formation of corrensite chlorite and chlorite mica stacks by replacement of detrital biotite in low grade pelitic rocks transmission and scanning electron microscopy were utilized to investigate the nature and mechanisms of alteration of abundant detrital biotite of volcanic origin and progressive modification of phyllosilicate aggregates in a prograde sequence of pelitic rocks illite crystallinity index 0 19 0 58 a28 from the gasp6 peninsula in quebec detrital biotite has been diagenetically altered to form corrensite and chlorite through two mechanisms 1 layer by layer replacement gave rise to interstratification of packets of layers and complex mixed layering via several kinds of layer transitions between biotite and chlorite corrensite or smectite 2 dissolution transport precipitation resulted in the formation of relatively coarse grained aggregates of randomly orientated corrensite rich flakes and fine grained corrensite intergrown with chlorite and illite in the matrix the data show that stacks consisting of alternating packets of trioctahedral and dioctahedral phyllosilicates originated during early diagenesis when lenticular fissures in strained altering biotite were filled by dioctahedral clays subsequent prograde evolution of dioctahedral clays occurred through deformation dissolution and crystallization and overgrowth illite evolved to muscovite with k in part provided through biotite alteration and corrensite chlorite to homogeneous chlorite the alteration of detrital biotite is closely related to the formation of titanite and magnetite in diagenetic rocks and pyrite calcite and anatase or rutile in the higher grade rocks the observations demonstrate that detrital biotite of volcanic origin may be the principal precursor of chlorite in chlorite rich metapelites originating in marginal basins the mineral parageneses suggest that the transitions from corrensite to chlorite and illite to muscovite may be a function of local chemistry and time

non destructive pxrf of mafic stone tools abstract archaeological use of non destructive pxrf has been most systematically applied to the classification and provenancing of volcanic glass obsidian artefacts comparable work has yet to be developed for non vitreous artefacts we report results of pxrf analysis for a sample of grey to black mafic aboriginal hatchets from sydney and adjacent coastal regions to the north and south the study shows both broad and detailed classification is achievable depending on rock type and degree of elemental depletion or enrichment of the samples pxrf analysis reveals not only distinct patterns of resource use between the three regions of this study but also enables a high degree of geographic resolution in the case of the basalt artefacts of our sample we conclude that non destructive pxrf is effective for reliable characterisation of non vitreous stone artefacts that have a sufficiently complex and enriched compositional signature i e unaltered basalts with 50 of the basalt hatchets in our sample matched with spatially and geologically specific sources

energy dispersive x ray fluorescence analysis of haleakalā basalt adze quarry materials maui hawai i abstract one of hawai i s major prehistoric basalt adze quarries sihp 50 50 11 2510 is located in the summit region of haleakal maui situated at approximately 2750 m above sea level 9000 ft the quarry shares a similar high altitude setting with the mauna kea adze quarry on hawai i island adding to a growing energy dispersive x ray fluorescence edxrf database for the hawaiian islands we present the results from 255 geological and archaeological lithic samples from the haleakal quarry site we also briefly discuss why this non destructive xrf technique is particularly applicable in the hawaiian cultural context

sourcing geochemically identical obsidian multiscalar magnetic variations in the gutansar volcanic complex and implications for palaeolithic research in armenia abstract in obsidian rich armenia one of the most archaeologically significant obsidian resources is the gutansar volcanic complex gvc numerous palaeolithic sites across armenia consist of little more than deposits of obsidian tools and debris and within the hrazdan gorge the vast majority of artifacts is crafted from gvc obsidian for example about 93 of the lithic assemblages from the lower palaeolithic site of nor geghi 1 and the middle palaeolithic site of lusakert cave 1 are gvc obsidian although erupted from multiple volcanic centers gvc obsidians are geochemically identical and cover an area more than 70 km2 for studies seeking to reconstruct movements of palaeolithic hunter gatherers throughout the local landscape the expansive gvc is problematic geochemically identical obsidians dominate the foraging territories of sites within and near the complex here we explore the potential of obsidian magnetic properties to reveal hitherto unobservable patterns in gvc obsidian utilization with the ultimate goal of elucidating palaeolithic behavioral patterns our results show that magnetic properties vary over multiple scales within the gvc allowing obsidian sourcing to become multiscalar these measurements are rapid inexpensive and entirely nondestructive for small artifacts measuring a few basic magnetic properties enables us to distinguish geochemically identical obsidians from three eruptive centers and potentially to attribute artifacts to specific quarrying sites recognize changes in provisioning strategy and estimate a minimum number of cores represented by a lithic scatter

tem and xrd determination of crystallite size and lattice strain as a function of illite crystallinity in pelitic rocks average crystallite size and mean square strain of illite in rock specimens and clay separates were measured independently in tem images and by single line fourier voigt method profile analysis of the c 1 nm peak of xrd patterns for a prograde sequence of pelitic rocks illite crystallinity indices 0 17 0 58 d2h from the gaspepeninsula quebec the tem determined crystallite sizes in clay separates approxi mate those determined by fourier profile analyses and those calculated from illite crystallinity indices by the scherrer equation with the exception of the diagenetic sample the crystallite sizes and mean square strains of illite in rock samples exhibit a trend similar to that determined by profile analyses but the average crystallite sizes are up to five times larger than those measured for clay separates tem images show that all rock samples have a wide range of crystallite sizes and the proportions of larger crystallites increase with metamorphic grade the diagenetic illite is defect rich fine grained mean thickness by volume c 70 nm 1m d material anchizonal illite tends to occur as separate aggregates of small 1m d and larger 2m 1 crystals c 200 nm comprising arrays of subparallel coalescing packets the epizone sample has thick c 400 nm defect free crystals of muscovite occurring in stacks of parallel layers or subhedral crystals intergrown with large angle boundaries cleaved crystals that are free of intracrystalline layer terminations are dominant in clay separates of all samples having ranges of smaller sizes with volume average thicknesses of c 43 43 and 81 nm c 14 28 67 nm by the voigt method respectively for the three zones the results suggest that illite crystallinity indices do not provide a direct measure of a single microstruc tural state of illite in rocks although they yield consistent limits for average crystallite sizes for the anchizone 23 48 nm here therefore they serve as a general parameter of the degree of recrystallization on a relative basis in part because the contributions of all peak broadening variables mixed layering size and strain decrease regularly with prograde regional metamorphism of pelites the microstructural changes caused by rock disaggregation are probably a function of those variables as well the data collectively demonstrate a trend from metastable defect rich small crystals towards a stable assemblage of larger defect free crystals through dissolution of strained crystals and neocrystallization consistent with the ostwald step rule

on suspended barite and the oxygen minimum in the southern ocean particulate ba profiles were measured in the indian sector of the southern ocean the largest fraction 80 of this barium is present as barite microcrystals the profiles of total barium are characterized by a subsurface maximum between 200 and 500 m depth in the vicinity of the oxygen minimum highest barium values are found just south of the polar front while lowest values occur close to the antarctic divergence between the divergence and the polar front a tight inverse relationship is observed between oxygen in the oxygen minimum and barium in the barium maximum this relationship disappears north of the polar front since suspended barite is known to be of biological origin the correlation of barite with oxygen suggests that the observed decrease of oxygen in the oxygen minimum between the divergence and the polar front is due to local consumption of oxygen it is proposed that deep low oxygen water is advected towards the divergence where upwelling occurs and where this water subsequently partly spreads out to the north north east as entrained by the antarctic circumpolar current oxidation of locally produced organic matter with which barite crystals are associated consumes oxygen and sets free individual discrete barites as a result oxygen decreases and barite increases away from the divergence with barite integrating former biological processes

40ar 39ar illite dating of late caledonian acadian metamorphism and cooling of k bentonites and slates from the welsh basin u k the vacuum encapsulation laser 40ar39ar technique allows extremely small 10 6 g samples of fine grained materials such as diagenetic clays to be dated here we show that the method can be extended to higher grade clay minerals the integration of transmission electron microscopic tem characterization with 40ar39ar dating of vacuum encapsulated samples permits the resolution of the timing of metamorphic growth cooling from the time of diagenesis we have applied this technique to well characterized lower paleozoic slates and k bentonites from the welsh basin which span the transition from anchizonal to epizonal grade which had been previously studied using rbsr and smnd dating tem observations of epizonal k bentonites and slate showed that illite in these samples is of 2m1 polytype of muscovite like composition and oriented parallel to cleavage suggesting that they are of metamorphic origin total gas ages equivalent to conventional kar ages for encapsulated epizonal k bentonites and slate 340 408 ma are considerably variable the ar retention ages calculated from 39ar and 40ar atoms retained in the sample after irradiation are more consistent 383 411 ma the 39ar recoil losses are minor for illites from whole rock samples of epizonal k bentonites but very significant for clay separates of epizonal slate plateaus in age spectra were observed in epizonal k bentonites and slate the plateau ages 414 421 ma and retention ages 383 411 ma can be correlated with the onset of acadian metamorphism and culmination of uplift and inversion of the welsh basin respectively these ages are significantly younger than the 450 ma ages previously reported for diagenetic clays using the same method suggesting that diagenetic history has been lost in these epizonal k bentonites and slate tem observations of anchizonal slates showed that there are two modes of illite the first mode is similar to that observed in epizonal samples suggesting a metamorphic origin the second mode consists of the 1md polytype has typical diagenetic illite composition and is oriented parallel to bedding suggesting a diagenetic origin total gas ages for encapsulated anchizonal slates vary considerably 361 422 ma the retention ages are more consistent 413 432 ma than the total gas ages the 39ar recoil losses are more significant than those for epizonal k bentonites and slate plateaus in age spectra are generally not observed however the consistent retention ages for the anchizonal slates correspond to the plateau ages for the epizonal samples and are inferred to represent the onset of acadian metamorphism these data when combined with our previously published results for diagenetic shales suggest that thermal conditions near the boundary of anchizonal and epizonal grades are necessary to completely reset ar systems in shales and slates

