CL5.1.4

CL5.1 EDI
Geochronological tools for environmental reconstructions 

The Quaternary Period (last 2.6 million years) is characterized by frequent and abrupt climate swings that were accompanied by rapid environmental change. Studying these changes requires accurate and precise dating methods that can be effectively applied to environmental archives. A range of different methods or a combination of various dating techniques can be used, depending on the archive, time range, and research question. Varve counting and dendrochronology allow for the construction of high-resolution chronologies, whereas radiometric methods (radiocarbon, cosmogenic in-situ, U-Th) and luminescence dating provide independent anchors for chronologies that span over longer timescales. We particularly welcome contributions that aim to (1) reduce, quantify and express dating uncertainties in any dating method, including high-resolution radiocarbon approaches; (2) use established geochronological methods to answer new questions; (3) use new methods to address longstanding issues, or; (4) combine different chronometric techniques for improved results, including the analysis of chronological datasets with novel methods, e.g. Bayesian age-depth modeling. Applications may aim to understand long-term landscape evolution, quantify rates of geomorphological processes, or provide chronologies for records of climate change.

Co-organized by GM2/SSP1, co-sponsored by PAGES
Convener: Kathleen WendtECSECS | Co-conveners: Arne RamischECSECS, Irka Hajdas, Andreas Lang
Presentations
| Wed, 25 May, 17:00–18:15 (CEST)
 
Room 0.49/50

Session assets

Session materials

Presentations: Wed, 25 May | Room 0.49/50

Chairpersons: Irka Hajdas, Andreas Lang
17:00–17:10
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EGU22-13260
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solicited
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Highlight
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On-site presentation
Amaelle Landais, Anaïs Orsi Orsi, Elise Fourré Fourré, Roxanne Jacob, Ilaria Crotti, Florian Ritterbusch, Zheng-Tian Lu, Guo-Min Yang, and Wei Jiang

In the search for very old ice, finding the age of the ice is a key parameter necessary for its interpretation. Most ice core dating methods are based on chronological markers that require the ice to be in stratigraphic order. However, the oldest ice is likely to be found at the bottom of ice sheets, where the stratigraphy is disturbed, or in ablation areas, where the classical methods cannot be used. Absolute dating techniques have recently been developed to provide new constraints on the age of old ice. In particular, 81Kr measurements provide strong dating constraints for the old ice cores. Still, these measurements are limited in deep ice cores because of the large sample size required (5-6 kg). In addition to 81Kr dating, we discuss here the analytical performances of a new technique for 40Ar dating, which allows us to provide a reliable age with 80g of ice rather than 800g, as previously published. Finally, we present two applications for the 81Kr and 40Ar dating on the bottom of the TALDICE and Dome C ice cores.

How to cite: Landais, A., Orsi, A. O., Fourré, E. F., Jacob, R., Crotti, I., Ritterbusch, F., Lu, Z.-T., Yang, G.-M., and Jiang, W.: Absolute dating of deep ice cores with argon and krypton isotopes., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13260, https://doi.org/10.5194/egusphere-egu22-13260, 2022.

17:10–17:15
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EGU22-8868
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Virtual presentation
Christof Pearce, Karen Søby Özdemir, Ronja Cedergreen Forchhammer, Henrieka Detlef, and Jesper Olsen

Radiocarbon (14C) dating is the standard method for obtaining the age of marine sediments of Holocene and late Pleistocene age. For accurate calibrations, however, this tool relies on precise knowledge of the local radiocarbon reservoir age of the surface ocean, i.e. the regional difference (ΔR) from the average global marine calibration dataset. This parameter has become impossible to measure from modern material samples because of 14C contamination from extensive testing of thermo-nuclear bombs in the second half of the twentieth century. The local reservoir age can thus only be calculated from the radiocarbon age of samples collected before AD 1950 or from sediment records containing absolute age markers, derived from e.g. tephrochronology or paleomagnetism.

Knowledge of the marine reservoir age around Greenland is sparse and relies on work by a few studies, represented by measurements clustered in local patches. In this study we add new radiocarbon measurements on samples from historical mollusk collections from Arctic expeditions of the late 19th and early 20th Century. The 92 new samples are from central east Greenland and the entire western Greenland coast. Although the new data is mostly coastal, it includes a few deeper sites from the Labrador Sea and northeastern North Atlantic Ocean, where deep waters were found to be very young. Together with existing measurements, the new results are used to calculate average ΔR values for different regions around Greenland, all in relation to Marine20, the most recent radiocarbon calibration curve. Despite the significant addition of new measurements, very few data exist for southeastern Greenland, while no data at all is available for the Arctic Ocean coast in northern Greenland.

