Articles | Volume 6, issue 4
https://doi.org/10.5194/gchron-6-697-2024
© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/gchron-6-697-2024
© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| 
20 Dec 2024
Research article |
| 20 Dec 2024
| 20 Dec 2024
Interpreting cooling dates and histories from laser ablation in situ (U–Th–Sm) ∕ He thermochronometry: a modelling perspective
Christoph Glotzbach
CORRESPONDING AUTHOR
Department of Geosciences, University of Tübingen, Tübingen, 72076, Germany
Todd A. Ehlers
School of Geographical and Earth Sciences, University of Glasgow, Glasgow, G12 8QQ, UK
Department of Geosciences, University of Tübingen, Tübingen, 72076, Germany
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Mirjam Schaller, Daniel Peifer, Alexander B. Neely, Thomas Bernard, Christoph Glotzbach, Alexander R. Beer, and Todd A. Ehlers
Earth Surf. Dynam., 13, 571–591, https://doi.org/10.5194/esurf-13-571-2025, https://doi.org/10.5194/esurf-13-571-2025, 2025
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This study reports chemical weathering, physical erosion, and denudation rates from river load data in the Swabian Alb, southwestern Germany. Tributaries to the Neckar River draining to the north show higher rates than tributaries draining to the southeast into the Danube River, causing a retreat of the Swabian Alb escarpment. Observations are discussed in light of anthropogenic impact, lithology, and topography. The data are further compared to other rates over space and time and to global data.
Andrea Madella, Christoph Glotzbach, and Todd A. Ehlers
Geochronology, 4, 177–190, https://doi.org/10.5194/gchron-4-177-2022, https://doi.org/10.5194/gchron-4-177-2022, 2022
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Cooling ages date the time at which minerals cross a certain isotherm on the way up to Earth's surface. Such ages can be measured from bedrock material and river sand. If spatial variations in bedrock ages are known in a river catchment, the spatial distribution of erosion can be inferred from the distribution of the ages measured from the river sand grains. Here we develop a new tool to help such analyses, with particular emphasis on quantifying uncertainties due to sample size.
Hemanti Sharma, Todd A. Ehlers, Christoph Glotzbach, Manuel Schmid, and Katja Tielbörger
Earth Surf. Dynam., 9, 1045–1072, https://doi.org/10.5194/esurf-9-1045-2021, https://doi.org/10.5194/esurf-9-1045-2021, 2021
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We study effects of variable climate–vegetation with different uplift rates on erosion–sedimentation using a landscape evolution modeling approach. Results suggest that regardless of uplift rates, transients in precipitation–vegetation lead to transients in erosion rates in the same direction of change. Vegetation-dependent erosion and sedimentation are influenced by Milankovitch timescale changes in climate, but these transients are superimposed upon tectonically driven uplift rates.
Lorenz Michel, Christoph Glotzbach, Sarah Falkowski, Byron A. Adams, and Todd A. Ehlers
Earth Surf. Dynam., 7, 275–299, https://doi.org/10.5194/esurf-7-275-2019, https://doi.org/10.5194/esurf-7-275-2019, 2019
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Mountain-building processes are often investigated by assuming a steady state, meaning the balance between opposing forces, like mass influx and mass outflux. This work shows that the Olympic Mountains are in flux steady state on long timescales (i.e., 14 Myr), but the flux steady state could be disturbed on shorter timescales, especially by the Plio–Pleistocene glaciation. The contribution highlights the temporally nonsteady evolution of mountain ranges.
Mirjam Schaller, Daniel Peifer, Alexander B. Neely, Thomas Bernard, Christoph Glotzbach, Alexander R. Beer, and Todd A. Ehlers
Earth Surf. Dynam., 13, 571–591, https://doi.org/10.5194/esurf-13-571-2025, https://doi.org/10.5194/esurf-13-571-2025, 2025
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This study reports chemical weathering, physical erosion, and denudation rates from river load data in the Swabian Alb, southwestern Germany. Tributaries to the Neckar River draining to the north show higher rates than tributaries draining to the southeast into the Danube River, causing a retreat of the Swabian Alb escarpment. Observations are discussed in light of anthropogenic impact, lithology, and topography. The data are further compared to other rates over space and time and to global data.
Daniel Boateng, Sebastian G. Mutz, Armelle Ballian, Maud J. M. Meijers, Katharina Methner, Svetlana Botsyun, Andreas Mulch, and Todd A. Ehlers
Earth Syst. Dynam., 14, 1183–1210, https://doi.org/10.5194/esd-14-1183-2023, https://doi.org/10.5194/esd-14-1183-2023, 2023
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We present model-based topographic sensitivity experiments that provide valuable constraints for interpreting past proxies and records of climate and tectonic processes. The study uses a climate model to quantify the response of regional climate and oxygen isotopic composition of precipitation to diachronous surface uplift scenarios across the European Alps. The results suggest that isotopic signal changes can be measured in geologic archives using stable isotope paleoaltimetry.
Hemanti Sharma and Todd A. Ehlers
Earth Surf. Dynam., 11, 1161–1181, https://doi.org/10.5194/esurf-11-1161-2023, https://doi.org/10.5194/esurf-11-1161-2023, 2023
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Seasonality in precipitation (P) and vegetation (V) influences catchment erosion (E), although which factor plays the dominant role is unclear. In this study, we performed a sensitivity analysis of E to P–V seasonality through numerical modeling. Our results suggest that P variations strongly influence seasonal variations in E, while the effect of seasonal V variations is secondary but significant. This is more pronounced in moderate and least pronounced in extreme environmental settings.
Hemanti Sharma, Sebastian G. Mutz, and Todd A. Ehlers
Earth Surf. Dynam., 10, 997–1015, https://doi.org/10.5194/esurf-10-997-2022, https://doi.org/10.5194/esurf-10-997-2022, 2022
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We estimate global changes in frost cracking intensity (FCI) using process-based models for four time slices in the late Cenozoic ranging from the Pliocene (∼ 3 Ma) to pre-industrial (∼ 1850 CE, PI). For all time slices, results indicate that FCI was most prevalent in middle to high latitudes and high-elevation lower-latitude areas such as Tibet. Larger deviations (relative to PI) were observed in colder (LGM) and warmer climates (Pliocene) due to differences in temperature and glaciation.
Astrid Oetting, Emma C. Smith, Jan Erik Arndt, Boris Dorschel, Reinhard Drews, Todd A. Ehlers, Christoph Gaedicke, Coen Hofstede, Johann P. Klages, Gerhard Kuhn, Astrid Lambrecht, Andreas Läufer, Christoph Mayer, Ralf Tiedemann, Frank Wilhelms, and Olaf Eisen
The Cryosphere, 16, 2051–2066, https://doi.org/10.5194/tc-16-2051-2022, https://doi.org/10.5194/tc-16-2051-2022, 2022
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This study combines a variety of geophysical measurements in front of and beneath the Ekström Ice Shelf in order to identify and interpret geomorphological evidences of past ice sheet flow, extent and retreat.
