Additional stratigraphic marker for an Anthropocene at the Karlsplatz reference site (Vienna, Austria)

Urban deposits pose many challenges compared to natural archives. Due do anthropogenic influence they often have only limited lateral continuity, highly variable deposition rates, are prone to (anthropogenic) erosion, reworking and resedimentation, and show omission surfaces. In Vienna (Austria) we investigated sediments from an archaeological excavation site near the city centre as part of a transdisciplinary project involving geosciences, isotope physics and urban archaeology. The study area at Karlsplatz is situated near the Wien River and records the change in land use of the expanding city. The site covers a section from natural flood sediments (17th century) and anthropogenic fill (before 1900) of the Wien River to the latest levelling period of the park area in the 1950s. Archaeological stratigraphy and historic data sets provide age constraints for the multiple deposition phases, with the oldest road structures dating from the 18th century and the youngest deposits dating around 1922, post-1945 and the park opening in 1959 (Mosser et al., 2022). Atmospheric bomb-testing fallout plutonium was used for further Anthropocene age constraints (Wagreich et al., 2023) dating the upper layer as deposited between 1952 and 1959.
The fine-grained matrix (< 2 mm grain size) of the deposits was used for X-Ray fluorescence (XRF) analysis of trace elements such as lead, copper and zinc. The highest levels of trace metals (Cu 330 ppm, Pb 633 ppm, Zn 852 ppm) are present in sediments of a 19th century deposit rich in charcoal and metal slags associated with nearby metal-working industry. The second highest peak occurs in a layer of WW2 rubble rich in technofossils of that era (Cu 71 ppm, Pb 208 ppm, 296 ppm). Overlying deposits of the 1950s show again much lower values (Cu 24 ppm, Pb 28 ppm, Zn 61 ppm) similar to the range of low contamination background and infill materials, although the uppermost topsoil layer shows a slight recent enrichment (Cu 35 ppm, Pb 56 ppm, Zn 99 ppm) compared to the 1950s. Spheroidal carbonaceous fly-ash particles (SCPs), the product of industrial coal and oil combustion, were found in elevated concentrations in the post-1945 levels. These results indicate both a local (iron industry of the 19th century, WW2 pollution) and a regional-global (e.g. lead from leaded gasoline, fly ash particles) control on trace metal and fly ash contamination and a correlation with technofossil findings. In conclusion, additional stratigraphic markers for the Anthropocene were identified and quantified in the urban anthropogenic sediments of the Karlsplatz site. Therefore, the site may be used as a correlative stratigraphic reference section for the Anthropocene.

 

References:

Mosser et al. 2022. Fundort Wien, 25, 2022, 4-53.

Wagreich et al., 2023. The Anthropocene Review, 2023, 10/1, 316-329. doi 10.1177/20530196221136427