We have discovered a new method to tell time in the Geological record, using core scanning XRF analyses, which we have now applied to Cambrian and Ordovician rocks to refine the Geological Time Scale. The study, led by my PhD student Zhengfu Zhao, is now published in Nature Communications.

The new method was first discovered by Aske Lohse Sørensen as part of his MSc thesis work and published in EPSL in 2020, pave the way for mapping out Earth’s 3rd dimension and get us closer to understand interesting details about Climate dynamics that we could otherwise only try and understand from models.

The Alum shale formation is found over large parts of Scandinavia and represent marine deposits from the Cambrian and Ordovician. The sedimentation rate and the time it took to deposits all this sediment is now constrained, which also allows us to reconstruct the dynamics of climate change in the past.

The Alum shale formation consist of black fine-grained mud with high concentrations of organic carbon and pyrite sulfur. Although invisible to the eye, the Alum shale formation contains chemical cycles expressed in the abundance of elements such as sulfur and aluminium that correlates with variations in solar insolation at the time the mud was deposited.