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Patrick Schmidt - One of the best experts on this subject based on the ideXlab platform.
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the antiquity of australian Silcrete heat treatment lake mungo and the willandra lakes
Journal of Human Evolution, 2020Co-Authors: Patrick Schmidt, Peter HiscockAbstract:Abstract The evolution of heat treatment for stone artefact production is a subject of major interest for our understanding of early modern humans. In this study, we examine the evidence from one region in Australia to provide a new record of the antiquity of heat treatment, explore chronological shifts in the frequency of heat treatment, and discuss the implications of these findings for early population dynamics and the technical knowledge early settlers might have brought with them. Until now, Australian heat treatment has only dated back 25000 years. This study of the Willandra Lakes, including Lake Mungo, has identified the oldest systematic evidence of heat treatment yet reported in Australia, dating to ∼42000 years. We also document time-dependent directional change in the frequency of the practice. At those early times, with over 60% of all Silcrete artefacts heat-treated, we hypothesize that the practice was mastered and integrated as a recurrent technical solution to the complexities of knapping Silcrete. Over time, the use of heat treatment decreased progressively until less than 10% of the artefacts were heat-treated in the terminal Holocene. This trajectory has implications for understanding the antiquity of heat treatment on the Australian continent and for investigating the factors that governed its use.
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when was Silcrete heat treatment invented in south africa
Palgrave Communications, 2020Co-Authors: Patrick Schmidt, Deano D Stynder, Nicholas J Conard, John ParkingtonAbstract:Silcrete heat treatment, along with a suit of other innovations, have been used to argue for an early onset of modern or complex behaviours in Middle Stone Age hominins. This practice was confined to South Africa’s southern and western Cape regions where it was continuously practised since the Still Bay industry. However, the exact moment that this technological advancement occurred still remains unclear. This is partly due to the scarcity of Silcrete assemblages dating to the first half of the Middle Stone Age. To determine when Silcrete heat treatment began to be well-established, we compare the Silcrete assemblages from two archaeological sites situated along the south western coast of South Africa: Hoedjiespunt 1, one of the earliest Middle Stone Age Silcrete assemblages dating to 119–130 ka, and Duinefontein 2, one of the latest Early Stone Age assemblages dating to 200–400 ka. Our results suggest that the invention of heat treatment occurred sometime between 130 ka and 200–400 ka, as it is still absent in the earlier assemblage but fully mastered and well-integrated in the recent one. This period corresponds to the time that Homo sapiens became the major hominin species in the southern African subcontinent and it is roughly the time that Silcrete use became widespread in the second half of the Cape-coastal Middle Stone Age. This opens interesting new questions on the relation between Silcrete use and heat treatment and on why early modern humans spontaneously invented heat treatment when they began using Silcrete in the Cape region.
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simple surface fire heat treatment significantly improves Silcrete flake quality and flaking efficiency
Journal of Archaeological Science: Reports, 2020Co-Authors: Justin Pargeter, Patrick SchmidtAbstract:Abstract Intentional stone heat treatment is a key marker for prehistoric behavioural variability. Yet, the relationship between differences in heat-treatment strategies and variations in stone tool-making processes remains heavily debated and poorly understood. We report on two experiments testing wood fuels and heating strategies applied to Silcrete nodules from ~60 km south of Diepkloof Rock shelter in South Africa with early evidence for intentional Silcrete heat treatment. We flaked the heated Silcrete nodules to maximize miniaturized flake production. The resulting cores and flakes were compared in terms of their utility (flake cutting edge to mass) and cutting edge quality (cutting edge angles) in addition to quantifying woody residues and heat induced fracture rates. Our results show that ‘simpler’ surface-fire heat treatment strategies provide significant increases in miniaturized core utility and flake quality over unheated Silcrete nodules. Some of these effects were obtained without more specialized knowledge than is required to maintain fires for cooking and other utilitarian purposes. Our results show that rapidly heating Silcrete to modify rocks for miniaturized stone tool production is efficient at relatively low levels of technological investment.