geochemical differentiation and prehistoric procurement of obsidian in the mount taylor volcanic field northwest new mexico abstract recently due to an increasing number of analyses of archaeological obsidian worldwide the reporting of chemically differentiated and compositionally zoned obsidian producing rhyolite domes has increased while these studies have been important and furthered our knowledge of the potential chemical variability of rhyolite magmas as they relate to archaeological obsidians they are rarely made relevant to archaeological issues in northwestern new mexico the grants ridge source in the mount taylor volcanic field exhibits two compositionally differing glasses derived from the same magma source that also exhibit significant megascopic variability correlating with raw material quality while grants ridge was previously seen as a single source this study suggests that one of the localities was considered a more viable raw material in prehistory at least in the local area the grants ridge study indicates the value of more intensive investigations of archaeological obsidian sources in the southwest including systematic geoprospection and chemical analysis the wavelength and energy dispersive x ray fluorescence analysis reported here provides the first systematic study of this high silica archaeological obsidian source in the mount taylor volcanic field

earliest direct evidence of monument building at the archaeological site of nan madol pohnpei micronesia identified using 230th u coral dating and geochemical sourcing of megalithic architectural stone abstract archaeologists commonly use the onset of the construction of large burial monuments as a material indicator of a fundamental shift in authority in prehistoric human societies during the holocene high quality direct evidence of this transition is rare we report new interdisciplinary research at the archaeological site of nan madol that allows us to specify where and when people began to construct monumental architecture in the remote islands of the pacific nan madol is an ancient administrative and mortuary center and the former capital of the island of pohnpei it was constructed over 83 ha of lagoon with artificial islets and other architecture built using columnar basalt and coral we employed geochemical sourcing of basalt used as architectural stone and high precision uranium thorium series dates 230th u on coral from the tomb of the first chief of the entire island to identify the beginning of monument building at nan madol in ad 1180 1200 over the next several centuries ad 1300 1600 monument building began on other islands across oceania future research should be aimed at resolving the causes of these social transformations through higher quality data on monument building

three dimensional reservoir characterization and flow simulation of heterolithic tidal sandstones tidal sandstone reservoirs contain significant intervals of hydrocarbon bearing heterolithic facies characterized by the presence of tide generated sedimentary structures such as flaser wavy and lenticular bedding millimeter to centimeter sand mud alternations we have characterized the reservoir properties sandstone connectivity effective permeability and displacement efficiency of these facies using three dimensional 3 d models reconstructed directly from large rock specimens the models are significantly larger than a core plug but smaller than a typical reservoir model grid block we find that the key control on reservoir quality is the connectivity and continuity of the sandstone and mudstone layers if the sandstone layers form a connected network they are likely to be productive even at low values of net to gross about 0 30 5 this may explain why the productivity of low net to gross heterolithic tidal sandstones is commonly underestimated or overlooked connectivity is the dominant control on the transition between productive pay and nonproductive nonpay heterolithic facies however connectivity is difficult to characterize because core plugs sampled from the subsurface are too small to capture connectivity whereas two dimensional outcrop measurements can significantly underestimate the true 3 d value our results suggest that core plug measurements of permeability and displacement efficiency are unlikely to yield representative values at the scale of a reservoir model grid block because the connectivity and continuity of sandstone and mudstone layers varies significantly with length scale

using portable energy dispersive x ray fluorescence edxrf analysis for on site study of ceramic sherds at el hibeh egypt as part of its geoarchaeological research program the el hibeh project of the university of california berkeley field tested at the site of el hibeh northern middle egypt the utility of a portable edxrf unit for obtaining geochemical analyses of pottery suitable for provenance and other ceramic classification studies when the geochemical ceramic data from the field test are combined with basic petrographic analysis for the pottery sample set compelling results are generated in particular a triangular scattergram using elemental iron strontium and rubidium data in parts per million provides excellent temporal and spatial separation of ceramic fabrics type origin and date the geochemical behavior of iron strontium and rubidium is discussed in relation to geological source materials utilized for pottery manufacture

environment and collapse eastern anatolian obsidians at urkesh tell mozan syria and the third millennium mesopotamian urban crisis the early to middle bronze age transition in northern mesopotamia has received great attention for the apparent concurrence of aridification deurbanisation and the end of the akkadian empire around 2200 bce our understanding of the crisis has been almost exclusively shaped by ceramics demography and subsistence exchange and the associated social networks have been largely neglected here we report our sourcing results for 97 obsidian artefacts from urkesh a large urban settlement inhabited throughout the crisis before the crisis six obsidian sources located in eastern anatolia are represented among the artefacts such a diversity of eastern anatolian obsidians at one site is hitherto unknown in mesopotamia it implies urkesh was a cosmopolitan city with diverse visitors or visitors with diverse itineraries during this crisis however obsidians came from only two of the closest sources two to three centuries passed before varied obsidians reappeared even when an obsidian source reappears the raw material seems to have come from a different collection spot we discuss the likely exchange mechanisms and related social networks responsible for the arrival of obsidians at urkesh and how they might have changed in response to climatic perturbations and regional government collapse

geochemical sourcing of basalt artifacts from kaua i hawaiian islands abstract we report on energy dispersive x ray fluorescence edxrf sourcing of 807 basalt artifacts and 34 basalt ecofacts recovered from stratified midden at nu alolo kai kaua i these data are compared with edxrf analyses of 473 alluvial pebbles from waimea canyon 34 adzes from the kaua i museum and published geochemical data for kaua i basalts formal tools such as adzes chisels and mirrors were predominantly manufactured from sources not available at nu alolo kai most adzes and chisels are consistent with sources available elsewhere on kaua i but two basalt mirrors are outside the expected geochemical range of kaua i basalts in contrast almost all expedient tools were manufactured from basalts available at nu alolo kai these findings support the existence of an island wide distribution system for adze material on kaua i and challenges extant models of pre contact hawaiian economics to consider the mechanisms through which specialized commodities were produced and distributed

the last frontier in sourcing the hopes constraints and future for iron provenance research abstract the socioeconomic importance of iron to the populations that make use of it is evidenced by the metal s incorporation into nearly every aspect of life from domestic chores and agriculture to large scale building construction transportation and warfare yet while provenance analysis or sourcing has a long history of generating insights concerning the circulation of most other archaeological materials iron has languished in what seems a perpetual stage of method development the past decade to be sure has witnessed a flurry of new iron provenance research that displays increasing sophistication of both data acquisition techniques and statistical applications it has also exposed divergent stances on what can or should serve as an object s potential source practical achievements beyond localized case studies however are few this paper reviews current practice in iron provenance research and evaluates it in terms of ironmaking technology and the provenance postulate constraints to iron provenance success are identified in the unique attributes of iron and ironmaking technology as well as some of the sourcing strategies employed some novel approaches however do present opportunities to empirically evaluate longstanding models of iron production and distribution and to generate seeds for new models the effective implementation of these emerging research programmes will require more extensive sampling of sources and efforts to ensure comparability of inter laboratory data

tongan and samoan volcanic glass pxrf analysis and implications for constructs of ancestral polynesian society a provenance study of volcanic glass specimens from 12 archaeological sites in the kingdom of tonga is carried out employing pxrf portable x ray fluorescence analysis to accomplish this volcanic glass samples from previously identified sources in northern tonga and the adjacent islands of samoa are analyzed results indicate inter island voyaging and interaction over a 600 km linear distance along the tongan island chain from first lapita settlement ca 2900 bp throughout later prehistory tongan volcanic glass however is not found in samoa and with the exception of one late prehistoric specimen samoan volcanic glass is not present in tonga this distribution challenges current concepts of an integrated ancestral society and homeland common to tonga and samoa from the lapita period onward

