This study investigates a sediment core (LSMo22-1) from crater lake Santa Maria del Oro situated in western Mexico within the Trans-Mexican Volcanic Belt. The aim is to evidence the main forcing factors influencing the sediment influx into the lake, including climate variability in the tropical North American Monsoon domain. Core LSMo22-1 is 97-cm long and covers the last similar to 1500 years based on Pb-210 and C-14 data. The core was analyzed for inorganic geochemistry by X-ray fluorescence core scanning (XRF-CS) and bulk mineralogy by X-ray diffraction (XRD). The core is dominated by smectite (68 +/- 4%), with smaller amounts of albite (5.8 +/- 2% plus traces of amphibole, pyroxene, and cristobalite) and quartz (5.3 +/- 2%); these minerals, also identified in surrounding soil samples, represent the detrital fraction supplied to the lake by surface runoff. In addition, the core contains variable endogenic carbonates (calcite 8 +/- 6%, aragonite 3 +/- 6%) and traces of gypsum, while amorphous components, biogenic silica (diatoms) and organic matter, account for 11% and 9% of the total sedimentary flux, respectively. XRF-CS data reveal an inverse correlation between Ti and Ca (r = -0.82). The Ti content reflects the detrital minerals released from the crater flanks by surface runoff. Detrital flux was greater during wetter periods and diminished during drier phases, with the lowest input around 1500 CE, interpreted as the driest interval of the record. Dry periods likely also resulted in lower lake levels promoting higher primary productivity. The covariation of Botryococcus and calcite abundance suggests that lower lake levels during dry periods enhanced nutrient and carbonate concentrations, promoting elevated primary productivity and calcite precipitation. Variations in Ca correspond to changes in endogenic minerals and covary with whole lake productivity. Within the last 1100 years, five intervals of reduced calcite flux coincide with cooler periods, broadly linked to solar minima. In the uppermost section of core LSMo22-1 (13-0 cm, 1957-2022 CE), elevated aragonite is favored by stronger evaporation and endogenic precipitation under lower lake levels, reflecting both recent climate warming and probably also water abstraction.

The foreseen "green" energy transition requires anticipating environmental hazards associated with hydropower and reservoir impoundment. Manicouagan Reservoir, the "Eye of Quebec," is a prominent annular reservoir formed in 1968 CE by the impoundment of a ring-shaped complex impact crater that raised the lake level of a 60-km-long fjord-type lake by 135 m. Sediment cores recovered from the drowned lake document the sedimentary regime shift from organo-clastic to organic-rich rhythmites following the impoundment. The coring dataset highlights numerous lithofacies interpreted as event layers (i.e., mass-transport deposits and turbidites) related to multiple slope failures previously mapped by acoustic swath bathymetry and subbottom imagery of the drowned lake. Multiproxy characterization and dating of event layers allowed us to reconstruct the chronology and spatial distribution of slope failures and underlying triggers over the past 500 years. Lake-wide slope failures were triggered by the strong 1663 CE earthquake with an epicenter located 450 km away in the Charlevoix-Kamouraska intraplate seismic zone. Subsequent event layers dated between the mid-seventeenth and the mid-twentieth century were caused by spontaneous slope failures and/or by regional hydroclimatic changes that modulated sedimentary inputs and the lake level, two factors conditioning lacustrine slope stability. The rapid filling of the reservoir by seasonal river inputs between 1964 CE and 1968 CE caused the failure of deltas in proximal zones and the deposition of a beige-reddish layer across the lake. The drowning of glaciofluvial sediments and forested slopes shut down clastic sedimentation and reduced the lake's sensitivity to slope hazards, although the onset of organic sedimentation likely fueled hypoxia in deep basins (depth >400 m). Lake Manicouagan provides a unique, high-resolution record of reservoir-induced slope failures, regional environmental changes, and natural hazards. This study further illustrates how earthquakes and water-level changes condition subaqueous slope stability and sedimentary regimes.

