The attenuation of X-ray is influenced by the density (electron density, ρe) and the elemental composition (effective atomic number, Zeff) of the object being imaged. The incident X-ray beams energy controls the relative importance of these two properties in the resulting X-ray attenuation. Yet, dual-energy X-ray computed tomography, or using two incident X-ray beams of different energy, has been used in medical sciences to distinguish the different compounds within a sample based on their density (electron density, ρe) and elemental composition (effective atomic number, Zeff).
An innovative approach, i.e., the stoichiometric calibration for dual-energy X-ray computed tomography, was already successfully implemented to identify single and homogeneous minerals easily and non-destructively. It is here applied for the first time to a varved sequence with three distinct facies. The output of dual-energy X-ray computed tomography was compared against elemental geochemistry obtained at the same resolution using a micro-XRF core scanner. The three individual facies can be successfully differentiated using dual-energy X-ray computed tomography because their range of ρe and Zeff values allow their discrimination. Correlations with elemental geochemistry are also discussed but are less conclusive, probably because of variations in grain size and porosity, and because these high-resolution analyses were not performed at the exact same location. We discuss the limitations when using dual-energy X-ray computed tomography on sediments but also demonstrates its potential to quantitatively study sediment cores in a non-destructive way.
This presentation is based on https://doi.org/10.1002/dep2.271
How to cite: Francus, P. and Martini, M.: Using dual-energy CT to discriminate sediment facies in a varved sequence , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7352, https://doi.org/10.5194/egusphere-egu25-7352, 2025.
Paleo data play a critical role in constraining the future evolution of climate in the Arctic, our planet`s most rapidly warming region. However, most proxies capture past change during the brief summers, when biological indicators are synthesized, and the availability of liquid water as well as the absence of snow allows sediment transport. As a result, far less is known about climate variability in other seasons. This bias is of consequence, because simulations hint at more extensive winter variability. Also, these changes affect regional and global climate by impacting surface albedo, glacier melt, and biodiversity. This work helps close this knowledge gap, by providing a 7000-year long record of abrupt and extreme Arctic winter climate change. For this purpose, we analyzed lake sediments – sensitive recorders of surface change, taken from a high-altitude basin – amplifying the imprint of winter season change, on Svalbard – a High Arctic climate change hotspot. By characterizing variations in geochemistry with X-Ray Fluorescence (XRF), density with Computed Tomography (CT), and anoxia with Hyperspectral Imaging (HI), we provide multiple lines of evidence for the presence of concretions that formed after extreme winters triggered widespread anoxia owing to residual lake ice feedbacks. Comparison with ice core records and climate model simulations suggests that these abrupt shifts were triggered by volcanic eruptions. Our findings highlight the potential of imaging techniques to fingerprint the geochemical imprint of winter climate change, and further challenge the notion that Holocene climate was stable.
How to cite: van der Bilt, W., Csiszár, B., Kong, S.-R., and Auer, A.: Integrated imaging fingerprints of anoxic concretions track 7000 years of abrupt and extreme Arctic winter climate change, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4815, https://doi.org/10.5194/egusphere-egu25-4815, 2025.
Wildfires are one of the most destructive climate-related hazards, causing significant economic and environmental impacts globally. Paleo-wildfire records provide insights into how climate change influences wildfire dynamics, including shifts in severity and frequency. In the western USA, studies using sedimentary charcoal have shown that long-term wildfire variations are closely tied to changes in temperature and aridity. However, short-term variability in paleo-wildfire activity remains understudied.
Here, we investigated high-accumulation varved sediment deposits from the Santa Barbara Basin (SBB) off California. The analyzed cores (SPR0901-05BC and MV0811-14TC) span the last two millennia. By analyzing monosaccharide anhydrides (MAs) as molecular fire-markers at sub-millimeter spatial resolution using mass spectrometry imaging (MSI), we obtained paleo-wildfire records with interannual to decadal temporal resolution. The MAs record shows a similar trend to historical fire data for the last century, demonstrating the feasibility of using MAs as proxies for paleo-wildfire reconstruction.
A mixture model was applied to decompose the raw MAs record into two components: (1) a low-resolution background signal, potentially from fire-derived markers deposited in soil and gradually released into the ocean through long-term erosion and transport, and (2) a high-resolution peak signal, likely reflecting aerosol and/or rapid river deposition following fires. The background signal aligns with wildfire history reconstructed from charcoal records in the western USA, showing high biomass burning during the Medieval Climate Anomaly (MCA) and the settlement era, and low biomass burning during the Little Ice Age (LIA).
By analyzing the density of high-resolution peak signals, we reconstructed a decadal-scale fire frequency record for Southern California. This record provides detailed insights into changes in wildfire frequency during the MCA and the subsequent transition to the LIA. Overall, the fire frequency correlates positively with pre-20th-century variations in temperature and aridity on decadal timescales, indicating that the wildfire frequency was significantly influenced by decadal fluctuations in climate conditions.
How to cite: Liu, W., Alfken, S., Wendt, J., Bhattacharya, T., Napier, T., Schimmelmann, A., Hinrichs, K.-U., and Wörmer, L.: Southern California’s 2000-year wildfire history: Long-term trends and decadal variability, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15770, https://doi.org/10.5194/egusphere-egu25-15770, 2025.