How to cite: Pearce, C., Özdemir, K. S., Forchhammer, R. C., Detlef, H., and Olsen, J.: The radiocarbon reservoir age of coastal Greenland waters, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8868, https://doi.org/10.5194/egusphere-egu22-8868, 2022.

17:15–17:20
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EGU22-8743
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ECS
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On-site presentation
Gregor Pfalz, Bernhard Diekmann, Johann-Christoph Freytag, Liudmila Syrykh, Dmitry A. Subetto, and Boris K. Biskaborn

Refined dating techniques and high-precision radiocarbon dating have enabled more accurate age controls for paleoenvironmental reconstruction of lake systems. However, low bioproductivity and the influence of old carbon have a profound impact on radiocarbon dating series of non-varved sediment records from Arctic lakes. Geochronological tools such as software systems for age-depth modeling provide sophisticated justifications for age-depth relationships. But because there are many different tools available with varying underlying mathematical methods and models, the model output can show diverging results, e.g., for problematic sediment cores with scatter age dating points. A detailed comparison of the results of individual modeling system is therefore often tedious and potentially error-prone. Due to time constraints and a lack of alternative options, users typically only select and apply one modeling system to provide a geochronological timeframe for paleoenvironmental interpretation. Therefore, we introduce our “Linked age and depth modeling” (LANDO) approach that links five modeling systems (Bacon, Bchron, clam, hamstr, Undatable) in a single multi-language Jupyter Notebook. LANDO reduces the effort of using established modeling systems for both single and multiple dating series and makes the results directly comparable. In addition, we introduce an ensemble age-depth model that uses the output from all models to create a data-driven, semi-informed age-depth relationship. In our talk we will highlight our adapted fuzzy change point method, in which we used independent proxy data to evaluate the performance of each modeling system in representing lithological changes. LANDO is already publicly available on GitHub: https://github.com/GPawi/LANDO.

How to cite: Pfalz, G., Diekmann, B., Freytag, J.-C., Syrykh, L., Subetto, D. A., and Biskaborn, B. K.: Using LANDO as a universal wrapper for applying multiple age-depth modeling systems for sediment records from Arctic lake systems, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8743, https://doi.org/10.5194/egusphere-egu22-8743, 2022.

17:20–17:25
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EGU22-2278
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Presentation form not yet defined
Fine structure of the Suigetsu atmospheric 14C record 10-27 cal. ka turns out as authentic base for improved global correlation of 14C-dated planktic records of ocean climate
(withdrawn)
Michael Sarnthein and Pieter M. Grootes
17:25–17:30
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EGU22-468
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ECS
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Virtual presentation
Rebecca Kearney, Markus J. Schwab, Ina Neugebauer, Nadine Pickarski, and Achim Brauer

The eastern Mediterranean region is located at divergent climatic zones and contrasting precipitation regimes of the humid Mediterranean climate and hyper-arid Saharo-Arabian desert belt. Important sedimentary archives from lakes allow past hydroclimatic variability to be reconstructed using multiple proxies. This can provide useful insight into potential future water budget scenarios. However, problems associated with chronological uncertainty can prevent insight into regional climatic (a)synchronies. The use of isochronous chronological markers of tephra (volcanic ash) can be a powerful tool in correlating palaeoclimatic records, particularly over vast distances with the development of cryptotephra analyses (non-visible volcanic glass shards).

            The TephroMed project aims to precisely synchronise two key ICDP palaeoclimatic records from eastern Mediterranean through the use of tephrostratigraphic investigations: to the north, in the Anatolian region, Lake Van (PALEOVAN, Litt et al., 2014) and to the south, in the Levant, the Dead Sea (DSDDP, Stein et al., 2011). Both records have undergone lake level reconstructions, indicating contrasting past regional responses to large-scale climatic events (e.g. Finne et al., 2019; Neugebauer et al., 2015). Though both records are dated through absolute and relative methods (radiocarbon, U-Th, varve counting, wiggle-matching), inherited large chronological uncertainties do not allow detailed insight into the potential climatic time-transgressive nature between the two sites. Yet, both records have tephra deposits within their lacustrine sediments, highlighting the potential to facilitate the alignment of both records using tephra (Neugebauer et al., 2021).

