The mineralogy and geochemistry of shales reflect the composition of the initially deposited precursor mud, subsequently modified by diagenetic processes. To see if significant geochemical differences exist between shales that mainly owe their present-day composition to either deposition or diagenesis, we compare the published mineralogical, bulk and clay-fraction geochemical, and clay-fraction O-isotopic compositions of 2 shales. One shale is from the Western Canada Sedimentary Basin (WCSB), and its composition mainly reflects primary (depositional) chemical and mineralogical variations (smectitic to illitic illite/smectite) within this unit. The other shale is from the United States Gulf Coast (USGC), and its composition mainly reflects mixed-layer illite/smectite (I/S) diagenesis of deposited smectitic clay material. The chemical and mineralogical trends of WCSB and USGC shales, including one of increasing illite content in I/S with depth or maturity, are essentially indistinguishable, in both bulk shale and clay fraction, despite the contrasting genetic interpretations for the origin of the contained I/S. Thus, similar mineralogical and chemical trends with depth or temperature can result either from inherited depositional compositional heterogeneity of the sediment, from burial metamorphism of shale or a combination of both. Interestingly, the O-isotopic compositions of the clay fractions from the WCSB and USGC are significantly different, a fact that reflects original clay formation from source material and water of quite different isotopic compositions. The discrimination between depositional and diagenetic contributions to shale composition continues to pose challenges, but a combination of bentonite, illite polytype, clay isotopic and trace and rare earth elemental analyses together with illite age analysis holds promise for future work.

Oxygen-isotope data were obtained for synthetic aluminum-hydroxide phases precipitated over 65–125 mo and have been compared to results from similar experiments conducted for 3–56 mo. The Al(OH)3 polymorphs, gibbsite, nordstrandite, and bayerite, were synthesized, but gibbsite was dominant in most samples, and commonly the only phase present. Using pure gibbsite samples, the following oxygen-isotope fractionation factors, ${\alpha }_{gibbsite-H_{2}O}$, were obtained: 1.0167 ± 0.0003 (9 ± 1°C), 1.0147 ± 0.0007 (24 ± 2°C), 1.0120 ± 0.0003 (51 ± 2°C). These values, and the associated equation for an oxygen-isotope geothermometer for the interval 0–60°C 103ln ${\alpha }_{gibbsite-H_{2}O}=2.04\times {10}^6/T^2-3.61\times {10}^3/T+3.65$ (T in K), are not significantly different from those obtained from experiments of much shorter duration. These results, and the good agreement with ${\alpha }_{gibbsite-H_{2}O}$ values obtained for well-constrained natural systems, suggest that the experimentally determined fractionation factors describe equilibrium conditions for gibbsite that has precipitated directly from solution.

As also proposed by others using a modified-increment calculation, our synthesis experiments suggest that ${\alpha }_{Al(OH{)}_3-H_{2}O}$ is polymorph-dependent at low temperatures and that a significant temperature-dependent trend exists in the values of ${\alpha }_{Al(OH{)}_3-H_{2}O}$. However, previously calculated fractionation factors obtained using the modified-increment method are higher than those obtained from the experiments, with this discrepancy becoming larger as temperature decreases.

Chlorite and illite are commonly associated with ubiquitous secondary K-rich feldspar in the rocks located immediately above and below the Precambrian-Paleozoic unconformity in southwestern Ontario, and elsewhere in the mid-continent of North America. This alteration assemblage is attributed to long-distance migration of hot brines driven westward by orogenic processes originating along the eastern seaboard of North America. The δD and δ18O values of chlorite and illite, plus K-Ar dates for secondary K-rich feldspar and illite, were used to determine the nature, origin, and timing of the fluids that altered Precambrian granites and their overlying rocks in southwestern Ontario. The δ18O values of the chlorite-forming fluids are best explained by initial hot brines (≥50°C) evolved mostly from seawater. Secondary K-rich feldspar formation followed shortly thereafter, as the fluids cooled and perhaps mixed with meteoric water. Regional migration of the brines was induced by Taconic orogenic events to the east. The hydrogen and oxygen isotopic compositions for the secondary illite of the early to mid-Carboniferous indicate its crystallization from local meteoric water at low temperatures (40–55°C). Infiltration of local meteoric water into the Paleozoic and uppermost altered Precambrian rocks occurred during uplift, erosion, and subaerial exposure of local arches in southern Ontario. The local basement reactivation and associated secondary illite formation in this portion of the North American hinterland was likely a distal expression of east-coast Acadian and Alleghanian orogenic activity.