The maximal extent of grounded ice in this region was 11 km away from the continental shelf break.
The thickness of palaeo-ice on the calving front around the LGM was estimated to be at least 305 to 320 m.
We provide essential boundary conditions for palaeo-ice-sheet models.
Andrea Madella, Christoph Glotzbach, and Todd A. Ehlers
Geochronology, 4, 177–190, https://doi.org/10.5194/gchron-4-177-2022, https://doi.org/10.5194/gchron-4-177-2022, 2022
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Cooling ages date the time at which minerals cross a certain isotherm on the way up to Earth's surface. Such ages can be measured from bedrock material and river sand. If spatial variations in bedrock ages are known in a river catchment, the spatial distribution of erosion can be inferred from the distribution of the ages measured from the river sand grains. Here we develop a new tool to help such analyses, with particular emphasis on quantifying uncertainties due to sample size.
Mirjam Schaller and Todd A. Ehlers
Earth Surf. Dynam., 10, 131–150, https://doi.org/10.5194/esurf-10-131-2022, https://doi.org/10.5194/esurf-10-131-2022, 2022
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Soil production, chemical weathering, and physical erosion rates from the large climate and vegetation gradient of the Chilean Coastal Cordillera (26 to 38° S) are investigated. Rates are generally lowest in the sparsely vegetated and arid north, increase southward toward the Mediterranean climate, and then decrease slightly, or possible stay the same, further south in the temperate humid zone. This trend is compared with global data from similar soil-mantled hillslopes in granitic lithologies.
Emilija Krsnik, Katharina Methner, Marion Campani, Svetlana Botsyun, Sebastian G. Mutz, Todd A. Ehlers, Oliver Kempf, Jens Fiebig, Fritz Schlunegger, and Andreas Mulch
Solid Earth, 12, 2615–2631, https://doi.org/10.5194/se-12-2615-2021, https://doi.org/10.5194/se-12-2615-2021, 2021
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Here we present new surface elevation constraints for the middle Miocene Central Alps based on stable and clumped isotope geochemical analyses. Our reconstructed paleoelevation estimate is supported by isotope-enabled paleoclimate simulations and indicates that the Miocene Central Alps were characterized by a heterogeneous and spatially transient topography with high elevations locally exceeding 4000 m.
Kirstin Übernickel, Jaime Pizarro-Araya, Susila Bhagavathula, Leandro Paulino, and Todd A. Ehlers
Biogeosciences, 18, 5573–5594, https://doi.org/10.5194/bg-18-5573-2021, https://doi.org/10.5194/bg-18-5573-2021, 2021
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Animal burrowing is important because it impacts the physical and chemical evolution of Earth’s surface. However, most studies are species specific, and compilations of animal community effects are missing. We present an inventory of the currently known 390 burrowing species for all of Chile along its climate gradient. We observed increasing amounts of excavated material from an area with dry conditions along a gradient towards more humid conditions.
Sean D. Willett, Frédéric Herman, Matthew Fox, Nadja Stalder, Todd A. Ehlers, Ruohong Jiao, and Rong Yang
Earth Surf. Dynam., 9, 1153–1221, https://doi.org/10.5194/esurf-9-1153-2021, https://doi.org/10.5194/esurf-9-1153-2021, 2021
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The cooling climate of the last few million years leading into the ice ages has been linked to increasing erosion rates by glaciers. One of the ways to measure this is through mineral cooling ages. In this paper, we investigate potential bias in these data and the methods used to analyse them. We find that the data are not themselves biased but that appropriate methods must be used. Past studies have used appropriate methods and are sound in methodology.
Hemanti Sharma, Todd A. Ehlers, Christoph Glotzbach, Manuel Schmid, and Katja Tielbörger
Earth Surf. Dynam., 9, 1045–1072, https://doi.org/10.5194/esurf-9-1045-2021, https://doi.org/10.5194/esurf-9-1045-2021, 2021
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We study effects of variable climate–vegetation with different uplift rates on erosion–sedimentation using a landscape evolution modeling approach. Results suggest that regardless of uplift rates, transients in precipitation–vegetation lead to transients in erosion rates in the same direction of change. Vegetation-dependent erosion and sedimentation are influenced by Milankovitch timescale changes in climate, but these transients are superimposed upon tectonically driven uplift rates.
Solmaz Mohadjer, Sebastian G. Mutz, Matthew Kemp, Sophie J. Gill, Anatoly Ischuk, and Todd A. Ehlers
Geosci. Commun., 4, 281–295, https://doi.org/10.5194/gc-4-281-2021, https://doi.org/10.5194/gc-4-281-2021, 2021
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Lack of access to science-based natural hazards information impedes the effectiveness of school-based disaster risk reduction education. To address this challenge, we created and classroom tested a series of earthquake education videos that were co-taught by school teachers and Earth scientists in the UK and Tajikistan. Comparison of the results reveals significant differences between students' views on the Earth's interior and why and where earthquakes occur.
Mirjam Schaller, Igor Dal Bo, Todd A. Ehlers, Anja Klotzsche, Reinhard Drews, Juan Pablo Fuentes Espoz, and Jan van der Kruk
SOIL, 6, 629–647, https://doi.org/10.5194/soil-6-629-2020, https://doi.org/10.5194/soil-6-629-2020, 2020
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In this study geophysical observations from ground-penetrating radar with pedolith physical and geochemical properties from pedons excavated in four study areas of the climate and ecological gradient in the Chilean Coastal Cordillera are combined. Findings suggest that profiles with ground-penetrating radar along hillslopes can be used to infer lateral thickness variations in pedolith horizons and to some degree physical and chemical variations with depth.
Clemens Schannwell, Reinhard Drews, Todd A. Ehlers, Olaf Eisen, Christoph Mayer, Mika Malinen, Emma C. Smith, and Hannes Eisermann
The Cryosphere, 14, 3917–3934, https://doi.org/10.5194/tc-14-3917-2020, https://doi.org/10.5194/tc-14-3917-2020, 2020
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To reduce uncertainties associated with sea level rise projections, an accurate representation of ice flow is paramount. Most ice sheet models rely on simplified versions of the underlying ice flow equations. Due to the high computational costs, ice sheet models based on the complete ice flow equations have been restricted to < 1000 years. Here, we present a new model setup that extends the applicability of such models by an order of magnitude, permitting simulations of 40 000 years.
Clemens Schannwell, Reinhard Drews, Todd A. Ehlers, Olaf Eisen, Christoph Mayer, and Fabien Gillet-Chaulet
The Cryosphere, 13, 2673–2691, https://doi.org/10.5194/tc-13-2673-2019, https://doi.org/10.5194/tc-13-2673-2019, 2019
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Ice rises are important ice-sheet features that archive the ice sheet's history in their internal structure. Here we use a 3-D numerical ice-sheet model to simulate mechanisms that lead to changes in the geometry of the internal structure. We find that changes in snowfall result in much larger and faster changes than similar changes in ice-shelf geometry. This result is integral to fully unlocking the potential of ice rises as ice-dynamic archives and potential ice-core drilling sites.