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heat treatment of kalahari and cape Silcretes impacts upon Silcrete chemistry and implications for geochemical provenancing
Archaeological and Anthropological Sciences, 2019Co-Authors: David J Nash, Sheila Coulson, Patrick SchmidtAbstract:Recent studies in southern Africa and eastern Australia have demonstrated the feasibility of using a geochemical fingerprinting approach to determine the source locations from which Silcrete raw materials were procured prior to their use in stone tool manufacture. The impact of intentional heat treatment of Silcrete upon its chemistry, however, is unknown, meaning that heat-treated Silcrete artefacts have to date been excluded from provenancing studies. This investigation presents the first high-resolution experimental analysis of the impacts of heat treatment upon the chemical composition of Silcrete. The study compares the composition of unheated control samples against samples heat-treated to target temperatures of up to 600 °C taken from four Silcrete blocks from South Africa and Botswana. Chemical compositions of samples are determined using ICP-MS and ICP-AES. Experimental results indicate that heat treatment has a limited impact upon Silcrete chemistry. Only 7 out of 65 minor, trace and rare earth elements analysed (Al2O3, Fe2O3, K2O, As, Cr, Cs and Cu) were depleted beyond expected error limits following controlled heating. There was no consistent pattern of elemental depletion across the four Silcrete samples, although a greater number of elements were depleted from chalcedony-cemented Kalahari Silcretes compared with microquartz-cemented Cape Silcretes. We conclude that it is safe to use chemical data from heat-treated artefacts from the Cape as part of geochemical fingerprinting studies; however, we recommend that Cu and Cs concentrations be omitted from any statistical analyses until the effects of heat treatment upon these elements are fully understood. We echo the conclusions of previous studies by recommending that chalcedony-cemented Silcrete artefacts that show signs of burning or intentional heat treatment be excluded from provenancing studies in the Kalahari and potentially elsewhere.
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how reliable is the visual identification of heat treatment on Silcrete a quantitative verification with a new method
Archaeological and Anthropological Sciences, 2019Co-Authors: Patrick SchmidtAbstract:Heat treatment of Silcrete was a major innovation in the southern African Middle Stone Age (MSA). It allowed for the first time to improve materials for tool knapping, and it may have represented an important step in the perception of natural resources as modifiable objects. Recognising heat treatment in Silcrete assemblages is therefore a crucial step for archaeologists working on the MSA. Two different methods, gloss analysis and visual estimation of surface roughness, have so far been used to identify heat treatment. Although both methods have advantages in specific situations, only visual heating proxy classifications allow to count heated vs. not-heated artefacts in assemblages. However, no objective independent data on the reliability and reproducibility of visual classifications are available today. This paper presents a new and promising non-destructive way to measure surface roughness and to verify the reliability of visual classifications: the replica tape method. The results show a rather good reliability of visual classifications: only few pieces are misclassified (n = 3), and the results of both replica tape measurements and visual classification agree within a 3% error range. These results also lay out the foundations for future developments of replica tape measurements to make it a stand-alone method for identifying heat treatment within Silcrete assemblages.
David J Nash - One of the best experts on this subject based on the ideXlab platform.
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heat treatment of kalahari and cape Silcretes impacts upon Silcrete chemistry and implications for geochemical provenancing
Archaeological and Anthropological Sciences, 2019Co-Authors: David J Nash, Sheila Coulson, Patrick SchmidtAbstract:Recent studies in southern Africa and eastern Australia have demonstrated the feasibility of using a geochemical fingerprinting approach to determine the source locations from which Silcrete raw materials were procured prior to their use in stone tool manufacture. The impact of intentional heat treatment of Silcrete upon its chemistry, however, is unknown, meaning that heat-treated Silcrete artefacts have to date been excluded from provenancing studies. This investigation presents the first high-resolution experimental analysis of the impacts of heat treatment upon the chemical composition of Silcrete. The study compares the composition of unheated control samples against samples heat-treated to target temperatures of up to 600 °C taken from four Silcrete blocks from South Africa and Botswana. Chemical compositions of samples are determined using ICP-MS and ICP-AES. Experimental results indicate that heat treatment has a limited impact upon Silcrete chemistry. Only 7 out of 65 minor, trace and rare earth elements analysed (Al2O3, Fe2O3, K2O, As, Cr, Cs and Cu) were depleted beyond expected error limits following controlled heating. There was no consistent pattern of elemental depletion across the four Silcrete samples, although a greater number of elements were depleted from chalcedony-cemented Kalahari Silcretes compared with microquartz-cemented Cape Silcretes. We conclude that it is safe to use chemical data from heat-treated artefacts from the Cape as part of geochemical fingerprinting studies; however, we recommend that Cu and Cs concentrations be omitted from any statistical analyses until the effects of heat treatment upon these elements are fully understood. We echo the conclusions of previous studies by recommending that chalcedony-cemented Silcrete artefacts that show signs of burning or intentional heat treatment be excluded from provenancing studies in the Kalahari and potentially elsewhere.
