Detrital geochronology points to early glaciation of West Antarctica.

Zircon U-Pb data acquired at the LGC, and statistical methods developed by us, demonstrated that the extent of the West Antarctic Ice Sheet (WAIS) was larger than previously thought during colder periods in the Miocene. This means it contributed a lot more to sea-level rise events millions of years ago than previously thought. This insight will help researchers more accurately predict the future of the WAIS as the world warms. 

 The work was carried out by an international team of geoscientists led by Imperial College Prof. Tina van de Flierdt and including LGC scientists Prof. Andy Carter and Prof. Pieter Vermeesch.

Marschalek, J. W., Zurli, L., Talarico, F., van de Flierdt, T., Vermeesch, P., Carter, A., ... & McKay, R. M. (2021). A large West Antarctic Ice Sheet explains early Neogene sea-level amplitude. Nature, 600(7889), 450-455.

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


High throughput geochronology by automated phase mapping and LAICPMS

The first step in most geochronological studies is to extract dateable minerals from the host rock, which is time consuming, removes textural context, and increases the chance for sample cross-contamination. A collaborative research effort between the LGC and Rocktype Ltd. has developed a new method to rapidly perform in-situ analyses by coupling a fast Scanning Electron Microscope (SEM) with Energy Dispersive X-ray Spectrometer (EDS) to a Laser Ablation Inductively Coupled Plasma Mass Spectrometer (LAICPMS) instrument.

Vermeesch, P., Rittner, M., Petrou, E., Omma, J., Mattinson, C. and Garzanti, E., 2017, High throughput petrochronology and sedimentary provenance analysis by automated phase mapping and LAICPMS, Geochemistry, Geophysics, Geosystems (doi: 10.1002/2017GC007109)

Widespread Antarctic glaciation during the Late Eocene

A provenance study of late Eocene marine sedimentary rocks drilled on the southeastern margin of the South Orkney microcontinent in Antarctica (Ocean Drilling Program Leg 113 Site 696) provides the first evidence for a continuity of widespread glacier calving along the coastline of the southern Weddell Sea embayment at least 2.5million yrs before the prominent oxygen isotope event at 34–33.5 Ma that is considered to mark the onset of widespread glaciation of the Antarctic continent.

Matt Fox joins the LGC

Matthew Fox joins the LGC as a NERC Independent Research Fellow. Matthew's work focuses on using thermochronometric data to study a range of earth surface processes from large scale geodynamics to the incision of canyons. Matthew integrates diverse datasets and fieldwork with both inverse and forward numerical models. More information about Matthew's work can be found here here.

The provenance of Taklamakan desert sand

In an article in EPSL, following the conclusion of a three-year, multidisciplinary research project, we analyse a 'Big Data' multi-proxy data set derived from samples collected in the Tarim Basin (Xinjiang, China), to understand the likely sediment sources and pathways in this area. The Taklamakan is a significant producer of atmospheric dust. Our larger goal was to compare the Tarim Basin sediments to the extensive aeolian sequences found on the Chinese Loess Plateau (CLP), and to establish whether the Taklamakan could be a source of this material. From chemical, mineralogical and petrological datasets derived from 39 sites, we determined that the bulk of Taklamakan desert sand comes from the Kunlun Mountains in the south, and is transported by seasonal fluvial processes against the dominant northerly wind direction. The Junggar Basin north of the Tian Shan plays no major role as a sediment source for the Tarim Basin. Compositional similarity between Taklamakan sands and the CLP likely reflects a common source, rather than direct aeolian transport from the former to the latter.

Rittner, M., Vermeesch, P., Carter, A., Bird, A., Stevens, T., Garzanti, E., Andò, S., Vezzoli, G., Dutt, R., Xu, Z., Lu, H., 2016. The provenance of Taklamakan desert sand. Earth Planet. Sci. Lett. 437, 127–137. doi:10.1016/j.epsl.2015.12.036