Sebastian G. Mutz and Todd A. Ehlers
Earth Surf. Dynam., 7, 663–679, https://doi.org/10.5194/esurf-7-663-2019, https://doi.org/10.5194/esurf-7-663-2019, 2019
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We apply machine learning techniques to quantify and explain differences between recent palaeoclimates with regards to factors that are important in shaping the Earth's surface. We find that changes in ice cover, near-surface air temperature and rainfall duration create the most distinct differences. We also identify regions particularly prone to changes in rainfall and temperature-controlled erosion, which will help with the interpretation of erosion rates and geological archives.
Lorenz Michel, Christoph Glotzbach, Sarah Falkowski, Byron A. Adams, and Todd A. Ehlers
Earth Surf. Dynam., 7, 275–299, https://doi.org/10.5194/esurf-7-275-2019, https://doi.org/10.5194/esurf-7-275-2019, 2019
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Mountain-building processes are often investigated by assuming a steady state, meaning the balance between opposing forces, like mass influx and mass outflux. This work shows that the Olympic Mountains are in flux steady state on long timescales (i.e., 14 Myr), but the flux steady state could be disturbed on shorter timescales, especially by the Plio–Pleistocene glaciation. The contribution highlights the temporally nonsteady evolution of mountain ranges.
Matthias Nettesheim, Todd A. Ehlers, David M. Whipp, and Alexander Koptev
Solid Earth, 9, 1207–1224, https://doi.org/10.5194/se-9-1207-2018, https://doi.org/10.5194/se-9-1207-2018, 2018
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In this modeling study, we investigate rock uplift at plate corners (syntaxes). These are characterized by a unique bent geometry at subduction zones and exhibit some of the world's highest rock uplift rates. We find that the style of deformation changes above the plate's bent section and that active subduction is necessary to generate an isolated region of rapid uplift. Strong erosion there localizes uplift on even smaller scales, suggesting both tectonic and surface processes are important.
Manuel Schmid, Todd A. Ehlers, Christian Werner, Thomas Hickler, and Juan-Pablo Fuentes-Espoz
Earth Surf. Dynam., 6, 859–881, https://doi.org/10.5194/esurf-6-859-2018, https://doi.org/10.5194/esurf-6-859-2018, 2018
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We present a numerical modeling study into the interactions between transient climate and vegetation cover with hillslope and fluvial processes. We use a state-of-the-art landscape evolution model library (Landlab) and design model experiments to investigate the effect of climate change and the associated changes in surface vegetation cover on main basin metrics. This paper is a companion paper to Part 1 (this journal), which investigates the effect of climate change on surface vegetation cover.
Christian Werner, Manuel Schmid, Todd A. Ehlers, Juan Pablo Fuentes-Espoz, Jörg Steinkamp, Matthew Forrest, Johan Liakka, Antonio Maldonado, and Thomas Hickler
Earth Surf. Dynam., 6, 829–858, https://doi.org/10.5194/esurf-6-829-2018, https://doi.org/10.5194/esurf-6-829-2018, 2018
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Vegetation is crucial for modulating rates of denudation and landscape evolution, and is directly influenced by climate conditions and atmospheric CO2 concentrations. Using transient climate data and a state-of-the-art dynamic vegetation model we simulate the vegetation composition and cover from the Last Glacial Maximum to present along the Coastal Cordillera of Chile. In part 2 we assess the landscape response to transient climate and vegetation cover using a landscape evolution model.
Byron A. Adams and Todd A. Ehlers
Earth Surf. Dynam., 6, 595–610, https://doi.org/10.5194/esurf-6-595-2018, https://doi.org/10.5194/esurf-6-595-2018, 2018
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Where alpine glaciers were active in the past, they have created scenic landscapes that are likely in the process of morphing back into a form that it more stable with today's climate regime and tectonic forces. By looking at older erosion rates from before the time of large alpine glaciers and erosion rates since deglaciation in the Olympic Mountains (USA), we find that the topography and erosion rates have not drastically changed despite the impressive glacial valleys that have been carved.
Michelle E. Gilmore, Nadine McQuarrie, Paul R. Eizenhöfer, and Todd A. Ehlers
Solid Earth, 9, 599–627, https://doi.org/10.5194/se-9-599-2018, https://doi.org/10.5194/se-9-599-2018, 2018
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We examine the Himalayan Mountains of Bhutan by integrating balanced geologic cross sections with cooling ages from a suite of mineral systems. Interpretations of cooling ages are intrinsically linked to both the motion along faults as well as the location and magnitude of erosion. In this study, we use flexural and thermal kinematic models to understand the sensitivity of predicted cooling ages to changes in fault kinematics, geometry, and topography.
Sebastian G. Mutz, Todd A. Ehlers, Martin Werner, Gerrit Lohmann, Christian Stepanek, and Jingmin Li
Earth Surf. Dynam., 6, 271–301, https://doi.org/10.5194/esurf-6-271-2018, https://doi.org/10.5194/esurf-6-271-2018, 2018
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We use a climate model and statistics to provide an overview of regional climates from different times in the late Cenozoic. We focus on tectonically active mountain ranges in particular. Our results highlight significant changes in climates throughout the late Cenozoic, which should be taken into consideration when interpreting erosion rates. We also document the differences between model- and proxy-based estimates for late Cenozoic climate change in South America and Tibet.
Heiko Paeth, Christian Steger, Jingmin Li, Sebastian G. Mutz, and Todd A. Ehlers
Clim. Past Discuss., https://doi.org/10.5194/cp-2017-111, https://doi.org/10.5194/cp-2017-111, 2017
Manuscript not accepted for further review
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We use a high-resolution regional climate model to investigate various episodes of distinct climate states over the Tibetan Plateau region during the Cenozoic rise of the Plateau and Quaternary glacial/interglacial cycles. The simulated changes are in good agreement with available paleo-climatic reconstructions from proxy data. It is shown that in some regions of the Tibetan Plateau the climate anomalies during the Quaternary have been as strong as the changes occurring during the uplift period.
Michael Dietze, Solmaz Mohadjer, Jens M. Turowski, Todd A. Ehlers, and Niels Hovius
Earth Surf. Dynam., 5, 653–668, https://doi.org/10.5194/esurf-5-653-2017, https://doi.org/10.5194/esurf-5-653-2017, 2017
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We use a seismometer network to detect and locate rockfalls, a key process shaping steep mountain landscapes. When tested against laser scan surveys, all seismically detected events could be located with an average deviation of 81 m. Seismic monitoring provides insight to the dynamics of individual rockfalls, which can be as small as 0.0053 m3. Thus, seismic methods provide unprecedented temporal, spatial and kinematic details about this important process.
