Sub‐micron spongiform porosity is the major ultra‐structural alteration occurring in archaeological bone

Total pore volume and pore size distribution are indicators of the degree of post‐mortem modification of bone. Direct measurements of pore size distribution in archaeological bones using mercury intrusion porosimetry (HgIP) and back scattered scanning electron microscopy (BSE‐SEM) reveal a common pattern in the changes seen in degraded bone as compared to modern samples. The estimates of pore size distribution from HgIP and direct measurement from the BSE‐SEM images show remarkable correspondence. The coupling of these two independent approaches has allowed the diagenetic porosity changes in human archaeological bone in the >0.01 µm range to be directly imaged, and their relationship to pre‐existing physiological pores to be explored. The increase in porosity in the archaeological bones is restricted to two discrete pore ranges. The smaller of these two ranges (0.007–0.1 µm) lies in the range of the collagen fibril (0.1 µm diameter) and is presumably formed by the loss of collagen, whereas the larger pore size distribution is evidence of direct microbial alteration of the bone. HgIP has great potential for the characterization of microbial and chemical alteration of bone. Copyright © 2002 John Wiley & Sons, Ltd.     

Gas breakthrough experiments on fine-grained sedimentary rocks

The capillary sealing efficiency of fine‐grained sedimentary rocks has been investigated by gas breakthrough experiments on fully water saturated claystones and siltstones (Boom Clay from Belgium, Opalinus Clay from Switzerland and Tertiary mudstone from offshore Norway) of different lithological compositions. Sand contents of the samples were consistently below 12%, major clay minerals were illite and smectite. Porosities determined by mercury injection lay between 10 and 30% while specific surface areas determined by nitrogen adsorption (BET method) ranged from 20 to 48 m² g ^{? 1}. Total organic carbon contents were below 2%. Prior to the gas breakthrough experiments the absolute (single phase) permeability (k_abs) of the samples was determined by steady state flow tests with water or NaCl brine. The k_abs values ranged between 3 and 550 nDarcy (3 × 10^?21 and 5.5 × 10^?19 m²). The maximum effective permeability to the gas‐phase (k_eff) measured after gas breakthrough on initially water‐saturated samples extended from 0.01 nDarcy (1 × 10^?23 m²) up to 1100 nDarcy (1.1 × 10^?18 m²). The residual differential pressures after re‐imbibition of the water phase, referred to as the ‘minimum capillary displacement pressures’ (P_d), ranged from 0.06 to 6.7 MPa. During the re‐imbibition process the effective permeability to the gas phase decreases with decreasing differential pressure. The recorded permeability/pressure data were used to derive the pore size distribution (mostly between 8 and 60 nm) and the transport porosity of the conducting pore system (10^‐5–10^‐2%). Correlations could be established between (i) absolute permeability coefficients and the maximum effective permeability coefficients and (ii) effective or absolute permeability coefficients and capillary sealing efficiency. No correlation was found between the capillary displacement pressures determined from gas breakthrough experiments and those derived theoretically by mercury injection.     

核磁共振(NMR)T2分布对云冈石窟风化的初步研究

云冈石窟的保护受到我国文物保护工作者的重视。恶劣的自然环境,加上人为的污染,使云冈石窟的保护问题日显严峻,必须综合治理。然而,在这些复杂因素中,岩体的风化治理最为关键。岩石的孔隙尺寸及其分布是表征岩石力学、水理性质的重要参数。同种岩石,其孔隙率越高或者孔隙分布越大,则表示岩石的力学和水理性质越差。由此可见,借助孔隙率及孔隙分布状况,可表征同种岩石的风化情况。核磁共振横向弛豫时间T2与岩石孔径分布具有一定的线性关系。随着石雕风化的加剧,岩石可视孔隙率增大,孔径大小的平均值也将相应增大。基于这一前提,本研究尝试采用核磁共振横向弛豫时间T2分析石雕文物不同深处的孔径分布情况,通过实验室对云冈石窟新鲜岩石样品,结合抗盐风化安定性实验,和对自然风化样品采用便携式核磁进行无损检测,探讨其风化程度和深度,以便深入研究石雕文物的风化状况。研究结果表明, 风化岩石的新鲜层只有一类小孔隙,弛豫时间约为2~6ms,风化层岩石有大孔隙生成,且随着岩石风化程度增强,小孔径孔隙所占孔隙比例降低,大孔径孔隙所占比例增多。根据不同深度岩样的孔径分布情况,及新鲜岩石的孔径分布情况,可以得出岩石的风化深度为5mm左右。本研究可为后续的现场保护措施提供有价值的信息。     

