We invite contributions that use sedimentological, geochemical, biological, and chronological tools in lake systems and their sedimentary records. Contributions should aim to deduce quantitative and spatial rates of change, causes and consequences of long- and short-term climate variability, and/or assess the impact, magnitude, and frequency of tectonic and volcanic activities in these systems. We particularly encourage submissions about novel analytical approaches (destructive and non-destructive) and data analysis (statistics, machine learning, AI) that guide future research directions in limnogeology.
Nitrogen (N) is a central component of all organisms, making it a key element in the production of organic matter in lakes. However, excessive bioavailable N originating from waste water or fertilizer input can exacerbate eutrophication, reduce oxygen levels, and promote the growth of toxic algal blooms. Understanding the sources, sinks, and internal cycling of N in lacustrine environments, both today and in the past, is crucial for providing paleolimnological information that can be related to past environmental changes. Traditionally, past changes in the lacustrine N cycle have been reconstructed using bulk sedimentary N isotope (δ15N) analyses. While this approach is relatively inexpensive and fast, it is widely known that bulk sediment δ15N values can be biased by diagenetic alteration and external organic and inorganic (e.g., clay-bound) N input. Here, we introduce a proxy that is relatively new to limnogeology, overcomes these issues, and has successfully been applied in paleoceanographic reconstructions for over two decades: diatom-bound nitrogen isotope ratios. The siliceous shells (called frustules) of diatoms contain small amounts of organic matter, whose nitrogen isotope composition is thought to be protected from diagenetic alteration and bacterial degradation. Previous studies have shown that the diatom-bound N isotopic composition correlates with the N isotopic composition of nitrate in the surface waters, which the diatoms assimilated during growth. Since the N isotopic composition of surface-water nitrate directly depends on N inputs/outputs (i.e., size of N fluxes and their respective δ15N), as well as internal N cycling processes, which all have a distinct impact on the N isotopic signature, diatom-bound δ15N can be used to infer past changes in the lacustrine N cycle.
Here, we present the first lacustrine application of the diatom-bound N isotope paleo-proxy, reconstructing nutrient cycling and paleoenvironmental conditions over the past centuries in Swiss lakes. In Lake Lugano (Switzerland), for example, we demonstrated that denitrification and N2 fixation were tightly coupled during the peak eutrophication period, and that changing redox conditions in the sediment influenced the extent of N-isotopic alteration of the bulk sediment (Studer et al., 2024). Furthermore, we will present our team's recent efforts to further ground-truth the diatom-bound N isotope proxy, including (i) data from natural lacustrine environments that provide insights into the acquisition of the diatom-bound N isotope signature during diatom growth, and (ii) data from degradation experiments under controlled laboratory conditions that address the resilience of the diatom-bound N isotope signature against early diagenetic alteration.
References
Studer, A.S., Wörmer, L., Vogel, H., Dubois, N., Hinrichs, K.-U., Bartosiewicz, M., Lepori, F., Lehmann, M.F. 2024. First lacustrine application of the diatom-bound nitrogen isotope paleo-proxy reveals coupling of denitrification and N2 fixation in a hyper-eutrophic lake. Limnology and Oceanography, 69, 1797-1809. https://doi.org/10.1002/lno.12627
How to cite: Studer, A. S., Millet, J., Baan, J., and Lehmann, M. F.: Diatom-bound nitrogen isotope ratios: A novel proxy in limnogeology for the reconstruction of the lacustrine nitrogen cycle, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11016, https://doi.org/10.5194/egusphere-egu25-11016, 2025.
Paleolake beach ridges, formed by wave-piled sediment, are exceptional markers of ancient lake-stands, providing critical proxies for paleohydrology. In dryland environments, where water is presently scarce and lakes are predominantly shallow and ephemeral, these proxies offer evidence of past wetter periods and potential insights into future hydrological scenarios. However, the atmospheric conditions responsible for the wind- and wave-storms that create beach ridges in shallow lakes remain uncertain. To investigate these conditions, we analysed the largest desert lake in the world, Kati Thanda-Lake Eyre (KT-LE) in Australia. We explored the factors behind ridge formation by combining wave modelling simulations driven by atmospheric reanalysis data with optically stimulated luminescence (OSL) dating of the lake’s historical shorelines. Our analysis focused on 12 of the most intense wind- and wave-storms, selected from a dataset of over 1,000 identified windstorms recorded between 1950 and 2023. We found that significant lake waves are predominantly generated by a synoptic dipole pattern, characterised by a high-pressure gradient between a cyclone and an anticyclone over southern Australia, often amplified by the passage of an atmospheric front. This pattern produces high-magnitude (>10 m s-1) southerly winds, driving waves that can exceed 0.75 m in significant wave height. Despite these findings, wave simulations based on historical water depth observations suggest that no single storm was likely responsible for the formation of KT-LE's modern beach ridge. This conclusion is further supported by OSL dating and high-resolution topographic analyses, showing composite barrier landforms with regressional features. The OSL chronology indicates that some sections of the modern barrier or paleo-shoreline are effectively “modern,” as evidenced by their very low residual OSL signal, while other locations preserve beach deposits that are centuries old. These findings suggest that the formation of the modern shoreline is most likely the result of cumulative sediment deposition over multiple windstorms, rather than a single large storm event. While the precise mechanisms behind the construction of such shorelines during the late-Pleistocene and Holocene remain uncertain, our study identifies potential atmospheric conditions involved and highlights the processes shaping desert lake systems.
How to cite: Armon, M., Bantouna, A.-P., Sprenger, M., and Cohen, T.: Unravelling the Winds of the Past: Atmospheric Drivers of Beach Ridge Formation in Kati Thanda-Lake Eyre, Australia, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4966, https://doi.org/10.5194/egusphere-egu25-4966, 2025.