evidence for syntectonic crystallization for the mudstone to slate transition at lehigh gap pennsylvania u s a data primarily for phyllosilicates have been obtained for the continuous transitional sequence from mudstone to slate with well developed slaty cleavage at lehigh gap pennsylvania and for slates from quarries in the same area samples were studied by optical microscopy powder x ray diffraction and electron microprobe analysis with emphasis on transmission and analytical electron microscopy mineral grains are virtually free of deformation induced strain concomitant with the gradual development of cleavage normal to bedding the following changes are observed or confirmed 1 the orientation of phyllosilicate grains changes discontinuously from being preferentially parallel to bedding to being parallel to cleavage 2 crystal imperfections as expressed in layer terminations low angle grain boundary like features and other defects decrease in density 3 complex mixed layering is replaced by homogeneous packets of layers of single phases and 4 illite transforms to muscovite with increase in k a1 and change from a lmd to 2m polytype slaty cleavage apparently develops due in part to pressure solution of phyllosilicates oriented parallel to bedding mass transport of components and crystallization to form new grains parallel to cleavage it reflects transitions from imperfect metastable phases toward ordered stable phases in a low temperature 225 c metamorphic environment

macusani obsidian from southern peru a characterization of its elemental composition with a demonstration of its ancient use transparent obsidian artifacts have been reported for the northern lake titicaca basin based on instrumental neutron activation analysis inaa of these artifacts a distinct chemical group was identified yet the location of the source of transparent obsidian in the southern andes remained unreported in the archaeological literature this paper reports on the chemical composition and geographic location of a source of transparent obsidian from the macusani region of peru through the use of inaa and portable x ray fluorescence pxrf we demonstrate that macusani obsidian or macusanite comprises at least two chemical groups one of these groups was used for making artifacts during the archaic period artifacts made of this obsidian were found more than 120 km from the source and yet one third of the obsidian artifacts encountered at macusani were from the non local source of chivay which is 215 km to the southwest

moving sources a preliminary study of volcanic glass artifact distributions in northeast china using pxrf recent studies have highlighted the long distance transport of obsidian from the paektusan tianchi or baitoushan in chinese volcano on the border between china and north korea to eastern russia and korea but little is known about the role of the local population in the production and movement or exchange of this important raw material this paper addresses this data lacuna by presenting sourcing results of 440 artifacts from 18 late paleolithic sites located in northeast china a portable xrf enabled rapid non destructive characterization of samples the results show that although paektusan obsidian was widely transported throughout northeast asia material from at least three other sources was also used in particular we highlight the significance of basaltic glass artifacts with the same geochemistry as sources found in the primorye region of far east russia in sites from northeast china this result indicates a two way movement of volcanic glass artifacts between primorye and the northeast of china rather than a unidirectional long distance exchange system originating from paektusan volcano

ten seconds in the field rapid armenian obsidian sourcing with portable xrf to inform excavations and surveys armenia has one of the most obsidian rich natural and cultural landscapes in the world and the lithic assemblages of numerous palaeolithic sites are predominantly if not entirely composed of obsidian recent excavations at the middle palaeolithic cave of lusakert 1 recovered on average 470 obsidian artifacts daily after sourcing more than 1700 artifacts using portable xrf pxrf in our field house our team sought to shift pxrf based obsidian sourcing into the field itself believing that the geological origins of artifacts would be useful information to have on site during an excavation or survey despite increasing use of portable instruments previous studies have principally focused on collections in museums and other archives and as a result obsidian sourcing has remained embedded in post excavation studies one critical factor in the uptake of obsidian sourcing in the field is the time needed to measure each artifact frequently 2 6 min in previous studies here we report our two methods of obsidian sourcing including source matching done automatically by the pxrf instrument s onboard software in only 10 s our tests with armenian geological specimens and palaeolithic artifacts demonstrate the high efficacy of our two methods which are sufficiently fast to become syncopated with our excavation and survey activities by reducing measurement times from a mode of 300 s in recent studies to just 10 s here we show how and why to shift pxrf based obsidian sourcing from the context of white lab coats to that of muddy boots

assessing xrf for the geochemical characterization of radiolarian chert artifacts from northeastern north america the purpose of this paper is to emphasize the benefits of adopting non destructive energy dispersive x ray fluorescence ed xrf as a first order technique to determine chert whole rock geochemistry for archaeological sourcing chemical signatures for the touladi and la martre prehistoric quarries from the lower st lawrence and gaspe peninsula region of quebec canada are determined and serve as references to test the provenance of regional chert artifacts chert experimental flakes created from quarry geological hand samples are analyzed and used to validate the method archaeological flakes and tools recovered from three archaeological sites are analyzed and tested against quarry samples geochemical diagrams and principal component analysis are used to establish artifact quarry relationships the effects of surface weathering on the geochemical analysis of archaeological chert artifacts are presented sample restoration and research avenues are discussed and proposed to further enhance the robustness of future chert geochemical data sets

non destructive geochemical and magnetic characterisation of group xviii dolerite stone axes and shaft hole implements from england thirty five polished stone axes and shaft hole implements which had been previously assigned by petrographic partially destructive study to group xviii assumed to be from the whin sill dolerite source in northern england were characterised non destructively using a combination of portable x ray fluorescence analysis pxrf and magnetic susceptibility measurements all the implements were compared with the whin sill and with other petrologically and or visually similar rock sources in the north of england and in scotland using a database of chemical elements constructed from the published literature and statistical atypicality testing twenty nine of the implements are good matches for the whin sill as expected but three do not match whin sill rocks and may therefore need to be re assessed as members of group xviii a further three implements have ambiguous characteristics perhaps as a result of surface weathering one axe an axe hammer and an adze that had not previously been assigned to implement groups were also analysed as a test of the robustness of the non destructive methods all three implements could be distinguished from group xviii on the basis of chemical and magnetic characteristics most of the distribution of group xviii implements is best explained by the opportunistic use of glacial erratics rather than trade from the primary source possible alternative sources for the non group xviii implements include the scottish old red sandstone age lavas which could also have been obtained as erratics the chemical and magnetic characteristics established in this paper provide a non destructive alternative to thin section study of potential group xviii artefacts

pxrf characterisation of obsidian from central anatolia the aegean and central europe the obsidian sources of central anatolia the aegean and central europe have been studied in detail over the past 50 years various analytical techniques have been employed to discriminate artefacts from each of these and to reconstruct their zones of distribution this paper presents a pxrf method that allows mass sampling of artefacts focusing on three neighbouring regions particularly where these zones overlap successful discrimination of the obsidian source for products could be achieved using three dimensional scatter plots of trace elements rb sr zr pxrf can thus be appreciated as a powerful tool in the region enabling non destructive on site analyses in contexts where the export of artefacts is often difficult if not impossible the ability to rapidly process large assemblages also has major implications for generating data sets of sufficient resolution to transform archaeological interpretation

a cost surface model of volcanic glass quarrying and exchange in hawai i abstract the spatial distribution of artifacts from the pu u wa awa a volcanic glass source north kona district hawai i island shows a pattern of direct access by those living in the immediately vicinity of the source with subsequent down the line exchange most quarrying and exchanges likely occurred within a single day s travel from sites where artifacts were deposited the exception to this is the discovery of non local direct access evident in assemblages from the extreme southern end of hawai i island these visits may have involved voyages by canoe while people did not often travel far for volcanic glass they nonetheless appear to have had unfettered accessed to source material and freely conducted inter community exchanges this implies volcanic glass was treated as a common pooled resource and the existence of informal exchange relationships

characterization of new zealand obsidian using pxrf abstract new zealand has some of the most active areas of rhyolitic volcanism in the world and this has produced numerous obsidian sources in the northern half of the north island in total archaeologists have recognized 27 named locations from which obsidian can be obtained scattered across 4 geological source regions shortly after colonization in the late 13th century ad polynesian settlers began transporting this material some thousands of kilometers throughout the country and across the sea in small quantities to distant neighbors in the kermadecs and chatham islands although considerable research has been conducted on obsidian sourcing in new zealand the complexity of geochemical source discrimination and the lack of a practical method of non destructive geochemical analysis has hindered progress we present the results of our use of pxrf to provide geochemical data on new zealand obsidian sources and to compare the use of discriminant analysis and classification tree analysis to discriminate among sources and attribute archaeological samples to sources our research suggests that classification tree analysis is superior to discriminant analysis in sourcing studies a large case study using an important settlement phase site s11 20 from the auckland region demonstrates the utility of the methods and the results support a model of high degrees of mobility and interaction during the early settlement of new zealand

ancient east polynesian voyaging spheres new evidence from the vitaria adze quarry rurutu austral islands the use of adze sourcing to study interaction spheres opens new perspectives on ancient polynesian voyaging our work contributes to this effort by documenting the discovery and geochemical signature of the vitaria adze quarry a major adze quarry complex in the central east polynesia core area we present wd xrf geochemical data for the vitaria raw material and ethnographically collected adzes from raivavae and tubuai islands also part of the australs comparison of our results with previously published artifact and source data shows that initial tool production at the vitaria adze quarry coincides with the human colonization of east polynesia artifacts from rurutu were exchanged within the australs as well as to neighboring archipelagoes indicating the importance of rurutu as a node in voyaging networks spanning the east polynesian homeland area large scale tool production at the vitaria adze quarry may have contributed to the rise of vitaria district as the seat of the paramount chief and the center of power on rurutu