Dioctahedral clays from an active continental geothermal system have been studied to assess their usefulness as proxies of paleo-hydrological and thermal conditions in the subsurface. Drill cuttings from Well WK244 in the Te Mihi area of the Wairakei Geothermal Field, New Zealand, were analyzed to determine the mineralogical, morphological, and isotopic characteristics of hydrothermal clays in these samples. Mixed-layer illite-dioctahedral smectite (I-S) and R0 chlorite-trioctahedral smectite are the main clay minerals, with I-S clays varying downward from R1 to R3 ordering and 50 to >90% illite over 160 m. The proportion of illite in I-S correlates positively with downhole temperature (r = 0.98) and I-S morphology changes from high aspect ratio ribbons, laths, and hairy fibers to pseudo-hexagonal plates with depth. Swelling clay percentages determined using the methylene blue method show a strong positive correlation with %S in I-S (r = 0.91), validating use of methylene blue as a rapid field tool for characterizing the smectite to illite transition in this active geothermal environment. The oxygen isotopic composition of I-S (dd18OI-S) decreases systematically with depth, and mostly reflects a progressive increase in subsurface temperature during clay formation. Estimates of water/rock ratios calculated using δ18OI-S values display stratigraphic variability that corresponds to variations in permeability. Oxygen isotopic measurements of I-S are a useful tool for understanding reservoir and permeability evolution in such geothermal systems and their related fossil analogs.

The occurrence of kerolite in association with various secondary Ca-Mg carbonate mineral deposits (speleothems) was identified in basaltic sea caves on the island of Kauai, Hawaii. Kerolite is the dominant clay mineral in the deposits. X-ray diffraction (XRD) peaks of the kerolite are characteristically broadened indicating its extremely poor crystallinity. Few changes were observed in the XRD patterns of this kerolite when it was subjected to various humidity, temperature and ethylene-glycol treatments. The crystals appear as flaky masses with irregular or jagged edges in scanning (SEM) and transmission electron microscopy (TEM). Electron probe and energy dispersive X-ray (EDX) microanalysis show that the clay material is dominated by Mg-Si-O, with minor amounts of Al and Ca in some samples. The chemical composition, thermal analysis and TEM observations suggest that smaller amounts of an amorphous serpentine-like phase are mixed with the kerolite. Kerolite is often the only mineral associated with poorly mineralized, actively-growing microbial mats in these caves and it is common in completely lithified microbial mats. The latter commonly have microstromatolitic structures with kerolite as a dominant phase. These features suggest that kerolite formation is at least in part a result of microbial activity. The abundant extracellular polymers of the mat-forming bacteria bind and concentrate ions (Mg2+, silica) from solution and serve as nucleation sites for kerolite precipitation. Conditions within the mats also probably lead to formation of Mg-Si-gels, amorphous Mg-silicate precursors and ultimately kerolite. Evaporation of the cave solutions may also contribute to kerolite formation.