Solmaz Mohadjer, Todd Alan Ehlers, Rebecca Bendick, Konstanze Stübner, and Timo Strube
Nat. Hazards Earth Syst. Sci., 16, 529–542, https://doi.org/10.5194/nhess-16-529-2016, https://doi.org/10.5194/nhess-16-529-2016, 2016
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The Central Asia Fault Database is the first publicly accessible digital repository for active faults in central Asia and the surrounding regions. It includes an interactive map and a search tool that allow users to query and display critical fault information such as slip rates and earthquake history. The map displays over 1196 fault traces and 34 000 earthquake locations. The database contains attributes for 123 faults mentioned in the literature.
R. M. Headley and T. A. Ehlers
Earth Surf. Dynam., 3, 153–170, https://doi.org/10.5194/esurf-3-153-2015, https://doi.org/10.5194/esurf-3-153-2015, 2015
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Within a landscape evolution model operating over geologic timescales, this work evaluates how different assumptions and levels of complexity for modeling glacier flow impact the pattern and amount of glacial erosion. Compared to those in colder climates, modeled glaciers in warmer and wetter climates are more sensitive to the choice of glacier flow model. Differences between landscapes evolved with different glacier flow models are intensified over multiple cycles.
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Simulating sedimentary burial cycles – Part 2: Elemental-based multikinetic apatite fission-track interpretation and modelling techniques illustrated using examples from northern Yukon
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How many grains are needed for quantifying catchment erosion from tracer thermochronology?
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Christopher T. Halsted, Paul R. Bierman, Alexandru T. Codilean, Lee B. Corbett, and Marc W. Caffee
Geochronology, 7, 213–228, https://doi.org/10.5194/gchron-7-213-2025, https://doi.org/10.5194/gchron-7-213-2025, 2025
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Sediment generation on hillslopes and transport through river networks are complex processes that influence landscape evolution. In this study, we compiled sand from 766 river basins and measured its subtle radioactivity to unravel timelines of sediment routing around the world. With these data, we empirically confirm that sediment from large lowland basins in tectonically stable regions typically experiences long periods of burial, while sediment moves rapidly through small upland basins.
Allison W. Jacobel, Kassandra M. Costa, Lily M. Applebaum, and Serena Conde
Geochronology, 7, 123–138, https://doi.org/10.5194/gchron-7-123-2025, https://doi.org/10.5194/gchron-7-123-2025, 2025
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The equatorial Pacific is an important region that helps determine Earth's climate. This work presents new age models for two sediment core sites located in that region, spanning the last 280 kyr. Our age models are based on new radiocarbon dates and oxygen isotope measurements. We also use the oxygen isotope data to infer changes in sea surface salinity patterns, finding evidence for a change in the position of the Intertropical Convergence Zone (ITCZ) on glacial and interglacial timescales.
Marie-Eugénie Meusseunan Pascale Jamba, Pierre Francus, Antoine Gagnon-Poiré, and Guillaume St-Onge
Geochronology, 7, 83–111, https://doi.org/10.5194/gchron-7-83-2025, https://doi.org/10.5194/gchron-7-83-2025, 2025
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This article presents a non-destructive method for studying laminated sediments with X-ray micro-computed tomography (μCT). It aims to study the possibility of using μCT as an analytical tool to analyse varved sediments in the context of paleoclimatic studies. As a result, µCT offers the possibility of doing fast analysis and constitutes a powerful tool to improve the quality of results through the access of a 3D view, allowing for choosing the most representative part of a varved record.
Chetan Nathwani, Dawid Szymanowski, Lorenzo Tavazzani, Sava Markovic, Adrianna L. Virmond, and Cyril Chelle-Michou
Geochronology, 7, 15–33, https://doi.org/10.5194/gchron-7-15-2025, https://doi.org/10.5194/gchron-7-15-2025, 2025
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We performed a statistical analysis of high-precision U–Pb zircon age distributions. This reveals that volcanic and porphyry zircon age distributions are skewed to younger ages, whereas plutonic age distributions are skewed to older ages. We show that this is caused by truncation of zircon crystallisation by magma evacuation rather than differences in magmatic flux. Our contribution has key implications for modelling of magma dynamics and eruption ages using zircon age distributions.
Pieter Vermeesch, Noah McLean, Anton Vaks, Tzahi Golan, Sebastian F. M. Breitenbach, and Randall Parris
EGUsphere, https://doi.org/10.5194/egusphere-2025-432, https://doi.org/10.5194/egusphere-2025-432, 2025
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U-Pb dating of cave sediments has provided important new time constraints on the evolution of cave-dwelling organisms (including early humans), and of Earth's climate during the past 5 million years. This paper shows that the most common type of U-Pb dating, which uses 238U and 206Pb, can be inaccurate beyond 2 million years ago. It proposes an alternative type of U-Pb dating, using 235U and 207Pb, as a more accurate alternative.
Steven Denyszyn, Donald W. Davis, and Denis Fougerouse
Geochronology, 6, 607–619, https://doi.org/10.5194/gchron-6-607-2024, https://doi.org/10.5194/gchron-6-607-2024, 2024
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Decay of U to Pb in baddeleyite is used for dating mafic rocks, but some daughter Pb atoms can be ejected out of the crystal, resulting in ages that seem too young. Atom probe tomography was used to map U and Pb atoms in 3D within baddeleyite crystals and estimate the average distance that Pb atoms are displaced by recoil. This allows us to test the relationship between crystal size and apparent age. There is also evidence for clustering of U atoms, inviting more work on how this may occur.
Jesús Muñoz-Montecinos, Andrea Giuliani, Senan Oesch, Silvia Volante, Bradley Peters, and Whitney Behr
Geochronology, 6, 585–605, https://doi.org/10.5194/gchron-6-585-2024, https://doi.org/10.5194/gchron-6-585-2024, 2024
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Dating the roots of plate boundaries is essential for understanding geologic processes, but geochemical limitations, particularly in young mafic rocks, make this challenging. Advancements in mass spectrometry now enable high-resolution analysis of micro-domains. We assess these limitations by dating rocks from Syros. Multi-phase mineral analysis improves age uncertainty 6-fold. We emphasize the importance of the local geologic context and propose strategies to mitigate uncertainties.
Jesse R. Reimink, Renan Beckman, Erik Schoonover, Max Lloyd, Joshua Garber, Joshua H. F. L. Davies, Alexander Cerminaro, Morgann G. Perrot, and Andrew J. Smye
Geochronology Discuss., https://doi.org/10.5194/gchron-2024-27, https://doi.org/10.5194/gchron-2024-27, 2024
Revised manuscript accepted for GChron
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This manuscript presents a new method to date geological events affecting sedimentary rocks. This method relies on the potential for the zircon U-Pb system to be disturbed during fluid-flow, alteration, and metamorphic events in sedimentary rocks. This manuscript presents synthetic datasets for testing the accuracy and precision of the discordance dating method, as well as data from detrital zircons found in the contact metamorphic aureole surround the Alta Stock.