Imaging techniques, such as micro-X-ray fluorescence (µ-XRF), are critical tools for paleoenvironmental reconstructions. Recent advances in two-dimensional (2D) mapping enable detailed spatial and temporal analyses of paleoclimate archives, providing unprecedented insights into past environmental changes. However, generating high-resolution geochemical maps often requires tradeoffs between measurement time and data quality. Limited exposure times per pixel result in low counts and frequent zero values, which increase noise and variability in the data. The compositional nature of count data introduces additional challenges, as zeros and zero replacement strategies can compromise the effectiveness of log-ratio transformations.
This study investigates the impact of low-count µ-XRF data using maps from laminated lake sediments in Lake Ammersee, Germany. The varves in this archive record seasonal changes, with Ca-enriched layers forming during summer and Ti-enriched detrital layers indicating flood events. We analyzed 2D maps from eight repetition measurements and simulated extended exposure times by stacking them. Additionally, synthetic datasets were used to simulate both low (mean count intensity < 10) and high (mean count intensity > 10,000) count rate scenarios.
Our results reveal that low-count data exhibit persistent artifacts in both native and log space. Spurious correlations and clusters of elemental ratios remain evident, even after log-ratio transformations, and are most pronounced in low-intensity datasets. These artifacts complicate the reconstruction of paleoclimate proxies and the interpretation of geochemical records. Increasing count rates by extending the measurement time may provide a short-term solution to reduce these artifacts. However, current methodologies for addressing low-count compositional data and zero-replacement strategies remain inadequate, particularly for high-resolution imaging techniques. Advancing statistical approaches is essential to develop robust frameworks for interpreting paleoclimate proxies.
How to cite: Schley, L., Tjallingii, R., Weltje, G. J., Mittelbach, K., Strasser, M., and Ramisch, A.: Low Counts, High Stakes: Challenges in micro- Geochemical Imaging of Paleoclimate Archives, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6204, https://doi.org/10.5194/egusphere-egu25-6204, 2025.
Wetlands are one of the most valuable yet most threatened terrestrial ecosystems. These ecosystems are essential in regulating the long-term carbon cycle, maintaining hydrological balance, and serving as local biodiversity hotspots. However, human activities have heavily impacted these ecosystems for centuries, changing them from carbon sinks into carbon sources. Current climate change and land use changes speed up this process globally. Conservation and restoration efforts require a better understanding of these negative phenomena. Studying how peat deposits change over time and across different areas is essential to make informed decisions. This research helps link environmental impacts to how wetlands respond, enabling more effective management strategies.
However, typical high-resolution spatiotemporal studies require numerous drill sites, abundant samples, and analytical techniques, substantially limiting the investigation scope. Non-destructive imaging techniques such as hyperspectral scanning imaging (HSI) might help overcome these limitations by allowing rapid analyses of lengthy peat profiles. Therefore, HSI is a promising tool for paleoenvironmental investigations and can potentially be used in conservation efforts of degraded peatlands.
We selected a peatland in northern Poland to test the HSI's ability to accurately trace organic matter accumulation and peat humification in several microhabitats. Peat excavation sites indicate that human activities have impacted this location in the past, and different processes (like drainage) might have been recorded affecting the peat, leading to the lowering of the water table. We cored in 5 sites and obtained 5.2 m of material, capturing undisturbed and heavily humified deposits. Cores were subsampled every 5 cm. We used estimated organic matter content (OM) by loss on ignition and von Post humification degree. We confronted these results with high-resolution hyperspectral scanning imaging (HSI) of peat cores in the VNIR (400–1000 nm) range. Finally, we compared both approaches using linear regression and machine learning approaches, i.e., random forest and gradient boosting, to find associations between the datasets. Overall, machine learning models generalize OM and humification tendencies in the deposits to a satisfactory level. Further investigation with numerous drills per site, more diverse material, and increased training set size might provide an invaluable opportunity to identify the current condition of the peatlands. In the future, they can provide a rapid and independent tool for checking restoration efforts.
The work was supported by the National Science Centre, Poland, under the research project „Exploring methods of hyperspectral imaging of lake sediments: proxy development and calibration,” no UMO-2023/51/D/ST10/00801
How to cite: Żarczyński, M., Kostrzewska, K., Zawistowska, B., and Czerwiński, S.: Preliminary Assessment of Peat Deposits Imaging Using VNIR (400–1000 nm) Hyperspectral Scanning: Organic Matter and Humification Case Study, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15503, https://doi.org/10.5194/egusphere-egu25-15503, 2025.
Over the past decades coral skeletons have become established as excellent archives of environmental changes, with seasonal banding in either skeletal density or trace element geochemistry providing a method of reconstructing annual to sub-annual processes. Density banding was first observed using radiography to produce two-dimensional images of a skeletal slab. More recently, micro-tomography has been used to develop three-dimensional reconstructions of a skeletal sample, which provides opportunities to understand microstructural changes and associated variations in bulk density in different compartments of coral skeletons. Here, we use micro-tomography to track changes in density in two species of Caribbean coral, Siderastrea siderea and Pseudodiploria strigosa. Specifically, we develop a method that involves unsupervised learning for instance segmentation of microstructrual features such as corallites. We then combine this with semantic segmentation to separate individual voxels as either open space or coral skeleton, from which we can calculate and then track changes in porosity and thus bulk density. The results show that there are clear changes in the rate of extension throughout an annual cycle, and by tracking these variations we observe clear changes in porosity associated with environmental disturbances such as volcanic eruptions. Additionally, we show that these changes manifest differently in different compartments of the coral skeleton. Finally, we develop panoptic segmentation methods as a tool to overcome non-linearities in coral extension across the surface of the coral, by following the extension of individual features throughout the growth of the skeletal sample.