BONE POROSITY AND THE USE OF MERCURY INTRUSION POROSIMETRY IN BONE DIAGENESIS STUDIES*

Porosity measurements made on archaeological bones have revealed very-close relationships between changes in the porosity, remaining protein content and mineral alterations. The results have important implications for models that attempt to quantify the rates and extent of chemical reaction between bone and its geochemical environment. We report here on a novel application of an established technique, mercury intrusion porosimetiy, to investigate in more detail the pore size distribution of archaeological bones. Mercury intrusion porosimetry measures an ‘intermediate’range of bone porosity, ‘mesoporosity’, and produces data which permit the observation of significant structure characteristics in the porosity of modern laboratory altered and diagenetically altered bones.     

Cyclic loading of an idealized clay‐filled fault: comparing hydraulic flow in two clay gouges

The flow of water along discontinuities, such as fractures or faults, is of paramount importance in understanding the hydrogeology of many geological settings. An experimental study was undertaken comprising two experiments on a 30° slip‐plane filled with kaolinite or Ball Clay gouge using a bespoke Angled Shear Rig (ASR). The gouge was initially loaded in equal step changes in vertical stress, followed by unloading of the sample in similar equal steps. This was followed by reloading to a new maximum stress, followed by unloading; the test history was therefore load‐unload‐reload‐unload (LURU). The transmissivity of the kaolinite and Ball Clay gouge showed a power‐law relationship with vertical stress. The LURU history showed considerable hysteresis, with flow effectively unchanged during unloading, even when vertical stress was close to zero. Reloading resulted in flow similar to that seen during unloading suggesting that the unloading‐reloading path is similar to the rebound‐reconsolidation line in classic soil mechanics. These observations show the importance of stress history on fracture flow; consideration of just the current stress acting upon a fracture may result in inaccuracies of predicted hydraulic flow. Once a new stress maximum was achieved the transmissivity of the fracture continued to reduce. No significant variation was seen in the flow response of kaolinite and Ball Clay gouge suggesting that the inclusion of illite and quartz did not have a significant influence on the form of the relationship between stress and flow, i.e. both described by a power‐law.     

Numerical model of pore‐pressure diffusion associated with the initiation of the 2010–2011 Guy–Greenbrier,Arkansas earthquakes

We model pore‐pressure diffusion caused by pressurized waste‐fluid injection at two nearby wells and then compare the buildup of pressure with the observed initiation and migration of earthquakes during the early part of the 2010–2011 Guy–Greenbrier earthquake swarm. Pore‐pressure diffusion is calculated using MODFLOW 2005 that allows the actual injection histories (volume/day) at the two wells to diffuse through a fractured and faulted 3D aquifer system representing the eastern Arkoma basin. The aquifer system is calibrated using the observed water‐level recovery following well shut‐in at three wells. We estimate that the hydraulic conductivities of the Boone Formation and Arbuckle Group are 2.2 × 10^?2 and 2.03 × 10^?3 m day^?1, respectively, with a hydraulic conductivity of 1.92 × 10^?2 m day^?1 in the Hunton Group when considering 1.72 × 10^?3 m day^?1 in the Chattanooga Shale. Based on the simulated pressure field, injection near the relatively conductive Enders and Guy–Greenbrier faults (that hydraulically connect the Arbuckle Group with the underlying basement) permits pressure diffusion into the crystalline basement, but the effective radius of influence is limited in depth by the vertical anisotropy of the hydraulic diffusivity. Comparing spatial/temporal changes in the simulated pore‐pressure field to the observed seismicity suggests that minimum pore‐pressure changes of approximately 0.009 and 0.035 MPa are sufficient to initiate seismic activity within the basement and sedimentary sections of the Guy–Greenbrier fault, respectively. Further, the migration of a second front of seismicity appears to follow the approximately 0.012 MPa and 0.055 MPa pore‐pressure fronts within the basement and sedimentary sections, respectively.     

