Late-Glacial Paleoecology of the Middle Susitna Valley, Alaska: Environmental Context for Human Dispersal

We present here the results of multi-proxy analyses (sediment geochemistry, diatoms, and pollen) from sediment cores collected at four lakes in the middle Susitna Valley, Alaska. These lakes form a transect from the tundra to the boreal forest. The retrieved cores span from ∼12,000 cal yr BP to the present, with age control provided by radiometric dates and tephra deposits, some of which are newly identified. Results indicate that deglaciation occurred before 12,000 cal yr BP and that by that time, the lakes were deep, productive, and surrounded by shrub tundra. The lake with the highest sampling resolution indicates a brief climatic reversal ∼11,500 cal yr BP with decreased diatom-inferred lake level and lowered lake productivity, and reduced shrub presence. During the early to middle Holocene, all of the sedimentary records provide evidence of climatic amelioration with tree expansion and productive lakes. A middle to late Holocene climatic deterioration with reduced trees and a shallower, less productive lake is also indicated. In addition, the prominent Watana tephra at ∼4,000 cal yr BP likely reduced lake productivity and affected the vegetation. Even though the region was relatively productive soon after deglaciation, people did not occupy the region until ∼11,000 cal yr BP, about 1000 years later, and then only sparsely. By the middle and late Holocene, the region was more densely populated and this shift in human occupancy presumably reflects changes in resource abundance, especially caribou. Whether the Watana ashfall influenced caribou abundance and thus people, is still under investigation, but given the tephra’s effect on vegetation and lake productivity, it seems likely

Strontium and Oxygen Isotope Profiles of Sequentially Sampled Modern Bison (Bison bison bison) Teeth from Interior Alaska as Proxies of Seasonal Mobility

Studies addressing prehistoric mobility in animals typically use isotopic analyses of sequentially formed tissues, such as the growth layers in teeth, to infer physical movement on the landscape. Strontium isotope ratios (87Sr/86Sr values), which vary geographically, are particularly useful for this purpose, especially when paired with stable oxygen isotope ratios (δ18O), which vary seasonally. Together, these two isotope systems can provide information about past animal movement patterns on a seasonal scale. However, while many studies have used 87Sr/86Sr and δ18O values from analyses of sequentially formed tissues for this purpose, there have been limited analyses on modern animals of known movement patterns across high-latitude regions. In this pilot study, we sequentially sampled and analyzed one second molar (M2) and two third molars (M3) from two bison (Bison bison bison) from the Delta bison herd, which resides in interior Alaska and has known and documented seasonal mobility patterns. The resulting 87Sr/86Sr values from the teeth were compared to a high-resolution 87Sr/86Sr isoscape for the region and were paired with δ18O analyses to determine whether the seasonal 87Sr/86Sr values matched the predicted values for each of the seasonal bison habitat areas. The results indicate that the 87Sr/86Sr and δ18O values reliably reflected the known seasonal mobility patterns of bison and suggest that this approach could be used to investigate the mobility patterns of prehistoric bison in Alaska and surrounding high-latitude regions.En général, les études qui portent sur la mobilité des animaux préhistoriques se servent d’analyses isotopiques des tissus séquentiellement formés, y compris les couches de développement des dents, afin d’en déduire les mouvements physiques dans l’environnement. Les rapports isotopiques du strontium (87Sr/86Sr) sont particulièrement utiles à cette fin, car ils varient géographiquement, surtout lorsqu’ils sont jumelés avec les rapports isotopiques stables de l’oxygène (δ18O), dont la variabilité est saisonnière. Ensemble, ces deux isotopes peuvent fournir des informations sur les habitudes de déplacement des animaux dans un paysage en fonction des saisons. Cependant, même si plusieurs études ont utilisé les valeurs 87Sr/86Sr et δ18O découlant des analyses des tissus séquentiellement formés à cette fin, peu d’analyses ont été effectuées chez les animaux modernes dont les habitudes de déplacement sont connues dans les régions de haute latitude. Dans cette étude pilote, nous avons séquentiellement échantillonné et analysé une deuxième molaire (M2) et deux troisièmes molaires (M3) de deux bisons (Bison bison bison) du troupeau de bisons du delta, troupeau qui réside dans l’intérieur de l’Alaska et dont les modèles de mobilité saisonnière sont connus et documentés. Les valeurs 87Sr/86Sr obtenues à partir des dents ont été comparées à un paysage isotopique de haute résolution 87Sr/86Sr pour la région et ont été jumelées aux analyses δ18O pour déterminer si les valeurs 87Sr/86Sr saisonnières correspondaient aux valeurs prévues pour les zones d’habitat saisonnières du bison. Les résultats indiquent que les valeurs 87Sr/86Sr et δ18O reflètent fidèlement les modèles connus de mobilité saisonnière du bison, et suggèrent que cette méthode pourrait servir à étudier les modèles de mobilité des bisons préhistoriques en Alaska et dans les régions de haute latitude environnantes