Site E19 (19:N1W5), near Tlailotlacan, the “Zapotec Barrio” of Teotihuacan, contains evidence of both Tlailotlacan and Michoacan affiliation. To verify and better understand the Michoacan relationship, 22 enamel and 19 bone samples from five E19-affiliated burials were analyzed to determine their oxygen isotope compositions, which provide an indication of an individual's area of residence when that particular tissue was forming. Because prismatic blades and Thin Orange ceramics from Teotihuacan occur widely in the Lakes Region of north central Michoacan we obtained samples from several sites there for comparative purposes. The results show that most of the E19 people had passed their later years in the Patzcuaro Basin of the Lakes Region. Although in E19 the archaeological evidence of this relationship declined over time, the isotopic evidence indicates that Patzcuaro ties continued to the end of E19's occupation. It seems that the people of E19, originally Michoacanos, gradually adopted a core identity as Teotihuacanos while continuing to deploy their Michoacan ancestry during their stays in Michoacan.

Biogeochemical analyses of organisms’ tissues provide direct proxies for diets, behaviors, and environmental interactions that have proven invaluable for studies of extant and extinct species. Applying these to Cretaceous ecosystems has at times produced anomalous results, however, as dinosaurs preserve unusually positive stable carbon isotope compositions relative to extant C3-feeding vertebrates. This has been hypothesized to be a unique property of dinosaur dietary physiology, with potential significance for our interpretations of their paleobiology. We test that hypothesis through multi-taxic stable carbon isotope analyses of a spatiotemporally constrained locality in the Late Cretaceous of Canada, and compare the results to a modern near-analogue environment in Louisiana. The stable carbon isotope anomaly is present in all sampled fossil vertebrates, dinosaur or not. This suggests another more widespread factor is responsible. Examinations of diagenetic effects suggest that, where present, they are insufficient to explain the isotope anomaly. The isotope anomaly is therefore not primarily the result of a unique dietary physiology of dinosaurs, but rather a mix of factors impacting all taxa, such as environmental and/or source-diet differences. Our study underscores the importance of multi-taxic samples from spatiotemporally constrained localities in testing hypotheses of extinct organisms and ecosystems, and in the use of modern data to “ground truth” when evaluating analogue versus non-analogue conditions in greenhouse paleoecosystems.

The city of Teotihuacan (AD 1–550) was a major multiethnic urban center that attracted migrants from as far away as west Mexico and the Maya region. Past research in the Tlajinga district at Teotihuacan using oxygen isotopes from human remains estimated that nearly 30% of the population of Tlajinga 33, a single apartment compound, were migrants. This study takes a dual-isotope approach (87Sr/86Sr and δ18Op) to reevaluate the proportion of in-migration at Tlajinga and includes data from two additional apartment compounds, Tlajinga 17 and 18 (n = 23). New results indicate that migrants comprised ~45% of the Tlajinga population. Previously acquired radiocarbon dates combined with mortuary and isotope data suggest that immigration to Tlajinga was highest during the first centuries of compound occupation. Nevertheless, migration was a continual process throughout its history. Additionally, a new finding suggests that residents of Tlajinga 33 ingested foods with higher 87Sr/86Sr ratios than did those of Tlajinga 17 and 18. We hypothesize that the incorporation of imported lime for the nixtamalization process skewed the 87Sr/86Sr ratios of human remains, a potentially important finding for future studies at Teotihuacan.

Cervids living in high latitudes have evolved to thrive in ecosystems that experience dramatic seasonal changes. Understanding these seasonal adaptations is important for reconstructing cervid life histories, ecosystem dynamics, and responses in the distant and not-so-distant past to changing seasonality caused by climate change. Cervid antlers provide a rare opportunity for insight into faunal seasonal ecology, as they are grown and shed each year. Stable isotopes of carbon and nitrogen measured directly from antlers have the potential to provide seasonal dietary data for individuals. If the isotopic signals in bone and antler are controlled by the same metabolic processes, then the stable carbon and nitrogen isotope compositions of collagen (δ13CColl and δ15NColl) from incrementally grown antler tissue provide time-constrained dietary signals from the spring and summer growth season. Bone, by comparison, provides an average signal over several years. The amino acid (glutamate and phenylalanine) δ15N in antlers from modern captive caribou showed similar trophic discrimination factors to earlier results for other collagenous tissues (bone, tooth dentin, and cementum). Hence, growth rate was not the primary control on the stable isotope composition of antler collagen. We applied this knowledge to assess seasonal shifts in Quaternary fossils of three Cervidae species: elk (Cervus elaphus), moose (Alces alces), and caribou (Rangifer tarandus). Paired antler–bone δ13CColl and δ15NColl from the same individual were used to identify differences between summer and annual diet and ecology. Intra-antler isotopic variability from serially sampled antlers was used to examine seasonal dietary shifts and specialization.

