DETERIORATION DIAGNOSIS AND WEATHERING CHARACTERISTICS...

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12th International Congress on the Deterioration and Conservation of Stone Columbia University, New York, 2012

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DETERIORATION DIAGNOSIS AND WEATHERING CHARACTERISTICS OF THE DINOSAUR FOOTPRINT FOSSILS

IN HAENAM UHANGRI, REPUBLIC OF KOREA

J. H. Yoo,1 Y. H. Jo,1 Y. G. Chun2 and C. H. Lee1

1Department of Cultural Heritage Conservation Sciences, Kongju National University, Gongju, 314-701, Republic of Korea

2Conservation Science Division, National Institute of Cultural Heritage, Daejeon, 305-380, Republic of Korea

Abstract The purpose of the study is to interpret the weathering characteristics of the dinosaurs footprint fossils sites of Haenam Uhangri, which is a natural monument of Korea, and to reduce their deterioration. To achieve these purposes, the characteristics of the materials of the fossils has been determined and the assessment of the rate of deterioration. Also the analysis on the various surface pollutants on the fossils has been performed and microclimatic monitoring carried out. The results obtained from these investigations will be used as the basic data for the conservation of the dinosaurs footprint fossils.

Keywords: Dinosaurs footprint fossils, rock properties, pollutant analysis, deterioration assessment, microclimatic monitoring 1. Introduction

Fossil sites are generally found in sedimentary rock deposits. Their heterogeneous properties including vertical mineral composition changes, stratification and bedding, and other structural features make them susceptible to deterioration along the mechanical weak zones (Jeong and Kim 2004). Therefore, to maintain the long-term conservation and to reduce the deterioration rate on the fossils, it is necessary to establish the approach to conservation based on precise, non-destructive diagnosis and conservation environment research.

Little conservation science research has been carried out on natural monuments such as the dinosaur fossil sites and much more research will be needed to conserve and manage the up to 10,000 footprint fossil sites in Korea.

2. Methodology

The sites of the dinosaurs, pterosaurs, webbed feet bird footprint fossils, which are the research objects of this paper, are situated in Uhangri area of Korea (Figure 1A). At present, three protective buildings have been constructed. But in the area in which the fossil sites are situated, the ground water is high due to Kumho lake, which used to be the sea. Except for the dry season, the ground water flowed into the lower part of the slope and, as a result, puddles are made. Accordingly the original shape of this site has

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been destroyed by various physical-chemical-biological factors and environmental factors.

This research has revealed the material characteristics on the sites of dinosaurs, pterosaurs, webbed feet bird footprint fossils in Haenam Uhangri (Figure 1B-1F). And the quantitative evaluation of the degree of damage has been made by performing non-destructive inspection. In addition, the analysis on the ingredients of the various pollutants that are on the surface of the fossil sites has been performed by a P-XRF (portable X-ray fluorescence) analyzer. Finally, temperature and humidty monitoring has been performed and the resulting data interpreted.

Figure 1. Location and foreground of research object. (A) Location map of the Uhangri footprint fossils. (B) Aerial photograph of all over the Uhangri fossil sites. (C) Ornithopods fossils at protection hall no.1. (D) Pterosaurs and webbed feet birds fossils at protection hall no.2. (E) Giant dinosaur fossils at protection hall no.3. (F) Giant dinosaur fossils outside of protection hall no.3. 3. Results and discussion 3.1 Rock properties

To investigate the petrologic and mineralogical properties of the footprint fossils, we collected stone samples near each area and examined them in thin-section with a polarizing light microscope. The results show that the ornithopod footprint fossils at the first protection hall are conserved in pelite layer showing cryptocrystalline light brown ground mass and phenocrysts of quartz, calcite, plagioclase (Figure 2A). The pterosaurs and webbed feet bird fossils at the second protection hall appeared in black shale showing laminated foliated structure (Figure 2B). The giant dinosaurs fossils at the third

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protection hall are composed of black shale mixed with colored and black, the giant dinosaurs fossils at the building outside are also composed of tuffaceous sandstone with rhyolitic ground mass and anhedral phenocrysts of quartz and albite (Figure 2C). The results of identification by XRD analysis show the same mineral compositions observed by polarization microscope (Figure 2D).