Paleomagnetic and rock magnetic analyses were conducted on sediment cores from the northeastern Greenland Shelf and Young Sound along the western edge of Fram Strait. The paleomagnetic signal in all three sediment cores is characterized by a strong and stable single component magnetization carried by low coercivity ferrimagnetic single domain or vortex state grains, attesting to the quality of the recorded relative paleointensity (RPI) and paleomagnetic secular variation (PSV) signals. Comparison with other archives from the northern North Atlantic, northern Greenland, and northern Europe and with geomagnetic field model outputs indicates broad similarities between the records, particularly with Finnish, Swedish and southern Greenland records. Comparison of the new RPI records with global geomagnetic field models and cosmogenic isotope production rates highlights the global character of the geomagnetic variations from the northeastern Greenland Shelf. Virtual geomagnetic pole (VGP) paths for the last 8 kyr compared to geomagnetic field strength maps at the core-mantle boundary over the same time interval illustrate that, at times of high intensity, geomagnetic flux lobes could have an effect on VGP migration. We suggest that High Arctic PSV is most likely driven by millennial-scale hemispheric geomagnetic flux lobe geometry changes.

Arctic permafrost coastlines are retreating faster as climate warming intensifies. Accurate modelling of the thermomechanical process is hindered by a lack of direct measurement of heat flux or heat transfer coefficients (h(w)) at the water-permafrost interface. This study presents the first, direct laboratory measurements of wave-induced convective heat transfer coefficients. In twelve wave-flume experiments, artificial permafrost samples were exposed to air, still water, and irregular waves (0.02-0.04 m height; 0.8-1.2 s period). Embedded resistance temperature detectors tracked temperature changes at high spatial and temporal resolution, allowing for precise heat flux and heat transfer coefficient calculations. Under wave action, thaw-front advanced rapidly into the permafrost blocks at about 160-350 mmh(-1) compared to 3.24 mmh(-1) in air and 50.14 mmh(-1) in still water. Similarly, heat transfer coefficient ranged from 459 to 1210 Wm(-2) K-1 in wave tests, significantly exceeding those for still water (similar to 165 Wm(-2) K-1) and air exposure (similar to 4.4 Wm(-2) K-1) tests. Heat flux correlated most strongly with wave height; higher ice content slowed thawing but did not evidently affect h(w) magnitude. A novel empirical model was developed that pioneers the linking of h(w) to surf similarity and dimensionless wave height and period. With strong predictive performance (R-2 = 0.89, RMSE = 81.1 Wm(-2) K-1), the model provides a practical, experimentally validated tool for specifying h(w) in coastal permafrost erosion models, eliminating the reliance on parameter tuning required by previous analytical approaches. Overall, this study demonstrates the critical role of waves in heat delivery to permafrost coastlines.

Accurate characterization of fine-grained lake sediments is important for paleolimnological reconstructions. Conventional granulometric methods are often time-consuming and destructive, whereas hyperspectral imaging (HSI) provides a non-destructive alternative for estimating sediment particle size. Previous studies integrated HSI with deep learning models trained on coarse-grained lake datasets, showing promising results. However, the coarse range of the particle size distribution limited their accuracy when tested in silty sediments typical of deep, undisturbed lake depocenters often used for paleoclimate studies. This study addressed this limitation through the fine-tuning of a previously validated convolutional neural network model with silty sediment cores from Grand Lake, a fjord-lake in Labrador, northeastern Canada. The primary objective was to improve the model's performance in fine-particle environments and its ability to detect mean particle size (MPS) signals in deep-water cores. An additional objective was to determine the optimal training parameters for its fine-tuning, providing a methodological basis for future applications. Results showed the reliability of the retrained model in reproducing mean particle size predictions when compared to granulometric data, as well as capturing trends in MPS variations as long as training data with similar geochemical and depositional characteristics are used. These results attest to the potential applicability of the method for high-resolution MPS analysis in fine-grained sediment cores from deep-lake settings and in long sediment sequences, offering an effective tool for paleoenvironmental reconstructions. This study emphasizes that similar sedimentary characteristics and depositional structures are key factors when determining whether a model trained at one sampling site can be applied to other sites.