testing the accuracy of portable x ray fluorescence to study aztec and colonial obsidian supply at xaltocan mexico abstract this article demonstrates the accuracy of non destructive portable x ray fluorescence p xrf for the study of obsidian in central mexico obsidian sources were identified for a sample of 103 artifacts from the site of xaltocan which spanned the rise and fall of the aztec empire and the first centuries of spanish colonial rule ad 900 1700 sources were assigned by comparing p xrf measurements with previously published source data and were verified using the standard techniques of laboratory xrf l xrf and instrumental neutron activation analysis inaa additional tests of potentially confounding factors show that neither length of read time presence of surface residue nor incomplete detector coverage due to small artifact size compromised our ability to attribute sources to artifacts concave surfaces did decrease the accuracy of readings because of the greater distance between the artifact and the detector our results provide new insight into the stability of supply networks and markets well into the colonial period as well as the homogenizing tendencies of the aztec market system

reorientation mechanisms of phyllosilicates in the mudstone to slate transition at lehigh gap pennsylvania abstract the mudstone to slate transition of the martinsburg formation at lehigh gap pennsylvania was re examined using a new transmission mode x ray texture goniometer supplemented by sem xrd and optical studies three mesoscopic zones are recognized in the outcrop i mudstone ii transition and iii slate zone in the mudstone zone the mica basal planes are parallel to bedding whereas the preferred orientation of the chlorite basal planes is up to 30 shallower than bedding the angular difference between chlorite and mica decreases towards the transition zone becoming subparallel at ca 50 m from the contact with the overlying shawangunk formation in the transition zone the preferred orientations of both mica and chlorite are intermediate to bedding and cleavage orientations which is consistent with mechanical reorientation of phyllosilicates this is supported by a decrease in march strain with a minimum at ca 95 m from the contact for both mica and chlorite sem observations similarly show the importance of grain rotation in large detrital grains in the slate zone both chlorite and mica orientations are parallel to cleavage chlorite and mica in the cleavage orientation of the slate zone have high fe contents whereas low fe mica and mg fe chlorite dominate in the mudstone and transition zone which indicates that dissolution neocrystallization is the dominant mechanism in the slate zone thus mechanical rotation of large detrital grains is important in the early stages of cleavage development with dissolution neocrystallization occurring at all stages and becoming dominant in the more evolved stages

review of major shale dominated detachment and thrust characteristics in the diagenetic zone part i meso and macro scopic scale there is considerable variability in the thickness structure and macroscopic deformation style within shale prone major thrust zones which also impacts the structural style in the overlying and sometimes the underlying section the properties and percentages of clay minerals and percentages of organic material quartz and calcite affect fault zone weakness and behaviour the distribution of competent units within a shale prone zone can also significantly affect fault zone architecture even over short strike distance of 10s to 100s of metres other influences include high pore fluid pressures and associated veins deformation of the fault zone may disrupt the original principal displacement zones and force them to relocate including switching lithologies calcite veins can become concentrated locally in the fault zone and become a focus of fault zone weakness we still need many more descriptions of shale prone fault zones to understand the potential variations in thrust sheet structural style caused by differences in shale detachment characteristics the variations in structural style in the hanging walls of shale detachments are broad and range between the sledge runner style in many appalachian examples and the extensive closely spaced imbricate style of the osen roa detachment southern norway such contrasts are related to several factors including thrust sheet mechanical stratigraphy thickness of the overburden lateral continuity of the detachment detachment mechanical properties composition pore fluid pressures presence absence of higher level detachments and strain rate in many structural locations and at many scales shale prone sequences will pile up to produce over thickened masses cleavage duplexes s c fabrics duplexes imbricates pseudo duplexes and vein formation can all contribute to the thickening at nested scales a mixture of brittle and solution diffusion processes overall cause the affected unit to exhibit flow like characteristics while the broad principles are now well established considerable work remains to be done understanding the full range of structural geometries associated with shale detachments what factors regarding the nature of the detachments affect overlying structural styles rates of deformation and the controls on deformation mechanisms within the thrust zones

realising the potential of portable xrf for the geochemical classification of volcanic rock types abstract the ability to geologically classify stone artefact materials is crucial because it is the first step in provenance allocation and geochemical grouping that inform archaeological models used for understanding exchange systems within prehistoric social networks geochemical analyses have revolutionised exchange studies by making it possible to match stone artefacts back to quarry sources sometimes hundreds or thousands of kilometres away most archaeological basalt characterisation and provenance studies have relied on destructive sampling techniques to obtain the major trace elements nao2 k2o and sio2 wt to identify volcanic rock types on the total alkali silica tas diagram to overcome this limitation this paper presents an alternative method the pearce w f diagram that determines volcanic rock type and alkalinity using elements tio2 zr y and nb that are accurately detected by non destructive portable x ray fluorescence pxrf this new method is proven to be effective in a comparison with recent xrf archaeological basalt studies in the pacific the power to classify volcanic rock types non destructively with pxrf significantly increases the number of artefacts and museum objects available for inclusion in archaeological exchange studies

x ray fluorescence analysis and intra island exchange in the society island archipelago central eastern polynesia abstract we apply x ray fluorescence xrf geochemical analysis to a collection of opunohu valley lithic artifacts from mo orea island to investigate the local scale of raw material procurement adze production use and exchange within the society island archipelago we use these data to document the distribution of non local versus local volcanic artifacts in opunohu valley house sites ritual sites and specialized sites as a means for establishing intra site production and consumption patterns and access to exotic possibly superior stone resources and how these two themes correlate with site function or household wealth and status overall 30 of the artifacts analyzed via wdxrf derive from non local sources notably two other islands in the archipelago outside of the political boundaries of moorean chiefdoms our case study thus provides the first direct material evidence of intra archipelago trade and exchange in the society islands intra archipelago trade in adzes was certainly in place by as early as a d 1350 if not earlier and continued up until the time of european contact in addition our analyses have identified a local adze production locale in the afareaitu district of mo orea island the patterns of local versus non local adze production and exchange strongly suggest that dual interaction spheres were involved the correlation between adzes and adze related debris produced from off island sources and sites with specialized use which were often reserved for the social ritual and political elites in ma ohi society suggests that some of the exotic adzes derived from gift exchange between mo orea and ruling elites in tahiti and the leeward islands these adzes from afar would have solidified socio political and ideological alliances between elites in the windward and leeward sectors of the archipelago

deformation of chlorite in naturally deformed low grade rocks the intracrystalline deformation of chlorite in naturally deformed low grade rocks was investigated with transmission electron microscopy tem as in other phyllosilicates the deformation of chlorite is dominated by the 001 slip plane slip along this plane is very easy through the generation and movement of partial dislocations with burgers vector b 1 n uv0 after initial bending of the 001 planes through a flexural slip mechanism accommodated by slip along 001 the misorientation is concentrated in tiltwalls subnormal to 001 which are formed by partial dislocations with b 1 n uv0 tiltwalls subparallel to 001 are formed by arrays of dislocations with a total burgers vector 001 these boundaries are either initiated at the grain boundary and move inwards by dislocation climb or form by movement of free dislocations towards the tip of propagating boundaries by glide along planes inclined to 001 once a boundary is formed the increasing misfit is accommodated by climb of these dislocations along 001 due to the combination of very easy slip along 001 and the ability to form subgrain boundaries subparallel to 001 by dislocation climb and activation of hard slip systems chlorite deforms plastically even at temperatures below 300 c

interlaboratory standardization and calibration of day mineral crystallinity and crystallite size data clay mineral crystallinity and crystallite domain size data determined by x ray diffraction xrd are methods extensively used in the characterization of very low grade metamorphic conditions however the lack of sufficient interlaboratory standardization has made comparisons between different research groups unreliable due to significant variations in numerical results obtained a consequence of the different machine conditions measurement methods and sample preparations used during analysis a calibration approach to the standardization of data using rock chip standards is presented which allows data sets produced by different research groups to be directly and quantitatively compared a standardized scale the crystallinity index standard cis is proposed with illite crystallinity anchizonal boundary limits of 0 25d 2 and 0 42d 2 and equivalent illite crystallite sizes of 52 and 23 nm respectively determined by the warren averbach method calibrating both old and new data will enable more reliable comparisons between similar and contrasting geological environments and should improve the accuracy and reliability of correlations made between xrd data and other indicators of very low grade metamorphism hence increasing the value of such clay mineral studies