Early Triassic mastodonsaurids (Temnospondyli,Stereospondyli) from Western Australia,with remarks on mastodonsauroid palaeobiogeography

A newly discovered partial skull of a temnospondyl from the Early Triassic Blina Shale of the Erskine Range, Western Australia, is referred to the mastodonsaurid species Watsonisuchus aliciae. A partial skull described as ‘Parotosuchus’ sp. by Warren (1980) is also referred to W. aliciae. Both taxonomic assignments should be treated with caution because of the relatively poor state of preservation of the specimens. W. aliciae is the fourth temnospondyl species to be described from the Blina Shale. The worldwide distribution of mastodonsauroids at the base of the Triassic suggests a rapid phase of radiation and dispersal following the Permo-Triassic extinction event.     

Injection‐induced seismicity in Carbon and Emery Counties,central Utah

Utah is one of the top producers of oil and natural gas in the United States. Over the past 18 years, more than 4.2 billion gallons of wastewater from the petroleum industry has been injected into the Navajo Sandstone, Kayenta Formation, and Wingate Sandstone in Carbon and Emery Counties, central Utah, where seismicity has increased during the same period. Previous studies have attributed this seismicity to coal mining. Here, we present evidence for wastewater injection being a major cause of the increased seismicity. We show that, in the coal mining area, seismicity rate increased significantly 1–5 years following the wastewater injection, and the earthquakes, mostly with magnitudes <3.0, are concentrated in areas seismically active prior to the injection. Using simple analytical and numerical models, we show that the injection in central Utah can sufficiently raise pore pressure to trigger seismicity within 10–20 km of the injection wells, and the time needed for the diffusion of pore pressure may explain the observed lag of seismicity increase behind the commencement of injection. The b‐value of these earthquakes increased following the wastewater injection, which is consistent with these events being injection‐induced. We conclude that the marked increase in seismicity rate in central Utah is induced by both mining activity and wastewater injection, which raised pore pressure along preexisting faults.     

New evidence of early use of artificial pozzolanic material in mortars

Hydraulic building composites, such as mortars and plasters, produced with artificial pozzolanic materials, became widely popular thanks to the Romans. Reports on earlier uses of such composites can also be found, mainly in archaeological and historic documents. These date back as far as the time of Minoan and Mycenaean civilizations. Here, we present a holistic analytical investigation of Late Bronze Age mortars from various archaeological sites of Cyprus. We focus on petrographic observations of thin sections, scanning electron microscopy and energy dispersive X-ray microanalyses and we investigate the microstructure and texture of the samples and the chemical composition and interface of their binders. Results of powder X-ray diffraction analyses are also presented, alongside a series of measurements using mercury intrusion porosimetry and vacuum saturation, aiming to estimate the pore size distribution and the physical properties (i.e. open porosity and bulk density) of the specimens under investigation. We also report on tests carried out to assess the drilling resistance of the mortars using a novel, portable system. The results thoroughly confirm, for the first time, the earliest intentional use of crushed brick as an artificial hydraulic additive in lime mortars in Cyprus, in order to enhance their performance and longevity in the absence of natural pozzolanas.     

Fluid effect on hydraulic fracture propagation behavior: a comparison between water and supercritical CO2‐like fluid

The initiation of hydraulic fractures during fluid injection in deep formations can be either engineered or induced unintentionally. Upon injection of CO₂, the pore fluids in deep formations can be changed from oil/saline water to CO₂ or CO₂ dominated. The type of fluid is important not only because the fluid must fracture the rock, but also because rocks saturated with different pore fluids behave differently. We investigated the influence of fluid properties on fracture propagation behavior by using the cohesive zone model in conjunction with a poroelasticity model. Simulation results indicate that the pore pressure fields are very different for different pore fluids even when the initial field conditions and injection schemes (rate and time) are kept the same. Low viscosity fluids with properties of supercritical CO₂ will create relatively thin and much shorter fractures in comparison with fluids exhibiting properties of water under similar injection schemes. Two significant times are recognized during fracture propagation: the time at which a crack ceases opening and the later time point at which a crack ceases propagating. These times are very different for different fluids. Both fluid compressibility and viscosity influence fracture propagation, with viscosity being the more important property. Viscosity can greatly affect hydraulic conductivity and the leak‐off coefficient. This analysis assumes the in‐situ pore fluid and injected fluid are the same and the pore space is 100% saturated by that fluid at the beginning of the simulation.     