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heat treatment as a universal technical solution for Silcrete use a comparison between Silcrete from the western cape south africa and the kalahari botswana
PLOS ONE, 2017Co-Authors: Patrick Schmidt, David J Nash, Sheila Coulson, Matthias B Goden, G AwcockAbstract:Heat treatment was one of the first transformative technologies in the southern African Middle Stone Age (MSA), with many studies in the Cape coastal zone of South Africa identifying it as an essential step in the preparation of Silcrete prior to its use in stone tool manufacture. To date, however, no studies have investigated whether heat treatment is necessary for all Silcrete types, and how geographically widespread heat treatment was in the subcontinent. The aim of this study is to investigate experimentally whether heat treatment continued further north into the Kalahari Desert of Botswana and northernmost South Africa, the closest area with major Silcrete outcrops to the Cape. For this we analyse the thermal transformations of Silcrete from both regions, proposing a comprehensive model of the chemical, crystallographic and `water'-related processes taking place upon heat treatment. For the first time, we also explore the mobility of minor and trace elements during heat treatment and introduce a previously undescribed mechanism - steam leaching - causing depletion of a limited number of elements. The results of this comparative study reveal the Cape and Kalahari Silcrete to respond fundamentally differently to heat treatment. While the former can be significantly improved by heat, the latter is deteriorated in terms of knapping quality. These findings have important implications for our understanding of the role of fire as a technical solution in MSA stone tool knapping, and for the extension of its use in southern Africa. Silcrete heat treatment - at least in the form we understand it today - may have been a strictly regional phenomenon, confined to a narrow zone along the west and south coast of the Cape. On the basis of our findings, Silcrete heat treatment should not be added as a new trait on the list of behaviours that characterise the MSA of the southern African subcontinent.
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distinguishing pedogenic and non pedogenic Silcretes in the landscape and geological record
Proceedings of the Geologists' Association, 2016Co-Authors: Stewart J Ullyott, David J NashAbstract:Silcrete is a type of duricrust formed by the near-surface accumulation of secondary silica within a soil, sediment, rock or weathered material. A variety of models of formation have been put forward, involving silicification in both pedogenic and non-pedogenic settings. The resulting Silcrete types differ in terms of their macroscale characteristics, micromorphology, areal extent and behavioural properties. Such differences have significant implications in a range of geological, geomorphological, archaeological and engineering contexts, making the correct identification of Silcrete type of considerable importance. This paper reviews the properties of pedogenic, groundwater, drainage-line and pan/lacustrine Silcretes, and identifies many characteristics that may be diagnostic. It also discusses a number of more problematic macro- and micro-scale features common to both pedogenic and non-pedogenic Silcretes. It concludes with a short checklist to aid the future identification of different Silcrete types in the landscape and geological record.
