3D mapping as a tool for the planning of preservation measures on sculptures made of natural stone

The article deals with the comparison between 2D and 3D evaluation of surface areas of sculptures. The objects chosen for investigation were Apollo (Carrara Marble, Potsdam Sanssouci), Flora (Laas Marble, Castle and Park Nymphenburg Munich) and Juno (Cotta Sandstone, Baroque Garden Großsedlitz/Dresden). Photographs showing the sculptures from all sides were used for calculating 2D surface areas with AutoCAD 2018 software. 3D models were generated with T-Scan 2 (Steinbichler Company), and 3D surface areas were evaluated with CAD software Geomagic Studio. The results show that 3D total surface area determinations of virtual 3D models are much more precise than 2D determinations on photographs. The values of the total surface area differ significantly. In case of Apollo 2D measurement captures only 66% of the real total surface. For measuring surface roughness, standardized Bosch sandpapers with P classification were used. Microphotographs of marble and sandstone surfaces show the development and the general optical appearance of increasing roughness. As expected, 2D calculation gives smaller values than 3D calculation also in case of surface roughness. In case of Apollo the P400 roughness area calculated with 2D measurement yields only 26% of the real area calculated with 3D. The accuracy of the surface 2D measurement clearly depends on the complexity of the sculpture because undercuts cannot be captured on photographs. It is shown that accurate information about the distribution of damage phenomena helps to improve planning conservation measures.     

Decay and preservation of stone in modern environments

Stone objects decay in all environments, but the modes of decay vary from one region to another. In the modern industrial countries acid deposition has accelerated the decay of stone. Many objects that survived centuries of weathering without serious damage have, in the present century, decomposed beyond recognition. The black crusts seen on stone structures mostly contain gypsum formed by SO₂ reactions with calcareous minerals. These crusts exfoliate, destroying the sculptural form. Because of the absence of proven technology to treat and restore these objects, the caryatids at the Acropolis had to be moved indoors to save them from further disfiguration.In arid climates, the salts in stone and the meteorologic conditions combine to disrupt stone structures. The Great Sphinx at Giza is a prominent example of this mode of stone decay. In humid, tropical regions, such as in southern India, hydrolysis disrupts the mineral structure, causing rapid damage even to such durable stone as granite.The human effort to save the deteriorating structures has often aggravated the problem. The sandstone at the Legislative Building in Olympia, Washington has, because of the protective acrylic coating, suffered greater damage than the similar but unprotected sandstone at a nearby school building.It appears that proper management can greatly help to reduce the decay of the stone. A scientifically designed cleaning can inhibit the formation of crusts and the accumulation of efflorescences. The absence of the crusts and efflorescence and application of appropriate impregnants, which consolidate yet maintain the "breathability" of stone, may prolong the life of historic structures.     

Use of tombstones in investigation of deterioration of stone monuments

A number of researchers have used tombstones to study the deterioration of stone. The tombstones can provide a large number of samples for statistical analyses. Measurements have included index of legibility, microrelief of resistant inclusions, and loss of thickness. Lack of information about past exposure conditions makes it difficult to derive quantitative relationships. The most useful results involve ranking of stone durability, and identification of time periods or geographic regions with high rates of stone deterioration.     

The surface archaeological record in arid Australia: Geomorphic controls on preservation,exposure, and visibility

The conventional approach to assessing the archaeological record in most parts of the world involves a combination of excavation of stratified deposits and extensive survey of surface deposits. Although widely applied in Australia, in both research‐based and management archaeology, the method does not conform well to the nature of the surface archaeological record here. Over much of semi‐arid and arid Australia, archaeological “sites” are, in fact, accretion phenomena that are not easily interpreted as the outcome of short‐term behavioral events. Using results from twelve years of geoarchaeological research in western New South Wales, we demonstrate that there is considerable variability in landsurface age, and hence the “availability” of archaeological surfaces, over relatively short distances. Therefore, it cannot be assumed that stone artifact deposits, for example, that appear to be similar in character are of similar age. Data are also presented that demonstrate that the presence of artifacts on the surface, their apparent absence in sediments buried beneath the surface, and the apparent recent ubiquity of the archaeological record are all a function of geomorphic processes that, at the same time, expose some artifact deposits at the surface and erode and bury others amid large volumes of sediment. Interpreting the surface artifact record within a spatial and temporal geomorphic framework is crucial to understanding the past human behavior that the artifact deposits represent. © 2009 Wiley Periodicals, Inc.     

