Geochemical, molecular, biogenic and pyrogenic content in a 175 cm long wetland sediment sequence, Free State, South Africa

Jenny Sjöström, Antonio Martínez-Cortizas, Alice Hardman, Andreas Nylund, Joeri Kaal, Rienk Smittenberg, Jan Risberg, Daniel Schillereff, Elin Norström

This dataset contains geochemical, molecular, biogenic, and pyrogenic results derived from analysis of a 175 cm long wetland sequence from Marais Geluk wetland, south-eastern South Africa (28°17'53"S, 29°25'10.9"E). The sequence covers the last 10,000 years.

The geochemical data-set consists of elemental (Si, K, Ti, Al, Rb, Mn, Ca, Sr, Fe, Y, Ga, C and N), and carbon isotope variability through time.

The molecular composition was retrieved through FTIR-ATR analysis and contains information about organic and inorganic compounds. The biogenic data is based on grass phytolith analysis conducted at selected depths. The pyrogenic data file contains information about combustion residues in the sequence, based on pyrolysis-GC-MS analysis. The chronological framework was retrieved through AMS radiocarbon dating of seven bulk samples.

The results from this data-set was used to infer hydrological, grassland composition and wildfire variability throughout the last 10,000 years in the study area (see reference below).

Citation

Jenny Sjöström, Antonio Martínez-Cortizas, Alice Hardman, Andreas Nylund, Joeri Kaal, Rienk Smittenberg, Jan Risberg, Daniel Schillereff, Elin Norström (2023) Geochemical, molecular, biogenic and pyrogenic content in a 175 cm long wetland sediment sequence, Free State, South Africa. Dataset version 1. Bolin Centre Database. https://doi.org/10.17043/sjostrom-2023-south-africa-1

References

Sjöström, J. K., Martínez Cortizas, A., Nylund, A., Hardman, A., Kaal, J., Smittenberg, R. H., Risberg, J., Schillereff, D., & Norström, E. (2023). Complex evolution of Holocene hydroclimate, fire and vegetation revealed by molecular, minerogenic and biogenic proxies, Marais Geluk wetland, eastern Free State, South Africa. In Quaternary Science Reviews (Vol. 314, p. 108216). Elsevier BV. https://doi.org/10.1016/j.quascirev.2023.108216

Data description

This dataset contains six semicolon separated value csv files.

1. age depth model.csv Contains result of the age-depth modelling organised in 7 columns. Each row representing one centimeter, the indicated depth represents the vertical location (in cm) from the surface. The data is presented in ascending order.

   • Column 1-7:
     • depth (cm): the vertical location (in cm, from the surface) of each analysed sample
     • min (Cal yr BP): minimum calibrated age, years before present
     • max (Cal yr BP): maximum calibrated age, years before present
     • median (Cal yr BP): median calibrated age, years before present
     • mean (Cal yr BP): mean calibrated age, years before present
     • mean, accumulation rate, yr: the mean accumulation rate, given in years per cm
     • standard deviation, accumulation rate, yr: standard deviation of the accumulation rate, given in years per cm
     • mm, per year: sedimentation rate, millimeters per year

2. cs-xrf.csv Contains the raw data from the CS-XRF analysis and includes the results for elements Si, K, Ca, Ti, Mn, Fe, Ga, Rb, Sr and Y. The data is organised in 15 columns. Each row represents the vertical depth of the analysis, in 3 mm increments.

   • Column 1-2:
     • mean: age (Cal yr BP)
     • depth, cm: depth in centimetre
   • Column 3-15: elemental intensities (in total counts). The column header contains the chemical symbol: Al, Si, P, S, K, Ca, Ti, Mn, Fe, Ga, Rb, Sr, Y.

3. FTIR-ATR.csv Contains the absorbance result of the FTIR-ATR analysis. The file contains 86 columns. One sample in each column and results (per wavenumber) presented in rows.

   • Column 1:
     • Wavenumber: wavenumber 401 to 3999, in ascending order.
   • Column 2-86:
     • The absorbance results of each sample is presented in columns 2-86. The header contains information on the calibrated age (Cal yr BP) of the sample.

4. pyrolysis.csv contains downcore concentration (ascending order) of eight combustion compounds. The file is organised in 10 columns, with each row representing one analysed sample.

   • Column 1-2:
     • depth (cm): vertical location (from the surface) of the analysed sample, cm
     • age (cal yr BP): calibrated age, years before present, for each analysed sample
   • Columns 2-10:
     • percentage of the total quantified peak area (%, TPQA) for each combustion compound. Compound name described in each column header.

5. LOI TOC TN δ13C.csv Contains 8 columns. The file contains results from different sampling resolution, separated by a blank column. The first 5 columns contains the concentration of carbon and nitrogen, together with stable isotopes of carbon content. Followed by one blank column. The subsequent three columns contains the loss on ignition (LOI, %) data, conducted at a distinct sample resolution.

   • Column 1-5:
     • depth (cm): the vertical depth of the analysed sample, from the surface, cm.
     • age (cal yr BP): the mean age, calibrated years before the present
     • δ13C (‰): ratio of stable isotopes of carbon (against the PDB standard), reported in per mille
     • TOC, %: total organic carbon, percent
     • TN, %: total nitrogen, percent
   • Column 6: blank (separation between results from different sampling resolution)
   • Column 7-9:
     • depth (cm): the vertical depth of the analysed sample, from the surface, cm
     • age (cal yr BP): the mean age, calibrated years before the present
     • LOI, %: result of the LOI analysis, presented in %

6. phytolith.csv This file contains the results of the GSSC phytolith analysis organised in 7 columns. The results are presented in rows, with each row representing one analysed sample. Column 3-7 contains the the total number of observed morphotypes, per grass subfamily, for each sample.

   • Column 1-2:
     • depth (cm): depth in centimetre
     • cal yr BP: calibrated age (cal yr BP)
   • Column 3-7:
     • Paniocoideae: total number of identified diagnostic Panicoideae morphotypes
     • Pooideae: total number of identified diagnostic Pooideae morphotypes
     • Chloridoideae: total number of identified diagnostic Chloridoideae morphotypes
     • Undiagnostic: GSSC phytoliths not related to a specific grass subfamily
     • Sum (diagnostic): sum of the diagnostic morphotypes (column 3-5)

Comments

Abbreviations

• CS-XRF: core scanning X-ray fluorescence
• FTIR-ATR: Fourier transform infra-red attenuated reflectance
• Pyrolysis-GC-MS: pyrolysis–gas-chromatography–mass spectrometry
• Cal yr BP: calibrated years before the present (1950)
• LOI: loss on ignition
• GSSC: grass silica short cell