Magnetic susceptibility of fossil stone shows low values less than 0.1 (×10-3 SI units) at all sites. The results mean that is closely related to petrological properties with a high content of organic matter. Magnetic susceptibility of sediments composed of sedimentary rock implies the environment conditions at the creation time (Anderson and Rippey 1988; Hilton and Lishman 1985; Boar and Harper 2002). It also means that the dinosaur fossils at Haenam Uhangri show the nearly same sedimentary environmental conditions.

Figure 2. Photomicrograph of the Uhangri footprint fossils. (A) Photomicrograph of ornithopods fossils at protection hall no.1. (B) Photomicrograph of pterosaurs and webbed feet bird fossils at protection hall no.2. (C) Photomicrograph of giant dinosaurs fossils at protection hall no.3. (D) Photomicrograph of giant dinosaurs fossils outside of protection hall no.3.

3.2. Weathering characteristics and deterioration evaluation

The evaluation of deterioration of the dinosaur fossils shows that cracks, scaling, cataclastic zone, attenuated conservation materials appear as main physical weathering phenomena. In addition, efflorescence, discoloration, and zone of saturation were also observed as main chemical weathering phenomena (Figure 3). Figure 4 shows comprehensive evaluation of the forms of deterioration based on the deterioration map.

Figure 3. Various weathering forms appeared in the Uhangri footprints fossils.

In case of cracks, the giant dinosaur fossils at the third protection hall show the

severest crack deterioration level, and the giant dinosaur fossils at the building outside

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show the lowest crack deterioration level. That means the results were caused by the material differences between fossils at the protection hall and at the building outside. The fossils at the protection hall are composed of mudstone or shale, and the fossils at the building outside are composed of tuffaceous sandstone.

Comprehensive deterioration evaluation of the ornithopods fossils at the first protection hall show mixed results with 8.54 % scaling, 4.32 % cataclastic zone, and 0.93 % attenuated conservation materials. Efflorescence appeared at 4.75 % and saturated zone also appeared at 8.73 %. These values indicate the second deterioration level among all the fossils. Biological weathering indicates 11.22 %, and that also means the severest deterioration level.

Figure 4. Comprehensive deterioration rate of the Uhangri footprints fossils.

Pterosaurs and webbed feet birds fossils at the second protection hall show the

following values: scaling is 11.66 %, attenuated conservation material is 0.10 %, efflorescence is 1.42 %, saturated zone is 3.48 %, biological weathering is 7.58 %. These values imply that the physical weathering problem is more serious in the fossils at this protection hall.

Giant dinosaur fossils at the third protection hall show the following results: scaling is 5.78 % and cataclastic zone is 4.92 %. This means the fossils have a high level of physical deterioration. The share of attenuated conservation material indicates 1.13 %, and which means the highest level of conservation treatment was performed for the fossils at this protection hall. Efflorescence shows the highest level, 75.75 %. The saturated zone is 11.43 %, and the biological weathering is 5.41 %.

The investigation results of the giant dinosaur fossils at building outside show that scaling is 11.95 % and cataclastic zone is 33.11 %. The results imply these fossils have the severest physical deterioration level among all investigated fossils. The results also imply that this area has a very high deterioration possibility because no conservation

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treatment has been done. We can also know the chemical weathering in this area affected the color change such as the brown discoloration as 30.21 %, the black discoloration as 52.71 %. Biological weathering shows a value of 0.05 %. 3.3 Nondestructive diagnosis

Ultrasonic velocity is constant in the same medium and has a close relationship with medium, modulus of elasticity, and density (Goodman 1989). From the perspective of rock mechanics, medium stress and material properties have been investigated at this site by using the ultrasonic test method. The ultrasonic velocity method has some disadvantages such as reliability problems according to test methods, surface roughness, internal structure difference, and experience of tester. To increase the reliability for this method, various quantitative background researches have been performed.

In this research we diagnose the material properties of the dinosaur footprints fossils in Haenam Uhangri. The method to estimate the coefficient of weathering (k) of rock proposed by Iliev (1966) was adapted in our research. A coefficient of weathering (k) is defined by the following expression and is based on the ultrasonic velocity difference between unweathered rock and weathered rock. A coefficient of weathering (k) is the criterion for classifying the degree of rock weathering (Table 1).