How to cite: Sheldrake, T. and Vincent, J.: Opportunities and challenges in the reconstruction of environmental processes using segmented micro-CT scans of coral skeletons, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8607, https://doi.org/10.5194/egusphere-egu25-8607, 2025.
Eastern African geochemical and paleovegetation records hint at the presence of C4 photosynthesis in the Early Miocene (~21 Ma), long before the origin and diversification of hominins, and during a period of relative global climatic stability. Evidence of C4 proliferation and its impact on faunal behavior and ecosystem structure, however, is lacking from stable isotope records in mammalian tooth enamel, one of the most abundant and resilient archives of past diet and ecological change. We present novel and published enamel stable oxygen and carbon isotope records from 22 eastern African fossil assemblages; totaling 1252 specimens dating from 29 to 4 Ma. Oxygen isotope compositions indicate cooling and drying from the Oligocene into a hydrologically diverse Miocene, setting the stage for a shift to the consumption of C4 resources potentially as early as 13 Ma and in larger amounts beginning at 10 Ma. Faunal stable isotope variability within and between Early Miocene sites suggest that a C3-dominated eastern Africa nevertheless hosted varied hydrological regimes and animal behaviors across different sites. Taxa such as anthracotheres and giraffoids occupy consistently semi-aquatic or sub-canopy browsing niches. Primates, however, exhibit exceptional behavioral plasticity, with the large-bodied Early Miocene ape Afropithecus deriving most water from flowing surface sources at Buluk (Turkana Basin, Kenya) instead of from canopy vegetation as at other sites. The ecological and hydroclimate transformations from the Paleogene into the Neogene help explain how C3 landscapes became primed for Late Miocene C4 expansion and hosted behavioral diversity that shaped an emerging African savanna fauna, and the behavioral plasticity of our ancestors.
Turkana Miocene Project coauthors include: Eipa Aoron, Sneha Bapana, Catherine Beck, Paul Barrett, Mikael Fortelius, Craig Feibel, Aryeh Grossman, Greg Henkes, Ashley House, Francis Kirera, Martin Kirinya, Daeun Lee, Cynthia Liutkus-Pierce, Sam Lavin, Ellen R. Miller, Christopher Poulsen, Patricia Princehouse, John Rowan, Gabrielle Russo, William Sanders, Mae Saslaw, Ruth Tweedy, Linet Sankau, Natasha S. Vitek, and Indrė Žliobaitė.
How to cite: Green, D. and Uno, K. and the Turkana Miocene Project Coauthors: Late Cenozoic Eastern African Aridification, Vegetation Change, and Behavioral Diversity from Enamel Isotopes, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-21298, https://doi.org/10.5194/egusphere-egu25-21298, 2025.
The time interval between 4 Ma and 0.8 Ma is pivotal for the evolutionary history of hominids in eastern Africa, and particularly in the Turkana Depression (East African Rift System, Kenya / Ethiopia). It coincides with a number of major evolutionary events, including the evolution and disappearance of the genus Australopithecus, the appearance of the genus Homo, the first expansions to Eurasia, and many technological innovations, especially the Lomekwian, Oldowayan and Acheulean lithic industries. This period is also marked by pronounced environmental changes, relatively well constrained at the global scale using marine records, but still poorly documented on the continents. Indeed, little information exists on their impact on landscapes, whose configuration, dynamics, spatial expansion are inevitably intertwined with other factors at play at the regional and local scale.
In this contribution, we aim at reconstructing the evolution of sedimentary environments and landscapes in the Lower Omo Valley (Ethiopia) for the past four million years to provide a better understanding of the physical environments in which local biological and cultural evolutions took place. To do so, we investigated the evolution of sedimentary systems and landscape dynamics in the Lower Omo Valley combining a Landscape Evolution Model (Landlab) to constrain the input sediment flux with a stratigraphic forward model (DionisosFlow, Beicip-Franlab). To assess the consistency of model reconstructions, we compare model outputs to sedimentary architectures, volumes of eroded and deposited sediments and facies distribution derived from field observations and seismic data. Subsequently, we will present and discuss the roles of the different forcings, such as changes in precipitation and tectonic uplift, that drove the evolution of the sedimentary system.
How to cite: Poirier, P., Nutz, A., Godard, V., Granjeon, D., Schuster, M., Barboni, D., Gassier, G., and Boisserie, J.-R.: Evolution of sedimentary environments in an axial rift system: the Lower Omo Valley (Turkana Depression, Ethiopia) for the past four million years, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9522, https://doi.org/10.5194/egusphere-egu25-9522, 2025.