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going the distance mapping mobility in the kalahari desert during the middle stone age through multi site geochemical provenancing of Silcrete artefacts
Journal of Human Evolution, 2016Co-Authors: David J Nash, Sheila Coulson, Sigrid Staurset, Mosarwa Babutsi, John Ullyott, Martin SmithAbstract:Abstract This study utilises geochemical provenancing of Silcrete raw materials, in combination with chaine operatoire analyses, to explore lithic procurement and behavioural patterns in the northern Kalahari Desert during the Middle Stone Age (MSA). New data from the sites of Rhino Cave, Corner Cave, and ≠Gi in northwest Botswana, combined with earlier results from White Paintings Shelter, reveal that the long distance transport of Silcrete for stone tool manufacture was a repeated and extensively used behaviour in this region. Silcrete was imported over distances of up to 295 km to all four sites, from locations along the Boteti River and around Lake Ngami. Significantly, closer known sources of Silcrete of equivalent quality were largely bypassed. Silcrete artefacts were transported at various stages of production (as partially and fully prepared cores, blanks, and finished tools) and, with the exception of ≠Gi, in large volumes. The import occurred despite the abundance of locally available raw materials, which were also used to manufacture the same tool types. On the basis of regional palaeoenvironmental data, the timing of the majority of Silcrete import from the Boteti River and Lake Ngami is constrained to regionally drier periods of the MSA. The results of our investigation challenge key assumptions underlying predictive models of human mobility that use distance–decay curves and drop-off rates. Middle Stone Age peoples in the Kalahari appear to have been more mobile than anticipated, and repeatedly made costly choices with regard to both raw material selection and items to be transported. We conclude that (i) base transport cost has been overemphasised as a restrictive factor in predictive models, and (ii) factors such as source availability and preference, raw material quality, and potential sociocultural influences significantly shaped prehistoric landscape use choices.
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cap structures as diagnostic indicators of Silcrete origin
Sedimentary Geology, 2015Co-Authors: Stewart J Ullyott, David J Nash, Jennifer M HuggettAbstract:Abstract Cap structures within Silcretes have long been used as a diagnostic indicator of pedogenic silicification. However, a growing number of studies of the micromorphology of non-pedogenic Silcretes indicate that this may no longer be appropriate. This paper presents the first systematic investigation of the micro-fabric, geochemistry and mineralogy of cap structures in groundwater Silcretes, through an analysis of conglomeratic varieties (puddingstones) from the southern UK. Our results suggest that cap structures in groundwater Silcretes fall within a spectrum of types, related to the degree of sorting in the inter-gravel host sediment. At one end of this spectrum are well-defined caps within otherwise well-sorted, overgrowth-dominated Silcretes. These caps exhibit a grain-supported fabric, are cemented by micro- and/or cryptocrystalline silica, and contain floating silt-sized quartz and Ti-oxide grains. We propose that these structures developed mainly as a result of in-washing of fine sediments that were subsequently silicified. At the other end of the spectrum are Silcretes with caps defined by concentrations of Ti-oxide grains, as opposed to cement type and grain size. These formed mainly as a result of the remobilisation and precipitation of Ti during the silicification of gravels containing interstitial clay-rich sandy sediment. Between these end-members are Silcretes with cap structures formed by a combination of in-washing and redistribution of fines plus some local remobilisation of Ti. Overall, the cap structures in this study exhibit a simple micromorphology, lacking the alternating Ti- and silica-rich lamellae typical of pedogenic Silcrete. We conclude that the presence of cap structures alone should not be considered diagnostic of pedogenic silicification unless accompanied by other indicators such as a differentiated profile and abundant, complex, way-up structures within the micro-fabric.
Anne Alexandre - One of the best experts on this subject based on the ideXlab platform.
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Methodological improvements for investigating Silcrete formation: petrography, FT-IR and oxygen isotope ratio of Silcrete quartz cement, Lake Eyre Basin (Australia)