San José 520 is a Classic period hamlet of single-family residences in the urban periphery of Teotihuacan, just beyond the southeast edge of the city. Three burial features were associated with one of the residences, AF2. One of the features contained the burial of a single adult, another the successive burials of eight adults and one neonate, and the third held a neonate. We analyzed 29 bone and enamel samples from the adults for bioapatite phosphate oxygen-isotope composition; we also considered isotopic data for another five bone samples analyzed in a separate project. The isotopic results suggest a pattern of birth in the Teotihuacan region and then movement in early childhood to a “relocation” region, the geographic location of which is unknown. Later, probably in adolescence, the individuals returned to live, and eventually die, in San José 520. Without knowing more about the occupation of the relocation region, it is difficult to say what concerns or beliefs underlay this unusual but long-established settlement system.

Continuing isotopic investigation of the sacrificial burials and trophies beneath the Feathered Serpent Pyramid (Temple of Quetzalcoatl) in ancient Teotihuacan, Mexico, has produced new results. Isotopic proveniencing using bioapatite strontium and structural carbonate oxygen isotopes in tooth enamel was applied to 39 samples, 24 from the sacrificial victims and 15 from the trophy jaws. Both the strontium and oxygen isotope ratios suggest that most or all of the sacrificial victims came from the central highlands of Mexico, which includes the area of Teotihuacan. In this sense, we find somewhat less multiethnicity represented among the military at Teotihuacan than previously thought. Analysis of carbon isotope ratios in enamel structural carbonate indicated a childhood diet dominated by maize, relatively homogeneous among the victims at the pyramid, and typical for much of pre-Hispanic Mesoamerica.

We present the results of stable carbon and nitrogen isotope analyses of bone collagen and bone bioapatite from the ancient Maya center of Minanha, Belize (ca. 100 B.C. to A.D. 1260). The purpose of this research was to reconstruct diet and investigate the influence of sociopolitical and environmental factors. Overall, diet was relatively stable over time, with maize being a staple in all periods. Maize consumption reached its peak in the transitional Early to Middle Classic periods and decreased over time. When isotope data from dry periods were compared to normal periods, there were no significant differences, although comparisons of isotope data by burial location and type suggest that the apical or ruling elite consumed a more diverse diet, with more animal protein, relative to the lesser elites. The temporal variability in maize consumption seems best explained by sociopolitical factors documented at Minanha and within the Vaca Plateau. This study demonstrates the resilience of ancient subsistence practices in the face of climatic instability and highlights the impact that social and political factors can have on diet and subsistence economy.

Mammoth (Mammuthus sp.) teeth are relatively abundant in Quaternary deposits from Eurasia and North America, and their isotopic compositions can be used to reconstruct past seasonal patterns in precipitation, diet, and migration. Strategies for collecting and interpreting such data, however, are strongly dependent on growth rates, which can vary among species, individuals, and within teeth. In this study, we use histological and isotopic measurements to determine enamel growth rates for a Columbian mammoth (Mammuthus columbi) tooth in two directions. Using histology, the growth rate through the enamel thickness (ET; perpendicular to the height of the tooth) is estimated at 0.8 to 1.5 mm/yr. Isotopic sampling through the innermost 0.36 mm of the ET recovered less than half a period of variation (i.e., half an inferred year of growth), which is consistent with the histological estimate for ET growth rate. A combination of histological and isotopic measurements suggests that the enamel extension rate (growth in the height of the tooth) is 13–14 mm/yr. Knowledge of enamel growth rates should improve the design and interpretation of future isotopic studies of mammoth teeth. The combination of histological and isotopic measurements may also prove useful in determining growth rates for other extinct taxa.