The Olorgesailie Basin in the South Kenya Rift preserves the oldest known evidence for the emergence of the Middle Stone Age (MSA) in eastern Africa between 320 and 295 ka. The MSA permanently replaced Acheulean technology in the South Kenya Rift following its persistence in the Olorgesailie Basin between 1.2 Ma and 500 ka. The transition in hominin technologies between 500 and 320 ka is significant as the MSA is typical of early Homo sapiens and is furthermore distinguished by novel behaviours like social exchange networks and symbolic communication. Contemporaneous with the emergence of the MSA was a turnover in mammal species in the South Kenya Rift – one of the largest Pleistocene turnovers recorded in East Africa – from large-bodied grazers to smaller-sized species of broader ecology. This fundamental biotic and behavioural shift suggests that considerable environmental change occurred in the region during that time. To test this hypothesis, we drilled the adjacent Koora basin and recovered a 139-m-long sediment core for evidence of past environmental dynamics in the South Rift. With 22 40Ar-39Ar ages we established the most-precisely dated core record for the past 1 Myr from East Africa. A combination of microfossil, isotope, geochemical, and sedimentological analyses was used to reconstruct freshwater availability, vegetation cover, hydroclimate and aquatic conditions. Diatom and XRF-elemental records indicate a phase of relatively stable high lake levels from 1 Ma to 470 ka dominated by freshwater conditions. The remainder of the record shows highly fluctuating lake levels with numerous periods of desiccation and shifting fresh to saline lake waters. Similarly, vegetation reconstruction based on phytoliths and carbon isotopes shows a mixed woody grassland environment, typical of savannas until 400 ka, followed by a phase in which rapid shifts between woody and grassland cover occurred, during which grassland composition shifted between C3 and C4 dominance. Collectively, the lake level and vegetation records point to highly variable moisture supply and associated disruptions in ecological resources after 400 ka, which impacted both hominins and mammal communities. We propose that a combination of climate variability and enhanced tectonic activity in the rift resulted in spatial and temporal variations in freshwater availability and habitats that favoured hominins and mammals with broader ecological flexibility and resilient adaptations.
How to cite: Dommain, R., Potts, R., Behrensmeyer, A. K., Deino, A., Riedl, S., deMenocal, P., Beverly, E., Kinyanjui, R., Lupien, R., Muiruri, V., Owen, R. B., Stockhecke, M., Brown, E., and Russell, J.: Disruptions in ecological resources as a driver for human and mammalian evolution in the South Kenya Rift: the 1 million-year-long Olorgesailie core record, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10624, https://doi.org/10.5194/egusphere-egu25-10624, 2025.
Whether excessive hunting of Homo sapiens caused the extinction of Late Pleistocene megafauna or whether deglacial climate change was the main culprit has remained a controversial issue. Previous studies have focused on statistical relationships between human arrival time and megafauna disappearance, but so far no quantitative dynamical model has been presented that addresses this important issue. Here we introduce a new dynamical Lotka Volterra reaction diffusion partial differential equation model that explicitly simulates biomass variations of 2178 mammal species (including H. sapiens) across the globe, as well as predator/prey relationships and competition. Key demographic parameters of this realistic model are estimated from allometric bodymass scaling relationships and the herbivore carrying capacity is obtained by combining habitat information and net primary information. The model simulates the patterns of key biological parameters, such as species richness, diversity, evenness and predator/prey relationships in close agreement to observational estimates. Changes in carrying capacity and climate parameters across the last glacial termination and into the Holocene have been estimated using the 3 million year transient paleo climate simulation conducted with the CESM1.2 earth system model at the IBS Center for Climate Physics. For Homo sapiens, the model also accounts for cultural carrying capacity. By turning on and off the human component during our transient simulations, we can determine the impact of agressive hunting on mammal populations and on megafauna in particular. Furthermore, by repeating these experiments for fixed climate time slices (Last Glacial Maximum, Mid Holocene), we can assess the climatic effect. Our model results demonstrate that 1) megafauna extinction was caused by excessive human predation, 2) in the absence of human hunting, there is no megafauna extinction, 3) deglacial climate change accelerates the overkill, because it increases the habitat suitability of humans in key areas of Eurasia.
How to cite: Timmermann, A., Venugopal, T., and Raia, P.: Quantifying the effects of climate change and human predation on the extinction of Late Pleistocene megafauna , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2929, https://doi.org/10.5194/egusphere-egu25-2929, 2025.
Posters on site: Mon, 28 Apr, 08:30–10:15 | Hall X5
The Human and Earth System Coupled Research (HESCOR) project at the University of Cologne aims to increase interdisciplinary discussion in research related to the Earth and Human Systems by collaborating across disciplines to create model-tested hypotheses and analyze data. Given the broad range of jargon and data from researchers across the humanities, natural sciences, and social sciences, HESCOR promotes methods that lower barriers and encourage interdisciplinary discourse and data sharing to better link often diverse and distinct data from different disciplines. Within HESCOR, clearly defined workflows, protocols, and a 3-tiered database serve as the foundation of the interdisciplinary process. Standard workflows and protocols help structure conversations and set expectations so that HESCOR researchers can continue interdisciplinary dialogue and documentation throughout data processing. By organizing HESCOR data in well-defined tiers (Tier I – standardized metadata, Tier II – reorganized and quality-controlled data within a HESCOR framework, and Tier III – interpreted data), the HESCOR Database reflects the research stages of data analysis – processing data for modelling along the way. This structure allows HESCOR members to better communicate data interpretations across academic fields and formulate models that can help reconstruct causal links between the Human and Earth Systems. The HESCOR database prioritizes uniform metadata, substantial documentation, and clearly defined interpretations to provide orderly data across the natural sciences, social sciences, and humanities applicable to a broader set of researchers. Utilizing a soon-to-be published Late Pleistocene paleoenvironmental record from Lake Nakuru, Kenya, we demonstrate the workflow created at HESCOR to increase communication across disciplines to further understanding of the interplay between the Human and Earth Systems.
How to cite: Robakiewicz, E., Schlüter, P., and Foerster, V.: The HESCOR Database: Bridging Human and Earth Science Data, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10919, https://doi.org/10.5194/egusphere-egu25-10919, 2025.