Two contemporaneous mitogenomes from terminal Pleistocene burials in eastern Beringia

Pleistocene residential sites with multiple contemporaneous human burials are extremely rare in the Americas. We report mitochondrial genomic variation in the first multiple mitochondrial genomes from a single prehistoric population: two infant burials (USR1 and USR2) from a common interment at the Upward Sun River Site in central Alaska dating to ~11,500 calendar years before present (cal B.P.). Using a targeted capture method and next-generation sequencing we determined that the USR1 infant possessed variants that define mitochondrial lineage C1b, while the USR2 genome falls at the root of lineage B2, allowing us to refine younger coalescence age estimates for these two clades. C1b and B2 are rare to absent in modern populations of Northern North America. Documentation of these lineages at this location in the Late Pleistocene provides evidence for the extent of mitochondrial diversity in early Beringian populations, which supports the expectations of the Beringian Standstill Model

New insights into Eastern Beringian mortuary behavior: A terminal Pleistocene double infant burial at Upward Sun River

Here we report on the discovery of two infant burials dating to 11,500 calibrated years (cal) B.P. at the Upward Sun River site in central Alaska. The infants were interred in a pit feature with associated organic and lithic grave goods, including the earliest known North American hafted bifaces with decorated antler foreshafts. Skeletal and dental analyses indicate that Individual 1 died shortly after birth and Individual 2 was a late-term fetus, making these the youngest-aged late Pleistocene individuals known for the Americas and the only known prenate, offering, to our knowledge, the first opportunity to explore mortuary treatment of the youngest members of a terminal Pleistocene North American population. This burial was situated 40 cm directly below a cremated 3-y-old child previously discovered in association with a central hearth of a residential feature. The burial and cremation are contemporaneous, and differences in body orientation, treatment, and associated grave goods within a single feature and evidence for residential occupation between burial episodes indicate novel mortuary behaviors. The human remains, grave goods, and associated fauna provide rare direct data on organic technology, economy, seasonality of residential occupations, and infant/child mortality of terminal Pleistocene Beringians

Steppe-tundra composition and deglacial floristic turnover in interior Alaska revealed by sedimentary ancient DNA (sedaDNA)

When tracing vegetation dynamics over long timescales, obtaining enough floristic information to gain a detailed understanding of past communities and their transitions can be challenging. The first high-resolution sedimentary DNA (sedaDNA) metabarcoding record from lake sediments in Alaska—reported here—covers nearly 15,000 years of change. It shows in unprecedented detail the composition of late-Pleistocene “steppe-tundra” vegetation of ice-free Alaska, part of an intriguing late-Quaternary “no-analogue” biome, and it covers the subsequent changes that led to the development of modern spruce-dominated boreal forest. The site (Chisholm Lake) lies close to key archaeological sites, and the record throws new light on the landscape and resources available to early humans. Initially, vegetation was dominated by forbs found in modern tundra and/or subarctic steppe vegetation (e.g., Potentilla, Draba, Eritrichium, Anemone patens), and graminoids (e.g., Bromus pumpellianus, Festuca, Calamagrostis, Puccinellia), with Salix the only prominent woody taxon. Predominantly xeric, warm-to-cold habitats are indicated, and we explain the mixed ecological preferences of the fossil assemblages as a topo-mosaic strongly affected by insolation load. At ca. 14,500 cal yr BP (calendar years before C.E. 1950), about the same time as well documented human arrivals and coincident with an increase in effective moisture, Betula expanded. Graminoids became less abundant, but many open-ground forb taxa persisted. This woody-herbaceous mosaic is compatible with the observed persistence of Pleistocene megafaunal species (animals weighing ≥44 kg)—important resources for early humans. The greatest taxonomic turnover, marking a transition to regional woodland and a further moisture increase, began ca. 11,000 cal yr BP when Populus expanded, along with new shrub taxa (e.g., Shepherdia, Eleagnus, Rubus, Viburnum). Picea then expanded ca. 9500 cal yr BP, along with shrub and forb taxa typical of evergreen boreal woodland (e.g., Spiraea, Cornus, Linnaea). We found no evidence for Picea in the late Pleistocene, however. Most taxa present today were established by ca. 5000 cal yr BP after almost complete taxonomic turnover since the start of the record (though Larix appeared only at ca. 1500 cal yr BP). Prominent fluctuations in aquatic communities ca. 14,000–9,500 cal yr BP are probably related to lake-level fluctuations prior to the lake reaching its high, near-modern depth ca. 8,000 cal yr BP

Late Glacial and Early Holocene Geoarchaeology and Terrestrial Paleoecology in the Lowlands of the Middle Tanana Valley, Subarctic Alaska

This dissertation project focuses on three study areas in the middle Tanana Valley (mTV) to provide records of local terrestrial ecological contexts and environmental changes in lowland settings that dated to the Late Glacial and early Holocene (16,000 to 6,000 cal. years ago) in interior Alaska and Eastern Beringia. The archaeological record of the mTV provides a rich history of hunter-gatherer land use dating over 14,000 years old. This project is part of two larger projects focused on prehistoric human ecology and foraging behavior in Eastern Beringia: the Quartz Lake-Shaw Creek Flats Multidisciplinary and Upward Sun River Site Projects. The study areas are spread out across a 4,000 km2 area in the mTV and contain the presence of archaeological sites that have records of well-developed stratification of sediments and soils and preserved macrofossils. Two of the study areas are dune fields: the Little Delta Dunes (including the Upward Sun River Site) and Rosa-Keystone Dunes Fields; the third area is Quartz Lake, one of the largest lakes within the region. As a whole they provide important information to understand the evolution of regional landscapes, paleoecological systems, and paleoenvironmental conditions dating back to 25,000 years ago, over 10,000 years prior to the currently accepted earliest human occupation of the region. Late Glacial and early Holocene landscapes of the mTV were ones of moderate stability and landscape disturbance with high rates of loess and aeolian sand deposition, and the presence of early-to-middle successional vegetation communities (herbs and forbs, shrubs, and deciduous trees) that fostered the presence of diverse mammalian faunal communities that no longer coexist in the region. As the middle Holocene approached, landscapes became increasingly stable with the expansion of the boreal forest and aeolian deposition drastically decreased throughout the mTV. The disturbances that fostered the highly productive early-to-middle successional vegetative communities in the Late Glacial and early Holocene became progressively partitioned in the middle Holocene and primarily relegated to active floodplains. These local ecological contexts can be used to assess changes in Late Glacial and Holocene faunal diversity and in human ecology and foraging behavior in interior Alaska and Eastern Beringia

An analysis of radiocarbon assays produced by three laboratories: a case study on the Croxton site, locality J, northern Alaska