The impacts of extreme coastal events (ECEs), such as marine inundations or extreme wind events, on lake ecosystems vary widely from minimal to catastrophic. Accurately predicting the response of a specific system remains challenging due to a limited understanding of the attributes that drive the resilience of lakes. In an attempt to better understand the possible impacts of ECEs on shallow brackish lakes, we employed a paleolimnological approach to reconstruct the responses of Broad Pond to four ECEs identifiable from clear sedimentary markers and dated to ca. 1740, 1790, 1862, and 1993 CE. We aimed to evaluate the overall impacts of ECEs on Broad Pond and their specific effects on various hydrobiont groups. We investigated the sediment core covering the last ca. 400 years by examining terrestrial and aquatic pollen, spores and nonpollen palynomorphs, cladocerans, chironomids, and diatoms. Overall, Broad Pond exhibited resilient responses to ECEs, as indicated by mostly limited compositional turnovers in our proxy records. Statistically significant relationships between species composition and ECEs were observed only for diatoms. The only prolonged change identified is the spread of previously near-absent chironomids in the aftermath of a slight lake refreshment likely associated with the ca. 1740 CE event. This event was also followed by a short-lived (ca. 15 years) five-fold increase in the abundance of Scenedesmus that could have been triggered by the effects of the ECE on nutrient availability. The impact of the remaining three ECEs was discernible only in the diatom record, consistently showing a decline in two calcifobic and oligotrophic species, Achnanthidium petersenii and Platessa oblongella, also evident for the ca. 1740 CE event. The relatively minor ecosystem alteration induced by ECEs in Broad Pond lacks a single explanation and requires consideration of multiple site- and event-specific factors.
How to cite: Pleskot, K., Cwynar, L., Kołaczek, P., Gruszczyńska, A., Suchora, M., Kowalczyk, C., and Kokociński, M.: Impact of extreme coastal events on a brackish lake on the Burin Peninsula, Newfoundland, Canada, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6150, https://doi.org/10.5194/egusphere-egu25-6150, 2025.
The Es4S section of the Paleocene in the Dongying Depression of the Bohai Bay Basin represents semi-saline lake-phase deposition, characterized by the development of thick shale layers spanning hundreds of meters. Due to paleoenvironmental fluctuations, the shale facies exhibit frequent and complex changes within the high-frequency lake-phase gyres, leading to significant heterogeneity in the shale reservoirs. This complexity poses challenges to the systematic exploration and development of shale oil resources. To investigate the relationships between shale lithological assemblages, high-frequency cycles (HF cycles), and paleoenvironmental changes, core samples from coring wells in the study area were analyzed using various methods, including core observation, XRF and GR scanning, thin-section analysis, XRD of whole-rock samples, and organic carbon and elemental geochemistry studies. The following insights were obtained: (i) Within the six-stage high-frequency sedimentary cycles, shale primarily deposits carbonate minerals during arid phases and clay minerals during wet phases. Grain layer thickness increases under conditions of extreme drought or extreme wetness. (ii) Shales showed an increased deposition of feldspathic minerals during periods of strong source supply, whereas carbonate mineral deposition was dominant during weaker source supply conditions. (iii) A palaeoclimate indicator and a palaeo-source indicator were developed based on mineral content ratios. Using these indicators, the Es4S section was classified into four four-level sedimentary cycles. The palaeoclimate evolution exhibited a progression from arid to semi-arid, semi-arid to semi-humid, and back to semi-arid conditions, accompanied by a gradual weakening of material source supply. This study introduces a novel approach to reconstructing palaeoenvironments in lacustrine shales, offering valuable insights for guiding shale facies development.
How to cite: Yin, Z., Wang, G., Zhang, Y., and Bai, Y.: Paleoenvironmental reconstruction of lacustrine shale under high-frequency cyclonic constraints --an example from the upper subsection of the fourth section of the Shahejie Formation (Es4S) in the Dongying Depression, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8381, https://doi.org/10.5194/egusphere-egu25-8381, 2025.
Lake Baikal is the world's oldest lake, lying in a rift zone in south eastern Siberia that began to form over 20 million years ago. In addition to containing c. 20% of global surface freshwater, the lake contains a high degree of biodiversity with over 2,500 flora and fauna, the majority of which are endemic. As such, Lake Baikal is cited as the “most outstanding example of a freshwater ecosystem” and this, together with its high level of endemicity, led to the lake being designated a World Heritage Site in 1996.
Industrial development, changes in catchment land-use and anthropogenic climate change raise serious concerns over the future sustainability of the lake's unique ecosystem. This presentation combines new chlorophyll and carotenoid pigment analyses from sediment cores across the lake, together with geochemical and observational records from the region, to document how the ecosystem and limnological conditions of Lake Baikal have evolved over the last 2,000 years.
With results showing that significant changes in the lake ecosystem began in the 20th Century, we assess the extent to which these changes can be attributed to economic development in Lake Baikal’s catchment and/or to global anthropogenic climate change. Our findings show a clear link between changes in the lake biotic assemblages and climate change, driven by declines in seasonal lake ice-cover over the last 100 years.
How to cite: Swann, G., Roberts, S., Panizzo, V., Mackay, A., Vologina, E., Piotrowska, N., Sturm, M., and McGowan, S.: Constraining the environmental and anthropogenic impacts on Lake Baikal: the world’s oldest lake, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16245, https://doi.org/10.5194/egusphere-egu25-16245, 2025.
Lake sediments are excellent natural archives of environmental change. These records provide valuable insights for predicting the potential impacts of future changes, particularly in the context of anthropogenic climate change and biodiversity loss. Tropical high-mountain regions, known as biodiversity hotspots, are particularly vulnerable to climate change, with profound implications for the ecosystems and millions of people who rely on their resources and services. To better understand the landscape evolution and past environmental change in the northern Andes, we analyzed lake sediment archives from three areas near Ecuador's capital, Quito, located at elevations of 3000-4000 m a.s.l. Our pilot study combined sub-bottom profiling (SBP) with a multi-proxy analysis of short sediment cores from lakes San Pablo, Muertepungo (SBP only), and Caricocha and Chiriyacu in the Mojanda Lake Region. All of these lakes are of different volcanic origins: Caricocha is a caldera lake, San Pablo developed from a flank collapse, and Muertepungo was formed by blockage from a lava flow.
In this contribution, we focus on SBP data to understand the bathymetry (first record for Muertepungo), morphology, and sediment infill characteristics of the studied lakes, providing a first interpretation of the sedimentary evolution. An Innomar “compact” parametric sediment profiler was used to record sub-bottom profiles in lakes with maximum water depths ranging from a few meters to more than 100 m. Stratigraphic correlation was supported by five short sediment cores collected from different water depths. Radiocarbon and tephra analysis was used to establish a chronological framework. Preliminary results indicate differences in sediment properties and thicknesses, as well as distinct layering patters, possibly linked to past environmental conditions such as shifts in water levels, temperature, trophic state and other factors.
The long-term goal of the pilot study is to integrate the findings on lake evolution with local knowledge, fostering a collaborative transdisciplinary approach to address the impacts of climate change and biodiversity loss while supporting adaptative strategies for the future.