Here, we present new major and minor element volcanic glass chemical data from several tephra layers from both Lake Van and the Dead Sea ICDP cores. New geochemical data from selected visible tephra layers in Lake Van are given. The cryptotephra results from the Dead Sea show particular significant findings with volcanic glass derived from potentially several volcanic regions within the Mediterranean (e.g. Anatolia, Italy). This new data can help to facilitate a chronological alignment between the Dead Sea, Lake Van and other important climatic archives in the Mediterranean. In addition, it highlights the importance of distal records in understanding past volcanic eruptions. As a result of these findings, we can now start to answer questions associated with regional expression of past climatic events and their temporal transgression.

References

Finné, M., Woodbridge, J., Labuhn, I., Roberts, C.N., 2019. Holocene hydro-climatic variability in the Mediterranean: A synthetic multi-proxy reconstruction. Holocene 29(5), 847–863

Litt, T., Anselmetti, F.S., 2014. Lake Van deep drilling project PALEOVAN. Quat. Sci. Rev. 104, 1-7.

Neugebauer, I., Brauer, A., Schwab, M.J., Dulski, P., Frank, U., Hadzhiivanova, E., Kitagawa, H., Litt, T., Schiebel, V., Taha, N., Waldmann, N.D., DSDDP Scientific Party, 2015. Evidences for centennial dry periods at ~3300 and ~2800 cal. yr BP from micro-facies analyses of the Dead Sea sediments. Holocene 25, 1358-1371.

Neugebauer, I., Müller, D., Schwab, M.J., Blockley, S., Lane, C.S., Wulf, S., Appelt, O., Brauer, A., 2021. Cryptotephras in the Lateglacial ICDP Dead Sea sediment record and their implications for chronology. Boreas 50 (3), 844-861.

Stein, M., Ben-Avraham, Z., Goldstein, S.L., 2011. Dead Sea deep cores: A window into past climate and seismicity. Eos, Transactions American Geophysical Union 92, 453-454

How to cite: Kearney, R., Schwab, M. J., Neugebauer, I., Pickarski, N., and Brauer, A.: The TephroMed project: Precise synchronising of two key palaeoclimatic ICDP records of the eastern Mediterranean using tephra, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-468, https://doi.org/10.5194/egusphere-egu22-468, 2022.

17:30–17:35
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EGU22-11178
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ECS
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Virtual presentation
Andrew Mitchell, Joanne Lim, Anandh Gopal, Aron Meltzner, Andrew Chan, Gina Sarkawi, Xinnan Li, Ace Matthew Cantillep, Loraine Faye Sarmiento, Junki Komori, Tsai-Luen Yu, Chuan-Chou Shen, Shou-Yeh Gong, Jennifer Weil-Accardo, Kathrine Maxwell, Ke Lin, Yanbin Lu, Xianfeng Wang, and Noelynna Ramos

Coral microatolls allow for the reconstruction of relative sea level (RSL) and the inference of tectonic deformation along tropical coastlines over the Holocene. Microatolls track RSL with unparalleled vertical precision, and their annual banding allows us to count years precisely over an individual coral’s lifetime; however, RSL histories reconstructed from multiple corals depend on accurate and precise radiocarbon (14C) or uranium-thorium (230Th) ages.

We collected coral microatoll slabs from sites in Ilocos Region, northwestern Luzon, Philippines, and dated them with 14C and 230Th techniques. Notably, initial RSL reconstructions for some sites disagreed markedly depending on the dating technique used. Attempts to replicate geochronologic analyses have shown that the coral skeletons are susceptible to diagenesis, complicating efforts to accurately determine coral ages.

We are developing a strategy to overcome this limitation. We extracted multiple samples from each microatoll slab for paired 14C and 230Th dating. The number of annual bands separating any dated sample was used to further constrain the age of the coral; by subtracting the number of years from each dated sample, samples taken from different parts of the slab can produce independent estimates of the outermost preserved band. After excluding anomalously young replicate 14C ages and samples flagged as partly calcified by x-ray diffraction, we find that 230Th ages from a single coral disagree at 4σ in 4 of 8 cases, whereas calibrated 14C dates overlap at 2σ in 8 of 9 cases for an arbitrary radiocarbon marine reservoir correction, ∆R = 0 yr.

Using OxCal and the Marine20 calibration curve, we apply Bayesian statistics to combine 14C and 230Th ages, to estimate ∆R, and to determine the coral ages using the best available data. We further analyze the ∆R value for each coral, and account for overdispersion and underdispersion, whilst generating a ∆R value per site, and an overall ∆R value (inclusive of all sites). We find no statistically significant difference in ∆R for each site, and we calculate an overall ∆R of -155 ± 117 yr for sites in Ilocos Region since the mid-Holocene, though century-scale variability in ∆R may occur.