Table 1. Classification of Weathering grade by Iliev (1966).

Weathering grade Ultrasonic

Velocity(m/s) Coefficient of Weathering(K)

Fresh (F) >5,000 0

Slightly weathered (SW) 5,000-4,000 0-0.2

Moderately weathered (MW) 4,000-3,000 0.2-0.4

Strongly weathered (HW) 3,000-2,000 0.4-0.6

Very strongly weathered (CW) <2,000 0.6-1.0

Table 2 shows the average coefficient of weathering (k) of each fossil. The k value

of ornithopod fossils at the first protection hall and those of giant dinosaurs fossils at the building outside were shown as 0.55, which value means the most weakness. The k value of pterosaur and webbed feet bird fossils at the second protection hall is 0.49. The k value of giant dinosaur fossils at the third protection hall is 0.50. All the fossils have a severe weathering grade of HW.

Infrared thermal image analysis was also used in this study to investigate the scaling region of fossils. Infrared thermal image technology is a non-contact and non-destructive method. This method has been used widely in non-destructive safety diagnosis for cultural heritage because of the fast and accurate failure detection properties (Grinzato et al. 2002; Avedelidis and Moropoulou 2004; Kandemir-Yucel et

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al. 2007). The infrared thermal image camera used in this study was made by FLIR company: ThermaCam B200 and SC600 and for analysis of thermal image image, ThermaCAM Researcher Pro 2.8 image analysis program by FLIR company was also used to analyze the temperature distribution and the calculated scaling region. A calculated scaling region indicated on the deterioration map.

Table 2. Classification of Weathering grade of the Uhangri footprint fossils.

Ornithopods fossils at

protection hall no.1

Pterosaurs and webbed feet

birds fossils at protection hall

no.2

Giant dinosaurs fossils at

protection hall no.3

Giant dinosaurs fossils outside of protection hall

no.3

Rock type mudstone black shale black shale Tuffaceous sandstone

K 0.55 0.49 0.50 0.55

Degree of weathering

HW HW HW HW

3.4 Pollutant Analysis

To determine the reason for the occurrence reason and mechanism of the pollutant deposition, which cause the discoloration of the fossils sites and chemical weathering, in situ P-XRF has also been performed. P-XRF is a research tool to analyze the multiple elements simultaneously and is nondestructive and easily performed method. It has also has the advantage of a direct analysis on the pollutants without other preparation works at the research site.

The results of P-XRF measurement on the brown and black discoloration spots and efflorescence spots showed that the main reasons of the pollutants are Fe, Mn, Ca, S and Cl. The results by SEM-EDS and XRD analyses show that the white salt crystals produced on efflorescence spots are Na2SO4. These salt crystals were formed along the liquid trace of the water, which flowed into the fossils sites and these have some close relations with the underground water.

3.5 Microclimatic environment assessment

Microclimate is the synthesis of the ambient physical conditions due to either atmospheric variables or exchanges with other bodies over a period of time representative of all the conditions determined by the natural and manmade factors (Camuffo 1998).

The main factors affecting microclimate are temperature, humidity, wind, atmospheric turbulence, dew, frost, thermal balance and evaporation etc., and the microclimate environment due to interaction among these factors can affect natural weathering of cultural heritage directly and indirectly. Thus it is important to control the microclimate for the long-term conservation of cultural heritage.

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For analysis of microclimate for fossils at the protection hall, we have performed the monitoring to detect and compare the temperature and humidity inside and outside buildings. Especially, at the third protection hall we measured the temperature and humidity inside and outside of the fossils and inside building (because this protection hall exhibited dew condensation).

To know the effect on the fossils by the climate in Haenam area, the adaptation of the diagram proposed by Fook et al. (1971) shows that Haenam is located in between the moderate decomposition and the strong decomposition areas (Figure 5A). Because Haenam is located in the southern part of Korea and also located near the west sea of Korea, all year round Haenam is warm and has a high amount of rainfall.

To know the environmental properties throughout the year, we investigated the data for the temperatures and the relative humidities at Haenam area and obtained the values from January 1, 2010 to May 28, 2011 (Figure 5B). The graph indicates that the temperatures in each protection hall show higher values compared with the temperatures outside the building, the temperature differences between inside and outside building are larger in winter season compared with summer season.