How to cite: Feist, L., Heyer, B., Karius, V., Halaś, A., Słowiński, M., Pérez, L., Mothes, P., Velarde-Cruz, E., Valdés-Uribe, A., Mariscal Chávez, A., and Dietze, E.: Reconstructing Landscape Changes in the Northern Ecuadorian Andes using Lake Sediment Archives, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10439, https://doi.org/10.5194/egusphere-egu25-10439, 2025.
Intramountain basins serve as records of paleoclimatic, paleobiogeographic and tectonic histories of past continental environments. This offers a crucial glimpse into the evolution orogens during and after the main mountain-building phase, and their effect on modifying local climatic and environmental conditions. In this work, we test the hypothesis that the Dinarides significantly influenced the development of a rain shadow, leaving the range's eastern flank (Internal Dinarides) dry during the Miocene Climatic Optimum. We do so by looking at the lacustrine successions of the Serbian Lake System (SLS), stretching across the eastern flank of the mountain range. We conducted outcrop and core logging in the Valjevo-Mionica Basin (VMB, western Serbia), as well as LA-ICP-MS U-Pb dating of intercalated tuff layers, to assess the effects of global vs regional climate change on basin development and the correlation with regional tectonic events. The basin fill consists of polymict conglomerates and sandstones in the lower part, followed by laminated marls with microbial mat intercalations and tufa deposits. In the middle part, laminated to massive marls predominate. The upper part comprises dolomitic marlstones with evaporitic minerals (notably searlesite and analcime), and sandstone intercalations, pointing to an arid climate. Radiometric dating of intercalated volcanic ash horizons implies lacustrine conditions developing after ~14.5 Ma and persisting until the Sarmatian, correlating with the global cooling trend of the Middle Miocene climatic transition (MMCT) and opening of the neighbouring Pannonian Basin. In contrast to several other intramountain basins in the region, our new data from the VMB suggest the arid phase in the Internal Dinarides was likely induced by the MMCT, post-dating the MCO. Considering published sedimentological, radiometric and paleontological datasets, this study implies that a prolonged arid phase affected the Internal Dinarides during MCO and MMCT. During the MCO, the arid phase was likely caused by tectonic influences on the local climate. Later, the MMCT helped maintain the arid environment.
How to cite: Šamarija, R., Andrić-Tomašević, N., Mandic, O., Bradić-Milinović, K., Zeh, A., Rundić, L., Potić, B., Arifović, A., and Schwotzer, M.: Depositional evolution of the Valjevo-Mionica Basin (Internal Dinarides, Serbia) revealed through U-Pb zircon dating: correlation with regional tectonics and Miocene climate change, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19132, https://doi.org/10.5194/egusphere-egu25-19132, 2025.
Earthquakes imprint their signatures on lake sediments through event deposits, which serve as paleoseismological archives. Among these deposits, homogenite layers are commonly associated with lake oscillations, i.e., seiches. Here, we investigate the seiche mechanism and the formation of homogenite related sediment deposit within a lacustrine environment. This study focuses on the 1822 CE earthquake in the Western European Alps, which triggered subaqueous landslides in Lake Bourget (France). This event caused oscillations in the lake's water, which subsequently resulted in the formation of a homogenite layer in the deep basin. The underlying mechanism is resolved by presenting the first comprehensive numerical model via coupling coseismic displacement, seismic wave propagation, and mass movement with the tsunami model. The numerical simulations show excellent agreement with the geological and historical observations. The water disturbances caused by subaqueous landslides generated small tsunami waves with a maximum runup height of approximately 2.5 m. By analyzing the tsunami signals via Fourier spectral analysis and fast iterative filtering, we determined that seismic waves are the primary drivers of seiche, which excite the natural modes of Lake Bourget. Our findings confirm that the sediments found in the deep basin originated from one main subaqueous landslide and from tsunami erosion of littoral sands (backwash). However, the seismically induced seiche was solely responsible for keeping the fine-grained sediment cloud in suspension for several days and led to the formation of the homogenite layer (or seiche deposit) with typical grain orientation characteristics and could also be effective in identifying whether landslides or delta collapses (linked to homogenite/megaturbidites) in closed lakes were triggered by seismic or nonseismic sources which is crucial for reconstructing the history of past earthquakes and associated hazards.
How to cite: Zafar, M. N., Sabatier, P., Dutykh, D., Jomard, H., Rapuc, W., Lajeunesse, P., and Chapron, E.: Modeling earthquake-induced seiche process and subsequent homogenite deposits in lacustrine setting, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2461, https://doi.org/10.5194/egusphere-egu25-2461, 2025.
The East Eifel Volcanic Field (EEVF) in the west of Germany has received increased scientific attention in recent years due to new findings on ongoing deep magma-related seismicity and regional uplift. The most recent volcanic event in the EEVF was the eruption of the Laacher See Volcano around 13 ka BP, which is well-studied in central Europe due to the Laacher See Tephra frequently being used as a regional chronostratigraphic marker. This eruption event featured several phreatomagmatic and Plinian phases, as well as vent migration and magma chamber collapse, resulting in the formation of a caldera which subsequently filled with groundwater to form a lake. Present-day activity of the Laacher See system is evidenced by degassing vents in the lake and along its shores, emitting CO2 of magmatic origin. Although the Laacher See Eruption has been the topic of many studies in the past, the structure and infill of the caldera has not yet been fully documented. During two surveys at Laacher See in 2019 and 2021, several types of geophysical data were collected to investigate the lake floor and subsurface. High-resolution seismic reflection profiles were acquired with different acoustic sources, using different frequencies. These profiles were used to construct a seismic stratigraphy of the lake's sedimentary infill. Additionally, a multibeam echosounder was used to produce a high-resolution bathymetric map of the lake floor. Our results show two vent-shaped subbasins within the caldera depression, which are mostly filled with acoustically laminated sediment, reaching a thickness of at least 50 m in the northernmost subbasin. Several stratigraphic units can be distinguished, which are not always evenly distributed across the different subbasins, pointing at different phases of basin infill. In the central part of the lake, we identify a large gas accumulation zone through enhanced reflections and acoustic blanking, preventing visualization of the basin infill and structure underneath. Along the slopes of the lake, the lake sediments often contain mass-transport deposits, occurring along at least 9 different stratigraphic horizons. In order to reconstruct the sedimentation history of the lake since the 13 ka BP eruption, a total of 4 sediment cores were taken during coring surveys in 2019 and 2023, with recoveries between ~3.5 and ~8.5 meter below the lake floor. These sediment cores will be integrated with the reflection seismic data to further characterize different phases of sedimentation in the lake. The acquired data shows promising results that will help to reconstruct the sedimentary evolution of Laacher See since its eruption and aid in a better understanding of the caldera formation and structure, and its sedimentary infill history.
