SSP2.6

EDI
The physical record of the Anthropocene in geological archives

The session asks for well-dated geoarchives that document the physical evidence of the transition from the Late Holocene (Meghalayan) to the Anthropocene. These may include artificial deposits, lake, estuary or marine sediments, peat, speleothems, ice core or biological hosts such as trees or corals, displaying good chronologies. The evidence for an Anthropocene can include transitions in the types and abundance of physical materials, biota, or distinct geochemical signals; ideally the study should provide multiple proxies or consider innovative new techniques in recognising the Anthropocene. We are interested in presentations that show continuous to near continuous records that can extend hundreds or even thousands of years back in time, but should also include comparable analysis through the mid-20th century to near present day. The presentations should explain how, if at all, the Anthropocene can be distinguished in these archives. Studies from any continent will be considered, though presentations on archives from South America and Africa are especially encouraged.

Co-organized by CL3.1/GM12
Convener: Michael Wagreich | Co-conveners: Irka Hajdas, Kira LappéECSECS, Colin N. Waters
vPICO presentations
| Wed, 28 Apr, 14:15–15:00 (CEST)

vPICO presentations: Wed, 28 Apr

Chairperson: Michael Wagreich
14:15–14:20
14:20–14:30
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EGU21-3226
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solicited
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Highlight
Simon Turner and the AWG-HKW-MPIWG Anthropocene GSSP

The Anthropocene Working Group (AWG) has assembled scientific teams to analyse stratigraphic successions, as potential stratotypes, in order to facilitate a formal submission to the Subcommission on Quaternary Stratigraphy. The aim is to seek ratification of the Anthropocene as a geological epoch starting in the mid-twentieth century. Stratigraphic records, including a range of novel materials, geochemical and biological signals spanning the mid-twentieth century interval of unprecedented human activity and industrialisation, are being gathered by international teams of scientists, working on eleven contrasting depositional settings from around the planet. Interwoven with this scientific process to define a Global Boundary Stratotype Section and Point (GSSP), from which a specific year for the onset of the Anthropocene will be established, is a decades long collaborative exploration of the Anthropocene between the AWG, Haus der Kulturen Welt (HKW) and Max Planck Institute for the History of Science (MPIWG).  

While the compilation of stratigraphic data to define a new epoch is as old as the science of geology, the demarcation of one within living history that signifies human activity as a global geological agent is unparalleled. Similarly, there is no precedent of a stratigraphic formalisation process being pivotal to the framing of so much contemporary social, ecological, artistic, historical and political thought. In May 2022 along with the publication of the results and data, an exhibition including a discursive and performative programme will occur at HKW in Berlin as a public forum for the scientific, cultural and socio-political impact of the geochronological research carried out by the international research project on the Anthropocene.

This presentation provides an introduction to the interdisciplinary and collaborative research project between the AWG, HKW and MPIWG. The talk will introduce the prospective sites and stratigraphy of the proposed successions and an update on progress towards the official ratification of the GSSP, as well as collaborative artistic and cultural work embedded in the process.

How to cite: Turner, S. and the AWG-HKW-MPIWG Anthropocene GSSP: Progress in the formalisation of the Anthropocene GSSP, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3226, https://doi.org/10.5194/egusphere-egu21-3226, 2021.

14:30–14:32
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EGU21-6685
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ECS
M. Allison Stegner, SeanPaul La Selle, Brian Sherrod, Anthony Barnosky, and Elizabeth Hadly

Human activities changed our planet over the course of the Holocene, but the scale of impacts increased dramatically around the mid-20th century, representing the start of the Anthropocene. These pervasive anthropogenic impacts, including pollution, road-building, the rise of plastics, etc., are comparable in magnitude, uniqueness, and geologic perseverance to global changes that mark previous major geologic time intervals. To identify the preservable global and local signals that might be used to characterize the Anthropocene, we examine sediment cores from Searsville Reservoir, a 129-year-old reservoir located in the eastern foothills of the San Francisco Peninsula. We collected eight sediment cores ranging from 7.4 to 8.5 meters in length that appear to have bottomed out on the pre-reservoir surface, indicating average sedimentation rates of 6 to 7 cm per year. This exceptionally high sedimentation rate allows us to explore the Anthropocene geologic record on a sub-annual scale.

