Zhang Jie, Li Shengfeng, Chen Shufan, Yang Tianqi
Natural damage to ancient stone sculptures or cultural relicts,especial the biodeterioration,has become a new research topic.The Liang stone sculptures during the Liang Dynasty in the suburb of Nangjing,which are a group of limestone sculptures and inscripted tablets of the Liang tombs,built in the period of 522-526 AD,have been enrolled in the list of National Cultural Heritages of China.The Liang stone Sculptures have been situated in the open air for more than 1400 years since they were built.The damages to them belong to a kind of karst geomorphological phenomena,This paper presents a micro-morphological approach to the study on weathering of the stone sculptures.I. Observation on micro morphology of produced by natural damage.A. Observation in situLiang stone sculptures include stone sculptures of the mausoleums of Xiao Dan,Xiao Hui,XiaoJing and Xiao Xiu,The main types of sculptures are Bixie (a symbolic divine beast as evil-spirits exorciser),ornamental colums and inscripted tablets.The main types of the damage phenomenon can be classified in accordence to section morphology into: a) Solutional fissures and furrows,mainly along the suture line;b) Solutional pits, c) Meandering furrows, distributed on sculpture below the buried surface,d) Selective corrosional features.In order to understand the penetrating character of the fissures,we measured the weathering(solution) fissure along suture line on Xiao Hui’ s Sculpture.The parameters measured included:a) Width of fissure mouth,b) The depth of the fissure with plug gauge of 0. 5mm and 0.1mm,The measured data show a trend that the wider the fissure mouth,the deeper the total fissure.We also calculated the outer angle and the inner angle between the corroded fissures ong rock walls,where the inner angle refers to the angle between rock walls of the fissure from 0.5mm to 0.1mm wide and the outer angle from mouth to 0.1mm wide.The data indicate that:a)Inner angles are smaller than outer angle generally,b) There is a trend that the larger the total depth of the fissure,the larger thd outer angle will be.The main results of the observation in situ are summed up as follows:a) The damage to sculpture surface is mainly due to the solution with several section types,b) The solution fissure formed along suture line is an initial fatal damage,which may cause the disintegration of the whole sculpture,c) There is a difference between the surface damage on the burried line and that below the line.d) There are lichen and algal covered surfaces with obvious biodeterioration.B.Lab ObservationWe identified the epi-and endolithic lichen and alage collected from the sculpture surface.The lichens identified are Caloploca sp.;Collama sp.,Diploschistes actinostomus,Lecanora muralis;and Verrucarin sp.,The algae include Gloeocapsa sp.and the species from the order of Chamaesiphomales and Chroococales.With optical stereo microscape observation,the micro solutional fissures with chasmolithic algae along suture line can be observed.The chasmolithic algae may form the patched solutional pits and the related relict micro steps with a height of about o.1-0. 3mm.Calcite vein often forms a ridge with micro corrosion furrow on both sides.Algal coating may become full of crack with the tension of mucus while in dry season.With observation on certain minor solutional features under Scanning Electronic Microscope (SEM),the related ultral corrosional features were identified as follows:a) Bore-hole with diameter around 10μm formed by fungi filament of lichen,b) Ultral etched pits on minor patched erosional pits,composed of networks of ultral furrows which 1.5-3μm wide.Under SEM,we observed the ultral features of the normal solution surface.The main characters are that:a) Ultral solutional pits are basically along the cleavage plane of calicite or fissure among calcite grains, b)There are still organisms and a few bioerosinal features,c) Calcite grain or micrite may loosen or even come off during the weathering (solution) processes.II.Discussion A. Micro-morphologic mechanism of natural damage The basi
