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陆生蜗牛壳体化石碳酸盐(文石,CaCO3)稳定碳同位素组成已被用于解释过去古植被C3/C4光合作用类型的变化,但是蜗牛壳体碳同位素组成是否取决于其食物碳同位素组成一直是争议的问题.对黄土高原等地现生蜗牛软体躯干有机碳和壳体文石无机碳同位素组成测量表明,壳体文石无机碳同位素δ13Ca分布范围为-13.1‰~-4.3‰;对应的软体躯干有机碳同位素δ13Corg分布范围为-26.8‰~-18.0‰,两者之间存在显著的相关关系(δ13Ca=1.021δ13Corg+14.38;R=0.965;N=31),壳体文石13C相对于躯干平均富集(14.2±0.8)‰.由于蜗牛软体和食物碳同位素组成一致,这样结果表明黄土高原陆生蜗牛壳体碳同位素组成可以反映其食物的同位素特征和潜在生态背景.进而认为:(1)蜗牛碳酸盐壳体中的碳主要来自于蜗牛代谢(呼吸)作用产生的CO2;(2)蜗牛休眠、壳体封闭时期壳内CO2与体液HCO3-之间碳同位素处于平衡分馏状态;蜗牛活动时期CO2的释放,壳体文石形成,碳同位素动力分馏作用发生,导致壳体文石13C富集程度显著高于同位素平衡分馏值.
The stable carbon isotope composition of the terrestrial snail shell fossil carbonate (aragonite, CaCO3) has been used to explain the changes of photosynthesis types in the past Paleozoic C3 / C4. However, whether the carbon isotope composition of the snail shell depends on its food carbon isotope Composition has always been a controversial issue.The measurements of the inorganic carbon isotopic composition of the organic carbon and the aragonite of the emerging snail molluscs in the Loess Plateau show that the δ13Ca range of the inorganic aragonite is -13.1 ‰ -4.3 ‰, The δ13Corg distribution range of the body of the software corresponds to -26.8 ‰ ~ -18.0 ‰, with a significant correlation (δ13Ca = 1.021δ13Corg + 14.38; R = 0.965; N = 31) (14.2 ± 0.8) ‰ with respect to the trunk.The results show that the carbon isotope composition of the terrestrial snail shells in the Loess Plateau can reflect the isotopic composition and potential ecological background of the food.So that : (1) The carbon in the shell of snail carbonate mainly comes from the CO2 produced by snail metabolism (respiration); (2) The snail dormancy, the carbon isotope between shell CO2 and body fluid HCO3- is in equilibrium Fractionation state; release of CO2 during the snail’s active period, formation of aragonite and carbon isotope dynamic fractionation resulted in the enrichment of aragonite 13C significantly higher than isotope equilibrium fractionation.