Our analyses to date include sedimentary DNA (sedDNA), pollen, computed tomography (CT) scanning, Carbon and Nitrogen isotopes, radionuclides, Mercury, and X-ray fluorescence (XRF). We find a strong relationship between sediment type and both sedDNA and pollen frequency: sedDNA and pollen are more abundant in the thin, low-density units that are thought to be associated with lower sedimentation rates and high organic inputs during the dry season. SedDNA analyses successfully identified a diversity of insects and vertebrates to the species level, including invasive fish and mosquitos. Computed tomography scans of the cores revealed >300 distinct layers ranging in thickness from <1mm to ~30mm. Many of the thicker laminae show upward-fining, indicative of individual storm events. Sediment density generally decreases from the bottom to the top of the cores, consistent with both sediment compaction and increasing organic inputs as the reservoir filled with sediment and eutrophied. δ15N declined over the record, reflecting global δ15N depletion due to fossil fuel combustion and artificial nitrogen fertilization for agriculture. δ13C was fairly stable prior to around 1950, then became highly variable, possibly related to changes in aquatic productivity (algal blooms) that began in the 1950s. A sharp and well-defined peak in 137Cs provides evidence of nuclear testing in the 1950s and ‘60s, and serves as a secure chronological tie point for the year 1963. The 137Cs peak correlates well with the chronology estimated by counting back suspected annual couplets of high density (wet season)/low density (dry-season) sediments. Our analyses reveal a complex interplay between local and global human impacts at Searsville Reservoir, and document the onset of the Anthropocene epoch at fine scale. Searsville is particularly appropriate as a candidate Global Boundary Stratotype Section and Point for the Anthropocene not just because of the unique and highly resolved nature of the sediments, but because the record itself is a direct consequence of human activity—the emplacement of a dam.

How to cite: Stegner, M. A., La Selle, S., Sherrod, B., Barnosky, A., and Hadly, E.: Dynamics of biotic and abiotic markers of the Anthropocene at Jasper Ridge Biological Preserve, California, USA, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6685, https://doi.org/10.5194/egusphere-egu21-6685, 2021.

14:32–14:34
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EGU21-15133
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ECS
Stephen Himson, Mark Williams, Mary McGann, Neil Rose, Ian Wilkinson, Jan Zalasiewicz, and Colin Waters

Modification of ecosystems through the introduction of non-native species (neobiota) is one part of the major human impact on the biosphere. Neobiota are now present worldwide and often significantly outnumber native fauna and flora. In many places they have left a distinctive biostratigraphic record of anthropogenic changes to the biosphere in the 20th century. Few ecosystems have been as severely affected by the arrival of neobiota as San Francisco Bay. Some 234 introduced species comprising up to 97% of individuals and in some places up to 99% of the biomass are known to be present in the bay (Cohen and Carlton, 1998). Among the multitude of neobiotic species established are Trochammina hadai, a benthic foraminifer that is native to Japan and was introduced in 1983 (McGann 2008), and Potamocorbula amurensis, a bivalved mollusc native to the Amur River region of East Asia that was introduced in 1986 (Carlton et al. 1990). Here we present sediment core data showing the arrival and proliferation of T. hadai and P. amurensis in addition to three introduced ostracod species, Spinileberis quadriaculeata, Eusarsiella zostericola and Bicornucythere bisanensis. The introduction of T. hadai is thought to have occurred through ballast water exchange from trans-Pacific shipping, and has produced a major perturbation to the foraminiferal record of San Francisco Bay. Pb-210 radiometric dating has established a high-resolution chronology for the core and analysis of fly ash particles (Rose 2015) emitted from coal-fired power stations allow time horizons, and the chronologies they define, to be correlated to a further 18 cores collected across the bay. This quantifies both the temporal and spatial extent of a human-induced biostratigraphic assemblage of neobiota, one that is correlatable with a biostratigraphic record of changes to ecosystems across the world in the late 20th century.