Lake primary production and organic carbon (OC) sequestration represent globally important ecosystem services, yet their responses to global change remain obscure. This is especially true in understudied regions, such as the tropics. We investigated multidecadal patterns and controls of lake primary production and OC burial rates in five tropical crater lakes spanning Central Mexico, addressing prevailing spatial and temporal data biases. Sediment biogeochemical trends since the late 1800s were assessed relative to lake morphometry and catchment land use, as well as population and climate trends. The lakes displayed overall trends of increasing primary production and OC burial rates during the past century, reshaped by heterogeneous natural and cultural landscapes. No single anthropogenic predictor was consistently related to the lake productivity shifts. Rather, productivity increases likely arose from the interacting effects of nutrient enrichment and lake-level reductions driven by increasing evaporative demand and water use. The timing and extent of the OC burial increases did not align with spatial and temporal lake productivity trends, despite the predominantly autochthonous origin of the sediment carbon pools. Rather, OC burial rates increased in tandem with detrital erosional inputs during the latter half of the last century, promoting the burial of the labile autochthonous OC. The largest productivity increases were associated with the smallest lakes, whereas the extent of OC burial increases showed no consistent connection to lake morphometry. Our results show how increasing regional human pressures and climate change have fundamentally shaped critical lake ecosystem functions in Central Mexico.

Peatlands play a crucial role in carbon storage and climate regulation. Traditional gravity-based and loss-on-ignition methods have been widely used to acquire bulk density and thus organic carbon estimates in peat sequences. However, these methods are time-consuming, and the measurement resolution frequently ranges from half to a few centimetres, hampering the understanding of carbon accumulation history at finer temporal resolution. Here, we explore the potential of non-destructive X-ray computed tomography (XCT), a method for analyzing 3D material structure and mass density, for obtaining proxy measurements for bulk density parameters using peat cores collected in eastern boreal Quebec, Canada. We find that the Hounsfield Unit (HU) of medical XCT scans is a robust surrogate for the bulk density of wet peat (BDwet). A universal linear model can be applied to calibrate HU values for a wide range of peat stratigraphy from different microforms: Sphagnum hummock, lichen hummock, lawn, and hollow. Moreover, HU of dry peat is indicative of both dry and organic matter bulk density (BDdry and BDom). It is possible to develop case-specific logarithmic models to calibrate HU with BDdry. In addition, the precise measurement of the peat sample volumes using XCT suggests that traditional methods can be subject to substantial uncertainties when estimating bulk density and carbon content. Medical XCT can be applied to quantify bulk density in peat soils in a more time-efficient manner, with a resolution up to 0.6 mm, approximately equivalent to the yearly accumulation rate.

Atlantic Canada experiences frequent major storms, particularly tropical cyclones transitioning into post-tropical storms. Events such as Hurricane Fiona (2022), Dorian (2019), and Juan (2003) have caused significant damage, loss of life, and coastal erosion, exacerbated by sea level rise and warming waters. Despite this, centennial- to millennial-scale storm records in the region remain scarce. Existing studies in North America focus primarily on marine and coastal overwash records, with limited use of aeolian mineral inputs in ombrotrophic peatlands as storm proxies. Here, we address these gaps by analysing grain-size and geochemical data from two peatlands in Quebec, Canada's Magdalen Islands. Our 4000-year peat-based storm reconstructions reveal consistent storm signals with three key intervals of increased activity: 800–550 BCE, 500–750 CE, and 1300–1700 CE. These records align with marine overwash archives from eastern Canada, the US, and the Bahamas, supporting reduced storminess during the Medieval Climate Anomaly and heightened activity during the Little Ice Age. This regional coherence suggests storm variability at higher latitudes is strongly influenced by local climatic drivers, such as sea surface temperature gradients and storm intensification mechanisms, rather than tropical cyclone formation alone. Despite broad similarities, notable discrepancies in geochemical and mineralogical profiles between our two peatlands highlight the influence of site-specific factors, including proximity to sediment sources, bog size, and local geomorphology, on sediment deposition and storm signal strength. These findings underscore the importance of site selection and local context when interpreting peat-based storm records. Furthermore, challenges remain in calibrating peat proxies to historical storm events, limiting direct event attribution over the past 150 years. Our study demonstrates the complementary value of peatland archives alongside marine overwash records in reconstructing paleo-storm activity, enriching understanding of storm dynamics and expanding potential reconstruction sites, particularly in mid-latitude coastal regions. Continued research is needed to refine calibration methods and clarify climatic mechanisms driving storm variability, which is essential for projecting future storm impacts in Atlantic Canada.