The Blombos Cave, located on the southern coast of South Africa, is a key site for understanding the behavioural evolution of modern humans during the Middle Stone Age. This study examines the seasonal timing of shellfish collection and the marine climate's seasonality near Blombos Cave through stable oxygen isotope analysis of the marine gastropod Turbo sarmaticus. By analyzing the δ18O values in sequential growth increments of T. sarmaticus shells from archaeological layers, we reconstruct past sea surface temperatures (SSTs) and infer patterns of human occupation over the period 100–70 ka. The δ18O data show distinct seasonal fluctuations in SSTs with an amplitude of approximately 4°C. These fluctuations are consistent with the present-day seasonal variation in sea surface temperatures at Blombos Cave, which is influenced by the interaction between the Agulhas Current (bringing warmer waters from the Indian Ocean) and the Benguela Current (bringing cooler waters from the Atlantic). The isotopic evidence also provides insight into the seasonality of human occupation at Blombos Cave. Preliminary findings suggest that early Homo sapiens primarily inhabited the site during the warmer seasons, likely focusing on marine resource exploitation at that time. Ongoing research will incorporate clumped isotope analysis to provide an independent temperature proxy, improving our estimates of past oxygen isotopic composition in coastal waters and enhancing reconstructions of SST and occupation seasonality.
How to cite: Andersson, C., Milic’, J., Göktürk, O., and van Niekerk, K.: Seasonal Timing of Shellfish Collection and Paleoenvironmental Reconstruction from Archaeological Shells at Blombos Cave, South Africa, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16739, https://doi.org/10.5194/egusphere-egu25-16739, 2025.
Archaeological culture reflects ancient human activities and cultural characteristics in a certain time and space, and its evolution process is of great significance to archaeological research and the exploration of civilization. In this paper, we took the Taihu Lake region in the lower Yangtze River of China during the Neolithic period as the research area (Fig.1). Based on the site information automatically obtained from the corresponding Chinese archaeological text data by the information extraction method in this research area, we adopted the complex network analysis method and constructed the network model for the four consecutive archaeological cultures of Majiabang, Songze, Liangzhu, and Maqiao, respectively, with the parameters of the cost distance between the sites calculated taking into account the topographical factors of the slope, undulation, etc.(Fig.2) The structural characteristics of prehistoric societies in the four different periods were deeply explored from three aspects: small-worldness, network accessibility and network stability. The law and trend of regional cultural evolution were analyzed. The results are as follows: (1) The Neolithic cultures of the circum-Taihu region as a whole exhibit the property of small-worldness, suggesting that prehistoric societies showed a homogeneous and uniform pattern of connections in the overall region. (2) The network structure of sites from Majiabang to Liangzhu period showed a tight and stable evolution trend. However, from Liangzhu to Maqiao period, the cultural development began to decline, showing signs of entering a depression. The archaeological cultural network model proposed in this paper provides a new way of thinking for quantitatively understanding the social structure and evolutionary laws of early human societies around the Taihu Lake area, and provides a quantitative analysis method for exploring the characteristics and laws of regional cultural evolution, and promotes scientific archaeological research by providing an important method.
Keywords：Taihu Lake in China; Neolithic period; Complex network model; Archaeological culture; Culture evolution
Fig.1 Schematic diagram of the area around Taihu Lake
Fig.2 Spatial structure network of archaeological sites (a) Majiabang culture; (b) Songze culture; (c) Liangzhu culture; (d) Maqiao culture
How to cite: Yang, L., Li, H., and Zhao, Y.: Network Model Construction and Evolution of Prehistoric Archaeological Cultures Based on Textual Data of Archaeological Sites—Taking Neolithic Archaeological Sites in Circum-Taihu Lake Region in China as an Example, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7973, https://doi.org/10.5194/egusphere-egu25-7973, 2025.
Reconstructing past wind directions is critical in constraining synoptic scale climate regimes in the geologic past. Such wider scale understanding of past climate helps frame the climatic and environmental conditions that past human populations were exposed to. This is particularly important in regions such as Сentral Asia, at the interface of a range of climate zones. Palaeolithic tools are extensively embedded within the loess-palaeosol sequences of the Khovaling Loess Plateau, Southern Tajikistan, yet little is known about the environmental conditions these hominin groups faced.
Magnetic techniques applied to loess-palaeosol sequences are particularly insightful for investigating dust transport dynamics and variations in the intensity of hydroclimate. Anisotropy of magnetic susceptibility (AMS) in particular measures the magnetic fabric, i.e., the orientation of magnetic particles in an oriented sample, which can provide insights into palaeowind directions and post-depositional processes. Here we apply AMS to three different loess-palaeosol sections of the Khovaling Loess Plateau, approximately spanning the past 1 Ma, in order to assess if this technique allows us to reconstruct palaeowind directions for this region of Central Asia.
Our results reveal the first palaeowind directions reconstructed for the Khovaling Loess Plateau. We present AMS data from three sites on the Khovaling Loess Plateau and demonstrate the potential and limitations of this data for reconstructing palaeowind directions. We investigate the question to which degree local winds, responsible for loess deposition on the Khovaling Loess Plateau, are related to broader atmospheric circulation patterns. We also explore how AMS data can be combined with other palaeoenvironmental proxies, such as frequency-dependent magnetic susceptibility as an indicator of palaeoprecipitation, and how this technique can be used to assess sediment reworking.
How to cite: Schneider, R., Kulakova, E., Almqvist, B., and Stevens, T.: Magnetic fabric of Tajik loess-palaeosols as a palaeowind and process indicator, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3636, https://doi.org/10.5194/egusphere-egu25-3636, 2025.