The S5 is the most prominent paleosol unit in the Chinese Loess Plateau, and is distinguished by its great thickness, dark color, and well-developed clay coatings. Previous studies led to the proposal that the S5 developed under much warmer and wetter conditions than at present, implying a “climatic optimum.” However, the S5 is a paleosol complex corresponding in time to a period of weak glacial–interglacial oscillations, as recorded by marine oxygen-isotope stages 15 through 13. To understand the character of this climatic interval, two profiles of the paleosol S5 in the Guanzhong basin were studied, with most of the emphasis being placed on the uppermost and best-developed pedon, S5-I. Grain-size, mineralogical, and chemical data indicate that the major pedogenic processes experienced by the S5-I included complete decalcification and mechanical translocation of fine particles. Chemical alteration of silicate minerals has been weak. Stable carbon-isotope analyses of organic matter showed that C4 plant remains are abundant throughout the profiles. These results suggest that grasslands dominated the paleovegetation during S5-I development. The prominent development of the S5 paleosol complex may reflect a prolonged period of pedogenesis. In contrast to previous reports, paleoclimatic conditions perhaps even drier than at present are implied by the data for the S5 profiles. The relative strength of the glacial–interglacial oscillation in this region (related to the East Asian monsoon) was similar to that indicated for global climate during S5 time.

We investigate seasonal variations in the diet and drinking water of four Great Lakes mastodon (Mammut americanum) specimens using stable isotope analysis of serially sampled inner-enamel bioapatite structural carbonate (δ13Csc, δ18Osc), and previously published bulk analyses. Isotopic analyses and thin section measurements showed that mastodon tooth enamel extension rates (~ 12–4 mm/yr, decreasing toward the cervix) were lower than those of mammoths or modern elephants. Mastodons had distinct and highly regular seasonal variations in δ13Csc and δ18Osc, which we interpret in the context of local glacial history and vegetation changes. Seasonal variations in δ18O were large but variations in δ13C were small, and may have been obscured if coarser sampling methods than our inner-enamel sampling approach were used. Thus, our approach may be particularly useful for understanding relatively small seasonal changes in δ13C within C3 environments. The seasonal patterns, though not entirely conclusive, suggest that the Ontario mastodons did not migrate over very long distances. Rather, the climate and seasonal dietary patterns of mastodons within the region changed over time, from ~ 12,400 to 10,400 14C yr BP (~ 15,000 – 12,000 cal yr BP). Insights gained using these methods can contribute to a better understanding of megafaunal extinctions and Paleoamerican lifeways.

Only about 19 of the 70 or so skeletons excavated at Cerro Portezuelo were brought back to UCLA, and adequate information is lacking for most of these. A detailed analysis of the excavation and curation records, as well as of the skeletons, was conducted in an attempt to identify their contexts and to evaluate their potential for contribution to our knowledge of the Cerro Portezuelo community. Although subadult dental health was good, adult levels of caries and antemortem loss were comparable to those of other Mesoamerican populations. Oxygen-isotope data suggest only limited long-distance immigration into the area. Further interpretation, however, is hampered by poor contextual data and the inability to assign most individuals to a specific period.