Grand Lake is a large 250 m deep fjord lake located in Labrador, Canada. Previous studies on short and shallow sediment cores identified seasonal hydrological signals and connections with North Atlantic modes of climate variability. This study presents a new 20 m composite sequence from the deepest basin of Grand Lake, providing high-resolution insights into sedimentary processes over the last ca. 3300 years. As a potential key environmental archive for north-eastern Canada, a region where high-resolution palaeoclimate records are scarce, Grand Lake offers a unique opportunity to examine long-term sedimentary and climatic interactions. Previous research did not examine temporal changes in sedimentary processes or the specific mechanisms driving mass sediment deposition, limiting the distinction and interpretation of climate controls on longer time scales. Here, sedimentological and geochemical characteristics are used to reconstruct sedimentation dynamics and erosional processes. Several rapidly deposited layers are characterised over changing depositional environments during the Late Holocene, from a phase when the lake was connected to the sea to a more stable state conducive to varve formation. A combination of end-member modelling analysis, lithofacies descriptions and high-resolution mu-XRF proxies revealed density currents as the dominant sedimentation process. Their origins ranged from proximal sources (gully systems) to distal sources (tributary rivers), with contributions varying over time, reflecting the transition from a marine-influenced system to a post-glacial fjord lake. The results provide a framework for future palaeoclimate studies in the region by contributing to a better understanding of sedimentary dynamics in a deep glacial lake, with implications for regional palaeoclimate reconstructions. Additionally, this study highlights the broader applicability of statistical unmixing for interpreting grain-size variations in both lacustrine and marine environments.

Lakes bury significant amounts of organic carbon (OC) in their sediments contributing to the removal of carbon from the short-term carbon cycle. Mounting evidence points to broadscale increases in lake OC burial rates under growing human perturbation; however, the extent and mechanisms giving rise to this trend are not well understood in the context of tropical regions. We sought to expand knowledge of natural and anthropogenic controls of lake carbon cycling at lower latitudes by investigating four centuries of changes in the carbon sink of two tropical lakes in Central Mexico. Multiple biogeochemical and paleoecological indices were used to track temporal trends in OC production, inflow and burial, and to identify underlying environmental drivers. We uncovered systematic patterns in lake carbon dynamics in both studied lakes, including a three- to seven-fold increase in OC burial over recent decades. Marked increases in OC production over the 1900s in both lakes may have contributed to the enhanced carbon sink. However, increased sediment accumulation rates, particularly over the past couple of decades, suggest that the predominant factor influencing increased OC burial rates was related to growing local human disturbance. Over the last four centuries, sediment biogeochemistry in both lakes suggested shifts in water balance and lake levels that appear to be important drivers of OC production and organic enrichment in the lakes, linking them to regional climate variability.

Permafrost coastal systems are critical to Arctic environmental processes, and understanding their erosion dynamics is essential for addressing climate change impacts. These coastlines undergo unique thermomechanical erosion, where wave action, rising sea levels, and thermal degradation jointly drive a rapid coastline recession. This study demonstrates advancements in physically modeling coastal permafrost erosion using a laboratory setup that replicates natural Arctic coastal conditions. A wave flume with a representative nearshore slope and reproducible permafrost specimen preparation methodology allowed isolation of the hydrodynamic and thermodynamic effects. Distinct erosion patterns and rates were quantified under varying wave heights, periods, and thermal conditions. Results indicate that wave height is a dominant mechanical driver, with mean erosion rates increasing by over 100% from low to high wave conditions. Even low-energy waves (H = 0.02 m) enhanced erosion by more than 50% compared to still-water conditions. Additionally, a higher ice content reduced niche deepening rates by 38%, which is attributed to latent heat delaying thawing. A new scalable thermomechanical model for erosional niche incision on an Arctic bluff is proposed based on a power-law relationship that integrates the Froude, Iribarren, and Stefan numbers. This dimensionless approach captures the coupled influence of wave-induced forces and permafrost thermal properties, exhibiting a strong predictive capability (R 2 = 0.90) and outperforming existing analytical models. The experimental framework and new model offer new insights into Arctic coastal retreat mechanisms and provide a promising foundation for regional-scale applications in coastal management under changing climatic conditions.

