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东濮凹陷古近系锶、硫、氧同位素组成及古环境意义 总被引:6,自引:0,他引:6
东濮凹陷是渤海湾地区一个典型的盐湖盆地,其古近系沙河街组发育多套盐岩.通过对古近系锶、硫、氧同位素组成特征的研究,讨论了古近系盐类沉积的成因及当时的古环境.研究表明: (1)东濮凹陷古近系的盐岩为陆相成因而并非来源于海水的侵入,其湖水锶同位素的主要控制因素为高87Sr/86Sr(0.720±0.005)的壳源硅铝质岩石;(2)东濮凹陷古近系盐岩中的δ34S((28~33)×10-3)普遍偏高且大于现代海相蒸发盐中的δ34S(20×10-3),表明盐类形成时的沉积环境对硫酸盐是封闭的,而对H2S是开放的;(3)锶和氧的同位素变化特征表明: 东濮凹陷在由Es4上段向Es3上段过渡时气候较为湿润,降雨量逐渐增大,导致δ18O的降低和87Sr/86Sr值的升高;而由Es3上段向Es1段过渡时,气候骤然变得干旱,导致降雨量减小,蒸发量增大. 相似文献
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Elva Escobar Briones Javier Alcocer Edith Cienfuegos Pedro Morales 《International Journal of Salt Lake Research》1998,7(4):345-355
Carbon stable isotope ratios were determined in dominant biotic components of pelagic and littoral systems in Alchichica crater-lake.
Results showed that carbon signatures were significantly different between both systems. The pelagic environment was more
depleted (−26.15 to −15.14 per mille) than the littoral zone (−21.03 to −17.91 per mille). The potential source end-point
in the simplified pelagic community was established to be diatomaceous phytoplankton; its predicted value was −21.7 per mille.
There is a clear evidence thatNodularia does not sustain the pelagic food chain. In contrast, the highly diverse littoral community was sustained by epiphytes. No
allochthonous sources seemed to influence this food web.13C enrichment was observed along the components of both systems with fractionations of 0.8 to 1.4 per mille. The contribution
of the seagrassRuppia maritima is probably associated with the detritus pathway. Carbon source partitioning between both systems was not recorded. The δ13C in Alchichica crater-lake was more enriched than in other saline lakes and could be attributed to different salinity and
CO2 concentrations among lakes. 相似文献
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