In recent years the use of aeolian sand influx (ASI) analyses on ombrotrophic peat sequences (c.f. Björck and Clemmensen, 2004) has become an increasingly popular method for reconstructing past storminess. This method is based on the assumption that all mineral grains deposited on the surface of the hydrologically isolated bog must have been brought to the site by wind. Thus, changes in the amount and size of the mineral grains found over time/depth can be related to past storm frequency and intensity. During the last two decades, several different methods of quantifying ASI have been developed. Three major drawbacks of these methods are that they are (i) often time- and labour intensive; (ii) rely on high temperature dry ashing to remove organic material from samples before ASI quantification and (iii) non-continuous, requiring discrete sampling.
In an attempt to address these issues, we investigate whether X-ray computed tomography (CT) can be used to count and measure sand grains in peat. Drawing from the methods used by Cederstrøm et al. (2021) for IRD quantification in marine sediments, we added known amounts of sand (manually counted) in certain grain size fractions (63-1000, 125-1000, 63-125, 125-250, 250-500 and 500-1000 µm) and with known grain size distributions (laser diffraction) to test peat samples. The samples were then CT-scanned at a voxel resolution of 27.5 µm, and in the resulting 3D imagery, sand grains were identified, counted and measured using basic image processing tools. Our preliminary results indicate that it is possible to reliably count and measure sand grains in peat using a CT-based method, especially for grain sizes larger than 4-5 voxels (≥125 µm in this study). Grain size distributions for peat samples with sand grains ≥125 µm acquired through the CT method are strongly correlated to standard laser diffraction results (r = 0.81–0.98, p < 0.01). Similarly, CT-based and manual grain counts show a strong correlation (r = 0.94–1.00, p < 0.01) and the number of grains counted using the CT method differs on average by only 4 % from manual counts. Early-stage trials with full peat sequences further indicate that CT could be a reliable and efficient method for quantifying ASI and reconstructing past storm variability.
References
Björck, S., Clemmensen, L., 2004. Aeolian sediment in raised bog deposits, Halland, SW Sweden: A new proxy record of Holocene winter storminess variation in southern Scandinavia? Holocene 14, 677–688. https://doi.org/10.1191/0959683604hl746rp
Cederstrøm, J.M., van der Bilt, W.G.M., Støren, E.W.N., Rutledal, S., 2021. Semi-automatic ice-rafted debris quantification with computed tomography. Paleoceanography and Paleoclimatology 36, e2021PA004293. https://doi.org/10.1029/2021PA004293
How to cite: Palmgren, Y., O'Regan, M., and Kylander, M.: Reconstructing storminess from aeolian sand influx to peat bogs using X-ray computed tomography, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10564, https://doi.org/10.5194/egusphere-egu25-10564, 2025.
The Mediterranean Sea is expected to be one of the regions most severely impacted by current and future climate change. In fact, it is already experiencing more frequent and severe hydro-extremes (floods and droughts), which are to be exacerbated in the near future, together with thermal-extremes (heat and cold waves) as yet to be evaluated in seasonality and predictability.
While past centennial-scale climate fluctuations in this region have already been investigated, however, little is known about higher frequency variability, i.e. variability at human timescales. This study aims to investigate the hydroclimate dynamics and Sea Surface Temperature (SST) variability over the past ~2,000 years at unprecedented temporal resolution, by using high-resolution biomarker analyses.
Therefore, we integrated Mass Spectrometry Imaging (MSI) and conventional alkenone analysis to achieve sub-annual to decadal resolution in SST reconstructions from marine sediments collected in the Western Mediterranean and the Tagus areas from the Iberian margin. MSI is further combined with elemental proxies derived from μXRF mapping, including indicators of continental input and marine productivity.
Preliminary results reveal significant centennial-scale SST fluctuations and hydroclimate variability over the past ~2,000 years, including climatic transitions such as the Late Little Ice Age (LaLIA; 6th–7th centuries), the Little Ice Age (LIA; ca. 13th–19th centuries) and the Post-Industrial period (19th century onwards). We will present an overview of how these transitions impacted interannual to decadal climate variability. Such knowledge will advance our understanding of climate dynamics and their regional consequences, which is essential for addressing the associated societal-economic challenges.
Acknowledgements: The project that gave rise to these results received the support of a fellowship from the ”la Caixa” Foundation (ID LCF/BQ/DI24/12070003).
How to cite: Kapiri, M.-S., Wörmer, L., Lebreiro, S., Liu, W., Platikanov, S., Rodrigues, T., Salgueiro, E., Tobias, A., Taubner, H., Wendt, J., Obreht, I., Ziveri, P., and Martrat, B.: Interannual to decadal climate variability during the past 2,000 years in the Western Mediterranean using Mass Spectrometry Imaging, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18824, https://doi.org/10.5194/egusphere-egu25-18824, 2025.
Hyperspectral imaging (HSI) is revolutionising sediment core analysis in environmental and geoscience research, providing high-resolution, non-destructive insights into biogeochemical processes. However, analysing the large, complex datasets generated by HSI requires specialised tools. Existing commercial solutions often lack flexibility and transparency, hindering open science practices.
To address this, we introduce napari-sediment, an open-source plugin for the napari image analysis platform. This plugin provides a user-friendly graphical interface to implement a complete workflow for hyperspectral sediment core analysis, including:
- Preprocessing: Background correction and noise reduction.
- Data exploration: Interactive visualisation and statistical analysis of spectral data.
- Endmember extraction: Identification of pure spectral signatures.