assessing the applicability of portable x ray fluorescence spectrometry for obsidian provenance research in the maya lowlands recent innovations in portable energy dispersive x ray fluorescence pxrf spectrometry have increased its utility for the geochemical characterization of obsidian artifacts for archaeological provenance research however concerns over the utility of pxrf instrumental analyses have been raised focused on the validity and reliability of the geochemical data produced here we adopt the framework of richard hughes on reliability validity and scale in obsidian sourcing research 1998 whereby reliability addresses instrument stability and issues of measurement while validity pertains to an instrument s ability to discern geochemical source provenance this is done in order to test the utility of pxrf instruments for archaeological provenance research k means cluster analysis was used to test the accuracy of pxrf through statistical comparison of data acquired via laboratory and portable energy dispersive xrf instruments multivariate analysis was employed to demonstrate obsidian source representation at two classic maya archaeological sites in southern belize uxbenka and ek xux and to test the validity of data obtained from a pxrf instrument in answering archaeological research questions pertaining to regional interactions between lowland maya polities results suggest that portable xrf instruments produce internally consistent results however data acquired from a pxrf instrument are not statistically equivalent to other xrf instruments this is to say that while pxrf is not a reliable technique it is valid for questions pertaining to geochemical source representation

comparison of xrf and pxrf for analysis of archaeological obsidian from southern peru abstract chemical sourcing is becoming an increasingly important component of archaeological investigation instruments used for elemental analysis generally must be operated in a controlled laboratory environment further many methods require destruction of a small portion of the objects under investigation these facts inhibit the application of chemical sourcing studies in a number of research contexts use of portable non destructive instruments would resolve these issues sixty eight obsidian artifacts from the site of jiskairumoko in southern peru were examined by x ray fluorescence spectrometry xrf and portable x ray fluorescence spectrometry pxrf results were compared for consistency in terms of source determination and individual element concentrations both instruments determined that the same sixty six artifacts derived from the chivay obsidian source and both identified the same two artifacts that could not be assigned to source individual element comparisons showed significant differences but these can be resolved through instrument cross calibration and differences had no bearing on source identification pxrf was found suitable for determining obsidian sources in southern peru and for identifying specimens that require more sensitive analytical methods such as instrumental neutron activation analysis inaa regular use of chivay at jiskairumoko suggests consistent trade relationships developed during the archaic

evaluating effects of chemical weathering and surface contamination on the in situ provenance analysis of building stones in the cuzco region of peru with portable xrf as the only type of instrument capable of determining artifact geochemistry in a wide variety of settings portable x ray fluorescence pxrf may be frequently utilized as probably the best option for collecting data when removal of objects in part or in whole is unfeasible however using pxrf in circumstances where sample selection and preparation diverge from standards developed for lab based instrumentation requires assessing the impact of new and potentially limiting factors to establish the validity of the method in these new contexts here we examine the effects of surface contamination and chemical weathering on the ability to assess provenance of igneous building stones used in the cuzco region of peru surface contamination was assessed through comparing low impact cleaning methods on diorite and andesite blocks and weathering was examined by comparing weathered vs fresh surfaces of samples from two andesite quarries in general the lightest elements were most impacted by contamination and weathering while measurements of many of the heavier elements commonly used in provenance studies were relatively unaffected concentrations of pb and zn were problematic in the urban context of cuzco because of pollution ability to determine provenance of building stones within those limitations i e the validity of this application of pxrf was demonstrated in a preliminary study by comparing measurements from uncleaned exposed building stones in the region to fresh quarry samples

measuring stone artefact transport the experimental demonstration and pilot application of a new method to a prehistoric adze workshop southern cook islands this paper presents a new method based on the calculation of a cortex ratio capable of contributing towards measures of stone artefact transport in polynesia a set of ratios can be calculated by comparing the observed amount of cortical surface area and volume in an assemblage with what is expected should all the products of reduction remain because raw material shape and size is controlled for using geometric equations an estimate for the number of preforms produced from an assemblage also is possible the method is experimentally demonstrated and applied to an archaeological early stage adze manufacturing assemblage from moturakau rockshelter aitutaki island in the southern cook islands application of the method in combination with geochemical and chronological analyses shows that the number of preforms produced and transported as well as the frequency of their transport changed over time but the geographic scale of distribution remained the same essentially local to aitutaki

establishing statistical confidence in cortex ratios within and among lithic assemblages a case study of the middle paleolithic of southwestern france abstract recent studies have demonstrated the usefulness of the cortex ratio for quantifying the cortex composition in lithic assemblages and as a viable index of prehistoric artifact transport yet the lack of means for assigning statistical confidence to archaeologically observed cortex ratios inhibits the approach s utility for objective comparisons and interpretation here we derive statistical confidence for archaeological cortex ratios through monte carlo and resampling techniques experimental data with known geometric properties and measured cortex values were employed as a reference for attaching a probability to an archaeological assemblage s cortex ratio the method is demonstrated on assemblages from the middle paleolithic sites of roc de marsal pech de l aze iv and combe capelle bas in southwestern france

new insights into the formation of diagenetic illite from tem studies diagenetic illite from the proterozoic chuanlinggou formation china has been investigated using the techniques of transmission electron microscopy tem selected area electron diffraction saed x ray diffraction xrd scanning electron microscopy sem and energy dispersive spectrometer eds polytypes of 1 m d and 1 m illite coexist in the diagenetic illite the 1 m d polymorph is predominant in the 0 2 m size fraction which has high al and low mg contents and irregular crystal shapes lattice fringe imaging and one dimensional structural imaging show abundant structure defects the 1 m d illite has both layer and sheet terminations caused by edge dislocations and layer displacements along c caused by screw dislocations these observations indicate that the disordered 1 m d structure of the diagenetic illite resulted from abundant dislocations the dislocation serves as nucleation sites for the illite nano particles to spontaneously nucleate in the initial stage of illite formation such a nucleation process obeys the ostwald ripening rule the illite only shows a 1 0 nm thickness for each layer in high resolution tem images which suggests that the illite crystals have no mixed smectite layer and the 1 m d illites are authigenic and not illitized from smectite or illite smectite heterogeneous nucleation led to directly crystallization of the 1 m d illite during the initial growth of illite in shale under a low temperature and tectonic stress free environment the results have implications for interpreting the distribution of 1 m d illite in sedimentary rocks

trace element partitioning in pantellerites and trachytes abstract in order to investigate the effect of increasing melt peralkalinity on partitioning partition coefficients have been determined using neutron activation analyses of coexisting phenocrysts and glass of five samples from pantelleria spanning the range trachyte to pantellerite alkali feldspar partition coefficients for fe rb ba sr and eu vary with melt peralkalinity due to changes in melt polymerization and to the systematic increase in xor and decrease in xan of the feldspar in going from trachyte to pantellerite fe partition coefficients increase from 0 04 to 0 10 presumably because fe 3 increasingly substitutes in the feldspar tetrahedral site as melt activity of al declines and fe concentrations increase partition coefficients for trivalent light rees decrease and the partitioning pattern becomes flatter the most evolved samples having some of the lowest published values for feldspar the hundredfold decline in eu partition coefficients 2 5 to 0 024 and the decrease in the size of the positive partitioning anomaly are attributed to increasing eu3 eu2 in the melt as it becomes more peralkaline as well as to concomitant decrease in the ca content of feldspar as a result the behavior of eu during fractional crystallization of peralkaline suites is fundamentally different from that in metaluminous suites absolute abundances rise and the size of the negative eu anomaly changes little with fractionation beyond pantelleritic trachyte barium and strontium do not decline to extremely low concentrations in pantellerites as they do in highly evolved metaluminous rhyolites because the feldspar partition coefficients drop precipitously with peralkalinity similarly rb contents do not get large because the partition coefficient increases slightly 0 11 to 0 25 with peralkalinity and is sufficient to make rb only weakly incompatible in the feldspar dominated assemblage partition coefficients calculated for sr and ba from natural phenocryst matrix pairs can be gross over estimates in these feldspar rich felsic rocks if phenocrysts are zoned this effect is severe for assemblages with bulk distribution coefficients d greater than 4 even at very small crystal contents and for 4 d 2 it is significant if crystal contents exceed about 25 some of the very high values and much of the variability reported in the literature for ba and sr feldspar partition coefficients may be a result of this effect in contrast to feldspar partition coefficients for apatite and mafic phases change little with peralkalinity partition coefficients for rees and the compatible elements sc co and cr are all less than half those in fe rich clinopyroxene and olivine of similar composition in high silica rhyolite although absolute levels of partition coefficients are a function of melt polymerization the shapes of the ree partitioning patterns appear to be related to the composition of the clinopyroxene scandium is most strongly concentrated in clinopyroxene partition coefficient 27 60 having larger values in more fe rich compositions apatite shows a wide range in composition within the suite the concentrations of si fe rees and y increasing and mg ca and p decreasing in more evolved samples these trends however parallel those in coexisting glasses so that partition coefficients are essentially constant in peralkaline suites cs is the most incompatible of commonly analyzed elements but its great mobility during alteration and weathering limits its use as a differentiation index next in order of incompatibility are th u hf zr and ta which have small but finite values of d due to the partitioning of th and u into apatite 2 the accommodation of zr and hf by clinopyroxene 0 4 and titanomagnetite 0 2 and relatively high concentrations of ta in cossyrite and fe ti oxides the next most incompatible are the lightest and the heaviest rees and finally the middle trivalent rees and rb plots of pairs of relatively incompatible elements form straight line trends over large compositional ranges in peralkaline suites because the replacement of olivine titanomagnetite by cossyrite as the melt becomes more peralkaline causes little change in d the ree patterns of titanomagnetite and cossyrite are both approximately flat at values less than 0 1 and the relatively high titanomagnetite partition coefficients for ta 2 zr and hf when combined with the very low partition coefficients for these elements for olivine approximate the moderate partition coefficients for cossyrite