Andrew L. Gorin, Joshua M. Gorin, Marie Bergelin, and David L. Shuster
Geochronology, 6, 521–540, https://doi.org/10.5194/gchron-6-521-2024, https://doi.org/10.5194/gchron-6-521-2024, 2024
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The multiple-diffusion domain (MDD) model quantifies the temperature dependence of noble gas diffusivity in minerals. However, current methods for tuning MDD parameters can yield biased results, leading to underestimates of sample temperatures through geologic time. Our "MDD Tool Kit" software optimizes all MDD parameters simultaneously, overcoming these biases. We then apply this software to a previously published 40Ar/39Ar dataset (Wong, 2023) to showcase its efficacy.
Jarred Cain Lloyd, Carl Spandler, Sarah E. Gilbert, and Derrick Hasterok
EGUsphere, https://doi.org/10.5194/egusphere-2024-2908, https://doi.org/10.5194/egusphere-2024-2908, 2024
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Laser-based dating of rocks and minerals is invaluable in geoscience. This study presents a significant advancement in our ability to model and correct for a process called downhole fractionation (DHF) that can impact the accuracy and uncertainty of dates. We develop an algorithm that quantitatively models DHF patterns. The implications are far-reaching: improved accuracy, reduced uncertainty, and easier comparisons between different samples and laboratories.
Niklas Hohmann, David De Vleeschouwer, Sietske Batenburg, and Emilia Jarochowska
EGUsphere, https://doi.org/10.5194/egusphere-2024-2857, https://doi.org/10.5194/egusphere-2024-2857, 2024
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Age-depth models assign ages to sampling locations (e.g., in drill cores), making them crucial to determined timing and pace of past changes. We present two methods to estimate age-depth models from sedimentological and stratigraphic information, resulting in richer and more empirically realistic age-depth models. As a use case, we determine (1) the timing of the Frasnian-Famennian extinction and (2) examine the duration of PETM, an potential deep time analogue for anthropogenic climate change.
Guilhem Hoareau, Fanny Claverie, Christophe Pecheyran, Gaëlle Barbotin, Michael Perk, Nicolas E. Beaudoin, Brice Lacroix, and E. Troy Rasbury
EGUsphere, https://doi.org/10.5194/egusphere-2024-2366, https://doi.org/10.5194/egusphere-2024-2366, 2024
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We present an approach to U-Pb dating of carbonates using isotopic image maps. The maps are divided into squares called virtual spots. For each virtual spot, statistical values (mean, uncertainty) are used to determine the age. The user can modify the size and location of the virtual spots and select those that give the most robust age. This approach, applied to high spatial resolution images, makes it possible for the first time to obtain satisfactory ages on images as small as 100 µm x 100 µm.
Marcel Guillong, Elias Samankassou, Inigo A. Müller, Dawid Szymanowski, Nathan Looser, Lorenzo Tavazzani, Óscar Merino-Tomé, Juan R. Bahamonde, Yannick Buret, and Maria Ovtcharova
Geochronology, 6, 465–474, https://doi.org/10.5194/gchron-6-465-2024, https://doi.org/10.5194/gchron-6-465-2024, 2024
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RA138 is a new reference material for U–Pb dating of carbonate samples via laser ablation inductively coupled plasma mass spectrometry. RA138 exhibits variable U–Pb ratios and consistent U content, resulting in a precise isochron with low uncertainty. Isotope dilution thermal ionization mass spectrometry analyses fix a reference age of 321.99 ± 0.65 Ma. This research advances our ability to date carbonate samples accurately, providing insights into geological processes and historical timelines.
Hevelyn S. Monteiro, Kenneth A. Farley, and Paulo M. Vasconcelos
Geochronology Discuss., https://doi.org/10.5194/gchron-2024-13, https://doi.org/10.5194/gchron-2024-13, 2024
Revised manuscript accepted for GChron
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We have built a database of (U-Th)/He ages and U and Th contents of goethites from various weathering environments. The database contains 2597 (U-Th)/He ages of goethites from 10 countries. The findings presented in this manuscript contribute insights onto the distribution of dated goethites from different environments globally and into the Earth's Cenozoic weathering history.
Nil Irvalı, Ulysses S. Ninnemann, Are Olsen, Neil L. Rose, David J. R. Thornalley, Tor L. Mjell, and François Counillon
Geochronology, 6, 449–463, https://doi.org/10.5194/gchron-6-449-2024, https://doi.org/10.5194/gchron-6-449-2024, 2024
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Marine sediments are excellent archives for reconstructing past changes in climate and ocean circulation. Yet, dating uncertainties, particularly during the 20th century, pose major challenges. Here we propose a novel chronostratigraphic approach that uses anthropogenic signals, such as the oceanic 13C Suess effect and spheroidal carbonaceous fly-ash particles, to reduce age model uncertainties in high-resolution marine archives over the 20th century.
Birk Härtel and Eva Enkelmann
Geochronology, 6, 429–448, https://doi.org/10.5194/gchron-6-429-2024, https://doi.org/10.5194/gchron-6-429-2024, 2024
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We present a new data analysis workflow for thermochronological data based on plots of radiogenic daughter vs. radioactive parent concentration. The daughter–parent relationship helps to identify the sources of age variation. Our workflow classifies the daughter–parent relationship and provides further suggestions, e.g., if a dataset can be described by a sample age and which type of sample age to report. We also introduce Incaplot, which is software for creating daughter–parent plots.
Pieter Vermeesch
Geochronology, 6, 397–407, https://doi.org/10.5194/gchron-6-397-2024, https://doi.org/10.5194/gchron-6-397-2024, 2024
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The age of some geological materials can be estimated from the ratio of certain radiogenic "daughter" isotopes to their radioactive "parent". However, in many cases, the age estimation process is complicated by the presence of an inherited component of non-radiogenic daughter isotopes. This paper presents an improved algorithm to estimate the radiogenic and non-radiogenic components, either separately or jointly.
André Navin Paul, Anders Lindskog, and Urs Schaltegger
Geochronology, 6, 325–335, https://doi.org/10.5194/gchron-6-325-2024, https://doi.org/10.5194/gchron-6-325-2024, 2024
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The “Likhall” bed helps to constrain the timing of increased meteorite bombardment of the Earth during the Ordovician period. It is important to understand the timing of this meteorite bombardment when attempting to correlate it with biodiversity changes during the Ordovician period. Calibrating a good age for the “Likhall” bed is, however, challenging and benefited in this study from advances in sample preparation.
Megan A. Mueller, Alexis Licht, Andreas Möller, Cailey B. Condit, Julie C. Fosdick, Faruk Ocakoğlu, and Clay Campbell
Geochronology, 6, 265–290, https://doi.org/10.5194/gchron-6-265-2024, https://doi.org/10.5194/gchron-6-265-2024, 2024
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Sedimentary provenance refers to the study of the origin of sedimentary rocks, tracing where sediment particles originated. Common sedimentary provenance techniques struggle to track mafic igneous and metamorphic rock sources and rutile forms in these rock types. We use rutile form ancient sedimentary rocks in Türkiye to present new recommendations and workflows for integrating rutile U–Pb ages and chemical composition into an accurate sedimentary provenance reconstruction.