- Quantitative analysis: Calculation of spectral indices for substance quantification and visualisation of spatial distributions.
napari-sediment streamlines the analysis of hyperspectral sediment core data, enabling researchers to efficiently extract valuable information on pigment distributions, mineral composition (limited), and organic matter content (qualitative). By leveraging the napari framework, the plugin fosters reproducibility and collaboration in the growing field of hyperspectral sedimentology. Here, we demonstrate the capabilities of napari-sediment and highlight its potential for advancing paleoclimate research, environmental monitoring, and geological investigations.
How to cite: Zahajská, P., Witz, G., and Grosjean, M.: napari-sediment: An open-source plugin for hyperspectral sediment core analysis, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3814, https://doi.org/10.5194/egusphere-egu25-3814, 2025.
Alkenones in marine sediments are a key proxy for the reconstruction of past sea surface temperatures. Recent advances in mass spectrometry imaging (MSI) allow the Uk’37 proxy to be measured at the micrometer scale. Such high resolutions can theoretically provide a resolution similar to the observational record and hold the promise of reconstructing continuous climate records from subseasonal or interannual to centennial and millennial timescales. However, due to processes occurring during and after deposition, as well as the sampling and measurement procedures, it is unclear how much climate signal is preserved at these small spatial scales.
Here, we investigate this question using biomarker MSI on sediment records from the Santa Barbara Basin (SBB), a key site for Californian Current and Northeast Pacific SST reconstructions. We perform replicated MSI measurements on sediments with varying degrees of lamination to analyze the spatial structure and spatial reproducibility of the alkenone signal.
We find that biomarker distributions are spatially heterogeneous even within laminae but exhibit small scale clustering. Spatial maps exhibit increased similarity in submm scale and with longer ranges and less overall variability within laminated horizons.
These findings have implications for the conversion of spatial biomarker data to time series reconstructions, as spatial heterogeneity patterns can act as an additional noise source during processing but can be accounted for using optimized 2D map to 1D timeseries conversion methods.
Using the replicated setup, we can derive the signal content and independent noise levels across varying sediment conditions. For our MSI-derived SST reconstructions this leads to signal-to-noise ratios ranging from ~1-3 integrated SNR at interannual resolution to ~4-6 integrated SNR at subdecadal (ENSO) timescales. The resulting SNRs can be used to infer optimal sampling strategies to tailor the resolution to the desired timescales of the studies for MSI based reconstructions as well as for discrete, traditional sampling efforts.
The findings imply that MSI based alkenone Uk’37 records at SBB during the Holocene and late Pleistocene, supported by careful noise & uncertainty estimations, can provide an upper limit for the reconstruction of SST variability beyond the instrumental record.
How to cite: Viola, J., Wörmer, L., Hinrichs, K.-U., and Laepple, T.: Microscale Alkenone Heterogeneity and Replicability of Ultra-High-Resolution SST Proxies in Laminated Marine Sediments, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12973, https://doi.org/10.5194/egusphere-egu25-12973, 2025.
Understanding lithofacies, defined by distinct sedimentary characteristics, is fundamental for deciphering depositional processes and reconstructing paleo-environments. While conventional methods like visual core description and grain size analysis are widely employed, they often face challenges, such as incomplete observation of internal structures, discrete sampling intervals, and potential for subjective interpretations, which may hinder the accuracy of lithofacies identification. X-ray Computed Tomography (CT), a non-destructive, high-resolution, and widely applicable imaging technique, addresses these limitations by enabling three-dimensional visualization and quantitative analysis of sediment cores. This study evaluates the feasibility of CT in assisting lithofacies identification by analyzing two sediment cores from the Dapeng Bay region in southwestern Taiwan. Beyond its qualitative capability to reveal imperceptible structures, CT-derived parameters were employed to quantify sedimentary features, such as grain size variability and internal structures, including ratios of different CT-intensity ranges (indicating materials of varying density or composition), mean CT intensity, coefficient of variation, and morphological characteristics. By combining these parameters, fourteen lithofacies were identified and further grouped into three sedimentary facies: lagoonal, channel, and tidal flat. This facilitates the reconstruction of a 500-year depositional history, highlighting the transition from lagoonal to tidal flat systems and elucidating depositional mechanisms influenced by high-energy events. This study establishes an objective and standardized framework that integrates qualitative CT imaging with quantitative parameterization to assist lithofacies identification. By reliably capturing subtle sedimentary variations and enabling consistent application across multiple sediment cores, this approach also supports systematic examination of spatial coverage and provides valuable insights into sedimentary environments across temporal and spatial scales.
How to cite: Wu, Y.-H., Huang, J.-J. S., Yu, N.-T., Yen, J.-Y., Chyi, S.-J., and Chen, J.-H.: Enhancing Lithofacies Identification Through X-Ray Computed Tomography, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15147, https://doi.org/10.5194/egusphere-egu25-15147, 2025.
Annually laminated sediments (varves) are excellent paleoclimate archives because of their high temporal resolution and because they contain their own chronology that can be converted to calendar years. However, their studies can be tedious because they can be disturbed, irregular or very thin, sometimes less than a mm. Here we explore the potential of micro-computed tomography (µCT) to unlock paleoclimate signals from varved records.
First, we show the added value of performing varve counts and thickness measurements from a 3D volume instead of a randomly sampled single 2D plane that is commonly used.
Second, we investigate the possibility to obtain density measurements for each varve, allowing calculating annually resolved sediment fluxes in gr cm-2 a-1. To achieve this, we µCT-scanned several varved sequences containing sediments covering a wide range of density and extracted their linear attenuation. Then, discrete volumetric samples were subsampled, weighted, gradually dried every 30 minutes and µCT-scanned each time at two different incident energies. This allowed establishing a calibration of water content based on linear attenuation coefficients. Once the density and water content were obtained, the next step was to calculate the density and the mass accumulation rate for each varve.