In this article, we discuss new stable isotope data obtained from human dental tissue at the Krieger site, a Late Woodland Western Basin Tradition occupation from southwestern Ontario, Canada. These data point to significant maize consumption within an otherwise diffuse subsistence economy and settlement pattern geared toward the occupation of short-term campsites. The degree of maize consumption at Krieger implies the necessity for storage and year-round use. We suggest that maize horticultural practices during this time were as intensive as those suggested for contemporary and more sedentary Iroquoian groups to the east yet were accommodated without major changes to other aspects of the subsistence-settlement regime. Furthermore, the absence of a breastfeeding signal in the dental tissue not only implicates women in the role of maize production but might also imply demographic consequences. Accordingly, and with reference to comparative data, we suggest that notions of food production be recast and decoupled from the advent of sedentary lifeways in the lower Great Lakes region.

This article presents stable nitrogen and carbon isotopie analyses of diet at the Maya sites of Marco Gonzalez and San Pedro, Belize. This study, which provides important insight into social organization, trade, and subsistence economy for the Postclassic and Historic periods (ca. A.D. 900–1650), also expands our understanding of the distribution of stable carbon and nitrogen isotopes within coral reef food webs off coastal Belize. Marco Gonzalez and San Pedro represent the first documented ancient Maya populations whose diet consisted mostly of marine resources with a minimal reliance upon maize. Although these sites do not appear highly stratified, and there are no dietary differences between sexes or status, the inhabitants of Marco Gonzalez incorporated more mainland-terrestrial animals and maize into their diet than the people of San Pedro. This finding supports the postulated roles of these two settlements, where Marco Gonzalez had trade ties to the mainland site of Lamanai and San Pedro was a small fishing village.

The stable carbon and nitrogen isotope values (δ13C, δ15N) of collagen and the carbon isotope value of structural carbonate in bioapatite were measured in the bones and teeth of Early Classic to Historic period Maya buried at Chau Hiix, Belize. Diet at Chau Hiix comprised a mixture of resources but contained an unusual amount of protein from high trophic levels. There were no differences between the diets of males and females, and there were no consistent changes in diet from birth to age 12. However, children consumed more maize than adults during all time periods. Similarities in general diet and temporal changes at Chau Hiix, Lamanai, and Altun Ha suggest their participation in a regional socioeconomic system. The diets of the highest-status Early Classic individuals at Chau Hiix, Lamanai, and Altun Ha were different from one another and from those of other individuals buried at their respective sites. We suggest that elites created or attempted to create hierarchies of food consumption within sites during the Classic period and that a heterarchy existed among elites from different sites. During the Postclassic period the major protein component of the Chau Hiix diet shifted from terrestrial animal and/or freshwater resources to reef resources, which suggests increased associations with coastal sites. Temporal changes in diet at Chau Hiix closely paralleled changes at Lamanai, but diets at the two sites were distinct during all time periods.

To investigate geographic origins of the sacrificial Burials 2–5 from the Moon Pyramid at Teotihuacan and to reconstruct changes in residence since their childhoods, we analyzed tooth enamel for oxygen- and strontium-isotope ratios and bone just for oxygen-isotope ratios. The combination of these analytical techniques involves both climatic and geological variables, therefore enhancing resolution of geographic identification. Most of the sacrificed individuals appear to have been born in a foreign location. These regions probably include other areas within the Basin of Mexico and the central highlands, as well as the Gulf Coast and the Sierra Madre del Sur. Other possible regions of origin are the southern highlands, the Motagua Valley, and the Maya Lowlands. There is considerable overlap in the oxygen-isotope ratios between the Moon Pyramid and Feathered Serpent Pyramid victims, but each structure contains a group of isotopically distinct individuals. The Moon Pyramid sacrifices include some individuals with high oxygen-isotope ratios, possibly indicating the Gulf Coast or Maya Lowlands, whereas the Feathered Serpent Pyramid contains a distinct group with very low oxygen-isotope ratios, possibly indicating Oaxaca, Michoacan, or the coastal plain and piedmont of Guatemala. The sacrifices in the two pyramids also differ in their patterns of movement. Most of the Moon Pyramid victims appear to have arrived in the city recently, but the majority of those from the Feathered Serpent Pyramid had lived in Teotihuacan for a long time before their death.