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Methods

The main methods in the project are sedimentological analyses, supported by further geological methods (geochemistry, chronometric dating):

  • sedimentological analyses. These will consist a set of analyses focused on the reconstruction of sedimentary and post-sedimentary processes (type of deposition factors, direction of geological transport, provenance of material). These analyses will also be used in evaluation of the usefulness of clastic material for OSL dating, (i.e., checking if the material was re-deposited and mixed). The analytical methods include:
    • micromorphological analysis of the thin section of undisturbed monoliths. This microscopic method allows to recognize the deposition factors and microscale sedimentary features (Stoops et al. 2003). The use of polarized light enable to detect differences in fine matrix, and recognize the admixtures of other sediment. Extensive analysis covering the whole sedimentary profile enable to indicate the strata being the sources of re-deposited material. This method has been developed in last years for cave sediments and offers wide research perspectives (e.g., Goldberg et al. 2007, Miller 2015).
    • grain size distribution. These includes granulometry of both coarse fractions (>2 mm, mostly limestone debris, analyzed in field by sieving), and fines (analyzed by laser diffraction on samples, outsourced to external laboratory, results interpreted by investigators). This method allows to connect the layers with periods of intensive frost weathering (Madeyska 1981) and to link the strata with sedimentary processes (Mycielska-Dowgiałło & Ludwikowska-Kędzia 2011).
    • quartz grains morphology. Analysis of coarse fractions (methodology adopted from Krajcarz & Madeyska 2010, Turk & Turk 2010) allows to reconstruct main types and intensity of weathering conditions. Analysis of sand-sized quartz grains enable the reconstructions of sedimentary process, but also impact of periglacial conditions (Woronko & Pisarska-Jamroży 2016).
  • chronometric dating of sediments. So called ‘absolute’ dating is necessary to anchor the stratigraphic scheme in the timescale, but also for reliable inter-site correlation. The widely used radiocarbon method has limited importance here due to weak preservation state of organic remains (confirmed low content of collagen in fossil bones), but also because the expected chronology stays out of radiocarbon scale. It may be used for Holocene sediments and Strashnaya (relatively cold climate). However, the most important dating method will be:
    •  U-series (U/Th) dating of tooth enamel (abundant material at all sites) and speleothems (occurring in Sel’Ungur). The applicant unit, IGS PAS, has an experienced staff and laboratory facility for U/Th dating;
    • OSL dating of aeolian sediments (loess is the most common sediment at all studied sites). The OSL dating will be subcontracted to external laboratory, and results interpreted by project’s investigators.
  • geochemical analyses of sediments will allow to recognize horizons of depletion and enrichment in particular compounds, related to climate-controlled weathering and pedogenic processes (Madeyska 1981, Krajcarz et al. 2015b):
  • content of trace elements (ICP-MS analysis, outsourced to external laboratory, results interpreted by investigators), e.g., to calculate weathering indexes such as based on Al/Ti, K/Na, Sr/Ba ratios and others; 
  • content of carbonates and organic matter in sediments (CHNS elemental analysis with HCl-decalcification).
  • geochemical analyses of fossil bones  – this method allows to determine the homogeneity of bone assemblages in particular layers, based on assumption that trace element composition is related to lithology of sediment (Krajcarz 2017):
  • content of trace elements (ICP-MS – as in case of sediments) – for geochemical provenance analysis;
  • FTIR spectroscopy – to determine structural position of the ions of external origin, such as arsenate, what will allow to conclude on pre- or post-mortem enrichment, and to evaluate the linkage between fossil bones geochemistry and fossilization processes.

Field works, including sampling at the sites and some preliminary analyses, will be conducted during trips to Russian Altai, Kyrgyzstan and Uzbekistan. 

Additional analyses in the project is archive query. This includes sedimentological analysis of archaeological documentation for studied sites, library survey and works in institutions storing the collections (Novosibirsk, Tashkent, Bishkek – material selection, sampling). This stage needs close cooperation between geologists (P.I. and PhD student) and archaeologists experienced in excavation work in Central Asian sites (Co-investigator Archaeo-Altai, Co-investigator Archaeo-Ferghana). When possible, the trips will be jointed with field trips to reduce the travel costs.

Data processing – statistical analysis will be applied to numerical data, such as results of grain size or chemical analysis. Multi-variate analysis (PCA and cluster analysis) will be the most important methods to evaluate the variability and to detect trends. The centered log-ratio transformation (CLR) or similar ones (e.g., IRL) will be used to de-constrain the large datasets. Final stage will be integration of the results of different methods into lithostratigraphical schemes and building the deposition models for each site. An attempt of stratigraphic correlation between sites, but also correlation with other regional scales (e.g., loess-paleosol sequences), will be undertaken.

Equipment – the Institute provides well equipped laboratories, useful for this project: sample preparation lab (crushing, powdering), thin section preparation lab, FTIR spectroscopy lab, U/Th dating lab, CHNS elemental analysis lab, petrographic microscopes with digital cameras.