Durability of carbonate rock as building stone with comments on its preservation

Carbonate rocks have been extensively used as building stones because of their availability, workability, and attractiveness. Unfortunately, however, some stones suffer from chemical attack or freeze-thaw activity. The environmental affects, especially those due to pollution of the atmosphere, are discussed in terms of weathering processes, salt crystallization, and acid deposition. A review of some recent research in relation to deterioration of stone in urban environments is given and carbonate rocks are classified in relation to position within a building, geographical location, and degree of pollution. Some comments on stone preservation are provided, especially in terms of the properties a preservative should possess.     

香港的考古文物、古迹与岩画

香港地区考古发现多种石器及离岛的"石壁画龙"-岩画,均属新石器时代文物.发现铜器、陶器等也不少,有些有隶书年号,为周、秦时代文物.香港自南北朝以来,与两广、福建和中原地区来往密切,遗留许多名胜古迹.     

The role of aluminium in the preservation of microbial biosignatures

Demonstrating the biogenicity of presumptive microfossils in the geological record often requires supporting chemical signatures, including isotopic signatures. Understanding the mechanisms that promote the preservation of microbial biosignatures associated with microfossils is fundamental to unravelling the palaeomicrobiological history of the material. Organomineralization of microorganisms is likely to represent the first stages of microbial fossilisation and has been hypothesised to prevent the autolytic degradation of microbial cell envelope structures. In the present study, two distinct fossilisation textures(permineralised microfossils and iron oxide encrusted cell envelopes)identified throughout iron-rich rock samples were analysed using nanoscale secondary ion mass spectrometry(NanoSIMS). In this system, aluminium is enriched around the permineralised microfossils, while iron is enriched within the intracellularly, within distinct cell envelopes. Remarkably,while cell wall structures are indicated, carbon and nitrogen biosignatures are not preserved with permineralised microfossils. Therefore, the enrichment of aluminium, delineating these microfossils appears to have been critical to their structural preservation in this iron-rich environment. In contrast,NanoSIMS analysis of mineral encrusted cell envelopes reveals that preserved carbon and nitrogen biosignatures are associated with the cell envelope structures of these microfossils. Interestingly, iron is depleted in regions where carbon and nitrogen are preserved. In contrast aluminium appears to be slightly enriched in regions associated with remnant cell envelope structures. The correlation of aluminium with carbon and nitrogen biosignatures suggests the complexation of aluminium with preserved cell envelope structures before or immediately after cell death may have inactivated autolytic activity preventing the rapid breakdown of these organic, macromolecular structures.Combined, these results highlight that aluminium may play an important role in the preservation of microorganisms within the rock record.     

Palaeoecological,archaeological and historical data and the making of Devon landscapes. I. The Blackdown Hills

This paper presents the first systematic study of the vegetation history of a range of low hills in SW England, UK, lying between more researched fenlands and uplands. After the palaeoecological sites were located bespoke archaeological, historical and documentary studies of the surrounding landscape were undertaken specifically to inform palynological interpretation at each site. The region has a distinctive archaeology with late Mesolithic tool scatters, some evidence of early Neolithic agriculture, many Bronze Age funerary monuments and Romano‐British iron‐working. Historical studies have suggested that the present landscape pattern is largely early Medieval. However, the pollen evidence suggests a significantly different Holocene vegetation history in comparison with other areas in lowland England, with evidence of incomplete forest clearance in later‐Prehistory (Bronze?Iron Age). Woodland persistence on steep, but poorly drained, slopes, was probably due to the unsuitability of these areas for mixed farming. Instead they may have been under woodland management (e.g. coppicing) associated with the iron‐working industry. Data from two of the sites also suggest that later Iron Age and Romano‐British impact may have been geographically restricted. The documented Medieval land management that maintained the patchwork of small fields, woods and heathlands had its origins in later Prehistory, but there is also evidence of landscape change in the 6th–9th centuries AD. We conclude that the Blackdown Hills area was one of many ‘distinctive subregions’, which due to a combination of edaphic, topographic and cultural factors could qualify as an eco‐cultural region or ‘pays’. It is argued that the use of such eco‐culturally distinctive regions or pays can provide a spatial and archaeological framework for palaeoecology, which has implications for landscape research, designation and heritage management.     