Additionally, to improve the reliability of our dates, our final dating strategy in OxCal is to apply the previously determined ∆R, to a code that places the corals in sequence (based on precise elevation measurements, morphological similarities, and coral die-down events), along with the 14C dates that are dated to the outermost preserved band.

How to cite: Mitchell, A., Lim, J., Gopal, A., Meltzner, A., Chan, A., Sarkawi, G., Li, X., Cantillep, A. M., Sarmiento, L. F., Komori, J., Yu, T.-L., Shen, C.-C., Gong, S.-Y., Weil-Accardo, J., Maxwell, K., Lin, K., Lu, Y., Wang, X., and Ramos, N.: Geochronologic methods for dating coral microatolls in the Philippines , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11178, https://doi.org/10.5194/egusphere-egu22-11178, 2022.

17:35–17:40
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EGU22-8328
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Virtual presentation
Anne-christin Melcher, Elda Miramontes, Walter Geibert, Susann Henkel, Henriette Wilckens, Thomas Pape, Male Köster, Jessica Volz, Thomas Frederichs, Graziella Bozzano, Cristiano Chiessi, Nnamdi Chukwuebuka Chidolue, Orock Shelly Ngui, Tilmann Schwenk, and Sabine Kasten

We investigated sediments from three different depositional environments along the northern Argentine continental margin to assess the main processes controlling sediment deposition since the last glacial period. Further, we evaluated how different depositional conditions affect (bio)geochemical processes within sediments. Sediment cores were collected during expedition SO260 in 2018[1]. Two sites are located at ~1100 m water depth north and south of the Mar del Plata Canyon (N- and S-Middle Slope Site). Another site is situated at the lower continental slope at 3600 m water depth (Lower Slope Site). Reliable age constraints of sediments deposited during the last glaciation at the Argentine margin are difficult to obtain due limited amounts of carbonate. We overcame this issue by combining radio-isotope analyses (14C,230Thex) with sedimentological, geochemical and magnetic data demonstrating that all sites experienced distinct changes over time.

Both, N- and S-Middle Slope Sites, record at least the last 30 ka. The S-Middle Slope Site is dominated by continuously organic carbon-starved and winnowed sandy deposits, which according to geochemical and magnetic data leads to insignificant sulfate reduction and sulfidation of iron (oxyhydr)oxides. Glacial sedimentation rates at the Middle Slope increase northwards suggesting a decrease in bottom-current strength. The N-Middle Slope Site records a transition from the last glacial period, dominated by organic carbon-starved sands, to the early deglacial period when mainly silty and organic carbon-rich sediments were deposited between 14-15 ka BP. Concurrently, glacial sedimentation rates of ~50 cm/ka significantly increased to 120 cm/ka. We propose that this high sedimentation rate relates to lateral sediment re-deposition by current-driven focusing as response to sea level rise. Towards the Holocene, sedimentation rates strongly decreased to 8 cm/ka. We propose that the distinct decrease in sedimentation rates and change in organic carbon contents observed at the N-Middle Slope Site caused the nonsteady-state pore-water conditions and deep sulfate-methane-transition (SMT) at 750 cm core depth. The Lower Slope Site records the last 19 ka. Continuously high terrigenous sediment input (~100 cm/ka) prevailed during the Deglacial, while sedimentation rates distinctly decreased to ~13 cm/ka in the Holocene. Here, pore-water data suggest current steady-state conditions with a pronounced SMT at 510 cm core depth. Our study confirms previous geochemical-modelling studies at the lower slope, which implied that the observed SMT fixation for ~9 ka at specific depth relates to a strong decrease in sedimentation rates at the Pleistocene/Holocene transition[2].

During the Holocene, total organic and inorganic carbon contents, inorganic carbon mass accumulation rates and XRF Si/Al ratios (preserved diatom flux) increase at our sites. We relate this to increased primary production in surface waters and less terrigenous input along the continental margin. Our multidisciplinary approach presents improved age constraints at the northern Argentine Margin and demonstrates that lateral/vertical sediment transport and deposition was strongly linked to Glacial/Interglacial variations in bottom currents, seafloor morphology, sea level and sediment supply. The dynamic depositional histories at the three sites still exert a significant control on modern sedimentary (bio)geochemical processes.

 

[1]Kasten et al. (2019).Cruise No. SO260. Sonne-Berichte.