How to cite: Albers, S., Vandorpe, T., Caudron, C., Schmidt, B., Van Daele, M., Ritter, J., Reicherter, K., and De Batist, M.: Seismic and sedimentological characterization of the post-eruption infill of the Laacher See caldera lake in Germany, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1389, https://doi.org/10.5194/egusphere-egu25-1389, 2025.
This study focuses on the carbonate-laminated mud-shale from the upper segment of the Sha-4 Formation in the Fengshen area of the Dongying Depression. Employing a comprehensive suite of analytical techniques, including X-ray whole-rock diffraction, pyrolysis experiments, core scanning, thin-section analysis, and well logging curve analysis, we conducted an in-depth investigation of mudstone samples from a depth range of 3573.00m to 3637.86m. The research revealed that the primary mineral compositions of the mud-shale in this region include carbonate minerals (such as calcite and dolomite), clay minerals, quartz, along with minor amounts of feldspar, anhydrite, siderite, and pyrite. Quartz, as the most common terrigenous detrital mineral, comprises between 4% and 35% of the samples, with an average content of 22.72%.
By integrating thin-section identification with core scanning results, three fundamental types of laminae were identified: felsic laminae, clay mineral laminae, and carbonate laminae. Further, three binary combinations of laminae were distinguished: "organic-rich + micritic calcitic," "organic-rich + aragonitic," and "organic-rich + felsic." These distinct laminae types reflect the diagenetic processes occurring under different depositional environments.
The study found that the distribution of carbonate laminae within the mud-shale exhibits pronounced heterogeneity, with individual layer thicknesses primarily ranging from 1mm to 10mm, a development frequency of 50 to 350 layers per meter, and occupying 7% to 100% of the total mud-shale thickness. Notably, the thickness distribution of carbonate laminae shows a power-law characteristic, conforming to fractal geometry principles, which can be described using the N-S (Number-Size) model. According to this model, the number of layers and cumulative thickness of carbonate laminae in different thickness intervals can be calculated, with estimated values closely matching the actual measurements, thereby validating the effectiveness of the N-S model.
Moreover, the study demonstrated a positive correlation between the fractal dimension value D of carbonate laminae and their heterogeneity; that is, carbonate laminae with stronger heterogeneity have higher fractal dimension values D, and vice versa. This characteristic makes the fractal dimension value D an effective indicator for determining shale lithofacies types and their depositional environments, aiding in the reconstruction of paleoenvironments and identifying potential hydrocarbon enrichment zones, providing crucial scientific support for the exploration and development of shale oil and gas resources.
In summary, this study not only deepens our understanding of the types of laminae and their vertical heterogeneity in the mud-shale of the upper segment of the Sha-4 Formation in the Fengshen area of the Dongying Depression but also establishes a distribution model for carbonate laminae based on fractal characteristics. This provides valuable reference materials for subsequent geological studies and assessments of hydrocarbon resources.
How to cite: Feng, C., Zhang, L., and Yan, Y.: Types of Carbonate Laminations and Characteristics of Vertical Heterogeneity Distribution in the Fengshen Area of the Dongying Depression, China, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1358, https://doi.org/10.5194/egusphere-egu25-1358, 2025.
Sublacustrine spring activity in karstic lakes, including variations in discharge rates and patterns, has been shown in previous studies to correlate with both climate change and local neotectonic activity. This study aims at better understanding the influence of the interplay between karst groundwater dynamics and environmental drivers on sediment deposits in the small groundwater-fed lake Hintersteiner See (lake surface = 56.6 ha, max. depth = 39.78 m), located at the foothills of the mountain massif Wilder Kaiser in the Northern Calcareous Alps.
Recent multibeam bathymetry mapping has revealed multiple pockmarks and the lake´s sedimentary record is hypothesized to comprise a high-resolution record for paleo-environmental, paleo-hydrogeological and, possibly, paleoseismic activity.
Here, we present initial results from high-resolution reflection seismic, water column sampling and sediment coring surveys, along with subsequent multi-method stratigraphic, sedimentological and geochemical analyses, to investigate sedimentary evidence of high sublacustrine groundwater discharge and subaqueous landslides events in Hintersteiner See.
Mapped pockmarks are up to 8.5 m in diameter and 3 m deep and occur predominantly on the northwestern, more gently dipping and terraced slope, characterized by buried scarps and irregular bulges. A seismic profile across this pockmark evidences reflector truncation and interbedded high-amplitude reflection adjacent to the pockmark, indicating variable ground-water discharge activity eroding overlying lake sediments and possible sediment extrusion events. In the deep and flat depocenter of the lake seismic profiles indicate several stratigraphic horizons comprising Mass Transport Deposits (MTDs), some of which indicating that multiple simultaneous slope failures have occurred, possibly caused by past earthquakes.
Sediment cores recovered adjacent to the pockmarks, on both sides, show a 5 cm thick layer with increased density and magnetic susceptibility values, comprising a sharp coarser base and upward fining, and composed mainly of detrital carbonate silt. This layer stratigraphically correlates with the high-amplitude reflection in the seismic data and is interpreted to be genetically linked to an elevated groundwater discharge and sediment expulsion event in the pockmark. Ongoing analyses, including radiocarbon dating, aim to establish a precise temporal framework for the observed sedimentary events, to improve our understanding of high groundwater discharge and subsurface sediment mobilization processes and test links to environmental and tectonic drivers.
How to cite: Rössl, H., Kaiser, K., Schletterer, M., Moernaut, J., and Strasser, M.: Sedimentary Evidence of High Sublacustrine Groundwater Discharge and Subaqueous Landslide Events in Hintersteiner See, Austria , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6184, https://doi.org/10.5194/egusphere-egu25-6184, 2025.
High-quality source rocks are the material basis for the formation of oil and gas enrichment. Exploring the development mechanism of high-quality source rocks is of great significance for the selection of potential hydrocarbon-rich depressions. By comprehensively applying geochemical and seismic data, and combining the tectonic evolution and sedimentary background of the depression, the paleolake environment and development model of the high-quality source rocks of the Wenchang Formation in the hydrocarbon-rich depression of the Zhu I Depression were analyzed.