Fracture-fill calcite as a record of microbial methanogenesis and fluid migration: a case study from the Devonian Antrim Shale, Michigan Basin

The Devonian Antrim Shale is an organic‐rich, naturally fractured black shale in the Michigan Basin that serves as both a source and reservoir for natural gas. A well‐developed network of major, through‐going vertical fractures controls reservoir‐scale permeability in the Antrim Shale. Many fractures are open, but some are partially sealed by calcite cements that retain isotopic evidence of widespread microbial methanogenesis. Fracture filling calcite displays an unusually broad spectrum of δ¹³C values (+34 to ?41‰ PDB), suggesting that both aerobic and anaerobic bacterial processes were active in the reservoir. Calcites with high δ¹³C values (>+15‰) record cementation of fractures from dissolved inorganic carbon (DIC) generated during bacterial methanogenesis. Calcites with low δ¹³C values (13C values between ?10 and ?30‰ can be attributed to variable organic matter oxidation pathways, methane oxidation, and carbonate rock buffering. Identification of ¹³C‐rich calcite provides unambiguous evidence of biogenic methane generation and may be used to identify gas deposits in other sedimentary basins. It is likely that repeated glacial advances and retreats exposed the Antrim Shale at the basin margin, enhanced meteoric recharge into the shallow part of the fractured reservoir, and initiated multiple episodes of bacterial methanogenesis and methanotrophic activity that were recorded in fracture‐fill cements. The δ¹⁸O values in both formation waters and calcite cements increase with depth in the basin (?12 to ?4‰ SMOW, and +21 to +27‰ PDB, respectively). Most fracture‐fill cements from outcrop samples have δ¹³C values between ?41 and ?15‰ PDB. In contrast, most cement in cores have δ¹³C values between +15 and +34‰ PDB. Radiocarbon and ²³⁰Th dating of fracture‐fill calcite indicates that the calcite formed between 33 and 390 ka, well within the Pleistocene Epoch.     

The graptolite Glossograptus Emmons and its proximal structure

Ni Yunan & Cooper, R. A., 1994:03:28. The graptolite Glossograptus Emmons and its proximal structure. Alcheringa 18, 161–167. ISSN 0311-5518.

New specimens of Glossograptus acanthus from the Ningkuo Shale of China, preserved in relief, help to resolve the much debated problem of the structure of Glossograptus. A model for the proximal structure of the genus is proposed, based on the new material and on Finney's (1978) Athens Shale specimens. The model confirms that Glossograptus has homologous structure and development with Pseudisograptus, and isograptid development type is primitive for the group containing both genera. A cladogram is presented in which the suborder Glossograptina Jaanusson (with families Glossograptidae and Cryptograptidae) together with family Corynoididae Bulman are subsumed within a redefined family Glossograptidae.     

Influence of porosity on lipid preservation in the wall of archaeological pottery

Porosity of archaeological pottery is a key parameter used to assess its ability to trap lipids during the use of the pot and to preserve them over time. Mercury intrusion porosimetry and gas chromatography were used to study the distribution of porosity and the preservation of lipids in different chrono‐cultural contexts. The data obtained show that the porosity pattern, related to the raw materials and the savoir‐faire of the potters, influences the amount of lipids accumulated in the pottery. A significant overall porosity together with a high level of small pores is generally favourable for the preservation of lipids, but variations related to the environmental context are observed.     