[2]Riedinger et al. (2005).Geochim. Cosmochim. Acta. 69.

 

How to cite: Melcher, A., Miramontes, E., Geibert, W., Henkel, S., Wilckens, H., Pape, T., Köster, M., Volz, J., Frederichs, T., Bozzano, G., Chiessi, C., Chidolue, N. C., Ngui, O. S., Schwenk, T., and Kasten, S.: Strong changes in depositional conditions during the Late Glacial and the Holocene along the northern Argentina Continental Margin: a multiproxy approach. , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8328, https://doi.org/10.5194/egusphere-egu22-8328, 2022.

17:40–17:45
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EGU22-312
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ECS
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Virtual presentation
Rivoningo Khosa, Stephen Tooth, Vela Mbele, and Robyn Pickering

Many classical models of landscape evolution in South Africa have previously relied on large-scale, predominantly qualitative, field observations. In recent decades, however, the development of the accelerator mass spectrometer (AMS) has allowed for greater use of cosmogenic nuclide analyses in landscape evolution studies to quantify rates of denudation and establish timescales of landscape development. In South Africa, various field areas and isotopes have been studied to understand the development of the landscape on Quaternary and longer timescales. The aim of our study is to use a cosmogenic nuclide (10Be) to investigate the development of geographically separate parts of the South African landscape, and so contribute towards the growing database of landscape evolution rates across southern Africa. Samples of granitic bedrock have been collected along the Olifants River (local/original names: Lepelle, Obalule or iBhalule) in the Kruger National Park in the subtropical east and are being compared to samples of similar composition from the Orange River (local/original names: Gariep, Senqu,) near the Augrabies Falls National Park in the arid west. Both rivers have similar multi-channel morphologies (e.g. mixed bedrock-alluvial anabranching).  A comparison of erosion rates along these otherwise similar rivers at opposite sides of the country will enable an investigation of the effects of climatic differences on erosion rates. Results will allow us to test previous, largely qualitative hypotheses of landscape evolution using state-of-the-art cosmogenic nuclide data analysed at the African continent’s only AMS facility.

How to cite: Khosa, R., Tooth, S., Mbele, V., and Pickering, R.: A Tale of Two Rivers: Comparing erosion rates from two sides of the South African landscape , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-312, https://doi.org/10.5194/egusphere-egu22-312, 2022.

17:45–17:50
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EGU22-12232
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Virtual presentation
Zoë Thomas, Haidee Cadd, Chris Turney, Heather Haines, Chris Marjo, Lorena Becerra Valdivia, Steffi Carter, and Paul Brickle

Creating high resolution chronologies in sediment sequences is important for understanding past carbon-climate dynamics, including accurately dating the timing of climate events, and calculating carbon accumulation changes through time. Here we present >100 14C dates from UNSWs high-throughput MICADAS (Turney et al. 2021) that help answer key questions about carbon-climate dynamics in the Southern Hemisphere. Peatlands from the southern mid-high latitudes have an important role in the global carbon budget but are underrepresented in global syntheses due to paucity of data. Developing accurate age-depth models from peat sequences is notoriously difficult. Outliers are common, with peat being susceptible to issues such as root penetration and in-wash of sediment. With careful consideration to site selection (Thomas et al. 2019) and material preparation (e.g. sieving out root and rootlet material), the age-depth models presented here demonstrate stratigraphic integrity with no evidence of significant outliers, providing robust and detailed chronologies to enable a range of scientific questions to be answered.

To better constrain the understanding of southern peatland dynamics, we collected and radiocarbon-dated 25 basal peats from across sub-Antarctic islands of the South Atlantic region, doubling the existing available data. We then collated basal peat radiocarbon ages from >35°S and analysed their temporal and spatial distribution. We find two distinct phases of peat formation, at ~16,000 cal years BP and ~13,000 cal years BP, independent of northern hemisphere peat growth. Well-constrained age models from these regions (including a 6 m peat sequence with 55 14C dates) show changes in carbon accumulation rates that are consistent with these phases. Potential drivers of these phases include growth disruption via the Antarctic Cold Reversal, and the latitudinal movement of the southern hemisphere westerly winds, with implications for future carbon storage in these under-studied regions.

