安徽齐云山晚白垩世恐龙蛋矿物和元素组成及古环境分析

安徽齐云山新发现的恐龙蛋化石保存完好,是研究该地区晚白垩世恐龙动物群生活环境及绝灭的关键。本文采用粉晶X射线衍射法(XRD)、电感耦合等离子体发射光谱/质谱法(ICP-OES/MS)分析齐云山恐龙蛋壳、蛋核及围岩的宏观矿物及主量、微量元素组成,以探讨齐云山晚白垩世古环境和古气候特征。结果表明:恐龙蛋壳主要矿物组成为方解石和石英,且蛋内外物质矿物组成相似,主要为石英和长石;而元素组成包括常量元素Ca、Na、Mg、K、Al和Fe及微量元素Sr、Zn、Ba、As、Ti、V、Cr、Co、Ni、Cu、Mn、Pb、La、U和Ir,其中Sr在蛋壳中含量的平均值为6199.3×10~(-6),高于河南西峡及广东南雄大部分恐龙蛋壳中的Sr含量,蛋壳中Ir含量的平均值为59.6×10~(-12),Sr和Ir与背景值相比均有明显异常,分析认为是恐龙与外界进行物质交换时吸收有害元素引起的。而As、Mn和Pb的富集及Zn的不足可能使恐龙机体中毒进而灭绝。围岩中Fe含量的增加表明齐云山地区晚白垩世为干旱炎热的气候条件,与Fe呈正相关性的Ir元素随Fe含量的增加而富集,且越靠近K/T界线,围岩中Sr和Ir元素含量越高,这是导致该地区恐龙动物群绝灭的原因之一。此结论为研究齐云山地区恐龙动物群的生活环境提供了依据。

Mineral and Elemental Composition of Late Cretaceous Dinosaur Eggs in Qiyunshan Area, Anhui Province and Its Implication for Palaeoenvironmental Analysis

The well-preserved dinosaur egg fossils recently found in Qiyunshan area, Anhui Province are the key to study the living environment and extinction of dinosaur fauna in Late Cretaceous. In this paper, in order to discuss the palaeoenvironment and palaeoclimate, X-ray Diffraction (XRD), Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES), and Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) were used to analyze the composition of macro mineral, major elements and trace elements of the dinosaur eggshells, egg core and the surrounding rock. The results show that the main minerals of dinosaur eggshells are calcite and quartz whereas the mineral of the interior is the same as the exterior of the eggshell and is mainly quartz. Major elements include Ca, Na, Mg, K, Al, Fe, whereas trace elements include Sr, Zn, Ba, As, Ti, V, Cr, Co, Ni, Cu, Mn, Pb, La, U, Ir. The average content of Sr in the eggshells was 6199.3×10^-6, higher than most of the eggshells from Xixia of Henan province and Nanxiong of Guangdong province. The average content of Ir in the eggshells was 59.6×10^-12. Sr and Ir show obvious abnormality compared with the background values, which may be caused by absorption of harmful elements during material exchange between dinosaur body and the outside world. The accumulation of As, Mn, and Pb and the lack of Zn may lead to the poisoning of dinosaurs and then extinction. The increased Fe content in the surrounding rock indicates that the palaeoclimate in Qiyunshan area during the Late Cretaceous was dry and hot, and the content of Ir, which has a positive correlation with Fe, increase with the increase of Fe. Moreover, the closer to the Cretaceous-Paleogene (K/T) boundary, the higher content of Sr and Ir in the surrounding rock, which may be one of the reasons for the extinction of the dinosaur fauna in the area. This conclusion provides a basis for the study of the living environment of the dinosaur fauna in Qiyunshan area.