 

Carlton, J.T., Thompson, J.K., Schemel, L.E. and Nichols, F.H. 1990. Remarkable invasion of San Francisco Bay (California, USA), by the Asian clam Potamocorbula amurensis. I. Introduction and dispersal. Marine Ecology Progress Series, 81-94.

Cohen, A.N. & Carlton, J.T. 1998. Accelerating invasion rate in a highly invaded estuary. Science 279, 555-558.

McGann, M. 2008. High-resolution foraminiferal, isotopic, and trace element record from Holocene estuarine deposits of San Francisco Bay, California. Journal of Coastal Research 24, 1092-1109.

Rose, N.L. 2015. Spheroidal carbonaceous fly ash particles provide a globally synchronous stratigraphic marker for the Anthropocene. Environmental Science & Technology 49, 4155-4162.

How to cite: Himson, S., Williams, M., McGann, M., Rose, N., Wilkinson, I., Zalasiewicz, J., and Waters, C.: A biostratigraphic record of Anthropocene ecological change in one of the world's most invaded aquatic ecosystems, San Francisco, CA., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15133, https://doi.org/10.5194/egusphere-egu21-15133, 2021.

14:34–14:36
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EGU21-3744
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ECS
Andrii Oleksandrenko, Peter Appleby, Tommy Noernberg, and William Shotyk

Americium-241 (241Am) is present in the terrestrial and aquatic environment around the globe as a result of the atmospheric testing of high yield thermonuclear weapons carried out mainly in the 1950s and 1960s. Radioactive debris (including mainly 137Cs, 90Sr, and various Pu isotopes) from the tests was injected high into the stratosphere where it was rapidly dispersed around the world. Over a period of months this material slowly returned to the troposphere, and from there was quickly removed by wet and dry fallout onto the earth’s surface. Amounts of 241Am in freshly deposited weapons test debris were essentially zero. Its presence today is through in-growth from its short-lived precursor 241Pu (half-life 14.4 years). By this process concentrations of 241Am have steadily increased with time and will continue to do so through to around 2040. Widely considered to be immobile in soils and sediments, with its well-known origins and long half-life (432 years), 241Am is in many ways an ideal chronostratigraphic marker of the nuclear age. Calculations show that the 241Am record in any ideal natural archive is a faithful representation of the history of weapons test fallout. Beginning in the early 1950s, fallout reached a peak in 1963 and then declined rapidly following the implementation of the test ban treaty. A number of scientists have proposed that the weapons test fallout peak could be used to mark the start of the Anthropocene. Various geological archives preserve the record of fallout, though with varying degrees of fidelity. They include polar snow and ice, marine and lacustrine sediments, and peat bogs. Bogs are ombrotrophic peatlands in that the plants growing there receive nutrients and contaminants exclusively from the atmosphere. The purpose of this study is to determine the fidelity of 241Am records in peat bog cores.
Specifically, we compare the position of the 241Am concentration peak with the 1963 depth determined by 210Pb dating. We use 39 peat cores from Europe, North America, and Indonesia collected by our team during the past 30 years for studies of atmospheric deposition of trace metals, all of which had been independently dated using 210Pb. We find that 18 of the cores provide an excellent agreement between the 241Am and 210Pb dates, 12 were in good agreement, and 9 agreed poorly. Possible reasons for the discrepancy in the 9 cores with the poor agreement are 1) the sensitivity of the gamma spectrometer for detecting 241Am, and 2) disruptions to the fallout records caused e.g. by disturbances to the peat bog or changes in the peat topography or hydrology. Small scale horizontal and vertical variations in bogs help explain why in a triplicate of peat cores collected from Wildseemoor in the Black Forest of Germany, excellent agreement was found in one core, good agreement in a second, and poor agreement in the third. A peat core collected from Gola di Lago, a small fen in Switzerland, showed excellent agreement; this suggests that samples from minerotrophic peatlands may also be useful to mark the start of the Anthropocene.