 

References

Thomas, Z.A., Turney, C.S.M., Hogg, A., Williams, A.N., Fogwill, C.J., 2019. Investigating Subantarctic 14 C Ages of Different Peat Components: Site and Sample Selection for Developing Robust Age Models in Dynamic Landscapes. Radiocarbon 61, 1–19. doi:10.1017/rdc.2019.54

Turney, C., Becerra-Valdivia, L., Sookdeo, A., Thomas, Z.A., Palmer, J., Haines, H.A., Cadd, H., Wacker, L., Baker, A., Anderson, M., Jacobsen, G., Meredith, K., Chinu, K., Bollhalder, S., Marjo, C., 2021. Radiocarbon protocols and first intercomparison results from the Chronos 14Carbon-Cycle Facility, University of New South Wales, Sydney, Australia. Radiocarbon 63(3), 1003–1023. doi:10.1017/RDC.2021.23

How to cite: Thomas, Z., Cadd, H., Turney, C., Haines, H., Marjo, C., Becerra Valdivia, L., Carter, S., and Brickle, P.: Phases of peatland carbon accumulation in the southern mid-latitudes, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12232, https://doi.org/10.5194/egusphere-egu22-12232, 2022.

17:50–17:55
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EGU22-11331
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Presentation form not yet defined
Novothny Ágnes, Sipos György, Filyó Dávid, Surányi Gergely, Végh Tamás, Csonka Diána, Bartyik Tamás, Magyar Gergő, Újvári Gábor, and Horváth Erzsébet

Loess-paleosol sequences are among the most important and detailed terrestrial records of local climate and environmental changes during the Pleistocene. The Carpathian Basin can offer a unique opportunity to investigate temporal and spatial variations in dust accumulation, since 20-25% of its area is covered by loess and the thickness of these material is considerable (80-90 m at max).

High-resolution data are available for some loess sections (Jingbian, Sanbahuo, Toshan, Dunaszekcső) making it possible to develop reliable age-depth models and to calculate more precise mass accumulation rates (MARs), being among the most important input data of paleoclimate models. However, these measurements are mostly limited at around 50 k age, because they are based on radiocarbon or quartz luminescence ages.  In our project, the 20 m thick loess-paleosol profile at Süttő, in the northern part of the Carpathian Basin, was investigated first. More than 130 luminescence and some radiocarbon samples were collected during the sampling campaign during the winter of 2020-21. A systematic sampling for porosity/density measurement was also carried out parallel to luminescence sampling.

This profile was previously dated by Novothny et al. using multiple aliquot additive dose Infrared Stimulated Luminescence (IRSL), single aliquot regeneration IRSL with fading correction, and it resulted in the deposition period of the dust during MIS 6 - MIS 2. The luminescence ages in this study are calculated based on the Optically Stimulated Luminescence signal of quartz for the younger part of the sequence and using the post-Infrared IRSL signal of polymineral fine-grains for the older than ~50 ka part of the sequence. The samples were collected from every 20 cm, and every 10th samples are considered as primary or benchmark samples and therefore complete luminescence tests, residual dose, a-value, and fading measurements are carried out on them. The secondary samples are only measured by shortened measurement routine to optimize the measurement strategy and save measurement time.

Age-depth modelling will be carried out using an R-package specially developed for the Bayesian and inverse modelling of luminescence ages. Based on the constructed age-depth models and the already available datasets MARs will be calculated for each MI stages.

Luminescence properties and variation of dose rate may also have a paleo-environmental relevance, e.g. the luminescence sensitivity of the quartz fraction can refer to the provenance of the dust. Dose rate measurements will be performed by two Canberra type gamma spectrometers equipped with a GX2018 extended range Ge detector and a MiDose alpha/beta counter, which also enables microdosimetric analyses and comparison between the different kinds of detectors.

The research was supported by the NKFIH project K 135509.

How to cite: Ágnes, N., György, S., Dávid, F., Gergely, S., Tamás, V., Diána, C., Tamás, B., Gergő, M., Gábor, Ú., and Erzsébet, H.: High resolution luminescence dating of the Süttő loess-paleosol sequence (MIS 6-2) to create an age depth model and calculate mass accumulation rates - as input data for paleoclimate models, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11331, https://doi.org/10.5194/egusphere-egu22-11331, 2022.

