哈密翼龙骨骼及其蛋(胚胎)化石差异风化原因分析

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...

Study on the unusual weathering of the bones and eggs accumulation with embryos fossils of Hamipterus tianshanensis

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 CaCl₂,Ca(NO₃)₂·4H₂O and NaCl,while the salts in the no weathered rock are mainly NaCl and Na₂SO₄.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.