Ruohong Jiao, Shengze Cai, and Jean Braun
Geochronology, 6, 227–245, https://doi.org/10.5194/gchron-6-227-2024, https://doi.org/10.5194/gchron-6-227-2024, 2024
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We demonstrate a machine learning method to estimate the temperature changes in the Earth's crust over time. The method respects physical laws and conditions imposed by users. By using observed rock cooling ages as constraints, the method can be used to estimate the tectonic and landscape evolution of the Earth. We show the applications of the method using a synthetic rock uplift model in 1D and an evolution model of a real mountain range in 3D.
Erin E. Donaghy, Michael P. Eddy, Federico Moreno, and Mauricio Ibañez-Mejia
Geochronology, 6, 89–106, https://doi.org/10.5194/gchron-6-89-2024, https://doi.org/10.5194/gchron-6-89-2024, 2024
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Chemical abrasion (CA) is a technique that reduces or eliminates the effects of Pb loss in zircon U–Pb geochronology. However, CA has yet to be applied to large-n detrital zircon (DZ) analyses. We show that CA does not negatively impact or systematically bias U–Pb dates, improves the resolution of age populations defined by 206Pb/238U dates, and increases the percentage of concordant analyses in age populations defined by 207Pb/206Pb dates.
Glenn R. Sharman and Matthew A. Malkowski
Geochronology, 6, 37–51, https://doi.org/10.5194/gchron-6-37-2024, https://doi.org/10.5194/gchron-6-37-2024, 2024
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The mineral zircon is widely used to determine the age of rocks based on the radioactive decay of U to Pb, but the measured U–Pb date can be too young if the zircon loses Pb. We present a method for estimating the distribution of apparent Pb loss by mathematical convolution. Applying this approach to 10 samples illustrates contrasting patterns of apparent Pb loss. This study highlights the importance of quantifying Pb loss to better understand its potential effects on zircon U–Pb dates.
Stijn Glorie, Sarah E. Gilbert, Martin Hand, and Jarred C. Lloyd
Geochronology, 6, 21–36, https://doi.org/10.5194/gchron-6-21-2024, https://doi.org/10.5194/gchron-6-21-2024, 2024
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Radiometric dating methods, involving laser ablation as the sample introduction, require robust calibrations to reference materials with similar ablation properties to the analysed samples. In the case of the rubidium–strontium dating method, calibrations are often conducted to nano powder with different ablation characteristics than the crystalline minerals. We describe the limitations of this approach and recommend an alternative calibration method involving natural minerals.
Alex Lipp and Pieter Vermeesch
Geochronology, 5, 263–270, https://doi.org/10.5194/gchron-5-263-2023, https://doi.org/10.5194/gchron-5-263-2023, 2023
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We propose using the Wasserstein-2 distance (W2) as an alternative to the widely used Kolmogorov–Smirnov (KS) statistic for analysing distributional data in geochronology. W2 measures the horizontal distance between observations, while KS measures vertical differences in cumulative distributions. Using case studies, we find that W2 is preferable in scenarios where the absolute age differences in observations provide important geological information. W2 has been added to the R package IsoplotR.
W. Marijn van der Meij, Arnaud J. A. M. Temme, Steven A. Binnie, and Tony Reimann
Geochronology, 5, 241–261, https://doi.org/10.5194/gchron-5-241-2023, https://doi.org/10.5194/gchron-5-241-2023, 2023
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We present our model ChronoLorica. We coupled the original Lorica model, which simulates soil and landscape evolution, with a geochronological module that traces cosmogenic nuclide inventories and particle ages through simulations. These properties are often measured in the field to determine rates of landscape change. The coupling enables calibration of the model and the study of how soil, landscapes and geochronometers change under complex boundary conditions such as intensive land management.
Michael C. Sitar and Ryan J. Leary
Geochronology, 5, 109–126, https://doi.org/10.5194/gchron-5-109-2023, https://doi.org/10.5194/gchron-5-109-2023, 2023
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We developed code to automatically and semi-automatically measure dimensions of detrital mineral grains in reflected-light images saved at laser ablation–inductively coupled plasma–mass spectrometry facilities that use Chromium targeting software. Our code uses trained deep learning models to segment grain images with greater accuracy than is achievable using other segmentation techniques. We implement our code in Jupyter notebooks which can also be run online via Google Colab.
Peter E. Martin, James R. Metcalf, and Rebecca M. Flowers
Geochronology, 5, 91–107, https://doi.org/10.5194/gchron-5-91-2023, https://doi.org/10.5194/gchron-5-91-2023, 2023
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There is currently no standardized method of performing uncertainty propagation in the (U–Th) / He system, causing data interpretation difficulties. We present two methods of uncertainty propagation and describe free, open-source software (HeCalc) to apply them. Compilation of real data using only analytical uncertainty as well as 2 % and 5 % uncertainties in FT yields respective median relative date uncertainties of 2.9 %, 3.3 %, and 5.0 % for apatites and 1.7 %, 3.3 %, and 5.0 % for zircons.
Stella Birlo, Wojciech Tylmann, and Bernd Zolitschka
Geochronology, 5, 65–90, https://doi.org/10.5194/gchron-5-65-2023, https://doi.org/10.5194/gchron-5-65-2023, 2023
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Sediment cores from the volcanic lake Holzmaar provide a very precise chronology based on tree-ring-like annual laminations or varves. We statistically combine this varve chronology with radiometric dating and tested three different methods to upgrade the age–depth model. However, only one of the three methods tested improved the dating accuracy considerably. With this work, an overview of different age integration methods is discussed and made available for increased future demands.
Peter van der Beek and Taylor F. Schildgen
Geochronology, 5, 35–49, https://doi.org/10.5194/gchron-5-35-2023, https://doi.org/10.5194/gchron-5-35-2023, 2023
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Thermochronometric data can provide unique insights into the patterns of rock exhumation and the driving mechanisms of landscape evolution. Several well-established thermal models allow for a detailed exploration of how cooling rates evolved in a limited area or along a transect, but more regional analyses have been challenging. We present age2exhume, a thermal model that can be used to rapidly provide a synoptic overview of exhumation rates from large regional thermochronologic datasets.
Marianna Corre, Arnaud Agranier, Martine Lanson, Cécile Gautheron, Fabrice Brunet, and Stéphane Schwartz
Geochronology, 4, 665–681, https://doi.org/10.5194/gchron-4-665-2022, https://doi.org/10.5194/gchron-4-665-2022, 2022
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This study is focused on the accurate measurement of U and Th by wet chemistry and laser ablation methods to improve (U–Th)/He dating of magnetite and spinel. The low U–Th content and the lack of specific U–Th standards significantly limit the accuracy of (U–Th)/He dating. Obtained U–Th results on natural and synthetic magnetite and aluminous spinel samples analyzed by wet chemistry methods and LA-ICP-MS sampling have important implications for the (U–Th)/He method and dates interpretation.
