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

New paper in Chemical Geology



There is a lot to do on the Internet about the concept of 'Big Data', in which huge online databases are 'mined' to reveal previously hidden trends and relationships in society. One could argue that sedimentary geology has entered a similar era of 'Big Data', as modern provenance studies routinely use multiple proxies to dozens of samples, resulting in large multivariate datasets comprising thousands of data points. Just like the Internet, sedimentary geology now requires specialised statistical tools to visualise and interpret such large datasets. Pieter Vermeesch (LGC) and Eduardo Garzanti (University of Milan - Bicocca) introduce 3-way multidimensional scaling and Procrustes analysis as simple yet powerful tools to achieve this goal.

Reference: Vermeesch, P. and Garzanti, E., 2015, Making geological sense 'Big Data' in sedimentary provenance analysis. Chemical Geology, doi:10.1016/j.chemgeo.2015.05.004, v.409, 20-27