【作者】 程红光；

【导师】 李心清；

【作者基本信息】 中国科学院研究生院（地球化学研究所） ， 环境地球化学， 2006， 硕士

【摘要】 海相碳酸盐岩中的碳、氧同位素组成及其演化特征分析是古气候、古海洋环境研究的一种常用手段。古代海相碳酸盐岩稳定同位素组成能近似地反映古海洋稳定同位素的组成。因此，研究海相碳酸盐岩稳定同位素组成对于了解古海洋平面变化、构造活动、全球气候冷暖变化、生物灭绝以及古海水温度、盐度等具有十分重要的意义。40多年碳酸盐岩碳、氧同位素研究历史表明：腕足化石分布广泛、壳体为低镁方解石成分，因而具有较强抵抗成岩后生作用改造能力，是重建地质历史时期原始海洋碳、氧同位素的理想分析对象。本论文对来自四川龙门山泥盆纪的腕足化石进行碳、氧同位素分析。通过对其碳、氧同位素不同影响因子的分析，结合四川龙门山泥盆纪时期的构造活动、地理位置以及其海平面变化的探讨，本论文得出如下初步认识： 1：四川龙门山腕足化石微体结构识别、阴极发光实验、微量元素识别以及碳、氧同位素研究表明：绝大多数腕足化石保存着原始的海水碳、氧同位素特征。 2：腕足化石的碳、氧同位素组成显示：其演化趋势同四川龙门山泥盆纪时期岩相古地理所反演的海平面变化有着良好的相关性。氧同位素呈负相关，碳同位素呈正相关。吉维特早、中期和弗拉斯早期的海侵、吉维特晚期和弗拉斯晚期的海退都在碳、氧同位素演化特征中有所反映。 3：通过对腕足化石中的氧同位素组成演化原因探讨中，氧同位素对应于海平面变化，可能受控于引起海平面变化的冰川效应、大洋深层水的形成以及温度。初步估计冰川效应及大洋深层水可能影响氧同位素变化幅度为2.5‰，温度因蒸发作用所造成的氧同位素变化2‰，同时温度的变化加强冰川效应。三者共同作用造成四川龙门山泥盆纪腕足化石氧同位素变化达5‰。碳同位素变更多还原

【Abstract】 The carbon and oxygen isotope composition and its evolution of Marine carbonate rock is commonly means to the study of the ancient climate and ancient marine environment. The stable isotope composition of Ancient marine carbonate rock approximate reflect the stable isotope composition. of the ancient oceans. Therefore, the study of marine carbonate rock stable isotope composition is of great significance to understanding the changes of paleocean level, tectonic activity, global climate changes, biological extinction, ancient seawater temperature and salinity. Last 40 years studies shows: brachiopods fossils is the ideal target to reconstruct the stable isotope composition of the ancient oceans for they are widely distributed, low magnesium calcite shell components, and thus have a stronger resistance to the transformation of the role of geneticive capacity geological history.This paper analysed the carbon and oxygen isotope composition of brachiopods fossils from the Devonian Period in Sichuan Province. Through analysis the influence factors that impact its carbon and oxygen isotope composition of brachiopods fossils, the Devonian Period tectonic activity, geographical location and its sea-level change, we reach the following preliminary understanding:1: Passes means of petrographic, trace element, cathodoluminescence, oxygen and carbon isotope analysis: the most of brachiopods from Devonian in Longmen mountain, Sichuan province presered the original oxygen and carbon isotope feature of seawater.2: the carbon, oxygen isotope composition of brachiopods fossils shows: the trends of its evolution have good relationship with the sea-level that reflected by lithofacies paleography. The Sichuan Longmen Mountain Devonian period. The heavy values of oxygen and the light values of carbon reflect the low sea-level. The variations in the oxygen and carbon isotopic signals reflect the transgression happened in the lower and middle Givetian stage and the lower Frasnian stage and the regression happened in the upper Givetian stage and the upper Frasnian stage.3: By discuss the carbon and oxygen isotope composition of brachiopods fossils and its evolution更多还原