The stoichiometric calibration method for dual‐energy computed tomography (DECT) can be used in geosciences to characterise materials based on their effective atomic number ( Z eff ) and their electron density ( ρ e ) without previous knowledge of the incident X‐ray beam. A stoichiometrically calibrated DECT method was applied here to measure these two properties on three different sedimentary rocks using three different X‐ray CT instruments to determine which one is best to reveal the chemical composition or the mineralogical variations at the meso‐scale. The three tested instruments: (1) a medical CT, (2) a custom‐built micro‐CT, and (3) a commercial micro‐CT. Several acquisition settings were tested to identify the most suitable parameters for the characterisation the samples. Some parameters such as incident energies, resolution and calibration materials proved to have a significant impact on the accuracy of the characterisation. The determination of a general measurement protocol for geological samples was found to be difficult because of several complicating factors, including the nature of the sample, objectives of the study, and instrumental limitations that influence DECT characterisation. Nonetheless, comparison of the results obtained by the three scanners brings out the key parameters to be considered to perform a useful rock sample characterisation with DECT.

Grand Lake, located in Labrador, at the northeastern margin of North America, is a deep lacustrine basin that contains a well-preserved annual laminations record spanning the interval 493 to 2016 CE (1524 years). The chronology of this new varved sequence is established from layer counting of high-resolution images of thin sections. Radiometric dating (137Cs and 14C) validates the reliability of the varve chronology. Varve thickness is significantly correlated (r = 0.38) with the total precipitation recorded at the nearest weather station Goose A. The varve thickness series reveals high values during the 1050-1225 CE period, which corresponds to the Medieval Climate Anomaly, whereas the 15th-19th centuries, related to the Little Ice Age, shows low values. The teleconnections between several Goose A instrumental data series and some modes of climate variability such as the winter Greenland Blocking (negative North-Atlantic Oscillation) and the significant correlations between our varve thickness record and three other Northern Hemisphere high-resolution proxy records suggest that the Grand Lake record tracks North-Western Atlantic large-scale modes of hydroclimate variability over the past similar to 1500 years.

Understanding how lake ecosystems respond to anthropogenic disturbances including mining, agriculture, deforestation, and more is often best answered with historical time series. Unfortunately, a lack of long-term monitoring data can make this difficult; paleolimnology offers an alternative, allowing for the reconstruction of past conditions using proxies from sediment records. As part of the nationally funded Canadian Lake Pulse Network, we analyzed sediment cores from 116 lakes across Canada using micro-X-ray fluorescence core-scanning (µXRF). µXRF served to generate abundance profiles for several elements (e.g., Ca, Sr, Ti, Pb, Cu, Zn), allowing for the assessment of spatiotemporal geochemical changes in Canadian lakes dating back to ~1850 AD. We calibrated µXRF core-scanning with conventional geochemical methods in a 48-lake subset and found strong correlations for numerous elements between conventional wet chemistry and µXRF-measured concentrations (Zilkey et al., accepted, Environmental Advances). We then assessed the temporal variability in sediment cores using constrained hierarchical cluster analysis and generalized additive models. Our preliminary results indicate that geochemical change demonstrates significant regional structure. On balance, lakes in eastern Canada predominantly demonstrated a temporal enrichment in metallic elements (e.g., Pb and Zn), while lakes in central and western Canada had a temporal enrichment of elements commonly associated with catchment erosion (e.g., Ti, Sr, K). Our results highlight the heterogeneity in responses across a vast landscape with diverse geological characteristics and land uses, and in the relative importance of anthropogenic disturbances shaping lake sediment geochemistry over time. Key next steps include the investigation of lakes that are distinct relative to their regional trends and the local environmental factors that might explain their contrasting response.

The Cuenca Oriental, a semi-arid region in east-central Mexico, has long supported complex societies, yet its hydroclimatic variability and human-environment interactions-particularly during the Classic, Postclassic, and Colonial periods-remain poorly understood. Here, we present high-resolution proxy records from Lake Alchichica, a crater lake located 18 km from the ancient city of Cantona (600-1050 CE), to reconstruct environmental conditions in the Cuenca Oriental over the past five millennia. Isotope records reveal three major dry periods: (I) ca. 500-1300 CE, encompassing and extending beyond the Late Classic Drought (770-1100 CE); (II) the 17th century CE, corresponding to a colder phase of the Little Ice Age; and (III) post-1970 CE, coinciding with the peak of ongoing global warming. Anthropogenic indicators-including maize and other anthropogenic pollen, as well as Glomus spores and titanium (Ti) intensity (proxies for soil erosion)-demonstrate sustained human-environment interactions. Maize cultivation began by the mid-first millennium BCE and peaked during the Postclassic period (ca. 1000-1500 CE), followed by a sharp and prolonged decline after the Spanish Conquest, most likely due to demographic collapse driven by the introduction of Old World diseases. Agricultural activity never returned to Postclassic maxima, marking a lasting transformation in land use and food production. Notably, the entire urban lifespan of Cantona was encompassed by the extended drought period (500-1300 CE), and its collapse occurred under climatic conditions comparable to those during its peak. Furthermore, the concurrent intensification of agriculture near Lake Alchichica and the abandonment of Cantona suggest that climate alone does not fully explain the decline of the city, instead pointing to additional factors such as warfare, socio-political instability, and economic disruption.