effective flow properties of heterolithic cross bedded tidal sandstones part 2 flow simulation tidal heterolithic sandstone reservoirs are heterogeneous at the submeter scale because of the ubiquitous presence of intercalated sandstone and mudstone laminae core plug permeability measurements fail to sample a representative volume of this heterogeneity here we investigate the impact of mudstone drape distribution on the effective permeability of heterolithic cross bedded tidal sandstones using three dimensional surface based minimodels that capture the geometry of cross beds at an appropriate scale the impact of seven geometric parameters has been determined 1 mudstone fraction 2 sandstone laminae thickness 3 mudstone drape continuity 4 toeset dip 5 climb angle of foreset toeset surfaces 6 proportion of foresets to toesets and 7 trough or tabular geometry of the cross beds we begin by identifying a representative elementary volume of 1 m3 35 ft3 confirming that the model volume of 9 m3 318 ft3 yields representative permeability values effective permeability decreases as the mudstone fraction increases and it is highly anisotropic vertical permeability falls to approximately 0 5 of the sandstone permeability at a mudstone fraction of 25 whereas the horizontal permeability falls to approximately 5 and approximately 50 of the sandstone value in the dip across mudstone drapes and strike parallel to mudstone drapes directions respectively considerable spread exists around these values because each parameter investigated can significantly impact effective permeability with the impact depending upon the flow direction and mudstone fraction the results yield improved estimates of effective permeability in heterolithic cross bedded sandstones which can be used to populate reservoir scale model grid blocks using estimates of mudstone fraction and geometrical parameters obtained from core and outcrop analog data

phyllosilicates in very low grade metamorphism transformation to micas phyllosilicates produced mostly by weathering of magmatic metamorphic and sedimentary rocks are widespread in the surficial and near surface zones of the earth s crust these phyllosilicates display very fine grain sizes disordered crystal structures and greatly varying chemical compositions and they represent structurally and chemically metasable phases they are subjected to heat during diagenesis and concomitant metamorphism which provides a long life source of energy for transforming the metastable phases into thermodynamically more stable phases through a long series of partly continuous partly discontinuous reactions the present review summarizes some major mineralogical aspects of these processes with special reference to petrogenetic applications forty years have passed since the first petrogenetic application of the illite structural changes for characterizing diagenetic processes in sedimentary basins weaver 1960 weaver s sharpness ratio as well as kubler s 1964 1968 empirical illite crystallinity index have been easy to use x ray powder diffraction xrd measures of the manifold inter related changes that the hydrous mica like phyllosilicates experience during increasing burial in the first two decades after the introduction of the illite crystallinity concept it was applied to metamorphic petrogenetic studies in certain areas of europe especially to the external fold and thrust belts of the european alps variscides etc these studies were the starting point of important further developments which include awareness of the phyllosilicate transformations during deep burial in sedimentary basins hower et al 1976 inoue et al 1990 amouric and olives 1991 lanson and champion 1991 lindgreen and hansen 1991 eberl 1993 huang et al 1993 whitney and velde 1993 huggett 1995 elliott and matisoff 1996 nieto et al 1996 dong et al 1997 and recognition of the nature of interstratified clay minerals see reynolds and hower 1970 moreover using the theory of powder x ray powder diffraction e g

comparison of diagenetic and low grade metamorphic evolution of chlorite in associated metapelites and metabasites an integrated tem and xrd study chlorite is a common sheet silicate that occurs in various lithologies over a wide grade range involving diagenesis and low grade metamorphism thus the reaction progress of chlorite overs a unique oppor tunity for direct correlation of zonal classification of metasedimentary rocks based on illite crystallinity with metabasite mineral facies to provide such correlation chlorite crystallinity indices apparent mean crystallite sizes and lattice strains crystallite size distributions and compositions of chlorite from coexisting metapelites and metabasites were determined by x ray divraction xrd scanning electron microscopy sem transmission electron microscopy tem analytical electron microscopy aem and electron microprobe emp methods samples were from palaeozoic and mesozoic formations of the bukkium innermost western carpathians hungary that underwent alpine cretaceous orogenic metamorphism metapelites range in grade from late diagenesis to epizone whereas metabasites vary from prehnite pumpellyite through pumpellyite actinolite to greenschist facies despite significant diverences in composition mineral assemblages and textures reaction progress as measured in part by chlorite crystallinity in metapelites paralleled that in metabasites chlorite crystal linity and mean crystallite size increase and the proportion of mixed layers in chlorite decreases whereas the calculated lattice strain does not change significantly with increasing metamorphic grade similar trends but especially at higher grades significant diverences were found in mean crystallite size values using various methods for xrd line profile analyses the increase in crystallite size with increasing grade was demonstrated also by direct tem measurements on ion milled whole rock samples but with a larger scatter of data at higher grades in spite of the diverent kinds of mixed layering in chlorite mg rich smectitic mostly random local corrensite like units in metabasites and fe rich berthierine and diocta hedral smectite in metapelites xrd calculated and tem measured parameters were found to be reliable tools for measuring reaction progress and metamorphic grade of the same degree in both lithotypes

validity of off the shelf handheld portable xrf for sourcing near eastern obsidian chip debris handheld portable xrf hhpxrf has received considerable recent attention in archaeology especially for obsidian sourcing published studies largely suggest a high potential for success hhpxrf though has been met with debate and scepticism concerns fall into three categories 1 low accuracy and precision 2 data correction schemes and calibration and 3 ignorance of fundamental xrf issues such as specimen size limits and morphology effects the result is that archaeological interpretations in hhpxrf based studies are cast into doubt should interpretations be believed if authors did not follow the perceived best practices to address such questions the validity of hhpxrf for near eastern obsidian sourcing was tested under deliberately sub optimal conditions irregular obsidian debitage near the minimum size limits was sourced with a success rate of 94 based on a rank matches to 100 based on a and b rank matches even under conditions chosen to mimic off the shelf operation

initial source evaluation of archaeological obsidian from the kuril islands of the russian far east using portable xrf obsidian artifacts recently have been recovered from 18 archaeological sites on eight islands across the kuril island archipelago in the north pacific ocean suggesting a wide ranging distribution of obsidian throughout the island chain over the last 2 500 years although there are no geologic sources of obsidian in the kurils that are known to have been used prehistorically sources exist in hokkaido japan and kamchatka russia the southern and northern geographic regions respectively from which obsidian may have entered the kuril islands this paper reports on the initial sourcing attempt of kuril islands obsidian through the analysis of 131 obsidian artifacts data from this research were generated through the application of portable xrf technology and are used to address research questions concerning prehis toric mobility exchange and social networking in the kuril islands

on the provenance of prehistoric obsidian artifacts in south korea abstract using a series of geochemical data from obsidian samples taken from unmodified rocks and prehistoric sites we investigated the provenance of some obsidian artifacts found in south korea by using la icp ms and shrimp methods we analyzed rare earth elements rees and lead pb isotopic ratios of obsidian samples from the north korean side of the baekdusan mountain nk and artifacts from a neolithic site in gadeokdo southeast coast of south korea bg published accounts on the elemental correlation of previously analyzed samples were re examined in consideration of their geological compatibility it appears that the prehistoric artifacts from the middle to northern part of south korea have a genetic relationship with obsidians from the baekdusan area whereas those of the southern part are related to kyushu japan ree patterns of the bg and the nk samples demonstrate a prominent contrast between them suggesting their different provenances presumably the bg obsidians are related to the volcanic rocks of kyushu given that pb isotopic ratios are indicative of the relative contribution of crust versus mantle component to the volcanic magma they indicate the addition of a crustal component to the volcanic magma for the baekdusan volcanic rocks and the nk obsidians the kyushu volcanics and the bg obsidians have a relative affinity to the mantle component the geochemical approach adopted in the current research may be regarded as an accurate and effective means to discriminate and isolate obsidian sources helpful for provenance and other archaeological study of obsidian artifacts

the distinction between caledonian burial and regional metamorphism in metapelites from north wales an analysis of isocryst patterns in snowdonia and ll n three prograde stages in metapelites gwna group to wenlock are recognized stage i with white mica crystallinity values 0 43 2 stage ii 0 43 0 26 2 stage iii isocrysts at 0 03 2 intervals are drawn separately for pelites above and below the sub arenig unconformity approximately concordant isocryst patterns characterize the unconformity in the northwestern and southeastern limbs of the snowdonia syncline whereas discordant patterns are developed northwest of the aber dinlle fault and at the closure of the ynyscynhaiarn anticline the contrasting patterns are the result of a pre arenig burial metamorphism in post tremadoc pelites belts of steep metamorphic gradient coincide with belts of high strain and a broad area of higher grade caradoc pelites coincides with the core of the snowdonia syncline the later metamorphism is related to caledonian deformation rather than to burial pelite alteration adjacent to small intermediate to acid plutons suggests emplacement before the caledonian regional metamorphism a close correlation exists between metabasite zones and metapelite stages

