Corrections for initial isotopic disequilibrium in the speleothem U-Pb dating method

Engel, John; Woodhead, Jon; Hellström, John; Maas, Roland; Drysdale, Russell N.; Ford, Derek C.

doi:10.1016/j.quageo.2019.101009

Cited by 12 publications

(7 citation statements)

References 35 publications

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“…Hopley et al, 2019) because the low abundances of these isotopes in comparison to 238 U and 206 Pb are major limitations 52 N. M. W. Roberts et al: LA-ICP-MS U-Pb carbonate geochronology on the uncertainty of the measurements. Engel et al (2019) have provided a solution that will potentially increase the accuracy of age estimates for speleothems, utilising the 235 U decay chain as well as using 208 Pb in place of 204 Pb as the initial-lead composition. This approach is based on ID, and it is unclear how effective it will be for LA-ICP-MS dating, given that 204 Pb is difficult to measure at high precision.…”

Section: Dating Young Materials -Dealing With Disequilibriamentioning

confidence: 99%

Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) U–Pb carbonate geochronology: strategies, progress, and limitations

et al. 2020

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Abstract. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) U–Pb geochronology of carbonate minerals, calcite in particular, is rapidly gaining popularity as an absolute dating method. The high spatial resolution of LA-ICP-MS U–Pb carbonate geochronology has benefits over traditional isotope dilution methods, particularly for diagenetic and hydrothermal calcite, because uranium and lead are heterogeneously distributed on the sub-millimetre scale. At the same time, this can provide limitations to the method, as locating zones of radiogenic lead can be time-consuming and “hit or miss”. Here, we present strategies for dating carbonates with in situ techniques, through imaging and petrographic techniques to data interpretation; our examples are drawn from the dating of fracture-filling calcite, but our discussion is relevant to all carbonate applications. We review several limitations to the method, including open-system behaviour, variable initial-lead compositions, and U–daughter disequilibrium. We also discuss two approaches to data collection: traditional spot analyses guided by petrographic and elemental imaging and image-based dating that utilises LA-ICP-MS elemental and isotopic map data.

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Section: Dating Young Materials -Dealing With Disequilibriamentioning

confidence: 99%

Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) U–Pb carbonate geochronology: strategies, progress, and limitations

et al. 2020

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“…Notably, the highest of the three horizontal/sub-horizontal levels of the Corchia Cave system, about 500 m above the GdS, hosted the CC17-f2 stalagmite dated by Engel et al [71] about 1.9 Ma. This age testifies a Corchia karst system well developed, at least in its higher part, with galleries already formed and speleothems growing.…”

Section: Exhumation/uplift History From Thermochronological Dating For the Alpi Apuanementioning

confidence: 87%

“…AFT constrain the Apuane Metamorphic Complex, as covered by the Tuscan and Ligurian Units already juxtaposed by low-angle normal faults (LANFs) [3,41] still at a depth of 3.5-2.8 km (with a 25 • C or 30 • C geothermal gradient, respectively) at about 3.8 Ma. The Apuane metamorphic core, including the zone hosting the Corchia Cave system, rose from depth to surface with at least three significant stillstand phases, as testified by the three major horizontal/sub-horizontal levels of galleries at around 1400, 1200-1100, and 900 m above the present sea level [26], the higher of which was carved, and partially filled by alluvial sediments of non-metamorphic carbonate sandstone [26], before 1.9 Ma [71]. This testifies that before that time, surface waters were drained through the Corchia system coming from a catchment area partially formed by the Tuscan and Ligurian Units overlaying the metamorphic ones.…”

Section: Sediment Sourcesmentioning

confidence: 99%

New Chronological Constraints from Hypogean Deposits for Late Pliocene to Recent Morphotectonic History of the Alpi Apuane (NW Tuscany, Italy)

et al. 2021

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A sedimentary sequence of fluvial deposits preserved in the Corchia Cave (Alpi Apuane) provides new chronological constraints for the evolution of the cave system and the timing and rate of uplift of this sector of the Alpi Apuane since the late Pliocene. Supported by magnetostratigraphic analysis performed on fine-grained fluvial deposits, and by radiometric dating of speleothems, we suggest that the deposition of fluvial sediments occurred between ~1.6–1.2 Ma. This implies that the host volume of rock was already located close to the local base level, adding key information about the recent tectonic evolution of the Alpi Apuane. A few before ~1 Ma, an erosive phase occurred due to the base-level lowering, followed by continuous speleothem deposition since at least 0.97 Ma. From that time, Monte Corchia uplifted at a maximum rate of ~0.5 mm/year, which is consistent with isostatic uplift mainly driven by erosional unloading. The petrographical study of the fluvial deposits highlights the presence of material derived from the erosion of rocks that today are absent in the cave’s catchment area, suggesting a different surface morphology during the Early Pleistocene. This study highlights the potential of cave sediments as archives for reconstructing the uplift history of mountain ranges.

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“…DQPB allows users to compute disequilibrium 206 Pb/ 238 U, with low detrital content, it is also possible to reference to 208 Pb under the assumption that 232 Th has produced negligible radiogenic 208 Pb since the time of system closure (Getty et al, 2001). The two formulations are mathematically equivalent, but the latter can be advantageous where accurate measurement of 204 Pb proves difficult, such as in ICP-MS dating of young samples (Engel et al, 2019). While U-Pb isochron approaches can be less reliable than concordia-intercept ages, especially for young data sets incorporating the low abundance 204 Pb isotope, they are offered in DQPB because of their potential utility in computing ages for Pb-rich materials where the disequilibrium state of only one of the U-series decay chains is well constrained.…”

Section: Introductionmentioning

confidence: 99%

DQPB: software for calculating disequilibrium U-Pb ages

Pollard

Woodhead²,

Hellström³

et al. 2022

Preprint

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Abstract. DQPB is software for calculating U-Pb ages while accounting for the effects of radioactive disequilibrium among intermediate nuclides of the U-series decay chains. The software is written in Python and distributed both as a pure Python package, and a stand-alone GUI application that integrates with standard Microsoft Excel spreadsheets. The software implements disequilibrium U-Pb equations to compute ages using various approaches, including concordia-intercept ages on a Tera-Wasserburg diagram, disequilibrium U-Pb isochron ages, Pb/U ages based on single analyses, and modified 207Pb ages. These age calculation approaches are tailored toward young materials that cannot reasonably be assumed to have attained radioactive equilibrium at the time of analysis, although they may also be applied to older materials where disequilibrium is no longer analytically resolvable. The software allows users to implement a variety of regression algorithms using both classical and robust statistics approaches, compute weighted average ages, and construct customisable, publication-ready plots of U-Pb age data. Age uncertainties are propagated using Monte Carlo methods.

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Corrections for initial isotopic disequilibrium in the speleothem U-Pb dating method

Cited by 12 publications

References 35 publications

Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) U–Pb carbonate geochronology: strategies, progress, and limitations

Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) U–Pb carbonate geochronology: strategies, progress, and limitations

New Chronological Constraints from Hypogean Deposits for Late Pliocene to Recent Morphotectonic History of the Alpi Apuane (NW Tuscany, Italy)

DQPB: software for calculating disequilibrium U-Pb ages

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