Abstract Dual‐energy X‐ray computed tomography consists of imaging objects using two incident X‐ray beams of different energy to distinguish the different compounds within a sample based on their density (electron density, ρe) and elemental composition (effective atomic number, Zeff). The stoichiometric calibration for dual‐energy X‐ray computed tomography was already successfully implemented to identify single and homogeneous minerals easily and non‐destructively. It is here applied for the first time to a more complex and heterogeneous sample, a varved sediment core with three distinct facies. The output of dual‐energy X‐ray computed tomography was compared against elemental geochemistry obtained at the same resolution using a micro‐XRF core scanner. The three individual facies can be successfully differentiated using dual‐energy X‐ray computed tomography because their range of ρe and Zeff values allow their discrimination. Correlations with elemental geochemistry are also discussed but are less conclusive, probably because of variations in grain size and porosity, and because these high resolution analyses were not performed at the exact same location. The paper not only eventually discusses the limitations when using dual‐energy X‐ray computed tomography on sediments but also demonstrates its potential to quantitatively study sediment cores in a non‐destructive way.

Sediment geochemistry is one lens through which lake sediments are studied to reconstruct local and regional environmental processes. The measurement of sediment elemental composition has historically relied on expensive and destructive methods that limit the spatial and temporal scale of study. Micro-X-ray fluorescence (µXRF) core scanning offers a non-destructive, high-resolution alternative, but its results (i.e., intensity expressed as counts per second) are considered semi-quantitative and comparison among sites requires calibration. Calibration methods are emerging, although they are not yet widely employed and require further assessment of their efficacy. Using 135 sediment samples from 48 lakes across Canada, we assessed the congruence between µXRF and conventionally measured element compositions with various normalization and calibration techniques. Normalization of µXRF data to common proxies (e.g., Ca, Si, Ti, coherence:incoherence ratio, and total counts per second) often improved correlations between µXRF and conventional data, but increases were modest and not consistent for all elements. Our results suggest that µXRF normalization techniques should be applied cautiously, as no proxy represents a “one-size-fits-all” solution. The performance of multivariate log-ratio calibration (MLC) was more consistent, yielding moderate to strong improvement of the correlations between reference and predicted element concentrations. Random forest regression models outperformed partial least squares regression models for almost all elements. MLC may be applied where knowledge of elemental concentration is of great importance, or when comparing across multiple sites with diverse sediment geochemistries. Overall, our results reinforce uncalibrated µXRF core scanning as a strong investigative tool for measuring sediment geochemistry. Although calibrated µXRF data shows promise, conventional methods for measuring sediment geochemistry are still necessary for comparing element concentrations with sediment quality guidelines.

Abstract. X-ray micro-computed tomography (μCT) scans were performed on four varved sediment cores collected in Grand Lake (Labrador) and previously studied with thin sections. These scans allowed to investigate the possibility of using µCT as a substitute for thin sections to carry out counts and thickness measurements of varved sediments. Comparing varve counts of these two methods, μCT counts are slightly higher than the ones made with thin sections. The difference in counts suggests that the petrographic study and a SEM analysis of a thin section remain necessary for determining the varve character of the laminae. Yet, µCT allows measurements in multiple directions, improving the robustness of the counts and allowing avoiding the manufacturing of continuous thin sections along sediment sequence. As to the thickness measurement, the µCT analyses were made in two perpendicular directions. Not surprisingly, measurements made on the same cutting plane as the thin section are quite similar to the ones made on the latter. However, there are significant differences with measurements made on the perpendicular plane. This highlights the need to perform varve thickness measurements in at least two perpendicular directions for better estimates of varved sediment thicknesses. In addition, the study illustrates that µCT is an effective way to select the least deformed zones with parallel varves to carry out the best possible thickness measurements.