CARBON ISOTOPE FRACTIONATION IN OSTRACOD EUCYPRIS MAREOTICA FROM CULTURE EXPERIMENTS AND ITS IMPLICATION FOR PALAEOENVIRONMENT RECONSTRUCTION
-
摘要: 选取青海湖咸水介形虫——埃及真星介为研究对象,通过温度培养实验评价胖真星介壳体的碳氧同位素分馏状况及对古环境重建的意义。实验结果表明,埃及真星介壳体的碳同位素组成来自其生长水体DIC,10℃、15℃和19℃下埃及真星介与其生长水体DIC之间的平均碳同位素差值分别为-0.48‰、-0.59‰和0.7‰。介壳与水体DIC之间存在明显的碳同位素分馏,但是两者之间的碳同位素分馏几乎不受温度的影响。与碳同位素平衡分馏条件下形成的无机方解石相比,随水体pH值的升高,埃及真星介壳体与水体DIC之间的碳同位素分馏越接近平衡分馏。因此,在利用介形虫的碳同位素组成进行古环境重建时,应该考虑不同水体生长环境中介形虫的碳同位素分馏对重建结果产生的可能影响。Abstract: Culture experiments under controlled temperatures were conducted to study the carbon and oxygen isotopic fractionation between water and ostracod shells, as well as its significance in paleoclimatic reconstructions. The carbon isotopic composition of ostracod shells is mainly controlled by the carbon-isotope of water DIC in which the shells formed. The average offsets between δ13C of shells and the co-existing water DIC are -0.48‰,-0.59‰ and 0.7‰ for culture temperature 10℃, 15℃and 19℃ respectively. Our experiments show that temperature is probably not a significant factor controlling the carbon isotopic fractionation between ostracod shells and DIC. However, the carbon fractionation factors of E. mareotica are very close to those of the synthetic inorganic calcite formed in isotopic equilibrium with the increase in water pH. So, the carbon isotopic fractionation of different species living in different water environment should be considered, if the measurements of 13C/12C ratios of non-marine ostracod valves are used in palaeoenvironmental reconstruction.
-
-
[1] Xia J, Ito E, Engstrorn D R. Geochemistry of ostracod calcite:Part 1.An experimental determination of oxygen isotope fractionation[J]. Geochimica et Cosmochimica Acta, 1997, 61:377-382.
[2] Von Grafenstein U, Erlernkeuser H,Trimborn P. Oxygen and carbon isotope in modern fresh-water ostracod valves:assessing vital offsets and autecological effects of interest for palaeoclimate studies[J]. Palaeogeography, Palaeoclimatology, Palaeoecology, 1999, 148:133-152.
[3] Keatings K W, Heaton T H E, Holmes J A. Carbon and oxygen isotope fractionation in non-marine ostracods:results from a natural culture environment[J]. Geochimica et Cosmochimica Acta, 2002, 66:1701-1711.
[4] Belis C A,Ariztegui D. The influence of biological and environmental factors on the stable isotopic composition of ostracods-the Late Pleistocene record from Lake Albano, Central Italy[J]. Journal of Paleolimnology, 2004, 63(2):219-232.
[5] Li X Z, Liu W G, Zhang P X, et al. Species, valve size, and pretreatment effects on δ18O and δ13C values of ostracod valves from Lake Qinghai, Qinghai-Tibet Plateau[J]. Chemical Geology, 2007, 46:124-134.
[6] Li X Z,Liu W G. Oxygen isotope fractionation in the ostracod Eucypris mareotica:results from a culture experiment and implications for paleoclimate reconstruction[J]. Journal of Paleolimnology, 2009.
[7] Wetterich S, Schirrmeister L, Meyer H, et al. Arctic freshwater ostracods from modern periglacial environments in the Lena river delta (Siberian Arctic, Russia):geochemical applications for palaeoenvironmental reconstructions[J]. Journal of Paleolimnology, 2008, 39:427-449.
[8] Liu W G, Liu Z H, Fu M Y, et al. Distribution of the C37 tetra-unsaturated alkenone in Lake Qinghai, China:a potential lake salinity indicator[J]. Geochimica et Cosmochimica Acta, 2008, 72:988-997.
[9] Mook W G,Vogel J C. Isotopic equilibrium between shells and their environment[J]. Science, 1968, 159:874-875.
[10] Williams W D. Chinese and Mongolian saline lakes:a limnological overview[J]. Hydrobiologia,1991, 210:39-66.
[11] Duplessy J C, Shackleton N J, Matthews R K, et al. 13C record of benthic foraminifera in the last interglacial ocean:Implications for the carbon cycle and the global deep water circulation[J]. Quaternary Research, 1984, 21:225-243.
[12] Romanek C S, Grossmann E L, Morse J W. Carbon isotopic fractionation in synthetic aragonite and calcite:effects of temperature and precipitation rate[J]. Geochimica et Cosmochimica Acta, 1992, 56:419-430.
[13] 张玲,孙镇城,安芷生,等. 青海湖地区不同水体介形类分布特征的初步研究[J]. 微体古生物学报,2006,23(4):425-436.
[ZHANG Ling, SUN Zhencheng, AN Zhisheng, et al. A preliminary distribution analysis on ostracoda of different water bodies from Qinghai Lake area, NW China[J]. Acta Micropa 1aeon to 1oca Sinica, 2006, 23(4):425-436.]
[14] Spero H J, Bijma J, Lea D W, et al. Effect of sea water carbonate concentration on foraminiferal carbon and oxygen isotopes[J]. Nature, 1997, 390:497-500.
[15] 张彭熹, 张保珍, 杨文博. 青海湖冰后期以来古气候波动模式的研究[J]. 第四纪研究,1989,9(1):66-77.
[ZHANG Pengxi, ZHANG Baozhen, YANG Wenbo. On the model of post-glacial palaeoclimatic fluctuation in Lake Qinghai region[J]. Quaternary Sciences, 1989, 9(1):66-77.]
[16] Lister G S, Kelts K, Chen K Z, et al. Lake Qinghai, China:closed-basin lake levels and the oxygen isotope record for Ostracoda since the latest Pleistocene[J]. Palaeogeography, Palaeoclimatology, Palaeoecology, 1991, 84:141-162.
[17] Liu X Q, Shen J, Wang S M, et al. Southwest monsoon changes indicated by oxygen isotope of ostracod shells from sediments in Lake Qinghai since the late Glacial[J]. Chinese Science Bulletin, 2007, 52:539-544.
[18] Henderson A C G, Holmes J A, Zhang J W, et al. A carbon-and oxygen-isotope record of recent environmental change from Qinghai Lake, NE Tibetan Plateau[J]. Chinese Science Bulletin, 2003, 48:1463-1468.
[19] Mischke S, Fuchs D, Riedel F, et al. Mid to Late Holocene palaeoenvironment of Lake Eastern Juyanze (north-western China) based on ostracods and stable isotopes[J]. Geobios, 2002, 35:99-110.
[20] Zhang J W, Holmes J A, Chen F H, et al. An 850-year ostracod-shell trace-element record from Sugan Lake,northern Tibetan Plateau, China:Implications for interpreting the shell chemistry in high-Mg/Ca waters[J]. Quaternary International, 2009, 194:119-133.
-
计量
- 文章访问数: 851
- PDF下载数: 1
- 施引文献: 0
下载: