The chronostratigraphy of the Anthropocene in southern Africa: Current status and potential

The process for the formal ratification of the proposed Anthropocene Epoch involves the identification of a globally isochronous stratigraphic signal to mark its starting point. The search for a Global Boundary Stratotype Section and Point (GSSP), a unique reference sequence that would be used to fix the start of the epoch, is in progress but none of the candidate sections are located in Africa. We assessed the currently available stratigraphic evidence for the possible markers of the Anthropocene in southern Africa and found that, although most markers have been identified in the region, the robustly dated, high resolution records required for the GSSP are very sparse. We then assessed the extent and stratigraphic resolution of a range of potential natural archives and conclude that a small number of permanent lakes, as well as marine sediments, corals and peats from selected locations in southern Africa could provide the temporal resolution required. With sufficient chronological control and multi-proxy analyses, one of these archives could provide a useful auxiliary stratotype thereby helping to confirm the global reach, and extending the utility, of the selected Anthropocene GSSP.

Environmental DNA variability in lake sediment cores

Lake sediments are natural archives that accumulate information about biological communities and their surrounding catchments. Paleolimnology has traditionally focussed on identifying fossilized organisms to reconstruct past environments. In the last decade, the application of molecular methodologies has increased in paleolimnological studies, but further studies investigating factors such as sample heterogeneity and DNA degradation are required. Here we investigated bacterial community heterogeneity (16S rRNA metabarcoding) within depth slices. Sediment cores were collected from three lakes with differing sediment compositions. Samples were collected from a variety of depths (1-cm width) which represent a period of time of approximately 1,200 years. Triplicate samples were collected from each slice and bacterial 16S rRNA metabarcoding was undertaken on each sample. Rarefaction curves showed that except for the deepest (oldest) slices, the combination of three replicate samples were insufficient to characterise the entire bacterial diversity. However, shared Amplicon Sequence Variants (ASVs) accounted for the majority of the reads in each slice (max. shared proportional read abundance 96%, 86%, 65% in the three lakes). Within slice similarity was higher than between slice similarity. No general trend was observed in variability among replicates with depth amongst the lakes. In one core. there was a higher community dissimilarity in older sediment, which may be due to laminae not being horizontal. These results highlight the fact that microbial communities can be differentiated with depth however it is critical to interpret these results in the context of the stratigraphic data of the core.

Evaluating the potential of buried soils and colluvial layers for tracking natural and human-induced transformation of landscapes in the middle taiga of Western Siberia

<p>The activities of ancient population strongly affected the development of landscapes and soils in Western Siberia during the late Holocene. It should be noted that studies devoted to the processes of natural and anthropogenic evolution within this vast territory are extremely irregular. Thus, the significant proportion of the materials on the dynamic of Siberian landscapes in the Holocene, related to the studies of various natural archives and archeological monuments, falls on the southern part of region. On the one hand, this situation is due to the relatively recent development of Western Siberia in relation to the development of hydrocarbon deposits, on the other hand, on the peculiarities of the relief and landscapes prevailing in the central and northern parts of the West Siberian Plain. A significant part of the territory under consideration is characterized by low, poorly dissected relief, which largely contributes to its bogging and widespread distribution of organogenic peat soils. It is not surprising that the deposits of lakes and peat bogs are the main natural archives that provide information on the dynamics of the natural environment within the central parts of Western Siberia and, first of all, the taiga zone, while the potential of mineral soils and sediments from this point of view is insignificant, compared to other regions. At the same time the boreal zone of Western Siberia is very large and includes regions with more complex geomorphological conditions.</p><p>To assess the possibility of using buried soils and colluvial layers in the middle taiga of Western Siberia for reconstruction of the Holocene landscape’s dynamics, we carried out research on two key sites with rather contrast relief and high frequency of archeological sites: in the middle Yugan River Basin and in the North of the Kondinskaya Lowland. Buried soils and colluvial sediments in a number of sections characterizing foots of the steep slopes on the border with peat bogs were selected as objects for our study. Based on the obtained radiocarbon dates it is possible to preliminarily identify several stages of the activation of erosional processes. For the north of the Kondinskaya lowland three remarkable phases of erosional activity were identified, while for the Yugan River Basin the number of phases was larger - 6. It is interesting to note that the obtained results make it possible to correlate these two regions. The presence of a larger number of recorded erosion-pyrogenic events for the Yugan River basin reflects a longer permanent human presence in the area under consideration, which is also consistent with archaeological data.</p><p>The study was funded by the Ministry of Science and Higher Education of the Russian Federation and was performed as a part of project FEWZ-2020-0007 “Fundamentals of the natural environment history of the south of Western Siberia and Turgay in the Cenozoic: sequence sedimentology, abiotic geological events and the evolution of the Paleobiosphere“. The studies were carried out using the equipment of the Center for Collective Use "Bioinert Systems of the Cryosphere", Tyumen Scientific Center, SB RAS and RFBR, project number 20-04-00836.</p>

Palaeoecological reconstructions in the Tobol-Ishim interfluve: combination of on-site pollen data from cultural layers and off-site peatland records

The study, based on uniformed criteria, summarizes a large series of palynological data and is aimed at re-construction of the vegetation history of the second half of the Holocene based on pollen data from peatlands. The main objective of this work is to compare the results of palynological studies from cultural layers of 30 Neo-lithic-Medieval archaeological sites (on-site data) and five natural archives (off-site records) in the sub-taiga and forest-steppe areas of Tobol River region and on the territory of the Ishim Plain (south of Western Siberia). The main analytical and correlation tools were the calculated indicators of pollen indices and biomes. Baseline pa-laeoecological changes have been analysed by the pollen index of openness/forestness (the ratio of wood vs grass pollen), the aridity index (the ratio of the summed amount of wormwood and chenopod pollen to that of ce-reals) and the dynamics of forest and steppe biome of peatlands; similar pollen indices have been calculated for the cultural layers. All indicators have been synchronized by age and fixed on a single timeline for comparison. The increasing role of forest vegetation in the forest-steppe has been considered as an indicator of increased effective hydration, forest degradation has been associated with the lack of it. The aridity index has been used as an indirect argument, reflecting the condition of grass communities outside the forest, it increases with the syn-chronous aridization and warming, but is also subject to strong distortion under the influence of human activity. Six stages of vegetation change have been identified: 6.0–4.2 ka — increase in proportion of forests in the northern forest steppe; 4.2–3.3 ka — minimal forestation of the territory; 3.3–2.5 ka — gradual regeneration of forest areas; 2.5–1.9 ka — reduction of the proportion of forests; 1.9–0.7 ka — the most pronounced forestation of the territory; 0.7–0 ka — reduction of the proportion of forests. In general, the outlined stages correspond with the overall scheme of development of landscape and climatic conditions in the southern regions of Western Siberia, though have regional specifics. Comparison of palynological data from natural archives (peatlands) and cultural layers by pollen indices demonstrates, that the anthropogenic disturbance of the composition of grass vegetation near the sites in most cases prevents objective assessment of natural conditions, but characterizes the appearance of the settlement landscape near the sites during its functioning and is associated with economic activity.

Past pandemics and climate variability across the Mediterranean

The influence that meteorological, climatological and environmental factors had on historical disease outbreaks is often speculated upon, but little investigated. Here, we explore potential associations between pandemic disease and climate over the last 2,500 years in Mediterranean history, focusing on ancient disease outbreaks and the Justinianic plague in particular. We underscore variation in the quality, quantity and interpretation of written evidence and proxy information from natural archives, the comlexity of identifying and disentangling past climatological and environmental drivers, and the need to integrate diverse methodologies to discern past climate-disease linkages and leverage historical experiences to prepare for the rapid expansion of novel pathogenic diseases. Although the difficulties entailed in establishing historical climate-pandemic linkages persist to the present, this is a research area as urgent as it is complex and historical perspectives are desperately needed.