How to cite: Oleksandrenko, A., Appleby, P., Noernberg, T., and Shotyk, W.: Americium-241 in peat bogs as a marker of the beginning of the Anthropocene: examples from Europe and North America., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3744, https://doi.org/10.5194/egusphere-egu21-3744, 2021.

14:36–14:38
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EGU21-15795
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ECS
Sara Todorović, Henry C. Wu, Braddock Linsley, Delphine Dissard, Henning Kuhnert, Albert Benthien, Klaus-Uwe Richter, Markus Raitzsch, and Jelle Bijma

Massive tropical corals represent one of the most important natural archives of modern climate change. Coral based reconstructions give us the possibility to extend the instrumental oceanographic records and observe hydrographic variability on seasonal to interdecadal scales in tropical oceans. South Pacific convergence zone (SPCZ) variability, Interdecadal Pacific Oscillation (IPO) and El Niño-Southern Oscillation (ENSO) events are major drivers of global climate and may exert control on regional CO2 absorption, outgassing and pH variability.

Porites sp. corals from Tonga and Rotuma (Fijian dependency) are being analyzed for multi-proxy (e.g. Sr/Ca, δ18O, δ13C, δ11B, B/Ca) reconstructions of sea surface temperature and salinity (SST, SSS) and carbonate chemistry, on a monthly to annual resolution. Preliminary data of the Rotuma Porites sp. coral shows δ18O has been decreasing by 0.004 ‰ per year at the end of the 20th century, suggesting freshening and/or warming of the surface water. In the same period, we observe a δ13C decrease of 0.017 ‰ per year in-line with the anthropogenic CO2 driven Suess effect. Initial results of the δ11B Tonga Porites sp. show high interannual variability, and a strong trend of decrease of -0.0626 ‰ per year in the last five decades of the record (1949-2004) suggesting acidification. The results are in agreement with published coral-based reconstructions from the region.

When completed, the new records will facilitate exploring the effects of modern anthropogenic influence on ocean carbonate system and pH variation, and the relationship between them and interannual and decadal-interdecadal climatic fluctuations.

How to cite: Todorović, S., C. Wu, H., Linsley, B., Dissard, D., Kuhnert, H., Benthien, A., Richter, K.-U., Raitzsch, M., and Bijma, J.: Tracking the South Pacific convergence zone variability and recent acidification reconstructed from tropical corals, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15795, https://doi.org/10.5194/egusphere-egu21-15795, 2021.

14:38–14:40
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EGU21-10221
Luigi Bruno

Mid-Late Holocene stratigraphy beneath the town of Bologna, in northern Italy, records an upward increase in the amount, thickness, width and connectivity of anthropogenic deposits and a parallel decrease in alluvial sediments. Anthropogenic deposits, spanning from the Neolithic to the Present, occur at three stratigraphic intervals separated by alluvial strata.

The lower interval, dated to the Neolithic-Early Eneolithic, includes sparse lithic, ceramic and copper artefacts, post holes, charcoals, shallow wells and ditches. These evidences of human presence are scattered along a pedogenized horizon developed during a phase of river stability lasting more than 3 millennia. Early Eneolithic rests are aligned along paleo river courses.

The second horizon consists of an uninterrupted archaeological sequence spanning from the Late Bronze Age to the Late Antiquity. Late Bronze and Iron Age remains include ceramic and metal artefacts, charcoals, huts, dwellings, wells, ditches, and cemetery sites. Iron age remains are pervasive and their distribution is irrespective of riverbed location. The elevated number of dwellings and cremation jars testifies to a significant local population growth. A dense grid of ditches and embankments denotes a widespread control of the drainage network. Roman deposits include large dwellings, public buildings, productive sites, wells, aqueducts, ditches, landfills, roads, bridges, cemetery sites. Romans introduced in the geological record huge amounts of anthropogenic materials with high preservation potential such as bricks and mortars. Large quantities of different rock types were imported from European and Mediterranean areas. These materials constitute a laterally continuous horizon buried at depth of 3-4 metres, which testifies to the development the colony of Bononia, founded in 189 BC. The amount and connectivity of roman rests, decreases away from the historical centre, where large farms, reclaimed lands and centuriae highlight an anthropogenically modified rural landscape. Fluvial gravels deposited since the Roman period are commonly enriched in brick clasts.