The role of armadillos in the movement of archaeological materials: An experimental approach

Armadillos are medium‐sized animals whose burrowing behavior can be significant in archaeological settings ranging from South America to the central United States. Although archaeologists are well aware that these animals can move archaeological materials across stratigraphic layers, few data are available about the magnitude of mixing, number of burrows per individual, dimension of burrows, and their impact on archaeological sites. This paper addresses the problem from an experimental perspective. Specifically, we monitored the action of the yellow armadillo (Euphractus sexcintus) in translocating cultural materials. Our results suggest that: (1) the vertical movement of artifacts has no preferential direction; (2) cultural horizons at least 20 cm apart can be mixed; (3) the animal's activity leaves some distinct traces that can be recognized during an excavation; and (4) there is no significant correlation between size, shape, or weight of artifacts and amount of displacement. © 2003 Wiley Periodicals, Inc.     

Gypsum: a review of its role in the deterioration of building materials

The deterioration of buildings and monuments by gypsum is the result of crystallization cycles of this salt. Although gypsum can dehydrate to a hemihydrate, the mineral bassanite, and to an anhydrate, the mineral anhydrite, this reaction occurs in nature on a geological time scale and therefore it is unlikely to occur when gypsum is found on and in building materials. The CaSO₄–H₂O system appears deceptively simple, however there are still discrepancies between the experimental and thermodynamically calculated data. The reason for the latter can be attributed to the slow crystallization kinetics of anhydrite. Apart from this, the large numbers of studies carried out on this system have focused on industrially important metastable phases, such as the hemihydrate and soluble anhydrite. The paper presents a review of the studies dealing with the phase equilibria of the CaSO₄–H₂O system as well as the influence of other salts on the solubility of gypsum. It tries to glean out the relevant information that will serve to explain the deterioration observed on building materials by the crystallization of gypsum and thus allows developing improved conservation methods.     

典型斜坡滚石运动的理论计算研究

在分析滚石运动形式的基础上,简化斜坡滚石运动模型,从运动学角度出发,推导出一套计算斜坡滚石运动特征的方程。该数理模型符合滚石运动的规律,可用于斜坡区滚石运动特征的预测,并可作为斜坡区滚石灾害防治的依据。     

The role of the Mediterranean region in the development of sedimentary geology: a historical overview

The Mediterranean region, source of so much knowledge in the world, is the site of major advances in sedimentary geology. In addition to its economic and cultural richness, the geological and geographic diversity of the region, plus its active geological processes, have long stimulated indigenous scholars, along with attracting talented outsiders such as Steno, Lyell, Walther, Kuenen and Bagnold. Since classical Hellenic times, debates about the origin of fossils and the changing positions of sea-level served as catalysts for studies of sediments, sedimentary rocks and ancient life. The presence of geologically young and easily interpreted marine shell beds in many Mediterranean coastal areas adjacent to their modern analogues was a particular stimulus for progress in sedimentary geology, for example, the very advanced stratigraphic ideas of Leonardo da Vinci, expressed solely in his unpublished notebooks. Impeding progress was the geological complexity of facies, faunas and structure in the circum-Mediterranean Alpine belts. Once the secrets of these were unlocked, however, the Mediterranean region became the source of major discoveries about syn-sedimentary tectonics, carbonate platforms, pelagic and anoxic sediments, turbidites, evaporites, aeolian processes, cyclostratigraphy, magnetic stratigraphy and impact events. In many of these Mediterranean discoveries, the critical element is the occurrence of extensive Mesozoic-Cenozoic pelagic successions whose precise age dating was made possible by pioneering biostratgraphic studies using microfossils.     

Piperno from Campi Flegrei: a relevant stone in the historical and monumental heritage of Naples (Italy)

This paper reports novel data concerning the volcanic formation of the Piperno, a stone that has been used for a long time in the monumental architecture of Naples and the Campanian region (Southern Italy). A careful field survey of the outcrops or underground sites so far accessible allowed us to draw a lithostratigraphic reconstruction of the formation and enabled the recognition of the three main layers exploited in past centuries and which provided dimension stones for architectural and structural purposes. Petrophysical and mineralogical characterization also enabled us to discriminate the same layers previously identified. Different scoriae/matrix ratio, scoriae dimension and welding degree are the most peculiar features of these horizons. The combination of these three parameters, even though they did not affect the use of Piperno as dimension stone, somehow determined its variable susceptibility to the weathering agents. However, a linear relationship between the exposure time and the decay of the stone itself, at a parity of weathering intensity, was not observed. This assumption was proved by verifying that the specific layers of the volcanic sequence controlled the weathering degree of Piperno from monuments disregarding their age of emplacement.     