The research shows that the coupling of medium and small-scale sedimentary material input and fault activity controlled the development of deep and semi-deep lakes; a warm and humid climate was a prerequisite for the vigorous growth of aquatic planktonic algae; the input of nutrients such as deep hydrothermal activities, volcanic ash, and granitic sedimentary materials enhanced the initial productivity of the lake basin; and two development models of high-quality source rocks were formed: the "productivity - preservation conditions" co-controlled type and the "preservation conditions" mainly controlled type. Among them, when there is both magmatic activity and terrestrial input of nutrients in the deep and semi-deep lakes, it has a high initial productivity and good preservation conditions, which is the best model for the development of high-quality source rocks.
How to cite: Li, H., Liu, H., Peng, G., and Long, Z.: Paleolacustrine environment and development pattern of high-quality source rock of Eocene the hydrocarbon-rich depression of Zhu I depression, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8262, https://doi.org/10.5194/egusphere-egu25-8262, 2025.
In Grünbach-Neue Welt (Lower Austria), the Campanian portion of the Gosau Group is exposed along the boundary between the Northern Calcareous Alps and the Vienna Basin, including the Grünbach Formation (Lower Campanian) and the Piesting Formation (Upper Campanian). The paleoenvironment exhibits transitions from terrestrial to shallow marine settings, driven primarily by subsidence and relative sea-level fluctuations. However, the detailed processes governing this depositional environment transition have not been thoroughly studied. To address this gap, this study collected sediment samples from the transitional section across the two formations, including two artificial trenches and one outcrop in Maiersdorf, as well as one outcrop in the Lupard Quarry. Lithological, paleontological, mineralogical, and geochemical characteristics were analyzed comprehensively to reconstruct the paleoenvironmental evolution. The upper Grünbach Formation, characterized by variable clastic beds interspersed with coal layers, was deposited in a predominantly terrestrial environment with occasional marine influences. In contrast, the lower Piesting Formation, composed of fine- to coarse-grained sandstones containing orbitoids and bivalve fragments, indicates deposition in a shallow marine environment. Geochemical analyses corroborate the environmental transition of the strata, highlighting a shift from terrestrial conditions with intermittent marine influences to a shallow marine setting with ongoing terrestrial input. The sediment source remained strongly altered and relatively consistent during the mid-Campanian, although changes in depositional environment and the effects of marine transgression likely affected sediment composition. This study provides a detailed examination of the paleoenvironmental and provenance characteristics of the Campanian Gosau Group in Austria. It offers better insights into the change of depositional environments driven by tectonic subsidence, sea-level fluctuation, and associated marine transgressions during the Campanian.
How to cite: Xiang, X., Lee, E. Y., and Michael, W.: Sedimentary and Geochemical Records of Paleoenvironmental transition in the Campanian Gosau Group, Grünbach-Neue Welt, Austria, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10424, https://doi.org/10.5194/egusphere-egu25-10424, 2025.
Located in the eastern branch of the East African Rift System, the Turkana Basin preserves an exceptional archive of eastern African climate and primate (especially hominin) evolution over the last 20 Ma. As a desert lake, Lake Turkana experiences intense evaporative loss that results in 18O enrichment relative to its tributaries. During the wet season, the discharge from the Omo River increases causing the entire lake to become less enriched in 18O, especially near the river’s mouth. Ostracods, a class of sand-sized crustaceans that produce molts every few months, record the δ18O and temperature fluctuations in their shells. By analyzing δ18O from a large number of individual ostracod valves, we determined the spread in δ18O from an assemblage to reconstruct past seasonal intensity. We attribute the spread in δ18O to seasonal runoff changes rather than evaporation as water temperatures remain relatively constant throughout the year.
Previous studies indicate that increased tropical solar insolation intensifies the eastern African monsoon and boosts overall humidity. The mechanisms through which this increase in rainfall manifests over seasonal timescales remain poorly understood. If high insolation is correlated with a large δ18O spread in the lake, it would suggest a stronger seasonal signal with concentrated rainfall in the wet season (low δ18O) and intense evaporation (leading to 18O enrichment) in the dry season. We compared the δ18O spread among Limnocythere from the Galana Boi (Southwest Turkana 13-11 kyrs) and Kibish (Omo River-Kibish Member II, 194-104 kyrs) Formations. The dominance of Limnocythere in both the Kibish (100% of ostracods) and Galana Boi (87% of ostracods) assemblages suggests that waters were alkaline with high concentrations of sodium carbonate. The Limnocythere from Kibish (n = 25) showed a larger standard deviation in δ18O (2.3‰ vs. 0.9‰, p < 0.001) and a lower mean δ18O (-5.1‰ vs. 0.9‰, p < 0.001) compared to those from Galana Boi (n = 53). The difference in mean δ18O is due to the Limnocythere in Kibish living more proximal to the Omo River. We interpret the larger standard deviation in the Kibish assemblage as evidence of heightened seasonal variability in Omo discharge.
How to cite: Fredericks, A., Beck, C. C., Bedaso, Z. K., and van der Lubbe, J. H. J. L.: Determining seasonal variability in the Omo-Turkana Basin from the Pleistocene to modern using ostracod stable isotope analysis, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14197, https://doi.org/10.5194/egusphere-egu25-14197, 2025.
Mass movements on slopes adjacent to and beneath lakes and fjords can produce destructive tsunami. Reconstructing past events is crucial for understanding the extent and frequency of this hazard. Current reconstruction approaches involve identifying large landslide deposits preserved on the lakebed and analysing landslide dimensions and dynamics to estimate tsunami magnitude. However, in active tectonic settings, much of the morphological evidence is eroded or buried over time, which impedes the development of long event records that are needed to quantify lacustrine tsunami hazard.
This study tested the hypothesis that lake tsunami leave diagnostic sedimentary imprints in the stratigraphic record of lakes that can be reliably used to develop long records of tsunami frequency. The hypothesis was tested by examining the sedimentological signature and spatial heterogeneity of deposits produced by a coseismic tsunamigenic delta collapse in Lake Rotoroa, New Zealand. Extensive bathymetric mapping, seismic imaging, sediment coring and numerical modelling were used to establish evidence of a destructive lacustrine tsunami generated by the catastrophic collapse of D’Urville and Sabine River deltas between 800 - 979 CE. The delta collapse was triggered directly by the rupture of the northern section of the Alpine Fault, where the fault ruptured through the delta fronts instigating the deep-seated delta collapse with heightened tsunamigenic capacity.