Chemical Geology, 2020Co-Authors: Anne Alexandre, Jeandominique Meunier, Emmanuelle Llorens, Steve M. Hill, Samuel M. SavinAbstract:The oxygen isotopic composition (δ18O) of the cement of a Silcrete sample from the “Cordillo Silcrete” (Late Eocene/Early Oligocene) of Lake Eyre Basin (Australia) was investigated. The massive structure of the Silcrete outcrop and the absence of pedogenic features suggest that this Silcrete formed by precipitation from groundwater. In order to avoid errors inherent in estimates of the cement δ18O value from isotopic analyses of bulk material and mass balance considerations, methodological improvements are described. The Silcrete cement is physically separated from the detrital phases. Its purity is checked using cathodoluminescence (CL) spectroscopy. Optical microscopy, X-ray diffraction (XRD) analyses, and Fourier transform infrared (FT-IR) spectroscopy show the cement is made of three phases: (i) overgrowth; (ii) crypto-crystalline quartz; and (iii) micro-crystalline quartz. Thus, its δ18O value must be interpreted as that of a mixture, although the mixture consists mainly of crypto-crystalline quartz. As the amount of Si–OH-exchangeable oxygen in the cement would bias the results by an amount less than the analytical error (0.09‰), it is unnecessary to go through an equilibration procedure prior to isotopic analysis. The δ18O value of the cement sample is between 24.8‰ and 25.8‰ relative to V-SMOW. Assuming an Eocene/Oligocene temperature of 15–20 °C, in agreement with published regional temperature estimates, the inferred δ18O value of the quartz-forming solution was between −6.9‰ and −12.2‰. This is lower than the minimum δ18O value of −6.70‰ estimated for the modern groundwater near the sample site. A plausible paleoenvironmental scenario is that Silcrete formed in a climate colder and wetter than the modern one, from shallow groundwater frequently recharged, in a setting of slow tectonic uplift.Anne Alexandre, Jean-Dominique Meunier, Emmanuelle Llorens, Steve M. Hill and Samuel M. Savinhttp://www.elsevier.com/wps/find/journaldescription.cws_home/503324/description#descriptio
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oxygen isotope analyses of fine silica grains using laser extraction technique comparison with oxygen isotope data obtained from ion microprobe analyses and application to quartzite and Silcrete cement investigation
Geochimica et Cosmochimica Acta, 2006Co-Authors: Anne Alexandre, Isabelle Basiledoelsch, Corinne Sonzogni, Florence Sylvestre, Claude Parron, Jeandominique Meunier, Fabrice ColinAbstract:The laser fluorination technique reported here for analyzing the oxygen isotope composition (d 18 O) of fine quartz size fractions 50-20, 20-10, 10-5, 5-2, 2-1 and <1 lm has been validated by comparison with the ion microprobe technique. It yields accurate d 18 O data with an external precision better than 0.15&. This is a significant methodological improvement for isotopic studies dealing with materials such as soil or biogenic oxides and silicates: particles are often too small and recovered in insufficient amount to be easily handled for ion microprobe analysis. Both techniques were used to investigate d 18 O composition of a Cretaceous quartzite and Silcrete sequence from the SouthEast of France. Quartzite cements average 31.04 ± 1.93&. They formed from Mid-Cretaceous seawater. Higher in the series, Silcretes cements average 26.66 ± 1.36&. They formed from Upper-or post-Upper-Cretaceous soil water and groundwater. Oxygen isotope data show that the silicification steps from one mineralogical phase to another and from one layer to another (including from an upper pedogenic Silcrete to a lower groundwater Silcrete) occurred in a closed or weakly evaporating hydrological system.
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Methodological improvements for investigating Silcrete formation: petrography, FT-IR and oxygen isotope ratio of Silcrete quartz cement, Lake Eyre Basin (Australia)
Chemical Geology, 2004Co-Authors: Anne Alexandre, Jeandominique Meunier, Emmanuelle Llorens, Steve Hill, Samuel SavinAbstract:The oxygen isotopic composition (δ18O) of the cement of a Silcrete sample from the “Cordillo Silcrete” (Late Eocene/Early Oligocene) of Lake Eyre Basin (Australia) was investigated. The massive structure of the Silcrete outcrop and the absence of pedogenic features suggest that this Silcrete formed by precipitation from groundwater. In order to avoid errors inherent in estimates of the cement δ18O value from isotopic analyses of bulk material and mass balance considerations, methodological improvements are described. The Silcrete cement is physically separated from the detrital phases. Its purity is checked using cathodoluminescence (CL) spectroscopy. Optical microscopy, X-ray diffraction (XRD) analyses, and Fourier transform infrared (FT-IR) spectroscopy show the cement is made of three phases: (i) overgrowth; (ii) crypto-crystalline quartz; and (iii) micro-crystalline quartz. Thus, its δ18O value must be interpreted as that of a mixture, although the mixture consists mainly of crypto-crystalline quartz. As the amount of Si–OH-exchangeable oxygen in the cement would bias the results by an amount less than the analytical error (0.09‰), it is unnecessary to go through an equilibration procedure prior to isotopic analysis. The δ18O value of the cement sample is between 24.8‰ and 25.8‰ relative to V-SMOW. Assuming an Eocene/Oligocene temperature of 15–20 °C, in agreement with published regional temperature estimates, the inferred δ18O value of the quartz-forming solution was between −6.9‰ and −12.2‰. This is lower than the minimum δ18O value of −6.70‰ estimated for the modern groundwater near the sample site. A plausible paleoenvironmental scenario is that Silcrete formed in a climate colder and wetter than the modern one, from shallow groundwater frequently recharged, in a setting of slow tectonic uplift.
