Preprints  

We obtained a cosmogenic ³He (³He_c) exposure age of 10.9 ka ± 1.1 ka for the youngest lava flow at Volcano Mountain (VM) in Yukon, Canada. Initially, olivine grains from the flow were crushed to release mantle He from fluid inclusions and subsequently fused to release ³He_c from the matrix. However, mantle He was significantly retained in fusions. We circumvented this problem by step-heating powdered olivine at three temperature steps, where the lowest temperature step successfully isolated ³He_c.

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 Island. Multi-phase mineral analysis improve age uncertainty by sixfold. We emphasize the importance of the local geologic context and propose strategies to mitigate uncertainties.

We present a pioneering method for high-precision absolute dating of individual growth zones in mineral zircon. The micrometer-wide growth zones record key processes in Earth and Planetary sciences, such as conditions in magma reservoirs prior to supereruptions or planetary formation during the early stages of the Solar system. In our approach, we directly sample the growth zones with a focused ion beam and high pulse laser, allowing to tackle a number of long-standing research questions.

Cosmogenic nuclide exposure dating is an exceptional tool for reconstructing glacier histories, but reconstructions based on common target nuclides (e.g., ¹⁰Be) can be costly and time consuming to generate. Here, we present a low-cost proof-of-concept ²¹Ne exposure age chronology from Lassen Volcanic National Park, CA, USA that broadly agrees with nearby ¹⁰Be chronologies but at lower precision.

A standalone data analysis application for Th/U dating on multi-collector inductively coupled plasma mass spectrometers features a Python-based algorithm with a graphical user interface. It handles data treatment, corrections, age calculus, and error estimation and supports various detector layouts including Faraday and electron multiplier detectors. Key features include reproducibility, user-friendly reanalysis, and automated data storage. A case study demonstrated the software’s performance.

The (U-Th)/He dating method helps understand rock’s cooling history. Synthetic modeling 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.

Understanding how volcanic landscapes, such as Iceland, grow and evolve through time is important for constraining the role volcanism plays in driving variations in geography, climate, and ocean circulation. Here we provide a new method for determining the timescales of volcanic terrain construction using argon geochronology on individual grains of Icelandic sand. This allows us to determine the timing of volcanic eruptions along drainage basins using a small number of strategic sampling sites.

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.

We study the use of zircons as dosimeters using modern techniques, highlighting their advantages such as time-invariant dose rates. We explore the correlation between zircon geochemistry and luminescence properties, observe fast zircon optically stimulated luminescence (OSL) bleaching rates, and assess the potential of auto-regeneration. Low OSL sensitivities require combining natural OSL and auto-regenerated thermoluminescence (TL), with the potential to enhance age accuracy and precision.

Goethite is one of the most common Fe- (oxy)hydroxide minerals which is formed during hydrolyzation of the rocks, implying it is a desired mineral for dating various surface and subsurface geological processes. Nowadays (U-Th)/He dating of goethite is widely used in geochronological studies. Here, on the example of goethite from the Chukchi Borderland, we introduce a new simple methodological approach for accurate (U-Th)/He dating of goethite.

This paper describes how krypton isotopes produced by nuclear fission can be used to determine the age of microscopic particles of used nuclear fuel. This is potentially useful for international safeguards applications aimed at tracking and identifying nuclear materials, as well as geoscience applications involving dating post-1950's sediments or understanding environmental transport of nuclear materials.

Cosmogenic nuclide geochronology requires accurately scaling production rates with altitude. The energy spectrum of cosmic radiation changes with altitude and reactions that are sensitive to different energies may have different scaling behavior. Here, we model the altitude scaling of ³⁶Cl production from Fe and evaluate this model against calibration data. The data are broadly consistent with the prediction of larger altitude scaling factors for ³⁶Cl from Fe than for other reactions.

We present an improved workflow for extracting and measuring chlorine isotopes in rocks and minerals. Experiments on seven geologic samples demonstrate that our workflow provides reliable results while offering several distinct advantages over traditional methods. Most notably, our workflow reduces the amount of isotopically enriched chlorine spike used per rock sample by up to 95 %, which will allow researchers to analyze more samples using their existing laboratory supplies.

Cosmogenic nuclides, such as ¹⁰Be, are rare isotopes produced in rocks when exposed at Earth’s surface and are valuable for understanding surface processes and landscape evolution. However, ¹⁰Be is usually measured in quartz minerals. Here we present advances in efficiently extracting and measuring ¹⁰Be in the pyroxene mineral. These measurements expand the use of ¹⁰Be as a dating tool for new rock types and provide opportunities to understand landscape processes in areas that lack quartz.

RA138 is a new reference material for U-Pb dating of carbonate samples via LA-ICP-MS. RA138 exhibits variable U/Pb ratios and consistent U content, resulting in a precise isochron with low uncertainty. ID-TIMS analyses fix a reference age of 321.99 ± 0.65 Ma. The observed systematic uncertainty challenges previous estimates. This research advances our ability to date carbonate samples accurately, providing deeper insights into geological processes and historical timelines.

We have discovered a new way of measuring the three-dimensional distribution of radioactive elements in individual crystals by shining a very bright light on apatite crystals at the Advanced Photon Source at Argonne National Laboratory. This allows us to learn about the rates and timing of geologic processes, and to help resolve problems that previously were unsolvable because we had no way to make this type of measurement.