2. CONSTRUCTIONS OF “HOME,”“FRONT,” AND WOMEN'S MILITARY EMPLOYMENT IN FIRST‐WORLD‐WAR BRITAIN: A SPATIAL INTERPRETATION

In First‐World‐War Britain, women's ambition to perform noncombatant duties for the military faced considerable public opposition. Nevertheless, by late 1916 up to 10,000 members of the female volunteer corps were working for the army, laying the foundation for some 90,000 auxiliaries of the official Women's Services, who filled support positions in the armed forces in the second half of the war. This essay focuses on the public debate in which the volunteers overcame their critics to understand how they obtained sufficient popular consent for their martial work. I explain the process in terms of shifting hegemonic understandings of space. As critics' arguments in the debate indicate, the gender attribution of war participation was organized and represented spatially, assigning men to the warlike “front” as warriors and women to the peaceful “home” as civilians. To redefine the meaning of these gendered wartime spaces, women volunteers deployed rival spatial discourses and practices in their campaign for martial employment. The essay explores the progress of these competing definitions through feminist and spatial theories, including gender performativity, discursively constructed and constructive spaces, and heterotopias. I argue that the upheaval caused by the war in gender and spatial norms undermined absolute conceptualizations of space with dichotomous binary areas on which critics drew for their arguments and reinforced more recent, relative spatialities, including the cultural construction of militarized heterotopic sites in between and paralleling both “home” and “front” for soldiers in training or recovery. The volunteers' efforts to gain access to military employment both contributed to and were supported by this shift. Heterotopic sites offered ideal discursive locations for constructing the new gender role of auxiliary soldiering through the performance of martial training and work, and competing spatial definitions provided arguments through which they could justify their activities to both critics and supporters.     

Materials Characteristics of Roman and Arabic Mortars and Stuccoes from the Patio De Banderas in the Real Alcazar of Seville (Spain)

This study discusses the materials and traditional knowledge used in the manufacture and application of lime mortars and stuccoes by Romans and Arabs in Seville (southern Iberian Peninsula). All of the samples studied contain calcite as a binder, combined with aggregates based on river sand from the filling materials of the Guadalquivir River's depression, located in the vicinity of the Real Alcazar Palace in Seville, Spain, where the artefacts were discovered. The Romans used high‐quality production technology, as evidenced by the careful selection of raw materials as well as by the adequate binder‐to‐aggregate ratio and the elevated homogeneity of the mortars and stuccoes. The suitable distribution of aggregates resulted in higher density values for Roman fragments than for Arabic ones. Results derived from Arabic samples suggest a decline in technology manufacture over time. This work provides useful information, particularly regarding the Roman and Arabic periods in the Iberian Peninsula. The analytical techniques employed in this study were X‐ray diffraction (XRD), X‐ray fluorescence (XRF)—using conventional and portable systems, scanning electron microscopy (SEM), petrographic microscopy, differential thermal analysis/thermogravimetry (DTA/TG), particle‐size analysis and mercury intrusion porosimetry.     

Clay‐shoveler's fracture: an uncommon diagnosis in palaeopathology

An archaeological case of clay‐shoveler's fracture was observed in an adult male exhumed from a Roman necropolis dated to the 1st–3rd century AD and located in the city of Barcelona, Spain. Clay‐shoveler's fracture is a breakage of a lower cervical or upper thoracic spinous process as a result of mechanical stress. Different mechanisms have been related to this injury, generally in labour‐related contexts. This paper reviews the literature concerning this uncommon finding, focusing especially on its mechanism and on activity‐related lesions. Copyright © 2006 John Wiley & Sons, Ltd.     

Post‐CO2 injection alteration of the pore network and intrinsic permeability tensor for a Permo‐Triassic sandstone