Six 6-m long sediment cores distributed across the lake basin were examined to characterise the tsunami deposit. A lithofacies model for lake tsunami deposits was then developed by correlating the textural and structural characteristics of the event deposit to numerical tsunami simulations and sediment transport principles. The findings from Lake Rotoroa show that lacustrine tsunami lead to the formation of megaturbidite deposits with distinct subunits that preserve evidence of high-velocity bottom currents, prolonged water column motion, and tsunami backwash. Comparisons to historic event deposits within Lake Rotoroa and globally highlighted that lacustrine tsunami deposits consistently display diagnostic sedimentary signatures that are distinct from other event deposits.
We conclude that lake tsunami deposits can be differentiated from turbidites produced by non-tsunamigenic mass-wasting, demonstrating that lake sediment records can be used to reconstruct the frequency of lake tsunami over millennial time scales. This research presents a promising new avenue for the quantitative reconstruction of lacustrine tsunami hazard in active tectonic settings.
How to cite: Hughes, K. E., Howarth, J. D., Fitzsimons, S. J., Moody, A., and Wang, X.: Diagnostic sedimentary imprints of lacustrine tsunami: evidence from tsunamigenic fault-contact delta collapse in Lake Rotoroa, New Zealand, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14694, https://doi.org/10.5194/egusphere-egu25-14694, 2025.
The Pliocene (5.33-2.58 Ma) was comparatively warmer (1.8-3.6C) than today and was characterized by elevated CO2 concentrations (400 ppmv). Thus, this interval can serve as an excellent analogue for comparing present conditions. Yet, while most studies rely on marine archives, continental data dating back to this interval is scarce, particularly from the eastern Mediterranean. Sediments from the Erk-el-Ahmar Fm. (~4.5-3.15 Ma, Jordan Valley, Israel) highlights as one of the few continuous lacustrine archives in the region that date back to that time. In the present contribution we reconstruct the limnological setting and how this responded to the regional changing hydroclimatic conditions. To achieve the goals, a multi-proxy approach has been applied to both cores and outcrop samples, including: grain size, magnetic properties, elemental geochemistry, mineralogy, and analysis of biological remains.
The ~150 m long sedimentary record consist of well-layered clay intercalated with silt, and sand units with scattered mollusk shells, ostracod bivalves, and occasional mammalian bone fragments. The identified sedimentary facies intercalate exhibiting a general fining upward pattern, with interpreted shorter drier periods transitioning to longer intervals of increase in wetness. The drier phases are characterized by high authigenic Ca, coarser sediments, and an increase in total inorganic carbon content. Conversely, the wetter phases are typified by high detrital signature (e.g., Al, Si, and Ti), finer sediments, and high total organic carbon content. These cycles reflect fluctuations in the lake hypsometry, which stand for the hydroclimate balance of the region with the local environment becoming drier through time. In addition, the sedimentary archive appears to record several event layers, testifying to the ever-present influence of tectonism on this perennial water body.
How to cite: Danish, M., Greenlee, J., Parth, S., Olabayo, O., Taha, N., and Waldmann, N.: Insights from a promising lacustrine archive for reconstructing Pliocene hydroclimate in the Eastern Mediterranean: the Erk-el-Ahmar paleolake, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18011, https://doi.org/10.5194/egusphere-egu25-18011, 2025.
Key words: seismic interpretation, asymmetric simple – shearing, core complex, flower structure,
detachment
The Drmno Basin, local depression at the southeastern edge of the Pannonian Superbasin in Serbia,
represents a peri - Pannonian part of the Drmno - Zagajica – Plandište regional structure. Drmno
Basin is formed by regional normal faulting during the Early Miocene extensional field in the Western
Carpathian area, and is closely related with regional fault – Morava detachment, one of the prominent
structures in this part of Serbo – Macedonian tectonic unit.
Although main tectonic regime of this part of the Pannonian Basin is already described in the earlier
studies (Marović et al., 2007; Matenco and Radivojević, 2012), detailed observations of the tectonic
conditions and deformations styles in the Drmno Basin are yet to be defined. In order to give more
perspective to basin – scaled structures and their characteristics, we conducted detailed tectonic
interpretation of available 2D and 3D seismic data, as well as geophysical logging and well core data
from the Drmno Basin.
The sediments within the basin are deformed by a series of listric faults converging with Morava
detachment in the deeper parts of the basin. They usually have asymmetric simple shearing
characteristics, with half – graben basin architecture and many synthetic, and few antithetic faults.
On the northwestern part of the basin, metamorphic core complex Gaj has been uplifted by extension
in the footwall block of the Morava detachment. At the younger part of basin fill strike slip structures
can be recognized, pointing to basin deforming tectonic. The presence of negative flower structures
can be connected with reactivation of predisposed fault surfaces as result of changed tectonic
conditions, from extensional which created normal faults, to transtensional that created strike – slip
movements.
Based on the fault tracking seismic attribute, that is utilized on 3D seismic cube of this area, main
fault strike directions are recognized. The older, listric faults primarily have strike directions of east –
west and northeast – southwest. Younger, transtensional tectonic structures exhibit similar strike
directions due to the reactivation of existing fault surfaces.
All tectonic structures clearly indicate regional extensional field in the first tectonic phase, creating
accommodation space, which persisted during the basin thermal subsidence. The extensional phase
is characterized by domination of listric faults created on the asymmetrical simple shearing model,
as well as presence of core complex closely connected to detachment. Unlike other depressions in
this part of the Pannonian Superbasin, the Early Miocene sediments in the Drmno Basin have
significant thickness, indicating an earlier basin opening. The second, transtensional phase had
influence on sediments in the upper part of the basin, creating negative flower structures.
References:
1. Marović, M., Toljić, M., Rundić, L. and Milivojević, J. 2007. Neoalpine Tectonic of Serbia.
Serbian Geological Society, Belgrade.
2. Matenco, L. and Radivojević, D. 2012. On the formation ́ and evolution of the Pannonian
Basin: constraints derived from the structure of the junction area between the Carpathians
and Dinarides. Tectonics, 31, 2–31, https://doi.org/10.1029/2012TC003206
How to cite: Ninić, A., Stanković, S., Sovilj, J., and Radivojević, D.: Insight in tectonic evolution of the Drmno Basin (SE Pannonian Superbasin), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1911, https://doi.org/10.5194/egusphere-egu25-1911, 2025.
During the retreat of the Würm ice sheet in the Jura region, numerous glacial paleolakes took place in the French and Swiss Jura. Lake deposits are excellent continental archives for recording climatic fluctuations as well as extreme events such as volcanism through the deposition of tephra layers. Two sites were investigated: the Amburnex Valley site (Switzerland) and the Lake Val (France). During the Late Glacial period, both sites were glacial lakes characterized by significant accumulation of lacustrine sediments allowing a better and complete paleoclimatic and paleoenvironmental evolution record.