Aratz Beranoaguirre, Iuliana Vasiliev, and Axel Gerdes
Geochronology, 4, 601–616, https://doi.org/10.5194/gchron-4-601-2022, https://doi.org/10.5194/gchron-4-601-2022, 2022
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U–Pb dating by the in situ laser ablation mass spectrometry (LA-ICPMS) technique requires reference materials of the same nature as the samples to be analysed. Here, we have explored the suitability of using carbonate materials as a reference for sulfates, since there is no sulfate reference material. The results we obtained are satisfactory, and thus, from now on, the sulfates can also be analysed.
Pieter Vermeesch
Geochronology, 4, 561–576, https://doi.org/10.5194/gchron-4-561-2022, https://doi.org/10.5194/gchron-4-561-2022, 2022
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Secondary ion mass spectrometry (SIMS) is the oldest and most sensitive analytical technique for in situ U–Pb geochronology. This paper introduces a new algorithm for SIMS data reduction that treats data as
compositional data, which means that the relative abundances of 204Pb, 206Pb, 207Pb, and 238Pb are processed within a tetrahedral data space or
simplex. The new method is implemented in an eponymous computer programme that is compatible with the two dominant types of SIMS instruments.
Emily H. G. Cooperdock, Florian Hofmann, Ryley M. C. Tibbetts, Anahi Carrera, Aya Takase, and Aaron J. Celestian
Geochronology, 4, 501–515, https://doi.org/10.5194/gchron-4-501-2022, https://doi.org/10.5194/gchron-4-501-2022, 2022
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Apatite and zircon are the most widely used minerals for dating rocks, but they can be difficult to identify in some crushed rock samples. Incorrect mineral identification results in wasted analytical resources and inaccurate data. We show how X-ray computed tomography can be used to efficiently and accurately distinguish apatite from zircon based on density variations, and provide non-destructive 3D grain-specific size, shape, and inclusion information for improved data quality.
Dale R. Issler, Kalin T. McDannell, Paul B. O'Sullivan, and Larry S. Lane
Geochronology, 4, 373–397, https://doi.org/10.5194/gchron-4-373-2022, https://doi.org/10.5194/gchron-4-373-2022, 2022
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Phanerozoic sedimentary rocks of northern Canada have compositionally heterogeneous detrital apatite with high age dispersion caused by differential thermal annealing. Discrete apatite fission track kinetic populations with variable annealing temperatures are defined using elemental data but are poorly resolved using conventional parameters. Inverse thermal modelling of samples from northern Yukon reveals a record of multiple heating–cooling cycles consistent with geological constraints.
Michael Dietze, Sebastian Kreutzer, Margret C. Fuchs, and Sascha Meszner
Geochronology, 4, 323–338, https://doi.org/10.5194/gchron-4-323-2022, https://doi.org/10.5194/gchron-4-323-2022, 2022
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The R package sandbox is a collection of functions that allow the creation, sampling and analysis of fully virtual sediment sections, like having a virtual twin of real-world deposits. This article introduces the concept, features, and workflows required to use sandbox. It shows how a real-world sediment section can be mapped into the model and subsequently addresses a series of theoretical and practical questions, exploiting the flexibility of the model framework.
Gregor Pfalz, Bernhard Diekmann, Johann-Christoph Freytag, Liudmila Syrykh, Dmitry A. Subetto, and Boris K. Biskaborn
Geochronology, 4, 269–295, https://doi.org/10.5194/gchron-4-269-2022, https://doi.org/10.5194/gchron-4-269-2022, 2022
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We use age–depth modeling systems to understand the relationship between age and depth in lake sediment cores. However, depending on which modeling system we use, the model results may vary. We provide a tool to link different modeling systems in an interactive computational environment and make their results comparable. We demonstrate the power of our tool by highlighting three case studies in which we test our application for single-sediment cores and a collection of multiple sediment cores.
Andrea Madella, Christoph Glotzbach, and Todd A. Ehlers
Geochronology, 4, 177–190, https://doi.org/10.5194/gchron-4-177-2022, https://doi.org/10.5194/gchron-4-177-2022, 2022
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Cooling ages date the time at which minerals cross a certain isotherm on the way up to Earth's surface. Such ages can be measured from bedrock material and river sand. If spatial variations in bedrock ages are known in a river catchment, the spatial distribution of erosion can be inferred from the distribution of the ages measured from the river sand grains. Here we develop a new tool to help such analyses, with particular emphasis on quantifying uncertainties due to sample size.
Yang Li and Pieter Vermeesch
Geochronology, 3, 415–420, https://doi.org/10.5194/gchron-3-415-2021, https://doi.org/10.5194/gchron-3-415-2021, 2021
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A conventional isochron is a straight-line fit to two sets of isotopic ratios, D/d and P/d, where P is the radioactive parent, D is the radiogenic daughter, and d is a second isotope of the daughter element. The slope of this line is proportional to the age of the system. An inverse isochron is a linear fit through d/D and P/D. The horizontal intercept of this line is inversely proportional to the age. The latter approach is preferred when d<D, which is the case in Re–Os and K–Ca geochronology.
Cécile Gautheron, Rosella Pinna-Jamme, Alexis Derycke, Floriane Ahadi, Caroline Sanchez, Frédéric Haurine, Gael Monvoisin, Damien Barbosa, Guillaume Delpech, Joseph Maltese, Philippe Sarda, and Laurent Tassan-Got
Geochronology, 3, 351–370, https://doi.org/10.5194/gchron-3-351-2021, https://doi.org/10.5194/gchron-3-351-2021, 2021
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Apatite and zircon (U–Th) / He thermochronology is now a mainstream tool to reconstruct Earth's evolution through the history of cooling and exhumation over the first dozen kilometers. The geological implications of these data rely on the precision of measurements of He, U, Th, and Sm contents in crystals. This technical note documents the methods for He thermochronology developed at the GEOPS laboratory, Paris-Saclay University, that allow (U–Th) / He data to be obtained with precision.
Kalin T. McDannell and Dale R. Issler
Geochronology, 3, 321–335, https://doi.org/10.5194/gchron-3-321-2021, https://doi.org/10.5194/gchron-3-321-2021, 2021
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We generated a synthetic dataset applying published kinetic models and distinct annealing kinetics for the apatite fission track and (U–Th)/He methods using a predetermined thermal history. We then tested how well the true thermal history could be recovered under different data interpretation schemes and geologic constraint assumptions using the Bayesian QTQt software. Our results demonstrate that multikinetic data increase time–temperature resolution and can constrain complex thermal histories.
