摘要
翼龙骨骼及其蛋与胚胎化石对研究翼龙生殖和胚胎发育方面具有重要意义。在哈密戈壁发现的一件超过200枚翼龙蛋、胚胎和骨骼三位一体保存的哈密翼龙化石标本从极干旱强盐碱的戈壁滩搬运至相对潮湿的环境后,就会发生明显的风化破碎,表现为由外向内逐渐蚕食性风化,富含骨骼/蛋化石的区域风暴岩快速发生崩解,造成化石脱落,不含化石的区域砂岩情况稳定。针对在同一件标本上发生差异风化的现象,本文利用PLM、XRD、MIP、IC、Raman、FTIR、SEM-EDS等多种分析方法,对出现风化的围岩与稳定区域围岩进行对比研究,探寻出现不同风化表现的原因。结果表明,风化区域围岩的黏土矿物(Ca型蒙脱石为主)含量较低,孔隙较大,孔径是稳定区域围岩的7倍以上,可溶盐含量较高,是稳定区域的约36倍,可溶盐种类以极易潮解的CaCl_(2)和Ca(NO_(3))_(2)·4H_(2)O为主,而稳定区域围岩中可溶盐主要是NaCl和Na_(2)SO_(4)。通过模拟风化实验说明,造成化石标本出现差异风化的原因有以下两点,一是富集翼龙骨骼和蛋(胚胎)区域的风暴岩结构不均一、孔隙较大,结构疏松,内部胶结较弱;二是该化石区域中对温湿度变化敏感的易潮解钙盐含量较高,加之化石与围岩边界不均一性极大,与稳定区域围岩的致密均匀不同,在北京四季温湿度变化下更容易迅速风化。根据风化原因对此类标本的风化治理提出一些初步建议。本研究对发掘出的干旱地区特异埋藏的化石标本的保存及保护具有一定的指导意义。
Objectives:The skeletons,eggs and embryos are of great importance in the study of pterosaur reproduction and embryonic development.One specimen with more than 200 pterosaur eggs,embryos and skeletons was found in the Hami Gobi.However,after the fossils are transported from extremely arid and strong saline—alkali Gobi desert to the relatively humid environment,such as Beijing,they will undergo severe weathering and become broken gradually from the outside to the inside.The tempestite(surrounding rock)rich in bones and eggs,is prone to disintegration and pulverization,causing precious fossil to fall off due to lack of support from surrounding rock,while tempestite without fossil is stable.In order to understand this unusual weathering phenomenon on the same fossil specimen,the surrounding rocks with weathered fossils of bones and eggs(embryos)were compared with no weathered surrounding rocks in this paper.Methods:A series of analytic methods,involved polarized light microscope observation,X-ray diffraction(XRD)analysis,mercury intrusion test(MIP),ion chromatography(IC)analysis,Raman spectroscopy(Raman)analysis,Fourier transform infrared spectroscopy(FTIR)analysis and scanning electron microscopy(SEM-EDS)analysis.Results:The results show that compared with the no weathered surrounding rock,the weathered surrounding rock rich of fossils,the content of clay minerals(mainly calcium montmorillonite)is lower,and the pore size is larger,which is more than 7 times that of the former,and soluble salts content is higher,which is 36 times that of the former.The soluble salts of weathered surrounding rock are mainly deliquescent CaCl_(2),Ca(NO_(3))_(2)·4H_(2)O and NaCl,while the salts in the no weathered rock are mainly NaCl and Na_(2)SO_(4).Conclusions:It could be speculated by simulated weathering experiments that there are two reasons for the weathering mechanism of this fossil specimen.First,the tempestite in the area enriched with pterosaur bones and eggs(embryo)are heterogenous and of large pores,with loose structure and weak internal cementation.The second is the high content of strong deliquescent calcium salts in the fossils,which are sensitive to temperature and humidity changes.In addition,different from the dense and uniform surrounding rocks in the stable area,the boundary between the fossil and the surrounding rocks is great inhomogeneity,which is more prone to rapid weathering under the frequently changing temperature and humidity in Beijing.According to the weathering causes,some suggestions on the protection treatment of this specimen were put forward.This study has a guiding significance for the preservation and conservation of special buried fossils after excavation from arid region.
作者
韩向娜
赵文华
陈熜
蒋顺兴
汪筱林
HAN Xiangna;ZHAO Wenhua;CHEN Cong;JIANG Shunxing;WANG Xiaolin(Institute for Cultural Heritage and History of Science&Technology,University of Science and Technology Beijing,Beijing,100083;Key Laboratory of Vertebrate Evolution and Human Origins of Chinese Academy of Sciences,Institute of Vertebrate Paleontology and Paleoanthropology,Chinese Academy of Sciences,Beijing,100044;CAS Center for Excellence in Life and Paleoenvironment,Beijing,100044;College of Earth and Planetary Sciences,University of Chinese Academy of Sciences,Beijing,100049)
出处
《地质论评》
CAS
CSCD
北大核心
2022年第1期81-92,共12页
Geological Review
基金
国家自然科学基金资助项目(编号:41572020,41688103)
中央高校基本科研业务费项目(编号:FRF-BR-19-019A)
哈密市政府合作项目的成果。
关键词
哈密翼龙
蛋与胚胎
风化机理
潮解盐
新疆哈密
Hamipterus tianshanensis
eggs and embryos
weathering mechanism
deliquescent salt
Hami
Xinjiang
