How to quantify U-Pb discordance?



In a new Geochronology paper, Vermeesch (2021) 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.

Vermeesch, P., 2021. On the treatment of discordant detrital zircon U-Pb data, Geochronology, 3, 247-257, 2021.

Tim Band joins the group



Tim Band is a Senior Research Software engineer who will work on the NERC-funded "Beyond Isoplot" project (Standard Grant #NE/T001518/1). This project aims to create a 'software revolution' in geochronology, by building an internally consistent ecosystem of computer programs to account for inter-sample error correlations. The proposed software will modify existing data reduction platforms and create entirely new ones. It will implement a data exchange format to combine datasets from multiple chronometers together whilst keeping track of the correlated uncertainties between them.

Before taking on this post, Tim's experience involved numerous programming languages, including C++, Java, Python, JavaScript, TypeScript, C#, Ruby, Go, Haskell and a few others. He has worked on PlayStation games, the Symbian mobile phone operating system, loads of command-line tools, some desktop apps in various frameworks, and back end code with databases like Postgres and MySQL. We are lucky to have such an experienced programmer among us to help improve geochronological data processing at the LGC and beyond.

Sir David Attenborough visits the lab



On Tuesday April 17, we had the great pleasure of giving a lab tour to Sir David Attenborough, who was the guest of honour at the Kathleen Lonsdale Building reopening ceremony. After a brief introduction to U-Pb, U-Th-He and K-Ar geochronology, our esteemed guest asked the pertinent question as to whether these chronometers could be cross-calibrated. Interestingly, improving such cross calibrations turns out to be one of our top priorities for the coming years!

Further information about Sir David's visit to the Department can be found here.

IsoplotR released to the world



IsoplotR is a free and open-source substitute for Kenneth Ludwig's popular Isoplot add-in to Microsoft Excel. The program is written in R and includes functions for U-Pb, Pb-Pb, 40Ar/39Ar, Rb-Sr, Sm-Nd, Lu-Hf, Re-Os, U-Th-He, fission track and U-series disequilibrium dating. IsoplotR can be run in three different modes: online, offline and from the command line. Its underlying principles are described in a paper that has been accepted for publication in:


Vermeesch, P., 2018, IsoplotR: a free and open toolbox for geochronology. Geoscience Frontiers, doi: 10.1016/j.gsf.2018.04.001.

Geologists discover 60 million-year-old meteorite impact

 

The LGC were part of a team of geologists who discovered the first recorded occurrence of vanadium-rich osbornite on Earth, from two sites on Skye, northwest Scotland, which are interpreted as part of a meteoritic ejecta layer. Vanadium-rich osbornite has only previously been reported in space dust from NASA missions, but on Skye it has been identified as an unmelted phase.


Drake, S.M., Beard, A.D., Jones, A.P., Brown, D.J., Fortes, D., Millar, I.A., Carter, A., Baca, J. B., Downes, H. (2017) Discovery of a meteoritic ejecta layer containing unmelted impactor fragments at the base of Paleocene lavas, Isle of Skye, Scotland. Geology, https://doi.org/10.1130/G39452.1