中文摘要：

南雄盆地白垩纪-古近纪（K/Pg）界线剖面脊椎动物化石（恐龙蛋壳和龟类骨化石）的地球化学研究结果表明,从白垩纪晚期到古近纪早期中国华南地区曾发生过3次以多个铱异常为标志的地球化学环境变化事件：第一次地球化学环境变化事件发生在67 Ma前,除了有很多蛋壳显示出病理组织结构特征外,由它们为代表的恐龙种群多样性并没有发生明显变化.第二次地球化学环境变化事件规模较大,正好发生在根据孢粉组合变化划分的K/Pg界线及其附近.恐龙在K/Pg交界开始灭绝,然后持续至古新世早期.这一灭绝过程大约经历了250 ka.恐龙灭绝的原因是多次以铱异常、微量元素异常和氧同位素异常为标志的环境变化引起的,短期和长期地球化学环境的不断恶化,使恐龙无法正常繁殖后代而逐渐灭绝.第三次地球化学环境变化事件出现在早-中古新世,表明当时的环境变化及其效应可能长时间推迟陆相生态环境的恢复和哺乳动物的完全复苏.南雄盆地获得的地球化学资料、恐龙渐变灭绝模式以及古新世哺乳类的复苏在年代上与印度德干火山喷发及持续时间比较一致.

英文摘要：

Geochemical analysis of the vertebrate fossils （dinosaur eggshell fragments and chelonian bones） from the K/Pg boundary section exposed in the Nanxiong Basin, Guangdong Province, South China shows that at least three geochemical environmental events, marked by Ir anomalies, took place during the latest Cretaceous （Maastrichtian） and early Paleocene. The first geochemical environmental event occurred at about 67 Ma. In this event dinosaur diversity was hardly reduced, although it appears to have led to an increased incidence of eggshell pathology. The second event was larger, and occurred at or near the pollen-defined K/Pg boundary interval. Enrichment of other trace elements, such as Cr, Ni, Co, Zn, Pb, Cu, Mn and V, within the eggshells occurs mostly at and near the interval, and eggshells in this stratigraphic zone also show positive oxygen-18 excursions and anomalies in thickness and microstructure. Abundant Ix and other trace elements in the dinosaur eggshells reflect changes in their original mineral composition that took place before fossilization began. The anomalously abundant elements were taken into the dinosaurs＇ bodies in food, and then passed into their eggs. This process would have affected the normal physiological functioning of the dinosaurian body, as well as causing the observed eggshell pathologies. The extinction of the dinosaurs in the Nanxiong Basin did not occur instantaneously, but was spread out within 250 ka with major extinction beginning at the boundary interval. The cause may have been environmental poisoning and adverse climatic changes, as indicated by geochemical analyses of the dinosaur eggshells. Through the food chain, trace elements were taken into the dinosaurian body in excessive amounts, causing imbalances in trace element levels. This affected the dinosaurs＇ reproduction, leading to the formation of pathologic eggshells. The eggshells became so brittle that they failed to protect the developing embryos, contributing to the extinction of the dinosaurs. The thi