Detrital Zircon Microtextures as a Powerful New Tool to Interpret the Precambrian Sedimentary Record

Before entering the stratigraphic record, sediments are transported across Earth’s surface via a multitude of environmental flows such as winds, waves, or currents. These different transport modes are known to influence the size and shape distributions of sediments, and to impart distinct microtextures on quartz grains in particular. For decades, analyses of quartz microtextures from scanning electron microscope (SEM) images have proven critical to paleoenvironmental interpretations of Phanerozoic sedimentary rocks. However, quartz is prone to recrystallization during metamorphism and alteration, significantly decreasing the likelihood of microtexture preservation with depositional age. In practice, exceedingly few quartz microtextures have been recovered from Precambrian sedimentary rocks. Yet, the Precambrian represents ~90% of Earth’s history, and its record lacks many of the other clues often used to interpret depositional environments. Here, we show that detrital zircons, which are more resistant than quartz, also develop and retain microtextures that are characteristic of transport environment. First, we systematically document microtextures from detrital zircons extracted from a suite of modern aeolian, fluvial, and beach environments. Second, we show by means of a principal component analysis that the occurrence rate of certain microtextures, together with grain-shape parameters, can be used to diagnose transport environment. Third, we show that a supervised machine learning classifier can robustly diagnose transport environment from just twenty SEM images of grains, removing the need for cataloguing individual microtextures and eliminating operator bias. Finally, we illustrate the potential of this approach through automated analyses of disaggregated zircon grains from well constrained Phanerozoic deposits.