Hugo G Nami - One of the best experts on this subject based on the ideXlab platform.
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Silcrete as a valuable resource for stone tool manufacture and its use by paleo american hunter gatherers in southeastern south america
Journal of Archaeological Science: Reports, 2017Co-Authors: Hugo G NamiAbstract:Abstract In the mid-eastern part of the southern cone of South America, sources of Silcrete extend from eastern Entre Rios province in Argentina to mid-western Uruguay. As a material for stone tool manufacture this rock was used with different levels of intensity in the regional archaeological record. In areas currently covered by Buenos Aires province in Argentina and the Republic of Uruguay in particular, diverse Paleo-American artifacts were made with this material between ~ 13 and 12 cal. ka BP. Due to this material's exploitation by early human occupiers, this paper addresses and discusses its distribution, source location, quality, use, and its probable preference by one of the earliest groups of foragers living during the late Pleistocene.
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Silcrete as a valuable resource for stone tool manufacture and its use by Paleo-American hunter–gatherers in southeastern South America
Journal of Archaeological Science: Reports, 2017Co-Authors: Hugo G NamiAbstract:Abstract In the mid-eastern part of the southern cone of South America, sources of Silcrete extend from eastern Entre Rios province in Argentina to mid-western Uruguay. As a material for stone tool manufacture this rock was used with different levels of intensity in the regional archaeological record. In areas currently covered by Buenos Aires province in Argentina and the Republic of Uruguay in particular, diverse Paleo-American artifacts were made with this material between ~ 13 and 12 cal. ka BP. Due to this material's exploitation by early human occupiers, this paper addresses and discusses its distribution, source location, quality, use, and its probable preference by one of the earliest groups of foragers living during the late Pleistocene.
Samuel Savin - One of the best experts on this subject based on the ideXlab platform.
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Methodological improvements for investigating Silcrete formation: petrography, FT-IR and oxygen isotope ratio of Silcrete quartz cement, Lake Eyre Basin (Australia)
Chemical Geology, 2004Co-Authors: Anne Alexandre, Jeandominique Meunier, Emmanuelle Llorens, Steve Hill, Samuel SavinAbstract:The oxygen isotopic composition (δ18O) of the cement of a Silcrete sample from the “Cordillo Silcrete” (Late Eocene/Early Oligocene) of Lake Eyre Basin (Australia) was investigated. The massive structure of the Silcrete outcrop and the absence of pedogenic features suggest that this Silcrete formed by precipitation from groundwater. In order to avoid errors inherent in estimates of the cement δ18O value from isotopic analyses of bulk material and mass balance considerations, methodological improvements are described. The Silcrete cement is physically separated from the detrital phases. Its purity is checked using cathodoluminescence (CL) spectroscopy. Optical microscopy, X-ray diffraction (XRD) analyses, and Fourier transform infrared (FT-IR) spectroscopy show the cement is made of three phases: (i) overgrowth; (ii) crypto-crystalline quartz; and (iii) micro-crystalline quartz. Thus, its δ18O value must be interpreted as that of a mixture, although the mixture consists mainly of crypto-crystalline quartz. As the amount of Si–OH-exchangeable oxygen in the cement would bias the results by an amount less than the analytical error (0.09‰), it is unnecessary to go through an equilibration procedure prior to isotopic analysis. The δ18O value of the cement sample is between 24.8‰ and 25.8‰ relative to V-SMOW. Assuming an Eocene/Oligocene temperature of 15–20 °C, in agreement with published regional temperature estimates, the inferred δ18O value of the quartz-forming solution was between −6.9‰ and −12.2‰. This is lower than the minimum δ18O value of −6.70‰ estimated for the modern groundwater near the sample site. A plausible paleoenvironmental scenario is that Silcrete formed in a climate colder and wetter than the modern one, from shallow groundwater frequently recharged, in a setting of slow tectonic uplift.