The main goal of this study is to reconstruct the paleoclimatic and the paleoenvironmental evolution recorded in lacustrine sediments deposits since the last 19’000 years, and to determine whether major volcanic events have been recorded during this period. The Amburnex core exhibit a basal morainic deposit from the Würm period, overlain by three meters of lacustrine deposits and four meters of peatland deposits. The Lake Val core consists of the same lithological succession. A multiproxy approach based on palynological, mineralogical and geochemical analyses (TOC, Nitrogen, Phosphorus, stable isotopes) have been used to characterize the hydrological and climatic fluctuations, the trophic level and the origin of organic matter in order to reconstruct the paleoenvironmental and paleoclimatic evolution of this area.
The Bølling-Allerød, the Younger Dryas and the beginning of the Preboreal period have been recognized in the Amburnex site, by palynological analyses and carbon 14 dating. During the Oldest Dryas, oligotrophic conditions took place as suggested by the very low concentrations in nitrogen and organic matter. Then, during the warmer Bølling period, an enrichment in total organic carbon (TOC) implying the development of eutrophic conditions. Later in the Allerød period, low TOC and phosphorus contents, associated with varved carbonate deposits, indicate a return to more oligotrophic conditions. New organic matter enrichments are observed in the interval corresponding to the colder Younger Dryas period. These trends are quite consistent with those observed in the Lake Val and reflect significant changes in runoff and nutrient inputs at least at regional scale.
Tephra layers are absent in the Amburnex core. The latter are indeed not always well preserved in sediments due to mineralogical transformation. But thanks to magnetic susceptibility and to phosphorus anomalies (linked to apatite present in ash deposits), two fallouts of atmospheric volcanism such as the Laacher See Tephra event (Eifel, Germany) and the Vedde Ash tephra event (Iceland) have been highlighted.
How to cite: Bomou, B., Rachoud-Schneider, A.-M., Haas, J.-N., Font, E., Zappa, D., Gärtner, M., Spangenberg, J., Bichet, V., and Adatte, T.: Lacustrine archives in Jura lakes since the Late Glacial Period, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18861, https://doi.org/10.5194/egusphere-egu25-18861, 2025.
Tidal Lake Hamana is located near the Nankai-Suruga Trough, which is repeatedly affected by tsunamogenic megathrust earthquakes. The lake represents a good sedimentary archive for past earthquakes and extreme wave events (EWEs), triggered by tsunamis and tropical storms (typhoons). By applying a broad range of surveying methods, sedimentological analyses and dating techniques, a 7.5-kyr-long record of ≥ 22 megathrust and EWE deposits was extracted. Event deposits are embedded in fine-grained (silty) lacustrine sediments and have a thickness between 1 and ~50 cm. They are often sandy and typically display an erosive base, a fining-upward sequence, semi-parallel to chaotic or deformational layering, stronger X-ray attenuation, an increased magnetic susceptibility and high values for ratios of Ca/Fe and Sr/Fe. They correspond to strong reflectors on seismic images and are interpreted as products of EWEs (sandy, fining-upward) and earthquake shaking (silty, deformed). Most event layers become thinner or even disappear and/or become finer-grained towards ocean-distal lake sites. Radionuclide dating and independent tephrostratigraphy show that ages of event deposits go back to 7.5 ka BP, with main recurrence modes of 150-200 years. Especially going back beyond 5 ka BP, the Lake Hamana record adds complementary information to existing megathrust and EWE records along the Eastern Nankai Trough.
How to cite: De Batist, M., Boes, E., Fujiwara, O., Yokoyama, Y., Miyairi, Y., Shishikura, M., Kempf, P., Schmidt, S., Nakamura, A., Heyvaert, V. M. A., and Brückner, H. and the QuakeRecNankai team: A 7,500-year-long record of extreme wave events from tidal Lake Hamana, south-central Japan, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-21322, https://doi.org/10.5194/egusphere-egu25-21322, 2025.
Saline-alkaline lakes commonly occur in semi-arid tectonically active regions, and their deposition is influenced by tectonic, surface and hydrothermal processes, and climate. This study explores the effects of climate and hydrothermal fluid flow on the formation of the saline-alkaline succession of the Ibar Basin, southern Serbia, using sedimentological analysis, U-Pb geochronology of carbonates (via LA-ICP-MS), geochemistry, and fluid inclusion analysis.
The basin’s predominantly clastic sedimentation includes alluvial fan, floodplain, delta, marginal, and profundal lake facies. Microbiolites and littoral to sublittoral oil shales are deposited in areas lacking the clastic input. Stratigraphically, the basin transitioned from alluvial to lacustrine environments, whose Early to Middle Miocene onset at ~ 17 Myrs is revealed by U-Pb dating of microbiolites.
The hydrologically closed lake phase is associated with borate-rich facies, primarily colemanite with secondary ulexite, within profundal lake settings. Syn-depositional colemanite precipitated near the sediment-water interface in a deep lake environment. Post-depositional colemanite and associated calcite filled the pore space within the microlites or intrabasinal breccias. Primary fluid inclusions in post-depositional colemanite and calcite reveal brine evolution under evaporitic, redox conditions, with diagenetic temperatures reaching 200–220°C.
High Ca²⁺/Na⁺ ratios in the brine promoted colemanite precipitation. Subsequent Ca²⁺ depletion and clay breakdown led to ulexite and borax formation. B, Ca, and Na were transported into the basin by streams carrying weathered volcanic material and thermal fluids leaching basement rocks. The arid climate-induced evaporation-initiated precipitation of syndepositional colemanite, while subsequent enrichment and growth of post-depositional colemanite and calcite were driven by fluid reflux during diagenesis.
How to cite: Andrić-Tomašević, N., Walter, B. F., Simić, V., Raza, M., Životić, D., Novković, Ž., Kolb, J., Gerdes, A., and Beranoaguirre, A.: The role of the arid climate and hydrothermal fluids in depositional processes in saline alkaline lakes: inferences from Ibar intramountain basin (Serbia), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16714, https://doi.org/10.5194/egusphere-egu25-16714, 2025.
Posters virtual: Wed, 30 Apr, 14:00–15:45 | vPoster spot 2
EGU25-4626 | Posters virtual | VPS26
The origin and lithofacies development characteristics of fine particle composition in the shale of the second member of Fengcheng Formation in Mahu SagWed, 30 Apr, 14:00–15:45 (CEST) | vP2.1
Shale oil, as one of the most important unconventional oil and gas resources, has become the key target of oil and gas exploration in recent years. The Fengcheng formation in Mahu Sag is the best source rock in the sag, which has great potential for shale oil resources and is the key area for shale oil exploration in Junggar Basin.