In spite of these differences, the temperatures inside and outside the building show some close relations. To know the relations of the temperatures between inside and outside buildings, we drew the graph using the detected temperature values at every hour and calculated the R2. The results show the close relations of temperatures between inside and outside buildings. The values are higher than 0.8 at all positions.

The small temperature differences inside and outside buildings are reported that it is caused by good ventilation (Frederick et al. 2008). Thus, it is reasonable to estimate that every protection hall has a high effective ventilation condition. In the case of humidity, a different trend appears. The humidity at the outside building was observed to show a bigger difference compared with the inside building.

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Figure 5. The result of microclimatic analysis. (A) Diagram of climate-weathering of The Haenam Uhangri area. (B) Comparison with in and outside temperature and relative humidity in daily means. (C) Dew point and surface temperature of the third protection hall.

To investigate the cause of the dew condensation occurring on the fossils at the third protection hall, we compared the measurement of the temperature and the humidity on the surface of the fossils sites with those of the viewing roads. According to this, there was no big difference between the temperature on the surface of the third protection hall fossils sites and that of the inside of protection hall. But in case of relative humidity, the surface of the fossils sites has a higher measured value than the inside of protection hall and this seemed to deepen the dew condensation (Figure 5C). 4. Conclusions

In Haenam dinosaur footprints fossils, physical weathering and chemical weathering occurred. Chemical weathering especially has a close relationship with the hydrologic environment of fossils. Fossils sites are situated near Kumho lake, which used to be the sea. For this reason, the ground water can flow into the inside of the fossils, especially in the summer season. The ground water can infiltrate the rocks along the cracks and can dissolve the weak mineral in the rocks. This creates oxide mineral inside the rocks and changes the colors on the rock surfaces. Also the ground water induces that the fossils have a high humidity condition and again this causes a biological

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weathering. Furthermore, the salt dissolved in the ground water can make efflorescences on fossils and changes the appearance of the fossils. Therefore, desalinization and installation of drainage pumps will help the conservation of fossils.

The deterioration evaluation results show that the fossils at the first protection hall and the giant dinosaur footprints outside building indicate a high deterioration rate and a weak rock property, so the original aspects can be damaged. All the fossils are classified as HW, so an urgent conservation treatment such as consolidation, on weak zones, is required. The results obtained from the P-XRF, XRD and SEM-EDS analysis on brown and dark-gray discoloration and points of efflorescence showed that the main causes of the pollutants are Fe, Mn, Ca, S and Cl.

By the microclimate evaluation, indoor microclimate at the protection halls with the fossils has close relations with changes in weather outside the building. The second protection hall has the largest relation, and the third protection hall and the first protection hall follow. Also, the difference between the temperature and relative humidity at each protection hall shows the highest value in the winter and the lowest one in the summer. The results from the microclimate assessment at the third protection hall indicate that the dew condensation is caused by humidity imbalance in the protection hall. Therefore, it is recommended that the installation of additional HVAC is very helpful for the prevention of the dew formation.

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Frederick, K.T., Mikko, H., Matti, P., Jaan, P., Imbi, V., Väino, P., Aime, P., Tapani, K. and Jukka, A. 2008, ‘Microclimate and ventilation in Estonian and Finnish dairy buildings’. Energy and Buildings, 40(7): 1194-1201.

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Iliev, I.G. 1966. ‘An attempt to measure the degree of weathering of intrusive rocks from their physico-mechanical properties’. Proceedings of the first congress of the international society of rock mechanics, Lisbon, Portugal, 1: 109-114.

Jeong , G.Y. and Kim, S.J. 2004. ‘Applied Mineralogy for the Conservation of Dinosaur Tracks in the Goseong Interchange Area’. Journal of the Mineralogical Society of Korea, 17(3): 189-199.

Kandemir-Yucel, A., Tavukcuoglu, A. and Caner-Saltik, E.N. 2007, ‘In situ assessment of structural timber elements of a historic building by infrared thermography and ultrasonic velocity’. Infrared Physics & Tech nology, 49(3): 243-248.

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