geochemical characterization of lorraine limestones from the saint paul cathedral of liege belgium assumptions for the true provenance of the building stones we investigate the provenance of the ochre building stones called lorraine limestones used for architectural specific elements of the saint paul cathedral in liege belgium between the thirteenth and fifteenth century a multi analytical approach including archives study petrography and rare earth elements geochemistry has been performed to characterize the stones used in the church and to compare them with ochre limestones outcropping in the north east of the paris basin our study suggests that a very restricted geographical area near the ancient port of donchery ardennes france including dom le mesnil and hannogne ancient quarries of bajocian limestones middle jurassic should clearly be regarded as the potential origin location for the stones used in the saint paul cathedral

a transmission electron microscope study of white mica crystallite size distribution in a mudstone to slate transitional sequence north wales uk high resolution transmission electron microscopy hrtem measurements of the thickness of white mica crystallites were made on three pelite samples that represented a prograde transition from diagenetic mudstone though anchizonal slate to epizonal slate crystallite thickness measured normal to 001 increases as grade increases whereas the xrd measured 10 a peak profile the kubler index decreases the mode of the tem measured size population can be correlated with the effective crystallite size n 001 determined by xrd the results indicate that the kubler index of white mica crystallinity measures changes in the crystallite size population that result from prograde increases in the size of coherent x ray scattering domains these changes conform to the scherrer relationship between xrd peak broadening and small crystallite size lattice strain broadening is relatively unimportant and is confined to white mica populations in the diagenetic mudstone rapid increases in crystallite size occur in the anchizone coincident with cleavage development changes in the distribution of crystallite thickness with advancing grade and cleavage development are characteristic of grain growth by ostwald ripening the kubler index rapidly loses sensitivity as an indicator of metapelitic grade within the epizone

three dimensional modeling of a shoreface shelf parasequence reservoir analog part 2 geologic controls on fluid flow and hydrocarbon recovery wave dominated shoreface shelf parasequences are commonly modeled as simple layer cake reservoirs yet analysis of modern and ancient analogs demonstrates that these intervals contain a more complex physical stratigraphy we investigate the impact of depositional and diagenetic heterogeneity associated with gently dipping clinoform surfaces on fluid flow and recovery during water flooding using a three dimensional model reconstructed from a well exposed outcrop analog we demonstrate that the volume of oil in place is affected by variations in facies thickness associated with interfingering along clinoforms whereas waterflood sweep efficiency is affected by barriers to flow along clinoform surfaces such as calcite cemented layers mudstones and siltstones sweep efficiency is low when water flooding is down depositional dip because oil is bypassed at the toe of each clinothem as water flows preferentially through high quality sandstone facies in the upper part of the parasequence sweep efficiency is higher when water flooding is up depositional dip because the gravity driven downward flow of water sweeps poorer quality sandstone facies in the lower part of the parasequence in both cases injectors may offer limited pressure support to producers water flooding along depositional strike yields good pressure support but poor sweep because the gravity driven flow of water into the lower part of the parasequence is significantly reduced this yields highly variable fluid saturations but a uniform pressure gradient which is consistent with pressure and fluid saturation data from the mature rannoch formation reservoir brent field united kingdom north sea simple layer cake models fail to capture the range of flow behaviors described above and overpredict recovery by up to 20 as a result

the middle triassic evolution of the bangong nujiang tethyan ocean evidence from analyses of oib type basalts and oib derived phonolites in northern tibet in this paper we present new major and trace element chemical data for the basalts and phonolites of the nare ocean island fragment naoi as well as zircon u pb age data and hf isotope compositions for the naoi phonolites in the middle segment of the bangong nujiang suture zone northern tibet our aim is to assess the genesis of these rocks and to reconstruct the middle triassic evolution of the bangong nujiang tethyan ocean bnto the naoi retains an ocean island type double layered structure comprising a basaltic basement and an oceanic sedimentary cover sequence conglomerate and limestone the latter accompanied by layers of erupted phonolite near the top of the sequence the basalts in the naoi are enriched in light rare earth elements and high field strength elements nb ta zr hf and ti and they exhibit chondrite normalized ree patterns and primitive mantle normalized trace element patterns similar to those of ocean island basalts taking into consideration their high dy yb sm yb and la sm ratios we conclude that the naoi basalts were derived from the partial melting of garnet peridotite in the mantle the naoi phonolites have lree enriched chondrite normalized ree patterns with negative eu anomalies eu eu 0 41 0 43 and primitive mantle normalized trace element patterns with enrichments in nb ta zr and hf and depletions in ba u sr p and ti given the high contents of nb 172 256 ppm ta 11 8 16 0 ppm zr 927 1117 ppm and hf 20 8 26 9 ppm and the very low contents of mgo 0 11 0 25 wt the very low mg values 5 10 and the near zero contents of cr 1 27 7 59 ppm ni 0 43 7 19 ppm and co 0 11 0 38 ppm and the small and homogeneously positive e hf t values 4 9 to 9 5 we infer that the naoi phonolites were formed by the fractional crystallization of an oib derived mafic parent magma the phonolites of the naoi contain zircons that yielded u pb ages of 239 and 242 ma indicating that the naoi formed during the middle triassic these data combined with data from modern ocean islands e g canary islands cape verde fernando de noronha tristan da cunha and gough in the atlantic ocean and society and austral cook in the pacific ocean lead us to infer that the bnto was open for a long time before the middle triassic and that the ocean had already developed into a mature ocean with a thick oceanic lithosphere by at least the middle triassic

pxrf calibrations for volcanic rocks and the application of in field analysis to the geosciences advances in portable x ray fluorescence pxrf technologies have made such instruments an attractive choice for geologists who wish to collect chemical data in the field the acceptance of pxrf data for research purposes such as for example petrogenetic studies by the geologic community has been hampered by a perception of poor quality here we show that current generation pxrf instruments can yield high quality data when deployed either in the laboratory or as a base camp field instrument we have developed four calibrations for major minor and trace elements in geological materials using minimal sample preparation one for the broad range of geologic compositions 0 100 sio2 using rock powders and three with an emphasis on volcanic rock samples rock billets ranging from primitive basalt to rhyolite basalt rock powder and rhyolitic pumice powder the calibrations use influence coefficients to correct for absorbance and secondary enhancement of one element by x rays of other elements present in the sample nugget effects can have a significant influence over the determination of the concentration of elements such as zr if proper care in sample homogenization is not taken we evaluate data quality for each element in each calibration and find that for several elements ti mn fe ca k p cr ni zn rb sr y zr nb precision and accuracy approach those obtainable from full size wavelength dispersive xrf analysis maximization of data quality is achieved by matching of calibration material types and unknowns

diagenetic and low grade metamorphic terranes of gaspe peninsula related to the geological structure of the taconian and acadian orogenic belts quebec appalachians illite crystallinity ic measurements determination of the proportion of 2m mica polytypes and organic matter reflectance measurements establish regional diagenetic low grade metamorphic trends for the taconian and acadian belts of gaspe peninsula ic varies as a function of many factors besides maximum burial temperature and heating time correlation between ic and 2m illite polytypes for the fortin group and temiscouata formation suggests i that the amount of high grade detrital mica in the samples is low and ii that ic can be used with some confidence as an estimator of regional thermal maturation levels correlation of these parameters with available organic reflectance values further supports this assumption the illites of the temiscouata and western fortin groups are mostly phengitic in composition whereas in the eastern outcrop belt they are more mg and fe rich celadonitic but generally also of lower grade and lower 2m content the d 060 values for illites measured on the unorientated 2 m fraction of samples fall between 1 502 and 1 503 a range 1 500 1 504 a indicating relatively low octahedral occupancy by mg and fe between one fifth and one third of the available spaces pyrophyllite and paragonite were not detected chlorites are fe rich and ripidolitic the ic map for the acadian belt of the peninsula displays general congruence between ic contours 2200 sample points and structural trends for the 27 000 km2 area the highest grades anchimetamorphic are associated with the oldest rocks honorat and matapedia groups exposed in the cores of major anticlines anchimetamorphic grades associated with the western outcrop belt of the lower devonian fortin group require 7 8 km of subsidence to accommodate sufficient thickness of overlying younger rocks on top of 4 5 km of fortin group deep water clastics to explain the grades in terms of burial metamorphism assuming a geothermal gradient of 30 c km 1 the lowest grade diagenetic rocks occupy a large area in the northeastern part of the peninsula smaller areas in the northwestern part of the acadian belt in the centre of chaleurs bay synclinorium and in the ordovician mictaw group the contact between the taconian and acadian belt is marked by a distinct maturation discontinuity the grand pabos fault juxtaposes rocks of contrasting maturation levels matapedia group against fortin group in the west but shows no maturation offset further east in the honorat group the fault zone limiting the fortin group in the north is also associated with a major ic jump