Volcanic activity was frequent during the sedimentary period of Fengcheng Formation in the northern part of Mahu Sag. The sediments are mainly composed of tuff material of volcanic activity, evaporation material of caustic lake and a small amount of detrital material. The terrigenous detrital material mainly comes from long-distance transport, while the pyroclastic material is closely related to the proximal volcanic activity. The lithofacies development of shale is characterized by frequent overlapping of various lithologies, diverse combination types and rapid changes. The microfabric of fine-grained sedimentary rocks is characterized, the lithofacies types of fine-grained sedimentary rocks are summarized, and the assemblage relationship and development law of lithofacies in different environments are analyzed. The formation process of lacustrine fine-grained sedimentary rocks is discussed from the perspective of provenance supply and sedimentary dynamics, and the lithofacies development model of fine-grained sedimentary rocks is established. To a certain extent, the theory of lacustrine sedimentology is enriched and perfected, and it can also provide basic geological basis for tight oil exploration in this area.
How to cite: zhuang, Y.: The origin and lithofacies development characteristics of fine particle composition in the shale of the second member of Fengcheng Formation in Mahu Sag, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4626, https://doi.org/10.5194/egusphere-egu25-4626, 2025.
EGU25-4736 | ECS | Posters virtual | VPS26
Sedimentary Evolution and Morphological Characteristics of Modern Lake Shoreline Delta under the Influence of Coast CurrentWed, 30 Apr, 14:00–15:45 (CEST) | vP2.2
Abstract：Lake deltas are located in the complex zone of lake and river interaction, influenced by the dual effects of material exchange between the two. There are not only climate and water level influences, but also topography and geomorphology and waves and other lake hydrodynamic influences, resulting in a more complex lake delta evolution process. To explore the sedimentary characteristics and the impact of lake dynamics during different stages of delta development under the influence of coast current, the Muhuahe Delta in Daihai Lake is taken as the study object for modern sedimentary investigations. Through the analysis of high-precision satellite photos and the interpretation of profile information collected by UAV oblique photography, the sedimentary evolution of the delta in the study area was analyzed in detail. The results show that delta deposits are developed in the eastern gentle slope zone of Daihai, and the delta front subfacies are widely distributed. The profile shows that the sand bodies are affected by strong hydrodynamics, and a large number of wave-formed structures are developed and lateral migration is obvious on the plane. Satellite remote sensing data suggest the sedimentary sand bodies' development and distribution characteristics, indicating the control of coast current in the development and evolution of the delta. The delta is asymmetric, with well-developed sand dams at the delta front, growing parallel to the shoreline. Although influenced by provenance supply, during this period, the delta is controlled by littoral currents, and its expansion toward the lake basin is suppressed. Generally, coast current plays a significant role in modifying the plane distribution and scale of the delta front sand bodies. Reservoir heterogeneity is often generated due to different dominant hydrodynamic conditions, providing a reference for further exploration into the influence of coast current on reservoir development and distribution.
Keywords: coast current; gentle slope delta; sedimentary evolution
How to cite: Jiang, Y.: Sedimentary Evolution and Morphological Characteristics of Modern Lake Shoreline Delta under the Influence of Coast Current, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4736, https://doi.org/10.5194/egusphere-egu25-4736, 2025.
EGU25-4788 | ECS | Posters virtual | VPS26
Middle-to-Late Holocene Climate Change in Lagoon Lake Mert (NW Black Sea) and Its Hydrological Connection with the Black Sea: evidences from multi-proxy recordsWed, 30 Apr, 14:00–15:45 (CEST) | vP2.3
Coastal areas and related sedimentary environments are remarkable providers of valuable information about climatic changes and sea level oscillations. Lake Mert was formed as a shallow Black Sea coastal lagoon that contains various mixtures of marine and freshwater sources. This study presents sedimentological, geochemical and paleontological analyses of five sediment cores recovered from the lake which has been severely influenced by sea level change and local climate over the last 6.5 cal. ka BP. The environmental and climatic records obtained by multi-proxy analyses of the cores (µ-XRF, total organic carbon, stable isotope, pollen analysis and foram content) that are confidently correlated with other regional and global climate signals. In addition, Lake Mert also remains a challenge to identify and quantify dynamic changes in time on the coastal plain, thus, it possibly reflects hydrologic changes in the Black Sea since the middle Holocene. Analysis of lithology together with paleontological content of the studied cores reveal three main depositional units, each of them indicates varying areal facies distribution due to highly dynamic depositional settings in lake. Accordingly, the main lithofacies in the cores from bottom to top are defined as a relict lacustrine sediment older than 6.5 cal. ka BP (Unit 3), coastal and deltaic facies deposited between 6.5 to 4.5 cal. ka BP (Unit 2) and the younger lagoon-marine sediment (Unit 1).
Moreover, the correlation of well-dated sedimentological and geochemical proxies with the sea level and sea surface salinity records from the Black Sea allows us differentiate various phases of hydrologic changes due to connections with the Lake Mert during the middle-to-late Holocene. Our preliminary results suggest that the relict Mert Lake was first invaded by the Black Sea waters prior to 6.5 cal. ka BP, and then remained its fully connection until ~5.3 cal. ka BP due to subsequent inflow of the Mediterranean Sea via Bosporus. Furthermore, the decelerated sea level rise between 5.3 and 4.5 cal. ka BP gave rise to return semi-closed lagoon phase, restricting mixture with the Black Sea waters as inferred from stable oxygen isotope record. The later period, particularly after 3.5 cal. ka BP, was associated with more Euryhaline condition in the lake based on the paleontological content of the core sediment. The local climate changes are recorded in Lake Mert as a wet period between 6.5 and 4.5 cal. ka BP, a dry period between 4.5 and 2.9 cal. ka BP and wetter period after 2.9 cal. ka BP, respectively.
How to cite: Yakupoglu, C., Eriş, K. K., Karlıoğlu Kılıç, N., Yılmaz Dağdeviren, R., Nazik, A., Acar, D., Yakupoğlu, N., Sabuncu, A., and Kırkan, E.: Middle-to-Late Holocene Climate Change in Lagoon Lake Mert (NW Black Sea) and Its Hydrological Connection with the Black Sea: evidences from multi-proxy records , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4788, https://doi.org/10.5194/egusphere-egu25-4788, 2025.