Geoenvironmental studies on conservation of archaeological sites at Siwa oasis, Egypt

Siwa oasis is located in the extreme western part of the Egyptian western desert. There are several archaeological sites in the oasis; the most distinct ones are Alexander the Great temple at Aghormi hill and the Gebel El Mota tomb excavations. They have suffered due to deterioration and cracks of different kinds and some parts are getting worse as rock falls occur. From field inspection and lab analysis, it is clear that lithology plays an important role on the extent of damage. Alexander the Great temple was built over the northern edge of Aghormi hill, which consists of two distinct beds—an upper limestone bed and a lower shale one. From field survey and laboratory analysis, the shale is considered as a high expanded bed and weak in its bearing capacity, as its clay content (mainly smectite) experienced swelling due to wetting from the ground water spring underneath. Consequently, the upper limestone bed suffered from map cracking associated with rock falls due to the differential settlement of the swelled lower shale one. The temple was threatened by slope instability and had experienced many cracks. At Gabal El Mota tomb excavations, it was noticed that a comparison of tombs of the same opening size revealed that those that excavated on shale beds had cracked much more than those that excavated on limestone. This may be attributed to the low bearing capacity of excavated shale walls. The remedial measures suggested to overcome the stability problems on these archaeological sites are grouting or construction of retaining walls.     

The role of interactions among environmental conditions in controlling historical fisheries variability

We developed categorical time-series regression models to evaluate the roles of lagged stock abundance history, hydrographic variability, and anthropogenic factors in controlling the variation in abundance of striped bass and American shad in the Potomac, Delaware, and Hudson rivers. These models can be used to evaluate directly the role of interactions of variates to produce greater than average recruitment to commercial fish stocks. Whereas hydrographic factors dominate striped bass dynamics in all three estuaries for the period 1929–1976 compared to the pollution variables tested (i.e., sewage loading, dissolved oxygen, and biological oxygen demand), American shad shows strong dependence on the anthropogenic factors compared to hydrographic variates in all three estuaries.     

The role of friction in the seismic risk mitigation of freestanding art objects

The problem of reducing the seismic risk for art objects, that are the objects generally contained within Museums, is of great interest. The first studies were performed in Japan and were successively organized in a general framework by a research program performed at Southern California University and sponsored by the Getty Museum at Malibu, California. In these papers and in the following Italian studies, the theoretical models for the problem concerning vases and statues are based on the dynamic behavior of rigid blocks and have been deeply developed. Unfortunately, because of the great lack of experimental data, determinant parameters for the problem characterization (like the friction between two superimposed blocks or between the art object and the support plane) are often assumed without reference to real values derived from laboratory tests. This paper presents the results of a research program containing the experimental determination of the friction coefficient between the art object and the support (by means of a testing apparatus on purpose realized) together with dynamic tests performed on simple-shaped objects made of different materials. The dynamic tests were performed using an unidirectional shaking table and different supporting surfaces, so that the influence of different friction coefficients has been analyzed.     

The AD 365 Crete earthquake and possible seismic clustering during the fourth to sixth centuries AD in the Eastern Mediterranean: a review of historical and archaeological data

Historical and archaeological data are used to test geological claims that, in the fourth to sixth centuries AD, the Eastern Mediterranean experienced an unusual clustering of destructive earthquakes (the ‘Early Byzantine Tectonic Paroxsym’). A review of historical accounts of a notable earthquake at this time, that of 21 July AD 365, indicates that this event destroyed nearly all the towns in Crete and was followed by a tsunami which devastated the Nile Delta. The AD 365 event was also probably responsible for reported or observed destruction in ancient towns of west Cyprus and Libya. This earthquake is most likely to be identified with a Hellenic Arc subduction-zone event of ‘great’ (M>8) magnitude, as testified by up to 9 m of uplift in western Crete dated by previous geological studies to around this time. Historical and archaeological data also support the hypothesis that the fourth to sixth centuries AD was a period of abnormally high seismicity in the Eastern Mediterranean. The high seismicity rates of this period may reflect a reactivation of all plate boundaries in the region (Dead Sea Transform, East Anatolian Fault, North Anatolian Fault, Hellenic Arc, Cyprus Arc Fault).     