digital core analysis improved connectivity and permeability characterization of thin sandstone layers in heterolithic rocks abstract heterolithic thin beds reservoirs contain significant amounts of hydrocarbons we characterized the reservoir properties sandstone connectivity continuity and permeability of sandstone layers in heterolithic rocks using three dimensional imaging and analysis of heterolithic core plugs and mini plugs the high resolution three dimensional models of the samples are smaller than a typical reservoir model grid block and similar the millimetre to centimetre beddings in heterolithic rocks we find that the key to reservoir quality in heterolithic rocks is the connectivity and continuity of thin reservoir sandstone layers also we show that these well connected and continuous thin sandstone layers have higher effective permeabilities that are comparable to a reference reservoir sandstone these results can provide further information as to why some low resistivity heterolithic intervals with low net to gross values of the sandstone produced a significant amount of hydrocarbon despite lower production forecast based on well logs and core plug data determining the connectivity and continuity of thin sandstone layers is difficult due to limitations of well logs and core plug analysis that do not resolve and capture the connectivity of thin beddings we show that 3 d image visualization is effective in characterizing the connectivity and continuity of thin sandstone layers in heterolithic rocks also our digital core analysis method computed permeability of thin sandstone layers in 3 d models of mini plugs representing thin sandstone layers in heterolithic core plugs our results represent information and reservoir properties at the millimetre to centimetre scale that are similar to the thickness of thin sandstone beddings in heterolithic rocks

correlating tephras and cryptotephras using glass compositional analyses and numerical and statistical methods review and evaluation abstract we define tephras and cryptotephras and their components mainly ash sized particles of glass crystals in distal deposits and summarize the basis of tephrochronology as a chronostratigraphic correlational and dating tool for palaeoenvironmental geological and archaeological research we then document and appraise recent advances in analytical methods used to determine the major minor and trace elements of individual glass shards from tephra or cryptotephra deposits to aid their correlation and application protocols developed recently for the electron probe microanalysis of major elements in individual glass shards help to improve data quality and standardize reporting procedures a narrow electron beam diameter 3 5 m can now be used to analyze smaller glass shards than previously attainable reliable analyses of microshards defined here as glass shards in part 2 of the review we describe critically assess and recommend ways in which tephras or cryptotephras can be correlated in conjunction with other information using numerical or statistical analyses of compositional data statistical methods provide a less subjective means of dealing with analytical data pertaining to tephra components usually glass or crystals phenocrysts than heuristic alternatives they enable a better understanding of relationships among the data from multiple viewpoints to be developed and help quantify the degree of uncertainty in establishing correlations in common with other scientific hypothesis testing it is easier to infer using such analysis that two or more tephras are different rather than the same adding stratigraphic chronological spatial or palaeoenvironmental data i e multiple criteria is usually necessary and allows for more robust correlations to be made a two stage approach is useful the first focussed on differences in the mean composition of samples or their range which can be visualised graphically via scatterplot matrices or bivariate plots coupled with the use of statistical tools such as distance measures similarity coefficients hierarchical cluster analysis informed by distance measures or similarity or cophenetic coefficients and principal components analysis pca some statistical methods cluster analysis discriminant analysis are referred to as machine learning in the computing literature the second stage examines sample variance and the degree of compositional similarity so that sample equivalence or otherwise can be established on a statistical basis this stage may involve discriminant function analysis dfa support vector machines svms canonical variates analysis cva and anova or manova or its two sample special case the hotelling two sample t2 test randomization tests can be used where distributional assumptions such as multivariate normality underlying parametric tests are doubtful compositional data may be transformed and scaled before being subjected to multivariate statistical procedures including calculation of distance matrices hierarchical cluster analysis and pca such transformations may make the assumption of multivariate normality more appropriate a sequential procedure using mahalanobis distance and the hotelling two sample t2 test is illustrated using glass major element data from trachytic to phonolitic kenyan tephras all these methods require a broad range of high quality compositional data which can be used to compare unknowns with reference training sets that are sufficiently complete to account for all possible correlatives including tephras with heterogeneous glasses that contain multiple compositional groups currently incomplete databases are tending to limit correlation efficacy the development of an open online global database to facilitate progress towards integrated high quality tephrostratigraphic frameworks for different regions is encouraged

machine learning classifiers for attributing tephra to source volcanoes an evaluation of methods for alaska tephras glass composition based correlations of volcanic ash tephra traditionally rely on extensive manual plotting many previous statistical methods for testing correlations are limited by using geochemical means masking diagnostic variability we suggest that machine learning classifiers can expedite correlation quickly narrowing the list of likely candidates using well trained models eruptives from alaska s aleutian arc alaska peninsula and wrangell volcanic field were used as a test environment for 11 supervised classification algorithms trained on nearly 2000 electron probe microanalysis measurements of glass major oxides representing 10 volcanic sources artificial neural networks and random forests were consistently among the top performing learners accuracy and kappa 0 96 their combination as an average ensemble effectively improves their performance using this combined model on tephras from eklutna lake south central alaska showed that predictions match traditional methods and can speed correlation although classifiers are useful tools they should aid expert analysis not replace it the eklutna lake tephras are mostly from redoubt volcano besides tephras from known holocene active sources holocene tephra geochemically consistent with pleistocene emmons lake volcanic center dawson tephra but from a yet unknown source is evident these tephras are mostly anchored by a highly resolved varved chronology and represent new important regional stratigraphic markers

calibration of the anchizone a critical comparison of illite crystallinity scales used for definition instrumental settings for determination of illite muscovite crystallinity half height width of the 10 a x ray diffraction peak and the limits of the anchimetamorphic zone adopted by various authors fall into several groups the variation in the limiting peak widths between the authors that have adopted kubler s neuch tel boundary values of 0 42 and 0 25 2 can be interpreted in terms of variation in the instrumental settings the choice of time constants higher than those given by the formula causes peak broadening this effect is particularly marked at high scan rates the peak broadening is by constant increments that are virtually independent of the absolute peak width the differences between the kubler neuch tel derived limiting values and some other scales are appreciably greater than can be accounted for by these differences in instrumental settings many of these scales are not equivalent in particular the limits adopted by dunoyer de segonzac 1969 and subsequent workers at strasbourg are too broad their anchizone represents a range of grades of metamorphism lower than that of kubler widely overlapping the latter s diagenetic zone those adopted by some other mainly french authors are too narrow the limits of the anchizone should be calibrated by inter laboratory standards and the instrumental settings should be specified in full

variation of illite muscovite 40 ar 39 ar age spectra during progressive low grade metamorphism an example from the us cordillera 40ar 39ar step heating data were collected from micron to submicron grain sizes of correlative illite and muscovite rich cambrian pelitic rocks from the western united states that range in metamorphic grade from the shallow diagenetic zone zeolite facies to the epizone greenschist facies with increasing metamorphic grade maximum ages from 40ar 39ar release spectra decrease as do total gas ages and retention ages previous studies have explained similar results as arising dominantly or entirely from the dissolution of detrital muscovite and precipitation recrystallization of neo formed illite while recognizing the importance of these processes in evaluating our results we suggest that the inverse correlation between apparent age and metamorphic grade is controlled primarily by thermally activated volume diffusion analogous to the decrease in apparent ages with depth observed for many thermochronometers in borehole experiments our results suggest that complete resetting of the illite muscovite ar thermochronometer occurs between the high anchizone and epizone or at roughly 300 c this empirical result is in agreement with previous calculations based on muscovite diffusion parameters which indicate that muscovite grains with radii of 0 05 2 m should have closure temperatures between 250 and 350 c at high anchizone conditions we observe a reversal in the age grain size relationship the finest grain size produces the oldest apparent age which may mark the stage in prograde subgreenschist facies metamorphism of pelitic rocks at which neo formed illite muscovite crystallites typically surpass the size of detrital muscovite grains it is also approximately the stage at which neo formed illite muscovite crystallites develop sufficient ar retentivity to produce geologically meaningful 40ar 39ar ages results from our sampling transect of cambrian strata establish a framework for interpreting illite muscovite 40ar 39ar age spectra at different stages of low grade metamorphism and also illuminate the transformation of illite to muscovite at frenchman mtn nv where the cambrian bright angel formation is at zeolite facies conditions illite muscovite 40ar 39ar data suggest a detrital muscovite component with an apparent age 967 ma the correlative carrara fm is at anchizone conditions in the panamint and resting spring ranges of eastern california and in these locations illite muscovite 40ar 39ar data suggest an early permian episode of subgreenschist facies metamorphism the same type of data from equivalent strata at epizone conditions greenschist facies in the footwall of the bullfrog fluorspar canyon detachment in southern nevada reveals a period of slow to moderate late cretaceous cooling