Thesis (M.S.) University of Alaska Fairbanks, 2003Radiocarbon assays produced by three different laboratories are compared to examine potential discrepancies among them: Dicarb Radioisotope Co., Geochron Laboratories, and Beta Analytic, Inc. A semi-formal assumption that radiometric assays produced by Dicarb are "too young" when compared to those produced by other laboratories is statistically tested. Radiometric assays and accelerator mass spectrometry (AMS) dates produced from materials excavated at the Croxton site, Locality J, Tukuto Lake, Northern Alaska, will be used as the primary data set within this research. Statistical analyses demonstrate that radiocarbon assays produced by Dicarb tend to be "younger" when compared to those produced by other laboratories on crosscheck samples. In addition, an unsystematic pattern is exhibited among the discrepancies between Dicarb and crosscheck assays. Radiocarbon assays are calibrated using the CALIB rev4.3 program in order to assess statistical overlap among the dates (Stuiver and Reimer 1993b; Stuiver et al. 1998a, 1998b). Radiocarbon assays produced by Beta Analytic and Geochron on materials recovered from the Croxton site, Locality J, support both "traditional" and "alternative" cultural-historical frameworks constructed for North Alaskan prehistory (Anderson 1978, 1984; Dumond 1980, 1984; Gerlach and Hall 1988; Gerlach 1989; Gerlach and Mason 1992; Mason and Gerlach 1995)

Testing the “Dicarb Problem”: A Case Study from North Alaska

An assumption exists in North Alaskan archaeological literature that radiometric assays produced by the nowdefunct Dicarb Radioisotope Co. (Dicarb) are too young or more recent when compared to those produced by other laboratories. This assumption is statistically tested by comparing radiocarbon assays produced by Dicarb to those produced by Beta Analytic, Inc.; Geochron Laboratories; and the NSF-Arizona AMS Facility. The primary data set consists of radiometric and accelerator mass spectrometry (AMS) assays produced from materials excavated at the Croxton site, Locality J, Tukuto Lake, northern Alaska. Statistical analyses demonstrate that 14C assays produced by Dicarb tend to be "younger" than assays produced by other laboratories on crosscheck samples, with differences ranging between 350 and 1440 yr.The Radiocarbon archives are made available by Radiocarbon and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform February 202

Task-Specific Sites and Paleoindian Landscape Use in the Shaw Creek Flats, Alaska

The Shaw Creek Flats and nearby middle Tanana river, in central Alaska, constitute one of the areas in the Americas with the densest known distribution of Late Glacial (about 14,500-11,700 cal. B.P.) archaeological sites. Local high rates of sediment deposition and low post-depositional disturbance allow for the interpretation of the function of archaeological occupations within larger economic and mobility strategies. Residential sites used over the long term seem to be located near critical but immovable resources such as clear water and vegetation. The spatial association of artifacts and faunal remains at other sites in the Flats suggest that they were specialized, short-lived locations dedicated to a single or few activities. For instance, the site of Swan Point Cultural Zone 4b is interpreted as a workshop related to the production of composite tools, particularly on mammoth ivory, and the site of Keystone Dune is interpreted as a camp related to wapiti (Cervus elaphus) hunting. These task-specific sites and others were probably used as part of a predominantly logistical mobility and economy strategy, which maximized efficiency in harvesting and processing resources that were distributed heterogeneously on the landscape.National Science Foundation [BCS-1504654]; Lewis and Clark Fellowship of the American Philosophical Society; Otto Geist Fund of the University of Alaska Museum of the North; Social and Behavioral Sciences Research Institute; School of Anthropology at the University of Arizona12 month embargo; published online: 08 December 2017This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Possible Factors Causing Older Radiocarbon Age for Bulk Organic Matter in Sediment from Daihai Lake, North China

Many factors may influence the radiocarbon age results of lacustrine sediments, among which the hardwater effect is particularly important. Daihai Lake is a closed lake located in the semi-arid region of Inner Mongolia, China. High concentrations of (HCO3)- and (CO3)2- and high pH values in the lake water imply that there is a hardwater effect when using bulk lacustrine sediment samples for 14C dating. To correct the apparent 14C age, we present a pilot study based on a series of 14C ages of lake surface sediment, lake water, submerged aquatic plant (Myriophyllum), fish bone (Cyprinus carpio), and surface soil samples from and around Daihai Lake. Assuming that the relationship between the 14C/12C ratio of DIC and of atmospheric CO2 was constant (at 0.816), the hardwater effect ages calculated for the past 8000 yr would have varied from 949 to 1788 yr. Together with the reservoir effect and soil organic matter input, the hardwater effect is a major factor causing changes in apparent age when using bulk organic matter for 14C dating.The Radiocarbon archives are made available by Radiocarbon and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform February 202