The significance of vivianite in archaeological settings

Vivianite is a bluish mineral sometimes encountered in archaeological deposits. It is notable for its tendency to change color from white or grayish to blue on exposure to air. Vivianite requires specific conditions for its formation—sources of iron, phosphate, and water, as well as low levels of oxygen and sulfide. Microbial activity is also thought to play a part in vivianite formation. The majority of archaeological texts do not discuss vivianite to any great degree, preventing a more detailed interpretation of site conditions and features. Vivianite was found in 25 exhumed burials from the North Brisbane Burial Ground, Queensland, Australia. Research indicated that bone or tissue samples for DNA analysis are best taken from areas distant from vivianite encrustations and that presence of vivianite has implications for artifact conservation. Vivianite at the North Brisbane Burial Grounds helped protect some skeletal and dental elements, preserved the impressions of metal coffin lacing, and also corroborated the oral history of temporary waterlogging and acted as a measure of pollution levels across the site. © 2006 Wiley Periodicals, Inc.     

The role of heterogeneous strain in the development and preservation of a polymetamorphic record in high-P granulites, western Canadian Shield

Mafic rocks in the Chipman domain of the Athabasca granulite terrane, western Canadian Shield, provide the first well‐documented record of two distinct high‐P granulite facies events in the same domain in this region. Textural relations and the results of petrological modelling (NCFMASHT system) of mafic granulites are interpreted in terms of a three‐stage tectonometamorphic history. Stage 1 involved development of the assemblage Grt + Cpx + Qtz ± Pl (M₁) from a primary Opx‐bearing igneous precursor at conditions of 1.3 GPa, 850–900 °C. Field and microstructural observations suggest that M₁ developed synchronously with an early S₁ gneissic fabric. Stage 2 is characterized by heterogeneous deformation (D₂) and synkinematic partial retrogression of the peak assemblage to an amphibole‐bearing assemblage (M₂). Stage 3 involved a third phase of deformation and a return to granulite facies conditions marked by the prograde breakdown of amphibole (Amph₂) to produce matrix garnet (Grt_3a) and the coronitic assemblage Cpx_3b + Opx_3b + Ilm_3b + Pl_3b (M_3b) at 1.0 GPa, 800–900 °C. M₁ and M_3b are correlated with 2.55 and 1.9 Ga metamorphic generations of zircon, respectively, which were dated in a separate study. Heterogeneous strain played a crucial role in both the development and preservation of these rare examples of multiple granulite facies events within single samples. Without this fortuitous set of circumstances, the apparent reaction history could have incorrectly led to an interpretation involving a single‐cycle high‐grade event. The detailed P–T–t–D history constructed for these rocks provides the best evidence to date that much of the east Lake Athabasca region experienced long‐term lower crustal residence from 2.55 to 1.9 Ga, and thus the region represents a rare window into the reactivation and ultimate stabilization processes of cratonic lithosphere.     

Quantitative evaluation of stability changes in historical stone bridges in Kagoshima,Japan, by weathering

This study deals with a weathering problem of historic arch stone bridges built of welded tuff about 150 years ago in Kagoshima, Japan. Based on a detailed comprehensive weathering evaluation we previously carried out, the way in which the weathering affects the structural stability of the bridges is quantitatively evaluated herein by using a distinct element method (DEM).The suitability of this method of analysis was confirmed through a comparison of the numerical analysis results with the in situ load testing data. The analysis results show that when considering the stability of a stone bridge, the slide safety factor and eccentric safety factor are more important than the compressive safety factor. That is, the types of possible failure include sliding and openings between arch blocks. In 150 years of weathering, the shear stress in the arch ring generally increased about 20%. The eccentric safety factor decreased about 9%, from 4.35 to 3.97, and the slide safety factor decreased about 20%, from 8.02 to 6.46. Deflections at the arch crown increased about two times, from 0.60 to 1.28 mm. Despite these changes, the stone bridges are considered to be still in a good condition after 150 years of weathering.