOC value again significantly positive, up to -28 · 4 ‰; 3) since the Holocene (11 · 7kaB · P · so far), the variation of δ13CTOC value is not large (-30 · 85 ‰ ~ -27 · 37 ‰), which are all basically on the average -29 · 1 ‰. The results show that the change of atmospheric CO2 concentration is the dominant factor that affects the δ13CTOC value of Four Ma Longwan Lake Maar since 18.5kaB · P.