Birk Härtel, Raymond Jonckheere, Bastian Wauschkuhn, and Lothar Ratschbacher
Geochronology, 3, 259–272, https://doi.org/10.5194/gchron-3-259-2021, https://doi.org/10.5194/gchron-3-259-2021, 2021
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We carried out thermal annealing experiments between 500 and 1000 °C to determine the closure temperature of radiation-damage annealing in zircon (ZrSiO4). Our results show that the different Raman bands of zircon respond differently to annealing. The repair is highest for the external rotation Raman band near 356.6 cm−1. The closure temperature estimates range from 250 to 370 °C for different bands. The differences in closure temperatures offer the prospect of multi-T zircon Raman dating.
Pieter Vermeesch
Geochronology, 3, 247–257, https://doi.org/10.5194/gchron-3-247-2021, https://doi.org/10.5194/gchron-3-247-2021, 2021
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This paper shows that the current practice of filtering discordant U–Pb data based on the relative difference between the 206Pb/238U and 207Pb/206Pb ages is just one of several possible approaches to the problem and demonstrably not the best one. An alternative approach is to define discordance in terms of isotopic composition, as a log ratio distance between the measurement and the concordia line. Application to real data indicates that this reduces the positive bias of filtered age spectra.
Blair Schoene, Michael P. Eddy, C. Brenhin Keller, and Kyle M. Samperton
Geochronology, 3, 181–198, https://doi.org/10.5194/gchron-3-181-2021, https://doi.org/10.5194/gchron-3-181-2021, 2021
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We compare two published U–Pb and 40Ar / 39Ar geochronologic datasets to produce eruption rate models for the Deccan Traps large igneous province. Applying the same approach to each dataset, the resulting models agree well, but the higher-precision U–Pb dataset results in a more detailed eruption model than the lower-precision 40Ar / 39Ar data. We explore sources of geologic uncertainty and reiterate the importance of systematic uncertainties in comparing U–Pb and 40Ar / 39Ar datasets.
Nicholas P. McKay, Julien Emile-Geay, and Deborah Khider
Geochronology, 3, 149–169, https://doi.org/10.5194/gchron-3-149-2021, https://doi.org/10.5194/gchron-3-149-2021, 2021
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This paper describes geoChronR, an R package that streamlines the process of quantifying age uncertainties, propagating uncertainties through several common analyses, and visualizing the results. In addition to describing the structure and underlying theory of the package, we present five real-world use cases that illustrate common workflows in geoChronR. geoChronR is built on the Linked PaleoData framework, is open and extensible, and we welcome feedback and contributions from the community.
Leonie Peti, Kathryn E. Fitzsimmons, Jenni L. Hopkins, Andreas Nilsson, Toshiyuki Fujioka, David Fink, Charles Mifsud, Marcus Christl, Raimund Muscheler, and Paul C. Augustinus
Geochronology, 2, 367–410, https://doi.org/10.5194/gchron-2-367-2020, https://doi.org/10.5194/gchron-2-367-2020, 2020
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Orakei Basin – a former maar lake in Auckland, New Zealand – provides an outstanding sediment record over the last ca. 130 000 years, but an age model is required to allow the reconstruction of climate change and volcanic eruptions contained in the sequence. To construct a relationship between depth in the sediment core and age of deposition, we combined tephrochronology, radiocarbon dating, luminescence dating, and the relative intensity of the paleomagnetic field in a Bayesian age–depth model.
Roger Powell, Eleanor C. R. Green, Estephany Marillo Sialer, and Jon Woodhead
Geochronology, 2, 325–342, https://doi.org/10.5194/gchron-2-325-2020, https://doi.org/10.5194/gchron-2-325-2020, 2020
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The standard approach to isochron calculation assumes that the distribution of uncertainties on the data arising from isotopic analysis is strictly Gaussian. This excludes datasets that have more scatter, even though many appear to have age significance. Our new approach requires only that the central part of the uncertainty distribution of the data defines a "spine" in the trend of the data. A robust statistics approach is used to locate the spine, and an implementation in Python is given.
Simon J. E. Large, Jörn-Frederik Wotzlaw, Marcel Guillong, Albrecht von Quadt, and Christoph A. Heinrich
Geochronology, 2, 209–230, https://doi.org/10.5194/gchron-2-209-2020, https://doi.org/10.5194/gchron-2-209-2020, 2020
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The integration of zircon geochemistry and U–Pb geochronology (petrochronology) allows us to improve our understanding of magmatic processes. Here we could reconstruct the ~300 kyr evolution of the magma reservoir that sourced the magmas, fluids and metals to form the Batu Hijau porphyry Cu–Au deposit. The application of in situ LA-ICP-MS and high-precision CA–ID–TIMS geochronology to the same zircons further allowed an assessment of the strengths and limitations of the different techniques.
Julia Kalanke, Jens Mingram, Stefan Lauterbach, Ryskul Usubaliev, Rik Tjallingii, and Achim Brauer
Geochronology, 2, 133–154, https://doi.org/10.5194/gchron-2-133-2020, https://doi.org/10.5194/gchron-2-133-2020, 2020
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Our study presents the first seasonally laminated (varved) sediment record covering almost the entire Holocene in high mountainous arid Central Asia. The established floating varve chronology is confirmed by two terrestrial radiocarbon dates, whereby aquatic radiocarbon dates reveal decreasing reservoir ages up core. Changes in seasonal deposition characteristics are attributed to changes in runoff and precipitation and/or to evaporative summer conditions.
Pieter Vermeesch
Geochronology, 2, 119–131, https://doi.org/10.5194/gchron-2-119-2020, https://doi.org/10.5194/gchron-2-119-2020, 2020
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The U–Pb method is one of the most powerful and versatile methods in the geochronological toolbox. With two isotopes of uranium decaying to two different isotopes of lead, the U–Pb method offers an internal quality control that is absent from most other geochronological techniques. U-bearing minerals often contain significant amounts of Th, which decays to a third Pb isotope. This paper presents an algorithm to jointly process all three chronometers at once.
Jon Woodhead and Joseph Petrus
Geochronology, 1, 69–84, https://doi.org/10.5194/gchron-1-69-2019, https://doi.org/10.5194/gchron-1-69-2019, 2019
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Recently developed methods for in situ U–Pb age determination in carbonates have found widespread application, but the benefits and limitations of the method over bulk analysis approaches have yet to be fully explored. Here we use speleothems – cave carbonates such as stalagmites and flowstones – to investigate the utility of these in situ dating methodologies for challenging matrices with low U and Pb contents and predominantly late Cenozoic ages.
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Short summary
The (U–Th–Sm) / He dating method helps understand the cooling history of rocks. Synthetic modelling experiments were conducted to explore factors affecting in situ vs. whole-grain (U–Th) / He dates. In situ dates are often 30 % older than whole-grain dates, whereas very rapid cooling makes helium loss negligible, resulting in similar whole-grain and in situ dates. In addition, in situ data can reveal cooling histories even from a single grain by measuring helium distributions.
The (U–Th–Sm) / He dating method helps understand the cooling history of rocks. Synthetic...
