Dating fractures using luminescence

Rock fracturing (cracking) is a universal process that drives and limits chemical degradation, sediment pro-duction and erosion, and deterioration of infrastructure. Despite extensive research gains in rock mechanics on one hand and geochronology on the other, there remains a glaring gap in our ability to understand the long term evolution of natural, in situ fractures. Here we develop a novel fracture exposure dating technique, grounded in modern advances in luminescence geochronology. We apply our new dating method to a granitic boulder from a glacial outwash terrace in California, US. We conclude that the longest, clast-splitting E-W fracture appeared shortly after the boulder's deposit, whereas the secondary N-S fracture appeared 5 ka after the deposition, approximately correlating with the Last Glacial Maximum and Younger Dryas periods of the region, respectively. However, dating of the third fracture (<< 50 mu m width) which does not fully split the rock, is ambiguous due to negligible daylight penetration and poor determination of fracture width. The fracture dating method presented herein brings with it the potential to decipher relationships that are crucial for the interpretation and modeling of, for example, long-term landscape and atmospheric evolution relating rock weathering to climate change and erosion.

Automated summary

Rock fracturing is a common process that affects chemical degradation, sediment production, erosion, and infrastructure deterioration. However, our understanding of the long-term evolution of natural fractures is still limited. In this study, a new fracture exposure dating technique was developed and applied to a granite boulder in California, providing insights into the timing of fracture formation. This fracture dating method has the potential to enhance our interpretation and modeling of long-term landscape and atmospheric evolution.