17:55–18:00
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EGU22-13299
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ECS
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Virtual presentation
Simon Dominik Steidle, Kathleen Wendt, R. Lawrence Edwards, Yuri Dublyansky, and Christoph Spötl

234U-238U is a powerful geochronometer that can provide absolute ages of secondary carbonates over a greater interval of time than the well-established 230Th-U. In this study, we apply 234U-238U dating techniques to subaqueous calcite deposits in Devils Hole cave, located in the Amargosa Desert (Nevada, USA). Subaqueous calcite deposits record paleo water table elevations within the cave. Previous work used 230Th-U dating techniques to reconstruct fluctuations in the local water table over the last 350,000 years (Wendt et al. 2018). We have extended the Devils Hole water table record up to and beyond the 230Th-U dating limit using both 230Th-U and 234U-238U dating techniques. Precise control (±60.5‰) of the initial 234U/238U ratio is possible due to its low variability and high correlation with δ13C and δ18O (Li et al., 2020). Resulting 234U-238U age uncertainties are on the order of ±16,000 years for 800,000-year old calcite. The new 234U-238U ages allow us to extend the Devils Hole water-table record across the full range of deposition. The resulting 800,000-year record reveals local water-table fluctuated on glacial-interglacial times scales, reaching maximum heights of 20m above modern-day levels. The observed orbital- to millennial-scale fluctuations are interpreted to be primarily driven by climate. Assessing the sensitivity of the Devils Hole water table to various climate modes is key to predicting future water availability in this water-stressed region.

 

Wendt, K. A., Dublyansky, Y. V., Moseley, G. E., Edwards, R. L., Cheng, H. & Spötl, C., 2018, Moisture availability in the southwest United States over the last three glacial-interglacial cycles Science Advances, 4, https://doi.org/10.1126/sciadv.aau1375.

Li, X.; Wendt, K. A.; Dublyansky, Y.; Moseley, G. E.; Spötl, C. & Edwards, R. L., 2020 Novel method for determining 234U-238U ages of Devils Hole 2 cave calcite, Geochronology, https://doi.org/10.5194/gchron-2020-26

How to cite: Steidle, S. D., Wendt, K., Edwards, R. L., Dublyansky, Y., and Spötl, C.: U-series dating of water-table fluctuations in Devils Hole cave (Nevada, USA) over the last 800,000 years, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13299, https://doi.org/10.5194/egusphere-egu22-13299, 2022.

18:00–18:05
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EGU22-4751
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ECS
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Virtual presentation
Inga Kristina Kerber, Fabian Kontor, René Eichstädter, Andrea Schröder-Ritzrau, Sophie Warken, and Norbert Frank

Carbonate based archives, such as speleothems and cold-water corals, yield valuable information on past states of the climate system. The key chronometer to access the deposition times of these archives is 230Th/U dating, typically measured using multi-collector inductively coupled plasma mass spectrometers (MC-ICP-MS). Here, we present our Python-based data treatment, correction and age calculation algorithm equipped with a graphical user interface (GUI) which ensures reproducibility and allows for customized calculation constants. We outline the relevance of proper data outlier treatment and review hardware settings such as fade-out times of Faraday cups (FC).  Furthermore, we systematically analyse the effect of variation in different MC-ICP-MS raw data corrections as tailing and process blank on the accuracy of the atomic ratios 230Th/238U and 234U/238U and the ages. To do so, three speleothem samples of different isotopic concentrations and ages were employed. We find that already a variation in tailing of 10 % causes a deviation on the permille level from the actual age for older samples (~150 ka), whilst younger samples are hardly affected. Process blank (instrumental background) measurements in turn affect the youngest samples strongest, as we found that an unnoticed increase of 50 % of the process blank results in a deviation on the percent level for the youngest sample (few hundred years). On contrary, hydride correction is minor for all samples, thus all time scales. In conclusion, the methods presented here permit routine precision levels of isotope analysis in the order of 5 ε units (1 ε-unit = 10-4).

How to cite: Kerber, I. K., Kontor, F., Eichstädter, R., Schröder-Ritzrau, A., Warken, S., and Frank, N.: Data treatment and systematic analysis of MC-ICP-MS 230Th/238U-dating of secondary carbonates, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4751, https://doi.org/10.5194/egusphere-egu22-4751, 2022.

18:05–18:10
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EGU22-9533
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Virtual presentation
Tian Xia, Tong-Yan Xia, Wei-Wei Sun, Hui-Min Zhu, Wei Jiang, and Zheng-Tian Lu

On earth, Calcium-41 is produced as a cosmogenic isotope via neutron capture process, leaving a natural isotopic abundance of 10-15 on earth surface. Calcium is also of vital importance for the metabolism of biological organisms. Consequently, analysis of the long lived radioactive isotope Calcium-41 is of great importance in geoscience, archeology and life sciences. The half-life of Calcium-41 is 1.03 x 105 years. It is a good candidate in dating rock and bone samples ranging from 50,000 to 1,000,000 years old.