This approach will pave the way for “forward modelling,” namely the modelling of climate indicators (proxy) contained in natural archives. This method is recognized as a way of improving paleoclimate reconstructions, as it is less sensitive to the non-linearity of the physical processes involved in the formation of proxies than the statistical models that are commonly used.
How to cite: Francus, P. and Jamba, M.-E.: Using micro-computed tomography (µCT) to measure annually resolved sediment fluxes in varved sediments, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7319, https://doi.org/10.5194/egusphere-egu25-7319, 2025.
Climate warming is projected to intensify the eutrophication and deoxygenation of lakes globally, exacerbating the already severe consequences for society and ecosystems. Sedimentary archives record the complex interplay between climate, lake mixing, algal production, nutrient dynamics, anoxia and related chemical feedback. However, eutrophication phases could be short-lived, and relevant changes may happen at sub-decadal timescales. Often, eutrophic or anoxic phases are preserved in a few centimetres of sediment and cannot be studied in detail with conventional methods. Imaging techniques aid in investigating eutrophication and deoxygenation in the past by providing continuous, high-resolution and very large data sets for statistical analysis. This study utilises high-resolution techniques — hyperspectral imaging and X-ray fluorescence — to analyse hysteresis behaviour, leads and lags among drivers and responses, and temperature-eutrophication-anoxia relationships in the well-dated Late-Glacial lacustrine sediments of Soppensee (Switzerland).
Soppensee got eutrophic and developed anoxia during the second half of the Bølling. Phosphorus (P) was efficiently recycled (reductive dissolution) further fuelling eutrophication. Eutrophication lagged warming by 300 years suggesting that warm temperatures were pre-conditional to eutrophication and anoxia while not directly triggering it; Instead, eutrophication responded non-linearly to vegetation dynamics and tree cover around the lake, exhibiting a threshold at 75% tree pollen (TP) and showing hysteresis behaviour. At the onset of eutrophication, the response of anoxia was immediate. Cyanobacteria bloomed with a lead of ~50 years before other phototrophic primary producers, highlighting their potential role as early ecosystem pioneers.
When eutrophication decreased due to landscape opening (TP < 75%) caused by a cold interval (GI1d, Older Dryas), the lake became well-mixed, and P started to become sequestered in sediments, further remediating lake eutrophication. During the warm phases of the Allerød, two more eutrophic and anoxic phases occurred. However, their amplitudes further decreased due to the effective sequestration of P (suppressed chemical feedback). Eutrophication disappeared at the start of the Younger Dryas when the landscape opened, and the lake was well mixed.
This high-resolution study demonstrates the potential of sedimentary imaging techniques to detect short-lived events, rapid regime shifts, leads and lags between forcing and responses in ancient ecosystems.
How to cite: Schouten, S., Zahajská, P., and Grosjean, M.: High-Resolution Insights into Climate-Eutrophication-Anoxia Interactions in Late-Glacial Soppensee , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5809, https://doi.org/10.5194/egusphere-egu25-5809, 2025.
Mg/Ca and δ18O in foraminiferal shells are the most commonly used paleoclimate proxies for ocean temperature, salinity, and global ice volume. It is hypothesized that preferential dissolution of more soluble shell features and heterogenous shell chemistry as well as recrystallization can alter original shell chemistry as foraminifera sink below the lysocline into the deep ocean to be deposited as sediments. Core top studies have provided valuable insight into this process using closely grouped core tops with similar calcification conditions at the sea surface and different bottom water carbonate chemistry. They have proposed corrections for downcore Mg/Ca and/or δ18O based paleoclimate records using size normalized shell weights or past carbonate chemistry. However, it is impossible to unequivocally disentangle the effects of original calcification conditions and dissolution on core top shell chemistry at multiple sites. Recent studies have shown that foraminiferal shell dissolution can be simulated through lab-based experiments and dissolution intensity constrained using X-ray microcomputed tomography (Micro-CT) scans of the dissolved shells. We investigated dissolution effects by simulating dissolution of Neogloboquadrina pachyderma, the dominant polar foraminiferal species. Living N. pachyderma were collected from one station in the Greenland Sea via plankton tows and frozen at -80°C prior to dissolution experiments. Aliquots of 200 and 300 picked shells were dissolved in acidified Labrador Sea bottom water on a shaker table for two and three days respectively. An additional 189 shells were kept undissolved as a control. Micro-CT scans show that the average percentage of low-density calcite increased from 33.3 ± 3.6% for the undissolved shells, to 39.2 ± 4.3% for the two-day dissolved shells, to 44.8 ± 6.5% for the three-day dissolved shells, demonstrating an increase in dissolution intensity with an increase in dissolution time. We present δ18O and solution and LA-ICPMS based Mg/Ca results from the experiments that constrain the impact of dissolution on foraminiferal shell chemistry and propose a new framework for handling dissolution when generating foraminiferal chemistry-based paleoclimate records.
How to cite: Weiss, T., Morley, A., Fabbrini, A., Ninnemann, U., Foster, G., and Brown, R.: Experimental Constraints on the Impact of Shell Dissolution on the Mg/Ca Temperature Relationship in the Polar Foraminifera Species Neogloboquadrina pachyderma, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19047, https://doi.org/10.5194/egusphere-egu25-19047, 2025.