The aim of this study was to determine the process–structure–property relationships between the pre‐ and post‐CO₂ injection pore network geometry and the intrinsic permeability tensor for samples of core from low‐permeability Lower Triassic Sherwood Sandstone, UK. Samples were characterised using SEM‐EDS, XRD, MIP, XRCT and a triaxial permeability cell both before and after a three‐month continuous‐flow experiment using acidic CO₂‐rich saline fluid. The change in flow properties was compared to those predicted by pore‐scale numerical modelling using an implicit finite volume solution to the Navier–Stokes equations. Mass loss and increased secondary porosity appeared to occur primarily due to dissolution of intergranular cements and K‐feldspar grains, with some associated loss of clay, carbonate and mudstone clasts. This resulted in a bulk porosity increase from 18 to 25% and caused a reduction in mean diameter of mineral grains with an increase in apparent pore wall roughness, where the fractal dimension, D_f, increased from 1.68 to 1.84. All significant dissolution mass loss occurred in pores above c. 100 μm mean diameter. Relative dilation of post‐treatment pore area appeared to increase in relation to initial pore area, suggesting that the rate of dissolution mass loss had a positive relationship with fluid flow velocity; that is, critical flow pathways are preferentially widened. Variation in packing density within sedimentary planes (occurring at cm‐scale along the ‐z plane) caused the intrinsic permeability tensor to vary by more than a factor of ten. The bulk permeability tensor is anisotropic having almost equal value in ‐z and ‐y planes but with a 68% higher value in the ‐x plane (parallel to sedimentary bedding planes) for the pretreated sample, reducing to only 30% higher for the post‐treated sample. The intrinsic permeability of the post‐treatment sample increased by one order of magnitude and showed very close agreement between the modelled and experimental results.     

Grain‐scale permeabilities of faceted polycrystalline aggregates

Porous synthetic quartzites and amphibolites, each with faceted pore walls, were synthesized and evaluated to examine the permeability of pore networks similar to those of the lower crust and mantle. Quartzite with a fluid in equilibrium with an Mg–clinopyroxene contained connected networks of pores with a dihedral angle of 30° bounded by walls that were 10–50% faceted. The relationship of their permeability (k) to porosity (φ) is approximated by the previously determined relationship for relatively nonfaceted synthetic quartzite Amphibolite with an HF fluid contained fluorotremolite and a connected network of pores bounded by walls exhibiting 78–90% faceting. These materials showed much lower k for a given φ, with an apparent permeability threshold at φ_c = 0.04. A curve fit to these data yields The results suggest that moderate faceting has little effect on the transmission of fluids through rocks, but extensive faceting significantly alters permeability. This difference is most likely produced through isolation of the fluid to the grain corners at low φ with extensive faceting. Rocks with pores that tend toward faceting may impede the flow of fluids and melt.     

Performance and Risks of Salt-Accumulating Renders in Relation to Their Moisture Transport Properties

Salt-accumulating renders are usually applied in several layers with different specific properties of moisture transport. An extensive experimental programme was carried out to establish a relationship between those properties of individual layers and the performance of combined systems on a salt-laden substrate. Each of the 20 renders was characterized separately in absorption and drying tests, vacuum saturation tests, dry cup tests, mercury intrusion porosimetry, and ultrasound wave velocity measurements. Each of the 12 combined render systems was applied on a brick, which was then saturated with a concentrated NaCl solution by free capillary uptake. Subsequently the assembly was closed at the bottom and subjected to an accelerated drying test (50° C and 15% relative humidity). Moisture and salt profiles over the depth were taken regularly during 1 month. The results reveal very different degrees of effectiveness and levels of risk for the substrate, which are related to the moisture transport properties.     

IBERIAN CERAMIC PRODUCTION FROM BASTI (BAZA,SPAIN): FIRST GEOCHEMICAL,MINERALOGICAL AND TEXTURAL CHARACTERIZATION

Ceramic fragments from the archaeological excavation of the Iberian–Roman city of Basti (Spain) were studied from a geochemical point of view and by applying a statistical tool to X‐ray fluorescence data to discover similarities between ceramic materials. The analysis of these samples was completed by performing a mineralogical analysis, textural observation, and by characterizing the porous system and the colour of the pieces. Our results enabled us to identify the source area of the clayey raw material in the surroundings of Basti and to estimate the firing temperature of the ceramics. Differences in the chemistry were confirmed by characteristics of the pastes and the mineralogical composition of the pieces. Some samples show black cores, which would suggest the presence of organic matter in the raw material and fast firing of the ceramics. The main types of temper were quartz grains and gneiss fragments, although carbonate grains were also identified. Our evidence suggests that most of the samples were well fired. New silicate phases were found to be present in several samples. The mercury intrusion porosimetry verified and confirmed the firing temperature of non‐carbonated samples. Colorimetry showed that the colour of the ceramics varied according to the amount of CaO that they contained.