The available techniques for trace analysis of Calcium-41 include accelerator mass spectrometry (AMS) and resonance ionization mass spectroscopy (RIMS). The detection limit of RIMS is on the level of 10-11 due to the interference of Potassium-41, which is difficult to remove from the sample. The analysis with high-energy AMS is more expensive than the table top apparatus, and it also faces similar problem as RIMS method.

We develop an atom trap trace analysis(ATTA) apparatus for Calcium-41 analysis to the sensitivity of 10-16 abundance level by one day of single atom counting. ATTA uses laser tuned at the resonant wavelength for a specific element and isotope to slow down and capture single atom by fluorescence radiation. It has a very high selectivity of element and isotope, which is more advantageous than AMS and RIMS to avoid isobar interference. ATTA has been used in analysis of Krypton-81, Argon-39 dating of the hydrological samples. This work on high sensitivity Calcium-41 analysis is very promising in dating the geochemical sample to determine the exposure ages of rocks or in cosmochemistry for investigations on terrestrial ages.

How to cite: Xia, T., Xia, T.-Y., Sun, W.-W., Zhu, H.-M., Jiang, W., and Lu, Z.-T.: Analyzing Ca-41 sample at E-16 abundance level with cold atom trap techniques, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9533, https://doi.org/10.5194/egusphere-egu22-9533, 2022.

18:10–18:15
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EGU22-11906
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ECS
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On-site presentation
Joanne Elkadi, Rabiul H. Biswas, Vjeran Visnjevic, Florence Magnin, Benjamin Lehmann, Georgina E. King, and Frédéric Herman

Our ability to quantify past climate conditions is crucial for understanding and predicting future climate scenarios as well as landscape evolution. One of the most drastic climatic changes in Earth’s history was the Last Glacial Maximum (LGM) where a significant area of the planet’s surface was covered in ice (Clark et al., 2009). However, most reconstructions of the Earth’s past climate rely on the use of climate proxies (e.g. Jones and Mann, 2004 for a review), which are particularly poorly preserved in terrestrial settings previously covered by ice- thus limiting the applicability of existing methods.

Here, we apply feldspar thermoluminescence (TL) surface paleothermometry (Biswas et al., 2018; 2020) to better constrain the temperature history of exposed bedrock surfaces since the Last Glacial Maximum to present day. The aim of this study is to contribute towards a more detailed understanding of glacial and interglacial temperature fluctuations across the Central and Western Alps. Feldspar TL paleothermometry is a recently developed technique that exploits the dependence of trapped charge on temperature (Biswas et al., 2018). The trapped charge is sourced from feldspar’s crystalline lattice. While a TL signal can be extracted between room temperature and 450°C, traps sensitive to typical surface temperature variations (e.g.10°C) are found between 200°C and 250°C (Biswas et al., 2020). As a result, five thermometers (200°C to 250°C in 10°C intervals) can be used together as a multi-thermometer, and subsequently combined with a Bayesian inversion approach to constrain thermal histories over the last50 kyr (Biswas et al., 2020).

The temperature histories of bedrock samples collected down two vertical transects adjacent to the Gorner (Switzerland) and the Mer de Glace (France) glaciers, which have been exposed progressively since the LGM, will be presented. Preliminary results suggest a temperature difference of ∼10 °C in both locations, which is promising and in agreement with past surface temperatures obtained from other studies.

References:

Biswas, R.H., Herman, F., King, G.E., Braun, J., 2018. Thermoluminescence of feldspar as a multi-thermochronometer to constrain the temporal variation of rock exhumation in the recent past. Earth and Planetary Science Letters, 495, 56-68.

Biswas, R.H., Herman, F., King, G.E., Lehmann, B., Singhvi, A.K., 2020. Surface paleothermometry using low temperature thermoluminescence of feldspar. Climate of the Past, 16, 2075-2093.

Clark, P. U., Dyke, A. S., Shakun, J. D., Carlson, A. E., Clark, J., Wohlfarth, B., Mitrovica, J. X., Hostetler, S. W., and McCabe, A. M., 2009. The Last Glacial Maximum. Science, 325 (5941), 710-714.

Jones, P.D., Mann, M.E., 2004. Climate over past millennia. Reviews of Geophysics, 42, 2004.

How to cite: Elkadi, J., Biswas, R. H., Visnjevic, V., Magnin, F., Lehmann, B., King, G. E., and Herman, F.: Constraining Last Glacial Maximum bedrock surface temperatures in the Western Alps using thermoluminescence paleothermometry., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11906, https://doi.org/10.5194/egusphere-egu22-11906, 2022.