We introduce a new statistical method for determining the time of "peak cooling" in thermochronological inversions. Specifically, we focus on the time-temperature paths that intersect the half-maximum cooling isotherm, signifying the zenith or most rapid cooling within a defined interval. The resultant interpolated time distribution provides a systematic metric, particularly applicable for evaluating model cooling characterized by relatively smooth histories featuring a single inflection point.

This note details a development of the (U-Th)/He method for dating apatite crystals in low-temperature thermochronology. Our innovation simplifies analysis protocols for gases (He) and crystals (U, Th, etc.), aiming to expedite data production and enhance study reliability.

Decay of U to Pb in the mineral baddeleyite is used for precisely dating mafic rocks, but some daughter Pb atoms can be ejected out of the crystal, resulting in an age that appears too young. Atom Probe Tomography was used to map the distribution of U and Pb atoms in 3 dimensions within a baddeleyite crystal and estimate the average distance that Pb atoms are displaced by decay of U. This allows us to correct the measured age on a baddeleyite crystal knowing its size and shape.

Radiocarbon serves as powerful dating tool, but there remain significant challenges in the calibration of marine radiocarbon dates. This is because the whole surface ocean cannot be represented by a single calibration curve. Here we use climate model outputs to assess a novel method for developing regional marine calibration curves. Our results are encouraging, particularly for the high latitude regions, and point a way forward for solving the marine radiocarbon age calibration problem.

Marine sediments are excellent archives for reconstructing past changes in climate and ocean circulation. Yet, dating uncertainties, particularly during the 20^th 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 20^th century. 

Decay of U to Pb in the mineral baddeleyite is used for precisely dating mafic rocks, but some daughter Pb atoms can be ejected out of the crystal, resulting in an age that appears too young. Atom Probe Tomography was used to map the distribution of U and Pb atoms in 3 dimensions within a baddeleyite crystal and estimate the average distance that Pb atoms are displaced by decay of U. This allows us to correct the measured age on a baddeleyite crystal knowing its size and shape.

We investigate the relationship between damage trails from uranium fission in apatite and the etched tracks measured with an optical microscope. We aim to understand sampling biases and to improve etching, selection and measurement protocols. The track orientation and length, apatite and track etch rate, and effective etch time co-determine whether a track is suitable for measurement. Reliable data are attainable because the specific sample properties have but a limited effect on these factors.

As a result of increasing precision and accuracy in geochronology, interpreting complicated age spectra has become increasingly important, since individual mineral ages often do not directly date the actual geologic process of interest. Here we propose a method for estimating the age of eruption or deposition of a set of minerals dated by the U-Pb system which, in contrast to previous approaches, remains accurate even when the dated minerals have experienced loss of the daughter product Pb.

Volcanic ash layers are a common tool to synchronize records of past climate, and their estimated age relies on external dating methods. Here, we show that the chemical composition of the well-known, 12000 year-old Vedde Ash is indistinguishable with several other ash layers in Iceland that are ~1000 years younger. Therefore, chemical composition alone cannot be used to identify the Vedde Ash in sedimentary records.

The Great Unconformity represents an enormous amount of time lost from the sedimentary record. Its origin is debated, in part, due to different approaches used to interpret zircon (U–Th)/He ages. This thermochronometric system is ideal for this problem because the temperature sensitivity varies according to radiation damage. Here we explore the uncertainty associated with the radiation damage model and show how this limits our ability to resolve the origin of the Great Unconformity.

We proposed a new non-destructive mineralogical methodology on inframilimetric grains that allows to quantify the hematite and goethite content and hematite/goethite ratio of grains prior to (U-Th)/He geochronological analysis. (U-Th)/He data performed on different aliquots with different acquisition time shows no remarkable differences in age, opening a new way to investigate the (U-Th)/He data evolution in supergene lateritic duricrusts.

Paleomagnetic data from Cascade Lake (Brooks Range, Alaska) extend the radiometric-based age model of the sedimentary sequence extending back 21 kyr. Correlated ages based on prominent features in paleomagnetic secular variations (PSV) diverge from the radiometric ages in the upper 1.6 m, by up to about 2000 years at around 4 ka. Four late Holocene cryptotephra in this section support the PSV chronology and suggest the influence of hard water or aged organic material.

Prehistoric volcanic eruptions are often dated by wiggle matching series of radiocarbon ages on tree rings to standard calibration curves, ignoring potential contamination by 'old' carbon given off by the volcano. We modeled the effects of low amounts of contamination on wiggle match dates for the 10th century Changbaishan eruption and found evidence of contamination in all. We propose a new protocol to identify the presence of contamination, and provide more secure dates for major eruptions.

The timing and duration of fluid activity within a gold deposit enables a greater understanding of how the deposit evolved and thus help future mineral exploration. This research uses high resolution dating methods to unravel the overprinting fluid activity at the Martabe gold field in Sumatra. Methods outline in this report can be applied to deposits globally.

Potassium-based geochronology, including the ⁴⁰Ar/³⁹Ar and K-Ar methods, provides critical constraints on the timing and duration of many events and processes in earth history. These methods assume that a key parameter, the fraction of potassium with a mass of 40, does not vary in some relevant materials. Some recent work has identified some variability in these materials. This work examines the effects of this variability on calculated K-Ar and ⁴⁰Ar/³⁹Ar ages.