The uppermost anthropogenic interval is dated to the last millennia. Its base is a time-transgressive erosional surface which testifies to the progressive expansion of the Bologna urban area, with a minor pulse dated to Middle Ages (1200-1300 AD) and a major to the last 70 years. Particularly, in the 20th century the urban area of Bologna became 20 times larger and merged with adjacent villages. Post-1950 deposits are up-to-30 m thick and deeply cut into older stratigraphic units. Concrete, metal, and plastic are the most abundant materials. The last 70 years also record the spread of pollutants within shallow acquifers and dramatically increased subsidence rates due to water withdrawal.

Anthropogenic deposits beneath Bologna record an overall upward transition from a river-dominated to a man-dominated environment. Iron Age and Roman deposits represent the first evidence of a landscape heavily modelled by human activities. However, the thickness, lateral extent and pervasiveness of post-1950 anthropogenic units support the recently proposed idea to place the base of the Anthropocene in the mid-20th century.

How to cite: Bruno, L.: From a river- to a man-dominated environment. Insights from the geo-archaeological record of Bologna (northern Italy), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10221, https://doi.org/10.5194/egusphere-egu21-10221, 2021.

14:40–14:42
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EGU21-11930
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ECS
Maria Meszar, Karin Hain, Michael Wagreich, Kira Lappé, Martin Mosser, Katrin Hornek, Veronika Koukal, Constance Litschauer, and Nikolaos Piperakis

Urban anthropogenic strata forms the layered archaeosphere in the underground of large cities. In a transdisciplinary project involving geosciences, isotope physics and urban archaeology, funded by the Vienna Science and Technology Fund (WWTF), we looked for artificial isotopes in urban layers around the proposed starting date of the Anthropocene in the middle of the 20th century. The tested archaeological site is situated in the heart of Vienna, in a park area at Karlsplatz, adjacent to the renovated Vienna Museum. Excellent and detailed 3D archaeological stratigraphy sets age constraints around 1922, post-1945, and around the 1960s. A layer on top of the WWII rubble that fills fundaments of a 1922 building post-dates 1945, and pre-dates the finishing shaping of the human-made park ground of 1959, the date of the opening of the Vienna Museum. We focused on the fine-grained (clayey-sandy) sediment matrix on top of the WWII rubble, at the base of and mixed with backfilled soil material. The sieved fraction below 2 mm grain size was dried and pulverised. This sediment sample was prepared for chemical separation of actinides which were then analysed by Accelerator Mass Spectrometry (AMS) using the setup at the Vienna Environmental Research Accelerator (VERA, Isotope Physics Group). We identified several artificial radionuclides including U-236, Np-237, Pu-239, Pu-240. Isotope ratios like Pu-240/Pu-239 and in particular U-233/U-236, which was only recently introduced as anthropogenic tracer by the VERA group, clearly point to atmospheric atomic bomb fallout material of the 1950s to 1960s. A significant input of Chernobyl (1986) material can be excluded based on the ratio Pu-241/Pu-239. Thus, the 1952-1964 bomb-spike as the possible primary (GSSP) marker of the Anthropocene can be identified and used even in coarse urban anthropogenic sediments of big cities, exemplifying the correlation potential of these radionuclide markers.

How to cite: Meszar, M., Hain, K., Wagreich, M., Lappé, K., Mosser, M., Hornek, K., Koukal, V., Litschauer, C., and Piperakis, N.: Tracing the Anthropocene bomb-spike in urban strata of Vienna, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11930, https://doi.org/10.5194/egusphere-egu21-11930, 2021.

14:42–15:00